Rihong Zhu

Frustrated total internal reflection evanescent switching

Abstract The mechanism of frustrated total internal reflection was analyzed according to the theory of optical film. The transmission and reflection functions were developed and the curves of transmission and reflection changing from the relative gap width d / λ , incident angle θ 0 , and refraction index n were shown in graphs. We proposed a scheme of experimental device to test the theoretical conclusion. A self-made electronic actuator drove the piezoelectric ceramics of FTIR. Experiments showed that the evanescent of transmission is 80% for He–Ne laser and smaller for YAG laser and Er:glass laser.

New algorithm on phase-shifting interferometry: the overlapping averaging 4-frame algorithm

Phase shifting interferometry (PSI) is a highly efficient and accurate phase measuring method. The accuracy of PSI is most seriously impaired by calibration error and nonlinearity in the phase shifter. This paper presents a new algorithm, the overlapping averaging 4-frame (OAF) algorithm, which can reduce the phase error due to phase shifter errors. The relationship between the accuracy of OAF algorithm and phase shifter errors is given. From this relationship, it is verified that the OAF algorithm can reduce the phase error due to phase shifter errors. The computer simulation providing the magnitude of a calibration error and nonlinearity in the phase shifter are shown for a number of different phase-measurement algorithms. From the analysis, the result is obtained that the OAF algorithm is more highly accurate than other phase-measurement algorithms.

Hyperspectral image compression using low complexity integer KLT and three-dimensional asymmetric significance tree

A lossy to lossless three-dimensional (3D) compression of hyperspectral images is presented. On the spectral dimension, a low complexity reversible integer Karhunen-Loève transform (KLT) is used to fully exploit the spectral redundancy, while two-dimensional spatial combinative lifting algorithm (SCLA)-based integer wavelet transform is applied on the spatial dimension. At the low complexity KLT, the calculation processing of covariance matrix is carried out on a subset of vectors that is pseudorandomly selected from the complete set of spectral vectors. The transform matrix is factorized into triangular elementary reversible matrices (TERM) for reversible integer mapping and the lifting scheme is applied to implement integer KLT. The 3D asymmetric significance tree structure is then constructed from the 3D asymmetric orientation tree in 3D transformed domain. Each coefficient is then encoded by the significance test of the 3D asymmetric significance tree node at each bitplane instead of ordered lists to track the significance status of the tree or block sets and coefficients. This algorithm has low complexity and can be applied to lossy to lossless progressive transmission.

Processing technique for interference pattern with step using phase-shift interferometry

Based on introducing the principle and method of processing technique for interference pattern with step using the characteristic of phase-shift interferometry. The paper has discussed a new phase-unwrapping algorithm for the phase map containing discontinuities. The correct phase values in the presence of discontinuities, especially those caused by the object with height steps, can be obtained. This algorithm is fast and accurate. The results of the measurement of three- dimensional object with height steps are presented. These techniques have been successfully applied to measure the surface and wave aberration of the system with step.

System for measurement of CCD parameters

This paper presents a system for measurement of CCD parameters that combines a photo-injection system and auto- focus systems. In the photo-injection system, a reverse microscope with plano-achromatic objective is used to produce a small light spot of (Phi) 2 micrometers . In the auto- focus system, astigmatic auto-focus method is applied. The auto-focus signal is detected by a simulation quadrate simulated by CCD. A piezoelectric transducer with high sensitivity and resolution is used to drive the focusing objective for a real-time control of the position of the small light spot which was required to be injected into one of pixels of CCD measured.

Ronchi test using overlapping averaging 4-frame algorithm

An automatic technique to process Ronchigrams is presented. The phase shifting error introduced by a phase shifter is reduced using overlapping averaging four-frame algorithm. A standard plano-convex lens is tested to verify the accuracy of this technique.

Realization of spherical absolute testing

Today, high quantities lens is more and more important to the optic-electric fields, and it brought about the demand of high accuracy testing of spherical surfaces. Absolute interferometric testing of spherical surfaces is a technical basis for establishing the spherical standard, and it is also an important application of computer aid interferometry. Partly work in the course of establishing the national spherical standard is introduced. A new method based on image processing has been developed instead of typical absolute testing which requires an eight-dimension mount whose cost is expensive and adjustment is very difficult. Interferograms sampled by phase-shifting interferometry can be processed to recognize the border of spherical surfaces. The key coefficients of position are in real time feedback to the operator to adjusting sphere precisely relative to the interferometer. This method can get more accuracy because of the high unison of three interferograms. This paper shows results of testing a 1/10 wave P-V sphere using two aplanats. It is easy to measure spherical surfaces to the accuracy better than 1/15 wave p- v.

Computer-aided testing for contact-type interferometer

Contact type interferometer is widely used equipment for testing relative length. It has been used to verify gauge block by metrology department because of its high accuracy. A computer-aided system based on it is introduced. There is a data acquisition system, including CCD and grabber etc., to detect and digitize interferograms instead of estimated by operator and avoids eyestrain. This system can analyze 2D interferogram automatically and quickly while both calibrate with monochromatic fringes and test with achromatic fringes. Many methods were used to analyze the 2D interferogram. It has been used by metrology department and its accuracy is better than 0.02 micrometers . Its resolution is better than the range per 1000 which is higher than the resolution estimated by operator. Different software has been developed to suit for different applications. One is the process-controlling software for verifying gauge block. The other is continuous- measuring software for testing tiny displacement about micron, such as measuring the responsive function of PZT.

Fiber geometry parameter measurement

An automatic method of measuring fiber geometry parameters is described. The parameters include core diameter, cladding diameter, core non-circularity, cladding non-circularity and core/cladding concentricity. The image of the fiber under test is received by a CCD camera and transferred to an image grabber plugged in a microcomputer for further analysis. Several digital image-processing methods are used to remove the noise in fiber image. The image segment algorithm is used to extract data points. The data is analyzed using different algorithms to give the geometry parameters of the fiber. Sophisticated software is programmed. An instrument is developed based on the hardware and software described above. All of the parameters and graphics can be obtained within 30 seconds. The repeatability of the instrument is as follows: core diameter, cladding diameter, core non- circularity, cladding non-circularity, core/cladding concentricity.

New technique for testing large optical flat

This paper discusses the development of a new technique (including theory, method, and equipment, etc.) for testing larger optical flat only by means of a smaller interferometer. It is an overlapping subaperture interference testing (OSIT) technique. The author has established a mathematics model for OSIT to retrieve the surface of the full aperture. The theoretical accuracy of the retrieved surface of the full aperture reached (lambda) /200 (p-v). The relationship between the accuracy of the retrieved wavefront of full aperture and errors (such as system error of interferometer or position error of subapertures, etc.) has been investigated. A computer program was established to simulate the real procedure from testing surface data of subaperture to retrieved wavefront of full aperture.