JP2001043539A - Off-track detecting circuit and disk drive device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce an accurate off-track detecting circuit. SOLUTION: The off-track detecting circuit is constituted in the manner of providing an envelope detecting means 31 for detecting the envelope of a reflected light quantity signal produced from the reflected light at the time when a recording medium is irradiated by a laser beam, a filter means 32 for cutting the DC component of the envelope signal detection by the envelope detecting means 31, and a comparison means 33 for comparing an output of the filter means 32 with a prescribed level to output the comparison result as the off-track detecting signal. That is, the accurate off-track detecting signal is obtained by detecting the difference in the reflected light quantities which is generated by crossing the groove/land at the time of traversing, even though the modulation degree of an RF signal is small in a CD-R (recordable), CD-RW (rewritable), etc.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an off-track detection circuit and a disk drive device equipped with the off-track detection circuit.

[0002]

2. Description of the Related Art In a disk drive device for recording / reproducing data on / from an optical disk, a laser beam is output from the optical pickup to the disk, a recording mark is formed on the disk, or reflected light of the laser beam is detected. To reproduce information. The laser light output from the optical pickup is focused on the recording surface of the disk by a focus servo, so that an appropriate laser spot is obtained.
At the time of recording / reproduction, a tracking servo is applied so as to accurately trace tracks on the disk.

[0003] CD-DA (CD-Digital Audio) and CD-
In a read-only disc medium such as a ROM, embossed pits are formed on the disc, and the pit train is formed as a track. Therefore, a tracking servo is applied so that the laser spot traces the track as the pit train. Will be. On the other hand, CD-R
(CD-Recordable = CD-WO), CD-RW (CD-R
In a data writable disk medium such as ewritable, a groove is formed on the disk recording surface, and the groove or a land between the grooves is used as a data recording track.

Here, the structure of the CD-R will be described with reference to FIGS. The layer structure of the disc 90 as a CD-R is as follows:
As shown in FIG. 7 as a cross-sectional view, a transmission layer 94 made of polycarbonate and a recording layer 9 of a spin-coated organic dye are provided.
3. It is formed of a reflective film 92 deposited with gold and a protective film 91 made of a UV curable resin. Then, a pre-groove GV and a land LD are formed on the recording layer 93 as shown. The pregroove GV is slightly wobbling as shown in FIG. 8, and the wobbling is formed based on a signal whose address is FM-modulated. Therefore,
By extracting the meandering information, the absolute address (time information) on the disc can be determined.

Recording on a CD-R is performed by using a pre-groove GV to control the intensity of a laser output to be irradiated in accordance with data "1" and "0" while performing tracking servo and spindle servo. Done. The portion of the CD-R where no data is recorded (unrecorded area)
Although the portion having high reflectivity (about 65 to 70%), the optical property of the recording layer 93 in the pre-groove GV is changed by the heat in a portion irradiated with a strong laser output, and the CD-DA having a low reflectivity is obtained. It is the same part as the pits. on the other hand,
The portion irradiated with the weak laser output remains at a high reflectance. Therefore, by controlling the intensity of the laser output in accordance with the recording data, a pit row of pits having changed reflectance is formed. Such a pit row is formed in the pre-groove GV.

[0006]

When recording and reproducing data on and from an optical disk, a track jump is frequently made to move the trace position to another track.
This track jump is executed by moving the objective lens in the radial direction of the disk by a two-axis mechanism in the optical pickup (if a long distance track jump is performed, sled movement (movement of the entire optical pickup))
Also accompanies). In track jump, the tracking servo is turned off and the laser spot is forcibly moved in the direction across the track.When the laser spot reaches the target track, the tracking servo is turned on at that point and the laser spot is turned on. Is set on the target track. However, if an actuator such as a biaxial mechanism is not settled properly, tracking may be performed on a track that deviates from a target track even if the tracking servo is turned on.

In order to improve the setting at the end of the track jump, when the track jump is excessive, the relative movement direction of the objective lens and the disk is detected, and the actuator is braked. It is possible to settle to the target track in a short time. That is, a brake is applied to the actuator by applying a voltage to the actuator in a direction opposite to the moving direction by the track jump. For this purpose, it is necessary to detect the moving direction of the actuator.
An off-track detection signal (inter-track detection signal) called an RR signal is obtained, and the moving direction of the actuator is determined from the phase difference between the MIRR signal and the tracking error signal.

The off-track detection signal is a signal for detecting that the laser spot is in an off-track state, that is, at a position between tracks, and an off-track detection circuit for obtaining the off-track detection signal is shown in FIG. 9
It is configured as shown in FIG.

FIG. 9 shows an off-track detection circuit 120 and a tracking servo system. The optical pickup 101 guides laser light from a laser diode 104 to an objective lens 102 via an optical system (not shown), and irradiates the disk with laser light using the objective lens 102 as a laser output terminal. The objective lens 102 can be moved in a radial direction (tracking direction) and a contact / separation direction (focus direction) of the disk by a biaxial mechanism 103. The light reflected from the disk is received by the photodetector 105, and the photodetector 105 outputs a current signal corresponding to the amount of received light. The RF amplifier 106 generates various signals by performing current / voltage conversion, matrix calculation, and the like on the current signal from the photodetector 105, and generates a tracking error signal TE for tracking servo. Tracking error signal TE
Is an error signal indicating the amount of deviation of the laser spot from the track center.

The tracking error signal TE from the RF amplifier 106 is supplied to a tracking servo circuit 107. The tracking servo circuit 107 performs processing such as amplification and phase compensation on the tracking error signal TE to generate a tracking drive signal.
To the two-axis driver 110 via the. The two-axis driver 110 drives the tracking coil of the two-axis mechanism 103 according to the tracking drive signal.
As a result, the pickup 101, the RF amplifier 106,
Tracking servo circuit 107, two-axis driver 110,
A tracking servo loop is formed by the biaxial mechanism 103. In other words, the biaxial mechanism 103 controls the position of the objective lens 102 based on the tracking error signal TE, which is track error information, so that the laser spot traces the track on the disk as a tracking servo operation. Is done.

When a track jump is performed, such a tracking servo loop is turned off. That is, based on the track jump instruction signal TJ from the control unit (not shown), the tracking servo circuit 107 generates a jump drive signal for forcibly moving the objective lens in the disk radial direction instead of a tracking drive signal based on the tracking error signal TE. Generated and supplied to the biaxial driver 110. And the two-axis driver 110
By driving the tracking coil of the two-axis mechanism 103 according to the jump drive signal, a track jump is executed.

An off-track detection circuit 120 is provided for such a tracking servo system as shown in FIG. The off-track detection circuit 120 includes a peak hold circuit 121, a bottom hold circuit 122, an attenuator 123, and a comparator 124. For the off-track detection circuit 120, the RF amplifier 106
A signal (sum signal of the amount of reflected light) is supplied. The peak hold circuit 121 and the bottom hold circuit 122 detect a peak envelope and a bottom envelope of the RF signal, respectively. Then, after the peak envelope from the peak hold circuit 121 is attenuated by a required level in the attenuator 123, the peak envelope is compared with the bottom envelope from the bottom hold circuit 122 by the comparator 124. The result of this comparison is the off-track detection signal MIRR.

The off-track detection signal MIRR is supplied to a brake circuit 108. The brake circuit 108 determines the moving direction at the time of the track jump by observing the phase difference between the off-track detection signal MIRR and the tracking error signal TE, and determines a braking voltage which is a voltage for moving in a direction opposite to the moving direction. Output. Therefore, when the track jump is excessive as described above, the control unit connects the switch 109 to the terminal b, so that a voltage in a direction opposite to the moving direction by the track jump is supplied to the biaxial driver 110. Then, a drive current in the opposite direction is applied to the tracking coil of the biaxial mechanism 103, so that the track jump movement of the objective lens 102 is braked. This enables quick settling at the end of the track jump.

However, such control is, of course, based on the premise that the off-track detection signal MIRR is a signal that correctly detects off-track. If the off-track detection signal MIRR is not an accurate signal, the brake circuit 108 cannot accurately determine the direction of the track jump movement, and thus cannot perform appropriate brake control.

The operation of generating the off-track detection signal MIRR by the off-track detection circuit 120 will be described with reference to FIG. FIGS. 10A and 10B show CD-DA and CD-ROM.
For example, a tracking error signal TE and an RF signal at the time of a track jump (traverse state) crossing a plurality of tracks from the inner circumference side to the outer circumference side of a disk on which data is recorded by emboss pits. ing. Note that the RF signal has a large modulation degree on the track, while the modulation degree is small when the track is off-track.

In the above off-track detection circuit 120,
First, the peak hold circuit 121 and the bottom hold circuit 122 extract the peak envelope Epk and the bottom envelope Ebtm of the RF signal. The attenuator 123 attenuates the peak envelope Epk by a predetermined level (for example, about 0.4 to 0.6),
For example, a peak envelope EpkATT having an attenuated level as shown is obtained. By comparing the peak envelope EpkATT and the bottom envelope Ebtm with the comparator 124, an off-track detection signal MIRR as shown in FIG. 10C is obtained. That is, during the traverse period, the on-track state (t
ON) and the off-track state (tOF) appear alternately, and an accurate off-track detection signal MIRR is obtained accordingly.

FIG. 10 shows the case of a track jump from the inner circumference to the outer circumference of the disk. In this case, the phase relationship between the off-track detection signal MIRR and the tracking error signal TE is as shown in FIG. That is, when the off-track detection signal MIRR becomes “H”, the phase relationship is such that it corresponds to the rising period of the tracking error signal TE. On the other hand, when the track jumps from the outer circumference to the inner circumference of the disk, when the off-track detection signal MIRR becomes “H”, the phase relationship corresponding to the falling period of the tracking error signal TE is reversed. Becomes Accordingly, the brake circuit 108 in FIG. 9 can determine the track jump movement direction by checking the phase relationship between the off-track detection signal MIRR and the tracking error signal TE.

However, in the case of a CD-R, for example, if the track crosses a track as an unrecorded area, an accurate off-track detection signal MIRR cannot be obtained. FIG.
(A) and (b) show a disc as a CD-R.
The tracking error signal TE and the RF signal at the time of a track jump (at the time of a traverse state) are shown. In addition,
In FIG. 11, the left side shows the time of traversing an unrecorded area, and the right side shows the time of traversing a recorded area.

In the recorded area, since the modulation degree of the RF signal is sufficiently large, the accurate off-track detection signal MIR
R is obtained. That is, as described above, in the off-track detection circuit 120, the peak envelope Epk is attenuated by a predetermined level to obtain a peak envelope EpkATT having an attenuated level as shown in the figure, and the peak envelope EpkATT and the bottom envelope Ebtm are compared by the comparator 124. By doing so, an accurate off-track detection signal MIRR as shown in the right part of FIG.

However, in the unrecorded area shown on the left side, the modulation degree of the RF signal is extremely small, and the peak envelope Epk and the bottom envelope Ebtm have substantially the same value. Therefore, the peak envelope EpkATT and the bottom envelope attenuated as described above are used. When the Ebtm is compared with the comparator 124, the off-track detection signal M
The IRR is always "H" as shown in the left part of FIG. In other words, an erroneous off-track detection signal MIRR that is an off-track period for the entire traverse period is generated. In such a case, the moving direction cannot be accurately determined by the brake circuit 108, and the settling process at the end of the track jump cannot be efficiently executed. This leads to a prolonged seek time and occurrence of a seek error.

[0021]

SUMMARY OF THE INVENTION In view of the above problems, the present invention provides accurate off-track detection even when a sufficient degree of modulation cannot be obtained, such as in an unrecorded area of a CD-R / CD-RW. It is intended to be able to generate a signal.

For this purpose, the off-track detecting circuit of the present invention comprises an envelope detecting means for detecting an envelope of a reflected light amount signal generated from reflected light when a recording medium is irradiated with laser light, and an envelope detecting means. Filter means for cutting the DC component of the detected envelope signal, and comparing the output of the filter means with a predetermined level,
And comparing means for outputting the comparison result as an off-track detection signal. That is, CD-R, CD-R
In a disc such as W, even if the modulation degree of the RF signal is small, a difference in the amount of reflected light (so-called radial contrast) occurs when crossing a groove / land during traversing. , An accurate off-track detection signal can be obtained.

Further, a servo-off detecting means for detecting an off period of the tracking servo based on a tracking error signal generated from a reflected light when the recording medium is irradiated with the laser light, and a tracking servo by the servo-off detecting means. And a mask means for preventing the off-track detection signal from being output from the comparing means during periods other than the off period. In the off-track detection configuration as described above, during the tracking servo-on period (the period when the off-track detection signal should be "L"), the output of the filter means is only a noise component. Although it cannot be obtained, the off-track detection signal output from the off-track detection circuit can be made correct by forcibly setting it to "L" by the mask means during that period.

In the disk drive apparatus of the present invention, an optical pickup means for irradiating a disk recording medium with laser light and receiving the reflected light, and a reflection light generated from the reflected light obtained by the optical pickup means Off-track detection means for detecting an envelope signal of the light amount signal, comparing a predetermined level after cutting a DC component of the envelope signal, and outputting the comparison result as an off-track detection signal, and using the off-track detection signal Moving direction determining means for determining a moving direction at the time of a track jump and performing a predetermined process. That is, an off-track detecting means having the configuration of the above-mentioned off-track detecting circuit is provided, and by obtaining an accurate off-track detection signal, the moving direction at the time of a track jump can be accurately determined. The off-track detecting means is configured to detect the off-period of the tracking servo, and to output no off-track detection signal as a comparison result except during the off-period of the tracking servo. I do.

In addition to the above-mentioned off-track detecting means, an envelope top signal and an envelope bottom signal of a reflected light amount signal generated from the reflected light obtained by the optical pickup means are detected, and the envelope top signal and the envelope bottom signal are detected. And a second off-track detecting means for generating and outputting an off-track detection signal based on That is, in addition to the above-described off-track detecting means capable of accurately detecting an unrecorded area of a CD-R, a second off-track detecting means suitable for a CD-DA, a CD-ROM or the like is used in combination. To enable more accurate off-track detection.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A drive apparatus corresponding to a CD-R and a CD-RW will be described below as an embodiment of the present invention. The CD-R is a write-once type medium using an organic dye for the recording layer as described above.
It is a medium whose data can be rewritten by using the phase change technology. FIG. 1 illustrates the configuration of a disk drive device according to the present embodiment capable of recording and reproducing data on a disk such as a CD-R or a CD-RW. In FIG. 1, the disk 90 is a CD-R or a CD-RW. Note that a CD-DA, a CD-ROM, and the like can be reproduced as the disk 90 here.

The disk 90 is loaded on the turntable 7 and is driven by the spindle motor 1 during recording / reproducing operation at a constant linear velocity (CLV) or a constant angular velocity (CA).
V). Then, the optical pickup 1 reads out pit data (pits due to phase change pits or organic dye change (reflectance change)) on the disk 90. In the case of a CD-DA or a CD-ROM, the pits are embossed pits.

In the pickup 1, a laser diode 4 as a laser light source, a photodetector 5 for detecting reflected light, an objective lens 2 as an output end of the laser light,
An optical system (not shown) for irradiating the laser beam to the disk recording surface via the objective lens 2 and guiding the reflected light to the photodetector 5 is formed. A monitor detector 22 that receives a part of the output light from the laser diode 4
Is also provided.

The objective lens 2 is held by a biaxial mechanism 3 so as to be movable in a tracking direction and a focusing direction. The entire pickup 1 can be moved in the disk radial direction by a thread mechanism 8. The laser diode 4 in the pickup 1 is driven to emit laser light by a drive signal (drive current) from a laser driver 18.

The information on the reflected light from the disk 90 is detected by the photodetector 5, converted into an electric signal corresponding to the amount of received light, and supplied to the RF amplifier 9. The RF amplifier 9 includes a current-voltage conversion circuit, a matrix operation / amplification circuit, and the like corresponding to output currents from a plurality of light receiving elements as the photodetector 5, and generates necessary signals by matrix operation processing. For example, it generates an RF signal as reproduction data, a focus error signal FE for servo control, a tracking error signal TE, and the like. The reproduction RF signal output from the RF amplifier 9 is supplied to a binarization circuit 11, and the focus error signal FE and the tracking error signal TE are supplied to a servo processor 14. The RF signal and the tracking error signal TE are output from the off-track detection circuit 23.
Is also supplied.

On the disk 90 as a CD-R or CD-RW, grooves (grooves) serving as guides for recording tracks are formed in advance as described with reference to FIGS. Time information indicating an absolute address on the disc is wobbled (meandering) by a signal modulated by FM. Therefore, during the recording operation, tracking servo can be applied from the groove information, and the absolute address can be obtained from the wobble information of the groove. The RF amplifier 9 extracts the wobble information WOB by a matrix operation process and supplies it to the address decoder 20. The address decoder 20 obtains absolute address information by demodulating the supplied wobble information WOB, and supplies the absolute address information to the system controller 10. Also, by injecting the groove information into the PLL circuit,
By obtaining the rotation speed information of the spindle motor 6 and comparing it with the reference speed information, the spindle error signal SPE
Is generated and output.

The reproduced RF signal obtained by the RF amplifier 9 is 2
The signal is binarized by the value conversion circuit 11 to be a so-called EFM signal (8-14 modulated signal), which is supplied to the encoding / decoding unit 12. The encoding / decoding unit 12 includes a functional part as a decoder during reproduction and a recording part as an encoder during recording. During reproduction, processing such as EFM demodulation, CIRC error correction, deinterleaving, and CD-ROM decoding are performed as decoding processing.
The reproduction data converted into the ROM format data is obtained. Further, the encoding / decoding unit 12 is provided with a disk 90
The sub-code extraction process is also performed on the data read from the sub-system, and the TOC and address information as the sub-code (Q data) are supplied to the system controller 10. Further, the encoding / decoding unit 12 generates a reproduction clock synchronized with the EFM signal by PLL processing,
The decoding process is executed based on the reproduced clock. The rotational speed information of the spindle motor 6 is obtained from the reproduced clock, and is compared with the reference speed information to generate a spindle error signal SPE. it can.

At the time of reproduction, the encoding / decoding unit 12
Accumulates the data decoded as described above in the buffer memory 20. As the reproduction output from the drive device, the data buffered in the buffer memory 20 is read and transferred and output.

The interface unit 13 is connected to an external host computer 80,
The communication of recording data, reproduction data, various commands, and the like is performed with the communication device. Actually, SCSI, ATAPI interface and the like are adopted. At the time of reproduction, the reproduced data decoded and stored in the buffer memory 20 is transferred and output to the host computer 80 via the interface unit 13. Note that a read command, a write command, and other signals from the host computer 80 are supplied to the system controller 10 via the interface unit 13.

On the other hand, at the time of recording, the host computer 8
Recording data (audio data or CD-ROM data) is transferred from 0, and the recording data is sent from the interface unit 13 to the buffer memory 20 and buffered. In this case, the encoding / decoding unit 1
2 is a process for encoding CD-ROM format data into CD format data (when supplied data is CD-ROM data), CIRC encoding and interleaving, adding subcode, Executes EFM modulation and the like.

The EFM signal obtained by the encoding process in the encoding / decoding unit 12 is subjected to a process called write equalization by an equalizer 21, and then the laser driver 1 as write data WDATA.
8 and written to disk. That is, the laser driver 18 gives the laser drive pulse modulated by the write data WDATA to the laser diode 4,
By performing the laser emission driving, pits (phase change pits and dye change pits) corresponding to the write data WDATA are formed on the disk 90.

APC circuit (Auto Power Control) 19
Is a circuit unit for controlling the output of the laser so as to be constant irrespective of the temperature while monitoring the laser output power by the output of the monitoring detector 22. The target value of the laser output is given from the system controller 10,
The laser driver 18 is controlled so that the laser output level becomes the target value.

From the focus error signal FE and tracking error signal TE from the RF amplifier 9 and the spindle error signal SPE from the encode / decode unit 12 or the address decoder 20, the servo processor 14 determines the focus, tracking, thread and spindle. Generate various servo drive signals and execute servo operation. That is, the two-axis driver 1 generates the focus drive signal FD and the tracking drive signal TD according to the focus error signal FE and the tracking error signal TE.
6 The two-axis driver 16 drives the focus coil and the tracking coil of the two-axis mechanism 3 in the pickup 1. As a result, a tracking servo loop and a focus servo loop are formed by the pickup 1, the RF amplifier 9, the servo processor 14, the two-axis driver 16, and the two-axis mechanism 3.

In response to a track jump command from the system controller 10, the tracking servo loop is turned off and a jump drive signal is output to the biaxial driver 16 to execute a track jump operation.

The servo processor 14 further sends a spindle error signal S to the spindle motor driver 17.
A spindle drive signal generated according to the PE is supplied. The spindle motor driver 17 applies, for example, a three-phase drive signal to the spindle motor 6 according to the spindle drive signal, and executes the CLV rotation of the spindle motor 6. In addition, the servo processor 14 generates a spindle drive signal in response to a spindle kick / brake control signal from the system controller 10, and causes the spindle motor driver 17 to execute operations such as starting, stopping, accelerating, and decelerating the spindle motor 6.

The servo processor 14 generates a thread drive signal based on, for example, a thread error signal obtained as a low-frequency component of the tracking error signal TE and an access execution control from the system controller 10 and supplies the thread drive signal to the thread driver 15. I do. The thread driver 15 drives the thread mechanism 8 according to a thread drive signal. Although not shown, the thread mechanism 8 has a mechanism including a main shaft for holding the pickup 1, a thread motor, a transmission gear, and the like.
5 drives the sled motor 8 according to the sled drive signal, whereby the required sliding movement of the pickup 1 is performed.

The various operations of the servo system and the recording / reproducing system as described above are controlled by a system controller 10 formed by a microcomputer. The system controller 10 executes various processes according to a command from the host computer 80. For example, when a read command requesting transfer of certain data recorded on the disk 90 is supplied from the host computer 80,
First, seek operation control is performed for the designated address. That is, a command is issued to the servo processor 14 to execute the access operation of the pickup 1 targeting the address specified by the seek command. afterwards,
An operation control necessary for transferring the data in the designated data section to the host computer 80 is performed. That is, data reading / decoding / buffering from the disk 90 is performed, and the requested data is transferred.

When a write command (write command) is issued from the host computer 80, the system controller 10 first picks up the pickup 1 at the address to be written.
To move. Then, the encoding / decoding unit 12 causes the data transferred from the host computer 80 to perform the encoding process as described above.
FM signal. Then, the write data WDATA equalized as described above is supplied to the laser driver 18 so that the recording is executed.

In such a disk drive device, when the track jump is performed to move the trace position by the laser spot from the pickup 1 to another track, the objective lens 2 is moved to the disk by the biaxial mechanism 3 in the pickup 1. This is performed by moving the optical pickup in the radial direction (the entire optical pickup may be moved by the sled mechanism 8). As described above, in the track jump, the tracking servo is turned off and the laser spot is forcibly moved in the direction crossing the track, but when the laser spot reaches the target track, the tracking servo is turned on at that point And set the laser spot on the target track. Here, in order to stabilize and speed up the setting, when the track jump is excessive, the relative movement direction of the objective lens 2 and the disk 90 is detected to apply a brake to the biaxial mechanism 3. I have to. Here, an off-track detection signal MIRR is used to detect the moving direction of the track jump, and an off-track detection circuit 23 is provided to obtain the off-track detection signal MIRR.

FIG. 2 shows the off-track detection circuit 23 and the tracking servo system in the configuration shown in FIG. 1 in detail. As described above, a current signal corresponding to the amount of reflected light obtained by the photodetector 5 of the pickup 1 is supplied to the RF amplifier 9 to generate various signals.

The tracking error signal TE generated by the RF amplifier 9 is supplied to a portion of the servo processor 14 as a tracking servo circuit 14a. The tracking servo circuit 14a performs processing such as amplification and phase compensation on the tracking error signal TE to generate a tracking drive signal,
c to the two-axis driver 16. The two-axis driver 16 drives the tracking coil of the two-axis mechanism 3 according to the tracking drive signal. As a result, a tracking servo operation is realized.

When a track jump is performed, such a tracking servo is turned off. That is, the tracking servo circuit 14a is
, A jump drive signal for forcibly moving the objective lens 2 in the disk radial direction is generated instead of a tracking drive signal based on the tracking error signal TE, based on the track jump instruction signal TJ, and supplied to the biaxial driver 16. . And the two-axis driver 16
The track jump is executed by driving the tracking coil of the two-axis mechanism 3 according to the jump drive signal.

The tracking error signal TE and the RF signal from the RF amplifier 9 are supplied to the off-track detection circuit 23.
Is also supplied. As shown in FIG. 2, the off-track detection circuit 23 includes a peak hold circuit (or a bottom hold circuit) 31, a high-pass filter (hereinafter, HPF).
32, a comparator 33, a tracking error detection circuit 35, and an AND gate 34.

The peak hold circuit 31 detects a peak envelope of the RF signal. The peak envelope from the peak hold circuit 31 is the HPF 32
Thus, the DC component is cut off and supplied to the comparator 33. The other end of the comparator 33 is supplied with a ground potential (zero level), and functions as a so-called zero cross comparator. This comparator 33
Becomes the off-track detection signal MIRR, and is output via the AND gate 34. (And Gate 3
4 and the function of the tracking deviation detecting circuit 35 will be described later.)

The off-track detection signal MIRR is supplied to a portion of the servo processor 14 as a brake circuit 14b. The brake circuit 14b determines the moving direction at the time of the track jump by observing the phase difference between the off-track detection signal MIRR and the tracking error signal TE, and determines a braking voltage which is a voltage for moving in a direction opposite to the moving direction. Output. Therefore, at the end of the track jump, the system controller 10 sends the control signal SB
By connecting the switch 14c to the terminal b by L, a voltage in the opposite direction to the moving direction by the track jump is supplied to the biaxial driver 16, and a driving current in the opposite direction is applied to the tracking coil of the biaxial mechanism 3. Therefore, a brake is applied to the track jump movement of the objective lens 2. This enables quick settling at the end of the track jump.

Here, the off-track detection circuit 23 of this embodiment
Is capable of accurately detecting an off-track detection signal MIRR even in an unrecorded area such as a CD-R. The generation operation of the off-track detection signal MIRR by the off-track detection circuit 23 will be described with reference to FIG. FIG. 3 (a)
11B shows the tracking error signal TE and the RF signal at the time of a track jump (at the time of a traverse state) for the disk 90 as a CD-R as in the case of FIG. The time and the traverse time of the recorded area are also shown on the right side.

As described with reference to FIG. 11, the modulation degree of the RF signal is sufficiently large in the recorded area, but the modulation degree of the RF signal is extremely small in the unrecorded area, and the peak envelope Epk and the bottom envelope Ebtm are almost equal. It has the same value. Here, the peak envelope Epk and the bottom envelope Ebtm have waveforms as shown in the figure as the amount of reflected light changes as the laser spot alternately crosses the groove and the land during traverse. In the peak hold circuit 31, such a peak envelope E
The peak envelope Epk becomes an alternating signal centered on the zero level as shown in FIG. 3C by detecting the pk and cutting the pk by the HPF32. Therefore,
When the peak envelope Epk output from the HPF 32 is zero-cross-compared by the comparator 33, an off-track detection signal MIRR as shown in FIG. 3E is obtained. That is, the off-track period tOF
, And an off-track detection signal MIRR that becomes “L” during the on-track period tON is obtained.

That is, an accurate off-track detection signal MIRR can be obtained even in a non-recorded area of a CD-R. Therefore, in the brake circuit 14b, regardless of the unrecorded area and the recorded area, the off-track detection signal MIRR is obtained. By performing a phase comparison between the signal MIRR and the tracking error signal TE,
Since the moving direction of the track jump can be accurately determined, the setting at the end of the track jump can be executed quickly and stably. Thereby, the seek operation can be stabilized and speeded up.

In the off-track detection circuit 23 of this embodiment, the portion of the peak hold circuit 31 may be a bottom hold circuit. In this case, the bottom envelope Ebtm of the RF signal is detected and DC cut by the HPF 32. The bottom envelope Ebtm as the output of the HPF 32 is an alternating signal centered on the zero level as shown in FIG. . Accordingly, even when the bottom envelope Ebtm output from the HPF 32 is zero-cross-compared by the comparator 33, an accurate off-track detection signal MIRR as shown in FIG. 3E can be obtained regardless of the unrecorded area and the recorded area. Will be done.

The disc 90 is a CD-DA, a CD-R
In the case of OM or the like, the RF signal is as described with reference to FIG. 10A, but in this case, the bottom envelope E
If a DC cut is performed on btm and zero-cross comparison is performed, an accurate off-track detection signal MIRR can be obtained. Therefore, in the case of a disk drive device assuming reproduction of a CD-DA, a CD-ROM, or the like, it is preferable to change the peak hold circuit 31 to a bottom hold circuit. Alternatively, the configuration may be such that the peak hold circuit and the bottom hold circuit can be switched between when reproducing a CD-R or CD-RW and when reproducing a CD-DA or CD-ROM.

Incidentally, the off-track detecting circuit 23
Then the peak hold circuit (or bottom hold circuit) 3
1, the accurate off-track detection signal MIRR can be obtained at the time of traverse by the HPF 32 and the comparator 33. However, during the period when the tracking servo is turned on (that is, during the period when the track on the groove is being traced), Since there is no change in the amount of light due to the crossing of the land, the envelope signal that has passed through the HPF 32 is only a noise component. Therefore, the output of the zero-cross comparator by the comparator 33 (that is, the off-track detection signal MIRR) is an undefined signal.

Since the tracking servo is on during the on-track state, the off-track detection signal MIRR should always be "L". Therefore, in this example, the off-track period (traverse period) is detected by the tracking deviation detection circuit 35, and “L” is output for the on-track period, so that the on-track period (tracking servo-on period) The output is set to “L”. In other words, during the tracking servo ON period, the comparator 33
Is masked so that the indefinite off-track detection signal MIRR is not output.

FIG. 4 shows a configuration example of the tracking error detection circuit 35. The tracking deviation detection circuit 35 includes, for example, a comparator 35a and a mono-multi timer 35b. The tracking deviation detection circuit 35 has RF
The tracking error signal TE from the amplifier 9 is supplied, and the tracking error signal TE
At 5a, a comparison is made with a predetermined comparison level Lcp.

For example, as shown in FIG. 5A, the tracking error signal TE is zero level (actually, a certain offset level) because the servo control works to converge the tracking error signal TE during the tracking servo ON period. , The amplitude of the tracking error signal TE increases in the traverse state (track servo off period) due to track crossing. Therefore, the tracking error signal TE at a predetermined comparison level Lcp by the comparator 35a.
5 (b) only during the traverse period
Can be obtained.

The pulse of FIG. 5 (b) is shaped by the mono-multi timer 35b so that the pulse shown in FIG.
A tracking deviation detection signal as shown in FIG. That is, the signal is "H" only during the traverse period (and the period based on the time constant of the mono-multi timer 35b), and is "L" during the tracking servo-on period. By supplying the tracking deviation detection signal to the AND gate 34, the off-track detection circuit 23 outputs the off-track detection signal MIR from the comparator 33 during the traverse period.
R is output. On the other hand, during the tracking servo ON period, the off-track detection signal MIRR in which the output of the comparator 33 is masked and forcibly set to “L” is output. That is, regardless of the traverse period and the tracking servo ON period, the accurate off-track detection signal MI
RR is output.

Next, another configuration example of the off-track detection circuit 23 will be described with reference to FIG. FIG. 6 shows the off-track detection circuit 23 and the tracking servo system in the configuration of FIG. 1 in the same manner as FIG. 2, and shows in detail the first off-track detection circuit 23 in this example. Detecting section 23A as a circuit, detecting section 23B as a second off-track detecting circuit, and AND gate 40
Is provided.

The detection section 23A is a part having the same configuration as the off-track detection circuit 23 shown in FIG. That is, the peak hold circuit (or bottom hold circuit) 31, H
This is a circuit unit that generates an off-track detection signal MIRR-1 by performing a zero-cross comparison after the DC component of the top (or bottom) envelope signal of the RF signal is cut by the PF 32 and the comparator 33. Further, a tracking deviation detecting circuit 35 and an AND gate 34
During the period in which the tracking servo is turned on, the output of the comparator 33 is masked to “L”.
The off-track detection signal MIRR-1 is output.

On the other hand, the detecting section 23B includes a peak hold circuit 36, a bottom hold circuit 37, an attenuator 38,
It comprises a comparator 39. The peak hold circuit 36 and the bottom hold circuit 37 detect the peak envelope and the bottom envelope of the RF signal, respectively. The off-track detection circuit 38 attenuates the peak envelope by a predetermined level, and then compares the peak envelope and the bottom envelope with a comparator 39. To generate the off-track detection signal MIRR-2. That is, the off-track detection circuit having the configuration described with reference to FIG. 9 is obtained.

The detectors 23A and 23B generate off-track detection signals MIRR-1 and MIRR-2, respectively, and the outputs of the detectors 23A and 23B are output via the AND gate 40 to the corresponding detectors 23A and 23B. The off-track detection signal MIRR from the off-track detection circuit 23 is used.

As can be understood from the description given with reference to FIG. 11, according to the configuration of the detecting section 23B, accurate off-track detection cannot be performed in an unrecorded area such as a CD-R.
Off-track detection signal MI output from detection section 23B
RR-1 is always "H". Therefore AND gate 40
From the off-track detection signal MIR from the detection unit 23A.
R-1 is directly output as the off-track detection signal MIRR. A recorded area such as a CD-R, and a CD-R
In the case of DA, CD-ROM, etc., detection units 23A, 23B
, The off-track detection signals MIRR-1 and MIRR-2 from the detection units 23A and 23B are the same, and are output as the off-track detection signal MIRR via the AND gate 40. You. Therefore, the off-track detection circuit 23 shown in FIG. 6 can also output an accurate off-track detection signal MIRR regardless of whether the area is an unrecorded area such as a CD-R. Also, the recorded area of the CD-R and the CD-R
In the case of DA or the like, the two detectors 23A and 23B can output a more reliable off-track detection signal MIRR.

In this example, the outputs of the two detectors 23A and 23B are used as the off-track detection signal MIRR via the AND gate 40. However, the detectors 23A and 23B are used in accordance with the disc type and area. May be switched and used. For example, CD-R, CD-R
During W playback, the off-track detection signal MIRR-1 from the detection unit 23A becomes the off-track detection signal MIRR. On the other hand, during playback of CD-DA and CD-ROM, the off-track detection signal MIRR-2 from the detection unit 23B becomes
A selection configuration may be adopted such that the off-track detection signal MIRR is obtained. Of course, the detection unit 23A may be selected only in the unrecorded area of the CD-R or CD-RW.

The disk drive apparatus and the off-track detection circuit as the embodiments have been described above. However, the present invention is not limited to the above-described example, and various modifications of the circuit configuration and the operation function can be considered. Needless to say, CD-R, CD
-Not only disk drive devices corresponding to CD type disks such as RW, CD-DA, CD-ROM, etc.
The present invention can also be applied to a disk drive device corresponding to another type of disk, such as a system type disk.

[0068]

As can be seen from the above description, according to the present invention, the envelope signal of the reflected light amount signal is detected, the DC component of the envelope signal is cut, and the envelope signal is compared with a predetermined level. Since the signal is output as a signal, the CD-
Even when a sufficient modulation factor cannot be obtained for a reflected light amount signal such as an unrecorded area in the R / CD-RW, there is an effect that an accurate off-track detection signal can be generated. By obtaining an accurate off-track detection signal, even in the case of a disk such as a CD-R / CD-RW, the moving direction at the time of a track jump can be accurately determined,
As a result, the setting (brake control) at the end of the track jump can be performed efficiently and accurately, so that the seek operation can be stabilized and speeded up.

In the tracking servo-on period (the period during which the off-track detection signal should be "L"), the off-track detection signal is forcibly set to "L", so that the off-track detection signal during the servo-on period is also accurate. It can be. Further, by using the second off-track detecting means for generating and outputting the off-track detection signal based on the envelope top signal and the envelope bottom signal of the reflected light amount signal, off-track detection can be performed more accurately. .

[Brief description of the drawings]

FIG. 1 is a block diagram of a drive device according to an embodiment of the present invention.

FIG. 2 is a block diagram of a tracking servo system and an off-track detection circuit according to the embodiment;

FIG. 3 is an explanatory diagram of off-track detection signal generation according to the embodiment;

FIG. 4 is a block diagram of a tracking deviation detection circuit according to the embodiment;

FIG. 5 is an explanatory diagram of an operation of the tracking deviation detection circuit according to the embodiment;

FIG. 6 is a block diagram of a tracking servo system and an off-track detection circuit according to the embodiment;

FIG. 7 is an explanatory diagram of a layer structure of a CD-R.

FIG. 8 is an explanatory diagram of a track structure of a CD-R.

FIG. 9 is a block diagram of a conventional tracking servo system and off-track detection circuit.

FIG. 10 is an explanatory diagram of conventional off-track detection signal generation.

FIG. 11 is an explanatory diagram of a conventional off-track detection signal generation.

[Explanation of symbols]

1 pickup, 2 objective lens, 2 biaxial mechanism, 4
Laser diode, 9 RF amplifier, 10 system controller, 12 encoding / decoding unit, 13
Interface section, 14 servo processor, 14a
Tracking servo circuit, 14b brake circuit, 1
4c switch, 16 two-axis driver, 19 APC circuit, 20 buffer memory, 22 monitor detector, 23 off-track detecting circuit, 23A, 23B detecting section, 31, 36 peak hold circuit, 32 HPF,
33, 39 comparator, 37, 40 AND gate, 35 tracking error detection circuit, 37 bottom hold circuit, 38 attenuator, 80 host computer, 90 disk

Claims (5)

[Claims] 1. An envelope detecting means for detecting an envelope of a reflected light amount signal generated from reflected light when a recording medium is irradiated with a laser beam; and a DC component of the envelope signal detected by the envelope detecting means. An off-track detection circuit, comprising: a filter means for cutting; and a comparison means for comparing an output of the filter means with a predetermined level and outputting a comparison result as an off-track detection signal. 2. A servo-off detecting means for detecting an off-period of a tracking servo based on a tracking error signal generated from a reflected light when a recording medium is irradiated with a laser beam; 2. The off-track detection device according to claim 1, further comprising: mask means for preventing the off-track detection signal from being output from the comparing unit during periods other than the off-period detection period. circuit. 3. An optical pickup means for irradiating a laser beam to a disk recording medium and receiving the reflected light, and detecting an envelope signal of a reflected light amount signal generated from the reflected light obtained by the optical pickup means. And
Off-track detection means for comparing a predetermined level after cutting the DC component of the envelope signal and outputting the comparison result as an off-track detection signal; And a moving direction discriminating means for discriminating and performing a predetermined process. 4. The off-track detecting means detects an off-period of a tracking servo and prevents an off-track detection signal as a result of the comparison from being output except during the off-period of the tracking servo. 4. The disk drive device according to claim 3, wherein the disk drive device is configured. 5. An envelope top signal and an envelope bottom signal of a reflected light amount signal generated from reflected light obtained by the optical pickup means, in addition to the off-track detection means, and the envelope top signal and the envelope bottom signal are detected. 4. The disk drive device according to claim 3, further comprising: a second off-track detection unit that generates and outputs an off-track detection signal based on the following.