JPS60175225A - Objective lens holding device for optical head - Google Patents

Abstract

PURPOSE:To obtain an objective lens holding device of an optical head which can be easily produced with high accuracy by burying an end of a pair of holding members which are extended in parallel to the optical axis of an objective lens and have the elasticity into the cymmetrical position of the objective lens. CONSTITUTION:An objective lens 13 is produced by a plastic or glass molding process and has an edge part 16 protruded rectangularly to an optical axis 14 at the outer peripheral part of the main body part (effective diameter part) 15. An end of a pair of belt-shaped holding members 17 which have the elasticity such as phosphor bronze and are extended in parallel to the axis 14 is buried into the symmetrical position where the axis 14 serves as a symmetrical axis. This omits the assembling process between the lens 13 and members 17 and also improves the accuracy of the positional relation between them.

Description

[Detailed description of the invention] Technical field of invention The present invention relates to an objective lens holding device (1) for an optical head.

Prior Art and Problems In general, disc-shaped recording media with concentric or spiral information tracks on which information is recorded or reproduced, such as optical discs such as video discs or compact discs, are rotated at high speed. While recording or reproducing information, information is usually recorded or reproduced by irradiating the information track with a light spot from a light bed consisting of a semiconductor laser serving as a light source and an objective lens converging the laser light from the semiconductor laser.

Therefore, each information track on a recording medium has an extremely narrow width, and the distance between adjacent tracks is also extremely narrow, and the diameter of the light spot is naturally extremely small.

Therefore, it is necessary to minimize the relative positional deviation between the light spot and the information track, that is, the tracking error, and it is also necessary to perform tracking control.

Conventionally, as a device for holding an objective lens of an optical head in order to enable the above-mentioned tracking control, for example, Japanese Patent Laid-Open No. 5
The one described in Japanese Patent No. 5-146636 is known.

In this device, an objective lens 4 of an optical head, which is disposed perpendicularly facing the recording medium I, is provided around the main body portion (effective diameter portion) 5 in order to irradiate a light spot 3 onto an information track 2 of the recording medium 1. The lens holding frame IC 2 made of a magnetic material surrounds and encloses the projecting edge 6, and the lens holding frame 7 is attached to a pair of fixing systems such as a head casing (not shown). Suspended via plate spring 8,
The objective lens 4 is deflected in a direction perpendicular to its front axis 9, in other words, in the radial direction of the recording medium 1 (in the horizontal direction in the figure), to correct and control the relative positional deviation between the information trunk 2 and the light spot 3. Do: It's two-pronged.

However, the above conventional technology has various problems as described below.

+1) Attach the objective lens 4 to the lens holding frame 1 and plate 8
Therefore, the cumulative errors associated with manufacturing and assembly become large, and it is extremely difficult to adjust the optical axis, tilt, offset, etc., and it takes a lot of time to assemble.

(2) Since the lens holding frame 7 is made of a magnetic material, it is difficult to process, requires precision, and is expensive.

OBJECTS OF THE INVENTION In view of the above-mentioned problems, it is an object of the present invention to provide an objective lens holding device for an optical head that is easy to manufacture and has excellent precision.

SUMMARY OF THE INVENTION The present invention has been developed to achieve the above objects.
A first aspect of the present invention is an objective lens holding device for an optical head that irradiates a light spot onto a recording medium such as an optical disk, in which a pair of holding members that extend parallel to the optical axis of the objective lens and have elasticity are provided at symmetrical positions of the objective lens. This embedding is performed by insert molding when molding a lens made of plastic or glass.

Further, the second invention is such that, in addition to the configuration of the first invention, a magnetic material or a permanent magnet is fixed to the outer circumference ζ of the objective lens, and a part of the tracking control mechanism is additionally configured.

Example Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 2 is a partially omitted and cutaway front view of the first embodiment of the present invention. In this embodiment, a disc-shaped recording medium 10 such as an optical disc such as a video disc or a compact disc is used. An objective lens 13 forming part of the optical head to illuminate the information track 11 with a light spot 12
whose optical axis 14 is perpendicular to the plate surface of the recording medium 10,
It is arranged as follows.

The objective lens 13 is formed by plastic molding or glass molding, and its main body part (effective diameter part)
15 is provided with a protruding edge 16 projecting in a direction perpendicular to the optical axis 14, and at a symmetrical position with the optical axis 14 of this protruding edge 1B as an axis of symmetry, a material having elasticity such as phosphor bronze is provided. At the same time (2), one end of a pair of holding members 17 in the shape of a band extending C parallel to the optical axis 14 is buried.

In addition, the embedding of the protruding edge portion 1B+2 of each holding member 17 is as follows:
This is done by inner molding when molding the objective lens 13. Moreover, at one end of each holding member 11,
A rectangular window hole 18 is provided to increase the bonding strength with the projecting edge portion IB. Further, the other end of each holding member 17 is appropriately attached to a casing of an optical head (not shown).

Further, the projecting edge portion 16 of the objective lens 13 has a radial direction (second
Ring-shaped permanent magnet 1 magnetized in the horizontal direction (in the figure)
9 is fitted. This permanent magnet 1B works together with an electromagnet (not shown) to partially suppress the tracking control mechanism.The operation of the electromagnet causes the holding member to correct the positional deviation between the information track 11 and the light spot 12. 17 in a direction perpendicular to the optical axis 14.

Note that the part of the tracking control mechanism is not limited to the permanent magnet 19, and may also be a magnetic body such as an iron ring.

4, 5, 6 and 7 respectively show the second embodiment, the third embodiment, the fourth embodiment and the fifth embodiment of the present invention.
In these embodiments, an oval, triangular, rhomboid, or rectangular window hole 20 is formed in the holding member 17 in order to prevent and attenuate resonance during tracking control. , each with one or more.

FIG. 8 is a side view of a main part showing a sixth embodiment of the present invention. In this embodiment, the holding member 11 is
A triangular cutout 21 is provided on both sides of the cutout.

FIG. 9 is a front sectional view of main parts showing a seventh embodiment of the present invention,
In this embodiment, a weight 22 of an appropriate shape is provided as appropriate to prevent resonance during tracking control.

FIG. 10 is a front sectional view of a main part showing an eighth embodiment of the present invention, and this embodiment is designed to prevent resonance.

Note that the individual holding members 17 are not limited to a single or three-layer structure, and may be, for example, two layers made of metals or synthetic resins with different elastic modulus joined together, two pieces spaced appropriately apart, or four layers joined together. The above may be sufficient.

Further, C2 for preventing resonance etc. is not limited to the above-mentioned embodiments, but for example, the mounting position of the other end of each holding member 17 to the casing is changed, in other words, the length in the direction of the optical axis 14 is changed relative to each other. It may be different.

Effects of the Invention As described above, according to the first invention, compared to the prior art, the process of assembling the objective lens and the holding member is unnecessary, and
The positional relationship between the two can be made highly accurate.

Further, since a lens holding frame is not required, weight can be reduced and followability during tracking correction can be improved.

According to the second invention, in addition to the effect C1 of the first invention, it is possible to have a part of the function of the tracking control mechanism, and C2, the shape can be made simple. It has the effect of being able to do things.

[Brief explanation of drawings]

FIG. 1 is a front view showing the prior art with some parts omitted and cut away, FIG. 2 is a front view showing the first embodiment of the present invention with some parts omitted and cut away, and FIG. 3 is the main part. Enlarged side sectional view,
4, 5, 6, 7 and 8 respectively show the second, third, fourth and fifth embodiments of the present invention.
FIGS. 9 and 10 are side views of the main parts showing the embodiment and the sixth embodiment, and FIGS. 9 and 10 are front sectional views of the main parts showing the seventh and eighth embodiments of the present invention, respectively. 10...Recording medium 11...Information track 12...Light spot 13...Objective lens 14...Optical axis 15...Body portion 16...Long edge portion 11...Holding member 18 ... Window hole 19 ... Permanent magnet 20 ... Window hole 21 ... Notch 22 ... Weight 23 ... Elastic body 24 ... Spring member Fig. 1 Fig. 2 Fig. 9 Figure 10

Claims (1)

[Scope of Claims] (1) An objective of an optical head that irradiates a light spot to record or reproduce information on a disc-shaped recording medium having concentric or spiral information tracks for recording or reproducing information. Lens holding device 5: An objective lens holding device for an optical head, characterized in that one end of a pair of holding members extending parallel to the optical axis and having elasticity is embedded in a symmetrical position of the objective lens. (2) The objective lens holding device for an optical head according to claim 1, wherein the holding member is made of an elastic metal. (3) The objective lens holding member for an optical head according to claim 2, wherein the holding member made of metal has a suitably shaped window hole. (4) The objective lens holding device for an optical head according to claim M2, wherein the holding member made of metal has a notch of an appropriate shape. (5) The objective lens holding device for an optical head according to claim 2, wherein the holding member has a weight having an appropriately shaped shape. (6) The holding member has at least two different elastic moduli.
The objective lens holding device for an optical head according to claim 1, characterized in that it is made of a combination of m metals. (Force) The holding member has at least two
The objective lens holding device for an optical head according to claim 1, characterized in that it is made of a combination of metal and synthetic resin. (8) The objective lens holding device for an optical head according to claim 1 or 2, wherein the holding members have different lengths in the optical axis direction. (9) In an objective lens holding device for an optical head that irradiates a light spot to record or reproduce information on a disc-shaped recording medium having concentric or spiral information tracks for recording or reproducing information, One end of a pair of elastic holding members extending parallel to the optical axis of the objective lens is buried in a symmetrical position of the objective lens, and a magnetic material or a permanent magnet is fixed to the outer circumference of the objective lens. Objective lens holding device for optical head. (1) The objective lens holding device for an optical head according to claim 9, wherein the holding member is made of a metal having elasticity. An objective lens holding device for an optical head according to claim 10, characterized in that the holding member made of metal has a notch of an appropriate shape. The objective lens holding device for an optical head according to claim 10. aj The holding member has an appropriately shaped weight. I The holding member for an objective lens according to claim 10. 19. The objective lens holding device for an optical head according to claim 9, wherein the member is made of a combination of at least two metals having different elastic coefficients. 2
The objective lens holding device for an optical head according to claim 9, characterized in that it is made of a combination of seed metal and synthetic resin. αe The objective lens holding device for an optical head according to claim 9 or 10, wherein the holding members have lengths in the optical axis direction that differ from each other by C1. Claim 9, wherein the magnetic body or permanent magnet is in the form of a ring fitted into a lens.
Section 10, Section 11, Section 12, Section 13, Section 14
16. An objective lens holding device for an optical head according to item 1, item 15, or item 16.