A new instrument to measure the <i>in situ</i> bidirectional reflectance distribution function (BRDF) of surfaces is described. This instrument measures the BRDF for eight illumination angles from 0 to 65 deg, three colors (475, 570, and 658 nm), and at over 100 selected viewing angles. The viewing zenith angles range from 5 to 65 deg, and the azimuth angles, relative to the illumination direction, range from 0 to ∓180 deg. Many tests of the system have been run and show that for flat surfaces the BRDF of a sample surface can be measured with a precision of 1–5% and an accuracy of 10% of the measured reflectance. The BRDF for a dry and wet sand sample is presented as a demonstration of the instrument.
© 2000 Optical Society of America
(010.4450) Atmospheric and oceanic optics : Oceanic optics
(120.4640) Instrumentation, measurement, and metrology : Optical instruments
(120.5700) Instrumentation, measurement, and metrology : Reflection
(240.6700) Optics at surfaces : Surfaces
Kenneth J. Voss, Albert Chapin, Marco Monti, and Hao Zhang, "Instrument to Measure the Bidirectional Reflectance Distribution Function of Surfaces," Appl. Opt. 39, 6197-6206 (2000)