Radiant energy – Photocells; circuits and apparatus – Photocell controlled circuit
Patent
1997-11-05
1999-11-09
Le, Que T.
Radiant energy
Photocells; circuits and apparatus
Photocell controlled circuit
250214R, 257461, 348308, H01J 4014
Patent
active
059819324
ABSTRACT:
Disclosed is a method and associated apparatus for compensating for kTC noise in individual pixels of an MOS imaging array. The kTC noise at issue forms when a pixel is disconnected from a reset voltage by turning off an MOS transistor which controls access to the pixel photodiode. Compensation is accomplished by first exposing the photodiode to the reset voltage and then disconnecting the well region from V.sub.dd to cause it to float. By allowing the well to float, the kTC charge subsequently introduced (at the conclusion of the reset process) redistributes so that most of it accumulates on the capacitor between the well and the substrate. Later, the well is reclamped to V.sub.dd, and the noise contribution stored in the well-substrate capacitor is canceled. A disclosed apparatus includes an array of pixels, each having a separate well. In addition, access of the well to a source of power (V.sub.dd) must be switchable. Therefore, a transistor is included at each pixel's connection to a V.sub.dd.
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Eiji Oba, et al., "A 1/4 Inch 330k Square Pixel Progressive Scan CMOS Active Pixel Image Sensor," Feb. 7, 1997, Digest of Technical Papers, pp. 180-181.
McGrath, R. Daniel, et al., "Current-Mediated, Current-Reset 768.times.512 Active Pixel Sensor Array," Feb. 7, 1997, Digest of Technical Papers, pp. 182-183.
Eric R. Fossum, "CMOS Image Sensors: Electronic Camera On a Chip," Dec. 10-13, 1995, International Electron Devices Meeting Technical Digest, pp. 17-25.
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Guerrieri Roberto
Rambaldi Roberto
Tartagni Marco
Galanthay Theodore E.
Jorgenson Lisa K.
Le Que T.
STMicroelectronics Inc.
Weaver Jeffrey K.
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