Browse Prior Art Database

FOCUSING AID FOR AN IIT

IP.com Disclosure Number: IPCOM000025986D
Original Publication Date: 1989-Jun-30
Included in the Prior Art Database: 2004-Apr-04
Document File: 2 page(s) / 67K

Publishing Venue

Xerox Disclosure Journal

Abstract

Image input terminals (IIT's) often use a lens to image the input document on a sensor. This lens must be at or near best focus if optimum IIT performance is to be achieved. In a typical focus arrangement, an operator observes the output of a sensor (an optical/electrical transducer) on an oscilloscope and manually moves the lens until a signal modulation reaches a peak. However, the peak tends to be indistinct, and thus an unreliable indicator of machine performance.

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XEROX DISCLOSURE JOURNAL

FOCUSING AID FOR AN IIT

Richard H. Tuhro Richard A. Beck Robert J. Morante Ned J. Seachman

Proposed Classification

US. C1.358/285 Int. C1. H04n 1/04

Image input terminals (IIT's) often use a lens to image the input document on a sensor. This lens must be at or near best focus if optimum IIT performance is to be achieved. In a typical focus arrangement, an operator observes the output of a sensor (an optical/electrical transducer) on an oscilloscope and manually moves the lens until a signal modulation reaches a peak. However, the peak tends to be indistinct, and thus an unreliable indicator of machine performance.

It is proposed that high frequency transfer function components tend to be better indications of focus than low frequency transfer function components. Apparatus to perform focus calibration includes an optical target with a number of lines, a sensor, a high pass filter separating high frequency components of the transfer function and a readout system or servo system using the output of the transfer function to provide focus information, or directly move the lens to appropriate position. Special targets optimize focus for each lens axes, (sometimes referred to as sagittal and tangential axes) by providing sets of lines parallel to the sagittal and tangential axes, for sequential focus of each axis or provide compromise focus between the axes, by providing line sets tilted or slanted with respect to both axes.

Thus, by using only...