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5 September 2000 High-resolution eye-safe time-of-flight laser rangefinding
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In this paper, a digital time of flight laser range finder is presented. This measurement method has been simulated and experimentally evaluated using an eye-safe (class IIIA) laser range finder based on a passively Q-switched microchip laser as emitter and an avalanche photodiode as receiver. This new concept of measurement overcomes instability of classical time of flight laser range finder versus the reflectivity of the target, the atmospheric transmittance and the photoelectric noise. Classical laser range finder uses analog techniques to measure the time elapsed between the start and stop laser pulses: start time and stop time are defined by analog thresholds, therefore accuracy is greatly affected by the SNR in the receiver and associated electronics. This SNR is also dependent on emitter and receiver geometric configuration. Therefore the power seen by the receiver as a function of the distance measurement has been estimated theoretically and observed in experiments in order to optimize SNR over a chosen range. A new technique to overcome this lack of accuracy has been implemented using a fast digitizer with an acquisition rate of 10 GS/s and digital signal processing algorithms. Accuracy of about +/- 5 mm for a single shot without averaging and +/- 0.5 mm for averaging 20 shots have been demonstrated from 10 meters to 250 meters using only one photodetector for the start and stop pulse. Such a system will have an interest in the area of 3D vision laser ranging where there is a need of high accuracy measurements.
© (2000) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Vincent Delaye and Pierre Labeye "High-resolution eye-safe time-of-flight laser rangefinding", Proc. SPIE 4035, Laser Radar Technology and Applications V, (5 September 2000);

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