JP4461894B2 - Hologram information recording medium - Google Patents

Description

  The present invention relates to a hologram information recording medium, and more particularly to a reflection type hologram information recording medium.

  In a reflection type hologram information recording medium that records and reproduces holograms from the same main surface side, a hologram information recording medium in which an information recording layer and a position information layer for obtaining position information are formed has been proposed (for example, Patent Documents). 1).

In a reflection type hologram information recording medium having a two-layer structure in which functions of an information recording layer on which hologram recording / reproduction is performed and a position information layer are different, for example, a blue laser beam having a short wavelength is used as a recording / reproducing laser beam, Recording and reproduction are performed using a long-wavelength laser beam as the detection laser beam.
However, when the position information layer has a position information uneven surface due to fine pits or grooves and a reflection film is formed on this position information uneven surface, the hologram recording / reproducing laser beam is transmitted to the position information layer. When the light reaches and is reflected, it is affected by the uneven surface of the position information, and the wavefront of the hologram recording / reproducing light is disturbed, and stable information recording / reproducing is inhibited.

  In order to achieve stable hologram recording / reproduction, a wavelength selective reflection film is provided between the hologram information recording layer and the position information layer, and the short wavelength laser light for hologram recording / reproduction is reflected by this wavelength selective reflection. The configuration is such that the hologram recording / reproduction is not affected by the above-described uneven reflection surface so that the position detection can be performed by reflecting only on the film and transmitting only the long wavelength position detection laser beam. It is taken.

Such a wavelength selective reflection film is usually composed of a dielectric multilayer film.
However, since the laser light applied to the hologram information recording medium has a wide incident angle converged by the lens, when the wavelength selective reflection film is configured by the dielectric multilayer film, In order to be able to exhibit wavelength selectivity, a considerably large number of films are required, and there are problems such as an inhibition of productivity, a decrease in yield, and a resulting increase in cost.
Patent No. 3430012

  The present invention relates to a reflection type hologram information recording medium having a first information layer and a second information layer, and a wavelength selective reflection film between the first and second information layers. In addition to avoiding deterioration of information recording / reproducing characteristics due to going to the information layer on the opposite side of the surface, the wavelength selective reflection film has a dielectric multilayer film structure. It is an object of the present invention to provide a hologram information recording medium that can solve the problem and high cost.

A hologram information recording medium according to the present invention includes a first information recording layer, a second information recording layer, and a wavelength selective reflection film interposed between the first and second information recording layers. Type hologram information recording medium, wherein the first information recording layer is a hologram information recording layer on which hologram recording / reproduction is performed by a first laser beam, and the second information recording layer is information on an uneven reflection surface. An information recording layer having a recording surface and extracting information by a second laser beam, wherein the first laser beam is a short wavelength light, and the second laser beam The light is long wavelength light, and the wavelength selective reflection film has a single film configuration of an amorphous Si material .

In the present invention, the second information recording layer is a position detection information layer for detecting the irradiation position of the first laser beam for hologram recording / reproduction with respect to the first information recording layer. It is characterized by.
Further, according to the present invention, in the above-described configuration, the first laser light is blue laser light having a wavelength range of 390 nm to 450 nm, and the second laser light is red or near in the wavelength range of 630 nm to 830 nm. It is an infrared laser beam .

  As described above, the hologram information recording medium according to the present invention includes the first information recording layer, the second information recording layer, and the wavelength selective reflection film interposed between the first and second information recording layers. It is based on a reflection type hologram information recording medium having a single film structure, particularly in the present invention, by adopting a material structure in which the optical characteristics relating to the wavelength selective reflection film are specific in film thickness dependency. It is what.

  That is, in the configuration of the present invention, the optical information of the wavelength selective reflection film is the hologram information recording of the first information layer within the required film thickness range in the film thickness dependence characteristics of the reflectance and transmittance in FIG. As shown by the curves LMT and LMR, the transmittance characteristics and the reflectance characteristics of the first laser beam with respect to the layer show almost no film thickness dependence, the transmittance is almost zero, and the reflectance is A material layer having high characteristics and having a film thickness dependency indicating an interference characteristic, as indicated by curves LST and “LSR”, the transmittance characteristic and the reflectance characteristic related to the second laser light with respect to the second information layer It consists of more.

  By utilizing this characteristic, the film thickness of the wavelength selective reflection film is selected to be a film thickness that shows a characteristic that the characteristic curve LST is high and the reflection curve LSR is low. In contrast, it is possible to efficiently reflect the light without transmitting the light, transmit only the second laser light and direct it toward the second information layer, and further, as will be described later, with respect to a wide incident angle. The wavelength selectivity can be maintained.

  As described above, in the present invention, a reflection type hologram information recording medium having a wavelength selective reflection film with a single film is configured. Therefore, when a wavelength selective reflection film with a plurality of dielectric layers is laminated as in the prior art. For example, it is possible to effectively improve the productivity, yield, and cost problems described at the beginning.

FIG. 1 is a schematic sectional view of an embodiment of a reflective hologram medium 10 according to the present invention.
However, the present invention is not limited to this embodiment.
In this example, a hologram information recording layer 2 as a first information recording layer, a first transparent spacer film 3, a wavelength selective reflection film 4, and a second transparent spacer film 5 are sequentially laminated on the transparent substrate 1. Is done.
On the surface of the second transparent spacer film 5 opposite to the wavelength selective reflection film, a pit for position information such as address information and tracking information, and a concavo-convex surface 6 formed by a groove constituting a tracking guide groove are formed. The second information recording layer 8 is formed by depositing the reflective film 7 on the uneven surface 6.
The first and second laser light irradiation to the first and second information layers 2 and 8 of the hologram information recording medium 10 is performed from the first information recording layer 2 side, that is, from the transparent substrate 1 side.

  Next, a hologram recording / reproducing apparatus capable of performing hologram recording / reproducing with respect to the reflection type hologram information recording medium 10 according to the present invention will be described. FIG. 2 shows a schematic configuration diagram of a hologram recording / reproducing apparatus adopting a collinear method. In this case, a first laser light source 11 for hologram recording / reproduction, a collimating lens 12, a beam splitter 13, a spatial modulator 14 such as an array-type reflective liquid crystal panel, a mirror 15, and a dichroic prism 16, The objective lens 17, the array type photodetector 18, a second laser light source 19 for position detection, a collimator lens 20, a beam splitter 21, a condenser lens 22, and a photodetector 23 are included.

Information recording on the hologram information recording medium 10 in this apparatus will be described.
In this case, the laser light from the first laser light source 11 is the hologram recording / reproducing light LM, and passes through the beam splitter 13 via the collimator lens 12. A part of the light that has passed through the beam splitter 13 is modulated by the spatial modulator 14 according to the recording information for each pixel, introduced into the beam splitter 13 as signal light having a light intensity modulation pattern, reflected by the beam splitter 13, It is introduced into the objective lens 17 by the dichroic prism 16.

On the other hand, the remaining part of the light that has passed through the beam splitter 13 is reflected by the mirror 15, reflected by the beam splitter 13 as reference light, and introduced into the dichroic prism 16 and the objective lens 17.
In this way, a holographic recording / reproducing apparatus called a collinear system is configured by passing the signal light and the reference light through the same objective lens 17.
Then, the signal light and the reference light are subjected to interference fringes, that is, hologram recording, on the hologram information recording layer, that is, the first information recording layer 2 in the hologram information recording medium 10 by the objective lens 17.

  Next, the reproduction of information from the hologram information recording medium 10 will be described. In this case, the first laser light for optical information recording / reproduction from the first laser light source 11 passes through the beam splitter 13 via the collimator lens 12. A part of the light that has passed through the beam splitter 13 is blocked by the spatial modulator 14 in which the reflectance of all the pixels is controlled to 0%, and only the reference light reflected by the mirror 15 is reflected by the beam splitter 13. The hologram recorded on the hologram information recording medium 10 is illuminated via the dichroic prism 16 and the objective lens 17.

  The light diffracted by the hologram is reflected by the reflection film 7 constituting the position information layer of the hologram information recording medium 10, passes through the objective lens 17, the dichroic prism 16, and the beam splitter 13, and detects the light in the form of an array. A reproduced image is formed on the device 18, and the spatial distribution of the light intensity of the reproduced image is detected by the photodetector 9. The photodetector 9 is a CCD (Charge Coupled Device) sensor, a CMOS sensor, or the like.

By the way, it is necessary to precisely control the relative positional relationship between the objective lens 17 and the hologram information recording medium 10 with respect to the hologram medium 10 that moves in the recording / reproducing process described above.
One of the methods is information by embossed pits or grooves formed on the hologram information recording medium 10 using the second laser light LS as the position detecting laser from the second laser light source 19 shown in FIG. In this method, the position is precisely controlled based on address information or tracking information created in the second information recording layer 8 formed by attaching the reflective film 7 to the uneven surface 6.

  The second laser light source 19 for detecting position information obtains a second laser light LS having a wavelength λ2 different from the wavelength λ1 of the first laser light LM of the first laser light source 11 for recording and reproducing information. Laser light source. The laser LS having the wavelength λ2 has a wavelength λ2 that does not show recording sensitivity with respect to the hologram information recording layer 2 of the hologram information recording medium 10.

The light emitted from the second laser light source 19 passes through the collimator lens 20 and the beam splitter 22, is reflected by the dichroic prism 6 that reflects the wavelength from the laser light source 19, and is reflected by the objective lens 7. Then, the light is condensed on the second information recording layer 8 by the reflection film 7 on the above-described built-in uneven surface 6 of the hologram information recording medium 10.
The light diffracted and reflected by the information on the reflecting surface 7 of the second information recording layer 8 passes through the objective lens 17 and the dichroic prism 16, is reflected by the beam splitter 21, and is detected by the condenser lens 22. Guided to vessel 23. Then, by the photodetector 23, the in-plane information of the hologram information recording medium 10 such as the address information by the second information recording layer 8 and the position of the condensing spot on the one-dimensional guide groove (groove) by the groove. Location information is detected.

Further, the vertical position information of the hologram information recording medium 10 can also be detected by adding a focus detection mechanism.
Detection of in-plane position information and detection of vertical position information by the photodetector 23 described above can be performed by a method similar to that of a pickup device in a CD (Compact Disc).

Here, since the relative positions of the first laser light source 11 and the second laser light source 19 in the hologram information recording medium 10 are unchanged, the position information detected by the second laser light source 19 is unchanged. Based on the above, it is possible to recognize and control the position of the first laser light source 11 in the hologram information recording medium 10 to record and reproduce hologram information at a predetermined position.
That is, the laser beam LS from the second laser light source 19 is used as an auxiliary means for recording / reproducing with the first laser beam LM from the first laser light source 11.

  For the first and second laser beams LM and LS, the first laser beam LM for recording and reproducing information is a blue laser beam having a short wavelength (wavelength λ1 is 390 nm to 450 nm), and the second laser beam LM for position detection is used. The laser beam LS is a red or near-infrared laser beam having a longer wavelength than the first laser beam LM (wavelength λ2 is 630 nm to 830 nm).

  In this way, in the hologram information recording medium 10 according to the present invention, the reflection film 7 is formed on the uneven surface 6 by the wavelength selective reflection film 4 by the second laser light LS by the red or near infrared laser light. While the address information and the two-dimensional position information are obtained from the position-detected second information recording layer 8, the short-wavelength first laser light LM that performs recording and reproduction is transmitted to the second information recording layer. Reaching 8 is avoided. Therefore, the wavefront of the first laser beam LM that performs recording and reproduction is prevented from being disturbed by the second information recording layer 8.

Further, a specific example of the hologram information recording medium 10 according to the present invention will be described in detail.
The hologram information recording medium 10 includes, for example, a hologram information recording layer 2, a first transparent spacer film 3, a wavelength selective reflection film 4, a second transparent spacer film 5 on a transparent substrate 1 made of, for example, glass or polycarbonate resin. A reflective film 7 is formed.

The second transparent spacer film 5 has an uneven surface 6 formed with pits and grooves such as the address information and tracking information described above on the surface thereof. The reflective film 7 is formed on the uneven surface 6. Is formed.
The reflective film 7 is formed by depositing a metal film having a high reflectance in the red or near-infrared region of the wavelength λ2 of the above-described second laser beam such as Al by a method such as vapor deposition.

That is, in this configuration, the hologram information recording layer of the first information recording layer 2 is sandwiched between the transparent substrate 1 and the first transparent spacer film 3.
The position detection information layer of the second information recording layer 8 has an uneven surface 6 formed by address information and guide grooves (grooves) on the surface of the second transparent spacer film 5 and is covered by the above-described reflective film 7. Is formed.
The first transparent spacer film 3 is formed of a dielectric thin film, a transparent resin, or the like. In some cases, the first transparent spacer film 3 is not always necessary.
The second transparent spacer film 5 is made of a transparent resin having a thickness of about several tens to 100 microns, for example, a UV resin (ultraviolet curable resin) polycarbonate resin, or the like capable of forming address information and guide groove grooves.

The wavelength selective reflection film 4 can be constituted by a single layer film of amorphous Si (a-Si).
This a-Si has a large absorption coefficient for blue lasers, is almost transparent for red or near infrared lasers, has a transmittance of 0% for blue lasers, and has a constant reflectance. For a red or near-infrared laser, a wavelength selective reflection film having a certain transmittance can be realized.
FIG. 3 shows the film thickness dependence characteristics of λ1 = 405 nm and λ2 = 660 nm of the reflectance and transmittance of amorphous Si. The optical refractive index with respect to each used 4.3 + 2.1i, 4.3 + 0.4i.

As shown in FIG. 3, the amorphous Si has a film thickness range of about 50 nm or more with respect to λ1 = 405 nm, and the transmittance characteristic (curve LMT) and the reflectance characteristic (curve LMR) depend on the film thickness. The reflectivity is about 33%, and the transmittance is almost 0% due to absorption.
On the other hand, with respect to λ2 = 660 nm, it has an interference characteristic as shown in the transmittance characteristic (curve LST) and the reflectance characteristic (curve LSR).

  In the present invention, using this characteristic, the wavelength selective reflection film 4 has a film thickness that exhibits a characteristic with a high characteristic curve LST and a low reflection curve LSR, in this example, about 75 nm, for example, about 75 ± 5 nm. The film thickness is a single layer. At this film thickness, a transmittance of about 45% with respect to 660 nm can be obtained, that is, about half of the incident light can be transmitted to the position detection layer of the second information layer 8, and address information and two-dimensional position information Can be used to detect

Thus, by configuring the wavelength selective thin film 4 with amorphous Si selected to have a predetermined film thickness, the first laser beam (hologram information recording / reproducing laser beam) LM and As schematically shown the irradiation state of the two laser beams (position detection laser beam) LS in the hologram information recording medium 10, the hologram information recording / reproducing laser beam of the first laser beam LM is wavelength selective reflection. Since the film 4 does not pass through, the recording / reproduction of the first information recording layer with respect to the hologram information recording layer 2 can be performed with high accuracy without being affected by the second information recording layer 8.
The position detection laser beam of the laser beam LS does not show sensitivity to the hologram information recording layer 2, that is, has a wavelength that does not absorb, so that the laser beam LS is transmitted through the hologram information recording layer 2. Further, since the wavelength selective reflection film 4 is also highly transmissive, it can efficiently reach the position detection information layer 8 of the second information recording layer, and the reflected light modulated in accordance with this information can be extracted. .

Next, the incident angle dependence of the P wave and S wave of the reflectance and transmittance of the wavelength selective reflection film 4 will be described.
FIG. 5 shows the incident angle dependence of the transmittance and reflectance of S-polarized light and P-polarized light at a wavelength of 405 nm with respect to amorphous Si having a thickness of 75 nm. The curves STM and PTM show the transmittance of S-polarized light and P-polarized light. Curves, curves SRM and PRM show S-polarization and P-polarization reflectance curves.
According to FIG. A. Until the incident angle corresponding to 0.5 (numerical aperture) is about 20 degrees, the change in reflectance and the dependence on P-polarized light and S-polarized light are small. In addition, the transmittance is 0%.

On the other hand, FIG. 6 shows the incident angle dependence of the transmittance and reflectance of S-polarized light and P-polarized light having a wavelength of 660 nm with respect to amorphous Si having a thickness of 75 nm, and curves STS and PTS are S-polarized light and P-polarized transmittance curves, curves SRS and PRS, show reflectance curves for S-polarized light and P-polarized light.
According to FIG. A. Up to an incident angle of about 20 degrees corresponding to 0.5, there is little change in transmittance, P polarization and S polarization. That is, it can be seen that substantially constant reflection and transmission characteristics can be exhibited even for the laser beam converged by the objective lens 17.

  In FIGS. 5 and 6, the wavelengths 405 nm and 660 nm are shown. However, as the wavelength range of the existing short wavelength blue semiconductor laser, the wavelength 390 nm to 450 nm, the red or near infrared laser wavelength 630 nm to 830 nm, The optical refractive index at 450 nm, the upper limit of the blue laser wavelength, is 4.5 + 1.5i, while the optical refractive index, 630 nm, which is the lower limit of the red laser wavelength, is 4.2 + 0.4i. The same effect can be obtained.

  As described above, according to the configuration of the present invention, in the single film configuration, the first laser beam is efficiently reflected without being transmitted, and only the second laser beam is transmitted and the second information is transmitted. It can be directed to the layer, and can maintain wavelength selectivity for a wide incident angle.

  As described above, in the present invention, a reflection type hologram information recording medium having a wavelength selective reflection film made of a single film is formed, so that the wavelength selective reflection film is formed by stacking a plurality of dielectric layers as in the prior art. In this case, for example, the problems of productivity, yield, and cost can be effectively improved.

  Note that the present invention is not limited to the embodiment described above. For example, the first and second laser light sources are not limited to semiconductor lasers as long as they are in the above wavelength range.

It is a schematic sectional drawing of an example of the hologram information recording medium by this invention. It is a block diagram of an example of the hologram recording and reproducing apparatus with which it uses for description of this invention. It is a characteristic curve figure of the thickness dependence of the reflectance and transmittance | permeability of the wavelength selection reflection film of the hologram information recording medium by this invention. A and B are explanatory views of the operation of the wavelength selective reflection film for the hologram information recording medium according to the present invention. It is a characteristic curve figure which shows the incident angle dependence of the reflectance and transmittance | permeability about P wave and S wave about wavelength 405nm. It is a characteristic curve figure which shows the incident angle dependence of the reflectance and transmittance | permeability about P wave and S wave about wavelength 660nm.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Transparent substrate, 2 ... 1st information recording layer (hologram information recording layer), 3 ... 1st transparent spacer film, 4 ... Wavelength selective reflection film, 5 ... 2nd Transparent spacer film, 6 ... uneven surface, 7 ... reflective film, 8 ... second information recording layer (position detection information layer), 10 ... hologram information recording medium, 11 ... first 1 laser light source, 12 ... collimating lens, 13 ... beam splitter, 14 ... spatial modulator, 15 ... mirror, 16 ... dichroic prism, 17 ... objective lens, 18 ... Array type photodetector, 19 ... second laser light source, 20 ... collimating lens, 21 ... beam splitter, 22 ... condensing lens, 23 ... photodetector, LM ... First laser beam (hologram recording / reproducing laser beam), LS ... Of the laser beam (the position detection laser beam)

Claims (3)

A reflection hologram information recording medium comprising a first information recording layer, a second information recording layer, and a wavelength selective reflection film interposed between the first and second information recording layers,
The first information recording layer is a hologram information recording layer on which hologram recording / reproduction is performed by a first laser beam,
The second information recording layer is an information recording layer having an information recording surface with a concavo-convex reflecting surface and extracting information by a second laser beam,
In the first and second laser lights, the first laser light is short wavelength light, the second laser light is long wavelength light,
It said wavelength-selective reflective layer is formed sulfo program information recording medium has a single layer structure of the amorphous Si material. The second information recording layer, the hologram information recording medium according to 請 Motomeko 1 Ru position detection information layer der to detect the irradiation position of the first laser beam of a hologram recording and reproducing for the first information recording layer . The first laser beam is a blue laser beam having a wavelength range 390Nm～450nm, the second laser beam is 請 Motomeko wavelength range Ru laser beam der red or near-infrared 630nm~830nm 1. The hologram information recording medium according to 1.

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