Four Optical Coating Degradation Examples:
Use of Nomarski phase interference contrast microscopy to indicate areas of damage and subsequent chemical attack or contamination in anti-reflective coatings on optical elements or delamination failures
Humidity acting upon an underlayer film in a multi-layer optical coating through a surface pinhole in the outer protective layer caused the damage above and the surface debris.
An unusual form of underlayer moisture attack in an anti-reflective coating in which the attack followed a rather random appearing path, but likely one of maximal lattice defects such as might be caused by a highly oxygen-deficient oxide.
Damage caused to an anti-reflective coating upon attempted cleaning of high-value optical elements due to chemical attack through defects by the cleaning chemical.
Delamination of an optical coating occurred when it was subjected to a low-adhesion tape pull test. The optical coating could not be seen on the tape by the naked eye, but with the use of the Nomarski phase interference contrast microscopy, it was easily visible, as were the size, elongation, and completeness of the film failure.