JP2776822B2 - Optical disc recording / reproducing method and apparatus therefor - Google Patents

Description

Description: BACKGROUND OF THE INVENTION [Field of Industrial Application] The present invention relates to a recording / reproducing method for an optical disk device, and particularly to a format configuration suitable for recording / reproducing.

[Conventional technology]

Conventionally, as a tracking method, a method of recording data between the prepits by using a prepit that is slightly meandered to the left and right is known (JP-A-56-3439).

[Problems to be solved by the invention]

In this conventional example, a tracking operation is disclosed. For recording and reproduction, only a write-once medium is described.
However, recently, reversible media have been developed as optical disc media, and overwritable media have received particular attention. Among them, an overwriting method using magnetic field modulation is promising. When an optical disk device is to be configured using this method, it is necessary to reconfigure the tracking method and to adopt a configuration that operates as an apparatus, such as an access method and data recording / reproduction.
Conventionally, there has been no proposal of such an overall configuration.
There are the following issues as viewed from such a system.

When a medium that can be overwritten is used as a medium, the domain formed at the time of recording is shifted in timing from the recording pulse.

When comparing the signal amount of the magneto-optical signal with the signal from the pre-pit, the signal amount from the pre-pit is large, so that the pre-pit signal leaks into the magneto-optical signal.

It is necessary to have a means for reliably examining the meandering phase of the prepit.

For access, means for detecting the phase information of the light spot from the disk surface is required.

[Means for solving the problem]

In the present invention, regarding the problem of the above, self-clocking is used as a data clock generation method.

As for the problem described above, an empty area is provided between the data recording area and the prepit.

With respect to the problem (1), a synchronization mark that is not included in the pattern of the prepit or that is not included in the data pattern is provided in advance together with the prepit. And
Recognize this during playback.

With respect to the problem (1), a special access pattern is provided on the disk surface so that the track address can be substantially detected just by passing the light spot through the track, and this pattern is provided in advance in the synchronization area together with the synchronization mark. In order to detect finer track position information, the position of the meandering pit,
Or change the position of the special pit.

[Action]

Since the deviation between the recording pulse and the formed domain is constant within the same sector, the deviation can be absorbed by performing self-clocking.

By providing an empty area, interference between prepits and magneto-optical signals can be reduced.

Even if data and pre-pits exist, a synchronous pattern can be detected with high reliability.

The position information of the light spot can be detected directly from the disk surface, and the actuator can be controlled to access the target track at high speed.

The above actions are combined to realize an optical disk drive.

〔Example〕

Hereinafter, an embodiment of the present invention will be described with reference to FIG.
About JAPANESE JAOURNA
L OF APPLIED PHYSICS Vol.26 (1987) Suppl.26-4, pp1
49-154, and the operating principle of the recording / reproducing optical system is described in pp. 117-120 of the same book. Therefore, the description is omitted here, and the system configuration as an optical disk device is described. In FIG. 1, a disk 1 is driven by a rotating spindle 2, and a magnetic coil 3 is set on the disk surface and floats from the disk surface with a gap of several microns. An optical head 4 is placed facing the magnetic head, and a light spot from the optical head is positioned in a magnetic field region generated by the magnetic head. The signal detected by the optical head 4 is calculated by an arithmetic processing circuit 10.
, Where it is divided into a magneto-optical signal and a signal from a pre-pit, and the magneto-optical signal enters a data demodulation circuit 11, where it is demodulated by a reproduction clock PCK and a gate signal RDT indicating the location of the data, and sent to a data controller 15. .

The pre-pit signal from the arithmetic processing circuit 10 first enters the clock generation circuit 12, and generates clocks RCK and WCK necessary for data recording / reproduction and tracking. Further, the pre-pit signal enters the track shift detecting circuit 14 and generates a track shift signal TE using a control signal from the timing generating circuit 13. Further, the pre-pit signal enters a timing generation circuit 13 and uses a clock signal from the clock generation circuit 12 to control a signal for detecting a track deviation, a control signal for detecting position information for access, and a recording / reproduction signal. A signal for controlling data is generated, and a track shift detecting circuit 14 and an access controller 1 are respectively provided.
6. Send to data controller 15.

A signal from a pre-pit is input to the access controller 16, and information representing the position of the light spot is detected using a signal from the timing generation circuit 13. Further, a signal from the track shift detecting circuit 14 is input to detect minute track information. These signals and the upper
The command information FA and CA for controlling the two actuators are transmitted based on the target track number (input via the bus 18) designated by the CPU 17.

The reproduction data processed by the data controller 15 is sent to the host CPU 17 via the bus 18. On the other hand, the data to be recorded is sent from the upper CPU 17 to the data controller via the bus 18 and added with control data such as ECC (23-correction code) and subjected to processing such as interleaving. Sent to In this circuit, signals WCK and WCK from the clock generation circuit 12 and the timing generation circuit 13 are output.
Using WDT, create data pulses to be actually recorded on the disk surface. According to this signal, the coil driver 7
To modulate the magnetic field. The power of the spot on the disk surface is controlled by the laser drive circuit 6,
This timing is synchronized with a signal WRC indicating a recording / reproducing state output from the host CPU 17.

Some of the detection signals from the optical disk 1 were input to a focus error detection circuit 19 to create a control signal AF for an autofocus servo system, which was input to a light spot control circuit 9 to perform phase compensation and the like. The voice coil lens 21 in the halo head 4 is driven to perform focus control. The track deviation signal TE is input to the light spot control circuit 9, and after processing such as phase compensation, a signal for controlling the fine actuator and the coarse actuator is created. The coarse actuator control signal is transmitted through the coarse drive circuit 8
The coarse actuator 5 is driven to move the entire head in the disk radial direction.

The signal FA from the access controller is input to the light spot control circuit 9 to control a fine actuator (not shown) in the optical head 4 and to control a minute and high-speed light spot at the time of access. Further, the signal CA is input to the course drive circuit 8, and controls the macro movement of the entire optical head at the time of access.

The signal WRC indicating recording / reproduction is a clock generation circuit 12,
It is input to the timing generation circuit 13 and controls each output signal according to the recording / reproducing state. The above is the overall configuration of the optical disk device according to the present invention.

Next, the pre-pit shape will be described with reference to FIG. Each track on the disk surface is provided with a repeated pit pattern for each data division unit and each lid. This sector has address information and other control information at the beginning.
An ID section is provided, and prepits meandering by a small amount to the left and right with respect to the center of the track are arranged. Data is recorded during this pre-pit. In the conventional method, a pit pulse indicating a pit position is created from the pre-pits as shown in FIG. 4, and a clock signal for recording and reproducing data and a track shift signal are simultaneously detected from the pit pulse. FIG. 3 shows a specific waveform of the track shift signal. As the meandering state of the pre-pits, there are an in-phase pit and a phase inversion pit as shown in FIG. For these pit patterns, a track shift signal when the servo operation is OFF and a follow-in state when the servo operation is ON are shown.

For the data, a clock signal synchronized with the pit pulse shown in FIG. 4 is created, the recording data is modulated using this clock, and the data area between the prepits is recorded. In the magnetic field modulation overwrite method, the formed magnetic domain has a strip shape as shown in FIG. Also in the case of reading this, the clock created from the pre-pit has been conventionally used. This has the following problems. That is, in FIG. 5, due to the irradiation of the data pulse, the temperature distribution on the surface is matched with the intensity distribution of the light spot, and becomes a distribution that trails by Δ1 behind the light spot.
According to the principle of magnetic field modulation overwriting, a point on the disk surface where the temperature is lower than the Curie temperature is recorded according to the magnetization direction of the external magnetic field. For this reason, assuming that the temperature becomes equal to or lower than the Curie point at a position shifted by Δ2 from the center of the distribution, a shift Δ3 between the edge of the data pulse and the edge of the recording domain
Is the sum of Δ1 and Δ2.

From the above, in the magnetic field modulation overwrite method, the recording pulse and the domain deviate in principle. However, although this deviation amount depends on the irradiation power, the linear velocity, the disk sensitivity, and the like, it is considered that it is almost constant within the same sector and each domain does not change. For this reason, a self-clocking method of generating a clock from data is adopted as a reproduction clock generation method.

There is another problem. When the magneto-optical signal and the signal from the pre-pit are detected by the difference and the sum of the two polarization components as described later, the intensity ratio of the two signals is about 1:50 to 100, and the pre-pit signal leaks into the magneto-optical signal. Come in. For example, the spot diameter is 1.5 μmφ again, the pre-pit diameter is
If it is 0.6 μmφ, the pre-pit signal becomes equal to the magneto-optical signal at a distance of about 1.3 μm, and the data must be separated by about 2 to 2.5 μm from the center of the pit in consideration of a signal detection margin. Therefore, an empty area of about 4 to 5 μm is provided around the pre-pit.

Further, when the pits are differentiated in order to detect the position of the pre-pit, an erroneous signal is generated due to noise, a defect, or the like on the disk, and an erroneous signal is generated from the pre-pit position. In addition, it is necessary to know the phase of meandering in order to detect a track shift signal. For this purpose, a synchronization mark is formed on the disk in the form of a pre-pit in advance, and the synchronization mark is detected to determine the meandering phase and to identify the position of the pre-pit.

FIG. 6 shows a track format considering the above. One track includes N sectors, one sector includes M blocks, and one block includes one prepit pair area. One pre-pit pair area includes pre-pits, an empty area sandwiching the pre-pits, and a data area. Now, taking a 3.5 optical disk as an example, the number of data bytes in one track is 18 KB in unformatted data, the number of sectors N is about 20 to 24, and the number of sectors M is about 8 to 16 for 20 to 40L.
Also, the number of prepits per track related to the ability to create a tracking servo and a clock is about 6000 to 3,000.

As a modulation method, a fixed-length code is preferable because data is cut at a fixed length. 8/9 conversion, 4/5 conversion,
There are certain 2-7 modulation schemes and the like. However, a variable length code is also applicable in consideration of recording density efficiency.

Above all, 2-7 modulation and 1-7 modulation are excellent methods, and 2-7 modulation is advantageous from the viewpoint of density, and 1-7 modulation is advantageous from the viewpoint of detection margin. Like a magneto-optical disk
In a recording / reproducing system where the S / N is severe and the amplitude deterioration at the used data frequency is small, there is a margin in the detection margin.
Seven modulations are advantageous.

As a recording method, there is a pit position recording as shown in FIG. 6 or an edge recording as shown in FIG. The pit position recording does not require special consideration for the modulation method, but the recording density is lower than that of the pit edge recording. In pit edge recording, since the data has a fixed length, there is a restriction that the starting point and the ending point of the recording data must match one of the recording levels. To avoid this, add an additional bit according to the data before modulation so that the end point of the data after modulation always matches one of the recording levels, or add an additional bit to the data after modulation and record it. You have to do the same level.

7 and 8, a method of processing a detection signal using this format will be described. When the light spot 70 on the disk 1 passes through the tracks 71 and 72, the reflected light is transmitted to the voice coil lens 21 and the galvanomirror deflector.
After passing through 34, a part of the light is reflected by the beam splitter 30 and further separated by the beam splitter 33, and one part enters the defocus detection system 19. The other is 1/2
The polarization components are split by the polarizing beam splitter 36 through the plate 35 and focused by the lenses 37 and 39 to the detectors and 40, respectively. By adding and subtracting the signals from the detectors 38 and 40, respectively, the pre-pits and the reflected light from the disk can be detected from the sum signal, and only the magneto-optical signal component can be obtained from the difference signal. The sum signal 73 changes corresponding to the pre-pits as shown in FIG. 8 by passing through the pre-pits 74 to 83. A reduction filter for removing this signal 73 through the amplifier 41 to remove high-frequency noise
The output is differentiated by a differentiating circuit 43. The differentiated signal 88 is compared with a certain threshold by the comparator 44 to obtain a signal 89, which is expanded in pulse width by the monomultivibrator 45 to obtain a signal 90.
Then, a signal 91 at the zero cross point of the differential signal 88 is obtained by the cross point detection circuit 46, and a logical product of the signal 91 and the signal 90 is obtained, thereby obtaining a pit signal 92 indicating only the pre-pit portion. This signal 92 is input to the shift register 48, the pit signal is time-shifted by the specific clock 47, and the pre-pits 86, 87 and the pre-pits 86, 8
The synchronization mark consisting of 7 is used to generate a synchronization timing 93 from the delay time of the register 48. The bit signal 92 is input to a PLL (phase, locked loop) 49 for generating a clock, and a clock WCK synchronized with the pit signal is generated. This signal WCK is divided by a frequency dividing circuit 50 composed of a counter.
And an estimated pulse 94 is generated at the pre-pit period in accordance with the timing at which the pre-pit exists. counter
The start timing of 50 is performed by the above-described synchronization timing 93. The signal 94 is input to the flip-flop 53 to generate a signal having a period twice as long as the period of the pre-pit.
ANDing them with each other gives signals φ1 and φ2, which become timing information corresponding to the position of the pit on the left or right side with respect to the track center, respectively. Further, the clock signal WCK is input to the frequency dividing circuit 51 composed of a counter, and the start timing of the counter is set by the signal 94 so that a pulse is generated just in the middle of the pre-pit. The signal is φ3.

Outputs of the reduction filter 42 are input to sample and hold circuits 57 and 58, respectively, and sample and hold are performed by signals φ1 and φ2, respectively. Each output is output to a differential amplifier 59
And take the difference. Although this output can be used as a track shift signal, the signal passed through the inverting circuit 60 and the signal as it is are input to the respective inputs of the analog switch 61, and this signal is inverted by the signal φ3 and the inverter 62. , The sampling frequency for detecting the track deviation can be effectively doubled.

As the synchronization pattern, a specific pattern having a time arrangement which is not in the example of the pre-pits meandering left and right, such as the pull pits 86 and 87, may be used. However, as shown in FIG. But it is good. Also, the slots can be arranged between the tracks. Similarly, pits 84, 85, 86, 8
7 patterns can be inserted between tracks. In this way, the synchronization mark can be detected even if the light spot is between the tracks. Further, in consideration of future applications of optical discs, it is necessary to reproduce the write-once discs which have been used up to now even with this apparatus. At this time, the data is detected from the sum signal, and the track shift signal,
And a signal of the same level as the synchronization mark. In order for the synchronization mark to be distinguished, a pit pattern that does not exist in the recording data may be selected.

Data modulation will be described. The difference signal is converted into a digital signal by a binarization circuit 54 and input to a phase comparator 55. The other input is clock WCK from PLL49.
The phase shift circuit 56 is controlled by the output of the phase comparator 55. In this way, even if there is a domain shift at the time of recording, it is possible to synchronize only with the recording data by moving only the phase. The reproduction block RCK is input to the demodulation circuit 11 and the data is demodulated. With this configuration, since the clock WCK synchronized with the pre-pit is used at the time of recording, recording can be performed without being affected by disc eccentricity and rotation fluctuation.

On the other hand, at the time of reproduction, a clock having the same frequency as the recording data is detected without being affected by disk eccentricity and rotation fluctuation in synchronization with the pre-pits. Here, if only the phase shift is detected from the data and the phase is adjusted, a reproduced clock RCK synchronized with the data can be obtained.

Another embodiment for generating a reproduction clock will be described with reference to FIG. The signal φ4 is input to the F / V converter 101,
The frequency is converted to a voltage, and then compared with the reference speed voltage by the differential amplifier 102.
Via 03, it enters the adder 104. The other side of the adder 104 detects the phase shift between the output of the voltage controlled oscillator 105 and the binarized signal of the magneto-optical signal by the phase comparator 107, and inputs the result of passing this output through the phase compensation circuit 106. I do. In this way, a two-input, one-output control system is obtained. This loop is composed of an F / V system and a normal PLL phase control system, and its loop characteristics are desired to have a configuration as shown in FIG. Since the F / V system has inertia, the crossover frequency fc2 is not selected to be about 2 to 5 KHz. The phase control system has a frequency of several hundred KHz in normal self-clocking. However, if the band is expanded in this way, the effect of noise will increase.
Hz is desirable. In this way, the reproduced clock does not run away due to a defect or the like.
In addition, as compared with a normal self-clock, jitter due to coarseness is reduced, and furthermore, since a double loop is formed, gain in reduction is increased and tracking characteristics are improved.

Next, a format for access will be described with reference to FIGS. 11 to 14. FIG. For access, it is necessary to always correctly detect the position even if the moving speed of the light spot changes from high speed to low speed. In the case of a 3.5 ″ optical disk, if the track pitch is 1.5 to 1.4 μm, the number of tracks is 15,000 to 11,000, and 14 bits can be sufficiently expressed.

In this format, as a basic configuration, address information is put into a synchronization area together with a synchronization mark. For example, the eleventh
As shown in the figure, after the synchronization mark (represented by a cross in the figure), the most significant bit B13 to the least significant bit B0 are inserted. However, in the basic configuration, when moving at a high speed during access, for example, at a speed of 1 m / sec, there is a high probability that the light spot passes through the track without reading all the bits.

Therefore, as shown in FIG. 11, a bit pattern of at least the upper 9 bits is arranged between tracks. That is, since the uncertainty of the number of 5 bits passing at the maximum speed always remains, higher bits can be reliably detected during high-speed movement. During high-speed movement, speed control at the time of access can be sufficiently performed using only the upper bits. Regarding the lower bits, the reliability of the track address detection is improved by arranging the pre-pits between the tracks as shown by the dotted line.

In the embodiment shown in FIG. 11, the address bits require 14 bits, and cannot be applied when there is not enough room in the number of data that can be recorded in the synchronization area. Therefore, as shown in FIG. 12, the upper 9 bits are distributed one bit at a time in the synchronization area of 9 blocks, and the lower 5 bits are arranged in the synchronization area of each block. In this way, the upper bits can be detected only after reading 9 blocks, but control is possible at a certain speed. If there are many 9 blocks, it is sufficient to disperse them by 2 bits or 3 bits.

In the embodiment of FIG. 12, when the number of blocks is large, it is good. However, when the number is small, the sample value of the speed control becomes small, so that it becomes unstable, and high-speed seek becomes difficult. Therefore, the lower 5 bits of FIG. 11 are represented by using left and right meandering pits. That is, as shown in FIG. 13, the prepit is shifted by Δ1 from the position where the prepit should be (indicated by a dotted line). Also, the other pre-pit is shifted from the original position by Δ2. Specifically, as shown in FIG. 14, the free area is increased by another bit, and the position of the pre-pit is shifted by 1/2 bit at a time so that each phase corresponds to the lower bit.

In this case, Δ1 and Δ2 are shifted in the same time axis direction by the same value.

In another embodiment, as shown in FIG. 14 (b), the lower bits are represented at the shift positions of the pair pits.

Alternatively, each bit may be represented by dividing the lower bits into two using Δ1 and Δ2. By doing so, the overhead of the empty area is reduced, and the data use efficiency is improved.

In the embodiment shown in FIG. 13, since a clock cannot be generated from the pre-pits, the phase of the PLL should be synchronized in the SYNC area, or the mark for PLL synchronization should be replaced with a pattern as shown in FIG. It is formed as a continuous example in the radial direction, and the phase is thus synchronized.

In this way, the passing track address can be accurately detected only by passing through the pre-pits.

As described above, an alternating binary code (gray code) is used for the 14-bit encoding used as the access pattern. In this case, since the sign change is only one bit,
Error checking can be performed.

〔The invention's effect〕

According to the present invention, even in an overwritable optical disk, a tracking signal and clock information can be detected with high reliability from pre-pits meandering left and right, and light spot phase information for access can be detected.
In addition to write-once discs, other media can be used between devices,
Compatibility between media can be ensured. That is, a signal from a pre-pit is received by a single photodetector, and a new optical disc which does not cause a track shift due to disc tilt and movement of a light spot and which is not affected by a time shift of recording data due to thermal recording. Implement the device.

[Brief description of the drawings]

FIG. 1 is a diagram showing a system configuration of an optical disk device according to the present invention, FIG. 2 is a diagram showing a track format,
FIG. 3 is a diagram showing detection signals from pre-pits and pits, FIG. 4 is a diagram showing a disc format and a reproduction signal, FIG. 5 is a diagram for explaining a recording timing shift, and FIG. FIG. 7 is a diagram showing an example of a track format, FIG. 7 is a block diagram of a detection system, FIG. 8 is a time chart of track deviation detection, FIG. 9 is a diagram showing an example of SYNC, and FIG. Diagram showing the eleventh
FIG. 12, FIG. 13, and FIG. 13 are diagrams showing examples of the SYNC zone pattern for access, and FIG. 14 is a diagram showing a specific example of the pattern of FIG.

Claims (2)

(57) [Claims] 1. An optical disk having a synchronization mark and recording data between the synchronization mark and the next synchronization mark, detecting a track shift signal from a pulse based on light reflected from the synchronization mark, and A clock signal having a shorter cycle than the pulse is generated in synchronization with the pulse, the data is recorded on the optical disk based on the clock signal, and the data recorded based on a signal obtained by phase-shifting the clock signal A recording / reproducing method for an optical disc, characterized by reproducing the information. 2. An optical head having a synchronization mark and recording data between the synchronization mark and the next synchronization mark, wherein the optical head forms a detection signal from light reflected from the synchronization mark; A track shift detection circuit that detects a track shift from the detection signal corresponding to the mark, a clock generation circuit that synchronizes with the detection signal corresponding to the synchronization mark, and generates a clock signal having a shorter cycle than the detection signal; A data modulation circuit that creates a data pulse to be recorded on the optical disk based on the clock signal; a phase shift circuit that creates a signal obtained by shifting the phase of the clock signal; and a data signal that is recorded based on an output signal of the phase shift circuit. An optical disk recording / reproducing apparatus, comprising: a demodulation circuit for reproducing the data.