JP2005071395A - Optical disk drive - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To substantially reduce the possibility of failing in focusing a laser beam onto the recording surface of an optical disk in the case of focus-ON operation in an optical disk drive using an axis sliding type optical pickup. <P>SOLUTION: In a focus-on operation, a triangular waveform wobble signal of a predetermined voltage and frequency is applied to a tracking coil 62 arranged on a lens holder 57, a bearing part 57a of the lens holder 57 is made to repeat minute displacements in the direction perpendicular to the optical axis of an objective lens 54 relative to a guide shaft 58, and the focus-on operation is performed in that state by driving a focusing coil 63. Hence the macroscopic movement of the lens holder 57 becomes smooth and variation in the moving speed is made small. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to stabilization of a focus-on operation of an optical disc apparatus.
[0002]
[Prior art]
In recent years, in an optical disc apparatus, in order to stabilize the posture of the objective lens of the optical pickup, an optical pickup in which a lens holder holding the objective lens is slidably fitted to a guide shaft parallel to the optical axis of the objective lens Has been proposed. In such a shaft sliding type optical pickup, the focusing servo is performed by moving the lens holder up and down in a direction parallel to the guide shaft. The tracking servo is performed by reciprocatingly rotating the lens holder around the guide shaft.
[0003]
The following patent documents are known as techniques relating to focusing in an optical disc apparatus. In Patent Document 1, focus information is corrected using tracking information in order to prevent the focusing servo from being removed due to track interference of a focusing error signal during seek. In Patent Document 2, in order to stabilize the focusing servo pull-in regardless of variations in the signal characteristics of the optical pickup and the reflectivity of the optical disc, the objective lens is moved in the focus direction before the focus pull-in, and the amplitude of the focusing error signal is measured. The focusing servo gain is corrected. In Patent Document 3, the focusing servo is stabilized during seek by canceling the crosstalk of the focusing error signal.
[0004]
[Patent Document 1]
JP-A-6-295448 [Patent Document 2]
JP-A-8-287488 [Patent Document 3]
Japanese Patent Application Laid-Open No. 7-169070
[Problems to be solved by the invention]
When performing a focus-on operation in an optical disc apparatus equipped with the above-described shaft-sliding type optical pickup, the lens holder is rotated to the end in either direction around the axis without driving the tracking servo mechanism. The focus-on operation is performed by driving the focusing servo mechanism. However, since the bearing portion of the lens holder is constantly pressed in a predetermined direction with respect to the guide shaft, the lens holder tends to slide in a direction parallel to the guide shaft. Specifically, even if it is attempted to move the lens holder by driving the focusing mechanism, the lens holder is caused by adhesion of foreign matters such as dust between the guide shaft and the bearing portion or friction between the surface of the guide shaft and the bearing portion. Is caught on the guide shaft and does not move immediately. Then, the driving force by the focusing mechanism is gradually increased, and when the driving force overcomes the load caused by these catches, the lens holder suddenly starts moving. Microscopically, the lens holder is moved up and down in a direction parallel to the guide shaft while repeating the sudden movement by the release of the hook and the stop by the hook.
[0006]
In order to focus the laser beam on the recording surface of the optical disc in the focus-on operation, it is necessary that the movement of the lens holder is smooth and the moving speed is stable. However, if the lens holder repeats abrupt movement and stop as described above, the change in the movement speed of the lens holder is large, and there is a high possibility that the focus on of the recording surface of the laser beam on the optical disk will fail. Had.
[0007]
In each of Patent Documents 1 to 3, the focusing servo is stabilized by processing an electric signal such as a focusing error signal, and unstable operation at the time of focus-on due to the mechanical factor is performed. It cannot be resolved.
[0008]
The present invention has been made to solve the above-described problems of the conventional example, and an object of the present invention is to stabilize the focus-on operation in an optical disc apparatus provided with a shaft sliding type optical pickup.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, a first aspect of the present invention provides a semiconductor laser that outputs a laser beam to an optical disc, and an objective for focusing the laser beam output from the semiconductor laser on a data recording surface of the optical disc. A lens, a light detection element that receives light reflected from the optical disk and converts it into an electrical signal, a lens holder that holds the objective lens, and a bearing provided in the lens holder, and the lens holder Is slidable in a direction parallel to the optical axis of the objective lens, and is rotatably supported in a direction orthogonal to the optical axis, and the lens holder is moved in a direction parallel to the optical axis. A focusing servo mechanism including a focusing coil, a yoke and a permanent magnet for rotating the lens holder in a direction perpendicular to the optical axis In an optical disk apparatus equipped with a shaft-sliding optical pickup having a tracking servo mechanism including a tracking coil, a yoke and a permanent magnet, a triangular waveform having a predetermined voltage and a predetermined frequency in the tracking coil during a focus-on operation A focus-on operation is performed by driving the focusing coil in a state where a wobbling signal is applied and the bearing portion of the lens holder is repeatedly subjected to minute displacement in a direction perpendicular to the optical axis with respect to the guide shaft. To stabilize the focus-on operation.
[0010]
In this way, by driving the tracking coil by applying a triangular waveform wobble signal having a predetermined voltage and a predetermined frequency, the lens holder holding the objective lens repeats a minute displacement with respect to the guide shaft. The state in which the bearing portion of the lens holder is separated from the guide shaft repeatedly occurs. By performing the focus-on operation in this state, the distance between the movement and stop of the micro lens holder is shortened, and the amount of displacement is reduced. As a result, the movement of the macro lens holder is smooth and the change in the moving speed is small, so that the possibility of failing to focus on the recording surface of the optical disk of the laser beam can be greatly reduced. The focus-on operation can be stabilized. The voltage and frequency of the wobble signal are elements that vary depending on the weight of the objective lens and the lens holder, the material of the bearing portion of the lens holder and the guide shaft, the surface roughness, and the like. And the optimum value is set.
[0011]
According to a second aspect of the present invention, in an optical disc apparatus provided with a shaft-sliding optical pickup, a focus-on operation is performed while a wobble signal having a predetermined voltage and a predetermined frequency is applied to the tracking coil during the focus-on operation. .
[0012]
In this way, when the wobbling signal is applied to the tracking coil and driven, the lens holder holding the objective lens repeats a slight displacement with respect to the guide shaft, so the bearing portion of the lens holder instantaneously leaves the guide shaft. Repeatedly occurs. By performing the focus-on operation in this state, the distance between the movement and stop of the micro lens holder is shortened, and the amount of displacement is reduced. As a result, the movement of the macro lens holder is smooth and the change in the moving speed is small, so that the possibility of failure of focusing on the recording surface of the laser beam on the optical disk can be greatly reduced. .
[0013]
According to a third aspect of the present invention, in the optical disc apparatus of the second aspect, the optical pickup includes a semiconductor laser that outputs a laser beam to the optical disc, and a laser beam output from the semiconductor laser for data recording on the optical disc. An objective lens for focusing on a surface, a light detection element that receives light reflected from the optical disc and converts it into an electrical signal, a lens holder that holds the objective lens, and a bearing provided in the lens holder A guide shaft that is slidable in a direction parallel to the optical axis of the objective lens and is rotatably supported in a direction perpendicular to the optical axis, and the lens holder is A focusing servo mechanism including a focusing coil, a yoke and a permanent magnet for moving in a direction parallel to the optical axis; Tracking coils for rotating the holder in a direction orthogonal to the optical axis, having a tracking servo mechanism including a yoke and permanent magnets.
[0014]
With such a configuration, a drive signal to be applied to the tracking servo mechanism can be generated without providing a new mechanism for an optical disc apparatus having a shaft sliding type optical pickup having a general configuration that has been conventionally proposed. The optical disk apparatus of the present invention can be realized only by changing the software to be controlled.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
An optical disc apparatus according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows the configuration of the optical disc apparatus 1 according to the present embodiment. The optical disk device 1 irradiates, for example, a laser beam of a predetermined wavelength toward the optical disk 2 to reproduce data recorded on the optical disk, and records data such as DVD-R, DVD-RW, and DVD-RAM. The data is recorded by irradiating a laser beam having a higher intensity (power) than that at the time of data reproduction onto an optical disc capable of recording data.
[0016]
As shown in FIG. 1, an optical disk apparatus 1 includes a table 3 that holds an optical disk 2, a spindle motor 4 that rotationally drives the table 3 and the optical disk 2 held thereon, and irradiates the optical disk 2 with a light beam. Then, an optical pickup 5 for recording and / or reproducing data, an optical pickup driving mechanism 6 for moving the optical pickup 5 in the radial direction of the optical disc 2, a spindle motor 4, an optical pickup 5, and an optical pickup driving mechanism 6 are provided. A control unit 7 for controlling, an RF signal processing unit 8 for processing an RF signal output from the optical pickup 5, and an interface (I / F) for outputting the processed RF signal to a personal computer or a monitor display device 9) for displaying the operation status of the optical disc apparatus 1 and a message to the user. A display section 10 such as LCD, and an input unit 11 such as a push button switch or the remote control device for performing such operation selection of the optical disc apparatus 1.
[0017]
2 is a front view showing the configuration of the optical pickup 5, and FIG. 3 is an exploded perspective view thereof. The optical pickup 5 converts a semiconductor laser 51 that outputs a laser beam L having a predetermined wavelength, a half mirror 52 that reflects the laser beam L toward the optical disk 2, and converts the laser beam L reflected by the half mirror 52 into a parallel beam. A collimator lens 53, an objective lens 54 for focusing the collimated laser beam L on the recording surface of the optical disc 2, and a reflected beam L ′ from the optical disc 2 for receiving it and converting it into an electrical signal. A light detection element 55 and the like are provided.
[0018]
As shown in FIG. 3, the objective lens 54 is held by a lens holder 57. The lens holder 57 has a bearing portion supported by a guide shaft 58 so that the lens holder 57 can slide in a direction parallel to the optical axis of the objective lens 54 and can rotate in a direction perpendicular to the optical axis. Yes. The lens holder 57 is provided with a tracking coil 62 that performs tracking servo control, a focusing coil 63 that performs focusing servo control, a circuit board 64, and the like.
[0019]
The guide shaft 58 is implanted in the base member 61. Further, on the base member 61, two permanent magnets 59 and a yoke 60 for forming a magnetic path by passing a magnetic flux by the permanent magnets 59 are attached. ing. Each permanent magnet 59 is attached such that the N pole side faces the guide shaft 58. Details of the base member 61 are shown in FIG. The yoke 60 is provided so as to penetrate the opening 61 b upward from the lower surface of the base member 61 and to face each permanent magnet 59. The base member 61 is provided with a transmission port 61a for transmitting the laser beam L and the reflected beam L ′.
[0020]
FIG. 5 shows a state in which the lens holder 57 is fitted to the guide shaft 58 implanted in the base member 61. The lens holder 57 has a bearing portion 57 a that fits with the guide shaft 58 and two openings 57 b that are provided on both sides of the lens holder 57 and penetrate the yoke 60. The tracking coil 62 is provided substantially symmetrically with respect to the bearing portion 57a. The lens holder 57 floats from the base member 61 due to the magnetic action of the two permanent magnets 59. When the focusing coil 63 is energized in this state, the lens holder 57 moves up and down along the guide shaft 58 with respect to the base member 61 by the magnetic action of the two permanent magnets 59 and the focusing coil 63. The vertical movement of the lens holder 57 enables adjustment of the focal position of the laser beam in a direction parallel to the optical axis of the objective lens 54, that is, focusing servo control. Further, by energizing the tracking coil 62, the lens holder 57 is rotated around the guide shaft 58 to the extent that the opening 57b and the yoke 60 do not interfere with each other. The rotation of the lens holder 57 enables adjustment of the focal position of the laser beam in the direction orthogonal to the optical axis of the objective lens 54, that is, tracking servo control.
[0021]
As shown in FIG. 3, a lens in which an objective lens 54, a tracking coil 62, a focusing coil 63, a circuit board 64, and the like are fixed to a base member 61 to which a guide shaft 58, a permanent magnet 59, a yoke 60, and the like are fixed. The movable part of the optical pickup 5 is modularized by mounting the holder 57 and fitting the cover member 65 from above. Then, the optical pickup 5 is configured by fixing the modular movable part to the main body 66 of the optical pickup 5 with a screw or the like.
[0022]
Next, a focus-on operation in the optical disc apparatus 1 according to the present embodiment will be described. For example, when the user operates the input unit 11 to instruct reading of data recorded in a specific track, the control unit 7 drives the optical pickup driving mechanism 6 to move the optical pickup 5 in the radial direction of the optical disc 2. And the optical pickup 5 is driven to read data from the optical disk 2. At that time, the controller 7 applies a triangular wobble signal having a predetermined voltage and a predetermined frequency to the tracking coil 62 and repeats the lens holder 57 in a direction orthogonal to the optical axis of the objective lens 54. Small displacement (vibration). On the other hand, a focusing drive signal corresponding to a focusing error signal is applied to the focusing coil 63 as in the normal focus-on operation.
[0023]
In the conventional optical disk apparatus, when performing the focus-on operation, the focusing servo mechanism is driven while the tracking servo mechanism is stopped without applying the tracking drive signal to the tracking coil. Therefore, as described above, there is a problem that the movement of the lens holder is not smooth due to friction between the bearing portion of the lens holder and the guide shaft. On the other hand, in the optical disc apparatus 1 according to the present embodiment, a triangular waveform wobble signal having a predetermined voltage and a predetermined frequency is applied to the tracking coil 62 and driven, so that the lens holder that holds the objective lens 54 is used. 57 repeats a minute displacement with respect to the guide shaft 58, and a state in which the bearing portion 57a of the lens holder 57 is instantaneously separated from the guide shaft 58 repeatedly occurs. By performing the focus-on operation in this state, the interval between the movement and stop of the micro lens holder 57 is shortened and the amount of displacement is reduced, so that the macro lens holder 57 moves smoothly, and The change in moving speed is also reduced.
[0024]
Changes in the displacement of the lens holder 57 and changes in the speed thereof during the focus-on operation by the optical disc apparatus 1 according to the present embodiment are shown in FIGS. 6 (a) and 6 (b), respectively. 7A and 7B respectively show the change in the displacement of the lens holder and the change in the speed during the focus-on operation by the conventional optical disk apparatus (the optical disk apparatus 1 driven by the conventional method). Shown in In each figure, (a) is obtained by measuring the movement of the lens holder 57 with a displacement meter, and (b) is obtained by differentiating the measured displacement. Comparing FIG. 6 and FIG. 7, by applying a wobble signal to the tracking coil 62 to vibrate the lens holder 57 in a direction orthogonal to the optical axis of the objective lens 54, the lens holder 57 seen from a macro view is seen. It can be seen that the movement is very smooth and the change in speed is small. As a result, the possibility of failing to focus on the recording surface of the optical disc 2 of the laser beam L can be greatly reduced.
[0025]
Next, FIG. 8 shows an example of the waveforms of the focusing drive signal, tracking drive signal, and focusing error signal actually displayed on the oscilloscope during the focus-on operation by the optical disc apparatus 1 according to the present embodiment. In FIG. 8, (a) shows the waveform of the focusing drive signal, (b) shows the waveform of the tracking drive signal, and (c) shows the waveform of the focusing error signal. In addition, the triangular wave part of the center part of (b) is a wobble signal. In these examples, when the focus is successfully turned on, the application of the wobble signal to the tracking coil is stopped and the tracking drive signal is switched based on the tracking error signal. FIG. 9 is an enlarged view of each signal waveform in the vicinity of focus-on in FIG. 8 on the time axis (horizontal axis) 1000 times, (a) shows the waveform of the focusing drive signal, and (b) shows the tracking drive. (C) shows the waveform of the focusing error signal. FIG. 9 shows that the focus is turned on very smoothly.
[0026]
Next, how to obtain the optimum wobble signal will be described. The voltage and frequency of the wobble signal are factors that vary depending on the weight of the objective lens 54 and the lens holder 57, the material of the bearing portion of the lens holder 57 and the material of the guide shaft 58, the surface roughness, and the like. 5 is set to an optimum value that is unique to 5. For example, the maximum value of the absolute value of the operating speed of the lens holder 57 shown in FIG. 6B is measured while the frequency is fixed and the triangular wave voltage (peak-to-peak) is gradually increased from 0V to 6V. Plot on top. The same measurement is performed while changing the frequency from 100 Hz to 2 kHz in order. An example of the measurement result thus obtained is shown in FIG. In FIG. 10, the speed of the lens holder 57 is converted into a voltage and displayed.
[0027]
In the region where the voltage is 2 V or less, it can be seen that the higher the frequency, the faster the speed, except for the case of 100 Hz, and the lower the effect. In the region where the voltage is 2 V or more, except for 100 Hz and 2 kHz, the speed is substantially constant and a relatively low value regardless of the voltage. This is presumably because the higher the frequency, the shorter the displacement time in one direction and the smaller the displacement. Therefore, it is necessary to increase the voltage in order to increase the amount of displacement. On the other hand, if the frequency is too low, the displacement is increased, but the operation is delayed, which is considered to have another adverse effect. Therefore, in this measurement example, it is preferable that the frequency of the wobble signal is 200 Hz or more and 1 kHz or less, and the voltage is 2 V or more and 4 V or less. For example, the frequency of the wobble signal is 500 Hz and the input voltage is 3.5V. These values are for the samples measured by the present inventors, and are not necessarily limited to this range.
[0028]
In this way, a smooth focus-on operation can be performed by applying various wobble signals whose voltages and frequencies are actually changed to the optical pickup 5 and finding optimum conditions. Furthermore, since the hardware configuration of the optical pickup 5 of the optical disc apparatus 1 according to the present embodiment is substantially the same as the existing one, the software configuration of the optical disc apparatus using the conventional shaft sliding type optical pickup is By changing the focus on operation so that a wobble signal having a predetermined voltage and a predetermined frequency is applied to the tracking coil, the optical disc apparatus according to the present embodiment can be easily realized.
[0029]
【The invention's effect】
As described above, according to the present invention, during the focus-on operation, a triangular waveform wobble signal having a predetermined voltage and a predetermined frequency is applied to the tracking coil so that the bearing portion of the lens holder is optically aligned with respect to the guide axis. Since the focusing coil is driven and the focus-on operation is performed in a state where minute displacement is repeated in a direction orthogonal to the direction, the movement of the lens holder becomes smooth and the change in the moving speed is reduced, and the laser The possibility of failing to focus on the recording surface of the optical disk with the beam can be greatly reduced.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of an optical disc apparatus according to an embodiment of the present invention. FIG. 2 is a front view showing a configuration of an optical pickup in the embodiment. FIG. 3 is an exploded view showing a configuration of the optical pickup. FIG. 4 is a perspective view showing details of a base member of the optical pickup. FIG. 5 is a plan view showing a configuration of a base member and a lens holder mounted thereon in the optical pickup. FIG. 7 is a graph showing a change in the displacement of the lens holder during the focus-on operation in the optical disc apparatus according to the embodiment, and FIG. 7B is a graph showing a change in the speed. FIG. 7A is a focus in the conventional optical disc apparatus. FIG. 8B is a graph showing a change in the speed of the lens holder during the ON operation, and FIG. 8A is a graph showing a change in the speed. FIG. 8A is an optical disc apparatus according to the embodiment. FIG. 9 is a graph showing the focusing drive signal, FIG. 9B is a graph showing the tracking drive signal, and FIG. 9C is a graph showing the focusing error signal. FIG. FIG. 10 is a graph showing a focusing drive signal, (b) a graph showing a tracking drive signal, and (c) a graph showing a focusing error signal. Showing the change in the speed of the lens holder when the voltage and frequency of the wobble signal are changed in the optical disc apparatus according to the present invention.
DESCRIPTION OF SYMBOLS 1 Optical disk apparatus 2 Optical disk 5 Optical pick-up 6 Optical pick-up drive mechanism 7 Control part 51 Semiconductor laser 54 Objective lens 55 Photodetection element 57 Lens holder 57a (Lens holder) bearing part 58 Guide shaft 62 Tracking coil 63 Focusing coil

Claims (3)

A semiconductor laser that outputs a laser beam to an optical disk, an objective lens that focuses the laser beam output from the semiconductor laser onto the data recording surface of the optical disk, and light that is reflected from the optical disk and is electrically A photodetecting element for converting into a signal, a lens holder for holding the objective lens, and a bearing provided in the lens holder are fitted, and the lens holder is slid in a direction parallel to the optical axis of the objective lens. A focusing servo that includes a guide shaft that can be rotated in a direction orthogonal to the optical axis, and a focusing coil, a yoke, and a permanent magnet for moving the lens holder in a direction parallel to the optical axis. A mechanism, a tracking coil for rotating the lens holder in a direction perpendicular to the optical axis, a yoke, and In the optical disk apparatus including an optical pickup shaft sliding type having a tracking servo mechanism including a permanent magnet,
During focus-on operation, a triangular waveform wobble signal having a predetermined voltage and a predetermined frequency is applied to the tracking coil so that the bearing portion of the lens holder is slightly displaced in a direction perpendicular to the optical axis with respect to the guide axis. An optical disc apparatus characterized by stabilizing a focus-on operation by driving the focusing coil in a repeated state to perform a focus-on operation. An optical disc apparatus provided with a shaft sliding type optical pickup, wherein the focus on operation is performed while a wobble signal having a predetermined voltage and a predetermined frequency is applied to the tracking coil during the focus on operation. The optical pickup includes a semiconductor laser that outputs a laser beam to the optical disc, an objective lens that focuses the laser beam output from the semiconductor laser on the data recording surface of the optical disc, and the optical pickup that is reflected from the optical disc. A light detecting element that receives light and converts it into an electrical signal, a lens holder that holds the objective lens, and a bearing provided in the lens holder, and the lens holder is parallel to the optical axis of the objective lens A guide shaft that is slidable in any direction and is rotatably supported in a direction perpendicular to the optical axis, a focusing coil, a yoke, and a permanent for moving the lens holder in a direction parallel to the optical axis A focusing servo mechanism including a magnet, and a tracker for rotating the lens holder in a direction perpendicular to the optical axis Gukoiru optical disk apparatus according to claim 2, characterized in that it comprises a tracking servo mechanism including a yoke and permanent magnets.

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