JPH07105628A - Optical disk and track address regenerating device - Google Patents

Abstract

PURPOSE:To shorten the time required for starting recording and reproducing and the seek time. CONSTITUTION:The optical disk has plural servo areas 1 and plural data areas 8, and track addresses coded in grey on the whole by a pit position encoder is divided into an upper word and a lower word, and they are regarded as access codes 2, and are dispersed and recorded in each servo area 1 in order to make frequency of the access codes 2 in the lower word higher than frequency of the access codes 2 in the upper word. Then, parity information 3 is added to a least significant bit word of the access modes 2 recorded, for instance, at intervals of one segment, and is recorded. Thus, by the parity information 3 recorded at intervals of one segment, errors are corrected at intervals of the one segment so that the accurate track addresses can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disc of a so-called sample servo system in which the entire track address is gray coded and recorded, and a track address reproducing apparatus for reproducing the track address from the optical disc.

[0002]

2. Description of the Related Art Optical discs known today are rotatably driven by a spindle motor at a constant linear velocity (CLV) or a constant angular velocity (CAV), and are recorded on a recording track spirally or concentrically provided on the disc. Data is to be recorded.

The so-called self-clock method and the external clock method are known as the clock synchronization methods at the time of recording and reproducing the data of such an optical disk.

In the external clock system, a segment consisting of a servo area in which a servo signal is recorded and a data area in which data is recorded is arranged in a track direction which is a recording / reproducing direction, and a clock signal is generated by a servo signal in the servo area. A sample servo method (discrete block method) for performing synchronization and tracking servo control is known.

In FIG. 11, the track of the optical disk of the sample servo system is composed of a plurality of sectors as a recording unit of n data, and one sector is m.
It is composed of individual segments. It should be noted that the first segment (first segment) of the plurality of segments
Is a header 104 in which address data and the like are recorded.

The header 104 has a servo area 102.
And a sector mark area 105 in which a sector mark indicating the beginning of a sector is recorded, and an address area 106 in which the track address, sector address and the like are recorded. The segments other than the header 104 are composed of a servo area 102 and a data area 107.

In the servo area 102, a clock pit 108 for synchronizing clocks, and a pair of wobbles deviated to the outer and inner circumferences with respect to the track center for obtaining a tracking error signal and the like. A synchronization pattern 110 composed of pits 109 and an access code 111 are recorded.

That is, the sync pattern 110 and the access code 111 have a recording form as shown in FIG. 12, and as the access code 111, the data of the lower 4 bits of the track address is a gray code. It is recorded in two pits. This access code is recorded in a 16-track cycle so that adjacent tracks satisfy the characteristics of the gray code in which only one pit position is different.

By thus gray-coding the access code 111 and recording the lower 4 bits of the track address, it is possible to obtain address data from the access code 111 for short distance access such as seek, and perform high-speed seek. be able to.

However, in such an optical disc, since only the lower 4-bit track address is recorded in the access code 111, the header in which the track address, the sector address, etc. are recorded in order to obtain accurate address data. Needed 104. Therefore, the recording capacity of the data is reduced because the header 104 has to be recorded.

[0011] Here, the applicant of the present application has filed Japanese Patent Application Laid-Open No. 3-130.
Japanese Patent No. 929 discloses a recording medium in which not only the lower part of the track address but all track addresses (including sector addresses) and synchronization patterns are recorded as access codes.

This recording medium can be applied to, for example, an optical disc, and as shown in FIG.
At 0, an access code 121 having a track address recorded therein and a synchronization pattern 122 are recorded in that order.

That is, the track addresses are all 15
If it is a bit, each track address is a 3-bit least significant (LSB) word (0th bit to 2nd bit).
Bit), 4SB word (3rd to 5th bits),
It is divided into a total of 5 words, 3SB word (6th bit to 8th bit), 2SB word (9th bit to 11th bit), and most significant (MSB) word (12th bit to 14th bit). Word is the above access code 121
, And is recorded in gray code by pit position coding as shown in FIG.

Access code 121 of these five words
Are recorded dispersedly on the optical disc as shown in FIG. In FIG. 15, a plurality of straight lines shown in the radial direction of the optical disk indicate the servo area 120. The servo area 120 and the servo area 1
The area between 20 and 20 is a data area 123. For example, if one round of the optical disc is composed of 1024 segments, the servo area 120 also has 102 segments.
There are four, and in this servo area 120, 512 LSB words of the above access code 121, 4SB per cycle.
256 words per cycle, 128 3SB words per cycle
, 2 SB words are recorded in one round, 64 MSB words are recorded in 32 rounds, and so on. In other words, the access code 121 is recorded in a higher number in the lower word and a smaller number in the higher word.

When more track addresses are required, 16 tracks are further allocated to one round. Of the remaining 32 access codes, 8 are recorded with unique codes for rotation synchronization, and the other 8 are recorded with information for identifying the segment number in which the unique code exists. The remaining 16 pieces are for recording other information.

In this recording medium, not only the lower part of the track address but also all track addresses are dispersed and recorded as the access code 121 of each word as described above. It can be reproduced, and recording of the header segment can be omitted to increase the data recording area.

Further, the applicant of the present application has filed Japanese Patent Application Laid-Open No. 4-3625.
Japanese Patent Publication No. 75 discloses an optical disc in which the entire track address is gray coded and recorded as the access code.

In this optical disc, the coding rule of the lower word is changed according to whether the upper word of the access code is odd or even,
The entire track address is gray coded.

That is, the value of the upper word of the access code is the original value (value before encoding). Therefore, when the upper word is an even number, the same value is taken, and when the upper word is an odd number, the complement (7's complement in FIG. 14, for example, 0 → 7, 1 → 6, etc.) is taken (first step). Processing), the conversion is performed for the whole gray coding, and the converted code is pit position coded by the rule shown in FIG. 14 and recorded as the access code (second step). processing).

As shown in FIG. 15, the pit position-coded access code has an LSB word once every two segments, a 4SB word once every four segments, and a 3SB word once every eight segments. Is recorded on the optical disc as follows. In addition, in practice, the access code is the pit position coding (the second code
It will be recorded in the embossed pit by
In FIG. 15, the first part is shown for the sake of clarity.
It is shown as a gray coded access code after staged processing.

The pit pattern of each word of the access code is as shown in FIG. However,
The access code (octal) shown in FIG. 16 does not indicate the actual arrangement on the disk, but indicates each word after the first stage processing. The five-digit number in the upper right of the figure shows the track address before the processing in the first step, and each digit of the five-digit number is the value of each word of the access code.

Here, using such an optical disc,
For example, when recording / reproducing is performed from the track 00007 shown in FIG. 17, the optical pickup moves along a locus A in the drawing. That is, in this case, the optical pickup first seeks and starts tracking near the segment position n-3. Since there is a pit difference between the track 00007 and the adjacent track 00100 only in the 3SB words in the access code in which the whole is gray coded, the track 00100 is located at the segment position n.
3 SB word = 1 can be read, the track moves to the track 0977 near the segment position n + 1, and the tracking becomes stable near the segment position n + 3. As a result, it is possible to accurately control the movement of the optical pickup to the track 00007, and it is possible to perform recording and reproduction from the track 0977.

As described above, the entire track address is gray-coded and recorded on the optical disk. Since the track address is wholly and partially gray-coded and recorded, the track address is accurately reproduced. be able to.

Further, by gray-coding the entire track address and recording it on the optical disk, it is possible to perform the seek by using the information as position control and speed control while reading the track address.

That is, since accuracy is not required so much at the time of high-speed seek, it is possible to perform the seek by using the high-order side (MSB word etc.) of the access code which is infrequent, and the accuracy at the time of low-speed seek (landing). Therefore, the lower side of the track address (LSB word) recorded on the optical disc once every two segments is used, and the MSB word is interpolated by this LSB word to perform slide servo. You can seek.

[0026]

However, an optical disc in which the entire track address is gray-coded and recorded is
It is good that the track address can be reproduced accurately, but the following 3 at the segment position n + 8 shown in FIG.
There was a problem that the track address could not be confirmed while the SB word could not be read.

That is, when the recording / reproducing of the locus A shown in FIG. 17 is performed, the track address reproduced with time is as shown in FIG. This Figure 1
8 is the time (segment position: n-5, n-4, n-3
...), the reproduced 5-word access code (00
171,00171,00170 ...), and the decoded track address (00101,00101,00
100 ...), accurate track address (0010
1,00101,00100 ...). As can be seen from FIG. 18, in this case, the correct track address can be finally confirmed from the segment position n to the segment position n + 8 of the eighth segment. Therefore, the correct track address can be confirmed only in the 8-segment cycle.

Similarly, when performing a seek, when the optical pickup moves as shown in the locus B of FIG. 17, the reproduced track address has an error of 1 bit from the segment position n as shown in FIG. This error begins to occur, and this error gradually increases up to the segment position n + 8.

That is, in the track addresses 00007 and 00100 shown in FIG. 19, only the 3SB word changes, and the others do not change. Therefore, when the optical pickup moves along the locus B, the error on the lower word side gradually increases from the segment position n at which the 3SB word is read to the segment position n + 8 at which the next 3SB word is read. Specifically, while the optical pickup is moving from the segment position n to the segment position n + 8,
An error of 6 tracks will occur.

This error cannot be corrected unless the next 3SB word is read at the segment position n + 8 enclosed by a square in FIG.

Further, since the 3SB word of the track address can be reproduced in an 8-segment cycle, an accurate track address can be obtained in the 8-segment cycle, but the 2SB word has a 16-segment cycle,
Since the MSB word can be reproduced only in the 32 segment cycle, it takes a considerable time to obtain an accurate track address depending on the track.

As described above, if it takes time to obtain an accurate track address, it takes time before recording / reproducing is started, and seek also takes time.

The present invention has been made in view of the above-mentioned problems, and an accurate track address can be obtained in a short time, and the time required to start recording / reproducing and the time required for seek can be shortened. An object of the present invention is to provide an optical disc capable of performing the above, and a track address reproducing device for reproducing a track address from the optical disc.

[0034]

An optical disk according to the present invention has a plurality of servo areas and a plurality of data areas, and a track address which is entirely gray-coded by pit position encoding is divided into an upper word and a lower word, An optical disc in which these are used as access codes and are distributed and recorded in each servo area so that the frequency of the access code of the lower word is higher than the frequency of the access code of the upper word. The above problem is solved by recording parity information.

Further, the optical disc according to the present invention solves the above-mentioned problems by the fact that the parity information is recorded by being added to the access code of the least significant word.

Next, the track address reproducing apparatus according to the present invention has a plurality of servo areas and a plurality of data areas, and divides the track address, which is entirely gray coded by pit position encoding, into an upper word and a lower word, These are used as access codes, and the data are distributed and recorded in each servo area so that the frequency of the access code of the lower word is higher than the frequency of the access code of the upper word. A track address reproducing device for reproducing a track address from an optical disc recorded with added parity information, comprising a reproducing means for reproducing the access code and the parity information recorded in the servo area, and a reproducing means reproduced by the reproducing means. Gray-decode the access code A track address reproducing means for reproducing the track address; an error detecting means for detecting an error in the track address reproduced by the track address reproducing means based on the parity information reproduced by the reproducing means; and the error detecting means. When no error is detected in the track address, the track address reproduced by the track address reproducing means is outputted as it is, and when an error is detected in the track address by the error detecting means, it is reproduced by the track address reproducing means. The track address correction means for outputting a word whose pit position changes among the generated track addresses by adding 1 or subtracting 1 to the higher track address to correct and output the corrected track address is provided. Solve.

Further, in the track address reproducing apparatus according to the present invention, the track address correcting means detects the maximum value of the track address of the least significant word of the access code reproduced by the track address reproducing means. Value detecting means, and based on the maximum value detecting means, when the track address of the least significant word is the maximum value, among the track addresses reproduced by the track address reproducing means, the word whose pit position changes is When the track address of the lowest word is not the maximum value, the word whose pit position changes is added to the higher-order track address when the track address of the lowest-order word is not the maximum value. To perform correction by subtracting 1 to the upper track address To solve the above problems as a symptom.

Further, in the track address reproducing apparatus according to the present invention, the track address correcting means detects the minimum value of the track address of the least significant word of the access code reproduced by the track address reproducing means. Value detecting means, and based on the minimum value detecting means, when the track address of the least significant word is the minimum value, the word whose pit position changes among the track addresses reproduced by the track address reproducing means is When the track address of the least significant word is not the minimum value, the word whose pit position changes among the track addresses reproduced by the track address reproducing means To add 1 to the upper track address for correction To solve the above problems as a symptom.

Further, the track address reproducing apparatus according to the present invention comprises the re-gray coding means for gray-coding the track address from the track address correcting means and reproducing and outputting the access code, and the re-gray coding means. And the access code from the reproducing means are supplied, and the track address is corrected by the selecting means for selecting any one of the access codes and supplying it to the track address reproducing means and the track address correcting means. In the case where the track address is corrected next time by the track address correction means, the gray coded access code of the corrected track address is selected and output by the re-gray coding means. And a selection control means for controlling the selection means DOO solve the above problems as characterized.

[0040]

The optical disk according to the present invention has a plurality of servo areas and a plurality of data areas, and the track address, which is entirely gray-coded by pit position encoding, is divided into an upper word and a lower word, which are used as access codes. An optical disc in which the access code of the lower word is distributed and recorded in each servo area so that the frequency of the access code of the upper word is higher than that of the upper word, and parity information is recorded in the servo area together with the access code. There is.

Specifically, for example, the parity information is
It is recorded by being added to the access code of the lowest word.

The track address reproducing device according to the present invention is a track address reproducing device for reproducing the track address from the optical disc in which the parity information is recorded together with the track address as described above. The access code and parity information recorded in the area is reproduced.

The track address reproducing means gray-decodes the access code reproduced by the reproducing means to reproduce the track address.

The error detecting means detects an error in the track address reproduced by the track address reproducing means based on the parity information reproduced by the reproducing means.

When no error is detected in the track address by the error detecting means, the track address correcting means outputs the track address reproduced by the track address reproducing means as it is, and the error detecting means outputs the track address to the track address. When an error is detected, of the track addresses reproduced by the track address reproducing means, the word whose pit position is changed is added to or subtracted from the upper-order track address to correct the track address. To do.

That is, since the parity information is added and recorded in the least significant word of the access code, even if an error occurs in the least significant word, it is corrected by the parity information, and the error is added to the track address of the least significant word. Does not occur. Therefore, if the error detection means determines that there is an error, the error exists not in the lower word of the access code but in the upper word unless the optical pickup has a defect on the disk or moves at an abnormally high speed. Will be done. Therefore, the track address correcting means corrects the track address of the word whose pit position changes when the error detecting means detects an error in the track address.

Here, the track address correcting means corrects one track at a time, but there is actually an error for one track, and the least significant word of the access code has no error. This is the case where the track address of the lowest word of the access code reproduced by the track address reproducing means is the maximum value or the minimum value.

Therefore, the track address correcting means detects, by the maximum value detecting means, whether or not the track address of the lowest word of the access code reproduced by the track address reproducing means is the maximum value, and the track is corrected. When the address is the maximum value, the word in which the pit position changes is added to the upper track address by 1 to correct it to the minimum value, and when the track address is not the maximum value, the word in which the pit position changes Corrects the maximum value by subtracting 1 from the higher track address.

Alternatively, the track address correcting means detects, by the minimum value detecting means, whether or not the track address of the least significant word of the access code reproduced by the track address reproducing means is the minimum value, and the track address is detected. Is a minimum value, the word whose pit position changes is subtracted from the upper track address by 1 to correct it to the maximum value, and when the track address is not the minimum value, the word whose pit position changes is 1 is added to the upper track address to correct it to the maximum value.

For example, the least significant word of the access code is recorded every other segment on the optical disc. Therefore, an accurate track address can be obtained every other segment, and the time until an accurate track address can be obtained can be shortened.

Next, in the track address reproducing apparatus according to the present invention, the re-gray coding means re-gray-codes the track address from the track address correcting means to reproduce the access code, and reproduces the access code. The access code from is supplied to the selection means.

When the track address correcting means corrects the track address, the selection control means keeps track of the corrected track address until the track address correcting means corrects the track address next time. The selecting means is controlled so that the gray-coded access code is selected and output by the re-gray coding means.

As a result, the corrected track address can be output until the next track address is corrected by the track address correction means.
The track address can be output more accurately.

[0054]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of an optical disk and track address reproducing apparatus according to the present invention will be described below with reference to the drawings.

First, the optical disk according to the present invention can be applied to a so-called sample servo type optical disk. In this sample servo type optical disc, one track is composed of a plurality of sectors, and one sector is composed of a plurality of segments. The one segment is composed of a plurality of servo areas and a plurality of data areas. It should be noted that, for example, 1024 servo areas are provided for one circumference of the optical disk, and the data area is between this servo area and the next servo area.

In FIG. 1, in the servo area 1,
For example, in a track address of 15 bits, 0th bit to 2nd bit, 3rd bit to 5th bit, 6th bit ...
In addition to the access code 2 indicating any 3 bits of the 8th bit, the 9th bit to the 11th bit, and the 12th bit to the 14th bit, it is added to the access code 2 indicating the 0th bit to the 2nd bit of the track address. The recorded parity information 3 and servo pattern 4 are sequentially recorded.

The access code 2 is the lowest (LS) indicating the track address of the 0th bit to the 2nd bit.
B) word, 4SB word indicating track address of 3rd to 5th bits, 3SB word indicating track address of 6th to 8th bits, 9th bit to 11th bit
2 SB word indicating the track address of the bit and the first
It is divided into a total of 5 words of the most significant (MSB) word indicating a track address of 2 bits to 14th bits, and is distributed and recorded on the disc.

The access code 2 is the MS
The conversion of the lower word is different depending on whether the B word is odd or even.

That is, when the MSB word is an odd word, for example, the LSB word is recorded as an octal positive logic gray code (2 out of 8) shown in FIG. 2A, and the MSB word is an even word. , The LSB word is recorded as an octal negative logic gray code shown in FIG.

The gray coded access code 2 is 8 in total, as shown in FIG.
Since the data is divided into two recording positions for recording, the gray code is also recorded as a whole. (Pit position coding).

When the access code 2 is gray-coded and recorded on the disc in this manner, the MSB word to the LSB word of the access code 2 have a pit pattern as shown in FIG. Although the access code 2 is actually recorded in embossed pits by the pit position coding, it is shown by the gray coded access code in FIG. 3 for easy understanding.

Next, in FIG. 15, the gray coded access code 2 is recorded so that the frequency of the lower word is higher than that of the upper word. Specifically, the access code 2 is, for example, the LSB word every 1 segment, the 4SB word every 4 segment, the 3SB word every 8 segment, and the 2SB every 2 segment.
Words are recorded to appear every 16 segments and MSB words to appear every 32 segments.

Further, as shown in FIG. 3, the parity information 3 is added and recorded in each LSB word recorded every other segment, and as will be described later, the parity information 3 causes It enables error correction for every two segments.

The servo pattern 4 is composed of a clock pit 5 for synchronizing clocks and a pair of wobble pits deviated to the outer and inner circumference sides from the track center for obtaining tracking error signals and the like. 6 and 6.

Next, as shown in FIG. 4, the track address reproducing apparatus according to the first embodiment of the present invention for reproducing the track address from the gray coded and recorded access code is as shown in FIG. A pit position detection unit 18 for detecting the pit positions of the access code 2, parity information 3, servo pattern 4, etc. recorded in the servo area 1 as embossed pits, and the servo area 1 is detected and recorded in this servo area 1. Access code reproducing unit 1 for reproducing the access code 2
9, a gray decoding section 20 (track address reproducing means) for reproducing a track address from the access code 2 reproduced by the access code reproducing section 19, and a track address reproduced by the gray decoding section 20 by using the parity information. 3, and an address correction unit 21 (track address correction means) that corrects the data based on 3).

The pit position detector 18 digitizes the reproduced signal (RF signal) of the access code 2, the parity information 3 and the servo pattern 4 and outputs the digitized A / D signal.
The converter 23, the first register 24 in which the maximum value of the reproduction data from the A / D converter 23 is stored, and the A / D converter
The value of the current reproduction data from the D converter 23 and the first value
The reproduction data from the register 24 are compared with each other, and the comparison output is supplied to the timing controller 26.

The access code reproducing section 19 starts counting by the inverted inhibit data (inverted INIT) from the timing controller 26, which indicates the recording start position of the access code 2, and 0 to 7 are started.
Counter 27 that counts and the inversion enable data (inversion EN) from the timing controller 26.
Is loaded with the count value from the counter 27, and the MSB word, the 2SB word, and the 3S of the access code 2 of, for example, 3 bits corresponding to the count value are loaded.
Value of B word, 4SB word, LSB word (C2, C
1, C0) and a second register 28 for outputting 1-bit parity (C0).

The pit position detecting section 18, the access code reproducing section 19 and the timing controller 26 constitute a reproducing means.

The gray decoding unit 20 receives the MSB word of the access code 2 from the second register 28,
The values of the 2SB word, 3SB word, 4SB word, LSB word and the parity information 3 are inverted MSB enable data (inverted MSB) and inverted 2SB enable data (inverted 2) from the timing controller 26, respectively.
SB), inversion 3SB enable data (inversion 3SB),
Inversion 4SB enable data (inversion 4SB), inversion LS
B enable data (inverted LSB) and inverted PTY enable data (inverted PTY)
It has eight registers 29 to 34.

Further, the gray decoding unit 20 outputs the 3-bit MS output from the third register 29.
First to first gray-decoding the 2SB word by exclusive-ORing the first bit of the B word and the first to third bits of the 2SB word output from the fourth register 30. Exclusive logic of 3 exclusive OR gates (EXOR gates) 30a to 30c, the output from the third EXOR gate 30c, and the first to third bits of the 3SB word output from the fifth register 31. Fourth to sixth EXOs for gray-decoding the 3SB word by taking the respective sums
It has R gates 31a to 31c.

Further, the gray decoding section 20 outputs the output from the sixth EXOR gate 31c and the first to third 4SB words output from the sixth register 32.
The 7th to 9th EXs for gray-decoding the 4SB word by taking the exclusive OR of the respective bits
By taking the exclusive OR of the outputs from the OR gates 32a to 32c, the ninth EXOR gate 32c, and the first to third bits of the LSB word output from the seventh register 33, respectively, A tenth to a twelfth EXOR gate 33 for gray-decoding the LSB word
a to 33c.

Further, the gray decoding unit 20 takes the exclusive OR of the output of the twelfth EXOR gate 33c and the parity output from the eighth register 34 to obtain the parity of the LSB word. Thirteenth EXOR gate 41 (error detection means) for checking
And the tenth to twelfth EXOR gates 33a to 33.
AND gate 42 (maximum value detection means) that becomes active when the maximum value of the LSB word gray-decoded by c is 7.

The address correction unit 21 outputs 15-bit +1 data (000000000000001) when the output from the AND gate 42 is active, and outputs 15-bit data when the output from the AND gate 42 is inactive. Addition processing of the first selector 43 that outputs 1 data (111111111111111), the track address of 15 bits gray-decoded by the gray decoding unit 20 and the +1 data or -1 data from the first selector 43 And an adder 46 that forms and outputs a corrected track address.

Further, the address correction section 21 is supplied with the track address from the gray decoding section 20 and the corrected track address from the adder 46, and an error occurs due to the parity check in the thirteenth EXOR gate 41. When detected, that is, when the output of the thirteenth EXOR gate 41 becomes active, the corrected track address is selected and output,
It has a second selector 47 for selecting and outputting the track address from the gray decoding unit 20 when the EXOR gate 41 becomes passive.

Next, the operation when the track address recorded on the above-mentioned optical disk is reproduced by the track address reproducing device will be described.

First, at the time of recording or reproduction, the optical disk is rotationally driven by a spindle motor at a constant angular velocity, for example, and the data such as the access code 2, parity information 3, servo pattern 4 on the disk is reproduced, This is supplied as an RF signal to the A / D converter 23 via the input terminal 22 of the pit position detection unit 18 shown in FIG.

The A / D converter 23 is supplied with a system clock from, for example, the timing controller 26. The RF signal is sampled based on the system clock, and the RF signal is digitized to generate RF data. Is formed and is supplied to the first register 24 and the comparator 25.

The timing controller 26 outputs the RF signal of the access code 2 to the A / D converter 2.
Inversion enable data (inversion EN data) is supplied to the first register 24 at the timing of being supplied to the third register 24, and the first register 24 is forcibly controlled to the load state.
As a result, the RF data of the access code 2 is loaded into the first register 24. The RF data loaded in the first register 24 is supplied to the comparator 25.

The comparator 25 receives the current RF data,
Compare with the RF data from the first register 24,
This comparison output is supplied to the timing controller 26.

When the comparison output indicates that the current RF data is larger than the RF data from the first register 24, the timing controller 26 outputs the inverted data to the first register 24. Supply EN data. The timing controller 26 outputs the RF signal of the access code 2 to the A / D converter 23.
Such an operation is repeated while being supplied. As a result, the first register 24 stores the maximum value of the RF data of the access code 2, that is, the RF data indicating the maximum value of the reproduced waveform of the access code 2.

On the other hand, the counter 27 of the access code reproducing unit 19 counts the access code 2 recorded for each of the above eight positions from 0 to 7, and supplies the count value to the second register 28.

The inverted EN data supplied to the first register 24 is supplied to the second register 28, and the count value from the counter 27 is loaded by the inverted EN data. ing. Therefore, the count value from the counter 27 is set to the second value at the timing when the maximum value of the RF data of the access code 2 is detected, that is, at the timing when the accurate pit position of the access code 2 is detected. Register 28
Will be loaded into.

When the count value is loaded into the second register 28, the MSB word, 2SB word, 3SB word of the access code 2 having, for example, 3 bits respectively corresponding to the loaded count value,
Value of 4SB word, LSB word (C2, C1, C0)
And 1-bit parity (C0) is output.

The timing controller 26 receives the MSB of the access code 2 from the second register 28.
When the word (C0, C1, C2) is output, inverted ENMSB data is output via the output terminal 48. The inverted ENMSB data is supplied to the third register 29 via the input terminal 35.

When the 2SB word (C0, C1, C2) of the access code 2 is output from the second register 28, the inverted EN2SB is output via the output terminal 48.
Output the data. The inverted EN2SB data is supplied to the fourth register 30 via the input terminal 36.

When the 3SB word (C0, C1, C2) of the access code 2 is output from the second register 28, the inverted EN3SB is output via the output terminal 48.
Output the data. The inverted EN3SB data is supplied to the fifth register 31 via the input terminal 37.

When the 4SB word (C0, C1, C2) of the access code 2 is output from the second register 28, the inverted EN4SB is output via the output terminal 48.
Output the data. The inverted EN4SB data is supplied to the sixth register 32 via the input terminal 38.

When the LSB word (C0, C1, C2) of the access code 2 is output from the second register 28, the inverted ENLSB is output via the output terminal 48.
Output the data. The inverted ENLSB data is supplied to the seventh register 33 via the input terminal 39.

When the parity information 3 (1 bit data C0) is output from the second register 28, inverted ENPTY data is output via the output terminal 48. The inverted ENPTY data is input to the input terminal 4
It is supplied to the eighth register 34 via 0.

As a result, the third to seventh registers 2 are
9 to 33 are the MSBs of the above access code 2 respectively.
Words to LSB words are loaded, and parity information 3 is loaded into the eighth register 34.

The MSB word loaded in the third register 29 is output as it is, and is used as, for example, the 14th, 13th, and 12th bits (A14, A13, A12) of the track address of 15 bits in total.

The data of each bit of the 2SB word loaded in the fourth register 30 is EXO respectively.
In the R gates 30a to 30c, the exclusive OR of the 12th bit data output from the third register 29 is obtained, gray-decoded, and the 11th, 10th, and 9th bits of the track address ( A11, A10,
A9).

The data of each bit of the 3SB word loaded in the fifth register 31 is EXO respectively.
In the R gates 31a to 31c, exclusive OR with the data of the 9th bit output from the fourth register 30 is obtained, gray-decoded, and the 8th, 7th and 6th bits of the track address ( A8, A7, A6).

The data of each bit of the 4SB word loaded in the sixth register 32 is EXO respectively.
In the R gates 32a to 32c, the exclusive OR of the sixth bit data output from the fifth register 31 is calculated, gray-decoded, and the fifth, fourth, and third bits of the track address ( A5, A4, A3).

The data of each bit of the LSB word loaded in the seventh register 33 is EXO respectively.
In the R gates 33a to 33c, the exclusive OR with the data of the third bit output from the sixth register 32 is taken, gray-decoded, and the second, first, and 0th bits of the track address ( A2, A1, A0).

Specifically, in the gray decoding, for example, when the least significant bit (12th bit) of the MSB word is an even number, the 2SB word from the fourth register 30 is directly used in the EXOR gates 30a ... Three
0c and the least significant bit of the MSB word is an odd number, the 2S from the fourth register 30.
The complement of the B word is output via the EXOR gates 30a to 30c.

When the least significant bit (9th bit) of the 2SB word is an even number, the 3SB word from the fifth register 31 is output as it is through the EXOR gates 31a to 31c, and the 2SB word is output. If the least significant bit of the word is odd, then the fifth register 31
The complement of the 3SB words from the EXOR gate 3
It is output via 1a to 31c.

Thereafter, in the same manner, gray decoding is performed in the EXOR gates 32a to 32c and 33a to 33c to reproduce the track address of all 15 bits A0 to A14. This track address is supplied to the adder 46 and the second selector 47.

The EXOR gates 33a to 33c are also provided.
The outputs of the above are respectively supplied to the AND gate 42. The AND gate 42 includes the EXOR gates 33a to 33a.
The maximum value bit (MAX) is detected from the track address of the 0th to 2nd bits forming the LSB word of the access code 2 supplied from 33c. And
The AND gate 42 becomes active only when the maximum value is 7. The output of the AND gate 42 is supplied to the first selector 43.

The input terminal 4 is connected to the first selector 43.
15-bit +1 data via 4 (000000000000001)
And 15-bit -1 data (11
1111111111111) is being supplied. In the track address reproducing apparatus according to the present embodiment, the above-mentioned track address is corrected for each track, but there is actually a deviation of one track, and there is no error in the LSB word. Indicates that the value of the LSB word is 7 (maximum value)
Or 0 (minimum value) only. Therefore, the LS
When the value of the B word is 7, 1 is added to the gray coded track address and corrected so as to be 0. When the LSB word is 0, 1 is subtracted from the track address. And correct it to 7.

In other words, the first selector 43 operates when the output of the AND gate 42 becomes active (when the maximum value bit of the track addresses of the 0th to 2nd bits is 7). Select +1 data,
This is supplied to the adder 46, and the AND gate 42
When the output of is not active, the -1 data is selected (because the 16th bit is ignored), and this is supplied to the adder 46.

The adder 46 corrects the gray-decoded track address by adding the gray-decoded track address to the +1 data or -1 data, and uses this as the corrected track address. It is supplied to the second selector 47.

On the other hand, the output of the EXOR gate 33c, which is the least significant bit (LSB) of the track address, is output to the eighth register 34 in the EXOR gate 41.
The parity is checked by the parity output from the. The output of the EXOR gate 41 becomes active only when there is an error in the parity check, and becomes passive when there is no error. The output from the EXOR gate 41 is supplied to the second selector 47.

Since the parity information 3 is added to the LSB word as described above, no error occurs in the LSB word. Therefore, if the parity check determines that there is an error, the error is higher than the 4SB word of the access code 2 unless there is a defect on the disk or the optical pickup moves at an abnormally high speed. Will exist.

Therefore, the second selector 47 operates when the output from the EXOR gate 41 becomes active (when there is an error in the parity check).
Select the corrected track address from the adder 46,
This is output through the output terminal 49, and when the output from the EXOR gate 41 becomes passive (when there is no error due to the parity check), the gray-decoded track address is selected and is output to the above-mentioned output. Output through the terminal 49.

As described above, the parity information 3 is added to the LSB word recorded every other segment on the disk. Therefore, error correction can be performed for every two segments, and the track address in which the error has occurred can be corrected to output an accurate track address. In addition, an accurate address can be detected even at the time of seek, and the seek speed can be increased.

When the optical pickup crosses the track at a speed exceeding the correction limit of the track address error due to high-speed seek or the like, it may be uncorrectable or may be erroneously corrected, but this error amount is a problematic value. is not. When the optical pickup crosses the track at a speed equal to or lower than the correction limit of the track address error, the access code 2
This is not a problem in the above-mentioned circuit configuration because the LSB word of is not parity-checked with a value other than 0 and 7.

Here, a NOR gate (minimum value detecting means) is provided in place of the AND gate 42, and -1 data (111111111111111) is supplied from the first selector 43 via the input terminal 44 to the above. +1 data (00000000000000) to the first selector 43 via the input terminal 45.
1) may be supplied. As a result, the above NO
The R gate becomes active when 0, which is the minimum value, is detected in the 3-bit LSB word, becomes -1 data by the first selector 43, and becomes passive when 0 is not detected. +1 data is selected by the first selector 43. Therefore, the same effect as when the AND gate 42 is provided can be obtained.

Next, such a track address correcting operation will be described with a specific example. First, for example, when recording / reproducing is performed from the track 00007 shown in FIG. 17, the optical pickup moves along a locus A. The track address reproduced with the passage of time is as shown in FIG. FIG. 5 shows the time (segment position), the reproduced access code of 5 words, the decoded track address, the parity, and the correct track address in order.

That is, the optical pickup first seeks and starts tracking near the segment position n-3. As a result, the access codes 0170 to 00007 ... Of the segment positions n−3 to n + 8 ... Which are shown in FIG. 5 are reproduced.

The access code reproduced at the segment position n-3 is 00170, and the track address formed by decoding this is 00100. The LSB of this track address is 0, and the parity is also 0.
Is. Therefore, it can be seen that the track address of the segment position n-3 has been correctly reproduced. Therefore,
The output of the EXOR gate 41 of the track address reproducing device shown in FIG. 4 becomes passive, and the gray-decoded track addresses A0 to A14 are selected by the second selector 47 and output.

In the following, from the segment position n-3 to the segment position n-1, since the LSB of the decoded track address and the parity match, the track address A0 to A14 is selected by the second selector 47. Although it is output, the LSB of the decoded track address and the parity do not match in the segment positions n + 1 to n + 8. Therefore, the output of the EXOR gate 41 of the track address reproducing device shown in FIG. 4 becomes active, whereby the corrected track address corrected by the adder 46 is selected by the second selector 47 and output.

That is, when the LSB of the decoded track address and the parity do not match, the decoded track address 00100 shown in and after the segment position n + 1 shown in FIG. . Track address 0
When 0100 is entirely gray-coded, the access codes are 00171 for 00170 and 00101, and
00007 is 00007. 00170 and 0017
The difference in the pit positions of 1 is the LSB word.
The pit position difference between 0 and 00070 is 3 SB words. As described above, in the above optical disc, the higher-order word has a lower appearance frequency, and thus the influence of the radial deviation is large, and the probability of an error is large. On the contrary, the lower word has a higher appearance frequency, is less influenced by the radial deviation, and is less likely to cause an error. Therefore, in the whole gray coding, the word whose pit position changes is selected in the higher order and the decoded access code 00170 is set to 0.
Corrected to 0070, that is, track address 0010
Correct 0 to 00007.

Since the above-mentioned parity is recorded every other segment as shown by the box in FIG. 5, an accurate track address can be obtained every other segment. Further, since an accurate track address can be obtained every other segment, an accurate track address can be confirmed in a short time even if the frequency of appearance of the upper word such as the MSB word is low, and high speed access, Can contribute to high-speed seek.

In the example shown in FIG. 5, since the track is updated in the segment in which the LSB word is recorded, it is possible to correct each segment.
If the track is updated in a segment other than a word, no correction can be made in that segment. But,
Since the LSB word is recorded every other segment, it can be corrected in the next segment, and the correct track address can be obtained every other segment without increasing error accumulation.

Next, a track address reproducing apparatus according to the second embodiment of the present invention for reproducing the track address recorded on the above-mentioned optical disk will be described.

The track address reproducing apparatus according to the second embodiment, as shown in FIG. 7, is the gray level output from the second selector 47 to the track address reproducing apparatus according to the first embodiment. A gray coding circuit 61 that re-gray codes the decoded track address or the corrected track address to form an access code.
(Re-gray coding means), the access code from the gray coding circuit 61 and the access code from the second register are selected, and each of the registers 29 to 33 is selected.
And a selection circuit 60 (selection means) to be supplied to.

The gray coding circuit 61 is the second coding circuit.
Of the 15-bit track address output from the selector 47 of FIG. 1 is composed of EXOR gates 73a to 73m for gray-coding the 11th bit to the 0th bit, respectively.

The selection circuit 60 is provided with the MSB word of the access code formed by the re-gray coding and the MSB of the access code from the second register 28.
A third selector 62 to which a word is supplied respectively, and a fourth SB to which the 2SB word of the re-gray coded access code and the 2SB word of the access code from the second register 28 are respectively supplied. A selector 63, a fifth selector 64 to which the 3SB word of the access code formed by the re-grey coding and the 3SB word of the access code from the second register 28 are respectively supplied, and the re-grey coding A sixth selector 65 to which the 4SB word of the access code formed by the above and the 4SB word of the access code from the second register 28 are respectively supplied, and the L of the access code formed by the re-grey coding.
The SB word and the seventh selector 66 to which the LSB word of the access code from the second register 28 is respectively supplied.

Each of the selectors 62 to 66 is selected and controlled all at once by the select data (SEL) from the timing controller 26 which is the selection control means.

Next, the operation of the track address reproducing apparatus according to the second embodiment having such a configuration will be described.
In the description of the operation of the track address reproducing apparatus according to the second embodiment, the same operation as that of the track address reproducing apparatus according to the first embodiment described above will be denoted by the same reference numeral, and detailed description thereof will be given. Is omitted.

First, in FIG. 7, the track address or the corrected track address which has been gray-decoded by the gray decoding section 20 and is output from the second selector 47 is output via the ninth register 74 and the output terminal 49. While being output, the 12th to 14th bits are supplied to the third selector 62, and the 11th to 0th bits are supplied to the EXOR gates 73a to 73l, respectively.

The EXOR gate 73a reproduces the track address of the 11th bit by taking the exclusive OR of the 12th bit and the 11th bit of the track address. The EXOR gate 73b reproduces the track address of the 10th bit by taking the exclusive OR of the 12th bit and the 10th bit of the track address. The EXOR gate 73c reproduces the track address of the 9th bit by taking the exclusive OR of the 12th bit and the 9th bit of the track address. The 2SB words of the access code, which are the ninth to eleventh track addresses, are supplied to the fourth selector 63.

Further, the EXOR gate 73d reproduces the track address of the 8th bit by taking the exclusive OR of the 9th bit and the 8th bit of the track address. The EXOR gate 73e reproduces the track address of the 7th bit by taking the exclusive OR of the 9th bit and the 7th bit of the track address. The EXOR gate 73f reproduces the track address of the 6th bit by taking the exclusive OR of the 9th bit and the 6th bit of the track address. The 3SB word of the access code, which is the sixth to eighth track addresses, is supplied to the fifth selector 64.

Further, the EXOR gate 73g reproduces the track address of the fifth bit by taking the exclusive OR of the sixth bit and the fifth bit of the track address. The EXOR gate 73h reproduces the track address of the fourth bit by taking the exclusive OR of the sixth bit and the fourth bit of the track address. The EXOR gate 73i reproduces the track address of the third bit by taking the exclusive OR of the sixth bit and the third bit of the track address. The 4SB word of the access code, which is the third to fifth track addresses, is supplied to the sixth selector 65.

Further, the EXOR gate 73j reproduces the track address of the second bit by taking the exclusive OR of the third bit and the second bit of the track address. The EXOR gate 73k reproduces the track address of the first bit by taking the exclusive OR of the third bit and the first bit of the track address. The EXOR gate 73l reproduces the track address of the 0th bit by taking the exclusive OR of the 3rd bit and the 0th bit of the track address. The LSB word of the access code, which is the 0th to 2nd track address, is supplied to the seventh selector 66.

That is, the gray coding circuit 61
Outputs the lower word as it is if the least significant bit (12th, 9th, 6th, 3rd bit) of each word of the reproduced access code is an even number, and outputs the complemented number if it is an odd number. It has become.

As described above, each of the selectors 62 to 66 described above.
Is the MS of the access code from the second register 28.
B word to LSB word are respectively supplied.

In the timing controller 26, when the address correcting unit 21 corrects a track address, the timing controller 26 outputs the select data (SEL) via the output terminal 72 until the next track address is corrected. ) Is output. The select data is supplied to the selectors 62 to 66 via the input terminals 67 to 71.

When each of the selectors 62 to 66 is supplied with the select data, the gray coding circuit 61 is supplied.
Select the access code from the
Are supplied to the registers 29 to 33.

The reproduced access codes in each segment are stored in the third to seventh registers 29 to 33, which are output from the gray coding circuit 61 when the track address is corrected. Since the track address to be recorded is the access code of the corrected track address, the access code stored in each of the registers 29 to 33 is also corrected by the selection operation of each of the selectors 62 to 66. .

Therefore, in the address correction unit 21, until the next track address is corrected,
An accurate track address can be output.

Specifically, for example, when seeking, the above-mentioned FIG.
Assuming that the optical pickup has moved as shown by the locus B of 3), the 3SB word corrected from 1 to 0 at the segment position n + 1 shown in FIG. 6 is also used at the segment position n + 2 and thereafter. After this segment position n + 2, the reproduced access code itself has a corrected value at this time, and until the next 3 SB words are reproduced at the segment position n + 8, the corrected access code (track address) is reproduced. ) Is used. Thereby, the error of the track address can be corrected.

In the track address reproducing apparatus according to the first embodiment described above, if the optical pickup moves at a speed exceeding one track within the appearance period of the upper word of the access code, it cannot be corrected due to the nature of the gray code. However, as in the track address reproducing apparatus according to the second embodiment, by using the previously corrected access code, parity is added to the LSB word recorded every other segment. Therefore, correction can be performed until the optical pickup moves at a speed not exceeding one track in two segments. Therefore, it is possible to seek while reading the address, which can contribute to an increase in seek speed.

When the track is updated in the segment in which the LSB word is not recorded, this cannot be corrected, but since the LSB word is recorded in the next segment, the above correction must be performed. Therefore, an accurate track address can be obtained.

In the description of the above embodiments, the access code 2 and the parity information 3 are recorded separately in the servo area 1 of the optical disc according to the present invention. Parity may be added by changing the recording position of the servo pattern as shown in FIG. In this case, the parity recording area can be reduced and the data area 8 can be expanded.

As shown in FIGS. 9 and 10, the track address may be recorded in the first half portion 80a of the LSB word of the access code 80 and the parity may be recorded in the second half portion 80b. Also in this case, the recording area of the parity can be reduced and the data area 8 can be expanded.

Finally, in the description of the above-mentioned embodiments, the optical disc according to the present invention records parity information 3 by adding it to the LSB word of the access code 2, but this is, for example, 4 SB words, 3 SB. Words, 2SB words, or MSB words may be added and recorded.

[0139]

The optical disk and track address reproducing apparatus according to the present invention can confirm the correct track address in a short time. Therefore, it is possible to shorten the time required to start recording / reproducing and the time required for seeking.

[Brief description of drawings]

FIG. 1 is an access code recorded in a servo area of an optical disk according to a first embodiment of the present invention, a parity,
It is a figure which shows a servo pattern.

FIG. 2 is a diagram for explaining how to gray code the access code.

FIG. 3 is the gray-coded access code L
It is a figure which shows the pit pattern of SB word-MSB word.

FIG. 4 is a block diagram of a track address reproducing apparatus according to a first embodiment of the present invention for reproducing track addresses from the optical disc.

FIG. 5 is a diagram for explaining an error correction operation of the track address reproducing device according to the first embodiment.

FIG. 6 is a diagram for explaining an error correction operation of the track address reproducing device according to the first embodiment.

FIG. 7 is a block diagram of a track address reproducing apparatus according to a second embodiment of the present invention for reproducing track addresses from the optical disc.

FIG. 8 is a diagram showing an optical disc according to a second embodiment of the present invention in which the above-mentioned servo pattern is pit position coded and used as an access code parity.

FIG. 9 is a diagram showing an optical disc according to a third embodiment of the present invention in which a part of the access code is parity.

FIG. 10 is a diagram showing pit patterns of LSB words to MSB words of an access code recorded on the optical disc in the third embodiment.

FIG. 11 is a diagram showing a recording format of a conventional optical disc in which a track address is gray-coded and recorded.

FIG. 12 is a diagram for explaining pit position coding for gray-coding the access code of the conventional optical disc.

FIG. 13 is a diagram showing an access code and a servo pattern recorded in a servo area of a conventional optical disc.

FIG. 14 is a diagram for explaining pit position coding for gray-coding the access code of the conventional optical disc.

FIG. 15 is a diagram showing access codes (distributed address format) which are distributed on MSB words to LSB words and are recorded on a disc.

FIG. 16 is a diagram showing pit patterns of MSB words to LSB words of the access codes recorded on the dispersed and conventional optical disc.

FIG. 17 is a diagram showing a locus of an optical pickup moving on an optical disc of the distributed address format.

FIG. 18 is a diagram showing track addresses reproduced from an optical disc of the distributed address format.

FIG. 19 is a diagram showing track addresses reproduced from an optical disc of the distributed address format.

[Explanation of symbols]

1 ・ ・ ・ ・ ・ ・ ・ ・ ・ Servo area 2 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Access code 3 ・ ・ ・ ・ ・ ・・ ・ Parity information 4 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Servo pattern 5 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Clock pit 6 ・ ・ ・ ・・ ・ ・ ・ Wobble pit 8 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Data area 18 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Pit position detector 19 ・ ・ ・ ・・ ・ ・ ・ ・ ・ ・ ・ Access code playback unit ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Gray decoding unit 21 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Address correction unit 22 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ RF signal input terminal 23 ・ ・ ・ ・ ・ ・ ・ ・ ・ A / D converter 24 ・ ・ ・ ・ ・ ・... First register 25・ ・ ・ ・ ・ ・ ・ ・ ・ Comparator 26 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Timing controller 27 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Counter 28 ・ ・........... Second register 29 to 34 ... 3rd to 8th register 30a to 30c ..... EXOR Gates 31a to 31c ..... EXOR gates 32a to 32c ..... EXOR gates 33a to 33c ..... EXOR gates 41 ..・ ・ ・ ・ ・ ・ ・ ・ EXOR gate 42 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ AND gate 43 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ First selector 46 ・ ・ ・········· Adder 47 ··············· Second selector 62 to 66 Third to seventh selector 73a~73m ········· EXOR gate 74 .............. ninth register

Claims (6)

[Claims] 1. A track address having a plurality of servo areas and a plurality of data areas, which is entirely gray-coded by pit position encoding, is divided into an upper word and a lower word, which are used as access codes, and an access code of a lower word. An optical disc in which the parity information is recorded together with the access code in the servo area so that the frequency is higher than the frequency of the access code of the upper word and is recorded in each servo area. . 2. The optical disc according to claim 1, wherein the parity information is recorded by being added to the access code of the least significant word. 3. A track address having a plurality of servo areas and a plurality of data areas, which is entirely gray-coded by pit position encoding, is divided into an upper word and a lower word, which are used as an access code, and an access code of a lower word. The disc is recorded in a distributed manner in each servo area so that the frequency is higher than the frequency of the access code of the upper word, and the parity code is added to the access code of the lowest word of the above access code to record from the optical disc. A track address reproducing device for reproducing an address, comprising reproducing means for reproducing the access code and parity information recorded in the servo area, and gray-decoding the access code reproduced by the reproducing means to obtain a track address. Track address to play Error detecting means for detecting an error in the track address reproduced by the track address reproducing means based on the parity information reproduced by the reproducing means, and an error in the track address detected by the error detecting means. Otherwise, the track address reproduced by the track address reproducing means is output as it is, and when an error is detected in the track address by the error detecting means, among the track addresses reproduced by the track address reproducing means, A track address reproducing device comprising: a track address correcting unit for adding 1 or subtracting 1 to a higher-order track address of a word whose pit position is changed, and correcting and outputting the corrected address. 4. The track address correction means comprises maximum value detection means for detecting that the track address of the least significant word of the access code reproduced by the track address reproduction means is the maximum value, and the maximum value detection is performed. Based on the means, when the track address of the lowest word has the maximum value, the word whose pit position changes among the track addresses reproduced by the track address reproducing means adds 1 to the higher track address. When the track address of the least significant word is not the maximum value, the word whose pit position changes among the track addresses reproduced by the track address reproducing means subtracts 1 from the upper track address. 4. The track address reproducing device according to claim 3, wherein the correction is performed by Place 5. The track address correcting means comprises minimum value detecting means for detecting that the track address of the least significant word of the access code reproduced by the track address reproducing means is the minimum value, and the minimum value detecting means. Based on the means, when the track address of the least significant word is the minimum value, the word whose pit position changes among the track addresses reproduced by the track address reproducing means subtracts 1 from the upper track address. If the track address of the least significant word is not the minimum value, the word whose pit position changes among the track addresses reproduced by the track address reproducing means adds 1 to the upper track address. 4. The track address reproducing device according to claim 3, wherein the correction is performed by Place 6. A re-gray coding means for gray-coding the track address from the track address correcting means to reproduce and output an access code, an access code from the re-gray coding means and an access from the reproducing means. When a code is supplied and the track address is corrected by the selecting means for selecting one of the access codes and supplying it to the track address reproducing means and the track address correcting means, next, the track address correcting means. Selection control for controlling the selecting means so that the gray-coded access code of the corrected track address is selected and output until the track address is corrected by Claim 3, Claim 4 or Claims characterized by having a means. Track address reproducing apparatus according.