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Xerox Scientists Develop New Calibration Technology For Truer Printer Color

Monday, November 10, 2003

Press release from the issuing company

SCOTTSDALE, Ariz.--Nov. 7, 2003-- Xerox Corporation scientists have created a novel color-calibration technique that could one day be used in color printers and other devices, such as LCD panels, to deliver richer, more accurate color. Their research is part of the news presented at the 11th annual Color Imaging Conference, hosted here by the Society for Imaging Science and Technology. The printing process depends on "transforms" -- mathematical instructions that tell machines how much of each ink or toner is needed so that the colors on paper replicate the colors we see with the human eye. Currently, the standard industry approach to printer calibration uses "one-dimensional transforms," which individually adjust each of a printer's colors -- cyan, magenta, yellow and black (CMYK) -- one at a time. One-dimensional transforms are appealing because of their low cost and simplicity. But if a machine's color-print output changes, as it might when wear or other factors change the way color toner is transferred onto paper, changing an individual color won't correct the entire system. On the other hand, three- and four-dimensional calibrations can handle the problem and simultaneously adjust the red, green, blue or the CMYK values, but the cost of incorporating the more complex adjustment system in printers and the manpower required to account for changes in the printer's behavior would be prohibitive. The answer: two-dimensional calibration, which combines the advantages of both approaches. "We see two-dimensional calibration as adding affordable quality," said Raja Bala, the research's presenter and a principal scientist at Xerox's Imaging and Services Technology Center. "Our research focuses on the once-forgotten two-dimensional realm as a cost-effective means of providing more accurate color output in not only printers but even color LCD devices." At the conference, Bala highlighted Xerox's work in developing full-resolution two-dimensional calibration tables, on which patents are pending. The Xerox scientists wrote software to mathematically construct the two-dimensional tables, which allow for simultaneous corrections of the primary printing colors as well as grays and flesh tones, to which the human eye is quite sensitive. Today's one-dimensional calibration is far more limited, forcing manufacturers to choose between the control of one color or another. Bala showed samples of printer color correction accomplished with minimal additional mathematical computations, using less computer space. Results show significant improvement in color accuracy and stability when compared to traditional one-dimensional calibration. "A few years ago, the half a megabyte of computer disk space required for two-dimensional calibration would have been considered prohibitive," Bala said. Recent advances in technology, however, will make it more possible for manufacturers to inexpensively embed the new two-dimensional calibration tables inside printers or print controllers. In addition to Baja, nine other Xerox researchers will be presenting at the conference, covering topics such as image quality, image reproduction, color management and multiplexed imaging.




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