JP2654766B2 - Information playback device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for reproducing a digital signal recorded on a disc-shaped information medium on which information is recorded, and more particularly, to an information medium such as an optical disk used for an external storage device of a computer. The present invention relates to an apparatus for increasing a recording capacity.

[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 diffraction 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. Also, during recording, a larger amount of light beam is emitted than during reading, so the amount of reflected light also increases proportionally. In such a case, consideration should be given to obtaining an error signal correctly and performing control. Is needed.

On the other hand, in the sample servo system, a guide groove is not used as means for obtaining servo information, but a servo area and a data (information) area are divided on a track and a servo area and a data area are alternately formed. And control is performed so that the light beam passes over this servo area. The control error signal has a small offset 1 in the servo area in the opposite direction to the track position.
The set (two) pits are recorded in advance, and are obtained by detecting the difference in the amount of reflected light when the light beam passes through both pits. As described above, according to the sample servo method, there is no influence of the guide groove, and the control error signal is obtained only in the servo area. Further, in this area, only the operation for obtaining the servo information is always performed. Some of the problems of the continuous servo system are solved, such as the effect of increasing the amount of laser light does not occur. Regarding this sample servo system, SPIE, Proceedings, Optical Mass Data Storage I
I, 695 (1986), pp. 239-246
Page (SPIE, Proceedings, Optical Mass DataS
torageII, vol. 695 (1986) pp239-2
46).

On the other hand, in the information processing apparatus using such as an optical disk or a magnetic disk, but devices of larger capacity than with the amount of information increases to handle has been demanded. For this purpose,
It is necessary to improve the recording density on the disk. A so-called C.I. which performs recording and reproduction by rotating a disk at a constant angular velocity. A. In the V (Constant Angular Velocity) method, the pit period is limited at the innermost circumference where the linear velocity is the slowest. Therefore, 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.

[0005] On the other hand, C.I.
L. V. In the (Constant Linear Velocity) method, the same recording density is obtained from the inner periphery to the outer periphery, 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 apparatus for a computer that requires random access and high-speed access. Therefore, as one of the methods aimed at eliminating the disadvantages of both types, there is a device that divides a disk into a plurality of regions in the radial direction and sets different rotation speeds so that the recording density is increased in each region. It is described in JP-A-61-17223. Japanese Patent Application Laid-Open No. Sho 61 (1994) 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. 175968.

[0006]

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 reproducing apparatus for reproducing information on a disc-shaped information medium by a sample servo method in which a recording capacity is increased without changing a sample period of servo information.

[0008]

An object of the present invention is to drive a disc-shaped information medium in which information areas and servo areas are alternately arranged on the same track and the servo areas are arranged at constant angular intervals, at a constant angular velocity. Means for irradiating the information medium with a light beam and detecting reflected light from the information medium; and obtaining servo information based on a reflected light signal of the servo area detected by the optical means. An information reproducing apparatus including a servo unit for controlling the optical unit,
First clock generating means for generating a servo clock in synchronization with a recording cycle of servo information in the servo area using a reflected light signal from the servo area as a reference signal, and equally dividing a detection time interval of the servo area; A second clock generating means for generating a plurality of clocks having different frequencies synchronized with the reference signal; and a clock having any frequency among the plurality of clocks generated by the second clock generating means. Control means for instructing whether or not to use the information , and replay of information in the information area based on the clock selected by the control means.
This is attained by providing a reproducing means for performing the life .

[0009]

The first clock generating means always reproduces a clock having a constant frequency using predetermined information (clock pit) in the servo area as a reference signal. Using this clock, servo information is detected and a stable servo operation is performed. The second clock generation means similarly uses a clock pit in the servo area as a reference signal, but changes the reproduction clock frequency according to the track position. This allows information
While maintaining Honakadachi body rotational speed (disk) to be constant,
It is possible to change the information recording density according to the track position in the radial direction.

That is, in recording data on the disk, for example, recording is performed based on a clock of a frequency designated by the control means from among reproduction clocks generated by the second clock generation means. For example, by increasing the clock frequency toward the outer periphery,
The recording density on the disc can be improved, and the recording capacity can be increased. Then, the data in the data area is reproduced based on a clock having the same frequency as the clock designated by the control means at the time of the recording.

[0011]

An embodiment of the present invention will be described with reference to FIG. FIG. 1 is a configuration diagram of an information processing apparatus using an optical disk according to a sample servo method using the present invention, but does not show parts that are not involved in the description of 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, and 9a to 9d are clock reproduction. Circuit, 10
Denotes a selection circuit, 11 denotes a tracking error detection circuit, and 12 denotes 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. 2, 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 tracking control by such a sampling method, a clock signal for accurately extracting a reproduction signal from a tracking pit is required. In order to obtain the clock signal, the clock bit 2 which is the third bit of the servo area signal shown in FIG.
Obtain from 3. A clock for equally dividing a predetermined number of clock pits is generated based on a clock pit reproduction signal obtained for each servo area. By forming the above-mentioned tracking pit in advance so that the reproduced signal can be obtained at a position synchronized with this clock signal,
The reproduction 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. .

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 rp
The appropriate number when rotating at m is 1 per disk
2,000 to 2,000. In order to record and reproduce data by moving the pickup randomly from the inner circumference to the outer circumference of the disk, it is necessary that the intervals on the time axis of the servo areas be constant over the entire area of the disk. Therefore, the servo areas are linearly arranged from the center of the disk toward the outer circumference at regular intervals. Even if the pickup is moved in the radial direction of the disk, a reproduction signal in the servo area is obtained at a constant interval, so that a constant servo characteristic is always obtained, and a tracking operation can be performed immediately at the moving destination, so that high-speed access can be realized.

However, the fact that the servo area is constant on the time axis, that is, the reproduction time interval of the servo area is constant, requires that the above-mentioned clock be constant, and as a result, the same clock is used. Since the recording and reproduction of data also have a fixed period, the recording density is reduced toward the outer periphery of the disk.

Therefore, in the present invention, the recording density of data 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, configuring one segment by a servo area and a data area and other data of 16 bytes is 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 320 MByte when all areas are recorded with the setting of a.
43.5 MBytes, which is 1.35 times as large as that of FIG. The generation of the clock frequency is performed by the four clock generation circuits 9a to 9d in FIG. Clock generation circuit a
Is 11.1456 MHz, and the clock generation circuit b is 13.
9526 MHz, the clock generation circuit c is 16.718
4 MHz, clock generation circuit d is 19.5254 MHz
Respectively. Each clock output is input to the selection circuit 10, and the generated clock of the clock generation circuit a is input to the tracking error detection circuit 11, which is used for extracting a tracking pit reproduction signal. As for each clock input to the selection circuit 10, one clock is selected by a selection signal output from a control device 12 composed of a microprocessor or the like according to a track number for performing recording and reproduction, and is supplied to a modulation circuit and a demodulation circuit. Is entered.

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. Voltage control is performed so that the phase of the output of the frequency divider 94 matches the phase of a reference signal input from the outside. The oscillation frequency and phase of the oscillator 93 are controlled. Therefore, the output of the voltage controlled oscillator 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,
The output clock signals are the four types of clock signals described above. For example, in the clock recovery circuit a, the frequency divider 9
4 is 270, and the voltage controlled oscillator 93 generates 11.456 MHz at the center value of the control voltage.
The oscillation frequency control element is adjusted. Clock generation circuit b
Similarly, a predetermined frequency division ratio and oscillation frequency are set in the case of .about.d.

FIG. 6 shows the relationship between the reproduced signal and the clock on the actual optical disk. A to d in FIG.
They correspond to the areas a to d in FIG. 3, respectively. 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 area is equally divided into four areas, the areas b, c, and d are 1.25 times and 1.5, respectively, based on the area a.
A 1.75 times recording capacity can be obtained. Assuming that the total number of clocks is 270, the servo area and the data area are divided into 30 clocks in the servo area and 240 clocks in the data area (15 clocks × 16 clocks).
Bytes). When the same distribution ratio is applied to region b, 1.
25 times, 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 generation circuit needs to be an integer, the number of possible clocks is 337 or 338. In the former case, the servo area is 37
0.5 clock shorter than the original length
The interval between the clock pit and the data pit or the interval between the first tracking pit and the data pit is shorter than in the case of 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. Inner radius 30m
In the case where recording and reproduction are performed at a pitch of 1.5 μm on a disc having an outer circumference of 60 mm and an outermost radius of 60 mm, this can be achieved by shifting the start point of the area b by 0.57 mm from the point of 37.5 mm. 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. In the regions c and d, the clock frequency is determined based on the same concept.

FIG. 7 shows a second embodiment of an information processing apparatus using an optical disk according to the present invention. In the figure, the same components as those in FIG. 1 are denoted by the same reference numerals. In this example, there are two clock generation circuits. The operation will be described assuming that the optical disk shown in FIGS. 3 and 4 is used. The first clock generation circuit 9 generates a clock of 11.456 MHz for detecting a tracking pit, and the second clock generation circuit 9 'controls the control device. Four types of clocks are generated by twelve selection signals. FIG. 8 shows a configuration example of the second clock generation circuit 9 '. The frequency division ratio variable frequency divider 95 receives signals 270, 338, 405, 4
A divide-by-73 is 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. 9 shows a second configuration example of the second clock generation 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 generation circuit in this case does not need to have a wide pull-in range as in the embodiment of FIG.

The embodiment of FIG. 7 can reduce the number of clock generation circuits as compared with the embodiment of FIG. But,
Each time the boundary of the area is exceeded, the synchronous operation of the clock generation 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 in the case of dividing into four regions as an example, the gist of the present invention is not limited to the number of divisions and the numerical values described above. And various combinations are possible.

[0026]

According to the present invention, the recording capacity of the optical disk by the sample servo method can be increased without affecting the servo circuit.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a first embodiment according to the present invention.

FIG. 2 is a waveform diagram of a reproduction signal of an optical disk.

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

FIG. 4 is a diagram illustrating a numerical example in the case of performing four-region division.

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

FIG. 6 is a waveform diagram when divided into four regions.

FIG. 7 is a configuration diagram of a second embodiment according to the present invention.

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

FIG. 9 illustrates a second example of the clock generation 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 generation 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 (6)

(57) [Claims] 1. A drive means for rotating at a constant angular velocity a disc-shaped information medium in which an information area and a servo area are alternately arranged on the same track and the servo areas are arranged at a constant angular interval, and a luminous flux on the information medium. Optical means for irradiating light and detecting reflected light from the information medium, and servo means for obtaining servo information based on a reflected light signal of the servo area detected by the optical means and controlling the optical means in the information reproducing apparatus provided with the door, the reflected light signal from the servo area as a reference signal, a first clock generating means for generating a servo clock in synchronism with the recording period of the servo information of the servo region, the Second clock generation means for equally dividing the detection time interval of the servo area and generating a plurality of clocks of different frequencies synchronized with the reference signal; and the second clock generation means Control means for instructing which frequency of the plurality of clocks to use, and reproducing means for reproducing information in the information area based on the clock selected by the control means. An information reproducing apparatus characterized in that: 2. The information reproducing apparatus according to claim 1, wherein the second clock generating means is constituted by one clock generating circuit, and the one clock generating circuit is configured to control the servo clock by an instruction of the control means. An information reproducing apparatus which generates a clock having a frequency equal to or higher than the frequency of the information. 3. The information reproducing apparatus according to claim 1, wherein said second clock generating means includes: a plurality of clock generating circuits for respectively generating said plurality of clocks; and said plurality of clock generating circuits output from said plurality of clock generating circuits. And a selection circuit that receives a plurality of clocks as inputs.
The control means is intended for selecting one clock of the plurality of clocks based instruction to the information reproducing clocks the plurality of wherein said at or greater than equal to the frequency of the servo clock apparatus. 4. The information reproducing apparatus according to claim 1, wherein said control means selects one of a plurality of clocks generated by said second clock generation means according to a track number of said information medium. An information reproducing apparatus, wherein a higher frequency is selected for a track on the outer peripheral side. 5. The information reproducing apparatus according to claim 1, wherein the control unit divides the track of the information medium into a plurality of groups, and the plurality of groups of the second clock generating unit according to the groups. Select the clock step by step,
An information reproducing apparatus wherein a clock having the same frequency as the servo clock is selected in an innermost group, and a clock having a higher frequency is selected in an outermost group. 6. The information processing apparatus according to claim 1, wherein the control unit is configured to control a plurality of clocks generated by the second clock generation unit in common for all track numbers of the information medium. An information reproducing apparatus for selecting one of the above.