JP2000260071A - Optical disc and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make realizable reduction in the level of crosstalk signal from adjacent tracks, a high density recording, improvement in jitters of a reproduced signal, and the cost reduction in a reproducing circuit by making the reproduced signal level constant regardless of pit length and land length. SOLUTION: This optical disk forms such pits 21, 22, 23 of which the amplitudes of a reproduced signal 15 obtained by the scanning with a reproducing beam light spot 14 are almost constant (V1, V2, V3), and forms lands 32, 33 of which the amplitudes of the reproduced signal 15 obtained by the scanning with the reproducing light beam spot 14 are made almost constant (V2, V4, V6).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a concentric or spiral track having substantially equally spaced tracks, representing information signals by alternate appearance of pits and lands, and the length of each pit and land. The present invention relates to an optical disc for recording an information signal and a method for manufacturing the same by changing the discontinuity in accordance with the information signal, and more particularly, to an optical disc for recording at an equal track pitch, using a binarized information read signal. , Each information has a different time interval composed of one or more, and by keeping the different time interval information substantially constant, signal leakage from adjacent tracks is suppressed, resulting in high density recording And an optical disk manufacturing method.

[0002]

2. Description of the Related Art Conventionally, for example, tracks having concentric or spiral shapes and having approximately equal intervals are used, and an information signal is expressed by alternate appearance of pits and lands, and the length of each pit and land is determined. There is known a recording method for recording an information signal on an optical disk by changing the information signal discontinuously according to the information signal.

FIG. 9 shows a schematic configuration of a master disk manufacturing apparatus for manufacturing a master disk as an original mold when forming an optical disk on which an information signal is recorded by the above-described recording method. FIG. 9 shows a schematic configuration example of a master disc manufacturing apparatus when molding an optical disc such as a so-called compact disc (CD).

In FIG. 9, a laser light oscillator 101
Generates a laser beam 102 continuously oscillated at a constant wavelength and a predetermined (constant) optical power. This laser beam 102
Enters the optical modulator 103.

The signal generator 110 converts a digital signal to be recorded on the master disk into a TT of a predetermined format.
An L (Transistor Transistor Logic) level modulation signal 111 is output. The modulated signal 111 is transmitted to the optical modulator 1
Enter 03.

The optical modulator 103 includes a laser oscillator 101
Is intermittently intermittent according to the modulation signal 111 from the signal generator 110. Thereby, the laser beam 105 modulated by the modulation signal 111 is emitted from the optical modulator 103. The laser beam 105 emitted from the optical modulator 103 is reflected by the reflection mirror 1
04.

[0007] The reflection mirror 104 is formed integrally with the recording lens 106, and the laser light 105 from the optical modulator 103 is provided.
Is reflected and made incident on the recording lens 106.

The recording lens 106 focuses the laser beam 105 from the reflection mirror 104 on a photoresist board 107.

The photoresist disk 107 is formed by applying a photoresist 113 sensitive to the wavelength of the laser light (102, 105) generated by the laser light oscillator 101 on the upper surface of the glass disk 112 on the recording lens 106 side. Therefore, the laser beam 105 is formed on the photoresist coated surface of the photoresist board 107 via the recording lens 106.
Is condensed, and the photoresist 113 on the focal point (recording light beam spot) 108 is exposed (exposed).
Will do.

Here, simultaneously with the exposure of the photoresist 113 by the laser beam 105 modulated as described above, the photoresist disk 107 is driven to rotate in the direction of the arrow R in the figure by a rotating mechanism (not shown), and integrated. By moving the reflecting mirror 104 and the recording lens 106 in the direction of arrow T in the figure, a concentric or spiral exposure pit row 109 is formed on the photoresist applied surface of the photoresist board 107. become.

Thereafter, the photoresist board 107 on which the exposure pit row 109 is formed is sent to a development step, and only the exposed portion is washed away in the development step, whereby a pit row is formed on the photoresist board 107. Will be.

The pit row formed on the photoresist board 107 is transferred to a transparent base such as plastic in the final step, although the intermediate steps are omitted, thereby forming concentric or spiral pits on the optical disk. It will be formed as a row (track).

Next, FIG. 10 shows a relationship between a pit row formed on the optical disc as described above and a reproduction light beam spot when reproducing the optical disc on which the pit row is formed.

In FIG. 10, reference numeral 12 in FIG.
A reference numeral 0 indicates a pit, a portion indicated by a reference numeral 130 in the drawing indicates a land portion, and a reference numeral 114 in the drawing indicates a reproduction light beam spot. At the time of reproduction of this optical disk, the reproduction light beam spot 114 moves in the direction of arrow A in the figure as the optical disk rotates.

Here, as described above, the laser beam oscillator 101 shown in FIG.
2 is constant, and the recording light beam spot diameter when the laser light of the constant light power is condensed by the recording lens 106 and condensed on the photoresist board 107 is also substantially constant. It has become. Therefore, each pit 1 on the optical disk finally formed using the master is
The pit width W of 20 is substantially constant.

Each pit 120 on the optical disk is
The pit length L of the signal generator 110 shown in FIG.
Has a relationship corresponding to the modulated signal 111 in which.

Although the example of FIG. 10 is not shown because it is expressed two-dimensionally, each pit 1
The pit depth H of 20 is the same as that of the photoresist plate 107 shown in FIG.
Photoresist 113 applied on a glass plate 112
Has a relationship substantially equal to the thickness of the layer.

Further, during the production of the master, the laser beam 105 irradiated on the photoresist board 107 shown in FIG.
The light is incident on the photoresist board 107 almost vertically. Therefore, the cross-sectional shape of each pit 120 on the optical disk finally formed by using the master is a mortar-shaped trapezoid in both the cross-sectional shape in the pit length direction and the cross-sectional shape in the pit width direction.

Generally, the laser wavelength of the reproduction laser beam used for reproducing the optical disk is longer than the laser wavelength of the recording laser beam 102 used for producing the master, and the reproduction laser beam is used for reproducing the optical disk. The numerical aperture (NA) of the objective lens for condensing the light depends on the recording lens 10 for condensing the recording laser beam 105 during the production of the master.
6 is smaller than the numerical aperture (NA). Therefore, the spot diameter of the reproduction light beam spot 114 during reproduction of the optical disk is larger than the pit width W of each pit 120 on the optical disk.

Next, FIG. 11 shows the relationship between the pit train formed on the optical disk as described above and the level of the reproduced signal reproduced from the optical disk by the reproduction light beam spot.

FIG. 11A shows an example of a pit row and a land formed on an optical disk and a reproducing light beam spot, and reference numerals 121, 122, and 12 in FIG.
3 indicate pits, and reference numerals 131 and 1 in FIG.
The portions indicated by 32 and 133 represent land portions, and the portion indicated by reference numeral 114 in the drawing represents a reproduction light beam spot.

FIG. 11B shows the position of the reproduction light beam spot 114 when the reproduction light beam spot 114 moves on the pit row and land in the direction of arrow A in FIG. 11A. And the reproduction signal 11 reproduced from the optical disk by the reproduction light beam spot 114
5 shows the relationship with the fifth level.

In FIG. 11, each pit 121, 1
22, 123, on each land 131, 132, 133,
The reproduction light beam spot 114 moves in the direction of arrow A in the figure, and the reflected light of the reproduction light beam is detected by a light-receiving element such as a photodetector (not shown), so that the level of the reproduction signal 115 obtained from the light-receiving element becomes The result is as shown in FIG.

That is, the reproduction signal portion S10 obtained by scanning the pit 121 with the reproduction light beam spot 114
1 is V101, the level of the reproduction signal portion S102 obtained by scanning the land 131 with the reproduction light beam spot 114 is V102, and similarly, the level of the reproduction signal portion S103 of the pit 122 is V103,
The level of the reproduced signal portion S104 of the land 132 is V10
4. The level of the reproduced signal portion S105 of the pit 123 is V
It becomes 105.

As can be seen from FIG. 11, the reproduced signal 1
In the waveform of No. 15, the polarity is inverted between the pit and the land,
Also, the signal level increases as the length of both the pits and lands increases, and conversely, the signal level decreases as the lengths of both the pits and lands decrease.

[0026]

By the way, when reproducing an optical disk such as a so-called compact disk (CD), digital video disk or digital versatile disk (DVD), a reproduced signal from a light receiving element such as a photodetector is generated. Generally, the level of a reproduced signal portion from a pit or land having a short length is increased through a waveform equivalent circuit (equalizer), and thereafter, a process of performing an analog / digital conversion to obtain a digital signal is performed.

Here, the reproduced signal 115 reproduced from the pits and lands includes two components, one of which is a signal level height (magnitude of amplitude), and the other is each component. This is a position component corresponding to the positions of the pits and lands.

On the other hand, looking at the former signal level from the signal reproduction, it is sufficient that the signal level is equal to or higher than a predetermined level for extracting the position component, and a level exceeding the predetermined level is not necessary for reproduction.

However, as described above, since the recording is performed with a constant laser power and a substantially constant recording light beam spot diameter when the master is manufactured, the pit width of each pit formed on the optical disk is set. W is substantially constant regardless of the length of the pit. Further, since the spot diameter of the reproduction light beam spot 114 during reproduction is substantially constant, as a result, as described with reference to FIG. 11, during reproduction of the optical disk, for example, the pits 121 and 123 having a long pit length are used. Signal portion S101 from
The levels V101 and V105 of S105 are the level V of the reproduced signal portion S103 from the pit 122 having a short pit length.
It is larger than 103.

Conversely, when the land portion of the optical disk has a flat reflecting surface, and the land portion is scanned by the reproduction light beam spot 114 having a spot diameter that is substantially constant, for example, as described with reference to FIG. Long land 132
Is higher than the level V102 of the reproduced signal portion S102 from the land 131 having a shorter length.

In other words, from a different point of view, if there is at least a signal level corresponding to a reproduction signal level from a pit having the shortest pit length and a land having the shortest land length during reproduction of the optical disk, the reproduction signal of the optical disk is reproduced. If the position components corresponding to the positions of the pits and lands can be extracted from, the level higher than the reproduction signal level from the shortest pits and the shortest lands,
This is a level that is too high for signal processing when reproducing the optical disc.

Also, a signal having a level that is sufficiently higher than the reproduction signal level from the shortest pit or shortest land may be mixed as, for example, a crosstalk signal from an adjacent track. When the crosstalk signal is mixed, it becomes an obstacle when reading recorded information from the reproduced signal.

Therefore, when a certain track is reproduced, a sufficient distance (track pitch) between the tracks is required at the time of recording so that the influence of crosstalk from a track adjacent to the track is not exerted. There is a need.

However, widening the track pitch is an obstacle to realizing high-density recording by narrowing the track pitch.

As described above, when the level of the reproduced signal varies depending on the length of the pits and lands (when the peak level of the reproduced signal varies), the reproduced signal indicated by C101 to C106 in FIG. Is determined not by the pits and lands on the track in the reproduction light beam traveling direction but by the physical boundary positions of the lands and pits, but by the area of the pits and lands occupying the area of the reproduction light beam 114. That is, FIG.
L141, L151, L142, L152, L143
The pit lengths and land lengths on the track shown as, and the corresponding T201, T202, T20 in FIG.
3, the signal levels shown as T204 and T205 are 1
Does not correspond to one. This is called intersymbol interference and causes fluctuation components and jitter failure in the reproduced signal.

Further, conventionally, when reproducing an optical disk as described above, a waveform equivalent circuit (equalizer) for performing a process of raising the level of a reproduction signal portion from a pit or land having a short length is required. Is one of the reasons for an increase in the cost of the disk reproducing circuit.

The present invention has been made in view of the above-mentioned problems, and the reproduction signal level of the pits and lands other than the shortest pit and the shortest land can be made equal to those of the shortest pit and the shortest land. An optical disc and a disc that can reduce the level of a talk signal, realize a high-density recording by narrowing a track pitch with an adjacent track, improve jitter of a reproduction signal, and further reduce the cost of a reproduction circuit. It is intended to provide a manufacturing method thereof.

[0038]

According to a first aspect of the present invention, there is provided an optical disk in which pits and lands are alternately arranged on tracks at substantially equal intervals, and an information signal is generated by the alternate appearance of the pits and lands. And a pit recorded so that the amplitude of a reproduction signal obtained by scanning with a reproduction light beam is substantially constant, and a reproduction light beam as a means for solving the above-mentioned problem. There are lands where the amplitude of the reproduced signal obtained by scanning the beam is substantially constant.

According to a second aspect of the present invention, in the method of manufacturing an optical disk, pits and lands are alternately arranged on tracks at substantially equal intervals, and an information signal is expressed by the alternate appearance of the pits and lands. In the optical disc manufacturing method for manufacturing an optical disc, in order to solve the above-described problems, pits other than the shortest pit are formed by narrowing the width of the central portion, and lands other than the shortest land are formed.
A minute pit is formed at the center.

According to a third aspect of the present invention, there is provided a method for manufacturing an optical disk, wherein pits and lands are alternately arranged on tracks at substantially equal intervals, and an information signal is expressed by the alternate appearance of the pits and lands. In order to solve the above-mentioned problem, in the optical disk manufacturing method for manufacturing an optical disk, the combined amplitude of the reproduction signal obtained by scanning the reproduction light beam with the independent shortest pit is substantially constant. At intervals, a plurality of shortest pits are continuously arranged and formed, and for lands excluding independent shortest lands, at intervals at which the combined amplitude of a reproduction signal obtained by scanning with a reproduction light beam is substantially constant. And a plurality of minute pits smaller than the shortest pit are continuously arranged and formed.

The shape of the pits and lands may be changed, for example, by changing the exposure amount by controlling the recording laser power, or by keeping the recording laser power constant and swinging the recording light beam spot in the radial direction of the disk, or This can be realized by superposing a plurality of recording light beam spots.

[0042]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of an optical disk and a method of manufacturing the same according to the present invention will be described below in detail with reference to the drawings. According to the method of manufacturing an optical disc according to the present invention, according to the laser wavelength λ of the reproduction optical pickup and the numerical aperture (pupil) NA of the objective lens, the amplitudes of the reproduction signals of the land portion and the pit portion become substantially equal. This is a method for manufacturing an optical disc by changing the pit shape and land shape, and the manufactured optical disc is the optical disc according to the present invention.

[First Embodiment] First, FIG. 1 shows a first embodiment of the present invention in which the amplitudes of the reproduced signals of the land portion and the pit portion can be made substantially equal. The relationship between the pits and lands on the optical disk and the reproduction signal levels obtained by scanning the pits and lands of the optical disk with the reproduction light beam spot is shown.

FIG. 1A shows an example of pits and lands and a reproduction light beam spot formed on the optical disk according to the first embodiment of the present invention.
Reference numerals 22 and 23 indicate pits, portions indicated by reference numerals 31, 32 and 33 in the drawing indicate lands, respectively, and reference numeral 14 indicates a reproduction light beam spot. Here, the pit 22 is a pit having the shortest pit length, and the pits 21 and 23 are pits longer than the shortest pit length. Although the details will be described later, the pits 21 and 23 longer than the shortest pit length are shaped to substantially match the reproduction signal level of these pit portions to the reproduction signal level of the shortest pit. The reference numerals 41 and 42 in the figure denote micro-width pits for substantially adjusting the reproduction signal level of the land except the shortest land to the reproduction signal level of the shortest land.

The example of FIG. 1 is shown corresponding to FIG. 11 for comparison with the example of FIG. 11 described above, and the pit 21 of FIG. Pit 12 of
1, pits 22 in FIG. 1A correspond to pits 122 in FIG. 11A, and similarly, pits 23 in FIG. 1A correspond to pits in FIG. The land 31 in FIG. 1A corresponds to the land 131 in FIG. 11A, and the land 32 in FIG. 1A corresponds to the land 132 in FIG. The land 33 in FIG. 1A corresponds to the land 133 in FIG.

Further, FIG. 1B shows a case where the reproducing light beam spot 14 moves on the pit row and the land in the direction of arrow A in FIG. 1A with the rotation of the optical disk. The relationship between the position of the light beam spot 14 and the level of a reproduction signal 15 reproduced from the optical disk by the reproduction light beam spot 14 is shown.

In FIG. 1, each pit 21, 22, 22
The reproduction light beam spot 14 moves in the direction of arrow A in FIG. 3 and on each of the lands 31, 32, and 33, and the reflected light of the reproduction light beam is detected by a light receiving element such as a photodetector (not shown). The level of the reproduced signal 15 obtained from the element is as shown in FIG.

That is, the level of the reproduction signal portion S1 obtained by scanning the pit 21 with the reproduction light beam spot 14 becomes V1, and the level of the reproduction signal portion S2 obtained by scanning the land 31 with the reproduction light beam spot 14 is obtained. Level is V
2 and the same applies to the reproduced signal portion S3 of the pit 22.
Is V3, the level of the reproduced signal portion S4 of the land 32 on which the small-width pit 41 is formed is V4,
3, the level of the reproduced signal portion S5 is V5, and the level of the reproduced signal portion S6 of the land 33 on which the minute width pits 42 are formed is V6.

As can be seen from FIG. 1, the reproduced signal 15
In the waveform of the pit, the polarity is inverted between the pit and the land, and the pits 21, 22, 23 and the lands 31, 32, 3
3 reproduced signal portions S1, S2, S3, S4, S5, S6
Of the levels V1, V2, V3, V4, V5, and V6 are substantially equal to each other.

Here, in the present embodiment, as described above, the level of the reproduced signal portion of each pit and land becomes substantially equal for the following reason.

In general, the diameter of the reproducing light beam spot irradiated on the optical disk from the reproducing optical pickup is determined by the ratio (λ / N) of the wavelength λ of the reproducing light laser to the numerical aperture NA of the objective lens.
It is known that it is proportional to the value of A). For example, in the case of a so-called compact disc (CD), the wavelength λ of the reproduction light laser is 780 nm, and the numerical aperture NA of the objective lens is
= 0.45, and for example, a so-called digital video disc or digital versatile disc (D
VD), the wavelength λ of the reproduction light laser is 650 nm,
The numerical aperture NA of the objective lens is 0.6.

As described above, the laser wavelength .lambda. And the numerical aperture NA of the objective lens are uniquely determined by the specifications of the optical disk. Therefore, the reproduction optical pickup irradiates the optical disk onto the optical disk. The light beam spot diameter is also uniquely determined.

Therefore, the shape of each of the pits and lands for making the reproduction signal levels from the pits and lands on the optical disk substantially constant is determined by the laser wavelength λ of the reproduction optical pickup and the numerical aperture NA of the objective lens. The pits 21, 22, 23 and lands 3 of the first embodiment of the present invention shown in FIG.
The shapes 1, 32, and 33 are examples.

However, the shapes of the pits and lands of the first embodiment of the present invention shown in FIG. 1 are two-dimensionally represented, and the actual pits and lands have a certain depth. It has a three-dimensional shape. That is,
The cross-sectional shape of the pits and lands of the first embodiment shown in FIG. 1 is rectangular or trapezoidal in both the length direction and the width direction. The shapes of pits and lands to which the present invention is applied are variously conceivable. However, if the levels of the reproduced signals of the pits and lands are substantially constant, they are included in the scope of the present invention.

In the first embodiment of the present invention shown in FIG. 1, when the reproduction light beam spot 14 moves on pits 21 and 23 longer than the shortest pit length, the reproduction signal generated from the reflected light In order to reduce the level (absolute value level), the width Wc at the center of the pit is made smaller than the width W at both ends of the pit.

That is, in the first embodiment, the shape of the pits 21 and 23 longer than the shortest pit length is made such that the width Wc at the center of the pit is smaller than the width W at both ends of the pit. The levels V1 and V5 of the reproduced signal portions S1 and S5 of the pits 21 and 23 are substantially equal to the level V3 of the reproduced signal portion S3 of the shortest pit 22. In other words, as the width Wc of the pit central portion of each of the pits 21 and 23, the level of the reproduced signal portion obtained when the reproduced light beam spot 14 is moving on the pit central portion is smaller than the level of the shortest pit 22. The width is selected so as to be substantially equal to the level V3 of the reproduced signal portion S3 obtained when the movement is made.

In the first embodiment, the reason why the width W at both ends of the pits 21 and 23 longer than the shortest pit length is wider than the width Wc at the center of each pit is that of the reproduction light. When the bit spot 14 moves on each of the pits 21 and 23, the rising and falling characteristics of the reproduced signal at the start end and end end of each pit are determined by the shortest pit 2
This is to make it approximately equal to 2.

In the first embodiment of the present invention shown in FIG. 1, when the reproducing light beam spot 14 moves on the lands 32 and 33 longer than the shortest land length, the reproducing light beam generated from the reflected light is used. The small width pit 4 is located at the center of the land so that the signal level (absolute value level) is reduced.
1, 42 are provided.

That is, in the first embodiment, for the lands 32 and 33 longer than the shortest land length, the minute width pits 41 and 42 are provided at the center of the lands, so that the reproduced signals of the lands 32 and 33 are reproduced. Level V4 of parts S4 and S6
V6 is the level V of the reproduction signal portion S2 of the shortest land 31
It is set to be approximately equal to 2. In other words, the minute width pit 41 at the center of each land 32, 33,
Reference numeral 42 denotes a level of the reproduction signal portion obtained when the reproduction light beam spot 14 moves on the center of the land, and a level V2 of the reproduction signal portion S2 obtained when the reproduction light beam spot 14 moves on the shortest land 31. Micro-width pits are selected that are approximately equal and have a width such that the rising and falling characteristics of the reproduced signal are equal at the start and end ends of each land.

In the first embodiment, the minute width pits 41, 42 are provided at the land centers of the lands 32, 33 longer than the shortest land length. In other words, each land 32, 33 The reason why minute width pits 41 and 42 are not provided at both ends of 33 is that
For the same reason as described above for the shape of the pit longer than the shortest pit length, by making the effective width of both ends of each land wider than the effective width of the center of each land, The reproduction light bit spot 14 is located on each land 32, 33.
This is to make the rising and falling characteristics of the reproduced signal at the start end and the end end of each of these lands approximately equal to those of the shortest land 31 when moving upward.

[Effects of the First Embodiment] As is clear from the above description, according to the first embodiment, the reproduction signal levels of the pits and lands other than the shortest pits and shortest lands are set to The reproduction signal level can be made substantially equal to the shortest pit and shortest land, and as a result, the level of the crosstalk signal from the adjacent track can be reduced.

Further, since the level of the crosstalk signal from the adjacent track can be reduced, the track pitch between each adjacent track can be narrowed, and as a result, high-density recording on the optical disk can be realized.

Further, since the peak level of the reproduction signal can be kept constant, the position of the zero cross point of the reproduction signal does not fluctuate depending on the length of the pits and lands. As a result, the jitter of the reproduction signal can be improved. it can.

Furthermore, since the peak level of the reproduction signal can be kept constant, a waveform equivalent circuit (equalizer) for performing the process of raising the level of the reproduction signal portion from pits or lands having a short length, which has been conventionally required, is performed. Is unnecessary, and as a result, the cost of the disk reproducing circuit can be reduced.

[Second Embodiment] Next, FIG. 2 shows a second embodiment of the present invention in which the amplitudes of the reproduced signals of the land portion and the pit portion can be made substantially equal. The relationship between the pits and lands on the optical disk and the reproduction signal level obtained by scanning the pits and lands of the optical disk with the reproduction light beam spot is shown.

FIG. 2A shows an example of pits and lands and a reproduction light beam spot formed on the optical disk of the second embodiment, and reference numerals 51 and 5 in FIG.
The pits indicated by reference numerals 2 and 53 are designated by reference numeral 6 in the figure.
The portions indicated by 1, 62 and 63 indicate land portions, and the portion indicated by reference numeral 14 in the drawing indicates a reproduction light beam spot. Here, each of the pits 51 and 5 shown in FIG.
The pits 2 and 53 have the shortest pit lengths. Reference numerals 71 and 72 in the figure denote minute isolated pits for substantially adjusting the reproduction signal level of the land portion excluding the shortest land to the reproduction signal level of the shortest land.

The example of FIG. 2 is shown in correspondence with FIG. 11 for comparison with the above-mentioned FIG. 11, and the shortest pits 51 of a set of three consecutive ones in FIG. Corresponding to the pit 121 in FIG. 11A, one independent shortest pit 52 in FIG. 2A is the pit 12 in FIG.
2, and similarly, a set of three consecutive pits 53 in FIG. 2A corresponds to the pit 123 in FIG. 11A, and the independent land 61 in FIG. 11A corresponds to the land 131 of FIG. 11A, the land 62 of FIG. 2A corresponds to the land 132 of FIG. 11A, and the land 63 of FIG. This corresponds to the land 133 in FIG.

Further, FIG. 2B shows a case where the reproduction light beam spot 14 moves on the pit row and the land in the direction of arrow A in FIG. 2A with the rotation of the optical disk. The relationship between the position of the light beam spot 14 and the level of the reproduction signal 17 reproduced from the optical disk by the reproduction light beam spot 14 is shown.

In FIG. 2, each pit 51, 52,
53, the reproduction light beam spot 14 moves on each of the lands 61, 62, 63 in the direction of arrow A in the figure, and the reflected light of the reproduction light beam is detected by a light receiving element such as a photodetector (not shown) to receive the light. The level of the reproduced signal 17 obtained from the element is as shown in FIG.

That is, the level of the reproduction signal portion S11 obtained by scanning the shortest pits 51 of a set of three consecutive light beams with the reproduction light beam spot 14 is V11, and the reproduction light beam spot 14 is formed on the independent land 61. The level of the reproduced signal portion S12 obtained by scanning is V12, and similarly, the level of the reproduced signal portion S13 of one independent shortest pit 52 is V13. The level of the reproduced signal portion S14 of the formed land 62 is V14, the level of the reproduced signal portion S15 of the set of three shortest pits 53 is V15, and the land 6 on which a set of minute isolated pits 72 is formed.
The level of the reproduction signal portion S16 of No. 3 is V16.

As can be seen from FIG. 2, the reproduced signal 17
In the waveform of, the polarity is inverted between each pit and the land, and the pits 51, 52, 53 and the lands 61, 62, 6
3 reproduced signal portions S11, S12, S13, S14, S
15, S16 levels V11, V12, V13, V1
The levels of V4, V15, and V16 are substantially the same.

Here, in the second embodiment of the present invention, the levels of the reproduced signal portions of each pit and land become substantially equal as described above for the following reason.

In the second embodiment, pits other than the shortest pit are represented by a plurality of continuous short pits, and lands other than the shortest lands are represented by a plurality of continuous small isolated pits. expressing.

That is, since the reproduced signal of each shortest pit is substantially a half-wave of a sine wave, in the second embodiment, one set of a plurality of continuous pits other than the shortest pit is formed. The positional relationship of the shortest pits is arranged so that the reproduction signals of a set of the shortest pits in succession are approximately 120 degrees at electrical angle intervals. Similarly, since the reproduction signal of each shortest land is substantially a half-wave of a sine wave, in the second embodiment, a set of a plurality of continuous small isolated pits constituting a land other than the shortest land is used. Are arranged such that the reproduction signals of a set of a plurality of these minute isolated pits are approximately 120 degrees at electrical angle intervals.

That is, the fact that the electrical angle interval of a plurality of continuous half-waves that are substantially sinusoidal is approximately 120 degrees means that a signal obtained by adding each half-wave by their integration effect. Means That is, when the reproduction light beam spot 14 passes over a set of a plurality of shortest pits that constitute pits other than the shortest pit, a half-wave of a substantially sinusoidal wave generated by each of the shortest pits has an electric potential of approximately 120 degrees. Continuously generated with an angular phase difference, the final reproduced signal becomes a reproduced signal 17 to which a half-wave of a substantially sine wave having an electrical angle phase difference of approximately 120 degrees is added. Similarly, when the reproduction light beam spot 14 passes over a set of a plurality of small isolated pits constituting a land other than the shortest land, a half-wave of a substantially sine wave by each small isolated pit becomes approximately 120 degrees. And the final reproduced signal is a reproduced signal 17 to which a half-wave of a substantially sinusoidal wave having an electric angle phase difference of approximately 120 degrees is added.

By the way, various methods for forming the pits and the lands as in the first and second embodiments of the present invention on the photoresist disk at the time of manufacturing the master are conceivable. The following are some techniques.

[First Method] First, as a first method, the diameter of the recording light beam spot at the time of manufacturing the master is reduced to, for example, a diameter smaller than the minimum width of the pit width finally formed on the optical disk. By irradiating the focused recording light beam onto the photoresist on the rotating photoresist disc and wobbling the recording light beam spot in the disk radial direction, the photo on the photoresist disc is narrowed down. A method of controlling the range (pit width) where the resist is actually exposed can be considered.

That is, the first method will be described with reference to FIG. 3 for a pit having the shape described in the first embodiment, for example. In the case of the first method, the recording light at the time of producing the master is described. The diameter of the beam spot 16 is narrowed down to a diameter smaller than the minimum pit width (for example, the width Wc of the pit center in FIG. 3) finally formed on the optical disk, and the narrowed down recording light beam is rotated. By irradiating the recording light beam spot 16 in the radial direction of the disk while irradiating the photoresist on the photoresist disk which is being used, the width W at both ends and the width Wc at the center are increased as shown in FIG. Exposure should be made narrow and without gaps. In the example of FIG. 3, the locus of the recording light beam spot 16 is indicated by an arrow M in the figure.

The first method is not limited to the pit having the shape shown in FIG. 3 described in the first embodiment.
When forming the shortest pit 22 and the minute width pits 41 and 42 in FIG. 1, each pit 5 described in the second embodiment is used.
The present invention can be similarly applied to the case where 1, 52, 53 and minute isolated pits 71, 72 are formed.

[Specific Example of First Method] Next, using the above-described first method, pits and lands as in the first and second embodiments of the present invention are removed by photo One specific configuration example for forming on a resist board will be described below.

FIG. 4 shows a first method of controlling the range (pit width) where the photoresist is actually exposed by wobbling the recording light beam spot at the time of manufacturing the master in the radial direction of the disk. The first 1,
A specific configuration example for forming the pits and lands described in the second embodiment on a photoresist disk at the time of manufacturing a master is shown. FIG. 4 shows a schematic configuration example of a master disc manufacturing apparatus when molding an optical disc such as a so-called compact disc (CD).

In FIG. 4, the laser light oscillator 1 comprises:
A laser beam 2 that is continuously oscillated at a constant wavelength and a predetermined (constant) optical power is generated. The laser light 2 enters an optical modulator 91 described later. The signal generator 10 outputs a signal of a predetermined format as a signal to be recorded on the master disk.
A TL (Transistor Transistor Logic) level modulation signal 11 is output. The modulated signal 11 is input to the optical modulator 3 and a wobbling signal generator 90 described later.

The light modulator 3 interrupts the laser light 2 from the laser light oscillator 1 via the light modulator 91 in accordance with the modulation signal 11 from the signal generator 10. As a result, the laser light 5 modulated by the modulation signal 11 is emitted from the optical modulator 3. The laser light 5 emitted from the light modulator 3 enters the reflection mirror 4.

The reflection mirror 4 is formed integrally with the recording lens 6 and reflects the laser beam 5 from the optical modulator 3 to make it incident on the recording lens 6. The recording lens 6 focuses the laser beam 5 from the reflection mirror 4 on a photoresist board 7.
In the case of the present embodiment, the laser light wavelength λ from the laser light oscillator 1 and the numerical aperture NA of the recording lens 6 are such that the diameter of the recording light beam spot 16 is finally determined as described in FIG. The value can be set to a diameter smaller than the minimum pit width formed on the optical disc (for example, the width Wc of the center of the pit in FIG. 1).

The photoresist disk 7 is provided with the laser light oscillator 1
A photoresist 13 sensitive to the wavelength of the laser light (2, 5) in which 0 is generated is applied to the upper surface of the glass disk 12 on the recording lens 6 side. Therefore, by condensing the laser beam 5 on the photoresist coated surface of the photoresist disc 7 via the recording lens 6, the photoresist 13 on the focal point (recording light beam spot) 8 is exposed (exposed). ).

The laser beam 5 modulated as described above
At the same time as the exposure of the photoresist 13 by this, the photoresist disk 7 is driven to rotate in the direction of the arrow R by a rotating mechanism (not shown), and the integrated reflecting mirror 4 and recording lens 6 are moved in the direction of the arrow T in the figure. By moving
A concentric or spiral exposure pit row 9 is formed on the photoresist applied surface of the photoresist board 7.

Here, the wobbling signal generator 90 provided in the configuration of FIG. 4 generates a recording light beam spot formed on the photoresist disc 7 based on the modulation signal 11 from the signal generator 10. This is to generate a wobbling signal for oscillating (wobbling) the emission direction of the laser light 2 from the laser light oscillator 1 so as to wobble in the disk radial direction.

Further, based on the wobbling signal from the wobbling signal generator 90, the optical modulator 91 provided in the configuration of FIG.
The emission direction of the laser light 2 from the laser light oscillator 1 is swung (wobbled) so that the recording light beam spot formed thereon is wobbled in the radial direction of the disk.

Further, in the example of FIG. 4, the order of modulation of the laser beam is the order of wobbling and signal modulation. However, the same effect can be obtained by reversing the configuration in the order of signal modulation and wobbling. it can.

Thus, according to the structure of FIG. 4, the pits and lands as shown in FIGS. 1 to 3 are formed on the photoresist disk 7 at the time of manufacturing the master by the first method described above. It becomes possible.

Thereafter, the photoresist disk 7 on which the exposure pit row 9 is formed in the configuration shown in FIG. 4 is sent to a developing step, and only the exposed portions are washed away in the developing step, thereby leaving the photoresist disk 7 on the photoresist disk 7. Means that a pit row is formed.

The pit rows formed on the photoresist board 7 are transferred to a transparent base such as plastic in the final step, although the intermediate steps are omitted, thereby forming concentric or spiral pit rows on the optical disk. (Track).

In the example shown in FIG. 4, the operation of the optical modulator 91 is controlled by the wobbling signal from the wobbling signal generator 90. However, another example for realizing the first method is described. As a typical configuration, based on the wobbling signal from the wobbling signal generator 90, the reflection mirror 4 is driven so that the recording light beam spot finally formed on the photoresist disk 7 is wobbled in the disk radial direction. It is also possible to swing (wobble) the reflection direction of the laser light 5.

[Second Method] Next, as a second method, the power of the recording laser at the time of manufacturing the master is changed and the recording laser is irradiated onto the photoresist on the rotating photoresist. A method of controlling the exposure amount of the photoresist on the photoresist disk, in other words, a range (width) where the photoresist is actually exposed can be considered.

That is, the second method is described in, for example, the pits 21 and 2 of FIG. 1 described in the first embodiment.
For example, a pit having a wide width W at both ends and a narrow width Wc at the center of the pit, such as No. 3, will be described as an example. In the case of the second method, the diameter of the recording light beam spot at the time of manufacturing the master is described. Is the width W of the both ends of the pits 21 and 23 in FIG.
The recording light beam is irradiated onto the photoresist on the rotating photoresist plate. At this time, when exposing the photoresist at the positions corresponding to the both ends of the pit, By increasing the power of the recording laser, the photoresist in the same range as the diameter of the recording light beam spot formed on the position is sufficiently exposed, while the position corresponding to the central part of the pit is exposed. When exposing the photoresist, by lowering the power of the recording laser, the range actually exposed at that position is the central portion (the diameter portion having a width of about Wc) where the power is the strongest in the recording light laser spot. The width W at both ends like the pits 21 and 23 in FIG.
Is formed so that the width Wc of the central portion of the pit becomes narrower.

Note that the second method is not limited to the pits 21 and 23 of FIG. 1 described in the first embodiment, as well as the pits of FIG. When the shortest pit 22 and the minute width pits 41 and 42 are formed, the pits 51 and 5 described in the second embodiment are used.
2 and 53 and minute isolated pits 71 and 72 can be similarly applied.

[Specific Example of Second Method] Next, using the above-described second method, pits and lands as in the first and second embodiments of the present invention are removed by photo About the specific configuration for forming on the resist board,
This will be described below.

In FIG. 5, the second method for controlling the range (pit size) where the photoresist is actually exposed by changing the power of the recording laser at the time of manufacturing the master is described above. A specific configuration example for forming the pits and lands described in the first and second embodiments on a photoresist disk at the time of manufacturing a master will be described. FIG. 5 also shows a schematic configuration example of a master disc manufacturing apparatus when molding an optical disc such as a so-called compact disc (CD), similarly to the example of FIG. In addition,
5, the same components as those shown in FIG. 4 described above are denoted by the same reference numerals as those in FIG. 4, and detailed description thereof will be omitted.

In FIG. 5, the laser light 2 from the laser light oscillator 94 enters the optical modulator 3, and the modulation signal 11 from the signal generator 10 is input to the optical modulator 3 while controlling the laser power. It is also input to the container 92.

Here, the laser power controller 92 provided in the configuration shown in FIG. 5 records on the photoresist disk 7 based on the modulation signal 11 generated by the signal generator 10. The optical power of the light beam, ie
This is for generating a laser power control signal for adjusting the optical power of the laser light 2 emitted from the laser light oscillator 94.

Thus, according to the structure of FIG. 5, the pits and lands as shown in FIGS. 1 to 3 are formed on the photoresist disk at the time of manufacturing the master by the above-described second method. Becomes possible.

In the example shown in FIG. 5, the optical power of the laser light emitted from the laser light oscillator 94 is directly controlled by the laser power control signal from the laser power controller 92. As another specific configuration for realizing the method, for example, by using an optical element capable of adjusting the transmittance of the incident laser beam based on the modulation signal 11, the final configuration on the photoresist disc 7 is achieved. It is also possible to adjust the optical power of the laser beam applied to the laser beam.

[Third Method] Next, as a third method,
As shown in FIG. 6, a plurality of lights may be used at the time of manufacturing the master to form beam diameters each having a different pit or land width, and these may be realized in combination.

That is, in FIG.
The laser beam 202 from 00 is split into a laser beam 204 and a laser beam 205 by a half mirror 203. One of the laser beams 204 is converted into a laser beam 5 by an exposure controller 210, a signal modulator 250, and a prism 209. The other laser beam 205 is converted into a laser beam 5 by a mirror 207, an exposure controller 220, a signal modulator 260, a mirror 208, and a prism 209.

The exposure controller 210 determines the exposure required to form the pits 51 to 53 shown in FIG. 2, and the signal modulator 250 controls the recording signal 241 to be recorded as the pits 51 to 53. Is subjected to light modulation processing. Similarly, the exposure controller 220 determines the exposure required to form the lands 62 and 63 shown in FIG. 2, and the signal modulator 260 controls the recording signal 24 to be recorded on the lands 62 and 63.
1 is subjected to light modulation processing.

The signal generator 230 converts a digital signal to be recorded on the master disk into a TT of a predetermined format.
An L (Transistor Transistor Logic) level modulation signal is output, and the pit land signal generator 240 outputs the pits shown in FIG.
A pit recording signal 241 corresponding to a land row and a land recording signal 242 are formed. The prism 209 combines the two split lights again to form one light axis light, and irradiates the photoresist board 7 via the reflection mirror 4 and the recording lens 6. As described above, by independently adjusting the pits and the lands, it is possible to facilitate the operation of making the amplitudes of the pits and the lands substantially equal.

[Other methods] In addition, the above-described first to third methods
As another method, for example, only a portion having a width W, for example, of the pits 21, 22, and 23 in FIG. 1 described in the first embodiment is first formed on a photoresist plate, and thereafter, Then, a portion having a width Wc of the pits 21 and 22 of FIG. 1 is formed on a photoresist plate, and thereafter,
It is also possible to adopt a method of forming portions to be the minute width pits 41 and 42 in FIG. 1 on a photoresist disk. When the method of this example is applied to the second embodiment, only the pits 51, 52, and 53 of FIG. 2 are formed on a photoresist board first, and then the micro-isolation of FIG. A method of forming the pits 71 and 72 on the photoresist disk will be adopted. However, since the first to third methods described above require fewer steps in producing a master, it is considered more preferable to employ these first to third methods.

[Effects of the Second Embodiment] As is clear from the above description, according to the second embodiment, the reproduction signal levels of the pits and lands other than the shortest pit and the shortest land are set to The same effect as that of the first embodiment described above can be obtained, for example, the reproduction signal level can be made substantially equal to the shortest pit and shortest land, and as a result, the level of the crosstalk signal from the adjacent track can be reduced. be able to.

[Third Embodiment] Next, a third embodiment of the present invention will be described.
The optical disk according to the embodiment will be described. The optical disk according to the third embodiment is an optical disk in which the ratio between the maximum pit length and the minimum pit length and the ratio of the amplitude of the signal level between the maximum land length and the minimum land length are predetermined such as a so-called CD or DVD. This is an example in which the present invention is applied.

That is, the optical disk of the third embodiment has pits 75 and lands 76 having the shapes as shown in FIG. The pit 75 indicates the pit having the maximum pit length. As can be seen from FIG. 7A, it is assumed that a larger iron ball is provided at the grip portion of the iron array provided with iron balls at both ends. It has a pit shape. The reproduced waveform is as shown in FIG. 7 (b), and the signal level W2 of the portion corresponding to the gripped portion appears larger than the signal level W1 of both end portions.

On the other hand, the land 76 indicates the land having the maximum land length. As can be seen from FIG. 7A, the land 76 has an iron array shape in which a bar-shaped grip portion is provided between iron balls at both ends. Have. The reproduced waveform is as shown in FIG. 7 (b), and the signal level W4 of the portion corresponding to the grip portion of the iron array appears larger than the signal level W3 of both ends.

By forming the pits and lands of the optical disk in such a shape, the ratio of the amplitude of the signal level between the maximum pit length and the minimum pit length and the maximum land length and the minimum land length as in the case of a CD or DVD are previously determined. Even in the optical disc as defined, in addition to the above-mentioned zero cross point fluctuation, it is possible to suppress the jitter due to the intersymbol interference between the pit and the land, and it is possible to obtain the same effects as those of the above embodiments.

[Fourth Embodiment] Next, a fourth embodiment of the present invention will be described.
The optical disk according to the embodiment will be described. Similarly to the optical disk according to the third embodiment, the optical disk according to the fourth embodiment has the signal levels of the maximum pit length and the minimum pit length and the maximum land length and the minimum land length of a CD or a DVD. This is an example in which the present invention is applied to an optical disk having a predetermined amplitude ratio.

That is, the optical disk of the fourth embodiment has lands 77 and pits 78 having the shapes as shown in FIG. The land 77 indicates the land having the maximum land length. As can be seen from FIG. 8A, the land 77 has circular pits 77a and 77b smaller than usual at both ends of the land (in other words, in other words). For example, the land between the pits 77a and 77b is a land.) The reproduced waveform is as shown in FIG.
The pits 7 are higher than the signal level W5 of the portions a and 77b.
The signal level W6 in the portion between 7a and 77b appears larger.

On the other hand, the pit 78 indicates the pit having the maximum pit length. As shown in FIG. 8A, the pit 78 has three circular pits 78a to 78c, and the middle pit 78b is It is larger than the pits 78a and 78c on both sides. The reproduced waveform is as shown in FIG. 8B, and the signal level W7 of the pits 78a and 78c on both sides is obtained.
The signal level W8 of the middle pit 78b is larger than that of the middle pit 78b.

By forming the pits and lands of the optical disk in such a shape, the ratio of the amplitude of the signal level between the maximum pit length and the minimum pit length and the maximum land length and the minimum land length as in the case of a CD or DVD are previously determined. Even in the optical disc as defined, in addition to the above-mentioned zero cross point fluctuation, it is possible to suppress the jitter due to the intersymbol interference between the pit and the land, and it is possible to obtain the same effects as those of the above embodiments.

[Other Application Examples of the Present Invention] Finally, the description of each of the above embodiments is an example of the present invention. Therefore, the present invention is not limited to the above embodiments. For example, in each of the above-described embodiments, the formation of each pit or land at the time of manufacturing a master disc such as a CD or DVD has been described as an example. However, the present invention can be applied to an optical disc such as a so-called CD-R. The present invention is also applicable to those that form physical pits. Of course, various changes can be made according to the design and the like within a range not departing from the technical idea according to the present invention.

[0118]

According to the optical disk of the present invention, the pits other than the independent shortest pits are spaced such that the composite amplitude of the reproduced signal obtained by scanning with the reproduced light beam is substantially constant. A plurality of shortest pits are successively arranged at the lands, and the shortest pits at lands excluding the independent shortest lands are arranged at intervals such that a combined amplitude of a reproduction signal obtained by scanning with a reproduction light beam is substantially constant. By continuously arranging a plurality of smaller pits smaller than the shortest pit and the shortest land, the reproduction signal level by the pits and lands other than the shortest pit and the shortest land can be made equal to those shortest pits and the shortest land. And the level of the crosstalk signal from the adjacent track can be reduced, and the track pitch between adjacent tracks can be narrowed to achieve high-density recording. To improve the jitter of the reproduced signal, and further, it is also possible the cost of the reproducing circuit.

According to a second aspect of the present invention, in the method of manufacturing an optical disk, pits are formed such that the amplitude of a reproduction signal obtained by scanning with a reproduction light beam is substantially constant, and the reproduction light beam is scanned. By forming lands in which the amplitude of the reproduction signal obtained by performing the above operation is substantially constant, the reproduction signal level of each pit and land can be made substantially constant. As a result, the crosstalk signal from the adjacent track can be obtained. The level can be reduced, the track pitch between adjacent tracks can be narrowed, high-density recording can be achieved, the jitter of a reproduction signal can be improved, and the cost of a reproduction circuit can be reduced.

According to a third aspect of the present invention, there is provided a method of manufacturing an optical disk according to the present invention, wherein the pits other than the shortest pits have a narrower width at the center, and the lands other than the shortest lands have minute pits formed at the center. By this, the reproduction signal level by the pits and lands other than the shortest pits and shortest lands can be made equal to those shortest pits and shortest lands,
As a result, the level of the crosstalk signal from the adjacent track can be reduced, the track pitch with the adjacent track can be narrowed, high-density recording can be achieved, the jitter of the reproduction signal can be improved, and Cost reduction is also possible.

[Brief description of the drawings]

FIG. 1 shows a relationship between a pit row and a land formed on an optical disc and a reproduction light beam spot according to a first embodiment of the present invention, and a reproduction signal reproduced from the optical disc by the reproduction light beam spot. FIG. 4 is a diagram illustrating a relationship between a level and a spot position.

FIG. 2 shows a relationship between a pit row and a land formed on an optical disk and a reproduction light beam spot according to a second embodiment of the present invention, and a reproduction signal reproduced from the optical disk by the reproduction light beam spot. FIG. 4 is a diagram illustrating a relationship between a level and a spot position.

FIG. 3 is a diagram used to explain a first method (formation of pits by wobbling of a recording beam spot) that can be employed in each embodiment of the present invention.

FIG. 4 is a diagram showing a schematic configuration of a master disk manufacturing apparatus for manufacturing a master as an original mold when forming an optical disk by employing the first technique.

FIG. 5 is a diagram showing a schematic configuration of a master disk manufacturing apparatus for manufacturing a master disk serving as an original mold when forming an optical disk by employing the second technique.

FIG. 6 is a diagram showing a schematic configuration of a master disk manufacturing apparatus for manufacturing a master as an original mold when an optical disk is formed by employing a third technique.

FIG. 7 is a diagram showing pit rows and lands formed on an optical disc according to a third embodiment of the present invention, and their reproduction waveforms.

FIG. 8 is a diagram showing pit rows and lands formed on an optical disc according to a fourth embodiment of the present invention, and their reproduction waveforms.

FIG. 9 is a diagram showing a schematic configuration of a master disk manufacturing apparatus for manufacturing a master as an original mold when an optical disk is formed by a conventional recording method.

FIG. 10 is a diagram showing a relationship between a pit row formed on an optical disc by a conventional recording method and a reproduction light beam spot when reproducing the optical disc on which the pit row is formed.

FIG. 11 shows a relationship between a pit row and a land formed on an optical disk by a conventional recording method and a reproduction light beam spot, and a level and a spot position of a reproduction signal reproduced from the optical disk by the reproduction light beam spot. FIG.

[Explanation of symbols]

1,94 ... laser light oscillator, 2,5 ... laser light, 3,9
DESCRIPTION OF SYMBOLS 1 ... Optical modulator, 4 ... Reflection mirror, 6 ... Recording lens, 7 ...
Photoresist disc, 8 focus point, 9 concentric or spiral exposure pit array, 10 signal generator, 11 modulation signal, 12 glass disc, 13 photoresist, 14
... Reproduction light beam spot, 16 recording light laser spot, 21, 23 pit longer than the shortest pit length, 22,
52: shortest pit, 31, 61: shortest land, 32, 3
3, 62, 63 ... land longer than the shortest land, 41, 4
2 ... micro-width pits, 51, 53 ... consecutive shortest pits,
90: wobbling signal generator, 92: laser power controller, 93: laser power control signal

Claims (3)

[Claims] 1. An optical disk in which pits and lands are alternately arranged on tracks at substantially equal intervals, and an information signal is expressed by the alternate appearance of the pits and lands. The optical disk is obtained by scanning with a reproduction light beam. Pits recorded so that the amplitudes of the reproduced signals are substantially constant, and lands where the amplitudes of the reproduced signals obtained by scanning with the reproducing light beam are substantially constant. optical disk. 2. An optical disk manufacturing method for manufacturing an optical disk in which pits and lands are alternately arranged on tracks at substantially equal intervals and an information signal is expressed by the alternate appearance of the pits and lands. The method for manufacturing an optical disc according to claim 1, wherein the center portion is formed to have a small width, and a small pit is formed at the center portion of each of the lands excluding the shortest land. 3. An optical disk manufacturing method for manufacturing an optical disk in which pits and lands are alternately arranged on tracks at substantially equal intervals and an information signal is expressed by the alternate appearance of the pits and lands. For the pits excluding, the shortest pits are formed by continuously arranging a plurality of shortest pits at intervals at which the composite amplitude of the reproduction signal obtained by scanning with the reproduction light beam is substantially constant. Is characterized in that a plurality of small pits smaller than the shortest pit are continuously arranged at intervals at which a combined amplitude of a reproduction signal obtained by scanning with a reproduction light beam is substantially constant. An optical disc manufacturing method.