Browse Prior Art Database

Reflective Object Sensor

IP.com Disclosure Number: IPCOM000050328D
Original Publication Date: 1982-Oct-01
Included in the Prior Art Database: 2005-Feb-10
Document File: 3 page(s) / 35K

Publishing Venue

IBM

Related People

Routt, WM: AUTHOR

Abstract

In the sensing of the presence or absence of an object such as a sheet of paper, it is not always possible to control the Position of the object with respect to the light source and photosensor of the detection apparatus and, with light sources and photodetectors oriented at an angle with respect to each other, the converging paths of the illumination and the detection zone must intersect at approximately the plane in which the object is expected to be detected. If the object is substantially displaced from the plane of detection, then the light provided by the illumination source will not be reflected by the object into the photosensor and, therefore, an erroneous signal will result.

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Reflective Object Sensor

In the sensing of the presence or absence of an object such as a sheet of paper, it is not always possible to control the Position of the object with respect to the light source and photosensor of the detection apparatus and, with light sources and photodetectors oriented at an angle with respect to each other, the converging paths of the illumination and the detection zone must intersect at approximately the plane in which the object is expected to be detected. If the object is substantially displaced from the plane of detection, then the light provided by the illumination source will not be reflected by the object into the photosensor and, therefore, an erroneous signal will result. Relatively small displacements of the object from the predicted object plane can result in sufficiently diminished light collection by the photosensor so as to give an erroneous reading.

The most efficient technique for overcoming this criticality of the object position is to make the illumination path and the rays passing from the object to the photosensor coaxial.

Heretofore, techniques have involved partially silvered mirrors, beam splitters and other devices which are both very expensive and which severely limit the light transmission of the device.

The figure above illustrates a device which permits the light source 10 to be displaced from photosensor 12. Each of the light sources 10 and photosensor 12 are placed adjacent semi-collimating lenses 14. The lenses 14 are molded as a part of the overall device 16, together with a concentrating lens 18 on the opposite surface from lenses 14. Also provided are totally reflecting surfaces 20 and 22 molded as the outside surface of the device. The angles with respect to the axis of lenses 14 are chosen to reflect light from the light-emitting diode (LED) through collimating lens 14, off surf...