Patent ID: 6982408
Filing Date: 2006-01-03
Classification: G01S

Abstract:
1. A photo-detecting device, comprising: an oscillation circuit provided with a plurality of constant current sources for outputting a plurality of signals having different oscillation frequencies; light-emitting means for projecting toward an object a light that is pulse-modulated in response to a signal from said oscillation circuit; light-receiving means for receiving either light reflected from the object or light transmitted through the object, and for converting the received light into a light-receiving signal; counting means for counting the light-receiving signal a plurality of times in synchronism with a modulation frequency of the projected light; detecting means for detecting the object in response to said counting means; and frequency changing means for, in accordance with a count of the counting means, controlling the plurality of constant current sources to vary an oscillation frequency of said oscillation circuit in a determinable manner, while said counting means counts the light-receiving signal a plurality of times.