JP2612830B2 - Information recording medium - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a disk-shaped information recording medium used for recording and reproducing digital signals, and more particularly to an increase in the recording capacity of an information recording medium such as an optical disk used as an external storage device of a computer. About things.

[0002]

2. Description of the Related Art Hitherto, in this type of optical disk apparatus, a tracking method is often used in which a guide groove is provided on a disk in advance, and control is performed so that a light beam is positioned on the guide groove. The control error signal in this case is continuously obtained by detecting the diffracted light by the guide groove from the reflected light of the light beam, and is called a continuous servo method. In the continuous servo system, there is a problem that a difference in the shape and reflectance of the guide groove affects an error signal and deteriorates tracking accuracy. Further, at the time of recording, a larger amount of light beam is applied than at the time of reading, so that the amount of reflected light also increases in proportion. Therefore, even in such a case, an error signal is correctly obtained and control is performed. Such considerations are needed.

On the other hand, in the sample servo system, as a means for obtaining servo information, a guide groove is not used, but a servo area and a data area are divided on a track and servo areas and data areas are alternately arranged. Then, control is performed so that the light beam passes over this servo area.
In the control error signal, a set (two) of pits, which are slightly offset in the opposite directions with respect to the track position in the servo area, are recorded in advance in the servo area, and when the light beam passes through both pits. It is obtained by detecting the difference in the amount of reflected light. According to such a sample servo method, there is no influence of the guide groove, and the control error signal is obtained only in the servo area, and only the operation for obtaining the servo information is always performed in this area. Some of the problems of the continuous servo system, such as the fact that the increase in the amount of laser light does not occur, are solved. Regarding this sample servo system, SPIE, Proceedings, Optical Mass Data Storage I
I, 695 (1986), pp. 239-246
Page (SPIE, Proceedings, Optical Mass Data)
Storage II, vol. 695 (1986) pp239-
246).

On the other hand, information recording media such as optical disks and magnetic disks are required to have larger capacities as the amount of information handled increases. For that purpose, it is necessary to improve the recording density on the disk. In this regard, the so-called C.I. A. In the case of the V (Constant Angular Velocity) method, the pit period is limited at the innermost circumference where the linear velocity is the slowest. As a result, a margin is generated toward the outer periphery, and for example, the recording density is reduced to で は at the outer periphery having a diameter twice as large as the innermost periphery. Thus, C.I. A. V. The method does not make full use of the recording capability of the disc, and causes waste.

On the other hand, C.I.
L. V. In the (Constant Linear Velocity) method, the same recording density is obtained from the inner peripheral side to the outer peripheral side, and the maximum recording capacity can be obtained. However, C.I.
L. V. In the method, the number of rotations of the disk must be changed according to the track position, and the access time is C.I. A. V.
However, there is a problem as a data recording / reproducing medium for a computer in which random access is performed and high-speed access is required.

Therefore, as one of the methods aimed at eliminating the disadvantages of both systems, the disk is divided into a plurality of areas (zones) in the radial direction, and different areas are provided so that the recording density is increased in each area. Apparatus for setting rotation speed is disclosed in
No.-17223. Japanese Patent Application Laid-Open No. 61-1 / 1986 discloses an apparatus for increasing the recording capacity by dividing the area into a plurality of areas and changing the pit period in each area while keeping the rotation speed constant.
No. 75968.

[0007]

The above prior arts all relate to an optical disk device of a continuous servo system, and do not take into consideration an optical disk device of a sample servo system. The sample servo method uses a so-called embedded clock method in which a clock pit recorded in a servo area is detected and a clock is reproduced based on the detected clock pit. Since the reproduced clock is a reference for all operations including the servo, it is necessary to always obtain a stable clock. In addition, since the cycle at which the servo information is obtained affects the servo characteristics, it is necessary to make the cycle constant. However, if the number of rotations or the recording data cycle is changed according to the area on one disk, the cycle of the servo information also changes at the same time, and the servo characteristics also change, so the servo characteristics must be switched. is there.

An object of the present invention is to provide an information recording medium used in an information recording / reproducing apparatus of a sample servo system, in which it is not necessary to change a sampling period of servo information and which has an increased recording capacity. It is in.

[0009]

[0010]

[0011]

SUMMARY OF THE INVENTION The above objects, the servo signal is detected at every predetermined period and servo regions and information regions are arranged alternately in the circumferential direction of the recording medium on the disc, and at a constant angular velocity rotation Servo areas are arranged at a constant angular interval as described above, divided into a plurality of zones composed of a plurality of tracks in the radial direction, and two tracks are offset by sandwiching the tracks.
Of it and record the servo signal tracking pits at least including the servo area in all zones at fixed time intervals equally dividing the detection interval of the servo area during a constant angular velocity rotation, the servo area during a constant angular velocity rotation in the information area in aliquoted detection interval and constant within each zone, zone
This is achieved by providing an information recording medium in which signals are recorded on a track at different recording time intervals for each .

In this case, the recording time interval to the information area at the constant angular velocity rotation is shorter in the zone on the outer peripheral side, or the recording time interval to the information area at the constant angular velocity rotation is the innermost circumference. In the zone on the side, the signal recording time interval in the servo area can be made the same. Also, the servo area
The information area forms a segment, which is included in one track.
The more sectors on the outer periphery, the more sectors
The number of the included segments is smaller in the zone on the outer peripheral side.
This is achieved by using an information recording medium that has been completed.

[0013]

In the servo area, since a servo signal is recorded with a constant servo clock that equally divides the arrangement interval of the servo area, an information recording medium (hereinafter, referred to as a disk) is rotated at a constant angular velocity. If that servo signal is detected,
A servo clock with a constant frequency can be reproduced. If servo information is detected using this servo clock, a stable servo control operation can be ensured. On the other hand, since the arrangement interval of the servo area is equally divided and recording is performed in the information area with a clock having a frequency different from the servo clock, even if the disc is rotated at a constant angular velocity, information is reproduced according to the track position. By changing the clock frequency of
It becomes possible to change the recording density on the disc.

For example, the further toward the outer periphery of the disc,
By increasing the clock frequency for information recording and reproduction, the recording density on the disk can be improved, and the recording capacity can be increased.

Then , the disk is divided into a plurality of zones in the radial direction, and the recording of the information area is performed based on a clock having a constant frequency in each zone and a different frequency for each zone. with so high as the outer peripheral side zone, compared with the case of continuously changing the frequency of the record reproduction clock can be simplified the structure of the recording and reproducing apparatus.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described with reference to the embodiments shown in FIGS. FIG. 1 shows a waveform diagram of an embodiment of a reproduction signal of a servo area and a clock for data recording / reproduction applied to the optical disk according to the present invention. As shown in (iv) to (vii), clocks 24a to 24d for data recording and reproduction are used.
Is set so that the optical disk is divided into four regions in the radial direction as shown in FIG. 3, and the clock frequency of each region increases from the inner periphery toward the outer periphery.

FIG. 2 is a block diagram of an optical disk apparatus using a sample servo system suitable for recording and reproducing information on and from an optical disk according to the present invention. However, FIG. 2 does not show parts that are not involved in the description of the features and operations of the present invention. In the figure, 1 is an optical disk, 2 is a disk motor, 3
Is an optical pickup device, 4 is a laser driver, 5 is a preamplifier, 6 is a peak detection circuit, 7 is a modulation circuit, 8 is a demodulation circuit, 9a to d are clock recovery circuits, 10 is a selection circuit,
11 is a tracking error detection circuit, and 12 is a control circuit.

The optical disk 1 is rotated at a constant angular velocity by a disk motor 2. Writing / reading of data to / from the disk is performed by the optical pickup 3. The write data is subjected to a predetermined modulation by the modulation circuit 7, and then input to the laser driver 4, where the laser diode is driven and converted into a light beam. The optical disc 1 changes its reflectivity according to the intensity of the irradiated light beam, and data is recorded by the change in reflectivity remaining after the light beam passes. For reading, the laser diode emits a light beam that is weak enough not to cause a change in reflectivity as in writing, and the light detector detects the reflected light when the light beam is applied to the optical disc 1 and detects the reflectivity. The difference in reflected light amount due to the difference is converted into an electric signal. The detected signal is amplified by the preamplifier 5 and then demodulated by the demodulation circuit 8 to restore the original data.

In order to realize data recording / reproducing with such a light beam, a light beam is accurately irradiated onto a previously set track on an optical disk.
So-called tracking control is required. In the sample servo method, as shown in FIG. 1 (i), servo areas and data areas are alternately arranged, and servo information such as tracking control is obtained only from the servo areas. Therefore, the servo information is obtained not as a continuous signal but as a discrete signal. The tracking error information is obtained based on the light amount difference between the first tracking pit 21 and the second tracking pit 22 when the light beam passes through the servo area. In other words, since these two tracking pits are recorded on both sides of the track center line offset by the same distance, if the irradiation position of the light beam is shifted from the center of the track, the tracking pits on the shifted side are shifted. And the reflected light amount of the opposite tracking pit decreases. When the center of the track is correctly irradiated with the light beam, the reflected light amounts of both tracking pits are the same. Therefore, the amount and direction of the tracking deviation can be determined from the difference and the polarity of the reflected light amounts of the two tracking pits, and the tracking control is performed by controlling the light beam so as to cancel this.

In order to realize such tracking control by the sampling method, a clock signal for accurately extracting a reproduction signal from the tracking pit shown in (ii) of FIG. 1 is required. In order to obtain the servo clock signal, the servo clock signal is obtained from the clock pit 23 which is the third bit of the servo area signal shown in FIG. A predetermined number of clock pits are equally divided based on a clock pit reproduction signal obtained for each servo area,
The clock 24 shown in (iii) of FIG. 1 is generated. By forming the above-mentioned tracking pits in advance so that the reproduced signal can be obtained at a position synchronized with the clock signal, the reproduced signal of the tracking pit can be accurately extracted.

As described above, the sample servo method is characterized in that a clock synchronized with the rotation of the disk is used. This clock is used not only for obtaining servo information but also for recording and reproducing data in a data area (information area) . It is also used for As the number of pieces of servo information per round of the disk increases, better servo characteristics can be obtained, but the data area decreases and the recording capacity decreases. Conversely, if the number of servo areas is reduced, sufficient servo characteristics cannot be obtained. 1800
An appropriate number when rotating at rpm is 1000-2000 per disk revolution. In order to record and reproduce data by randomly moving the pickup from the inner circumference to the outer circumference of the disk, the intervals on the time axis of the servo areas, that is, the arrangement intervals of the servo areas, must be constant over the entire area of the disk. is necessary. Therefore, the servo areas are linearly arranged from the center of the disk toward the outer circumference at regular intervals. As a result, even if the pickup is moved in the radial direction of the disk, the reproduction signal in the servo area is obtained at constant intervals, so that a constant servo characteristic is always obtained. realizable.

However, the fact that the servo area is constant on the time axis requires that the above-mentioned clock also be constant.
As a result, the recording and reproduction of data performed using the same clock also has a constant period, so that the recording density decreases as it goes to the outer peripheral side of the disk. Therefore, in the present invention, the data recording density can be increased by making the clock for servo signal detection and the clock for data recording / reproduction different. FIG. 3 shows an example of the optical disk according to the present invention. The optical disc 1 has servo areas arranged radially from the center of the disc, and a read signal is obtained at regular time intervals when rotated at a constant rotation.

On the other hand, the data area is divided into four areas as shown in the figure, and recording and reproduction are performed at different clocks. However, the dividing lines in the drawing are imaginary for explanation, and the tracks are continuous even at the boundary between the regions.

FIG. 4 shows an example of division of each area. Each area is 5
000 is divided for each track, the region a is 32 sectors per round, when configuring one segment by a servo area and data area, the data is 16 bytes are recorded in one segment, the recording clock frequency is 11 .14
56 MHz. This clock frequency is the same as a clock for detecting a servo signal, and is a clock that divides the clock pit into 270 parts based on the aforementioned clock pit. Area b is 39 sectors per round, 20 bytes per segment, and recording clock frequency is 13.9
526 MHz, and this frequency is 3 clock pits.
It is divided into 38 equal parts. Similarly, areas c and d are set as shown in the figure, and the recording clock frequencies correspond to 405 and 473 equal parts of the clock pit, respectively.

The recording capacity is 432.5 MB which is 1.35 times that of 320 MByte when the entire area is recorded with the setting of a.
yte is obtained. The generation of the clock frequency is performed by the four clock recovery circuits 9a to 9d in FIG.
The clock recovery circuit a is 11.1456 MHz, the clock recovery circuit b is 13.9526 MHz, the clock recovery circuit c is 16.7184 MHz, and the clock recovery circuit d is 1
Generate 9.5254 MHz respectively. Each clock output is input to the selection circuit 10, and the clock generated by the clock recovery circuit a is input to the tracking error detection circuit 11, which is used to extract a tracking pit reproduction signal.

Each clock input to the selection circuit 10 is
One clock is selected by a selection signal output from the control device 12 composed of a microprocessor or the like according to a track number for performing recording and reproduction, and is input to a modulation circuit and a demodulation circuit.

The clock recovery circuits 9a to 9d are provided with a so-called PLL (Phase Locked Loop) shown in FIG.
(Locked loop) circuit. This PLL
The circuit includes a phase comparator 91, a low-pass filter 92, a voltage controlled oscillator 93, and a frequency divider 94.
The oscillation frequency of the voltage controlled oscillator 93 and its phase are controlled so that the phase of the output of the voltage controlled oscillator 93 and the phase of the reference signal input from the outside match. Therefore, the output of the voltage controlled oscillator 93 is a clock signal whose frequency is a value obtained by multiplying the reference signal by the frequency division ratio of the frequency divider 94, and whose phase is always a constant value with respect to the reference signal. In this example, the reference signal is a clock pit, which is the third pit in the servo area described above, and the output clock signal is the four types of clock signals described above. Therefore, for example, in the clock recovery circuit a, the frequency division ratio of the frequency divider 94 is 270, and the voltage-controlled oscillator 93 outputs the central value of the control voltage of 11.1456 MH.
The oscillation frequency control element is adjusted to generate z. Similarly, predetermined division ratios and oscillation frequencies are set in the clock recovery circuits b to d.

FIG. 1 shows the relationship between the reproduced signal on the actual optical disc and the clocks 24a to 24d for recording and reproducing information.
(Iv) to (vii). 3A to 3D respectively correspond to the regions a to d in FIG. 23 is a clock pit, and 25a to 25d are head pits of the data area. Since each clock is generated in synchronization with the clock pit, all the clocks have the same phase at this point in time. However, since the frequencies are different, a phase shift occurs between the clocks. The start position of the data area is set at a certain interval or more (time distance) in order to prevent the additional data from affecting the clock pit. Similarly, the interval between the end point of the data area and the first tracking pit is kept at a certain interval or more.

As shown in FIGS. 3 and 4, when the region is equally divided into four regions, the regions b, c, d
Can provide 1.25 times, 1.5 times, and 1.75 times the recording capacity, respectively. As for the distribution of the servo area and the data area between one segment in the area a, when the total number of clocks is 270, the servo area has 30 clocks and the data area has 240 clocks (15 clocks × 16 bytes). When the same distribution ratio is applied to the area b, it is multiplied by 1.25, and the total number of clocks is 337.5 clocks, the servo area is 37.5 clocks, and the data area is 300 clocks. However, since the frequency division ratio of the clock recovery circuit needs to be an integer, the number of possible clocks is 337 or 338. In the former case, the servo area is 37 clocks, which is 0.5 clock shorter than the original length, and the interval between the clock pit and the data pit or the first tracking pit and the data pit is shorter than that in the area a. In the latter case, the servo area has 38 clocks, and the interval from the data area does not matter. However, the pit interval of the first track of the area b is shorter than the first part of the area a, that is, the innermost circumference of the disk. I will. A solution to this problem is realized by shifting the start point of the area b around the outer circumference. Considering the case where recording and reproduction are performed at a pitch of 1.5 μm on a disk having an innermost radius of 30 mm and an outermost radius of 60 mm, the starting point of the area b is 0.57 m from the point of 37.5 mm.
This is achieved by shifting the outer periphery of m. The number of tracks in this portion is 57 tracks, and the recording capacity is reduced by that amount, but this is not a problem in view of the total capacity. Which of the three methods is adopted is determined by the margin setting of the entire optical disk device. Region c,
In d, the clock frequency is determined based on the same concept. In any case, as shown in FIG.
The number of sectors included in a track is larger in the outer zone.
And the number of segments contained in one sector is
Or less.

FIG. 6 shows a second embodiment of the optical disk apparatus suitable for the optical disk of the present invention. 2, the same components as those in FIG. 2 are denoted by the same reference numerals. In this example, there are two clock recovery circuits. FIG.
The operation will be described assuming that the optical disk shown in FIG. 4 is used. The first clock reproducing circuit 9 generates a clock 11.1456 MHz for detecting tracking pits, and the second clock reproducing circuit 9 ' Four types of clocks are generated by the selection signal.

FIG. 7 shows a configuration example of the second clock recovery circuit 9 '. The dividing ratio variable frequency divider 95 has 27
0, 338, 405, and 473 frequency divisions are set. The oscillation element of the voltage controlled oscillator 93 is adjusted so as to oscillate four center frequencies at the center value of the control voltage. Also, the entire clock recovery circuit needs to have a pull-in range that covers all four frequencies.

Next, FIG. 8 shows a second configuration example of the second clock recovery circuit. In this example, the switching element 96 is switched by the switching circuit 96 in order to switch not only the frequency division ratio but also the center frequency of the voltage controlled oscillator by the selection signal. Each oscillation element is adjusted so that any one of the four frequencies becomes the center frequency. The clock recovery circuit in this case does not need to have a wide pull-in range as in the embodiment of FIG.

The embodiment of FIG. 6 can reduce the number of clock recovery circuits as compared with the embodiment of FIG. But,
Each time the boundary of the area is exceeded, a synchronous operation of the clock recovery circuit is performed, so that the access speed is reduced. Also, continuous recording and reproduction beyond the boundary cannot be performed.

As described above, according to this embodiment, in the optical disk of the sample servo system, the capacity can be increased without changing the servo characteristics. Also,
If the clock frequency is not switched using this apparatus, recording and reproduction of an optical disk to which the present invention is not applied can be performed without any problem.

Although the present embodiment has been described using numerical values by taking as an example the case of dividing into four regions, the gist of the present invention is not limited by the number of divisions or the numerical values described above. And various combinations are possible.

[0036]

According to the present invention, the recording capacity of an information recording medium such as an optical disk by the sample servo method can be increased without changing the sampling period of the servo information.

[Brief description of the drawings]

FIG. 1 shows a waveform diagram of an embodiment of a reproduction signal and a clock for information recording / reproduction obtained by an optical disk according to the present invention.

FIG. 2 is a configuration diagram of a first embodiment of an optical disk device using a sample servo system suitable for recording and reproducing information on and from an optical disk according to the present invention.

FIG. 3 is a schematic diagram showing area division of an optical disc.

FIG. 4 is a diagram showing a numerical example when an optical disc is divided into four areas.

FIG. 5 is a configuration diagram of a clock recovery circuit.

FIG. 6 is a configuration diagram of a second embodiment of an optical disk device using a sample servo method suitable for recording and reproduction on an optical disk according to the present invention.

FIG. 7 illustrates a first example of the clock recovery circuit according to the second embodiment.
It is a lineblock diagram of an Example of a.

FIG. 8 illustrates a second example of the clock recovery circuit according to the second embodiment.
It is a lineblock diagram of an Example of a.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 optical disk 3 optical pickup 7 modulation circuit 8 demodulation circuit 9 a to 9 d clock recovery circuit 10 selection circuit 11 tracking error detection circuit 12 control device 91 phase comparator 92 low-pass filter 93 voltage-controlled oscillator 94 frequency divider

Continuation of the front page (56) References JP-A-64-91323 (JP, A) JP-A-63-211137 (JP, A) JP-A-61-294640 (JP, A) JP-A-61-175968 (JP, A) , A)

Claims (4)

(57) [Claims] A plurality of tracks composed of a plurality of tracks;
A disk-shaped recording medium having a
Two tracking pits offset by
Servo area including at least a certain angle on the track
And the servo area adjacent to the track in the circumferential direction.
Equally divide the detection interval between areas and keep the zone constant within each zone.
Record signals on the track at different recording time intervals for each track
Information recording medium and composed. 2. The information recording medium according to claim 1, wherein
Therefore, the recording time interval becomes shorter in the zone on the outer peripheral side.
An information recording medium characterized by the following . 3. The information recording medium according to claim 1, wherein
The servo area in all zones
Servo signal at fixed time intervals that equally divide the detection interval of the area
And the above recording time interval is the zone on the innermost side.
Is the same as the fixed time interval of the servo area.
Information recording medium according to symptoms. 4. A plurality of tracks composed of a plurality of tracks.
A disk-shaped recording medium having a
Two tracking pits offset by
Servo area including at least a certain angle on the track
And the servo area adjacent to the track in the circumferential direction.
An information area is provided between the areas, and the servo area and the information area
Configure the segment and determine the number of sectors contained in one track
The zone on the outer peripheral side is more numerous and is included in one sector.
An information recording medium in which the number of segments is smaller in the zone on the outer peripheral side .