Noise reduction for photodiode arrays

Details Noise reduction for photodiode arrays Noise reduction for photodiode arrays

1989-01-23

1990-02-20

Nelms, David C.

Radiant energy

Photocells; circuits and apparatus

Photocell controlled circuit

250578, H01J 4014

Patent

active

049028863

ABSTRACT:
A method and apparatus for reducing noise in a light sensing circuit having a photodiode array coupled to a charge amplifier through a field effect transistor transfer switch. Thermal noise generated by the transfer switch is combined with image signals inputted to the charge amplifier resulting in an outputted noisy image signal. The invention eliminates this noise by taking two consecutive readings of the charge amplifier output, one before and one after closing the transfer switch and after opening it. The thermal noise generated by the transfer switch, and added to the next reading of the charge amplifier output, is equal to the difference between these two readings. Once stored, this difference can be subtracted from the previously mentioned "next reading", resulting in the elimination of this noise term.

REFERENCES:
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patent: 4600843 (1986-07-01), Kizu et al.
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patent: 4797546 (1989-01-01), Berger et al.
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