Scatter intensity mapping of laser-illuminated coating defects

The ability to detect and locate defects nondestructively in multilayer optical coatings has been demonstrated using a video microscopy system. The system uses laser-excited scattering to illuminate defects responsible for laser-induced damage in multilayer dielectric coatings. Intensity maps and contours can be generated by digitizing the video images of scattering from individual defects. These can reveal characteristic defect scatter features possibly related to damage probability, and they offer a means to follow the development of these features from incipient to catastrophic damage. Examples of defect scatter maps and intensity contours for an antireflection dielectric coated window are presented and discussed.