JPS6420485A - Human body detector - Google Patents

Abstract

PURPOSE:To exactly detect a human body irrespective of whether the human body is moving or not, by leading alternately infrared rays from the inside of a detection area and infrared rays from a reference part of the inside of a device, to an infrared-ray detecting element of variation portion detection type. CONSTITUTION:An output of an infrared-ray detecting element 1 is amplified by an amplifying part 3, and thereafter, passes through a band pass filter 41 having such a frequency characteristic as a chopping frequency passes, and a waveform having the amplitude corresponding to a difference of the quantity of infrared rays of a light shielding part of a chopper 22 and the detection area is obtained. An output of this band pass filter 41 is inputted to a peak detecting circuit 42, and a positive peak value is brought to peak holding and converted to a digital signal by an A/D converter 43, and stored in a storage part 45 by a microcomputer 44. In the storage part 45, input data which has been detected when no person exists is stored in advance as reference data. Also, a difference between the input data and the reference data has exceeded a threshold level, it is decided that the human body exists, and an existence detecting signal is generated from an output part 5.