Browse Prior Art Database

CRT Phosphor Subtraction System

IP.com Disclosure Number: IPCOM000053092D
Original Publication Date: 1981-Aug-01
Included in the Prior Art Database: 2005-Feb-12
Document File: 2 page(s) / 31K

Publishing Venue

IBM

Related People

Fritz, RJ: AUTHOR

Abstract

This arrangement for a CRT scanner uses an optical beam splitter to divide the light from the CRT into a first portion directed to the document via a folded optical system and a second portion directed to a photo-multiplier which detects variation in the light output of the CRT.

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CRT Phosphor Subtraction System

This arrangement for a CRT scanner uses an optical beam splitter to divide the light from the CRT into a first portion directed to the document via a folded optical system and a second portion directed to a photo-multiplier which detects variation in the light output of the CRT.

The scanner tube 3, or CRT, projects the scanning light beam 5 to a beam splitter 7, which may be, for example, a partially silvered mirror which reflects a certain percentage of the incident light, and transmits the remainder of the light. The ratio of transmitted to reflected light, T-R, can be varied.

A first photo-multiplier tube 9 looks at the light 11 transmitted from the beam splitter. This will be a percentage of the total output of CRT 3. An electrical signal proportional to the light will be supplied to one input of a subtraction circuit 13 of conventional design.

The reflected portion 15 of the light from the scanner is transmitted to and through a folded optical system including a lens system indicated diagrammatically by a single lens 17 to a mirror 19, from which it is reflected to the surface of a document 21, which is to be scanned. The light 23 reflected from document 21 is detected by a second photo-multiplier 25, and the electrical signals developed are supplied to a second input of the subtractor circuit 13. Systems employing none, one or two mirrors can also be provided.

The output signal supplied on a line 27 from the subtractor circui...