JP2004151698A - Hologram recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hologram recording medium that achieves improved data recording characteristics and data reproduction characteristics using a object beam and a reference beam and concurrently realizes desired positioning of the object beam and the reference beam, or only the reference beam, and detection of the address of the region in which data are being recorded or from which data are being reproduced using a position control beam. <P>SOLUTION: The hologram recording medium has a hologram record carrier in which data can be holographically recorded, a 1st antireflective film 21 formed on one surface of the hologram record carrier, and a 2nd antireflective film 22 formed on the other surface of the hologram record carrier. Optical characteristics of the 1st antireflective film and optical characteristics of the 2nd antireflective film 22 are set different from each other. <P>COPYRIGHT: (C)2004,JPO

Description

  The present invention relates to a hologram recording medium, and more specifically, it is possible to improve the recording characteristics and the reproduction characteristics of data using object light and reference light, and at the same time, to obtain desired data using position control light. Thus, the present invention relates to a hologram recording medium capable of positioning an object beam and a reference beam or a reference beam and detecting an address of a region where recording or reproduction is performed.

  Conventionally, write-once optical recording media represented by CD-R and DVD-R and rewritable optical recording media represented by CD-RW and DVD-RW have been widely used as recording media for recording digital data. It's being used. When data is recorded on these conventional optical recording media, an intensity-modulated laser beam is applied to the recording layer of the optical recording medium to locally, chemically and / or physically change the area of the recording layer. To form a recording mark. The data is represented by the length from the leading edge to the trailing edge of the recording mark (recording mark length) and the length from the trailing edge of the recording mark to the leading edge of the next recording mark (blank length). That is, in these optical recording media, data is represented one-dimensionally and recorded two-dimensionally.

  However, with the rapid development of the information-oriented society in recent years, there is a demand for an optical recording medium for recording digital data that has a larger capacity and a higher recording / reproducing speed. In order to realize this, various types of next-generation optical recording media have been proposed at present. Among them, among them, data is not recorded two-dimensionally on an optical recording medium, but image-like data is recorded. Accordingly, a technique for increasing the capacity and increasing the speed of recording / reproducing has attracted attention. Such a technique includes hologram recording. In hologram recording, image data is recorded three-dimensionally (three-dimensionally) in an optical recording medium. A recording medium on which data can be recorded by the hologram recording method is called a hologram recording medium ('Holographic Data Storage' Springer series in optical sciences 76).

  In the hologram recording method, two coherent laser beams called an object beam and a reference beam, respectively, are irradiated on a recording layer (hologram recording layer) of a hologram recording medium at different angles to generate interference fringes. Is three-dimensionally recorded on the recording layer as a hologram. When reproducing recorded data, the recording layer on which interference fringes are formed is irradiated with reference light to restore data recorded as a hologram.

  Also, as described in JP-A-2002-63733, the substrate of the hologram recording medium is used for positioning the object light and the reference light or the reference light and detecting the address of the area where recording or reproduction is performed. An uneven pattern may be provided. In this case, at the time of data recording or reproduction, a spot of a third laser beam called a position control light is adjusted to the uneven pattern so that the object light and the reference light or The reference beam can be positioned, and the address of the area where recording or reproduction is currently performed can be detected.

  As described above, since data is three-dimensionally recorded on the hologram recording medium, reflection of the laser beam on the substrate surface, which was not a problem in the conventional optical recording medium on which two-dimensional recording is performed, is not a problem. It is considered that this has a great effect on data recording and reproduction. For this reason, in the hologram recording medium, it is considered necessary to provide an antireflection film on the surface of the substrate, thereby suppressing the reflection of the laser beam on the substrate surface which is harmful to data recording and reproduction.

  However, when the surface reflection of the substrate is largely suppressed by the anti-reflection film, even if the concave / convex pattern provided on the substrate is irradiated with the position control light, the obtained reflected light is not sufficiently modulated. There is a problem in that it becomes difficult to detect the position of the reference light or the position of the reference light or the address of the area where the recording or reproduction is performed.

  Therefore, an object of the present invention is to improve the recording and reproduction characteristics of data using the object light and the reference light, and at the same time, using the position control light, as desired, as the object light and the reference light or It is an object of the present invention to provide a hologram recording medium capable of positioning a reference beam and detecting an address of an area where recording or reproduction is performed.

  The object of the present invention is to form a hologram record carrier capable of hologram recording data, a first antireflection film formed on one surface of the hologram record carrier, and a second antireflection film formed on the other surface of the hologram record carrier. This is achieved by a hologram recording medium comprising a second antireflection film, wherein the optical characteristics of the first antireflection film and the optical characteristics of the second antireflection film are different from each other.

  In the present invention, even if the hologram record carrier includes at least a hologram recording layer and is constituted by a pair of light-transmitting substrates and a hologram recording layer formed between the pair of light-transmitting substrates, May be constituted by a transparent substrate and a hologram recording layer formed on one surface of the light transmissive substrate, or may be constituted solely by the hologram recording layer.

  According to the present invention, the first anti-reflection film and the second anti-reflection film have different optical characteristics from each other, so that the optical characteristics of the first anti-reflection film and the second anti-reflection film are different from each other. By appropriately setting the optical characteristics, the reflection of the position control light on the surface of the hologram record carrier can be ensured while suppressing the reflection of the object light and the reference light on the surface of the hologram record carrier. It is possible to improve the recording characteristics and the reproduction characteristics of the data using, and at the same time, using the position control light, position the object light and the reference light or the reference light as desired, and perform the recording or the reproduction. It is possible to detect the address of the area in which it exists.

  In a preferred embodiment of the present invention, the hologram record carrier is configured to be capable of recording and reproducing data by irradiating a first laser beam, and the other surface of the hologram record carrier has an uneven pattern. By irradiating a second laser beam to the concavo-convex pattern, the first laser beam can be positioned, and an address of an area where data is recorded or reproduced can be detected. It is configured.

  In a further preferred aspect of the present invention, the reflectance of the second anti-reflection coating for the second laser beam is higher than the reflectance of the second anti-reflection coating for the first laser beam. The second antireflection film is formed so as to be large.

  According to a further preferred embodiment of the present invention, it is possible to secure the reflection of the second laser beam while suppressing the reflection of the first laser beam on the other surface of the hologram record carrier.

  In a further preferred aspect of the present invention, the reflectance of the second anti-reflection coating for the second laser beam is higher than the reflectance of the first anti-reflection coating for the second laser beam. The first antireflection film and the second antireflection film are formed so as to be large.

  According to a further preferred embodiment of the present invention, the reflection of the second laser beam on the other surface of the hologram record carrier is ensured while the reflection of the second laser beam on one surface of the hologram record carrier is suppressed. Can be.

  In the present invention, the reflectance of the first antireflection film and the reflectance of the second antireflection film for the first laser beam are both preferably 1.0% or less, and preferably 0.5% or less. Is more preferable.

  If the reflectance of the first anti-reflection film and the reflectance of the second anti-reflection film for the first laser beam are both 1.0% or less, the first and second anti-reflection films have the first and second anti-reflection films on both surfaces of the hologram record carrier. It is possible to effectively suppress the adverse effect of the reflection of the laser beam on data recording and reproduction.

  In the present invention, the reflectance of the second antireflection film to the second laser beam is preferably 2.0% or more, more preferably 3.0% or more, and more preferably 4.0%. The above is particularly preferred.

  When the reflectance of the second antireflection film with respect to the second laser beam is 2.0% or more, the second laser beam reflected by the uneven pattern can be largely modulated.

  Further, in the present invention, it is preferable that the wavelength of the first laser beam is shorter than the wavelength of the second laser beam.

  When the wavelength of the first laser beam is shorter than the wavelength of the second laser beam, the irradiation of the second laser beam exposes the hologram record carrier, and the data is deteriorated or lost. This can be reliably prevented.

  In the present invention, it is preferable that the thickness of each of the first antireflection film and the second antireflection film is 1.5 times or less the wavelength of the first laser beam.

  When the thickness of the first antireflection film and the second antireflection film is 1.5 times or less the wavelength of the first laser beam, not only can material cost be reduced, but also Since the time for forming the first antireflection film and the second antireflection film can be shortened, the manufacturing cost can be reduced, and further, the first antireflection film and the second antireflection film can be reduced. It is possible to prevent peeling due to stress of the prevention film.

  In a preferred embodiment of the present invention, the first antireflection film is formed on a surface of the hologram record carrier on which the first laser beam is incident.

  In a preferred embodiment of the present invention, the hologram record carrier includes a first light-transmitting substrate, a second light-transmitting substrate, the first light-transmitting substrate, and the second light-transmitting substrate. And a hologram recording layer provided therebetween.

  According to the present invention, it is possible to improve the recording characteristics and the reproduction characteristics of data using the object light and the reference light, and at the same time, using the position control light, as desired, as the object light and the reference light or the reference light. And a hologram recording medium capable of detecting the address of the area where recording or reproduction is being performed.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a substantially cutaway perspective view showing the appearance of a hologram recording medium according to a preferred embodiment of the present invention, and FIG. 2 is a substantially enlarged partial sectional view of a portion indicated by A in FIG.

  As shown in FIG. 1, the outer shape of the hologram recording medium 10 according to the present embodiment is disk-shaped, and a hole is provided in a central portion thereof.

  The outer diameter / thickness of the hologram recording medium 10 is not particularly limited, but considering the ease of handling on the drive (hologram recording / reproducing apparatus) side, the outer diameter / thickness of a current optical recording medium such as a CD or DVD ( (120 mm and 1.2 mm, respectively).

  As shown in FIG. 2, the hologram recording medium 10 includes light transmitting substrates 11 and 12, a hologram recording layer 20 provided therebetween, and a reflection layer provided on a surface 11 a of the light transmitting substrate 11. An anti-reflection film 21 and an anti-reflection film 22 provided on the surface 12a of the light-transmitting substrate 12 are provided. The object light a, the reference light b, and the position control light are provided from the surface on which the anti-reflection film 21 is provided. c is irradiated, and thereby data recording or reproduction is performed.

  As will be described in detail below, the object light a and the reference light b are laser beams emitted from the same laser light source, and the wavelength is defined as λ0 in this specification.

  Further, the position control light c is a laser beam emitted from a laser light source different from the object light a and the reference light b, and its wavelength is defined as λ1 (≠ λ0) in this specification.

  The relationship between the wavelength λ0 and the wavelength λ1 is preferably λ0 <λ1, and more preferably 1.2 × λ0 <λ1 <2.0 × λ0.

  By setting the relationship between the wavelength λ0 and the wavelength λ1 in this manner, the hologram recording layer 20 is not exposed to light by the irradiation of the position control light c, and the data is not deteriorated or lost.

  Further, in order to realize a large capacity and a high speed, it is preferable that the wavelength λ0 is set in a range of 350 nm to 550 nm. Further, if the wavelength of λ1 is too long, the resolution is deteriorated, and it is necessary to enlarge or deepen the uneven pattern described below. Therefore, the wavelength of λ1 is preferably less than twice λ0.

  The light-transmitting substrates 11 and 12 are disk-shaped substrates made of a material having a sufficiently high light transmittance at least at the wavelengths λ0 and λ1. The light-transmitting substrate 11 transmits the object light a, the reference light b, and the position control light c, and the light-transmitting substrate 12 serves to transmit the reference light b and the position control light c. Numerals 11 and 12 physically and chemically protect the hologram recording layer 20 and also serve as a base for ensuring the mechanical strength required of the hologram recording medium 10. Therefore, it is necessary to determine the material and thickness of the light transmitting substrates 11 and 12 in consideration of these.

  The light-transmitting substrates 11 and 12 can be formed using various materials. For example, glass, ceramics, and resin can be used, and among them, resin or glass is preferably used. Examples of such a resin include a polycarbonate resin, an acrylic resin, an epoxy resin, a polystyrene resin, a polyethylene resin, a polypropylene resin, a silicone resin, a fluororesin, an ABS resin, a urethane resin, and a polyolefin resin. A polyolefin resin, particularly an amorphous polyolefin resin, is very preferable from the viewpoint of reducing the size. Examples of the glass include soda lime glass, aluminosilicate glass, and synthetic quartz glass.

  The material of the light-transmitting substrates 11 and 12 preferably has a refractive index substantially equal to that of the hologram recording layer 20 in order to prevent reflection at the interface with the hologram recording layer 20.

  On the surface 12a of the light-transmitting substrate 12, the object light a and the reference light b are positioned from the vicinity of the center to the outer edge thereof, and at the same time, the address of the area where recording or reproduction is currently performed is specified. Is formed spirally.

  As will be described in detail below, the concavo-convex pattern 13 is irradiated with a beam spot of the position control light c, and by detecting the obtained reflected light, the positioning of the object light a and the reference light b is performed. Alternatively, it is possible to detect the address of the area where reproduction is performed.

  Therefore, the specific configuration of the concavo-convex pattern 13 is not particularly limited as long as the positioning and address detection of the object light a and the reference light b are possible, and the pits formed on a substrate such as a CD-ROM are not limited. A pattern similar to a row may be used as the concavo-convex pattern 13, or a pattern similar to a pre-groove formed on a substrate such as a CD-R may be used as the concavo-convex pattern 13.

  When a pattern similar to the pit row is used as the concavo-convex pattern 13, the length of the pits and the length between the pits can have address information, and a pattern similar to the pre-groove is used as the concavo-convex pattern 13. In this case, the wobble can have address information.

  In addition, the concavo-convex pattern 13 may be concentric, and may be linearly connected when the substrate is in a card shape or the like. Further, the uneven pattern 13 does not need to be formed continuously, but may be formed intermittently.

  The hologram recording layer 20 is a layer in which a coherent object beam a and a reference beam b are irradiated and interference fringes generated are recorded as a hologram.

  The material for forming the hologram recording layer 20 is not particularly limited, and a photosensitive material such as a photopolymer can be used.

  The hologram recording layer 20 and the light-transmitting substrates 11 and 12 may be in direct contact with each other, or a protective film for preventing the hologram recording layer 20 from deteriorating may be interposed between them. When a protective layer is provided between the light transmitting substrates 11 and 12 and the hologram recording layer 20, the protective layer has a refractive index substantially equal to that of the light transmitting substrates 11 and 12 and the hologram recording layer 20. Is preferred.

  Hereinafter, the laminated body including the light transmitting substrates 11 and 12 and the hologram recording layer 20 is referred to as a “hologram recording carrier”.

  The antireflection films 21 and 22 are thin films for reducing the reflection of light on the surfaces 11a and 12a of the light transmitting substrates 11 and 12, respectively, and are not particularly limited. It is preferred to be constituted by a body (inorganic multilayer film).

  In the present embodiment, the antireflection films 21 and 22 are provided directly on the surfaces 11 a and 12 a of the light transmissive substrates 11 and 12, respectively, but between the antireflection film 21 and the light transmissive substrate 11. Other layers may be interposed, and another layer may be interposed between the antireflection film 22 and the light-transmitting substrate 12. Further, another layer may be interposed between the antireflection film 21 and the light transmitting substrate 11 and between the antireflection film 22 and the light transmitting substrate 12. When another layer is provided between the light-transmitting substrates 11 and 12 and the antireflection films 21 and 22, the other layers have substantially the same refractive index as the light-transmitting substrates 11 and 12 and the hologram recording layer 20. It is preferable to have.

  The optical characteristics of the anti-reflection film 21 and the optical characteristics of the anti-reflection film 22 are different from each other. Specifically, in the present invention, the reflectance of the anti-reflection film 21 with respect to the laser beam having the wavelength λ0 is R21 (λ0), The reflectance of the antireflection film 21 for the laser beam of wavelength λ1 is R21 (λ1), the reflectance of the antireflection film 22 for the laser beam of wavelength λ0 is R22 (λ0), and the reflection of the antireflection film 22 for the laser beam of wavelength λ1. The ratio R22 (λ1) preferably satisfies at least one of the following expressions (1) and (2), and more preferably satisfies both.

R22 (λ0) <R22 (λ1) (1)
R21 (λ1) <R22 (λ1) (2)
The antireflection film 21 and the antireflection film 22 of the hologram recording medium 10 according to the present embodiment satisfy both the expressions (1) and (2).

  When the expression (1) is satisfied, the reflection of the object light a and the reference light b on the surface 12a of the light transmissive substrate 12 is suppressed while the position control light c on the surface 12a of the light transmissive substrate 12 is suppressed. Since the reflection can be secured to some extent, the position control light c can be obtained by irradiating the concave / convex pattern 13 with suppressing the adverse effect on the data recording and reproduction due to the reflection of the object light a and the reference light b. The reflected light can be sufficiently modulated.

  When Expression (2) is satisfied, the reflection of the position control light c on the surface 12a of the light transmissive substrate 12 is suppressed while the reflection of the position control light c on the surface 11a of the light transmissive substrate 11 is suppressed. Can be secured to some extent, so that the reflected light obtained when the position control light c is irradiated onto the concave / convex pattern 13 can be sufficiently reduced while suppressing the adverse effect on the data recording and reproduction due to the reflection of the position control light c. Can be modulated.

  To give an explanation with specific numerical values, R21 (λ0), which is the reflectance of the antireflection film 21 for the laser beam having the wavelength λ0, is preferably 1.0% or less, and is preferably 0.5% or less. Is more preferable. If the reflectivity R21 (λ0) is set to 1.0% or less, the adverse effect of the reflection of the object light a and the reference light b on the surface 11a of the light transmitting substrate 11 on data recording and reproduction is effectively suppressed. When the reflectivity R21 (λ0) is set to 0.5% or less, the adverse effect of the reflection of the object light a and the reference light b on the surface 11a of the light transmissive substrate 11 on the recording and reproduction of data is prevented. It is possible to more effectively suppress it. As will be described later, the object light a and the reference light b are irradiated to the anti-reflection film 21 at a predetermined incident angle, so that the incident angle is as wide as possible, preferably 0 to 45 degrees, more preferably 0 to 45 degrees. In the range of 55 degrees, the reflectivity R21 (λ0) is preferably within the above-described preferable range.

  Further, R22 (λ0), which is the reflectivity of the antireflection film 22 to the laser beam having the wavelength λ0, is preferably 1.0% or less, more preferably 0.5% or less. When the reflectance R22 (λ0) is set to 1.0% or less, the adverse effect of the reflection of the object light a and the reference light b on the surface 12a of the light transmitting substrate 12 on data recording and reproduction is effectively suppressed. If the reflectance R22 (λ0) is set to 0.5% or less, the reflection of the object light a and the reference light b on the surface 12a of the light transmissive substrate 12 adversely affects data recording and reproduction. Can be suppressed more effectively. It is preferable that the reflectivity R22 (λ0) is within the above-described preferred range in the widest possible angle of incidence, preferably in the range of 0 ° to 45 °, more preferably in the range of 0 ° to 55 °.

  Further, R21 (λ1), which is the reflectance of the antireflection film 21 with respect to the laser beam having the wavelength λ1, is preferably 1.5% or less, more preferably 1.0% or less. If the reflectance R21 (λ1) is set to 1.5% or less, it is possible to effectively suppress the adverse effect of the reflection of the position control light c on the surface 11a of the light transmissive substrate 11 on data recording and reproduction. When the reflectance R21 (λ1) is set to 1.0% or less, the adverse effect of the reflection of the position control light c on the surface 11a of the light transmitting substrate 11 on data recording and reproduction can be more effectively prevented. It can be suppressed. Here, as the upper limit of the preferable value of the reflectivity R21 (λ1), a value higher than the upper limit of the preferable value of the reflectivity R21 (λ0) is permitted because the object light on the surface 11a of the light transmissive substrate 11 is allowed. This is because the influence of the reflection of the position control light c on the surface 11a of the light transmitting substrate 11 on the recording and reproduction of data is smaller than the influence of the reflection of the reference light beam a and the reference light b on the recording and reproduction of data. .

  R22 (λ1), which is the reflectivity of the antireflection film 22 for the laser beam having the wavelength λ1, is preferably 2.0% or more, more preferably 3.0% or more, and 4.0%. The above is particularly preferable. If the reflectance R22 (λ1) is set to 2.0% or more, it is possible to greatly modulate the reflected light obtained when the position control light c is irradiated on the concave / convex pattern 13, and the reflectance R22 (λ1) is increased. If it is set to 3.0% or more, the reflected light can be modulated more greatly. If the reflectance R22 (λ1) is set to 4.0% or more, the reflected light can be extremely modulated. Become.

As described above, it is preferable that the antireflection films 21 and 22 be configured by a laminate (inorganic multilayer film) of a plurality of inorganic films. Examples of the material for forming the inorganic film include oxides such as TiO ₂ , Y ₂ O ₃ , SiO ₂ , Al ₂ O ₃ , ZrO ₂ , CeO ₂ and ZnO, and fluorides such as MgF ₂ and AlF _3. , ZnS, and other sulfides, and mixtures thereof. The antireflection films 21 and 22 can be formed by laminating two or more inorganic films. The optical characteristics of the antireflection films 21 and 22 can be adjusted by the material of each inorganic film, the thickness and the layer configuration of each inorganic film, and therefore, the material of each inorganic film, the thickness of each inorganic film and By appropriately selecting the layer configuration, it is possible to form the antireflection films 21 and 22 having the above characteristics.

  FIG. 3 is a schematic sectional view of the antireflection films 21 and 22.

  The anti-reflection films 21 and 22 shown in FIG. 3 are formed by laminating seven inorganic films 31, 32, 33, 34, 35, 36 and 37 in this order. Among these, the inorganic films 31, 35, and 37 are formed of a material having a lower refractive index than the light-transmitting substrates 11 and 12 (referred to as “low-refractive index material”). The inorganic film 33 is formed of a material having a slightly higher refractive index than the transmissive substrates 11 and 12 (referred to as a “medium refractive index material”), and the inorganic film 33 has a higher refractive index than the medium refractive index material (“high refractive index material”). ").

  Here, the refractive index means a refractive index at a wavelength λ0.

When the transmissive substrates 11 and 12 have a refractive index of 1.47 to 1.60, the low-refractive-index material may be a single substance of a fluoride such as MgF ₂ or AlF ₃ and SiO ₂ , a mixture thereof, or a mixture thereof. Can be used. As the medium refractive index material, Y ₂ O ₃ , Al ₂ O ₃ , ZrO ₂ , a mixture of ZnO and SiO ₂ , or a composition containing these as a main component is used. As the high refractive index material, a sulfide such as TiO ₂ , CeO ₂ , ZnS, or a composition containing these as a main component can be used.

  These inorganic films 31, 32, 33, 34, 35, 36, and 37 can be formed by a sputtering method, a vacuum evaporation method, a sol-gel method, and the like. It is preferable to use a vapor deposition method or a sputtering method.

  Thus, the inorganic films 31, 35, and 37 formed of the low refractive index material, the inorganic films 32,, and 36 formed of the medium refractive index material, and the inorganic film 33 formed of the high refractive index material are formed. By laminating such that the inorganic film 33 formed of the high refractive index material is located between the inorganic films 32 and 34 formed of the medium refractive index material, over a wide incident angle range in a specific wavelength region. It is possible to form the antireflection films 21 and 22 having a very low reflectance.

  Therefore, when the antireflection films 21 and 22 have the layer configuration shown in FIG. 3, the material and film thickness of each of the inorganic films 31, 32, 33, 34, 35, 36 and 37 are appropriately selected. By doing so, it is possible to form the antireflection films 21 and 22 having the above-described preferable optical characteristics.

  Further, it is preferable that the thickness of the antireflection films 21 and 22 be set to 1.5 × λ0 or less. If the film thickness of the anti-reflection films 21 and 22 is set to a value larger than this, the material cost increases and the film formation takes a long time, so that the manufacturing cost increases and the stress of the anti-reflection films 21 and 22 increases. The anti-reflection films 21 and 22 may peel off, which is not preferable.

  Next, a method for recording and reproducing data on the hologram recording medium 10 according to this embodiment will be described.

  FIG. 4 is a diagram of a hologram recording / reproducing apparatus that records and reproduces data on the hologram recording medium 10.

  As shown in FIG. 4, the hologram recording / reproducing apparatus 100 includes a first laser light source 101, a second laser light source 102, a beam splitter 103, a shutter 104, a spatial light modulator 105, and a half mirror 106. , 107, a mirror 108, lenses 109, 110, 111, a position detector 112, and an image sensor 113.

  The first laser light source 101 is a light source that generates a laser beam having a wavelength λ0. The laser beam emitted from the first laser light source 101 is separated by the beam splitter 103 into object light a and reference light b.

  On the other hand, the second laser light source 102 is a light source that generates a laser beam having the wavelength λ1, and the laser beam generated by the second laser light source 102 is used as the position control light c.

  A shutter 104, a spatial light modulator 105, a half mirror 106, and a lens 109 are arranged on the optical path of the object light a. The light is incident perpendicularly (incident angle φ = 0 degrees) on the surface of the substrate 21.

  On the other hand, at the time of data reproduction, the object light a is blocked by the shutter 104, so that the object light a is applied to the hologram recording medium 10 only at the time of data recording. The spatial light modulator 105 provided on the optical path of the object light “a” is a device that planarly modulates the object light “a” according to data to be recorded.

  On the other hand, after being reflected by the mirror 108, the reference light b is incident on the surface of the antireflection film 21 of the hologram recording medium 10 at a predetermined incident angle θ via the lens 110. Since no shutter is provided on the optical path of the reference light b, the hologram recording medium 10 is irradiated with the reference light b both during data recording and during data reproduction.

  Therefore, when data is recorded, the hologram recording medium 10 is irradiated with both the object light a and the reference light b, whereby the hologram recording layer 20 included in the hologram recording medium 10 contains the object light a and the reference light b. Interference fringes due to light b are generated and recorded as a hologram.

  On the other hand, at the time of data reproduction, the hologram recording medium 10 is irradiated with only the reference light b, whereby the hologram formed in the hologram recording layer 20 is reproduced in the form of light, and the hologram image is reproduced. Is received by the image sensor 113 via the lens 111. The hologram image included in the reproduction light is converted into data by the image sensor 113.

  On the other hand, after passing through the half mirror 107, the position control light c is reflected by the half mirror 106 and travels on the same optical path as the object light a. The focus of the position control light c is adjusted to the concavo-convex pattern 13 provided on the light transmissive substrate 12, and the position control light e reflected by the concavo-convex pattern 13 is detected by the position detector 112, and the object light is detected. a and the reference light b or the reference light b are positioned, and the address of the area where recording or reproduction is currently performed is detected.

  That is, first, the position detector 112 generates a focus signal based on the reflection from the surface 12 a of the light transmitting substrate 12, and generates a position signal based on the uneven pattern 13. The focus signal and the position signal are supplied to a driving unit (not shown). The driving unit accurately moves the hologram recording medium 10 in the thickness direction based on the focus signal, and outputs a hologram based on the position signal. The recording medium 10 is accurately moved in the plane direction. As a result, the object light a and the reference light b or the reference light b are accurately positioned. Instead of moving the hologram recording medium 10 by the driving means, the object light a and the reference light b or the reference light b can be positioned by moving the entire optical system including a mirror and a lens.

  When data is recorded on the hologram recording medium 10 and data is reproduced from the hologram recording medium 10 by using the hologram recording / reproducing apparatus 100 configured as described above, the hologram recording medium 10 according to the present embodiment has a wavelength Since the reflectivity R22 (λ1) of the antireflection film 22 with respect to the position control light c having the wavelength λ1 is set to be sufficiently large, the light is reflected by the antireflection film 22 formed on the surface 12a of the light transmitting substrate 12. The intensity of the position control light e is sufficiently large. Therefore, by detecting the position control light e reflected by the antireflection film 22 by the position detector 112, the position of the object light a and the reference light b can be determined and recorded. Alternatively, it is possible to reliably detect the address of the area where reproduction is performed.

  The antireflection film 22 has a reflectance R22 (λ0) for the object light a and the reference light b set to be smaller than a reflectance R22 (λ1) for the position control light c. The reflection of the object light a and the reference light b on the surface 12a is suppressed, and therefore, adverse effects on data recording or reproduction due to the reflection of the object light a and the reference light b on the surface 12a of the light transmitting substrate 12 are suppressed. It can be suppressed effectively.

  Further, in this embodiment, the reflectance R21 (λ1) of the antireflection film 21 for the position control light c is set to be smaller than the reflectance R22 (λ1) of the antireflection film 22 for the position control light c. The reflection of the position control light c on the surface 11a of the light transmissive substrate 11 is suppressed, so that the position control light c is reflected on the surface 11a of the light transmissive substrate 11 to adversely affect data recording or reproduction. Can be effectively suppressed.

  FIG. 5 is a diagram illustrating another example of the hologram recording / reproducing apparatus that records and reproduces data on the hologram recording medium 10.

  As shown in FIG. 5, the hologram recording / reproducing apparatus 200 includes a first laser light source 201, a second laser light source 202, a beam splitter 203, a shutter 204, a spatial light modulator 205, a mirror 206, 208, a half mirror 207, lenses 209, 210, 211, 212, a position detector 213, and an image sensor 214.

  The first laser light source 201 is a light source that generates a laser beam having a wavelength λ0. The laser beam emitted from the first laser light source 201 is separated by the beam splitter 203 into object light a and reference light b. .

  On the other hand, the second laser light source 202 is a light source that generates a laser beam having the wavelength λ1, and the laser beam generated by the second laser light source 202 is used as the position control light c.

  A shutter 204, a mirror 206, a spatial light modulator 205, and a lens 209 are arranged on the optical path of the object light a. The object light a is applied to the anti-reflection film 21 of the hologram recording medium 10 when recording data. At a predetermined incident angle φ.

  On the other hand, at the time of data reproduction, the object light a is blocked by the shutter 204, so that the object light a is applied to the hologram recording medium 10 only at the time of data recording. The spatial light modulator 205 provided on the optical path of the object light a is a device that planarly modulates the object light a according to data to be recorded.

  On the other hand, after being reflected by the mirror 208, the reference light b is incident on the surface of the antireflection film 21 of the hologram recording medium 10 at a predetermined incident angle θ via the lens 210. Since no shutter is provided on the optical path of the reference light b, the hologram recording medium 10 is irradiated with the reference light b both during data recording and during data reproduction.

  Therefore, when data is recorded, the hologram recording medium 10 is irradiated with both the object light a and the reference light b, whereby the hologram recording layer 20 included in the hologram recording medium 10 contains the object light a and the reference light b. Interference fringes due to light b are generated and recorded as a hologram.

  On the other hand, at the time of data reproduction, the hologram recording medium 10 is irradiated with only the reference light b, whereby the hologram formed in the hologram recording layer 20 is reproduced in the form of light, and the hologram image is reproduced. Is received by the image sensor 214 via the lens 212. The hologram image included in the reproduction light is converted into data by the image sensor 214.

  On the other hand, after passing through the half mirror 207, the position control light c is perpendicularly incident on the surface of the antireflection film 21 of the hologram recording medium 10 via the lens 211.

  The focus of the position control light c is adjusted to the concavo-convex pattern 13 provided on the light transmissive substrate 12, and the position control light e reflected by the concavo-convex pattern 13 is detected by the position detector 213, and the object light is detected. a and the reference light b or the reference light b are positioned, and the address of the area where recording or reproduction is currently performed is detected.

  When data is recorded on the hologram recording medium 10 and data is reproduced from the hologram recording medium 10 using the hologram recording / reproducing apparatus 200 configured as described above, the hologram recording medium 10 according to the present embodiment has a wavelength Since the reflectivity R22 (λ1) of the antireflection film 22 with respect to the position control light c having the wavelength λ1 is set to be sufficiently large, the light is reflected by the antireflection film 22 formed on the surface 12a of the light transmitting substrate 12. The intensity of the position control light e is sufficiently large. Therefore, by detecting the position control light e reflected by the antireflection film 22 by the position detector 213, the position of the object light a and the reference light b can be determined and recorded. / It is possible to reliably detect the address of the area where reproduction is performed.

  The antireflection film 22 has a reflectance R22 (λ0) for the object light a and the reference light b set to be smaller than a reflectance R22 (λ1) for the position control light c. The reflection of the object light a and the reference light b on the surface 12a is suppressed, and therefore, adverse effects on data recording or reproduction due to the reflection of the object light a and the reference light b on the surface 12a of the light transmitting substrate 12 are suppressed. It can be suppressed effectively.

  Further, the reflectance R21 (λ1) of the antireflection film 21 for the position control light c is set to be smaller than the reflectance R22 (λ1) of the antireflection film 22 for the position control light c. The reflection of the position control light c on the surface 11a of the light transmitting substrate 11 is suppressed, so that the adverse effect on data recording or reproduction due to the reflection of the position control light c on the surface 11a of the light transmitting substrate 11 is effectively suppressed. be able to.

  In general, the sum (φ + θ) of the incident angle φ of the object beam a to the hologram recording medium 10 and the incident angle θ of the reference beam b to the hologram recording medium 10, that is, the angle (φ + θ) formed by the object beam a and the reference beam b is 90 The closer to °, the greater the multiplicity of the hologram and the higher the density.

  In order to increase the diffraction efficiency, it is preferable that one of the incident angle φ of the object beam a to the hologram recording medium 10 and the incident angle θ of the reference beam b to the hologram recording medium 10 is close to 90 °.

  Considering the arrangement of the optical system, the volume of the object beam a and the reference beam b that overlap in the hologram recording layer 20, and the like, in order to multiplex hologram recording and achieve high density, the object on the hologram recording medium 10 is required. It is preferable that one of the incident angle φ of the light a and the incident angle θ of the reference light b with respect to the hologram recording medium 10 can be changed to 45 ° or more, and more preferably to 55 ° or more.

  Even when a spherical wave is used for the object light a and the reference light b, it is possible to use light having a high incident angle component of 45 ° or more, more preferably 55 ° or more, with respect to the hologram recording medium 10, It is preferable to achieve high density. For this reason, the reflectances R21 (λ0) and R22 (λ0) are suppressed to a low value, preferably 1.0% or less, more preferably 0.5% or less at the widest possible angle of incidence. There is a need.

  Further, when the uneven pattern 13 is on the optical path of the object light a, the reference light b, or the reproduction light d, the wavefront of the object light a, the reference light b, or the reproduction light d is caused by the uneven pattern 13, and the recording signal or Noise may be generated in the reproduced signal. Therefore, it is preferable to irradiate the object light a and the reference light b such that the uneven pattern 13 is not positioned on the optical path of the object light a, the reference light b, and the reproduction light d. In this embodiment, since the uneven pattern 13 is provided on the light transmitting substrate 12 located on the opposite side to the incident direction of the object light a and the reference light b, the uneven pattern 13 and the reproduction light d The relationship with the optical path may be considered.

  As described above, the hologram recording medium 10 according to the present embodiment includes the antireflection film 21 provided on the surface 11a of the light transmitting substrate 11 and the antireflection film 22 provided on the surface 12a of the light transmitting substrate 12. And the reflectances of the antireflection films 21 and 22 are set so as to satisfy the above-described expressions (1) and (2). Therefore, the recording characteristics of data using the object light a and the reference light b And the reproduction characteristics can be improved. At the same time, the position control light is used to position the object light a and the reference light b or the reference light b as desired, and the address of the area where recording or reproduction is performed is performed. Can be detected.

  Hereinafter, in order to further clarify the effects of the present invention, examples will be described.

Example 1
An amorphous polyolefin substrate having a thickness of 0.6 mm and a refractive index of 1.52 is prepared, and a mixture of MgF ₂ and SiO ₂ having a thickness of 87 nm and a refractive index of 1.39 is provided on the amorphous polyolefin substrate. An inorganic film composed of Y ₂ O ₃ having a thickness of 91 nm and a refractive index of 1.75; an inorganic film composed of TiO ₂ having a thickness of 66 nm and a refractive index of 2.40; An inorganic film made of Y ₂ O ₃ having a thickness of 76 nm and a refractive index of 1.75; an inorganic film made of a mixture of MgF ₂ and SiO ₂ having a thickness of 129 nm and a refractive index of 1.39; An inorganic film made of Y ₂ O ₃ having a refractive index of 1.75;
A sample provided with an anti-reflection film including a plurality of inorganic films by forming an inorganic film made of a mixture of MgF ₂ and SiO ₂ having a thickness of 110 nm and a refractive index of 1.39 in this order by a sputtering method. # 1 was produced.

Then, another amorphous polyolefin substrate having a thickness of 0.6 mm and a refractive index of 1.52 is prepared, and MgF ₂ having a thickness of 118 nm and a refractive index of 1.39 is formed on the amorphous polyolefin substrate. An inorganic film made of a mixture of SiO _2, an inorganic film made of Y ₂ O ₃ having a thickness of 101 nm and a refractive index of 1.75, and a TiO ₂ film having a thickness of 46 nm and a refractive index of 2.40 An inorganic film, an inorganic film made of Y ₂ O ₃ having a thickness of 108 nm and a refractive index of 1.75, and an inorganic film made of a mixture of MgF ₂ and SiO ₂ having a thickness of 86 nm and a refractive index of 1.39. A film, an inorganic film made of Y ₂ O ₃ having a thickness of 112 nm and a refractive index of 1.75, and a mixture of MgF ₂ and SiO ₂ having a thickness of 107 nm and a refractive index of 1.39 Samples # 2 provided with an antireflection film including a plurality of inorganic films were formed by sequentially forming an inorganic film made of a material by a sputtering method in this order.

Further, an amorphous polyolefin substrate having a thickness of 0.6 mm and a refractive index of 1.52 is prepared, and MgF ₂ and SiO ₂ having a thickness of 117 nm and a refractive index of 1.39 are provided on the amorphous polyolefin substrate. an inorganic film made of a mixture of a thickness of 102 nm, an inorganic film made of _Al 2 _{O 3} having a refractive index of 1.62, and a thickness of 63 nm, an inorganic film made of ZnS having a refractive index of 2.30 , An inorganic film made of a mixture of ZrO ₂ and SiO ₂ having a thickness of 72 nm and a refractive index of 1.85, and an inorganic film made of a mixture of MgF ₂ and SiO ₂ having a thickness of 140 nm and a refractive index of 1.39. A film, an inorganic film made of Y ₂ O ₃ having a thickness of 96 nm and a refractive index of 1.75, MgF ₂ and Si having a thickness of 106 nm and a refractive index of 1.39. An inorganic film made of a mixture of O ₂ was formed in this order by a sputtering method to prepare Sample # 3 on which an antireflection film including a plurality of inorganic films was formed.

  The refractive index is a value for a doubled-YAG laser having a wavelength λ of 532 nm, and the film thicknesses of the antireflection films of samples # 1m to # 3 are 1.23 times the wavelength of the doubled-YAG laser, respectively. It was 1.27 times and 1.31 times, and both were less than 1.5 times.

  Samples # 1, # 2, and # 3 were irradiated with a laser beam having a wavelength λ at an incident angle of 5 degrees, and the reflectance was measured. The wavelength λ of the laser beam was changed in a range from 500 nm to 800 nm.

  The measurement results are shown in FIG.

  As shown in FIG. 6, in all of Samples # 1, # 2, and # 3, the reflectance at a wavelength λ of around 530 nm was 0.5% or less.

  On the other hand, the reflectance at a wavelength λ of around 780 nm was about 3.1% in sample # 1, about 0.9% in sample # 2, and about 5.0% in sample # 3.

  Thus, when an amorphous polyolefin (refractive index: 1.52) is used as the material of the light-transmitting substrate, the anti-reflection film of Sample # 2 is made to transmit the light transmitted by the object light, the reference light, and the position control light. And the antireflection film of sample # 1 or sample # 3 is provided on the surface of the other light-transmitting substrate, the wavelength λ0 of the object light and the reference light is set to about 530 nm, and the position control light If the wavelength λ1 is set to about 780 nm, the recording and reproducing characteristics of data using the object light a and the reference light b can be improved, and at the same time, the position It has been found that it is possible to position the light a and the reference light b or the reference light b and detect the address of the area where recording or reproduction is performed.

  For example, a doubled-YAG laser having a wavelength λ of 532 nm can be used as a light source of a laser beam having a wavelength λ0, and an infrared semiconductor laser for a CD having a wavelength λ of 780 nm can be used as a light source of a laser beam having a wavelength λ1. Can be used.

Example 2
A sample # 4 was prepared in the same manner as the sample # 1, except that a soda lime glass substrate having a thickness of 0.6 mm and a refractive index of 1.52 was used instead of the amorphous polyolefin substrate of the sample # 1. A sample # 5 was fabricated in the same manner as the sample # 2 except that a soda lime glass substrate having a thickness of 0.6 mm and a refractive index of 1.52 was used instead of the amorphous polyolefin substrate of the sample # 2. did.

  When the relationship between the reflectances of the samples # 4 and # 5 thus obtained and the wavelength λ of the laser beam was measured, the same results as those of the samples # 1 and # 2 were obtained.

Example 3
Samples # 1, # 2, and # 3 were irradiated with a doubled-YAG laser having a wavelength λ of 532 nm at different incident angles, and the reflectances of Samples # 1, # 2, and # 3 were measured.

  The measurement result for sample # 1 is shown in FIG. 7, the measurement result for sample # 2 is shown in FIG. 8, and the measurement result for sample # 3 is shown in FIG.

  As shown in FIGS. 7 to 9, even when the incident angle of the laser beam changes in a wide range from 0 to 60 degrees, the reflectance of samples # 1, # 2, and # 3 is almost 0.5% or less. It was found that it did not exceed 1%.

Example 4
The reflectance of Samples # 4 and # 5 produced in Example 2 was measured in the same manner as in Example 3, and the same result as that of Samples # 1 and # 2 was obtained.

  The present invention is not limited to the above embodiments and examples, and various modifications can be made within the scope of the invention described in the claims, which are also included in the scope of the present invention. It goes without saying that it is a thing.

  For example, in the above embodiment, the hologram recording medium of the hologram recording medium 10 includes the pair of light-transmitting substrates 11 and 12 and the hologram recording layer 20 provided therebetween. It is not always necessary that the hologram record carrier includes a pair of light-transmitting substrates 11 and 12 and a hologram recording layer 20 provided therebetween, and the hologram record carrier has a different layer configuration. For example, a single light transmitting substrate and a hologram recording layer may constitute a hologram recording carrier, and an antireflection film may be formed on the surfaces of the light transmitting substrate and the hologram recording layer, respectively. If the hologram recording layer has sufficient mechanical strength, the hologram recording carrier is composed of Tomemaku may be Yo formed on both sides of the hologram recording layer.

  Further, in the above embodiment, the concavo-convex pattern 13 is provided on the light transmissive substrate 12 located on the opposite side to the incident direction of the object light a and the reference light b. It is not always necessary to provide the light transmitting substrate 12 on the opposite side to the incident direction of the reference light b, and it is necessary to provide the uneven pattern 13 so as not to hinder the optical paths of the object light a and the reference light b. Although the design of the concavo-convex pattern 13 is complicated, the anti-reflection film 22 and the light-transmitting substrate 12 on which the concavo-convex pattern 13 are formed are connected by the anti-reflection film 22 so that the object light a and the reference light b are incident. It can also be arranged to be located on the side.

  Further, in the hologram recording / reproducing apparatus shown in FIGS. 4 and 5, the position control light c is applied to the concave / convex pattern 13 from the light transmissive substrate 11 side. It is not always necessary to irradiate the concavo-convex pattern 13 from the substrate 11 side, and the position control light c is irradiated to the concavo-convex pattern 13 from the light-transmitting substrate 12 side, and the position control light c reflected by the concavo-convex pattern 13 is detected. Thus, the position of the object light a and the reference light b and the address detection of the area where the data is recorded or reproduced may be detected.

  Further, in the above embodiment, the hologram recording medium 10 has a disk-shaped outer shape, but the hologram recording medium 10 does not necessarily have to have a disk-shaped outer shape. It may have a card-shaped outer shape, a sheet-shaped outer shape, a block-shaped outer shape, or the like, and may be configured to be built in a cartridge.

FIG. 1 is a partially cutaway perspective view showing the appearance of a hologram recording medium according to a preferred embodiment of the present invention. FIG. 2 is a substantially enlarged partial sectional view of a portion indicated by A in FIG. FIG. 3 is a schematic sectional view of the antireflection film. FIG. 4 is a diagram of a hologram recording / reproducing apparatus that records and reproduces data on a hologram recording medium. FIG. 5 is a diagram illustrating another example of a hologram recording / reproducing apparatus that records and reproduces data on a hologram recording medium. FIG. 6 is a graph showing the result of measuring the relationship between the reflectance of samples # 1, # 2, and # 3 and the wavelength of the laser beam in Example 1. FIG. 7 is a graph showing the result of measuring the relationship between the reflectance of Sample # 1 and the incident angle of the laser beam in Example 3. FIG. 8 is a graph showing the result of measuring the relationship between the reflectance of Sample # 2 and the incident angle of the laser beam in Example 3. FIG. 9 is a graph showing the result of measuring the relationship between the reflectance of Sample # 3 and the incident angle of the laser beam in Example 3.

Explanation of reference numerals

Reference Signs List 10 hologram recording medium 11, 12 light transmitting substrate 11a, 12a surface 13 uneven pattern 20 hologram recording layer 21, 22 antireflection film 31, 32, 33, 34, 35, 36, 37 inorganic film 100 hologram recording / reproducing device 101 1 laser light source 102 2nd laser light source 103 Beam splitter 104 Shutter 105 Spatial light modulator 106, 107 Half mirror 108 Mirror 109, 110, 111 Lens 112 Position detector 113 Image sensor 200 Hologram recording / reproducing device 201 First laser Light source 202 Second laser light source 203 Beam splitter 204 Shutter 205 Spatial light modulator 207 Half mirror 206, 208 Mirror 209, 210, 211, 212 Lens 213 Position detector 214 Image sensor a Object light b Reference light c Position control light d Reproduction light e Reflected position control light

Claims (10)

A hologram record carrier capable of hologram recording, a first antireflection film provided on one surface of the hologram record carrier, and a second antireflection film provided on the other surface of the hologram record carrier. A hologram recording medium, comprising: an optical characteristic of the first anti-reflection film and an optical characteristic of the second anti-reflection film different from each other. The hologram record carrier is configured to be able to record and reproduce data by irradiating a first laser beam, and the other surface of the hologram record carrier is provided with a concavo-convex pattern, By irradiating a second laser beam, the first laser beam can be positioned and an address of an area where data is recorded or reproduced can be detected. Item 2. A hologram recording medium according to Item 1. The second reflection is performed such that the reflectance of the second anti-reflection film for the second laser beam is higher than the reflectance of the second anti-reflection film for the first laser beam. The hologram recording medium according to claim 2, wherein an anti-reflection film is formed. The first reflection is performed such that the reflectance of the second anti-reflection film to the second laser beam is higher than the reflectance of the first anti-reflection film to the second laser beam. The hologram recording medium according to claim 2, wherein an anti-reflection film and the second anti-reflection film are formed. 5. The reflectivity of the first anti-reflection film and the reflectivity of the second anti-reflection film for the first laser beam are both 1.0% or less. 6. The hologram recording medium according to claim 1. The hologram recording medium according to claim 5, wherein a reflectance of the second anti-reflection film with respect to the second laser beam is 2.0% or more. 7. The hologram recording medium according to claim 2, wherein a wavelength of the first laser beam is shorter than a wavelength of the second laser beam. 8. The method according to claim 2, wherein each of the first and second antireflection films has a thickness of 1.5 times or less the wavelength of the first laser beam. 9. Hologram recording medium. The hologram recording medium according to any one of claims 2 to 8, wherein the first antireflection film is formed on a surface of the hologram record carrier on which the first laser beam is incident. . The hologram recording carrier, a first light-transmitting substrate and a second light-transmitting substrate, and a hologram recording layer provided between the first light-transmitting substrate and the second light-transmitting substrate The hologram recording medium according to any one of claims 1 to 9, comprising:

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