JPH08114775A - Lens for correcting presbyopia - Google Patents

Abstract

PURPOSE: To make objects at a distance slightly further from a close distance and at the close distance easily visible and to obtain a broader and brighter visual field by using a lens having a specific lens refraction surface. CONSTITUTION: This lens has a low-diopter center B, near vision center A and high-diopter center C and is provided with a region having a progressively increasing refracting power between the low-diopter center B and the high- diopter center C. The difference in the refracting power between the low-diopter center B and the high-diopter center C is within a range of 0.50 to 4.00D. The lens has the bright viewing area and quasi-bright viewing area respectively defined by the conditions (n-1)×|C1-C2|<=0.5 and (n--1)×|C1-C2|<=0.75 by using the refractive index (n) of the lens blanks and the main curvatures C1, C2 (m<-1> ) in the different directions on the refraction face in this increasing region. The width in the horizontal direction of the bright viewing area in the increasing region is maximized in the position near the geometrical center O of the lens and is nearly constant in the position from the low-diopter center B to the high-diopter center C. The width in the horizontal direction of the quasi-bright viewing region is max. in the position near the geometrical center O.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a presbyopia-correcting lens, and more particularly, to an object at a short distance when deskwork, reading, newspaper reading, etc. are performed indoors by a person who has little accommodation power due to presbyopia. The present invention relates to a presbyopia-correcting lens that is optimal for viewing a wide range of.

[0002]

2. Description of the Related Art Conventionally, in elderly people (for example, people in their late 40s or more), the elasticity of the crystalline lens of the eye is weakened, which reduces the accommodation function when viewing an object at a short distance. As a lens suitable for work mainly
There are lenses such as single focus lenses and progressive multifocal lenses.

A monofocal lens is a lens that compensates for the lack of accommodation power of a patient and focuses on the position of a short distance object to be viewed. This lens has a small aberration (particularly, astigmatism) unless the power is extremely strong, so that a clear visual field can be obtained by using almost the entire surface of the lens. Further, since the convex surface and the concave surface are spherical lenses, there is no non-rotationally symmetric prism effect, so there is no unnatural shaking, but there is distortion, so the object appears distorted. However, the distortion is not limited to presbyopia and is generally the same as the distortion due to the rotationally symmetric prism effect that people with myopia and hyperopia experience when wearing spectacles. There is no.

The basic structure of the progressive multifocal lens is as follows. Generally, the convex surface of a progressive multifocal lens is
It is formed in an aspherical shape having partially different surface refracting powers, and has a function of giving a refracting power of a lens suitable for seeing a distant object to the hand. The concave surface is formed into a spherical surface or a toric surface shape, and functions to correct myopia, hyperopia, astigmatism, etc. according to the prescription of each eye of the eyeglass user.

The structure of the convex surface, which is a feature of the progressive power multifocal lens, will be described in more detail. As shown in FIG. 18A, the surface (refractive surface) thereof has a distance portion F, an intermediate portion M, and a near portion M. Each part region N is provided. The distance portion area F is an area having a refractive power suitable for viewing an object at a distance of more than about 1 m to 2 m (hereinafter referred to as distance vision). The middle region M is 50 cm to 1 m to 2 m
When looking at a medium-distance object (hereinafter referred to as intermediate vision), the near portion area N has a refractive power suitable for viewing a near-distance object before approximately 50 cm (hereinafter referred to as near vision). Is.

A central reference line S is provided so as to extend in the vertical direction substantially at the center of the lens surface, and the lens refracting surface is divided into right and left. The central reference line S is a line in which the astigmatism is almost equal to zero from the upper side to the lower side, and the refracting power progressively changes, and brings about the basic function of the progressive multifocal lens. As shown in FIG. 18A, the central reference line S may be called a “main meridian” when it is divided symmetrically, and a “main gaze line” otherwise.

The point A existing on the central reference line S is generally called the distance center and is located near the geometric center of this lens. Further, the point B existing on the central reference line S below the point A is called the near center. Therefore, point A
The upper part can be considered as the distance portion region F, the lower part than the point B can be considered as the near portion region N, and the portion between them can be considered as the intermediate portion region M. These regions F, M, N are generally adopted because they are effective in considering the structure of the lens, and the refracting power changes continuously on the refracting surface of the lens. However, the areas F, M, and N cannot be clearly divided.

FIG. 18B shows a change in the refractive power on the central reference line S. As shown in this figure, the refracting power (unit is diopter: D) progressively increases from the point A to the point B, and the refracting powers D1 and B in the distance portion region F above the point A are pointed. Refractive power D2 in the near portion area N below
Is almost constant. The difference between the refracting powers D2 and D1 is called the addition, which is usually added within the range of 0.5 diopter (hereinafter referred to as D) to 3.5D.

Here, the refracting power of the convex surface of the lens, that is, the surface refracting power will be described. The surface refractive power has the following relationship with the curvature of the convex surface. S = (n-1) * C (diopter) Note that S: surface refractive power (unit: D), n: refractive index of the lens material, C: curvature (unit: m- ¹ ). In this formula, since the refractive index n is constant, the curvature and the surface refractive power are in a proportional relationship. Therefore, FIG. 18B can be regarded as a change in the curvature of the central reference line S. Since the curvature changes in the central reference line S provided in the approximate center of the lens in this way, the convex surface of the progressive power multifocal lens has an aspherical shape from the distance portion area F to the near portion area N. There is. In the aspherical shape, the curvature at one point on the convex surface varies depending on the direction, and according to the difference between the maximum value C1 and the minimum value C2 (these are called the main curvature) of the curvature at that point, A difference in the surface power as expressed by the formula is generated at a point on the lens surface.

(N-1) × | C1−C2 | (Diopter) This appears as astigmatism in the optical performance of the lens. Hereinafter, astigmatism means the difference in surface refractive power, and diopter (D). Is used as a unit. Since the progressive power multifocal lens has a smooth curved surface at the portions having different refracting powers as described above, the progressive multifocal lens must take an aspherical shape, which causes astigmatism in the lens.

FIG. 19 shows the distribution of astigmatism in the conventional progressive multifocal lens corresponding to FIG. 18 (a). In this figure, astigmatism is shown in the same way as the contour lines on the map, with isoastigmatism lines of 0.50D to 1.00D from the center side of the lens at intervals of 0.25D. In general,
It is 0.5D that a person perceives astigmatism and feels the image blur.
That is all. Therefore, astigmatism becomes large in the region with the narrowest hatching pitch in the figure, that is, in the lateral parts of the lens, especially in the lateral parts of the intermediate and near vision regions, and the object cannot be viewed correctly due to the blurred image. It will be. Further, since the image is distorted by this astigmatism, it is perceived as a displacement of the image when the head is moved, which gives discomfort during use. On the other hand, the portion where the astigmatism is 0.5 D or less (white portion in the figure) is empirically called, because the object can be visually seen without feeling blurring, and is therefore called the clear viewing zone. The clear viewing area in the middle area is generally called a progressive area. It should be noted that this clear viewing area can be accurately expressed as the shape of the lens refracting surface by the following equation.

(N-1) × | C1−C2 | ≦ 0.5 (diopter) where n is the refractive index of the lens material, and C1 and C2 are different directions at arbitrary points on the lens refracting surface within the clear vision region. Is the principal curvature (unit is m ⁻¹ ).

As described above, it is preferable that there is no astigmatism, but it is impossible to eliminate astigmatism due to the basic structure of the progressive power multifocal lens. That is, for example, even if the distance portion area and the near portion area are formed as perfect spherical surfaces to eliminate astigmatism in that portion, an intermediate portion that smoothly connects the distance portion area and the near portion area having different curvatures The area is forced to undergo a sudden change in shape. As a result, large astigmatism occurs in the intermediate area. On the contrary, if the clear vision area of the distance portion area and the near portion area is narrowed and the astigmatism is diffused to the side, the astigmatism in the middle portion area is reduced and the visual field in that area is reduced. It is wide and the image blur is reduced, but far vision and near vision are impaired. Therefore, in designing a progressive multifocal lens, it is necessary to minimize the adverse effects of astigmatism on the intended use of the wearer.

[0014]

In the above-mentioned monofocal lens, since the shortage of accommodation power of the patient is simply compensated for, the visible distance is limited, and for example, near 50 cm. There is a problem that an object at a distance and an object at a short distance of 25 cm cannot be seen at once.
Therefore, in order to see an object, for example, closer than a predetermined short distance with this lens, a certain amount of adjustment power is required. For example, 25 cm with a lens that can see a distance of 50 cm
If you try to see objects at a short distance, the required adjustment force is 2D
Is. That is, 2 to see an object at a distance of 50 cm.
To see an object at a distance of D (1 / 0.5 m), 25 cm, a refractive power of 4 D (1 / 0.25 m) is required. Therefore, an adjustment force of 4D-2D = 2D is required. For this reason, people who have little adjustment power used the single-focus lens to move their heads to adjust the distance to look over a desk or read a newspaper that was unfolded.

In terms of age, a person in his or her 40's to early 50's whose accommodation power has deteriorated slightly has a slight margin of accommodation power even when using a monofocal presbyopia, and therefore sees a certain distance range. be able to. However, for example, there is a problem in that all the accommodation power that can be possessed is used to look all over the desk, and eye strain is felt due to long-term visual work.

It is inevitable to look closer than the short distance (near point) that can be seen. For example, when reading a vertical Japanese sentence written in a normal-sized book, the distance from the eye changes about 10 cm between the upper and lower parts of the sentence. Therefore, if you make eyeglasses with the power to look at the near point that is suitable for natural reading, it is actually unsuitable for reading, especially if you look at the entire surface of a large object such as a newspaper or your own body. It's also unsuitable for overlooking the entire desk, which extends all the way up to the chest.

In a general monofocal presbyopia, 30 cm to 5 cm
The power is prescribed so that objects at a distance of 0 cm can be seen clearly. Since the range of the viewing distance is limited for people who have little accommodation power, the present situation is that they wear lenses with a prescription such that the distance is 30 cm or 40 cm, which is suitable for individual reading. .

When a book or desk is viewed with a monofocal lens, the visible range is an ellipse that is long in the horizontal direction when viewed from the wearer. This is because the width of the clear vision range in the vertical direction (front-back direction) is narrower because the range of visible distance is narrower, and the width of the clear view range in the horizontal direction (left-right direction) is smaller than that in the vertical direction. This is because it is small and wide. The narrow width of the vertical clear range is not only inconvenient for reading and writing vertically written text, but it is also necessary to cover the narrow vertical field of view during deskwork. There is the inconvenience of having to move it back and forth. Moving the head back and forth to move the line of sight is more painful and unnatural than rotating the neck and shaking the head left and right.

In the progressive multifocal lens described above, even a person who has little accommodation power can see a certain distance range. However, since the clear vision area is extremely narrower than that of a single-focus lens, the visible range is limited. In a general progressive multifocal lens, the width W1 of the clear vision region in the distance portion region F is wide, but the width W3 of the clear vision region in the near portion region N is narrow. Further, the width W2 of the clear viewing area (progressive portion) of the intermediate area M is extremely narrow as compared with the widths W1 and W3. Therefore, there is a problem that a wide and clear visual field cannot be obtained when an object at a short distance is viewed in the near portion area N.

In the middle area M, an object at a distance farther than that at a short distance can be seen. However, since the width W2 of the clear viewing zone is narrow, especially when the addition power exceeds 2.50D, It was as if I was looking through the gap between, and it was difficult to see in the middle. In order to see an object at a distance closer than that at a near distance in the near portion area N, an area having a strength number higher than the near dioptric power may be provided at the lower portion of the area N, but it is too low and extremely low. Difficult to use. Also, if you still have control,
It is easy to cause eye strain because you will see the object in the area of the strength number by using the adjustment power to the maximum.

Further, the progressive power multifocal lens has a characteristic that should be explained by the concept of a quasi-clear vision zone in addition to the clear vision zone.
Research has revealed. The quasi-clear vision region can be accurately expressed as the shape of the lens refracting surface by the following equation.

(N-1) × | C1−C2 | ≦ 0.75 (diopter) where n is the refractive index of the lens material, and C1 and C2 are different directions at arbitrary points on the lens refracting surface within the clear vision region. Is the principal curvature (unit is m ⁻¹ ).

When looking at an object with the progressive power multifocal lens, not only the clear vision area but also the area outside the clear vision area is unconsciously used. Therefore, it is desirable that the astigmatism is as small as possible even in a region other than the clear vision region. That is,
It is desirable to secure a wide area around the clear vision area such that a value exceeding astigmatism 0.5D is as small as possible.

If the lens has a wide quasi-clear vision region, it will no longer unknowingly see an object in an area having a larger astigmatism outside the quasi-clear vision region. A wide field of view with little distortion can be obtained.

This quasi-clear viewing region is (n-1) × | C1-
It can be defined as C2 | ≤1.00 (diopter), but it is desirable that the quasi-clear vision region is 0.75D or less in order to obtain a clear visual field with less distortion.

In the conventional progressive-power multifocal lens, in the quasi-clear vision area, the widths of the distance portion area F and the near portion area N are wide, and the width of the intermediate portion area M is narrow, as in the clear vision area. . This is because the distance vision and the near vision are emphasized, and the intermediate vision is sacrificed. Therefore, when an eye point (not shown) provided in the vicinity of the distance center A is set as a normal line-of-sight position, a region with large astigmatism is arranged in the vicinity of the eye point, and a visual field with little distortion is obtained. It is getting narrower.

The present invention has been made in order to solve the above-mentioned problems, and its purpose is to use objects at a short distance such as desk work and reading, which are extremely rarely used when seeing objects at long and medium distances. This is ideal for performing visual work, in which not only a person without accommodation can see an object at a predetermined short distance, but also an object at a distance or a distance slightly closer than that short distance. The object of the present invention is to provide a presbyopia-correcting lens capable of obtaining a wide and clear visual field when viewing an object at a short distance.

[0028]

In order to achieve the above object, the invention according to claim 1 is characterized in that, in at least one lens refraction surface of two refraction surfaces constituting a lens, a vertical direction of the lens refraction surface. A central reference line that extends so as to minimize the astigmatism and divides the refracting surface into left and right, a near center provided on the central reference line, and on the central reference line and more than the near center. A weakness center that is provided above and provides a weaker refractive power than the near center, and is provided on the central reference line and below the near center, and is less than the near center refractive power. Is provided between the intensity center that gives a strong refractive power and the weakness center and the intensity center, and a predetermined refractive power progresses from the weakness center to the intensity center through the near vision center. And a region that increases Difference in refractive power between the degrees center and the intensity center is in the range of 0.50D～4.00D, in the incremental region, n: the lens refractive index of the material, C1, C
2: Using the principal curvatures in different directions (units are m ⁻¹ ) at points on the lens refracting surface, the following expression, (n−1) × | C 1 −C 2 | ≦ 0.5 (m ⁻¹ ) And a quasi-clear vision region defined by the following equation: (n-1) × | C1 −C2 | ≦ 0.75 (m ⁻¹ ) The horizontal width of the clear viewing area becomes maximum at a position near the geometric center of the lens, or is substantially constant from the weakness center to the intensity center through the near vision center, The gist is that the width in the horizontal direction of the quasi-clear viewing region in the increasing region is maximum at a position near the geometric center.

A second aspect of the present invention is based on the lens of the first aspect, wherein the near center is located within 2 mm to 15 mm below the geometric center of the lens.

The invention according to claim 3 is the invention according to claim 1 or 2.
The gist of the lens described in (1) is that the lens has a wearing point located within 15 mm above the near center. The invention according to claim 4 is the lens according to any one of claims 1 to 3, wherein a length in a vertical direction in the increasing region is 20 mm or more, and the weakness center and the strength center. The difference in refractive power between
The gist is that it is within the range of 2.00D.

According to a fifth aspect of the present invention, in the lens according to any one of the first to third aspects, the vertical length in the increasing region is 14 mm or more and less than 25 mm, and the weakness center is The difference in the refractive power between the center of intensity and the center of intensity is in the range of 0.50D to 1.50D.

According to a sixth aspect of the present invention, in the presbyopia-correcting lens according to any one of the first to fifth aspects, an area above the geometric center passes through the geometric center and the center reference. Assuming a plane perpendicular to the line, the first intersection line between the plane parallel to the plane and the refraction surface is a non-circular curve whose curvature increases as it moves away from the intersection of the central reference line in the horizontal direction, In a region lower than the geometric center, a plane that passes through the geometric center and is perpendicular to the central reference line is assumed, and the second intersection line between the plane parallel to the plane and the refracting surface is the central reference line. A non-circular curve whose curvature decreases as it moves away from the intersection of the lines in the horizontal direction,
Assuming a horizontal line passing near the geometric center, the distance from the horizontal line in the upper region and the lower region is equal, and the distance from the central reference line in the upper region and the lower region is equal. The increase rate of the curvature of the first intersection line passing through any two points, and the second
The gist is that the rate of decrease of the curvature of the intersecting line is almost equal.

According to the first aspect of the present invention, in the increasing region above the near vision center, the refractive power gradually decreases from the near vision center toward the weakness center.
It is possible to easily see an object from a predetermined short distance that can be seen at the near center to a distance slightly longer than the short distance. In addition, in the increasing region below the near vision center, the refractive power gradually increases from the near vision center toward the strength center, so that the distance from the predetermined near distance to a distance slightly shorter than the near distance. It is possible to easily see without adjusting the object. Therefore, in an increase area above and below the center of near vision, a person who has little accommodation to adjust his / her head, for example, can look over the entire desk or read an unfolded newspaper over the entire surface without moving his / her head back and forth. It becomes possible to perform such visual work.

The difference in refractive power between the center of weakness and the center of intensity is set to 0.50D to 4.00D for the following reason. When the refracting power becomes smaller than 0.50D, not only a predetermined short distance but also a far distance and a near distance that can be overlooked are almost the same as the above-mentioned predetermined short distance, and a single focus lens is used. It will be almost the same. When the refracting power is larger than 4.00 D, the difference in refracting power from the weakness center to the strength center becomes too large, which is difficult for the user to use.

For example, the refractive power of the near center is 2.50D.
In the case of (diopter), even a person with normal vision who has little accommodation power is 40 cm (1 / 2.5
0 = 0.4m, distance is calculated by the same calculation below)
You can see objects at a close distance. Here, if the difference in refractive power is set to 0.50D, an object at a distance of about 44 cm can be seen in the weakness center and its vicinity, and an object at a distance of about 36 cm can be seen in the strength center and its vicinity. You can see. Also, if the difference in refractive power is 4.00D, an object at a distance of about 2 m can be seen in the weakness center and its vicinity, and an object at a distance of about 22 cm can be seen in the strength center and its vicinity. be able to.

Further, the horizontal width of the quasi-clear viewing zone is maximized near the geometric center of the lens, so that astigmatism is diffused to the left and right of the upper part of the lens and the left and right of the lower part of the lens. As a result, lateral astigmatism in the vicinity of the geometric center is reduced, so that a wide and clear visual field can be obtained in the central portion of the lens near the geometric center that is relatively frequently used as a presbyopia-correcting lens.

According to the second aspect of the present invention, since the near vision center is located within 2 mm to 15 mm below the geometric center of the lens, an arbitrary point near the near vision center and the near vision center In between, the wearer can move his / her eyes in the vertical direction without burden and can see an object from a short distance to a distance slightly longer than the short distance.

According to the third aspect of the present invention, the wear point is arranged within 15 mm above the near wear center, so that the wearer can move his / her eyes vertically without burden between the wear point and the near wear center. It becomes possible.

According to the fourth aspect of the invention, the vertical length in the increasing region is set to 20 mm or more, so that the refractive power between the weakness center and the intensity center on the central reference line of the increasing region is increased. The gradient is relatively small, and the generated aberration is small. In particular, by setting the difference in the refracting power in the increasing region to be 1.00D to 2.00D, the gradient of the refracting power is not tight and the aberrations (astigmatism and distortion) that occur are reduced. Therefore, the clear vision region and the quasi-clear vision region are widened, and the fluctuation or distortion of the image is reduced when the line of sight is moved between the weakness center and the intensity center.

For example, assume that the refractive power at the near center is 2.50D and the short distance visible at the near center is about 40 cm. If the difference in refractive power is set to 1.00D, an object at a distance of about 50 cm can be seen in the weakness center and its vicinity, and an object at a distance of about 33 cm can be seen in the strength center and its vicinity. it can. If the difference in refractive power is set to 2.00 D, an object at a distance of about 67 cm can be seen in the weakness center and its vicinity, and an object at a distance of about 29 cm can be seen in the strength center and its vicinity. be able to.

According to the fifth aspect of the present invention, even if the length in the vertical direction in the increasing region is 14 mm or more and less than 25 mm, the difference in refractive power is set to 0.50D to 1.50D. It is possible to obtain a lens in which the force gradient does not increase and the image does not shake or distort.

For example, when the near power is set to 2.50D and the near distance visible at the near center is set to 40 cm, and the difference in refractive power is set to 0.50D, the action of the above-mentioned claim 1 is achieved. Similar to the example in, the object at a distance of 36 to 44 cm can be seen. Refractive power difference 1.50D
With this, an object at a distance of about 57 cm can be seen in the weakness center and its vicinity, and an object at a distance of about 31 cm can be seen in the strength center and its vicinity.

According to the sixth aspect of the present invention, in the region above the geometric center, the refracting power of the horizontal section increases as the distance from the center reference line increases in the horizontal direction, and in the region below the geometric center, the center reference line increases. As the distance from the line increases in the horizontal direction, the refractive power of the horizontal section decreases. This increase or decrease in refractive power reduces the difference in power between the upper and lower regions. As a result, the connection of the surface from the upper region to the lower region is smooth, the concentration of astigmatism and distortion on the side of the geometric center is reduced, and the lateral vision near the geometric center is improved.

In the upper region and the lower region, a horizontal line passing through the geometric center is assumed, and an increasing rate of the first curvature and an decreasing rate of the second curvature passing through arbitrary two points vertically symmetrical with respect to the horizontal line. As a result, the curvature in the horizontal direction of the lens changes symmetrically with respect to the horizontal line passing through the geometric center. As a result, astigmatism is suppressed to be small in the area near the center of the lens that is most frequently used, and the astigmatism is dispersed in the left and right areas of the upper and lower portions of the lens that are least frequently used.

Further, in the lower region, the refracting power of the horizontal section decreases as the distance from the central reference line increases in the horizontal direction. Therefore, it becomes convenient when, for example, the side surface of the desk or the front side of the newspaper is viewed in the area near the strength center. This is because the distance when looking at the front side surface on a desk or the like is larger than the distance when looking at the front side. According to the present invention, the distance that can be viewed laterally is increased due to the decrease in the above-mentioned refractive power, and it is possible to relatively clearly see the side surface located at a distance slightly farther than the distance when the front is viewed from the vicinity of the intensity center. It will be possible.

[0046]

BEST MODE FOR CARRYING OUT THE INVENTION

(First Embodiment) A first embodiment of the present invention will be described below with reference to FIGS.

As shown in FIG. 1A, a central reference line S is provided on the lens refracting surface 2 on the convex side of a presbyopia-correcting lens (hereinafter, simply referred to as a lens) 1 so as to extend in the vertical direction. ing. A near center A is provided 2 mm below the geometric center O of the lens 1 on the central reference line S. The geometric center O does not have to be on the central reference line S.
A weakness center B is provided 13 mm above the geometric center O on the central reference line S. 17 mm below the geometric center O on the central reference line S, the strength center C
Is provided.

As shown in FIG. 2, a weakness region 3 is provided above the weakness center B of the lens refracting surface 2.
An intensity region 4 is provided below the intensity center C of the lens refracting surface 2. An intermediate region 5 is provided between the weakness region 3 and the strength region 4 of the lens refracting surface 2.
The lens 1 has a diameter of 50 mm.

The central reference line S is a line (so-called navel curve) where the astigmatism is the smallest and becomes almost zero. Even if a line is a virtual line, the line cannot be visually confirmed.

The near vision center A corrects the presbyopia of a person who is presbyopia, which is neither hyperopia nor nearsightedness, and corrects the presbyopia (2 in this case). ．
50D: diopter). In this embodiment, since the refractive power is 2.50D, the short distance (near point) suitable for viewing is 40 cm. Where 40c
The distance of m is based on the calculation 1 / 2.50D = 0.40 (m). The weakness center B has a weaker refractive power (1.75D in this case) than the near power A, and the weakness region 3 has almost the same refractive power as the weak refractive power. . Therefore, in the weakness center B and the weakness region 3,
It is possible to see objects that are a little farther than the near point. In this embodiment, since the refractive power is 1.75D, the distant visible distance is 57 cm. Here, 57 cm is 1 / 1.75D = 0.57.
It is based on the calculation of (m).

The intensity center C has a refractive power stronger than that of the near vision center A (3.25 D in this case), and the intensity region 4 has a refractive power almost the same as that of the near power center A. There is.
Therefore, in the intensity center C and the intensity region 4, it is possible for a person without accommodation to see an object at a distance slightly closer than the near point. In this embodiment, since the refractive power is 3.25D, the visible distance is 31 cm. Here, 31 cm is 1 / 3.25D = 0.3
It is based on the calculation of 1 (m).

The intermediate region 5 is a region in which a predetermined refractive power is progressively increased from the weakness center B to the strength center C via the near vision center A. As shown in FIG. 1B, in the intermediate region 5, in the present embodiment, the difference in refractive power between the weakness center B and the intensity center C is 1.50D, and in the intermediate region 5, The 1.50D refractive power (the degree of change within the lens)
Is increasing progressively. Therefore, in the middle region 5,
The frequency varies from a weak frequency of 1.75D to an intensity frequency of 3.25D. Here, the power means a refractive power (lens power) obtained by combining the refractive power of the convex surface of the lens 1 and the refractive power of the concave surface of the lens 1. The intermediate region 5 has a progressive portion 6 in the region including the central reference line S, which is a clear visual region with an astigmatism of 0.50D or less. The gradient of the refractive power in the progressive portion 6 can be represented by the changing power and the length of the progressive portion 6, and in the present embodiment, the gradient = 1.50D / 30 m.
m = 0.05 (D / mm).

Next, the power distribution of the lens 1 will be described. As shown in FIG. 3, the frequency distribution is represented by an equal frequency curve connecting points of equal magnitude. Middle area 5
In the horizontal direction of, the power of 2.50D is represented by a substantially straight isocurve curve 101 passing through the near vision center A. 2.25 in the intermediate region 5 above the iso-power curve 101.
The frequency of D is the constant-frequency curve 102, and 2.00 is further above.
The frequency of D is represented by a constant frequency curve 103. In the weakness region 3, a frequency of 1.75D is represented by a constant power curve 104 passing through the weakness center B.

In the intermediate region 5 below the iso-power curve 101, a frequency of 2.75D is represented by a power curve 105, and further below is represented by a power curve 106. In the intensity region 4, the frequency of 3.25D is the intensity center C.
It is represented by a constant power curve 107 passing through. Each iso-power curve 101-107 is actually invisible.

In the intermediate region 5 and the weakness region 3 above the iso-power curve 101, the iso-power curves 102-104.
Has a shape that is curved upward and then downward as it is separated from the center reference line S by about 15 mm in both left and right directions. That is, the frequency increases as it moves away from the central reference line S, and then decreases.

In the intermediate region 5 below the iso-power curve 101, the iso-power curves 105-107 are curved downward as they are separated from the central reference line S by about 15 mm in both left and right directions, and then are curved upward. ing. That is, the frequency decreases and then increases as the distance from the central reference line S increases. And the iso-frequency curve 1
02-104 and the iso-power curves 105-107 are substantially vertically symmetric, and the change in the frequency from increase to decrease in the regions 5 and 3 above the iso-power curve 101,
The manner in which the frequencies in the lower regions 5 and 4 change from decrease to increase is symmetrical in the vertical direction.

Further, in the progressive portion 6, each iso-power curve 1 is separated from the central reference line S by about 10 mm in both left and right directions.
The curve of 02 to 106 is gentle and 10 mm
Compared to the above areas, the change in the frequency is small and the area has a relatively stable frequency. Therefore, in the middle area 5, especially in the area of the progressive portion 6, the
It is possible to satisfactorily view an object at a distance between the visual distance of 7 cm and the visual distance of 31 cm at the intensity center C.

As shown in FIGS. 1A and 2, at a position 2 mm above the geometric center O and displaced by 2 mm from the geometric center O to the ear side of the lens 1 (right side of the lens in FIG. 1), The wearing point P is set. The wearing point P may be arranged at the same height as the geometric center O. When viewed from the wearing point P, the near-center A is located 4 mm below the wearing point P and 2 mm on the nose side. The wearing point P is a point through which the line of sight when looking at a distance from the front passes when the lens 1 is worn in a spectacle frame. In the present embodiment, by disposing the wearing point P on the ear side, the entire lens moves to the nose side during wearing, and it is possible to cope with eye convergence when viewing an object at a short distance from the near center A. You can do it.

Next, the clear viewing area and the quasi-clear viewing area in the weakness area 3, the strength area 4, and the intermediate area 5 will be described. The clear vision region and the quasi-clear vision region are defined according to the following equations (1) and (2), respectively.

Clear visual field (n-1) × | C1−C2 | ≦ 0.50 (m− ¹ ) (1) Quasi-clear visual field (n−1) × | C1−C2 | ≦ 0. 75 (m ^-1 ) ... (2) n: Refractive index of lens material, C1, C2: Principal curvatures in different directions at points on the lens refracting surface (unit is m ^-1 ) A region with a point aberration of 0.5 D or less is a clear vision region, and a region with an astigmatism of 0.75 D or less is a quasi-clear vision region according to the above formula (2).

Further, as shown in FIG. 1A, the lens refracting surface 2 has a magnitude of astigmatism in the unit of diopter,
These are represented by iso-astigmatism curves AS1 to AS3 of 0.25D, 0.50D and 0.75D, respectively. The area surrounded by the isoastigmatism curve AS2 is the clear vision area, and the area surrounded by the isoastigmatism curve AS3 is the quasi-clear vision area. These isoastigmatism curves AS1 to AS3 are actually invisible to the eye.

The width of the progressive portion 6 in the horizontal direction is approximately 12 mm, which is substantially constant. Strictly speaking, the progressive portion 6 has a geometric center O
It has a maximum width of 12 mm at a position 2 mm below and a minimum width of 11 mm at the positions of the weakness center A and the strength center C. Therefore, the maximum width is 1.1 times the minimum width.

The quasi-clear viewing zone of the intermediate area 5 is 40 m at the position of the geometric center O (in this case, 2 mm above the near center A).
has a maximum width W _max in the horizontal direction of m, and the center of weakness A
And a minimum width W of 20 mm in the horizontal direction at the position of the strength center C
have _min . Therefore, the maximum width W _max is the minimum width W
It is 2.0 times longer than _min .

Next, the refractive power distribution of the lens refracting surface 2 which brings about the above-described dioptric power, the clear vision region and the quasi-clear vision region will be described. As shown in FIG. 4, although not shown, a plane that passes through the geometric center O and is perpendicular to the central reference line S is assumed, and a plurality of planes (hereinafter, referred to as horizontal sections) parallel to the plane and the lens refracting surface. Lines L1 to L8 of intersection with 2 are assumed.
In this embodiment, the refractive power ((n-1) /
R (D: diopter), n: refractive index of lens material,
R: radius of curvature) is used.

The intersection line L1 passes through the weakness center A 15 mm above the near vision center A. The intersection line L2 is 1 more than the near center A
It passes through the intersection E1 of the central reference line S on 0 mm. Intersection line L3
Is the intersection E of the central reference line S 5 mm above the near center A
Go through 2. The line of intersection L4 passes through the near vision center A.

The intersection line L5 passes through the intersection point E3 of the central reference line S 5 mm below the near vision center A. The intersection line L6 passes through the intersection E4 of the central reference line S 10 mm below the near vision center A.
The intersection line L7 is the strength center C 15 mm below the near center A
Pass through. The intersection line L8 passes through the intersection point E5 of the central reference line S 20 mm below the near vision center A.

As shown in FIG. 5A, the intersection lines L1 to L4
Is the refracting power as it moves away from the near center A, the intersections E1, E2 and the weakness center B by about 15 mm in the horizontal direction, that is, the refracting power of the horizontal section (hereinafter referred to as the horizontal refracting power)
Has a non-circular curve that increases and then decreases.

The intersection lines L5 to L8 are non-circular curves in which the horizontal refracting power decreases as the distance from the intersection points E3 to E5 and the intensity center C increases by about 15 mm in the horizontal direction, and increases again. Since the increase and decrease of the refractive power are symmetrical, only the right side is shown.

Next, though not shown in the drawing, the geometrical center O is passed,
Further, assuming a plane perpendicular to the central reference line S, a line of intersection between the plane and the refracting surface (hereinafter referred to as a progressive surface) in the intermediate region 5 is a horizontal reference line, and a plane perpendicular to the horizontal reference line (hereinafter , Vertical section) and the refracting surface 2 intersecting line (not shown)
Suppose This line of intersection is a line that intersects with each of the lines of intersection L1 to L8.

As shown in FIG. 5B, the intersection lines L1 to L
At the intersection of 8 and an intersection line (not shown), the refractive power of the vertical section (hereinafter referred to as vertical refractive power) is the near center A and the intersection E.
1 to E4, there is almost no change as the distance from the weakness center B and the strength center C increases, and the values are almost constant. Therefore, the vertical refractive power on the progressive surface has a smaller rate of change in the horizontal direction than the horizontal refractive power.
In the lens 1 configured as described above, the intermediate region where the predetermined refractive power (1.50D) progressively increases between the weakness center B and the near vision center A to the intensity center C. 5 is provided. Therefore, in the intermediate region 5 above the near vision center A, the refractive power gradually decreases from the near vision center A toward the weakness center B, so that it is possible to see at the near vision center A. It is easy to see objects from a short distance (40 cm) to a distance (57 cm) farther than the short distance. Further, in the intermediate region 5 below the near vision center A, the refractive power gradually increases from the near vision center A toward the strength center C, so that from a predetermined short distance (40 cm) to the near distance. A little closer than the distance (31
(cm) can be easily viewed without adjustment.

Further, since the weakness region 3 having the same refractive power as that of the weakness center B is provided above the weakness center B,
You can see a wide range of objects at a distance (57 cm). By providing the intensity region 4 having a refractive power substantially the same as that of the intensity center C below the intensity center C, an object at a slightly short distance (31 cm) can be seen in a wide range.
Therefore, in a region above and below the near-use center A, a person who has little adjusting power does not move his / her head back and forth, for example, looking over the entire desk or reading a spread newspaper over the entire surface. Such visual work can be performed. Also, there are extremely few opportunities to see objects at long and medium distances,
It is most suitable for visual work mainly at short distances, such as indoor desk work, reading, newspaper reading, medical operation such as surgery, and machine tool work such as lathe. Furthermore, since adjustment power is not required when viewing an object at a distance or nearer than a short distance, eye fatigue is less likely to occur even when the lens 1 is worn for a long time, and a comfortable wearing feeling is obtained. be able to.

In the lens 1 constructed as described above, the horizontal refractive power in the region above the near center A increases until it is separated from the central reference line S by about 15 mm.
On the contrary, it decreases in the lower region. Therefore, for the intersection line L4 passing through the near vision center A, another intersection line L1
The rate of increase and decrease of its horizontal refractive power is smaller than that of .about.L3. Also, the rate of change in vertical refractive power in the horizontal direction is small. Therefore, at the position of the near center A, the waviness of the curved surface is suppressed and the horizontal cross section becomes a shape close to a circle.
The image magnification in the horizontal direction is almost constant. As a result, the astigmatism in the horizontal direction is reduced at the position of the near center A, the width of the progressive portion 6 is made substantially constant, or the width at the position of the near center A is maximized in the horizontal direction. Is
The width of the quasi-clear viewing zone can be maximized at a position near the near vision center A.

As the horizontal width of the quasi-clear viewing region is maximized at the position of the geometric center O, astigmatism is diffused to the left and right of the upper part of the lens 1 and the left and right of the lower part of the lens 1.
As a result, the lateral astigmatism at the position of the near vision center A is reduced, so that the area most frequently used as a presbyopia-correcting lens, that is, the center of the lens 1 in the vicinity of the near vision center A or the geometric center O. A wide and clear field of view can be obtained in the part.

The width of the progressive portion 6 is about 12 mm, and the minimum width of the progressive portion 6 between the distance center and the near center of the conventional general progressive power multifocal lens is 3 to 7 mm. In the progressive portion 6 of the present embodiment, an object a little farther or closer than a short distance can be seen, and in the conventional progressive portion, an intermediate distance object between a long distance and a short distance can be seen. However, it can be seen that the progressive portion of this embodiment is sufficiently wide from a numerical point of view.

The width (12 mm) of the progressive portion 6 is 6 to 15 m, which is the maximum width of the near portion area of the conventional progressive multifocal lens.
Since the value is equal to or larger than m, the clear vision region for near vision is sufficiently secured. Therefore, a clear visual field can be obtained in near vision. Since the progressive portion 6 is a region where the astigmatism is 0.50D or less, image distortion is suppressed as much as possible in that region. FIG. 6 shows a distortion diagram when a square lattice is viewed through the lens 1. As shown in this figure, in the region where the astigmatism (shown by the broken line) is 0.50D or less, the grating seen through the lens 1 is slightly enlarged in the intensity region 4, but is almost equal to the original square. Has become. Therefore, in the region where the astigmatism is 0.50D or less, the distortion of the image can be suppressed as much as possible, and
It is possible to reduce the fluctuation when moving the line of sight.

Since the astigmatism region is a region where the astigmatism is 0.75D or less, image distortion is relatively suppressed in that region. This quasi-clear vision area is wider than that of a general progressive multifocal lens as shown in FIG. 19 in the comparison in the lower half of the lens. Therefore, the lower half of the lens has significantly less distortion than the conventional progressive multifocal lens.

Further, since the rate of change in the vertical refractive power in the horizontal direction is small, the rate of occurrence of prisms in the vertical direction is reduced, and the swaying feeling that an object moves up and down when the face is swung left and right is reduced. be able to. Furthermore, since the change rate of the vertical refractive power in the horizontal direction is small, the difference between the vertical refractive power and the horizontal refractive index is not enlarged, and astigmatism can be further reduced.

Further, in the lens 1 of the present embodiment, the progressive power 6 increases the refractive power for obtaining a power slightly weaker and a power stronger than the near power for the near power. Therefore, unlike the case where the power for obtaining the near power is added to the distance power of a general progressive power lens in the progressive portion, the refracting power to be increased in the progressive portion 6 of the lens 1 can be small. Therefore, for example, even if the length of the progressive portion of the conventional progressive multifocal lens and the length of the progressive portion 6 provided between the weakness center B and the intensity center C are the same, The increasing refractive power is smaller than the addition power of the conventional progressive power multifocal lens. As a result, the gradient of the refracting power on the central reference line S of the progressive portion 6 (in this embodiment, the gradient =
0.05) becomes loose, and the aberration (astigmatism or distortion) generated in the progressive portion 6 becomes small. Then, the clear vision region and the quasi-clear vision region are widened, and when the line of sight is moved between the weakness center B and the intensity center C in the progressive portion 6, the image shake is reduced.

Next, eyeglasses using the presbyopia-correcting lens 1 of the first embodiment will be described. As shown in FIG. 7, the spectacles 7 are composed of a spectacle frame 8 and two presbyopia-correcting lenses 1. In the spectacle frame 8, the lens 1 is edged so that the wearing point P of the lens 1 coincides with an eye point (distance eye point) (not shown) set on the left and right rims 9 according to the wearer. Each is framed. The eye point is a point through which the line of sight passes when looking at a distance, and is also called a fitting point. Each lens 1 is framed in a state of being rotated a predetermined angle θ (two degrees in this case) to the nose side with respect to the vertical direction about the geometric center O. Therefore, the intensity center C is displaced from the wearing point P toward the nose side by 2.5 mm (so-called inward alignment) in consideration of the convergence in the near vision.

In the spectacles 7 configured as described above, near vision can be performed in a state where a wide clear vision region is secured in the intermediate region 5 including the wearing point P and the near vision center A. Further, when the line of sight is moved between the weakness center B and the intensity center C in the region of the progressive portion 6 to perform near vision, image fluctuation is reduced.

(Second Embodiment) Next, a second embodiment will be described. The same components as those in the first embodiment are designated by the same reference numerals.

As shown in FIG. 8A, the weakness center B is located 7 mm above the geometric center O on the central reference line S.
Is provided. Geometric center O on the central reference line S
The strength center C is provided 11 mm below.

The center of weakness B is the refractive power (2.
The weakness region 3 has a refracting power weaker than 50D (2.00D in this case), and has the same refracting power as the weak refracting power. In this embodiment, since the refracting power is 2.00 D, the visible distance is 50 cm.

The intensity center C has a refractive power (3.00D in this case) stronger than that of the near vision center A, and the intensity region 4 has a refractive power almost the same as the strong refractive power. There is.
In this embodiment, since the refractive power is 3.00D, the visible distance is 33 cm.

As shown in FIG. 8B, in the present embodiment, the difference in refractive power between the weakness center B and the strength center C is 1.00.
D, which is 1.00 in the middle area 5.
The refractive power of D (the degree of change within the lens) progressively increases. Therefore, in the middle region 5, the power changes from the weak power of 2.00 D to the power of 3.00 D, and in the progressive portion 6, a person without accommodation has a near vision of 50 cm to 33 cm. Is suitable.

The length of the progressive portion 6 is 18 mm,
The gradient of the refracting power in the progressive portion 6 is 1.00D / 1
8 mm = 0.06 (D / mm). Progressive part 6
The horizontal width of is approximately 10 mm, which is substantially constant. Strictly speaking, the progressive portion 6 has a maximum width of 11 mm at the position of the geometric center A that is 2 mm below the geometric center O, and has a minimum width of 10 mm at the positions of the weakness center A and the strength center C. are doing. Therefore, the maximum width is 1.1 times the minimum width.

The quasi-clear viewing region has a maximum horizontal width W _max of 34 mm at the position of the geometric center O (in this case, 2 mm above the near center A). It has a minimum width W _min of 17 mm at position C. Therefore, the maximum width W _max is 2.0 with respect to the minimum width W _min .
It is twice as long.

Although not shown, the equal power curves E1 to E7 are almost the same as the manner of the change in the power increase and decrease in the first embodiment. As shown in FIG. 9A, the refracting powers at the intersections E3 to E5 and the intensity center C excluding the near vision center A are slightly smaller than the refracting power in the first embodiment, and the intersections E1, E2 and the weakness are weak. The refractive power at the center B is slightly larger than that in the first embodiment. Each of the intersecting lines L1 to L8 is a non-circular curve in which the horizontal refractive power increases or decreases in accordance with the slightly smaller or larger refractive power as in the first embodiment.

In the lens 1 configured as described above, the difference in refractive power between the weakness center B and the strength center C is 1.00.
Since it is D, even if the length of the progressive portion 6 becomes as short as 18 mm, the gradient of the refractive power can be maintained at a value (0.06) substantially the same as the value (0.05) of the first embodiment. . As a result, it is possible to obtain the same effect as that of the first embodiment and obtain a lens with less image shake and distortion.

(Third Embodiment) Next, a third embodiment will be described. The same components as those in the first embodiment are designated by the same reference numerals.

As shown in FIG. 10, a meridian T extending vertically through the geometric center O is determined. The central reference line S1 in the region above the geometric center O (the region including the upper portion of the intermediate region 5 and the weakness region 3) is displaced parallel to the meridian T by about 1.0 to 2.0 mm toward the nose side. are doing. or,
The central reference line S2 in the region below the geometric center O (the region including the lower portion of the intermediate region 5 and the strength region 4) is displaced toward the nose side as it goes downward with respect to the meridian T. There is.

A near center A is provided 2 mm below the geometric center O and on the center reference line S2 on the nose side 2 mm. On the central reference line S1 7 mm above the geometric center O,
A weakness center B is provided. 11 mm from geometric center O
An intensity center C is provided on the lower central reference line S2. On the central reference line S1 2 mm above the geometric center O,
A wearing point P is provided. Further, in this embodiment, the length of the progressive portion 6 is 18 mm, which is the same as that of the second embodiment. The refractive powers at the near vision center A, the weakness center B, and the strength center C are the same as those in the second embodiment, and the gradient of the refractive power on the central reference line S of the progressive portion 6 is 1.00D / 18 mm. ≈0.06.
The diameter of this lens 1 is 70 mm.

The refracting surface 2a in the region above the geometric center O has an astigmatism distribution in a region within 15 mm from the central reference line S1 to the nose side and the ear side with respect to the horizontal direction during wearing. It is asymmetrical. Further, the refractive surface 2a has a distribution in which the astigmatism distribution on the ear side in the horizontal direction changes more slowly than the distribution of astigmatism on the nose side.

The refractive surface 2b in the region below the geometric center O has an astigmatism distribution in the region within 15 mm from the center reference line S2 to the nose side and the ear side with respect to the horizontal direction during wearing. It is asymmetrical. Further, the refractive surface 2b has a distribution in which the astigmatism on the ear side in the horizontal direction changes more slowly than the distribution of astigmatism on the nose side.

The refractive power distribution of the lens refracting surface 2 is shown in the graph of horizontal refractive power in FIG. 12 and the graph of vertical refractive power in FIG. In FIG. 12, intersection lines L1 to L4 are about 14 from the near center A, the intersections E1 and E2, and the weakness center B toward the nose side.
mm, the horizontal refracting power increases as it moves away from the ear side by about 16 mm, and again becomes a non-circular curve that decreases.

The intersection lines L5 to L8 are non-circular curves in which the horizontal refracting power decreases and increases again as the distance from the intersection points E3 to E5 and the center of intensity C increases by about 12 mm to the nose side and about 18 mm to the ear side. .

In FIG. 13, at the intersections of the intersections L1 to L8 and the intersections not shown, the refractive power of the vertical section (hereinafter,
The vertical refractive power is the near center A, intersections E1 to E4,
As the distance from the center of weakness B and the center of strength C to the nose side and the ear side respectively, there is almost no change and the values are almost constant.

In the lens 1 configured as described above, not only the same effects as those of the first embodiment but also the central reference lines S1 and S2 are displaced to the nose side so that the respective refracting surfaces 2a are located on the ear side in the horizontal direction. The following effects can be obtained by making the distribution of the astigmatism of No. 2 have a slower change than the distribution of the astigmatism on the nose side.

As shown in FIG. 14, when an object at a short distance is viewed laterally with both eyes, the amount of movement α of the line of sight of the right eye ER to the ear side is α.
It is known that 1 becomes larger than the movement amount α2 of the line of sight of the left eye EL toward the nose side. According to this embodiment, since the distribution of astigmatism on the ear side is slow, it is possible to perform good binocular lateral vision with less image fluctuation in the slow region.

Further, by displacing the central reference line S2 toward the nose side as it goes downward with respect to the meridian T, and providing the strength center C on the central reference line S2,
The intensity center C is always displaced toward the nose side. Therefore, when the lens 1 is framed in a spectacle frame, it is possible to save the labor of rotating the lens 1 by a predetermined angle so that the intensity center C is located on the nose side as in the second embodiment.

(Fourth Embodiment) Next, a fourth embodiment will be described. The same components as those in the first embodiment are designated by the same reference numerals.

As shown in FIG. 15A, the central reference line S
A weakness center B is provided 13 mm above the geometrical center O above. A strength center C is provided 17 mm below the geometric center O on the central reference line S. The near center A is disposed on the central reference line S that is located 7 mm downward from the geometric center, and has a refractive power of 2.50D.

The weakness center B is the refractive power (2.
50D), which is weaker (1.50D in this case), and the weakness region 3 has almost the same refractive power as that weak power. Therefore, an object at a distance of 0.67 m (= 1 / 1.50 D) can be seen through the weakness center B and the weakness region 3.

The intensity center C has a refractive power (3.00D in this case) stronger than that of the near center A, and the intensity region 4 has a refractive power substantially the same as that of the near vision center A. There is.
Therefore, 0.33 through the intensity center C and the intensity region 4.
You can see objects at a distance of m (1 / 3.00D).

As shown in FIG. 15B, in this embodiment, the difference in refractive power between the weakness center B and the strength center C is 1.50.
D, which is 1.50 in the middle area 5.
The refractive power of D (the degree of change within the lens) progressively increases. Therefore, in the middle region 5, the frequency varies from a weak frequency of 1.50D to an intensity frequency of 3.00D, and in the progressive portion 6, a person without accommodation can see a distance of 57 cm to 33 cm. The length in the vertical direction of the progressive portion 6 in the intermediate region 5 is 30 mm.
The gradient of the refractive power at 1.50 D / 30 mm = 0.
It is 05 (D / mm).

The width of the progressive portion 6 in the horizontal direction is approximately 12 mm, which is substantially constant. Strictly speaking, the progressive portion 6 has a geometric center O
Has a maximum width of 12 mm at a position 2 mm below
It has a minimum width of 11 mm at the weakness center A and the strength center C. Therefore, its maximum width is 1.1 times the minimum width.

The semi-clear viewing zone has a maximum horizontal width W _max of 40 mm at a position 2 mm below the geometric center O,
Moreover, it has a minimum width W _min of 20 mm at the weakness center A and the strength center C. Therefore, its maximum width W
_max is 2.0 times the minimum width W _min .

In the fourth embodiment, the near vision center A is disposed 9 mm downward from the wearing point P and 2 mm away from the nose side. By arranging the near vision center A in this way, even when the wearer looks at a nearby object, the line of sight passes through the near vision center A even if the upper body leans forward and the line of sight is directed downward. Therefore, the wearer can obtain optimum near vision through the near vision center A. That is, when the wearer sits on a chair and looks at the desk, the person tilts his / her face about 40 degrees forward and further turns his eyes down about 20 degrees. With this operation, the line of sight directed downward by about 60 degrees passes through the near vision center A.

The change of the increase and decrease of the frequency in the fourth embodiment is almost the same as that of the equal frequency curves 101 to 107 shown in FIG. 3 of the first embodiment, and the description thereof will be omitted.

As shown in FIG. 16, in the fourth embodiment, the intersection line L4 is located 2 mm below the geometric center O and 5 mm above the near vision center A, and has an intersection E3 overlapping the central reference line S. are doing. The intersection line L5 has a near vision center A on the central reference line S. Other intersection lines L1 to L3 and L6
.About.L8 have the same intersections as in the first embodiment.

As shown in FIG. 17A, in the fourth embodiment, the horizontal refractive power of each of the intersecting lines L1 to L8 is larger than that in the first embodiment shown in FIG. 5A. It is getting smaller. In the lens region above the geometric center O, the horizontal refractive power of each of the intersection lines L1 to L3 increases as it moves away from the central reference line S in the horizontal direction, as in the first embodiment. Further, in the lens region below the geometric center O, the horizontal refracting powers of the intersection lines L5 to L7 decrease as the distance from the central reference line S increases in the horizontal direction. Furthermore,
The increasing rate of the horizontal refractive power of the intersection lines L1 to L3 and the intersection lines L5 to L
The reduction rate of the horizontal refractive power of 7 is almost equal to that of the first embodiment. Therefore, the horizontal refractive power of the convex surface 2 changes symmetrically above and below the line of intersection L4. As a result, it is possible to suppress the astigmatism from concentrating on the central part of the lens that is frequently used, disperse the astigmatism in the left and right regions of the upper and lower lenses that are less frequently used, and widen the progressive portion 6.

As shown in FIG. 17 (b), in the fourth embodiment, the vertical refracting power at the intersection line (not shown) orthogonal to each of the intersection lines L1 to L8 is shown in FIG. 5 (b). It is generally smaller than the horizontal refractive power in the first embodiment. Similar to the first embodiment, this vertical refractive power shows a substantially constant value in the direction away from the central reference line S. Therefore, the number of prisms generated in the vertical direction of the lens is reduced, and the feeling of shaking generated when the face is swung left and right is reduced.

As described in detail above, the lens of the present invention is not only suitable for a person who has little or no accommodation power to perform work mainly on short distance such as desk work, but also It is useful for people to wear.

A person who uses a perspective type progressive multifocal lens, but who uses a monofocal presbyoscope in near work because near vision is difficult. A person who uses a monofocal presbyopscope but has a narrow visible range so that when he or she looks at a newspaper, his or her face is brought closer to the newspaper.

The present invention can be embodied as follows, and in that case, the same effect as that of the above embodiment can be obtained. (1) In the first embodiment, the range of the refractive power that can be increased from the weakness center B to the strength center C is 0.
50D to 4.00D, and the preferred range is 1.00
2.00D, and the optimum range is 1.25D to 1.75.
It is D.

The increased refractive power (addition power within the lens) is
It is preferable that the decision is made in consideration of being able to look over the entire surface of, for example, a desk even for a person who has lost controllability.
Further, when the increasing refractive power in the intermediate region 5 becomes small, the astigmatism of the convex surface becomes small, and a wide clear vision region and a quasi-clear vision region can be secured, and since distortion becomes small, distortion and shake are suppressed. Can be made smaller. Also, as the refractive power increases, the range from a far distance to a near distance becomes wider than the short distance that can be seen. For example, when the near center A is 2.50D and the refractive power is 4.00D,
A person with no adjusting ability can see objects in the range of 2 to 22 cm.

(2) The gradient of the progressive refracting power from the weakness center B to the strength center C is preferably smaller than that of the conventional progressive multifocal lens, that is, 0.10 (D / mm) or less. The value of the gradient in a general progressive multifocal lens is
It is in the range of approximately 0.15 to 0.25 (D / mm).
This value corresponds to the case where a person who has almost no adjustment ability wears a lens having an addition power of 3.00 D and a progressive portion length of 12 to 20 mm. As this gradient is smaller, a presbyopia-correcting lens with less astigmatism, distortion, and shaking can be obtained. Therefore, for example, when the progressive power is 4.00 D, the length of the progressive portion 6 is preferably 40 mm or more.

(3) The length of the progressive portion 6 may be changed to 20 mm or more. At this time, the progressive refractive power is 1.00D to
It is preferable that it is in the range of 2.00D or 1.25D to 1.75D from the viewpoint of reducing the gradient of the progressive refractive power. For example, when the length of the progressive portion 6 is 25 mm and the progressive refracting power is within the range of 1.25D to 1.75D,
Gradient of progressive refractive power is 0.05 to 0.07 (D / mm)
Becomes Further, the length of the progressive portion 6 is 14 mm or more and 25 m.
You may change arbitrarily in the range less than m. In this case, the progressive refractive power is 0.50D to 1.50D or 0.75D.
It is preferable to be in the range of ˜1.25 D from the viewpoint of reducing the gradient. For example, the length of the progressive portion 6 is 16 m
When the progressive power is in the range of 0.75D to 1.25D at m, the gradient is 0.05 to 0.08 (D / mm).

(4) In the above embodiment, the maximum width of the quasi-clear vision area is twice the minimum width, but it may be changed to 1.5 times to 3 times. The reason for setting 1.5 times to 3 times is because the balance between the minimum width and the maximum width is taken into consideration. The minimum width of the quasi-clear vision area in the intermediate area 5 is at least 12 mm. This is because if the minimum width is narrower than this, the field of view becomes as narrow as the conventional progressive multifocal lens. Therefore,
The upper limit of the ratio of the maximum width to the minimum width should be about 3 times. If the magnification is within this range, the semi-clear vision region can be arranged so that the width in the horizontal direction becomes maximum at the central portion of the lens 1, that is, in the vicinity of the near vision center A. Further, the width of the quasi-clear vision area is not limited to 1.5 to 3 times, but the maximum width may be simply larger than the minimum width by 10 mm or more. Furthermore, the ratio of the maximum width to the minimum width may be 1.3 or less within a range of ± 10 mm in the vertical direction from the geometric center O.

(5) The position at which the quasi-clear viewing zone has the maximum width is 5 to 10 mm above and below the geometric center O, preferably 5 to 7 m above and below.
m, if optimal, may be set within a range of 5 mm above and below. The reason is that the maximum width W _max is 10 above and below the geometric center O.
This is because the quasi-clear vision region deviates from the frequently used region (intermediate part 6) when it exists outside the range of mm. At this time, a wide and clear visual field cannot be obtained in that area.

(6) In the first embodiment, the wearing point P is 2 mm above the near center A and 2 mm on the ear side. However, even if the near center A is displaced to the ear side by 2.5 to 3 mm. Good. With this configuration, when the lens 1 is framed, the rotation angle of the lens 1 is set to be smaller than 2 degrees, for example, 0.
Even if it is rotated (not rotated), the intensity center C is located on the nose side, so that it is possible to cope with radiation. The wearing point P may be arranged within 2 mm above the geometric center and 15 mm above the near center A, preferably 13 mm, and optimally 10 mm.
It may be placed within. Thus, by disposing the wearing point P within 15 mm above the near center A,
Between the wearing point P and the near wear center A, the wearer can move his eyes in the vertical direction without burden. On the contrary, when the wearing point P is arranged at a position exceeding 15 mm above the near center A, the burden on the wearer's eyes is increased.

(7) Set the position of the near vision center A between 2 mm and 15 mm below the geometric center O, preferably between 2 mm and 12 mm.
It may be arranged between mm. Within this range, the wearer can move his / her eyes in the vertical direction between any point near the center of near vision and the center of near vision, and the distance from the short distance to a distance slightly longer than the short distance. It becomes possible to see the thing. On the contrary, if the near vision center A is arranged below the geometrical center O by 15 mm, the angle of the eyes of the wearer when looking at a nearby object becomes large, which is burdensome and difficult to use.

(8) The weakness center B and the strength center C may be arbitrarily changed. (9) In the first embodiment, 4 of the wearing points P
In addition to framing the lens 1 so that the near center A is located 2 mm below the nose side, the near center A is positioned between 4 mm below and 4 mm to 6 mm above the wearing point of the target lens 9. You may put a frame in.

(10) In the third embodiment described above, the amount of movement of the line of sight when looking at an object in the upper half of the lens 1 at a distance farther than the near point is as follows. It is smaller than the amount of movement of the line of sight when looking. Therefore, the distribution of astigmatism on the nose side in the region above the geometric center O may not be slower than the distribution of astigmatism on the nose side in the region below. As a result, the central reference line S1 is set to the meridian T
A small amount of displacement is required. In addition, a region where the distribution of astigmatism is asymmetric is defined as a region within 15 mm on each of the nose side and the ear side with the central reference line S as a boundary.
The area may be within 0.0 mm.

(11) In each of the above embodiments, the convex lens refracting surface 2 of the presbyopia-correcting lens 1 is embodied, but a concave refracting surface may be embodied. In this case, the increase / decrease in the refractive power of the intersection lines L1 to L8 in the first to fourth embodiments is completely opposite.

The progressive portion in the present invention is defined as follows. Progressive part: In the intermediate region between the weakness region and the strength region, the refractive power increases progressively from the weakness center to the strength center through the near vision center including the central reference line, and This is a portion of the clear vision region where the point aberration is 0.50D or less.

The technical ideas other than the claims that can be understood from the above embodiment will be described below along with their effects. (1) Use the presbyopia-correcting lens according to any one of claims 1 to 6 for near vision between 4 mm below and 6 mm above a distance eyepoint set in a lens shape of a spectacle frame. Eyeglasses characterized by being framed so that the center is located. By doing so, the performance of the lens can be sufficiently exerted when worn as eyeglasses.

(2) In the lens for presbyopia correction according to claim 3, 2.5 mm to 3.0 m in the direction toward the ear when the lens is worn with the wearing point as the near center.
It was provided at a position displaced by m. By doing so, it is possible to reduce the rotation angle of the lens or to frame the lens without rotating.

[0129]

As described above in detail, according to the invention described in claim 1, the frequency of use is extremely low when viewing an object at a long distance or a medium distance, and mainly at a short distance such as desk work or reading. Ideal for visual work, not only can a person without accommodation see a certain short-distance object, but also easily see an object at a distance or a near distance from that short-distance object. A wide and clear field of view can be obtained when looking at an object at a short distance.

According to the invention as defined in claim 2, since the near vision center is arranged within 2 mm to 15 mm below the geometric center of the lens, an arbitrary point near the near vision center and the near vision center can be obtained. In between, the wearer can see an object at a distance slightly longer than the short distance from the short distance by moving the eyes in the vertical direction without burden.

According to the third aspect of the present invention, the wear point is arranged within 15 mm above the near center so that the wearer can move his / her eyes vertically without burden between the wear point and the near center. It becomes possible.

According to the invention described in claim 4, in addition to the above effects, the gradient of the refractive power between the center of weakness and the center of intensity on the central reference line of the intermediate region is relatively small, so that a wide range is obtained. A clear viewing area and a quasi-clear viewing area are obtained, and it is possible to reduce image shake and distortion when the line of sight is moved between the weakness center and the intensity center.

According to the invention described in Item 5, it is possible to obtain a lens in which the gradient of the refracting power does not become large and the image shake or distortion is small. According to the invention described in claim 6, the concentration of astigmatism and distortion on the sides of the geometric center is reduced, and good lateral viewing can be achieved at the lens central portion including the geometric center. Further, in the side view near the intensity center, the side face located at a distance slightly longer than the distance when the front is seen from the intensity center can be seen relatively clear.

[Brief description of drawings]

1A and 1B show a presbyopia-correcting lens according to the first embodiment, FIG. 1A is an explanatory view showing a distribution of astigmatism, and FIG. 1B is a graph showing a change in refractive power.

FIG. 2 is an explanatory diagram showing each region of a lens.

FIG. 3 is an explanatory diagram showing a power distribution of a lens.

FIG. 4 is a plane passing through the geometric center and perpendicular to the central reference line,
And an explanatory view showing a line of intersection between a plane group parallel to the plane and the refracting surface.

5A and 5B show a distribution of refractive power on a lens refracting surface, FIG. 5A is a graph showing a relationship between a horizontal refractive power of each intersection line and a distance from a central reference line, and FIG. 5B is a vertical refractive power and a central reference line. A graph showing the relationship with the distance from.

FIG. 6 is a distortion diagram in which a square lattice is viewed through a lens.

FIG. 7 is a front view showing spectacles in which the lens of the first embodiment is framed.

8A and 8B show a lens according to a second embodiment, FIG. 8A is an explanatory diagram showing a distribution of astigmatism, and FIG. 8B is a graph showing a change in refractive power.

9A and 9B show a distribution of refractive power on a lens refracting surface, FIG. 9A is a graph showing a relationship between horizontal refractive power of each intersection line and a distance from a central reference line, and FIG. 9B is a vertical refractive power and a central reference line. A graph showing the relationship with the distance from.

FIG. 10 is an explanatory diagram showing a distribution of astigmatism of the lens of the third embodiment.

FIG. 11 is an explanatory diagram showing a plane that passes through the geometric center and is perpendicular to the central reference line, and a line of intersection between the plane group parallel to the plane and the refracting surface.

FIG. 12 is a graph showing the relationship between horizontal refractive power and the distance from the central reference line.

FIG. 13 is a graph showing the relationship between the vertical refractive power and the distance from the central reference line.

FIG. 14 is a schematic diagram showing the amount of movement of the eyeball when the line of sight is moved laterally.

15A and 15B show a presbyopia-correcting lens according to the fourth embodiment, FIG. 15A is an explanatory diagram showing a distribution of astigmatism, and FIG. 15B is a graph showing a change in refractive power.

FIG. 16 is an explanatory diagram showing a plane that passes through the geometric center and is perpendicular to the central reference line, and a line of intersection between the plane group parallel to the plane and the refracting surface.

FIG. 17 is a graph showing the refractive power distribution of the lens refracting surface, (a) is a graph showing the relationship between the horizontal refractive power of each intersection and the distance from the central reference line, and (b) is the vertical refractive power and the central reference line. A graph showing the relationship with the distance from.

FIG. 18 shows a progressive multifocal lens in a conventional example,
(A) is explanatory drawing which shows each area | region, (b) is a graph which shows the change of refractive power.

FIG. 19 is an explanatory diagram showing a distribution of astigmatism of a progressive multifocal lens of a conventional example.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Lens for presbyopia correction, 2 ... Lens refraction surface, 3 ... weakness area | region, 4 ... intensity area | region, 5 ... middle part area | region, S ... center reference line,
A ... near center, B ... weakness center, C ... strength center, O ... geometric center, P ... wearing point, L1 to L4 ... intersection line (first intersection line), L5 to L8 ... intersection line (second) Intersection line), E1 to E5 ...
Intersection.

Claims (6)

[Claims] 1. In at least one lens refracting surface of two refracting surfaces forming a lens, a center that extends in the vertical direction of the lens refracting surface so as to minimize astigmatism and divides the refracting surface into left and right sides. A reference line, a near center provided on the center reference line, a near center provided on the central reference line and above the near center, and a weaker refractive power than the near center. Center of strength, on the central reference line, and below the center of near vision, an intensity center that gives a stronger refractive power than the refractive power of the near vision center, and between the weakness center and the intensity center Provided between the weakness center and the strength center, the predetermined refractive power progressively increases from the weakness center to the strength center via the near vision center, and between the weakness center and the strength center. The difference in the refractive power of 0.
Within the range of 50D to 4.00D, in the increasing region, n is the refractive index of the lens material, C1,
C2: Using the principal curvatures in different directions (unit is m ⁻¹ ) at points on the lens refracting surface, the following equation, (n−1) × | C1 −C2 | ≦ 0.5 (m ⁻¹ ) And a quasi-clear vision region defined by the following equation: (n-1) × | C1 −C2 | ≦ 0.75 (m ⁻¹ ) The horizontal width of the clear viewing area becomes maximum at a position near the geometric center of the lens, or is substantially constant from the weakness center to the intensity center through the near vision center, The presbyopia-correcting lens, wherein the horizontal width of the quasi-clear vision region in the increasing region is maximum at a position near the geometric center. 2. The presbyopia-correcting lens according to claim 1, wherein the near vision center is located below the geometric center of the lens.
A lens for presbyopia correction, which is arranged within a range of 15 mm to 15 mm. 3. The presbyopia-correcting lens according to claim 1 or 2, wherein the presbyopia-correcting lens has a wearing point located within 15 mm above the near vision center. 4. The presbyopia-correcting lens according to claim 1, wherein a length in a vertical direction in the increasing region is 20 mm or more, and the weakness center and the strength are the same. The difference in refractive power between the center is 1.00D ~
A presbyopia-correcting lens having a range of 2.00D. 5. The presbyopia-correcting lens according to claim 1, wherein a length in a vertical direction in the increasing region is 14 mm or more and less than 25 mm, and the weakness center and the weakness center are included. The difference in refractive power from the intensity center is 0.5
A presbyopia-correcting lens having a range of 0D to 1.50D. 6. The presbyopia-correcting lens according to claim 1, wherein in a region above the geometric center, a plane that passes through the geometric center and is perpendicular to the central reference line is used. Assuming that the first intersecting line between the plane parallel to the plane and the refracting surface is a non-circular curve whose curvature increases as the distance from the intersecting point of the central reference line increases in the horizontal direction, and is lower than the geometric center. In a region, assuming a plane that passes through the geometric center and is perpendicular to the central reference line, the second intersection line between the plane parallel to the plane and the refraction surface is the horizontal direction from the intersection of the central reference line. A non-circular curve whose curvature decreases as it goes away, assuming a horizontal line passing near the geometric center, the distances from the horizontal line in the upper region and the lower region are equal, and from the central reference line. And the upper region and the rate of increase in the curvature of the first intersection line passing through each distance and any two points equal in the lower region, the second
A presbyopia-correcting lens characterized in that the rate of decrease in the curvature of the line of intersection is substantially equal.