Optical measuring apparatus

Details Optical measuring apparatus Optical measuring apparatus

1994-08-30

1996-07-09

Hellner, Mark

Optics: measuring and testing

Range or remote distance finding

With photodetection

356 509, G01C 308

Patent

active

055349927

ABSTRACT:
Laser light from LD (laser diode) is guided through a fiber to be projected onto a reflector. A receiver detects a return beam of modulated light reflected by the object and outputs a signal reflecting a phase difference between the laser light and the modulation signal. The frequency of the modulation signal is changed based on the signal value so as to finally achieve phase lock. When the phase lock fixes the frequency of the modulation signal, the frequency always corresponds to a distance from LD to the reflector or a group index of a substance filling the optical path. Thus, the distance to the object or the group index of the substance filling the optical path at the time of phase lock can be determined in a simple manner and with a high accuracy, based on the output frequency at the time of phase lock.

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patent: 4715706 (1987-12-01), Wang
patent: 5097476 (1992-03-01), Thiessen
patent: 5115294 (1992-05-01), Sudbo et al.
"Rangefinders", Research Disclosure, No. 252, Apr. 1, 1985, Emsworth, Hampshire, Great Britain, pp. 187-189.
Baustert et al, "Electromagnetic Interference at Electrooptical Interfaces", Ire Wescon Convention Record, No. 32, Nov. 1, 1988, North Hollywood, US, pp. 1-7 XP99212.
Sugeta, et al: "Metal-Semiconductor-Metal Photodetector for Hihg-Speed Optoelectronic Circuits", Japanese Journal of Applied Physics, vol. 19 (1980), supplement 19-1, pp. 469-464.
Ito et al: "Low Dark Current GaAs Metal-Semiconductor-Metal (MSM) Photodiodes Using WSi.sub.x Contacts", IEEE Journal of Quantum Electronics, vol. QE-22, No. 7, Jul. 1986, pp. 1073-1077.

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