Three-dimensional tomographic imaging camera

摘要

A detection apparatus and method for FMCW LIDAR employ signals whose frequencies are modified so that low-cost and low-speed photodetector arrays, such as CCD or CMOS cameras, can be employed for range detection. The LIDAR is designed to measure the range z to a target and includes a single mode swept frequency laser (SFL), whose optical frequency is varied with time, as a result of which, a target beam which is 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. By first modulating at least one of the target and reference beams such that 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, the need for high-speed detector arrays for full-field imaging is obviated.

主权项

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 one of said launched beam, said combined output beam, said target beam and said reference beam to generate a modulation sideband with a frequency offset equal to the relative difference between a frequency of the reflected target beam and a frequency of the reference beam; wherein said means for modulating comprises an optical modulator selected from the group including an intensity modulator, an optical amplifier, a variable optical attenuator, and a phase modulator; 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 frequency offset of said modulation sideband and the difference in frequencies between said reflected target beam and said reference beam.