KR100316381B1 - Angular multiplexing type hologram data storage system - Google Patents

Abstract

The present invention relates to an angular multiplexing type hologram data storage system, and more particularly, to an angular multiplexing type hologram data storage system that includes a beam splitter for separating a laser beam emitted from a laser into a reference beam and an object beam, Wherein the refractive index variable optical element comprises a transparent body formed in a hollow triangular cylinder shape with a transparent material, a refractive index change material contained in an inner closed space of the transparent body, and a heating material for heating the refractive index change material Element.

According to the present invention, the angular multiplexing can be realized by continuously changing the proceeding angle of the laser beam by changing the refractive index of the refractive index variable optical element by the temperature change, and the displacement is controlled by the refractive index variable optical element capable of making a large change Fine angular multiplexing becomes possible and storage density is improved. Further, the configuration of the refractive index variable optical element is simple, contributing to miniaturization and cost reduction.

Description

ANGULAR MULTIPLEXING TYPE HOLOGRAM DATA STORAGE SYSTEM [0002]

[0001] The present invention relates to an angular multiplexing type hologram data storage system, and more particularly to an angular multiplexing type hologram data storage system in which an angular multiplexing is realized by continuously varying a progress angle of a laser beam by changing a refractive index of an optical element by a temperature change, And a registration system.

[0003] Holographic memories are becoming more and more popular as the age of the multimedia age has come to record a great deal of information and the need for systems that require fast data transfer has increased.

Such holographic recording records not only the intensity of the object light reflected from the object but also the phase, and the intensity and phase of the light of the object are constituted by the interference between the object light and the reference light. The object light and the reference light form an interference fringe. The interference fringe thus formed is recorded in a material responsive to the intensity of the interference fringe. The hologram, which is a three-dimensional image of the object, is reproduced by irradiating the reference light to the recorded interference fringe.

The hologram is stored in the cube, and only the reference light used in the recording process can be read out of the hologram recorded in the cube. The reference light having a different wavelength and phase from the reference light used for recording passes through the hologram recorded in the cube without any effect .

Using the inherent nature of a volume hologram, it is possible to store vast amounts of data inside a small cube by recording many holograms in the same location of the storage material with different reference light. One method of making different reference beams is angular multiplexing, which changes the angle of the reference beam for each recording. With this method, hundreds to thousands of holograms, which consist of page units of binary data, can be stored in the same place. That is, by recording and reproducing a large amount of data in the same place on a page basis, it becomes possible to record and reproduce data with a high storage density and a high data transmission rate, thereby realizing a digital data storage system using holography.

In a conventional 90 ° geometry digital data storage system, a laser beam generated by a laser oscillator is incident on a beam splitter and divided into a reference beam and an object beam, and the object beam is split into input data Therefore, a spatial light modulator (SLM) modulates the binary data of the light and darkness of the pixels, and the reference light corresponding to the angle of the rotating mirror is correspondingly generated in each page.

Thereafter, the object light and the reference light interfere with each other in the storage medium for recording the hologram. In accordance with the intensity of the interference fringes generated at this time, a light oil phenomenon occurs in the movement charge inside the storage medium, and the interference fringes are recorded through this process. In order to read the data recorded on the storage medium, when only the reference light is irradiated on the storage medium, the interference fringe is diffracted to reconstruct a checkered pattern composed of light and shade of the original pixel, and then the read image is converted into a charge coupled device (CCD) ) To restore the original data.

Such a conventional 90 ° arrangement type hologram data storage system is a method for performing angular multiplexing by rotating a mirror disposed between a beam splitter on the reference light side and a hologram recording medium to change the angle of a beam incident on the hologram recording medium Recording / reproducing is performed. However, since the angle adjustment by the mirror uses a mechanical rotating device, there is a limitation in adjusting the angle, and there is a problem that the cost is increased due to the complexity of the rotating device.

It is an object of the present invention to provide an angular multiplexing system capable of realizing an angular multiplexing by continuously varying a progress angle of a laser beam by changing a refractive index of an optical element by a temperature change, Type hologram data storage system.

In order to achieve the above object, an angular multiplexing type hologram data storage system of the present invention includes a beam splitter for separating a laser beam oscillated by a laser into a reference beam and an object beam, and a beam splitter for splitting the progression angle of the reference beam on the reference beam side optical path of the hologram recording medium And a variable-refractive-index optical element for displacing the optical element.

The refractive index variable optical element is composed of a transparent body formed as a transparent triangular cylinder with a transparent material, a refractive index change material contained in an inner confined space of the transparent body, and a heating element for heating the refractive index change material.

In addition, glass is used for the transparent body, methylbenzoate and glycerin are used for the refractive index change material, and a reflective layer is formed on the surface of the transparent body where the beam is bent to prevent loss of the beam.

Further, a heating coil wound on the outer side of the transparent body is used as the heating element, and a temperature sensing element is coupled to the transparent body to sense the temperature.

Figs. 1 to 6 are views related to the present invention,

1 is a block diagram of an angular multiplexing type hologram data storage system;

2 is a longitudinal front view of a refractive index variable optical element.

3 is a longitudinal side view of a refractive index variable optical element.

Figures 4A-4C illustrate an angular multiplexing.

FIG. 5 is a dispersion curve of glass and filter liquid according to temperature change. FIG.

FIG. 6 is a graph showing a refractive index change according to a temperature change. FIG.

7 is a circuit configuration diagram for changing the temperature of the refractive index variable optical element.

Description of the Related Art

10: laser 20: beam splitter

30: variable refractive index optical element 31: transparent body

32: refractive index change material 33: heating element

34: reflective layer 35: temperature sensing element

60: Hologram recording medium

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

2 is a longitudinal end elevational view of a refractive index variable optical element, and FIG. 3 is a longitudinal side view of a refractive index variable optical element. In this figure, The angular multiplexing type hologram data storage system of the present invention includes an optical element for separating the laser beam into the reference beam and the object beam on the optical path of the laser beam generated by the laser 10, for example, a beam splitter 20 . A refractive index variable optical element 30 for continuously changing the traveling angle of the reference light is disposed on the optical path of the reference light. A mirror 40 is disposed on the optical path of the object light, and a spatial light modulator (SLM A Spatial Light Modulator) 50 and a hologram recording such as an iron-doped lithium niobate crystal doped with Fe for recording hologram data on the optical path of the reference light and the object light A medium 60 is disposed and a photoelectric conversion element 70 such as a CCD (Charge Coupled Device) is disposed adjacent to the hologram recording medium 60.

As shown in FIGS. 2 and 3, the refractive index variable optical element 30 includes a transparent body 31, which is hollow and hollow and made of a transparent material such as glass, and a refractive index change material (32), and a heating element (33) for heating the transparent body (31) and more precisely the refractive index changing material (32).

Methylbenzoate, glycerin or the like is used for the refractive index changing material 32 and a mirror coating layer (not shown) is formed on one surface of the transparent body 31 where the beam is bent. 34 may be formed.

A heating coil wound around the transparent body 31 is used as the heating element 33 and a temperature sensing element 35 such as a thermocouple is coupled to the transparent body 31 to sense the temperature.

FIG. 5 is a graph showing dispersion curves of the glass and the filter liquid according to the temperature change. FIG. 6 is a graph showing the refractive index change according to the temperature change. As shown therein, And the refractive index is decreased when the temperature of the built-in refractive index changing material 32 is increased by heating by the heating means 33.

4A to 4C are diagrams for explaining the operation of the angular multiplexing. Referring to FIG. 4A and FIG. 4C, when a laser beam is incident on the inside of the transparent body 31, that is, when n ₂ is incident on a material having a refractive index n ₁ , the following equations are established.

That is, the beam proceeding to? ₁ is refracted at? ₂ according to Snell's law of incidence on a material having a refractive index n ₂ , and n ₁ sin? ₁ = n ₂ sin? ₂ (1) do.

In addition, the angle c in the triangle abc of Figure 4b 180 - (90 - α) - (90 + θ 2) = α - and the θ _2, θ ₃ = 90 in Fig. 4b - α + θ ₂ .... ... (2).

And the angle of d in the triangle cde of FIG. 4c is 180 - (α - θ ₂ ) - (α + β) = 180 - 2α + θ ₂ - β and θ ₄ = 2α + β - θ ₂ - 90. ... (3).

When the beam proceeding at? ₄ goes out to a medium having a refractive index of n ₁ ,

n ₂ sin? ₄ = n ₁ sin? ₅ (4)

, And by substituting the equation (3)

. Here, (1)

≪ / RTI >

A sin-1 of the brace of this type is denoted by sin-1 to recognize the following one to be indicated by the original sin ^-1, Hangul formula parts error.

Here, n ₁ is assumed to be air, n ₁ = 1, and α, β, and θ ₁ are constant, so θ ₅ is affected only by n ₂ . That is, when n ₂ changes, θ ₅ also changes.

In the angular multiplexing type hologram data storage system of the present invention, the laser beam generated from the laser 10 is incident on the beam splitter 20, divided into the reference beam and the object beam, and the object beam is incident on the mirror 40, And then modulated by the spatial light modulator 50 in units of one page of the binary data of the light and darkness formed by the pixels according to the input data to reach the hologram recording medium 60. The reference light is reflected by the variable- (30) and reaches the hologram recording medium (60).

At this time, as the heating element 33 is heated by the control of the microprocessor, the refractive index variable optical element 30 changes the temperature of the built-in refractive index changing material 32 and changes the refractive index of the refractive index variable optical element 30 The proceeding angle of the passing reference light is continuously changed.

7, the heating coil 33, which is not shown in the figure, is not wound around the central portion of the transparent body 31 so that the beam can pass therethrough, When the temperature is sensed, it is input to the microprocessor, and the microprocessor outputs a predetermined current value based on the input value so that the heating element 33 generates heat to change the temperature of the refractive index changing material 32, Techniques relating to temperature control are common techniques.

Thereafter, the object light and the reference light interfere with each other in the hologram recording medium 60 for recording the hologram, and the light oil phenomenon of the movement charge in the hologram recording medium 60 occurs according to the intensity of the interference fringe generated at this time. Through this process, the interference pattern is recorded.

In order to read the data recorded on the Hologram recording medium 60, when only the reference light is irradiated to the hologram recording medium 60, the interference fringe diffracts the reference light and is restored into a checkerboard pattern composed of light and shade of the original pixel, And the image is projected onto the photoelectric conversion element 70 to restore the original data.

As described above, according to the present invention, it is possible to realize an angular multiplexing by continuously varying the advancing angle of the laser beam by changing the refractive index of the refractive index variable optical element by the temperature change, and by changing the refractive index variable optical element By controlling the displacement, fine angular multiplexing becomes possible and the storage density is improved. Further, the configuration of the refractive index variable optical element is simple, contributing to miniaturization and cost reduction.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not to be limited to the disclosed embodiments, and that various changes and modifications within the true spirit and scope of the invention It should be understood.

Claims (2)

An angular multiplexing type hologram data storage system comprising a beam splitter for separating a laser beam generated from a laser light source into a reference beam and an object beam, and a mirror and a spatial light modulator disposed on the optical path of the object beam separated by the beam splitter As a result, A refractive index variable optical element for displacing the traveling angle of the reference light on the optical path of the reference light separated by the beam splitter, wherein the refractive index variable optical element comprises: a transparent body formed as a transparent triangular cylinder with a transparent material; And a heating element for heating the refractive index changing material, and a heating element for heating the refractive index changing material. The hologram data storage system of claim 1, The angular multiplexing type hologram data storage device according to claim 1, wherein a heating coil wound around the transparent body is used as the heating element, and a temperature sensing element is coupled to the transparent body to sense temperature. system.