Patent ID: 6198951
Filing Date: 2001-03-06
Classification: A61B

Abstract:
A reflection type photodetection apparatus, having a light emitting element for emitting light to a detected object, for detecting the intensity of light reflected by the detected object, said reflection type photodetection apparatus comprising:a first photoelectric conversion element for receiving and converting light reflected by the detected object and externally-sourced light to a first electrical output signal;a second photoelectric conversion element for receiving and converting externally-sourced light to a second electrical output signal; anda difference means for detecting and outputting a difference signal representing a difference between the first output signal of the first photoelectric conversion element and the second output signal of the second photoelectric conversion element;wherein the first photoelectric conversion element, second photoelectric conversion element, and light emitting element are arranged so that a distance from a photodetection center of the second photoelectric conversion element to a light emitting center of the light emitting element is different from a distance from the light emitting center of the light emitting element to a photodetection center of the first photoelectric conversion element, andthe first photoelectric conversion element and second photoelectric conversion element are positioned so that externally-sourced light reaches each with substantially equal intensity, such that the intensity of light reflected by the detected object can be detected without significant affect from externally-sourced light.