Patent ID: 6791087
Filing Date: 2004-09-14
Classification: G01D

Abstract:
An improved differential infrared detector of the type having: a detection element which detects infrared radiation in a predetermined detection area, converts a radiation energy thereof into an electric signal, and outputs the signal; and a discrimination circuit which calculates, based on the output signal, a variation amount of the radiation energy which varies on entry of a person into the detection area, the discrimination circuit comparing the variation amount with a predetermined level and, if the variation amount is equal to or greater than the predetermined level, generating a human body detection signal,wherein the improvement comprises: an ambient temperature detection circuit which generates a voltage, based on an ambient temperature in the detection area; and a sensitivity correction circuit which receives the voltage from the ambient temperature detection circuit and discriminates, based on the received voltage, whether the ambient temperature is within a predetermined temperature range, the sensitivity correction circuit being arranged to increase detection sensitivity of the output signal produced by the detection element, if the ambient temperature is within the predetermined temperature range.