JP2001319358A - Optical pickup - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical pickup which does not allow an objective lens to contact with an optical disk even when a lens having a small distance to the optical disk surface at the time of recording/reproducing and a lens having a large distance thereto are disposed. SOLUTION: The first objective lens 13 which performs recording/reproducing with the small distance WD1 for the first optical disk 16 and the second objective lens 24 which performs recording/reproducing with the large distance WD2 for the second optical disk 21 are attached to a holder 12 of a movable part 37 in such a manner that the side of the second objective lens 24 parts from the medium surface. Further, the movable part 37 is made to be more apart from the medium surface when the recording/reproducing is performed for the second optical disk 21 than when the recording/reproducing is performed for the first optical disk 16 and, thereby, the first objective lens 16 is made so as not to contact with the optical disk 21.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for recording information on and / or recording information on an optical recording medium such as a magneto-optical disk drive, a write-once optical disk drive, a phase-change optical disk drive, a CD-ROM, a DVD, and an optical card. Alternatively, the present invention relates to an optical pickup used for an information recording / reproducing apparatus for reproducing.

[0002]

2. Description of the Related Art Magneto-optical disk drives, write-once optical disk drives, phase-change optical disk drives, CD-Rs
An optical pickup is used in an information recording / reproducing apparatus for recording and / or reproducing information on / from an optical recording medium such as an OM, a DVD, and an optical card. Optical recording media include, for example, CDs and CD-Rs. In this medium, the cover glass has a thickness of 1.2 mm and an NA of 0.43-
Recording and / or reproduction is performed using an objective lens whose distance WD from the objective lens surface during recording / reproduction is about 0.8 to 1.5 mm.

[0003] With the increase in recording density, 0-
For a medium with a thin cover glass of about 0.1 mm, N
A is increased to about 0.7-0.9 and WD is set to 0-0.2m
There is an apparatus that performs higher-density recording and reproduction using an objective lens reduced to about m. Some of such objective lenses are combined with SIL. An apparatus for recording and / or reproducing a plurality of media having different cover glass thicknesses and recording densities is disclosed in Japanese Patent Application Laid-Open No. H11-1205.
87 discloses an apparatus as shown in FIG.

[0006] In an optical pickup device 51 shown in FIG. 6, a first optical system 53 arranged to face a third optical disk 52 and a second optical system 53 arranged to face first and second optical disks 54 and 55. It has an optical system 56. The first optical system 53 includes a light source 57, a collimator lens 58, a diffraction grating 5
9, anamorphic prism 60, half-wave plate 61,
A quarter-wave plate 62 and a second-group objective lens 63 are provided. The second-group objective lens 63 has a front lens 64 disposed on the third optical disk 52 side, and a rear lens 65 disposed so that the optical axis of the front lens 64 coincides with the front lens 64.

The first optical system 53 reflects the laser light emitted from the anamorphic prism 60 and
While being incident on the four-wavelength plate 62, the third optical disk 5
Polarizing beam splitter 6 for passing the reflected light from 2
6, a collimator lens 67, a multi-lens 68, and a photodetector 69, and a condensing lens 70 for condensing the surface reflected light of the anamorphic prism 60, and an output adjustment photodetector 71.

The second optical system 56 has a laser coupler 72 that emits two types of laser light and receives reflected light, a collimator lens 73, a hologram element 74, and an objective lens 75. And the second group objective lens 63
And a bobbin 76 on which the objective lens 75 is disposed, respectively,
The bobbin 76 is connected to the front lens 64 of the second group objective lens 63.
And an electromagnetic drive mechanism for moving in a first direction parallel to the optical axis of the objective lens 75 and in a second direction orthogonal to the optical axis.

In order to increase the NA, the two-group objective lens 63 is a two-group objective lens having two lenses 64 and 65 provided so that their optical axes coincide with each other. A first lens (hereinafter, referred to as a front lens) 64 disposed on the facing side, and a second lens (hereinafter, referred to as a front lens) disposed with the optical axis coincident with the first lens. 65), and the first and second lenses 64 and 65 have a numerical aperture NA.
Is realized to 0.7 or more.

[0008]

However, in the apparatus disclosed in JP-A-11-120587, the bobbin 76 is not provided.
No consideration is given to the surface positions of the first and second optical disks 54 and 55 and the third optical disk 52 with respect to the above.

At the time of recording / reproduction of the objective lens 64 with respect to the objective lens 75, that is, the optical disc 5 in a focused state.
Since the distance (abbreviated as WD) to the first and second optical disks 54 and 55 is small, the cover glass surfaces of the first and second optical disks 54 and 55
There is a possibility of contact with the front lens 64 of the group objective 63, and damage to the front lens 64 of the second group 63.

(Object of the Invention) The present invention has been made in view of the above-mentioned problems. Even when a lens having a small distance WD to the optical disk surface during recording / reproduction and a lens having a large lens are arranged. It is another object of the present invention to provide an optical pickup in which an objective lens does not contact an optical disc.

[0011]

A light source, a first objective lens used for recording / reproducing on the first optical recording medium and having a small distance to a recording / reproducing medium surface, and a second optical recording medium A second objective lens having a large distance to a medium surface during recording / reproduction used for recording / reproduction, a movable portion having at least the first and second objective lenses, and a driving unit for driving the movable portion And an optical pickup having a light receiving element for receiving reflected light from both optical recording media, wherein the position of the movable portion at the time of recording / reproducing on / from the first optical recording medium is higher than the position of the movable portion. By providing a means for separating the position of the movable part from the medium surface when recording / reproducing on the medium, the position of the movable part during recording / reproducing on the second optical recording medium can be changed. Distance to the second optical recording medium Because away from the position of the movable portion at the time of recording / reproducing with the first objective lens is prevented occur may like to contact the medium surface.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. (First Embodiment) FIGS. 1 to 4 relate to a first embodiment of the present invention, FIG. 1 shows a configuration of an optical pickup according to the first embodiment of the present invention, and FIG. FIG. 3 shows the appearance of the pickup, FIG. 3 shows the state of the positional relationship between the optical system of the movable section and the optical disk during recording / reproduction, and FIG. 4 shows the movable state during recording / reproduction when a field coil is provided in the movable section. 2 shows the state of the positional relationship between the optical system of the unit and the optical disk.

As shown in FIG. 1, in the optical pickup 1 of the first embodiment, light emitted from a semiconductor laser 2 having a wavelength of, for example, 680 nm as a light source is converted into parallel light by a collimating lens 3 and the beam of a prism 4 is emitted. The light enters the forming prism unit 5. The reflected light partially reflected by the surface of the beam shaping prism unit 5 is condensed by a lens 6 and received by a monitor photodiode 7, and the amount of light emitted from the semiconductor laser 2 is output by photoelectric conversion by the monitor photodiode 7. Is monitored and the amount of emitted light is controlled (APC).

A part of the light incident on the beam shaping prism portion 5 is beam-shaped and transmitted through the half mirror portion 8, and a mirror 10 (see FIG. 2) arranged on its optical path such that the reflection surface is inclined. And is incident on the first objective lens 13 attached to the holder 12 of the actuator 11 as parallel light. FIG. 1 shows the mirror 10 in a simplified manner.

The first objective lens 13 is constituted by a two-group lens including a first lens 14 and a second lens 15. The two-group lens has a numerical aperture NA of 0.8 and is used for recording / reproducing (that is, focusing). State WD1 to the surface of the first optical disk 16 as an optical recording medium is 0.1 mm
Is formed.

The first lens 14 is substantially hemispherical, and is adhered to the tip of the holder 12. The second lens 15 disposed rearward on the optical axis of the first lens 14 has a larger diameter than the first lens 14 and is aspherical on both surfaces. The two lenses are fixed to the holder 12 by bonding.

The light incident on the second lens 15 is condensed and incident on the first lens 14, and the first lens 14
Are further condensed and emitted. This stand 1 lens 14
Is incident on the first optical disk 16 at a distance of 0.1 mm from the first lens 14 and has a cover glass thickness of 0.1 mm.
The light spot P1 is connected to the recording surface 16a through the distance mm. The light reflected from the recording surface 16a follows the same path and returns to the half mirror 8, and the light reflected here is condensed by a lens 17 and diffracted by a hologram 18 so that the photodetector 1
9 is incident. From the output of the photodetector 19, a recording / reproducing signal, a tracking signal (push-pull method), and a focus error signal (beam size method) are obtained.

Next, a second cover glass having a cover glass thickness of 1.2 mm
Recording and / or reproduction on the optical disk 21 will be described. For example, light emitted from a laser 22 having a wavelength of 780 nm as a light source passes through a hologram 23, and its 0th-order light is reflected by a mirror 10, and is incident on a second objective lens 24 as divergent light. The light collected by the second objective lens 24 is separated from the objective lens 24 by 1.0 mm, that is, the second optical disk 21 having WD2 = 1.0 mm.
To form a light spot P2 on the recording surface 21a via a cover glass thickness of 1.2 mm. The second objective lens 24 is composed of one lens, and has an NA of 0.55, WD
2 forms an objective lens of 1.0 mm.

The light reflected from the recording surface 21a follows the same path and returns to the hologram 23, where it is diffracted, and the ± first-order light enters the photodetector 25. A recording / reproducing signal, a tracking signal (push-pull method), and a focus error signal (beam size method) are obtained from the output photoelectrically converted by the photodetector 25. The first and second objective lenses 13 and 24 are both bonded and fixed to the holder 12, and are supported and driven by the actuator 11 in the focusing direction and the tracking direction.

The first and second objective lenses 13 and 24 are arranged so as to be adjacent to each other in the tangential direction of the recording track as shown in FIG. Therefore, when the two objective lenses 13 and 24 are provided adjacent to each other, and when any one of the objective lenses accesses the innermost track of the optical disc 16 or 21, the operation can be performed without interference with the spindle motor 26. .

As can be seen from FIG. 2, the second objective lens 24 is positioned with respect to the first lens 14 of the first objective lens 13 in a direction away from the optical disk by b (specifically, 0.6 mm). I have.

As shown in FIG. 2, one end of four springs 31 is fixed to the holder 12, and the other end of the spring 31 is fixed to a fixing member 32. A focus coil 33 is wound around the holder 12, and tracking coils 34 are fixed on both sides of the focus coil 33. These coils 34 are opposed to a magnetic circuit composed of a yoke 35 and a magnet 36.

The holder 12, the objective lenses 13, 2
4. The focus coil 33 and the tracking coil 34 are integrated into a movable part 37. With these configurations, the movable section 37 is movably supported in the focus direction and the tracking direction. FIG. 3 is a diagram showing the height relationship of the main part. Although two objective lenses 13 and 24 are shown in FIG. 3 as being adjacent to each other in the radial direction of the optical disk 16 and the like, they are actually arranged in the tangential direction as shown in FIG.

The first optical disk 16 and the second optical disk 21 have their hubs 27 connected to a turntable 26 of a motor 26.
a. The second optical disk 21 is a hub 27
Are parallel plate-like with no steps.
In the optical disk 16 of which the recording / reproducing unit is
It is configured such that only a step that protrudes is provided. In this embodiment, a is 0.3 mm.

When recording / reproducing the first optical disk 16,
The movable section 37 is located at the position shown in FIG.
6 and the first objective lens 13 have a WD1 =
0.1 mm apart. At this time, the second objective lens 24
Is b (that is, 0.6 mm), and the first optical disk 16
, The second objective lens 24 does not hit the surface of the first optical disc 16.

On the other hand, when recording / reproducing the second optical disk 21, the movable portion 37 is located at the position shown in FIG. 3, and the surface of the second optical disk 21 on the movable portion side indicated by the two-dot chain line and the second objective are shown. The lens 24 is separated by WD2 = 1 mm. At this time, the movable part 3
The first objective lens 13 in FIG.
WD1 + a, that is, 0.4 mm. Therefore, even if the thickness of the cover glass of the second optical disc 21 varies by about 0.1 mm, the first objective lens 13 of the movable portion 37 does not hit the surface of the second optical disc 21.

In this embodiment, the position of the motor 26 with respect to the turntable 26a in the focus direction in the movable section 37 during recording / reproduction is the same for both the objective lenses 13 and 24, but the objective lens 13 with a small WD1 is used. The surface of the first optical disc 16 is provided with a step on the optical disc 16 so that the movable section 3 is provided with a step compared to the case of the surface of the second optical disc 21 using the second objective lens 24 having a large WD2.
7 (the objective lens 13).

Thus, when recording / reproducing the optical disk 21 having a large WD2, the objective lens 13 having a small WD1 can be used.
Can be greatly separated from WD1 of the objective lens 13 or more.

Therefore, even when the thickness of the optical disk 21 varies or the surface of the optical disk 21 is displaced as described above, the objective lens 13 can be reliably prevented from contacting the optical disk 21 (the first optical disk 21). It is clearly prevented that the second objective lens 24 hits the surface of the optical disk 21 during recording / reproducing on the 16).

As described above, according to the present embodiment, WD1
When performing recording or reproduction on the first optical disk 16 with the objective lens 13 having a small WD2, the second objective lens 24 having a large WD2 is larger than the distance at which the second objective lens 24 may hit the first optical disk 16 due to variation or the like. When the objective lens 24 having a large WD2 is used for recording or reproduction on the second optical disc 21, the first objective lens 16 having a small WD1 is disposed on the movable section 37 so as to maintain a predetermined interval. It is arranged on the movable part 37 so as to keep a predetermined distance from the optical disk 21.

In other words, the second objective lens 24 is attached to the holder 12 such that the medium-side surface of the second objective lens 24 is largely separated from the first objective lens 13, specifically, is separated by about b. As shown in FIG. 3, the movable portion 37 is a first movable portion for recording / reproducing.
The position of the surface of the optical disk 16 is made closer to the position of the surface of the second optical disk 21 during recording / reproduction.

In other words, when recording / reproducing on / from the first optical disk 16, the first objective lens 13 has a small WD1.
Is closer to the first optical disk 16, but when recording / reproducing on / from the second optical disk 21, the distance from the surface of the second optical disk 21 is larger than WD1. Especially the first lens 14 of the lens 13
Can be reliably prevented from coming into contact with the surface of the second optical disk 21.

As described above, according to the present embodiment, the recording or reproduction is performed in both the case of recording or reproducing on the first optical disk 16 and the case of recording or reproducing on the second optical disk 21. Objective lens 2 not used
4 or 13 can reliably be prevented from hitting the first optical disk 16 or the second optical disk 21.

Further, in the present embodiment, the movable portion 37 is moved in the same direction in the focusing direction when the first optical disk 16 is mounted on the turntable 26a and when the second optical disk 21 is mounted on the turntable 26a. With the position set at the position, the first objective lens 13 and the second objective lens 24 can be set to a recording / reproducing state, that is, a focus state.

For this reason, it is not necessary to increase the moving distance of the movable section 37 in the focus direction because the two objective lenses 13 and 24 have the same distance (in other words, 1).
In the case of only one objective lens, it is only necessary to be able to move by the same distance as that in the focus direction).

FIG. 4 shows the state of the positional relationship between the optical system of the movable part and the optical disk during recording / reproduction when the field coil 41 is provided on the movable part 37. In this case W
It is assumed that the distance FWD between the first optical disc 16 and the plane on the emission side of the first objective lens 13 and the first lens 14 whose D is 0.3 mm is 0.1 mm.

A field coil 41 formed on a silicon substrate 42 having a thickness T = 0.12 mm may be arranged on the movable part 37 to perform magnetic field modulation recording. In this case, the field coil 41 is used. What is necessary is just to set the distance between the second objective lens 24 and b as described above. (Second Embodiment) Next, a second embodiment of the present invention will be described with reference to FIG. In the present embodiment, a first optical disk 16 'and a second optical disk 21' are provided without a step between the first optical disk 16 and the second optical disk 21 in the first embodiment.

FIG. 5A shows a state in which the first optical disk 16 'is mounted on the turntable 26a and recording / reproducing is performed by the first objective lens 13, and FIG. ′ Is mounted on the turntable 26a to perform recording / reproducing with the second objective lens 24.

In the case of FIG. 5A, the first objective lens 13
Indicates a state in which recording / reproduction is performed with the first optical disk 16 'and WD1. In this case, the second objective lens 24 connects the light spot P2 above the first optical disk 16'. FIG. 5B shows a state in which recording / reproduction is performed with the second objective lens 24 set to the second optical disk 21 'and WD2, and in this case, the first objective lens 13 is set to the second optical disk 21'. The light spot P1 is connected below the optical disk 21 '(that is, at a position just before reaching the second optical disk 21').

Assuming that the position of the movable portion 37 at the time of recording / reproducing with respect to the first optical disk 16 'of FIG. 5A is 37a, the movable portion 37 at the time of recording / reproducing of the second optical disk 21' of FIG. The position of the portion 37 is set in the direction away from the optical disk 16 '(or 21') by c than 37a as shown by 37b.

In the present embodiment, c = 0.5 mm. In the present embodiment, the position of the objective lens 24 with respect to the objective lens 13 is shifted toward the direction closer to the optical disk 16 '(or 21') with respect to the first embodiment, and the holder 12 is moved.
Has been placed.

In this embodiment, two types of optical discs 1
At the time of recording / reproducing at 6 'and 21', the position of the movable portion 37 of the actuator in the focus direction is changed. Therefore, it is not necessary to provide a step on the surface of the optical disk. The rest of the configuration is the same as that of the first embodiment, and the same components are given the same reference numerals and description thereof is omitted.

In this embodiment, either in the case of recording or reproducing on the first optical disk 16 'or in the case of recording or reproducing on the second optical disk 21', as in the first embodiment. In addition, it is possible to reliably prevent the objective lens 24 or 13 which is not used for recording or reproduction from hitting the first optical disk 16 'or the second optical disk 21'.

[0044]

As described above, according to the present invention, even when a small WD1 objective lens and a large WD2 objective lens are arranged, a small WD1 objective lens is used for recording / reproducing on an optical disk using the WD2 objective lens. It is possible to prevent the objective lens from coming in contact with the optical disk without approaching it.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an optical pickup according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a state of a positional relationship between an optical system of a movable unit and an optical disk during recording / reproduction.

FIG. 3 is a perspective view showing the appearance of the optical pickup.

FIG. 4 is a diagram showing a state of a positional relationship between an optical system of a movable unit and an optical disk during recording / reproduction when a field coil is provided in the movable unit.

FIG. 5 is a diagram illustrating a state of a positional relationship between an optical system of a movable unit and an optical disk during recording / reproduction according to a second embodiment of the present invention.

FIG. 6 is a configuration diagram of a conventional optical pickup.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Optical pickup 2 ... Semiconductor laser 3 ... Collimating lens 4 ... Prism 5 ... Beam shaping prism part 6, 17 ... Lens 7 ... Photodiode 8 ... Half mirror part 10 ... Mirror 11 ... Actuator 12 ... Holder 13 ... (1st ) Objective lens 14 First lens 15 Second lens 16 Optical disk 16a, 21a Recording surface 18, 23 Hologram 19, 25 Photodetector 21 Optical disk 22 Semiconductor laser 24 ... (second) objective lens 26 ... spindle motor 37 ... movable part

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5D029 KB15 5D118 AA26 BA01 BB02 BF02 BF03 CD02 CD03 CD08 CG07 CG26 DC03 EA08 5D119 AA11 AA22 AA31 AA32 AA41 BA01 CA06 CA09 CA15 DA01 DA05 EC45 EC47 FA08 JA44 JC04 JC07

Claims (3)

[Claims] 1. A light source, a first objective lens having a small distance to a recording / reproducing medium surface used for recording / reproducing of a first optical recording medium, and recording / reproducing of a second optical recording medium. A second objective lens having a large distance to a medium surface at the time of recording / reproducing, a movable unit having at least the first and second objective lenses, a driving unit for driving the movable unit, In an optical pickup having a light receiving element for receiving reflected light from an optical recording medium, the position of the movable portion at the time of recording / reproducing on / from the first optical recording medium is more than the position of the movable part with respect to the second optical recording medium. An optical pickup characterized in that a means for separating the position of the movable part from the medium surface when recording / reproducing is provided. 2. The optical pickup according to claim 1, wherein said means is formed by providing a step on the surface of said first optical recording medium. 3. The position of the movable part during recording / reproducing on the second optical recording medium is different from the position of the movable part during recording / reproducing on the first optical recording medium from the medium surface. 2. The optical pickup according to claim 1, wherein the optical pickup is set at a position away from the optical pickup.