| 摘要 |
A polychromatic diffractive lens is usable with broadband or multi-spectral illumination to bring a plurality of spectral components of the illumination to a common focus in space. The lens has a Fresnel zone structure of zones and a profile which provides a phase jump delay at each zone boundary to the illumination of at least one of the spectral components which is greater than one period (wave) of that wavelength, and more particularly, a multiple of 2 pi p, where p is an integer greater than or equal to two. The parameter p and the width of the zones are selected so that the spectral components are directed, and if desired directed so as to be brought to the common focus with high diffraction efficiency in distinct diffractive orders, the lens thereby being a multi-order diffractive (MOD) lens. Applications for MOD lenses are in color (RGB) displays, color laser printers, which printers may utilize one MOD lens to image laser beams in red, blue and green wavelengths (multi-spectral illumination) to the same focal spot for forming color images as the beams scan an image forming element, such as a xerographic receptor.
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