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Browse Prior Art Database

MIRROR SCANNING SYSTEM

IP.com Disclosure Number: IPCOM000025267D
Original Publication Date: 1984-Apr-30
Included in the Prior Art Database: 2004-Apr-04
Document File: 2 page(s) / 98K

Publishing Venue

Xerox Disclosure Journal

Abstract

A novel mirror scanning system 10 is disclosed in Figure 1 that comprises two mirrors 12 and 14 that are fashioned helically about a roller 20. A laser beam brought in from laser source 30 parallel to roller shaft 21 strikes each mirror in turn and reflects off at an angle equal to the angle of incidence. As the roller is rotated, the point of incidence of the laser beam traverses along the face of a mirror such that each mirror produces one scan line at a time. With lens 40 in the system with its focal point at A, the image plane of the resulting spot will be at an angle to the roller. A long focal length lens also has a large region where the spot is in sharp focus, i.e., a considerable depth of focus. Spot intensity can be controlled by modulator 50.

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MIRROR SCANNING SYSTEM (Cont'd)

A novel mirror scanning system 10 is disclosed in Figure 1 that comprises two mirrors 12 and 14 that are fashioned helically about a roller 20. A laser beam brought in from laser source 30 parallel to roller shaft 21 strikes each mirror in turn and reflects off at an angle equal to the angle of incidence. As the roller is rotated, the point of incidence of the laser beam traverses along the face of a
mirror such that each mirror produces one scan line at a time. With lens 40 in the system with its focal point at A, the image plane of the resulting spot will be at an angle to the roller. A long focal length lens also has a large region where the spot is in sharp focus, i.e., a considerable depth of focus. Spot intensity can be controlled by modulator 50.

Additional mirrors with concomitant benefits can be employed, each occupying its fraction of the roller circumference. For example, if a roller has a 3" outside diameter to mirror edge and has 20 mirrors (one every 18 degrees of roller arc) fabrication would be eased since less helical curvature for a given roller length would be needed. Since useful laser beams are -1mm or less, mirror heights need only be somewhat greater than the beam diameter.

With this system, to print 200 lines per inch at 2 inches per second would require 20 roller revolutions per second which would be accomplished with a 1200 RPM motor which is very low speed for a scanner. A greater number of mirrors will further reduce RPM requi...