A two-step phase-retrieval method in Fourier-transform ghost imaging

A two-step phase-retrieval method, based on Fourier-transform ghost imaging, was demonstrated. For the complex objects, the phase-retrieval process was divided into two steps: first got the complex object's amplitude from the Fourier-transform patterns of the squared object function, then combining with the Fourier-transform patterns of the object function to get the phase. The theoretical basis of this technique is outlined, and the experimental results are presented. (C) 2008 Elsevier B.V. All rights reserved.

自由空间激光远距离传输的地面模拟研究

根据透镜的傅里叶变换性质，提出了采用光学傅里叶变换加级联光学成像放大并结合有限口径接收的方法来实现自由空间激光光束远距离传输的实验室模拟。由此原理设计了自由空间激光远距离传输模拟装置，该装置主要由大口径、长焦距的傅里叶变换平行光管和三级成像放大镜所组成，最大等效传输距离达2.4×10^5km，可用于星间激光通信终端综合通信性能的评估，在设定的误码率下测量终端可能的通信距离，或者在设定的作用通信距离下检测通信的误码率。

Optical interconnection for neural networks by use of a self-imaging function

A grating-lens combination unit is developed to form a scaling self-transform function that can self-image on scale. Then an array of many such grating-lens units is used for the optical interconnection of a two-dimensional neural network, and experiments are carried out. We find that our idea is feasible, the optical interconnection system is simple, and optical adjustment is easy. (C) 1998 Optical Society of America.

Large-aperture automatic focimeter for the measurement of optical power and other optical characteristics of ophthalmic lenses

We propose an optical apparatus enabling the measurement of spherical power, cylindrical power, and optical center coordinates of ophthalmic lenses. The main advantage of this new focimeter is to provide a full bidimensional mapping of the characteristics of ophthalmic glasses. This is made possible thanks to the use of a large-area and high-resolution position-sensitive detector. We describe the measurement principle and present some typical mappings, particularly for progressive lenses. We then discuss the advantages in terms of speed and versatility of such a focimeter for the measurement of complex lens mappings. (C) 2002 Optical Society of America.

基于光栅成像投影的微位移检测方法

提出了一种基于光栅成像投影的微位移检测方法，利用光学傅里叶变换原理给出了具体的理论分析。准直激光束照明的光栅通过一个4f系统成像投影在被测物体表面上，光栅投影经过被测物体表面反射后由另一个4f系统成像在探测光栅上。探测光栅由一个透镜组成像在光电探测器上，其中采用由起偏器、光弹调制器和检偏器组成的偏振调制单元对探测光强进行调制。通过在4f系统的频谱面上设置滤波光阑，在光电探测器上获得了与被测物体的微位移成正弦关系的光强变化，检测出光电探测器上的光强变化即可以获得被测物体的位移量。实验验证了该检测方法的可行性

Wave-front analysis method of circular aperture sampling for collimation testing

A new type of wave-front analysis method for the collimation testing of laser beams is proposed. A concept of wave-front height is defined, and, on this basis, the wave-front analysis method of circular aperture sampling is introduced. The wave-front height of the tested noncollimated wave can be estimated from the distance between two identical fiducial diffraction planes of the sampled wave, and then the divergence is determined. The design is detailed, and the experiment is demonstrated. The principle and experiment results of the method are presented. Owing to the simplicity of the method and its low cost, it is a promising method for checking the collimation of a laser beam with a large divergence. © 2005 Optical Society of America.

Phase-space analysis of wavefront coding imaging systems

We explore the use of the Radon-Wigner transform, which is associated with the fractional Fourier transform of the pupil function, for determining the point spread function (PSF) of an incoherant defocused optical system. Then we introduce these phase-space tools to analyse the wavefront coding imaging system. It is shown that the shape of the PSF for such a system is highly invarient to the defocous-related aberrations except for a lateral shift. The optical transfer function of this system is also investigated briefly from a new understanding of ambiguity function.

Collimation testing using axial intensity

We proposed a new method of measuring the degree of collimation of laser beam using axial intensity information near paraxial focus. Preceding methods for collimation testing are mainly either based on self-imaging or interferometric techniques. The new method is to employ the diffraction behavior of noncollimated wave in circular aperture diaphragm. The principle of the proposed method and experiment results are presented. Due to simplicity of the method and its low cost, it is a promising method for checking the collimation of laser beam. (c) 2005 Published by Elsevier GmbH.

Analytic expression of the diffraction of a circular aperture

Recurring to the characteristic of Bessel function, we give the analytic expression or the Fresnel diffraction by a circular aperture, thus the diffractions on the propagation axis and along the boundary of the geometrical shadow are discussed conveniently. Since it is difficult to embody intuitively the physical meaning from this series expression of the Fresnel diffraction, after weighing the diffractions on the axis and along the boundary of the geometrical shadow, we propose a simple approximate expression of the circular diffraction, which is equivalent to the rigorous solution in the further propagation distance. It is important for the measurement of the parameter or the beam, such as the quantitative analysis of the relationship of the wave error and the divergence of the beam, In this paper, the relationship of the fluctuation of the transverse diffraction profile and the position of the axial point is discussed too. (c) 2005 Elsevier GrnbH. All rights reserved.

A novel three-dimensional imaging array recording and computational method by means of coded cameras reconstruction

In this paper, we propose a novel three-dimensional imaging method by which the object is captured by a coded cameras array (CCA) and computationally reconstructed as a series of longitudinal layered surface images of the object. The distribution of cameras in array, named code pattern, is crucial for reconstructed images fidelity when the correlation decoding is used. We use DIRECT global optimization algorithm to design the code patterns that possess proper imaging property. We have conducted primary experiments to verify and test the performance of the proposed method with a simple discontinuous object and a small-scale CCA including nine cameras. After certain procedures such as capturing, photograph integrating, computational reconstructing and filtering, etc., we obtain reconstructed longitudinal layered surface images of the object with higher signal-to-noise ratio. The results of experiments show that the proposed method is feasible. It is a promising method to be used in fields such as remote sensing, machine vision, etc. (c) 2006 Elsevier GmbH. All rights reserved.

Series representation of the Gaussian beam far-field diffracted by annular aperture

Accurate, analytical series expressions for the far-field diffraction of it Gaussian beam normally incident on a circular and central obscured aperture are derived with the help of the integration of parts method. With this expression, the far-field intensity distribution pattern can be obtained and the divergence angle is deduced too. Using the first five items of the series, the accuracy can satisfy most laser application fields. Compared with the conventional numerical integral method, the series representation is very convenient for understanding the physical meanings. (C) 2007 Elsevier GmbH. All rights reserved.