JP2003059073A - Disk device, tracking method, and program for generating tracking error signal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a disk device which can make an optical pickup follow up a target track even if the optical pickup straddles a plurality of tracks as the position error to the target track increases. SOLUTION: This device has the optical pickup 4 which receives reflected light from an optical disk 2, an actuator 5 which moves the optical pickup 4, a tracking error signal generating circuit 6 which generates a tracking servo signal E having a value corresponding to the displacement of the optical pickup 4 from the center of an opposite track and also having periodicity depending upon the track pitch and a pull-in signal P having a 90 deg. phase difference from the signal E according to the intensity distribution of the reflected light, an encoder part 7 which generates a phase error signal F having linearity according to the signals E and P, and a tracking servo control part 8 which makes the optical pickup 4 follow up the target track according to the position error signal F.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a disc device for reproducing at least information from an optical recording medium.

[0002]

2. Description of the Related Art In general, data is recorded on and reproduced from an optical disk by a disk device. FIG. 12 is a block diagram showing an example of the tracking servo system of the disk device. In FIG. 12, a disc device 200 includes a spindle motor 202 that rotates an optical disc 201, an optical pickup 203 that is arranged to face the rotating optical disc 201, and an actuator 205 that moves the optical pickup 203 in the radial direction of the optical disc 203. I have it.

The optical pickup 203 is equipped with, for example, a laser light source such as a laser diode, an objective lens, a half mirror, and a photodetector such as a photodiode.
The optical disc 201 is irradiated with laser light and the reflected light is received. At the time of reproducing the data recorded on the optical disc 201, the actuator 205 is controlled so that the spot of the laser beam output from the optical pickup 203 follows the target track of the optical disc 201 while rotating the optical disc 201.
The data recorded on the optical disc 201 is reproduced by the optical pickup 203 while being controlled by 7.
The control for causing the optical pickup 203 to follow the target track in this way is called tracking servo. The tracking servo controller 207 controls the actuator 205 based on the tracking error signal TE generated by the tracking error signal generation circuit 206.

A push-pull method is known as a method of detecting a tracking error signal TE which is an error in tracking the target track of the optical pickup 203 during the tracking servo operation. In the push-pull method, the intensity distribution of the reflected light of the laser light output from the optical pickup 203 is received by a photodetector that is divided in half in the track pitch direction, and the amount of light received by the divided photodetector is detected. The tracking error signal generator 206 generates a tracking error signal TE based on the difference. Tracking error signal TE obtained by push-pull method
For example, as shown in FIG. 13, when the optical pickup 203 is located at the track center (on-track), its value becomes zero. As the position of the optical pickup 203 moves away from the track center, the tracking error signal TE has a value other than zero. The tracking servo is to control the position of the optical pickup 203 so that the tracking error signal TE becomes zero.

[0005]

By the way, on the optical disc 201, tracks are formed at a pitch of, for example, several hundred nm. On the other hand, the optical disc 201 always has eccentricity. Therefore, the optical pickup 20
When the tracking servo of No. 3 is not performed, for example, as shown in FIG.
Indicates that the optical disk 201 is 1
While rotating, it will sway over about 50 to 100 tracks Tr. When the optical pickup 203 moves on the locus K as shown in FIG. 14, the tracking error signal TE is, for example, as shown in FIG.
It becomes a sine wave with the track pitch as one cycle. If the track pitch is relatively wide and the optical pickup 203 can follow the track Tr, no problem occurs in the conventional tracking servo method, but the track pitch becomes narrower and higher-performance tracking servo operation can be performed. When necessary, the optical pickup 203 may not be able to quickly follow the target track. In this way, when the optical pickup 203 cannot follow the target track and the optical pickup remains on the adjacent track due to the eccentricity or vibration of the optical disc, the optical pickup is not picked up for another track which was not originally the target. Tracking servo will be applied to. This is because the tracking error signal TE, which is a detected value, has periodicity, so that the same amplitude value appears at each track pitch.

When such a condition occurs, it cannot be determined whether the track on which the tracking servo is applied is the true target track unless the address information prepitted on the track is read. Therefore, as shown in FIG. 12, the RF signal amplifier 208 and the address information detector 209 for detecting the address information are required in addition to the tracking servo control system. As described above, in the tracking servo using the tracking error signal TE, the track pitch of the optical disc 201 is narrowed and the optical pickup 20 is relatively moved.
When the performance of No. 3 deteriorates, the following problems occur. First, when the optical pickup 203 straddles a plurality of tracks due to eccentricity or the like, it is not possible to return the optical pickup 203 to the original target track only by the normal tracking servo operation. Secondly, in order to solve the first problem, in addition to the tracking servo control system, a system for detecting the address information on the track, such as the RF amplifier 208 and the address information detection unit 209 in FIG. It becomes necessary, and the configuration of the servo system becomes complicated. Further, even if a system for detecting address information is added, if the optical pickup is separated from the target track by one or more tracks due to eccentricity or vibration, the following tracking processing is required to return the optical pickup 203 to the target track. Is required.

(1) The address information detecting section detects the track number and the track where the optical pickup is currently located. (2) Stop the tracking servo operation. (3) The operation amount for moving the optical pickup to the vicinity of the target track is calculated. (4) Perform a track jump. (5) Start the tracking servo operation for the latest track (settling operation). (6) Address information is detected for the settled track, and it is determined whether or not it matches the target track. (7) If they match, the tracking servo is continued. If they do not match, the process returns to the above process (2).

As described above, in the conventional disk device, in order to perform the tracking servo, not only a system for detecting the address on the track is required, but also when the optical pickup is displaced across a plurality of tracks. However, there is a disadvantage that the tracking servo operation of is more complicated than the normal servo operation.

The present invention has been made in view of the above-mentioned problems, and an object thereof is to increase the positional error between the optical pickup and the target track so that the optical pickup straddles a plurality of tracks. Even in that case, it is an object of the present invention to provide a disc device capable of causing an optical pickup to follow a target track without using address information recorded on the optical disc. Another object of the present invention is to provide a tracking method capable of causing an optical pickup to follow a target track without using address information recorded on an optical disc even when the optical pickup straddles a plurality of tracks. To provide. Further, another object of the present invention is to generate a tracking error signal according to a position error from a target track of the optical pickup without using address information, even when the optical pickup straddles a plurality of tracks. To provide such a program.

[0010]

DISCLOSURE OF THE INVENTION A disk device according to the present invention is an optical head which is disposed so as to face a recording medium, irradiates the recording medium with laser light, and receives reflected light of the laser light, and the optical head described above. Based on the moving means for moving the track of the recording medium in the direction of the track pitch and the intensity distribution of the reflected light received by the optical head, it has a value corresponding to the displacement of the optical head from the center of the facing track. And a phase of 90 ° with respect to the first signal having a periodicity depending on the track pitch.
First error signal generating means for generating different second signals, and tracking having linearity uniquely corresponding to a position error of the optical head from a target track based on the first and second signals. Second error signal generating means for generating an error signal regardless of the magnitude of the position error,
Tracking servo means for generating a control signal for causing the optical head to follow the target track based on the tracking error signal generated by the second error signal generating means and outputting the control signal to the moving means.

Preferably, the second error signal generating means has the first and second signals as variables and is capable of approximately calculating a signal having linearity from a signal having periodicity. The position error signal is calculated using a calculation function.

The first signal and the second signal are represented by a sine function and a cosine function having the position of the optical head in the track pitch direction as a variable.

More preferably, in the disk device of the present invention, the error signal calculation function is divided into a plurality of areas divided between the adjacent tracks based on the magnitude relation between the sine function and the cosine function. Based on a plurality of element functions that are associated with each other and that can approximately calculate a signal having linearity with the first and second signals as variables, and the magnitude relationship between the values of the first and second signals. The position error signal is calculated by adding a plurality of weighting functions each having a determined weight and weighting each of the element functions, and adding the weighting functions weighted by the element functions. .

Preferably, the plurality of weighting functions weight the plurality of weighting functions so that a discontinuity does not occur in the position error signal continuously calculated by the error signal calculating function.

More preferably, the disk device of the present invention determines the number of relative tracks from the target track to the track opposite to the optical head based on the magnitude relationship between the values of the first and second signals. Further comprising relative track number calculating means for calculating, wherein the error signal calculating function is
The tracking error signal is calculated using the relative track number and the first and second signals as variables.

According to the tracking method of the present invention, an optical head which is arranged so as to face a recording medium and which irradiates the recording medium with a laser beam and receives reflected light of the laser beam, and a track which the optical head has in the recording medium are provided. In a disk device having a moving means for moving in the track pitch direction, a tracking method for causing the optical head to follow a target track, wherein the optical head of the optical head is based on an intensity distribution of reflected light received by the optical head. A first signal having a value corresponding to the displacement from the center of the opposing track and having a periodicity depending on the track pitch, and a second signal having a phase difference of 90 ° with respect to the first signal. And a tracking error that uniquely corresponds to a position error of the optical head from a target track based on the first and second signals. Generating regardless signal to the magnitude of the position error, based on the generated tracking error signal, and outputs the optical head to said moving means generates a control signal to follow the target track.

The tracking error signal generating program of the present invention is arranged so as to face a recording medium, and an optical head for irradiating the recording medium with laser light and receiving reflected light of the laser light, and the optical head for recording Moving means for moving the track in the direction of the track pitch of the medium,
In a disk device having a tracking servo means for generating a control signal for causing the optical head to follow a target track and outputting the control signal to the moving means, a tracking error signal according to a position error of the optical head from the target track. Is a program for generating a track having a value according to the displacement from the center of the track of the optical head which is obtained based on the intensity distribution of the reflected light received by the optical head, and A step of capturing a first signal having a pitch-dependent periodicity and a second signal having a phase difference of 90 ° with respect to the first signal; and capturing the captured first and second signals Based on the first and second signals, the position error of the optical head from the target track is uniquely addressed. A tracking error signal generating step of the Tsu King error signal generating regardless of the magnitude of the position error, to execute an output step of outputting the generated the tracking error signal to said tracking servo means, said computer means.

In the present invention, the position error signal uniquely corresponding to the position error from the target track of the optical head is generated based on the first and second signals which are periodic signals. Therefore, even when the optical head straddles a track adjacent to the target track, the generated position error signal uniquely corresponds to the position error of the optical head, so that the optical head is set again to the target track. Can be followed.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a schematic configuration of a tracking servo system of a disk device according to an embodiment of the present invention. The disc device 1 shown in FIG. 1 includes an optical disc 2, a spindle motor 3 for rotating the optical disc 2, an optical pickup 4 arranged to face the optical disc 2, an actuator 5, a tracking error signal generation circuit 6, and an encoder unit 7. It has a tracking servo control unit 8, a driver 9 and a system controller 10. The disk device 1 shown in FIG.
In fact, in addition to the above components, the optical disc 2
Although well-known components such as a focus servo system, a spindle servo system, a sled servo system, and a signal processing system, which are necessary for reproducing, are provided, description of these configurations will be omitted.

The optical disk 2 has tracks concentrically or spirally at a predetermined pitch. The track pitch is, for example, about several hundred nm. Optical disc 2
On the track, lands and grooves, or pits, for example, are formed along the track. For example, the center of the land or the center of the pit coincides with the center of the track.

The spindle motor 3 is driven by a driver (not shown) to rotate the optical disk 2. The spindle motor 3 is controlled to a desired number of rotations by a control command from the system controller 10 via a driver (not shown).

The optical pickup 4 is, for example, a laser diode that outputs a laser beam L, an objective lens that focuses the laser beam L that is output from this laser diode as a spot on the optical disc 2, and a reflected beam of the laser beam from the optical disc 2. And a photodetector including a photodiode for receiving the reflected light and the like. This optical pickup 4
Are movably supported by a support mechanism (not shown) in a substantially radial direction of the optical disc 2, which is indicated by arrows A1 and A2 in FIG. 1, that is, in a track pitch direction of the optical disc 2.

The photodetector provided in the optical pickup 4 has two divided light receiving portions for detecting the position error signal of the tracking servo by the push-pull method, and photoelectrically converts the detected signal into an electric signal. Output 4s. The push-pull method uses the fact that the intensity distribution of the laser light reflected and diffracted by the optical disc 2 and incident on the objective lens again changes due to the relative position change of the spot of the laser light with respect to the track, This is a method of detecting a tracking error based on the difference between the outputs of the two light receiving portions of the above-mentioned photodetector arranged symmetrically with respect to.

The actuator 5 is an optical pickup 4
Is moved in a substantially radial direction of the optical disc 2. For the actuator 5, for example, a linear motor is used.

The tracking error signal generation circuit 6 receives the detection signal 4s of the photodetector of the optical pickup 4,
Based on this detection signal 4s, the tracking error signal E
And a pull-in signal P is generated. FIG. 2 shows a tracking error signal E generated by the tracking error signal generation circuit 6.
(FIG. 2A) and a graph showing an example of waveforms of a pull-in signal P (FIG. 2B). In FIG. 2, the horizontal axis represents the position of the optical pickup 4, and the vertical axis represents the amplitude of the tracking error signal E and the pull-in signal P. Further, Trc in FIG. 2 indicates the center position of each track. Figure 2
As can be seen from the above, the tracking error signal E is a sine wave having a value of zero at each track center Trc and having a track pitch Trp as one cycle. The tracking error signal E has a phase of π / 2 [r compared to the pull-in signal P.
ad], and the pull-in signal P is a cosine wave. The tracking error signal E is a specific example of the first signal of the present invention, and the pull-in signal P is a specific example of the second signal of the present invention.

The encoder section 7 uniquely corresponds to a position error from the target track of the optical pickup 4 based on the tracking error signal E and the pull-in signal P having the periodicity inputted from the tracking error signal generating circuit 6. The error signal F is generated. The position error signal F is a specific example of the tracking error signal of the present invention. A specific method of generating the position error signal F in the encoder unit 7 will be described later.

The tracking servo control section 8 is
A control signal 8s for causing the optical pickup 4 to follow the target track is generated based on the position error signal F output from the encoder unit 7, and is output to the driver 9. The driver 9 supplies the drive current corresponding to the control signal 8s input from the tracking servo control unit 8 to the actuator 5
Supply to.

The system controller 10 comprehensively controls the disk device 1. This system controller 1
0 indicates the information 10s of the target track on which the optical pickup 4 is to be positioned, and the tracking servo control unit 8
Output to.

FIG. 3 shows the encoder unit 7 and the tracking servo control unit 8 of the disk device 1 having the above-mentioned configuration.
It is a figure which shows an example of the hardware constitutions for comprising. In FIG. 3, the A / D converter 31 converts the tracking error signal E, which is an analog signal input from the tracking error signal generation circuit 6, into a digital signal at a predetermined sampling rate, and inputs the digital signal to the processor 33.

The A / D converter 32 converts the pull-in signal P, which is an analog signal input from the tracking error signal generation circuit 6, into a digital signal at a predetermined sampling rate and inputs the digital signal to the processor 33.

The ROM 34 stores a program for calculating the above-mentioned position error signal F and a program for calculating a control signal for tracking servo. The processor 33 executes the program stored in the ROM 34 and calculates the position error signal F and the control signal 8s. The RAM 35 temporarily stores the data input to the processor 33, and stores various data necessary for the processing in the processor 33 and the like.

The D / A converter 36 converts the control signal for tracking servo calculated by the processor 33 into an analog signal, and the driver 9 outputs the control signal 8s.
Output to.

Next, a specific method of generating the position error signal F in the encoder section 7 will be described. As described in FIG. 2, the tracking error signal E changes periodically according to the position of the optical pickup 4. Therefore, for example, when the amplitude of the tracking error signal E is zero, that is, when the optical pickup 4 is located at any of the track centers Trc, the optical pickup 4 can be detected only from the amplitude information of the tracking error signal E. It is not possible to uniquely determine which track 4 is located in the center. Therefore, if the optical pickup 4 moves from the target track over a plurality of tracks while performing the tracking servo of the optical pickup 4, it is not possible to return to the target track again with only the amplitude information of the tracking error signal E. In order to return the optical pickup 4 to the target track, the address information recorded on each track is required.

On the other hand, in the encoder section 7 according to the present embodiment, the position of the optical pickup 4 is uniquely read without reading the address information recorded on the optical disc 2 regardless of the position where the optical pickup 4 has moved. The position error signal F for specifying By performing tracking servo using this position error signal F, it is possible to return to the target track without using address information.
The principle of calculating the position error signal F will be described below.

First, at time t, when the optical pickup 4 is moving to a track separated from the target track by the relative track number n, the position of the optical pickup 4 from the center of the track separated by the relative track number n. Let the error be x (t). As described above, the tracking error signal E and the pull-in signal P each have an amplitude of 1
Can be expressed by the sine function and the cosine function having the position error x (t) as a variable, as shown in the following equations (1) and (2).

E (X) = sin (X) (1) P (X) = cos (X) (2)

Further, the position error of the optical pickup 4 from the target track can be expressed by x (t) + 2πn, where the track pitch Trp is 2π. As an initial condition, the position error x (t) at time t = 0 is x (0) = 0, and the relative track number n up to the track where the optical pickup 4 is located at time t = 0 is n =
When it is 0, the tracking error signal E (x) is 0 and the pull-in signal P (x) is 1 at time t = 0.

FIG. 4 shows a position error signal uniquely corresponding to a position error from the target track of the optical pickup 4 based on the tracking error signal E (x) and the pull-in signal P (x) expressed as described above. It is a conceptual diagram for demonstrating the generation principle of F. First, as shown in FIG.
Tracking error signal E (x) and pull-in signal P (x)
Based on the magnitude relation with
a, Rb, Rc and Rd.

The area Ra is an area in which P (X) has the maximum value among (E (X), P (X), -E (X), -P (X)). This area Ra
Is in the range of −π / 4 ≦ x <π / 4. The region Rb is
(E (X), P (X),-E (X),-P (X)) is the region where E (X) has the maximum value. This region Rb has π / 4 ≦ x <3π / 4
Is the range. The region Rc is (E (X), P (X),-E (X),-P (X))
Is the region where -P (X) has the maximum value. This region Rc is in the range of 3π / 4 ≦ x <5π / 4. Region R
d is the area where -E (X) has the maximum value in (E (X), P (X), -E (X), -P (X)). This region Rc is 5π / 4 ≦ x
It is in the range of <7π / 4.

In the regions Ra, Rb, Rc and Rd, in the vicinity where the amplitudes of the tracking error signal E (x) and the pull-in signal P (x) are zero, the amplitude is normalized to π, and in FIG. 4 (b). As shown by L _{1 to} L ₄ ,
Either P (x) or E (x) must have a region where the slope can be approximated by a linear function of 1 or -1. By utilizing this property, the error signal calculation function F for calculating the position error signal F as shown in the following equation (3)
(X) can be obtained. Error signal calculation function F
(X) changes in proportion to the position error x as shown in FIG.

F (X) = F ₁ (X) t ₁ (X) + F ₂ (X) t ₂ (X) + F ₃ (X) t ₃ (X) + F ₄ (X) t ₄ (X)… ( 3)

In the error signal calculation function F (x), the four element functions F ₁ (x) to F ₄ (x) are weighted t ₁ (x) to t ₄
Each of them is weighted by (x) and is superposed. Four element functions F ₁ (x) to F ₄
(X) corresponds to the linear functions L _{1 to} L ₄ shown in FIG. 4B and is defined by the following equations (4) to (7).

F ₁ (X) = 2πn + {3E (X) / (2 + P (X))} (4) F ₂ (X) = 2πn + {-3P (X) / (2 + E (X))} + π / 2 (5) F ₃ (X) = 2πn + {-3E (X) / (2 + P (X))} + π (6) F ₄ (X) = 2πn + {3P (X) / (2 + E (X)) } + 3π / 2 (7)

The relative track number n in the equations (4) to (7) increases by one when the position error x changes from the area Rd to the area Ra, and the position error x changes from the area Ra to the area Rd. Sometimes it decreases by one.

Also, the weighting function t ₁ (x) to
t ₄ (x) is, for example, as shown in FIG.
It is a rectangular function having a value of amplitude 1 corresponding to a, Rb, Rc and Rd.

When the tracking error signal E (x) and the pull-in signal P (x) are taken into the encoder unit 7 at an arbitrary time t, the position error signal F is calculated according to the equation (3). This position error signal F is input to the tracking servo control unit 8. Accordingly, the tracking servo control unit 8 calculates a control signal for causing the optical pickup 4 to follow the target track based on the position error signal F, and outputs this to the driver 9. As a result, the actuator 5 is driven and the optical pickup 4 follows the target track.

By the way, in this embodiment, as described above, the push-pull method is used to detect the tracking error signal E and the pull-in signal P. In this push-pull method, when the position of the objective lens provided in the optical pickup 4 changes, the position of the spot of the reflected light from the optical disc 2 moves on the photodetector, resulting in a tracking error signal. E and pull-in signal P
There may be a case where a DC offset occurs. When a DC offset occurs in the tracking error signal E and the pull-in signal P, when calculating the position error signal F by the function F (x), for example, as shown in the circle H in FIG. 6, each element function F ₁ ( There is a possibility that deviation occurs near the boundary between x) to F ₄ (x), and discontinuity occurs in the obtained position error signal F. When the position error signal F is discontinuous, the differential component of this position error signal F is the element function F ₁
There is a possibility that the tracking servo system may become unstable due to extreme fluctuations near the boundary between (x) and F ₄ (x).

In order to avoid the discontinuity of the position error signal F as described above, the weighting functions t ₁ (x) to t ₄ (x) used in the error signal calculation function F (x) are set to, for example, ,
It is preferable to use a weighting function as shown in the following equations (8) to (11).

T ₁ (X) = maximum value (minimum value (0.5, P (X) − | E (X) |), -0.5) +0.5 (8) t ₂ (X) = maximum value (minimum values (0.5, E (X) - | P (X) |), - 0.5) +0.5 ... (9) t 3 (X) = the maximum value (minimum value (0.5, -P (X) - | E ( X) |), -0.5) +0.5 ... (10) t ₄ (X) = maximum value (minimum value (0.5, -E (X)-| P (X) |), -0.5) +0.5 ... (11)

When the pull-in signal P (x) and the tracking error signal E (x) are given, the weighting function t ₁ (x) shown in the equation (8) is the pull-in signal P (x) and the tracking error signal E. The difference from the absolute value of (x) is compared with 0.5, and the smaller value is specified. Further, the smaller value is compared with -0.5 to specify the larger value. The value obtained by adding 0.5 to this larger value is the weight. The pull-in signal P (x) and the tracking error signal E (x) are normalized to 1. Formulas (9) to (1
The weighting functions t ₂ (x) to t ₃ (x) shown in 1) are also subjected to the same procedure as the pull-in signal P (x) and the tracking error signal E.
Determine the weight given (x).

FIG. 7 is a graph showing the relationship between the weighting functions t ₁ (x) to t ₄ (x) shown in the equations (8) to (11) and the regions Ra to Rd. As can be seen from FIG. 7, each of the weighting functions t ₁ (x) to t ₄ (x) has a trapezoidal shape, and the value changes like a linear function at the boundary between the regions Ra to Rd.

FIG. 8 is a graph showing the result of calculating the position error signal F using the weighting functions t ₁ (x) to t ₄ (x) shown in the equations (8) to (11). As can be seen from FIG. 8, the boundaries of the element functions F ₁ (x) to F ₄ (x) are smoothed, and it can be seen that discontinuity does not occur.

Next, a program for calculating the position error signal F in the encoder section 7 will be described. Note that this program is stored in the ROM 34 and is executed by the processor 33. FIG. 9 is a flowchart of a program for calculating the position error signal F. As shown in FIG. 9, when the tracking servo is started, various variables for calculating the position error signal F are first initialized (step S1). In particular,
The track on which the optical pickup 4 is located is set as a target track, and the relative track number n for counting the deviation from the target track is initialized to zero. Further, the position error signal F is initialized to zero.

Next, the tracking error signal E and the pull-in signal P are fetched into the processor 33 through the A / D converters 31 and 32, respectively (step S2). The tracking error signal E and the pull-in signal P fetched by the processor 33 are stored in the RAM 35.

Then, the tracking error signal E and the pull-in signal P thus fetched are normalized to 1 (step S3). Based on the magnitude relation between the normalized tracking error signal E and the pull-in signal P, it is uniquely specified which of the above-mentioned regions Ra to Rd the current position of the optical pickup 4 is.

Then, the weighting functions t ₁ (x) to t ₄ (x)
Is calculated based on equations (8) to (11). Figure 10
FIG. 6 is a flowchart for explaining a calculation procedure of the weight function t ₁ (x). Note that here, the weighting function t ₁
Only the calculation procedure of (x) will be described, and the weighting function t
The calculation procedure of ₂ (x) to t ₄ (x) is the weighting function t ₁ (x)
The description is omitted because it is performed according to the calculation procedure of.

As shown in FIG. 10, first, the normalized tracking error signal E (x) and pull-in signal P are obtained.
The absolute value | E (x) | is obtained from (x) and P (x)-
Calculate | E (x) |. And P (x)-| E
It compares which of (x) | and 0.5 is smaller (step S41). If 0.5 is smaller, the weighting function t ₁ (x) becomes 0.5 + 0.5 = 1, and the weighting becomes the maximum value 1 (step S42). On the contrary, if 0.5 is larger, it is compared which of P (x)-| E (x) | and -0.5 is larger (step S43). As a result of comparison, when −0.5 is larger, the weighting function t ₁
(X) becomes 0.5-0.5 = 0, and the weight becomes the minimum value 0 (step S44). As a result of comparison, P (x)-|
If E (x) | is larger, the weighting function t ₁
(X) is 0.5 + P (x) - | E (x) | , and the weighting function t ₁ (x) takes any value from 0 to 1 (step S45). The weighting function t ₁
Calculate (x).

The weighting function t _{1 is} calculated by the above calculation procedure.
When (x) to t ₄ (x) are calculated, each weighting function becomes a trapezoidal function with an amplitude of 1, as shown in FIG. 7. Since the hypotenuse of this trapezoid overlaps with other weighting functions, the discontinuity caused by the offset of the input wave is smoothed when the position error signal F is calculated. After the calculation of the weighting functions t ₁ (x) to t ₄ (x) is completed, the process returns to step S5.

Next, the relative track number n is calculated (step S5). FIG. 11 is a flowchart for explaining the calculation procedure of the relative track number n. The number of tracks n is an integer, and as described above, the value of n changes when the optical pickup 4 moves from the area Ra to the area Rd or from the area Rd to the area Ra. From this, first, it is determined whether the optical pickup 4 is located in the area Ra at the current time t (step S51). Whether the optical pickup 4 is present in the area Ra is determined based on the magnitude relationship between the tracking error signal E (x) and the pull-in signal P (x) as described above.

If it exists in the area Ra, it is judged whether or not the optical pickup 4 is located in the area Rd at the time (t-1) one sampling time before (step S5).
2). Whether the optical pickup 4 is located in the region Rd one sampling time before is determined by the tracking error signal E (x) and the pull-in signal P (x) one sampling time before.
Based on the size relationship with. When the optical pickup 4 is located in the area Rd one sampling time before, it is determined that the optical pickup 4 has moved to the track on the outer side of one round, and 1 is added to the relative track number n (step S53).

In step S51, if the optical pickup 4 is not located in the area Ra at the current time t, it is determined whether the optical pickup 4 is located in the area Rd at the current time t (step S54). . Region Rd
If it is located at, go to step S55.

When the optical pickup 4 is located in the region Rd at the current time t in step S54, and when the optical pickup 4 is not located in the region Rd one sampling time before in step S52. Determines whether the optical pickup 4 was located in the area Ra one sampling time ago (step S5).
5). If the optical pickup 4 is located in the area Ra one sampling time before, it is determined that the optical pickup 4 has moved to the track inward by one round, and 1 is subtracted from the relative track number n (step S56).

In step S54, if the optical pickup 4 is not located in the area Rd at the current time t, and if it is not located in the area Ra one sampling time before in step 55, the optical pickup is selected. 4 does not change over the tracks and does not change the relative track number n (step S5).
7).

After calculating the relative track number n in the above procedure, the element functions F ₁ (x) to F ₄ (x) are calculated based on the equations (4) to (7) (steps). S
6). Furthermore, the calculated element functions F ₁ (x) to F ₄
Using (x) and the weighting functions t ₁ (x) to t ₄ (x), the error signal calculation function F (x) is calculated based on the equation (3) (step S7). As a result, the position error signal F is calculated.

Then, the calculated position error signal F is output to the tracking servo control unit 8 (step S
8). After outputting the position error signal F, the processes of steps S1 to S8 are performed again.

As described above, in the present embodiment, the position error from the target track of the optical pickup 4 is uniquely corresponded to based on the tracking error signal E (x) and the pull-in signal P (x) having the periodicity. The position error signal F having linearity can be calculated regardless of the magnitude of the position error. For example, when the tracking error signal E (x) having the periodicity depending on the track pitch is directly used to perform the tracking servo, when the position error of the optical pickup 4 from the target track becomes larger than the track pitch, the tracking is performed. Error signal E (x)
It is not possible to uniquely specify the position error from only this. Therefore, when the optical pickup 4 deviates from the target track and straddles an adjacent track due to eccentricity or vibration, the tracking servo is turned off, and then the optical pickup 4 is moved to the vicinity of the target track based on the address information. It is necessary to apply the tracking servo again and pull in the target track. However, in the present embodiment, even if the optical pickup 4 deviates from the target track and crosses an adjacent track due to eccentricity or vibration, the position error signal F is calculated. Can be quickly returned to the target track, and high-speed tracking becomes possible.

[0067]

According to the present invention, the address information recorded on the optical disc can be recorded even if the optical pickup crosses over a plurality of tracks due to an increase in the positional error between the optical pickup and the target track. The optical pickup can be made to follow the target track without using it. As a result, after the optical pickup deviates from the target track and straddles a plurality of tracks, the optical pickup can be returned to the target track at high speed.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic configuration of a tracking servo system of a disk device according to an embodiment of the present invention.

FIG. 2 is a graph showing an example of waveforms of a tracking error signal E (FIG. 2A) and a pull-in signal P (FIG. 2B) generated by a tracking error signal generation circuit 6.

3 is a diagram showing an example of a hardware configuration for configuring an encoder unit 7 and a tracking servo control unit 8 of the disk device 1. FIG.

FIG. 4 is a conceptual diagram for explaining a generation principle of a position error signal F.

FIG. 5 is a graph showing an example of waveforms of weighting functions t ₁ (x) to t ₄ (x).

FIG. 6 is a tracking error signal E and a pull-in signal P.
It is a figure for demonstrating the influence when a DC offset generate | occur | produces in FIG.

FIG. 7 is a weighting function t for smoothing the position error signal F.
Is a graph showing ₁ (x) ~t ₄ (x) the relationship between the region Ra to Rd.

FIG. 8 is a graph showing a result of calculating a position error signal F using smoothing weighting functions t ₁ (x) to t ₄ (x).

FIG. 9 is a flowchart of a program for calculating a position error signal F.

FIG. 10 is a flowchart for explaining a calculation procedure of a weight function t ₁ (x).

FIG. 11 is a flowchart for explaining a calculation procedure of a relative track number n.

FIG. 12 is a configuration diagram showing an example of a tracking servo system of a disk device.

FIG. 13 is a graph showing an example of the waveform of the tracking error signal TE obtained by the push-pull method.

FIG. 14 is a diagram for explaining an example of the locus of the optical pickup when the optical disc has eccentricity.

FIG. 15 is a tracking error signal T when the optical pickup 203 moves on the locus K as shown in FIG.
It is a graph which shows an example of E.

[Explanation of symbols]

1 ... Disk device, 2 ... Optical disk, 3 ... Spindle motor, 4 ... Optical pickup, 5 ... Actuator, 6
... tracking error signal generation circuit, 7 ... encoder section,
8 ... Tracking servo control section, 9 ... Driver, 10 ... System controller.

Claims (18)

[Claims] 1. An optical head, which is arranged so as to face a recording medium, irradiates the recording medium with laser light, and receives reflected light of the laser light; and the optical head in the direction of the track pitch of tracks of the recording medium. Based on the moving means for moving and the intensity distribution of the reflected light received by the optical head, the optical head has a value according to the displacement from the center of the track which the optical head faces, and has a periodicity depending on the track pitch. First error signal generating means for generating a first signal and a second signal having a phase difference of 90 ° with respect to the first signal; and the optical signal based on the first and second signals. Second error signal generating means for generating a tracking error signal having linearity uniquely corresponding to a position error from a target track of the head, regardless of the magnitude of the position error; Based on the tracking error signal generated by the error signal generating means generates the control signal to follow the optical head to the target track, the disk device having a tracking servo means for outputting to the moving means. 2. The second error signal generating means includes the first error signal generating means.
2. The disk according to claim 1, wherein the tracking error signal is calculated by using an error signal calculation function capable of approximating a signal having linearity from a signal having periodicity with the second signal as a variable. apparatus. 3. The disk device according to claim 2, wherein the first signal and the second signal are represented by a sine function and a cosine function having a displacement of the optical head from the center of the track as a variable. 4. The error signal calculation function is respectively associated with a plurality of regions divided between the adjacent tracks on the basis of the magnitude relation between the sine function and the cosine function, and the first and second regions. And a plurality of element functions capable of approximately calculating a signal having a linearity and having a signal of a variable, and a weight determined based on a magnitude relation between the values of the first and second signals, and each element 4. The disk device according to claim 3, further comprising a plurality of weighting functions for weighting each function, and calculating the tracking error signal by adding the respective weighting functions weighted by the respective element functions. 5. The weighting function according to claim 4, wherein the plurality of weighting functions weight the plurality of weighting functions so that discontinuity does not occur in the position error signal continuously calculated by the error signal calculating function. Disk device. 6. A relative track number calculating means for calculating a relative track number from the target track to a track opposite to the optical head based on the magnitude relation between the values of the first and second signals. 3. The disk device according to claim 2, wherein the error signal calculation function calculates the tracking error signal by using the relative track number and the first and second signals as variables. 7. An optical head, which is arranged so as to face a recording medium, irradiates the recording medium with laser light and receives reflected light of the laser light, and the optical head in the direction of the track pitch of the track of the recording medium. In a disk device having a moving means for moving, a tracking method for causing the optical head to follow a target track, the center of the track being opposed by the optical head based on an intensity distribution of reflected light received by the optical head. Generating a first signal having a value according to the displacement from and having a periodicity depending on the track pitch, and a second signal having a phase difference of 90 ° with respect to the first signal, Based on the first and second signals, the tracking error signal uniquely corresponding to the position error from the target track of the optical head is set to the magnitude of the position error. A tracking method of generating a control signal that causes the optical head to follow the target track based on the generated tracking error signal and outputs the control signal to the moving unit. 8. A variable having the first and second signals,
The tracking method according to claim 7, wherein the tracking error signal is calculated using an error signal calculation function capable of approximately calculating a signal having linearity from a signal having periodicity. 9. The tracking method according to claim 8, wherein the first signal and the second signal are represented by a sine function and a cosine function having a displacement of the optical head from the center of the track as a variable. 10. The error signal calculating function is respectively associated with a plurality of regions divided between the adjacent tracks based on the magnitude relationship between the sine function and the cosine function, and the first and second regions are respectively associated with each other. A plurality of element functions capable of approximating a signal having linearity and a signal having a variable and a weight determined based on a magnitude relationship between the values of the first and second signals, and each element The tracking method according to claim 9, further comprising a plurality of weighting functions for weighting each function, and calculating the tracking error signal by adding the respective weighting functions weighted by the respective element functions. 11. The tracking method according to claim 10, wherein weighting is performed by the plurality of weighting functions so that discontinuity does not occur in the tracking error signal continuously calculated by the error signal calculating function. 12. A relative track number from the target track to a track opposite to the optical head is calculated based on the magnitude relation between the values of the first and second signals, and the relative track number and the first track are calculated. The tracking method according to claim 8, wherein the tracking error signal is calculated by using the first and second signals as variables. 13. An optical head, which is arranged so as to face a recording medium, irradiates the recording medium with laser light and receives reflected light of the laser light, and the optical head in the direction of the track pitch of tracks of the recording medium. Moving means to move,
In a disk device having a tracking servo means for generating a control signal for causing the optical head to follow a target track and outputting the control signal to the moving means, a tracking error signal according to a position error of the optical head from the target track. Which is a program for generating a value obtained according to the intensity distribution of the reflected light received by the optical head, the value having a value corresponding to the displacement from the center of the tracks of the optical head facing each other, and A capturing step of capturing a first signal having a pitch-dependent periodicity and a second signal having a phase difference of 90 ° with respect to the first signal; and the capturing of the first and second signals. Based on the first and second signals, the position error of the optical head from the target track is uniquely addressed. A tracking error signal for causing the computer means to perform a tracking error signal generating step for generating a racking error signal regardless of the magnitude of the position error and an output step for outputting the generated tracking error signal to the tracking servo means. Program for generating. 14. The tracking error signal generating step has an error signal calculation function capable of approximately calculating a signal having linearity from a signal having periodicity, using the first and second signals as variables. The program for generating a tracking error signal according to claim 13, wherein the tracking error signal is calculated using the program. 15. The tracking error signal according to claim 14, wherein the first signal and the second signal are represented by a sine function and a cosine function having a position of the optical head in the track pitch direction as a variable. Program for generating. 16. The error signal calculating function is respectively associated with a plurality of regions divided between the adjacent tracks based on the magnitude relation between the sine function and the cosine function, and the first and second regions are respectively associated with each other. A plurality of element functions capable of approximating a signal having linearity and a signal having a variable and a weight determined based on a magnitude relationship between the values of the first and second signals, and each element And a plurality of weighting functions for respectively weighting the function, each weighting function is weighted by each of the element functions,
16. The program for generating a tracking error signal according to claim 15, further causing the computer means to execute a calculation step of calculating the tracking error signal by adding them together. 17. The weighting function according to claim 16, wherein weighting is performed by the plurality of weighting functions so that discontinuity does not occur in the tracking error signal continuously calculated by the error signal calculating function by the plurality of weighting functions. A program for generating tracking error signals. 18. A step of calculating a relative track number from the target track to a track opposite to the optical head based on the magnitude relation between the values of the first and second signals, and the relative track number. 15. The computer means is caused to execute the step of calculating the tracking error signal using the first and second signals as variables.
A program for generating the tracking error signal described in.