JP6915839B2 - Hologram recording / playback device - Google Patents

Description

The present invention relates to a hologram recording / reproducing device. More specifically, hologram recording / reproduction capable of simplifying the hologram recording / reproduction optical system in constructing a large-capacity optical memory by multiple-recording a two-dimensional digital bit pattern as a hologram on a recording medium. Regarding the device.

Conventionally, a hologram recording / reproducing device for two-dimensionally recording / reproducing digital information using a hologram has been proposed. In a hologram recording / reproducing device, a signal light carrying digital information (data information) modulated by a spatial light modulator composed of a plurality of pixels is made to interfere with the signal light and a coherent reference light in a recording medium. The interference fringes obtained by this are recorded as a hologram. Further, when reproducing a hologram recorded on a recording medium, diffracted light is generated by irradiating the hologram with reference light used for recording, and the hologram is recorded as a hologram on an image sensor such as a CCD. Form an image of digital information.

As one of such hologram recording / reproducing methods, for example, a spherical reference light shift multiple recording method using a spherical wave (hereinafter, also referred to as “spherical reference light”) as a reference light is known (for example, Patent Document). See 1.).
In the spherical reference optical shift multiple recording method, if the recording medium on which the hologram is recorded is shifted by a small distance in one direction along the surface of the recording medium, the wave vector relationship deviates from Bragg's diffraction condition. , The already recorded hologram cannot be reproduced, and a new hologram can be recorded in a state where a part of the recording area overlaps with the already recorded hologram recording area.

FIG. 6 is an explanatory diagram schematically showing the configuration of an optical system in an example of a hologram recording / reproducing device adopting a conventional spherical reference optical shift multiple recording method.
This hologram recording / reproducing device includes a recording / reproducing light source 21, an optical separation means 22 that divides the light from the recording / reproducing light source 21 into light for signal light and light for reference light, and signal light from light for signal light. A signal light irradiation optical system that generates and irradiates the recording medium 10, a reference light irradiation optical system that converts light for reference light into a spherical wave and irradiates the recording medium 10 as reference light, and records on the recording medium 10. It is equipped with a regenerated light detection optical system that detects the regenerated light of the hologram. Reference numeral 23 is a shutter, 24 is a polarizing plate, and 25 is a beam shaping lens.

The signal light irradiation optical system includes a spatial light modulator (SLM) 30 that modulates light for signal light using spatial information corresponding to page data to be recorded to generate signal light Ls, and a spatial light modulator 30. A spatial filter 37 that adjusts the frequency band of the signal light from the It is provided with a focusing objective lens 34. Reference numeral 31 is a beam expander that expands the beam diameter of the signal light from the light separation means 22, and 32 is a spatial light modulation that reflects the light for the signal light incident through the beam expander 31. The polarizing prism beam splitter 38, which is incident on the device 30 and transmits the light emitted from the spatial light modulator 30, is a phase plate that cuts unnecessary DC component light on the Fourier plane of the light from the space filter 37. .. In this signal light irradiation optical system, the relay lens 36 is arranged so that the front focal point of one lens 36a and the posterior focal point of the other lens 36b coincide with each other. The spatial light modulator 30 is arranged at the posterior focal point of one lens 36a, and the signal light condensing objective lens 34 is arranged so that the posterior focal point coincides with the anterior focal point of the other lens 36b. ..

The spherical reference light generation 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, and a reference light condensing objective lens 40 that converts the light for reference light into a spherical wave and irradiates the recording medium 10 as spherical reference light. Reference numerals 45 and 46 are reflection mirrors.

The reproduced light detection optical system includes, for example, an image pickup device 50 made of a CCD and an imaging lens 51 that forms an image of the reproduced light from the hologram recorded on the recording medium 10 on the image pickup device 50.

The relay lens 36, the signal light condensing objective lens 34, and the imaging lens 51 are all made of a plurality of lenses, for example, two or three lenses so that the emitted light beam is substantially aberration-free and the Fourier transform characteristic can be obtained. It is composed of a Fourier transform lens in which lens elements are combined. In the Fourier transform lens, for example, when the spatial light modulator is arranged at the position of the rear focal point of the Fourier transform lens, the amount of light emitted from each pixel of the spatial light modulator is light according to the emission angle. It has the characteristic of having a light distribution that is focused on.

In this hologram recording / reproducing device, the signal light from the spatial light modulator 30 is Fourier-transformed (or Fourier inverse-transformed) by the relay lens 36 and the signal light condensing objective lens 34, and the recording medium 10 is irradiated with the spherical reference light. By doing so, the Fourier transform hologram is recorded on the recording medium 10. Then, for example, multiple recording of the Fourier transform hologram is performed by shifting the optical mechanism or the recording medium 10 that irradiates the signal light and the spherical reference light by a relatively small distance in one direction along the surface of the recording medium 10. ..

Japanese Unexamined Patent Publication No. 2016-219066

Therefore, in the above-mentioned hologram recording / reproducing device, as described above, in order to record / reproduce the Fourier transform hologram, the Fourier transform lens is used as the relay lens 36, the signal light condensing objective lens 34, and the imaging lens 51. It is used. Further, in order to irradiate the recording medium 10 with signal light in an aberration-free state and to form an image of the reproduced light from the Fourier transform hologram in an aberration-free state, a hologram recording / reproducing optical system in which highly accurate aberration correction is performed. Is required to be configured. Therefore, there is a problem that the cost of the entire system is increased due to the increase in the cost of the lens.
Further, when constructing a large-capacity optical memory, it is conceivable to multiple-record a transmissive hologram and a reflective hologram. In this case, it is necessary to irradiate the spherical reference light from both sides of the recording medium, but it is structurally difficult to arrange the reference light condensing lens on each of the one side and the other side of the recording medium. Therefore, it was difficult to use both the transmissive hologram recording and the reflective hologram recording together.

The present invention has been made based on the above circumstances, and an object of the present invention is to achieve desired spherical reference optical shift multiplex recording while simplifying the configuration of a hologram recording / reproducing optical system. An object of the present invention is to provide a hologram recording / reproducing device capable of increasing the density of recorded information in a recording medium.

In the hologram recording / reproducing device of the present invention, a hologram obtained by interfering a signal light carrying data information with a reference light is multiple-recorded on a recording medium by a shift multiplexing method, and the reference light is recorded on the recording medium on which the hologram is recorded. In a hologram recording / reproducing device that reproduces data information recorded on a hologram by irradiating
A recording / reproducing light source, an optical separation means for dividing the light from the recording / reproducing light source into light for signal light and light for reference light, and spatial light that modulates the light for the signal light to generate signal light. A modulator, a signal light condensing lens that irradiates a recording medium with signal light, a reference light irradiation optical system that converts the reference light light into a spherical wave and irradiates the recording medium as reference light, and a recording medium. It is equipped with an imaging element that detects the reproduced light of the hologram recorded in.
The optical system from the spatial light modulator to the recording medium via the signal light condensing lens and the optical system for detecting the reproduced light of the hologram recorded on the recording medium do not have Fourier conversion characteristics. can be,
The propagation direction of the signal light is the positive direction, the focal distance of the signal light condensing lens is f, and the distance between the light emitting surface of the spatial light modulator and the main surface of the signal light condensing lens is -La. , the principal surface of the imaging surface and the signal light condensing lens of the imaging device the light is disposed on the imaging plane is imaged by the optical signal condensing lens from each pixel in the spatial light modulator When the distance of is + Lb, the signal light condensing lens satisfies the relationship of 1 / Lb-1 / La = 1 / f, and is a plane parallel to the main plane of the signal light condensing lens. The recording medium is arranged so that the light from each pixel of the spatial optical modulator is arranged on a plane on which the light from each pixel overlaps with each other.

In the hologram recording / reproducing device of the present invention, it is preferable that a spatial filter for removing high frequency components in the spatial frequency distribution of the data information related to the signal light is arranged near the surface of the recording medium.

Furthermore, in the hologram recording / reproducing device of the present invention, the signal light condensing lens is configured so that the distance between the main surface of the signal light condensing lens and the imaging surface of the image sensor can be adjusted. Is preferable.

Furthermore, in the hologram recording / reproducing device of the present invention, the reference light irradiation optical system includes a plurality of reference light condensing objective lenses.
At least one reference light condensing objective lens is arranged on each of one side and the other side of the recording medium.
It is preferable that the reflective hologram and the transmissive hologram are multiple-recorded in the same recording area on the recording medium.

In the hologram recording / reproducing device of the present invention, the optical system from the spatial light modulator to the recording medium via the signal light condensing lens and the optical system for detecting the reproduced light recorded on the recording medium have Fourier conversion characteristics. It is configured as not to. Further, a plane parallel to the main surface of the signal light condensing lens, in which light from each pixel of the spatial light modulator irradiated toward the recording medium through the signal light condensing lens overlaps with each other. The recording medium is located on the top. In a recording / reproducing optical system provided with such a signal light irradiation optical system, even if the hologram recorded on the recording medium has aberrations, a problem actually occurs in the finally obtained reproduced image. There is no. Therefore, according to the hologram recording / reproducing device of the present invention, it is not necessary to install a relay lens or the like in the optical system from the spatial light modulator to the recording medium, and the reproduced light from the hologram is imaged on the image sensor. It is not necessary to install an imaging lens. As a result, the hologram recording / reproducing optical system can be simplified, and the hologram recording / reproducing device having the desired performance can be manufactured economically.
Further, since the imaging lens is not required, it becomes easy to install the reference light condensing lens on each of the one side and the other side of the recording medium, and the transmission type hologram recording and the reflection type hologram recording can be performed. Will be able to do. Therefore, the shift multi-recording hologram of the reflective hologram can be overwritten in the same recording area as the recording area in which the shift multi-recording hologram of the transmissive hologram is recorded on the recording medium, and the number of multiple shift multi-holograms can be further facilitated. Can be improved.

It is explanatory drawing which shows schematic the structure of the main part of the optical system in the hologram recording / reproduction apparatus of this invention. FIG. 5 is an explanatory diagram showing a state in which the distance between the main surface of the signal light condensing lens and the image pickup surface of the image pickup device is adjusted in the optical system shown in FIG. (A) is an explanatory view schematically showing a state in which a spatial filter is arranged in the vicinity of a recording medium, and (b) is an enlarged view showing a part of (a). It is explanatory drawing which shows the outline of the structure of the signal light irradiation optical system, the reference light irradiation optical system, and the reproduction light detection optical system in an example of the hologram recording / reproduction apparatus of this invention. It is explanatory drawing which shows an example of the main part structure in the hologram recording / reproduction apparatus of this invention. It is explanatory drawing which shows the main part structure in an example of the hologram recording / reproduction apparatus which adopted the conventional spherical reference light shift multiplex recording system.

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

The hologram recording / reproducing device of the present invention is a hologram recording / reproducing device using a spherical reference light shift multiplexing method, and is recorded on an optical system and a recording medium from a spatial light modulator to a recording medium via a signal light condensing lens. It is characterized in that the optical system for detecting the reproduced light of the hologram is configured to have no Fourier conversion characteristic. That is, the hologram recorded and reproduced in the hologram recording / reproducing apparatus of the present invention is not a Fourier transform hologram but a non-Fourier transform hologram.

FIG. 1 is an explanatory diagram schematically showing a configuration of a main part of an optical system in the hologram recording / reproducing device of the present invention.
In this hologram recording / reproducing device, the propagation direction of the signal light is the positive direction (right direction in FIG. 1), the focal distance of the signal light condensing lens 35 that irradiates the recording medium 10 with the signal light is f, and spatial light modulation. The distance between the light emitting surface 30a of the device and the main surface 35a of the signal light condensing lens 35 is -La, and the light from each pixel p in the spatial light modulator is imaged by the signal light condensing lens 35. When the distance between the imaging surface 50a of the imaging element arranged on the image plane and the main surface 35a of the signal light condensing lens 35 is + Lb, the signal light condensing lens 35 has 1 / Lb-1 / La = It is arranged in a state that satisfies the relationship of 1 / f. Further, the signal light condensing lens 35 is a plane parallel to the main surface 35a of the signal light condensing lens 35, and is a space irradiated toward the recording medium 10 via the signal light condensing lens 35. The recording medium 10 is arranged so that the recording medium 10 is located on a plane in which the light from each pixel p of the optical modulator overlaps with each other. In FIG. 1, reference numeral H indicates a hologram.

The signal light condensing lens 35 is made of, for example, a rotationally symmetric lens in which a plurality of lenses, for example, 2 to 4 lens elements are combined, and does not have a Fourier transform characteristic.
As the signal light condensing lens 35, one having a function of emitting a light flux having little or no aberration (aberration correction function) may be used.

Further, it is preferable that the signal light condensing lens 35 is configured so that the distance Lb between the main surface 35a of the signal light condensing lens 35 and the image pickup surface 50a of the image pickup element can be adjusted. The distance Lb can be changed, for example, by adjusting the size of the focal length of the signal light condensing lens 35. The signal light condensing lens 35 itself may be moved in the optical axis direction by a drive mechanism (not shown).
With such a configuration, as shown in FIG. 2, the shape size of the hologram H recorded on the recording medium 10 can be adjusted, and for example, the size of the hologram H can be reduced to reduce the size of the recording information. Higher density can be achieved.

The reference light irradiation optical system that irradiates the recording medium with spherical reference light has the same configuration as the reference light irradiation optical system in the conventional hologram recording / reproducing device. That is, the reference light light separated from the light from the same recording / reproducing light source as the signal light is converted into a spherical wave by the reference light condensing objective lens and irradiated to the recording medium.

In this hologram recording / reproducing device, even if the hologram formed on the recording medium has optical aberration, the reproduced light emitted from the hologram is imaged on the image pickup device in a state with little aberration. It becomes. That is, the optical system in this hologram recording / reproducing device is configured to reduce the influence of aberration in the entire optical system from the image pickup device to the image pickup device via the hologram recorded on the recording medium.

In this hologram recording / reproducing device, as described above, the optical system is configured so that the light from each pixel p in the spatial light modulator is imaged on the image pickup surface 50a of the image pickup element by the signal light condensing lens 35. Has been done. Therefore, as shown in FIG. 3, a spatial filter 37 for removing high frequency components in the spatial frequency distribution of the data information related to the signal light Ls is arranged near the surface of the recording medium 10. can do. In FIG. 3, 35 is a signal light condensing lens, 40 is a reference light condensing objective lens, and 50 is an image pickup element on which the reproduced light Lg of a hologram is imaged.
With such a configuration, it becomes easy to limit the spread of the optical spot of the recording / reproducing light (signal light Ls and spherical reference light Lr) formed on the recording medium 10, and a hologram having an appropriate shape and size is surely obtained. Can be formed. Further, in the conventional configuration for forming the Fourier transform hologram, the relay lens system composed of the Fourier transform lens, which is required to incident the signal light on the spatial filter that limits the frequency band, becomes unnecessary. Cost reduction can be achieved by reducing the number of lenses.

Further, in this hologram recording / reproducing device, since an imaging lens for forming an image of the reproduced light from the hologram recorded on the recording medium on the imaging surface of the image pickup device is not required, one surface side and the other surface side of the recording medium are not required. It is structurally easy to install a reference light condensing lens in each of the above. Therefore, this hologram recording / reproducing device can be configured to be capable of performing transmissive hologram recording and reflective hologram recording.
In such a configuration, at least one reference light condensing objective lens is arranged on each of one side and the other side of the recording medium. Each reference light condensing objective lens is arranged so as to be irradiated with spherical reference light having a wave number vector that can obtain recording lattice vectors in different directions in relation to the wave number vector of the signal light. For example, as shown in FIG. 4, when one reference light condensing objective lens 40a and 40b are arranged on each of the one side and the other side of the recording medium 10, each of them is used. Reference: The light condensing objective lenses 40a and 40b are preferably arranged so that the recording lattice vector of the transmissive hologram and the recording lattice vector of the reflective hologram are opposite to each other.

In such a configuration, the signal light Ls emitted through the signal light condensing lens 35 arranged on one side of the recording medium 10 and one reference arranged on the one side of the recording medium 10 By performing spherical reference light shift multiple recording with the spherical reference light Lr1 emitted through the light condensing objective lens 40a, the shift multiple hologram sequence by the transmissive hologram is recorded on the recording medium 10. Further, the spherical reference light shift multiple recording is performed by the signal light Ls and the spherical reference light Lr2 irradiated through the reference light condensing objective lens 40b arranged on the other surface side of the recording medium 10. The shift multiplex hologram sequence of the transmission type hologram is overwritten in the same recording area as the shift multiplex hologram sequence of the transmission type hologram. As a result, it is possible to easily increase the density of the recorded information without causing crosstalk.

When reproducing the data information related to the hologram recorded on the recording medium 10, only the spherical reference light for reproduction with a significantly reduced amount of light is applied to the recording medium 10 via one of the reference light condensing objective lenses 40a. As a result, the reproduced light Lg1 is emitted from the transmissive hologram recorded under the same reference light irradiation conditions as the spherical reference light for reproduction. Then, when the reproduced light Lg1 is detected by the image sensor 50, the data information recorded in the transmissive hologram is reproduced. Further, only the spherical reference light for reproduction is irradiated to the recording medium 10 through the other objective lens 40b for condensing the reference light, so that the light is recorded under the same reference light irradiation conditions as the spherical reference light for reproduction. Regenerated light Lg2 is emitted from the reflective hologram. Then, when the reproduced light Lg2 is detected by the image sensor 50, the data information recorded in the reflective hologram is reproduced.

In the hologram recording / reproducing device of the present invention, for example, spherical reference optical shift multiple recording is performed on a certain region of the recording medium to record the first shift multiple hologram sequence, and then the recording medium is rotated. In the state, spherical reference optical shift multiple recording is performed, and a new shift multiple hologram sequence is overlapped with the recording area of the shift multiple hologram sequence in which a part of the recording area has already been recorded, and multiple recording (cross shift multiple recording) is performed. The method of doing so may be implemented.
In a hologram recording / reproducing device in which such a method is carried out, for example, a recording medium rotating mechanism that rotates (rotates) a recording medium in a plane along the surface of the recording medium and a flat surface of the recording medium along the surface thereof. The configuration may be configured to include a recording medium moving mechanism for moving within.

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

FIG. 5 is an explanatory diagram showing an example of a main part configuration in the hologram recording / reproducing device of the present invention.
This hologram recording / reproducing device includes an optical mechanism that irradiates the recording medium 10 with signal light and spherical reference light carrying data information, a recording medium driving mechanism (not shown), and a spherical shape on the hologram recorded on the recording medium 10. It is provided with a regenerated light detection optical system that detects regenerated light (diffracted light) emitted from the hologram when the reference light is irradiated.

The optical mechanism is an optical separation means 22 including, for example, a recording / reproducing light source 21 made of a blue laser light source and, for example, a deflection prism beam splitter that divides the light from the recording / reproducing light source 21 into light for signal light and light for reference light. A signal light irradiation optical system that irradiates the surface of the recording medium 10 with light for signal light as signal light Ls carrying data information, and a recording medium that converts light for reference light into spherical waves and uses it as spherical reference light. It is provided with a spherical reference light irradiation optical system that irradiates the surface of 10. A shutter 23, a polarizing plate 24, and a beam shaping lens 25 are arranged on the optical path of the laser beam between the recording / reproducing light source 21 and the light separating means 22.

The signal light irradiation optical system is modulated using a beam expander 31 that expands the beam diameter of the signal light from the light separation means 22, and spatial information corresponding to page data for recording the signal light. A signal that condenses and irradiates the spatial light modulator (SLM) 30 that emits light by rotating the polarization direction (polarization plane) by 90 ° and the signal light Ls generated by the spatial light modulator 30 on the recording medium 10. It includes a light condensing lens 35.
Reference numeral 32 denotes a polarizing prism beam splitter that reflects light for signal light incident through the beam expander 31 and causes it to enter the spatial light modulator 30 and transmits light emitted from the spatial light modulator 30. ..
In this hologram recording / reproducing device, for example, a transmissive disk-shaped recording medium 10 is used, and the recording medium 10 is a plane parallel to the main surface of the signal light condensing lens 35 and is a signal. The light from each pixel of the spatial light modulator 30 emitted toward the recording medium 10 via the light condensing lens 35 is located on a plane on which they overlap each other.

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, and a reference light condensing objective lens 40a that converts the light for reference light into a spherical wave and irradiates the spherical reference light from one side of the recording medium 10. Reference numerals 45 and 46 are reflection mirrors that allow light for reference light from the half-wave plate 42 to be incident on the reference light condensing objective lens 40a.
As described above, when the transmission type hologram recording and the reflection type hologram recording are performed, as shown by the broken line in FIG. 5, in order to irradiate the spherical reference light from the other surface side of the recording medium 10. The second spherical reference light irradiation optical system of the above is configured. The second spherical reference light irradiation optical system refers to the other reference light condensing objective lens 40b arranged on the other surface side of the recording medium 10 and the light for reference light from the half-wave plate 42. It includes reflection mirrors 47 and 48 that are incident on the light condensing objective lens 40b. Each of the reference light condensing objective lenses 40a and 40b is irradiated with spherical reference lights Lr1 and Lr2 having wavenumber vectors that can obtain recording lattice vectors in different directions in relation to the wavenumber vector of the signal light Ls. , Will be placed.
In such a configuration, switching of the optical path for the reference light can be performed, for example, by adopting a configuration in which the reflection mirror 45 is detachably arranged with respect to the optical path of the light for the reference light. can.

The reproduced light detection optical system is located on the other side of the recording medium 10, and includes, for example, an image pickup device 50 made of a CCD. The image pickup device 50 is arranged in a state where the image pickup surface is positioned on the image pickup surface on which the light from each pixel of the spatial light modulator 30 is imaged by the signal light condensing lens 35.

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.

In this hologram recording / reproducing device, the laser light emitted from the recording / reproducing light source 21 is divided into light for signal light and light for reference light by the light separating means 22. The light for signal light is incident on the polarizing prism beam splitter 32 via the beam expander 31. The light for signal light is reflected by the polarizing prism beam splitter 30 and is applied to the spatial light modulator 30. The spatial light modulator 30 modulates the light for signal light into a data pattern in which the plane of polarization is changed by 90 °. The signal light Ls generated by the spatial light modulator 30 passes through the polarizing prism beam splitter 32, is incident on the signal light condensing lens 35, is condensed by the signal light condensing lens 35, and is collected on the recording medium 10. Be irradiated. On the other hand, the light for reference light is incident on, for example, one reference light condensing objective lens 40a through the ND filter 41 and the half-wave plate 42, and is converted into a spherical wave by one reference light condensing objective lens 40a. Then, the recording medium 10 is irradiated with the spherical reference light Lr1. As a result, in the recording medium 10, interference fringes due to the signal light Ls and the spherical reference light Lr1 are recorded as a transmission hologram.

Then, in a state where the recording medium 10 is moved (shifted) by a slight distance in one direction along the surface thereof, the operation of recording a new hologram is repeated so that the plurality of holograms partially overlap each other. A shift multiple hologram sequence recorded so as to line up in one direction is recorded. One hologram has a substantially circular shape in a plan view, and its size is, for example, 500 μm in diameter. The shift amount of the recording medium is, for example, about 10 μm.
In this example, access to the unit recording area (book) on the recording medium 10 is performed, for example, by biaxial movement and rotation (rotation) of the recording medium 10.

Further, after the above-mentioned spherical reference optical shift multiple recording is performed to record the first shift multiple hologram sequence, the spherical reference optical shift multiple recording is performed in a state where the recording medium 10 is rotated, whereby a new spherical reference optical shift multiple recording is performed. Multiple recording (cross-shift multiple recording) is performed in a state where the shift multiple hologram sequence overlaps the recording area of the shift multiple hologram sequence in which a part of the recording area has already been recorded.

Furthermore, spherical reference light shift multiple recording is performed by the signal light Ls and the spherical reference light Lr2 irradiated through the other reference light condensing objective lens 40b arranged on the other surface side of the recording medium 10. As a result, the shift multiple hologram sequence of the reflective hologram is overwritten in the same recording area as the shift multiple hologram sequence of the transmissive hologram.

When reproducing the data information related to the hologram recorded on the recording medium 10, only the spherical reference light for reproduction in which the amount of light for reference light is adjusted by the ND filter 41 and the amount of light is significantly reduced as compared with the time of hologram recording. Is irradiated on the recording medium 10. As a result, the regenerated light Lg1 (Lg2) is emitted from the hologram recorded under the same reference light irradiation conditions as the spherical reference light for reproduction. The reproduced light Lg1 (Lg2) from the hologram is imaged on the image sensor 50 in a state of substantially no aberration. When the reproduced light Lg1 (Lg2) is detected by the image sensor 50, the data information recorded on the hologram is reproduced. When the transmissive hologram and the reflective hologram are multiple-recorded, the transmissive hologram is reproduced by irradiating the spherical reference light for reproduction through one of the reference light condensing objective lenses 40a. The reflective hologram is reproduced by irradiating the spherical reference light for reproduction through the other reference light condensing objective lens 40b.

Thus, in the hologram recording / reproducing device of the present invention, the reproduced light recorded in the optical system and the recording medium 10 from the spatial light modulator 30 to the recording medium 10 via the signal light condensing lens 35 is detected. The optical system is configured so that it does not have Fourier transform characteristics. Further, the light from each pixel of the spatial light modulator 30 which is a plane parallel to the main surface of the signal light condensing lens 30 and is irradiated toward the recording medium 10 through the signal light condensing lens 30. The recording medium 10 is positioned on a plane on which the two are overlapped with each other. In such an optical system, even if the hologram recorded on the recording medium 10 has aberrations, there is practically no problem in the finally obtained reproduced image. Therefore, according to the hologram recording / reproducing device, it is not necessary to install a relay lens or the like in the optical system from the spatial light modulator 30 to the recording medium 10, and the reproduced light from the hologram is connected to the image sensor 50. It is not necessary to install an imaging lens to image. As a result, the hologram recording / reproducing optical system can be simplified, and the hologram recording / reproducing device having the desired performance can be manufactured economically.

Further, since the imaging lens is not required, it becomes easy to install the reference light condensing lens on each of the one side and the other side of the recording medium 10, and the transmission type hologram recording and the reflection type hologram recording can be easily performed. And will be able to do. Therefore, the shift multiplex recording hologram sequence of the reflective hologram can be overwritten in the same recording area as the recording area in which the shift multiplex recording hologram sequence of the transmissive hologram on the recording medium 10 is recorded, and the shift multiplex hologram sequence can be multiplexed. The number can be increased more easily.

10 Recording medium 21 Recording / playback light source 22 Light separation means 23 Shutter 24 Polarizing plate 25 Beam shaping lens 30 Spatial light modulator (SLM)
30a Light emitting surface 31 Beam expander 32 Polarized prism Beam splitter 34 Signal light condensing objective lens 35 Signal light condensing lens 35a Main surface 36 Relay lens 36a One lens 36b The other lens 37 Spatial filter 38 Phase plate 40 Light condensing lens 40a One reference light condensing objective lens 40b The other reference light condensing objective lens 41 ND filter 42 Half-wave plate (λ / 2 wavelength plate)
45 Reflective mirror 46 Reflective mirror 47 Reflective mirror 48 Reflective mirror 50 Imaging element 50a Imaging surface 51 Imaging lens H Hologram Lg Reproduced light Lg1 Transmitted hologram reproduced light Lg2 Transmitted hologram reproduced light Lr Spherical reference light Lr1 Spherical reference light Lr2 Spherical reference light Ls signal light

Claims (4)

The hologram obtained by interfering the signal light carrying the data information with the reference light is multiple-recorded on the recording medium by the shift multiplexing method, and is recorded on the hologram by irradiating the recording medium on which the hologram is recorded with the reference light. In a hologram recording / playback device that reproduces the data information
A recording / reproducing light source, an optical separation means for dividing the light from the recording / reproducing light source into light for signal light and light for reference light, and spatial light that modulates the light for the signal light to generate signal light. A modulator, a signal light condensing lens that irradiates a recording medium with signal light, a reference light irradiation optical system that converts the reference light light into a spherical wave and irradiates the recording medium as reference light, and a recording medium. It is equipped with an imaging element that detects the reproduced light of the hologram recorded in.
The optical system from the spatial light modulator to the recording medium via the signal light condensing lens and the optical system for detecting the reproduced light of the hologram recorded on the recording medium do not have Fourier conversion characteristics. can be,
The propagation direction of the signal light is the positive direction, the focal distance of the signal light condensing lens is f, and the distance between the light emitting surface of the spatial light modulator and the main surface of the signal light condensing lens is -La. , the principal surface of the imaging surface and the signal light condensing lens of the imaging device the light is disposed on the imaging plane is imaged by the optical signal condensing lens from each pixel in the spatial light modulator When the distance of is + Lb, the signal light condensing lens satisfies the relationship of 1 / Lb-1 / La = 1 / f, and is a plane parallel to the main plane of the signal light condensing lens. A hologram recording / playback device, wherein the recording medium is arranged so that the light from each pixel of the spatial optical modulator is arranged on a plane on which the light from each pixel overlaps with each other. The hologram recording / playback apparatus according to claim 1, wherein a spatial filter for removing high frequency components in the spatial frequency distribution of the data information related to the signal light is arranged near the surface of the recording medium. The first or second aspect of the signal light condensing lens is characterized in that the distance between the main surface of the signal light condensing lens and the imaging surface of the image pickup element can be adjusted. The hologram recording / playback device described. The reference light irradiation optical system includes a plurality of reference light condensing objective lenses.
At least one reference light condensing objective lens is arranged on each of one side and the other side of the recording medium.
The hologram recording / reproducing apparatus according to any one of claims 1 to 3, wherein the reflective hologram and the transmissive hologram are multiple-recorded in the same recording area on the recording medium.

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