JPH01128276A - Information recording and reproducing device - Google Patents

Abstract

PURPOSE:To increase a storage capacity without exerting an influence on a servo circuit by providing a clock reproducing circuit generating clocks which obtain servo information and plural clock reproducing circuits generating clocks which record and reproduce data. CONSTITUTION:In an optical disk 1, servo areas are radially arranged from the center of the disk, and data areas are divided into areas (a)-(d). The clock generation circuits 9a-9d generate clock frequencies. Respective clock outputs are inputted to a selection circuit 10 and the generation clocks of the circuit 9a are inputted to a tracking error detection circuit 11 and are used for the extraction of a tracking bit reproduction signal. One clock among respective clocks inputted to the selection circuit 10 is selected by the selection signal outputted from a controller 12 in accordance with the track number executing recording and reproduction, and it is inputted to a modulation circuit and a demodulation circuit. Thus, the storage capacity of the optical disk by a sample servo system can be increased without exerting influence on the servo circuit.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an apparatus for recording and reproducing digital signals,
In particular, the present invention relates to a device for increasing the recording capacity of an optical disk device used as an external storage device for a computer.

[Conventional technology]

Conventionally, in this type of optical disk device, a tracking method is often adopted 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 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 this continuous servo system, a problem arises in that differences in the shape and reflectance of the guide grooves affect the error signal and deteriorate tracking accuracy. Furthermore, since a larger amount of light beam is emitted during recording than when reading, the amount of reflected light also increases proportionally, so care must be taken to ensure that accurate error signals are obtained and control is performed even in such cases. It has become necessary.

On the other hand, in the sample servo method, instead of using guide grooves as a means of obtaining servo information, the servo area and data area are arranged alternately on the track, and the light beam is is controlled so that it passes over this servo area.The control error signal is
A pair of pits (two pits) slightly offset in opposite directions centered on the track position are recorded in advance in the servo area, and the difference in the amount of reflected light when the light beam passes through both pits is calculated. are obtained by detecting.

In this way, according to the sample servo method, there is no influence of the guide groove, and only the servo area obtains control error signals.Furthermore, since only the operation to obtain servo information is always performed within this area, there is no influence during recording. Some of the problems of the continuous servo system are solved, such as not having the effect of increasing the amount of laser light.

Regarding this sample servo system, please refer to NIS P.I.E., Proceedings, Optical Mass Data Storage II, Vol. 695 (1986), No. 2.
Pages 39 to 246 (SPIE.

Proceedings, 0pti, cal Mas
s Data Storage II, vol.

695 (1986) PP 239-246).

On the other hand, in information recording and reproducing devices such as optical disks and magnetic disks, larger capacity devices are required as the amount of information handled increases, and for this purpose, it is necessary to improve the recording density on the disks. The so-called C, A,
, V (Constant Angu), a-r
In the Velocity method, the pit period is limited at the innermost circumference where the linear velocity is the slowest. therefore,
There is more margin toward the outer periphery, and for example, at the outer periphery, which has a diameter twice that of the innermost periphery, the recording density decreases to 1/2. In this way, the C, A, and V systems do not fully utilize the recording capacity of the disk, resulting in waste. On the other hand, if the linear velocity is kept constant, C, L, V, (Con
In the (stant linear velocity) method, the recording density is the same from the inner circumference to the outer circumference, and the maximum recording capacity can be obtained. However, C,L
In the ,V, method, the number of rotations of the disk must be changed depending on the track position, and the access time is longer than in the C, A, V, method, and random access is performed.
There are problems with data recording and reproducing devices for computers that require high-speed access. Therefore, one method aimed at resolving the drawbacks of both methods is to develop a device that divides the disk into multiple areas in the radial direction and sets different rotational speeds for each area to increase the recording density. JP-A-61-1
It is described in Publication No. 7223. Also, in JP-A-61-175, there was a device that similarly divided into multiple areas and increased the recording capacity by changing the pit period within the square head area while keeping the rotation speed constant.
It is stated in Publication No. 968.

[Problem that the invention seeks to solve]

All of the above conventional techniques relate to continuous servo type optical disk devices, and do not take into consideration optical disk devices using sample servo type. The sample servo method uses a so-called embedded clock method in which a clock bit recorded in a servo area is detected and clock reproduction is performed based on this detected clock bit. Since this reproduced clock serves as the reference for all operations including the servo, it must be stable and locked at all times. Also, since the period of obtaining servo information affects the servo characteristics, it is necessary to set it to a constant period of 6 periods. However, if the rotation speed and recording data cycle are changed depending on the area on the - disk, the cycle of the servo information will also change at the same time, and the servo characteristics will also change, so there is a problem that the servo characteristics must also be changed. There is.

An object of the present invention is to increase the recording capacity of an optical disk device using a sample servo method without changing the sampling period of servo information.

[Means for solving problems]

The above purpose is to divide an optical disk in which servo areas are arranged so that servo information can be obtained at regular intervals from a disk rotating at a constant rotation speed into multiple areas in the radial direction, and to increase the recording density of each area. By changing only the recording frequency, the drive device is provided with a first clock reproducing circuit that generates a clock for obtaining servo information and a second clock reproducing circuit that generates a clock for recording and reproducing data. This is achieved by

[For production]

The first clock regeneration circuit always regenerates a clock at a constant frequency using a clock pit in the servo area as a reference signal. This clock is used to detect servo information and perform stable servo operation. The second clock reproducing circuit similarly uses the clock pit in the servo area as a reference signal, but changes the reproduced clock frequency according to the track position, increasing the frequency toward the outer circumference. This improves the recording density on the disc and increases the recording capacity.

〔Example〕

An embodiment of the present invention will be described with reference to FIG. This figure is a configuration diagram of an optical disk device using a sample servo method using the present invention, but portions not related to the description of the features and operation of the present invention are not shown. In the same 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 decompression circuit, 9a-d
1 is a clock regeneration circuit, 10 is a selection circuit, 11 is a tracking error detection circuit, and 1-2 is a control circuit.

The optical disc 1 is rotated by a disc motor 2 at a constant angular velocity. Writing data to disk
Reading is performed by an optical pickup 3. The write data is modulated in a predetermined manner by a modulation circuit 7 and then input to a laser driver 4, which drives a laser diode and converts the intensity of a light beam. The reflectance of the optical disc 1 changes depending on the intensity of the irradiated light beam, and data is recorded because this change in reflectance remains even after the light beam has passed. For reading, a laser diode emits a weak light beam that does not cause changes in reflectance like during writing, and this light beam is used to write an optical disc.
An optical detector detects the reflected light when it is irradiated onto the surface of the sensor, and converts the difference in the amount of reflected light due to the difference in reflectance into an electrical signal. The detected signal is amplified by a preamplifier 5 and then demodulated by a demodulation circuit 8 to restore the original data. In order to realize data recording and reproduction using such a light beam,
A so-called 1-racking control is required to cause the light beam to fall precisely onto a predefined track on the optical disk. In the sample servo method, as shown in FIG. 2, servo areas and data areas are arranged alternately, and servo information such as tracking control is obtained only from the servo areas.

Therefore, servo information is obtained not as a continuous signal but as a discrete signal. The tracking error information is obtained from the difference in the amount of light between the first tracking pit 21 and the second tracking pit 22 when the light beam passes through the servo area. In other words, these two tracking pits are recorded equidistantly offset on both sides of the center line of the track, so if the irradiation position of the light beam shifts from the center of the track, the tracking pit on the shifted side・The amount of reflected light from the tracking pit on the opposite side decreases. If the light beam is irradiating the center of the track correctly, both tracking pins 1
The amount of reflected light of ~ will be the same. Therefore, the amount and direction of deviation of 1-racking can be determined from the difference in the amount of reflected light from both 1-racking pits and the polarity, and tracking control is performed by controlling the light beam so as to cancel this difference. In order to realize 1~ racking control using such a sampling method, a clock signal is required to accurately extract the reproduced signal from the tracking pins 1~. In order to obtain the clock signal, the tarok pit 2, which is the second pitch 1 of the servo area signal shown in Figure 2, is used.
Obtained from 3. Clock pitch 1 obtained for each servo area
A clock is generated that equally divides the clock pits into a predetermined number based on the reproduced signal of -. By forming the above-mentioned tracking pits in advance so that their reproduced signals are obtained at positions synchronized with this clock signal, the reproduced signals of the tracking pits can be extracted accurately. As described above, the sample servo method is characterized by the use of a clock synchronized with the rotation of the disk, and this clock is used not only to obtain servo information but also to record and reproduce data in the data area. The larger the number of servo areas in one rotation of the disk, the better the servo characteristics.]1.

However, the data area becomes smaller and the recording capacity decreases. Conversely, if the number of servo areas is reduced, sufficient servo characteristics cannot be obtained. When rotating at 1.80 rpm, a suitable number is 1000 to 2000 per disk revolution. 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 of the servo areas on the time axis be constant over the entire area of the disk. Therefore, the servo areas are arranged on a straight line from the center of the disk toward the outer periphery at regular angle intervals. Even when the pickup is moved in the radial direction of the disk, reproduction signals in the servo area are obtained at regular intervals, so constant servo characteristics are always obtained, and tracking operation can be performed immediately at the destination, achieving high-speed access. However, in order for the servo area to be constant on the time axis, the clock mentioned earlier must also be constant, and as a result, data recording and playback performed using the same clock will also have a constant cycle. The recording density decreases toward the outer circumference. Therefore, the present invention, 1
At 2°, the data recording density can be increased by using different clocks for servo signal detection and data recording/reproducing. FIG. 3 shows an example of an optical disc according to the present invention. This optical disc 1 has servo areas arranged radially from the center of the disc, and when rotated at a constant rotation, reproduced signals are obtained at regular time intervals. On the other hand, the data area is divided into four areas as shown in the figure, and recording and reproduction are performed in each area using different clocks. However, the dividing line in the figure is a virtual one as described in Explanation-42, and the numbers 1 to 4 are continuous even at the boundary of the area. FIG. 4 shows an example of dividing each area. Each area is divided into 50,001-rack units, and area a has 32 sectors per round, and if the data area sandwiched between the servo areas is 1 segment I, the data recorded during this period is 16 pie 1~, The recording clock frequency is 1 ], ,
1.4.56 M, Hy.

This clock frequency is the same as the clock for detecting the servo signal, and is a clock that divides the period into 270 equal parts based on the aforementioned clock pitch 1~. The area is 39 sectors per round, 20 bytes per segment, and the recording clock frequency is 13.9526MT (z, which is the frequency obtained by dividing the clock pit into 338 equal parts. Similarly, areas c and d are also shown in the figure. The recording clock frequency is set to 40 of each clock pit.
It is divided into 5 equal parts, which corresponds to 473 equal parts. Recording capacity covers the entire area. Compared to 320 MB when recorded with the settings of
4.32.5 Mbytes, which is 1.35 times larger, are obtained. Generation of the clock frequency is performed by 4' clock recovery circuits 9a to 9d in FIG. Tarock regeneration circuit a is 1:L, 1456MHz, clock regeneration circuit is 13.9526MHz, clock regeneration circuit C is 16
．． 71.84M] (z, clock regeneration circuit d is 19.5
254 MHz respectively. Each clock output is input to the selection circuit 1-0, and the generated lock of the clock reproduction circuit a is input to the tracking error detection circuit 11, and is used to extract the 1-racking pit reproduction signal. Each clock input to the selection circuit 0 is selected according to the track number for recording/reproduction, and one clock is selected by the selection signal output from the control device 2, which is composed of a microprocessor, etc. It is input to the demodulation circuit. The clock regeneration circuits 9a to 9d are so-called PLL (Phase Locked Loo) shown in FIG.
It is composed of a phase locked loop (p; phase locked loop) circuit. This PLL circuit is composed of a phase comparator 91°, a low-pass filter 92, a voltage controlled oscillator 939, and a frequency divider 94. The oscillation frequency and phase of the controlled oscillator 93 are controlled. Therefore, the output of the voltage controlled oscillator becomes 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 the clock pitch 1- which is the third pitch j- of the servo area mentioned above, and the output clock signals are the four types of clock signals mentioned above. Therefore, for example, in the clock regeneration circuit σ, the frequency division ratio of the frequency divider 94 is 270, and the voltage controlled oscillator 93 has a frequency division ratio of 11 at the center value of the control voltage.
．． Five oscillation frequency control elements are adjusted to generate 1456MT ox. Similarly, predetermined frequency division ratios and oscillation frequencies are set in the tarock reproducing circuits b-d. The relationship between the playback signal and the tarokku on an actual optical disc is explained in the sixth section.
As shown in the figure. A to d in the figure correspond to areas ad in FIG. 3, respectively.

23 is a clock pit i-, and 250 to 25d are the leading pits of the data area. Since each clock is generated in synchronization with a clock pit, all the clocks have the same phase at this point, but thereafter, since the frequencies differ, a phase shift occurs between the clocks. The starting position of the data area is clock pick 1 according to the additional data.
It is set at a certain time distance to prevent the influence on ~. Similarly, a constant interval is maintained between the end point of the data area and the first tracking pin 1. As shown in Fig. 3 and Fig. 4, when divided into four areas equally, with area a as the reference, areas c, d are 1.25 times and 1.5 times, respectively.
1.75 times the recording capacity can be obtained.

Assuming that the total number of clocks is 270, the distribution of the servo area and the data area between one segment in the area θ is 30 clocks for the servo area and 240 clocks for the data area (15 clocks x]-6pi1~). If the same distribution ratio is applied to the area, it will be multiplied by 1.25, and the total number of clocks will be 337.
5 clocks, 37.5 clocks for the servo area, and 300 clocks for the data area. However, since the division ratio of the clock recovery circuit must be an integer, the possible number of clocks is 373 or 338. In the former case, the servo area becomes 37 clocks, which is 0.5 times longer than the original length.
The clock is short, and the interval between the clock pit and the data pit 1~ or the first 1~ racking pit 1- and the data pit 1~ is shorter than in the case of area a. Also,
In the latter case, the servo area is 38 clocks, and there is no problem with the spacing from the data area, but the spacing from the first 1 of the area to the pitch 1 of the rack is an area. It is shorter than the first part of the disc, that is, the innermost circumference of the disc. A solution to this problem is to shift the starting point of the region to the outer periphery. In the case of recording and reproducing at a pitch of 1.5 μm on a disk with an innermost radius of 30 mm and an outermost radius of 60 mm, the starting point of the area is 0 from a point of 37.5 mm.
．． This is achieved by shifting the outer circumference by 57 mm. The number of tracks in this portion is 57, and although the recording capacity is reduced by this amount, it is not a problem when viewed from the overall capacity.

Which of these three methods to adopt is determined by margin settings for the entire optical disk device.

In areas c and d, the clock frequency is determined based on the same concept.

A second embodiment of the optical disk device according to the present invention is shown in FIG. In this figure, the same components as in FIG. 1 are given the same numbers. In this example, there are two clock recovery circuits.

To explain the operation assuming that the optical discs shown in FIGS. 3 and 4 are used, the first clock regeneration circuit 9 has a clock 11 for detecting a 1-ranking pit, a 1.4-
56 MH2 and the second clock regeneration circuit 9'
generates four types of clocks according to selection signals from the control device 12. An example of the configuration of the second clock recovery circuit 9' is shown in FIG. The frequency division ratio variable frequency divider 95 is set to 270 by the selection signal.
, 338. /1-05°473 frequency division is set. The oscillation element of the voltage controlled oscillator 93 is adjusted so that it oscillates at four center frequencies based on the center value of the control voltage. Further, the entire clock recovery circuit needs to have a pull-in range that covers all four frequencies. Next, a second configuration example of the second clock recovery circuit is shown in FIG. In this example, not only the frequency division ratio but also the center frequency of the voltage controlled oscillator is switched by the selection signal, so the oscillation element is switched by the switching circuit 9.
Switching at 6.

Each oscillation 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 shown in FIG. 7 allows the number of tarock reproducing circuits to be reduced compared to the embodiment shown in FIG. However, since the clock recovery circuit synchronizes each time the area boundary is crossed, the access speed decreases. Furthermore, continuous recording and reproduction cannot be performed beyond the boundary.

As described above, according to this embodiment, it is possible to increase the capacity of a sample servo type optical disc without changing the servo characteristics.

Furthermore, as long as the present apparatus is used and the clock frequency is not switched, recording and reproduction of optical discs to which the present invention is not applied can be performed without any problem.

Although this embodiment is explained using numerical values, taking as an example the case where the area is divided into four areas, the gist of the present invention is not limited by the number of divisions or the numerical values mentioned above. Combinations are possible.

〔Effect of the invention〕

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

[Brief explanation of the drawing]

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 disc, Fig. 3 is a schematic diagram showing the area division of an optical disc, Fig. 4 is a diagram showing a numerical example when dividing into 4 areas, and Fig. 5 is a clock regeneration circuit. Figure 6 is a waveform diagram when divided into 4 areas,
FIG. 7 is a block diagram of a second embodiment of the present invention, and FIG. 8 is a block diagram of a first embodiment of the clock recovery circuit in the second embodiment. FIG. 9 shows the second clock recovery circuit in the second embodiment.
It is a block diagram of an Example. DESCRIPTION OF SYMBOLS 1... Optical disc, 3... Optical pickup, 7... Modulation circuit, 8... Demodulation circuit, 9a-9d... Clock regeneration circuit, 10... Selection circuit, 11... Tracking error detection circuit , 12...control device, 9]...phase comparator. 92...Low pass filter, 93...Voltage controlled oscillator. 94... Frequency divider. View 2nd area, 5th area 4th area, 3rd image

Claims (1)

[Claims] 1. A disc-shaped information recording and reproducing medium in which arbitrary information recording and reproducing areas and servo information reproducing areas are arranged alternately on the same track, and a servo signal is prerecorded in the servo information area. , a driving means for rotating the information recording and reproducing medium at a constant angular velocity, an optical means for irradiating the information recording and reproducing medium with a light beam and detecting reflected light, and a reflected light signal of the servo area detected by the optical means. In an information recording/reproducing device comprising a servo means for mechanically controlling the optical means by obtaining servo information from the servo information area, the reflected light signal from the servo information area is used as a reference signal, and the recording period of the servo information in the servo area is determined as a reference signal. a first clock regeneration circuit that generates a clock having the same cycle; and a clock that uses a reflected light signal from the servo information area as a reference signal and generates a clock that has a cycle that is different from the recording cycle of the servo information in the servo area; and a plurality of second clock recovery circuits having mutually different clock periods; a selection circuit that selects one clock signal from a plurality of clock signals of the plurality of second clock recovery circuits; Information recording comprising: a control circuit that instructs which clock signal to select; and a recording and reproducing circuit that records and reproduces information in an arbitrary information recording and reproducing area according to the cycle of the selected clock signal. playback device. 2. The information recording/reproducing apparatus according to claim 1, wherein the control circuit selects the clock signal depending on the track number on which recording/reproduction is to be performed. 3. The information recording and reproducing apparatus according to claim 1, wherein the clock signal of the first clock reproducing circuit is input to the selection circuit.