基于背景光调制的复合光傅里叶变换轮廓术

Composite Fourier transform profilometry based on flat image modulation

提出一种基于背景光调制的用于傅里叶变换轮廓术测量范围的复合光栅,该光栅通过调制一正弦条纹和不含任何相位信息的背景光来抑制零频,较基于π相移技术的复合光栅有更大的优势:背景光只含直流分量,使得复合光栅的频谱更加简单,有利于滤出载波信息,提高测量精度;对从复合光栅中解调出来的背景光只涉及平均值校准,校准过程更为简单;解调出的背景光与物体表面的反射率成正比,具有潜在的应用价值。采用Matlab程序对该复合光栅进行了数值模拟,并对该光栅实用性进行了实验研究,结果证实了该光栅用于抑制零频、扩大傅里叶变换轮廓术测量范围的有效性,且提高了测量精度。

A novel composite grating based on flat mage modulation is proposed to enlarge the measuring range of the Fou- rier transform profilometry （FTP）. A sinusoidal image and a flat image without stripes are modulated into the grating to restrain the zero component in the Fourier spectrum. Compared with the composite grating based on the r~ phase-shifting technique, the spectrum of the proposed grating becomes simpler because only DC component is introduced by the flat image. So the modulated information is easier to be filtered and the measuring accuracy is improved. The intensity calibration of the flat image demodulated from the composite grating is simpler than the sinusoidal image because only mean value calibration is involved. Moreover, the in- tensity of the demodulated flat image is proportional to the reflectance of the measuring object, which has some application in the practice. The Matlab is used to simulate the proposed method, and the experiment is performed to verify the feasibility of the pro- posed grating. Both of them demonstrate the flat image can be used to restrain the zero component and enlarge the measuring range of the FTP, and the measurement accuracy is improved.