共查询到18条相似文献,搜索用时 140 毫秒
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双频光栅轮廓术的研究 总被引:5,自引:0,他引:5
在投影栅相位法轮廓检测中,当物体含突变部分时,包裹相位很难准确恢复,对此可用双频变精度技术来解决。如果用两种不同频率光栅分两次进行测量,无疑增加了测量负担,也无法满足实时检测的要求。提出用软件生成两种不同频率成分的复合正弦光栅,用液晶投影仪投影,针对不同物体具体突变部分的情况,可灵活生成各种不同灵敏度的复合光栅。只采一次图像就可以达到以往双频技术中多次采集的效果,该法具有快速和去包裹精度高的特点。最后,进行了实验测试,结果非常满意。 相似文献
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《中国光学与应用光学文摘》2005,(4)
TB92 2005043049 双频光栅轮廓术的研究=Study of profilometry with dual- frequency grating[刊,中]/周灿林(天津大学力学系,天津 (300072)),亢一澜//光学技术,-2005,31(1),-139-141 提出用软件生成两种不同频率成分的复合正弦光栅, 用液晶投影仪投影,针对不同物体具体突变部分的情况, 可灵活生成各种不同灵敏度的复合光栅。只采一次图像就可以达到以往双频技术中多次采集的效果,该法具有快 相似文献
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基于双频彩色条纹投影的相位测量去包裹方法 总被引:3,自引:0,他引:3
为了提高测量速度,提出一种基于双频彩色条纹投影的相位测量去包裹方法,只需采集一帧图像,就能实现高速测量以及动态物体轮廓测量中的相位去包裹。论述了双频相位测量和变精度去包裹原理,并详细分析影响测量精度的因素。该方法采用计算机生成一帧双频双色正弦条纹图,用液晶数字投影仪投影,并用傅里叶变换的方法对两个单色条纹图进行分析,获得高低两种精度的被测物体高度信息,从而进行变精度去包裹处理。结果表明,利用该方法提高了测量速度,可得到较高的去包裹精度,其测量最大绝对误差为 1.413~-1.582 mm,标准差为0.363 mm。 相似文献
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小波变换轮廓术在双频光栅条纹中的应用 总被引:2,自引:2,他引:0
为了解决非连续物体三维面形测量中所存在的非连续相位解包问题,采用计算机生成的两频率之比为一无理数的电子光栅作为空间载频光栅条纹投影到待测物体表面。另外结合伽博小波变换分析的相位解调原理,在一幅变形双频光栅图像中分析得到两个频率各自所对应的包络相位分布,并且应用钟金钢等所提出的双频条纹查表法进行解包得到确定的调制相位分布。提出的双频光栅-小波变换-查表相位解包法很好地解决了傅里叶变换轮廓术,以及连续相位解包法在非连续物体三维面形测量中所存在的问题。给出了详细完整的理论推导过程、计算机模拟以及实验验证,证实了该方法的可行性。 相似文献
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4f相位相干成像技术是测量三阶光学非线性的一种新方法.在4f相位相干成像系统中的相位光阑一直都足用具有一致相位延迟的相位物体,这种相位光阑只能产生单一的相衬信号.应用正负相位物体可以提高4f相位相干成像系统测量灵敏度.为了使含正负相位物体的4f相位相干成像系统的灵敏度进一步得到提高,理论分析了正负相位物体的半径和相移的大小对4f相位相干成像系统灵敏度的影响.结果表明系统的灵敏度随着相位物体半径与小孔半径的比值的减小而增大.当相位物体的大小一定时,在相移为0.43π的地方系统的灵敏度达到最大值. 相似文献
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莫尔测量法被广泛用于各类流场的结构显示和关键参量测量中,关于相位物体在光路中的放置位置已有不同的报道,针对该问题进行了理论和实验研究。理论分析表明,当相位物体放置于2个光栅前时,偏移量和相位主要取决于2个光栅之间的距离,偏折角取决于相位物体引起的相位扰动与2个光栅之间的间距的比值;而当相位物体放置于2个光栅之间时,偏移量和相位主要取决于相位物体到后面一个光栅之间的距离,偏折角则取决于相位物体引起的相位扰动与其到后面一个光栅之间的距离的比值。为了验证理论结果的正确性和合理性,实验中选取燃烧蜡烛火焰作为对象,对比发现在两种情况下,只要相应的距离选取适当,则相位物体的位置并不影响实验中重建的相位和偏折角等结果。相关研究成果可为莫尔测量法更好地用于各类流场的检测提供一定的参考。 相似文献
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Global illumination affects shape measurement accuracy, and phase unwrapping is an important problem in phase measuring profilometry. In this paper, a micro-phase measuring profilometry is proposed to reduce the effects of global illumination. The wrapped phase error level of the proposed method is lower than that of the traditional micro-phase shifting method. First, a frequency selection rule is developed in combination with the micro-phase rule to design the frequencies of the proposed phase measuring profilometry. The frequency rule is obtained by analysing the uncertainty of the wrapped phase caused by intensity noise. Then, phase unwrapping is regarded as a congruence problem, and the closed-form robust Chinese remainder theorem algorithm is adopted to determine the correspondence. Finally, the comparative experiments are conducted on a projector-camera system. Experimental results show that the effects of global illumination can be effectively reduced with the proposed phase measuring profilometry, and the proposed frequency selection rule is valid. In addition, the performance of the robust Chinese remainder theorem in addressing the phase error is better than that of traditional Chinese remainder theorem. Furthermore, the unwrapping accuracy can nearly reach 100% if the frequency selection rule is satisfied. Otherwise, the performance degrades. 相似文献
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Surface profile inspection of a moving object by using dual-frequency Fourier transform profilometry
The 2π phase ambiguity caused by surface isolations and large height step can be solved by dual-frequency projection grating profilometry. However, in the Fourier transform profilometry (FTP) of a moving object, only one single deformed fringe pattern can be obtained. In order to introduce the dual-frequency technique into the FTP of moving object, a novel experimental system is designed to capture two fringe patterns with different frequency at the same time. A grating structure comprising two regions with different frequencies is projected upon the surface of the detected object. Two line-scan CCD cameras are used to capture the surface images encoded by the two kinds of patterns, respectively. By getting the corresponding image intensity at the same point of the object surface in the two acquired images, the dual-frequency technique is applied to extract the real phase without phase ambiguity. The surface profile of a specimen with a large height step is measured to prove the feasibility of the proposed method. The experimental results show that the proposed method can solve the 2π phase ambiguity problem successfully in the surface profile inspection of a moving object. 相似文献
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A new 3D shape measurement method based on non-integral twin-frequency grating projection is proposed. In this paper, the projected composite grating is composed of two sinusoidal gratings, and the quotient of whose frequencies is not an integer. By using appropriate phase-shifting algorithms, two wrapped phases can be obtained from sixteen frames of the distorted grating patterns. In aid of appropriate phase unwrapping method, the unwrapped phase of high frequency fringe is obtained only from the relation of the two wrapped phases by a pixel-to-pixel phase unwrapping technique. Therefore the unwrapped phase of high frequency fringe pattern is independent of the low frequency fringe pattern, different from traditional integral twin-frequency grating projection methods in which the phase unwrapping error of low frequency fringe pattern may be propagated onto the unwrapped phase of high frequency fringe pattern. The new theory proves that the proposed method is applicable to measure discontinuous object, and has considerable measurement accuracy. 相似文献
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Phase unwrapping is a task common to many applications like interferometry imaging, medical magnetic resonance imaging, solid-state physics, etc. Fourier transform profilometry (FTP) values the height distribution of object, elaborating the interference between a plane reference grating and a deformed object grating. Since the height information is extracted from the phase of a complex function, the phase unwrapping is a critical step of the process. Several unwrapping algorithms are proposed in literature, but applied to measurement technologies different from FTP. The purpose of this paper is to define the performances of eight different unwrapping algorithms applied to FTP optical scan method and to define the best one. The algorithms chosen are: Goldstein's algorithm, quality guided path following method, Mask cut method, Flynn's method, multi-grid method, weighted multi-grid method, preconditioned conjugate gradient method and minimum Lp-norm method. The methods were tested on real images acquired by a FTP scanner developed and calibrated for these experiments. The objects used vary from simple geometries, like planes and cylinders, to complex shapes of common use objects. Algorithms were qualified considering the phase unwrapping errors, execution time and accuracy of the shape of objects obtained from the scan method in comparison with real ones. The results show that quality guided algorithm best fits in FTP application. 相似文献
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A novel phase-coding technique based on Fourier-transform profilometry (FTP) is proposed for three-dimensional object recognition. Two spatially multiplexed grating patterns of different spatial frequencies are projected simultaneously onto the objects-target, and the phase changes in the distorted patterns are detected. An algebraic addition or subtraction of these phase values is utilized to code the two-dimensional plans of the objects-target with spatial harmonic modulations. The phase-coded plans of the objects and the target are cross correlated digitally to yield a high correlation peak at the target location. The 2pi ambiguity of the phase associated with FTP has been resolved in correlation results without recourse to phase unwrapping. Experimental results show an excellent discrimination capability for target recognition. 相似文献
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基于结构光编码的相展开方法 总被引:9,自引:3,他引:9
探讨了一种新的基于结构光编码相展开技术。实现方法是先将计算机构造的用于解相的光栅由投影仪投射到物体上 ,再将计算机构造的一系列黑白相间的编码光栅也由投影仪投射到物体上 ,然后将畸变栅线图像由摄像机采集到计算机中 ,用解相光栅进行解相得到折叠在 [-π ,π]区间内的相主值 ,用所述结构光编码方法进行相展开得到相位的周期 ,二者相加得到真实相位值。与传统的相展开方法相比 ,该方法相展开过程变得相对简单 ,不依赖于路径 ,不存在误差的传播 ,对噪声的抗干扰能力强 ,能够得到准确的周期 ,并能够与解相过程有机结合起来。实验证明该方法获取光栅周期快速、准确 相似文献