基于空间光调制器的波面重建优化方法研究

针对不同非球面面形的实时检测需求,研究了基于空间光调制器的标准波面重建技术.基于空间光调制器波面重建的原理设计了干涉测量系统,依据空间光调制器的自身特点选取修正离轴计算全息编码方式实现对标准球波面的编码.针对实验中空间光调制器作为全息再现介质引起重建波面质量下降问题,提出了错位叠加优化方案,并将这一过程进行了模拟实验.结果表明,基于错位叠加方法的重建波面均方差值提高了近4.45倍.研究成果为非球面检测过程中标准波面的获取提供了可靠的理论基础.     

角谱衍射公式的快速傅里叶变换计算及在数字全息波面重建中的应用

从取样定理出发,对角谱衍射公式及逆运算的快速傅里叶变换(FFT)进行了研究.基于研究结果.讨论数字全息研究中物光通过一个光学系统到达CCD探测器的波面重建问题.提出物光场的逆运算追迹重建及像空间波面重建两种方法.最后,通过数字全息实验及波面重建计算,对两种波面重建方法的可行性作出证明.     

高质量数字全息波面重建系统研究

基于阿贝成像理论对数字全息波面重建系统进行研究. 结果表明,利用成像系统对物光场进行变换,可以让物光场的高频角谱分量到达电荷耦合器件（CCD）探测器.为研究重建物光场质量,导出了CCD在光学系统后任意位置波面重建的计算公式,研究了物光通过傍轴光学系统到达CCD时波面重建系统的脉冲响应. 理论及实验研究表明,将CCD平面置于物光场像平面附近可以对物光场进行高质量重建. 关键词： 信息光学 数字全息 波面重建     

大尺寸物光波面彩色数字全息高质量重建研究

为解决检测面尺寸较大时CCD难以得到高质量数字全息图的问题,本文利用负透镜设计光学系统让CCD接收来自物体的缩小虚像,以球面波为参考波,使用单色CCD近距离得到三种色光照射下的大尺寸彩色物体的数字全息图,然后采用可控放大率波面重建算法得到同一尺寸的数字全息重建像,合成彩色数字全息重建像.同时,使用两种消零级方法去除零级干扰,提高重建像质量,一种方法利用空间光调制器相移技术在参考光中加入一次任意相移,记录两幅数字全息图,消除重建零级像|另一种方法使用“无干扰全息图”消除重建零级像及共轭像.本文讨论结果可为大物体彩色数字全息及多波长数字全息检测应用提供有益的参考.     

基于液晶空间光调制器的全息显示

在传统的纯相位全息显示系统中, 一般基于快速傅里叶变换(FFT)算法来计算相位全息图, 在FFT的计算中需要遵循Nyquist采样定理, 因此, 重建图像的尺寸往往受限于空间光调制器的固定采样率. 这个限制可以通过卷积算法或者两步菲涅耳衍射算法来解决, 但是需要使用多个FFT的计算, 导致计算量增大. 鉴于此, 提出了一种基于透镜的纯相位全息图计算方法. 在全息图的计算中, 通过透镜的成像原理建立一个采样率可变的虚拟全息面, 通过调节相应的距离参数使得在全息图的计算中可以任意调节原始图像的采样率, 摆脱了传统方法中液晶空间光调制器带宽积对重建图像尺寸的限制, 并且这种算法只需使用一次FFT就能达到变采样率的衍射计算, 大幅提高了全息图的计算速度. 数值模拟及光学实验结果证明了此方法可以在全息显示光学系统中清晰地重建不同尺寸的图像. 同时该系统可以有效地消除由空间光调制器的像素化结构带来的零级衍射.     

空间光调制器曲面拼接实现全息三维显示视角拓展

本文对多空间光调制器不同拼接方式拓展全息三维再现像视角的方法进行了分析,基于多片空间光调制器拼接拓展视角的思想,利用平面反射镜、分光镜和两片透射式空间光调制器设计了曲面拼接系统,进行了全息三维再现像的视角拓展实验研究。用该系统对四棱锥物体的层析菲涅尔衍射全息图进行再现,结果表明,总视角由基于单片空间光调制器的1.7°增大到3.2°,即拓展到约1.9倍,分光镜能够消除两片空间光调制器间的间隙,实现无缝拼接。该方法同样适用于更多空间光调制器的曲面拼接中,可以有效地拓展全息再现像的视场角大小。     

空间光调制器特性及其在数字全息中的应用

空间光调制器特性及其在数字全息中的应用实验,教学内容丰富,包括空间光调制器的性质,如像素尺寸测量、振幅调制特性测定、相位调制特性测定和黑栅效应消除,还包括空间光调制器的实际应用——数字全息实验.通过该实验的学习学生可以掌握空间光调制器的基本工作原理,并了解其在数字全息中的应用.     

基于空间光调制器的计算全息成像特性

把基于高分辨空间光调制器(SLM)的动态计算全息波面变换系统看作一个相干光学成像系统,分析并推导了该系统的点扩展函数（PSF）,进而研究了SLM像素结构所引起的固有切趾和展宽效应. 通过计算机模拟考察了SLM填充因子和衍射距离对系统分辨率的影响,给出了满足抽样定理所要求的系统的最小衍射距离. 最后提出了一种消除SLM像素结构影响的物波频谱预处理方法. 这一研究为优化系统设计,完善波面变换系统提供了新的途径.     

基于液晶纯相位光调制器的4f系统去噪方法

分析了4f系统的噪声来源,提出使用液晶空间光调制器实时去除系统噪声.通过使用Zemike多项式拟合透镜等光学器件引入的像差,根据液晶纯相位光调制器利用位相共轭波进行静态波面校正的工作原理,提出了一种新的相位校正算法,模拟仿真美国BNS公司反射式256×256纯相位液晶空间光调制器,通过重构并逼近畸变波面,产生相位共轭波...     

基于像素结构空间光调制器的全息再现像问题研究

基于纯相位空间光调制器的全息显示系统在重构显示时,再现像的视觉效果受到空间光调制器像素结构引起的多级衍射光和多级再现像的干扰。在分析具有有限填充因子空间光调制器的像素结构对再现像影响的基础上,提出了一种提高全息再现像的视觉效果并且再现像成像位置和大小可调节的方法。先加载闪耀光栅到纯相位全息图,其次通过叠加会聚球面波相位,分离再现像与空间光调制器像素结构引起的多级衍射光的聚焦平面的位置,再利用光阑和高通滤波器的共同作用,消除高级衍射光、多级再现像以及零级光干扰对重构视觉效果的影响,最后引入成像透镜,调节再现像的成像位置与大小。建立了一套基于硅基液晶的全息显示系统用于实验验证。实验结果表明,最终的单一再现像清晰且可以方便地调节成像位置和大小。该方法同样适用于各种基于像素结构空间光调制器的全息光学系统。     

Experimental validation of closed-loop adaptive optics based on a self-referencing interferometer wavefront sensor and a liquid-crystal spatial light modulator

A closed-loop adaptive optics system based on a self-referencing interferometer wavefront sensor (SRI WFS) using phase-shifting point-diffraction technique and an electrically addressed phase-only liquid-crystal spatial light modulator (LC SLM) is built and validated experimentally. The wavefront aberration of incoming beam is directly measured by analyzing four frames phase-shifted interferograms captured by a single CCD camera in two camera shots, and then by loading the conjugate function onto the SLM the wavefront aberration is corrected. The proposed scheme does not rely on any complicated control algorithm or wavefront-reconstruction algorithm and can achieve high-resolution and high-accuracy correction. Closed-loop correction results of single order Zernike aberrations and a Kolmogorov turbulence phase screen show that considerable improvements in the Strehl ratio (of greater than 0.94) is achieved.     

基于Zernike多项式的波前传感器的光子受限的研究

应用基于Zernike多项式的波前探测和重构方法2,利用蒙特卡罗法,可求出探测器在不同的光子数下,其探测精度的变化。文章还给出了由不同的探测器组成的传感器,探测星等的变化情况。     

Spline based least squares integration for two-dimensional shape or wavefront reconstruction

In this work, we present a novel method to handle two-dimensional shape or wavefront reconstruction from its slopes. The proposed integration method employs splines to fit the measured slope data with piecewise polynomials and uses the analytical polynomial functions to represent the height changes in a lateral spacing with the pre-determined spline coefficients. The linear least squares method is applied to estimate the height or wavefront as a final result. Numerical simulations verify that the proposed method has less algorithm errors than two other existing methods used for comparison. Especially at the boundaries, the proposed method has better performance. The noise influence is studied by adding white Gaussian noise to the slope data. Experimental data from phase measuring deflectometry are tested to demonstrate the feasibility of the new method in a practical measurement.     

采用阵列波带片波前传感的激光波前重构

 在高功率激光系统，激光束小尺度相位畸变波前探测是实现激光束中频段波前补偿与控制的重要前提。采用阵列菲涅耳波带片作为激光束波前传感的子孔径分割器，利用区域重构的Southwell模型进行波前重构。并针对波前传感器子孔径数目、小尺度相位畸变波前的参数对波前重构精度影响进行分析与模拟计算，给出了阵列菲涅耳波带片合理的子孔径数目，为20×20～30×30；对小尺度相位畸变，激光束波前的重构误差小于十分之一波长。     

Wavefront reconstruction using iterative discrete Fourier transforms with Fried geometry

A new kind of wavefront reconstruction algorithm is proposed in this paper, which can estimate the wavefront from its orthogonal gradients at different sample points. We model the gradients measured by wavefront sensor with the Fried geometry. Iterative discrete Fourier transforms and the correspondent Fried inverse filter in spatial frequency domain are introduced. No special boundary control is required to process the boundary condition in this algorithm. The stimulation and the experimental results show that the new algorithm has strong capability to fit the wavefront and it is more available if the sample points are few.     

Common-path phase-shifting lensless holographic microscopy

We present an approach capable of high-NA imaging in a lensless digital in-line holographic microscopy layout even outside the Gabor's regime. The method is based on spatial multiplexing at the sample plane, allowing a common-path interferometric architecture, where two interferometric beams are generated by a spatial light modulator (SLM) prior to illuminating the sample. The SLM allows phase-shifting interferometry by phase modulation of the SLM diffracted beam. After proper digital processing, the complex amplitude distribution of the diffracted object wavefront is recovered and numerically propagated to image the sample. Experimental results are reported that validate the proposed method.     

Diffractive characteristics of the liquid crystal spatial light modulator

The liquid crystal spatial light modulator (LC SLM) is very suitable for wavefront correction and optical testing and can produce a wavefront with large phase change and high accuracy. The LC SLM is composed of thousands of pixels and the pixel size and shape have effects on the diffractive characteristics of the LC SLM. This paper investigates the pixel effect on the phase of the wavefront with the scalar diffractive theory. The results show that the maximum optical path difference modulation is 41\,$\mu$m to produce the paraboloid wavefront with the peak to valley accuracy better than $\la$/10. Effects of the mismatch between the pixel and the period, and black matrix on the diffraction efficiency of the LC SLM are also analysed with the Fresnel phase lens model. The ability of the LC SLM is discussed for optical testing and wavefront correction based on the calculated results. It shows that the LC SLM can be used as a wavefront corrector and a compensator.     

Measurement of transient near-infrared laser pulse wavefront with high precision by radial shearing interferometer

It is hard to measure the transient near-infrared pulse laser wavefront in inertial confinement fusion (ICF) system by conventional methods for its short pulse width, large energy, high power and large distortion. A circular radial shearing interferometer based on spatial phase modulation is proposed to measure the transient near-infrared laser pulse wavefront with high precision. Transient, highly precise measurement for near-infrared laser pulse wavefront, with pulse width of nanometer scale and central wavelength of 1064 nm, can be carried out with common path, no reference plane. The theory of wavefront reconstruction has been validated by the computer simulation, and an error less than 1/1000λ is obtained. Comparing with the results of ZYGO interferometer, an error less than 1/15λ for both peak valley and root mean square value, is gained with good repeatability. The system has already been used in the ICF system to test the pulsed laser wavefront, and can also be applied to other lasers of visible and infrared wavelengths.     

基于多对流速度的波前重构算法研究

 在气动光学研究中，Ronald J. Hugo 和Eric J. Jumper的小孔径光束技术(SABT)波前重构算法在理论推导中忽略了与涡结构尺度相关的对流速度的差异，因此必然会给波前重构带来误差。用小波分析提取了上、下游探测光束输出的不同尺度的光程信号，通过计算两个探测光束输出的同一尺度信号的互相关系数，并利用互相关系数达到最大值对应的延迟时间研究了尺度相关的对流速度，然后再进行尺度相关的小孔径光束波前重构。结果表明：相对于单一对流速度的小孔径光束波前重构算法，该尺度相关的波前重构算法能有效地提高波前重构的精度。