JP3875415B2 - Lens holder for optical pickup - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical pickup lens holder in an information recording / reproducing apparatus, and more particularly to an optical pickup lens holder having a plurality of lens mounting holes.
[0002]
[Prior art]
As an optical information recording / reproducing apparatus, for example, a video disc player, a digital audio player, an optical disc file, and the like are known. In recent years, a digital video disc (DVD) has been developed as a device capable of recording and reproducing a large amount of information. The optical pickup for performing focus control and tracking control of these devices collects the light beam that has passed through the objective lens on the disk surface and detects information. Must be imaged on the disk surface.
That is, the optical pickup needs to be recorded or reproduced on information recording media having a constant intensity distribution of the light beam incident on the objective lens, a fixed light spot shape, and different information recording densities.
[0003]
Furthermore, a digital video disc (DVD) may have two objective lenses, and in this case, it is necessary to minimize the focus shift at the time of lens switching. Also, if there is a deviation (optical axis radial deviation) between the signal track (information bit string) on the disc and the optical axis of the objective lens, accurate reading cannot be performed. It is necessary to make the optical axis of the lens coincide with the signal track. Such defocus compensation is performed by a focus servo, and signal track shift compensation is performed by a tracking servo.
[0004]
FIG. 4 shows an example of a method in which a drive unit support system of a DVD focus drive system uses a slide bearing. 4A is a plan view and FIG. 4B is a cross-sectional view. In this system, the drive unit is guided by a fixed support shaft 9 and moves in the focus direction, and at the same time, the drive unit rotates about the support shaft 9 to perform switching and tracking control of the two objective lenses 8a and 8b. It is a drive system of a type pickup. Here, the support shaft 9 is fixed to the base 11 together with the surrounding magnetic core 10. The lens holder 1 is fitted to the support shaft 9 via a bearing 2 in a rotatable state, and a driving coil 12 is provided on the outer peripheral surface thereof. At the eccentric position of the lens holder 1, there are lens mounting holes 4a and 4b provided with a lens receiving surface 3, and objective lenses 8a and 8b are respectively mounted. The driving coil 12 is opposed to the focus coil wound around the axis of the lens holder 1 and the optical axis direction of the objective lenses 8a and 8b, with the plane including the axis of the lens holder 1 as a symmetry plane. A tracking coil (not shown) arranged at a position is included, and the amount of movement and rotation of the lens holder 1 in the axial direction is controlled in accordance with the magnitude of the current flowing through the focus coil and the tracking coil.
In such an optical pickup drive system, the bearing 2 fitted to the support shaft 9 is required to have a high degree of squareness between the objective lenses 8a and 8b. Since the optical axis accuracy of twice or more is required compared to the above, a high degree of parallelism between the objective lenses 8a and 8b is required. In particular, high accuracy parallelism is required for write-once DVDs.
[0005]
FIG. 5 shows an example of the cantilever method among the four wire methods in which the lens holder 1 is supported by four parallel wires 13. FIG. 5A is a plan view and FIG. 5B is a cross-sectional view. In this method, a driving coil 12 including a focus coil and a tracking coil is provided on the outer peripheral surface of the lens holder 1 to which the objective lenses 8a and 8b are attached, and the lens holder according to the magnitude of the current flowing through these coils. 1 focus and tracking direction are controlled.
Even in this case, particularly in DVD, a high degree of parallelism between the objective lenses 8a and 8b is required.
[0006]
[Problems to be solved by the invention]
However, the lens holder 1 is generally manufactured by injection molding of a resin composition filled with a reinforcing material. Therefore, the lens mounting holes 4a and 4b can be welded. As a result, the unevenness of the weld formed on the lens receiving surface 3 prevents the lenses 8a and 8b from being stably fixed to the lens mounting holes 4a and 4b, and the perpendicularity to the bearing 2 cannot be maintained with high accuracy. There is.
There is also a problem that the parallelism between the objective lenses 8a and 8b cannot be maintained with high accuracy.
[0007]
Although the lens 8 is fixed to the side wall surface 14 of the lens mounting hole with an adhesive, the adhesive often flows out to the lens receiving surface 3, and in this case also, the parallelism between the objective lenses 8 a and 8 b is impaired. There is a problem of being. In particular, as the lens holder for the optical pickup is reduced in size, the adhesive flow-in portion is also reduced, and as a result, excessive parallel flow between the objective lenses 8a and 8b cannot be maintained due to excessive outflow of the adhesive. The lens 8 protrudes from the lower surface, and there is a problem that the focus and tracking control of the lens holder becomes difficult.
[0008]
The present invention has been made to cope with such problems, and maintains the squareness of the lens and the parallelism of a plurality of objective lenses with high accuracy without being affected by the unevenness caused by the weld during molding of the lens holder. In addition, an object of the present invention is to provide a lens holder for an optical pickup having high-precision recording / reproducing characteristics by suppressing the protrusion of the adhesive.
[0009]
[Means for Solving the Problems]
The lens holder for an optical pickup according to claim 1 is a lens holder for an optical pickup having a lens mounting hole provided with a lens receiver and formed by injection molding, wherein the lens receiver is in the lens mounting hole. the height position of the non-weld portion of the lens receiving surface is formed of three protrusion provided at the horizontal, the height of the three projections, receiving adhesive lens to fix the lens The height is such that the surface does not come into contact with the lens surface, and the three convex portions are arranged at substantially equal angles on the circumference of the lens receiving surface.
[0014]
Further, the present invention is characterized in that a plurality of the lens mounting holes are provided.
[0015]
If the lens holder of the lens mounting hole is formed with three convex portions, when the lens is mounted on the lens holder, it is always supported by the three convex portions. Therefore, if the level accuracy of the three protrusions can be maintained, the perpendicularity to the bearing 8 can be maintained.
Moreover, even if it is a several lens attachment hole, a mutual parallelism can be easily maintained by providing each with three convex parts.
In particular, in the case of a lens holder obtained by injection molding, the perpendicularity to the bearing and the parallelism of a plurality of lenses can be more easily maintained by providing the three convex portions at locations other than the weld portion. As a result, the accuracy of the optical pickup can be easily increased, so that the production cost of the lens holder can be greatly reduced.
In addition, since the height of the convex portion is set so that the adhesive on the lens receiving surface does not contact at least the lens surface, even if the adhesive protrudes, it does not reach the lens surface. It can be done with accuracy.
[0016]
As the adhesive for fixing the lens, a UV curable type having a high viscosity that is quickly cured by irradiation with ultraviolet rays is often used. For this reason, in the case of a resin lens, the internal stress change (distortion) of the lens often occurs due to the curing of the adhesive. However, by forming a plurality of recesses on the inner peripheral surface of the lens mounting hole, the circumferential By forming the upper uniform angle and applying an adhesive to the recess, distortion of the lens can be suppressed and high optical axis accuracy can be obtained.
In addition, when the depth of the concave portion serving as the adhesive application portion is 0.1 to 0.7 mm, it is particularly easy to maintain parallelism, and high optical axis accuracy with no defocusing can be obtained.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the lens holder of the present invention will be described with reference to FIGS. FIG. 1 is a plan view of a lens holder in a system using a slide bearing. FIG. 2 is a cross-sectional view showing a state in which the lens is attached to the lens holder.
The lens holder 1 has a bearing 2 and lens mounting holes 4 a and 4 b provided with a lens receiving surface 3. The lens receiving surface 3 is formed on the upper plane of a hollow disk provided concentrically on the inner peripheral surfaces of the lens mounting holes 4a and 4b. The lens receiving surface 3 supports a lens made of glass, a transparent resin such as acrylic or polycarbonate, and functions to limit a light beam incident on the lens. Further, an adhesive application portion 7 for fixing the lens with an adhesive is provided on the inner peripheral surface of the lens mounting holes 4a and 4b. In order to reduce the change in internal stress of the lens accompanying the solidification of the adhesive, the adhesive application portion 7 is provided not on the lens receiving surface 3 but on a part of the inner peripheral surface of the lens mounting hole.
[0018]
Three convex portions 5 according to the present invention are provided in the lens mounting hole, and preferably three are formed on the lens receiving surface 3. Further, three convex portions 5 are arranged on the lens mounting hole or the circumference of the lens receiving surface 3 at an angle of about 120 °, which is a substantially uniform angle. Thereby, a lens can be fixed to a fixed surface. Therefore, by providing the height of the three convex portions horizontally, the lens can be fixed horizontally, and even when there are a plurality of lenses, the parallelism of each lens can be maintained.
Specific methods for providing the heights of the three convex portions horizontally include, for example, a method of precisely adjusting in advance with an injection mold, a method of polishing and adjusting the surface after the convex portions 5 are formed, and the like.
In particular, when the lens holder is formed by injection molding, three convex portions 5 are formed at locations other than the weld 6 generated during molding. By avoiding the weld 6, the lens is supported by the convex portion 5 without being affected by the unevenness caused by the weld 6. The weld 6 can be determined by setting a gate in the mold.
[0019]
The shape of the convex portion 5 may be a shape that is convex from the lens receiving surface 3. Examples thereof include a spherical surface, a flat surface, and an R-shaped convex portion.
The height of the convex part 5 is higher than the convex part formed in the weld part, and even if the adhesive flows out into the lens mounting hole from at least the adhesive application part 7, the outflow amount is convex on the lens receiving surface. Any height that does not exceed the height of the portion 5, that is, when the lens is fixed in the lens mounting hole, may be a height at which excess adhesive accumulates on the lens receiving surface other than the convex portion 5. Thus, when the lens 8 is bonded to the lens mounting hole 4 of the lens holder 1, unnecessary adhesion of the adhesive to the lens surface 8c can be prevented, and the adhesive can be prevented from flowing out to other parts. Thus, the lens receiving surface 3 has a function as an adhesive reservoir by forming the convex portion 5.
Specifically, in the case of a lens having a diameter of about 4 mmφ, the height of the convex portion 5 is preferably in the range of 0.005 to 0.5 mm. Within this range, it is not affected by the convex part formed in the weld part. The lens receiving surface 3 functions as an adhesive reservoir while maintaining parallelism.
[0020]
Another embodiment of the lens holder of the present invention will be described with reference to FIG. FIG. 3 shows an example of a system in which the drive unit support system of the focus drive system uses a slide bearing. FIG. 3 (a) shows a plan view and FIG. 3 (b) shows a cross-sectional view.
The lens holder 1 has a bearing 2 and a lens 8 fitted in the lens mounting hole.
In this embodiment, a plurality of recesses 7a serving as adhesive application portions are formed on the inner peripheral surface of the lens mounting hole. The recesses 7a are preferably arranged at substantially equal angles on the circumference of the lens mounting hole, for example, at an angle of about 120 degrees. Thereby, by applying an adhesive to the recess 7a, distortion of the lens can be suppressed and high optical axis accuracy can be obtained.
[0021]
The shape of the concave portion serving as the adhesive application portion may be any shape that is concave from the lens surface, and the depth h of the concave portion is in the range of 0.1 to 0.7 mm, preferably 0.3 to 0.5 mm. By setting the shape of the recess in this way, adhesion of the adhesive to the lens surface can be prevented, and the outflow to the lens receiving surface can be prevented.
On the other hand, when the depth h is 0.7 mm or more, the adhesive flows out to the lens receiving surface, and the parallelism cannot be maintained, and the focus and tracking control of the lens holder becomes difficult. On the other hand, if the thickness is 0.1 mm or less, the adhesive may adhere to the lens surface, so that defocus occurs and an accurate optical axis cannot be obtained.
The lens holder shown in FIG. 3 does not have the convex portion 5 shown in FIG. 1, but the convex portion 5 may be provided on the lens receiving surface 3.
[0022]
When the lens holder of the present invention is produced by injection molding, it is preferable that the resin composition is excellent in mechanical strength and sliding characteristics required for the lens holder and has little unevenness in the weld portion.
Suitable resin compositions include resin compositions mainly composed of polyamideimide resin, polyphenylene sulfide resin, polyetheretherketone resin, polyetherketone resin, polyetherimide resin, and epoxy resin.
[0023]
The polyamide-imide resin is preferably a polyamide-imide resin having at least one residue selected from an aliphatic residue and an alicyclic residue between at least amide bonds, between imide bonds, or between amide bonds and imide bonds. . Here, a residue means the part except a functional group part, for example, the part except the diamine part of aromatic diamine.
Further, at least one resin selected from polyphenylene sulfide resin, polyester resin, liquid crystalline resin and polyphenylene ether resin can be blended with the above-mentioned polyamideimide resin.
[0024]
A resin composition comprising a polyamide-imide resin, a polyphenylene sulfide resin or the like and a fiber filler such as glass fiber, carbon fiber or whisker and / or a solid lubricant such as polytetrafluoroethylene is preferable. A plate-like or scale-like filler such as mica powder can be used as the filler.
[0025]
It is preferable that the resin composition according to the present invention has a composition in which the flexural modulus after injection molding is, for example, 14000 MPa or more, preferably 15000 MPa or more, more preferably 17000 MPa or more according to the measurement method of ASTM D790. .
The upper limit of the flexural modulus of the molded body made of the above resin composition depends on the characteristics of various materials, but is, for example, 50000 MPa or less, specifically 40000 MPa or less, more specifically 37000 MPa or less, or these Is less than
[0026]
An example of the resin composition according to the present invention is shown below.
1) Polyphenylene sulfide resin composition 1: Polyphenylene sulfide resin (Dainippon Ink Chemical Co., Ltd .: DCP C-115) 70% by weight and carbon fiber (Toray Industries, Inc .: Torayca T008A 6 mm) 30% by weight are melt blended.
2) Polyphenylene sulfide resin composition 2: Polyphenylene sulfide resin (Dainippon Ink Chemical Co., Ltd .: DCP C-115) 55 wt% and carbon fiber (Toray Industries, Inc .: Torayca T008A 6 mm) 30 wt% and tetrafluoroethylene resin ( Mitsui-DuPont Fluoro Chemical Co., Ltd .: Teflon 7J) is melt blended with 15% by weight.
3) Polyphenylene sulfide resin composition 3: 70% by weight of polyphenylene sulfide resin (manufactured by Toprene: PPS T4AG) and 30% by weight of carbon fiber (Toray Industries, Inc .: TORAYCA T008A 6 mm) are melt blended.
4) Polyetheretherketone resin composition (PEEK): Polyetheretherketone resin (manufactured by Victrex Limited: PEEK-150P) 70% by weight and carbon fiber (Toray Industries, Torayca T008A 6mm) 30% by weight Melt blend.
5) Polyetherimide resin composition (PEI): Polyetherimide resin (manufactured by GE USA: Ultem 1000) 70% by weight and glass fiber (Asahi Fiber Glass Co., Ltd., CSO3MA497) 30% by weight are melt blended. .
[0028]
【The invention's effect】
Since the lens holder for an optical pickup according to the present invention has three convex portions on the lens receiver, the perpendicularity between the lens bearing and the support shaft can be maintained. Further, even with a plurality of lens mounting holes, mutual parallelism can be easily maintained. As a result, the focus and tracking control of the optical pickup can be performed with high accuracy.
[0029]
In addition, in the lens holder of the optical pickup formed by injection molding, since there are three convex portions at locations other than the weld portion, the above perpendicularity and mutual parallelism can be achieved regardless of the irregularities of the weld portion. Can keep. As a result, the focus and tracking control of the optical pickup can be performed with high accuracy.
[0030]
Since the three convex portions are arranged at substantially equal angles on the circumference of the lens mounting hole, the lens can be more stably fixed to the lens mounting hole.
[0031]
In addition, since the height of the three convex portions is at least a height at which the adhesive does not contact the main surface of the lens, even if the adhesive protrudes, it does not hit the lens surface. As a result, the focus and tracking control of the optical pickup can be performed with high accuracy.
[0032]
With the above-described configuration, the present invention can greatly reduce the defocus when the lens is switched, particularly in the case of a lens holder for an optical pickup having a plurality of lens mounting holes.
[Brief description of the drawings]
FIG. 1 is a plan view of a lens holder in a system using a slide bearing.
FIG. 2 is a cross-sectional view showing a state in which a lens is attached to a lens holder.
FIG. 3 is a view showing another example of a lens holder in a system using a slide bearing.
FIG. 4 is a diagram showing a lens holder in a system using a slide bearing.
FIG. 5 is a diagram showing a lens holder in a cantilever system.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Lens holder 2 Bearing 3 Lens receiving surface 4 Lens attachment hole 5 Convex part 6 Weld 7 Adhesive application part 8 Lens 9 Support shaft 10 Magnetic core 11 Base 12 Driving coil 13 Wire 14 Side wall surface

Claims (2)

A lens holder for an optical pickup having a lens mounting hole with a lens receiver and formed by injection molding,
The lens received by the lens mounting Ri Na lens receiving surface height position of the non-weld portion in is formed from three projecting portions provided at horizontal hole, the height of the three projections The adhesive for fixing the lens has a height that does not contact the lens surface on the lens receiving surface, and the three convex portions are arranged at substantially equal angles on the circumference of the lens receiving surface. An optical pickup lens holder. The lens holder for an optical pickup according to claim 1, wherein a plurality of the lens mounting holes are provided.

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