KR100578183B1 - How to Process Holographic Data - Google Patents

Abstract

In the present invention, a method of processing holographic data is a method of storing data in a unit of page in a holographic medium and processing holographic data reproduced from the medium, wherein the input data is M1xM2 data in units of pages. The alignment data is generated by including a frame-aligning step and a separation frame composed of pixel layers all surrounded by the edges of the M1xM2 data frame, and then storing the alignment data in the holographic medium on a page-by-page basis. Outputting a reproduction data image including an M1xM2 data frame and a division frame, calculating a sum of intensity of pixels for each row and column of the reproduction data image, and a degree of change between pixels for each row and column, respectively; , Weighting the sum of the intensities of each row and column according to the degree of change And searching for rows and columns corresponding to the division frame.

As described above, according to the present invention, the position of the data frame is precisely determined by finding a row and a column corresponding to the divided frame A through a calculation between the change degree value and the intensity sum between the pixels or by assigning a weighted value according to the change degree value. Can be estimated reliably.

Description

Holographic data processing method {METHOD FOR PROCESSING DATA IN HOLOGRAPHIC SYSTEM}

1 is a block diagram of a conventional apparatus for storing and reproducing holographic data,

2 is a view showing the structure of a stored data image according to the prior art,

3 is a flowchart illustrating a process of storing and reproducing holographic data according to an exemplary embodiment of the present invention.

4 is a graph showing the intensity value distribution of each row and column for explaining the present invention,

5 is a graph showing the standard deviation distribution of each row and column for explaining the present invention,

FIG. 6 is a graph illustrating a distribution chart of difference values between intensity values and standard deviations for each row and column for explaining the present invention.

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

10 light source 20 light separator

30, 40: reflection mirror 50: SLM

60: storage medium 70: CCD

80: data alignment unit 85: data detection unit

90: signal processing unit

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a holographic data reconstruction and storage system, and to a method for processing holographic data reproduced from a holographic medium.

As is well known, there is an increasing demand for holographic digital data storage systems capable of storing large amounts of data. Accordingly, various types of holographic digital data storage systems have been recently developed to realize high density storage capacity.

The holographic digital data storage system causes the information signal and the reference light to interfere with each other to form an interference fringe between them, and to control the interference fringe to be stored in a storage medium made of optical refractive crystals. . Photorefractive crystals are materials that react differently depending on the amplitude and phase of the interference fringe.

Various holograms can be stored in a storage medium by changing the angle of incidence of the reference light (angle multiplexing) or by moving the storage medium to change the storage area (shift multiplexing). The hologram of may be stored in the storage medium in units of pages.

1 is a block diagram of a conventional apparatus for storing and reproducing holographic data, and FIG. 2 is a diagram showing the structure of a stored data image according to the prior art.

Referring to FIG. 1, an apparatus for storing and reproducing holographic data includes a light source 10, a light separator 20, two reflection mirrors 30 and 40, a shutter 45, and a spatial light modulator (SLM) 50. ), A storage medium 60, a CCD 70, a data alignment unit 80, a data detection unit 85, and a signal processing unit 90.

The light source 10 generates laser light. The optical modulator 20 divides the laser light into reference light and signal light, and transmits the separated reference light and signal light along two different optical paths. Here, the reference light and the signal light correspond to the transmitted light and the reflected light, respectively.

The reference light is reflected by the reflection mirror 30 and transmitted to the storage medium 60. On the other hand, the signal light is reflected by the reflection mirror 40 and transmitted to the SLM 50. Upon storage, the shutter 45 is open to allow signal light to be sent to the SLM 50.

Meanwhile, the binary input data to be stored is arranged in page units by M1 bits in rows and M2 bits in columns in the data sorting unit 80. Here, M1 and M2 are each positive integers. At this time, the data sorting unit 80 attaches a separator frame composed of pixels surrounding the edge of the M1xM2 data frame in order to easily detect the position of the data during data reproduction. Further intermediate frames are added to generate alignment data. That is, the data sorting unit 80 generates the sorting data composed of the M1xM2 data frame, the separating frame, and the intermediate frame, and provides the sorting data to the SLM 50, and the SLM 50 is provided at the reflected signal light and the data sorting unit 80. The transmitted alignment data is modulated to provide modulated signal light for each page. Here, the pixels of each row and column constituting the separator frame have a bright image, that is, a value of one.

The modulated signal light is transmitted to the storage medium 60. The reflection mirror 30 functions to slightly change the reflection angle of the reflected reference light to store data of another page.

An interference pattern of modulated signal light that interferes with the reference light is stored in the storage medium 60. In this case, the interference pattern stored in the storage medium 60 will consist of pixels corresponding to the frames constituting the alignment data, hereinafter referred to as storage data image. In general, a stored data image has a "bright" image and a "dark" image, where the "bright" image represents a logical value "1" and the "dark" image represents a logical value "0".

At the time of reproduction, the shutter 45 is closed to prevent the signal light from entering the storage medium 60. Thus, only reference light is incident on the storage medium 60.

When the reference light is incident on the storage medium 60 to reproduce the data, the reference light is diffracted by the interference pattern stored in the storage medium 60 so that the reproduced data image is reproduced page by page. In this case, the reproduced data image corresponds to the stored data image.

The reference light used for reproducing the data stored in the storage medium 60 should be incident at the same angle as the reference light used for storing the data.

The reproduced data image is transmitted to the CCD 70, detected by the CCD 70, and transmitted to the data detection unit 85. The CCD 70 outputs a page image, as shown in FIG. In this case, the page image includes a division frame corresponding to the reproduction data image.

The data detection unit 85 receives a page image composed of a data frame, a divided frame, and an intermediate frame, and detects a position of the data image composed of the M1xM2 data frame through extraction of the divided frame.

The process of extracting the data image by the data detection unit 85 is as follows.

The data detection unit 85 receives the page image as shown in FIG. 2 and sums the intensities in the vertical and horizontal directions using only some of the pixels of the whole or upper left corner or only some of the pixels of the lower right corner. , The row and column having the largest double sum are determined as the division frame (A), and only the data image inside the division frame (A) is extracted and provided to the signal processing unit (90). That is, the data detection unit 85 detects rows in which the sum of the pixels is relatively large after obtaining the sum of the pixels in the row direction, and detects columns in which the sum of the pixels in which the sum of the pixels in the column direction is relatively large is respectively. Thus, the position of the data image composed of the M1xM2 data frame is detected by detecting the rows and columns corresponding to the division frame A.

Thereafter, the data detection unit 85 extracts only the data image inside the row and column corresponding to the division frame and provides the same to the signal processing unit 90.

The signal processing unit 90 samples the pixels from the data image to generate a processed data image having an M1xM2 data frame equal to the size of the alignment data.

Since the holographic data storage and reproducing system has a characteristic of the laser light generated from the light source 10, that is, a Gaussian distribution, it is difficult to make the entire page have a uniform brightness. That is, in the holographic data storage / reproducing apparatus, the light intensity representing the logical value "1" or "0" in the page image is large in the center of the image pixel and becomes smaller toward the periphery. The greater this difference, i.e., the larger the page to be stored in the storage medium 60, the more similar the number of 1's and 0's in the center area is than the sum of the detection bits in the outer area when the data detection unit 85 extracts the data image. There is a problem in that the sum becomes larger and thus the extraction of the data image fails.

An object of the present invention is to provide a holographic data processing method for improving reliability in detecting a position of a data image by preventing a data image extraction error caused by a Gaussian distribution of laser light.

In order to achieve the above object, the present invention provides a method of storing data in a holographic medium on a page basis and processing holographic data reproduced from the medium, wherein the input data is in the form of a M1xM2 data frame on a page basis. And sorting the data into a holographic medium on a page-by-page basis after generating the alignment data by including a division frame including a pixel layer composed of all pixels that surrounds the edge of the M1xM2 data frame. And outputting a reproduction data image including the M1xM2 data frame and a division frame, and calculating intensity sums of pixels for each row and column of the reproduction data image and a degree of change between pixels for each row and column, respectively. And intensity of each row and column according to the change degree value. By the weighting comprises the steps of finding the row and column corresponding to the segment frame.

The present invention also provides a method for storing data in a holographic medium on a page-by-page basis and processing holographic data reproduced from the medium, wherein the input data is arranged in the form of an M1xM2 data frame on a page-by-page basis. And generating a sorting data by including a separator frame including a pixel layer composed of pixels on the edges of the M1xM2 data frame, and storing the sorting data in a holographic medium in units of pages. Outputting a reproduction data image including a data frame and a division frame, calculating a sum of intensity of pixels for each row and column of the reproduction data image, and a degree of change between pixels for each row and column, and each row The row after calculating the difference between the sum of intensity and the degree of change for the column And reading out the division frame by obtaining a row and a column having a relatively large difference between an intensity sum and a change degree value among the columns, and calculating a position of the M1xM2 data frame based on the read division frame.

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

FIG. 3 is a flowchart illustrating a process of storing and reproducing holographic data according to a preferred embodiment of the present invention. FIG. 4 is a graph illustrating an intensity value distribution of each row and column for explaining the present invention. Is a graph showing the standard deviation distribution of each row and column for explaining the present invention, Figure 6 is a graph showing the distribution of the difference between the intensity value and the standard deviation for each row and column for explaining the present invention. The holographic data processing process according to the present invention will be described with reference to FIGS. 1 to 6.

First, storing data in the storage medium 60 stores the input data in the same manner as the conventional method. That is, the data sorting unit 80 receives the binary input data to be stored and sorts them in units of pages in the form of M1xM2 data frames, and M1 and M2 are each positive integers. At this time, the border of the M1xM2 data frame is aligned so that the partition frame is surrounded in a rectangular shape. That is, the data alignment unit 80 generates the alignment data composed of the M1xM2 data frame and the division frame A and provides the same to the SLM 50.

In the present invention, the rectangular division frame A surrounding the M1xM2 data frame is composed of one pixel layer, as shown in FIG. 2. The pixel layer constituting the division frame A is composed of pixels that are all on to surround the M1xM2 data frame.

The data alignment unit 80 provides the alignment data generated through this process to the SLM 50, and the SLM 50 arranges the signal light reflected by the reflector 40 and the alignment data transmitted from the data alignment unit 80. Is modulated to provide modulated signal light for each page.

The modulated signal light is incident on the storage medium 60 together with the reference light incident through the reflection mirror 30.

In the storage medium 60, an interference pattern of modulated signal light that interferes with reference light incident through the reflection mirror 30, that is, a stored data image, is stored.

At the time of reproduction, the shutter 45 is closed to prevent the signal light from entering the storage medium 60. Therefore, only reference light, that is, reference light for reproduction, is incident on the storage medium 60.

A process of reproducing the stored data image composed of the divided frame A and the M1xM2 data frame through the above process will be described with reference to FIG. 3.

When the reproduction reference light is incident on the storage medium 60 to reproduce the data, as shown in FIG. 3, the reference light is diffracted by the interference pattern stored in the storage medium 60, so that the reproduction data image is paged. It is output (S300). In this case, the reproduction data image will be composed of an M1xM2 data frame and a division frame A and correspond to the stored data image.

The reference light used for reproducing the data stored in the storage medium 60 should be incident at the same angle as the reference light used for storing the data.

The reproduced data image is transmitted to the CCD 70, detected by the CCD 70, and transmitted to the data detection unit 85. The CCD 70 outputs a page image composed of M1xM2 data frames. In this case, the page image includes a division frame A corresponding to the reproduction data image.

The data detection unit 85 receives the page image composed of the M1xM2 data frame and the division frame A and detects the position of the data image consisting of the M1xM2 data frame through extraction of the division frame A (S302 to S310).

According to the present invention, the process of extracting the data image composed of the M1xM2 data frames by the data detection unit 85 is as follows.

The data detection unit 85 is provided with the reproduced data image to obtain intensity sums for each row and column (S302), and the distribution of intensity sums for each row and column, as shown in FIG. Due to the distribution, the middle row and column have a relatively large value compared to the other rows and columns compared to the row and column corresponding to the division frame (A).

Thereafter, the data detection unit 85 calculates a degree of change between pixels for each row and column, that is, a standard deviation or variance value (S304), so that the distribution of the degree of change for each row and column, for example, the standard deviation is As shown in FIG. 5, a row and a column corresponding to a division frame A including on pixels have a value of almost 0, but a row and a column of a data frame including on and off pixels are relatively large. Have

Then, the data detection unit 85 calculates a difference value between the sum of intensity of each row and column and the standard deviation (S306), and the distribution of the difference value for each row and column is as shown in FIG. That is, since the standard deviation of the rows and columns corresponding to the division frame A has a value close to zero, the value obtained by subtracting the standard deviation from the intensity sum is relatively larger than the rows and columns corresponding to the data frame and corresponds to the data frame. Rows and columns are nearly zero because they subtract a relatively large standard deviation from the sum of intensities.

Through the calculation process as in step S306, the data detection unit 85 regards the row and column having a relatively large difference value among the columns and columns as the separating frame A, and is surrounded by the rows and columns corresponding to the separating frame A. Accumulated M1xM2 data frames are detected (S308, S310).

In the preferred embodiment of the present invention, the standard deviation or variance value of each row and column is calculated to read the position of the division frame A, and the calculated standard deviation or variance value and the sum of intensity are described as an example. In another embodiment, the degree of change of pixels is calculated for each row and column, and for the row and column (s) (rows and columns corresponding to the data frame) where the degree of change is relatively large compared to other rows and columns. It is easy to find the rows and columns corresponding to the division frame A by assigning a large weight and giving a relatively small weight to the rows and columns whose change degree is relatively small compared to the other rows and columns.

The M1xM2 data frame detected in the above manner is provided to the signal processing unit 90, and the signal processing unit 90 samples pixels from the data image, so that the M1xM2 data frame equal to the size of the data image corresponding to the input data. A process data image having a generated is generated (S312).

That is, according to the present invention, M1xM2 corresponding to the data image can be found by accurately finding the rows and columns corresponding to the division frame A by weighting the change degree value and the intensity sum between the pixels or by applying the change degree value. It's easy to find data frames.

 As described above, according to the present invention, the position of a data frame is found by calculating a row and a column corresponding to the division frame A by performing a calculation between a change degree value between pixels and an intensity sum or by weighting the change degree value. Can be estimated accurately and reliably.

On the other hand, the present invention is not limited to the above-described embodiment, various modifications are possible by those skilled in the art within the spirit and scope of the present invention described in the claims to be described later.

Claims (5)

A method of storing data in page units in a holographic medium and processing holographic data reproduced from the medium, Sorting the input data in the form of M1xM2 data frame by page; Generating alignment data by including a division frame including a pixel layer composed of pixels on all edges of the M1xM2 data frame, and storing the alignment data in a holographic medium in units of pages; Outputting a reproduction data image including the M1xM2 data frame and a division frame; Calculating intensity sums of pixels for each row and column of the reproduction data image and a degree of change between pixels for each row and column, respectively; Finding rows and columns corresponding to the divided frames by weighting the sum of the intensity of each row and column according to the change degree value Holographic data processing method comprising a. The method of claim 1, Finding the rows and columns corresponding to the division frame, A large weight is given to the sum of the intensities of the small rows or the columns having a relatively small degree of change among the degree of change of the rows and columns, and the sum of the intensities of the rows or the columns having the relatively big degree of change among the degree of change. Holographic data processing method characterized by giving a small weight to the. The method of claim 1, And the change degree value is a standard deviation or variance value of each row and column. A method of storing data in page units in a holographic medium and processing holographic data reproduced from the medium, Sorting the input data in the form of M1xM2 data frame by page; Generating alignment data by including a division frame including a pixel layer composed of pixels on all edges of the M1xM2 data frame, and storing the alignment data in a holographic medium in units of pages; Outputting a reproduction data image including the M1xM2 data frame and a division frame; Calculating an intensity sum of pixels for each row and column of the reproduction data image and a degree of change between pixels for each row and column; After calculating the difference between the sum of intensities and the degree of change for each of the rows and columns, the row and column are obtained by reading the rows and columns having a relatively large difference between the sum of intensities and the degree of change among the rows and columns. Calculating a position of the M1xM2 data frame based on a division frame Holographic data processing method comprising a. The method of claim 4, wherein The degree of change between the pixels is a standard deviation or variance value of each row and column.

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