JP3582231B2 - Disc playback device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a disc reproducing apparatus for adjusting a tracking offset in a compact disc (CD) player or the like.
[0002]
[Prior art]
FIG. 3 is a block diagram showing a configuration of a conventional disk reproducing apparatus. In FIG. 3, a spindle motor 1 is driven by a drive signal from a spindle driver 2 so that a linear velocity becomes constant when a turntable on which a disk is placed is rotated. The optical pickup 3 is provided with a laser element (LD) for generating a laser beam, and the laser beam emitted by this laser element is irradiated as a focal point on the recording surface of the disc through an optical system. The laser light reflected by this disk is incident on a light receiving element (PD) via an optical system.
[0003]
The output of the light receiving element (PD) is input to the RF amplifier 4. Further, a focus error signal and a tracking error signal from the driver 5 are input to the focus actuator (FCAct) and the tracking actuator (TKAct) of the optical pickup 3. The traverse motor 6 moves the optical pickup 3 in the radial direction of the disk, and moves based on a signal output from the driver 5. The loading motor 7 transfers the disk inserted from the disk insertion slot to the turntable, and is driven by a signal from the loading driver 8. The disc switch 9 detects a disc inserted into the disc insertion slot, and the signal processing circuit 10 controls control signals such as focus servo, tracking servo, traverse servo, and spindle servo based on a signal input from the RF amplifier 4. Or an audio signal, and performs error correction or D / A conversion.
[0004]
The microcomputer 11 sends an operation command to the signal processing circuit 10 or the like according to the operation state of each unit of the player or based on a signal from the CPU (central processing circuit) 12. The high-frequency component of the audio signal output from the signal processing circuit 10 is removed by a low-pass filter (LPF) 13, and the audio signal is amplified by a power amplifier 14 and output from a speaker 15. Further, a direct current is supplied to each unit from the power supply circuit 16, and further, a battery voltage and the like are detected by the detection circuit 17. These processing data are displayed on the screen by the display operation unit 18 and the operation is performed.
[0005]
FIG. 4 is a perspective view showing the configuration of the optical system of the compact disc player. In FIG. 4, a laser beam is emitted from a light emitting element 21, and the laser beam is divided into three by a grating 22. The laser light reflected by the half mirror 23 becomes parallel light by the collimator lens 24, is reflected by the mirror 25, and is irradiated by the objective lens 26 as a focal point on the information recording surface of the disk 27. The laser beam reflected by the disk 27 passes through the objective lens 26, is reflected by the mirror 25, is incident on the photodetector 29 through the collimator lens 24, the half mirror 23, and the concave lens 28, and outputs a photoelectric conversion signal.
[0006]
FIG. 5 is a diagram showing an external configuration of an optical pickup driven by a 4WS wire, and FIG. 6 is a diagram for explaining an operation state of the optical pickup driven by a 4WS wire. 5 and 6, an objective lens 31 and an inner yoke 32 constituting a magnetic circuit are fixed to a yoke base 35. A coil (not shown) is wound around the bobbin 33, and the objective lens 31 is fixed. Further, the bobbin 33 is held and driven by the wire 34, and the wire 34 is fixed to the yoke base 35. The yoke base 35 is fixed to the opt base and is driven by a traverse driving device.
[0007]
In this case, the gap between the inner yoke 32 and the bobbin 33 is uniform on both the inner and outer peripheral sides. Usually, this position is the center of the actuator. At the time of reproducing the disc, a current is supplied to the tracking coil to make the objective lens 31 follow the signal recorded on the disc, and the bobbin is driven to the outer peripheral side as shown in FIG. The lens 31 is controlled.
[0008]
At this time, if the objective lens 31 is followed only by the tracking actuator with the opt base fixed, a deviation occurs in the optical axis composed of the optical system element fixed to the opt base, the objective lens 31 and the disk, and a focus error signal is generated. Therefore, the amplitude levels of the tracking error signal and the RF signal decrease.
[0009]
In addition, mechanically, the gap between the inner yoke 32 and the bobbin 33 on the inner peripheral side in FIG. 6 is reduced, and if the opt base is fixed as it is, the gap becomes zero, and the objective lens can be further recorded on the disc. Since the signal cannot be followed, the reproduction becomes impossible. Therefore, usually, a shift amount of the objective lens 31 is detected from a current value or the like supplied to the tracking coil, and a traverse servo that moves an opt base by a traverse driving device when a certain shift amount is detected is also used. By moving the opt base, the gap reduced in FIG. 6 can be returned to the initial value as shown in FIG.
[0010]
As described above, in the conventional traverse servo, the movement amount is detected based on the position of the objective lens when the current supplied to the tracking coil is zero, and the traverse driving device is controlled so as to be within a certain movement amount. . On the other hand, a slight offset current is supplied to the tracking coil, and tracking offset adjustment based on the position of the objective lens at that time is also performed. This conventional tracking offset adjustment aims at adjusting the offset voltage of the circuit and performing tracking adjustment at the time of passing through a flawed portion to prevent sound skipping during reproduction of a flawed disk. Alternatively, a fixed amount of tracking offset voltage is applied to correct the positional deviation of the objective lens due to gravity when the mounting posture of the CD player is inclined from the horizontal state, and the position of the objective lens at that time is used as a reference.
[0011]
The traverse servo is controlled based on the position of the objective lens in a state where the current supplied to the tracking coil is zero or a circuit offset or a tracking offset current for reproducing a scratched disk is supplied. In this case, if the optical pickup is completed in an ideal state at the time of manufacture and the CD player is mounted horizontally during use, the reference position of the objective lens is as shown in FIG.
[0012]
[Problems to be solved by the invention]
However, in the above-described conventional disk reproducing apparatus, if the 4WS wire is bent or the mounting lengths of the four wires vary when the optical pickup is completed, the reference position of the objective lens is in an ideal state as shown in FIG. It is shifted from the position. This is a phenomenon that occurs even when the mounting posture of the CD player is inclined from horizontal. At this time, if the reference position of the objective lens is displaced as shown in FIG. 6, the movable amount of the objective lens when reproducing the disc is reduced by the displacement amount of the reference position.
[0013]
That is, the shift amount of the reference position of the objective lens is a, the movable amount of the objective lens in the ideal state is b, and the shift amount c of the objective lens when the reference position of the objective lens is shifted by the shift amount a is represented by the following equation (1). ).
[0014]
c = ba (1)
In order to compensate for the shortage of the movable amount of the objective lens, it is necessary to improve the traverse followability. However, there is a limit in securing the reproduction ability when reproducing an eccentric disk or applying vibration to a CD player. . Further, even with the conventional technique of adding a tracking offset current according to the mounting angle, it is not possible to correct variations in the mounting length of the 4WS wire of the optical pickup. Here, the 4WS system is taken as an example of the optical pickup system, but similar problems occur in other systems in terms of product variation.
[0015]
As described above, in the above-described conventional disk reproducing apparatus, it is necessary to design and manufacture the optical pickup by strictly controlling the deviation amount of the reference position of the objective lens, and to limit the mounting angle of the CD player at the time of use. However, cost reduction and low design tolerance are problems.
[0016]
The present invention is to solve such a problem in the conventional technology, and can easily and reliably adjust a tracking offset when correcting a reference position deviation of an objective lens of an optical pickup, reduce its cost, and Provided is an excellent disk reproducing apparatus that can increase design tolerance.
[0017]
[Means for Solving the Problems]
In order to achieve the above object, a disk drive according to the present invention includes a tracking coil for driving an objective lens in an optical pickup , and a tracking offset current supplied to the tracking coil having a maximum value on a plus side and a maximum value on a minus side. And the amplitude of the tracking error signal corresponding to each offset current is stored. Based on the stored value, the tracking offset current is controlled so that the reference position of the objective lens becomes the maximum movable amount. Tracking servo control means. With this configuration, when correcting the reference position deviation of the objective lens of the optical pickup, for example, the deviation of the reference position deviation that occurs when the wire mounting length of the 4WS wire driven optical pickup or the mounting posture of the device is inclined from horizontal. Can be easily and reliably adjusted, the cost can be reduced, and the design tolerance can be increased.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
According to a first aspect of the present invention, there is provided an actuator for driving an objective lens in an optical pickup, an opt base provided with the actuator, a traverse drive device for driving the opt base, and a drive for driving the traverse drive device. Traverse servo control means for controlling the position of the objective lens within a predetermined range, detection means for detecting the position of the objective lens, and a reference for the objective lens when the detection means detects a displacement of the objective lens. Tracking servo control means for adjusting the tracking offset by supplying an offset current to the tracking coil so that the position becomes the maximum movable amount, and performs tracking when correcting the reference position deviation of the objective lens of the optical pickup. Easy and reliable offset adjustment, low cost It is, and has the effect that it is possible to increase the design tolerance.
[0019]
According to the second aspect of the present invention, the positional deviation of the objective lens is caused by a variation in a wire mounting length in an optical pickup driven by a 4WS wire or a reference positional deviation generated when the mounting posture of the device is inclined from horizontal. It was done.
[0020]
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
(Embodiment 1)
FIG. 1 is a block diagram showing a configuration of the disk reproducing apparatus according to the present embodiment. In FIG. 1, this example is a tracking servo system in the CD player or the like shown in FIG. 3 shown previously, and includes an optical pickup 46 and an RF amplifier 47 that outputs an RF signal, a focus error signal, a tracking signal, and the like. I have. Further, an A / D converter 48 for converting a tracking error signal into a digital signal and outputting the digital signal, a loop filter and an offset current supply circuit are provided. And a signal processing unit 49 that performs the processing.
[0021]
Further, it has a working RAM 40 and a variable gain amplifier 51 for variably amplifying a signal from the signal processing unit 49. Further, it has a driver 52 for outputting a signal from the variable gain amplifier 51 as a drive signal, and a tracking coil 53 for driving an objective lens (not shown) with the drive signal from the driver 52. FIG. 2 is a diagram for explaining an operation state of an optical pickup driven by a 4WS wire, and is similar to the configuration shown in FIG. That is, it has an objective lens 31, an inner yoke 32, a yoke base 35, a bobbin 33, a wire 34, and a yoke base 35.
[0022]
Next, the operation of this embodiment will be described.
First, the relationship between the tracking offset current and the tracking error signal amplitude when the reference position of the objective lens 31 is in the ideal state will be described. When the offset current supply circuit in the signal processing unit 49 of FIG. 1 is operated to change the current supplied to the tracking coil to plus or minus, the amplitude of the tracking error signal becomes zero when the offset current value is zero as shown in FIG. In comparison, the amplitudes decrease when currents of + a and -a shown in FIG. 2 are supplied to the tracking coil. This is because the optical axis shifts due to the shift of the objective lens 31 due to the offset current.
[0023]
Next, a case where the mounting length of the 4WS wire of the optical pickup 46 is uneven, or the mounting angle of the CD player is inclined from the horizontal, and the reference position of the objective lens 31 is shifted will be described. In this case, as compared with the case where the offset current is zero, the amplitude becomes larger when the current of -a is supplied, and the amplitude becomes equal to that when the offset is zero again when the current of -2a is supplied. On the other hand, the amplitude when the current of + a is supplied is smaller than when the offset is zero. At this time, if an attempt is made to reproduce the disk at a portion where the amplitude of the tracking error signal is large, the supply amount of the offset current becomes -a.
[0024]
To determine the supply amount of the offset current in this case, first, conditions for turning on the laser element, turning on the focus servo, turning on the spindle rough servo, and turning off the tracking servo are set. Further, the tracking offset amount is changed from the maximum value on the plus side to the maximum value on the minus side with a constant step amount, the amplitude of the tracking error signal corresponding to each offset amount is detected, and this data is stored in the RAM 40 . . After that, the allowable decrease amplitude Ts for the maximum amplitude is determined. In FIG. 2, 1/2 of the maximum amplitude of the tracking error signal is set as the allowable decrease amplitude Ts, but the set value of the allowable decrease amplitude Ts may be arbitrary.
[0025]
When the allowable decrease amplitude Ts is determined, a corresponding offset current amount is obtained from the data stored in the RAM 40 . This value is usually a binary value, and if these values are b and c, the offset value To required for correcting the reference position of the objective lens 31 is expressed by the following equation (2).
[0026]
To = (b + c) / 2 (2)
For example, in FIG. 2, in an ideal state, b = −a, c = + a, and the offset value To = 0 is obtained by substituting into (Equation 2), and the tracking offset becomes zero. On the other hand, when the reference position is shifted in FIG. 2, b = −2a and c = 0, and the offset value To = −a is obtained by substituting into (Equation 2). Will be supplied. At this time, the reference position of the object lens 31 is corrected to the maximum movable amount as shown in FIG.
[0027]
The maximum movable amount here is the movable amount with respect to each of the outer peripheral side and the inner peripheral side. Therefore, when the movable amount on the outer peripheral side is emphasized as a design concept and the movable amount on the inner peripheral side is sacrificed, (Equation 2) is expressed by the following equation (3).
[0028]
To = (b + c) / 2 + d (3)
Note that d is a correction value for securing a larger movable amount on the outer peripheral side.
[0029]
The offset amount determined in this manner can be further adjusted by an offset voltage of a circuit section or an offset adjustment for preventing sound skipping during reproduction of a scratched disk. As an example of the actual offset adjustment, for example, when the disc is reproduced, the laser element is turned on, the focus servo is turned on, the spindle rough servo is turned off, and the tracking servo is turned off. After that, the spindle control servo and the tracking servo are turned on and the reproduction state is set.
[0030]
【The invention's effect】
As is clear from the above description, according to the present invention, when correcting the reference position deviation, the tracking offset current is changed between the maximum value on the plus side and the maximum value on the minus side, and the respective offset currents are changed. The tracking servo control for tracking offset adjustment is performed by supplying the offset current to the tracking coil so that the reference position of the objective lens becomes the movable maximum based on the stored value and the amplitude of the tracking error signal corresponding to In addition, it is possible to easily and surely adjust the tracking offset when correcting the reference position deviation of the objective lens of the optical pickup, thereby reducing the cost and increasing the design tolerance.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a disc reproducing apparatus according to an embodiment of the present invention; FIG. 2 is an explanatory diagram showing an operation state of an optical pickup driven by a 4WS wire according to the embodiment; FIG. 4 is a perspective view showing a configuration of an optical system of the conventional example. FIG. 5 is an explanatory diagram showing an external configuration of a 4WS wire-driven optical pickup of the conventional example. Explanatory diagram showing the operating state of the conventional 4WS wire-driven optical pickup.
31 Objective lens 32 Inner yoke 35 Yoke base 33 Bobbin 34 Wire 35 Yoke base 46 Optical pickup 47 RF amplifier 48 A / D converter 49 Signal processing unit 50 RAM
51 variable gain amplifier 52 driver 53 tracking coil

Claims (2)

A tracking coil for driving an objective lens in an optical pickup, and a tracking offset current supplied to the tracking coil is changed between a maximum value on a plus side and a maximum value on a minus side to perform tracking corresponding to each offset current. storing the amplitude of the error signal, the disc reproducing apparatus where the reference position of the objective lens based on the stored value is and a tracking servo control means for supplying said tracking offset current so that the movable amount up. 2. The disk reproducing apparatus according to claim 1, wherein the optical pickup is a 4WS wire-driven optical pickup.

Images