JP4034259B2 - Objective lens driving device for optical disc apparatus - Google Patents

Description

  The present invention relates to an objective lens driving device for an optical disc apparatus that projects at least one of optical information by projecting a light spot onto the optical disc.

  In recent years, as an optical disk apparatus, development of an optical head apparatus capable of comprehensively processing optical disks having different purposes and different optical characteristics such as different thicknesses and recording densities has been regarded as important. As an example of such an optical head device, in Patent Document 1, a plurality of types of objective lenses corresponding to the respective optical discs are provided so that a plurality of types of optical discs having different thicknesses can be recorded and reproduced. These objective lenses are set so that the light spot converges on the recording surface when the target optical disk is set, and a light beam obtained by spectrally dividing the light from the light emitting unit common to these objective lenses is used. It has been proposed that the incident light and the reflected light from the optical disk are in focus, that is, a light beam with a sufficient amount of light can be obtained only when the target optical disk is set with the objective lens. Yes.

JP-A-6-333255

  The present invention provides an objective lens driving device for an optical disc apparatus having a plurality of types of objective lenses, which can narrow the required driving range of the whole of the plurality of objective lenses, so that the optical axis of the light beam and the optical axis of the objective lens can be reduced. It is an object of the present invention to provide a device capable of suppressing the shift and reducing the burden on the objective lens driving device.

An objective lens driving device of an optical disk device according to the present invention is an optical disk device that mounts an optical system on a movable table that is moved in the tracking direction of the optical disk and controlled in position, and performs at least one of recording and reproduction.
One lens holder is mounted on the movable table via a conductive elastic wire,
Magnets are provided on both sides in the direction orthogonal to the tracking direction of the lens holder in the drive device base provided on the movable table,
A plurality of types of objective lenses corresponding to a plurality of kinds of optical discs, together arranged in the tracking direction on the lens holder,
Within the required drive range of the focus direction of the required drive range biggest objective lens, to fit the need driving range of other objective lens, and sets the focus position of the objective lens at different positions, the objective Secure the lens to the lens holder ,
Objective lens switching means for matching one optical axis of the plurality of types of objective lenses with the optical axis of a single light beam emitted from the light emitting section of the optical system is provided .

According to the present invention, a plurality of types of objective lenses corresponding to a plurality of types of optical disks are aligned in the tracking direction and fixed to the lens holder, and the objective lens range having the largest required driving range in the focus direction of the plurality of types of objective lenses is obtained. Since the required drive range of other objective lenses is contained within, the required drive range of the entire plurality of objective lenses can be narrowed, and as a result, the deviation between the optical axis of the light beam and the optical axis of the objective lens can be suppressed. be able to. Moreover, the burden on the objective lens driving device can be reduced by reducing the required driving range of the lens holder.

  FIG. 1A is a plan view showing an embodiment of an objective lens driving device according to the present invention, and FIG. 1B is a side view thereof. In FIG. 1, reference numeral 1 denotes a movable base that is moved in the tracking direction of the optical disk 2 and is position-controlled. An optical system 3 is mounted. Reference numeral 4 denotes a lens holder, and 5a and 5b denote different types of objective lenses fixed on the lens holder 4 with respect to a plurality of different types of optical disks.

  The lens holder 4 is mounted on the movable table 1 via a drive device base 6 fixed to the movable table 1, an objective lens switching device 7 installed thereon, and a conductive elastic wire 8. The objective lens switching device 7 includes a fixing member 9 fixed on the driving device base 6 and a rectangular through hole provided in the tracking direction in the fixing member 9 as shown in the cross-sectional view of FIG. A support rod 10 having a rectangular cross section movably inserted in 9a, a coil 11 fixed to an inner wall in the enlarged portion 9b at the center of the through hole 9a, and a support rod 10 so as to penetrate the coil 11 A permanent magnet 12 fixed to the center of the support rod 10, a substrate 13 fixed to the vicinity of both left and right ends of the support rod 10, and a stopper fixed to the drive device base 6 so as to face both end surfaces of the support rod 10. 14a and 14b.

  The base end portion of the conductive elastic wire 8 is fixed to the substrate 13 fixed to the left and right of the support rod 10 by soldering, and the lens is fixed to the tip of each of the two left and right wires 8. The left and right sides of the holder 4 are fixed, the lens holder 4 is elastically supported by the four wires 8 and is indicated by an arrow T in the tracking direction (FIGS. 1A, 2C, and 2D). ) And the focus direction (indicated by an arrow F in FIG. 1B).

  The lens holder 4 has a rectangular shape, and the objective lenses 5a and 5b are fixed to the central portion of the lens holder 4 side by side in the tracking direction. Further, rectangular focusing coils 15a and 15b and tracking coils 16a and 16b are fixed to both ends in a direction perpendicular to the tracking direction of the lens holder 4, that is, in a tangential direction of the optical disc 2, respectively. The coil moves integrally with the lens holder 4.

Reference numerals 17a and 17b denote permanent magnets, and the permanent magnets 17a and 17b are fixed to yokes 18a and 18b fixed to the drive unit base 6 so as to face the focusing coils 15a and 15b and the tracking coils 16a and 16b, respectively. The lens holder 4 is provided on both sides in a direction orthogonal to the tracking direction . The focusing coils 15a and 15b are electrically connected in series, connected to two of the four conductive elastic wires 8, and the tracking coils 16a and 16b are also connected in series to connect the other conductive elastic wires 8 to each other. Two are electrically connected.

  Reference numeral 19 denotes a reflection mirror fixed to the movable base 1, and the reflection mirror 19 makes the light beam 20 from the optical system 3 incident on the objective lens 5 a or 5 b and returns the reflected light from the optical disk 2 to the optical system 3. Is.

  In FIG. 1A, reference numerals 21a and 21b denote switches that detect the position of the support rod 10 when pressed by the support rod 10 and actuate.

  In this objective lens driving device, when the coil 11 of the objective lens switching device 7 is energized in the direction a of FIG. 2 (A), the support rod 10 is shifted as indicated by the arrow b, and as shown in FIG. 3 (A). One end of the support rod 10 is in contact with one of the stoppers 14a fixed on the drive device base 6 and the knob of the switch 21a. In this state, as shown in FIG. 3, the optical axis of one objective lens 5 a coincides with the optical axis of the only light beam 20 emitted from 3. When the coil 11 is energized in the direction opposite to the direction a, the support rod 10 is shifted in the direction opposite to the arrow b as shown in FIG. In this state, the optical axis of the other objective lens 5b coincides with the optical axis of the light beam 20, as shown in FIG. 2 (D). . Since it becomes clear whether or not a predetermined objective lens has been selected and moved to the correct position by the generation of an electrical signal by the operation of the switches 21a and 21b, it is possible to prevent malfunction. The deviation of the optical axes of the objective lenses 5a and 5b from the optical axis of the light beam 20 is set to be within a range of ± 0.1 mm.

  Thus, by shifting and positioning the objective lenses 5 a and 5 b together with the lens holder 4, the optical axis of the objective lens 5 a or 5 b is made to coincide with the optical axis of the light beam 20 from the optical system 3. Compared with the case where the objective lens is selected by changing the angle of the reflecting mirror as in, high positioning accuracy is not required for the switching device for selecting the objective lens, and the optical axis coincides easily and with less error. can do.

  After the objective lenses 5a and 5b are thus shifted, the objective lenses 5a and 5b are moved to appropriate positions in accordance with surface wobbling and decentering of the optical disc 2, so that the focusing coils 15a and 15b and the tracking coils 16a and 16b are conductive. Focus control and tracking control are performed by energizing through the elastic elastic wire 8. That is, the tracking coil 16a or 16b is linked with the magnetic flux generated by the permanent magnets 17a or 17b, respectively, and the tracking coil 16a or 16b is energized via the conductive elastic wire 8 so that the lens holder 4 in the tracking direction. Is controlled in the minute range, and when the focusing coils 15a and 15b are energized, the position of the lens holder 4 is controlled in the focus direction by the linkage with the magnetic flux by the permanent magnet 17a or 17b, and the light flux is emitted to the target spot. Controlled to concentrate.

  In the present embodiment, since the lens holder 4 is moved together with the conductive elastic wire 8, the focusing coils 15a and 15b and the tracking coils 16a and 16b, the conductive elastic wire 8 and the objective lens 5a and 5b are switched when the objective lenses 5a and 5b are switched. No excessive force is applied to the connecting lead wire and there is no risk of disconnection of the lead wire. When the substrate 13 and the drive device base 6 are connected by a lead wire, the lead wire has a sufficient mounting space, and twisting due to rotation does not occur, so there is no fear of disconnection. Further, since the conductive elastic wire 8 is moved together with the lens holder 4 to switch the objective lenses 5a and 5b, the focus control and tracking control of the objective lenses 5a and 5b are performed with the support rod 10 fixed. (In the case of the lens holder rotating type, the lens holder slides in the axial direction around the axis and rotates around the axis in accordance with the focus control and tracking control.) Any objective lens 5a Whether or not 5b is selected can be detected by the switches 21a and 21b, and the switching state of the objective lens can be reliably displayed. In addition, one type of tracking coils 16a and 16b can be used in common corresponding to the two types of objective lenses 5a and 5b, and a switch for switching the tracking coils 16a and 16b is not required, so that the circuit configuration is simplified. Can be

  Here, as shown in FIGS. 3A and 3B, regardless of the position of the lens holder 4, the focusing coils 15a and 15b and the tracking coils 16a and 16b are all over the entire width in the tracking direction. The width in the tracking direction of the permanent magnets 17a and 17b so as to face the permanent magnet 17a or 17b is greater than the length obtained by adding the width of the focusing coils 15a and 15b and the tracking coils 16a and 16b to the movement amount of the lens holder 4. By setting, when the energization of the focusing coils 15a and 15b and the tracking coils 16a and 16b is applied, the force generated by the action of these coil currents and magnetic fluxes acts on the lens holder 4 in that the position of the lens holder 4 changes. Regardless. This prevents the rotational force from acting on the lens holder 4 due to the discrepancy between the action point of the electromagnetic force and the center of gravity in the lens holder 4, prevents the optical axes of the objective lenses 5 a and 5 b from being tilted, and the light beam 20. Can be made to coincide with the optical axes of the objective lenses 5a and 5b.

  When carrying out the present invention, focusing coils 15a and 15b and tracking coils 16a and 16b for driving the lens holder 4 are provided on the driving device base 6 side, and the permanent magnets 17a and 17b are fixed to the lens holder 4 side. Good. When the arrangement is reversed in this way, the width in the tracking direction of the focusing coil or tracking coil is equal to or larger than the sum of the tracking direction width of the permanent magnet fixed to the lens holder 4 side and the movement amount in the tracking direction. By doing so, the inclination of the lens holder 4 can be prevented for the reason described above.

  Further, the objective lens switching device 7 uses an electromagnet for the stoppers 14a and 14b in FIG. 1 and uses a magnetic material for the support rod 10 so as to attract and position the support rod 10 made of a magnetic material by any one of the electromagnets. It may be. Moreover, it can also be set as the structure which moves the support rod 10 with a plunger. The support rod 10 may have a circular cross section instead of a rectangular cross section. Further, after the support rod 10 is shifted, a mechanism is provided in which the support rod 10 is always in contact with the stopper 14a or 14b and the objective lens 5a or 5b is held at a predetermined position without continuing to pass current through the coil 11. It may be provided.

  FIG. 4 illustrates an example of installation in the focus direction according to the present invention in the lens holder 4 of the objective lenses 5a and 5b. As shown in FIG. 4A, the thicknesses and set positions of the optical disc 2A and the optical disc 2B are Z1. If the required driving range is different due to the energization of the focusing coils 15a and 15b of the corresponding objective lenses 5a and 5b, the objective lens 5a is set at the solid line position and the other objective lens 5b is shifted. Is set to the position indicated by the two-dot chain line, and the position of the optical disc side end is matched as shown by c and d, the objective having the larger required driving range is shown in FIG. The required drive range Z4 (f is its neutral point) of the objective lens 5b deviates from the required drive range of the objective lens 5a, whereas the required drive range Z3 (e is its neutral point) of the lens 5a. Necessary driving range as requires Z5, and the wide driving range.

  Therefore, as shown by the solid line in FIG. 4A, the objective lens 5b is closer to the optical disc than the optical disc side end g and the optical disc side end c of the objective lens 5a by the difference Z2 (see FIG. 4A). Here, L1 and L2 in FIG. 4 (A) are working distances, which are the gaps between the objective lenses 5a and 5b and the optical discs 2A and 2B, respectively. As shown in FIG. The required drive range Z4 (h is the neutral point) of the lens 5b can be within the required drive range Z3 of the objective lens 5a.

  As described above, the objective lens 5a, 5b as a whole is driven by arranging the objective lens in which the required drive device of the other objective lens is accommodated within the required drive range of the objective lens having the maximum required drive range. The range is narrowed, and as a result, the inclination of the lens holder 4 due to excessive bending of the conductive elastic wire 8 or the like is reduced, thereby suppressing the deviation between the optical axis of the light beam 20 and the optical axes of the objective lenses 5a and 5b. be able to. Further, by reducing the required driving range of the lens holder 4, the burden on the objective lens driving device can be reduced. Note that such a relative positional relationship of the objective lenses can be applied to a case where the objective lens is selected by using the movable reflecting mirror.

  FIG. 5A shows an example in which the objective lenses 5a and 5b are separately arranged in the lens holder 4 one by one, and FIG. 5B shows the objective lenses 5a and 5b that are integrally formed according to the present invention. According to the lens mounting structure of FIG. 5A, mounting angle errors with respect to the mounting surfaces A and B of the objective lenses 5a and 5b occur between the objective lenses 5a and 5b. It becomes difficult to align the direction in a certain direction. On the other hand, as shown in FIG. 5B, if the two objective lenses 5a and 5b are formed as one, the mounting surface C is one, and the deviation of the optical axes P2 and Q2 is formed. Since this is only a time error and does not cause the above-mentioned mounting error, the direction of the optical axis can be easily aligned in a certain direction, and as a result, the deviation between the optical axis of the light beam and the objective lens can be reduced. it can. Further, the distance between the centers of the lenses in the tracking direction when the objective lenses are arranged one by one can be reduced from the distance t1 in the case of the divided arrangement shown in FIG. 5A to t2 shown in FIG. 5B. Therefore, the movement amount of the lens holder 4 in the tracking direction can be shortened, and the scale of the lens holder 4 and the objective lens switching device 7 can be reduced.

  FIG. 6 shows another embodiment of the present invention, in which a shaft 22 serving as a guide for movement of the movable table 1 is shared by a guide for the support rod 10A, and the support rod 10A is made of a magnetic material. By attracting the support rod 10A by the electromagnet 23a or 23b fixed on the driving device base 6 fixed to the lens holder 4, the lens holder 4 moves together with the conductive elastic wire 8, so that the objective lenses 5a and 5b are switched. It is a thing. If such a structure shared by the shaft 22 is used, the structure is simplified, which can contribute to downsizing.

  In the present invention, the lens holder 4 is not supported in a cantilever manner by the conductive elastic wire 8 as shown in the embodiment, but at the intermediate portion of the conductive elastic wire 8 supported at both ends by the drive device base 6. A lens holder may be supported. Further, the optical disc targeted by the present invention may be one that performs not only optical recording but also magneto-optical recording. The drive device base 6 may be formed as a part of the movable table 1.

(A) is a top view which shows one Example of the objective lens drive device by this invention, (B) is the partially broken side view.

(A) is a cross-sectional view showing a part of the objective lens switching device of the present embodiment, (B) is a perspective view showing a coil used in the objective lens switching device, (C), (D) are in this embodiment. It is a perspective view of a reflecting mirror and an objective lens for explaining an objective lens switching operation.

(A), (B) is a top view of the objective lens drive device explaining the objective lens switching operation in the present embodiment.

(A) is a diagram for explaining an installation example of the objective lens in the focus direction in the present embodiment, and (B) shows a necessary drive range of the objective lens when the positions of the two end lenses on the optical disc side are aligned. FIG. 4C is a plan view showing a necessary drive range of the objective lens when the position of the optical disc side end of one objective lens is brought close to the optical disc side according to the present invention.

(A) is sectional drawing which shows the example which divided and arrange | positioned the objective lens to the lens holder one by one, (B) is sectional drawing which shows what formed two objective lenses integrally by this invention.

It is a top view which shows the other Example of the objective lens drive device of this invention.

Explanation of symbols

1: movable base, 2: optical disc, 3: optical system, 4: lens holder, 5a, 5b: objective lens, 6: drive device base, 7: objective lens switching device, 8: conductive elastic wire, 9: fixed member 10: support rod, 11: coil, 12: permanent magnet, 13: substrate, 14a, 14b: stopper, 15a, 15b: focusing coil, 16a, 16b: tracking coil, 17a, 17b: permanent magnet, 18a, 18b: Yoke, 19: reflection mirror, 20: light beam, 21a, 21b: switch, 22: shaft, 23a, 23b: electromagnet

Claims (1)

In an optical disc apparatus that performs at least one of recording and reproduction by mounting an optical system on a movable base that is moved in the tracking direction of the optical disc and controlled in position,
One lens holder is mounted on the movable table via a conductive elastic wire,
Magnets are provided on both sides in the direction orthogonal to the tracking direction of the lens holder in the drive device base provided on the movable table,
A plurality of types of objective lenses corresponding to a plurality of kinds of optical discs, together arranged in the tracking direction on the lens holder,
Within the required drive range of the focus direction of the required drive range biggest objective lens, to fit the need driving range of other objective lens, and sets the focus position of the objective lens at different positions, the objective Secure the lens to the lens holder ,
An objective lens for an optical disc apparatus, comprising objective lens switching means for causing one optical axis of the plurality of types of objective lenses to coincide with an optical axis of a single light beam emitted from a light emitting unit of the optical system. Drive device.

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