KR20060043593A - Hologram recording/reproduction apparatus and hologram recording/reproduction method - Google Patents

Abstract

According to the present invention, data reproduction without crosstalk is performed when the recording density is increased by shortening the distance between adjacent recording spots of the hologram recording medium.

The 4f system consisting of the lenses 14 and 15 in the reproduction light optical system, and the aperture 16 at the focal point of the lens 15, and the illumination reference light 200-1 at the time of reproduction, the hologram recording medium 13 Is irradiated to the recording spot 30-1, only the diffracted light 300 generated from the target recording spot 30-1 by this aperture 16 is imaged on the imaging device 18 by the lens 17. The diffracted light 300 'generated from the adjacent recording spots 30-2 is cut by the aperture 16. As a result, even if the distance between adjacent recording spots 30-1 and 30-2 is shortened, data without crosstalk can be reproduced, so that the recording density of the hologram recording medium 13 can be improved.

Hologram, diffraction light, aperture, crosstalk, lens.

Description

 HOLOGRAM RECORDING / REPRODUCTION APPARATUS AND HOLOGRAM RECORDING / REPRODUCTION METHOD}

 Fig. 1 is a configuration diagram showing the configuration of the main part of the hologram recording and reproducing apparatus according to the first embodiment of the present invention.

Fig. 2 is a block diagram showing the configuration of the main part of the hologram recording and reproducing apparatus according to the second embodiment of the present invention.

3 is a configuration diagram showing the configuration of the main part of the hologram recording and reproducing apparatus according to the third embodiment of the present invention.

4 is a schematic perspective view showing main parts of a conventional hologram recording and reproducing apparatus.

FIG. 5 is a diagram for explaining a problem when the distance between recording spots on the hologram recording medium is shortened in the hologram recording and reproducing apparatus shown in FIG.

<Explanation of symbols for the main parts of the drawings>

11: spatial light modulator 12, 14, 15, 21, 22: lens

13: hologram recording medium 16, 20: aperture

18: Imaging element 19: Phase mask.

The present invention relates to a hologram recording and reproducing apparatus and method, and more particularly to a configuration of a reproduction light optical system for improving the recording density of a hologram recording medium.

Recently, holographic technology is rapidly developing toward the practical use of holographic memory, which has attracted attention as a candidate for a powerful storage device competing with next-generation and next-generation optical disks. A holographic recording and reproducing system for recording and reproducing a large amount of data has been proposed, for example, by "Holographic data storage" IBM J. RES DEVELOP VOL44 NO.3 MAY 2000 and the like.

In recording and reproduction of this hologram, coherent signal light and reference light are generated by a beam splitter or the like from the coherent laser light emitted from the laser light source. The signal light is intensity modulated by a spatial light modulator displaying a data page, and then focused on the hologram recording medium through the recording light optical system, while reference light is holographic recording for irradiating the hologram recording medium through the reference light optical system. In the media, this signal light and the reference light overlap, and the resulting interference fringe is recorded on the hologram recording medium.

To reproduce the data recorded on the hologram recording medium, by irradiating the hologram recording medium with the same illumination reference light as the reference light, the data is reproduced as diffraction light corresponding to the interference fringe recorded on the hologram recording medium, and the diffracted light is reproduced. It forms in imaging elements, such as CCD and CMOS, through an optical system, an imaging element photoelectrically converts the received diffracted light, and the obtained light reception signal is analyzed and reproduced as image data.

By the way, in the holographic memory, multiple recording of data pages can be repeatedly performed by using the volume of the hologram recording medium, and a large capacity exceeding several 100 Gbytes can be realized. The multiplexing of conventional volume holograms allows for some variation without fixing the reference light for each data page, recording different interference fringes at the same place or at nearly the same place, and providing Bragg selectivity between different reference lights (lighting reference light). It is realized by having. Representative multiplexing methods include angular multiplexing, shift multiplexing, phase correlation multiplexing, wavelength multiplexing, phase modulation multiplexing, and the like.

Fig. 4 is a schematic perspective view showing the main part of a recording / reproducing apparatus for multiplexing data onto a hologram recording medium by an angular multiplexing method. The signal light 100 is light intensity modulated by the data page displayed on the spatial light modulator 1, and the recording spot (three-dimensional range) 30 of the hologram recording medium 3 by the lens 2 of the signal light optical system 30 -1) condensed At the same time, the reference light 200-1 is irradiated to the hologram recording medium 3 in a range covering the recording spot 30-1 by the reference light optical system, not shown, and the signal light 100 and the reference light 200-1 are provided. Interference fringes are recorded in the recording spot 30-1.

Thereafter, the data page displayed on the spatial light modulator 1 is changed, and the incident angle of the reference light is changed so that the hologram recording medium 3 is in a range in which the reference light 200-2 covers the recording spot 30-1. ), The interference fringes of the signal light 100 and the reference light 200-2 are recorded in the recording spot 30-1, and different data pages are written in the same recording spot 30-1 in an angular multiplexing manner. do. Similarly, when the data is multiplexed to this recording spot 30-1, the hologram recording medium 3 moves in the direction of the arrow 50 between the hologram distance L1 (moves to where no hologram is recorded at all), In the same manner as above, n multiple times of data are recorded in the next recording spot 30-2 of the hologram recording medium 3. Incidentally, the movement from the recording spot 30-1 to 30-2 may move the optical system in a state where the hologram recording medium 3 is stopped.

When reproducing the hologram recording medium 3 in which data pages have been recorded as described above, the hologram recording medium (not shown) covers the recording spot 30-1 of the hologram recording medium 3 with the same illumination reference light as the reference light 200-1. Investigate in 3). As a result, diffracted light 300 in accordance with the interference fringe of the recording spot 30-1 is generated, which is imaged on the image pickup device 5 such as a CCD through a reproduction light optical system, and this is photoelectrically converted to reproduce data. . By irradiating the hologram recording medium 3 with the irradiation angle of the illumination reference light changed in the same manner as in recording, data n-multiplexed to the recording spot 30-1 is sequentially reproduced. In this way, when the data recorded in the recording spot 30-1 is reproduced, the hologram recording medium 3 moves in the direction of the arrow 50 by the distance between holograms L1, and the recording spot is operated by the same reproducing operation as described above. Data multiplexed by n at 30-2 is reproduced.

 However, in the above-described conventional hologram recording / reproducing apparatus, since the distance between the holograms L1 between the recording spot 30-1 and the recording spot 30-2 becomes long, the recording density of the hologram recording medium 3 decreases. It becomes. Therefore, if the distance between holograms L1 is shortened, the recording density of the hologram recording medium 3 can be increased. However, when the distance L1 is narrowed as described above, a problem as shown in FIG. 5 occurs.

That is, when the recording spot 30-1 of the hologram recording medium 3 is irradiated with the illumination reference light 200-1, for example, and the data recorded in the recording spot 30-1 is reproduced, the recording is performed. The diffracted light generated at the spot 30-1 is represented by 300, which is formed on the imaging device 5 by the lens 4. At that time, since the illumination reference light 200-1 irradiates the adjacent recording spots 30-2, the diffraction light 300 'also occurs in this recording spot 30-2, and the diffraction light 300 ') Is formed on the image pickup device 5 by the lens 4, and as shown in the figure, an image of both diffracted light almost overlaps. In this case, when the image of the diffraction light 300 'is reproduced, since the image of the diffraction light 300' enters the imaging element 5, the crosstalk is increased, and the reproduction of data is virtually impossible. It becomes impossible.

SUMMARY OF THE INVENTION The present invention has been devised in view of the above circumstances, and an object of the present invention is to make hologram recording and reproduction capable of reproducing data without crosstalk even if the recording density is increased by making the distance between adjacent recording spots of the hologram recording medium as short as possible. An apparatus and a method for reproducing hologram recording are provided.

 SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a hologram reproducing apparatus for reproducing data by forming diffraction light generated by irradiating an illumination reference light on an interference fringe of a hologram recording medium to an imaging device, wherein the illumination reference light is recorded as a target on a hologram recording medium. When irradiated so as to cover the spot, it is provided with unnecessary light removing means for removing the insoluble light such that only diffraction light generated from the target recording spot is formed in the image pickup device.

In addition, the present invention records the interference fringes caused by the interference of the signal light and the reference light in the recording spot of the hologram recording medium, and reproduces the recording data by irradiating the recording spot of the hologram recording medium with the same illumination reference light as the reference light at the time of recording. A hologram recording and reproducing apparatus, comprising: undesired light removing means for removing insoluble light such that when the illumination reference light is irradiated to cover a target recording spot of a hologram recording medium, only diffraction light generated from the target recording spot is formed in the imaging element. Equipped.

Further, the present invention includes intensity distribution uniformity means for uniformizing the intensity distribution in the hologram recording medium of the signal light.

In addition, the present invention is a hologram reproducing method of reproducing data by forming diffraction light generated by irradiating an illumination reference light on an interference fringe of a hologram recording medium to an imaging device, wherein the illumination reference light is irradiated so as to cover a target recording spot of the hologram recording medium. In this case, the method includes the step of removing insoluble light so that only diffracted light generated from the target recording spot forms an image in the imaging device.

In addition, the present invention records the interference fringes caused by the interference of the signal light and the reference light in the recording spot of the hologram recording medium, and reproduces the recording data by irradiating the recording spot of the hologram recording medium with the same illumination reference light as the reference light at the time of recording. A hologram recording / reproducing method, comprising the steps of removing the high order diffracted light of the signal light irradiated onto the hologram recording medium, using only the first diffraction light, and irradiating the illumination reference light to cover the target recording spot of the hologram recording medium. And removing the insoluble light so that only the diffracted light generated from the target recording spot is formed in the image pickup device.

As described above, in the present invention, when the target recording spot of the hologram recording medium is irradiated with the illumination reference light, insoluble light such as diffraction light generated from the recording spot adjacent to the target recording spot is removed, and only the diffraction light generated from the target recording spot is removed. By forming the image into the imaging element, the distance between adjacent recording spots can be made as short as possible in the range in which the insoluble light can be removed, so that the recording density of the hologram recording medium can be improved. In addition, by uniformizing the intensity distribution on the hologram recording medium (fourier surface) of the signal light at the time of recording, the recording spot photosensitive amount of the hologram recording medium (for example, the amount in which the monomer is changed to polymer) is uniformized, and for example, The number of data pages that can be recorded in the same recording spot at multiple angles can be increased, and the synergy with the above effect can further improve the recording density of the hologram recording medium. In addition, by removing the high-order diffracted light of the second-order diffracted light or more from the signal light and reducing the range in which the signal light is irradiated to the hologram recording medium, the size of the recording spot in which the interference fringe due to the interference with the reference light is recorded can be reduced. The recording density of the hologram recording medium can be improved, and the recording density of the hologram recording medium can be further improved by the synergistic effect with the above effect.

 Even if the distance between adjacent recording spots of the hologram recording medium is shortened to increase the recording density, the target recording spot is applied to the target recording spot when the target recording spot of the hologram recording medium is irradiated with illumination reference light for the purpose of performing data reproduction without crosstalk. This was easily achieved by removing insoluble light such as diffracted light generated from adjacent recording spots and imaging only the diffracted light generated from the target recording spot in the imaging element.

Example 1

Fig. 1 is a configuration diagram showing the configuration of the main part of the hologram recording and reproducing apparatus according to the first embodiment of the present invention. However, the same parts as in the prior art are given the same reference signs, and description thereof is omitted as appropriate. The hologram recording and reproducing apparatus comprises the spatial light modulator 11, the lens 12 of the signal light optical system, the hologram recording medium 13, the lenses 14 and 15 constituting the 4f system, and the unnecessary light. The aperture 16 includes a lens 16 for cutting a lens, a lens 17 of a reproduction optical system, and an imaging element 18. The difference from the conventional example is that the lenses 14 and 15 and the aperture 16 forming the 4f system are inserted in the reproduction optical system.

Next, the operation of the present embodiment will be described. The signal light 100 which is light intensity modulated by the data page displayed on the spatial light modulator 11 is a recording spot (three-dimensional range) 30 of the hologram recording medium 13 by the lens 12 of the signal light optical system. The reference light 200-1 is irradiated onto the hologram recording medium 13 in a range covering the recording spot 30-1 by a reference light optical system, which is condensed at -1) and not shown at the same time, so that the signal light 100 and the reference light An interference fringe of 200-1 is recorded in the recording spot 30-1.

Thereafter, the data page displayed on the spatial light modulator 11 is changed, and at the same time, the reference light 200-2 whose angle of incidence is changed covers the recording spot 30-1 to the hologram recording medium 13. The different data pages are written into the recording spot 30-1 in an angular multiplexing manner. Similarly, when the data is multiplexed to this recording spot 30-1, the hologram recording medium 13 moves in the direction of the arrow 50 between the hologram distance L2 (shortest distance possible), and in the same manner as above. N multiple times of data are recorded in the next recording spot 30-2 of the hologram recording medium 13. Incidentally, the movement from the recording spot 30-1 to 30-2 may move the optical system in a state where the hologram recording medium 13 is stopped.

When reproducing the hologram recording medium 13 in which the data page has been recorded as described above, the hologram recording medium (not shown) covers the recording spot 30-1 of the hologram recording medium 13 with the same illumination reference light as the reference light 200-1. 13). As a result, diffracted light 300 according to the interference fringe of the recording spot 30-1 is generated, which is recorded through the 4f lenses 14 and 15, and the recording spot 30-1 of the hologram recording medium 13 is generated. ) Is narrowed down to the same size as when irradiated (Fourier space region), and the diffracted light 300 passing through the aperture 16 passes through the aperture 16 by the lens 17. Is imaged on.

In the above reproduction, since the illumination reference light identical to the reference light 200-1 also irradiates adjacent recording spots 30-2, diffraction light 300 'is generated accordingly, and the diffraction light 300' Through the lenses 14 and 15 of the 4f system, it is narrowed down to the same size as when the recording spot 30-1 of the hologram recording medium 13 is irradiated, and reaches the position of the aperture 16. The through hole of the aperture 16 opens at a size through which the recording spot 30-1 passes, and is provided at a position where the diffracted light 300 from the reproduction target recording spot 30-1 passes. Therefore, the diffracted light 300 'from the adjacent recording spots 30-2 cannot pass through the aperture 16. For this reason, only the diffracted light 300 from the recording spot 30-1 is imaged in the imaging element 18, and a reproduction image without crosstalk is obtained.

Here, the aperture 16 is disposed at a position to receive the light converging region (Fourier space region) in which the diffracted light 300 is collected through the 4f optical system in the through hole. The through hole size of the aperture 16 is a size through which a frequency necessary for reproduction of data is passed, and the distance L2 between the adjacent recording spots is set to a length substantially equal to the opening width of the through hole.

As shown by the reference light 200-2, the illumination reference light is irradiated at different angles of incidence to the hologram recording medium 13, thereby reproducing the data recorded at the angular multiplex in the recording spot 30-1. Since the path of the diffracted light generated in that case is the same as that of the diffraction light 300 described above, and the diffraction light of the adjacent recording spot 30-2 generated at that time is the same as the path of 300 'described above, Since only the diffracted light generated from the recording spot 30-1 passes through the aperture 16 and forms an image on the image pickup device 18 by the lens 17, even when multi-recorded data is reproduced, crosstalk is reduced. A missing playback image is obtained.

According to this embodiment, the diffraction light 300 generated from the target recording spot (for example, 30-1) of the hologram recording medium 13 is inserted by inserting 4f lenses 14 and 15 into the reproduction optical system. By narrowing down to the same range and providing the aperture 16 at this narrowed position, the unnecessary diffraction light 300 'from the adjacent recording spot can be cut, and only the diffraction light 300 can be imaged to the imaging element 18. Therefore, even if the distance L2 between adjacent recording spots 30-1 and 30-2 is at least necessary, i.e., approximately the same length as the opening width of the aperture 16, a reproduce image without crosstalk can be obtained. The recording density of the hologram recording medium 13 can be improved.

Example 2

Fig. 2 is a block diagram showing the configuration of the main part of the hologram recording and reproducing apparatus according to the second embodiment of the present invention. However, the same parts as in the first embodiment are denoted by the same reference numerals, and description thereof is omitted as appropriate. The hologram recording and reproducing apparatus of the present embodiment differs from the first embodiment in that a phase mask 19 is arranged close to the spatial light modulator 11 to uniform the intensity distribution of the signal light 100 on the Fourier plane. , The other configuration is the same.

According to the present embodiment, the signal light 100 is incident on the spatial light modulator 11 through the phase mask 19, is intensity modulated by the data page displayed on the spatial light modulator 11, and then the lens 12 is applied to the lens 12. By condensing on the recording spot 30-1 of the hologram recording medium 13, the intensity distribution of the signal spot 100 of the recording spot (fourier face) 30-1 becomes uniform due to the action of the phase mask 19. Since the amount of photosensitivity (monomer consumption) at the recording spot is also uniform, the number of angular multiplexed recordings can be increased in this recording spot 30-1. In addition, since the configuration of the reproduction optical system is the same as in the first embodiment, since unnecessary diffracted light 300 'generated from the adjacent recording spot is cut from the aperture 16, even if the distance between the recording spots is made as short as possible. The reproduction image without crosstalk can be obtained, and therefore, the recording density of the hologram recording medium 13 can be improved. However, the hologram recording medium 13 is more effective than the first embodiment by the operation of the phase mask 19 described above. Can improve the recording density.

The function of making the intensity distribution of the signal light 100 uniform on the Fourier surface is not limited to the phase mask 19, and may be, for example, an axicon.

Example 3

3 is a configuration diagram showing the configuration of the main part of the hologram recording and reproducing apparatus according to the third embodiment of the present invention. However, the same parts as in the conventional example are denoted by the same reference numerals, and description thereof is omitted as appropriate. The hologram recording and reproducing apparatus of this embodiment differs from the first embodiment in that the aperture 20 for cutting high-order diffracted light and the lenses 21 and 22 of the 4f system are inserted into the recording light optical system. Is the same.

Next, the operation of the present embodiment will be described. The signal light 100 which is light intensity modulated by the data page displayed on the spatial light modulator 11 is condensed at the through hole position of the aperture 20 by the lens 12 of the signal light optical system. The through hole of the aperture 20 passes only the first diffracted light and cuts the second or higher order diffracted light spread around it. Therefore, only the first diffraction light constituting the signal light 100 passes through the aperture 20 and is focused on the recording spot 30-1 of the hologram recording medium 13 by the lenses 21 and 22 of the 4f system. Then, the interference fringe with the reference light 200-1 irradiated separately is recorded in the recording spot 30-1. Subsequent recording operations are the same as those in the first embodiment, and data is recorded at angle multiples in the recording spots 30-1 and 30-2.

The operation of reproducing the hologram recording medium 13 recorded as described above is the same as in the first embodiment, and since the unnecessary diffracted light 300 'generated from the adjacent recording spot is cut from the aperture 16, the recording spot Even if the distance between them is as short as possible, since the data without crosstalk can be reproduced, the recording density of the hologram recording medium 13 can be improved.

In this case, for example, during reproduction, the diffracted light 300 generated from the recording spot 30-1 is composed of only the first diffracted light so that the image data formed on the image pickup device 18 is first diffracted. Although formed by light only, in order to binarize the photoelectrically converted signal to the imaging element 18, the obtained binarized data becomes the same data as that obtained by binarizing the complete image data including the higher order diffracted light by photoelectric conversion. The quality is the same as that of complete image data containing higher order diffracted light.

The recording density can be further improved by forming a phase mask in which the intensity distribution of the signal light 100 on the Fourier surface is uniform in proximity to the spatial light modulator 11 in the configuration of the present embodiment.

In addition, this invention is not limited to the said Example, A specific structure, a function, an effect, and an effect can also be implemented with other various forms in the range which does not deviate from the summary.

 According to the present invention, when irradiating the target recording spot of the hologram recording medium with the illumination reference light, insoluble light such as diffraction light generated from the recording spot adjacent to the target recording spot is removed, and only the diffracted light generated from the target recording spot is removed. By imaging the imaging element, the distance between adjacent recording spots can be made as short as possible in the range in which the insoluble light can be removed, so that the recording density of the hologram recording medium can be improved.

In addition, by removing the high order diffracted light of the signal light irradiated onto the hologram recording medium and using only the first diffraction light, the size of the recording spot of the hologram recording medium can be reduced, and the synergistic effect of the hologram recording medium can be achieved. The recording density can be further improved.

In addition, by uniformizing the intensity distribution of the signal light on the hologram recording medium (Fourier surface), it is possible to make the photosensitive amount of the recording spot uniform, and the synergistic effect with the above effect can further improve the recording density of the hologram recording medium. Can be.

Claims (18)

 A hologram reproducing apparatus for reproducing data by forming diffraction light generated by irradiating an illumination reference light onto an interference fringe of a hologram recording medium to an imaging device, When the illumination reference light is irradiated to cover the target recording spot of the hologram recording medium, unnecessary light removal is performed to remove insoluble light so that only diffraction light generated from the target recording spot is formed in the imaging device. Way Hologram playback device having a. The method of claim 1, And the insoluble light is diffracted light generated from a recording spot adjacent to the target recording spot. The method of claim 1, And said undesired light removing means is an aperture for passing only diffracted light generated from a target recording spot. The method of claim 3, And the aperture is disposed at a position to receive a light converging region in which a diffracted light is collected by a 4f optical system in a through hole. The method of claim 3, And a through hole size of the aperture is a size for passing a frequency necessary for reproducing data, and the distance between adjacent recording spots is approximately equal to the opening width of the through hole. The method of claim 1, And a data corresponding to an interference fringe recorded in an angular multiple manner in a target recording spot of the hologram recording medium by changing the angle at which the illumination reference light is incident on the hologram recording medium. The interference fringe generated by the interference of the signal light and the reference light is recorded in the recording spot of the hologram recording medium, and the diffraction light generated by irradiating the recording spot of the hologram recording medium with the same illumination reference light as the reference light at the time of recording is imaged on the image pickup device. A hologram recording and reproducing apparatus for playing, When the illumination reference light is irradiated to cover the target recording spot of the hologram recording medium, unnecessary light removing means for removing the insoluble light so that only diffraction light generated from the target recording spot is formed in the imaging element And a hologram recording and reproducing apparatus. The method of claim 7, wherein A hologram recording and reproducing apparatus comprising intensity distribution uniformity means for equalizing the intensity distribution in the hologram recording medium of the signal light. The method of claim 8, And the intensity distribution uniforming means is a phase mask. The method of claim 7, wherein And the undesired light removing means is an aperture for passing only diffracted light generated from a target recording spot. The method of claim 10, And a through hole size of the aperture is a size through which a frequency necessary for reproduction of data is passed, and a distance between adjacent recording spots of the hologram recording medium is approximately equal to the opening width of the through hole. The method of claim 7, wherein A hologram recording and reproducing apparatus, comprising filter means for removing high-order diffracted light included in the signal light irradiated onto the hologram recording medium and using the first-order diffracted light as the signal light. The method of claim 12, And the filter means is an aperture for passing only the first diffracted light of the signal light. The method of claim 13, And the aperture is arranged at a position to receive a condensing region in which a signal light is collected by a 4f optical system in a through hole. A hologram reproducing method for reproducing data by forming diffraction light generated by irradiating an illumination reference light on an interference fringe of a hologram recording medium to an imaging device, When the illumination reference light is irradiated to cover the target recording spot of the hologram recording medium, removing the insoluble light so that only diffracted light generated from the target recording spot is formed in the imaging element. Hologram playback method comprising a. The interference fringe generated by the interference of the signal light and the reference light is recorded in the recording spot of the hologram recording medium, and the diffraction light generated by irradiating the recording spot of the hologram recording medium with the same illumination reference light as the reference light at the time of recording is imaged on the image pickup device. As a hologram recording reproduction method to reproduce, Removing the high order diffracted light of the signal light irradiated to the hologram recording medium and passing only the first diffracted light; When the illumination reference light is irradiated to cover the target recording spot of the hologram recording medium, removing the insoluble light so that only diffracted light generated from the target recording spot is formed in the imaging element. Hologram recording reproduction method comprising a. The method of claim 16, In the removal step, when the insoluble light is removed by an aperture, and the size of the through hole is set to pass the frequency necessary for reproducing data, the space between the adjacent recording spots of the hologram recording medium is the through hole. And a step of shifting the recording position to be approximately equal to the opening width of the hologram recording and reproducing method. The method of claim 16, A hologram recording and reproducing method for recording an interference fringe generated by interference between the signal light and the reference light on the hologram recording medium by an angular multiplexing method.

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