Browse Prior Art Database

Precision Optical Emitters

IP.com Disclosure Number: IPCOM000052110D
Original Publication Date: 1981-Apr-01
Included in the Prior Art Database: 2005-Feb-11
Document File: 3 page(s) / 111K

Publishing Venue

IBM

Related People

Bateson, JE: AUTHOR [+3]

Abstract

Small emitter distances are detected without having close mechanical distances normally associated with a grid and an aperture. The optical emitters, such as that shown in Fig. 1, use a light source 1, such as a light-emitting diode (LED), a collimating lens 2, an optical grid 3, a 90 degrees prism 4, and a photodetector 5.

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Precision Optical Emitters

Small emitter distances are detected without having close mechanical distances normally associated with a grid and an aperture. The optical emitters, such as that shown in Fig. 1, use a light source 1, such as a light-emitting diode (LED), a collimating lens 2, an optical grid 3, a 90 degrees prism 4, and a photodetector 5.

A feature of the emitter structures is the ability to resolve small distances, typically .002" to .004", without close clearances between an aperture and grid. There are no close tolerances between the grid and the collimating lens or the face of the prism. See Fig. 2, for example. From a manufacturing standpoint this is desirable since it eliminates critical and costly mechanic~l adjustments. Since the light rays in practice are not precisely parallel, the distance from the collimating lens to the photodetector in each case should be kept at a minimum.

Fig. 2 shows the optical grid positioned so that the photodetector receives maximum light. By moving the grid one-fourth of the pitch of the grid as in Fig. 3, the light is eclipsed. The grid is moved only by P/4 of its cycle, and the light to the photodetector is determined by P/2. That is, the optical pulses are twice the frequency of the grid. If the optical grid is traversed across the light path, a series of pulses indicating displacement is generated. Light rays from the light source may not be precisely parallel. To help compensate for this, the ratio of the cl...