US Patent 7823701 Light monitoring device for an elevator system

The present invention relates to a monitoring device for a elevator system, including an optical sensor unit, which receives light emitted by a external light source existing in the vicinity of the elevator system and which transforms the light into contrast information and an evaluation unit, which evaluates the contrast information in order to monitor the elevator system. The present invention relates further to a method for monitoring a elevator system, including the steps of receiving light emitted by a external light source existing in the vicinity of the elevator system, transforming the light into contrast information, evaluation of the contrast information in order to monitor the elevator system, recognizing a situation of the elevator system and triggering of a reaction adapted to the situation.