Radiant energy – Photocells; circuits and apparatus – Photocell controlled circuit
Patent
1988-12-12
1990-04-10
Nelms, David C.
Radiant energy
Photocells; circuits and apparatus
Photocell controlled circuit
35821316, H01J 4014
Patent
active
049163078
ABSTRACT:
A light intensity detecting circuit using a charge storage type of optical sensor having a parallel capacitor eliminates the influence of the dark current of the optical sensor and/or the influence of the offset of the comparator included in the detecting circuit so that the accuracy of the light intensity detection is improved over that of the prior art. To eliminate the influence of the dark current of the optical sensor in an image sensor, there is provided an optically shielded mimic sensor having the same structure as that of the optical sensor including a corresponding parallel capacitor. In order to eliminate the influence of the offset of the comparator, there is provided a time constant circuit having a capacitor that may be composed partially of the parallel capacitor of the mimic sensor corresponding to the parallel capacitor of the optical sensor; with potential applying means for operating the time constant circuit.
REFERENCES:
patent: 4659930 (1987-04-01), Johnson et al.
patent: 4819071 (1989-04-01), Nakamura
Nishibe Takashi
Yokoyama Shotaro
Fuji Electric & Co., Ltd.
Nelms David C.
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