三灰度编码相位展开方法条纹投影轮廓术

为了通过减少条纹投影轮廓术所需投影和采集的条纹图像数量,提高三维测量速度,提出了一种用于条纹投影轮廓术的三灰度编码相位展开方法.投影仪投射5幅条纹图像到被测物体表面,包括三幅正弦相移条纹图像和两幅三灰度编码图像,由相机采集经物体表面调制的变形条纹图.通过相机采集到的三幅变形正弦相移条纹图像计算包裹相位.通过相机采集的三...     

基于DLP技术的刀具刃口检测系统

硬质合金刀具刃口是影响精密加工表面质量以及表面微观几何形貌的重要因素。针对目前测量过程中出现的问题,提出利用DLP技术来测量刀具刃口的三维形貌。其原理是用计算机产生正弦投影条纹,经数字投影仪投射到物体表面,条纹经物体表面调制产生变形,用CCD摄像机将变形条纹拍摄下来。再利用计算机进行相位场提取、相位去包裹,得到绝对相位值。最后经系统标定、坐标变换可得物体表面的三维数据基于数字条纹投射的光学3D传感器,这样能够很好很快地提取刀具刃口的三维形貌。     

基于结构光的反光工件在机三维重构

工件的在机三维重构对于实现智能制造中的加工检测一体化具有重要的意义。在立式加工中心外,设计了一种安装于地面的相机和投影仪的夹持机构。利用设计的机构,调整相机与投影仪的位置,以便投影仪能投射编码条纹图像至加工工件表面,同时相机能捕获经加工工件表面调制后的条纹图像,最终通过改进的算法对获取的条纹图像进行解码,重构出拍摄工件的表面三维形貌。改进的重构算法通过计算直接光分量与间接光分量,能够有效抑制工件表面反光对光学测量的影响,避免反光区域的点云大范围缺失。对用数控加工中心加工的汽车凸缘进行了在机三维重构实验,实验结果表明,该方法是一种快速有效的重构方法,算法执行时间为0.923s,重构的点云密度达9.07个/mm2。     

互补格雷码双 N 步相移的彩色编码光栅投影轮廓术

在三维轮廓测量领域,互补格雷码相移法能够得到连续的展开相位,然而,单组相移条纹导致其测量精度极易受到周围环境变化的影响,且传统投影方式增加了干扰的引入。针对此问题,本文提出了一种基于彩色编码光栅投影的互补格雷码双N步相移法。首先将双N步相移条纹和互补格雷码条纹混合编码成彩色条纹,然后依次投射到目标表面,最后从采集的彩色条纹中提取相位信息分别进行相位解算、融合后求得表面三维形貌。为了验证本文所提方法,将该方法与传统互补格雷码N步相移法以及三频外差法进行了对比实验。实验结果证明,本文方法能够获得高精度表面形貌信息,有效降低测量误差,同时检测效率提高50%。     

基于双频彩色光栅投影测量不连续物体三维形貌

为减少多频条纹相移法进行三维形貌测量时的投影条纹数量,提高测量速度, 提出了采用双频四步相移彩色条纹投影技术来准确测量具有台阶状不连续或孤立物体表面三维形貌的方法。利用计算机将高低两种不同频率的正弦条纹分别输入彩色图像的红色和蓝色通道合成为彩色条纹,由数字视频投影仪将四步相移彩色条纹投影到被测物体,然后利用彩色CCD或CMOS相机采集4幅彩色条纹图并存储于计算机中。基于色彩分离技术得到8幅两种不同频率的四步相移条纹图并由图像灰度算法获得1幅反映背景的灰度图像;由低频条纹确定台阶状的物体边缘,高频条纹计算物体的形貌,并通过背景图像的二值化定位阴影和不连续区域。提出的方法仅用4幅彩色图像完成了台阶状不连续或孤立物体三维形貌的准确测量。与现有的多频4步相移条纹投影形貌测量技术需要8~12幅图像相比,该方法有效地减少了条纹投影与图像采集的数量。     

基于光栅相位法三维重构技术研究

投影光栅相位法（PMP）是一种基于光栅投影和相位测量的光学三维轮廓测量技术,可实现物体表面三维轮廓的自动测量。提出了结合投影仪移轴技术的平行光轴系统,利用计算机编程生成具有高对比度和高亮度、有相差的正弦光栅,用数字投影仪LCD将这些条纹依次投射到被测物体表面,由CCD摄像机获取受物体表面面形调制的变形光栅像,根据数字相移算法计算出相位分布再通过相位展开恢复出连续相位分布,由相位．高度关系最终求出物体轮廓的三维数据信息。针对该原理进行了阐述,并给出了详尽的算法及实验结果。通过MATLAB实验仿真,对条纹图像进行处理和轮廓重构。模拟实验证明,这种测量方法快速高效、分辨率高,且易于实现。     

鲤鱼尾鳍瞬时三维形态测量

提出了鱼在自由游动状态下尾鳍实时三维形貌的测量方法。将影栅云纹投射在鲤鱼尾鳍表面,产生包含三维形态信息的云纹,由高速摄像机采集瞬时序列变形条纹,运用傅立叶变换轮廓术对序列图像进行处理,并将相位解包裹方法用于动态过程瞬时三维相位场的相位展开中,重建了鲤鱼尾鳍自由游动的瞬时三维形态,再现了尾鳍的连续摆动过程。     

采用相调制的三维人体图像采集与处理系统设计

根据投影栅相移法原理开发三维人体扫描仪,本文介绍了相位法的测量原理,设计出光学投影系统、相移机构及图像采集与处理模块构建三维人体测量系统.利用16位单片机搭建硬件控制平台并开发了相应的控制软件,利用VC++设计点云获取与数据处理模块.人体模型测量实验表明:该设计完全满足三维人体测量的需求,仪器具有体积小、操作方便、测量速度快、精度高等优点,且基于USB接口进行数据通信,具有通用性和移动性.     

基于数字光处理的结构光三维扫描系统的设计

结合结构光投影三维扫描的原理,设计了数字微镜器件(DMD)作为结构光的发生装置,主控芯片为FPGA,实现了高速的DMD的控制和相机的同步采集。搭建了一个嵌入式三维扫描光学平台,并应用四步相移法完成实验。首先指定不同方向和周期的正弦条纹结构光,同步采集图像;然后通过软件设计完成对采集图像的预处理、相位的解调、相位的展开、相位-高度映射还原得到三维的深度信息并建模;最终获得最高464.8帧/s不同方向和周期的正弦条纹结构光显示,达到194帧/s的相机触发采集,三维扫描效果图清晰,还原和重建效果理想。     

结合线结构光立体视觉和条纹反射法的三维轮廓检测系统

三维轮廓检测能力决定了光学自由曲面开发的进度和应用的范围。基于条纹反射法检测原理提出了一种结合线结构光立体视觉和条纹反射法的三维轮廓检测系统。该系统主要用于光学自由曲面轮廓的检测,以立体视觉测量得到的光学自由曲面轮廓数据作为初值,结合相位测量偏折法测量数据的迭代,得到精度更高的光学自由曲面轮廓测量结果。实验结果表明,该系统可测量直径为300 mm、倾斜角范围为±20°的自由曲面光学元件,系统的复合测量能力强,光学自由曲面的测量不确定度小于±1μm。     

Measurement of surface form of Johannesteijsmania altifrons leaf using phase-shift fringe projection

The design of thin-walled structures based on naturally occurring folded structures, such as the Johannesteijsmania altifrons leaf, is relatively unexplored. The main advantage of this particular type of folded leaf is that it is supported by a single main stem, which can be exploited in structural designs if the 3-D surface form is known. Since the leaf can deform if the surface form is measured using conventional contact methods, the non-contact phase-shifting fringe projection method was applied to determine the 3-D surface form of the leaf. The potential of the phase-shifting fringe projection method for reconstructing the 3-D surface of naturally occurring folded structures such as J. altifrons leaf has not been attempted in the past. The objective of this work is to investigate the potential of using this technique to measure the 3-D surface of the life folded leaf in its natural environment. Three fringe patterns were projected onto the leaf with phase-shifts of 0, 2π/3 and 4π/3, captured using a CCD camera and processed to obtain a phase map. The 3-D data of the leaf surface were successfully reconstructed from the phase map using a phase-unwrapping algorithm.     

Dynamics range enhancement in digital fringe projection technique

In this paper a new approach to enhance the dynamic range of a fringe projection system for measuring 3D profile of objects with wide variation in their optical reflections is proposed. The high dynamic range fringe images are acquired by recursively controlling the intensity of the projection pattern at pixel level based on the feedback from the reflected images captured by the camera. A four step phase shifting algorithm combined with a quality guided algorithm is used to obtain the unwrapped phase map of the object from the acquired high dynamic range fringe images. Simulation and experimental results show that the proposed technique can accurately measure the 3D profile of objects with wide variation in their optical reflectivity.     

Fourier transform profilometry employing novel orthogonal elliptic band-pass filtering for accurate 3-D surface reconstruction

The article proposes a novel orthogonal elliptic band-pass filtering methodology in Fourier Transform Profilometry (FTP) for significant improvement of accurate 3-D measurement surface reconstruction with arbitrary object colors. Compared with phase shifting profilometry (PSP), FTP using fringe projection can achieve a general 3-D surface profilometry more efficiently by employing one-shot imaging. However, a challenging problem commonly encountered by FTP using fringe projection is its unreliable extraction of precise spectral information from the spectral domain especially when the spectral domain is complicated to process. Various filtering methods previously proposed in FTP have been proved unsuccessful or nonrobust. Thus, a new band-pass filter is developed from an adaptive orthogonal elliptic region to achieve higher accuracy of 3-D surface reconstruction. A comprehensive theoretical analysis is performed to investigate the physical measurement limits of the proposed method. The experimental results obtained confirm that the measurement accuracy of dimension and sphericity can be greatly enhanced when compared with that achieved by the traditional circular band-pass filter. The proposed method is proved to outperform all the other existing FTP band-pass filtering approaches. The maximum dimensional error measured can be controlled within 1.25% of the overall measuring height with various surface colors. However, it is also verified that the traditional three-step PSP can achieve slightly better measuring repeatability than the proposed method.     

正交调制复合光栅投影的三维测量机理及仿真

介绍了采用复合光栅来进行快速测量获取物体三维信息的方法。该方法通过投影由载频光栅携带与其正交的相移光栅而形成的复合光栅来进行三维面形测量。建立了基于复合光栅方法的三维测量理论模型,运用复合光栅完整模拟物体恢复的过程,模拟结果证明了该方法的可行性。该方法具有祛噪功能,由于只需投影一幅复合光栅图像和采集一幅变形光栅图像就实现了物体的重建,因此适用于物体三维面形的快速实时测量。     

基于傅里叶变换轮廓术的磨痕形貌测量

往复冲击条件下,由磨损引起的接触表面磨痕的三维形貌的改变对接触润滑效应的研究具有非常重要的影响。在传统傅里叶变换轮廓术(Fourier transform profilometry,FTP)测量系统中引入正弦光强产生装置以及图像实时采集处理系统,利用单幅条纹图像,快速、准确地重构出磨痕表面三维形貌。利用该测量系统对施加PB2400型润滑油方式下快速冲击一万次后的磨痕形貌进行了测量,利用FTP对采集的条纹图进行处理,获得该磨痕的三维形貌。将测量结果与粗糙度轮廓测量仪所得结果进行对比分析,验证该方法的可行性和有效性。将该测量方法与高速摄像机相结合,可以实现连续冲击过程中磨痕的瞬时三维形貌测量,为进一步研究接触润滑效应提出一种新的试验依据和方法。     

Development of a dynamic surface shape measurement for magnetic fluid

Traditional measurement techniques such as fringe and stereo projection can hardly measure the black surface shape of magnetic liquid in revolving container which has a cover to prevent the liquid spilling out. To solve this problem, a multi-step measurement method based on linear laser projection is proposed. Modulated laser by synchronous revolving chopper is introduced to obtain the steady projection light curve on the measured location of the magnetic fluid surface. In order to capture the instantaneous reflected light of the projection light curve, a camera used a long exposure time of shooting is used. Taking the advantages of multiple exposure luminance enhancement effect of long exposure time, pictures with high brightness and contrast projection light are obtained. The overall surface shape of the fluid can be reconstructed by many laser projection lines extracted from the pictures captured at different angles of revolving container. A high transparency acrylic cover is adopted to provide good sealing performance and light transmission quality in the experiment. On the base of correction of influence of refractive index of the acrylic cover, the height formula of magnetic fluid surface is derived. The camera installation angle and distance between the camera and the container are not required as the size of container are utilized to calibrate the camera. The relationship between image coordinates and world coordinates is also obtained. According to the height curves of the projection lines and their measuring angles on the container, 3-D surface shape of magnetic fluid is reconstructed. The surface shape is verified indirectly by using the imbalance of the container, and the relative unbalance errors between the measurement results and the results by Shenk dynamic balancing machine under different conditions are between 0.8% and 11%. Another performance experiment on measuring the surface shape of an rubber block indicates that the measurement range of the proposed method is that the slope of the measured surface must be less than 3.94, and the sensitivity is 0.18 mm. All performance of the proposed method is acceptable, so such a complex industrial problem is solved only by a daily digital camera.     

Research and development of an accurate 3D shape measurement system based on fringe projection: Model analysis and performance evaluation

In this paper, the research and development of an accurate 3D shape measurement system based on fringe projection is presented. This system utilizes a sliding projection unit to project the desired encoding fringe patterns onto the object and the object shape can be obtained by analyzing the images captured with a camera for each projection. The sliding projection unit uses a high precision grating element fabricated by electron beam lithography to produce the accurate encoding fringe patterns thus to reduce the projection error. And a method based on gray-code and phase-period edge detection is developed to align the grating element with its sliding direction to guarantee the alignment between the projected patterns. The influence of the lens distortion of both the projection unit and the camera is also studied and an improved nonlinear system model is developed based on triangulation. This model gives a more accurate mathematical representation of the shape measurement system and thus improves the system measurement accuracy. The experimental results show that an overall measurement error of 0.04 mm with a variability of ±0.035 mm can be obtained for the developed system.     

基于光栅投影的多摄像机标定方法

多摄像机是解决结构光测量系统中视场小和自遮挡等问题的有效方案,但同时由于摄像机分布广、无公共视场,存在全局标定困难的问题。提出了一种基于条纹投影的多摄像机标定方法。加入辅助设备投影仪并向视场内投影大幅面的条纹图案,借助相位算法建立起全局相位场,反求景物的投影仪虚拟图像。利用平面靶标标定摄像机的内参和投影仪的外参获取靶标平面的移动信息,进而求解相邻摄像机的位置参数。最后的优化过程中,再根据相位值对相邻摄像机的图像完成亚像素匹配,通过最小化重建偏差对系统参数进行迭代优化。在搭建的多摄像机三维测量系统上进行试验,结果表明本文的多摄像机标定和测量方案切实可行。