JPH08279160A - Optical recording medium and optical disk device - Google Patents

Abstract

PURPOSE: To detect the radial skew by using an optical recording medium forming first and second patterns ranging to plural tracks so as to make reflection light quantities characteristics opposite to each other. CONSTITUTION: When no radial skew exists (radial skew=0), since laser spots 5 are a real circular shape though the laser spots 5 scanning on a present scan track 3B come to both positions of pit patterns A, B, laser beams converge only pits 4B1 .4B2 on the track 3B. Since a signal level RA and the signal level RB of information read in respective positions by the pit patterns A, B are equal to each other, when a difference between both of the signal level RA and the signal level RB is defined a detection level RDS, RDS=0 (RDS≡RA-RB=0), and the absence of the radial skew is detected.

Description

Detailed Description of the Invention

[0001]

[Table of Contents] The present invention will be described in the following order. Field of Industrial Application Conventional Technology Problems to be Solved by the Invention Means for Solving the Problems Action Example (1) Principle of radial scan detection (1-1) Form of radial scan (FIGS. 1 to 3) (1-2) Radial skew detecting pit pattern (FIGS. 4 to 7) (2) Disk format (FIG. 8) (3) Overall configuration of magneto-optical disk device (FIG. 9) (3-1) Radial scan Configuration of the You detect circuit (Fig. 10) (3-2) Track identification section (Figs. 11 to 14) (3-3) Gray code detection point (Fig. 15) (3-4) Timing chart of each timing signal ( 16 and 17) (4) Operation of magneto-optical disk device (FIG. 9) (4-1) Operation of radial skew detection circuit (FIG. 10) (4-1-1) Radial skew is applied to the optical disk 1. If it does not exist (4 1-2) Radial skew exists in optical disk 1 (RDS> 0) (4-1-3) Radial skew exists in optical disk 1 (RDS <0) (5) Effects of Examples (6) Other Examples Effects of the Invention

[0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording medium and an optical disc device, and is suitable for application to, for example, a magneto-optical disc device.

[0003]

2. Description of the Related Art Conventionally, in a magneto-optical disk device,
The light beam emitted from the laser light source is made incident on one of the recording tracks formed on the magneto-optical disk, and the return light reflected by this recording track is detected to obtain a reproduction signal.

By the way, the magneto-optical disk has a radial inclination (hereinafter referred to as a radial skew) due to the weight of the disk itself. Therefore, in the magneto-optical disc device, the radial skew is detected and the feed back control is performed so that the disc surface and the optical axis of the optical pickup portion are always orthogonal to each other.

The feedback control is performed by using a radial skew detecting lens which is provided coaxially and separately from the objective lens of the optical pickup unit. The radial skew is detected through this radial skew detecting lens so that the disk surface and the optical axis of the optical pickup portion are always orthogonal to each other.

[0006]

By the way, in the magneto-optical disk device having such a structure, the radial skew detecting lens is separately used in addition to the lens used for reproducing the recorded data. Therefore, the number of constituent elements increased, and the entire optical pickup part became larger and heavier. As a result, the magneto-optical disk device has a problem that it takes time to access desired data recorded on the magneto-optical disk.

The present invention has been made in consideration of the above points, and an optical recording medium and an optical disk capable of detecting and eliminating a radial skew with high accuracy with a simple structure without using a radial skew detecting lens. It is intended to propose a device.

[0008]

In order to solve such a problem, in the present invention, the reflected light amounts obtained according to the state of the radial skew are mutually provided at two different positions on the track in the area other than the information recording area. The first and second patterns are formed over a plurality of tracks so as to have opposite characteristics.

Further, in the present invention, the track position is identified based on the reproduced signal, two positions of the information portion provided on the identified track are specified, and two positions are specified.
Two signal levels are obtained by reading the light quantity of the reflected light of the light beam from the information part of the location, and the two signal levels obtained are stored, and then the two signal levels are calculated to determine the direction of the radial skew and Try to detect the amount.

[0010]

The first and second tracks are provided over a plurality of tracks so that the reflected light amounts obtained in accordance with the radial skew conditions are mutually opposite at two different locations on the track in areas other than the information recording area. By using the optical recording medium on which the pattern is formed, the radial skew can be detected.

The track position is identified based on the reproduction signal,
The signal level is obtained by designating two positions of the information section provided on the identified track and reading the light quantity of the reflected light of the light beam from the two designated information sections, and the two obtained signals are obtained. After storing the levels, the two signal levels are calculated to detect the direction and amount of the radial skew, so that the radial skew can be detected and eliminated without newly providing a radial skew detecting lens. it can.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings.

(1) Radial skew detection principle (1-1) Form of radial skew There are three types of radial skew, one of which is shown in FIG. 1 (A). In FIG. 1A, the recording surface in the radial direction (r) of an optical disk 1 as an optical recording medium is perpendicular to the optical axis of a laser beam emitted from an optical pickup 2 as an information reading means. This is an example of the case. In this case, the radial skew = 0. Incidentally, here, as the optical disc 1, one having a pit formed of a physical uneven pattern on the recording surface is used. In this case, the state of the pits formed on the optical disk 1 and the laser spot 5 on which the laser beam is focused is shown in FIG. 1 (B).

FIG. 1B is an enlarged view of a part of three tracks 3A, 3B and 3C adjacent to each other among a plurality of tracks arranged on a concentric circle on the optical disk 1. In this case, since there is no radial skew in the optical disk 1, the laser beam is focused as a substantially circular laser spot 5 at the center of the pit 4B formed on the central track 3B. .

On the other hand, as shown in FIG. 2 (A), the optical disk 1 is located on the far side (upper side) with respect to the optical pickup 2.
When the optical disc 1 is tilted at an angle of 90 °, the angle formed by the recording surface with respect to the radial direction of the optical disk 1 and the optical axis of the laser beam emitted from the optical pickup 2 becomes smaller than 90 °.
In this case, radial skew> 0. In this case, the state of the pits formed on the optical disk 1 and the laser spots 5 is shown in FIG. 2 (B).

FIG. 2B is an enlarged view showing a part of three tracks 3A, 3B and 3C adjacent to each other among a plurality of tracks arranged on a concentric circle on the optical disk 1. In this case, since there is a radial skew in the optical disk 1, the laser as an elliptical laser spot 5 straddling both the pit 4B formed on the central track 3B and the pit 4A on the track 3A. The beam is focused. Therefore, in the optical pickup 2, the information of the pick 4A on the track 3A leaks into the information read from the track 3B (hereinafter referred to as crosstalk).
This makes it impossible to accurately read the information of the pit 4B on the track 3B that should be read.

Similarly, as shown in FIG. 3A, when the optical disk 1 is tilted toward the near side (lower side) with respect to the optical pickup 2, the recording surface and the optical pickup are arranged in the radial direction of the optical disk 1. The angle formed by the optical axis of the laser beam emitted from 2 becomes larger than 90 [°]. In this case, radial skew <0. In this case, the state of the pits formed on the optical disk 1 and the laser spots 5 is shown in FIG. 3 (B).

FIG. 3B is an enlarged view of a part of three tracks 3A, 3B and 3C adjacent to each other among a plurality of tracks arranged on a concentric circle on the optical disk 1. In this case, since there is a radial skew in the optical disk 1, the laser as an elliptical laser spot 5 straddling both the pit 4B formed on the central track 3B and the pit 4C on the track 3C. The beam is focused. Therefore, the optical pick-up 2 cannot accurately read the information of the pit 4B on the track 3B which should be read because the information of the pit 4C on the track 3C cross-talks with the information read from the track 3B.

From the above, if there is a radial skew in the optical disk 1, the optical pickup 2 cannot accurately read the information of the pit, so it is necessary to eliminate this radial skew.

(1-2) Radial skew detection pit pattern FIG. 4 shows a radial skew detection pit pattern for eliminating the radial skew. This radial skew detecting pit pattern has two types of pit patterns A and B. One of them is the pick pattern A, in which the pick 4B ₁ on the current scanning line track 3B located at the center and the pick 4A ₁ on the track 3A adjacent to the track 3B are arranged in parallel and on the track 3C adjacent to the track 3B. Is a pattern in which no pit appears. Further, another pit pattern B is such that the pit 4B ₂ on the current scanning line track 3B located at the center and the lane 4C ₂ on the track 3C adjacent to the track 3B are arranged in parallel.
It is a pattern in which no pit appears on the track 3A adjacent to B.

For example, FIG. 5 shows the state of the laser spot 5 when there is no radial skew (radial skew = 0). Even if the laser spot 5 for scanning on the current scanning line track 3B comes to both positions of the pit patterns A and B, the laser spot 5 has a perfect circular shape.
The laser beam focuses only the pits 4B ₁ and 4B ₂ on B. Since the signal level RA and the signal level RB of the information read at the respective positions of the bit patterns A and B are equal, RDS = 0 when the difference between the signal level RA and the signal level RB is the detection level RDS.
Since (RDS≡RA-RB = 0), it can be detected that there is no radial skew. That is, crosstalk does not occur.

FIG. 6 shows the state of the laser spot 5 when the optical disk 1 is tilted to the far side (upper side) with respect to the radial direction and the radial skew exists (radial skew> 0). Show. In this case, at the position of the pit pattern A, the laser beam is condensed as an elliptical laser spot 5 over both the pits 4A ₁ and 4B ₁ , so that the pit 4A on the track 3A adjacent to the present scanning line track 3B is located. Part ₁ of the laser beam will once cross-talk. However, at the position of the pit pattern B, the pit does not appear on the adjacent track 3A, so that the laser beam is focused only on the pit 4B ₂ and does not crosstalk.

Therefore, the signal levels RA and RB at the respective positions of the pit patterns A and B are different,
Detection level R, which is the difference between both signal levels RA and RB
DS becomes RDS> 0 (RDS≡RA-RB> 0), and it can be detected that the optical disk 1 is tilted to the far side (upper side) and the radial skew exists. Here, since the larger the radial skew is, the larger the crosstalk is, the detection level RDS is also increased according to the size of the radial skew.

Next, referring to FIG. 7, the laser spot 5 when the optical disk 1 is tilted to the near side (downward side) with respect to the radial direction and a radial skew exists (radial skew <0). Indicates the state of. In this case, at the position of the pit pattern A, the laser beam is focused as the elliptical laser spot 5 only on the pit 4B ₁ on the present scanning line track 3B, and the pit does not appear on the adjacent track 3C. There is no. However, at the position of the pit pattern B, the laser beam is focused as an elliptical laser spot 5 over both the pits 4B ₂ and 4C ₂ , so that the pit 4C on the track 3C adjacent to the present scan line track 3B. _Second , part of the laser beam will once cross-talk.

Therefore, the signal levels RA and RB at the respective positions of the pit patterns A and B are different,
Detection level R, which is the difference between both signal levels RA and RB
DS becomes RDS <0 (RDS≡RA-RB <0), and it is possible to detect that the optical disk 1 is tilted to the near side (lower side) and the radial skew exists. Here, as the radial skew also increases, the crosstalk also increases, so that the detection level RDS also increases according to the magnitude of the radial skew.

From these facts, the detection level RDS = 0
Then we can detect that there is no radial skew. Further, if the detection level RDS> 0, it can be detected that the radial skew exists on the far side, and if the detection level RDS <0, the radial skew exists on the near side. Detection level RDS at the same time
It is possible to detect a specific amount of radial skew by the value of.

(2) Disk Format Next, the disk format for detecting the radial skew will be described. As shown in FIGS. 8A, 8B, and 8C, here, the optical disk 1 reproduced by a constant angular velocity method (hereinafter, referred to as CAV method) is tracking-controlled and rotation-controlled by the sampled servo method. It is assumed that Also, the entire surface of the optical disc 1 is circumferentially N
FIG. 8B shows an enlarged view of one equally divided region (FIG. 8A), and FIG. 8C shows an actual array of pits corresponding to FIG. 8B.

The pit numbers 1 and 5 of the optical disc 1 are tracking pits wobbled for the sampled servo system. The pitch number 3 is a clock pit for reproducing the clock. Further, the pitch numbers 0, 2, 4, and 6 are areas where nothing is recorded in order to avoid intersymbol interference from adjacent pitches, or to reliably perform tracking and to reproduce a clock.

The next pit numbers 7 to 18 are gray codes (hereinafter referred to as gray code areas) in which the information of the lower 4 bits of the track address is recorded. A radial skew detection pit pattern for radial skew detection and correction is formed in this gray code area. The pits on the optical disk 1 are arranged radially in the radial direction, of which the gray code area has a radial skew detection pit pattern in all tracks. At present, there are 16 types of Gray codes in total, and the same pattern is repeated every 16 tracks. Subsequent pit numbers 19 to 99 are arbitrary data areas changing in channel clock units. The radial skew of the optical disk 1 is detected and corrected by using the radial skew detecting pit pattern of the disk format.

(3) Overall Structure of Magneto-Optical Disk Device FIG. 9 shows the overall structure of a magneto-optical disk device 11 as an optical disk device. The optical disk 1 is rotated by a spindle servo circuit 12 while maintaining a constant angular velocity, and a focusing tracking servo circuit 13
Thus, the distance between the recording surface of the optical disc 1 and the objective lens is kept constant. In this state, the magneto-optical disk device 11
Accurately tracks the laser beam of the optical pickup 2 on the track on the optical disk 1 to reproduce the RF signal S1. The optical pickup 2 outputs the RF signal S1 to the head amplifier 14, and the head amplifier 14 amplifies the RF signal S1 and outputs the amplified RF signal S1 to an analog digital converter 17 for converting it into a digital signal, and a radial skew detection. Output to the circuit 31. The analog digital converter 17 receives the RF signal based on the timing signal S4 from the radial skew detection circuit 31.
After converting the signal S1 into a digital signal S2, the signal S1 is output to the signal processing system 18 and the radial skew detection circuit 31. The signal processing system 18 includes a radial skew detection circuit 3
The digital signal S2 is processed on the basis of the timing signal S3 from 1 and then output through the information output system 19.

Further, the radial skew detecting circuit 31 controls the digital signal S2 output from the analog digital converter 17 by a control signal S5 for radial skew correction.
And outputs to the optical head shaft drive motor 22 through the low pass filter 21 to control the optical pickup 2.

Here, this radial skew detection circuit 3
1 outputs the RF signal S1 to the PLL circuit 15 which reproduces the clock signal based on the clock component included in the RF signal S1 amplified by the head amplifier 14.
The clock signal CLK reproduced by the LL circuit 15 is output to the timing signal generator 16. The timing signal generator 16 generates a timing signal S4 for controlling the analog digital converter 17 and a timing signal S3 for controlling the radial skew correction circuit 20.

By the way, if the optical pickup 2 has a radial skew in the optical disc 1, the optical pickup 2 often mistakenly reads data due to crosstalk or the like. Therefore, when there is a radial skew in the optical disk 1, the radial skew correction circuit 20 in the radial skew detection circuit 31 converts the digital signal S2 converted by the analog digital converter 17 into a timing signal generator. A low-pass filter 2 for the purpose of signal processing for radial skew correction based on the timing signal S3 from 16 and removing the control signal S5 resulting from the processing.
1 to the optical head drive motor 22.

In this way, the magneto-optical disk device 11
Is designed to control the optical pickup 2 in order to eliminate the radial skew of the optical disc 1. As a result, the magneto-optical disk device 11 can accurately reproduce the RF signal S1 even on a disk having a large radial skew without causing erroneous reading of data due to crosstalk or the like.

(3-1) Configuration of Radial skew detection circuit FIG. 10 shows the overall configuration of the radial skew detection circuit 31. The radial skew detection circuit 31 amplifies the RF signal S1 obtained from the optical disk 1 by the head amplifier 14 and outputs it to the analog digital converter 17. The analog digital converter 17 includes a timing signal generator 1
RF signal S1 based on the channel clock signal CLK _RD for reading the Gray code from the decoder 40 of No. 6
Is converted into an 8-bit digital signal S2 and output to the delay circuit 33 for delaying by the time during which the track is identified. Here, each pit is a channel clock signal C.
Since it changes in units of channel clock of LK _RD ,
As the clock signal output to the analog digital converter 17, the channel clock signal CLK _RD is used as it is.

The delay circuit 33 delays the digital signal S2 and outputs the delayed digital signal S2 to flip-flop circuits 34 and 35 which temporarily hold the digital signal S2. Here, the delay circuit 33 has a structure in which flip-flops are connected in cascade, or a first-in first-out FIFO.
(First In First Out) memory may be used.

The flip-flop circuits 34, 35 output signal levels RA, RB for detecting radial skew based on the timing signals CLK _a , CLK _b from the decoder 39 of the timing signal generator 16 to the subtraction circuit 36. . The subtraction circuit 36 receives the signal levels RA and RB.
Is subtracted, and the detection level RDS which is the difference is output to the digital-analog converter 37. The digital analog converter 37 converts the detection level RDS from the subtraction circuit 36 into an analog signal S5 based on the clock signal CLK _DA from the decoder 40 of the timing signal generator 16. The digital analog converter 37 is a low-pass filter 21 for removing noise from the analog signal S5.
To the optical head shaft drive motor 22 to control the optical pickup 2.

Further, the head amplifier 14 is the amplified RF.
The signal S1 is output to the PLL circuit 15 for clock reproduction.
The PLL circuit 15 counts the reproduced clock signal CLK with the counter 38 and outputs the value to the decoders 39 and 40. The decoder 39 generates sampling signals CLK _a and CLK _b for obtaining signal levels RA and RB when detecting radial skew, and the decoder 40
Channel clock signal CLK _RD for reading gray code data, clock signal CL for converting the calculated detection level RDS of the radial skew into an analog signal
A latch signal CLK _LT for decoding K _DA and Gray code data is generated.

The decoder 39 outputs to the flip-flop circuit 34 a sampling signal CLK _a for obtaining a signal level RA at the time of detecting the radial skew, and the flip-flop circuit 35 outputs a signal level RB at the time of detecting the radial skew. A sampling signal CLK _b for obtaining Here, the sampling signals CLK _a and CLK _b are output at different timings for each track because the sampling points are different for each track.

Subsequently, the decoder 40 outputs the channel clock signal CLK _RD for reading the gray code data to the analog digital converter 17. Similarly, the decoder 40 outputs the channel clock signal CLK _RD for identifying the track position of the gray code to the track identifying section 41. Further, the decoder 40 outputs a clock signal CLK _DA for converting the radial skew detection value RDS to an analog signal to the digital-analog converter 37, and a latch signal CLK _LT for decoding the gray code data to the track discrimination unit. Output to 41.

Further, the head amplifier 14 outputs the amplified RF signal S1 to the track discriminating section 41, and the track discriminating section 41 outputs a gray code track based on the channel clock signal CLK _RD and the latch signal CLK _LT from the decoder 40. The position is identified and the track address signal S6 is output to the decoder 39.

(3-2) Track Identification Unit Next, the structure of the track identification unit 41 will be described. As shown in FIG. 11, the head amplifier 14 outputs the amplified RF signal S1 to the comparator 44, which binarizes the RF signal S1 and outputs the binarized signal S7 to the first flip-flop circuit 45. To do. The flip-flop circuit 45 fetches and holds the binarized signal S7 based on the timing of the channel clock signal CLK _RD given from the decoder 40. Then, the flip-flop circuit 45 transfers the binarized signal S7 to the next flip-flop circuit 46 and also to the flip-flop circuit 56. Next flip-flop circuit 46
Also captures and holds the transferred binary signal S7 based on the channel clock signal CLK _RD , transfers the binary signal S7 to the next flip-flop circuit 47, and also transfers it to the flip-flop circuit 56. . And so on
The flip-flop circuit 55 repeats eleven times until the binarized signal S7 is held, and when the gray code data is completed for 11 bits, the flip-flop circuit 56 transfers from the flip-flop circuits 45 to 55 based on the latch signal CLK _LT from the decoder 40. The respective binarized signals S7 that have been received are held. And the flip-flop circuit 56 is
Gray code data (GR1 at the identified track position)
0 to GR0) are output to the decoder 39 as the track address signal S6.

Next, as shown in FIG. 12, the gray code data (11) output from the flip-flop circuit 56 is output.
There are 16 types of bit), GS0 to GS15, and the track identifying section 41 identifies the position of the track based on the gray code data based on the channel clock signal CLK _RD and the latch signal CLK _LT from the decoder 40. are doing. In this case, the gray code data is identified by using 11-bit information for track identification, but since there are only 16 types of gray code data in total, the information of the lower 4 bits of the track address is shown in FIG. Can also be identified. In this case, as shown in FIG. 14, if the conversion table of FIG. 13 is input to the memory 57 and the gray code data acquired by the track identifying unit 41 is input to the memory 57, the memory 57 displays the track address corresponding to the gray code data. And output.

(3-3) Gray Code Detection Point FIG. 15A shows a dot pattern for radial skew detection in the gray code area. Here, the pits are arranged in a certain pattern, and when the optical disk 1 is tilted toward the near side and the radial skew is present,
Since the laser beam is focused as the laser spot 5 having an elliptical shape, for example, at the spot position 58, G which is originally scanned is used.
If the laser beam reaches the GS5 track and the GS6 track adjacent to the S4 track, the optical pick-up 2 does not have the GS4 track to the GS6 track, and therefore the information of the pit is not read. Further, at the spot position 59, similarly, the GS4 track, the GS5 track, and the GS5 track that are adjacent to the GS4 track that is originally scanned.
Since the laser beam will cover up to 6 tracks,
The optical pickup 2 will read the information in the pits 60, 61. Therefore, spot position 5 on the GS4 track
8 and the amount of information read by the optical pickup 2 at the spot position 59 are different, the signal level RA and the signal level R
B will make a difference.

When the optical disk 1 is tilted to the far side and the radial skew is present, the spot position 5 is set.
In the case of No. 8, assuming that the laser beam reaches the GS3 track adjacent to the originally scanned GS4 track,
In the optical pickup 2, the laser beam is applied to the GS3 track pit 62, and the information in the pit 62 is read. Further, at the spot position 59, the laser beam is similarly applied to the GS4 track which is originally scanned and the GS3 track which is adjacent to the GS4 track.
Since there is no pit in the S4 track and the GS3 track, the pit information is not read. Therefore, G
Spot position 58 and spot position 59 on the S4 track
Since the amount of information read by the optical pickup 2 at 2 is different, a difference occurs between the signal level RA and the signal level RB. As described above, in the pit pattern of the gray code portion, in all the tracks of GS0 to GS15, the pits are arranged so that the information of the pits of the adjacent pits is always read like the spot position 58 or the spot position 59. There is.

In this way, the sampling points are different for each track, and the order in which the pit patterns appear in the rotation direction is also different. Therefore, of all 16 types of Gray code,
It is necessary to identify which gray code corresponds to the track. The timing signals at the time of identification are the channel clock signal CLK _RD and the latch signal CLK _LT , and these timing signals CLK _RD , CLK _LT and the clock signals CLK and CLK _DA are used for radial skew detection in the gray code area. FIG. 15 (B) shows the correspondence with.

(3-4) Timing chart of each timing signal FIGS. 16 and 17 show the sampling signal CLK for obtaining the signal levels RA and RB when the radial skew is detected.
_a , CLK _b and respective timing signals CLK _RD , CLK _LT ,
Indicates the relationship with CLK _DA . The vertical axis represents each timing signal, and the horizontal axis represents the track number of the optical disk 1 on the track and the number of the pulse when delayed by the delay circuit 33.

Here, the clock signals CLK and CLK _DA , C
LK _RD and CLK _LT are timing signals for detecting which gray code data is for each track. The sampling signals CLK _a and CLK _b are signal levels RA and RB corresponding to detection points which are different for each track.
Is a timing signal for obtaining.

For example, in the GS4 track, the sampling signal CLK _a is the gray code area with the number 1
It rises at position 1 and falls at position pit number 12. The sampling signal CLK _b rises at the position of the pit number 15 in the gray code area, and the pit number 1
It falls at the position of 6. This sampling signal CL
The position of the pit number where K _a and CLK _b rise is the spot position 58 or the spot position 59 where the laser spot 5 in FIG. 15 is irradiated.

Similarly, at each track position, the sampling signals CLK _a and CLK _b rise at the position of the pit number corresponding to the spot position where the laser spot 5 is irradiated.
The signal levels RA and RB when the radial skew is detected are obtained based on K _a and CLK _b .

(4) Operation of Magneto-Optical Disk Device In FIG. 9, the RF signal S1 read from the optical disk 1 is amplified by the head amplifier 14 and output to the analog digital converter 17 and also to the radial skew detection circuit 31. Is output. The digital signal S2 converted by the analog digital converter 17 based on the timing signal S4 from the radial skew detection circuit 31.
Is output to the radial skew detection circuit 31 and is also output to the signal processing system 18. The digital signal S2 output to the signal processing system 18 is based on the timing signal S3 from the radial skew detection circuit 31.
8 and is output via the information output 19. The digital signal S2 output to the radial skew detection circuit 31 is also output to the low-pass filter 21 as a radial skew detection signal S5, and the low-pass filter 21.
The noise is removed by and is output to the optical head shaft drive motor 22. Based on the radial skew detection signal S5, the optical head shaft drive motor 22 controls the optical pickup 2 according to the detection result of the radial skew.

(4-1) Operation of Radial Skew Detection Circuit (4-1-1) When Radial Skew Does Not Exist in Optical Disk 1 The recording surface in the radial direction of the optical disk 1 from the optical pickup 2 When in a state perpendicular to the optical axis of the emitted laser beam (FIG. 1), the RF signal S1 read from the disk 1 in FIG. 10 is amplified by the head amplifier 14, and the amplified RF signal S1 is analog digital. The converter 17 converts it into an 8-bit digital signal S2 and outputs it to the delay circuit 33. This digital signal S
2 requires the time for aligning the gray code data in the 11-step flip-flops 45 to 55 for discriminating the track, and is delayed by the delay circuit 33 for that time and then temporarily held in the flip-flops 34, 35. . The RF discriminator 41 discriminates the track position of the RF signal S1, converts the RF signal S1 into a 11-bit digital signal S6, and outputs it to the decoder 39 in the timing signal generator 16. Based on the digital signal S6, the decoder 39 outputs sampling signals CLK _a and CLK _b to the flip-flops 34 and 35, respectively.
Based on LK _a and CLK _b , the signal levels RA and RB when detecting the radial skew are flip-flop 3
4 and 35, and subtracted in the subtraction circuit 36.

In this case, since there is no radial skew, the detection level RDS = RA-RB = 0, and this detection level RDS is output to the digital analog converter 37. And digital analog converter 3
7, the clock signal CL from the timing signal generator 16
The detection level RDS is returned to the analog signal S5 based on K _DA , the noise is removed through the low pass filter 21, and the signal is output to the optical head shaft drive motor 22. In this case, since there is no radial skew, the detection level becomes RDS = 0, and it is detected that the laser beam vertically irradiates the track of the optical disk 1 as the laser spot 5 having a substantially perfect circle.

(4-1-2) Radial skew exists in the optical disk 1 (RDS> 0) When the optical disk 1 is inclined to the far side with respect to the optical pickup 2 (FIG. 2) , Similarly the timing signal generator 1
Sampling signal CLK _a from the decoder 39 in 6
When the subtraction circuit 36 subtracts the signal levels RA and RB obtained based on CLK _b , the difference is the detection level RDS = RA−RB> 0. This detection level RDS
Is output to the digital analog converter 37, and is converted into an analog signal S5 by the digital analog converter 37 based on the clock signal CLK _DA from the timing signal generator 16. Noise is removed from the analog signal S5 via the low-pass filter 21, and the analog signal S5 is output to the optical head shaft drive motor 22. Detection level RDS> 0 in this case
Means that the optical disk 1 is inclined to the far side with respect to the optical pickup 2, and the detection level RDS = 0.
The laser beam is controlled so as to be focused perpendicularly to the recording surface of the optical disc 1 so that

(4-1-3) Radial skew exists in the optical disk 1 (RDS <0) When the optical disk 1 is tilted toward the near side with respect to the optical pickup 2 (FIG. 3). ), As well as the timing signal generator 1
Sampling signal CLK _a from the decoder 39 in 6
When the subtraction circuit 36 subtracts the signal levels RA and RB obtained based on CLK _b , the detection level RDS = RA−RB <0, which is the difference between them. This detection level RDS
Is output to the digital analog converter 37, and is converted into an analog signal S5 by the digital analog converter 37 based on the clock signal CLK _DA from the timing signal generator 16. Noise is removed from the analog signal S5 via the low-pass filter 21, and the analog signal S5 is output to the optical head shaft drive motor 22. Detection level RDS> 0 in this case
Means that the optical disk 1 is tilted toward the near side with respect to the optical pickup 2, and the detection level RDS = 0.
The laser beam is controlled so as to be focused perpendicularly to the recording surface of the optical disc 1 so that

(5) Effects of the Embodiments With the above configuration, the radial skew detection circuit 31 can detect and eliminate the radial skew regardless of the direction and size of the radial skew, so that the laser beam Can always be focused perpendicularly to the radial direction of the optical disc 1. As a result, it is possible to realize a magneto-optical disk device capable of accurately reading information without causing crosstalk even with respect to the optical disk 1 having a radial skew.

Further, the radial skew detecting circuit 31 can detect and eliminate the radial skew without individually using the radial skew detecting lens of the optical pickup 2. Therefore, the optical pickup unit 2 can be reduced in the number of constituent elements. As a result, the optical pickup unit 2 can be made lighter than in the case where the radial skew detecting lenses are individually used, so that the magneto-optical disk device capable of shortening the time required to access desired data can be realized.

Similarly, since the optical pickup 2 does not need to use a separate radial skew detecting lens, when the optical disk 1 is put in the cartridge, the shutter of the cartridge is an objective lens for picking up the light. Since it is only necessary to open the corresponding portion, it is possible to keep the opening small and prevent dust and the like from entering.

Since the objective lens of the optical pickup 2 also serves as a radial skew detecting lens,
Since an angle error due to the attachment of the objective lens and the radial skew detecting lens cannot occur, the radial skew can be accurately detected and eliminated.

Similarly, since the objective lens of the optical pickup 2 also serves as a radial skew detecting lens, the portion for picking up information and the portion for detecting radial skew are the same. Therefore, if the location where the information is picked up and the location where the radial skew is detected are different as in the conventional case, the radial skew can be completely corrected when the radial skew is unevenly present on the optical disk 1. However, in the present invention, even if the radial skew is unevenly present on the optical disk 1, the radial skew can be accurately eliminated.

Further, the radial skew is detected by a gray code pit pattern in which the information of the track address is recorded, so that it is necessary to record a special pattern on the optical disk 1 to detect the radial skew. There is no. Therefore, it is possible to realize an optical disk that can be effectively used without reducing the information recording surface.

(6) Other Embodiments In the above embodiment, the magneto-optical disk device 11 is used.
Described the optical disc 1 used as an optical recording medium, but the present invention is not limited to this, and a phase change type disc or a plastic card whose crystal state is changed by heating and cooling is provided by optical means. Then, an optical card for recording and reproducing information may be used.

[0063]

As described above, according to the present invention, the reflected light amounts obtained according to the radial skew condition are set to have mutually opposite characteristics at two different locations on the track in the area other than the information recording area. By using the optical recording medium in which the first and second patterns are formed over a plurality of tracks, a radial skew can be detected, and thus an optical recording medium capable of detecting the radial skew with a simple structure is provided. Can be realized.

As described above, according to the present invention, the track position is identified based on the reproduced signal, the positions of the information portion provided on the identified track are specified at two positions, and the information at the specified two positions is specified. The signal level is obtained by reading the light quantity of the reflected light of the light beam from the part, and the two signal levels obtained are stored, and then the two signal levels are calculated to detect the direction and amount of the radial skew. By doing so, the radial skew can be detected and eliminated without newly providing a radial skew detecting lens, and thus an optical disk device capable of detecting and eliminating the radial skew with a simple configuration can be realized.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an optical disk surface in the absence of radial skew.

FIG. 2 is a schematic diagram showing an optical disc surface when the disc is tilted upward.

FIG. 3 is a schematic diagram showing an optical disk surface when the disk is tilted downward.

FIG. 4 is a schematic diagram showing a radial skew detecting pit pattern.

FIG. 5 is a schematic diagram showing a laser spot state of a laser beam when there is no radial skew.

FIG. 6 is a schematic diagram showing a laser spot state of a laser beam when an optical disc is tilted upward.

FIG. 7 is a schematic diagram showing a laser spot state of a laser beam when an optical disc is tilted downward.

FIG. 8 is a schematic diagram showing a disk format.

FIG. 9 is a block diagram showing the configuration of a magneto-optical disk device.

FIG. 10 is a block diagram showing a configuration of a radial skew detection circuit.

FIG. 11 is a block diagram showing the configuration of a track identification unit.

FIG. 12 is a chart showing 16 types of Gray code data.

FIG. 13 is a table showing 16 types of gray code data by the lower 4 bits of the track address.

FIG. 14 is a block diagram showing a structure for identifying the lower 4 bits of a track address using a memory.

FIG. 15 is a schematic diagram showing gray code detection points.

FIG. 16 is a schematic diagram showing a timing chart of each timing signal.

FIG. 17 is a schematic diagram showing a timing chart of each timing signal.

[Explanation of symbols]

1 ... optical disk, 2 ... optical pickup, 3 ... track, 4,6,7 ... pit, 5 ... laser spot,
11 ... Magneto-optical disk device, 12 ... Spindle servo, 13 ... Focus tracking servo, 16 ...
Timing signal generator, 31 ... Radial skew detection circuit, 34, 35 ... Flip-flop, 36 ... Subtraction circuit, 41 ... Track identification section.

Claims (6)

[Claims] 1. A plurality of different tracks on an area other than an information recording area are provided over a plurality of tracks so that reflected light amounts obtained according to a radial skew condition have mutually opposite characteristics. And an optical recording medium having a second pattern formed thereon. 2. The first pattern and the second pattern have the same central track state, the two patterns adjacent to each other in the first pattern are different from each other, and the second pattern is adjacent to each other. The optical recording medium according to claim 1, wherein the states of the two tracks are opposite to those of the first pattern. 3. The optical recording medium according to claim 1, wherein the area portion is formed in an address information recording area. 4. The optical recording medium according to claim 1, wherein the pattern is formed by the presence or absence of uneven pits. 5. The optical recording medium according to claim 1, wherein the pattern is recorded in a combination of a crystalline state and an amorphous state. 6. A track identifying means for identifying a track position based on a reproduction signal, and an information part position specifying means for specifying two positions of an information part provided on the track identified by the track identifying means. An information reading unit that obtains two signal levels by reading the amount of reflected light of the light beam from the two information units, and a storage unit that stores the two signal levels obtained through the information reading unit. An optical disk device comprising: a radial skew detecting means for computing two information signals obtained via the storage means to detect the direction and amount of the radial skew.