Ailing Tian

Study on phase demodulation technique with fast and high accuracy for interference fringe pattern

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.

Research on rheological property of magnetorheological fluid

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.

Research of the wavefront detection method based on the scanning pentaprism

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.

Analysis of noise reduction performance with the rotated diffuser in Fizeau interferometer of a large aperture

Since the coherent noise affected the quality of the Fizeau’s interferograms in the large aperture, the coherence of the beam was changed by rotated diffuser to reduce the noise of the interfering system. The relationships between the frequency of the rotated diffuser, the contrast of the fringes and the SNR of the system were simulated. Then, the control parameters of rotated diffuser would be required in the optimum interference fringe. The interference images were obtained under different control parameters, and the fringe contrast and system SNR of each image were analyzed. The results showed that the contrast can be reduced by choosing the proper frequency of the rotated diffuser in a certain extent, but the SNR can be improved effectively and it was convenient to process the interference image later.

Study on light scattering characterization for polishing surface of optical elements

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.

Study on light scattering characterization for subsurface defect of optical element

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.

Front Matter: Volume 9449

This PDF file contains the front matter associated with SPIE Proceedings Volume 9449, including the Title Page, Copyright information, Table of Contents, Authors, Introduction (if any), and Conference Committee listing.

Microstructure measurement of digital holography

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.

Influence of shearing displacement error study on two dimensional lateral shearing interferometry

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

Study on polarization properties of particle's scattered light

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.