Analysis of Gloss Unevenness and Bidirectional Reflectance Distribution Function in Specular Reflection

Area of Science:

• Material Science
• Optics
• Surface Metrology

Background:

• Gloss unevenness significantly impacts material appearance and observer perception.
• Analyzing gloss unevenness is challenging due to its location within highlight areas and angular dependency.
• Recent advancements analyze gloss using specular reflection intensity and angular spread, or Bidirectional Reflectance Distribution Function (BRDF).

Purpose of the Study:

• To develop an apparatus for precise measurement of gloss unevenness.
• To analyze gloss unevenness and BRDF with high angular resolution.
• To establish a physical definition for gloss unevenness based on BRDF.

Main Methods:

• Developed a novel apparatus to measure gloss unevenness with 0.02° angular resolution.
• Analyzed gloss unevenness and BRDF by measuring specular reflection.
• Tested high-gloss (mirrors, plastics) and glossy (inkjet paper, coated paper) materials.

Main Results:

• Quantified gloss unevenness and BRDF using high angular resolution measurements.
• Observed that the magnitude of gloss unevenness is maximal at angles slightly deviating from the specular reflection center.
• Demonstrated the relationship between gloss unevenness and BRDF characteristics.

Conclusions:

• The developed apparatus enables detailed analysis of gloss unevenness.
• Gloss unevenness exhibits a distinct pattern relative to the specular reflection angle.
• Findings support a physically grounded definition of gloss unevenness derived from BRDF analysis.