EFFECTS OF A BUTTERFLY SCALE MICROSTRUCTURE ON THE IRIDESCENT COLOR OBSERVED AT DIFFERENT ANGLES

Multilayer thin-film structures in butterfly wing scales produce a col orful iridescence from reflected sunlight. Because of optical phenomen a, changes in the angle of incidence of light and the viewing angle of an observer result in shifts in the color of butterfly wings. Colors ranging from green to purple, which are due to nonplanar specular refl ection, can be observed on Papilio blumei iridescent scales. This refe rs to a phenomenon in which the curved surface patterns in the thin-fi lm structure cause the specular component of the reflected light to be directed at various angles while affecting the spectral reflectivity at the same time by changing the optical path length through the struc ture. We determined the spectral reflectivities of P. blumei iridescen t scales numerically by using models of a butterfly scale microstructu re and experimentally by using a microscale-reflectance spectrometer. The numerical models accurately predict the shifts in spectral reflect ivity observed experimentally. (C) 1998 Optical Society of America.