Multifocal diffractive ophthalmic lenses with evenly spaced echelettes
Certain embodiments described herein are directed to a multifocal ophthalmic lens including a base lens having a base curvature corresponding to a base power, and a diffractive structure comprising a central zone and a plurality of annular echelettes formed on a first surface of the base lens. A radial spacing of each of the plurality of annular echelettes is constant throughout the diffractive structure.
1 . A multifocal ophthalmic lens, comprising:
a base lens having a base curvature corresponding to a base power; and
a diffractive structure formed on a first surface of the base lens and comprising:
a central zone comprising a first echelette at a center of the diffractive structure; and
a plurality of annular echelettes surrounding the first echelette, wherein a radial spacing of each of the plurality of annular echelettes is constant throughout the diffractive structure, and wherein at least two echelettes of the plurality of annular echelettes have different sag profiles relative to each other.
2 . The multifocal ophthalmic lens of claim 1 , wherein:
the first surface is an anterior surface of the multifocal ophthalmic lens.
3 . The multifocal ophthalmic lens of claim 1 , wherein:
the first surface is a posterior surface of the multifocal ophthalmic lens.
4 . The multifocal ophthalmic lens of claim 1 , wherein:
the constant radial spacing of the each of the plurality of annular echelettes is between 1/60 and 1/20 of a diameter of the base lens.
5 . The multifocal ophthalmic lens of claim 1 , wherein:
a sag of each of the central zone and the plurality of annular echelettes is between −1.0 and 1.0 in a unit of a design wavelength.
6 . The multifocal ophthalmic lens of claim 5 , wherein:
a phase delay of each of the central zone and the plurality of annular echelettes is between −1.0 and 1.0 in the unit of the design wavelength.
7 . The multifocal ophthalmic lens of claim 1 , wherein:
a sag of each of the central zone and the plurality of annular echelettes from the first surface of the base lens varies from an inner radius to an outer radius thereof polynomially with respect to a radial distance r from the inner radius.
8 . The multifocal ophthalmic lens of claim 1 , wherein:
a sag of the j-th echelette (j=1, 2, 3, . . . ) from the first surface of the base lens varies from an inner radius r j−1 to an outer radius r j polynomially with respect to a radial distance r from the inner radius r j−-1 as
h
j
=
a
j
(
r
j
-
r
j
-
1
)
(
r
z
j
-
r
j
-
1
)
+
φ
j
,
z
j
being a positive number greater than or equal to 1(z j ≥1), or
h
j
=
-
a
j
(
r
j
-
r
j
-
1
)
(
r
z
j
+
r
j
-
1
)
+
φ
j
,
z
j
being a negative number (z j <0), wherein:
the first echelette is the central zone,
the plurality of annular echelettes are j-th echelettes (j=2, 3, . . . ),
α j is a step height of the j-th echelette, and
φ j corresponds to a phase delay of the j-th echelette.
9 . A multifocal ophthalmic lens, comprising:
a base lens having a base curvature corresponding to a base power; and
a diffractive structure formed on a first surface of the base lens generating a zero-order diffraction having a distance vision focal point determined by the base power, a first-order diffraction, a second-order diffraction having an intermediate vision focal point, and a third-order diffraction corresponding to a near vision focal point, wherein:
the diffractive structure comprises a central zone comprising a first echelette at a center of the diffractive structure and a plurality of annular echelettes surrounding the first echelette,
at least two echelettes of the plurality of annular echelettes have different sag profiles relative to each other,
a radial spacing of each of the plurality of annular echelettes is constant throughout the diffractive structure,
diffraction efficiency of the zero-order diffraction is between 35% and 50%,
diffraction efficiency of the first-order diffraction is between 3% and 10%,
diffraction efficiency of the second-order diffraction is between 10% and 15%, and
diffraction efficiency of the third-order diffraction is between 15% and 25%.
10 . The multifocal ophthalmic lens of claim 9 , wherein:
the first surface is an anterior surface of the multifocal ophthalmic lens, or a posterior surface of the multifocal ophthalmic lens.
11 . The multifocal ophthalmic lens of claim 9 , wherein:
the constant radial spacing of each of the plurality of annular echelettes is between 1/60 and 1/20 of a diameter of the base lens.
12 . The multifocal ophthalmic lens of claim 11 , wherein:
a sag of each of the central zone and the plurality of annular echelettes is between −1.0 and 1.0 in a unit of a design wavelength, and
a phase delay of each of the central zone and the plurality of annular echelettes is between −1.0 and 1.0 in the unit of the design wavelength.
13 . The multifocal ophthalmic lens of claim 11 , wherein:
a sag of each of the central zone and the plurality of annular echelettes from the first surface of the base lens varies from an inner radius to an outer radius thereof polynomially with respect to a radial distance r from the inner radius.
14 . A method for configuring an ophthalmic lens, comprising:
computing a constant radial spacing for each of a plurality of annular echelettes, to be formed on a first surface of a base lens, based on a predetermined add power, wherein:
the base lens comprises a central zone comprising a first echelette at a center of the base lens, and
the plurality of annular echelettes surround the first echelette,
at least two echelettes of the plurality of annular echelettes have different sag profiles relative to each other, and
forming the plurality of annular echelettes or causing the plurality of annular echelettes to be formed on the ophthalmic lens based on the computed constant radial spacing.
15 . The method of claim 14 , further comprising:
computing a sag for each of the central zone and the plurality of annular echelettes such that diffraction efficiency of a zero-order diffraction is between 35% and 50%, diffraction efficiency of a first-order diffraction is between 3% and 10%, diffraction efficiency of a second-order diffraction is between 10% and 15%, and diffraction efficiency of a third-order diffraction is between 15% and 25%, wherein the forming is further based on the computed sag of each of the central zone and the plurality of annular echelettes.
16 . The method of claim 14 , wherein:
the first surface is an anterior surface of the multifocal ophthalmic lens, or a posterior surface of the multifocal ophthalmic lens.
17 . The method of claim 14 , wherein:
the constant radial spacing of each of the plurality of annular echelettes is between 1/60 and 1/20 of a diameter of the base lens.
18 . The method of claim 14 , wherein:
a sag of each of the central zone and the plurality of annular echelettes is between −1.0 and 1.0 in a unit of a design wavelength, and
a phase delay of each of the central zone and the plurality of annular echelettes is between −1.0 and 1.0 in the unit of the design wavelength.
19 . The method of claim 14 , wherein:
a sag of each of the central zone and the plurality of annular echelettes from the first surface of the base lens varies from an inner radius to an outer radius thereof polynomially with respect to a radial distance r from the inner radius.
20 . The multifocal ophthalmic lens of claim 1 , wherein the central zone comprises a single first echelette at the center of the diffractive structure.