JPH0676290A - Method for writing data of optical disk device - Google Patents

Abstract

PURPOSE:To reduce a difference between an inner diameter and an outer diameter in a phase margin on reading data by compensating the difference between the inner diameter and the outer diameter occurring in a pit on a data code written by a recording level with a laser beam intensity on an optical disk provided with a phase transition type recording medium. CONSTITUTION:The inside of the surface of the optical disk 1 is divided to plural pieces of zones Zi, Zm, Zo, etc., in a radial direction, and a pit corresponding to 1 on a data code DC consisting of 0 and 1 is written in recording levels RLi, RLo in laser beam intensity LP for the recording medium 1a on the optical disk 1 by a laser beam LB. At this time, a time ti writing the pit in the inner diameter side zone Zi and the time to, etc., writing in the outer diameter side zone Zo are switched and controlled at every zones Zi, Zm, Zo, etc., further, it is desirable that recording levels RLi, RLo, etc., are switched and controlled at every zones.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for writing data in an optical disk device having a phase change recording medium so as to prevent an error from occurring when reading the data.

[0002]

2. Description of the Related Art As is well known, an optical disk device has an advantage that it can increase a data storage capacity by one to two digits as compared with a magnetic disk device, and it is roughly classified into a magneto-optical system and a phase change system. The phase-change type optical disk device targeted by the present invention is easy to write data so-called, and its future prospect is noted in that the access time at the time of data writing can be shortened as compared with the magneto-optical type.

That is, this phase change type optical disk device is the same as the magneto-optical type in that a chalcogen type recording medium is used for a disk and data is read from and written to the disk by a laser beam, but only the intensity of heating by the laser beam is different. The data code is stored in the recording medium in either the amorphous or crystalline phase state, so that the phase state indicating the old data that was written before that time is erased at the same time as the phase indicating the new data. By entering the state, data can be easily overwritten or overwritten as in the case of the magnetic recording system.

When data is overwritten on this phase-change recording medium, the laser beam intensity is set to, for example, an erasing level of 8 mW and a recording level of about 15 mW which is almost twice the laser beam intensity according to the code of 0 and 1 representing the data. Switch to. The recording medium heated at the erasing level of the laser beam becomes crystalline with high light reflectance after the previous phase state is erased, and the recording medium heated at the recording level becomes amorphous with low reflectance. When reading this data, a laser beam having a low reading level of, for example, 1 mW is applied to detect the position of a so-called pit, which is the above-mentioned amorphous portion having a low reflectance, from the reflected light.

It is customary that the number of data recording codes is smaller than 0 by 1. For example, in the case of the 2-7 code of the RLL modulation system, even if 1 is the largest, 001 is repeated. 0 other than the length of the pit
The length of the part corresponding to is larger and the ratio of both is 2
Although it should be above, since the code writing laser beam has a spot size similar to the track width, the actual pits are located in the circumferential direction of the disk from the theoretical size corresponding to the irradiation time of the recording level laser beam. It becomes longer, and the ratio between the length of the pit and the length of the other part in the case of the 001 repetition code is considerably smaller than 2. When the linear recording density of the data code is increased in order to increase the data storage capacity of the optical disk device, the unit length corresponding to the code of 0 or 1 is shortened, so that the above ratio is reduced and the data becomes difficult to read. In practice, however, the storage capacity can be increased by shortening the writing unit cycle of the code of 0 or 1 until the ratio drops to about 1.

Since the signal obtained by reading the code of the data written in this way has an analog waveform representing the difference in reflectance between the pit and the other portion, it is usual to make the differential waveform and then the positive and negative peaks. The position of the end of the pit is detected from the position and the original code of 0 and 1 is reproduced to be a read signal of the digital pulse train. However, since the peak shift due to the disturbance of the original analog waveform is likely to occur in the differential signal, it is necessary to synchronize the waveform of the above-mentioned read signal with the clock having the code write cycle, and then decode and convert it into data. It is customary.

At this time, if the peak shift of the differential signal is too large, it does not fit within the window frame for synchronization of the read signal called the window which is the period of the synchronization clock and a read error occurs, but the read signal occurs. The unit period for writing the code is set so as to allow a waveform margin called a phase margin to the extent that an error related to the above does not occur. It should be noted that although there is always a difference between the inner and outer diameters of the disc and this difference also appears in the phase margin, the code writing cycle is usually constant regardless of the radial position in the disc. The method of the present invention relates to an optical disc apparatus of the pit position detection system in which the unit period on the data code is always constant in the disc surface and the code is detected from the pit position as described above.

[0008]

The reason why the above-mentioned difference in inner and outer diameters appears in the phase margin is that the analog waveform obtained by reading the code from the disk surface originally has a difference in inner and outer diameters. In an optical disc device that uses a pit, the pits are written by heating the recording medium with a laser beam, so that the size and shape of the pits are likely to change depending on the radial position on the disc surface. There is an easy problem. of course,
Since the phase margin necessary for reading must be secured even in the worst condition on the disk, the unit period for writing the data code must be set with a considerable margin, and for this reason the recording medium is originally designed. The reality is that the available memory capacity cannot be fully utilized.

FIG. 2 schematically shows the difference between the inner and outer diameters of the above-mentioned pit. In the figure, an optical disk 1 of which only a sector-like portion is shown is rotatably driven by a spindle motor 2 at a constant speed, and pits Pi and Po are laser beams on the inner diameter side track Ti and the outer diameter side track To, respectively. Written by Spot SP. The optical disk 1 rotates by a slight angle θ within a writing unit cycle of usually several tens nS corresponding to one code corresponding to these pits Pi and Po. With pit Pi
The length of Po in the circumferential direction is almost equal to the arc length added to the angle θ plus the diameter of the spot SP, and the pit Po on the outer diameter side is not proportional to the radial dimension, but It will be longer than the pit Pi.

Further, since the heating densities due to the spots SP are different from each other due to the difference in the inner and outer diameters of the pits Pi and Po, the inner and outer diameter differences also tend to occur in the radial width. further,
Since the pit width is determined by the range in which the recording medium becomes amorphous according to the heating and cooling conditions, the pit originally tends to have an oval shape with a slightly different width at the circumferential start and end, This tendency is further amplified by the above-mentioned difference in heating density, so that the pit shape is likely to have a difference in inner and outer diameters. The above-mentioned difference in the inner and outer diameters of the phase margin is caused by the difference in the inner and outer diameters of the pit length, width, and shape, but the present invention compensates for the inner and outer diameter differences that may occur in the pits and reduces the inner and outer diameter differences of the phase margin as much as possible. The purpose is to

[0011]

According to the present invention, when a data code is written on an optical disk provided with a phase change type recording medium as described above while switching the intensity of the laser beam between the recording level and the erasing level, the recording level is changed. The above object is achieved by controlling the time for writing each pit on the code by the laser beam according to the radial position in the disk surface where the pit is written. It is practical to control or set the above-mentioned writing time of each pit to be shorter than the unit cycle for writing the data code. Further, in some cases, not only this writing time but also the writing laser beam of each pit It is advantageous to control the intensity of the recording level in accordance with the radial position in the disc surface on which it is written.

Further, although the advantageous mode for controlling the writing time of the pits varies depending on the type of the recording medium and the conditions such as the thermal conductivity of the heat insulator in contact therewith, a normal chalcogen type recording medium is used. In this case, make the pit writing time shorter on the outer diameter side of the writing position than on the inner diameter side.
For example, it is preferable to control so that the writing position is shortened in almost inverse proportion to the radial dimension within the optical disk surface. In this case, it is advantageous to control the recording level intensity of the writing laser beam for each pit so that it is stronger on the outer diameter side of the data writing position than on the inner diameter side. It is desirable to control so that it is slightly stronger on the inner side than on the inner diameter side. It is practical to control the writing time of each pit and the intensity of the laser beam by dividing the disk surface into a plurality of zones and switching the zones.

[0013]

Since the length, width and shape of the pits change very complicatedly due to factors such as the type of recording medium as described above, it is difficult to completely eliminate the difference between the inner and outer diameters by aligning all of them. In the present invention, the difference between the inner and outer diameters of the pit size and shape appears as the inner and outer diameter difference of the phase margin because the timing at which the analog waveform read from the pit changes corresponding to both ends of the analog waveform deviates according to the inner and outer diameter difference. By controlling the writing time of each pit according to the radial position in the disc, the timing at which the position of the pit edge and, therefore, the analog waveform read from it changes The control is performed so as to compensate for the difference.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a data writing method according to the present invention will be described below with reference to FIG. The figure (a) shows the structure of the part related to the implementation of the method of the present invention in the optical disk device, and the figures (b) and (c) respectively write the codes on the inner diameter side track and the outer diameter side track in the optical disk. An example of a waveform in which the intensity of the laser beam is controlled by the method of the present invention is shown. For convenience of explanation, it is assumed in this embodiment that the writing time of the pits is controlled to be shorter on the outer diameter side of the optical disc than on the inner diameter side.

First, an outline of the configuration of the optical disk device shown in FIG. 1A will be described. Optical disc 1 is spindle motor 2
Thus, for example, a chalcogen having a composition of Ge ₂ Sb ₂ Te ₅ is used for the recording medium 1a of the phase change type, which is rotated at a constant speed of 3600 rpm. In practice, for example, 1200 Å ZnS is deposited on a transparent polycarbonate disc substrate, and then Ge ₂ Sb ₂ Te ₅ is deposited to a film thickness of 300 Å, and further 400 Å
The ZnS film formed by depositing ZnS and 1000Å Al and sandwiching the Ge ₂ Sb ₂ Te ₅ film from both sides is for holding or heat insulating as usual, and the Al film is for reflecting the laser beam LB. .

The head 3 for reading / writing data from / into the optical disk 1 converts the laser beam LB generated by the light emitting element 3a into a parallel light flux by the lens 3b, and then converges it into a small spot of about 1 μm by the lens 3c. The light is applied to the recording medium 1a described above, and the reflected light is received by the light receiving element 3f via the lens 3c, the half mirror 3d, and the lens 3e when reading the data. The light emitting element 3a is provided with a light emitting drive circuit 4 for controlling the intensity or generated power of the laser beam LB, and the light receiving element 3f is amplified by the light detection signal to obtain the above-mentioned analog waveform. An amplifier circuit 5 is provided which emits the read signal RSa.

Further, as is usual, the reproducing circuit 6 produces a differential signal of the analog read signal RSa and then the read signal of the digital pulse train whose logic state is switched at the peak position.
This is for reproducing the RS, and the data separation circuit 7 that follows it
Synchronizes with the synchronizing clock SC as long as the phase margin of the reading signal RS is within the above-mentioned window set by establishing the synchronizing pulse SC from the synchronizing signal in the reading signal RS in the attached PLL circuit 7a. The read signal RS is output in a waveform. The read / write circuit 8 which receives the read signal RS from now on is a modulation system peculiar to the optical disk device, for example, RL.
It includes an L-modulation 2-7 code type encoder / decoder and a data processor, converts the read signal RS into read data and puts it on the internal bus 11 of the device via the RAM 8a.
Alternatively, on the contrary, it serves to read the write data from the internal bus 11 and convert it into the write signal WS of the above-mentioned modulation method, and then give it to the light emission drive circuit 4.

The controller 10 is a processor provided for controlling the data read / write operation of the optical disk device, and includes the internal bus 11, interface 12 and external bus 13 described above.
Is connected to a host computer (not shown) via. The control processor 20 is provided for various controls inside the optical disk device, such as movement control for the head 3, and operates under the interconnection with the controller 10 and the communication bus 14. Further, in the illustrated example, the collation information reading circuit 9
Is provided for the purpose of detecting the track number TN indicating the current position of the head 3 from the output of the amplifier circuit 5 mentioned above and informing the control processor 20. In addition, this role is the read / write circuit 8 and the controller.
It is possible to have ten.

In this embodiment, the inside of the optical disk 1 is divided into a plurality of zones in the radial direction, and the pit writing time is switched and controlled for each zone. This zone division is usually a number ~ 10
Although it is preferable to use individual pieces, FIG. 1 shows an inner diameter side zone Zi, an outer diameter side zone Zo, and an intermediate zone Zm. Correspondingly, a reference table 21 such as zone numbers and pit writing times is set in, for example, the ROM of the control processor 20, and the track number is read from the collation information reading circuit 9 described above.
Upon receiving TN, the stored value corresponding to the zone number to which it belongs is read and given to the light emission drive circuit 4. As a result, when writing data, the light emitting element of the head 3
The procedure for controlling the intensity of the laser beam LB generated in 3a will be described with reference to FIGS. 1 (b) and 1 (c).

FIG. 1 (b) shows the waveforms of the laser beam intensity LP for the inner diameter side zone Zi and FIG. 1 (c) for the outer diameter side zone Zo, respectively. The upper part of FIG. 1 (b) corresponds to them. The data code DC is indicated by 0 and 1. The data code DC in this example is a repetition of 001, and the unit cycle in writing a code of 0 or 1 is 50 nS. For the zone Zi on the inner diameter side in FIG. 1 (b), the erasing level ELi for the 0 code of the laser beam intensity LP is set to, for example, 8 mW and the recording level RLi for the 1 code is set to 15 mW. The pulse width ti of level RLi, that is, the pit writing time is set to 50 mS, which is equal to the unit period for code writing.

In this example, the outer diameter side zone Zo and the inner diameter side zone
Since Zi is set so that the ratio of the average radial dimension is 1: 0.6, in the outer diameter side zone Zo in Fig. 1 (c), the recording level RLo of the recording level RLo that specifies the pit writing time is correspondingly set. The pulse width to is set inversely proportional to this ratio to 30nS so that it becomes shorter than the inner diameter side, and the recording level RLo is set to 18mW, which is higher than the inner diameter side, to compensate for the speed difference between both zones Zi and Zo. . Further, the value of the erasing level ELo of the outer diameter side zone Zo is set slightly higher than that of the inner diameter side, for example, 9 mW. In the example shown in the figure, the recording level RLo on the outer diameter side is set to simplify control.
The rising timing of is matched with the recording level RLi on the inner diameter side.

As can be seen from FIGS. 1 (b) and 1 (c), the light emission drive circuit 4 keeps the light emitting element 3a always at the erase level ELi or EL
It is sufficient to drive to the recording level RLi or RLo only when the specified code by the write signal WS is 1 by driving at o. Further, in this example, the pit writing time is always less than or equal to the unit period for code writing, so the pulse width of the recording level is shown in the reference table 21 of FIG. It is stored together with the specified value, and the light emission command data is set according to the track number TN.
It is given to the light emission drive circuit 4 as PD.

According to the procedure of this embodiment described above, 130
RLL type 2-7 code data is written on the entire surface of the mm-diameter optical disc 1 by using the laser beam LB of 830 nm wavelength with the unit period of code writing set to 50 nS, and then by the laser beam LB of 1 mW. The reading test was performed, and the phase margin was measured while forcibly shifting the phase of the synchronous clock SC of the data separation circuit 7 by the phase adjustment circuit. As a result, the phase margin was almost evenly 80% from the inner diameter side to the outer diameter side of the optical disk 1, and the data read byte error rate was 10 ⁻⁶ or less. On the other hand, if the write time and the recording level of conventionally pits constant over the entire surface of the disk, the phase margin is easy to fall to about 50%, but the outer diameter is 80% at the inner diameter side, also the byte error rate 10 ^{- It} is difficult to reduce it to ⁵ or less. From this, it is understood that the present invention improves the read / write reliability of the optical disk device.

In the above embodiment, the zone setting in the optical disk and the pit writing time are fixedly set to R.
Although it is stored in the OM, these settings can be made for each device in order to compensate for the characteristics of the recording medium that may change for each optical disc. In this case, a phase adjustment circuit that shifts the phase of the synchronization clock in both the positive and negative directions is installed by the amount to secure the phase margin.For example, while checking the presence or absence of a read / write error in the state where the phase of the synchronization clock is shifted, It is preferable to check the characteristics, record the setting content determined based on the result in the optical disk, and read the setting content into the comparison table in the control processor when the apparatus is started.

Further, in the embodiment, the pit writing time is set to be equal to the unit period for code writing on the inner diameter side of the disk, but this setting mode can of course be variously selected according to the characteristics of the recording medium. Further, in the embodiment, the timing of the rising of the recording level is set to be the same as the starting point of the unit period for writing the code for convenience, but generally, the deviation of this timing is also set together with the zone and the pit writing time and stored in the comparison table. It's good to leave. As described above, the method of the present invention is not limited to the embodiments, and can be carried out in various modes within the scope thereof.

[0026]

As described above, according to the method of the present invention, when data is written on an optical disc having a recording medium of phase change type while switching the laser beam intensity between the recording level and the erasing level, each of the laser beams at the recording level is used. Since the pit writing time is controlled according to the radial position on the optical disc surface, even if the pit length, width, and shape change intricately depending on factors such as the radial position and the characteristics of the recording medium, It is possible to almost completely compensate for the difference between the inner and outer diameters that tend to occur in the timing of the time change of the analog waveform when the pit is read, and to even out the phase margin within the disk surface, which reduces the byte error rate of the read data. Read / write reliability of the optical disk device is dramatically improved, and further, the unit cycle of data code writing is shortened.憶容 amount can be increased.

The same effect as described above can be obtained by variably controlling the data code writing cycle according to the radial position in the disk, or variably controlling the rotational speed of the optical disk according to the head position. However, any of the means has a drawback that the structure of the optical disk device is considerably complicated, and the method of the present invention requires only a slight modification of the light emission drive circuit. Since it is also very reliable, it has the advantage of being highly practical.

[Brief description of drawings]

FIG. 1 shows an optical disk device as a target for carrying out a data writing method according to the present invention and a procedure for intensity control of a laser beam for data writing. FIG. 1A shows a configuration of a portion of the optical disk device related to the method of the present invention. FIG. 1B is a waveform diagram of the laser beam intensity with respect to the inner diameter side track in the optical disc, and FIG. 1C is a waveform diagram of the laser beam intensity with respect to the outer diameter side track in the optical disc.

FIG. 2 is a plan view showing a part of the optical disc in an enlarged manner in order to explain the difference between the inner diameter and the outer diameter caused by the length of pits in the optical disc.

[Explanation of symbols]

 1 optical disk 1a recording medium 3 data read / write head 3a laser beam generating light emitting element 3f data reading light receiving element 4 light emission drive circuit 6 read signal reproducing circuit 7 data separation circuit 21 pit writing time comparison table DC data code ELi Laser beam intensity erasing level on the inner diameter side ELo Laser beam intensity erasing level on the outer diameter side LB Laser beam for reading and writing data LP Laser beam intensity PD Emission command data for the emission drive circuit Pi Inner diameter side pit Po Outer diameter side Pit RLi Recording level on the inner diameter side of the laser beam intensity RLo Recording level on the outer diameter side of the laser beam intensity RS data read signal RSa Analog waveform read signal SC synchronization clock ti Inner diameter side pit writing time to outer diameter side pit writing Time WS Data write signal Zi Inner diameter side zone Zm Middle zone Zo Outer diameter side zone

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Tanio Urushitani, No. 1 Tanabe Nitta, Kawasaki-ku, Kawasaki-shi, Kanagawa Fuji Electric Co., Ltd. (72) Masakazu Ueno 1 Tanabe, Tabe-ku, Kawasaki-ku, Kanagawa Prefecture No. 1 within Fuji Electric Co., Ltd.

Claims (4)

[Claims] 1. A method of writing data on an optical disc having a phase change recording medium while switching the laser beam intensity between a recording level and an erasing level, each pit on a recording code of the data by the recording level laser beam. A data writing method for an optical disk device, wherein a writing time for writing data is controlled according to a radial position in the optical disk for writing data. 2. A method according to claim 1, wherein the writing time to each pit is controlled so that it is shorter on the outer diameter side of the data writing position in the optical disc than on the inner diameter side. Data writing method. 3. The data of an optical disk device according to claim 2, wherein the writing time to each pit is controlled so as to be shortened substantially inversely proportional to the radial dimension in the optical disk at the writing position. Writing method. 4. A method according to claim 1, wherein the intensity of the recording level of the writing laser beam for each pit is also controlled according to the radial position of the pit in the disc. Method.