JPH01221721A - Progressive multi-focus lens - Google Patents

Abstract

PURPOSE:To reduce the astigmatic difference over the whole refracting surface of the title lens and to make the gradient more gentle by not making the curvature of the lens surface monotonous, but providing specific gradients to the curvature. CONSTITUTION:In the area from the intermediate section P to the bottom section of the section for short distance, a curved surface, by which the difference DELTAq between the surface means refracting power Q and the value G obtained by multiplying the square root of the Gaussian curvature by the refractive index (n-1) can satisfy the condition of formula I, is formed on the side of the area, whose astigmatic difference of the surface refracting power is <=0.5Dptr and which can be used as a bright area along the main meridian in the area. Where, DELTAq=Q-G, G=(n-1)sq. rt. K, and K=Gaussian curvature. Moreover, the AD and PB of the formula respectively represent a progressive angle value (Dptr) and the reference mean refractive index (Dptr) at the section of long distance. Therefore, the density of the astigmatic difference of the surface refracting power is lowered and the astigmatic difference gradient becomes more gentle. In addition, deformation and oscillation of the image can be reduced also.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a progressive multifocal lens used as an aid to the accommodation power of the eye.

[Conventional technology]

The upper distance vision correction area (
There are various progressive multifocal lenses that have a lower near vision correction area (hereinafter referred to as a distance vision area), a lower near vision correction area (hereinafter referred to as a near vision area), and a progressive area in which the refractive power changes continuously between the two (hereinafter referred to as an intermediate area). Are known.

In a progressive multifocal lens, generally, if a wide clear vision area is secured between the distance and near vision areas and a progressive zone is connected between them, lens aberrations will be concentrated in the side areas of the progressive zone.
The presence of this area causes image distortion, including blurring of the image, and gives a bad impression to the wearer as it sways when the line of sight moves.

In order to solve such problems in visual characteristics, known progressive multifocal lenses have been designed and evaluated from various viewpoints. Regarding the shape of the lens surface, the line of intersection between the object-side lens surface and the cross section along the meridian that runs perpendicularly to the center of the lens surface or slightly inclined from the perpendicular direction is base 1! It is also used as an important reference line in the design of these lenses. In addition, even in progressive multifocal lenses in which the near vision part is arranged asymmetrically in consideration of the fact that the near vision part is closer to the nose side when the lens is worn, one lens passes vertically through the center of distance vision and the center of near vision. In the present invention, this reference line is referred to as the principal meridian curve.

In conventional progressive multifocal lenses, along the principal meridian curve,
A so-called soft point curve where the entire line is a series of microscopic spherical surfaces, or a surface shape in which the principal radius of curvature in directions orthogonal to each other is different instead of a curvature point in some areas on the principal meridian curve. Regarding the surface shape on the principal meridian curve, two methods have been proposed: one in which the surface shape is dotted along the entire principal meridian curve, and the other in which at least a part of the principal meridian curve is not a dotted point and is shaped like a dot on the principal meridian curve. The radius of curvature in the direction along the curve and the radius of curvature in the direction perpendicular to the curve have different values.

Optica Acta, published in July 1963.
^eta) As described in Vol. 10, No. 3, known as Minkwi's law, there is no soft point along the principal meridian curve, at least in the middle. is necessary. That is, according to Minkwinz's law, if there are points along the entire principal meridian curve, the astigmatism difference in the lens surface refractive power in the direction perpendicular to the principal meridian curve is
The refractive power increases at twice the rate of the surface refractive power along the dotted principal meridian curve, making it difficult to widen the clear vision region.

[Problem to be solved by the invention]

In such conventional technology, even if the visual characteristics of the intermediate part are improved to some extent by setting mutually orthogonal principal curvatures to different values in the intermediate part on the principal meridian curve according to Minkwitz's law, In order to further widen the clear vision range in the distance and near vision areas, there is a limit only from the viewpoint based on Minkwitz's law. Furthermore, in order to reduce the surface astigmatism difference, it is effective to lengthen the surface refractive power change gradually, but in practice, the length of the progressive zone is limited, so even such a measure alone is insufficient. Enough is enough.

In various conventional configurations, it is certainly possible to secure a somewhat wide clear vision range, but the distribution of astigmatism that is inevitable in progressive multifocal lenses, that is, the maximum amount of aberration called astigmatism, It is difficult to obtain excellent visual characteristics across the three regions of distance, intermediate, and near by reducing the gradient of the curve, and it is difficult to obtain excellent visual characteristics across the three regions of distance, intermediate, and near. However, it has been extremely difficult to realize a progressive multifocal lens that is excellent in practical use. Moreover, the methods for improving visual characteristics were a matter of fumbling around, with no clear design methods and no specific standards for evaluating performance.

The object of the present invention is not only to alleviate the aberration density in the aberration concentration area in the side part of the principal meridian curve from the lower part of the distance vision part to the near part, but also to To provide a progressive multifocal lens that reduces image distortion and shaking over the entire area and can be worn comfortably even by a person using this type of lens for the first time.

[Means to solve the problem]

The present invention has a distance portion F in the upper region of the lens, a near portion in the lower region, and an intermediate portion P between them, which refracts distance refractive power from the distance refractive power to the lower region. In a progressive multifocal lens as shown in FIG. 1 having a progressive zone in which the average surface refractive power changes continuously, the relationship between the average refractive power Q of the surface and the Gaussian curvature in the lateral region of the principal meridian curve MM' is By using the value G as a parameter, we have found that lens aberration can be quantitatively understood, and we have established a guideline for designing and evaluating progressive multifocal lenses from this new perspective.

That is, in the region from the intermediate portion P to below the near portion N,
On the sides of the area where the astigmatism difference in surface refractive power that can be used as a clear vision area along the principal meridian curve MM' within the area is within 0°5 Dptr, the surface average refractive power Q and the Gaussian curvature are The difference Δ from the value G obtained by multiplying the square root by the refractive index coefficient (n −1)
q is 500 (PI +1) (3Pl +
4Ao) However, Δq=Q-G G= (n-1) JK, Kni Gaussian curvature AD
: Addition power (Dptr) P6 ; A curved surface that satisfies the condition of the reference average refractive index (Dptr) in the distance portion is formed.

Note that P is a value also called the base curve of a progressive multifocal lens.

[Effect]

Prior to the present invention as described above, the inventors of the present application have conducted intensive research and study on the relationship between the surface shape of a progressive multifocal lens and lens aberrations, and as a result, they have found that the blurring of images that occurs significantly in the lateral regions of the progressive lens. It has been found that unpleasant visual characteristics such as image distortion, image distortion, and shaking when moving the line of sight are mainly affected by the density distribution of lens aberrations. Therefore, in addition to reducing the maximum value of lens aberration, it is possible to improve the visual characteristics of the progressive multifocal lens by reducing its density distribution and gradient as much as possible. .

As mentioned above, the difference Δq between the average refractive power Q of the surface and the value G related to Gaussian curvature has a close relationship with the density distribution of lens aberrations, and by making the surface shape such that this value satisfies the above conditions, It has been discovered that the density distribution and gradient of lens aberration can be made as small as possible.

The above conditional expression will be explained below.

According to the formula of differential geometry, it is known that the principal radius of curvature R of a free-form surface is generally determined by the second root of the following equation. (For example, see "Differential Geometry" by Tominosuke Otsuki, published by Asakura Shoten in September 1960) R" R However, ""'qvvqz□-(qy□)2b""qv
vHz 2 qvzHvz"qzzHvvc =
HyyHz (Hvz) "Differential Geometry First Basic Quantity Differential Geometry Second Basic Quantity QY 52 Here, the X-axis is taken in the optical axis direction, and the Y-axis is taken in the meridian curve direction.

If HH in this equation is respectively l/R,, 1/R□, then 2 R+ Rz 2 aqvyH
zz 2 qyzHyz +Q zzHyv2 C
qvvqzz (Qyz) ” )R+ Ri
a qvvQzz−(qvz)” is obtained.

Here, H is the average curvature and K is the Gaussian curvature.

Then, if the radius of principal curvature at a certain point is r, the surface refractive power P+ in the direction of the radius of principal curvature is P+ = (n-
t)/r+.

Here, when , is expressed in units of meters, the refractive power is expressed in units of diopters (Dptr).

Therefore, the relationship between the curvature and the refractive power of the surface is the refractive power of the surface when the curvature is multiplied by the coefficient of refractive index. Considering the average curvature H and Gaussian curvature, each surface layer refractive power is converted to Q = (n-1) xl ( is the average refractive power Q of the surface, and G = (n-1) Xy 'k can be expressed as the refractive power G of Gaussian curvature.

Therefore, the difference between these Δq=Q-G becomes Δ=Q-G= (n -1)()(-y'K),
The difference between the average curvature and the square root of Gaussian curvature multiplied by the refractive index coefficient is Δq.

These parameters accurately express the distribution of the astigmatism difference in the surface refractive power of the lens, that is, the amount of astigmatism difference and its slope. This provides conditions for the curved surface constituting the lens refractive surface that can reduce the degree of .

If the difference Δq between this average refractive power and the square root of the value determined from the Gaussian curvature increases beyond the upper limit of the above conditions, the astigmatism difference will increase, causing noticeable shaking and distortion, and blurring the range. The degree of blurring also worsens, making the lens difficult to use in practice.

On the other hand, when the value of Δq becomes small, as far as the distribution of astigmatic difference in surface refractive power is concerned, it becomes possible to obtain good visual characteristics with less shaking and distortion. , the length of the intermediate portion becomes longer than necessary, resulting in a lens that is difficult to use in practice. In addition, it is necessary to expand the range of astigmatism distribution to the lateral areas of the distance vision area, which narrows the clear vision area of the distance vision area. It becomes difficult to achieve a lens with a good balance of parts.

In the configuration of the present invention as described above, it is further possible to configure the following conditions to be satisfied within the lens aperture of 50 mmφ with respect to the geometric center of the lens that is effectively used for refractive correction within the eyeglass frame. desirable.

In addition, the astigmatism difference of the surface refractive power can be visually recognized.
It is effective to configure the above-mentioned side regions so that the above-mentioned conditional expressions are satisfied.

〔Example〕

FIG. 2 shows the values of Δq mentioned above for each point in the example of the present invention. This example is a lens with a diameter of 70n++s, and the values were shown at each point at 5IllI1 intervals along the principal meridian curve, and also at 51 intervals in the direction orthogonal to the principal meridian curve.

In this embodiment, since the addition power: An = 2.5 (Dptr), the above condition is 0.00208≦1∆q1≦0.25.

Therefore, looking at each value in this example, the lateral regions of the principal meridian curve MM' (within the thick line in FIG. 2) where the astigmatism difference exceeds 0.5 dayopter as the clear vision region are as above. It can be seen that the surface shape is within the condition range and has an appropriate amount of astigmatism and slope.

By the way, the state of the refractive power distribution along the principal meridian curve in the above embodiment is as shown in FIG. This example is a progressive multifocal lens with an average refractive power (base curve) of 5.0 dayopters in the distance vision part F and an addition power of 2.5 dayopters, so the distance vision center OF is approximately 5.0 dayopters. , the average refractive power at the near center 08 is approximately 7.5 dayopters.

In this embodiment, as shown in FIG. 3, the refractive power distribution curve in the direction along the principal meridian curve is maximum on the intermediate portion P side of the near portion N on the principal meridian curve; It begins to decrease toward the periphery of the near vision area N. Also,
The refractive power distribution is such that the refractive power increases toward the periphery of the distance portion and decreases at the periphery.

FIG. 4 is a diagram showing the isoastigmatism difference curve for the embodiment as described above, and FIG. 5 is a diagram showing an outline of the isastigmatism curve in a conventional progressive multifocal lens for comparison.

Conventional progressive multifocal lenses are not configured to satisfy the above conditions according to the present invention.
As shown in the figure, the density of the astigmatism difference becomes high (the amount of astigmatism difference and the gradient of the astigmatism difference become steep), and as a result, the image distortion becomes large, and when the line of sight moves, the image shakes. In addition, the astigmatism aberration from the intermediate lateral region seeps into the lower lateral region for distance vision, and when the eye is directed to this region, the image is distorted. Not only is the image blurry, but the image is also noticeably distorted and shakes.

In contrast, in this example, as shown in FIG. 4, the density of the astigmatism difference in surface refractive power is reduced, the gradient of the astigmatism difference is also gentle, and image distortion and shaking are reduced. is clear.

Note that the above embodiment is effective even when the surface shape on the principal meridian curve is a knee point over the entire line, and also in a configuration in which at least a part of the surface has a region that is not the origin.

By the way, each point serving as a reference for the progressive multifocal lens in the present invention will be explained.

The center OF for distance vision is a position on the principal meridian curve having a predetermined average surface refraction power in the distance vision area, and is a point that is practically used as a measurement reference point for the distance vision area.

Further, the near vision center ON is a position on the principal meridian curve having a predetermined average surface refractive power in the near vision area, and is a point that is practically used as a measurement reference point for the near vision area.

The distance eye point E is a position that is used as a reference when fitting the lens into the eyeglass frame, and serves as a distance reference point that matches the distance line of sight passing position when the eyeglass frame is worn. The position of such distance eye point (H) is determined independently of the geometric center of the lens, as shown in the average refractive power distribution curve on the principal meridian curve in FIG. Define. That is,
In the addition curve shown in Figure 3, in which the average power of the surface refractive power on the principal meridian curve is plotted for each position on the principal meridian curve, the distance center OF of the distance portion F and the near center OF of the near portion N Parallel to the straight line a connecting the center 08, the addition curve and the distance part F
The distance eyepoint is defined as the intersection point E of the straight line C, which is in contact with the eye on the side, and the straight line C representing the average refractive power at the distance center OF.

〔Effect of the invention〕

According to the present invention as described above, the curvature of the lens surface is not monotonous, but it is possible to provide a gentle power gradient with an allowable power within the above condition range, and it is possible to provide an astigmatic point over the entire refractive surface of the lens. The distance difference can be made small, the maximum value of the astigmatism difference can also be made small, and the gradient thereof can be made gentle. Therefore, the aberration density is not only alleviated in the aberration concentration area on the side part of the principal meridian curve from the distance lower power to the near vision, but also throughout the distance, intermediate, and near vision regions. image distortion,
To provide a progressive multifocal lens that reduces shaking and allows even a person using this type of lens for the first time to wear it without feeling uncomfortable. Moreover, based on the parameters according to the present invention, a design method for improving visual characteristics can be established, albeit only one-dimensionally, and it becomes useful as a standard for specific performance evaluation.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing an outline of the area division of the progressive multifocal lens of the present invention, FIG. 2 is a diagram showing the distribution of Δq as a condition corresponding value in an example of the present invention, and FIG. FIG. 4 is a diagram showing the refractive power distribution in the form of a principal meridian curve in an example. FIG. 4 is an isostitism difference curve diagram for the embodiment according to the present invention. FIG. 5 is a diagram showing an isostitism difference curve for a conventional progressive multifocal lens. It is. [Explanation of symbols of main parts] F...Distance part OF...Distance center P...Intermediate part ON...Near center N...Near part
E...Distance Eye Point Applicant Nippon Kogaku Kogyo Co., Ltd. Agent Patent Attorney Takashi Watanabe Figure 3

Claims (1)

[Claims] 1) The lens has a distance portion F in the upper region, a near portion N in the lower region, and an intermediate portion P between them, which is a distance refractor from the upper region to the lower region. A principal meridian curve M that has a progressive zone in which the average surface refractive power changes continuously from power to near refractive power, and passes through approximately the central portion of the progressive zone in the longitudinal direction approximately at the center of the lens.
M' is a progressive multifocal lens having an astigmatic surface refractive power that can be used as a clear vision area along the principal meridian curve MM' in the area from the intermediate part P to below the near part N. On the side of the region where the distance difference is within 0.5 Dptr, in the side region of the principal meridian curve MM', the surface average refractive power Q,
The difference Δq from the value G obtained by multiplying the square root of the Gaussian curvature by the refractive index coefficient (n-1) is A_D^2/500(P_B+1)≦|Δq|≦A_D
^2/(3P_B+4A_D) However, Δq=Q-PG G=(n-1)√K, K: Gaussian curvature A_D: Addition power (Dptr) P_B: Curved surface that satisfies the condition of the reference average refractive power in the distance part A progressive multifocal lens characterized by having. 2) The lens has a distance portion F in the upper region, a near portion N in the lower region, and an intermediate portion P between them, from the distance refractive power to the near refractive power from the upper region to the lower region. A principal meridian curve M that has a progressive zone in which the average surface refractive power changes continuously, and passes through approximately the central portion of the progressive zone in the longitudinal direction approximately at the center of the lens.
M' is a progressive multifocal lens having an astigmatic surface refractive power that can be used as a clear vision area along the principal meridian curve MM' in the area from the intermediate part P to below the near part N. On the sides of the region where the distance difference is within 0.5 Dptr, the surface average refractive power Q and the refractive index coefficient (
A_D^2/50(P_B+1)≦|Δq|≦2A_D
^2/(3P_B+4A_D) However, Δq=Q-PG G=(n-1)√K, K: Gaussian curvature A_D: Addition power (Dptr) P_B: Satisfies the condition of reference average refractive power in the distance part A progressive multifocal lens characterized by: