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Print Contrast Control for Iterative Scan and Print

IP.com Disclosure Number: IPCOM000051720D
Original Publication Date: 1981-Mar-01
Included in the Prior Art Database: 2005-Feb-10
Document File: 2 page(s) / 37K

Publishing Venue

IBM

Related People

Tsao, CS: AUTHOR

Abstract

In a succession of scan and print operations where the scan data is electronic rather than optical, the printed image gradually degrades. This is due to the fact that the scanner in every instance assumes increasing contrast for successive scanned copies. As shown above, a better technique is to scan the original document for contrast information as well as video data.

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Print Contrast Control for Iterative Scan and Print

In a succession of scan and print operations where the scan data is electronic rather than optical, the printed image gradually degrades. This is due to the fact that the scanner in every instance assumes increasing contrast for successive scanned copies. As shown above, a better technique is to scan the original document for contrast information as well as video data.

The contrast information of the original is transmitted with the video data to control printing at the printer. A very low speed areal light sensor 10 is mounted with print head 12 of the printer. As the print head moves across the print medium during printing, areal light sensor 10 is able to measure the output contrast ratio resulting from the particular printing technology and print medium.

At the end of the printing process, the resulting difference in print contrast ratio (C=C1-C0) between the original and the copy is recorded on the same output medium with an appropriate code. The recording is preferably not visible to the human eye but definitely readable by the next document scanner. Document scanner 2 can use this print contrast difference C to offset its digitizing thresholder to preserve the overall constancy of the contrast ratio through iterative scan and print.

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