Transparency measuring device e.g. for optical element positioned in front of sensor, uses separate radiation-sensitive element and/or element of sensor for monitoring transmitted radiation level

摘要

The measuring device uses a separate radiation-sensitive element (3) and/or a radiation-sensitive element (11) of the sensor (1) at the rear of the optical element (4), coupled to an evaluation circuit (8), providing a signal, e.g. a warning signal, dependent on the level of radiation passing through the optical element.