JP2529351B2 - Eccentricity correction device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording / reproducing apparatus for irradiating a rotating storage carrier with a light beam to record / reproduce information, and particularly to an eccentricity of the record carrier. The present invention relates to an eccentricity correction device that corrects a track shift of a light beam due to.

2. Description of the Related Art As a conventional eccentricity correction device, for example, Japanese Patent Application Laid-Open No. 54-1725
As described in Japanese Patent No. 59, there is one which stores a control signal at the time of track following and corrects a track shift of a light beam due to eccentricity. FIG. 4 is a block diagram showing a configuration of a conventional eccentricity correction device that stores such a control signal for tracking a track and corrects the eccentricity. A conventional eccentricity correction device will be described below with reference to FIG.

A light beam generated from a light source 1 such as a semiconductor laser is collimated by a coupling lens 2, reflected by an eccentric beam splitter 3, and passes through a λ / 4 plate 4 (λ is the wavelength of the light beam). Converging / irradiating the disk 7 rotated by the spindle motor 6 by the converging lens 5.

The reflected light from the disk 7 passes through the converging lens 5, the λ / 4 plate 4 and the polarization beam splitter 3, and is applied to the photodetector 8 having a two-divided structure.

The outputs A and B of the photodetector 8 are input to a differential amplifier 9, which outputs a difference signal between the two signals, that is, a track shift signal corresponding to the positional shift between the light beam on the disk 7 and the track. To do.

The track deviation signal passes through a phase compensating circuit 10 for compensating the phase of the tracking control system and a switch 11 for opening / closing a loop for tracking control, and is input to a drive circuit 12 via a combining circuit 15. Tracking control element 13
Is configured to move the converging lens 5 in the radial direction of the disk 7 in accordance with the output signal of the drive circuit 12, so that when the switch 11 is closed, the light beam is controlled to properly scan the track. To be done.

Further, the spindle motor 6 is equipped with a frequency generator 19 that generates a pulse (hereinafter referred to as an FG pulse) according to the number of revolutions of the spindle motor. The FG pulse causes the spindle motor control circuit 18 to control the rotation of the spindle motor 6. Are doing.

By the way, when the disk 7 is attached to the spindle motor 6, the center point C ₇ of the track on the disk 7 is changed as shown in FIG. 5 due to the accuracy of the center hole of the disk 7 and the error when fixing the disk 7 to the spindle motor 6. and not completely coincide with the rotation center C ₆ of the spindle motor 6. Therefore, when the spindle motor is rotated in this state, the disk 7 is eccentric and the light beam moves with respect to the center of the track as shown in FIG. Shows a waveform similar to that of FIG.

The track shift signal output from the phase compensation circuit 10 in FIG. 4 is also input to the waveform storage circuit 14. In addition, the FG pulse generated from the frequency generator 19 is
Each time the spindle motor makes one revolution, four pulses are output and input to the counting circuit 20 via the spindle motor control circuit 18. The counting circuit 20 counts the FG pulse,
Outputs one pulse signal per revolution.

The output signal of the counting circuit 20 is input to the waveform storage circuit 14, and the waveform storage circuit 14 stores the track shift signal by the signal that generates one pulse for one rotation.
Is performed for one rotation.

When the track shift signal due to the eccentricity during the one rotation of the disk 7 is stored in the waveform storage circuit 14, the waveform storage circuit 14 stores the track shift for the stored one rotation each time the signal of the counting circuit 20 is generated. Output a signal. This signal is added to the tracking control system by the synthesizing circuit 15 to realize the eccentricity correction. With this, conventionally, the accuracy of tracking control is increased and the jumping operation is stabilized.

SUMMARY OF THE INVENTION In the prior art, when vibration or impact is applied to the device from the outside, the spindle motor and the disk do not rotate integrally, that is, the disk slides on the turntable of the spindle motor. When a certain state (hereinafter referred to as disk slip) occurs, the rotational position of the disk fluctuates with respect to the rotational position of the spindle motor.
Therefore, before and after the disk slip occurs, the phase deviation of the track deviation signal occurs due to the eccentricity of the disk 7 as shown in FIG. 7, the effect of the eccentricity correction becomes small, and in the worst case, the operation of the eccentricity correction is controlled by the control system. It worked as a disturbance, deteriorated the tracking control accuracy, and made the jumping operation unstable.

The present invention has been made in view of the above problems, and performs accurate eccentricity correction even when a disk slip occurs due to external vibration, shock, etc., improves tracking control accuracy, and stabilizes jumping operation. It is an object of the present invention to provide a device that can be manufactured.

Means for Solving the Problems The present invention provides rotating means for rotating a record carrier, focusing means for focusing and irradiating a light beam generated from a light source on the record carrier, and reflected light or transmitted light from the record carrier. Track deviation detecting means for detecting a signal corresponding to the positional relationship between the light beam on the record carrier and the track, moving means for moving the light beam converged by the converging means in a direction perpendicular to the track direction, and the track Tracking control means for driving the moving means in response to a signal from the deviation detecting means to control the light beam on the record carrier to scan the track, and a signal detected by the track deviation detecting means are stored. Waveform storage means, frequency power generation means for generating a signal according to the rotation frequency of the rotation means, and a rotation cycle of the record carrier from the signal on the record carrier. Rotation cycle detecting means for detecting, and eccentricity correcting means for applying the storage signal of the waveform storage means to the tracking control means to correct the track deviation of the light beam, the signal of the frequency power generation means and the rotation cycle. The detector signals are compared, and when the amount of change in the phase relationship exceeds a predetermined value, the eccentricity correction means is disabled and the stored contents of the waveform storage means are updated.

The present invention has the above-described configuration and stores the track deviation signal generated by the eccentricity of the disk in synchronization with the signal (hereinafter referred to as INDEX signal) for detecting the rotation cycle read from the disk, and the track deviation signal for one rotation is stored. Then, the eccentricity correction is realized by adding the track deviation signal for one rotation stored every time the disk makes one rotation by the INDEX signal to the tracking control system.

At that time, since the phase difference between the INDEX signal obtained from the disk and the FG pulse obtained from the frequency generator equipped in the spindle motor is measured, the fluctuation in the rotational position of the disk relative to the rotational position of the spindle motor, that is, the disk Slip can be detected. When the detected fluctuation amount exceeds a predetermined amount, the eccentricity correction is re-executed from the memory operation.Therefore, the phase shift between the actual eccentricity and the correction signal applied to the tracking control system, which has conventionally occurred, is eliminated, and the eccentricity is always accurate. Corrections can be made.

Embodiment An eccentricity correction device according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of an eccentricity correction device that is an embodiment of the present invention. The same parts as those of the conventional eccentricity correction device are denoted by the same reference numerals, and the description thereof will be omitted.

The outputs A and B of the photodetector 8 having a two-division structure are input to the differential amplifier 9 to obtain a track deviation signal, and the combining circuit 16
It is input to the memory signal reading circuit 17 via.

The memory signal reading circuit 17 uses the sum signal of the outputs A and B of the photodetector 8 to store the INDE prestored on the disk 7.
The X signal is read and the signal is sent to the microcomputer 21.
Are typing in. Normally, the microcomputer 21 detects the rotation cycle of the disk 7 based on the input INDEX signal, and outputs a signal to the waveform storage circuit 14 every time the disk 7 makes one rotation. As in the case of the conventional eccentricity correction device, the waveform storage circuit 14 stores the track shift signal by the signal sent from the microcomputer 21 for one pulse per one rotation while the disk 7 makes one rotation.

When the track shift signal due to the eccentricity during the period in which the disk 7 makes one revolution is stored in the waveform storage circuit 14, the waveform storage circuit 14 stores the stored track for one revolution each time a signal is input from the microcomputer 21. A shift signal is output, and this signal is added to the tracking control system by the synthesis circuit 15 to realize the eccentricity correction.

Further, the frequency generator 19 provided in the spindle motor 6
The FG pulse obtained from this is the spindle motor control circuit 18
Is input to the microcomputer 21 via the. Thereby, the microcomputer 21 detects the rotation cycle of the spindle motor 6.

Next, the processing performed by the microcomputer 21 will be described with reference to the drawings.

2 (a) to 2 (d) are timing charts of signals before the disk slip occurs, and FIG. 2 (a) is an INDEX signal.
2B is an FG pulse, FIG. 2C is a track deviation signal generated by eccentricity, and FIG. 2D is a stored track deviation signal for correcting eccentricity.

FIGS. 3 (a) to 3 (d) are timing charts of signals after the occurrence of disk slip. Similar to FIG. 2, FIG. 3 (a) is an INDEX signal and FIG. 3 (b) is an FG pulse. , FIG. 3 (c) is a track deviation signal generated by eccentricity,
FIG. 6D shows a track shift signal stored to correct the eccentricity.

The microcomputer 21 measures the phase difference between the input INDEX signal and the FG pulse by measuring the time difference T ₁ between the two signals.

Before disc slip occurs, as shown in Fig. 2,
The time difference T ₁ between the INDEX signal and the FG pulse holds a constant value. Therefore, in this state, the track deviation signal actually generated by the eccentricity and the stored track deviation signal applied to the tracking control system for correcting the eccentricity have the same phase, whereby the track deviation due to the eccentricity of the disk 7 is prevented. , Corrected correctly.

However, when vibration or shock is applied to the device from the outside and a disk slip occurs, the time difference T ₁ between the INDEX signal and the FG pulse, that is, the phase difference between the two signals changes, as shown in FIG. Therefore, the phases of the stored track deviation signal added to the tracking control system each time the INDEX signal is generated and the track deviation signal generated by the actual eccentricity are as shown by the solid lines in FIGS. 3 (c) and 3 (d). Therefore, the track deviation due to the eccentricity cannot be corrected correctly.

Therefore, when the change amount of the time difference T ₁ between the INDEX signal and the FG pulse exceeds the predetermined time, the microcomputer 21
The operation of the waveform storage circuit 14 is temporarily disabled, the storage of the track deviation signal is started again by the INDEX signal whose phase is shifted with respect to the FG pulse, and the storage of the track deviation signal for one rotation is updated. Whenever occurs, the signal is added to the tracking control system again, and the eccentricity correction is restarted.

At this time, the stored track deviation signal applied to the tracking control system becomes like the dotted line in FIG. 3 (d), and the phase becomes equal to the track deviation signal due to the actual eccentricity in FIG. 3 (c). Thus, the track deviation due to the eccentricity of the disk 7 can be correctly corrected.

If the spindle motor 6 is equipped with a rotary position detector that generates one pulse per revolution, FG
Instead of a pulse, the output pulse of the rotation position detector (hereinafter referred to as PG pulse) is input to the microcomputer 21, the time difference between the INDEX signal and the PG pulse is measured, and the fluctuation amount of the phase difference between both signals is a predetermined amount. If the eccentricity correction is re-executed when the value exceeds, the eccentricity correction can be correctly performed even if the disk slip occurs.

Also, by applying this embodiment to a device that corrects the surface shake of the disk 7, the same effect can be obtained for the focus control system.

Further, when a very large shock is applied to the device or an abnormality occurs in the spindle motor 6 to cause a rapid disk slip or a steady disk slip, the microcomputer 21 sends the above-mentioned INDEX signal and FG pulse. The amount of change in phase difference is detected when it becomes much larger than a predetermined amount, or eccentricity correction is repeated many times.

In that case, the reliability of the device can be improved by arranging that the operation of the entire device is stopped in accordance with the magnitude of the variation in the phase difference or the number of times of re-execution of the eccentricity correction.

EFFECTS OF THE INVENTION As described above, according to the present invention, a disk slip occurs, and the track deviation due to the actual eccentricity and the phase difference between the track deviation signal stored in the tracking control system for correcting the eccentricity are deviated. However, since the fluctuation of the rotational position of the disk with respect to the rotational position of the spindle motor is detected, the track deviation signal due to eccentricity is updated, and the eccentricity correction is re-executed, accurate eccentricity correction can always be performed. Therefore, high precision tracking control,
The jumping can be stabilized and a highly reliable device can be provided.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an eccentricity correction device according to the present invention, FIG. 2 is a timing chart of signals before a disk slip occurs, and FIG. 3 is a timing chart of signals after a disk slip occurs. FIG. 4 is a block diagram showing a configuration of a conventional eccentricity correction device, FIG. 5 is a plan view showing an eccentric state of the optical recording / reproducing device, and FIG. 6 is the same as the optical beam in the eccentric state of the optical recording / reproducing device. FIG. 7 is a timing chart showing the movement amount, and FIG. 7 is a timing chart showing the output of the track deviation signal before and after the disk slip occurs in the state where the tracking control is performed. 1 ... Semiconductor laser, 2 ... Coupling lens, 3 ...
... eccentric beam splitter, 4 ... λ / 4 plate, 5 ... converging lens, 6 ... spindle motor, 7 ... disk, 8 ...
… Photodetector, 9 …… Differential amplifier, 10 …… Phase compensation circuit,
11 ... Switch, 12 ... Driving circuit, 13 ... Tracking control element, 14 ... Waveform storage circuit, 15 ... Synthesis circuit, 16 ...
… Synthesis circuit, 17 …… Record signal reading circuit, 18 …… Spindle motor control circuit, 19 …… Frequency generator, 20 …… Counting circuit, 21 …… Microcomputer.

Claims (2)

(57) [Claims] 1. A rotating means for rotating a record carrier, and a light beam generated from a light source is irradiated onto the record carrier, and reflected light or transmitted light thereof is used to determine the positional relationship between the light beam on the record carrier and the track. Track deviation detecting means for detecting a signal, moving means for moving the light beam converged by the converging means so as to cross a track, and driving the moving means according to the signal of the track deviation detecting means,
Tracking control means for controlling the light beam on the record carrier to scan over the track, waveform storage means for storing the signal detected by the track deviation detection means, and a signal according to the rotation frequency of the rotation means. Frequency shift generating means for generating, rotation cycle detecting means for detecting a rotation cycle of the record carrier from a signal on the record carrier, and a storage signal of the waveform storage means are applied to the tracking control means to correct the track deviation of the light beam. Eccentricity correction means for comparing the signal of the frequency power generation means with the signal of the rotation period detector, and when the amount of change in the phase relationship exceeds a predetermined value, the eccentricity correction means is made inoperative. An eccentricity correction device characterized by the above. 2. When the signal of the frequency power generation means and the signal of the rotation period detector are compared, and when the amount of change in the phase relation exceeds a predetermined value, the eccentricity correction means is once made inoperative and the stored contents of the waveform storage means. The eccentricity correction device according to claim (1), characterized in that the eccentricity correction means is operated again.