JPH1011781A - Optical pickup and optical pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the influence of a noise at the time of recording a signal, by providing a module circuit performing a high frequency modulation to a light source while superposing a high frequency on the driving current of the light source. SOLUTION: The module circuit 4 is connected to between a driving circuit 43 supplying a driving current to a semiconductor laser element 21 and the element 21 and performs a high frequency modulation while superposing a high frequency on the driving current and selectively supplies a driving voltage V1 or V2. Then, asstigmatism of light beams from the element 21 is compensated by an astigmatism compensating plate 22a and the beams are converted into parallel light beams by a collimating lens 24 and the light beams are reflected with a prism mirror 25 to be converged on the signal recording surface of an optical disk with an objective lens 26. Return light beams from the optical disk are reflected by the polarized light separating film of a beam splitter 23 to be converged on a photodetector 29. The recorded signal of the optical disk is reproduced based on the detection signal of the detector.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical pickup for recording and reproducing signals from a mini disk (MD), a magneto-optical disk (MO), a compact disk (CD), etc. The present invention relates to an optical disk device provided with a 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, a Wollaston prism 4a sequentially disposed in the separation optical path of the return light beam from the optical disk D reflected by the beam splitter 4, the collimator lens 5, the prism mirror 6, and the beam splitter 4 , A multi-lens 4 b and a photodetector 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 a beam. Then, the optical path of the parallel light beam is bent by the prism mirror 6 in the direction of the optical disk D, and is irradiated on the signal recording surface of the optical disk D by the objective lens 7. Then, the return light beam reflected by the signal recording surface is received by the light receiving surface of the photodetector 8, and a 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 optical pickup 1 described above, at the time of signal reproduction, the module circuit superimposes the driving current from the driving circuit of the semiconductor laser element 2 at a high frequency, thereby turning on and off at high speed. Noise countermeasures were taken, but no noise countermeasures were taken at the time of signal recording. For this reason, there is a problem that noise generated at the time of signal recording may be mixed into the recording signal, and the signal recording performance of the optical disc is reduced.

SUMMARY OF THE INVENTION In view of the above, it is an object of the present invention to provide an optical pickup which can reduce the influence of noise at the time of signal recording, and an optical disk device provided with the optical pickup.

[0007]

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 the optical pickup provided, it is achieved by providing a module circuit that operates during signal recording and signal reproduction, superimposes high frequency on the drive current of the light source, and modulates the light source with high frequency.

[0008] According to the above configuration, even during signal recording where no countermeasures against noise have been taken conventionally, the influence of noise is eliminated by high-frequency superimposition by the module circuit, so that signal recording performance can be improved.

[0009]

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 records a signal by irradiating a light beam onto a signal recording surface of the rotating optical disk 11 and records a signal from the signal recording surface of the rotating optical disk 11. An optical pickup 20 for reproducing a recording signal by a beam and a control unit 13 for controlling them 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 drive control of the spindle motor 12 is performed 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 corrects the error of 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. The servo circuit 19 moves the objective lens held by the biaxial actuator of the optical pickup 20 in the focusing direction and the tracking direction at the moved predetermined position.

FIG. 2 and FIG. 3 are a plan view and a plan view showing the embodiment of the optical pickup according to the present invention, as viewed from the back. The optical pickup 20 includes an astigmatism correction plate 22a as astigmatism correction means and a grating 22b as light division means which are sequentially arranged in the optical path of a light beam emitted from a semiconductor laser element 21 as a light source. ,
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. Further, the optical pickup 20 includes a module substrate 40 on which a module circuit for performing high-frequency superposition on a drive current to the semiconductor laser element 21 is configured.

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 using recombination light emission of a semiconductor, and emits a predetermined laser beam. The astigmatism correction plate 22 a is a parallel flat plate that is disposed at a predetermined angle with respect to the optical axis, and corrects the astigmatism of the light beam emitted from the semiconductor laser device 21.

The grating 22b is a diffraction grating for diffracting incident light, and converts a light beam incident from the semiconductor laser element 21 via the astigmatism correction plate 22a into a main beam composed of zero-order diffracted light and ± 1st-order diffracted light. Are divided into at least three light beams. Therefore, another division element such as a hologram element may be used as long as at least three light beams can be divided and generated.

The beam splitter 23 is a polarizing beam splitter provided with its polarization separating film 23a inclined at 45 degrees with respect to the optical axis. The beam splitter 23 reflects the light beam from the grating 22b and the signal from the signal recording surface of the optical disk 11. The return light beam is polarized and separated. That is, the semiconductor laser element 21
Is transmitted through the polarization splitting film 23a of the beam splitter 23, and a part of the return light beam is reflected by the polarization splitting film 23a of the beam splitter 23.

The collimator lens 24 is a laminated lens combining a convex lens and a concave lens, and converts the light beam from the beam splitter 23 into parallel light. The prism mirror 25 is a mirror having a triangular prism shape, and reflects the parallel light beam from the collimator lens 24 by 90 degrees in the vertical direction and reflects the return light beam from the optical disk 11 by 90 degrees in the horizontal direction. The objective lens 26 is a convex lens, and focuses the parallel light beam from the collimator lens 25 on a desired track on the signal recording surface of the optical disk 11 that is being rotationally driven. Here, the objective lens 26
Is supported movably in a biaxial direction, that is, a focusing direction and a tracking direction, by a biaxial actuator 30 of a shaft sliding rotation type.

The Wollaston prism 27 is a quadrangular prism, and emits a plurality of light beams by performing polarization separation based on a return light beam from the optical disk 11. The multi-lens 28 is a cylindrical lens and a concave lens, and adjusts an optical path length by giving astigmatism to a return light beam for detecting a focus error signal. The photodetector 29 is a photodetector and receives the return light beam transmitted 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 portion holder 32 is entirely made of a resin such as a rubber-like polyester elastomer. The movable portion 32a is attached to the lens holder 33, and the fixed portion 32b is attached to the XY base 31. 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 means for driving the objective lens is a lens holder 3
3 includes a focus 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.

FIGS. 8 and 9 are a side view and a plan view showing an example of a module substrate. This module substrate 40
The module circuit 41 is a high-frequency superimposed circuit including a feedthrough capacitor 42 connected to each terminal of the semiconductor laser element 21 and other electronic components such as a resistor, a capacitor, an inductance, and a transistor. I have. As shown in FIG. 10, the module circuit 41 is connected between a drive circuit 43 for supplying a drive current to the semiconductor laser element 21 and the semiconductor laser element 21 and performs high-frequency superposition on the drive current. High-frequency modulation is performed, and the driving voltage V1 or V2 is
Is selectively applied.

Here, the drive voltage V1 is
Relatively high voltage suitable for signal recording of, for example, 2.75
V, the drive current (consumption current) is, for example, 30 mA, and the drive voltage V2 is a relatively low voltage suitable for signal reproduction of the optical disc 11, for example, 2.10 V.
The drive current (current consumption) is, for example, 13 mA. For high-frequency superimposition during recording, a module circuit for high-frequency superimposition during reproduction, which has been conventionally used, can be used as it is. Therefore, only one module circuit is required, and the structure is simple. Does not increase.

The 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, at the time of signal reproduction, the switching circuit 44 is switched to the drive voltage V2 side, and the module circuit 41 operates at a relatively low drive voltage V2.
Then, the spindle motor 12 rotates, and the optical disc 11 rotates. Then, the optical pickup 20
Moves in the radial direction of the optical disk 11 along the guide 20a, and moves the optical axis of the objective lens 26 to a desired track position on the optical disk 11.

In this state, the light beam from the semiconductor laser element 21 is corrected for astigmatism by the astigmatism correction plate 22a and split into three light beams by the grating 22b. 23, and is converted into a parallel light beam by a collimator lens 24. Then, the light is reflected toward the optical disk 11 by the prism mirror 25 and is focused on the signal recording surface of the optical disk 11 via the objective lens 26.

The return light beam from the optical disk 11 again enters the beam splitter 23 via the objective lens 26, the prism mirror 25 and the collimator lens 24.
Then, the light is reflected by the polarization splitting film 23a of the beam splitter 23, and is reflected by the Wollaston prism 27 and the multi-lens 2
The light is converged on the photodetector 29 through 8. 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 a tracking error signal based on a detection signal from the photodetector 29 and a focusing error signal based on an 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, so that the lens holder 33 is moved and adjusted in the focusing direction, thereby performing 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, so that the lens holder 33 is moved and adjusted in the tracking direction to perform tracking. Further, at this time, since the semiconductor laser element 21 is superimposed at a high frequency by the module circuit 41 of the module substrate 40,
The effect of noise is reduced.

At the time of signal recording, the switching circuit 44 is switched to the driving voltage V1, and the module circuit 41 operates at a relatively high driving voltage V1. Then, the spindle motor 12 rotates, and the optical disc 11 rotates.
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 element 21 is corrected for astigmatism by the astigmatism correction plate 22a and split into three light beams by the grating 22b. 23, and is converted into a parallel light beam by a collimator lens 24. Then, the light is reflected toward the optical disk 11 by the prism mirror 25 and is focused on the signal recording surface of the optical disk 11 via the objective lens 26. As a result, the optical disk 11 is driven by the laser power of the semiconductor laser element 21.
Signal recording is performed on the signal recording surface. On this occasion,
Since the semiconductor laser element 21 is superimposed at a high frequency by the module circuit 41 of the module substrate 40, the influence of noise is reduced.

The optical disk device 1 according to the above embodiment
In the optical pickup 20 and the optical pickup 20, the two-axis actuator 30 is shown as having a movable portion holder 32. However, the present invention is not limited to this. It may be.

[0031]

As described above, according to the present invention,
Even when recording signals where noise countermeasures have not been taken before,
Since the influence of noise is eliminated by high-frequency superposition by the module circuit, signal recording performance can be improved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of an optical disk device according to 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 configuration 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;

FIG. 8 is a side view showing an example of a module substrate in the optical pickup of FIG. 2;

FIG. 9 is a plan view showing an example of a module substrate in the optical pickup of FIG. 2;

FIG. 10 is a block diagram showing an example of a module circuit in the optical pickup of FIG. 2;

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

FIG. 12 is a plan view showing an optical system in the optical pickup of FIG. 11;

[Explanation of symbols]

10 optical disk device, 11 optical disk, 1
2 ... Spindle motor, 13 ... Control unit, 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 plates, 22b ... gratings, 2
DESCRIPTION OF SYMBOLS 3 ... Beam splitter, 24 ... Collimator lens, 25 ... Prism mirror, 26 ... Objective lens, 27 ... Wollaston prism, 28 ... Multi lens, 29 ... Photodetector, 30 ... 2
Axis actuator, 31 ... XY base, 32 ...
Moving part holder, 33 ... lens holder, 34 ... focus coil, 35 ... tracking coil,
36 ... yoke, 37 ... magnet, 40 ...
Module board, 41 ... Module circuit, 42 ...
・ Through capacitor, 43 ・ ・ ・ Drive circuit, 44 ・ ・ ・ Switching circuit

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Masami Yuasa 6-35, Kita-Shinagawa, Shinagawa-ku, Tokyo Inside Sony Corporation (72) Inventor Takamichi Toyama 6-35, Kita-Shinagawa, Shinagawa-ku, Tokyo Sony Corporation

Claims (3)

[Claims] 1. An optical pickup comprising: 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. An optical pickup, comprising: a module circuit that superimposes a high frequency on a driving current of the light source and modulates the light source at a high frequency. 2. The optical pickup according to claim 1, wherein the module circuit operates at a relatively high voltage during signal recording and operates at a relatively low voltage during signal reproduction. 3. An optical disc apparatus for focusing a light beam emitted from a light source on a signal recording surface of an optical disc via a light focusing means and recording and reproducing signals on the optical disc, and operates during signal recording and signal reproduction. An optical disk device, comprising: a module circuit that superimposes a high frequency on a driving current of the light source and modulates the high frequency of the light source.