JP2019139120A - Bifocal lens and method of manufacturing bifocal lens - Google Patents

Abstract

To provide a bifocal lens that causes discontinuity of an image and never spoils a visual appearance of a wearer that others view, and a method of manufacturing such a bifocal lens.SOLUTION: The present invention relates to a spectacle lens 1 which is a bifocal lens having an upper region and a lower region for viewing a short-sight position relatively to the upper region set at an upper and a lower position during wearing to different lens diopters. The spectacle lens is provided with a belt-like border region extending in a lateral direction between the upper region and lower region, and the border region is such that omnidirectional prisms succeed in the border region and the upper region and lower region are connected at upper and lower ends thereof without any step.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a bifocal lens in which an upper region for far vision and a lower region for near vision are set at different lens powers, and a method for manufacturing the bifocal lens.

2. Description of the Related Art Conventionally, there is a bifocal lens in which a near lens is formed with an auxiliary lens called a small lens having a plus power with respect to the lens power of the far vision portion as spectacles for hyperopia or presbyopia. Patent document 1 is shown as an example of such a bifocal lens.

Japanese Patent Laid-Open No. 5-303063

  However, the conventional bifocal lens has a clear boundary line between the main lens and the auxiliary lens, so the image on the boundary line except for a specific position (mainly the top (top) position) This caused a discontinuity (prism jump). In addition, if the boundary line is clear as described above, the appearance is impaired, and the appearance of the wearer when viewed from another person is also unfavorable. SUMMARY OF THE INVENTION The main object of the present invention is to provide a bifocal lens that does not cause image discontinuity and that does not impair the appearance of the wearer when viewed by others, and a method for manufacturing such a bifocal lens. It is.

As a first means for solving the above-mentioned problem, a lens in which an upper region and a lower region for visually checking a short distance relative to the upper region are different from each other in a vertical direction when wearing glasses. A bifocal lens set in degrees, wherein a belt-like boundary region is provided between the upper region and the lower region, the boundary region has no step in the boundary region, and prisms in all directions are provided. The upper region and the lower region are connected to the upper region and the lower region without any step.
As a result, image discontinuity, which is a drawback of the conventional bifocal lens, does not occur. Moreover, it does not impair the aesthetic appearance when viewed by others.

Here, the “lens power” is information necessary for correcting the refractive power of the eye of the spectacle lens wearer, for example, spherical power, astigmatism power, astigmatism axis angle, prism power, prism axis angle, The degree of participation.
The “upper region” is a region in which a long distance is viewed relative to a lower region for viewing a short distance. In general, this region is used mainly by the spectacle lens wearer for viewing from a medium distance to a long distance. Further, the “lower area” is an area used for viewing a short distance.
The “band-like boundary region” is located between the upper region and the lower region, but the boundary region has continuous curvature in all directions without any step in the boundary region, and is connected to the upper and lower regions without any step at the upper and lower ends. For example, the boundary region may be designed such that part of the upper region and the lower region is deformed, or the upper region and the lower region may be designed separately. That is, a part or all of the boundary region may be a part of the upper region or the lower region, and may be designed separately from the upper region or the lower region so as to be adjacent to the upper region and the lower region. .
The boundary region only needs to be connected to the upper region and the lower region without a step at the upper and lower ends without a step in the boundary region. For example, there may be a case where the curvature is discontinuous at the upper and lower ends of the boundary region. In the present invention, the prisms are continuous in the boundary region and at the upper and lower ends thereof.

The bifocal lens of the present invention is preferably processed by first designing the front and back surfaces as an SV (single vision) lens and then superimposing the design of the lower region on such a lens. When processing the precursor lens, the processing may be performed by the processing device in the order of the SV lens → BF lens, or the precursor lens may be synthesized by synthesizing all the designs including the design of the lower region. You may make it process. As the processing device, for example, an NC device, a CAD / CAM device, or the like is preferable. In these apparatuses, machining data is input and machining is performed by controlling the computer with a program. The material of the precursor lens to be processed may be either glass or plastic. If the accuracy is not required, instead of processing the precursor lens directly, mold the mold after filling the upper and lower molds and filling and molding the synthetic resin into the mold cavity. You may make it like taking it out from. Further, the upper region and the lower region may be formed by processing one of the front and back surfaces of the lens surface, and the upper region and the lower region may be formed on different surfaces.
Further, when a prism is set for the lens, the prism may be set independently for the upper region and the lower region.
Accordingly, for example, a bifocal lens having a prism characteristic suitable for a wearer having different prism characteristics in a distance view and a near view can be provided. Further, the horizontal prism or the vertical prism may be set independently.

Further, as a second means, a boundary line formed between the upper region and the lower region and the boundary region is set below the fitting point, and the boundary region is a region close to the fitting point. The first region extending in the horizontal direction and the second region extending downward from the left and right positions of the first region.
The fact that the boundary line is below the fitting point means that at least the area above the boundary area is an area for viewing a long distance, and the boundary area does not hinder the distance view. Since the near area can be secured by the first area and the second area extends downward, the distance area is secured and the entire distance visual field can be easily grasped. Further, since the distance area is large when the face is moved to the left or right, the distortion can be reduced or the “smoothness” of the scenery when the line of sight is moved can be reduced.

“Extending in the lateral direction” means that the first region may not be completely horizontal, but may be horizontal. Further, the upper and lower boundary lines of the first region may be linear or curved. The second region extends downward from the left and right positions of the first region, but the direction in which the second region is directed does not necessarily have to be directly below. The first region and the second region are preferably not continuous and continuous.
In addition, a boundary line between the upper region and the lower region may be a curved line that exists in the boundary region and is convex upward.
As a result, the design of the boundary region can be designed so as to be combined with the design of the upper region and the lower region, so that the bifocal lens of the present invention can be easily created. In this case, the boundary area is also part of the upper and lower areas.
The “boundary line” is preferably in the boundary area, and the position of the boundary line can be arranged at a position other than the center position in the vertical direction of the boundary area. This depends on how much the boundary area is allocated to the upper and lower areas. Further, since there is no step in the present invention, a clear “line” does not actually appear. Since the upper region and the lower region are designed separately to the last, the boundary between the two regions is calculated and provided on the lens. However, in the present invention, the boundary region is smooth, so that is not the case.
The boundary region may be an inner region surrounded by the upper end curve and the lower end curve. In order to have a first region extending in the lateral direction in the region where the boundary region is close to the fitting point and a second region extending downward from the left and right positions of the first region, the upper end curve and the lower end curve are It is preferable that the curve is convex. The curve is preferably a multi-order curve of a quadratic curve or higher. It is not necessary to limit to an integer order, and a 3.5th order expression may be used. The polynomial curve, a cubic and quartic or in the form of addition as ^{a · x 3 + b · x} 4. Curves and straight lines may be combined. The upper end curve and the lower end curve may have different orders, and the upper end curve and / or the lower end curve may be different curves on the left and right sides. Further, the upper end curve or / and the lower end curve may be configured by connecting a plurality of different curves or straight lines. Further, a trigonometric function or the like may be used as a method for representing the shapes of the upper end curve and the lower end curve. Employing a polynomial is only one way of defining a curve and is not limited to this.

Further, as a third means, in the state of the circular precursor before the bifocal lens is processed into the target lens shape, the edge position point of the precursor that the end of the boundary region reaches is directly below the fitting point. Was in the range of 225 to 315 degrees, with 270 degrees around the geometric center of the precursor.
More specific areas for near and far use are shown. In such a range, the near area can be secured, and the second area extends downward, so that the far area is secured and the entire distance visual field can be easily grasped. Further, since the distance area is large when the face is moved to the left or right, the distortion can be reduced or the “smoothness” of the scenery when the line of sight is moved can be reduced.
The “lens shape” refers to a lens in a state in which, for example, a circular precursor is processed according to a frame.

As a fourth means, the x-axis surrounding the lens shape of the lens when the horizontal direction when the bifocal lens is worn is the x-axis direction and the vertical direction intersecting with the x-axis direction is the y-axis direction. A virtual rectangle parallel to the direction and the y-axis direction is assumed, and the point where the boundary region reaches the boundary of the rectangle is on the lower side of the rectangle.
As a fifth means, when the bifocal lens is worn, the x-axis direction surrounds the lens shape when the horizontal direction is the x-axis direction and the vertical direction intersecting the x-axis direction is the y-axis direction. A virtual rectangle parallel to the direction and the y-axis direction is assumed, and the point where the boundary line reaches the boundary of the rectangle is on the lower side of the rectangle.
More specific areas for near and far use are shown. If there is a boundary area or boundary line at such a position, the near area can be secured, and the second area extends downward, so that the far area is secured and it is easy to grasp the entire distance visual field. Further, since the distance area is large when the face is moved to the left or right, the distortion can be reduced or the “smoothness” of the scenery when the line of sight is moved can be reduced.
The “virtual rectangle” is a concept used to define the size of the lens in a concept of surrounding a so-called box shape called boxing.

As a sixth means, the boundary region has the narrowest width at the uppermost position, and the boundary region gradually increases in width from the center toward the left and right.
In the bifocal lens, when the lower region is simply formed in the upper region serving as the base, the step becomes larger as the distance from the center is increased. When designing to cancel the step, the width of the boundary region is narrowest at the upper position, and the width is increased as the distance from the center is increased. As a result, it is difficult for distortion to occur in the boundary region, and as a result, even if the line of sight passes right and left of the boundary region, it is difficult to feel uncomfortable.

Further, as a seventh means, the bifocal lens is designed so that the boundary region is rapidly widened at a portion near the outside of the lens in a state of being processed into a target lens shape. . In this way, by widening the boundary area at a position that is not the main part of the lens, there is a margin in the boundary area, so that it is possible to smoothly connect the near area and the far area.
Further, as an eighth means, in the bifocal lens described in the sixth means, as the prescription with a larger addition power, the width of the boundary area gradually increases as the distance from the fitting point increases. The ratio was designed to be large.
That is, when the power of the near area is plus with respect to the upper area and the degree of addition (addition degree) is large, it is preferable to design so that the width can be expanded more than when it is small. In a lens having a higher addition power, the step difference between the upper region and the lower region is larger before the boundary region is deformed, so that the curvature change in the boundary region can be suppressed by making the width of the deformed region wider. This is because distortion can be prevented from becoming extremely large. And by doing so, even if the addition becomes strong, the distortion in the boundary region is suppressed, and the boundary becomes inconspicuous when viewed from others. In addition, there is no unreasonableness in machining with an NC machining apparatus or the like.

Further, as a ninth means, in the bifocal lens according to the sixth means, prisms are independently set in the upper region and the lower region, respectively, and are set in the upper region and the lower region. The prescription with a larger prism difference is designed to increase the rate at which the width of the boundary region gradually increases as the distance from the fitting point increases.
If the horizontal prisms are not set independently in the upper and lower regions, the thickness difference between the upper and lower regions increases as the distance from the fitting point in the horizontal direction increases. The method is the same in both the direction toward the ear and the direction toward the nose. For example, if the upper region and the lower region are both negative power and the lower region is weaker, the lens thickness is relatively thinner in the lower region as the distance from the fitting point to the horizontal direction is increased. The degree is the same in the direction toward the ear and the direction toward the nose.
However, when the horizontal prism is set independently in the upper region and the lower region, a difference occurs between the ear side and the nose side. For example, when there is no prism prescription in the upper region and a base-in prism is prescribed in the lower region, the lens thickness of the lower region is further reduced on the ear side. The difference increases. For this reason, it is preferable to design a large proportion of the width of the boundary region.
When the vertical prisms are set independently in the upper region and the lower region, the difference in thickness between the upper region and the lower region changes in the same way on the ear side and the nose side. When a prism is strongly generated in the up direction in the lower region as compared with a normal bifocal lens, the difference in thickness between the upper region and the lower region increases on both the ear side and the nose side. For this reason, it is preferable to design a large proportion of the width of the boundary region.

Further, in the ninth means as the tenth means, the ratio of increasing the width of the boundary region is designed to be different between the ear side and the nose side.
For example, in the case where the horizontal prism is set independently for each of the upper region and the lower region, there is no prism prescription in the upper region as described above, and the base-in prism is prescribed in the lower region. In the lower region, the lens thickness is further reduced, but on the nose side, the difference in thickness between the upper region and the lower region is reduced. Therefore, it is not necessary to increase the width of the boundary region on the nose side. In other words, it is only necessary to design so that only the width of one necessary boundary region is widened.For example, it may be designed to increase the ratio of the width of the boundary region only on one side, for example, on one side You may design small the ratio which the width | variety of an area | region becomes wide.

Further, as the eleventh means, in the bifocal lens manufactured by the manufacturing method according to any one of the seventh to tenth means, astigmatism power is set independently in each of the upper region and the lower region, At least one of the astigmatism power and the astigmatism axis in the upper region and the lower region is not the same.
Accordingly, for example, a bifocal lens having astigmatism characteristics suitable for a wearer having different astigmatism characteristics between far vision and near vision can be provided.
Here, “independent astigmatism power is set” is intended in the first place even when the astigmatism power is 0D. There can be a case of setting and vice versa.

  According to the present invention, image discontinuity, which is a drawback of the conventional bifocal lens, does not occur. Moreover, it does not impair the aesthetic appearance when viewed by others.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a front view for explaining a layout of a spectacle lens of Example 1 of the present invention. Explanatory drawing explaining the direction of a sag at the time of processing the spectacle lens of Example 1, and a y-axis direction. FIG. 3 is an explanatory diagram for explaining a shape in a vertical direction around a boundary region on the near top on the back surface of the eyeglass lens of Example 1; Explanatory drawing explaining the shape of the orthogonal | vertical direction periphery of the boundary area | region of the position spaced apart from the near top on the back surface of the spectacle lens of Example 1. FIG. The front view explaining the layout of the spectacle lens of Example 2 of this invention. The front view explaining the layout of the spectacle lens of Examples 3-1 and 3-2 of the present invention. It is description of the setting of the inset position of the spectacle lens of Example 2, (a) is explanatory drawing of the calculation method of the distance to the near-sighted object, (b) planarly viewed the lens vicinity of (a). (C) is an enlarged view of the lens vicinity of (a) as seen from the side. FIG. 10 is an explanatory diagram for explaining the relationship between the angle of the lens inner surface and the lens outer surface when setting the prism amount in the design of the back surface of the spectacle lens of Example 3-2. The front view explaining the layout of the spectacle lens of Example 4 of this invention. The front view explaining the layout of the spectacle lens of Example 5 of this invention. The front view explaining the layout of the spectacle lens of Example 6 of this invention.

Hereinafter, embodiments of the spectacle lens of the present invention will be described with reference to the drawings. The following spectacle lenses are obtained by cutting a semi-finished blank as a precursor lens by inputting processing data to an NC apparatus, which is a processing apparatus incorporating a computer, and controlling the computer by a program.
Example 1
<Specific lens values>
FIG. 1 is a front view for explaining the layout of a spectacle lens 1 of a bifocal lens that is Embodiment 1 of the present invention. The spectacle lens 1 has a circular outer shape called a so-called round lens before the frame insertion process, and is cut into a frame shape (lens shape) according to a user's request at a manufacturer or a spectacle store. An example of specific data of the eyeglass lens 1 of Example 1 is as follows. Here, explanation will be made on the R eye side. The horizontal coordinate is x, and the vertical coordinate is y. The ear side is wider than the nose side. In the first embodiment, no prism is set.
・ Distance power S-4.00D C-1.00D AX180
・ Nearly used power S-2.00D C-1.00D AX180 (distance and near astigmatic power are the same)
・ Addition 2.00D ・ Center thickness CT = 1.5 (mm)
・ Base material refractive index n = 1.600 ・ Table curve 2.00 curve (base material refractive index conversion)
-Radius of curvature of outer surface r0 = 1000, (n-1) / 2 = 300 (mm)
-Curvature of outer surface Co = 1 / r0 = 0.00333 (mm ^-1 )
・ Rotation angle θ = θn = 0 (rad)
Main curvature for inner surface distance Cx = (2-(− 4)) / (1000 · (n−1)) = 0.01000 (mm ⁻¹ ) Cy = (2-(− 5)) / (1000 · (N−1)) = 0.01167 (mm ⁻¹ )
Main curvature for inner surface Cxn = (2-(− 2)) / (1000 · (n−1)) = 0.00667 (mm ⁻¹ ) Cyn = (2-(− 3)) / (1000 · (N−1)) = 0.00833 (mm ⁻¹ )
・ No distance prism specified (both horizontal and vertical prisms)
-Coefficient reflecting the prism effect Px = Py = Pxn = Pyn = 0 · For the R eye, the nose side of the x axis is positive Tx = 1.5 (mm), Ty = -3.0 (mm)
Upper-end curve formula y = Ty + 1−0.010 · (x−Tx) ²
Lower end curve formula y = Ty-1−0.015 · (x−Tx) ²
・ Vertical distance between eye point and geometric center 2.0mm
・ Vertical distance from near top to eye point 5.0mm ・ Horizontal distance between near top and geometric center (and eye point) 1.5mm
・ The distance from the near top to the upper end curve of the vertical line at the 20 mm horizontal point on the ear side is 3 mm.
・ The distance from the upper end curve of the perpendicular to the lower end curve at a point 20 mm horizontally from the near top to the ear side is 7 mm.
In the first embodiment, the belt-like boundary region has no step in the boundary region, and is connected to the upper region and the lower region in the upper and lower ends without a step. The boundary region has the narrowest vertical width at the uppermost position and gradually increases in width from the center toward the left and right. The upper end curve and the lower end curve are formed by quadratic curves, and have a hill-like shape that gently falls from side to side with the geometric center (and eye point) as a vertex.

<Processing Method> An example of processing the spectacle lens 1 as described above by calculating processing data based on the following calculation formula will be described. In the following, description will be given mainly focusing on the bifocal lens design method according to the present invention, and data relating to the lens power unique to the wearer, such as S power, C power, addition power, and prism, is set according to the wearer. Is done. In the near top of the first embodiment, a processing method for smoothly joining the upper region and the lower region without twisting is used as a standard method, and the following examples 5 to 7 are also used as a standard method.
Basically, the outer surface (convex surface) is a spherical surface, and the inner surface (concave surface) is a spherical surface when there is no astigmatism power, and a toric surface when there is an astigmatism power. Since the first embodiment has an astigmatic power, a toric surface is adopted. Further, the present invention is a bifocal lens, and different lens powers are set in the distance portion and the near portion. The near portion is designed by combining the sag amount cutting the toric surface with the sag amount unique to the near portion.
Further, when the spectacle lens 1 is processed, a sag is given in a direction perpendicular to the outer surface through the geometric center of the outer surface of the lens as shown in FIG. The sag is in the positive direction from the lens toward the eyeball. The sag direction does not consider the tilt when the lens is worn. Therefore, when wearing with the lens tilted forward, the direction of the sag is not horizontal (in many cases, the spectacle lens is tilted forward by about 10 degrees during wearing). The positive direction of the sag is from the lens toward the eyeball, with the geometric center of the lens inner surface as the coordinate origin. A plane that passes through the origin and has the sag direction as a normal line is considered, and a direction horizontal to the direction of gravity in the plane is defined as an x-axis and a direction perpendicular to the x-axis. In the y-axis, the upward direction is the positive direction. The positive direction of the x axis is the nose side direction of the R eye.

1) Lens outer surface As described above, the horizontal coordinate is x, the vertical coordinate is y, the curvature of the outer surface is Co = 1 / r0, and the center thickness of the lens is CT. It is represented by

2) Lens inner surface In order to form a toric surface on the lens inner surface side as needed, the inner surface principal curvature is expressed as Cx = 1 / r1 and Cy = 1 / r2. The main curvature is the reciprocal of the main curvature radius. These main curvature values are determined from the specified distance power, the outer surface curvature, the refractive index of the lens substrate, and the center thickness of the lens. However, in Example 1, the following equation 2 is used to calculate Sf (x, y), and since equation 2 is an approximate calculation formula, the lens center thickness is not used as a parameter. Equation 2 is an example, and the center thickness may be used as a parameter when performing a stricter calculation.
In Equation 2, x ′ and y ′ are calculated according to the angle θ of the astigmatic axis. For example, if the astigmatism axis is 180 degrees or 90 degrees, the calculation of the expression Sf (x, y) representing the inner surface sag is easy, but if not, that is, if it is oblique, x ′ according to the angle θ. , Y ′, and the converted x ′ and y ′ coordinates are substituted into the expression Sf (x, y).
Expression 2 is a known expression indicating a toric surface, and is disclosed as a prior document in, for example, Japanese Patent Application Laid-Open No. 2001-021846 and Japanese Patent No. 3852116.

  At the coordinate origin of the inner surface sag, Sf (0,0) = 0. The coordinate origin of the inner surface sag is the position on the inner surface side by the center thickness of the lens perpendicular to the outer surface at the geometric center of the lens outer surface (point to measure the prism). In the first embodiment, the designated value of the distance prism is 0 prism in both horizontal and vertical directions, and the inner surface and the outer surface are parallel at the origin. When the distance prism is designated, a primary term of Px · x + Py · y is added to the expression of Sf. Here, Px · Py is a coefficient determined by the designated values of the horizontal prism and the vertical prism and the refractive index of the lens substrate. When the distance prism is specified, the inner surface has an inclination at the coordinate origin of the inner surface sag. Therefore, the center thickness of the lens is defined as a direction perpendicular to the geometric center of the outer surface. In Example 1, since there is no prism, the term Px · x + Py · y is not used. In Examples 2 and 3 described later, since the prism is set, calculation is performed using Px · x + Py · y. Px · x + Py · y is an element not affected by the direction of the astigmatism axis.

3) About the near portion on the inner surface of the lens The near region is a region below the parabola with the near top position as an upward apex. The upper area is the far area and the lower area is the near area. The near top position refers to the highest position in the xy coordinates of the boundary line that is upwardly convex at the boundary line between the distance area and the near area. Here, an expression representing the inner surface sag of the near-use area is Sn (x, y). The near-use top position is (Tx, Ty). In the expression of Sn (x, y), the boundary line between the distance area and the near area is smoothly connected at the near top position (not necessarily on the boundary line other than the near top position. This is realized by synthesizing Here, the specific condition for the smooth connection is that the line of the cross section is not bent in all directions. To that end, Sf (x, y) and Sn (x, y) share the slope at the point (Tx, Ty). The condition is expressed by the following equation.
∂Sf / ∂x | Tx, Ty = ∂Sn / ∂x | Tx, Ty ∂Sf / ∂y | Tx, Ty = ∂Sn / ∂y | Tx, Ty Here, the symbols | Tx, Ty It represents a partial differential value in (Tx, Ty). When calculating the value of partial differentiation, it is preferable to calculate by using a computer by substituting x = Tx and y = Ty into the result of partial differentiation of the above-described equations 1 and 2 with x and y. Alternatively, Δx may be calculated as a minute value approximately by a computer using the following equation.
∂Sf / ∂x | Tx, Ty = (Sf (Tx + Δx, Ty) −Sf (Tx−Δx, Ty)) / (2 · Δx)
In order to satisfy these conditions, Sn cannot be expressed in the same format as Sf described above. Even if such a formula is created, the value at the near-use top position is different and a step is produced in the shape. Even if the correction is made for the level difference, there is a difference in inclination between the horizontal direction and the vertical direction, and the connection is not smooth. Therefore, it is preferable to create an expression for correcting the difference between the step, the horizontal inclination, and the vertical inclination as the expression of Sn (x, y). In order to satisfy these conditions, the inner surface sag of the near-use area is expressed by Equation 3. Snp in the formula of Formula 3 is expressed as Formula 4.
The Snp in Equation 4 is a curved surface expressed in the same format as Sf, and the rotation angle θn and the principal curvatures Cxn and Cyn are values determined from the designated near power and the astigmatic axis. Here, since the perspective designation independent of perspective is not considered, the values of Pxn and Pyn are the same as those of Px and Py. Accordingly, the terms representing the prisms by Snp (x−Tx, y−Ty) and Sf (x−Tx, y−Ty) are canceled out, and the terms representing the prism by Sn (x, y) and Sf (x, y). Are common.
Sf (x−Tx, y−Ty) is the value of the distance area inner surface sag of the origin at the near top position = 0.
Snp (x−Tx, y−Ty) is Snp (0, 0) = 0 at the near top position.
Even if the difference between Snp (x−Tx, y−Ty) and Sf (x−Tx, y−Ty) is partially differentiated by x or y, the value is 0 at the point (Tx, Ty). Become. The reason is that each first-order term is canceled out and each remaining term takes a local minimum value.

4) The shape of the boundary area on the inner surface of the lens By designing the sag with the formula 3 as described above, it is possible to smooth one point of the near vision top, but on the boundary line between the distance vision area and the near vision area In other points, a step is produced. Therefore, the boundary region is given a width, a curve (parabola) separated in the vertical direction is set, the vertical connection is smoothed at each point in each of the upper end curve and the lower end curve, and a certain point on the upper end curve The curve from the point to the point on the bottom curve just below is made smooth. Smooth means that there is no step and the slope is not discontinuous. If the vertical direction is smoothed in a common format within the entire boundary area and on the upper and lower curves, the horizontal direction is automatically smoothed. In the first embodiment, the shape in the vertical direction is determined so that the boundary line between the distance area and the near area is located between the upper end curve and the lower end curve.
As shown in FIG. 3, in the cross section including the near-use top, even if the distance-use shape Sf and the near-use shape Sn are not displaced intentionally, no step or bend occurs on the inner surface of the lens. However, the curve (longitudinal section curvature) discontinuously changes from the distance value to the near value at the near top position.
On the other hand, in a cross section at a position away from the near top in the left-right direction, a step is generated between the distance shape and the near shape. In order to eliminate the step and prevent the step and the boundary from being bent at the boundary upper end and the boundary lower end, the shape of the boundary region is determined by Sf + Sa as described below. Therefore, it is necessary to replace the cross-sectional shape from the “junction of the upper Sf and the lower Sn” with “Sf + Sa” even in the cross section including the near top. By performing the replacement with “Sf + Sa”, the positions where the longitudinal section curvature changes discontinuously are the upper and lower ends of the boundary region. Then, by using the following formulas 5 and 6, it can be seen that the longitudinal cross-sectional curvature changes discontinuously at the upper and lower ends of the boundary region as well as the near top position.
From this point, the periphery of the boundary region can be laid out as shown in FIG. However, since the difference between the two shapes in the cross section including the near top is very small, the cross section representing “Sf + Sa” is omitted for the near top.

As shown in FIG. 3, in the boundary region, the vertical cross section whose x coordinate is Tx is a smooth curve.
On the other hand, FIG. 4 shows a vertical section when the value of the x coordinate is x ₀ ≠ Tx. The sectional curve of the distance region is a function of y, and Sf (x ₀ , y) is the sectional curve of the near region, and Sn (x ₀ , y). Here, a cubic function Sa (p) in the y direction that adds a sag to Sf (x ₀ , y) from a point (x ₀ , y _T ) on the upper end curve to a point (x ₀ , y _B ) on the lower end curve. )think of. The direction of p is positive toward the bottom.
p is set to p = 0 at a point (x ₀ , y _T ) on the upper end curve. That is, p = y _T −y. Sa (0) = 0.
It is assumed that dSa (p) / dp | 0 = 0. The differential value at p = 0 is zero.
p is p = y _T −y _B at a point (x ₀ , y _B ) on the lower end curve.
_{Sa (y T -y B) =} Sn (x 0, y B) -Sf (x 0, y B) ··· ( Condition 1)
_{dSa (p) / dp | y} T -y B = ∂Sn / ∂y | y B -∂Sf / ∂y | from _y B · · · (Condition 2) or more conditions, and constant term Sa (p) The first-order term is not necessary and can be expressed by the following equation (5). A formula obtained by first-order differentiation of this is also shown.

From conditions 1 and 2, the values of a and b can be obtained to determine Sa (p). In vertical section of x = x _0, by adding this function, it is possible to represent the inner surface shape by 6 equations below. Note that below the boundary is the lower region, but still does not include the Sn equation. That is, inside the boundary region, the inner surface shape is expressed by a formula in which Sa is added to Sf, and the function smoothly connects to Sn on the lower end curve.

If the lens shape in the boundary region of the inner surface of the lens is smoothly connected in this way, no step is produced in the shape, and the “brass” that impairs the appearance of the conventional BF lens is inconspicuous. Further, since the inclination of the surface on the boundary line changes continuously, there is no prism jump. Therefore, “image discontinuity” which is a defect of the conventional BF lens does not occur. Next, the conditions under which the longitudinal section curvature continuously changes not only in the boundary region but also in the upper and lower ends by increasing the order in Equation 5 will be described.
p is set to p = 0 at a point (x ₀ , y _T ) on the upper end curve. That is, p = y _T −y.
Sa (0) = 0.
It is assumed that dSa (p) / dp | 0 = 0. The differential value at p = 0 is zero.
It is assumed that d ² Sa (p) / dp ² | 0 = 0. The second-order differential value at p = 0 is zero.
p is p = y _T −y _B at a point (x ₀ , y _B ) on the lower end curve.
_{Sa (y T -y B) =} Sn (x 0, y B) -Sf (x 0, y B)
_{dSa (p) / dp | y} T -y B = ∂Sn / ∂y | y B -∂Sf / ∂y | y B
d ² Sa (p) / dp ² | y _T −y _B = ∂ ² Sn / ∂y ² | y _B −∂ ² Sf / ∂y ² | y _B

The above three conditions on the upper curve and the lower curve are defined as (Condition 3) (Condition 4) (Condition 5).
From these conditions, it can be seen that Sa (p) does not require a second-order or lower term and can be expressed by the following equation (7). An expression obtained by first-order differentiation and an expression obtained by second-order differentiation are shown together. From (Condition 3) to (Condition 5), the values of a and b can be obtained to determine Sa (p).

In the above, an example in which a cubic function is used to represent Sa (formula 5) for smoothing the boundary line in the shape of the boundary region on the inner surface of the lens has been shown. The curve is continuous, but the curve is discontinuous on the bottom curve. This is because the second-order differential value of Sa by p does not always coincide with the second-order differential value of Sn-Sf by y. However, since the curve is discontinuous at the top of the near-use area, it is sufficient.
Here, if a higher order function than the third order is used to represent Sa, the curve values in the boundary region can be connected more smoothly. For example, if a quintic function is used, the vertical section curve can be smoothly and continuously changed.

(Example 2)
FIG. 5 is a front view for explaining the layout of the spectacle lens 2 of the bifocal lens that is Embodiment 2 of the present invention. The spectacle lens 2 is also in a state of a circular outer shape called a so-called round lens before the frame insertion processing similar to the spectacle lens 1 of the first embodiment. An example of specific data of the eyeglass lens 2 of Example 2 is as follows. Data common to the eyeglass lens 1 of Example 1 is omitted. The processing method is the same as that in the first embodiment. In the second embodiment, no prism is set as in the first embodiment.
・ Distance power S-1.00D C-0.00D AX180
・ Nearly used power S-0.00D C-0.00D AX180
・ Addition 1.00D
・ Expression of upper end curve y = −2−0.0015 ・ ABS ((x−1.5) ³ )
・ Formula of lower end curve y = −4−0.0022 ・ ABS ((x−1.5) ³ )
* Since the cubic function is an odd function, in order to make the nose side and the ear side symmetrical, it is necessary to take the third power after taking an absolute value. ABS is a function that returns the absolute value of an argument. The same applies below.

Even in the spectacle lens 2 of Example 2, the belt-like boundary region has no step in the boundary region and is connected to the upper region and the lower region at the upper and lower ends without a step. In the second embodiment, the boundary region is a region close to the fitting point, that is, a first region extending in a substantially horizontal lateral direction of about 10 mm on the left and right of the fitting point below the fitting point (strictly speaking, the first region is And a second region extending downward from the left and right positions of the first region. The first region and the second region are not clearly separated. The boundary region has a narrow vertical width near the center of the first region, and gradually widens in the horizontal direction from the center toward the left and right, respectively. It is wide. However, in Example 2, since the addition is weak and there is no prism in the near-use area, the rate of widening is set small. In the second embodiment, the ratio of the widest portion to the narrowest portion in the boundary region in the frame shape (lens shape) is set to about 1.3 to 1.5 times.
As shown in FIG. 5, when a boxing frame BF that is in contact with the frame shape (lens shape) is set, the boundary line that is the center position of the boundary passes on the lower side of the boxing frame BF.
In the eyeglass lens 3 of Example 2, the boundary area extends downward from the second area, and the distance area is set wide while the near area is maintained, so the distance area is secured. Easy to grasp the entire distance vision. Further, since the distance area is large when the face is moved to the left or right, the distortion can be reduced or the “smoothness” of the scenery when the line of sight is moved can be reduced.

(Example 3-1)
FIG. 6 is a front view for explaining the layout of the spectacle lens 3 of the bifocal lens that is Example 3-1 of the present invention. The spectacle lens 3 is also in a state of a circular outer shape called a so-called round lens before the frame insertion processing similar to the spectacle lens 1 of the first embodiment. An example of specific data of the eyeglass lens 3 of Example 3-1 is as follows. Data common to the eyeglass lens 1 of Example 1 is omitted. The processing method is the same as that in the first embodiment. In Example 3-1, the addition is large and there is no prism.
・ Distance power S-0.00D C-0.00D AX180
・ Nearly used power S + 3.00D C + 0.00D AX180
・ Degree of addition 3.00D
-Upper curve formula y = -2-0.0012 ABS ((x-1.5) ³ ))
-Lower-end curve formula y = -4-0.0026 ABS ((x-1.5) ³ ))

Also in the spectacle lens 3 of Example 3-1, the belt-like boundary region has no step in the boundary region, and is connected to the upper region and the lower region without steps in the upper and lower ends. In Example 3-1, the boundary region is a region close to the fitting point, that is, a first region extending in a substantially horizontal lateral direction of about 10 mm on the left and right sides of the fitting point below the fitting point (strictly speaking, the first region) The region is convex upward), and is composed of a second region that curves downward from the left and right positions of the first region and extends downward. The first region and the second region are not clearly separated. The boundary region has a narrow vertical width near the center of the first region, and gradually widens in the horizontal direction from the center toward the left and right, respectively. It is wide. Since the addition is stronger than in the second embodiment and there is a prism in the near area, the width is the same as that in the second embodiment in the vicinity of the first area, but the width becomes wider as the distance from the second area increases. Increase the ratio. In Example 3-1, the ratio of the widest portion to the narrowest portion in the boundary region in the frame shape (lens shape) is set to about 2.0 to 2.5 times.
As shown in FIG. 6, when the boxing frame BF in contact with the frame shape (lens shape) is set, the boundary line that is the center position of the boundary passes on the lower side of the boxing frame BF. In the spectacle lens 3 of Example 3-1, the distance area is set wide while the near area is maintained. Therefore, when the face is moved to the left and right, the distance area is large. It is the same as in the second embodiment that the “smoothness” of the landscape when the lens is moved is the same as in the second embodiment. However, unlike the eyeglass lens 2 in the second embodiment, the addition is large, so that the boundary region is not deformed. Since the step at the boundary between the upper and lower regions is larger in the stage, if the width of the boundary region is increased as the distance from the fitting point increases, the curvature change in the boundary region can be suppressed, and distortion distortion is extremely large. Can be prevented.

(Example 3-2)
Similarly, Example 3-2 of the present invention will be described with reference to FIG. In Example 3-2, the addition is not large, and the prism is set only in the near-use area. In the case where the addition is increased as in Example 3-1, and in the case where the prism is set in the near area, the aberration of the lens surface has the same influence, so the shape of the boundary area is the same design. However, in Example 3-2, the design is such that the vertical direction is smooth but twisted at the position of the near top where the distance region and the near region are joined to the standard system of Example 1.
An example of specific data of the eyeglass lens 3 of Example 3-2 is as follows.
・ Distance power S-0.00D C-0.00D AX180
・ Nearly used power S + 1.00D C + 0.00D AX180 Prism Inn 3.00PD
・ Addition 1.00D
-Upper curve formula y = -2-0.0012 ABS ((x-1.5) ³ ))
-Lower-end curve formula y = -4-0.0026 ABS ((x-1.5) ³ ))
In the eyeglass lens 3 of Example 3-2, the distance area is set wide while the near area is maintained. Therefore, when the face is moved to the left and right, the distance area is large. As in the case of the second embodiment, it is possible to reduce the “smoothness” of the scenery when the lens is moved. However, unlike the eyeglass lens 2 of the second embodiment, a prism is set in the near area. In the case where the prism is prescribed in such a near-use area, a difference occurs in the lens thickness between the ear side and the nose side. Here, since the base in prism is prescribed, the lens thickness becomes thin on the ear side. That is, the difference in thickness between the upper region and the lower region increases.
For this reason, in Example 3-2, as in Example 3-1, it is preferable to increase the width of the boundary region as the distance from the fitting point is greater than in the case of Example 2. By widening the width of the boundary region in this way, it is possible to connect the upper region and the lower region without difficulty.

Here, an example of a method for processing a horizontal prism in a spectacle lens having a lens design having a horizontal prism in the near region will be described.
In Example 1 and Example 2, Px = Py = Pxn = Pyn = 0 as a coefficient reflecting the prism effect. That is, in the lenses of Example 1 and Example 2, the prism is not set as the entire lens. However, since the lens has a prism effect, the line of sight in the oblique direction always shifts. In the second embodiment, it is considered that the horizontal prism is set to 0 so that a shift due to the prism effect does not occur in the position where the wearer converges when viewing with near vision, that is, the near vision at the inset position.

1) Setting of a position where the horizontal prism effect becomes 0 In the second embodiment, the horizontal prism effect is set to 0 at the inset position regardless of the lens power. For this purpose, the inset may be determined based on the position through which the line of sight of the wearer looking straight at the near object passes. For example, it is determined by the following conditions. The numerical value is a typical example for explaining the condition, and the numerical value varies depending on the wearer.
・ Distance from the center of eye rotation to the top of the cornea 13mm
・ Distance PD (Distance between left and right vertices when looking straight ahead without congestion) 62mm
・ Distance between vertices (distance from corneal vertex to lens) 12mm
・ Near distance (straight line distance from corneal apex to near object) 400mm
・ Passing height of near line of sight 7mm below geometric center (9mm below fitting point)

In this example, the passing height of the near line of sight is determined by the product standard as a position 3 to 7 mm below the near top position at the position where the near prism is measured. The vertical “passing height” and “inset horizontal coordinate” take different values on the outer surface and the inner surface in consideration of the thickness of the lens. Further, since the light beam does not pass perpendicularly to the lens surface, the light beam is different from the line that connects the near object straight from the center of eye rotation. The near prism may be set by adjusting the inner surface shape at the light beam passing point on the inner surface based on the exact light beam passing position, ignoring those errors. Here, an example by approximate calculation is shown. However, the near center coordinates have the inner surface of the lens as a light beam passing point.
Based on the approximate calculation, the point where the near-use prism is set is (x ₁ , y ₁ ). It is assumed that y ₁ = Ty-4 (mm) according to the product standard. On the other hand, the value of _{x 1} is determined by calculation. As shown in FIG. 7A, it is first considered to obtain the total length in a congested state up to the object when viewed near. Then, as shown in FIG. 7C, consider a right triangle having the entire length to the object as the hypotenuse m and the short side of 1/2 of the distance PD. Determine the value of _{x 1} in approximation based on the triangle with it similar as in FIG. 7 (b) (about 2.0 (mm)).

2) Prisms are applied to all near-use areas so that the horizontal prism effect becomes zero when the prism amount is set (x ₁ , y ₁ ).
The amount of prism is defined by how many centimeters the light beam is shifted per meter (100 cm). If the angle formed by the lens outer surface and the inner surface in Example 2 is θ, θ and θ ′ are expressed by the relationship between the lens outer surface and the inner surface as shown in FIG. At this time,
Horizontal prism amount = tan (θ′−θ) × 0.01 According to Snell's law, sin θ ′ = sin θ · n tan θ = (∂Sn / ∂x | x ₁ , y ₁ ) − (∂So / ∂x | x ₁ , y ₁ ).
Accordingly, in setting the near-use prism, the inner surface of the near-use region may be parallel to the outer surface in the horizontal section. For this purpose, a sag is added at a point other than the X coordinate x = Tx of the near top position (Tx, Ty) to cancel the horizontal prism at the ray passing point. Specifically, Snp in the above equation 4 is expressed by the following equation 8.

Here, in equation (8), if α = 0, the horizontal prism at the light beam passing point is canceled. When a value other than 0 is specified as the value of the near horizontal prism, the inner surface sag Snp is corrected by appropriately setting the value of α based on the base material refractive index n so that the specified horizontal prism is obtained. That's fine.
The value of tan θ is expressed as ∂Sn / ∂x obtained by partial differentiation of the above equation (3) with x, and ∂So / ∂x obtained by partial differentiation of the equation (1) with x, respectively, x = x ₁ , obtained by substituting _y = y _1. Also, as described in the first embodiment, Δx is a minute amount, and the difference between the value obtained by substituting x = x ₁ 1 + Δx and the value obtained by substituting x = x ₁ −Δx into the Sn equation is divided by 2 · Δx. Can be obtained. The same applies to an example in which a value other than 0 is designated as the value of the near horizontal prism and the value of α at that time.

3) Shape of the boundary area of the inner surface of the lens By setting the prism, the condition of ∂Sf / ∂x | Tx, Ty = ∂Sn / ∂x | Tx, Ty is maintained at the near top position (Tx, Ty). It is no longer being done.
However, the condition of ∂Sf / ∂y | Tx, Ty = ∂Sn / ∂y | Tx, Ty is maintained.
There is no step on the inner surface of the lens at the near top position, and the vertical connection is smooth, but “twist” is generated in the horizontal direction, and the position slightly separated from x = Tx on the boundary line There is a step. In Example 1, the step occurred as a quadratic function of x as x moved away from Tx. The second embodiment is different in that the step is generated as a linear function of x. Still, following the process of Example 1, “4) Shape of boundary region of lens inner surface”, this step is eliminated, and there is no step and bending at the upper and lower ends of the boundary region and everywhere in the boundary region. A smooth shape can be obtained.

Example 4
FIG. 9 is a front view for explaining the layout of the spectacle lens 4 of the bifocal lens that is Embodiment 4 of the present invention. The spectacle lens 4 is also in a state of a circular outer shape called a so-called round lens before the frame insertion processing similar to the spectacle lens 1 of the first embodiment. An example of specific data of the eyeglass lens 4 of Example 4 is as follows. Data common to the eyeglass lens 1 of Example 1 is omitted. The processing method is the same as that in the first embodiment.
In the fourth embodiment, a prism is set only in the near-use area as in the case of the third embodiment. In the boundary region of Example 4, the expressions of the upper end curve and the lower end curve of Example 2 were applied to the nose side, and the expressions of the upper end curve and the lower end curve of Example 3-1 (3-2) were applied to the ear side.
・ Distance power S-0.00D C-0.00D AX180
・ Nearly used power S + 1.00D C + 0.00D AX180 Prism Inn 3.00PD
・ Addition 1.00D
・ When the upper curve formula x ≧ 1.5,
y = -2-0.0015 (x-1.5) ³
When x <1.5,
y = -2 + 0.0012 (x-1.5) ³
・ When the lower end curve formula x ≧ 1.5,
y = −4−0.0022 (x−1.5) ³
When x <1.5,
y = -4 + 0.0026 (x-1.5) ³

  The spectacle lens 4 of Example 4 has the same effect as that of Example 3-2. Furthermore, since the lens thickness is reduced on the ear side by prescribing the base in prism, the nose side is designed in the same manner as in Example 2, and only the ear side is designed to increase the width of the boundary region. A distance area and a near area on the nose side can be secured.

(Example 5)
FIG. 10 is a front view for explaining the layout of the spectacle lens 5 of the bifocal lens that is Embodiment 5 of the present invention. The spectacle lens 5 is also in a state of a circular outer shape called a so-called round lens before the frame insertion processing similar to the spectacle lens 1 of the first embodiment. The fifth embodiment is an example in which the astigmatic power or the astigmatic axis is different for distance and near vision.
In the same manner as in Example 1, it was designed by a standard method. As for the astigmatism power and the astigmatism axis of the distance power, the sag is set by the formula 1 and the formula 2 as in the first embodiment. In the fourth embodiment, Cxn, Cyn, and θn are set independently of the distance for the astigmatism power and the axis for the near vision in the formula representing the Snp of the formula 4 in the formula for determining the near vision area of the formula 3. Therefore, the near area has an astigmatism power and an axis different from the distance area.
The values of Pxn and Pyn are the same as those of Px and Py when not considering the perspective-independent prism designation. However, when adjusting the near prism, the near prism is set by changing the values of Pxn and Pyn. The horizontal prism and the vertical prism at the point (x1, y1) can be set to arbitrary values. Smoothing the shape of the boundary region is the same as in the first to fifth embodiments. An example of specific data of the eyeglass lens 5 of Example 5 is as follows.

<Specific lens values>
An example of specific data of the spectacle lens of Example 4 is as follows.
Distance power S-4.00D C-1.00D AX180
Near-use frequency S-2.00D C-2.00D AX 45
Addition 1.50D (Difference in average frequency between distance and near distance)
Center thickness CT = 1.5 (mm)
Base material refractive index n = 1.600 Table curve 2.00 curve (base material refractive index conversion)
Curvature of outer surface Co = 2 / (1000 · (n−1)) = 0.00333 (mm−1)
Distance of rotation for distance θ = 0 (rad)
Near rotation angle θn = −45 / 180 · π = −0.7854 (rad)
Main curvature for inner surface distance Cx = (2-(− 4)) / (1000 · (n−1)) = 0.01000 (mm−1)
Cy = (2-(− 5)) / (1000 · (n−1)) = 0.01167 (mm−1)
Main curvature for inner surface Cxn = (2-(− 2)) / (1000 · (n−1)) = 0.00667 (mm−1)
Cyn = (2-(− 4)) / (1000 · (n−1)) = 0.01000 (mm−1)
For right eye, the nose side of the x axis is positive Tx = 1.5 (mm), Ty = -3.0 (mm)
Formula of upper curve y = -2-0.0001 (x-1.5) ⁴
Lower end curve formula y = −4−0.0002 (x−1.5) ⁴

Even in the spectacle lens 5 of Example 5, the band-shaped boundary region has no step in the boundary region, and is connected to the upper region and the lower region at the upper and lower ends without a step. In the fifth embodiment, the boundary region is a region close to the fitting point, that is, a first region extending in a substantially horizontal lateral direction of about 10 mm on the left and right sides of the fitting point below the fitting point (strictly speaking, the first region is And a second region extending downward from the left and right positions of the first region. The first region and the second region are not clearly separated. The boundary region has a narrow vertical width near the center of the first region, and gradually widens in the horizontal direction from the center toward the left and right, respectively. It is wide. However, in Example 5, since the addition power is weak and there is no prism in the near-use area, the ratio of increasing the width is set small. Since the curve is steep compared to Examples 2-4, the design is inferior to Examples 2-4. In the fifth embodiment, the ratio of the widest portion to the narrowest portion in the boundary region in the frame shape (lens shape) is set to about 1.3 to 1.5 times.
As shown in FIG. 10, when a boxing frame BF that is in contact with the frame shape (lens shape) is set, the boundary line that is the center position of the boundary passes over the lower side of the boxing frame BF. In Example 5, the upper end curve also passes over the lower side of the boxing frame BF.

  Also in the eyeglass lens 5 of Example 5, the boundary area extends downward from the second area, and the distance area is set wide while the near area is maintained, so that the distance area is secured. Easy to grasp the entire distance vision. Further, since the distance area is large when the face is moved to the left or right, the distortion can be reduced or the “smoothness” of the scenery when the line of sight is moved can be reduced.

(Example 6)
FIG. 11 is a front view for explaining the layout of the spectacle lens 6 of the bifocal lens that is Embodiment 6 of the present invention. The spectacle lens 6 is also in a state of a circular outer shape called a so-called round lens before the frame insertion processing similar to the spectacle lens 1 of the first embodiment. An example of specific data of the eyeglass lens 3 of Example 6 is as follows. Data common to the eyeglass lens 1 of Example 1 is omitted. The processing method is the same as that in the first embodiment. In Example 3-1, the addition is large, and a prism is set in the near-use area.
・ Distance power S-0.00D C-0.00D AX180
・ Nearly used power S + 3.00D C + 0.00D AX180 Prism Inn 3.00PD
・ Degree of addition 3.00D
・ When the formula of the upper curve x <-14.5
y = -2-0.0015 · 16 ³ + 0.0015 · 3 · 16 ² · (x + 14.5)
When -14.5 ≦ x <17.5,
y = −2−0.0015 · ABS ((x−1.5) ³ )
When 17.5 ≦ x,
y = −2−0.0015 · 16 ³ −0.0015 · 3 · 16 ² · (x-17.5)
・ Lower curve formula
y = −4−0.0023 · ABS ((x−1.5) ³ )

In Example 6, the formulas of the upper curve for defining the boundary region are a plurality of (here, three) equations connected in three different regions in the x direction. Specifically, the equation of Example 5 is modified so that when x <-14.5, a linear equation in contact with the cubic equation at the point of x = -14.5. The inclination at the connection point is obtained by differentiating the cubic expression before deformation and substituting x = -14.5. In the case of −14.5 ≦ x <17.5, the equation of the upper end curve of Example 5 was used, and in the case of x <17.5, the linear equation in contact with the cubic equation at the point of x = 17.5. The inclination at the connection point is obtained by differentiating the cubic expression before deformation and substituting x = 7.5. The position of the connection point can be changed as appropriate, and the width of the boundary region can be changed by changing the position.
Also in the spectacle lens 6 of Example 6, the belt-like boundary region has no step in the boundary region, and is connected to the upper region and the lower region at the upper and lower ends without a step. In the sixth embodiment, the boundary area is an area close to the fitting point, that is, a first area extending in a substantially horizontal lateral direction of about 10 mm on each of the left and right sides of the fitting point below the fitting point (strictly speaking, the first area is And a second region extending downward from the left and right positions of the first region. The first region and the second region are not clearly separated. The boundary region has a narrow vertical width near the center of the first region, and gradually widens in the horizontal direction from the center toward the left and right, respectively. It is wide. Since the addition is strong and there is also a prism in the near-use area, the width is the same as that of the second embodiment in the vicinity of the first area, but the ratio of the width becoming wider as the distance from the area increases. In Example 3-1, the ratio of the widest portion to the narrowest portion in the boundary region in the frame shape (lens shape) is set to about 2.0 to 2.5 times.
As shown in FIG. 11, when a boxing frame BF that is in contact with the frame shape (lens shape) is set, the boundary line that is the center position of the boundary passes on the lower side of the boxing frame BF.
In the spectacle lens 6 of Example 6, the distance area is set wide while the near area is maintained, so the distance area is large when the face is moved to the left and right, so the distortion is reduced and the line of sight is moved. In the same way as the second embodiment, it is possible to reduce the “smoothness” of the scenery when it is applied, but unlike the spectacle lens 2 of the second embodiment, since the addition is large and there is also a prism in the work area, Since the step at the boundary between the upper region and the lower region is larger in the stage before the deformation, if the width of the boundary region is made wider as the distance from the fitting point increases, the curvature change in the boundary region can be suppressed, and distortion fluctuations can be suppressed. Can be prevented from becoming extremely large.

The above embodiments are merely described as specific embodiments for illustrating the principle of the present invention and the concept thereof. That is, the present invention is not limited to the above embodiment. The present invention can also be embodied in the following modified form, for example.
-The top and bottom width of the near-use top is constant, and the ratio of widening the top and bottom width is increased as the strength is added. In other words, when the power of the near-use area is large (additional power) with respect to the upper area, it is preferable to design so that the vertical width is wider than when the frequency is small. For example, about 0.25-0.5D is assumed as a weak addition, and about 3.5-4.0D can be assumed as a strong addition. In a lens with a higher addition power, the step difference between the upper region and the lower region is larger in the stage before the boundary region is deformed. Therefore, if the vertical width of the region to be deformed is made wider, the curvature change in the boundary region is suppressed. And distortion distortion can be prevented from becoming extremely large. And by doing so, even if the addition becomes strong, the distortion in the boundary region is suppressed, and the boundary becomes inconspicuous when viewed from others. In addition, there is no difficulty in machining with an NC machining apparatus.
-The form of the support | pillar member 1 for rooting of the said embodiment is an example, Comprising: It is also free to implement in another aspect. For example:
-For example, in the addition as in Example 3-1, the shape of the boundary region as in the spectacle lens 3 as described above is used as an example. However, the addition is larger than that in Example 3-1. If there is, the ratio of the width of the boundary region gradually becoming wider than the lens 3 of Example 3-1 may be designed to be larger.
For example, in the case where the horizontal prism is set as in Example 3-2 or Example 6 above, the shape of the boundary region such as the spectacle lens 3 or the spectacle lens 6 as described above is an example. If the difference between the prisms set in the upper region and the lower region is larger than that in the above example, the rate of gradually increasing the width of the boundary region may be designed to be large.
In the above description, the case where the horizontal prism is set is illustrated and described. However, if the difference between the prisms set in the upper region and the lower region is large, the rate of gradually increasing the width of the boundary region is increased. The same applies to the case of adjusting the vertical prism.
In the above embodiment, the spherical lens is taken as an example. However, the inner surface or the outer surface of a certain region (meaning at least one region) may include an aspherical component. That is, an aspheric lens may be used. In that case, a term representing the sag of the aspherical component is added to the above equations 1, 2, and 4.
The upper area is not limited to the power for distance vision. For example, the indoor middle lens that covers the lower area of about 40 cm with the upper area of about 2 m, or the lower area of about 30 cm with the upper area of about 50 cm It may be a lens soon.
The viewing distance of either the upper region or the lower region or both may be included in the lens order information.
In Example 3-2 above, the setting is such that a horizontal prism is generated at the near center, but if this causes a sense of incongruity, it may be adjusted appropriately, for example, by halving the adjustment amount.

1-6 Eyeglass lenses that are bifocal lenses.

Claims (11)

A bifocal lens in which the upper region and the lower region for viewing a short distance relative to the upper region are set at different lens powers at positions that are in the vertical direction when wearing glasses,
A band-shaped boundary region is provided between the upper region and the lower region,
The bifocal lens is characterized in that the boundary region has no step in the boundary region, prisms in all directions continue, and the upper and lower ends are connected to the upper region and the lower region without a step.   A boundary line formed between the upper region and the lower region and the boundary region is set below a fitting point, and the boundary region is a first region extending in a lateral direction in a region near the fitting point. 2. The bifocal lens according to claim 1, further comprising a region and a second region extending downward from a left and right position of the first region.   In the state of the circular precursor before the bifocal lens is processed into a target lens shape, the edge position point of the precursor reached by the end of the boundary region is directly below the fitting point around the geometric center of the precursor. 3. The bifocal lens according to claim 1, wherein the bifocal lens is in a range of 225 to 315 degrees.   When the biaxial lens is worn, the horizontal direction is the x-axis direction, and the vertical direction intersecting the x-axis direction is the y-axis direction. The x-axis direction and the y-axis direction surrounding the lens shape of the lens are parallel to each other. The bifocal lens according to claim 1, wherein a virtual rectangle is assumed and a point where the boundary region reaches the boundary of the rectangle is on a lower side of the rectangle.   When the biaxial lens is worn, the horizontal direction is the x-axis direction, and the vertical direction intersecting the x-axis direction is the y-axis direction. The x-axis direction and the y-axis direction surrounding the lens shape of the lens are parallel to each other. The bifocal lens according to claim 2, wherein a virtual rectangle is assumed and a point where the boundary line reaches the boundary of the rectangle is on a lower side of the rectangle.   6. The bike according to claim 1, wherein the boundary region has the narrowest width at the uppermost position, and the boundary region gradually increases in width from the center toward the left and right. Focal lens.   7. The bifocal lens according to any one of claims 1 to 6, wherein the bifocal lens is designed so that the boundary region is rapidly widened at a portion near the outside of the lens in a state of being processed into a target lens shape. The manufacturing method of the bifocal lens as described in any one of.   7. The bifocal lens according to claim 6, wherein the boundary region is designed such that the larger the addition is, the larger the proportion of the boundary region that gradually becomes wider as the distance from the fitting point increases. The manufacturing method of the bifocal lens characterized by these.   7. The bifocal lens according to claim 6, wherein prisms are independently set in the upper region and the lower region, and the more prescription the difference between the prisms set in the upper region and the lower region is, the more fitting is possible. A method of manufacturing a bifocal lens, wherein the ratio of the width of the boundary region gradually increasing with increasing distance from the point is designed to be large.   The method for manufacturing a bifocal lens according to claim 9, wherein the ratio of the width of the boundary region to be widened is different between the ear side and the nose side. The bifocal lens manufactured by the manufacturing method according to any one of claims 7 to 10, wherein astigmatism power is set independently in each of the upper region and the lower region, and astigmatism power in the upper region and the lower region, and A bifocal lens characterized in that at least one of the astigmatic axes is not the same.