JPH0746433B2 - Tracking control device for optical playback device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Use of the Invention] The present invention provides information such as a video signal on a disc-shaped recording medium.
The present invention relates to an optical reproducing apparatus for recording or reproducing in the form of optical characteristic change in the medium, and particularly to a tracking control apparatus for the optical reproducing apparatus.

[Background of the Invention]

In such an optical recording / reproducing apparatus, for example, a disc-shaped recording medium is generally used, and an information signal is recorded on a disc-shaped recording medium as a spiral or concentric recording locus and reproduced from there. .
The concentric circular locus is suitable for recording information such as still image information that has a fixed interval, and conversely, spiral recording for recording and reproducing video signals such as moving images and continuous signals such as audio signals. A locus (hereinafter referred to as a track) is suitable.

In such information recording device or reproducing device,
Considering the economical efficiency of the recording medium and the miniaturization of the device, there is a tendency that the density will be further increased in the future regardless of the recording / reproducing means, and in order to achieve this, the recording wavelength is shortened and the track is narrowed. The demands are increasing.

One of the problems that accompanies this narrowing of tracks is that when a recording medium having recorded information tracks is attached to or detached from the device and then attached to the device again, it is caused by mechanical displacement of the attached recording medium. The eccentricity and the plastic deformation due to the thermal or mechanical stress of the recording medium may cause distortion of the information track beyond the track interval. Therefore, unless the tracking control that follows the distorted shape of the information track is performed, the distorted shape causes the reproduction scanning position of the reproducing means (specifically, the position of the light spot) and the relative position of the information track in the track orthogonal direction. Will have fluctuations.

Usually, most of the distortion of the information track is caused by eccentricity, which occurs in synchronization with the rotation of the disc-shaped recording medium, and its size and the disc-shaped recording medium depend on the mounting condition of the disc. The phase with respect to the rotation angle of is different. Although the information track distortion depends on the accuracy of the information reproducing apparatus or the disc-shaped recording medium, it is generated in the order of several tens to several hundreds of μm, and when the track interval is set to about 2 μm, it is large by one or two digits. It becomes a value.

Therefore, in a normal reproduction state, tracking control is performed so that the light spot for reproducing the information signal follows the distorted shape of the track. At this time, the relative positional deviation between the light spot and the track needs to be suppressed to an accuracy of about 0.1 μm or less in consideration of crosstalk from the adjacent track. However, when the distortion of the disk, especially the component caused by the eccentricity, becomes large, the relative positional deviation between the light spot and the track becomes large, and the crosstalk from the adjacent track becomes a problem. In order to reduce this positional deviation, the gain of the tracking control circuit should be increased, but if the gain of the control circuit is increased too much, problems such as oscillation of the control circuit occur and the circuit becomes unstable. The problem arises.

As a method for dealing with the above-mentioned drawbacks, for example, JP-A-56-7247
As described in No. 1, the waveform corresponding to the distortion shape of the information track is extracted from the tracking error signal obtained when the tracking control circuit is operating normally, and once stored in memory, There is a method in which the stored waveform is read in synchronism with the rotation of the disk and the signal read from this memory is applied to a tracking control circuit to correct the position fluctuation and position shift of the reproduction light spot and the information track.

This method is based on the assumption that the tracking control operates reliably. However, if the eccentricity caused by the mounting of the disc is too large, the tracking control may not be performed following the track distortion. If the tracking error signal is stored as a waveform and the stored signal is used for correction, there is a problem that it has an adverse effect.

In the case of the tracking control described in JP-A-56-7247, the waveform stored in the memory is read based on the rotation start signal provided on the disk. Type optical disk player cannot be used because the disk has no rotation start signal. In addition, the read-only optical disc player has a CAV system (Consta
nt Angular Velocity) and CLV method (Constant Li
near Velocity). In the CLV system, the rotation speed changes continuously at 1800 rpm (30 Hz) on the inner circumference of the disk and 600 rpm (10 Hz) on the outer circumference of the disk, so it is necessary to change the reading of the waveform stored in the memory accordingly.

As described above, the conventional tracking control device has some problems.

[Object of the Invention]

An object of the present invention is to correct the relative positional deviation between the position of the reproducing light spot and the information track and the position variation caused by the above-mentioned distorted shape of the information track, and in particular to eliminate the eccentric component of the disk. It is to provide a tracking control device for correction.

[Outline of Invention]

The feature of the present invention is that the distortion of the information track caused by the mounting of the disc is generated mainly in synchronization with the rotation of the disc, and a sine wave waveform of, for example, one cycle is stored in the storage circuit. On the other hand, the size and phase of the eccentricity of the disk is detected from the tracking error signal of the tracking control circuit which is controlled so as to follow the distortion of the information track, and the amplitude of the sinusoidal waveform is detected by the detected signal. The phase is corrected and stored in the memory means, and the optimum correction signal is generated by reading from the memory means at the address created according to the rotation speed of the disk. Further, this is characterized in that it can be applied to a system in which the number of rotations changes depending on the position of the light spot, such as the CLV system of a read-only optical disc player.

Example of Invention

An embodiment of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a block diagram showing an embodiment of the optical reproducing apparatus of the present invention. In the figure, 1 is a disk, 2 is a rotation motor, 3 is a laser diode, 4 is a coupling lens,
5 is a diffraction grating, 6 is a polarizing prism, 7 is a mirror, and 8 is ¹
/ ₄ wavelength plate, 9 is an objective lens, 10 is a cylindrical lens, 11 is a mirror, and 12 is a detector.

Further, 13 is a signal processing circuit, 14 is a sync separation circuit, 15 is a reference signal generation circuit, 16 is a motor control circuit, and 17 is a drive circuit. Further, 18 is a differential amplifier, 19 is a phase compensation circuit, 20 is a switch, 21 is an adder, 22 is a drive circuit, 23 is a tracking control actuator, 24 is a waveform shaping circuit, and 25 is a disc eccentricity detection and correction. An eccentricity correction signal generating circuit, 30 is a memory, 31 is a ^D / _A converter, 32 is a switch, 33
Is a frequency dividing circuit.

Next, the operation of this embodiment will be described.

In FIG. 1, a disk 1 is a disk rotation motor 2
It is rotated at high speed by. The light beam generated from the laser diode 3 is incident on the coupling lens 4 and the diffraction grating 5. The diffraction grating 5 is an optical element in which a large number of thin parallel lines are formed on the surface of a transparent plate, and is separated into three light beams which are emitted at a slight angle with each other due to the diffraction interference effect of light. Of the three light beams, the central light beam is for reading recorded information and controlling the focus position, and the two light beams on both sides are for detecting a tracking error signal. The light flux of the three is incident on the objective lens 9 passes through the polarizing prism 6, mirror 7, _^1/4-wave plate 8. The objective lens 9 is controlled by the well-known focus control (focus control) so that the three light beams form three light spots with a diameter of 1.6 μm which are 20 μm apart along the track on the pit surface on the disk 1. To be done.

The reflected light reflected on the disk 1 is again the direction is changed by the polarization prism 6 passes through the objective lens 9, _^1/4-wave plate 8, through the cylindrical lens 10 of the three in the optical detector 12 Images are formed on the light receiving surfaces P ₁ , P ₂ , and P ₃ , respectively. Two light beams for tracking error detection are imaged on the light receiving surfaces P ₁ and P ₂ on both sides, and a central light beam for reading recorded information is imaged on the central light receiving surface P ₃ . The central light-receiving surface P ₃ is divided into four, and the light-receiving output thereof is also used for focus error signal detection.

The output of the differential amplifier 18 is the light-receiving surface of the photodetector 12.
A difference signal between P ₁ and P ₂ is obtained, and this difference signal is the phase compensation circuit 1
It is input to the drive circuit 22 via 9, the loop switch 20, and the adder 21. The actuator 23 for tracking control is controlled by the output of the drive circuit 22, and known tracking control is performed.

On the other hand, the output of the light receiving surface P ₃ of the photodetector 12 is input to the signal processing circuit 13 where it is converted into a video signal. The converted video signal is synchronously separated by the synchronous separation circuit 14, and the motor control circuit 16, so that the horizontal synchronization signal obtained here and the reference horizontal synchronization signal output from the reference signal generation circuit 15 are in phase synchronization. The disk rotation motor 2 is controlled via the drive circuit 17.

Since the disk rotation motor 2 is controlled so that the horizontal sync signal of the video signal reproduced from the disk 1 and the reference horizontal sync signal are in phase synchronization, in the case of the CAV type disk, the disk rotates at a constant speed of 1800 rpm. Rotate by number.
On the other hand, in the case of the CLV system, the rotation speed automatically changes according to the reproduction position of the reproduction light spot, and the rotation speed is 1800 rpm at the innermost disc position and about 600 rpm at the outermost disc position.

FIG. 2 shows an example of the disk rotating motor 2. A brushless DC motor is generally used for reasons such as the life of the motor. Here, a DC three-phase brushless motor is shown as an example. In the figure, 34 is a turntable, 35 is a hub, 36 is a yoke, 37 is a magnet, 38 is a coil, 39 is a substrate on which the coil 38 is mounted, 40 is a yoke,
41 is a bearing, 42 is a thrust bearing, and 43 is a rotating shaft.

FIG. 3 shows an example of the magnetization pattern of the magnet 37.
As shown in the figure, it is magnetized to 8 poles.

FIG. 4 shows an example of a specific structure of the coil 38 mounted on the substrate 39. The coils 44-1, 44-2, 44-3, 44-5,
44-6, Hall elements 47-1, 47-2, 47-3, and a frequency power generation pattern 48 (hereinafter referred to as FG pattern).
Coil 44-1 and 44-4 (also called U-phase coil), coil 44-2
And 44-5 (also called V phase coil), coils 44-3 and 44-6 (W
Although not shown here, the phase coils are also connected in a pattern provided on the substrate, and the above U
The phase, V phase, and W phase coils are connected in a Y connection as shown in FIG.

Since the driving method of the motor is not directly related to the present invention, a detailed description thereof will be omitted, but the driving voltage of each coil changes the magnetic field that changes with the rotation of the magnet 37, and the Hall elements 47-1 and 47.
The rotation is performed by the magnetic force generated by the coil current at this time, the attraction force of the magnetic force of the magnet 37, and the repulsive force.

The FG pattern 48 provided inside the coil 44 is for detecting the number of rotations of the motor, and the number of pulses output for one rotation of the disk motor can be arbitrarily set by the configuration of the FG pattern.

FIG. 5 shows a specific example of the motor drive circuit 17 of FIG. As shown in FIGS. 6 (a), (b) and (c), the hall elements 47-1, 47-2 and 47-3 are magnetized with 8 poles, so that the motor rotates once. A 4-cycle sinusoidal waveform is obtained for this waveform.
After being input to 51, it is processed by the matrix circuit 52, and drive voltages for driving the coils as shown in FIGS. 6 (d), (e) and (f) are output to the drive circuits 53, 54 and 55. To do so. The amplitude of the drive voltage is controlled by the output (b) of the motor control circuit 16 shown in FIG. 1 so that the desired rotation speed is achieved. Further, the output of the FG pattern 48 is amplified by the limiter amplifier 56, and its amplitude is limited to the output (c).

Next, the operation of the eccentricity correction signal generation circuit, which is the main part of the present invention, will be described with reference to FIGS. 10 and 11 as necessary.

FIG. 7 shows the trajectory of the light spot when the tracking control is turned off. In this figure, O is the recording center of the information track, O'is the rotation center of the disc,
The solid line shows the information track, and the broken line shows the locus of the light spot. For example, if the rotation speed of the disk 1 is 1800 rpm, the eccentricity of the disk is represented as shown in FIG. 8 (a), the repetition frequency is 30 Hz, and the amplitude A represents the magnitude of the eccentricity. FIG. 8 (b) shows an output waveform of the tracking error signal obtained at the output side of the differential amplifier 18 of FIG. 1 at this time, and a sine wave-like waveform corresponding to the number of movements of the information track is obtained. To be One cycle of this sine wave waveform corresponds to the track pitch of the information track, and the eccentricity of the disk can be detected by counting the number of this sine wave waveform.

Therefore, as shown in FIG. 10, first, the switch 32 of FIG. 1 is turned off by the control of the microcomputer 25 so that the correction signal from the memory 30 is not applied to the actuator 32. Signal from system control (a) that controls the entire system but not
Then switch 20 is also turned off so that tracking control does not work (steps S1 and S2 in FIG. 10). Then, in this state, the waveform shown in FIG. 8B obtained by the differential amplifier 18 is shaped by the waveform shaping circuit 24. This shaped signal is input to the microcomputer 25.

The microcomputer 25 has, for example, a counter function 26, a calculation function 27, a memory function 28, a data / address control function 29.
Composed by. In addition to the above, the microcomputer 25 may also include, for example, a hysteresis comparator shown in FIG.
The output of 49 (the signal obtained by shaping the output of the Hall element 47-3) is divided by the frequency divider circuit 33 as shown in FIG. 6 (g), and then the rising edge detection circuit 34 as shown in FIG. 6 (h). Also, a signal in which a rising edge is detected and an output waveform (c) in which the signal of the FG pattern 48 shown in FIG. 5 is amplitude-limited by the limiter amplifier 56 are input.

The microcomputer 25 includes a rising edge detection circuit 34
The output pulse of the waveform shaping circuit 24 that is input once per rotation of the disk is synchronized with the rising edge of the pulse that is output once per rotation shown in FIG. Count with (Steps S3, S4, S5 in FIG. 10). The eccentricity amount δ _{1 of the} disc is calculated from the counted result (step S6 in FIG. 10). Required amplitude of the correction signal to be output from the ^D / _A converter 31
V ₁ is the voltage-current conversion coefficient of the drive circuit 22, gm (A / V),
The sensitivity of the actuator 23 is α (μm / A), and the eccentricity is δ ₁
given that Becomes The eccentricity amount δ ₁ and the correction signal V ₁ have a proportional relationship. By applying the eccentricity δ _{1 of the} disk to the above equation,
Calculate the required correction signal amplitude V ₁ (step in Fig. 10)
S7).

From the amplitude V ₁ obtained in step S8 and the time required for the disk 1 to make one rotation, the amplitude shown in FIG.
The sine waveform that becomes V ₁ is obtained and stored in the memory 30 using the data address control function 29 of the microcomputer 25 (step S8 in FIG. 10). As described above, the operation of adjusting the amplitude of the eccentricity correction signal is completed.

Next, after the switch 20 is turned off by the system control and the switch 32 is turned on by the microcomputer 25 (steps S11 and S12 in FIG. 11), the microcomputer 25 is made to output a pulse once per rotation. The pulse signal of the FG signal (c) output from the drive circuit 17 from the arbitrary memory address of the data in the memory 30 in synchronization with the output of the rising edge detection circuit 34 and using the data address control function 29. The data is output one after another. The data in the memory 30 is converted from a digital signal into an analog signal by the ^D / _A converter 31, the actuator 23 is excited by this signal, and the output of the waveform shaping circuit 24 is counted by the count function 26 of the microcomputer 25 as described above. .

To explain this operation in detail, first, the phase n = 0,
The phase step amount Δ is set as an initial condition (first
11 Figure step S13). Next, it is determined whether or not there is an output from the rising edge detection circuit 34 (step S1
4) If yes, data is output from the memory 30 so that the phase of the signal output from the ^D / _A converter 31 becomes n (step S15). Then, the output of the waveform shaping circuit 24 for one rotation of the disk is counted (step S1).
6).

Until the counted value N ₁ is close to the target value set in the memory function 28 of the microcomputer 25, the data / address control function 29 is used to change the start address of the data output from the memory 30. Wave shaping circuit
The operation of counting 24 pulses is repeated to find the optimum phase of the output signal of the ^D / _A converter 31 with respect to the pulse output from the rising edge detection circuit 34 (steps S17, S1).
8).

Figure 12 shows the signal waveform of each part at this time.
(A) is the output of the rising edge detection circuit 34 of FIG.
(B) is the eccentricity correction signal output of the ^D / _A converter 31, and (c) is the output of the differential amplifier 18. Θ in (b) indicates the amount of phase correction. When the optimum correction signal is obtained, the microcomputer 25 performs TOK for the system control for controlling the entire system, although not shown here.
A signal is output (step S19). By the above operation,
Finish phase matching.

Next, in the normal reproduction state, the switch 20 is turned on by the signal from the system control, the switch 32 is turned on by the microcomputer 25, and the correction signal output from the ^D / _A converter 31 and the phase compensation circuit 19 are output. The added signal is added by the adder 21 to drive the actuator 23. The data from the memory 30 is synchronized with the output of the rising edge detection circuit 34 in which a pulse is output once per rotation, and the data / address control function 29 of the microcomputer 25 is used to drive the circuit. FG output from 17
Each time the pulse signal of the signal (c) is input, it is sequentially output.

If you do this, the disk rotation speed will be C
Even in the case of the AV system, and also in the case of the CLV system in which the number of revolutions of the disc changes depending on the reproduction position of the light spot, the output of the frequency dividing circuit 33 outputted for one revolution of the disc and the output from the drive circuit 17 Since the number of FG pulses is always the same, the ^D / _A converter 31
The frequency of the correction signal output from the device also changes automatically.

Therefore, the present invention can be applied to both the CAV method and the CLV method.

In the above embodiment, the data of the memory is sequentially output every time the FG pulse signal output from the drive circuit 17 is input, but the present invention is not limited to this, and a signal obtained by frequency division or multiplication, Or by providing a dedicated pulse generator,
A method using a signal output from here may be used.
Also, the method of applying the correction signal to the tracking actuator has been described, but the invention is not limited to this.
For example, the correction signal may be applied to a device that drives the entire optical head.

Furthermore, the means for detecting the number of rotations of the motor is not limited to the FG48, and light or magnetic detection means can be used.

〔The invention's effect〕

As described above, according to the present invention, even in an apparatus involving distortion of an information track due to attachment / detachment or deformation of a recording medium, the influence of this distortion can be eliminated, and in the case of the CAV method in which the number of rotations of the disk is constant. Also, it has a feature that it can be applied to the case of the CLV system in which the rotation speed of the disc changes depending on the reproduction position of the light spot.

Further, since the influence of the distortion of the information track can be eliminated before the tracking control is activated, the pull-in can be performed stably.

Furthermore, since the reference position of the disk is detected by the disk rotation motor, the disk can be used even if there is no rotation start signal.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a sectional view of a disk rotating motor, FIG. 3 is a view showing a magnetizing pattern of magnets of the disk rotating motor, and FIG. 4 is a disk. FIG. 5 is a diagram showing the coil shape of the rotation motor, FIG. 5 is a block diagram showing a specific example of a drive circuit for the disc rotation motor, and FIG. 6 is a time chart diagram of the signals of FIG.
FIG. 7 is a diagram showing the locus of the light spot, FIG. 8 is a diagram showing the relationship between the eccentricity amount and the tracking signal, and FIG. 9 is a diagram showing an example of the stored contents of the memory, FIG. 10 and FIG. 11
The figure is the operation flowchart of the microcomputer, No. 12
The figure is a timing chart of the ^D / _A circuit output signal and the output waveform of the differential amplifier during tracking correction. 1 …… disc, 2 …… disc rotation motor, 16 ……
Motor control circuit, 17 ... Motor drive circuit, 18 ... Differential amplifier, 19 ... Phase compensation circuit, 21 ... Adder, 22 ... Drive circuit, 23 ... Actuator, 24 ... Waveform shaping circuit, 25
…… Microcomputer, 26 …… Counter function, 27…
… Math function, 28 …… Memory function, 29 …… Data / address control function, 30 …… Memory, 31 …… ^D / _A converter, 33…
… Dividing circuit, 47-1,47-2,47-3 …… Hall element, 48 …… Frequency power generation pattern

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masashi Sasaki 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa, inside Hiritsu Video Engineering Co., Ltd. (56) References JP-A-58-9226 (JP, A)

Claims (2)

[Claims] 1. An optical pickup for reading information from a disc-shaped information recording medium, and a transfer means for transferring the entire optical head equipped with the optical pickup in a direction orthogonal to a track.
In a tracking control device of an optical reproducing device having tracking control means for performing tracking control by following the distortion shape of an information track, tracking error detection means for obtaining a tracking error signal corresponding to the distortion shape of the information track And counter means for counting the output signal of the tracking error detection means, and means for creating an eccentricity correction signal curve having a cycle of the time required for the disk-shaped recording medium to make one rotation from the count value of the counter means. Memory means for storing the eccentricity correction signal curve, means for adjusting the phase of the eccentricity correction signal curve so that the eccentricity correction signal curve substantially matches the phase of the eccentricity of the disk, and the disk-shaped recording medium rotating. From the motor rotation control means for controlling, a frequency proportional to the rotation of the disk-shaped recording medium is And a reference position signal generation means for generating a reference position signal of one rotation per pulse from the motor rotation control means of the disk-shaped recording medium. Based on the reference position signal
A tracking control device for an optical reproducing apparatus, wherein the eccentricity correction signal is read from the memory means in synchronization with a signal output from the frequency generating means to perform tracking correction. 2. An optical system according to claim 1, wherein a tracking error signal corresponding to the distorted shape of the information track is taken in with the tracking control means in a non-operating state. Tracking control device for playback device.