JPH08315394A - Objective lens driving device for optical pickup - Google Patents

Abstract

PURPOSE: To obtain an objective lens driving device for optical pickup which has excellent reliability and is low in electric power consumption for optical disk devices, such as CD players and LD players. CONSTITUTION: This objective lens driving device is constructed by fixing a small-sized objective lens 104 with a cover 11 having a light transmissive hole 12 smaller than the diameter of this small-sized objective lens 104 and consisting of a material having a Young's modulus larger than the Young's modulus of an objective lens holder 9 and fixing this cover 11 and the objective lens holder 9 by adhesion, etc. Thereby, the deterioration of the optical characteristics of the small-sized objective lens 104 by the adhesion is eliminated and the rim on the outer periphery of the small-sized objective lens 104 is miniaturized. The objective lens driving device for optical pickup which has the excellent reliability and is low in electric power consumption is thus obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disc reproducing apparatus such as a CD (compact disc) player or an LD (laser disc) player, or an objective lens driving apparatus for an optical pickup used in an optical disc recording / reproducing apparatus.

[0002]

2. Description of the Related Art FIG. 6 is a schematic view of the structure of an optical pickup installed in an optical disk device.

A beam emitted from the semiconductor laser 1 passes through a beam splitter 2 and enters an objective lens 4 provided in a lens holder 3. Then, the laser light is condensed by the objective lens 4, and a minute beam spot is formed on the recording surface of the optical disc E. The lens holder 3 is provided with a driving unit 5 which is composed of a piezoelectric element and an electromagnetic circuit and can drive the objective lens 4 in the focus direction and the tracking direction. The objective lens 4 can follow the surface shake and eccentricity of the optical disc E. It is like this.

The beam reflected from the recording surface of the optical disk E passes through the objective lens 4 and returns, and is reflected by the beam splitter 2 in the direction perpendicular thereto. Then, according to the intensity of the beam detected by the pin photodiode 6,
The information pits of the optical disc E can be read.

Since the objective lens driving device equipped with the objective lens 4 follows the disk E rotating at a high speed, the objective lens 4 may be momentarily subjected to a gravitational acceleration of 100 m / s ² . In addition to this, a considerable force is expected to be applied to the objective lens under various environments, and the fixing structure of the objective lens 4 is required to have sufficient strength and reliability.

In the past, glass having high mechanical strength was mainly used as the material for the objective lens 4, but in recent years, for example, acrylic plastics have been used mainly for the purpose of cost reduction. In order to secure the mechanical strength and reliability, it is necessary to devise a bonding method such as providing a huge edge (a peripheral ring wall outside the effective diameter of the objective lens) on the outer periphery of the objective lens 4.

[0007] Conventionally, as a method of adhering a plastic objective lens having a huge edge, for example, an actual flat plate 1-170.
There is a publication No. 330. A conventional optical pickup will be described below based on Japanese Utility Model Laid-Open No. 1-170330.

FIG. 7 is a side sectional view of an internal structure of a holder of a conventional objective lens driving device for an optical pickup.

An objective lens 4 is housed in the lens holder 3. The objective lens 4 is integrally formed of plastic, and its upper surface 4a and lower surface 4b are spherical or aspherical convex curved surfaces. And there is an edge 4 on the outer circumference of the spherical surface.
c is formed, and a lens positioning wall 4d is formed in a lower portion of the edge 4c with a step.

The lens holder 3 has an aperture 3a at its inner diameter portion for narrowing the incident beam to the effective diameter of the objective lens 4.
Is provided. Due to the existence of the step 3c, the aperture 3a is formed with a hole diameter D smaller than that of the lower end hole 3b. The beam transmitted through the beam splitter 2 shown in FIG. 6 is focused by the aperture 3a into a beam having a diameter D,
The beam having the diameter D is made to enter the effective diameter of the objective lens 4.

Further, in the conventional objective lens holder 3,
An outer wall 7 is circumferentially formed on the upper portion of the aperture 3a. The position of the objective lens 4 is determined by the inner peripheral portion of the outer wall 7 and the lens positioning wall 4d, and the outer peripheral portion of the outer wall 7 and the outer peripheral portion of the edge 4c of the objective lens 4 are fixed by an adhesive 8.

[0012]

However, in the above conventional structure, the adhesive 8 causes stress in the edge 4c,
This stress causes a problem that the objective lens 4 is distorted and the optical characteristics are deteriorated.

Further, it is necessary to make the edge 4c large so that the objective lens 4 is not distorted. Therefore, the objective lens 4 becomes large and the lens holder 3 becomes large,
There is a problem that the power consumption of the objective lens driving device increases.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above problems of the prior art and to provide an objective lens driving device for an optical pickup which is excellent in reliability and consumes less power.

[0015]

To achieve this object, an objective lens driving device for an optical pickup according to the present invention has a cover having a Young's modulus higher than that of an objective lens holder and having a light transmitting hole smaller than the diameter of the objective lens. The objective lens is fixed by, and the cover and the objective lens holder are fixed.

[0016]

According to the present invention, since the objective lens is not directly adhered by the above structure, the distortion of the objective lens due to the adhesive is eliminated and the reliability is improved. Further, since the edge for distortion prevention can be made small and the objective lens can be made compact and lightweight, the power consumption of the objective lens driving device for the optical pickup can be reduced.

[0017]

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a side sectional view of an objective lens driving device for an optical pickup according to the first embodiment of the present invention.
The constituents having the same functions as those of the conventional example shown in FIGS. 6 and 7 are designated by the same reference numerals.

Reference numeral 9 is an objective lens holder. This objective lens holder 9 is arranged at the tip of the beam splitter 2 in the optical pickup of the optical disk device shown in FIG. A small objective lens (hereinafter referred to as a small objective lens) 104 supported in the objective lens holder 9 converges the beam transmitted through the beam splitter 2 to form a minute spot of the beam on the recording surface of the optical disc E. It is for forming.

The compact objective lens 104 has a convex shape whose upper and lower surfaces are spherical or aspherical, and has a flat edge 1 around the convex shape.
0 is formed.

The objective lens holder 9 has a hole 9a formed in the center thereof, and its upper portion projects in the inner diameter direction.
An aperture 3a is formed by the inner surface thereof. The beam radiated into the objective lens holder 9 is focused by the aperture 3a into a light beam having a diameter D.

Inside the objective lens holder 9, an upper hole 9c extending from the upper end of the aperture 3a in the radial outer peripheral direction is formed, and from the upper end of the upper hole 9c extending in the radial outer peripheral direction, the diameter is approximately equal to the diameter of the small objective lens 104. An insertion hole 9d is formed. The insertion hole 9d and the small objective lens 10
The small objective lens 104 is positioned by the plane edge 10 of 4.

Reference numeral 11 denotes a cover, which is adhered to the objective lens holder 9. A light transmission hole 12 is formed in the center of the cover 11.
Are formed. The hole diameter is smaller than the diameter of the small objective lens 104, and the converged light emitted from the small objective lens 104 is not blocked.

Reference numeral 13 denotes a damper, which is adhered to the upper surface of the cover 11 and prevents the optical disc E from being scratched when the objective lens driving device collides with the optical disc E.

Reference numeral 5 denotes a driving means composed of an electromagnetic circuit or a piezoelectric element, and drives the objective lens holder 9 including the small objective lens 104 in the focus direction and the tracking direction.

Next, a method of positioning and fixing the small objective lens 104 with respect to the objective lens holder 9 will be described.

The outer peripheral surface and the lower surface of the planar edge 10 of the small objective lens 104 are brought into contact with the side surface of the insertion hole 9d of the objective lens holder 9 and the step portion to be positioned. And cover 11
The lower surface of the is pressed against the upper surface of the flat edge 10, and in this state, the cover 11 and the objective lens holder 9 are adhered to each other to fix the small objective lens 104.

As described above, in the objective lens driving device for the optical pickup according to the present embodiment, the objective lens 104 is inserted into the insertion hole 9d in the upper part of the objective lens holder 9, and the light smaller than the outer diameter of the small objective lens 104 is used. Since the cover 11 having the transmission hole 12 presses the upper surface of the flat edge 10 and the cover 11 is fixedly adhered to the objective lens holder 9, the small objective lens 104 is not directly adhered to the small objective lens 104. Can be prevented. Further, since the edge of the objective lens 104 for preventing the occurrence of distortion can be reduced, it is possible to reduce the size and weight of the objective lens.

The second embodiment of the present invention will be described below with reference to the drawings. 2 is a perspective view of an essential part of an objective lens driving device for an optical pickup according to a second embodiment of the present invention, and FIG. 3 is a side sectional view of the same device.

The conventional example shown in FIGS. 6 and 7 and FIG.
The same reference numerals are given to constituent members having the same function as.

The difference from the configuration of FIG. 1 is that as a cushioning material,
The cushioning member 501 is made of an elastic material such as rubber, and is provided with a ring-shaped cushioning member 501. The cushioning member 501 is inserted between the upper surface of the flat edge 10 of the small objective lens 104 and the lower surface of the cover 11 to cover the cover 11. The small objective lens 104 is fixed by being fixed to the objective lens holder 19.

Next, a method of positioning and fixing the small objective lens 104 will be described. Small objective lens 10
The outer peripheral surface and the lower surface of the flat edge 10 of No. 4 are in contact with the side surface of the insertion hole 9d of the objective lens holder 19 and the step portion, and are positioned. The cushioning member 501 is attached to the small objective lens 104.
It is inserted between the upper surface of the flat edge 10 and the cover 11.
Then, the cover 11 is pressed against the cushioning material 501 and fixed to the objective lens holder 19, thereby fixing the objective lens 104.

As described above, the objective lens driving device for the optical pickup according to the present embodiment is made of an elastic material such as rubber and has the ring-shaped cushioning member 501, and the upper surface of the flat edge 10 of the small objective lens 104. This cushioning member 501 is inserted between the cover 11 and the lower surface of the cover 11,
Is fixed to the objective lens holder 19, the small objective lens 104 is fixed. Therefore, unnecessary vibration of the small objective lens 104 inside the objective lens holder 19 and stress on the small objective lens 104 due to the cover 11 occur. In addition to the effect of the first embodiment, good servo characteristics can be obtained in the control of the driving means 5.

The third embodiment of the present invention will be described below with reference to the drawings. FIG. 4 is a perspective view of an essential part of an objective lens driving device for an optical pickup according to a third embodiment of the present invention, and FIG. 5 is a side sectional view.

The conventional example shown in FIGS. 6 and 7 and FIG.
The same reference numerals are given to constituent members having the same function as.

The difference from the configuration of FIG. 1 is that the protrusion 1 is provided on the side surface.
An objective lens holder 90 with a projection in which 90 is formed,
A curved portion 120 as a pressure contact portion having a spring structure is formed around the light transmission hole 12 toward the small objective lens 104 side, and a cutout portion 130 is formed on the side surface, and the cover is made of a material having a spring property. 111, and the curved portion 120 allows the planar edge 10 of the small-sized objective lens 104.
The small objective lens 104 is fixed by pressing the upper surface.

Next, a method of positioning and fixing the small objective lens 104 will be described. Small objective lens 10
The outer peripheral surface and the lower surface of the flat edge 10 of No. 4 are in contact with the side surface of the insertion hole 9d of the objective lens holder 90 with a protrusion and the step portion to be positioned. The curved portion 120 of the cover 111 is
The small objective lens 104 is pressed against the upper surface of the flat edge 10. Then, the notch 130 of the cover 111 is inserted into the protrusion 190 on the side surface of the objective lens holder 90 with protrusions to perform positioning and fixing to the objective lens holder 9 and to fix the objective lens 104.

As described above, the objective lens driving device for the optical pickup according to the present embodiment has the protrusion 19 on the side surface.
The objective lens holder 90 with a projection in which 0 is formed, and the small objective lens 104 projecting around the light transmission hole 12,
A bending portion 120 having a spring structure is configured, and the side surface has
The cutout portion 130 is configured and includes a cover 111 made of a material having a spring property. The curved objective portion 120 presses the upper surface of the planar edge 10 of the small objective lens 104 to fix the small objective lens 104. The structure eliminates the need for a cushioning material, and in addition to the effects of the first and second embodiments, the number of parts can be reduced.

[0039]

As described above, according to the present invention, at least the objective lens holder having the insertion hole for inserting the objective lens and the light transmitting hole having a diameter smaller than that of the objective lens are fixed to the upper surface of the objective lens holder. It consists of a cover,
By fixing the objective lens by bringing the objective lens into contact with the cover, the objective lens is not directly bonded. Therefore,
Not only does the distortion of the objective lens due to the adhesive disappear and reliability is improved, but the edge for distortion prevention can be made smaller, and the objective lens can be made smaller and lighter. It can be realized.

[Brief description of drawings]

FIG. 1 is a side sectional view of an objective lens driving device for an optical pickup according to a first embodiment of the present invention.

FIG. 2 is a perspective view of a main part of an objective lens driving device for an optical pickup according to a second embodiment of the present invention.

FIG. 3 is a side sectional view of an objective lens driving device for an optical pickup according to a second embodiment of the present invention.

FIG. 4 is a perspective view of a main part of an objective lens driving device for an optical pickup according to a third embodiment of the present invention.

FIG. 5 is a side sectional view of an objective lens driving device for an optical pickup according to a third embodiment of the present invention.

FIG. 6 is a schematic view of a structure of a conventional optical pickup.

FIG. 7 is a side sectional view of a holder of a conventional objective lens driving device for an optical pickup.

[Explanation of symbols]

 9 Objective Lens Holder 9a Hole 9c Upper Hole 9d Insertion Hole 10 Flat Edge 11 Cover 12 Light Transmission Hole 13 Damper 104 Small Objective Lens

Claims (3)

[Claims] 1. At least an objective lens, and an objective lens holder having an insertion hole for inserting the objective lens,
A cover having a light transmission hole having a diameter smaller than that of the objective lens and having a Young's modulus higher than that of the objective lens holder, fixed to the upper surface of the objective lens holder, and the objective lens holder in the focus direction or the tracking direction. And an objective lens driving device for an optical pickup, wherein the objective lens is fixed to the cover and the objective lens holder, and the objective lens is fixed. 2. At least an objective lens, and an objective lens holder having an insertion hole for inserting the objective lens,
The objective lens has a light transmission hole having a diameter smaller than that of the objective lens, is made of a material having a Young's modulus higher than that of the objective lens holder, and is made of an elastic body and a cover fixed to the upper surface of the objective lens holder. It comprises a cushioning material inserted between the covers and a driving means for driving the objective lens holder in the focus direction or the tracking direction. The cushioning material is sandwiched between the cover and the objective lens holder, and the objective lens holder is fixed. An objective lens driving device for an optical pickup, characterized in that a lens is fixed. 3. At least an objective lens, and an objective lens holder having an insertion hole for inserting the objective lens,
A cover having a light-transmitting hole having a diameter smaller than that of the objective lens, made of a material having a spring property, having a pressure contact portion at a position in contact with the objective lens, and fixed to an upper surface of the objective lens holder; The objective lens holder is fixed by driving the objective lens holder in a focus direction or a tracking direction, and bringing the pressure contact portion of the cover into contact with the objective lens and fixing the cover to the objective lens holder. An objective lens driving device for an optical pickup, characterized in that