JP2002230785A - Optical disk, optical disk recorder, optical disk reproducing device, and information recording method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical disk which eliminates a redundant region of a tracking pit and can avoid lowering of its recording capacity, while maintaining performance of a tracking servo. SOLUTION: A synchronous pit Psync disposed at a synchronous area and serving as a synchronization reference at reproduction, a guard pit Pg disposed at a boundary part of the synchronous area and a data area, and two or more data pits Pdat disposed in the data area at the fixed pit period to record digital data and serving as a tracking reference at reproduction are formed in an optical disk in which digital data are recorded. An average ratio of the portion occupied by two or more data pits Pdat is fixed. Then, at the reproduction operation, a beam spot BS traces on a center line of two adjacent tracks, a tracking error is detected based on two data pits Pdat on these two tracks, and the tracking servo is carried out. Therefore, recording capacity of the optical disk can be increased, without separately preparing a tracking pit.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk on which digital data is recorded at a high density, an optical disk recording apparatus for recording digital data on the optical disk, an information recording method thereof, and an optical disk reproducing apparatus for reproducing digital data from the optical disk. Belongs to the technical field.

[0002]

2. Description of the Related Art In recent years, as a method of recording and reproducing digital data at a high density on an optical disk, there is known a pit edge multi-value recording method for modulating the position of a pit edge on an optical disk in multiple stages and recording digital data in a multi-level manner. Have been. The pit edge multi-level recording method and the RPR, which is a kind of reproduction signal processing technique using a partial response,
(Radial Direction Partial Response) A system that combines playback and reproduction has been proposed.
74322).

FIG. 13 shows an example of a pit arrangement of an optical disk employing such a method. In FIG. 13, on a track (shown as T1 to T8 in FIG. 13) formed on the optical disc, a synchronization pit Psync, a tracking pit Ptrk, a guard pit Pg, and a data pit Pdat are arranged in a line. Among them, the area where the synchronization pit Psync, the tracking pit Ptrk, and the guard pit Pg are arranged constitutes a servo area,
The area where the data pits Pdat are arranged constitutes a data area. When the RPR reproduction method is adopted, FIG.
As shown in FIG. 3, the beam spot BS of the reproduction laser light applied to the optical disk traces on the center line of two tracks.

In the above configuration, the synchronization pit Psyn
c is a pit serving as a synchronization reference during reproduction. The pit length of the synchronous pit Psync is longer than the pit lengths of the other pits and is aligned in the radial direction of the disk so that the optical disk reproducing device can easily detect it. The synchronization pit Psync is also used as a clock phase reference at the time of reproduction.

[0005] The tracking pit Ptrk is a pit serving as a tracking reference during reproduction. As shown in FIG. 13, a tracking pit Ptrk is provided in a mirror portion following the synchronous pit Psync, and the pit position changes in a four-track cycle. When tracking servo is performed in the optical disk reproducing apparatus, a reproduction signal of two tracking pits Ptrk located on two adjacent tracks is used as a reference.

The guard pit Pg is a pit for preventing the reproduction signals of the servo area and the data area from interfering with each other, and is provided at the boundary between the servo area and the data area.

Digital data is recorded in the data pits Pdat by a pit edge multi-level recording method, and forms a pit train having a constant period on a track. Each data pit Pdat can record ternary digital data by changing the position of the pit edge in three stages. In FIG. 13, three pit edge positions are illustrated in an overlapping manner, but the actual pit edge is 3
Take one of the streets.

Next, a description will be given of a reproduced signal waveform when the servo area and the area before and after the servo area are reproduced using the optical disk having the pit arrangement shown in FIG. FIG. 14 shows a reproduced signal waveform when the reproducing operation is normally performed. In FIG.
FIG. 14 shows a reproduced signal waveform when the beam spot BS traces on the center lines of the tracks T4 and T5 in FIG. In FIG. 14, the horizontal direction is the time axis, and the sampling timing of the reproduced signal by the reproduced clock is represented by the scale on the horizontal axis. The vertical direction is the reproduction signal level, and the center straight line represents the center level of the reproduction signal.
When the beam spot BS reproduces pits, the amount of reflected light is reduced, and the level of the reproduced signal is reduced.

[0009] As shown in FIG.
Reaches the servo area and reproduces the synchronous pit Psync, a large negative peak p1 is obtained. Next, when the beam spot BS advances and the tracking pit Ptrk of the track T5 is reproduced, a small negative peak p2 is obtained. Next, the beam spot BS advances and the track T4
When the tracking pit Ptrk is reproduced, a small negative peak p3 is obtained. As shown in FIG. 14, the negative peak p2 and the negative peak p3 have the same level.

[0010] In the tracking servo in the optical disk reproducing apparatus, a reproduction signal level corresponding to two tracking pits Ptrk located on two adjacent tracks is detected, and a level difference between the two is detected as a tracking error. Therefore, the tracking error T in the case of FIG.
E becomes TE = p2−p3 = 0. Therefore, when a normal reproducing operation is guaranteed in the optical disk reproducing device, by performing tracking servo so that the tracking error TE becomes 0, it is possible to accurately trace the center line of two tracks by the beam spot BS. .

[0011]

In the above-described optical disk reproducing apparatus, in order to perform accurate tracking servo, it is necessary to increase the frequency of appearance of a servo area provided on the optical disk. However, since digital data cannot be recorded in the servo area, the presence of the servo area causes a reduction in the recording capacity of the entire optical disc. In the case of an optical disk configured as shown in FIG.
%, The recording capacity is reduced. On the other hand, when the frequency of appearance of the servo area is reduced, the decrease in the recording capacity is suppressed, but the S / N of the detected tracking error is deteriorated, and it is difficult to speed up the response of the tracking servo loop. As described above, when tracking servo is performed using the tracking pit Ptrk in the servo area according to the conventional configuration, there is a problem that it is difficult to maintain the performance of the tracking servo while preventing a decrease in the recording capacity of the optical disk. Was.

Accordingly, the present invention has been made in view of such a problem, and forms a data pit that can be used as a tracking pit on an optical disk on which digital data is recorded by using a sample servo method, and forms a tracking servo. It is an object of the present invention to provide an optical disk or the like which can eliminate the redundant area of the tracking pit and maintain the recording capacity of the optical disk while maintaining the above performance.

[0013]

According to another aspect of the present invention, there is provided an optical disk in which a synchronous area and a data area are alternately provided in a disk circumferential direction. And a plurality of data pits, which are arranged in a row at a constant pit cycle in the data area and record data, and serve as a tracking reference at the time of reproduction. In the data area, an average ratio of a portion occupied by the data pit on a track is constant.

According to the present invention, the optical disc is provided with a synchronization area in which synchronization pits are arranged and a data area in which a plurality of data pits are arranged at a constant pit cycle. The plurality of data pits have a constant average ratio of the occupied portions, and have a role as a tracking reference in addition to a role of recording recording data. Therefore, the tracking error can be detected at a high frequency, the S / N of the tracking error can be increased, the accurate tracking servo can be performed, and the recording capacity of the optical disc can be increased because there is no need to provide a separate tracking pit. it can.

The optical disk according to the second aspect is the optical disk according to the first aspect.
3. The optical disc according to claim 1, wherein the pit train including the plurality of data pits has opposite phases between adjacent tracks.

According to the present invention, a plurality of data pits form a pit train having an opposite phase between adjacent tracks, so that the data pits are arranged on two adjacent tracks. The tracking error can be easily detected using the data pit thus obtained.

The optical disk according to the third aspect is the optical disk according to the second aspect.
Wherein the position of the pit edge of the data pit changes in multiple stages in accordance with the recording data.

According to the present invention, the position of the pit edge of the data pit can be controlled to adjust the average ratio of the portion occupied by the data pit on the track, and accurate tracking servo can be easily performed.

An optical disk recording apparatus according to claim 4 is
An optical disk recording apparatus for recording recording data on an optical disk, comprising: a data conversion means for converting information data into recording data; a synchronization pit serving as a synchronization reference during reproduction; Recording means for recording data pits carrying the data on the optical disc;
Wherein the information data is converted into the recording data so that the average ratio of the portion occupied by the data pits on the track is constant.

An information recording method according to a tenth aspect of the present invention is an information recording method for recording recording data on an optical disk, and serves as a data conversion step of converting information data into recording data and a synchronization reference at the time of reproduction. A recording step of recording, on the optical disk, synchronous pits and data pits which are arranged in a row at a constant pit period and carry the recording data, wherein an average ratio of a portion occupied by the data pits on a track is constant. Converting the information data into the recording data.

According to the fourth and tenth aspects of the present invention, in order to perform recording on the optical disk, synchronous pits are recorded and the average ratio of the portion occupied by the data pits is made constant. After converting the information data into recording data, this recording data is recorded in the data pit. Therefore, by performing such recording, accurate tracking servo is possible as described above, and recording on an optical disc can be performed with a sufficient recording capacity.

An optical disk recording apparatus according to claim 5 is
5. The optical disk recording apparatus according to claim 4, wherein the data conversion means converts the information data into the recording data by adding a random data sequence to the information data.

In the information recording method according to the eleventh aspect, in the information recording method according to the tenth aspect, the data conversion step includes adding a random data sequence to the information data to thereby convert the information data. The recording data is converted.

According to the fifth and eleventh aspects of the present invention, a random data sequence such as an M sequence is added to the information data to convert the information data into recording data. The recording data can be reliably randomized to suppress the DC component of the reproduction signal, and an accurate tracking error can be detected.

An optical disk recording apparatus according to claim 6 is
5. The optical disc recording apparatus according to claim 4, wherein the data conversion unit converts the information data into the recording data according to one conversion rule selected from a plurality of preset conversion rules, and Conversion data indicating another conversion rule is recorded in the data pit.

According to a twelfth aspect of the present invention, in the information recording method according to the tenth aspect, the data conversion step includes the step of converting one of a plurality of conversion rules set in advance. The information data is converted into the recording data according to a rule, and conversion data indicating the selected one conversion rule is recorded in the data pit.

According to the sixth and twelfth aspects of the present invention, a conversion rule for converting information data into recording data can be selected. By selecting a conversion rule that reduces the DC component of a reproduction signal, An accurate tracking error can be detected.

[0028] The optical disk reproducing apparatus according to claim 7 is
An optical disc reproducing apparatus for reproducing recorded data from an optical disc in which a synchronous area and a data area are alternately provided in a disc circumferential direction, irradiating the optical disc with a reproducing laser beam, and reproducing according to an amount of reflected light from a beam spot. Reading means for generating a signal, A / D converting means for sampling the reproduction signal in synchronization with a reproduction clock, and converting the signal into a sample sequence, based on a plurality of samples of the data area extracted from the sample sequence. Tracking error detecting means for detecting a tracking error; tracking servo means for controlling the beam spot to scan on the center line of two adjacent tracks according to the tracking error; and decoding information data based on the sample sequence. And data decoding means for performing the above.

According to the present invention, in order to reproduce the optical disk, a reading unit, an A / D conversion unit, a tracking error detecting unit, a tracking servo unit,
An optical disk reproducing apparatus provided with data decoding means is configured. During reproduction, a beam spot traces the center line of two adjacent tracks, decodes information data based on a sample sequence, and detects a tracking error. Therefore, an accurate tracking error can be detected at the time of reproduction, and the tracking servo is performed by using the data pits. Therefore, the reproduction can be performed by effectively utilizing the recording capacity of the optical disk.

An optical disk reproducing apparatus according to claim 8 is
8. The optical disc reproducing apparatus according to claim 7, wherein the tracking error detecting unit is configured to separate a sample corresponding to the center of the data pit on one track and a sample corresponding to the center of the data pit on an adjacent track, respectively. And extracting a level difference between the two samples as the tracking error.

According to the present invention, when tracing the center line of two adjacent tracks, two samples are extracted at the timing of the center of each data pit of one track and the other track, and the level difference is extracted. Since the detection is performed, the tracking error can be detected with a simple configuration in addition to the operation of the invention described in claim 7.

An optical disk reproducing apparatus according to claim 9 is
The optical disc playback apparatus according to claim 7, wherein the data decoding unit decodes, from the sample sequence, conversion data indicating one conversion rule selected when converting the information data into the recording data during recording, The information data is decoded according to a decoding rule corresponding to the converted data.

According to the present invention, the converted data is decoded from the sample sequence at the time of reproducing the optical disk, and the information data is decoded according to the decoding rule corresponding thereto. In addition, the original information data can be reliably decoded by performing a conversion reverse to the conversion rule corresponding to the conversion data at the time of recording.

[0034]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. In the present embodiment, a case will be described in which the present invention is applied to an optical disc and an optical disc reproducing apparatus that employ a scheme that combines the pit edge multilevel recording scheme and RPR reproduction.

FIG. 1 is a diagram showing the pit arrangement of the optical disk according to the present embodiment. In FIG. 1, like FIG.
The pit arrangement of the optical disc in the range of one track T1 to T8 is shown. On each track of the optical disk of FIG. 1, a synchronous pit Psync and a guard pit Pg
And data pits Pdat are arranged in a line.
Here, a synchronization area is formed by the synchronization pit Psync and the guard pit Pg, and a plurality of data pits Pdat
It is assumed that a data area is constituted by. FIG.
Similarly to 3, the beam spot BS of the reproduction laser beam applied to the optical disk traces on the center line of two tracks.

In the above configuration, the synchronization pit Psyn
c is a pit serving as a synchronization reference during reproduction. The pit length of the synchronous pit Psync is longer than the pit lengths of the other pits and is aligned in the radial direction of the disk so that the optical disk reproducing device can easily detect it. The synchronization pit Psync is also used as a clock phase reference at the time of reproduction.

The guard pit Pg is a pit for preventing the reproduction signals of the synchronization area and the data area from interfering with each other, and is provided at the boundary between the synchronization area and the data area.

In the data pits Pdat, digital data is recorded by a pit edge multi-level recording method, and forms a pit row having a constant period on a track. Each data pit Pdat can record ternary digital data by changing the position of the pit edge in three stages.

Specifically, as shown in FIG. 2, (0,
When recording ternary digital data of 1, 2),
If "0", the position of the pit edge is shifted by a certain distance in the direction in which the pit length becomes shorter, if "1", the position of the pit edge is left unchanged, and if "2", the position of the pit edge is shifted in the direction in which the pit length becomes longer. Shift by a certain distance. In this way, ternary digital data can be recorded as pit edge position information in each data pit Pdat. In FIG. 2, three pit edge positions are illustrated in an overlapping manner, but actually, the pit edge position is any one of the three pit edge positions.

In the optical disk shown in FIG. 1, a pit row composed of data pits Pdat has a constant pit period. The data pits Pdat have opposite phases between adjacent tracks, and the pit position is 2
The alternation arrangement changes with the track cycle. By alternately arranging the data pits Pdat in this manner, the increase or decrease in the pit area according to the position of the beam spot BS is suppressed, the fluctuation of the reproduction signal is reduced, and the timing offset and the jitter are improved.

In the optical disk according to the present embodiment, the data pit Pdat also plays a role as a tracking pit serving as a tracking reference during reproduction. That is, utilizing the fact that two adjacent tracks are arranged in opposite phases, the optical disc reproducing apparatus detects a tracking error based on a reproduction signal of each data pit Pdat located on the two tracks and performs tracking servo. . A specific method of detecting a tracking error will be described later.

FIG. 3 is a diagram showing a first configuration example of the optical disk recording apparatus according to the present embodiment. The optical disk recording apparatus shown in FIG. 3 includes a scramble circuit 31, a data conversion circuit 32, a precode circuit 33, a data pulse generation circuit 34, a synchronization pulse generation circuit 35, and a multiplex circuit 36.
And a disk mastering device 37.

In the above configuration, the information data which is binary data (0, 1) is externally supplied to the scramble circuit 3.
1 is input. Then, the scramble circuit 31 scrambles the information data by adding an M sequence which is a random data sequence (taking an exclusive OR). The data conversion circuit 32 converts binary data (0, 1) into ternary data (0, 1, 2) according to a predetermined conversion rule.

FIG. 4 shows an example of a conversion rule in the data conversion circuit 32. In the example shown in FIG. 4, (0,
Conversion rules corresponding to eight types of binary data from (0,0) to (1,1,1) and eight types of ternary data from (0,0) to (2,2) are defined. I have. In the data conversion circuit 32, conversion from binary data to ternary data is performed according to the conversion rule of FIG.

The precoding circuit 33 is provided with the data conversion circuit 3
The ternary data obtained in step 2 is subjected to a logical operation called precoding to convert the data into recording data to be recorded on an optical disk. The data pulse generation circuit 34 generates a data pulse corresponding to a data pit Pdat carrying recording data. This data pulse corresponds to the data pit Pdat
Has a waveform pattern that changes the position of the pit edge in three steps.

The synchronization pulse generation circuit 35 generates a synchronization pulse corresponding to the synchronization pit Psync in the synchronization area. The multiplexing circuit 36 performs time division multiplexing by periodically switching the data pulse from the data pulse generation circuit 34 and the synchronization pulse from the synchronization pulse generation circuit 35, and outputs a recording pulse. The disc mastering device 37 receives a recording pulse and forms a pit train on a track of the optical disc according to the recording pulse.

In the first configuration example shown in FIG. 3, since the M sequence is added to the information data in the scramble circuit 31, even if the information data includes a fixed pattern, the binary data is randomized. be able to. Therefore, the appearance probabilities of (0, 1, 2) in the recording data become equal, and the data pits Pd
The average ratio of the portion occupied by at becomes constant.

FIG. 5 is a diagram showing a second example of the configuration of the optical disk recording apparatus according to the present embodiment. The optical disk recording device shown in FIG. 5 includes a data conversion circuit 41, a precoding circuit 42, a ternary data exchange circuit 43, a data pulse generation circuit 44, a pulse duty detection circuit 45,
A selection circuit 46, a synchronization pulse generation circuit 47, a multiplexing circuit 48, and a disk mastering device 49 are provided. In the above configuration, the data conversion circuit 41, the precoding circuit 42, the synchronization pulse generation circuit 47, and the multiplexing circuit 48
The operation of the disk mastering device 49 is the same as that of the first configuration example shown in FIG.

In FIG. 5, ternary data exchange circuit 43
Exchanges 0 and 2 included in the recording data obtained by the precoding circuit 42, and outputs the first recording data before the exchange and the second recording data after the exchange, respectively. Then, the data pulse generation circuit 44 generates two types of data pulses based on the first and second recording data. As described above, the duty of the data pulse based on the second print data after replacing 0 and 2 is 5 times the duty of the data pulse based on the first print data before replacement.
The value is inverted around 0%.

The pulse duty detection circuit 45 detects a duty within a predetermined time for each data pulse based on the first and second recording data. For example, it is desirable to set a predetermined time corresponding to a range of several tens to several hundreds of data pits Pdat and detect the duty. Then, the selection circuit 46 selects and outputs one of the two data pulses whose duty within a predetermined time is closer to 50% based on the detection result of the duty in the pulse duty detection circuit 45. As described above, by forming a pit row on the optical disk by the recording pulse based on the data pulse selected by the selection circuit 46, the average ratio of the portion occupied by the data pits Pdat on the track becomes constant.

The conversion data indicating the selection result in the selection circuit 46 may be recorded at a predetermined position on the optical disk in association with the position of the data pit Pdat. This makes it possible to determine whether or not each data pit Pdat is one in which recording data 0 and 2 have been exchanged when reproducing an optical disk with an optical disk reproducing apparatus described later.

FIG. 6 is a diagram showing a schematic configuration of the optical disk reproducing apparatus according to the present embodiment. The optical disk reproducing apparatus shown in FIG. 6 includes a pickup 11, an amplification circuit 12, an A / D conversion circuit 13, and a synchronization detection circuit 14 for reproducing digital data recorded on the optical disk 10.
, A timing generation circuit 15, a clock phase error detection circuit 16, a D / A conversion circuit 17, an LPF 18,
CO 19, tracking error detection circuit 20, D /
A conversion circuit 21, LPF 22, data decoding circuit 23
It is comprised including.

In the above-described configuration, a reproduction laser beam is irradiated from the pickup 11 to the loaded optical disk 10, and a reflected signal from the beam spot BS is photoelectrically converted by the pickup 11 to output a reproduction signal. . After the reproduced signal is amplified by the amplifier circuit 12, the signal is sampled by the A / D converter circuit 13 in accordance with the reproduced clock, and a sample sequence is output.

The synchronization detection circuit 14 detects a sample corresponding to the synchronization pit Psync from the sample sequence, and outputs a synchronization detection signal serving as a synchronization reference. Further, the timing generation circuit 15 generates various kinds of cumming signals based on the synchronization detection signal output from the synchronization detection circuit 14 as a time reference, and supplies the signals to various parts of the optical disk reproducing apparatus.

Next, the clock phase error detection circuit 16
According to the timing signal from the timing generation circuit 15, two samples corresponding to the pit edges on both sides of the synchronous pit Psync in the sample sequence are extracted,
The level difference between the two is calculated, and this is output as phase error data. This phase error data is supplied to the D / A conversion circuit 17.
Is converted to an analog phase error signal by the LPF
The waveform is smoothed by 18.

VCO (Voltage Controlled Oscillato)
r) 19 uses the phase error signal output from the LPF 18 as an input voltage, changes the oscillation frequency of the clock, and generates a reproduced clock phase-synchronized with the reproduced signal. Then, the reproduced clock is supplied to the A / D conversion circuit 13. Thus, the A / D conversion circuit 13, the clock phase error detection circuit 16, the D / A conversion circuit 17, the LPF 1
8. The VCO 19 forms a PLL (Phase Locked Loop). This PLL is a servo loop for synchronizing the phase of the reproduction clock with the reproduction signal.

Next, the tracking error detection circuit 20
Extracts a sample corresponding to the center of the data pit Pdat of a predetermined track in a sample sequence and extracts a sample corresponding to the center of the data pit Pdat of an adjacent track in response to a timing signal from the timing generation circuit 15. , And calculates the level difference between these two samples, and outputs this as tracking error data. This tracking error data is D / A
After being converted into an analog tracking error signal by the conversion circuit 21, the waveform is smoothed by the LPF 22.

The pickup 11 controls the position of the beam spot BS by the reproduction laser light in the radial direction of the disk according to the tracking error signal output from the LPF 22. In the configuration of FIG. 6, the amplifier circuit 12, A /
D conversion circuit 13, tracking error detection circuit 20, D
/ A conversion circuit 21, LPF 22, pickup 11
A tracking servo loop is configured. This tracking servo loop is a servo loop for tracing the beam spot BS on the center line of two tracks.

The data decoding circuit 23 has a data pit Pd
A sample corresponding to the pit edge of at is extracted, and the sample is compared with a predetermined threshold to obtain determination data, and the original information data is restored using the determination data. here,
As the optical disk recording apparatus, the first configuration example and the second
Since the configuration of the data decoding circuit 23 differs depending on the configuration example, the description will be made with reference to FIGS. 7 and 8, respectively.

FIG. 7 is a diagram showing a first configuration example of the data decoding circuit 23 in the optical disk reproducing apparatus. The data decoding circuit 23 shown in FIG.
A remainder operation circuit 102, a data conversion circuit 103, and a descrambling circuit 104 are provided. With such a configuration, an operation opposite to that of the first configuration example of the optical disk recording device shown in FIG. 3 is performed. 7, the descrambling circuit 104 re-adds the M-sequence used in the scramble circuit 31 of FIG. 3 and performs descrambling (exclusive OR), thereby restoring information data.

FIG. 8 is a diagram showing a second example of the configuration of the data decoding circuit 23 in the optical disk reproducing apparatus. The data decoding circuit 23 shown in FIG.
A remainder operation circuit 112, a ternary data exchange circuit 113,
And a data conversion circuit 114. With such a configuration, a calculation reverse to that of the second configuration example of the optical disk recording device shown in FIG. 5 is performed. 8, the ternary data exchange circuit 113 controls whether or not the reproduced ternary data 0 and 2 are exchanged according to the conversion data corresponding to the selection result of the selection circuit 46 in FIG.

In the optical disk reproducing apparatus shown in FIG. 6, the period of the reproduction clock is set to に of the period of the pit train. That is, the frequency of the reproduced clock is four times the frequency of the pit train. In this case, during one pit cycle consisting of one pit and one space (a non-recording portion between pits on a track), the A / D conversion circuit 13 uses the reproduction clock four times. A / D conversion is performed to obtain four samples. These four samples respectively correspond to four positions of a front edge, a pit center, a pit rear edge, and a space center in each pit.

As described above, when the tracking error detection circuit 20 extracts a sample in accordance with the reproduction clock, the sample corresponding to the center of the specific data pit Pdat corresponds to the sample corresponding to the center of the space separated by two clocks from this sample. It is sufficient to extract two samples of each sample to be performed in each track. Since the pit trains of the adjacent tracks have phases opposite to each other, if the above two samples are extracted, the data pits P of a certain track can be obtained.
This means that a sample corresponding to the center of dat and a sample corresponding to the center of the data pit Pdat of the adjacent track have been extracted.

Next, a description will be given, with reference to FIGS. 9 to 12, of a tracking servo when reproducing the optical disk according to the present embodiment. FIG. 9 is a diagram showing a relationship between a pit row and a beam spot when a data area of an optical disc is reproduced. FIGS. 10 to 12 are diagrams showing the reproduction signal waveforms in the data area (indicating the range of two tracks T1 and T2) in FIG. 9 according to the position of the beam spot BS in the track radius direction. . here,
10 to 12, the horizontal direction is the time axis, and the vertical direction is the reproduction signal level. The equally-spaced vertical lines indicate the sampling timing t of the reproduced signal by the reproduced clock.
1 to t7. The equally spaced vertical lines in FIG.
The positions on the disk corresponding to the sampling timings t1 to t7 are shown. When the beam spot BS reproduces pits, the amount of reflected light is reduced, and the level of the reproduced signal is reduced.

FIG. 9A shows a case where the beam spot BS accurately traces the center lines of the tracks T1 and T2. In this case, the center of the beam spot BS traces on the solid line in FIG. Since the beam spot BS irradiates the track T1 and the track T2 evenly, the amount of light reflected by both tracks becomes constant.

FIG. 10 shows a reproduced signal waveform under the conditions of FIG. 9A. As shown in FIG. 10, the waveform of the reproduced signal changes according to the data pattern of the pit string in the data area. Specifically, timings t3 and t7 correspond to the center of the data pit Pdat of the track T1, and timings t1 and t5 correspond to the data pit Pd of the track T2.
Corresponds to the center of at. Further, at timings t2, t4,
t6 corresponds to the pit edge of each data pit Pdat of the tracks T1 and T2.

Here, timings t1, t3, t5, t
7 are S1 and S, respectively.
In the case of 3, S5, and S7, the average levels S1 and S3 are equal and the average levels S5 and S7 are equal in the reproduced signal waveform of FIG. Therefore, the level difference between the average levels S1 and S3, or the average levels S5 and S3
The level difference of 7 is the tracking error TE. That is, the tracking error TE in the case of FIG. 10, a _{TE 13 = S1-S3 = 0} TE 57 = S5-S7 = 0.

Next, FIG. 9B shows a case where the beam spot BS traces while being shifted upward from the center line of the track T1 and the track T2. In this case, the center of the beam spot BS traces on the broken line in FIG. 9B.
The beam spot BS is the track T1 for the track T1.
Since a larger amount of light is emitted than in the case of No. 2, the amount of reflected light strongly reflects the pit row of the track T1.

FIG. 11 shows a reproduced signal waveform under the conditions of FIG. 9B. As shown in FIG. 11, a sine wave-like undulation occurs in the waveform of the reproduced signal in the data area. In this case, the average levels S1 and S3 or the average levels S5 and S7 are not equal to each other, and a level difference occurs. As a result, the tracking error TE in the case of FIG. 11 is as follows: TE ₁₃ = S1−S3> 0 TE ₅₇ = S5−S7> 0

Next, FIG. 9C shows a case where the beam spot BS traces while being shifted downward from the center line of the track T1 and the track T2. In this case, the center of the beam spot BS traces on the broken line in FIG. 9C.
The beam spot BS has the track T2 in the track T2.
Since a larger amount of light is radiated than that of No. 1, the amount of reflected light strongly reflects the pit row of the track T2.

FIG. 12 shows a reproduced signal waveform under the conditions of FIG. 9C. As shown in FIG. 12, the waveform of the reproduced signal in the data area has a sinusoidal undulation in a direction opposite to that of FIG. Also in this case, the above average level S
1 and S3 or the average levels S5 and S7 are not equal to each other, and a level difference occurs. As a result, the tracking error TE in the case of FIG. 12 is as follows: TE ₁₃ = S1−S3 <0 TE ₅₇ = S5−S7 <0

The examples of FIGS. 9 to 12 correspond to the case where the beam spot BS traces between the track T1 and the track T2. On the other hand, when the beam spot BS traces between the track T2 and the track T3, the pit arrangement of the two data pits Pdat is inverted.
The relationship between the direction of the tracking offset and the polarity of the tracking error is also reversed. In this case, the tracking error detection circuit 20 may perform control so that the polarity of the tracking error is inverted according to the change between the tracks being traced.

By performing tracking servo as described above, if the beam spot BS traces off the center line of two tracks, a tracking error corresponding to the tracking offset is obtained. This tracking error is converted to a D / A conversion circuit 21 constituting a servo loop.
Then, the feedback is fed back to the pickup 11 via the LPF 22 and the tracking offset is corrected, so that accurate tracking servo can be performed.

Here, in the optical disk recording apparatus, the duty of the data pulse is controlled so as to approach 50% as described above, so that the average ratio of the portion occupied by the data pits Pdat on the track is constant. Therefore, tracking servo can be performed accurately. If the duty of the data pulse is biased, the average ratio of the portion occupied by the data pits Pdat on the track is not constant, and a DC component is generated in the reproduced signal. Then, an offset occurs in the tracking error, and the tracking servo becomes inaccurate. However, since the average ratio of the portion occupied by the data pits Pdat on the track of the optical disk according to the present embodiment is constant, an offset does not occur in the tracking error, and accurate tracking servo can be realized.

Next, a modification of the above embodiment will be described.
The optical disc reproducing apparatus shown in FIG. 6 has a configuration in which the tracking error signal is smoothed by the LPF 22. However, the tracking error detection circuit 20 may be configured to smooth the tracking error data. That is, the tracking error detection circuit 20 calculates a plurality of tracking error data, which is the level difference between two samples, and calculates the average value of these data by the D / A conversion circuit 21.
May be output. Further, while calculating the average level of the sample corresponding to the center of the data pit Pdat of the specific track obtained in the 4-clock cycle,
Similarly, the average level of the sample corresponding to the center of the data pit Pdat of the adjacent track obtained in the 4-clock cycle may be calculated, and the level difference between the two may be used as the tracking error data. By smoothing the tracking error data in the tracking error detection circuit 20 as described above, the resolution of the D / A conversion circuit 21 can be used effectively.

In the above embodiment, the case where the present invention is applied to a system in which pit edge multi-level recording and RPR reproduction are combined is described. However, the present invention is not limited to this, and pit edge multi-level recording and two-dimensional PRML reproduction are used. The present invention can also be applied to a system combining (for example, disclosed in JP-A-11-144250).

[0077]

As described above, according to the present invention, tracking servo can be performed without separately providing a tracking pit on an optical disk, so that a wide data area can be secured. Therefore, it is possible to record more digital data and increase the recording capacity of the entire optical disc as compared with an optical disc configured as in the related art.

Further, a tracking error can be obtained from all the data pits of the optical disk at a high frequency.
As the S / N of the detected tracking error increases, the speeding up of the response of the tracking servo loop can be easily realized. Therefore, accurate and high-speed tracking servo can be performed.

[Brief description of the drawings]

FIG. 1 is a diagram showing a pit arrangement of an optical disc according to an embodiment.

FIG. 2 is a diagram illustrating a change in the position of a ternary pit edge in a pit edge multi-level recording method.

FIG. 3 is a block diagram illustrating a first configuration example of an optical disc recording apparatus according to the embodiment.

FIG. 4 is a diagram illustrating an example of a conversion rule in a data conversion circuit of the optical disc recording device according to the first configuration example.

FIG. 5 is a block diagram showing a second configuration example of the optical disc recording device according to the embodiment.

FIG. 6 is a block diagram illustrating a schematic configuration of an optical disc reproducing device according to the embodiment.

FIG. 7 is a diagram illustrating a first configuration example of a data decoding circuit in the optical disc reproducing device.

FIG. 8 is a diagram illustrating a second configuration example of the data decoding circuit in the optical disc reproducing device.

FIG. 9 is a diagram showing a relationship between a pit row and a beam spot when a data area of the optical disc according to the embodiment is reproduced.

FIG. 10 is a reproduction signal waveform when a beam spot accurately traces the center line of two tracks.

FIG. 11 is a reproduction signal waveform in a case where a beam spot is traced while being shifted upward from the center line of two tracks.

FIG. 12 is a reproduction signal waveform in a case where a beam spot is traced while being shifted downward from the center line of two tracks.

FIG. 13 is a block diagram showing an example of a pit arrangement of a conventional optical disc.

FIG. 14 shows a reproduction signal waveform when a reproduction operation is normally performed when a servo area and before and after the servo area are reproduced using a conventional optical disc.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Optical disk 11 ... Optical pickup 12 ... Amplification circuit 13 ... A / D conversion circuit 14 ... Synchronization detection circuit 15 ... Timing generation circuit 16 ... Clock phase error detection circuit 17, 21 ... D / A conversion circuit 18, 22 ... LPF 19 ... VCO 20 ... Tracking error detection circuit 23 ... Data decoding circuit 31 ... Scramble circuit 32,41 ... Data conversion circuit 33,42 ... Precode circuit 34,44 ... Data pulse generation circuit 35,47 ... Synchronization pulse generation circuit 36,48 .. Multiplexers 37, 49 Disk mastering device 43 Tri-level data exchange circuit 45 Pulse duty detection circuit 46 Selection circuit BS Beam spot Psync Sync detection pit Pg Guard pit Ptrk Tracking pit Pdat Data pit

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Claims (12)

[Claims] 1. An optical disk in which a synchronization area and a data area are alternately provided in a disk circumferential direction, wherein a synchronization pit which is arranged in the synchronization area and serves as a synchronization reference at the time of reproduction; It is arranged in a line in the pit cycle,
And a plurality of data pits, which serve as a tracking reference at the time of recording, are formed, and an average ratio of a portion occupied by the data pits on a track in the data area is constant. optical disk. 2. The optical disk according to claim 1, wherein the pit train including the plurality of data pits has opposite phases between adjacent tracks. 3. The optical disk according to claim 2, wherein the position of a pit edge of the data pit changes in multiple stages according to recording data. 4. An optical disk recording apparatus for recording recording data on an optical disk, comprising: a data conversion means for converting information data into recording data; a synchronization pit serving as a synchronization reference at the time of reproduction; Recording means for recording the data pits, which carry the recording data, on the optical disc; and An optical disk recording device for converting. 5. The optical disk recording apparatus according to claim 4, wherein said data conversion means converts said information data into said recording data by adding a random data sequence to said information data. 6. The data conversion means converts the information data into the recording data in accordance with one conversion rule selected from a plurality of preset conversion rules, and converts the selected one conversion rule. 5. The optical disk recording apparatus according to claim 4, wherein the conversion data is recorded in the data pit. 7. An optical disk reproducing apparatus for reproducing recorded data from an optical disk in which a synchronous area and a data area are alternately provided in a disk circumferential direction, wherein the optical disk is irradiated with a reproducing laser beam and reflected from a beam spot. Reading means for generating a reproduction signal corresponding to the amount of light; A / D conversion means for sampling the reproduction signal in synchronization with a reproduction clock and converting it into a sample sequence; and a plurality of the data areas extracted from the sample sequence Tracking error detecting means for detecting a tracking error on the basis of the sample; tracking servo means for controlling the beam spot to scan on the center line of two adjacent tracks in accordance with the tracking error; and Data decoding means for decoding information data by An optical disc reproducing apparatus characterized by the above-mentioned. 8. The tracking error detecting means extracts a sample corresponding to the center of the data pit on one track and a sample corresponding to the center of the data pit on an adjacent track, and extracts the two samples. The optical disc reproducing apparatus according to claim 7, wherein a level difference between the samples is detected as the tracking error. 9. The data decoding means decodes, from the sample sequence, conversion data indicating one conversion rule selected when converting the information data into the recording data at the time of recording, and corresponds to the conversion data. The optical disc reproducing apparatus according to claim 7, wherein the information data is decoded according to a decoding rule. 10. An information recording method for recording recording data on an optical disk, comprising: a data conversion step of converting information data into recording data; a synchronization pit serving as a synchronization reference at the time of reproduction; Recording the data pits carrying the recording data on the optical disc, and recording the information data on the recording data such that the average ratio of the portion occupied by the data pits on a track is constant. An information recording method characterized by converting. 11. The information recording method according to claim 10, wherein in the data conversion step, the information data is converted into the recording data by adding a random data sequence to the information data. 12. The data conversion step converts the information data into the recording data in accordance with one conversion rule selected from a plurality of preset conversion rules, and converts the selected one conversion rule. 11. The information recording method according to claim 10, wherein the conversion data is recorded in the data pit.