Three-step self-calibrating generalized phase-shifting interferometry

An accurate and fast three-step self-calibrating generalized phase-shifting interferomertry(SGPSI) is proposed. In this approach, two new phase-shifting signals are constructed by the difference interferograms normalization and noise suppressing, then the unknown phase shift between the two difference phase-shifting signals is estimated quickly through searching the minimum coefficient of variation of the modulation amplitude, a limited number of pixels are selected to participate in the search process to further save time, and finally the phase is reconstructed through the searched phase shift. Through the reconstruction of phase map by the simulation and experiment, and the comparison with several mature algorithms, the good performance of the proposed algorithm is proved, and it eliminates the limitation of requiring more than three phase-shifting interferograms for high-precision SGPSI. We expect this method to be widely used in the future.

Phase-shifting digital holography in image reconstruction

A phase-shifting digital holography scheme developed to investigate internal defects in artworks is described. Phase-shifting is utilized to obtain a clear reconstructed object wave from a rough surface texture. A reverse-transform algorithm is employed to reconstruct the object wave on its original position of unknown distance or the imaging position from the object wave information on the holographic plane. To get the clearest reconstruction the exact registration of the unknown distance is determined by applying the intensity sum as the auto-focusing function, The spatial resolution of the reconstruction image is also investigated for a variety of affecting factors. Laboratory results of reconstruction images under deformation are presented.

An encryption scheme based on phase-shifting digital holography and amplitude-phase disturbance

In this paper, we propose an encryption scheme based on phase-shifting digital interferometry. According to the original system framework, we add a random amplitude mask and replace the Fourier transform by the Fresnel transform. We develop a mathematical model and give a discrete formula based on the scheme, which makes it easy to implement the scheme in computer programming. The experimental results show that the improved system has a better performance in security than the original encryption method. Moreover, it demonstrates a good capability of anti-noise and anti-shear robustness.

Two-step phase-shifting Fresnel incoherent correlation holography based on discrete wavelet transform

Fresnel incoherent correlation holography(FINCH)has the ability to generate three-dimensional images with a superresolution by using incoherent sources.However,there are unwanted direct current term and twin image in interferograms,so it is of great significance to find a method to eliminate them.Phase-shifting technology is a most widely used technique for this task,but its three-step phase-shifting is not suitable for the instantaneous measurement of dynamic objects,and the quality of reconstructed image with the traditional two-step phase-shifting is lower.In this paper,we present a method of enhancing the resolution through using a two-step phase-shifting technology based on the discrete wavelet transform.After two-step phase-shifting,the resulting hologram is a superposition of multiple forms.The frequency of the resulting hologram is decomposed into different levels through using discrete wavelet transform,then the image is reconstructed after retrieving the low frequency band.Various experiments have verified the effectiveness of this method.

计算全息综合性光电教学实验设计

基于傅里叶光学原理实现对目标光场进行精确重建,设计了从显示目标绘制,相应计算全息图生成到光学重建的综合性教学实验。具体的实验流程包含基于Visio的显示目标设计,基于MATLAB的相位型计算全息图生成算法编写和基于相位型液晶空间光调制器的目标重建光路搭建。实验设计结合了光学、数字电路和计算机软件技术,具有流程清晰、易于教学、学生参与度高和获得感强的优势,可有效增强学生对计算全息技术与光电信息技术的理论理解与实操能力。

使用多核CPU-GPU异构系统快速生成计算全息图

为了充分利用计算机的计算性能提高基于点源模型的计算全息图(CGH)的生成速度,设计了基于多核中央处理单元(CPU)和图形处理单元(GPU)的计算全息图快速生成系统,并对该系统进行了优化。首先采用统一架构平台设计并实现了基于点源模型的计算全息图生成系统,提出了计算的优化策略;然后根据优化的计算公式来减少计算量;最后对任务调试等进行优化,构建CPU的并行计算系统,其中一个核心负责启动函数和传输数据,其余核心承担一部分计算任务,进一步提高计算速度。结果表明,设计的系统能让CPU和GPU的性能均得到充分利用,在同等配置的计算硬件条件下,生成计算全息图的加速比较GPU系统计算全息图的加速比提高了4~4.75倍,可以有效提高计算全息图的生成速度。该研究对快速生成3维场景全息图是有帮助的。

Optical encryption of multiple three-dimensional objects based on multiple interferences and single-pixel digital holography

We present an optical encryption method of multiple three-dimensional objects based on multiple interferences and single-pixel digital holography. By modifying the Mach-Zehnder interferometer, the interference of the multiple objects beams and the one reference beam is used to simultaneously encrypt multiple objects into a ciphertext. During decryption, each three-dimensional object can be decrypted independently without having to decrypt other objects. Since the single- pixel digital holography based on compressive sensing theory is introduced, the encrypted data of this method is effectively reduced. In addition, recording fewer encrypted data can greatly reduce the bandwidth of network transmission. Moreover, the compressive sensing essentially serves as a secret key that makes an intruder attack invalid, which means that the system is more secure than the conventional encryption method. Simulation results demonstrate the feasibility of the proposed method and show that the system has good security performance.

计算机制一步彩色彩虹全息的研究

针对现有的彩色全息技术中存在的制作过程复杂、色串扰、技术条件要求高等问题,提出了一种计算机制一步彩色彩虹全息技术。该技术将光学一步法彩虹全息技术和多次曝光彩色全息技术相结合,首先根据线全息图理论,确定每个物点的线全息图在整个彩虹全息图中的区域范围,并计算线全息图,然后将每个物点的线全息图相加,直接获得计算机制一步彩虹全息图,大大减少了全息图的计算量。在此基础上,分别计算彩色物体的红、绿、蓝三分色计算全息图,并合成为彩色彩虹全息图,用白光再现获得真彩色全息再现像,大大简化了彩色彩虹全息图的制作过程、降低了技术条件要求,充分发挥了计算全息简单、灵活、方便的优点。给出了理论分析和实验结果。

计算全息补偿检测自由曲面的高精度位姿测量

为实现自由曲面的定位与位姿高精度测量,提出了“光学-机械”基准定位法,建立了位姿测量模型,并对该方法的定位误差和基准选择展开研究。根据三坐标测量机与计算全息提出了“光学-机械”基准定位法。然后,采用球形安装的回射器(Sphere Mounted Retroreflector,SMR)、猫眼、基准球作为基准,基于波像差理论与视差效应分别建立了3种基准的位姿测量模型,得到了位置误差与基准区域波前像差的函数关系,并对3种位姿测量模型进行对比。最后,对3种基准位姿测量方法进行仿真及实验验证,实测结果与模型的残差结果均小于0.05λ,相对误差均小于2.43%,验证了模型的准确性。实验结果表明,当检测距离为1000 mm时,猫眼法的轴向定位误差为24μm;基准球法的轴向定位误差为50μm;SMR靶球法的轴向定位误差为16μm,X,Y方向的定位误差为1μm,滚转角定位误差为3.26″。SMR靶球法的定位误差最小、检测动态范围最大且检测光学元件的自由度最多,更适用于自由曲面的高精度位姿检测。

基于深度学习的计算全息显示进展

计算全息作为一种三维显示手段,能够基于衍射计算实现对目标光场的精确重建,在元宇宙通讯、AR/VR头戴显示、车载抬头显示等方向均有着重要的应用。如何实现高速且高质量的相位全息图生成是计算全息领域发展的关键问题,也是当前该方向的重要研究课题。近年来,深度学习技术的飞跃式发展为上述问题的解决提供了一条新的技术路径。本文介绍了计算全息技术的基本原理及算法分类,综述了近年来所提出的基于深度学习的计算全息解决方案,比较了各类方案的优势与不足,展望了深度学习技术在计算全息领域的发展与挑战。

基于显著性物体检测和S-PCG算法的彩色全息显示系统

针对全息三维显示系统图像生成速度慢、重建精度低以及波前调制器件调制性能受限等问题,设计了一种面向真实物体的彩色全息三维实时显示系统.首先,利用深度相机采集真实物体的三维信息;其次,在采集端构建三维显著物体检测模型,采用显著性检测滤除冗余背景信息,获得准确的点云信息;最后,利用分割型点云网格化(segmented point cloud gridding,S-PCG)算法快速生成全息图,完成彩色全息三维实时显示系统的构建.实验结果表明,与传统方法相比,所提方法可有效降低全息系统的计算复杂度,提升采集端实时图像处理速度和重建精度.

基于全介质超表面的太赫兹波段偏振复用计算全息成像

提出利用全介质超表面实现太赫兹波段计算全息成像技术方案,采用基于几何相位调控的全介质超表面实现了频率0.95 THz~1.2 THz的宽带全息成像。在此基础上,设计了基于几何相位和传输相位同时调控的全介质超表面并实现了偏振复用全息成像。该研究提高了超表面的复用能力和工作效率,有望解决金属超表面存在的固有欧姆损耗和低极化转换效率等问题。同时可以激发Mie型电共振和磁共振实现波前调制,为开发高效、轻便、低成本的太赫兹功能器件提供了一种新途径。

贝叶斯正则化在球面等效源法中的应用研究

为拓宽空心球阵列的应用场景,提高三维空间声场重构精度,本文开展空心球阵列结合球面等效源方法的声场重建研究。在近场条件下,由空心球阵列采集到三维空间的声场信息,结合球面等效源法,对声场重构中存在的逆问题所常用的广义交叉验证正则化参数选择方法,提出贝叶斯正则化,并利用MATLAB对两种正则化方法的重建结果进行对比。分别探讨了两种正则化方法在不同声源距离、声源频率、重构球面半径和信噪比情况下对声场重建精度的影响。结果表明,贝叶斯正则化在基于空心球阵列的三维空间声场重建中具有明显优势。

Holography and speckle in phase-shifting digital holography(Invited Paper)

The correlation properties of the optical field diffusely reflected from a rough surface under coherent illumination are analyzed numerically. The cross-correlations of the complex amplitudes and the intensities before and after translation and/or tilt of the surface are calculated at an arbitrary observation plane in three-dimensional （3D） space. The results provide us with the 3D distributions of phase changes and speckle displacement that lead to the distributions measured by holographic interferometry and speckle relationships and physical interpretation of them are and signal-to-noise ratio of the displacement to be correlation technique. Comparisons with analytical also discussed.

计算全息法产生涡旋光束的实验

基于计算全息法,通过计算和模拟得到了涡旋光束与平面光束干涉所产生的位错条纹,用胶片记录位错条纹并制作成位错光栅,在自行设计搭建的光路中进行实验获得1-4阶的涡旋光束。实验结果表明,各阶涡旋光束的空心半径随着阶数的增大而逐渐增大,与理论分析相符合;实验进一步观察到各阶光栅的二级甚至三级衍射光束,当入射光束中心与光栅位错中心重合时,能够产生光强分布对称的涡旋光束,当光束中心和光栅中心不重合时,产生的涡旋光束的光强分布不对称。这为后续以涡旋光束为捕获光束的光镊实验的进一步拓展及应用提供了理论和技术支持。

彩色全息光电再现倍率色差的消除

针对基于空间光调制器的彩色全息光电再现系统在利用计算全息图进行光电再现时会由于三色激光波长不同造成再现像出现倍率色差,影响再现效果的问题,本文重点分析了倍率色差产生的原因。为了消除倍率色差,提高彩色光电再现像的质量,提出了在全息图计算过程中对物信息进行差别采样来消除倍率色差。基于时分复用方法搭建了彩色全息光电再现系统,以迭代傅里叶变换型全息图为例,对处理后的计算全息图进行了光电再现。实验表明,提出的方法可以消除波长不同造成的色差(33.6%(红色),12.5%(绿色)),实验结果验证了本文所提出方法的可行性。

基于声全息方法和双目视觉实现运动声源声场可视化

运动声源声场的可视化是一种重要的运动声源定位的技术手段,利用双目视觉测量技术实现运动声源声场空间的自动测量,自动确定运动声源表面的空间位置,针对声源表面,利用传声器阵列,基于声全息方法实现运动声源声场的重建,建立视频图像与声场的空间映射,并建立视频与声场之间的时序,实现实景视频图像与声场重建结果的融合,可以自动生成声源运动过程的视频。基于该方法所开发了一套试验测量系统,对运动声源的测量试验结果表明,该方法可以有效实现运动声源的视频可视化,使人可以直接从视频中看到声源及其变化过程,使声源的定位和识别变得更加简单。

利用ZYGO干涉仪进行非球面检测技术研究

为了能够利用ZYGO数字干涉仪检测大口径深度高次非球面,提出了一种新的波前补偿方法,即透镜补偿与计算全息相结合. 通过设计实例表明,对于相对孔径为 1: 1. 08的大口径深度高次非球面,利用简单的 2片式透镜补偿器、并与计算全息的-1级衍射波相结合,系统的波前残余误差的均方根 (RMS)值可以控制在 0 .01λ以内. 结果表明,该检测方法具有通用性强,测量精度高等特点,较好的克服了以往各种检测方法的局限性.

利用扭曲向列型液晶光阀实现对数字全息再现像质的改善

提出一种提高全息图像的清晰度的新方法。即原始图像经过微分运算和计算全息的变换后,得到它的边缘全息图,然后对该边缘全息图的对比度进行调节,再通过液晶光阀的调制作用,得到这幅调整后的全息图的再现像。这样得到的全息图的再现像比原来边缘全息图更为清晰。文中推导了黑色和白色的灰度调节函数,同时借助实验数据利用Matlab推导了光强与灰度的近似公式,并利用这些公式对图形进行了改善,实现了更为清晰的全息再现演示。

近场声全息试验用于医用制氧机噪声控制

为了降低家用制氧机的运行噪声,采用了近场声全息技术进行制氧机噪声场数据采集和声场重建。根据声压频谱图、声压辐射云纹图、声速频谱图、空间声速分布图以及时间/频率/声压图谱等可视化信息,选择了针对声源、传播途径的隔声罩、涂敷阻尼胶、石膏板吸声和加装部件减振胶垫等简单有效的噪声控制措施。试验表明,近场声全息技术是一种有效地进行噪声源控制和声辐射特性研究的重要工具。