Fiber optic coherent laser radar 3d vision system Page: 3 of 10
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A 3D vision system will provide live 3D monitoring for situations in which it is necessary to update the 3D geometry
of significant portions of the world model on the order of once per second. A 3D programmable mapper can less frequently
provide very high precision maps or can track single objects such as robot end effectors.
A 3D vision system will monitor the 3D position of all pixels of a scene simultaneously, keeping precise track of the
entire scene. Thus, whole scene, real-time, digitized data will be available to support autonomous vehicle operations and
operations in which robotic systems are altering the geometry of a scene as in waste removal, surface scarafacing or
equipment disassembly and removal.
Fiber-optic coherent laser radar (CLR) based systems such as the CLVS are immune to variations in lighting, color,
or surface shading, which have plagued the reliability of existing 3D vision systems, while providing substantially superior
range resolution. The primarily fiber-optic construction of the CLVS will be more resistant to shock and thermal effects
than bulk optic systems, and will be more economical to manufacture and maintain.
- The superior accuracy of the CLVS is a direct result of the orders of magnitude greater signal bandwidth involved
in the coherent range detection process. The coherent detection applied to optical frequency modulation (FM) is also the
source of the CLVS's immunity to amplitude distortions by lighting or surface shading, just as FM radio, unlike AM radio,
suppresses noise from lightning bursts. The fiber-optic implementation of the CLVS allows a more sophisticated optical
circuitry to be employed than would be practical with bulk optics, and with less cost for assembly and alignment during
manufacturing.
The CLVS fieldable prototype will be developed by Coleman Research Corporation (CRC) in a two phase program.
During the first development phase a baseline CLR 3D vision demonstration system will be developed with the
following projected performance:
Frame size: (128 x 128) 3D coordinates
Frame speed: 1 frame per second
Range accuracy: -a. = 1mm
During the second phase, the baseline system will be developed into a fieldable prototype 3D vision system with
expanded performance parameters including the ability to scan a (256 x 256) frame of 3D measurements at a one frame
per second rate. This enhanced performance will be accomplished by the implementation of "smart receiver" processing
algorithms which maximize the use of a priori range information to streamline the real-time CLR range processing
computation. The effort will also yield a compact, no moving parts 3D vision scanner.
The fieldable prototype CLVS will output both range and intensity images on both standard video and digital
interfaces.
2. TECHNICAL APPROACH
2.1 Technology description
The Coherent Laser Vision System (CLVS) is a fiber optic coupled FMCW coherent laser radar which is an advance
over bulk optical versions previously developed by the Digital Signal Division of Coleman Research Corporation (CRC).4
The radar uses the relatively large tuning range of injection laser diodes to achieve greater precision than available with
other techniques. As shown in Figure 2-1, the optical frequency of the laser is swept linearly as a function of time. The
laser output is divided and used both as a local oscillator (L.O.) and as the signal to be transmitted. After being time
delayed by the round trip transit time to the target, the received signal is mixed with the optical L.O. on a photodetector.
The resultant beat frequency is equal to the sweep rate of the optical signal multiplied by the time delay between the
received signal and the local oscillator. Since this time delay is proportional to target distance, the RF beat frequency is
also proportional to target distance.
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Sebastian, R.L.; Clark, R.B. & Simonson, D.L. Fiber optic coherent laser radar 3d vision system, article, December 31, 1994; United States. (https://digital.library.unt.edu/ark:/67531/metadc672470/m1/3/: accessed April 23, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.