Patent ID: 6265972
Filing Date: 2001-07-24
Classification: G08B

Abstract:
A passive infrared motion sensor for a security system said sensor comprising a single element passive infrared detector, a focussing arrangement in front of said detector for segmented focussing of infrared radiation from an area to be monitored onto said detector and processing circuitry for analyzing the signal from said detector and making a determination whether an intruder is present, said focussing arrangement being divided into at least 3 horizontal tiers comprising an upper distant tier, an intermediate tier and a close tier, and wherein said close tier has a series of horizontally spaced focussing facets, wherein each focussing facet has a detection region and each facet is segmented to vertically elongate and shape the detection region rendering the detection region less responsive to a small pet such that the processing circuitry distinguishes in the same manner between an intruder and a small pet throughout the area to be monitored.