光栅成像位置传感器中的偏振调制技术

Polarization Modulation Technology for a Position Sensor with Grating Imaging

提出了一种用于光栅成像位置传感器的偏振调制技术,利用米勒矩阵对其调制原理进行了详细的分析。该偏振调制器主要由起偏器、萨伐尔板、两块1/4波片、光弹调制器和检偏器构成。起偏器、萨伐尔板置于探测光栅之前,在探测光栅位置上形成两个错位的偏振方向正交的像光栅。两块1/4波片、光弹调制器和检偏器置于探测光栅之后,实现对莫尔信号的高频调制。该偏振调制技术消除了光源光强波动和电路增益变化引入的测量误差,抑制了杂散光、探测器噪声对测量结果的影响。实验验证了该偏振调制技术的有效性,结果表明这一技术使光栅成像位移传感器获得了优于12 nm的重复测量精度。

A polarization modulation technology for a position sensor with grating imaging is presented and its modulation principle is analyzed with Muller matrix. The polarization modulator is composed of a polarizer, a Savart plate, two 1/4 wave plates, a photoelastic modulator and an analyzer. The polarizer and the Savart plate are placed in front of the index grating to split the image of the image grating into two orthogonally polarized and mutually sheared images. The two 1/4 wave plates, photoelastic modulator and analyzer are placed behind the index grating to realize the modulation of the Moire signal with high frequency. With the polarization modulation, the errors induced by the change of the initial intensity and the gain of the signal processing circuit are removed and the influence of the stray light and the noise of the detector are suppressed in the position sensor with grating imaging. In experiments, the usefulness of the polarization modulation technology was verified. The repeatability of the position sensor with the polarization modulator is less than 12 nm.