Measuring BRDF for curved surfaces based on parabolic reflection

Abstract

In this study, we introduce a measurement method for the bidirectional reflectance distribution function (BRDF) for curved surfaces. Nearly all BRDF measurements assume that the target surface is planar. This is because if the object is non-planar, the reflection angle changes from position to position, making accurate measurement impossible. However, most real objects are curved. We have overcome this problem by applying the paraboloid reflection principle. If the curved target surface is a paraboloid, the light focused on its focal point is reflected as parallel light, as in a parabolic antenna. The BRDF can be measured as the deviation angle from this parallel light direction. Here, we demonstrate that this can significantly improve the BRDF measurement accuracy for curved surfaces.