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Variable Aperture Stop for a Reciprocating Lens Copier Design

IP.com Disclosure Number: IPCOM000081998D
Original Publication Date: 1974-Sep-01
Included in the Prior Art Database: 2005-Feb-28
Document File: 2 page(s) / 30K

Publishing Venue

IBM

Related People

Smith, GL: AUTHOR

Abstract

When a copier lens has a relatively short total conjugate length (24") and the lens reciprocates during scanning along the (14") axis of the document, some correction is required for the cos theta variation in light intensity along the axis of lens motion.

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Variable Aperture Stop for a Reciprocating Lens Copier Design

When a copier lens has a relatively short total conjugate length (24") and the lens reciprocates during scanning along the (14") axis of the document, some correction is required for the cos theta variation in light intensity along the axis of lens motion.

Cos/4/ theta correction along this axis can be achieved by using a stationary variable-width aperture stop 1, as in the illustration, placed near the reciprocating lens. More light is allowed to pass through the lens when the lens is off-axis. The shape of the variable-aperture stop is designed to provide the cos/4/ theta correction and other correction, as needed (such as vignetting).

The variable-aperture stop could be placed on either side of the reciprocating lens. However, if it is placed on the document side of the lens, the overall width of the variable-aperture stop is wider making the exact placement of the stop less critical.

The variable-aperture stop may also be used as a convenient mounting fixture for a chromatic filter in the optical system, if required.

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