JPS63119033A - Information recording medium - Google Patents

Abstract

PURPOSE:To prevent the generation of crosstalk even when a track pitch is made smaller by forming the boundary of a track to a protruding shape having a sharp peak part, and providing an information recording part having a smooth and continuous surface among respective tracks. CONSTITUTION:For a recording surface 32 of a disk substrate 31, a cross section in a radius direction R of an optical disk 25 is formed to a wave shape, a peak part 33 formed in a sharp angle shape and an information recording part 34 composed of a smooth surface formed between respective peak parts 33 are held, and a bit column 37 formed on an information recording part 34 constitutes the track in the optical disk 25. When a laser light converged by an objective lens, etc., discharged from a laser light source is irradiated in the vicinity of the boundary of the track of the media, the laser light is reflected in a different direction with a peak part as a boundary. Consequently, the information recorded at a mutually adjoining track is not simultaneously read and the crosstalk is hard to occur.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an information recording medium in which groups for recording information are provided in advance on the surface of a substrate.

(Prior Art) Conventionally, substrates for information recording media, such as optical disks, have groups (guide grooves) on the surface in addition to flat substrates.
A substrate provided with is often used. One of the advantages of providing this group is that when reproducing information, when a spot is irradiated onto the group, a slight track deviation will appear as an imbalance in the light intensity distribution of the reflected and diffracted light from the group, allowing accurate tracking. It is possible to do so.

As an example of an optical disc having such groups, a write-once optical disc is shown in FIG. 5. In the figure, a recording layer 12 is provided on the surface of an optical disc substrate 11.

The recording layer 12 is provided with a plurality of concentric croup 13. P in FIG. 0 indicates the pitch of these groups, and the plane between each group 13 is a portion called a land.

Predetermined information is recorded by condensing a laser beam emitted from a laser beam WL (not shown) onto the group 13 or land 14 using an objective lens or the like to form a bit string. Furthermore, during reproduction, the recorded bit string is irradiated with laser light from a laser light source, a change in the reflected light is detected by a predetermined photodetector, and information is extracted by converting this into an electrical signal.

(Problems to be Solved by the Invention) The optical disc as described above is well known as an information recording medium having an extremely large recording capacity.

By the way, when the information recorded on the above-mentioned optical disk is very fine like image information, an even larger capacity is desired. However, since the external dimensions of optical discs are standardized, in order to increase the capacity of optical discs, the track pitch P must be adjusted to
A conceivable solution is to make it even smaller than m to increase the density of recorded information. However, an optical disc having groups 13 configured as shown in FIG. 5 has a problem in that crosstalk occurs between adjacent tracks and the S/N ratio of the reproduced signal deteriorates.

Note that this problem similarly occurs when the information recording medium is a magneto-optical disk.

(Means for Solving the Problem) The problem of the prior art described above is that in an information recording medium in which tracks are provided adjacent to each other, the boundaries of the tracks are formed in a convex shape with a sharp top, and each This problem can be solved by an information recording medium characterized in that an information recording section consisting of a smoothly continuous surface is provided between tracks.

(Function) Since the information recording medium of the present invention is configured as described above, when laser light emitted from a laser light source and focused by an objective lens etc. is irradiated near the boundaries of the tracks of the medium, , the laser beam is reflected in different directions from the top. Therefore, information recorded on mutually adjacent tracks is not read simultaneously, and crosstalk is less likely to occur.

Furthermore, since the information recording section is composed of a smoothly continuous surface, the irradiated light is not lost due to diffraction or the like, and recording and reproduction can be performed efficiently.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic perspective view showing one embodiment of an information recording medium according to the present invention. Although an optical disk will be used as the information recording medium in this embodiment, this is not intended to limit the present invention. .

In the figure, an optical disc 25 is formed of a disc substrate 3L made of transparent plastic such as polycarbonate, glass, or the like. The recording surface 32 of the disk substrate 31 has a wavy cross section in the radial direction R of the optical disk 25 as shown in the figure, and preferably has an acute-angled apex 33 and a smooth surface formed between each apex 33. It has an information recording section 34 consisting of a surface. Reference numeral 37 denotes a bit string formed on the information recording section 34, which constitutes a track on the optical disc 25. T in the figure indicates the track direction, and is formed in the same circular shape on the optical disc 25.

Further, P in FIG. 1 indicates a track pitch, and the track pitch P is the track pitch 1. [
+ It is formed smaller than gm. This is possible due to the configuration of this embodiment, and the reason for this will become clearer from the effects of this embodiment described later. As a result, the optical disc 25 of this embodiment can record information at a higher density than conventional optical discs.

FIG. 2 is a schematic diagram of the optical system in the optical disc information recording and reproducing apparatus configured as described above.

In the figure, a laser beam emitted from a laser light source is partially reflected by a beam splitter 23 and partially transmitted. The transmitted light is focused onto the recording surface 32 of the optical disk 25 by the objective lens 24. The focused laser beam is reflected on the recording surface 32, passes through the objective lens 24 again, is reflected by the beam splitter 23, and enters the photodetector 22.

To record information on the recording surface 32, a laser light source is driven by a predetermined information signal, and the laser beam 1 (emitted from L and focused by the objective lens 24 is directed onto the recording surface 32). The laser beam [
The laser beam emitted from L is focused by the objective lens 24 and irradiated onto the recording surface 32. The amount of laser light reflected on the recording surface 32 is changed depending on the presence or absence of pits on the recording surface 32. The amount of returned light, which is changed depending on the presence or absence of this bit, is received by the photodetector 22, converted into an electrical signal, and the recorded information is read.

Next, the operation of this embodiment will be explained. As shown in FIG. 3, laser light irradiated onto the recording surface 32 from a laser light source (not shown) is reflected in different directions from the vertex 33 as a boundary. Therefore, even if a portion of the laser beam were to be irradiated onto a track adjacent to the target track, the reflected light would travel in a different direction from the reflected light on the target track, so no crosstalk would occur. This effect is effective even if the track pitch is smaller than that of the conventional method. Therefore, according to the optical disc of this embodiment, it is possible to realize a high-density recording medium in which crosstalk is prevented.

Furthermore, in the optical disc of this embodiment, since the information recording section 34 between the top portions 33 is formed with a smooth surface, the laser beam irradiated onto the recording section 34 is less likely to be lost due to diffraction or the like. In addition to this effect, it is also beneficial for improving the S/N ratio.

Furthermore, since the top portion 33 of the optical disk is provided in the track direction as described above and is provided at the boundary between adjacent tracks, it also functions effectively during tracking. That is, when tracking is performed using the well-known three-beam method, for example, if the two side beams are set so that they each cover both apexes 33 of the target track, when a track shift occurs, the reflected diffracted light of these side beams This makes it possible to easily and accurately detect tracking errors.

Next, an example in which the surface of the information recording section 34 is made flat is shown in FIG. 4. This embodiment has the same structure as the above embodiment except that the information recording section 34 is made flat. , diffraction of the irradiated light from the laser light source, etc. can be suppressed more effectively than in the above embodiments.

Although an optical disk has been described above as an information recording medium according to the present invention, the present invention is not limited thereto, and can also be applied to known magneto-optical disks. Furthermore, it is also applicable to carts with linear tracks such as optical carts.

(Effects of the Invention) As explained above, according to the information recording medium of the present invention, the occurrence of crosstalk can be effectively prevented even if the track pitch is made small. Therefore, high-density recording with a good S/N ratio is possible.

Furthermore, since the track on which the pit row is to be formed is formed of a smoothly continuous surface, the laser beam is not lost due to diffraction or the like, and efficient recording and reproduction are possible.

[Brief explanation of the drawing]

FIG. 1 is a schematic perspective view showing an embodiment of an information recording medium according to the present invention, FIG. 2 is a schematic configuration diagram showing an optical system of an optical disk recording/reproducing device, and FIG. 3 is the same as shown in FIG. 1. FIG. 4 is a schematic cross-sectional view of another embodiment of the present invention, and FIG. 5 is a schematic perspective view of a conventional information recording medium having groups. 25... Optical disk, 31-... Disc substrate, 32
...Record surface, 33-...Top, 34...Information Record Department Agent Patent Attorney Seki Yamashita Figure 1 R Figure 2 Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] In an information recording medium in which tracks are provided adjacent to each other, the boundaries of the tracks are formed in a convex shape with a sharp top, and an information recording portion is provided that has a smoothly continuous surface between each track. Characteristic information recording media.