多步相移中被测件径向相移不均匀引入误差比较及校正

不同步数相移算法下被测件径向相移不均匀引入的误差不同,对测量的影响也将不同。基于点衍射干涉测量光路,构建了误差分析模型,以5、6、7和13步相移算法为例,对不同相移算法下被测件径向相移不均匀引入的移相误差进行了分析,并将该移相误差的影响引入到实际干涉测量模型中,进一步分析比较了该误差对最终面形检测结果的影响,进而提出了一种基于误差预估计的多项式误差校正新方法。研究结果表明,相移算法步数越多,被测件径向相移不均匀引入的面形检测误差越大,误差均呈类抛物面分布;最终面形检测结果经Zernike多项式拟合消离焦项后已等同于进行了二次多项式校正,对于数值孔径为0.3以下的被测件,经二次多项式校正后该误差对测量的影响基本可以忽略。     

用于相移点衍射干涉仪的加权最小二乘相位提取算法

针对现有的相位提取算法只对某些特定的误差不敏感,不能满足高精度光学检测的要求,本文引入一种等间隔多步移相算法—权重待定的加权最小二乘算法。通过在最小二乘算法中添加待定的权重,分析移相点衍射干涉仪中多种误差源对算法的影响,获得多组约束方程,从而确定权重和新算法。对新算法和标准四步算法、Hariharan五步算法进行比对分析,验证了新算法对PZT线性和二阶非线性移相不准、光强的一阶二阶波动和光源频率一阶二阶波动等误差抑制能力远远优于标准四步算法和Hariharan五步算法;新算法对CCD的量化误差、光强噪声、频率噪声的抑制能力也具有一定优势,且对CCD的二阶响应非线性完全不敏感。     

几种任意步距步进相移算法的误差分析与对比

介绍了到目前为止的几种任意步距步进相移算法,并针对相移干涉仪的两种主要误差———移相误差和探测器非线性误差进行了计算仿真,进而比较分析了它们对这这些误差的抑制能力,其结果可为实际应用合理地选择算法提供理论依据。     

基于白光干涉测试技术的改进Carré相移算法

为了减小白光相移干涉法测量物体微观形貌时产生的误差,对极值法的搜索路径进行优化后与Carré相移算法相结合,提出一种基于白光干涉测试技术的改进Carré相移算法.该算法减小了光源扰动及电荷耦合元件散粒噪声带来的影响,且对相移器的线性误差不敏感,免去了相位解包裹过程,提高了运算效率.采用单刻线样块对扫描步距进行校准实现了光源中心波长的在线修正,减小了由于光源特性及环境扰动误差带来的影响.采用不同算法对标准粗糙度样块进行三维形貌恢复以及表面粗糙度的重复性测量实验,结果表明:该算法对表面粗糙度的测量结果较传统白光干涉算法准确度提高,测量重复性优于1%.     

用特征多项式构造相移干涉相位提取算式

用相移干涉术测量物体表面形貌时，各种误差因素特别是相移器移相误差的影响使得表面形貌的测量偏离了实际值，甚至会产生形貌失真的现象。采用傅里叶分析的方法对相位提取算式作了理论分析，并根据特征多项式设计分析理论构造了新的、对移相误差不敏感的相位提取算式。经实验验证，该算法有效地提高了相移干涉仪测量表面形貌的Ra值，重复测量精度达5倍以上，使测量结果更接近实际值。     

基于小孔点衍射的超精面形瞬态干涉测量技术

为解决时域相移小孔点衍射干涉仪中移相依赖昂贵压电陶瓷相移器,且长时间采集易受环境干扰影响的问题,提出一种基于偏振同步相移的小孔点衍射瞬态干涉检测方法.构建反射式结构的小孔点衍射干涉测量光路得到两束正交的圆偏振光,利用棋盘位相光栅分光与偏振片阵列移相,在CCD上同时获得4幅不同相移量的干涉图像,对单次采集的4幅瞬时干涉图...     

高精度干涉检验移相算法对振动误差的免疫能力

对移相干涉测量中影响移相稳定性,从而产生测量误差的小幅度机械振动进行了研究,建立了振动误差模型,仿真分析了Wyant84b三步算法、Hariharan87五步算法、七步算法和十三步算法4种不同移相算法对振动的免疫能力。模拟结果显示,十三步算法对振动的免疫能力最好,与已发表文献成果吻合,说明本文的模拟具有较高的可信度,在一定程度上能够对影响干涉仪精度的振动误差进行合理预测,并能够起到评价和筛选移相算法的作用。     

非偏振分光镜对外差干涉仪非线性误差的影响

除了激光源、偏振分光镜（PBS）和波片等偏振器件之外,非偏振分光镜（NPBS）也是外差干涉仪中重要的非线性误差源。研究了多层介质膜NPBS的退偏效应和方位角对非线性误差的影响。采用p、s分量透射比、反射比、反射相移和透射相移共同表征NPBS的退偏效应,并逐项分析了其非线性误差模型。如果入射光束为理想线偏振光,则只有NPBS的反射相移和透射相移影响测量精度。如果入射光束存在偏振椭圆化和非正交,则NPBS的方位角、透射比和反射比、相移等参数的变化都会引入非线性误差,误差曲线的斜率受椭圆率和非正交角的影响。因此选用不同的激光源,同一个NPBS产生的非线性误差大小不同,一般可达几个纳米量级。为了实现纳米/亚纳米级精度的外差干涉测量,选择性能稳定的NPBS,特别是NPBS退偏效应与激光源输出偏振态之间的匹配非常重要。     

双点干涉法位相缺陷检测中的解相算法比较

双点光源移相干涉测量是大口径光学元件位相缺陷检测的一种重要方法。为了分析双点干涉中误差对解相算法的影响,首先给出相位缺陷检测的系统结构和理论模型,在此基础上,针对测量过程中主要存在的一次移相误差、二次移相误差、光强误差和随机振动误差,研究了Hariharan 5帧移相算法、13帧移相算法和迭代随机移相算法的解相误差,并进行了仿真分析。结果表明,针对这几种误差源,13帧算法解相精度整体优于5帧法,迭代随机移相算法解相效果优于13帧法和5帧法,当这几种误差按实际指标同时作用时,迭代随机移相算法解相误差RMS小于5帧法和13帧法,PV值稳定在0.5 nm以内。由于随机振动占主要作用,说明迭代随机移相算法受误差影响很小。     

投影条纹相移法中图像饱和误差抑制算法研究

针对投影条纹相移法三维形貌测量中的图像饱和误差进行了深入研究,分析了基于条纹相移技术的图像饱和误差抑制算法的适用范围,推导了基于六步相移的饱和误差抑制算法公式.理论分析表明,相移条纹图的帧数越多,饱和误差抑制算法的适用范围越广.并通过数值模拟和实验进行了验证,基于六步相移的饱和误差抑制算法可以更加有效地抑制图像饱和引起的相位误差.     

一种解调阴影叠栅条纹的新方法

本文提出了一种叠栅条纹解调技术,我们称它为频移叠栅法,它不同于相移叠栅法,前者改变了叠栅条纹分布的频率,后者只是改变了叠栅条纹的相位.本文从阴影叠栅图分布的基本公式出发,借助于相移阴影叠栅法的思想推导并得出了频移阴影叠栅法的公式,在此基础上给出了特定条件下的实用公式.同时也分析了其相位图,将其主值范围从0～π拓展到0～2π,解决了其去包裹中正负号确定问题.最后给出了实验结果,并分析和模拟了由于频移的不准确给测量结果带来的影响.     

Discussions on phase-reconstructing algorithms for 3D digitizing structure-light profilometry

For the 3D digitizing structure-light profilometry, five kinds of phase reconstructing (PR) algorithms, including Schofield's S-FFT (with 4 pairs of FFT & Inverse FFT operators) algorithm, Volkov's deterministic V-FFT PR algorithm (with only one pair of FFT operators and one Inverse FFT operator), quality-guided (QG) method, weighted least-square (WLS) method and a proposed Discrete-Cosine-Transform-Based (DCT-B) algorithm have been implemented and discussed in detail. The computer-simulated data show that the WLS and V-FFT enjoy the least phase error, but the QG algorithm achieves the trade-off between reliability and computational time. The S-FFT together with V-FFT method almost fails to deal with the experimental data with abrupt phase variance. Among the other three algorithms, the DCT-B algorithm shows its advantage over QG and WLS algorithms in settling these problems. Considering phase error and computational time, it could win the priority in PR. The experimental results also demonstrate that the proposed DCT-B algorithm could be firstly considered in the application of structure-light profilometry, especially to process the abrupt-phase maps.     

Error-compensating algorithms in phase-shifting interferometry: a comparison by error analysis

In this paper, two families of phase-shifting algorithms with π/2 phase steps are studied. In family I, three new algorithms are derived by using the averaging technique based on the Surrel six-sample algorithm with phase shifts of π/2. Family II includes four well-known algorithms derived by the averaging technique based on the conventional four-sample algorithm with π/2 phase steps. A polynomial model of phase-shift errors used to describe general expressions for calculation of the correct object phase via the Fourier spectra analysing method as a function of the harmonic order in the fringe signal is presented. The error-compensating properties of the algorithms in families I and II are investigated by the Fourier spectra analysing method. It is found that the averaging technique, when used in any of the algorithm with π/2 phase steps, can improve the phase-shifting algorithm property: it is insensitive to phase-shift error when the fringe signal contains the first harmonic, but it can't be used to enhance the phase-shifting algorithm properties when the fringe signal contains higher order harmonics (n2). P–V (peak–valley) phase errors are calculated by the computer simulation and tables and plots are presented, from which the algorithms in families I and II are compared. It is shown that the algorithms in family I are more insensitive to phase-shift errors when the fringe signal contains the second harmonic and the algorithms in family II are more insensitive to phase-shift errors when the fringe signal is a sinusoidal waveform.     

泵浦光和信号光之间的相位漂移对级联PSA光传输系统传输性能影响的研究

本文研究相敏光放大器(PSA)中泵浦光相位不能完全跟踪信号光相位时,即两者之间存在相位漂移时,对以PSA作为光中继放大器的高速光纤通信系统传输性能的影响.通过计算机系统仿真,我们得到在不同的相位漂移下,高速信号脉冲眼图劣化度随光纤色散变化的曲线,以及不同传输速率下信号眼图劣化度随放大器相位漂移量变化的曲线.由仿真结果可知,如相位漂移控制在一定范围内,其对系统性能几乎没有影响.但超出此范围时,则系统性能迅速劣化.     

干涉仪自适应抗振的空间移相术

根据时域移相算法的概念,提出了一种空间移相术,它能够检测因外界振动导致条纹抖动而引起的干涉图样的空间相位变化.运用这种技术在TwymanGreen移相式干涉仪中建立了一套自适应抗振系统,它可以实时测量振动引起的相位变化大小,并通过反馈器件PZT实时校正干涉条纹的相位,使得干涉条纹稳定以保证光学测量的正常进行,与此同时PZT还作为移相器件.     

Smoothing filters in phase-shifting interferometry

The images used in phase-shifting interferometry are usually noisy and smoothing filters are frequently used. Filtering can be done on the fringe patterns before phase retrieving or on the phase map after phase retrieving. Filtering fringe patterns—a form of preprocessing, requires the same processing to be done on at least three patterns. Filtering phase map, on the other hand, needs processing of only one pattern. Preprocessing prevents noise from being carried through while post-processing might clip parts of the signal. Thus there is a need to evaluate which one is better. A theoretical analysis was carried out for this basic problem, followed by computer simulations and a real experiment for verification. The comparison was also extended to phase difference measurement which uses similar but slightly different phase retrieval algorithms.     

Interferometric 3-D displacement measurement using wavefront analysis

We propose and demonstrate a novel interferometric technique for 3-D displacement measurement. The method is based on the analysis of the phase difference distribution measured when two coherent curved wavefronts originating from different locations interfere. Both the in-plane and out-of-plane displacements are found simultaneously from a single phase difference distribution. We find that our system could measure with an accuracy better than 1.5 μm for in-plane displacements and 36 μm for out-of-plane displacements over 1 mm range. This accuracy was limited by the output lens performance. Theoretical analysis reveals that sub-micron accuracy may be possible with more careful calibration.     

无铬相移掩模光刻技术

本文论述了相移掩模(PSM)提高光刻分辨率的基本原理、主要类型、无铬PSM的制作方法,简述了曝光实验和实验结果.用NA=0.28的g线光刻机得到了0.5μm的实际分辨率.     

Three-dimensional profile measurement of the blade based on multi-value coding

As the blade must have precise size and accurate shape, three-dimensional (3D) profile measurement of the blade is very important. 3D profile measurement method based on multi-value coding is proposed. This method designs a multi-value coding stripe pattern combined with the four-step phase-shifting method. Two kinds of fringe patterns are projected onto the object respectively, one is sinusoidal intensity distribution used for wrapped phase, the other is multi-value coding fringe pattern for phase unwrapping. Because this encoding method is simple, and easy to implement, the absolute phase can be quickly implemented. Experimental results demonstrated that the proposed method can achieve a high precision, high speed and low cost 3D profile measurement of the blade.