Measurement of surface bidirectional reflectance distribution based on parabolic mirror

A novel approach and system based on parabolic mirror is proposed for measuring a surface's bidirectional reflectance distribution function (BRDF) rapidly and accurately. In virtue of a truncated paraboloid with reflecting film on the interior surface, the angular distribution of surface optical reflectance in tri-dimensional space is transformed into a two-dimensional planar image, which is collected by a CCD camera and goes though a followed angular mapping and data processing correspondingly, a fast measurement of in plane and out of plane reflectance distribution is realized within a few minutes. Furthermore, the laser beam is reflected by parabolic mirror to irradiate the sample surface in various incidence angles. Primary measurements and analysis of surface reflectance of varied substance along with various machining process are carried out with this system. Results indicates that this novel measurement system, compare with conventional ones, can avoid the measuring errors generated by the fluctuation of laser's power and the sensitivity of the detector, as well as dramatically shorten the acquisition time. In addition, a compact and portable configuration eases the measurement procedure consumedly.