JP2000311369A - Tilt correcting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a tilt correcting device capable of correcting the relative tilt between an information medium and a a head at a low cost. SOLUTION: In the tilt correcting device correcting the tilt between an information medium having a surface structure capable of generating an amplitude fluctuation in the difference signal of reflected lights and a head forming a light spot on the information medium, this device is provided with a photodetector 15 receiving lights reflected from the optical spot, means obtaining the difference signal of outputs of the photodetector 15 and tilt control means controlling the relative tilt between the information medium and the head so that an index approaches the extremun while using the amplitude of the obtained difference signal as the index.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for correcting a tilt (tilt) between an information medium and a head for emitting a light beam.

[0002]

2. Description of the Related Art In recent years, a medium for storing a larger amount of information, such as image information and video information, than conventional character information or audio information has been demanded. I have. In conventional recordable optical discs, guide grooves are formed in advance at the time of disc manufacture in order to control a recording / reproducing light beam around a track.
By the guide grooves, the convex (land) portion and the concave (groove) portion of the disk are formed spirally or concentrically. By using both the convex portions and the concave portions as recording tracks (land tracks and groove tracks), twice as much information can be recorded as in the case where either one is used as a recording track. Further, in order to improve data access performance, tracks (groove tracks) of grooves (grooves, concave portions) and tracks (land tracks) of inter-groove portions (lands, convex portions) are formed on the disk 1.
There is a method in which the recording tracks are alternately connected once in each circumference and are configured with one recording spiral (spiral (spiral) recording track). This method is called a single spiral land groove (SS L / G) recording format, and an example of a disk device using this is disclosed in Japanese Patent Application Laid-Open No. Hei 9-282669.

According to the conventional disk format, a recording track is divided into sectors in the track direction, and at the beginning of each sector, sector identification information such as a track number and a sector number has a physical shape change or a local optical constant. It is preformatted as a pit that creates a change. Further, in the sector format, the sector identification information is arranged with a predetermined distance displaced radially outward with respect to the center of the recording track and on the inner periphery with the predetermined distance displaced. A second identification information area, and a user information area in which user information and the like are recorded on the center line of the recording track following the sector identification information area.

Next, a description will be given of a disk device using an optical disk on which sector identification information is arranged as described above. FIG. 15 is a diagram showing a track layout of a conventional optical disc. FIG. 16 is a block diagram showing the configuration of a disk device for recording or reproducing information on or from such an optical disk.

FIG. 15 shows the track layout of a conventional optical disk, showing the arrangement of tracks and recording sectors in one zone and the configuration of recording sectors. As shown in the drawing, it is assumed that the width of the groove portion is equal to the width of the inter-groove portion in the SSL / G recording format. That is, the groove width and the width between the grooves are equal to the track pitch, and are set to の of the groove interval.

[0006] One recording track (one round of the disk) is composed of an integer number of recording sectors, and at the beginning of each sector, sector identification information indicating PLL pull-in information, address information, and the like is pre-recorded. A formatted sector identification information area (sector identification signal section) is added, and a user information area (information recording section) in which user data and various management information can be recorded is arranged following the sector identification signal section.

Further, the sector identification information area consists of two parts, a front part and a rear part, as viewed in the scanning direction, and the sector identification information is a predetermined distance radially outward (or inner) with respect to the track center. It is composed of a first identification information area displaced and arranged and a second identification information area arranged displaced on the inner peripheral side (or outer peripheral side) by the same distance as the predetermined distance.

Further, track offset correction will be described as one of the other functions and effects.
Optical disc standard ISO / IEC 9171.1, 2 "1
30mm Optical Disk Cartridge
Ge Write Once Forform Information
As described in “Inter Interchange”, 1990., etc., in a sample servo optical disk, a track offset detection pit pair is provided at a position displaced left and right by a fixed amount from the track center on a recording track, and a tracking offset is provided. Methods for detecting and correcting amounts are known.

When the light beam passes through the middle of the track offset detection pit pair, the reproduced signal amplitude of the detection pit pair becomes equal. If the track is off-track to one side, the reproduction signal amplitude of the pit on one side increases and the reproduction signal amplitude of the pit on the other side decreases, so that the amount of track offset of the light beam is detected and corrected. , So that the light beam passes through the center of the track. The same principle and effect can be incorporated in the conventional SS L / G recording format.

Now, the light beam is shifted from the user information area (user signal area) in the specific groove recording sector to the sector identification information area (sector identification signal area) of the next groove recording sector.
Suppose you enter. Since the head of the sector identification information area is shifted by 1/2 of the groove width to the inner circumference of the disk, a tracking error signal corresponding to the shift is output. After a while, there is an identification signal portion shifted by １ ／ of the groove width on the outer periphery of the disk, and a tracking error signal corresponding to the identification signal portion is output. Ideally, if these two error signals are detected as waveforms that are vertically symmetrical with respect to a reference level (= tracking error level at the time of running at the center of the track), it means that the center of the track is scanned. Therefore, by comparing the magnitude of the tracking error signal detected from the identification signal portion which is arranged to be shifted between the inner circumference and the outer circumference, it becomes possible to control the servo around the track center. Here, the arrangement order of the first identification information area and the second identification information area is switched depending on whether the track is a land track or a groove track. That is, the first identification information area in the land track,
If they are arranged in the order of the second identification information area, the reverse is true in the groove track.

According to the method of assigning the identification signal to the SSL / G recording disk, it is possible to simultaneously improve the servo characteristics.

Next, the configuration of a conventional disk drive for reproducing such a disk will be described with reference to FIG. In the figure, 10 is an optical disk, 11 is a semiconductor laser (LD) as a light source, 12 is a collimating lens, 1
3 is a beam splitter, 14 is an objective lens, 15 is a photodetector, 16 is an actuator, 17 is a differential amplifier, 18
Is a difference signal waveform shaping section, 19 is a reproduction difference signal processing section, 20 is a polarity control section, 21 is a polarity inversion section, 22 is a tracking control section, 23 is an addition amplifier, 24 is a sum signal waveform shaping section, 2
5 is a reproduction signal processing unit, 26 is a polarity information reproduction unit, 27 is an address reproduction unit, 28 is an information reproduction unit, 29 is a system control unit, 30 is a traverse control unit, 31 is a traverse motor, 32 is a recording signal processing unit, 33 is a laser (L
D) The drive unit 34 is an actuator drive unit. The optical head includes a semiconductor laser 11, a collimator lens 12, a beam splitter 13, an objective lens 14, a photodetector 15, and an actuator 16, and is mounted on a head base (not shown).

The operation of the conventional disk drive configured as described above will be described with reference to the drawings. Semiconductor laser 1
The laser light output from 1 is collimated by a collimator lens 12 and condensed on an optical disk 10 by an objective lens 14 via a beam splitter 13. The laser light reflected by the optical disk 10 has information of a recording track, is separated from incident light by a beam splitter 13 via an objective lens 14, and is guided to a photodetector 15. The photodetector 15 includes two light receiving units divided into two in a direction extending along the track direction of the disk in the far field of the reflected light in order to obtain a push-pull signal, and two I / V conversion units corresponding to the light receiving units ( Current / voltage converter), which converts a change in the light amount distribution of the received light beam into an electric signal, and outputs the electric signal to the differential amplifier 17 and the addition amplifier 23, respectively.
Output to

The differential amplifier 17 generates a push-pull signal obtained by calculating a difference between the input signals, and outputs the signal to the difference signal waveform shaping section 18 and the polarity inverting section 21. The difference signal waveform shaping section 18 converts the analog waveform push-pull signal from the differential amplifier 17 into a digital value by slicing it at a predetermined level, and converts the binary difference signal into a reproduction difference signal processing section 19.
Output to The reproduction difference signal processing unit 19 extracts the identification signal from the binary difference signal, determines the tracking polarity, and converts the polarity detection signal into the polarity control unit 20, the polarity information reproduction unit 26, the address reproduction unit 27, and the information reproduction unit 28. , To the system control unit 29.

The polarity control unit 20 includes a reproduction difference signal processing unit 19
And a control signal from the system control unit 29, the polarity inversion unit 21 and the tracking control unit 2
2 outputs a polarity setting signal and a control hold signal. The polarity inverting unit 21 determines whether the track being accessed is a land or a groove based on a control signal from the polarity control unit 20, and inverts the output signal polarity of the differential amplifier 17 only for a land, for example, to perform tracking. The error signal is output to the tracking control unit 22 (in the case of a groove, the signal is output without being inverted). Tracking control unit 22
Outputs a tracking control signal to the actuator drive unit 34 in accordance with the level of the tracking error signal input from the polarity inversion unit 21,
Supplies a drive current to the actuator 16 in response to this signal, and controls the position of the objective lens 14 in a direction crossing the recording track. Thus, the light spot scans the track correctly.

On the other hand, the addition amplifier 23 adds the output signals of the photodetector 15 and outputs the result to the sum signal waveform shaping section 24 as a sum signal. The sum signal waveform shaping unit 24 slices the data signal and the address signal of the analog waveform by a predetermined threshold value to form a pulse waveform, and outputs the pulse waveform to the reproduction signal processing unit 25. The reproduction signal processing unit 25 reproduces an identification signal including address information and polarity information from a binary sum signal obtained by performing waveform processing on the sum signal. The polarity information reproducing unit 26 extracts polarity information indicating the tracking polarity of the sector from the identification signal. The address reproducing unit 27 reproduces sector address information from the identification signal. The information reproducing unit 28 demodulates / error-corrects the user information recorded in the user information area on the disc from the binarized sum signal, and outputs it as a reproduced signal.

The polarity information output from the polarity information reproducing unit 26 and the sector address information output from the address reproducing unit 27 are sent to the system control unit 29, and are used for controlling the tracking polarity and the sample-hold state of the tracking control. . In such a configuration, it is possible to sample and hold the tracking error signal immediately before the sector identification information area in order to cut off extra disturbance to the tracking servo system, and pass this area by inertia with the tracking control operation off. It is. The system control unit 29 receives information about the identification signal from the reproduction difference signal processing unit 19, the polarity information reproduction unit 26, and the address reproduction unit 27, and receives the polarity control unit 20, traverse control unit 30, L
A control signal is output to the D drive unit 33 and the recording signal processing unit 32.

The system control unit 29 determines whether or not the light beam is currently at a desired address based on information on the identification signal including the address and the like from the address reproducing unit 27. The traverse control unit 30 outputs a drive current to the traverse motor 31 in accordance with a control signal from the system control unit 29 when moving the optical head, and moves the optical head to a target track. At this time, the tracking control unit 22 temporarily suspends the tracking control operation according to the control signal from the system control unit 29. At the time of normal reproduction, the system control unit 29 drives the traverse motor 31 via the traverse control unit 30 in accordance with the tracking error signal input from the tracking control unit 22, and moves the optical head radially along the progress of reproduction. Move slowly in the direction.

The recording signal processing section 32 adds an error correction code or the like to the recording data input at the time of recording, and outputs it to the LD driving section 33 as an encoded recording signal. When the system control unit 29 sets the LD driving unit 33 to the recording mode by the control signal, the LD driving unit 33 modulates the driving current applied to the semiconductor laser 11 according to the recording signal. As a result, the intensity of the light spot irradiated on the optical disk 10 changes according to the recording signal, and recording pits are formed. On the other hand, at the time of reproduction, the LD drive unit 33 is set to the reproduction mode by a control signal from the system control unit 29, and controls the drive current so that the semiconductor laser 11 emits light at a constant intensity. This makes it possible to detect recording pits and pre-pits on the recording track.

[0020]

The conventional disk drive constructed as described above detects a tracking error by the push-pull method for an optical disk having a guide groove such as an SSL / G recording disk. Is common. However, in this method, even when the light beam is traveling at the center of the track, the detected tracking error signal is vertically asymmetric with respect to the reference level due to the relative tilt (tilt) between the disk and the head. Waveform (hereinafter
It is called an optical offset. ) Is known in principle. That is, a state equivalent to an electric offset superimposed on the tracking error signal according to the tilt is obtained. Further, causes of the optically generated offset include misalignment of the optical system and eccentricity of the lens.

If the optical offset is processed assuming that it is the same as the electrically generated offset, that is, if the offset that makes the optical offset zero is corrected by electrically superimposing it, the light beam is shifted to the center of the track. (Detrack state), and the reliability of signal detection is reduced. In particular,
Signal quality degradation (reduction in S / N) is caused by cross-erasure of adjacent tracks during recording or remaining unerased by overwriting, or crosstalk from adjacent tracks during reproduction. Furthermore, the tilt causes optical aberrations, which leads to deterioration of the quality of the reproduced signal. This problem,
This may be detrimental to narrowing the track pitch, which is one means for improving the recording density.

The conventional disk drive utilizes the fact that the sector identification information is arranged in a zigzag manner at a predetermined distance from the center of the track to the outer circumference side and the inner circumference side in the disk format (described in FIG. 15). Thus, a method for correcting detrack is disclosed. In this method, the absolute value difference between the tracking error signal at the time of reproducing the first identification information area and the reference level (the level of the tracking error signal at the time of track center traveling) and the tracking error signal at the time of reproducing the second identification information area. The detrack is corrected so that the difference between the absolute value and the reference level becomes substantially the same. This method can be an effective method when there is only one detrack generation cause.

However, in an actual device, other factors that cause the tracking error signal to be vertically asymmetrical include an offset of an electric circuit (hereinafter, referred to as an electrical offset to distinguish it from the optical offset), an optical system, or an electric system. There is a shift in the gain balance of the circuit. These can be regarded as offsets superimposed on the tracking error signal if interpreted in a broad sense, but this offset cannot be removed by the above method.

For this reason, in the conventional disk device, it was difficult to perform optimal tilt correction and detrack correction only by reflected light from the disk. Therefore, a method has been adopted in which an optical tilt detection mechanism is separately arranged on the optical head, and tilt is corrected using this mechanism. However, in this method, only the tilt can be corrected independently, but on the other hand, it is necessary to newly add an optical tilt detecting mechanism, and there is a problem that the cost of the apparatus is inevitably increased.

Another method of correcting tilt without using an optical tilt detection mechanism is to combine a conventional detrack index with other indexes such as a reproduction signal jitter and a reproduction error rate. Something to use is also conceivable.

However, in this method, since the jitter and the error rate change depending on both the tilt and the detrack, it is necessary to perform a run-in operation based on repetitive control using a plurality of parameters. There are problems such that the track correction cannot be converged or the convergence time becomes long.

Further, a method of adopting a new signal processing method and corresponding thereto is also being studied. In other words, even if the quality of the signal reproduced from the disc is poor, a signal is detected with a detection error within a predetermined range. This is a maximum likelihood detection method such as Viterbi detection. However, also in this method, it is necessary to add a new configuration to the conventional signal detection system, so that an increase in the cost of the apparatus is inevitable.

The present invention has been made in order to solve such a problem, suppresses an increase in the cost of the apparatus, and can perform a tilt correction that is strong against an electrical offset and an optical offset. It is an object of the present invention to obtain a tilt correction device that can perform only tilt correction independently without receiving the tilt correction.

[0029]

SUMMARY OF THE INVENTION A tilt correction apparatus according to the present invention is provided between an information medium having a surface structure capable of causing amplitude fluctuation in a difference signal of reflected light and a head for forming a light spot on the information medium. In a device for correcting the inclination of, a light detector for receiving the light reflected by the light spot, a means for obtaining a difference signal of the output of the light detector, the amplitude of the obtained difference signal as an index, the index And a tilt control means for controlling a relative tilt between the information medium and the head so that the value approaches an extreme value.

Further, according to the tilt correcting apparatus of the present invention, the information medium is a disk on which information tracks are formed in a spiral or concentric shape, and the tilt control means controls the light spot on the disk. The relative inclination between the disk and the head is controlled such that the index approaches an extreme value, using the amplitude of the difference signal of the photodetector when crossing the information track as an index.

According to the tilt correcting apparatus of the present invention, the information medium is a disk in which information tracks are arranged in a spiral or concentric manner, and the information tracks are formed in a meandering manner. The tilt control means uses the amplitude of the difference signal of the photodetector when the light spot on the disk traces the information track as an index, and sets the index between the disk and the head such that the index approaches an extreme value. It is characterized in that the relative inclination between them is controlled.

[0032]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 Hereinafter, the present invention will be specifically described with reference to the drawings showing the embodiments. However, blocks with the same numbers as those in the conventional example are basically the same as those in the disk device shown in FIG.

FIG. 1 is a diagram showing a disk device provided with a tilt correction device according to Embodiment 1 of the present invention. In the figure, reference numeral 10 denotes an optical disk, such as the one shown in FIG. 15 described in the related art, which has a surface capable of causing an amplitude variation in the differential output of the photodetector that has received the reflected light. It has a structure. 11 is a semiconductor laser (LD) as a light source, 12 is a collimating lens, 13 is a beam splitter, 14 is an objective lens, 15
Is a photodetector, 16 is an actuator, 17 is a differential amplifier, 18 is a difference signal waveform shaping section, 19 is a reproduction difference signal processing section, 20 is a polarity control section, 21 is a polarity inversion section, 22 is a tracking control section, 23 Is an addition amplifier, 25 is a reproduction signal processing unit, 26 is a polarity information reproduction unit, 27 is an address reproduction unit,
28 is an information reproducing unit, 30 is a traverse control unit, 31 is a traverse motor, 32 is a recording signal processing unit, 33 is an LD drive unit, and 34 is an actuator drive unit, which is the same as or equivalent to that described in the conventional example. It has a function. The optical head includes a semiconductor laser 11, a collimating lens 12, a beam splitter 13, an objective lens 14,
It includes a photodetector 15 and an actuator 16 and is attached to a head base (not shown). Further, 100 is a first waveform shaping unit, 101 is a system control unit, 1
02 is a tilt control unit, and 103 is a second waveform shaping unit.

The operation of playing back an optical disk with the disk device configured as described above will be described with reference to FIGS. FIG. 2 shows a push-pull signal in a state where the operation is performed up to the focus control, that is, in a state where the light spot is focused on the disk and the tracking control is not operated. The push-pull signal is a signal indicating a difference between the light spot position and the center position of the land portion or the groove portion, that is, a tracking error. Each position)
, It becomes zero, and takes an extreme value (maximum value or minimum value) at the boundary between the land portion and the groove portion (each position of B and D in the figure). FIG. 3 shows waveforms at various points in FIG. 1 in a state where the operation is performed up to the tracking control.

When the apparatus is started, the system control unit 101 rotates the disk at a predetermined rotation speed via a disk rotation control unit (not shown). Next, the LD drive unit 33 is set to the reproduction mode by a control signal from the system control unit 101, and controls the drive current so that the semiconductor laser 11 emits light at a constant intensity. The laser light output from the semiconductor laser 11 is collimated by a collimator lens 12, passes through a beam splitter 13, and is condensed as a light spot on an optical disk 10 by an objective lens 14. With respect to the fluctuation of the distance between the head and the disk caused by the surface deviation or the like, a focus control unit (not shown) controls the objective lens 14 based on a focus error signal generated from the output of the photodetector, so that the laser beam is always emitted. The device has the function of focusing light on the disk. The laser beam reflected by the optical disk 10 has information of a recording track, and is guided to a photodetector 15 by a beam splitter 13 via an objective lens 14. Photodetector 15
Are two light receiving sections divided into two in the direction of track extension of the disk in the far field of the reflected light to obtain a push-pull signal, and two I / Vs corresponding to the light receiving sections.
A conversion unit converts the light quantity distribution change of the received light beam into an electric signal, and outputs the electric signal to the differential amplifier 17 and the addition amplifier 23, respectively.

The differential amplifier 17 generates a push-pull signal shown in FIG. 2 and FIG. 3A by taking the difference between the respective input signals, and generates a difference signal waveform shaping section 18, a polarity inverting section 21 and a 2 is output to the second waveform shaping unit 103. The tracking control unit 22, which will be described later, controls the objective lens 14 via the actuator driving unit 34 and the actuator 16 so that the push-pull signal becomes zero, and controls the position so that the light spot always runs on the track center.
FIG. 3 shows waveforms at various points in FIG. 1 in a state where the operation is performed up to the tracking control.

When tracking is performed, the difference signal waveform shaping section 18 converts the analog waveform push-pull signal from the differential amplifier 17 into two appropriate levels (TH) shown in FIG.
1, (TH2), and is converted into digital values shown in FIGS. 3 (c) and 3 (d), and this binarized difference signal is output to the reproduction difference signal processing unit 19. Here, the waveform (c) is the first waveform.
The waveform (d) shows the position of the second identification information area. The reproduction difference signal processing unit 19
The tracking polarity is determined based on the appearance timing of the digitized difference signals (c) and (d), and the polarity detection signal is output to the polarity control unit 20.
It outputs to the polarity information reproducing unit 26, the address reproducing unit 27, the information reproducing unit 28, and the system control unit 101. Further, the reproduction difference signal processing unit 19 also outputs the digital values shown in FIGS. 3C and 3D to the system control unit 101.

The polarity control unit 20 includes a reproduction difference signal processing unit 19
And a control signal from the system control unit 101, and outputs a polarity setting signal to the polarity inversion unit 21 and a control hold signal for defect countermeasures to the tracking control unit 22. The polarity inverting unit 21 inverts the polarity of the output signal of the differential amplifier 17 only when the track being accessed is a land, for example, in accordance with the polarity setting signal from the polarity control unit 20, and generates a tracking error signal as a tracking error signal. (When the track being accessed is a groove, the polarity of the output signal of the differential amplifier 17 is not inverted). The tracking control unit 22 outputs a tracking control signal to the actuator driving unit 34 according to the level of the tracking error signal input from the polarity reversing unit 21, and the actuator driving unit 34 supplies a driving current to the actuator 16 according to the signal. And the position of the objective lens 14 is controlled in a direction crossing the recording track. Thus, the light spot scans the track while being track-controlled.

On the other hand, the addition amplifier 23 adds the output signals of the photodetector 15 and outputs the sum signal shown in FIG. The first waveform shaping unit 100
As will be described in detail later, after performing predetermined processing on the sum signal of the analog waveform, data slice is performed at a predetermined threshold to generate a pulse waveform shown in FIG. Output to The reproduction signal processing unit 25 reproduces an identification signal including address information and polarity information from the input signal.

The polarity information reproducing section 26 extracts polarity information indicating the tracking polarity of the sector from the identification signal. The address reproducing unit 27 reproduces sector address information from the identification signal. The information reproducing unit 28 demodulates and error-corrects the user information recorded in the user information area of the disc,
Output as a reproduction information signal. Error correction information (for example,
The data error rate can be obtained by analyzing the number of corrections) and jitter. In general, the system control unit 101 appropriately reads the error correction information stored in the information reproducing unit 28, and calculates the data error rate by using a calculation process or a lookup table.

The polarity information output from the polarity information reproducing unit 26 and the sector address information output from the address reproducing unit 27 are sent to the system control unit 101 and used for controlling the tracking polarity and the sample-hold state of the tracking control. . In such a configuration, it is possible to sample and hold the tracking error signal immediately before the sector identification information area in order to cut off extra disturbance to the tracking servo system, and pass this area by inertia with the tracking control operation off. It is. The system control unit 101 receives information related to the identification signal from the reproduction difference signal processing unit 19, the polarity information reproduction unit 26, and the address reproduction unit 27, and receives the polarity control unit 20, the traverse control unit 3.
0, and outputs a control signal to the LD drive unit 33 and the recording signal processing unit 32.

The system control section 101 determines whether or not the light beam is present at a desired address based on information on the identification signal including the address and the like from the address reproducing section 27. The traverse control unit 30 outputs a drive current to the traverse motor 31 according to a control signal from the system control unit 101 when the optical head is moved,
Move the optical head to the target track. At this time, the tracking control section 22
The tracking control operation is temporarily interrupted by the control signal from. At the time of normal reproduction, the system control unit 101 drives the traverse motor 31 via the traverse control unit 30 in accordance with the tracking error signal input from the tracking control unit 22, and moves the optical head radially along the progress of reproduction. Move slowly in the direction.

The recording signal processing section 32 adds an error correction code or the like to the recording data input at the time of recording, and outputs it to the LD driving section 33 as an encoded recording signal. When the system control unit 101 sets the LD driving unit 33 to the recording mode by a control signal, the LD driving unit 33 modulates a driving current applied to the semiconductor laser 11 according to the recording signal. As a result, the intensity of the light spot irradiated on the optical disk 10 changes according to the recording signal, and recording pits are formed. On the other hand, at the time of reproduction, the LD drive unit 33 is set to the reproduction mode by a control signal from the system control unit 101, and controls the drive current so that the semiconductor laser 11 emits light at a constant intensity. This makes it possible to detect recording pits and pre-pits on the recording track.

The configuration and operation of the first waveform shaping section 100 will be described with reference to FIG. In the figure, 200 is the first A
TT (Attenuator), 201 is a DC control unit, 202 is an AGC (Auto Gain Control) unit, 2
03 is a waveform equalizer, 204 is a signal slicing means, 205
Denotes a first signal amplitude detector.

FIG. 3 (h) input from the addition amplifier 23.
The reproduction level of the sum signal shown in (1) is adjusted by the first ATT 200 with a predetermined gain. The gain of the first ATT 200 is set by a control signal from the system control unit 101. That is, the system control unit 1
01 is configured to obtain the optimum setting gain of the first ATT 200 based on the amplitude information of the output signal of the first ATT 200. The gain set in the first ATT 200 is set to a value that can ensure the quality of the reproduced signal after the DC control unit 201.

The sum signal whose gain has been adjusted by the first ATT 200 is input to the DC control unit 201, and the DC signal
The waveform shown in FIG. 3J is obtained by removing the components.
The DC control unit 201 is for effectively utilizing the dynamic range of the subsequent AGC 202, and removes DC components unnecessary for data reproduction. However, a large sag occurs in the output of the DC control unit 201 in an area where the DC component changes rapidly or an area where signal continuity is lost, such as a boundary between the sector identification information area and the user information area. Therefore, FIG. 3 input from the system control unit 101
The boost control gate shown in (f) has a function of reducing the time constant for removing the DC component and following the DC fluctuation of the input signal in a short time. The boost control gate shown in FIG. 3C, in which the system control unit 101 is input from the reproduction difference signal processing unit 19,
FIG. 3 (d) shows the determination based on the start points of the first and second identification information areas indicated by the rising edges of the respective signals and the address signal (reproduced by the address reproduction unit 27) included in the sector identification information area. This is a pulse having a predetermined time width generated starting from the start / end point of the user information area indicated by the rising edge or the falling edge of the signal indicated by e). Further, in the case where the DC level fluctuates due to a defect or the like, the time lag until the data can be normally detected after the defect is completed can be shortened by outputting the boost control gate starting from the time when the defect area ends.

The output waveform (j) of the DC control unit 201 is A
The signal is finely adjusted to a predetermined signal amplitude by the GC unit 202. This A
The GC unit 202 configures a feedback control system that monitors the signal amplitude of the input signal and controls its gain so that the output signal level always has a predetermined amplitude. Therefore, it is also possible to extract the amplitude information of the input signal, that is, the output signal of the first ATT 200, from the AGC unit 202.

The output signal of the AGC unit 202 is binarized by the signal slicing unit 204 as shown in FIG. Are output to the reproduction signal processing unit 25.
The signal slicing unit 204 optimally controls the slice level so that the reproduction error is minimized. The signal slicing unit 204 has a boost function like the DC control unit 201, and the system control unit 101
, The time constant of the slice level control is reduced based on the boost control gate, and the change in the input signal is followed in a short time.

The first signal amplitude detecting section 205 has a first A
The signal amplitude of the output signal of the TT 200 is detected and output to the system control unit 101 (FIG. 3 (i)). The system control unit 101 processes this detection result and sets the gain of the first ATT 200.

In the above-described operation, since the tilt correction has not been performed, it may be assumed that the quality of the reproduced signal, that is, the reliability of the data after error correction cannot be tolerated. For this reason, when the reliability of the reproduced data is impaired immediately after the optical disk 10 is mounted or due to a change over time, it is necessary to correct the tilt in order to secure the operation margin of the apparatus and achieve high reliability of the data reproduction. Regarding the signal quality, the system control unit 101 captures the jitter of the reproduced signal binarized by the signal slicing unit 204 and the number of error corrections (data error rate) obtained as a processing result of the information reproducing unit 28 at the subsequent stage, and calculates or calculates The processing can be determined by referring to the lookup table.

In the present embodiment, FIG. 2 is used as an index (hereinafter, referred to as a first index) for judging the amount of tilt capable of eliminating the relative tilt between the optical disk and the optical head.
In the focus control state shown in (1), the amplitude is obtained from the amplitude (level difference between the maximum value and the minimum value) of the tracking error signal (push-pull signal) when crossing the track.

The envelope of the output signal of the differential amplifier 17 corresponds to the second waveform shaping unit 10 whose internal block diagram is shown in FIG.
3 is detected. In the figure, reference numeral 206 denotes a second ATT (attenuator), and 207 denotes a second signal amplitude detector. The input / output signals of the system control unit 101 are limited to those related to the second ATT 206 and the second signal amplitude detection unit 207. Next, the operation will be described.

The first index is detected by controlling the second ATT 206 by the system control unit 101 and adjusting the signal level so that the second signal amplitude detection unit 207 can detect the amplitude with high accuracy. Start from. In a state where the system control unit 101 operates up to the focus control, the system control unit 101 uses the signal amplitude detection signal output from the second signal amplitude detection unit 207 to extract the amplitude information of the tracking error signal when traversing the land and the groove from the system. ADC (Analog t) provided in the control unit
o Digital Converter), processes the data, and based on the processing result, outputs the second AT 206 to a signal level within a predetermined range.
It controls T206.

The second signal amplitude detector 207 outputs the second ATT2 after the output signal level is adjusted to be within a predetermined range.
From the output of 06, the amplitude information of the tracking error signal at the time of traversing the land and the groove is output to the system control unit 101. The system control unit 101
ADC (Analog to Dig) provided inside
The first index is obtained by taking in the amplitude information by an ital Converter and performing an arithmetic processing. Since the first index is detected in a state where the tracking control is off, the first index changes depending only on the tilt amount without depending on the detrack amount. Also, since this index uses amplitude information, it has a feature that it is less susceptible to waveform asymmetry due to DC offset or gain balance deviation caused by drift or the like.

In the present embodiment, the second A is used for detecting the amplitude.
Although it is necessary to newly add the TT 206 and the second signal amplitude detection unit 207, the first unit, which is originally provided in the apparatus for detecting data from the reproduced signal, is used.
Of the ATT 200 and the first signal amplitude detection unit 205 of FIG.
The cost increase of the apparatus is insignificant.

As described above, the index for judging the amount of tilt for making the relative tilt between the optical disk and the optical head almost zero can be determined by the second signal amplitude detection unit 207 and the system control unit 101. The tilt correction means can be obtained by a system control unit 101 and a tilt control unit 102.

FIG. 6A is a graph in which the relationship between the tracking error signal amplitude, which is the first index obtained by the second waveform shaping section 103, and the radial tilt is actually measured and plotted. As understood from the figure, if the tilt control unit 102 is controlled so that the first index approaches a maximum (peak), the relative inclination between the optical disk and the optical head can be made closer to zero. . This relationship can be approximated to a quadratic function (convex type) having a negative quadratic coefficient having a point at which the radial tilt becomes substantially zero as an extreme value.

FIG. 6B shows reproduced data and data PLL.
The data / clock jitter with the reproduction clock synchronized with the reproduction data generated in step (1) is normalized with the period of the reproduction clock, and is plotted against the radial tilt. From the figure, when the tilt control unit is controlled so that the first index approaches the extreme value, the data /
It can be seen that the inter-clock jitter changes so as to approach the minimum value. This means that it is effective to use the first index for tilt correction. As described above, in the tilt correction according to the present embodiment, the system control unit 101 controls the tilt control unit 102 to set the amount of tilt such that the first index is the maximum point.

Next, a tilt correction method for a disk drive according to the present invention will be described with reference to FIG. When the apparatus is turned on and the optical disk 10 is mounted, the apparatus enters a start state (step 1). After this, the system control unit 1
01 initializes parameters of the entire drive (step 2). Then, the electric offset of the analog circuit for generating the focus error signal and the tracking error signal is corrected (step 3). Next, the optical disk 10 is rotated (Step 4), the LD 11 is turned on (Step 5), and the operation shifts to the focus pull-in operation (Step 6). Next, after the gain balance of the optical system and the electric circuit system is corrected (Step 7), the operation proceeds to the tilt correction operation.

First, a tilt index, here a first index, is measured, and the result is stored in a memory (storage means) (step 8). If the measurement of the first index is the first time,
The tilt control unit 1 according to an instruction from the system control unit 101
After changing the tilt amount by controlling 02 (step 10), the process returns to step 8 to measure the first index again and save the result in the memory. Next, based on the first index measured last time and the first index measured this time, it is determined whether or not the measurement result is within an allowable range including an extreme value (step 9).
As a result, when the tilt amount is not within the allowable value, the tilt control unit 102 is controlled by the instruction of the system control unit 101 to change the tilt amount again (step 10).
Returning to step 8, this operation is repeated. If it is within the allowable value, the operation is terminated and the tracking pull-in operation is started (step 11). When the tracking is pulled in and the data is ready for reproduction, it waits for the next command (step 12). Since the above-mentioned allowable range differs depending on each disk, it is necessary to obtain the allowable range before starting the apparatus.

In this embodiment, the tilt correction has been described. However, in the disk device, an offset due to an electrical offset, a deviation of an optical system balance, a gain balance of a detection circuit, and an offset based on a detrack are also considered. Exists. Therefore, in order to correct these offsets accurately, the following three steps are taken. First, an offset due to an electrical offset, an optical system balance deviation, and a gain balance of a detection circuit is corrected. Then, the tilt is corrected based on the index of the present invention, which changes depending only on the tilt amount without depending on the detrack amount. After that, the detrack is corrected.

Embodiment 2 FIG. 8 is a diagram showing a disk device including a tilt correction device according to the second embodiment of the present invention. In the figure, 10 is an optical disk, 11 is a semiconductor laser (LD) as a light source, 12 is a collimating lens, 13 is a beam splitter, 14 is an objective lens, 1
5 is a photodetector, 16 is an actuator, 17 is a differential amplifier, 22 is a tracking control unit, 23 is an addition amplifier, 2
7 is an address reproducing unit, 28 is an information reproducing unit, 30 is a traverse control unit, 31 is a traverse motor, 32 is a recording signal processing unit, 33 is an LD driving unit, and 34 is an actuator driving unit. It has the same or equivalent functions as those described above. The optical head includes a semiconductor laser 11, a collimator lens 12, a beam splitter 13, an objective lens 14, a photodetector 15, and an actuator 16, and is mounted on a head base (not shown). Furthermore, 35 is a wobble detection unit, 100 is a first waveform shaping unit, 102 is a tilt control unit, 103 is a second waveform shaping unit 103 and 104 are system control units.

The apparatus shown in FIG. 8 is a DVD-R disk (DV which can be written only once)
D disk), has a land portion and a groove portion,
Further, it has a function of obtaining an index indicating the amount of tilt from a disk in which the groove and the land meander (wobble) at a predetermined carrier frequency, and correcting the tilt.
The frequency of the wobble is usually 1 / integer of the channel frequency of the data recorded on the disk, and
It is set outside the tracking control band (high frequency side). Thus, the light beam controlled by the tracking control unit 22 traces the center of the wobble fluctuation without following the wobble, and as a result, a wobble detection signal can be obtained from the output of the differential amplifier 17. . If the frequency of the wobble is an integer fraction of the channel frequency, the rotation of the disk can be controlled using the wobble detection signal, and the rotation of the disk is controlled so that the frequency of the wobble detection signal becomes a predetermined value. Such discs include not only DVD-R discs but also CD-R discs (1
CD discs that can be written only once) and CD-RW discs (rewritable CD discs). For details, refer to “DVD technology” and “CD-R / CD-RW technology” published by Trikeps Corporation. It has been described. In the case of the DVD-R disc shown in FIG. 9, the address information is expressed as land pre-pits formed in the land as pre-pits at the time of manufacturing the disc. Again, C
In a DR / CD-RW disc, the time information is FM (F
frequency modulation) and superimposed on the wobble frequency. Such a disk also has a surface structure capable of causing amplitude fluctuation in the differential output of the photodetector that has received the reflected light, and the present invention is applicable.

The operation of reproducing the above optical disk by the disk device will be described with reference to FIGS. FIG.
0 indicates the waveform of each part in FIG. When the device is started,
The system control unit 104 rotates the disk at a predetermined rotation speed via a disk rotation control unit (not shown). Next, the LD driving unit 33 is set to the reproduction mode by a control signal from the system control unit 104,
The drive current is controlled so that the semiconductor laser 11 emits light at a constant intensity. The laser light output from the semiconductor laser 11 is collimated by a collimator lens 12, passes through a beam splitter 13, and is condensed as a light spot on an optical disk 10 by an objective lens 14. With respect to fluctuations in the distance between the head and the disk caused by surface deviation, etc., a focus control unit (not shown) controls the objective lens 14 based on a focus error signal generated from the output of the photodetector 15 and constantly controls the laser beam. The device has a function of condensing light on a disk. The laser beam reflected by the optical disk 10 has information of the recording track, and the objective lens 1
The light is guided to the photodetector 15 by the beam splitter 13 via the line 4. The photodetector 15 is composed of two light receiving sections divided into two in the direction in which the disk tracks extend in the far field of the reflected light to obtain a push-pull signal, and two I / V conversion sections corresponding to the light receiving sections. That is, the change in the light amount distribution of the received light beam is converted into an electric signal, which is output to the differential amplifier 17 and the addition amplifier 23, respectively.

The differential amplifier 17 generates a push-pull signal shown in FIG. 10A by taking the difference between the respective input signals, and outputs the push-pull signal shown in FIG.
7. Wobble detection unit 35 and second waveform shaping unit 103
Output to The tracking control unit 22 includes the differential amplifier 1
7 output signal to LPF (Low Pass Filter)
r), a tracking control signal is output to the actuator drive unit 34 in accordance with the level of the tracking error signal obtained by band limiting, and the actuator drive unit 34 supplies a drive current to the actuator 16 in response to this signal, Is controlled in the direction crossing the recording track. Thus, the light spot scans the track while being track-controlled.

The wobble detector 35 extracts a wobble signal component from the output signal of the differential amplifier 17 and then binarizes it, and outputs a wobble detection signal shown in FIG. The system control unit 104 generates a reference clock for driving the device based on this signal. At this time, the system control unit 104 controls the wobble signal (push-pull signal) detected by the second waveform shaping unit 103 in order to prevent the reference clock generation circuit from malfunctioning because the wobble signal cannot be normally detected due to a defect or the like. Amplitude level (FIG. 10)
(B)) is sliced at a predetermined slice level (TH3) to detect a wobble signal missing area (FIG. 10).
(L)) In the detected wobble signal missing area, the operation of the reference clock generation circuit may be held.

A disk rotation controller (not shown) controls a spindle motor (not shown) so that the reference clock has a predetermined frequency. After the number of rotations of the disk has been set to a predetermined value, the operation proceeds to a data recording or reproducing operation.

First, the operation during data reproduction will be described. The first waveform shaping section 100 performs a predetermined process on the sum signal (FIG. 10 (h)) obtained by adding the output signal of the photodetector 15 by the addition amplifier 23, and then performs a predetermined threshold value. The data is sliced to generate a pulse waveform shown in FIG. Information reproducing unit 28
Generates a data reproduction clock synchronized with a detected pulse waveform based on a control signal from the system control unit 104 and a reference clock, demodulates information recorded on a disk with the data reproduction clock, and corrects an error. Process and output as a reproduction information signal. By analyzing error correction information (for example, the number of corrections) and jitter when the information reproducing unit 28 performs the error correction processing, the data error rate can be obtained. In general, the system control unit 104 appropriately reads the error correction information stored in the information reproducing unit 28, and calculates the data error rate by using a calculation process or a lookup table.

The system control unit 104 determines whether the current light beam is at a desired address based on information for identifying the position of the reproduction track, such as the data ID included in the reproduction information signal. Traverse control unit 30
Outputs a drive current to the traverse motor 31 according to a control signal from the system control unit 104 when the optical head is moved, and moves the optical head to a target track.
At this time, the tracking control unit 22 temporarily suspends the tracking control operation according to the control signal from the system control unit 104. At the time of normal reproduction, the system control unit 104 drives the traverse motor 31 via the traverse control unit 30 according to the tracking error signal input from the tracking control unit 22, and moves the optical head radially along the progress of reproduction. Move slowly in the direction.

Next, the operation during data recording will be described. First, the address reproducing unit 27 converts the output signal (FIG. 10A) of the differential amplifier 17 into a predetermined slice level (TH).
The land pre-pit detection signal (FIG. 10C) obtained by slicing in 1) is detected by the reference clock obtained from the system control unit 104, and the address of the reproduction track (sector) is detected. At this time, in order to improve the detection accuracy of the land prepit, the system control unit 104 may generate a land prepit detection gate and use only the land prepit detection signal in this gate.

The recording signal processing section 32 adds an error correction code or the like to the input recording data, encodes the recording data into a recording signal, and outputs the resulting signal to the LD driving section 33. When the light beam reaches the data recording address, the system control unit 104
Sets the LD driving unit 33 to the recording mode, and sets the LD driving unit 3
Reference numeral 3 modulates a drive current applied to the semiconductor laser 11 according to the recording signal. As a result, the intensity of the light spot irradiated on the optical disk 10 changes according to the recording signal, and recording pits are formed.

The configuration and operation of the first waveform shaping section 100 will be described with reference to FIG. Basically, it is the same as described in the first embodiment. The sum signal shown in FIG. 10H input from the addition amplifier 23 is the first ATT 20
At 0, the reproduction level is adjusted with a predetermined gain. First A
The gain of the TT 200 is
Set by the control signal from. That is, the system control unit 104 is configured to obtain the optimal setting gain of the first ATT 200 based on the amplitude information of the output signal of the first ATT 200. This first AT
The gain set at T200 is set to a value that can ensure the quality of the reproduction signal after the DC control unit 201.

The sum signal whose gain has been adjusted by the first ATT 200 is input to the DC control unit 201, and the DC signal in the signal
The waveform shown in FIG. 10J is obtained by removing the components. The DC control unit 201 is for effectively utilizing the dynamic range of the subsequent AGC 202, and removes DC components unnecessary for data reproduction. However, in an area where a DC component abruptly changes due to a large missing area of a disk or an area where signal continuity is lost, the DC control unit 20 is used.
A large sag occurs at the output of No. 1. Therefore, the boost control gate shown in FIG. 10F input from the system control unit 104 has a function of reducing the time constant for removing the DC component and following the DC fluctuation of the input signal in a short time. . In the boost control gate, the system control unit 104 slices the amplitude level (FIG. 10 (i)) of the added signal detected by the first waveform shaping unit 100 at a predetermined slice level (TH4), and the added signal missing area Is detected, and a gate having a predetermined time width is generated from the end point of the detected addition signal missing area as a starting point.

The output waveform (j) of the DC control unit 201 is A
The signal is finely adjusted to a predetermined signal amplitude by the GC unit 202. This A
The GC unit 202 configures a feedback control system that monitors the signal amplitude of the input signal and controls its gain so that the output signal level always has a predetermined amplitude. The output signal of the AGC unit 202 is improved in waveform deterioration due to the frequency characteristic of the optical system by the waveform equalization unit 203, and then binarized by the signal slicing unit 204 as shown in FIG. It is output to the unit 28. The signal slicing unit 204 optimally controls the slice level so that the reproduction error is minimized. Further, the signal slicing means 204 has a boost function like the DC control section 201, and reduces the time constant of the slice level control based on the boost control gate from the system control section 104 to reduce the fluctuation of the input signal. Follow in time.

The first signal amplitude detection unit 205 outputs the first signal
The signal amplitude of the output signal of the TT 200 is detected and output to the system control unit 104 (FIG. 10 (i)). The system control unit 104 processes this detection result,
The gain of the first ATT 200 is set, and the above-mentioned added signal missing area is detected.

In this embodiment, a first index obtained in the same manner as described in the first embodiment is used as an index for judging the amount of tilt that can eliminate the tilt between the optical disk and the optical head. The second index using the amplitude information of the wobble signal obtained from the second signal amplitude detection unit 207 in the state where tracking is applied is used. This second
The index is used because the first index and the second index have different frequency bands of signals for detecting the respective indexes, but have the same detection principle. That is, as mentioned above,
The trace position of the light beam traces the center (virtual track center) of wobble fluctuation (amplitude) instead of the center of the wobbled track (microscopically) to be precise (microscopically). The detected wobble signal (push-pull signal) detects the error between the light beam position and the center of the wobbled track, and means that the second index can be used as an index for determining the amount of tilt. are doing. As a result, as in the case of the first index, if the system control unit 104 controls the tilt via the tilt control unit 102 so that the second index approaches an extreme value (peak), the distance between the optical disk and the optical head is reduced. Can be made closer to zero.

The second index is obtained by the second waveform shaping section 103 whose internal block diagram is shown in FIG. In the figure, 206 is the second
ATT (attenuator) 207 is a second signal amplitude detector. The input / output signals of the system control unit 104 are limited to those related to the second ATT 206 and the second signal amplitude detection unit 207. Next, the operation will be described.

The detection of the second index is performed by controlling the second ATT 206 by the system control unit 104 and adjusting the signal level so that the second signal amplitude detection unit 207 can detect the amplitude with high accuracy. Start from. The system control unit 104 controls the signal amplitude detection signal output from the second signal amplitude detection unit 207 in the tracking state and in the area other than the wobble signal missing area and the land pre-pit area. ADC (Analog to Analog) provided in the unit
Digital Converter)
The second ATT2 is processed so that the output of the second ATT 206 becomes a signal level within a predetermined range based on the processing result.
06 is controlled. After the setting of the second ATT 206 is completed, the system control unit 104 similarly obtains the amplitude level of the wobble signal output from the second signal amplitude detection unit 207 and calculates the second index by performing arithmetic processing.

In this example, the second ATT 20
6 and the second signal amplitude detector 207 need to be newly added, but the first ATT, which is originally provided in the device for detecting data from the reproduced signal, is used.
Since the circuit may be the same as the circuit 200 and the first signal amplitude detector 205, it is not necessary to develop a new circuit, and the cost of the apparatus is negligible.

As described above, the second index for judging the amount of tilt for making the relative tilt between the optical disk and the optical head substantially zero can be used, like the first index, for the second signal amplitude. The tilt can be obtained by the detection unit 207 and the system control unit 104, and the tilt correction unit can be constituted by the system control unit 104 and the tilt control unit 102.

Next, a tilt correction method for a disk drive according to the present invention will be described with reference to FIG. When the apparatus is turned on and the optical disk 10 is mounted, the apparatus enters a start state (step 1). Thereafter, the system control unit 104 initializes parameters for the entire drive (step 2). Then, the electric offset of the analog circuit for generating the focus error signal and the tracking error signal is corrected (step 3). Next, the optical disk 10 is rotated (Step 4), the LD 11 is turned on (Step 5), and the operation shifts to the focus pull-in operation (Step 6). Next, after the gain balance of the optical system and the electric circuit system is corrected (step 7), the process proceeds to the tilt correction operation using the first index in a state where tracking is not applied.

First, the first index is measured (step 8), and it is determined whether the measurement result is within an allowable range (step 9). That is, it is determined whether or not the first index is within the range of the allowable value including the extreme value.
After the tilt amount is changed by controlling 2 (step 10), the process returns to step 8, and this operation is repeated. If it is within the allowable value, the operation is terminated and the tracking pull-in operation is started (step 11). When the tracking is completed and the reproduction of the data is completed, the operation proceeds to the tilt correction operation using the second index.

First, the second index is measured, and the result is stored in a memory (storage means) (step 13). When the measurement of the second index is the first time, after the tilt control unit 102 is controlled by the instruction of the system control unit 104 to change the amount of tilt (step 15), step 1 is performed.
Returning to 3, the second index is measured again and the result is stored in the memory. Next, based on the second index measured last time and the second index measured this time, it is determined whether or not the measurement result is within an allowable range including an extreme value (step 14). As a result, if it is not within the allowable value, the tilt control unit 102 is controlled by the instruction of the system control unit 104 to change the tilt amount again (step 15), and then returns to step 13 and repeats this operation. If it is within the allowable value, the operation ends, and the process waits until the next command (step 12).

The tilt correction operation based on the second index is performed by comparing the magnitude of the second index obtained before and the second index obtained in units of sectors or blocks or predetermined time intervals, Perform tilt correction. In this case, it can be assumed that the second index indicates an abnormal value due to a defect or the like. In order to eliminate this effect, for example, a predetermined threshold value is set for the variation width of the second index in units of correction steps, and when the obtained second index exceeds this threshold value, May be controlled so that the index is not used for tilt correction. Alternatively, the index can be fetched a plurality of times within a sector or a block or within a predetermined time interval, and a correction operation can be performed using an average value of the indexes.

As described above, the tilt correction can be performed by the system control unit 104 controlling the tilt control unit 102 to change the tilt amount, and setting the tilt amount at which the first and second indices are extreme values. Will be. However, when the first and second indices are different in the amount of tilt at which the extreme value is taken, an intermediate value may be used. Here, the tilt correction unit can be configured by the system control unit 104 and the tilt control unit 102. In general, a mechanism for tilt correction is attached to a mechanical base on which an optical head and a traverse motor are mounted, but a detailed description is omitted here.

The case where a disk having a track format in which lands and grooves are wobbled has been described above. However, even if the target disk does not have lands and grooves, the information pits are spiral or concentric. Needless to say, the same effect can be obtained if the information track is wobbled.

Embodiment 3 FIG. 12 is a diagram showing a disk device provided with a tilt correction device according to another embodiment of the present invention. In the figure, 10 is an optical disk, 11 is
Is a semiconductor laser (LD) as a light source, 12 is a collimating lens, 13 is a beam splitter, 14 is an objective lens,
15 is a photodetector, 16 is an actuator, 17 is a differential amplifier, 18 is a difference signal waveform shaping section, 19 is a reproduction difference signal processing section, 20 is a polarity control section, 21 is a polarity inversion section, 22 is a tracking control section, 23 is an addition amplifier, 25 is a reproduction signal processing unit, 26 is a polarity information reproduction unit, 27 is an address reproduction unit,
28 is an information reproducing unit, 30 is a traverse control unit, 31 is a traverse motor, 32 is a recording signal processing unit, 33 is an LD drive unit, and 34 is an actuator drive unit, which is the same as or equivalent to that described in the conventional example. It has a function. The optical head includes a semiconductor laser 11, a collimating lens 12, a beam splitter 13, an objective lens 14,
It is composed of a photodetector 15 and an actuator 16,
It is attached to the head base. 35 is a wobble detection unit, 100 is a first waveform shaping unit, 102 is a tilt control unit, and second waveform shaping units 103 and 105 are system control units.

The disk device configured as described above
As in the case of a DVD-RAM disk whose disk shape is shown in FIG. 13, a recording track is divided into sector units in the track direction, and at the beginning of each sector, sector identification information such as a track number or a sector number has a physical shape change or a local change. Is preformatted as a pit causing a change in optical constant, and the sector format is such that the sector identification information is arranged with a predetermined distance displaced radially outward (or inward) from the center of the recording track. A second identification information area disposed on the inner circumference side (or outer circumference side) of the first identification information area at the same distance as the predetermined distance, and user information and the like following the sector identification information area on the recording track. And a user information area recorded on the center, and the groove and the land meander at a predetermined carrier frequency (W). It has a function of obtaining an index indicating the amount of tilt from a disk arranged in a tilted manner and correcting the tilt. That is, it is considered that the track layout of the disk shown in FIG. 13 has the features of the disk shown in FIG. 15 described in the conventional example and the disk described above with reference to FIG. For details of the DVD-RAM disk format, see “Nikkei Electronics” published by Nikkei BP7.
No. 00 and No. 701, "Complete DVD-RAM Standard,
The article is described in detail by the formulators (above) and (below). Also in this case, the first index and the second index are used as indices for determining the amount of tilt that can eliminate the tilt between the optical disk and the optical head, as in the previous example of the second embodiment. Becomes possible.

The operation of playing back the optical disk shown in FIG. 13 in the disk device of the present embodiment configured as described above will be described with reference to FIGS. When the apparatus is started, the system control unit 105 rotates the disk at a predetermined rotation speed via a disk rotation control unit (not shown). Next, the LD drive unit 33 is set to the reproduction mode by a control signal from the system control unit 105, and controls the drive current so that the semiconductor laser 11 emits light at a constant intensity. The laser light output from the semiconductor laser 11 is collimated by a collimator lens 12, passes through a beam splitter 13, and is condensed as a light spot on an optical disk 10 by an objective lens 14. With respect to fluctuations in the distance between the head and the disk caused by surface deviation or the like, a focus control unit (not shown) controls the objective lens 14 based on a focus error signal generated from the output of the photodetector 15 and constantly controls the laser beam. The device has a function of condensing light on a disk. The laser beam reflected by the optical disk 10 has information of a recording track, and is guided to a photodetector 15 by a beam splitter 13 via an objective lens 14. The photodetector 15 is composed of two light receiving sections divided into two in the direction in which the disk tracks extend in the far field of the reflected light to obtain a push-pull signal, and two I / V conversion sections corresponding to the light receiving sections. That is, the change in the light amount distribution of the received light beam is converted into an electric signal, which is output to the differential amplifier 17 and the addition amplifier 23, respectively.

The differential amplifier 17 generates the push-pull signal shown in FIG. 2 and FIG. 14A by taking the difference between the respective input signals, and generates a difference signal waveform shaping section 18, a polarity inverting section 21, a wobble detecting section. 35 and second waveform shaping unit 10
Output to 3. FIG. 2 shows a push-pull signal in a non-operating state of the tracking control, and FIG. 14 shows waveforms of respective parts in FIG. 12 in a state in which the operation is performed up to the tracking control.

When tracking is applied, the difference signal waveform shaping section 18 converts the analog push-pull signal from the differential amplifier 17 into two appropriate levels (T
H1 and TH2), which are sliced and converted into digital values shown in FIGS. 14C and 14D. Here, the waveform (c) shows the position of the first identification information area, and the waveform (d) shows the position of the second identification information area. The reproduction difference signal processing unit 19 determines the tracking polarity from the appearance timing of the binary difference signals (c) and (d), and outputs the polarity detection signal to the polarity control unit 20, the polarity information reproduction unit 26, the address reproduction unit 27, The information is output to the information reproducing unit 28 and the system control unit 105. Further, the reproduction difference signal processing section 19 also outputs digital values shown in FIGS. 14C and 14D to the system control section 105.

The polarity control unit 20 includes a reproduction difference signal processing unit 19
And a control signal from the system control unit 105, and outputs a polarity setting signal to the polarity inversion unit 21 and a control hold signal for countermeasures against disk defects to the tracking control unit 22. The polarity reversing unit 21 includes the polarity control unit 2
In accordance with the polarity setting signal from 0, the polarity of the output signal of the differential amplifier 17 is inverted only when the track being accessed is, for example, a land and is output to the tracking control unit 22 as a tracking error signal (the track being accessed). If is a groove, the polarity is not reversed). The tracking control unit 22 outputs a tracking control signal to the actuator driving unit 34 according to the level of the tracking error signal input from the polarity reversing unit 21, and the actuator driving unit 34 supplies a driving current to the actuator 16 according to the signal. And the position of the objective lens 14 is controlled in a direction crossing the recording track.

The wobble detector 35 extracts the wobble signal component from the output signal of the differential amplifier 17 in the user information area outside the sector identification information area where no wobble exists, and then binarizes the wobble signal component, as shown in FIG. The wobble detection signal is output to the system control unit 105. The system control unit 105 generates a reference clock for driving the device based on this signal. At this time, the system control unit 105 controls the wobble signal (push-pull signal) detected by the second waveform shaping unit 103 in order to prevent the reference clock generation circuit from malfunctioning because the wobble signal cannot be normally detected due to a defect or the like. May be sliced at a predetermined slice level (TH3) to detect a wobble signal missing area, and the operation of the reference clock generation circuit may be held in the detected wobble signal missing area. This operation is as described in the second embodiment.

A disk rotation controller (not shown) controls a spindle motor (not shown) so that the reference clock has a predetermined frequency. After the number of rotations of the disk has been set to a predetermined value, the operation proceeds to a data recording or reproducing operation.

First, the operation at the time of data reproduction will be described. The first waveform shaping section 100 has the same configuration and operation as in the first embodiment, and thus detailed description is omitted. However, the sum signal obtained by adding the output signal of the photodetector 15 by the addition amplifier 23 is omitted. After performing a predetermined process on (FIG. 14 (h)), the data is sliced at a predetermined threshold value, and FIG.
The pulse waveform shown in FIG.
Output to The reproduction signal processing unit 25 generates a data reproduction clock synchronized with the detected pulse waveform based on the control signal and the reference clock from the system control unit 105, and uses the data reproduction clock to generate address information and the like recorded on the disk. The identification signal including the polarity information is reproduced.

The polarity information reproducing section 26 extracts polarity information indicating the tracking polarity of the sector from the identification signal. The address reproducing unit 27 reproduces sector address information from the identification signal. The information reproducing unit 28 demodulates / error-corrects the user information recorded in the user information area on the disc from the binary sum signal from the reproduced signal processing unit 25, and outputs it as a reproduced information signal. By analyzing error correction information (for example, the number of corrections) and jitter when the information reproducing unit 28 performs the error correction processing, the data error rate can be obtained. Generally, the system control unit 105
Reads the error correction information stored in the information reproducing unit 28 as appropriate, and calculates the data error rate by using a calculation process or a lookup table.

The polarity information output from the polarity information reproducing section 26 and the sector address information output from the address reproducing section 27 are sent to the system control section 105 and used for controlling the tracking polarity and the sample-hold state of the tracking control. . In such a configuration, it is possible to sample and hold the tracking error signal immediately before the sector identification information area in order to cut off extra disturbance to the tracking servo system, and pass this area by inertia with the tracking control operation off. It is. The system control unit 105 receives information about the identification signal from the reproduction difference signal processing unit 19, the polarity information reproduction unit 26, and the address reproduction unit 27, and receives the polarity control unit 20, traverse control unit 3.
0, and outputs a control signal to the LD drive unit 33 and the recording signal processing unit 32.

The system control unit 105 determines whether or not the light beam is currently at a desired address based on information about the identification signal including the address and the like from the address reproducing unit 27. The traverse control unit 30 outputs a drive current to the traverse motor 31 according to a control signal from the system control unit 105 when the optical head is moved,
Move the optical head to the target track. At this time, the tracking control unit 22 is controlled by the system control unit 105
The tracking control operation is temporarily interrupted by the control signal from. At the time of normal reproduction, the system control unit 105 drives the traverse motor 31 via the traverse control unit 30 according to the tracking error signal input from the tracking control unit 22, and moves the optical head radially along the progress of reproduction. Move slowly in the direction.

Next, the operation during data recording will be described. The recording signal processing unit 32 adds an error correction code or the like to the recording data input at the time of recording, encodes the recording data into a recording signal, and outputs the encoded signal to the LD driving unit 33. When the light beam reaches the data recording sector, the system control unit 1
05 sets the LD driving unit 33 to the recording mode, and the LD driving unit 33 modulates the driving current applied to the semiconductor laser 11 according to the recording signal synchronized with the reference clock. As a result, the intensity of the light spot irradiated on the optical disk 10 changes according to the recording signal, and recording pits are formed.

In the above operation, since the tilt correction has not been performed, it may be assumed that the quality of the reproduced signal, that is, the reliability of the data after the error correction cannot be tolerated. For this reason, when the reliability of the reproduced data is impaired immediately after the optical disk 10 is mounted or due to a change over time, it is necessary to correct the tilt in order to secure the operation margin of the apparatus and achieve high reliability of the data reproduction. Regarding the signal quality, the system control unit 105 captures the jitter of the reproduced signal binarized by the signal slicing unit 204 and the number of error corrections (data error rate) obtained as a result of processing by the information reproducing unit 28 at the subsequent stage, and calculates or calculates The processing can be determined by referring to the lookup table.

In the present embodiment, the first index and the second index are used as indices for determining the amount of tilt that can eliminate the tilt between the optical disk and the optical head, as in the second embodiment.
Index is used.

To detect the first index, the system control section 105 controls the second ATT 206 constituting the second waveform shaping section 103 and the second signal amplitude detecting section 207
Starts by adjusting the signal level so that the amplitude can be detected with high accuracy. System control unit 1
Reference numeral 01 denotes a state in which the operation is performed up to the focus control (that is, a state in which tracking is not performed). ADC (Analog to Digita) provided in the system control unit stores the amplitude information of the error signal.
1 Converter), processes the data, and controls the second ATT 206 based on the processing result so that the output of the second ATT 206 becomes a signal level within a predetermined range.

The second signal amplitude detector 207 outputs the second ATT2 after the output signal level is adjusted within a predetermined range.
From the output of 06, the amplitude information of the tracking error signal at the time of traversing the land and the groove is output to the system control unit 105. The system control unit 105
ADC (Analog to Dig) provided inside
The first index is obtained by taking in the amplitude information by an ital Converter and performing an arithmetic processing. Since the first index is detected in a state where the tracking control is off, the first index changes depending only on the tilt amount without depending on the detrack amount.

The detection of the second index is performed by the system control section 101 in the same manner as the detection of the first index.
The second signal amplitude detector 207 controls the signal level so that the second signal amplitude detector 207 can detect the amplitude with high accuracy. However, the second index indicates the signal amplitude detection signal output from the second signal amplitude detection unit 207 in the tracking state and in the area other than the wobble signal missing area and the sector identification information area. ADC provided in the system control unit
(Analog to Digital Cover
ter), process the data, and perform a second
The second ATT 206 is controlled such that the output of the ATT 206 becomes a signal level within a predetermined range. Second ATT2
After the setting of 06 is completed, the system control unit 105
Similarly, the second index is obtained by taking in the amplitude level of the wobble signal output from the second signal amplitude detection unit 207 and performing arithmetic processing.

For tilt correction that can make the relative tilt between the optical disk and the optical head almost zero, the system control unit 105 controls the tilt control unit 102 to change the amount of tilt. What is necessary is just to set the tilt amount at which the index becomes an extreme value. However, the first and second
In the case where the amount of tilt at which the index takes an extreme value differs, an intermediate value may be used. Here, the tilt correction unit can be configured by the system control unit 105 and the tilt control unit 102. In general, a mechanism for tilt correction includes:
The optical head and the traverse motor are mounted on a mechanical base mounted thereon, but detailed description is omitted here.

The tilt correction operation based on the second index is performed by comparing the size of the second index obtained in units of a sector or a predetermined time with the size of the second index obtained before that. In this case, it can be assumed that the second index indicates an abnormal value due to a defect or the like. In order to eliminate this effect, for example, a predetermined threshold value is set for the variation width of the second index in units of correction steps, and when the obtained second index exceeds this threshold value, May be controlled so that the index is not used for tilt correction.
Alternatively, the index can be fetched a plurality of times within a sector or within a predetermined time interval, and a correction operation can be executed using an average value of the indexes. In this case, there is an advantage that the fluctuation of the second index in units of sectors or predetermined time intervals can be removed, and the burden on the tilt control mechanism can be reduced.

In the present embodiment, the second A
Although it is necessary to newly add the TT 206 and the second signal amplitude detector 207, the first ATT which is a means originally provided in the apparatus for detecting data from the reproduced signal is used.
Since the circuit may be the same as the circuit 200 and the first signal amplitude detector 205, it is not necessary to develop a new circuit, and the cost of the apparatus is negligible.

The tilt correction method of the disk device according to the present invention is the same as the method of FIG. 11 described in the previous embodiment of the second embodiment.

In this embodiment, the tilt correction has been described. However, in the disk device, there are also an offset due to an electrical offset, an optical system balance deviation, an offset due to a gain balance of a detection circuit, and an offset based on detrack. . Therefore, in order to correct these offsets accurately, the following three steps are taken. First, an offset due to an electrical offset, an optical system balance deviation, and a gain balance of a detection circuit is corrected. Then, the tilt is corrected based on an index that changes not depending on the detrack amount but only on the tilt amount. After that, the detrack is corrected.

Note that the tilt correction devices described in the first to third embodiments are not limited to an information medium as an optical disk, but cause an amplitude fluctuation in the output of a photodetector of light reflected by a light spot. Any information medium having such a surface structure, for example, an optical card, an optical tape, or the like can provide similar results. Further, according to the second and third embodiments, the case where the tilt correction is performed using both the first index and the second index has been described. However, tracking is canceled to measure the first index. For example, tracking should be performed once in a state where tracking is applied, such as when waiting for a command after starting up the device, or when correcting an inclination with time when the device is used for a long time. It is necessary to cancel.
Therefore, in such a case, it is also possible to configure the apparatus such that the inclination correction is not performed by the first index, but is performed only by the second index. In this case, steps 8 to 10 are deleted in FIG. 11 described above.

[0111]

Since the present invention is configured as described above, it has the following effects.

According to the tilt correcting apparatus of the present invention, the tilt between the information medium having the surface structure capable of causing the amplitude difference in the difference signal of the reflected light and the head forming the light spot on the information medium is corrected. In the apparatus, the amplitude information of the difference signal obtained from the light detector that receives the light reflected by the light spot is used as an index, and the relative distance between the information medium and the head is set so that the index approaches an extreme value. Since tilt correction can be performed by controlling the tilt, it is not necessary to separately provide a mechanism for tilt detection unlike the related art, so that an increase in the cost of the apparatus can be suppressed.

Since the index for tilt correction according to the present invention is signal amplitude information, it is not affected by DC fluctuations caused by an electrical offset or an optical offset, and is not affected by detrack correction. Hardly receive. Therefore, even when the detrack correction is performed together with the tilt correction, only the tilt correction can be easily performed without considering this.

[Brief description of the drawings]

FIG. 1 is a block diagram of a disk device according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating a tracking error signal.

FIG. 3 is a diagram showing output waveforms from each block constituting the disk device according to the first embodiment of the present invention;

FIG. 4 is a block diagram of a first waveform shaping unit included in the disk device according to the first to third embodiments of the present invention;

FIG. 5 is a block diagram of a second waveform shaping unit included in the disk device according to the first to third embodiments of the present invention;

FIG. 6 is a diagram illustrating a relationship between a first index and a tilt amount according to the first to third embodiments of the present invention.

FIG. 7 is an operation flowchart of the disk device according to the first embodiment of the present invention;

FIG. 8 is a block diagram of a disk device according to a second embodiment of the present invention.

FIG. 9 is a diagram showing a track layout of an optical disk according to the disk device of the second embodiment of the present invention.

FIG. 10 is a diagram showing output waveforms from respective blocks constituting a disk device according to Embodiment 2 of the present invention;

FIG. 11 is an operation flowchart of the disk device according to the second embodiment of the present invention;

FIG. 12 is a block diagram of a disk device according to a third embodiment of the present invention.

FIG. 13 is a diagram showing a track layout of an optical disk according to the disk device of the third embodiment of the present invention.

FIG. 14 is a diagram showing output waveforms from respective blocks constituting a disk device according to Embodiment 3 of the present invention;

FIG. 15 is a diagram showing a track layout of a conventional optical disc.

FIG. 16 is a block diagram of a conventional disk device.

[Explanation of symbols]

Reference Signs List 10 optical disk, 11 semiconductor laser, 12 collimating lens, 13 beam splitter, 14 objective lens, 15 photodetector, 16 actuator, 17 differential amplifier, 18 difference signal waveform shaping section, 19 reproduction difference signal processing section, 20 polarity control section , 21 polarity inverting section, 22 tracking control section, 23 addition amplifier, 24 sum signal waveform shaping section, 25 reproduced signal processing section, 26 polarity information reproducing section, 27 address reproducing section, 28 information reproducing section, 29
System control unit, 30 traverse control unit, 31
Traverse motor, 32 recording signal processing unit, 33 laser (LD) drive unit, 34 actuator drive unit, 35
Wobble detection unit, 100 First waveform shaping unit, 101
System control unit, 102 Tilt control unit, 1
03 second waveform shaping section, 104 system control section, 105 system control section, 200 first ATT, 201 DC control section, 202 AGC section, 20
3 waveform equalizer, 204 signal slicing means, 205
First signal amplitude detection unit, 206 Second ATT, 207
A second signal amplitude detector;

Claims (3)

[Claims] 1. A tilt correction device for correcting a tilt between an information medium having a surface structure capable of causing an amplitude variation in a reflected light difference signal and a head for forming a light spot on the information medium, A light detector that receives the light reflected by the light detector; a means for obtaining a difference signal of the output of the light detector; A tilt control unit for controlling a relative tilt with respect to a head. 2. The information medium is a disk on which information tracks are formed in a spiral or concentric shape, and the tilt control means controls the light detector when a light spot on the disk crosses the information tracks. 2. The tilt correction apparatus according to claim 1, wherein the relative tilt between the disk and the head is controlled such that the index approaches an extreme value, using the amplitude of the difference signal as an index. 3. The information medium is a disk on which information tracks are arranged spirally or concentrically, and the information tracks are formed in a meandering manner. Controlling the relative inclination between the disk and the head so that the index approaches an extreme value, using the amplitude of the difference signal of the photodetector when tracing the information track as an index. The tilt correction device according to claim 1, wherein: