New robot-based gonioreflectometer for measuring spectral diffuse reflection

Abstract

At the Physikalisch-Technische Bundesanstalt a new robot-based gonioreflectometer for measuring radiance factor and bidirectional reflectance-distribution function has been developed. The facility enables measurements of the directed reflection characteristics of materials with arbitrary angles of irradiation and detection relative to the surface normal.

Providing radiometric traceability for the calibration home base of DLR by PTB

“…This set-up ensures that the optical axis of each instrument intersects the panel center at an angle of 45°, thus minimizing errors caused by spatial or angular inhomogeneities. Five of the adapter fittings are used for radiometers (5,6) which monitor redundantly the stability of the system. The two remaining fittings on bottom left and right (7) are used for the instruments which shall be calibrated.…”

“…The robot-based gonioreflectometer facility of PTB uses broadband irradiation of the sample with spectrally selected detection of the reflected radiation [6][7][8]. The unfiltered broadband irradiation is generated by a special sphere radiator [9].…”

“…The relative standard measurement uncertainty (k = 1) for calibrations of the radiance factor β of highly reflecting samples (β ≈ 1) ranges from 0.1 % in the visible and adjacent spectrum to 0.25 % in the IR at 1700 nm and to 0.6 % in the UV at 350 nm [6].…”

Reflectance Modeling in Machine Vision: Applications in Image Analysis and Synthesis

“…To capture the reflection for more than one angle pair at a time, curved mirrors are widely used, like in the works of Ward (1992), Dana (2001), Ghosh et al (2007), Mukaigawa et al (2007). To add more mechanical degrees of freedom in the positioning of the material probe, robot arms have been used, e.g., Dana et al (1999), Sattler et al (2003), Hünerhoff et al (2006). Debevec et al (2000) constructed a light stage with multiple light sources and cameras at fixed positions to acquire the reflectance field of a human face.…”

Robot-based Gonioreflectometer

“…1) for measuring radiance factor and BRDF has been set-up (Hünerhoff et al, 2006). The facility enables measurements of the directed reflection characteristics of materials with arbitrary angles of irradiation and detection relative to the surface normal.…”