Tunable 1.3- to 5-um wavelength target reflectance measurement system

We describe a tunable, 1.3 to 5 micrometers wavelength reflectance measurement system using an optical parametric oscillator (OPO) as the light source. The OPO source consists of a 1 micrometers Nd:YAG laser which is frequently shifted to 1.3-5 micrometers wavelengths using a periodically poled lithium niobate nonlinear optical crystal. The system design, calibration, and measurement of the directional-hemispherical reflectance factor and the bi-directional reflectance distribution function of different target materials are presented.