Infrared filter disc for passive infrared intrusion detectors

摘要

Infrared filter discs for passive infrared intrusion detectors have an improved opacity for disturbing light, if they consist of a plastic which is transparent to infrared radiation and contains diamond particles having a particle size from 0.75 mu m to 1.25 mu m at a concentration of a few per cent by weight distributed uniformly therein. The limitation of the region of transparency of the filter discs is further improved if the grain size distribution of the diamond particles is as narrow as possible.