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P.G. Wareberg, B. Baumgartner, S.E. Wilson,
"High Resolution LED Printhead with Uniformity Compensation",
SPIE/SPSE Symposium on Electronic Imaging Science and Technology, 1990
(Santa Clara, California).
This paper describes the implementation and performance of high speed light-emitting-diode(LED) printheads.The printhead is essentially a line of LED's the width of a page and is used for printing on ordinary paper using the electro-photographic process. The printhead design approach adopted by Optotek uses a modular construction with 256 bits per module and a resolution of 300 DPI allowing construction of different sizes using a common building block.
The unique design allows uniformity compensation through pulse width modulation of LED drive currents giving nearly equal energy outputs for all pixels. Since the intensity is measured after the printhead has been completely assembled, the measurements incorporate variations in drivers, LED'S and optics. The intensity measurements are used to burn on board compensation EPROMS providing 4 bits of uniformity compensation for each pixel. A common control for average intensity adjustment is included. Units of various lengths have been provided to a number of printhead manufacturers in North America, Europe, and Japan.
A 6144 element printhead is presently in production. This unit operates at a peak LED emission wavelength of 667nm and provides a pixel power of 2.5 µW through self focusing fiber optics. A separate serial digital interface for each module allows an effective bitrate of 200 Mhz for this unit.
The modular design permits implementation of higher resolutions. LED emission wavelength can be tailored to match spectral sensitivity of photoreceptors.
J. Segel, P.G. Wareberg,
"LED Uniformity Compensation",
Second International Congress on Advances in Nonimpact Printing Technologies, 1984
(Arlington, Virginia).
This paper describes techniques for correcting the difference in radiant intensity received from pixels along the length of the printhead by first describing what the end goals of uniformity are and then describing what is realistically achievable in terms of component uniformities.Optotek's solution to the problem is explained and the achievable improvement is shown.
P.G. Wareberg,
"250 Lines/Inch LED Printstic for Nonimpact Printing",
National Print Quality Seminar, 1983 (Boston, Massachusetts).
This paper discusses the organization and performance of a 250 DPI LED printhead with a working length of 11 inches. LED uniformity compensation is an integral part of the printhead
