Active Multispectral Band Selection and Reflectance Measurement System

摘要

Due to system design requirements, an active multispectral laser radar system may be limited in the number of spectral bands that can be integrated into the system. To aid in the selection of these bands, a novel multispectral band selection technique is presented based on the cross-correlation of the material class reflectance spectra over a wavelength range of 1-5 microns. The algorithm uses directional hemispherical reflectance data from the Nonconventional Exploitation Factors database to select a number of spectral bands for classification purposes. Because the target material spectral reflectance is so important to the performance of an active multispectral system, an experimental monostatic bidirectional reflectance distribution function (BRDF) measurement system is developed and tested. A 1.06 micron Nd:YAG diode pumped laser is frequency shifted to 1.58-1.80 microns using a periodically poled lithium niobate nonlinear crystal. This laser provides the continuously tunable source necessary to measure the material BRDF at closely spaced wavelength intervals. A complete error analysis of the system is presented with measurement results from a number of military vehicle paint samples. An extended design is presented which is capable of operating at any wavelength in the 1 - 5 micron range. This design also reduces or removes the error sources observed in the initial experiment.