Method and apparatus for sensing a human body
First Claim
1. An apparatus for sensing a human body comprising a projector for projecting infra-red rays towards a human body sensing region, a photo-sensor for receiving infra-red rays reflected from said human body sensing region and outputting an electrical signal corresponding to an intensity of incident infra-red rays, a first integrator circuit connected to the output side of said photo-sensor and having a relatively small time constant, a second integrator circuit connected to the output side of said photo-sensor and having a relatively large time constant, and a response circuit means connected to the outputs of said first integrator circuit and said second integrator circuit for outputting a human body sense signal when the difference between said outputs is held at a predetermined level or higher consecutively for a predetermined period of time.
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Abstract
A method for sensing a human body has the steps of projecting infra-red rays from a projector, receiving infra-red rays reflected from a background and a human body by a photo-sensor, deriving a difference between a reflection amount from the background and that from the human body on the basis of an output from the photo-sensor by the action of first and second integrator circuits, and outputting a human body sense signal from a response circuit when the difference in the reflection amount is held at a predetermined period of time. The first integrator circuit has a relatively small time constant, while the second integrator circuit has a relatively large time constant.
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Citations
4 Claims
- 1. An apparatus for sensing a human body comprising a projector for projecting infra-red rays towards a human body sensing region, a photo-sensor for receiving infra-red rays reflected from said human body sensing region and outputting an electrical signal corresponding to an intensity of incident infra-red rays, a first integrator circuit connected to the output side of said photo-sensor and having a relatively small time constant, a second integrator circuit connected to the output side of said photo-sensor and having a relatively large time constant, and a response circuit means connected to the outputs of said first integrator circuit and said second integrator circuit for outputting a human body sense signal when the difference between said outputs is held at a predetermined level or higher consecutively for a predetermined period of time.
Specification