JP2006007551A - Processing method of lens mold - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a processing method of a lens mold capable of precisely processing the molding surface of a mold by simpler control. <P>SOLUTION: In the processing method for processing the lens mold 11 by a grinding tool 13 having a grindstone part 24 to form a cylindrical molding surface 11a, the grinding tool 13 of which the grindstone part 24 is formed into a columnar shape with a predetermined height (t) is repeatedly moved unidirectionally in its rotation axis direction (a) in a rotary state and, when grinding is performed while changing the relative distance between the grinding tool 13 and the lens mold 11, the grinding tool 13 is moved at a predetermined interval in the width direction of the mold 11 crossing the rotation axis direction (a) at a right angle to form the cylindrical molding surface 11a. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for processing a lens mold that can accurately process a lens mold used for an optical component.

  Some lens molding dies used for optical components have a cylindrical molding surface (also referred to as a cylindrical surface or a toric surface), and a method for processing a workpiece having such a molding surface is shown below. There are methods.

As shown in FIG. 6, this processing method is a disc shape attached to the tip of the rotating shaft 52 of the grindstone rotary table 51 and the cross-sectional shape of the outer peripheral end portion is formed into a spherical shape. While the grindstone 53 such as a ball is rotated, it is brought into contact with the surface of the lens molding die 54 and, as indicated by an arrow d, lens shaping is performed so that the tip of the grindstone 53 becomes a predetermined cylindrical molding surface 54a. This is a method of moving in a direction orthogonal to the axis of the cylindrical molding surface 54a of the mold 54 (see, for example, paragraph [0012] of Patent Document 1 and FIG. 2).
JP-A-5-69300

  However, according to the above conventional processing method, the cross-sectional shape of the tip of the grindstone 53 is spherical as shown in FIG. 6. In other words, the shape of the grindstone 53 is a horizontal cross-sectional shape like an abacus ball. In addition, since both the vertical cross-sectional shapes are arcuate, the truing operation of the grindstone is difficult, and the shape accuracy is lowered. As a result, the processing accuracy of the molding surface of the mold is lowered. .

  Further, since the horizontal cross-sectional shape and the vertical cross-sectional shape of the grindstone 53 are both arcuate and the grindstone 53 is moved as indicated by the arrow d, if the contact position of the grindstone 53 with respect to the molding surface 54a is different, the molding is performed. Since the relative distance between the surface 54a and the rotational axis e of the grindstone 53 changes, there is a problem that movement control (NC control) of the grindstone 53 becomes difficult.

  In particular, as semiconductor lasers used in optical disk devices change from red to blue (so-called Blu-ray), the required specifications of molding dies, such as specifications with a shape accuracy (processing accuracy) of 0.05 μm or less, have been achieved. However, it has become difficult to satisfy the specifications with conventional processing methods.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a method for processing a lens mold that can process the molding surface of the mold with high accuracy and simpler control.

In order to achieve the above object, a processing method of a lens molding die according to claim 1 of the present invention is a processing method for processing a cylindrical molding surface on a lens molding die with a grinding tool having a grindstone portion. There,
A grinding tool having a grindstone formed in a columnar shape with a predetermined height is repeatedly moved in one direction in the rotated state and in the direction of the rotation axis, and the relative distance between the grinding tool and the lens molding die is set. This is a method of forming a cylindrical molding surface by moving the grinding tool at predetermined intervals in the width direction of the mold perpendicular to the rotational axis direction when grinding while changing.

  Moreover, the processing method of the lens shaping die concerning Claim 2 is a method which makes the thickness of the grindstone part of a grinding tool the range of 0.05-1.0 mm in the processing method of Claim 1. .

  According to the above processing method, the cylindrical surface is used as the grindstone portion, and the molding surface is machined by moving the grindstone portion in the direction of the rotation axis and moving in the mold width direction at predetermined intervals. Therefore, for example, as compared with the conventional case where the grindstone is disk-shaped and the cross-sectional shape of the tip is spherical (so-called abacus ball shape), the processing accuracy (shape accuracy) in the grindstone, that is, the mold The surface accuracy of the molding surface can be improved, and the control for moving the grindstone can be performed more easily.

  In other words, high-precision truing work (contour accuracy) at the tip of the grindstone is not required, and the grinding device can also provide an optical mirror surface with good surface accuracy by simply controlling the offset amount of the rotation axis of the grindstone with respect to the forming surface. Obtainable.

Hereinafter, a method for processing a lens molding die according to an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a side view showing a schematic configuration of a grinding apparatus used in a method for processing a lens mold according to an embodiment of the present invention, and FIG. 2 is a diagram for explaining a method for processing a lens mold.

  As shown in FIG. 1, the grinding apparatus includes a first horizontal movement table 2 disposed so as to be movable in a horizontal direction toward one end side and the other end side of a base 1 having a rectangular shape in plan view, Similarly, a second horizontal movement table 3 disposed on the other end side of the base 1 and movably in a horizontal direction orthogonal to the movement direction of the first horizontal movement table 2, and stands on the second horizontal movement table 3. A vertically movable body 5 is provided on the provided support body 4 so as to be movable up and down.

  On the first horizontal movement table 2, a lens molding die (hereinafter simply referred to as a die) having a cylindrical molding surface (for example, an aspherical cylindrical surface, a toric surface, etc.) 11a. ) A mold holder 12 (of course, having a position indexing function) 12 is disposed, and the vertical moving body 5 is rotated at a high speed by an air turbine and a rotating shaft that holds the grinding tool 13 A body (also referred to as a rotating spindle) 14 is provided.

  Here, each movement direction of the tables 2 and 3 and the vertical moving body 5 will be briefly described. As shown in FIG. 1, when the movement direction of the first horizontal movement table 2 is the Z axis, the second horizontal movement table. The moving direction of 3 is the X axis, and the moving direction of the vertical moving body 5 is the Y axis, which is the vertical direction, so that the three axes are orthogonal to each other. As shown in FIGS. 2 and 3, the rotation axis a of the grinding tool 13 is naturally aligned with the Y-axis direction, and therefore the cylindrical molding surface 11a of the mold 11 which is a portion to be ground. The mold 11 is set on the mold holder 12 so that the center axis b of the mold is also in the Y-axis direction.

Next, the grinding tool will be described.
As shown in FIG. 2, the grinding tool 13 held downward on the rotary shaft body 14 is roughly composed of a thick base end side shaft portion 21 and a tip end side shaft portion 22 slightly narrower than that. Further, the distal end side shaft portion 22 is formed in a relief shaft portion 23 near the proximal end side shaft portion 21 and a cylindrical grindstone portion 24 having a predetermined thickness t on the distal end side thereof. A cylindrical molding surface 11 a is formed on the mold 11 by the cylindrical outer surface of the grindstone portion 24. Of course, as shown in FIG. 3, the radius r of the grindstone portion 24 is made smaller than the radius R of the molding surface 11a (more precisely, R in the aspheric definition formula).

  Thus, since the grinding surface of the grindstone portion 24 is formed in a cylindrical shape, for example, as shown in FIG. 4A, the distance r from the rotational axis a to the grinding surface is constant. As shown in FIG. 5B, the control (NC machine) when moving the grinding tool 13 is compared with the conventional method in which the distance r ′ to the grinding surface of the grinding wheel changes due to grinding wheel wear depending on the contact position. The control of the offset amount by the control becomes easier.

  The thickness t of the grindstone portion 24 is set to a value corresponding to the lens diameter formed by the mold. For example, when the lens diameter is 4 mm, the thickness t is so-called for Blu-ray. t is in the range of 0.05 to 1.0 mm. The reason for this range will be described later.

Next, a method for processing a mold with the grinding apparatus will be described.
First, a grinding tool 13 having a cylindrical grindstone portion 24 having a predetermined radius and a predetermined thickness t is attached to the rotary shaft body 14 and the mold 11 is held by the mold holder 12 on the first horizontal movement table 2. Let At this time, as shown in FIG. 3, the mold 11 is attached so that the central axis b of the cylindrical forming surface 11 a is in the same vertical direction as the rotational axis a of the grinding tool 13.

  Next, the grinding tool 13 is rotated at a high speed, the first horizontal movement table 2 is moved, and the vertical moving body 5 is moved up and down, so that the cylindrical molding surface 11 a is formed on the mold 11 by the grindstone portion 24. At this time, with respect to the second horizontal movement table 3, as shown by the arrow c in FIG. 2, when the grinding lowering operation of the grindstone portion 24 at a certain position is completed once, the width of the mold 11 is set at a predetermined interval. After moving in the direction, the next grinding descent operation is performed. This intermittent grinding down operation (repetitive movement in one direction) at predetermined intervals is sequentially repeated, and finally, a predetermined cylindrical forming surface 11a is processed (ground).

  That is, when the cylindrical grinding wheel portion 24 and the die 11 are controlled in three axial directions to process the cylindrical molding surface 11a on the die 11, the die 11 is placed on the grinding stone portion 24 and its rotation axis. By making contact in the Z-axis direction orthogonal to a, and the grindstone portion 24 by a combination of linear movement in the Y-axis direction and pitch feed divided in the X-axis direction orthogonal to the Z-axis, that is, the mold width direction Processing is performed.

Here, the reason why the thickness t of the grindstone portion 24 is in the range of 0.05 to 1.0 mm will be described.
Regarding the shape of the grindstone portion 24, if the thickness t is increased, the clearance shaft portion 23 becomes longer and the shaft rigidity is lowered, so that the processing accuracy is lowered. FIG. 5 shows the relationship between the thickness t of the grindstone portion 24 and the axial rigidity of the relief shaft portion 23 and the relationship between the thickness t of the grindstone portion 24 and the processing accuracy of the molding surface 11a of the mold 11. A graph is obtained.

  When a lens for Blu-ray is molded, since its wavelength is short, it is preferable that at least the processing accuracy (surface accuracy) of the molding surface 11a of the mold 11 is 0.05 μm (in addition, conventional processing) According to the method, only processing accuracy of about 0.12 μm can be obtained). Therefore, as can be seen from the graph of FIG. 5, in order to make the processing accuracy 0.05 μm or less, the thickness t of the grindstone portion 24 needs to be in the range of 0.05 to 1.0 mm. The case where the lens diameter is 4 mm is shown.

  As described above, a cylindrical shape is used as the grindstone portion, and the grindstone portion is moved in the direction of the rotational axis and moved in the mold width direction at predetermined intervals. Compared to the case where the portion is disk-shaped and the cross-sectional shape of the tip is spherical (so-called abacus ball shape), the shape accuracy in the grindstone, that is, the surface accuracy of the molding surface of the mold can be improved, The control for moving the grindstone can also be performed more easily.

  In other words, high-precision truing work (contour accuracy) at the tip of the grindstone is not required, and the grinding machine can also achieve machining accuracy (shape accuracy) simply by controlling the offset amount of the rotation axis of the grindstone with respect to the forming surface. An optical mirror surface having a roughness of Ry = 0.02 μm or less at 0.05 μm or less can be obtained.

  The processing method of the lens molding die according to the present invention can process a molding surface having a highly accurate shape surface, that is, an optical mirror surface, with a simpler control and with a higher accuracy. Ideal for processing lens molds.

It is a side view which shows schematic structure of the processing apparatus used for the processing method of the lens shaping die concerning embodiment of this invention. It is a figure explaining the processing method. It is a figure explaining the processing method. It is a figure explaining the processing method. It is a graph which shows the relationship between the axial rigidity of a grinding tool, and the processing precision with respect to the thickness of the grindstone part in the processing method. It is a side view explaining the processing method of the conventional lens shaping die.

Explanation of symbols

2 1st horizontal movement table 3 2nd horizontal movement table 4 support body 5 vertical movement body 11 lens molding die 11a molding surface 13 grinding tool 14 rotating shaft body 24 grindstone part

Claims (2)

A processing method for processing a cylindrical molding surface into a lens molding die with a grinding tool having a grindstone part,
A grinding tool having a grindstone formed in a columnar shape with a predetermined height is repeatedly moved in one direction in the rotated state and in the direction of the rotation axis, and the relative distance between the grinding tool and the lens molding die is set. When grinding while changing, a grinding tool is moved at predetermined intervals in the width direction of the mold perpendicular to the direction of the rotation axis to form a cylindrical molding surface. Processing method. The method for processing a lens molding die according to claim 1, wherein the thickness of the grindstone portion of the grinding tool is in the range of 0.05 to 1.0 mm.

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