为解决棱镜等效展开为玻璃平板后因腔长固定导致的移相困难问题, 提出一种变倾角移相测量反射棱镜光学平行差的方法。通过改变光束在反射棱镜入射端面上的倾角在干涉图中引入移相量, 实现干涉图中的相位提取。采用最小二乘法拟合相位计算反射棱镜的光学平行差。在实验中, 测试了一块弦长为56.5mm的等腰直角棱镜, 得到直角偏差Δ90°为-2.1435″、锐角偏差δ45°为-4.6216″、直角边对应棱差γC为0.3554″, 而Zygo GPI干涉仪仅可得到棱镜直角偏差, 与本文方法的测量值偏差在0.15″以内。所提方法移相光路设计简便, 并可实现小尺寸反射棱镜的测量。

In order to solve the problem that the cavity length of the equivalent glass plate of the prism wass fixed, a method to measure the optical parallel difference based on the variation of inclination angle was proposed. The amount of phase shift is obtained by changing the inclination of the beam on the incident surface of the reflective prism, implemented phase extraction in the interferogram. The phase was fitted using least squares method to obtain a fitted plane, then calculate the optical parallelism error of the prism. The design experiment tested an isobeles prism with a hypotenuse length of 56.5mm, the measured right angle deviation Δ90° is -2.1435″, the deviation from the measurement results of the Zygo GPI interferometer is within 0.15″'. The method can also obtain the acute angle deviation δ45° of the prism at the same time, which is -4.6216″, deviation of the corresponding ridge of the right angle γC is 0.3554″. The proposed method was not limited by the size of the prism and can be used for the measurement of small-sized reflective prisms.