JPH0581886B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the shape of a refractive surface of a progressive multifocal lens.

An object of the present invention is to provide a progressive multifocal lens that is ideal for use in active situations, such as when going out for shopping or when playing sports.

Progressive multifocal lenses were developed to correct the decline in the accommodative function of the crystalline lens of the eye in the elderly.Currently, various types of lenses are commercialized, but the basic structure is All are the same. In other words, a progressive multifocal lens has an area for viewing distant objects and an area for viewing near objects at the top and bottom of the lens, and a continuous area between the two areas. It has variable refractive power and has an area for viewing objects at intermediate distances. These regions are called a distance region, a near vision region, and an intermediate region, respectively, and are divided into left and right by a principal meridian that runs in the vertical direction. A lens has two refractive surfaces, a convex surface and a concave surface, and the refractive surface having each of the above regions is usually formed so that there is no visible boundary line on the convex surface side, and in this case, the concave surface side is a spherical or toric surface, Corrects farsightedness, nearsightedness, and astigmatism. FIG. 1 shows the convex refractive surface of the material lens 10 of such a conventional progressive multifocal lens, and shows the arrangement of each region. 1, 2, and 3 are a distance region, an intermediate region, and a near region, respectively, and M
is the principal meridian. Point A in FIG. 1 is the geometrical center of this lens, and is also the optical center. Therefore, point A is generally called the distance center.
Point B is also called the center of near vision. FIG. 2 shows changes in refractive power along the principal meridian M. Above point A, that is, within the distance vision region, the refractive power on the principal meridian M is constant at D ₁ (day of light), and below point B, that is, within the near vision region,
It is constant at D ₂ (day of trees). from point A to B
Toward the point, the refractive power increases gradually from D ₁ to D ₂ .
The difference between the refractive powers D ₁ and D ₂ is called the addition power, usually 0.5
It is within the range of 1 to 3.5 days. In the figure, the distance L between point A and point B is called the length of the intermediate portion or the length of the progressive zone.
In order to make the parts with different refractive powers into one smooth curved surface, the progressive multifocal lens has to be made into an aspherical surface, which causes astigmatism to occur in the lens periphery. Further, since the magnification of the image changes at each part of the refractive surface, image distortion also occurs. These are shown in FIGS. 3 and 4.

FIG. 3 is an isoastigmatism diagram showing the distribution of astigmatism. In the figure, the narrower the hatching pitch, the greater the astigmatism, which means that the image becomes blurred. Generally, it is said that people perceive astigmatism and feel discomfort when it is 0.5 days or more (hereinafter abbreviated as D) or more, but if you do not stare at things that much, 0.5~
It can also be used with 1.0D. In the figure, the unhatched area is an area where the astigmatism is 1.0D or less.

The principal meridian M is usually an umbilical curve. An umbilicus curve is a series of points having the same principal radius of curvature, that is, a series of minute spherical surfaces, and astigmatism is zero on this line.

FIG. 4 shows the distortion of an image when a square grid is viewed through a lens. In the image of a square lattice, due to the change in magnification, as shown in the figure, the vertical lines bulge downwards centering on the one passing through the principal meridian (41 in the figure), and the horizontal lines also curve toward the periphery. This image distortion is not only perceived as image distortion, but also
When a user follows a moving object with his or her eyes or moves his or her head, and the visible object moves relative to the user's line of sight, this causes significant discomfort as the image shakes. This type of viewing of moving objects is called dynamic vision, and it is also called dynamic vision.
Static vision refers to cases in which there is little movement of the gaze and objects, such as gazing at a single point. As is clear from the above explanation, static vision is primarily affected by astigmatism. That is, the smaller the astigmatism is as a whole, and the wider the area where the astigmatism is small (for example, an area of 1.0D or less), the more comfortable vision can be obtained. On the other hand, dynamic vision is mainly affected by image distortion. In other words, the smaller the distortion of the image, the more comfortable visual perception can be obtained. This relationship between static vision and dynamic vision is not independent;
When the area with small astigmatism is widened in order to obtain good static vision, the change in image magnification becomes rapid around that area, that is, on the sides of the lens, resulting in large image distortion and dynamic There is a contradictory relationship in which vision is impaired and, conversely, if dynamic vision is improved, the regions with small astigmatism in the distance and near vision regions become narrower, impairing static vision.

Furthermore, more generally, it can be said that improving one property will have an adverse effect on certain other properties. Therefore, when designing a progressive multifocal lens, it is said that it is important to consider the balance between static vision and dynamic vision. There are various progressive multifocal lenses with different designs.
This is simply because the emphasis placed on static vision and dynamic vision is different. Some lenses place emphasis on static vision, and have a distance vision area that is entirely spherical, and a near vision area that also has a wide spherical part in the center. Therefore, although static vision is good, dynamic vision is impaired due to large image distortions in the intermediate region and the lateral portions of the near region. Another lens emphasizes dynamic vision and has aspherical surfaces in both the distance and near vision areas in order to reduce overall image distortion. Therefore, the small area of astigmatism is narrowed and static vision is impaired. However, despite these differences, there is a common basic concept in the design of conventional progressive multifocal lenses. The aim is to create a single progressive multifocal lens eyeglass that can be used in all situations, that is, to design a universal progressive multifocal lens.

Therefore, it can be very inconvenient in some cases. For example, when playing sports (such as golf), when going out for shopping, or when driving a car. As mentioned above, the desired characteristics of a progressive multifocal lens used in such situations cannot be obtained from a general-purpose lens designed simply for static vision or dynamic vision. Until now, there have been no progressive multifocal lenses suitable for use in the above situations. However, although some types of low-addition lenses may be partially suitable (which is natural since they can reduce aberrations), the need for progressive multifocal lenses may be reduced. Among the lenses with a high medium or higher addition power, there were no suitable lenses. In order to perform optimization, we slightly change the conventional idea of static or dynamic vision, and emphasize both static and dynamic vision for distance and intermediate areas, and focus on both static and dynamic vision for distance and intermediate areas. Regarding the functional area, static vision and
The design should sacrifice some of the dynamic vision. This will be explained in detail. First, regarding the distance vision area, it is desirable that the image be blurred, distorted, and shaken so that even when the eyes are turned to the side while the face is facing forward, the image is hardly blurred, distorted, or shaken. It is even more preferable if this is true not only directly to the side, but also to the side slightly diagonally below the horizontal (the diagonally below part may be regarded as the middle region of the lens, but there is no difference in the desired characteristics). When making a golf swing, a wide distance field of view with little vibration is essential, and when driving a car, the wider the field of view without blurring or distortion, the better.

Next, regarding the middle region, it is desirable that the range in which the image can be seen without blurring is wide, and that distortion and shaking of the image are small in the side regions. When reading the grass on a golf green, when reading the display on a car's instrument panel,
This middle area plays a particularly important role when shopping and reading the prices and labels of items in the shop window. Finally, regarding the near vision area, the width of the area where the image can be seen without blurring should be kept to the minimum necessary. Of course, it is better to have a wider width, but this should be sacrificed in order to improve the characteristics of the distance and intermediate regions. This is because the near vision area does not play such a major role when used for golfing, driving, shopping, etc., and is hardly used for long periods of time. For example, in the case of golf, as long as you can keep score, you can achieve your goal.

None of the conventional progressive multifocal lenses has the above-mentioned favorable characteristics.
This will be explained with reference to FIG. 3 and the like. First, it is necessary to consider how to process the progressive multifocal lens 10, which is in the form of a circular material lens as shown in FIG. 3, into eyeglasses. One is where to set the fitting point. The fitting point is the position where the eyeglass wearer's line of sight passes over the lens when looking into the distance in a normal (relaxed) posture, and is sometimes referred to as the eye point. Generally, it is set somewhere between point A on the principal meridian M and a point 2 to 3 mm above it. In FIG. 3, the fitting point F is set on point A. The other is to take into account convergence (when looking at something close up, the line of sight comes closer to the inside than when looking far away), and make the distance between points B of the left and right lenses shorter than the distance between points A of the left and right lenses. It is the right thing to do. In general, the main meridian M as shown in Figure 3
To use a lens that is symmetrical with the axis of symmetry as the axis of symmetry, rotate the lens by around 10 degrees. That is, in FIG. 3, H' is the horizontal line when worn, and 11 is the shape of the eyeglass lens after processing. Now, regarding the characteristics of conventional progressive multifocal lenses, there is a large difference depending on the addition power, so we will explain the case with an addition power of 2.0D. Note that for progressive multifocal lenses that are currently in practical use, this is based on measurement results using a lens meter with an aperture diameter of 5 mm. First, the characteristics of the distance vision region are evaluated based on the position of the isoastigmatism line with an astigmatism of 1.0D. In a bilaterally symmetrical lens as shown in FIG. 3, the isoastigmatism line is generally 0 to 10 degrees above the horizontal line H. However, when actually processing the glasses, the lenses are rotated approximately 10 degrees to take convergence into consideration, so when worn, the lenses are rotated 10 to 20 degrees above the horizontal line H'. This is the case on the nasal side (left side in Figure 3). This makes the image blurry when viewed horizontally and laterally, making it difficult to use. In order to prevent the line of astigmatism 1.0D from rising due to rotation of the lens, there is also a progressive multifocal lens that has been made asymmetrical by bending the principal meridian M, as shown in Figure 5. astigmatism
The 1.0D line is generally 0 with respect to the horizontal line when worn.
degree or 10 degrees above. Although it has been improved somewhat, it is still difficult to use. Furthermore, this type of lens has the disadvantage that astigmatism, image distortion, and shaking become large from the lower part of the distance region to the upper part of the intermediate region on the nose side (left side in FIG. 5). Note that this drawback also exists in lenses that are bilaterally symmetrical and place emphasis on static visual field (for example, lenses that have a spherical front body above the horizontal line H). Next, the characteristics of the intermediate region are evaluated based on the minimum width S of the region within astigmatism 1.0D.

In conventional progressive multifocal lenses, this minimum width S is 3 to 8 mm, and in particular, many are 5 to 6 mm. S
For example, when looking at an object that is within arm's reach (for example, when looking at the instrument panel while driving a car), we found that a distance of approximately 60 cm is necessary for ease of use. It is convenient if you can see a width of 20 to 30 cm. Converting this to the width of S is about 8 to 12 mm.
The conventional ones are all too narrow.

Generally, the minimum width S is approximately determined by the length L of the progressive zone and the gradient of refractive power change on the principal meridian,
The longer L is, the gentler the slope, the wider S becomes. Therefore, it can be said that all conventional lenses have a short progressive zone length L. This is because all conventional lenses aim to be general-purpose lenses. That is, if the length L of the progressive zone is long,
When using the near vision area, it is necessary to turn the line of sight significantly downward. This makes near vision difficult, so as a general-purpose lens, the length of the progressive zone is L.
could not last very long.

The length L of the progressive zone of conventional lenses is 10 to 16 mm, but 16 mm is sometimes said to be too long.
From the perspective of the maximum gradient of refractive power change, it is 0.20~
It is 0.13D/mm.

The shorter the length L of the progressive band and the steeper the gradient, the greater the astigmatism, image distortion, and shaking in the lateral portions of the intermediate region, making it difficult to use. Finally, the characteristics of the near vision area are evaluated based on the maximum width W of the area within 1.0D of astigmatism. In conventional progressive multifocal lenses, this maximum width W is often around 20 mm, but some are as wide as 30 mm.
There are some that exceed. If this maximum width W is increased, it will have an adverse effect not only on the lateral parts of the near region but also on the lateral parts of the intermediate region, increasing astigmatism and increasing image distortion and shaking. It is also intended to push upward the 1.0D isoastigmatism line explained regarding the distance region. Further, this maximum width W is generally much wider than the minimum width S of the intermediate region. The ratio of the maximum width W to the minimum width S is 2 to 3 times as small as 7 to 8 times as large. This difference in width between the two causes a large distortion at the side portion 42 at point B shown in FIG. 4, which causes significant discomfort to the wearer.

Well, if it's limited to the kind of use we're thinking of here,
It will be enough if you can see the width of one page of a book (approximately 15 cm wide at a distance of about 30 cm). Then the maximum width W
can be 15mm or less, so all conventional progressive multifocal lenses can be said to be quite wide.

The present invention improves the drawbacks of the conventional progressive multifocal lenses described above, especially lenses with medium or higher addition power, and dramatically improves visibility in the distance area and the intermediate area. , it also completely eliminates the distortion and shaking of the image that the wearer feels.

As a result, the progressive multifocal lens according to the present invention:
It is especially suitable for sports such as golf, driving a car, going out for shopping, etc.

The present invention will be explained in detail below using examples.

First, an example in which the addition power is 2.0D will be described. FIG. 6 shows the convex refractive surface of the progressive multifocal lens of the present invention, where 1, 2, and 3 are the distance region, intermediate region, and near region, respectively, and M is the principal meridian. FIG. 7 shows the change in refractive power along the principal meridian M. The refractive power above point A is 6.0D, and the refractive power below point B is 8.0D, and increases almost linearly from point A to point B, except in the vicinity of each point. That is, the refractive power D ₁ in the distance region
is 6.0D, and the refractive power _D2 in the near vision area is 8.0D.
The distance between points A and B, that is, the length of the progressive zone L
is 20mm. The maximum slope of the refractive power change on the principal meridian M is 0.10 D/mm.

8a shows the change in refractive power on the line of intersection between the refractive surface in the distance region and a plane perpendicular to the principal meridian M. FIG. However, since the lens of this example has a bilaterally symmetrical design, only one half of the lens is shown. The refractive power remains constant at 6.0D up to a distance of 2 mm from the principal meridian M, then gradually increases to reach 6.5D at a distance of 25 mm from the principal meridian M, and then decreases. By keeping the maximum value at 6.5D, that is, by keeping the difference from the refractive power on the principal meridian M within 0.5D, the astigmatism in the distance region can be reduced to 0.5D. It is now possible to do the following.
Furthermore, by adopting an aspherical surface as described above, compared to a case where a spherical surface is used for the entire distance vision region, it is possible to improve the ease of use of the distance vision region and the intermediate region and the near vision region. This makes it possible to improve the characteristics of the side areas. That is, the magnification on the side of the distance vision region becomes higher and approaches the magnification on the intermediate region or the near vision region, so that distortion is reduced.

FIG. 8b shows the change in refractive power on the line of intersection between the refractive surface in the near vision region and the plane perpendicular to the principal meridian M. FIG. Similar to a in the distance region, a constant refractive power section is provided, but after that the refractive power increases and further decreases toward the side. The refractive power is set to 7.0D at a distance of approximately 7.5 mm from the principal meridian M, so that the width of the region within 1.0 D of astigmatism is approximately 15 mm. After determining the change in refractive power on the principal meridian M and the distance and near vision regions as described above, the intermediate region was designed using the method disclosed in Japanese Patent Application Laid-open No. 57-94714. As a result, the distribution of astigmatism became as shown in FIG. 9. In the figure, for example, the line marked 1.0 is a 1.0D isoastigmatism line. The minimum width S in the middle region of the region within 1.0D of astigmatism is approximately 10 mm, which is significantly wider than the conventional one. The maximum width W in the near vision region is approximately 15 mm, and the ratio of the maximum width W to the minimum width S is approximately 1.5 times.

Therefore, the 1.0D isoastigmatism line extends upward from the lower end of the refractive surface approximately parallel to the principal meridian M, and then
The shape is such that it points toward the side of the refracting surface.

In this way, unlike in the conventional case, the width of the isoastigmatism line does not suddenly become narrower, so there is no large distortion at the side portion of point B, and the wearing comfort is improved.

In other words, from the point of view of reducing distortion in the lateral area at point B, it is preferable that the ratio of the maximum width W to the minimum width S be close to approximately 1.0 (W≒S), but the width required for the near vision area is also Considering this, it should be at most about 1.5 or less.

Note that the length of the progressive zone is long and the width of the area suitable for near vision is narrow, but since the near vision area is only used occasionally, it is recommended to push the glasses slightly upwards. This can also be used in some cases since the width of the progressive band is wide. The 1.0D isoastigmatism line extends upward along the principal meridian M and then moves laterally. In this example, the Fitzteig point is set on point A, and the lens for convergence is The rotation of is 8 degrees. Starting from point A, draw a straight line tangent to the 1.0D isoastigmatism line,
The line is inclined approximately 20 degrees downward from the horizontal line H. Therefore, if we consider the horizontal line when worn as a reference, approximately 12
All of the refractive surfaces above the inclined line have astigmatism of 1.0D or less. Here, in the distribution diagram of the average refractive power of this example shown in FIG.
If we draw a straight line from the point that is tangent to the 6.5D equal mean refractive power line, it will be a line that is inclined downward at about 21 degrees from the horizontal line H. Therefore, initially, only the area above the horizontal line H was considered the distance vision area, but since the average refractive power differs by only 0.5D, the area from the horizontal line H to about 21 degrees below is considered a distance vision area from the perspective of refractive power. It can also be used for. Therefore, if we consider astigmatism and mean refractive power in total, we can consider that the entire area above a line inclined approximately 12 degrees downward from the horizon when worn is an area suitable for distance vision. Provides a wide distance field of view. In the present invention, the lens refractive surface is a distance portion,
It is divided into the intermediate region and the near vision region, but these names are for convenience; the upper part of the intermediate region can be considered as the region suitable for distance vision, and the intermediate region The lower part of the area can also be considered as an area suitable for near vision.

Next, an example in which the addition power is 3.0D will be described. The arrangement of each region, the change in refractive power on the principal meridian M, and the change in refractive power in the distance region and the near region are shown in FIGS. 11, 12, and 13, respectively. The difference when compared with the example in which the addition power is 2.0D is that, as shown in Fig. 11, the boundary line between the distance area and the intermediate area is closer to the distance area. be. Furthermore, as shown in Fig. 13b, the change in refractive power within the near vision area was determined so that the refractive power was 10.0D at a distance of about 5 mm from the principal meridian M (refractive power 9.0D). be. All of these mean that the region with small astigmatism becomes narrower in the distance region or the near region. This means that if the area with small astigmatism is made as wide as the case with an addition power of 2.0D,
This is to avoid the sudden increase in image distortion and shaking. Although it is a commonly used method to narrow the region with small astigmatism as the addition power increases, in the present invention, the following conditions are satisfied. It turns out that if you do this, you can create a progressive multifocal lens that is easy to use overall. When the addition power in units of diopters is expressed as ADD, (1) Astigmatism occurs above a line inclined downward by [50 - (ADD x 20)] degrees from the horizontal line when worn.
1.0D or less. (If the sign is negative, it means that the line is tilted upward.) (2) The maximum width of the area within 1.0D of astigmatism in the near vision area is less than [30÷ADD]mm.

This is the condition. Therefore, regarding (1), the addition
If it is 2.0D, the line is 10 degrees below, and if the addition is 3.0D,
This indicates that astigmatism above the 10 degree line should be 1.0D or less. Regarding (2), astigmatism
This indicates that the maximum width of the region within 1.0D is preferably 15 mm or less if the addition is 2.0D, and 10 mm or less if the addition is 3.0D. It goes without saying that the embodiment with an addition power of 2.0D also satisfies the above conditions. Now, the addition power 3.0D created in this way
FIG. 14 shows the distribution of astigmatism, and FIG. 15 shows the distribution of average refractive power in this example. addition degree
Assuming that the horizontal line when worn is rotated 8 degrees with respect to the horizontal line H as in the case of 2.0D, the area with astigmatism of 1.0D or less is the entire surface above a line that is inclined approximately 9 degrees upward from the horizontal line when worn. , the area where the average refractive power is within 6.0±0.5D is the entire surface above the line that is also inclined downward by about 2 degrees. Furthermore, since the maximum width W of the region where the astigmatism is 1.0D or less in the near vision region is about 10 mm, both of them satisfy the above conditions. The minimum width S of the region where the astigmatism is 1.0D or less in the intermediate region is approximately 7 mm, and the ratio of the maximum width W to the minimum width S is approximately 1.4 times.

In these examples, A on the principal meridian
The refractive power is kept constant above the point (distance area) and below the point B (near area), but it does not necessarily have to be strictly constant; Increase/decrease (about 0.5D)
The same effect can be obtained even if For example, the refractive power change along the principal meridian may be as shown in FIGS. 16 and 17. Figure 7 and 1
In the case of a lens that exhibits a change in refractive power as shown in Figure 2, point A, which is the lower end of the distance vision region, and point B, which is the upper end of the near vision region, are the points at which the refractive power begins to increase. The point where it ends is also the point where it ends. 1st
The same applies to the case of a lens as shown in FIG.
In the case of a lens as shown in FIG. 17, the positions where the gradient of increase in refractive power changes are point A and point B.
That is, point A is where the gradual increase changes to a relatively rapid increase, and point B is the opposite point. In any of the above cases, the refractive power at point A and point B is the refractive power in the distance area, respectively.
D ₁ is the refractive power D ₂ in the near vision region.

As described above in detail in accordance with the embodiments, the present invention incorporates an aspherical surface in the distance region to a degree that does not impair distance vision.
A wide distance field of vision and intermediate and near vision areas with reduced image distortion and shaking in the lateral areas can be obtained. In addition, the length of the progressive zone is significantly longer than before, and the gradient of the change in refractive power is made gentler, ensuring a wide intermediate field of view and far field of view, and reducing image distortion and shaking in the lateral areas. There is. Furthermore, by setting the near field of view narrower than before, a field of view of the same width is secured from the intermediate area to the near area, significantly reducing image distortion and shaking in the lateral areas. . In this way, a progressive multifocal lens has been realized that has a wider distance visual field and intermediate visual field, and has significantly less image distortion and shaking than conventional progressive multifocal lenses. Therefore, the lens according to the present invention is a progressive multifocal lens that is ideal for sports such as golf, driving a car, going out for shopping, and the like.

Note that the present invention is not limited to the embodiments described above. For example, although the length of the progressive zone is 20 mm, it has been found that a progressive multifocal lens capable of achieving the object of the present invention can be obtained even with a length of about 18 mm. At this time, if the refractive power is changed linearly, in the case of an addition of 2.0D, the minimum width S of the intermediate region is approximately 9 mm, which is sufficient, and the distortion and shaking of the image in the lateral region is sufficient. This is because you can get something small. However, even if the length of the progressive zone is 18 mm, if the refractive power change is like a sine curve,
This is not preferable because the gradient of the change in refractive power becomes large near the center of the progressive zone. In short, any lens is sufficient as long as the length of the progressive zone is 18 mm or more and the gradient of the change in refractive power is equal to or less than (addition power ÷ length of the progressive zone). In addition, in the embodiment, the refractive power on the principal meridian was considered to be almost constant in both the distance and near vision regions, but lenses such as those shown in FIGS. 18 and 19 are also used in this book. within the scope of the invention. In other words, the change in refractive power is almost constant within the distance vision region, but the gradient of increase in refractive power does not change much from the intermediate region to the near vision region, and from the point of view of the position where the gradient of increase in refractive power changes, is a lens in which point B cannot be clearly defined.
In the case of such a lens, a point on the principal meridian having a refractive power approximately 0.5D lower than the refractive power at the lowest end of the fabric lens 10 is defined as point B, and the area below this point is defined as the near vision region. It will be done. Although the near vision area becomes very narrow, the purpose of the present invention is to place emphasis on distance vision and intermediate vision, but not so much on near vision, so the near vision area may be as small as this.

Further, although the embodiment deals with a lens having a bilaterally symmetrical design, a lens having a bilaterally asymmetrical design having a principal meridian as shown in FIG. 5 may be used. It goes without saying that the principal meridian should have very little astigmatism, but it does not have to be an umbilicus curve. Furthermore, in the embodiment, the distance vision, intermediate vision, and near vision regions are arranged on the convex surface side, but these regions can also be arranged on the concave surface side.

[Brief explanation of drawings]

1 to 4 respectively show the structure of the convex refractive surface of a conventional general progressive multifocal lens, changes in refractive power on the principal meridian, distribution of astigmatism, and distortion of a square lattice image. FIG. 5 shows the distribution of astigmatism of another conventional progressive multifocal lens. 6 to 10 show examples of the present invention, in which FIG. 6 shows the structure of the convex refractive surface, FIG. 7 shows the change in refractive power on the principal meridian, and FIG. 8 shows the distance region and the near region. FIG. 9 shows the distribution of astigmatism, and FIG. 10 shows the distribution of the average refractive power. 11-15 are other embodiments of the present invention. 16 and 17 are other examples of changes in refractive power on the principal meridian of the progressive multifocal lens of the present invention. 18 and 19 show still another example of the structure of the convex refractive surface of the progressive multifocal lens of the present invention and the change in refractive power along the principal meridian. 1...Distance area, 2...Intermediate area, 3...
Near vision area, 10... Fabric lens (lens before edge processing), 11... Spectacle lens (lens after edge processing), M... Principal meridian, A... Distance center (refractive power D ₁ ), B... Center for near vision (refractive power D ₂ ), L... Length of progressive zone, S... Astigmatism in intermediate region 1.0D
W: Maximum width of the area within 1.0D of astigmatism in the near vision area, H: Horizontal line of the lens, H': Horizontal line when worn, F: Fitting point.

Claims (1)

[Claims] 1. The lens has a principal meridian extending in the longitudinal direction approximately at the center of the refractive surface, and a distance region in the upper part of the refractive surface;
The refractive surface has a near region in the lower part, and an intermediate region between the distance region and the near region, and the refractive power on the principal meridian is at least in the distance region. In the progressive multifocal lens, the refractive power is approximately constant and gradually increases in the intermediate region from the refractive power (D1 diopters) in the distance region to the refractive power (D2 diopters) in the near region; The refractive power on the line of intersection between the plane and the plane perpendicular to the principal meridian increases once and then decreases in the distance region as it moves away from the principal meridian, and once decreases and then increases in the near region. As an aspherical shape, both the left and right sides are inclined downward by [K] degrees from the horizontal line when worn, starting from a fitting point set near the boundary point between the distance region and the intermediate region on the principal meridian. Over the entire surface of the refractive surface above the line, the astigmatism is 1.0 diopters or less, and the average refractive power is within D1 ± 0.5 diopters, where K = 50 - (ADD × 20), and ADD is the above-mentioned The difference between the refractive power D1 of the distance vision region and the refractive power D2 of the near vision region, that is, ADD=D2
−D1, and further characterized in that ADD≧1.5.