Measurement and modeling of bidirectional reflectance distribution function (BRDF) on cutting surface based on the coaxial optical microscopic imaging

In this study, a new bidirectional reflectance distribution function (BRDF) measurement and modeling method are proposed for cutting surfaces to address problems in the use of the current measuring method and model to obtain BRDF: the range of measuring angle is limited, and more optical reflection information cannot be accurately described. The measuring method and principle of the BRDF are presented under the condition of coaxial optical microscopic imaging. The BRDF measuring platform comprised confocal laser scanning microscope, and BRDF measurements of different cutting sample surfaces were measured. The measured result demonstrates that the trend of variation in BRDF is related to the roughness and microtopography of the sample's surface. The parameters of the BRIM model are based on the sample surface reflection characteristics. Based on the genetic algorithm, the model parameters of BRDF were obtained through fitting processing of measured data, and the maximum fitting error was 9.97%. The result demonstrates that the BRDF model is feasible and can accurately describe the reflection characteristics of the cutting surface. The study will lay a foundation for the three-dimensional reconstruction of the cutting surface under the condition of microscopic imaging. (C) 2018 Published by Elsevier GmbH