JPH09259439A - Optical recording medium and track counting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical recording medium capable of recording information in a land part and a groove part without generating a track counting error and having a prepit part which is easily produced. SOLUTION: This is related to an optical recording medium having a preformat part where preformat information such as ID information is recorded by a prepit array and an optical recording part where information is optically recorded. The land part L1 and the groove part G1 provided between the land parts L1, forming a track are capable of recording information respectively, and the array of prepits P1 and P11 corresponding to the preformat information is formed to be shared between the adjacent land part L1 and groove part G1 in the preformat part. Then, the preformat part is provided with a counting groove G11 for track counting.

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 and a track having a preformatted portion in which preformatted information such as ID information is recorded by a row of prepits and an optical recording portion in which information is optically recorded. The present invention relates to a counting method.

[0002]

2. Description of the Related Art Optical discs include read-only optical discs such as CD-ROMs, write-once optical discs capable of additional recording only, rewritable magneto-optical discs and phase change discs, and are rapidly developing. Utilization is being considered as a recording medium which is the core of the multimedia development.

There are several methods for recording information on an optical disc as follows. A method for recording information by forming irregularities on a substrate or a reflective film deposited on the substrate. In the optical disc recorded by this method, information is recorded only for reproduction. The unevenness may be formed by directly irradiating the substrate with laser beam light to form pits, or by forming a glass master having pits formed by beam exposure and forming the substrate by injection formation. At the time of reproduction, reproduction light beam is applied to the formed concavities and convexities, and information is reproduced by making the light amount change of the reflected light correspond to 0 and 1.

A method of recording information by using a magnetic film as a recording film deposited on a substrate and changing the magnetization direction of the recording film by heating and applying an external magnetic field. In a magneto-optical disk using this recording method, information is rewritably recorded. At the time of recording, after the recording film is magnetized in one direction to be initialized, a magnetic field in the direction opposite to the initialization direction is applied to heat the recording film at the portion where the magnetic field is to be reversed to the Curie temperature or higher. At the time of reproduction, the recording film is irradiated with reproduction beam light, and information is reproduced by making the Kerr rotation directions depending on the magnetization directions correspond to 0 and 1. At the time of erasing, a magnetic field in the same direction as the initialization direction is applied.

A method of recording information by using a material having a different reflectance depending on the crystalline state as a recording film deposited on a substrate and changing the crystalline state by heating.
In a phase change type disc using this recording method, information is rewritable or recorded exclusively for reproduction. For example, in the case of changing the crystalline state between crystalline and amorphous, at the time of recording, the material is heated to a predetermined temperature peculiar to the material or more to be crystallized, and further heated to a predetermined temperature or higher to be amorphized. At the time of reproduction, the recording film is irradiated with a reproduction beam light, and information is reproduced by making the reflectance change of the reflected light correspond to 0 and 1. At the time of erasing, the crystallization is performed by heating to a temperature at which crystallization is easy.

On the substrate of the optical disc, grooves for guiding the irradiation of the light beam are formed in a concentric or spiral shape. The commercially available products up to now are V (shaped) grooves G at a pitch of about 1 μm as shown in FIG.
4 is provided, and the land portion L4 provided between the V-grooves G4 has the pre-pit P4 of the pre-format portion for recording the medium condition, the recording / reproducing condition and the address of each sector / track. Recording mark P
44 was to be provided.

However, in order to further increase the density, as shown in FIG. 17, the groove has a flat U-shaped bottom.
Formed in groove G5, and the bottom of this U groove G5 and U
It has been proposed to provide pits (not shown) for recording information on the land portion L5 provided between the grooves G5. In this case, it is difficult to provide a prepit having a further depth at the bottom of the U groove G5. Therefore, the U-groove G5 is not provided in the pre-format portion, and the pre-pit P5 is provided at a position ¼ of the groove pitch from the extension line of the center line of the U-groove G5 in the pre-format portion, and the pre-pit P5 and the track of the U-groove G5 are provided. Japanese Unexamined Patent Publication No. 7-29186 proposes that the prepit P5 is shared with the track of the land portion L5.

When recording and reproducing information on such an optical disc, it is important that the beam light accurately follows the tracks of the recording section and the preformat section. Therefore, when the light beam irradiates the optical disk at the time of recording / reproducing information, a tracking error signal for controlling the tracking of the light beam is detected. FIG. 16 is a configuration diagram showing a configuration of a tracking error signal detection optical system of a general optical recording medium. This detection optical system detects a tracking error signal of a rewritable optical disc D formed by forming a recording film on a transparent substrate. On the emission side of the laser diode 61 that emits a light beam, a perfect circle correction prism 62 that makes the incident light beam a circular light beam, a beam splitter 63 that transmits or reflects the light beam, and a position control by an actuator. The objective lens 64 is
They are arranged in this order.

A two-divided detector 65 is arranged on the reflection side of the beam splitter 63. Each reflected light input to the two-divided detector 65 is converted into an electric signal here, input to the differential amplifier 66 and the adder 67, and each output is input to the divider 68. The divider 68 calculates a divided push-pull signal (hereinafter referred to as a DPP signal) which is one of tracking error signals.
With such components, a light spot control signal detection system for performing tracking control of the spot of the light beam irradiated on the recording film is configured.

The light beam emitted from the laser diode 61 becomes a circular light beam by the perfect circle correction prism 62, and is condensed on the recording film of the magneto-optical disk D via the objective lens 64. On the recording film, the light beam is modulated by reflection in the groove, passes through the objective lens 64 again, is reflected by the beam splitter 63, and is split into two split detectors 6.
5 is input.

A differential signal is output from the differential amplifier 66 by the respective signals converted by the two-divided detector 65,
A sum signal is output from the adder 67. The divider 68 divides the difference signal by the sum signal to obtain the DPP signal.
At this time, when the optical depth of the groove is λ / 8,
A sufficient DPP signal can be obtained for tracking control,
It is known that a sufficient pit signal for reproduction can be obtained when the optical depth of the pits in the preformatted portion is λ / 4. The optical depth is the actual depth × refractive index (refractive index of the substrate: 1.5 to 1.6).

[0012]

The U-groove G5 is not provided in the pre-format portion, and the U-groove such as the position of ¼ of the groove pitch from the extension line of the center line of the U-groove G5 of this pre-format portion is provided. G5 and land part L5
When the pre-pit P5 is provided in the intermediate position between
As shown in (a), when the reproduction spot seeks the pre-formatted portion, and when the reproduction spot crosses the track like AA ', there is no problem in the DPP signal as shown in C of FIG. Does not happen. However, when the reproduction spot crosses without crossing any of the pre-pits P5 in the row like BB ', the DPP signal is not created and the track count error occurs as shown in D of FIG. 18 (b). There is a problem that occurs.

The present invention has been made in view of the above-mentioned circumstances, and information can be recorded in the land portion and the groove portion, and a prepit portion which is easy to manufacture without causing a mistake in track count is formed. It is an object of the present invention to provide an optical recording medium having the same and a track counting method.

[0014]

In the optical recording medium according to the first invention, information can be recorded on each track formed by a land portion and a groove portion provided between the land portions, and preformat information In the optical recording medium formed in the pre-formatted portion, the pre-formatted portion is provided with a counting groove for track counting so that the row of pre-pits corresponding to is shared by the adjacent land portion and groove portion. It is characterized by

In this optical recording medium, a divided push-pull signal (DPP), which is one of tracking error signals, is generated by either a counting groove for track counting or a prepit provided in the preformat section.
Since the signal) is created, it is possible to prevent the track count from being lost in the preformat section. In addition, even if the counting groove and the prepit are physically separated, if the distance is smaller than the light spot, the DP is doubled.
No P signal is generated. Further, since it is only necessary to provide the counting groove in the pre-format portion, the production is easy.

In the optical recording medium according to the second aspect of the present invention, the phase depth of the counting groove is approximately λ / 22n (λ: short wavelength of recording / reproducing laser, n: refractive index of optical recording medium substrate). Is characterized by.

In this optical recording medium, the counting groove is
Since it is larger than approximately λ / 22n (λ: short wavelength of recording / reproducing laser, n: refractive index of optical recording medium substrate), a DPP signal capable of counting tracks can be obtained.

In the optical recording medium according to the third aspect of the present invention, in the counting groove, a value obtained by dividing the difference in the amount of reflected light divided by two in the track direction by the total amount of reflected light is approximately 0.4. Characterized by being larger.

In this optical recording medium, the counting groove is
The DPP signal obtained by dividing the difference in the amount of the reflected light divided into two in the track direction by the total amount of the reflected light is approximately 0.
Since it is greater than 4, tracks can be counted by the counting groove.

An optical recording medium according to a fourth aspect of the present invention is characterized in that the counting groove is provided so as to overlap with each of the prepits.

In this optical recording medium, the counting groove is
Since it is provided by overlapping with each of the pre-pits,
Double D by both counting groove and pre-pit
No PP signal is created.

In the track counting method according to the fifth aspect of the invention, information can be recorded on each track formed by the land portion and the groove portion provided between the land portions, and the prepits corresponding to the preformat information are recorded. In the method of counting the tracks of the optical recording medium formed in the pre-formatted portion so that the rows of the same are shared by the adjacent land portion and groove portion, the pre-formatted portion is provided with a counting groove for counting tracks. It is characterized in that an offset is injected into a signal created for counting tracks of the optical recording medium and counting is performed.

In this method of counting tracks, a counting groove for counting tracks is provided in the preformat section, and an offset is injected into the signal created for counting tracks of the optical recording medium to perform counting. A weak signal for counting tracks, which is detected and created from the groove for use, is also counted at a countable level, and the tracks in the preformat section can be surely counted.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings showing the embodiments. Embodiment 1. FIG. 1 is a partially cutaway perspective view showing a structure of an optical disc which is an optical recording medium according to the present invention, and FIG. 2 is a partial plan view thereof. In this optical disc, the groove is formed in the groove G1 having a flat bottom, and the groove G1 is formed.
Pits (not shown) for recording information are formed in the bottom portion of the groove and the land portion L1 provided between the groove G1.

The groove G1 is not provided in the pre-format portion for recording the address of each sector / track, and the groove G1 is formed on the extension line of the approximate center line of the groove G1.
A counting groove G11 (counting mistake prevention groove) having an optical depth shallower than 1 and deeper than λ / 22n (λ: short wavelength of recording / reproducing laser, n: refractive index of optical disk substrate) is provided. The count error prevention groove G11 is provided so that the track count does not drop in the preformat section.

Further, a pre-pit P1 for creating a clock in the pre-formatted portion and a pre-pit P11 for recording information in the pre-formatted portion are provided so that their respective ends overlap the counting error preventing groove G11. . The pre-pit P1 and the pre-pit P11 are provided such that their centers are located between the center line of the groove G1 and the center line of the land.

A method of manufacturing such an optical disc will be described below. The substrate of the optical disc can be obtained by injection molding with a stamper made using a glass master having grooves and prepits formed therein. FIG. 3 is a block diagram of a beam exposure apparatus used when manufacturing an optical disc of an optical recording medium according to the present invention. First, a polished glass master G was coated with a photoresist having a thickness of 80 nm by a spin coating method, prebaked at 90 ° C. for 30 minutes in a clean oven, and then this glass master G was used.
Is placed on the sample stage 40 equipped with the spindle motor 52 of this beam exposure apparatus.

This beam exposure apparatus has an Ar laser light source 4
The beam light emitted from the No. 1 is transmitted and reflected by the half mirror 42a, and is separated into spectra. The first light beam reflected by the half mirror 42a is incident on the first condenser lens 43a. The light condensed by the first condenser lens 43a is incident on the first AOM (Acousto-Optic Modulator) 44a, and the light intensity is modulated.

The intensity-modulated light is incident on the first collimator lens 45a, is returned to parallel light here, and is incident on the first beam expander 46a. The beam diameter is expanded by the first beam expander 46a, reflected by the half mirror 47a, and incident on the half mirror 48. The first collimating lens 45a and the second collimating lens 45b described later are configured to be movable in a direction orthogonal to the optical axis, and by this movement, the first beam light and the second beam light described later are separated. The relative position is controlled.

On the other hand, the second light beam transmitted by the half mirror 42a is incident on the mirror 42b and follows the same path as the first light beam. That is, the light reflected by the mirror 42b and incident on the second condenser lens 43b is condensed here, and is incident on the second AOM 44b to modulate the light intensity. The intensity-modulated light is transmitted through the second collimator lens 45.
It is incident on the second beam expander 46b after being converted into parallel light by being incident on the second beam expander 46b. In the second beam expander 46b, the beam diameter is expanded, reflected by the mirror 47b, transmitted through the half mirror 47a, and the half mirror 4b.
It is incident on 8.

First and second light transmitted through the half mirror 48
Of the beam light of the first and second collimating lenses 45.
It is incident on the optical head 49 while maintaining the relative position controlled by a and 45b. The optical head 49 includes a dichroic mirror 50 and an objective lens 51, and is configured to be movable in the vertical and parallel directions with respect to the sample table 40. The first and second light beams are reflected by the dichroic mirror 50 and are condensed on the glass master G by the objective lens 51. Focusing on the glass master G is controlled by moving the optical head 49 in the vertical direction. Then, the glass master disk is irradiated with a laser beam having a wavelength of 780 nm at which the photoresist of the glass master disk G is not exposed to light, and the optical head 49 is moved in the vertical direction in accordance with a focusing error signal due to the reflected light to perform focus control. .

The position on the glass master G where the first beam light and the second beam light are irradiated is determined by the optical head 49.
The movement of the optical head 49 in the parallel direction is controlled by an instruction from the exposure control unit 53. In addition, the exposure control unit 53 uses the first and second AOMs 4
An instruction of exposure power is given to 4a and 44b to control the degree of light intensity modulation. By this control, the optical depths of the grooves and the prepits formed on the glass master G are controlled respectively.

The first beam light and the second beam light focused and reflected on the glass master G are reflected by the dichroic mirror 50, reflected by the half mirror 48, and incident on the beam relative position detection unit 54. . The beam relative position detector 54 can monitor the relative positions of the first light beam and the second light beam.

Using the beam exposure apparatus as described above, 1
As an example, the pitch between the grooves G1 is 1.4 .mu.m, the depth of the grooves G1 is 80 nm, the length of the pre-pit P1 for creating the clock in the preformat portion in the track direction is 0.64 .mu.m, and the space portion in the track direction is The length of the pre-pit P11 for recording information in the pre-formatted portion is 0.64 μm and the length in the track direction is 2.5.
6 μm, the length of the space portion in the track direction is 2.
A 56 μm glass master G is prepared. The count error prevention groove G11 has a V-groove with a depth of 30, 60, 80 nm and a half-value width of 50, 1 at a depth of ½ by changing the exposure power of the beam light.
Various depths, widths and shapes can be obtained, such as U-grooves of 00,150 nm.

In this embodiment, the case where the glass master is formed by using the beam exposure apparatus having the above-mentioned structure is described, but the present invention is not limited to this. For example, visible short wavelength laser or ultraviolet light. A laser may be used, or an EOM (electro-optic modulator) may be used to modulate the intensity of the beam light. Grooves and prepits are formed on the glass master G while controlling the intensity of the beam light. Any device that can be formed may be used.

The glass master G having the prepits and the grooves thus formed is carried into a vacuum evaporator, and Ni is vapor-deposited on the surface of the glass master G to a thickness of 0.2 μm to form an electrode for plating. Next, Ni is 0.3
After plating to a thickness of mm, the glass master G is peeled off to obtain a Ni stamper. A substrate made of polycarbonate is prepared by injection molding using this stamper. In this way, a substrate having prepits and grooves of the same size as the glass master G is obtained.

A SiN underlayer having a thickness of 70 nm is formed on this substrate by the RF magnetron sputtering method, and a reproducing layer of Gd ₂₂ (Fe ₇₀ Co ₃₀ ) ₇₈ having a thickness of 8 nm and Tb is formed on the surface thereof by the sputtering method. The recording layer of ₂₀ (Fe ₉₀ Co ₁₀ ) ₈₀ has a thickness of 17 nm, and the upper layer of SiN has a thickness of 15 nm.
The recording film is deposited by laminating the reflective layer of 1 with a thickness of 100 nm in this order. A rewritable signal is recorded on the optical recording portions of the groove G1 and the land portion L1 of the recording film. That is, the length in the track direction of the optical recording portion is 0.64.
By recording a repeating pattern of recording marks of μm,
And the optical disc of the first embodiment shown in FIG. 2 is obtained.

The number of tracks of the optical disk manufactured as described above is counted by using a tracking error signal detecting optical system of the optical recording medium as shown in FIG. This detection optical system detects a tracking error signal of a rewritable optical disc D formed by forming a recording film on a transparent substrate. On the emission side of the laser diode 61 that emits a light beam, a perfect circle correction prism 62 that makes the incident light beam a circular light beam, a beam splitter 63 that transmits or reflects the light beam, and a position control by an actuator. The objective lens 64 is arranged in this order.

A two-divided detector 65 is arranged on the reflection side of the beam splitter 63. Each reflected light input to the two-divided detector 65 is converted into an electric signal here, input to the differential amplifier 66 and the adder 67, and each output is input to the divider 68. The divider 68 calculates a divided push-pull signal (hereinafter referred to as a DPP signal) which is one of tracking error signals.
In the differential amplifier 70, this DPP signal is injected with the offset output from the offset injection circuit 69, amplified, and given to the comparator 71. Comparator 7
In 1, the polarity of the DPP signal is inverted between the groove and the land portion and is applied to the counter 72. The counter 72 counts the DPP signal to obtain the track count value.

In such a detection optical system, the light beam emitted from the laser diode 61 becomes a circular light beam by the perfect circle correction prism 62, and is collected on the recording film of the magneto-optical disk D via the objective lens 64. Be illuminated. On the recording film, the light beam is modulated by the reflection by the groove, passes through the objective lens 64 again, and passes through the beam splitter 63.
Is reflected by and is input to the two-divided detector 65.

A differential signal is output from the differential amplifier 66 by the respective signals converted by the two-divided detector 65,
A sum signal is output from the adder 67. The divider 68 divides the difference signal by the sum signal to obtain a DPP signal, which is applied to the differential amplifier 70. In the differential amplifier 70, this DPP signal is injected with the offset output from the offset injection circuit 69, amplified, binarized, and given to the comparator 71. The comparator 71 uses this DP
The polarity of the P signal is inverted between the groove and the land portion and is applied to the counter 72. The counter 72 counts the DPP signal to obtain the track count value.

FIG. 5 shows this optical disk as a magneto-optical disk measuring apparatus (numerical aperture (NA) = 0.55 of the objective lens 64) having the detection optical system shown in FIG. 6 is a graph showing the magnitude of a pit signal of a pre-pit P1 having a length of 0.64 μm in the track direction when loaded and tracked (moved in the track direction) on the land portion L1. The pit signal is standardized by the reflectance of the land portion L1. Count misprevention groove G11 was measured for a total of 6 kinds of V groove having a depth of 30, 60, 80 nm and U groove having a half width of 50, 100, 150 nm which is a width at a position where the depth is 1/2. .

According to this graph, the exposure power is 3 mW.
At ~ 5mW, the pit signal increases and the exposure power is 5mW.
Then, the pit signal becomes maximum and the exposure power becomes maximum 10.
It can be seen that the pit signal becomes the minimum at mW. Also,
No groove, V groove of 30 nm, 60 nm
V groove, 80 nm V groove, half width 50n
It can be seen that the pit signal is larger in the order of the m U groove, the U groove having a half width of 100 nm, and the U groove having a half width of 150 nm.

FIG. 6 shows these optical discs as 680n.
of a pit signal of a pre-pit P1 having a length of 0.64 .mu.m in the track direction when it is mounted on a magneto-optical disk measuring apparatus having a detection optical system shown in FIG. It is the graph which showed the size. The pit signal is standardized by the reflectance of the groove G1.

According to this graph, the exposure power is 3 mW
At ~ 5mW, the pit signal increases and the exposure power is 5mW.
Then, the pit signal becomes maximum and the exposure power is maximum of 9m.
It can be seen that at W, the pit signal is minimized. Also, no groove (groove), V groove of 30 nm, V groove of 60 nm, V groove of 80 nm, half-value width of 50 nm
It can be seen that the pit signal is larger in the order of the U groove, the U groove having a half width of 100 nm, and the U groove having a half width of 150 nm. From FIGS. 5 and 6, it can be seen that there is almost no difference in the normalized magnitude of the pit signal between when the land portion L1 is tracked and when the groove G1 is tracked.

FIG. 7 shows the case where this optical disk is mounted in a magneto-optical disk measuring apparatus having a detection optical system shown in FIG. 4 in which a 680 nm laser diode 61 is mounted.
7 is a graph showing the magnitude of the DPP signal from the count error prevention groove G11. The larger the exposure power, the larger the DPP signal from the count mistake prevention groove G11, but the DPP signal from the round / groove (D when the tracks of the round and the groove are moved in the radial direction).
It can be seen that it is about 1/2 of the PP signal). In this case, when the DPP signal was 0.4 or more, the tracks were correctly counted.

FIG. 8 is a partially cutaway perspective view showing the configuration of a modified example of the optical disc which is the optical recording medium shown in the first embodiment, and FIG. 9 is a partial plan view thereof. In this optical disc, a groove is formed in a groove G2 having a flat bottom portion, and pits (not shown) for recording information are formed in the bottom portion of the groove G2 and a land portion L2 provided between the groove G2. Is configured.

The groove G2 is not provided in the pre-format portion for recording the address of each sector / track and the groove G2 is formed on the extension line of the approximate center line of the groove G2.
2 is provided with a groove G22 for preventing counting error, which has an optical depth shallower than 2 and is deeper than λ / 22n (λ: short wavelength of recording / reproducing laser, n: refractive index of optical disk substrate). The count error prevention groove G22 is provided so that the track count does not drop in the preformat section.

Further, a pre-pit P2 for creating a clock in the pre-formatted portion and a pre-pit P22 for recording information in the pre-formatted portion are provided so as not to overlap the count mistake prevention groove G22. The pre-pit P2 and the pre-pit P22 are provided so that their centers are located at a distance of 1/4 of the pitch between the grooves G2 from the center line of the groove G2.

This optical disc cannot be discriminated by the magneto-optical disc measuring device if the distance between the prepit P2 and the prepit P22 and the count error preventing groove G22 is small. Therefore, the obtained DPP signal and pit signal are the same as those of the embodiment. The optical disc is the same as that shown in FIG. Further, since the track counting method, the manufacturing method, the configuration, etc. are the same, the description thereof is omitted.

Embodiment 2 FIG. 10 is a partially cutaway perspective view showing a structure of an optical disc which is an optical recording medium according to the present invention, and FIG. 11 is a partial plan view thereof. This optical disc has a groove formed in a flat bottom G3,
Pits (not shown) for recording information are formed on the bottom of the groove G3 and the land L3 provided between the grooves G3.

The groove G3 is not provided in the preformat portion for recording the address of each sector / track, but the prepit P3 for clock generation and the prepit P33 for recording information of the preformat portion are provided.
It is provided so that its center is located at a distance of ¼ of the pitch between the grooves G3 from the center line of the grooves G3.

Further, a counting groove G33 (counting error preventing groove) having an optical depth shallower than the groove G3 and deeper than λ / 22n (λ: short wavelength of recording / reproducing laser, n: refractive index of optical disk substrate) is The pre-pit P3 and the pre-pit P33 are provided so as to penetrate through the respective centers. The count mistake prevention groove G33 is provided so that the track count does not drop in the preformat section. The track counting method, the manufacturing method, and the DPP signal generating method of such an optical disc are the same as those of the above-described optical disc of the first embodiment, and the description thereof will be omitted.

FIG. 12 shows that this optical disk is 680 nm.
When the laser diode 61 is mounted on a magneto-optical disk measuring apparatus having a detection optical system shown in FIG. 4 and the land portion L3 is tracked (moved in the track direction), the length in the track direction is 0.64 μm. Pre-pit P3
5 is a graph showing the magnitude of the pit signal of FIG. The pit signal is standardized by the reflectance of the land portion L3. The count mistake prevention groove G33 has a depth of 30, 60, 8
A total of 6 types of measurements were performed for a V groove of 0 nm and a U groove having a half width of 50, 100, and 150 nm, which is a width at a position where the depth is 1/2.

According to this graph, the pit exposure power is 3 mW to 5 mW, the pit signal is increased, the exposure power is 5 mW, the pit signal is maximum, the exposure power is maximum 10 mW, and the pit signal is minimum. I see.
Also, no groove (groove), V groove of 30 nm, 6
It can be seen that the pit signal is larger in the order of 0 nm V-groove, 80 nm V-groove, half-width of 50 nm U-groove, half-width of 100 nm U-groove, and half-width of 150 nm U-groove.

FIG. 13 shows that these optical discs have 680
of a pit signal of a pre-pit P3 having a length of 0.64 .mu.m in the track direction when the magneto-optical disk measuring apparatus having the detection optical system shown in FIG. It is the graph which showed the size. Pit signal is groove G3
Is standardized by the reflectance of.

According to this graph, the exposure power is 3 mW.
At ~ 5mW, the pit signal increases and the exposure power is 5mW.
Then, the pit signal becomes maximum and the exposure power is maximum of 9m.
It can be seen that at W, the pit signal is minimized. Also, no groove (groove), V groove of 30 nm, V groove of 60 nm, V groove of 80 nm, half-value width of 50 nm
It can be seen that the pit signal is larger in the order of the U groove, the U groove having a half width of 100 nm, and the U groove having a half width of 150 nm.

FIG. 14 shows that this optical disk is 680 nm.
6 is a graph showing the magnitude of the DPP signal from the count error prevention groove G33 when the magneto-optical disk measuring apparatus having the detection optical system shown in FIG. The larger the exposure power, the larger the DPP signal from the count mistake prevention groove G33, but it is about 1/2 of the DPP signal from the round / groove (the DPP signal when the tracks of the round and the groove are moved in the radial direction). I know there is. In this case, when the DPP signal was 0.4 or more, the tracks were correctly counted. It should be noted that the recording film described above is an example, and any recording film capable of magneto-optical recording may be used, and the recording material and composition are not limited to the above.

[0059]

According to the optical recording medium of the first aspect of the present invention, since the divided push-pull signal (DPP signal) is created by either the counting groove or the prepit, the track count is lost in the preformat section. Can be prevented. Further, even if the counting groove and the prepit are physically separated, if the distance is smaller than the light spot, the DPP signal is not created twice. Further, since it is only necessary to provide the counting groove in the pre-format portion, the production is easy.

According to the optical recording medium of the second invention, the counting groove is larger than approximately λ / 22n (λ: short wavelength of recording / reproducing laser, n: refractive index of optical recording medium substrate).
A track countable DPP signal can be obtained.

According to the optical recording medium of the third aspect of the present invention, the DP for the counting groove is obtained by dividing the difference in the amount of reflected light divided by two in the track direction by the total amount of reflected light.
Since the P signal is larger than about 0.4, the tracks can be counted by the counting groove.

According to the optical recording medium of the fourth aspect of the present invention, since the counting groove is provided so as to overlap with each of the prepits, the DPP signal is doubly created by both the counting groove and the prepit. There is no such thing.

According to the track counting method of the fifth aspect of the present invention, the weak signal for track counting, which is detected and created from the counting groove, is also counted at a countable level. You can count tracks reliably.

[Brief description of drawings]

FIG. 1 is a partially cutaway perspective view showing a configuration of an optical recording medium according to the present invention.

FIG. 2 is a partial plan view showing a configuration of an optical recording medium according to the present invention.

FIG. 3 is a configuration diagram showing a configuration of an optical recording medium manufacturing apparatus according to the present invention.

FIG. 4 is a configuration diagram showing a configuration of a tracking error signal detection optical system of the optical recording medium according to the present invention.

FIG. 5 is a graph showing characteristics of a pit signal when tracking is performed on a land portion.

FIG. 6 is a graph showing characteristics of a pit signal when tracking is performed on a groove.

FIG. 7 is a graph showing the magnitude of the DPP signal from the count error prevention groove of the optical recording medium according to the present invention.

FIG. 8 is a partially cutaway perspective view showing the configuration of the optical recording medium according to the present invention.

FIG. 9 is a partial plan view showing the configuration of the optical recording medium according to the present invention.

FIG. 10 is a partially cutaway perspective view showing the structure of the optical recording medium according to the present invention.

FIG. 11 is a partial plan view showing the configuration of the optical recording medium according to the present invention.

FIG. 12 is a graph showing characteristics of a pit signal when tracking is performed on a land portion.

FIG. 13 is a graph showing characteristics of a pit signal when tracking is performed on a groove.

FIG. 14 is a graph showing the magnitude of the DPP signal from the count error prevention groove of the optical recording medium according to the present invention.

FIG. 15 is a partially cutaway perspective view showing the configuration of a conventional optical recording medium.

FIG. 16 is a configuration diagram showing a configuration of a tracking error signal detection optical system of a general optical recording medium.

FIG. 17 is a partially cutaway perspective view showing the configuration of a conventional optical recording medium.

FIG. 18 is an explanatory diagram for explaining a problem of a conventional optical recording medium.

[Explanation of symbols]

41 Ar laser light source 44a, 44b AOM 49 Optical head 69 Offset injection circuit 72 Counter D Optical disc (optical recording medium) G Glass master G1, G2, G3 Groove (part) G11, G22, G33 Count misprevention groove (counting groove) ) L1, L2, L3 Land P1, P2, P3, P11, P22, P33 Pre-pit

Claims (5)

[Claims] 1. Information can be recorded on each track formed by a land portion and a groove portion provided between the land portions, and a row of pre-pits corresponding to pre-format information has an adjacent land portion and a groove. An optical recording medium formed in a pre-formatted portion so that the pre-formatted portion is provided with a counting groove for counting tracks so as to be shared with the pre-formatted portion. 2. The phase depth of the counting groove is approximately λ.
The optical recording medium according to claim 1, which is larger than / 22n (λ: short wavelength of recording / reproducing laser, n: refractive index of optical recording medium substrate). 3. The counting groove is for reflecting the reflected light,
The optical recording medium according to claim 1 or 2, wherein a value obtained by dividing a difference in light quantity divided into two in the track direction by the total light quantity of the reflected light is larger than about 0.4. 4. The optical recording medium according to claim 1, wherein the counting groove is provided so as to overlap with each of the prepits. 5. Information can be recorded on each track formed by a land portion and a groove portion provided between the land portions, and a row of prepits corresponding to the preformat information has an adjacent land portion and a groove. In the method of counting the tracks of the optical recording medium formed in the preformat section so as to be shared with the section, the preformat section is provided with a counting groove for counting tracks, A method of counting tracks, which comprises injecting an offset into a signal generated for counting.