JP2009070440A - Optical pickup device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical pickup device in which an index value obtained from a reproduced signal is within a prescribed range, and recording and reproducing of a plurality of kinds of optical disks are improved. <P>SOLUTION: An objective lens drive part is provided with: a lens holder 18 holding two objective lenses 14, 15; a holder base 16 holding the lens holder 18 and a holder base 16 which holds the lens holder 18 and has a cone-shaped aperture part aligned with an optical axis of any one side of two objective lenses 14, 15; and a holder 30 which is attached at a lower plane of the holder base 16 along the cone-shaped aperture part so as to be moved in a tilt state and has a recess part which houses a chromatic aberration correction element 33 correcting coma-aberration caused by any one of objective lenses 14, 15 tilted opposite to the lens holder 18 and chromatic aberration of recording and reproducing light. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  According to the present invention, when information is recorded on or reproduced from a plurality of types of optical discs having different wavelengths used for laser light, the index value is within a predetermined range, and recording and reproduction of a plurality of types of optical discs are favorably performed. The present invention relates to an optical pickup device.

There are various types of standardized optical disks, and these optical disks are required to be recorded and reproduced by a single optical disk device.
In order to meet this demand, an optical disk device including an optical pickup device equipped with two objective lenses and an optical pickup device equipped with two optical systems has been proposed.
Patent Document 1 describes an optical pickup device equipped with two objective lenses.
The optical pickup device described in Patent Document 1 includes a moving base and an objective lens driving unit fixed on the moving base. In the moving base, a pair of bearing portions provided at both ends are slidably supported by a pair of guide shafts. The pair of guide shafts are fixed in the radial direction of the optical disc. The objective lens driving unit is a fixed block fixed to the moving base, a movable holder that is operated in the focusing direction, the tracking direction, and the tilt direction and holds two objective lenses, and a support that connects the fixed block and the movable holder. A spring is disposed between the two objective lenses and the fixed block, and includes a drive coil that is energized to operate in the focusing direction, tracking direction, or tilt direction.
As an optical disc, a DVD (Digital Versatile Disc), a CD (Compactact Disc), a BD (Blu-Ray Disc), and an AOD (Advanced Optical Disc) are used.
JP-A-2005-302164

However, when one objective lens is used for CD and the other objective lens is used for DVD, and the objective lens drive unit is slightly tilted and fixed to the moving base, coma aberration of the CD objective lens is allowed. However, coma aberration of the objective lens for DVD is not allowed and CD can be recorded / reproduced without any problem. On the other hand, DVD has a problem that jitter value is poor and good recording / reproduction cannot be performed.
Also, when recording / reproducing two optical discs with different recording densities close to each other, if the objective lens driving unit is fixed on the moving base in order to satisfactorily record / reproduce one of the optical discs, the other optical disc Since the coma aberration of the objective lens for use is not allowed, the other optical disc has a problem that the jitter value is poor and good recording and reproduction cannot be performed.

Furthermore, when an HD-DVD (High Density-Digital Versatile Disc) is used as an optical disc, the HD-DVD standard is based on a PRSNR (Partial Response Signal to which is obtained by special processing of amplitude information obtained from a reproduction signal. It is necessary to fix an objective lens driving unit on a moving base that has an index value such as a (Noise Ratio) value within a predetermined range and that can satisfactorily perform recording and reproduction of an optical disk.
For this reason, even if one objective lens is for HD-DVD and the other objective lens is for BD, even if the objective lens driving unit is fixed so as to be optically flat with respect to the moving base, It was not possible to obtain a recording / reproducing signal satisfying the HD-DVD standard.

  Accordingly, the present invention solves the above problems, and provides an optical pickup device in which an index value obtained from a reproduction signal is within a predetermined range, and recording / reproduction of a plurality of types of optical disks is favorably performed. It is intended.

In order to achieve the above object, the present invention has the following configuration.
That is,
(1) In an optical pickup device comprising a moving base slidable on a pair of guide shafts fixed in the radial direction of the optical disc, and an objective lens driving unit placed on the moving base,
The objective lens driving unit is
A lens holder for holding two objective lenses for condensing recording / reproducing light on the optical disc;
A holder base that supports the lens holder and is formed with a mortar-shaped opening that coincides with the optical axis of one of the two objective lenses;
A coma aberration and a chromatic aberration of the recording / reproducing light, which are attached to the lower surface of the holder base so as to be tiltable along the mortar-shaped opening and the one of the objective lenses is tilted to the side opposite to the lens holder side. An optical pickup device comprising: a holder in which a concave portion capable of accommodating a chromatic aberration correcting element for correcting the above is formed.
(2) The optical pickup device according to (1), wherein the holder is attached to the holder base with a spring and an adjusting screw having one end fixed to the holder base.

According to the present invention, the index value obtained from the reproduction signal is within a predetermined range, and the recording / reproduction of a plurality of types of optical discs can be improved.

Hereinafter, an optical pickup device according to an embodiment of the present invention will be described with reference to FIGS.
FIG. 1 is a view of an optical pickup device according to an embodiment of the present invention as viewed from the optical disc side.
FIG. 2 is a perspective view of the optical pickup device according to the embodiment of the present invention.
FIG. 3 is a diagram illustrating a specific configuration of the objective driving unit.
FIG. 4 is a perspective view showing a characteristic part of the optical pickup device.
FIG. 5 is a cross-sectional view of the base and the holder.
FIG. 6 is a cross-sectional view showing a state in which the holder is inclined with respect to the base.

As shown in FIGS. 1 and 2, the optical pickup device 1 according to the embodiment of the present invention includes an objective lens driving unit 3, a first device 4, a second device 5, and a polarization on a moving base 2. The beam splitter 6, the lens 7, the rising prism 8, and the rising mirror 9 are arranged.
Bearing portions 10 and 10 provided at both ends of the moving base 2 are slidably supported by a pair of guide shafts 11 and 11, respectively. The pair of guide shafts 11, 11 are arranged in the radial direction of the optical disc D, and the optical pickup device 1 can move in the radial direction of the optical disc D on the pair of guide shafts 11, 11.
In the initial state, the optical pickup device 1 is disposed in the vicinity of the turntable 13 directly connected to the rotary shaft 12A of the spindle motor 12 of the optical disc device, and the straight line connecting the rotary shaft 12A and the center of the objective lens 14 is in the radial direction. It is in the direction that matches.

As shown in FIG. 2, the first device 4 returns to the first laser element (not shown) that emits the P-polarized first laser light and the first laser light is reflected by the optical disk D. The first photodetector (not shown) for detecting the return light is integrated.
The first device 5 detects a second laser element (not shown) that emits an S-polarized second laser beam and a return beam that is returned by the second laser beam reflected by the optical disc D. In this configuration, two photodetectors (not shown) are integrated.
The polarization beam splitter 6 includes a polarization separation film 6A that transmits the P-polarized first laser light and reflects the S-polarized second laser light.
The lens 7 condenses the first or second laser light emitted from the polarization beam splitter 6.
The rising prism 8 reflects the first laser beam emitted from the polarization beam splitter 6 vertically upward, and transmits the second laser beam. The objective lens 14 condenses the first laser light reflected by the rising prism 8 on the optical disk D. The raising mirror 9 reflects the second laser light transmitted through the polarization beam splitter 6 vertically upward. The objective lens 15 condenses the second laser light reflected by the rising mirror 9 on the optical disk D.

As shown in FIG. 3, the objective lens driving unit 3 includes a fixing unit 17 bonded to a side surface formed by bending one end of the holder base 16, and an upper surface of the holder base 16, and the first and second devices. The two objective lenses 14 and 15 are opposed to the upper surface 18A and the fixed portion 17 on which the two objective lenses 14 and 15 for condensing the first and second laser beams emitted from the optical discs 4 and 5 are focused on the optical disc D. A lens holder 18 having side surfaces 18B, 18B formed with a pair of protrusions 19A, 19B protruding in a bisecting direction, and a pair of suspensions fixed between the pair of protrusions 19A, 19B and the fixing part 17 It consists of wires 20 and 20. Each of the pair of suspension wires 20 and 20 is made of three metal wires, and can be energized with current.
On both side surfaces 18C and 18D orthogonal to the side surface 18B of the lens holder 18, a focusing coil 21, a tracking coil 22 and a tilt coil 23 are formed. A pair of magnets 24 and 25 and a pair of yokes 26 and 27 closely attached to the pair of magnets 24 and 25 are formed in order from the side surfaces 18C and 18D, respectively, on both side surfaces 18C and 18D side where each coil is formed. Has been.

Further, as shown in FIGS. 4 and 5, the holder base 16 has a mortar-shaped opening 28 whose hole diameter increases downward and a screw hole 29 penetrating in the thickness direction. The holder 30 has a bottom 30A having a diameter slightly larger than the diameter of the opening 28 of the holder base 16, a slope 30B that is continuous with the bottom 30A, is in sliding contact with the mortar-shaped opening 28, and is continuous with the slope 30B. From a straight portion 30C that contacts the lower surface of the holder base 16, a screw hole 30D having the same diameter as the screw hole 29 formed in the straight portion 30C, and a mortar-shaped opening 28 formed on the surface opposite to the bottom portion 30A. Also has a wide recess 30E.
The opening 28 and the recess 30 </ b> E are formed so that their center axes coincide with the optical axis of the objective lens 15.

The holder 30 is adjusted and fixed to the holder base 16 by screwing adjustment screws 31 and 31 into the screw holes 29 of the holder base 16 from the screw holes 30D.
Furthermore, one end of the spring 32 is fixed on the holder base 16, and the other end is in contact so as to press the protrusion 30 </ b> F of the linear portion 30 </ b> C of the holder 30 against the holder base 16 side.
A chromatic aberration correction element 33 that corrects coma aberration and chromatic aberration of the entire component optical component including the objective lens 15 is fixed to the concave portion 30E of the holder 30.
Further, a wavelength selective filter 34 capable of narrowing down the first laser beam by the wavelength of the first laser beam is attached to the lower portion of the lens holder 18 so as to coincide with the optical axis of the objective lens 14. .

Next, the operation of the optical pickup device 1 will be described.
Here, the first laser light is BD laser light, the second laser light is HD-DVD laser light, and the objective lens 14 receives or emits the first laser light. The lens 15 is assumed to receive or emit the second laser beam.
The objective lens driving unit 3 is adjusted and fixed so as not to cause coma aberration with respect to the optical disc D for BD.
First, the case of reproduction when HD-DVD is used for the optical disc D will be described.
As shown in FIG. 1, after the optical disk D is placed on the turntable 13, it is rotated. As shown in FIG. 2, S-polarized second laser light is emitted from the second laser element of the second device 5, reflected by the polarization separation film 6 A of the polarization beam splitter 6, and raised by the lens 7. 8, the light is condensed on the rising mirror 9, reflected by the rising mirror 9, and then irradiated on the information track of the optical disc D by the objective lens 15 of the objective lens driving unit 3.

  The return light reflected by the information track of the optical disk D is reflected by the rising mirror 9 through the objective lens 15, reflected by the polarizing separation film 6 </ b> A of the rising prism 8, the lens 7, and the polarization beam splitter 6, 2 is detected by the second photodetector of the device 5. The information signal detected by the second photodetector is processed by a processing circuit (not shown) to obtain a reproduction signal. Information on the optical disk D can be reproduced by sequentially performing the above operations while sliding the optical pickup device 1 along the pair of guide shafts 11 and 11.

In focus control, tracking control, and tilt control, a processing signal processed by a processing circuit (not shown) is supplied to a focusing coil 21, a tracking coil 22, and a tilt coil 23, and a magnetic field generated thereby and a pair of magnets 24, 25 are formed. By interaction with the magnetic field.
At this time, coma aberration occurs due to the inclination of the objective lens driving unit 3 and the inclination of the objective lens 15, but the mortar-like shape of the holder base 16 by the spring 32 and the adjusting screws 31, 31 fixed to the holder base 16. The bottom 30A is brought into sliding contact with the opening 28, and the inclination of the objective lens driving unit 3 is adjusted as shown in FIG. 6, so that the index values such as the time difference distortion (jitter) and the PRSNR value of the reproduction signal become the best state. By doing so, coma aberration can be eliminated.

  Information is recorded on the optical disc D after the first laser beam is modulated by a modulation circuit (not shown) and then recorded in the information recording layer of the optical disc D in the same manner as described above.

  As described above, according to the embodiment of the present invention, the bottom 30 </ b> A is slidably brought into contact with the mortar-shaped opening 28 of the holder base 16 by the spring 32 and the adjusting screws 31, 31. Since the inclination is adjusted, the index values such as the time difference distortion and the PRSNR value of the reproduction signal obtained from the optical disc D can be optimized, so that the recording and reproduction of a plurality of types of optical discs can be improved.

It is the figure which looked at the optical pick-up apparatus which concerns on embodiment of this invention from the optical disk side. 1 is a perspective view of an optical pickup device according to an embodiment of the present invention. It is a figure which shows the specific structure of an objective drive part. It is a perspective view which shows the characteristic part of an optical pick-up apparatus. It is sectional drawing of a base and a holder. It is sectional drawing which shows the state which inclined the holder with respect to the base.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Optical pick-up apparatus, 2 ... Moving base, 3 ... Objective lens drive part, 4 ... 1st device, 5 ... 2nd device, 6 ... Polarizing beam splitter, 7 ... Lens, 8 ... Rising prism, 9 ... Raising mirror, 10 ... bearing portion, 11 ... guide shaft, 12 ... spindle motor, 12 ... rotating shaft, 13 ... turntable, 14, 15 ... objective lens, 16 ... holder base, 17 ... fixed portion, 18 ... lens holder , 19A, 19B ... projection, 20 ... suspension wire, 21 ... focusing coil, 22 ... tracking coil, 23 ... tilt coil, 24, 25 ... magnet, 26, 27 ... yoke, 28 ... opening, 29 ... screw hole, 30 ... Holder, 30A ... Bottom, 30B ... Inclined surface, 30C ... Linear part, screw hole ... 30D, 30E ... Recess, 31 ... Adjustment screw, 32 ... Pulling, 33 ... chromatic aberration correcting element, 34 ... wavelength selective filter

Claims (2)

In an optical pickup device comprising a moving base slidable on a pair of guide shafts fixed in the radial direction of an optical disk to be mounted, and an objective lens driving unit placed on the moving base,
The objective lens driving unit is
A lens holder for holding two objective lenses for condensing recording / reproducing light on the optical disc;
A holder base that supports the lens holder and is formed with a mortar-shaped opening that matches the optical axis of one of the two objective lenses;
A coma aberration and a chromatic aberration of the recording / reproducing light which are generated by tilting one of the objective lenses on the opposite side of the lens holder side and attached to the lower surface of the holder base so as to be tiltable along the mortar-shaped opening. An optical pickup device comprising: a holder in which a concave portion capable of accommodating a chromatic aberration correcting element for correcting the above is formed.   2. The optical pickup device according to claim 1, wherein the holder is attached to the holder base with a spring and an adjusting screw having one end fixed to the holder base.

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