JPS6247841A - Storage carrier for optical information - Google Patents

Abstract

PURPOSE:To prevent the increase of the diffraction loss of light due to a guide groove and to increase the quantity of detection signals, by using the projected part of the guide groove as a track when viewed from the lens side and at the same time setting the track width at >=1/2 track space. CONSTITUTION:An optical disk 1 consists of an optical spot guide layer 5, an information signal recording layer 2 and an adhesive layer 3 formed on a substrate 4 respectively. Then a part where an optical spot stopped down to the layer 2 through a lens 8 against the disk 1 is formed and corresponding to the projected part of a recess/projection area of the layer 5 is used as a track 7 when viewed from the side of the lens 8. Then the information bits 6 are written and read in accordance with the track 7. While the track retrieving signal is produced at a part of the track 7 and the light spot reads out the retrieving signal in accordance with the track 7. The width of the track 7 is set at >=P/2 compared with the track pitch P. This prevents the increase of the diffraction loss due to the layer 5 and can increase the quantity of detection signals.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an optical information storage carrier used for optically recording and reproducing information such as an optical disc, and in particular to an optical spot guide formed on the storage carrier. Regarding the shape of track grooves for

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 a storage capacity ten times greater than magnetic disk devices used as external storage devices for computers, and can record and reproduce 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 heightens the spot using a control signal detected from the optical disk. This is because it allows accurate control and allows information to be stored with a narrow track pitch. ``As described above, the track control signal detected from the optical disk plays an important role in high-density recording of information on the optical disk. Normally, this track control signal is generated by a guide groove for a light spot guide having an uneven shape formed on the information recording surface of the optical disk.

Hereinafter, the structure of an optical disc and how track control signals are detected will be described with reference to the drawings.

FIG. 3 is an enlarged view of a disk cross-sectional shape and a portion thereof in one example of an optical disk. The optical disc 1 is composed of a substrate 4, a light spot guide layer 6, an information signal recording layer 2, and an adhesive layer 3. In other examples of optical discs, the adhesive layer 3 may be an air layer.

Recording and reproduction of information using the optical disc 1 is performed mainly 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 spot guide layer 6. An uneven groove is formed in the portion where the light spot guide layer 5 and the information signal recording layer 2 are in contact with each other, and the light spot is guided by this groove.

Conventionally, a method has been adopted in which a convex portion of this uneven shape when viewed from the lens B side is used as a track, and an information signal is recorded on this track.

That is, a light spot is guided along this track 7, and information bits 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 far field method. Now, the fourth
Assuming that a light spot hits the center of the convex part of the guide groove 14 as shown in Figure (2), the light reflected from this convex part and turned into a parallel beam by the lens 12 has a uniform intensity distribution 15. The light flux becomes incident on the two-split photodetector 13. The output of the two-split photodetector is output from detectors 13-1 and 1.
The outputs of 3-2 are taken out independently, and a difference signal is obtained by the circuit. In the case of Figure 4 (2), it is uniformly 2
Since light is incident on two photodetectors, the difference signal becomes 0. On the other hand, in the case of FIG. 4 (1) or (3), 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 partially Due to the bias, the output of the two-split photodetector 13 is also 13-1 and 13.
-2, and the difference signal will not be 0 but will take a value of 10 or -. Therefore, if the optical spot is controlled by moving the lens 12 so that the difference signal between the outputs of the two-split photodetector becomes O, the optical spot will always follow the convex part of the guide groove and tracking will be possible. Become.

On the other hand, to reproduce information from an optical disc, 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 disc 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 disc having guide grooves.

Usually, the guide groove is designed for short-wavelength radiation of about 450 nm.
The search signal for track search is also made 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 then removing the photoresist in the areas hit by the laser beam through a development process. It is made by

A metal master 20 is made from the glass master 19 made in this way, and this metal master 20
As a result, a large number of replica disks 21 are produced, and an optical disk substrate having a guide groove for guiding a light spot and a track search signal is completed.

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 a protective substrate 26 to complete the optical disk.

As can be seen from FIG. 5, the convex portion of the guide groove of the optical disc is a portion where the photoresist is removed by laser irradiation and the surface of the glass plate 16 is exposed.

It is minute 26, and this is the track. In addition, the track search signal can be used to create a guide groove on a glass tile using a laser beam, by modulating the intensity of the laser beam and changing the width or depth of the guide groove according to the signal. Formed on the board. Therefore, the search signal is formed in the convex portion of the guide groove, that is, in a part of the track. Conventionally, guide grooves for track control of optical discs have a shape in which the groove width of the convex portion is smaller than the track pitch A, for example, a track pitch of 1.6 μm.
In this case, a convex portion having a width of about 0.6 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 obtain 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 reproduction will be explained. Describe the changes.

FIG. 6 shows the difference signal and sum signal obtained from the conventional guide groove when the light 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 depth of the guide groove is 700, and the width of the convex portion 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 part and the center of the concave part of the uneven shape, but the phase of the waveform of the difference signal 27 is different between the center of the concave part and the center position of the convex part. 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
have maximum and minimum values 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 light spot follows 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, so that the sum signal used when reproducing information stored on the optical disk is This has the problem that the quality of the reproduced signal that is obtained is lowered.

On the other hand, as a method for preventing the sum signal from becoming small, there is a method in which the concave portion of the guide groove is used as a track.

This attempts to record and reproduce information bits by using the mouth of the guide groove, which is wider than the convex portion, as a track. It is true that by doing this, the diffraction loss is reduced and the amount of signal light to be reproduced is increased, but since the track search signal enters the convex portion of the guide groove, the track cannot be searched. In addition, since the phase of the difference signal of the two-split photodetector detected as a track control signal is 1800 times different than when the convex part is used as a track, the convex part of the conventionally used guide groove is used as a track. Compatibility with optical discs will be lost.

Furthermore, the surface of the convex part of the guide groove is laser cut and the photoresist is removed during the production of the glass master, resulting in a highly accurate transfer of the surface of the glass plate, whereas the concave part of the guide groove Since the surface of the photoresist is directly transferred to the bottom surface, there is a lot of surface noise, and the track has a high noise level as an information track.

In this way, the method of using the recessed part of the guide groove as a track also
They have more problems than 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 the recessed track type disc, a method has been proposed in which a search signal is separately inserted into the recessed part of the guide groove. The issue of truck noise levels remains. In addition, if the search signal is input to the concave portions, the signal will also be input between the convex portions, and the pitch in the track direction of the portion where the search signal is present will be half of the original pitch, so it will be higher. 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 a conventional disk, 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 following optical discs 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, a track for guiding a light spot, and a predetermined track among the tracks on the substrate. A lens for focusing a light spot on the track, comprising a light spot guide layer in which a search signal for searching is formed in an uneven shape, and an information signal recording layer formed on the light spot guide layer. When viewed from the side, the track is constituted by a convex portion of the optical spot guide layer, the search signal is formed on a part of the track, and the width of the track is 1/2 of the track interval. It has a wider configuration.

Function: With the above-described configuration, the present invention does not use the convex portion of the guide groove as a track when viewed from the lens side, as in the conventional example.
By making the rack width wider than 1/2 of the track spacing, the increase in light diffraction loss due to the guide grooves is prevented, which increases the amount of signal light detected and enables 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.

Furthermore, in the present invention, since the tracks are the convex portions of the guide grooves that 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 Hereinafter, examples of the optical information storage carrier of the present invention will be described.
This will be explained 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, and a light spot guide layer 6.
It is composed of The light spot focused on the information signal recording layer 2 by the lens B on the optical disc 1 is as follows:
Among the uneven shapes formed on the optical spot guide layer 6, a portion 7 corresponding to a convex portion when viewed from the lens 8 side is defined as a track.
Writing and reading of information pits 6 are performed following the completion of this track. Further, the track search signal is formed on a part of the track 7, and has a value such that when the light spot follows the track 7, the search signal can be read out.

Next, changes in the difference signal and sum signal of the two-split photodetector for track control in this embodiment 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 embodiment when the light spot crosses the 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 depth of the guide groove is 700, and the width of the convex portion 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 is different from the difference signal 9 detected by the optical information storage carrier of the conventional example. Like the signal, the difference signal becomes 0 at the center of the track 11 formed by the convex portion of the guide groove, and has exactly the same phase characteristics as the conventional example. 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 of the track pitch, and therefore 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 canting machine or by vibrating the light spot on the glass master in a direction perpendicular to the track. can.

As described above, according to this embodiment, the track that the light spot follows 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 focuses the light spot. At the same time, by forming a track search signal on a part of the track and configuring the track width to be wider than 1/2 of the track pitch, it is possible to make the optical information storage carrier different from the conventional narrow track width optical information storage carrier. An equivalent track control signal 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.

Further, according to this embodiment, since the track search signal is also formed as a part of the track, the same process as the conventional one can be used when producing the storage carrier.

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

Effects of the Invention As described above, the present invention includes a substrate, and on this substrate, a track for guiding a light spot and a search signal for searching a predetermined track among the tracks are formed in an uneven shape. It has an optical spot guide layer and an information signal recording layer formed on the optical spot guide layer, and when viewed from the lens side that focuses the optical spot on the track, the track is composed of a convex part of the optical spot guide layer. At the same time, the search signal is
formed in a part of the track, and the width of the track is
By forming the track spacing to be wider than 1/2, it is possible to prevent an increase in light diffraction loss due to the guide grooves, thereby increasing the amount of signal light detected, and achieving high quality signal reproduction.

In addition, 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.
Compatible with conventional optical information storage carriers.

Furthermore, since the search signal is also formed as part of the track, the same process as in the past 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 structure of an optical information storage carrier in an embodiment of the present invention, and FIG. 2 is a waveform diagram showing the effect thereof.
3 is a perspective view showing the structure of a conventional optical information storage carrier, FIG. 4 is a schematic diagram illustrating the principle of track control, and FIG. 6 is a step illustrating the process of creating the optical information storage carrier. 6 are waveform diagrams illustrating signals detected from a conventional optical information storage carrier. 1... Optical disc, 2... Information signal recording layer, 3... Adhesive layer, 4... Substrate, 6...
... 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, 11°29...
Trunk, 12... Lens, 13... Two-split photodetector, 14... Guide groove cross section, 16... 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, 26... Protective substrate, 26... Glass plate surface portion . Name of agent: Patent attorney Toshio Nakao and 1 other person1-
11 Kozuki Su 7 Huuu 1-ylfu 8-1-Renos 1! Se1 ■ 1; Se1b Section 3 Part 3 +s--Bottle-beating relaxation molecule IE-p-La Z's and +7--77L Retus L No. 59 1"Stone'i' 1q--- Forces, Mazda District - Soldiers) Messengers

Claims (1)

[Claims] a substrate; an optical spot guide layer in which optical spot guiding tracks and search signals for searching a predetermined track among the tracks are formed in an uneven shape on the substrate;
an information signal recording layer formed on the optical spot guide layer, and the track is constituted by a convex portion of the optical spot guide layer when viewed from the lens side that focuses the optical spot on the track, An optical information storage carrier, characterized in that the search signal is formed on a part of the track, and the width of the track is wider than 1/2 of the track interval.