TITLE:
Establishment of a Robot-Based Bidirectional Reflectance Distribution Function Measurement System and Realization of Measurements at a Normal Incident Angle
AUTHORS:
Bazkir Ozcan, Meric Seval
KEYWORDS:
BRDF, Robot-Based Goniometer, Diffuse Reflectance
JOURNAL NAME:
Optics and Photonics Journal,
Vol.15 No.3,
March
28,
2025
ABSTRACT: In this work, the establishment of a bidirectional reflectance distribution function (BRDF) measurement system, which was developed in TUBITAK UME Optical Laboratory, and the measurements performed by this system are described. This system basically consists of two main components: a spectrometer and a robot-based goniometer. The internal structure of the spectrometer, which is used to provide light for the BRDF measurements, was modified such that the light intensity, uniformity, and stability were improved. The robot-based goniometer system, which consists of a robot arm, a rotation ring, a detector, and a control unit, is a new system designed and developed to perform BRDF measurements in TUBITAK UME Optical Laboratory. The robot arm can provide all necessary angles for absolute measurements with its 6-axis movement capability. The rotation repeatability of this robot was calculated as less than 0.01 degrees. The detector rotation ring has a diameter of 690 mm, and it also has the rotation ability between −85˚ and +85˚ around the robot arm. The 690 mm diameter was determined such that both to obtain uniform light on the sample surface and to ensure that the light beam reflected from the sample remained within the detection limit of the detector. The detector unit is an integrating sphere with two color detectors, covering the 250 nm to 2500 nm wavelength range. After this system was established and all optical characterizations were done, the BRDF measurements were carried out at normal incidence angle and at 500 nm wavelength, with accuracy varying from 0.2% to 0.6% depending on the detection angle of the detector.