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Browse Prior Art Database

Correction of E Beam Deflection Patterns

IP.com Disclosure Number: IPCOM000086881D
Original Publication Date: 1976-Nov-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 3 page(s) / 60K

Publishing Venue

IBM

Related People

Ryan, PM: AUTHOR

Abstract

This disclosure describes digital logic with which adjustments or corrections to the specified path of a physical object, such as an electron beam, may be defined and controlled despite systematic errors in the scanning mechanism. It represents an improvement over the correction technique described in U. S. Patent 3,644,700 and works in conjunction with digital hardware described in U. S. Patent 3,866,013.

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Correction of E Beam Deflection Patterns

This disclosure describes digital logic with which adjustments or corrections to the specified path of a physical object, such as an electron beam, may be defined and controlled despite systematic errors in the scanning mechanism. It represents an improvement over the correction technique described in U. S. Patent 3,644,700 and works in conjunction with digital hardware described in U.
S. Patent 3,866,013.

Each portion of a cyclic deflection pattern (e.g., all forward-going scans) contains a measurable positional error as a function of beam position. This error may be described by two error surfaces (one for error in X, one for error in Y) over the XY plane.

Once these error surfaces are known (through techniques described in
U. S. Patent 3,644,700), they may be separated into errors of initial position, at the beginning of each scan, and of speed, across each scan line.

Referring to Fig. 1, piecewise-linear correction to starting position is established by setting up a "running value" register and an "Increment" register. Each time a position value is needed (at the beginning of each line), the running value is gated to an output register, the increment is added to it, and the sum re- stored in the running value register. Periodically, new values are set into the increment register, resulting in a piecewise-linear correction of starting position.

Piecewise-linear correction of position error along each scan is achieved by piecewise constant adjustments of speed along each scan. This is accomplished with the circuit in Fig. 2.

At a sequence of points along each scan, a "correction sync is received from the pattern control section. This sync, together with YLSB, the LSB of the li...