JPH0677116B2 - Progressive multifocal lens with negative surface refractive power at the peripheral edge - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a spectacle lens, and more particularly to a progressive multifocal lens having a negative surface refractive power at its peripheral edge.

BACKGROUND ART The progressive multifocal lens referred to here is, as shown in FIG.
Of the two refraction surfaces on the front and back of the spectacle lens, when wearing the spectacle lens, not the eye side but the object (target)
On the generally convex refracting surface that is the side, there is one main meridian M that extends in the center of the refracting surface and in the vertical direction, and the radius of curvature of M along M There is a section on M in which the change of R0, R1, R2 ... R5 progressively decreases from the upper side to the lower side, and as a result, a progressive refractive power change is given to the wearer of the lens. It means all the spectacle lenses that are used.

Generally speaking, the progressive multifocal lens has the main meridian M
The so-called "navel-shaped meridian" with almost zero astigmatism along the line is used as the main meridian M, but the present invention is not limited to this.

Now, progressive multifocal lenses are often evaded in patients who require positive corrective refractive power when looking into the distance. This is an ordinary multifocal lens with the same refractive power (Fig. 2).
This is because the progressive multifocal lens (FIG. 3) requires a thicker center thickness as compared with the above, and as a result, it becomes unsatisfactory in appearance and becomes heavy. There are roughly two types of prior art for compensating for this drawback of the progressive multifocal lens. The first method is to add a prism vertically downward to the lens separately from the prescription value of the patient, as shown in FIG. This is a method of reducing the central wall thickness and weight by removing the portion (Fig. 4, Q) having the prism on the vertically upper side as a result, and the second method is shown in Fig. 5. As in the case of a lenticular lens (retracted lens), the peripheral edge of the refracting surface on the convex side of the lens is made flat (or spherical), and the effective portion of the lens is made small, thereby achieving the purpose of weight reduction. Is the way.

However, in the first method, since the shape on the convex surface side of the lens is not improved, it is less effective for a large spectacle frame or one with a small addition power, and it is simple but incomplete. However, there is a drawback that it can only be improved.

In addition, in the second method, since the boundary line of the effective portion EP is clearly distinguished from the outside, the aesthetics that the boundary line, which is one of the advantages of the progressive multifocal lens, cannot be seen. It will be damaged.

Further, since the prism action of the lens is extremely different between the inside and the outside of this boundary line, there is a defect that a blind spot (invisible visual field portion) occurs as shown in FIG. 5B.

SUMMARY OF THE INVENTION The present invention eliminates all the aforementioned drawbacks, is thin and light,
It is another object of the present invention to provide a more comfortable progressive multifocal lens having no boundary line or blind spot.

DETAILED DESCRIPTION OF THE INVENTION The specific contents of the present invention will be described in detail with reference to the embodiments shown in the drawings. In FIG. 6, S is an embodiment of the "progressive multifocal lens having a negative surface refractive power at the peripheral edge" according to the present invention, and M is the refracting surface on the object side when the lens is worn. Is the central meridian extending vertically and vertically, L is the geometric center axis of the lens, and G is the intersection of L and the refracting surface, which is called the geometric center point.

Now, there are innumerable lines of intersection between the infinite number of planes including L and the refracting surface, but these are called radial sectional curves, and examples thereof are shown in M ′ and M ″.

That is, the geometric center point G is an intersection of the radial cross-section curves (plurality), and in the present embodiment, G is M.
That is the point above.

Now, in these radial cross-section curves, a group of partial curves separated by a radius of about 20 mm or more from the point G constitutes an outer part of a circle having a diameter of 40 mm centering on G on the refraction surface. This is called the peripheral part.

The greatest feature of the present invention is that the value of the radius of curvature along the radial cross-section curve group is negative in the peripheral edge section, at least about 2 mm or more (in the direction along the radial cross-section curve. Length) is to exist.

That is, in FIG. 6, the distribution of the radii of curvature along the main meridian M is R6 to R10 and R11 over a length of at least about 2 mm at a position separated from the center G by a radius of about 20 mm or more. ~ R
As shown in 14, there is a section with a negative radius of curvature (R0 to R5 are positive radii of curvature corresponding to the prescription of the eye), and this also applies to M'and M ".

As is well known, the formula for converting the radius of curvature R into the surface refractive power D is: Where D is the surface refractive power (unit, diopter) R is the radius of curvature (unit is meter) N is the refractive index of the lens material (no unit).

Since N ≧ 1 always, a negative radius of curvature gives a negative surface power.

Now, FIG. 7 shows a sectional view of the progressive multifocal lens according to the present invention obtained in this manner. 3, 4 and 5
As can be seen from the comparison with the figure, it is possible to significantly reduce the central wall thickness, resulting in a lighter weight, and no visible boundary lines and no blind spots. A focusing lens is obtained.

Further, FIG. 8 shows an embodiment of the present invention in which the first method of the above-mentioned conventional techniques is used together. As is clear from FIG. 8, the upper part of the lens is thinner than that in FIG.

It goes without saying that both FIG. 7 and FIG. 8 have the same corrective refractive power as that of FIG.

As described above, it is preferable that the peripheral portion having the negative surface refractive power exists over the entire circumference, that is, in any direction of 360 ° about G, but the present invention is not limited to this. However, as shown by A ₁ ° and A ₂ ° in FIG. 9, the present invention can be applied to the peripheral portion in a total direction of 120 ° or more regardless of whether it is continuous or not. The objective of can be achieved. That is, the object of the present invention can be achieved if a negative surface refracting power is applied to the peripheral portion shown by the hatched lines in FIG.

In the embodiment of the present invention shown in FIG. 6, the main meridian M
It passes through the center G, but this is only one embodiment, and the present invention is not limited to this.

Further, in FIG. 6, negative radius of curvature R6 to R10 and R
I drew it as if the changes in the values of 11 to R14 were continuous,
The values of the radius of curvature do not necessarily have to be continuous, and even if they change discontinuously, the curves are connected smoothly and visually, and as a result, the boundary lines cannot be visually identified. With the continuous change, the object of the present invention is achieved.

[Brief description of drawings]

FIG. 1 is a perspective view showing a conventional progressive-power multifocal lens, FIGS. 2 to 5 are sectional views of the conventional progressive-power multifocal lens, and FIG. 6 is a perspective view showing an embodiment of the present invention. , FIG. 7 and FIG. 8 are sectional views showing other embodiments, respectively, and FIG.
The drawing is a front view showing still another embodiment. M …… Major meridian G …… Geometric center L …… Optical axis B …… Blind spot

Claims (2)

[Claims] 1. One of two refracting surfaces of a lens for spectacles, which is a generally convex convex refracting surface which is the object side when worn, and which extends substantially vertically through the center of the refracting surface. Of the main meridian is present, and there is a section on the main meridian on which the change in the radius of curvature of the main meridian along the main meridian is progressively decreasing from the upper side to the lower side, and as a result, In a so-called progressive multifocal lens which is designed to give a progressive refractive power change to a wearer, an intersection of an infinite number of planes including the geometric center axis of the progressive multifocal lens and the refracting surface. When a line is called a radial section curve and an intersection of the radial section curve and the geometrical center axis is called a geometrical center point, the refracting surface at a radius of about 20 mm or more from the geometrical center point At the peripheral edge of the A radial section curve having at least 2 mm or more in the radial direction in which the radius of curvature of the radial section curve along the radius direction monotonously changes in the radial direction, thereby making the surface refractive power progressively change A progressive multifocal lens having a negative surface refracting power at its peripheral portion, characterized by having: 2. The lens according to claim 1, wherein
A progressive multifocal lens having at least one peripheral portion having the negative surface refractive power and occupying about 1/3 or more of the area of the entire peripheral portion of the progressive multifocal lens.