阴影叠栅相移非线性误差补偿算法研究

相移阴影叠栅干涉场的相位(高度)存在非线性关系,而传统的相移阴影叠栅技术往往忽略了相位与高度的非线性关系,从而在测量系统中引入测量误差。对此提出了一种基于迭代相位解调自调算法相移阴影叠栅技术,该方法利用最小二乘技术获得相移量估算值,利用该估算值通过迭代算法消除相移阴影叠栅的全场相位误差,从而得到正确的相位分布。模拟计算表明该方法可以有效解决相移不均产生的相位测量误差问题,且可实现光栅移动量的精确估算,其误差不超过3.4%。对比实验进一步说明了所提出方法的正确性和优越性。     

套管井水泥环空间介质波阻抗与厚度反演方法

针对实际反射式超声波测井,把套管与地层环空间单层介质的波阻抗和厚度作为两个待反演参数,分别将相移正切函数及反正切函数形式下的方程作为目标函数,提出了对波阻抗和厚度反演的线性化最小二乘法.通过对两种反演方程误差函数的数值考察和对合成数据反演结果的分析,发现相移反正切函数形式下方程的线性化最小二乘法是较为稳定有效的方法,能够完全消除多极值的缺点,反演结果对波阻抗和厚度初值不敏感.     

EXAFS方法在金属玻璃结构研究中的误差分析

本文对EXAFS方法在金属玻璃结构研究中所得径向距离的误差进行了分析。所做的模拟计算表明当前流行的关于这个问题的误差理论不能圆满地解释这一现象。本文分析了玻璃态和晶态的相移函数,指出在相似的体系中玻璃态和晶态相移函数与k的关系采用线性函数近似时,其斜率可能是不同的,而且无序度相差越大,两者的偏差可能也越大。在EXAFS数据处理过程中,没有考虑这种偏差的影响是造成EXAFS方法结果中径向距离误差的一个原因。本文还提出了一个修正参考样品(晶态)相移函数斜率偏差的方法,并将它应用于Cu₅₅Zr₄₅金属玻璃的EXAFS数据处理中,所得结果与用X射线异常散射方法测定的结果符合得很好。 关键词：     

移相干涉测量术及其应用

为了对移相式数字干涉仪在光学元件测量中的应用有全面了解，介绍了移相干涉术的基本原理。结合激光数字波面干涉仪，阐述移相干涉术的四步重叠平均算法、压电晶体移相器(PZT)的结构、3 PZT的组合方法、移相器的标定误差和非线性误差的校正方法、波面相位解包的自适应种子算法、波面相位的评价指标等内容。结合移相数字波面干涉仪，叙述了移相干涉测量技术在普通光学元件、红外光学元件、大口径光学元件、非球面光学元件等测量中的应用并指出了应用过程中的注意事项。最后明确指出光干涉技术正沿着高相位分辨率、高空间分辨率、宽波段和瞬态高速测量的方向发展，并将会在瞬态波前测量、微机械的微结构动态分析等方面有着越来越广泛的应用。     

相移光腔衰荡高反射率测量中的拟合方法

 分析了相移光腔衰荡技术中由锁相放大器探测光腔输出信号一次谐波的振幅和相位随调制频率的变化曲线。拟合结果发现，联合幅频和相频曲线构造同时含有振幅和相位信息的均方差拟合函数，不同频率拟合范围得到的衰荡时间平均值为0.791 μs，最大误差由分别用幅频或相频曲线拟合得到的衰荡时间误差的8%减小到1.3%，均方差仅为0.5%。通过在拟合函数中加入系统响应时间、系统初始相位等参数，避免了相移光腔衰荡中直腔实验时测量系统频率响应曲线，提高了测量精度。     

基于剪切散斑干涉技术的物体变形动态检测

为使仅适用于静态测量的空间相移剪切散斑干涉系统可用于物体变形的动态测量,在对传统剪切散斑干涉系统加以改进的基础上,提出一种物体变形动态检测方法。将检测系统中的压电陶瓷控制器用参考镜代替,减少了物理装置控制与执行的时间。对于物体发生变形的同一状态,仅需采集一幅干涉图像即可满足后期计算,加以二维连续小波滤波和最小二乘相位解包算法,能满足物体变形动态在线检测的需求。理论和实测实验表明,该方法能快速可靠地检测出物体动态形变,整个系统的最大误差范围在-1.5 rad~1.5 rad之间,整个检测过程最大误差百分比为6.4%,有较高的精度和实用性,为新型剪切散斑干涉测量系统的改进和设计提供参考。     

Spatial-carrier phase-shifting digital holography utilizing spatial frequency analysis for the correction of the phase-shift error

We propose a single-shot digital holography in which the complex amplitude distribution is obtained by spatial-carrier phase-shifting (SCPS) interferometry and the correction of the inherent phase-shift error occurred in this interferometry. The 0th order diffraction wave and the conjugate image are removed by phase-shifting interferometry and Fourier transform technique, respectively. The inherent error is corrected in the spatial frequency domain. The proposed technique does not require an iteration process to remove the unwanted images and has an advantage in the field of view in comparison to a conventional SCPS technique.     

The problem of the unambiguity of phase-shift analysis I

For the discrimination of phase-shift solutions, the new so-calledτ-criterion, based on the calculation of some functionτ of the experimental data, is used. This method can be applied, in general, to an arbitrary ambiguous phase-shift analysis. Theτ-criterion is more powerful than theχ ²-criterion, e.g. for rejecting a less probable set it is necessary to have a smaller quantity of experimental points (in statistics this means that theτ-criterion gives a smaller Type II error). For the calculation of the quantityτ, the standard programme for phase-shift analysis with a small additional part can be used. A computer time of about only 5–10 min. on a computer of M-20 type is needed. A Type I error is then obtained from the tables of the normal distribution function.     

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.     

在随机和倾斜移相下光强归一化的迭代移相算法

由于存在振动和导向误差,干涉仪移相器在移相过程中产生随机的平移误差和倾斜误差,会给测量结果带来影响。因此高精度测量中对环境的稳定性和移相器的性能要求很苛刻。为了降低此种要求,针对随机和倾斜移相下干涉图背景光强和调制度的不均匀会影响移相平面计算的问题,对采集得到的干涉图做归一化处理,并利用迭代最小二乘法对归一化的干涉图做相位求解。迭代过程中,将干涉图分块来求解移相值,并对各移相值做平面拟合得到移相平面。仿真结果表明,该方法消除了背景光强和调制度的不均匀对倾斜系数计算的耦合作用,能够有效补偿倾斜移相误差对面形相位的影响,与其他方法相比,具有收敛速度快、求解精度高的特点。实验结果进一步验证了该方法的有效性。     

A single-shot pixellated phase-shifting interferometer utilizing a liquid-crystal spatial light modulator

We introduce a novel phase-shifting pixellated interferometer based on a liquid-crystal spatial light modulator and simulate the expected performance. The phase-shifted frames are captured simultaneously, which reduces problems arising from vibrations and air turbulence. The liquid-crystal spatial light modulator is flexible and can be configured to provide a large number of phase-shift levels and geometries to reduce measurement error.     

Accurate phase-shifting digital interferometry

In phase-shifting interferometry experiments, the accuracy of the phase shift is a major issue. Many experimental and data analyses are done to cancel phase-shift errors inherent to the modulation techniques used. We propose to remove most of the phase-shift error by recourse to a frequency-shifting method. This approach can be applied to both holography and interferometry. We validate the idea with a holographic experiment.     

基于相移光纤光栅的布拉格波长解调原理的分析

提出了一种基于相移光纤光栅(phase shifted fiber grating)的布拉格波长解调技术，相移光纤光栅在反射谱阻带中能打开线宽极窄的一个或多个通透窗口，而且窗口位置随所加相移量的大小呈线性变化。实验中应用电流调谐相移量以实现布拉格波长的解调。选用最大波长偏移量为2nm的相移光纤光栅进行调谐滤波，温度的测量范围可达到200℃，应变的测量范围可达到2000μs。实验表明利用相移光纤光栅进行布拉格波长解调，取得了预期的效果，为布拉格波长解调技术提出了新的思路。     

CCD噪声标定及其在边缘定位中的应用

成像过程中的CCD噪声将给图像测量结果带来误差,因此能否有效地抑制这些噪声是提高测量精度的关键。分析了CCD暗电流噪声和随机噪声的特性,并针对各自特性提出了相应的噪声标定技术以及抑制方法。结合精密图像测量任务,分别研究了暗电流噪声和随机噪声对一维边缘定位、结构光相移法相位提取的影响。通过仿真和实验,比较了噪声抑制前后的测量结果,结果表明,噪声抑制后边缘定位精度有很大的提高,证实了该CCD噪声标定技术和抑制方法的有效性和必要性。     

空间外差光谱仪光谱降噪方法研究

空间外差光谱仪是一种新式的超高分辨率光谱仪，可用于大气监测、卫星遥感等领域。为了减少空间外差光谱信号中的噪声，提出基于提升小波变换结合中值滤波方法来实现信号的降噪。改进的提升小波变换融合了一种双因子的阈值函数、分层阈值选取。与小波变换的软、硬阈值对比发现，它能提取空间外差光谱，减小峰宽和保留重要的细节特征，降噪效果优于小波变换的软、硬阈值法。最后用信噪比和均方误差两项定量指标来衡量算法的效果。实验结果表明:该算法比软阈值法在处理氙灯和积分球时信噪比提高了24.6%和31%，均方误差减少了43.2%和51.5%；与硬阈值法相比信噪比提高了21.5%和30.6%，均方误差减少了40.2%和51.2%。因此，算法在空间外差光谱降噪方面具有可行性。     

Phase-shift error as a result of molecular alignment distortions in a liquid-crystal point-diffraction interferometer

We report the observation of nematic director distortions around the diffracting element of a liquid-crystal point-diffraction interferometer. The observed director field distortions are similar to those reported in the literature for other liquid-crystal guest-host systems. We show how the alignment distortion changes as a function of the voltage applied to the liquid-crystal cell, leading to an observed phase-shift error. Tailoring of surface anchoring conditions and judicious choice of phase-shift algorithm can improve device accuracy.     

Exact analysis of a balanced receiver for differential phase-shift keying signals

The performance of differential phase-shift keying signals with a balanced receiver is exactly analyzed by using a closed-form expression without approximation. The numerical results are well matched with previous results based on the saddle-point approximation. The error probability is calculated exactly using the well-known Marcum Q function.     

3-D shape measurement based on complementary Gray-code light

A combination of phase-shift with Gray-code light projection into a three-dimensional (3-D) measurement system has been exploited to digitalize 3-D shape information of a tested object, even with a discontinuous surface. Unfortunately, the phase unwrapping will fall into an error, when an improper value of Gray coding is caused by mistake at the partial boundary of two adjacent binary words. To this end, a new complementary Gray-code method is proposed in this paper as well as the corresponding phase-unwrapping method. This problem of phase unwrapping could be cleverly solved by projecting an additional Gray-code pattern to extend this code and using the different and complementary boundary locations of the traditional and additional codes. The results of computer simulation and experiment confirm that this proposed method based on complementary Gray-code can reliably reconstruct the nature phase distribution of the tested object with only one extra fringe pattern.     

星敏感器低频误差在轨补偿方法

为了抑制地面标定与在轨工况差异引入的低频误差,提出了一种低频误差在轨补偿方法,基于地面标定求得主点、焦距初始值与畸变系数,筛选出符合条件的星对,以星对角距误差最小为准则,基于扩展卡尔曼滤波方法,实时更新星敏感器的焦距值.与现有的多参数同时更新方法相比,该方法具有更快的收敛速度与更高的鲁棒性.多次观星试验和在轨飞行验证了本方法的有效性,星对角距误差均值减小90%以上,低频误差减小40%以上.     

基于单一分光棱镜干涉仪的双通路定量相位显微术

仅仅使用一个单独的分光棱镜(BS),实现了一种用于生物细胞三维成像的双通路定量相位显微术.不同于传统的使用方法,将BS倾斜放置,使中央半反射层与入射光光轴之间存在一个非常小的角度.这样基于BS的分光特性,经过BS后的透射光束和反射光束将会叠加在一起并形成干涉.调节样品位置,利用相机拍摄同时获得了存在π相移的双通路干涉图.这种离轴干涉模式,只需要记录单幅干涉图就可以获得真实的相位信息,方法结构简单,易于操作,适用于微小透明样品的三维形貌测量.