Patent ID: 6965109
Filing Date: 2005-11-15
Classification: G01V,G08B

Abstract:
1. A multistage active infrared sensor having a plurality of light emitting means and a plurality of light receiving means which are opposed one by one to the light emitting means across a watch area, wherein each light emitting means emits an infrared signal to an opposite light receiving means, and the sensor detects intrusion of an object into the watch area when the infrared signal is broken, the multistage active infrared sensor comprising: a means for controlling a light emission operation, which supplies distinct channel information to an infrared signal to be emitted by each light emitting means and which allows each light emitting means to emit the infrared signal containing the channel information at a different timing from the rest of the light emitting means, and a means, provided in each light receiving means, for recognizing a received light, which judges whether an infrared signal received by the respective light receiving means contains channel information of an opposite light emitting means, and which cancels any received infrared signal which does not contain channel information of the opposite light emitting means wherein said plurality of light emitting means are each at a first single location, said plurality of light receiving means are each at a second single location and said watch area is defined as an area between said first location and said second location.