Browse Prior Art Database

Improving Resolution of a Scanning Laser Printer

IP.com Disclosure Number: IPCOM000047870D
Original Publication Date: 1983-Dec-01
Included in the Prior Art Database: 2005-Feb-08
Document File: 2 page(s) / 34K

Publishing Venue

IBM

Related People

Froess, RJ: AUTHOR

Abstract

This article describe a concept for stopping the movement of a laser beam spot on an electrophotographic medium during the exposure of each print element (pel). This is accomplished by varying the first order laser beam angle from the output of the acousto-optic modulator to cancel the movement caused by the rotating polygonal mirror. The horizontally scanning laser beam has a diameter of about one pel. If the beam is turned on for one pel and then off, it produces an elliptical exposure, as shown in Fig. 1. The elliptical shape is caused by the continuously rotating mirror's angular velocity in the direction A during the turn-on of the beam. Not only is the exposure wider but the slope of the intensity is less steep. Both these characteristics reduce the horizontal resolution.

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Improving Resolution of a Scanning Laser Printer

This article describe a concept for stopping the movement of a laser beam spot on an electrophotographic medium during the exposure of each print element (pel). This is accomplished by varying the first order laser beam angle from the output of the acousto-optic modulator to cancel the movement caused by the rotating polygonal mirror. The horizontally scanning laser beam has a diameter of about one pel. If the beam is turned on for one pel and then off, it produces an elliptical exposure, as shown in Fig. 1. The elliptical shape is caused by the continuously rotating mirror's angular velocity in the direction A during the turn-on of the beam. Not only is the exposure wider but the slope of the intensity is less steep. Both these characteristics reduce the horizontal resolution. The exposure shape depends on the shape of the beam and the distance it moves (also on rise and fall time of the intensity). The usual solution is to reduce the distance moved by delaying the turn-on of the beam. This helps, but the energy in the exposure is reduced proportionally, causing the exposure shape to shrink in both dimensions. Vertical 1 pel lines then "break up." A better solution is to extend the idea to every pel so that a horizontal line is exposed as a series of pulses. However, this may require more laser power. Another approach reduced the exposure ellipticity by shaping the laser beam so that it is narrower than its height...