Imaging Scatterometry with Extrapolation of Missing BRDF Data for Materials Used in Laser Material Processing

Area of Science:

• Optical Engineering
• Materials Science

Background:

• Imaging scatterometry measures reflection distribution via bidirectional reflectance distribution function (BRDF).
• Existing methods are limited by useless results at small illumination angles.

Purpose of the Study:

• To develop an approach for reconstructing reflection distribution by overcoming imaging scatterometry's limitations.
• To enhance the analysis of materials used in laser material processing.

Main Methods:

• A novel algorithm combines measurements at various illumination angles with extrapolation.
• Validation performed using bidirectional transmittance distribution function (BTDF) measurements.
• Bidirectional reflectance distribution function (BRDF) measurements conducted on common laser material processing substrates and coatings.

Main Results:

• Successfully reconstructed reflection distributions for various materials.
• Determined total reflection intensity by characterizing materials with reconstructed distributions.
• Validated the reconstruction approach using BTDF measurements.

Conclusions:

• The proposed method effectively reconstructs reflection distributions, overcoming limitations of traditional imaging scatterometry.
• This technique provides a more comprehensive understanding of material reflection properties.
• Applicable to materials commonly used in laser material processing.