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.