JPH09320099A - Optical pickup and optical disk device - Google Patents

Abstract

The present invention provides an optical pickup having a parallel light converting means that is low in cost and high in positioning accuracy, and an optical disk device provided with the optical pickup. SOLUTION: A light source 21 for emitting a light beam, a light focusing means 26 for focusing the light beam emitted from the light source on a signal recording surface of an optical disk 11, and a light source and a light focusing means which are composed of a plano-convex lens. And the parallel light conversion means 24 for converting the light beam emitted from the light source into parallel light.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to recording and / or reproducing signals from a mini disk (MD), a magneto-optical disk (MO), a compact disk (CD), a CD-ROM or the like (hereinafter referred to as "optical disk"). The present invention relates to an optical pickup and an optical disk device provided with the optical pickup.

[0002]

2. Description of the Related Art FIGS. 11 and 12 are a side view and a plan view showing an example of an optical system of a conventional optical pickup for an optical disk. The optical system of the optical pickup 1 includes an astigmatism correction plate 3a and a grating 3 which are sequentially arranged in the optical path of the light beam emitted from the semiconductor laser device 2.
b, the beam splitter 4, the collimator lens 5, the prism mirror 6 and the objective lens 7, and the Wollaston prism 4a sequentially arranged in the separation optical path of the returning light beam from the optical disc D reflected by the beam splitter 4. , A multi-lens 4b and a photo detector 8.

In the optical system of the optical pickup 1 having such a configuration, the light beam from the semiconductor laser element 2 sequentially passes through the astigmatism correction plate 3a, the grating 3b and the beam splitter 4, and is collimated by the collimator lens 5. Converted to beam. Then, the parallel light beam has its optical path bent toward the optical disc D by the prism mirror 6, and is irradiated onto the signal recording surface of the optical disc D by the objective lens 7. Then, the returning light beam reflected by the signal recording surface is received by the light receiving surface of the photodetector 8 and the recording signal is detected.

The objective lens 7 is moved to a predetermined servo position so that the light beam from the semiconductor laser element 2 forms a spot at a correct position on the signal recording surface of the optical disc D to enable accurate reproduction of the recorded signal. Fine movement is performed based on the signal. The servo of the objective lens 7 includes a tracking servo for finely moving the objective lens 7 along a radial direction with respect to a recording track of the optical disc D;
Focusing servo is performed to finely move the objective lens 7 in a direction to approach and separate from the signal recording surface of the optical disc D along the optical axis.

[0005]

By the way, in the conventional optical pickup 1, the collimator lens 5 for converting the light beam from the semiconductor laser element 2 into a parallel light beam is as shown in FIG. A so-called biconvex lens whose both surfaces are convex is used. In the illustrated case, the collimator lens 5 is two lenses, that is, a first lens 5a which is a biconvex lens, and a concave surface whose one surface is aligned with one surface of the first lens 5a and an uneven surface whose other surface is a convex surface. It is a cemented lens composed of two lenses 5b. Both surfaces of each of the lenses 5a and 5b, that is, four surfaces, are polished so that each has a predetermined radius of curvature, so that there is a lot of lens processing work and processing time is required, which causes a problem of high cost. .

Further, the collimator lens 5 is positioned with reference to its peripheral surface when the optical pickup 1 is attached to an optical base or the like, as shown in FIG. Therefore, particularly when the collimator lens 5 is a cemented lens, the individual lenses 5a, 5
There is a problem that the peripheral surface of b is processed with high accuracy and the individual lenses 5a and 5b are centered with high accuracy during the bonding, which causes a cost increase. Also,
The span of the reference point for positioning the collimator lens 5 is the thickness of the collimator lens 5 at the maximum, and the span is comparatively small, so a slight angular deviation may occur during positioning. There was also.

In view of the above points, an object of the present invention is to provide an optical pickup provided with a parallel light converting means having a low cost and a high positioning accuracy, and an optical disk device provided with the optical pickup.

[0008]

According to the present invention, a light source for emitting a light beam, and a light focusing means for focusing the light beam emitted from the light source on a signal recording surface of an optical disk are provided. In an optical pickup provided with a parallel light conversion unit arranged between the light source and a light focusing unit and converting a light beam emitted from the light source into parallel light, the parallel light conversion unit is composed of a plano-convex lens. It is achieved by

According to the above construction, since one surface of the parallel light converting means is flat, the processing is easy, so that the cost can be reduced and the flat surface can be used as a positioning reference. The positioning accuracy can be improved.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings. The embodiments described below are preferred specific examples of the present invention,
Although various technically preferred limitations are given, the scope of the present invention is not limited to these forms unless otherwise specified in the following description.

FIG. 1 is a block diagram showing an embodiment of an optical disk apparatus according to the present invention. The optical disk device 10 irradiates an optical beam onto the signal recording surface of the rotating optical disk 11 and a spindle motor 12 as a driving means for rotationally driving the optical disk 11 to record a signal. An optical pickup 20 which reproduces a recording signal by a returning light beam and a control unit 13 which controls these are provided. Here, the control unit 13 includes an optical disk drive controller 14, a signal demodulator 15, an error correction circuit 16, an interface 17, a head access control unit 18, and a servo circuit 19.

The optical disk drive controller 14 includes:
The spindle motor 12 is drive-controlled at a predetermined rotation speed.
The signal demodulator 15 demodulates the recording signal from the optical pickup 20 and sends it to the error correction circuit 16. The error correction circuit 16 error-corrects the recording signal from the signal demodulator 15 and sends it to an external computer or the like via the interface 17. Thus, an external computer or the like can receive a signal recorded on the optical disk 11 as a reproduction signal.

The head access control unit 18 moves the optical pickup 20 to a predetermined recording track on the optical disk 11, for example, by a track jump or the like. At the moved predetermined position, the servo circuit 19 moves the objective lens held by the biaxial actuator of the optical pickup 13 in the focusing direction and the tracking direction.

FIGS. 2 and 3 are a plan view and a plan view showing the embodiment of the optical pickup of the present invention, as viewed from the back. This optical pickup 20 has an astigmatism correction plate 22a as an astigmatism correction means, which is sequentially arranged in the optical path of an optical beam emitted from a semiconductor laser element 21 as a light source, and a light splitting means. Grating 22b,
A beam splitter 23 as a light separating unit, a collimator lens 24 as a parallel light converting unit, a prism mirror 25 as an optical path bending unit, an objective lens 26 as a light focusing unit, and return from the optical disk 11 reflected by the beam splitter 23. Wollaston prism 2 as a light splitting means sequentially disposed in the separation light path of the light beam
7. an optical system having a multi-lens 28 as a light focusing means and a photodetector 29 as a light detecting means, and 2 for holding and moving the objective lens 26 in two axial directions.
The shaft actuator 30 is fixedly held in an optical base 20b as shown in FIG. 4 which is supported movably in the radial direction of the optical disk 11 along a guide 20a provided on the optical pickup 20.

FIGS. 5 and 6 are a side view and a plan view showing an example of the optical system. The semiconductor laser device 21 is a light emitting device utilizing recombination light emission of a semiconductor and emits a predetermined laser light. The astigmatism correction plate 22 a is a parallel flat plate arranged at a predetermined angle with respect to the optical axis, and corrects the astigmatism of the light beam emitted from the semiconductor laser element 21.

The grating 22b is a diffraction grating that diffracts incident light. The light beam incident from the semiconductor laser element 21 through the astigmatism correction plate 22a is divided into a main beam composed of 0th-order diffracted light and ± 1st-order diffracted light. The side beam is divided into at least three light beams. Therefore,
As long as at least three light beams can be divided and generated, another dividing element such as a hologram element may be used.

The beam splitter 23 is a polarization beam splitter in which the polarization separation film 23a is inclined by 45 degrees with respect to the optical axis, and the light beam from the grating 22b and the signal recording surface of the optical disk 11 are arranged. The returning light beam is polarized and separated. That is, the semiconductor laser element 21
A part of the light beam from the light is transmitted through the polarization separation film 23a of the beam splitter 23, and a part of the returning light beam is reflected by the polarization separation film 23a of the beam splitter 23.

The collimator lens 24 is a cemented lens which is a combination of a convex lens and a concave lens, and converts the light beam from the beam splitter 23 into a parallel light beam. The prism mirror 25 is a triangular prism mirror,
The parallel light beam from the collimator lens 24 is reflected by 90 degrees in the vertical direction, and the return light beam from the optical disk 11 is reflected by 90 degrees in the horizontal direction. Objective lens 26
Is a convex lens, which focuses the parallel light beam from the collimator lens 25 on a desired track on the signal recording surface of the optical disc 11 which is being driven to rotate. Here, the objective lens 26 is supported by a biaxial actuator 30 of a shaft sliding type so as to be movable in biaxial directions, that is, a focusing direction and a tracking direction.

The Wollaston prism 27 is a prism having a quadrangular prism shape and emits a plurality of light beams by performing polarization separation on the basis of the returning light beam from the optical disk 11. The multi-lens 28 is a cylindrical lens and a concave lens, and applies astigmatism to the return light beam to detect a focus error signal and adjusts the optical path length. The photodetector 29 is a photodetector and receives the return light beam that has passed through the beam splitter 23.

FIG. 7 is a plan view showing an example of a biaxial actuator. The two-axis actuator 30 is attached to the optical base 20 b of the optical pickup 20 so as to be movable in the XY directions and is movable in the optical axis direction with respect to the XY base 31 by the movable portion holder 32. A lens holder 33 supported so as to be swingable about a swing axis, an objective lens 26 whose optical axis is held parallel to the swing axis with respect to the lens holder 33, and a driving unit for the objective lens 26, which will be described later. And

The movable part holder 32 is entirely made of resin such as rubber-like polyester elastomer. The movable part side 32a is attached to the lens holder 33, and the fixed part side 32b is XY base 31. Is fixed against. Further, the movable portion holder 32 has a link having a substantially parallelogram vertical cross section so that the movable portion side 32a can move in the vertical direction (focusing direction) indicated by the arrow Fcs in the drawing. Arrow Tr
A pair of vertically extending hinges 32c and 32d are provided so as to be movable in the horizontal direction (tracking direction) indicated by k.

The driving means for the objective lens is the lens holder 3
3, a focusing coil 34 and a tracking coil 35, a yoke 36 fixed to the XY base 31, and a magnet 37 attached to the yoke 36. By energizing the focusing coil 34 and the tracking coil 35, the magnetic flux generated in each of the coils 34 and 35 interacts with the magnetic flux generated by the yoke 36 and the magnet 37, so that the lens holder 33 and the objective lens 26 is driven and controlled in the focus direction and the tracking direction.

Optical pickup 20 according to this embodiment
The optical disk device 10 incorporating the above is configured as described above, and operates as follows. First, the spindle motor 12 rotates to drive the optical disk 11 to rotate.
Then, the optical pickup 20 moves in the radial direction of the optical disc 11 along the guide 20a, and the objective lens 2
The optical axis of No. 6 is moved to a desired track position on the optical disc 11.

In this state, the light beam from the semiconductor laser device 21 is split into three light beams by the grating 22b and then transmitted through the beam splitter 23,
It is converted into a parallel light beam by the collimator lens 24. Then, it is reflected toward the optical disc 11 by the prism mirror 25, and passes through the objective lens 26.
1 is focused on the signal recording surface. The returning light beam from the optical disk 11 is again the objective lens 26 and the prism mirror 2.
5 and the collimator lens 24 to enter the beam splitter 23. Then, the light is reflected by the reflecting surface 23 a of the beam splitter 23 and focused on the photodetector 29 via the Wollaston prism 27 and the multilens 28. Then, the recording signal of the optical disk 11 is reproduced based on the detection signal of the photodetector 29.

At this time, the signal demodulator 15 detects the tracking error signal by the detection signal from the photodetector 29 and the focusing error signal by the astigmatism method. Then, the servo circuit 19 servo-controls a drive current to the focusing coil 34 and the tracking coil 35 via the optical disk drive controller 14. That is, the magnetic field generated in the focusing coil 35 acts on the magnetic field generated by the magnet 37 and the coil 36, whereby the lens holder 33 is moved and adjusted in the focusing direction to perform focusing. Further, the magnetic field generated in the tracking coil 35 acts on the magnetic field generated by the magnet 37 and the yoke 36, whereby the lens holder 33 is moved and adjusted in the tracking direction to perform tracking.

As shown in FIG. 8, the collimator lens 24 characteristic of the optical disk device 10 incorporating the optical pickup 20 having the above-described structure is a plano-convex lens, that is, a first lens which is a biconvex lens having convex surfaces on both sides. 24a and a second plano-concave lens whose one surface is a concave surface having the same curvature as one surface of the first lens 24a and whose other surface is a flat surface
It is configured as a cemented lens including the lens 24b. Then, the second lens 24b is replaced by the first lens 2
The diameter is larger than 4a.

Here, in order to obtain an optical action as the collimator lens 24, if the refractive indices of the first lens and the second lens are n1 and n2 and the Abbe numbers are νd1 and νd2, the conditions of Equations 1 and 2 are satisfied. Is required.

[Equation 1]

[Equation 2] Conventionally, as a material of the first lens 5a and the second lens 5b, a glass material of n1 = 1.687 and νd1 = 48.5 and n
The above condition is satisfied by selecting a glass material of 2 = 1.825, νd2 = 23.8. On the other hand, according to this embodiment, the material of the first lens 24a and the second lens 24b is n1 = 1.687, ν
Glass material with d1 = 48.5 and n2 = 1.744, vd2
= 26.6 glass material is selected. That is, the second lens 2
By using a glass material having a relatively high refractive index as the material of 4b, the collimator lens 24 of a plano-convex lens can be realized.

The collimator lens 24 has a second
Since one surface of the lens 24b is formed as a flat surface and the second lens 24b is formed to have a larger diameter than the first lens 24a, it is possible to position the optical base 30b with the flat surface and the peripheral surface as a reference. That is, in the mounting portion of the collimator lens 24 of the optical base 20b, as shown in FIG.
The second lens 24 of the collimator lens 24
The first positioning surface 38 in the optical axis direction that should come into contact with the optical axis in the peripheral edge of the plane of b and the optical axis that comes into contact with the peripheral surface of the second lens 24b at a surface inclined by 45 degrees. A second positioning surface 39 in the vertical direction is formed. As a result, in the collimator lens 24, as shown in FIG. 9, the peripheral edge of the plane of the second lens 24b is the first positioning surface 38.
Since it abuts against the flat surface, it is positioned in the optical axis direction with this plane as a reference, and the peripheral surface of the second lens 24b is the second surface.
Since it comes into contact with the positioning surface 39 of, the positioning is performed in a plane perpendicular to the optical axis.

Therefore, when the collimator lens 24 is positioned on the plane and the peripheral surface of the second lens 24b, if the plane and the peripheral surface of the second lens 24b are processed with high accuracy, the first lens 24a is formed. Since it is not necessary to increase the accuracy of the peripheral surface of the lens so much, it is possible to reduce the processing cost, and it is not necessary to increase the accuracy of centering the lenses with each other, so that it is possible to reduce the assembly cost. Further, as shown in FIG. 10, since the span of the reference point for positioning on the plane of the second lens 24b can be made relatively large, the angular deviation at the time of positioning can be suppressed to be small, and the mounting The accuracy can be improved.

The optical disk device 1 according to the above embodiment
In the optical pickup 20 and the optical pickup 20, as the biaxial actuator 30, a structure having a movable portion holding body 32 is shown, but the biaxial actuator is not limited to this, and a suspension spring type or a shaft sliding rotation type biaxial actuator is provided. May be Although the configuration of the polarization optical pickup for reproducing the magneto-optical disk is shown, the invention is not limited to this, and the present invention is also applicable to a non-polarization optical pickup for a compact disk (CD) or a CD-ROM and an optical disk device. Can be applied.

[0031]

As described above, according to the present invention,
The cost of the parallel light conversion means can be greatly reduced, and the positioning accuracy can be greatly improved.
It is possible to provide an extremely excellent optical pickup and optical disc device.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of an optical disk device of the present invention.

FIG. 2 is a plan view showing an embodiment of the optical pickup of the present invention.

FIG. 3 is a plan view showing the embodiment of the optical pickup shown in FIG. 2 as viewed from the back.

FIG. 4 is a perspective view of an optical base in the optical pickup of FIG. 2;

FIG. 5 is a side view showing an optical system in the optical pickup of FIG. 2;

FIG. 6 is a plan view showing an optical system in the optical pickup of FIG. 2;

FIG. 7 is a plan view of a biaxial actuator in the optical pickup of FIG. 2;

8 is an enlarged side view of a collimator lens in the optical pickup of FIG.

9 is a partially enlarged plan view, a side view and a lateral cross-sectional view showing a state where the collimator lens of FIG. 8 is attached to an optical base.

10 is a schematic view showing a positioning reference of the collimator lens of FIG.

FIG. 11 is a side view showing an example of an optical system of a conventional optical pickup.

12 is a plan view showing an example of an optical system of the optical pickup of FIG.

13 is an enlarged side view of a collimator lens in the optical pickup of FIG.

FIG. 14 is a schematic view showing a positioning reference of the collimator lens of FIG.

[Explanation of symbols]

10 ... Optical disk device, 11 ... Optical disk, 1
2 spindle motor 13 optical pickup 14 optical disk drive controller 15
... Signal demodulator, 16 ... Error correction circuit, 17 ...
Interface 18: head access control unit 20, optical pickup, 20a guide, 20b optical base, 21 semiconductor laser element, 22a astigmatism correction plate, 22b ... Grating, 23 ... Beam splitter, 24 ...
Collimator lens, 25 ... Prism mirror, 26 ...
..Objective lenses, 27 ... Wollaston prisms, 2
8 ... Multi-lens, 29 ... Photo detector,
30 ... Biaxial actuator, 31 ... XY base, 32 ... Movable part holder, 33 ... Lens holder, 34 ... Focus coil, 35 ... Tracking coil, 36 ... -Yoke, 37 ... Magnet, 38 ... First positioning surface (optical axis direction), 39
... Second positioning surface (direction perpendicular to optical axis)

Claims (5)

[Claims] 1. A light source for emitting a light beam, a light focusing means for focusing the light beam emitted from the light source on a signal recording surface of an optical disc, and a light source disposed between the light source and the light focusing means. An optical pickup provided with a parallel light conversion means for converting a light beam emitted from a light source into parallel light, wherein the parallel light conversion means is composed of a plano-convex lens. 2. The optical pickup according to claim 1, wherein the parallel light converting means is positioned in the optical axis direction with reference to the plane portion of the plano-convex lens. 3. The parallel light conversion means is a cemented lens including a biconvex lens and a plano-concave lens, the biconvex lens is a glass material having a refractive index of 1.687, and the plano-concave lens is a glass material having a refractive index of 1.744. The optical pickup according to claim 1, which is composed of: 4. The optical pickup according to claim 1, wherein the parallel light converting unit is a cemented lens including a biconvex lens and a plano-concave lens, and the plano-concave lens has a larger diameter than the bi-convex lens. 5. A light beam emitted from a light source is converted into parallel light by a parallel light converting means and focused on a signal recording surface of an optical disk via a light focusing means to record and / or record a signal.
Alternatively, in the optical disk device for reproducing, the parallel light converting means is composed of a plano-convex lens.