Measurement of 0/45 reflectance factor using nonlinearity corrected array spectroradiometer.

Area of Science:

• Optical Engineering
• Metrology
• Spectroradiometry

Background:

• Reflectance factor measurement spans wide dynamic ranges, necessitating highly linear systems for accuracy.
• Existing methods face challenges with nonlinearity and spectral stray light, impacting measurement uncertainty.

Purpose of the Study:

• To describe an optical configuration for reflectance factor measurement.
• To enable linearity measurement within the same setup.
• To minimize measurement uncertainty in reflectance factor determination.

Main Methods:

• Developed a linearity calibration facility integrating a blackbody source, aperture, and white diffuser.
• Ensured spectral radiance and distribution match reflectance factor measurements from an integrating sphere.
• Modified an optical configuration for both reflectance factor and linearity assessment.

Main Results:

• The calibration facility achieves spectral radiance ranges identical to integrating sphere light sources.
• The setup significantly reduces nonlinearity and spectral stray light impacts.
• Achieved 0/45 reflectance factor measurement uncertainty of 1.20%-0.54% (k=2) for white diffuse targets from 380-780 nm.

Conclusions:

• The described optical configuration provides a convenient and accurate method for reflectance factor measurement using array spectroradiometers.
• The integrated linearity calibration minimizes uncertainty, enhancing the reliability of spectral measurements.
• This approach offers improved accuracy for diffuse reflectance measurements across the visible spectrum.