title: Structured surface bidirectional reflectance distribution function reciprocity: theory and counterexamples.
abstract: I address the question of whether the bidirectional reflectance distribution function (BRDF) of a structured surface has the same value when the incident and reflected angles are reversed. In particular, I examine the validity of some recent counterexamples and contrary measurements. On the basis of a new definition for structured surfaces, I conclude that the BRDF should be reciprocal. I show that designed counterexamples are flawed and suggest that measurements that do not exhibit reciprocity can be attributed to uncertainty and uncontrolled factors.
authors.affiliation: Alphatech, Incorporated, Burlington, Massachusetts 01803, USA. wcsnyder@ieee.org
authors.forename: William C
authors.initials: WC
authors.lastname: Snyder