JP2001018233A - Method and device for producing mold for lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a mold for forming a lens having two different curved surfaces with high precision at a low cost. SOLUTION: The mold for forming a lens having different curved surfaces 5, 3, in which the outer peripheral part and the inside part are continued through inflection points 4, is produced by moving a tool while rotating molding material and by cutting or grinding the same. In the production method, after the curved surface of the outer peripheral part is cut or ground up to the inflection points 4, the above-mentioned tool is retracted from the predetermined cutting or grinding face of the curved surface of the inside part. After the tool is made to again pass the inflection points 4, the curved surface of the inside part is cut or ground.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel method for manufacturing a lens mold and an apparatus for manufacturing a lens mold. More specifically, the present invention relates to a technique for manufacturing a lens molding die having two different curved surfaces with high accuracy and at low cost.

[0002]

2. Description of the Related Art A lens having an optical aperture provided with a spherical surface having no focal point outside an optically effective surface, a so-called bifocal lens having an inner curved surface and an outer curved surface each having a different focal point, and the like. There is a lens in which a portion is formed by different curved surfaces that are continuous through a bending point.

[0003]

When there is another curved surface outside one curved surface, even if the curved surface is continuous at a boundary (bending point), generally, the next curved surface is determined by differentiating one curved surface. Is impossible, and if such an indifferentiable point exists, it is impossible to continuously process both sides of the bending point by a normal curved surface processing machine. In such a case, after processing the first curved surface up to the bending point, the machine must be stopped once, the second curved surface must be reprogrammed, and then the second curved surface must be processed. For this reason, extra setup man-hours are required, which not only takes time to manufacture, but also increases costs.

Therefore, when manufacturing a large number of such dies, only the first curved surface is continuously processed to reduce the number of programming steps, and then the second curved surface is continuously processed. Take the method of processing. However, according to this method, before processing the second curved surface, the work (mold material) is once removed from the machine, and as a result, eccentricity occurs between the two curved surfaces, and the accuracy is reduced. There is a problem that it causes the deterioration of.

Accordingly, an object of the present invention is to manufacture a lens molding die having two different curved surfaces with high precision and at low cost.

[0006]

In order to solve the above-mentioned problems, a method of manufacturing a lens mold according to the present invention is to cut or grind a curved surface of an outer peripheral portion to the above-mentioned bending point, and then cut or grind the tool to a curved surface of an inner portion. The tool is retracted from the surface to be ground, the tool is passed through the bending point again, and then the inside curved surface is cut or ground.

Therefore, in the manufacturing method of the lens mold of the present invention, since the cutting or grinding is performed firmly up to the bending point and the tool is passed through the bending point again after retreat, the bending point is formed reliably. Therefore, cutting or grinding can be performed by a continuous program.

Further, the apparatus for manufacturing a lens mold according to the present invention comprises:
In order to solve the above-described problems, a mold material rotating unit that rotates the mold material and a tool that cuts or grinds the rotating mold material by moving a locus defined by a program given in advance. An apparatus for manufacturing a lens mold for manufacturing a lens molding die having a different curved surface in which an outer peripheral portion and an inner portion are continuous through a bending point, wherein the program has the outer peripheral curved surface described above. After cutting or grinding to the inflection point, the tool is retracted from the cutting or grinding surface of the inner curved surface, and then the tool is passed through the inflection point again to cut or grind the inner curved surface. Things.

Therefore, in the manufacturing apparatus of the lens mold of the present invention, the cutting or grinding is performed firmly up to the bending point, and after the retreat, the tool is passed again through the bending point, so that the bending point is reliably formed. Therefore, cutting or grinding can be performed by a continuous program.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a method for manufacturing a lens mold and a device for manufacturing a lens mold according to the present invention will be described below with reference to the accompanying drawings.

The illustrated embodiment is directed to the present invention, in which a second focal point having no focal point outside a first aspheric surface which is an optically effective surface is used.
This is applied to the manufacture of a mold for molding a lens with an optical aperture having an aspheric surface.

FIG. 1 shows Example 1 of a lens mold manufactured by the present invention.

The mold 1 has a lens forming surface 2 formed thereon. The lens forming surface 2 includes a second aspherical surface 3 corresponding to the aspherical surface of the optically effective surface of the lens, and the first aspherical surface. 3 has a second aspherical surface 5 which is continuous with the bending point 4 and corresponds to the aspherical surface as an optical aperture of the lens. As shown in FIG. 2, these aspheric surfaces 3 and 5 have, for example, a function f (x)
= First aspherical surface 3 and g (x) = second aspherical surface 5. The intersection (boundary) between f (x) and g (x) is B, and this is the bending point 4.

For example, when cutting, a cutting tool (bite) is moved from the outside to a point B along a curve g (x), and from the point B, a point y = 0 along a curve f (x). If the tool is moved to a position where the first aspherical surface 3 and the second aspherical surface 5 are continuous with each other, it is impossible to make the cutting tool perform such a movement.

Therefore, in the present invention, after moving the cutting tool along the curve g (x) to the point B, the cutting tool is retracted from the curve f (x) = (cutting surface of the first aspherical surface 3). And then pass curve B again through point B
It is moved along (x).

By moving the cutting tool as described above, the bending point 4 is reliably formed, so that cutting can be performed by a continuous program.

Next, a description will be given of a specific method of calculating the moving locus of the cutting tool.

As shown in FIG. 3, x1 from the point B in the x direction.
And points on f (x) separated by x2 (both about several tens of μm) are A1 and A2, and points on g (x) separated by x1 and x2 in the x direction are C1 and C2 ( (See FIG. 3).

Next, as shown in FIG.
An arc A passing through 2, B and an arc C passing through three points C1, C2, B are obtained (see FIG. 4).

Next, as shown in FIG. 5, a point on the arc A away from the point B by x '(about several tens of μm) in the x direction is represented by A', and a point on the arc A is represented by x 'in the x direction. A point on the distant arc C is defined as C '(see FIG. 5).

Therefore, as shown in FIG. 6, the trajectory of the cutting tool (bite) 6 of the aspherical surface processing machine (lens mold manufacturing apparatus) is represented by C1, C2, B, C ', A', B, and A2. If programming is performed in the order of → A1, machining can be continuously performed from the second aspherical surface 5 to the first aspherical surface 3 with a halfway retreat period therebetween without stopping the machine. In the above trajectory, the portion B → C ′ (→ A ′) is referred to as a “retreat trajectory”, and the portion A ′ → B is referred to as a “re-entry trajectory”.

In the above description, the tool is a cutting tool (cutting tool).
A grinding tool will be used.

The trajectory (retreat trajectory) with which the tool retreats from the planned cutting surface of the first aspherical surface 3 is changed to the second aspherical surface 5 (g).
(X) two points C1 taken on the minute part on the bending point B side,
A trajectory taken on the inner extension of the arc C passing through the three points C2 and the inflection point B, and immediately before the cutting tool 6 again passes through the inflection point B and moves on the first aspheric surface 3 (f (x)). The outer extension of the arc A passing through two points A1 and A2 and the three points B in which the (re-entry trajectory) is taken on the minute part on the bending point B side of the first aspheric surface 3 (f (x)) I took it on the line, but this was the first
The trajectory is not limited to the above, as long as the trajectory is such that the cut surface of the aspheric surface 3 can be retracted and can smoothly move to the curve f (x) through the bending point B.

For example, each aspheric surface 3 (f
(X)) It may be applied to an extension beyond the bending point B of 5 (g (x)). However, in this case, each aspheric surface 3,
5 has an inflection point in the vicinity of the bending point B or in the vicinity thereof, there is a case where the cutting is performed beyond the cut surface of the first aspheric surface 3 or the cut surface of the second aspheric surface 5. You need to be careful.

In this regard, if the trajectory is taken on the arcs A and C described above, the cut surface of the first aspheric surface 3 and the cut surface of the second aspheric surface 5 can be reliably avoided.

It is to be noted that in order to surely retreat the to-be-cut surface of the first aspheric surface 3 and the already-cut surface of the second aspheric surface 5,
There are several alternatives to the arcs A and C described above.

For example, on the inside extension of the tangent of the minute part of the second aspherical surface 5 on the bending point B side, or on the outside extension of the tangent of the minute part of the first aspherical surface 3 on the bending point B side. May be.

The retreat trajectory and the re-entry trajectory are not limited to one kind, but may be used in combination of two kinds. For example, using an extension of the curve g (x) for the retreat trajectory (when there is no inflection point near the inflection point B),
By appropriately combining the above-described trajectories, such as using the above-described arc A for the re-entry trajectory, the one most suitable for forming the curved surface can be selected.

In the above embodiment, the curved surface to be cut is described as an aspherical surface. However, this does not mean that the curved surface in the present invention is limited to an aspherical surface.

The mold manufactured according to the present invention comprises:
It can be widely used as a mold for various lenses, and is not limited to an aspherical lens mold having an optical aperture.

In addition, the shapes and structures of the respective parts shown in the above-described embodiments are merely examples of the specific embodiments to be carried out when carrying out the present invention, and the technical scope of the present invention is not limited thereto. Is not to be construed as limiting.

[0032]

As is apparent from the above description, the method for manufacturing a lens mold according to the present invention is suitable for molding a lens having a different curved surface in which an outer peripheral portion and an inner portion are continuous through a bending point. A method of manufacturing by moving a tool while rotating a mold material and cutting or grinding a mold, wherein the outer surface curved surface is cut or ground to the bending point and then the tool is cut or ground on an inner surface curved surface. The inner surface curved surface is cut or ground after the tool is retreated from the predetermined surface and the tool is passed through the bending point again.

Therefore, in the manufacturing method of the lens mold of the present invention, since the cutting or grinding is performed firmly up to the bending point, and the tool is passed through the bending point again after retreat, the bending point is formed reliably. Therefore, cutting or grinding can be performed by a continuous program. Therefore, the number of setup steps is reduced, and the lens mold can be manufactured in a short time and at low cost.

Further, since it is not necessary to remove the mold material on the way and all the curved surfaces can be processed while being initially attached, a lens mold having a highly accurate curved surface without eccentricity between different curved surfaces. Molds can be manufactured.

According to the second aspect of the present invention, the tool is moved on the inner extension line of the outer peripheral curved surface and retracted from the cutting or grinding surface of the inner curved surface, and the tool is moved on the outer extension line of the inner curved surface. , And the inner curved surface is cut or ground by passing through the bending point again, so that the retreat trajectory and the re-entry trajectory can be easily calculated.

According to the third aspect of the present invention, the tool is moved on the inner extension of the tangent to the minute portion on the bending point side of the outer peripheral curved surface, and is retracted from the surface to be cut or ground on the inner curved surface. Since the tool is moved along the outer extension line of the tangent of the minute portion on the bending point side of the inner curved surface to pass through the bending point again to cut or grind the inner curved surface, cutting or grinding of the inner curved surface is performed. It is possible to reliably avoid cutting of the surface to be ground and the curved surface of the outer peripheral portion or excessively removing the curved surface that has been ground, and furthermore, it is easy to calculate the evacuation locus and the re-entry locus.

According to the fourth aspect of the present invention, the tool is moved on the inner extension of an arc passing through two points taken on the minute part on the bending point side of the outer peripheral curved surface and three points on the bending point. Retreats from the surface to be cut or ground on the inside curved surface, and moves the tool along the outside extension of an arc passing through two points taken on the minute part on the bending point side of the inside curved surface and three points on the bending point The inner curved surface is cut or ground by passing through the bending point again, so it is ensured that the inner curved surface is cut or ground and the outer curved surface is cut or ground. It can be avoided and the calculation of the retreat trajectory and the re-entry trajectory is easy.

The apparatus for manufacturing a lens mold according to the present invention cuts or rotates a mold material which rotates by moving along a locus defined by a program given in advance and a mold material rotating means for rotating the mold material. An apparatus for manufacturing a lens mold for manufacturing a lens mold having a different curved surface having an outer peripheral portion and an inner portion continuous through a bending point, comprising a grinding tool, and the program, After cutting or grinding the outer curved surface to the bending point, the tool is retracted from the surface to be cut or ground on the inner curved surface, and then the tool is passed through the bending point again to cut or grind the inner curved surface. It is characterized by doing so.

Therefore, in the manufacturing apparatus of the lens mold of the present invention, cutting or grinding is performed firmly up to the bending point, and the tool is passed through the bending point again after retreat, so that the bending point is formed reliably. Therefore, cutting or grinding can be performed by a continuous program. Therefore, the number of setup steps is reduced, and the lens mold can be manufactured in a short time and at low cost.

Further, since it is not necessary to remove the mold material on the way and all the curved surfaces can be processed while being initially attached, a lens mold having a highly accurate curved surface without eccentricity between different curved surfaces. Molds can be manufactured.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating an example of a lens mold manufactured by a method for manufacturing a lens mold and a lens mold manufacturing apparatus according to the present invention.

FIG. 2 is a graph for explaining an example of two curved surfaces of a lens mold manufactured by the present invention.

FIG. 3 is a graph showing an example of a procedure for determining a movement trajectory of a cutting or grinding tool together with FIGS. 4 and 5;
9 shows a procedure for determining two points in the vicinity of a bending point of one curved surface.

FIG. 4 is a view for explaining a procedure for determining an arc passing through the above two points and a bending point.

FIG. 5 shows a procedure for determining an arbitrary point in the arc shape.

FIG. 6 is a graph showing a movement locus of a cutting tool.

[Explanation of symbols]

Reference numeral 1 denotes a lens mold, 3 denotes a first aspheric surface (an inner curved surface),
4 ... Bending point, 5 ... Second aspherical surface (outer surface curved surface), 6 ... Bite (tool), A1, A2 ... Two points taken on the minute part on the bending point side of the inner curved surface, C1, C2 ... Two points taken on a minute portion on the bending point side of the outer peripheral curved surface, A: arc, C: arc,

Claims (5)

[Claims] 1. A mold for molding a lens having a different curved surface having an outer peripheral portion and an inner portion continuous through a bending point is manufactured by cutting or grinding by moving a tool while rotating the mold material. The method, after cutting or grinding the outer peripheral curved surface up to the bending point, retracting the tool from the planned cutting or grinding surface of the inner curved surface, passing the tool again through the bending point, and then removing the inner curved surface A method for producing a lens mold, characterized by cutting or grinding. 2. A tool is moved on the inner extension of the outer curved surface to retreat from a surface to be cut or ground on the inner curved surface, and the tool is moved along the outer extension of the inner curved surface to set the bending point again. The method for manufacturing a lens mold according to claim 1, wherein the inner surface curved surface is cut or ground by passing through. 3. A tool is moved on an inner extension of a tangent to a minute portion on the bending point side of the outer peripheral curved surface to retract from a cutting or grinding surface of the inner curved surface, and the tool is moved to the bending point side of the inner curved surface. 2. The method for manufacturing a lens mold according to claim 1, wherein the minute portion is moved along an outer extension line of a tangent to the minute portion so as to pass through a bending point again to cut or grind an inner curved surface. 4. A cutting or grinding surface of an inner curved surface by moving a tool on an inner extended line of an arc passing through two points taken on a minute part on the bending point side of the outer peripheral curved surface and three points of the bending point. The tool is moved along the outer extension of the arc passing through the two points taken on the minute part on the bending point side of the inner part curved surface and the three points of the bending point, and the tool is passed again through the bending point and The method for manufacturing a lens mold according to claim 1, wherein the curved surface is cut or ground. 5. A mold material rotating means for rotating a mold material, and a tool for cutting or grinding the mold material which rotates by moving along a locus defined by a program given in advance. An apparatus for manufacturing a lens mold for manufacturing a lens mold having a different curved surface in which a curved surface is continuous through a bending point, wherein the program cuts an outer peripheral curved surface to the bending point. Alternatively, after grinding, the tool is retracted from the surface to be cut or ground on the inside curved surface, and then the tool is passed through the bending point again, and then the inside curved surface is cut or ground. An apparatus for manufacturing a lens mold.