Reduction of Lens Reflexion by the “Moth Eye” Principle

Abstract

THE problem of surface reflexion from lenses has led¹ to the development of multilayer interference structures which can suppress the reflexion from glass surfaces by a factor of 10 or more throughout the visible spectrum. But observations on the corneas of nocturnal insects indicate that nature may have anticipated the problems². Electron microscope studies of the corneal lenses of moths reveal that the outer surface is covered in a regular array of conical protuberances, typically of about 200 nm height and spacing. Bernhard² proposed that the function of this structure might be to suppress reflexions by effectively proving a graded transition of refractive index between the air and the cornea. The proposal was substantiated by measurements with microwave radiation reflected from a model of the array, scaled up appropriately for the longer wavelengths.