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Copying Low Contrast Masters

IP.com Disclosure Number: IPCOM000077338D
Original Publication Date: 1972-Jul-01
Included in the Prior Art Database: 2005-Feb-25
Document File: 2 page(s) / 31K

Publishing Venue

IBM

Related People

Williams, GT: AUTHOR

Abstract

A dichroic mirror filters both infrared and red light from a tungsten halogen source, while reflecting the remaining light to a document.

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Copying Low Contrast Masters

A dichroic mirror filters both infrared and red light from a tungsten halogen source, while reflecting the remaining light to a document.

Inherent in the use of the tungsten lamp is the problem of copying red on a white background. This problem is reduced, if some of the red light is filtered from the source before the light energy reaches the photoconductor. An appropriately tailored dichroic mirror 10 situated between the tungsten source 11 and the document 12 is an ideal place to filter the red light.

The tungsten lamp allows the illumination level to be reduced by selectively reducing the voltage to the lamp to improve low-contrast copying. It has been demonstrated that the general run of low-contrast masters, such as hard pencil on yellow pad, can be copied well if the illumination level is lowered.

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