JP2004070991A - Optical recording medium, its reproducing device and reproducing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical recording medium of high recording density in which information signals are reproduced at a high speed and to provide its reproducing device and method. <P>SOLUTION: Light beams A1 to E1 and A2 to E2, which are reflected from five recessed shape pits 11A to 11E, respectively interfere with each other on the surface of photodetectors 31A to 31E in accordance with their wave surfaces and distribution of light intensity is formed on the photodetectors 31A to 31E in accordance with the respective depths of the pits 11A to 11E. Information signals recorded on an optical recording medium 1 is reproduced by reading the distribution of the light intensity as phase information on the photodetectors 31A to 31E. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an optical recording medium from which an information signal is reproduced using a light beam, a reproducing apparatus and a reproducing method thereof.
[0002]
[Prior art]
The optical recording medium includes a read-only ROM disk (CD-ROM, DVD-ROM, etc.) and a rewritable disk having a ROM area and a recordable area.
[0003]
In order to reproduce an optical recording medium having a ROM area as described above using an optical disc system as an information reproducing apparatus, a light beam from a laser light source is focused on a signal recording surface of the optical recording medium. The light beam is reflected almost as it is where there is no pit on the signal recording surface. On the other hand, where there is a pit on the signal recording surface, the light beam is diffracted by the pit, and a part of the incident light beam returns to the photodetector.
[0004]
In this manner, the information signal is reproduced from the optical recording medium using the fact that the intensity of the returning light is modulated by the pits.
[0005]
[Problems to be solved by the invention]
However, in the above-mentioned conventional reproducing method for an optical recording medium, pits on the optical recording medium are reproduced one by one along a time axis by a beam spot obtained by condensing a light beam on a signal recording surface of the optical recording medium. Therefore, there is a problem that it is difficult to increase the data transfer rate.
[0006]
Also, in the above-described conventional optical recording medium reproduction, pits having the same size as the beam spot diameter of the light beam are reproduced, so the recording density of the optical recording medium is limited by the size of the beam spot. There was a problem that would.
[0007]
The present invention has been made in view of such a problem, and an object of the present invention is to provide an optical recording medium having a high recording density capable of reproducing an information signal at high speed, a reproducing apparatus and a reproducing method thereof.
[0008]
[Means for Solving the Problems]
An optical recording medium according to the present invention has a substrate on which pits are formed and a reflective film formed on the pits, and a light beam is focused on a signal recording surface which is a surface of the reflective film. An optical recording medium on which an information signal is reproduced by a light transmitting film formed on the signal recording surface so that the surface is located within the depth of focus of the light beam focused on the signal recording surface. I have.
[0009]
In the optical recording medium according to the present invention, since the surface of the light transmitting film is formed so as to be located within the depth of focus of the light beam focused on the signal recording surface, the reflection of the light beam reflected on the signal recording surface The information signal recorded on the signal recording surface can be reproduced by detecting the phase difference between the wavefront of the light and the plane wavefront of the reflected light of the light beam reflected by the surface of the light transmitting film.
[0010]
Another recording medium according to the present invention includes a substrate on which pits are formed, a light transmitting film formed on the pits, and a reflective film formed on the light transmitting film. An optical recording medium in which an information signal is reproduced by condensing a light beam on a signal recording surface, which is a substrate-side surface of a transmission film, wherein the reflection film forms a light beam condensed on the signal recording surface. It is formed so that the surface on the light transmitting film side is located within the depth of focus.
[0011]
In another optical recording medium according to the present invention, since the surface of the reflective film on the light transmitting film side is formed so as to be located within the depth of focus of the light beam focused on the signal recording surface, the light is reflected on the signal recording surface. Information recorded on the signal recording surface by detecting the phase difference between the wavefront of the reflected light of the reflected light beam and the planar wavefront of the reflected light of the light beam reflected on the light transmitting film side surface of the reflecting film. The signal can be reproduced.
[0012]
A reproducing apparatus for an optical recording medium according to the present invention includes a laser light source for emitting a light beam, an objective lens for condensing the light beam on a signal recording surface of the optical recording medium, and a light intensity of the light beam reflected by the optical recording medium. And a light detecting means for detecting an optical signal.The reproducing apparatus for an optical recording medium for reproducing an information signal by an output signal from the light detecting means, wherein the optical recording medium has a substrate on which pits are formed, A reflective film formed on the pits and having a signal recording surface, and a light transmitting film formed on the signal recording surface such that the surface is located within a depth of focus of a light beam focused on the signal recording surface. Having a signal recording surface as a first reflection surface of the light beam, and a surface of the light transmitting film as a second reflection surface of the light beam, and the light detection means is provided from the first reflection surface. The reflected light of the light beam and the reflected light of the light beam from the second reflecting surface The causes interference and detects the phase information as a light intensity.
[0013]
In the reproducing apparatus for an optical recording medium according to the present invention, reproduction is performed on an optical recording medium formed such that the surface of the light transmitting film is located within the depth of focus of the light beam focused on the signal recording surface. The light detection means reflects the light beam reflected by the signal recording surface, which is the first reflection surface of the optical recording medium, and the light beam reflected by the surface of the light transmitting film, which is the second reflection surface. The information signal recorded on the signal recording surface can be reproduced by detecting the phase information as the light intensity by causing interference with light.
[0014]
Also, a reproducing apparatus for an optical recording medium according to the present invention includes a laser light source for emitting a light beam, an objective lens for condensing the light beam on a signal recording surface of the optical recording medium, and a light beam reflected by the optical recording medium. A light detecting means for detecting light intensity, a reproducing apparatus for an optical recording medium for reproducing an information signal by an output signal from the light detecting means,
The optical recording medium includes a substrate on which a plurality of pits are formed in the width direction of the groove and / or the land, a reflective film formed on the plurality of pits and having a signal recording surface, and a light condensing on the signal recording surface. A light transmitting film formed on the signal recording surface such that the surface is located within the focal depth of the light beam to be formed, wherein the signal recording surface is a first reflecting surface of the light beam, and the surface of the light transmitting film is Is a second reflection surface of a light beam, and an information signal is recorded by modulating the depth of a plurality of pits. The light detecting means includes a plurality of light beams formed in a width direction of a groove and / or a land. A plurality of photodetectors for detecting phase information as light intensity by interfering reflected light of the light beam from the first reflecting surface and reflected light of the light beam from the second reflecting surface on each pit. .
[0015]
In the reproducing apparatus of the optical recording medium according to the present invention, the surface of the light transmitting film is formed so as to be located within the focal depth of the light beam focused on the signal recording surface, and the information signal is recorded by the modulation of the depth, respectively. The optical recording medium on which a plurality of pits are formed is reproduced. On each pit, reflected light of the light beam reflected by the signal recording surface, which is the first reflection surface, of the optical recording medium, and light reflected by the surface of the light transmitting film, which is the second reflection surface, by the light detection means. The information signal recorded on the signal recording surface can be reproduced by detecting the phase information as the light intensity by causing the reflected light of the light beam to interfere with the reflected light.
[0016]
The reproducing method of an optical recording medium according to the present invention comprises a substrate having pits formed thereon, a reflective film formed on the pits and having a surface as a signal recording surface, and a focal point of a light beam focused on the signal recording surface. A light transmitting film formed on the signal recording surface such that the surface is located within the depth, the signal recording surface serving as a first reflecting surface of the light beam, and the surface of the light transmitting film serving as a second light beam. A method of reproducing an optical recording medium for reproducing an information signal with respect to an optical recording medium having a reflection surface, wherein the reflection light of the light beam from the first reflection surface and the reflection light of the light beam from the second reflection surface And reproduce the information signal by detecting the phase information as the light intensity.
[0017]
In the reproducing method of the optical recording medium according to the present invention, reproduction is performed on the optical recording medium formed so that the surface of the light transmitting film is located within the focal depth of the light beam focused on the signal recording surface. The reflected light of the light beam reflected on the signal recording surface, which is the first reflecting surface of the optical recording medium, and the reflected light of the light beam reflected on the surface of the light transmitting film, which is the second reflecting surface, interfere with each other. Then, the information signal recorded on the signal recording surface is reproduced by detecting the phase information as the light intensity.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIGS. 1A and 1B show a schematic configuration of an optical recording medium according to the present embodiment. This optical recording medium has two main surfaces for reflecting a light beam emitted from a laser light source such as a semiconductor laser.
[0019]
The optical recording medium 1 shown in FIG. 1A has a substrate 12 on which pits 11 are formed, a reflective film 13 made of, for example, aluminum or the like formed on the pits 11, and a reflective film 13 formed on the reflective film 13. A first light transmitting film 14 and a second light transmitting film 15 formed on the first light transmitting film 14 are provided.
[0020]
In the pit 11, for example, a plurality of concave pits are formed, for example, along the lateral direction (width direction) of the land, and are recorded line-sequentially along the extending direction of the land. The pit depth of each pit 11 is formed so as to have a plurality of depths, for example, five depths including a case where the depth is zero.
[0021]
The first light transmitting film 14 and the second light transmitting film 15 are respectively formed of materials having different refractive indexes. The first light transmitting film 14 is made of a material such as niobium oxide, tantalum oxide, titanium oxide, silicon oxide, alumina (aluminum oxide), aluminum nitride, silicon nitride, gallium nitride, zinc sulfide, tin sulfide, and tin selenide. Is formed. The second light transmitting film 15 is formed of, for example, a material such as an ultraviolet curing resin, polycarbonate, and PMMA (polymethyl methacrylate).
[0022]
Note that the first light transmitting film 14 and the second light transmitting film 15 may be made of materials having different refractive indexes from each other. Can be replaced with each other, the material of the second light transmitting film 15 may be selected from the materials of the first light transmitting film 14 described above, or the second material described above may be selected. The material of the first light transmitting film 14 may be selected from the materials of the light transmitting film 15.
[0023]
The optical recording medium 1 has two surfaces, a first reflecting surface 10A and a second reflecting surface 10B, which are main surfaces that reflect a light beam. The first reflection surface 10A is a surface on the first light transmission film 14 side of the reflection film 13 which is a signal recording surface of an information signal. The second reflection surface 10B is a surface of the first light transmission film 14 on the second light transmission film 15 side, and is defined by a boundary between the first light transmission film 14 and the second light transmission film 15. Is formed. Here, the surface of the first light transmitting film 14 which is the second reflecting surface 10B on the side of the second light transmitting film 15 is a light beam focused on the information signal recording surface which is the first reflecting surface 10A. Within the depth of focus. In addition, the surface of the first light transmission film 14, which is the second reflection surface 10B, on the second light transmission film 15 side is formed to be smooth.
[0024]
The ratio of the amount of reflected light of the light beam from the first reflecting surface 10A to the amount of reflected light of the light beam from the second reflecting surface 10B depends on the reflection film 13, the first light transmitting film 14, and the second light transmitting film. 15 It can be adjusted by selecting each material and the like and selecting the refractive index.
[0025]
The optical recording medium 2 shown in FIG. 1B has a substrate 22 on which pits 21 are formed, a reflective film 23 made of, for example, aluminum formed on the pits 21, and a reflective film 23 formed on the reflective film 23. Only one layer of the light transmitting film 24 is provided.
[0026]
The light transmitting film 24 is formed of a material having a different refractive index from air (n = 1). Even when only one of the light transmitting films 24 is used, the first reflection surface 20A and the second reflection surface 20B can be formed.
[0027]
The first reflection surface 20A is a surface of the reflection film 23 which is a recording surface of the information signal. The second reflection surface 20B is formed by the surface of the light transmitting film 24. Here, the surface of the light transmitting film 24 as the second reflection surface 20B is located within the depth of focus of the light beam focused on the information signal recording surface as the first reflection surface 20A.
[0028]
In the present embodiment, the second reflecting surfaces 10B and 20B are formed within the depth of focus of the light beams focused on the first reflecting surfaces 10A and 20A. Thus, for example, if it is assumed that both the first reflecting surfaces 10A, 20A and the second reflecting surfaces 10B, 20B are plane, the wavefront of the light beam from the first reflecting surfaces 10A, 20A Then, the wavefronts of the reflected light beams of the light beams from the second reflection surfaces 10B and 20B become substantially uniform wavefronts. Therefore, when the plurality of concave pits 11 and 21 are formed on the substrates 12 and 22, the reflected light of the light beam including the recording data from the concave and convex first reflecting surfaces 10A and 20A, The information signals recorded on the first reflecting surfaces 10A and 20A can be reproduced by examining the phase relationship between the reflected light beams of the light beams from the second reflecting surfaces 10B and 20B which are plane surfaces.
[0029]
More specifically, the principle of reproducing an information signal from the optical recording medium of the present embodiment will be described with reference to FIG. The reproduction principle of the optical recording medium having the two-layer light transmitting film shown in FIG. 1A will be described. The reproduction principle of the optical recording medium having only one light transmitting film shown in FIG. The same is true for
[0030]
The light beams A1 to E1 reflected by the first reflection surface 10A of the optical recording medium 1 have wavefronts corresponding to the pit shapes recorded as the concave pits 11 below the first reflection surface 10A. You. Since the concave pits 11A to 11E are recorded with the pit depth modulated in five steps, the wavefronts of the light beams A1 to E1 reflected by the first reflecting surface 10A according to the pit depth are recorded. Is formed.
[0031]
On the other hand, since the second reflection surface 10B is formed smoothly, the wavefronts of the reflected light beams A2 to E2 are substantially flat.
[0032]
The shape of the wavefront 1 of the light beams A1 to E1 reflected in this way and the shape of the wavefront 2 of the reflected light beams A2 to E2 are divided into five photodetectors 31A to 31A through a condenser lens. It is reproduced by being condensed on 31E. The photo detectors 31A to 31E are divided and arranged corresponding to the five concave pits 11A to 11E.
[0033]
Accordingly, the light beams A1 to E1 and A2 to E2 reflected on the five concave pits 11A to 11E interfere with the photodetectors 31A to 31E in accordance with the phase difference of the wavefronts, thereby causing the light beams A1 to E1 to change on the photodetectors 31A to 31E. A light intensity distribution corresponding to the depth of each of the plurality of pits 11A to 11E is formed. Therefore, the information signal recorded on the optical recording medium 1 can be reproduced by reading the distribution of the light intensity as the phase information on the photodetectors 31A to 31E.
[0034]
As described above, since the wavefronts of the reflected light beams A2 to E2 are made flatter by forming the second reflecting surface 10B to be smooth, the second reflecting surface 10B is formed on the five concave pits 11A to 11E. It is possible to more accurately detect the phase difference between the wavefronts of the light beams A1 to E1 and A2 to E2 reflected at.
[0035]
FIG. 3 and FIG. 4 show a schematic configuration of an information reproducing apparatus for reproducing an information signal recorded on an optical recording medium according to the present embodiment. The information reproducing apparatus 3 includes a semiconductor laser 32 as a laser light source, a collimator lens 33, a beam splitter 34, an objective lens 35, a condenser lens 36, and five divided detectors 31A to 31E. are doing.
[0036]
In order to reproduce an information signal recorded on an optical recording medium by the information reproducing device 3, first, a light beam for reproduction is emitted from a laser light source, for example, a semiconductor laser 32. This light beam is converted into parallel light by the collimating lens 33 and passes through a beam splitter 34 composed of, for example, a polarizing beam splitter (PBS). The light beam transmitted through the beam splitter 34 is transmitted through a 波長 wavelength plate (not shown) and is incident on the objective lens 35.
[0037]
The light beam incident on the objective lens 35 is focused on the first reflection surface 10A, which is the signal recording surface of the optical recording medium 1. At this time, the light beam is reflected on the first reflecting surface 10A and also on the second reflecting surface 10B. The light beam reflected by the first reflecting surface 10A passes through the objective lens 35 and a quarter-wave plate (not shown) together with the light beam reflected by the second reflecting surface 10B, and is reflected by the beam splitter 34. You.
[0038]
The light beams reflected by the beam splitter 34 are condensed by the condenser lens 36 on the photodetectors 31A to 31E, respectively. On the photodetectors 31A to 31E, the light beam reflected by the first reflecting surface 10A and the light beam reflected by the second reflecting surface 10B interfere with each other. Then, in each of the photodetectors 31A to 31E, the phase information of the reflected light beam is detected as light intensity, and is converted into an electric signal independently according to the light intensity and output. The electric signal is input to a signal reproduction processing unit (not shown), and the signal reproduction processing unit performs processing of reproducing the information signal.
[0039]
On the signal recording surface of the optical recording medium 1, for example, five concave pits are formed along the horizontal direction (width direction) of the land, and the data of the five pits is line-sequentially extended along the extending direction of the land. It is recorded in. That is, multi-value recording is possible. For this reason, when the light beam is scanned along the extension direction of the land, five data can be simultaneously reproduced line by line as a set of five data.
[0040]
In a conventional optical recording medium, information signals are recorded in series on a land in a line-sequential manner.However, according to the conventional reproducing method, only one pit can be read at a time with a focused beam spot, and bit by bit. Because it was recorded in. On the other hand, in the present invention, since the information signal is reproduced from the phase information in the beam spot of the light beam, a plurality of data can be reproduced simultaneously by one light beam.
[0041]
As described above, in the present embodiment, a plurality of data can be simultaneously reproduced by one light beam emitted from the laser light source, so that the information signal of the optical recording medium can be reproduced at a high speed.
[0042]
Further, in the present embodiment, for example, an optical recording medium in which a plurality of pits are formed in a lateral direction of a land can be reproduced, and a pit having a size equal to or smaller than the diameter of a focused beam spot can be reproduced. Thus, an optical recording medium with a high recording density can be reproduced.
[0043]
Furthermore, in the present embodiment, an optical recording medium that could not reproduce an information signal unless an objective lens having a large aperture ratio can be reproduced in the past can be reproduced with an objective lens having a small aperture ratio. Thus, a highly reliable information reproducing apparatus and information reproducing method can be realized.
[0044]
As described above, the present invention has been described with reference to the embodiments. However, the present invention is not limited to the above embodiments, and can be variously modified. For example, in the above embodiment, an example in which five pits are formed in the width direction of the land of the optical recording medium has been described. However, the number of pits is not limited to five, and may be five or more or less. Further, even if pits are recorded bit by bit, it is possible to record multi-values in one pit. Also, the depth of the pit depression is not limited to five levels, but may be five levels or more. The pits may be formed not only in the width direction of the land but also in the width direction of the groove or in the width direction of both the land and the groove.
[0045]
Furthermore, other than the configuration of the optical recording medium described in the above embodiment is possible, and FIG. 5 shows a configuration example of another optical recording medium of the present invention. In the optical recording medium 4, a light transmitting film 44, a reflecting film 43, and a protective film 46 are sequentially laminated on a substrate 42 on which pits 41 are formed. In the optical recording medium 4, the substrate 42 plays a role of a light transmitting film. The light beam from the laser light source enters from the substrate 42 side.
[0046]
The first reflection surface 40A is a signal recording surface of an information signal, and is a surface of the light transmitting film 44 on the substrate 42 side. The second reflection surface 40B is a surface of the reflection film 43 on the light transmission film 44 side.
[0047]
The surface on the light transmission film 44 side of the reflection film 43 that is the second reflection surface 40B is located within the depth of focus of the light beam focused on the first reflection surface 40A. Thereby, by examining the phase relationship between the reflected light of the light beam including the recording data from the first uneven reflecting surface 40A and the reflected light of the light beam from the flat second reflecting surface 40B, The information signal recorded on the first reflection surface 40A can be reproduced.
[0048]
Further, in the present invention, the second light transmitting film 15 in the above embodiment may be formed by a partially reflecting film that partially reflects a light beam. When the partial reflection film is used as described above, the difference in refractive index between the first light transmission film 14 and the second light transmission film 15 becomes unnecessary. The partial reflection film is formed of, for example, a material such as aluminum, titanium, tantalum, gold, silicon, chromium, or an alloy containing these. The partial reflection film may be formed of, for example, an extremely thin metal film using the above-described material. By forming the partial reflection film as an extremely thin metal film using the above-described material, more effective partial reflection can be realized.
[0049]
Further, a non-reflection coating may be applied to the surface of the second light transmitting film 15 in the above embodiment.
[0050]
【The invention's effect】
As described above, according to the optical recording medium of the present invention, since the information signal is reproduced based on the phase information of the reflected light beam, the recording density is improved, and the information signal can be reproduced at a high speed. It becomes possible.
[0051]
Further, according to the reproducing apparatus and the reproducing method of the optical recording medium of the present invention, the information signal of the optical recording medium is reproduced by the phase information of the reflected light beam. The signal can be reproduced at high speed.
[Brief description of the drawings]
FIG. 1 is a configuration diagram illustrating a schematic configuration of an optical recording medium according to an embodiment of the invention.
FIG. 2 is an explanatory diagram for explaining a principle of reproducing an information signal from an optical recording medium according to an embodiment of the present invention.
FIG. 3 is a configuration diagram illustrating a schematic configuration of a reproducing apparatus for an optical recording medium according to an embodiment of the present invention.
FIG. 4 is a configuration diagram illustrating a schematic configuration of a reproducing apparatus for an optical recording medium according to an embodiment of the present invention.
FIG. 5 is a cross-sectional view illustrating a schematic configuration of another example of the optical recording medium of the present invention.
[Explanation of symbols]
1,2,4 ... optical recording medium, 3 ... information reproducing device, 11,21,41 ... pit, 12,22,42 ... substrate, 13,23,43 ... reflecting film, 14 ... first light transmitting film, 15: second light transmitting film, 24, 44: light transmitting film, 10A, 20A, 40A: first reflecting surface, 10B, 20B, 40B: second reflecting surface, 31A to 31E: photo detector, 32: semiconductor Laser, 35 ... objective lens

Claims (22)

A light having a substrate on which pits are formed and a reflective film formed on the pits, wherein an information signal is reproduced by converging a light beam on a signal recording surface which is a surface of the reflective film; A recording medium,
An optical recording medium, comprising: a light transmitting film formed on the signal recording surface such that a surface is located within a depth of focus of a light beam focused on the signal recording surface. The signal recording surface as a first reflection surface of the light beam, the surface of the light transmitting film as a second reflection surface of the light beam,
An information signal is reproduced by causing the reflected light of the light beam from the first reflecting surface and the reflected light of the light beam from the second reflecting surface to interfere with each other to detect phase information as light intensity. The optical recording medium according to claim 1, wherein: The optical recording medium according to claim 1, wherein a plurality of the pits are formed in a width direction of a groove and / or a land formed on the substrate. 2. The optical recording medium according to claim 1, wherein the information signal is recorded by modulating depths of the plurality of pits. 2. The optical recording medium according to claim 1, wherein the surface of the light transmitting film is flat. The light-transmitting film is formed as a first light-transmitting film on the first light-transmitting film, and has a second light-transmitting film having a different refractive index from the first light-transmitting film. The optical recording medium according to claim 1, wherein The signal recording surface as a first reflection surface of the light beam, the surface of the first light transmission film on the side of the second light transmission film as a second reflection surface of the light beam,
An information signal is reproduced by causing the reflected light of the light beam from the first reflecting surface and the reflected light of the light beam from the second reflecting surface to interfere with each other to detect phase information as light intensity. 7. The optical recording medium according to claim 6, wherein: 7. The optical recording medium according to claim 6, wherein a plurality of the pits are formed in a width direction of a groove and / or a land formed on the substrate. 7. The optical recording medium according to claim 6, wherein the information signal is recorded by modulating depths of the plurality of pits. The optical recording medium according to claim 6, wherein a surface of the first light transmitting film on the side of the second light transmitting film is flat. 2. The optical recording medium according to claim 1, further comprising a partial reflection film formed on the light transmission film. The optical recording medium according to claim 11, wherein the partial reflection film is formed of a material selected from the group consisting of aluminum, titanium, tantalum, gold, silicon, chromium, and alloys containing these. A substrate on which the pits are formed, a light transmitting film formed on the pits, and a reflective film formed on the light transmitting film; and a surface of the light transmitting film on the substrate side. An optical recording medium on which an information signal is reproduced by converging a light beam on a signal recording surface,
The optical recording medium according to claim 1, wherein the reflection film is formed such that a surface on the light transmission film side is located within a depth of focus of a light beam focused on the signal recording surface. The signal recording surface as a first reflection surface of the light beam, the surface of the reflection film on the light transmission film side as a second reflection surface of the light beam,
An information signal is reproduced by causing the reflected light of the light beam from the first reflecting surface and the reflected light of the light beam from the second reflecting surface to interfere with each other to detect phase information as light intensity. 14. The optical recording medium according to claim 13, wherein: 14. The optical recording medium according to claim 13, wherein a plurality of the pits are formed in a width direction of a groove and / or a land formed on the substrate. 14. The optical recording medium according to claim 13, wherein the information signal is recorded by modulating depths of the plurality of pits. 14. The optical recording medium according to claim 13, wherein a surface of the reflection film on the light transmission film side is flat. A laser light source that emits a light beam; an objective lens that focuses the light beam on a signal recording surface of an optical recording medium; and a light detection unit that detects light intensity of the light beam reflected by the optical recording medium. And a reproducing apparatus for an optical recording medium for reproducing an information signal by an output signal from the light detecting means,
The optical recording medium has a substrate on which pits are formed, a reflective film formed on the pits and having a surface serving as the signal recording surface, and a focal depth of a light beam focused on the signal recording surface. A light transmitting film formed on the signal recording surface such that the surface is located, the signal recording surface serving as a first reflection surface of the light beam, and the surface of the light transmitting film serving as a second light beam. Of the reflective surface,
The light detecting means detects phase information as light intensity by causing reflected light of the light beam from the first reflecting surface to interfere with reflected light of the light beam from the second reflecting surface. Playback device for an optical recording medium. A laser light source that emits a light beam; an objective lens that focuses the light beam on a signal recording surface of an optical recording medium; and a light detection unit that detects light intensity of the light beam reflected by the optical recording medium. And a reproducing apparatus for an optical recording medium for reproducing an information signal by an output signal from the light detecting means,
The optical recording medium includes a substrate having a plurality of pits formed in a width direction of a groove and / or a land, a reflective film formed on the plurality of pits and having a surface as the signal recording surface; A light transmitting film formed on the signal recording surface such that the surface is located within the depth of focus of the light beam focused on the surface, and the signal recording surface is used as a first reflection surface of the light beam. The surface of the light transmitting film as a second reflecting surface of the light beam, the information signal is recorded by modulation of the depth of the plurality of pits,
The light detecting means includes a light beam reflected from the first reflection surface and a light beam reflected from the second reflection surface on a plurality of pits formed in a width direction of the groove and / or the land. A plurality of photodetectors for detecting phase information as light intensity by causing interference with reflected light of the optical recording medium. The optical recording medium is formed on the first light transmitting film, using the light transmitting film as a first light transmitting film, and a second light transmitting film having a different refractive index from the first light transmitting film. 20. The optical recording medium reproducing apparatus according to claim 19, wherein a surface of the first light transmitting film on the side of the second light transmitting film is a second reflection surface of a light beam. A substrate on which pits are formed, a reflective film formed on the pits and having a surface as a signal recording surface, and the surface is positioned within a depth of focus of a light beam focused on the signal recording surface. A light transmitting film formed on a signal recording surface, wherein the signal recording surface is a first reflection surface of the light beam, and the surface of the light transmission film is a second reflection surface of the light beam. A method for reproducing an optical recording medium for reproducing an information signal for a medium,
Reproducing the information signal by detecting the phase information as light intensity by causing the reflected light of the light beam from the first reflecting surface to interfere with the reflected light of the light beam from the second reflecting surface. Characteristic reproduction method of an optical recording medium. The optical recording medium is formed on the first light transmitting film, using the light transmitting film as a first light transmitting film, and a second light transmitting film having a different refractive index from the first light transmitting film. 22. The reproducing method for an optical recording medium according to claim 21, wherein a surface of the first light transmitting film on the side of the second light transmitting film is used as a second reflection surface of a light beam.

Images