What is 80-50 surface quality?

Understanding 80-50 Surface Quality

Surface quality is a crucial optical specification that describes the quality and condition of an optical component's surface. It is particularly important in applications where light transmission, scatter, and wavefront distortion are critical. The specification is typically given in a scratch-dig format, which is a shorthand notation used to describe the allowable imperfections on an optical surface. The 80-50 surface quality specification is one such example of this notation.

Scratch-Dig Notation Explained

In the scratch-dig format, the first number (80 in the case of 80-50 surface quality) refers to the maximum allowable scratch width as defined by a standardized set of comparison samples. The second number (50 in this instance) refers to the maximum allowable size of digs or pits, also based on a standardized set of comparison samples. These numbers are derived from a visual inspection of the optical surface against a controlled light source.

Details of 80-50 Surface Quality

• Scratch Number (80): This indicates that the surface may have scratches that are no more visible or severe than those found on a standard sample rated at 80. This is considered moderate quality, suitable for less demanding applications where some level of light scatter is acceptable.
• Dig Number (50): This specifies that the size of digs or pits on the surface should not exceed those on a standard sample rated at 50. This is indicative of a surface with moderate to low dig quality, where small imperfections are permissible.

It's important to note that the scratch-dig specification does not directly correlate to the optical performance such as transmission or wavefront distortion; rather, it provides a guideline for the physical condition of the surface. Components with an 80-50 surface quality are generally used in applications where the optical performance is not critically affected by surface imperfections, such as in some types of beam shaping or non-imaging optics.

For applications requiring high precision and minimal light scatter, such as laser systems or high-power imaging applications, a higher surface quality (e.g., 10-5 or 20-10) would be necessary.