JPH0481816B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an optical information storage carrier such as an optical disk used for optically recording and reproducing information, and in particular to an optical information storage carrier such as an optical disc that is used for optically recording and reproducing information. This relates to the shape of the guide track groove.

2. Description of the Related Art In recent years, optical disk devices have been commercialized as large-capacity storage devices that are applied to image files, document files, or data files.
Optical disks have more than 10 times the storage capacity of magnetic disk devices used as external storage devices for computers, and can record and read information without contact. This uses a highly monochromatic laser beam to record and reproduce information on an optical disk, focuses this light onto a small spot using a high-magnification lens with little aberration, and at the same time uses a control signal detected from the optical disk. This is because the spots can be controlled with high precision and information can be stored in a narrow track pitch.

In this way, the track control signal detected from the optical disk plays an important role in recording information on the optical disk at high density. Usually, this track control signal is generated by a guide groove for an optical spot guide having an uneven shape formed on the information recording surface of the optical disk.

The structure of an optical disk and how track control signals are detected will be described below with reference to the drawings.
FIG. 3 is a cross-sectional view of an example of an optical disk and an enlarged view of a portion thereof. The optical disk 1 is composed of a substrate 4, an optical spot guide layer 5, an information signal recording layer 2, and an adhesive layer 3. In other examples of optical disks, the adhesive layer 3 may be an air layer.

Recording and reproduction of information using the optical disc 1 is as follows:
This is mainly performed by focusing light from a laser as a light source onto the information signal recording layer 2 using a lens 8. At this time, the light beam is focused onto the information signal recording layer 2 via the substrate 4 and the optical spotting guide layer 5. An uneven groove is formed in the portion where the optical spot guide layer 5 and the information signal recording layer 2 are in contact with each other, and the optical spot is guided by this groove.

Conventionally, a method has been adopted in which a convex portion of the uneven shape when viewed from the lens 8 side is used as a track, and an information signal is recorded on this track.
In other words, a light spot is guided along this track 7, and the information pits 6 are written and read.

Next, the principle by which a track control signal is detected from this uneven shape will be explained. FIG. 4 is a diagram explaining the principle of extracting a track control signal from this uneven shape, which is called the push-pull method or the far-field method. Now, if a light spot hits the center of the convex part of the guide groove 14 as shown in FIG. The light beam has a uniform distribution as shown in FIG.
incident on . The output of the two-split photodetector is the detector 13
The outputs of -1 and 13-2 are taken out independently, and a difference signal between them is determined by a circuit. Fourth
In the case of FIG. 2, the light is uniformly incident on the two photodetectors, so the difference signal is zero. On the other hand, in case 1 or (3) 3 in Fig. 4, the center of the convex part of the guide groove 14 is shifted from the center of the light spot, so the intensity distribution of the reflected light is only partially distributed at 15" and 15". From a biased perspective,
The output of the two-split photodetector 13 is also 13-1 and 13-2.
The difference signal is not 0, but
It will take a + or - value. Therefore, these two
If the light spot is controlled by moving the lens 12 so that the difference signal between the outputs of the divided photodetectors becomes 0,
The light spot always follows the convex portion of the guide groove, allowing tracking.

On the other hand, to reproduce information from the optical disk, a sum signal of the outputs of each of the two-split photodetectors is used. This is to reproduce a signal with good quality using all the light reflected from the optical disk and received by the photodetector.

Next, a process for manufacturing an optical disk having guide grooves for track control will be described with reference to the drawings. FIG. 5 is a diagram illustrating the manufacturing process of an optical disk having guide grooves.

Usually, the guide groove is produced by a laser cutting machine using a short wavelength laser of about 450 nm, and the search signal for track search is also produced in an uneven shape at the same time. Such guide grooves and search signals are created by irradiating a laser beam 18 onto a glass disc 16 coated with a photoresist 17 to create a latent image, and through a developing process, the photoresist in the area hit by the laser beam is removed. Created by removing. From the glass master 19 produced in this way,
A metal master 20 is made, and a large number of replica disks 21 are made from this metal master 20, thereby completing an optical disk substrate having a guide groove for an optical spot guide and a track search signal. An information signal recording layer 22 made of an optical recording material is applied onto the uneven shape of the substrate surface by coating, vapor deposition, sputtering, etc., and is adhered to another disk or protective substrate 25 to form an optical disk. Complete.

As can be seen from FIG. 5, the convex portion of the guide groove of the optical disk is a portion 26 where the surface of the glass plate 16 is exposed after the photoresist is removed by laser irradiation, and this serves as a track.
In addition, the track search signal can be used to create an uneven shape by modulating the intensity of the laser beam and changing the width or depth of the guide groove according to the signal when creating a guide groove on a glass plate using a laser beam. formed on a glass plate. Therefore, the search signal is formed on a convex portion of the guide groove, that is, a part of the track.
Conventionally, as guide grooves for track control of optical disks, the groove width of the convex part was 1/2 of the track pitch.
Smaller shapes are taken, e.g. track pitch
When the thickness is 1.6 μm, a convex width of about 0.5 to 0.7 μm is used. This is because when producing the convex portion of the guide groove, the laser beam is focused using a lens with high magnification in order to achieve precision on the side surfaces of the groove.

Hereinafter, with reference to the drawings, the difference signal of the output of the two-split photodetector for track control obtained when using a conventional guide groove, and the sum signal of the output of the two-split photodetector for signal regeneration will be explained. Describe the changes.
FIG. 6 shows the difference signal and sum signal obtained from the conventional guide groove when the optical spot crosses one track from the convex part of the guide groove forming the information track and moves to the center of the next track. This is a graph showing changes in . The horizontal axis represents the position of the optical spot, and the vertical axis represents the levels of the sum signal and difference signal when the optical spot reaches that position. In this figure, the track pitch is 1.6 μm, the guide groove depth is 700 Å, and the convex width is 0.6 μm. Further, below the graph, the cross-sectional shape of the guide groove is shown. As described above, the difference signal 27 becomes 0 at the center of the convex portion and the center of the concave portion of the uneven shape, but the phase of the waveform of the difference signal 27 differs between the center of the concave portion and the center position of the convex portion. By controlling the lens so that the difference signal 27 becomes 0 with the same phase, the light spot is controlled to always follow the center of the track 29. On the other hand, the sum signal 28 has a maximum value and a minimum value at the centers of the concave and convex portions of the guide groove, respectively. This is because the light irradiated by the guide groove is diffracted. Therefore, the sum signal 28 always takes the minimum value when the optical spot is following the track 29. This is because light is diffracted by the guide groove, and especially when the light hits a narrow convex portion, diffraction loss increases.

Problems to be Solved by the Invention In the guide groove for track control with such a conventional configuration, the width of the track portion followed by the light spot is narrow. This has the problem that the signal becomes smaller and the quality of the reproduced signal that is obtained is therefore lowered.

On the other hand, as a method for preventing the sum signal from becoming small, there is a method in which a recessed portion of a guide groove is used as a track. This attempts to record and reproduce information bits by using the recessed portions of the guide groove, which are wider than the convex portions, as tracks. Indeed, if you do it this way, the diffraction losses will be lower,
Although the amount of signal light to be reproduced increases, it becomes impossible to search for a track because the track search signal enters the convex portion of the guide groove. In addition, since the phase of the difference signal of the two-split photodetector detected as a track control signal is 180° different than when the concave portion is used as the track, the convex portion of the conventionally used guide groove is used as the track. Interoperability with optical disks will be lost.

Furthermore, the surface of the convex part of the guide groove is laser cut when the glass master is made, the photoresist is removed, and the surface of the glass plate with high precision is transferred, whereas the concave part of the guide groove is Since the bottom surface of the photoresist is directly transferred, there is a lot of surface noise, making it a track with a high noise level as an information track.

As described above, the method of using the concave portions of the guide grooves as tracks also has more problems than the conventional disks in terms of search signal detection, compatibility with conventional disks, and track noise level.

Regarding the search signal, which is one of the problems with recessed track type discs, a method has been proposed in which a search signal is separately inserted into the recessed part of the guide groove. The problem of truck noise levels remains. Also, if a search signal is applied to the concave portions, the signal will also be input between the convex portions, and the pitch in the track direction of the portion with the search signal will be half of the original pitch, resulting in a higher pitch. Another problem is that it becomes necessary to create a highly accurate uneven shape.

In view of the above-mentioned problems, the present invention detects a track control signal equivalent to that of conventional disks, and also detects a large amount of signal light that affects the quality of the reproduced signal. An object of the present invention is to provide an optical information storage carrier which is compatible with the optical discs of 2004 and 2000, and further has a guide groove for track control with a low track noise level.

Means for Solving the Problems In order to solve the above problems, the optical information storage carrier of the present invention includes a substrate, and on the substrate,
one or more tracks for an optical spot guide formed in an uneven shape, and a search signal formed in an uneven shape in each track to search for a predetermined track from the one or more tracks; and an information signal recording layer formed on the optical spot guide layer, and the track is formed of the optical spot guide layer when viewed from the side of the lens that focuses the optical spot on the track. The width of the track is 1/1 of the track spacing.
It has a wider configuration than 2.

Effects The present invention has the above-mentioned structure, and as in the conventional example, when viewed from the lens side, the convex portion of the guide groove is used as a track, and the width of the track is made wider than 1/2 of the track interval. This prevents an increase in light diffraction loss due to the grooves, thereby increasing the amount of signal light detected and allowing high-quality signal reproduction.

Moreover, in the present invention, since the convex portion of the guide groove is used as a track as in the conventional example, the phase of the track control signal is the same as in the conventional example, and it is compatible with the conventional optical information storage carrier. There is.

Furthermore, in the present invention, since the search signal is also formed as a part of the track, the same process as conventional methods can be used when producing the information storage carrier.

Further, in the present invention, since the tracks are the convex portions of the guide grooves which are transferred from the glass surface during the preparation of the glass master, it is possible to provide good tracks with a low noise level.

Examples Examples of the optical information storage carrier of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of the optical information storage carrier of the present invention. In FIG. 1, an optical disc 1 includes an information signal recording layer 2, an adhesive layer 3, a substrate 4,
It is composed of a light spot guide layer 5. With respect to the optical disc 1, the light spot focused on the information signal recording layer 2 by the lens 8 is located at a portion 7 of the uneven shape formed on the optical spot guide layer 5, which corresponds to a convex portion when viewed from the lens 8 side. As the track,
Following this track 7, the information pit 6 is written and read. Further, the track search signal is formed on a part of the track 7, and when the optical spot follows the track 7, the search signal can be read out. Here, the width of this track 7 is set to a value larger than P/2 with respect to the track pitch P.

Next, in this embodiment, two
Changes in the difference signal and sum signal of the split photodetector will be explained with reference to the drawings. FIG. 2 shows changes in the difference signal for track control and the sum signal for information signal reproduction obtained from the optical information storage carrier of this example when a light spot crosses a track. . In FIG. 2, the horizontal axis represents the position of the optical spot, and the vertical axis represents the levels of the sum signal and the difference signal when the optical spot is at that position. In this figure, the track pitch is 1.6 μm, the guide groove depth is 700 Å, and the convex width is 1.0 μm.

In FIG. 2, graph 9 shows changes in the difference signal of the outputs of the two-split photodetector detected by the optical information storage carrier of this embodiment, and graph 10 similarly shows changes in the sum signal. As is clear from FIG. 2, the difference signal 9 of the two-split photodetector for track control detected by the optical information storage carrier of this embodiment
becomes 0 at the center of the track 11 formed by the convex portion of the guide groove, similar to the difference signal detected by the conventional optical information storage carrier, and has exactly the same phase characteristics as the conventional example. It has become a differential signal. On the other hand, the sum signal reaches its maximum at the center position of the track 11, indicating that, unlike the conventional example, good information signal reproduction can be performed. This is because the width of the convex portion 11 of the guide groove forming the track is made wider than 1/2 the track pitch.
This is because the diffraction loss due to the guide groove is reduced. Guide grooves with such wide convex parts can be obtained by lowering the numerical aperture of the condensing lens of the laser cutting machine or by vibrating the light spot perpendicular to the track on the glass master. can.

As described above, according to this embodiment, the track followed by the light spot in the light spot guide layer of the optical information storage carrier is set so that it hits the convex part of the guide groove when viewed from the lens side that condenses the light spot. However, at the same time, a track search signal is also formed in a part of the track, and the width of the track is configured to be wider than 1/2 of the track pitch.
A track control signal equivalent to that of a conventional optical information storage carrier with a narrow track width can be obtained, and at the same time, high-quality signal reproduction can be achieved because there is little light diffraction loss due to the guide groove.

Furthermore, according to this embodiment, since the track search signal is also formed as a part of the track, the same process as in the prior art can be used when producing the storage carrier.

Furthermore, according to this embodiment, since the tracks are the convex portions of the guide grooves that are transferred from the glass surface when the glass master was created, it is possible to obtain tracks with a low noise level.

Effects of the Invention As described above, the present invention includes a substrate, one or more tracks for a light spot guide formed in an uneven shape on the substrate, and one or more tracks in the one or more tracks formed on the substrate. It consists of an optical spot guide layer having a search signal formed in an uneven shape in each track to search for a predetermined track from the track, and an information signal recording layer formed on the optical spot guide layer. The track is constituted by a convex portion of the spot guide layer when viewed from the lens side that focuses the light spot on the spot guide layer, and
By making the track width wider than 1/2 of the track spacing, it prevents an increase in light diffraction loss due to the guide groove, which increases the amount of signal light detected and enables high-quality signal reproduction. I can do it.

Further, since the convex portion of the guide groove is used as a track as in the conventional example, the phase of the track control signal is the same as in the conventional example, and it is compatible with the conventional optical information storage carrier.

Furthermore, since the search signal is also constructed in each track, the same process as before can be used when producing the information storage carrier.

Furthermore, since the convex portions of the guide grooves to which the glass surface was transferred during the preparation of the glass master are used as tracks, it is possible to provide an optical information storage carrier having good tracks with a low noise level.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing the configuration of an optical information storage carrier according to an embodiment of the present invention, FIG. 2 is a waveform diagram showing its effect, and FIG. 3 is a configuration of a conventional optical information storage carrier. 4 is a schematic diagram illustrating the principle of track control, FIG. 5 is a process diagram illustrating the manufacturing process of an optical information storage carrier, and FIG. 6 is a conventional optical information storage carrier. FIG. 1... Optical disk, 2... Information signal recording layer, 3
...Adhesive layer, 4...Substrate, 5...Light spot guide layer, 6...Information pit, 7...Track, 8...
...Lens, 9, 27...Difference signal of two-split photodetector, 10,28...Sum signal of two-split photodetector, 1
1, 29...Truck, 12...Lens, 13...
...2-split photodetector, 14... Guide groove cross section, 15
...Reflected light intensity distribution, 16...Glass plate, 17...
...Photoresist, 18...Laser light, 19...
...Glass Master, 20...Metal Master, 21
... Replica disk, 22 ... Information signal recording layer, 23 ... Optical disk, 24 ... Lens, 25
...Protection board, 26...Glass plate surface portion.

Claims (1)

[Claims] 1 a substrate, one or more tracks for light spot guiding formed in an uneven shape on the substrate, and each track for searching a predetermined track from among the one or more tracks; It consists of a light spot guide layer having a retrieval signal formed in an uneven shape therein, and an information signal recording layer formed on the light spot guide layer, and when viewed from the lens side that focuses the light spot on the track. An optical information recording carrier characterized in that said tracks are formed of convex portions of said optical spot guide layer, and the width of said tracks is wider than 1/2 of the track spacing.