JPS63313117A - Spectacles lens - Google Patents

Abstract

PURPOSE:To reduce the astigmatism of a sideward visual field by swelling a lens surface smoothly and reducing the swelling downward at a part where a far-sightedness correction area changes into a short-sightedness correction area. CONSTITUTION:A far-sight spectacles lens 1 has a far-sightedness correction area 2 and a short-sightedness correction area 3, which have a common meridian 4, and respective astigmatism contours which encircle the short-sightedness correction area 3 shift in center upward more and more as they are outside and outside and forms convex from the optical center of the short-sightedness correction area 3 toward the outside. The spectacles lens is smaller in the astigmatism in the sideward visual field as compared with a progressive focus lens, and the distortion of an image in the sideward visual field is reduced correspondingly. Further, the astigmatism is varied smoothly at the intermediate part between the far-sightedness correction area 2 and short-sightedness correction area, so the discontinuity of an image of a double focus lens is eliminated and the distortion of the image due to the astigmatism at the intermediate part is a little and causes no problem in practical use.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a spectacle lens, and particularly to a spectacle lens having a distance vision correction region and a near vision correction region.

[Prior Art] Conventionally, bifocal lenses and progressive focus lenses have been known as this type of bifocal am lens.

As is well known, a bifocal lens has a structure in which a lens for correcting distance vision is arranged in the upper field of view and a convex lens for correcting near vision in the lower field of vision. A convex lens portion with a high refractive index called a small bead is joined by fusing or the like.

On the other hand, a progressive focal lens is a single lens whose power changes continuously in the vertical direction, and like the bifocal lens, the upper field of view is for distance vision correction, and the lower field of view is for near vision correction. (for example, JP-A-55-118013
, Japanese Patent Application Laid-Open No. 56-128916), since such a progressive focus lens has a continuous focal point within one lens surface, astigmatism, which causes image distortion, occurs.

Although it is impossible in principle to eliminate this astigmatism over the entire lens surface, it is possible to eliminate it along any arbitrary line on the lens. Therefore, in the conventional progressive focus lens, a line (umbilicus line) where the astigmatism becomes 0 is set in the vertical direction from the upper visual field to the lower visual field.

[Problems to be Solved by the Invention] However, the former bifocal lens has a problem in use that image discontinuity (image jump) occurs because the refractive power changes rapidly at the boundary between the concave lens and the convex lens. It's annoying. Another disadvantage is that the boundary between the concave lens and the convex lens is visually noticeable, resulting in poor appearance.

On the other hand, the latter progressive-focus lenses do not have the problems of image discontinuity and conspicuous boundaries between the lenses that are found in bifocal lenses, but they do not have the problem of image discontinuity or noticeable border between the lenses, but they do The astigmatism becomes thick (the visual field), and the image distortion becomes significant in that area, resulting in noticeable distortion when looking left and right.
It has the disadvantage of causing a feeling of seasickness.

By the way, there is a bifocal lens that blurs the boundary and connects them with narrow concentric curved surfaces called r blend lens j (U.S. Patent No. 2,405,9).
No. 89), this type of lens blurs the boundaries, so
It has the advantage that it is hard to notice that it is a bifocal in appearance, but the curved surface that connects the border has no optical function, so the image jumps occur in the same way as a normal bifocal. .

The present invention solves these conventional drawbacks, and the boundary between the distance vision correction area and the near vision correction area is not noticeable, there is no image discontinuity, and it is more effective than bifocal. The objective is to provide a spectacle lens that has a wide range of clear vision (and has no image distortion in the lateral field of view).

[Means for Solving the Problems] The inventors of the present invention have conducted intensive research to eliminate the drawbacks of the conventional bifocal lenses as described above, and have come to the following conclusion.

With bifocal lenses, the refractive power changes rapidly at the boundary between the concave and convex lenses, resulting in image discontinuity.
If you look at the distance vision correction area and the near vision correction area individually, there is no astigmatism and it is easy to see.On the other hand, with conventional cumulative focus lenses, the navel line is set along the vertical direction of the lens, so it is easy to see. The visible range is wide and it is easy to see in the vertical direction, but astigmatism is imposed on the left and right sides of the lens, making it extremely difficult to see from the side9.Human eyes have the ability to accommodate, so images due to slight astigmatism Although blurring is not a concern, image distortion due to sudden changes in astigmatism causes discomfort to the user and is sometimes dangerous, so it must be avoided.

The spectacle lens according to the present invention obtained based on the above conclusion has both the advantages of conventional bifocal lenses and progressive focal lenses, and its configuration is as follows.

q That is, the present invention provides a spectacle lens having a distance vision correction area and a near vision correction area each formed of a rotationally symmetrical curved surface on at least one of the two lens surfaces constituting the lens. , the distance vision correction area and the near vision correction area are connected by a smooth curved surface, and the direction of principal curvature is on the meridian connecting the optical center of the distance vision correction area and the optical center of the near vision correction area. The average power of It is characterized by being set to less than twice the addition power.

The optical material used in the eyeglass lens according to the present invention may be either optical glass or optical plastic. For example, the optical plastic material may include aliphatic vinyl monomers such as diethylene glycol bisallyl carbonate. is used. In addition, as a preferable material, a polyfunctional organic vinyl monomer containing an aromatic ring and capable of radical polymerization is used, which is an organic compound having a refractive index of 1.50 or higher and capable of forming a crosslinked structure. Examples of such monomers include bisallyl terephthalate, bisallyl isophthalate, triallyl trimellitate, and the like.

The smooth curved surface connecting the distance vision correction area and the near vision correction area is preferably a curved surface with continuity of class 03. Here, the curved surface of class 03 refers to the smoothness of the curved surface. This is Gauss's genus representation expressed analytically (for example, it is described in Fundamental Mathematics Course Vol. 16, "Differential Geometry 1, Kyoritsu Shuppan (first edition 1955), 6.7.86").

The principal curvature direction at each point on the meridian connecting the optical center of the distance vision correction area and the optical center of the near vision correction area is preferably set to the meridian and a direction substantially perpendicular to the meridian. .

In the spectacle lens according to the present invention, the average power in the principal curvature direction on the meridian connecting the optical center of the distance vision correction area and the optical center of the near vision correction area has one extreme value between the two optical centers. Taking the front surface of a spectacle lens as an example, this means that the near vision correction area is raised on the lens surface. This will be explained below with reference to FIG.

FIG. 2 shows a cross section of the lens taken along the meridian in the vertical direction at the center of the lens. In the figure, a solid line A is the lens surface of a single focus lens for correcting distance vision, and this lens surface is approximately spherical. On the other hand, in order to provide a near vision correction area N at the bottom of the lens, conventional progressive-focus lenses gradually increase the curvature at the bottom of the lens (as shown by the dashed line B in the figure) (thus creating a convex lens effect). Therefore, in the near vision correction area N, the gap between curve A and curve B is wide (and this gap is absorbed by the lateral field of the lens, so there is a large astigmatism in that area). Aberrations appear.

On the other hand, in the spectacle lens according to the present invention, as shown by the broken line C in FIG. A convex lens effect is provided by a curve C that gradually approaches curve A as it moves further downward. Therefore, since the gap between the curve C and the curve A in the near vision correction region N becomes smaller, astigmatism in the lateral visual field is reduced accordingly.

Now, if we look at the change in the average power in the principal curvature direction on the meridian connecting the optical center of the distance vision correction area N and the optical center of the near vision correction area N, we can see that the conventional progressive focal lens Since the curvature gradually increases downward from
As shown in FIG. 3(a), the average dioptric power does not have an extreme value. In contrast, the spectacle lens according to the present invention has a portion that transitions from the distance vision correction region to the near vision correction region N. Because the curved surface of the lens is raised, there are places where the positive and negative curvatures are reversed. Therefore, as shown in FIG. 3, in the case of the present invention, the average dioptric power temporarily decreases during the transition from the distance vision correction area to the near vision correction area, and then increases. The frequency has one extreme value.

Furthermore, in the spectacle lens according to the present invention, the isoastigmatism curves on the lens surface form a group of curves surrounding the near vision correction region N. It is preferable that these curve groups have a convex shape outward from the optical center of the near vision correction region N. However, all of the isoastigmatism curves do not necessarily have to be closed curves.

In the group of isoastigmatism curves surrounding the near vision correction area, it is preferable that the center of the group of isoastigmatism curves shift toward the distance vision correction area as the isoastigmatism curves move outward.

By doing this, the distance between the isoastigmatism curves between the distance vision correction area N and the near vision correction area N, which are areas through which the line of sight frequently passes, is widened, and changes in astigmatism are reduced. Since the correction is slow, distortion of the image between the distance vision correction area and the near vision correction area N can be reduced.

Furthermore, in the spectacle lens according to the present invention, in order to reduce astigmatism between the distance vision correction region N and the near vision correction region N, and to make image distortion less noticeable, the lens surface is The maximum value of astigmatism is set to less than twice the addition power. Preferably, the maximum value of astigmatism on the lens surface is set to be less than or equal to the addition power.

Here, the addition power refers to the difference between the power in the distance vision correction area and the power in the near vision correction area N.

An example of the distribution of astigmatism of the spectacle lens according to the present invention configured as described above will be explained in comparison with that of a conventional example.

FIG. 1(a) shows an example of the distribution of the isoastigmatism curve of the spectacle lens according to the present invention, and FIG.
An example of change in astigmatism along line 1-1 is shown.

Figure 1 (@, 1 is a bifocal eyeglass lens, 2 is a distance vision correction area, 3 is a near vision correction area, and 4 is the optical center of the distance vision correction area 2 and the near vision correction area 3. Each meridian connecting the optical center is shown.

In each of the isoastigmatism curves surrounding the near vision correction area 3, the center of each isoastigmatism curve is shifted upward as the outer isoastigmatism curve becomes more convex outward from the optical center of the near vision correction area 3. It has become. In addition, in this example, the addition power +2.0D (
diopter), the maximum value of astigmatism is 1.0D.

On the other hand, Fig. 8 (6), Q)) and Fig. 9 (萄, (c))
1 shows the distribution of the isoastigmatism curve and the change in astigmatism of a conventional eyeglass lens for comparison with the eyeglass lens according to the present invention. In particular, Fig. 8 (a) shows the distribution of the isoastigmatism curve of a conventional bifocal lens, and Fig. 8 (b) shows the change in astigmatism along the line ■-■ in the calf. Fig. 9 shows the distribution of the isoastigmatism curve of a conventional progressive focus lens, and Fig. 9 (c) shows the I-1 distribution of the conventional progressive focus lens.
It shows the variation of astigmatism along the line.

As is clear from a comparison of FIG. 1 with FIGS. 8 and 9, the spectacle lens according to the present invention has smaller astigmatism in the lateral visual field than the conventional progressive focus lens, The distortion of the image in the lateral field of view is that much less (also,
In the intermediate part between the distance vision correction area 2 and the near vision correction area 3,
Because the astigmatism changes smoothly, there is no image discontinuity like in conventional bifocal lenses.Although there is slight image distortion due to astigmatism in the intermediate area, it is difficult for humans to This is not a problem in actual use as the eye gets used to it.

FIG. 1O is a diagram schematically comparing the focal point of the spectacle lens according to the present invention with that of a conventional example.

In the figure, the focal point is indicated by a thick line. That is, the eyeglass lens according to the present invention shown in FIG. Same figure (6)
It is characterized by less lateral distortion than the conventional progressive focus lens shown in .

[Example] Examples of the present invention will be described below.

FIG. 4 shows a distribution diagram of the isoastigmatism curve of the first embodiment, and FIG. 5 shows a distribution diagram of the isastigmatism curve of the second embodiment.

In these figures, the same parts as in FIG. 1 are designated by the same reference numerals.

The addition powers of the II mirror lenses in these examples are both +2.0D, and the maximum value of astigmatism is 1.5D in the first example and 2.0D in the second example. It is set to OD.

In the first embodiment, the group of isoastigmatism curves surrounding the near vision correction region 3 are all closed curves, but in the second embodiment, the outer isastigmatism curves are closed curves.

FIG. 6 shows the distribution of the average power in the principal curvature direction along the meridian connecting the optical center of the distance vision correction area 2 and the optical center of the near vision correction area 3 for the first and second embodiments. are shown respectively. As is clear from this figure, in both Examples, the average diopter value is observed.

FIG. 7 shows the distribution of astigmatism along the meridian connecting the optical center of the distance vision correction area 2 and the optical center of the near vision correction area 3 for the first and second embodiments, respectively. There is. In either embodiment, the astigmatism at each optical center of the distance vision correction area 2 and the near vision correction area 3 is 0.
The astigmatism changes smoothly between the distance vision correction region 2 and the near vision correction region 3 within a range equal to or less than the addition power.

[Effects of the Invention] As is clear from the above description, in the spectacle lens according to the present invention, the distance vision correction region and the near vision correction region are connected by a smooth curved surface, and the optical center of the distance vision correction region is The average dioptric power in the principal curvature direction on the consonant line connecting the optical center of the near vision correction area reaches one extreme value between the two optical centers, and the isoastigmatism curve at that lens surface is the near vision correction area. It forms a group of curves surrounding the visual correction area, and the maximum value of astigmatism is set to less than twice the addition power, so the boundary between the concave and convex lenses is not noticeable like in conventional bifocal lenses, The image does not become discontinuous (it has a clear vision range close to that of a progressive focal point, each focal point is relatively wide, and there is no significant distortion of the image in the lateral field of vision as with conventional progressive focal lenses). This eyeglass lens is very suitable for practical use.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing an example of distribution of the isoastigmatism curve and an example of change in astigmatism of the eyeglass lens of the present invention. FIG. 2 is an explanatory diagram comparing the lens surfaces of the present invention and a conventional example. Figure 3 is a comparative illustration of changes in the average power in the principal curvature direction between the present invention and the conventional example, Figure 4 is a distribution diagram of the isoastigmatism curve of the first embodiment of the present invention, and Figure 5 is the diagram of the present invention. A distribution diagram of the isoastigmatism curve of the second embodiment of the invention, FIG. 6 is an explanatory diagram showing changes in the average power of the first embodiment and the second embodiment, and FIG. 7 is a diagram of the distribution of the isoastigmatism curve of the second embodiment of the invention. FIG. 8 is an explanatory diagram showing the change in astigmatism of the second embodiment; FIG. The figure is an explanatory diagram showing the distribution of the isoastigmatism curve and the change in astigmatism of a conventional progressive focus lens, and Fig. 10 schematically shows the focal portion of the spectacle lens according to the present invention compared to that of the conventional example. This is a comparative diagram. DESCRIPTION OF SYMBOLS 1...Spectacle lens, 2...Distance vision correction area, 3...Near vision correction area, 4...Meridian. Applicant Higashi Shi Co., Ltd. Company Agent Patent Attorney Tsutomu Sugitani @ Soro Doubt Mi C Teihikina (Ko 9 Paralysis? @ Lead Keigo Hito Figure 4 Figure 6 Figure 5 Figure 7

Claims (3)

[Claims] (1) A spectacle lens having a distance vision correction area and a near vision correction area each formed of a rotationally symmetrical curved surface on at least one of the two lens surfaces constituting the lens; The use vision correction area and the near vision correction area are connected by a smooth curved surface, and the average power in the principal curvature direction on the meridian connecting the optical center of the distance vision correction area and the optical center of the near vision correction area is , wait for one extreme value between the two optical centers, and the isoastigmatism curve on the lens surface forms a group of curves surrounding the near vision correction area, and the maximum value of the astigmatism is 2 of the addition power. A spectacle lens characterized by being set to less than twice as much. (2) In claim 1, the smooth curved surface connecting the distance vision correction area and the near vision correction area is C^3
Eyeglass lenses made of curved surfaces. (3) In claim 1, the center of the group of isoastigmatism curves surrounding the near vision correction area shifts toward the distance vision correction area as the isoastigmatism curves move outward. glasses lenses.