JPH07122014A - Tracking servo device - Google Patents

Abstract

PURPOSE:To perform always stable track jump in a disk of either a continuous servo system or a sample servo system. CONSTITUTION:At the time of a track jump operation, a position target signal S6 is generated by a position signal generating circuit 15, and an error difference between a tracking error signal S1 of an output of a tracking error generating circuit 8 and the position target signal S6 is detected by an error difference detecting circuit 16, and is inputted via a polarity inversion circuit 17 and a switch 18, etc., to a driver 7, so that a tracking actuator 6 is driven to move a light spot. At this time, the tracking error signal S1 is compared with a 1st comparison potential E1 and a 2nd comparison potential E2 by a window comparator 9, and when the signal S1 is in the vicinity of a peak value being S1>=E1 or <=E2, the switch 18 is cut off to open a position control system, and an objective lens 2 is moved by inertia.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tracking servo device which is used in a recording / reproducing device for recording / reproducing information on / from an optical disk and which controls a track jump.

[0002]

2. Description of the Related Art In a recording / reproducing apparatus for recording / reproducing information on / from a recording medium such as an optical disk, a track of a tracking servo apparatus is used when a track jump is performed to move a pickup from one track to another adjacent track during recording / reproduction. The jump control means controls the pickup so that it can be moved to a target track position.

The structure of a general track jump control means is shown in FIG. FIG. 5 shows an example of an optical disk device. The pickup unit includes an objective lens 52 that collects a light beam on the disk 51 to form a light spot, a light source 53 that generates a light beam, and a light source 53. A beam splitter 54 that reflects the light to enter the objective lens 52 and transmits the reflected light from the disk 51, the objective lens 5
2 and a photodetector 55 that receives reflected light from the disk 51 that has passed through the beam splitter 54, a tracking actuator 56 that drives an optical system including the objective lens 52, and a driver 57 that supplies a drive signal to the tracking actuator 56. ing. The photo detector 55 has a tracking error generating circuit 58.
The tracking error generating circuit 58 generates a tracking error signal based on the output of the photodetector 55.

In this track jump control means, in the track following mode, a tracking error signal representing a positional deviation between the optical spot for recording / reproducing information and the track is instructed by the controller 60 to select the selector 61.
Selected and input to the phase compensation circuit 59 for stabilizing the control loop from the tracking error generation circuit 58 to perform phase compensation, and then input to the driver 57 for amplifying the signal and supplied from the driver 57 to the tracking actuator 56. By doing so, a position control system is formed.

At the time of a track jump, instead of the output of the phase compensation circuit 59, an acceleration pulse and a deceleration pulse for the track jump are sent to the controller 60.
Is selected by the selector 61 according to the instruction, and is input to the driver 57 from the jump pulse generation circuit 62 and supplied to the tracking actuator 56. When the jump is completed, the output of the phase compensation circuit 59 is input to the driver 57 again.

In such a track jump control system, since the position control system does not operate during the track jump, the jump pulse ends due to external disturbance such as external vibration or variation in driving sensitivity of the actuator. There is a problem in that the light spot position at that time is displaced from the position of the target track to be moved, and there is a high possibility that the track jump will fail.

Therefore, in order to solve the above problems,
An apparatus in which a track jump is performed while operating a position control system is disclosed in JP-A-64-66829.

The device of this publication is an example of a device using a so-called sample servo system disk, and FIG. 6 shows the pits on the track of the disk to explain the track jump operation in the sample servo system of the device of the above publication. .

In FIG. 6, reference numerals 71 and 72 denote wobbled pits in the so-called sample servo system, which are arranged at positions laterally displaced from the track centers of the tracks a, b, and c. 73 is a clock pit,
It is located in the center of the track.

There is a light spot of the beam emitted from the pickup with a tracking error and the pits 71,
Regarding the amplitude of the reflected light when irradiating 72, 73,
The magnitude of the amplitude of the pits of 1 and 72 and the amplitude of the pit of 73 are compared. Here, when the amplitude of the pit 73 is larger, the light spot is located within ± 1/4 track from the center of the track, and in the opposite case, the light spot is located in an intermediate region between tracks.

The apparatus of the above publication utilizes this property to determine whether or not the light spot is within ± 1/4 track from the track center, and the light spot is within ± 1/4 track from the track center. In the area of 1), the tracking error signal is generated, and in the area separated by ± 1/4 tracks or more, the signal based on the error signal between the signal obtained by inverting the tracking error signal and the offset signal generated by the offset signal generation circuit is used. By controlling the position of, the jump operation to the adjacent track is performed. By performing a track jump while operating the position control system in this way, a stable track jump is possible.

[0012]

However, the above-mentioned conventional track jump control is premised on the disk of the sample servo system. Therefore, even if it is applied to a disk of the continuous servo system, it cannot be determined whether the area is within ± 1/4 track, and stable track jump by position control is impossible.

In addition, the tracking error signal is close to the peak value in the vicinity of the ± 1/4 track deviation, and the tracking error signal amplitude variation or the offset target rather than the tracking error signal change amount with respect to the light spot position deviation. There is a problem that the influence of the deviation from the position signal becomes larger, a position control error occurs, and the track jump becomes unstable.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a tracking servo device capable of performing a stable track jump in any disk of the continuous servo system and the sample servo system. Has an aim.

[0015]

A tracking servo apparatus according to the present invention, based on a tracking error signal corresponding to a relative positional deviation in a disk radial direction between an information reading point of a pickup and a recording track of a disk-shaped recording medium, An apparatus for controlling the relative position, an actuator means for moving an information reading point of the pickup, and a first level detecting means for detecting that the tracking error signal becomes larger than a first reference level. And the tracking error signal is the second
Second level detecting means for detecting that the target level signal has become smaller than the reference level, target value generating means for generating a change target position signal during a track jump operation according to the passage of time, the tracking error signal and the target. Error detecting means for outputting an error from the position signal, and an error signal for outputting either a first error signal in phase with the error detected by the error detecting means or a second error signal in antiphase with the error Output means, signal cutoff means for cutting off the first and second error signals by cutting off the connection between the error signal output means and the actuator means, and an information reading point of the pickup is recorded on the recording medium. When performing a track jump operation for jumping over a track, in response to the output of the first and second level detecting means together with the control of the target value generating means. , The error signal output means, in which a control means for controlling the operation of the signal cutoff means.

[0016]

When the information reading point of the pickup jumps over the recording track of the recording medium, the control means controls the target value generating means to generate a change target position signal according to the passage of time. Then, the error between the tracking error signal and the target position signal is obtained by the error detecting means, and the error signal output means outputs either the first error signal having the same phase as the error or the second error signal having the opposite phase. Further, the first level detecting means and the second level detecting means detect whether the tracking error signal becomes larger than the first reference level or becomes smaller than the second reference level. On the other hand, the signal cutoff means cuts off the connection between the error signal output means and the actuator means to cut off the first and second error signals. At this time, the control means controls the operations of the error signal output means and the signal cutoff means according to the outputs of the first and second level detection means,
The first error signal or the second error signal is output from the error signal output means.
Error signal is output and the input from the error signal output means to the actuator means is conducted or cut off by the signal cutoff means so that the error signal is not input when the tracking error signal exceeds the upper and lower reference levels. To do.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. 1 and 2 relate to a first embodiment of the present invention.
2 is a block diagram showing the configuration of the tracking servo device, and FIG. 2 is an operation waveform diagram of each part for explaining the operation of the device of this embodiment.

The present embodiment shows an example of the structure of an optical disk device using an optical disk as a recording medium.

As shown in FIG. 1, the pickup section of the optical disk device includes an objective lens 2 that focuses a light beam on the disk 1 to form a light spot, a light source 3 that generates the light beam, and a light source 3. A beam splitter 4 which reflects the light of the above-mentioned and makes it enter the objective lens 2 and transmits the reflected light from the disc 1, and a photodetector 5 which receives the reflected light from the disc 1 passing through the objective lens 2 and the beam splitter 4. A tracking actuator 6 that drives an optical system including the objective lens 2 and a driver 7 that supplies a drive signal to the tracking actuator 6 are configured.

The light emitted from the light source 3 is reflected by the reflecting surface of the beam splitter 4, condensed by the objective lens 2 and incident on the disc 1. The disc 1 has tracks for recording and reproducing information. The light flux reflected by the disk 1 passes through the objective lens 2 and the beam splitter 4, and enters the photodetector 5.

The photodetector 5 is connected to a tracking error generating circuit 8 and the photodetector 5
Outputs a current according to the amount of incident light and inputs the current to the tracking error generation circuit 8. Based on the output of the photodetector 5, the tracking error generation circuit 8 generates the tracking error signal S1 indicating the positional deviation between the light spot on the disk 1 and the track. The tracking error generation circuit 8 has the first and second
Is connected to a window comparator 9 as a level detecting means, and the window comparator 9 compares the tracking error signal S1 with the first comparison potential E1 and the second comparison potential E2.

The first and second comparison potentials E1 and E2
2 is set on the positive side and the negative side at a level whose absolute value is smaller than the peak value of the tracking error signal. Here, when the tracking error signal S1 is between the first comparison potential and the second comparison potential, the output S2 of the window comparator 9 becomes a low (L) level, and the tracking error signal S1 is higher than the first comparison potential. When the level is higher or lower than the second comparison potential, S2 becomes high (H) level.

A flip-flop circuit 10 and a NOT circuit 11 are connected to the output terminal of the window comparator 9, and the output S2 of the window comparator 9 is input to each circuit. The output of the flip-flop circuit 10 is inverted at each falling edge of the input signal, and the output S3 of the flip-flop circuit 10 is at L-level at each falling edge of the output S2 of the window comparator 9.
Change from H to H → L.

Further, there are provided a controller 20 as a control means for issuing a track jump control instruction and the like, and a clock generation circuit 12 for outputting a reference clock signal at a preset frequency. A track jump mode start signal S4 for instructing the start is output. The controller 20 and the clock generation circuit 12 are connected to the AND circuit 13, and the track jump mode start signal S4 is A together with the clock signal output from the clock generation circuit 12.
It is input to the ND circuit 13. Here, the AND circuit 13
Is designed to pass the clock signal when the track jump start signal S4 is at the H level, and to interrupt the clock signal when the S4 is at the L level.

The AND circuit 13 and the NOT circuit 11 are connected to the AND circuit 14, and the output of the AND circuit 13 is input to the AND circuit 14 together with the output of the NOT circuit 11, that is, the output S2 of the window comparator 9. To be done. The AND circuit 14 passes the clock signal only when the window comparator output S2 is at L level.

The AND circuit 14 is connected to the position signal generating circuit 15 as the target value generating means, and the AND circuit 1
A clock signal which is intermittently output as an output S5 from 4 is input to the position signal generation circuit 15. The position signal generation circuit 15 is composed of a digital memory and a D / A converter, and changes target position signal at the time of track jump according to the passage of time stored in the memory in advance as data according to an input clock. Are read in sequence and this is D /
The signal is A-converted and output as the position target signal S6. Further, a reset signal output from the controller 20 is input to the position signal generation circuit 15, and this reset signal causes data to be read again from the beginning of the memory after the track jump is completed. It is reset.

Further, an error detection circuit 16 is provided so that the tracking error signal S1 and the position target signal S6 are input. In addition, the error detection circuit 16
The polarity inverting circuit 1 serving as error signal output means is provided on the output side of the
7, a switch 18 as a signal cutoff unit, and a phase compensation circuit 19 are sequentially provided, and an output terminal of the phase compensation circuit 19 is connected to the driver 7. The error detection circuit 16 includes S1 and S
The difference signal of 6 is output, and this difference signal is input to the polarity inverting circuit 17. The polarity inverting circuit 17 inverts and outputs the polarity of the input signal when the output S3 of the flip-flop 10 is at H level, and outputs the input signal as it is when S3 is at L level, and this output is output to the switch 18. Is entered. The switch 18 is controlled by the output S2 of the window comparator 9, and when S2 is H level, the switch is in the cutoff state, and when S2 is L level, the switch is in the conduction state. The output of the switch 18 is input to the phase compensating circuit 19, where the phase compensation for stabilizing the control system is performed and the input to the driver 7. The driver 7 amplifies the input signal and inputs it to the tracking actuator 6 as an actuator drive signal, thereby driving the tracking actuator 6.

Next, the operation of this embodiment will be described with reference to FIGS. When performing a track jump, the controller 20 outputs a track jump mode start signal S4, and when S4 goes high, the track jump operation is started.

In the initial state, the window comparator 9
Output S2 of the flip-flop circuit 10 and the output S3 of the flip-flop circuit 10 are both at the L level, the clock signal from the clock generation circuit 12 passes through the AND circuits 13 and 14, and the input signal is output as it is at the polarity inverting circuit 17. The switch 18 is in a conducting state.

Therefore, at this time, the clock signal is input to the position signal generation circuit 15 by the output S5 of the AND circuit 14, and the position signal generation circuit 15 reads the data according to the clock to generate the position target signal S6. It
Then, the difference between the position target signal S6 output by the position signal generation circuit 15 and the tracking error signal S1 is calculated by the error detection circuit 16, and this difference signal is calculated by the polarity inversion circuit 1.
The signal is input to the tracking actuator 6 as an actuator drive signal via the switch 7, the switch 18, the phase compensation circuit 19, and the driver 7. The tracking actuator 6 moves the position of the objective lens 2 in the direction perpendicular to the track based on the drive signal. With these closed loops, a position control system for moving the objective lens 2 in the vertical direction with respect to the track to position the light spot at the target point is formed so that the difference between the position target signal S6 and the tracking error signal S1 becomes zero. To be done.

When the tracking error signal S1 reaches the level of E1, the output S2 of the window comparator 9
Becomes H level, and the switch 18 cuts off the circuit. That is, from time t1 to time t2 when S1 exceeds the level of E1, the position control system is in the open state and the objective lens 2
Continues to move by inertia due to the speed at time t1 when the position control system is opened. During this period, the operation of the AND circuit 14 stops the supply of the clock signal to the position signal generation circuit 15, so that the output S of the position signal generation circuit 15 is output.
6 continues to maintain the value at time t1.

When S1 again becomes smaller than E1 at time t2, S2 changes to L level, and S3 accordingly changes to H level. At this time, the switch 18 is closed and the position control system is closed again, but since S3 is at the H level, the polarity inversion circuit 17 inverts the polarity of the output of the error detection circuit 16. The polarity-inverted signal is input to the tracking actuator 6 via the phase compensation circuit 19 and the driver 7 to maintain the negative feedback control.

After that, when S1 becomes smaller than E2 at time t3, S2 becomes H level and the switch 1 is turned on again.
8 cuts off the circuit. That is, the position control system is opened again from time t3 to time t4, and the objective lens 2 continues to move by inertia. During this period, the AND circuit 14 stops the supply of the clock signal to the position signal generation circuit 15, so that the output S6 of the position signal generation circuit 15 keeps the value at the time t3.

When S1 again becomes larger than E2 at time t4, S2 changes to L level, and S3 also changes to L level accordingly. At this time, the switch 18 is closed and the position control system is closed again, and since S3 is at the L level, the polarity reversing circuit 17 outputs the output of the error detecting circuit 16 as it is without inverting it. Therefore, the output of the error detection circuit 16 is directly input to the phase compensation circuit 19 via the switch 18, and the position control is restarted.

At time t5, the output signal S4 of the controller 20 becomes L level, and the supply of the clock signal to the position signal generating circuit 15 is stopped. Further, the controller 20 outputs a reset signal to the position signal generation circuit 15 to return the internal state of the position signal generation circuit 15 to the initial state in preparation for the next track jump. At this time, the light spot completely moves to the adjacent track, and thereafter, the position control system continues the track following operation.

As described above, in this embodiment, the track jump control system is adopted in which the position control system is opened and the pickup is moved by inertia near the position where the tracking error signal reaches the peak value. When performing the track jump by the position control, it is possible to make it less likely to be affected by the variation in the amplitude of the tracking error signal and the offset, and it is possible to always perform the stable track jump. Further, in the present embodiment, a stable track jump can be performed while operating the position control system in any disk of the continuous servo system and the sample servo system.

3 and 4 relate to the second embodiment of the present invention, FIG. 3 is a block diagram showing the configuration of the tracking servo device, and FIG. 4 is an operation of each part for explaining the operation of the device of the present embodiment. It is a waveform diagram.

The second embodiment is a modification of the configuration of the first embodiment. Instead of the clock generation circuit 12, the position signal generation circuit 15, etc., the first reference voltage (1) V1 and the second reference voltage are used.
(2) V2, a selector 23 for selecting and outputting one from two reference voltages, a switch 24, and an integrator 25 are provided,
These constitute a position signal generation circuit. Further, there is provided a controller 26 which outputs a track jump mode start signal and an output signal S7 serving as a reset signal to the integrator 25 to issue a track jump control instruction.

The selector 23 is switched by the output S3 of the flip-flop 10, selects the reference voltage V1 when S3 is at the L level, and selects and outputs the reference voltage V2 when S3 is at the H level. ing. The switch 24 is controlled by the output S2 of the window comparator 9, and when S2 is at the H level, the switch is in the cutoff state, and when S2 is at the L level, the switch is in the conductive state. The output S8 of the switch 24 is input to the integrator 25, integrated, and output as the position target signal S9.

In the present embodiment, as shown in FIG. 4, when the output signal S7 from the controller 26 becomes H level, the track jump operation is started and the integrator 25 is started. After that, the selector 23 selects the reference voltage V1 or V2 according to the change of the output S3 of the flip-flop 10, and the switch 24 is switched according to the change of the output S2 of the window comparator 9.
The signal S8 as shown in the figure is input from the switch 24 to the integrator 25. Then, S8 is integrated in the integrator 25, and a position target signal S9 that is substantially the same as S6 of the first embodiment is obtained. By this position target signal S9, the movement of the objective lens 2 is controlled as in the first embodiment, and the track jump is performed.

When the output signal S7 of the controller 26 becomes the L level which is the reset signal, the integrator 25 is reset, and thereafter, the position control system continues the track following operation.

The structure and operation of the other parts are the same as those of the first embodiment, and the description thereof will be omitted.

In the second embodiment, since the position signal generating circuit is configured to use no digital memory, it has the same effect as that of the first embodiment, but the device structure can be simplified as compared with the first embodiment. The effect is that it can be constructed at low cost.

[0044]

As described above, according to the present invention, there is an effect that a stable track jump can be performed in both the continuous servo type disk and the sample servo type disk.

[Brief description of drawings]

1 and 2 relate to a first embodiment of the present invention, and FIG. 1 is a block diagram showing a configuration of a tracking servo device.

FIG. 2 is an operation waveform diagram of each part for explaining the operation of the apparatus of this embodiment.

3 and 4 relate to a second embodiment of the present invention, and FIG. 3 is a block diagram showing a configuration of a tracking servo device.

FIG. 4 is an operation waveform diagram of each part for explaining the operation of the apparatus of this embodiment.

FIG. 5 is a block diagram showing a configuration example of general track jump control means.

FIG. 6 is an explanatory view showing pits on a track of a sample servo type disc.

[Explanation of symbols]

 1 ... Disk 2 ... Objective lens 5 ... Photodetector 6 ... Tracking actuator 7 ... Driver 8 ... Tracking error generation circuit 9 ... Window comparator 10 ... Flip-flop circuit 12 ... Clock generation circuit 15 ... Position signal generation circuit 16 ... Error detection circuit 17 ... Polarity inversion circuit 18 ... Switch 19 ... Phase compensation circuit 20 ... Controller

Claims (1)

[Claims] 1. A tracking servo device for controlling the relative position of a pickup based on a tracking error signal according to a relative displacement between a reading point of a pickup and a recording track of a disc-shaped recording medium in a disc radial direction. And an actuator means for moving the information reading point of the pickup, a first level detecting means for detecting that the tracking error signal has become larger than a first reference level, and a second tracking error signal for the tracking error signal. Second level detection means for detecting that the level is lower than the reference level, target value generation means for generating a change target position signal during track jump operation according to the passage of time, the tracking error signal and the target position An error detecting means for outputting an error between the signal and the error detecting means. Error signal output means for outputting either a first error signal in phase with the issued error or a second error signal in reverse phase with the error, and disconnection of the connection between the error signal output means and the actuator means By doing so, a signal cutoff means for cutting off the first and second error signals, and control of the target value generation means when performing a track jump operation in which the information reading point of the pickup jumps over a recording track of the recording medium At the same time, a tracking servo device comprising: control means for controlling the operations of the error signal output means and the signal cutoff means in accordance with the outputs of the first and second level detection means.