JP2005242346A - Method for designing spectacle lens and spectacle lens - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a designing method for a spectacle lens that can make an edge of the spectacle lens having minus refracting power thick while sufficiently securing a center part by properly determining a border between the center part and marginal part of an internal surface. <P>SOLUTION: The designing method for the lens includes a surface shape determination stage of determining the shapes of both the surfaces of the spectacle lens as prescribed, a light beam passing point detection stage of finding light beam passing points where a light beam crosses both the surfaces by tracing the light beam passing an eyeball convolution point, a border determination stage of determining a border demarcating the internal surface into the center part and marginal part based upon the light beam passing point obtained when a specified light beam is traced, and a marginal part shape determination stage of determining the shape of the marginal part so that the marginal part is smoothly connected to the center part having the internal surface shape determined at the surface shape determination stage while varying the shape of the marginal part to less than the edge thickness of the determined internal surface shape. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a spectacle lens, and more particularly to a refraction correction spectacle lens having a negative refractive power.

  The refractive correction spectacle lens having a negative refractive power has the smallest thickness in the vicinity of the design reference point, and the thickness gradually increases toward the periphery. For this reason, a negative lens having a large outer diameter has an extremely large edge thickness. Such a lens is required to be improved because it may be pointed out that it becomes heavier, looks bad, or narrows the selection range of the frame.

  In general, in a lens having a large outer diameter, the entire region is not used for refraction correction, and the peripheral edge where the edge thickness tends to be large is often not used for refraction correction. Conventionally, several spectacle lenses that make use of this point to reduce the edge thickness have been proposed. The spectacle lens is disclosed in, for example, the following Patent Documents 1 to 4.

JP 58-195826 A JP 2000-47144 A JP-A 61-167902 Japanese Patent Laid-Open No. 11-2785

  In each of the above Patent Documents 1 to 3, the lens inner surface (eye-side surface when worn) is a fixed region (hereinafter referred to as the central portion in the text) near the design reference point that needs to maintain a predetermined vertex refractive power and aberration. And a region that is around the central portion and does not need to maintain a predetermined vertex power and aberration, in other words, is not used for refractive correction (hereinafter referred to as a peripheral portion in the text). Then, the edge thickness is reduced while securing a certain degree of outer diameter by changing the curve at the peripheral part in a direction in which the edge thickness becomes thinner than the extension of the central part. Here, the boundary between the central portion and the peripheral portion is made inconspicuous by smoothly connecting the central portion and the peripheral portion.

  However, each of the above documents 1 to 3 does not disclose a method for appropriately setting the boundary between the central portion and the peripheral portion. For example, Patent Document 1 does not describe at all how to determine the boundary between the central portion and the peripheral portion.

  Further, Patent Document 2 merely describes that the optically effective portion in the central portion has a diameter of 30 mm or more, and does not disclose any upper limit value in the central portion. Further, in Patent Document 2, the boundary between the central portion and the peripheral portion is determined without considering the prescription frequency of the spectacle lens. Therefore, in the configuration of Patent Document 2, in the weak minus lens, a portion that should be included in the effective visual field (that is, a portion that should originally belong to the central portion) is included in the peripheral portion, and the peripheral visual field is unnecessarily narrowed. There is a risk that. In addition, in a minus lens with high intensity, unnecessary portions that are not included in the effective field of view (that is, portions that should originally belong to the peripheral portion) are also included in the central portion, and the edge thickness may become unnecessarily thick. There is.

  Patent Document 3 discloses a spectacle lens having a boundary between a central portion and a peripheral portion at least (0.2 × Abbe number) prism diopter, preferably (0.3 × Abbe number) prism diopter. It is disclosed. However, if the boundary is unambiguously determined based on such a criterion, there is a possibility that the peripheral field includes a portion that should be included in the effective field of view and the peripheral field of view is narrowed as in the spectacle lens of Patent Document 2. is there.

  Further, Patent Document 4 discloses a spectacle lens in which the curvature of the peripheral portion where the light beam on the inner surface does not pass is reduced by using a deep base curve in order to improve the wearing feeling of the minus lens. However, Patent Document 4 does not describe how to determine whether or not a light beam passes.

  Each of the above Patent Documents 1 to 4 relates to a single-focus spectacle lens, and appropriately determines the boundary between the central portion and the peripheral portion in a progressive-power lens in which the refractive power continuously changes depending on the location. No method is disclosed. The following non-patent document 1 is exemplified as a configuration in which the peripheral thickness of the progressive power lens is reduced.

Tokai Optical Co., Ltd., “Product Lineup (Internal Progressive Power Lens)”, [online], [Search April 7, 2003], Internet <URL: http://www.tokaiopt.com/lens/product1a4. html>

  According to Non-Patent Document 1, an explanatory diagram called “fine edge processing” is disclosed in which an optically effective area is determined by a straight line passing through the edge of the front surface of the lens, and the edge thickness is made thinner than the area to reduce the edge thickness. Yes. However, it is not shown which point the straight line passes through with the edge of the front surface of the lens. The straight line is drawn ignoring the refraction phenomenon caused by the lens inner surface. That is, it is difficult to say that the explanatory diagram of Non-Patent Document 1 accurately determines the optically effective area.

  In view of the above-described problems of the prior art, the present invention provides a boundary between a central portion used for refractive correction and a peripheral portion not used in a refractive power spectacle lens having a negative refractive power, particularly a progressive power lens. An object of the present invention is to provide a spectacle lens design method capable of reducing the edge thickness of the lens while appropriately determining and securing a central portion as necessary and sufficient, and a spectacle lens designed by the design method To do.

  In order to solve the above-described problems, the spectacle lens design method according to the present invention determines the shape of the outer surface (the object-side surface when worn) and the inner surface of a spectacle lens having negative correction refractive power based on prescription. A ray that crosses the inner surface and the outer surface by tracing a ray that passes through an assumed eyeball rotation point with respect to the spectacle lens whose shape is determined by the surface shape determination step and the surface shape determination step. Refraction for correcting the inner surface with reference to the ray passing point obtained when tracing a predetermined ray among the ray passing points obtained by the ray passing point detecting step for obtaining the passing point and the ray passing point detecting step. Boundary determination stage for determining the boundary to be divided into a central part having force and a peripheral part having no refractive power for correction, and a direction in which it becomes thinner than the edge thickness in the inner surface shape determined in the surface shape determination stage While changing the shape of the peripheral portion, and a peripheral portion shape determination step of determining the shape of the peripheral portion so that the peripheral portion is smoothly connected to the central unit with the determined inner shape.

According to the above design method, since the boundary between the central portion and the peripheral portion can be determined based on the position through which the light passes, an appropriate boundary can be set according to the frequency, and the central portion is carelessly narrowed. It is possible to reduce the edge thickness without doing so.

  In the light beam passing point detection step, a light beam incident on the outer surface from the lens medium side at a critical angle can be a predetermined light beam. In this case, in the boundary determination stage, a position where a light ray incident at a critical angle from the lens medium side to the outer surface passes through the inner surface is defined as a boundary. Since light rays incident on the outer surface at an angle larger than the critical angle are totally reflected, even if the central portion is extended to the outside of the position of the light rays incident at the critical angle, the substantial visual field does not expand. Therefore, by using the passage position as a boundary, the edge thickness can be reduced without narrowing the field of view.

  Further, in the light ray passing point detecting step, the light ray passing through the edge of the outer surface may be a predetermined light ray. In this case, in the boundary determination stage, the position where the light beam passing through the edge of the outer surface passes through the inner surface is defined as the boundary. Since the light ray passing through the outer edge hits the lens edge (periphery), it is diffusely reflected. Therefore, even if the central portion is extended outward from the position of the light ray passing through the outer edge, the substantial field of view does not widen. Therefore, by using the passage position as a boundary, the edge thickness can be reduced without narrowing the field of view.

  Which of the light beam incident on the outer surface from the lens medium side at a critical angle and the light passing through the edge of the outer surface is determined as a predetermined light beam is determined according to the refractive power, the diameter, etc. of the lens. For example, since the diameter is as large as 65 to 70 mm at the stage of the lens blank before edging, it is desirable to determine the boundary according to the critical angle condition. After the edging process, it is highly likely that the boundary is not determined under the critical angle condition for the lens at the time of frame insertion. Therefore, it is desirable to determine the boundary based on the condition of the light beam passing through the edge of the outer surface. If both directions can be mixed depending on the orientation, both the critical angle condition and the condition of the light ray passing through the edge are obtained, and the smaller boundary may be adopted.

  When the inner surface of the spectacle lens having negative refractive power is an aspherical surface or a progressive surface (Claim 4), a phenomenon that the lens thickness increases geometrically toward the peripheral portion tends to appear. Therefore, the reduction of the edge thickness by dividing the central portion and the peripheral portion as described above is more effective in the aspherical spectacle lens.

  Further, according to the spectacle lens designing method of the fifth aspect, it is preferable to design the outer surface to be a spherical surface. As a result, the outer surface is formed by molding in advance, and the central portion and the peripheral portion of the inner surface can be easily processed through a series of processes in accordance with the contents of the order, for example, the frequency of prescription.

  The peripheral portion may be a surface whose edge thickness is smaller than the surface obtained by extending the central portion, but it is desirable that the boundary with the central portion is not conspicuous. Therefore, a straight line passing through the design reference point and perpendicular to the inner surface is defined as the z-axis, a straight line passing through the intersection of the inner surface and the z-axis and perpendicular to the z-axis is defined as the h-axis, and a plane including the z-axis and the h-axis When a curve that is an intersecting line is expressed by a function z = f (h), it is desirable that the first derivative f ′ (h) of the function f (h) is continuous at the boundary, and continues to the second derivative f ″ (h). In order to facilitate the polishing of the inner surface, the shape of the peripheral portion represented by the function f (h) is represented as a function having no inflection point. (Claim 7) Further, in order to continue the boundary between the central portion and the peripheral portion up to the second derivative f ″ (h) and to prevent the shape of the peripheral portion from having an inflection point, It is desirable that the shape of the peripheral part represented by the function f (h) is a quadratic function.

  On the other hand, when emphasizing the reduction of the edge thickness rather than the ease of polishing, the target edge thickness is set while setting the target edge thickness and continuing the boundary between the central part and the peripheral part to the second derivative. It is also possible to determine the function f (h) as obtained (claim 9). When the function f (h) determined in this way is used, the function representing the peripheral part may have an inflection point, but the edge thickness can be reduced.

  The spectacle lens according to the present invention has a negative refractive power, and the inner surface is divided into a central portion having a correcting refractive power and a peripheral portion having no correcting refractive power. It is connected smoothly and designed by the method of determining the boundary between the central part and the peripheral part by ray tracing as described above (claim 10). This provides a spectacle lens with a thin edge thickness while ensuring a sufficient field of view.

  From another viewpoint, the spectacle lens according to the present invention has a negative correcting refractive power, and the inner surface is divided into a central part having a correcting refractive power and a peripheral part having no correcting refractive power, The peripheral portions are smoothly connected at the boundary satisfying a predetermined condition, and the distance from the design reference point to the boundary is an increasing function with respect to the refractive power (claim 11).

  In the eyeglass lens according to the present invention, the central portion of the inner surface can be formed as an aspherical surface or a progressive surface.

但し、Ｅ＝29.0Ｎ−265
Ｆ＝−2.57Ｎ＋7.59
Ｇ＝3.41Ｎ＋2.61
Ａ＝−0.585＋0.0433Ｎ＋0.0624Ｈ−0.0180ＮＨ
Ｂ＝14.3−8.16Ｎ＋0.289Ｈ＋0.392ＮＨである。 The eyeglass lens according to claim 12 or 13, wherein a straight line passing through the design reference point and perpendicular to the inner surface is the z axis, and a straight line passing through the intersection of the inner surface and the z axis is perpendicular to the z axis. The refractive index of the lens is N, the refractive power of the lens in the plane including the z-axis and the h-axis is D [Dioptre], the distance from the z-axis to the boundary between the central portion and the peripheral portion is h _k [mm], from the z-axis It is desirable to satisfy the following condition (1) or (2), where the distance to the outer surface edge of the lens is H [mm].

However, E = 29.0N-265
F = −2.57N + 7.59
G = 3.41N + 2.61
A = -0.585 + 0.0433N + 0.0624H-0.0180NH
B = 14.3-8.16N + 0.289H + 0.392NH.

  If the boundary is determined so as to satisfy the above condition (1), the same result as that obtained when the position where the light ray incident at the critical angle with respect to the outer surface intersects the inner surface is determined as the boundary can be obtained. On the other hand, when the boundary is determined so as to satisfy the condition (2), the same result as that obtained when the position where the light beam incident on the outer peripheral edge intersects the inner surface is determined as the boundary is obtained.

但し、ＳＰＨは球面屈折力を、
ＣＹＬは乱視屈折力を、
ＡＸは乱視軸方向を、
ＡＤＤは加入屈折力を、
θは屈折力Ｄを求めようとする断面と水平断面とのなす角を、それぞれ表す。 Further, the spectacle lens can be configured as a progressive power lens having an inner surface as a progressive surface. When the spectacle lens is a progressive power lens, the refractive power D can be approximated by the following expression (3) on a plane passing through the z-axis.

However, SPH is the spherical refractive power,
CYL is the power of astigmatism,
AX is the astigmatic axis direction,
ADD gives the addition power,
θ represents an angle formed between a cross section for which the refractive power D is to be obtained and a horizontal cross section.

  In addition, the spectacle lens series according to the present invention has a negative refractive power, and the inner surface is divided into a central portion having a correcting refractive power and a peripheral portion having no correcting refractive power. The distance from the design reference point to the boundary between the central portion and the peripheral portion is an increasing function with respect to at least one of refractive power and refractive index. It is characterized by that.

  As described above, according to the present invention, in a refractive correction spectacle lens having a negative refractive power, the boundary between the central part used for refractive correction and the peripheral part not used is appropriately determined, and the central part is necessary. The lens edge thickness can be reduced while sufficiently securing. Further, the design method according to the present invention can be suitably used not only for a single focus lens but also for a progressive power lens.

  Hereinafter, four embodiments of the spectacle lens design method according to the present invention will be described. The first embodiment assumes a light ray incident at a critical angle from the lens medium side to the outer surface. And it is the design method which determines the boundary of a center part and a peripheral part by calculating | requiring the position (light ray passing point) where this light ray and an inner surface cross | intersect. The second embodiment is a design method in which the boundary is determined by obtaining a light beam passing point with the inner surface with respect to a light beam incident on the peripheral edge of the outer surface. In the third embodiment and the fourth embodiment, the first and second conditions are obtained by using a conditional expression regarding the boundary statistically obtained by using the design method of the first and second embodiments, respectively. This is a design method for determining a boundary without ray tracing as in the embodiment.

(First embodiment)
FIG. 1 is a flowchart showing a design method according to a first embodiment of the present invention. In the present embodiment, a design method of a single-focus spectacle lens whose outer surface is spherical and whose inner surface is aspherical is shown. The design method of the first embodiment will be described below based on the flowchart of FIG.

In S1, the aspherical shape of the inner surface is optimized by a known method. In S1, optimization is performed so that the entire inner surface is represented by one function without dividing the inner surface into a central portion and a peripheral portion. As an aspheric function, for example, the following equation (4) is adopted. First, the curvature C ₁ , the center thickness T, and the refractive index N of the outer surface are given. Then, the paraxial curvature C ₂ of the inner surface is obtained so that the refractive power corresponding to the prescription can be obtained, and the surface shape parameters are optimized using an algorithm such as an attenuation least square method so that the aberration is minimized. In the case of a progressive power lens, a two-dimensional polynomial or a two-dimensional spline function can be used as a formula representing the surface shape.

In Equation (4), z is a sag amount (from a tangential plane perpendicular to the reference axis) of a point on the aspheric surface whose distance from a straight line passing through the design reference point and orthogonal to the inner surface (hereinafter referred to as the reference axis) is h. (Distance in the reference axis direction), κ is a conic coefficient, and A _2i (i = 2 to j) is an even-order aspheric coefficient of the fourth order or higher.

Next, the boundary which divides | segments an inner surface into a center part and a peripheral part is calculated | required in S3-17, S21, and S23. In the present embodiment, a light ray that is emitted from the eyeball turning point and is incident on the inner surface at a distance h ₂ from the reference axis is tracked. Then, while the distance h ₂ is changed as appropriate, light rays incident at the critical angle with respect to the outer surface (hereinafter, referred to as a reference beam in the body) seek. Note that the position (distance h ₂ ) where the reference light beam enters the inner surface is _defined as the boundary position h _k .

First, in S3, provide a distance h ₂ a predetermined initial value. The initial value must be a value corresponding to a position where the light beam always passes through the lens, that is, a position where the incident angle with respect to the outer surface is surely equal to or smaller than the critical angle. For example, h ₂ = 0. In S5, the sag amount z ₂ at the position of the distance h ₂ from the reference axis on the inner surface is obtained by the above equation (4).

In S7, the eyeball rotation point position is set to a position 25 mm behind the inner surface vertex of the lens, and a light beam directed from the eyeball rotation point to the position (h ₂ , z ₂ ) on the inner surface is assumed. In the following text, the position (h ₂ , z ₂ ) on the inner surface is referred to as a ray passing point on the inner surface. Next, in S9 to S13, ray tracing regarding the ray assumed in S7 is performed.

First, in S9, a direction vector when the light ray enters the lens medium while being refracted on the inner surface is obtained. In S11, a position (h ₁ , z ₁ ) where a light beam traveling in the lens medium is incident on the outer surface is obtained. In the following text, the position (h ₁ , z ₁ ) incident on the outer surface is referred to as a ray passing point on the outer surface. In S13, the incident angle θ from the inner surface side to the outer surface of the light beam is obtained based on the normal vector of the outer surface and the direction vector of the light beam at the obtained light ray passing point (h ₁ , z ₁ ).

In S15, the critical angle θc determined by the refractive index of the medium is compared with the incident angle θ. The critical angle θc is expressed by the following equation (5),
θc = sin ^-1 (1 / N) (5)
Is calculated by Then, it is determined whether or not the difference | θ−θc | is within a predetermined allowable error ε (for example, about 0.1 °). If it is within the range (| θ−θc | ≦ ε), it is determined that the ray incident on the ray passing point (h ₂ , z ₂ ) on the inner surface is the reference ray, and the distance h _{2 is set} to the inner surface in S17. It is assumed that the boundary position h _k between the central part and the peripheral part. In S19, a function representing the shape of the peripheral portion is obtained, and the design process is terminated.

In the comparison of S15, when the difference between the incident angle θ and the critical angle θc does not fall within the allowable error ε, it is determined that the light beam assumed in the immediately preceding S7 is not the reference light beam. Then, the distance h ₂ is changed (S21, S23), and the processes from S5 are repeated.

Here, the incident angle θ increases as the incident position of the light beam on the inner surface becomes farther from the reference axis. Therefore, if it is determined in S15 that θ−θc <−ε, that is, if it is determined that the incident angle θ is smaller than the critical angle θc, the distance h ₂ from the reference axis of the incident position is set to a predetermined value in S21. Increase by a small amount Δh ₂ (expand the center) and repeat the process from S5. On the other hand, if it is determined in S15 that θ−θc> ε, that is, if it is determined that the incident angle θ is larger than the critical angle θc, the distance h ₂ from the reference axis of the incident position is set to a predetermined minute value in S23. Decrease by a small amount Δh ₂ (narrow the center) and repeat the process from S5.

Note that the minute amount Δh ₂ is set to a predetermined minute constant (for example, about 0.1 mm). However, the minute amount Δh ₂ may be determined as the following formula (6) based on the rate of change of θ with respect to the distance h ₂ .
Δh ₂ = − (θ−θc) / (δθ / δh ₂ ) (6)

  When determining a function representing the shape of the peripheral portion in S19, a function representing the aspherical shape of the central portion and a function representing the surface shape of the peripheral portion so that the boundary between the central portion and the peripheral portion is not conspicuous. The peripheral function is determined so that is smoothly connected at the boundary.

For example, if the function f (h) representing the aspherical shape is f _i (h) inside the boundary (h ≦ h _k ) and f _o (h) outside the boundary (h> h _k ), the boundary is In order to be smooth so that it does not appear, it is necessary not only to make both function values equal at the boundary, but also to make the first and second derivatives of both functions equal. That is, the following equations:
f _i (h _k ) = f _o (h _k )
f _i ′ (h _k ) = f _o ′ (h _k )
f _i ″ (h _k ) = f _o ″ (h _k )
The function f _o (h) at the peripheral portion is determined so as to satisfy Furthermore, the lens edge thickness target value, in other words, the function value target z _H at the lens edge H (ie, hmax) is given,
f _o (H) = z _H
The function f _o (h) at the peripheral portion is determined so that the following condition is also satisfied.

  In S19, if there is an inflection point in the peripheral portion, unevenness of the contact of the polishing pad with the inner surface tends to occur in the subsequent polishing process, particularly the inner surface polishing process. Therefore, in order to simplify the polishing process of the inner surface, the function representing the peripheral portion is determined as a function having no inflection point, for example, a quadratic function.

(Second Embodiment)
FIG. 2 is a flowchart showing a design method according to the second embodiment of the present invention. This example also mainly shows a design method for a single-focus spectacle lens whose outer surface is spherical and whose inner surface is aspherical. The second embodiment will be described below based on FIG.

S31 performs the same process as S1 of 1st Embodiment, and optimizes the shape of an inner surface. Next, in S33 to 45, S49, and S51, the boundary between the central portion and the peripheral portion on the inner surface is obtained. In the second embodiment, to track the light beam incident at a distance h ₂ from the reference axis on the inner surface originating from eyeball rotation point, while the distance h ₂ is changed, the light rays passing through the edge of the outer surface (second In this embodiment, a reference ray) is obtained, and a position (distance h ₂ ) at which a ray passing through this edge enters the inner surface is defined as a boundary position (more precisely, a distance from the reference axis to the boundary 3) h _k .

Each process performed in S33 to S41 is the same as S3 to S11 of the first embodiment. That is, a light ray incident from the eyeball rotation point to a position at a distance h ₂ from the inner reference axis is traced, and a light ray passing point (h ₁ , z ₁ ) on the outer surface of the light ray is obtained. In S43, the distance h ₁ from the reference axis of the incident position of the light ray on the outer surface is compared with the distance H from the design reference point to the edge. Then, it is determined whether or not the difference | h ₁ −H | between the two is within a predetermined allowable error φ (for example, about 0.1 mm).

In comparison S43, the difference between the distance h ₁ and the distance H is when entering the range of the allowable error φ is light assumed in S37 in just before it is determined that not the reference ray. Then, the distance h ₂ is changed (S49, S51), and the processing from S35 is repeated.

Here, the distance h ₁ of the incident position with respect to the outer surface increases as the incident position of the light beam on the inner surface becomes farther from the reference axis. Therefore, if it is determined in S43 that h ₁ −H <−φ, that is, if it is determined that the incident position on the outer surface is inside the edge of the lens, the distance h from the reference axis of the incident position in S49. ₂ is increased by a predetermined minute amount Δh ₂ (the central portion is expanded), and the processing from S35 is repeated. On the other hand, if it is determined in S43 that h ₁ −H> φ, that is, if it is determined that the incident position on the outer surface is outside the edge of the lens, the distance h ₂ from the reference axis of the incident position in S51. Is reduced by a predetermined minute amount Δh ₂ (the center portion is narrowed), and the processing from S35 is repeated.

Note that the predetermined minute amount Δh ₂ in the second embodiment is also determined in the same manner as in the first embodiment.

In S43, if the difference | h ₁ −H | is within the range (| h ₁ −H | ≦ φ), the light beam incident on the light beam passing point (h ₂ , z ₂ ) on the inner surface is the reference light beam. Judge that there is. Then, after the distance h ₂ to the boundary position h _k between the central portion and the peripheral portion of the inner surface in S45, it obtains a function representing the shape of the peripheral portion in S47, and ends the design process. Since the processes performed in S45 and S47 are the same as S17 and S19 in the first embodiment, description thereof is omitted here.

  The design method of the second embodiment is effective when all the light beams emitted from the eyeball rotation point enter the outer surface at a critical angle or less, that is, when the refractive power of the lens is relatively weak or the outer diameter is relatively small. It is.

(Third embodiment)
In the first and second embodiments described above, the boundary between the central portion and the peripheral portion is determined for each lens by actually performing ray tracing. On the other hand, in the third and fourth embodiments, the boundary is determined based on a mathematically obtained mathematical expression. In the third and fourth embodiments, first, a basic description will be given with a single-focus spectacle lens as a design object, and then the application of each embodiment to a progressive power lens will be described.

但し、
Ｅ＝29.0Ｎ−265
Ｆ＝−2.57Ｎ＋7.59
Ｇ＝3.41Ｎ＋2.61
である。 In the design method of the third embodiment, the reference axis is the z axis, the straight line passing through the intersection of the inner surface and the z axis and orthogonal to the z axis is the h axis, the refractive index of the lens is N, and the plane includes the z axis and the h axis. In the lens, the refractive power of the lens is D [Dioptre], and the distance from the z-axis to the boundary between the central portion and the peripheral portion is h _k [mm], so that the central portion and the peripheral portion satisfy the following condition (1) Determine the boundaries.

However,
E = 29.0N-265
F = −2.57N + 7.59
G = 3.41N + 2.61
It is.

The inventor of the present invention has a boundary position h determined by light rays (reference light rays in the first embodiment) that are emitted from the eyeball rotation point and incident on the outer surface with a critical angle for single-focus spectacle lenses having various different vertex powers D. _k was examined. FIG. 3 is a graph showing the relationship between the vertex refractive power and the boundary position h _k when the refractive index of the lens material is 1.5. FIG. 4 is a graph showing the relationship between the vertex refractive power and the boundary position h _k when the refractive index of the lens material is 1.8. CASE1 to CASE4 shown in FIGS. 3 and 4 are examples in which the base curve and the center thickness are set as shown in Table 1 below.

From the results shown in FIGS. 3 and 4, it was found that the boundary position h _k determined by the reference ray can be approximated as the following formula (7).
h _k ≈ E / (D−F) + G (7)
The above condition (1) is obtained by adding the plus and minus tolerances to the right side of the equation (7). When the boundary is determined so as to satisfy the condition (1), the boundary can be determined almost equal to the case where the boundary is determined by the light ray incident at the critical angle with respect to the outer surface without actually tracing the light ray.

When this embodiment is applied to a progressive-power lens, the approximate cross-sectional refractive power D calculated by the following equation (3) is used as an alternative to the vertex refractive power D in the single focus lens, and the above result is obtained. Substantially identical results can be obtained.

但し、
Ａ＝−0.585＋0.0433Ｎ＋0.0624Ｈ−0.0180ＮＨ
Ｂ＝14.3−8.16Ｎ＋0.289Ｈ＋0.392ＮＨ
である。 (Fourth embodiment)
In the design method of the fourth embodiment, the refractive index of the lens is N, the distance from the z-axis to the outer edge of the lens is H [mm], and the central portion and the peripheral portion satisfy the following condition (2): Determine the boundaries.

However,
A = -0.585 + 0.0433N + 0.0624H-0.0180NH
B = 14.3-8.16N + 0.289H + 0.392NH
It is.

The inventor determines the boundary position h _k determined by a ray (a reference ray in the second embodiment) that originates from the eyeball rotation point and passes through the edge of the outer surface for a single-focus spectacle lens having various different vertex powers D. investigated. FIG. 5 is a graph showing the relationship between the vertex refractive power and the boundary position h _k when the refractive index of the lens material is 1.5. FIG. 6 is a graph showing the relationship between the vertex refractive power and the boundary position h _k when the refractive index of the lens material is 1.8. In each figure, two types of lenses having a lens diameter of φ50 mm and φ70 mm are listed. Note that CASE 1 to CASE 4 shown in FIGS. 5 and 6 are the same as those in the third embodiment, and a description thereof will be omitted.

From the results shown in FIGS. 5 and 6, it was found that the boundary position h _k determined by the reference ray can be approximated by the following equation (8).
h _k ≈AD + B (8)
The above condition (2) is obtained by adding the plus and minus tolerances to the right side of the equation (8). When the boundary is determined so as to satisfy the condition (2), the boundary can be determined almost equivalent to the case where the boundary is determined by the light ray passing through the edge of the outer surface without actually tracing the ray.

  When this embodiment is applied to a progressive-power lens, as in the third embodiment, the approximate cross-sectional refraction calculated by the above equation (3) is used as an alternative to the vertex refractive power D of the single focus lens. Use force D.

  Next, eight examples of single-focus spectacle lenses in which the boundary between the central portion and the peripheral portion is determined by the design method of each embodiment described above will be shown. In all of the single-focus spectacle lenses shown in Examples 1 to 8 below, the refractive index N of the lens medium is 1.67, the center thickness T is 1.0 mm, and the eyeball rotation point is 25 mm behind the inner vertex. Examples 1 to 7 target a circular lens blank before edge trimming, and the outer diameter thereof is φ70 mm. In Example 8, the design object is a lens matched to the frame shape after edge trimming.

  The eyeglass lens of Example 1 is designed by the design method of the first embodiment. FIG. 7 shows the eyeglass lens of Example 1, (A) is a sectional view of the lens, (B) is a graph showing the change of the first derivative dz / dh of the sag amount z with respect to the distance h from the reference axis, (C). Is a graph showing a change in cross-sectional refractive power Dm with respect to distance h. 7A to 7C, broken lines indicate shapes and numerical values when the aspheric shape defining the central portion is extrapolated to the lens periphery without dividing the central portion and the peripheral portion. A solid line indicates the shape and numerical value of the spectacle lens of Example 1 in which the central portion and the peripheral portion are designed in different shapes. The same applies to each figure shown below.

  As shown in FIG. 7A, the outer surface 1 is a spherical surface and the inner surface is a rotationally symmetric aspherical surface. The inner surface 2 is divided into a central portion 2a having a correcting refractive power and a peripheral portion 2b having no correcting refractive power. The central portion 2a and the peripheral portion 2b are smoothly connected at the boundary 3. The boundary 3 is defined as a position (a light ray passing point on the inner surface 2) where the reference light beam 4 that is emitted from the rotation point 5 of the eyeball 6 and enters the outer surface 1 with a critical angle intersects the inner surface. The z axis (reference axis) 8 passing through the design reference point 7 and perpendicular to the inner surface coincides with the optical axis of the spectacle lens in this example and Examples 2 to 8 described below. The h-axis is defined as a straight line passing through the intersection of the inner surface and the z-axis and orthogonal to the z-axis.

なお、断面屈折力Ｄmとは、一方の面（図７（Ｃ）においては内面２。以下の各図においても同様。）における屈折力である。これに対し、上述した条件（１）、（２）および式（３）に現れるレンズの屈折力（式（３）にあっては近似断面屈折力）Ｄは、外面１と内面２の双方の屈折力が合わさったものである。従って、両者は異なる。 The cross-sectional refractive power Dm shown in FIG. 7C is calculated by the following equation (9).

The cross-sectional refractive power Dm is the refractive power on one surface (inner surface 2 in FIG. 7C, the same applies to the following drawings). On the other hand, the refractive power of the lens appearing in the above conditions (1), (2) and equation (3) (approximate cross-sectional refractive power in equation (3)) D is the value of both the outer surface 1 and the inner surface 2. It is a combination of refractive power. Therefore, they are different.

In the design stage, the aspherical shape of the inner surface is optimized based on the given prescription (S1). Here, it is assumed that the vertex power (SPH) -8.00 [D] and the outer surface 1 is a spherical surface having a surface power 2.00 [D]. The shape of the inner surface 2 obtained by the optimization is a rotationally symmetric aspherical surface expressed by the equation (4), and the cone coefficient and aspherical coefficient for defining the aspherical surface are shown in Table 2 below. The paraxial surface refractive power of the inner surface 2 is 10.00 [D].

  When the rotationally symmetric aspherical surface represented by Table 2 and Equation (4) is applied to the entire inner surface 2, the change in the sag amount z increases toward the periphery as shown by the broken line in FIG. Further, as shown by the broken line in FIG. 7C, the cross-sectional refractive power Dm increases rapidly. As a result, the edge thickness increases as shown by the broken line in FIG. Therefore, the peripheral portion 2b that is not used for refractive power correction is configured as a surface having a smaller edge thickness than a curve (aspherical shape) drawn by a function that defines the central portion 2a. However, if the boundary 3 between the central portion 2a and the peripheral portion 2b is not properly determined, the range of the central portion 2a is inadvertently narrowed to obstruct the visual field, or the central portion 2a is made wider than the effective visual field range. The edge thickness cannot be reduced.

In Example 1, the incident angle with respect to the outer surface 1 is obtained while changing the incident position (distance h ₂ ) of the light beam emitted from the rotation point 5 of the eyeball 6 with respect to the inner surface, and the incident angle and the critical angle are compared (S5 to S5). S15, S21, S23). Then, a light ray passing point where the reference light beam incident on the outer surface 1 at a critical angle intersects the inner surface 2 is defined as a boundary 3 (S17). In the case of Example 1, the distance from the reference axis to the boundary 3 is h _k = 27.5 [mm], and a circle having a radius of 27.5 mm around the reference axis is defined as the boundary 3. The inner side (that is, the optical axis 8 side) of the boundary 3 is defined as the central portion 2a, and the outer side is defined as the peripheral portion 2b.

The peripheral portion 2b is a rotationally symmetric curved surface defined as a locus obtained by rotating a parabola around the z axis (S19). That is, in S19, the cross-sectional shape of the peripheral part 2b of Example 9 is defined as a parabola represented by the following formula (10). The central portion 2a is defined by the above formula (4).

Here, since the central portion 2a and the peripheral portion 2b are smoothly connected at the boundary 3, the coordinate value z (= f (h)) and the first derivative dz / dh (= f ′) at the boundary 3 in the equation (10). (h)), the second derivative d ² z / dh ² (= f ″ (h)) is matched with each value of the equation (4).

At the boundary 3, the coordinate value z (= f (h)) of the function (formula (4)) representing the central portion 2a is 5.880, the first derivative dz / dh (= f ′ (h)) is 0.452, and the second derivative d. ² z / dh ² (= f ″ (h)) is 0.0229. Therefore, in the first embodiment, the sag amount z of the peripheral portion 2b is expressed by the above formula (11).
z = 5.880 + 0.452 (h−h _k ) +0.0115 (h−h _k ) ² (11)

The central portion 2a defined by the equation (4) and the peripheral portion 2b defined by the equation (11) maintain continuity up to the second derivative at h _k . That is, the central portion 2a and the peripheral portion 2b are smoothly connected.

  In the first embodiment, the edge thickness is 9.3 mm when extrapolated to the lens periphery according to the formula representing the shape of the central portion 2a, whereas the edge thickness is 0.3 mm by making the cross section of the peripheral portion 2b a parabola. It can be reduced to 9.0mm. Moreover, it can suppress that a curvature increases in a peripheral part. In addition, since the peripheral portion 2b of the spectacle lens of Example 1 is drawn as a parabola, there is no inflection point. Therefore, the lens inner surface 2b can be easily polished.

  FIG. 8 shows a spectacle lens of Example 2, (A) is a sectional view of the lens, (B) is a graph showing a change in the first derivative dz / dh of the sag amount z with respect to the distance h from the reference axis, (C). Is a graph showing a change in cross-sectional refractive power Dm with respect to distance h.

  Similarly to Example 1, the spectacle lens of Example 2 is also designed by the design method of the first embodiment. As shown in FIG. 8A, in the spectacle lens of Example 2, the outer surface 1 is a spherical surface and the inner surface 2 is a rotationally symmetric aspherical surface. The inner surface 2 is divided into a central portion 2a and a peripheral portion 2b. The central portion 2a and the peripheral portion 2b are smoothly connected at the boundary 3. The boundary 3 is defined as a position where the reference light beam 4 that is emitted from the rotation point 5 of the eyeball 6 and shines at a critical angle with respect to the outer surface 1 intersects the inner surface (a light beam passing point on the inner surface).

The eyeglass lens of Example 2 is optimized to a spherical surface having a vertex power (SPH) of -10.00 [D] and an outer surface 1 having a surface power of 0.50 [D] in S1 described above. The shape of the inner surface 2 obtained by the optimization is a rotationally symmetric aspherical surface expressed by the equation (4), and the cone coefficient and aspherical coefficient for defining the aspherical surface are shown in Table 3 below. The paraxial surface refractive power of the inner surface 2 is 10.50 [D].

Subsequently, a boundary 3 between the central portion 2a and the peripheral portion 2b is obtained (S3 to S17, S21, S23). The light ray passing point on the inner surface of the reference light beam 4 is at a distance h _k = 24.3 [mm] from the reference axis in the configuration of the second embodiment. Therefore, a circle having a radius of 24.3 mm with the reference axis as the center is defined as the boundary 3, and the inner side (that is, the optical axis 8 side) of the boundary 3 is defined as the central portion 2a and the outer side as the peripheral portion 2b. Next, the peripheral portion 2b is a rotationally symmetric curved surface defined as a locus obtained by rotating the parabola around the z axis (S19). In S19, the peripheral portion 2b is expressed by the function shown in Expression (10) as in the first embodiment. Accordingly, the sag amount z of the peripheral portion 2b is obtained by substituting the coordinate value, the first derivative, and the second derivative at the boundary position h _k in equation (4) into equation (10).

At the boundary 3, the coordinate value z (= f (h)) of the function representing the central portion 2a is 4.682, the first derivative dz / dh (= f ′ (h)) is 0.390, and the second derivative d ² z / dh ² ( = F ″ (h)) is 0.0177. Therefore, the sag amount z of the peripheral portion 2b is expressed by the following equation (12).
z = 4.682 + 0.390 (h−h _k ) +0.00886 (h−h _k ) ² (12)

  That is, the spectacle lens of Example 2 is also maintained in continuity up to the second derivative, and the central portion 2a and the peripheral portion 2b are smoothly connected.

  In Example 2, the edge thickness when extrapolating to the lens periphery is 10.7 mm according to the expression representing the shape of the central portion 2 a, whereas the edge thickness is 0.3 mm by making the cross section of the peripheral portion 2 b a parabola. It can be reduced to 10.4mm. Moreover, it can suppress that a curvature increases in a peripheral part. Moreover, the spectacle lens of Example 2 does not have an inflection point in the periphery as in Example 1. Therefore, the lens inner surface can be easily polished.

  FIG. 9 shows a spectacle lens of Example 3, (A) is a sectional view of the lens, (B) is a graph showing a change in the first derivative dz / dh of the sag amount z with respect to the distance h from the reference axis, (C). Is a graph showing a change in cross-sectional refractive power Dm with respect to distance h. The lens of Example 3 has the same vertex refractive power, the shape of the outer surface 1, the shape of the central portion 2a of the inner surface 2, and the position of the boundary 3 as in Example 2. Only the shape of the peripheral portion 2b of the inner surface 2 is different from that of the second embodiment. The eyeglass lens of Example 3 is designed by the method of the first embodiment in the same manner as Example 1 and Example 2.

  In Example 1 and Example 2, the shape of the peripheral portion is determined with emphasis on the ease of polishing, but in Example 3, the periphery is focused on the reduction of the edge thickness rather than the ease of polishing. The shape of the part 2b is determined. That is, a target edge thickness is set, and a function that can obtain the target edge thickness is obtained while the boundary between the central portion and the peripheral portion is continued to the second derivative.

The peripheral portion 2b of the inner surface 2 in the third embodiment is a function _obtained by adding B ₄ · (h−h _k ) ⁴ to the function of the central portion 2a represented by the formula (4) (hereinafter referred to as a first additional function). expressed. Here, when the target value of edge thickness reduction is the thinning amount target value ΔT and the distance from the z axis to the edge is H, the value of the fourth-order coefficient B ₄ of the first additional function is expressed by the following equation (13): Is required.
B ₄ = ΔT · (H−h _k ) ⁻⁴ (13)

In Example 3, since the target value ΔT is set to −2.9 mm, B ₄ = −2.231 × 10 ⁻⁰⁴ is obtained from the equation (13). When designing the peripheral portion 2b using coefficients B ₄ calculated, the edge thickness becomes 7.8 mm. Further, since h = h _k at the boundary 3, the value at the boundary 3 of the first additional function, the first derivative of the first additional function, and the second derivative of the first additional function are all zero. Therefore, the continuity between the central portion 2a and the peripheral portion 2b at the boundary 3 is maintained. In addition, if it designs to the periphery by the function (namely, Formula (4)) showing the center part 2a, edge thickness will be 10.7 mm. From the above, the spectacle lens of Example 3 is disadvantageous for polishing because of a large change in the curvature of the peripheral portion of the inner surface, but the effect of thinning is great.

  FIG. 10 shows a spectacle lens of Example 4, (A) is a sectional view of the lens, (B) is a graph showing a change in the first derivative dz / dh of the sag amount z with respect to the distance h from the reference axis, (C). Is a graph showing a change in cross-sectional refractive power Dm with respect to distance h.

  The spectacle lens of Example 4 is also designed by the design method of the first embodiment. As shown in FIG. 10A, in the spectacle lens of Example 4, the outer surface 1 is a spherical surface and the inner surface 2 is a rotationally symmetric aspherical surface. The inner surface 2 is divided into a central portion 2a and a peripheral portion 2b. The central portion 2a and the peripheral portion 2 are smoothly connected at the boundary 3. The boundary 3 is defined as a position where a reference light beam 4 that originates from the rotation point 5 of the eyeball 6 and enters the outer surface 1 at a critical angle intersects the inner surface (a light beam passing point on the inner surface 2).

The spectacle lens of Example 4 has a vertex power (SPH) of 12.00 [D] in S1 described above, and the outer surface 1 is optimized to be a spherical surface having a surface power of 0.50 [D]. The shape of the inner surface 2 obtained by the optimization is a rotationally symmetric aspherical surface expressed by Expression (4). The conic coefficient and the aspherical coefficient for defining the aspherical surface are shown in Table 4 below. The paraxial surface refractive power of the inner surface 2 is 12.50 [D].

Subsequently, a boundary 3 between the central portion 2a and the peripheral portion 2b is obtained. The light ray passing point on the inner surface of the reference light beam 4 that originates from the rotation point 5 of the eyeball 6 and enters the outer surface 1 at a critical angle is at a position h _k = 22.3 [mm] from the reference axis in the configuration of the fourth embodiment. . Therefore, a circle having a radius of 22.3 mm with the reference axis as the center is defined as the boundary 3, and the inner side of the boundary 3 is defined as the central portion 2a and the outer side is defined as the peripheral portion 2b. Next, the peripheral portion 2b is designed as a rotationally symmetric curved surface defined as a locus obtained by rotating a parabola around the z axis. That is, the peripheral part 2b is represented by the function shown in the above-described equation (10). Accordingly, the sag amount z of the peripheral portion 2b is obtained by substituting the coordinate value, the first derivative, and the second derivative at the boundary position h _k in equation (4) into equation (10).

At the boundary 3, the coordinate value z (= f (h)) of the function representing the central portion 2 a is 4.795, the first derivative dz / dh (= f ′ (h)) is 0.447, and the second derivative d ² z / dh ₂ ( = F ″ (h)) is 0.0240. Therefore, the sag amount z of the peripheral portion 2b is expressed by the following equation (14).
z = 4.795 + 0.447 (h−h _k ) +0.0120 (h−h _k ) ² (14)

  That is, the spectacle lens of Example 4 also maintains continuity up to the second derivative, and the central portion 2a and the peripheral portion 2b are smoothly connected.

  In Example 4, the edge thickness when extrapolating to the lens periphery is 13.9 mm according to the expression representing the shape of the central portion 2 a, whereas the edge thickness is 0.9 mm by making the cross section of the peripheral portion 2 b a parabola. It can be reduced to 13.0mm. Moreover, it can suppress that a curvature increases in a peripheral part. In addition, since there is no inflection point in the peripheral portion 2b, the lens inner surface can be easily polished.

  FIG. 11 shows a spectacle lens of Example 5. The lens of Example 5 is an astigmatism correction lens having a spherical refractive power SPH-10.00 [D], an astigmatism refractive power CYL-2.00 [D], and an astigmatism axis AX180 [°], and is shaped in a vertical section and a horizontal section. The performance is different. 11A is a vertical sectional view of the lens, FIG. 11B is a graph showing a change in the first derivative dz / dh of the sag amount z in the vertical section, and FIG. 11C is a graph showing a change in the sectional refractive power Dm in the vertical section. It is a graph to show. The shape in the horizontal cross section is the same as that of the third embodiment shown in FIG. 9A including the outer surface 1, the central portion 2a of the inner surface 2 and the peripheral portion 2b. 9 as shown in (B) and (C). In addition, the shape in the vertical cross section of the center part 2a of the inner surface 2 is the same as that of Example 4 shown to FIG. 10 (A).

  The spectacle lens of Example 5 is designed by the design method of the first embodiment. The outer surface 1 is a spherical surface, and the inner surface 2 is a rotationally asymmetric surface having different refractive powers in the horizontal direction and the vertical direction. The inner surface 2 is divided into a central portion 2a and a peripheral portion 2b. The central portion 2a and the peripheral portion 2b are smoothly connected at the boundary 3. The boundary 3 is defined as a light ray passing point on the inner surface of the reference light beam 4 that originates from the rotation point 5 of the eyeball 6 and enters the outer surface 1 at a critical angle in the horizontal section and the vertical section. In the configuration of the fifth embodiment, an ellipse having a horizontal cross section of 24.3 mm from the reference axis and a vertical cross section of 22.3 mm from the reference axis is defined as the boundary 3, the inner side from the boundary 3 is the central portion 2 a, and the outer side is the peripheral portion 2 b.

In the fifth embodiment, like the third embodiment, the shape of the peripheral portion 2b is determined with emphasis on the reduction of the edge thickness. That is, the peripheral part 2b is represented by the first additional function. In Example 5, in the horizontal cross section, the thinning amount target value ΔT is set to −2.9 mm with respect to the edge thickness 10.7 mm when extrapolated using the function of the central portion 2a. Therefore, from the equation (13), the coefficient B ₄ of the first additional function is −2.231 × 10 ⁻⁰⁴ and the edge thickness is 7.8 mm. In the vertical section, the thinning amount target value ΔT is set to −6.1 mm with respect to the edge thickness 13.9 mm when extrapolated using the function of the central portion 2a. Therefore, the coefficient B ₄ of the first additional function is −2.249 × 10 ⁻⁰⁴ and the edge thickness is 7.8 mm. Thus, according to Example 5, the edge thickness of a vertical cross section and a horizontal cross section can be equalized. The spectacle lens of Example 5 is disadvantageous for polishing because of a large change in the curvature of the peripheral portion of the inner surface, but the effect of thinning is great.

  FIG. 12 shows a spectacle lens of Example 6, (A) is a sectional view of the lens, (B) is a graph showing a change in the first derivative dz / dh of the sag amount z with respect to the distance h from the reference axis, (C). Is a graph showing a change in cross-sectional refractive power Dm with respect to distance h.

  In the case of the lens of Example 6, in the range of the lens diameter φ70 mm, the light beam that is emitted from the rotation point 5 of the eyeball 6 and is incident on the outer surface 1 from the inner surface side is not totally reflected at any angle. Accordingly, the boundary cannot be determined by the design method of the first embodiment. Therefore, it is designed by the method of the second embodiment. The outer surface 1 is divided into a spherical surface, and the inner surface 2 is divided into a central portion 2a and a peripheral portion 2b. The central portion 2a and the peripheral portion 2b are smoothly connected at the boundary 3. The boundary 3 is defined as a position where the reference light ray 9 that starts from the rotation point 5 of the eyeball 6 and passes through the edge of the outer surface 1 intersects the inner surface (a light ray passing point on the inner surface 2).

In the design stage, the aspherical shape of the inner surface is optimized based on the given prescription (S31). Here, it is assumed that the vertex power (SPH) -6.00 [D] and the outer surface 1 is a spherical surface having a surface power 4.00 [D]. The shape of the inner surface 2 obtained by optimization is a rotationally symmetric aspherical surface with a paraxial surface refractive power of 10.01 [D] expressed by the equation (4). Table 5 shows conical coefficients and aspheric coefficients that define the aspheric surface.

Subsequently, the boundary 3 between the central portion 2a and the peripheral portion 2b is obtained (S33 to S45, S49, S51). The light ray passing point on the inner surface of the reference light beam 9 is at a position h _k = 30.2 [mm] from the reference axis in the configuration of the sixth embodiment. Therefore, a circle having a radius of 30.2 mm with the reference axis as the center is defined as the boundary 3, and the inner side from the boundary 3 is defined as the central portion 2a and the outer side is defined as the peripheral portion 2b.

Next, the shape of the peripheral portion 2b is obtained (S47). In the sixth embodiment, like the third embodiment, the shape of the peripheral portion 2b is determined with emphasis on the reduction of the edge thickness. That is, the peripheral part 2b is represented by the first additional function. In Example 6, the thinning amount target value ΔT is set to −1.1 mm with respect to the edge thickness 7.6 mm when extrapolated using the function of the central portion 2a. Therefore, the coefficient B ₄ = -1.935 × 10 ^{-03 of} the first additional function and the edge thickness is 6.5 mm. As in Example 6, when none of the light rays emitted from the rotation point 5 are totally reflected, attention is paid to the point that the light rays do not pass through the region outside the light ray passing through the edge of the outer surface 1. Then, the outer side of the light ray passing point of the light ray passing through the edge of the outer surface 1 (reference light ray in Example 6) is defined as the peripheral portion 2b. The edge thickness can be reduced by using a function that defines the shape of the peripheral portion 2b that is different from the function of the central portion 2a.

FIG. 13 shows a spectacle lens of Example 7. The lens of Example 7 has the same spherical power (SPH) -10.00 [D], astigmatic power (CYL) -2.00 [D], and astigmatic refraction correction of the astigmatic axis (AXIS) 180 [°] as in Example 5. It is a lens. FIG. 13A is a table showing the relationship between the refractive power D in the radius direction of the angle θ with respect to the horizontal direction around the reference axis, and the distance h _k from the reference axis to the boundary 3 along this radius. FIG. 13B is a front view showing the inner surface 2 of the lens.

  The spectacle lens of Example 7 is designed by the design method of the third embodiment. The outer surface (not shown) is a spherical surface, and the inner surface 2 is a rotationally asymmetric surface having different refractive powers in the horizontal direction and the vertical direction. The inner surface 2 is divided into a central portion 2a and a peripheral portion 2b. The central portion 2a and the peripheral portion 2b are smoothly connected at the boundary 3.

The boundary 3 is determined using Expression (7) so as to satisfy the condition (1) described in the third embodiment. The spectacle lens of Example 7 has a circular outer diameter of φ70 (H = 35) mm, but has a different refractive power D for each cross-sectional direction θ. Therefore, the distance h _k to the boundary 3 position is determined for each cross-sectional direction. Table 6 shows the refractive power D and distance h _{k for} each cross-sectional direction θ, and the relationship between the distance h _k and the condition (1). As shown in Table 6, the distance h _k is determined within the range of about 22.4 mm to 24.6 mm while satisfying the condition (1). Therefore, the boundary 3 is elliptical. In the seventh embodiment, the edge thickness of the spectacle lens can be reduced by designing the outer side of such an elliptical boundary 3 as a peripheral portion 2b and a curved surface different from the central portion 2a.

FIG. 14 shows a spectacle lens of Example 8. The lens of Example 8 is an example in which a lens having a refractive power (SPH) of −8.00 [D] is edge-rubbed according to the shape of the spectacle frame. FIG. 14A shows the distance H from the reference axis to the edge of the lens along the direction of the angle θ with respect to the horizontal direction around the reference axis, and the distance h _k from the reference axis to the boundary 3 along this direction. A table showing the relationship, FIG. 14B, is a front view showing the inner surface 2 of the lens.

  The spectacle lens of Example 8 is designed by the design method of the fourth embodiment. The outer surface not shown is a spherical surface. The inner surface 2 is a rotationally symmetric aspheric surface and is divided into a central portion 2a and a peripheral portion 2b. The central portion 2a and the peripheral portion 2b are smoothly connected at the boundary 3.

The boundary 3 is determined using Expression (8) so as to satisfy the condition (2) described in the fourth embodiment. In the spectacle lens of Example 8, the refractive power D is the same in all directions, but the distance H from the reference axis to the edge of the lens is different for each cross-sectional direction θ. Therefore, the distance h _k to the boundary 3 position is determined for each cross-sectional direction. Table 6 shows the distance H and distance h _{k for} each cross-sectional direction θ, and the relationship between the distance h _k and the condition (2). As shown in Table 7, the distance h _k is determined within the range of about 20.0 mm to 26.0 mm while satisfying the condition (2). Therefore, the boundary 3 is almost similar to the outer shape of the lens. Thus, by defining the outside of the boundary 3 as the peripheral portion 2b and designing the surface shape of the peripheral portion 2b to be a curved surface different from the central portion 2a, the edge thickness can be reduced.

  The above is a specific example of a single focus spectacle lens designed by the design method of each embodiment. Next, four examples of the progressive power lens in which the boundary between the central portion and the peripheral portion is determined by the design method of each embodiment described above will be shown. In all the following examples, the eyeball rotation point is 25 mm behind the inner surface vertex. Examples 9 to 11 have a circular lens blank before edge trimming as a design object, and Example 12 has a lens that matches the target lens shape after edge trimming as a design object.

  First, the progressive-power lens of Example 9 will be described with reference to FIGS. 15 to 19. 15 (A) to 15 (D) are cross-sectional views of the progressive-power lens of Example 9. (A) is a 0 ° / 180 ° cross section, (B) is a 45 ° / 225 ° cross section, (C ) Shows a 90 ° / 270 ° cross section, and (D) shows a 135 ° / 315 ° cross section. In each figure described below, (A), (B), (C), and (D) represent the same meaning, and the description thereof is omitted. 16A to 16D are graphs showing changes in the first derivative dz / dh of the sag amount z with respect to the distance h from the reference axis, and FIGS. 17A to 17D are graphs showing the cross-sectional refractive power Dm with respect to the distance h. It is a graph which shows a change. The cross-sectional refractive power Dm is calculated by the equation (9) in the same manner as each embodiment in the single focus lens.

  In each figure, the broken line indicates the shape and numerical value when the progressive surface shape defining the central portion is extrapolated to the lens periphery without dividing the central portion and the peripheral portion. A solid line indicates the shape and numerical value of the progressive-power lens of Example 9 in which the central portion and the peripheral portion are designed in different shapes. The same applies to the following drawings.

  The progressive-power lens of Example 9 is designed by the design method of the first embodiment. The outer surface 1 is a spherical surface, and the inner surface 2 is a progressive surface. The inner surface 2 is divided into a central portion 2a and a peripheral portion 2b. The central portion 2a and the peripheral portion 2b are smoothly connected at the boundary 3. The boundary 3 is defined as a position (a light ray passing point on the inner surface) where the reference light beam 4 that originates from the rotation point 5 of the eyeball 6 and enters the outer surface 1 at a critical angle intersects the inner surface 2.

  In the design stage, the progressive surface shape of the inner surface is optimized based on the given prescription (S1). In Example 9, the distance portion vertex power SPH-10.00 [D], the addition power ADD2.00 [D], the refractive index N1.67, the center thickness T1.1 [mm], the outer diameter φ70 mm, the outer shape is The spherical surface with a surface refractive power of 0.45 [D] and the inner surface shape were designed as a two-dimensional spline curved surface.

  When the optimized two-dimensional spline curved surface is applied to the entire inner surface, the change in the sag amount z increases toward the periphery as shown by the broken lines in FIGS. 16 (A) to 16 (D). In addition, as shown by broken lines in FIGS. 17A to 17D, the refractive power increases rapidly. As a result, the edge thickness increases as shown by the broken lines in FIGS. Therefore, the portion not used for refractive power correction is configured as a surface in which the peripheral portion 2b has a smaller edge thickness than the curve drawn by the function defining the central portion 2a. However, if the boundary 3 between the central portion 2a and the peripheral portion 2b is not properly determined, the range of the central portion 2a is inadvertently narrowed to obstruct the field of view, and conversely, the range of the central portion 2a is reduced to an effective visual field. It may not be possible to reduce the edge thickness by making it wider than the range.

  In Example 9, while changing the incident position (distance h2) of the light beam emitted from the rotation point 5 of the eyeball 6 with respect to the inner surface, the incident angle with respect to the outer surface 1 is obtained, and the incident angle and the critical angle are compared (S5 to S15). , S21, S23). Then, a light ray passing point where the reference light beam incident on the outer surface 1 at a critical angle intersects the inner surface 2 is defined as a boundary 3 (S17). In the case of the ninth embodiment, the inner side from the boundary 3 is set as the central portion 2a and the outer side is set as the peripheral portion 2b.

  In S19, the cross-sectional shape of the peripheral portion 2b of Example 9 is defined as a parabola represented by the above formula (10).

FIG. 18 is a front view of the inner surface 2 of the progressive-power lens according to the ninth embodiment. FIG. 19 shows the distance h _k to the boundary in the angle θ direction and the sag amount z _k , the slope dz / dh _k , the second derivative d ² z / dh ² , and the edge position H and the sag at that position. It is a table | surface which shows quantity zH and the amount of sag zH0 when this invention is not applied. As shown in FIGS. 18 and 19, the position of the boundary 3 varies depending on the direction θ.

  In the ninth embodiment, by designing the cross section of the peripheral portion 2b to be a parabola, the edge thickness can be reduced by 0.56 to 2.34 mm as compared with the case where the lens periphery is extrapolated by an expression representing the shape of the central portion 2a. . Moreover, it can suppress that a curvature increases in a peripheral part. Moreover, there is no inflection point in the peripheral portion 2a of the progressive-power lens of Example 9. Therefore, the lens inner surface is easily polished.

  Next, the progressive-power lens of Example 10 will be described with reference to FIGS. FIGS. 20A to 24D are cross-sectional views of the progressive-power lens of Example 10. FIGS. 21A to 21D are first-order differentials dz of the sag z with respect to the distance h from the reference axis. FIG. 22A to FIG. 22D are graphs showing changes in the cross-sectional refractive power Dm with respect to the distance h.

  The progressive-power lens of Example 10 is designed by the design method of the second embodiment. The outer surface 1 is a spherical surface, and the inner surface 2 is a progressive surface. The inner surface 2 is divided into a central portion 2a and a peripheral portion 2b. The central portion 2a and the peripheral portion 2b are smoothly connected at the boundary 3. The boundary 3 is defined as a position (a light ray passing point on the inner surface) where the reference light ray 9 that starts from the rotation point 5 of the eyeball 6 and passes through the edge of the outer surface 1 intersects the inner surface.

  In the progressive-power lens of Example 10, in S31 shown in FIG. 2, the distance portion vertex power SPH-6.00 [D], astigmatic power CYL-3.00 [D], astigmatic axis AX45 [°], addition power ADD2.00 [D], refractive index N1.67, center thickness T1.1 [mm], outer diameter φ70mm, outer surface 1 is a spherical surface with a surface refractive power of 0.90 [D], and the inner surface shape is optimized as a two-dimensional spline curved surface. .

  In Example 9 described above, the shape of the peripheral portion is determined with emphasis on the ease of polishing. On the other hand, in Example 10, the shape of the peripheral portion 2b is determined with emphasis on the reduction of the edge thickness rather than the ease of polishing. Specifically, after the position of the boundary 3 is determined by ray tracing (S33 to S45, S49, S51), a target edge thickness is first set. Then, a function that obtains the target edge thickness is obtained while the boundary 3 between the central portion 2a and the peripheral portion 2b is continued to the second derivative.

The peripheral portion 2b of the inner surface 2 in the tenth embodiment is expressed by a function (hereinafter referred to as a second additional function) obtained by adding B ₄ · (h−hk) ⁴ to the two-dimensional spline function obtained by the optimization process of S31. Is done. In Example 10, the thinning amount target value ΔT is set to 2.0 mm. Incidentally, B ₄ is obtained by the above-mentioned formula (13). Since h = h _k at the boundary 3, the value, the first derivative, and the second derivative at the boundary 3 of the second additional function are all zero. Therefore, the continuity between the central portion 2a and the peripheral portion 2b at the boundary 3 is maintained.

FIG. 23 is a front view of the inner surface 2 of the progressive-power lens according to the tenth embodiment. FIG. 24 shows the distance h _k to the boundary in the angle θ direction and the sag amount z _k of the inner surface at that position, the slope dz / dh _k , the second derivative d ² z / dh ² , and the edge position H and the sag at that position. It is a table | surface which shows quantity zH and the amount of sag zH0 when this invention is not applied. As shown in FIGS. 23 and 24, the position of the boundary 3 varies depending on the direction θ. The spectacle lens of Example 2 is disadvantageous for polishing because of a large change in the curvature of the peripheral portion of the inner surface, but the effect of thinning is great.

  Next, the progressive-power lens of Example 11 will be described with reference to FIGS. 25 to 29. FIG. The progressive-power lens of Example 11 is designed by the design method of the third embodiment. 25A to 25D are cross-sectional views of the progressive-power lens of Example 11, and FIGS. 26A to 26D are first-order differentials dz of the sag z with respect to the distance h from the reference axis. FIG. 27A to FIG. 27D are graphs showing changes in the cross-sectional refractive power Dm with respect to the distance h.

  In the progressive-power lens of Example 11, the shapes of the outer surface 1 and the inner surface 2 are previously optimized based on the prescription before the boundary 3 between the central portion 2a and the peripheral portion 2b is determined. Here, the outer surface is based on the following prescriptions: vertex distance power SPH-12.00 [D], addition power ADD3.00 [D], refractive index N1.67, center thickness T1.1 [mm], outer diameter φ70mm 1 was optimized as a spherical surface with a surface refractive power of 0.45 [D], and the inner surface 2 was optimized as a two-dimensional spline curved surface.

Similar to Examples 9 and 10, the progressive-power lens of Example 11 is a progressive surface in which the outer surface 1 is a spherical surface and the inner surface 2 is divided into a central part 2a and a peripheral part 2b at a boundary 3. The boundary 3 is defined by the equation (7) so as to satisfy the condition (1). In the eyeglass lens of Example 11, the approximate cross-sectional refractive power D calculated by Expression (3) is different for each cross-sectional direction θ. Therefore, the boundary position h _k is different for each cross-sectional direction θ. Table 8 shows the relationship between the approximate cross-sectional refractive power D and the distance h _{k for} each cross-sectional direction θ, and the distance h _k and the condition (1).

As shown in Table 8, the distance h _k satisfies the condition (1) in any cross-sectional direction θ. As shown in FIGS. 25 (A) to 25 (D), the boundary position h _k obtained by the equation (7) is a reference that is emitted from the rotation point 5 of the eyeball 6 and is incident on the outer surface 1 at a critical angle. It substantially coincides with the position where the light beam 4 intersects the inner surface 2 (the light beam passing point on the inner surface 2). After the position of the boundary 3 is determined by the equation (7), the cross-sectional shape of the peripheral portion 2b is determined as a parabola that is smoothly connected to the central portion 2a, as in the ninth embodiment.

FIG. 28 is a front view of the inner surface 2 of the progressive-power lens according to the eleventh embodiment. FIG. 29 shows the distance h _k to the boundary in the angle θ direction and the sag amount z _k of the inner surface at that position, the slope dz / dh _k , the second derivative d ² z / dh ² , and the edge position H and the sag at that position. It is a table | surface which shows quantity zH and the amount of sag zH0 when this invention is not applied. As shown in FIGS. 28 and 29, the position of the boundary 3 varies depending on the direction θ. In Example 11, by designing the cross section of the peripheral portion 2b to be a parabola, the edge thickness can be reduced by 1.14 to 2.35 mm as compared to the case where the lens periphery is extrapolated by an expression representing the shape of the central portion 2a. . Moreover, it can suppress that a curvature increases in a peripheral part. In addition, since there is no inflection point in the peripheral portion, the inner surface of the lens can be easily polished.

  Next, the progressive-power lens of Example 12 will be described with reference to FIGS. 30 to 34. The progressive-power lens of Example 12 is designed by the design method of the fourth embodiment. 30A to 30D are cross-sectional views of the progressive-power lens of Example 12, and FIGS. 31A to 31D are first-order differentials dz of the sag z with respect to the distance h from the reference axis. FIG. 32A to FIG. 32D are graphs showing changes in the cross-sectional refractive power Dm with respect to the distance h. FIG. 33 is a front view of the inner surface 2 of the progressive-power lens according to the twelfth embodiment. As shown in FIG. 33, the progressive-power lens of Example 12 is edge-rubbed in accordance with the shape of the spectacle frame.

  As in the case of the eleventh embodiment, the progressive-power lens of the twelfth embodiment also optimizes the shapes of the outer surface 1 and the inner surface 2 based on the prescription before determining the boundary 3 between the central portion 2a and the peripheral portion 2b. Here, the outer surface 1 is surface refracted according to the prescriptions of the distance vertex power SPH-9.00 [D], the addition power ADD 2.00 [D], the refractive index N 1.60, and the center thickness T 1.3 [mm]. The spherical surface with a force of 0.41 [D] and the inner surface 2 were optimized as a two-dimensional spline curved surface.

Similar to the ninth to eleventh embodiments, the progressive-power lens of the twelfth embodiment is a progressive surface in which the outer surface 1 is a spherical surface and the inner surface 2 is divided into a central portion 2a and a peripheral portion 2b at a boundary 3. The central portion 2a and the peripheral portion 2b are smoothly connected at the boundary 3. The boundary 3 is defined by the equation (8) so as to satisfy the condition (2). In the eyeglass lens of Example 12, similar to Example 11, the approximate cross-sectional refractive power D calculated by the expression (3) is different for each cross-sectional direction θ. In addition, since the progressive-power lens of Example 12 is edge-rubbed, the distance H from the reference axis to the edge of the lens also differs for each cross-sectional direction θ. As a result, the boundary position h _k is different for each cross-sectional direction θ. Table 9 shows the relationship between the distance H in each cross-sectional direction θ, the approximate cross-sectional refractive power D and the distance h _k , and the distance h _k and the condition (2).

As shown in Table 9, the distance h _k satisfies the condition (2) in any cross-sectional direction θ. As shown in FIGS. 30 (A) to 30 (D), the boundary position h _k obtained by the equation (8) is such that the reference ray 9 emanating from the rotation point 5 of the eyeball 6 and passing through the edge of the outer surface 1 is the inner surface. 2 substantially coincides with the position intersecting 2 (light ray passing point on the inner surface).

After the position of the boundary 3 is determined by the equation (8), the peripheral portion 2b of the inner surface is a function obtained by adding B ₃ · (h−h _k ) ³ to the two-dimensional spline function obtained by the optimization process (hereinafter, This is expressed as a third additional function). In the twelfth embodiment, the target value of the edge thickness is set to 2.7 mm on the entire circumference, and the thinning amount target value ΔT for each direction θ is determined based on the target value. Then, assuming that the distance from the z axis to the edge is H, the value of the third-order coefficient B ₃ of the third additional function is obtained by the following equation (15).
B ₃ = ΔT · (H−h _k ) ⁻³ (15)

Here, since h = h _k at the boundary 3, the value at the boundary 3 of the additional function, the first derivative, and the second derivative are all zero. Therefore, the continuity between the central portion 2a and the peripheral portion 2b at the boundary 3 is maintained. FIG. 34 shows the distance h _k to the boundary in the angle θ direction and the sag amount z _k of the inner surface at that position, the slope dz / dh _k , the second derivative d ² z / dh ² , and the edge position H and the sag at that position. It is a table | surface which shows quantity zH and the amount of sag zH0 when this invention is not applied. As shown in FIGS. 33 and 34 described above, the position of the boundary 3 varies depending on the direction θ.

  In the twelfth embodiment, the edge thickness can be reduced by 2.11 to 5.00 mm as compared with the case where the lens periphery is extrapolated by an expression representing the shape of the central portion 2a. For this reason, the edge thickness of the lens lens can be almost uniform over the entire circumference, and the finish when framed can be made beautiful.

  In each of the examples described above, the outer surface is a spherical surface and the inner surface is an aspherical surface or a progressive surface. However, in the design methods of the above-described embodiments, the inner and outer surfaces are both spherical and aspherical (progressive surface). In this case, the present invention can be applied to the case where the outer surface is an aspheric surface (progressive surface) and the inner surface is a spherical surface. In addition, assuming that the glasses are displaced during wearing, an appropriate margin can be given to the boundary position obtained by the present invention to set the final boundary position.

It is a flowchart which shows the design method of 1st Embodiment. It is a flowchart which shows the design method of 2nd Embodiment. It is a graph showing the relationship between the vertex refractive power and boundary position of a single focus lens with a refractive index of 1.5 of 3rd Embodiment. It is a graph showing the relationship between the vertex refractive power of a single focus lens with a refractive index of 1.8 of 3rd Embodiment, and a boundary position. It is a graph showing the relationship between the vertex refractive power and boundary position of a single focus lens with a refractive index of 1.5 of 4th Embodiment. It is a graph showing the relationship between the vertex refractive power of a single focus lens with a refractive index of 1.8 of 4th Embodiment, and a boundary position. 1 shows a spectacle lens of Example 1, (A) is a sectional view of the lens, (B) is a graph showing the inclination of the aspheric surface of the inner surface of the lens, and (C) is a sectional refractive power of the aspheric surface of the inner surface of the lens. It is a graph. 2 shows a spectacle lens of Example 2, wherein (A) is a sectional view of the lens, (B) is a graph showing the inclination of the aspheric surface of the inner surface of the lens, and (C) is a sectional refractive power of the aspheric surface of the inner surface of the lens. It is a graph. 3 shows a spectacle lens of Example 3, where (A) is a sectional view of the lens, (B) is a graph showing the inclination of the aspheric surface of the inner surface of the lens, and (C) is a sectional refractive power of the aspheric surface of the inner surface of the lens. It is a graph. 4 shows a spectacle lens of Example 4, where (A) is a cross-sectional view of the lens, (B) is a graph showing the inclination of the aspheric surface of the inner surface of the lens, and (C) is a cross-sectional refractive power of the aspheric surface of the inner surface of the lens. It is a graph. 5 shows a spectacle lens of Example 5, wherein (A) is a vertical sectional view of the lens, (B) is a graph showing the inclination of the aspherical vertical section of the inner surface of the lens, and (C) is a vertical of the aspherical surface of the inner surface of the lens. It is a graph showing the cross-sectional refractive power of a cross section. 8 shows a spectacle lens of Example 6, (A) is a sectional view of the lens, (B) is a graph showing the inclination of the aspheric surface of the inner surface of the lens, and (C) shows the sectional refractive power of the aspheric surface of the inner surface of the lens. It is a graph. 7 shows a spectacle lens of Example 7, (A) is a table showing the refractive power in the angle θ direction and the distance to the boundary, and (B) is a front view of the lens viewed from the inner surface side. 8 shows a spectacle lens of Example 8, (A) is a table showing the distance from the reference axis in the angle θ direction to the edge of the lens and the distance to the boundary, and (B) is a front view of the lens viewed from the inner surface side. is there. 10 is a cross-sectional view of a progressive-power lens according to Example 9. FIG. 10 is a graph showing the inclination of the inner surface of the progressive-power lens of Example 9. FIG. 10 is a graph showing the cross-sectional refractive power of the inner surface of the progressive-power lens of Example 9. 10 is a front view of the inner surface of a progressive-power lens according to Example 9. FIG. The distance to the boundary in the angle θ direction of the progressive-power lens of Example 9, the inner surface sag amount, the inclination (first derivative), the second derivative, and the edge position and the sag amount at that position, the present invention is applied. It is a table | surface which shows the amount of sag when not doing. 10 is a cross-sectional view of a progressive-power lens according to Example 10. FIG. 14 is a graph showing the inclination of the inner surface of the progressive-power lens of Example 10. 14 is a graph showing the cross-sectional refractive power of the inner surface of the progressive-power lens of Example 10. FIG. 10 is a front view of the inner surface of a progressive-power lens according to Example 10. The distance to the boundary in the angle θ direction of the progressive-power lens of Example 10, the sag amount of the inner surface at that position, the inclination (first derivative), the second derivative, and the edge position and the sag amount at that position, applying the present invention It is a table | surface which shows the amount of sag when not doing. 12 is a cross-sectional view of a progressive-power lens according to Example 11. FIG. 14 is a graph showing the inclination of the inner surface of the progressive-power lens of Example 11. 14 is a graph showing the cross-sectional refractive power of the inner surface of the progressive-power lens of Example 11. 14 is a front view of the inner surface of a progressive-power lens according to Example 11. FIG. The distance to the boundary in the angle θ direction of the progressive-power lens of Example 11 and the sag amount of the inner surface at that position, the slope (first derivative), the second derivative, and the edge position and the sag amount at that position, applying the present invention It is a table | surface which shows the amount of sag when not doing. 14 is a cross-sectional view of a progressive-power lens according to Example 12. FIG. 14 is a graph showing the inclination of the inner surface of the progressive-power lens of Example 12. 14 is a graph showing the cross-sectional refractive power of the inner surface of the progressive-power lens of Example 12. 14 is a front view of the inner surface of a progressive-power lens according to Example 12. FIG. The distance to the boundary in the angle θ direction of the progressive-power lens of Example 12, the sag amount of the inner surface at that position, the inclination (first derivative), the second derivative, and the edge position and the sag amount at that position, applying the present invention It is a table | surface which shows the amount of sag when not doing.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Outer surface 2a Inner surface center part 2b Inner surface peripheral part 3 Inner surface center part and peripheral boundary 4, 9 Light ray emitted from the eyeball rotation point (reference light beam)
5 Eye rotation point 6 Eye ball 7 Design reference point 8 z-axis

Claims (18)

A surface shape determination step for determining the shape of the outer surface and inner surface of the spectacle lens having negative correction refractive power based on the prescription;
A ray passing point where the ray intersects the inner surface and the outer surface is traced with respect to the spectacle lens whose shape of each surface has been determined by the surface shape determining step by tracing the ray passing through the assumed eyeball rotation point. A ray passing point detection stage to be obtained;
Out of the light passing points obtained in the light passing point detection step, the inner surface has a central portion having a refractive power for correction and a correction for the inner surface with reference to a light passing point obtained when a predetermined ray is traced. A boundary determination stage for determining a boundary to be divided into a peripheral portion having no refractive power;
The peripheral portion is smooth with respect to the central portion having the determined inner surface shape while changing the shape of the peripheral portion in a direction that becomes thinner than the edge thickness in the inner surface shape determined in the surface shape determining step. A spectacle lens design method comprising: determining a shape of the peripheral portion so as to be connected;   The spectacle lens design method according to claim 1, wherein, in the light ray passing point detection step, the predetermined light ray is a light ray that is incident on the outer surface from a lens medium side at a critical angle.   The spectacle lens design method according to claim 1, wherein in the light beam passing point detection step, the predetermined light beam is a light beam that passes through an edge of the outer surface.   4. The spectacle lens design method according to claim 1, wherein the central portion is an aspherical surface or a progressive surface.   The spectacle lens design method according to claim 1, wherein the outer surface is a spherical surface. A plane that passes through the design reference point of the spectacle lens and is perpendicular to the inner surface is the z-axis, a straight line that passes through the intersection of the inner surface and the z-axis and is orthogonal to the z-axis is a plane that includes the z-axis and the h-axis. And the curve that is the intersection of the inner surface and the inner surface is expressed by the function z = f (h),
In the peripheral shape determination step, at the boundary between the central portion and the peripheral portion, the function f (h), the primary differential f ′ (h), and the secondary differential f ″ (h) are all continuous. The method for designing a spectacle lens according to claim 1, wherein the shape of the portion is determined.   The spectacle lens design method according to claim 6, wherein the function f (h) is expressed as a function having no inflection point in the peripheral portion.   The spectacle lens design method according to claim 6 or 7, wherein the function f (h) is a quadratic function in the peripheral portion.   In the peripheral shape determination step, a target value of the edge thickness is set, the continuity of the function f (h), the first derivative f ′ (h), the second derivative f ″ (h) at the boundary, and the edge thickness The spectacle lens design method according to claim 6 or 7, wherein a function f (h) in the peripheral portion is determined on the condition of a target value.   A spectacle lens, which is designed by the method according to claim 1.   The spectacle lens according to claim 10, wherein a central portion of the inner surface is an aspherical surface or a progressive surface. Has negative correction power,
An inner surface is divided into a central portion having the correction refractive power and a peripheral portion having no correction refractive power,
The central portion and the peripheral portion are smoothly connected at a boundary that satisfies a predetermined condition,
A spectacle lens, wherein a distance from a design reference point to the boundary is an increasing function with respect to refractive power.   The spectacle lens according to claim 12, wherein a central portion of the inner surface is an aspherical surface or a progressive surface. A straight line passing through the design reference point and perpendicular to the inner surface is the z axis, a straight line passing through the intersection of the inner surface and the z axis and perpendicular to the z axis is the h axis, the refractive index of the lens is N, and the z axis and the h axis are included. The following condition (1) is satisfied, wherein the refractive power of the lens in a plane is D [Dioptre], and the distance from the z-axis to the boundary between the central portion and the peripheral portion is h _k [mm]. The spectacle lens according to Item 12 or Claim 13.

However,
E = 29.0N-265
F = −2.57N + 7.59
G = 3.41N + 2.61
It is. A straight line passing through the design reference point and perpendicular to the inner surface is the z axis, a straight line passing through the intersection of the inner surface and the z axis and perpendicular to the z axis is the h axis, the refractive index of the lens is N, and the z axis and the h axis are included. The refractive power of the lens in the plane is D [Dioptre], the distance from the z axis to the boundary between the central portion and the peripheral portion is h _k [mm], and the distance from the z axis to the outer edge of the lens is H [mm]. The eyeglass lens according to claim 12 or 13, wherein the following condition (2) is satisfied.

However,
A = -0.585 + 0.0433N + 0.0624H-0.0180NH
B = 14.3-8.16N + 0.289H + 0.392NH
It is.   The spectacle lens according to claim 12, wherein the spectacle lens is a progressive power lens. The refractive power D is expressed by the following formula (3),

However, SPH is the spherical refractive power,
CYL is the power of astigmatism,
AX is the astigmatic axis direction,
ADD gives the addition power,
θ represents an angle formed between a cross section for which the refractive power D is to be obtained and a horizontal cross section.
The spectacle lens according to claim 16, which is approximated by: The negative portion has a negative refractive power, and the inner surface is divided into a central portion having a refractive power for correction and a peripheral portion having no refractive power for correction, and the central portion and the peripheral portion are smoothly connected. In a spectacle lens series which is a set of spectacle lenses according to any one of claims 11 to 17,
A spectacle lens series, wherein a distance from a design reference point to a boundary between the central portion and the peripheral portion is an increasing function with respect to at least one of refractive power and refractive index.

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