JP4473591B2 - Hologram recording medium, recording / reproducing method, and recording / reproducing apparatus - Google Patents

Description

  The present invention relates to a recording medium made of a light-transmissive photosensitive material such as a photorefractive material, a so-called holographic memory, and more particularly to a hologram recording / reproducing method and an optical information recording / reproducing apparatus using the holographic memory.

  A volume holographic recording system is known as a digital information recording system using the principle of hologram. A feature of this system is that recording information is recorded as a change in refractive index on a recording medium made of a photosensitive material such as a photorefractive material.

  One of the conventional hologram recording / reproducing methods is a method of recording / reproducing using Fourier transform.

  As shown in FIG. 1, in a conventional 4f hologram recording / reproducing apparatus, a reference light beam of a laser light beam 12 emitted from a laser light source LED is split into light 12a and 12b by a beam splitter 13. The light 12a is expanded in beam diameter by the beam expander BX, and is applied as parallel light to a spatial light modulator SLM such as a transmissive TFT liquid crystal display (LCD) panel. The spatial light modulator SLM receives the information to be recorded, which has been signal-converted by the encoder, as an electric signal, and forms two-dimensional data, that is, recording information such as a bright and dark two-dimensional dot pattern on a plane. When the light 12a passes through the spatial light modulator SLM, the light 12a is optically modulated to become a signal light beam including a data signal component. The signal light beam 12 a containing the dot pattern signal component passes through the Fourier transform lens 16 separated by the focal length f, the dot pattern signal component is Fourier transformed, and is condensed in the recording medium 10. On the other hand, the reference light beam 12b split by the beam splitter 13 is guided as reference light into the recording medium 10 by mirrors 18 and 19, and crosses and interferes with the optical path of the signal light beam 12a inside the recording medium 10. An optical interference pattern is formed, and the entire optical interference pattern is recorded as a diffraction grating such as a change in refractive index.

  In this way, diffracted light from dot pattern data illuminated with coherent parallel light is imaged with a Fourier transform lens, and the distribution on the focal plane, that is, the Fourier plane, is converted into a coherent reference to the result of the Fourier transform. The interference fringes are recorded on a recording medium near the focal point by interference with light. When the recording of the first page is completed, the rotation mirror 19 is rotated by a predetermined amount, the position is translated by a predetermined amount, and the incident angle of the reference light beam 12b with respect to the recording medium 10 is changed, and the same procedure is performed on the second page. Record with. In this way, angle multiplex recording is performed by performing sequential recording.

  On the other hand, at the time of reproduction, an inverse Fourier transform is performed to reproduce a dot pattern image. In information reproduction, as shown in FIG. 1, for example, the optical path of the signal light beam 12 a is blocked by the spatial light modulator SLM, and only the reference light beam 12 b is irradiated onto the recording medium 10. At the time of reproduction, the mirror position and angle are controlled by changing the combination of rotation and linear movement of the mirror so as to have the same incident angle as the reference light when the page to be reproduced is recorded. On the side opposite to the incident side of the signal light beam 12a of the recording medium 10 irradiated with the reference light beam 12b, a reproduction wave reproducing the recorded signal light appears. When this reproduced wave is guided to the inverse Fourier transform lens 16a and inverse Fourier transformed, the dot pattern signal can be reproduced. Further, the dot pattern signal is received by the image detection sensor 20 at the focal length position, reconverted into an electrical digital data signal, and then sent to the decoder 26, the original data is reproduced.

Conventionally, in order to record information at a high density in a certain volume in a recording medium, multiplex recording is performed in a volume of about several square mm using angle multiplexing or wavelength multiplexing (see Patent Document 1). In a recording medium system in which the reference light and the signal light are incident at a predetermined angle from the same side, it is difficult to separate the reproduction reference light and the reproduction light during information reproduction. Therefore, there is a problem that the read performance of the reproduction signal is deteriorated. Also, stray light prevention means is required, which is disadvantageous for system miniaturization.
Japanese Patent Laid-Open No. 2001-184637.

  Therefore, the problem to be solved by the present invention includes, as an example, providing a hologram recording and reproducing method and a hologram recording and / or reproducing apparatus that can be miniaturized.

The hologram recording medium according to claim 1 is a hologram recording medium recording or reproducing information by the diffraction grating arising Ri by the irradiation of the zeroth-order light and diffracted light coherent light beam is carried out, the light transmittance A recording medium portion made of a first photosensitive material having a magnetic property, and the recording medium portion provided on the opposite side of the incident side of the zero-order light and diffracted light of the light beam of the recording medium portion and transmitted through the recording medium portion reflectance depending on the intensity of the 0-order light, and the second consisting of the photosensitive material incident light processing area portion of at least one characteristic value of the absorption and transmittance changes, have a, the light beam the recording medium The incident light processing region portion is located at or near the position of the beam waist on the optical axis of the light beam, and is focused on the opposite side to the incident side. In the incident light processing of the light beam Information is recorded or reproduced by a diffraction grating corresponding to optical interference between the zero-order light before being reflected by the area and the diffracted light before being reflected by the incident light processing area or after being reflected. and wherein the dividing.

  7. The hologram recording method according to claim 6, wherein a coherent reference light beam is spatially modulated in accordance with recording information to generate a signal light beam, and the signal light beam is converted into a light transmissive first photosensitive material. The recording medium unit is irradiated so that the recording medium unit passes from the recording medium unit to the incident light processing region unit, and light interference occurs at a portion of the recording medium unit where the 0th-order light and diffracted light interfere with each other. A hologram recording method comprising: forming a diffraction grating region by a pattern, wherein the recording medium portion is incident on the recording medium portion through the recording medium portion on the opposite side of the signal light beam incidence side. An incident light processing region portion made of a second photosensitive material in which at least one characteristic value of reflectance, absorptance, and transmittance changes depending on the intensity of the 0th-order light of the signal light beam is provided.

10. The hologram reproducing method according to claim 9, wherein a signal light beam is generated by spatially modulating a coherent reference light beam according to recording information, and the signal light beam is converted into a light-transmitting first photosensitive material. The recording medium unit is irradiated so that the recording medium unit passes from the recording medium unit to the incident light processing region unit, and light interference occurs at a portion of the recording medium unit where the 0th-order light and diffracted light interfere with each other. A hologram reproducing method for reproducing recorded information recorded by a recording step of forming a diffraction grating region by a pattern,
In the recording step, incident light processing comprising a second photosensitive material in which at least one characteristic value of reflectance, absorptance, and transmittance varies depending on the intensity of the 0th-order light of the light beam transmitted through the recording medium portion Providing the region portion; and irradiating the region of the diffraction grating so that the reference light beam passes from the recording medium portion to the incident light processing region portion in the region of the diffraction grating formed. A reproducing step of generating a reproduction wave corresponding to the light beam and forming a region in which at least one characteristic value of reflectance, absorptance, and transmittance with respect to the reference light beam is changed in the incident light processing region part. Features.

The hologram device according to claim 12 is a hologram device for recording record information as a region of a diffraction grating and / or reproducing record information from the region of the diffraction grating,
A second photosensitive material in which at least one characteristic value of reflectance, absorptance, and transmittance varies depending on the intensity of the 0th-order light of the recording medium portion made of the light-transmissive first photosensitive material and the light beam transmitted therethrough. A holographic recording medium having an incident light processing region portion made of a material, a support portion for holding the holographic recording medium, and a mounting portion;
A light source for generating a coherent reference light beam;
A signal light generation unit including a spatial light modulator that spatially modulates the reference light beam according to recording information to generate a signal light beam;
The signal light beam is applied to the recording medium unit so as to pass from the recording medium unit to the incident light processing region, and the 0th-order light and the diffracted light of the signal light beam in the recording medium unit interfere with each other. A region of a diffraction grating by an optical interference pattern is formed in a part, and the signal light is irradiated to the region of the diffraction grating so that the reference light beam passes from the recording medium unit to the incident light processing region unit. An interference unit that generates a reproduction wave corresponding to the beam;
And a detector for detecting recording information imaged by the reproduction wave.

The hologram apparatus according to claim 15, wherein the recording information is recorded and / or reproduced from the diffraction grating area as a diffraction grating area,
A support portion for holding a recording medium portion made of a light-transmitting first photosensitive material in a freely attachable manner;
A light source for generating a coherent reference light beam;
A signal light generation unit including a spatial light modulator that spatially modulates the reference light beam according to recording information to generate a signal light beam;
The signal light beam is irradiated onto the recording medium unit to enter and pass through the recording medium unit, and diffraction is caused by a light interference pattern at a portion of the recording medium unit where the 0th-order light and diffracted light of the signal light beam interfere. An interference unit that forms a region of a grating, and irradiates the region of the diffraction grating with the reference light beam to generate a reproduction wave corresponding to the signal light beam;
The second recording medium portion is disposed on the opposite side to the incident side of the signal light beam, and has at least one characteristic value of reflectance, absorptance, and transmittance depending on the intensity of the 0th-order light of the incident light. An incident light processing region made of a photosensitive material;
And a detector for detecting recording information imaged by the reproduction wave.

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

<Hologram recording medium>
FIG. 2 shows a rectangular parallel plate card-type hologram recording medium 11 as an example of the embodiment. The hologram recording medium 11 is configured by integrally coupling a recording medium unit 10 and an incident light processing region R provided on the opposite side of the light incident side. The recording medium unit 10 and the incident light processing region R may be separated and the incident light processing region R may be provided on the apparatus side.

  In the hologram recording medium 11, the coherent light beam passes through the recording medium unit 10 and is condensed so as to focus on the opposite side to the incident side, and the incident light processing region R is positioned at the beam waist of the light beam. Or it is used so that it may be located in the vicinity (on an optical axis). In the recording medium unit 10, information is recorded or reproduced by a diffraction grating corresponding to an optical interference distribution generated by irradiation of a signal light beam (0th order light and diffracted light).

  The recording medium unit 10 is made of a light transmissive first photosensitive material. The first photosensitive material has photoconductivity and electro-optic effect (shows a change in refractive index proportional to the first order term of the applied electric field), and the donor level and the acceptor level exist at a deep band gap level. Materials So-called photorefractive materials, hole burning materials, photochromic materials, and the like are used. That is, a material capable of preserving the light intensity distribution is used for the first photosensitive material. Since the photorefractive material can write a refractive index grating inside without using a chemical reaction or the like, it is suitable for a reversibly rewritable memory. Photorefractive materials include semiconductor materials such as AlGaAs / GaAs, InGaN / InGaN quantum wells, dielectric materials such as LiNbO3, and organic materials such as PVK (polyvinylcarbazole) / TNF (trinitrofluorenone). There are organic photosensitive materials (including colored ones).

  The incident light processing region R is made of a second photosensitive material in which at least one characteristic value of reflectance, absorptance, and transmittance changes depending on the intensity of the 0th-order light of the coherent incident light beam.

  The second photosensitive material to be used is roughly classified into a photosensitive transmissive material having a characteristic value that is lower than the transmittance at the time of non-irradiation and the reflectance at the time of irradiation of the light beam. And a photosensitive reflective material having a characteristic value lower than the reflectance at the time of irradiation.

  First, examples of the photosensitive transmissive material include a phase change material, a photochromic material, and a quantum confinement layer having a quantum well structure.

  The phase change material is usually opaque (when it is not irradiated or irradiated below a predetermined light intensity), but the temperature at the center of the light beam is high, and the phase changes in a region exceeding a certain temperature and becomes transparent. If it falls, it will change again and return to the original opaque state. An example is antimony.

  Photochromic materials are usually transparent (non-irradiated or when irradiated with less than a predetermined light intensity), but change to an unstable opaque state due to absorption of the irradiated light beam (the central part where the intensity is strong), and the intensity of the light beam becomes weaker. Return to the original transparent state.

  The quantum confinement layer having the quantum well structure has a high reflectance in the central portion where the intensity of the light beam is strong due to the quantum confinement effect, but the reflectance is kept low in the surrounding region where the light beam intensity is weak.

  By using such a photosensitive transmission material for the incident light processing region R, a transmission type hologram recording medium can be configured. In the transmission type hologram recording medium, the reflectance or the absorptance of the incident light processing region R is higher than usual at a portion where the intensity of the irradiation light beam is strong, and the transmission intensity of the light beam is reduced. Therefore, when information is reproduced from the transmission type hologram recording medium by the reference light beam (0th order light), it contributes to separation of the reference light beam and the reproduction wave.

  Next, examples of the photosensitive reflective material include an oxide material, a semiconductor fine particle material, and an inverse photochromic material.

  Oxide material is normally transparent (when it is not irradiated or irradiated at a light intensity below a certain level), but it is opaque due to the reduction reaction in the region where the temperature at the center of the light beam is high and the temperature exceeds a certain temperature. However, when the temperature drops, it will oxidize again and become transparent. Examples thereof include silver oxide.

  The semiconductor fine particle material is usually opaque (when it is not irradiated or irradiated with less than a predetermined light intensity), but the temperature at the center of the light beam is high, and only the region above a certain temperature becomes transparent. Return to state.

  Inverse photochromic materials are usually opaque (non-irradiated or when irradiated with less than a predetermined light intensity), but change to an unstable transparent state due to absorption of the irradiated light beam (strong central part), and the intensity of the light beam is weak If it becomes, it will return to the original opaque state.

  Thermochromic materials are usually opaque (non-irradiated or under irradiation below a certain light intensity), but the temperature at the center of the light beam is high and only the region above a certain temperature becomes transparent, and the original opaque when the temperature decreases Return to state. Alternatively, the thermochromic material is usually transparent (non-irradiated or irradiated with less than a predetermined light intensity), but only the region above a certain temperature becomes opaque and returns to its original transparent state when the temperature decreases.

  By using such a photosensitive reflective material for the incident light processing region R, a reflection type hologram recording medium can be constructed. In the reflection type hologram recording medium, the transmittance of the incident light processing region R is higher than usual at the portion where the intensity of the irradiation light beam is strong, and the reflection intensity of the light beam is reduced. Therefore, when information is reproduced from the reflection type hologram recording medium by the reference light beam (0th order light), it contributes to separation of the reference light beam and the reproduced wave.

  In any of the transmission type and reflection type hologram recording media, the incident light processing region R is not provided with a region for separately processing the 0th-order light and the diffracted light separately. Using a photosensitive material whose optical characteristics change depending on the intensity of the emitted light, a region (zero-order light processing region) for processing (acting) only the reference light beam (zero-order light) at the time of beam irradiation is formed. That is, a zero-order light processing region that is spatially separated is formed in the incident light processing region R during beam irradiation.

<Example 1>
FIG. 3 shows a hologram recording / reproducing apparatus which is an example of a hologram apparatus for recording and / or reproducing information on the hologram recording medium of the present embodiment. This reproduces information from a hologram recording medium in which the incident light processing region transmits almost all incident light. That is, the irradiating portion of the 0th-order light is made lower in light transmittance than the other portions, and the diffracted light (including the reproduction wave) and the 0th-order light are separated.

For the light source LED, for example, a DBR (Distributed Bragg) with a near infrared laser beam wavelength of 850 nm is used.
(Reflector) laser is used. On the optical path of the reference light beam 12, a shutter SHs, a beam expander BX, a spatial light modulator SLM, and a Fourier transform lens 16 are arranged for interference. The shutter SHs is controlled by the controller 32 to control the irradiation time of the light beam to the recording medium unit.

  The beam expander BX irradiates the reference light beam 12 having passed through the shutter SHs so that the diameter of the reference light beam 12 is enlarged to be a parallel light beam and incident on the spatial light modulator SLM.

  The spatial light modulator SLM receives electrical data (two-dimensional dot pattern data) supplied from the encoder 25 and displays a light and dark dot matrix signal. When the reference light beam passes through the spatial light modulator SLM on which data is displayed, the reference light beam is optically modulated to become a signal light beam 12a including data as a dot matrix component.

  The Fourier transform lens 16 performs Fourier transform on the dot matrix component of the signal light beam 12a, and condenses the focal point behind the mounting position of the recording medium unit 10 of the hologram recording medium 11 (incident light processing region). . When the shutter SHs is opened by the Fourier transform lens 16, the signal light beam 12a or the reference light beam 12 is irradiated onto the incident surface of the recording medium unit 10 at a predetermined incident angle, for example, zero degree. The spatial light modulator SLM is disposed at the focal length of the Fourier transform lens 16.

  The inverse Fourier transform lens 16 a is disposed on the same axis so as to be confocal with the Fourier transform lens 16. The image detection sensor 20 is disposed at the focal length of the inverse Fourier transform lens 16a, and includes an array such as a charge coupled device CCD and a complementary metal oxide semiconductor device.

  Furthermore, a decoder 26 is connected to the image detection sensor 20. The decoder 26 is connected to the controller 32. When the hologram recording medium 11 is previously labeled according to the type of the second photosensitive material, the controller 32 is mounted when the hologram recording medium 11 is mounted on the movable stage 60 that is a support unit for moving the hologram recording medium 11. Can automatically read this mark by an appropriate sensor and perform movement control of the hologram recording medium 11 and recording / reproduction control suitable for the recording medium unit 10.

  Recording is performed as follows. When the light source light passes through the spatial light modulator SLM, it is light-modulated to become a signal light beam 12a (0th-order light and diffracted light), Fourier-transformed by the Fourier transform lens 16, and 0th-order light in the recording medium unit 10. The diffracted light forms a light interference pattern and is recorded as a diffraction grating such as a change in refractive index according to the intensity distribution. Hologram recording is performed by interference between the polarization components of the same order in the directions of the polarization planes of the zero-order light and the diffracted light in the recording medium unit 10.

  On the other hand, during reproduction, the spatial light modulator SLM directly irradiates the recording medium unit 10 with a non-modulated reference light beam (0th-order light). A reproduction wave (reproduced diffracted light) corresponding to the recorded signal light appears in the incident light processing region R provided on the opposite side of the incident side of the recording medium portion 10 irradiated with the reference light beam. The reproduced wave is guided to the inverse Fourier transform lens 16a and inverse Fourier transformed. The image detection sensor 20 receives the dot pattern image by the reproduced wave and reconverts it into an electrical digital data signal, which is then sent to the decoder 26. The original data is reproduced.

  It has an incident light processing region R made of a second photosensitive material having a characteristic value that is lower than the transmittance at the time of non-irradiation (characteristic value at which the transmittance at the time of non-irradiation is higher than the transmittance at the time of irradiation). FIGS. 4A and 4B show the operation of the second photosensitive material at the time of recording / reproducing on the transmission type hologram recording medium.

  In the incident light processing region R before recording (FIG. 4A), the incident light processing region R has a uniformly high transmittance. By irradiation with a signal light beam (0th order light and diffracted light) at the time of recording, a predetermined threshold value TH (a degree of blocking transmission of the 0th order light of the signal light beam at and around the 0th order light center portion of the signal light beam) In the R1 portion of the incident light processing region that has been irradiated with light having a stronger intensity (a value at which the low transmittance of the second photosensitive material is expressed) (FIG. 4B), the transmittance is lowered. On the other hand, the diffracted light of the signal light beam is applied to the incident light processing region R. In the range where the diffracted light of the signal light beam in the incident light processing region R is irradiated, the light intensity of the diffracted light of the signal light beam is weaker than the 0th order light of the signal light beam, so the transmittance remains high, The diffracted light of the signal light beam passes through the incident light processing region R without being attenuated. Accordingly, at least a diffraction grating corresponding to this is stored in the recording medium unit 10 due to optical interference between the 0th-order light and the diffracted light of the signal light beam.

In the incident light processing region R before reproduction (FIG. 4A), the incident light processing region R has a uniformly high transmittance. By irradiation with the reference light beam (0th order light) at the time of reproduction, the second photosensitive material exhibits a predetermined threshold value TH (a low transmittance enough to prevent transmission of the reference light) at and near the center of the reference light beam. (Value) In the R1 portion of the incident light processing region that has been irradiated with light having a stronger intensity (FIG. 4B), the amount of reference light reaching the inverse Fourier transform lens 16a decreases due to the decrease in transmittance. . On the other hand, the reproduction wave generated when the reference light is applied to the diffraction grating in the recording medium unit 10 is applied to the incident light processing region R. In the range irradiated with the reproduction wave in the incident light processing region R, the light intensity of the reproduction wave is weaker than that of the reference light beam, so that the transmittance remains high, and the reproduction wave is hardly attenuated and the incident light processing region. The light passes through the portion R and is guided to the image detection sensor 20 through the inverse Fourier transform lens 16a. Such an operation of the incident light processing region R makes it possible to reduce the amount of reference light unnecessary for reproduction by the image detection sensor 20 and facilitate the detection of reproduction information.

  In this embodiment, the second photosensitive material having a higher characteristic value than the transmittance at the time of non-irradiation is used for the incident light processing region R. However, the light-transmissive second photosensitive material is used. It is apparent that a material that increases at least one of the reflectance and the absorptance at the time of irradiation as compared with that at the time of non-irradiation can also be used.

<Example 2>
As shown in FIG. 5, Example 2 has the same configuration as Example 1 except that the recording medium unit 10 and the incident light processing region R are separated and the incident light processing region R is provided on the apparatus side. The recording / reproducing process is the same.

<Example 3A>
In the above embodiment, the hologram recording / reproduction is shown in the form in which the incident light processing region R transmits the incident light. However, even if the incident light processing region R reflects the incident light, the same effect can be exhibited. .

  FIG. 6 shows a hologram recording / reproducing apparatus according to the third embodiment. In the third embodiment, information is reproduced from a hologram recording medium in which the incident light processing region R reflects most of the incident light. That is, the irradiating portion of the 0th order light is made more light transmissive than the other portions, and the diffracted light (including the reproduction wave) and the 0th order light are separated.

  In the third embodiment of FIG. 6, the inverse Fourier transform lens 16a on the optical system side that generates the reproduction wave shown in FIG. 3 is omitted, and the beam splitter 15 is added to the irradiation side optical system. The image detection sensor 20 is aligned at the imaging position of the reflected reproduction wave, and the reproduction wave (reproduced diffracted light) reflected by the incident light processing region R is branched from the optical path of the reference light and detected. Otherwise, the apparatus is the same as that shown in FIG.

  It has an incident light processing region R made of a second photosensitive material having a characteristic value that is lower in reflectance than that in non-irradiation (a characteristic value in which reflectance during non-irradiation is higher than that during irradiation). FIGS. 7A and 7B show the operation of the second photosensitive material at the time of recording / reproducing on the reflection type hologram recording medium.

In the incident light processing region R before recording (FIG. 7A), the incident light processing region R has a uniformly high reflectance. By irradiation with the signal light beam (0th-order light and diffracted light) during recording, a predetermined threshold TH (a degree that prevents reflection of the 0th-order light of the signal light beam at and near the center of the 0th-order light of the signal light beam) In the R1 portion of the incident light processing region that has been irradiated with light having a stronger intensity (a value at which a low reflectance is expressed in the second photosensitive material) (FIG. 7B), the reflectance decreases. On the other hand, the diffracted light of the signal light beam is applied to the incident light processing region R. In the range where the diffracted light of the signal light beam in the incident light processing region R is irradiated, the light intensity of the diffracted light of the signal light beam is weaker than the 0th order light of the signal light beam, so the reflectance remains high, Most of the diffracted light of the signal light beam is reflected. Accordingly, the light interference between the front of the diffracted light reflected by the 0 order light and the incident light processing area portion R of the front that reflects the incident light processing area portion R of the signal light beam, the incident light processing area portion R of the signal light beam Due to optical interference between the zero-order light before reflection and the diffracted light of the signal light beam reflected by the incident light processing region R, at least a diffraction grating corresponding to these is stored in the recording medium unit 10.

In the incident light processing region R before reproduction (FIG. 7A), the incident light processing region R has a uniformly high reflectance. By irradiation with the reference light beam (0th order light) at the time of reproduction, the second photosensitive material exhibits a predetermined threshold value TH (reflectance low enough to prevent reflection of the reference light) at and near the center of the reference light beam. (Value) In the R1 portion of the incident light processing region that has received light irradiation with a stronger intensity (FIG. 7B), the amount of reference light that reaches the Fourier transform lens 16 is reduced due to a decrease in reflectance. The amount of light reaching the beam splitter 15 is reduced. On the other hand, the reproduction wave generated when the reference light is applied to the diffraction grating in the recording medium unit 10 is applied to the incident light processing region R. In the range irradiated with the reproduction wave in the incident light processing region R, since the light intensity of the reproduction wave is weaker than that of the reference light beam, the reflectance remains high, and most of the reproduction wave is reflected. And is guided to the image detection sensor 20 via the beam splitter 15. Such an operation of the incident light processing region R makes it possible to reduce the amount of reference light unnecessary for reproduction by the image detection sensor 20 and facilitate the detection of reproduction information.

  In this embodiment, the second photosensitive material having a higher characteristic value than the reflectance at the time of non-irradiation is used for the incident light processing region R, but this is a reflective second photosensitive material. Obviously, a material in which at least one of the transmittance and the absorptance at the time of irradiation is increased as compared with the non-irradiation that affects the reflectance at the time of non-irradiation.

<Example 3B>
In Example 3B, as shown in FIG. 8, the beam splitter 15 in FIG. 6 is replaced with a polarizing beam splitter PBS, and a quarter-wave plate λ / 4 is provided between the polarizing beam splitter PBS and the Fourier transform lens 16. Otherwise, the configuration is the same as in Example 3A. The recording / reproducing process is the same.
The use efficiency of the light beam is improved by providing a separation unit that separates the reproduction wave from the optical path of the reference light beam composed of the polarization beam splitter PBS and the quarter wavelength plate λ / 4.

<Example 4A>
As shown in FIG. 9, Example 4A has the same configuration as Example 3A except that the recording medium unit 10 and the incident light processing region R are separated and the incident light processing region R is provided on the apparatus side. The recording / reproducing process is the same.

<Example 4B>
Example 4B has the same configuration as Example 3B except that recording medium unit 10 and incident light processing region R are separated from each other and incident light processing region R is provided on the apparatus side, as shown in FIG. The recording / reproducing process is the same.

As described above, basically, in any of the embodiments, the incident light processing region R is an operation in which the transmittance decreases in the case of the transmission type in the region where the light beam intensity is high, and the reflectance decreases in the case of the reflection type. do. The reference light and the reproduction wave that are reproduced from the recording medium part are irradiated from the recording medium part R to the incident processing area. At this time, there is a light intensity difference between the reference light and the reproduction wave, that is, the light intensity of the reference light is larger than that of the reproduction wave, so that the incident light processing region R has a different action between the reference light and the reproduction wave. do.
In the case of a reflection type (Example 3A, Example 3B, Example 4A, Example 4B)
In the incident light processing region R, the amount of light that reaches the Fourier transform lens decreases as the reflectance decreases in the range irradiated with the reference light. On the other hand, since the reflectance of the range irradiated with the reproduction wave remains high, it is guided to the Fourier transform lens with almost no attenuation. By such an operation of the incident light processing region R, it is possible to reduce the amount of reference light unnecessary for reproduction by the image detection sensor, and it becomes easy to detect reproduction information. Further, since there is no region defined in advance in the incident light processing region R, it is not necessary to process the fine structure, and noise to the reproduction signal due to diffraction or scattering at the boundary can be reduced.

<Other examples>
Further, the form of the recording medium unit 10 can be configured in various shapes such as a card. As shown in FIG. 11, the disc-shaped recording medium unit 10 is accommodated in the cartridge CR, and the incident light processing area unit is formed on the inner wall surface of the case. R can also be provided. By providing a medium side position marker fitted to the clamp and a cartridge side position marker for fixing to the apparatus at the clamp joint at the center of the disk-shaped recording medium unit 10, accurate alignment is possible.

  In the above embodiment, the hologram recording / reproducing method and the hologram recording / reproducing apparatus have been described as examples. However, the present invention clearly includes a hologram recording method, a hologram reproducing method, a hologram recording apparatus, and a hologram reproducing apparatus. In the above embodiment, an example of so-called two-dimensional modulation in which spatial modulation is performed according to two-dimensional data has been described. However, the present invention is a one-dimensional modulation hologram recording that is spatially modulated according to one-dimensional data. It can also be applied to playback.

It is a schematic block diagram which shows the conventional hologram recording / reproducing system. It is a schematic perspective view which shows an example of the hologram recording medium by this invention. It is a schematic block diagram explaining the hologram recording / reproducing apparatus of embodiment by this invention. It is the graph and diagram explaining the recording / reproducing process of the hologram recording medium in the hologram recording / reproducing apparatus of embodiment by this invention. It is a schematic block diagram explaining the hologram recording / reproducing apparatus of other embodiment by this invention. It is a schematic block diagram explaining the hologram recording / reproducing apparatus of other embodiment by this invention. It is the graph and diagram explaining the recording / reproducing process of the hologram recording medium in the hologram recording / reproducing apparatus of embodiment by this invention. It is a schematic block diagram explaining the hologram recording / reproducing apparatus of other embodiment by this invention. It is a schematic block diagram explaining the hologram recording / reproducing apparatus of other embodiment by this invention. It is a schematic block diagram explaining the hologram recording / reproducing apparatus of other embodiment by this invention. It is a schematic block diagram explaining the hologram recording / reproducing apparatus of other embodiment by this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Recording medium part 11 Hologram recording medium 15 Beam splitter 20 Image detection sensor 25 Encoder 26 Decoder 32 Controller 16a, 16 Lens LED light source SHs Shutter BX Beam expander SLM Spatial light modulator

Claims (19)

A coherent light beam of the 0th order light and the holographic recording medium recording or reproducing of information is performed by the I Ri resulting Ru grating irradiation of the diffracted light,
A recording medium portion made of a light-transmitting first photosensitive material;
Reflectance and absorption depending on the intensity of the 0th- order light that is provided on the opposite side of the light beam on the recording medium portion from the incident side of the 0th-order light and diffracted light and is transmitted through the recording medium portion. a second a photosensitive material incident light processing area portion of at least one characteristic value of the rate and transmittance changes, was closed,
The light beam passes through the recording medium part and is condensed so as to focus on the opposite side to the incident side, and the incident light processing region part is positioned at or near the position of the beam waist on the optical axis of the light beam. In the recording medium unit, the zero-order light before the light beam is reflected by the incident light processing region and the diffracted light before or after being reflected by the incident light processing region. A hologram recording medium , wherein information is recorded or reproduced by a diffraction grating corresponding to the optical interference .   2. The hologram recording medium according to claim 1, wherein the second photosensitive material has a characteristic value in which the transmittance when irradiated with the light beam is lower than the transmittance when not irradiated.   2. The hologram recording medium according to claim 1, wherein the second photosensitive material has a characteristic value in which the reflectance when irradiated with the light beam is lower than the reflectance when not irradiated. The hologram recording medium according to claim 1, wherein the incident light processing region has a linear track in a part thereof.   The hologram recording medium according to claim 4, wherein the track has position information of the incident light processing region portion in the recording medium portion.   A coherent reference light beam is spatially modulated according to recording information to generate a signal light beam, and the signal light beam is processed from the recording medium portion made of a light-transmissive first photosensitive material into the incident light processing unit. The recording medium unit is irradiated so as to pass through the region unit, and a diffraction grating region based on an optical interference pattern is formed in a portion of the recording medium unit where the 0th-order light and diffracted light of the signal light beam interfere. A hologram recording method including a step, wherein the intensity of the 0th-order light of the signal light beam transmitted through the recording medium part and incident on the opposite side of the recording medium part from the incident side of the signal light beam A hologram recording method, comprising: an incident light processing region portion made of a second photosensitive material in which at least one characteristic value of reflectance, absorptance, and transmittance varies depending on the second photosensitive material.   7. The hologram recording method according to claim 6, wherein the second photosensitive material has a characteristic value in which the transmittance when irradiated with the light beam is lower than the transmittance when not irradiated.   7. The hologram recording method according to claim 6, wherein the second photosensitive material has a characteristic value in which the reflectance when irradiated with the light beam is lower than the reflectance when not irradiated. A coherent reference light beam is spatially modulated according to recording information to generate a signal light beam, and the signal light beam is processed from the recording medium portion made of a light-transmissive first photosensitive material into the incident light processing unit. The recording medium unit is irradiated so as to pass through the region unit, and a diffraction grating region based on an optical interference pattern is formed in a portion of the recording medium unit where the 0th-order light and diffracted light of the signal light beam interfere. A hologram reproducing method for reproducing recorded information recorded by a process,
In the recording step, incident light processing comprising a second photosensitive material in which at least one characteristic value of reflectance, absorptance, and transmittance varies depending on the intensity of the 0th-order light of the light beam transmitted through the recording medium portion Providing the region portion, and irradiating the region of the diffraction grating so that the reference light beam passes from the recording medium portion to the incident light processing region portion in the region of the diffraction grating formed. A reproducing step of generating a reproduction wave corresponding to the light beam and forming a region in which at least one characteristic value of reflectance, absorptance, and transmittance with respect to the reference light beam is changed in the incident light processing region part. A hologram reproducing method characterized by the above.   10. The hologram reproducing method according to claim 9, wherein the second photosensitive material has a characteristic value in which the transmittance when irradiated with the light beam is lower than the transmittance when not irradiated.   10. The hologram reproducing method according to claim 9, wherein the second photosensitive material has a characteristic value in which the reflectance when irradiated with the light beam is lower than the reflectance when not irradiated. A hologram apparatus for recording recorded information as a diffraction grating area and / or reproducing recorded information from the diffraction grating area,
A second photosensitive material in which at least one characteristic value of reflectance, absorptance, and transmittance varies depending on the intensity of the 0th-order light of the recording medium portion made of the light-transmissive first photosensitive material and the light beam transmitted therethrough. A holographic recording medium having an incident light processing region portion made of a material, a support portion for holding the holographic recording medium, and a mounting portion;
A light source for generating a coherent reference light beam;
A signal light generation unit including a spatial light modulator that spatially modulates the reference light beam according to recording information to generate a signal light beam;
The signal light beam is applied to the recording medium unit so as to pass from the recording medium unit to the incident light processing region, and the 0th-order light and the diffracted light of the signal light beam in the recording medium unit interfere with each other. A region of a diffraction grating by an optical interference pattern is formed in a part, and the signal light is irradiated to the region of the diffraction grating so that the reference light beam passes from the recording medium unit to the incident light processing region unit. An interference unit that generates a reproduction wave corresponding to the beam;
And a detection unit that detects recording information imaged by the reproduction wave.   13. The hologram apparatus according to claim 12, wherein the second photosensitive material has a characteristic value in which the transmittance when irradiated with the light beam is lower than the transmittance when not irradiated.   13. The hologram apparatus according to claim 12, wherein the second photosensitive material has a characteristic value in which the reflectance when irradiated with the light beam is lower than the reflectance when not irradiated.   The hologram apparatus according to claim 14, further comprising a separation unit that separates the reproduction wave from an optical path of the reference light beam. A hologram apparatus for recording recorded information as a diffraction grating area and / or reproducing recorded information from the diffraction grating area,
A support portion for holding a recording medium portion made of a light-transmitting first photosensitive material in a freely attachable manner;
A light source for generating a coherent reference light beam;
A signal light generation unit including a spatial light modulator that spatially modulates the reference light beam according to recording information to generate a signal light beam;
The signal light beam is irradiated onto the recording medium unit to enter and pass through the recording medium unit, and diffraction is caused by a light interference pattern at a portion of the recording medium unit where the 0th-order light and diffracted light of the signal light beam interfere. An interference unit that forms a region of a grating, and irradiates the region of the diffraction grating with the reference light beam to generate a reproduction wave corresponding to the signal light beam;
The second recording medium portion is disposed on the opposite side to the incident side of the signal light beam, and has at least one characteristic value of reflectance, absorptance, and transmittance depending on the intensity of the 0th-order light of the incident light. An incident light processing region made of a photosensitive material;
And a detection unit that detects recording information imaged by the reproduction wave.   17. The hologram apparatus according to claim 16, wherein the second photosensitive material has a characteristic value in which the transmittance when irradiated with the light beam is lower than the transmittance when not irradiated.   17. The hologram apparatus according to claim 16, wherein the second photosensitive material has a characteristic value in which the reflectance when irradiated with the light beam is lower than the reflectance when not irradiated.   The hologram apparatus according to claim 18, further comprising a separation unit that separates the reproduction wave from an optical path of the reference light beam.

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