JP2019175269A - Lens model generating method, and method of generating lens for eyeglass - Google Patents

Abstract

To provide an eyeglass lens generating method which prevents a design surface from being deformed due to rotational operations and the like and prevents calculation therefor from being complexed.SOLUTION: The present invention relates to a method of generating a lens model having a convex plane 10 and a concave plane 20. The method has a step of defining a convex plane data of parametric type indicating a shape of the convex plane 10 based on the prescribed information, a step of defining a concave plane data consisting of data of parametric type indicating a shape of the concave plane 20 in accordance with the prescribed information, and a positional relation defining step of defining positional relationship between the convex plane 10 and the concave plane 20 in accordance with the prescribed information.SELECTED DRAWING: Figure 5

Description

  The present disclosure relates to a method for creating a lens model having a first surface and a second surface, and a method for creating a spectacle lens using the lens model.

Conventionally, when designing a spectacle lens, the shape of the spectacle lens is calculated based on prescription data for design, and the surface shape of the spectacle lens is expressed by z = f (x, y) as shown in FIG. It was recorded by the represented nonparametric data. The non-parametric type data discretely specifies the surface shape of the spectacle lens by a set of z-axis values at the respective lattice points of the x and y coordinates. Since the non-parametric surface shape data is in the form of z = f (x, y ), there is an advantage that the surface position identification and the differential calculation at the position are simple.

  However, when using non-parametric type data, when moving or rotating, the surface shape of the spectacle lens is estimated by regenerating the plane between the lattice points by the least square method or the like. FIG. 9 is a distribution diagram showing astigmatism when the surface shape of the spectacle lens expressed by nonparametric data is rotated by 45 degrees, (A) shows astigmatism before rotation, B) shows astigmatism after rotation. As shown in FIG. 9, when non-parametric data is used, there is a problem that the design surface is deformed when a rotation operation is performed.

  Further, in non-parametric data, it is necessary to treat the surface shape as a rectangular region. For this reason, when the surface shape of a spectacle lens having a large curvature is handled, as shown in FIG. There is a problem that becomes complicated.

  The present invention has been made in view of the above-described problems, and provides a method for creating a spectacle lens model in which a design surface is not deformed even when a rotation operation or the like is performed, and the calculation is not complicated. With the goal.

A lens model creation method according to an embodiment of the present invention is a lens model creation method having a first surface and a second surface, and is parametric first surface data indicating the shape of the first surface based on prescription information. A first definition S that defines the second surface data consisting of parametric data indicating the shape of the second surface based on the prescription information, a first surface and a second based on the prescription information A positional relationship definition S that defines a positional relationship with the surface.
According to the above embodiment, since the first surface and the second surface are defined by parametric data, the design surface is not deformed even if a rotation operation or the like is performed. Even in the region, the shape does not warp, and the calculation is not complicated.

  According to the present invention, it is possible to provide a method for creating a spectacle lens model that does not cause complicated design even if a rotating operation or the like is performed, and that does not complicate calculation.

It is a flowchart which shows the production method of the spectacle lens model by one Embodiment of this invention. It is a figure which shows a mode that the parametric type convex surface data and concave surface data which define the shape of a convex surface and a concave surface are produced. It is a figure for demonstrating the method to convert nonparametric type curve data into parametric type curve data. The figure shows an example of a quadratic curve. It is a figure for demonstrating the method to convert nonparametric type curved surface data into parametric type curved surface data. It is a figure which shows a mode that the positional relationship of a convex surface and a concave surface is defined based on the thickness d of a lens, and the amount of prisms (angle D). It is a figure which shows a mode that a convex surface and a concave surface are arrange | positioned, (A) is the figure which looked at the convex surface from the front, (B) is sectional drawing of a prism direction. It is a figure which shows a mode that the line segment which defines a side surface from a convex surface is penetrated to a concave surface, and the physical coordinate and parameter coordinate of the intersection of each surface and a line segment are calculated. It is a figure which shows the nonparametric type data which show the surface shape of a spectacle lens. It is a distribution diagram showing astigmatism when the surface shape of a spectacle lens expressed by non-parametric data is rotated by 45 degrees, (A) shows astigmatism before rotation, and (B) shows rotation. The subsequent astigmatism is shown. It is a figure which shows a mode that the shape which curved in the area | region (area | region enclosed with the circle | round | yen) outside the spectacle lens produced in nonparametric type data.

Hereinafter, an embodiment of a method for creating a spectacle lens model of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a flowchart illustrating a method for creating a spectacle lens model according to an embodiment of the present invention. First, a patient's eye is examined in ophthalmology or the like, and prescription information for spectacle lenses is created. The spectacle lens prescription information includes concave and convex shape information (design values), spectacle lens thickness, and prism direction and amount of the spectacle lens. As shown in FIG. 2, in order to create a spectacle lens model, first, parametric type convex surface data and concave surface data that define the shapes of the convex surface 10 and the concave surface 20 based on prescription information on the convex surface and the concave surface are generated (S101). , Corresponding to the first and second definition steps). The parametric surface only needs to be larger than the diameter of the actual spectacle lens, and the shape is not limited.

The parametric surface is, for example, the following B-spline surface


Defined by


m + 1: Number of control points in the u direction
n + 1: Number of control points in the v direction
k: Order of curve in u direction
l: Curve order in the v direction
_{knot vector {u 0, u 1} , u 2, ···, u m + k}: u 0 ≦ u 1 ≦ u 2 ≦ ··· becomes _{≦ u m + k m + k} + 1 single parameter defined by the node A vector sequence defining coordinates.
knot vector {v ₀ , v ₁ , v ₂ ,..., v _{n + l} }: Parameters defined by n + l + 1 nodes satisfying v ₀ ≦ v ₁ ≦ v ₂ ≦ ... ≦ v _{n + l} A vector sequence defining coordinates.

In addition, what is necessary is just to convert into the parametric type data as follows, when the convex surface and concave surface which are determined by prescription information are nonparametric type data.
First, consider converting non-parametric curve data into parametric curve data. FIG. 3 is a diagram for explaining a method of converting non-parametric curve data into parametric curve data. In the figure, an example of a quadratic curve is shown.

For example, a parametric B-Spline curve can be expressed as follows.


here,


n + 1: Total number of De Boor control points
k: Order
_{knot vector {u 0, u 1} , u 2, ···, u n + k}: u 0 ≦ u 1 ≦ u 2 ≦ ··· ≦ u n + k to become n + k + 1 single parameter defined by the node A vector sequence defining coordinates.

Here, a B-spline curve that interpolates a curve given by non-parametric data can be defined as follows.


In the above formula (1),
n + 1: Total number of De Boor control points
knot vector: {x ₀ , x ₁ , x ₂ , x ₃ , ..., x _{n + k} }
It is.

Then, d _{i in} equation (1) is
And the y coordinate of the de Boor control point.

Therefore, equation (1) is


It becomes.

The x coordinate of the de boor control point is given by Greville abscissae (WJ Gordon and RFRiesenfeld, B-Spline curves and surfaces, Computer Aided Geometric Design, pages 95-126, Academic Press, Inc. 1974). It is established approximately.

Therefore, non-parametric curve
If the knot vector is given, the coordinates of the de boor control point can be calculated by the equations (2) and (3).

Next, consider converting a non-parametric surface to a parametric surface. FIG. 4 is a diagram for explaining a method of converting non-parametric surface data into parametric surface data. A B-spline surface that interpolates a surface given by nonparametric data can be defined as follows.


m + 1: Total number of de Boor control points in the x direction
n + 1: Total number of de Boor control points in the y direction
k: Order of curve in x direction
l: Order of curve in y direction
knot vector: {x ₀ , x ₁ , x ₂ , x ₃ , ..., x _{m + k} }
knot vector: {y ₀ , y ₁ , y ₂ , y ₃ , ..., y _{n + l} }

Here, it is assumed that the parametric coordinate system of u and v coincides with the x and y coordinate system.


Then, the following formula is approximately established by the relationship of Greville abscissae.


As a result, de Boor control points can be calculated, and a non-parametric curved surface can be converted into a parametric curved surface.

  Next, based on the actual shape conditions, that is, the lens thickness d and the prism amount (angle D), as shown in FIG. 5, the positional relationship between the convex surface and the concave surface is defined (S103, positional relationship definition step) Equivalent)).

  6A and 6B are views showing a state in which a convex surface and a concave surface are arranged. FIG. 6A is a diagram of the convex surface viewed from the front, and FIG. 6B is a sectional view in the prism direction. The prism direction P is specified by an angle θ around the prism reference point R. In this section in the prism direction, as shown in FIG. 6B, an axis A inclined by an angle D corresponding to the prism amount from the normal direction n at the prism reference point R of the convex surface 10 is considered. Then, the normal line of the concave design center O coincides with this axis A, and the distance between the design center O of the concave surface 20 and the prism reference point R of the convex surface 10 is the specified thickness d with respect to the convex surface 10. The concave surface 20 is disposed. That is, the moving and rotating process is performed on the parametric curved surface data indicating the concave surface 20.

  Next, in order to determine the lens shape, as shown in FIG. 7, a line segment defining a side surface from the convex surface 10 is passed through the concave surface 20, and the physical coordinates and parameter coordinates of the intersection of each surface and the line segment Is calculated (S105).

  Next, a parametric curve that smoothly connects the intersections calculated on the convex surface and the concave surface is defined. At this time, the parametric curve created by the convex surface and the concave surface is determined so that the order and the knot vector are the same (S107).

  Next, the side surface of the lens model is defined as a ruled surface from the parametric curve created by the convex surface and the concave surface, and is defined by an annular curved surface (corresponding to S109, side surface defining step).

  Next, as necessary, new parametric surfaces indicating the regions within the closed curve defined by the intersection of the convex and concave surfaces and the annular curved surface are created. Specifically, the lens surface in the convex (or concave) closed curve is divided into a large number of triangular surfaces. Next, parametric data is generated using a method such as Barycentric Transform to create a new parametric surface (S111, corresponding to a closed region defining step).

  The spectacle lens model data created as described above is input to a processing device such as a grinding device for grinding a spectacle lens blank, for example. Then, the spectacle lens blank is created by processing the spectacle lens blank such as grinding and polishing by the processing apparatus.

According to this embodiment, the following effects are produced.
Since the data indicating the shape of the convex surface and the concave surface is parametric data, the accuracy of the shape does not deteriorate even if the data is moved or rotated. Parametric data is also used in the data format of a CAD or 3D printer, so that data can be input / output to / from the CAD or 3D printer.

  Further, since the data indicating the shape of the convex surface and the concave surface is parametric data, even a spectacle lens having a large curvature does not cause a warped portion in the lens model.

  Further, since new parametric data indicating the shape of the region within the closed curve on the convex surface and the concave surface is created in S111, only the data of the spectacle lens region alone can be handled. As a result, there is no inconvenience that a warped part occurs in a region other than the spectacle lens.

Hereinafter, the manufacturing method of the mold for the spectacle lens of the present disclosure will be summarized.
One embodiment of the present disclosure is a method of creating a lens model having a convex surface 10 and a concave surface 20, the step of defining parametric convex surface data indicating the shape of the convex surface 10 based on prescription information, and a concave surface based on prescription information A step of defining concave surface data made up of parametric data indicating the shape of 20 and a positional relationship defining step of defining the positional relationship between the convex surface 10 and the concave surface 20 based on prescription information.

10 Convex 20 Concave

Claims (7)

A method of creating a lens model having a first surface and a second surface,
A first definition step of defining parametric first surface data indicating the shape of the first surface based on prescription information;
A second definition step of defining second surface data comprising parametric data indicating the shape of the second surface based on the prescription information;
A lens model creating method comprising: a positional relationship defining step for defining a positional relationship between the first surface and the second surface based on the prescription information.   The lens model creation method according to claim 1, further comprising a side surface defining step of defining a side surface of the lens model by an annular curved surface passing through the first surface and the second surface.   The lens model creation method according to claim 2, further comprising a closed region defining step of defining parametric data indicating each region surrounded by the annular curved surface of the first surface and the second surface.   4. The lens model according to claim 1, wherein the positional relationship defining step defines a positional relationship between the first surface and the second surface based on a lens thickness and a prism amount. 5. How to make.   The lens model creation method according to claim 4, wherein in the positional relationship defining step, the first surface or the second surface is inclined by an angle corresponding to the prism amount.   The lens model creation method according to claim 1, wherein the first surface data and the second surface data are defined as parametric B-spline curved surfaces.   A spectacle lens creation method in which a spectacle lens is created by processing based on the lens model created by the lens model creation method according to claim 1.