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Calibration of Flying Spot Scanner

IP.com Disclosure Number: IPCOM000093508D
Original Publication Date: 1967-Oct-01
Included in the Prior Art Database: 2005-Mar-06
Document File: 4 page(s) / 61K

Publishing Venue

IBM

Related People

Anderson, RJ: AUTHOR [+10]

Abstract

A flying-spot scanner is often used in a pattern recognition system. Such a scanner is depicted in drawing 1 by cathode ray tube CRT 10 directing a spot of light onto document 12. Photomultiplier tube PMR 14 picks up light reflected from document 12. The signal from the PMT 14 must be coordinated with the position of the scanning beam in directing a spot of light onto document 12. Photomultiplier tube PMR 14 picks up light reflected from document 12. The signal from the PMT 14 must be coordinated with the position of the scanning beam in order for the reflected signal to be useful for machine recognition of patterns on document 12. The purpose of the electronic system in drawing 1 is to check the scanning motion of the beam from CRT 10 and the positioning of document 12 under window 16.

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Calibration of Flying Spot Scanner

A flying-spot scanner is often used in a pattern recognition system. Such a scanner is depicted in drawing 1 by cathode ray tube CRT 10 directing a spot of light onto document 12. Photomultiplier tube PMR 14 picks up light reflected from document
12. The signal from the PMT 14 must be coordinated with the position of the scanning beam in directing a spot of light onto document 12. Photomultiplier tube PMR 14 picks up light reflected from document
12. The signal from the PMT 14 must be coordinated with the position of the scanning beam in order for the reflected signal to be useful for machine recognition of patterns on document 12. The purpose of the electronic system in drawing 1 is to check the scanning motion of the beam from CRT 10 and the positioning of document 12 under window
16. The system checks the following seven conditions.
1. Scanning beam velocity across the surface of document 12,
2. Pincushion correction,
3. Location of an electronic scan window with respect to window

16,
4. Orientation of the electronic window with respect to window

16,
5. Location of document 12 with respect to window 16,
6. Orientation of document 12 with respect to window 16, and
7. Incremental distance document 12 is moved by a document

transport when such document is indexed under window 16.

The seven conditions are checked by the system by use of vertical calibration document 12, drawing 3, horizontal calibration document 42, drawing 4, and central processing unit CPU 18, drawing 1.

Documents 12 and 42 are fed under window 16 separately and scanned separately. The calibration marks on documents 12 and 42 are a predetermined distance apart. The video information detected by PMT 14 when documents 12 and 42 are scanned is fed to CPU 18 for analysis. The analysis in CPU 18 indicates the status of the seven conditions. If any condition does not meet specifications, an operator can adjust the scanning equipment or the document transport equipment to bring the system back within specifications.

Before examining the scanning of documents 40 and 42, drawing 2 shows window 16 is shaded and the electronic windows are shown in dashed lines. These windows are defined electronically in beam control

In drawing 1, the video signal from PMT 14 is amplified by amplifier 24. The amplified video signal is then sampled by a clock signal from clock 26 operating on And 28. The clock signal effectively divides the video signal into time bits of information. These video bits of information are then passed by Or 30 back to logic 20 or to CPU 18 when gate 32 is on. Clock 26 also controls the beam velocity by acting on logic 20. In addition, clock 26 specifies the bit rate for pseudo video generator 34 which generates fixed patterns of video bits under certain conditions.

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Document 12 is moved by a document transport until the top one third of document 12 is positioned under window 16. Document 12 is shown positioned in t...