Rotary beam light curtain

Details Rotary beam light curtain Rotary beam light curtain

1976-10-15

1978-08-15

Nelms, David C.

Radiant energy

Photocells; circuits and apparatus

Optical or pre-photocell system

250236, G01D 2104

Patent

active

041075226

ABSTRACT:
A light curtain for scanning rectangular openings with an oscillating light beam originating in a corner of the opening. A photo-detector is placed in the same corner. Retroreflectors, such as triple reflectors are placed on adjacent sides of the opening which are opposite the light source for reflecting light back to the photo-sensor. Above a critical reflection angle for the retroreflector, a plane mirror is provided which directs light from the source to the retroreflector on the adjacent side so that light impinging on the mirror at an angle exceeding the critical angle is received by the adjacent retroreflector at an angle that is within the critical angle. Consequently, such light is reflected via the plane mirror back to the photo-sensor. The light can be modulated to facilitate the monitoring of the area encompassed by the opening.

REFERENCES:
patent: 2769374 (1956-11-01), Sick
patent: 3025406 (1962-03-01), Stewart et al.
patent: 3360654 (1967-12-01), Muller
patent: 4012635 (1977-03-01), Walter et al.

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