Patent ID: 6545821
Filing Date: 2003-04-08
Classification: G02B

Abstract:
A diffraction type lens, disposed in a luminous flux, having a wavelength selectivity;wherein a substrate constituting said lens has one surface formed with a zone plate exhibiting a smaller converging action with respect to a first wavelength &lgr;1 of light and a greater converging action with respect to a second wavelength &lgr;2 of light, and the other surface formed with a zone plate exhibiting a smaller converging action with respect to said second wavelength &lgr;2 of light and a greater converging action with respect to said first wavelength &lgr;1 of light, said substrate being transparent to said first and second wavelengths &lgr;1 and &lgr;2 of light; and wherein each of said zone plates comprises concentric gratings having a stepped cross section; wherein said one surface and other surface are on opposite sides of the lens and overlap each other.