JP2907166B2 - Optical disk tracking controller - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tracking control device for an optical disk, and more particularly to a tracking control device for adjusting a tracking offset of each land / groove in land / groove recording of a phase change medium or the like.

[0002]

2. Description of the Related Art When land / groove recording is performed with a conventional one-beam type phase change medium optical head, an offset of a tracking error signal occurs due to a difference in groove shape between the inner and outer circumferences of an optical disk and a shape of a focused beam. As a cause, as shown in FIG. 6, a recording state may occur in which the recording mark row 503 is shifted from the centers 501 and 502 of the lands / grooves.

[0003] Such a shift of the mark array can be confirmed by destroying the optical disk, melting the plastic part of the optical disk, extracting only the thin film part, and observing this with a transmission electron microscope. In FIG. 6, a record mark row is recorded shifted from the center of each land / groove track in the direction indicated by the hollow arrow 504.

The land / groove recording method presupposed here is a method of recording by changing the polarity of the land / groove, groove / land and track at a predetermined position every one rotation of the disk. FIG. 7 shows an example of the track structure according to this. In FIG. 7, an optical disk having two spiral grooves is shown, with a solid line 601 indicating a groove and a broken line 602 indicating a land. Then, the optical head scans from the inner circumference to the outer circumference of the disk, and kicks one inner track each time the disk makes one rotation, so that land / groove / land / groove is sequentially made every rotation. The land / groove is switched and recorded. This kick operation is indicated by an arrow 603 in FIG.

On the other hand, in the land / groove recording method, in addition to the above-mentioned example, land recording is continuously performed from the inner periphery to the outer periphery of the disk, and the recording is returned to the inner periphery of the disk again. Some are performed continuously. But,
In this method, it is necessary to move the optical head at high speed from the outer circumference to the inner circumference of the disk, and it takes 15 ms even if the moving time is shortened. It requires capacity and memory control. In view of these circumstances, the present application presupposes a method of switching lands / grooves every rotation, and aims to improve a track offset generated in a recording mark row in land / groove recording.

[0006]

However, in the recording method in which the land / groove is switched every one rotation in the two spiral discs assumed in the present application, the land / land kick operation or the groove / groove required especially during the still operation is performed. The tracking offset generated by the kick operation continues after the end of the kick operation. Even if the tracking error signal converges to 0, the track offset of the light spot is continued, and as described above, the deviation of the recording mark train from the track center is caused. This causes inconvenience that cross erasure and crosstalk occur between adjacent tracks, and good reproduction characteristics cannot be obtained.

Here, the still operation is an operation in which a spiral track is kicked and the same track is repeatedly scanned for each revolution of the disk. The reason why the offset continues even after the kick operation ends is that the optical system of the optical head is moving while correcting the deviation from the objective lens.
This is because the optical head main body cannot follow the movement of the objective lens at the time of high-speed access, and a shift occurs between the optical axis of the collimator and the optical axis of the objective lens.

[0008]

An object of the present invention is to improve the disadvantages of the prior art, and in particular, in the above-described land / groove recording method involving a track kick for each round of the disc, the deviation of the recording mark array from the track center is suppressed. It is another object of the present invention to provide a tracking control device for an optical disc which prevents cross erasure and crosstalk between adjacent tracks and can obtain sufficient recording / reproducing characteristics.

[0009]

In order to achieve the above object, according to the first to third aspects of the present invention, a tracking actuator for positioning a focused beam spot on a predetermined track of a land-groove recording type optical disk, and a tracking error signal of zero are provided. And a main control unit for outputting a kick signal to the tracking control unit in response to an external access signal to execute a predetermined track kick. Further, a normalization offset calculation unit is provided for calculating a normalization offset based on a value obtained by dividing a difference between a maximum value and a minimum value of a track error signal generated at the time of a track kick by a sum thereof. Then, the main control unit outputs a kick signal to the tracking control unit and inputs an offset correction amount based on the normalized offset to the tracking control unit. Further, the tracking control unit is configured to add the operation amount based on the offset correction amount received from the main control unit to the operation amount of the tracking actuator based on the tracking error signal.

Further, according to the first aspect of the present invention, the main control unit includes a TO controller provided on an inner periphery of a recording area of the optical disk.
Attempt a track kick with C, and
Normalized offset calculated based on the track error signal
In this case, the offset correction amount is set on the basis of the offset value .

According to the second aspect of the present invention, the main control unit attempts a track kick with the TOC provided on the outer periphery of the recording area of the optical disc, and performs a normal kick calculated based on a track error signal at the time of the track kick. The offset correction amount is set based on the generalized offset.

[0012] In the invention according to claim 3, the main control unit includes: T
Attempt a track kick in a predetermined pattern in the OC area,
From the normalized offset calculated at that time, the kick
Calculate the offset correction amount corresponding to the turn and store it in memory.
And then kick the track with the same pattern
When executing, the kick pattern stored in the memory
Read the offset correction amount corresponding to the
The input is input to the logging control unit.

[0013] Accordingly, the above-mentioned object is achieved.

In FIGS. 1A and 1B, the land 1
Optical disk 1 on which grooves 01 and grooves 102 are alternately formed
FIG. 3 shows a section taken along the radial direction of No. 03, showing a state where the focused beam 104 from the optical head is irradiated. Further, the plan view of the optical disk is extended to the right side, the center of the land is indicated by a broken line 105, and the center of the groove is indicated by a solid line 106.
Indicated by

FIG. 1A shows that a beam 104 focused on a land 105 is transmitted from a land 105 to a land 107.
5 shows an ideal trajectory of the focused beam 104 when moving to the land 107 after passing through the groove 106 between the two by the kick to.

The tracking error signal 108 of the one-beam push-pull type at this time is shown below the track diagram.
This tracking error signal 108 is
During the transition from the land 105 to the groove 106, the pulse waveform 109 becomes negative,
During the transition to 07, a positive pulse waveform 110 is obtained.

On the other hand, FIG. 1B shows a non-ideal track kick in which a track offset occurs when a kick is made from the land 111 to the land 112.

The tracking error signal 113 at this time is shown in the lower part of FIG. In this case, the amplitude A of the negative pulse waveform 114 appearing while the focused beam travels from the land 111 to the groove 115 and the amplitude A of the positive pulse waveform 116 appearing while the focused beam travels from the groove 115 to the land 112. > B occurs.

Such a situation also occurs in a normal kick operation to an adjacent track, but is particularly remarkable when a still operation is performed on a two-spiral optical disk, that is, an operation of repeatedly scanning the same track every rotation of the disk is performed. . In this case, a kick from land to land or a kick from groove to groove is required. At this time, if the optical head is moved at a high speed in the radial direction of the optical disc, the collimator optical axis of the optical head and the optical axis of the objective lens are not affected. This is because a larger deviation from the axis occurs.

Here, the deviation of the focused beam from the track center, that is, the track offset, caused by the above-mentioned causes,
Considering the relationship with the track error signal shown in FIG. 1 (b), the value m obtained by dividing the difference between the maximum value A and the minimum value B of the track error signal by the sum of them and the track It was found that there was a proportional relationship with the offset amount.

M = (AB) / (A + B) (1)

FIG. 2 shows this relationship. The horizontal axis represents the normalized value m (× 100%) of the pulse amplitude of the tracking error signal,
The vertical axis is the actual track offset.

In the present invention, a correction amount for making the track offset close to 0 is calculated from the tracking error signal based on this relationship, and the tracking actuator is corrected and controlled so that the position of the focused beam on the track is at the track center.

[0024]

FIG. 3 shows an embodiment of the present invention.
It will be described based on.

The tracking control device shown in FIG. 3 outputs an operation amount to a tracking actuator 17 for positioning a focused beam spot on a predetermined track of a land / groove recording type optical disk and to the tracking actuator so that a tracking error signal TE approaches zero. The tracking control unit 20 includes a tracking control unit 20 and a main control unit 9 that outputs a kick signal K to the tracking control unit 20 in response to an external access signal to execute a predetermined track kick. Further, a normalized offset is calculated based on a value (AB) / (A + B) obtained by dividing a difference AB between the maximum value A and the minimum value B of the track error signal TE generated at the time of the track kick by the sum A + B. And a normalized offset calculating unit 10 for performing the above operations. Reference numeral 11 denotes a memory for storing an offset correction amount for each track kick pattern.

The main control unit 9 outputs the kick signal K to the tracking control unit 20 and outputs the offset correction amount δ based on the normalized offset to the tracking control unit 2.
Enter 0. In addition, the tracking control unit 20 adds the operation amount based on the offset correction amount δ received from the main control unit 9 to the normal operation amount of the tracking actuator based on the tracking error signal TE.

The relationship between the calculated value of the normalized offset shown in FIG. 2 and the actually generated offset is experimentally obtained in advance in the memory 11 and stored for each track kick pattern.

Next, the operation of this embodiment will be described.

When the apparatus is set to the operation state, the main control unit performs a track kick from the land to the next land,
A track kick from the groove to one adjacent groove is tried, and a normalized offset at this time is calculated for each track kick pattern based on the above equation (1). Then, the main controller 9 calculates an offset correction amount for each track kick pattern based on the relationship between the normalized offset stored in the memory 11 and the actually generated track offset, and stores the offset correction amount in the memory 11.

Subsequently, when the recording operation on the optical disk is started, the tracking error signal TE is input to the tracking control section 20, and the tracking control section 20 executes the conventional general tracking control.

When the main control section 9 determines to execute a track kick in response to an external access signal, the main control section 9 inputs a kick signal K to the tracking control section 20 to execute a conventional general track kick operation. Then, the offset correction amount corresponding to the track kick pattern is read from the memory 11 and input to the tracking control unit 20. The tracking control unit 20 adds the operation amount based on the offset correction amount to the operation amount of the actuator corresponding to the normal track error signal TE, and adjusts the tracking actuator 1 so that the offset after the track kick approaches zero.
7 is controlled.

[0032]

Next, an example of this embodiment will be described with reference to FIG.

In FIG. 4, a normalized offset calculating section 1
0 is a maximum value detection circuit 1 for detecting the maximum value A of the tracking error signal TE, a minimum value detection circuit 2 for detecting the minimum value B of the tracking error signal TE, and a difference A between the maximum value A and the minimum value B. The differential amplifier 3 includes a differential amplifier 3 for calculating −B, an adder 4 for calculating the sum A + B of the maximum value A and the minimum value B, and a calculation unit 5 for calculating a normalized offset m by the following equation.

M = {(AB) / (A + B)} × 100 (2)

On the other hand, the tracking control section 20 comprises a conventional phase compensator 12 for compensating the phase of the tracking error signal TE, and a switch 13 for turning on and off the output of the phase compensator 12 in accordance with a signal from the CPU 9. A pulse generator 16 for outputting a rectangular kick / brake pulse in response to a kick signal K from the CPU 9, an output of the pulse generator 16 connected to the positive electrode, and an output of the phase compensator 12 via the switch 13 Differential amplifier 14 connected to negative electrode
And an offset adder 7 for adding the offset correction signal output from the CPU 9 to the output of the pulse generator 16 in accordance with the output of the rotation synchronization system of the optical disk. Further, a current feedback amplifier 15 is provided which inputs the output of the differential amplifier 14 to the positive electrode and outputs a drive signal to the tracking actuator 17.

The tracking actuator 17
Has a solenoid 17L and a resistor 17R connected in series between the output stage of the current feedback amplifier 15 and a ground point. Between the solenoid 17L and the resistor 17R is connected to the negative electrode of the current feedback amplifier 15.

The CPU 9 and the memory 11 are connected to a bus 19. The output of the normalized offset calculating unit 10 is input to the CPU 9 after being converted by the A / D converter 6,
The output of the offset correction signal from U9 is a D / A converter 8
Is input to the offset adder 7 after conversion. The memory 11 previously stores experimentally obtained data on the relationship between the normalized offset and the actual offset amount (FIG. 2).

In the present embodiment, the CPU 9 executes a trial of a track kick for calculating a normalized offset in a TOC located on the inner periphery of the recording area of the optical disk shown in FIG. Instead, it may be performed at the TOC on the outer periphery of the recording area.

Next, the overall operation of this embodiment will be described.

When the apparatus is set in the operating state, the CPU 9
Inputs a kick signal to the pulse generator 16 via the bus 19, executes a predetermined track kick, and sets the optical head to T
It is arranged at a predetermined position on the OC. Next, a kick from an adjacent land to a land, a kick from a groove to a groove, a kick from a groove to a land, and a kick from a land to a groove are executed, respectively. From the change in the track error signal TE obtained at that time, A normalized offset is calculated for each kick pattern. Then, these normalized offset values are converted into actual offset values with reference to the conversion data in the memory 11, respectively. Then, an offset correction amount for bringing the offset closer to 0 is calculated for each kick pattern, and is stored in the memory 11.

Next, when the writing operation of the optical disk is executed, the positioning control of the conventional general tracking actuator 17 is performed by the tracking control unit 20 based on the track error signal TE. Here, the CPU 9
However, when the stage of execution of the track kick is reached in response to the external access signal, the CPU 9 outputs a predetermined kick signal to the tracking control unit 20 to execute the designated track kick, and outputs a kick signal corresponding to the kick pattern. The offset correction amount thus read is read from the memory 11 and a correction signal is added to the output of the pulse generator 20 via the offset adder 7.

As a result, the output of the operational amplifier 14 acts in the direction of suppressing the offset caused by the track kick, so that the position of the light spot after the track kick executed by the tracking actuator 17 on the track is smaller than that of the conventional track. The situation in which the recording mark row is shifted from the track center by approaching the center is effectively suppressed.

Here, in the present embodiment, the calculation of the normalized offset does not depend on the analog circuit system shown in FIG.
It may be performed by a digital circuit system using SP.

[0044]

Since the present invention is constructed and functions as described above, according to the present invention, the difference between the maximum value and the minimum value of the track error signal obtained at the time of the track kick is divided by the sum thereof. When a normalized offset is calculated and a track kick is performed when data is recorded on an optical disk, the position of the tracking actuator is adjusted so that the normalized offset approaches zero. An unprecedented superior optical disc tracking control that can be closer to the track center than in the example, and can reduce cross erasure and crosstalk between adjacent tracks in land / groove recording and obtain stable recording and reproduction characteristics. An apparatus can be provided.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram for explaining a principle of correcting an offset generated by a track kick in the present invention. FIG. 1A shows an ideal state of a light spot position after a track kick and a tracking error corresponding thereto. FIG. 1B shows a change in the signal, and FIG. 1B shows a state where the light spot position is shifted from the track center after the track kick and a change in the tracking error signal corresponding thereto.

FIG. 2 is a characteristic diagram showing a relationship between a normalized offset and an actually generated track offset.

FIG. 3 is a block diagram showing one embodiment of the present invention.

FIG. 4 is a block diagram showing one example of the embodiment shown in FIG. 3;

FIG. 5 is a diagram showing T on the inner circumference of a recording area formed on an optical disc.
It is the schematic block diagram which abbreviate | omitted partially showing OC.

FIG. 6 is a state diagram showing a problem of a conventional example.

FIG. 7 is a schematic configuration diagram showing an example of a track configuration of a conventional optical disc.

[Explanation of symbols]

 9 Main control section 10 Normalized offset calculation section 10 11 Memory 17 Tracking actuator 20 Tracking control section A Maximum value B Minimum value TE Tracking error signal

Claims (3)

(57) [Claims] 1. A predetermined method for a land-groove recording type optical disk
Track to position focused beam spot on track
And the tracking error signal is close to 0
Operation amount to the tracking actuator
Outputs tracking control and external access signals
Outputs a kick signal to the tracking control
A main control unit for executing a fixed track kick, and a maximum of a track error signal generated at the time of the track kick.
Value based on the difference between the value and the minimum value divided by their sum
A normalized offset calculator for calculating a normalized offset.
The main control unit sends a kick signal to the tracking control unit.
And outputs an offset based on the normalized offset.
The tracking control unit receives the correction amount from the main control unit.
The operation amount based on the offset correction amount is
To the operation amount of the tracking actuator based on the difference signal
In the tracking control apparatus for an optical disc to be added, the main control unit includes:Inner circumference than the recording area of the optical disk
Try a track kick at the TOC provided in the
Calculated based on the track error signal during rack kick
The offset correction amount based on the normalized offset
Set,  An optical disk tracking control device, characterized in that: (2)Prescribed land / groove recording type optical disc
Track to position focused beam spot on track
And the tracking error signal is close to 0
Operation amount to the tracking actuator
Outputs tracking control and external access signals
Outputs a kick signal to the tracking control
A main control unit for executing a fixed track kick, The maximum of the track error signal generated at the time of the track kick
Value based on the difference between the value and the minimum value divided by their sum
A normalized offset calculator for calculating a normalized offset.
Prepared, The main control unit sends a kick signal to the tracking control unit.
And outputs an offset based on the normalized offset.
Input the correction amount to the tracking control unit. , The tracking control unit has received from the main control unit
The operation amount based on the offset correction amount is
To the operation amount of the tracking actuator based on the difference signal
In the tracking control device of the optical disc to be added, The main control unit is located outside the recording area of the optical disc.
Try a track kick at the TOC provided in the
Calculated based on the track error signal during rack kick
The offset correction amount based on the normalized offset
Set, Characterized by Optical disk tracking controller. (3)Prescribed land / groove recording type optical disc
Track to position focused beam spot on track
And the tracking error signal is close to 0
Operation amount to the tracking actuator
Outputs tracking control and external access signals
Outputs a kick signal to the tracking control
A main control unit for executing a fixed track kick, The maximum of the track error signal generated at the time of the track kick
Value based on the difference between the value and the minimum value divided by their sum
A normalized offset calculator for calculating a normalized offset.
Prepared, The main control unit sends a kick signal to the tracking control unit.
And outputs an offset based on the normalized offset.
Input the correction amount to the tracking control unit, The tracking control unit has received from the main control unit
The operation amount based on the offset correction amount is
To the operation amount of the tracking actuator based on the difference signal
In the tracking control device of the optical disc to be added,  The main control unit performs tracking of a predetermined pattern in the TOC area.
Attempt to kick and calculate the normalization off at that time
Offset compensation corresponding to the kick pattern from the set
Calculate the positive amount, store it in memory, and then
When performing a track kick, the memory
Offset compensation corresponding to the stored kick pattern
Reading a positive amount and inputting it to the tracking control unit,Characterized by Optical disk tracking controller.