Abstract

Most methods for fabrication of optical materials produce, in addition to the desired result (dimensional accuracy, surface figure, and surface roughness, etc.), the undesirable side effect of cracks or fractures in the material known as sub-surface damage. The "sub" prefix denotes the absence of clear evidence on the surface as to the existence of the damage below, particularly if the surface is subsequently polished. As a source of scattered light, figure instability, or in some cases, total failure of an optic, sub-surface damage can be detrimental in high precision optical systems. Detection and measurement of this sub-surface damage has become vital to the improvement of optical fabrication techniques. This paper describes the methods by which we detect and measure sub-surface damage (SSD).

© 1990 Optical Society of America