Image reading apparatus having a function for correcting dark signals generated in a photoelectric conversion element

U.S. Patent Number: 5278658

Abstract: An image reading apparatus includes a photoelectric conversion element which has a plurality of cells, the plurality of cells including shielded cells which are optically shielded so that each shielded cell outputs only the dark signal, a dark signal data generating system for generating dark signal data for each cell of the photoelectric conversion element, the dark signal data corresponding to a ratio of an image signal output from each cell under a no-exposure condition to a first reference dark signal which is obtained based on the dark signals output from the shielded cells under the no-exposure condition, a dark signal data memory for storing the dark signal data for each cell, a dark signal component generating system for generating a dark signal component for each cell, the dark signal component corresponding to a product of the dark signal data for each cell multiplied by a second reference dark signal which is obtained based on the dark signals output from the shielded cells under the exposure condition, and a subtracter for subtracting the dark signal component from an image signal obtained for each corresponding cell under the exposure condition.

Inventors: Takase; Osamu (Yokohama, JP)

Assignee: Ricoh Company, Ltd. (Tokyo, JP)

Application Number: 07/699,597

Issued: 1994-01-11

Expired: 2006-01-11

Classes: 348/243 ; 348/250

Field of search: 358/209,213.15,213.16,213.17,213.18,167,177,461,463,466

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