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Browse Prior Art Database

Aligning a Laser Beam With the Crystal in an Acousto-Optic Modulator

IP.com Disclosure Number: IPCOM000044352D
Original Publication Date: 1984-Dec-01
Included in the Prior Art Database: 2005-Feb-05
Document File: 2 page(s) / 51K

Publishing Venue

IBM

Related People

Arnold, RC: AUTHOR

Abstract

The concept of acousto-optic modulators in laser printers is not new. However, when using more than one frequency, the laser alignment is critical. Previous methods of aligning the laser beam were not only slow and inaccurate but were also not repeatable. The new beaconing method uses the two location pins on the modulator for laser alignment. When the modulator is raised by 0.014 inch, or a channel is milled 0.014 inch in the modulator mounting plate, the locating pins are exposed to the laser beam. I suggest using the milled channel method because, if the modulator is raised at each end, the optical center is also raised. When the laser beam is directed through this channel and translated in a horizontal direction, the beam will strike the locating pins.

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Aligning a Laser Beam With the Crystal in an Acousto-Optic Modulator

The concept of acousto-optic modulators in laser printers is not new. However, when using more than one frequency, the laser alignment is critical. Previous methods of aligning the laser beam were not only slow and inaccurate but were also not repeatable. The new beaconing method uses the two location pins on the modulator for laser alignment. When the modulator is raised by 0.014 inch, or a channel is milled 0.014 inch in the modulator mounting plate, the locating pins are exposed to the laser beam. I suggest using the milled channel method because, if the modulator is raised at each end, the optical center is also raised. When the laser beam is directed through this channel and translated in a horizontal direction, the beam will strike the locating pins. The resulting effect will be a sweeping or beaconing of the beam in relation to the laser's position on the pins. When this position is at the pin center, the beam into the pin will be reflected back upon itself. Thus, the beam is aligned on the center of the locating pins. Adding the pin radius to the given value of the optical center will align the laser. Alignment is required in both horizontal and vertical directions. The horizontal direction is given as a specific distance, d1, from the edge of the two alignment pin holes. This distance is set by the vendor as the distance from the optical center of the crystal to the edge of the alignment pin holes. The vertical alignment is given as a specific distance, d2, from the bottom of the modulator base. This distance is set by the vendor as the distance from the optical center of the crystal to the bottom of the modulator. See Fig. 1. The problems encountered in alignment are two: (1) In the horizontal plane, it is difficult to find accurately the absolute optical bottom of the modulator with the laser beam; and
(2) in the vertical plane, placing the beam on the ed...