JPH08195034A - Information recording medium - Google Patents

Abstract

PURPOSE: To provide an information storage medium which does not require the changing of the sample period of servo information and is increased in recording capacity. CONSTITUTION: Servo regions and information regions are alternately arranged in the circumferential direction of a recording medium on a disk and these servo regions are arranged at specified angle intervals in such a manner that servo signals 23 are detected at every specified period at the time of rotation at a specified angular velocity. This information recording medium is recorded with the servo signals at the specified servo clock 24 to equally divide the detection intervals of the servo regions at the time of rotation at the specified angular velocity in the servo regions and is recorded with the information at the clocks 24a to d of the frequency different from the frequency of the servo clock 24 by equally dividing the arrangement intervals of the servo regions in the information regions. For example, the frequencies of the clocks for recording and reproducing are made higher toward the outer peripheral side of the disk, by which the recording density on the disk is improved and the recording capacity is increased.

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 Heretofore, in this type of optical disk apparatus, a tracking system is often employed in which a guide groove is provided on the disk in advance and control is performed so that the light beam is positioned above the guide groove. The control error signal in this case is obtained continuously by detecting the diffracted light from the guide groove from the reflected light of the light beam, and is called a continuous servo system. In this continuous servo system, there is a problem that the difference in the shape of the guide groove and the reflectance affects the error signal and deteriorates the tracking accuracy. In addition, since a large amount of light beam is emitted during recording as compared with reading, the amount of reflected light also increases in proportion, so that an error signal can be correctly obtained and control can be performed even in such a case. Such consideration is needed.

On the other hand, in the sample servo system, the guide groove is not used as a means for obtaining servo information, but the track is divided into a servo area and a data area, and the servo areas and the data areas are alternately arranged. Then, control is performed so that the light beam passes over this servo area.
The control error signal is recorded in advance in the servo area as a set (two) of pits that are delicately offset in opposite directions centering on the track position, and 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 system, 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. That is, some of the problems of the continuous servo system are solved, such as the effect of the increase in the laser light amount of 1. does not occur. Regarding this sample servo system, SP I E, Proceedings, Optical Mass Data Storage I
I, Vol. 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 a larger capacity as the amount of information handled increases. For that purpose, it is necessary to improve the recording density on the disc. In this regard, the so-called C.I. A. In the case of the V (Constant Angular Velocity) method, the pit cycle is limited in the innermost circumference where the linear velocity is the slowest. As a result, there is a margin toward the outer circumference, and for example, the recording density is reduced to 1/2 in the outer peripheral portion having a diameter twice the innermost circumference. Thus, C.I. A. V. In the method, the recording capacity of the disc is not fully utilized, resulting in waste.

On the other hand, C.I.
L. V. In the (Constant Linear Velocity) method, the recording density is the same from the inner peripheral side to the outer peripheral side, and the maximum recording capacity can be obtained. However, C.I.
L. V. In this 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 drawbacks of both methods, the disk is divided into a plurality of areas (zones) in the radial direction, and different methods are adopted so that the recording density becomes high in each area. A device for setting the rotation speed is disclosed in Japanese Patent Laid-Open No. 61
No.-17223. Similarly, there is 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.
It is described in Japanese Patent 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 the servo area is detected and clock reproduction is performed based on this. Since this reproduced clock serves as a reference for all operations including the servo, it is necessary to always obtain a stable clock. Further, since the cycle of obtaining the servo information affects the servo characteristics, it is necessary to make the cycle constant. However, if the number of revolutions or the recording data cycle is changed depending on the area on one disk, the cycle of servo information changes at the same time and the servo characteristics also change, so the problem of having to switch the servo characteristics also arises. is there.

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

[0009]

The above object is to arrange servo areas and information areas alternately in the circumferential direction of a recording medium on a disk, and to detect a servo signal at a constant cycle when rotating at a constant angular velocity. The servo areas are arranged at constant angular intervals as shown in the figure. In the servo areas, servo signals are recorded at constant time intervals that equally divide the servo area detection intervals during constant angular velocity rotation. The recording signal is recorded at recording time intervals that equally divide the detection interval of, and at least the recording signal is recorded at a recording time interval of the information area different from the recording time interval of the servo area. This is achieved by using an information recording medium.

In this case, the recording in the information area is
It is possible that the recording time interval of the signal is different depending on the radial direction of the recording medium when rotating at a constant angular velocity, and the recording interval is shorter on the outer peripheral side.

[0011]

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,
The servo clock of constant frequency can be reproduced. If servo information is detected using this servo clock, stable servo control operation can be secured. On the other hand, since the servo area arrangement interval 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.

[0012] For example,
By increasing the clock frequency for information recording / reproducing, the recording density on the disk can be improved and the recording capacity can be increased.

[0013]

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 recording / reproducing data applied to an optical disc according to the present invention. As shown in (iv) to (vii), clocks 24a to d for data recording / reproducing
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 device of the sample servo system suitable for information recording / reproduction of the optical disk of the present invention. However, FIG. 2 does not show parts that are not related to the description of the features and operations of the present invention. In the figure, 1 is an optical disk, 2 is a disk motor, and 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,
Reference numeral 11 is a tracking error detection circuit, and 12 is a control circuit.

The optical disk 1 is rotated by a disk motor 2 at a constant angular velocity. 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 the intensity of the light beam. Data is recorded on the optical disc 1 by changing the reflectance of light according to the intensity of the irradiated light beam and leaving the change of reflectance even after the light beam passes. In reading, the laser diode emits a weak light beam that does not cause a change in reflectance as in writing, and the reflected light when the light beam is applied to the optical disc 1 is detected by a photodetector to detect the reflectance. The difference in the amount of reflected light 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 the recording / reproducing of data by such a light beam, the light beam is accurately applied onto a previously reserved track on the optical disk.
So-called tracking control is necessary. In the sample servo method, as shown in (i) of FIG. 1, 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 as a discrete signal rather than as a continuous signal. The tracking error information is obtained by 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. That is, since the two tracking pits are recorded on both sides of the center line of the track with an equal distance offset, when the irradiation position of the light beam deviates from the center of the track, the tracking pits on the deviated side are formed. The amount of reflected light of the track pit increases and the amount of reflected light of the tracking pit on the opposite side decreases. When the light beam irradiates the center of the track correctly, the reflected light amounts of both tracking pits are the same. Therefore, the amount and direction of tracking deviation can be discriminated by the difference between the amounts of reflected light of both tracking pits and the polarity, and tracking control is performed by controlling the light beam so as to cancel it.

In order to realize the tracking control by such a sampling method, a clock signal for accurately extracting the reproduction signal from the tracking pit shown in (ii) of FIG. 1 is required. To obtain this servo clock signal, it 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. The tracking pit reproduction signal can be accurately extracted by forming the tracking pit in advance so that the reproduction signal can be obtained at a position synchronized with the clock signal.

As described above, the sample servo system is characterized in that the clock synchronized with the rotation of the disk is used, and this clock is used not only for obtaining servo information but also for recording / reproducing data in the data area. . The larger the number of servo information in one round of the disk, the better the servo characteristics can be obtained, but the data area becomes small and the recording capacity decreases. Conversely, if the number of servo areas is reduced, sufficient servo characteristics cannot be obtained. When rotating at 1800 rpm, an appropriate number is 1000-per disk circumference.
It is 2000 pieces. In order to record and reproduce data by moving the pickup randomly from the inner circumference to the outer circumference of the disc, it is necessary that the interval of the servo areas on the time axis, that is, the arrangement interval of the servo areas is 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 periphery at regular intervals. As a result, even if the pickup is moved in the radial direction of the disc, the reproduced signals in the servo area can be obtained at constant intervals, so that constant servo characteristics can always be obtained, and since the tracking operation can be performed immediately at the destination, high-speed access is possible. realizable.

However, the fact that the servo area is constant on the time axis requires that the above-mentioned clock is also constant,
As a result, the recording / reproducing of data performed using the same clock also has a constant cycle, so that the recording density decreases toward 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 an optical disc according to the present invention. In this optical disc 1, servo areas are arranged radially from the center of the disc, and when rotated at a constant rotation, a reproduction signal is obtained at a constant time interval.

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

An example of division of each area is shown in FIG. Each area is 5
Each segment is divided into 000 tracks, and the area a is 32 sectors per round, and if one segment is composed of the servo area and the data area, the data recorded in one segment is 16 bytes, and the recording clock frequency is 11.14.
56 MHz. This clock frequency is the same as the clock for detecting the servo signal, and is a clock that divides the clock pits into 270 equal parts based on the clock pits described above. Area b is 39 sectors per round, 20 bytes per segment, and recording clock frequency is 13.9.
It becomes 526MHz and this frequency is 3 between clock pits.
It will be divided into 38 equal parts. Similarly, areas c and d are also set as shown in the figure, and the recording clock frequencies correspond to 405 equal parts and 473 equal parts of clock pits, respectively.

The recording capacity is 43.35 MB, which is 1.35 times as large as 320 MB when the entire area is recorded with the setting a.
You get yte. The clock frequency is generated 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 16.187 MHz, and the clock recovery circuit d is 1.
Each generates 9.5254 MHz. Each clock output is input to the selection circuit 10, and the clock generated by the clock reproduction circuit a is input to the tracking error detection circuit 11 and used for extracting the tracking pit reproduction signal.

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

The clock recovery circuits 9a to 9d are so-called PLL (Phase Locked Loop) shown in FIG.
Locked loop) circuit. This PLL
The circuit is composed of a phase comparator 91, a low pass filter 92, a voltage controlled oscillator 93, and a frequency divider 94.
The oscillation frequency and the phase of the voltage controlled oscillator 93 are controlled so that the output of the voltage control oscillator 93 and the reference signal input from the outside are in phase with each other. 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 the reference signal. In this example, the reference signal is the 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 reproduction circuit a, the frequency division ratio of the frequency divider 94 is 270, and the voltage controlled oscillator 93 has a central value of the control voltage of 11.1456 MH.
The oscillation frequency control element is adjusted to generate z. Similarly, in the clock recovery circuits b to d, a predetermined frequency division ratio and oscillation frequency are set.

FIG. 1 shows the relationship between the reproduced signal and the information recording / reproducing clocks 24a to 24d on the actual optical disk.
(Iv) to (vii). In the figure, a to d correspond to the regions a to d in FIG. 3, respectively. Reference numeral 23 is a clock pit, and 25a to 25d are head pits of the data area. Since the clocks are generated in synchronization with the clock pits, the phases of all the clocks are aligned at this point, but thereafter, the frequencies are different, so that there is a phase shift between the clocks. The start position of the data area is set at a certain interval or longer (time distance) in order to prevent the additional write data from affecting the clock pit. Similarly, the interval between the end point of the data area and the first tracking pit is also maintained at a certain interval or more.

As shown in FIGS. 3 and 4, when the area is equally divided into four areas, areas a, b, c and d are used as a reference.
Can obtain recording capacities of 1.25 times, 1.5 times, and 1.75 times, respectively. When the total number of clocks is 270, the allocation of the servo area and the data area between one segment in the area a is 30 clocks in the servo area and 240 clocks (15 clocks × 16 bytes) in the data area. If the same allocation ratio is applied to the area b, it is multiplied by 1.25, 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 clocks that can be taken is 337 or 338. In the former case, the servo area is 37 clocks, which is shorter than the original length by 0.5 clocks, 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 there is no problem with the interval with the data area, but the pit interval of the first track in area b is shorter than the first part of area a, that is, the innermost circumference of the disk. I will end up. 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 / reproducing is performed on a disc having an innermost radius of 30 mm and an outermost radius of 60 mm at a pitch of 1.5 μm, the start point of the area b is 0.57 m from the point of 37.5 mm.
This is achieved by displacing the outer circumference. The number of tracks in this portion is 57, and the recording capacity is reduced by this amount, but this is not a problem from the viewpoint of the total capacity. Which of the three methods is adopted is determined by the margin setting of the entire optical disk device. Area c,
Also in d, the clock frequency is determined based on the same idea.

FIG. 6 shows a second embodiment of an optical disk device suitable for the optical disk of the present invention. In the figure, the same components as those in FIG. 2 are designated by the same reference numerals. In this example, it has two clock recovery circuits. FIG.
The operation will be described assuming that the optical disk of FIG. 4 is used. The first clock reproduction circuit 9 generates a clock 11.1456 MHz for detecting a tracking pit, and the second clock reproduction circuit 9 ′ of the control device 12. Four types of clocks are generated according to the selection signal.

FIG. 7 shows a configuration example of the second clock recovery circuit 9 '. The dividing ratio variable frequency divider 95 is set to 27 by the selection signal.
Frequency divisions of 0, 338, 405 and 473 are set. The oscillating element of the voltage controlled oscillator 93 is adjusted so as to oscillate the center frequency of 4 frequencies at the center value of the control voltage. The clock recovery circuit as a whole must 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, not only the division ratio but also the center frequency of the voltage controlled oscillator is switched by the selection signal, so that the switching element 96 switches the oscillation element. Each oscillating element is adjusted so that 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,
The access speed decreases because the synchronous operation of the clock recovery circuit is performed every time the area boundary is crossed. In addition, continuous recording and reproduction beyond the boundary cannot be performed.

As described above, according to this embodiment, in the sample servo type optical disk, 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 the case of dividing into four areas as an example, the gist of the present invention is not limited by the number of divisions or the numerical values described above. , Various combinations are possible.

[0033]

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 drawings]

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

FIG. 2 is a configuration diagram of a first embodiment of an optical disc apparatus by a sample servo system suitable for recording / reproducing of an optical disc according to the present invention.

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

FIG. 4 is a diagram showing an example of numerical values 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 by a sample servo system suitable for recording / reproducing of an optical disk according to the present invention.

FIG. 7 shows a first clock recovery circuit according to the second embodiment.
It is a block diagram of the Example of.

FIG. 8 is a second clock recovery circuit according to the second embodiment.
It is a block diagram of the Example of.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 optical disk 3 optical pickup 7 modulation circuit 8 demodulation circuit 9a-9d clock reproduction 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

Claims (2)

[Claims] 1. A servo area and an information area are alternately arranged in a circumferential direction of a recording medium on a disk, and a servo area is arranged at a constant angular interval so that a servo signal is detected at a constant cycle when rotating at a constant angular velocity. In the servo area, the servo signal is recorded at a constant time interval that evenly divides the servo area detection interval during constant angular velocity rotation, and in the information area, the servo area detection interval is equally divided during constant angular velocity rotation. An information recording medium, wherein recording signals are recorded at time intervals, and at least a portion in which the recording signals are recorded at a recording time interval of the information area different from a recording time interval of the servo area. 2. The information recording medium according to claim 1, wherein the recording in the information area has a different signal recording time interval depending on the radial direction of the recording medium when rotating at a constant angular velocity, and is shorter on the outer peripheral side. An information recording medium characterized by being performed at intervals.