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High Speed Slit Scanning Optics System

IP.com Disclosure Number: IPCOM000075760D
Original Publication Date: 1971-Nov-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 3 page(s) / 58K

Publishing Venue

IBM

Related People

Libby, EL: AUTHOR

Abstract

This slit scanning optics system has a stationary flat document plane on which objects, such as books, can be copied conveniently, and a separate station where single sheet documents can be copied at up to twice the rate of "book copy rate". This system also has a simple reduction system.

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High Speed Slit Scanning Optics System

This slit scanning optics system has a stationary flat document plane on which objects, such as books, can be copied conveniently, and a separate station where single sheet documents can be copied at up to twice the rate of "book copy rate". This system also has a simple reduction system.

The optics system is a four mirror scanning device, Fig. 1. This system provides a simple mechanism for scanning a flat document but is limited in output rate because of the flyback time. The output rate, CPM=1/cycle time where the cycle time, T, is the total of the scan time plus the flyback time, or CPM=1/(ts+tf).

For a given scan time, the output rate can be maximized by reducing the flyback. The maximum, of course, is when the flyback time is zero. This is accomplished in the four-mirror system by moving the scanning mirrors off the flat document to a stationary position slit. The four-mirror system does not require a larger lens (the viewing angle of the lens remains the same), or require a different light level (cos/4/theta).

The system is capable of reducing or magnifying the image by changing the spacing between the first and second mirrors to change the total conjugate length (TCL), by moving the lens, and by changing the scan velocity.

In the full-size mode, the first mirror and carriage moves from point A1 to point A2 while the second carriage moves from B1 to B2. The first carriage moves at the scan velocity and the second carriage moves at one-half that velocity, Fig. 2.

For a higher copy output rate the first carriage is moved to the right (keeping the conjugate length constant) and remains fixed while the documents are fed past the viewing slit. The feed device controls the document so that the velocity past the slit is the scan ve...