KR100256657B1 - Improved volume holographic digital storage/reproducing system and/recording data monitoring method - Google Patents

Abstract

PURPOSE: A system for storing and reproducing improved volume holographic digital data and a method for monitoring recording data are provided to reproduce recorded hologram data and perform monitoring a diffraction efficiency of hologram data which were reproduced by using a reading beam obtained by changing a path of a reference beam used in recording hologram data. CONSTITUTION: A light source(102) creates a laser beam requested in a holography. A storing medium(134)(for example, light refraction crystal) stores hologram data(that is, interference pattern) on the three dimensions. A reference light processing path(PS1) and an object light processing path(PS2) having each optical system are formed between the light source(102) and the storing medium(134). A light separating unit(104) separates a reference light and an object light from the laser beam generated and inputted from the light source(102). A reference light of the separated vertical deflected light is provided to the reference light processing path(PS1), and an object light of the separated vertical deflected light is provided to the object light processing path(PS2). A shutter(106), a waist construction lens(108), a beam extending unit(110) having two lenses, a reflection mirror(112) and an actuator(114) are provided on the reference light processing path(PS1) in the output direction of the reference light successively. The reference light processing path(PS1) creates a reference light needed at a recording or reproducing the hologram data, and offers the light to the storing medium(134) by the pre-fixed bias angle.

Description

Improved Volume Holographic Digital Storage and Playback System and Record Data Monitoring Method

The present invention relates to a volume holographic digital data storage / reproducing system, and more particularly to recording hologram data in a storage medium (e.g., optical refractive crystal). An improved volume holographic digital storage and playback system and method for monitoring recorded data suitable for monitoring the recorded state so that the hologram data maintains the optimal recorded state.

Recently, the field of technology using volume holographic digital data storage is being actively researched everywhere due to the remarkable development of semiconductor laser, charge coupled device (CCD), liquid crystal display (LCD), etc. As a result of this research, fingerprint recognition systems for storing and reproducing fingerprints have been put to practical use, and are being expanded to various fields that can apply the advantages of large capacity and ultra-fast data transfer rate.

The volume holographic digital storage and reproducing system as described above is a storage medium, for example, optically, which reacts to the intensity of the interference fringes by interference fringes generated when the object light from the target object and the reference light interfere with each other. By recording to a storage medium such as a refractive crystal, recording the intensity and phase of the object light by a method of changing the angle of the reference light, etc., it is possible to display a three-dimensional image of the object, Hundreds to thousands of holograms, organized in pages, can be stored in the same place.

On the other hand, a typical volume holographic digital storage and reproducing system, in recording mode in which hologram data is recorded in a storage medium, splits the laser light generated from the light source into the reference light and the object light, and the object light is divided into pixels according to external input data. The hologram data corresponding to the input data is an interference fringe obtained by modulating the contrast binary data and interfering with the recording reference light reflecting the modulated object light (ie, signal light) and the branched reference light at a predetermined deflection angle. Write to storage media.

In this case, the hologram data is superimposed (multiplexed) when recorded on the storage medium. Such multiplexed recording methods include, for example, angular superposition, wavelength superposition, and phase code superposition.

Further, the volume holographic digital storage and reproducing system, in the reproducing mode, blocks the object light branched from the laser light generated from the light source, irradiates the storage medium with the reproduced light deflecting the branched reference light at a predetermined reproducing angle. Then, the interference fringe recorded through this irradiation diffracts the reference light for reproduction to demodulate one page of binary data composed of the original pixel contrast, thereby reproducing the desired specific hologram data. At this time, the reproduction reference light used to reproduce the data recorded on the storage medium is a reference light having substantially the same angle as the reference light applied when recording the hologram data on the storage medium.

On the other hand, as described above, when recording hologram data on the storage medium in a system for recording the hologram data on the storage medium and reproducing the recorded hologram data, conventionally, hologram data is unilaterally stored on the storage medium according to a predetermined recording time schedule. In the case of superimposing recording, in this case, due to various factors (for example, changes in the output of the reference light and the signal light, etc.), the diffraction efficiency of the superimposed hologram data may be recorded unevenly.

Therefore, when reproducing hologram data in which diffraction efficiency is recorded in this manner, there is a problem in that an image quality defect occurs in the reproduced signal, thereby increasing the bit error rate.

Accordingly, the present invention has been made to solve the above-mentioned problems of the prior art, and reproduces the recorded hologram data using the read light obtained by changing the optical path of the reference light used for recording the hologram data, and diffraction of the reproduced hologram data. The aim is to provide an improved volume holographic digital storage and playback system that can monitor efficiency.

Another object of the present invention is to reproduce recorded hologram data using the read light obtained by changing the reference light used for recording the hologram data into an optical path, check the diffraction efficiency of the reproduced hologram data, and the checked diffraction efficiency is a reference value. The present invention provides a recording data monitoring method of a volume holographic digital storage and reproducing system capable of rewriting the corresponding hologram data when the following is used.

The present invention according to a consistent point to achieve the above object, the light separation means for splitting the laser light for the target object generated from the light source into the reference light and the object light; A first reflector reflecting the branched vertically polarized reference light at a predetermined deflection angle; A second reflector reflecting the branched object light at a predetermined angle; A spatial light modulator for generating signal light through modulation between the reflected object light and external input data; A storage medium for storing an interference fringe obtained by interfering a recording reference light with the signal light as hologram data of the external input data; And a CCD for irradiating a reproduction signal from said storage medium and converting the reproduction signal from said storage medium into an electrical signal in a reproduction mode, said holographic data being recorded in said storage medium in accordance with a recording mode. Reading light generating means for converting the reference light of the vertically polarized light transmitted through the storage medium into an optical path, converting the reference light into a horizontally polarized reading light, and then re-incident to the storage medium; A reproduction output system irradiating the CCD with the reproduction output of the hologram data recorded immediately before exiting from the storage medium based on the read-in read-in light and restoring the original signal before modulation; An output data processing block for detecting diffraction efficiency of the restored reproduction output and generating a rewrite control signal for rewriting the hologram data recorded immediately before the detected diffraction efficiency is equal to or less than a predetermined reference value; And a system control block for controlling the rewrite operation of the system such that when the rewrite control signal is generated, the hologram data recorded immediately before is rewritten.

According to another aspect of the present invention, a laser beam generated by a light source is split into a reference light and an object light, and the signal light obtained by modulation between the branched object light and the input data and the reference light of the split vertically polarized light. A method for monitoring recording data in a volume holographic digital storage and reproducing system for interfering and recording a desired hologram data on a storage medium, comprising: for recording recording of vertically polarized light incident at a predetermined deflection angle in a recording mode; A first step of interfering signal light generated through modulation between reference light, branched object light, and input data to record hologram data on the storage medium; A second step of converting the reference light of the vertically polarized light passing through the storage medium into an optical path, converting the reference light of the horizontally polarized light into the read light of the horizontally polarized light, and then reincident to the storage medium; A third step of converting the reproduction output of the hologram data recorded immediately before exiting from the storage medium by the read light into an electrical signal to restore the original signal before modulation; A fourth step of detecting a diffraction efficiency of the restored reproduction output and checking whether the detected diffraction efficiency is lower than a predetermined reference value; A fifth process of repeating the first to fourth processes if the detected diffraction efficiency is lower than a preset reference value to perform a rewrite operation on the hologram data recorded immediately before the storage medium; And when the detected diffraction efficiency is not lower than a preset reference value, storing reproduction angle address information on the hologram data recorded immediately before, and then repeating the steps 1 to 5 to record the data on the storage medium. A recording data monitoring method of a volume holographic digital storage and reproducing system comprising a sixth process of performing a recording operation on a next hologram data is provided.

1 is an overall schematic diagram of an improved volume holographic digital storage and playback system in accordance with a preferred embodiment of the present invention;

Fig. 2 is a flowchart showing a process of recording while monitoring holographic data in the storage medium while monitoring the recording state thereof in accordance with the present invention.

<Description of the code | symbol about the principal part of drawing>

102: light source 104,132: optical separator

106,116: shutter 108: waist configuration lens

110, 120, 124: beam expander 112, 122: reflector

114: actuator 118, 140: reimaging lens

126: spatial light modulator 128: field lens

130: Fourier lens 134: storage medium

136: prism type reflection mirror 138: polarizing plate

142: CCD 144: system control block

146: output data processing block 148: memory block

The above and other objects and various advantages of the present invention will become more apparent from the preferred embodiments of the present invention described below with reference to the accompanying drawings by those skilled in the art.

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

1 shows an overall schematic diagram of an improved volume holographic digital storage and playback system according to a preferred embodiment of the present invention.

As shown in the figure, the volume holographic digital storage and reproducing system of the present invention stores a light source 102 for generating laser light required in holography and a storage medium for storing three-dimensional hologram data (i.e., interference fringes). 134 (e.g., a photorefractive crystal), and between these light sources 102 and the storage medium 134 are two paths comprising respective optical systems, namely the reference light processing path PS1 and the object light processing Path PS2 is formed.

Referring to FIG. 1, the optical splitter 104 splits the incident laser light generated from the light source 102 into the reference light and the object light, wherein the reference light of the vertically polarized light is provided to the reference light processing path PS1. The branched and vertically polarized object light is provided to the object light processing path PS2.

Next, on the reference light processing path PS1, the shutter 106, the waste construction lens 108, the two-lens beam expander 110, the reflector 112, and the actuator 114 are sequentially provided in the emission direction of the reference light. In the reference light processing path PS1 having such an optical structure, reference light required for recording or reproducing hologram data is generated and provided to the storage medium 134 at a predetermined deflection angle.

That is, the vertically polarized reference light branched from the optical separator 104 and incident through the aperture of the shutter 106 is adjusted through the waste construction lens 108 and then expanded to a predetermined size through the beam expander 110, eg For example, if the object light processing path PS2 described below is extended to a size sufficient to cover the size of the object light extending through the beam expander, the expanded reference light is transmitted to the reflector 112.

On the other hand, the reflector 112 deflects the reference light (beam) extended to a predetermined size through the beam expander 110 to a predetermined angle, for example, a recording angle during recording or a predetermined reproduction angle for reproduction. Reference light deflected at an angle or reproduction angle is incident on the storage medium 134.

In this case, the reference light used during recording or reproduction is controlled by rotating the reflector 112 to change the deflection angle θ each time binary data of each page unit is recorded. Hundreds to thousands of holograms can be stored or played back on the storage medium 134.

Here, the angle adjustment of the reflector 112 is performed by a motor driven by the actuator 114, where the deflection angle θ of the reference light is an angle measuring instrument (for example, an encoder) attached to a predetermined portion of the motor. Is controlled through the measurement of.

On the other hand, the shutter 116, the reimaging lens 118, the beam expander 120, the reflector 122, the beam expander 124 and the spatial light modulator 126 are emitted from the object light on the object light processing path PS2. Direction sequentially, and between the spatial light modulator 126 and the storage medium 134, a field lens 128, a Fourier lens 130, and an optical separator 132 are sequentially provided, and the optical separator 132 records. In the mode, the signal light provided from the Fourier lens 130 is incident on the storage medium 134, and the reproduction signal emitted from the storage medium 134 is recorded when monitoring the recording data according to the present invention (i.e., in the monitoring reproduction mode). Reflected by the reimaging lens 140.

That is, in the recording mode, the object light branched from the optical separator 104 and incident through the opening of the shutter 116 is reimaged through the reimaging lens 118, and has a predetermined magnitude 1 through the beam expander 120. The object light, which is first expanded, is reflected at a predetermined deflection angle through the reflector 122. At this time, the shutter 116 maintains an open or cut state in accordance with a control signal from the system control block 144 described later. The shutter 116 maintains an open state in the recording mode and a cut state in the reproducing mode.

Next, the first extended object light reflected by the reflector 122 is second extended through the beam expander 124 and then transmitted to the spatial light modulator 126 (eg, LCD).

At this time, extending the object light through the two beam expanders 120 and 124 to a predetermined size is the source of the laser light from the light source 102 and branched through the light splitter 104 has a very small size of the object light modulator 126 This is because it is inadequate to perform light modulation in the above, and through this second-order expansion, the separated object light is expanded to a size corresponding to the size of the spatial light modulator 126.

On the other hand, the spatial light modulator 126 modulates the extended object light transmitted from the beam expander 124 in units of one page of binary data of light and shade of pixels according to data input from the system control block 144. That is, as an example, when the input data is image data in one frame unit of the image, the extended object light incident on the spatial light modulator 126 is modulated into signal light in one frame unit.

Next, the object light modulated in units of one page of binary data output from the spatial light modulator 126 described above is stored in the storage medium 134 through the field lens 128, the Fourier lens 130, and the optical separator 132. ), And then enters the storage medium 134 in synchronization with the reference light incident on the reflector 112 of the reference light processing path PS1.

Accordingly, in the storage medium 134, in the recording mode, the incident light is input from the reflector 112 with the signal light modulated in units of pages of binary data provided from the optical separator 132 and the deflection angle θ corresponding thereto. An interference fringe obtained through interference between recording reference lights is recorded. That is, the light induced phenomenon of the kinetic charge occurs in the storage medium 134 according to the intensity of the interference fringe obtained by the interference between the modulated object light and the reference light. An interference fringe of the image hologram data is recorded.

On the other hand, in the monitoring reproduction mode, the reference light incident on the storage medium 134 for recording passes through the storage medium 134 and is then changed by the prism-type reflection mirror 136 to change the optical path, that is, the storage medium (for recording). The light is also changed to the same angle as the initial recording angle incident on the light source 134 and is incident again to the storage medium 134 through the polarizing plate 138 as a reading beam.

At this time, the polarizing plate 138 converts the recording reference light of the vertically polarized light transmitted through the storage medium 134 into the λ / 2 polarizing plate into the reading light of the horizontally polarized light. Here, the reason for changing the read light into the horizontally polarized beam is to exclude interference with the reference light and the signal light incident on the storage medium 134. That is, by setting the polarization states of the read light for recording and monitoring, the reference light for recording and the signal light to a 90 degree structure, interference with each other is eliminated.

Next, the storage medium 134 diffracts the read light incident with the recorded interference fringe when the read light is incident through the polarizing plate 138, so that one page of binary data (i.e., checkerboard) composed of original pixel contrasts is diffracted. Demodulated, and the reproduced monitoring signal for demodulation is emitted to the optical separator 132 and reflected to the reimaging lens 140.

As a result, the three-dimensional reproduction output demodulated in units of one page of binary data reflected by the optical separator 132 is reimaged through the reimaging lens 140 and then irradiated onto a charge coupled device (CCD) 142. The original data, i.e., the electrical signal, is then restored to the output data processing block 146.

Accordingly, the output data processing block 146 detects the diffraction efficiency of the restored reproduction signal, determines whether the detected diffraction efficiency is equal to or less than the predetermined reference value, and when the determined diffraction efficiency is equal to or less than the predetermined reference value A rewrite control signal for rewriting the hologram data on the storage medium 134 is generated and provided to the system control block 144. At this time, for example, a logic signal having a high or low level can be used as the rewrite control signal.

Next, in the system control block 144, in response to the rewrite control signal, the rewrite mode for the hologram data having a diffraction efficiency below the reference value is performed by controlling the system so that the hologram data recorded immediately before the storage medium 134 is rewritten. do.

In this case, the system control block 144 may control various operations of the entire system, including, for example, a microprocessor, that is, an operation control signal of the light source 102, a control signal for opening and closing the shutters 106 and 116, and a reflector ( It generates a drive signal of the actuator 114 to rotate 112, a control signal for the operation of the spatial light modulator 126, respectively to control various operations, and also to control the recorded data in monitoring the recording data according to the present invention. When the diffraction efficiency of the reproduction output is below the reference value, the rewriting of the hologram data is controlled.

Next, a description will be given of a process of rewriting the hologram data when the hologram data is recorded on the storage medium and monitored when the diffraction efficiency of the recorded hologram data is equal to or less than a reference value.

FIG. 2 is a flowchart showing a process of recording the hologram data in the storage medium while monitoring the recording state according to the present invention.

Referring to FIG. 2, when the recording mode in which the specific hologram data is to be recorded in the storage medium 134 is entered, the shutter 106 on the reference light processing path PS1 side according to the shuttering control signal from the system control block 144. And the shutter 116 on the object light processing path PS2 side is opened, and laser light for the target object is generated from the light source 102 (step 202).

Next, the recording reference light of vertical polarization branched at the optical separator 104 is incident on the storage medium 134 at a predetermined deflection angle through the reflector 112, and the object of vertical polarization branched at the optical separator 104. Signal light is generated through modulation between the light and the input data provided in the system control block 144 (step 204), and the signal light thus generated is incident on the storage medium 134 in synchronization with the recording reference light (step 206), An interference fringe corresponding to the hologram data to be recorded is recorded in the storage medium 134 (step 208).

On the other hand, the reference light transmitted through the storage medium 134 for recording the hologram data changes the optical path through the prismatic reflection mirror 136, that is, the optical path at the same angle as the initial recording angle incident on the storage medium 134 for recording. And incident again into the storage medium 134 as readout light for monitoring reproduction, where the readout light is a horizontally polarized beam through the polarizer 138.

As a result, in the storage medium 134, an interference fringe recorded just before diffracts the monitoring read light to demodulate a page of binary data composed of original pixel contrast, and the reproduced signal to be demodulated is an optical separator ( 132 is emitted to the reimaging lens 140 (step 210).

Thus, the three-dimensional reproduction output demodulated in units of one page of binary data reflected by the optical separator 132 is reimaged through the reimaging lens 148 and then irradiated to the CCD (: 142), thereby providing original data. That is, the signal is restored to the electric signal (step 214).

Next, the output data processing block 146 detects the diffraction efficiency of the restored reproduction output (step 216), and then checks whether the diffraction efficiency of the detected reproduction output is equal to or less than a predetermined reference value (step 218). .

If the result of the check in step 218 determines that the diffraction efficiency of the detected reproduction output is equal to or less than a predetermined reference value, the output data processing block 146 indicates a rewrite control signal (e.g., high level) corresponding to the determination result. Is generated and provided to the system control block 144.

Therefore, the system control block 144 generates various control signals for rewriting the hologram data recorded immediately before, and inputs the data again to the spatial light modulator 126 (step 220), so that the rotation efficiency is lower than the reference value. By rewriting the hologram data, that is, by repeating the process after the above-described step 204, if the rotational efficiency is less than the reference value, the rewriting of the hologram data is performed.

That is, according to the present invention, when the diffraction efficiency of the hologram data recorded on the storage medium 134 is equal to or less than a predetermined reference value, the hologram data is rewritten by performing the repetition of the steps 204 to 220 as described above. Repeat the process. In this case, the above-described rewriting operation of the hologram data may be repeated until the diffraction efficiency for the reproduction output of the hologram data exceeds a predetermined reference value.

On the other hand, if the check result in step 218 determines that the diffraction efficiency of the detected reproduction output is not less than or equal to the predetermined reference value, the output data processing block 146 controls the control signal for recording the next data corresponding to the determination result. (Eg, a low level logic signal) is generated and provided to the system control block 144.

Accordingly, the system control block 144 stores the reproduction angle information (i.e., the reproduction address information) for the hologram data recorded immediately before in the memory block 148 (step 222), and determines whether there is the next recording data that follows. It is checked whether or not (step 224).

At this time, whenever the hologram data is recorded in the storage medium 132, the memory block 148 stores the reproduction angle information for each recorded hologram data, and the reproduction angle information reproduces each hologram data in the reproduction mode. It is used as information (i.e., reference light deflection angle information for reproduction in the reflector 112).

As a result of the check in the step 224, if there is the next recording data that follows, the process returns to the step 204 described above and repeats the subsequent steps, whereby the monitoring recording mode of the hologram data as described above is It is carried out continuously.

On the other hand, if the result of the check in step 224 is that there is no next recording data, the system control block 144 releases the current recording mode and ends the data recording operation (step 226).

As described above, according to the present invention, the diffraction efficiency of the recording data is detected through the diffraction efficiency check on the hologram data recorded in the data recording mode, and the hologram data is detected when the diffraction efficiency of the recording data is below the reference value. By rewriting, it is possible to fundamentally prevent the occurrence of an error of the hologram data recorded on the storage medium.

Therefore, the present invention can improve the diffraction efficiency of the reproduced light by improving the diffraction efficiency of the reproduced light by checking and rewriting the occurrence of the error of the recorded hologram data simultaneously with the recording.

Claims (4)

Light separation means for splitting the laser light for the target object generated from the light source into the reference light and the object light; A first reflector reflecting the branched vertically polarized reference light at a predetermined deflection angle; A second reflector reflecting the branched object light at a predetermined angle; A spatial light modulator for generating signal light through modulation between the reflected object light and external input data; A storage medium for storing an interference fringe obtained by interfering a recording reference light with the signal light as hologram data of the external input data; And a CCD for irradiating a reproduction signal from the storage medium and converting the reproduction signal from the storage medium into an electrical signal in a reproduction mode, the volume holographic digital storage and reproduction system comprising: Reading light generating means for converting the reference light of the vertically polarized light transmitted through the storage medium into an optical path by converting the reference light of the horizontally polarized light into the readout light of the horizontally polarized light when hologram data is recorded in the storage medium according to a recording mode; A reproduction output system irradiating the CCD with the reproduction output of the hologram data recorded immediately before exiting from the storage medium based on the read-in read-in light and restoring the original signal before modulation; An output data processing block for detecting diffraction efficiency of the restored reproduction output and generating a rewrite control signal for rewriting the hologram data recorded immediately before the detected diffraction efficiency is equal to or less than a predetermined reference value; And And a system control block for controlling the rewrite operation of the system such that when the rewrite control signal is generated, the hologram data recorded immediately before is rewritten. The method of claim 1, wherein the reading light generating means is: A prism type reflecting mirror for reflecting the read light, which has changed the reference light of vertical polarization, which is incident for recording hologram data and transmitted through the storage medium, into an optical medium; And And a polarizing plate which horizontally polarizes the read light of the changed vertically polarized light and reincarnates it into the storage medium. The system of claim 1, wherein the regenerative output system is: A light incident to the storage medium in synchronization with a corresponding recording reference light in the recording operation, and reflecting a reproduction output emitted from the storage medium by the read light at a predetermined angle; Separator; And And a reimaging lens for reimagining the reproducing output reflected through the optical splitter and irradiating the CCD with the CCD. Volume for splitting the laser light generated from the light source into the reference light and the object light, interfering the signal light obtained by the modulation between the branched object light and the input data and the reference light of the branched vertical polarization to record the target hologram data in the storage medium A method of monitoring recorded data in a holographic digital storage and playback system, In the recording mode, a first process of recording hologram data on the storage medium by interfering a signal polarity generated through modulation between a branched recording reference light of vertically polarized light incident at a predetermined deflection angle and a branched object light and input data. ; A second step of converting the reference light of the vertically polarized light passing through the storage medium into an optical path, converting the reference light of the horizontally polarized light into the read light of the horizontally polarized light, and then reincident to the storage medium; A third step of converting the reproduction output of the hologram data recorded immediately before exiting from the storage medium by the read light into an electrical signal to restore the original signal before modulation; A fourth step of detecting a diffraction efficiency of the restored reproduction output and checking whether the detected diffraction efficiency is lower than a predetermined reference value; A fifth process of repeating the first to fourth processes if the detected diffraction efficiency is lower than a preset reference value to perform a rewrite operation on the hologram data recorded immediately before the storage medium; And If the detected diffraction efficiency is not lower than a predetermined reference value, the reproduction angle address information on the hologram data recorded immediately before the data is stored, and then the first to fifth steps are repeatedly performed to record on the storage medium. A recording data monitoring method of a volume holographic digital storage and reproducing system comprising a sixth process of performing a recording operation on a next hologram data.

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