阅读说明：本技术 菲涅尔透镜模具制造方法、加工装置和切削工具 (Fresnel lens mold manufacturing method, Fresnel lens mold machining device and cutting tool ) 是由 社本英二 于 2020-03-26 设计创作，主要内容包括：提供一种用切削工具对被加工材料进行切削加工而制造透镜面和直立面交替配置的菲涅尔透镜的模具的方法。切削工具具有半径r1的圆弧形状的第一切削刃和与第一切削刃相连续的第二切削刃。加工装置反复实施使用第一切削刃而形成成为菲涅尔透镜的透镜面的模具的透镜模具面的第一工序(S1)和使用第二切削刃而形成成为菲涅尔透镜的直立面的模具的直立模具面的第二工序(S2),从而制造菲涅尔透镜的模具。(Provided is a method for manufacturing a mold for a Fresnel lens having a lens surface and a vertical surface alternately arranged by cutting a work material with a cutting tool. The cutting tool has a first cutting edge in the shape of a circular arc having a radius r1 and a second cutting edge continuous with the first cutting edge. The processing apparatus repeatedly performs a first step (S1) of forming a lens mold surface of a mold to be a lens surface of a fresnel lens using a first cutting edge and a second step (S2) of forming a standing mold surface of a mold to be a standing surface of a fresnel lens using a second cutting edge, thereby manufacturing the mold of the fresnel lens.)

1. A method for manufacturing a Fresnel lens mold by cutting a work material with a cutting tool to manufacture a Fresnel lens mold having a lens surface and an upright surface alternately arranged,

the cutting tool has a first cutting edge in the shape of a circular arc having a radius r1 and a second cutting edge continuous with the first cutting edge,

the manufacturing method of the Fresnel lens mould comprises the following steps: a first step of forming a lens mold surface of a mold to be a lens surface of a Fresnel lens by using the first cutting blade, and a second step of forming a standing mold surface of a mold to be a standing surface of a Fresnel lens by using the second cutting blade,

the first step and the second step are repeated to manufacture a mold for a Fresnel lens.

2. The Fresnel lens mold manufacturing method according to claim 1, characterized in that,

the second cutting edge has a circular arc shape having a radius r2 and being continuous with the first cutting edge.

3. The Fresnel lens mold manufacturing method according to claim 2, wherein,

the second cutting edge is a round nose cutting edge at the front end of the tool, and the radius r2 is smaller than the radius r 1.

4. The Fresnel lens mold manufacturing method according to claim 3, characterized in that,

the arc center of the first cutting edge is located outside the cutting tool, and the arc center of the second cutting edge is located inside the cutting tool.

5. The Fresnel lens mold manufacturing method according to claim 2, wherein,

the arc center of the first cutting edge and the arc center of the second cutting edge are both located outside the cutting tool.

6. A machining apparatus for manufacturing a die for a Fresnel lens having a lens surface and an upright surface arranged alternately by cutting a workpiece with a cutting tool by cutting, characterized in that,

the cutting tool has a first cutting edge in the shape of a circular arc having a radius r1 and a second cutting edge continuous with the first cutting edge,

the processing device comprises:

a moving unit that moves the cutting tool relative to the material to be processed; and

and a control device that controls the operation of the movement unit to repeatedly perform processing of a lens mold surface of a mold that forms a lens surface of the fresnel lens using the first cutting edge and processing of a standing mold surface of a mold that forms a standing surface of the fresnel lens using the second cutting edge.

7. A cutting tool used for manufacturing a mold for a fresnel lens, comprising:

a first cutting edge having an arc shape with a radius r1, for finishing a lens mold surface of a mold to be a lens surface of a fresnel lens; and

and a second cutting edge continuous with the first cutting edge, for finishing a vertical mold surface of a mold to be a vertical surface of the fresnel lens.

8. The cutting tool of claim 7,

the second cutting edge is a round nose cutting edge at the front end of the tool, and the radius r2 is smaller than the radius r 1.

9. The cutting tool of claim 7,

the arc center of the first cutting edge and the arc center of the second cutting edge are both located outside the cutting tool.

Technical Field

The present disclosure relates to a technique of manufacturing a mold for a fresnel lens.

Background

Fig. 1 shows a cross section of a Fresnel lens (Fresnel lens). The fresnel lens 20 has a surface shape in which lens surfaces 21 and rising surfaces (also referred to as "rising surfaces") 22 are alternately arranged concentrically. The fresnel lens 20 is mass-produced by Injection molding (Injection molding) a plastic resin material such as acrylic (acrylic) or polycarbonate (polycarbonate) using a mold. The mold for the fresnel lens 20 has a rotationally symmetrical shape, and is therefore often manufactured by turning.

Fig. 2 is a diagram for explaining a conventional finishing process of a fresnel lens mold. The fresnel lens mold 30 has a surface shape in which lens mold surfaces 31 and upright mold surfaces 32 are alternately arranged concentrically, the lens mold surfaces 31 being molds of the lens surfaces 21 of the fresnel lens 20, and the upright mold surfaces 32 being molds of the upright surfaces 22 of the fresnel lens 20. In a conventional finishing process of the mold 30, a round nose cutting edge 26 having a minute circular arc shape (nose radius) r at the tip of the cutting tool 25 is fed to a rotating workpiece along a trajectory of r, which is a target cross-sectional shape, from the center 27 of the round nose (nose), and a lens mold surface 31 and a vertical mold surface 32 are alternately finished (see, for example, patent document 1). The single-dot chain line shown in fig. 2 indicates the feed locus of the round nose center 27.

According to the above-described finish, the corner 33 that defines the boundary between the transparent die surface 31 and the upright die surface 32 is formed into an arc shape with the radius r of the round nose cutting edge 26. Since the region of the lens surface 21 where the rounded corner 33 is transferred is an ineffective region for the lens, the radius r of the circular arc of the corner 33 is preferably small.

(Prior art document)

(patent document)

Patent document 1: japanese patent laid-open publication No. 2011-121146

Disclosure of Invention

(problems to be solved by the invention)

It is known that the finished surface roughness Rth of the lens mold surface 31 of the mold to be a fresnel lens surface can be theoretically predicted by the following formula (1).

[ number 1]

Where "r" is the nose radius of the nose cutting edge 26, and "f" is the feed amount of the cutting tool 25 fed along the tool trajectory ("the trajectory of the nose center" in fig. 2) during each rotation of the material to be machined. Referring to the equation (1), it is understood that the finished surface roughness Rth can be reduced and the lens performance can be improved by increasing the round nose radius r and/or decreasing the feed amount f.

However, since the radius r of the round nose is the radius of the arc of the corner 33 as described above, the radius r of the round nose cannot be increased in order to reduce the ineffective area in the lens surface 21 of the fresnel lens 20. Further, if the feed amount f is reduced, the finished surface roughness Rth can be reduced, but on the other hand, the machining efficiency is reduced, which is not preferable from the viewpoint of cost. Further, if the feed amount f is reduced, there is a problem that the cutting distance of the cutting tool 25 becomes long, and the tool is easily worn.

For example, when the radius r of the round nose is 5 μm, the feed amount f per one revolution is set to 1 μm, thereby realizing the finish surface roughness Rth (about 0.025 μm) of a mirror surface level. However, high processing efficiency cannot be achieved with a feed amount f of 1 μm per revolution.

The present disclosure has been made in view of such circumstances, and an object thereof is to provide a technique for manufacturing a mold for a fresnel lens with high processing efficiency.

(measures taken to solve the problems)

In order to solve the above problems, one embodiment of the present invention relates to a method for manufacturing a mold for a fresnel lens in which lens surfaces and vertical surfaces are alternately arranged by cutting a workpiece with a cutting tool. The cutting tool used has a first cutting edge in the shape of a circular arc of radius r1 and a second cutting edge continuous with the first cutting edge. The mold manufacturing method comprises the following steps: the method for manufacturing a Fresnel lens mold includes a first step of forming a lens mold surface of a mold to be a lens surface of a Fresnel lens by using a first cutting blade and a second step of forming a standing mold surface of the mold to be a standing surface of the Fresnel lens by using a second cutting blade, and the first step and the second step are repeated to manufacture the Fresnel lens mold.

Another embodiment of the present invention relates to a processing apparatus for manufacturing a mold of a fresnel lens in which lens surfaces and vertical surfaces are alternately arranged by cutting a workpiece with a cutting tool. The cutting tool used has a first cutting edge in the shape of a circular arc of radius r1 and a second cutting edge continuous with the first cutting edge. The machining device is provided with: a moving unit that moves the cutting tool relative to the material to be processed; and a control device that controls the operation of the movement means and repeatedly performs processing of a lens mold surface of a mold that forms a lens surface of the fresnel lens using the first cutting edge and processing of a standing mold surface of a mold that forms a standing surface of the fresnel lens using the second cutting edge.

Another embodiment of the present invention relates to a cutting tool used for manufacturing a mold for a fresnel lens. The cutting tool comprises: a first cutting edge having an arc shape with a radius r1, for finishing a lens mold surface of a mold to be a lens surface of a fresnel lens; and a second cutting edge continuous to the first cutting edge, for finishing a vertical mold surface of a mold to be a vertical surface of the fresnel lens.

In addition, any combination of the above constituent elements, and conversion of the expression of the present disclosure between a method, an apparatus, a system, and the like are effective as a mode of the present disclosure.

Drawings

Fig. 1 is a view showing a cross section of a fresnel lens.

Fig. 2 is a diagram for explaining a conventional finishing process.

Fig. 3 is a diagram showing a schematic configuration of a processing apparatus according to an embodiment.

Fig. 4 is a diagram showing an outline of the shape of the cutting edge of the cutting tool according to the first embodiment.

Fig. 5 is a view showing a process sequence of the fresnel lens mold.

Fig. 6 is a diagram for explaining the finishing step in the first embodiment.

Fig. 7 is a diagram showing a state of the cutting edge of the cutting tool 5 positioned at the corner.

Fig. 8 is a diagram for explaining a finishing process in example two.

Detailed Description

Fig. 3 shows a schematic structure of the processing apparatus 1 of the embodiment. The machining apparatus 1 is a cutting apparatus that performs turning by bringing a cutting edge of a cutting tool 5 into contact with a workpiece 8. The machining device 1 includes: a spindle head 2 that rotatably supports a spindle 3; and a tool holder 4 that movably supports a cutting tool 5. The rotating unit 6 is provided inside the headstock 2 and rotates the spindle 3 to which the workpiece 8 is attached. The feeding unit 7 moves the cutting tool 5 relative to the workpiece 8.

The rotation unit 6 and the feed unit 7 constitute a moving unit that moves the cutting tool 5 relative to the material 8 to be processed. The movement unit may include a unit that rotates the posture of the cutting tool 5 about the cutting movement direction. Further, a tool-posture rotating unit may be provided as a part unit of the feeding unit 7 for relatively changing the posture of the cutting tool 5 with respect to the material 8 to be processed.

The control device 10 includes: a rotation control unit that controls rotation of the spindle 3 by the rotating unit 6; and a movement control unit that performs machining by the cutting tool 5 by bringing the cutting tool 5 into contact with the workpiece 8 while the feed unit 7 is operated during rotation of the spindle 3. The machining apparatus 1 may be an NC machine tool. The movement unit including the rotation unit 6 and the feeding unit 7 is configured to have a driving portion such as a motor, respectively, and the rotation control portion and the movement control portion control the operations of the rotation unit 6 and the feeding unit 7 by adjusting power supply to the driving portion, respectively.

In the machining device 1 according to the embodiment, the workpiece 8 is attached to the spindle 3 and rotated by the rotation unit 6, but in another example, the cutting tool 5 may be attached to the spindle 3 and rotated by the rotation unit 6. The feeding unit 7 may move the cutting tool 5 relative to the workpiece 8 or change the posture thereof, and may have a unit that moves at least one of the cutting tool 5 and the workpiece 8 or changes the posture thereof. The control device 10 controls the operation of the moving means including the rotating means 6 and the feeding means 7 to cut the workpiece 8, thereby manufacturing the fresnel lens mold.

(embodiment one)

Fig. 4 shows an outline of the cutting edge shape of the cutting tool 5 according to the first embodiment. The cutting tool 5 is preferably a diamond tool suitable for ultra-precision machining, and more preferably a single crystal diamond tool. The cutting tool 5 of the first embodiment has a circular-arc-shaped first cutting edge 40 having a radius r1 and a circular-arc-shaped second cutting edge 42 having a radius r2 and continuous with the first cutting edge 40. In fig. 4, point Q is the boundary of the first cutting edge 40 and the second cutting edge 42. The ridge line between the point P and the point Q constitutes a first cutting edge 40 of circular arc shape of radius R1 centered on the first center 41, and the ridge line between the point R and the point Q constitutes a second cutting edge 42 of circular arc shape of radius R2 centered on the second center 43.

In the cutting tool 5, a first center 41, which is the arc center of the first cutting edge 40, is set outside the cutting tool 5, and a second center 43, which is the arc center of the second cutting edge 42, is set inside the cutting tool 5. As shown, the second cutting edge 42 of the first embodiment is a rounded nose cutting edge at the front end of the cutting tool 5, and thus the radius r2 is a rounded nose radius smaller than the radius r 1. In the first embodiment, the machining apparatus 1 performs a cutting process on a workpiece 8 using a cutting tool 5 as shown in fig. 4.

Fig. 5 shows a process of manufacturing the fresnel lens mold. The controller 10 drives the rotating unit 6 to rotate the workpiece 8 attached to the spindle 3. The control device 10 controls the feeding unit 7 to move the cutting tool 5 relative to the workpiece 8. The controller 10 alternately repeats a first step (S1) of forming a lens mold surface of a mold to be a lens surface of a fresnel lens using the first cutting edge 40, and a second step (S2) of forming a standing mold surface of a mold to be a standing surface of a fresnel lens using the second cutting edge 42 (S2). The first step (S1) and the second step (S2) are repeated until all the lens mold surfaces are formed (no in S3), and when all the lens mold surfaces are formed (yes in S3), the fresnel lens mold is completed, and the cutting process is terminated.

Fig. 6 is a diagram for explaining a finishing process of the first embodiment of the fresnel lens mold. Fig. 6 shows a state of a first step in which the first cutting edge 40 finishes the lens mold surface 51. The fresnel lens mold 50 has a surface shape in which lens mold surfaces 51 and upright mold surfaces 52 are alternately arranged concentrically, the lens mold surfaces 51 being molds of the lens surfaces 21 of the fresnel lens 20, and the upright mold surfaces 52 being molds of the upright surfaces 22 of the fresnel lens 20.

In the first step, the controller 10 feeds the cutting tool 5 along a trajectory having a first center 41 of the first cutting edge 40 and a target cross-sectional shape r1 from the lens mold surface 51 to finish the lens mold surface 51. At the end of the first step, a corner 53 is formed to which the shape of the second cutting edge 42 is transferred. In the second step, the controller 10 feeds the cutting tool 5 along a trajectory having a second center 43 of the second cutting edge 42 and a target cross-sectional shape r2 from the upright die surface 52 to finish the upright die surface 52. In the first step and the subsequent second step, the control device 10 preferably does not change the posture of the cutting tool 5, but may rotate the posture of the cutting tool 5 around the second center 43 when switching from the first step to the second step. The one-dot chain line shown in fig. 6 shows the locus along which the first center 41 moves in the first process and the second process. In the first step and the other first step, the control device 10 needs to change the posture of the cutting tool 5 depending on the inclination of the lens mold surface 51. As described above, when the feeding unit 7 includes the rotating unit having the tool posture, the control device 10 controls the feeding unit 7 to change the tool posture every time the first step of forming the lens mold surface 51 is performed.

In both the first step and the second step, the third cutting edge (in fig. 4, a cutting edge continuing in the opposite direction from the point R to the point Q) facing the first cutting edge 40 with the second cutting edge 42 interposed therebetween does not contribute to the production of the finished surface. The third cutting edge may be a straight line smoothly connected to the second cutting edge 42, or may be inclined in the separating direction with respect to the intended upright die surface 52. Furthermore, the trajectory of the feed movement may also be a trajectory in the opposite direction.

Fig. 7 shows a state where the cutting edge of the cutting tool 5 is positioned at the corner 53. The inclination of the point Q at which the second cutting edge 42 and the first cutting edge 40 are connected is preferably substantially the same as the inclination of the position where the inclination of the lens mold surface 51 is the smallest (closest to horizontal). More precisely, in a state where the second cutting edge 42 finishes machining the corner portion 53, the tangential direction of the first cutting edge 40 at a position separated by f/2 from the point Q along the side where the radius of the lens mold surface 51 becomes larger is preferably the same as or closest to the minimum inclination of the lens mold surface 51 to be the target.

In the first step, since the posture (rotational posture about the cutting motion direction) of the cutting tool 5 is constant, the control device 10 preferably determines the rotational posture about the cutting motion direction of the cutting tool 5 in the first step so that the tangential direction of the first cutting edge 40 at a position separated by f/2 from the point Q along the side where the radius of the lens mold surface 51 becomes larger is the same as or closest to the minimum inclination of the lens mold surface 51 to be the target. By determining the posture of the cutting tool 5 in this manner, the entire lens mold surface 51 can be efficiently finished by the first cutting edge 40. The posture of the cutting tool 5 may be set according to the minimum inclination angle of each lens mold surface 51.

In the first example, when the radius r1 of the first cutting edge 40 is 1mm, the finished surface roughness Rth (about 0.0245 μm) at the mirror surface level can be achieved even if the feed amount f per revolution is set to 14 μm. By machining the lens mold surface 51 with the first cutting edge 40 having a larger diameter than the round nose cutting edge in this manner, the feed amount f can be increased, and high machining efficiency can be achieved.

Although the cutting tool 5 has been described as having the first cutting edge 40 having an arc shape with the radius r1 and the second cutting edge 42 having an arc shape with the radius r2 and continuing from the first cutting edge 40, the second cutting edge 42 may be a sharp corner (acute corner) with the radius 0. In this case, since there is no arc remaining in the corner 53, the transfer position causing optical loss can be eliminated. Further, since the second cutting edge 42 configured as an acute angle portion may be broken during machining, it is preferable to perform rounding or chamfering called edge cutting treatment particularly when the hardness of the workpiece 8 is high and the toughness of the tool edge is low.

(second embodiment)

Fig. 8 is a diagram for explaining a finishing process of a second embodiment of the fresnel lens mold. In the second embodiment, the control device 10 uses a cutting tool 5a different from the first embodiment. In the second embodiment, the control device 10 also manufactures the fresnel lens mold according to the processing steps shown in fig. 5.

The cutting tool 5a of the second embodiment has a circular-arc-shaped first cutting edge 40 having a radius r1 and a circular-arc-shaped second cutting edge 42a having a radius r3 and continuing to the first cutting edge 40. In the cutting tool 5a, a first center 41 as a circular arc center of the first cutting edge 40 and a second center 43a as a circular arc center of the second cutting edge 42a are both set outside the cutting tool 5a, and radii r1 and r3 are large. Further, r1 ≧ r3 is preferable. The cutting tool 5a does not have a round nose cutting edge, and the first cutting edge 40 and the second cutting edge 42a are connected at a nose ridge line. The nose ridge thus forms a sharp acute angle portion.

Referring to fig. 5, control device 10 alternately repeats a first step (S1) of forming lens mold surface 51 of a mold to be a lens surface of a fresnel lens using first cutting edge 40 and a second step (S2) of forming standing mold surface 52 of a mold to be a standing surface of a fresnel lens using second cutting edge 42a (S1). The first step (S1) and the second step (S2) are repeatedly performed until all the lens mold surfaces 51 are formed (no in S3), and when all the lens mold surfaces 51 are formed (yes in S3), the fresnel lens mold is completed, and the cutting process is completed.

Compared to the finished surface shown in fig. 6, since the cutting tool 5a does not have a round nose cutting edge, there is no arc remaining in the corner 53, and the transfer position causing optical loss can be eliminated. When the cutting edge line is an acute angle portion, rounding or chamfering called cutting edge processing is preferably performed as described above.

The vertical mold surface 52 in the molding mold is often formed as a slightly inclined draft angle (draft angle) (in fig. 6 and 8, the inclined angle is inclined to the left as it goes upward). The finish surface roughness Rth of the upright mold surface 52 is not optically significant, but is preferably small for the sake of mold releasability. Therefore, in the second embodiment, in order to reduce the finish surface roughness Rth of the upright die surface 52 and increase the feed amount f in finish machining of the upright die surface 52, the cutting tool 5a having the arc-shaped second cutting edge 42a having the large radius r3 continuous with the first cutting edge 40 is used. By using the cutting tool 5a, the tool feed amount f in the lens mold surface 51 and the upright mold surface 52 can be increased, achieving high processing efficiency.

Further, when a mold having a general fresnel lens shape is machined by the cutting tool 5 shown in example two, it is necessary to change the posture of the tool between the first step and the second step. That is, it needs to rotate around the tool tip point (a point on the tool tip side of the intersection of the arc of the first cutting edge 40 and the arc of the second cutting edge 42 a). This is because in a normal fresnel lens shape, the inclination of each transparent mold surface 51 gradually changes depending on the radial position, in the same manner as the inclination of each vertical mold surface 52.

The present disclosure has been described above based on the embodiments. As will be appreciated by those skilled in the art: this embodiment is an example, and various modifications can be made by combining each member and each process, and these modifications also fall within the scope of the present disclosure.

In the embodiment, a method of manufacturing a mold of a fresnel lens in which lens surfaces and vertical surfaces are alternately arranged in a concentric manner by using the machining device 1 as a cutting device for turning the workpiece 8 is described. In the modification, the machining device 1 is a cutting device for planing the workpiece 8, and may be a mold for manufacturing a linear fresnel lens in which the lens surface and the upright surface are alternately arranged in a straight line. When the machining device 1 is a cutting device for planing, the movement means does not include the rotation means 6 for rotating the spindle, but it is necessary to include a feed means for moving the workpiece 8 or the cutting tool 5 linearly in the cutting movement direction relative to each other.

An outline of the embodiments of the present disclosure is as follows.

One embodiment of the present disclosure relates to a method for manufacturing a mold for a fresnel lens in which lens surfaces and vertical surfaces are alternately arranged by cutting a workpiece with a cutting tool. The cutting tool used has a first cutting edge in the shape of a circular arc of radius r1 and a second cutting edge continuous with the first cutting edge. The mold manufacturing method comprises the following steps: the method for manufacturing a Fresnel lens mold includes a first step of forming a lens mold surface of a mold to be a lens surface of a Fresnel lens by using a first cutting blade and a second step of forming a standing mold surface of the mold to be a standing surface of the Fresnel lens by using a second cutting blade, and the first step and the second step are repeated to manufacture the Fresnel lens mold.

According to this embodiment, by using different cutting edges in the first step and the second step, the feed amount in the first step can be increased without increasing the corner radius of the boundary between the lens mold surface and the upright mold surface.

The second cutting edge has a circular arc shape continuous with the first cutting edge and having a radius r 2. The second cutting edge is a nose-rounded cutting edge at the front end of the tool, and the radius r2 of the second cutting edge may be smaller than the radius r1 of the first cutting edge, in which case the center of the arc of the first cutting edge may be located outside the cutting tool and the center of the arc of the second cutting edge may be located inside the cutting tool. Further, the arc center of the first cutting edge and the arc center of the second cutting edge may be both located outside the cutting tool.

Another embodiment of the present disclosure relates to a processing apparatus for manufacturing a mold of a fresnel lens in which lens surfaces and vertical surfaces are alternately arranged by cutting a workpiece with a cutting tool. The cutting tool used has a first cutting edge in the shape of a circular arc of radius r1 and a second cutting edge continuous with the first cutting edge. The machining device is provided with: a moving unit that moves the cutting tool relative to the material to be processed; and a control device that controls the operation of the movement means and repeatedly performs processing of a lens mold surface of a mold that forms a lens surface of the fresnel lens using the first cutting edge and processing of a standing mold surface of a mold that forms a standing surface of the fresnel lens using the second cutting edge.

According to this embodiment, the use of different cutting edges in the first step and the second step makes it possible to increase the feed amount in the first step without increasing the corner radius of the boundary between the lens mold surface and the upright mold surface.

Another embodiment of the present invention relates to a cutting tool used for manufacturing a mold for a fresnel lens. The cutting tool comprises: a first cutting edge having an arc shape with a radius r1, for finishing a lens mold surface of a mold to be a lens surface of a fresnel lens; and a second cutting edge continuous to the first cutting edge, for finishing a vertical mold surface of a mold to be a vertical surface of the fresnel lens.

(availability in industry)

The present disclosure can be applied to the field of machining.

(description of reference numerals)

1: a processing device; 3: a main shaft; 5. 5 a: a cutting tool; 6: a rotation unit;

7: a feeding unit; 8: a material to be processed; 10: a control device; 20: a Fresnel lens;

21: a lens surface; 22: a vertical surface; 25: a cutting tool; 26: a round nose cutting edge;

27: the center of the round nose; 30: a mold; 31: a lens mold face; 32: a vertical mold surface;

33: a corner portion; 40: a first cutting edge; 42. 42 a: a second cutting edge;

50. 50 a: a mold; 51: a lens mold face; 52: a vertical mold surface;

53. 53 a: a corner portion.