Detailed experimental characterization of reflectance spectra ofSasakia charondabutterfly using multispectral optical imaging

Abstract

A multispectral acquisition system to examine the bidirectional reflectance distribution function of structurally colored biological materials in the visible range is presented. We focus on the purple-blue and white-pearl wing scales of the male butterfly Sasakia charonda. Multispectral imaging was done by changing the illumination angular position around the sample as well as that of the specimen around the multispectral sensor axis. Reflectance spectra were transformed to color coordinates and visualized in different color spaces. Spectral analysis shows distinct iridescent patterns in purple-blue and white-pearl scales. Colorimetric analysis indicates that purple-blue scales enhance blue coloring and exhibit higher color saturation. Principal component analysis reveals that the number of principal components that account for more than 99% of reflectance vari- ability was higher in white-pearl scales. This suggests a higher spectral complexity in their spatial color pattern formation. Reconstruction of reflectance spectra from the principal components is discussed. We conclude that multispectral imaging provides new insights into spatial reflectance mapping that result from the combination of structural colorations and variable amounts of absorption pigments. © 2014 Society of Photo-Optical Instrumentation Engineers