Diffractive multifocal lens
There is provided a diffractive multifocal lens, wherein a diffraction phase structure of a diffraction pattern has a structure expressed by the following formula: ϕ ( ξ ) = { p 1 ξ , 0 ≤ ξ < w p 2 ( ξ - 0.5 ) - q π , w ≤ ξ < 1 - w p 1 ( ξ - 1 ) , 1 - w ≤ ξ ≤ 1 ( 1 ) wherein ξ indicates a position in a radial direction of the lens in one period of the diffraction pattern, and φ(ξ) indicates a value (radian) of a phase shift amount of light passing through the position of ξ from the phase of light passing through a reference plane.
1. A diffractive multifocal lens, having an annular diffraction pattern for exhibiting a light diffraction effect, which is formed concentrically repeatedly on a surface of a lens,
wherein a diffraction phase structure of the diffraction pattern has a structure expressed by the following formula:
ϕ
(
ξ
)
=
{
p
1
ξ
,
0
≤
ξ
<
w
p
2
(
ξ
-
0.5
)
-
q
π
,
w
≤
ξ
<
1
-
w
p
1
(
ξ
-
1
)
,
1
-
w
≤
ξ
≤
1
(
1
)
wherein each symbol is as follows:
ξ indicates a position in a radial direction of the lens in one period of the diffraction pattern, having values from 0 to 1;
w indicates a position where a form of the formula of φ(ξ) is changed;
φ(ξ) indicates a value (radian) of a phase shift amount of light passing through the position of ξ from the phase of light passing through a reference plane;
p 1 indicates a value defining a gradient of a straight line φ(ξ), when satisfying 0≦ξ<w, and 1−w≦ξ≦1;
p 2 indicates a value defining the gradient of the straight line φ(ξ) when satisfying w≦ξ<1−w; and
q indicates a parallel moving amount over the reference plane of the straight line φ(ξ) when satisfying w≦ξ<1−w.
2. The diffractive multifocal lens according to claim 1 , wherein the q satisfies 0<|q|≦1.
3. A diffractive multifocal lens, having an annular diffraction pattern for exhibiting a light diffraction effect, which is formed concentrically repeatedly on a surface of a lens,
wherein a diffraction phase structure of the diffraction pattern has a structure expressed by a curve which is obtained by smoothing and optimizing a curve showing a diffraction phase structure of claim 1 , using curve approximation, filtering, or convolution integration.
4. The diffractive multifocal lens according to claim 1 , wherein the diffractive multifocal lens is an ocular lens such as a contact lens and an intraocular lens.
5. The diffractive multifocal lens according to claim 2 , wherein the diffractive multifocal lens is an ocular lens such as a contact lens and an intraocular lens.
6. The diffractive multifocal lens according to claim 3 , wherein the diffractive multifocal lens is an ocular lens such as a contact lens and an intraocular lens.
7. A diffractive multifocal lens, having an annular diffraction pattern for exhibiting a light diffraction effect, which is formed concentrically repeatedly on a surface of a lens,
wherein a diffraction phase structure of the diffraction pattern has a structure expressed by a curve which is obtained by smoothing and optimizing a curve showing a diffraction phase structure of claim 2 , using curve approximation, filtering, or convolution integration.
8. The diffractive multifocal lens according to claim 7 , wherein the diffractive multifocal lens is an ocular lens such as a contact lens and an intraocular lens.