JPH0660571A - Recording medium and recording and reproducing device - Google Patents

Abstract

(57) [Summary] [Object] The present invention provides a recording medium capable of high density and capable of generating a reproduction clock phase-synchronized with all data even at high speed rotation, and capable of high-speed seek of recorded information, and recording / reproduction. It is intended to realize the device. [Structure] Among the servo bytes arranged by the zoning method, servo bytes arranged so as to be radially arranged from the innermost peripheral side to the outermost peripheral side of the disk are provided, and rotation is performed based on the radially arranged servo bytes. By controlling the speed, it is possible to realize a high-speed rotation operation such as a high-speed seek by CAV control, and the phase lock of the PLL is zoned by generating the reproduction clock based on the servo bytes provided radially. It is possible to avoid the temporary cancellation during this period, and it is possible to generate a reproduction clock phase-synchronized with all data even during high-speed rotation.

Description

Detailed Description of the Invention

[0001]

[Table of Contents] The present invention will be described in the following order. Industrial Application Conventional Technology (FIGS. 7 and 8) Problems to be Solved by the Invention Means for Solving Problems (FIGS. 1 and 4) Actions (FIGS. 1 and 4) Embodiments (FIGS. 1 to 1) Figure 6) Effect of the invention

[0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording medium and a recording / reproducing apparatus, and is particularly suitable for being applied to a recording medium and a recording / reproducing apparatus adapted to record / reproduce by a sample servo system.

[0003]

2. Description of the Related Art Conventionally, for example, an optical disk or a magneto-optical disk is used as a recording medium for recording / reproducing by a sample servo system. In the sample servo system, the recording area is divided into a servo area and a data area, so that the amount of signal leaking into the servo area is reduced and a tracking error can be reliably detected. Further, in the sample servo system, a clock signal is extracted from the servo area and PLL control is performed based on this clock signal.

In a recording / reproducing apparatus for recording / reproducing various data by using an optical disk or a magneto-optical disk as a recording medium, CAV (constant rotational speed) is used as a method of controlling the disk rotational speed at the time of recording / reproducing data. ) There are a control method and a CLV (constant linear velocity) control method.

In the CAV system, the speed control on the recording / reproducing apparatus side is relatively simple, and the control information such as the track address can be recorded so as to be aligned in the disk radial direction.
There is an advantage that the address search can be easily performed. However, since the recording density on the outer peripheral side of the disk is sparser than that on the inner peripheral side, there is a drawback that the information recording amount as a whole is reduced.

On the other hand, the CLV system has an advantage that the information recording amount can be increased as compared with the CAV system because the recording density can be made constant on the inner and outer circumference sides, while the CLV system rotates according to the position of the optical pickup. There is a drawback that the speed control system becomes complicated because it is necessary to change the speed. Also CLV
In the method, it is difficult to align and record the control information such as the track address in the disk radial direction, and therefore, there is a drawback that the address search takes time.

In general, in the case of a recording medium having a large storage capacity, for example, a magneto-optical disk, in order to make it easy to access desired data, the CA can be easily searched for an address.
The V method is often adopted. However, since the CAV system has a drawback that the information recording amount becomes small as described above, the zoning recording system has been proposed as a method for increasing the information recording amount in the CAV system.
As shown in FIG. 7, the zoning recording method divides the recording area of the disk into three zones from zone A to zone C from the inner circumference side to the outer circumference side, and a plurality of concentric circles formed in each zone. The tracks are recorded / reproduced at the same rotation speed, while the rotation speed or the clock frequency is changed for each zone, thereby improving the information recording amount.

Here, the pit data recorded from zone A to zone C are as shown in FIG.
The recording densities of the innermost tracks T _A1 , T _B1 and T _C1 of _C are set to be the same, and the recording densities become lower as the tracks on the outer peripheral side in each zone A, B and C are set. It is set. Therefore, in the zoning recording method, when the spindle motor is constantly driven at a constant rotation speed to change the clock frequency of the PLL when the zone changes, or when the zone changes while the clock frequency is always kept constant. Recording / reproducing is performed by changing the rotation speed.

Thus, the zoning recording method can compensate for the defect of the CAV control method in which the recording linear density decreases toward the outer circumference side, and the information recording amount can be greatly increased.

[0010]

By the way, in such a zoning method, the servo bits are arranged so as to be aligned in the radial direction of the disk in the same zone, but the servo bits are arranged between the zones. Since there is no correlation between the positions, the phase lock due to the PLL is temporarily canceled when the zone changes during recording / reproducing, which causes the seek time between the zones to be delayed.

The present invention has been made in consideration of the above points. It is possible to record / reproduce recorded information at a high recording linear density and to generate a reproduction clock phase-synchronized with all data even at high speed rotation. The present invention aims to realize a recording medium and a recording / reproducing apparatus capable of achieving high-speed seeking of recorded information.

[0012]

In order to solve such a problem, in the present invention, a predetermined number of zones Zone 1, Zone 2, Zone 3, Zone 4 ... Are formed in the radial direction of the disk 1, and the zones Zone 1, Zone 1 are formed. 2, Zone 3, Zone
4 ... Based on the sample information of the servo bytes SB ₀ and SB ₁ provided at predetermined positions within at least the zones Zone 1, Zone 2, Zone 3, Zone 4 ... While keeping the rotation speed constant. Each Zone Zone 1, Zone
In the recording medium 1 of the sample servo system in which tracking control is performed at different rotation speeds or different clock frequencies between 2, Zone 3, Zone 4, ..., Of the servo bytes SB ₀ and SB ₁ , A first servo bite SB ₀ and servo bits SB ₀ and S B provided so as to be radially arranged from the inner peripheral side to the outermost peripheral side.
Zones of B ₁ , Zone 1, Zone 2, Zone 3, Zone
e 4 ... All track Tr on the innermost side
₁₁ , Tr ₂₁ , Tr ₃₁ , Tr _41, ... Are arranged so that the arrangement intervals are equal, and the zones Zone 1, Zone 1 are arranged.
2, Zone 3, Zone 4 ... Second servo bits SB arranged radially in the disk 1 in the radial direction.
Be prepared with ₁ .

Further, in the present invention, the recording medium 1 is always rotated at a high speed at a constant rotation speed based on the sample information obtained from the first servo byte SB ₀ , and the zone Zone is used.
1, the Zone 2, the Zone 3, the Zone 4, ..., The clock frequency is variably controlled, and / or the recording medium 1 is set to the Zone Zone based on the sample information obtained from the first and second servo bytes SB ₀ and SB _1. 1, Zone 2, Zone 3,
Rotate at low speed at different rotational speeds in Zone 4 and control the clock frequency constant.

In the present invention, the first servo byte SB ₀ is the first and second pits P2 and P3, respectively.
And the second servo bite SB ₁ has a first pit P1 and first and second pits P2 and P3.
Of the first and second servo bytes SB ₀ and SB ₁ have different pit shapes with respect to the pits forming the other recording information.

[0015] Further, in the present invention, by detecting the second pit P3 of the first servo byte SB ₀ detects the first servo byte SB _0, the first servo byte SB ₀ first pit The recording medium 1 is rotated at a constant rotation speed so that the read interval time of P2 becomes constant, and the read interval time of the first pit P2 and the second
Based on the shape of the pit P3 of each zone Zone 1, Zon
The clock frequency is variably controlled for each of e 2, Zone 3, Zone 4 ...

[0016]

The servo byte SB ₀ arrayed so as to be aligned from the innermost periphery to Wataru connexion radially outermost side of the disk 1 of the servo byte SB ₀ and SB ₁ arranged by [action] zoning scheme provided, disposed on the radially Servo byte S
By controlling the rotation speed based on B ₀ , CAV
It is possible to realize a high-speed rotation operation such as a high-speed seek by control, and the reproduction clock is generated based on the servo bytes SB ₀ radially provided, so that the phase lock of the PLL is set to the zones Zone 1, Zone 2, Zon
It is possible to avoid being temporarily released between e3, Zone 4, ... And it is possible to generate a reproduction clock phase-synchronized with all data even at high speed rotation.

[0017]

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

(1) Recording Format In FIG. 1, reference numeral 1 denotes a magneto-optical disk of a sample servo system as a whole, and sample information is extracted from servo bytes SB ₀ and SB ₁ provided on a track to determine a rotation speed and a clock. It is designed to control the frequency. The magneto-optical disk 1 has a plurality of zones in the radial direction.
1, Zone 2, Zone 3, Zone 4 ... And each zone has a plurality of tracks formed concentrically.

Here, each zone Zone 1, Zone 2, Zone
Tracks Tr ₁₁ , Tr on the innermost side of e 3, Zone 4 ...
Numerals ₂₁ , Tr ₃₁ , Tr ₄₁ ... Servo bits SB _{0 in the} form of prepits are provided on the magneto-optical disks 1 so as to be radially arranged from the innermost side to the outermost side.

Further, each of the tracks Tr ₁₁ , Tr ₂₁ , Tr ₃₁ ,
Tr ₄₁ …… Above servo byte SB ₀ and servo byte SB
_{Between 0} and ₀ , the prepito shaped servo bite SB ₁ is

[Equation 1] The number of units represented by the proportional expression is arranged.

Where R1, R2, R3, R4 and N1,
N2, N3 and N4 respectively represent the radial distance from the center of the magneto-optical disk 1 to the tracks Tr ₁₁ , Tr ₂₁ , Tr ₃₁ , Tr ₄₁ and the number of servo bytes SB ₁ arranged between the servo bytes SB _0. It is a thing. As a result, each of the tracks Tr ₁₁ , Tr ₂₁ , Tr ₃₁ , Tr ₃₁ , Tr _41, ... Between the servo bytes SB _{0 of the} tracks Tr ₁₁ , T ₂₁ , respectively.
The servo bite SB ₁ is arranged so that the linear density is constant between r ₂₁ , Tr ₃₁ , Tr _41, ....

Further, each zone Zone 1, Zone 2, Zone
3 and Zone 4 ... other than the innermost track, the positions shown by the dotted line in FIG. 1 are based on the servo bytes SB ₁ of the innermost tracks Tr ₁₁ , Tr ₂₁ , Tr ₃₁ , Tr ₄₁ . That is, the servo bits SB ₁ are arranged at positions radially arranged in the disk radial direction. Magneto-optical disk 1
The servo pattern as described above is formed over the entire disk.

As a result, the recording / reproducing apparatus variably controls the rotation speed of the magneto-optical disk 1 in zone units with the clock frequency set to a constant value as shown in FIG. 2, or as shown in FIG. Further, by adjusting the clock frequency to a predetermined value in units of zones while the rotation speed of the magneto-optical disk 1 is constantly controlled,
All of the above servo bytes SB ₀ and SB ₁ can be extracted.

Here, the servo bytes SB ₀ and SB ₁ are composed of pits of a predetermined shape, and the recording / reproducing apparatus reads the pit shape and the pit pattern to read each zone Z.
The rotation speed or the clock frequency is controlled for each one 1, Zone 2, Zone 3, Zone 4 ...

In practice, the servo bytes SB ₀ and SB ₁ are
As shown in FIG. 4, it comprises servo areas SBA and SBB for 2 bytes provided on the front side of the data area DS,
A pit corresponding to the servo byte SB ₀ or SB ₁ is formed in each of these servo areas SBA and SBB. The servo byte SB ₁ is shown in FIG.
As shown in (A), the longest pit P1 is formed in the servo area SBA as compared with other pits. As shown in FIG. 4B, the servo byte SB ₀ has the longest bit P2 similar to the servo byte SB ₁ formed in the servo area SBA and the servo area SB 0.
A pit P3 having a predetermined length is formed on B.

As a result, the recording / reproducing apparatus sets the read interval time of the pits P1 and P2 formed in the servo area SBA based on the servo bytes SB ₁ and SB ₀ to the zone Z.
If the spindle motor is rotationally driven so as to be constant among one 1, Zone 2, Zone 3, Zone 4, ..., As shown in FIG. 2, the magneto-optical disk 1 is moved to each zone Zone 1, Z.
CLV control can be performed between one 2, Zone 3, Zone 4 ... On the other hand, if the recording / reproducing apparatus rotationally drives the spindle motor so that the reading interval time of the pit P2 formed in the servo area SBA is always constant based on only the servo byte SB ₀ , as shown in FIG. In addition, CAV control is possible on all disks.

The recording / reproducing apparatus for recording / reproducing such a magneto-optical disk 10 has a CLV control circuit and a CAV control circuit, whereby the recording / reproducing apparatus switches between these circuits so that the zones are switched. The CLV mode in which the rotation speed of the spindle motor can be changed and the CAV mode in which the spindle motor is constantly driven to rotate at a constant rotation speed on all disks can be selected.

(2) Structure of CLV control circuit In FIG. 5, reference numeral 10 indicates a CLV control circuit as a whole,
It is composed of a spindle motor control unit 11 and a clock generation unit 12, and an optical pickup 1 of a recording / reproducing unit 13.
The reproduction signal S1 reproduced by 3A is sent to the prepit detection circuit 14 of the spindle motor control unit 11 and to the data extraction circuit 15 of the clock generation unit 12.

The prepit detection circuit 14 sequentially measures the input reproduction signal S1 by the length measuring circuit 16 and the longest detecting circuit 17.
And the pit detecting circuit 14 detects the pit information S2 such as servo data and address data contained in the reproduction signal S1 and the length measuring circuit 1
6 measures the length of each pit based on the pit information S2.

The longest detection circuit 17 detects the longest pit from the measurement results. The longest detection circuit 17 detects the read interval time of the longest pit detected next from the longest pit detected at a certain time point and sends the detection result to the subsequent comparison circuit 18. By the way, the longest pit detected here is the servo area SB of the servo bytes SB ₁ and SB _0.
The pits P1 and P2 formed on A.

The comparison circuit 18 receives the read interval time of the longest pits P1 and P2, and the reference time generation circuit 1
9 receives the reference time output from the reference signal 9, and compares the read interval time with the reference time, and outputs the drive signal S3 that makes the read interval time equal to the reference time.
It is configured to be sent to the spindle motor 21 via the.

The reproduction signal S1 is output from the data extracting circuit 15
Is sent to the longest pit position detecting circuit 22 through the signal line, and the longest pit position detecting circuit 22 detects the position of the longest pit as a phase and sends it to the phase comparing circuit 23 of the PLL circuit as a phase detection signal S4.

The phase comparison circuit 23 inputs the phase detection signal S4 and the frequency division output S5 output from the voltage controlled oscillation circuit (VCO) and obtained through the frequency division circuit 24, and inputs the phase detection signal S4. And the frequency-divided output S5 are compared in phase, and a drive signal S6 obtained according to the comparison result is input to the voltage controlled oscillator circuit 26 via the low-pass filter 25.

The voltage control oscillation circuit 26 outputs an oscillation output having a frequency corresponding to the drive signal S6 to the signal processing section 13B of the recording / reproducing section 13 as a reproduction clock signal S7. As a result, it is possible to obtain a reproduction clock phase-synchronized with the servo bytes SB ₀ and SB ₁ .

(3) Structure of CAV control circuit When it is necessary to rotate the recording medium at high speed such as when performing high-speed seek, the recording / reproducing apparatus, as shown in FIG. 6, includes a spindle motor control unit 31 and a clock. The connection is switched to the CAV control circuit 30 composed of the generator 32.

[0036] Here, the CAV control circuit 30 by detecting the servo bytes SB _0, the servo bytes SB ₀
The rotation speed and the clock frequency are controlled on the basis of the sample information. That is, the CAV control circuit 30 inputs the reproduction signal S1 reproduced by the optical pickup 13A to the longest detection circuit 34 via the prepit detection circuit 33.

The longest detection circuit 34 detects the longest pit to detect the servo byte SB ₀ and the servo byte SB _1.
Is detected and the pit information S10 is sent to the servo byte detecting circuit 35. The servo byte detection circuit 35 extracts the servo bytes SB ₀ and the servo bytes SB ₀ corresponding to the bits formed in the servo area SBB from the servo bytes SB ₀ and SB ₁ and detects the bit information S11 of the servo bytes SB ₀ in time. To the circuit 36.

The time detection circuit 36 detects the pitch P detected at a certain time based on the pitch P2 of the servo byte SB _0.
2, the read interval time of the pit P2 detected next is detected, and the read interval time information S13 is compared with the comparison circuit 3
7 and the arithmetic circuit 38. The comparison circuit 37 reads the read interval time information S13 of the pit P2.
In addition to receiving the reference time information output from the reference time generation circuit 39, the read interval time is compared with the reference time, and the drive signal S12 that makes the read interval time equal to the reference time is driven and amplified by the drive amplifier circuit. It is adapted to be sent to the spindle motor 21 via 40.

The reproduced signal S1 is sent to the servo byte detection circuit 41 of the clock generation unit 32. The servo byte detection circuit 41 detects the pit P3 of the servo byte SB ₀ and also detects the read time of the pit P3, and based on this read time, each zone Zone 1, Zone 2,
The number of servo bytes SB ₁ arranged between the servo bytes SB _{0 of} Zone 3, Zone 4, ... Is detected and the number information S14 is sent to the arithmetic circuit 38.

Here, the read time of the pit P3 becomes shorter as the radius distance becomes longer according to the disk radius distance at which the servo byte SB ₀ is arranged, and the servo byte SB becomes shorter.
The number of servo bytes SB ₁ between ₀ is the number of servo bytes SB _0.
Is proportional to the radius distance of the disposed disk, the servo byte detection circuit 41 determines that the servo byte SB between the servo byte SB _{0 and} the read time of the pit P3.
It is designed to detect the number of ₁ 's.

The arithmetic circuit 38 reads interval time information S13 in between the servo byte SB ₀ with receiving the number information S14 in the servo bytes SB ₁ between the servo bytes SB ₀
And the servo byte S between the servo bytes SB ₀
The number of servo bytes SB ₁ per unit time is calculated by dividing the number of B ₁ by the read time between the servo bytes SB ₀ , and the operation result S15 is calculated by the phase comparison circuit 42.
It is designed to be sent to.

The phase comparison circuit 42 inputs the operation result S15 and the frequency division output S16 output from the voltage controlled oscillator circuit (VCO) and obtained through the frequency divider circuit 43, and divides the operation result S15 from the operation result S15. Phase comparison is performed with the frequency output S16, and the drive signal S17 obtained according to the comparison result is input to the voltage controlled oscillator circuit 45 via the low pass filter 44. The voltage control oscillator circuit 45 outputs an oscillation output having a frequency corresponding to the drive signal S17 to the signal processing unit 13B of the recording / reproducing unit 13 as the reproduction clock signal S18. As a result, it is possible to obtain a reproduction clock phase-synchronized with the servo bytes SB ₀ and SB ₁ .

(4) Operation of the Embodiment With the above configuration, when recording / reproducing the magneto-optical disc 1 at a low speed rotation, the recording / reproducing apparatus is the CLV control circuit 1.
0, and the spindle control unit 11 and the clock generation unit 12 of the CLV control circuit 10 detect the longest bits P1 and P2 of the servo bytes SB ₀ and SB ₁ , and thereby the longest bits P1 and P2. Spindle motor 2 based on the read interval time of
1 is rotationally driven, and servo bytes SB ₀ and S ₀
Reproducing clock S7 phase-synchronized is generated at the B _1.

Thus, in the low speed rotation mode, as shown in FIG. 2, the rotation speed of the magneto-optical disk 1 is variably controlled in units of zones with the clock frequency always set to a constant value.

On the other hand, when recording / reproducing the magneto-optical disc 1 at high speed or performing high-speed seek, the recording / reproducing apparatus is controlled by the CAV control circuit 30.
Only the pit information of the servo byte SB ₀ is detected by the spindle control unit 31 and the clock generation unit 32 of the CAV control circuit 30, whereby the spindle motor 21 is rotationally driven based on the read interval time of the pit P2, and the pit information is read. P2 read interval time and pitch P
Servo bytes SB ₀ and S based on the read time of 3
Reproducing clock S18 phase-synchronized is generated at the B _1.

Thus, in the high-speed rotation mode, as shown in FIG. 3, the clock frequency is adjusted to a predetermined value on a zone-by-zone basis while the rotation speed of the magneto-optical disk 1 is constantly controlled. .

(5) Effects of the Embodiments With the above configuration, in the magneto-optical disk 1 in which servo bytes are recorded by the zoning method, the magneto-optical disk 1 is radially formed from the innermost side to the outermost side. Since the servo bytes SB ₀ are arranged side by side, if the spindle motor 21 is rotationally driven so that the detection time interval of the servo bits SB ₀ is constant, the magneto-optical disk 1 will be generated.
Can be CAV controlled, and if a reproduction clock is generated based on the detection time interval of the pit P2 of the servo byte SB ₀ and the read time of the pit P3, P
It is possible to prevent the phase lock of the LL from being released between the zones, which makes it possible to realize a high-speed rotation operation such as a high-speed seek.

(6) Other Embodiments In the above-mentioned embodiments, the case where the magneto-optical disk 1 is used as the recording medium has been described, but the recording medium of the present invention is not limited to this, and the servo byte is used by the zoning method. The present invention can be applied to various recording media provided with.

Further, in the above-mentioned embodiment, the servo bytes SB ₀ and SB ₁ are formed with the pits P1 and P of the predetermined length.
2 and P3, the servo byte SB ₀
And SB ₁ may be constituted by, for example, wobbling pin bracts, the shape of the servo byte SB ₀ and SB ₁ can be applied a variety of shapes that can identify the servo byte SB ₀ and SB ₁ from other data .

In the above embodiment, the CLV control circuit and CA are used as the recording / reproducing device for the magneto-optical disk 10.
The case of having a V control circuit and selectively switching connection with these circuits has been described, but the recording / reproducing apparatus of the present invention is not limited to this, and has a CLV control circuit or a CAV control circuit. Can also be applied.

Further, in the above-mentioned embodiment, the servo bits SB ₀ are provided radially from the innermost peripheral side to the outermost peripheral side of the disk, but the present invention is not limited to this.
Instead of the servo byte SB ₀ , an index sector is provided along the radial direction of the disk, a frequency generator is provided in the spindle motor, and the index sector is extracted by the frequency generator to servo between the index sectors. A gate signal corresponding to the byte SB ₁ may be generated to sample the servo byte included in the gate signal.

[0052]

As described above, according to the present invention, among the servo bytes arranged by the zoning method, the servo bits arranged so as to be radially arranged from the innermost peripheral side to the outermost peripheral side of the disk are provided, By controlling the rotation speed based on the radial servo bits, C
It is possible to realize high-speed rotation operation such as high-speed seek by AV control. In addition, PL is generated by generating the reproduction clock based on the servo bytes provided in the radial direction.
It is possible to prevent the phase lock of L from being temporarily released between zones, and it is possible to generate a reproduction clock phase-synchronized with all data even at high speed rotation.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a servo byte recording position of a recording medium according to the present invention.

FIG. 2 is a characteristic curve diagram for explaining the CLV control operation of the recording medium according to the present invention.

FIG. 3 is a characteristic curve diagram for explaining the CAV control operation of the recording medium according to the present invention.

FIG. 4 is a schematic diagram showing an embodiment of a pit shape of a servo bite according to the present invention.

FIG. 5 is a block diagram showing an embodiment of a CLV control circuit according to the present invention.

FIG. 6 is a block diagram showing an embodiment of a CAV control circuit according to the present invention.

FIG. 7 is a schematic diagram showing a zoning recording method according to a conventional example.

FIG. 8 is a schematic diagram showing a zoning recording method according to a conventional example.

[Explanation of symbols]

1 ... Magneto-optical disk, 10 ... CLV control circuit, 1
1, 31 ... Spindle control unit, 12, 32 ... Clock generation unit, 30 ... CAV control circuit, SB ₀ , SB ₁ ...
… Servo bytes, P1 to P3… pits.

Continuation of front page (51) Int.Cl. ⁵ Identification number Office reference number FI technical display location G11B 20/12 9295-5D 20/14 351 A 8322-5D

Claims (4)

[Claims] 1. A predetermined number of zones are formed in the disk radial direction, and based on sample information of a servo bite provided at a predetermined position in the zone, at least in each zone, the rotational speed is kept constant while each zone is kept constant. In a recording medium of a sample servo system in which tracking control is performed at different rotation speeds or different clock frequencies, the servo bytes are arranged radially from the innermost side to the outermost side of the recording medium. Of the first servo bite provided in the above-mentioned servo bite and all of the tracks on the innermost circumference side of each of the above-mentioned zones are arranged so as to have the same spacing. And a second servo bite arranged so as to be radially arranged on the recording medium. 2. The recording medium is always rotated at a high speed at a constant rotation speed based on sample information obtained from the first servo bite, and the clock frequency is variably controlled between the zones, and / or the first and the first. 2. A recording / reproducing apparatus characterized in that the recording medium is rotated at a low speed at different rotation speeds between the zones and the clock frequency is controlled to be constant based on sample information obtained from the second servo byte. 3. The first servo bite has first and second pits, respectively, the second servo bite has the first pit, and the first and second pits have the following: 2. The recording medium according to claim 1, wherein the recording medium has different pit shapes with respect to the pits for forming other recording information except the first and second servo bytes. 4. The first servo byte is detected by detecting the second pit of the first servo byte, and the read interval time of the first pit of the first servo byte is constant. As described above, the recording medium is rotated at a constant rotation speed, and the clock frequency is variably controlled for each zone based on the read interval time of the first pit and the shape of the second pit. Recording / reproducing apparatus characterized by.