光学棱镜的角度误差,如90°误差、等腰棱镜底边的两角差、塔差等,通常是用平行光束通过被检验棱镜的光学方法进行检验的。此时,具有反射棱面的棱镜,其入射角小于全内反射角(БП-90°,БУ-45°,ВР-45°等)时,应在对诸反射棱面做金属镀膜之后进行检验。这是因为内反射造成的光能损失很大,最初的检验较为困难。 Optical prism angle error, such as 90 ° error, the bottom edge of the isosceles prism difference between the two sides, etc., is usually parallel to the prism through the prism of the optical method of inspection. In this case, prisms having a reflecting facet should be inspected after metal coating on the reflecting facets when the incident angle is less than the total internal reflection angle (БП-90 °, БУ-45 °, ВР-45 °, etc.) . This is because the light energy loss caused by the internal reflection is very large, the initial test is more difficult.