Spatial and Temporal Coding of GaAs Lasers for a Laser Line Scan Sensor.

摘要

Line of scanning laser sensors which measures range and reflectance are currently being developed to be used as the front end of real-time image processors. This paper establishes the coding combination of intensity modulation and scan pattern for N GaAs laser sources which results in the optimum system performance. A noise model based upon the Poisson point process behavior of a direct (optical intensity) detector is developed. Estimation theory, based upon the Poisson statistics of the detector, is used to develop the maximum-likelihood (ML) processor for both range and reflectance. The realization of the ML estimator for range is shown to be a correlator or matched filter; a suboptimum realization of the reflectance estimator is shown to be a measurement of the detected signal energy, given the range estimate. Performance expressions are presented to relate the variance of the range and the reflectance to the line scan system parameters and the variance of both is shown to be inversely proportional to the detected signal energy. Various combinations of spatial and temporal coding of the N laser sources to separate the return signal energy from each ground resolution cell while increasing the returned energy per cell, are evaluated. Based upon the variance of the range and reflectance estimates, the optimum spatial-temporal coding combinations is chosen. It is shown that if a large maximum unambiguous range is not required, the best performance possible is achieved with N sources scanned in parallel, each source being sinusoidally modulated.