一种针对彩色物体的光栅投影三维测量方法

针对传统彩色编码光栅三维轮廓术中光栅易受到物体表面彩色纹理的干扰,从而造成编码条纹颜色误判和相位误差增大这一问题,提出一种基于互补彩色光栅的三维测量方法,给出了理论分析、光栅设计原理、补偿算法与实验分析。对图像进行初步的解耦校正后,通过预先设计的光栅互补特性,依据彩色响应模型求取物体表面逐点的反射率,并对红绿蓝(RGB)三通道反射率的不平衡进行补偿,消除物体表面彩色纹理的干扰,改善光栅的正弦性。以补偿后的图像来指导彩色编码条纹的分割解码并用傅里叶变换法提取出包裹相位,依据解码结果指导相位展开,继而完成整个三维测量过程。实验证明该方法对彩色纹理的补偿准确有效,降低了彩色纹理对测量的影响。     

基于彩色编码光栅投影的双N步相移轮廓术

双N步相移轮廓术虽然可以大大降低由于光栅条纹的非正弦性所导致的相位误差,但增加了一倍的投影条纹数量,降低了测量效率。针对此问题,本文提出一种基于彩色编码光栅投影的双N步相移轮廓术,它将原相移条纹和附加相移条纹编码成双色条纹,融合到一幅彩色光栅条纹中投影,然后从采集的彩色条纹中提取两套条纹的相位信息,分别解包裹相位后,融合两包裹相位以减小相位误差。为验证所提方法的有效性,将该方法与两种典型的相位展开算法结合进行实验。实验结果证明,所提方法能有效降低相位误差,且不需要增加任何额外的光栅条纹,测量效率提高了46%。     

一种新型单帧彩色复合光栅投影的实时三维测量方法

提出了一种新型单帧彩色复合光栅投影的实时三维测量方法。采用三帧具有π2的相移正弦条纹分别编码到红色(R)、绿色(G)和蓝色(B)三个颜色通道中,组合成单帧彩色复合光栅,当该彩色复合光栅投影到待测物体上,仅需获取单帧彩色变形条纹并从中分离出相应的具有π2相移的三帧单色相移变形条纹,由于不同颜色通道之间存在颜色串扰以及色度不均衡问题,采用最小二乘法对分离出的三帧单色相移变形条纹直流项进行背景一致性校正,从而获得三帧校正后的单色相移变形条纹,运用所建立的三维重构物理模型,即可恢复物体的三维形貌。实验验证了该方法的可行性和实用性。进一步的实验表明,该方法的测量精度优于传统单帧彩色PMP。因为所提方法仅需一帧彩色复合光栅即可恢复物体的三维形貌,在实时三维测量中具有很好的应用前景。     

基于单幅彩色正弦光栅投影的三维形貌测量

提出了一种新的基于单幅彩色正弦光栅投影的三维形貌测量方法.利用计算机产生一幅正弦条纹图和两幅单一强度图分别通过红绿蓝(RGB)三个通道合成为一幅彩色条纹图,并由液晶投影仪投影到被测物体表面,彩色变形条纹由彩色电荷耦合器件(CCD)采集并保存在计算机中.对畸变的彩色条纹进行三色分离处理,利用其中的红色条纹分量与蓝色背景相...     

基准光栅重构傅里叶变换轮廓术

应用傅里叶轮廓变换术进行三维形貌测量中,为了获得待测物体的高度相位信息,通常需要采集两幅图像.因此当光学系统发牛变动时,必须重新采集基准光栅图像,不利于快速测量.提出一种从变形光栅图像中获取基准光栅图像信息的测量方法.首先在变形光栅图像中记录基准光栅信息,然后通过傅里叶分析提取基准光栅频率信息,通过图像分析获得基准光栅相位信息,最后重构出一幅完整的基准光栅图像,实现三维物体形貌测量.实验结果验证了该方法的可行的.     

单幅彩色条纹投影的不连续物体表面三维形貌测量

提出了基于单幅彩色条纹投影的不连续物体及动态三维形貌的测量方法。该方法利用计算机产生一幅正弦条纹图和两幅单一强度图分别通过红蓝绿三个通道合成为一幅彩色条纹图,由液晶投影仪投影到被测物体表面,彩色CCD采集变形条纹图并保存在计算机中。通过三色分离,同时获得正弦条纹图和反映表面反射率分布及背景信息图,通过图像除法运算及亚像素精度归一化处理实现物体三维形貌的恢复。对于表面形貌不连续的物体,利用蓝色分量的灰度图像进行二值化处理定位阴影或暗背景,从而引导正确的相位求解。实验验证了该方法对不连续物体动态测量方面的可行性。     

基于波长分离的结构光采集系统

彩色结构光系统利用彩色投影机与摄像机中的三个颜色通道,同时投影和采集三幅条纹图像,拍摄一次即可实现形貌测量,但其无法测量彩色物体,通道间的串扰也降低了精度。提出了一种新的系统,利用三个摄像机采集三个通道,并利用严格设计的分色棱镜和滤光片,消除了彩色结构光系统中常见的波长通道间的颜色串扰。基于三步位移法,分析了拍摄两次图像获得彩色物体形貌的过程,并针对该系统提出了校正方法。利用上述方法,拍摄两次即可得到彩色的物体形貌。     

采用二维载频条纹的二维伽博小波变换轮廓术

为解决三维形貌测量中非连续相位解包问题并提高测量精度,提出了采用二维网格光栅作为空间载频条纹的二维伽博小波变换轮廓术。与采用一维单一频率载频条纹轮廓术比较,该方法可以获得两倍的测量信息,并且可以达到相同的测量精度。提取二维网格条纹中的两个调制相位时,该方法不必设计带通滤波器来分离两个一维条纹,而是直接应用二维伽博小波变换。通过检测小波脊,从一幅变形网格光栅图像中直接提取两个方向光栅条纹各自所对应的包裹相位分布,结合查表法进行解包从而得到确定的调制相位分布。给出了详细的理论推导,实验结果证实了该方法的可行性。     

基于点阵投影的彩色复合光栅傅里叶变换轮廓术

传统傅里叶变换轮廓术(FTP)采用单一频率条纹测量时存在着由于待测物体高度变化剧烈导致的相位展开困难。结合数字点阵和正弦条纹投影的复合编码三维数字成像方法能有效解决相位模糊和误差传播的问题,但在实际测量中需要分别采集点阵图像和正弦条纹图像,影响了测量的实时性。提出一种新型彩色复合光栅测量方法,实现了从一帧图像中分别得到点阵图像和正弦条纹图像,并以点阵图像为依据对正弦条纹图的截断相位进行展开。理论分析和实验结果表明,该方法适合于不连续物体的三维测量,同时抑制误差传播能力强,具有较高的测量效率。     

基于光栅投影的轮廓测量改进方法

传统傅里叶变换轮廓方法(FTP)在测量表面突变的物体时,受物体高度变化所引起的非截断相位变化的影响,相位难以正确展开。利用双频光栅投影可以解决这一问题。在总结了传统测量方法与双频光栅测量方法的基础上,提出采用彩色复合光栅投影的测量方法。该方法只需一次采集,就能消除图像背景分量与高次分量对测量的影响,在扩大测量范围的同时可达到双频技术测量突变效果。最后,对3种方法的实际测量结果作了对比分析,证明彩色复合光栅投影方法得到的测量精度最高。     

用于动态测量的双通道光学相位测量轮廓术

提出了利用编码光两个采样值实现相位测量轮廓术的原理。设计了一种偏振分光双通道测量系统，实现了两个采样值的同时记录，因而实现了动态测量，拓展了相位测量轮廓术的应用范围。文中给出了实验结果。     

Dual-channel phase-shifting interferometry for microscopy with second wavelength assistance

Dual-channel phase-shifting interferometry for simultaneous phase microscopy is presented. Red and blue light beams are used for microscope illumination. A 45 tilted beamsplitter replicates the object and reference waves in red light together with the object wave in blue light into two parallel beams. The two resulting quadrature phase-shifting interferograms in red light and the object waves in blue light are generated in the two channels. The two interferograms are recorded simultaneously by a color charge-coupled device (CCD) camera, and can be separated via RGB components of the recorded color patterns without crosstalk. As a result, the phase of tested specimen can be retrieved. The feasibility of the proposed method is demonstrated by test performed on a microscopic specimen.     

彩色组合编码条纹光栅轮廓术

研究了一种新的编码光栅投影三维轮廓术。其中投影光栅利用彩色空间红、绿、蓝三基色相互独立的特性,用彩色条纹对光栅进行编码,以白色条纹为起始位,后接红、绿、蓝（R、G、B）三种颜色的条纺组成一组。改变红、绿、蓝的排列顺序可使各组有不同的编码。根据排列组合原理,红、绿、蓝三色可有6种不同的排列方式。经过编码处理的光栅在保证测量精度不变的前提下,加大了高度测量的范围。由于每条纹只采用0和255两个状态,因此具有较强的抗干扰能力。测量的精度主要取决于图像的分辨率。     

Optical color image encryption based on Arnold transform and interference method

In this paper, we propose a novel method to encrypt a color image based on Arnold transform (ART) and interference method. A color image is decomposed into three independent channels, i.e., red, green and blue, and each channel is then encrypted into two random phase masks based on the ART and interference method. Light sources with corresponding wavelengths are used to illuminate the retrieved phase-only masks during image decryption. The influence of security parameters on decrypted images is also analyzed. Numerical simulation results are presented to illustrate the feasibility and effectiveness of the proposed method.     

Color image encryption based on interference and virtual optics

We propose two approaches to encrypt color images based on interference and virtual optics. In the first method, a color image is first decomposed into three independent channels, i.e., red, green and blue. Each channel of the input image is encrypted into two random phase-only masks based on interference. In the second method, a color image is first converted into an image matrix and a color map, and only the image matrix is encrypted into random-phase masks based on interference. After the phase masks are retrieved, a concept based on virtual optics is further applied to enhance the security level. Numerical simulations are demonstrated to show the feasibility and effectiveness of the proposed methods.     

Securing color image by using phase-only encoding in Fresnel domains

We propose a novel color image hiding scheme with three channels of cascaded Fresnel domain phase-only filtering. The original color image is encoded into three phase masks by using the Gerchberg–Saxton iterative phase retrieval algorithm with another predefined phase key. The individual phase masks are placed in the inputs of the Fresnel domains of the red–green–blue channels and the phase key in the public channel, during the optical retrieval. The physical parameters in the optical system will be regarded as the additional keys for security enhancement. Numerical simulation is performed to test the validity of our scheme.     

基于双色条纹投影的快速傅里叶变换轮廓术

在实际傅里叶变换轮廓术测量中，获取的条纹图扩展的零频分量对傅里叶变换轮廓术的测量精度和测量范围有很大影响，甚至妨碍正确三维面形的恢复。π相移技术常被用来消除零频分量对测量的影响，但需要在测量系统中安装精密相移装置，并需要采集两帧具有π相位差的条纹图。传统傅里叶变换轮廓术中，完成精密相移需要较长的时间，影响了傅里叶变换轮廓术测量方法的实时性。提出了采用双色正弦光栅投影来实现从一帧条纹图中消除零频对傅里叶变换轮廓术测量的影响。该方法同传统的π相移方法相比，不需要相移装置，测量系统简单，并且能真正实现高速测量。     

An improved stair phase encoding method for absolute phase retrieval

An improved phase unwrapping method is proposed to reduce the projection fringes in three-dimensional (3D) surface measurement. Color fringe patterns are generated by encoding with sinusoidal fringe and stair phase fringe patterns in red and blue channels. These color fringe patterns are projected onto the tested objects and then captured by a color CCD camera. The recorded fringe patterns are separated into their RGB components. Two groups of four-step phase-shifting fringe patterns are obtained. One group of the stripes are four sinusoidal patterns, which are used to determine the wrapped phase. The other group of stripes are four sinusoidal patterns with the codeword embedded into stair phase, whose stair changes are perfectly aligned with the 2π discontinuities of sinusoidal fringe phase, which are used to determine the fringe order for the phase unwrapping. The experimental results are analyzed and compared with those of the method in Zheng and Da (2012. Opt Express 20(22):24139–24150). The results show that the proposed method needs only four fringe patterns while having less error. It can effectively reduce the number of projection fringes and improve the measuring speed.