Patent ID: 6373044
Filing Date: 2002-04-16
Classification: H03K

Abstract:
A photoelectric sensing circuit comprising: a photosensor capable of receiving light and generating an output signal indicating the amount of light incident on said photosensor, said photosensor generating a first output signal when a level of received light is above a first predetermined level, and a second output signal when a level of received light is below a second predetermined level,a light source for generating and emitting said light incident on said photosensor, said emitted light having a variable intensity, a power source coupled to said light source, said power source having a variable output level for controlling the intensity of said light emitted by said light source, and a control circuit coupled to said power source for varying the output level of said power source, wherein if said photosensor is outputting said first output signal, said control circuit reduces the output level of said power source so that the intensity of said emitted light results in a level of received light received by said photosensor which is below said first predetermined level, and if said photosensor is outputting said second output signal, said control circuit increases the output level of said power source so that the intensity of said emitted light results in a level of received light received by said photosensor which is above said second predetermined level, said photosensor having a preset hysteresis, said first predetermined level and said second predetermined level defining said hysteresis of said photosensor.