JP6653505B2 - Hologram recording / reproducing method and hologram recording / reproducing apparatus - Google Patents

Description

  The present invention relates to a hologram recording / reproducing method and a hologram recording / reproducing device. More specifically, a hologram recording / reproducing method capable of increasing the capacity in forming a large-capacity optical memory by multiplex-recording a two-dimensional digital bit pattern as a hologram on a recording medium, and an effective hologram recording / reproducing Related to the device.

  2. Description of the Related Art Hitherto, a hologram recording / reproducing apparatus for two-dimensionally recording and reproducing digital information using a hologram has been proposed. In this hologram recording / reproducing apparatus, when recording digital information, a signal light carrying digital information (data information) modulated by a spatial light modulator composed of a plurality of pixels and a coherent signal light with the signal light are used. A hologram is formed by causing the reference light to interfere with the recording medium, and the hologram is recorded as the digital information. When reproducing digital information recorded on a recording medium, the hologram is irradiated with reference light used for recording to generate diffracted light, which is recorded as a hologram on a CCD (imaging device). An image of digital information is formed.

  In such a hologram recording / reproducing method, specific hologram recording methods include an angle multiplex recording method, a spherical reference light shift multiplex recording method, and a speckle reference light multiplex recording method.

  In the hologram recording method based on the angle multiplex recording method, the irradiation angle of a reference beam on a recording medium is minutely changed, and multiplex recording of a hologram is performed on a certain area of the recording medium. When the thickness of the recording medium is large (specifically, 1 mm or more), the Bragg diffraction condition becomes angularly strict, and when the angle is about 0.1 °, the Bragg diffraction angle condition deviates and reading becomes impossible. . Using this principle, several hundred holograms are recorded (multiplexed) in the same area on a recording medium. In the angle multiplex recording method, multiplex recording is performed in book units. That is, after performing multiplex recording of a hologram in a certain area, the irradiation area of light (signal light and reference light) is changed, and multiplex recording of a new hologram is performed in another area that does not overlap with the one area. It is performed sequentially for each book.

  In the hologram recording method using the speckle reference light multiplex recording method, the reference light is modulated by a speckle pattern. The reference light and the signal light modulated by the speckle pattern interfere with each other on the recording medium, and the hologram is recorded. For this reason, when reproducing the hologram recorded on the recording medium, reproduction can be performed only when the reference light has the same speckle pattern as at the time of recording. Thus, if the recording medium is shifted by a small distance (specifically, about 10 μm), the conformity of the speckle pattern (correlation of the speckle pattern) is broken, and the hologram cannot be reproduced. Using this principle, multiplex recording of a hologram is performed by shifting the recording medium. That is, a new hologram can be recorded by slightly shifting the recording medium, and shift multiplex recording can be repeated.

  The hologram recording method using the spherical reference light shift multiplex recording method performs multiplex recording by slightly shifting the recording medium in the same manner as the above-described speckle reference light multiplex recording method except that the reference light is a spherical wave. By using a spherical wave as the reference light, the same effect as the speckle pattern is exhibited, and the hologram is not reproduced just by shifting the recording medium by a small distance, and a new hologram can be recorded. Multiple recording can be repeated.

In the angle multiplex recording method which has been studied conventionally, it is necessary to set the irradiation angle of the reference light with an accuracy of about 0.01 to 0.02 °. Angle adjustment with such accuracy is within a range that is easily affected by slight environmental temperature changes and drive vibrations. For this reason, in an actual use environment, advanced angle control technology is required. Further, it is difficult to expand the angle change region due to the limitation of the numerical aperture of the lens system, and it is difficult to improve the recording density.
Further, in the spherical reference light shift multiplex recording method which has been conventionally studied, a slight shift occurs in a uniaxial direction along a plane formed by the optical axis of the signal light and the optical axis of the reference light. Multiple recording is possible, but shift selectivity is weak in the direction perpendicular to the axis, and two-dimensional multiple recording is difficult. Therefore, it is difficult to increase the density of recorded information only by the spherical reference light shift multiplex recording method.
Also, in the speckle reference light multiplex recording method, it is necessary to modulate the reference light in a form in which a speckle pattern (amplitude or phase pattern) is randomized. There is a problem in that In addition, since pattern matching must be performed with strict accuracy, it is difficult to ensure drive / medium compatibility.

On the other hand, a conventional hologram recording / reproducing apparatus for performing such a hologram recording / reproducing method includes a high-power laser light source having a relatively large size and a heavy weight, and a non-distortion type for performing transmission of two-dimensional images without distortion. A hologram memory recording / reproducing optical system including an aberration lens group and optical components, or a spatial light modulator (SLM), an image pickup device such as a CCD, and the like is provided. In this hologram recording / reproducing apparatus, considering an idea similar to that of the optical disk recording / reproducing apparatus, an optical head is formed by integrally forming the components of the hologram memory recording / reproducing optical system to achieve miniaturization. It is conceivable to realize high-speed access by movement. However, it is difficult for the above-mentioned constituent devices to be integrally configured, and it is difficult at present to perform high-speed access as an optical head.
Thus, as an alternative, a method is employed in which the optical system is not moved and two-dimensional access is performed by accessing the recording medium (disk medium) in the orthogonal one-dimensional axis direction, and the medium surface is accessed by rotating the recording medium. Have been. However, since the disk medium and the moving / rotating stage are heavy, there is a problem that high-speed access is hindered and high-speed access performance as a memory device is greatly restricted.

JP 2010-61750 A

The present invention has been made in view of the above circumstances, and an object of the present invention is to achieve efficient recording of information and increase the density of information recorded on a recording medium. It is an object of the present invention to provide a hologram recording / reproducing method which can be performed.
Another object of the present invention is to increase the density of recording information on a recording medium, and to facilitate the alignment of the recording medium when performing shift multiplex recording, thereby increasing the speed. An object of the present invention is to provide a hologram recording / reproducing apparatus which can be achieved.

The hologram recording / reproducing method of the present invention records an interference fringe between a signal light carrying data information and a reference light as a hologram on a recording medium, and irradiates the recording medium on which the hologram is recorded with the reference light to the hologram. In a hologram recording / reproduction method for reproducing recorded data information,
Using a spherical wave as the reference light,
The optical mechanism for irradiating the recording medium with light from the recording / reproducing light source as signal light and reference light is relatively moved in one direction along the surface of the recording medium to perform shift multiplex recording in only one direction on the recording medium. After recording the first shift multiplexed hologram sequence, the recording medium is rotated in a plane including the one direction by an angle φ _B (NA) [rad] or more calculated by the following equation (1). in a state in which in is rotated, by performing a new shift multiple recording, that a second shift multiplexed holograms column part of the recording area multiplex recording in a state overlapping with the recording region of the first shift multiplexed holograms column Features.

[In the formula (1), m is the order of Bragg null, λ is the wavelength [mm] of light from the recording / reproducing light source, n is the refractive index of the recording medium, L is the thickness [mm] of the recording medium, and ζ (NA) is This is a value represented by Expression (2).
In equation (2), θ _r is the incident angle [rad] of the reference light in the recording medium, d is the radius [mm] of the reference light in the recording medium, and NA is the objective for making the reference light a spherical wave. The numerical aperture of the lens, θ _s, is the incident angle [rad] of the signal light in the medium, and f is the working distance [mm] of the objective lens. ]

In addition, the hologram recording / reproducing method of the present invention records an interference fringe between a signal light carrying data information and a reference light as a hologram on a recording medium and irradiates the recording medium on which the hologram is recorded with the reference light. In a hologram recording and reproducing method for reproducing data information recorded on a hologram,
Using a spherical wave as the reference light,
The optical mechanism for irradiating the recording medium with the signal light and the reference light is relatively moved in one direction along the surface of the recording medium to perform the shift multiplex recording in only one direction on the recording medium, thereby performing the primary shift. After recording the multiplexed hologram sequence, in the same area as the recording area where the primary shifted multiplexed hologram sequence was recorded, the reference light was transmitted from an incident direction different from the reference light used for recording the primary shifted multiplexed hologram sequence. By repeatedly performing a hologram sequence multiplex recording process of irradiating and multiplex-recording a new shift multiplex hologram sequence, after recording a first multi-hologram sequence in which a plurality of shift multiplex hologram sequences are multiplex-recorded in the same area,
By repeatedly performing the hologram array multiplex recording process in a state where the recording medium is rotated in a plane including the one direction, a second multi hologram array in which a plurality of shift multiplex hologram arrays are multiplex-recorded in the same area. The hologram array is multiplex-recorded with a part of its recording area overlapping the recording area of the first multi-hologram array.

  In such a hologram recording / reproducing method, when a new shift multiplex hologram sequence is multiplex-recorded in the same region as the recording region where the primary shift multiplex hologram is recorded, the moving direction of the optical mechanism and the signal light recording medium In the virtual plane including the incident direction with respect to the reference light, the reference light along the optical axis whose direction approaching the incident optical axis of the signal light is opposite to the optical axis of the reference light used for recording the primary shift multiplexed hologram array. Is preferably irradiated.

Still further, in the hologram recording / reproducing method of the present invention, an interference fringe between a signal light carrying data information and a reference light is recorded as a hologram on a recording medium, and the recording medium on which the hologram is recorded is irradiated with the reference light. A hologram recording / reproducing method for reproducing data information recorded on a hologram by
Using a spherical wave as the reference light,
The optical mechanism for irradiating the recording medium with the signal light and the reference light is relatively moved in one direction along the surface of the recording medium to perform the shift multiplex recording in only one direction on the recording medium, thereby performing the primary shift. After recording the multiplexed hologram sequence, in the same region as the recording region where the primary shifted multiplexed hologram sequence was recorded, a reference beam having a polarization direction different from that of the reference light used for recording the primary shifted multiplexed hologram sequence is used. By repeatedly performing a hologram sequence multiplex recording process of irradiating and recording a new shift multiplex hologram sequence, after recording a first multi-hologram sequence in which a plurality of shift multiplex hologram sequences are multiplex-recorded in the same area,
By repeatedly performing the hologram array multiplex recording process in a state where the recording medium is rotated in a plane including the one direction, a second multi hologram array in which a plurality of shift multiplex hologram arrays are multiplex-recorded in the same area. The hologram array is multiplex-recorded with a part of its recording area overlapping the recording area of the first multi-hologram array.

Still further, in the hologram recording / reproducing method of the present invention, an interference fringe between a signal light carrying data information and a reference light is recorded as a hologram on a recording medium, and the recording medium on which the hologram is recorded is irradiated with the reference light. A hologram recording / reproducing method for reproducing data information recorded on a hologram by
Using a spherical wave as the reference light,
The recording medium is simultaneously irradiated with the first signal light and the second signal light having different polarization directions, and the same as the first reference light and the second signal light having the same polarization direction as the first signal light. Moving the optical mechanism for simultaneously irradiating the recording medium with the second reference light having the polarization direction of different directions along the surface of the recording medium in one direction. By performing only shift multiplex recording, the first shift multiplexed hologram sequence by the first signal light and the first reference light and the second shift multiplexed hologram sequence by the second signal light and the second reference light are formed. It is characterized in that a multiplexed hologram sequence recorded in the same area is recorded.

  In such a hologram recording / reproducing method, in a virtual plane including the moving direction of the optical mechanism and the incident direction of the signal light on the recording medium, the direction approaching the incident optical axis of the signal light is the first reference light. It is preferable to irradiate the second reference light along an optical axis opposite to the optical axis.

After recording the first multi-hologram sequence in which the first shift multi-hologram sequence and the second shift multi-hologram sequence are multiplex-recorded,
By performing a new shift multiplexing recording in a state where the recording medium is rotated in a plane including the one direction, the second shift multiplexing hologram sequence and the fourth shift multiplexing hologram sequence are multiplex-recorded. Is preferably multiplex-recorded in a state where a part of its recording area overlaps with the recording area of the first multi-hologram row.

  Furthermore, the recording area of the recording medium in which the multi-hologram row is recorded is irradiated with the first reference light for reproduction and the second reference light for reproduction having different polarization directions from each other, and Of the plurality of holograms recorded in the same place under the same reference light irradiation conditions as the first reference light and the second reference light for reproduction, and the reproduction light from each hologram is separated by the polarization separation means. It is preferable that the data information recorded on each of the plurality of holograms is simultaneously reproduced in parallel by separation.

In the hologram recording / reproducing method of the present invention described above, the recording / reproducing area on the surface of the recording medium is divided into a plurality of block units, and a plurality of shift multiplexed hologram rows or a plurality of multi-hologram rows are multiplex-recorded for each block unit. Is preferred.
Alternatively, the recording / reproducing area on the surface of the recording medium is divided into a plurality of block units arranged in the circumferential direction around the rotation center axis of the recording medium, and a plurality of block units point-symmetric with respect to the rotation center of the recording medium. It is preferable that a plurality of shift multiplexed hologram rows or a plurality of multi hologram rows be multiplex-recorded successively for each of.
Alternatively, the recording / reproducing area on the surface of the recording medium is divided into a plurality of annular block units radially arranged from the rotation center of the recording medium toward the outer peripheral edge, and a plurality of shifts are performed in the annular block unit on the rotation center side. After multiple hologram rows or a plurality of multi-hologram rows are multiplex-recorded and fixed, a plurality of shift multiplex hologram rows or a plurality of multi-hologram rows are multiplex-recorded and multiplex-recorded shift multiplex holograms in a block unit adjacent to the block unit. It is preferable to repeatedly fix the rows or the multiplex-recorded multi-hologram rows.

The hologram recording / reproducing apparatus of the present invention records an interference fringe between a signal light carrying data information and a reference light as a hologram on a recording medium, and irradiates the recording medium on which the hologram is recorded with the reference light to the hologram. In a hologram recording / reproducing device for reproducing recorded data information,
A recording / reproducing light source, light separating means for dividing light from the recording / reproducing light source into light for signal light and light for reference light, and the light for signal light on a recording medium as signal light carrying data information. An optical mechanism for irradiating a signal light generating optical system, and a spherical reference light generating optical system for converting light for reference light into a spherical wave and irradiating the recording medium as reference light,
An optical mechanism moving mechanism that relatively moves the optical mechanism in one direction along the surface of the recording medium,
Bei example a recording medium driving mechanism for moving rotating and parallel in a plane including the moving direction of the optical mechanism recording medium,
A plurality of shift multiplexed hologram rows recorded by moving one of the optical mechanism and the recording medium relative to the other in one direction and performing shift multiplex recording in only one direction on the recording medium are crossed. It is characterized by being multiplex-recorded in a state where it is set .

The hologram recording / reproducing apparatus of the present invention records an interference fringe between a signal light carrying data information and a reference light as a hologram on a recording medium, and irradiates the recording medium on which the hologram is recorded with the reference light to the hologram. In a hologram recording / reproducing device for reproducing recorded data information,
A recording / reproducing light source, light separating means for dividing light from the recording / reproducing light source into light for signal light and light for reference light, and the light for signal light on a recording medium as signal light carrying data information. An optical mechanism for irradiating a signal light generating optical system, and a spherical reference light generating optical system for converting light for reference light into a spherical wave and irradiating the recording medium as reference light,
An optical mechanism moving mechanism that relatively moves the optical mechanism in one direction along the surface of the recording medium,
A recording medium driving mechanism for rotating and translating the recording medium in a plane including the moving direction of the optical mechanism;
With
The optical mechanism is driven relatively to the fixed unit including the recording / reproducing light source and the light separating unit, and to the fixed unit including the signal light generation optical system and the reference light generation optical system. It comprises a movable part, and the light for signal light and the light for reference light emitted in the same direction from the fixed part are incident on the movable part without intersecting with each other,
The movable mechanism is moved by the optical mechanism moving mechanism in the optical axis direction of the signal light and the reference light incident from the fixed part to the movable part .

Further, in the hologram recording and reproducing apparatus of the present invention, the recording medium is a disk-shaped recording medium or a card-shaped recording medium,
It is preferable that shift multiplex recording in only one direction is performed by moving the movable portion relatively in one direction along the surface of the recording medium.

Still further, in the hologram recording / reproducing apparatus of the present invention, the optical system for generating a signal light includes a spatial light modulator into which light for the signal light is incident, a light emitted from the spatial light modulator, and a relay lens. A polarizing beam splitter that enters through a phase plate, a movable mirror that receives light from the polarizing beam splitter through a quarter-wave plate, and is repeatedly reflected between the movable mirror and the polarizing beam splitter. A signal light focusing objective lens that irradiates the recording medium with light that is polarized in a predetermined polarization direction and emitted from the polarization beam splitter as signal light,
The movable part is a secondary movable part movable in a direction perpendicular to the moving direction of the movable part on a plane including a moving direction of the movable part and a direction in which an optical path extending from the spatial light modulator to the movable mirror extends. The secondary movable section includes the polarizing beam splitter, the quarter-wave plate, the movable mirror, and the signal light focusing objective lens, and the movable mirror includes a secondary movable section. It is arranged variably in the moving direction of the part,
The position of the movable mirror is moved in the direction of movement of the secondary movable part with the movement of the secondary movable part, so that the signal light focusing objective lens and the relay constituting the signal light generating optical system It is preferable that the optical path length between the lens and the lens is kept constant.

Furthermore, in the hologram recording / reproducing apparatus of the present invention, the optical system for generating spherical reference light includes a plurality of objective lenses for condensing reference light for converting light for reference light into spherical waves, and a light for reference light. And an optical path switching unit for guiding the selected reference light focusing objective lens to the selected reference light focusing objective lens. Preferably, they are arranged so as to extend in directions different from each other.
In such a configuration, when the spherical reference light generation optical system includes two reference light focusing objective lenses, each of the reference light focusing objective lenses is In a virtual plane including the moving direction of the optical mechanism and the incident direction of the signal light, it is preferable that the signal light is disposed on both sides of the optical axis of the incident light with respect to the recording medium.

  Still further, in the hologram recording / reproducing apparatus of the present invention, the spherical reference light generating optical system includes a reference light focusing objective lens that converts light for reference light into a spherical wave, and a light beam for the reference light. It is preferable to provide a configuration including a polarization unit that adjusts the polarization direction.

Further, the hologram recording / reproducing apparatus of the present invention records an interference fringe between a signal light carrying data information and a reference light as a hologram on a recording medium, and irradiates the recording medium on which the hologram is recorded with the reference light. In a hologram recording and reproducing apparatus for reproducing data information recorded on a hologram,
A recording / reproducing light source; a plurality of light separating means for temporally dividing light from the recording / reproducing light source into two signal light lights and two reference light lights; a signal light generating optical system; An optical mechanism having a light generation optical system;
A moving mechanism that relatively moves the optical mechanism in one direction along the surface of the recording medium,
The signal light generating optical system converts the two signal light beams separated in time into a first signal light and a second signal light having different polarization directions and carrying different data information. A first optical system and a second optical system,
The spherical reference light generating optical system includes a reference light focusing objective lens that converts the reference light into a spherical wave, and converts one reference light into the same polarization direction as the first signal light. A third optical system for converting the reference light into a first reference light, and a reference light converging objective lens for converting the reference light into a spherical wave. And a fourth optical system that converts the light into a second reference light having the same polarization direction as the light. The two reference light condensing objective lenses each have an optical axis having an optical axis incident on the recording medium of the signal light. Are arranged so as to extend in directions different from each other.

In such a configuration, the two reference light focusing objective lenses have an axis perpendicular to the surface of the recording medium in a virtual plane including the moving direction of the optical mechanism and the incident direction of the signal light. It is preferable to adopt a configuration arranged on both sides sandwiched.
In addition, it has a reproduction light detecting optical system provided with a polarization separation means, and the reproduction first reference light and the reproduction second reference light having different polarization directions are simultaneously irradiated to the reproduction light detection optical system. The reproduction light emitted from each of the plurality of holograms recorded at the same location under the same reference light irradiation conditions as the first reproduction reference light and the second reproduction reference light is separated by the polarization separation means. It is preferable that the data information recorded on each of the plurality of holograms is simultaneously reproduced in parallel.
Further, it is preferable that the recording medium is further provided with a recording medium driving mechanism for rotating and translating the recording medium in a plane including the moving direction of the optical mechanism.

  According to the hologram recording / reproducing method of the present invention, a hologram is multiplex-recorded by a shift multiplex recording method using a spherical wave as a reference light. Since multiplex recording can be performed, the density of information recorded on the recording medium can be increased, and hologram recording can be performed for each unit recording area (book) with respect to the entire recording / reproducing area of the recording medium. Therefore, the hologram can be efficiently recorded.

  Further, according to the hologram recording / reproducing apparatus of the present invention in which the above-mentioned hologram recording / reproducing method is performed, it is possible to increase the density of information recorded on the recording medium, and it is possible to achieve uniaxial movement by the recording medium moving mechanism. Since the unit recording area (book) on the recording medium is accessed by the rotation of the recording medium rotating mechanism, the position of the recording medium can be easily adjusted when performing the shift multiplex recording, and the speed can be increased. it can.

FIG. 3 is an explanatory diagram illustrating an outline of a hologram recording method and a hologram reproducing method. FIG. 3 is an explanatory diagram showing a shift multiplexed hologram array obtained by spherical reference beam shift multiplexed recording in the hologram recording / reproducing method of the present invention. FIG. 3 is an explanatory diagram showing an outline of spherical reference beam shift multiplex recording in the hologram recording / reproducing method of the present invention. FIG. 3 is an explanatory diagram showing an outline of cross-shift multiplex recording in the hologram recording / reproducing method of the present invention. 5 is a graph used to obtain an angle φ _B (NA) [rad] calculated by Expression (1) in the hologram recording / reproducing method of the present invention. FIG. 3 is an explanatory diagram for describing a first cross-shift multiplex recording method in the hologram recording / reproducing method of the present invention. FIG. 4 is an explanatory diagram for explaining a second cross-shift multiplex recording method in the hologram recording / reproducing method of the present invention. FIG. 3 is an explanatory diagram showing the mutual relationship between wave number vectors of two shift multiplexed hologram arrays obtained by spherical reference beam shift multiplexed recording in the hologram recording / reproducing method of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory schematic diagram showing an example of the configuration of a hologram recording / reproducing apparatus of the present invention together with a recording medium. FIG. 4 is an explanatory schematic diagram showing another example of the configuration of the hologram recording / reproducing apparatus of the present invention together with a recording medium. FIG. 11 is an explanatory schematic diagram showing still another example of the configuration of the hologram recording / reproducing apparatus of the present invention together with a recording medium. It is an explanatory view showing a configuration of an optical mechanism in still another example of the hologram recording / reproducing apparatus of the present invention. It is an explanatory view showing a configuration of an optical mechanism in still another example of the hologram recording / reproducing apparatus of the present invention. It is an explanatory view showing a configuration of an optical mechanism in still another example of the hologram recording / reproducing apparatus of the present invention.

  Hereinafter, embodiments of the present invention will be described.

(Recording / reproducing method of the present invention)
The hologram recording / reproducing method of the present invention is a method of multiplex-recording a hologram on a recording medium by shift multiplex recording using a spherical wave as a reference beam (hereinafter referred to as “spherical reference beam shift multiplex recording”). In the same area of the medium, a plurality of shift multiplexed hologram rows are recorded in a state where a part of the area where each shift multiplexed hologram row is recorded overlaps with each other. That is, by performing cross-shift multiplex recording in which a plurality of shift multiplex hologram sequences recorded by spherical reference beam shift multiplex recording are recorded in a state where a part of the recording area of each shift multiplex hologram sequence overlaps each other, the density is increased. It is intended. Further, by irradiating the spherical reference light to the recording medium on which the hologram is recorded, each of the holograms recorded in the same recording area is independently reproduced.
As the recording medium, for example, a medium having a recording layer made of a photoreactive monomer is used. The photoreactive monomer is converted into a polymer when irradiated with light, and as a result, a region having a different refractive index is formed, which becomes a hologram.

  In the hologram recording / reproducing method of the present invention, as shown in FIG. 1, the reference light (the spherical reference light) that travels along the optical path L2 toward the recording medium 10 and is converted into a spherical wave by the reference light focusing objective lens 47. ) Travels along the optical path L1 toward the recording medium 10, and the signal light condensed by the signal light condensing objective lens 45 interferes on the recording medium 10, thereby forming a hologram. The reproduction light emitted from the hologram by irradiating the recording medium 10 on which the hologram is formed with the reference light is detected by the imaging element 41 via the reproduction light focusing lens 46 and recorded on the hologram. The data information is reproduced.

  In the spherical reference light shift multiplex recording, after recording an interference fringe of the signal light and the spherical reference light as a hologram in a predetermined area of a recording / reproducing area in the recording medium, the optical mechanism is moved in one direction along the surface of the recording medium. This operation is performed by repeatedly performing an operation of recording a new hologram in a state where a part of its recording area overlaps with a recording area of a hologram that has already been recorded in a state where the hologram is relatively moved. As a result, as shown in FIG. 2, a shift multiplexed hologram array 6 in which a plurality of holograms 1 are recorded so as to be arranged in one direction while partially overlapping each other is recorded. Here, one hologram 1 is substantially circular in plan view, and its size is, for example, 50 μm in diameter. The shift amount of the optical mechanism is, for example, about 10 μm.

  Such spherical reference light shift multiplex recording in only one direction may be performed by moving the optical mechanism for irradiating the signal light and the reference light with respect to the recording medium, or moving the recording medium without moving the optical mechanism. Although it may be performed, the optical mechanism is preferably moved with respect to the recording medium.

Here, the principle of spherical reference beam shift multiplex recording will be described with reference to FIG.
It is considered that the spherical reference light has a plurality of plane waves. Therefore, as shown in FIG. 3A, the recording medium 10 on which the hologram 1 is recorded is moved in one direction (the right side in FIG. 3A) along the surface of the recording medium 10 (the upper surface in FIG. 3A). If the hologram 1 is shifted by a small distance in the direction, the reproduction of the already recorded hologram 1 becomes impossible, and a new hologram can be recorded in a state where a part of the recording area overlaps the recording area of the already recorded hologram 1. It becomes possible. The shift amount of the recording medium 10 is usually about 10 μm or more.
As shown in FIG. 3B, the condition under which reproduction is possible is when the wave vector ks of the signal light, the wave vector kr of the reference light, and the wave vector (grating vector) kg of the hologram satisfy the Bragg diffraction condition. When the recording medium 10 is shifted, as shown in FIG. 3C, the relationship between the wave numbers is out of the Bragg diffraction condition, and the hologram 1 cannot be reproduced.
Here, FIG. 3B shows the relationship between the wave number vector ks of the signal light, the wave number vector kr of the reference light, and the wave number vector (grating vector) kg of the hologram in an area α surrounded by a dashed line in FIG. It is explanatory drawing which shows a relationship. FIG. 3C shows the relationship between the wave number vector ks of the signal light, the wave number vector kr of the reference light, and the wave number vector (grating vector) kg of the hologram in the region β surrounded by the broken line in FIG. FIG.

The cross shift multiplex recording will be described focusing on one unit recording area (book) of the recording / reproducing area on the recording medium. As shown in FIG. 4A, the first shift multiplex recording is performed by spherical reference light shift multiplex recording. The recording medium on which the hologram array is recorded in the unit recording area (book) B is rotated in a plane including the one direction (for example, the moving direction of the optical mechanism). Here, as a method of rotating the recording medium, the recording medium may be rotated around its center position (shape center position), or may be set in an area where the first shift multiplexed hologram row is recorded. May be rotated about an axis extending perpendicular to the surface of the recording medium.
In this state, a new spherical reference light shift multiplex recording is performed on the unit recording area B on which the first shift multiplex hologram sequence is recorded, so that the second shift multiplex hologram sequence is shifted to the second shift hologram sequence. A part of a recording area (a region surrounded by a solid line in FIG. 4A) in which a multiplexed hologram sequence is recorded is partially recorded in a recording region (a broken line in FIG. 4A) in which a first shift multiplexed hologram sequence is recorded. Multiplex recording is performed in a state of overlapping with (enclosed area) 7a. FIG. 4B schematically shows a state in which two shift multiplexed hologram arrays are multiplex-recorded by cross-shift multiplex recording. Reference numeral 1 in FIG. 4B indicates one hologram. 6a shows a previously recorded shift multiplexed hologram sequence, and 6b shows a newly recorded shift multiplexed hologram sequence.

  In the example shown in FIG. 4, one unit recording area B has four linear tracks arranged at a track pitch of a predetermined size. First, spherical reference light shift multiplex recording is performed for each track. To record the first shift multiplexed hologram sequence on each track. Thereafter, when the recording medium is rotated at a rotation angle θ1 of a predetermined size and is translated in a plane along the surface of the recording medium to record the unit recording area B in the first shift multiplexed hologram sequence. Position. In this state, the second shift multiplexed hologram sequence is recorded by sequentially performing new spherical reference beam shift multiplexed recording. This makes it possible to obtain a state in which the first shift multiplexed hologram sequence and the second shift multiplexed hologram sequence are multiplex-recorded in a state where a part of the recording area of each shift multiplexed hologram sequence overlaps with each other. B0 in FIG. 4 indicates a unit recording area at the time of recording the first shift multiplexed hologram sequence.

In the hologram recording / reproducing method of the present invention, the optical mechanism is rotated by an angle at which the recording medium is rotated, specifically, in a plane including the surface of the recording medium, ie, when performing spherical reference light shift multiplex recording. It is preferable that the angle of rotation (rotation) in a plane including one direction of relative movement along is based on the following equation (1), and crosses at an angle or more. That is, the rotation angle of the recording medium is preferably equal to or larger than the angle φ _B (NA) [rad] calculated by the equation (1). Here, the angle φ _B (NA) [rad] is a rotation angle at which the diffracted light amount of the higher-order recording medium becomes zero.
In Equation (1), m is the order of Bragg null, λ is the wavelength [mm] of light from the recording / reproducing light source, n is the refractive index of the recording medium, L is the thickness [mm] of the recording medium, and ζ (NA) is (2).

Here, in equation (2), θ _r is the incident angle [rad] of the reference light in the recording medium, d is the radius [mm] of the reference light in the recording medium, and NA is the conversion of the reference light into a spherical wave. Is the numerical aperture of the objective lens, θ _s is the incident angle [rad] of the signal light in the medium, and f is the working distance [mm] of the objective lens.

Specifically, for example, in the above formula (1), n = 1.5, nL / λ = 3500, θ _s = π / 8 [rad], θ _r = −π / 8 [rad], f / d If = 30, the angle φ _B [rad] is calculated by a graph as shown in FIG. FIG. 5 shows a plurality of curves used for the calculation.
By setting the angle of rotation of the recording medium to an angle range larger than the numerical aperture NA of the objective lens according to the angle determined by the above equation (1), the occurrence of crosstalk is reduced. The angle at which the recording medium is rotated is preferably an angle φ _B (NA) [rad] + 5 ° calculated by the above equation (1) in consideration of the design margin. .

  The hologram recording / reproducing method of the present invention can be applied to a recording medium having any shape such as a disk shape and a card shape, but particularly when a disk-shaped recording medium is used as a recording medium, recording on the surface of the recording medium is possible. It is preferable that the reproduction area is divided into a plurality of block units, and that each block unit is used as a unit recording area, and a plurality of shift multiplex hologram rows are cross-shift multiplex-recorded for each block unit.

  Hereinafter, a specific method of cross-shift multiplex recording on a disk-shaped recording medium (disk-shaped medium) by the hologram recording / reproducing method of the present invention will be described.

(First cross-shift multiplex recording method)
In the first cross-shift multiplex recording method, a recording / reproducing area on the surface of a disk-shaped medium is divided into a plurality of block units arranged in a circumferential direction of the recording medium, and each block unit is set as a unit recording area (book). . Further, each of the plurality of block units arranged in the circumferential direction is further divided into a plurality of block units arranged in the radial direction from the rotation center of the disk-shaped medium toward the outer peripheral edge, and each block unit is used as a unit recording area (book). May be set.
Then, after the spherical reference light shift multiplex recording is continuously performed on each of the two unit recording areas positioned at point symmetry with respect to the center position of the disk-shaped medium, the disk-shaped medium is rotated. In this method, new spherical reference beam shift multiplex recording is continuously performed on each of the two unit recording areas.

  Specifically, referring to FIG. 6, in this example, the recording / reproducing area on the surface of the disk-shaped medium 10a is divided into a plurality of recording / reproducing portions 10P arranged in the circumferential direction of the disk-shaped medium 10a. The recording / reproducing portion 10P is divided into a plurality of block units radially arranged from the rotation center C of the disk-shaped medium 10a toward the outer peripheral edge, and each block unit is set as a unit recording area (book) B.

First, as shown in FIG. 6 (a), two unit recording areas (books) B1 and B1 of a plurality of unit recording areas B which are located at point-symmetric positions with respect to the rotation center C of the disk-shaped medium 10a. In each of B2, the spherical reference light shift multiplex recording is continuously performed to record the first shift multiplex hologram sequence.
Next, as shown in FIG. 6B, in a state where the disk-shaped medium 10a is rotated at a predetermined rotation angle, each of the two unit recording areas B1 and B2 in which the first shift multiplexed hologram row is recorded. Then, by continuously performing new spherical reference light shift multiplex recording, the second shift multiplex hologram sequence is multiplex-recorded in a state where a part of its recording region overlaps with the recording region of the first shift multiplex hologram sequence.
Further, as shown in FIG. 6C, in a state where the disk-shaped medium 10a is rotated at a predetermined rotation angle, the unit recording in which the first shift multiplex hologram row and the second shift multiplex hologram row are recorded. By continuously performing a new spherical reference light shift multiplex recording in each of the areas B1 and B2, the third shift multiplex hologram sequence is partially changed to the recording region of the first shift multiplex hologram sequence and the second shift multiplex hologram sequence. Multiple recording may be performed in a state of overlapping the recording area of the one-shift multiplex hologram row.
In FIG. 6, the moving direction of the optical mechanism is indicated by a double-headed arrow, and the rotating direction of the disk-shaped medium 10a is indicated by a dashed arrow.

  In the first cross-shift multiplex recording method, each unit recording area (book) B is accessed by moving the optical mechanism and by biaxial movement and rotation (rotation) of the disk-shaped medium 10a. Done by

(Second cross-shift multiplex recording method)
In the second cross-shift multiplex recording method, the recording / reproducing area on the surface of the disk-shaped medium is divided into a plurality of substantially annular block units arranged in a radial direction from the center of rotation of the disk-shaped medium toward the outer peripheral edge. The block unit is set as a unit recording area (book).
Then, for each unit recording area, cross-shift multiplex recording of a plurality of shift multiplex hologram rows and fixing (post-curing) of the multiplex-recorded hologram are performed on the innermost unit recording area and the outermost unit recording area. This is a method that is repeatedly performed in the radial direction sequentially from one or both of the recording areas.

More specifically, referring to FIG. 7, first, for example, cross-shift multiplex recording of a plurality of shift multiplex hologram rows is performed in the innermost unit recording area B3 of the disk-shaped medium 10a. In the unit recording area B3, the hologram is fixed, that is, post-cured (fixed) when the number of multiplexed holograms is saturated. The hologram can be fixed by irradiating the entire surface of the recording / reproducing area of the disk-shaped medium 10a with the reference light.
Next, cross-shift multiplex recording of a plurality of shift multiplex hologram rows is performed in a unit recording area B4 adjacent to the unit recording area B3 where the hologram is fixed. The spherical reference light shift multiplex recording on the unit recording area B4 is performed by skipping the post-cured innermost unit recording area B3. When the number of holograms recorded in the unit recording area B4 reaches saturation, the hologram recorded in the unit recording area B4 is post-cured. Similarly, the cross-shift multiplex recording and the fixing of the hologram to each unit recording area are sequentially performed from the center side of the disk-shaped medium 10a toward the outer peripheral side, and the hologram is recorded on the entire surface of the disk-shaped medium 10a.
In FIG. 7, the moving direction of the optical mechanism is indicated by a solid double-headed arrow, the moving direction of the disc-shaped medium 10a is indicated by a two-dot chain line, and the rotational direction of the disc-shaped medium 10a is indicated by a broken line. Indicated by arrows.

  In the second cross-shift multiplex recording method, the cross-shift multiplex recording and the fixation of the hologram for each unit recording area are sequentially performed from the outer peripheral edge side to the center side of the disk-shaped medium 10a. May be multiplex-recorded on the entire surface. Also, by performing cross-shift multiplex recording and fixing of the hologram on each unit recording area sequentially from both the center side and the outer peripheral side of the disk-shaped medium 10a, the hologram is multiplex-recorded on the entire surface of the disk-shaped medium 10a. You may.

  According to the hologram recording / reproducing method of the present invention described above, a hologram is multiplex-recorded by a shift multiplex recording method using a spherical wave as a reference light. And multiplex recording, it is possible to increase the density of information recorded on the recording medium, and to record holograms on the entire recording / reproducing area of the recording medium for each unit recording area (book). Therefore, the hologram can be efficiently recorded.

  In the hologram recording / reproducing method of the present invention, a plurality of multi-hologram rows may be cross-shift multiplex-recorded in a state where recording regions partially overlap each other. The multi-hologram sequence is obtained by multiplex-recording a plurality of shift-multiplexed hologram sequences recorded by spherical reference beam shift multiplex recording in a state where the recording regions overlap each other in the same region.

  There are two methods of recording a multi-hologram row: (a) a method of changing the incident direction of the spherical reference light, (b) a method of changing the polarization direction of the spherical reference light, and (c) two methods having different polarization directions from each other. Any of the methods of simultaneously irradiating the signal light and the two spherical reference lights having the same polarization direction as each signal light can be used.

  Specifically, the method (a) will be described. First, a primary shift multiplexed hologram sequence is recorded by performing a spherical reference light shift multiplexed recording. After that, the spherical reference light is irradiated onto the same area as the recording area where the primary shift multiplexed hologram array is recorded from an incident direction different from that of the spherical reference light used for recording the primary shift multiplexed hologram array. A new shift multiplexed hologram sequence is recorded by performing optical shift multiplexed recording. As a result, a multi-hologram row in which two shift-multiplexed hologram rows are multiplex-recorded in the same area can be obtained. In addition, the multi-hologram array repeats the spherical reference light shift multiplex recording, in which the spherical reference light is irradiated from a different incident direction from the spherical reference light used for recording the already recorded shift multiplex hologram array, as necessary. It may be formed by performing.

When the multi-hologram row is composed of, for example, two shift-multiplexed hologram rows, the relationship between the wave number vectors of each shift-multiplexed hologram row will be described with reference to FIG. 8, as shown in FIG. When the recording medium 10 on which the holograms 1a and 1b are recorded is shifted by a small distance along the surface of the recording medium 10 (the upper surface in FIG. 8A), the individual shift multiplexed hologram rows are already recorded. The holograms 1a and 1b cannot be reproduced, and a new hologram can be recorded in a state where a part of the recording area overlaps with the recording areas of the holograms 1a and 1b already recorded.
As shown in FIG. 8B, the conditions under which the hologram 1a can be reproduced by the first spherical reference light are a wave number vector ks of the signal light, a wave number vector kr1 of the first spherical reference light, and a wave number vector (grating) of the hologram. Vector) kg1 satisfies the Bragg diffraction condition. When the recording medium 10 is shifted, as shown in FIG. 8C, the relationship of the wave vector kg1 is out of the Bragg diffraction condition, and the reproduction of the hologram 1a becomes impossible. The same applies to the conditions under which the hologram 1b can be reproduced by the second spherical reference light. In other words, as shown in FIG. 8D, the wave vector ks of the signal light, the wave vector kr2 of the second spherical reference light, and the wave vector (grating vector) kg2 of the hologram satisfy the Bragg diffraction condition. When the recording medium 10 is shifted, as shown in FIG. 8E, the relationship of the wave vector kg2 is out of the Bragg diffraction condition, and the reproduction of the hologram 1b becomes impossible.

  As described above, under the condition that the first shift multiplex hologram sequence and the second shift multiplex hologram sequence multiplex-recorded in the same area can be reproduced, the hologram 1a and the second shift multiplex hologram forming the first shift multiplex hologram sequence Since the directions of the wave vectors kg1 and kg2 are different from those of the hologram 1b constituting the column, it is possible to avoid the occurrence of crosstalk.

  As described above, in the case of recording a multi-hologram sequence composed of two shift-multiplexed hologram sequences, it is necessary to multiplex-record the secondary shift-multiplexed hologram sequence in the same region as the recording region where the primary shift-multiplexed hologram sequence is recorded. For example, in a virtual plane including the moving direction of the optical mechanism and the incident direction of the signal light on the recording medium, the direction approaching the incident optical axis of the signal light is the first used for recording the primary shift multiplexed hologram array. It is preferable to irradiate the second reference light along an optical axis opposite to the optical axis of the reference light. As a result, it is possible to reliably avoid occurrence of crosstalk during reproduction.

  The method (b) will be specifically described. First, a first-order multiplexed hologram sequence is recorded by performing spherical reference light shift multiplexed recording. Thereafter, the same area as the recording area in which the primary shift multiplexed hologram sequence is recorded is irradiated with spherical reference light having a polarization direction different from that of the spherical reference light used for recording the primary shift multiplexed hologram sequence, thereby obtaining spherical reference light. By performing the shift multiplex recording, a new shift multiplex hologram sequence is recorded. This makes it possible to obtain a multi-hologram row in which two shift-multiplexed hologram rows are multiplex-recorded in the same recording area. Even by such a method, it is possible to reliably avoid occurrence of crosstalk during reproduction.

  More specifically, the method (c) will be described. First and second signal lights having different polarization directions obtained by temporally dividing light from the same recording / reproducing light source; Simultaneously irradiating the recording medium with a first spherical reference light having the same polarization direction as the first signal light and a second spherical reference light having the same polarization direction as the second signal light, and spherical reference light shift multiplex recording. I do. Thereby, the first shift multiplexed hologram sequence based on the first signal light and the first spherical reference light and the second shift multiplexed hologram sequence based on the second signal light and the second spherical reference light are multiplex-recorded in the same area. Thus, a multi-hologram row can be obtained. The first spherical reference light and the second spherical reference light irradiate the recording medium from different incident directions, for example, in a virtual plane including the moving direction of the optical mechanism and the incident direction of the signal light on the recording medium. It is preferable to irradiate the second spherical reference light along an optical axis whose direction approaching the incident optical axis of the signal light is opposite to the optical axis of the first spherical reference light. As a result, it is possible to reliably avoid occurrence of crosstalk during reproduction.

  In the hologram recording / reproducing method of the present invention, by irradiating the spherical reference light for reproduction, data information on the hologram recorded under the same reference light irradiation condition as the spherical reference light for reproduction is independently reproduced. .

  The hologram recording / reproducing method of the present invention as described above can be easily implemented by the hologram recording / reproducing apparatus of the present invention described later.

  Hereinafter, a specific example of the hologram recording / reproducing apparatus of the present invention will be described with reference to the drawings.

(First hologram recording / reproducing device)
FIG. 9 is an explanatory schematic diagram showing an example of the configuration of the hologram recording / reproducing apparatus of the present invention together with a recording medium. FIG. 9 is a structural view of the hologram recording / reproducing apparatus from the side.
The first hologram recording / reproducing apparatus includes an optical mechanism for irradiating the recording medium with the signal light and the reference light, an optical mechanism moving mechanism for relatively moving the optical mechanism along the surface of the recording medium 10 in one direction, A recording medium drive mechanism for rotating and translating the recording medium 10 in a plane including the moving direction of the optical mechanism. In the first hologram recording / reproducing apparatus, a transmission type disc-shaped medium is used as the recording medium 10.

  The optical mechanism includes a recording / reproducing light source, light separating means for dividing light from the recording / reproducing light source into signal light light and reference light light, and the signal light as signal light carrying data information. The optical system includes a signal light generation optical system that irradiates the recording medium 10, and a spherical reference light generation optical system that converts reference light into a spherical wave and irradiates the recording medium 10 as spherical reference light.

  The optical mechanism preferably includes a fixed part 21 and a movable part 23 driven relatively to the fixed part 21, and it is preferable that only the movable part 23 is configured to be moved by the optical mechanism moving mechanism.

  The fixing unit 21 is, for example, a recording / reproducing light source 31 composed of a blue laser light source, and light (laser light) from the recording / reproducing light source 31 is incident via a shutter 33, a polarizing plate 34, and a beam shaping lens 35, for example, a half And a light separating means 32 composed of a mirror prism. The light for signal light and the light for reference light are emitted from the fixed part 21 in the same direction, and are incident on the movable part 23 without intersecting with each other. Specifically, the light for signal light from the light separating means 32 is emitted from the fixed part 21 via the relay lens 36. Further, the light for reference light traveling in a direction different from the light for signal light from the light separating means 32 is reflected by the reflection mirror 39 and the traveling direction is changed to the same direction as the light for signal light, and ND The light is emitted from the fixed part 21 via the filter 37 and the half-wave plate 38. That is, an optical path L1 for signal light and an optical path L2 for reference light are formed between the fixed part 21 and the movable part 23 so that their optical axes extend in parallel with each other.

  The movable unit 23 includes an optical system for generating a signal light, an optical system for generating a spherical reference light, and an optical system for detecting a reproduction light. The movable unit 23 enters the movable unit 23 from the fixed unit 21 by the optical mechanism moving mechanism. Are moved in the optical axis direction of the signal light and the reference light.

  The optical system for generating signal light is located on the surface side of the recording medium 10, and receives a signal from the fixing unit 21 for signal light, and a signal transmitted through the polarizing prism beam splitter 40. A spatial light modulator (SLM) 42 into which light for light is incident, and a signal from which the light from the spatial light modulator 42 is reflected by the polarizing prism beam splitter 40 and is incident via the relay lens 44 and the phase plate 48. And a light focusing objective lens 45. Reference numeral 43 denotes a Nyquist filter which is arranged between, for example, two lenses constituting the relay lens 44.

  The spherical reference light generating optical system is located on the surface side of the recording medium 10, and converts the light for reference light from the fixed portion 21 into a spherical wave and irradiates the recording medium 10 as spherical reference light. A focusing objective lens 47 is provided. Reference numeral 49 denotes a reflection mirror for causing the light for reference light to enter the reference light focusing objective lens 47.

  The reproduction light detection optical system is located on the back surface side of the recording medium 10, and condenses reproduction light from a hologram recorded on the recording medium 10 to the image pickup element 41 by, for example, a CCD. And a reproducing light condensing lens 46 for incidence.

  The recording medium driving mechanism includes a recording medium rotating mechanism that rotates (rotates) the recording medium 10 in a plane along the surface thereof, and a recording medium moving mechanism that moves the recording medium 10 in a plane along the surface. It has. The recording medium moving mechanism can be constituted by, for example, a two-axis stage that moves the recording medium 10 in a direction perpendicular to the moving direction of the optical mechanism and the moving direction of the optical mechanism in a plane along the surface of the recording medium 10. .

In the first hologram recording / reproducing apparatus, the laser light emitted from the recording / reproducing light source 31 is split by the light separating means 32 into light for signal light and light for reference light.
After the polarization plane of the reference light is rotated by 90 ° by the half-wave plate 38, the light is converted into a spherical wave by the reference light converging objective lens 47 and is applied to the recording medium 10 as spherical reference light.
On the other hand, the light for the signal light is enlarged by the relay lens 36, and then passes through the polarizing prism beam splitter 40 to irradiate the spatial light modulator (SLM) 42. The spatial light modulator (SLM) 42 modulates the signal light into a data pattern whose polarization plane has been changed by 90 °. Since the light for signal light emitted from the spatial light modulator (SLM) 42 has its polarization plane rotated by 90 °, it is reflected by the polarizing prism beam splitter 40 and its traveling direction is changed by 90 °. The signal light from the polarizing prism beam splitter 40 passes through the phase plate 48 after the spatial frequency band is adjusted by the Nyquist filter 43. The phase plate 48 has a random phase pattern, and has a function of suppressing unnecessary DC components in the spatial frequency distribution and modulating the consumption of monomers by modulating the signal light with a random phase. The signal light generated by transmitting the signal light through the phase plate 48 is condensed by the signal light converging objective lens 45 and irradiated on the recording medium 10.
By irradiating the recording medium 10 with the signal light and the spherical reference light, interference fringes between the signal light and the spherical reference light are formed on the recording medium 10, and the interference fringes are formed as a hologram carrying data information. Recorded at 10.

Then, the movable portion 23 of the optical mechanism is moved in the radial direction of the recording medium 10 by the optical mechanism moving mechanism, and the shift multiplexed hologram train is recorded by performing the spherical reference light shift multiplexed recording. Thereafter, the hologram should be recorded by rotating the recording medium 10 at a predetermined rotation angle by the recording medium rotating mechanism and moving the recording medium 10 in a plane along the surface by the recording medium moving mechanism. Position the recording area. In this state, by performing the spherical reference beam shift multiplex recording, the new shift multiplex hologram sequence is multiplex-recorded in a state where at least a part of the recording region overlaps with the recording region of the shift multiplex hologram sequence that has already been recorded.
Access to the unit recording area (book) is performed by biaxial movement and rotation (rotation) of the recording medium 10 in addition to access by movement of the optical mechanism.

  At the time of reproducing the data information related to the hologram recorded on the recording medium 10, the recording medium 10 is irradiated with only the spherical reference light for reproduction whose light quantity is greatly reduced. As a result, reproduction light is emitted from the hologram recorded under the same reference light irradiation conditions as the spherical reference light for reproduction, and the reproduction light is detected by the image pickup device (specifically, for example, a CCD) 41. The data information recorded on the hologram is reproduced.

(Second hologram recording / reproducing device)
FIG. 10 is an explanatory schematic diagram showing another example of the configuration of the hologram recording / reproducing apparatus of the present invention together with a recording medium. FIG. 10 is a configuration diagram of the hologram recording / reproducing apparatus viewed from a side.
In the second hologram recording / reproducing apparatus, as a recording medium 10, a reflection type disk-shaped medium, that is, a reflection layer 11 is provided on the back surface side (the lower surface side in FIG. 10) of the surface irradiated with signal light and reference light. In the movable section 23 constituting the optical mechanism, the reproduction light detection optical system is configured to be located on the surface side of the recording medium 10, and the first part shown in FIG. It has the same configuration as the hologram recording / reproducing device. 10, the same components as those of the first hologram recording / reproducing apparatus shown in FIG. 9 are denoted by the same reference numerals.

  In the reproduction light detecting optical system of the second hologram recording / reproduction apparatus, reproduction light from the hologram reflected by the reflection layer 11 of the recording medium 10 is emitted from the polarizing prism beam splitter 40 toward the recording medium 10. The optical path of the signal light is reversed. Therefore, the imaging element 41 is provided facing the surface (the upper surface in FIG. 10) of the recording medium 10 at a position where the reproduction light from the hologram is transmitted through the polarizing prism beam splitter 40 and is incident.

In the second hologram recording / reproducing apparatus, similarly to the first hologram recording / reproducing apparatus, the movable portion 23 of the optical mechanism is moved in the radial direction of the recording medium 10 by the optical mechanism moving mechanism to shift the spherical reference light. By performing multiplex recording, a shift multiplexed hologram sequence is recorded. Thereafter, the recording medium 10 is rotated at a predetermined rotation angle by the recording medium rotating mechanism, and the recording medium 10 is moved in a plane along the surface by the recording medium moving mechanism, thereby recording the hologram to be recorded. Align the position of the area. In this state, by performing the spherical reference beam shift multiplex recording, the new shift multiplex hologram sequence is multiplex-recorded in a state where at least a part of the recording region overlaps with the recording region of the shift multiplex hologram sequence that has already been recorded.
Access to the unit recording area (book) is performed by biaxial movement and rotation (rotation) of the recording medium 10 in addition to access by movement of the optical mechanism.

  At the time of reproducing the data information related to the hologram recorded on the recording medium 10, the recording medium 10 is irradiated with only the spherical reference light for reproduction whose light quantity is greatly reduced. As a result, reproduction light is emitted from the hologram recorded under the same reference light irradiation conditions as the spherical reference light for reproduction, and the reproduction light is reflected by the reflective layer 11 and emitted from the surface side of the recording medium 10. The reproduction light travels backward along the optical path of the signal light traveling from the polarizing prism beam splitter 40 toward the recording medium 10 and enters the polarizing prism beam splitter 40. At this time, the reproduction light has the same polarization plane as the reproduction-use spherical reference light. Therefore, the polarization plane of the reproduction light is rotated by 90 ° with respect to the polarization plane of the signal light. The light passes through the beam splitter 40 and enters the image sensor 41. When the reproduction light is detected by the imaging element 41, the data information recorded on the hologram is reproduced.

(Third hologram recording / reproducing device)
FIG. 11 is an explanatory schematic diagram showing still another example of the configuration of the hologram recording / reproducing apparatus of the present invention together with a recording medium. (A) is an explanatory top view showing a configuration of a fixed part and a movable part in the hologram recording / reproducing apparatus, and (b) is an explanatory side view showing a configuration of a secondary movable part in the movable part.
In the third hologram recording / reproducing apparatus, an optical mechanism for irradiating the recording medium with signal light and reference light includes a fixed portion and a movable portion driven relatively to the fixed portion. Thus, two-dimensional access to the recording medium is made possible. In the third hologram recording / reproducing apparatus, a transmission type disc-shaped medium is used as the recording medium 10.

  The fixed part 21 in the optical mechanism of the third hologram recording / reproducing apparatus includes a recording / reproducing light source 31 composed of, for example, a blue laser light source, and a light (laser light) from the recording / reproducing light source 31 being a shutter 33, a polarizing plate 34 and a beam shaping. And a light separating means 32 made of, for example, a half mirror prism, which is incident through the lens 35 for use. The light for signal light and the light for reference light are emitted from the fixed part 21 in the same direction, and are incident on the movable part 23 without intersecting with each other. Specifically, the light for signal light from the light separating unit 32 is emitted from the fixed unit 21 via the beam expander 51. Further, the light for reference light that travels in a direction different from the light for signal light from the light separating means 32 enters the reflection mirror 39 via the ND filter 37 and the half-wave plate 38, and is reflected by the reflection mirror 39. As a result, the traveling direction is changed to the same direction as the signal light, and the light is emitted from the fixed portion 21. That is, an optical path L1 for signal light and an optical path L2 for reference light are formed between the fixed part 21 and the movable part 23 so that their optical axes extend in parallel with each other.

  The movable section 23 irradiates the recording medium 10 with light for signal light as signal light carrying data information, and converts the light for reference light into a spherical wave and records it as spherical reference light. An optical system for generating a spherical reference light for irradiating the medium 10 and an optical system for detecting a reproduction light from a hologram are provided.

  The signal light generating optical system is located on the front surface (lower surface in FIG. 11B) of the recording medium 10, and the first polarizing prism beam splitter into which the light for signal light from the fixed part 21 is incident. 40a, a spatial light modulator (SLM) 42 on which the light for signal light reflected by the first polarizing prism beam splitter 40a is incident, and a light emitted from the spatial light modulator 42 being a first polarizing prism. The second polarizing prism beam splitter 52, which is transmitted through the beam splitter 40a and is incident through the relay lens 44 and the phase plate 48, and the light transmitted through the second polarizing prism beam splitter 52 passes through the quarter-wave plate 53. And a predetermined polarization direction by being repeatedly reflected between the movable mirror 55 and the movable mirror 55 and the second polarizing prism beam splitter 52. And a second polarizing prism beam splitter 52 the signal light focusing objective lens 45 for irradiating the recording medium 10 as a signal light the light reflected by being polarized. Reference numeral 43 denotes a Nyquist filter which is arranged between, for example, two lenses constituting the relay lens 44.

  The reference light generating optical system is located on the surface side of the recording medium 10 and reflects the light for reference light from the fixed part 21 to change its traveling direction to the same direction as the light for signal light. A first reflection mirror 49a, a second reflection mirror 56 that reflects the light for reference light from the first reflection mirror 49a and makes it incident on the reference light focusing objective lens 47, and a spherical surface for the light for reference light. A reference light focusing objective lens 47 for converting the wave into a wave and irradiating the recording medium 10 as spherical reference light.

  The reproduction light detecting optical system is located on the back surface (upper surface in FIG. 11B) of the recording medium 10. The reproduction light from the hologram recorded on the recording medium 10 and the imaging element 41 composed of, for example, a CCD. And a condensing lens 46 for reproduction light, which condenses the light and makes it incident on the image pickup device 41.

The movable section 23 is movable in a plane (plane along the surface of the recording medium 10) including a moving direction of the movable section 23 and a direction in which an optical path L1a extending from the spatial light modulator 42 to the movable mirror 55 extends. It has a secondary movable section 50 that is movable in a direction perpendicular to the direction of movement of the 23.
The secondary movable section 50 includes a second polarizing prism beam splitter 52, a quarter-wave plate 53, a movable mirror 55, and a signal light condensing objective lens 45 constituting a signal light generating optical system, and a reference light generating objective lens 45. The optical system includes a second reflection mirror 56 and a reference light focusing objective lens 47 that form an optical system, and an image pickup device 41 and a reproduction light focusing lens 46 that form a reproduction light detection optical system.
The movable mirror 55 is arranged variably in the moving direction of the secondary movable unit 50, and the position of the movable mirror 55 is moved in the moving direction of the secondary movable unit 50 with the movement of the secondary movable unit 50. Thus, the optical path length between the signal light focusing objective lens 45 and the relay lens 44 (specifically, the emission side lens 44a constituting the relay lens 44) is kept constant.

The third hologram recording / reproducing apparatus moves the entire movable section 23 of the optical mechanism relatively in one direction along the surface of the recording medium 10 and moves only the secondary movable section 50 in the moving direction of the entire movable section 23. It has an optical mechanism moving mechanism for moving in an orthogonal direction. The optical mechanism moving mechanism can be constituted by, for example, a two-axis stage.
The third hologram recording / reproducing apparatus rotates the recording medium 10 about a rotation center axis extending perpendicularly to the surface of the recording medium 10 passing through the center position (shape center position). The moving mechanism 15 is provided.

In the third hologram recording / reproducing apparatus, the laser light emitted from the recording / reproducing light source 31 is split by the light separating means 32 into light for signal light and light for reference light.
The reference light is emitted from the fixed part 21 after the polarization plane is rotated by 90 ° by the half-wave plate 38, and then converted into a spherical wave by the reference light converging objective lens 47 in the movable part 23, and the spherical light is converted into a spherical wave. The recording medium 10 is irradiated as reference light.
On the other hand, the light for signal light is expanded by the beam expander 51 and emitted from the fixed part 21, and then reflected by the first polarizing prism beam splitter 40 a in the movable part 23 to be converted into a spatial light modulator (SLM) 42. Is irradiated. The spatial light modulator (SLM) 42 modulates the signal light into a data pattern whose polarization plane has been changed by 90 °. The light for signal light emitted from the spatial light modulator (SLM) 42 is transmitted through the first polarizing prism beam splitter 40a because the polarization plane is rotated by 90 °. The light transmitted through the first polarizing prism beam splitter 40a is incident on the phase plate 48 via the relay lens 44. At this time, the spatial frequency band of the signal light is adjusted by the Nyquist filter 43. The phase plate 48 has a random phase pattern, and has a function of suppressing unnecessary DC components in the spatial frequency distribution and modulating the consumption of monomers by modulating the signal light with a random phase. The light transmitted through the phase plate 48 is transmitted through the second polarizing prism beam splitter 52 and is incident on the movable mirror 55 via the quarter-wave plate 53. The light whose polarization plane has been changed to a predetermined direction by reciprocating the optical path between the polarizing prism beam splitter 52 and the movable mirror 55 a plurality of times (two reciprocations in this example) is reflected by the second polarizing prism beam splitter 52. Then, the light is incident on the signal light focusing objective lens 45, is focused by the signal light focusing objective lens 45, and is irradiated on the recording medium 10 as signal light.
By irradiating the recording medium 10 with the signal light and the spherical reference light, interference fringes between the signal light and the spherical reference light are formed on the recording medium 10, and the interference fringes are formed as a hologram carrying data information. Recorded at 10.

  Then, the entire movable section 23 of the optical mechanism is moved in the radial direction of the recording medium 10 by the optical mechanism moving mechanism, and the shift multiplexed hologram train is recorded by performing the spherical reference light shift multiplexed recording. Thereafter, the hologram is recorded by rotating the recording medium 10 at a predetermined rotation angle by the recording medium rotating mechanism 15 and moving the recording medium 10 in a plane along the surface thereof by the recording medium moving mechanism. The position of the recording area to be recorded is aligned. In this state, by performing the spherical reference beam shift multiplex recording, the new shift multiplex hologram sequence is multiplex-recorded in a state where at least a part of the recording region overlaps with the recording region of the shift multiplex hologram sequence that has already been recorded.

In the third hologram recording / reproducing apparatus, the spherical reference light shift multiplex recording on the recording medium 10 is performed by moving the movable section 23. Access to each unit recording area (book) in the recording medium 10 is performed by rotation (rotation) of the recording medium 10 in addition to access by movement of the entire movable section 23 and movement of only the secondary movable section 50. Will be
Thus, in the hologram recording / reproducing apparatus, in order to form a Fourier transform hologram, the distance (optical path length) between the signal light focusing objective lens 45 and the relay lens 44 (specifically, the emission side lens 44a) is increased. It must always be kept at a certain distance. However, in the above-mentioned third hologram recording / reproducing apparatus, the light from the relay lens 44 (specifically, the emission-side lens 44a) passes through the plurality of optical paths L1b from the second polarizing prism beam splitter 52 to the movable mirror 55. It is configured to be changed to a predetermined polarization direction by being reciprocated once and to enter the signal light focusing objective lens 45, and the movable mirror 55 is provided variably in the movement direction of the secondary movable unit 50. ing. Therefore, by moving the movable mirror 55 in conjunction with the movement of the secondary movable section 50, the distance between the signal light focusing objective lens 45 and the relay lens 44 can be adjusted to always maintain a constant distance.
As described above, in the third hologram recording / reproducing apparatus, the traveling direction of the light from the fixed portion 21 with respect to the recording medium 10 (the vertical direction in FIG. 11A) and the direction perpendicular to the traveling direction of the light (FIG. 11 (a) in the left-right direction).
In FIG. 11A, the movable direction of the movable portion 23 is indicated by a double arrow, and in FIG. 11B, the movable direction of the secondary movable portion 50 is indicated by a double arrow.

  In the third hologram recording / reproducing apparatus, at the time of reproducing the data information on the hologram recorded on the recording medium 10, the recording medium 10 is irradiated only with the spherical reference light for reproduction whose light quantity is greatly reduced. As a result, reproduction light is emitted from the hologram recorded under the same reference light irradiation conditions as the spherical reference light for reproduction, and when the reproduction light is detected by the image sensor 41, the data information recorded on the hologram is obtained. Is played.

According to the hologram recording / reproducing apparatus of the present invention described above, it is possible to increase the density of the information recorded on the recording medium, and record the information by uniaxial movement by the recording medium moving mechanism and rotation by the recording medium rotating mechanism. Since the unit recording area (book) in the medium is accessed, the position of the recording medium can be easily adjusted when performing the shift multiplex recording, and the speed can be increased.
In particular, in the third hologram recording / reproducing device, two-dimensional access to the recording medium of the optical mechanism becomes possible, and hologram recording and reproduction can be performed efficiently.

  Hereinafter, a hologram reproducing apparatus for performing a hologram recording / reproducing method of performing cross-shift multiplex recording on a plurality of multi-multiplex hologram rows in a state where recording regions of the respective multi-multiplex hologram rows overlap with each other will be described. . As described above, the multi-multiplex hologram sequence is obtained by multiplex-recording a plurality of shift multiplex hologram sequences obtained by the spherical reference beam shift multiplex recording in the same area.

FIG. 12 is an explanatory diagram showing a configuration of an optical mechanism in still another example of the hologram recording / reproducing apparatus of the present invention.
The optical mechanism in the hologram recording / reproducing apparatus includes a recording / reproducing light source, light separating means for dividing light from the recording / reproducing light source into light for signal light and light for reference light, and converting the light for signal light into data information. An optical system for generating a signal light that irradiates the recording medium 10 as a signal light carrying the same, and an optical system for generating a spherical reference light that converts the light for the reference light into a spherical wave and irradiates the recording medium 10 as the spherical reference light It has.

  The optical mechanism preferably includes a fixed part 21 and a movable part 23 driven relatively to the fixed part 21, and it is preferable that only the movable part 23 is configured to be moved by the optical mechanism moving mechanism.

  The fixing unit 21 is, for example, a recording / reproducing light source 31 composed of a blue laser light source, and light (laser light) from the recording / reproducing light source 31 is incident via a shutter 33, a polarizing plate 34, and a beam shaping lens 35. And a light separating means 32 composed of a prism beam splitter (PBS). The light for signal light and the light for reference light are emitted from the fixed part 21 in the same direction, and are incident on the movable part 23 without intersecting with each other. Specifically, the light for signal light from the light separating unit 32 is emitted from the fixed unit 21 via the beam expander 51. Further, the light for reference light that travels in a direction different from the light for signal light from the light separating means 32 enters the reflection mirror 39 via the ND filter 37 and the half-wave plate 38, and is reflected by the reflection mirror 39. As a result, the traveling direction is changed to the same direction as the signal light, and the light is emitted from the fixed portion 21. That is, an optical path L1 for signal light and an optical path L2 for reference light are formed between the fixed part 21 and the movable part 23 so that their optical axes extend in parallel with each other.

  The movable unit 23 includes an optical system for generating a signal light, an optical system for generating a spherical reference light, and an optical system for detecting a reproduction light. The movable unit 23 enters the movable unit 23 from the fixed unit 21 by the optical mechanism moving mechanism. Are moved in the optical axis direction of the signal light and the reference light. In FIG. 12, the movable direction of the movable portion 23 is indicated by a white double arrow.

  The optical system for generating signal light is located on the surface side of the recording medium 10, and is reflected by the polarizing prism beam splitter 40 to which the light for signal light from the fixing unit 21 is incident and the polarizing prism beam splitter 40. A spatial light modulator (SLM) 42 into which light for signal light is incident, and light from the spatial light modulator 42 passes through the polarizing prism beam splitter 40 and enters through a relay lens 44 and a phase plate 48. A signal light focusing objective lens 45. Reference numeral 43 denotes a Nyquist filter which is arranged between, for example, two lenses constituting the relay lens 44.

  The reference light generating optical system is located on the surface side of the recording medium 10, and converts a plurality of reference light beams into spherical waves and irradiates the recording medium 10 with the reference light as spherical reference light. A lens and an optical path switching unit for guiding the light for reference light from the fixing unit 21 to one selected reference light focusing objective lens are provided.

  It is preferable that the plurality of reference light converging objective lenses are arranged such that their optical axes extend in directions different from each other with respect to the optical axis of the signal light incident on the recording medium 10. As shown in FIG. 12, when the reference light generating optical system is configured to include, for example, two reference light collecting objective lenses 47a and 47b, each of the reference light collecting objective lenses 47a. , 47b are located on both sides of the optical axis of the signal light with respect to the recording medium 10 in a virtual plane including the moving direction of the optical mechanism (indicated by a solid double-headed arrow in FIG. 12) and the incident direction of the signal light. Preferably, they are arranged. By arranging the two reference light focusing objective lenses 47a and 47b in such a positional relationship, it is possible to reliably avoid the occurrence of crosstalk during reproduction of the hologram.

  The optical path switching means is constituted by, for example, an optical path switching mirror 60 which is arranged so as to be insertable into and removable from the optical path of the light for reference light incident from the fixed part 21. In this example, in a state where the optical path switching mirror 60 is inserted on the optical path, the light for the reference light is reflected by the optical path switching mirror 60 and further reflected by the first reflection mirror 61a to perform the first reference. The light is incident on the light focusing objective lens 47a. On the other hand, when the optical path switching mirror 60 is retracted, the light for the reference light is reflected by the second reflection mirror 61b and is incident on the second reference light focusing objective lens 47b.

  The reproduction light detection optical system is located on the back surface side of the recording medium 10, and condenses reproduction light from a hologram recorded on the recording medium 10 to the image pickup element 41 by, for example, a CCD. And a reproducing light condensing lens 46 for incidence.

In the hologram recording / reproducing apparatus of this example, the laser light emitted from the recording / reproducing light source 31 is split by the light separating means 32 into light for signal light and light for reference light.
The reference light is emitted from the fixed part 21 after the polarization plane is rotated by 90 ° by the half-wave plate 38. The light for the reference light from the fixing unit 21 is reflected by, for example, the optical path switching mirror 60 and is incident on the first reference light focusing objective lens 47a via the first reflection mirror 61a. As a result, the reference light is converted into a spherical wave by the first reference light condensing objective lens 47a and applied to the recording medium 10 as spherical reference light.
On the other hand, the signal light is expanded by the beam expander 51, reflected by the polarizing prism beam splitter 40, and irradiated to the spatial light modulator (SLM) 42. The spatial light modulator (SLM) 42 modulates the signal light into a data pattern whose polarization plane has been changed by 90 °. The light for signal light emitted from the spatial light modulator (SLM) 42 is transmitted through the polarizing prism beam splitter 40 because the polarization plane is rotated by 90 °. The signal light from the polarizing prism beam splitter 40 passes through the phase plate 48 after the spatial frequency band is adjusted by the Nyquist filter 43. The phase plate 48 has a random phase pattern, and has a function of suppressing unnecessary DC components in the spatial frequency distribution and modulating the consumption of monomers by modulating the signal light with a random phase. The signal light generated by transmitting the signal light through the phase plate 48 is condensed by the signal light converging objective lens 45 and irradiated on the recording medium 10.
By irradiating the recording medium 10 with the signal light and the spherical reference light, interference fringes between the signal light and the spherical reference light are formed on the recording medium 10, and the interference fringes are formed as a hologram carrying data information. Recorded at 10.

Then, the movable part 23 in the optical mechanism is moved in the radial direction of the recording medium 10 by the optical mechanism moving mechanism to perform the spherical reference light shift multiplex recording, thereby recording the primary shift multiplex hologram sequence. Next, the optical path switching mirror 60 is retracted to switch the optical path of the light for reference light, that is, the light for reference light is reflected by the second reflection mirror 61b and the second reference light focusing objective lens. In the state where the light is incident on 47b, the spherical reference light is applied to the same area as the recording area where the primary shift multiplexed hologram array is recorded from a different incident direction from the spherical reference light used for recording the primary shift multiplexed hologram array. Irradiation performs spherical reference beam shift multiplex recording. As a result, a new shift multiplexed hologram sequence is multiplex-recorded in the same region as the primary shift multiplexed hologram sequence, thereby obtaining a multi-hologram sequence.
Thereafter, the hologram should be recorded by rotating the recording medium 10 at a predetermined rotation angle by the recording medium rotating mechanism and moving the recording medium 10 in a plane along the surface by the recording medium moving mechanism. Position the recording area. In this state, by performing the spherical reference light shift multiplex recording to obtain the above-described multi-hologram array, the new multi-hologram array is overlapped with the recording area of the multi-hologram array in which at least a part of the recording area has already been recorded. Multiple recording is performed.
The hologram recording / reproducing apparatus includes a recording medium rotating mechanism for rotating (rotating) the recording medium 10 in a plane along its surface, and a recording medium moving mechanism for moving the recording medium 10 in a plane along its surface. The unit recording area (book) is accessed by biaxial movement and rotation (rotation) of the recording medium 10 in addition to access by movement of the optical mechanism.

  At the time of reproducing the data information related to the hologram recorded on the recording medium 10, the recording medium 10 is irradiated with the first spherical reference light for reproduction or the second spherical reference light for reproduction, the light amount of which is greatly reduced. . As a result, reproduction light is emitted from the hologram recorded under the same reference light irradiation conditions as the spherical reference light for reproduction, and the reproduction light is detected by the image pickup device (specifically, for example, a CCD) 41. The data information recorded on the hologram is reproduced.

FIG. 13 is an explanatory diagram showing a configuration of an optical mechanism in still another example of the hologram recording / reproducing apparatus of the present invention.
This hologram recording / reproducing apparatus uses a spherical surface having a polarization direction different from that of the spherical reference light used for recording the primary shift multiplexed hologram sequence in the same region as the recording region of the primary shift multiplexed hologram sequence already recorded on the recording medium. By irradiating reference light, a new shift multiplexed hologram sequence is multiplex-recorded to obtain a multi-hologram sequence.
The optical mechanism in this example has the same configuration as the optical mechanism shown in FIG. 12 except that the configuration of an optical system for generating reference light constituting the movable section 23 is different. The same components as those of the optical mechanism shown in FIG. 12 are denoted by the same reference numerals, and description thereof will be omitted.

  The reference light generating optical system in this example includes a reference light converging objective lens 47 that converts the light for reference light into a spherical wave, and a reflection that causes the light for reference light to enter the reference light converging objective lens 47. The mirror 49 includes a mirror 49 and a polarization unit 63 that adjusts the polarization direction of the reference light incident on the reference light focusing objective lens 47. The polarizing means 63 can be composed of, for example, a half-wave plate. Even if the polarizing means 63 is configured such that it can be inserted into and removed from the optical path of the reference light incident from the fixed part 21 to the reference light focusing objective lens 47, the polarizing means 63 It may be configured to be rotatably provided on the optical path leading to the objective lens 47.

In the hologram recording / reproducing apparatus of this example, an interference fringe between the signal light and the spherical reference light having a predetermined polarization direction is recorded on the recording medium 10 as a hologram carrying data information. Then, the movable part 23 in the optical mechanism is moved in the radial direction of the recording medium 10 by the optical mechanism moving mechanism to perform the spherical reference light shift multiplex recording, thereby recording the primary shift multiplex hologram sequence.
Next, in the same area as the recording area where the primary shift multiplexed hologram sequence is recorded, the polarization means 63 sets the polarization direction different from the spherical reference light (for example, p-polarized light) used for recording the primary shift multiplexed hologram sequence. The adjusted spherical reference light (for example, s-polarized light) is irradiated, and the spherical reference light shift multiplex recording is performed. As a result, a new shift multiplexed hologram sequence is multiplex-recorded in the same region as the recording region in which the primary shift multiplexed hologram sequence is recorded, whereby a multi-hologram sequence is obtained.
After that, while the recording medium 10 is rotated at a predetermined rotation angle by the recording medium rotation mechanism and the recording medium 10 is moved by a recording medium moving mechanism within a plane along the surface thereof, By performing the spherical reference light shift multiplex recording to obtain the above-described multi-hologram row, a new multi-hologram row is multiplex-recorded in a state where at least a part of the recording area overlaps with the recording area of the already recorded multi-hologram row. .
Access to the unit recording area (book) is performed by biaxial movement and rotation (rotation) of the recording medium 10 in addition to access by movement of the optical mechanism.

  At the time of reproducing the data information related to the hologram recorded on the recording medium 10, the light amount is largely reduced, and the polarization direction is adjusted by the reproduction spherical reference light whose polarization direction is adjusted by the polarization means 63 or the polarization means 63. The recording medium 10 is irradiated with a spherical reference beam for reproduction. As a result, reproduction light is emitted from the hologram recorded under the same reference light irradiation conditions as the spherical reference light for reproduction, and the reproduction light is detected by the image pickup device (specifically, for example, a CCD) 41. The data information recorded on the hologram is reproduced.

FIG. 14 is an explanatory diagram showing a configuration of an optical mechanism in still another example of the hologram recording / reproducing apparatus of the present invention.
The optical mechanism in the hologram recording / reproducing apparatus includes: a recording / reproducing light source; a plurality of light separating means for temporally dividing light from the recording / reproducing light source into two signal light lights and two reference light lights; A signal light generating optical system for irradiating the recording medium 10 with signal light as signal light carrying data information, and a spherical surface for converting the reference light into a spherical wave and irradiating the recording medium 10 as reference light A reference light generating optical system.

  The optical mechanism preferably includes a fixed part 21 and a movable part 23 driven relatively to the fixed part 21, and it is preferable that only the movable part 23 is configured to be moved by the optical mechanism moving mechanism.

  The fixing unit 21 includes, for example, a recording / reproducing light source 31 composed of a blue laser light source, a first light separating unit 65a that divides laser light incident from the recording / reproducing light source 31 via the shutter 33 and the beam shaping lens 35, and And two light separating means 65b. Each of the first light splitting means 65a and the second light splitting means 65b is composed of, for example, a half mirror prism. In this example, part of the laser light from the recording / reproducing light source 31 reflected by the first light separating means 65a is used as the first signal light. Further, of all the other lights transmitted through the first light separating means 65a, a part of the light reflected by the second light separating means 65b is used as the second signal light, and the second light is used. All other light transmitted through the separation means 65b is used as reference light.

  The two signal light beams and the reference light beam are emitted from the fixed portion 21 in the same direction and are incident on the movable portion 23 without intersecting with each other. Specifically, the light for the first signal light and the light for the second signal light are emitted from the fixed part 21 via the beam expander 51, respectively. The light for reference light that passes through the second light separating means 65b and travels in a direction different from the light for signal light enters the reflection mirror 39 via the ND filter 37 and is reflected by the reflection mirror 39. As a result, the traveling direction is changed to the same direction as the light for the first signal light and the light for the second signal light, and emitted from the fixed portion 21. That is, between the fixed part 21 and the movable part 23, the optical path L1a for the first signal light, the optical path L1b for the second signal light, and the reference light An optical path L2 of light is formed.

  The movable unit 23 includes an optical system for generating a signal light, an optical system for generating a spherical reference light, and an optical system for detecting a reproduction light. The movable unit 23 enters the movable unit 23 from the fixed unit 21 by the optical mechanism moving mechanism. Are moved in the optical axis direction of the signal light and the reference light.

  The signal light generating optical system converts the two signal light separated in time into a first signal light and a second signal light having different polarization directions and carrying different data information. And a second optical system.

  The first optical system includes a first polarizing prism beam splitter 40a to which light for the first signal light (for example, p-polarized light) incident from the fixing unit 21 is incident, and a first polarizing prism beam splitter 40a. The first spatial light modulator (SLM) 42a into which the light for the first signal light reflected by the first spatial light modulator 42a enters, and the light (for example, s-polarized light) from the first spatial light modulator 42a is transmitted to the first spatial light modulator 42a. A third polarizing prism beam splitter 40c transmitted through the polarizing prism beam splitter 40a and incident via the relay lens 44 and the phase plate 48, and a first signal light transmitted through the third polarizing prism beam splitter 40c. An objective lens 45 for condensing signal light into which light (for example, p-polarized light) is incident via the Nyquist filter 43 is provided.

  The second optical system includes a second polarizing prism beam splitter 40b into which light for the second signal light (for example, s-polarized light) from the fixed unit 21 is incident via a polarizing unit 64 made of, for example, a half-wave plate. A second spatial light modulator (SLM) 42b into which the light for the second signal light reflected by the second polarizing prism beam splitter 40b is incident; and light from the second spatial light modulator 42b. A third polarizing prism beam splitter 40c and a third polarizing prism beam splitter 40c (for example, p-polarized light) that pass through the second polarizing prism beam splitter 42b and enter through the relay lens 44 and the phase plate 48. And a signal light converging objective lens 45 into which the second signal light (eg, s-polarized light) reflected through the Nyquist filter 43 is incident. Here, the optical path from the third polarizing prism beam splitter 40c to the signal light focusing objective lens 45 is common to the first optical system and the second optical system. Reference numeral 66 denotes a reflection mirror for causing the light for the second signal light transmitted through the phase plate 48 to enter the third polarizing prism beam splitter 40c.

  The reference light generating optical system includes a third light separating unit 65c that divides the light for reference light from the fixing unit 21 into light for first reference light and light for second reference light, A third optical system including a first reference light converging objective lens 47a for converting the light for reference light into a spherical wave and irradiating the recording medium 10 as spherical reference light; And a fourth optical system including a second reference light converging objective lens 47b for converting the light into a spherical wave and irradiating the recording medium 10 as spherical reference light.

  The first reference light focusing objective lens 47a and the second reference light focusing objective lens 47b are arranged such that their optical axes extend in directions different from each other with respect to the optical axis of the signal light incident on the recording medium 10. ing. More specifically, the first reference light focusing objective lens 47a and the second reference light focusing objective lens 47b have a moving direction of the optical mechanism (indicated by a white double arrow in FIG. 14) and a signal. The signal light is preferably disposed on both sides of the optical axis of the signal light with respect to the recording medium 10 in a virtual plane including the light incident direction. By arranging the two reference light focusing objective lenses 47a and 47b in such a positional relationship, it is possible to reliably avoid the occurrence of crosstalk during reproduction of the hologram.

  The third light separating means 65c is formed of, for example, a half mirror prism, and a part of the light reflected by the third light separating means 65c is used as the first reference light as a first reference light. While being incident on the light objective lens 47a, all other light transmitted through the third light separating means 65c is incident on the second reference light focusing objective lens 47b as light for the second reference light. You. On the optical path from the third light separating means 65c to the second reference light focusing objective lens 47b, for example, a polarizing means 63 composed of a half-wave plate is provided, and the first reference light focusing objective lens 47b is provided. Light for second reference light (for example, s-polarized light) having a different polarization direction from light for first reference light (for example, p-polarized light) incident on the lens 47a is used for condensing the second reference light. The light is incident on the objective lens 47b.

  The reproduction light detecting optical system has a first hologram and a first signal light, which are recorded in the same place on the recording medium 10 and have different polarization directions from the first hologram and the first spherical reference light. The second signal light and the first spherical reference light are polarized light separating means 68 for separating reproduction lights having different polarization directions from each other emitted from each of the second holograms by the second spherical reference light having different polarization directions; A first image pickup device 41a and a second image pickup device 41b into which the reconstructed light of the first hologram and the reconstructed light of the second hologram separated by the polarization separating means 68 are respectively provided. The first imaging device 41a and the second imaging device 41b are configured by, for example, CCDs. Reference numeral 46 denotes a reproducing light condensing lens for condensing the reproducing light and making it incident on the polarization splitting means.

  In the hologram recording / reproducing apparatus of this example, the light for the first signal light from the fixed part 21 is incident on a first spatial light modulator (SLM) 42a and is modulated into a data pattern. The first signal light emitted from the first spatial light modulator (SLM) 42a is incident on the Nyquist filter 43 via the phase plate 48 and the third polarizing prism beam splitter 40c. Then, the first signal light having a predetermined polarization direction, which is generated by adjusting the spatial frequency band by the Nyquist filter 43, is condensed by the signal light converging objective lens 45 and is irradiated on the recording medium 10. You. Further, the light for the second signal light from the fixing unit 21 is incident on the second spatial light modulator (SLM) 42b via the polarization means 64, and is mutually separated from the light for the first signal light. Modulated into different data patterns. The second signal light emitted from the second spatial light modulator (SLM) 42b enters the Nyquist filter 43 via the phase plate 48 and the third polarizing prism beam splitter 40c. Then, the second signal light having a polarization direction different from that of the first signal light generated by adjusting the spatial frequency band by the Nyquist filter 43 is condensed by the signal light condensing objective lens 45 and recorded. The medium 10 is irradiated.

  On the other hand, the first reference light beam separated by the third light separating means 65c from the reference light beam incident from the fixed portion 21 is spherically shaped by the first reference light focusing objective lens 47a. After being converted into a wave, the recording medium 10 is irradiated as the first spherical reference light having the same polarization direction as the first signal light. Further, the second light for reference light separated by the third light separating means 65c from the light for reference light incident from the fixing part 21 is supplied to the second light collecting means via the polarizing means 63. The light enters the objective lens 47b. The light for the second reference light is converted into a spherical wave by the second reference light focusing objective lens 47b, and is polarized in the same polarization direction as the second signal light, that is, the first spherical reference light. The recording medium 10 is irradiated as a second spherical reference light having a different direction from an incident direction different from that of the first spherical reference light.

  As described above, the recording medium 10 is irradiated with two signal lights having different polarization directions at the same time, and the recording medium 10 is simultaneously irradiated with two spherical reference lights having different polarization directions from different incident directions. In the recording medium 10, interference fringes between the first signal light and the first spherical reference light and interference fringes between the second signal light and the second spherical reference light are formed. Is simultaneously recorded on the recording medium 10 as a hologram carrying the.

Then, the movable section 23 in the optical mechanism is moved in the radial direction of the recording medium 10 by the optical mechanism moving mechanism to perform the spherical reference light shift multiplex recording, whereby the two shift multiplex hologram arrays are multiplex-recorded in the same area. The resulting multi-hologram row is obtained.
Thereafter, the hologram should be recorded by rotating the recording medium 10 at a predetermined rotation angle by the recording medium rotating mechanism and moving the recording medium 10 in a plane along the surface by the recording medium moving mechanism. Position the recording area. In this state, by performing the above-described spherical reference light shift multiplex recording, a new multi-hologram row is multiplex-recorded in a state where at least a part of the recording area overlaps with the recording area of the already recorded multi-hologram row.

  Access to the unit recording area (book) is performed by biaxial movement and rotation (rotation) of the recording medium 10 in addition to access by movement of the optical mechanism.

  At the time of reproducing the data information related to the hologram recorded on the recording medium 10, the recording medium 10 is irradiated with the first spherical reference light for reproduction and the second spherical reference light for reproduction whose light quantity is greatly reduced. Thereby, the reproduction light beams having different polarization directions from the two holograms recorded at the same location under the same reference light irradiation conditions as the first spherical reference light beam for reproduction and the second spherical reference light beam for reproduction. Emitted at the same time. These reproduction lights are separated into reproduction light for one hologram and reproduction light for the other hologram by the polarization separation means 68, and are incident on the first image sensor 41a and the second image sensor 41b, respectively. Then, when the reproduction light is detected by each image sensor (specifically, for example, a CCD) 41, the data information recorded on the two holograms is reproduced in parallel at the same time.

According to the hologram recording / reproducing apparatus as described above, basically, the same effects as those of the hologram recording / reproducing apparatus shown in FIGS. 9 to 11 can be obtained, and the density of recording information on a recording medium can be further increased. Can be achieved.
Further, in particular, according to the hologram recording / reproducing apparatus shown in FIG. 14, two holograms recorded in the same location can be reproduced in parallel at the same time, so that the speed can be further increased.

The recording / reproducing method and the hologram recording / reproducing apparatus of the present invention are not limited to the above embodiment, and various changes can be made.
For example, the recording / reproducing method of the present invention can be implemented by a hologram recording / reproducing device other than the hologram recording / reproducing device of the present invention.
Further, the hologram recording / reproducing apparatus of the present invention can be used for a recording / reproducing method other than the recording / reproducing method of the present invention.

Reference Signs List 1 hologram 1a hologram 1b hologram 6 shift multiplexed hologram sequence 6a shift multiplexed hologram sequence 6b shift multiplexed hologram sequence 7a recording area 7b recording area 10 recording medium 10a disk-shaped medium 10P recording / reproducing portion B unit recording area (book)
B0 Unit recording area (book)
B1 Unit recording area (book)
B2 Unit recording area (book)
B3 Unit recording area (book)
B4 Unit recording area (book)
C Rotation center of recording medium 11 Reflective layer 15 Recording medium rotating mechanism 21 Fixed part 23 Movable part 31 Recording / reproducing light source (blue laser light source)
32 Light separation means (half mirror prism)
Reference Signs List 33 shutter 34 polarizing plate 35 beam shaping lens 36 relay lens 37 ND filter 38 half-wave plate 39 reflecting mirror 40 polarizing prism beam splitter 40a first polarizing prism beam splitter 40b second polarizing prism beam splitter 40c third polarizing prism Beam splitter 41 Image sensor 41a First image sensor 41b Second image sensor 42 Spatial light modulator (SLM)
42a first spatial light modulator 42b second spatial light modulator 43 Nyquist filter 44 relay lens 44a emission side lens 45 signal light focusing objective lens 46 reproduction light focusing lens 47 reference light focusing objective lens 47a First reference light focusing objective lens 47b Second reference light focusing objective lens 48 Phase plate 49 Reflection mirror 49a First reflection mirror 50 Secondary movable section 51 Beam expander 52 Second polarizing prism beam splitter 53 quarter-wave plate 55 movable mirror 56 second reflection mirror 60 optical path switching mirror 61a first reflection mirror 61b second reflection mirror 63 polarizing means 64 polarizing means 65a first light separating means 65b second light separating Means 65c Third light separating means 66 Reflecting mirror 68 Polarized light separating means

Claims (22)

A hologram that records interference fringes between a signal light carrying data information and a reference light as a hologram on a recording medium, and reproduces the data information recorded on the hologram by irradiating the recording medium on which the hologram is recorded with the reference light. In the recording / playback method,
Using a spherical wave as the reference light,
The optical mechanism for irradiating the recording medium with light from the recording / reproducing light source as signal light and reference light is relatively moved in one direction along the surface of the recording medium to perform shift multiplex recording in only one direction on the recording medium. After recording the first shift multiplexed hologram sequence, the recording medium is rotated in a plane including the one direction by an angle φ _B (NA) [rad] or more calculated by the following equation (1). in a state in which in is rotated, by performing a new shift multiple recording, that a second shift multiplexed holograms column part of the recording area multiplex recording in a state overlapping with the recording region of the first shift multiplexed holograms column A hologram recording / reproducing method characterized by the following.

[In the formula (1), m is the order of Bragg null, λ is the wavelength [mm] of light from the recording / reproducing light source, n is the refractive index of the recording medium, L is the thickness [mm] of the recording medium, and ζ (NA) is This is a value represented by Expression (2).
In equation (2), θ _r is the incident angle [rad] of the reference light in the recording medium, d is the radius [mm] of the reference light in the recording medium, and NA is the objective for making the reference light a spherical wave. The numerical aperture of the lens, θ _s, is the incident angle [rad] of the signal light in the medium, and f is the working distance [mm] of the objective lens. ] A hologram that records interference fringes between a signal light carrying data information and a reference light as a hologram on a recording medium, and reproduces the data information recorded on the hologram by irradiating the recording medium on which the hologram is recorded with the reference light. In the recording / playback method,
Using a spherical wave as the reference light,
The optical mechanism for irradiating the recording medium with the signal light and the reference light is relatively moved in one direction along the surface of the recording medium to perform the shift multiplex recording in only one direction on the recording medium, thereby performing the primary shift. After recording the multiplexed hologram sequence, in the same area as the recording area where the primary shifted multiplexed hologram sequence was recorded, the reference light was transmitted from an incident direction different from the reference light used for recording the primary shifted multiplexed hologram sequence. By repeatedly performing a hologram sequence multiplex recording process of irradiating and multiplex-recording a new shift multiplex hologram sequence, after recording a first multi-hologram sequence in which a plurality of shift multiplex hologram sequences are multiplex-recorded in the same area,
By repeatedly performing the hologram array multiplex recording process in a state where the recording medium is rotated in a plane including the one direction, a second multi hologram array in which a plurality of shift multiplex hologram arrays are multiplex-recorded in the same area. A hologram recording / reproducing method, wherein a hologram row is multiplex-recorded in a state where a part of its recording area overlaps with the recording area of the first multi-hologram row . When multiplex-recording a new shift multiplex hologram sequence in the same area as the recording area where the first-order shift multiplex hologram is recorded, a new shift multiplex hologram is recorded in a virtual plane including the moving direction of the optical mechanism and the incident direction of the signal light on the recording medium. And irradiating the reference light along an optical axis whose direction approaching the incident optical axis of the signal light is opposite to the optical axis of the reference light used for recording the primary shift multiplexed hologram array. 3. The hologram recording / reproducing method according to item 2 . A hologram that records interference fringes between a signal light carrying data information and a reference light as a hologram on a recording medium, and reproduces the data information recorded on the hologram by irradiating the recording medium on which the hologram is recorded with the reference light. In the recording / playback method,
Using a spherical wave as the reference light,
The optical mechanism for irradiating the recording medium with the signal light and the reference light is relatively moved in one direction along the surface of the recording medium to perform the shift multiplex recording in only one direction on the recording medium, thereby performing the primary shift. After recording the multiplexed hologram sequence, in the same region as the recording region where the primary shifted multiplexed hologram sequence was recorded, a reference beam having a polarization direction different from that of the reference light used for recording the primary shifted multiplexed hologram sequence is used. By repeatedly performing a hologram sequence multiplex recording process of irradiating and recording a new shift multiplex hologram sequence, after recording a first multi-hologram sequence in which a plurality of shift multiplex hologram sequences are multiplex-recorded in the same area,
By repeatedly performing the hologram array multiplex recording process in a state where the recording medium is rotated in a plane including the one direction, a second multi hologram array in which a plurality of shift multiplex hologram arrays are multiplex-recorded in the same area. A hologram recording / reproducing method, wherein a hologram row is multiplex-recorded in a state where a part of its recording area overlaps with the recording area of the first multi-hologram row . A hologram that records interference fringes between a signal light carrying data information and a reference light as a hologram on a recording medium, and reproduces the data information recorded on the hologram by irradiating the recording medium on which the hologram is recorded with the reference light. In the recording / playback method,
Using a spherical wave as the reference light,
The recording medium is simultaneously irradiated with the first signal light and the second signal light having different polarization directions, and the same as the first reference light and the second signal light having the same polarization direction as the first signal light. Moving the optical mechanism for simultaneously irradiating the recording medium with the second reference light having the polarization direction of different directions along the surface of the recording medium in one direction. By performing only shift multiplex recording, the first shift multiplexed hologram sequence by the first signal light and the first reference light and the second shift multiplexed hologram sequence by the second signal light and the second reference light are formed. A hologram recording / reproducing method characterized by recording a multi-hologram sequence multiplex-recorded in the same area . In a virtual plane including the moving direction of the optical mechanism and the incident direction of the signal light on the recording medium, the direction approaching the incident optical axis of the signal light is opposite to the optical axis of the first reference light. The hologram recording / reproducing method according to claim 5, wherein the second reference light is irradiated along the hologram. After recording the first multi-hologram row in which the first shift multi-hologram row and the second shift multi-hologram row are multiplex-recorded,
By performing a new shift multiplexing recording in a state where the recording medium is rotated in a plane including the one direction, the second shift multiplexing hologram sequence and the fourth shift multiplexing hologram sequence are multiplex-recorded. 7. The hologram recording / reproducing method according to claim 5, wherein the multi-hologram row is multiplex-recorded in a state where a part of the recording area overlaps with the recording area of the first multi-hologram row . The recording area of the recording medium in which the multi-hologram row is recorded is irradiated with the first reference light for reproduction and the second reference light for reproduction having different polarization directions from each other, and the first first light for reproduction is irradiated. Reproducing each of a plurality of holograms recorded at the same location under the same reference light irradiation conditions as the reference light and the second reference light for reproduction, and separating the reproduced light from each hologram by polarization separation means. 8. The hologram recording / reproducing method according to claim 5, wherein data information recorded on each of the plurality of holograms is simultaneously reproduced in parallel . The recording / reproducing area on the surface of the recording medium is divided into a plurality of block units, and a plurality of shift multiplex hologram arrays or a plurality of multi hologram arrays are multiplex-recorded for each block unit. 9. The hologram recording / reproducing method according to any one of 8 . The recording / reproducing area on the surface of the recording medium is divided into a plurality of block units arranged in a circumferential direction around a rotation center axis of the recording medium, and each of the plurality of block units point-symmetric with respect to the rotation center of the recording medium is 9. The hologram recording / reproducing method according to claim 1, wherein a plurality of shift multiplex hologram rows or a plurality of multi hologram rows are continuously multiplex-recorded . The recording / reproducing area on the surface of the recording medium is divided into a plurality of annular block units radially arranged from the rotation center of the recording medium toward the outer peripheral edge, and a plurality of shift multiplexed holograms are formed in the annular block unit on the rotation center side. After multiplex-recording a row or a plurality of multi-hologram rows and fixing them, in a block unit adjacent to the block unit, a plurality of shift-multiplex hologram rows or a plurality of multi-hologram rows are multiplex-recorded and a multiplex-recorded shift-multiplex hologram row or 9. The hologram recording / reproducing method according to claim 1, wherein fixing of the multiplex-recorded multi-hologram sequence is repeatedly performed . A hologram that records interference fringes between a signal light carrying data information and a reference light as a hologram on a recording medium, and reproduces the data information recorded on the hologram by irradiating the recording medium on which the hologram is recorded with the reference light. In a recording / reproducing device,
A recording / reproducing light source, light separating means for dividing light from the recording / reproducing light source into light for signal light and light for reference light, and the light for signal light on a recording medium as signal light carrying data information. An optical mechanism for irradiating a signal light generating optical system, and a spherical reference light generating optical system for converting light for reference light into a spherical wave and irradiating the recording medium as reference light,
An optical mechanism moving mechanism that relatively moves the optical mechanism in one direction along the surface of the recording medium,
A recording medium driving mechanism for rotating and translating the recording medium in a plane including the moving direction of the optical mechanism;
With
A plurality of shift multiplexed hologram rows recorded by moving one of the optical mechanism and the recording medium relative to the other in one direction and performing shift multiplex recording in only one direction on the recording medium are crossed. A hologram recording / reproducing apparatus characterized by being multiplex-recorded in a state where the hologram is recorded. A hologram that records interference fringes between a signal light carrying data information and a reference light as a hologram on a recording medium, and reproduces the data information recorded on the hologram by irradiating the recording medium on which the hologram is recorded with the reference light. In a recording / reproducing device,
A recording / reproducing light source, light separating means for dividing light from the recording / reproducing light source into light for signal light and light for reference light, and the light for signal light on a recording medium as signal light carrying data information. An optical mechanism for irradiating a signal light generating optical system, and a spherical reference light generating optical system for converting light for reference light into a spherical wave and irradiating the recording medium as reference light,
An optical mechanism moving mechanism that relatively moves the optical mechanism in one direction along the surface of the recording medium,
A recording medium driving mechanism that rotates and translates the recording medium in a plane including the moving direction of the optical mechanism ,
The optical mechanism is driven relatively to the fixed unit including the recording / reproducing light source and the light separating unit, and to the fixed unit including the signal light generation optical system and the reference light generation optical system. It comprises a movable part, and the light for signal light and the light for reference light emitted in the same direction from the fixed part are incident on the movable part without intersecting with each other,
A hologram recording / reproducing apparatus , wherein the movable portion is moved by the optical mechanism moving mechanism in an optical axis direction of signal light and reference light incident from the fixed portion to the movable portion . The recording medium is a disk-shaped recording medium or a card-shaped recording medium,
14. The hologram recording / reproducing apparatus according to claim 13, wherein shift multiplex recording in only one direction is performed by moving the movable portion relatively in one direction along the surface of the recording medium . The signal light generating optical system, a spatial light modulator into which light for signal light is incident, and a polarizing beam splitter into which light emitted from the spatial light modulator is incident via a relay lens and a phase plate, The light from the polarizing beam splitter is incident on the movable mirror via a quarter-wave plate, and is repeatedly reflected between the movable mirror and the polarizing beam splitter. A signal light focusing objective lens for irradiating the emitted light to the recording medium as signal light,
The movable part is a secondary movable part movable in a direction perpendicular to the moving direction of the movable part on a plane including a moving direction of the movable part and a direction in which an optical path extending from the spatial light modulator to the movable mirror extends. The secondary movable section includes the polarizing beam splitter, the quarter-wave plate, the movable mirror, and the signal light focusing objective lens, and the movable mirror includes a secondary movable section. It is arranged variably in the moving direction of the part,
The position of the movable mirror is moved in the direction of movement of the secondary movable part with the movement of the secondary movable part, so that the signal light focusing objective lens and the relay constituting the signal light generating optical system 15. The hologram recording / reproducing apparatus according to claim 14, wherein an optical path length between the lens and the lens is kept constant. The spherical reference light generating optical system includes a plurality of reference light condensing objective lenses that convert the light for reference light into spherical waves, and one reference light condensing objective lens that selects the light for reference light. The plurality of reference light converging objective lenses are arranged such that their optical axes extend in mutually different directions with respect to the optical axis incident on the recording medium of the signal light. The hologram recording / reproducing apparatus according to any one of claims 12 to 14, wherein: The spherical reference light generating optical system includes two reference light focusing objective lenses,
Each reference light condensing objective lens is disposed on both sides of an optical axis of the signal light incident on the recording medium in a virtual plane including the moving direction of the optical mechanism and the incident direction of the signal light. The hologram recording / reproducing apparatus according to claim 16, wherein: The spherical reference light generating optical system includes a reference light focusing objective lens that converts the light for reference light into a spherical wave, and a polarization unit that adjusts a polarization direction of the light for reference light. The hologram recording / reproducing apparatus according to any one of claims 12 to 14, wherein: A hologram that records interference fringes between a signal light carrying data information and a reference light as a hologram on a recording medium, and reproduces the data information recorded on the hologram by irradiating the recording medium on which the hologram is recorded with the reference light. In a recording / reproducing device,
A recording / reproducing light source, a plurality of light separating means for temporally dividing light from the recording / reproducing light source into two signal light lights and two reference light lights, a signal light generating optical system, and a spherical surface. An optical mechanism including a reference light generation optical system,
A moving mechanism for relatively moving the optical mechanism in one direction along the surface of the recording medium;
With
The signal light generating optical system converts the two signal light beams separated in time into a first signal light and a second signal light having different polarization directions and carrying different data information. A first optical system and a second optical system,
The spherical reference light generating optical system includes a reference light focusing objective lens that converts the reference light into a spherical wave, and converts one reference light into the same polarization direction as the first signal light. A third optical system for converting the reference light into a first reference light, and a reference light converging objective lens for converting the reference light into a spherical wave. And a fourth optical system that converts the light into a second reference light having the same polarization direction as the light. The two reference light condensing objective lenses each have an optical axis having an optical axis incident on the recording medium of the signal light. A hologram recording / reproducing apparatus , wherein the hologram recording / reproducing apparatus is arranged so as to extend in directions different from each other . The two reference light focusing objective lenses are disposed on both sides of an axis perpendicular to the surface of the recording medium in a virtual plane including the moving direction of the optical mechanism and the incident direction of the signal light. 20. The hologram recording / reproducing apparatus according to claim 19, wherein: It has a reproduction light detection optical system equipped with polarization separation means,
Simultaneously irradiating the reproduction first reference light and the reproduction second reference light having different polarization directions, the same as the reproduction first reference light and the reproduction second reference light The reproduction light emitted from each of the plurality of holograms recorded at the same location under the reference light irradiation condition is separated by the polarization separation means, and the data information recorded on each of the plurality of holograms is simultaneously reproduced in parallel. The hologram recording / reproducing apparatus according to claim 19 or 20, wherein: 22. The hologram recording / reproducing apparatus according to claim 19, further comprising a recording medium driving mechanism for rotating and translating the recording medium in a plane including the moving direction of the optical mechanism. .

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