“Lightdrum – Surface Reflectance Measurement on Site” by Havran, Hošek, Němcová, Čáp and Bittner

  • ©Vlastimil Havran, Jan Hošek, Šárka Němcová, Jiří Čáp, and Jiří Bittner



Entry Number: 80


    Lightdrum – Surface Reflectance Measurement on Site



    We present a portable instrument for on site measuring of surface reflectance represented by the bidirectional texture function (BTF) and the bidirectional reflectance distribution function (BRDF). Our device allows for measurement application scenarios outside the laboratory without the necessity to extract the measured sample from its environment because the instrument is taken to the measured sample. The concept is a rotational lightweight light stage with a compact hemispherical dome and cameras along the meridian and light emitting diode (LED) modules illuminating the sample surface. The LED modules are fixed on the hemisphere and the six cameras can move along the arc in the range of the elevation angle from 0 to 75 degrees. By rotating the hemispherical dome along its axis we can set all possible camera directions to a measured sample. We use an auto-collimator to adjust the correct perpendicular direction of the instrument against the sample. The proposed instrument is portable and fast while maintaining a high degree of accuracy achieving a quality similar to existing stationary BTF gantries that can be only used in a laboratory. The instrument design provides a good tradeoff between the accuracy of measurements and the practical applicability for measurement of locally flat samples. The instrument provides approximately 1000 HDR photographs in a minute that are necessary to capture spatially varying surface reflectance.



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