为了解决物体微小位移或微小振动的超低频高精度检测与装调间的矛盾,提出一种倒置差动式4f激光多普勒光栅检波系统。它利用两个相位光栅分别实现频移和混频,提高了位移测量精度;且采用4f结构,提高了空间相干性,使装调更为方便;增设λ/4波片、沃拉斯顿棱镜并与差动放大器结合,不仅得到识别位移方向的正弦、余弦信号,而且将±1,±3级衍射光能量都充分利用,使多普勒信号强度和信噪比更高。

To resolve the contradiction between the measurement of micro-displace or high-accuracy detecting of micro-vibration of ultra-low frequency and the convenience of building and adjusting, a inverted differential 4f grating demodulation system of laser Doppler is put forward. Using two phase gratings to realize frequency shift and mixing, the measurement accuracy is enhanced. Adopting 4f configuration to enhance the spatial coherence, building and adjusting of the system are more convenient. Further more, adding λ/4 wave plate and Wollaston lens cooperating with differential amplifier in order to get sin, cos signals judging displacement direction, and that the energy of both ±1 and ±3 diffraction lights is taken use to improve the intensity and signal to noise ratio (SNR) of Doppler signal.