JP2010139620A - Image recording and reproducing device by light of plurality of wavelengths - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device for multiplexing recording of color images and selectively reproducing images from multiple recorded images. <P>SOLUTION: An image recording and reproducing device achieves wavelength multiplexing in addition to disorder multiplexing by using interference light changing disorder patterns in each color image with a hologram recording device. The image recording and reproducing device records in time division in each wavelength in wavelength multiplexing, and in reproduction it collectively radiates each wavelength light to be directly observed or to be imaged. In other words, a light source of coherent light of different wavelength is provided to branch the output light so as to make reference light and object light. The object light is modulated with a spatial optical modulator, and the reference light passes through a wave face disordering means. In recording, light of each wavelength is sequentially output based on the same setting of the wave face disordering means, and different object light is modulated with the same spatial optical modulator to be recorded in time division. In reproduction, setting of the wave face disordering means is matched in preparation, and a plurality of the reference light beams are simultaneously radiated on a recording medium to observe the transmissive light or scattering light. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention is a holographic multiplex recording apparatus using a plurality of wavelengths of light, for example, by moving a fiber bundle that distorts the light wavefront and using the variability of turbulence to multiplex and multiplex color image recording. The present invention relates to an image recording / reproducing apparatus using a plurality of wavelengths of light that is selectively reproduced from recorded images.

  By using a hologram, it is known that multiple recordings of images and digital data are possible, and the amount of information can be accumulated 1000 times or more compared to the case of recording in a two-dimensional form on a recording medium. In hologram storage devices that perform recording and reproduction using holograms, recording and reproduction have been performed by branching laser light to generate object light for irradiating an object and reference light.

  As is well known, in a hologram storage device, laser light emitted from a laser light source is branched into object light and reference light by a semi-transmissive branch mirror. The object light is modulated with information to be recorded using a spatial modulator, and the recording disk is irradiated. Further, the direction of the other branched reference light is adjusted so that the same spot as the place where the object light irradiates the recording board is irradiated. By simultaneously irradiating the recording plate with the object beam and the reference beam in this way, information can be recorded by the hologram. Also. In reading, the object light is blocked by the spatial modulator, and the recording disk is irradiated with only the reference light. The recorded information can be read by detecting the light diffracted by the hologram of the recording board with a photodetector.

  In addition, as a storage device that records and reads out holograms in a multiplexed manner, Japanese Patent Laid-Open No. 2006-78944 discloses that a random wavefront is generated for each image, whereby multiple accumulation and readout are possible. As described above, a hologram multiplex recording apparatus that performs multiplex recording of holograms without changing the wavelength is disclosed. In this apparatus, the laser light is branched into object light and reference light, the object light is modulated, the reference light having a rough wavefront is generated from the reference light, and the modulated object light and the rough reference light having the wavefront are generated. On the recording medium, and the interference pattern is recorded. In order to record on the same part of the recording medium, reference light with a random pattern changed for each stored information is used. The reference light having a random wavefront is generated by passing the reference light having a uniform wavefront through a multimode optical fiber or through a fiber bundle made up of a plurality of optical fibers having different lengths. Further, further multiplexing is attempted by changing the optical path length to the recording board and the incident angle to the recording board.

Further, in Patent Document 2 (Japanese Patent Laid-Open No. 2006-84485), by generating a random wavefront for each image, multiple accumulation and readout are possible, and hologram multiplexing is performed without changing the wavelength as in the conventional example. A hologram multiplex recording apparatus that performs recording is disclosed. This is a feature of the above-described hologram multiplex recording apparatus, particularly in the method of changing the random pattern for each recording information, and uses a wavefront randomizing element that makes its wavefront random when the branched reference light passes. In this method, multiplexing is performed by changing a random pattern by rotating around a predetermined axis.
JP 2006-78944 A JP 2006-84485 A

  An apparatus for recording three primary color images using the hologram multiple recording apparatus disclosed in Patent Document 1 cannot be realized simply by using three primary color light sources or using a spatial light modulator for each primary color. It can be easily imagined that it becomes a complicated device. However, the present invention proposes an image recording / reproducing apparatus using multi-wavelength light capable of recording / reproducing multi-primary color images only by making the above-described hologram multiplex recording apparatus slightly complicated.

  According to the present invention, a color hologram multiplex recording apparatus having a relatively simple configuration can be easily realized. That is, an image recording / reproducing apparatus that performs multiplexing based on the wavelength of light used in addition to multiplexing based on the randomization mode can be realized with a simple configuration.

  The present invention roughly divides a laser beam into an object beam and a reference beam, modulates the object beam, and generates a random reference beam having a wavefront generated from the branched reference beam and the modulated object beam. Is a hologram recording apparatus that records the interference pattern on the recording medium, and uses interference light in which random patterns are changed for each stored information in the same part of the recording medium. This is a method of multiplexing by. As for multiplexing based on the wavelength of light, recording is performed in a time division manner, but reproduction can be performed in a lump, so that a color image can be directly observed or imaged.

More specifically, the present invention is an image recording / reproducing apparatus using a plurality of wavelengths of light, which includes a plurality of coherent light sources having different spectra, branches light emitted from any one or a plurality of the coherent light sources, and generates reference light. And a light source unit that generates the object light, a spatial light modulator that modulates the object light, and a wavefront randomization unit that can randomize the reference light wavefront and set a plurality of predetermined different states. An optical system is used that irradiates the object light modulated by the spatial light modulator and the reference light randomized by the wavefront randomizing means from directions intersecting each other on the recording medium.
In creating a hologram, the light from the plurality of coherent light sources is individually output sequentially from the light source unit under the same predetermined setting of the wavefront randomization means, and the object light by each coherent light is output. Are modulated by the spatial light modulators, and holograms of the coherent lights are sequentially created on the recording medium.
In the image reproduction from the hologram, the setting of the wavefront randomizing means is set to the same setting as the setting for creating the hologram, and reproduction is performed using a plurality of coherent lights. That is, the reference light by light including at least two of all the coherent lights is messed up by the wavefront messing means having the same setting as that at the time of creating the hologram, and then irradiated to the recording medium, and the transmitted light or The scattered light is detected by a two-dimensional or three-dimensional detector, or observed by an observer.
In this way, for example, three primary colors of red, green and blue can be recorded in multiple recording by changing the setting of the wavefront randomizing means.

  The spatial light modulator may be composed of a plurality of pixels, and one that controls the light transmittance of each of the pixels can be used.

  The spatial light modulator may be composed of a plurality of pixels and controls the polarization direction of transmitted light in each of the pixels.

  Further, the spatial light modulator may be composed of a plurality of pixels and control the reflection direction in each of the pixels.

  The light source unit includes a plurality of pulse light sources having different wavelengths, a beam expander, and an optical splitter, and the intensity of light incident on the spatial light modulator is adjusted by an optical attenuator. Thereby, the intensity ratio between the object beam and the reference beam can be optimized.

  The light source unit includes a beam expander, a laser light source, a half-wave plate, and a polarization splitter, and adjusts the intensity ratio of light output from the optical splitter by rotating the half-wave plate. It may be. The intensity ratio between the object beam and the reference beam is adjusted by rotating the polarization plane of the light incident on the polarization splitter with a half-wave plate.

  As the wavefront disordering means, a fiber bundle obtained by bundling optical fibers disclosed in FIGS. 2 to 5 of Patent Document 2 can be used. By rotating the fiber bundle around the rotation axis, the randomness imparted to the wavefront can be changed. The index for setting the randomness in this case is the rotation angle of the fiber bundle.

  Further, as the wavefront randomizing means, a light-transmitting plate similar to that described in FIG. 2C of Patent Document 1 is provided on the surface thereof with a concavo-convex structure having a size equal to or smaller than the cross-sectional size of the reference light beam. A reflective surface or a transmissive surface can be used for the reference light having a rough wavefront. However, the irregularity given to the wavefront is changed by changing the structure of the uneven surface. In this case, in the concavo-convex structure, the number assigned to the orthogonal surface mode, which is the same as the orthogonal mode of the vibration surface, is an index for setting the randomness.

  The wavefront randomization means passes through a sodium olivine similar to that described in FIG. 3B of Patent Document 1 to generate a rough reference light with a wavefront. In this case, the voltage applied to the wollastonite is an index for setting randomness.

  Further, a polarizing filter for aligning the polarization direction of the light beam is provided between the wavefront randomizing means and the recording medium. In this polarizing filter, since the purity of the polarization plane is lowered by the wavefront randomization means, the polarization plane is aligned again. The polarizing filter can also be used to adjust the intensity of the reference light.

  As is well known, the hologram is written in the crystal by the interference between the object light branched from the coherent light and the reference light, and the object light recorded by the same reference light is reproduced. However, if the reference light used for writing and reading is different, the hologram is not read. Therefore, as described above, if this is actively used, multiple accumulation and readout are possible by generating a random wavefront for each image.

  It is well known that wavelength multiplexing is possible by changing the wavelength of coherent light.

  The present invention performs multiple recording / reproduction of a color image made up of, for example, three primary colors of red, green, and blue by using wavelength multiplexing and random multiplexing. However, in image recording, instead of using three spatial light modulators, a single spatial light modulator is used in a time-sharing manner for simplification.

  Embodiments of the present invention will be described below in detail with reference to the drawings. In the following description, devices having the same function or similar functions are denoted by the same reference numerals unless there is a special reason.

FIG. 1 shows an embodiment of an image recording / reproducing apparatus using multiple wavelengths of light according to the present invention.
When creating a hologram, the object light 17 and the reference light 18 from the light source 50 are used. The object light 17 and the reference light 18 are generated by branching the coherent light from the multi-color light source 40 by an optical branching device composed of a wave plate 3 and a polarizing prism 4 that can rotate. The branching ratio of the light amount is adjusted by rotating the wave plate 3. In this case, the polychromatic light source 40 sequentially generates coherent light having different wavelengths. The object light 17 has its optical path direction changed by the reflecting mirror 9, and then the information to be recorded as a hologram is superimposed by the spatial light modulator 10 and irradiated onto the recording medium. Further, the reference light 18 is changed in the optical path direction by the reflecting mirror 9, passes through the rotating fiber bundle that is the wavefront disordering means 6, and then the unnecessary polarized light is removed by the polarization filter, and the recording medium 11 is irradiated. The In this recording medium 11, the information superimposed by the spatial light modulator 10 is recorded as a hologram. Here, under the same predetermined setting of the wavefront randomization means 6, a plurality of wavelengths of coherent light are sequentially used, and holograms of the respective wavelengths of coherent light are sequentially created on the recording medium 11. To do.

  In the configuration of FIG. 1, since the polarization directions of the object beam 17 and the reference beam 18 are orthogonal to each other, it is necessary to align the polarization directions in order to produce an interference document on the recording medium 11 in order to create a hologram. is there. Further, it is possible to superimpose image information by adjusting the polarization direction for each position. In order to utilize this phenomenon, the spatial light modulator 10 used here is, for example, a liquid crystal retarder capable of controlling the phase delay for each pixel as shown in FIG.

  Here, the polychromatic light source 40 includes the multi-wavelength coherent light source 1 and the beam expander 2 shown in FIG. In the multi-wavelength coherent light source 1, laser light from a pulse laser (for example, red, green, and blue) controlled by the controller 13 is transmitted on the same optical path by using a color synthesis optical system that is already well known for a liquid crystal projector, for example. The beam diameter is enlarged to such an extent that it can be used as the reference beam 18 or the object beam 17 by the beam expander 2, and is output.

  Moreover, as shown in FIG.5 (b), the polychromatic light beam source 40 may interrupt the light from the continuous wave laser of the multiple wavelength coherent light source 1 with a shutter. In particular, when a semiconductor laser can be used as the continuous wave laser, the applied current may be intermittent. An advantage of this configuration is that a relatively long exposure time can be set.

  The light source unit individually outputs light from the plurality of coherent light sources one after another, and the object light 17 by each coherent light is modulated by the spatial light modulator 10 for each wavelength, and the coherent light Each hologram is sequentially created on the recording medium.

  In the image reproduction from the hologram, the setting of the wavefront randomizing means 6 is set to the same setting as that in the creation of the hologram, and reproduction is performed using a plurality of coherent lights simultaneously. That is, only the reference light 18 by the light including at least two of all the coherent lights is messed up by the wavefront scrambler 6 having the same setting as that at the time of creating the hologram, and then irradiated to the recording medium 11. The transmitted light or scattered light is detected by a two-dimensional (for example, a normal camera) or three-dimensional light (for example, a stereo camera) photodetector 51 or observed by an observer. Here, the synchronism when the recording medium 11 is irradiated with the plurality of reference lights 18 is an afterimage that the observer feels on the premise that the setting of the wavefront randomization means 6 is not changed when the observer observes. Is an effective time for color synthesis and is approximately 50 milliseconds or less. That is, when the reference light 18 composed of the coherent light having the different wavelengths is generated within 50 milliseconds, it is considered to be simultaneous. In addition, when detecting with the above-described two-dimensional or three-dimensional photodetector, it is possible to easily store and reproduce the reproduced images with the respective wavelengths in the storage device, so until the setting of the wavefront randomization means 6 is changed. , Can be considered as simultaneous.

  Further, in order to irradiate the recording medium 11 only with the reference light 18, the modulation condition may be set so that the object light 17 does not pass through the spatial light modulator 10. A separate shutter may be provided to block the object light 17 itself.

  A hologram is created as described above, and image reproduction from the hologram is performed under the control of the controller 13. First, the principal axis direction of the wave plate 13 is rotated around the axis in the optical path direction, and the rotational position of the rotating fiber bundle that is the wavefront disordering means is determined. Next, when creating a hologram, the multicolor light source 40 sequentially outputs coherent light having a plurality of wavelengths. In accordance with the output timing, the modulation contents in the spatial light modulator 10 are sequentially set. When reproducing an image from a hologram, a plurality of wavelengths of coherent light are simultaneously output.

  Here, it is desirable that the wavefront randomization means 6 gives as fine a random pattern as possible. As described above, information to be recorded by the spatial modulator is given to the object light 17, but if the pattern is not a precise random pattern, crosstalk occurs between the information. The fineness necessary to avoid such crosstalk is determined by the code used for recording. Therefore, it is clear that in order to set the randomness, it is necessary to consider the characteristics of the code used for recording and the multiplicity to be realized.

  For example, the wavefront randomizing means 6 uses a multimode optical fiber. As is well known, in a multi-mode optical fiber, incident light is slightly reflected at the optical fiber wall surface due to a slight difference in the incident site, and the wavefront becomes messy. In this case, it is desirable to positively spread the incident position using a lens.

  The wavefront randomizing means 6 is a bundle of optical fibers having various lengths. A bundle of about four optical fibers can also be used, but it is desirable to bundle a large number of optical fibers of various random lengths and use them as an optical fiber bundle (fiber bundle). Since the lengths of the optical fibers are different, the propagation distance of the light is different, and as a matter of course, the wave front becomes messy. The positional relationship between the input side and output side optical fibers need not have any symmetry.

  Further, the wavefront randomizing means 6 may be a light transmitting plate that is rotatable with a rough irregular pattern on the surface. Alternatively, the wavefront randomizing means 6 may use a light reflecting plate that can be rotated with a rough uneven pattern on the surface that also serves as a reflecting mirror.

  It is already well known that the wavefront of light passing through Ulexite is disturbed. It is also known that this disturbance can be controlled by providing electrodes on the olivine and controlling the electric field applied thereto. For this reason, by using electric field-controlled sodium borosilicate for the wavefront randomizing means 6, the wavefront randomizing means 6 with easy voltage control can be realized.

  The configuration of FIG. 2 uses a multicolor light source 40 whose output light is coherent light, uses the partial reflector 16 instead of the polarizing prism 4, and further adjusts the light intensity of the object light 17. An attenuator 14 is provided. In the configuration of FIG. 2, the branching ratio by the partial reflection mirror 16 is preferably set so that the ratio of the reference light 18 is higher than that of the object light 17. As the spatial light modulator 10 that can be used here, in addition to a liquid crystal retarder that can control the phase delay for each pixel as shown in FIG. 6, a liquid crystal attenuator that can adjust the light transmittance for each pixel, As shown in FIG. 7, a display plate that partially irradiates a saturable absorber with laser light to partially adjust the light transmittance can be used.

  In FIG. 3, the coherent light from the polychromatic light source 40 is passed through the wave plate 3 to set the polarization direction, and is branched into the object light 17 and the reference light 18 by the partial reflection mirror 16. A polarization component is extracted from the object light 17 by the polarization filter 14. In this configuration, by setting the polarization direction of the object light 17 with the polarization filter 14, the polarization direction of the object light 17 with respect to the polarization direction of the reference light 18 can be freely set. Further, the polarization direction and the amount of light of the object light 17 can be adjusted by the polarization direction of the output light of the polychromatic light source 40, the rotation angle of the wave plate 3, and the rotation angle of the polarization filter 14. That is, the configuration of FIG. 3 has the arbitraryness of FIG. 1 and FIG.

  The configuration of FIG. 4 uses a multicolor light source 40 whose output light is coherent light, uses a partial reflecting mirror 16 instead of the polarizing prism 4 of FIG. The attenuator 14 for adjusting the light intensity is provided, and instead of the reflecting mirror 9 and the spatial light modulator 10, a minute reflecting mirror array 15 configured by a plurality of pixels and controlling the reflecting direction of each of the pixels is provided. . If the branching ratio of the partial reflector 16 is appropriate, the attenuator 14 can be omitted. The feature of this configuration is that the number of components can be reduced.

  In the above description, it has been described that the three primary colors of red, green, and blue light are used. However, the plurality of different wavelengths may be, for example, light of wavelengths selected from the red region. When used in the present invention, any coherent light having a wavelength that does not interfere with each other can be used.

  In the above description, the recording of image information has been described. However, the present invention can also be used when multiple recordings of digital information are performed.

  Since the wavefront randomizing means 6 functions as a key unique to recording on the recording medium, this combination can be used as an encryption means. In particular, holograms obtained by emulating the present invention with a computer can record a larger number of dummy information than conventional ones, so that it is easy to make decryption by a third party more difficult. .

It is a block diagram which shows the 1st Example of this invention. It is a block diagram which shows the 2nd Example of this invention. It is a block diagram which shows the 3rd Example of this invention. It is a block diagram which shows the 4th Example of this invention. It is a block diagram which shows the structural example of a polychromatic light source. It is a figure which shows the example which used the liquid crystal retarder which can control a phase delay for every pixel for a spatial light modulator. It is a figure which shows the example which used the saturable absorber which can be permeate | transmitted for every pixel for the spatial light modulator. It is a figure which shows the example which used the micro reflector array for the spatial light modulator.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Multiple wavelength coherent light source 2 Beams expander 3 Wave plate 4 Polarizing prism 5 Reflecting mirror 6 Wavefront disordering means 7 Polarizing filter 9 Reflecting mirror 10 Spatial light modulator 11 Recording medium 12 Reference light 13 Controller 14 Attenuator 15 Micro reflector array 16 Partial Reflector 17 Object Light 18 Reference Light 40 Multicolor Light Source 50 Light Source 51 Photodetector

Claims (11)

A light source unit that includes a plurality of coherent light sources having different spectra, splits light emitted from any one or more of the coherent light sources, and generates reference light and object light;
A spatial light modulator for modulating the object light;
Wavefront randomization means capable of randomizing the reference light wavefront and making a plurality of different predetermined settings;
An optical system for irradiating the object light modulated by the spatial light modulator and the reference light randomized by the wavefront randomizing means from directions intersecting each other on a storage medium, and
In creating the hologram, the light from the plurality of coherent light sources is sequentially output from the light source unit under the same predetermined setting of the wavefront randomization means, and the object light by each coherent light is output to the space. Each is modulated by an optical modulator, and a hologram by each coherent light is sequentially created in the storage medium,
In the image reproduction from the hologram, after the reference of light including at least two of all the coherent lights is randomized by the wavefront randomizing means under the setting of the wavefront randomizing means. An image recording / reproducing apparatus using a plurality of wavelengths of light, which irradiates the storage medium and detects or observes the transmitted light or scattered light.   2. The image recording / reproducing apparatus according to claim 1, wherein the spatial light modulator is composed of a plurality of pixels and controls the light transmittance of each of the pixels.   2. The image recording / reproducing apparatus according to claim 1, wherein the spatial light modulator includes a plurality of pixels and controls a polarization direction of transmitted light in each of the pixels.   2. The image recording / reproducing apparatus according to claim 1, wherein the spatial light modulator is composed of a plurality of pixels and controls a reflection direction in each of the pixels. The light source unit includes a plurality of pulse light sources having different wavelengths, a beam expander, and an optical splitter.
5. The apparatus according to claim 1, wherein the intensity of light incident on the spatial light modulator is adjusted by an optical attenuator. The light source unit includes a beam expander, a laser light source, a half-wave plate, and a polarization splitter.
5. The image recording by the multi-wavelength light according to claim 1, wherein the half-wave plate is rotated to adjust the intensity ratio of the light output from the optical splitter. Playback device.   7. The multi-wavelength according to claim 1, wherein the wavefront randomizing means is a fiber bundle, and is wavefront randomizing means that rotates around a rotation axis of the fiber bundle. Image recording / playback device using light.   2. The wavefront disordering means is configured to pass through a light transmission plate provided on a surface thereof with a concavo-convex structure having a size equal to or smaller than a cross-section size of the light flux of the reference light to obtain a rough reference light with a wavefront. 7. An image recording / reproducing apparatus using a plurality of wavelength lights according to any one of items 1 to 6.   The wavefront disordering means is configured to reflect a concavo-convex structure having a size equal to or smaller than the cross-sectional size of the light beam of the reference light on a light reflection plate provided on a surface thereof to obtain a rough reference light of the wavefront. 7. An image recording / reproducing apparatus using multiple wavelength light according to any one of 1 to 6.   7. The image recording / reproducing apparatus using multi-wavelength light according to claim 1, wherein the wave front randomizing means is a reference light having a rough wave front that is passed through sodium olivine. .   11. The image recording by multiple wavelength light according to claim 1, further comprising a polarization filter for aligning a polarization direction of a light beam between the wavefront randomization means and the storage medium. Playback device.

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