Patent ID: 6919567
Filing Date: 2005-07-19
Classification: G08B

Abstract:
1. An active infrared sensor comprising: optical transmitter means for transmitting at least one infrared signal toward one or more protected areas; transmitted pulse modulation means for causing an optical output of the at least one infrared signal transmitted from said optical transmitter means to be made variable; and optical receiver means for receiving the at least one infrared signal transmitted from said optical transmitter means, said optical receiver means arranged on at least one optical axis of said optical transmitter means; wherein entry of one or more objects into at least one protected area is detected when the at least one infrared signal transmitted from said optical transmitter means is interrupted; wherein said optical transmitter means produces the at least one infrared signal by a repeated alternation between one or more infrared output periods and one or more infrared non-output periods such that a plurality of infrared pulses are output during at least one infrared output period; wherein said transmitted pulse modulation means causes the optical output of the at least one infrared signal transmitted from said optical transmitter means to be made variable due to an adjustment of at least one ratio between an infrared pulse ON time and an infrared pulse OFF time during at least one infrared output period; wherein a plurality of optical transmission patterns having mutually different ratios between infrared pulse ON times and infrared pulse OFF times are previously stored at said transmitted pulse modulation means; wherein said transmitted pulse modulation means causes the optical output of the at least one infrared signal transmitted from said optical transmitter means to be made variable due to at least one infrared pulse output during at least one infrared output period being output in accordance with an optical transmission pattern selected from among the plurality of optical transmission patterns; wherein at least one of said optical transmitter means and said optical receiver means comprises activation means for activating said transmitted pulse modulation means to vary the optical output of the at least one infrared signal transmitted from said optical transmitter means; and wherein said activation means is operated in correspondence to at least one of environmental conditions and conditions under which said active infrared sensor is used.