Abstract: A system for detecting leaks in a mechanical system includes a dye injector for injecting dye into the mechanical system, and a borescope having one or more tubes. Each tube includes a UV light source. The system further includes an image detector connected with at least one of the one or more tubes and configured to image a field-of-view of dye in the mechanical system being illuminated by the UV light source, the image detector including a light-filtering lens cap configured for filtering a first portion of UV rays from the UV light source to allow passage of a second portion of UV rays of the dye being illuminated by the UV light source.