JPH07294859A - Progressive multi-focus lens - Google Patents

Abstract

PURPOSE:To obtain a wide and clear field of view while viewing at an object located at a medium to a short distance, to increase the width of the clear vision region in a progressive section and to reduce image fluctuation and an eyeball rotational work load as much as possible while looking at an object located at a short distance. CONSTITUTION:A middle range center A is provided on a central reference line S to add an 1.00D degrees against a far sighted degrees when one wishes to look at an object located at a long distance. The degrees (1.00D), which is obtained by subtracting the degrees (1.00D) that is added at the center A from a degrees (2.00D) that provides a near sighted degrees against a far sighted degrees, is progressively added in a progressive section 6 located between the center A and a near range center B. A minimum width F of a progressive clear vision region is made to be 7.5mm, a maximum width W1 of a medium clear vision region is made to be 44mm and a maximum width W2 of a near sighted clear region is made to be 18mm. The center A is made to be an eye point P and the center B is arranged at 12mm below from the point P.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a progressive multifocal lens used for correcting presbyopia, and more specifically, it shows medium and short distances in indoor desk work and medical operations such as surgery. The present invention relates to a progressive multifocal lens most suitable for.

[0002]

2. Description of the Related Art A progressive multifocal lens was developed to compensate for the deterioration of the accommodation function when viewing a short-distance object due to the weak elasticity of the crystalline lens of the eye in the elderly. The basic structure is as follows.

Generally, the convex surface of the progressive power multifocal lens is formed in an aspherical shape having partially different surface refracting powers, and has a function of giving the refracting power of the lens suitable for seeing from a distant object to the hand. is doing. 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. It is possible to adopt a structure in which the functions of the convex surface and the concave surface are exchanged, but the structure described above is widely adopted because it is easy to manufacture.

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. 14A, the surface (refractive surface) 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 refracting power suitable for viewing at a distance from approximately 1 m to 2 m (hereinafter referred to as distance vision). The middle region M is 50 cm to 1 m to 2
When looking at a medium distance between m (hereinafter referred to as intermediate vision), the near portion region N is a refractive power suitable for viewing a near distance closer than 50 cm (hereinafter referred to as near vision). Is a region having.

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 (surface refracting power) progressively changes, which brings about the basic function of the progressive multifocal lens. As shown in FIG. 14A, 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 at 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, an area above the point A is a distance portion area F, an area below the point B is a near portion area N,
The part between them can be considered as the middle 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. 14B shows the change in the refractive power on the central reference line S. As shown in this figure, the refracting power (unit is diopter: D) gradually increases from the point A to the point B, and the refracting power D1 in the distance portion area F above the point A and below the point B The refractive power D2 in the near portion area N is substantially constant. The difference between the refractive powers D2 and D1 is called the addition, which is usually 0.5 diopters (hereinafter D
It is added within the range of 3.5) to 3.5D. In the figure, the point A and the point B are called a progressive portion, and the distance between them is called the length of the progressive portion.

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. 14B 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) × | C 1 −C 2 | (Diopter) This appears as astigmatism in the optical performance of the lens, and 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. 15 (a) shows the distribution of astigmatism in the conventional progressive-power multifocal lens corresponding to FIG. 14 (a). In this figure, astigmatism is represented by 0.25D intervals of 0.25D to 2.00D isoastigmatism lines from the center of the lens, similarly to the contour lines of the map. Generally, it is said that a person perceives astigmatism and perceives a blur of an image as 0.5D or more. 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. 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) Note that n is the refractive index of the lens material, and C1 and C2 are principal curvatures (units are m ^-1 ) in different directions at arbitrary points on the lens refracting surface within the clear vision region.

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 multifocal lens, it is necessary to minimize the adverse effects of astigmatism on the intended use of the wearer.

Under these circumstances, the progressive multifocal lenses developed to date include the standard type lens shown in FIG. 15 (a) with equal emphasis on distance vision and near vision, and FIG. There is a far-medium type lens that emphasizes far vision and intermediate vision shown in (b).

The standard type progressive multifocal lens has a length of 12 to 16 mm between points A and B (progressive portion) where addition is added on the central reference line. The maximum horizontal width (hereinafter, all widths are in the horizontal direction) W1 of the clear vision area in the distance portion area (hereinafter, abbreviated as the distance clear vision area) is at least about 40 mm. Clear area in the middle area (hereinafter abbreviated as the middle clear area)
Minimum width W2 of 3 to 5 mm (at addition of 2.00 D)
It is a degree. Further, the maximum width W3 of the clear vision area in the near portion area (hereinafter, abbreviated as near vision area) is about 10 to 15 mm (when the addition is 2.00 D).

In the far-medium type progressive power multifocal lens, the length of the progressive portion is 18 mm or more. The maximum width W1 of the distance clear vision region is wide to the side edge of the lens and is substantially the same as the lens diameter. The minimum horizontal width W2 of the intermediate clear viewing area is 5 to 8 mm
(When the addition is 2.00D). Further, the maximum horizontal width W3 of the near vision region is 6 to 10 mm (addition degree 2.
(When 00D).

In the standard type progressive power multifocal lens described above, the distance portion area and the near portion area each have a width W1 of the clear vision area.
Although W3 is wide, there is a problem that the width W2 of the intermediate clear vision region is narrow. For this reason, in the middle area, especially when the addition power exceeds 2.50D, the intermediate vision is difficult to see, as if it were seen through the door gap.

Further, in the far-medium type progressive multifocal lens, the width W1 of the far clear vision region is very wide, and the width W2 of the intermediate clear vision region is also wider than that of the standard type. Visual and intermediate vision are good. However, the progressive part is 1
Due to the long length of 8 mm, the near center (point B)
Is far from the eye point (point A in this case) (18 mm in this case), so the burden of rotation of the eyeball increases, and the width W3 of that region is narrow, which makes near vision difficult. The eye point is a passing position on the lens of the line of sight of a spectacle wearer looking at a distance in a natural posture in a state where the spectacle lens is framed in a spectacle frame, and is also called a fitting point. Further, it can be said that the burden on the eyeball rotation is small when the near center is located within about 12 mm from the eye point. Therefore, each of the above-mentioned lenses is not sufficient when performing work for viewing at intermediate and short distances, such as indoor desk work, medical surgery such as surgery, and machine tool work such as a lathe.

Therefore, as a progressive multifocal lens suitable for visual work mainly at medium and short distances, Japanese Patent Laid-Open No. 62-1061 has been proposed.
The one shown in Japanese Patent Publication No. 7 has been proposed. As shown in FIG. 16, in this middle-near type lens, the length of the progressive portion between points A and B is set to 25 mm or more, and the gradient of the refractive power in the progressive portion is made small. The image fluctuation when the line of sight is moved from to the near area is reduced.

Further, by inserting astigmatism in the distance portion area so that the maximum width W1 of the distance vision area is 30 mm or less, the astigmatism in the intermediate portion area is reduced and the intermediate vision area is reduced. The width of the area is wide (4 to 7 mm). The maximum width W3 of the near vision region is the same as that of the standard type (10 to 15 mm).

[0020]

However, the above-mentioned middle-near type progressive power multifocal lens has the following problems.

The middle-near type lens has a width W2 of the intermediate clear vision region.
Is wide, the intermediate vision is good.For example, when a person who wears a standard type lens wears a middle-near type lens, the standard type originally has a difficulty in intermediate vision. There is little dissatisfaction with intermediate vision.
However, the middle-near type lens has a progressive length of 2
It is as long as 5 mm or more, and when the lens is framed in a spectacle frame, the distance center (point A) is the eye point (in this case,
For example, 10 from the same position as the geometric center O shown in FIG.
mm above. For this reason, the distance center is located above the standard type distance center, so that the user sees distant distances with a high degree of eyesight, which causes a problem of far vision.

Further, the light incident from a position 10 mm away from the eye point has a considerable angle with respect to the lens surface, so that astigmatism (in this case, astigmatism is a difference in surface refractive power). However, it is an aberration that occurs when the convergent position of the light beam is not constant.) There is also a problem that the distance cannot be clearly seen. In addition, the distance W1
Is narrower than the width W1 of a standard type lens or the like, the field of view is narrowed in that region, and there is a problem in that the image is greatly shaken when the head is moved, resulting in discomfort.

Further, since the width W1 of the distance clear vision region is narrow, there is a problem that the distance vision clear vision region deviates from right above the eye point when the lens is tilted and put in a spectacle frame. That is, a lens that is bilaterally symmetric with the central reference line S as the axis of symmetry takes into consideration the convergence (when looking at a near object, the line of sight is closer to the inside than when looking at a far object). The lens is inclined about 8 to 10 degrees so that (point B) is located inside (nose side).
Therefore, the distance center (point A) is located on the outer side (ear side),
The distance clear vision region deviates from directly above the eye point, and the region immediately above is a distance portion region with astigmatism of 0.5 D or more. Therefore,
When the lens is tilted, it is difficult to wear the lens because the user looks far away and is affected by aberrations, causing many image fluctuations and seeing astigmatism in a region of 0.5D or more. . If the tilt angle is reduced in order to prevent this, the convergence in near vision cannot be dealt with.

This middle-near type lens is mostly used for intermediate vision and near vision, and is suitable for a person who wears far vision less frequently, so that it is difficult to see far. There is also the idea that there is no help for it. However, when a person who wears a standard type lens wears the lens, it is more worrisome that distance vision becomes more difficult than it is at an intermediate distance. And for those who are used to standard type lenses,
At the beginning of wearing, middle-near type lenses will be difficult to use. However, even if it is determined that it is difficult to use at first, the use frequency of far vision will be extremely reduced while wearing, and it will be used in the form of using almost intermediate vision and near vision. Therefore, it can be said that, in extreme terms, a progressive multifocal lens suitable for visual work mainly for medium and short distances does not require the distance portion area unless the distance is viewed outdoors. .

Those who wear other standard type lenses before wearing the middle-near type lens, even if they feel dissatisfaction with distance vision as described above, those who wear the middle-near type lens for the first time , You may be able to put up with the fact that it is difficult to see in the distance if you give enough explanations before wearing.
However, in addition to the difficulty in far vision with this lens, there is a problem that the burden of rotation of the eyeball during near vision is large, as is the case with the perspective type lens, in comparison with lenses focusing on medium and short distances. .

That is, in this middle-near type lens, by increasing the length of the progressive portion between points A and B to be 25 mm or more, the gradient of the refracting power of the progressive portion is reduced, and the width of the intermediate clear vision region is reduced. It has a wide W2 and is designed to reduce the image blur when the line of sight is changed from far vision to near vision. For this reason, the near portion is sacrificed to some extent. For example, when the distance portion has a length of 25 mm and the distance center (point A) is located 10 mm above the eye point (geometric center O), the near vision center (Point B) is 15 mm below the eye point.
Therefore, at such a position of the near-distance center, the burden of rotation of the eyeball at the time of near vision becomes large, and the near-distance region that can be used when such a lens is framed in a spectacle frame. Area will be reduced. In addition, since the width of the intermediate clear vision region in the progressive portion is widened, there is a problem that the width W3 of the near clear vision region is narrower for the lens that places importance on the middle and near.

The present invention has been made in order to solve the above problems, and its purpose is to perform visual work mainly at medium and short distances when it is used at a long distance. This is ideal for cases where a wide and clear visual field can be obtained when looking at medium and short-distance objects, the width of the clear visual field in the progressive portion is wide, and there is little image fluctuation. An object of the present invention is to provide a progressive multifocal lens that can reduce the burden of eye rotation when looking at an object as much as possible.

[0028]

In order to solve the above problems, the invention according to claim 1 provides at least one lens refraction surface of two refraction surfaces constituting a lens, wherein A central reference line that extends in the vertical direction to minimize astigmatism and divides the refracting surface into left and right, and is provided near the geometric center of the lens on the central reference line, when looking at a long distance. The medium-use center having a refractive power to which a power of 0.50 to 2.50 D (diopter) is added to the distance-use power of, and near-use provided below the center for middle use on the central reference line. Provided above the center and the center for medium use of the lens refracting surface,
Provided below the middle-use area of the lens refracting surface for viewing the middle-use area for viewing a medium-distance object having a refractive power substantially equal to or greater than that of the middle-use center and the refractive power of the center. Is provided between the near portion area for viewing a short distance object, the intermediate portion area and the near portion area, and an intermediate portion area for viewing a short distance object from a medium distance, It is provided in the middle region including the central reference line, and is added at the center for medium use from the addition power for obtaining the near power with respect to the distance power between the center for middle use and the center for near use. From a wearing point set near a boundary point between the middle-use area and the middle-use area, the progressive power being added progressively to a predetermined power subtracted from the power The near center is arranged at a distance of 6 mm to 18 mm and includes the central reference line. Serial in a region, in the progressive portion and the near portion, n: a 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 equation, (n−1) × | C 1 −
C2 | ≦ 0.5 (m ⁻¹ ) has a clear visual field defined by the condition, and the horizontal minimum width F of the clear visual field of the progressive portion is equal to the length (mm) of the progressive portion. , Using the frequency (m ⁻¹ ) that is progressively added between the center for medium use and the center for near use, the following formula: F ≧ 0.5 (m ⁻¹ ) × length of progressive portion /
The maximum width W1 of the clear viewing zone of the middle-use area is the minimum width F of the clear viewing zone of the progressive portion and the following equation, 3 × F ≦ W1 ≦ 8 × F (mm). ), The maximum width W2 of the clear viewing zone of the near portion area is the same as the minimum width F of the clear viewing zone of the progressive portion and the following equation: 1.5 × F ≦ W2
The relationship of ≦ 4 × F (mm) was satisfied.

According to a second aspect of the present invention, in the intermediate portion area, a line of intersection between the plane perpendicular to the central reference line and the refracting surface has a radius of curvature as it moves away from the intersection of the central reference line in the horizontal direction. Is a non-circular curve that decreases, and the reduction rate of the radius of curvature in the region near the central reference line is 5 mm above the center for medium use except for the vicinity of the connecting portion between the medium use region and the intermediate region. Is substantially constant, and in the near portion area, a line of intersection between the plane perpendicular to the central reference line and the refracting surface is a non-circular curve whose radius of curvature increases as the distance from the intersection of the central reference line increases in the horizontal direction. The increase rate of the radius of curvature in the region near the central reference line is substantially constant up to 10 mm below the near center, except near the connecting portion between the near portion region and the intermediate portion region. Is the gist.

According to a third aspect of the present invention, when the progressive power multifocal lens is worn, a meridian extending vertically through the wearing point is defined, and the central reference line in a region below the wearing point is , Is displaced to the nose side with respect to the meridian, and the refraction surface of the lower region is within 15 mm from the central reference line to the nose side and the ear side with respect to the horizontal direction during wearing. The gist is that the distribution of astigmatism is asymmetrical to the left and right, and the distribution of astigmatism on the ear side in the horizontal direction has a slower change than the distribution of astigmatism on the nose side.

[0031]

According to the invention described in claim 1, the center for medium use on the central reference line has a power of 0.50 to 2.50 D (dioptre) with respect to the power for far vision when viewing a far object. It has an added refractive power (surface refractive power). In addition, a middle-use part region for seeing a medium-distance object having a refractive power substantially equal to or greater than the refractive power of the middle-use center on the lens refracting surface above the middle-use center. Provided.
Therefore, it becomes possible to see medium-distance objects in the middle-use center and middle-use area, and the usage frequency is extremely low when looking at long-distance objects, and visual work is performed mainly for middle and short distances. It will be the best case.

The power to be added is set to 0.50 to 2.50D because it is 0.50 when the intermediate distance is 40 cm to 2 m.
This is because if the power of D is added, it is possible to see a medium distance of 2 m, and if the power of 2.50 D is added, it is possible to see a medium distance of 40 cm.

Further, the power added in the progressive portion is the power obtained by subtracting the power added at the center for medium use from the power used for obtaining near power with respect to the power for distance use, which is the same as the conventional center for distance use. A value smaller than the addition power added in the progressive portion between the near center and the near center is sufficient. Therefore, for example, even if the length of the progressive portion in the conventional progressive power multifocal lens having the distance portion area and the length of the progressive portion provided between the center for medium use and the center for near use are the same, The power added in the progressive portion between the center for medium use and the center for near use is smaller than the addition power. Therefore, the gradient of the refractive power on the central reference line of the progressive portion is small, and the fluctuation of the image is reduced when the line of sight is moved between the center for medium vision and the center for near vision in the progressive portion. This image fluctuation is reduced as the power added at the center for medium use increases, and the power added at the progressive portion becomes smaller. Therefore, it is possible to add about 1.00D or more at the center for medium use. preferable.

Further, the minimum width F of the clear visual field of the progressive portion is F ≧ 0.5 (m ⁻¹ ) × length of progressive portion / frequency (mm), and Significantly W1 is set to 3 × F ≦ W1 ≦ 8 × F (mm), and further, the maximum width W2 of the clear vision region of the near vision region is set to 1.5 × F ≦ W2 ≦ 4 × F (mm). As a result, the astigmatism is diffused to the middle-use portion area and the near-use portion area side while ensuring the clear vision areas of the middle-use portion area and the near-use portion area to be sufficiently wide, and the progressive power in the middle portion area is increased. Astigmatism lateral to the part is reduced. As a result, the minimum width F of the clear vision area of the progressive portion is widened, and the clear vision areas of the middle-use portion area 3 and the near-use portion area 4 are sufficiently secured. A clear field of view is obtained when looking.

In the progressive power multifocal lens, if the widths W1 and W2 of the clear viewing zone in the middle portion portion or the near portion portion are widened, the astigmatism generated on the refracting surface is diffused into the intermediate portion and the progressive portion is increased. There is a relationship that the width F of the clear viewing zone becomes smaller. Therefore,
Based on the above equations, the maximum widths W1 and W2 of the clear regions of the medium portion and the near portion regions are ensured to be necessary and sufficient, while the minimum width F of the clear region of the progressive portion is made as wide as possible. There is a need.

The maximum width W1 of the clear viewing zone in the middle-use area is 3 × F
If it is made smaller than the above range, image distortion in the side view in the middle-use area and fluctuation when moving the line of sight in the horizontal direction occur. Further, if the maximum width W1 is made larger than 8 × F, the minimum width F of the clear visual region of the progressive portion becomes narrower, and image distortion and shake in the side visual field of the intermediate region occur.

The maximum width W2 of the clear viewing zone of the near vision area is 1.5
When the value is smaller than × F, image distortion in the side view in the near portion area and fluctuation when moving the line of sight in the horizontal direction occur. When the maximum width W2 is made larger than 4 × F, the minimum width F of the clear visual field of the progressive portion becomes narrower as described above, and the image distortion or the shake occurs in the lateral visual field of the intermediate area.

Further, by disposing the near wear center at a distance of 6 mm to 18 mm from the wear point set near the boundary point between the middle wear area and the middle area, the distance from the wear point to the near wear center Does not become longer, and the burden of eye rotation is reduced as much as possible. The wearing point may be at the same position as the center for middle use or at a position deviated from the center for middle use. Distance from wearing point to near center is 12m
In the case of exceeding m, the wearing point may be shifted from the center of middle use to the upper middle use region by the distance (for example, 6 mm in the case of 18 mm). By doing so, it becomes possible to reduce the burden of rotation of the eyeball in the range of the distance from the wearing point of 6 mm to 18 mm to the near center.

According to the second aspect of the present invention, in the intermediate portion region, the intersection line between the plane perpendicular to the central reference line and the refracting surface is moved away from the intersection of the central reference line in the horizontal direction and the radius of curvature is increased. It was a non-circular curve with a decrease. For this reason,
The refractive power increases as the distance from the central reference line increases in the horizontal direction. Further, in the near portion area, the line of intersection between the plane perpendicular to the central reference line and the refracting surface is a non-circular curve whose radius of curvature decreases as the distance from the intersection of the central reference line increases in the horizontal direction. Therefore, the refractive power decreases as the distance from the central reference line increases in the horizontal direction. Therefore, an increase in the refractive power in the medium-use portion region and a decrease in the refractive power in the near-use portion region reduce the difference in power between the middle-use portion region and the near-use portion region. As a result, the connection from the middle-use area to the near-use area through the middle area becomes smooth, the concentration of astigmatism and distortion on the side of the middle area is reduced, and the side of the middle area is reduced. The direction is good.

Further, the reduction rate of the radius of curvature in the medium-use portion area near the central reference line is almost constant up to 5 mm above the center of the medium-use portion except for the vicinity of the connecting portion between the medium-use portion area and the intermediate portion area. . Further, the increase rate of the radius of curvature in the near portion area near the central reference line is substantially constant up to 10 mm below the near center except for the vicinity of the connecting portion between the near portion area and the intermediate portion area. Therefore, in the vicinity of the central reference line in the region of this range, the shape of the refracting surface becomes smooth, and astigmatism and distortion are less concentrated. As a result, in the areas with the highest frequency of use, the middle-use portion area and the near-use portion area, the fluctuation of the image when moving the line of sight in the vertical direction near the central reference line is reduced.

Further, in the near portion area, the refracting power decreases as the distance from the central reference line increases in the horizontal direction. It becomes possible to see relatively far distances relatively clear.

In the medium-use area, for example, the viewing angle when viewing a medium-distance object from end to end in deskwork may be narrower than the viewing angle when viewing a short-distance object from end to end in the near-use area. I can say. Therefore, even if the refracting power increases as the distance from the center reference line increases in the horizontal direction in the middle-use area, the lateral viewing angle in the middle-use area is narrow, so the maximum width W1 of the clear viewing area is 3 × F. ≤W1 ≤8 ×
If it is within the range of F, there will be no hindrance to lateral vision at a medium distance.

According to the third aspect of the present invention, in the region below the wearing point, the central reference line is displaced toward the nose side by a larger amount than the displacement amount of the central reference line in the upper region, The refractive surface of the area 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. Therefore, when laterally looking at a short distance with both eyes, the amount of movement of the line of sight to the ear side of one eye,
In contrast to the fact that the amount of movement of the other eyeball toward the nose side becomes larger, the distribution of astigmatism on the refractive surface on the ear side is slow, so good binocular lateral vision with less image shake It will be possible.

The area above the wearing point is an area for viewing a medium distance, so that the moving amount of the line of sight to the ear side is less than the moving amount to the nose side. Even if the astigmatism is not asymmetrical as in the lower region, side vision does not become difficult.

The distribution of astigmatism is defined for the refracting surface within a region of 15 mm from the central reference line.
This is because this area is the most important part of the spectacle lens.

[0046]

【Example】

(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 convex lens refracting surface 2 of the progressive power multifocal lens 1. A center A for middle use is provided on the central reference line S, and a center B for near use is provided below the center A for middle use.
Is provided. The progressive power multifocal lens 1 has a diameter of 50 mm.

The central reference line S is a line with the smallest astigmatism and almost zero (a so-called navel curve), which cannot be visually confirmed. The middle-use center A is located 2 mm above the geometric center O of the progressive multifocal lens 1, and is 1.0 with respect to the far-distance dioptric power when viewing a long-distance object.
The frequency of D (diopter) is added. The near vision center B is located 10 mm below the geometric center O, and the power added to the intermediate vision center A from the addition power (2.00 D in this case) for obtaining the near vision power with respect to the far vision power. (In this case, the frequency (1.00D) obtained by subtracting 1.00D) is added.

As shown in FIG. 2, a middle-use part region 3 for viewing a medium-distance object (hereinafter referred to as middle view) is provided above the middle-use center A of the lens refracting surface 2 for near use. Center B
A near portion region 4 for viewing a near object (hereinafter, referred to as near vision) is provided below. An intermediate area 5 is provided between the intermediate area 3 and the near area 4 of the lens refracting surface 2 for viewing an object at a medium distance to an object at a short distance (hereinafter referred to as intermediate vision). .

The middle-use portion area 3 has a refracting power substantially the same as that of the middle-use center A, and is an area suitable for middle vision with a distance of 1 m (because the addition of the power of 1.00 D). Has become. The near portion area 4 has almost the same refractive power as that of the near center B and is suitable for near vision nearer than a distance of 50 cm (because the addition of 2.00 D is added). Has become. A progressive portion 6 is provided in a portion including the central reference line S of the intermediate portion region 5. As shown in FIG. 1B, the progressive portion 6 on the central reference line S is close to the center A for medium use. The power (1.00D) obtained by subtracting the power D1 (1.00D) added to the middle power center A from the addition power D2 (2.00D) is progressively added to the power center B. Therefore,
The middle area including the progressive portion 6 is 50 cm from a distance of 1 m.
This area is suitable for intermediate vision at a distance of.

As shown in FIGS. 1A and 2, a wearing point (hereinafter referred to as an eye point) P when the progressive power multifocal lens 1 is worn on a spectacle frame is at the same position as the center A for medium use, that is, It is set to be located 2 mm above the geometric center O. Therefore, the near center A is the eyepoint P.
It is arranged 12 mm below.

Next, the clear vision areas in the middle-use area 3, the near-use area 4, and the intermediate area 5 will be described. First, the clear visual field is defined according to the following formula.

(N-1) × | C1−C2 | ≦ 0.5 (m− ¹ ) n: Refractive index of lens material C1, C2: Principal curvatures in different directions at points on the lens refracting surface A region with a point aberration of 0.5 D or less is a clear vision region.

Further, as shown in FIG. 1A, the lens refracting surface 2 has an astigmatism magnitude in the unit of diopter,
It is represented by isoastigmatism lines of 0.25D, 0.50D, and 0.75D. This astigmatic line is not actually visible to the eye.

In this figure, the progressive portion 6 of the intermediate region 5 is
The horizontal minimum width F of the clear visual field (hereinafter, referred to as progressive clear visual field) is 7.5 mm. The numerical value of the minimum width F satisfies the conditional expression “F ≧ 0.5 × length of progressive portion / frequency”. That is, the length of the progressive portion is the length from the center A for medium use to the center B for near use, and is 12 mm in this embodiment. or,
The power is a power progressively added between the center A for near vision and the center B for near vision, and is 1.00 D in this embodiment. Therefore, 7.5 ≧ 0.5 × 12 / 1.00 = 6, which satisfies the condition.

The maximum horizontal width W1 of the clear vision area in the middle-use area 3 (hereinafter referred to as the middle-use clear vision area) is 44 mm. The value of this maximum width W1 is F = 7.5 mm,
5.9 × F, and the maximum width W1 condition “3 × F ≦ W1 ≦
8 × F ”is satisfied.

The maximum horizontal width W2 of the clear vision area in the near vision area 4 (hereinafter referred to as "near vision clear vision area") is 18 mm. The value of this maximum width W1 is F = 7.5 mm,
2.4 × F, and the maximum width W2 condition "1.5 × F≤W
2 ≦ 4 × F ”is satisfied.

In the progressive multifocal lens 1 constructed as described above, the center A for medium use on the central reference line S is 1.00 D (diopter) with respect to the distance dioptric power when looking at a long distance. The frequency is added. Further, a middle-use portion area 3 having a refractive power substantially the same as that of the middle-use center A is provided on the lens refracting surface above the middle-use center A. Therefore, in the center A for medium use and the region 3 for medium use, it is possible to see in the distance of 1 m, and the frequency of use when looking at a long distance is extremely low.
For example, it is most suitable for indoor desk work, medical surgery such as surgery, and machine tool work such as lathe.

Further, the power added by the progressive section 6 is the addition power for obtaining the near power with respect to the far power (in this case,
It is not 2.00D) but the power (1.00D) obtained by subtracting the power added at the center A for medium use from the addition power. Therefore, for example, the length of the progressive portion in the conventional progressive power multifocal lens having the distance portion area is the same as the length of the progressive portion 6 provided between the middle-use center A and the near-use center B. However, the power progressively added in the progressive portion 6 becomes smaller than the addition power. Therefore, the gradient of the refracting power on the central reference line S of the progressive portion 6 is small,
At, when the line of sight is transferred between the center A for near vision and the center B for near vision, the image shake is reduced.

The gradient of this refractive power can be expressed by the added power and the length of the progressive portion 6, and in this embodiment, the gradient =
1.00D / 12 mm≈0.08, which is almost the same as the gradient of the refractive power of the conventional middle-near type progressive power multifocal lens.

Based on the above equations, the minimum width F of the progressive clear vision region is 7.5 mm and the maximum width W1 of the intermediate clear vision region is 44 m.
By setting the maximum width W2 of the clear vision area for the near portion to 18 mm, the following action and effect can be obtained.

That is, assuming that the maximum widths of the medium-range clear vision region and the near-range clear vision region are as described above, the astigmatism is diffused to the medium-division region 3 and the near-distance region 4 side, and the intermediate region 5 is formed. Astigmatism on the side of is reduced. As a result, it is possible to widen the minimum width F of the clear visual field of the progressive portion 6. The value of this minimum width F is 7.5 m
m is the value 3 of the minimum width of the clear visual region of the progressive portion between the distance center and the near center of the conventional lens (for comparison, for convenience).
Since it is larger than mm to 7 mm, it can be seen that the progressive bright visual region is wide.

The value 44 mm of the maximum width W1 of the clear region for medium use is
It can be seen that since the maximum width of the distance portion area of the conventional standard type lens (which is a comparison target for the sake of convenience) is 40 mm larger, the intermediate clear vision area is sufficiently secured. Therefore, it is possible to obtain a clear visual field in the middle direction. Further, in the intermediate clear vision region, the maximum width (not shown) of the region where the astigmatism is 0.25D or less is 20 mm. Therefore, when performing the mid-range view in this area, it is possible to clearly see small objects, for example, the end portion when the newspaper is unfolded, and small characters such as memos and calendars placed on the edge of the desk.

The value 18 mm of the maximum width W2 of the near vision area is
The maximum width value 6 in the near portion area of each type of conventional lens
Since it is larger than 15 mm, it can be seen that the near vision region is sufficiently secured. Therefore, a clear visual field can be obtained in near vision. In addition, the medium-range clear vision area, progressive clear vision area,
In the near vision region, the astigmatism is 0.50D or less, so that image distortion is suppressed as much as possible in that region.
FIG. 3 shows a distortion diagram when a square lattice is viewed through the progressive power multifocal lens 1. As shown in this figure, in the region where the astigmatism (illustrated by the broken line) is 0.50D or less, the grating seen through the lens 1 is slightly enlarged in the near portion region 4, but the original square is formed. It is almost equal. 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 the fluctuation when moving the line of sight can be reduced.

Further, the center A for middle use is set as an eye point P,
By disposing the near vision center B 12 mm below the eye point P, the distance from the eye point P to the near vision center B does not become long, and the eyeball rotation burden is reduced as much as possible.

(Second Embodiment) Next, an embodiment of eyeglasses using the progressive multifocal lens 1 of the first embodiment will be described.

As shown in FIG. 4, the spectacles 7 are composed of a spectacle frame 8 and two progressive multifocal lenses 1.
In the spectacle frame 8, the lens 1 is edged so that the eyepoint P set according to the wearer on the left and right rims 9 and the center A of the progressive power multifocal lens 1 coincide with each other. Each is framed. Each lens 1 has a geometric center O
The frame is framed in a state of being rotated by a predetermined angle (in this case, 12 degrees) to the nose side with respect to the vertical direction. Therefore, the near vision center B is displaced from the eye point P to the nose side by 2.5 mm in consideration of the convergence in near vision (so-called inward alignment).
is doing.

The spectacles 7 configured as described above can perform middle vision in a state in which a wide clear vision region is secured in the middle-use portion region 3 including the eyepoint P, that is, the center A for middle use.
Further, near vision is performed in the near portion region 4 including the near vision center B 12 mm below (in this case, diagonally below) from the eye point P in a state where a wide clear vision region is secured and the eyeball rotation burden is small. be able to. Further, in the progressive portion 6, intermediate vision can be performed in a state where the width of the clear vision region is wide and the image shake is small.

(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 and the description thereof will be omitted.

As shown in FIG. 5 (a), the center A for medium use is located 6 mm above the geometric center O of the progressive power multifocal lens 1, and is for the distance dioptric power when looking at a far object. 1.25D frequency is added. Therefore, in the middle-use portion area 3, it is possible to see from the inside of 80 cm. In the progressive portion 6 on the central reference line S, from the center A for near vision to the center B for near vision, the power obtained by subtracting the power D1 (1.15D) added to the center A for middle use from the addition power D2 (2.00D). (0.75D) is progressively added. Therefore, the progressive portion 6 is suitable for intermediate vision of 80 cm to 50 cm. The length of the progressive portion 6 is 16 mm. In this embodiment, the eye point P is located 2 mm above the geometric center O, and the eye point P has a power of 1.44D added thereto.

The minimum width F of the progressive bright visual region is 15 mm (15 ≧
0.5 × 16 / 0.75 = 10.7), and the maximum width W1 of the intermediate clear vision region is 49 mm (3 × 15 ≦ 49 ≦ 8 × 15). The maximum width W2 of the near vision region is 26 mm (1.
5 × 15 ≦ 26 ≦ 4 × 15).

In the progressive power multifocal lens 1 configured as described above, the power added to the middle-use center A is increased by 0.25D and the power added to the progressive portion 6 is set to 0. 25D, and the length of the progressive portion 6 is increased by 4 mm. Therefore, as shown in FIG. 5B, the gradient of the refractive power on the central reference line S of the progressive portion 6 becomes smaller. That is, the gradient = 0.75D / 16 mm≈0.05. As a result, when performing mesoscopic vision, intermediate vision, and near vision within 80 cm, the image shake is less, and the middle-use area 3,
In the near portion area 4 and the intermediate portion area 5, a clear visual field can be obtained in a wider clear vision area.

(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. 6, the position of the center A for medium use and the added frequency are the same as those in the first embodiment (1.00D).
Is. The near vision center B is arranged 8 mm below the geometric center O, and the added frequency is the same as that in the first embodiment (1.00D). Therefore, in the fourth embodiment, the length of the progressive portion 6 is 10 mm, which is 2 mm shorter than that in the first embodiment. Therefore, the gradient of the refracting power on the central reference line S of the progressive portion 6 is 1.00 D / 10 mm≈0.10. The diameter of the progressive multifocal lens 1 is 70
mm.

The minimum width F of the progressive bright visual region is 6.5 mm (6.
5 ≧ 0.5 × 10 / 1.00 = 5.0) and the maximum width W1 of the intermediate clear vision region is 50 mm (3 × 6.5 ≦ 50 ≦ 8 × 6.
5), the maximum width W2 of the near vision area is 26 mm (1.5 x
6.5 ≦ 26 ≦ 4 × 6.5).

In the progressive power multifocal lens constructed as described above, the gradient of the refracting power is steeper than that of the first embodiment, so that astigmatism is concentrated on the side of the intermediate region 5,
There is a problem that the image shake is noticeable when looking laterally (hereinafter referred to as lateral viewing). Therefore, in this embodiment, the side view in the intermediate region 5 is improved by the following configuration.

That is, as shown in FIGS. 7 and 8, the line of intersection between the plane perpendicular to the central reference line S and the refracting surface 2 is the following curve. In the middle-use portion region 3 10 mm above the geometric center O, the intersection line L1 has a radius of curvature that decreases as it moves away from the intersection E1 of the central reference line S by about 10 mm in the horizontal direction, that is, the surface refractive power (D: diopter). ) Is an increasing non-circular curve. Intersection line L1 is intersection point E1
After about 10 mm away from the
Again, it is a non-circular curve in which the surface refractive power decreases from the distance of about 25 mm from the intersection E1. In this embodiment, the surface refractive power (equation (n-1) / R, n: refractive power of lens material, R: radius of curvature) is used to represent the line of intersection.

Medium portion area 3 4 mm above the geometric center O
In the above, the line of intersection L2 is a non-circular curve in which the surface refracting power increases with a distance of about 10 mm from the intersection E2 of the central reference line S in the horizontal direction, and thereafter, the surface refracting power decreases again at a constant value of about 15 mm. Has become.

Here, only the intersection line L2 which is 4 mm above the geometric center O (2 mm above the center A for medium use) is shown.
All the intersection lines in the middle-use area 3 up to 5 mm above the middle-use center A have a constant surface refractive power as they move away from the central reference line S by about 10 mm except for the connection with the middle-use area 5. It is a non-circular curve that increases with.

Intermediate region 3 3 mm below the geometric center O
In the line L3, the surface refracting power decreases as it moves away from the intersection E3 of the central reference line S by about 10 mm in the horizontal direction, and then becomes a non-circular curve with a constant surface refracting power.

10 mm below the geometric center O (near-center B
In the near portion area 4 (2 mm below), the intersection line L4 is
The surface refracting power decreases at a constant rate as the distance E10 from the intersection E4 of the central reference line S increases in the horizontal direction.
The non-circular curve is almost constant up to about 30 mm.

Here, only the intersection line L4 10 mm below the geometric center O (2 mm below the near vision center B) is shown, but all intersections in the near vision region 4 up to 10 mm below the near vision center B are shown. The line is a non-circular curve in which the surface refractive power decreases at a constant rate as the surface refractive power moves away from the central reference line S by about 10 mm, except for the connection portion with the intermediate region 5.
Further, the reduction rate of the surface refractive power is maximum near the near vision center B, as shown by the intersection line L4 in FIG.

In the near portion area 4 20 mm below the geometric center O, the intersection line L5 is a non-circular curve whose surface refractive power decreases as it moves away from the intersection E5 of the central reference line S by about 30 mm in the horizontal direction. ing.

In the near portion area 4 which is 30 mm below the geometric center O, the intersection line L6 decreases in surface refractive power as it moves away from the intersection E6 of the central reference line S by about 10 mm in the horizontal direction, and then increases. It is a circular curve.

In the progressive power multifocal lens 1 configured as described above, the surface refracting power is increased in the horizontal direction in the middle-use area 3 and the horizontal refracting power in the middle area 5 and the near-use area 4. By reducing, the difference in frequency between the middle-use portion area 5 and the near-use portion area 4 is reduced. Therefore,
The connection from the middle-use area 3 to the near-use area 4 via the middle area 5 becomes smooth, and the concentration of astigmatism and distortion on the side of the middle area 5 is reduced. In addition to the effect of the first embodiment, the side view in the intermediate region 5 becomes good.

Further, the increase rate of the surface refractive power in the medium-use portion region 3 near the central reference line S is kept substantially constant from the center A of the medium use portion 5 mm upward, and in the near-use portion region 4 near the central reference line S. The reduction rate of the surface refractive power is 10 m below the near center B.
It was made almost constant up to m. Therefore, in the vicinity of the central reference line S in the region of this range, the shape of the refracting surface 2 becomes smooth, and astigmatism and distortion are less concentrated. As a result, in the most important portions (the portions that are frequently used) of the middle-use portion area 3 and the near-use portion area 4, there is less image fluctuation when moving the line of sight in the vertical direction near the central reference line S. Become.

Further, in particular, the intersection lines L2 to L4, L6 are about 1 in the horizontal direction from the intersections E2 to E4, E6 of the central reference line S.
Since the curve is such that the surface refractive power increases and decreases as it goes away by 0 mm, the curve of the middle-use area 3 coincides with the curve of the near-use area 4 through the intermediate area 5 by about 10 mm. Therefore, from the central reference line S including the progressive portion 6, about 10
In the region up to mm, the complex waviness on the refracting surface 2 is reduced, and the astigmatism is reduced. As a result, the minimum width F of the progressive bright visual region can be realized as the above wide value (6.5 mm). As a comparative example, a conventional standard type progressive multifocal lens (distance dioptric power 0.00
The intersection line of D and the near power 2.00D is added (not shown), but the curve of the distance portion region coincides with the curve of the near portion region although the upper region is the distance portion region. The distance to is as long as about 20 mm. Therefore, the progressive power multifocal lens 1 of this embodiment has a short distance (about 10 mm).
Since the curvatures coincide with each other, it is possible to increase a portion where astigmatism is less concentrated on the side of the middle portion area 3, the near portion area 4 and the intermediate portion area 5, and it is possible to improve the lateral vision. it can.

Further, the intersection lines L1 and L2 of the middle-use portion area 3 are made to be curves after the surface refracting power is once increased and then made constant, and the intersection line L6 of the near-use portion area 4 is changed to the surface refracting power. Was once reduced, then kept constant, and then increased again. Therefore, the difference in astigmatism does not increase at the sides of the intermediate region 3, the near region 4, and the intermediate region 5, that is, at the end of the lens 1, and the astigmatism at the end and It is possible to suppress an increase in distortion.

In the near portion area 4, the central reference line S
Since the refracting power decreases as it moves away from the horizontal direction in the horizontal direction, in the side view in the near portion region 4, the near center B
It is suitable for viewing an object at a distance slightly longer than the distance for viewing an object. For example, looking at the center of the desk near the center reference line S of the near portion area 4 in desk work,
This is suitable for performing side view in which the desk end is viewed at the end of the near portion area 4.

In addition, for example, the viewing angle when viewing a medium-distance object from end to end in the mid-use area 3 is more than the viewing angle when viewing a short-distance object in the near-use area 4 from end to end. Can be said to be narrow. Therefore, even if the refractive power increases as the distance from the central reference line S increases in the middle-use area 3 in the horizontal direction, the lateral viewing angle in the middle-use area 3 is narrow, and the maximum width W1 of the clear viewing area is 3 × F ≦
Since it is within the range of W1 ≦ 8 × F, it does not hinder the lateral vision at a medium distance.

(Fifth Embodiment) Next, a fifth 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 progressive multifocal lens 1
A meridian T extending vertically through the eyepoint P when wearing is determined. Area above the eyepoint P (area including the upper part of the intermediate area 5 and the intermediate area 3)
The central reference line S1 at is displaced parallel to the meridian T by about 0.3 to 0.4 mm toward the nose side. The central reference line S2 in the area below the eye point P (the area including the lower part of the intermediate area 5 and the near area 4) is
The amount of displacement increases toward the meridian T, and the amount of displacement on the nose side is larger than that of the central reference line S1.

The medium center A on the central reference line S1 is located 2 mm above the geometric center O, and the near center B on the central reference line S2 is located 10 mm below the geometric center O. Therefore, in the fifth embodiment, the length of the progressive portion 6 is 12 mm,
It has the same length as that of the first embodiment.

The frequency added to the center A for medium use is 0.5.
It is 0D. The near center B has a frequency of 1.50.
It is D. Therefore, the gradient of the refracting power on the central reference line S of the progressive portion 6 is 1.50D / 12 mm≈0.13. The diameter of the progressive multifocal lens 1 is 70 m.
It has become m. Furthermore, the minimum width F of the progressive clear vision area is 5.0.
mm (5.0 ≧ 0.5 × 12 / 1.50 = 4.0), the maximum width W1 of the intermediate clear region is 40 mm (3 × 5.0 ≦ 40 ≦
8 × 5.0), maximum width W2 in the near vision zone is 26 mm
(1.5 × 5.5 ≦ 26 ≦ 4 × 6.5).

The refractive surface 2a in the region above the geometric center O has an astigmatism distribution in the region within 15 mm from the center reference line S1 to the nose side and the ear side with respect to the horizontal direction during wear. 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 to the nose side and the ear side with respect to the horizontal direction at the time of wearing with the central reference line S2 as the boundary. 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.

As shown in FIGS. 11 and 12, this embodiment also has a plane perpendicular to the central reference lines S1 and S2 and refracting surfaces 2a and 2b.
The intersecting lines L1 to L6 with and are the non-circular curves similar to those in the fourth embodiment. However, the line of intersection L3 is 4 from the geometric center O
mm, and the intersection line L4 is 12 mm below the geometric center O. The changes in the surface refractive power at the intersection lines L1 to L6 in the fifth embodiment are almost the same as the changes in the surface refractive power in the fourth embodiment.

In the progressive multifocal lens 1 configured as described above, the central reference lines S1 and S2 are displaced toward the nose side,
The following effects are obtained by making the distribution of astigmatism on the ear side in the horizontal direction of each refracting surface 2a change more slowly than the distribution of astigmatism on the nose side.

As shown in FIG. 13, when a person at a medium or particularly short distance is laterally viewed with both eyes, the amount of movement α1 of the line of sight of the right eye ER to the ear side is to the nose side of the left eye EL. It is known that the amount of movement of the line of sight of α2 is larger than α2.
In this embodiment, since the distribution of astigmatism on the ear side is slow,
It is possible to perform good binocular lateral vision with little image fluctuation. Further, by displacing to the nose side of the central reference line S2, even if the lens 1 is put in the spectacle frame without rotating, it is possible to cope with the congestion in the near vision.

The intersection lines L1 to L6 between the planes perpendicular to the central reference lines S1 and S2 and the refracting surfaces 2a and 2b are non-circular curves similar to those in the fourth embodiment. Astigmatism and distortion are less concentrated, and as a result, lateral viewing in the intermediate region 5 is improved. In addition, in a part of the middle-use portion area 3 from the middle-use center A to 5 mm above and in the near-use portion area 4 from the near-use center B to 10 mm below,
When the line of sight is moved up and down in the vicinity of the central reference line S, the fluctuation of the image is reduced.

As described in detail above, the present invention is not only optimal when performing work mainly at medium and short distances, but also useful for the following people to wear. People with presbyopia who have not progressed, but who are not wearing progressive multifocal lens spectacles, and who cannot wear it with a perspective type progressive multifocal lens (for example, 2.00D).

A person who is using a progressive-power type multifocal lens, but who uses monofocal reading glasses in near work because near vision is difficult. People who use single-focal reading glasses but whose distance to see is narrow, so when they look at a newspaper, their face should be close to the newspaper.

A person who is worried about shaking when walking using a perspective type progressive multifocal lens. The present invention can be embodied as follows. (1) The frequency of joining at the center A for medium use is 0.5D to
You may change arbitrarily between 2.50D. In this case, the frequency steps are, for example, 0.50D, 0.75D. ． ．
And every 0.25D. Also, the range of frequency is 0.5D ~
It may be 2.00D or 1.00 to 1.50D.

(2) The refractive power of the middle-use portion area 3 is set to the center A for middle use.
The refractive power may be about the same as the refractive power of (. +-. 0.25D) or larger than the refractive power of the center A for medium use. (3) In the second embodiment, when the progressive power multifocal lens 1 is rotated to be framed, the eyepoint P set according to the wearer on the target lens 9 and the center A for middle use are made to coincide with each other. But,
The middle use center A may be displaced to the nose side by 0.3 to 0.5 mm. By doing so, the near center A can be shifted to the nose side with a small rotation angle of the lens 1. In addition to framing so that the center A of the lens 1 is aligned with the position of the eye point P, 2 mm below the eye point P of the lens 9
It may be framed so that the middle use center A is located between 6 mm and 4 mm above.

(4) In the fifth embodiment, the amount of movement of the line of sight when looking at a medium distance is smaller than the amount of movement of the line of sight when looking at an object at a short distance. The distribution of the nasal astigmatism in the area of 1 may not be slower than the distribution in the area of the lower side. Therefore, the displacement amount of the central reference line S1 in the upper region is equal to the geometric center O
It may be smaller than the displacement amount of the central reference line S2 in the region below. Further, the center reference line S1 may not be displaced if necessary. Further, the region where the distribution of astigmatism is asymmetric is left and right within 15 mm on the nose side and the ear side with respect to the central reference line S, but it may be within 17.5 mm.

(5) Even if the frequencies added at the center A for medium use and the center B for near use are different from the nominal power, it does not depart from the gist of the present invention. For example, the nominal power added at the center A for medium use is 0.50D, and the actual power is 0.75.
D, and the nominal power added at the near vision center B is 1.00
In D, the actual frequency may be 0.80D.

(6) In each of the above embodiments, the convex lens refracting surface 2 of the progressive power multifocal lens 1 is embodied, but it may be embodied as a concave refracting surface. In this case, the increase and decrease of the radius of curvature in the fourth and fifth embodiments are completely opposite.

The center for medium use in the present invention is defined as follows. Center for middle use: a part which has a dioptric power when looking at a medium distance of 40 cm to 2 m on the central reference line and serves as an entrance to the progressive portion.

The progressive portion in the present invention is defined as follows. Progressive part: A part near the central reference line of the intermediate part region between the middle-use part region and the near-use part region, which is a part where the frequencies are progressively added from the middle-use center to the near-use center.

The technical ideas other than the claims that can be understood from the above-described embodiments will be described below along with their effects. (1) Using the progressive power multifocal lens according to any one of claims 1 to 3, a middle-use center is located between 2 mm below and 6 mm above the wearing point set on the lens of the spectacle frame. Eyeglasses characterized by being framed. By doing so, the performance of the lens can be sufficiently exerted when worn as eyeglasses.

(2) The progressive multifocal lens according to claim 1 or 2 is used, and the middle-use center is located between 2 mm below and 6 mm above the wearing point set on the lens of the spectacle frame, and Eyeglasses characterized by being framed with the center for middle use displaced by 0.3 to 0.5 mm toward the nose. By doing so, the rotation angle of the lens can be reduced.

[0112]

As described above in detail, according to the invention described in claim 1, when a long-distance object is used, the frequency of use is extremely low and the visual work mainly for medium and short distances is performed. It is suitable for wide range and clear field of view when looking at medium and short distance objects, and has a wide clear vision area in the progressive portion and little image fluctuation, and even for short distance objects. It is possible to reduce the burden of rotation of the eyeball when looking at as much as possible.

According to the second aspect of the invention, in addition to the above effects, the connection from the middle-use portion region to the near-use portion region through the middle portion region is smooth, and the side portion of the middle portion region is provided. Astigmatism and distortion are less concentrated, and the lateral view of the intermediate region is improved. In addition, in the medium-use portion area and the near-use portion area, which are most frequently used, the fluctuation of the image when moving the line of sight in the vertical direction near the central reference line is reduced.

According to the third aspect of the present invention, in addition to the above effects, since the distribution of astigmatism on the refractive surface on the ear side is slow, good binocular lateral vision with less image shake is obtained. Is possible.

[Brief description of drawings]

1A and 1B show a progressive-power multifocal lens in a first embodiment of the present invention, FIG. 1A is an explanatory diagram showing a distribution of astigmatism of the progressive-power multifocal lens, and FIG. It is a graph which shows the change of refractive power.

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

FIG. 3 is a distortion diagram of a square lattice viewed through a progressive multifocal lens.

FIG. 4 is a front view showing spectacles in which a progressive multifocal lens in a second example is framed.

FIG. 5 shows a progressive-power multifocal lens according to a third embodiment,
(A) is an explanatory view showing the distribution of astigmatism of the progressive power multifocal lens, and (b) is a graph showing the change of the refracting power on the center reference line of the lens.

FIG. 6 is an explanatory diagram showing a distribution of astigmatism of the progressive-power multifocal lens of the fourth example.

FIG. 7 is an explanatory diagram showing a line of intersection between a plane perpendicular to a central reference line and a refracting surface.

FIG. 8 is a graph showing a change in surface refractive power of each intersection line.

FIG. 9 is a graph enlarging and showing a change in surface refractive power of a part of intersection lines.

FIG. 10 is an explanatory diagram showing a distribution of astigmatism of the progressive-power multifocal lens of the fifth example.

FIG. 11 is an explanatory diagram showing a line of intersection of a plane perpendicular to the central reference line and a refracting surface.

FIG. 12 is a graph showing a change in surface refractive power at each intersection line.

FIG. 13 is a schematic diagram showing the amount of movement of the eyeball when moving the line of sight to the side.

FIG. 14 is an explanatory diagram showing a region of a progressive multifocal lens in a conventional example.

FIG. 15 shows an astigmatism distribution of a progressive multifocal lens of a conventional example, (a) is an explanatory diagram showing an astigmatism distribution of a standard type lens, and (b) is a far-middle type lens. It is explanatory drawing which shows the distribution of the astigmatism.

FIG. 16 is an explanatory diagram showing a distribution of astigmatism of a middle-near type progressive power multifocal lens of a conventional example.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Progressive multifocal lens, 2 ... Lens refraction surface, 3 ... Middle area, 4 ... Near area, 5 ... Intermediate area, 6 ... Progressive area,
S ... Central reference line, A ... Medium center, B ... Near center, O ... Geometric center, P ... Eye point as wearing point, L1
~ L6 ... Intersection line, E1 ~ E6 ... Intersection point, T ... Meridian line.

Claims (3)

[Claims] 1. At least one lens refraction surface of the two refraction surfaces constituting the lens extends in the vertical direction of the lens refraction surface such that astigmatism is minimized,
A central reference line that divides the refracting surface into right and left and a central reference line that is provided in the vicinity of the geometric center of the lens on the central reference line, and is 0.
A medium-use center having a refractive power to which a power of 50 to 2.50 D (dioptre) is added, a near-use center provided below the middle-use center on the central reference line, and the lens refracting surface of the lens refraction surface. A medium-use portion region provided above the center for medium use for viewing a medium-distance object having a refractive power substantially equal to or greater than the refractive power of the center for medium use, and the lens refraction It is provided below the near vision center of the surface, and is provided between the near vision area for seeing a short distance and the intermediate vision area and the near vision area. In order to obtain a near dioptric power with respect to a distance dioptric power between the mid-distance center and the near-distance center, which is provided in the mid-distance region for seeing an object and the intermediate-distance region including the central reference line. After subtracting the power added at the center for medium use from the power of addition of And a progressive portion in which the refractive power changes progressively, and the distance is 6 mm to 18 mm from the wearing point set near the boundary point between the middle-use area and the middle-area. A center is disposed, and in the middle-use portion area, the progressive portion and the near-use portion area including the central reference line, n is a refractive index of the lens material, C
1, C2: Using the principal curvatures in different directions (unit is m ⁻¹ ) at points on the lens refracting surface, the following equation is obtained: (n−1) × | C1 −C2 | ≦ 0.5 (m ⁻¹ ) The minimum width F in the horizontal direction of the clear visual field of the progressive portion is the length (mm) of the progressive portion, the middle-use center, and the near-use center. And the frequency (m ⁻¹ ) progressively added between the following equation, F ≧ 0.5 (m ⁻¹ ) × length of progressive portion / frequency (mm) The maximum width W1 of the clear region of the medium-use portion satisfies the following formula: 3 × F ≦ W1 ≦ 8 × F (mm) with the minimum width F of the clear region of the progressive portion, Similarly, the maximum width W2 of the clear viewing area of the region is the same as the minimum width F of the clear viewing area of the progressive portion and the following expression: 1.5 × F ≦ W2 ≦ 4 × F (mm) Focus lens. 2. In the middle-use portion area, a line of intersection between the plane perpendicular to the central reference line and the refracting surface is a non-circular curve whose radius of curvature decreases as the distance from the intersection of the central reference line increases in the horizontal direction. The reduction rate of the radius of curvature in the region near the central reference line is substantially constant up to 5 mm above the center for medium use except for the vicinity of the connecting portion between the medium use region and the intermediate region. In the near portion area, a line of intersection between the plane perpendicular to the central reference line and the refracting surface is a non-circular curve whose radius of curvature increases as it moves away from the intersection of the central reference line in the horizontal direction, and the central reference line 2. The progressive multiple according to claim 1, wherein an increase rate of the radius of curvature in a region in the vicinity is substantially constant up to 10 mm below the center of the near vision, except in the vicinity of a connecting portion between the near vision region and the intermediate region. Focus lens. 3. A meridian that extends vertically through the wearing point when the progressive power multifocal lens is worn is defined, and the central reference line in a region below the wearing point is a nose with respect to the meridian. The refraction surface in the lower region is displaced to the side, and the distribution of astigmatism is left and right in the region within 15 mm to the nose side and the ear side with respect to the horizontal direction at the time of wearing with the center reference line as a boundary. Asymmetric,
3. The distribution of astigmatism on the ear side in the horizontal direction has a slower change than the distribution of astigmatism on the nose side.
The progressive multifocal lens described in.