Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Patent
1988-12-12
1990-02-20
Nelms, David C.
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
250225, 250231R, H01J 516
Patent
active
049028880
ABSTRACT:
An optical fiber sensor for detecting a change of an external subject, based on measuring and reference beams. The sensor includes an optical fiber or fibers for optically coupling a light transmitter/receiving portion and a sensor head portion. Where the measuring and reference beams are transmitted through the single optical fiber to the sensor head portion in respective two transmission modes having mutually perpendicular polarization planes, the sensor head portion may include a Faraday effect element for rotating the polarization planes of the measuring and reference beams, in order to switch the two transmission modes when the beams are returned through the fiber to the transmitter/receiver portion. The sensor head portion may include a device for returning the measuring and reference beams through the optical fiber as two linearly polarized beams having mutually perpendicular polarization planes and a phase difference of 90.degree.. Where the measuring and reference beams are transmitted to the sensor head portion by the respective first and second fibers, the sensor head portion may employ a device for directing the two beams so that the measuring and reference beams are returned to the transmitter/receiver portion through the second and first fibers.
REFERENCES:
patent: 4800266 (1989-01-01), Poorman
patent: 4818064 (1989-04-01), Youngquist et al.
Brother Kogyo Kabushiki Kaisha
Nelms David C.
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