Coherent backscatter: measurement of the retroreflective BRDF peak exhibited by several surfaces relevant to ladar applications

Thomas J. Papetti; William E. Walker; Charles E. Keffer; Billy E. Johnson

doi:10.1117/12.731428

13 September 2007 Coherent backscatter: measurement of the retroreflective BRDF peak exhibited by several surfaces relevant to ladar applications

Thomas J. Papetti, William E. Walker, Charles E. Keffer, Billy E. Johnson

Author Affiliations +

Proceedings Volume 6682, Polarization Science and Remote Sensing III; 66820E (2007) https://doi.org/10.1117/12.731428
Event: Optical Engineering + Applications, 2007, San Diego, California, United States

Abstract

The sharp retroreflective peak that is commonly exhibited in the bidirectional reflectivity distribution function of diffuse surfaces was investigated for several materials relevant to ladar applications. The accurate prediction of target cross-sections requires target surface BRDF measurements in the vicinity of this peak. Measurements were made using the beamsplitter-based scatterometer at the U.S. Army's Advanced Measurements Optical Range (AMOR) at Redstone Arsenal, Alabama. Co-polarized and cross-polarized BRDF values at 532 nm and 1064 nm were obtained as the bistatic angle was varied for several degrees about, and including, the monostatic point with a resolution of better than 2 mrad. Measurements covered a wide range of incidence angles. Materials measured included polyurethane coated nylons (PCNs), Spectralon, a silica phenolic, and various paints. For the co-polarized case, a retroreflective peak was found to be nearly ubiquitous for high albedo materials, with relative heights as great as 1.7 times the region surrounding the peak and half-widths between 0.11° and 1.3°. The shape of the observed peaks very closely matched coherent backscattering theory, though the phenomena observed could not be positively attributed to coherent backscattering or shadow hiding alone. Several data features were noted that may be of relevance to modelers of these phenomena, including the fact that the widths of the peaks were approximately the same for 532 nm as for 1064 nm and an observation that at large incidence angles, the width of the peak usually broadened in the in-plane bistatic direction.

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Thomas J. Papetti, William E. Walker, Charles E. Keffer, and Billy E. Johnson "Coherent backscatter: measurement of the retroreflective BRDF peak exhibited by several surfaces relevant to ladar applications", Proc. SPIE 6682, Polarization Science and Remote Sensing III, 66820E (13 September 2007); https://doi.org/10.1117/12.731428

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