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

Adrian Zakrzewski,Jacek Reiner,Piotr Jurewicz,Piotr Koruba,Michał Ćwikła

doi:10.3390/s21010008

Abstract

Imaging scatterometry is a method for determining the reflection distribution based on bidirectional reflectance distribution function (BRDF) measurements. However, it has a well-known limitation that results obtained by imaging scatterometry for small illumination angles are practically useless. Therefore, we propose an approach for reconstruction of the reflection distribution based on a series of measurements at different illumination angles and extrapolation of the missing results to overcome this limitation. The developed algorithm was validated using bidirectional transmittance distribution function (BTDF) measurements. The BRDF measurements were carried out for materials that are commonly used in laser material processing, i.e. substrates and functional coatings. The obtained data were subsequently used to determine the total reflection intensity from all considered materials, which were characterized by reconstructed distributions.

Highlights

The result result of of reconstruction reconstruction confirms confirms that that the silver mirror is characterized by a narrow reflection distribution and high the silver mirror is characterized by a narrow reflection distribution and high specular specular
The result result of of reconstruction reconstruction confirms confirms 7that that of 9 the silver mirror is characterized by a narrow reflection distribution and high the silver mirror is characterized by a narrow reflection distribution and high specular specular reflection
The purpose of the presented study was to determine the total reflection intensity from different materials commonly used in laser material processing

Summary

Introduction

Analysis of materials surfaces becomes crucial because of increasing quality requirements and repeatability control of components production, especially in the case of structured materials [1,2] or performance quality of typical optical components [3,4]. The surface quality is related to roughness and to local defects and every type of bulk inhomogeneity. These aspects are directly associated with the kind of light scattering on the material’s surface. In case of smooth surfaces, analysis based on specular reflection is sufficient in order to assess the surface quality. In the case of most studies on surface quality, analysis of diffuse reflection is required. The reflection distribution provides comprehensive information about the directivity and intensity of the light reflected from the sample

Methods

Results

Discussion

Conclusion