Compact photosensor circuit having automatic intensity range con

Details Compact photosensor circuit having automatic intensity range con Compact photosensor circuit having automatic intensity range con

1995-06-06

1996-11-05

Shoop, Jr., William M.

Electrical transmission or interconnection systems

Switching systems

Condition responsive

307113, 363 23, 250200, 250206, 2502081, 250214R, 250214AG, 330250, H01H 4724

Patent

active

055720749

ABSTRACT:
A compact photosensor circuit provides automatic intensity range control for machine vision systems. The circuit may be implemented with standard CMOS integrated circuit technology to provide high sensitivity, fully static operation, and automatic exposure control with no moving parts. For each pixel of an imaging array, a photodetector provides an input photocurrent to a corresponding photosensor circuit. The photodetector is connected to provide an output voltage and an input to the gates of a pair of series-connected FETs that act as an attenuator. The attenuator is connected to a biasing source that provides a floor bias voltage. An output of the attenuator is connected to the gate of a third FET connected to the input photocurrent. The output voltage responds as a function of the light intensity at the photodetector while the bias voltage determines the range of light intensity for normal operation of the photosensor circuit. In a photosensor array with an appropriate bias current, the image scene contrast is amplified while the photosensor circuits automatically adapt to the overall light intensity.

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