Progressive multifocal lens and method of designing the same
To provide a new progressive multifocal lens having eyesight corrective power and astigmatism corrective power in the same refracting interface by forming an eyeball-side refracting interface 2 or an object-side refracting interface 3 into a curved surface denoted by a combined refracting interface 14+15 composed of an original progressive refracting interface 14 set only to exhibit a desired eyesight corrective characteristic and an original toric surface 15 set only to exhibit a desired astigmatism corrective characteristic with a combination expression denoted by combination expression (1) or (2).
1. A progressive multifocal lens for correcting eyesight comprising:
a progressive refracting interface, said progressive refracting interface is located on a side of an eyeball or on a side of an object,
wherein the progressive refracting interface comprises:
a distance portion,
a near portion with different refractive powers, and
a progressive portion of which refractive power varies progressively therebetween,
wherein the eyeball-side refracting interface or the object-side refracting interface is a combined refracting interface comprising an original progressive refracting interface set only to exhibit a desired eyesight corrective characteristic and an original toric surface set only to exhibit a desired astigmatism corrective characteristic,
wherein, when z-axis is an axis passing through the center of the progressive refracting interface from the object toward the eyeball, x-axis is cylinder axis of the original toric surface, and y-axis is an axis perpendicular to the x-axis and the z-axis, value z p in any point P (x p , y p , z p ) in the combined refracting interface is expressed by a first expression (1) or a second expression (2) by using approximate curvature Cp of the original progressive refracting interface, curvature Cx in the x-axis direction, and curvature Cy in the y-axis direction,
wherein the first expression (1) is expressed as
z
p
=
(
c
p
+
c
x
)
x
2
+
(
c
p
+
c
y
)
y
2
1
+
1
-
(
(
c
p
+
c
x
)
x
2
+
(
c
p
+
c
y
)
y
2
)
2
x
2
+
y
2
(
1
)
and
wherein the second expression (2) is expressed as
z
p
=
(
c
p
+
c
x
)
x
2
1
+
1
-
(
c
p
+
c
x
)
2
(
x
2
+
y
2
)
+
(
c
p
+
c
y
)
y
2
1
+
1
-
(
c
p
+
c
y
)
2
(
x
2
+
y
2
)
.
(
2
)
2. A progressive multifocal lens according to claim 1 , wherein an eyeball-side refracting interface surface or an object-side refracting interface surface opposite to the surface having the combined refracting interface is spherical or rotation-symmetry aspherical in shape.
3. A method for designing a progressive multifocal lens for correcting eyesight having a progressive refracting interface on a side of an eyeball or on a side of an object, the progressive refracting interface comprising a distance portion, a near portion with different refractive powers, and a progressive portion of which refractive power varies progressively therebetween, the method comprising:
obtaining an original progressive refracting interface only in order that the eyeball-side refracting interface or the object-side refracting interface exhibits an eyesight corrective characteristic;
obtaining an original toric surface only in order that the eyeball-side refracting interface or the object-side refracting interface exhibits a desired astigmatism-corrective-characteristic; and
obtaining a combined refracting interface as the eyeball-side refracting interface or the object-side refracting interface, the combined refracting interface comprising the original progressive refracting interface set only to exhibit a desired eyesight corrective characteristic and the original toric surface set only to exhibit a desired astigmatism corrective characteristic,
wherein in the obtaining of the combined refracting interface, when z-axis is an axis passing through the center of the progressive refracting interface from the object toward the eyeball, x-axis is the cylinder axis of the original toric surface, and y-axis is an axis perpendicular to the x-axis and the z-axis, value z p in any point P (x p , y p , z p ) in the combined refracting interface is obtained by a first expression (1) or a second expression (2) by using an approximate curvature Cp of the original progressive refracting interface, a curvature Cx in the x-axis direction, and a curvature Cy in the y-axis direction,
wherein the first expression (1) is expressed as
z
p
=
(
c
p
+
c
x
)
x
2
+
(
c
p
+
c
y
)
y
2
1
+
1
-
(
(
c
p
+
c
x
)
x
2
+
(
c
p
+
c
y
)
y
2
)
2
x
2
+
y
2
(
1
)
wherein the second expression (2) is expressed as
z
p
=
(
c
p
+
c
x
)
x
2
1
+
1
-
(
c
p
+
c
x
)
2
(
x
2
+
y
2
)
+
(
c
p
+
c
y
)
y
2
1
+
1
-
(
c
p
+
c
y
)
2
(
x
2
+
y
2
)
.
(
2
)
4. The progressive multifocal lens according to claim 1 , wherein, the value z p in any point P (x p , y p , z p ) in the combined refracting interface is expressed by the second expression (2).
5. The progressive multifocal lens according to claim 1 , wherein the object-side has the combined refracting interface and the eyeball-side surface is spherical in shape.
6. The progressive multifocal lens according to claim 1 , wherein an eyeball-side refracting interface surface or an object-side refracting interface surface opposite to the surface having the combined refracting interface is rotation-symmetry aspherical in shape.
7. The method for designing a progressive multifocal lens according to claim 3 , wherein the original toric surface is obtained by a third expression expressed as:
z
=
c
x
x
2
+
c
y
y
2
1
+
1
-
(
c
x
x
2
+
c
y
y
2
)
2
x
2
+
y
2
wherein z represents a circular arc of the original toric surface.
8. The method for designing a progressive multifocal lens according to claim 3 , wherein the original toric surface is obtained by a fourth expression expressed as:
z
=
c
x
x
2
1
+
1
-
c
x
2
(
x
2
+
y
2
)
+
c
y
y
2
1
+
1
-
c
y
2
(
x
2
+
y
2
)
.
wherein z represents a circular arc of the original toric surface.