Browse Prior Art Database

Detection Range Expansion of a CRT Scanner

IP.com Disclosure Number: IPCOM000074505D
Original Publication Date: 1971-May-01
Included in the Prior Art Database: 2005-Feb-23
Document File: 2 page(s) / 53K

Publishing Venue

IBM

Related People

Frechette, GA: AUTHOR [+2]

Abstract

This is a technique for expanding the signal range of a CRT film scanner with linear light detectors such as photomultipliers.

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Detection Range Expansion of a CRT Scanner

This is a technique for expanding the signal range of a CRT film scanner with linear light detectors such as photomultipliers.

Drawing A shows a typical CRT transparency scanner composed of a CRT light source 1 with beam positioning, a light servo photomultiplier 2, an objective lens 3, a transparency holder 4, a condenser lens 5, and a signal photomultiplier
6. The CRT 1 provides a timed sequence source of light which can be directed over an array of points. The electron beam of CRT is positioned to a specified point and turned-on to excite the phosphor.

The light servo photomultiplier 2 and its associated circuitry 7 correct for variations in CRT light output. The circuitry 7 maintains a constant amount of light energy directed to the transparency being scanned by the objective lens 3 by detecting the light intensity from the CRT spot, integrating the resulting photoelectric current, comparing the integrated voltage to a fixed reference, and time modulating the CRT turnoff.

The condenser lens 5 renders the light transmitted through the transparency spatially independent on the signal photomultiplier 6. The signal photomultiplier 6 with its control circuitry 8 integrates the transparency transmission dependent light signal, amplifies the signal, and converts this analog signal into discrete digital values via an analog to digital converter 9. After the A/D conversion, the crowbar circuit 10 discharges the integrator 12...