KR100256666B1 - Holographic memory system using dual multiplexing - Google Patents

Abstract

PURPOSE: A device for storing a holographic based on a complex multiplexing is provided to store ultra large-sized capacity of information in a light refraction storing medium by performing an angle multiplexing through rotating a light refraction storing medium discretely in accordance with a predetermined minute angle in a spatial area and performing a wavelength multiplexing through a wavelength variable laser. CONSTITUTION: A wavelength variable laser varies a wavelength of a laser beam and creates a wavelength variable laser beam for a wavelength multiplexing of input data. A beam splitter separates the wavelength variable laser beam optically and makes a reference beam and an object beam for forming different light paths thereto. A spatial light modulating unit makes a signal beam by being irradiated by the object beam. A light refraction storing medium stores holographic data formed by interfering the signal beam and the reference beam. A stepping motor provides a rotating force for making the holographic data be recorded in the light refraction storing medium. The first iris diaphragm penetrates or cuts-off the object beam. The second iris diaphragm penetrates or cuts-off the reference beam. The first reflection mirror changes a progress direction for making the signal beam look toward the light refraction storing medium. The second reflection mirror changes a progress direction for making the reference beam look toward the light refraction storing medium. A holographic memory control unit generally controls the above elements. A video sensing unit reads the holographic data reproduced from the light refraction storing medium by controlling of the holographic memory control unit.

Description

Complex Multiplexed Holographic Storage

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a holographic storage device based on complex multiplexing. More particularly, in a holographic memory system, ultra-large-capacity information can be efficiently transferred to a photorefractive recording medium based on a complex multiplexing method combining angular multiplexing and wavelength multiplexing. A multiplexing based holographic storage device that allows for storage.

Current semiconductor memory technology is anticipated to encounter limitations in the near future, and this indication is already being detected in various fields. For example, DRAM semiconductors have to increase the density by thinning the circuit line every four times the memory capacity.In the memory device structure of 16Gbit or more, the movement distance of the electron is narrowed minutely, and the electron loses direction and irregular movement. The memory device structure loses its function. Therefore, experts in this field are expected to develop new concept devices in order to make more than 16Gbit chips, and face the limitations in the near future unless technological breakthroughs such as new materials and ultra-fine process technology that can control atomic units are prepared. Doing.

The information and communication demanded by the 21st century high information society is expected to require astronomical storage far beyond our imagination, so that next-generation data storage technology can record and process this huge amount of information more effectively. As an alternative to this, hologram storage technology is the next generation of communications storage that can simultaneously provide the benefits of ultra-large capacity (i.e. terabytes or more) of data storage and ultra-fast parallel access to stored information. It is analyzed by technology.

Hologram storage technology that uses non-linear photorefractive materials that are the size of a sugar can be analyzed and analyzed as a next-generation data storage system that can simultaneously provide the advantages of high-capacity (more than TByte) data storage capacity and high-speed (μsec) parallel access. It is evaluated.

In fact, such holographic memory has been studied in earnest since around 1970, but the progress of research has been cursed because no additional optical and electro-optical devices have been developed and there is little demand for high capacity memory. There are two reasons for the research.

First, the development of effective holographic recording media and the development of related optoelectronic devices such as small semiconductor lasers, liquid crystal device (LCD) spatial light modulators, and coupled charge device (CCD) photodetector technologies have facilitated the development of this field.

Second, because of the massive amount of information, such as multimedia information communication, video on demand, network computing, personal mobile communication, large moving image recording media, large computer servo, ultra-large digital database, stereoscopic and sensory communication require a mass storage device.

In response to such technical trends, a number of prior applications are known in relation to holographic storage devices. Representative prior applications include US Patent Application No. 3883216, US Patent Application No. 5689351, and US Patent Application No. 4988153. US Patent Application No. 4739496, US Patent Application No. 4163290, US Patent Application No. 4034355, US Patent Application No. 976354, US Patent Application No. 3851948, US Patent Application No. 5007690, US Patent Application No. 4750153, United States Patent Application No. 4145945, United States Patent Application No. 3833281, United States Patent Application No. 3854791, United States Patent Application No. 3761155, United States Patent Application No. 5661577, United States Patent Application No. 5648856, United States Patent Application No. 5550779, United States Patent Application No. 5132835, United States Patent Application No. 4318581, United States Patent Application No. 4138189, United States Patent Application No. 4040039, United States Patent Application No. 3959784, United States Patent Application No. 3919698, United States Patent Application No. 3871740, United States Patent Application No. 3833893, United States Patent Application No. 3781830, United States Patent Application No. 3744871, United States Patent Application No. 3627402, United States Patent Application No. 5694488, United States Patent Application No. 5691989, United States Patent Application No. 5684611, United States Patent Application No. 5566387, United States Patent Application No. 5491570, United States Patent Application US Patent No. 5481523, US Patent Application No. 5440669, US Patent Application No. 5438439, US Patent Application No. 5383038, US Patent Application No. 5377179, US Patent Application No. 5335098, US Patent Application No. 5031112, US Patent Application Examples such as 4934779 and the like can be given.

The present invention relates to holographic storage technology, which is a somewhat unfamiliar field, and a general description of holographic storage technology using a photorefraction effect will be described to help the understanding of the present invention.

Again, the hologram storage technique uses the photorefractive effect.

The photorefractive effect refers to the change in the refractive index caused by light in the photorefractive recording medium, which is represented by a grating of refractive indices corresponding to the interference pattern due to two interfering light waves in the volume of the crystal.

The basic mechanism of the photorefractive effect is that light is incident on the photorefraction recording medium, followed by photoionization, diffusion, recombination, space charge formation, and electric field formation. The information is recorded as the change of.

In other words, the charges generated by photoionization have non-uniform densities, resulting in non-uniform spatial charge distribution through diffusion or drift. This spatial charge distribution forms an internal electric field within the crystal, which can store input information by locally changing the refractive index of the material by the electro-optic effect.

For reference, the Pockel effect refers to a phenomenon in which the refractive index of light changes in proportion to the intensity of an electric field applied thereto in transparent crystals, and is often used when constructing an optical signal modulator.

In general, in a holographic optical memory system, when two laser beams (a signal beam and a reference beam) interfere in the optical refraction recording medium, a grating pattern is formed and stored in the medium by the optical refraction effect.

In order for input data to be stored in the form of a lattice pattern in a crystal, the data is first made into an input pattern in the form of light intensity modulation in a spatial light modulator such as a liquid crystal-spatial light modulator (LC-SLM).

The blue laser beam is irradiated through LC-SLM page data, such as a crossword puzle pattern, and imaged by a lens to produce a signal beam. When such a signal beam meets a reference wave aligned at a plurality of angles (or wavelengths and phase codes) in an optical refraction recording medium, more than a thousand pages of hologram data are multiplexed and recorded.

After this recording process, the data of a specific page can be reproduced holographically by injecting the reference wave again at the same angle (or wavelength, phase code) as the reference wave used at the time of recording. That is, when passing through the diffraction grating formed in the optical refraction recording medium, the reference wave is diffracted in the direction of reproducing the image of the information on the original page.

The reproduced image is incident on an image sensor such as a charge coupled device (CCD) to read all the information stored in one page at a time. This data is again stored and processed electronically by the digital computer.

Here, it is obvious that the reference wave should use the same one used for storing. When the reference wave is incident on the optical refraction recording medium, its accuracy depends on the thickness of the optical refraction recording medium. The thicker the optical refraction recording medium, the more accurately the reference beam should be irradiated. For example, in the case where the crystal is 10 mm thick, when the incident angle deviates by 0.001 degrees, the reproduced image is completely lost.

As described above, the holographic multiplexing technique for storing a large amount of information can be implemented by varying the incident angle of the reference beam (or reference wave), which is an angle that changes the angle, wavelength, and phase of the reference beam. Multiplexing, wavelength multiplexing, phase code multiplexing techniques, and spatial multiplexing techniques of spatial variation are known, and descriptions of the individual techniques are described in detail in the above-listed applications.

In general, in general holographic storage systems, holographic multiplexing techniques such as angular multiplexing, wavelength multiplexing, phase code multiplexing, spatial multiplexing, and the like, are generally applied in a separate and independent form.

However, it is easy to predict that if the multiplexing technique that can apply each multiplexing technique to the holographic storage system can increase the storage space accordingly, it can be easily realized in various aspects. Efforts are being made, but the technical approach is very low, and more advanced technologies are being expected to combine and apply multiple holographic multiplexing techniques to photorefractive recording media.

Accordingly, the present invention has been made to meet such technical requirements, and in the holographic storage system, angular multiplexing is performed by discretely rotating an optical refractive recording medium in a spatial region according to a predetermined fine angle. In addition, by performing wavelength multiplexing using a wavelength tunable laser, a complex multiplexing based holographic storage device capable of storing ultra-large-capacity information in a photorefractive recording medium is realized by realizing complex multiplexing combining self-neutralization and wavelength multiplexing. There is this.

1 is a block diagram illustrating a preferred embodiment of a complex multiplexing based holographic storage device in accordance with the present invention;

2 is a block diagram illustrating the holographic memory controller of FIG. 1;

3 is an exemplary diagram illustrating a timing diagram of a rotation angle, a laser wavelength, and input data of a reference wave and an object wave.

<Explanation of symbols for main parts of drawing>

10: wavelength tunable laser 20: beam splitter

21: first aperture 22: second aperture

30: spatial light modulator 31: first reflecting mirror

32: second reflector 40: optical refractive recording medium

50: step motor 100: holographic memory control unit

110: host computer 120: interface card unit

121: interface integrated circuit unit 122: digital / analog converter

123: first operational amplifier 124: power amplifier

125: second operational amplifier 200: image sensor

In order to achieve the above object, the multiplexing-based holographic storage device according to the present invention is a holographic storage system for electro-optically storing input data based on a photorefraction effect.

A tunable laser for generating a tunable laser beam by varying the wavelength of the laser beam to multiplex the input data;

A beam splitter for optically separating the incident wavelength-tunable laser beam to form a reference beam and an object beam, respectively, for forming different optical paths;

A spatial light modulator positioned on an optical path through which the object beam passes, and generating a signal beam when irradiated by the object beam in a state of forming an input pattern of a light intensity modulation type corresponding to the input data. );

An optical refraction recording medium for electro-optically storing holographic data in the form of an interference grating pattern formed by the interference between the signal beam and the reference beam by the optical refraction effect; And

And a step motor providing stepwise rotational force so that the holographic data is multiplexed onto the optical refraction recording medium and recorded by discretely rotating the optical refraction recording medium according to a predetermined fine angle. to be.

Hereinafter, the present invention increases the capacity of information that can be stored by simultaneously using angle multiplexing and wavelength multiplexing, and will be described in detail for angular multiplexing and wavelength multiplexing. Shall be.

First, angular multiplexing is based on the fact that a volume hologram recorded with a signal beam having a specific angle and a reference beam is restored depending on the angle between the reference beam at the time of recording and the reference beam at the time of restoration.

Angular selectivity can be best described and quantified for the case of a simple sinusoidal grating recorded by two plane waves. Photorefractive recording medium (For convenience of description, the thickness of the photorefractive recording medium is L _z Each of the incident angles of the reference beam and the object beam θ _R and θ _O Wave vector of the reference beam k ₀ And wave vectors of object beams k _R Are represented by Equation 1, respectively.

here, n Is the refractive index of the medium and is the wavelength of light in the vacuum.

Where the grid vector in the wave vector spatial shape K Is the set of all possible wave vectors that correspond to the plane waves traveling in the medium, and for simplicity the surface radius k ₀ When considering only the isotropic sphere, the Bragg's matching condition to be satisfied for scattering the input reference wave is given by Equation 2.

From here k _O ′ Is the scattered object wave vector k _R ′ Is the incident reference wave vector, and ▵k _z Represents the degree of predetermined phase mismatch that may occur due to the thickness of the medium. Typically for weak scattering (ie diffraction efficiency η << 1 ), The diffraction efficiency is shown in Equation 3.

η ∝ sinc ² (▵k _z L _z )

While reading the information, the direction of the reference beam must be within the range defined by Equation 4 to cause diffraction to be fully observed.

Where the reference vector is k _R and k _O It can be rotated in a direction perpendicular to the plane defined by, and can satisfy the Bragg condition with zero phase mismatch as opposed to an increase in mismatch that occurs when the rotation in the plane increases.

Angular selectivity in the plane is approximately given by the width of the angle between the first zero points in equation (3).

Normally, Equation 5 is small θ _O Is correct against. In addition, the angular selectivity is best when the angle between the object beam and the reference beam is 90 DEG, and the angular selectivity starts to fall symmetrically about this angle.

In order to store multiple holograms in the same volume, an image without cross talk may be obtained by multiplexing and restoring the same plane using reference beams spaced by an increment of an angle given by Equation 5.

Angle of reference beam θ ₁ in θ _m The number of holograms that can be multiplexed within a given range up to is given by Equation 6.

Therefore, when the multiplexing is used, M pieces of information can be stored as shown in Equation (6).

Next, referring to wavelength multiplexing, wavelength multiplexing is a method of recording data while varying the wavelength of the laser at each exposure while the angles of the reference beam and the object beam are kept constant.

The reproduction of data is individually accessed by the reference beam tuned such that the wavelength desired for reproduction matches the recorded "address" wavelength. Hologram optical frequency ν (In other words At the same angle ν-▵ν When the hologram is read with the reference beam of ▵ν There is a phase mismatch given by.

This, together with Equation 4, leads to an acceptable optical frequency spacing.

For example, suppose that the wavelength of a given laser can be modulated from 800 nm to 820 nm. This corresponds to a frequency range of 9,146 GHz, L _z = 1 cm ego n = 2.2 If the frequency interval from ▵ν = 2.95 GHz. Thus, up to 3,100 pieces of information can be multiplexed in the same volume since the wavelength changes.

Hereinafter, the configuration and operation of the preferred embodiment of the present invention in which angular multiplexing and wavelength multiplexing are combined will be described with reference to FIG. 1.

1 is a block diagram illustrating a preferred embodiment of a complex multiplexing based holographic storage device in accordance with the present invention.

A preferred embodiment of the complex multiplexing based holographic storage device according to the present invention is a holographic storage system for electro-optically storing input data based on a photorefractive effect, as shown in FIG.

A wavelength tunable laser (10) for generating a tunable laser beam by varying the wavelength of the laser beam to multiplex the input data;

A beam splitter 20 which optically separates the incident wavelength-tunable laser beam to form a reference beam and an object beam, respectively, which form different optical paths;

A spatial light modulator (30) positioned on an optical path through which the object beam passes, and generating a signal beam by being irradiated by the object beam in a state of forming an input pattern of a light intensity modulation type corresponding to the input data;

An optical refraction recording medium (40) for electro-optically storing holographic data in the form of an interference grating pattern formed by interference between the signal beam and the reference beam by the optical refraction effect;

A step motor (50) which provides a stepwise rotational force to discretely rotate the optical refraction recording medium according to a predetermined fine angle so that the holographic data is multiplexed and recorded on the optical refraction recording medium;

A first aperture 21 positioned between the beam splitter and the spatial light modulator to transmit or block the object beam;

A second aperture 22 positioned between the beam splitter 20 and the optical refraction recording medium 40 to transmit or block the reference beam;

A first reflector (31) positioned between the beam splitter (20) and the optical refraction recording medium (40) to change the direction of travel of the signal beam toward the optical refraction recording medium (40);

A second reflector 32 positioned between the second aperture 22 and the optical refraction recording medium 40 to change the direction of travel of the reference beam toward the optical refraction recording medium 40;

By varying the control voltage applied to the variable wavelength laser 10 in stages, the laser beams having different wavelengths are generated, and the step motor control signal applied to the step motor 50 is varied in stages. Wavelength multiplexing and angular multiplexing the input data on the optical refraction recording medium 40 through a combination between the laser beams having the respective wavelengths and the respective rotation angles by controlling the respective rotation angles according to the respective rotation angles. A holographic memory control unit 100 for controlling the components of the present invention such as controlling the optical path to record and reproduce the data, and recording / reproducing the holographic data; And

And an image sensor unit 200 which performs photoelectric conversion to read the holographic data reproduced from the optical refractive recording medium 40 under the control of the holographic memory controller 100.

Here, the material of the photorefractive recording medium 40 may be a nonlinear crystal such as LiNbO ₃ , BSO, BaTiO ₃ or the like.

An operation of a preferred embodiment of the complex multiplexing based holographic storage device according to the present invention configured as described above will be described in detail with reference to the accompanying drawings.

As shown in FIG. 1, input data to be stored through the holographic memory controller 100 is displayed on the spatial light modulator 30, and all recording and reproducing operations are represented by a holographic memory represented by a host computer or a microprocessor. It is strictly controlled by the controller 100.

In the present invention, instead of changing the angle of the reference wave to use the angular modulation method, the same effect can be obtained by discretely rotating the optical refractive recording medium 40 using the step motor 50. The rotation angle for storing the data is the angle of the reference beam as shown in Equation 6. θ ₁ in θ _m It is until.

In order to apply the wavelength modulation method, the angle of the reference beam θ ₁ After fixing to, the wavelength of the tunable laser 10 is changed for each input data to be stored and data D is recorded through exposure. (D _11, D _12, ..., D _1m = θ ₁ λ _1, θ ₁ λ _2, ..., θ ₁ λ _m ) .

The change rate of the wavelength can be obtained from Equation (8). Then, the angle satisfying the Bragg condition of Equation 6 θ _2, θ ₃ ... According to the angle θ ₂ Change to.

Similarly angle θ ₂ If you save the data while changing the wavelength D _21, D _22, D _2m = θ ₂ λ _1, θ ₂ λ _2, ..., θ ₂ λ _m Can be obtained.

In conclusion, according to the present invention, it is possible to store as much information as the allowed values of Equations 6 and 8 D _11, D _12, D _{1 m} , D _21, D ₂₂ , D _{2 m,} D _m2 , D _mm As much information can be stored.

Therefore, it is possible to store as much information as the amount of information that can be stored using wavelength multiplexing to the data that can be stored using angular multiplexing.

1 is a detailed block diagram illustrating the holographic memory controller 100 of the present invention.

As shown in FIG. 2, the holographic memory controller 100 includes a host computer 110 and an interface card unit 120.

The holographic memory controller 100 controls the tunable laser 10, the first aperture 21, the second aperture 22, and the step motor 50 using a host computer 110 such as an IBM PC. Angular multiplexing and wavelength multiplexing are used to record and reproduce information in the optical refraction recording medium 40.

In order to control various devices with a computer, it is preferable to attach the interface card unit 120 to an expansion slot of the host computer 110 to externally control the holographic storage device through a program.

As can be seen in FIG. 2, the interface card unit 120 is largely composed of a tunable laser controller, a step motor controller, and an aperture controller.

The purpose of using the step motor 50 is to rotate the optical refractive recording medium 40 to implement angular multiplexing. By outputting data to the expansion slot in the program, the step motor control signal is transmitted to the second output port port2 through the interface integrated circuit unit 121, and the signal is supplied to the power amplifier unit with power capable of driving the step motor 50. After the amplification in the power amplifier 124 is input to the control terminal of the step motor 50 to drive the step motor 50 to rotate at a desired angle.

The purpose of using the tunable laser 10 is to implement wavelength multiplexing by changing m wavelengths. The tunable laser 10 can be changed to m wavelengths via the half-wave plate 11 by controlling the contact pressure. A digital / analog converter 122 and a first operational amplifier 123 are used to control the program.

Since m wavelengths can be controlled by n control bits by m = 2 ⁿ , the n bits of the first output port port1 of the interface integrated circuit unit 121 are changed to D ₁₁ ... D _1n . use.

The digital signal combined with n bits is converted into an analog signal by the digital / analog converter 122, and then amplified by the wavelength variable laser control voltage by the first operational amplifier 123, and then converted into an amplified signal. ).

The purpose of using the first aperture 21 and the second aperture 22 is to control the exposure timing of the light. By using the digital shutter system (Digital Shutter System) to convert the signal output through the third output port (port3) of the interface integrated circuit unit 121 to the input signal of the aperture using the second operational amplifier 125 to control. .

The second aperture 22 is used to control (block and transmit) the reference wave, and the first aperture 21 is used to control the object wave. In order to record information in the optical refractive recording medium 40, the following operation is performed.

In the first step, the tunable laser control voltage A ₁ is output to the first output port port1 of the holographic memory controller 100 so that the wavelength of the tunable laser 10 becomes λ ₁ .

In the second step, the program outputs the first step motor control signal B ₁ to the second output port port2 of the holographic memory controller 100 so that the angle of the step motor 50 becomes θ ₁ .

In the third step, the first information (that is, input data) is displayed on the spatial light modulator 30.

In the fourth step, the program outputs the first aperture control signal C ₁ to the third output port port3 of the holographic memory controller 100 to open the first aperture 21 and the second aperture 22 to enter the incident beam. It penetrates.

Accordingly, the reference wave and the object wave of the angle θ ₁ and the wavelength λ ₁ store the first information in the optical refraction recording medium 40. After exposing the light for a recording time, the second aperture control signal C ₂ is output to the third output port 3 to block the first aperture 21 and the second aperture 22.

Subsequently, the second information is displayed on the spatial light modulator 30 to record the next second information, and the second output port port2 is fixed at each θ ₁ and A ₂ is output at the first output port port1. So that the wavelength is λ ₂ .

After that, the first aperture control signal C ₁ is output to the third output port 3 to open the first aperture 21 and the second aperture 22 to transmit the incident beam, thereby allowing the optical refractive recording medium 40 to pass through. The second information will be recorded in. As the first output port port1 is changed to A _m , m pieces of information are recorded at each θ ₁ while the wavelength λ value is changed to λ _m .

angle θ _2, while the second step-motor and outputting a control signal B ₂ changes the wavelength as described above, after having fixed the angle θ ₂ with λ ₁ ..λ _m to a second output port (port2) Record the m pieces of information, Record m pieces of information about.

In this manner, by repeatedly recording m pieces of information at different θ values while varying θ ₁ ..θ _m , the optical refraction recording medium 40 is concluded. m × m Information is recorded.

Angle: θ ₁ (A ₁ ), θ ₂ (A ₂ ) ... θ _m (A _m )

Wavelength: λ ₁ (B ₁ ), λ ₂ (B ₂ ) ... λ _m (B _m )

Aperture: C ₁ => penetrating the second aperture, penetrating the first aperture

C ₂ => 2nd Aperture Block, 1st Aperture Block

C ₃ => penetrating the second aperture, blocking the first aperture

The reproduction is output in the third aperture control signal C ₃ through the second output port ₃ to block the first aperture 21, and then transmit only the reference wave and proceed in the same manner as recording. In order to reproduce desired information in order, playback is performed by the following procedure.

In the same manner as in writing, the tunable laser control signal A ₁ is output to the first output port port1 of the holographic memory controller 100 so that the wavelength of the tunable laser 10 becomes λ ₁ . The program outputs B ₁ to the second output port port2 of the holographic memory controller 100 so that the angle of the step motor 40 becomes θ ₁ .

In the program, the third aperture control signal C ₃ is output to the third output port port3 of the holographic memory controller 100 so as to pass through the second aperture 22 and block the first aperture 21.

The first information is reproduced by exposing the reference wave of the angle θ ₁ and the wavelength λ ₁ to the optical refractive recording medium 40. In order to see the following information, only the second aperture 22 is transmitted and the first aperture 21 is blocked, the angle θ ₁ is fixed, the wavelength is converted into λ ₂ , and the reference wave is transmitted to the optical refraction recording medium 40. Exposure exposes the second information.

Thus, m pieces of information can be reproduced by changing the lambda value into lambda ₁ ... lambda _m . After converting the wavelength λ value to λ ₁ again, B ₂ is output to the second output port ₂ so that the angle of the stepper motor 50 becomes θ ₂ , and the λ value is changed to λ ₁ ... λ _m . By doing so, m pieces of information for each θ ₂ can be reproduced.

Then by changing the θ value to θ _m by changing the λ value for each θ value m × m Information can be played back.

3 is an exemplary diagram illustrating a timing diagram of a rotation angle, a laser wavelength, and input data of a reference wave and an object wave.

The present invention includes an image sensor unit 200 that performs photoelectric conversion to read the holographic data reproduced from the optical refractive recording medium 40 under the control of the holographic memory control unit 100. As mentioned above. That is, the reproduced image is incident on the image sensor unit 200 such as a charge coupled device (CCD) to read all the information stored in one page at a time. This data is again stored and processed electronically by the digital computer.

As described above, the holographic memory is expected to be capable of data transfer rates of 1 Gbit / s, fast random access times of less than 100 microseconds, and storage capacity of more than terabytes. The biggest advantage of hologram memory is that it can store thousands of pages of data with Mbit information on one page in a coin-sized volume. To this end, each page data is stored in interference with individual reference waves that can change the angle, wavelength, phase, and the like of the beam. Certain holographic page groups can also be stacked separately through the thickness of the recording medium, further increasing storage capacity. Another major advantage of hologram memory is redundancy. This is because some pixel pixels of a single hologram image are distributed and stored throughout the storage medium, so that some defects in the recording medium may affect the signal level of the entire data page, but each data bit is not erased. This can ensure the complete integrity of the stored data. Another advantage is that if all data pages are defined as reference wave angles with random access time, each page can be recorded and played back as fast as the angle of the beam changes.

Terminologies used herein are terms defined in consideration of functions in the present invention, which may vary according to the intention or customs of those skilled in the art, and the definitions should be made based on the contents throughout the present application. will be.

In addition, since the present invention has been described through the preferred embodiment of the present invention, in view of the technical difficulty aspects of the present invention, those having ordinary skill in the art can easily be different from another embodiment of the present invention. Since modifications may be made, it is obvious that both the embodiments and modifications cited in the above description belong to the claims of the present invention.

As described in detail above, in a holographic storage system that electro-optically stores input data based on a photorefraction effect, a wavelength-variable laser beam is generated by varying a wavelength of a laser beam in order to multiplex the input data. A tunable laser; A beam splitter for optically separating the incident wavelength-tunable laser beam to form a reference beam and an object beam, respectively, for forming different optical paths; A spatial light modulator positioned on an optical path through which the object beam passes, and generating a signal beam when irradiated by the object beam in a state of forming an input pattern of a light intensity modulation type corresponding to the input data. ); An optical refraction recording medium for electro-optically storing holographic data in the form of an interference grating pattern formed by the interference between the signal beam and the reference beam by the optical refraction effect; The present invention includes a step motor which provides a stepwise rotational force so that the holographic data is multiplexed onto the optical refractive recording medium and recorded by discretely rotating the optical refractive recording medium according to a predetermined fine angle. According to the multiplexing-based holographic storage device according to the present invention, the optical refraction recording medium is discretely rotated according to a predetermined fine angle in a spatial domain, and the wavelength multiplexing is performed by using a wavelength tunable laser. The complex multiplexing combined with the neutralization and the wavelength multiplexing realizes the advantage of storing extremely large amounts of information in the optical refraction recording medium.

Claims (5)

A holographic storage system for electro-optically storing input data based on photorefractive effects, A tunable laser for generating a tunable laser beam by varying the wavelength of the laser beam to multiplex the input data; A beam splitter for optically separating the incident wavelength-tunable laser beam to form a reference beam and an object beam, respectively, for forming different optical paths; A spatial light modulator positioned on an optical path through which the object beam passes, and generating a signal beam when irradiated by the object beam in a state of forming an input pattern of a light intensity modulation type corresponding to the input data. ); An optical refraction recording medium for electro-optically storing holographic data in the form of an interference grating pattern formed by the interference between the signal beam and the reference beam by the optical refraction effect; And And a step motor providing a stepwise rotational force for discretely rotating the optical refraction recording medium according to a predetermined fine angle so that the holographic data is multiplexed and recorded on the optical refraction recording medium. Complex multiplexed based holographic storage. The method of claim 1, A first aperture positioned between the beam splitter and the spatial light modulator to transmit or block the object beam; A second aperture positioned between the beam splitter and the optical refraction recording medium to transmit or block the reference beam; A first reflector positioned between the beamsplitter and the optical refraction recording medium to change a direction of travel of the signal beam toward the optical refraction recording medium; And And a second reflector positioned between the second aperture and the optical refraction recording medium to change a direction of travel so that the reference beam is directed toward the optical refraction recording medium. The method of claim 2, The laser beams having different wavelengths are generated by varying the control voltage applied to the variable wavelength laser step by step, and the step motor control signals applied to the step motor are varied step by step. The optical path is controlled to have a rotation angle so as to record and reproduce the wavelength data by multiplexing and angularly multiplexing the input data on the optical refractive recording medium through a combination between the laser beams having the respective wavelengths and the respective rotation angles. The holographic storage device of claim 1, further comprising a holographic memory controller. The method of claim 3, wherein And an image sensor unit configured to perform photoelectric conversion to read the holographic data reproduced from the optical refraction recording medium under the control of the holographic memory control unit. The material of claim 1, wherein the material of the optical refractive recording medium is A multiplexing based holographic storage device, characterized in that any one of LiNbO ₃ , BSO, BaTiO ₃ .