JPS61239427A - Rewritable optical disk device - Google Patents

Abstract

PURPOSE:To improve the recording density of a rewritable optical disk device by providing previously a crystallized guide track to perform scanning with a modulated light beam and in response to the record information and forming the information recording pits turned into an amorphous state. CONSTITUTION:An area corresponding to an address signal is crystallized in an address area 1 and then the address signal recording pits 3 are recorded in the area 1. While the linear recording pits 4 are recorded in a data area 2 through the continuous crystallization. When the information is recorded, the pits 4 formed in a product shipment mode are turned into the amorphous state according to the information for production of information signal recording pit 5. Thus the information can be recorded. While the areas turned into the amorphous state on the pits 4 are returned to the crystallized state by means of an erasion beam. Thus the information is erased.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a rewritable optical disc device that records and erases information by irradiating a recording medium with a light beam.

[Prior art]

In recent years, optical disk devices have been actively developed as a method for recording large-capacity information. Compared to conventional magnetic disk devices, optical disk devices have a density of 10 to 1 per unit area.
It has excellent features such as being capable of high-density recording approximately 00 times higher, being non-contact and durable for long-term use, and being easy to copy data.

At present, there are two main types of optical discs: a method in which holes are formed in the recording thin film using the thermal energy of the Rede light, and a method in which the optical properties of the recording thin film, such as refractive index and reflectance, are changed. . The former cannot be erased and therefore cannot be rewritten, but the latter is attracting attention as a rewritable optical disc. As a recording medium for this rewritable optical disk, for example, a TeOx thin film containing Ge or Sn is known.

This TeOx thin film is amorphous in the as-deposited state. By irradiating this with a laser beam and gradually cooling it to remove heat, it crystallizes and the refractive index increases, and the reflectance and transmittance change accordingly. Information is reproduced by optically reading changes in reflectance or transmittance.

Conversely, it is also possible to return a crystallized film to a shearmorphous state by rapidly heating and cooling it. That is, information is recorded by utilizing the fact that the laser beam reversibly changes into two states depending on the irradiation method.

Such optical disc devices generally use two laser beams, one for recording and reproduction and one for erasing.

FIG. 2 is a conceptual diagram showing the recording and erasing method of such a conventional optical disc device. In FIG. 2, 100 is a recording bit, and 1101 + 1102 *1103 is a groove track for tracking guide. Reference numeral 120 denotes a laser spot for recording, which is approximately 1 μm in diameter, and 130 is a laser spit for erasing, which is formed into an oval shape of approximately 1×10 μm. In FIG. 2, the shaded area is a crystallized area and the other area is an amorphous area.

As mentioned above, a slightly stronger laser beam focused to the diffraction limit is used for recording, and the recording medium is rapidly heated and cooled to become shear amorphous. For erasing, if the laser power of the erasing beam is made to be about the same as that of the recording beam, the power per unit area will be small, and the recording medium will be irradiated with low power for a relatively long time. Therefore, the recording medium is gradually cooled to remove heat, and the amorphous region is crystallized and erased.

However, in order to perform erasing and re-recording in this manner, accurate tracking of the laser beam is required.

Generally, tracking is carried out in a readout device that detects irradiated light.

One of the tracking methods is to provide a tracking guide groove track on the surface of a recording medium, and record, reproduce, and erase information along this groove track.

The width of this groove track is approximately 0.5 to 1 mm.

A two-split photodetector is used to detect the tracking error signal, and their differential output is used as the tracking error signal.

FIG. 3 is a diagram schematically showing the distribution of the amount of reflected light received by the photodetector when the optical beam bit crosses the groove track.

In FIG. 3, 140 is a recording medium, 150 is a groove track, and 160 is a light beam. 170 is the recording medium 1
180 shows the light amount distribution of the light received by the left photodetector among the reflected light of the light beam 160 irradiated to 40, and 180 shows the light amount distribution of the light received by the right photodetector.

If the center of the light beam 160 coincides with the center of the groove track 150 as shown in FIG. 3(b), the outputs of the two photodetectors are equal and the irradiation position of the light beam 160 does not change. However, when the end of the groove track 150 is irradiated with the light beam 160 (as shown in FIGS. 3(a) and 3(c)), the depth of the groove track 150 is 1/8n wavelength (n: the refractive index of the disk). ), the groove track 150 and the groove track 150
Both reflected lights from other parts cause interference, and the outputs of the two photodetectors are no longer equal. For example, when the left side of the groove track 150 is irradiated with the light beam 160 as shown in FIG. Due to the differential, the light beam 160 moves to the right.

By using the above tracking method, the light beam can accurately track the recording pits. 1 more
Since recording, reproduction, and erasing can be performed using the light beam of the book, the number of optical components can be reduced, and the optical system can be adjusted relatively easily.

[Problem that the invention seeks to solve]

However, the optical disc apparatus using the above-mentioned tracking method requires a minute unevenness IP turn on the recording medium, which has the drawback of increasing the number of manufacturing steps compared to a non-grooved disc, resulting in a significant increase in cost.

On the other hand, when a disk without groove tracks is used, there is a drawback that crosstalk between recorded pit rows is likely to occur due to external vibrations, etc., since there is no object to be tracked during recording. For discs without groove tracks,
Although there is a method of separately providing recording pits exclusively for tracking, this method has the disadvantage that the track pitch cannot be reduced due to the provision of extra recording pits, making it difficult to achieve high density.

[Means for solving problems]

According to the present invention, in order to solve the above-mentioned problems, in an optical disk device using a recording medium in which a crystallized form that can be optically determined by irradiation with a light beam reversibly changes to an amorphous state, Forming information recording pits in an amorphous state by providing a pre-crystallized guide track on an amorphous recording medium and scanning the guide track with a light beam modulated according to recorded information. A rewritable optical disc device is provided which is characterized by:

〔Example〕

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

FIG. 1 is a conceptual diagram showing the recording and erasing method of the rewritable optical disc device of the present invention.

In FIG. 1, the shaded areas indicate recording pits on the crystallized recording medium, the 1 area indicates the address area, and the 2 area indicates the data area.

In addition, Fig. 1(,) is the state before information recording, Fig. 1(b)
indicates the state after recording.

The optical disk of the present invention is in an amorphous state in advance, and at the time of shipment, while the track surface is being fed by a feeding device with extremely little speed variation, an optical head exclusively for recording is used to move the address area as shown in FIG. 1(a). 1, address signal recording pits 3 are recorded by crystallizing an area corresponding to the address signal, and in data area 2, line-shaped recording pits 4 are recorded by continuous crystallization. Be sure to record it.

The linear recording pits 4 also serve as guide tracks when recording information, and tracking along these guide tracks (that is, the linear recording bits 4) can be performed using a known three-beam method or the like. It is easier.

When recording information using the optical disk of the optical disk device of the present invention, as shown in FIG. 1(b), the linear recording pits 4 provided at the time of product shipment are made amorphous according to the information. Recording can be performed by creating signal recording pits 5.

In addition, when erasing the information recorded as described above, an erasing beam is used to return the amorphous region on the linear recording pit 4 to a crystallized state.
Delete information.

In the present invention, since a phase change from crystal to amorphous due to rapid heating and cooling is used when recording information, it has the advantage that high frequency recording can be performed and the recording time can be shortened.

Note that in the present invention, the direction of the signal in the address area 1 and the direction of the signal in the data area 2 are opposite, but when reading the signal in the data area 2, it is read through an inverting circuit. There is no problem as it can be easily solved.

Furthermore, as the amorphous magnetic film used in the present invention, in addition to the TeOx thin film described in the conventional example, a CdDyF'e thin film can also be used, and the laser beam irradiation method (intensity, Any material can be used as long as it changes to an amorphous state or a crystallized state by changing the irradiation time, wavelength, etc., and as a result changes the transmittance or reflectance of the irradiated area.

〔Effect of the invention〕

As described in detail above, according to the present invention, it is possible to provide an inexpensive rewritable optical disk device that can perform high-density recording using a grooveless disk that is inexpensive to manufacture.

[Brief explanation of the drawing]

FIG. 1 is a conceptual diagram showing the recording and erasing method of the rewritable optical disc device of the present invention. FIG. 2 is a conceptual diagram showing a recording and erasing method of a conventional optical disc recording device. FIG. 3 is an explanatory diagram showing an example of a tracking method for a conventional grooved disk. 1: Near address area, 2: Data area, 3: Near address signal recording pit, 4: Near guide track, 5: Information signal recording bit. Agent Patent Attorney Seki Yamashita Children Figure 2 Figure 3

Claims (2)

[Claims] (1) In an optical disk device using a recording medium that reversibly changes to an optically distinguishable crystallized state or amorphous state by irradiation with a light beam, a pre-crystallized guide track is placed on the amorphous recording medium. What is claimed is: 1. A rewritable optical disk device, characterized in that information recording pits are formed in an amorphous state by scanning the guide track with a light beam modulated according to recording information. (2) The rewritable optical disk device according to claim 1, characterized in that the amorphous recording medium is provided with pre-crystallized guide tracks and pre-crystallized address signal recording pits. .