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Spectral tri-function automated reference reflectometer (STARR)

STARR performs directional-hemispherical, specular, and bidirectional reflectance measurements of spectrally neutral, non-fluorescent samples at room temperature. It uses a lamp-based, quasi-monochromatic system for illumination of the sample and broadband detection for the reflected radiation. Directional-hemispherical measurements are acquired using an integrating sphere and require comparison to a calibrated standard, pressed polytetrafluoroethylene (PTFE). All specular and bidirectional measurements are collected in-plane, meaning the sample normal, illumination axis, and receiver axis are in the same plane.

STARR currently serves as the national reference instrument for directional-hemispherical reflectance measurements. The Robotic Optical Scattering Instrument (ROSI) is the national reference instrument for specular and bidirectional reflectance measurements. We are currently developing the capability to provide directional-hemispherical reflectance using ROSI.

Specifications/Capabilities

Conditions for directional/hemispherical reflectance measurements using STARR

Geometrical

Illumination Angle

6° (specular included)
0° (specular excluded)

Viewing Angle

Hemisphere

Sample size

Minimum 25 mm

Sampling Aperture

17 mm

Spectral

Wavelength

250 nm to 2500 nm

Bandwidth

14 nm

Polarization

Slight

Measurand

Quantity

Reflectance Factor

Technique

Relative to PTFE

Range

0.001 to 1

Relative uncertainty (k=2)*

0.4%

*The listed relative uncertainty is the minimum expected value. Actual values vary due to sample-dependent factors.

Created October 21, 2009, Updated March 5, 2021