Two-frequency distance and displacement measuring interferometer

Details Two-frequency distance and displacement measuring interferometer Two-frequency distance and displacement measuring interferometer

1990-06-05

1992-04-21

Turner, Samuel A.

Optics: measuring and testing

By particle light scattering

With photocell detection

356358, 356363, G01B 902

Patent

active

051061910

ABSTRACT:
Semiconductor-laser length measuring apparatus includes first and second semiconductor lasers that oscillate in different wavelength regions. A frequency modulator modulates the oscillation frequency of the first semiconductor laser and a light beam splitter divides the first and second light beams output from the first and second semiconductor lasers into third, fourth, fifth and sixth light beams which are projected onto and are reflected from an object to be measured. The phase difference between the third and fourth light beams and the phase difference between the fifth and sixth light beams are detected and the difference in optical paths between the divided light beams is obtained according to the detection result. Incremental measurements are performed by obtaining the optical path difference between the divided laser light beams, for example, a difference between a beat signal produced from interference between the third and fourth laser light beams or from interference between the fifth and sixth laser light beams and an oscillation frequency driving the first and second modulators. The apparatus may be arranged to switch to incremental measurement after a measurement of the absolute optical path difference.

REFERENCES:
patent: 4821273 (1989-04-01), Hori
patent: 4886363 (1989-12-01), Jungquist
patent: 4906095 (1990-03-01), Johnston
patent: 4912530 (1990-03-01), Bessho
"Interferonmeter for Measuring Displacement and Distance" by Toshihiro Kubota et al., Optical Letters/vol. 12, No. 5/May, 1987, pp. 310-312.

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