Vigneron Jean Pol, Simonis Priscilla, Aiello Annette, Bay Annick, Windsor Donald M, Colomer Jean-François, Rassart Marie
Research Center in Physics of Matter and Radiation, University of Namur, Belgium.
Phys Rev E Stat Nonlin Soft Matter Phys. 2010 Aug;82(2 Pt 1):021903. doi: 10.1103/PhysRevE.82.021903. Epub 2010 Aug 4.
The butterfly Pierella luna (Nymphalidae) shows an intriguing rainbow iridescence effect: the forewings of the male, when illuminated along the axis from the body to the wing tip, decompose a white light beam as a diffraction grating would do. Violet light, however, emerges along a grazing angle, near the wing surface, while the other colors, from blue to red, exit respectively at angles progressively closer to the direction perpendicular to the wing plane. This sequence is the reverse of the usual decomposition of light by a grating with a periodicity parallel to the wing surface. It is shown that this effect is produced by a macroscopic deformation of the entire scale, which curls in such a way that it forms a "vertical" grating, perpendicular to the wing surface, and functions in transmission instead of reflection.
月神蝶（蛱蝶科）呈现出一种迷人的彩虹般的虹彩效应：当沿着从身体到翅尖的轴线照亮雄性的前翅时，其前翅会像衍射光栅一样分解白色光束。然而，紫光沿着掠射角在靠近翅面的地方出现，而其他颜色，从蓝色到红色，则分别以逐渐接近垂直于翅面方向的角度射出。这个顺序与具有平行于翅面周期性的光栅通常的光分解顺序相反。研究表明，这种效应是由整个鳞片的宏观变形产生的，鳞片卷曲形成一个垂直于翅面的“垂直”光栅，并以透射而非反射的方式起作用。
