Optical reference plate (original instrument) is referred to as the sample plate, which includes the reference plate, work sample plate, curvature sample plate, etc. It is based on the phenomenon of light wave interference to measure the optical surface error of a shape sample, and has become the most widely used in the manufacturing process of optical parts, the most simple a precision measurement tool, so its surface shape accuracy than the general optical parts to high, in order to ensure quality, the spherical surface must be concave and convex in pairs Manufacturing, processing also need to be repeatedly measured with instruments to ensure the radius of curvature and surface accuracy.

   According to the national standard of the People's Republic of China GB1240-76