JPH10246801A - Plastic lens - Google Patents

Abstract

(57) [Problem] To provide a plastic lens capable of accurately positioning a lens during assembly. A plastic lens 1 constitutes a pickup lens of an optical disk optical head.
A lens portion 2 is provided at a central portion, and a ring-shaped rim 3 is formed at an outer peripheral portion thereof. The rim 3 is formed with a pair of opposing surfaces, one of which forms a reference surface 31 for positioning when fixing the plastic lens 1 to the lens holder. A gate portion 4 for injecting molten plastic at the time of molding is provided on the outer peripheral surface of the rim 3.
Are formed to protrude. The gate portion 4 is cut by moving the pair of cutting blades 6 a and 6 b so as to approach each other in a direction substantially parallel to the optical axis 23 of the lens portion 2. As a result of this cutting, burrs 41 projecting in a direction parallel to the plane with the optical axis 23 as a normal line are formed at the end of the gate portion 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plastic lens, and more particularly to a pickup lens constituting an optical head such as an optical disk and a magneto-optical disk.

[0002]

2. Description of the Related Art Optical disks, magneto-optical disks, etc.
An optical head for reading information recorded on an optical disc is mounted on a drive device (collectively referred to as an “optical disc”).

In this optical head, a pickup lens (objective lens) is fixed to a lens holder of a movable part of an actuator. It is configured to drive independently and perform focusing control and tracking control.

In this case, the positioning of the pickup lens when fixing it to the lens holder is performed by applying a positioning reference surface formed on the outer peripheral portion of the lens portion of the pickup lens to a plane on the lens holder side. .

[0005] Incidentally, the pickup lens is generally manufactured by injection molding of a plastic material. In this case, since the gate for injecting the molten plastic into the molding die is located on the side of the cavity (molding space) corresponding to the shape of the pickup lens, the molded pickup lens has a projection on its outer peripheral surface. Are integrally formed.

Since the gate portion is essentially unnecessary, an intermediate portion thereof is cut and removed by a pair of cutting blades. Conventionally, the cutting direction (= moving direction of the cutting blade) is the same as that of the lens. Was in a direction parallel to a plane whose normal line was the optical axis.

Therefore, burrs protrude in a direction parallel to the optical axis at the end of the gate portion remaining on the lens side after the cutting, and the burrs exceed the reference plane, so that the position of the pickup lens with respect to the lens holder can be determined. There was a problem that it could not be performed accurately.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide a plastic lens capable of accurately positioning a lens during assembly.

[0009]

This and other objects are attained by the present invention which is defined below as (1) and (2).

(1) A plastic lens injection-molded with a plastic material, wherein a gate portion for injecting molten plastic at the time of molding is protrudingly formed on an outer peripheral portion of a lens portion having a curved surface on at least one side, and the gate is formed. A plastic lens, wherein an end of the portion is cut by a cutting blade in a direction substantially parallel to an optical axis of the lens portion.

(2) A plastic lens which is injection-molded from a plastic material and has a lens portion having a curved surface on at least one side, and a pair of opposed lens members formed integrally with the lens portion on an outer peripheral portion of the lens portion. One of the surfaces is a rim that constitutes a reference surface for positioning when fixing the plastic lens to the lens support member, and is formed integrally with the rim on the outer periphery of the rim, and molten plastic is injected during molding. And an end portion of the gate portion is cut by a cutting blade in a direction substantially parallel to an optical axis of the lens portion, and is configured not to exceed the reference plane. A plastic lens.

[0012]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a plastic lens according to the present invention.

1 and 2 are perspective views showing an embodiment of the plastic lens of the present invention, FIG. 3 is a plan view showing a configuration example of a lens holder, and FIG.
-A line sectional view, FIG. 5 is a plan view showing a state where the plastic lens of the present invention is fixed to a lens holder, and FIG.
FIG. 6 is a sectional view taken along line BB in FIG. 5.

FIG. 1 shows a state before cutting the gate portion (projection) of the plastic lens, and FIG. 2 shows a state after cutting the gate portion (projection) of the plastic lens.

The plastic lens 1 of this embodiment constitutes a pickup lens of an optical disk optical head. As shown in FIGS. 1 and 2, a lens portion (a portion which effectively functions as a lens) is provided at a central portion. Two.

A first curved surface 21 having a spherical surface is formed on one surface of the lens portion 2, and a second curved surface 22 having a spherical surface is formed on the other surface. First curved surface 2
The curvature of 1 is set larger than the curvature of the second curved surface 22.

A ring-shaped rim 3 is formed on the outer periphery of the lens portion 2. A pair of opposing surfaces are formed on the upper and lower sides of the rim 3 in FIG.
That is, the surface on the first curved surface 21 side constitutes a reference surface 31 for positioning when fixing the plastic lens 1 to the lens holder (lens support member) 5.

On the outer peripheral surface of the rim 3, a gate (projection) 4 serving as a flow path for injecting molten plastic during molding is formed so as to protrude outward.

The lens portion 2, rim 3, and gate portion 4 are integrally formed of the same plastic material. Examples of the plastic material include polymethyl methacrylate, polycarbonate, polystyrene, acrylonitrile-styrene copolymer, poly (-4-methylpentene-1), and cyclic olefin copolymer.

As shown in FIG. 1, the gate portion (before cutting)
4 ′ is cut in the middle by a pair of cutting blades 6a and 6b to form a gate portion 4 having a shape as shown in FIG. In this case, the cutting direction, that is, the moving direction of the cutting blades 6a and 6b is a direction substantially parallel to the optical axis 23 of the lens unit 2, as indicated by arrows 61 and 62 in FIG.

By this cutting, the end of the gate portion 4
The burrs 41 are generated, and the projecting direction of the burrs 41 is a direction parallel to a plane having the optical axis 23 of the lens unit 2 as a normal line. Therefore, as described below, the positioning of fixing the plastic lens 1 to the lens holder 5 is not affected by the burr 41.

In this embodiment, the cutting blades 6a, 6b
Move in a direction where they both approach each other. As a result, the burr 41 is formed substantially at the center of the rim 3 in the thickness direction (near １ ／ of the thickness of the rim 3).

However, the present invention is not limited to this, and one of the cutting blades 6a and 6b may be fixed and the other may move so as to approach it. In this case, the position of the burr 41 is unevenly distributed from the center in the thickness direction of the rim 3 to the first curved surface 21 side or the second curved surface 22 side.
It does not affect the positioning when fixing the lens to the lens holder 5.

As shown in FIGS. 3 and 4, a lens holder 5 has a first circular opening 5
1, a second circular opening 52 which is open to the other surface side and communicates with the first circular opening 51, and which is formed on the outer periphery of the second circular opening 52 and communicates with the second circular opening 52 And a substantially rectangular concave portion 53.

The first circular opening 51 has an inner diameter equal to or slightly larger than the diameter of the lens portion 2, and the second circular opening 52 has an inner diameter substantially equal to the diameter of the rim 3. I have.

The bottom surface 521 of the second circular opening 52 and the recess 5
The bottom surface 531 of the lens 3 forms a continuous same plane, and the reference surface 31 of the plastic lens 1 abuts on this plane to position the plastic lens 1 with respect to the lens holder 5 in the direction of the optical axis 23.

That is, as shown in FIGS. 5 and 6,
When the plastic lens 1 is inserted into the lens holder 5 so that the gate portion 4 and the concave portion 53 coincide with each other, the rim 3 is fitted into the second circular opening 52, and is inserted in the lateral direction (the direction perpendicular to the optical axis 23). The positioning is performed, and the reference surface 31 of the rim 3 contacts the bottom surface 521, so that the plastic lens 1 is positioned with respect to the lens holder 5 in the direction of the optical axis 23.

At this time, the first curved surface 21 is located inside the first circular opening 51. Further, the gate portion 4 is housed in the concave portion 53 and is in contact with the bottom surface 531.

At this time, the burr 41 at the end of the gate portion 4
Protrudes not in a direction parallel to the optical axis 23 but in a direction parallel to a plane with the optical axis 23 as a normal line. Therefore, the end of the gate portion 4 does not deform and exceed the reference plane 31 downward in FIG.

That is, there is no inconvenience that the burrs 41 come into contact with the bottom surface 531 to lift the plastic lens 1, and therefore, the positioning of the plastic lens 1 with respect to the lens holder 5 in the direction of the optical axis 23 is not affected at all.

Further, the width W of the recess 53 is set to have a sufficient margin in consideration of the protrusion of the burr 41 in housing the gate portion 4. There is no hindrance to storage and lateral positioning.

In the present invention, the portion cut as described above may be a projection other than the gate.

Although the plastic lens of the present invention has been described based on the embodiment shown in the drawings, the present invention is not limited to this, and the structure of each part may be any one that can exhibit the same function. Can be replaced by

Needless to say, the use of the plastic lens of the present invention is not limited to the pickup lens of the optical head as described above.

[0035]

As described above, according to the plastic lens of the present invention, it is possible to eliminate the influence of burrs caused by cutting the gate portion, and to accurately position the lens during assembly.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an embodiment of a plastic lens of the present invention.

FIG. 2 is a perspective view showing an embodiment of the plastic lens of the present invention.

FIG. 3 is a plan view showing a configuration example of a lens holder.

FIG. 4 is a sectional view taken along line AA in FIG. 3;

FIG. 5 is a plan view showing a state where the plastic lens of the present invention is fixed to a lens holder.

FIG. 6 is a sectional view taken along line BB in FIG. 5;

[Explanation of symbols]

 Reference Signs List 1 plastic lens 2 lens portion 21 first curved surface 22 second curved surface 23 optical axis 3 rim 31 reference surface 4 gate portion 4 'gate portion (before cutting) 41 burr 5 lens holder 51 first circular opening 52 second Circular opening 521 Bottom surface 53 Concave portion 531 Bottom surface 6a, 6b Cutting blade 61, 62 Arrow (cutting direction)

Claims (2)

[Claims] 1. A plastic lens injection-molded from a plastic material, wherein a gate portion for injecting molten plastic at the time of molding is protrudingly formed at an outer peripheral portion of a lens portion having a curved surface on at least one side, and the gate portion is formed. A plastic lens, wherein an end of the plastic lens is cut by a cutting blade in a direction substantially parallel to an optical axis of the lens unit. 2. A plastic lens injection-molded from a plastic material, comprising: a lens portion having a curved surface on at least one side; and a pair of opposed lens portions formed integrally with the lens portion on an outer peripheral portion of the lens portion. One of the surfaces is a rim constituting a reference surface for positioning when fixing the plastic lens to the lens support member, and is formed integrally with the rim on the outer peripheral portion of the rim, and the molten plastic is injected during molding. An end of the gate portion is cut by a cutting blade in a direction substantially parallel to an optical axis of the lens portion, and is configured not to exceed the reference plane. Features plastic lens.