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Browse Prior Art Database

Printer/Plotter

IP.com Disclosure Number: IPCOM000082884D
Original Publication Date: 1975-Feb-01
Included in the Prior Art Database: 2005-Feb-28
Document File: 2 page(s) / 47K

Publishing Venue

IBM

Related People

May, GH: AUTHOR [+2]

Abstract

This is an apparatus for making a screen used in the printing of halftones comprising a high-gamma photosensitive plate, a monochromatic light source focused on the plate and having a symmetric Gaussian-like energy distribution across the beam width. It also includes means for both scanning the plate and for intensity modulating the beam, such that for a constant exposure time the spot diameter on the plate is a linear function of beam intensity.

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Printer/Plotter

This is an apparatus for making a screen used in the printing of halftones comprising a high-gamma photosensitive plate, a monochromatic light source focused on the plate and having a symmetric Gaussian-like energy distribution across the beam width. It also includes means for both scanning the plate and for intensity modulating the beam, such that for a constant exposure time the spot diameter on the plate is a linear function of beam intensity.

One mechanism for implementing the apparatus would be to wrap photo sensitized papers into a position around a transparent drum. If a laser beam were directed peripherally around the drum at a constant radius or distance from the papers, then a stepping motor could step the beam longitudinally with respect to the drum to produce print lines.

The combination of a high-gamma film at a Gaussian-shaped beam width energy distribution provides a threshold-controlled system for originating the spots. Relatedly, the focused laser beam Gaussian-energy distribution is shown in Fig. 1. Also, the size of the dark spots that are produced when the laser beam is turned on is a function of the exposure of the plate. If the exposure time is constant, the size of the dark spots is a function of beam intensity as shown, for example, in Fig. 3. Parenthetically, the tone reproduction diagram is a replot of several exposure levels represented as the log of Gaussian-exposure function in Fig. 2.

It is apparent from the tone repr...