两步相移实现投影栅相位测量轮廓术

提出一种新的投影栅相位测量方法--两步相移法。该方法只需两幅相移条纹图，因此计算量小，速度快。给出了实验及计算结果，并同四步相移法进行了比较，证明了该方法具有较高的精度。     

Secure optical system that uses fully phase-based encryption and lithium niobate crystal as phase contrast filter for decryption

In this paper, the implementation of a secure optical system using fully phase encryption is described. A two-dimensional phase image obtained from an amplitude image is encrypted and decrypted by using a spatial light modulator working in phase mode. The fully phase encryption is achieved using double random phase encoding. The encrypted image is holographically recorded in a photorefractive crystal and is then decrypted by generating, through phase conjugation, the conjugate of the encrypted image. A lithium niobate crystal has been used as a phase contrast filter to change the decrypted phase image into an amplitude image, thus alleviating the need for alignment of the phase contrast set-up in the Fourier plane. Simulation results are provided to verify the proposed study. The mean square error between the primary image and decrypted image has been calculated to study the sensitivity of the system.     

Wavelength-Tunable Laser-Diode Interferometer

Laser diodes (LDs) have been applied to a phase-measuring interferometer through the wavelength tunability of LDs by controlling their currents. Laser-diode interferometers based on a heterodyne technique are reviewed. A two-wavelength laser-diode interferometer is demonstrated with current control of dual LDs in opposite directions. A synthetic wavelength makes it possible to extend the range of interferometric measurements. The wavelength is controlled by the laser injection current and is stepwise or rampwise changed to introduce a time-varying phase difference between the two beams of an interferometer with unbalanced optical path lengths. The optical output is demodulated with a phase-extraction algorithm. Systematic phase errors caused by the LD-power variation and by the difference between the beat frequency and ramp frequency are analyzed. A feedback interferometer with electronics is used to eliminate the phase error by locking the interferometer on a preset phase. Typical experimental results are shown.     

Criterion for phase separation in one-dimensional driven systems

A general criterion for the existence of phase separation in driven density-conserving one-dimensional systems is proposed. It is suggested that phase separation is related to the size dependence of the steady-state currents of domains in the system. A quantitative criterion for the existence of phase separation is conjectured using a correspondence made between driven diffusive models and zero-range processes. The criterion is verified in all cases where analytical results are available, and predictions for other models are provided.     

一种新的360°三维轮廓术

提出了运用相移技术的光刀投影式测量３６０°回转物体三维轮廓的新方法。该方法对投影光刀引入正弦分布光场,利用相移技术对光刀投影狭缝进行相位计算,可得出各点的包裹相位分布,然后再利用光刀投影测量原理得到的高度信息对相位进行去包裹处理,从而得到具有较高精度的相位测量结果。最后根据相位与物体高度的几何关系,得到物体的三维轮廓数据。文中详细介绍了这一技术的原理及实验结果     

Phase transition in a three-states reaction-diffusion system

A one-dimensional reaction-diffusion model consisting of two species of particles and vacancies on a ring is introduced. The number of particles in one species is conserved while in the other species it can fluctuate because of creation and annihilation of particles. It has been shown that the model undergoes a continuous phase transition from a phase where the currents of different species of particles are equal to another phase in which they are different. The total density of particles and also their currents in each phase are calculated exactly.     

Construction of the Phasing System for BEPCⅡ Linac

In order to get high beam quality, a RF distribution system is required, with minimal phase drifts and errors in the BEPCⅡ linac. The additional installation of phase reference cables and monitoring equipments and stable RF distribution for BEPC linac are finished. The master oscillator is chosen to offer RF signal with low phase noise and a stable phase distribution system is built to deliver RF signal to each klystron. A phase and amplitude detector is constructed to measure the phase precisely and an IΦA unit is used for a phase shifter. Control software based on EPICS is used to connect all the units of the system, and a phasing method based on BPM is adopted to optimize the phase of each klystron. Now the phasing system is installed and tested in the klystron gallery of the BEPCⅡ linac.     

Automated image processing algorithm for Young's fringe pattern analysis

An automatic of image processing for the analysis of Young's fringe pattern is proposed. A Young's fringe patttern is first FFT treated to get two patterns of 0 degree and 90 degree phase shifted. Regular two pattern shift algorithm is used to calculate the phase of the Young's pattern. One or two times of phase shift iteration are carried out to improve the phase. Then the phase is least square fitted to get a phase plane. The displacement magnitude and direction are eaasily induced from the phase plane. Because every step is full field treatment, very precise result is achieved. The algorithm is simple and easy to implement. Theory and experiment are presented to prove the proposal. A program is designed to execute the algorithm and the processing is automated by a Personal Computer with an image board.     

基于条纹反射的类镜面三维面形测量方法

提出了一种基于条纹反射和相移技术的类镜面三维面形测量的新方法。首先在平板显示器上显示正弦条纹,然后用CCD相机分别记录由待测面和标准面反射的正弦条纹像,通过相移得到各自的相位分布,与标准面相位分布相比较得到待测表面起伏引起的相位变化。推导了相位变化量与待测表面梯度的对应关系,分别对待测面进行水平和垂直两个方向光栅相位测量,通过计算可得到梯度分布并由梯度分布恢复待测表面面形。同时初步分析了影响条纹反射技术测量精度的因素。测量中,光栅由计算机产生,可以实现精确的相移,而且可以方便地调节光栅的周期及方向,通过预设标记点来引导相位展开有效地解决待测面和标准面的条纹对应问题。实测了建筑用釉面瓷砖表面起伏,验证了该方法的可行性。     

An Improvement of Spatial Carrier Phase-shifting Method

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An Improvement of Spatial Carrier Phase-shifting Method

Spatial-carrier phase-shifting method (SCPM) retrieves the phase distribution from carrier interferograms by assuming that the phases of the processed pixel and its adjacent pixels are uniform,which introduces considerable theoretical error. A new method is presented in this paper to improve the SCPM accuracy: (1) A quadric curve is used to describe the phase distribution of the adjacent pixels; (2) The linear and quadric terms of the phase are considered as phase shifter errors; (3)Suitable phase shifting algorithms insensitive to these errors are selected. Two "5-step" algorithms are used and their properties are analyzed. An example ofphase retrieving by SCPM is given and the result shows that SCPM has high theoretical accuracy. With the potential high accuracy, ability of measuring dynamic phase andcomputational simplicity, SCPM will become a much more useful phase measurement method.     

平行式向列液晶实现相移剪切电子散斑干涉术的研究

研究了向列型液晶的相位调制特性，采用平行式向列液昌作为相移器建立了相移剪切电子散斑干涉计量系统。该方法将相移技术引入到剪切电子散斑干涉术中，提高了检测精度，采用了相关条纹法求解相位，简化了计算；相移方法简单，可靠。用该系统进行应变场的测量实验，取得了满意的效果。     

Phase retrieval of optical fringe patterns from the ridge of a wavelet transform

A new method for phase retrieval of optical fringe patterns is presented. This method is based on a wavelet transform and is capable of extracting the full 2D phase distribution from a single fringe pattern. An important conclusion that the phase of the optical fringe pattern is equal to the phase of its wavelet transform on the ridge of the wavelet transform is theoretically clarified. The method is compared with the Fourier transform and the integration methods. A numerical simulation and an experimental example of phase retrieval are shown.     

紫外光诱导液晶相位光栅

使用紫外光诱导取向技术制作了可转换的液晶相位光栅,通过光掩模两次曝光的方法形成光栅条纹.这种光栅制作工艺较为简单,不需要上下基板精确的对准,驱动电压较低.采用He-Ne激光器和光探测器进行测试,结果表明,衍射效率具有电场调制性并出现同预测一致的衍射条纹.对液晶光栅的偏振特性进行了研究,利用琼斯矩阵和衍射理论对液晶相位光栅衍射强度进行了分析和模拟计算.     

A new method for generating and analysing digital speckle shearing correlation fringe patterns

A method for generating a high visibility digital speckle shearing fringe pattern is proposed. A three-step phase shifting technique which involves the introduction of arbitrary phases is utilized. The phase shifting technique is carried out using a rotating mirror and a theoretical model which involves a linear correlation algorithm is discussed. Experimental results showing correlation fringe patterns and a deformation phase map are presented.     

Modified phase contrast for recording of holographic optical elements

A modified phase contrast method is described for the fabrication of holographic optical elements with in-line diffraction patterns. In this method, a liquid crystal phase modulator is addressed by computer-generated holograms to achieve variable phase gratings. The phase gratings are imaged onto photosensitive material by a phase contrast method without a Fourier filter. We show the analytical treatment of the modified phase contrast method and demonstrate the application in holographic recording.     

Carrier squeezing interferometry: suppressing phase errors from the inaccurate phase shift

The carrier squeezing interferometry algorithm is proposed to retrieve the phase from interferograms with phase shift errors. A linear carrier is introduced in the interferograms, and the image data is rearranged by the squeezing interferometry technology. In the spectrum of the rearranged image, the error lobe and the phase lobe are separated so the error-free phase can be retrieved by filtering. The simulated interferograms with phase shift errors are computed, and the precisions are better than 8.4×10(-4)λ. Its validation is verified by experiments, where a mean precision of 0.0040λ is obtained.     

Parastatistics and phase transition from a cluster as a fluctuation to a cluster as a distinguishable object

A phase transition of the first kind is a jump of a function, a phase transition of the second kind is a jump of its first derivative, a phase transition of the third kind, a jump of the second derivative. A phase transition from one statistic to another is very gradual, but finally it is as considerable as the phase transition of the first kind. However, we cannot introduce a clearly defined parameter to which this transition corresponds. This is due to the fact that the fluctuations near the critical point are huge, and this violates, in the vicinity of that point, the main law of equilibrium thermodynamics, which asserts that fluctuations are relatively small. The paper describes the transition in the supercritical fluid region of equilibrium thermodynamics from parastatistics to mixed statistics, in which the Boltzmann statistics is realized for long-living clusters. In economics this corresponds to a negative nominal credit rate. Examples of this non-standard situation are presented.     

The Phase Diagram of a Spin Glass Model

A spin glass problem on a Cayley tree with ferromagnetic interactions is solved rigorously. Using a level-I large deviation argument together with the martingale approach used by Buffet, Patrick and Pulé,⁽¹⁾ explicit expressions for the free energy are derived in different regions of the phase diagram. It is found that there are four phases: a paramagnetic phase, a spin-glass phase, a ferromagnetic phase and a mixed phase. The nature of the phase diagram depends on the power with which the ferromagnetic term occurs in the Hamiltonian.