Multilevel diffractive optical element
First Claim
1. A multilevel diffractive optical element comprising a base and a plurality of phase zones, each phase zone being defined by a local modulation depth d and having a local number N of complete levels of identical local width W and, in at least one phase zone, one incomplete level whose width w is less than the width W of the complete levels in said zone, the phase levels in each Phase zone being spaced, in the direction along the modulation depth, by a distance h which is substantially invariant along the entire optical element;
- a total number of phase levels in each phase zone being defined by a parameter ξ
=d/h, which is a real number whose integer equals to said local number N of the complete levels and whose fraction indicates to the existence of said incomplete level;
said parameter ξ
=ξ
(x, y), said width W and said width w varying among different phase zones so as to provide corresponding variation of said local modulation depth d=d(x, y) whereby local diffraction efficiencies and consequently an overall diffraction efficiency of the optical element is arbitrarily controlled.
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Abstract
A multilevel diffractive optical element comprising a base and a plurality of phase zones having phase levels of a substantially identical height h, each phase zone being defined by a local modulation depth d and a local number of phase levels ξ=d/h, the local number of phase levels ξ per phase zone being a real number, an integer of which defines the number of complete levels in the phase zone, which complete levels have identical widths, and a fraction of which, in at least one phase zone, defines an incomplete level which is narrower than the complete levels, said local number of phase levels ξ=ξ(x, y) varying among different phase zones so as to provide corresponding variation of said local modulation depth d=d(x, y) whereby local diffraction efficiencies and consequently an overall diffraction efficiency of the optical element is arbitrarily controlled.
18 Citations
13 Claims
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1. A multilevel diffractive optical element comprising a base and a plurality of phase zones, each phase zone being defined by a local modulation depth d and having a local number N of complete levels of identical local width W and, in at least one phase zone, one incomplete level whose width w is less than the width W of the complete levels in said zone, the phase levels in each Phase zone being spaced, in the direction along the modulation depth, by a distance h which is substantially invariant along the entire optical element;
- a total number of phase levels in each phase zone being defined by a parameter ξ
=d/h, which is a real number whose integer equals to said local number N of the complete levels and whose fraction indicates to the existence of said incomplete level;
said parameter ξ
=ξ
(x, y), said width W and said width w varying among different phase zones so as to provide corresponding variation of said local modulation depth d=d(x, y) whereby local diffraction efficiencies and consequently an overall diffraction efficiency of the optical element is arbitrarily controlled. - View Dependent Claims (2, 3, 4, 5, 6, 7)
- a total number of phase levels in each phase zone being defined by a parameter ξ
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8. A multilevel diffractive optical element comprising a base and a plurality of phase zones, each consisting of a local number N of identical phase levels of a local width W and, in at least one phase zone, of an additional level of a local width w that is less than the local width W of said identical phase levels in said zone;
- each phase zone being defined by a local modulation depth d, and the phase levels in each zone being spaced, in the direction along the modulation depth, by a distance h which is substantially invariant along all the phase zones of the optical element;
the local number N and the width W of the identical phase levels, and the width w of the additional level, if any, varying among different phase zones so as to provide corresponding variation of said local modulation depth, providing thereby a desired distribution of local diffraction efficiencies over the optical element. - View Dependent Claims (9, 10, 11, 12, 13)
- each phase zone being defined by a local modulation depth d, and the phase levels in each zone being spaced, in the direction along the modulation depth, by a distance h which is substantially invariant along all the phase zones of the optical element;
Specification