KR100765922B1 - Holographic storage system - Google Patents

Abstract

A holographic storage system is provided to simplify an optical system structure, and to minimize the size and weight of an optical system by emitting reference beam and object beam through one integrated beam path. A holographic storage system comprises a fixed part(501), a moving part(502), a signal processing part(504), a driving part, and a CPU(central processing unit,503). The moving part is installed with a light source for generating a servo signal. The driving part controls the moving part according to a signal of the signal processing part. The CPU processes the data detected from the optical disk. Only the moving part is moved according to the servo signal to detect the data. The moving part includes light sources(521), an objective lens(523), and an optical detector(524). The reference beam and the object beam are emitted from an optical modulator through one integrated beam path.

Description

Holographic Storage Device {HOLOGRAPHIC STORAGE SYSTEM}

1 is a conventional holographic storage device comprising fixed media.

2 is a conventional holographic storage device comprising rotating media.

3A and 3B illustrate a method of storing data on a recording medium.

4A and 4B illustrate a method of reproducing data on a recording medium.

5 is a block diagram of a holographic storage device in accordance with an embodiment of the present invention.

{Description of Signs of Major Parts of Drawings}

501: fixing part 502: moving part

503: central processing unit 504: signal processing unit

505: driving unit 511: first light source

512: reflecting mirror 513: optical modulator

514: first beam splitter 515: second beam splitter

516: first shutter 517: second shutter

518: filter 519: image sensor

520: First lens 521: Second light source

522: third beam splitter 523: objective lens

524: photodetector 525: second lens

526: optical disc

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a holographic storage device, and more particularly, to a servo / signal information signal during holographic information storage / reproduction as well as a pickup for use as a separate optical system of a holographic storage device. The present invention relates to an apparatus for efficiently including red lasers and optical apparatuses.

Recently, the multimedia industry is developing into a highly technology-intensive industry in which various industries such as home appliances, computers, communication, video, and broadcasting are converged. To meet this multimedia industry environment, a new information environment is needed. In other words, as the amount of information is enormous, ultra large capacity, ultra high speed, and ultra small size of information storage media are required. For example, in order to commercialize video-on-demand of multimedia information communication, a video server requires 10 ³ Tb or more and a data transfer rate of 1 Gb / sec or more.

However, current semiconductor memories, magneto-optical discs (MOD) and compact discs (CD) have a technical and economic limitation in this information storage process, and a new generation of ultra-large capacity information storage devices is urgently needed. Currently, CD memory has a capacity of 640MB (1 hour 40 minutes of music or more than 300,000 pages of double-sided documents), but hundreds to tens of thousands in hospitals, law, companies, government agencies, libraries, etc. He's using an expensive Jukebox that stacks disks and accesses them with a robotic arm.

Conventional CD / DVD storage has been a two-dimensional storage method for storing information on one side of media using beam spots collected from a laser light source. In this case, the data storage capacity was increased by adjusting the pitch interval between tracks or increasing the number of layers. However, the reduction of the pitch interval and the increase of the layers have physical limitations. It becomes impossible.

Therefore, the holographic storage method, which is a three-dimensional three-dimensional storage method introduced to overcome this problem, can record information inside the storage medium by using the diffraction and interference effects of light dozens ~ Hundreds of times the storage capacity is available.

Holographic means to reproduce the same light waves used in the stored state or stored state. In the holographic memory, two-dimensional light patterns are stored and reproduced. This method of storage can be read separately from each other even if they are stored in a superimposed manner by an appropriate multiplexing technique, and the parallel access memory system of ultra-large capacity can be read because two-dimensional images are read at the same time. Implementation of.

1 illustrates the basic structure of a conventional holographic memory system.

The laser 1 is split into a reference beam 10 and an object beam 9 to which a signal is to be carried by a beam splitter 2. The object light is modulated into a two-dimensional pattern by desired input data while passing through a spatial light modulator (SLM) 4. This light interferes with the reference light 10 in the media 7 of the photorefractive material to store information. When reading the information, only the reference light 10 is irradiated to the photorefractive material. Then, the signal light carrying the original information is reproduced and incident on a detector array 8 such as a CCD (Charge Coupled Device).

2 is a block diagram of a disk rotating holographic storage device. If FIG. 1 is a holographic storage device using fixed media, the holographic storage device of FIG. 2 is formed by rotating the media similar to an optical disk media of a general CD / DVD, and data is sequentially rotated along a track. Stored. However, the media of the disk rotating holographic storage device does not rotate at high speed like a normal CD / DVD, but rather a predetermined page (a predetermined space in which data is stored) in a predetermined page (a screen stored in one book). When the unit is saved, it is rotated in stepping format.

As a technical method of increasing storage capacity in relation to a holographic drive, an angular multiplexing, a phase multiplexing, a wavelength multiplexing method and the like have been introduced.

3A and 3B show a method of recording data on a recording medium using an angular multiplexing method, and FIGS. 4A and 4B show a method of reproducing data stored on the medium.

In the angular multiplexing method, the disc incident angle of the reference light is adjusted to improve the storage density of the media so that data recorded at a specific angle can be reproduced only by irradiating the laser again at that specific angle.

In this way, the section in which the angle of the reference light can be selected so that data can be recorded and reproduced is called each selectivity. Currently, a method in which the mirror of the reference light is rotated in one direction and overlapped is selected.

The holographic storage device has a complicated optical path for implementing multiplexing, making it difficult to manufacture a miniaturized pickup, and it is not easy to obtain an information signal for servo control using only a light source used for holographic information.

In order to solve this problem, a method of adding a light source for generating a servo signal separately from a light source used for storing and reproducing holographic information, and a method of simplifying an optical structure by integrating the paths of reference light and information light when storing data It is proposed. This method can obtain very simple optical structure and sophisticated servo information signal, but it requires additional design of light source and corresponding optical system for generating servo signal. Due to this there is a problem that the volume of the overall system can be rather increased.

Therefore, there is a need for a method that can be easily added to an existing system by minimizing the volume of a separate light source for generating an information signal for servo.

The present invention has been made to solve the above problems, and its object is to integrate the path of the reference light and the information light, which is suitable for the holographic optical storage device, to simplify the structure of the optical system and to be used for generating the servo signal. It is to provide a small pickup while adding a light source of.

In order to achieve the above object, the holographic storage device of the present invention includes a fixed part for recording and reproducing data, a moving part having a light source for generating a servo signal, and a signal for processing the servo signal generated by the moving part. A processing unit, a driving unit controlling the moving unit according to a signal of the signal processing unit, and a central processing unit processing data detected by the optical disc.

In the present invention, the moving unit preferably includes a light source for emitting a laser light, an objective lens for adjusting focusing using the light generated by the light source, and a photodetector for detecting the light reflected back to the optical disk.

In the present invention, the light source preferably uses a red laser light source.

In the present invention, the light source is preferably a light source of 650nm wavelength band.

In the present invention, the fixing unit includes a first light source for emitting a laser light for recording and reproduction, an optical modulator for generating a reference light and a reflected light pattern by the laser emitted from the light source, and an image sensor for detecting an image recognized by the optical disc. It is desirable to.

In the present invention, it is preferable that the moving part and the fixing part form a relay of light through a predetermined lens.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. In adding reference numerals to components of the following drawings, it is determined that the same components have the same reference numerals as much as possible even if displayed on different drawings, and it is determined that they may unnecessarily obscure the subject matter of the present invention. Detailed descriptions of well-known functions and configurations will be omitted.

5 is a block diagram of a holographic storage device according to an embodiment of the present invention.

In this embodiment, the holographic storage device includes a fixing unit 501, a moving unit 502, a central processing unit 503, a signal processing unit 504, and a driving unit 505.

The embodiment schematically shows a state in which the mobile unit 502 for generating server signals is provided.

Referring to FIG. 5, the holographic storage device includes a fixing part 501 for recording and reproducing the holographic storage device, a moving part 502 for generating a servo signal, and a driving part for controlling the moving part 502. 504, a signal processing unit 504 for signal processing of the generated servo signal, and a central processing unit 503 in charge of all signals and control.

The fixing part 501 includes a first light source 511, a reflection mirror 512, an optical modulator 513, a first beam splitter 514, a second beam splitter 515, a first shutter 516, and a first light source. And a second shutter 517, a filter 518, an image sensor 519, and a first lens 520.

The first light source 511 emits light for recording and reproduction of the holographic storage device, and preferably uses a laser diode that emits laser light. The laser diode preferably uses a green laser or a blue laser used for storing and reproducing data in a general holographic data storage device. The wavelength band of the green laser is preferably 532 nm and the wavelength band of the blue laser is 405 nm.

The laser light emitted from the first light source 511 is reflected by the reflection mirror 512 and input to the light modulator 513. The optical modulator 513 is patterned into the reference light and the object light through the image by using the input laser light.

Light patterned by the optical modulator 513 is transmitted to the moving unit 502 via the first beam splitter 514 and the second beam splitter 515.

The first beam splitter 514 is provided with two shutters 516 and 517. One is a first shutter 516 for controlling the light transmitted from the optical modulator 513, and the other is a second shutter 517 for detecting data stored in the optical disk 526 and controlling signal transmission thereto. . When the holographic storage device requires a servo control signal during initial driving, since the light necessary for recording and reproducing the holographic storage device is not needed, the first shutter 516 is closed to prevent the related light from entering the moving unit. The second shutter 517 is opened to detect the data stored in the optical disk 526 when the drive by the servo control is completed and transmits the detected pattern to the image sensor 519. That is, in the initial server control, both the first shutter 516 and the second shutter 517 are closed, and in the subsequent recording, only the first shutter 516 is opened, and the data pattern recorded on the optical disk 526 is detected. If so, the second shutter 517 is opened.

The light generated by the fixing unit 501 is transmitted to the moving unit 502, which is preferably relayed using the first lens 520.

The moving unit 502 is a part for generating a server control signal of the holographic storage device, and includes a second light source 521, a third beam splitter 522, an objective lens 523, and a photodetector 524. .

The second light source 521 is for generating a server signal, and preferably uses a light source for emitting a laser. It is preferable to use a laser diode as the light source, and it is preferable to use a light source of the same red wavelength as that used in a general CD / DVD. The wavelength band of the red wavelength laser is preferably used 650nm band.

The light generated by the light source moves to the optical disk 526 via the third beam splitter 522 and the objective lens 523. Light moved to the optical disc 526 is reflected by the optical disc 526 and moved to the photodetector 524. The light moved to the photodetector 524 is signal-processed by the signal processor 504. The signal processing unit 504 sends the processed signal to the driving unit 505 to instruct the driving unit 505 to move the moving unit 502 to a predetermined position.

Hereinafter, the servo signal generation and a method of controlling the same will be described in more detail.

The second light source 521 emits laser light and transmits the laser light to the optical disk 526. The light transmitted to the optical disc 526 is reflected by the optical disc 526 and input to the photodetector, and the photodetector 526 transmits a corresponding signal to the signal processor 504. The driver 505 receiving the signal from the signal processor 504 starts focusing control of the moving unit 502. The focusing control method may be implemented in various ways to suit those skilled in the art. Generally, astigmatism method, critical angle detection method, knife edge prism method, beam eccentricity method, skew beam method, wobbling method, phase difference detection method, etc. can be implemented in various ways, but in this embodiment, it is generally used to use astigmatism which is commonly used. desirable. That is, the photodetector 524 is divided into four to detect a light source and measures the optical signal at each of the four divided positions to determine whether the current light source is accurately focused on the optical disk 526. When the focusing error is detected, the driving unit 505 drives the objective lens 523 up and down to achieve optimal focusing control.

Tracking control begins after the focusing control ends. The tracking control process is also controlled by using the light emitted from the second light source 521 reflected back to the optical disk 526. The tracking control method may also be implemented in various ways to those skilled in the art. In general, a three-beam method, a push-pull method, a differential push-pull method, a carriage tracking method, a weaving method, etc. are used, but in this embodiment, it is preferable to use a differential push-pull method which is generally used. By using the differential push-pull method, the main beam and the sub-beam are generated, and the offset is removed to perform tracking control. The driving unit 505 preferably performs tracking control by moving the objective lens 523 from side to side.

The central processing unit 503 controls the fixing unit 501 for detecting an image stored in the optical disk 526 and the moving unit 502 for servo control of the holographic storage device.

Optical instruments for generating servo signals used in the mobile optical system can be added simply by using a commercial pickup used for a CD or a DVD, and volume can be minimized.

In addition, it can be used as a general optical disc system capable of simply playing a CD or DVD disc by blocking a light source used for reproduction of holographic data.

As described above, it has been described with reference to the preferred embodiment of the present invention, but those skilled in the art various modifications and changes of the present invention without departing from the spirit and scope of the present invention described in the claims below I can understand that you can.

As described above, according to the present invention, optical devices for storing and reproducing holographic data, an image sensor, an optical modulator, and the like are placed in a fixed optical device, and used for focusing a servo optical device, a photodetector, and a light source. The size and weight of the moving optical system are minimized by positioning the objective lens.

In addition, optical instruments for generating servo signals used in mobile optical systems can be added simply by using commercial pickups used for CDs or DVDs, and volume can be minimized.

In addition, by blocking the light source used for the reproduction of the holographic data, there is an advantage that can easily play a CD or DVD disc.

Claims (7)

In a holographic storage device, A fixing unit for recording and reproducing data, a moving unit having a light source for generating a servo signal, a signal processing unit for processing the servo signal generated by the moving unit, a driving unit for controlling the moving unit according to a signal of the signal processing unit, and A central processing unit for processing data detected by the optical disc, Holographic storage device, characterized in that the moving unit only moves in accordance with the servo signal for the detection of data. The apparatus of claim 1, wherein the moving unit comprises a light source for emitting laser light, an objective lens for adjusting focusing using the light generated by the light source, and a photodetector for detecting light reflected from the optical disk and returning to the optical disk. Holographic storage. 3. The holographic storage device of claim 2, wherein the light source uses a red laser light source. 3. The holographic storage device of claim 2, wherein the light source uses a light source having a wavelength range of 650 nm. The apparatus of claim 1, wherein the fixing unit is configured to detect a first light source emitting a laser light for recording and reproduction, an optical modulator for generating a reference light and an object light pattern by the laser emitted from the light source, and an image recognized by the optical disk. Holographic storage device comprising an image sensor. The holographic storage device of claim 1, wherein the moving unit and the fixing unit form a relay of light through a predetermined lens. The method of claim 5, And the reference light and the object light use one optical path when emitted from the optical modulator.

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