JP2859092B2 - How to design ophthalmic lenses - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for designing a lens surface shape of an eye such as a contact lens or an intraocular lens or a lens to be worn or buried in the eye (hereinafter referred to as an "ophthalmic lens"). The present invention relates to a method for designing an ophthalmic lens that can obtain a refractive power with high precision and is easy to manufacture.

[0002]

2. Description of the Related Art Conventionally, various types of ophthalmic lenses as described above have been proposed, including a single focus lens having a constant refractive power and a multifocal lens having a refractive power varied concentrically. I have.

Incidentally, a single-focus ophthalmic lens is generally designed to have a spherical shape in which both surfaces of the lens have a single curvature. In addition, a multifocal ophthalmic lens generally divides a lens surface into a plurality of concentrically positioned divided surfaces, and each of the divided surfaces has a spherical shape with a different curvature having a center point on the lens optical axis. Designed by giving.

However, in such a single-focus ophthalmic lens, since the influence of spherical aberration is not taken into consideration at all, the desired refractive power cannot be obtained at the peripheral portion of the lens where the influence of aberration is large, In some cases. Further, in the multifocal ophthalmic lens as described above, since a ridge-shaped discontinuous portion is formed at the boundary of each divided surface, the refractive power becomes discontinuous, and glare and the like are likely to occur, and the sufficient In addition to the inability to obtain optical performance, there is a problem that the feeling of wearing is poor.

[0005] The discontinuous portion formed in such a multifocal ophthalmic lens can be reduced by polishing, but such polishing is not only difficult and time-consuming, but also requires a long time. Polishing reduces the accuracy of the lens surface, and changes the tilt angle and coordinate values of the lens surface, so that the desired refractive power cannot be obtained.

On the premise that a manufacturing method using a cam member for guiding a cutting tool is adopted, it is also possible to design a multifocal ophthalmic lens in which the lens surface changes continuously in the radial direction. However, in order to manufacture such a multifocal ophthalmic lens, since the cam members must be replaced one by one according to the shape of each lens surface, the operation is extremely troublesome and requires a great deal of labor and time. In addition, it is impossible to stock all the cam members corresponding to various lens surface shapes, and in fact, the inclination angle and coordinate values of the lens surface are not realized as designed values. There is a problem that an ophthalmic lens having a high refracting power cannot be obtained.

[0007]

The present invention has been made in view of the above-described circumstances, and an object of the present invention is to prevent the influence of spherical aberration as much as possible and to improve the design of each design. It is an object of the present invention to provide a method for designing an ophthalmic lens that can advantageously realize a tilt angle and a coordinate value of a lens surface at a point as designed values and can obtain a target refractive power with high accuracy.

Another object of the present invention is to provide a method for designing an ophthalmic lens in which the occurrence of discontinuous portions on the lens surface is effectively prevented, and excellent optical performance and wearing feeling are exhibited. I do.

Still another object of the present invention is to provide a method of designing an ophthalmic lens which can be easily manufactured without using a cam member or the like.

[0010]

In order to solve such a problem, the feature of the present invention is as follows. (A) In a cross section including a lens optical axis of an ophthalmic lens, one lens surface shape and the one Determining a target refractive power at a plurality of reference points on the lens surface and a set point of the other lens surface on a predetermined reference axis; and (b) at the reference point adjacent to the reference axis, Obtaining a refracted ray of light incident on the reference point in a linear direction passing through the focal point by the one lens surface; and (c) converting the refracted light beam by the one lens surface into a ray parallel to the lens optical axis. Obtaining a tilt angle of the other lens surface to be refracted; (d)
Determining an intersection angle α between the normal line of the tangent line having the inclination angle of the other lens surface and the reference axis; and (e) setting the reference axis at the set point of the other lens surface on the reference axis. Intersecting angle: a step of obtaining an intersection of a straight line intersecting at β, β = (180 ° −α) / 2 and the refracted light beam by the one lens surface, and determining the intersection as one point on the other lens surface. (F) a set point of the other lens surface on the reference axis as an arc surface centered on the intersection of the reference axis with the normal of the tangent passing through one point on the other determined lens surface. (G) determining the shape of the other lens surface between the determined one lens point and the one point on the other lens surface; and (g) passing through the one point on the other lens surface determined in the step (e). Assuming that the normal of the tangent is the reference axis, A step of repeating the steps, in the design method of an ophthalmic lens comprising.

[0011]

In the method for designing an ophthalmic lens according to the present invention, the path of light rays incident on each reference point on one lens surface whose shape has already been determined is taken into consideration, and the path of such light rays is considered. The angle of inclination at a point on the other lens surface located on the passing path is determined so as to exert a desired refractive power on the light beam.

Therefore, according to the method of the present invention, the lens surface shape having the desired refractive power can be designed with high accuracy at each reference point of the ophthalmic lens, and the influence of the spherical aberration also occurs at the outer peripheral portion. Can be prevented as much as possible.

In the method for designing an ophthalmic lens according to the present invention, the lens surface shape between each set point on the other lens surface is an arc cross section passing through both set points, and both set points are formed. In (2), the inclination angle is determined to be the center of the intersection of the tangent to the tangent to the lens surface to give the desired refractive power.

Therefore, according to the method of the present invention, the other lens surface is designed as a plurality of divided surfaces each having an arc-shaped cross section, and the adjacent divided surfaces are all located at their boundaries. Since the design is made with an arc cross-section centered on the normal to the tangent to the lens surface at the set point located, no discontinuities will occur on those boundaries, and therefore the discontinuity of the refractive power The occurrence of parts is prevented, and an excellent wearing feeling can be exhibited.

Moreover, since each of the divided surfaces has an arcuate cross section, the cutting can be easily performed by turning the cutting tool around a predetermined axis without using a cam member or the like. In addition, by such a cutting process, the inclination angle and the coordinate value of the lens surface at each design point can be advantageously realized according to the design value, and the target refractive power can be obtained with high accuracy.

[0016]

Next, an example of designing a contact lens according to the method of the present invention will be described.

First, as shown in FIG. 1, the sectional shape of the lens inner surface 12 in the section including the lens optical axis 10 is determined. In addition, in the case of a contact lens, it is preferable that the shape of the lens inner surface 12 correspond to the shape of the corneal surface of the wearer in order to facilitate wearing and improve a feeling of wearing, for example, a spherical surface, an elliptical surface, or It is determined as a composite surface of an elliptical surface and a spherical surface or the like.

Further, a plurality of reference points are set on the determined cross section of the lens inner surface 12, and a desired lens refractive power to be exerted on a ray passing through each reference point, that is, at each reference point, Determine the desired refractive power. The plurality of reference points are set at portions having different target refractive powers, that is, at positions different in distance from the lens optical axis 10 on the cross section of the lens inner surface 12. In the present embodiment, it is assumed that a first reference point: P1 and a second reference point: P2 are set at points away from the lens optical axis 12 by ΔX1 and ΔX2.

Since the interval between these reference points is related to the accuracy of the obtained lens outer surface, it should be determined according to the shape of the lens outer surface of the target lens, the required curved surface accuracy, and the like. It is. Further, the method of determining each reference point position is not particularly limited, and it is not necessary to make the distances between the division points the same.

Further, using the lens optical axis 10 as a reference axis, the thickness T of the target lens on the lens optical axis 10 is determined. In addition, such a lens thickness: T
Is determined, the position (set point) G of the lens outer surface on the lens optical axis 10 is also determined.

Next, as shown in FIG. 1, from the focal point: O1 at the first reference point: P1 of the target lens, the light ray 14 incident on the first reference point: P1
The direction of the refracted ray 16 by the lens inner surface 12 is determined. The direction of the refracted light beam 16 is as follows: the refractive index of air: n1, the refractive index of the lens material: n2, and the light beam 14 at the first reference point P1.
Angle of incidence: θ1, and refracted ray 1 according to Snell's law
6 can be obtained by calculating the emission angle θ2 based on the following equation. θ2 = sin ⁻¹ {(n1 · sin θ1) / n2} (Equation 1)

Further, with respect to the refracted light beam 16 at the first reference point P1, an inclination angle θ4 of the lens outer surface for making the refracted light beam 16 an outgoing light beam 18 parallel to the lens optical axis 10 is determined. Angle of inclination of this lens outer surface:
θ4 can be calculated based on the following equation. θ4 = 90 ° −sin ⁻¹ [{M2 / (M1 + M2)}] (Equation 2) M1 = (cos θ3-n1 / n2) ² M2 = sin ² θ3 (where θ3 is the refracted ray 16) , Intersection angle with lens optical axis 10)

That is, the straight line 20 having such an inclination angle: θ4 represents a tangent of the outer surface of the lens on the optical path of the refracted light beam 16 to make the refracted light beam 16 an outgoing light beam 18 parallel to the lens optical axis 10. Become.

Next, as shown in FIG. 2, the normal 2 perpendicular to the tangent (straight line) 20 obtained as described above
Ask for 2. And the lens optical axis 10 of this normal 22
Angle of intersection with: Obtain α.

Further, the base angle β of the isosceles triangle having the intersection angle α as the apex angle is calculated based on the following equation. β = (180 ° −α) / 2 (Equation 3)

Then, as shown in FIG. 3, a straight line 24 whose intersection angle with the lens optical axis 10 is β is determined from a predetermined set point G of the lens outer surface on the lens optical axis 10, and further, as shown in FIG. The intersection point H1 of the straight line 24 and the refracted light beam 16 is obtained. Then, with respect to a normal line 22 of the tangent line 20 (see FIG. 2) passing through the intersection point H1, an intersection point Q1 between the normal line 22 and the lens optical axis 10 is determined.

That is, the intersection point Q1 thus obtained is given as the vertex of the isosceles triangle Q1GH1.

The lens outer surface 2 between the points G and H1
6 at two points G,
It is determined as an arc passing through H1.

That is, the lens outer surface 26 thus determined is orthogonal to the normal 22 at the intersection point H1, and its inclination angle is set to θ4 (see FIG. 1). Accordingly, the parallel light beam incident on the intersection H1 on the lens outer surface 26 passes through the first reference point P1 on the lens inner surface 12 and reaches the focal point O1, and the intersection H1 on the lens outer surface 26 and At the first reference point P1 on the lens inner surface 12, the desired refractive power is given.

Subsequently, the same operation as that shown in FIGS. 1 to 4 is repeated toward the outer peripheral side of the lens, thereby sequentially determining the shape of the outer surface 26 of the lens. Hereinafter, a procedure for determining the shape of the lens outer surface 26 corresponding to between the first reference point P1 and the second reference point P2 of the lens inner surface 12 will be briefly described with reference to FIGS.

As shown in FIG. 5, the intersection point H1 of the already determined lens outer surface 26 is set as a set point, and the normal 22 passing through the set point H1 is regarded as a reference axis. This is performed by performing the above-described operation.

Specifically, first, as shown in FIG. 5, the light beam 1 incident on the second reference point: P2 from the focal point: O2 at the second reference point: P2 of the target lens.
For 4 ', the direction of the refracted ray 16' by the lens inner surface 12 is determined according to (Equation 1). Note that the focus: O2 at the second reference point: P2 is the same as the first reference point:
Focus at P1: It is not necessary to match O1.

Further, with respect to the refracted ray 16 'at the reference point P2, an inclination angle θ4' of the lens outer surface for obtaining the refracted ray 16 'as an exit ray 18' parallel to the lens optical axis 10 is determined. The inclination angle θ4 ′ of the lens outer surface can be calculated according to the above (Equation 2).

Next, as shown in FIG. 6, a straight line having the inclination angle θ4 ′ obtained as described above (in order to convert the refracted ray 16 ′ into the exit ray 18 ′ parallel to the lens optical axis 10). A normal line 22 'orthogonal to the tangent line 20' of the lens outer surface on the optical path of the refracted ray 16 'is obtained. Then, an intersection angle α ′ of the normal 22 ′ with the reference axis 22 is obtained, and the base angle β ′ of the isosceles triangle having the intersection angle α ′ as the apex angle is calculated according to (Equation 3). .

Thereafter, as shown in FIG. 7, a predetermined set point of the lens outer surface on the reference axis 22 is determined as follows:
From H1, a straight line 2 whose intersection angle with respect to the reference axis 22 is β ′
4 'is obtained, and the intersection of the straight line 24' and the refracted ray 16 'is defined as H2. Then, with respect to a normal line 22 'of the tangent line 20' (see FIG. 6) passing through the intersection point H2, an intersection point Q2 between the normal line 22 'and the reference axis 22 is obtained.

Then, the shape of the lens outer surface 26 between the points H1 and H2 is changed to the two points H around the intersection Q2.
1, determined as an arc passing through H2.

That is, the lens outer surface 26 thus determined is orthogonal to the normal 22 'at the point H2, and its inclination angle is set to θ4' (see FIG. 5). From this, the parallel light beam incident on the point H2 on the lens outer surface 26 becomes the reference point P on the lens inner surface 12.
2, the focal point O2 is reached, and both the set point H2 on the lens outer surface 26 and the reference point P2 on the lens inner surface 12 are given the desired refractive power.

Hereinafter, although the description is omitted, the shape of the lens outer surface 26 is changed over the entire surface by repeating the above-described operation for the reference point set radially outward of the lens. By deciding, the shape of the contact lens is designed.

In the contact lens designed as described above, the lens inner surface 1 whose shape has already been determined
Reference points 2 on the outer surface 26 of the lens so that a desired refractive power can be exerted on rays incident on P1 and P2.
Since the slopes of the corresponding points H1 and H2 above are determined, the lens surface shape having the intended refractive power can be designed with high accuracy at the points P1, P2, H1 and H2. The influence of spherical aberration on the outer peripheral edge can be prevented as much as possible.

The lens outer surface 26 designed as described above has an arc surface G to H1 centered on the point Q1.
And at a point H1 where the arc surfaces H1 to H2 centered at the point Q2 are connected, the two arc surfaces have a common tangent and are connected with a continuous curved surface. That is, the lens outer surface 26 is constituted by a plurality of spherical divided surfaces having different centers from each other, and the inclination angles of the two divided surfaces are made to coincide with each other at a connection portion of the divided surfaces. Thereby, a step, a ridge-shaped portion, or a discontinuous portion of refractive power in such a connection portion is prevented from being generated, and an excellent feeling of wearing can be exhibited.

Moreover, since the lens outer surface 26 designed as described above is constituted by a plurality of circular cross sections, the cutting tool can be rotated around the points Q1 and Q2 without using a cam member or the like. It can be easily cut by turning, etc., and by such cutting, the inclination angle and coordinate value of the lens surface at each design point can be advantageously realized as designed values, and the desired refraction can be achieved. The force can be obtained with high precision.

Incidentally, in order to add the additional power shown in FIG. 9 to the basic lens having a refractive index (n2) of the lens material of 1.44 and a refractive index of -5.00 Dptr. Are shown in Table 1 below as XY coordinate values with the set point on the outer surface of the lens: G as the origin. In addition, an elliptical cross section having a vertex radius of curvature of 7.8 mm and an eccentricity (e) of 0.4 is set on the inner surface of the lens, and the lens thickness on the lens optical axis (Y axis) is set to 0.
It was set to 16 mm. In addition, a reference point (Bx,
By) were set at 20 at intervals of 0.2 mm in the lens radial direction (X-axis direction). Further, in Table 1, I represents the inclination of each set point (Fx, Fy) on the outer surface of the lens, and indicates the inclination of the normal to the lens optical axis at each set point.

[0043]

[Table 1]

As described above, as one embodiment of the present invention, the case where the shape of the lens inner surface is determined in advance so as to obtain a desired lens refractive power after the shape of the lens inner surface is determined has been described. The invention, on the contrary, also determines the shape of the lens outer surface after determining the shape of the lens outer surface, so that the desired lens refractive power is obtained.
Similarly, it can be applied. About the example,
Add a description.

First, as shown in FIG. 10, in the section including the lens optical axis 30, the sectional shape of the lens outer surface 32 is determined, and the determined lens outer surface 32 is determined.
A plurality of reference points (only one reference point: P located adjacent to the lens optical axis 30 is shown in the figure) are set on the cross section of, and the target refractive power at each reference point is determined. Also, with the lens optical axis 30 as a reference axis, the thickness of the target lens on the lens optical axis 30: T,
Subsequently, the position (set point) of the lens inner surface on the lens optical axis 30: G is determined.

Next, with respect to the light beam 34 incident from the lens outer surface 32 side in a linear direction passing through the focus point O at the reference point P of the objective lens, the direction of the refracted light beam 36 by the lens outer surface 32 of the incident light beam 34 Ask for. The direction of the refracted light beam 36 can be obtained in the same manner as in the above (Equation 1).

Further, an inclination angle of a tangent line 40 on the inner surface of the lens for obtaining the refracted light beam 36 as an emitted light beam 38 parallel to the lens optical axis 30 is obtained. The inclination angle of the tangent line 40 can be calculated in the same manner as in (Equation 2).

Next, as shown in FIG. 11, the lens on the optical path of the refracted light beam 36 for converting the refracted light beam 36 obtained as described above into an exit light beam 38 parallel to the lens optical axis 30. A normal 42 perpendicular to the tangent 40 of the inner surface is obtained. Then, the intersection angle α between the normal 42 and the lens optical axis 30 is obtained, and the base angle β of the isosceles triangle having the intersection angle α as the apex angle is calculated.

Thereafter, as shown in FIG. 12, a straight line 44 whose intersection angle with the lens optical axis 30 is β is determined from a predetermined set point G of the inner surface of the lens on the lens optical axis 30. The point of intersection of the straight line 44 and the refracted light ray 36 is denoted by H. Then, with respect to a normal 42 of the tangent 40 (see FIG. 11) passing through the intersection H, an intersection Q between the normal 42 and the lens optical axis 30 is determined.

The lens inner surface 46 between the points G and H
Is determined as an arc passing through the two points G and H with the intersection point Q as the center.

Subsequently, as described above, the same operation as that shown in FIGS. 10 to 13 is performed by setting the already determined intersection point H of the lens inner surface 46 as a set point and setting the set point H to the set point. The normal line 42 passing through (see FIG. 13) is regarded as a reference axis, and is repeated toward the outer periphery of the lens.
Are sequentially determined.

Therefore, it is possible to determine the shape of the lens inner surface 46 by the same method as in the first embodiment, and thereby to obtain the desired refractive power at each reference point as in the first embodiment. Is set with high accuracy,
It is possible to design a lens surface shape that can be easily cut and can prevent the occurrence of a step, a ridge-shaped portion, and a discontinuous portion of refractive power.

Although the embodiments of the present invention have been described above in detail, these are literal examples, and the present invention is not limited to these specific examples.

For example, in the above embodiment, according to the present invention,
Although the case where a contact lens is designed has been described, the present invention can also be similarly applied to the design of various ophthalmic lenses such as an intraocular lens.

The present invention is not limited to an ophthalmic lens having a refractive power of (+), but has various refractive powers such as an ophthalmic lens having a refractive power of (-), a single focus lens, and a multifocal lens. It is applicable when designing an ophthalmic lens.

In addition, although not enumerated one by one, the present invention
Based on the knowledge of those skilled in the art, various changes, modifications, improvements, and the like can be made, and unless such embodiments depart from the spirit of the present invention.
It goes without saying that both are included in the scope of the present invention.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram for explaining one process of designing a contact lens as one embodiment of the present invention.

FIG. 2 is an explanatory diagram for explaining a contact lens design process following the process shown in FIG. 1;

FIG. 3 is an explanatory diagram for explaining a contact lens design process subsequent to the process shown in FIG. 2;

FIG. 4 is an explanatory diagram for explaining a contact lens design process following the process shown in FIG. 3;

FIG. 5 is an explanatory diagram for explaining a contact lens design process subsequent to the process shown in FIG. 4;

FIG. 6 is an explanatory diagram for explaining a contact lens design process following the process shown in FIG. 5;

FIG. 7 is an explanatory diagram for explaining a contact lens design process following the process shown in FIG. 6;

FIG. 8 is an explanatory diagram for explaining a contact lens design process subsequent to the process shown in FIG. 7;

FIG. 9 is a graph showing a set value of a refractive power when an outer surface of a contact lens is actually designed according to the steps shown in FIGS.

FIG. 10 is an explanatory diagram for explaining one process of designing a contact lens as another embodiment of the present invention.

FIG. 11 is an explanatory diagram for explaining a contact lens design process following the process shown in FIG. 10;

FIG. 12 is an explanatory diagram for explaining a contact lens design process following the process shown in FIG. 11;

FIG. 13 is an explanatory diagram for explaining a contact lens design process subsequent to the process shown in FIG. 12;

[Explanation of symbols]

 10, 30 Lens optical axis 12, 46 Lens inner surface 14, 34 Incident light beam 16, 36 Refracted light beam 18, 38 Outgoing light beam 20, 40 Tangential line 22, 42 Normal line 24, 44 Straight line 26, 32 Lens outer surface

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int. Cl. ⁶ , DB name) G02C 7/00-7/04 G02B 3/00-3/06

Claims (1)

(57) [Claims] (A) In a cross section including a lens optical axis of an ophthalmic lens, one lens surface shape, target refractive power at a plurality of reference points on the one lens surface, and a predetermined reference axis Determining a set point of the other lens surface above; and (b) at the reference point adjacent to the reference axis,
Obtaining a refracted ray of light incident on the target lens in a linear direction passing through the focal point at the reference point by the one lens surface; and (c) converting the refracted light beam by the one lens surface to the lens optical axis. (D) obtaining an inclination angle of the other lens surface which refracts the light beam parallel to the above, and (d) obtaining an intersection angle α between a normal to a tangent having the inclination angle of the other lens surface and the reference axis. (E) a straight line that intersects with the reference axis at the set point of the other lens surface on the reference axis at an intersection angle: β, β = (180 ° −α) / 2, and a refracted ray by the one lens surface. (F) determining a point of intersection between the tangent line normal and the reference axis passing through the determined point on the other lens surface. As an arc surface centered on the intersection, Determining the other lens surface shape between a set point of the other lens surface on a reference axis and the determined one point on the other lens surface; and (g) performing the step (e). Considering the normal of the tangent passing through one point on the other determined lens surface as the reference axis,
Repeating the steps (b) to (f).