JPH0235637A - Optical information recording medium - Google Patents

Abstract

PURPOSE:To easily suppress the crosstalks from adjacent tracks and to effectively shorten track pitches by forming recording marks to the different depths of a magnetic material layer alternately to each of adjacent recording arrays. CONSTITUTION:The recording arrays 12, 14 on the recording medium 11 are formed with the recording marks to the different depths of the material layer alternately to each of the adjacent recording arrays. The depths at which the recoding marks are formed between the adjacent tracks can, therefore, be largely varied even if the guide grooves have about the depth of the conventional guide grooves. The decrease of the crosstalks between the adjacent tracks is possible in this way while the trouble by increasing the depth of the guide grooves is averted. The higher density of recording is thus obt. by shortening the track pitches.

Description

[Detailed description of the invention] [Purpose of the invention] (Industrial application field) The present invention relates to an optical information recording medium.

(Prior art) Conventionally, a disk is used as an information recording medium, information is recorded on the surface along spiral or concentric tracks, and information signals are optically irradiated with a light beam such as a laser beam. There is a device that plays back a digital audio disc using a compact disc system, or a video disc using a laser viewing system.There is also a document file system, which is a device that allows the user to record information signals onto an optical disc using a laser. etc. have been commercialized, and in recent years, products for use as peripheral storage devices for computers that require higher reliability have also been put into practical use.Furthermore, recorded information signals can be erased and rewritten. Such devices have been actively researched, and many publications have been published in nine academic conferences.Furthermore, optical card memory devices, which apply similar technology to card-shaped recording media, are being developed.

FIG. 3 shows an example of a recording medium surface used in a conventional optical information recording/reproducing apparatus. In FIG. 3, a converging light beam 32 on a medium 31 forms a source spot 33 and records or reproduces a recording mark 34. In FIG. Recording is performed by modulating the intensity of the irradiated laser light, and during reproduction, a weak power laser light is irradiated and the amount of reflected light is detected to read the presence or absence of marks. The light spot 33 is mechanically scanned over the medium surface to access the required recording position.

In this example, track guide grooves are formed in advance on the medium substrate, and tracking control is performed using diffracted light from the grooves to form recording rows along the guide grooves. It has a size determined by the limit and has a diameter of approximately 1 μm. Therefore, the size of the mark is also about the same size. Further, the distance between adjacent tracks (track pitch) is determined so that crosstalk from adjacent tracks is sufficiently small due to the size of such marks and spots.

With the expansion of the field of application of these optical information recording and reproducing devices as storage devices, there is a demand for even higher speeds and higher density devices. Various methods have already been considered for increasing the density of optical recording. For example, methods to reduce the convergent light spot by using a condensing lens with a high numerical aperture or a light source with a short wavelength, methods to use a highly efficient modulation method, and methods to increase the recording density by using multilevel recording, multilayer recording, or multiplex recording. Methods are being considered. In particular, multilevel, multiplex, or multilayer recording systems are expected to dramatically improve current recording densities. However, the characteristics required of these media are severe, and there are many technical problems such as control methods and optical systems necessary for recording and reproduction before they can be put into practical use. Therefore, the challenge is to develop a method that achieves higher density by improving the current method.

FIG. 4 schematically shows a recording medium in an example of an apparatus in which the recording density is improved by recording on both sides between the grooves and equivalently shortening the track pitch. In the figure, 41 indicates marks recorded on the grooves, and 42 indicates marks recorded between the grooves. In this example, it's trackbi.

Te becomes half of Bi and Chi in the groove. Therefore, by making the group pitch smaller than twice that of FIG. 3, the density can be improved. Therefore, the problems w1 in manufacturing that are caused by creating minute grooves when high-density forgery is to be achieved by connecting track pitches are eliminated. Although the polarity of the tracking error signal changes between the grooves and between the grooves, it can be detected at a high signal level because the grooves are large. However, for example, while focusing on a mark on the groove, The influence from the marks between the grooves mixes in, resulting in crosstalk.Therefore, it is difficult to reduce the track pitch to less than the size of the convergent light spot.

Figure 5 schematically shows a recording medium in another example of an apparatus in which recording is performed both on the Kll and between the grooves and the recording density is improved by equivalently shortening the track pitch. Marks recorded on the grooves, 52 indicate marks recorded between the grooves.In this example, the depth of the grooves is lowered by depth<mb compared to normal.Therefore, the focus is on the marks on the grooves. Between the grooves, the marks between the grooves are slightly out of focus.As a result, the resolution of the optical system for the marks between the grooves is reduced, effectively reducing crosstalk.The track pitch is shortened compared to the case in Figure 4. However, it is difficult to form deep grooves with high precision as in this example due to the plate technology, and there are problems such as uneven groove widths causing large noise. The impact is large;
As mentioned above by Mark, it has been difficult to realize a recording medium that can suppress the influence of crosstalk and improve resolution while pursuing high density.

SUMMARY OF THE INVENTION The present invention has been developed in view of the above circumstances, and its purpose is to provide an optical information recording medium that suppresses the effects of crosstalk and has high resolution and high density.

The present invention provides an optical information recording medium that optically writes or reads a recorded information sequence by irradiating a light beam.
The recording rows on the recording medium are optical information recording media in which recording marks are alternately formed at different depths of the recording material layer for each adjacent recording row.

(Function) With the above-described means, even if the guide groove has a conventional depth, the depths at which recording marks are formed between adjacent tracks can be made to differ greatly. Therefore, it is possible to reduce the crosstalk between adjacent tracks while avoiding the adverse effects of deepening the guide groove, and it is possible to achieve higher recording density by reducing the track pitch. An embodiment of the invention will be described in detail with reference to the drawings. Fig. 1 is a diagram schematically showing the configuration of a recording medium in an apparatus according to an embodiment of the invention.

In the figure, 11 is a disk substrate on which guide grooves have been formed in advance, 12 is a first recording layer formed by depositing a film on the substrate, and a film containing an organic dye can be considered as the first or second recording layer. It is desirable that the thickness of the zero or intermediate layer is set to 3 to 15 μm.

Recording and reproduction are performed by irradiating laser light from the side of the 11 disk substrate.

Tracking control is performed by detecting diffracted light from a guide groove formed on the disk substrate and using this as a tracking error signal. By reversing the polarity of the sign of the tracking error signal, the light spot can be made to follow both on the groove and between the grooves.

In the apparatus according to this embodiment, the circuit is configured to cause the optical spot to follow either on the groove or between the grooves, and thus intentionally adds a bias signal to the focusing control. Therefore, this bias signal can be set so that the depth of the focal point when the light spot is following the track on the groove is slightly different from the depth of the focal point when the light spot is following the track between the grooves. When the laser beam is following the track on the groove, it is focused on the 12 first recording layers, and when it is following the track between the grooves, it is focused on the 14 second recording layer. By adjusting the depth of the recording layer, marks can be formed in the recording layer at different depths for each adjacent track, or the marks can be reproduced.

With these configurations, it is possible to make the shape of the guide groove suitable for detecting the tracking control signal, and to change the recording depth for each adjacent track to be greater than the focal depth of the convergent light. As a result, even if the track hit is made smaller than before, crosstalk from adjacent tracks does not increase, making it possible to record at a higher density than before.

FIG. 2 is a diagram schematically showing the configuration of a recording medium in an apparatus according to another embodiment of the present invention.
1 is a disk substrate on which tracking control bits and bits such as address information and synchronization signals that define the configuration of sectors that are units of information recording and reproduction are formed in advance; 2;
2 is a first recording layer formed on the substrate, 23 is an optically transparent intermediate layer, and 24 is a second recording layer formed thereon. Recording and reproduction are performed by irradiating laser light from the side of the disk substrate 21.

Since the tiger and king control is performed by sampling the signals from the tiger and king control bits, a guide groove as in the first embodiment is not used. Even when such a disk substrate is used, crosstalk from the l1il contact track can be suppressed by changing the recording layer to be accessed for each adjacent track as in the previous example. Therefore, the present invention can be applied even to a disk in which a guide groove is not formed, such as a disk in which control information is extracted by a sampling method, and the recording density can be improved.

Although the embodiments of the present invention have been described above, the present invention is not limited to these embodiments. For example, in the embodiments of the present invention, a write-once type or a rewritable type optical disk is assumed, but a read-only type may also be used, and the present invention is not limited by these types. Moreover, although the medium shape is exemplified as a disk-shaped medium, it may also be card-shaped, and is not limited to the embodiments.

〔Effect of the invention〕

According to the present invention, it has become possible to easily suppress crosstalk from @-adjacent tracks in an optical information recording/reproducing device, and it has become possible to effectively narrow the track pitch. In other words, it has become possible to provide an optical information recording and reproducing device that is capable of recording and reproducing information at a higher density than before, with a relatively simple configuration.

[Brief explanation of the drawing]

Figure 1 is a diagram schematically showing the configuration of a recording medium in an apparatus according to an embodiment of the present invention, and Figure 2 is a diagram schematically showing the configuration of a recording medium in an apparatus according to another embodiment of the invention. Fig. 3 is a diagram schematically showing an example of the recording medium surface used in a conventional optical information recording/reproducing device, and Fig. 4 is a diagram showing an example of the surface of a recording medium used in a conventional optical information recording/reproducing device. FIG. 2 is a diagram schematically showing a recording medium by reducing the track pitch.

Claims (3)

[Claims] (1) In an optical information recording medium in which recorded information strings are optically written or read by irradiation with a light beam, the recording strings on the recording medium are formed by alternating layers of recording material for each adjacent recording string. An optical information recording medium characterized in that recording marks are formed at different depths. (2) The recording material layer has a multilayer structure of two or more layers, and the recording rows are formed by alternately forming recording marks on different recording material layers for each adjacent recording row. Optical information recording medium. (3) The optical information recording medium according to claim 1 or 2, wherein a track guide groove is formed, and the recording rows are formed on the guide groove and between adjacent guide grooves.