A photographic exposure meter in visualization equipment for detecting the presence or absence of a pulse of laser light on a target. Light from a laser pulse which forms a hologram, is scattered when it impinges on the target plate and detected by a photodetector, the resultant pulse signal being integrated...http://www.google.de/patents/US4334776?utm_source=gb-gplus-sharePatent US4334776 - Holographic plate exposure meter
