PMP测量系统中正弦光栅的优化设计

Optimal Design of Sinusoidal Grating in PMP Measuring System

提出一种基于光强传递函数(ITF)正弦光栅的优化设计方法,并应用于相位测量轮廓术(PMP)系统进行复杂三维面形测量。PMP测量系统由光栅投影和变形条纹的信息采集系统组成。由于信息采集受到DLP、CCD以及环境等诸多因素的影响,整个系统的光强传递函数是非线性的。通过对该系统的光强传递函数的测量,可以看到其函数图像整体上为非线性,而局部的连续区间是线性关系。传统正弦光栅一般采取条纹对比度最大且灰度值范围最大化的设计方法,该设计在信息采集时存在非线性,影响PMP的测量精度。如果设计的正弦光栅的峰值和谷值正好落在传递函数线性区间的上限和下限,会提高PMP的测量精度;当峰值和谷值落在线性区间而对比度较低时,则会影响测量精度。因此,灰度值落在线性区且对比度最大化时的正弦光栅正是优化的最佳目标。实验验证了该方法的有效性。

A method is proposed to design and optimize the sinusoidal grating based on the intensity transfer function（ ITF）,and it is applied to the complex 3D measurement in phase measuring profilometry（ PMP） system. There are the grating projection and the information collection system of detorming stripe in PMP measuring system. Because of the influence of DLP,CCD and the environment and so on,the ITF of the whole system is nonlinear. Through the measurement of the ITF,we can know that its function image is nonlinear as a whole but linear in continuous interval locally. Traditionally the sinusoidal grating is designed by the way of maximizing the visibility and the range of gray value,but it will be nonlinear when collected by CCD camera,therefore this will affect the precision in PMP. And if the maximum and minimum of the grating is just the upper and lower limits of the linear interval,this will improve the precision. However it will also destroy the precision if the visibility is too low. Therefore the grating is the best choice with its range of gray value between the linear interval and the visibility maximized. The experiment demonstrates the effectiveness of the proposed method.