U.S. patent application number 09/271454 was filed with the patent office on 2001-10-18 for progressive power spectacle lens.
Invention is credited to YAMAMOTO, CHIKARA.
Application Number | 20010030735 09/271454 |
Document ID | / |
Family ID | 13367608 |
Filed Date | 2001-10-18 |
United States Patent
Application |
20010030735 |
Kind Code |
A1 |
YAMAMOTO, CHIKARA |
October 18, 2001 |
PROGRESSIVE POWER SPECTACLE LENS
Abstract
A progressive power spectacle lens includes a distance portion
having a dioptric power for distance vision, a near portion having
a dioptric power for near vision; and an intermediate portion
having a progressive dioptric power for vision at ranges
intermediate between distance and near. A main meridian is not an
umbilical line. A predetermined surface astigmatism is provided on
the main meridian. In the near portion, the surface astigmatism
decreases and then increases as the distance from the main meridian
increases in a horizontal direction.
Inventors: |
YAMAMOTO, CHIKARA; (TOKYO,
JP) |
Correspondence
Address: |
GREENBLUM & BERNSTEIN, P.L.C.
1941 ROLAND CLARKE PLACE
RESTON
VA
20191
US
|
Family ID: |
13367608 |
Appl. No.: |
09/271454 |
Filed: |
March 18, 1999 |
Current U.S.
Class: |
351/159.42 |
Current CPC
Class: |
G02C 7/065 20130101;
G02C 7/061 20130101 |
Class at
Publication: |
351/169 ;
351/168; 351/170; 351/171; 351/172 |
International
Class: |
G02C 007/06 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 18, 1998 |
JP |
10-68223 |
Claims
What is claimed is:
1. A progressive power spectacle lens, including: a distance
portion having a dioptric power for distance vision; a near portion
having a dioptric power for near vision; and an intermediate
portion having a progressive dioptric power for vision at ranges
intermediate between the distance and near portions; wherein a
predetermined surface astigmatism is provided on a main meridian,
the surface astigmatism decreasing and then increasing as the
distance from the main meridian increases in a horizontal direction
within said near portion.
2. The progressive power spectacle lens according to claim 1,
wherein the variation of said surface astigmatism satisfies the
condition (1) on at least one point in the range of
-30<-Y<-15, and further satisfies the condition (2) on at
least one point in the overlapped range of -30<Y<-15 and
3<.vertline.X-Xm.vertline.<10, when a rectangular coordinate
(unit: mm) is defined by a fitting point O as an origin, a
horizontal X-axis and a vertical Y-axis; AS(Xm, Y)>0.2, and (1)
AS(Xm, Y)-AS(X, Y)>0.05, (2) where AS (x, y) is the surface
astigmatism at the point (x, y), and Xm is a displacement of the
main meridian from the Y-axis defined by Xm=f(Y).
3. The progressive power spectacle lens according to claim 2,
wherein the condition (2) is satisfied on at least one point in the
overlapped range of -30<Y<-15 and
5<.vertline.X-Xm.vertline.<10.
4. The progressive power spectacle lens according to claim 2,
wherein the maximum curvature direction .theta.(x, y) that is
defined as an angle (unit: degree) with respect to the X-axis at
the point (x, y) satisfies the conditions (3) and (4);
-100<.vertline.(Xm, Y)<10.degree., and (3)
60.degree.<.vertline..theta.(Xm.+-.10,
Y).vertline.<90.degree., (4) where the surface astigmatism at
the points satisfying the conditions (3) and (4) are larger than
0.2.
5. A progressive power spectacle lens, including: a distance
portion having a dioptric power for distance vision; a near portion
having a dioptric power for near vision; and an intermediate
portion having a progressive dioptric power for vision at ranges
intermediate between the distance and near portions; wherein a
predetermined surface astigmatism is provided on a main meridian,
and there are portions having the lower surface astigmatism than
that at said main meridian at the right and left sides of said main
meridian within said near portion.
6. The progressive power spectacle lens according to claim 5,
wherein the maximum curvature direction in said near portion varies
along the horizontal direction as a monotonic function.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a progressive power
spectacle lens with a dioptric power varying progressively between
a distance portion and a near portion.
[0002] FIG. 17 is a front view (viewed from an object side) of a
progressive power spectacle lens 1 for a right eye. The lens 1
includes:
[0003] a distance portion 2 having a dioptric power for distance
vision at an upper area of the lens;
[0004] a near portion 3 having a dioptric power for near vision at
a lower area of the lens; and
[0005] an intermediate portion 4 between the near and distance
portions.
[0006] A dioptric power in the intermediate portion 4 progressively
varies from the upper portion to the lower portion. Such a power is
given by the asymmetrical shape formed on the front or rear
surface, which is referred to as a progressive side surface.
[0007] A rectangular coordinate is defined by a fitting point O as
an origin, a horizontal X-axis, and a vertical Y-axis. The fitting
point O is the point on the progressive side surface of the lens 1
determined by a manufacturer as a reference point for positioning
the lens in front of the eye.
[0008] The power of the progressive side surface varies along a
main meridian MM' that is a virtual centerline extending
substantially along the vertical direction. Specifically, the main
meridian MM' is coincident with the Y-axis in the distance portion
2, while it is bent toward a nasal side in the intermediate portion
4, and extends vertically with being shifted toward the nasal side
in the near portion 3 by an amount Xm.
[0009] The progressive power spectacle lens 1 must include surface
astigmatism on the progressive side surface since the distance
portion and the near portion, which have different dioptric powers,
are smoothly connected. In particular, a zone along the main
meridian MM' is a center of a view field of a user, and
accordingly, it is desirable that the astigmatism along the main
meridian MM' is minimized in order to provide a clear vision zone.
The clear vision zone is a zone through which a user obtains a
natural and comfortable view.
[0010] In one type of the conventional progressive power lenses,
the main meridian MM' is designed as an umbilical line along which
a surface astigmatism has a value of zero.
[0011] Conventionally, a progressive power lens is designed with a
surface performance evaluation of a progressive side surface
(referred hereinafter as "a surface evaluating design") to reduce
complicated and expensive calculation work. The lens having the
umbilical main meridian results in good performance in terms of the
surface performance evaluation. However, the lens having a good
surface performance does not always have a good transmission
performance in a transmitting performance evaluation using the
ray-tracing method. The transmission performance (which corresponds
to a worn condition) is more important than the surface performance
for actual products.
[0012] It should be noted that two types of astigmatism are used in
the specification. "A surface astigmatism" is an absolute value of
the difference between the dioptric power of the progressive side
surface in a maximum curvature direction where the curvature has
the maximum value, and the dioptric power of the surface in a
direction where the curvature has the minimum value. The surface
astigmatism is only determined by the shape of the progressive side
surface. On the other hand, "a resultant astigmatism" is an
astigmatism caused on a fundus of an eye through the lens.
[0013] When a progressive power spectacle lens is provided with a
large base curve, the transmission performance is substantially
coincident with the surface performance. This means that the good
transmission performance lens can be designed by the surface
evaluating design. However, the large curvature of the lens results
in a heavy and thick lens.
[0014] Recently, a small base curve is generally required to obtain
a light and thin lens even in the field of the progressive power
spectacle lens. When the progressive power spectacle lens is
designed so as to have a small base curve, the transmission
performance is not coincident with the surface performance. That
is, the lens having the umbilical main meridian results in
insufficient transmission performance.
[0015] Japanese provisional patent publication Nos. SHO 59-58415,
HEI 1-221722, HEI 8-136868 and HEI 4-500870 (the counterpart of PCT
international patent publication W091/01508) disclose the
progressive power spectacle lenses that have non-umbilical main
meridians. Although each of the publications teaches the surface
astigmatism along the main meridian, none of the publications
disclose the variation of the surface astigmatism along the
horizontal direction.
SUMMARY OF THE INVENTION
[0016] It is therefore an object of the present invention to
provide an improved progressive power spectacle lens, which has an
enlarged clear vision zone with employing a small base curve.
[0017] For the above object, according to the present invention,
there is provided a progressive power spectacle lens, which
includes:
[0018] a distance portion having a dioptric power for distance
vision;
[0019] a near portion having a dioptric power for near vision;
and
[0020] an intermediate portion having a progressive dioptric power
for vision at ranges intermediate between the distance and near
portions;
[0021] wherein a predetermined surface astigmatism is provided on a
main meridian, and the surface astigmatism decreases and then
increases as the distance from the main meridian increases in a
horizontal direction within the near portion.
[0022] The variation of the surface astigmatism is desirable to
satisfy the condition (1) on at least one point in the range of
-30<Y<-15, and further to satisfy the condition (2) on at
least one point in the overlapped range of -30<Y<-15 and
3<.vertline.X-Xm.vertline.<- 10, when a rectangular
coordinate (unit: mm) is defined by a fitting point O as an origin,
a horizontal X-axis and a vertical Y-axis;
AS(Xm, Y)>0.2, and (1)
AS(Xm, Y)-AS(X, Y)>.sub.0.05, (2)
[0023] where
[0024] AS(x, y) is the surface astigmatism at the point (x, y),
and
[0025] Xm is a displacement (i.e., a distance along the X-axis) of
the main meridian from the Y-axis defined by Xm=f(Y).
[0026] Further, the maximum curvature direction .theta.(x, y) that
is defined as an angle (unit: degree) with respect to the X-axis at
the point (x, y) is desirable to satisfy the conditions (3) and
(4);
-10.degree. <.theta.(Xm, Y)<10.degree., and (3)
60.degree.<.vertline..theta.(Xm.+-.10, Y) <90.degree.,
(4)
[0027] where the surface astigmatism at the points satisfying the
conditions (3) and (4) are larger than 0.2.
DESCRIPTION OF THE ACCOMPANYING DRAWINGS
[0028] FIG. 1 is a map showing a surface astigmatism distribution
on a progressive side surface of a spectacle lens according to a
first embodiment;
[0029] FIG. 2 is a graph showing a variation of the surface
astigmatism of the lens shown in FIG. 1 along a horizontal line at
Y=-25;
[0030] FIG. 3 is a graph showing a variation of a maximum curvature
direction of the lens shown in FIG. 1 along a horizontal line at
Y=-25;
[0031] FIG. 4 is a distribution map showing a resultant astigmatism
distribution of the lens shown in FIG. 1;
[0032] FIG. 5 is a distribution map of a surface astigmatism
distribution on a progressive side surface of the spectacle lens
according to a comparative example 1 that is not an embodiment;
[0033] FIG. 6 is a graph showing a variation of the surface
astigmatism of the lens shown in FIG. 5 along a horizontal line at
Y=-25;
[0034] FIG. 7 is a distribution map showing a resultant astigmatism
distribution of the lens shown in FIG. 5;
[0035] FIG. 8 is a distribution map showing a surface astigmatism
distribution on a progressive side surface of the spectacle lens
according to a second embodiment;
[0036] FIG. 9 is a graph showing a variation of the surface
astigmatism of the lens shown in FIG. 8 along a horizontal line at
Y=-25;
[0037] FIG. 10 is a graph showing a variation of the maximum
curvature direction of the lens shown in FIG. 8 along a horizontal
line at Y=-25;
[0038] FIG. 11 is a distribution map showing a resultant
astigmatism distribution of the lens shown in FIG. 8;
[0039] FIG. 12 is a distribution map showing a surface astigmatism
distribution on a progressive side surface of the spectacle lens
according to a comparative example 2 that is not an embodiment;
[0040] FIG. 13 is a graph showing a variation of the surface
astigmatism of the lens shown in FIG. 12 along a horizontal line at
Y=-25;
[0041] FIG. 14 is a distribution map of a resultant astigmatism
distribution of the lens shown in FIG. 12;
[0042] FIG. 15 shows rectangular coordinates on a progressive power
spectacle lens;
[0043] FIG. 16 is a graph showing the definition of the maximum
curvature direction; and
[0044] FIG. 17 shows a general distribution of portions on the
progressive side surface of a progressive power spectacle lens.
DESCRIPTION OF THE EMBODIMENTS
[0045] First and second embodiments will be described hereinafter
in contrast to comparative examples. The progressive power
spectacle lens according to each of the embodiments includes a
distance portion having a dioptric power for distance vision, a
near portion having a dioptric power for near vision, and an
intermediate portion having a progressive dioptric power for vision
at ranges intermediate between distance and near portions.
[0046] A main meridian is not an umbilical line. A predetermined
surface astigmatism is provided on the main meridian as defined by
condition (1) on at least one point in the range of -30<Y<-15
when a rectangular coordinate (unit: mm) is defined by a fitting
point O as an origin, a horizontal X-axis, and a vertical
Y-axis;
AS(Xm, Y)>0.2, (1)
[0047] where
[0048] AS(x, y) is the surface astigmatism at the point (x, y),
and
[0049] Xm is a displacement (i.e., a distance along the X-axis) of
the main meridian from the Y-axis defined by Xm=f(Y).
[0050] FIG. 15 shows the rectangular coordinate on the progressive
power spectacle lens. The range of -30<Y<-15 is indicated by
"A".
[0051] In the near portion, the surface astigmatism decreases and
then increases as the distance from the main meridian MM' increases
in a horizontal direction (i.e., in the X-axis direction) within a
clear vision zone. Such a distribution of the surface astigmatism
is effective to enlarge the width of the clear vision zone. The
variation of the surface astigmatism satisfies condition (2) on at
least one point in the overlapped range of -30<Y<-15 and
3<.vertline.X-Xm.vertline.<- 10;
AS(Xm, Y)-AS(X, Y)>0.05. (2)
[0052] In FIG. 15, the range of 3<.vertline.X-Xm.vertline.<10
is indicated by "B". Condition (2) is satisfied in the ranges
(shown by hatching) where the ranges A and B overlap. Optionally,
the range B may be limited to
5<.vertline.X-Xm.vertline.<10.
[0053] Further, the maximum curvature direction .theta.(x, y) that
is defined as an angle (unit: degree) with respect to the X-axis at
the point (x, y) satisfies conditions (3) and (4);
-10.degree.<.vertline..theta.(Xm, Y)<10.degree., and (3)
60.degree.<.vertline..theta.(Xm.+-.10, Y)<90.degree., (4)
[0054] where the surface astigmatism at the points satisfying
conditions (3) and (4) are larger than 0.2.
[0055] The dioptric power at a point on the progressive side
surface can be described as an ellipse as shown in FIG. 16. The
size of the ellipse indicates the dioptric power at the point (x,
y). The point having the surface astigmatism is indicated by an
ellipse, while an umbilical point is indicated by a circle. A major
axis Cmax of the eclipse represents the direction of the maximum
curvature thereof, and the angle of the major axis Cmax with
respect to the X-axis is the maximum curvature direction .theta.(x,
y).
[0056] Condition (3) requires that the maximum curvature direction
on the main meridian MM' is substantially parallel to the
horizontal direction (X-axis), and condition (4) requires that the
maximum curvature direction at the points distant from the main
meridian by .+-.10 mm is substantially perpendicular to the
horizontal direction.
[0057] Satisfaction of the condition (3) reduces the resultant
astigmatism on the main meridian MM'. When the condition (4) is
satisfied, a distortion can be effectively corrected.
[0058] [First Embodiment]
[0059] FIG. 1 is a map of a surface astigmatism distribution on a
progressive side surface of the progressive power spectacle lens
according to the first embodiment. Specifications of the lens are
as follows:
[0060] Base curve: 5.00 [D]
[0061] SPH (a dioptric power at a distance design reference point
): +2.00 [D]
[0062] Addition power: 2.00 [D]
[0063] As shown in FIG. 1, the near portion of the lens includes a
zone C (shown by hatching) in which the surface astigmatism is
larger than 0.20 [D] along the main meridian MM'. The displacement
Xm is equal to 2.5 mm in a range of -40<Y<-19.
[0064] FIGS. 2 and 3 are graphs showing a variation of the surface
astigmatism AS(X, -25) and a variation of the maximum curvature
direction .theta.(X, -25) of the lens shown in FIG. 1 respectively.
As shown in FIG. 2, the surface astigmatism decreases and then
increases as the distance from the main meridian MM' increases
within the clear vision zone. Further, the maximum curvature
direction varies along the horizontal direction as a monotonic
function as shown in FIG. 3. The first embodiment satisfies
conditions (1) though (4) as follows.
[0065] (1) AS(Xm, Y)=AS(2.5, -25)=0.33. This value is larger than
0.2 and thus the condition (1) is satisfied.
[0066] (2) AS(Xm, Y)-AS(X, Y)=AS(2.5, -25)-AS(0, -25)>0.05 If
the range B (shown in FIG. 15) is defined by
3<.vertline.X-Xm.vertline.<10, condition (2) is satisfied in
a range R1 (shown in FIG. 2) of -4.5<X<-0.5 and in a range R2
of 5.5<X<7.4 under the condition of Y=-25. If the range B is
defined by 5<.vertline.X-Xm.vert- line.<10, condition (2) is
satisfied in a range R3 of -4.5<X-2.5 under the condition of
Y=-25.
[0067] (3) .theta.(Xm, Y)=.theta.(2.5, -25)=0.degree.. This value
falls within the range of condition (3).
[0068] (4) .theta.(Xm-10, Y)=.theta.(-7.5, -25)=69.degree., and
.theta.(Xm+10, Y)=.theta.(12.5, -25)=-69.degree.. These values fall
within the range of the condition (4).
[0069] Since the surface astigmatism AS(2.5, -25)=0.33, AS(-7.5,
-25)=0.75 and AS(12.5, -25)=1.22, the premise of conditions (3) and
(4) are satisfied.
[0070] A distribution of the resultant astigmatism, which is
obtained by the transmitting evaluation, according to the first
embodiment is shown in FIG. 4. The width of the clear vision zone
S, in which the resultant astigmatism is lower than 0.5, is equal
to 11 mm.
COMPARATIVE EXAMPLE 1
[0071] FIG. 5 shows a map of a surface astigmatism distribution on
a progressive side surface of the comparative example 1. This
example is described for indicating the compared effect of the
first embodiment and it is not an embodiment of the invention. The
lens of the example 1 has the same specification as the first
embodiment in the base curve, SPH and the additional power, while
the lens is designed so that the surface performance is optimized.
That is, the main meridian is designed as an umbilical line.
[0072] FIG. 6 is a graph showing a variation of the surface
astigmatism AS (X, -25) of the lens shown in FIG. 5. As shown in
FIG. 6, the surface astigmatism is almost equal to zero on the main
meridian MM' and it monotonically increases as the distance from
the main meridian MM' increases.
[0073] A distribution of the resultant astigmatism according to the
example 1 is shown in FIG. 7. The width of the clear vision zone s
is 4 mm.
[0074] It is understood, by comparing the first embodiment with the
comparative example 1, that the distribution of the surface
astigmatism of the first embodiment is effective to enlarge the
clear vision zone S.
[0075] [Second Embodiment]
[0076] FIG. 8 is a map of a surface astigmatism distribution on a
progressive side surface of the progressive power spectacle lens
according to the second embodiment. Specifications of the lens are
as follows:
[0077] Base curve: 2.00 [D]
[0078] SPH: -4.00 [D]
[0079] Addition power: 2.00 [D]
[0080] As shown in FIG. 8, the near portion of the lens includes a
zone D (shown by hatching) in which the surface astigmatism is
larger than 0.20 [D] along the main meridian MM'. The displacement
Xm is equal to 2.5 mm in a range of -40<Y<-19.
[0081] FIGS. 9 and 10 are graphs showing a variation of the surface
astigmatism AS (X, -25) and a variation of the maximum curvature
direction .theta.(X, -25) of the lens shown in FIG. 8 respectively.
As shown in FIG. 9, the surface astigmatism decreases and then
increases as the distance from the main meridian MM' increases
within the clear vision zone. Further, the maximum curvature
direction varies along the horizontal direction as a monotonic
function as shown in FIG. 10. The second embodiment satisfies the
conditions (1) though (4) as follows.
[0082] (1) AS(Xm, Y)=AS(2.5, -25)=0.26. This value is larger than
0.2 and thus the condition (1) is satisfied.
[0083] (2) AS(Xm, Y)-AS(X, Y)=AS(2.5, -25)-AS(0, -25)>0.05 If
the range B (shown in FIG. 15) is defined by
3<.vertline.X-Xm.vertline.<10, the condition (2) is satisfied
in a range R4 (shown in FIG. 9) of -2.7<X<-0.5 and in a range
R5 of 5.5<X<8.2 under the condition of Y=-25. If the range B
is defined by 5<.vertline.X-Xm.vert- line.<10, the condition
(2) is satisfied in a range R6 of -2.7<X<-2.5 under the
condition of Y=-25.
[0084] (3) .theta.(Xm, Y)=.theta.(2.5, -25)-0.degree.. This value
falls within the range of the condition (3).
[0085] (4) .theta.(Xm-10, Y)=.theta.(-7.5, -25)=67.degree., and
.theta.(Xm+10, Y)=.theta.(12.5, -25)=-70.degree.. These values fall
within the range of the condition (4).
[0086] Since the surface astigmatism AS(2.5, -25)=0.26, AS(-7.5,
-25)=0.78 and AS(12.5, -25)=0.85, the premise of the conditions (3)
and (4) are satisfied.
[0087] A distribution of the resultant astigmatism, which is
obtained by the transmitting evaluation, according to the second
embodiment is shown in FIG. 11. The width of the clear vision zone
s is equal to 12 mm.
COMPARATIVE EXAMPLE 21
[0088] FIG. 12 shows a map of a surface astigmatism distribution on
a progressive side surface of the comparative example 2. This
example is not an embodiment of the invention. The lens of the
example 2 has the same specification as the second embodiment in
the base curve, SPH and the additional power, while the lens is
designed so that the surface performance is optimized. That is, the
main meridian is designed as an umbilical line.
[0089] FIG. 13 is a graph showing a variation of the surface
astigmatism AS(X, -25) of the lens shown in FIG. 12. As shown in
FIG. 13, the surface astigmatism is almost equal to zero on the
main meridian MM' and it monotonically increases as the distance
from the main meridian MM' increases.
[0090] A distribution of the resultant astigmatism according to the
example 2 is shown in FIG. 14. The clear vision zone is limited at
only the center portion of the lens. The width of the clear vision
zone s is 7 mm.
[0091] It is understood, by comparing the second embodiment with
the comparative example 2, that the distribution of the surface
astigmatism of the second embodiment is effective to enlarge the
clear vision zone.
[0092] The present disclosure relates to the subject matter
contained in Japanese Patent Application No. HEI 10-068223, filed
on Mar. 18, 1998, which is expressly incorporated herein by
reference in its entirety.
* * * * *