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Robotic Optical Scattering Instrument (ROSI)


ROSI (Robotic Optical Scattering Instrument)

ROSI performs specular and bidirectional reflectance measurements of spectrally neutral, non-fluorescent specular and diffuse samples at room temperature. It serves as the national reference instrument for specular and bidirectional reflectance measurements. The national reference instrument for directional-hemispherical reflectance measurements is the Reference Integrating Sphere for Spectral Reflectance.

ROSI uses a quasi-monochromatic system for illumination of the sample and broadband detection for the reflected radiation. Sample angles and positioning are controlled by a robotic-arm-based goniometer. Specular and bidirectional calibrations are collected in-plane, meaning the sample normal, illumination axis, and receiver axis are in the same plane. ROSI can also perform out-of-plane bidirectional reflectance measurements for research and special tests.


'ROSI' the Robot
'ROSI' the Robot
Lots of companies care about how lighting affects the color and "look" of their product, whether it's a car, a magazine ad, a pantsuit, or a paint sample. NIST's Robotic Optical Scattering Instrument -- called “ROSI” for short -- is a new system that industry customers can use to measure precisely how light reflects and scatters off of materials to produce these different colors and appearances. To use ROSI, scientists first mount a sample to the end of the robotic arm. ROSI's articulated wrist, shoulder, and elbow allow the machine to move the sample in almost any direction with respect to a beam of light. Meanwhile, a receiver can be positioned to collect the light reflecting off of the material from different angles. Credit: Jennifer Lauren Lee/NIST


Conditions for specular and bidirectional reflectance measurements using ROSI


Illumination Angle

0° to 80°

Viewing Angle

0° to 80°

Sample size

25 mm to 300 mm

Illumination beam size

10 mm



250 nm to 2400 nm


14 nm


0° to 90° linear





     Bidirectional Diffuse

Reflectance Factor, BRDF



Nominal Uncertainty (k=2)


0.2 %

     Bidirectional Diffuse

0.65 %

Created May 9, 2018, Updated February 7, 2023