Continuous optical path monitoring of optical flame and radiation detectors

摘要

Apparatus for the optical detection of flames or explosions, having an optical structure to perform continuous optical path monitoring of the optical window receiving the optical radiation, to ensure against the buildup of radiation absorbing or scattering materials. A light source internal to the housing illuminates a straight optically transmissive quartz or sapphire rod that protrudes through the housing beyond the optical window. The protruding tip of the light rod is beveled and metallized on the bevel to provide internal reflection of the light from the source, the angle of the bevel being such that the reflected light on exiting the light rod illuminates the optical window and the optical detector behind it, thereby providing a test for the cleanliness of the optical window. This optical technique for checking the cleanliness of the optical viewing element can be utilized by other optical instruments including imaging arrays, surveillance cameras and weapons.