Optics: measuring and testing – Range or remote distance finding – With photodetection
Reexamination Certificate
2001-03-06
2003-05-27
Tarcza, Thomas H. (Department: 3662)
Optics: measuring and testing
Range or remote distance finding
With photodetection
C356S005110, C356S028000
Reexamination Certificate
active
06570646
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to method and apparatus for obtaining measurements and, more particularly, to a method and apparatus of measuring with increased accuracy.
BACKGROUND OF THE INVENTION
Distance measurement devices usually measure short distances with good accuracy or long distances with poor accuracy. Currently devices that can measure with good accuracy or long range are expensive and complicated. The short range measurement devices (i.e., microns to meters range) are usually mechanical or optical. The mechanical devices measure the distances directly and the optical devices measure optical fringes to count the distance to the measurement plane. Long distances are measured most commonly by time of flight and result in centimeter scale resolution.
SUMMARY OF THE INVENTION
Aspects of the present invention include a device comprising: a light source capable of transmitting an outgoing light beam toward a target; a frequency source coupled to the light source and capable of modulating the outgoing light beam; a first beam splitter configured to divide the outgoing light beam; a second beam splitter configured to combine a return ranging light beam from the target and a reference light beam from the first beam splitter; a first detector optically coupled to the second beam splitter and configured to produce a voltage signal; and a second detector coupled to the first detector and configured to determine target distance information from the voltage signal.
Further aspects of the invention include a method comprising: transmitting an outgoing light beam toward a target; modulating the light beam with a first frequency; splitting the outgoing light beam; combining a first return ranging light beam with a first reference light beam; detecting the first return ranging light beam and the first reference light beam and producing a first voltage signal representing distance dependent phase information; and detecting the first voltage signal and determining target distance information from the first voltage signal.
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Rogowski, et al., “An amplitude modulated laser system for distance and displacement measurement,” SPIE vol. 663, Laser Radar Technology and Applications (1986), pp. 86-89.
Andrea Brian K
Tak James S.
Tarcza Thomas H.
The Regents of the University of California
Thompson Alan H.
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