PROBLEM TO BE SOLVED: To obtain a compact optical sensor circuit which gives automatic intensity range control for an artificial sensation system. SOLUTION: A photodetector 12 gives an input photoelectric current to a corresponding light sensor circuit 10 for each pixel of an image array. The photodetector 12 is connected to give an output voltage and also to give an input to the gates of a pair of FETs 14 and 16, which works as an attenuator and are serially connected. The attenuator is connected to a bias source which gives a floor bias voltage. An output of the attenuator is connected to a gate of a 3rd FET 18 which is connected to input photoelectric current. Output voltage responds as a function of the light intensity of the photodetector, and the bias voltage determines the range of light intensity for a normal operation of the circuit 10. In a light sensor array of appropriate bias current, the contrast of an image scene is amplified, and the light sensor circuit is automatically adapted to the overall light intensity.
PHOTOSENSOR CIRCUIT