JP2000251264A - Disk unit - Google Patents

Abstract

(57) [Problem] To provide an optical disc device capable of improving the reading accuracy of information in a PID section and controlling a light irradiation means in accordance with a change in the state of a disc such as a land section and a groove section. Kind Code: A1 A difference signal detection (HPP signal) or sum signal detection, which is a detection method capable of performing reading determination of PID information when an error occurs during disc loading or recording / reproducing processing and reading PID information. By employing a detection method that has a high probability of reading PID information among (RF signals), an optical disc device capable of performing stable recording and reproduction processing can be realized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an information recording / reproducing technique for a recording medium (hereinafter, simply referred to as "disk") on which information can be optically written and read.

[0002]

2. Description of the Related Art Information recorded on a disk is reproduced by focusing a laser beam on an information recording surface of the disk and detecting reflected light modulated by recording marks or pits.

[0003] One of such disks is DVD-
There is a RAM disk, land part (part between grooves)
And a groove (single spiral) in which tracks in the groove portion (groove portion) alternately appear approximately every round.
In addition, the pit including the address information for each sector is separated from the center position of the land portion or the groove portion by a quarter of the distance between the center positions of the land portions adjacent to the land portion in the inner circumferential direction and the outer circumferential direction. There is a disk formed by offsetting alternately at positions. These pit information is PI
It is called D (Physical Identification Data), and 17 to 40 pits are arranged in one round depending on the sector. In order to reproduce a recording mark formed on a disc having such a PID and having a land portion or a groove portion, the condensing position of the laser beam emitted from the light irradiating means on the information recording surface is changed to the land portion or the laser beam. It is necessary to scan along the center of the groove in the radial direction of the disk. Control (focus control) must also be performed.

At this time, a deviation amount (tracking deviation amount) substantially proportional to the distance from the center position of the land portion or the groove portion of the condensing position of the laser light can be obtained by detecting the diffracted light of the laser light by the groove. A tracking error signal (HPP signal) is used to perform tracking control of the condensing position of the laser beam using the deviation amount. In the land portion and the groove portion, the polarity of the deviation amount is inverted.

Here, the distance between the center of the land and the groove is a quarter of the distance between the center of the land and the land or the groove adjacent to the land and the groove of the groove adjacent to the land. FIG. 10 shows a schematic view of the disk surface near the PID portion in which pits are alternately offset at positions separated in the circumferential direction and the outer circumferential direction. Groove track center 30 as recording area 302
3 or a distance of one quarter of the distance between the center positions of the land portion and the land portion or the groove portion adjacent to the land portion or the groove portion and the groove portion adjacent thereto from the land track center 304 in the inner circumferential direction and the outer circumferential direction. PID areas 301 are formed alternately at different positions. 306 shows an HPP signal waveform based on the tracking deviation amount generated when the light spot moves on the groove portion and the land portion in the radial direction of the disk (from left to right on the paper) (305). As apparent from this, the polarity of the HPP signal is different between the land portion and the groove portion.
That is, when the HPP signal is negative in the groove portion, FIG.
It is determined that the light spot is shifted to the right of the paper surface of No. 0, and tracking is performed by moving the light spot to the left of the paper surface. In the land portion, when the HPP signal is negative, the light spot moves to the left of the paper surface. It will be shifted.

Accordingly, in order to continuously reproduce data from the land portion to the groove portion or from the groove portion to the land portion, the deviation amount is determined at the position where the land portion and the groove portion are switched (hereinafter referred to as "polarity reversal sector"). It is necessary to control the focus position of the laser light corresponding to the reversal of the polarity of the laser beam. Therefore, as disclosed in JP-A-6-176404 or JP-A-8-221821, a PID area is set on a track of a disk in sector units divided at substantially equal intervals in a circumferential direction, A pit is formed in that area.

For example, in a DVD-RAM disc, the PID of the -2nd sector, the -1st sector and the polarity inversion sector from the polarity inversion sector can recognize the position where the land portion and the groove portion are switched. Information indicating each of them is recorded in advance, and states such as polarity switching in tracking control and offset in focus control are switched between the land portion and the groove portion based on the information.

[0008]

In general, information is read by processing an information signal (RF signal) based on a change in the total amount of reflected light. When reading the information of the pits in the PID portion using the RF signal to perform the tracking control and the focus control on the disk having the pits formed at the positions of and 再生, the pits are １ ／ of the track center.
Since it is formed offset by the track, the signal amplitude cannot be made large, and it may be difficult to read the pit information of the PID portion. In this case, it becomes difficult to detect the polarity reversal sector, and it becomes difficult to perform tracking control, focus control, and the like. As a result, information recording and reproduction of recorded information may be extremely difficult.

[0009] From such a technical background, in the DVD standard, PID reading is performed by reading information of the PID portion using an HPP signal, thereby improving the SN ratio and symmetrically disposing the track. Of the two left and right PIDs (these PIDs include two pieces of address information), the HPP signal is recommended instead of the RF signal because one of the PIDs can be reliably read even if the track is offset.

However, since the HPP signal is easily affected by the aberration of the light irradiating means, the amplitude of the PID reproduced signal by the RF signal is larger than the amplitude of the PID reproduced signal by the HPP signal in some cases. It has been found for the first time through the research and development of the inventor.

An object of the present invention is to solve the above problems,
It is an object of the present invention to provide an information recording / reproducing technique capable of improving the reading accuracy of information in a PID section and controlling a light irradiation unit in accordance with a change in the state of a disc such as a land section and a groove section.

[0012]

As shown in FIG. 10, a pit is equivalent to a circumferentially short groove arranged in the circumferential direction, and therefore, along the groove track center 303 or the land track center 304. When the position of the light spot follows, depending on the presence or absence of a pit in the PID area 301, a signal is output between a level at the boundary between the land and the groove and a state without a groove, that is, a no-signal level.

Normally, by using the HPP signal, the reproduced signal amplitude of the pit can be made sufficiently large as compared with the case of using the RF signal, so that the reading accuracy of the information contained in the pit is increased. Further, by reading this information, it is possible to detect the polarity reversal sector in which the land and the groove are switched, and it is possible to control the light irradiation means suitable for each of the land and the groove.

However, since the HPP signal is easily affected by the aberration of the light irradiation means, in some cases, the amplitude of the reproduction signal by the RF signal is larger than the amplitude of the reproduction signal by the HPP signal. Therefore, in the present invention, before actually recording or reproducing data, it is determined whether reading the information of the PID portion using the RF signal or the HPP signal has a higher reading probability. The information of the PID section is read using a signal.

As described above, P by the RF signal and the HPP signal
By selectively reproducing the ID section, the P
The reading accuracy of the information in the ID section can be further increased.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a disk drive to which the present invention is applied will be described.

FIG. 1 shows an example of an information recording / reproducing apparatus which achieves the first object. A recording medium 1 for recording and reproducing information is held by a spindle motor 2 and rotates. As a recording film for forming the recording medium 1, a phase change recording film (GeSbTe) or the like applied to a DVD-RAM is used. There is.
A semiconductor laser that emits laser light for recording and reproducing information, an optical system that forms light from the semiconductor laser as a light spot of about 1 micron on a disk surface, and information that is reflected by light reflected from the recording medium 1. The recording and reproduction of information on the recording medium 1 are performed by an optical head 3 having a photodetector for performing light reproduction, automatic focus control, and light spot control such as track tracking. The optical head 3 constitutes a linear motor (not shown) which drives and positions the optical head 3 at high speed in the disk radial direction.

Usually, the optical disk device is a host computer 4 such as a personal computer or a workstation.
(Hereinafter abbreviated as host) and, for example, SCSI (Small Computer
System Interface) and ATAPI (AT Attached Packet)
Interface), which is connected by an interface cable conforming to the standard of the optical disk device. The interface control circuit 5 in the optical disk device decodes a command including a command and information data from the host 4 and a control circuit 6 including a microcomputer.
Through which information recording, reproduction and seek operations are performed.

First, the recording operation will be described. The recording data is issued after a recording command is issued from the host 4 with the recording position information (address information) on the recording medium 1 added, and stored in a buffer memory (not shown) in the control circuit 6. The signals are sequentially sent to the modulation circuit 7. In the modulation circuit 7, the recording data is converted into a code string corresponding to a run length limited (RLL) code, for example, a (2,10) RLL code, and further a pulse train corresponding to a mark shape formed on the recording film, for example, a mark position At the time of recording, a pulse train corresponding to the code “1” is converted to a pulse train corresponding to the pulse edge at the time of mark edge recording. These pulse trains are guided to the laser drive circuit 8 to turn the semiconductor laser on the optical head 3 into O.
N, OFF to emit a high output pulse, and a recording mark is formed on the recording medium 1 by a minute spot converged by the optical head 3.

Next, the reproducing operation will be described. During reproduction, a light spot from the optical head 3 is positioned on a track on the recording medium 1 specified by a reproduction command from the host 4, and a signal is reproduced from the track. First, when the semiconductor laser on the optical head 3 emits low-power DC light and irradiates the recording film on the recording medium 1, reflected light corresponding to the recording mark is obtained, and the reflected light is received by the photodetector in the optical head 3. After the data is photoelectrically converted into an electric signal and input to the reproduction circuit 9, the data is reproduced. Normally, the reproduction circuit 9
Is an automatic gain control circuit (AGC) for maintaining a constant signal amplitude, a waveform equalization circuit (EQ) for correcting optical spatial frequency deterioration, a binarization circuit (ASC), and a PLL (Phase
It is composed of a Locked Loop circuit and a discrimination circuit, and converts a reproduced data signal into binary data after binarizing the reproduced data signal. The discriminated binary data is input to the demodulation circuit 10 and demodulates the (2,10) RLL code to demodulate the original data. The demodulated data is guided to the control circuit 6 and error-corrected by an ECC (Error Correction Code), and then transferred from the interface control circuit 5 to the host 4 in response to a reproduction command from the host 4.

The photodetector in the optical head 3 detects, in addition to the data reproduction signal, an automatic focus signal for controlling the focus of the light spot on the recording film and a track tracking signal for performing track tracking control for positioning the track on an arbitrary track. The automatic focus signal and the track tracking signal for controlling the light spot are guided to the servo control circuit 11. The servo control circuit 11 includes an error signal generation circuit, a phase compensation circuit, and a drive circuit, and records and reproduces information by positioning the optical head 3 on an arbitrary track.

FIG. 2 is a schematic block diagram of the reproducing circuit 9 of the present invention.

A reproduction signal obtained by receiving the return light of the reflected light from the disk from the optical head 3 by a detector divided in the track direction is led to a reproduction circuit 9, and an arithmetic circuit 101 in the reproduction circuit A signal corresponding to an RF signal as a sum signal obtained by adding the reproduction signals obtained by receiving light from the respective detectors and an HPP signal as a difference signal obtained by subtracting the reproduction signals obtained by receiving light from the respective detectors is obtained. can get. Each signal controls a signal amplitude, and gain controllers (GCA) 102 and 1 that can set an optimum reproduction amplitude voltage for a subsequent circuit.
03 respectively. The difference signal HPP signal is also guided to the servo control circuit 11 as a tracking signal.

In the GCA, a constant gain is set, and the two GCA outputs are input to the switch 104. The switch 104 switches according to the PID portion and the data area on the disk according to the switching signal from the control circuit 6,
The RF signal of the sum signal is used as the recording data signal and the HPP of the difference signal is used.
The signal is led to the DC correction circuit 105 as a PID signal. D
The C corrector 105 suppresses a DC fluctuation component of an HPP signal or an RF signal including two types of PID information, and
(Automatic gain control unit) 106. AGC10
At 6, the output is output so as to be substantially constant, and input to the waveform equalizer (EQ) 107. After compensating for the high-frequency component of the reproduced signal lowered by the optical system or the like in the EQ 107 and securing the signal amplitude, the output of the EQ 107 has a duty ratio of the signal component of about 50% in an ASC (automatic slice level controller) 108. The binarization is automatically performed at such a slice level.

The binarized signal is output to PLL 109 and discriminator 110. The PLL 109 generates a substantially constant playback clock that follows the edge interval of the input signal (self-clocking), and the discriminator 110 discriminates the output of the ASC 108 at the timing of the edge of the playback clock and outputs it as a signal train. . The signal sequence is the demodulator 10
For example, in the case of (2, 10) RLL modulation, demodulation is performed according to a predetermined modulation rule such as conversion from a 16-bit signal sequence to 8-bit data, and the data in the recording area undergoes error correction in the ECC in the control circuit 6.

On the other hand, the data signal sequence of the PID information is similarly controlled by the control circuit 6 in accordance with the (2, 10) RLL modulation and the demodulator 1
At 0, the address information is demodulated. The PID information includes position information for the polarity-reversed sector. For example, it is possible to read information such as the second sector, the -1st sector, and the polarity-reversed sector from the polarity reversed sector. As a result, states such as polarity switching in tracking control and offset in focus control are switched between the land portion and the groove portion based on the information.

The minimum recording unit in a DVD-RAM disk is a sector unit, and its recording capacity is 2 Kbytes (B). Further, recording and reproduction processing is performed in 32 KB which is an ECC block unit, that is, in 16 sector units. At the time of normal recording, a PID determination is performed to confirm that the located sector is the specified sector, and if the PID cannot be read beyond a specified value among 16 PIDs in one block, the recording operation is performed. To stop. The specified value of the PID error is a minimum of 1, thereby preventing data destruction due to double writing. On the other hand, even if the PID cannot be read at the time of reproduction, there is no possibility of data destruction in the reproduction operation, so the specified value is, for example, 6. This is the demodulated PI
This is because it is possible to predict the position and content of the PID to be reproduced next from the D information content, and even if the information of the PID area at a plurality of locations cannot be reproduced, control is performed based on the PID information before the PID error. It is possible to generate a signal.

The PID is usually detected from the difference signal HPP signal of the split photodetector as described above. However, when aberrations related to the aperture lens of the optical head occur, the PID reproduction performance may be higher when the PID is detected from the RF signal of the sum signal. Factors that cause aberration include:
(1) Spherical aberration caused by disc substrate thickness deviation,
(2) Various aberrations are generated due to mechanical expansion and contraction of the optical system due to temperature change and the like, and (3) Coma aberration is generated due to disc tilt. Since the data area containing the information is read from the RF signal of the sum signal, the servo automatic focus control (A
The target point adjustment in F) is controlled so that the RF signal is maximized. However, since the detection method of the difference signal of the PID signal and the detection method of the sum signal of the data are different, when head aberration occurs, the optimal target point of AF for each may be different, so that the RF signal is maximized. It has been found for the first time from the research and development of the inventor that a controlled apparatus performs a stable recording process when a PID is detected from an RF signal.

According to the present invention, when loading a disc or when an error occurred in the recording / reproducing process is caused by a PID error, a PID error is generated so that a recording and reproducing operation can be stably performed even if a head aberration occurs. It is determined whether the reading performance of the difference signal detection or the sum signal detection is easier to read, and a detection system that is easier to read is selected.

FIG. 3 shows a setup process when a disc is loaded in the optical disc apparatus. First, after loading (111) the disk, the head is positioned at the innermost home position (11).
2). After the laser is turned on (113), an automatic focus (AF) servo pull-in operation (114) is performed, and at the same time, as a learning operation, the amplitude of the FE signal as an error signal is adjusted (115). After pulling in AF, tracking (T
R) The servo pull-in operation (116) is performed, and as in the case of the FE signal, as a learning operation, the amplitude of the TE signal as an error signal is adjusted (117). FE in the next step,
By performing gain adjustment (118) of each servo system of TE, variations in head characteristics, variations in circuit characteristics, and variations in actuator characteristics are absorbed, including amplitude adjustment learning of each servo system in the preceding stage. In this state, the optimum target point for automatic focusing is obtained by FE offset adjustment (119). Here, in the land portion and the groove portion, the RF signal amplitude, which is a data signal recorded while changing the FE offset, is sampled, and the offset having the maximum amplitude is the optimal target point offset. Therefore, the land portion and the groove portion have different offset values.

After the laser beam can be controlled to a desired position in the above steps, a PID determination (120) is performed. Here, in the state where the optimum target point offset is applied, the one having a higher probability of reading the PID during the PID reproduction operation using the difference signal HPP signal and the PID reproduction operation using the sum signal RF signal is selected. Specifically, for example, one block (1
The PID information is reproduced in (6 sectors), and the detection method (difference signal or sum signal) with the larger number of read sectors is selected. In FIG. 2, the PID determination is performed by the control circuit 6 in FIG.
Is input to the switching circuit 104. Where HP of the difference signal
To select the P signal, select the output of GCA103,
In addition, when the RF signal of the sum signal is selected, it is realized by selecting the output of the GCA 102.

Thus, by always adopting a signal which is easy to read the PID, the detection of the polarity reversal sector is stabilized, and the offset setting in the focus control corresponding to the land portion and the groove portion and the polarity switching in the tracking control are performed. As a result, stable recording and reproduction processing can be realized.

Thereafter, in order to determine the optimum recording power,
The test writing process (121) is performed. This processing is performed by the drive test on the innermost and outermost disks.
While changing the recording power in the track, the recording power that minimizes the data error is determined as the optimum power. When the trial writing process is completed, the state changes to the Ready state, which corresponds to a recording / reproducing command from the host.

Subsequently, when an error occurred in the recording / reproducing process is caused by a PID error, it is determined whether the PID reading performance is easier to read, the difference signal detection or the sum signal detection, and a PID for selecting a detection system which is easier to read is used. An example of performing the determination processing will be described. FIG. 4 shows the case of the recording process (123).

First, when a WRT command from the host 4 is received (124), the optical head is positioned on the designated track (125), and WRT (recording, 126) is executed in units of one block or a plurality of blocks on the target track. In the optical disk device, when importance is placed on data reliability, the recording track is reproduced in the next round by RAW (Read After Write) (127) processing, and ECC (Error C
The error correction (128) is performed by performing an ECC check in a state where the correction capability is lower than that in the normal reproduction by using the (orrection code). If no error occurs in the RAW processing (127), the WRT is terminated normally to wait for the next WRT command.
The process returns to the command reception (124). By performing this RAW check, the quality of the mark left on the disc for rewriting in the case of a poor quality recording state is assured, and a reproduction margin is ensured even when reproducing with another optical disc device. And playback compatibility is improved.

If an error occurs, the track is re-located to the same track and the same data is re-written (WRT) (129).
Then, an error is determined (131) by the RAW check (130) as in the above-described operation. As a result, if no error has occurred, the process returns to the original WRT command reception (124).

If an error occurs in the second RAW check, there is a possibility of a PID error, so the offset of the error signal (FE) of the autofocus system is adjusted (13).
2) By correcting the position deviation of the light spot,
Further, PID reading determination (133) is executed. Here, the PID reading performance based on the difference signal reproduction is compared with the PID reading performance based on the sum signal, and the one having the higher reading probability is selected.

Thereafter, as described above, the same data is again positioned on the same track, and the same data is redetermined (136) by WRT (134) and RAW check (135). If no error occurs after executing the autofocus target point adjustment and the PID reading determination, (1)
Return to 24). If an error has occurred, a test writing process (137) is executed to correct the recording power abnormality. After that, the same data is again positioned on the same track as described above, and the same data is re-WRT (138) and RAW check (13).
An error is determined (140) according to 9). If no error occurs after recording power adjustment by trial writing, WRT
Return to (124) to receive the command. If an error occurs, a WRT error report (14
1) to end the WRT processing.

As described above, in the recording process, by performing the PID determination process, the RAW check can be performed with high accuracy.
T error can be reduced.

Next, the contents of the PID determination process in the reproduction process will be described with reference to FIG. In the reproduction process (142), after receiving the RD command from the host 4 (143), the optical head is positioned on the designated track (144). R in units of one or more blocks from the target first sector
The D processing (145) is started. Thereafter, ECC correction is performed with the maximum correction capability of the ECC performance (146), and an error is determined (147). If no error occurs, the process returns to (143) to receive the RD command. If an error occurs, RD processing for retry (148), ECC correction (149),
An error determination (150) is performed. If an error occurs after the second ECC correction, there is a possibility of a PID error. Therefore, by adjusting the offset of the error signal (FE) of the automatic focusing system (151), the positional deviation of the light spot can be reduced. Correction and PID reading determination (152)
Execute

Here, as in the case of recording, the PID read performance by the difference signal reproduction and the PID read performance by the sum signal are compared, and the one with the higher read probability is selected. afterwards,
As described above, the same track is repositioned, and the RD (15
3) Perform ECC check (154). If the target point adjustment of the automatic focus and the PID reading determination are executed and no error occurs, the process returns to (143) to receive the WRT command. If an error occurs, the RD parameter such as the waveform equalization constant is changed (156), and the RD (157) and the ECC check (158) are performed in the same manner as described above.
If no error occurs, the process returns to (143) to receive the RD command again. However, if an RD error occurs here, an RD error report (1
60) Then, the RD command ends.

As described above, by performing the PID determination processing in the reproduction processing, the RD error can be reduced.
As described above, the validity of the method using the sum signal for reading the PID has been described.
It has been found for the first time from the research and development of the inventor that it is necessary to pay attention to the fact that the slice level in the ASC 108 is different from that at the time of reproducing the difference signal. This will be described with reference to FIG.

This is because the pit length at the time of PID cutting, the level of the duty of 50% in the reproduced signal, and the AC
This is a simulation of a level difference. Calculation parameters are shown in the figure. This is a signal level difference when a pit length of 0.82 μm corresponding to 4 Tw (Tw: window width time), which is a VFO pattern in a DVD-RAM, is repeated. In a normal sum signal, when the pit length is 0.82 μm, the difference between the 50% duty level and the AC level when the high frequency component is cut off by the reproducing system is 0, but it is shifted by 1/4 track pitch from the track. When the set pit group is read by a difference signal, the level difference is about 5%. For example, in the DVD-RAM standard that recommends reading the PID by the difference signal method, the pit length may be recorded at 0.964 μm in order to make the level difference 0. At this time, when the signal is reproduced with the sum signal, the level difference becomes -6.4%. When the signal is binarized at the same slice level as that of the difference signal, the pulse duty is shifted and the PLL is locked at another timing. May cause a data error.

FIG. 7 shows this state. In this figure,
The horizontal axis indicates the applied offset amount during the sum signal reproduction, and the vertical axis indicates the data transfer speed during recording. If a data error does not occur, retransfer retry does not occur, so the transfer speed takes the maximum value. If an error occurs, a re-recording retry occurs, so that the transfer speed drops rapidly. Also,
The optimum slice level differs depending on the disk. For a signal amplitude of 500 mV on one side, 60 mV for the disk, 80 mV for the disk, and 9 for the disk
0 mV is the optimum level. As described above, since the slice level differs for each disk, it is necessary to execute learning of the optimum slice level for each PID determination process. In the optimal slice level learning, the number of readable PIDs is counted while varying the slice level, and the slice level at which the number of readouts is the largest including the margin is determined as the optimal slice level.

FIG. 8 shows an embodiment for changing the slice level. In this embodiment, the equalizing circuit (EQ) 107
This is an example in which a DC offset applying circuit is added between the ASC 108 and the ASC 108. In a circuit that transmits a difference signal, a DAC (Digit) is applied to one of the signals as a DC offset applying circuit.
al to Analog Converter). The timing at which the DC offset is applied is only at the PID portion where the slice level is shifted, and the DAC instruction data is sent from the control circuit 6. After applying a DC offset, each signal is input to the ASC 108 through buffer (BUF) circuits 161, 162 and capacitors 164, 165. The capacitor and the input resistance of the ASC form a high frequency cutoff filter circuit (HPF).

FIG. 9 shows the signal waveform of each part. (A) is an HPP signal (GCA103 input) in the difference signal detection, and PID1, 2 (negative level) and PID3, 4 (positive level) are located above and below the average level. This PI
The polarity of the D waveform is inverted between when passing through the land portion and when passing through the groove portion. Since the data portion takes the difference, no data signal is output. Only the wobble signal appears in this data portion.

(B) shows the RF signal (G
In the PID section, PIDs 1 to 4 appear in the same direction. Record data exists in the data section.
(C) is the output of the switching switch 104, which is normally P
The ID section obtains a signal obtained by selecting an HPP signal for detecting a difference signal, and the data section obtains a signal obtained by selecting an RF signal for detecting a sum signal.

(D) is an output waveform of the DC correction circuit 105 when the difference signal PID is detected. In this case, since the AC level matches the 50% duty level in the PID portion and the data portion, the slice level can be reproduced with the AC level as the slice level.

(E) shows the DC correction circuit 10 when the sum signal is detected.
These are five output waveforms. In this case, the 50% duty level and the AC level match in the data part,
Since ΔV is generated as a level difference between the 50% duty level and the AC level in the ID section, a method of applying a DC offset shown in FIG. 8 only in the PID section, or duty feedback capable of following the 50% duty level at high speed Can be realized by:

(F) shows the waveform when the DC offset shown in FIG. 8 is applied and ΔV is corrected.
D also has a waveform in which the 50% duty level matches the AC level. As a result, PID reading errors can be reduced.

As described above, according to the present embodiment, the HPP signal or the RF signal which has a high reading probability of the PID information is selected, so that the probability of detecting the polarity inversion position is high. , Focus control, tracking control, and the like corresponding to the above can be stably performed.

[0052]

According to the present invention, the HPP signal or R
By selecting a signal having a high PID reading probability from the F signals, focus control, tracking control, and the like corresponding to the land portion and the groove portion can be stably performed, and stable recording and reproduction processing can be realized. it can.

[Brief description of the drawings]

FIG. 1 is a block diagram of an optical disk device to which the present invention has been applied.

FIG. 2 is a block diagram of a reproduction circuit of the optical disk device to which the present invention has been applied.

FIG. 3 is a flowchart at the time of disc loading for performing PID determination according to the present invention.

FIG. 4 is a flowchart at the time of recording processing for performing PID determination according to the present invention.

FIG. 5 is a flowchart at the time of reproduction processing for performing PID determination according to the present invention.

FIG. 6 is a simulation result of a difference between a 50% duty level and an AC level when detecting a difference signal / sum signal according to the present invention.

FIG. 7 shows measurement results of a correction applied offset and a WR transfer rate in a disc of each company when a sum signal is detected according to the present invention.

FIG. 8 is a block diagram showing an embodiment of a circuit for applying a correction DC offset at the time of detection of a sum signal according to the present invention.

FIG. 9 is a waveform of each part in the reproduction circuit 9 of the present invention.

FIG. 10 is a schematic view of a disk surface near a PID portion of a disk used in the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Optical disk, 2 ... Spindle motor, 3 ... Optical head, 4 ... Host, 5 ... Interface control circuit,
6 control circuit, 7 modulation circuit, 8 laser drive circuit, 9 reproduction circuit, 10 demodulation circuit, 11 servo control circuit, 12 PID error Detection circuit, 101 arithmetic circuit, 102, 103 GCA, 104 switching circuit, 105 DC correction circuit, 106 AGC, 107
EQ, 108 ASC, 109 PLL, 110 discriminator, 163 DAC.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Toru Kawashima 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Inside Hitachi Image Information System (72) Inventor Kuki Sugiyama 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Hitachi, Ltd. Video and Information Media Division (72) Inventor Tetsuya Fushimi 292, Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture F-term in Hitachi, Ltd. Video and Information Media Division F-term (reference) GG10 GG27

Claims (4)

[Claims] 1. A method according to claim 1, wherein lands and grooves are alternately formed on tracks formed on the information recording surface, and light is applied to an information recording medium provided with pre-formatted pre-pits shifted from the track center. In a disk device that detects return light of light emitted by an irradiation unit and reads information based on a change in the return light, a difference signal obtained by receiving the return light of the irradiation light by a detector divided in a track direction. First reading means for reading the information of the pre-pits based on the following information; second reading means for reading the information of the pre-pits based on a sum signal obtained by receiving light with the detector divided in the track direction; Comparing means for comparing the probability of reading the information of the pre-pits based on the difference signal with the probability of reading the information based on the amplitude of the sum signal; A disk device for reading information of the pre-pit based on a signal having a high probability of removal. 2. The disk device according to claim 1, wherein a tracking control or a focus control corresponding to the lands and the grooves is performed based on a result of reading the information of the pre-pits. 3. The disk device according to claim 1, wherein the comparison by said comparing means is performed when loading a disk or when an error occurs in a recording / reproducing process. 4. The disk drive according to claim 1, wherein said second reading means for reading said pre-pit information based on said sum signal applies a DC offset only when said pre-pit information is read.