This PDF file contains the front matter associated with SPIE Proceedings Volume 9297, including the Title Page, Copyright information, Table of Contents, Introduction (if any), and Conference Committee listing.

Laser has been widely used in spectroscopic and metrological measurement. High-precision laser metrology is affected by the refractive index of air. In order to apply the algorithm for the refractive index of air in some situation where low calculation complexity and high-precision are needed, the algorithm of the refractive index of Rueger is updated. As the errors of Rueger’s algorithm are mainly affected by temperature, humidity, and the concentration of carbon dioxide in the atmosphere as well as laser wavelength, we do some revisions about these effects of the factors of atmosphere in Rueger’s algorithm. The conditions of standard air is redefined in this paper because of the average concentration of carbon dioxide in the atmosphere has been changed in the past few decades. As the concentration of carbon dioxide in the air is not constant, the effect of carbon dioxide on the refractive index of air is taken into consideration in the updated algorithm. The updated algorithm adapts to the real atmosphere well. The effects of dry air and humid air on the algorithm are also corrected, and the refractive index of air calculated by the updated algorithm is much closer to that of Philip E.Ciddor’s algorithm defined as reference algorithm in the paper because of its high-precision. The performance of the updated algorithm is also analyzed in this paper. It is compared to that of the reference algorithm and the real measured data. Comparing results show that the performance of the algorithm has been improved after the correction. Comparing to the reference algorithm, the performance of the updated algorithm is a little bit lower, but the updated algorithm is much simpler and easier to be applied. Comparing to Rueger’s algorithm, the performance of the updated algorithm is much higher and the complexity of the updated algorithm increases very small. The updated algorithm meets low calculation complexity and high-precision requirements.

A totally self-designed experimental system based on dynamic light scattering is developed. The method of photon correlation spectroscopy is used to simulate the autocorrelation of measured scattering photons and scattering field. The dynamic autocorrelation software is self-compiled to replace the popular hardware digital correlator for much more correlation channels and much lower costs. Several inverse algorithms such as 1^st-order Cumulants, 2^nd-order Cumulants, NNLS, CONTIN and Double Exponents are used to compute the particle sizes and decay linewidths of both monodisperse systems and polydisperse systems. The programs based on these inverse algorithms are all self-compiled except the CONTIN. Influences of systematical parameters such as sample time, the last delay time, elapsed time, suspension's concentration and the baseline of scattering photons autocorrelation on the scattering photon counts, the autocorrelations of scattering photons and scattering field and the distribution of particle sizes are all investigated detailedly and are explained theoretically. The appropriate choices of systematical parameters are pointed out to make the experimental system more perfect. The limitations of the inverse algorithms are described and explained for the self-designed system. The methods of corrected 1^st-order Cumulants and corrected Double Exponents are developed to compute particle sizes correctly at wide time scale. The particle sizes measured by the optimized experimental system are very accurate.

Lidar(Light Detection And Ranging) is a remote sensing technology that measures distance by illuminating a target with a laser and analyzing the reflected light . The pulsed laser ranging precision depends on receiving channel bandwidth, SNR (Signal-to-Noise Ratio), time discrimination precision and TOF (Time of Flight) measurement precision. However, the ranging precision is mainly determined by the TOF measurement precision. Various methods are developed to realize the TOF measurement and can be classified into coarse counting method, analog method, and interpolator method. The interpolator method combined with the advantage of the former two methods is proved be effective, but its realization principle is complex and difficult to realize in hardware. Here, Similar to the interpolation method, a new TDC method based on a reference sine signal is introduced to measure the TOF and can attain high precision and wide measurement range. At first, in principle how to use a reference sine signal to realize TOF measurement is analyzed and proved in detail. The TOF measurement is converted to measure the phase shift of reference sine signal. Then the factors that affect the measurement precision are quantitatively analyzed, which indicates that the frequency and the noise of reference sine signal are the main factors which affect the TOF measurement precision. Finally, numerical simulation and confirmatory experiment are presented, both showing that the proposed method is feasible to realize high precision by using low frequency reference sine signal. This proposed TOF measurement method can be applied in pulsed laser ranging and Three-dimensional imaging system.

A new technique for precise wavefront measurement of lens with a hologram is presented. In diffraction, the Fresnel-zone plate hologram emulates the reflective properties of a spherical mirror for use during transmission null tests of an optic by use of a phase-shifting interferometer. Experiment shows that the Fresnel-zone hologram method result is quite similar with that of the traditional interferometry testing method, in which retroreflecting spherical surfaces are used as the reference. The benefit of this methodology is the higher degree of precision at lower cost of manufacturing the reflecting hologram, compared with retrospheres capable of delivering similar precision. This technique is widely applicable and is particularly useful for measuring long focus lens.

A rapid optic bacteria detecting system based on the principle of Adenosine triphosphate(ATP) bioluminescence was presented in this paper. This system consisted of bioluminescence-based biosensor and the high-sensitivity optic meter. A photon counting photomultiplier tube (PMT) module was used to improve the detection sensitivity, and a NIOS II/f processor based on a Field Programmable Gate Array(FPGA) was used to control the system. In this work, Micrococcus luteus were chosen as the test sample. Several Micrococcus luteus suspension with different concentration was tested by both T2011 and plate counting method. By comparing the two group results, an calibration curve was obtained from the bioluminescence intensity for Micrococcus luteus in the range of 2.3×10² ~ 2.3×10⁶ CFU/mL with a good correlation coefficient of 0.960. An impacting Air microorganism sampler was used to capture Airborne Bacteria, and 8 samples were collected in different place. The TBC results of 8 samples by T2011 were between 10 ~ 2×10³ cfu/mL, consistent with that of plate counting method, which indicated that 8 samples were between 10 ~ 3×10³ cfu/mL. For total airborne bacteria count was small, correlation coefficient was poor. Also no significant difference was found between T2011 and plate counting method by statistical analyses.

We present a novel method of stabilizing a distributed-feedback laser. It’s the first time to our knowledge that the timemeasurement technique is used in laser frequency stabilization. We obtain the laser frequency deviation information from the Fabry-Perot interferometer based on the pulse delay time. In contrast to traditional approaches, the laser can be stabilized in the quasi-continuous spectrum that the interferometer covering. Our method can obtain the error signal from a high signal to noise ratio (SNR) of the voltage signal and not limited by the frequency references. It also avoids many traditional problems, such as power insensitive, modulation, low-level signal, and finite frequency references. A relative frequency fluctuation less than 0.1 MHz is achieved and the root of an Allan variance is about 10^-11 for an average time of 10 s.

Terahertz (THz) digital holography is a combination of THz technology and digital holography which has drawn wide attention. Exact measurements of real recording distances in terahertz (THz) digital holography are important. Autofocusing experimental researches have been conducted based on the holograms in THz off-axis digital holography. Five criterion functions are utilized in this paper. Autofocusing performance of these criterion functions has been analyzed and compared by changing the numbers of the superposition frames of holograms. Experiment results show that five criterion functions all have preferable autofocusing performance with the 5-frame averaged holograms; standard deviation–based correlation criterion function has the worst autofocusing performance.

This paper presents the preliminary investigation of glucose measurement based on tunable pulsed laser induced photoacoustic technique. A photoacoustic glucose detection set-up with forward mode was established. Meanwhile, a 532nm pumped Nd:YAG optical parametric oscillator(OPO) pulsed laser was employed as the photoacoustic signal excitation light source and a confocal PZT transducer was used as photoacoustic signal detector. In experiments, glucose aqueous solutions with several different concentrations were loaded in quartz cuvette in turn and irradiated by focused laser beam, the time-resolved photoacoustic signals were gotten with average of 512 times, the photoacoustic peak-to-peak(PP) value of all concentrations were gotten from 1300nm to 2300nm with interval of 10nm, the characteristic wavelengths of glucose were found via the difference and one order derivative spectral technique. Two optimum characteristic wavelengths were preliminarily chosen via the least square fitting algorithm, their predicted concentration errors were all less than 0.62mmol/dl.

Point array is proposed as the cooperated target to achieve the precise detection for rolling angle in an optical collimated path. The point array image is generated according to the rolling angle, and the algorithm for precise rolling angle detection is described. The factors which impact the detection error of the rolling angle are analyzed in detail. The results of numerical simulations indicated that sub-arcsecond precision detection for rolling angle is achieved by point array, which is superior to that attained by any other targets.

The beam expander is a device used for extending the action radius of the optical system by removing the optical axis parallel. It is usually composed by a pair of plane mirror or two total reflection prism which is installed parallel. However, limited by manufacturing and installation progress, optical axis parallelism errors can be generated while it is hardly to guarantee the two plane mirror or the two total reflection prism installed completely parallel to each other. To detect the optical axis parallelism error of the beam expander quantitatively, a digital optical axis parallelism error detection method for the beam expander is designed taking advantage of the CCD technology and the Image processing technology. In this method, the reticule of the collimator is regarded as the target at infinity. Firstly, the reticule of the collimator images on the CCD camera directly. Keep the pose of the CCD camera unchanged. Then the parallel optical beam is shifted into the beam expander detected by removing of the pentaprism, and the reticule of the collimator images on the same CCD camera again. The location of the collimator reticule center image on the CCD camera is determined respectively through the corresponding image processing. The error of the beam expander is calculated by comparing the coordinate of the collimator reticule center image. An experiment platform is set up based on and the feasibility of this method is verified that the accuracy of the detection method is less than 3’’; this method has the advantage of simple operation, high practicality and high accuracy.

Ranging ability valuation for high-repetition laser ranging system (High-repetition LRS) is essential in space debris measurement. Traditional approaches are usually based on system parameters, such as laser transmission frequency, single pulse energy, transmission aperture, etc. However, precision is not properly evaluated when system conditions varies from ideal conditions. In this paper, a degradation model with a new decrement process based on precision curves is proposed. First, the equation of detection probability and ranging distance is derived. Then, a degradation model to get detection-probability-dependent precision curves is established——a decrement process of data sparsity is simulated, by gradually decreasing effective data while keeping all the noisy data remained. From the curve, a detection probability “threshold” can be seen, from which the ranging ability of the LRS system can be evaluated. In this degradation model, the demanded ranging precision is satisfied automatically. The novel method is reliable and simple with only the detection-probability-dependent precision curve needed. Degradation modeling based on high-repetition ranging experiments for space debris——NORAD 10861, 11574, 16182, 25530 shows an improvement by about 20% in ranging ability evaluation without sacrificing the ranging precision.

Range accuracy and efficiency are two important indicators for Frequency modulated continuous wave (FM/CW) laser radar, improving the accuracy and efficiency of extracting beat frequency are key factors for them. Multiple Modulation Zoom Spectrum Analysis (ZFFT) and the Chirp-Z Transform (CZT) are two widely used methods for improving frequency estimation. The paper through analyze advantages and disadvantages of these methods, proposes a high accuracy and fast signal processing method which is ZFFT-CZT, it combines advantages that ZFFT can reduce data size, and CZT can zoom in frequency of any interested band. The processing of ZFFT-CZT is following: firstly ZFFT is conducted by conducting Fourier transform on short time signal to calculate amount of frequency shift, and transforming high-frequency signal into low-frequency signal of long time sampling, then CZT is conducted by choosing any interested band to continue subdividing the spectral peaks, which can reduce picket fence effect. By simulate experiment based on ZFFT-CZT method, two closed targets at distance of 50m and 50.001m are measured, and the measurement errors are 40μm and 34μm respectively. It proved that ZFFT-CZT has a small amount of calculation, which can meet the requirement of high precision frequency extraction.

Zernike Polynomial fitting method is an effective way to reconstruct absolute surface for three-flat test. However, the Zernike circle polynomials are not orthogonal over the circular area, hence they are not suitable for square flat. We present an absolute testing of a square flat with Legendre polynomial fitting method, which relies on calculating the coefficients of the Legendre terms by least-square fitting method. To obtain the three-dimensional surface data, one additional measurement that rotate the test flat through 90° should be introduced. The formulas are derived theoretically in detail, and validity has been proved by simulated experiment. Vertical profiles of the three surfaces are compared with the measurement results obtained by three-flat test. Good agreement validates our method.

In order to fabricate the optimized LED plant lamp we demonstrated an optical spectral exploration. According to the mechanism of higher plant photosynthesis process and the spectral analysis we demonstrate an optical design of the LED plant lamp. Furthermore we built two kins of prototypes of the LED plant lamps which are suitable for the photosynthesis of higher green vegetables. Based on the simulation of the lamp box of the different alignment of the plants we carried out the growing experiment of green vegetable and obtain the optimized light illumination as well as the spectral profile. The results show that only blue and red light are efficient for the green leave vegetables. Our work is undoubtedly helpful for the LED plant lamping design and manufacture.

This letter reports the low noise control and wavelength shift of a commercial fixed-wavelength high-power DFB laser emitting at 785 nm. In this control system, a novel current driving module integrated with PID temperature controller is designed to provide precise injection current and stable operating temperature. The start- up and stop characteristic of this system is improved as well, to optimize output response and extend service life of the DFB laser. Experimental results show that the optical output power can be accurately controlled in the range of 0 to 600 mW, with the stability better than 2 ‰. In addition, we could effectively control the center wavelength from 785 nm to 793 nm maintaining the linewidth less than 0.9 nm. The research will enhance the performance and extend the use of present commercial DFB laser.

Laser ranging has become an important method for both distance measurements and acquisition of threedimensional (3D) images. In this paper, a laser ranging system based on Time-Correlated Single-Photon Counting technology (TCSPC) is developed. A Geiger-mode avalanche photodiode (G-APD), which has the ability of detecting single-photon events, is used to capture the weak light scattered from the long-range target. In order to improve the ranging resolution of TCSPC based measurement system, a high repetition frequency of subnanosecond narrow pulse generator circuit based on the avalanche effect of RF-BJT is designed and applied as the light source. Moreover, some optimized optical light designs have been done to improve the system signal to noise rate (SNR), including using a special aspherical lens as projecting lens, adopting a telephoto camera lens with small view angle and short depth of field before detector. Experimental tests for evaluation of the laser raging system performance are described. As a means of echo signal analysis, three different algorithms have been introduced, in which the cross-correlation algorithm was demonstrated to be the most effective algorithm to determining the round trip time to a target, even based on histograms with a significant amount of background noise photons. It was found that centimeter ranging resolution can be achieved thanks to the use of Time-to-Digital Converter (TDC) with picosecond resolution and the Cross-Correlation algorithm. The proposed laser ranging system has advantages of high range resolution, short response time and simple structure, which was potential applications for 3D object recognition, computer vision, reverse engineering and virtual reality.

The multi-pulsed laser ranging technology is prominent on improving the maximum measuring range of laser active detection，laser range finder and other long-distance measurement. For all laser echo detection techniques, the weak signal detection is an important step, which aims to increase the detection range. Most algorithms are based on the priori knowledge of laser echo or the improvement of laser power. However, we cannot know or estimate the waveform accurately in many applications. Moreover, these means are difficult to satisfy the real-time needs. The present paper proposes an improved algorithm which extended the signal accumulation algorithm for the high power burst laser. This method is mainly based on signal accumulation and tri-cumulant algorithm which can improve the signal to noise SNR of the weak laser echo; moreover it does not need more prior knowledge of echo. In order to reduce the detection time, the algorithm is realized based on FPGA using signal retiming and parallel pipeline structure. The simulations and experiments results demonstrate that the minimum detecting SNR is -5dB and the maximum detecting time is only less than 1us.

Optical three-dimensional (3-D) profilometry is gaining increasing attention for its simplicity, flexibility, high accuracy, and non-contact nature. Recent advances in imaging sensors and digital projection technology further its progress in high-speed, real-time applications, enabling 3-D shapes reconstruction of moving objects and dynamic scenes. In traditional 3-D measurement system where the processing time is not a key factor, camera lens distortion correction is performed directly. However, for the time-critical high-speed applications, the time-consuming correction algorithm is inappropriate to be performed directly during the real-time process. To cope with this issue, here we present a novel high-speed real-time 3-D coordinates measuring technique based on fringe projection with the consideration of the camera lens distortion. A pixel mapping relation between a distorted image and a corrected one is pre-determined and stored in computer memory for real-time fringe correction. And a method of lookup table (LUT) is introduced as well for fast data processing. Our experimental results reveal that the measurement error of the in-plane coordinates has been reduced by one order of magnitude and the accuracy of the out-plane coordinate been tripled after the distortions being eliminated. Moreover, owing to the merit of the LUT, the 3-D reconstruction can be achieved at 92.34 frames per second.

According to the expression of the phase delay and diffraction efficiency of the diffractive optical elements(DOEs), the expression of diffraction efficiency of multilayer diffractive optical element(MLDOEs) with the height error in fabrication process was described in this paper. We selected the PC and PMMA used usually at optics as substrate material of MLDOEs, and analyze the height error range of multilayer diffractive optical element with consideration of polychromatic integral diffraction efficiency basing on the mathematical analysis model of the relationship between height error and diffraction efficiency for MLDOEs. The range of height error the diffraction efficiency of MLDOEs was given. This model can be used to guide the design and fabrication process of hybrid diffraction refractive optical system for optical engineer.

Usually the intensity distribution of laser is Gaussian, but practical laser applications often require beam shaping. A ring-shaped pattern may be required in the confocal scanning microscopic imaging. Because phase-only spatial light modulators (SLMs) can be flexibly used to convert light wave fronts, the investigation of beam shaping by SLMs has become an active research area. In this paper, a phase-only liquid crystal spatial light modulator is used to transform a single-mode He-Ne laser into a ring-shaped pattern. This generated ring beam is investigated experimentally, and the experimental results with the pinhole size are analyzed.

In this paper, we propose to obtain the optical characteristics on material surface by Mueller calculus. In our research, a new metric for Mueller matrices, named R(M) , is defined to describe the polarization and depolarization characteristics on material surface by analyzing the constitute of Mueller matrices. The definition of R(M) is derived from the definition of the depolarization scalar metric for Mueller matrices named Q (M ) which can show the diattenuation and depolarization characteristics. With the advantage of Q (M ) , we assumed and proved the advantage of R(M) against the traditional metrics, the polarizance parameter P(M) and the depolarization index DI (M ) . This comparison can fully illustrate the value of R(M) . It is considered that P(M) and DI (M ) which cannot analyze the optical characteristics commonly to give a comprehensive evaluation. However, composed of P(M) and DI (M ) , R(M) can comprehensively reflect the optical signification which P(M) and DI (M ) represent. R(M) can be used to analyze different optical polarized characteristics on material surface with five bounds as totally depolarizing, partially depolarizing, totally polarizing, partially polarizing, nondepolarizing nonpolarizing. This means that R(M) can enable us to distinguish different materials by their different polarized characteristic on surface. With the definition of R(M) , it can be known that how the optical polarized characteristics work to change the polarized state of incident light on material surface.

The technology of terahertz (THz) is a major research area in the 21st century. THz imaging is an important research direction. The single-frequency continuous-wave THz technology is combined with coaxial reflection-mode confocal scanning microscopic imaging in this article. Under the given system parameters, the transverse response character of 2.52THz (118.83μm) coaxial reflection-mode confocal scanning microscopic imaging is emulated and analyzed. The results of emulation show that coaxial reflection-mode confocal scanning microscopic imaging is feasible in THz region.

Comparison and analysis for several usual types of atmospheric turbulence simulator are first given in this paper. Considering the Tatarskii spectrum and the conditions of laboratory, secondly, the numerical calculations of the M² factor and the spatial and angular widths of coherent Gaussian beams in turbulence are performed. Finally, a kind of a hot-wind atmospheric turbulence generator is designed and its characteristics are analyzed. The results show that the turbulence generator is very suitable to use in studying the effects of turbulence on the M² factor of cw laser beams. Also, the values of both the structure constant of refractive index fluctuations C_n² and the inner scale of turbulence required by the generator are still in accordance with those of actual atmospheric turbulence.

This paper reports an advanced Czerny-Turner optical structure which is used for the application in imaging spectrometers. To obtain the excellent imaging quality, a cylindrical lens with a wedge angle is used between the focusing mirror and the imaging plane to remove astigmatism in broadband. It makes the advanced optical system presents high resolution over the full bandwidth and decreases the cost. An example of the imaging spectrometer in the waveband of 260nm~520nm has been designed to prove our theory. It yields the excellent modulation transfer functions (MTF) of all fields of view which are more than 0.75 over the broadband under the required Nyquist frequency (20lp/mm).

The design and development of the swept laser for optical coherence tomography is presented. It is manifested by a semiconductor optical amplifier, a fiber coupler, two fiber isolators, a semiconductor optical amplifier (SOA) and an acousto-optic tunable filter (AOTF) for frequency tuning within a unidirectional all-fiber ring cavity. Light output from the coupler is further amplified and spectral shaped by a booster SOA terminated at both ends with two isolators. The total loss in ring cavity is 8.2 dB. The gain SOA provides fiber-to-fiber small signal gain of 22.2 dB with saturation output power of 9.0 dBm. The developed laser source provides up to 100 kHz over a full-width wavelength tuning range of 140 nm at center wavelength of 1308 nm with an average power of 8 mW, yielding an axial resolution of 5.4 μm in air for OCT imaging. Theoretically, the measurement principle and the feasibility of the system are analyzed. Implementing the laser source in swept source based OCT (SS-OCT) system, real-time structural imaging of biological tissue is realized.

We use double reversing wavefront Michelson interferometer to measure the spatial coherence properties of high power broad area Fabry Perot edge emitting blue laser. The measurements are done at different bias current, from lasing threshold up to 1A. The laser is driven in both continuous-wave, CW and pulsed-wave modes. It is found that the magnitude of complex degree of coherence decrease when the laser is driven in pulsed mode. Among driving currents for each mode just for 700 mA bias current more uniform and rather visible interference fringes attained.

A nondestructive, accurate and fast method for measuring the grating parameters of relief gratings is proposed in this paper. At first, the 0th diffractive transmission efficiency spectrum from 600nm to 700nm is obtained according to a certain relief grating model with the rigorous coupled-wave analysis (RCWA). Under the condition of normal incidence, the 0th diffractive transmission efficiency will behave as a function of duty cycles, depths and profiles of grooves for both TE and TM polarization. Then the data of the 0th diffractive transmission efficiency spectrum for TE polarization is regarded as measured values of simulation. Finally, grating parameters are obtained with the library matching method. Theoretical analysis and numerical simulation results demonstrate the feasibility and validity of the proposed method. Being accurate, repeatable and nondestructive, this kind of method will obtain the grating parameters quickly in practice without comprehensive and expensive but only commonly spectrometer that will be convenient for measurement of grating parameters in situ.

Synthetic aperture digital holography can effectively increase the recording area of digital hologram, which is propitious to extend the range and improve the resolution of the reconstruction image. However, the area of synthetic aperture digital hologram is usually very large, and thus if it is directly reconstructed, the numerical reconstruction process may can’t progress in order for the limitation of the disposal capability of computer. Therefore, a screen-division reconstruction method for synthetic aperture digital Fresnel hologram is proposed in the paper. Relatively to the direct reconstruction method, the screen division reconstruction method can effectively reduce the area of the hologram participant in the numerical operation process and thus make it possible to reconstruct the synthetic aperture digital Fresnel hologram which area exceeds the disposal capability of computer. The synthetic aperture digital Fresnel hologram with large area is acquired by the precise control for the removal of CCD array and then reconstructed by the proposed screen division reconstruction method. The experimental results show that, the introduced numerical reconstruction method can well correct the position and phase distribution of the sub-reconstructed-images and obtain accurate synthetic numerical reconstruction image.

In the practical application of terahertz reflection-mode confocal scanning microscopy, the size of detector pinhole is an important factor that determines the performance of spatial resolution characteristic of the microscopic system. However, the use of physical pinhole brings some inconvenience to the experiment and the adjustment error has a great influence on the experiment result. Through reasonably selecting the parameter of matrix detector virtual pinhole (VPH), it can efficiently approximate the physical pinhole. By using this approach, the difficulty of experimental calibration is reduced significantly. In this article, an imaging scheme of terahertz reflection-mode confocal scanning microscopy that is based on the matrix detector VPH is put forward. The influence of detector pinhole size on the axial resolution of confocal scanning microscopy is emulated and analyzed. Then, the parameter of VPH is emulated when the best axial imaging performance is reached.

Research on detonation process is of great significance for the control optimization of pulse detonation engine. Based on absorption spectrum technology, the filling process of fresh fuel and oxidant during detonation is researched. As one of the most important products, H₂O is selected as the target of detonation diagnosis. Fiber distributed detonation test system is designed to enable the detonation diagnosis under adverse conditions in detonation process. The test system is verified to be reliable. Laser signals at different working frequency (5Hz, 10Hz and 20Hz) are detected. Change of relative laser intensity in one detonation circle is analyzed. The duration of filling process is inferred from the change of laser intensity, which is about 100~110ms. The peak of absorption spectrum is used to present the concentration of H₂O during the filling process of fresh fuel and oxidant. Absorption spectrum is calculated, and the change of absorption peak is analyzed. Duration of filling process calculated with absorption peak consisted with the result inferred from the change of relative laser intensity. The pulse detonation engine worked normally and obtained the maximum thrust at 10Hz under experiment conditions. The results are verified through H₂O gas concentration monitoring during detonation.

In the process of the high speed pay-off of the optical fiber cables, there are some problems unsolved such as testing the broken fibers or cables, monitoring the working states of the pay-off, and so on. In this paper, in order to solve these problems, a kind of dynamic testing technology to test the bending losses and the bending parameters of optical fiber pay-off cables based on the dual-wavelength, at the high pay-off speed, is proposed. Using the dual-wavelength method, the distribution of bending radius and bending length near the stripping points of the fibers on the optical fiber cable steel can be inversed by the difference of the bending loss index. On the other hand, a kind of dynamic dual-wavelength testing device is designed and developed, which is of broad band and high sensitivity and can obtain the periodic signals of the cable loss index with the changing of strong bending in real time. Besides, the static and dynamic calibration devices are designed, and the relationship between the two calibration methods is also established. Furthermore, the relationship between the curvature radius and the strong bending losses when the curvature radius is less than 6mm and the relationship between the bending length and the loss is studied experimentally. The results show that it has fast time response, strong anti-interference ability and high sensibility. There is obvious difference of the bending states between the scanning interval and the retrace interval, and the loss in the retrace interval increases greatly more than in the scanning interval. It is important to note that the minimum curvature radius of the strong bending cable is about 0.5mm at the speed of 200m/s. Our work will be beneficial to analysis the process and the mechanism of the fault of the fiber broking, as well as the fiber communication, fiber sensor, and so on.

As the development of high powered laser system, the measuring accuracy of optic’s transmissivity need to be improved in order to guarantee all the optics’ quality. This paper analyses all the factors which largely influence the testing accuracy of optics transmissivity when using the spectralphotometer. Experiments are carried out to verify all the deduced results. The results show that the accuracy of wavelength, error of incident angle and divergence of measuring beam would influence the testing result of transmissivity, and the divergence of measuring beam would contrubite to the largest error. Therefore, the testing accuracy could be greatly increased by decreasing the divergence angle of measuring beam.

Multiple surfaces transform interferometery is a preferred technology for surface profile and index homogeneity measurement using a Fourier based analysis method combined with phase-shifting interferometer. As a four-surface cavity for example, the surface form and index inhomogeneity of the parallel plate are deduced by extracting the information from the corresponding interference frequency. The errors of surface form and index homogeneity are simultaneously simulated and analyzed with different sampling buckets. The results show the feasibility and high precision of this approach compared with traditional methods.

It is obvious that those recently developed dithering techniques could improve measurement quality. However, those optimization methods are still imperfect since they are sensitive to the amount of defocusing. This paper presents a new optimization method based on minimizing a proposed objective function named intensity residual error (IRE) to construct binary patterns for high-quality 3D shape measurement. Both the simulation and experimental results demonstrate that the proposed algorithm can achieve phase quality improvements over other developed dithering techniques with various amounts of defocusing especially when the fringe period is larger.

Three-flat test can separate the reference surface error from the test part surface in the surface measurement by interferometry. The solution based on mirror symmetry of three-flat test is compact and highly accurate. In practice, the error will be introduced when the position of three flats are misalignment or the relative rotation angle are not accurate. The influence of rotation angle error are simulated and discussed. Then the experiment was carried out on three reference flats and the flat surface profiles were derived by mirror symmetry method. The experiment results show good agreement and the difference is in a nanometer level.

The laser stealth of space target is useful, important and urgent in practice. This paper introduces the definition expression of laser radar cross section (LRCS) and the general laws of the influencing factors of space target’s LRCS, including surface materials types, target’s shape and size. Then this paper discusses the possible laser stealth methods of space target in practical applications from the two view points of material stealth methods and shape stealth methods. These conclusions and suggestions can provide references for the next research thinking and methods of the target’s laser stealth.

This article uses the external cavity laser to realize FMCW high precision absolute distance measurement, as the external cavity laser owns the advantage of large tuning range of frequency. Firstly, aim at the problem of nonlinear tuning of the external cavity laser, a study of method of frequency-sampling has been shown. Secondly, in this article the mathematical model of the absolute dis tance measurement system has been established, and the sources of the errors of the FMCW absolute distance measurement has been analyzed, and the accuracy model has been established. Finally, a ball which is put at a distance about 3 meters is measured, and the random error is 0.3479μm, the standard uncertainty of measurement system is 0.3479μm+3.141Rppm.

A experimental method measuring laser energy and energy distributing of large-aperture beam is presented. The experimental equipment is established. The energy and energy distribution of beam, the beam size is Φ100mm and Φ360mm, are measured. The result show measuring error for laser energy is less than 8%. The energy distribution is basically consistent.

A new type of direct transmission visibility measuring device is developed. The device can obtain the visibility by measuring the atmosphere transmittance ratio of laser beam in sampling space. The measuring principle and the design scheme of the device are described. The measuring comparison experiments of this device and the reference transmittance meter are carried out. The experiment results verify the correction of test theory and technique scheme. The relative measurement error is under 20% within the test range of 10 km.

Accurate measurements of forces applied to the optical cable reels with high spinning speeds, will render information on the breakdown of optical fibers, and thus improve the odds of success and un-winding efficiency. In this paper we analyze and deduce the cable wire stress at high pay-off speeds. A high-sensitive opti-mechanical testing sensory device is designed to measure both the axial tension of the cables and the radial pressure of the cable reels at varying stress points simultaneously. The time resolution of this new device is less than 0.015ms, the response time is up to 15μs, and its sensitivity is about 500pc/N, which satisfies the mechanical testing requirements at high spinning speeds. In addition, the spinning speed of 260m/s led to the break-down of the optical fibers, and the spinning speed of 250m/s tested finally led to a deceleration near the end of the broken fibers. It is obvious that this kit can meet the requirement to obtain the periodic signals of the varying forces for each layer and each turn of optical fiber cables. Moreover, we found that the pay-off fiber cable is safe with the unwinding speed of 250m/s and the break-down of optical cables happens during the deceleration process. However, it is under the unwinding speed of 260m/s that pay-off fiber cables broke during the experiment. The abnormal breakdown signals are captured at these unwinding speeds, respectively.

Research on terahertz wave transmission through plasma is significant for researches on plasma itself and transmission discipline of terahertz wave through plasma. It is possible for plasma with suitable density to be an available stealth outerwear for plane or missile in THz waveband. In this paper, plasma is gotten by ionizing inert gases such as argon and helium gases with pulsed high alternating voltage. With electro-optic pump-probe measurement, THz transmission phenomena through plasma have been studied. The experiments show that some parts of THz frequency components have been cut off by plasma, and with the density of plasma rising, the starting frequency of THz prohibited by plasma is going higher. Experiments also provide an assistant scheme for plasma diagnose with terahertz technique.

In the test for the laser seeker in the hardware-in-loop simulation, acquiring the effect of polarization laser echo wave to optical stress polarization of the seeker and to the polarization guidance performance was not considered. A new method to generating the dynamic polarization laser echo signal was provided based on the scene model; furthermore, the method to adding the polarization characters to the energy scene was introduced. At last, the insufficient of the method to generating and simulating the dynamic polarization signal was analyzed.

A test environment is established to obtain experimental data for verifying the positioning model which was derived previously based on the pinhole imaging model and the theory of binocular stereo vision measurement. The model requires that the optical axes of the two cameras meet at one point which is defined as the origin of the world coordinate system, thus simplifying and optimizing the positioning model. The experimental data are processed and tables and charts are given for comparing the positions of objects measured with DGPS with a measurement accuracy of 10 centimeters as the reference and those measured with the positioning model. Sources of visual measurement model are analyzed, and the effects of the errors of camera and system parameters on the accuracy of positioning model were probed, based on the error transfer and synthesis rules. A conclusion is made that measurement accuracy of surface surveillances based on binocular stereo vision measurement is better than surface movement radars, ADS-B (Automatic Dependent Surveillance-Broadcast) and MLAT (Multilateration).

In recent years machine vision technology obtained the application in many fields, such as the industry, medical systems and national defence. Researches on the machine vision of the on-line and real-time detecting system. By the aid of optical engineering software ZEMAX, a telecentric optical system is designed, which uses a 1 inch CCD image sensor with 5.5μm pixel size. It can measure the target size and non-contact, with the maximum measurement range of 300mm and the resolution of 0.2mm, magnification is -0.053, the distortion is less than 0.1 percent. The MTF of this system is more than 0.5 in 70lp/mm, and all sorts of the aberrations are corrected well, and the image quality is uniform in all the fields. As the limits of magnification and pixel size of the CCD, the technology of CCD pixel subdivision can be used, and the accuracy can be increased to dozens of times, the accuracy of on-line non-contact measurement System can reach the micron-size. The telecentric degree of the double telecentric lens is very small when the object moves along the optical axis.

In order to lower production cost of Laser Doppler velocimeter (LDV) and simplify the system structure, a grating Doppler detection system has been designed. This LDV was carried out by differential measurement mode. Two beams of diffracted light from the grating are mixed, and the beat frequency will be detected by a detector when the grating is moving. Fundamentals also have been introduced and partial experiment results of this system are given out. The result indicates the experimental value is agreement with the theoretical value. Errors have been analyzed and the main factors affecting the accuracy were discussed. Upon inspection, the inexpensive and ease LDV is efficient to administer and feasible.

Collimation system is an indispensable part of the photoelectric detection equipment. Aimed at meeting the demand of field on-line detection for photoelectric system, the system must have higher requirements for its volume, quality and the anti-interference ability of all sorts of complex weather conditions. In order to solve this problem, this paper designed a kind of high temperature adaptability reflex cassegrain collimation system. First the technical indexes of the system was put forward according to the requirements of practical application, then the initial structure parameters was calculated by gaussian optical computing and optimized processing through Zemax. The simulation results showed that the MTF of the system was close to the diffraction limit, which had a good image quality. The system structure tube adopted hard steel material; the primary mirror and secondary mirror used low expansion coefficient of microcrystalline glass, which effectively reduced the deformation due to temperature difference and remained little change in quality and volume at the same time. The experiment results in high and low temperature environments also showed that the collimation system could keep within 30 "beam divergence angle, which proved to have good temperature adaptability, so that it can be used in the field of complex bad conditions.

In this paper, we report an abnormal laser deflection phenomena based on quadratic electro-optic effect in copper doped KTN crystal. Cu:KTa_0.62Nb_0.38O₃ block with size a×b×c = 2.8mm×2.6mm×12.5mm was used as beam deflection element. 75mrad beam deflection angle were observed under 1KV voltage when the laser beam across the c direction of the sample at room temperature. The special features of our experiment are that the direction of laser beam deflect perpendicular to the electric field direction, and the angular size and direction of the deflection beam remain unchanged when the electric field direction reverse. We believe that the interaction of graded refractivity and electro-optic effect leads to these special features. Besides of the special deflection mode, the deflection efficiency of our experiment also reached the world advanced level.

Dynamic feature of Weapon equipments is one of important performance index for evaluating the performance of the whole weapon system. The construction of target range in our country in fire control dynamic testing is relatively backward; therefore, it has greatly influenced the evaluation on the fire control system. In order to solve this problem, it's urgent to develop a new testing instrument so as to adjust to the armament research process and promote weapon system working more efficiently and thereby meeting the needs of modernization in national defense. This paper proposes a new measure which is used to test the stability precision of the fire control system, and it is installed on the moving base. Using the method, we develop a testing system which can test the stability precision of the fire control system and achieve a high precision results after testing. The innovation of the system is we can receive the image not only by CCD, but our eyes. It also adopts digital image-forming and image processing technique for real-time measurement and storing of the target information; it simultaneously adopts the method adjusting the platform and the corresponding fixture mounted on a sample to measure the stable precision and the precision of corner of stabilizator. In this paper, we make a description on the construction of the system and the idea of the designing of the optical system. Finally, we introduce the actual application of the system and testing results.

Lensless digital holography could improve the resolution of digital holography reconstruction and has drawn wide attention. The complex wave-front could be reconstructed through Fourier transformation of a single hologram. It’s crucial to reconstruct the phase precisely. However the phase constructed from a single hologram usually contains a quadratic aberration. Many methods are proposed to remove the item. In this paper the method of lateral shearing interferometry is studied to compensate the quadratic aberration. First we show the aberration in lensless digital holography and the lateral shearing interferometry. Then numerical simulations are carried out to test the method. It can be concluded that the method of linear fitting could effectively extract the quadratic aberration. The drawback is that the quadratic phase information extracted could not discern the additional aberration and the quadratic item included by the object wave field. A small local smooth area couldn’t guarantee good estimation of quadratic aberrations. A larger area could get better results even in the presence of noises. However the aberration compensation depends greatly on noises. The reason of larger residual aberrations in the presence of noises is that noises influence greatly on the phase reconstruction including unwrapping.

Electrical Speckle Shearing Phase-shifting Pattern Interferometry (ESSPPI) is a kind of full-field nondestructive measurement technology and has many merits such as noncontact, full-field measurement, high precision and anti-vibration-noise, etc. ESSPPI has been used in the fields of deformation measurement and nondestructive testing. The theory and methods are studied with statistical optics in the paper and the corresponding mathematical model, which is used to describe the relation between vertical displacement gradient to object surface and distribution of speckle stripes, is set up. The algorithms of three-step method, four-step method and five-step method are deduced on the basis of above model. The factors that may reduce the phase precision are analyzed. The results of analysis indicate that the measurement precision is mainly affected by phase-shifting linear error. The phase error with five-step method is obviously less than that with three-step method or four-step method, but it can’t be eliminated. Therefore a new four-step method no affected by phase-shifting error is put forward. The difference between phase distribution gained with above method and the real phase distribution is regarded as a fixed value and can be eliminated. Four phase-shifting interference pattern figures are accessed by an experiment of aluminum plate deformation and a packaged phase distribution figure is obtained with the new four-step method. The real phase distribution figure, obtained with unpackaged algorithm, is shown in the paper to prove the validity of the new four-step method.

A frequency stabilization technique for a 632.8nm He-Ne laser with a high finesse Fabry-Perot cavity is introduced in this paper. The resonant frequency of the cavity is taken as the frequency standard .In this system the Fabry-Perot cavity is composed of a glass-ceramic spacer, with thermal expansion coefficient smaller than 2×10^-8/°C ， which means an excellent thermal stabilization which greatly decreases the thermal impacts on the cavity length in the desired constant-temperature environment.The intra-cavity spherical mirror is specially designed, which makes the Fabry-cavity a sensor element in our subsequent experiments for a new practical optical accelerometer .Both cavity mirrors were custom made in our laboratory which have reflectivities greater than 99.995% at 632.8nm, so the Fabry–Perot cavity has a finesse of about 62830. The half-maximum transmission line width is about 55.48 KHz and the free spectral range is 3.5GHz .In the experimental setup, we adopt the frequency stabilization circuit with small dithering .With proper dithering voltage, the laser can be precisely locked to the Fabry-Perot cavity minimum reflection point. Theoretically the frequency stability can reach 10^-10 order.

The phase unwrapping procedure is the most important step to achieve high accuracy, high resolution three-dimensional (3-D) shape data of objects. Among numerous techniques of phase unwrapping, the region-based algorithms are outstanding, which provide a trade-off between robustness and the computational complexity. However, there is indeed a weakness in the region-based algorithms that the unwrapped data may be incorrect due to the wrapped process generating the same wrapped data of two different areas. To overcome these problems, we propose a novel phase-unwrapping method which depended on region-based methods and quality guided techniques. First, in principle the whole procedure of generating, capturing images and three-step phase-shifting algorithm are introduced and analyzed in detail. Then, the size of the region can be calculated automatically to divide the wrapped image into homogenous areas. Afterwards, based on the method described here, a non-continuous region joining method is applied to reconstruct the continuous unwrapped phase map. In addition, Itoh and Iso phase-unwrapping methods are implemented to unwrap the phase data for the comparison and the results indicate that the proposed method can unwrap phase data accurately. At last, some reconstruction images are presented and the results are analyzed. Experimental results have demonstrated that the proposed algorithm can resolve the problems the Iso phase-unwrapping method encounter in complex wrapped phase cases.

A new method and its principle are presented for measuring the each component gas pressures in Rubidium (Rb) by the analysis of absorption spectral profile. The experiment system is set up to obtain Rb absorption spectra. And then each component gas pressures in atom vapor cell is estimated. First, the relationships between transmittance of probe light, atom density and absorption cross section are introduced, and the factors which influence the absorption spectral profile and methods to measure gas pressures are given. Second, the frequency-dependence curves of transmittance and the absorption spectra are obtained through tuning the laser frequency through the Rb D1 transition. Finally, the gas pressures of Rb, N2 and He are achieved, through fitting absorption spectral profile referring to half-width and minimum transmittance value of absorption spectra. The experiment results show that gas pressures in Rb atom vapor cell can be accurately measured by absorption spectrometric methods, which will be helpful for the following study of atom vapor cell. The gas pressures of N2 and He measured by the experiments are well matched with design values. The Rb gas pressure is 30%~50% less than the saturated vapor pressure and the suppression may be due to the adsorption of the cell surfaces coated with octadecyltrichlorosilane (OTS) film.

There has been a considerable increase in the abuse of drugs during the past decade. Combing drug use with driving is very dangerous. More than 11% of drivers in a roadside survey tested positive for drugs, while 18% of drivers killed in accidents tested positive for drugs as reported in USA, 2007. Toward developing a rapid drug screening device, we use saliva as the sample, and combining the traditional immunoassays method with optical magnetic technology. There were several methods for magnetic nanoparticles detection, such as magnetic coils, SQUID, microscopic imaging, and Hall sensors. All of these methods were not suitable for our demands. By developing a novel optical scheme, we demonstrate high-sensitivity detection in saliva. Drugs of abuse are detected at sub-nano gram per milliliter levels in less than 120 seconds. Evanescent wave principle has been applied to sensitively monitor the presence of magnetic nanoparticles on the binding surface. Like the total internal reflection fluorescence microscope (TIRFM), evanescent optical field is generated at the plastic/fluid interface, which decays exponentially and penetrates into the fluid by only a sub-wavelength distance. By disturbance total internal reflection with magnetic nanoparticles, the optical intensity would be influenced. We then detected optical output by imaging the sensor surface onto a CCD camera. We tested four drugs tetrahydrocannabinol (THC), methamphetamine (MAMP), ketamine (KET), morphine (OPI), using this technology. 100 ng mL-1 sensitivity was achieved, and obvious evidence showed that this results could be improved in further researches.

The spider is the dominate stiffness to suspend the cone for a moving-coil loudspeaker unit, and is most commonly a concentrically corrugated fabric disk. A subwoofer closed box is designed to excite the tested spiders pneumatically, and the Laser Doppler Vibrometer (LDV) is used to measure the velocity of the moving spiders. The effective stiffness, loss factor and some viscoelastic behaviors such as level dependent stiffness have been investigated. The results find that, this pneumatic non-contact dynamic technique successfully measured the viscoelastic behaviors of spiders from extremely low frequency 5 Hz to 200 Hz, and the effective stiffness of spiders is dependent on the input voltage level, which is higher level with lower stiffness.

3D(Three-dimensional) measurement has found its applications in the fields of automation process, Reverse engineering(RE), machine vision, as well as medical diagnostic. There are some disadvantages in the present 3D measurement methods. In this paper, a 2D laser displacement sensor-based and fast-dimensional surface measurement method for small size objects was proposed after analyzing the existing three-dimensional measurement methods. This method uses the information collected by 2D laser displacement sensor and encoder in pan-tilt to three-dimensional reconstruct 3D model. And then discuss the restrictive relation between angular velocity of pan-tilt and parameters (measurement range, signal sample rate, precision, etc.) of 2D laser displacement sensor. The sources of error and methods of improving precision were analyzed. Theoretical analyses and experiments have proved the feasibility, high-precision and practical of this method.

We use the time-resolved degenerated PO pump-probe technique to investigate the nonlinear absorption and nonlinear refraction dynamics of a novel porphyrin derivate, Indium-Porphyrin functionalized with polymethylmethacrylate (InPor-MMA₂₆), dissolved in DMF at 532 nm in picosecond domain simultaneously. The results indicate that the nonlinear optical responses are induced by solution molecular excited state nonlinearity only, without the existence of two-photon absorption or Kerr refraction. Combined with five-energy-level model, all nonlinear optical parameters are determined by analyzing the experimental curves and confirmed by 4 ns Z-scan at 532 nm. The sample has a good reverse saturable absorption and reasonable positive refraction. With the proper lifetime and intersystem crossing time, this sample can be a candidate for optical limiting. The polymer attached to porphyrin directly by chemical bonds. This makes it have better homogeneity compared to physical mixing in the form of film.

The third-order nonlinear refractive response in a kind of thin phthalocyanine film has been investigated using two types of top-hat Z-scan techniques with a picoseconds pulses laser at wavelength of 532nm. The nonlinear phase shift of this sample is so week because of the very small thickness of the films, and the normal top-hat Z-scan technique is often difficult to measure the results. To research the nonlinear response of this thin film, we also has been measured it using the modified top-hat Z-scan technique under the experimental conditions of the same. The curve of the modified top-hat Z-scan for the nonlinear refraction is only a single peak and the result shows this kind of film has obvious response of nonlinear refraction with 19 picoseconds pulses. Furthermore, we have been carried on the theoretical analysis and the numerical simulation with the result of the experiment, and the theoretical simulation fit well with experimental results, the value of the nonlinear refraction index is obtained to be n₂ = 6.25×10⁻¹⁵ m² /W . By comparing the measured curve of the two, the results indicate that the sensitivity of the modified top-hat Z-scan measurement is greatly enhanced.

In this paper, we present a new technology to enhance the sensitivity by absorbing part of the light at the entry of the Z-scan system. Compared to the top-hat Z-scan, the curves of the modified top-hat Z-scan for the nonlinear refraction show higher peak-to-valley values, which mean higher sensitivity with our modified method. Nonlinear refraction of CS₂ is investigated using this technique with 19ps pulses at wavelength of 532 nm.

The optical nonlinearities of semiconductor bulk material Indium nitride (InN) have been investigated by Reflection Z-scan technique (RZ-scan) at the wavelength of 532nm with 21ps laser pulse. Top hat beam is used in order to get high spatial quality. Different from the normal RZ-scan device, instead of moving the sample, the lens before the sample is moved along z-axis. This can guarantee the stability of the spot on the surface of the sample and the measurement accuracy. The measurement of nonlinear refraction without aperture should be tested first, and then with a small aperture nonlinear absorption coefficient is measured. The experimental results show that InN has positive nonlinear refraction and saturable absorption effect. Nonlinear refraction and absorption coefficient are obtained by fitting theoretical simulation with experimental data.

The measurement of aspheres and freeforms poses several challenges to interferometric and other optical testing methods which are well established for spherical surfaces. Accuracy, measurement time and flexibility are requirements encountered in a production environment. The approach of tilted-wave-interferometry is to illuminate the specimen with a whole ensemble of wavefronts. Each of these wavefronts has a different amount of tilt with respect to the optical axis. The surface under test is completely covered by interferogram patches where rays from one source hit the surface such that resolvable fringe densities result. Yet, one still deviates from the null setup which requires that the interferometer is calibrated precisely. This is obtained by recording interferograms of a known reference object placed in the test space. The aberrations of the interferometer are described within a black box model. A sophisticated set of algorithms is used to reconstruct these coefficients with high accuracy. The non-null configuration prohibits a direct evaluation of the measurement from the interferograms. Instead, the surface is reconstructed by the solution of an inverse problem. A second step gives access to the remaining high-frequency errors. The key ideas and implementations in the process of measurement and calibration are explained and the differences to other common concepts in optical testing are elaborated. As an example, results of a freeform measurement, including both form and high-frequent deviations from design, are discussed.

Optical coherence tomography (OCT) is a non-invasive 3D imaging technology which has been applied or investigated in many diagnostic fields including ophthalmology, dermatology, dentistry, cardiovasology, endoscopy, brain imaging and so on. Optical resolution is an important characteristic that can describe the quality and utility of an image acquiring system. We employ 3D printing technology to design and fabricate a test target for characterizing 3D resolution of optical coherence tomography. The test target which mimics USAF 1951 test chart was produced with photopolymer. By measuring the 3D test target, axial resolution as well as lateral resolution of a spectral domain OCT system was evaluated. For comparison, conventional microscope and surface profiler were employed to characterize the 3D test targets. The results demonstrate that the 3D resolution test targets have the potential of qualitatively and quantitatively validating the performance of OCT systems.

Guidance precision is the key indexes of the guided weapon shooting. The factors of guidance precision including: information processing precision, control system accuracy, laser irradiation accuracy and so on. The laser irradiation precision is an important factor. This paper aimed at the demand of the precision test of laser irradiator，and developed the laser precision test system. The system consists of modified cassegrain system, the wide range CCD camera, tracking turntable and industrial PC, and makes visible light and near infrared target imaging at the same time with a Near IR camera. Through the analysis of the design results, when it exposures the target of 1000 meters that the system measurement precision is43mm, fully meet the needs of the laser precision test.

Tunable diode laser absorption spectroscopy (TDLAS) is a high-resolution infrared laser absorption spectroscopy technique with a non-contact measurement, high spatial and temporal resolution, extensive measurement information, which has been a hot research area at present. Compared to traditional techniques, TDLAS technology has many advantages, but in engineering applications under complex environmental conditions, TDLAS technology is still facing many difficulties. Because of the impact of environmental factors, the measured spectral signal would be distorted, and cannot be used to extract useful information. Therefore, to extract useful information from the raw signal, it is essential to improve the signal to noise ratio. To eliminate interference information contained in the spectral signal, the absorption spectra of the laboratory intends to take data preprocessing methods. In the preprocess, the Empirical Mode Desperation (EMD) method is developed in recent years, which is a new self-adaptive local frequency analysis method. Compared to the method of wavelet denoising, EMD method with adaptive filters is able to achieve a multi-scale decomposition of the noise signal. In this paper, EMD method is taken to eliminate noise and interference signal source decomposition. By reconstructing the actual signal and eliminating the noise components, a better SNR can be achieved.

TDLAS system is the use of the wavelength tuning characteristics of the laser diode, for detecting the absorption spectrum of the gas absorption line. Detecting the gas space, temperature, pressure and flow rate and concentration. The use of laboratory techniques TDLAS gas detection, experimental simulation engine combustion water vapor and smoke. using an optical lens system receives the signal acquisition and signal interference test analysis. Analog water vapor and smoke in two different environments in the sample pool interference. In both experiments environmental interference gas absorption in the optical signal acquisition, signal amplitude variation analysis, and records related to the signal data. In order to study site conditions in the engine combustion process for signal acquisition provides an ideal experimental data .

The double-pulse Digital Speckle Pattern Interferometry (DSPI) in the laboratory is established. Two good performances have been achieved at the same time, which is uniform distribution of laser beam energy by space filter and recording two successive pictures by a CCD camera successfully. Then two-dimensional discrete orthogonal wavelet transform method is used for the process of filtering method. By using the DSPI, speckle pattern of a vibrated object is obtained with interval of (2~800)μs, and 3D plot of the transient vibration is achieved. Moreover, good agreements of the mode shapes and displacement are obtained by comparing with Laser Doppler Vibrometer (LDV) .

The strap-down inertial navigation system (SINS), especially the SINS composed by dithered ring laser gyroscope (DRLG) is a kind of equipment, which providing high reliability and performance for moving vehicles. However, the mechanical dither which is used to eliminate the “Lock-In” effect can cause vibration disturbance to the INS and lead to dithering coupling problem in the inertial measurement unit (IMU) gyroscope triad, so its further application is limited. Among DRLG errors between the true gyro rotation rate and the measured rotation rate, the frequently considered one is the input axis misalignment between input reference axis which is perpendicular to the mounting surface and gyro angular rate input axis. But the misalignment angle between DRLG dither axis and gyro angular rate input axis is often ignored by researchers, which is amplified by dither coupling problem and that would lead to negative effects especially in high accuracy SINS. In order to study the problem more clearly, the concept of misalignment between DRLG dither axis and gyro angle rate input axis is researched. Considering the error of misalignment is of the order of 10^-3 rad. or even smaller, the best way to measure it is using DRLG itself by means of an angle exciter as an auxiliary. In this paper, the concept of dither axis misalignment is explained explicitly firstly, based on this, the frequency of angle exciter is induced as reference parameter, when DRLG is mounted on the angle exciter in a certain angle, the projections of angle exciter rotation rate and mechanical oscillation rate on the gyro input axis are both sensed by DRLG. If the dither axis has misalignment error with the gyro input axis, there will be four major frequencies detected: the frequency of angle exciter, the dither mechanical frequency, sum and difference frequencies of the former two frequencies. Then the amplitude spectrum of DRLG output signal obtained by the using LabVIEW program. if there are only angle exciter and the dither mechanical frequencies, the misalignment may be too small to be detected, otherwise, the amplitude of the sum and difference frequencies will show the misalignment angle between the gyro angle rate input axis and the dither axis. Finally, some related parameters such as frequency and amplitude of the angle exciter and sample rate are calculated and the results are analyzed. The simulation and experiment result prove the effectiveness of the proposed method..

Concentrating Photovoltaic (CPV) modules are getting thinner and using smaller cells now days. Correspondingly, large area intensive lens arrays with smaller unit dimension and shorter focal length are wanted. However, the size and power center of lens array focal spots usually differ from the design value and are hard to measure, especially under large area situation. It is because the machining error and deformation of material of the lens array are hard to simulate in the optical design process. Thus the alignment error between solar cells and focal spots in the module assembly process will be hard to control. Under this kind of situation, the efficiency of CPV module with thinner body and smaller cells is much lower than expected. In this paper, a design of large area lens array focal spots automatic measurement system is presented, as well as its prototype application results. In this system, a four-channel parallel light path and its corresponding image capture and process modules are designed. These modules can simulate focal spots under sunlight and have the spots image captured and processed using charge coupled devices and certain gray level algorithm. Thus the important information of focal spots such as spot size and location will be exported. Motion control module based on grating scale signal and interval measurement method are also employed in this system in order to get test results with high speed and high precision on large area lens array no less than 1m×0.8m. The repeatability of the system prototype measurement is ±10μm with a velocity of 90 spot/min. Compared to the original module assembled using coordinates from optical design, modules assembled using data exported from the prototype is 18% higher in output power, reaching a conversion efficiency of over 31%. This system and its design can be used in the focal spot measurement of planoconvex lens array and Fresnel lens array, as well as other kinds of large area lens array application with small focal spots.

Laser reflection characteristics from the two-dimensional randomly rough sea surface are affected by the sea state, weather conditions, the incident laser parameters and other factors. All of the factors could not be artificially changed except the incident laser parameters. Therefore, the research of the relationship between laser reflection characteristics from 2-D randomly rough sea surface and incident laser parameters will give support to laser detection on the sea surface. This paper deals with the simulated calculation of the Gaussian beam reflection characteristics from the 2-D randomly rough sea surface with different incident laser parameters. In this paper, the 2-D rough sea surface is simulated with fractal method, after which the sea surface is divided into a lot of small planes, the width or length of which is much greater than the wavelength of the incident laser. Then the geometrical optics method is used to calculate the Gaussian beam reflection from 2-D randomly and rough sea surface. After that, the Gaussian beam reflection characteristics varies different incident laser parameters are numerical calculated. Finally, the detailed discussion of some factors including the divergence angle and the incident angle of the Gaussian beam which have influences on reflection properties is given.

Atom interferometry gravimeter with stimulated Raman transitions is realized by atom matter wave, it is now widely used in gravity measurements. We are now building a feasible system of cold atom gravimeter, it is based on the atom interferometry technology by coherently manipulating the cold atoms in a fountain with specific Raman lasers, the cold atom wave packet is splitted, combined, and then re-splitted in the process. Then the atomic wave packet will acquire different phase because of the different evolution path. The precise acceleration can be deduced through the precision measurement of atomic interference fringes phase, and this will be a high precision standard of acceleration. At present, the preparation of Raman laser and the precise control of the laser Frequency have been finished, and they have been proved to meet the requirements of the experiment.

Geometric error is the main error of the industrial robot, and it plays a more significantly important fact than other error facts for robot. The compensation model of kinematic error is proposed in this article. Many methods can be used to test the robot accuracy, therefore, how to compare which method is better one. In this article, a method is used to compare two methods for robot accuracy testing. It used Laser Tracker System (LTS) and Three Coordinate Measuring instrument (TCM) to test the robot accuracy according to standard. According to the compensation result, it gets the better method which can improve the robot accuracy apparently.

The unburned carbon particle, formed due to incomplete combustion of fossil fuel, biofuel, and biomass, raises great environmental and health problems. During the measurement of flames, a non-intrusive and in situ optical method is preferred rather than probe sampling method. Also the method with high spatial resolution and high temporal resolution is required for fast dynamic reactions such as combustion research. The technique based on laser-induced incandescence (LII) has been developed to characterize the soot particles. In this work, the simulation of LII signals have been did. In the simulation, different parameters have been applied and acquired corresponding results. The method provides theoretical results to analyze LII signals, and will eventually use in experimentation

The method of a multiple configuration on high ratio systems in image sensor is an important subject. In such an experimental configuration, for aim to break through to large ratio multiple configuration systems bottlenecks, achieve the field of continuous transformation, effect system close to the theoretical limit and configuration dexterity, such as the purpose, method in the design of the integrated sensor system process, the core technology of such a system are thoroughly analyzed and the factors important to the compromise. Theory is studied based on the theory of Gaussian optical system error distribution and comprehensive balancing algorithm; Global optimization method, developed at a system design thought and the optimization model. Results solved the MTF matching problem, research and evaluations shows that the zoom ratio of more than one hundred results in system MTF and so on as qualitative criterion to achieve requirements.

According to the working principle of laser active detection system, the paper establishes the optical target laser active detection simulation system, carry out the simulation study on the detection process and detection performance of the system. For instance, the performance model such as the laser emitting, the laser propagation in the atmosphere, the reflection of optical target, the receiver detection system, the signal processing and recognition. We focus on the analysis and modeling the relationship between the laser emitting angle and defocus amount and “cat eye” effect echo laser in the reflection of optical target. Further, in the paper some performance index such as operating range, SNR and the probability of the system have been simulated. The parameters including laser emitting parameters, the reflection of the optical target and the laser propagation in the atmosphere which make a great influence on the performance of the optical target laser active detection system. Finally, using the object-oriented software design methods, the laser active detection system with the opening type, complete function and operating platform, realizes the process simulation that the detection system detect and recognize the optical target, complete the performance simulation of each subsystem, and generate the data report and the graph. It can make the laser active detection system performance models more intuitive because of the visible simulation process. The simulation data obtained from the system provide a reference to adjust the structure of the system parameters. And it provides theoretical and technical support for the top level design of the optical target laser active detection system and performance index optimization.

A refrigeration system with fluid cycle, semiconductor cooler and air cooler is designed to solve the problems of thermal lensing effect and unstable output of high-repetition-frequency solid-state lasers. Utilizing a circulating water pump, water recycling system carries the water into laser cavity to absorb the heat then get to water cooling head. The water cooling head compacts cold spot of semiconductor cooling chips, so the heat is carried to hot spot which contacts the radiating fins, then is expelled through cooling fan. Finally, the cooled water return to tank. The above processes circulate to achieve the purposes of highly effective refrigeration in miniative solid-state lasers.The refrigeration and temperature control components are designed strictly to ensure refrigeration effect and practicability. we also set up a experiment to test the performances of this refrigeration system, the results show that the relationship between water temperature and cooling power of semiconductor cooling chip is linear at 20°C-30°C (operating temperature range of Nd:YAG), the higher of the water temperature, the higher of cooling power. According to the results, cooling power of single semiconductor cooling chip is above 60W, and the total cooling power of three semiconductor cooling chips achieves 200W that will satisfy the refrigeration require of the miniative solid-state lasers.The performance parameters of laser pulse are also tested, include pulse waveform, spectrogram and laser spot. All of that indicate that this refrigeration system can ensure the output of high-repetition-frequency pulse whit high power and stability.

The thermal lensing effect of crystal is the biggest problem for the output of laser pulse with high power and high beam quality. Through the design of laser cavity, this effect can be removed a certain extent. In this paper, a high-repetition-frequency laser based on electro-optic Q-switch made of LGS is designed. Using flat-flat cavity, the purposes of simple structure and steady output are achieved. Firstly, using a LGS as Q-switched crystal, a Brewster plate as a polarizer, a xenon flash-lamp pumped 1064 nm high-repetition-frequency pulsed Nd:YAG laser with flat-flat cavity is demonstrated. Then, the stability of the laser cavity is analysed. Considering the thermal lensing effect of Nd:YAG crystal, the focal length of thermal lens is calculated. Utilizing MathCAD, the ABCD matrix of laser cavity is calculated, and the G value is obtained, that is G=0.792<1, so the laser cavity is steady. Furthermore, the distribution of light beam in the laser cavity is also simulated by using LAS-CAD, the results indicate that the laser works at stead state. Thirdly, the thermal lensing effect of Nd:YAG crystal is analysed by using LAS-CAD. The temperature and refractive index distributions of Nd:YAG crystal are simulated, the results show that the crystal can be equivalented as a lens with certain focal length. Furthermore, utilizing finite element analysis (FEA) method, the three-dimensional view of temperature field is obtained.

A two-rod V-type telescope resonator is proposed to obtain the single-frequency 659.5nm high power red laser output with possessing the advantages of both the flat-flat symmetrical resonator and telescope resonator. This resonator extracts the pumping power by equalizing the fundamental mode volumes to the greatest extent possible at the tandem two rods. Simultaneously, it aggrandizes the SHG (second-harmonic generation) efficiency by sharply compressing the spot size in the relatively independent focus cavity. In the experiment, the red laser power reaches 63.1W under total 1000W LD pumping power.

An inner surface of straight pipe has been investigated using digital holographic technique. Both contour images for surface profile and color reconstructed images are used to the detection of artificial defects made on the inner wall of copper pipe. For the inspection, a cone-shaped mirror glued to one end of a metal rod is inserted into the pipe and illuminated from the other open end of the pipe. The new algorithm in which a deviation of the cone-shaped mirror from the pipe axis can be directly evaluated from the experimental height profile reduces the amount of calculation for correcting the distorted experimental profile. The pipe inspection has been done using the developed images of both the color intensity image and height profile for the inner wall of pipe.

Frequency Modulated Continuous Wave laser radar is one of the most important ways to measure the large-size targets , combining the advantages of laser with conventional FMCW radar. Dispersion compensation and non-linear calibration are two key aspects in FMCW laser radar measurement. The paper studies the method of frequency-sampling to correct the Nonlinearity and analyzes the importance of dispersion compensation. We set up experimental verification platform, choose 1550nm band continuously tunable external cavity infrared laser as the light source, use all-fiber optical device structures, choose balanced detectors as photoelectric conversion, and finally acquire data with high speed PCI-E data acquisition card, write a measurement software with Labview. We measured the gage block 1 meter away. The experiment results show that the frequency sampling method correct the Nonlinearity well and there is a significant impact on the accuracy because of the fiber dispersion, dispersion must be compensated to obtain high accuracy. The experiment lays the foundation for further research on FMCW Laser radar.

The star sensor simulation system is uesed to test the star sensor performance on the ground，which is designed for star identification and spacecraft attitude determnation of the spacecraft. The computer star scene based on the astronomical star chat is generated for hardware-in-the-loop simulation of the star sensor simulation system using by openGL.

Solar occultation flux (SOF), a new optical technology to detect the gas based on the traditional Fourier transformed infrared spectroscopy (FTIR) developed quickly recently. In this paper, the system and the data analysis is investigated. First a multilayer transmission model of solar radiation is simulated. Then the retrieval process is illustrated. In the proceeding of the data analysis, the Levenberg-Marquardt non-linear square fitting is used to obtain the gas column concentration and the related emission ratio. After the theory certification, the built up system is conducted in a fertilizer plant in Hefei city .The results show SOF is available in the practice and the retrieved gas column concentration can give important information about the pollution emission and dispersion

This paper presents a 3D small-field imaging system by using the color fringe projection technique to measure the small objects having large slopes and/or discontinuous surface. A stereo microscope is used to generate a small-field projecting field and to capture the deformed fringe patterns on the measured small objects, respectively. Three fringe sets having the optimum fringe numbers are coded into one major color channel to generate color fringe patterns having the maximum fringe contrast of the captured fringe images. Through one channel of the stereo microscope, a DLP (Digital Light Processing) projector projects these generated color fringe pattern images onto the measured objects surface. From another channel, the fringe patterns are deformed with regard to the object surface and captured by a color CCD camera. The absolute phase of each pixel can be calculated from the captured fringe patterns by using the optimum three-fringe numbers selection method. Experimental results on measuring 3D shape of small objects show the accuracy and availability of the developed 3D imaging system.

Coded structure light is widely used for 3D scanning, and different coding strategies are adopted to suit for different goals. In this paper, three coding strategies are compared, and one of them is selected to implement a low cost structure light scanner under the cost of €100. To reach this goal, the projector and the video camera must be the cheapest, which will lead to some problems related to light coding. For a cheapest projector, complex intensity pattern can’t be generated; even if it can be generated, it can’t be captured by a cheapest camera. Based on Gray code, three different strategies are implemented and compared, called phase-shift, line-shift, and bit-shift, respectively. The bit-shift Gray code is the contribution of this paper, in which a simple, stable light pattern is used to generate dense(mean points distance<0.4mm) and accurate(mean error<0.1mm) results. The whole algorithm details and some example are presented in the papers.

Freeform shape is usually designed by reverse engineering method thorough a 3D scanner, which is often expensive to most persons. The paper proposes a new scanning system combining shape from structured light and shape from silhouette, which can be implemented easily with low cost. The two methods are very complementary. For shape from silhouette, it can capture correct topological information of the object and obtain a closed envelop, and for shape from hand-held laser line, precise point clouds with some holes can be obtained. To gain their complementary advantages, a new data fusion strategy based a mesh energy functional is proposed to integrate the information from the two scanning methods, in which the points resulted from laser light will attract closed envelop from silhouette. After fusion, the precision of shape from silhouette is increased, and the topological error of shape from structured light is corrected. The design details are introduced, and a toy model is used to test the new method, which is difficult to scan using other systems. The test results proof the validity of the new method.

The hand-held 3D laser scanner sold in the market is appealing for its port and convenient to use, but price is expensive. To develop such a system based cheap devices using the same principles as the commercial systems is impossible. In this paper, a simple hand-held 3D laser scanner is developed based on a volume reconstruction method using cheap devices. Unlike convenient laser scanner to collect point cloud of an object surface, the proposed method only scan few key profile curves on the surface. Planar section curve network can be generated from these profile curves to construct a volume model of the object. The details of design are presented, and illustrated by the example of a complex shaped object.

Temperature measurement system has been applied in industrial areas extensively. The fiber optic distributed temperature system is one of the most popular means. Measurement error is relatively large when using the distributed temperature sensors (DTS) based on Raman scattering to measure ambient temperature in harsh environments. In this paper, we propose a novel calibration technique to measure the temperature highly accurately over a wide range of temperatures. We also propose an improved double-ended configuration that is insusceptible to the differential loss change in the fiber. By using the improved double-ended configuration, through the anti-Stokes and Stokes signal intensity comparison, the differential mode signal loss in the temperature measurement can be suppressed in optical fiber. So, the measurement results of automatic calibration are irrespectively with the wastage of optical fiber sensors. The result shows that we can obtain the temperature parameters accuracy in wide temperature range, and temperature measurement system has high robustness in harsh environments, suitable for field use.

A new method based on a distributed optical fiber sensor (DOFS) to locate the position of lightning stroke on the optical fiber ground wire (OPGW) is proposed and experimentally demonstrated. In the method, the lightning stroke process is considered to be a heat release process at the lightning stroke position, so Brillouin optical time domain reflectometry (BOTDR) with spatial resolution of 2m is used as the distributed temperature sensor. To simulate the lightning stroke process, an electric anode with high pulsed current and a negative electrode (the OPGW) are adopted to form a lightning impulse system with duration time of 200ms. In the experiment, lightning strokes with the quantity of electric discharge of 100 Coul and 200 Coul are generated respectively, and the DOFS can sensitively capture the temperature change of the lightning stroke position in the transient electric discharging process. Experimental results show that DOFS is a feasible instrument to locate the lightning stroke on the OPGW and it has excellent potential for the maintenance of electric power transmission line. Additionally, as the range of lightning stroke is usually within 10cm and the spatial resolution of a typical DOFS is beyond 1m, the temperature characteristics in a small area cannot be accurately represented by a DOFS with a large spatial resolution. Therefore, for further application of distributed optical fiber temperature sensors for lightning stroke location on OPGW, such as BOTDR and ROTDR, it is important to enhance the spatial resolution.

An approach for reflectivity measurement of ultra-weak fiber Bragg gratings is demonstrated. The scheme uses a referenced high-reflectivity FBG to combine with the measured FBG. They have different center wavelengths. By using two referenced FBGs, the reflectivity of one measured FBG is calculated to be 0.298% and 0.287% respectively. For reflectivity measurement of ultra-weak FBG, to eliminate the influence of the reflection spectra side lobe for the referenced FBG, we get the reflection spectrum of the referenced FBG and measured FBG respectively under the same input intensity. The reflectivity of an ultra-weak FBG is measured to be 0.00916% (-40.38dB) and 0.00803%(-40.95dB) based on the two referenced FBGs. The results presents that the method is feasible.

Faraday magneto-optic effect of fiber optic gyroscope(FOG) is nonreciprocal error source that affects the performance of FOG, especially the precision of FOG. The magnetic sensitivity mechanism of FOG is introduced in this paper and the main source of radial and axial magnetic sensitivity error is analyzed. The circular birefringence of the fiber is improved by twisting. With coupled wave equations of twist fiber, an expression that can evaluate circular birefringence degree of fiber is obtained. Based on the above analysis, this paper puts forward an approach that a length of reverse twist fiber is spliced onto the original fiber coil of FOG. This approach can produce high circular birefringence. The reciprocity phase of original fiber coil is compensated so that the purpose that restrains magnetic sensitivity error of FOG is achieved. The feasibility of this method is discussed.

An asymmetric fiber (Fabry-Pérot,F-P) interferometric cavity with good linearity and wide dynamic range is successfully designed basing on optical thin film characteristic matrix theory; by choosing the material of two different thin metallic layers, the asymmetric fiber F-P interferometric cavity is fabricated by depositing the multi-layer thin films on the optical fiber’s end face. The demodulation method for the wavelength shift of fiber Bragg grating (FBG) sensor basing on the F-P cavity is demonstrated and a theoretical formula is obtained. And the experimental results coincide well with computational results obtained from the theoretical model.

BOTDR monitoring technology is using Brillouin light scattering spectroscopy and optical time domain measurement techniques, which can be distributed monitoring axial strain along the fiber. It has the characteristics of distributed, long distance, high precision and long durability etc. Based on the diagnosis of Wangjiatan bridge as a example, this paper introduces the application of this technology to bridge strain monitoring plan and monitoring result analysis method, and gives the health diagnosis of the Wangjiatan bridge. Research results show that: the application of this technology is feasible in safety monitoring and health diagnosis of bridge, is also very effective.

This paper takes LabVIEW2012 as a development platform, creating a J-type thermocouple sensor and the NI USB-6229 data acquisition card and other hardware emulation circuitry which combined with the PC designed a single-point temperature monitoring system. Through simulation experiments, the system has a collection interval, the sampling rate per channel sampling on the temperature limit set by the user function and it also has the function of real-time display the current temperature, the temperature limit alarm, maximum temperature, minimum temperature display and a temperature history data query. This system can be used for temperature monitoring of life, research, industrial control, environmental monitoring, biomedical, tobacco processing, greenhouse cultivation, livestock breeding and other fields, which has important significance and practical value.

In view of the circuit miniaturization need in project application of fiber optic gyroscope(FOG), a new integrated technical scheme adopting system in package(SIP) for signal processing circuit of FOG was put forward. At first, the principle on signal processing circuit of FOG was analyzed, and the technical scheme adopting SIP based on low-temperature co-fired substrate technology was presented according to circuit characteristic and actual condition. Secondly, under the prerequisite of the concept introduction of SIP and LTCC, the SIP prototype of signal processing circuit of FOG was trialed produced，and it passed through the debug test. This SIP modular is an overall circuit complete integrated the signal processing circuit of FOG, and only a potentiometer and EPROM do not case outside. The testing results indicate that SIP is a kind of feasible scheme that carries out miniaturization for signal processing circuit of FOG.

A novel high sensitivity humidity sensor based on micro-ring resonator with three coupling points (MRRTCP) is reported. Since the dielectric constant of Polyimide is highly sensible to the relative humidity of the environment, we choose the Polyimide (PI) as the moisture material. The effective refractive index of the sensing part of the sensor changes as the relative humidity of the environment changes, this leading to an obvious shift of the output spectrum. The sensing range of the relative humidity sensor is 0~100%RH, and the sensitivity is 0.0017μm/%RH, and the structure is relatively simple and could be used in micro-scale humidity sensing.

In order to verify the validity of the regional reference grating method in solve the strain/temperature cross sensitive problem in the actual ship structural health monitoring system, and to meet the requirements of engineering, for the sensitivity coefficients of regional reference grating method, national standard measurement equipment is used to calibrate the temperature sensitivity coefficient of selected FBG temperature sensor and strain sensitivity coefficient of FBG strain sensor in this modal. And the thermal expansion sensitivity coefficient of the steel for ships is calibrated with water bath method. The calibration results show that the temperature sensitivity coefficient of FBG temperature sensor is 28.16pm/°C within -10~30°C, and its linearity is greater than 0.999, the strain sensitivity coefficient of FBG strain sensor is 1.32pm/με within -2900~2900με whose linearity is almost to 1, the thermal expansion sensitivity coefficient of the steel for ships is 23.438pm/°C within 30~90°C, and its linearity is greater than 0.998. Finally, the calibration parameters are used in the actual ship structure health monitoring system for temperature compensation. The results show that the effect of temperature compensation is good, and the calibration parameters meet the engineering requirements, which provide an important reference for fiber Bragg grating sensor is widely used in engineering.

We have carried out a detailed simulative study of the tapered fiber Bragg grating (TFBG) evanescent wave sensor sensitivity by using 3-D Coupled-Mode Theory method. The method is based on the spectral interrogation mode of operation. We also make numerical simulations to figure out how the uniform waist diameter and the difference of the relative refractive indexes between fiber core and external medium affect the sensitivity of this proposed sensor. The simulation results show that the sensitivity of the tapered fiber Bragg grating will be improved when the diameter of the uniform waist decrease as well as the difference of the relative refractive indexes between fiber core and external medium. And with the fixed uniform waist diameter and tapered length, when the difference of the relative refractive index of fiber core and external medium varies is 0.015RIU, the values of wavelength shift is 5.08nm, the sensitivity of the tapered fiber Bragg grating is 317.5nm/RIU. The sensitivity is higher than that of the common FBG. The results are consistent with theoretical models. The simulation results can supply the guidance for the further experimental study and refractive index sensor design, optimization and application.

In the monitoring system of coal mine gas, due to the use of optical fiber sensing gas, there were some defects include less monitoring points, low utilization rate of equipment and especially high cost, etc.Arming at the existing problem, through the study of network model for methane concentration detection, the monitoring system could achieve multi-point, wide-range online monitoring of methane concentration in real time.Based on the optical multiplexing technology, this paper proposed a optical network model of mixed multiplexing technology combined with the time division multiplexing (TDM) and the space division multiplexing (SDM) technology.The model realized 32 points of gas concentration monitoring with 4 points of space division multiplexing and 8 points of time division multiplexing which is more mature and stable.The experiment show that the accuracy of the 32 sensors’ minimum detectable gas has reached 5ppm and the changes in responsiveness and gas concentration trends are consistent with the theoretical analysis, which is linear in a certain range.Considering the characteristics of EFPI optical fiber sensor, the model makes full use of the advantages of two multiplexing technologies, time division multiplexing and space division multiplexing technology.The network model combines the use of optical fiber in a gas concentration monitoring system to improve the efficiency of the light source and optical signal processing equipment and greatly reduce the cost of system.The accuracy and stability of each sensor can meet the actual requirements to make the monitoring system achieve the goals of stable dynamic wide-rage detection of coal mine gas.

The distributed optical fiber detection technology plays an important role in many fields, such as key regional security monitoring, pipeline maintenance and communication cable protection. It is superior to the traditional detector, and has a good prospect. This paper presents an overview of various distributed optical fiber sensors. At first, some related technologies of the optical fiber detection schemes are introduced in respect of sensing distance, real-time ability, signal strength, and system complexity; and the advantages and limitations of fiber gratings sensors, reflection-based optical fiber sensors, and interference- based optical fiber sensors are discussed. Then some advanced distributed optical fiber detection systems are mentioned. And the double-loop Sagnac distributed system is improved by adding photoelectric modulators and depolarizers. In order to denoise and enhance the original signal, a spectral subtraction-likelihood ratio method is improved. The experiment results show the spatial resolution is ±15m per kilometer. Finally, based on the development trends of optical fiber detection technology at home and abroad, development tendency and application fields are predicted.

In this paper, the 120fs pulse transmission experiment was carried out using disordered birefringent microstructure fibers with cladding ventages. Thought this experiment, properties of the two waves under the effect of femtosecond laser pulses with different parameters were studied. The results show that the central wavelength of anti-stokes waves and stokes waves produced under the two orthogonal polarization states shift by 63nm and 160nm, respectively. The strength and central position of the two waves in birefringent fibers can be controlled by adjusting the phase match condition and the polarization direction of incident pulses.

High temperature detection of micro structure area with high sensitivity has aroused more and more interest recently. A high temperature sensor based on ultra-abrupt tapered fiber Mach-Zehnder interferometer (MZI) is proposed and fabricated by using a fusion-splicing method.The two normal cleaved ends are separated by a distance and become ellipsoidal by one time discharge using a fiber fusion splicer. Then the two ellipsoidal fiber heads contacted between the splicer electrodes are fused together to form the taper. And the other is formed through the same process separated by a distance of L. The thermal characteristic is investigated in 25–1100 °C, which temperature limit is highest of tapered fiber MZIs. It is observed that sensitivity varies with temperature ranges, which are 25 pm/°C in low-temperature range(25-300°C) and 105 pm/°C in high-temperature range(300-1100°C) respectively. The sensor demonstrates good thermal stability after annealing at 400 °C and 800 °C for 8 h respectively. The simple ultra-taper based MZI sensor has potential application prospect in the field of high temperature detection, such as the temperature of aeroengine.

We propose a novel highly birefringent photonic crystal fiber (PCF). It is composed of a triple defect core and a cladding with squeezed hexagonal lattice circular air holes. Using a full-vector finite element method (FEM) simulator (COMSOL Multiphysics), we study the modal birefringence of the fundamental modes in such PCFs. Numerical results show that the birefringence of the proposed PCF reaches the order of 10^-2, which is larger than the triple defect core PCF without squeezed cladding, also is much larger than the single defect core PCF with squeezed cladding. Moreover, the proposed PCF also has a low confinement loss about 10dB/km at wavelength λ=1.55μm.

Due to the limit of the channel isolation in the TDM system or the WDM system, the crosstalk usually exists between the fiber laser sensors in the multiplexing system. In this paper, the relationship between the channel crosstalk and the channel isolation is investigated. By means of studying on the phase generated carrier (PGC) demodulation and the passive homodyne demodulation based on the 3×3 coupler, which are usually used in the fiber laser sensor system, the crosstalk between two channels were discussed separately. The output mathematic models of the demodulation system were analyzed, when the sensing channel including the leak laser from the other channel. The mathematic models were set up used for theoretical analyses of the non-coherent crosstalk between two channels in the system, and the mathematic models show that the channel crosstalk between the two channels have relation to the power of the leak laser and have a slowly varying random factor which represents an environmentally induced variation. The acoustic sensing experiment shows that the models are suitable to calculate the crosstalk between two channels of the fiber laser sensor in the multiplexing system. In the acoustic sensing experiment, the channel crosstalk of the experiment is -18.7 dB, and the channel crosstalk should be -19.36 dB according to the mathematic models.

The hydrophone which use DFB fiber laser as sensing element has many advantages such as thin diameter, high sensitivity, easy to multiplex array, wide dynamic range, immunity to electromagnetic interference and no need of impedance matching. A 4-element fiber laser hydrophone towed linear array is studied. A sleeve with grooves type fiber laser hydrophone is designed and realized. The sensitivity experiment of the hydrophone element shows that the sensitivity is about -135dB（re 1rad/μPa）in the range of acoustic frequency from 20Hz to 1000Hz, and the amplitude fluctuate of the frequency response curve is less than±1.5dB. Based on the hydrophone of this structure and the WDM technology, the 4-element fiber laser hydrophone towed linear array that is encapsulated with polyurethane sleeve is established, and its diameter is 15mm. The experiments of the hydrophone towed linear array in the lake test show that the localization and tracking of the target can be realized by the towed linear array.

In this paper, the crosstalk of a time division multiplexed (TDM) system of distributed feedback (DFB) fiber laser (FL)hydrophones based on optical switch using Phase Generated Carrier (PGC) method was quantitatively analyzed. After mathematical deduction, the relationship among crosstalk, multiplexing scale and extinction ratio of optical switch was given. The simulation results show that to realize a TDM system of DFB fiber laser hydrophones with crosstalk lower than -40dB, the average extinction ratio should be higher than 24.78dB for a 4- channel system, while higher than 28.45dB for an 8- channel system. Two experiments to analyze the array crosstalk to a certain channel in an 8- channel array were conducted in this paper. Firstly, by testing the powers of leak laser to a certain channel from others, the array crosstalk to this channel was obtained according to the equation mathematically deduced in this paper. The result shows the array crosstalk to a certain channel of the 8-channel array was -7.6dB. An experiment of underwater acoustic detection was carried out finally to get the real array crosstalk to this certain channel, and the experimental result shows that the array crosstalk to this channel is -8.8dB, which is close to the calculated result.

In this paper, a fiber Bragg grating (FBG) demodulation system based on high-birefringence fiber loop mirror (Hi-Bi FLM) is proposed and demonstrated. The approximate linear edge of the transmittance of the Hi-Bi FLM, which is a sinusoidal function of wavelength, is used to interrogate the sensing FBGs. The relationship between the wavelength period of the transmittance of the Hi-Bi FLM and the length of Hi-Bi fiber is studied and the results shows that the linear range of Hi-Bi FLM is in Inverse proportion to the length of the Hi-Bi fiber. To get wider linear range, the length of the Hi-Bi fiber must be shorter and it is limited by the fiber fusing technic. Two sections of Hi-Bi fiber is orthogonal fused and its effect is equal to one segment of fiber whose length is equal to the difference of that of the two section of fibers. Using this method, a Hi-Bi FLM with a wide linear range of 20nm is made and used to demodulate FBG sensing signal. The demodulator has advantages of all-fiber design, low price and high speed.

A novel interferometric fiber optic geophone is introduced in this paper. This geophone is mainly used for geo-acoustic signal detection. The geophone use one of the three orthogonal components of mandrel type push-pull structure in mechanically and single-mode fiber optic Michelson interferometer structure with Faraday Rotation Mirror (FRM) elements in optically. The resonance frequency of the geophone is larger than 1000Hz. The acceleration sensitivity is as high as 56.6 dB (0dB re 1rad/g) with a slight sensitivity fluctuation of ±0. 2dB within the frequency band from 20Hz to 200Hz. The geo-acoustic signals generated by underwater blasting are detected successfully. All the channels show good uniformity in the detected wave shape and the amplitudes exhibit very slight differences. The geo-acoustic signal excitated by the engine of surface vehicles was also detected successfully.

In this paper, fibers with different depths of hermetically coated carbon are hydrogen loaded and radiated, and it’s found that too thick of carbon layer around fiber can’t bring best radiation-resistant properties, because the thick carbon layer would make the entering of hydrogen difficult although it can help to stop the hydrogen escaping. We also research the duration of saturated hydrogen loading under the temperature of 60°C and 100°C respectively, and it’s found that after 120h and 48h, the fibers’ photo sensitivities tend to be flat. We also reload hydrogen into the fibers which have been loaded once, and these fibers are etched then, this help us to deep understand the mechanism of hydrogen loading for the fiber gratings.

In order to realize good detection of low frequency acceleration signals, a new kind of low frequency Fiber Bragg Grating (FBG) acceleration sensing system is designed. The theoretical model of the FBG acceleration sensor is deduced, while the acceleration sensitivity and the natural frequency of the sensor are educed. The influences of different parameters on the acceleration sensitivity and the natural frequency of the FBG acceleration sensor are discussed. This new designed FBG acceleration sensor has an excellent performance, its acceleration sensitivity reaches 54.8dB re pm/g and its fluctuation is less than 1.5 dB over the frequency range of 0~100Hz.

To realize the miniature of fiber laser accelerometers, a metal-shell-packaged single-cylinder mandrel-structured distributed feedback (DFB) fiber laser accelerometer was proposed, whose key sensing component is the DFB fiber laser with a cavity length of 16mm. Simulation results show that when the weight of the mass is 400g, the radius of the thin shell cylinder is 0.5cm, we will find that the resonance frequency of the sensor is 900Hz and its sensitivity reaches 18.1pm/g. It is also shown that its sensitivity achieved 42.8dB.re.rad/g while demodulated by an unbalanced Michelson optical fiber interferometer with 1m path difference. In addition, the effects of its structure and material parameters on the acceleration sensitivity are also studied.

A fiber optic accelerometer based on fiber Bragg grating Fabry-Perot (FBG-FP) interferometer is presented. The sensor is a FBG-FP cavity which is formed with two weak fiber Bragg gratings (FBGs) in a single-mode fiber. The reflectivity of the two FBGs is 9.42% and 7.74% respectively, and the fiber between them is 10 meters long. An optical demodulation system was set up to analyze the reflected light of FBG-FP cavity. Acceleration signals of different frequencies and intensities were demodulated correctly and stably by the system. Based on analyzing the optical spectrum of weak FBG based FBG-FP cavity, we got the equivalent length of FBG-FP cavity. We used a path-matching Michelson interferometer (MI) to demodulate the acceleration signal. The visibility of the interference fringe we got was 41%~42% while the theory limit was 50%. This indicated that the difference of interferometer’s two arms and the equivalent length of FBG-FP cavity were matched well. Phase generated carrier (PGC) technology was used to eliminate phase fading caused by random phase shift and Faraday rotation mirrors (FRMs) were used to eliminate polarization-induced phase fading. The accelerometer used a compliant cylinder design and its’ sensitivity and frequency response were analyzed and simulated based on elastic mechanics. Experiment result showed that the accelerometer had a flat frequency response over the frequency range of 31-630Hz. The sensitivity was about 31dB (0dB=1rad/g) with fluctuation less than 1.5dB.

This paper reports laboratory comparison of fiber laser geophones and moving-coil geophones. A fiber laser geophone and a 20 DX geophone geophone were tested. The fiber laser geophone is based on a L shape beam structure and demodulated with an interferometric method. The signal of the moving-coil geophone is measured by a 24-Bit DAQ. Typical features of geophones include sensitivity, frequency response, spurious frequency, dynamic range, damp and noise character were compared. The results show that the fiber laser geophone has comparable performances with moving-coil geophone, and exhibits very high sensitivity and better high-frequency signal to noise ratio than moving-coil geophone. The fiber laser geophone is expect to be applied in micro-seismic monitoring of unconventional oil and gas hydraulic fracturing.

The weak light-leaking phenomenon of fibers will definitely decrease the output precision and working reliability of the Interferometric Fiber Optic Gyroscope (IFOG). Unfortunately, because of the small scratches or damages on the surface of fiber cannot be avoided when manufacturing IFOG, it is necessary to develop a method to monitor and evaluate that light leakage phenomenon and harm. In this paper, to evaluate and control that light-leaking defect, on one hand, a lightleaking energy function, which uses the image analysis method and the radiometry theory, is designed to represent the energy loss of light; on the other hand, we build a relationship between that energy function and the assembling quality of IFOG by Support Vector Machine (SVM): (1) we utilize an infrared CCD camera to make a traversal scan of the fibers inside of IFOG. (2) We use graph cut model and flood fill algorithm to make a segmentation of that light-leaking region. (3) We define a new energy function to estimate the light leakage level. (4) We use SVM to build a connection between the light-leaking energy function and the final output of IFOG. Here the image energy function is regarded as the training data of SVM, while the bias of IFOG is treated as the supervising data of it. A practical application case of IFOG light path quality evaluation is shown in the end of this paper.

We propose a simple optical fiber current sensors based on the Lorentz force to measure the current. We use two copper carrying wires, and the two carrying wires are parallel fixed to the insulated coil spring. Then, the two optical fibers are vertically fixed on two copper, respectively. When the current input the wires, Loren magnetic force will be existed between wires. The force causes deformation of the spring and leads to the displacement of the fiber’s end faces. So the spectra should be changed. The experimental device is used to measure the current at range for the 1-5 A, the response time is about 0.1 seconds, and resolution sensitivity of the sensor is 10 nm/A. The results show that the device is simple and low costs. It has a potential applied in high current sensing.

A novel method based on piezoelectric transducer (PZT) modulation for detecting the crosstalk of optical circulator has been demonstrated. In the experiment, the lightwave emitted from a low-noise single-frequency laser passed through the circulator, reflected on the surface of the PZT, and returned to the circulator again. The PZT can modulate the frequency of the lightwave reflected on it due to the Doppler effect. Then the crosstalk of the circulator is obtained by measuring the induced optical difference frequency based on a difference-frequency detection technology. The results show that this method is very effective in detecting weak crosstalk of circulator.

Total-internal-reflection (TIR) typed fiber sensors based on photonic crystal fibers (PCFs) are made by filling samples into PCF cladding holes, where the interaction of light wave occurs between the evanescent wave of fiber core and the filled samples. This can avoid common transmission losses caused by fiber surface roughness. The interaction region of the evanescent wave in a PCF and the filled samples are almost coincident, so increasing fiber length can enhance the light-matter interaction and enable accurate detection of tiny changes of samples. However, it is difficult to inject sample materials into stomatal cladding of TIR-typed PCF sensors due to small volume of pores. In addition, the energy utilization rates of TIR-typed sensors are relatively low, only about 6%. A main influencing factor on the sensitivity of TIR-typed PCF sensors is the power fraction of pores in the whole cross section. In order to improve the sensitivity, one can elevate the power fraction of PCF pores. Based on the above considerations, a novel three-core double-clad PCF is designed, where samples are injected into the middle hole and two Yd-doped cores are arranged on its two sides for active excitation. Our theoretical calculation and experimental test show that this kind of structure can not only increase the coupling efficiency of the evanescent wave into the air holes effectively, but also gain higher detection sensitivity of trace samples.

Rayleigh backscattering induces mode hopping of DFB fiber lasers in the sensor array, and the critical length related to Rayleigh backscattering limits the size of DFB fiber laser sensor networking. Based on three-mirror cavity model, the critical length for DFB fiber lasers are derived. It increases nearly exponentially with the coupling coefficient for the ideal π-shifted DFB fiber lasers. While the reflectivity of the sub-FBG at lasing wavelength is the main factor to resist Rayleigh backscattering for a non-ideal DFB fiber laser. The corresponding experiments have been carried out, and the results agree with the predictions.