JPS6273436A - Tracking control device for optical reproducing device - Google Patents

Abstract

PURPOSE:To correct a component due to the eccentricity of a disc by reading an eccentricity correction signal from a memory means synchronously with a signal outputted from a frequency generating means so as to apply a tracking correction. CONSTITUTION:The distortion of an information track caused by a disc device is generated mainly synchronously with the revolution of disc. Thus, e.g., one cycle sinusoidal wave is stored in a storage circuit 28 and the amplitude and phase of the eccentricity of the disc from a tracking error signal of a tracking control circuit controlled in following to the distortion of an information track are detected and the detected signal corrects the amplitude and phase of the sinusoidal waveform, which is stored in a memory means 28 and read from an address formed in response to the revolution speed of the disc thereby generating a proper correction signal.

Description

[Detailed Description of the Invention] [Field of Application 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 that records or reproduces information in the form of optical characteristic changes in the medium, and particularly relates to a tracking control device for the optical reproducing apparatus.

[Background of the invention]

In such optical recording and reproducing devices, a disk-shaped recording medium is generally used, and an information signal is recorded as a spiral or concentric recording trajectory on the disk-shaped recording medium, and is reproduced from there. .

Concentric recording trajectories are suitable for recording information separated by fixed intervals, such as information on a single still image. The recording trajectory (hereinafter referred to as track) is suitable.

In such information recording or reproducing devices,
Considering the economic efficiency of recording media and the miniaturization of devices, there is a trend toward higher densities in the future regardless of the recording and reproducing means, and in order to achieve this, it is necessary to shorten the recording wavelength and narrow the track. Demand has increased by 14.

One of the problems that arises with this narrowing of tracks is that when a recording medium with recorded information tracks is removed from the device and then reinstalled into the device, the mechanical position of the installed recording medium may shift. Distortion of information tracks that exceeds the trunk spacing may occur due to eccentricity or plastic deformation of the recording medium due to thermal or mechanical stress. Therefore, unless tracking control is performed fj that follows the distorted shape of the information track, this distorted shape will cause the reproduction scanning value 11 of the reproduction means (specifically, the position of the optical spot) and the information track to be relative to each other in the direction perpendicular to the track. It will have a position of 1&movement.

Normally, most of the distortion in information tracks is caused by eccentricity, which occurs in synchronization with the rotation of the disk-shaped recording medium, and depends on the mounting condition of the disk, etc., and the size of the disk-shaped recording medium. The phases differ depending on the rotation angle.

Distortion of information tracks occurs in the order of tens to hundreds of micrometers, depending on the accuracy of the information reproducing device or disk-shaped recording medium, and if the track spacing is about 2 micrometers, the distortion will be one or two orders of magnitude larger. value.

Therefore, in a normal reproduction state, tracking control is performed so that the optical spot for reproducing the information signal follows the distorted shape of the track. At this time, the relative positional deviation between the original spot and the track needs to be kept to an accuracy of about 0.1 pm or less, taking into account crosstalk from adjacent tracks. However, the distortion of the disk,
In particular, when the component due to eccentricity becomes large, the relative positional deviation between the light spot and the track becomes large, and crosstalk from adjacent tracks becomes a problem. In order to reduce this positional deviation, it is sufficient to increase the gain of the tracking control circuit, but if the gain of the control circuit is increased too much, problems such as activation of the control circuit may occur, and the circuit may become unstable. The problem arises that

As a method to counter the above-mentioned drawbacks, for example, JP-A-5-6
- As described in No. 7247, a 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 is once stored in memory and used as a primary There is a method in which the stored waveform is read out in synchronization with the rotation of the disk, and the signal read out from the memory is applied to a tracking control circuit, thereby correcting the positional deviation between the reproduction light spot and the information track. be.

This method assumes that tracking control operates reliably, but if the eccentricity caused by disk installation is too large, tracking control may not be performed due to trunk distortion. There is a problem in that if the tracking error signal is stored in waveform and then corrected using this stored signal, it will have the opposite effect.

In addition, in the case of the tracking control described in the above-mentioned Japanese Patent Application Laid-Open No. 56-7247, the waveform stored in the memory is read out based on the rotation start signal provided on the disk. In the case of a dedicated type original disk player, it is not convenient because a disk ζζ rotation start signal is not provided. In addition, playback-only optical disc players use the CAV system (Con5tantλngular Vel
ocity) and CLV method (Con5tant
Linear Velocity). C.L.
In the V method, tso at the inner circumference of the disk.

rpm (30Hz), 600 rpm at the outer circumference of the disc
Since the rotational speed changes continuously (10 Hz), it is necessary to change the readout of the waveform stored in the memory accordingly.

As described above, conventional tracking control devices have some problems.

[Purpose of the invention]

It is an object of the present invention to correct the position of a reproduction light spot caused by the distorted shape of the information track as described above and the relative positional deviation 5 and position it fluctuation with the information track, especially the eccentric component of the disk. An object of the present invention is to provide a trafking control device that corrects the trafking control device.

[Summary of the invention]

A feature of the present invention is that it focuses on the fact that the distortion of the information track caused by the mounting of the disk mainly occurs in synchronization with the rotation of the disk, and stores, for example, a sine wave-like waveform of 1 cycle in the storage circuit. .

On the other hand, the magnitude and phase of the eccentricity of the disk are detected from the tracking error signal of the tracking control circuit which is designed to follow and control the distortion of the information track, and the detected signal is used to determine the amplitude and phase of the sinusoidal waveform. By correcting and storing it in a memory means, and reading it from the memory means at an address created according to the rotational speed of the disk,
The point is that an optimal correction old ridge is generated. Also,
This makes it possible to cope with a system in which the number of revolutions changes depending on the position of the light spot, such as the CLV system of a read-only optical disc player.

[Embodiments of the 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 an 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, 8 is 1
/4 wavelength plate, 9 is objective lens, 10 is cylindrical lens% 1
1 is a mirror, and 12 is a detector.

Further, 13 is a signal processing circuit, 14 is a synchronous separation circuit, is
1 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, 25 is an eccentricity correction signal generation circuit for detecting and correcting the eccentricity of the disk%, 30 is a memory, 31
32 is a switch, and 33 is a frequency dividing circuit.

Next, the operation of this embodiment will be explained.

In FIG. 1, a disk 1 is connected to a disk rotating motor 2.
is being rotated at high speed. The original beam generated from the laser diode 3 enters a coupling lens 4 and a diffraction grating 5. The diffraction grating 5 is an optical element in which a large number of thin parallel lines are carved on the surface of a transparent plate, and due to the diffraction interference effect of light, it is separated into three beams of light that are emitted at slight angles to each other. Of the three beams, the central beam is used for reading recorded information and controlling the focal position, and the two on both sides are used for detecting tracking error signals. These three beams pass through a polarizing prism 6, a mirror 7, and a V4 wavelength plate 8, and are incident on an objective lens 9. The objective lens 9 uses well-known focus control (focus control #) so that the three beams form three light spots with a diameter of 1.6 μm spaced apart by 20 μm along the track on the pit surface of the disk 1. controlled by

The reflected light reflected on the disk l passes through the objective lens 9 again.
, passes through a 1/4 wavelength plate 8, is changed in direction by a polarizing prism 6, passes through a cylindrical lens 10, and is detected by a photodetector 12.
The image is formed on three light-receiving surfaces P1゜p, , p, respectively. Two light beams for tracking error detection are formed on the light receiving surfaces P1.degree.P on both sides, and a central light beam for reading recorded information is imaged on the central light receiving surface P. The central light-receiving surface P is divided into four parts, and the light-receiving output thereof is also used for detecting a focus error signal.

A difference signal between the light receiving surfaces P, , P, in the photodetector 12 is obtained as the output of the differential amplifier 18, and this difference signal is sent to the phase compensation circuit 19, the loop switch 20 . It is input to the drive circuit 22 via the adder 21. An actuator 23 for tracking control is controlled by the output of this drive circuit 22, and well-known tracking control is performed.

On the other hand, the output of the light receiving surface P of the photodetector 12 is input to a signal processing circuit 13, where it is converted into a video signal.

The converted video signal is synchronously separated in the synchronous separation circuit 14, and the motor control circuit 16 is operated so that the phase of the water + synchronous signal obtained here and the reference horizontal synchronous signal output from the reference signal generation circuit 15 are synchronized. , the disk rotation motor 2 is controlled via the drive circuit 17.

Since the disc rotation motor 2 is controlled so that the horizontal synchronization signal of the video signal reproduced from the disc 1 and the reference horizontal synchronization signal are phase-synchronized, the disc rotates at a constant speed of 1800 rpm in the case of a CAV type disc. On the other hand, in the case of the CLV method, the number of rotations changes automatically according to the playback position of the playback source spot.
The speed is 1800 rpm at the innermost position of the disc, and approximately 60 Qrpm at the outermost position of the disk.

FIG. 2 shows an example of the disk rotation motor 2. As shown in FIG. For reasons such as the lifespan of the motor, brushless DC motors are generally used, and here, a three-phase DC 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 board on which the coil 38 is mounted, 40 is a yoke, 41 is a bearing, 42 is a thrust bearing, and 43 is a It is the axis of rotation.

FIG. 3 shows an example of the magnetization pattern of the magnet 37, which is magnetized into eight poles as shown in the figure.

FIG. 4 shows an example of a specific configuration of the coil 38 mounted on the board 39, including coils 44-1, 44-2.
44-3.44-5.44-6° Hall element 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), coil 44-3
and 44-6 (also referred to as W-phase coils) are not shown here, but are connected by a pattern provided on the board, and the U-phase, V-phase, and W-phase coils are shown in FIG. They are connected in a Y-connection as shown in the figure.

Since the drive method of the motor is not directly related to the present invention, a detailed explanation will be omitted.
1% 47-2. Switched by the signal detected in 47-3, the magnetic force generated by the coil current at this time,
Rotation is performed by the attractive force and repulsive force of the magnetic force of the magnet 37.

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 per 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 shown in FIG. Hall element 47-1゜47-2.47
-3, the magnet 37 is magnetized to eight poles as shown in Fig. 6 (a) * (b) + (C), so the motor 1
A sinusoidal waveform of 4 cycles of rotation is obtained, and after inputting this waveform to the hysteresis comparator 49°50.51, it is processed by the matrix circuit 52, and the drive circuit 53
．． Figure 6(d) at 54.55.

Drive voltages for driving each coil as shown in (e) and (f) are outputted. The amplitude of the driving voltage is the first
It is controlled by the output (b) of the motor control circuit 16 shown in the figure, and is controlled to achieve the desired rotation speed. Further, the output of the FG pattern 48 is amplified by a limiter amplifier 56, and the amplitude is limited to output (c).

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

FIG. 7 shows the locus of the light spot when tracking control is turned off. In this figure, 0 indicates the recording center of the information track, 0' indicates the rotation center of the disk, the solid line indicates the information track, and the broken line indicates the locus of the light spot. For example, set the rotation speed of disk 1 to 180Orpm.
Then, the eccentricity of the disk is expressed as shown in FIG. 8(a), the repetition frequency is 30 Hz, and the flea width A represents the magnitude of the eccentricity. FIG. 8(b) shows the output waveform of the tracking error signal obtained at the output side of the differential amplifier 18 of FIG. It will be done. One cycle of this sinusoidal waveform corresponds to the track pitch of the information track, and by counting the number of sinusoidal waveforms, the amount of eccentricity of the disk can be detected.

Therefore, as shown in Figure 10, first gllf
The fl switch 32 is turned off under the control of the microcomputer 25, so that the correction signal from the memory 30 is not applied to the actuator 23, and a signal (not shown here) from the system control that controls the entire system is applied. Switch 20 is also turned OFF to prevent tracking control from working (Step 8 in Figure 10).
1.82).

In this state, the eighth
A waveform shaping circuit 24 shapes the waveform shown in FIG.

This shaped signal is input to the microcombiner 25.

For example, the micro combination function 25 has a counter function 26.
It is composed of a % calculation function 27, a memory function 28, and a data address control function 29.

In addition to this, the micro combinator 25 includes, for example, a fifth
The output of the hysteresis comparator 49 shown in the figure (a signal obtained by shaping the output of the Hall element 47-3) is divided by the frequency dividing circuit 33 as shown in FIG. A signal with a detected rising edge as shown in (h) and an output waveform (c) obtained by amplitude-limiting the signal of the FG pattern 4B shown in FIG. 5 by the limiter amplifier 56 are also input.

The microcomputer 25 operates a waveform shaping circuit 24 that is input to one revolution of the disk in synchronization with the rising edge of a pulse of 14 VA per one revolution as shown in FIG. The output pulses of are counted by the counter function 26 of the micro combinator 25 (10th @step S3, S4, 85). The eccentricity δ1 of the disk is calculated from this counting result (step 3s in Figure 10).

Necessary amplitude 1 of the correction signal to be output from the Vmu converter 31
gV+ is the voltage-current conversion coefficient of the drive circuit 22, gm
('Vy) s The sensitivity of the actuator 23 is α(μ
m/A), and the amount of eccentricity is δ. Eccentricity δ1
and the correction signal V have a proportional relationship. By applying the disk eccentricity δ1 to the above equation, the necessary correction signal excavation width v1 is calculated and determined (Step 87 in Fig. 10).
.

From the vibration mv+ determined in step S8 and the time required for one rotation of the disk 1, a sine waveform with an image width of V as shown in FIG. It is stored in the memo IJ 30 using the function 29 (step SS in FIG. 1O). With the above, the amplitude adjustment operation of the eccentricity correction signal is completed.@Next, turn off the switch 20 using the system control,
After turning on the switch 32 in the micro combinator 25 (steps S11 and S' in Figure 11), the micro combinator 25 turns on the rising edge detection circuit 34, which outputs a pulse once every L rotation. In synchronization with the output of the FG multiplication signal c) output from the drive circuit 17, the data in the memory 30 is sequentially transferred from an arbitrary memory address using the data/address control Wk function 29. Make it output. memory 30
The data is converted from a digital signal into an analog signal by the V-mu converter 31, and the actuator 23 is excited with this signal.

Similarly to the above, the output of the waveform shaping circuit 24 is counted by the count function 26 of the micro combinator 25.

To explain this operation specifically, first, the phase ψn wt
Ql phase step amount Δψ is set as an initial condition (step 813 in FIG. 11). next.

It is determined whether or not there is an output from the rising edge detection circuit 34 (step 814), and if the result is % YES,
Data is output from the memory 3G so that the phase of the signal output from the Vmu converter 31 becomes ψn (step 5).
15). Next, the waveform shaping circuit 24 for one rotation of the disk
(step 816).

The data address control function 29 is used to change the start address of the data stored in the memory 30 until the counted value 1N becomes close to the target value set in the memory function 28 of the micro combinator 25. By repeating the operation of counting the pulses of the waveform shaping circuit 24 while changing the pulses, the optimum phase of the output signal of the Vm converter 31 with respect to the pulse output from the rising edge detection circuit 34 is determined (steps 817 and 1318).

Figure 12 shows the signal waveforms of each part at this time.
(a) shows the output of the rising edge detection circuit 34 in FIG.
b) is the eccentricity correction signal output of the - converter 31, and (c) is the output of the differential amplifier 1B. θ in (b) indicates the phase correction amount. Once the optimum correction signal has been obtained, the micro combinator 25 is turned on to the system control, which controls the entire system (not shown here).
A K signal is output (step 819). With the above operations, phase matching is completed.

Next, in the normal playback state, the switch 20 is turned on by a signal from the system control.

Switch 32 is turned on by microcomputer 25
Then, the correction signal output from the D/A converter 31 and the signal output from the phase compensation circuit 19 are added by an addition of $1i21, and the actuator 23 is driven. The data from the memory 30 is synchronized with the output of the rising edge detection circuit 34, which outputs a pulse once per revolution, and
Micro Combiator 25 data address system whl
Using f@zs, the pulse signal of the FG flaw signal e) output from the drive circuit 17 is sequentially output every time it is input.

In this way, the rotation speed of the disc will be 180° rpm.
Even in the case of the CAV method, which is constant, and in the case of the CLV method, in which the number of revolutions of the disc changes depending on the playback position of the original spot, the output of the frequency dividing circuit 33 output per one revolution of the disc and the output from the drive circuit 17 Since the number of FG pulses generated is always the same, the frequency of the correction signal output from the VM converter 31 also automatically changes depending on the number of rotations of the disk.

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

Note that in the above embodiment, the F output from the drive circuit 17
Although the data in the memory is sequentially output every time the G pulse signal is input, the present invention is not limited to this, and a branched or multiplied signal, or a dedicated pulse generation means can be provided, and the data can be output from there. A method using a signal may also be used. Furthermore, although a method has been described in which the correction signal is applied to the tracking actuator, the present invention is not limited to this, and the correction signal may be applied to a device that drives the entire optical head.

Furthermore, as a means of detecting the rotation speed of the motor.

- Not limited to FG 48 , detection means using light or magnetism can be used.

〔Effect of the invention〕

As explained above, according to the present invention, even in a device where the information track is distorted due to the attachment/detachment or deformation of the recording medium, the influence of this distortion can be removed, and in the case of the CAV method where the rotational speed of the disk is constant. It also has the feature that it can be applied to the CLV system in which the rotational speed of the disc changes depending on the reproduction position of the original spot.

In addition, since the influence of distortion on the information track can be eliminated before tracking control is activated, it is possible to perform stable pull-in.

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

[Brief explanation of drawings]

Fig. 1 is a block diagram showing an embodiment of the present invention, Fig. 2 is a sectional view of a disk rotation motor, Fig. 3 is a diagram showing a magnetization pattern of the magnet of the disk rotation motor, and Fig. 4 is a disk rotation motor. A diagram showing the coil shape of the rotation motor, FIG. 5 is a block diagram showing a specific structure of the drive circuit of the disk rotation motor, and FIG. 6 is a time chart diagram of the signals in FIG. 5.
FIG. 7 is a diagram showing the trajectory of the light spot, FIG. 8 is a diagram showing the relationship between the eccentric lid and the tracking signal, FIG. 9 is a diagram showing an example of the contents stored in the memory, and FIGS. FIG. 11 is an operation flowchart of the micro combiator, and FIG. 12 is a timing chart of the output waveform of the VM circuit and the differential amplifier during tracking correction. 1...Disk, 2...Motor for rotating the disk. 16... Motor control circuit, 17... Motor drive circuit, 18... Differential amplifier, 19... Phase compensation circuit %2
1... Adder, 22... Drive circuit % 23... Actuator, 24... Waveform shaping circuit, 25... Micro combinator, 26... Counter function, 27...
...Arithmetic function, 28...Memory function, 29...Data address control function, 30...Memory, 31...
Vmu converter, 33... Branch circuit, 47-1.47-2
゜47-3...Hall element, 4B...Patent attorney for frequency power generation pattern Michihito HirakiFigure 2Figure 3Figure 4Figure 5Figure 6Figure 7Figure 9Figure 12 Figure 10 Figure 11

Claims (3)

[Claims] (1) An optical pickup that reads information from a disk-shaped information recording medium, a transport means for transporting the entire optical head equipped with the optical pickup in a direction perpendicular to the track, and tracking control that follows the distorted shape of the information track. In a tracking control device for an optical playback device, the tracking control device includes a tracking error detection device for obtaining a tracking error signal corresponding to a distortion shape of an information track, and an output signal of the tracking error detection device for counting the output signal of the tracking error detection device. counter means for
means for creating an eccentricity correction signal curve whose period is the time required for the disk-shaped information recording medium to make one revolution from the count value of the counter means; a memory means for storing the eccentricity correction signal curve; and a memory means for storing the eccentricity correction signal curve; means for adjusting the phase of the correction signal curve so as to substantially match the phase of the eccentricity of the disk; a frequency generating means for outputting a signal with a frequency proportional to the rotational speed of the disk-shaped recording medium; and the disk-shaped recording medium. means for detecting a reference position of the rotation of the medium, and reading out the eccentricity correction signal from the memory means in synchronization with the signal output from the frequency generating means, using the reference position detected by the means as a reference. A tracking control device for an optical playback device, characterized in that tracking correction is performed. (2) The optical reproducing apparatus according to claim 1, wherein the tracking error signal corresponding to the distorted shape of the information track is captured with the tracking control means inactive. tracking control device. (3) The eccentricity correction signal read from the memory means excites a tracking control means or a transport means equipped with an optical pickup. Tracking control device for an optical playback device according to item 2.