直线度测量中往往存在有限的测量范围、精度低和阿贝误差等问题。本文提出了一种高精密直线度外差干涉测量装置, 该装置由Koester棱镜、角锥棱镜、1/4波片、楔面棱镜和楔面反射镜构成。楔面棱镜为直线度传感元件, 角隅棱镜和楔面反射镜是测量信号的回光元件。双频激光信号进入直线度干涉仪后组成几何空间对称四光路测量信号。四路测量光走过几乎完全相同的路径有效地提高了干涉仪的稳定性, 并且使空程误差最小化。使用楔角为1°的楔角棱镜和2π/512细分的相位计, 直线度测量分辨力为17.71 nm。该方法不需要与行程同长的大反射参考镜, 但同样能实现高分辨率, 理论和实验证明空间对称测量结构避免了由俯仰, 偏转和滚转角引起的阿贝误差的串扰, 而且光学元件少, 结构简单, 方便易用, 结果可以直接溯源到米的定义。

An interferometer is proposed for high precision straightness measurement. This instrument consists of a Koester prism, corner cube, quarter-wave plate, wedge prism, and wedge reflector. The wedge prism acts as the straightness sensor while the corner cube and wedge reflector are used to reflect the measurement signal. During operation, the two frequency interferometer signal is decomposed into four beams with a spacially symmetrical measurement structure. The beams have common paths, which result in an improved stability of the interferometer and the minimization of dead path. A measurement resolution of 17.71 nm was determined with a phasemeter which has a resolution of 2π/512 and a wedge prism with one wedge angle. The setup does not require a mirror, which typically has a size that is comparable to that of the stroke of a linear moving stage. However, it can be used to measure straightness with very high resolution. The theoretical and experimental results demonstrate that the crosstalk of the Abbe error caused by pitch, yaw, and roll angle is avoided due to the spacially symmetrical measurement structure. The proposed interferometer has several advantages such as fewer optical components, a simple structure, ease of use, and repeatability of measurement results.