Effects of coherence on imaging systems problem has been discussed previously using many criterions and methods. But they don't consider the polarimetric properties of light. Polarization imaging of an edge object with partially coherent and partially polarized light are investigated and related to the parameters of an imaging system. Theoretical results are presented to describe the imaging parameters and the coherent and polarized field effects. the Fourier transform of the generalized Stokes parameters is discussed by it modulus and phase.
Based on the principle of bidirectional reflectance distribution function (BRDF), the relationship between the surface roughness and the spatial scattering distribution of the optical elements were studied. First, a series of optical components with different surface roughness was obtained by the traditional polishing processing, and measured by Talysurf CCI 3000. Secondly, the influences of different factors on the scattering characteristics were simulated and analyzed, such as different surface roughness, incident wavelength and incident angle. Finally, the experimental device was built, and the spatial distribution of scattered light was measured with the different conditions, and then the data curve variation was analyzed. It was shown that the experimental method was reliable by comparing the simulation and experimental results. Base on this to know, many studies on light scattering characteristics for optical element polishing surface can try later.
With the rapid developing of science and technology, large aperture optical system plays an important role in the hightech fields including space optics, astronomical optics, inertial confinement fusion, the detecting and recognizing of space target. However, the problems of the wavefront sensing about large aperture optical system has been totally solved because of the equipment expenses and long manufacturing periods. In order to test the large aperture elements in optical system with cheaper costs and higher resolution, more and more attentions are paid into the wavefront sensing of large aperture optical systems. The scanning pentaprism system is introduced to divide the wavefront of the interferometer into a series of sub-wavefront, and the relative positions of the spot centroid accroding to every sub-wavefront are recorded on the CCD camera. The normal directions of every sub-wavefront are obtained to reconstruct the tested wavefront. Experimental results are accord with the interferometer measure results. The feasibility of the pentaprism scanning method has been validated. Finally the influences of measurement apparatus and environment on the measuring precision is discussed. Which is useful to expand the measuring range to keep high spatial resolution and reduce cost.
In order to solve the injury of optical sight to shooters, which is produced by recoil for using artillery or firearms, and the usage problems of shooters’ eye mask, headband and gas mask, the ocular with long exit pupil distance has been designed based on optical sighting system. The optical properties and aberration characteristics of ocular with long exit pupil distance has been analyzed, the structural style with positive-positive-negative three lens groups has been put forward. According to the aberration theory and the isoplanatic image formation principle, the focal power assignment expression has been deduced by adopting analytical method. By using of optical design software ZEMAX, the ocular with long exit pupil distance has been designed, the focal length of system is 20mm, the exit pupil diameter is 4mm, the field angle is 40°, the distance of exit pupil is 41mm, and the relative eye relief is greater than 2. The design results show if this method has been adopted, the transfer functions of each field are all greater than 0.15 when the ocular with long exit pupil distance locates on 45lp/mm, which can meet the use requirements of visual optical instruments.
Although most scientists and engineers working in the field of image acquisition and processing are well aware of the partially polarized nature of the optical fields used to form images, the effect of coherence on polarization imaging systems seems to have gone largely unnoticed. In this paper, the effects of polarization imaging of an edge object with partially coherent light are investigated theoretically and experimentally. We have extended the use of edge trace analysis in the evaluation of optical system performance and presented theoretical analysis on polarization imaging of an edge object with partially coherent and partially polarized illumination. Some interesting effects, such as the edge ringing and shifting in Stokes vector image construction, have been demonstrated experimentally.
Aiming at the effect of converge laser light scattering caused by subsurface micro-defect, and the change rule of laser scattering modulation was studied. First, the geometry model is built by defect type; then, by finite element method based on electromagnetic theory, the scattering light intensity distribution and variation curve with different detection defect depth, which convergence light spot focus on, were researched by numerical simulation. Finally, simulation model was verified by comparing experiment. This research results are important to setup the mathematical relation between subsurface defect and light scattering, and realize quantitative detection for the subsurface defect of optical element.
Large aperture parabolic mirrors are widely used in high technology areas, such as astronomical optics, space optics et.al. In order to obtain better optical performance, the lateral shearing interferometer was developed for characterizing the surface figure of parabolic mirror. Firstly, based on penta-prism and shearing optical flat, lateral shearing interferometry device was installed; secondly, the shearing phase was calculated by four-step phase shifting algorithm, the transform from shearing phase to primary phase was reconstructed through the selection of discrete sampling points and wave-front fitting, and the shearing interferometry software was programed. Lastly, through a concave parabolic mirror inspection, the precision of the shearing interferometer and the anti-vibration characteristic were verified.
In scalar coherence theory, the van Cittert-Zernike theorem plays an importance role for studying the propagation processes of partially coherent fields. In the past few years, a lot of work has been done to describe an extension of the van Cittert-Zernike theorem in terms of the 2×2 matrix to examine coherence and polarization properties of the field generated by a partially polarized incoherent electromagnetic beam. In this paper, we would like to experimentally demonstrate the unified theory of coherence and polarization of random electromagnetic beams by a modified radial shearing interferometer, which may be regarded as a tensor version of van Cittert-Zernike theorem. The experimental results show that the mutual intensity matrix of the electromagnetic field produced by a polarized incoherent source increases on propagation whereas the degree of the polarization remains unchanged.
Miniaturization is a development trend of electronics, machinery and information systems, while micro structure brought a large amount of new development for industrial and research applications, whereas, slow measuring speed and two-dimensional results of traditional micro measurement could not meet our needs, it’s urgent to find a matching testing techniques with more sensitivity, more effectiveness and better to have a real-time three-dimensional display. Digital holography applied to the measurement of micro structure, it made up for the lacking of traditional micro structure measure systems of too much time consuming, poor immunity, easily damaging samples with its simple structure, high accuracy, non contact features and three-dimensional reproduction. This paper analyzed the key factors of digital holographic recording and reproducing process.In order to solve the low quality of holograms captured by traditional recording system, holograms and pre-processing algorithm was combined for real-time, by observing the holograms and delicate adjusting the system, to ensure that the collected holograms with full use of CCD width while convenient for subsequent processing. In the processing of reproduction,the influence of spectrum choice, reconstruction wavelength and algorithms and unwrapping algorithm was been studied, and finally obtained an accurate three-dimensional topography of the object. The improved rerecording system and reconstruction algorithm mentioned above solved the low holography quality, much noise and not clear shortcomings of the reconstructed image. Experiment on a raster, compared with traditional system and algorithm results, results showed that the recording system and determine algorithms can reproduce the three-dimensional topography of the object with high precision and has a broader applicability.
Lateral shearing interference detection is a economically efficient method which is used to the online testing process of aspheric surface. Whereas, when shear plate is used in lateral shearing interference to detect large aperture aspherical surface, the real moving shear plate can produce shearing error, which brings error into the two-dimensional wavefront reconstruction of aspheric surface. So, for shearing error, Zernike polynomial fitting method is used to study shearing displacement error on the influence of two-dimensional wavefront information reconstruction by computer simulation. For the same measured non-spherical surface, different shearing displacement error influences on the precision of wavefront reconstruction are compared by computer simulation，and finally build the corresponding relations between wave information integrity and shearing displacement error
Due to environmental interference and atmospheric disturbance and other factors, the interference fringes are always drifting. So, the traditional hardware phase shift could not meet the high accuracy demodulation of interference. In this paper, virtual phase shift based on moiré fringes are introduced to realize the phase demodulation of interference fringe. The virtual digital phase shifting interference fringes are generated by computer, and superposed with tested interference fringe to generate phase shifting moire fringe, which are processed through applying phase shift demodulation techniques and the Fourior transform then to obtain the phase information tested. To verify the technique here, a specific experiment for a diameter of 50mm flat optics is executed, and the experimental result is compared with ZYGO-verifire PE interferometer. Our method eliminates the nonlinear error of the hardware phase shifter while improving the processing accuracy, and especially suitable for high-precision testing for optical component with complex environment or for large-aperture optical component, or even the system greatly simplifies the structure of interferometer.
In order to design a online diameter measurement system for Hot-rolled seamless steel tube production line. On one hand, it can play a stimulate part in the domestic pipe measuring technique. On the other hand, it can also make our domestic hot rolled seamless steel tube enterprises gain a strong product competitiveness with low input. Through the analysis of various detection methods and techniques contrast, this paper choose a CCD camera-based online caliper system design. The system mainly includes the hardware measurement portion and the image processing section, combining with software control technology and image processing technology, which can complete online measurement of heat tube diameter. Taking into account the complexity of the actual job site situation, it can choose a relatively simple and reasonable layout. The image processing section mainly to solve the camera calibration and the application of a function in Matlab, to achieve the diameter size display directly through the algorithm to calculate the image. I build a simulation platform in the design last phase, successfully, collect images for processing, to prove the feasibility and rationality of the design and make error in less than 2%. The design successfully using photoelectric detection technology to solve real work problems
It is important for particle detection technology to research the polarization properties of particle’s scattered light and explore the relationship between particle size and polarization degree of its scattered light. Particle scattering model was established and polarization properties of spherical particle’s scattered light with different sizes and different scattering angles was simulated using the finite element method. The polarization degree of particle scattered light were explored with different sizes, also were the polarization degree with different scattering angles. Results show that relationship curves between polarization degree and scattering angles can be described as parabolas. Polarization degree increases when scattering angles increase in the range of 0°-90° and reached the maximum value at 90°. Polarization degree decreases when the size of particle increase and this change more obvious gradually. The polarization degree of particle scattered light reached 1 at 90°when the particle size is much smaller than the wavelength and the maximum value of polarization degree decreases gradually when particle size increase further. In order to verify the correctness of the finite element simulation model, the polarization degrees were calculated in different particle sizes and different scattering angles by classical Mie scattering theory. Polarization simulation model of particle scattered light is proved to be correct and effective by making comparisons between simulation results and theoretical calculation results. This model lays a foundation for the further research on polarization characteristics of particle scattered light with different morphology and distribution.
Because of larger measurement ability of wave-front deviation and no need of reference plat, the lateral shearing interferometry based on four step phase shifting has been widely used for wave-front measurement. After installation shearing interferograms are captured by CCD camera, and the actual phase data of wave-front can be calculated by four step phase shift algorithm and phase unwrapping. In this processing, the pixel resolution and gray scale of CCD camera is the vital factor for the measurement precision. In this paper, Based on the structure of lateral shearing surface interferometer with phase shifting, pixel resolution more or less for measurement precision is discussed. Also, the gray scale is 8 bit, 12 bit or 16 bit for measurement precision is illustrated by simulation.
Micro optics characterization by use of digital holographic microscopy (DHM) is proposed recently. DHM can provide
phase image and very suitable for the quantitative mapping of transmission material with a certain refractive index.
However, it has been found that in DHM the microscope objective introduces a spherical phase curvature to the object
wave which may disturb the measurement especially for the micro-lens array. We present single lens characterization
and uniformity inspection of micro-lens array by use of a new concept DHM system developed recently. The new
concept DHM is based on a single cube beam-splitter (SCBS) configuration using an MO to provide high resolution on
the test specimen. The SCBS is put into the optical path with a small angle between the optical axis and its central semireflecting
layer. In this way, light is split into two parts when in and combined to form two holograms when out of SCBS.
For the symmetrical configuration of the beam splitter cube, the spherical phase curvature introduced by the MO can be
physically compensated during interference. Because no separated light propagation outside the SCBS, the whole system
is insensitive to vibration. As light coming out of the MO serves not only the object beam but also the reference beam, it
enables the inspection of the uniformity across a whole micro-lens array. Geometrical characterisation of the shape and
surface roughness of micro-lens is given as well as the uniformity analysis across the whole array.
In the technology of aspherical surface measurement, the phase shifting aspherical surface interferometer have widely
used, but the vibration error from the environment is the main factor that directly affects the measurement accuracy of
the phase shifting interferometer. In this paper, based on the structure of lateral shearing aspherical surface
interferometer, the resources and sorts of vibration error were introduced, and some methods to eliminate errors were
mentioned. The vibration influence on measurement results was analyzed. In order to reduce error, a new error
compensation algorithm was put forward. In this method, first, a vibration measurement theory was built. Then Based on
optic-electrical detection technology and image acquisition system and image process technology, the vibration mode of
lateral shearing interferometer was obtained. Finally the vibration error of fringe image can be compensated by image
correction. The measurement results can be obtained by the four-step phase shifting interferogram. The theoretical
analysis and simulative results demonstrate the feasibility of this approach to improve measurement accuracy.
Determining the location of the zero order fringes is one of the key aspects in scanning white-light interferometry.
The measurement principle of the scanning white-light interferometry is introduced at first; then the location of the
zero order fringes as calculated by four different algorithms; namely Weight-center, Phase-shift, Frequency Domain
Analysis (FDA), and Coherent Correlation are compared. Finally, numerical simulations on random generated
surfaces are done to reach conclusions by comparing and analyzing the results. The research is important in the
understanding and development of white-light interferometry.
As a new holographic display device, TFT-LCD (Thin Film Transistor Liquid Crystal Displays) is key technical component of holographic representation for easy controlled by computer. With the development of exquisite processing technology, that it instead of the traditional holographic plate become historical necessity and would be the development direction of holographic optics. Based on principles of holography and display character of LCD, the property which the LCD was used as a holographic plate was analyzed. The emphasis on discuss influence of LCD black matrix on holographic representation. First, analyzed on LCD pixel structure, the LCD pixel structure mathematical model was established. LCD was character representation by pixel structure parameters. Then, the influence of LCD pixels structure on holographic representation was analyzed by computer simulation. Meanwhile, the SONY LCX023 was chosen for holographic plate, the He-Ne laser which the wavelength is 0.6328um was holographic representation light source. The holographic representation system was established for test influence of LCD on holographic representation. Final, compared between computer simulations and optical experimental results, the mathematical model of LCD was proved to be true. When aperture ratio is 0.625, the holographic representation wouldn't be distinguished between representation images. At the same time, some useful results was acquired for improve application effects of LCD in holographic representation.
Referring to phase-shifting interferometry technology, the phase shifting error from the phase shifter is the main factor that directly affects the measurement accuracy of the phase shifting interferometer. In this paper, the resources and sorts of phase shifting error were introduction, and some methods to eliminate errors were mentioned. Based on the theory of phase shifting interferometry, the effects of phase shifting error were analyzed in detail. The Liquid Crystal Display (LCD) as a new shifter has advantage as that the phase shifting can be controlled digitally without any mechanical moving and rotating element. By changing coded image displayed on LCD, the phase shifting in measuring system was induced. LCD's phase modulation characteristic was analyzed in theory and tested. Based on Fourier transform, the effect model of phase error coming from LCD was established in four-step phase shifting interferometry. And the error range was obtained. In order to reduce error, a new error compensation algorithm was put forward. With this method, the error can be obtained by process interferogram. The interferogram can be compensated, and the measurement results can be obtained by four-step phase shifting interferogram. Theoretical analysis and simulation results demonstrate the feasibility of this approach to improve measurement accuracy.
The magnetorheological (MR) fluid is a new functional material. It is colloidal solution that solid grain was spread around fluid equably. It has been used in many regions for good controllable feature and mechanical feature. As for advanced optical manufacturing technology, magnetorheological finishing (MRF) was decided by the rheological property of MR fluid to a great extent. Take into account the need of MRF, the components of MR fluid were chosen, the evaluate system of rheological property of MR fluid was established. The effect on MR fluid by component scale is researched by experiments on measurement equipment. From that, the rheological property that magnetorheological fluids in the presence of an applied magnetic field and in the different shear strain rate was obtained. Meanwhile, the effect on MRF is researched by experiments on the MRF prototype machine e tool. The influence to surface quality was analyzed. The results shows that the relationship among the rheological property and the component scale of MR fluid and applying effect can be established by the theoretically analyzed and experiment research. The results provide the basis for MR fluid engineering development and engineering applications.
The aspherical measuring technology that based on computer-generated hologram (CGH) was introduced. The advantage
of this method is that the phase shifts can be controlled digitally, no any mechanical moving and rotating element. By
changing CGH coding which displayed on the Liquid Crystal Display (LCD), the wavefront and phase shifts in
measuring system were induced. Based on the characteristics of aspherical measurement and LCD structure, the CGH
encode technology used in LCD was discussed. Then a new encode method which applied to aspherical measurement
was put forward. In this method, the LCD modulates functions of amplitude and phase was coexistent, and the character
of LCD diffraction frequency spectrum was considered, and phase hologram was applied. This aspherical measuring
technology is more flexible than usual method. In this paper, the hologram encode method based on LCD were
illuminated in detail. In order to verify the correction of encode technology, the aspherical surface with standard
wavefront was generated by coaxial hologram reconstruct system when hologram encode image was displayed on SONY
LCX023 LCD, it interfere with the standard spherical wavefront, then the interferogram was sampled to computer by
Charge Coupled Device (CCD) and A/D transfer, the wavefront of hologram reconstruct was obtained by image process
finally. All calculation is completed by Matlab. An aspherical measuring system based on LCD was built experimentally.
Both the theoretical analysis and experimental results demonstrate the feasibility of this approach.
A profile measurement technique for objects with spatially isolated surfaces is presented. The technique is based on the Fourier fringe analysis combined with temporal phase unwrapping. A sequence of sinusoidal fringe patterns with a varying pitch is projected onto objects, and the temporal variation of the fringe signal is recorded with a CCD camera. The phase of the temporal fringe signal is detected at each pixel by the Fourier transform method, and is temporally phase unwrapped, independently from other pixels. The temporal frequency of the fringe signal estimated from the time slope of the unwrapped phase provides the information about the absolute surface heights of the objects. It will be shown that, because of its filtering function that can exclude higher order harmonics, the Fourier transform method is more robust to the nonlinear characteristics of a LCD projector and a CCD image sensor, than the phase shift technique that assumes a pure sinusoidal fringe signal. The measurement of objects with large discontinuities and/or spatially isolated surfaces is demonstrated by experiment.