JP3546535B2 - Optical disk drive - Google Patents

Description

[0001]
[Industrial applications]
The present invention relates to an optical disc device that treats an optical disc as a disc-shaped recording medium and detects off-track.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, as a disk-shaped recording medium, for example, an optical disk such as a so-called compact disk (CD) or a mini disk (MD: Mini Disc, a trademark of Sony Corporation) has been known.
[0003]
Here, among the disc-shaped recording media, for example, the MD is a disc capable of recording and reproduction (recordable disc), a disc dedicated to reproduction (pre-master disc), and a recordable area recordable in the disc. There are discs (hybrid discs) provided with a premaster area in which pits are formed, and the like. The basic physical parameters and recording density of these various MDs are the same as those of the CD.
[0004]
FIG. 8 schematically shows the disk format of the three types of MDs. FIG. 8A shows the premaster disk, FIG. 8B shows the recordable disk, and FIG. (C) schematically shows a cross section of the hybrid disk.
[0005]
In these discs, the innermost part of the information area is a lead-in area. Here, information for setting laser power called TOC (Table Of Contents) and basic information for handling discs are provided. Information is recorded as pit information. The information area of each of these discs other than the innermost lead-in area is formed as a pit area or a recordable groove according to the disc characteristics such as read-only or recordable / reproducible.
[0006]
Further, for example, the recordable disc shown in FIG. 8B will be described in more detail with reference to FIG. 9. The disc has a radius of 32.0 mm, and the boundary between the lead-in area and the recordable area is: It is 16.0 mm from the center of rotation of the disc, and the recordable area is 14.5 mm from the lead-in area to the outer periphery.
[0007]
In the recordable disk, cluster and sector address information called ADIP (Address In Pregroove) is formed by wobbling in a recording groove around the entire recordable area when the disk is molded. Using this, not only tracking and control of the spindle servo for CLV (constant linear velocity), but also system control including access operations at the time of recording and reproduction are performed. The ADIP signal is obtained by modulating a 22.05 kHz carrier with address information, and the recording groove meanders by about 30 nm in this carrier. The optical pickup can read the address information by the wobbling groove independently of the recording signal, and at the time of recording, recording is performed in cluster units based on the address information.
[0008]
[Problems to be solved by the invention]
When seeking (traversing) in an optical disk apparatus that handles an optical disk as described above, conventionally, a track crossing signal that outputs one pulse per track crossing, such as a so-called track zero cross signal, is generated and the number of pulses is calculated. , The moving distance of the optical pickup was controlled. In this case, if, for example, a beard-like noise pulse is included in the track crossing signal, an erroneous number of tracks may be counted unnecessarily. Also, when the tracks cross in the opposite direction due to the eccentricity of the optical disk or the swing of the objective lens of the optical pickup, the wrong number of tracks is counted.
[0009]
Accordingly, the present invention has been proposed in view of the above-described circumstances, and has as its object to provide an optical disk device that does not count an incorrect number of tracks during a seek operation.
[0010]
[Means for Solving the Problems]
The present invention has been proposed to achieve the above-described object, and in an optical disc apparatus capable of measuring the number of tracks traversing when a light beam spot traverses a track on a disc, the position of the light beam spot is determined. Off-track signal generation means for indicating whether the distance is within a predetermined range from the track center, track zero-cross signal generation means whose state changes at each zero cross of the tracking error signal, and track crossing measurement means for measuring the number of crossing tracks The track crossing measuring means is configured to determine that the off-track signal is out of the range, and that the track zero-cross signal changes from the first state to the second state with the movement of the light beam spot, While the track zero-cross signal is in the second state, the off-track signal is shifted from outside the range to the range. The count value of the number of track traversals is added when the number of tracks crosses, and the off-track signal indicates out of the range, and the track zero cross signal changes from the second state to the first state with the movement of the light beam spot. And when the off-track signal changes from outside the range to within the range while the track zero cross signal is in the first state, the count value of the number of track crossings is subtracted. Is what you do.
[0011]
[Action]
According to the present invention, when measuring the number of traversing tracks during a seek, the sequential change of both the track zero-cross signal and the off-track signal is observed, and when both signals change to a predetermined state, the number of traversing tracks is reduced. By adding or subtracting the measured value, pulse-like noise included in the track zero-cross signal or the off-track signal is prevented from being erroneously measured as the track crossing.
[0012]
【Example】
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0013]
FIG. 1 shows a schematic configuration of an optical disk device of the present invention.
[0014]
First, before describing the measurement of the number of tracks at the time of seeking performed in the optical disc apparatus of the embodiment of the present invention, the overall configuration and operation of the apparatus of the embodiment will be described.
[0015]
That is, in the optical disk apparatus shown in FIG. 1, a magneto-optical disk 2 such as a recordable MD, which is driven to rotate by a spindle motor 9, is used as a recording medium. Here, the magneto-optical disk 2 is used for recording and reproducing data other than music data such as program data, images, characters, and the like.
[0016]
The optical pickup 4 includes, for example, a laser light source such as a laser diode, a collimator lens, an objective lens 3, optical components such as a polarizing beam splitter and a cylindrical lens, and a photodetector having a light receiving section having a predetermined pattern. In addition, the photodetector corresponds to a sub-spot, in addition to a so-called four-segment photodetector corresponding to the zero-order light of the main spot and two photodetectors corresponding to ± 1st-order light used in a normal CD reproducing apparatus. In this case, two photodetectors are provided. The objective lens 3 is driven by a biaxial actuator, and the optical pickup 4 can be moved in the radial direction of the magneto-optical disk 2 by a stepping motor 10.
[0017]
The optical pickup 4 is provided at a position facing the recording magnetic head 1 via the magneto-optical disk 2. When data is recorded on the magneto-optical disk 2, the recording magnetic head 1 is driven by an OWH (overwrite head) driver 5, which is a recording-system head drive circuit, and a modulation magnetic field corresponding to the recording data is applied to the magneto-optical disk 2. A laser beam of a predetermined power (power for recording) is applied to the target track of the magneto-optical disk 2 via the objective lens 3 by the optical pickup 4 while being applied to the recording surface. Make a record.
[0018]
At the time of this recording, data to be recorded is supplied from, for example, a host computer or an external device via a SCSI (small computer systems interface) controller 24 and a terminal 35. The data supplied via the terminal 35 and the SCSI controller 24 is supplied to a buffer memory controller for controlling the dynamic RAM 22 as a buffer memory, and when the MD is used for data recording and reproduction (called MD DATA). Is temporarily stored in the RAM 22 via a control IC 21 comprising an MD / ECC encoder / decoder for adding an error correction code and performing error correction processing, and then read out and transmitted to the encoder of the signal processing circuit 6. Can be
[0019]
The control IC 21, the SCSI controller 24, and the system controller 15 perform various control operations based on program data stored in a ROM (read only memory) 23 connected via a bus. ing.
[0020]
The RAM 22 as the buffer memory also functions as a shockproof memory for storing data for a time required to return to a desired track when tracking of the optical pickup 4 is lost due to an impact during recording or reproduction, for example. are doing.
[0021]
The signal processing circuit 6 converts the data to be recorded into a recording signal by applying an error correction code and 8-14 modulation (EFM) to the data to be recorded. The recording signal is sent to the OWH driver 5, and the driver 5 drives the recording magnetic head 1 according to the recording signal. At the same time, the optical pickup 4 is controlled by an APC (Auto Power Control) / LD driver 39 so that the laser light becomes the power for recording, whereby the temperature of the recording surface of the recording track is raised to the so-called Curie point. To raise.
[0022]
At the time of reproduction, a recording track of the magneto-optical disk 2 is traced by a laser beam by the optical pickup 4 to perform magneto-optical reproduction using the so-called Kerr effect.
[0023]
The optical pickup 4 detects the reflected light of the laser light applied to the target track, and sends the detection signal to the RF amplifier 8. The detection signal includes a reproduction signal corresponding to a difference in the polarization angle (Kerr rotation angle) of the reflected light of the laser beam from the target track during reproduction, and a focus error signal during recording and reproduction, for example, by a so-called astigmatism method. And a tracking error signal by a so-called push-pull method, and furthermore, address information by the wobbling groove used at the time of recording.
[0024]
When reproducing data from the magneto-optical disk 2, the RF amplifier 8 extracts the reproduction signal from the output signal of the optical pickup 4 and sends the signal to the signal processing circuit 6. At this time, the signal processing circuit 6 obtains reproduction data by performing EFM demodulation and error correction processing on the reproduction signal by a decoder unit.
[0025]
The reproduction data via the RF amplifier 8 is temporarily stored in the RAM 22 via the control IC 21 and then read out, and is transmitted via the SCSI controller 24 to, for example, a host computer.
[0026]
If the data read from the magneto-optical disk 2 is compression-encoded audio data in the MD format, the compressed audio data is expanded by the expansion decoding circuit 31 from the control IC 21. The signal is decoded and then converted into an analog audio signal by the digital / analog conversion circuit 32. This analog audio signal is sent to an external line connection terminal via a line amplifier 33 and a terminal 36, or to a headphone connection terminal via a headphone amplifier 34 and a terminal 37.
[0027]
As the compression encoding of the audio data, so-called ATRAC (trademark of SONY Corporation, Adaptive Transform Acoustic Coding) which adopts the MD format and compresses the information amount to about 1/5 in consideration of human auditory characteristics. ) Is used. Although not shown, the apparatus of this embodiment also has a configuration in which, when an audio signal is supplied, the data is compressed and encoded and recorded on the MD disc 2.
[0028]
The RF amplifier 8 extracts the focus error signal and the tracking error signal from the output signal of the optical pickup 4 during recording and reproduction, and sends these error signals to the servo circuit 13.
[0029]
The servo circuit 13 generates a focus servo signal and a tracking servo signal using the focus error signal and the tracking error signal read by the optical pickup 4, and sends these servo signals to the optical pickup 4 via a driver 39. send. As a result, focus servo and tracking servo in the optical pickup 4 are performed. That is, for the focus servo, the focus control of the optical system of the optical pickup 4 is performed so that the focus error signal becomes zero. For the tracking servo, the tracking control of the optical system of the optical pickup 4 is performed so that the tracking error signal becomes zero.
[0030]
The servo circuit 13 also includes a track traversing circuit that measures the number of traversing tracks during a seek according to the present invention described later based on the tracking error signal, a mirror signal described later, and a signal from the four-division photodiode. A measurement circuit 50 is also provided.
[0031]
Further, the servo circuit 13 has a configuration for the rotation servo of the spindle motor 9 for rotating the magneto-optical disk 2 in addition to the configuration for the focus servo and the configuration for the tracking servo described above. . That is, the servo circuit 13 drives the spindle motor 9 via the spindle driver 11 for driving the spindle motor 9 so as to rotate the magneto-optical disk 2 at a predetermined rotation speed (for example, a constant linear velocity: CLV). Perform the servo.
[0032]
The rough servo of the spindle motor 9 is performed by the motor control and command conversion circuit 14 based on the FG signal from the spindle driver 11. Further, the motor control and command conversion circuit 14 controls the rotation speed (CLV control) of the magneto-optical disk 2 according to the position of the optical pickup 4 with respect to the magneto-optical disk 2. The CLV control in the motor control and command conversion circuit 14 is performed based on a count value for the feed amount of the stepping motor 10. Further, the motor control and command conversion circuit 14 also performs serial / parallel conversion and various command conversions.
[0033]
In this optical disk apparatus, the optical pickup 4 and the recording magnetic head 1 are moved to target track positions of the magneto-optical disk 2 specified by the system controller 15. These movements are realized by the motor control and command conversion circuit 14 controlling the stepping motor 10 as a drive source of the thread feed mechanism based on the designation from the system controller 15. In other words, the system controller 15 uses the count value obtained by counting the number of steps of the stepping motor 10 (the number of steps corresponding to the thread feed amount, that is, the step address) in the radial direction of the optical pickup 4 on the magneto-optical disk 2. The position can be known. Further, the system controller 15 can also know the radial position of the optical pickup 4 on the magneto-optical disk 2 from the address information corresponding to the wobbling groove read by the optical pickup 4.
[0034]
The address decoder 7 generates an address signal and an FM carrier signal in accordance with the signal corresponding to the wobbling groove on the magneto-optical disk 2 extracted via the RF amplifier 8, and sends this to the signal processing circuit 6.
[0035]
At this time, the signal processing circuit 6 sends the read address to the system controller 15 in response to the request, and always compares the FM carrier signal with a predetermined reference clock signal. Controls the spindle servo section.
[0036]
The system controller 15 includes, for example, a CPU (Central Processing Unit), and controls each unit, and also controls data transmission / reception with a host computer externally connected via the SCSI terminal 35.
[0037]
Next, in the optical disk device according to the embodiment of the present invention having the above-described configuration, the number of traversing tracks at the time of seek is measured by the following configuration.
[0038]
That is, the optical disk device of the embodiment of the present invention indicates by a state change whether or not the magnitude of the tracking error is within a predetermined range from the track center as shown in FIG. An off-track signal (１ ／ off-track signal, for example, becomes “H” when the area exceeds ± 1/4 track from the center of the track) is generated, and the zero-crossing of the tracking error signal as shown in FIG. A track zero cross signal whose state changes (for example, “H” when the tracking error signal is positive and “L” when the tracking error signal is negative) is generated, and the state change between the ４ off-track signal and the track zero cross signal is generated. The track crossing measuring circuit 50 is provided for measuring (counting) the number of crossing tracks based on the above.
[0039]
More specifically, in the track crossing measurement circuit 50 of the optical disk device of the present embodiment, the 1/4 off-track signal changes to "H" and the track zero-cross signal changes from "H" to "L". When the 1/4 off-track signal changes from "H" to "L" while the zero-cross signal is "L", the count value of the number of track crossings is incremented by one. Conversely, in the track crossing measurement circuit 50, the 1/4 off-track signal changes to "H" and the track zero cross signal changes from "L" to "H", and then the track zero cross signal changes to "H". When the 1/4 off-track signal changes from "H" to "L", the count value of the number of track crossings is decremented by one.
[0040]
That is, the logic algorithm in the track crossing measurement circuit 50 is as shown in the flowchart of FIG.
[0041]
In FIG. 3, in step S1, the count value of the number of track crossings is initialized to 0, and in step S2, it is determined whether the track zero-cross signal Z is "H" and the 1/4 off-track signal Q has risen. .
[0042]
When the determination is Yes in step S2, the process proceeds to step S3. In step S3, it is determined whether or not the 1/4 off-track signal Q is "H". If No, the process returns to step S2. On the other hand, when it is determined Yes in step S3, the process proceeds to step S4. In step S4, it is determined whether or not the track zero cross signal Z has fallen. If the determination is No, the process returns to step S3, and if the determination is Yes, the process proceeds to step S5. In this step S5, the count value is incremented by one, and thereafter, the process proceeds to step S7.
[0043]
When the determination is No in step S2, the process proceeds to step S6. In this step S6, it is determined whether or not the track zero cross signal Z is "L" and the 1/4 off-track signal Q has risen. If No is determined in step S6, the process returns to step S2, and if Yes is determined, the process proceeds to step S7. In this step S7, it is determined whether or not the 1/4 off-track signal Q is "H". If the determination is No, the process returns to step S2. If the determination is Yes, the process proceeds to step S8. In step S8, it is determined whether or not the track zero cross signal Z has risen. If the determination is No, the process returns to step S7. If the determination is Yes, the process proceeds to step S9. In this step S9, the count value is decremented by 1, and then the process proceeds to step S3.
[0044]
Next, FIG. 4 shows a specific configuration of a 1/4 off-track detection circuit that generates the 1/4 off-track signal in the track crossing measurement circuit 50. The 1/4 offset detection circuit is a circuit that is normally used to generate a traverse signal when a light beam spot crosses a track formed by a groove on a disk.
[0045]
In FIG. 4, four signals from four-segment photodiodes (each photodiode is usually represented by four of A, B, C, and D) provided in the optical pickup 4 described above are connected to a terminal 46. Is supplied. The sum signal of the four signals corresponding to A, B, C, and D of the four-division photodiode supplied to the terminal 46 is AC-coupled and amplified by the capacitor C1 and the inverting amplifier 41, and transmitted to the comparator 42. Can be The comparator 42 compares the AC-coupled and amplified signal with a level in which the signal is offset. These configurations are for detecting that the amount of light becomes maximum on the track (the center of the groove). By further applying an offset, the off-track signal becomes "L" at the time of normal tracking ON. The output of the comparator 42 is output from a terminal 47 via a changeover switch 43 as a 1/4 off-track signal.
[0046]
Here, in accordance with a switching control signal supplied from a terminal 45, the changeover switch 43 outputs an off-track signal based on a signal from the four-division photodiode and a mirror signal described later supplied through a terminal 44. Is used to switch over. The mirror signal is used when the signal from the optical disk is a signal from a track composed of pits, and the signal from the four-division photodiode is obtained from the recording area (ie, groove) of the magneto-optical disk. Signal.
[0047]
In any case, the mirror signal and the 1/4 off-track signal based on the signal from the four-division photodiode are signals that are "L" on tracks and "H" between tracks. Note that the ト ラ ッ ク off-track signal may also have a whisker-like noise due to a defect on the disk, electric noise, or the like, but as described above, the の off-track signal and the track zero cross signal Since the number of crossing tracks is measured using both signals, there is no measurement error.
[0048]
Next, the mirror circuit for generating the mirror signal is configured as shown in FIG. The mirror circuit is usually a circuit for generating a traverse signal when a light beam spot crosses a track formed by pits on a disk, and is "L" on a track and "L" on a mirror section between tracks. The traverse signal which becomes H "is output as a mirror signal. Further, the mirror circuit outputs a mirror signal which becomes “H” even when a defect on the disk is detected.
[0049]
5, an RF signal from the optical pickup 4 as shown in FIG. 6A is supplied to a terminal 80, for example. This RF signal is inverted and amplified by an inverting amplifier 81 via a DC component cutting capacitor C41 to be a signal shown in FIG. 6B, and is sent to a peak hold circuit 82 and a bottom hold circuit 83 at the subsequent stage.
[0050]
The capacitance of the capacitor C42 is set so that the peak hold circuit 82 can follow a traverse of, for example, 30 kHz. On the other hand, the bottom hold circuit 83 has a time constant that can follow the fluctuation of the envelope of the mirror unit in the disk rotation period. The capacitance of the capacitor C43 is set to be set. The signal held by the peak hold circuit 82 becomes a peak hold signal H as shown in FIG. 6C, and the signal held by the bottom hold circuit 83 is a bottom hold signal as shown in FIG. It becomes signal I.
[0051]
Each of the hold signals H and I is converted into a signal J shown in FIG. In the configuration including the voltage dividing resistors of the resistors R44 and R45 in the next stage, the differential amplifier 85, and the diode D41, the level of 2/3 of the peak value of the signal J is peak-held with a large time constant in FIG. Is generated by the comparator 86, and the output of the comparator 86 is output from the terminal 87 as a mirror signal as shown in FIG.
[0052]
The track zero cross signal can be generated by a track zero cross detection circuit using a comparator 101 as shown in FIG. 7, for example. That is, in FIG. 7, a tracking error signal TE is supplied to a terminal 100, the tracking error signal TE is compared with a predetermined reference value by a comparator 100, and a comparator output is output from a terminal 102 as a track zero cross signal. .
[0053]
As mentioned above, although one Example of this invention was described, this invention is not limited to this Example, Various changes are possible based on the technical idea of this invention. The above-described measurement of the number of traversing tracks according to the present invention can be realized not only by a hardware configuration but also by software.
[0054]
Furthermore, in the above-described embodiment, an example has been described in which the present invention is applied to an MD optical disk device used for recording and reproducing data other than music, such as program data, video, characters, and the like. The present invention is also applicable to an apparatus for recording and reproducing an MD optical disc.
[0055]
【The invention's effect】
As described above, in the optical disc apparatus of the present invention, when the number of traversing tracks is measured at the time of seek, the measured value of the number of traversing tracks is added or subtracted by the sequential change of both the track zero cross signal and the off-track signal. Since pulse-like noise included in the track zero-cross signal and off-track signal is not incorrectly measured as track crossing, the track crossing direction and the number of crossing tracks can be accurately counted, and there is no wrong measurement. In addition, the seek time can be reduced.
[Brief description of the drawings]
FIG. 1 is a block circuit diagram showing a schematic configuration of an optical disk device according to an embodiment of the present invention.
FIG. 2 is a waveform diagram showing a relationship among a tracking error signal, a track zero-cross signal, and a 1/4 off-track signal in the device of the present embodiment.
FIG. 3 is a flowchart illustrating a logic algorithm of a track crossing measurement circuit.
FIG. 4 is a circuit diagram showing a specific configuration of a 1/4 off-track detection circuit.
FIG. 5 is a circuit diagram showing a specific configuration of a mirror circuit.
FIG. 6 is a waveform chart showing waveforms at various parts of the mirror circuit.
FIG. 7 is a circuit diagram showing a specific configuration of a track zero cross detection circuit.
FIG. 8 is a diagram showing a disc type and a recording layout of an MD.
FIG. 9 is a diagram schematically showing a recordable disc format.
[Explanation of symbols]
1 Recording magnetic head
2 Magneto-optical disk
4 Optical pickup
5 OWH driver
6. Signal processing circuit
7 Address decoder
8 RF amplifier
9 Spindle motor
10 Stepping motor
11 Spindle driver
13 Servo circuit
14 Motor control circuit
15 System controller
16 ROM
50 Track crossing measurement circuit

Claims (2)

In an optical disc device capable of measuring the number of crossing tracks when a light beam spot crosses tracks on a disc,
Off-track signal generating means indicating whether the position of the light beam spot is within a predetermined range from the track center ,
Track zero-cross signal generating means whose state changes at each zero cross of the tracking error signal ,
Track crossing measuring means for measuring the number of crossing tracks ,
The track crossing measuring means is configured to determine that the off-track signal is out of the range, and that the track zero-cross signal changes from a first state to a second state with the movement of the light beam spot. Adding the count value of the number of track traverses when the off-track signal changes from outside the range to within the range during the second state, the off-track signal indicates outside the range, and the light With the movement of the beam spot, the track zero-cross signal changes from the second state to the first state, and then the off-track signal changes from outside the range while the track zero-cross signal is in the first state. An optical disc device, wherein a count value of the number of track crossings is subtracted when the count value has changed within the range . The off-track signal generating means sets a range of approximately 1/4 track from the center of the track toward the outside or inside of the disk and indicates whether or not the range is outside the range. Item 2. The optical disk device according to item 1.

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