Method and apparatus for compensating for dirt or etched areas o

Details Method and apparatus for compensating for dirt or etched areas o Method and apparatus for compensating for dirt or etched areas o

1992-04-09

1993-05-25

Braun, Fred L.

Photocopying

Projection printing and copying cameras

Detailed holder for original

355 77, 355230, 358474, 382 54, G03G 2100, G03B 2762

Patent

active

052144704

ABSTRACT:
A method and apparatus are provided for detecting the presence of dirt or abrasions or etched areas on a document platen and for preventing these defects from being reproduced as unwanted spots on output copies. The platen is first scanned without a document placed thereon and an electronic image is generated and stored which contains information on the location of a dirt spot or inherent defects such as etched marks. Upon the initiation of a scanning mode with a document placed on the platen, the scanned electronic document image is subjected to a logical XOR process to correlate the previously stored spot location with the same location on the document image which is generated and stored. Once the spot location is determined, the spot is erased. A further logical step is used to determine whether the spot lies wholly or partially within any informational areas of the document image. To the extent there is such an overlap, the spot is restored to black in the overlapping areas.

REFERENCES:
patent: 4215930 (1980-08-01), Miyakawa et al.
patent: 4335173 (1982-06-01), Caraballo
patent: 4646355 (1987-02-01), Petrick et al.
patent: 4698843 (1987-10-01), Burt et al.
patent: 4747156 (1988-05-01), Wahl
patent: 4769849 (1988-09-01), Alsing
patent: 4970606 (1990-11-01), Shima
patent: 5029226 (1991-07-01), Klein et al.

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