Imaging System Free of Dyes and Pigments - Study of the Structural Color of Organisms -

Abstract

Structural color is of significant research interest as it may yield novel coloring systems that use neither dyes nor pigments. The origin of their coloring principle is their extremely minute physical structures, the sizes of which are comparable to the wavelengths of light. Structural color is observed in many organisms such as insects, shells, and birds, and models of their coloring mechanisms have been proposed. This study aims to confirm the mechanisms of the structural color of different organisms. Coloring mechanisms of a Jewel beetle, a Morpho butterfly, a Turban shell, and a Peacock, for which models have been suggested, are verified by observing their colors when (1) the colored surfaces are immersed in two liquids with of different refractive indices, and (2) through a polarizing filter. The results invalidate one of the conventional explanations for the jewel beetle: a grating structure on a Jewel beetle was not agreed by our experimental results. For the Morpho butterfly, the results suggest a better explanation, a grating structure, than the conventional one: multilayer reflection. This decision is supported by the results of a spectrum analysis. Our approach to the examination of structural color mechanisms can be expected to suggest new imaging systems that are completely different from the systems in current use.