Browse Prior Art Database

ADD LENS IRRADIANCE COMPENSATION WITH CHROMATIC CONTROL

IP.com Disclosure Number: IPCOM000024063D
Original Publication Date: 1979-Aug-31
Included in the Prior Art Database: 2004-Apr-02
Document File: 2 page(s) / 233K

Publishing Venue

Xerox Disclosure Journal

Abstract

The figure illustrates an exposure for a copier at a 1:1 magnification. A document to be copied is placed on platen 22. Lens 30 is positioned midway along the optical path 34 of the optical system and projects an image of the document onto an image plane 20 via a mirror 25. When changing to a second magnification, such as a

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XEROX DISCLOSURE JOURNAL

ADD LENS IRRADIANCE COMPEN~ SATION WITH CHROMATIC CONTROL Richard Vandewarker

22

Proposed Classification

U.S. CL 350/183 mt. CL G02b 15/02

The figure illustrates an exposure for a copier at a 1:1 magnification. A document to be copied is placed on platen 22. Lens 30 is positioned midway along the optical path 34 of the optical system and projects an image of the document onto an image plane 20 via a mirror 25. When changing to a second magnification, such as a

reduction in image size, lens 30 is moved axially along the optical path 34 in order to change the magnification of the document as it appears at the image plane 20. In order to maintain this system without realignment or change of conjugate length, an "add~lens 32 having a relatively long focal length is pivoted into the optical path. The use of lens 32, however, introduces two problems which must be compensated for. The first problem, irradiance change, is commonly controlled via a complex, automatic aperture diaphragm control or by inclusion of a neutral density coating on the add lens elements. These coatings are expensive and tend to introduce stray light into the imaging system resulting in reduction of image contrast. Loss of contrast due to added chromatic aberration goes uncorrected by either of these methods. It is proposed that instead of limiting the intensity of transmitted radiation by addition of a neutral density coating, exposure is controlled by limiting the chroma...