JPH0330941B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a center runout adjustment device for a compact disk player or the like that reduces center runout caused by eccentricity of a disk center hole, eccentricity of a turntable, or the like.

<Prior art> In compact disc players, 1.6μ
In addition to correctly positioning the beam spot on the m-pitch track, the beam spot must be moved correctly on the track in accordance with the rotation of the disk. And the positioning accuracy is ±0.1μm
It must be possible to control position errors within ±70 μm at maximum. For this reason, compact disc players are equipped with a tracking servo mechanism, which generates a tracking error signal having a voltage value according to the deviation between the spot position and the track, and performs servo control using the tracking error signal. The beam spot is positioned directly above the track, and the beam spot is moved in accordance with the rotation of the disk to correctly track the track.

<Problems to be solved by the invention> According to this tracking servo, even if distortion occurs in the track TK on the disk DK (the dotted line is an ideal track) during the manufacturing process, as shown in FIG. Or, as shown in Figure 4, even if there is an eccentricity of δ between the track center TC and the center HC of the disk hole HL (referred to as disk eccentricity), or even if there is a center deviation in the rotation axis of the turntable ( This deviation from the center is called eccentricity of the turntable) so that the turntable can follow the track correctly.

However, if the disk is mounted in a direction in which the eccentricity of the disk and the eccentricity of the turntable are added, the center runout becomes large and the position is close to the limit where the position can be corrected. In such a case, an ordinary disk of good quality can correctly follow the track, but a disk with dust or dirt on it, or a scratched disk, causes a problem in that track jumps occur.

From the above, an object of the present invention is to be able to reduce the center runout to a permissible value or less even if the center runout becomes large;
Therefore, it is an object of the present invention to provide a center runout adjusting device that can always perform stable tracing.

<Means for Solving the Problems> The center runout adjusting device of the present invention includes first and second motors that respectively move the rotating shaft of the spindle motor in two axial directions parallel to the disk surface, and a beam spot position adjusting device. a low-pass filter that outputs the low-frequency signal component included in the tracking error signal according to the deviation between A comparator that compares the low frequency signal component with an allowable value, and a motor drive unit that drives the first and second motors based on the comparison result.

<Function> When reading information recorded in the lead-in area of the disk, the low frequency signal component included in the tracking error signal is output as a center runout signal via a low pass filter, and the low frequency signal component is and a preset tolerance value, and if the low frequency signal component is larger than the tolerance value, the first and second motors are driven to change the position of the spindle motor rotation axis relative to the turntable. Fine adjustment is made to bring the low frequency signal component below the allowable value, thereby reducing center runout.

<Embodiment> Fig. 1 shows main blocks of a compact disc player according to an embodiment of the present invention, in which 1 is a compact disc, 2 is an optical pickup, 3 is a waveform processing circuit, 4 is a signal processing circuit, and 5 is a compact disc player. is a DA converter, 6 is an audio circuit, 7 is a rotational speed control section, 8 is a spindle motor, 9 is a tracking control section, 10 is a focusing control section, 11 is a display device, 12 is a center runout adjustment device, and 13 is a turntable. be.

Acoustic signals are digitally recorded on the compact disc 1, and control data called frame synchronization signals and subcoding are recorded for each predetermined number of data. The optical pickup 2 optically reads digital information recorded on the compact disk 1 and inputs it to the waveform processing circuit 3. The waveform processing circuit 3 receives the RF output from the optical pickup 2.
The signal is amplified and waveform shaped at a predetermined slice level, and the signal obtained by waveform shaping (EFM
signal) is input to the signal processing circuit 4. The signal processing circuit 4 demodulates the EFM signal, separates the audio data and sub-coding, performs error detection/correction processing on the audio data, performs DA conversion with the DA converter 5, and outputs the signal to the audio circuit 6.

Further, the signal processing circuit 4 analyzes the sub-coding Q channel, extracts data indicating the current song number, elapsed time for each song, total elapsed time, etc., and displays the data on the display device 11 as appropriate.

The CLV circuit 7a of the rotational speed control section 7 generates an EFM signal and a crystal oscillator built in the signal processing circuit 4.
A drive signal SMD for rotating the spindle motor 8 at a constant linear velocity is generated using the 4.3218 MHz clock signal CLS, and the drive circuit 7b rotates the spindle motor 8 based on the drive signal.

The tracking signal calculation section 9a of the tracking control section 9 generates a tracking error signal using the detection signal derived from the optical pickup 2, and applies it to the tracking actuator drive circuit 9b.
The tracking actuator drive circuit 9b drives a tracking actuator (not shown) to move the objective lens OBL in the horizontal direction and controls the laser beam spot to come to the center of the pit.

A focus error signal calculation section 10a of the focusing control section 10 generates a focus error signal using the detection signal derived from the optical pickup 2, and applies it to the focus actuator drive circuit 10b. Drive circuit 10
In b, a focus actuator (not shown) is driven to move the objective lens OBL relative to the disk signal surface DS in the perpendicular direction, so that the disk signal surface becomes the focal plane.

By the way, the above configuration is no different from the conventional device, and during performance (play), the rotational speed control section 7 performs servo control to maintain a constant linear velocity.
Further, the tracking control section 9 performs tracking servo control, and the focusing control section 10 performs focusing servo control.
As a result, acoustic data etc. can be accurately read from the compact disk 1 by the optical pickup 2,
Music etc. are output from the audio circuit 6 via the signal processing circuit 4.

However, if the disc is attached to the player in such a way that the eccentricity of the disc and the eccentricity of the turntable are added together as described above, the center runout becomes large and stable tracing cannot be performed, and the disc Malfunctions such as track jumps may occur due to dirt or dust attached to the drive or scratches.

Therefore, in the present invention, a center runout adjustment device 12 is further provided.

The center runout adjustment device 12 includes a low-pass filter 12a, a microcomputer 12b, and first and second comparators 12c, 1
2d, first and second motor drive circuits 12e, 1
2f, and first and second motors (X-axis and Y-axis motors) 12g and 12h.

The low-pass filter 12a is applied with the tracking error signal TRE output from the tracking control section 9, and when reading information recorded in the lead-in area of the disk signal surface DS, the tracking error signal TRE included in the tracking error signal TRE is applied. Outputs the low frequency signal component as the center runout signal CSS. still,
Since the influence of eccentricity occurs almost at the rotation period and mainly consists of low frequency components of 10 Hz or less, the low-pass filter (which can be regarded as a smoothing circuit) 12a is configured to output low frequency signal components of 10 Hz or less.

The microcomputer 12b sets and outputs a voltage _value (tolerable value) V _A corresponding to the allowable amount of core runout, and also controls the core runout adjustment operation. Finish the adjustment operation.

The first and second comparators 12c and 12d compare the center runout signal value V _C and the allowable value V _A , and transmit the comparison result to the microcomputer 12b, the first and second drive circuits 12e,
Output to 12f.

Now, if the initial center runout signal value (absolute value) V _C is smaller than the allowable value V _A (V _C ≦V _A ), the microcomputer 12
b does not perform the center runout adjustment operation.

However, if V _C >V _A , the microcomputer 12b stores the center runout signal value V _C. In addition, in order to first perform the center runout adjustment in the X-axis direction and then the center runout adjustment in the Y-axis direction, the microcomputer 12b initially sets the second comparator 12d to V _S (value such that V _S >V _C ). and set
The second motor drive circuit 12f is prevented from generating a motor drive signal, in other words, the Y-axis motor is not driven.

If V _C > V _A , the first motor drive circuit 12e
applies a pulse of a predetermined width to the X-axis motor 12g as a motor drive signal. As a result, X-axis motor 1
2g rotates to drive the rack and pinion mechanism (rack LX, pinion PX) shown in Fig. 2A, and moves the frame FM, to which the spindle motor 8 is attached, in the X-axis direction on a plane parallel to the disk surface. Move by a predetermined amount. By the way, turntable 13
The rotation axis SSH of the spindle motor 8 is shown in Figure 2B.
As shown in the figure, they are connected by magnets MG and MG', and the space between the two magnets can be slipped with a predetermined driving force. Therefore, the X-axis motor 12
When g rotates and the rack and pinion mechanism is driven, magnet MG' moves a predetermined amount while slipping relative to magnet MG, and as a result, the rotation axis
The SSH moves by a minute amount with respect to the turntable 13. Note that since the position of the turntable 13 serves as a reference, the clamper position of the turntable 13 (not shown) is fixed.

After the rotation axis SSH moves in the X-axis direction, the center runout signal value V _C output from the low-pass filter 12a is the allowable value.
When the value becomes smaller than V _A , the center runout adjustment operation ends.
However, if V _C > V _A , the microcomputer 12b compares the previously stored core runout signal value (referred to as V _C ′) with the current core runout signal value V _C and determines that V _C ′>V If it is _C , the first comparator circuit 12e stores the V _C as V _C ', and outputs a pulse of a predetermined width as a motor drive signal to the X-axis motor 12g as before,
The same operation will be performed thereafter.

If V _C ′≦V _C before V _C ≦V _A , the microcomputer 12b then sends the second comparator 12d to the allowable value V _A in order to finely adjust the rotation axis SSH in the Y-axis direction. and the first comparator 12c
Set V _S to , and store V _C as V _C ′. still,
Since V _S > V _C , the first motor drive circuit 12e
will no longer generate motor drive signals.

Since V _C >V _A , the second motor drive circuit 12f applies a pulse having a predetermined width to the Y-axis motor 12h as a motor drive signal. As a result, the Y-axis motor 12h rotates, driving the rack and pinion mechanism (LY is rack and PY is pinion) shown in FIG.
Move SSH a specified amount in the Y-axis direction. After moving in the Y-axis direction, if the center runout signal value V _C output from the low-pass filter 12a becomes smaller than the allowable value V _A , the center runout adjustment operation ends.

However, if V _C > V _A , the microcomputer 12b compares the previously stored center runout signal value V _C ′ with the current center runout signal value V _C , and if V _C ′> V _{C ,} then Similarly to _the previous time, the second comparator circuit 12f outputs a pulse with a predetermined width as a motor drive signal to the Y-axis motor 12h.
Repeat the same operation until V _C ≦V _A , and V _C ≦V _A
If V _C ′≦V _C before this happens, then the set value is switched in order to move the rotating shaft SSH in the X-axis direction again.

After that, the same operation is repeated and finally V _C
≦V _A.

<Effects of the Invention> According to the present invention, the tracking error signal of the first and second motors that respectively move the rotating shaft of the spindle motor in two axial directions parallel to the disk surface is a low-pass filter that outputs a frequency signal component as a run-out signal; a control unit that outputs a run-out tolerance value and controls a run-out adjustment operation; a comparator that compares the run-out signal value and the tolerance value; A motor drive circuit is provided to drive the first and second motors using the comparator output, and the spindle motor rotation axis position is finely adjusted with respect to the turntable according to the magnitude of core runout. Even if the disc is mounted in a direction where the eccentricity of the disc and the eccentricity of the turntable are added together and the runout becomes large, the amount of runout can be kept below the allowable value. Or, even if scratches occur, no track jump occurs and stable tracing is possible.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a compact disk including a run-out adjustment device according to the present invention, Fig. 2 is an explanatory diagram of the run-out adjustment operation of the present invention, Fig. 3 is an illustration of track distortion, and Fig. 4 is a diagram of the disc. It is an eccentric explanatory diagram. DESCRIPTION OF SYMBOLS 1... Compact disk, 2... Optical pickup, 7... Rotation control unit, 8... Spindle motor, 9... Tracking control unit, 10... Focusing control unit, 12... Center runout adjustment device, 12
a...Low-pass filter, 12b...Microcomputer, 12
c, 12d...first and second comparators, 12g, 1
2h...first and second motors, 13...turntable, SSH...rotating shaft.

Claims (1)

[Claims] 1. In a center runout adjustment device that reduces center runout due to eccentricity of a disk center hole, eccentricity of a turntable, etc., a first device that relatively moves the rotating shaft of a spindle motor in two axial directions parallel to the disk surface, The second motor and a reduction filter that outputs the low frequency signal component included in the tracking error signal as a runout signal compare the value Vc of the low frequency signal component with a preset tolerance value Va. Then, if Vc>Va, the comparator changes the first motor to Vc<Va as long as Vc continues to decrease.
If the center runout in the first axis direction is adjusted by driving the motor until Vc becomes Va, and if Vc stops decreasing without becoming Vc<Va, then the second motor is driven until Vc continues to decrease. <Va, then drive the second
A center runout adjustment device comprising a control section that adjusts center runout in the axial direction and thereafter repeatedly drives the first and second motors in the same manner until Vc<Va.