Abstract: Fluorescence microscopy is a useful tool to image defect nanostructures in the bulk of dielectric materials. The application of microscopy with KrF laser induced fluorescence on optics to detect the damage of optical film was researched. A fluorescence image system was built and in-situ test for the damage of the optical film was performed to test capabilities. The tested results were checked by an ex-situ Normaski microscope, and the both are in agreement.