JPH02103752A - Optical disk and its production - Google Patents

Abstract

PURPOSE:To perform satisfactory cutting by using two beams to form pits with a uniform track pitch even when single pits corresponding to an information signal are different in pit width from one another. CONSTITUTION:A first beam to cut a user area 3 and a standard formatted part (SFP) and a second beam to form a pit wider than the pit formed by the first beam are prepared, and a phase encoded par (PEP) is cut by the second beam. Or optical axes of first and second beams are shifted from each other and the PEP is cut with the same modulation signal by both beams. Thus, a discontinuous part of the track pitch is eliminated, and satisfactory cutting is performed.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an optical disc on which optical information signals can be recorded and reproduced, and a method for manufacturing the same, and in particular, an optical disc capable of recording and reproducing optical information signals and a method for manufacturing the same. The present invention relates to a pit forming method.

[Conventional technology]

Tracking methods used in information recording and reproducing devices using optical disks include continuous servo methods and sample servo methods. Regarding these methods, please refer to the 16th issue of Nikkei Electronics published on December 15, 1986.
The article "Double feature of continuous groove method and sample servo method" written on pages 3 to 170, and the article published on December 3, 1986 by the Optical Disk Council of the Optical Industry and Technology Promotion Association and the Incorporated Association This is stated in the ``Optical Tisp Standardization Trend Explanation Meeting Materials'' by the Information Processing Society of Japan's Information Standards Study Group. The continuous groove servo method is a method that has been developed for some time. On the other hand, the sample servo method is a method that has been actively developed recently because it has attracted attention for its good tracking stability.

Since there are two types of tracking methods as mentioned above,
A wide variety of optical discs can be made (continuous servo systems include land recording and groove recording, and recording films include perforated systems, phase change systems, organic dye systems, etc.).

For this reason, it is impossible to perform good recording and reproduction suitable for each disc using a fixed drive with fixed various conditions. In order to eliminate such inconveniences, the aforementioned standards committee provided a control track outside the user area on the disc surface that specifies information on the disc format and recording/playback conditions.

FIG. 2 shows a schematic plan view and a partially enlarged view of the optical disc.

The control track 12 is located inside the user area 13 on the disc substrate 11 of the optical disc.Part j
SFP).

The PEP section is a section that provides information for reproducing the SFP section, and the SFP section is a section that provides information on conditions for recording and reproducing in the user area.

The PEP section can be played back on any drive.
It is a low-density format that can be played back without the need for tracking servo.

For this reason, it is necessary to increase the crosstalk from adjacent tracks in the PEP section, and as a method for this, the standards committee described a method of making the track pitch TP1 of the PEP section narrower than the track pitch Tp2 of the SFP section and user area. ing. It's true. There are concerns that this may cause long-term problems such as variations in the conversion area during track pitch conversion and adverse effects on the cutting device.

[Problem to be solved by the invention]

In the above-mentioned conventional technology, since the PEP section, the SFP section, and the user area are formed with different track pitches,
In the smuttering process during disk manufacturing, between areas with different track pitches, 4. (,) pitch variation areas are provided. (A) Divide the cutting. However, a discontinuous portion occurs on the same disk surface.

An object of the present invention is to set the track pitch to one type on the disk surface, eliminate discontinuous portions of the track pitch, and reduce the adverse effect on the cutting device.

[Means to solve the problem]

The above objective is achieved by two-beam cutting. That is, a first beam that cuts the user area and the SFP section, and a second beam that can form a pit width wider than that formed by the first beam are prepared, and the second beam cuts the PEP section. Perform cutting. Alternatively, this can be achieved by shifting the optical axes of the first and second beams and simultaneously cutting both beams using the same modulation signal when cutting the PEP section.

[Effect]

・5 FIG. 3 shows the relationship between the pit width W and the tracking error signal and cross-track loss in the sample servo method. The specifications for pit formation at this time are that the track pitch is 1.5 μm and the optical pit depth is λ/4.

In addition, the specifications of the reproduction optical system are that the numerical aperture NA is approximately 05, the laser wavelength λ is 8 SOnn * its beam cross section is approximately 1.8
μ-.

Note that the cross-track loss is defined as the attenuation of the reproduced signal due to the optical beam running between tracks from the level of the reproduced signal when the optical beam is running over the tracks.

As is clear from FIG. 5, the pit width WT that achieves the target specification of 25- or more for the tracking error signal in the user area
is 0.5±02μm, PEP section cross-track loss specification 1. The pit width Fc that provides dB or less is 0.8±01
μ book, and the two do not coexist.

Therefore, if the track pitch is kept constant at 1.5 μm and you try to stably obtain the tracking error signal in the user area and the cross-track loss in the PEP section, the pit width is set to 0.5 μm and 0.5 μm in each area. It is necessary to realize 8 μm. However, it is extremely difficult to achieve this pit width difference of 0.3 μm with one beam.

On the other hand, by using two beams according to the present invention, two types of pit widths having a pit width difference of 03 μm can be easily obtained.

In the first method described above, two systems of laser beams are prepared on the cutting device, one of which has a light spot diameter φ1 that provides a pit width of 0.5 μm, and the other light spot diameter φB that provides a pit width of 0.5 μm. The diameter is set to 8 μm. The two systems of beams are adjusted so that they pass through the center of the optical axis of the same objective lens. Then, when forming the PEP portion during cutting, pits are formed using the φB system, and when forming the user area, pits are formed using the φA system.

Furthermore, in the second method, two systems of laser beams are prepared in the same manner as described above, and the beam diameter is adjusted as φA−φB. Then, the centers of the optical axes are adjusted so as not to coincide with each other, and a wide pit width is obtained by applying the same modulation and signal to both at the PEP section.

FIG. 4 shows the relationship between the distance between the beams and the focus width according to the second method. These are the results obtained when irradiation was performed with the optical axis shifted using a beam that can obtain a focal width of 05μ in one beam. Required focus width at PEP section (08μm)
It can be seen that in order to obtain this, the beam spacing S should be set to about 04 μm.

〔Example〕

<Example 1> Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a schematic plan view and a partially enlarged view of a sample servo type optical disk according to a first embodiment of the present invention.

In FIG. 1, a disk substrate 1 is made of polycarbonate (
The disk substrate 1 has an inner diameter φ of 15 mm, an outer diameter φ of 130 mm, and a thickness t of 1.2 mm. The radius r of the user area 6 is 30 to 60 m.
The control track area 2 has a radius r of 2.
The paradigmatic pit depth λ/4 from 9 to 29.7 m is about 130 wm, assuming a PC refractive index of about 1.59. Here, the laser wavelength λ for recording and reproduction is 8504 m. The light source of the cutting laser device is helium cadmium (gg) with a wavelength λC of 4416 mm.
-crt) laser was used. Furthermore, a positive resist was used as the photoresist. 4 in the figure is a sector address section, which is provided at 32 locations per track.

In addition, the pre-pit, which is a feature of the sample servo system and consists of a sample mark for tracking and a clock pit for detecting the position of the data point, is one per track lap.
There are 376 locations, and they are formed in the user area including the spp section (not shown).

A specific method for forming pits will be described below.

FIG. 5 is a diagram schematically showing the optical system of the cutting device.

50 is a Ha-Cd laser light source, and 51 and 52 are beam splitters (BSl, B52), which serve to split the output laser beam 70 from the light source 5o. That is, the optical path is divided into an optical path m and an optical path l. The divided laser beam 7164 is converted into parallel light by the collimating lens 53 (incorporated) and enters the optical modulator AOM55 (to), and the light modulated by the 1,40M55 (g) is converted into parallel light again by the collimating lens 57@. will be returned to. The light on the optical path m is deflected by an optical deflector AOD 59 and passes through an objective lens 60 to form the sample mark on the glass master.

On the other hand, the laser beam 72 is aligned with the optical axis of the undeflected clock pit of the laser beam 71, and
By setting the light quantity ratio of optical paths m and n to 8:2 in E51, the pit width formed is 0.5 μm for the laser beam in optical path m and 0.8 μm for the laser beam in optical path L.
μm was obtained. Then, a signal was applied to the AOM 56 when forming the PEP section, and a pit signal other than the PEP section was applied to the AOM 55. As a result, a pit shape shown in the locally enlarged view (a) of FIG. 1 was obtained, and optical discs with different pit widths (WI, Wt) were obtained without changing the track pitch TP.

<Example 2> The disk configuration was the same as in <Example 1>, and the outline of the optical system was also the same as that shown in FIG. 5, and the ratio of the amount of light between the optical paths m and l was set to 6:4 in B551. As a result, the light intensity of optical path m is AO
After passing through D, the amount of light in the optical path L was set to be equal to the amount of light incident on the objective lens 60.

When forming the pxp section, a deflection signal is given to the AOD 59, the distance S between both laser beams is set to be approximately 0.4 μm, and a PEP forming signal is simultaneously applied to the AOMs 55 and 56. As a result, the local part shown in FIG. The pit shape shown in the enlarged view (A+) was obtained. This shows the pit shape when a time delay occurs due to the laser beam 71 passing through the optical path control AOD 59. To eliminate this phenomenon is AO by the time delay caused by AOD59.
By reducing the time delay caused by M55, it is possible to obtain the 10-bit shape shown in FIG.

As described above, by using two beams as in this embodiment, it is possible to achieve the target specifications of the cross-track loss in the PEP section and the tracking error signal in the user area without changing the track pitch (11. You can get additional optical discs.

In addition, in this second embodiment, A is used as means for shifting the optical axis.
Although OD is used, the same effect can be obtained even if the optical axes of both beams are made different when adjusting them.

〔Effect of the invention〕

According to the present invention, in an ISO standard write-once optical disc, since the track pitch does not change between the control track section and the user area section, discontinuous sections can be eliminated. Further, according to the present invention, since the cutting device does not apply signals with different track pitches during cutting, it is possible to perform good cutting.

[Brief explanation of drawings]

FIG. 1 is a schematic plan view and a partially enlarged view of an optical disc as an embodiment of the present invention, and FIG. 2 is a schematic plan view and a partially enlarged view of an optical disk according to the prior art. FIGS. 1, 3, and 4 are respectively Characteristic diagram 1 No. 5 for explaining the present invention
The figure is a schematic configuration diagram of an optical system of a cutting device for producing an original disc according to the present invention. ．． 11...Disk board, 2.12...
...Tap/control track section, 3.13...
...User area.

Claims (1)

[Claims] 1. An optical disc in which a metal reflective film, a recording film, etc. is formed on the disc surface on which pit shapes are formed, and this is optically read as an information signal by an optical head, which corresponds to the information signal. An optical disc characterized in that even when single pits have different pit widths, they can be formed at the same track pitch by using two beams. 2. In the method for manufacturing an optical disk having different pit widths on the optical disk surface, the first beam forms a first pit width among the different pit widths, and the second beam forms a second pit width among the different pit widths. A method for manufacturing an optical disc, characterized in that a second beam is prepared, and by switching between the two beams, different pit widths are formed on the surface of the optical disc.