Range determination with waveform recording laser systems using a Wiener Filter

Current pulsed laser scanning systems determine the range to an objectsurface by a time-of-flight measurement. Critical measurement situationsoccur in discriminating the ranges of surfaces close to their edgesor of small objects within the beam footprint which are closely locatedin range. Capturing the complete waveform of the laser pulse allowsdiscriminating differences in a range smaller than the length ofthe laser pulse. The capabilities of this technique can be predictedby modeling the emitted pulse, the surface, and the backscatteredpulse. Due to the varying waveforms of the emitted pulses each individualemitted pulse is recorded and considered for the determination ofthe surface features. A deconvolution is used to remove the characteristicof the transmitted waveform from the received waveform to obtaina surface response. A Wiener Filter reduces the noise of the determinedsurface response. For extraction of temporal position, length, andamplitude the corresponding surface features are approximated byGaussians using the Levenberg–Marquardt Method. Experiments haveshown that a stepped surface within the beam with a step smallerthan ten times of the pulse length can be distinguished.     «

Current pulsed laser scanning systems determine the range to an objectsurface by a time-of-flight measurement. Critical measurement situationsoccur in discriminating the ranges of surfaces close to their edgesor of small objects within the beam footprint which are closely locatedin range. Capturing the complete waveform of the laser pulse allowsdiscriminating differences in a range smaller than the length ofthe laser pulse. The capabilities of this technique can be predictedby modeling the emitt...     »