JPH0750014A - Optical recording medium - Google Patents

Abstract

PURPOSE:To obtain an optical recording medium suitable for high-density recording, which can perform highly accurate tracking control and can be manufactured readily. CONSTITUTION:Two spiral-shaped groove tracks 104 of a protruding groove track 102 and a recess-shaped groove track 103 are provided on an optical recording medium 101. A sector 108 is constituted of an ID region 105, a servo region 106 and an information region 107. A plurality of sectors are provided for one round of the groove tracks 104. Pits 109 in the ID region 105 are formed so as to stride both of the recess-shaped track 10 and the protruding groove track 102. First wobble pits 111 and second wobble pits 112 are separately provided in the direction of the track in the symmetrical pattern with respect to a central line 110 of the groove tracks 104. Therefore, the width of the pit 109 can be made wide, and the manufacture of the optical recording medium becomes easy. The center of the groove track 104 can be accurately detected with the first and second wobble pits, and the highly accurate tracking control can be performed readily.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording medium for irradiating a converged light beam and recording information by heat generated by the light beam, and more particularly to an optical recording medium having a groove track having an uneven shape.

[0002]

2. Description of the Related Art In recent years, optical recording media capable of recording information have been
Since it can hold a large amount of data, voice information data
It is occupying an important position as a storage of video information data and various types of information equipment data. However, there is a demand for a larger capacity, and in order to meet this demand, the information recording density on the optical recording medium must be further improved. The information density of an optical recording medium is determined by the pitch of information tracks and the information density in the track direction, that is, the linear density of information. To improve the information density on the optical recording medium, it is necessary to narrow the track pitch and increase the linear density. is there.

As a conventional optical recording medium, a spiral groove track having a fine 0.8 μm width and a pitch of 1.6 μm is formed on the surface of a disk-shaped resin substrate, and a method such as sputtering is formed on the surface of the substrate. It is known that a thin film of a ternary phase-change recording material containing Te, Sb, and Ge as main components is formed, and a protective layer is provided on the thin film. This resin substrate is made into a stamper on the basis of a master disc having concave and convex groove tracks, and a large amount of it is reproduced by a method such as injection using this stamper.

Since this conventional optical recording medium is configured to record information on the groove track which is either concave or convex, if the track pitch is made narrower, the track width becomes narrower. Is difficult to duplicate. Further, when reproducing the information recorded on the groove track, the quantity of reflected light or transmitted light from the groove track is reduced, so that the quality of the reproduced signal is deteriorated.

Further, one purpose of providing the concave and convex grooves is to detect a position shift signal between the light beam irradiated on the optical recording medium and the groove track so that the light beam can be accurately positioned on the groove track. This is for controlling the position. Generally, a position shift signal between a light beam on an optical recording medium and a groove track, that is, a track shift signal is detected by a push-pull method. The push-pull method is a method in which a far-field pattern of reflected light or transmitted light from an optical recording medium is detected by a two-divided photodetector having two light-receiving areas, and light is detected based on the difference in photocurrent detected in both light-receiving areas. This is a method of detecting the positional deviation between the groove track on the recording medium and the light beam. The magnitude and dynamic range of the track deviation signal are determined by the groove track width and pitch. When the width of the groove track is narrowed to narrow the pitch, the amplitude of the track deviation signal becomes small and the dynamic range also becomes narrow, and the quality of the track deviation signal deteriorates, which makes tracking control unstable and causes disturbances such as vibration shock. On the other hand, track jumps are likely to occur.

In order to solve the above-described problems, concave tracks and convex tracks are formed alternately in the radial direction of an optical recording medium, and information is recorded on both the concave and convex tracks. It has been proposed to realize high density by using the above method (for example, JP-A-57-503).
30 publication). Also in this case, the track shift signal is detected by the push-pull method, and based on this signal, tracking control is performed so that the light beam on the optical recording medium is positioned on the groove track of the unevenness.

[0007]

As described above, the conventional optical recording medium configured to record information on either the concave or convex groove track has a problem that the master or the resin is reduced when the track pitch is narrowed. Duplicate the substrate becomes difficult. Further, the quantity of reflected light or the quantity of transmitted light from the groove track is lowered, so that the quality of the reproduced signal is deteriorated, the amplitude of the track deviation signal is small, and the dynamic range is narrowed, so that the tracking control is not stable.

Further, in an optical recording medium for recording information on both concave and convex tracks, if identification information for identifying a recording area is provided on both concave and convex tracks, a pit width for the identification information is provided. Must be less than half the width of the concave and convex tracks, the light beam that cuts the concave or convex track, the light beam that cuts the identification information of the concave track, the identification information of the convex track. The cutting machine was complex and expensive because it required three light beams. Furthermore, when tracking control is performed so that the light beam is positioned on the groove track based on the track shift signal detected by the push-pull method, the light beam irradiated on the photodetector moves according to the eccentricity of the groove track. A pseudo signal is generated. Therefore, even if the track shift signal detected by the push-pull method is zero, the light beam on the optical recording medium is not located at the center of the groove track. This pseudo signal is also generated by the tilt of the surface of the optical recording medium. When the track pitch is narrowed, the accuracy of tracking control must be improved. However, since the track shift signal detected by the push-pull method includes a pseudo signal due to eccentricity or tilt of the optical recording medium, highly accurate tracking control cannot be performed and the pitch cannot be narrowed.

In view of the above problems, the present invention is to provide an optical recording medium suitable for high-density recording, which enables highly accurate tracking control even if the pitch is narrowed and is easily manufactured.

[0010]

In order to solve the above problems, according to the present invention, a recording thin film is formed on a substrate having concave and convex groove tracks, and the recording thin film is formed on concave groove tracks and convex groove tracks. In a disc-shaped optical recording medium in which information is recorded on both sides, a pit for identification information and a concave or convex shape formed so as to straddle both a concave groove track and a convex groove track for identifying a recording area. Two wobble pits are provided which are symmetrical with respect to the center line of the grooved track and are separated in the track direction.

[0011]

According to the present invention, since the identification information pit is formed so as to extend over both the concave groove track and the convex groove track, the pit width can be widened and the identification information pit can be formed in the concave or convex shape. The identification information pit can be cut with a light beam that cuts the groove track. Further, since two wobble pits that are symmetrical with respect to the center line of the concave or convex groove track and are separated in the track direction are provided, the center of the concave or convex groove track can be accurately detected from the wobble pit. Therefore, highly accurate tracking control can be easily performed.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An optical recording medium according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic view of an optical recording medium according to an embodiment of the present invention. FIG. 1A is a plan view of an optical recording medium 101, in which two spiral groove tracks 104, a convex groove track 102 and a concave groove track 103, are provided, and information is recorded in the convex groove track 102. And concave groove tracks 103 are recorded. 105 is an ID area, 106 is a servo area,
Reference numeral 107 is an information area, and the groove track 104 for one round is 4
It is divided into one sector 108. Figure 1 (b) shows ID
FIG. 6 is a partially enlarged view in which a region 105 and a servo region 106 are enlarged. The identification information pits 109 provided in the ID area 105 are arranged substantially on the boundary line between the convex groove track 102 and the concave groove track 103, and the adjacent convex groove track 102 and concave groove track 103 are provided. The information area is formed so as to be identified based on the same identification information. That is, the convex groove track 102a and the concave groove track 103a, and the convex groove track 102b and the concave groove track 103b are provided so as to be identified based on the same identification information. When the convex groove track 102 and the concave groove track 103 detect the track deviation signal by the push-pull method and perform tracking control, the polarities of the track deviation signal become opposite.

Therefore, even if the identification information pits of the information areas of the convex groove track 102 and the concave groove track 103 are the same, the convex groove track 102 and the concave groove track 103 are judged from the polarity of the tracking control. There is no problem because you can do it. The alternate long and short dash line 110 indicates the convex groove track 10
2 and the center of the concave groove track 103. In the servo area 106, a first wobble pit 111 and a second wobble pit 112 are provided symmetrically with respect to the track center 110. The first and second wobble pits 111 and 112 are for correcting the pseudo signal included in the track shift signal detected by the push-pull method. First and second wobble pits 111 and 112
The wobble track deviation signal to be detected more is performed by the level difference between the peak amplitudes of the first wobble pit 111 and the second wobble pit 112. For this purpose, it is necessary to detect the peaks of the signals of the first wobble pit 111 and the second wobble pit 112. For this purpose, the positions of the first wobble pit 111 and the second wobble pit 112 are designated. A gate signal is required. Optical recording medium 1 of FIG.
In 01, the first wobble pit 111 and the second wobble pit 112 are arranged after the identification information so that a gate signal designating a position based on the identification information can be easily produced. That is, in terms of the reproduction signal, the signals of the first wobble pit 111 and the second wobble pit 112 are arranged so as to appear after the identification information in terms of time.

The optical recording medium 101 according to the embodiment of FIG. 1 of the present invention.
Has two spiral groove tracks 104.
When the two spiral groove track 104 is cut, for example, when the continuous convex groove track 102 is cut in a spiral shape, the convex groove track 102 is cut.
A concave groove track 103 having a continuous space is formed. When the identification information is separately provided to the convex groove track 102 and the concave groove track 103, at least the concave information is provided in addition to the light beam for cutting the identification information for the convex groove track 102 and the identification information for the convex groove track 102. A light beam is needed to cut the identification information for the groove track 103. However, if the convex groove track 102 and the concave groove track 103 share the identification information as in the embodiment of FIG. 1,
It is possible to use only the convex groove track 102 and the light beam for cutting the identification information. Further, as shown in FIG. 1B, the width of the convex groove track 102 or the width of the concave groove track 103, and the pit 1 in the ID area 105.
09 width and first and second wobble pits 111, 1
If the widths of 12 are made substantially equal, it is necessary to slightly move the optical recording medium 101 in the radial direction using an optical deflector or the like when cutting the pit 109 and the first and second wobble pits 111 and 112. Is the same light beam that cuts the groove track 104, ie 1
It is possible to cut with the light beam of a book. As described above, the optical recording medium 101 of the present invention of the embodiment shown in FIG. 1 can be cut with one light beam, so that the structure of the cutting machine is simple and the pits can be enlarged, so that the optical recording medium 101 can be easily formed.

FIG. 2 is an enlarged and exaggerated sectional view of the optical recording medium 101 cut in the radial direction. A convex groove track 102 and a concave groove track 103 are formed on one surface of a substrate 201 made of polycarbonate resin or the like. Then, a dielectric film 202 such as SiO ₂ , a recording material film 203, a dielectric film 204, and a reflective layer 205 such as aluminum are sequentially provided thereon, and the reflective layer 205 is further provided.
And the protective layer 207 are bonded by an adhesive. Two
Reference numeral 06 is an adhesive layer made of an adhesive. The reflective layer 205 is
It is provided in order to improve sensitivity, improve heat dissipation, and protect the recording material film 203 from thermal shock. The recording material film 203 is formed, for example, by a method such as sputtering using a phase change recording material containing Te (tellurium), Sb (antimony), and Ge (germanium) as main components. The dielectric films 202 and 204 are for protecting the recording material film 203 from humidity or thermal shock and can be omitted.

The phase-change recording material has a property of becoming crystalline when heated and gradually cooled, and becomes amorphous when melted and rapidly cooled. Utilizing this property, the phase-change recording medium reversibly changes the crystalline state and the amorphous state, and like the magnetic recording medium such as a floppy disk or hard disk, the information can be overwritten in the same place many times. it can. When recording information on a phase-change recording medium, the recording medium is rotated at a predetermined speed and tracking control is performed so that the light beam is positioned on the groove track, and the intensity of the light beam is adjusted according to the signal to be recorded. The intensity is modulated between the amorphous level and the crystallization level. For example, when recording is performed so that the recording mark is in an amorphous state, a light beam having a light amount sufficient to melt the thin film is formed to form an amorphous state mark, and a mark other than the recording mark is not melted. Crystallization is performed by irradiating a light beam of a light amount. Therefore, during the period other than the recording mark, whether the previous state is amorphous or crystalline, the state is crystalline, and overwriting can be performed even at a place where information is already recorded. Information recorded on the phase-change recording medium is reproduced by utilizing the difference in reflectance or transmittance between the amorphous state and the crystalline state. For example, a weak constant light beam is emitted, reflected light from the recording medium is received by a photodetector, and information is reproduced by changing the amount of reflected light.

A device for recording or reproducing information by loading the above-mentioned optical recording medium 101 will be briefly described with reference to FIG. In FIG. 3, the optical recording medium 101 is attached to the rotation shaft of the motor 301 and rotated at a predetermined rotation speed. An optical beam generated from a light source 302 such as a semiconductor laser is collimated by a coupling lens 303, passes through a polarizing beam splitter 304 and a quarter wavelength plate 305, and is a total reflection mirror. The light is reflected by 306, and converged and irradiated onto the optical recording medium 101 by the converging lens 307. The reflected light reflected by the optical recording medium 101 passes through the converging lens 307, is reflected by the total reflection mirror 306, passes through the quarter-wave plate 305, and then is reflected by the polarization beam splitter 304, thereby detecting light. It is irradiated on the container 308. The converging lens 307 is attached to the movable portion of the actuator 309. The actuator 309 is composed of a tracking coil provided in the movable part and a permanent magnet attached to the fixed part. When a current is applied to this coil, the converging lens 307 moves in the radial direction of the optical recording medium 101, that is, across the groove track on the optical recording medium 101 due to the electromagnetic force received by the coil. In addition, a coil for focus is attached to the movable part of the actuator 309,
When a current is applied to this coil, the converging lens 307 is configured to move in a direction perpendicular to the surface of the optical recording medium 101 by the electromagnetic force received by the coil. The converging lens 307 is focus-controlled so that the optical beam irradiated onto the optical recording medium 101 is always in a predetermined converging state.

A light source 302, a coupling lens 303, a polarization beam splitter 304, and 1 are provided on the transfer table 310.
A quarter wave plate 305, a total reflection mirror 306, a photodetector 308, and a fixed part of an actuator 309 are attached, and the transfer table 310 is integrally moved in the radial direction of the optical recording medium 101 by a linear motor 311. Is configured to. The photodetector 308 has a two-part structure, and its output is an I / V converter 31 that converts current into voltage.
2 and 313 respectively. I / V converter 3
The output signals of 12 and 313 are input to the differential amplifier 314, and the differential amplifier 314 outputs a signal according to the difference between the two signals. The output signal of the differential amplifier 314 is the optical beam focused on the optical recording medium 101 and the groove track 104.
The signal represents the positional deviation between the track shift signal and the track shift signal, and the method of detecting the track shift signal is called the push-pull method.

Reference numeral 315 is an adding circuit, which is an I / V converter 3
A signal obtained by adding the signals of 12 and 313 is output. The adder circuit 315 is recorded in the pit 109 in the ID area 105, the first wobble pit 111 in the servo area 106, the signal corresponding to the second wobble pit 112, and the information area 107 shown in FIG. A signal is output according to the difference in reflectance between the amorphous state and the crystalline state of the information mark. The identification signal and the information recorded in the information area are read from this output signal. Further, the added signal of the adder circuit 315 is inputted to the wobble track deviation detection circuit 316 which detects the track deviation from the wobble mark. The wobble track shift detection circuit 316 detects the peak amplitudes of the first wobble pit 111 and the second wobble pit 112 provided in the servo area of FIG. 1 based on the identification information, and outputs a signal corresponding to the difference between the two levels. To the differential amplifier 317. The differential amplifier 317 is the differential amplifier 314.
The difference between the output signal of the above and the signal of the wobble track shift detection circuit 316 is calculated. The output signal of the differential amplifier 317 is actuated via a polarity switching circuit 318 for inverting the polarity of tracking control, a phase compensation circuit 319 for compensating the phase of the tracking control system, and a drive circuit 320 for power amplification. The optical beam focused on the optical recording medium 101, which is added to the tracking coil of the optical recording medium 309, is tracking-controlled so that it is always located on the groove track 104. The signal of the differential amplifier 317 is the polarity switching circuit 318, the phase compensation circuit 319,
321 and a drive circuit 322 for power amplification are applied to the linear motor 311, and transfer control is performed so that the converging lens 307 moves around a natural state.
A selection signal for selecting whether to position the light beam on the convex groove track 102 or the concave groove track 103 is input to the terminal 323, and the polarity switching circuit 318 changes the polarity according to the selection signal. Switch. For example, when the light beam is positioned on the convex groove track 102, the terminal 323 becomes low level and the polarity switching circuit 318 outputs a signal in the same phase as the output signal of the differential amplifier 317, and on the concave groove track 103. When the light beam is positioned, the terminal 323 becomes high level and the polarity switching circuit 318 outputs a signal having a phase opposite to the output signal of the differential amplifier 317.

The principle of track shift signal detection by the push-pull method will be briefly described with reference to FIG. FIG. 4 illustrates the irradiation state of the light beam on the photodetector 308. The photodetector 308 is divided by the dividing line 405 into the light receiving area
It is divided into 8a and 308b. The dividing line 405 is in the track direction on the photodetector 308, that is, the arrow 4
It is set in the 04 direction. Reference numeral 401 denotes the zero-order light of the reflected light beam, and 402a and 402b denote the + 1st-order light and the -1st-order light, respectively. 403 is the zero-order light 401 and ± 1
The portion where the next light overlaps and interferes is shown. In the interference portion 403, the left and right interference patterns, that is, the light intensity distribution changes according to the positions of the groove tracks 104 on the optical recording medium 101 and the light beam. Therefore, the light receiving regions 308a and 308
If the photocurrent difference of b is obtained, it corresponds to the difference in the light intensity distribution on the left and right of the interference portion 403, and a track deviation signal corresponding to the positional deviation between the groove track 104 on the optical recording medium 101 and the light beam can be obtained. .

Next, a pseudo signal mixed in the track shift signal detected by the push-pull method will be described with reference to FIG. FIG. 5 shows the irradiation state of the light beam on the photodetector 308 similarly to FIG. 4, but the zero-order light 40 is simply shown.
Only one is shown. The groove track 104 on the optical recording medium 101 is generally eccentric. Therefore, when tracking control is performed so that the light beam is positioned on the groove track 104, the converging lens 307 shown in FIG. 3 moves in the direction perpendicular to the track direction according to the eccentricity of the optical recording medium 101. When the converging lens 307 moves according to the eccentricity,
The zero-order light 401 on the photodetector 308 is 401a, 401b.
To move. When the zero-order light 401 on the photodetector 308 moves, the photocurrents of the light receiving regions 308a and 308b change corresponding to the movement of the zero-order light 401, and this becomes a pseudo signal. Since the pseudo signal mixes with the original track deviation signal, the light beam is not positioned on the center of the groove track 104 even though tracking control is performed so that the photocurrent difference between the light receiving regions 308a and 308b becomes zero. . Actually, when the converging lens 307 moves,
The eclipsed state of the light beam by the converging lens 307 and the like also changes, and this also generates a pseudo signal. Such a pseudo signal is also generated due to the inclination of the surface of the optical recording medium 101. The pseudo signal generated by the inclination of the surface of the optical recording medium 101 is due to the movement of the reflected light beam on the photodetector 308, the change in the eclipse state of the reflected light beam, and the aberration of the light beam on the optical recording medium 101. is there.

On the other hand, the wobble track deviation signal detected from the wobble pits in the servo area 106 is the light receiving area 3
Since the detection is performed based on the sum of photocurrents of 08a and 308b, a pseudo signal is not generated even if the light beam on the photodetector 308 moves. Further, the change in the eclipsed state of the light beam and the aberration of the light beam on the optical recording medium 101 are extremely small. Therefore, if the difference between the track shift signal detected by the push-pull method, that is, the output signal of the differential amplifier 314 shown in FIG. 3 and the wobble track shift signal, that is, the output signal of the wobble track shift detection circuit 316 is calculated by the differential amplifier 317, Since the generated pseudo signal is canceled out, accurate tracking control can be performed.

Next, the groove tracks 104, I shown in FIG.
A more preferable width relationship between the pit 109 in the D area 105 and the first and second wobble pits 111 and 112 will be described with reference to FIG. In FIG. 6, W1 is the width of the convex groove track 102, and W2 is the concave groove track 103.
, W3 is the width of the pit 109, and W4 is the width of the first and second wobble pits 111 and 112, respectively. Convex groove track 102 and concave groove track 103
Since the width W3 of the pit 109 is too small, it becomes difficult to read the identification information. W
If 3 ≧ W1 or W3 ≧ W2, approximately half or more of the light beam spot scans the pit 109 while the light beam is scanning the convex groove track 102 or the concave groove track 103, so that the quality is improved. Good identification information can be obtained. Further, if the width W3 of the pit 109 is excessively increased, crosstalk from adjacent identification information increases,
This crosstalk makes it difficult to read the identification information. According to the experiment, if W3 ≦ (W1 + W2) × 0.8, the result that the identification information can be read with high reliability is obtained. Also, the first and second wobble pits 11
To detect the positional deviation between the center 110 of the groove track 104 and the light beam from 1 and 112, when the light beam deviates from the center 110 of the groove track 104, the signal amplitude of one wobble pit decreases and the other wobble pit decreases. The amplitude of must be increased. Then, the first and second wobble pits 111 and 112 with respect to the unit track deviation
The larger the amplitude difference between the two, the more accurate the signal obtained. First
The width W4 of the second wobble pits 111 and 112 is slightly smaller than the width W1 of the groove track 102 and the width W2 of the concave groove track 103. The amplitude difference becomes large. That is, W4 <W1 or W4 <W
When set to 1, a wobble track deviation detection signal of higher quality can be obtained. According to the experiment, a good quality wobble track deviation detection signal is obtained in the range of 0.5 to 0.8 of W1 or W2. As is clear from the above description, the relationship between the width W4 of the first and second wobble pits 111 and 112 and the width W3 of the pit 109 is preferably W4 <W3.

As described above, the groove track 104, the pit 109, the first and second wobble pits 111, 1
It is better to make the widths of 12 slightly different than to make them the same, but the widths of the first and second wobble pits 111 and 112 will be slightly different if the power of the light beam is reduced or the recording pulse width is made smaller during cutting. Since the width of the pit 109 becomes slightly wider as the power of the light beam is increased or the recording pulse width is increased, the optical recording medium 101 of the present invention uses one light beam to form the groove track 104, the identification information pit 109, 1 and 2 wobble pits 1
11, 112 can be cut.

Although the present invention has been described in detail above, the present invention is not limited to the examples. For example, the optical recording medium 101 of the embodiment of FIG. 1 has four sectors per round,
It is not limited to four. The larger the number of sectors per round, the more accurate the correction by the wobble track shift detection signal. The present invention can also be applied to an optical recording medium in which one spiral track is formed by switching between a convex groove track and a concave groove track for each circumference. Furthermore, the present invention can be applied to an optical recording medium which is divided into a plurality of zones in the radial direction and the number of sectors per revolution is changed from the inner zone to the outer zone. It goes without saying that the present invention does not relate to the recording material and can be applied to, for example, a magneto-optical recording material.

[0027]

According to the optical recording medium of the present invention, an identification information pit and a concave or convex groove track are formed so as to extend over both the concave groove track and the convex groove track for identifying the recording area. Since two wobble pits that are symmetric with respect to the center line and are separated in the track direction are provided, the pit width for identification information can be widened, and identification is made by a light beam that cuts a concave or convex groove track. The information pit can be cut. Further, since two wobble pits that are symmetrical with respect to the center line of the concave or convex groove track and are separated in the track direction are provided, the center of the concave or convex groove track can be accurately detected from the wobble pit. Therefore, highly accurate tracking control can be easily performed.

[Brief description of drawings]

FIG. 1A is a schematic surface view of an optical recording medium according to an embodiment of the present invention, and FIG. 1B is a partially enlarged view of a surface of an optical recording medium according to an embodiment of the present invention.

FIG. 2 is an enlarged sectional view of an optical recording medium according to an embodiment of the present invention.

FIG. 3 is a block diagram of an apparatus suitable for recording or reproducing information on an optical recording medium according to an embodiment of the present invention.

FIG. 4 is a reflected light beam pattern diagram on a photodetector for explaining the principle of track shift signal detection by the push-pull method.

FIG. 5 is a movement explanatory diagram of a reflected light beam on a photodetector for explaining a pseudo signal mixed in a track deviation signal by the push-pull method.

FIG. 6 is a partially enlarged view of the surface of the optical recording medium for explaining the relationship between the groove track width, the identification information pit width, and the wobble pit width in the optical recording medium of the present invention.

[Explanation of symbols]

 101 optical record carrier 102 convex groove track 103 concave groove track 104 groove track 105 ID area 106 servo area 107 information area 108 sector 109 identification information pit 110 groove track center 111 first wobble pit 112 second Wobble pit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shinichi Yamada 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (5)

[Claims] 1. A disk-shaped optical recording medium in which a recording thin film is formed on a substrate having concave and convex groove tracks, and information is recorded on both concave groove tracks and convex groove tracks. A pit for identification information formed so as to straddle both the concave groove track and the convex groove track for identifying a recording area, and a center line of the concave or convex groove track. An optical recording medium provided with two wobble pits which are symmetrical and are separated in the track direction. 2. The pit width for identification information is made substantially equal to the convex groove track width or the concave groove track width.
The optical recording medium described. 3. A pit width for identification information is made wider than a convex groove track width or a concave groove track width, and is 80% or less of a value obtained by adding the convex groove track width and the concave groove track width. The optical recording medium according to claim 1, 4. The optical recording medium according to claim 1, wherein the width of the wobble pit is narrower than the width of the convex groove track or the width of the concave groove track. 5. The optical recording medium according to claim 1, wherein two wobble pits are provided after the identification information pit.