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Optical Record Presence Detector

IP.com Disclosure Number: IPCOM000084523D
Original Publication Date: 1975-Nov-01
Included in the Prior Art Database: 2005-Mar-02
Document File: 2 page(s) / 36K

Publishing Venue

IBM

Related People

Keller, RJ: AUTHOR [+2]

Abstract

Card readers and similar record-handling equipment usually require means for detecting the presence or absence of a record at a particular location. In conventional optical detectors, a separately manufactured mask confines the light from a source to a small area aligned with a photo-detector.

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Optical Record Presence Detector

Card readers and similar record-handling equipment usually require means for detecting the presence or absence of a record at a particular location. In conventional optical detectors, a separately manufactured mask confines the light from a source to a small area aligned with a photo-detector.

Fig. 1 shows a detector using a unitary molded-plastic housing 10 which does not require a separate mask. As in conventional practice, a light source 20 has a light-emitting diode (LED) 21 mounted in substrate 22 and covered by a transparent plastic housing 23. Detector 30 has a phototransistor (PTX) 31 mounted in a substrate 32 affixed to the machine across a record path 40 from source 20.

Instead of having an apertured opaque material to constrain the light between LED 21 and PTX 31, transparent plastic housing 10 has a notch in its upper surface 11. A thin, horizontal top 12 is aligned with LED 21 and PTX 31, and allows light in a narrow area to impinge directly upon PTX 31. Angled sides 13 reflect or refract light outside this area away from PTX 31, depending upon the choice of angle and wavelength of LED 21, for a particular plastic material. Horizontal surfaces 14 are sufficiently far from the optical axis of the detector that light passing through them does not reach PTX 31.

Fig. 2 is a side view of housing 10. Surfaces 12-14 are in a head portion 15 having a notch 16 for receiving substrate 32. Locating pins 17, and a tab 18 having a...