This PDF file contains the front matter associated with SPIE Proceedings Volume 11053, including the Title Page, Copyright information, Table of Contents, and Conference Committee listing.

Ways of improving autocollimators for monitoring angular displacements are analyzed. The results of an analysis of control elements based on tetrahedral reflectors with flat reflecting sides are presented. The technical characteristics of experimental models of control elements are presented. The features of tetrahedral reflector as the control elements for three-axis autocollimators are discussed.

This paper proposes a machine-vision-based system for the inspection of the geometrical features of cell phone rubber gaskets. The system consists of two industrial cameras and an industrial computer. To begin the inspection process, the cell phone gaskets inside the camera field were identified and a novel transparent fixture were employed to guide the lighting to highlight the defects. To characterize the metrological features of cell phone gaskets, image preprocessing procedure was then implemented and defect classification algorithmic strategies was described in detail. Finally, experimental results on images of different type of the cell phone gaskets are reported together with the metrological classification of the proposed measurement system. The geometrical quality of every individual silicone rubber gasket, which could be evaluated and guaranteed to the full grade of assessment which the proposed system can achieve.

In-process measurement can provide feedback for control of workpiece precision in terms of size, form error, and roughness. It can be used for precision control of a machining process, therefore to improve productivity and reduce defect rates. Optical measurement methods have greater advantages in the in-process form profile measurement systems due to their non-contact type and high precision. However, use of opaque coolant in precision machining will introduce an opaque barrier problem, making the workpiece surface y(x, z) inaccessible to the optical measurement devices. To solve this problem, several approaches, including the water beam approach, the single air beam approach, the multiple air beam approach, and the dual coolant displacing medium method, are examined in terms of coolant removal capability, level of acceptance to surface complexity, flow rate and velocity of the coolant displacing media, and also errors induced by the coolant removal methods. The results of the study show that the multiple air beam method and the dual coolant displacing media method are more advantageous than the other methods.

In this paper, an orthogonal type two-axis Lloyd’s mirror interference lithography technique was employed to fabricate two-dimensional planar scale gratings for surface encoder application. The two-axis Lloyd’s mirror interferometer is composed of a substrate and two reflective mirrors, which are placed edge by edge perpendicularly. An expanded and collimated beam was divided into three beams by this interferometer, a direct beam and two reflected beam. The unnecessary beam section was blocked by a home designed filter. These two reflected beams interfere with the direct beam respectively, generates perpendicularly cross patterns for forming two-dimensional scale gratings. The two reflected beams also interfere with each other and generate an undesired grating pattern along a 45 degree direction, which influence the pattern uniformity in a certain degree. The undesired grating pattern can be eliminated by polarization modulation, yet which will influence the grating area. Theoretical and experimental study was carefully carried out to evaluate the fabrication quality with and without polarization modulation. Two-dimensional scale gratings with a 1 μm period in X- and Y-directions were achieved by using the constructed experiment system with a 442 nm HeCd laser source. Atomic force microscope (AFM) images and diffraction performances verified that the two-axis Lloyd’s mirror interferometer with a small undesired interference between two reflected beams under an order of nominal value of 0.1 can provide a better fabrication result for scale gratings application.

Wireless ad hoc sensor networks have been used more and more in recent years, and they are mainly used in the continuous monitoring of complex environment. The low power and dual frequency characteristics of the SimpleLink CC1350 LaunchPad micro control platform are very suitable for the research of wireless ad hoc sensor networks. Because the synchronization of each node clock is the premise of the normal work of wireless sensor network, this paper mainly studies the time synchronization problem of CC1350 development board. In this paper, the advantages and disadvantages of the existing time synchronization methods are analyzed, then the LTSP algorithm is selected at the end, and the experimental verification is carried out on MATLAB software platform and CC1350 system. The experiment result shows that the time synchronization precision and extensibility of the algorithm can meet the requirement of networking.

The mirror construction of the radiotelescope RT-70 (Suffa) for millimetre wave range requires measuring the line deformation of mirror's surface. Following issues dealing with this problem are described in this article: 1) the possibility of the design of deformation measurement system based on triangular method 2) the new scheme of optic-electronic measurement system. The great attention during the research was paid to the experimental approval of the theoretical results. The model of the described system had the following characteristics: infrared emission diode AL107B by power 15 mWt as sources of radiation; the objective by the focal length 405 mm as aperture of receiver video-camera, the CMOS matrix receiver by type OV05610 Color CMOS QSXGA with 2592*1944 pixels and one pixel size (2.8*2.8) μm² produced OmniVision as image analyzer . The computer simulation error and the experimental error measurement was 0.05 mm at the range 30 mm on a working distance 25 m, which allows measuring the deformation of radiotelescope construction with the mirror diameter 70 m.

The increasing capabilities of roll-to-roll (R2R) printing processes present challenges for quality control, requiring inprocess inspection of large substrates with high resolution at high speed. In this paper, an all-optical difference engine (AODE) sensor has been developed for in-process defect inspection for R2R printed electronics. The AODE sensor achieves high-speed inspection by utilising the principle of coherent optical subtraction to minimise data processing. The capability of the developed sensor is demonstrated using industrial printed electrical circuity samples and the sensor is capable of inspecting areas of 4 mm width with a resolution of the order of several micrometres.

We present a simple method to measure the 3 dB linewidth of the sharp peak in the spectrum of the fiber Bragg gratingbased Fabry–Perot (FBG-FP) interferometer. A narrow linewidth tunable laser is used for sweeping the FBG-FP to achieve the reflection spectrum. A triangle wave is used to drive the narrow linewidth tunable laser. The linewidth of the sharp peak is measured with a resolution of 0.001 pm.

In this paper, a weather phenomenon called a hurricane is considered. Major components areconsidered and selected. After the analysis of the components, the indicator substances are chosen, according to which the detection of the incipient phenomenon will be carried out in the future. The method of remote sensing is considered for detecting small concentrations of indicator substances in the air. The sounding area is chosen to study the atmosphere for the presence of indicator substances. The results of calculating the backscattering power for some indicator substances are presented, depending on the range.

The work is devoted to the research of the polarization-optical parameters of a solid-state matrix photomultiplier. The main parameters of the performance of the SiPM form from the sensitivity of the photodetector. As an object of study, a silicon photomultiplier ARRAY-C 60035-4P was chosen, which consists of 4 photosensitive sites. The pixels of the SiPM are avalanche photodiodes that are separated from each other by elements that do not participate in the formation of the useful signal and serve to suppress the secondary optical signal due to the optical coupling between. In this paper, experimental studies of the state of polarization reflected from the surface of each of the active regions of the matrix of a silicon photomultiplier are performed using a laser photoelectric ellipsometer LEF-3F-1. The action of the ellipsometer is based on the zero method of determining the polarization angles. In the course of the experiment the contractions of ellipsometric angles were determined. The experiment was carried out at four angles of incidence on the surface of the receiver, which corresponds to a set of reflective characteristics of a silicon photoelectric multiplier. With the help of these data, the estimation of the distribution of the reflection and transmission coefficients becomes possible, as well as the sensitivity distribution over the different sites of the SiPM.

The existing infrared thermal imaging detection methods usually process the whole video stream data collected by a thermal camera, which involve large amounts of data and have a negative effect on the efficiency of defect detection. In this paper, we propose an infrared thermal imaging detection method which considers the spatial correlation of the adjacent images in the video stream data. By extracting the edge information and analyzing the correlation between two adjacent frames, the defect area and the non-defect area show different correlation coefficients, and only part of the video data is required for defect detection. Furthermore, the fusion method is introduced to enhance the image quality. The experiment results demonstrate that the proposed method can not only reflect the change of heat in the defect area during the heating process but also reduce computation time involved in the subsequent processing.

In this paper, a novel randomly encoded hybrid grating (REHG) interferometric wavefront sensor with the features of high-precision, high-resolution, high-dynamic-range and anti-vibration is proposed. The REHG consists of a randomly encoded binary amplitude grating and a phase chessboard. The far filed Fraunhofer diffractions only contain ±1 orders in two orthogonal directions. Different from the cross grating lateral shearing interferometer (CGLSI), there is no need of order selection mask for quadriwave lateral shearing interference. Without the influence of periodical Talbot effect, a continuously variable shear ratio can be obtained with the REHG, which makes it possible to control the dynamic range and measurement sensitivity of the wavefront sensor. A high-precision calibration method for shear ratio based on the shearing wavefront feature extraction and the generalized wavefront retrieval algorithm are employed to ensure the accuracy of the wavefront measurement results. The REHG wavefront sensor can work in collimated beam and convergent beam modes. Due to self-referenced and common-path characteristics, the REHG wavefront sensor can applied to different application fields in situ. Compared to the ZYGO interferometer, the results of the optical aberration and spherical surface measured by the REHG are highly precise and also show good repeatability. By applying two REHG wavefront sensors with different shear ratio, a wideband sensitivity-enhanced interferometric microscopy with real-time visualization can retrofit existing bright-field microscopes into quantitative phase microscopes.

This paper proposes an energy analysis method of the laser tracing measurement optical system. Based on the principle of the laser tracing measurement optical system, an energy model is established to analyze the effects of non-ideal optical elements on the energy of the optical system. The simulation results show that the interference pattern is the most obvious when the split ratios of the beam splitters in the interference part and the tracing part are respectively 6:4 and 7:3. Under the above split ratios, the interference signal energy values of four receivers are close to each other and the visibility of fringe pattern reaches 0.99. The visibility of fringe patterns of four interference signals is reduced when the reflectivity of all polarization beam splitters is under non-ideal conditions in an entire optical system. The non-ideality of the transmittance of the polarization beam splitters does not affect the visibility of fringe patterns. The paper provides the theoretical basis for the accuracy improvement, reliability evaluation, optical system design and the selection of optical elements of laser tracing measurement systems.

With the rapid development of high-speed railway, there are many problems with the traditional railway slab assessment method. The traditional method is slow, and its precision is limited by the precision of specified tools for railway slab inspection. Scholars have developed a variety of inspection systems for railway slab geometry. Since those systems’ precision assessment relies on railway slab testing tools that are complex for operation, this paper proposes a novel method to assess the precision of an intelligent slab inspection system itself by using the spatial position deviation between the point cloud of a benchmark slab and the corresponding digital 3D model. The proposed method takes the RMSE of the deviation value of points in the key surfaces as the evaluation index. The key surfaces are the two shoulder surfaces and the rail-bearing surface of the rail-bearing platform, which can be extracted by the region growing algorithm associated with surface normals. Based on the real point cloud processed by an intelligent slab inspection system, the experimental results show that the system can align the slab point cloud to its corresponding 3D digital model. The deviation is distributed on the model uniformly, and its precision is 0.1 mm. In addition, this procedure is consistent with that of general slab inspection and can be used as a self-verification tool for daily precision evaluation of the system itself.

The equivalent circuit model based on the average period for periodic overlapping circle metallic mesh is proposed in this paper. The equivalent reactance coefficient b in the equivalent circuit model is revised according to the simulation results of Ansoft designer software. In order to guide the optimization of the electromagnetic shielding effectiveness of periodic overlapping circle mesh, the effects of the diameter 2R and period g on the electromagnetic shielding efficiency were simulated and analyzed. The simulation results show that the electromagnetic shielding effectiveness is better than 22dB in the 2-18GHz band. The periodic overlapping circle mesh can be applied to the area where the strong shielding effectiveness,high optical transmittance and low image-degradation are required simultaneously.

X-ray computed tomography (CT) is a non-destructive approach to verify internal features of various industrial components built by additive manufacturing (AM) or other processing methods. However, the measurement results was highly impacted by numerous factors. In this study, DoE (Design of Experiments) was conducted to statistically study impacts of error source of X-ray CT metrology; optimal settings were recommended for different internal geometrical features. Measurement comparison between X-ray CT and CMM (Coordinate Measuring Machine) is also provided in this paper to analyze the principle difference of these two measurement technology.

The traceability of cleanness parameter has received high attention from the metrology industry of light-scattering airborne particle counter. Based on the metrology method of the big particle concentration and the traceability method of airborne particle counter’s counting performance on small particle size by statistical analysis, this paper tries to build a coordinate system of the particles distribution on anodic aluminum oxide (AAO) membrane through the counter, choose the statistical samples by aerodynamics, observe these samples on membrane by field emission scanning electron microscope (FESEM), evaluate the uncertainty of measurement on standard particle statistics, analyze the uncertainty range and the key affecting factor, and put forward a method of improving statistics accuracy in process control. The test results prove that the method has important value on improvement of the theory of the cleanness traceability system based on FESEM and statistical analysis.

The long fiber frequency sampling method has been widely used to eliminate the nonlinearity of laser tuning in the frequency-modulated continuous wave laser ranging technique. Then, fast Fourier transform (FFT) is performed on the resampling signal to obtain the distance spectral information. However, due to the picket fence and leakage of FFT-based methods, it is hard to find the precise location and achieve better range precision. In this paper, we propose a novel frequency estimation method, multiple signal classification (MUSIC), to be used instead of the conventional fast Fourier transform (FFT)-based algorithm to obtain better range precision. In addition, the induced-fiber dispersion could also lead to poor accuracy and precision in the large-bandwidth and long-distance measurements scenes. To solve this problem, a phase compensation method for resolution-enhancement is proposed.

This paper dedicated to the development of a surface profile measurement system based on the SLD (Super Luminescent Diode) light source for silicon wafer. The silicon wafer is very important as a substrate of semiconductor products such as integrated circuit (IC) chips, light emitting diodes (LEDs), solar cells and MEMS devices ^[1] . In this paper, Michelson interferometer is used to generate double beams in order to achieve interference. According to the acquired interference fringe image, we obtain the surface profile of the tested silicon wafer. As a light source, SLD has good spatial coherence and due to its higher transmittance to silicon wafers than other wavelength sources, high fringe visibility can be achieved. It can also perform a full scan in a larger step and achieve rapid on-line measurement of the target surface.

Existing axial support for segments mostly adopts the Whiffletree support mode. The location of the support point will have a great influence on the surface precision of the primary mirror, and then influence the final imaging quality of the telescope. At present, there is no special support technology for traditional and thin mirror.In this paper, the research is based on LOT’s hexagonal segment (the surface is hyperboloid, diagonal line is 1.2m, thickness is 45mm, material is Zerodur), which is designed by Huazhong university of science and technology. The optimization of the Whiffletree axial support point of the segment is carried out. Efficient optimization algorithm is used in the research. After building parameterized model of segment support point location, FEM is used to obtain segment surface deformation. Taking the minimum RMS of deformation on segment surface under gravity as the goal, optimized software ISIGHT is applied to find the best support point location. Zernike orthonormal polynomials for hexagonal pupils is used to remove rigid-body motion. Finally, the best support point location point is obtained, the RMS of the segment surface deformation is 11.56nm and the PV is 63.98nm. The result can meets the requirement of LOT design well.

In order to cover the high dynamic exposure range requirement of high reflective surface, a multiple-exposure adaptive selection algorithm of phase shifting 3D measurement is developed. At first, the camera response curve function is calibrated with the sequence images of different exposure times. The nonlinear curve function shows the relationship between the image intensity value and exposure amount. The relative irradiance value of all the image pixels is computed based on the linear relation between the exposure time and exposure amount. Both relative irradiance value cover the highest and lowest gray value of the fringe image is set the threshold. Then, the adaptive selection algorithm for exposure time is proposed based on the double threshold principle. At last, different exposure time node is selected adaptively. The sequences images with multi-exposure time are fused. In order to evaluate the performance of this method, some typical metal parts and blade with high range of reflectivity surfaces are used for 3D measurement and construction. The experiment results verify the feasibility of the proposed method.

Wavefront modulation devices are of great significance in optical information processing systems. These devices capable of phase modulation are used in a variety of optical applications: wavefront correction, optical metrology, adaptive optics, aberration compensation, etc. The liquid crystal spatial light modulators (LC-SLMs) and deformable mirrors (DMs) have been regarded as the promising device for their flexibility and programmability on wavefront modulations. This paper presents applications of LC-SLMs and DMs when they are used as aberration compensators in testing of aspheric and freeform. Besides, a pixel-wise method based on analysis of the phase maps obtained by a Fizeau interferometer for calibrating the phase modulation characteristics of the LC-SLM is proposed. A PLUTO-VIS-020 LC-SLM produced by the Holoeye Company is employed in the calibrating experiment. A Zygo interferometer based on Fizeau interference theory is also employed. The experimental results demonstrate that the phase modulation characteristics of LC-SLM and a specific lookup table (LUT) for every pixel of the LC-SLM aperture can be obtained by utilizing the proposed method with convenience and high efficiency. The device calibrated in this paper provides a high phase shift up to 6π at 632.8nm wavelength and has a linearized phase distribution. It coincides well with the average modulation curve offered in the manual of the device. This paper provides a simple and accurate method for pixel-wise phase modulation characteristics calibration.

We build a two-wavelength off-axis quasi-common-path digital holography for quantitative phase imaging (QPI) using polarization-multiplexing and flipping. The interference is performed by flipping the relative position of a sample and reference beam, and the dual-wavelength information is spatially multiplexed onto a monochromatic CCD camera simultaneously using polarization-multiplexing. Due to orthogonal interference fringes of two-wavelengths, the unwrapped information on the phase and thickness for the sample can be extracted from a single interferogram. Our setup requires no pinholes, gratings or dichroic mirror with straightforward alignment. Additionally, a division algorithm for dual-wavelength off-axis digital holography with the help of a specimen-free multiplexed interferogram is proposed to extract the phase of a specimen. We demonstrate the operation of the setup with step target and circular pillar.

Light emitting diodes (LEDs) have recently gained much interest as projection light sources. In this work, a compound parabolic concentrator (CPC) coupled to a biologically inspired compound-eye array is designed and fabricated as a light collection engine of a pico-projector. The results indicate that more than 90% light emitted by a monolithic LED array can be collected by the CPC coupled to a compound-eye array and transmitted within the designed angle. This method is advantageous in many respects compared with those available, such as compact volume, high collection efficiency, rectangular radiation pattern and controllable output divergence angle. The result validates that the system reaches a collection efficiency of 87% of micro-LED emitted light. Moreover, the beam collimation quality has been analyzed obtaining a residual divergence of less than 2º. Thus, the results achieved by the proposed optical system improve those obtained with several commercially available devices.

When fringe projection profilometry is applied for real-time 3D shape measurement, several problems remain to be solved such as multi-wavelength heterodyne phase unwrapping is sensitive to motion and the computation cost is high. In this paper, a real-time 3D shape measurement method with optimized multi-wavelength heterodyne phase unwrapping and GPU parallel computing is proposed. Experimental results demonstrate that the proposed method can acquire 3D shape at 40 fps. Dynamic object with discontinuities can be measured and the phase unwrapping mistakes are eliminated by smoothing the phase of beat frequency during multi-wavelength heterodyne phase unwrapping.

In the modern industrial manufacturing, how to effectively obtain the three-dimensional data of the parts profile is the key component for precision test and subsequent analysis. A light-duty design scheme for optical vision probe, which can be installed with a PH10T motorized probe head in CMM, is discussed in this paper. The optical probe can overcome several defects of the traditional measurement mode of CMM, such as poor efficiency and sparse point cloud. Therefore, the problem of 3D measurement and quality analysis for complicated parts can be solved. To splice data in different fields of view, a registration method using a new designed artifact is proposed. Experiments demonstrated the feasibility of the designed non-contact CMM integrated with optical 3D probe for precise 3D shape measurement. The measurement uncertainty of the optical probe can reach 0.012mm within the measuring volume width 200mm and the measurement uncertainty of the global 3D measurement is less than 0.03mm in 1500mm.

Measurement is the prerequisite technology for assembling precise devices in order to guarantee the quality requirements. As a typical category of assembly, peg-in-hole is the most widely employed assembly method in industrial fields, including precision instruments and machinery. Some of the measurement problems and solutions of two major categories of the peg-in-hole assembly, i.e. clearance fits and interference fits, were discussed. The parts to be assembled are small in size. The precision clearance fits require mating surfaces to avoid collisions during assembly; for the precision interference fits, the mating surfaces should not be damaged or generating abrasive chips during press-fit. The hole-shaft alignment and attitude adjustment are the main task need to be carried out precisely in assembly. Furthermore, real-time monitoring and connection strength measurement is also the important for interference fit assembly. Therefore, the purpose of this paper is to achieve precise hole-shaft alignment and attitude adjustment of these two kinds of fits and to real-time monitor the assembly process, as well as connection strength assessment of the interference fit. Two assembly instruments were built for interference fits and clearance fits to achieve precise alignment, attitude adjustment, and real-time monitoring. In addition, an ultrasonic testing apparatus was built to evaluate the connection strength. After calibration, the precision press-fit instrument can achieve high assembly accuracy and demonstrated with experiments. The prediction results of connection strength are in good agreement with experimental results with a relative error less than 20%. Furthermore, the instrument for clearance fits was also designed and introduced.

Linear laser scanner has been widely used in industrial applications, such as 3D reconstruction. Breakpoint detection of the laser stripe centerline is a fundamental step. In practical applications, the centerline is always not perfect due to various noises. A novel breakpoint detection method named Fixed Dynamic Programming (FDP) is proposed. Firstly, the centerline fitting error is illustrated in detail, which is to be used as the criterion in the FDP. Secondly, principle of the FDP method is described, which modified the traditional DP method by utilizing the foreknown breakpoints information of the centerline. Finally, experiment is implemented to detect breakpoints of the noisy laser stripe centerline by using a linear laser scanning system. From the experiment result verifies that the prosed FDP method can avoid the influence of noise and improve the computation efficiency.

The high rotational speed standard device based on brushless DC coreless micro motor and FPGA technology for highaccuracy rotational speed control was investigated and established, with resolution of 1 r/min in the measurement range of 40000 r/min to 100000 r/min. The expanded calibration uncertainty of this standard device is 1×10^-5, k=3 The structure of the device and key technology involved were described．The dual closed-loop control solution was explained. The calibration results were provided．This high rotational speed standard device is used as an important working standard for the feasible traceability of high-precision optical tachometers and rotational speed measuring instruments at measurement range above 40000 r/min.

A line encoder composed of a two-probe reading head an arrayed scale grating stitched by multiple separate gratings was proposed, constructed and evaluated in this research for expanding the measurement range. The scale grating is stitched by multiple separate short gratings fabricated by a holographic lithography that is able to provide sub-micron order grating period. Differing from the conventional stitched grating, in which the gap of the adjacent two gratings should be strictly controlled so that a continuous phase can be ensured, the gap in this research is not necessary to be controlled, neither the gap width nor the phases, by using a two-probe reading head. In contrast to the reading head in conventional linear encoder, the two-probe reading head was designed in such a manner that a collimated laser beam with a diameter of 1mm was divided into two parallels probes (probe A/B) by a specially designed prism lens. These two probes are projected perpendicularly onto the transmission type arrayed scale grating. Taking probe A as an example, after passing the grating, the positive and negative first-order diffraction beams follow a typical grating interferometry principle, including propagating direction changing, co-path by a beam splitter and a polarize for a phase delay module and finally interfere with each other, from which the displacement can be obtained. The two probes propagate along similar optical path. The two probes can ensure as least one can be projected onto the grating. By stitching the two probe outputs suitably, the continuous output of the scale grating can be measured accurately. The jig for stitching the separate gratings was investigated and tested. The two-probe reading head prototype was constructed and evaluated.

A method to measure the magnetic field inside the Giant Magnetostrictive Actuator (GMA) is proposed. Improved Preisach Model is applied to eliminate the unavoidable nonlinearity error in the measurement. The effect of temperature on measurement can be eliminated by double Fiber Bragg Grating (FBG) structure. The double-sagnac loop combined with Polarization Maintaining Fiber (PMF) is used to demodulate the center wavelength. Sensing model of the FBG is established to realize temperature compensation for the measurement system. Experiment results show that resolution of 2.1×10^-4 T can be achieved over a range of 127 mT, and the repeatability of overall measurement is 0.227%. Therefore, the proposed method can be used to measure the internal magnetic field of GMA effectively and reliably.

As the ultra-precision machining technology is developing in various directions and evolving into a higher level, the micro-nano measurement technology is also developing constantly. According to the different manufacturing processes and texture of measurement objects, the requirements of micro-nano measurement technology vary a lot. Optical Microscopy (OM), Scanning Probe Microscopy (SPM) or Scanning Electron Microscopy (SEM) cannot meet requirements of high efficiency, high resolution and three-dimensional morphology characteristics obtaining at the same time. Hence a hybrid measuring system including the Atomic Force Microscopy (AFM) and vertical scanning white-light interferometry is built. The measurement function of the dual feedback AFM system was verified by scanning a one-dimensional grid and the measurement function of white light vertical scanning interferometer was verified by measuring the step structure and comparing it with a three-dimensional optical profiler. And then the micro-arrayed structure is measured by white light vertical scanning interferometry. The vertices of the micro-arrayed unit structure is scanned by using AFM in the same coordinate system to verify the complex measurement function of the system on the complex micro-arrayed surface.

The measurement of spindle radial error motion is achieved based on target trajectory tracking (TTT). Error analysis of TTT method is performed in this paper. Target trajectory doesn’t contain information about axial error motion. The tilt error motion is included in the target trajectory. However, the tilt error motion is small enough to be ignored. The roundness error of the target trajectory is assessed to obtain the radial error motion of the spindle. The experimental results confirm that the proposed method can be applied to measure the radial error motion of a high-speed spindle having a maximum rotational speed of 6000r/m.

In this paper, a quality detection method for battery FPC (Flexible Printed Circuit) connectors based on active shape model template matching is proposed. It can deal with different kinds of connector appearance defects. Firstly, construct template data set of connector, acquire test images and apply cutting operation to original image, then execute tilt correction and image reconstruction by means of least square method and affine transformation to fulfil the pre-processing stage. Then, match and locate connector region in per-processing image with the help of the active shape model (ASM) based template matching method. To deal with different kinds of defect (soldering offset/tilt, exposed copper clad layer in FPC, broken edge in FPC, defects in center area of connector, defects on metal and plastic components), independent detection algorithm units are integrated in the system. Template can also be real-timely updated according to detection result. Finally, the defects will be classified, located and marked in detection image. In addition, aimed at the need of battery industry, a set of detection system with low cost, high performance and strong stability has been designed. It can be concluded from online and offline experiments that the proposed method is of high detection rate, good real-time performance and strong robustness.

Joule balance is one of the precise instruments to measure the Plank constant for redefining the kilogram. During the measurement of the joule balance, two electrified coils produce an electromagnetic force to balance the gravity of a standard mass on the mass pan. However, if the mass pan is in a misalignment state, it will waggle and change the posture of the suspended coil during the mass exchanging progress. Then the alignment errors will be induced. In joule balance, the posture of the mass pan cannot be directly measured, which however can be decoupled by measuring the posture of the suspended coil. In this paper, the recognition method of the mass pan misalignment status will be discussed. By measuring and calculating the positon changing of the suspended coil, the alignment states of the mass pan can be evaluated.

This paper presents analysis of the possibility to design all-weather pulse laser altimeters for measuring lowaltitudes above the sea surface. We proposed special design features which consider the low reflection coefficient and the reflective properties of random rough sea surface. Backscattering by fog with various density was analyzed. With considering the reflection coefficient from the sea surface less than 4%, we proposed measurement method based on the drop of the backscattering signal. We examined the measurement range and measurement errors depending on the transfer function of the receiving-amplifying circuit for inertial and non-inertial detection. The energy compensation for specified measurement precision was carried out.

Dyson concentric configuration has advantages of 1:1 magnification ratio, compact size, light mass, large numerical aperture, less smile and distortion. However, volume of initial structure calculated by two-wavelength astigmatism method is relatively large. Meanwhile, we only obtain one smaller structure for long wavelength infrared range through another improved method widening aberrations. In this paper, we proposed improved design principle of Dyson concentric push-broom infrared imaging spectrometer, which can calculate all smaller initial Dyson structures satisfying requirements of spectral range and resolution in different infrared wavebands. First, obtain initial grating groove density using two-wavelength astigmatism. Then widening aberration, search all of initial Dyson structures satisfying ideal imaging condition under 1 to 10 times of initial grating groove density. Lastly, select infrared materials and detectors suitable for short infrared, medium-wave infrared and long-wave infrared wavebands respectively to demonstrate feasibility of this new method. As results shown, volume of Dyson configuration has reduced about 60% in short-wave infrared waveband, 77% in mid-wave infrared waveband, about 50% in long-wave infrared waveband. So improved design principle proposed in this paper benefits for infrared concentric imaging spectrometer. © 2018 Optical Society of America.

A novel two-dimensional reflective grating encoder is introduced. The optical encoder is developed by a binary amplitude reflective scale grating and a two-dimensional slit displacement sensor, which is fabricated by MEMS technology. Based on Talbot effort, the proposed method can achieve millimetric measurement with high accuracy, where the displacement difference within 0.1% and 0.2% for 1 mm and 20 mm measurement, respectively. By using the eight-segment data division program, the proposed method can easily distinguish 1 μm displacement measurement. Furthermore, in measurement speed tests, the proposed method can reach the movement speed about 5000 μm/s. The experimental results showed the proposed method can achieve high resolution, high speed and long-range measurement, which is potential in the industries and workshops application.

The currently existing incremental optical-electronic linear displacement encoders (OELDE) use raster conjugation, which allows for the measurement of linear motion with high accuracy by means of the conversion of optical signals in the opto-electronic path. In such devices, informative signals constantly undergo transformations associated with their processing. Variable environmental factors, especially temperature, have a harmful effect on signal conversion processes and cause additional error. The aim is to analyze the results of theoretical and experimental studies of the additional error from the effect of changes in ambient temperature on incremental OELDE’s. Analyzing the effect of temperature on the course of information transformation, it is possible to divide the main emerging partial components of the additional error into two groups: - errors due to changes in the relative spatial position of the elements of the OELDE; - errors due to changes in parameters and characteristics of elements of the OELDE.

The deep learning models have recently shown outstanding performance in many computer vision applications. However, this superior performance requires a very large number of annotated image samples, pre-venting application to problems with limited training data. To overcome this limitation, we propose a Do-main Adaptation Deep Transfer Model (DADTM) in this paper. The DADTM improves the classical transfer models by the proposed domain invariance value metric and a domain invariance reconstruction, increasing the model transferability and enhancing the classification performance. The comparative experiments are performed to evaluate the DADTM-based classification algorithm. The results show that the proposed mod-el and algorithm outperform the traditional methods.

During the measurement,The traditional lever type measuring instrument will introduce a nonlinear error due to the rotation of the lever, which will affect the measurement result.A magnetic levitation stylus measuring instrument was designed based on it. It changed the lever supporting mode from the stylus shaft to the vertical direction linear translation which can eliminate the nonlinear error and improve the measurement accuracy.This paper introduces the measuring principle based on the magnetic levitation bearing stylus surface topography sensor, designs the electronic control system of the magnetic levitation contact measuring instrument, and finally conducts the surface topography measurement test.The experimental results show that the designed electronic control system can meet the design requirements of the magnetic levitation system.

Smart electricity meters are playing an indispensable role in modern society, and their measurement accuracy affects the economic interests of both power units and users. In this paper, a compensating method based on neural network approximate modeling is proposed to increase the accuracy of electric energy measurement among the whole range of operational temperature. Based on the measurement data and the internal structure of the smart electricity meter, a MATLAB/Simulink model of the meter is built to evaluate the consistency of power measurement at different temperature levels. The FEM (finite element method) thermal simulation model of the meter device is carried out in ANSYS Icepak to obtain the temperature contours of the smart meter in different operating conditions. Afterwards, based on the simulation data, the component temperature in the metering circuit is evaluated according to the approximation model built by RBF (Radial basis function) neural network. At last, a temperature compensation program is realized in the MCU (Micro-Controller Unit) to adjust the metering accuracy. According to the final testing results, the proposed method significantly enhances the metering accuracy among full temperature range.

The refractive indexes of prisms are affected by temperature, hence the optical characteristics of triangular prisms ring cavity is disturbed enough to affect the stability of the laser gyro. Considering the temperature perturbation, the transmission matrices of the reflected and refracted beams on the prism surfaces have been modified. The modified results are the old 2×2 beam transfer matrices are corrected to new 3×3 matrices and the temperature perturbations are added. According to the self-consistent theory of the laser ring cavity, a physical model of the ring cavity light transmission with the temperature disturbance has been established. The theoretical analysis shows that when the temperature varies from -40℃ to 70℃, the changes of the optical cavity-length, frequency offset, and scale factor are 49μm, 0.011MHz and 1.96×10^-10, respectively. An experimental system of the prism laser gyroscope has been established whose temperature can be changed, and the experimental results agree with the theoretical values.

A compact diffracting grating based laser wavemeter is constructed in this paper. Wavelength is the length unit of laser interferometers, it must be very accurate and stable during the length measurement. An air sensor, which is employed to correct the air refractive index through an empirical equation, is essential in laser interferometers. However, the empirical equation is suffered from indirect measurement, the correction accuracy is depended on the measurement accuracy of the air sensor. Slow response is other disadvantages of the empirical equation. Additional, the empirical equation is not applicable to correct the laser diode wavelength. Therefore, a direct measurement method of laser diode wavelength, based on the diffraction principle, is proposed and a compact, low-cost and simple wavemeter is constructed in this paper. Laser beam drift is recognized as one of critical error source in laser measurement. Therefore, a novel laser beam drift active compensation method is thus proposed in this study that integrates the functions of automatic type angle turning and PID controlled fine angle motion. After introducing the principles of wavelength measurement and laser beam drift compensation, the effectiveness of the wavemeter in real-time wavelength measurement is well verified by the experimental results.

It is difficult to control consistency of light source and large volume in current linear time-grating displacement sensor with four-channel alternating light field. A novel integrated linear time-grating displacement measurement system with single alternating light field is proposed. Single alternating light field and micro-controlling phase-shift method are used to synthesize a signal of traveling wave. And the measurement of linear displacement is achieved by measuring a difference of zero-crossing time between a signal of traveling wave and a reference signal. Design of structural miniaturization, design of integrated circuit, design of transmitting surface of cosine and design of optimization of existing time-grating displacement sensor are analyzed in detail. According to measuring principle, manufacture of light source and photoelectric receiver are completed, and corresponding experimental platform is built. Experimental results indicate that the measuring errors of optimized sensor are reached within±0.2μm using grating pitch of 0.1mm in the measuring range of 100mm.

Based on the principle of orthogonal demodulation, a Pound-Drever-Hall laser frequency locking scheme is developed. In the orthogonal demodulation Pound-Drever-Hall system, three sine signals are generated simultaneously using a direct digital synthesizer. A 0° phase sine signal is used to drive an electro-optic modulator to produce the phase sidebands, and 180° and 270° phase sine signals are used as reference signals for phase demodulation. The phase-modulated laser beam is coupled with a reference Fabry–Pérot cavity, and the reflected beam is sent into a photo-detector, whose output is mixed with two orthogonal reference signals to obtain two orthogonal components of the error signal. Using an analogto- digital converter, the two orthogonal components are processed using orthogonal phase sensitive detection to obtain the error signal on a host computer. The Pound-Drever-Hall laser frequency discrimination and tracking system is established and investigated experimentally using the orthogonal demodulation method. A frequency discrimination curve is obtained, and it is observed that the resonant frequency of the Fabry–Pérot cavity can automatically track laser frequency variation.

Particle charging is a universal phenomenon due to the collision and contact between particle and particle, particle and wall in the powder pneumatic conveying process. The linear electrostatic sensor matrix (LESM) is able to capture the dynamic information of the moving charged particles in pipeline, whose spatial filtering characteristics has been employed to obtain the flow velocity of particles in gas-solid flow. The spatial filtering characteristics of LESM are closely related to its dynamic sensitivity (DS) distribution. In this paper, the 3D simulated model of the LESM was built by finite element method and the effects of its structural parameters on its dynamic sensitivity and spatial filtering characteristics were studied. The geometric dimensionless model of dynamic sensitivity of LESM was further established. Finally the experiment was carried out on a gravity-fed solids flow rig, and the experimental results was verified the simulation results.

Automatic assembly is widely used in precision component fabrication, and the manually assembled task for a small batch of the precise component is replaced by automatic system gradually. One of the key issues is manipulating the workpiece reliably. With the quick updating of the products, the end effectors need to pick more parts with different dimensions and configurations. In this paper, an exchangeable end effector for laser gyroscope assembly is presented. The end effector integrated with adsorption and clamping is designed to suitable for different type of workpieces. The three-position two-way magnetic valve is used to switch the adsorption and clamping. Based on the dimension and shape characteristics of the parts, the adsorption and clamping position of the end-effector was calculated. The maximum weight of the part is 0.5N, thus vacuum degree required for adsorption is 0.078MPa and the reaction time is 0.653s. The clamp for this gas circuit can generate the clamping force of 10N, which meets the requirement of clamping. Finally, the assembly tests were carried out to prove the feasibility of this exchangeable end effort.

Carbon nanotube membrane (CNTM) has been employed as the counter electrode in a two-electrode voltammetric electronic tongue system. Owing to its large surface area, CNTM provides significant double layer capacitance at the solid/solution interface, and offer a constant potential during the electrochemical detection. In order to characterize the analytical possibilities of the electronic tongue system, hydrogen peroxide has been detected. Principal component analysis (PCA) is used for identification. From the PCA plots, the electronic tongue system by using CNTM counter electrode shows much better performance and more promising than the conventional voltammetric two-electrode electronic tongue system by using large surface stainless steel counter electrode.

In this paper, the dynamic and static contact characteristics of the aerostatic bearing stylus displacement sensor are analyzed, including static contact damage and dynamic response. The dynamic response at frequency and different speeds is studied and obtained the relationship between the measured force and frequency and velocity. The stylus does not contact well from the surface when the measuring force is less than 0. In this case, the traceability of the tip can be analyzed based on the characteristics of the amplitude. Finally, the experimental verification of the relevant theory is obtained by measuring the aluminum turning sample at different speeds.

Cellulose nanocrystal (CNC) is an emerging nanomaterial that has drawn increasing attention recently. It is abundant, sustainable, renewable, and biodegradable. They have unique chemical and mechanical characteristics that cannot be met by traditional cellulose-derived materials, such as high aspect ratio, low density, high stiffness, high tensile strength and very low coefficients of thermal expansion. This paper is focused on the formation and characterization of CNC films and the subsequent traceable metrology of CNC film thickness by atomic force microscopy (AFM). The AFM is calibrated by a series of certified reference materials, and thus the measured values can be traceable to the laser wavelength reference (meter definition). Results show that CNC films with negative charges on surface can be formed via physisorption to an amine-terminated thiol layer on gold through spin coating. The CNC film thickness can be controlled by CNC solution concentration. A thorough understanding of CNC metrology is the foundation for further study of CNC chemical and mechanical characteristics and applications.

Recently, fiber Bragg gratings (FBGs) have played significant roles in a variety of fields such as optical communication, dimensional metrology, buildings health monitoring, ultrasonic waves and vibration measurement, petrochemical and other harsh/remote environments owing to their excellent performances like electromagnetic insensitivity, high accuracy and long term stability. In general, FBGs-based sensors are usually decoupled by detecting the variations of FBGs’ central wavelength, wherein, the accuracy and dynamic characteristics of the FBGs-based sensing are directly dependent on the spectral resolutions and response speed of the interrogation method. However, conventional spectral interrogation methods, which directly utilize an optical spectrum analyzer (OSA) with low resolutions and response speeds cannot satisfy the requirements of detecting small and dynamic variations of the FBGs’ central wavelength accurately. It is therefore of significance to find a FBGs interrogation method with high resolution and high response speed. In this paper, a high resolution and response speed interrogation method based on reflective-matched Fiber Bragg Gratings scheme is investigated in detail. The nonlinear problem of the reflective-matched FBGs sensing interrogation scheme is solved by establishing and optimizing the mathematical model. A mechanical adjustment to optimize the interrogation method by tuning the central wavelength of the reference FBG is investigated to improve the stability and antitemperature perturbation performance. To satisfy the measuring requirement of the optical and electric signal processing, an acquisition circuit board is well-designed, and experiments on the performance of the interrogation method are carried out. Experimental results indicate that the optical power resolution of the acquisition circuit border is better than 8 pW, and the stability of the interrogation method with the mechanical adjustment can reach 0.06%. Moreover, the linearity of the interrogation method is 3.3% in the measurable range of 60 pm; the influence of temperature is significantly reduced to 9.5%; the wavelength resolution and response speed can achieve 0.34 pm and 500 kHz, respectively.

Based on artificial compound eyes and human vision mechanisms, we propose a hybrid bionic imaging method to achieve field of view (FOV) extension and foveated imaging simultaneously. The imaging model of the proposed method is built, and the key parameters are deduced. Then, simulations are carried out to estimate the properties of the model, including FOV extension ratio (FER), foveal ratio, fovea moving range and so on. Finally, a prototype is developed, and imaging experiments are carried out. The experimental results accord with the simulations well, proving the potential of the proposed method for intelligent surveillance, automatic object detection and recognition with low cost.

A novel super resolution reconstruction method is proposed to improve super resolution image performances. The proposed method uses bionic vision sampling model to obtain low resolution images and performs super resolution reconstruction in logarithmic polar coordinates. We carry out comparative experiments between the proposed method and the traditional method in terms of Peak Signal to Noise Ratio (PSNR), Structural Similarity Index Measure (SSIM) and Mean Squared Error (MSE). The results show that the performances of proposed method are better than that of the traditional method. Especially the SSIM of global image (butterfly), the proposed method is 34.45% higher than the traditional method.

This paper presents an automatical crack recognition approach. Compared with the existing methods, it has a significant increase in robustness and efficiency when faced with widely varying field conditions. Inherent characteristics of crack images are exploited using proportional segmentation, combined with robust feature extraction to improve machine learning classifier performance. Experiments show that this method perform well in crack images recognition across different concrete conditions.

In inertial confinement fusion system, the intermittent scratches on the polished surface of single-sided polished and bottom surface frosted optical components are complex, and it’s of great difficulty to extract them completely. In order to solve this problem, established in the light-field surface detection system, this paper brings forward a novel intermittent scratch detection method based on adaptive sector scanning algorithm (ASC) cascading mean variance threshold algorithm (MVTH). In the preprocessing step, dividing the original image into subimages with a number of integer multiple of cpu cores so as to fully compress image processing time utilizing parallel processing, using mean filter to balance background and then obtaining binary subimages utilizing morphology and threshold operations, finally, utilizing Two-pass algorithm to label the connected domains of binary subimages. In the detection step, considering the complexity of the pattern of intermittent scratches, ASC is first used for routine intermittent scratches stitching and then supplemented by MVTH. In the verification step, in order to prove that the detected intermittent scratches satisfy the criteria for scratches in human eyes, the method of support vector machine (SVM) pattern recognition is utilized to compare the detected results with the continuous scratch samples detected by human eyes. This algorithm has high degree of parallelism, high speed and strong robustness. The experimental results illustrate that the complete extraction rate of intermittent scratches is 93.59% , the average processing time of single image is merely 0.029 second and the accuracy rate of detection is up to 98.72% by SVM verification.

Polarization distortion is a phenomenon which the polarization state of output light deviates from the theoretical expectation. Due to the design defects and process limitations, polarization distortion in beam splitter is inevitable, which results in the significant errors in the optical systems. A theoretical analysis method based on Mueller matrix is proposed for characterizing the beam splitter. In the propose approach, polarization distortion in the beam splitter including depolarization, linear and circular birefringence, and linear diattenuation, circular dichroism have been considered. With the proposed method, we can characterize the beam splitters and extract the related effective optical parameters of polarization distortion. The Mueller matrices of two different commonly used beam splitters measured by a commercial Mueller matrix ellipsometer (MME) are consistently fitted by the proposed method and the residual errors have shown the improvement compared to the conventional methods.

Under the condition that comparison results are Gaussian distributed with a common mean, a chi-square statistics of arithmetic mean is proposed and investigated through the Monte Carlo simulation. Simulation results show that the arithmetic mean has its own (n – 1)th-order chi-square statistics under the condition that the uncertainties of participants are comparable. Furthermore, the density curve of the proposed statistics is confined between the (n - 1)th-order and first-order chi-square under the condition that the uncertainties of participants are incomparable. However, the expected value of this statistics equals n – 1, which is unaffected by the uncertainties. Based on these properties, the proposed statistics is applied to the consistence testing of arithmetic mean by examples.

As the basic element of a road, road edges are of great significance for intelligent transportation and urban foundational geographic information construction. Mobile laser scanning (MLS) provides an effective way to extract road information, but it is difficult to extract accurate road edges from a large-scale dataset with complex road conditions. In this paper, we propose a method to extract road edges from MLS data based on a local planar fitting algorithm. First, scanning lines are extracted based on the horizontal projection distance between the laser points. Second, a planar fitting method is adopted to extract road curb points. Road curb points are then clustered and optimized by differentiating the distance between road curb points and the auxiliary line. Finally, a linear least squares fitting method is applied to obtain the road edges. Three experimental datasets with multi-type road markings were used to evaluate the performance of the proposed method. The results demonstrate the feasibility and effectiveness of the proposed method.

The angular displacement sensor based on time-grating is a novel kind of displacement sensor, but there is a limitation in some applications with harsh environment owing to extracting angular information uses the analog phase detector. To reduce the error comes from solution and improve the static stability of sensor, a novel signal process system is presented. In comparison to the traditional method using analog electrical technology to obtain angular displacement, the proposed method uses the All phase Fast Fourier transform (AP-FFT), that has a perfect performance on suppressing the spectrum leakage and the property of phase invariant, to obtain the phase angle. In the paper, we design the core system for data sampling and processing. Firstly, it utilizes AP-FFT to transform the sensing signal from time domain to frequency domain; in addition, the angle is calculated in the phase spectrum. Finally, the experimental platform is designed to verify the performance of the proposed technique. The error of the novel method is compared to that of the traditional method, it can be concluded that the proposed method is very effective in suppressing noise and enhances the stability in a static condition.

With the maturing of liquid crystal technology, liquid crystal variable retarder (LCVR) has been widely used in optical systems. In practice, it is of great importance to characterize the polarization properties of the LCVR for its control and applications to accurately modulate the polarization state of the light in the optical systems. In this paper, the Mueller matrix ellipsometry (MME) is applied to comprehensively characterize the polarization properties including the retardance and the fast axis azimuth of the LCVR versus the driving voltage, the wavelength, as well as the incidence and the azimuth of the light. An analytical model is constructed to describe the LCVR based on the Mueller matrix calculus, in which the influences of the incidence and the azimuth of the light are considered. A house-developed spectroscopic Mueller matrix ellipsometer is employed to perform the experiments. Simulations and experiments about a commercial LCVR product are presented and discussed to verify the proposed method.

Aimed at the problem of strong background interference introduced in digital image processing from complex surfaces under industrial defect detection, a method for complex surface defect detection based on human visual characteristics and feature extracting is proposed. Inspired by the visual attention mechanism, defect areas can be identified from the background noise conveniently by human eyes. We introduce the improved grayscale adjustment and frequency-tuned saliency algorithm combined with the salient region mask obtained by dilation and differential operation to eliminate the background noise and extract defect areas. Meanwhile the directional feature matching and merging algorithm is applied to enhance directional features and retain details of defects. Testing images are captured by our established detecting system. Experimental results show that our method can retain defect information completely and achieve considerable extracting efficiency and detecting accuracy.

Quantitative determination of dimensional properties like length, diameter, height, etc. is essential in research, development and in production process control. To meet these requirements, the widely used approach is the coordinate measurement technique. The equipments - the coordinate measuring machines (CMMs) – using the mentioned technique cover a wide measurement range from meter to nanometer. Below a newly developed equipment for the micro scale is presented. The system – the micro coordinate measuring machines (μCMM) - consists of a probing system, voice coil based actuators and an integrated interferometric measurement system. The key component - in addition to the probing system – is the positioning stage, since the characteristics of the position acquisition and control directly influences the achievable accuracy of the complete measurement system. In contrast to a standard interferometer the presented system utilizes a 2D CMOS image sensor to capture the measurement signal. To drive the stage, a commercial voice coil actuator is used: the scanning range of the introduced system covers about 15 mm, and can be easily extended. The applied probing system uses a ruby ball stylus probe. It is a measuring probe, which means that it provides a signal corresponding to the occurring deflections of the probe ball for all three spatial directions. The probe achieves nanometer resolution.

Probe tip of the Micro-coordinate Measuring Machine (Micro-CMM) is a microsphere with diameter of several hundred microns, and its sphericity is generally controlled at tens to hundreds of nanometers. Due to the small size and high precision requirement, the measurement of the microsphere morphology is difficult. In this paper, a measurement method for probe microsphere of Micro-CMM is proposed based on two SPM (Scanning Probe Microscope) probes, and a ruby microsphere of a Renishaw commercial CMM stylus is measured by the proposed method. In the experiment, the repeatability error of a maximum section profile is test, and the repeatability error is 41 nm (peak-to-peak value). Two perpendicular maximum section profiles are measured, and the corresponding diameter and roundness are estimated by the least squares method.

In order to alleviate the ill-posed problem of the ill-conditioned equation, the regularization algorithm combined with averaging method is used to retrieve the aerosol particle size distribution. In this method, the selection of the optimal average interval is crucial. According to the spectral of LED, fourteen wavelengths for the LEDs are selected, and different optical parameter combinations are set. By the retrieval of multiple sets of original volume concentration distribution and error statistics, the optimal average interval of each optical parameter combination is obtained. The retrieval simulations of logarithmic-normal volume concentration distribution were completed. The simulation results show that when using a combination of ten backscatter and ten extinction coefficients, the reconstructed monomodal distribution has the best fitting effect, and the relative error of effective radius and volume are the smallest. And when using a combination of six backscatter and six extinction coefficients, the reconstructed bimodal distribution has the best fitting effect, and the relative error of effective radius and volume are the smallest.

CG-6 is a new generation of full-automatic relative gravimeter produced by Scintrex Company, Canada. It can be used to measure the vertical gravity gradient. This paper mainly addresses dynamic precision of CG-6 relative gravimeters in the vertical gravity gradient measurements during the Comparison of Absolute Gravimeters. This paper analyzes the repeatability and consistency of 4 CG-6 gravimeters in dynamic test. We process the static and dynamic experimental data of 4 CG-6 gravimeters. Results show that the dynamic precision of CG-6 gravimeters in vertical gravity gradient measurements is better than 3μGal¹. The static drift rates are all less than 3μGal ∙ h^-1. One of the CG-6 gravimeters has been used to monitor the NIM (National Institute of Metrology, China) local gravity network, especially in measuring the vertical gravity gradients. This allows for an evaluation of the overall dynamic performance of CG-6 gravimeters and their stability concerning highly precise determination of vertical gravity gradients for the micro-gravity network.

An extrinsic Fabry-Perot interferometric fibre microphone based on polydimethylsiloxane, or PDMS, diaphragm was proposed. The large free-standing PDMS diaphragm, with a diameter of 4 mm, is prepared by a simple “spin-strip” process. The experimental result shows that the fabricated sensor has a high dynamic pressure sensitivity of about -136 dB re 1 rad/μPa in the range of 100~2000Hz. The noise equivalent acoustic signal level of the microphone, limited by the environmental noise, is about 1000 μPa/Hz^1/2. And the dynamic range is tested to be more than 47.48 dB. The proposed microphone is expected to be used in the field of weak acoustic pressure testing.

For the mechanical industry, bolts are an important guarantee for the safety of connection between parts. The traditional method for monitoring bolt loosening is mainly through human judgment, but this method has a large error and cannot be monitored online. At present, the dynamic change process of the bolt loosening can be learned in more detail through the Lamb wave monitoring technology. In this paper, the piezoelectric transducer(PZT) is used to generate the Lamb wave in aluminum structure to monitor the looseness of the bolt on it. The signal with bolt looseness information received by another PZT is analyzed and processed. The S0 modal of the signal is chosen to extract the amplitude of it. After analysis it can be seen that the amplitude of the S0 modal reduces as the bolt gone loose. The relationship between the amplitude and bolt looseness have been drowned. And the functional relationship is presented.

Aiming at the requirement of high-precision and high-efficiency measurement of crankshaft grinding machining, a new method for measuring the geometrical characteristics of crankshaft in-situ is proposed and a crankshaft grinding in-situ measurement system is constructed by this method.In the first place, the overall plan for in-situ measurement system is formulated to confirm the composition of the in-situ measurement system.In the second place, the new type of measurement device is designed and constructed to convert the change in size into the change in inductance to analyze the geometric characteristics of the workpiece during machining.Geometric error operation operator based on the new generation Geometrical Product Specification (GPS) is constructed.And mathematical models for on-site machining measurement such as shaft diameter and roundness are established.The final step is to design the measurement and active measurement controller then develop its corresponding software. The real-time geometric feature information of the crankshaft machining acquired by the measuring device is obtained, analyzed and applied to the control and adjustment of the workpiece geometry in the grinding process.Through experiments, it can be proved that the in-situ measurement device can greatly improve the production efficiency and precision of crankshaft grinding.

With the development of portable intelligent instrumentations, the demand for high-precision, absolute-positioning, low-cost and compact-size angular position sensors has substantially increased. In this paper, a novel miniaturized capacitive angular position sensor based on time-grating, which adopts a reflective structure to realize absolute position measurement and simultaneously achieve high-precision, is proposed. The sensor is comprised of a stator and a rotor both covered with three rings of metal electrodes. The middle ring of the sensor adopts a single-row structure to obtain a high-precision initial travelling signal and reflect it to the stator through the outer ring. The inner loop obtains the final travelling signal through the second modulation signal. The phase difference between the final travelling wave signals and initial travelling wave signals varies periodically with a period of 360° when the rotor rotates; thus, this phase difference can be used to realize the coarse absolute position measurement. Phase detection is realized using the time pulses interpolation technology of time-grating, and the angular displacement is measured with time. High-precision absolute angular positioning is achieved through a compact structure. A prototype sensor with an outer diameter of 60 mm and an inner diameter of 24 mm is fabricated by printed circuit board technique to evaluate the performance. Experimental results show that the proposed sensor achieves a ±3″ measurement accuracy over an entire circumference. Moreover, the rotor is wireless owing to the reflective structure, which has a wider range of applications in engineering.

The analysis of Key Comparison data is to determine the Key Comparison Reference Value (KCRV) and its uncertainty. In the current model, the weighted mean is used as KCRV which is put forward by M, G, Cox. However, the method qualifies the measurement results as Gaussian distribution and does not apply to T distribution or other, which causes the risks of chi-square test failure. When the data analysis is invalid based on conventional statistics, the Bayesian approach may be a valid and welcome alternative. Bayesian inference is often required to solve high-dimensional integrations which Markov chain Monte Carlo (MCMC) is such a method. Here is a simple example used to illustrate the application of this method in metrology. The Metropolis-Hastings algorithm is the most flexible and efficient algorithm in MCMC method. In this paper, its basic concepts are explained and the algorithm steps are given. Besides, we obtain the KCRV and its uncertainty using the Metropolis-Hastings algorithm through MATLAB. Then, the convergence of MCMC is diagnosed. In principle, the MCMC method works for any starting value and any proposal distribution. In practice, however, both choices affect performance. We illustrate this influence with the example.

Tensile, compressive and universal testing machine (Hereinafter referred to as testing machine) is an important instrument for analyzing the pressure of materials. In order to reasonably assess the influence of the deformation of the beam and fixture on the strength analysis of the tested material, the deformation of the beam and fixture of the tested machine, which under the stress state, should be studied. Firstly, the laser interference method is proposed to measure the mechanical deformation characteristics of the beam and fixture. Secondly, we should analyze the structure and theory of measurement technology, give the test method and then calculate the relationship between the deformation of crossbeam and fixture and the stress. Finally, the experimental data are summarized, and the numerical correction method of material shape variables is obtained when testing materials are measured. The experimental results show that the shape variables between the beam and fixture of the testing machine reaches to 0.57mm when the force value reaches to 5 kN. By using this measurement method, the shape variables of the beam and fixture of the testing machine can be measured accurately, and the material deformation can be corrected relevantly during test and analysis of the material strength, which can improve the measurement accuracy of the material deformation for the testing machine.

As for chromatic confocal sensor system with limited computational capacity, a fast peak extraction algorithm with considerate accuracy is in urgent demand. However, current peak extraction algorithms such as the centroid algorithm (CA) and nonlinear fitting algorithms can not balance the accuracy and computational efficiency. Thus, we propose an accurate peak extraction algorithm with good computational efficiency called corrected differential fitting algorithm (CDFA). At first, the differential signal derived from the original axial response signal is linearly fitted for initial peak extraction. Then corresponding systematic error of this linear fitting operation is analyzed using a first-order linear nonhomogeneous differential equation. At last, error compensation, that is, the solution to this equation is implemented with an introduction of "sum differences of sampling intensity". The performance of CDFA is compared with two conventional peak extraction algorithms including the CA and Gaussian fitting algorithm (GFA) using Monte Carlo simulations. CDFA is found to have a comparable accuracy performance with GFA while have a much higher computational efficiency.

This paper aims to evaluate the task specific measurement uncertainty for gear measuring instrument (GMI) using virtual gear measuring instrument (VGMI). With the aid of Modular Simulation and Monte Carlo method, the uncertainty evaluation model is established on VGMI. The measurement uncertainty of the tooth profile deviation is evaluated by VGMI taking the tooth profile deviation of the involute cylindrical gear as the measured parameter. The uncertainty sources are considered in the simulation including the geometric error, the head error and the workpiece installation error. To verify the measurement uncertainty model of VGMI, we designed three involute tooth surface models with different reference precision, and their profile deviation measurement uncertainties are simulated by VGMI. The results show that VGMI is feasible, effective and correct for the measurement uncertainty evaluation. VGMI provides a new tool for evaluating the task specific measurement uncertainty for the gear measurement instrument. It can realize the seamless connection with the real measurement software. The ability to change measured workpiece model without reestablishing the VGMI model is also a significant advantage.

Dual-comb generation with bidirectional fiber ring laser is highly prospective for its compactness and coherency. In this paper, we propose a dual-ring hybrid mode-locked fiber laser for dual-comb generation. The dual-ring laser contains elements of hybrid mode-locking for each sub-ring individually, while sharing the bidirectionally pumped erbium-doped fiber (EDF). The hybrid mode-locking is realized by transmission semiconductor saturable absorber (SESA) and nonlinear polarization evolution (NPE). With the help of two three-port optical circulators, non-ideal reflection of two SESAs are eliminated. Accordingly, two series of short pules are generated in each sub-ring with different direction individually. Experimental observations and analyses demonstrate that dual comb of about 300 kHz difference in repetition rates are generated by inserting a 10 cm cavity length difference between the two sub-rings. With the help of hybrid mode-locking and large power bidirectional pumping, the mode-locking of dual combs are stable and self-starting.

In order to reduce the additional influence of the thermal-force coupling deformation of the Computerized Numerical Control(CNC)machine tools bed based on the grating measurement, the concept of the thermal-force coupling deformation critical point in the direction of the grating installation line of the machine bed is proposed. In order to accurately determine the thermal-force coupling deformation critical point of the machine bed, the BV75 CNC machine tool is taken as an example. The factors that cause the deformation of CNC machine bed are analyzed by using material theory, thermos-elastic and nonlinear thermal deformation theory. According to the actual structure size of the machine tool ,a 3D model is established. The heat sources and load conditions of the machine bed deformation are theoretically analyzed, and the finite element thermal- force coupling analysis of worktable is carried out. The deformation critical point in the direction of grating installation line of machine tool bed is determined by theoretical modeling and finite element analysis. Under loading single heat source, the multi heat sources and the different size and position load, the comparison experiments of the thermal deformation of the machine bed and the zero shift errors of the grating measurement are carried out. The experimental results show that the bed thermal deformation is the main source of the grating additional error, and the workpiece loading position will cause the bed deformation. The position of thermal-force coupling deformation critical point is different from the thermal deformation critical point. The zero position and the indication error of the grating can be reduced by fixing the grating on the thermal-force coupling deformation. An accurate grating error prediction compensation model can be established, which is use for the subsequent error compensation of the on-machine measurement system of the CNC machine tools.

In order to achieve a large area of deep soil moisture monitoring, a soil moisture sensor based on fiber Bragg grating was designed. The polyimide with high water sensitivity and high linear expansion coefficient was coated to the surface of FBG. The center wavelength of the FBG will change due to moisture absorption and expansion of the polyimide material when moisture changes. Using this basis principle, the soil moisture can be measured. A stainless steel tube with a hole is used as a sensor package and wrapped in polyurethane nets to maintain consistent with the external temperature and moisture environment and prevent soil from entering the sensor. A fiber Bragg grating without a PI coating layer was packaged in the same package structure with the soil moisture sensor as a reference fiber for temperature compensation. An experimental system was set up, calibration experiments were performed on the sensors, and various performances of the sensors were tested. The experimental results show that the measuring range of moisture is 15%RH~75%RH, the sensitivity is 12.6pm/%RH, and the accuracy of the sensor is ±10.26%.

The Articulated Arm Coordinate Measuring Machine (AACMM) is a kind of coordinate measuring devices in the form of an articulated robot. To improve the accuracy of AACMM, a kinematic identification method is presented in this paper. Firstly, we perform the kinematics modeling and simulation to realize the kinematic transformation from the joint space to the coordinate space. Then, we establish an error model and use least squares method to identify kinematic parameters. And the effectiveness of the least squares method for kinematic parameter identification is studied. Finally, the experiments of single point repeatability accuracy and the standard gauge accuracy are performed. The experimental results show that proposed the kinematic identification method can effectively improve the measurement accuracy of the joint coordinate measuring machine.

With the continuous improvement of equipment measurement accuracy and production efficiency requirements, calibration method with external reference standard can no longer meet the quality and efficiency requirements. In order to solve the online calibration problem and effectively improve the calibration efficiency of the Articulated Arm Coordinate Measuring Machines (AACMMs) in practical application, a self-calibration system of circular grating angle sensor which is applied to joints of the AACMMs was established. Based on the harmonic analysis of the angle measurement error, this paper deduces and analyzes the error suppression principle of the layout of the scanning heads on the calibration result, and establishes a non-uniform layout of the scanning heads to eliminate more and higher order harmonic errors. The simulation and test results show that the self-calibration method using this layout form of multiple reading heads can effectively reduce the measurement angle error without increasing the number of scanning heads, and improve the calibration efficiency and measurement accuracy of AACMMs.

In order to research a new detection principle of capacitive sensor, a new capacitive sensor based on the edge effects of non-parallel polar plates is proposed in this paper. The capacitance field of the sensor includes two parts, the electric field between the polar plates and the edge electric field. When a special medium is in the edge electric field, it will change the distribution of the electric field line of the edge electric field and cause the change of the capacitance value of the sensor, and then the non-contact detection of the detected object can be realized. This paper studies the relationship between the range of the edge electric field and the basic parameters of the sensor. The model and formula of the sensor are analyzed theoretically in this paper, and these typical projects were simulated by ANSYS. The results show that the detection principle of the new capacitive sensor is reasonable and correct.

Laser tracker has been introduced successfully for geometric deviations calibration of multi-axis machine tools. In this paper, a new method called “pose measurement principle” is developed for measuring geometrical error of rotary axes by means of a single laser tracker and NC precise table. The reflector is mounted on the NC precise table with eccentricity, and the NC precise table is mounted on rotary table. A single laser tracker located at different base stations in order is used for coordinate determination of three fixed points of the reflector to get the pose information of rotary axes, then calculate the pose deviations and identify all the errors. For the error identification, first of all, with the extension of the definition of geometric errors, the 6 geometric errors is represented by pose deviation. Second, 3 angular errors are identified geometrically first, then eliminate the angular errors of all measuring coordinates to obtain the 3 straightness errors. Finally, the 6 errors mathematical model for rotary table is developed. The validity of the proposed method has been confirmed by simulations and experiments. From both of them, it has been confirmed that the proposed method gives precise results and is able to apply to the measurement of rotary axes effectively.

In order to measure the squareness of large-size workpieces, a method of squareness measurement based on laser alignment system was introduced. The structure and principle of the laser alignment system were presented. The squareness measuring method of the squareness measuring system and the laser alignment system were described respectively. This paper improved the method of squareness measurement based on laser alignment system and made the accuracy satisfied with the requirement of most in-site measurement. The experiments show that the squareness measurement accuracy of the laser alignment system can be improved to 5 μm/500 mm.

The resolution of optical microscopy fundamentally limited by diffraction is at best 200 nm. Super-resolution structured illumination microscopy (SR-SIM) provides an elegant way of overcoming the diffraction limit in conventional widefield microscope by superimposing a grid pattern generated through interference of diffraction orders on the specimen while capturing images. The use of non-uniform illumination field “shift” high specimen frequencies which are out-ofband into the pass-band of the microscope through spatial frequency mixing with the illumination field. Therefore the effective bandwidth of SR-SIM is approximately twice as conventional microscopy, corresponding to a 2-fold resolution enhancement, if the difference between excitation and emission wavelength is ignored. However, such a wide-field scheme typically can only image optically thin samples and is incompatible with multiphoton processes. In this paper, we propose a Super-resolution scanning scheme with virtually structured illumination, utilizes detection sensitivity modulation on line by programming or off line by numerical processing together with temporally cumulative imaging, the excitation intensity is constant while capturing images. In this case a nondescanned array detector such as CCD camera is needed. When combined with multiphoton excitation, this scheme can image thick samples with threedimensional optical sectioning and much improved resolution.

In visual detection fields based on line-structured light, the analysis of optical stripe image is a key problem. For the cross-line target image, through measuring the angle between two linear optical stripes the target position or some system’s parameters can be obtained. The traditional technique usually needs many preprocessing steps including image filtering, threshold segmentation, thinning processing and so on. For the images with low signal noise ratio or non-uniform intensity distribution, their application performance will be challenged. Based on the characteristic of translation invariance and rotation synchronization of two-dimensional Fourier transform, the paper combines Fourier transform with polar transform to form new Fourier-polar transform algorithm. It implements the angle measurement in the frequency-domain replaced in the spatial domain. At the same time, to improve the convenient of compute, the polar transform is adopted to calculate the distribution direction of amplitude spectrum energy. The proposed Fourier-polar transform algorithm uses the overall information of the image, and the calculating process is simple and no requirement of image preprocessing. Therefore, it can be applied to measure the angle of cross-line target image in low quality image such as low signal-to-noise ratio or with noise.

This paper proposes the microfluidic contact lenses for continuous non-invasive intraocular pressure (IOP) monitoring. The microfluidic contact lenses are the reference-sensing structure, fabricated by using the chemical assisted bonding and next thermoforming technologies. The curvature of contact lenses are made corresponds substantially to that of cornea, so as that, the PDMS (Polydimethylsiloxane) sensing layer can wear on cornea to “feeling” its expansion. The cornea’s deformation is varied in pace with IOP, while the IOP can be simply monitored by using the smart phone to optically detect the movement of visible liquid in the microchannels. The simulated and measured results of the devices with different parameters are presented, showing a good linearity. Also, we have found that the devices with outer distributed chamber or with the smaller microchannel were more sensitive. In next work, the devices will be redesigned to meet the needs of intraocular pressure monitoring and test in vivo.

Eye positioning is an important prerequisite for vehicle-mounted fatigue driving monitoring. In this paper, a windowed gray-scale integral projection algorithm based eye-positioning method is introduced. Firstly, the human eye is positioned by Adaboost algorithm, then the eyebrows are separated by the windowed gray-scale integral projection algorithm, consequently, the accurate positioning of human eye parts is achieved. The experimental results show that the separation effect is obvious and the speed of human eye positioning is significantly improved.

Advanced low frequency vibration calibration is imperative required as the wide applications of low frequency accelerometers. Low frequency calibration is commonly realized by the Earth’s gravity method or the laser interferometry. However, affected by the limited stroke of the standard vibration shaker, the calibration precision of laser interferometry at very low frequency is usually not ideal. Although the Earth’s gravity method can avoid this low calibration precision at very low frequency, its calibration frequency usually <5 Hz due to the influence of rotator centripetal acceleration. In this paper, the Earth’s gravity method mentioned in ISO 16063-16 is improved by using an effective image feature detection method. This method detects the angel between Earth’s gravity field direction and acceleration sensitivity axis direction to improve the Earth’s gravity static calibration accuracy.

The phase shifting shadow moiré is an efficient technique for 3-D shape measurement. Our recent research focuses on improving its measurement accuracy without addition the complication of the experimental set-up. Considering that the existing measurement process of shifting shadow moiré technique is complex, we had been looking for ways to make it easier. In this paper we propose some effective techniques to fulfil the aim. In the proposed method, the binocular stereovision technique is used to calibrate the geometric parameters of our setup. Then a method is developed to determine the grating translation difference. After that an iterative self-tuning algorithm is use to retrieve the accurate phase. The proposed method is fast and can be implemented easily in many applications. Optical experiments are implemented to verify the feasibility of this method.

In this paper, the quadrupole electromagnetic tweezer installed in a fluorescent microscope was developed for the purpose of achieving precise control of magnetic microspheres’ motion trajectory. The key technologies of magnetic microsphere control and positioning by such quadrupole magnetic tweezers were systematically studied. An electromagnetic quadrupole magnetic tweezer system was designed and constructed, a current-magnetic force model of the quadrupole magnetic tweezer was established, and the magnetic force-current inverse force model was derived and simplified. A fluorescence microscopy imaging system was set up and the related program design was completed. The position of magnetic fluorescent microspheres was monitored by a high-speed CCD with sampling frequency of 200 Hz. A proportional-integral closedloop feedback controller was built up for magnetic microspheres. The experimental results demonstrated that the magnetic force range available at the center of the work area was [-80pN, 80pN]. Besides, magnetic microspheres were tested to possess a displacement resolution up to 400 nm as well as the capacity of moving in any direction in a two-dimensional plane. Based on the obtained results, it is expected that the quadrupole electromagnetic tweezer can function one of the effective devices for evaluation of cell mechanical properties.

Robotic mass measurement system, which used automatic measurement and data processing, has become the trend of the high accuracy mass measurements. In international comparison and mass-related scientific research, automatic measurement system together with ABABAB weighing cycles can reduce or eliminate the linear drift greatly and improve the accuracy of measurement results further. In this paper, three linear drift error elimination methods of ABABAB weighing cycle model were analyzed, and the corresponding mathematical expressions of error calculation were given, then experimental data was analyzed and compared. All of these three methods based on ABABAB weighing cycle can be applied for automatic measurement in the future.

The motion measurement based on machine vision has been more and more widely used in robots, object tracking and other fields. However, the relative motion between camera and object often causes images blurred, which decreases the reliability of detection. To improve the detection accuracy of the motion-blurred images edges, a comprehensive method is proposed. By analyzing the grayscale distribution of the object images in different motion directions, we used different methods to enhance the low frequency sub-band images which were obtained by wavelet transform. The subpixel edge detection method based on cubic spline interpolation was applied to detect the edges of the blurred and enhanced images, respectively. Experimental results show that the proposed method avoids the misdetection of the blurred images edges, and obtains higher edge detection accuracy.

Atmospheric disturbance influence the measurement accuracy greatly in laser precision measurement of long distance. A real-time filtering algorithm based on time series analysis theory is proposed in this paper. Firstly, ARMA (Auto-Regressive and Moving Average) model of sample data is set up based on the theory of time series analysis, then the mathematical expectation is obtained according to the model as the filtering result, finally, it is integrated into the laboratory laser beam drift measurement system for real-time filtering measurement. It is evident from the simulation results that high accuracy can be obtained after filtering. The experimental results show that the stability of the filtered drift increases by about 20%.

The paper describes a new torque standard machine at NIM. The new reference torque standard machine is designed to calibrate the reference torque wrench and torque transducer. The relative expanded uncertainty of this torque standard from 10Nm to 5000Nm is better than 5×10^-4（k=2）. The calibration experiment of three kinds of reference torque wrenches by the new reference torque standard machine is described in the paper.

The strain transfer characteristics of resistance strain-type transducer were theoretically investigated. A resistance straintype transducer was modeled to be a four-layer and two-glue (FLTG) structure model, which comprises successively an elastomer, a ground adhesive, a substrate layer, an upper adhesive, a sensitive grids layer, and a polymer cover. The strain transfer progress in a resistance strain-type transducer was described by the FLTG structure model. The strain transitional zone (STZ) was defined and the strain transfer ratio (STR) of the FLTG structure was formulated. The dependence of the STR and STZ on both the structural sizes and material parameters were calculated. The results indicate that the ground adhesive (including its thickness, and shear modulus) have a greater influence on the strain transitional zone ratio and strain transitional zone. In order to ensure a higher sensitivity of the resistance strain-type transducer, the ground adhesive layer should be as thin as possible, while its shear modulus should be as large as possible. Selecting a ground adhesive with a large elasticity modulus can effectively reduce the influence of the thickness of the ground adhesive on the strain transfer ratio.

In order to balance the high translation stiffness and low twist stiffness in an H-drive precision stage with a large span, a design method based on flexure hinges combination is proposed. Firstly, various stiffness requirements in different degrees of freedom (DOF) of an H-drive precision stage with a large span are analyzed. Secondly, half-cartwheel flexure hinges combination is applied to balance these stiffness requirements. Thirdly, based on the Timoshenko beam theory, stiffness matrices of a single flexure hinge and combined hinges are established. Then, various structural parameters of the flexure hinge are determined by analyzing their influence on two performance indicators, including stiffness and motion precision. After that, finite element method is applied to verify these theoretical results. Finally, a stiffness identification experiment and a modal analysis experiment are conducted to test the 2-DOF stiffness of a single half-cartwheel flexure hinge and the natural frequency of the H-drive precision stage. The maximum error of stiffness between theoretical, simulation and experimental results is 13.4%. The natural frequency is up to 176.563 Hz, which could satisfy the control bandwidth requirement of the H-drive precision stage.

The 10^th International Comparison of Absolute Gravimeters (ICAG-2017) was held in Changping campus of National Institute of Metrology (NIM), China in October 2017. The observation of gravity variations using relative gravimeters plays an important role in absolute gravimeter comparison and the link of gravity reference value after comparison. We carried out a continuous observation of gPhone gravimeter-119 simultaneously alongside a superconductive gravimeter iGrav-012 for several months. The calibration factor of gPhone-119 is determined to be 0.99355±0.00004 with a precision of 0.004%. When the observation time exceeds 33000 minutes, the calibration values and uncertainties tend to be stable and the precision is better than 0.01%. The non-tidal gravity changes during ICAG-2017 recorded by gPhone-119 are analyzed. The tendency of gravity variations is roughly consistent with that recorded by iGrav-012. The result indicates that the peak-to-peak value of gravity changes is less than 1.5 μGal during the period of ICAG-2017.

High precision occupies an extremely important position in the field of mechanical processing and laser measurement. Under these high precision requirements, image processing is widely applied and is especially demanding. As the essential pre-processing step in the process of image processing, the quality of image edge extraction directly affects the processing precision of the whole image, and then affects the final measurement or machining precision. The traditional edge detection method has the defects of no noise immunity, and cannot achieve high-activity processing of sophisticated image edge problems. Through the in-depth research and analysis of various knowledges concerning edge extraction, a novel anti-noise edge detector based on multi-structure elements morphology of different directions for binary, gray scale and color images is proposed in this paper. We get the final edge information by using eight morphological operations respectively and synthetic weighted method. It can remove the noise effectively while detecting complete edge information. Experimental results show that, comparing with conventional edge detection operations, the proposed method attains the outcome of eliminating the image noise and maintaining good edge effectively for simulated image.

In view of the traditional method of corner extraction, the main idea is to improve the corner extraction algorithm and ignore the imaging process of the calibration image, in this paper, an optimal polarization angle image corner extraction algorithm based on linear polarization feedback is introduced in the process of camera calibration, this method is mainly aimed at the problem of high-light regions which are difficult to detect and eliminate in the multi-position calibration image of space under natural light. The method firstly adopts the linear feedback of Stokes variable through a CCD camera with polarizing plates and obtains the corner image of the optimal angle of the checkerboard lattice in different positions in space, then we use the sub-pixel level detection algorithm and GAUSS's fitting method to precisely locate the corner points in the image and to solve the sub-pixel coordinates of the image corner, at last, the two-dimensional pixel coordinates of the corner points in each checkerboard image are extracted.

The curved wavefronts of a Gaussian beam used in absolute gravimeters introduce a systematic error in the measured gravity value. Diffraction correction is defined to denote the correction of the error. This paper presents an evaluation of the diffraction correction for some absolute gravimeters participated in the 10^th International Comparison of Absolute Gravimeters. An automatic M²-measurement instrument is introduced to achieve an efficient and accurate measurement of the beam waist diameter. On the basis, the diffraction corrections are calculated and estimated. The results indicate that the waist diameter of two laser beams deviates from the typical value. After optimized, the diffraction corrections of all the estimated AGs are less than 2.4 μGal. The accuracy of the correction is better than 0.1 μGal. This work is of great significance for improving the accuracy of the gravity measurements in the comparison.

An improved two dimensional micro-/nanoradian angle generator (2D-MNAG) with single rotation center located on the tilting plane and error compensation of capacitive sensors is presented in this study. The 2D-MNAG is structured on an optimized flexure hinge with single rotation center in orthogonal axes. The rotation center is located on the center of tilting plane of 2D-MNAG so that there is no linear displacement coupled in the angular output of the tilting plane. Three capacitive sensors are used in the 2D-MNAG to monitor the angular output for feedback control. The principle error of capacitive sensor while used in angle measurement is compensated using an established model, thus to improve the accuracy and repeatability of the angular output. A synthetic output error of 0.212 arcsec of 2D-MNAG is obtained using Monte Carlo simulation while the distance from rotation center to each driving and angle monitoring point is 40 mm with manufacturing and mounting errors in the range of [-0.01, 0.01] mm in rectangular distribution. The performance of the angular output monitoring unit and the strategy for closed-loop control are the key for improving the 2D-MNAG while the mechanical structure and driving unit are optimized.

We investigated the determinations by the micro-morphology of the sensitive grids of resistance strain gauge on their stress distributions. The micro-morphologies of the sidewalls for four typical resistance strain gauges were observed by scanning electron microscopy (SEM), and then the microscopic images were binarized to obtain the micromorphological characteristics of the sensitive grids. The observation shows that the sidewalls of the sensitive grids have periodic microstructures. A geometrical model of sinusoidal contour and a strain transfer model was established following the observed micro-morphological features. The influence of the amplitude and period parameters of the sinusoidal contour on the stress level of the sensitive grid was calculated numerically. The results show that the maximum stress increases, however the average stress decreases, with the increase of the profile amplitude with a certain periodicity. For a sinusoidal profile having a fixed amplitude, its maximum stress decreases with the increase of the cycle, wherever the average stress increases. The smaller side wall defects and longer interval in a sensitive grid would make the stress distribution more uniform. The obtained results would provide guidance for the fabrication of the resistance strain gauge.

Standard geometry element fitting software is a critical important part of the coordinate measuring machine ( CMM ). It is used for coordinate data processing and data evaluation. At present, the commercial fitting software of the coordinate machine manufacturer is not disclosed to the public. So it is inconvenient to develop secondary applications. This work developed a kind of geometric element fitting software based on open source code. The software can be used to fit CMM measurement data to common geometric elements including lines, circles, planes, spheres, cylinders, and cones. The core algorithm of software is based on a least-squares algorithm and a Gauss-Newton iterative algorithm. Least squares is a data optimization technique that seeks the best function match of the data by the sum of the squares of the smallest errors. The basic idea of the Gauss-Newton iteration method is to replace the nonlinear regression model with the Taylor series expansion approximation. Then through multiple iterations, the regression coefficient is modified several times so that the regression coefficient continuously approaches the optimal regression coefficient of the nonlinear regression model. Finally, the residual square sum of the original model is minimized. The accuracy of fitting results are verified with the standard reference data developed by national institute of standards and technology. The software can be used to the geometry element measurement uncertainty evaluation.

Optical fringe is one of important output information from the optical systems. Some important optical or system parameters can be obtained by analyzing the fringe information from optical system such as interferometer system or diffraction setup. The straight fringe is a kind of optical fringes frequently appearing in Young’s double slit interference and single-slit diffraction and other optical structures. For the information extraction of straight fringes, it is often necessary to calculate the fringe spacing parameters. Popular straight fringes analysis methods include the fringe center method and the Fourier transform method. In addition, some image processing methods realized line detection can also be used to analyze this straight fringes image, which include Hough transform and Radon transform. In this paper, four algorithms for fringe analysis are discussed and compared, which focus on method’s principle, algorithm’s simulation and performance when they be applied to detect the fringes spacing. At the same time, the anti-noise performance of two image processing algorithms including Hough transform and Radon transform are analyzed.