Method and arrangement for automatic exposure control in color c

Details Method and arrangement for automatic exposure control in color c Method and arrangement for automatic exposure control in color c

1981-12-22

1983-09-27

Gellner, Michael L.

Photocopying

Projection printing and copying cameras

Multicolor picture

355 38, 355 77, G03B 2773

Patent

active

044065388

ABSTRACT:
A color copier has a control circuit for controlling the exposure of an original to be copied. The control circuit has a processing channel for each of the three primary colors. Each of the channels is associated with photodetectors which is sensitive to the color of the respective channel. The photodetectors sense the intensity of the light in the respective color transmitted through the original and generate signals indicative of the density of the original in that color. The density of the original in each color is compared with the neutral gray density of the original. The difference between the density of each color and the neutral gray density is used to calculate an undercorrection factor for the respective color. The undercorrection factor is used to regulate the exposure time for light of the respective color or the intensity of light of the respective color during exposure. The undercorrection factor lies on a graph of undercorrection factor versus difference between the respective color density and the neutral gray density having at least one change in slope. The slope may change continuously or at a threshold value on the difference axis. The magnitude of the undercorrection factor increases more rapidly after passing through a change in slope in a direction of increasing difference than before. Regulation of the exposure of an original in the above manner makes it possible to at least partially eliminate in the copy sharp color contrasts which appear in the original while simultaneously obtaining good reproductions of color dominants which appear in the original.

REFERENCES:
patent: 4192605 (1980-03-01), Fergg et al.

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