JP2017162524A - Hologram recording reproduction device and hologram recording reproduction method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hologram recording reproduction device and a hologram recording reproduction method in which a spherical reference light shift multiple recording method is employed, and which allows high speed recording reproduction.SOLUTION: A hologram recording reproduction device comprises reference light radiation position displacement means, in which a spherical reference light radiation optical system for radiating a spherical reference light to the recording medium slightly displaces a position of a radiation area of a spherical reference light in the recording medium. In a resting state of the recording medium, by the reference light radiation position displacement means, a position of the radiation area of the spherical reference light is shifted in one direction to a position of the radiation area, in performing shift multiple recording, so that a shift multiple hologram row, in which the plural holograms are arranged in one direction in a state in which parts of recording areas of the plural holograms are overlapped, is recorded.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a hologram recording / reproducing apparatus and a hologram recording / reproducing method. More particularly, the present invention relates to a hologram recording / reproducing apparatus and a hologram recording / reproducing method capable of performing high-speed recording / reproducing when a large-capacity optical memory is configured by multiplexly recording a two-dimensional digital bit pattern as a hologram on a recording medium.

  2. Description of the Related Art Conventionally, hologram recording / reproducing apparatuses that record and reproduce digital information two-dimensionally using holograms have been proposed. In a hologram recording / reproducing apparatus, signal light carrying digital information (data information) modulated by a spatial light modulator composed of a plurality of pixels and the signal light and coherent reference light interfere with each other in a recording medium. The resulting interference fringes are recorded as a hologram. Also, when reproducing a hologram recorded on a recording medium, a digital beam recorded as a hologram on a CCD (imaging device) is generated by diffracting light by irradiating the hologram with reference light used for recording. An image of information is formed.

  As one of such hologram recording / reproducing methods, for example, a spherical reference light shift multiplex recording method using a spherical wave (hereinafter also referred to as “spherical reference light”) as reference light is known (for example, Patent Documents). 1).

The principle of spherical reference light shift multiplex recording will be described with reference to FIG. 9. The spherical reference light is considered to have a plurality of plane waves. Accordingly, as shown in FIG. 9A, the recording medium 10 on which the hologram 1 is recorded is placed in one direction (the right side in FIG. 9A) along the surface of the recording medium 10 (the upper surface in FIG. 9A). When a slight distance shift is made in the direction), the already recorded hologram 1 cannot be reproduced, 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. 9B, the reproducible condition is when the wave number vector ks of the signal light, the wave number vector kr of the reference light, and the wave number vector (lattice vector) kg of the hologram satisfy the Bragg diffraction condition. When the recording medium 10 is shifted, as shown in FIG. 9C, the relationship between the wave vectors deviates from the Bragg diffraction condition, and the hologram 1 cannot be reproduced.
Here, FIG. 9B shows the wave number vector ks of the signal light, the wave number vector kr of the reference light, and the wave number vector (lattice vector) kg of the hologram in the region α surrounded by the one-dot broken line in FIG. It is explanatory drawing which shows a relationship. FIG. 9C shows the relationship among the wave number vector ks of the signal light, the wave number vector kr of the reference light, and the wave number vector (lattice vector) kg of the hologram in a region β surrounded by a broken line in FIG. It is explanatory drawing shown.

  In this way, in spherical reference beam shift multiplex recording, by using a spherical wave as the reference beam, a hologram that has already been recorded cannot be reproduced just by shifting the recording medium by a slight distance, and a new hologram is recorded. This makes it possible to repeat shift multiplex recording.

JP 2014-098797 A

Thus, as a technique for controlling the relative position between a light beam (signal light and reference light) and a recording medium in a conventional hologram recording / reproducing apparatus, for example, an optical mechanism that irradiates signal light and reference light does not move, and recording is performed. A method of performing access by biaxial movement and rotation of the medium is employed. In this method, the irradiation position of the signal light from the optical mechanism and the reference light on the recording medium is fixed, the recording medium is moved and then stopped, a hologram is formed in this state, and the recording medium is moved again. The process of stopping and forming a new hologram is repeated (stop-and-go method).
However, since the data transfer speed at the time of recording and reproducing the hologram is limited by the speed of the mechanical mechanism that moves the recording medium, the high-speed access is hindered and the high-speed access performance as a memory device is greatly limited. There is a problem. Specifically, in a stop-and-go operation by a normal mechanical mechanism, for example, a stationary time of about 100 ms is required, and there are about 10 holograms that can be recorded and reproduced per second.

  The present invention has been made based on the above circumstances, and is a hologram recording that enables high-speed recording / reproducing in a hologram recording / reproducing apparatus and hologram recording / reproducing method adopting a spherical reference light shift multiplex recording method. An object is to provide a reproducing apparatus and a hologram recording / reproducing method.

The hologram recording / reproducing apparatus of the present invention records interference fringes between signal light carrying data information and reference light on a recording medium as a hologram, and irradiates the recording medium on which the hologram is recorded with reference light on the hologram. In a hologram recording / reproducing apparatus for reproducing recorded data information,
An optical mechanism comprising a signal light irradiation optical system for irradiating the recording medium with signal light and a spherical reference light irradiation optical system for irradiating the recording medium with spherical reference light;
The spherical reference light irradiation optical system includes a reference light irradiation position displacement unit that minutely displaces the position of the irradiation area of the spherical reference light on the recording medium,
In a state where the recording medium is stationary, the position of the irradiation area of the spherical reference light is shifted in one direction with respect to the position of the irradiation area of the signal light by the reference light irradiation position displacing means, and shift multiplex recording is performed. Thus, the shift multiplex hologram sequence arranged in the one direction is recorded in a state in which a plurality of holograms partially overlap each other in the recording area.

In the hologram recording / reproducing apparatus of the present invention, the half-value width of the spherical reference light applied to the recording medium is larger than the half-value width of the signal light,
The reference light irradiation position displacing means preferably shifts the position of the irradiation area of the spherical reference light within a range in which the irradiation area of the signal light is included in the irradiation area of the spherical reference light.

In the hologram recording / reproducing apparatus of the present invention, the signal light irradiation optical system includes signal light irradiation position displacement means for minutely displacing the position of the signal light irradiation area on the recording medium,
By means of the signal light irradiation position displacement means, the position of the signal light irradiation area on the recording medium is shifted in the one direction with respect to the position of the signal light irradiation area at the time of recording the shift multiplex hologram sequence already recorded on the recording medium. In this state, the position of the irradiation area of the spherical reference light is shifted in the one direction by the reference light irradiation position displacing means, and shift multiplex recording is performed, so that a new shift multiplex hologram sequence is recorded in the recording area. It is preferable that the recording is performed so that a part thereof overlaps the recording area of the already recorded shift multiplexed hologram sequence.

Furthermore, the hologram recording / reproducing apparatus of the present invention includes a moving mechanism for moving one of the optical mechanism and the recording medium relative to the other in the one direction,
In the state where the position of the irradiation area of the signal light is moved relative to the position of the irradiation area of the signal light at the time of recording of the shift multiplex hologram sequence already formed on the recording medium by the moving mechanism, the reference The position of the irradiation area of the spherical reference light is shifted by the light irradiation position displacing means, and shift multiplex recording is performed, so that a new shift multiplex hologram sequence is a shift multiplex hologram in which a part of the recording area is already recorded. It is preferable that the recording is performed so as to overlap the recording area of the row.

  Furthermore, in the hologram recording / reproducing apparatus of the present invention, the reference light irradiation position displacement means relatively shifts the position of the irradiation area of the spherical reference light, or any of the reference light irradiation position displacement means and the moving mechanism. The configuration in which each hologram constituting the shift multiplexed hologram sequence recorded on the recording medium is reproduced by moving the position of the irradiation area of the spherical reference light relative to the recording medium by one or both of them. It is preferable that

  Furthermore, in the hologram recording / reproducing apparatus of the present invention, it is preferable that the reference light irradiation position displacing means is composed of a scanning mirror device or an acousto-optic element.

The hologram recording / reproducing method of the present invention records interference fringes between signal light carrying data information and reference light as a hologram on a recording medium, and irradiates the hologram with reference light on the recording medium on which the hologram is recorded. In a hologram recording / reproducing method for reproducing recorded data information,
A spherical wave is used as reference light,
Shift multiplex recording is performed by shifting the position of the reference light irradiation area in one direction with respect to the position of the signal light irradiation area on the recording medium by the reference light irradiation position displacement means while the recording medium is stationary. Thus, the shift multiplex hologram sequence arranged in the one direction is recorded in a state where a plurality of holograms partially overlap each other in the recording area.

In the hologram recording / reproducing method of the present invention, the recording medium is irradiated with reference light having a half-value width larger than the signal light,
It is preferable to shift the position of the reference light irradiation region within a range in which the signal light irradiation region is included in the reference light irradiation region.

  In the hologram recording / reproducing method of the present invention, the position of the signal light irradiation area on the recording medium is changed by the signal light irradiation position displacing means to the position of the signal light irradiation area at the time of recording the shift multiplex hologram sequence already recorded on the recording medium. In a state where the position is shifted in one direction with respect to the position, the reference light irradiation position displacement means shifts the position of the reference light irradiation area in the one direction to perform shift multiplex recording, whereby a new shift multiplex hologram is obtained. It is preferable to record the column in a state where a part of the recording region overlaps the recording region of the already recorded shift multiplexed hologram sequence.

  In the hologram recording / reproducing method of the present invention, one of the optical mechanism for irradiating the recording medium with the signal light and the reference light and the recording medium is moved in the one direction relative to the other by the moving mechanism. Thus, the reference light irradiation area is shifted by the reference light irradiation position displacing means in the state where the irradiation position of the signal light is shifted with respect to the irradiation position of the signal light at the time of recording the shift multiplexed hologram sequence already recorded on the recording medium. Is shifted in the one direction to perform shift multiplex recording, whereby a new shift multiplex hologram sequence is recorded in a state where a part of the recording region overlaps the recording region of the already recorded shift multiplex hologram sequence. It is preferable.

  Furthermore, in the hologram recording / reproducing method of the present invention, the reference light irradiation position displacement means shifts the position of the reference light irradiation area with respect to the recording medium, or the reference light irradiation position displacement means and the reference light irradiation position displacement means It is preferable to reproduce the respective holograms constituting the shift multiplexed hologram sequence recorded on the recording medium by shifting the position of the reference light irradiation region with respect to the recording medium by either one or both of the moving mechanisms.

  In the hologram recording / reproducing apparatus of the present invention, the reference light irradiation position displacing means is driven to change the relative position between the irradiation position of the spherical reference light and the recording position on the recording medium, thereby performing the spherical reference light shift multiplex recording. Is called. The time required for shifting the position of the irradiation area of the spherical reference light by the reference light irradiation position displacing means is extremely short compared to the stationary time in the stop-and-go operation of the moving mechanism for moving or rotating the recording medium. According to the hologram recording / reproducing apparatus of the present invention and the hologram recording / reproducing method of the present invention, the hologram can be recorded and reproduced at high speed. In addition, since only the reference light irradiation position displacing means needs to be driven, the relative position of the spherical reference light irradiation position on the recording medium with respect to the signal light irradiation position can be reliably controlled by a simple mechanism. .

It is explanatory drawing which shows schematically the structure of the hologram recording / reproducing apparatus of this invention. It is explanatory drawing which shows the outline | summary of the spherical reference light shift multiplex recording in the hologram recording / reproducing apparatus of this invention. It is the schematic explaining the function of the reference light irradiation position displacement means by a scanning mirror device. It is the schematic for description which shows the principal part structure in an example of the hologram recording / reproducing apparatus of this invention. It is the explanatory schematic which shows the principal part structure in the other example of the hologram recording / reproducing apparatus of this invention. It is the schematic for description which shows the principal part structure in the further another example of the hologram recording / reproducing apparatus of this invention. It is the schematic explaining the function of the reference light irradiation position displacement means by an acousto-optic device. It is explanatory drawing which shows the outline | summary of the spherical reference light shift multiplex recording in the hologram recording / reproducing apparatus shown in FIG. It is explanatory drawing which shows the outline | summary of the spherical reference light shift multiplex recording in the past.

  Hereinafter, embodiments of the present invention will be described in detail.

  The hologram recording / reproducing apparatus of the present invention performs multiplex recording of holograms by the spherical reference light shift multiplex recording method, and the position of the irradiation area of the spherical reference light on the recording medium is determined when the recording medium is stationary. Spherical reference beam shift multiplex recording is performed by shifting in one direction with respect to the position of the signal light irradiation region.

The hologram recording / reproducing apparatus of the present invention includes an optical signal irradiation optical system that irradiates a recording medium with signal light carrying data information, and a spherical reference light irradiation optical system that irradiates the recording medium with spherical reference light. It has a mechanism.
As shown in FIG. 1, the signal light irradiation optical system includes a signal light condensing objective lens 36 that condenses the signal light Ls carrying data information and irradiates the recording medium 10.
The spherical reference light irradiation optical system collects the spherical reference light Lr and irradiates the recording medium 10 with the reference light focusing objective lens 40 and the reference light converted into a spherical wave by the reference light focusing objective lens 40. The position of the irradiation area of the spherical reference light Lr on the recording medium 10 is changed in one direction with respect to the position of the irradiation area of the signal light Ls by changing the incident direction of the light for the reference light focusing objective lens 40 (FIG. 1). And a reference light irradiation position displacing means 45 for relatively displacing in the left-right direction).

In the hologram recording / reproducing apparatus of the present invention, the spherical reference light Lr is irradiated onto the recording medium 10 under irradiation conditions in which the half width is larger than the half width of the signal light Ls.
The half-value width of the spherical reference light Lr is preferably 1.5 to 2.0 times as large as the half-value width of the signal light Ls.

The reference light irradiation position displacing means 45 shifts the position of the irradiation area of the spherical reference light Lr within a range in which the irradiation area of the signal light Ls is included in the irradiation area of the spherical reference light Lr. A scanning mirror device such as a mirror, an acoustooptic device, or the like can be used.
The reference light irradiation position displacing means 45 in this example is constituted by a scanning mirror device, and the mirror device is configured by an appropriate driving means to provide the optical axis of the signal light Ls to the recording medium 10 and the light of the spherical reference light Lr. The mirror angle is adjusted by rotating about a rotation axis C extending in a direction perpendicular to a plane including the axis.

Hereinafter, spherical reference light shift multiplex recording performed in the hologram recording / reproducing apparatus of the present invention will be described.
FIG. 2 is an explanatory diagram showing an outline of spherical reference light shift multiplex recording in the hologram recording / reproducing apparatus of the present invention. FIG. 3 is a schematic diagram for explaining the function of the reference light irradiation position displacement means by the scanning mirror device.
In the hologram recording / reproducing apparatus according to the present invention, first, as shown in FIG. 2A, the mirror angle of the mirror device constituting the signal light and the reference light irradiation position displacing means is set to the reference mirror angle. Interference fringes obtained by causing interference with spherical reference light irradiated in a state are recorded as holograms. In FIG. 2A, As is an irradiation area of signal light, and Ar is an irradiation area of spherical reference light. Thereafter, in a state where the position of the signal light irradiation area As is fixed, as shown in FIG. 3, the mirror device constituting the reference light irradiation position displacing means 45 is rotated by a predetermined angle so that the light for the reference light is transmitted. The incident direction with respect to the reference light collecting objective lens 40 is changed. Thereby, as shown in FIG. 2B, the position of the irradiation area Ar of the spherical reference light on the recording medium is made relatively to the position of the irradiation area As of the signal light by the reference light irradiation position displacement means 45. In this state, a new hologram is recorded in a state where a part of the recording area overlaps the recording area of the already recorded hologram. At this time, the incident angle of the spherical reference light Lr with respect to the recording medium 10 is the same as the incident angle of the spherical reference light at the time of recording the already recorded hologram.
By repeating such an operation, a shift multiplex hologram sequence is recorded in which a plurality of holograms are arranged in the one direction with a part of the recording area overlapping each other. FIG. 2C shows a state in which the position of the irradiation area Ar of the spherical reference light is further slightly displaced in one direction from the state shown in FIG. 2A to 2C show the irradiation intensity distribution Is of signal light and the irradiation intensity distribution Ir of spherical reference light, respectively.
Here, one hologram has a substantially circular shape in plan view, and its size is, for example, 50 μm in diameter. The shift amount d of the position of the irradiation area As of the spherical reference light is, for example, about 10 μm.

In the hologram recording / reproducing apparatus of the present invention, it is preferable that the signal light irradiation optical system includes signal light irradiation position displacement means for minutely displacing the position of the signal light irradiation region on the recording medium.
Similarly to the reference light irradiation position displacement means, the signal light irradiation position displacement means can be constituted by a scanning mirror device such as a galvanometer mirror, for example. The mirror device that constitutes the signal light irradiation position displacement means is driven independently of the mirror device that constitutes the reference light irradiation position displacement means.

  In such a configuration, the position of the irradiation area of the spherical reference light is slightly displaced (shifted) in one direction by the reference light irradiation position displacing means, and the spherical reference light shift multiplex recording is performed, whereby the shift multiplex hologram sequence is performed. After the signal is recorded, the signal light irradiation position displacing means moves the signal light irradiation area on the recording medium so that the position of the signal light irradiation area is the same as the position of the signal light irradiation area at the time of recording the already recorded shift multiplex hologram sequence. Shifted in the direction. In this state, the position of the irradiation area of the spherical reference light is shifted in the one direction by the reference light irradiation position displacing means, and the spherical reference light shift multiplex recording is performed. Is recorded in a state where it partially overlaps the recording area of the already-recorded shift multiplex hologram sequence.

Furthermore, in the hologram recording / reproducing apparatus of the present invention, the recording / reproducing area on the surface of the recording medium is divided into a plurality of block units, and each block unit is defined as a unit recording area, and spherical reference beam shift multiplex recording is performed for each block unit. Is done. For this reason, as one means for accessing each block unit, a moving mechanism for moving one of the optical mechanism and the recording medium relative to the other in the one direction is provided.
Therefore, in the state where the position of the signal light irradiation area on the recording medium is relatively shifted (moved) by the moving mechanism, the position of the spherical reference light irradiation area is slightly displaced by the reference light irradiation position displacing means. Spherical reference beam shift multiplex recording may be performed.

  In such a configuration, the position of the irradiation area of the spherical reference light is slightly displaced (shifted) in one direction by the reference light irradiation position displacing means and the spherical reference light shift multiplex recording is performed, whereby the shift multiplex hologram is formed. After the formation, the position of the irradiation area of the signal light on the recording medium is moved relative to the position of the irradiation area of the signal light at the time of recording the already recorded shift multiplex hologram sequence by the moving mechanism. In this state, the position of the irradiation area of the spherical reference light is shifted in the one direction by the reference light irradiation position displacing means, and the spherical reference light shift multiplex recording is performed. Is recorded in a state where it partially overlaps the recording area of the already-recorded shift multiplex hologram sequence.

Furthermore, in the hologram recording / reproducing apparatus of the present invention, for example, after performing the above-described spherical reference beam shift multiplex recording to record the first shift multiplex hologram sequence, the recording medium is tilted and tilted. A method may be implemented in which spherical reference beam shift multiplex recording is performed on the area where the first shift multiplex hologram sequence is recorded, and the second shift multiplex hologram sequence is multiplex recorded (tilt shift multiplex recording). Alternatively, after performing the above-described spherical reference beam shift multiplex recording to record the first shift multiplex hologram sequence, in a state where the recording medium is rotated, the spherical reference beam shift multiplex recording is performed to obtain a new shift multiplex hologram sequence. A method of performing multiplex recording (cross-shift multiplex recording) in a state where a part of the recording area overlaps the recording area of the shift multiplex hologram sequence that has already been recorded.
In a hologram recording / reproducing apparatus in which such a method is performed, for example, a recording medium rotating mechanism that rotates (rotates) a recording medium in a plane along the surface thereof, and a disk-shaped medium along the surface thereof. A configuration including a recording medium moving mechanism that moves in a plane, or a configuration that further includes a recording medium tilt mechanism that rotates the recording medium to tilt the surface of the recording medium with respect to the reference plane.

  In the hologram recording / reproducing apparatus of the present invention, when reproducing the hologram, the position of the irradiation area of the spherical reference light is shifted with respect to the recording medium by the reference light irradiation position displacing means, or the reference light irradiation position Each of the plurality of holograms constituting the shift multiplexed hologram sequence recorded on the recording medium by shifting the position of the irradiation area of the spherical reference light with respect to the recording medium by one or both of the displacement means and the moving mechanism Is played.

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

FIG. 4 is an explanatory schematic diagram showing the main configuration of an example of the hologram recording / reproducing apparatus of the present invention.
In this hologram recording / reproducing apparatus, for example, a transmissive disk-shaped device is used as the recording medium 10, and an optical mechanism for irradiating the recording medium 10 with signal light carrying data information and spherical reference light, and recording A medium driving mechanism.

  The optical mechanism includes a recording / reproducing light source 21 made of, for example, a blue laser light source, and a light separating unit made of, for example, a deflecting prism beam splitter that divides the light from the recording / reproducing light source 21 into light for signal light and light for reference light. 22, a signal light irradiation optical system that irradiates the surface of the recording medium 10 with signal light as signal light Ls carrying data information, and converts the reference light into spherical waves to obtain spherical reference light Lr. A spherical reference light irradiation optical system for irradiating the surface of the recording medium 10 and a reproduction light for detecting reproduction light (diffracted light) Lg emitted from the hologram when the hologram recorded on the recording medium 10 is irradiated with the reference light. And a detection optical system. On the optical path of the laser light between the recording / reproducing light source 21 and the light separating means 22, a shutter 23, a polarizing plate 24, and a beam shaping lens 25 are arranged.

  The signal light irradiation optical system modulates the beam expander 31 for expanding the beam diameter of the signal light from the light separation means 22 and the spatial information corresponding to the page data to be recorded with the signal light. A spatial light modulator (SLM) 32 that emits light with its polarization direction (polarization plane) rotated by 90 °, and a Nyquist filter 34 that adjusts the frequency band in the Fourier plane of the light modulated by the spatial light modulator 32; The phase plate 35 for cutting unnecessary DC component light on the Fourier plane of the light from the Nyquist filter 34, and the signal light collection for condensing the light transmitted through the phase plate 35 as the signal light Ls and irradiating the recording medium 10 And an optical objective lens 36. 30 reflects the signal light incident through the beam expander 31 so as to enter the spatial light modulator (SLM) 32 and transmit the light emitted from the spatial light modulator (SLM) 32. It is a polarizing prism beam splitter. Reference numeral 33 denotes a relay lens for causing the light modulated by the spatial light modulator 32 to enter the phase plate 35 via the Nyquist filter 34. Reference numeral 38 denotes a reflection mirror that causes the light transmitted through the phase plate 35 to enter the signal light focusing objective lens 36.

  The spherical reference light irradiation optical system includes an ND filter 41 that adjusts the amount of light for reference light from the light separation means 22 and a half-wave plate (λ / 2 wavelength plate) that changes the polarization direction of the light for reference light. 42, a reference light condensing objective lens 40 that converts the light for reference light into a spherical wave, condenses it as spherical reference light Lr, and irradiates the recording medium 10, and condenses the reference light for the light for the reference light The reference light irradiation position for slightly changing the position of the irradiation area of the spherical reference light Lr in the recording medium 10 in one direction relative to the position of the irradiation area of the signal light Ls by changing the incident direction with respect to the objective lens 40 for recording Displacement means 45 is provided. Reference numeral 48 in FIG. 4 denotes a reflection mirror for irradiating the reference light irradiation position displacing means 45 by changing the traveling direction of the reference light.

  The reference light irradiation position displacing means 45 in this example is configured by a scanning mirror device such as a galvanometer mirror, for example, and the optical axis of the signal light Ls and the spherical reference light Lr with respect to the recording medium 10 are appropriately driven. The mirror angle is adjusted by rotating about the rotation axis C in the direction perpendicular to the plane including the optical axis.

  The reproduction light detection optical system is located on the back side of the recording medium 10. The reproduction light detection optical system includes, for example, an imaging element 51 made of a CCD and a reproduction light Lg from a hologram recorded on the recording medium 10. The light condensing lens 52 is provided.

  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 thereof. It has. Further, as described above, when the so-called tilt shift multiplex recording is performed, the recording medium driving mechanism rotates the recording medium 10 so that the surface of the recording medium 10 is set with respect to the reference plane. The recording medium tilt mechanism for tilting is further provided.

  In this hologram recording / reproducing apparatus, laser light emitted from a recording / reproducing light source 21 made of, for example, a blue laser light source is split into light for signal light and light for reference light by a light separating means 22. The light for reference light is irradiated to a mirror device set at a reference mirror angle, which constitutes the reference light irradiation position displacement means 45, via the ND filter 41 and the half-wave plate 42, and a predetermined mirror angle is applied by this mirror device. The light is incident on the reference light collecting objective lens 40 at an incident angle. The light for reference light incident on the reference light condensing objective lens 40 is converted into a spherical wave and irradiated onto the recording medium 10 as spherical reference light Lr. On the other hand, the signal light is incident on the polarizing prism beam splitter 30 via the beam expander 31. The signal light is reflected by the polarizing prism beam splitter 30 and applied to the spatial light modulator (SLM) 32. The spatial light modulator (SLM) 32 modulates the signal light into a data pattern whose polarization plane is changed by 90 °. The light emitted from the spatial light modulator (SLM) 33 passes through the polarizing prism beam splitter 30 and is incident on the signal light focusing objective lens 36 via the relay lens 33 and the phase plate 35. At this time, the spatial frequency band of the signal light is adjusted by the Nyquist filter 43. The light incident on the signal light condensing objective lens 36 is condensed and applied to the recording medium 10 as signal light Ls. Thereby, in the recording medium 10, the interference fringes by the signal light Ls and the spherical reference light Lr are recorded as a hologram.

Then, the mirror angle of the mirror device constituting the reference light irradiation position displacing means 45 is rotated by a predetermined angle with respect to the reference mirror angle, and the incident direction of the reference light to the reference light condensing objective lens 40 is changed. Thus, a new hologram is recorded in a state where the position of the irradiation area of the spherical reference light Lr from the reference light focusing objective lens 40 is slightly displaced. By the spherical reference beam shift multiplex recording by repeating such an operation, a shift multiplex hologram row in which a plurality of holograms are arranged in one direction is recorded.
Further, the position of the irradiation area of the signal light Ls and the position of the irradiation area of the spherical reference light Lr and the relative position of the recording medium 10 are adjusted by moving the recording medium 10 in one direction along the surface. , The reference light irradiation position displacing means 45 performs spherical reference light shift multiplex recording by minutely displacing the position of the irradiation area of the spherical reference light Lr, so that a plurality of shift multiplex hologram sequences are recorded in a part of the recording area. They are recorded so as to be lined up in one direction while overlapping each other.

  In this example, access to a unit recording area (book) in the recording medium 10 is performed by, for example, biaxial movement and rotation (rotation) of the recording medium 10.

  At the time of reproducing the data information related to the hologram recorded on the recording medium 10, only the reproduction spherical reference light having a significantly reduced amount of light, while the position of the irradiation area is slightly displaced by the reference light irradiation position displacing means 45, The recording medium 10 is irradiated. Thereby, the reproduction light Lg is emitted from the hologram recorded under the same reference light irradiation conditions as the reproduction spherical reference light. The reproduction light Lg from the hologram is emitted from the back side of the recording medium 10 and is incident on the image sensor 51 through the reproduction light condensing lens 52. By detecting the reproduction light Lg by the image sensor 51, the data information recorded in the hologram is reproduced.

Thus, in the hologram recording / reproducing apparatus described above, the mirror device constituting the reference light irradiation position displacement means 45 is driven to change the relative position between the irradiation position of the spherical reference light Lr and the recording position on the recording medium 10. Thus, spherical reference beam shift multiplex recording is performed. The rest time required in the stop-and-go operation of the mirror device (for example, galvano mirror) constituting the reference light irradiation position displacement means 45 is the rest time in the stop-and-go operation of the recording medium moving mechanism that moves the recording medium 10. Compared to the hologram recording / reproducing apparatus in which the spherical reference light shift multiplex recording is performed by the above method, the hologram can be recorded / reproduced at high speed. Specifically, for example, the stationary time in the stop-and-go operation of the galvanometer mirror constituting the reference light irradiation position displacement means is about 0.2 ms (200 μs), and the time required for recording the hologram on the recording medium is, for example, 0.3 ms. Taking this into account, one hologram can be recorded in a total time of 0.5 ms. Therefore, about 2000 holograms can be recorded in one second time.
Further, since only the mirror device constituting the reference light irradiation position displacement means 45 needs to be driven, the relative position of the irradiation position of the spherical reference light Lr on the recording medium 10 with respect to the irradiation position of the signal light Ls by a simple mechanism. Can be reliably controlled.

FIG. 5 is an explanatory schematic diagram showing the main configuration of another example of the hologram recording / reproducing apparatus of the present invention.
The hologram recording / reproducing apparatus has a configuration in which the signal light irradiation optical system includes a signal light irradiation position displacement unit 39 that minutely displaces the position of the irradiation region of the signal light Ls in the recording medium 10. It has the same configuration as the hologram recording / reproducing apparatus shown in FIG. The same components as those in the hologram recording / reproducing apparatus shown in FIG. 4 are denoted by the same reference numerals, and description thereof will be omitted.

In the signal light irradiation optical system of this hologram recording / reproducing apparatus, instead of the reflection mirror 38 in the hologram recording / reproducing apparatus shown in FIG. 4, a signal light irradiation position displacing means constituted by a scanning mirror device such as a galvanometer mirror, for example. 39 is arranged.
As described above, the mirror device constituting the signal light irradiation position displacement unit 39 is driven independently of the mirror device constituting the reference light irradiation position displacement unit 45.

  In this hologram recording / reproducing apparatus, in the state where each of the mirror device constituting the signal light irradiation position displacement means 39 and the mirror device constituting the reference light irradiation position displacement means 45 is set to the reference mirror angle, the signal light A hologram is recorded on the recording medium 10 by irradiation with Ls and spherical reference light Lr. Thereafter, only the mirror device that constitutes the reference light irradiation position displacing means 45 is rotated by a predetermined angle around the rotation axis C1 to be changed to a mirror angle different from the reference mirror angle. Thereby, the incident direction of the reference light to the reference light focusing objective lens 40 is changed, and the position of the irradiation region of the spherical reference light Lr from the reference light focusing objective lens 40 is slightly displaced. In this state, a new hologram is recorded by irradiating the signal light Ls and the spherical reference light Lr. By the spherical reference beam shift multiplex recording by repeating such an operation, a shift multiplex hologram sequence in which a plurality of holograms are arranged in one direction with a part of the recording area overlapping each other is recorded.

  Next, the mirror device constituting the signal light irradiation position displacing means 39 is rotated by a predetermined angle about the rotation axis C2 and changed to a mirror angle different from the reference mirror angle. Thereby, the position of the irradiation area of the signal light Ls in the recording medium 10 is slightly displaced in one direction with respect to the position of the irradiation area of the signal light Ls at the time of recording the already recorded hologram. In this state, spherical reference light shift multiplex recording is performed by minutely displacing the position of the irradiation area of the spherical reference light Lr by the reference light irradiation position displacing means 45, so that a plurality of shift multiplex hologram sequences are recorded in the recording area. For example, the parts are recorded so as to be aligned in one direction in an overlapping state.

  Further, the recording medium 10 is moved in one direction along the surface thereof, and the position of the irradiation area of the signal light Ls and the position of the irradiation area of the spherical reference light Lr and the relative position of the recording medium 10 are adjusted. , The reference light irradiation position displacing means 45 performs spherical reference light shift multiplex recording by minutely displacing the position of the irradiation area of the spherical reference light Lr, so that a plurality of shift multiplex hologram sequences are recorded in a part of the recording area. For example, they may be recorded so as to be aligned in one direction in an overlapping state.

  According to the hologram recording / reproducing apparatus having such a configuration, the hologram can be recorded / reproduced at a high speed similarly to the hologram recording / reproducing apparatus shown in FIG.

FIG. 6 is an explanatory schematic diagram showing the configuration of the main part in still another example of the hologram recording / reproducing apparatus of the present invention.
In this hologram recording / reproducing apparatus, an acousto-optic element is used as a reference light irradiation position displacing means instead of a scanning mirror device, and a signal light irradiation position for minutely displacing the position of the irradiation area of the signal light Ls in the recording medium 10 The basic structure is the same as that of the hologram recording / reproducing apparatus shown in FIG. 4 except that the displacement means 39 is provided. The same components as those in the hologram recording / reproducing apparatus shown in FIG. 4 are denoted by the same reference numerals, and description thereof will be omitted.

  In this hologram recording / reproducing apparatus, a signal light irradiation position displacing means 39 made of, for example, a scanning mirror device is disposed on the optical path of the laser light between the recording / reproducing light source 21 and the light separating means 22, and the signal An anamorphic prism 26 for beam shaping for allowing the laser beam from the light irradiation position displacing means 39 to enter the light separating means 22 is disposed.

  The spherical reference light irradiation optical system in this hologram recording / reproducing apparatus has an acousto-optic device as the reference light irradiation position displacement means 45 on the optical path of the laser light between the half-wave plate 42 and the reference light focusing objective lens 40. Is arranged. In FIG. 6, reference numeral 48 a denotes a reflection mirror that causes the reference light light transmitted through the half-wave plate 42 to enter the acousto-optic element, and 48 b causes the reference light light to enter the reference light focusing objective lens 40. It is a reflection mirror. Reference numeral 47 denotes a relay lens that collects light from the acoustooptic device and makes it incident on the reflection mirror 48b.

As the acousto-optic element, an acousto-optic deflector (AOD) that diffracts a traveling laser beam by generating an ultrasonic wave in an optical medium can be used.
The operation principle of the acousto-optic deflector will be described. As shown in FIG. 7, the frequency-modulated driving input signal S is given from the outside to the ultrasonic transducer 46b such as a piezoelectric element bonded to the acousto-optic medium 46a. As a result, an ultrasonic wave U is generated, and the ultrasonic wave U is propagated to the acousto-optic medium 46a, whereby a periodic refractive index density is formed in the acousto-optic medium 46a. Since the degree of diffraction of the laser light incident on the acousto-optic deflector 46, in this example, the light Lr ′ for reference light, changes according to the frequency of the drive input signal S, the light Lr ′ for reference light is changed. Angle modulation can be performed.

  In this hologram recording / reproducing apparatus, first, the mirror device constituting the signal light irradiation position displacement means 39 is set to the reference mirror angle, and the acoustooptic deflector 46 constituting the reference light irradiation position displacement means 45 is set. In a state where a predetermined driving input signal is input, the hologram is recorded on the recording medium 10 by irradiation with the signal light Ls and the spherical reference light Lr. Next, by changing the frequency of the drive input signal S for the acousto-optic deflector 46 constituting the reference light irradiation position displacement means 45, as shown in FIG. 8, the reference light condensing of the light Lr ′ for reference light is performed. The incident direction with respect to the objective lens 40 is changed, and the position of the irradiation region of the spherical reference light Lr from the reference light focusing objective lens 40 is slightly displaced. In this state, a new hologram is recorded by irradiating the signal light Ls and the spherical reference light Lr. By the spherical reference beam shift multiplex recording by repeating such an operation, a shift multiplex hologram sequence in which a plurality of holograms are arranged in one direction with a part of the recording area overlapping each other is recorded.

  Thereafter, the mirror device constituting the signal light irradiation position displacing means 39 is rotated by a predetermined angle about the rotation axis C2 and changed to a mirror angle different from the reference mirror angle. Thereby, the position of the irradiation area of the signal light Ls in the recording medium 10 is slightly displaced in one direction with respect to the position of the irradiation area of the signal light Ls at the time of recording the already recorded hologram. In this state, spherical reference light shift multiplex recording is performed by minutely displacing the position of the irradiation area of the spherical reference light Lr by the reference light irradiation position displacing means 45, so that a plurality of shift multiplex hologram sequences are recorded in the recording area. For example, the parts are recorded so as to be aligned in one direction in an overlapping state.

  Further, the recording medium 10 is moved in one direction along the surface thereof, and the position of the irradiation area of the signal light Ls and the position of the irradiation area of the spherical reference light Lr and the relative position of the recording medium 10 are adjusted. , The reference light irradiation position displacing means 45 performs spherical reference light shift multiplex recording by minutely displacing the position of the irradiation area of the spherical reference light Lr, so that a plurality of shift multiplex hologram sequences are recorded in a part of the recording area. For example, they may be recorded so as to be aligned in one direction in an overlapping state.

  Thus, in the above hologram recording / reproducing apparatus, the frequency of the driving input signal of the acousto-optic deflector 46 constituting the reference light irradiation position displacement means 45 is adjusted to adjust the irradiation position of the spherical reference light Lr and the recording medium 10. Spherical reference beam shift multiplex recording is performed by changing the relative position with respect to the recording position. Since the acousto-optic deflector 46 does not have a mechanically movable portion, the hologram recording / reproducing apparatus can achieve higher recording / reproducing speed. In addition, there is no problem of a decrease in position accuracy due to deterioration of the mechanically movable portion over time, so that the desired performance can be stably obtained over a long period of time.

  In the above hologram recording / reproducing apparatus, a scanning mirror device (galvano mirror) is used as the signal light irradiation position displacing means 39, but an acousto-optic element may be used. Good.

DESCRIPTION OF SYMBOLS 1 Hologram 10 Recording medium 21 Recording / reproducing light source 22 Light separation means 23 Shutter 24 Polarizing plate 25 Beam shaping lens 26 Anamorphic prism 30 Polarizing prism beam splitter 31 Beam expander 32 Spatial light modulator (SLM)
33 Relay lens 34 Nyquist filter 35 Phase plate 36 Signal light focusing objective lens 38 Reflecting mirror 39 Signal light irradiation position displacement means 40 Reference light focusing objective lens 41 ND filter 42 Half-wave plate (λ / 2 wavelength plate)
45 Reference light irradiation position displacement means 46 Acousto-optic deflector 46a Acousto-optic medium 46b Ultrasonic transducer 47 Relay lens 48 Reflecting mirror 48a Reflecting mirror 48b Reflecting mirror 51 Imaging element 52 Condensing lens for reproduction light As Signal light irradiation area Ar Spherical surface Reference light irradiation region C, C1, C2 Rotating axis Ir Irradiation intensity distribution of spherical reference light Is Signal light intensity distribution Lg Reconstructed light Lr Spherical reference light Lr 'Light for reference light (laser light)
Ls Signal light S Drive input signal U Ultrasound

Claims (14)

A hologram that records interference fringes between signal light carrying data information and reference light as a hologram on a recording medium, and reproduces data information recorded on the hologram by irradiating the recording medium on which the hologram is recorded with reference light In the recording / reproducing apparatus,
An optical mechanism comprising a signal light irradiation optical system for irradiating the recording medium with signal light and a spherical reference light irradiation optical system for irradiating the recording medium with spherical reference light;
The spherical reference light irradiation optical system includes a reference light irradiation position displacement unit that minutely displaces the position of the irradiation area of the spherical reference light on the recording medium,
In a state where the recording medium is stationary, the position of the irradiation area of the spherical reference light is shifted in one direction with respect to the position of the irradiation area of the signal light by the reference light irradiation position displacing means, and shift multiplex recording is performed. Thus, the hologram recording / reproducing apparatus is characterized in that a plurality of holograms are recorded in the shift multiplex hologram sequence arranged in the one direction in a state where a part of the recording area thereof is overlapped with each other. The half-value width of the spherical reference light irradiated to the recording medium is larger than the half-value width of the signal light,
The reference light irradiation position displacing means shifts the position of the irradiation area of the spherical reference light within a range in which the irradiation area of the signal light is included in the irradiation area of the spherical reference light. 1. The hologram recording / reproducing apparatus according to 1. The signal light irradiation optical system includes signal light irradiation position displacement means for minutely displacing the position of the signal light irradiation area on the recording medium,
By means of the signal light irradiation position displacement means, the position of the signal light irradiation area on the recording medium is shifted in the one direction with respect to the position of the signal light irradiation area at the time of recording the shift multiplex hologram sequence already recorded on the recording medium. In this state, the position of the irradiation area of the spherical reference light is shifted in the one direction by the reference light irradiation position displacing means, and shift multiplex recording is performed, so that a new shift multiplex hologram sequence is recorded in the recording area. 3. The hologram recording / reproducing apparatus according to claim 1, wherein a part of the hologram is recorded so as to overlap with a recording area of the already-recorded shift multiplexed hologram sequence. A moving mechanism for moving one of the optical mechanism and the recording medium relative to the other in the one direction;
In the state where the position of the irradiation area of the signal light is moved relative to the position of the irradiation area of the signal light at the time of recording of the shift multiplex hologram sequence already formed on the recording medium by the moving mechanism, the reference The position of the irradiation area of the spherical reference light is shifted by the light irradiation position displacing means, and shift multiplex recording is performed, so that a new shift multiplex hologram sequence is a shift multiplex hologram in which a part of the recording area is already recorded. 4. The hologram recording / reproducing apparatus according to claim 1, wherein the hologram recording / reproducing apparatus is recorded so as to overlap a recording area of the row.   The holograms constituting the shift multiplex hologram sequence recorded on the recording medium are reproduced by relatively shifting the position of the irradiation area of the spherical reference light by the reference light irradiation position displacing means. The hologram recording / reproducing apparatus according to claim 1.   The shift multiplex hologram sequence recorded on the recording medium by moving the position of the irradiation area of the spherical reference light relative to the recording medium by one or both of the reference light irradiation position displacing means and the moving mechanism. The hologram recording / reproducing apparatus according to claim 4, wherein each of the holograms constituting the hologram is reproduced.   7. The hologram recording / reproducing apparatus according to claim 1, wherein the reference light irradiation position displacing means is a scanning mirror device.   7. The hologram recording / reproducing apparatus according to claim 1, wherein the reference light irradiation position displacing means is an acousto-optic element. A hologram that records interference fringes between signal light carrying data information and reference light as a hologram on a recording medium, and reproduces data information recorded on the hologram by irradiating the recording medium on which the hologram is recorded with reference light In the recording / reproducing method,
A spherical wave is used as reference light,
Shift multiplex recording is performed by shifting the position of the reference light irradiation area in one direction with respect to the position of the signal light irradiation area on the recording medium by the reference light irradiation position displacement means while the recording medium is stationary. Thus, the hologram recording / reproducing method is characterized in that a plurality of holograms are recorded on the shift multiplex hologram sequence arranged in the one direction with a part of the recording area overlapping each other. Irradiating the recording medium with a reference beam having a half-value width larger than the signal beam,
10. The hologram recording / reproducing method according to claim 9, wherein the position of the reference light irradiation region is shifted within a range in which the signal light irradiation region is included in the reference light irradiation region.   The signal light irradiation position displacing means shifts the position of the signal light irradiation area on the recording medium in the one direction with respect to the position of the signal light irradiation area at the time of recording the shift multiplexed hologram sequence already recorded on the recording medium. In this state, the position of the reference light irradiation area is shifted in the one direction by the reference light irradiation position displacing means to perform shift multiplex recording, so that a part of the recording area of the new shift multiplex hologram sequence is 11. The hologram recording / reproducing method according to claim 9, wherein recording is performed in a state of being overlapped with a recording area of an already recorded shift multiplex hologram sequence.   By moving one of the optical mechanism and the recording medium that irradiates the recording medium with the signal light and the reference light in the one direction relative to the other by the moving mechanism, the irradiation position of the signal light is already applied to the recording medium. In a state of being shifted with respect to the irradiation position of the signal light at the time of recording the recorded shift multiplex hologram sequence, the position of the irradiation area of the reference light is shifted in the one direction by the reference light irradiation position displacing means. 12. A new shift multiplex hologram sequence is recorded by recording so that a part of the recording area overlaps a recording region of the already recorded shift multiplex hologram sequence. The hologram recording / reproducing method according to any one of the above.   The reference light irradiation position displacing means reproduces each hologram constituting the shift multiplex hologram sequence recorded on the recording medium by shifting the position of the reference light irradiation area with respect to the recording medium. The hologram recording / reproducing method according to claim 9. Each of the shift multiplexed hologram trains recorded on the recording medium by shifting the position of the reference light irradiation area with respect to the recording medium by one or both of the reference light irradiation position displacing means and the moving mechanism. The hologram recording / reproducing method according to claim 12, wherein a hologram is reproduced.

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