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Printing Plate Recording by Direct Exposure

IP.com Disclosure Number: IPCOM000076037D
Original Publication Date: 1971-Dec-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Lipp, J: AUTHOR

Abstract

The vertical deflection of a laser beam is controlled by digital light-deflection apparatus which provides a raster of discrete, essentially diffraction-limited spots of light along a vertical line to expose a photosensitive medium on a printing plate.

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Printing Plate Recording by Direct Exposure

The vertical deflection of a laser beam is controlled by digital light-deflection apparatus which provides a raster of discrete, essentially diffraction-limited spots of light along a vertical line to expose a photosensitive medium on a printing plate.

In the preferred embodiment, the particular beam trace on the photosensitive medium is determined by computer control of the digital light deflector; and horizontal displacement of the vertical lines transversely on the photosensitive medium is accomplished by light coupling means, which reciprocates across the plane of the medium.

The light-deflection apparatus comprises two distinct and different sets of deflectors. Both sets comprise a number of digitally indexed, fast acting, crystal deflectors in which the light team is controlled by electro-optic switches, e.g. as described in IBM Journal of Research and Development of January 1964, pages 64-67.

A deflection stage of the first set is capable of yielding diffraction-limited output beams and providing minimum separation between adjacent positions of the deflected output beams. The separation is o ordinarily limited only by Rayleigh's criterion and may be termed a diffraction-limited separation. Light- deflection apparatus to perform these functions is well known to those of skill in this art; e.g., split-angle (SA) deflectors may be used, such as described in US patent 3,499,700.

It is known, however, that SA deflectors introduce astigmatic aberrations in one of the two possible convergent beams in each deflection stage. These aberrati...