JPH0935312A - Objective lens mounting structure for optical pickup - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an objective lens mounting structure for an optical pickup which is free from optical distortions and has excellent reliability for optical disk devices, such as CD players and LD players. SOLUTION: The small-sized objective lens 104 is inserted into a lens holder 3 which is formed by dividing the side wall of a lens insertion hole 30a with dividing recessed parts 340 and includes recessed parts 300 broader than the width of the side wall on a circular part 31. The objective lens is adhered and fixed thereto by applying an adhesive on adhering grooves 80. As a result, the excess adhesive accumulates in the recessed parts 300 and the adhesive area is limited by the dividing recessed parts 340, by which the infiltration of the adhesive to the rear surface of an outer ring 104c is prevented and the adhesive area is made uniform. In addition, the miniaturization of an outer ring 104c is made possible. The optical disk device of a small size and thin type which is free from the deterioration in the optical characteristics and has the excellent reliability is obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure for mounting an objective lens for an optical pickup in an optical disc device such as a CD (compact disc) player and an LD (laser disc) player.

[0002]

2. Description of the Related Art FIG. 8 is a schematic view of the structure of an optical pickup installed in an optical disk device. The optical pickup will be briefly described below. The beam emitted from the semiconductor laser 1 passes through the beam splitter 2 and enters the objective lens 4 provided in the lens holder 3. Then, the laser light is condensed by the objective lens 4, and a minute beam spot of about 1 micron is formed on the recording surface of the optical disc E. The lens holder 3 is provided with a driving means 5 composed of a piezoelectric element and an electromagnetic circuit and capable of driving the objective lens 4 in the focus direction and the tracking direction, and with respect to the surface shake and eccentricity of the optical disc E, the objective is carried out with submicron accuracy. It can follow the lens 4.

Further, the beam reflected from the recording surface of the optical disc E is transmitted through the objective lens 4 and returned, 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. Thus, the objective lens 4 used in the optical pickup
In order to condense the beam of the semiconductor laser 1 to about 1 micron, a wavefront aberration of 1/100 level of the laser wavelength is required as an optical characteristic, and it is necessary to prevent deterioration of lens aberration due to adhesive distortion.

Further, since the objective lens 4 is made to follow the disk E rotating at a high speed, the objective lens 4 may be momentarily subjected to gravitational acceleration of up to 100 m / s ² . That is, the mounting structure of the objective lens 4 is required to have sufficient strength without causing optical distortion. Conventionally, it has been a mainstream to use glass having high mechanical strength as a material for the objective lens 4, but in recent years, for example, acrylic plastics have been used mainly for the purpose of cost reduction, and mechanical strength is increased. In order to ensure reliability, it was necessary to devise a bonding method such as providing a huge outer ring (a peripheral ring wall outside the effective diameter of the objective lens) on the outer circumference of the objective lens 4.

In particular, since the wraparound of the adhesive on the lower surface of the objective lens 4 deteriorates the optical aberration of the objective lens,
Various proposals have been made in the past. As a method for adhering a plastic objective lens having a huge outer ring, there is, for example, Japanese Utility Model Laid-Open No. 1-170330. A conventional objective lens mounting structure for an optical pickup will be described below with reference to FIG.

FIG. 9 is a side sectional view of the internal structure of a conventional lens holder having an objective lens mounting structure for an optical pickup.
The 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 forming lens surfaces. An outer ring 4c is formed on the outer periphery of the spherical surface, and a lens positioning wall 4d is formed in a lower portion of the outer ring 4c with a step.

The lens holder 3 is made of a resin molded product whose rigidity is enhanced by glass fiber or carbon, and has an aperture 3a in its inner diameter portion for narrowing the incident beam to the effective diameter of the objective lens 4. Due to the presence of the step 3c, the aperture 3a is formed with a hole diameter smaller than that of the lower end hole 3b. The beam that has passed through the beam splitter 2 shown in FIG. 8 has its beam diameter narrowed by the aperture 3 a, and the beam whose diameter has been narrowed enters the effective diameter of the objective lens 4.

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

[0009]

However, in the above-mentioned conventional structure, a minute gap is formed between the upper surface of the outer wall 7 and the lower surface of the outer ring 4c, and the wraparound of the adhesive on the lower surface of the outer ring 4c is sufficiently suppressed. I couldn't finish it. In order to reduce this effect, the outer ring 4c other than the spherical surface functioning as a lens becomes large, and the diameter of the objective lens becomes large. for that reason,
This has hindered the miniaturization and thinning of the optical disc device.

The present invention solves the above-mentioned problems of the prior art. Even when a small plastic objective lens having a small outer ring is adhered, the objective lens mounting structure for an optical pickup is highly reliable and has no optical aberration deterioration. The purpose is to provide.

[0011]

In order to achieve this object, an objective lens mounting structure for an optical pickup according to the present invention has an objective lens provided with an outer ring having a flat surface on the outer periphery of a lens curved surface, and a side wall divided into a plurality of parts. , Having a hole into which the objective lens is inserted, the bottom of the hole has an annular portion having an inner diameter equal to or greater than the inner circumference of the outer ring, and a wider side wall than the upper side wall on the annular portion. The lens holder has a concave portion, and the outer ring and the lens holder are fixed to each other with an adhesive at a position where the concave portion is located.

[0012]

According to the present invention, with the above-described structure, the adhesive flows down the outer ring side surface of the objective lens and flows downward, and is accumulated in the concave portion of the annular portion. Further, the side wall of the divided hole limits the adhesion area of the adhesive that propagates along the side wall and diffuses to the surroundings. Therefore, it is possible to prevent excess adhesive from wrapping around the lower surface of the outer ring of the objective lens, and the adhesion area becomes constant, so that even in a small objective lens with a small outer ring, deterioration of optical aberration of the objective lens due to contraction of the adhesive is not only eliminated. Not only that, the reliability and stability of the bond are improved.

[0013]

【Example】

(Embodiment 1) An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is an exploded perspective view of an essential part of a structure for mounting an objective lens for an optical pickup according to a first embodiment of the present invention, FIG. 2 is a perspective view of an essential part of the same structure in the embodiment, and FIG. It is a sectional side view of the same structure in an example. It should be noted that constituent members having the same functions as those of the conventional example shown in FIGS. 8 and 9 are denoted by the same reference numerals.

In FIGS. 1, 2, and 3, reference numeral 104 denotes a small objective lens (hereinafter referred to as a small objective lens), which converges the beam transmitted through the beam splitter 2 shown in FIG. It is for forming a minute spot of the beam on the surface. The small objective lens 104 is
The upper spherical surface 104a and the lower spherical surface 104b are spherical or aspherical convex shapes, and an outer ring 104c having a flat surface on the upper surface and a lower surface is formed around the spherical surface.

In the lens holder 3, 30a is a lens insertion hole as a hole into which the small objective lens 104 is inserted, and 30b is an intermediate hole for letting out the convex portion of the lower spherical surface 104b. Reference numeral 340 is a dividing concave portion that divides the side wall of the lens insertion hole 30a, reference numeral 80 is an adhesive groove to which an adhesive is applied, and the bottom surface is inclined toward the lens insertion hole 30a.
Reference numeral 31 is an annular portion for positioning the height of the small-sized objective lens 104, and reference numeral 300 is a concave portion in which an excessive amount of the adhesive 8 flows. The concave portion 300 is formed on the annular portion 31, and the lens insertion hole 30 located above the concave portion 300.
It is arranged wider than the side wall of a. Reference numeral 330 is a groove for releasing burrs at the end of the small objective lens 104.

Next, a method of positioning and fixing the small objective lens 104 with respect to the lens holder 3 will be described. When the small objective lens 104 is inserted into the lens insertion hole 30a, the lower spherical surface 104b enters the intermediate hole 30b, and the outer ring 1
The lower surface of 04c contacts the upper surface of the annular portion 31, and the position of the small objective lens 104 with respect to the lens holder 3 is determined by the lens insertion hole 30a and the annular portion 31. And the adhesive groove 8
The adhesive 8 is applied to 0, and the small objective lens 104 is adhered and fixed.

Here, the adhesive 8 applied to the adhesive groove 80
Diffuses circumferentially and downward from the gap between the outer ring 104c and the side wall of the lens insertion hole 30a. Of these, the adhesive 8 that diffuses in the circumferential direction is prevented from spreading unnecessarily because the diffusion is limited by the division recess 340. Further, the unnecessary adhesive 8 that tends to flow downward in the small objective lens 104 flows into the concave portion 300 and accumulates therein.

As described above, according to the objective lens mounting structure for the optical pickup of this embodiment, the side wall of the lens insertion hole 30a in the lens holder 3 is divided into the dividing grooves 34.
It is divided by 0, and an adhesive groove 80 is provided on the upper portion of this side wall.
Then, the annular portion 3 formed below the lens insertion hole 30a
A concave portion 300 corresponding to the position of the bonding groove 80 and wider than the width of the side wall is provided on the first surface. In this lens holder 3, the adhesive 8 is applied to the adhesive groove 80, and the small objective lens 1
By bonding and fixing 04, the excess adhesive 8 is removed by the recess 30.
0, the diffusion of the adhesive 8 in the circumferential direction is limited by the dividing groove 340, and it is possible to prevent the adhesive from wrapping around the lower surface of the outer ring 104c, and to keep the adhesive area constant, so that the small objective lens 104 can be used. In addition to eliminating the deterioration of the optical aberration of, the reliability and stability of the adhesion are improved.

(Second Embodiment) A second embodiment of the present invention will be described below with reference to the drawings. FIG. 4 is an exploded perspective view of a main part of an objective lens mounting structure for an optical pickup in the same embodiment, and FIG. 5 is a perspective view of a main part of the same structure in the same embodiment. The components having the same functions as those of the conventional example shown in FIGS. 8 and 9 and FIGS. 1 and 2 to 3 are designated by the same reference numerals.

4 and 5 are different from the configurations of FIGS. 1 to 3 in that the side wall of the lens insertion hole 30a is divided and the bottom portion is provided with a division recess 345 lower than the annular portion 31. is there. Next, a method of positioning and fixing the small objective lens 104 with respect to the lens holder 3 will be described.

The small objective lens 104 is attached to the lens insertion hole 30.
When inserted into a, the lower spherical surface 104b enters the intermediate hole 30b, the lower surface of the outer ring 104c abuts the upper surface of the annular portion 31, and the position of the small objective lens 104 with respect to the lens holder 3 is the same as the lens insertion hole 30a. Determined by the ring portion 31. Then, the adhesive 8 is applied to the adhesive groove 80 to apply the small objective lens 10
4 is adhesively fixed.

Here, the adhesive 8 applied to the adhesive groove 80
Diffuses circumferentially and downward from the gap between the outer ring 104c and the side wall of the lens insertion hole 30a. Of these, the adhesive 8 that diffuses in the circumferential direction is prevented from spreading unnecessarily because the diffusion is limited by the division recess 345, and the bottom area is lower than the annular portion 31, so that the outer ring 104c.
It is possible to store the adhesive agent 8 which is transmitted along the side surface of the above and overflows from the side wall. Further, the unnecessary adhesive 8 that tends to flow downward in the small objective lens 104 flows into the concave portion 300 and accumulates therein.

As described above, according to the objective lens mounting structure for the optical pickup of this embodiment, in addition to the effect of the first embodiment, the split concave portion 345 having a lower bottom than the annular portion 31 is provided. Thus, the adhesive 8 that has passed through the side surface of the outer ring 104c and overflows from the side wall can be collected, and the adhesive 8 can be prevented from entering the gap between the outer ring 104c and the annular portion 31.

(Embodiment 3) A third embodiment of the present invention will be described below with reference to the drawings. FIG. 6 is an exploded perspective view of a main part of an objective lens mounting structure for an optical pickup in the same embodiment, and FIG. 7 is a perspective view of a main part of the same structure in the same embodiment. The components having the same functions as those of the conventional example shown in FIGS. 8 and 9 and FIGS. 1 and 2 to 3 are designated by the same reference numerals.

6 and 7, the difference from the configuration of FIGS. 1 to 3 is that the lens insertion hole 30a is divided by a dividing groove 350 whose bottom is lower than the annular portion 31, and the adhesive groove 80 is arranged. In addition to the side wall, a side wall that comes into contact with the outer circumference of the outer ring 104c is provided. Next, a method of positioning and fixing the small objective lens 104 with respect to the lens holder 3 will be described.

The small objective lens 104 is attached to the lens insertion hole 30.
When inserted into a, the lower spherical surface 104b enters the intermediate hole 30b, the lower surface of the outer ring 104c abuts the upper surface of the annular portion 31, and the position of the small objective lens 104 with respect to the lens holder 3 is the same as the lens insertion hole 30a. Determined by the ring portion 31. Then, the adhesive 8 is applied to the adhesive groove 80 to apply the small objective lens 10
4 is adhesively fixed.

Here, the adhesive 8 applied to the adhesive groove 80
Diffuses circumferentially and downward from the gap between the outer ring 104c and the side wall of the lens insertion hole 30a. Of these, the adhesive 8 that diffuses in the circumferential direction is prevented from spreading unnecessarily because the diffusion is limited by the dividing groove 350, and the bottom portion is lower than the annular portion 31, so that the outer ring 104c of the outer ring 104c is The adhesive agent 8 can be accumulated along the side surface and over the side wall. Since the side wall of the lens insertion hole 30a is arranged in a portion other than the portion where the adhesive groove 80 is arranged, the area of the side wall for positioning the compact objective lens 104 can be increased. Further, the unnecessary adhesive 8 that tends to flow downward in the small objective lens 104 flows into the concave portion 300 and accumulates therein.

As described above, according to the objective lens mounting structure for the optical pickup of this embodiment, in addition to the effects of the first and second embodiments, the bottom is lower than the annular portion 31 and the width is narrow. The lens insertion hole 30 is formed by the dividing groove 350.
By dividing the side wall of a and arranging the side wall other than the side wall where the adhesive groove 80 is arranged, the area in contact with the side surface of the outer ring 104c can be increased, so that the small objective lens 104 can be positioned stably. You can

[0029]

As described above, according to the present invention, the objective lens having the outer ring having the flat surface on the outer periphery of the curved surface of the lens is divided into a plurality of side walls of the hole, and the hole for inserting the objective lens and the hole At the bottom, insert into a lens holder having an annular portion having an inner diameter equal to or larger than the inner circumference of the outer ring, and a concave portion wider on the annular portion than the upper side wall, and the side wall of the hole and the circle. By positioning the objective lens with the ring portion and by fixing the outer ring and the lens holder with an adhesive at the position where the concave portion is located, the adhesive propagates along the outer ring side surface of the objective lens, and the downward direction is applied. It flows in and accumulates in the concave part of the annular part. Also, the side wall of the divided hole limits the bonding area. Therefore, it is possible to prevent excess adhesive from wrapping around the lower surface of the outer ring of the objective lens, and the adhesion area becomes constant, so that even in a small objective lens with a small outer ring, optical aberration deterioration of the objective lens due to contraction of the adhesive is eliminated. It is also possible to provide an objective lens mounting structure for an optical pickup, which is excellent in reliability and stability.

[Brief description of drawings]

FIG. 1 is an exploded perspective view of essential parts of an objective lens mounting structure for an optical pickup according to a first embodiment of the present invention.

FIG. 2 is a perspective view of the same.

FIG. 3 is a sectional view of the same side.

FIG. 4 is an exploded perspective view of essential parts of an objective lens mounting structure for an optical pickup according to a second embodiment of the present invention.

FIG. 5 is a perspective view of the same.

FIG. 6 is an exploded perspective view of essential parts of an objective lens mounting structure for an optical pickup according to a third embodiment of the present invention.

FIG. 7 is a perspective view of the same.

FIG. 8 is a schematic diagram of a structure of a conventional optical pickup.

FIG. 9 is a side sectional view of a conventional lens holder having an objective lens mounting structure for an optical pickup.

[Explanation of symbols]

 30a Lens insertion hole 30b Intermediate hole 31 Annular portion 80 Adhesive groove 104 Small objective lens 104a Upper spherical surface 104b Lower spherical surface 104c Outer ring 300 Recessed portion 330 Groove 340 Divided recessed portion

Claims (5)

[Claims] 1. An objective lens having at least an outer ring for condensing a light beam and having a flat surface on the outer periphery of a curved surface of the lens,
The side wall is divided into a plurality of holes, has a hole for inserting the objective lens, the bottom of the hole has an annular portion having an inner diameter equal to or greater than the inner circumference of the outer ring, and the upper portion on the annular portion. An objective lens mounting structure for an optical pickup, comprising a lens holder having a concave portion wider than the side wall located at, and fixing the outer ring and the lens holder with an adhesive at a position where the concave portion is located. 2. The objective for an optical pickup according to claim 1, wherein the bottom of the dividing recess that divides the side wall of the hole into which the objective lens is inserted is lower than the annular portion arranged at the bottom of the hole. Lens mounting structure. 3. A side wall of the hole is divided into a plurality of parts by a dividing groove having a hole into which the objective lens is inserted, the bottom part of which is lower than the annular part, and other than the bonding portion between the objective lens and the lens holder. The objective lens mounting structure for an optical pickup according to claim 1, further comprising a side wall that comes into contact with a side surface of the outer ring of the objective lens. 4. The objective lens mounting structure for an optical pickup according to claim 1, further comprising an annular groove on the outer circumference of the annular portion. 5. A second recess having a width narrower than that of the recess is provided around the hole of the lens holder and above the recess of the annular portion, and the second recess has an inclined bottom surface. The objective lens mounting structure for an optical pickup according to claim 2, characterized in that it has.