JPH01232538A - Recording/reproducing method for phase changing type optical disk - Google Patents

Abstract

PURPOSE:To enhance an erasing rate at the time of overwriting by initializing the intensity of a single optical beam, which writes, erases and reads a phase changing type optical disk, at >= a writing level. CONSTITUTION:According to the designation of the respective modes of initialization, writing, erasing and reading from an operating part 13, a controller 14 sets the intensity of the optical beams in a power setting circuit 12. At such a time, the optical beam intensity set in the circuit 12 at the time of the initialization is set at >= the writing level. A current corresponding to a power set value is added from a current driving circuit 15 through a switching circuit 11 to the reading current held in a sample-and-hold circuit 6, and drives a laser 1. Thus, in the initialization, a crystalized area can be broadly secured, and the erasing rate at the time of the overwriting can be enhanced.

Description

[Detailed Description of the Invention] Technical Field The present invention relates to a recording and reproducing method for a phase change optical disc,
In particular, the present invention relates to a recording/reproducing method for writing, erasing, and reading information on an overwritable phase-change optical disk using a single light beam.

Erasable and rewritable optical discs are being put into practical use. There are two types of optical disks of this kind: magneto-optical and phase-change types. Among these, phase-change optical disks utilize the difference in reflectance caused by a phase change between crystalline and amorphous, for example. The structure of this phase change optical disc is shown in FIG. In the figure, the base material 31 is made of resin such as acrylic or polycarbonate, and the base material 31 has groups (guide grooves) 3 for tracking when recording information.
2 is preformed. Then, a recording material thin film (hereinafter simply referred to as a recording film) 33 is formed by vacuum evaporation or sputtering, and a protective layer 34 is further provided thereon. Although not shown, the base material 31 and the recording film 3
A protective layer is also provided between 3 and 3.

In such (one-piece optical disc 30), the state of the recording film 33 immediately after steaming is different from the amorphous state during phase change, but is in a kind of amorphous state, and in order to write information to this recording film 33, First, the recording film 33 is initialized by irradiating a laser beam along the groups 32. In this initialization, when the laser beam is irradiated along the groups 32 in a condensed state, the recording film 33 is mainly Heat acts on the group portion of the membrane 33,
When that part exceeds the melting point, it becomes amorphous, and the surrounding part does not exceed the melting point but exceeds the crystallization temperature, so it becomes crystallized. As a result, an initialization region consisting of an amorphous region and a crystallized region sandwiching the amorphous region is obtained.

However, according to the applicant's research, when writing information, the peripheral portion of the recording bit that is crystallized by the erasing light beam power and then amorphized by the recording light beam power is as shown in FIGS. As shown in Figure 6, the crystallization will protrude from the initialized area, and if overwriting is performed under these conditions, the crystallized protrusion will be erased. It was found that the remaining data remained, and it was found that this remained as noise and had a negative impact on the information after overwriting.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned points, and provides a recording and reproducing method for a phase change optical disk, which improves the erasure rate during overwriting by widening the crystallized region during initialization. The purpose is to provide.

The recording and reproducing method for a phase change optical disc according to the present invention is such that the intensity of a single light beam for writing, erasing, and reading information on an overwritable phase change optical disc is set to an initialization level equal to or higher than a writing level. It is characterized in that the recording film of the optical disc is initialized by irradiating the optical disc with a light beam.

Further, the recording and reproducing method for a phase change optical disk according to the present invention lowers the intensity of a single light beam for writing, erasing, and reading information to an overwritable phase change optical disk to an initial level below the writing level. The recording film of the optical disc is initialized by irradiating the optical disc as a recording level and rotating the optical disc at a linear velocity slower than the linear velocity at the time of writing.

Example Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

FIG. 1 shows a recording 11 of a phase change optical disc according to the present invention.
FIG. 2 is a block diagram showing the configuration of a recording/reproducing apparatus to which the f-recording method is applied. In the figure, a semiconductor laser 1 is provided as a light source that emits a write/read light beam for writing information on an optical disk and reading recorded information from the disk, and a monitor diode 2 is provided in this semiconductor laser 1. Built-in. This monitor diode 2 receives the beam emitted from the rear of the semiconductor laser 1, and its output is supplied to a subtracter 4 via a monitor amplifier 3, and is subtracted from the output of a power setting circuit 5 that sets the power of the readout optical beam. be lost. That is, by feeding back the output of the monitor diode 2 and comparing it with the target power setting value set in the power setting circuit 5, automatic control is performed so that a constant optical power is always obtained without being affected by temperature changes. It will be done. The output of the subtracter 4 is sampled and held in a sample and hold circuit 6 when an inverted signal of the write gate signal inverted by an inverter 7 is applied. This sample and hold output becomes a drive current for the semiconductor laser 1 through a current drive circuit 8 and an addition 'ri9.

On the other hand, write data is supplied to the switching circuit 11 via the old gate circuit 10. When writing data, a larger light beam intensity (writing power) is required than when reading data, and this writing power is set by the power setting circuit 12.

The power setting circuit 12 sets not only the write power but also the initialization power when initializing the recording film of the optical disc and the erasing power when erasing recorded information. The magnitude relationship of the respective light beam intensities during writing, erasing, and reading on the disk is as shown in FIG. The light beam intensity at the time of initialization is set to a level higher than the writing level. Setting of each of these levels is performed using the operation unit 13.
This is performed by the controller 14 in accordance with the mode designation from. When a power value corresponding to each operation mode is set in the power setting circuit 12, a current corresponding to the set power value is supplied from the current drive circuit 15 to the switching circuit 11. The current in the initialization mode and the erase mode is constantly switched during the mode period, and the current in the write mode is switched according to write data, and is added to the read current held by the sample and hold circuit 6 in an adder 9. Semiconductor laser 1 in initialization, erase or write mode
The driving current will be .

FIG. 3 shows an example of the configuration of the optical system.

In the figure, a laser beam emitted from a semiconductor laser 1 is passed through a collimator lens 21 and a beam shaping prism 2.
2 and enters the polarizing prism 23. polarizing prism 2
3, the beam passes through the λ/4 plate 2, the metal plate 4, and the objective lens 2.
5, and by this objective lens 25, the optical disc 3
0 in a condensed state. The beam reflected by the optical disk 30 enters the polarizing prism 23 via the objective lens 25 in the opposite path. A part of the beam reflected by the polarizing prism 23 passes through the half prism 26 and enters the tracking servo detector 27, and the remaining beam is reflected by the half prism 26 and then passes through the astigmatism generating optical element 28. The light enters the focus servo detector 29 in an astigmatic state.

Note that the tracking servo based on the output of the tracking servo detector 27 and the focus servo based on the output of the focus servo detector 29 are well known in the field of optical recording/reproducing devices, so their explanation will be omitted.

Next, initialization of the recording film 33 of the optical disc 30 will be explained.

First, when the beam power in the initialization mode (hereinafter simply referred to as initialization power) is set lower than the beam power in the write mode (hereinafter simply referred to as write power), for example, the initialization power is set to 11 mW, and the write power is set to 11 mW. 1
Consider the case where it is set to 8 mW. When an 11 mW initialization beam is irradiated along the group 32 of the optical disk 30 in a condensed state, heat mainly acts only on the center portion of the group 32, so the initialization area does not expand, and as shown in FIG. The width of the initialization area is approximately equal to the effective writing beam diameter (for example, an area of 1/2 or more of the maximum intensity of the light beam) shown by the dashed line in the figure. Therefore, when irradiated with a writing beam of 18 mW, the central part of the group 32 exceeds the melting point and becomes amorphous by being rapidly cooled, but the ends of the group 32 do not exceed the melting point but exceed the crystallization temperature. As is clear from FIGS. 5 and 6, the peripheral portion of the recording bit is crystallized in a state protruding from the initialization area. If overwriting is performed under these conditions, as mentioned above, the crystallized protruding parts will remain as unerased parts, which will become noise and have an adverse effect on the information after overwriting. This will affect the In addition, Fig. 5 shows the initialization power of 11 mW.
After initializing with
Recording film 3 observed with a transmission electron microscope when information was overwritten at mW (recording) and 11 mW (erasing)
A photograph showing the crystal structure of No. 3, FIG. 6, is a schematic representation of FIG. 5 for easy understanding.

Next, if the initialization power is set higher than the write power, for example, the initialization power is set to 18 mW and the write power is set to 1.
Consider the case where it is set to 8 mW.

When initialization is performed with an initialization beam with a power higher than the writing power, the central part of group 32 becomes amorphous, but heat also acts on the peripheral part of group 32, and although it does not exceed the excitation point, it exceeds the crystallization temperature. Therefore, it is crystallized widely and uniformly, and as shown in FIG. 8, an initialization area wider than the effective writing beam diameter is obtained. The recording area can be either amorphous or crystalline, so even if information is written under these conditions, it is unlikely that it will protrude beyond the initialization area and become crystallized. As is clear from the figure and FIG. 8, the occurrence of unerased areas is reduced.

In addition, in Fig. 7, recording was performed after initialization with an initialization power of 18 mW, and an overwrite power of 18 mW (recording) and 1
FIG. 8 is a photograph showing the crystal structure of the recording film 33 observed with a transmission electron microscope when information is overwritten at 1 mW (erasing), and is a schematic representation of FIG. 7 for easy understanding.

According to the applicant's experimental results, 5bTe was used as a phase change abrasive material.
Using SeGe-based material, the overwriting power conditions were 18 mW and 11 mW, and the initialization power was 11 mW.
When the initialization power was set to
An erasure rate of 0 dB was obtained.

In the above embodiment, a case has been described in which the recording film 33 is initialized by irradiating the optical disk with the intensity of the light beam at an initialization level higher than the writing level. It is also possible to initialize the recording film 33 by irradiating the optical disc with the irradiating light at a recording level and rotating the optical disc at a linear velocity slower than the linear velocity at the time of writing.

In other words, by making the linear velocity at the time of initializing the optical disk slower than that at the time of writing, the amount of light irradiated per unit area at the time of initialization becomes greater than that at the time of writing, so the intensity of the light beam can be increased. The same effect can be obtained by doing so.

According to this, the burden on the laser, servo system, etc. used can be reduced compared to the case of the previous embodiment, and the initialization area can be wider because the amount of irradiation light per unit area is large. become.

In each of the above embodiments, the case of group recording has been described, but the same effect can be achieved even in the case of land recording.

As described in detail, according to the recording and reproducing method for a phase change optical disk according to the present invention, an initializing beam having a power higher than the writing power is irradiated onto the first disk, or the linear velocity is lower than the linear velocity during writing. By initializing the recording film of the optical disk by rotationally driving the optical disk at a linear velocity, a wide crystallized region can be ensured, so that the erasing rate during overwriting can be improved.

Furthermore, in a recording and reproducing apparatus to which such a recording and reproducing method is applied, the initialization state can be changed simply by controlling the drive current of the semiconductor laser or the rotational speed of the spindle motor, and the same Since initialization can be performed using an optical system, initialization can be performed within the same device, which also contributes to reducing the cost of the disk itself.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a recording and reproducing apparatus to which a recording and reproducing method for a phase change optical disc according to the present invention is applied;
Figure 2 is a diagram showing the magnitude relationship of each light beam intensity during writing, erasing, and reading on the disc, Figure 3 is a configuration diagram of the optical system, Figure 4 is a structural diagram of the optical disc, and Figure 5 is initialization. Figure 6 shows the crystal structure of the recording film observed with a transmission electron microscope when recording was performed after initialization with a power of 11 mW, and information was overwritten with overwrite powers of 18 mW and 11 mW. Figure 6 shows Figure 5. A simplified schematic diagram, Figure 7, shows recording after initialization with an initialization power of 18mW, and further overwrite powers of 18mW and 11mW.
FIG. 8 is a photograph showing the crystal structure of the recording film observed by a transmission electron microscope when the information is overwritten in the image, and FIG. 8 is a schematic diagram showing FIG. 7 in an easy-to-understand manner. Explanation of symbols of main parts 1... Semiconductor laser 5.12... Power setting circuit 8.15... Current drive circuit 23... Polarizing prism 25. ...Objective lens 26...Half prism 30...
...Optical disc 32...Group 3
3...Recording film applicant Pioneer Corporation

Claims (3)

[Claims] (1) A recording and reproducing method for writing, erasing, and reading information by irradiating an overwritable phase change optical disk with a single light beam at high, medium, and low levels of intensity, the light beam A recording and reproducing method for a phase-change optical disc, characterized in that a recording film of the optical disc is initialized by irradiating the optical disc with an intensity at an initialization level equal to or higher than the high level. (2) A recording and reproducing method for writing, erasing, and reading information by irradiating an overwritable phase change optical disk with a single light beam at high, medium, and low levels of intensity, the light beam The recording film of the optical disc is initialized by irradiating the optical disc with an intensity at an initialization level equal to or lower than the high level and rotating the optical disc at a linear velocity slower than a linear velocity during writing. A recording and reproducing method for phase change optical discs. (3) The method for recording and reproducing a phase change optical disc according to claim 1 or 2, wherein the light beam is a circular beam.