Introduction to Optics for Ophthalmology (4)　Principles of Diffractive Lens

Abstract

The principle of diffractive lenses, recently often applied to intraocular lenses (IOLs), is described. A diffractive IOL is constructed using a normal reflective lens, upon which is pasted a diffractive surface with many concentric thin microprisms. A light ray that enters the diffractive surface splits into two rays; the lens then becomes bifocal, with the focal points close to each other and the phase differences of the exit rays well controlled. The energy distribution of the exit rays varies with the wavelength, since the dispersion of the prism material is not equivalent to the dispersion of the diffractive phenomenon itself.