JP2859001B2 - Aspherical ophthalmic lens and manufacturing method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aspherical ophthalmic lens in which at least one of a lens convex surface and a concave surface has an axisymmetric aspherical surface, and a method of manufacturing the same.

[0002]

BACKGROUND ART As a kind of ophthalmic lens such as a contact lens or an intraocular lens, at least one of a lens convex surface and a concave surface such as an elliptical aspheric lens, a seamless concentric bifocal lens, and a multifocal lens. There is a so-called aspherical ophthalmic lens in which the lens surface has an axisymmetric aspherical shape.

[0003] By the way, such an aspherical ophthalmic lens is generally manufactured by cutting a lens surface with a predetermined cutting tool while attaching an ophthalmic lens material to a predetermined spindle and rotating the lens at high speed around one axis. As a cutting method for providing an aspherical shape, conventionally, two methods are generally roughly known.

The first method uses a cam member of a predetermined shape for guiding a cutting tool, and moves the cutting tool along a curve that gives a target aspherical cross-sectional shape. The second method is to cut and form a spherical lens surface, and the second method divides the lens surface into a plurality of annular portions around the axis of symmetry, and those divided surfaces are orthogonal to the rotation axis of the ophthalmic lens material. When performing cutting with a cutting tool that is turned around the turning axis, the turning axis of the cutting tool is sequentially moved on the rotation axis, and each divided surface is cut with a spherical shape having a different radius of curvature from each other. In this method, a lens surface approximate to the target aspherical surface is formed by cutting.

However, in the first method, it is necessary to prepare a cam member corresponding to each aspherical shape, but it is necessary to stock all the cam members. It has to be said that it is impossible in practice. Therefore, usually, it is necessary to cope with the cutting and forming of the aspherical ophthalmic lens with a limited cam member, so that a desired curved lens surface cannot always be obtained. In addition, in such a method, a large number of cam members are stocked, and the cam members must be replaced one by one according to the curved shape of the objective lens. However, there was also a problem that it was required.

On the other hand, in the second method, since there is no need to use a cam member or the like, no labor or the like for replacing the cam member is required, but the boundary between the divided surfaces corresponding to the changing point of the curvature radius is required. In the line, a ridge-shaped discontinuous portion is formed, which has a problem that an optical problem such as glare and a problem such as a feeling of wearing are easily caused. In addition, such a discontinuous portion can be reduced by performing a polishing process after the cutting process.However, such a polishing process is different from a case of simply finishing a cut surface, because it is necessary to adjust a shape. However, there is a problem that the work is difficult and takes time. Also, in the case of curved surface forming by polishing, it is difficult to secure sufficient surface accuracy, and since it is less reliable than cutting, it is difficult to obtain a desired curved surface shape, and optical quality stability is poor. It was.

[0007]

The present invention has been made in view of the above-described circumstances, and an object of the present invention is to provide an arbitrary aspherical shape with a ridge-shaped discontinuous portion or the like. The present invention provides an aspherical ophthalmic lens having an improved lens surface shape which can be advantageously realized without using the aspherical ophthalmic lens, and an aspherical ophthalmic lens which can be advantageously manufactured by cutting. An object of the present invention is to provide a method for manufacturing a lens.

[0008]

According to the present invention, there is provided an aspherical ophthalmic lens in which at least one of a lens convex surface and a concave surface has an axisymmetric aspheric shape. A plurality of circular arcs having different curvatures, each having a cross section including the axis of symmetry on the surface of the aspherical lens, are positioned on both sides in the radial direction of the vertex on the axis of symmetry: O. Each of the division points G1 to Gn, which are constituted by Cn and are located at the boundary between the plurality of arcs C1 to Cn, respectively satisfies a basic equation of a curve that gives a desired sectional shape of the aspherical ophthalmic lens. A vertex: O, and a first division point: G adjacent to the vertex: O
C1 is an arc centered on the intersection point of the vertical bisector of the chord connecting the vertex O and the first division point G1 with the axis of symmetry: α1. At the same time, among the plurality of division points: G1 to Gn, arcs located between two division points adjacent to each other: Ga, G (a + 1):
A vertical bisector of a string connecting C2 to Cn, respectively, two adjacent dividing points: Ga, G (a + 1);
Of these two division points: Ga, G (a + 1), a line passing through the apex: a division point located on the O side: Ga and an arc located adjacent to the division point: Ga: a center point of Ca: αa Intersection with: An aspherical ophthalmic lens having an arc centered at α (a + 1).

Further, in the present invention, the ophthalmic lens material is mounted on a spindle which rotates around one axis, and the ophthalmic lens material is cut with a cutting tool which can be moved around a rotation axis perpendicular to the rotation axis of the spindle. (A) a lens surface of a desired aspherical ophthalmic lens, wherein at least one of the lens convex surface and the concave surface has an axisymmetric aspherical surface. Obtaining a basic equation of a curve giving the cross-sectional shape of (b); and (b) dividing a vertex of the curve: one side sandwiching O into a plurality of ranges on the curve given by the basic equation. Point: a step of determining G1 to Gn;
(C) The vertex of the curve given by the basic equation: O
And a vertical bisector at a chord connecting the first division point G1 adjacent to the vertex O among the plurality of division points G1 to Gn is a symmetry of a curve given by the basic equation. (D) determining the distance R1 between the intersection point α1 and the vertex O or the first division point G1 while obtaining the coordinates of the intersection point α1 intersecting with the axis; : A vertical bisector of a chord connecting the first division point: G1 and the second division point: G2 adjacent to the outside of the first division point: G1 among G1 to Gn: The coordinates of an intersection: α2 that intersects a straight line passing through the first division point: G1 and the intersection: α1 are obtained, and the intersection: α2 and the first division point: G1 or the second division point G2 are determined. Determining a distance between: R2; and (e) the plurality of division points:
Of G1 to Gn, two adjacent dividing points: Ga, G (a + 1) in the first dividing point: G2 to Gn located outside of the first dividing point: G1, and the intersection: α2 and In accordance with the operation for obtaining the distance: R2, the same operation is repeated from the inside to the outside in order, so that the intersection: α3 to αn and the distance: R3 to R
and (f) the division points: G1 to Gn on the lens surface of the ophthalmic lens material.
Each of the machining surfaces: S1 to Sn divided by the rotation locus of the curve given by the basic equation around the symmetry axis, the intersections: α1 to αn, respectively, and the distance:
A method for manufacturing an aspherical ophthalmic lens, comprising a step of performing a cutting process using a cutting tool that can be moved with a radius of R1 to Rn, is also characterized.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In manufacturing an aspherical ophthalmic lens having a lens surface having an axisymmetric aspherical shape according to the present invention, first, a desired lens surface shape is determined. Here, since the lens surface is axially symmetric, its shape is determined by obtaining a basic equation of a curve giving a cross-sectional shape including the axis of symmetry.

The basic equation of such a curve should be such that the following processing is facilitated, and the vertex of the curve located on the axis of symmetry of the lens: O is the origin, and the axis of symmetry is the Y axis. Therefore, it is desirable to obtain the function as a function represented by the following (Equation 1). Y = F (X) (Equation 1)

The aspherical shape to which the present invention can be applied covers all possible curved surfaces symmetrical with respect to the rotational axis, and the basic equation of a curve giving a cross-sectional shape including the axis of symmetry is a parabola, an ellipse, or the like. Eccentricity such as hyperbola: a curve represented by e and a vertex curvature, an Nth-order curve represented by the following general formula (Equation 2), a curve represented by a mathematical formula obtained by general geometry, and the like. It is possible to employ equations that give a very wide range of curves.

[0013]

(Equation 2)

Next, on a curve given by the obtained basic equation, a plurality of division points: G1 for dividing one side of the curve with the vertex: O therebetween into a plurality of ranges.
To Gn. Note that these division points: G1 to Gn
Is approximated by an arc having a constant radius of curvature: C1 to Cn as described later, and therefore, the dimension between each of the division points is obtained as follows. Since it affects the accuracy of the lens surface to be manufactured, it is determined according to the surface accuracy, curvature, and the like required for the ophthalmic lens to be manufactured.

Each of the division points G1 to Gn is usually specified by the X and Y coordinate values on the same coordinate axis as the basic equation.
There is no particular limitation, and there is no need to make the distance between the division points the same. Specifically, those division points: G1
For Gn, any of various division methods such as, for example, equal division on the X axis, equal angle division on the declination around the vertex: O, and exponential division can be adopted.

Then, after that, each range on the curve given by the basic equation, which is divided by each of the division points thus determined: G1 to Gn, is divided into a plurality of circular arcs having different curvatures: C1 to Cn. And the center points and the radii of curvature of the arcs C1 to Cn so that the normals of the arcs adjacent to each other coincide at the division points G1 to Gn located at the boundaries of the arcs. Ask for.

Hereinafter, a method of obtaining the center point and the radius of curvature of each of the arcs C1 to Cn will be described with reference to a specific example shown in FIG. In this specific example,
The sectional shape of the target curved surface is represented by a basic equation: Y = F (X) in which the Y axis is a symmetric axis and the vertex: O is located at the coordinate origin, and each division point: G1 to Gn
Is determined as an equally divided point on the X axis on such a curve.

The center point and the radius of curvature of each of the arcs C1 to Cn are sequentially determined from the apex: O side outward.

That is, when determining the center point of the first arc C1 located between the vertex O and the first division point G1 adjacent to the vertex O, first, the vertex O
Consider a string: l1 connecting the first division point: G1 and a vertical bisector: L1 of the string: l1. Then, the intersection of the perpendicular bisector: L1 with the axis of symmetry (Y axis) of the curve given by the basic equation: α1, the first arc:
The center point of C1 is determined. Further, the radius of curvature of the first arc: C1 is represented by the intersection: α1 and the vertex:
The distance between O and the first division point: G1 is obtained as R1.

Next, when obtaining the center point of the second arc C2 located between the first division point G1 and the second division point G2, first, the first division point G1 And a second division point: G2, consider a string: l2, such a string: l2
Vertical bisector: L2 is determined. The vertical bisector: L2 is composed of a first division point: G1 and a first arc: C1.
The center point of the second arc C2 is determined as the intersection point α2 intersecting with the straight line L1 ′ passing through the intersection point α1 as the center of curvature. The radius of curvature of the second arc C2 is determined as the distance R2 between the intersection point α2 and the first division point G1 or the second division point G2.

In the remaining plurality of arcs: C3 to Cn, two division points: Ga, G (a + 1) [where a = 2 to n-1] are located on both sides of each of the arcs. By repeating the same operation sequentially from inside to outside according to the operation for obtaining the intersection point: α2 and the distance: R2, the center point and the radius of curvature in each of the arcs C3 to Cn can be obtained. It is.

That is, an arc having the thus determined center point: α1 to αn and a radius of curvature: R1 to Rn:
In the case of C1 to Cn, division points adjacent to each other on a curve given by the basic equation: Y = F (X) are approximated by a circular curve having a constant curvature and connected. : By C1 to Cn, the target curve is
It can be realized approximately advantageously. In addition, this
Each arc: C1 to Cn is a target curve: Y = F
(X) is not always exactly the same,
For the sake of simplicity, in FIG.
Parts should be marked with parentheses.
You. "

In the case of the circular arcs C1 to Cn, the dividing points G1 to G, which are adjacent boundary points, respectively.
n, the directions of the normals coincide with each other. In other words, two arcs positioned on both sides of each of the division points: G1 to Gn: Ca, C (a +
1) has one common tangent at the dividing point: Ga which is the boundary point. Therefore, the curved surface constituted by the plurality of circular arcs: C1 to Cn does not have a discontinuous portion even at the boundary point between the circular arcs, and is a continuous surface at which the boundary point cannot be easily recognized. It is formed as a simple curve.

In the present invention, when an aspherical ophthalmic lens is manufactured by performing a cutting process with a predetermined cutting tool while rotating the ophthalmic lens material about one axis, the cutting tool is replaced with the ophthalmic lens material. By moving along the approximate curve represented by the arcs C1 to Cn determined as described above with the rotation axis of
The lens surface is cut and formed with an aspherical shape approximating a curved surface given as a rotating body about the axis of symmetry of a curve satisfying the basic equation.

That is, each of the division points G1 to G1 given on the above-mentioned basic equation on the lens surface of the ophthalmic lens material which is rotated about one axis.
A plurality of annular machined surfaces divided by the trajectory of the Gn about the rotation axis: S1 to Sn, in other words, each of the arcs: C
With respect to a plurality of annular processing surfaces: S1 to Sn appearing as trajectories around the rotation axis of 1 to Cn, axes perpendicular to the rotation axis of the ophthalmic lens material passing through the respective intersections: α1 to αn, respectively. Spherical cutting is performed by a cutting tool that can be moved with the above-mentioned distances R1 to Rn as radii as a turning axis.

More specifically, for example, when the present invention is applied to the cutting of a concave lens surface of a contact lens, it is moved on a base 10 by orthogonal coordinates X and Y as shown in FIG. Cutting tool 1 to be controlled
The contact lens material 18 is fixedly held by a chuck 20 with respect to a spindle 16 rotated by a rotation driving device (not shown) using a numerical control lathe 14 having The cutting tool 12 is rotated at high speed around the rotation axis 22.
Are obtained from the plurality of arcs obtained as described above: C1 to Cn
, The intended lens concave surface is cut and formed. When such a numerically controlled lathe is used, the cutting point of the cutting tool 12 is set to each of adjacent division points: G1 to G on the approximate curve.
In the interval n, the object is moved at a predetermined radius of curvature: Rn by using an orthogonal biaxial arc interpolation method.

The lens surface thus cut and formed is further polished, if necessary, to be finished.

Therefore, in the aspherical ophthalmic lens having the lens surface cut and formed as described above, the cross section including the vertex: O on the lens surface is formed on both radial sides of the vertex: O. It is composed of a plurality of arcs having different curvatures, which are positioned: C1 to Cn.
Each of these arcs: a division point as a boundary point between C1 and Cn: G
Since 1 to Gn have a common tangent,
On the lens surface provided as a rotating body about the axis of symmetry of such a cross section, a ridge-like or step-like discontinuous surface does not appear on a boundary line having different curvatures, and a continuous aspherical shape is advantageously used. It can be realized.

In the above description, a specific example of the case where the aspherical lens concave surface is formed by cutting according to the method of the present invention has been described. However, the present invention relates to an aspherical lens convex surface. It is needless to say that the present invention can be similarly applied to the case of forming by cutting. Also,
The configuration of the present invention is not to be construed as being limited to the specific examples in the specific examples described above and the examples described below, and the present invention is based on the knowledge of those skilled in the art.
Various changes, modifications, improvements, and the like can be made in embodiments, and any such embodiments are included in the scope of the present invention unless departing from the spirit of the present invention. Some things are, of course, obvious.

[0030]

As is clear from the above description, in the aspherical ophthalmic lens having the structure according to the present invention, the objective is achieved by a plurality of curved surfaces having a common tangent line on the boundary where the curvature changes. Since the lens surface approximating the aspherical shape is provided with a continuous curved surface shape, optical problems such as glare are not caused, and excellent wearability and visual acuity correcting performance are advantageously exhibited. You get it.

According to the method of the present invention, an aspherical lens constituted by a plurality of curved surfaces having a common tangent line on a boundary line where the curvature changes as described above, using a cutting apparatus similar to the conventional one. Aspherical ophthalmic lenses with surfaces can be easily manufactured, and various aspherical lens surfaces can be stably cut without the need to replace special members. It can be formed.

[0032]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS When a basic equation giving a desired sectional shape of a lens concave surface is expressed as an elliptic equation having a vertex curvature of 7.8 mm and an eccentricity of 0.5, a contact lens material having a diameter of 10 mm is used. In cutting and forming according to the method of the present invention, coordinate values of division points: G1 to G10 for dividing the curve given by such a basic equation at equal pitches on the X-axis are obtained, and the curve between these division points is approximated. Arc to do: C
Center coordinates of 1 to C10: α1 to α10 and radius of curvature:
R1 to R10 were determined. The results are shown in Table 1 below as examples.

In this embodiment, the vertex given by the basic equation is the coordinate origin, the symmetric axis of the curve is the Y axis, and one coordinate unit is 1 in both the X and Y directions.
mm.

[0034]

[Table 1]

[Brief description of the drawings]

FIG. 1 shows a process of obtaining a center coordinate and a center of curvature in an arc C1-Cn that approximates a curve between respective division points on a curve given by a basic equation when manufacturing an aspherical ophthalmic lens according to the method of the present invention. It is an explanatory view for explaining.

FIG. 2 is a schematic plan view showing a specific example of a cutting tool used for cutting a contact lens material when manufacturing an aspheric contact lens according to the method of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Base 12 Cutting tool 14 Numerical control lathe 16 Spindle 18 Contact lens material 20 Chuck 22 Rotation axis

Claims (2)

(57) [Claims] An aspherical ophthalmic lens in which at least one of a lens convex surface and a concave surface has an axisymmetric aspherical surface, wherein an axis of symmetry in the aspherical lens surface is defined as an aspherical lens. The cross section includes a plurality of arcs having different curvatures, C1 to Cn, respectively positioned on both sides in the radial direction with the vertex on the symmetry axis: O interposed therebetween, and the plurality of arcs: C1 to Cn. Division point located at the boundary of: G
1 to Gn are respectively located at points satisfying the basic equation of a curve that gives a desired cross-sectional shape of the aspherical ophthalmic lens, while the vertex: O and the vertex adjacent to the vertex: O An arc between one division point: G1 and C1 is
The intersection of the vertical bisector of the chord connecting the vertex: O and the first division point: G1 with the symmetry axis: an arc centered on α1, and the plurality of division points: G1 to G1 Gn, two division points adjacent to each other: Ga, G (a +
Each arc located between 1): C2 to Cn are respectively
Two adjacent dividing points: Ga, G (a + 1)
Vertical bisector of the string connecting the two and the two split points: G
a, G (a + 1), the apex: a dividing point located on the O side: Ga and an arc located adjacent to the dividing point: Ga:
Intersection with a straight line passing through the center point of Ca: αa: α (a +
An aspherical ophthalmic lens, characterized in that it is an arc centered on 1). 2. A lens having an ophthalmic lens material attached to a spindle which rotates about one axis, and a cutting tool which is moved around a rotation axis perpendicular to the rotation axis of the spindle, thereby cutting the lens convex and concave surfaces. A method of manufacturing an aspherical ophthalmic lens in which at least one lens surface has an axisymmetric aspherical shape, wherein a basic equation of a curve giving a desired sectional shape of the lens surface of the aspherical ophthalmic lens is provided. And determining a plurality of division points: G1 to Gn on the curve given by the basic equation, which divide one side of the curve sandwiching O into a plurality of ranges; A vertical bisecting of a chord connecting the vertex O of the curve given by the basic equation and the first division point G1 adjacent to the vertex O among the plurality of division points G1 to Gn The coordinates of the intersection: α1 at which the line intersects the symmetry axis of the curve given by the basic equation are determined, and the intersection: α1
And calculating a distance: R1 between the vertex: O or the first division point: G1; and a first division point: G1 among the plurality of division points: G1 to Gn; A vertical bisector of a chord connecting one division point: G1 and a second division point adjacent to the outside of G1 intersects a straight line passing through the first division point: G1 and the intersection point: α1. Intersection: The coordinates of α2 are obtained, and the intersection:
calculating a distance R2 between α2 and the first division point G1 or the second division point G2; and a first division point G1 of the plurality of division points G1 to Gn. Two division points adjacent to each other in the division points G2 to Gn that are located further outside: Ga, G (a
For +1), the same operation is repeatedly performed from inside to outside according to the operation for obtaining the intersection: α2 and the distance: R2, thereby obtaining the intersection: α3 to αn and the distance: R3 to Rn. And each processing surface divided by the rotation locus of the curve at the division point: G1 to Gn around the symmetry axis given by the basic equation on the lens surface of the ophthalmic lens material:
A step of cutting each of S1 to Sn with a cutting tool that can be moved by using each of the intersections: α1 to αn as a rotation axis and a distance: R1 to Rn as a radius. Manufacturing method of lens for use.