JP2800778B2 - Optical disk rotation controller - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disc for changing the number of revolutions of a spindle motor in order to cope with a change in radius from an optical disc center point to a light beam spot due to eccentricity of an optical disc or a disc turntable. The present invention relates to a rotation control device.

[0002]

2. Description of the Related Art Since information on an optical disk is recorded at a constant linear velocity, it is necessary to perform reproduction at a constant linear velocity even when reproducing an optical disk. However, the linear velocity may change during reproduction due to a change in the distance from the center point of the optical disk to the light beam spot based on the eccentricity of the optical disk or the disk turntable. Therefore, at the time of reproducing the optical disk, in order to cope with a radius change from the optical disk center point to the light beam spot,
An optical disk rotation control device is required.

Hereinafter, a conventional optical disk rotation control device will be described with reference to the drawings.

FIG. 3 shows a conventional optical disk rotation control device. The servo control of the spindle motor in the reproducing apparatus for the optical disk 3 having a constant linear velocity is generally performed as follows.

[0005] In FIG. 3, the optical pickup 4 is fixed in the rotation direction, and the spindle motor 1 is drive-controlled and rotated to rotate the optical disc 3 mounted on the turntable 2 fixed to the axis of the spindle motor 1. Rotate. Thus, the signal recording pits carved on the optical disc 3 are scanned by the light beam spot projected from the optical pickup 4, and the reflected light from the optical disc 3 is
A light receiving element provided in the optical pickup 4 receives the light and converts it into an electric signal, whereby a reproduced electric signal 13 is obtained.

Since the period of the reproduced electric signal 13 is an integral multiple of the channel bit clock used for processing the reproduced signal, the edge period when the reproduced electric signal 13 is binarized and the channel bit clock generating oscillator 5 The phase of the channel clock is tracked by the phase locked loop (PLL) 6 and the channel bit clock generating oscillator 5 is controlled in accordance with the comparison result so that the cycle of the channel bit clock follows the cycle of the reproduced electric signal 13. Let it.

On the other hand, the phase of the system clock 7 is compared with the output clock of the reproduction reference oscillator 8 by the PLL 9, and the reproduction reference oscillator 8 is controlled in accordance with the comparison result. Follow the cycle of the system clock 7.

Further, the phase of the channel bit clock is compared with the phase of the reproduction reference clock by the PLL 10 to obtain a spindle motor rotation error signal. The spindle control signal generator 11 controls the phase of the reference clock based on the spindle motor rotation error signal to generate a spindle control signal. The power driver 12
The spindle control signal drives the spindle motor 1 to rotate. In this way, the rotation of the optical disc 3 is controlled so that the cycle of the reproduced electric signal 13 from the optical pickup 4 matches the cycle of the system clock, and the linear velocity becomes constant.

In an optical disk having a constant linear velocity, the line length of a signal pit string to be followed and scanned in a reproducing apparatus is constant per unit time. Therefore, if the radius of rotation changes according to the distance from the center point of the disk to the light beam spot, it is necessary to change the number of rotations of the optical disk accordingly.

The signal recording pit row recorded on the optical disk 3 is spiral, and the spiral recording interval is a CD (Compact Diode).
In the case of sk), it is extremely small at 1.6 [μm], so that the spiral shape of one rotation can be approximated to a circle. However, the disk has an eccentric dimension allowed by the standard as a manufacturing error and an allowable value of the rate of change of the signal recording pit row spiral expressed by the centripetal acceleration and fixed on the spindle motor shaft There is also eccentricity in the turntable that was set.

For these reasons, in the optical disc reproducing apparatus, control following eccentricity is required. The presence of the eccentric component means that there is a radius change, and since the light beam spot is scanned at a constant linear velocity, the spindle servo follows control so that the rotation speed changes according to the eccentricity. Is required. Therefore, as described with reference to FIG. 3, the rotation speed control of the optical disc is performed so that the linear velocity is kept constant by following the rotation number change determined by the reproduction position and following the rotation number change due to the eccentricity.

As a method for coping with a change in the number of revolutions based on the eccentricity, for example, as disclosed in Japanese Patent Application Laid-Open No. 60-059567, the rotation of a track read at a constant linear velocity on a recording medium is considered. By compensating the servo transfer function according to the radial position, the required response characteristics can be obtained over the inner and outer circumferences of the track, and the linear velocity unevenness at that time can be reduced, and the linear velocity due to eccentricity from the recording medium, etc. There is also known a method of achieving a uniform linear velocity performance with less unevenness.

As described in JP-A-2-247831, when the servo loop is open,
While rotating the disk at a rotation speed lower than the performance rotation speed at the current position of the information reading point, a plurality of sample values representing the magnitude of the amplitude of the tracking error signal obtained at this time are taken in, and the plurality of samples are read. A method of setting a loop gain based on a value to set an optimum loop gain for each disk to be played without being affected by the eccentricity of the disk is also known.

Further, in Japanese Patent Application Laid-Open No. 4-74359, a PLL circuit synchronized by sample servo bits formed on a magneto-optical disk,
A spindle motor for rotating the magneto-optical disc by the output of the phase comparing means and the output of the resonator, comprising: a phase comparing means for comparing the output signal of the circuit with the reference frequency; and a resonator which resonates at an eccentric period of the magneto-optical disc. There is disclosed a spindle motor servo method which is useful when rotating a magneto-optical disk on which sample servo bits are formed at a constant angular speed by controlling the rotation speed.

[0015]

SUMMARY OF THE INVENTION In an optical disc,
While following the rotation speed change determined by the reproduction position occurs gradually, following the rotation speed change due to eccentricity involves a rapid change. The control signal extraction of the spindle servo is performed by a PLL or the like using the reproduced electric signal as described in the section of the related art. The control of the PLL involves a delay due to a long time constant.

The delay of the control signal of the spindle servo means a delay in following the change in the rotation speed of the spindle motor. In order to compensate for this delay, generally, the PLL for controlling the channel bit clock generation oscillator described in the section of the prior art is made to follow at high speed, and a memory element is used to absorb the following delay of the spindle motor. I have.
However, there is a limit to this, and if a delay exceeding the capacity of the memory element occurs, an error occurs in data obtained from the reproduced electric signal.

Therefore, it is necessary to minimize the delay in following the change in the rotation speed of the spindle motor.

For this purpose, it is conceivable to use a tracking error signal for the pit row of the optical pickup 4. Conventionally, however, an output obtained by inputting the tracking error signal to a circuit having frequency characteristic processing and gain control means is obtained. A voltage is applied to a tracking actuator coil that drives the optical pickup 4 in the radial direction, and the light receiving lens of the optical pickup 4 is moved in the radial direction of the optical disc 3 to trace the recording signal pit row, It was only used to get column traversal information.

An object of the present invention is to solve such a problem of the prior art, and it is possible to reduce a delay in following a change in the rotation speed of a spindle motor by using a tracking error signal. It is an object of the present invention to provide an optical disk rotation control device.

[0020]

According to the present invention, a servo control signal by an eccentricity detecting means having a small time delay is newly added to the configuration of a conventionally used spindle servo system, so that a spindle motor is provided. A control signal is generated.

In this case, as the servo control signal by the eccentricity detecting means having a small time delay, a tracking error signal or a tracking servo control signal obtained by correcting the phase or processing the frequency characteristic thereof is used. These signals, like the reproduced electric signals, are obtained by scanning the signal recording pits engraved on the optical disc with the light beam spot projected from the optical pickup, and receiving the reflected light obtained from the optical disc by the light receiving element. It is obtained by converting it into an electric signal, and represents an eccentric state in real time.

Hereinafter, specific means for solving the problems of the present invention will be described.

(1) In an optical disk reproducing apparatus for reading an optical disk 3 recorded at a constant linear velocity by an optical pickup 4, a first PLL 6 causes a channel bit clock to follow a reproduced electric signal from the optical pickup 4. The second PLL 9 causes the reproduction reference clock to follow the system clock, and the third PLL 10 obtains a spindle motor rotation error signal by comparing the phase of the channel bit clock with the reproduction reference clock. The spindle control signal generator 15 controls the phase of the reference clock based on the addition result of the spindle motor rotation error signal and the tracking error signal from the optical pickup 4 to generate a spindle control signal. The power driver (spindle motor drive unit) 12 drives the spindle motor 1 for rotating the optical disc 3 by the spindle control signal. This controls the reproduced electric signal from the optical pickup 4 to have a constant linear velocity regardless of the eccentricity of the optical disk 3 during rotation.

(2) In the optical disk reproducing apparatus for reading the optical disk 3 recorded at a constant linear velocity by the optical pickup 4, the first PLL 6 causes the channel bit clock to follow the reproduced electric signal from the optical pickup 4, The second PLL 16 causes the reproduction reference clock to follow the signal resulting from the addition of the system clock and the tracking error signal from the optical pickup 4, and the third
, A spindle motor rotation error signal is obtained by comparing the phase of the channel bit clock with the reference clock for reproduction. Spindle control signal generator 11
Generates a spindle control signal by controlling the phase of the reference clock based on the spindle motor rotation error signal. Power driver (spindle motor driver) 12
Is a spindle motor 1 for rotating the optical disc 3,
It is driven by this spindle control signal. As a result, the amplitude of the spindle motor rotation error signal is reduced with respect to the eccentric component during rotation of the optical disc 3.

(3) In the case of (1) or (2), a tracking servo control signal obtained by correcting the phase of the tracking error signal and / or processing the frequency characteristics is used instead of the tracking error signal.

[0026]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment (1) of the present invention, in which the same components as those in FIG. 3 are indicated by the same reference numerals. In FIG. 1, a tracking error signal and the like are obtained from the optical pickup 4 in addition to the reproduced electric signal 13.
In the present embodiment, a tracking error control signal or a tracking servo control signal 14 obtained by performing circuit processing such as phase correction and / or frequency characteristic processing on the tracking error signal is added to a spindle control signal generation unit 15.

The tracking error signal or tracking servo control signal 14 is obtained by converting an optical signal detected by the light receiving element of the optical pickup 4 into an electric signal and detecting the signal. In comparison, eccentricity information can be detected earlier. Therefore, in the spindle control signal generation unit 15, the tracking error signal or the tracking servo control signal 14 is
By adding to the output signal of the PLL 10 to generate eccentricity information with a small delay and applying the obtained spindle control signal to the spindle motor 1 via the power driver 12, a more rapid spindle motor 1 Can be followed.

FIG. 2 shows an embodiment (2) of the present invention, in which the same components as those in FIG. 3 are indicated by the same reference numerals. In FIG. 2, a tracking error signal and the like are obtained from the optical pickup 4 in addition to the reproduced electric signal 13.

In this embodiment, the tracking servo control signal 14 obtained by subjecting the tracking error signal or the tracking error signal to circuit processing such as phase correction and / or frequency characteristic processing is used for reproduction from the reproduction reference oscillator 8. By controlling the reproduction reference oscillator 8 in addition to the PLL 16 for causing the reference clock to follow the system clock, the output reproduction reference clock changes according to the eccentricity. It can operate to produce a frequency change similar to a clock. Accordingly, the amplitude of the spindle motor rotation error signal output from the PLL 10 for obtaining the rotation speed control signal of the spindle motor 1 can be reduced with respect to the eccentric component.
Servo control can be performed without greatly changing the number of rotations.

Note that the addition of the tracking signal in the embodiment (1) and the addition of the tracking signal in the embodiment (2) may be performed together.

[0032]

As described above, according to the rotation control device of the first or third aspect, since the rotation speed of the spindle motor can be quickly followed, the error in following the rotation speed is reduced, and the rotation following is reduced. Since the disturbance on the time axis of the reproduced electric signal due to the error is reduced, the error rate when this is converted into a digital code can be reduced.

According to the rotation control device of the second or third aspect, since the servo control can be performed without greatly changing the rotation speed of the spindle motor, a change in the rotational movement of the optical disk can be reduced. The small change in the rotational motion of the optical disk means that the required energy is reduced. Therefore, the power supply current in the optical disk reproducing device can be reduced, and the cost of the power supply unit can be reduced.

Also, since the required change in the rotational motion is reduced, the required torque performance of the spindle motor can be reduced. This not only has an effect on cost reduction but also reduces mechanical system stress. Life can be extended. Further, since the reproduction reference clock changes in response to the eccentricity, the servo system operates without requiring a large change in the rotation speed of the spindle motor due to the eccentricity, so that the reproduced electric signal due to the rotation following error is generated. Disturbance on the time axis is reduced, and the error rate when converted to a digital code is reduced.

In the case of the second or third aspect of the present invention, C
It is unsuitable for D-DA reproduction because an eccentric component will appear in the analog audio output as uneven rotation if it is left as it is, but if it is implemented together with a sound skip prevention function using a memory element or the like, Applicable.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment (1) of the present invention.

FIG. 2 is a block diagram showing an embodiment (2) of the present invention.

FIG. 3 is a block diagram showing a conventional optical disk rotation control device.

[Explanation of symbols]

 Reference Signs List 1 spindle motor 3 optical disk 4 optical pickup 6 first PLL 9, 16 second PLL 10 third PLL 11, 15 spindle control signal generator 12 power driver (spindle motor driver)

Claims (3)

(57) [Claims] 1. A rotation control device for controlling the rotation of an optical disk, which is used in an optical disk reproducing device for reading an optical disk recorded at a constant linear velocity by an optical pickup. A first PLL for following a bit clock, and a second PLL for following a reproduction reference clock to a system clock
A third PLL that obtains a spindle motor rotation error signal by comparing the phase of the channel bit clock with the reproduction reference clock, and the result of adding the spindle motor rotation error signal and the tracking error signal from the optical pickup. An optical disc rotation control device, comprising: a spindle control signal generation unit that controls a phase of a reference clock to generate a spindle control signal; and a spindle motor drive unit that drives a spindle motor that rotates the optical disc by the spindle control signal. . 2. A rotation control device for controlling the rotation of the optical disk, the rotation control device being used for an optical disk reproducing device for reading an optical disk recorded at a constant linear velocity by an optical pickup. A first PLL for following a bit clock, a second PLL for following a reproduction reference clock to a signal obtained by adding a system clock and a tracking error signal from an optical pickup, the channel bit clock and the reproduction reference A third PLL that obtains a spindle motor rotation error signal by comparing a phase with a clock, a spindle control signal generation unit that generates a spindle control signal by controlling the phase of a reference clock based on the spindle motor rotation error signal, Spindle motor to rotate Serial and a spindle motor driving unit for driving the spindle control signal, the rotation control device of an optical disk. 3. The optical disk rotation control device according to claim 1, wherein a tracking servo control signal obtained by phase correcting and / or frequency characteristic processing the tracking error signal is used instead of the tracking error signal. Optical disk rotation control device.