Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Patent
1981-02-18
1984-05-22
Nelms, David C.
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
250237R, G01N 2188
Patent
active
044503598
ABSTRACT:
Faults in a material web 47 are detected by scanning the web with a beam of light 37 along a line transversely to its direction of movement F and by detecting the angular ranges into which the incident light is scattered by these faults. For this purpose an elongate light receiving device 33, which is preferably a light conducting rod, extends parallel to the line of scanning on the web with the axis of the light conducting rod and the line of scanning defining a reception plane. An elongate angular range filter 34 is arranged in this plane between the line of scanning and the light conducting rod and serves to deflect beams of light 35 close to the angle of specular reflection away from the light conducting rod. Light which is scattered in other angular ranges within the reception plane is however transmitted by the angular range filter 34 to the light conducting rod and is detected by a photoelectric detector positioned at the end face thereof. The system can also operate in transmission in which case the normally transmitted ray is deflected away from the light conducting rod. In this way the scattered beams which contain the useful information are detected without being swamped by the remainder of the light. A number of different angular range filters are disclosed including holograms 34, grids of thin plates 41, an array of stepped prisms 39 and an array of photoelectric detectors 43. Possible scanning devices include a fluorescent tube and beam scanning apparatus using a scanning beam 37 which is either continuously displaced parallel to itself (FIG. 1) or swept angularly through a sector-like range (FIG. 2).
REFERENCES:
patent: 3478218 (1969-11-01), Wuellner et al.
patent: 3748047 (1973-07-01), Millgard et al.
patent: 4099884 (1978-07-01), Nash
patent: 4197011 (1980-04-01), Hudson
patent: 4306808 (1981-12-01), Vander Neut
patent: 4306813 (1981-12-01), Sick
Ostertag Klaus
Ross Dieter
Erwin Sick GmbH - Optik-Elektronik
Nelms David C.
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