Browse Prior Art Database

Light Beam Servoing System

IP.com Disclosure Number: IPCOM000075870D
Original Publication Date: 1971-Dec-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 2 page(s) / 34K

Publishing Venue

IBM

Related People

Eaton, JH: AUTHOR

Abstract

Described is a device for generating an error signal to servo a light beam to a selected spot. The device 1 is schematically shown in the figure. A set of parallel oriented lines 2 is arranged on a glass plate for example, around a hole 3 through which the beam is desired to be directed. These lines do not reflect the light beam while the area inbetween the lines does. They serve as diffraction gratings and diffract light incident on them orthogonal to the direction of the lines, as indicated by the arrows A,B,C,D. Photodetectors are placed in directions dictated by the arrows A,B,C,D. Photodetectors are placed in directions A,B,C,D at an elevation consistent with detecting the diffracted beam. When all four photodetectors receive the same amount of light, the beam is centered.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 100% of the total text.

Page 1 of 2

Light Beam Servoing System

Described is a device for generating an error signal to servo a light beam to a selected spot. The device 1 is schematically shown in the figure. A set of parallel oriented lines 2 is arranged on a glass plate for example, around a hole 3 through which the beam is desired to be directed. These lines do not reflect the light beam while the area inbetween the lines does. They serve as diffraction gratings and diffract light incident on them orthogonal to the direction of the lines, as indicated by the arrows A,B,C,D. Photodetectors are placed in directions dictated by the arrows A,B,C,D. Photodetectors are placed in directions A,B,C,D at an elevation consistent with detecting the diffracted beam. When all four photodetectors receive the same amount of light, the beam is centered. If the "A" direction receives more light than the "C" direction photodetector, the beam must be moved in the C direction to center it. Thus, this plate serves the function of a four-way servo correction plate. Special servo effects can be achieved by varying the grating spacings in each quadrant.

1

Page 2 of 2

2

[This page contains 1 picture or other non-text object]