JPH0344873A - Optical information recording and reproducing device - Google Patents

Abstract

PURPOSE:To prevent erroneous detection of an access mark by providing a difference circuit, an out-of-modulation detecting circuit, a pit position data correcting switch and an access mark decoding ROM. CONSTITUTION:An N/M modulated data is used for the access mark, and is converted by the difference circuit 51 into (N+1) pieces of pit position data from the largest signal amplitude out of M transfer pits of a regenerative signal of the access mark. When an access mark demodulated from N pieces of pit position data from the largest signal amplitude in the aforementioned data is detected to be out of modulation by the 1st out-of-modulation detecting circuit 94, the pit position data correcting switch 97 is controlled, so that the Nth pit position data from the largest signal amplitude is replaced with the (N+1)th pit position data from the largest one and outputted to the decoding ROM 96. By this method, the access mark accurately is decoded by amending the out-of-modulation pattern.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an optical information recording and reproducing device that optically records and reproduces information, and in particular, it relates to an optical information recording and reproducing device that optically records and reproduces information. The present invention relates to an optical information recording and reproducing device that performs track access.

[Prior Art] Information is optically recorded and reproduced on a disk-shaped information storage medium. One of the formats of so-called optical disk systems is the sampled format.
Format) is known. This method is described in Proceedings of Niss P.I.E. Volume 695, Optical Mass Data Storage ■, 1986, pp. 112 to 115 and pp. 239 to 242 (Proc.
eeding of 5PIE, vol 695.0
ptical Mass DataStorage■,
1986. p112-p115. p239-p242
) is discussed in detail. As shown in FIG. 5, this format uses sample marks provided on the disk in advance to obtain a tracking error signal and a timing signal. In FIG. 5, 701 to 718,
801 to 818 and 901 to 918 are sample marks, and 601 to 618 indicate the centers of virtual tracks (actually, no track grooves exist). The positions of the first sample marks 701 to 718 change in the track direction every 16 tracks (in Fig. 5, the positions are 716 and 717).
). This is to obtain a track crossing signal during seek.

The data format is as shown in Figure 6.
The circumference is divided into 32 sectors, one sector is divided into 43 segments, and each segment is divided into 18 bytes. One byte is further divided into 15 channel bits. One of the segments is for sector identification information (ID), and the sector identification information (ID) is recorded by pre-pits. Data is recorded in the remaining 42 segments.

One segment consists of a 2-byte sample mark and a 16-byte data area, so there are 672 data in one sector.
Bytes of data are recorded. The 672 bytes of data include 512 bytes of user data, 16 bytes of control data, and 144 bytes of error correction code.

During recording, data is converted from 8 bits per byte into 15 channel bits (=1 symbol) using a modulation method called 4/15 conversion, and is recorded in the data area between sample marks. The 4/15 conversion is detailed in the aforementioned literature. In 4/5 modulation, 1
The fifth channel pit is always O, and of the other 14 channel bits, two odd-numbered channel bits and two even-numbered channel bits are 1. There can be up to four consecutive 1's, but if there is an O between 1's, there will be at least two O's (at the data byte break, there can be only one 0, but this is always O So it's not a problem)
. If 0's are consecutive, up to 17 O's will follow (for example, if the data is 00.EE in hexadecimal notation, 1.2, 5.6th of the first data and 9 of the second data) ，
10.13.The 14th channel bit becomes 1, and the others become O).

During playback, which playback signal amplitude is detected for each channel bit, the top two playback signal amplitudes (the two with the smallest signal potential) are selected for each odd-numbered and even-numbered bit, and a pit, that is, 1, is placed at that position. judge that it exists. Reversely obtain data from the conversion table of 4/15.

The recording area of the disc has, for example, an inner diameter of 60 mm.

The outer diameter is 120 mm, the track density is 1.5 μm/track, the linear recording density is 0.95 μm/bit, and the disk rotation speed is usually 1800 rpm, but this is not specified. The number of sample marks per track round is 1376, and the sampling frequency is approximately 41k.
Hz.

In this method, since tracking servo is performed using only information from sample marks, the amount of track movement at the time of access is also obtained from the sample marks.

As shown in FIG. 5, the positions of the first wobbling pits 701 to 718 change every 16 tracks, so by detecting the positions of these pits, the amount of track movement for every 16 tracks can be detected.

However, this method has the following problems regarding access. That is, (King) Since the track movement amount detection signal has only two types of patterns, the movement direction of the pickup cannot be detected at the time of access.

(2) The resolution for detecting the amount of track movement is insufficient at 16 tracks. However, if the pattern repetition period is set to 16 tracks or less in order to improve the resolution of the track movement amount detection signal, the detection limit speed becomes insufficient.

In order to solve the above problems, three or more types of patterns are periodically repeated according to changes in the track. This solves the above-mentioned problems (an example is shown as access mark I in FIG. 3).

(1) The moving direction of the pickup at the time of access can be detected.

(2) Even if the resolution is increased (even if the pattern change period is shortened), the repetition period can be lengthened by increasing the number of patterns, making it possible to simultaneously secure the detection limit speed and resolution. Become.

Such a code for detecting the amount of track movement is an access mark.

[Problems to be Solved by the Invention] When performing track access, the relative movement direction, movement amount, and movement speed between the pickup and the optical disk are detected from the access mark decoded from the reproduction signal. Therefore, erroneously detecting an access mark will impair track access performance. In particular, the possibility of false detection increases in the following cases.

(1) When the access speed is high (2) When there is a defect on the disk An object of the present invention is to provide an optical information recording/reproducing device that prevents erroneous detection of access marks and realizes stable track access. It is in.

[Means for Solving the Problems] In order to solve the above problems, the present invention employs the following technical means.

(1) When the access mark demodulated to 4/11 from the reproduced signal has a modulation error, swap the positions of the 4th and 5th transmission pits from the one with the smallest reproduced signal value among the 11 transmission bits and perform 4/11 demodulation. A modulation deviation detection circuit is provided.

(2) When the access mark demodulated to 4/11 from the reproduced signal has a modulation error, the reproduced signal value at the transmission bit position where there is no possibility of a pit (according to the access mark modulation rules) is 4 from the smallest. If the transmission bit position is within the fifth transmission bit position, an access mark protection circuit is provided that performs 4/11 demodulation by exchanging the transmission bit position with the fifth transmission bit position from the smallest one.

(3) When the access mark demodulated by 4/1↓ from the playback signal has a modulation error, specific pit position data is output to the decoding read-only memory (ROM) circuit and the second signal is demodulated by 4/1↓. An access mark protection circuit will be provided.

[Operation] Converts the playback signal obtained from the disc into digital data using an analog/digital (A/D) converter,
The digitized reproduction signal is converted by a differential circuit into five pit position data among the 11 channel bits, starting from the one with the largest signal amplitude. When the first modulation deviation detection circuit detects that the access mark demodulated from the four pit position data, starting from the one with the largest signal amplitude among the five pit position data, is out of modulation, the pit position data correction switch is controlled. Then, the fourth pit position data from the one with the largest signal amplitude and the fifth pit position data from the one with the largest signal amplitude are exchanged and output to the decoding ROM. Thereby, the modulation deviation pattern can be corrected and the access mark can be correctly decoded.

[Example] Embodiments of the present invention will be described in detail below with reference to the drawings.

First, a first embodiment will be explained with reference to FIG. 1 and subsequent figures. Note that this embodiment shows a case where a 4/11 modulation layer is used as a data modulation method. CN/M modulation is a method in which pits are formed in N pits among M transmission pits synchronized with a data transmission unit. (indicates the modulation method).

As shown in FIG. 2, 1 is a disc-shaped information recording medium, on which a spiral or concentric virtual track 2 is formed, and sample marks 3 are periodically formed on the virtual track 2. It is provided.

As shown in FIG. 3, two sample marks 3 are wobbled in opposite directions relative to the virtual track center 2
The timing pit 9 is placed on the virtual track center 2, and the access mark 11 is made up of a plurality of pits (a first wobbling pit 7 and a second wobbling pit 8).

The access mark 11 in FIG. 3 is constructed according to the 4/11 modulation rule. The 4/11 modulation rule is a modulation rule that projects 8-bit data onto one transmission bit when recording or reproducing information, and converts it into a pattern in which pits are arranged on four transmission bits. Figure 14 (1) to 1
Figure 4 (4) shows an example of the modulation table. The left column is the information data and the right column is the modulated 11-bit pattern.

Access mark 11 is from the table.

Select a pattern in which 3 of the 4 pits are placed in the 3rd to 8th transmission bits, and the remaining epits are placed in the 11th transmission bit. The pit is configured as a first wobble pit 7. The arrangement of pits in the access mark 11 changes periodically according to changes in the track.

In this example, 16 types of patterns are used (Tl-
Tl 6), one cycle consists of 16 tracks.

FIG. 4 shows the data format of the information recording medium shown in FIG. 2. One track consists of 22 sectors, and one sector consists of 76 segments. One segment consists of 10 bytes including a 2-byte sample mark and an 8-byte data area.

Disc diameter is 48mm inner diameter in user area and 80mm outer diameter.
, the inner diameter is 46 including the lead-in and lead-out areas.
m m + outer diameter 82 mm, rotation speed 1800 rpm
m, the linear recording density is 1°08 μm/bit (0
, 785 μm/channel bit), 1672 sample marks per track-period (sample period 50.16
kHz), and the user data capacity is 100 Mbytes or more.

The amount of movement of the track is detected using an access mark, and its resolution is one track. Since the access mark follows the data modulation side, it can be decoded as data. In addition, the detection limit for the moving speed of a track is approximately 1 m / 16 tracks per sample period.
It becomes s.

The first access mark in Figure 3 is 3 between adjacent tracks.
Only one of the pits changes its position. In this case, the change in position is limited to the following two cases.

■Change in the relative position of one transmission bit in one pit (for example, seen in the change from track 1 to track 2)■
(For example, seen in the change from track 9 to track 10) Relative position change of 2 transmission bits of only one pit with one fixed pit (7th transmission bit) in the middle, data demodulation is performed by differential detection Assuming that this is done, as a result of the above, even if the reading light spot scans between tracks, the error in the read access mark is guaranteed to be within one track. In N/M modulation, differential detection refers to a method in which the signal amplitude of each of M transmission bits corresponding to one byte of data is measured, and the Nth transmission pit position from the one with the largest amplitude value is demodulated as the pit position.

FIG. 7 shows a first embodiment of an optical disc reproducing apparatus using the disc shown in FIG. Reference numeral 1 denotes an optical disk, and as shown in FIG. 2, sample marks 3 are previously provided on the disk surface. A spindle motor 20 rotates the disk 1. Reference numeral 21 denotes an optical pickup, which converts the laser beam irradiated from the laser 22 into a collimating lens 23.
, a polarizing beam splitter 24. The light is focused on a recording surface 27 of the disk 1 through a 4/4 wavelength plate 25 and an objective lens 26. The light reflected from the recording surface 27 of the disk 1 travels in the opposite direction to the direction in which it was incident, and passes through the polarizing beam splitter 24.
The light is reflected by the detection lens 28 and focused onto the photodetector 29 . The photodetector 29 is divided into two regions and is configured so that a focus error signal can be detected based on the difference in light amount between each region.

A differential amplifier circuit 30 amplifies the difference signal between the detection signals of the photodetector 29. Reference numeral 32 denotes a sample and hold circuit, which detects and holds a detected focus error signal (a value detected from the mirror surface at the center of the sample mark by the astigmatism method). Reference numeral 33 denotes a servo circuit for performing focus servo, which moves an actuator 34 that rotates the objective lens 26 in the focus direction to perform focus servo.

31 is an amplifier circuit that detects the total amount of light incident on the photodetector 29. Reference numeral 35 denotes a peak detection circuit composed of a differential circuit and a zero cross circuit, which detects the peak position of the reproduced signal corresponding to the timing pit 9 from the reproduced signal detected by the amplifier circuit 31. Of the servo mark reproduction signals, the positions of the first wobbling pit 7, the second wobbling pit 8°, and the timing pit 9 do not change over the disk surface, and are always constant even when the tracking servo is not applied. It appears in patterns. Further, these pit groups can be identified because they appear at regular intervals, and the clock regeneration circuit 36 uses the peak signal corresponding to the timing pit 9 to generate P L L (Phase Locked
Loop) circuit multiplies the clock by 110 and extracts a clock for recording and reproducing data. The period of sample mark 3 is 50.1 kHz (at 1800 rms), and the clock frequency is 5.5 MH2. Clock regeneration 83
The output signal of 6 is used as a clock for the digital processing circuit 37.

38 detects the positions of transmission pits having up to the fourth amplitude in order from the maximum value of the reproduced signal amplitude in each symbol,
This is a detection/decoding circuit that simultaneously decodes data and detects an access mark that conforms to the above-mentioned modulation rule from the servo mark position, and detects and protects access marks from errors (details of this circuit will be described later). 43 is a digital/analog (D/A) converter, and 41 is a tracking servo circuit. The tracking error signal is D
The signal is outputted through the /A converter 43, opens the actuator 42 in the tracking direction, moves the objective lens 26 slightly in the tracking direction, and performs tracking. Reference numeral 4o denotes a track movement amount detection circuit, which detects the track movement amount, track movement speed, and movement direction from the signal of the decoded value of the access mark output from the detection decoding circuit 38. Reference numeral 44 denotes a control circuit composed of a microcomputer, which controls not only the entire drive device but also track access.

The current position is calculated from the track movement amount signal output from the track movement amount detection circuit 40, and the D/A converter 48
Output the linear motor control voltage through. Reference numeral 46 denotes a servo circuit for a linear motor for track access, which opens a linear motor 47 in accordance with a linear motor control voltage to move the entire optical pickup 21 in the track direction.

Reference numeral 60 indicates an opening circuit for the semiconductor laser 22, and reference numeral 49 indicates a data modulation circuit, which modulates the input recording data by 4711 and converts it into serial data.The drive circuit 60 converts it into a laser beam intensity signal, and records the data on the disk drive. A thermal change is generated on the surface to form pits and record data.

Next, the detection/decoding circuit 38 will be explained using FIGS. 8 and 9.

First, in FIG. 8, the reproduced signal is output by the A/D converter 50 to the detection/decoding circuit 38 with the amplitude of the transmission pit as digital data. The reproduced signal converted into digital data is taken into the differential circuit 51.

Further, FIG. 9 is a diagram showing the configuration of the differential circuit 51. 8
1 is a latch circuit that latches A/D converted data for each channel bit, 821 to 825 are latch circuits that latch data at mark positions among 11 transmission bits, and 86 is latch circuit 821 to 825, five types of latch data. A selection circuit that compares and selects data with the largest amplitude among
87 is a comparison circuit that compares the output signal of the selection circuit 86 and the output signal from the latch circuit 81; 88 is a comparison circuit that compares the output signal of the selection circuit 86 with the output signal from the latch circuit 81; and 88, based on the output result of the comparison circuit 87, the data with the largest amplitude of the latch circuits 821 to 825 is latched by the launch circuit 81. When it is determined that the data amplitude is small, the latch circuits 821 to 825
A latch control circuit controls the value of the latch circuit 81 to be relatched to the latch that holds the data with the largest amplitude among the latch circuits, and the latch control circuit 89 counts by the transmission lock of the first transmission bit and counts every data ebyte. A counter 90 that outputs a synchronization signal is a shift register that transmits the synchronization signal of the counter 89 and shifts it for each lock, and always indicates the transmission bit number of the input signal for A/D conversion. 9
1 is a latch circuit group that latches the output data of the shift register 90 using five latch control signals output from the latch control circuit, each of which has a 1-bit configuration, and is connected to the A/D.
Each time data with a larger amplitude value is latched as a result of comparison of conversion inputs, the transmission bit position is indicated. Reference numeral 92 is an encoding circuit that encodes the latch data of each latch circuit group 91 using an OR circuit to obtain bit position data of one transmission bit. The data is always compared with the data with the largest amplitude among the latch circuits 821 to 825, and the latch control circuit 88
The contents of 21 to 825 are updated for each transmission lock, and finally, the five data with the largest amplitudes in one symbol are held in the latch circuits 821 to 825. At the same time, a synchronizing signal with a constant period from the counter 89 is transmitted and shifted for each lock, and is similarly recorded in the latch circuit group 91 by the latch control circuit 88.
2. Pit position data is acquired via the latch circuit 93 in one symbol period.

Now, FIG. 8 will be explained again. Output signals of the difference circuit 51, that is, the three pit position data with the highest signal amplitudes among the five pit position data with the largest signal amplitudes among the 11 channel bits are output to the decoding ROM circuit 96. 81 in FIG. 8 is pit position data with the largest signal amplitude, and is outputted in descending order of signal amplitude up to S5. Furthermore, among the output signals of the difference circuit 51, the four signals with the highest signal amplitudes are output to the first modulation deviation detection circuit 94, and among the output signals of the difference circuit 51, the two signals with the highest signal potential are output to the data correction switch 97. . Note that the I-th modulation deviation detection circuit 94
．． Data correction switch 97. Timing detection circuit 100
．． AND circuit 101 will be explained later. Decryption RO
In the M circuit 96.

Of the five pit position data with the highest signal amplitudes in one channel bit, which is the output signal of the difference circuit 51, four pit position data are taken in. Based on these four pit position data, the data is decoded according to the conversion rules shown in FIG. 14 and output as read data.

The output signal of the decoding ROM circuit 96 is a modulation error signal 304 indicating that a modulation error pattern has been input where the data decoded according to the conversion rule and the input data do not conform to the conversion rule (mark length is 4 transmission pits, etc.). The modulation of No. 2 is transferred to the deviation detection circuit 99, and the result is supplied to the track movement amount detection circuit 40.

The function of the second modulation deviation detection circuit 99 will be explained with reference to FIG. In FIG. 10, 302 is read data. The read data 302 has an 11-bit configuration and b
1 to bll correspond to the 1st to 11th transmission bits on the disk, respectively. Reference numeral 111 is a gate that detects the nature of the access mark (in this example, the pattern is fixed except for the third to eighth transmission bits). Gate 11
outputs It I It when the read data 302 deviates from the characteristics of the access mark. 303 (previous value holding signal) indicates whether the read data 302 deviates from the characteristics of the access mark or the modulation error signal is II I I
Output u 1 u when I, otherwise I/O
Output II.

98 is a previous value holding circuit, and the previous value holding signal 303 is 11.
1 II, that is, when the read data 302 deviates from the characteristics of the access mark or the output of the decoding ROM circuit 96 does not follow the conversion rule, the read data 30
Hold the previous value of 2.

Previous value holding signal 303 which is the output signal of the previous value holding circuit 98
is output to the track movement amount detection circuit 4o, so
The track movement amount detection circuit 40 has incorrectly read data 3.
02 can be recognized, and malfunctions can be effectively prevented.

Reference numeral 95 denotes a tracking error calculation circuit which inputs the amplitude data of each pair of wobble pits 1 in the sample mark from the A/D converter 50, calculates the difference, and holds the difference until the next sample mark. The output signal of the circuit 95 is supplied to the D/A conversion circuit 43.

Next, the first out-of-modulation detection circuit 94. Data correction switch 97. Timing detection circuit 100. AND circuit 101
will be explained using FIGS. 1, 3, and 13.

As shown in FIG. 3, the access mark of each track in this embodiment has pits arranged at three positions between the third transmission bit and the eighth transmission bit, and the pit of the 11th transmission bit is placed in the first wobble position. This is designated as pit 7.

The total number of patterns that match this rule is p, as shown in Figure I3.

There are 20 types of ~p19. For example, the access mark of this embodiment shown in FIG. 3 is p○.

p7. It is configured using everything except p12+ P19.

FIG. 1(a) shows an example in which the reading light spot scans the 13th to 15th tracks in FIG. 3. 13) The -th rack is p15 in FIG. 13, the 14th track is p14, and the 13th track is pH. Further, 200 is the locus of the center of the reading light spot. FIG. 1(b) shows a reproduced signal (reproduced waveform 900) when the reading light spot passes through as shown in FIG. 1(a). The signal amplitudes from t1 to t5 on the time axis show five signal amplitudes with the largest signal amplitudes among the differentially demodulated signals (differential time, output signal of $51), tl, t2°t3. t4. t5
The signal amplitude increases in this order.

The output of the difference circuit 51, that is, the top 4 of the 5 pit position data with the highest signal amplitude among the 11 channels focused
is taken into the first modulation deviation detection circuit 94. 1st
When the reading light spot passes as shown in figure (a),
The four pit position data taken into the first modulation deviation detection circuit 94 correspond to that shown in FIG. 1(c).

The first out-of-modulation detection circuit 94 includes four tracks that do not correspond to any of the tracks of the information storage medium (see FIG.
When a combination of two pit position data is input (for example, as shown in FIG. 1(c)), trln is output; otherwise, "O"' is output.

A timing detection circuit 100 detects the timing when the read data is an access mark based on the tarok. The timing detection circuit 10O outputs "1" when the read data is an access mark, and outputs "O" when it is not. When any of the output signals of the circuit 94 is '1', it outputs '1' to the data correction switch 97.

The pit position data correction switch 97 receives from the difference circuit 51 the pit position data with the fourth largest signal amplitude value and the pit position data with the fifth largest signal amplitude among the channel pits. Then, when "1" is input from the AND circuit 101, the fifth largest pit position data is output to the decoding ROM circuit 96, and when II OTT is input from the first modulation loss detection circuit 94, the fourth largest pit position data is output. The pit position data is output to the decoding ROM circuit 96.

By controlling in this manner, even when the reading light spot passes through as shown in Fig. 1(a) and a reproduced waveform as shown in Fig. 1(b) is obtained, it corresponds to Fig. 1(d). Four pit position data are output to the decoding ROM circuit 96. This pattern (pH) corresponds to the pattern of track positions through which the reading light spot has passed (the bottom track in FIG. 1(a)).

As explained above, according to the first embodiment, even when the reading light spot accesses between tracks at high speed,
The track position scanned by the reading light spot can be detected with high precision.

A second embodiment of the present invention will be described below using FIGS. 11 and 12. Regarding Figure 11, 1
Everything other than 02 is the same as the explanation of FIG. 8 in the first embodiment, so the explanation thereof will be omitted.

FIG. 12a shows an example in which the reading light spot scans the 13th to 15th tracks in FIG. 3.

The 13th track is p15 in FIG. 13, the 14th track is p14, and the 13th track is pH. 2
01 is a defect on the information storage medium, and 202 is the locus of the center of the reading light spot. FIG. 12(b) shows a reproduced signal (reproduced waveform 901) when the reading light spot passes through as shown in FIG. 12(a). t1 to t on the time axis
5 (output signals of the differential circuit 51) with large signal amplitudes among the differentially demodulated signals, tl, t2 . t
3. t4. The signal amplitude increases in the order of t5.

The output signal of the difference circuit 51 (that is, the five pit position data with the highest signal amplitude among the 11 channel bits) is taken into the access mark protection circuit 102. Sl is the pit position data with the largest signal amplitude, and is hereinafter referred to as S
Up to 5 are output along with j@, which has a large signal amplitude.

The access mark protection circuit 111102 performs the following operation when the output signal of the timing detection circuit 100 is 1''.

That is, any one of the five input pit position data is the first transmission bit, the second transmission bit, the ninth transmission bit, and the tenth transmission bit.

, the data is shown as S'
Output as 5. Then, the remaining pit position data are arranged in descending order of signal amplitude from S'l to S'4 and output. Among the five input pit position data, the first
transmission bit, second transmission bit, ninth transmission bit,
When there is no signal indicating the position of any one of the tenth transmission bits, the output signals of the difference circuit 51 are arranged and outputted from S'l to S'5 in descending order of signal amplitude. Further, in any case when the output signal of the timing detection circuit 100 is "□It", the output signals of the difference circuit 51 are arranged and output from S'↓ to S'5 in descending order of the signal potential of the pit position data.

By controlling in this way, even when the reading light spot scans as shown in Fig. 12(a) and a signal as shown in Fig. I2(b) is reproduced, the signal as shown in Fig. 12(c) Marks can be decoded. Note that this decoding pattern p14 is the first
As shown in FIG. 2(a), it is equal to the access mark of the track traversed by the reading light spot.

As described above, according to the second embodiment, even if a scratch occurs on the information storage medium, the access mark of the track scanned by the reading light spot can be normally decoded.

A third embodiment of the present invention will be described below using FIGS. 1, 3, 15, and 16.

Regarding FIG. 15, all the components other than 105, 106, and 107 are the same as the configuration of FIG. 8 in the first embodiment, so a description thereof will be omitted.

FIG. 1(a) shows an example in which the reading light spot scans the 13th to 15th tracks in FIG. 3. The 13th track is p15 in FIG. 13, the 14th trunk is p14, and the 13th track is pH.

200 is the locus of the center of the reading light spot. 1st
FIG. 1(b) shows a reproduced signal (reproduced waveform 900) when the reading light spot passes through as shown in FIG. 1(a). The signal amplitudes from t1 to t5 on the time axis show five signal amplitudes (output signals of the difference circuit 51) having the largest signal amplitude among the differentially demodulated signals, tl, t2 . t3. The signal amplitude increases in the order of t4 and t5.

Next, FIG. 16 is a diagram showing the configuration of the second difference circuit 105. In FIG. 16, 481 is a latch circuit that latches A/D converted data for each channel bit;
82, 4, 83, 484, and 485 are latch circuits that latch data at pit positions among 11 transmission bits, and 486 is a latch circuit that compares the data with the largest signal amplitude among the four types of latch data 482 to 485. A selection circuit 487 selects the output signal of the selection circuit 486 and the latch circuit 48
A comparison circuit 488 compares the output signal from the comparison circuit 487 with the output signal from the comparison circuit 487.
When determining that the amplitude of the data latched by the latch circuit 481 is smaller than the data with the maximum amplitude of the launch circuit 48
This is a latch control circuit that controls the value of the latch circuit 481 to be relatched to the latch that holds the data with the largest amplitude among the data of 2 to 485.

Further, 489 is a counter that counts with the transmission lock of 11 transmission bits and outputs a synchronization signal for each byte of data, and 490 is a shift register that transmits the synchronization signal of the counter 489 and shifts it every lock. This indicates the transmission bit number of the conversion input. 491 is a latch circuit group that latches the output data of the shift register 490 using four latch control signals output from the latch control circuit, each of which has a 1-bit configuration, and
Each time data with a larger amplitude value is latched as a result of comparison of D conversion inputs, the transmission pit position is indicated. Reference numeral 492 denotes an encoding circuit that encodes the latch data of each latch circuit group 491 using an OR circuit (not shown) to obtain pit position data of 11 transmission bits.

The first transmitted bit signal, which is the last in the symbol, is:

The data is latched by the latch circuit 481, and is constantly compared with the maximum amplitude value in the latch circuits 482 to 485.The latch control circuit 488 transmits the contents of the latch circuits 482 to 485 and updates them for each lock. The top four data with the largest amplitude in one symbol are stored in the latch circuit 48.
2 to 485. At the same time, a synchronization signal of one symbol period from the counter 489 is transmitted and shifted for each lock, and is similarly recorded in the latch circuit group 491 by the latch control circuit 488. This is to acquire pit position data.

Now, FIG. 15 will be explained again. The output signal of the second difference circuit 105 (that is, the four pit position data with higher signal amplitude among the 11 channel bits) is taken into the second access mark protection circuit 107 and the third modulation deviation detection circuit 106. . Sl is the pit position data with the largest signal amplitude, and is outputted in descending order of signal amplitude up to S4. The third modulation deviation detection circuit 106 uses the input four mark position data as the first
In the case of the pattern shown in FIG. 13C, that is, p7 in FIG. 13, "1" is output to the AND circuit 101.

Conversely, the input four mark position data is shown in Figure 1(c).
Otherwise, 1101+ is output to the AND circuit 101.

The second access mark protection circuit 107 includes an AND circuit 1
When the output signal of the AND circuit 101 is tt I 11, a mark position signal corresponding to FIG. 1(d) is output, and when the output signal of the AND circuit 101 is It Ou, the input is output as is.

By controlling in this way, when the reading spot scans as shown in Fig. 1(a) and the signal as shown in Fig. 1(b) is reproduced, the mark shown in Fig. 1(d) will appear. Can be decrypted. Note that this pattern (pH) corresponds to the pattern of the track position through which the reading light spot passed (the bottom track in FIG. 1(a)).

As explained above, according to the third embodiment, even when the reading light spot accesses between tracks at high speed,
The track position of the reading light spot can be detected with high precision.

[Effects of the Invention] As described above, the reliability of access mark decoding for realizing track access can be improved.

In particular, (1) it is possible to decode the access mark even if there is a defect on the track, (2) it is possible to prevent false detection of the access mark when the access speed is high, and (2) it is possible to detect failure in decoding the access mark.

Therefore, according to the present invention, it is possible to provide an optical information recording/reproducing device that prevents erroneous detection of access marks and realizes stable track access.

[Brief explanation of drawings]

4 is a diagram for explaining an example of the operation of the first embodiment of the present invention, FIGS. 2 and 3 are diagrams showing an optical information recording medium used in the embodiment of the present invention, and FIG. The figures are diagrams for explaining the data format in the embodiment of the present invention, Figure 5 is a diagram for explaining sample marks used in the conventional example, and Figure 6 is a diagram for explaining the data format of the conventional example. FIG. 7 is a block diagram showing the configuration of an embodiment of the optical information recording/reproducing apparatus of the present invention, and FIG. 9 and 10 are block diagrams showing a more detailed configuration of the embodiment shown in FIG. 1
FIG. 2 is a diagram for explaining an example of the operation of the second embodiment of the present invention, FIG. 13 is a diagram showing an access mark pattern table, and FIG. 14 is a diagram showing an example of a modulation table for 4/11 modulation. 15 is a block diagram of a detection/decoding circuit according to a third embodiment of the present invention, and FIG. 16 is a block diagram showing a more detailed configuration of the embodiment shown in FIG. 15. 1...Information recording medium, 2...Virtual track center, 3...Sample mark, 11
... Access mark, 38 ... Detection decoding circuit, 40 ... Track movement amount detection circuit, 4
4...Control circuit, 50...A/D converter, 51...Differential circuit, 81...Latch circuit, 86...Selection Circuit, 87... Comparison circuit, 92... Encoding circuit, 94...
...Modulation deviation detection circuit, 96...Decoding ROM
Circuit, 99...Second modulation deviation detection circuit, 1
00... Timing detection circuit, 102...
...Access mark protection circuit, 105...2nd
differential circuit, 106...Third modulation deviation detection circuit, 1.07...Second access mark protection circuit, 302...Read data, 303...
...Previous value holding signal, 304...Modulation is off Fig. 1 Fig. 2 Virtual track center Fig. 3 (r; z34saya91ottt2j4sevay1
on) Sample mark Figure 4 Figure 6 Figure 12 Figure 201 2 '-5 11 Access mark 7 Signal amplitude 2 1 3 5 4 Time I3 Figure 1 Access mark page 14z (2) Page 14 Figure (3) Page 14 Figure (4) Procedural amendment (method) Indication of case ei Year patent application No. 178151000 Relationship with the person making the amendment 11 cases

Claims (1)

[Claims] 1. An optical system having a pattern row consisting of one or more pits arranged at regular intervals on a track, changing every track or several tracks, and whose changes are periodically repeated. In an optical information recording and reproducing device that records and reproduces information on and from an information recording and reproducing medium, N/M modulated data is used for access marks, and M transmission bits of the access mark reproduction signal are used. a differential circuit that detects the pit positions of at least [N+1] transmission bits in the order of signal amplitude having the largest amplitude; A first modulation deviation detection circuit detects that an access mark consisting of N mark positions is out of modulation; An optical system characterized by having a pit position data correction switch that switches between the eye pit position and the [N+1]th pit position from the largest one, and a decoding ROM that decodes the access mark from the signal indicating the N pit positions. information recording and reproducing device. 2. In the optical information recording and reproducing device according to claim 1,
Using N/M modulated data for the access mark, outputting N pit positions from the one with the largest amplitude among the pit positions detected by the difference circuit excluding pit positions that cannot be used as an access mark. 1. An optical information recording/reproducing device comprising a modulation deviation detection circuit. 3. In the optical information recording and reproducing device according to claim 1,
a second difference circuit that uses N/M modulation for the access mark and detects the pit position of the N transmission bits from the one with the largest signal amplitude among the M transmission bits of the access mark signal; and the second difference circuit. A third modulation deviation detection circuit detects that a combination of N pit positions detected in is out of modulation, and an access mark output circuit outputs a specific pit position of N transmission bits. Optical information recording and reproducing device.