Three-dimensional tomographic imaging camera
First Claim
1. An apparatus for detecting the range of one or more targets comprising:
- a swept frequency laser source for generating an output launched laser beam whose frequency varies as a function of time over a predetermined optical bandwidth;
an interferometer for receiving said launched laser beam and dividing said laser beam into a target beam and a reference beam, said interferometer including a first, target arm for directing said target beam to a target whose range is to be determined, receiving a reflected target beam from said target;
a second, reference arm for transmitting said reference beam; and
a combiner for combining said reference beam in said reference arm with said reflected target beam in said target arm and forming a combined output beam;
means for modulating at least one of said target beam and said reference beam to reduce the relative difference between a frequency of the reflected target beam and a frequency of the reference beam; and
an optical detector for receiving said combined output beam and generating an output signal from said photodetector that indicates the range of said target based on the reduced difference in frequencies between said reflected target beam and said reference beam.
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Accused Products
Abstract
A detection apparatus and method for FMCW LIDAR employ signals whose frequencies are modified so that low-cost and low-speed photodetector arrays can be employed for range detection. The LIDAR includes a single mode swept frequency laser (SFL), whose optical frequency is varied with time, as a result of which, a target beam reflected back by the target is shifted in frequency from a reference beam by an amount that is proportional to the relative range z to the target. The reflected target beam is combined with the reference beam and detected by the photodetector array. The difference between the frequencies of the reflected target beam and the reference beam is reduced to a level that is within the bandwidth of the photodetector array by first modulating the target and/or reference beam.
28 Citations
22 Claims
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1. An apparatus for detecting the range of one or more targets comprising:
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a swept frequency laser source for generating an output launched laser beam whose frequency varies as a function of time over a predetermined optical bandwidth; an interferometer for receiving said launched laser beam and dividing said laser beam into a target beam and a reference beam, said interferometer including a first, target arm for directing said target beam to a target whose range is to be determined, receiving a reflected target beam from said target;
a second, reference arm for transmitting said reference beam; and
a combiner for combining said reference beam in said reference arm with said reflected target beam in said target arm and forming a combined output beam;means for modulating at least one of said target beam and said reference beam to reduce the relative difference between a frequency of the reflected target beam and a frequency of the reference beam; and an optical detector for receiving said combined output beam and generating an output signal from said photodetector that indicates the range of said target based on the reduced difference in frequencies between said reflected target beam and said reference beam. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A method for detecting the range of one or more targets comprising the steps of:
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generating an output launched laser beam whose frequency varies as a function of time over a predetermined optical bandwidth; dividing said launched laser beam into a first, target beam and a second, reference beam; changing the optical frequency of at least one of said target and reference beams to reduce the relative difference between that target beam frequency and the reference beam frequency after that target beam has been transmitted to and received back from a target; directing said target beam to a target whose range is to be determined; receiving said target beam after being reflected by said target; combining said reference beam with said reflected target beam to form a combined output beam; optically detecting said combined output beam with a photodetector; and generating an output signal from said photodetector that indicates the range of said target based on the reduced difference in frequencies between said reflected target beam and said reference beam. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20, 21, 22)
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Specification