JPH04217225A - Near/intermediate distance region no-distortion farsighted lens - Google Patents

Abstract

PURPOSE:To eliminate distortion aberration of a lens for an old person so as to contrive substantial widening of a clear visible region by successively correcting refractive force of a lens surface. CONSTITUTION:In an far sighted lens 11, a radius of curvature in a front surface 11F of the lens 11 is set small relating to a radius of curvature r2 in a rear surface 11R of the lens 11. Further, the radius of curvature r'1 in the front surface 11F of the lens 11 is successively corrected, in accordance with placed distant from the vicinity of a geometric center 12 of the lens 11 to the outer of a radial direction, and successively set large so that side magnification relating to all the main light beams is made equal to side magnification of a paraxial region. That is, the radius of curvature r'1, after correction, of the front surface 11F of the lens 11 is successively corrected so as to be enlarged as shown by a full line in accordance with placed distant from the geometric center 12 of the lens 11 to the outer of the radial direction, relating to a radius of curvature r1 before correction shown by a virtual line.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-distortion presbyopic lens for short and intermediate distances, which corrects the visual acuity of presbyopia.

0002

2. Description of the Related Art Generally, in the case of presbyopia, where the accommodation power of the crystalline lens in the eyeball is weakened and the near point is far away, it becomes impossible to make the accommodation necessary to see nearby objects. It is a good idea to compensate for the lack of accommodation ability by wearing glasses with convex lenses.

Conventionally, such lenses for presbyopia include:
For example, there was a convex lens having a structure as shown in FIG. That is, this is a lens for presbyopia in which the radius of curvature r(1) of the front surface 50F of the lens 50 is set smaller than the radius of curvature r(2) of the rear surface 50R of the lens 50.

Specifically, if we take a 2 degree (dioptre) lens as an example, r(1)=116.754 mm,
This is a lens for presbyopia in which r(2)=218.667 mm and r(1)<r(2).

In the case of this conventional lens for presbyopia, the lens 5
Since the radii of curvature r(1) and r(2) are both set constant from the geometric center 51 of 0 to the outside in the radial direction, the size of the object and the virtual image viewed through the lens 50 is Since the ratio (lateral magnification) changes depending on the position of the object, distortion occurs, and this phenomenon becomes more pronounced as the power of the lens increases.

In addition, as shown by hatching in FIG. 5, the conventional lens 50 has a narrow clear vision range, for example, 2
For example, in the case of a patient wearing a prescription lens, the corrected near point on the optical axis a is 300 m.
m (the numerical value is the distance from the angle of the eyeball 52), and assuming that the far point of this patient's naked eye is infinite, the corrected far point is 504 mm (focal length of the lens), and the optical axis The angle θ1, θ formed by a and the line of sight direction b of the eyeball
Even if 2 is set to 30 degrees, the periapsis is 300 m.
m, the far point is 504 mm, and there is a problem that the clear vision range is narrow, and this phenomenon becomes more pronounced as the power of the lens increases.

Therefore, when wearing a lens 50 with such a conventional structure, the clear vision range is limited to short distances, and at the same time, the image is deformed due to distortion, making it difficult to obtain comfortable vision. In some cases, there was a problem in that it caused serious eye fatigue.

[0008]

[Problems to be Solved by the Invention] This invention has no distortion aberration, can significantly expand the clear visual field, does not deform the image when worn, provides comfortable vision, and provides long-term vision. The purpose of the present invention is to provide a non-distortion presbyopic lens (hereinafter simply abbreviated as presbyopic lens) for short and intermediate distances that causes less eye fatigue even when worn for a long time.

[0009]

[Means for Solving the Problems] The present invention provides a lens for presbyopia in which the radius of curvature of the front surface of the lens is smaller than the radius of curvature of the rear surface of the lens. A lens for presbyopia is characterized in that the refractive power is sequentially corrected and the refractive power is sequentially set to be small so that the lateral magnification for all principal rays becomes equal to the lateral magnification in the paraxial region.

0010

[Effects of the Invention] According to the present invention, the refractive power of the lens surface is sequentially changed so as to be equal to the lateral magnification in the paraxial region, and this lens surface is created with a unique aspherical structure, thereby reducing distortion. There is no distortion at all, and it is possible to significantly expand the clear visual field, and there is no image deformation when worn, providing comfortable vision and reducing eye fatigue even when worn for a long time.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As an embodiment of the present invention, a case in which the refractive power of the front surface of a lens is corrected will be exemplified, and the embodiment will be described in detail below with reference to the drawings.

The drawing shows a lens for presbyopia, and in FIG. 1, this lens 11 for presbyopia has a radius of curvature of the front surface 11F of the lens 11 set to be smaller than a radius of curvature r2 of the rear surface 11R of the lens 11, and 11 geometric centers 12
As the distance from the vicinity of the lens 11 increases radially outward,
The radius of curvature r'(1) of the front surface 11F of There is.

That is, with respect to the radius of curvature r(1) before correction shown by the virtual line in FIGS. 1 and 2, the front surface 11F of the lens 11 is corrected as it moves away from the geometric center 12 of the lens 11 in the radial direction outward. The later radius of curvature r'(1) is shown in Figures 1 and 3.
As shown by the solid line, the correction is made so that the value becomes larger (r'(1)>r(1)).

The specific structure of the lens 11 for presbyopia of 2 degrees will be described below as an example. Now, as shown in FIG. 1, when the lens 11 is worn, the separation distance E on the optical axis a between the anterior surface of the cornea of the eyeball 13 and the posterior surface 11R of the lens is
'P' is set to 18 mm, and the thickness d(
1) to 3 mm, the distance d(0) on the optical axis a between the lens front surface 11F and the object 14 to 300 mm, and the lens rear surface 1
The radius of curvature r(2) of 1R is 218.667 mm, and the radius of curvature r(1) of the lens front surface 11F on the optical axis a is 1.
The refractive index N′ of air is set to 16.754 mm, respectively.
(0)=1, and the refractive index N'(1) of the transparent acrylic resin lens 11=1.492, when calculating the lateral magnification β in the paraxial region, β=2.44136. In addition, the rear surface 11 of the lens
The distance d(2) between R and the virtual image 15 on the optical axis a is -73
It becomes 1.11mm.

Next, the height of the object 14 y(0)=10mm
When, the height y'(3) of the virtual image 15 is the above-mentioned lateral magnification β
The radius of curvature r'(
1) from r(1)=116.754mm to r'(1)
Corrected to =116.8539962768555mm,
If the height y(3) of the virtual image 15 before correction is configured to be the height y'(3)=24.413 mm after correction, the lateral magnification β=y'(3)/y(0)=2 It becomes .44134.

In other words, as shown in FIG. 2, the horizontal length x(1) and the vertical length y(1) of the coordinates of the intersection of the principal ray and the curved surface before correction are determined by the curved surface after correction. The front surface of the lens 11 is corrected to the horizontal length x'(1) and the vertical length y'(1) of the coordinates of the intersection of
Increase the radius of curvature of F from r(1) to r'(1).

Next, when the height y(0) of the object 14 = 20 mm, the radius of curvature r'( 1
), r'(1)=116.953994750976
If the height of the virtual image 15 is corrected to 6 mm and the height y(3) of the virtual image 15 before the correction becomes the height y'(3)=48.8331 mm after the correction, then the lateral magnification β=y'(3)/y (0)=2.44166.

Next, when the height y(0) of the object 14 = 30 mm, the radius of curvature r'( 1
), r'(1)=117.453987121582
mm and the height y(3) of the virtual image 15 before correction becomes height y'(3)=73.2479 mm after correction, then the lateral magnification β=y'(3)/y (0) =
It becomes 2.4416.

[0019] Hereinafter, the height y(0) of the object 14 is 10 mm.
Since the radius of curvature r'(1) of the lens front surface 11F is increased in the same manner as described above until y(0)=170 mm, only numerical values are shown for convenience of explanation. In this way, the radius of curvature r'(1) of the lens front surface 11F is gradually increased so that the lateral magnification for all principal rays is equal to the lateral magnification β of the paraxial region, and this lens front surface 1
Since the 1F is created to have a unique aspherical structure, it has the effect of completely eliminating distortion, making it possible to construct a distortion-free lens.

In addition, as shown by hatching in FIG. 4, there is an effect that the clear visual field can be greatly expanded. To take the above-mentioned 2 degree lens 11 as an example, the near point on the optical axis a is 300 mm, the far point is 504 mm, and the near point is 30 degrees at the position where the angles θ1 and θ2 between the optical axis a and the principal ray b are set to 30 degrees. The point is approximately 373 mm, and the far point is approximately 780 mm, which significantly expands the clear vision range compared to the conventional lens shown in FIG. This effect becomes more pronounced as the power of the lens increases.

[0021] Therefore, when the lens 11 having the above configuration is worn, there is no image fluctuation (fractuation) due to movement of the eyeballs, and a clear visual range is obtained from the short distance range to the middle distance range, ensuring comfortable vision. It also has the effect of reducing eye fatigue even when worn for a long time.

Furthermore, as mentioned above, by setting the radius of curvature of the lens front surface 11F to be gradually larger (setting the refractive power of the lens to be successively smaller), the amount of protrusion, so-called bulge, of the lens front surface 11F is reduced, and the amount of the bulge is reduced by this amount. Since the thickness of the lens 11 can be made thinner, this reduction in the thickness of the lens has the effect that a brighter field of view can be obtained and the weight of the lens 11 can be reduced.

Note that in the above embodiments, the refractive power of the lens is gradually decreased by increasing the radius of curvature of the front surface of the lens, but the correction is not limited to only the front surface of the lens; It goes without saying that the correction or both the front and rear sides may be corrected.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing a lens for presbyopia of the present invention.

FIG. 2 is an explanatory diagram showing the state of the front surface of the lens before correction.

FIG. 3 is an explanatory diagram showing the state of the front surface of the lens after correction.

FIG. 4 is an explanatory diagram showing the clear vision area of the lens of the present invention.

FIG. 5 is an explanatory diagram showing the clear vision area of a lens with a conventional structure.

[Explanation of symbols]

11... Lens 11F... Lens front surface 11R... Lens rear surface 12... Lens geometric center r(1)... Lens front surface curvature radius r'(1) before correction...
Radius of curvature of the front surface of the lens after correction r'(2)...Radius of curvature of the rear surface of the lens

Claims (1)

[Claims] [Claim 1] In a presbyopic lens in which the radius of curvature of the front surface of the lens is smaller than that of the rear surface of the lens, the geometry of the lens is such that the lateral magnification for all principal rays is always equal to the lateral magnification of the paraxial region. A non-distortion lens for presbyopia in the short and medium distance range, in which the refractive power of the lens surface is corrected sequentially as it moves away from the center in the radial direction.