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Application of grayscale expansion for accuracy improvement in phase-measuring profilometry
Displays ( IF 4.3 ) Pub Date : 2019-09-01 , DOI: 10.1016/j.displa.2019.06.001
Lizhen Zhang , Yiping Cao , Guangkai Fu , Chengmeng Li

Abstract A method based on grayscale expansion for improving measurement accuracy in phase-measuring profilometry (PMP) is proposed. Digital light projector (DLP) has been widely used for projecting phase-shifting sinusoidal grating in PMP. However, due to its international standardization, DLP can only project at most 256 grayscales for all gray patterns. Moreover, the gray digitalization error may cause lower fidelity for the projected sinusoidal grating. In order to reduce the gray digitalization error, the sinusoidal grating can thus be designed as a 10-bit static pattern with 766 grayscales at most and then is split into three 8-bit static patterns to synthesize a repeated video. While this repeated video, rather than the static pattern, is projected onto the measured object by strictly controlling CCD camera integral time to be an integral multiple of three video refresh cycles, the captured deformed patterns are of 766 grayscales and can provide much more detailed information in phase calculation than those with 256 grayscales. Experimental results demonstrate the feasibility and validity of the proposed method. Both the measuring precision and the repeatability of PMP are improved efficiently.

中文翻译:

灰度扩展在相位测量轮廓测量中提高精度的应用

摘要 提出了一种基于灰度扩展的相位测量轮廓仪(PMP)测量精度方法。数字光投影仪 (DLP) 已广泛用于投影 PMP 中的相移正弦光栅。但是,由于其国际标准化,DLP 最多只能为所有灰度模式投影 256 个灰度。此外,灰度数字化误差可能导致投影正弦光栅的保真度较低。为了减少灰度数字化误差,可以将正弦光栅设计为最多766个灰度的10位静态图案,然后分成三个8位静态图案合成重复视频。虽然这个重复的视频,而不是静态的模式,通过严格控制CCD相机积分时间为三个视频刷新周期的整数倍,将图像投影到被测物体上,捕获的变形图案为766灰度,比256灰度可以提供更详细的相位计算信息。实验结果证明了该方法的可行性和有效性。PMP 的测量精度和重复性均得到有效提高。
更新日期:2019-09-01
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