Ambient light compensating circuit

摘要

An automatic ambient light compensating circuit for use in conjunction with a light sensing device to render the light sensing device insensitive to variations in ambient light conditions and which is particularly adapted for use with reflective sensor systems. An optical sensor, including a source of light and a first photodetector, is disposed to detect the presence of an object in proximity thereto. The optical sensor provides an output signal which is a function of the amount of light received by the first photodetector and includes light from the source of light and ambient light. The output signal of the optical sensor is provided as an input to a signal level detection means. A second photodetector responsive only to ambient light is operatively connected in parallel with the output of the optical sensor to the level detection means to compensate the output signal of the optical sensor for ambient light conditions.