The surface quality of optical lens is used to measure the surface characteristics of optical lens, and covers some defects such as scratches and pits. Most of these surface defects are purely surface defects, and will not have a great impact on the performance of the system, although they may cause a slight decline in the light flux of the system, resulting in a more subtle scattering of scattered light. However, some surfaces are more sensitive to these effects, such as:

(1) The surface of the image plane, because these defects produce focus

(2) Surfaces with high power levels because these defects increase energy absorption and destroy the optical lens.

The most commonly used specifications for surface quality are scratch and pitting specifications described by mil-prf-13830b. The scratch name is determined by comparing the scratch on the surface with a series of standard scratches provided under controlled lighting conditions. Therefore, the scratch name does not describe the actual scratch, but compares it with the standard scratch according to mil specification. However, the names of pits are directly related to the points or pits on the surface. The pit name is calculated by dividing the diameter of the pit in micrometers by 10. Generally, the scratch pit size between 80 and 50 will be regarded as the standard mass, between 60 and 40 as the accurate mass, and between 20 and 10 as the high-precision mass.