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Browse Prior Art Database

Optical Angle Sensor

IP.com Disclosure Number: IPCOM000077075D
Original Publication Date: 1972-Jun-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 2 page(s) / 41K

Publishing Venue

IBM

Related People

Burke, MJ: AUTHOR [+3]

Abstract

Shown in Fig. 1 is an angle-sensing system which operates off the back surface of a pair of deflector mirrors.

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Optical Angle Sensor

Shown in Fig. 1 is an angle-sensing system which operates off the back surface of a pair of deflector mirrors.

The angle sensor measures the overlay area between aperture 2 and aperture 1 imaged on aperture 2. Aperture 1 is uniformly illuminated by a light- emitting diode LED 3 and condenser lens L1.

Spacing T1 is set to give a collimated beam of light (i.e., image LED 3 at infinity). Spacing T2 is set so that lens L2 forms an image of Ml at infinity and an image of LED 3 on the mirror surface 4. L3 forms an image of LED 3 at infinity and a demagnified image of M1 at M2. The image of M1 falls on M2 as shown in Fig. 2, when the mirror is undeflected (0 degrees). When the mirror deflects by an angle Theta, the image of M1 moves by X - f3 tan 2 Theta. The amount of light passing through M2 is proportional to the overlap area between M1 and M2. A (X) = Ao - f3 h2 tan 2 Theta where

f3 = Focal length of L3

h2 = Height of aperture M2.

The light passing through the overlap area 5 is focused onto solar cell SC1 by L4 (i.e., L4 forms an image of LED 3 on SC1). The double-imaging system is used to form images of M1 and LED 3 in different planes to limit the size of the aperture required at the deflecting mirror and at SC1. The aperture required at these planes is only the size of the LED image. An added advantage of this layout is the image of the LED on the solar cell moves very little as the mirror deflects, minimizing nonlinearities due to sensitivit...