Bidirectional reflectance measurements over a micrometric surface area using a goniospectrophotometer.

Area of Science:

• Optics and Photonics
• Metrology
• Materials Science

Background:

• Spatially varying bidirectional reflectance distribution function (svBRDF) is increasingly used for object appearance.
• Measuring BRDF at smaller scales is crucial for understanding material properties.
• Existing metrology scales for BRDF do not extend to micrometer levels.

Purpose of the Study:

• To introduce a novel goniospectrophotometer for micrometer-scale BRDF measurements (μBRDF).
• To extend the BRDF metrological scale from centimeters down to micrometers.
• To validate the credibility of the developed μBRDF measurement technique.

Main Methods:

• Development of a goniospectrophotometer capable of μBRDF measurements with a 31 µm diameter.
• Utilizing a custom test sample with uniform diffuse white dots on a black background.
• Measuring bidirectional reflectance at numerous spatial locations in a fixed geometrical configuration.

Main Results:

• Successful demonstration of μBRDF measurements with a small measurement surface diameter.
• Validation of measurement credibility through comparison with a simplified physical model.
• Agreement between experimental μBRDF data and model predictions.

Conclusions:

• The new goniospectrophotometer effectively measures BRDF at the micrometer scale.
• The μBRDF measurement technique is credible and extends BRDF metrology to micro-scales.
• This advancement supports detailed analysis of object appearance at fine resolutions.