JP2006178245A - Spectacle lens for for astigmatism correction - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a spectacle lens for astigmatism correction with which distortion aberration can be balanced. <P>SOLUTION: A toric surface as an astigmatism correction surface is formed on an object side (outside surface) of the lens and a toric surface as an astigmatism correction surface is also formed on the surface (inside surface) on the eyeball side of the lens. The direction where the curvature on the outside surface is maximized on these astigmatism correction surfaces is so set as to coincide with the direction where the curvature on the inside surface is maximized. As a result, the spectacle lens for astigmatism correction with which the distortion aberrations are balanced more satisfactorily than heretofore can be provided. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a spectacle lens for correcting astigmatism used for spectacles for correcting astigmatism.

Astigmatism is one of the visual impairments caused by distortion of the cornea. Astigmatism is a state in which a point light source cannot be clearly seen because it does not form a point as a circle, ellipse, or line. When astigmatism occurs, it is difficult to see the object and it may cause eye strain and headache, so it is preferable to correct it unless it is very mild. In order to correct astigmatism, it is necessary to wear lenses (astigmatic lenses) having different powers depending on the angle around the optical axis. In such an astigmatism correcting lens that corrects such astigmatism, an astigmatism correcting surface is generally formed on the inner surface (eyeball side) of the lens. However, in recent years, a progressive power lens especially for presbyopia correction has been proposed in which the astigmatism correction surface is set on the outer surface (object side) of the lens as the progressive refractive surface is set on the back surface. . Patent Document 1 is an example in which an astigmatism correction surface is set on the inner surface of the lens, and Patent Document 2 is an example in which an astigmatism correction surface is set on the outer surface of the lens.
JP 2004-309588 A JP 2002-311397 A

However, these conventional spectacle lenses for correcting astigmatism have the following problems regarding distortion. That is, when an object is viewed through a lens, more or less distortion occurs. However, since an astigmatism correction spectacle lens generally has a trick surface for correcting astigmatism on the lens surface, the balance is not uniform in the direction in which distortions intersect 90 degrees (for example, vertical and horizontal). It was supposed to collapse. In particular, in a person with strong astigmatism, since the astigmatism power needs to be set large, the balance of distortion aberration has been a serious problem. However, when correcting astigmatism with either the internal or external lens surface, as in the conventional spectacle lens for correcting astigmatism, it is difficult to sufficiently correct the distortion of the balance of distortion. For this reason, there are many cases to deal with by using spectacle lenses for correcting astigmatism whose frequency is weaker than actual. Therefore, a spectacle lens for correcting astigmatism with a balanced distortion has been demanded.
The present invention has been made paying attention to such problems existing in the prior art. An object of the present invention is to provide a spectacle lens for correcting astigmatism capable of balancing distortion aberration.

In order to solve the above problems, in the invention of claim 1, the curvature of the cross-sectional curve formed by the intersection of the lens surface and the plane perpendicular to the lens surface including the center of the lens body is the direction of the cross section in the vicinity of the center of the lens body. Separately different astigmatism correction surfaces, the direction of maximum curvature and the direction of minimum curvature of each cross-sectional curve near the center of the lens body are substantially orthogonal and the curvature is monotonous between the maximum curvature direction and the minimum curvature direction. The gist of the present invention is to form the lens body on both the object-side surface and the eyeball-side surface of the lens body, and to set a desired astigmatism power by the both astigmatism correction surfaces.
The gist of the invention of claim 2 is that, in addition to the configuration of the invention of claim 1, the direction in which the curvature of the outer surface is maximized substantially coincides with the direction in which the curvature of the inner surface is maximized.
The gist of the invention of claim 3 is that, in addition to the configuration of the invention of claim 2, the direction in which the curvature of the outer surface is maximized substantially coincides with the direction in which the curvature of the inner surface is minimized.
In addition, in the invention of claim 4, in addition to the configuration of any one of claims 2 and 3, the direction in which the curvature of the outer surface is maximum coincides with the direction in which the transmission refractive power of the spectacle lens has the minus maximum intensity in the minus lens. The gist of the plus lens is that it coincides with the direction where the plus maximum intensity is obtained.

According to a fifth aspect of the present invention, in addition to the configuration of any of the first to fourth aspects of the present invention, a cross-sectional curve formed by the intersection of the lens surface and the plane in which the astigmatism correction surface intersects perpendicularly to the lens surface including the center of the lens is provided. The gist is that it is composed of non-trick surfaces that include non-circles.
Further, in the invention of claim 6, in addition to the structure of any one of claims 1 to 5, in order to add the addition in the near portion to both surfaces of the lens body or to only one of the surfaces. The gist of this is to synthesize the progressive refracting surface shape.

  In the astigmatism correcting spectacle lens configured as described above, the astigmatism correction surfaces are set on both the object side surface of the lens (lens outer surface) and the lens eyeball side surface (lens inner surface) to balance distortion aberration. Making it possible. The astigmatism correction surface includes the center of the lens body, and the curvature of the cross-sectional curve formed by the intersection of the lens surface and the plane perpendicular to the lens surface differs depending on the direction of the cross section in the vicinity of the lens body center. The direction in which the curvature of the cross-sectional curve is maximum and the direction in which the curvature is minimum are orthogonal, and the curvature changes monotonously between the maximum curvature direction and the minimum curvature direction. An example of such an astigmatism correction surface is a trick surface. The trick surface is a curved surface drawn when rotating around a straight line that does not pass through the center of the circle, and there are two types: “tal type” and “donut type”. Since trick surfaces have different vertical and lateral (circumferential) curvatures, a trick surface having a predetermined vertical and horizontal curvature is set to correct astigmatism. Here, the “cross-section curve formed by the intersection of the lens surface and the plane perpendicular to the lens surface including the center of the lens body” varies depending on the direction of the cross-section in the vicinity of the center of the lens body, and the curvature of the cross-section curve is maximum. The minimum direction and the minimum direction may be substantially orthogonal, and the curvature may change monotonously between the maximum curvature direction and the minimum curvature direction. That is, it may be a cross-sectional curve that does not meet such a condition at a position away from the vicinity of the lens body center.

In other words, the trick surface is assumed to be a surface that can be rotated by a circle, but in the present invention, an extended trick surface that is formed by rotating a shape other than a circle is used, or a so-called non-trick surface is used. Also means that it is possible. The non-trick surface is a combination of the aspheric lens concept and the trick surface in order to reduce astigmatism or distortion and to reduce the thickness of the lens.
In principle, the astigmatism correction surface is designed so that the direction in which the curvature of the cross section curve is minimum (that is, the astigmatism axis) and the direction in which the curvature of the cross section curve is maximum are orthogonal. However, astigmatism correction ability in actual wearing does not pose a problem even if it is not completely orthogonal, it may be approximately orthogonal. More specifically, for example, a range of 70 to 110 degrees is included substantially orthogonally, and there is no problem in actual wearing. Further, to change the curvature monotonically, it is sufficient that the change in curvature can be expressed by a function of second order or higher.

With such a configuration, it becomes possible to correct the distortion of balance of distortion, which has been a problem in conventional spectacle lenses for correcting astigmatism.
Conventional spectacle lenses for correcting astigmatism have lost the balance of distortion due to the following lens characteristics.
FIG. 5 is a comparison of the shapes of the outer surface astigmatism correcting lens p and the inner surface astigmatism correcting lens q in a minus lens (lens for near vision, the same applies hereinafter). Further, in both lenses, the cross sections of the lenses in two directions of the astigmatism axis direction and the astigmatism intensity direction which are shifted by 90 degrees are shown with + symbol and-symbol, respectively. The outer surface astigmatism correction lens p is spherical on the inner surface side, and the inner surface astigmatism correction lens q is spherical on the outer surface side. These are virtual lenses set so that the average values of the refractive powers of the front and back surfaces of the lenses are substantially equal. For the sake of simplicity, the astigmatism correction surface is a simple trick surface.
First, in both lenses p and q, since the astigmatism intensity direction curve on the outer surface is shallow, particularly in the outer surface astigmatism correction lens p, distortion in this direction (in this case, the aberration in the reduction direction due to the concave lens) is considerably large. On the other hand, the distortion aberration in the astigmatic axis direction is not so great because the curve becomes deep, and as a result, the deformation ratio in the vertical and horizontal directions becomes large. As a result, the outer astigmatism correcting lens p tends to have a greater degree of deformation due to distortion than the inner astigmatism correcting lens q. On the other hand, the inner astigmatism correction lens q is excellent in that the deformation ratio does not increase as in the outer surface astigmatism correction lens p because the curve in the astigmatism intensity direction is deep on the inner surface, but lacks the freedom to suppress the degree of deformation due to distortion. Therefore, a sufficient distortion balance could not be achieved. Note that a plus lens (a hyperopic lens, hereinafter the same) has characteristics opposite to those of a minus lens.

On the other hand, in the present invention, when the predetermined astigmatism power is set on the lens surface, the astigmatism correction surfaces are formed on both surfaces of the lens body. For example, in the case of the negative lens described above, the astigmatism intensity direction side of the lens outer surface By making this curve deeper and following it, the astigmatism intensity direction curve on the inner surface of the lens is also made deeper, so that a predetermined astigmatism power can be set on the lens surface (the same applies to the case of a plus lens). Examples of the image include lenses as shown in FIGS. 6 (a) and 6 (b).
FIG. 6A is a perspective view when the present invention is applied to a minus lens. The horizontal direction is the negative astigmatism intensity direction, and the vertical direction is the astigmatism axis direction. The lens outer surface curve is deep (that is, the curvature is large) in the astigmatism intensity direction, and the astigmatism intensity direction on the lens inner surface side is also deeply formed accordingly. On the other hand, the astigmatic axis direction is formed with a shallower curve (that is, a smaller curvature) than the astigmatic intensity direction on both the inside and outside surfaces of the lens.
FIG. 6B is a perspective view when the present invention is applied to a plus lens. The horizontal direction is the positive astigmatism intensity direction, and the vertical direction is the astigmatism axis direction. The lens outer surface curve is deep (that is, the curvature is large) in the astigmatism intensity direction, and the astigmatism intensity direction on the lens inner surface side is also deeply formed accordingly. On the other hand, the astigmatic axis direction is formed with a shallower curve (that is, a smaller curvature) than the astigmatic intensity direction on both the inside and outside surfaces of the lens.

Here, the most preferable setting for both the inner and outer surfaces in order to balance the distortion is to make the direction in which the curvature of the outer surface is maximized coincide with the direction in which the curvature of the inner surface is maximized. However, since it is possible to determine that the distortion aberration is balanced in the range having a certain degree of tolerance including completely matched phases, it may be substantially matched here. That is, it is a concept including a slight deviation (about ± 5 degrees). In this case, it is of course preferable that the direction in which the curvature is maximum is the astigmatism intensity direction.
Further, in the case of a minus lens, the transmission refractive power of the lens has a minus maximum intensity in the direction in which the curvature of the outer surface is maximum, and in the plus lens, the transmission refractive power of the lens has a plus maximum intensity in the direction of having the maximum curvature of the outer surface. This is preferable in terms of balancing the distortion. The minus maximum intensity means the case where the value of the transmission refractive power indicated by the absolute value is maximum in the minus lens, and the plus maximum intensity means that in the plus lens.
However, when the astigmatic axis is set vertically as in the minus lens of FIG. 6A, the appearance of the lens deteriorates if the curve in the outer surface intensity direction is too deep. For example, the curve in the intensity direction of the outer surface is shallower. In addition, it is possible to set the correction of astigmatism while deepening the curve in the strength direction of the inner surface. In other words, there may be a possibility that the direction in which the curvature of the outer surface is maximized substantially coincides with the direction in which the curvature of the inner surface is minimized.

The present invention is particularly suitable for application to a progressive power lens (for example, a progressive surface shape is synthesized on the outer surface, the inner surface, and both surfaces of a double-sided trick lens). This is due to the following reason. For example, many people who have a prescription that includes positive astigmatism and an astigmatic power are difficult to get used to the distortion and distortion of the progressive power lens. Originally, an additional power for near vision is added to the lower part of the progressive-power lens, so when the distance power is positive, the power of the entire lens becomes positive and the magnification of the image increases, and astigmatism This is because the effect that the object looks distorted by the effect and the effect that the image in the lower field of view is enlarged due to the addition are combined.
In addition, a positive person with a weak distance power can see the distance well without glasses, so there are many cases where glasses were not originally worn before wearing a progressive power lens. Therefore, when wearing a progressive-power lens as the first glasses, astigmatism correction is still performed at the same time.
In the present invention, a trick surface and a non-trick surface can be set in combination with the inner and outer surfaces of the lens. For example, a lens that combines a trick surface and a non-trick surface on the inner and outer surfaces, such as an outer surface non-trick + an inner surface trick, may be configured.
The lens generally has a meniscus shape (a convex surface on the outer surface and a concave surface on the inner surface). However, as long as it is a plus lens, it may be a double lens having both surfaces convex. It is also possible to add a small lens for near vision (so-called bifocal lens) using the spectacle lens for correcting astigmatism of the present invention as a pedestal.

  According to the inventions of the above claims, it is possible to provide an astigmatism correcting spectacle lens in which the distortion aberration is balanced as compared with the related art.

Hereinafter, the result of simulating distortion for each example of the spectacle lens for correcting astigmatism of the present invention will be described.
(About simulation method)
The comparative lens and the example lens were set to have the same astigmatism power, and the distortion aberration of these lenses was simulated. In this simulation, visual observation as shown in FIG. 7 was assumed. The distance from the center of the eyeball to the apex of the inner surface of the lens is 25 mm, the linear distance from the center of the eyeball to the front grid is 10 m, and the distance from the front is 5 m (26.6 degrees viewing direction) and 10 m (45 degrees viewing direction). The degree of distortion was used as an index. The lattice spacing was 2 m. Therefore, if there is no distortion (if the material refractive index of the lens is 1 and the transmission refractive index of the lens is 0), the line of sight in the 45 degree direction coincides with the grid at the 10 m position. When the lens is actually put in a frame and worn, the lens is tilted forward by about 10 degrees. However, in order to simplify the explanation, the lens was not tilted with respect to the eyes.

Simulation 1
In simulation 1, a simulation was performed on a minus lens composed of a simple spherical surface and a trick surface. The comparison lens 1 in which the outer surface was set as a spherical surface and the inner surface was set as an astigmatism correction surface was compared with Examples 1A and 1B of the present invention in which the inner and outer surfaces were set as an astigmatism correction surface. In both cases, the power of the lens was S-4.00D C-1.00D AX90. Astigmatism power was set to -4.00D in the vertical direction and -5.00D in the horizontal direction. In other words, a lens was produced in which the vertical direction is the astigmatic axis and the horizontal direction is the astigmatic intensity direction. In all cases, the material refractive index of the glass constituting the lens was 1.6, the lens diameter was 60 mm, and the lens center thickness was 1 mm. All astigmatism correction surfaces were trick surfaces.
The surface refractive power of the lens was calculated based on the following calculation formula with the outer surface of the lens of Comparative Example 1 configured as a spherical surface having a curvature radius of 300 mm.
Surface refractive power of outer surface = (material refractive index−refractive index of air) × 1000 / radius of curvature (1)
Surface refractive power of the inner surface = surface refractive power of the outer surface / (1-surface refractive power of the outer surface × lens center thickness (m) / material refractive index) −astigmatism power formula (2)

(Comparative Example 1)
The outer surface of the lens of Comparative Example 1 was a curved spherical surface having a refractive power of 2.00. Based on the above equation (1), the radius of curvature of this curve is 300 m. Further, based on the above formula (2), the surface refractive power of the inner surface of the lens of Comparative Example 1 is set to a 6.00 curve in the vertical direction and 7.00 curve in the horizontal direction (rounded to the second decimal place). And display). Table 1 shows the refractive power of Comparative Example 1.
Example 1A
On the outer surface of the lens of Example 1A, the curve in the lateral direction (astigmatism intensity direction) was set to a refractive power of 4.50. Accordingly, the lateral curve of the inner surface of the lens of Example 1A is set to a refractive power of 9.51 from the above formula (2). Thereby, a deeper curve is formed with respect to the comparative example 1 in both the inner and outer surfaces in the astigmatic intensity direction. The longitudinal direction (astigmatic axis direction) is the same as that in Comparative Example 1. Table 1 shows the refractive power of Example 1A.
(Example 1B)
On the outer surface of the lens of Example 1B, the curve in the lateral direction (astigmatism intensity direction) was made refractive power 3.50. Accordingly, the lateral curve of the inner surface of the lens of Example 1B is made to have a refractive power of 8.51 from the above formula (2). The lens of Example 1B is designed to suppress the curve compared to Example 1A, although the curve is deeper than Comparative Example 1 in the astigmatism intensity direction (the surface refractive power is large). In the longitudinal direction (astigmatism axis direction), the curve was made shallower than that of Comparative Example 1, and the refractive power was 1.00 on the outer surface, and the refractive power was 5.00 on the inner surface. Table 1 shows the refractive power of Example 1B.
-Results Table 1 shows the actual distances of the positions viewed with distortion in the 26.6-degree viewing direction and the 45-degree viewing direction. In Comparative Example 1, as shown in FIG. 1 (a), in Example 1A, as shown in FIG. 1 (b), in Example 1B, distortion as shown in FIG. 1 (c) is visually observed. Become. As can be seen from the lattice spacing, in Comparative Example 1, the horizontal direction extends compared to the vertical direction, so the distortion balance in the vertical and horizontal directions is lost, but in Examples 1A and 1B, the horizontal and vertical distortions are smaller than those in Comparative Example 1. Balanced.

Simulation 2
In simulation 2, a simulation was performed on a plus lens composed of a simple spherical surface and a trick surface. The comparison lens 1 in which the outer surface was set as a spherical surface and the inner surface was set as an astigmatism correction surface was compared with Examples 1A and 1B of the present invention in which the inner and outer surfaces were set as an astigmatism correction surface. In all cases, the lens power was S + 2.00D C + 0.50D AX90. Astigmatism power was set to + 2.00D in the vertical direction and + 2.50D in the horizontal direction. Similarly to the above, a lens in which the vertical direction is the astigmatic axis and the horizontal direction is the astigmatic intensity direction was produced. In either case, the material refractive index of the glass constituting the lens was 1.6, and the lens diameter was 60 mm. The center thickness of the lens was 2.88 mm for the comparative lens 2, 2.92 mm for Example 2A, and 2.91 mm for Example 2B. All astigmatism correction surfaces were trick surfaces.
The surface refractive power of the lens was calculated based on the above formulas (1) and (2).

(Comparative Example 2)
The outer surface of the lens of Comparative Example 2 was a curved spherical surface with a refractive power of 3.00. Based on the above formula (1), the radius of curvature of this curve is 200 m. Further, based on the above formula (2), the surface refractive power of the inner surface of the lens of Comparative Example 2 is a trick surface having a 1.02 curve in the vertical direction and a 0.52 curve in the horizontal direction (rounded to the second decimal place). display). Table 2 shows the refractive power of Comparative Example 2.
(Example 2A)
On the outer surface of the lens of Example 2A, the curve in the lateral direction (astigmatism intensity direction) was made refractive power 6.50. Accordingly, the lateral curve of the inner surface of the lens of Example 2A was determined to have a refractive power of 4.08 from the above formula (2). As a result, a deeper curve is formed with respect to the comparative example 2 in both the inner and outer surfaces in the astigmatism intensity direction. The vertical direction (astigmatic axis direction) is the same as that in Comparative Example 2. Table 2 shows the refractive power of Example 2A.
(Example 2B)
On the outer surface of the lens of Example 2B, the curve in the lateral direction (astigmatism intensity direction) was set at a refractive power of 6.00. Accordingly, the lateral curve of the inner surface of the lens of Example 1B is determined to have a refractive power of 3.57 from the above equation (2). The lens of Example 2B is designed to suppress the curve compared to Example 2A, although the curve in the astigmatism intensity direction is deeper than Comparative Example 2 (having a large surface refractive power). In the longitudinal direction (astigmatism axis direction), the curve is shallower than that of Comparative Example 2, and the refractive power is 2.50 on the outer surface, and the refractive power is 0.51 on the inner surface. Table 2 shows the refractive powers of Example 2B.
-Results Table 2 shows the actual distances of the positions viewed with distortion in the 26.6-degree viewing direction and the 45-degree viewing direction. In Comparative Example 2, as shown in FIG. 2 (a), in Example 2A, as shown in FIG. 2 (b), in Example 2B, distortion as shown in FIG. 2 (c) is visually observed. Become. As can be seen from the lattice spacing, in Comparative Example 2, the vertical direction is reduced compared to the horizontal direction, and thus the distortion balance in the vertical and horizontal directions is lost. In Examples 2A and 2B, the horizontal and vertical distortions are reduced. Balanced.

Simulation 3
In simulation 3, a simulation was performed by adding an aspherical minus lens to a minus lens composed of a simple spherical surface and a trick surface. The comparison lens 3 having the outer surface set as a spherical surface and the inner surface set as an astigmatism correction surface was compared with Examples 3A and 3B of the present invention in which the inner and outer surfaces were set as an astigmatism correction surface. In all cases, the power of the lens was S-4.00D C-2.00D AX90. Astigmatism power was set to -4.00D in the vertical direction and -6.00D in the horizontal direction. In other words, a lens was produced in which the vertical direction is the astigmatic axis and the horizontal direction is the astigmatic intensity direction. In all cases, the material refractive index of the glass constituting the lens was 1.6, the lens diameter was 60 mm, and the lens center thickness was 1 mm. The astigmatism correction surface was set as a trick surface for the comparative lens 3 and Example 3A, and in Example 3B, the outer surface was a trick surface and the inner surface was a non-trick surface. In Example 3B, in order to simplify the calculation, the longitudinal cross section of the non-trick surface is a spherical surface, and only the horizontal cross section is an aspheric surface.
The surface refractive power of the lens was calculated based on the above formulas (1) and (2).

(Comparative Example 3)
The outer surface of the lens of Comparative Example 3 was a curved spherical surface having a refractive power of 2.00. Based on the above equation (1), the radius of curvature of this curve is 300 m. Further, based on the above formula (2), the surface refractive power of the inner surface of the lens of Comparative Example 1 is a trick surface having a 6.00 curve in the vertical direction and a 8.00 curve in the horizontal direction (rounded off to two decimal places). ). Table 3 shows the refractive power of Comparative Example 3.
(Example 3A)
The outer surface of the lens of Example 3A has a lateral power (astigmatism intensity direction) curve with a refractive power of 3.00. Accordingly, the lateral curve of the inner surface of the lens of Example 3A was determined to have a refractive power of 9.01 from the above formula (2). As a result, a deeper curve is formed with respect to the comparative example 3 in both the inner and outer surfaces in the astigmatism intensity direction. In the vertical direction (astigmatism axis direction), the curve is shallower than that of Comparative Example 2, and the refractive power is 1.00 on the outer surface, and the refractive power is 5.00 on the inner surface. Table 3 shows the refractive power of Example 3A.
(Example 3B)
The curve of the inner and outer surfaces of the lens of Example 3B was set to the same value as that of Example 3A. However, since the inner surface is a non-trick surface (the cross section in the lateral direction is aspheric), the lateral border thickness is thin. That is, it is 5.80 mm compared with 5.87 mm in Example 3A. Table 3 shows the refractive power of Example 3B.
-Results Table 3 shows the actual distances of the positions viewed with distortion in the 26.6-degree viewing direction and the 45-degree viewing direction. In Comparative Example 3, as shown in FIG. 3A, in Example 3A, as shown in FIG. 3B, in Example 3B, distortion as shown in FIG. 3C is visually observed. Become. As can be seen from the lattice spacing, in Comparative Example 3, the horizontal direction extends slightly compared to the vertical direction, so the distortion balance in the vertical and horizontal directions is lost, but in Examples 3A and 3B, the vertical and horizontal directions are longer than those in Comparative Example 3. Is balanced. In particular, in Example 3B, the distortion in the lateral direction is reduced, and the distortion aberration is more balanced.

Simulation 4
In simulation 4, a simulation was performed by adding an aspherical plus lens to a plus lens composed of a simple spherical surface and a trick surface. The comparison lens 3 having the outer surface set as a spherical surface and the inner surface set as an astigmatism correction surface was compared with Examples 3A and 3B of the present invention in which the inner and outer surfaces were set as an astigmatism correction surface.
Here, the comparison lens 4 having the outer surface set as a spherical surface and the inner surface set as an astigmatism correction surface was compared with Examples 4A and 4B of the present invention. In all cases, the power of the lens was S + 2.00D C + 1.00D AX90. Astigmatism power was set to + 2.00D in the vertical direction and + 3.00D in the horizontal direction. In other words, a lens was produced in which the vertical direction is the astigmatic axis and the horizontal direction is the astigmatic intensity direction. In any case, the material refractive index of the glass constituting the lens is 1.6, the lens diameter is 60 mm, the lens center thickness is 3.25 mm for the comparative lens 4, 3.28 mm for Example 4A, and 3.16 mm for Example 4B. did. The astigmatism correction surface was set as a trick surface for the comparative lens 4 and Example 4A, and in Example 4B, the outer surface was a trick surface and the inner surface was a non-trick surface. In Example 4B, in order to simplify the calculation, the non-trick surface has a spherical cross section in the lateral direction and only the vertical cross section is set to an aspheric surface.
The surface refractive power of the lens was calculated based on the above formulas (1) and (2).

(Comparative Example 4)
The outer surface of the lens of Comparative Example 4 was a curved spherical surface having a refractive power of 3.50. Based on the above equation (1), the radius of curvature of this curve is about 171.4 m. Further, based on the above formula (2), the surface refractive power of the inner surface of the lens of Comparative Example 4 is a trick surface having a 1.53 curve in the vertical direction and a curve of 0.53 in the horizontal direction (rounded off to the second decimal place). display). Table 4 shows the refractive power of Comparative Example 4.
(Example 4A)
The outer surface of the lens of Example 4A has a refractive power of 5.50 in the curve in the lateral direction (astigmatism intensity direction). Accordingly, the lateral curve of the inner surface of the lens of Example 4A was determined to have a refractive power of 2.56 from the above formula (2). As a result, a deeper curve is formed with respect to the comparative example 4 in both the inner and outer surfaces in the astigmatism intensity direction. In the longitudinal direction (astigmatism axis direction), the curve is shallower than that of Comparative Example 4, and the refractive power is 2.50 on the outer surface, and the refractive power is 0.51 on the inner surface. Table 4 shows the refractive power of Example 4A.
(Example 4B)
The curve of the inner and outer surfaces of the lens of Example 4B was set to the same value as that of Example 4A. However, since the inner surface is a non-trick surface (longitudinal cross section is aspherical), the vertical border thickness is thin. That is, it is 1.69 mm compared with 1.78 mm in Example 4A. Table 4 shows the refractive power of Example 4B.
Results As shown in FIG. 4A in Comparative Example 4, as shown in FIG. 4B in Example 4A, distortion as shown in FIG. 4C is seen in Example 4B. It will be. As can be seen from the lattice spacing, in Comparative Example 4, the horizontal direction extends slightly compared to the vertical direction, so the distortion balance in the vertical and horizontal directions is lost. In Examples 4A and 4B, the vertical and horizontal directions are compared with Comparative Example 4. Is balanced. In particular, in Example 4B, the distortion in the lateral direction is reduced, and the distortion aberration is more balanced. Table 4 shows the actual distances of the positions viewed with distortion in the 26.6-degree viewing direction and the 45-degree viewing direction.

It is the figure which simulated the distortion aberration of the spectacle lens for astigmatism correction of this invention, (a) is the comparative example 1, (b) is Example 1A, (c) is Example 1B. It is the figure which simulated the distortion aberration of the spectacle lens for astigmatism correction of this invention, (a) is the comparative example 2, (b) is Example 2A, (c) is Example 2B. It is the figure which simulated the distortion aberration of the spectacle lens for astigmatism correction of this invention, (a) is the comparative example 3, (b) is Example 3A, (c) is Example 3B. It is the figure which simulated the distortion aberration of the spectacle lens for astigmatism correction of this invention, (a) is the comparative example 4, (b) is Example 4A, (c) is Example 4B. Explanatory drawing which compared the case where astigmatism correction was carried out on the outer surface side in the minus lens, and the case where astigmatism was corrected on the inner surface side. (A) is a perspective view of the minus lens explaining the concept of the present invention, (b) is a perspective view of the plus lens. Explanatory drawing explaining the method of the simulation in an Example.

Claims (6)

An astigmatism correction surface in the vicinity of the center of the lens body in which the curvature of the cross-sectional curve formed by the intersection of the plane that includes the center of the lens body perpendicular to the lens surface and the lens surface differs depending on the direction of the cross section near the center of the lens body The surface of the lens body on the object side so that the direction of the maximum curvature and the direction of the minimum curvature of each of the cross-sectional curves are substantially orthogonal and the curvature is monotonously changed between the maximum curvature direction and the minimum curvature direction. A spectacle lens for correcting astigmatism, which is formed on both surfaces of the eyeball side surface, and a desired astigmatism power is set by the both astigmatism correction surfaces. 2. The spectacle lens for correcting astigmatism according to claim 1, wherein a direction in which the curvature of the outer surface is maximized substantially coincides with a direction in which the curvature of the inner surface is maximized. The spectacle lens for correcting astigmatism according to claim 1, wherein a direction in which the curvature of the outer surface is maximized substantially coincides with a direction in which the curvature of the inner surface is minimized. The direction in which the curvature of the outer surface is maximum coincides with the direction in which the transmission refractive power of the spectacle lens has the minus maximum intensity in the minus lens, and coincides with the direction in which the plus maximum intensity in the plus lens. Or the spectacle lens for astigmatism correction of 3. 2. The astigmatism correction surface is constituted by a non-trick surface in which a cross-sectional curve formed by the intersection of a lens surface with a plane perpendicular to the lens surface including the center of the lens includes a non-circular surface. The spectacle lens for astigmatism correction according to any one of? The progressive refractive surface shape for adding the addition in the near part to only one of the two surfaces of the lens body or combining only one of the surfaces is synthesized. The spectacle lens for correcting astigmatism as described.

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