Image reading apparatus having shading correction means using a

Details Image reading apparatus having shading correction means using a Image reading apparatus having shading correction means using a

1997-11-20

1999-08-24

Mancuso, Joseph

Facsimile and static presentation processing

Facsimile

Specific signal processing circuitry

382274, H04N 140, G06K 940

Patent

active

059431415

ABSTRACT:
This invention is related to an image reading apparatus for use in a digital copy machine and a facsimile machine. The invention is made possible to obtain the simple flat average value of the white reference data used for a shading correction obtained with a photoelectric conversion elements arranged in a line by sensing the reflected light upon a white reference plate. The image reading apparatus comprises an n-bit memory for the white reference data and another n-bit memory for the black reference data and a reference data processing circuit for summing white reference data after 2.sup.m times of line readings on the white reference plate. The summation of the data is carried out with the use of an n+m bit memory region, consisting of an upper n bit section and a lower m bit section, that is made up with the n-bits of the n-bit memory of the white reference data and m-bits of the n-bit memory of the black reference data. Then after summation of 2.sup.m data is completed, the data stored in the upper n-bit region of the (n+m) bit memory region coincides with 1/2.sup.m .times.(summation of the 2.sup.m white reference data), that is in fact a simple average value of the summed up data.

REFERENCES:
patent: 5146351 (1992-09-01), Maehara
patent: 5181118 (1993-01-01), Kimura
patent: 5455690 (1995-10-01), Ishikawa
patent: 5644409 (1997-07-01), Irie et al.
patent: 5717790 (1998-02-01), Kanesaka et al.

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