基于光栅成像投影的微位移检测方法

提出了一种基于光栅成像投影的微位移检测方法，利用光学傅里叶变换原理给出了具体的理论分析。准直激光束照明的光栅通过一个4f系统成像投影在被测物体表面上，光栅投影经过被测物体表面反射后由另一个4f系统成像在探测光栅上。探测光栅由一个透镜组成像在光电探测器上，其中采用由起偏器、光弹调制器和检偏器组成的偏振调制单元对探测光强进行调制。通过在4f系统的频谱面上设置滤波光阑，在光电探测器上获得了与被测物体的微位移成正弦关系的光强变化，检测出光电探测器上的光强变化即可以获得被测物体的位移量。实验验证了该检测方法的可行性

A method to measure micro-displacements based on grating projection is proposed and analyzed theoretically. A grating is illuminated by a collimated laser beam and projected onto an object to be measured through a 4f optical system with an aperture in its frequency plane. The grating projection is imaged on a detection grating through another 4f optical system after reflected by the surface of the object. The detection grating is imaged on a detector and its imaging beam is modulated by a photoelastic modulator. The micro-displacement of the object is obtained by detecting the light intensity on detector. In experiments, the feasibility is verified and the repeatability of the method is less than 25 nm (1σ).