KR100579617B1 - Apparatus for controlling track servo in a holographic worm system - Google Patents

Abstract

The present invention relates to a track servo control apparatus for a holographic worm system, comprising: an optical splitter installed at a position corresponding to a light source for generating coherent light necessary for holography to separate the coherent light into a reference light and an object light; A spatial light modulator positioned on the optical path of the object light and carrying input data to the object light, and an optical path interposed between the object light output from the spatial light modulator and the reference light and interfering with the object light and the reference light A holographic worm recording medium in which a track pattern having a constant data value is recorded along a position at which a data pattern generated by the recording medium is recorded and an optical path of an interference fringe generated when the reference medium is irradiated to the recording medium. Photoelectric conversion means for converting the data pattern into an original electrical signal when the data pattern is restored; When the reference light is irradiated to a conventional recording medium, a light detecting unit positioned on the optical path of the track pattern to detect track light, and adjusting the data recording or reproducing position according to the light detection value by the light detecting unit to perform tracking servo control. It includes a control unit for performing, by performing a track servo control by recording a track pattern having a constant data value in the production of the holographic worm recording medium and using it as a tracking signal during recording and playback, it is possible to always perform precise tracking control There is an advantage to that.

Description

Track servo control device for holographic worm system {APPARATUS FOR CONTROLLING TRACK SERVO IN A HOLOGRAPHIC WORM SYSTEM}

1 is a configuration diagram of a general holographic worm system recording / reproducing apparatus;

2 is a block diagram of a holographic worm system recording / reproducing apparatus to which a track servo control apparatus according to the present invention is applied;

3 is a pattern configuration diagram of a holographic worm recording medium used in the track servo control apparatus according to the present invention.

The present invention relates to a track servo control apparatus for a holographic worm system, and more particularly to a tracking servo control for recording and reproducing data stored in a recording material layer of a holographic worm recording medium.

Currently, research and development of holographic recording media capable of storing hundreds to hundreds of Gbytes as optical recording media and their recording / reproducing apparatuses are being actively conducted for large-capacity and high-speed processing of data storage memories.

Holographic data recording is achieved by recording the intensity and direction of the object light reflected from the object. The intensity and direction of the light of the object is composed of the interference between the object light and the reference light to form an interference fringe, and the interference fringe is formed in a holographic recording medium made of a material that responds to the intensity of the interference fringe. When the reference light is irradiated to the recorded interference fringe, the hologram, which is a three-dimensional image of the object, is reproduced.

At this time, the hologram data recorded in the storage crystal can only be read by the reference light used in the recording process, and the hologram data recorded in the storage crystal can not be read by the reference light having a different wavelength or phase from the reference light used in the recording process. Done.

By using this hologram property, a large amount of hologram data can be stored in the same place of a recording medium with different reference light, thereby storing a large amount of data inside a small recording medium.

The commonly used angular multiplexing technique is to change the angle of the reference light at each recording time to create different reference light. This method allows hundreds to thousands of holograms to form binary data in pages. Can be stored in place. In other words, by recording and reproducing a lot of data in the unit of a page in the same place, it is possible to record and reproduce with high storage density and fast data transfer rate.

The general holographic data storage system as shown in FIG. 1 is a coherent beam required for holography, that is, a light source 10 for generating a laser light, a position corresponding to the light source 10. A beam splitter 20 which is installed in the light source 10 to separate the coherent light generated from the light source 10 into a reference beam and a signal beam, that is, an object beam, and is positioned on an optical path of the reference beam. The rotating mirror 30 for converting the angle of light little by little, the mirror 40 for changing the direction of the object light, and positioned on the optical path of the object light reflected from the mirror 40 and input data, i.e., in units of pages, to the reflected object light. The spatial light modulator (SLM) 50, which carries binary data of a plurality of pixels, and the object light output from the spatial light modulator 50 and the reference light reflected from the rotating mirror 30 cross each other. Optical path A recording medium 60 positioned to record an interference fringe generated by the interference of the object light and the reference light, and restore and output the interference fringe recorded by the irradiation of the reference light, and interference generated when the reference medium is irradiated to the recording medium 60. It consists of a CCD (Charge Coupled Device) 70 which is located on the optical path of the fringe and converts the interference fringe recorded on the recording medium 60 into an original electric signal.

The recording process of the holographic data by the conventional holographic data storage system configured as described above is repeated by varying the angle of the reference light for each page recording by using the angular superposition technique to superimpose and record the data inside the recording medium. do.

In this way, if the angle of the reference light is changed and recorded by using the angle superposition technique, the same pattern of reference light at the same angle must be irradiated to the recording medium to restore the checkered pattern composed of the original pixel contrast. Is restored to the original data.

In addition, as described above, the recording / reproducing process performed at a predetermined position of the recording medium is repeatedly performed while changing the position of the recording medium, thereby recording / reproducing data of several to hundreds of Gbytes using a small recording medium. Can be.

Therefore, in order to accurately record / reproduce data during holographic recording / playback, a track servo control which is already generalized in CD or DVD recording / playback is required. In the holographic worm system, the recording / playback method of CD / DVD recording / playback is performed. It is totally different from the reproduction method, and a new track servo control device is required.

The present invention has been proposed to solve such a problem of the prior art, by recording a track pattern having a constant data value in the production of a holographic worm recording medium, and then performing track servo control by using it as a tracking signal during recording and playback. The aim is to enable precise tracking control.

The track servo control apparatus for the holographic worm system according to the present invention for achieving this object is installed at a position corresponding to a light source for generating the coherent light required for holography to separate the coherent light into a reference light and an object light. And a spatial light modulator positioned on an optical path of the object light to load input data to the object light, and an optical path intersected with the object light output from the spatial light modulator and the reference light. A holographic worm recording medium having a pair of track patterns in which a constant data value is recorded around both sides of a data pattern generated by interference between light and reference light, and generated when the reference light is irradiated to the recording medium. Is located on the optical path of the interference fringe, which is the original electrical signal when restoring the data pattern. Photoelectric conversion means for converting the light into a second light; a first and second light detectors for detecting track light when the reference light is irradiated to the recording medium and positioned on an optical path of the pair of track patterns; And a control unit for performing tracking servo control by adjusting a data recording or reproducing position according to the light detection value by the detecting unit.

Hereinafter, exemplary embodiments will be described in detail with reference to the accompanying drawings. This embodiment allows for a better understanding of the objects, features and advantages of the present invention. However, the present invention is not limited to this embodiment, of course.

FIG. 2 is a block diagram of a holographic worm system to which a track servo control device according to the present invention is applied. In comparison with the holographic worm system shown in FIG. 1, the same components have the same reference numerals.

3 is a pattern configuration diagram of a holographic worm recording medium 110 fabricated for a track servo control apparatus according to the present invention, and shows a constant data value around both sides along a position where a data pattern 116 is to be recorded during recording. By recording, a pair of track patterns 111 and 113 are arranged.

As shown in FIG. 2, the holographic worm system for recording and reproducing holographic data using the recording medium 110 of FIG. 3 is a light source for generating a coherent beam required for holography, that is, a laser beam. 10, a beam splitter installed at a position corresponding to the light source 10 to separate the coherent light generated from the light source 10 into a reference beam and a signal beam, that is, an object beam. 20, located on the optical path of the reference light, the rotating mirror 30 for converting the angle of the reference light little by little, the mirror 40 for changing the direction of the object light, the optical path of the object light reflected from the mirror 40 Spatial Light Modulator (SLM) 50 and Spatial Light Modulator 50 for inputting input data, that is, binary data of a plurality of pixels in units of pages, to the reflected object light, and the object light outputted from the spatial light modulator 50 Reflections in the mirror 30 A recording medium positioned on an optical path where the reference light beams cross each other, recording an interference fringe generated by the interference of the object light and the reference light, that is, the data pattern 116 and restoring and outputting the data pattern 116 recorded by irradiation of the reference light. 110 and located on the optical path of the interference fringe generated when the recording medium 110 is irradiated with the reference light, and converted to the original electrical signal when restoring the data pattern 116 recorded on the recording medium 110. The distance between the CCD (Charge Coupled Device) 70, which is a photoelectric conversion means, and a pair of track patterns 111 and 1113 recorded on the recording medium 110 when the reference medium is irradiated with the reference light. Tracking servo control by adjusting data recording and reproducing positions according to the light detection values of the first and second light detectors 120 and 130 and the first and second light detectors 120 and 130 that detect the track light. It is configured to include a control unit 140 to perform.

The operation of the holographic data storage system of the present invention configured as described above will be described.

The coherent light irradiated from the light source 10 is divided into the reference light and the object light in the optical separator 20.

In this case, the object light is inputted to the spatial light modulator 50 and modulated by the mirror 40 in a 90 ° direction. That is, the object light is inputted to the predetermined position of the recording medium 110 after the data input from the spatial light modulator 50 is modulated in units of one page of the binary data of the contrast made by the actual pixels.

In addition, the reference light is incident on the recording medium 60 after the angle is changed by the rotating mirror 30. That is, reference light that slightly changes the angle of the rotating mirror 30 corresponding to each page is incident on the recording medium 110.

At this time, since the pair of track patterns 111 and 113 are formed in the recording medium 110, the reference light is diffracted by the pair of track patterns 111 and 113, and the track light is emitted from the recording medium 110. The emitted track light is detected by the first light detector 120 and the second light detector 120, respectively.

Next, the light amount values detected by the first and second light detectors 120 and 130 are transmitted to the controller 140, and the controller 140 detects the light by the first and second light detectors 120 and 130. Tracking servo control is performed to adjust the recording position of the data pattern 116 according to the value.

At this time, the control unit 140 records the data pattern 116 at a position where the light detection values of the first and second light detection units 120 and 130 are the same, and after setting the threshold range, the first and second light detection units 120 , Even when the difference of the light detection value by 130 is included in the threshold range, it may be determined as a normal tracking state.

Thus, the object light and the reference light cause interference in the recording medium 110 for recording the hologram, and light-induced generation of internal kinetic charges of the recording medium 110 according to the intensity of the interference fringes generated at this time. mobile charge) is generated and an interference fringe, that is, a data pattern 116 is recorded.

In order to read the data recorded on the recording medium 110, only the reference light needs to be irradiated to the recording medium 110. That is, when the reference light is irradiated, the interference fringe is diffracted by the reference light to restore the checkered pattern composed of the contrast of the original pixel, and then the read image is reflected on the CCD 70 to restore the original data.

In this way, after recording one page, a reference light having a slightly different angle of the rotating mirror 30 is applied to the next page. That is, the reference light is correspondingly applied to each page according to the change of the angle of the rotating mirror 30. After recording the first page of data on the recording medium, the angle of the reference light is increased until the reproduction restoration image of the first hologram disappears completely. In this case, a new data page is input again with reference light of a different angle to be recorded on the recording medium 110.

In other words, the process of changing the angle of the reference light every time each page is recorded using the angular superposition technique is repeated to superimpose data on the recording medium.

As described above, when the angle of the reference light is changed and recorded using the angle superposition technique, the same pattern of reference light at the same angle must be irradiated to the recording medium 110 at the time of reproduction to restore the checkered pattern consisting of the contrast of the original pixel. The image is restored to the original data by the CCD 70.

In addition, during the reproduction, tracking servo control by the controller 140 is performed as in the above-described recording operation. Since the pair of track patterns 111 and 113 are formed on the recording medium 110, the reference light for reproduction is limited. The track light is diffracted by the pair of track patterns 111 and 113, and the track light is emitted from the recording medium 110, and the emitted track light is detected by the first light detector 120 and the second light detector 120. FIG.

Next, the light amount values detected by the first and second light detectors 120 and 130 are transmitted to the controller 140, and the controller 140 detects the light by the first and second light detectors 120 and 130. Tracking servo control is performed to adjust the recording position of the data pattern 116 according to the value.

At this time, the control unit 140 reproduces the data pattern 116 at a position where the light detection values of the first and second light detection units 120 and 130 are the same, and after setting the threshold range, the first and second light detection units 120 , Even when the difference of the light detection value by 130 is included in the threshold range, it may be determined as a normal tracking state.

In the above description, but limited to one embodiment of the present invention, it is obvious that the technology of the present invention can be easily modified by those skilled in the art. Such modified embodiments should be included in the technical spirit described in the claims of the present invention.

As described above, the present invention performs precise tracking control by recording a pair of track patterns having a constant data value in the production of a holographic worm recording medium and then performing track servo control using the tracking signal during recording and playback. It can work.

Claims (3)

An optical splitter installed at a position corresponding to a light source for generating interfering light necessary for holography and separating the coherent light into a reference light and an object light; A spatial light modulator positioned on an optical path of the object light and carrying input data to the object light; A pair of constant data values recorded on both sides of the object light output from the spatial light modulator on the optical path where the reference light intersects each other, and along the position where the data pattern generated by the interference of the object light and the reference light is to be recorded. A holographic worm recording medium having a track pattern of Photoelectric conversion means which is located on an optical path of an interference fringe generated when said reference light is irradiated to said recording medium and converts it into an original electric signal when restoring said data pattern; First and second light detectors each of which is located on an optical path of the pair of track patterns when the reference light is irradiated to the recording medium to detect track light, respectively; A control unit which performs tracking servo control by adjusting a data recording or reproducing position according to the light detection values by the first and second light detecting units Track servo control device for a holographic worm system comprising a. The method of claim 1, The first and second light detectors are arranged in plural distances between the pair of track patterns, and the controller records or reproduces the data patterns at positions where the light amount values detected by the first and second light detectors are the same. Track servo control device for a holographic worm system, characterized in that for performing. The method of claim 1, The first and second light detectors are disposed in plural distances between the pair of track patterns, and the controller is configured to control the data patterns at positions where a difference in the amount of light detected by the first and second light detectors is included in a preset threshold range. Track servo control device for a holographic worm system, characterized in that for performing recording or playback.

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