Shading correction device

Details Shading correction device Shading correction device

1983-04-08

1985-11-19

Chin, Tommy P.

Facsimile and static presentation processing

Facsimile

Specific signal processing circuitry

358284, H04N 514

Patent

active

045545839

ABSTRACT:
A method and apparatus for correcting the photoelectric converter of a document reading unit for non-linearities produced by the optics of the system. A test document having no image data thereon is scanned to produce a shade correction signal which is subjected to A/D conversion and stored in a memory. In binary-encoding the picture data of the original, a switch is operated according to the data stored in the memory so as to change a threshold level for the picture signal, whereby digital picture data whose shading has been corrected is obtained. In the case where the picture data of the original are represented by an analog signal, the picture data are also subjected to A/D conversion, and division is carried out with the data stored in the memory being employed as dividends. From the results of such a division, corrected multi-level picture data is obtained.

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