BROADBAND DIFFRACTIVE DIFFUSER AND ASSOCIATED METHODS

摘要

A broadband diffractive diffuser contains at least three levels, with approximately a phase shift of a between at least two of the at least three levels. Such a diffuser provides light with more than two phasor vectors at the zero order. The presence of the more than two phasor vectors reduces the zero order diffraction efficiency at non-desi gn wavelength, increasing the usefulness of the diffuser at wavelengths other than the design wavelength. Preferably, the diffractive diffuser includes a plurality of regions, approximately 50 % of an area of the plurality of regions presenting a phase shift of .pi. at a design wavelength, approximately 25 % of the area of the plurality of regions presenting a phase shift of 2.pi. at the design wavelength, and approximately 25 % of the area of the plurality of regions presenting a phase shift of 0 at the design wavelength. Such a diffractive diffuser may b e formed by logical operations between two diffractive diffuser patterns, by adding two diffractive diffuser patterns, or by pixel-by-pixel scanning.