RESUMO
The BRDF values of several samples of Martin Black have been measured at 10.6 microm and several angles of incidence. The values are in good agreement with data taken recently on an identical sample with a different instrument and with data from an identical sample taken several years ago with a similar instrument.
RESUMO
The BRDF values of a special, striated gold sample at 10.6 and 118 microm were measured. For 118-microm radiation the values decrease from beta - beta(0) = 0.1 to 1 for both orientations, but the vertical orientation of stria always produces a higher value. At 10.6 microm the horizontal orientation produces BRDF values that start at approximately 10(-2) at 0.1 and decrease to approximately 5 x 10(-4) at 1. The vertical orientation generates curves that are considerably higher.
RESUMO
The bidirectional transmittance distribution function (BTDF) is used to evaluate the scattering properties of chemically vapor-deposited (CVD) zinc selenide (ZnSe). Conceptually, the BTDF is a logical extension of the bidirectional reflectance distribution function (BRDF) relation. A working equation for BTDF based on the practical limitations of the instrumentation has been developed. The practical limitations inherent in making BTDF measurements are the finite detector size, the two scattering surfaces of the sample, and the linear radiometric responses of the detector. The instrumentation used to measure BTDF and the data collection procedure are described. Plots of BTDF vs angle from the sample normal are presented for CVD ZnSe at room temperature. The plots are for three thicknesses of ZnSe (6, 19, and 25 mm) at three laser wavelengths (0.6328, 3.39 and 10.6 microm).
