KR100739311B1 - Method for detecting pixel in holographic data storage system - Google Patents

Abstract

The present invention relates to a method of reproducing a data image in which first and second marks are respectively inserted at positions corresponding to each other on an upper end of a data frame. Determining whether the pixel lines are equally positioned at the first and second marks when the pixel lines reach the first and second marks, and if the first and second marks are equally positioned, Performing a signal processing process and skipping a signal processing process of the data image when the first and second marks are not located identically. According to the present invention, it is possible to determine whether the image is rotated by detecting only a part of the lines of the pixel data of the camera, so that it is very simple to implement the rotation discrimination algorithm after all the images are stored as in the prior art. In addition, since data is input for each line, pixel data of a line in which data is not yet input to the signal processing hardware is not input at the time of determining whether the image is to be rotated. Therefore, since the signal processing can be performed from the captured image in real time, the system speed is increased. It can also be improved.

Description

Image detection method for playback data in holographic data storage system {METHOD FOR DETECTING PIXEL IN HOLOGRAPHIC DATA STORAGE SYSTEM}

1 is a diagram illustrating a reproduction data image detection technique through image capturing in a conventional holographic data storage system;

2 is a diagram for explaining a technique of detecting a playback data image using intensity information in a conventional holographic data storage system;

3 is a schematic diagram of a typical holographic data storage system;

4A to 4C illustrate reproduction data images irradiated to the image sensor of the holographic data storage system of FIG. 3, and show changes of the disc as the disc rotates.

5 is a graph showing the change in the SNR of the reproduction data image according to the disc rotation;

6 is a camera pixel data clock timing diagram of the holographic data storage system of FIG.

7 is a view showing a data image in which an on-pixel mark is inserted and stored according to the present invention;

8 is a diagram illustrating a case where there is no image rotation as a detection result of a reproduction data image in which an on-pixel mark is inserted according to the present invention;

9A and 9B are graphs illustrating an output result of intensity sums of pixel lines of the reproduction data image of FIG. 8;

10 is a diagram illustrating a case in which an image is rotated as a detection result of a reproduction data image in which an on-pixel mark is inserted according to the present invention;

11A and 11B are graphs illustrating an output result of intensity sum for each pixel line of the reproduction data image of FIG. 10;

12 is a flowchart of a playback data image detection process in a holographic data storage system according to a preferred embodiment of the present invention.

<Explanation of symbols for the main parts of the drawings>

700, 800, 1000: Data Frame

702a, 802a, 1002a: first on-pixel mark

702b, 802b, 1002b: second on-pixel mark

The present invention relates to a holographic data storage system, and more particularly, to a method for detecting a reproduced data image of a holographic data storage system suitable for determining whether a reproduced data image is rotated.

Recently, the field of technology using holographic digital data storage has been actively researched by the remarkable development of components such as semiconductor laser, charge coupled device (CCD) and liquid crystal display (LCD). In addition to being used as a fingerprint recognition system for reproducing, there is a trend of expanding into various fields that can apply the advantages of large storage capacity and ultra-fast data transfer rate.

Such a holographic digital storage system records an interference fringe generated by interfering a signal light from a target object and a reference light, and records the interference fringe in a storage medium, for example, a crystal, etc. in response to the amplitude of the interference fringe. By recording the intensity and phase of signal light by changing the angle of light, etc., it is possible to realize a three-dimensional image of an object, and to store hundreds to thousands of holograms composed of pages of binary data in the same place. Will be.

In a typical holographic data storage system, the more pages of binary data recorded in the same space, the higher the signal-to-noise ratio during recording and playback. In particular, the "on pixel" stored in the storage material The more, the higher the signal-to-noise ratio. This is because unwanted scattering and diffraction occur during recording and reproduction due to interference fringes recorded on the storage material by on-pixels.

In conventional holographic data storage systems, original data is modulated and used such that the same number of on-pixels and " off pixels " are included in one binary data page.

That is, in the holographic data storage system, the interference fringes of the signal light and the reference light including on / off-pixel information are recorded in the storage material reacting to the intensity of the interference fringe, and during reproduction, the reference light at the time of recording is irradiated to the storage material. The stored signal light is reproduced by diffraction with the interference fringe recorded in the storage material.

At this time, when reproducing data in the holographic data storage system, it is necessary to implement error-free data restoration by signal processing only an accurate data image.

Due to this need, a variety of techniques have been proposed for holographic data storage systems to reproduce data images on a predetermined basis.

Among these techniques, the reproduction data image detection through image capturing is illustrated in FIG. 1.

1 shows an image captured by a camera, especially when a disc is constantly rotating, in a holographic WORM system using angular multiplexing. That is, the image looks as if it is flowing through the camera. At this time, it is necessary to select an image in which all data images are included in the pixel area of the camera as shown in the center of FIG.

The single image thus selected is decoded and restored to the original data. You must capture the image at the right time to get this desired image.

2 is a diagram illustrating a technique of detecting a playback data image using intensity information in a conventional holographic data storage system.

2 aims at photographing an image when it is present inside a camera sensor. 2 shows a case of capturing an image when the intensity of the entire camera pixel is equal to or greater than a specific threshold value.

The center diagram of FIG. 2 illustrates a case where an extra mark is inserted into a recorded image and the image is captured when the intensity of the extra mark is greater than or equal to the threshold value using a specific area of the camera pixel.

2 shows a case where two separate marks are inserted and the image is captured when the intensity of the mark is greater than or equal to the threshold value using a detector rather than a camera pixel.

Such a conventional reproduction data image detection technique is designed to operate when the threshold value is more than an arbitrary threshold value. However, since the intensity may vary depending on the image recording state, the threshold value may or may not be appropriate according to the experimental image state because the threshold value is an estimate obtained through an experiment.

In other words, the higher the threshold, the overall image data may be bright, or the entire captured data image may appear dark. In the latter case, the SNR (signal-to-noise ratio) of the reproduced image is low, which increases the possibility that the signal processing circuit cannot eliminate the error.

In addition, a data image reproduced in the holographic storage device may not maintain a constant intensity level. In this case, when the threshold is increased to obtain a data image having a high SNR, a page having a low intensity level of the reproduced data image may not be captured and may be lost.

3 is a schematic diagram of a holographic data storage system, such as a holographic WORM system, and includes a hologram disk 30, a lens 32, a camera 34, and a DSP circuit unit 36. .

The holographic data storage system of FIG. 3 is characterized in that a plurality of data images are recorded in one spot on an rotating hologram disk 30 in an interference fringe pattern. When the data recorded in the form of an interference pattern is irradiated with the reference light used at the time of recording, the reference light is diffracted by the interference pattern recorded on the holographic disk to restore the data image of the recorded binary pattern. At this time, the reproduced data image is detected by the camera 34 mounted with an image sensor of CCD or CMOS, and the detected data is transferred to the DSP circuit unit 36 which is in charge of signal processing so as to accurately restore the digital data.

On the other hand, data images reproduced through such holographic data storage systems do not necessarily move along straight tracks. That is, as shown in Figs. 4A to 4C, since the rotating disk moves along a large circumference, even if the playback data image is captured in the sensor area of the camera, the data image captured by the camera is rotated as in Figs. 4A and 4B. It is done.

Therefore, when the binary reproduction image in the form of a pixel is detected by a camera arranged in the form of a two-dimensional pixel array, the best SNR is detected when the reproduction data image and the pixel arrangement of the camera are the same as shown in FIG. 4C.

5 is a graph measuring the change in the SNR of the rotated playback data image.

As can be seen in the graph of FIG. 5, it can be seen that a change in SNR occurs because the data image rotates as the disk rotates. Therefore, it is necessary to perform signal processing on an image with the maximum SNR to recover data without error.

As described above, in the conventional holographic data storage system, since the reproduced data image is moved while rotating along a large circumference, in order to restore the correct data, the entire data image is temporarily stored in RAM or the like, and then the degree of rotation of the image is changed. It is necessary to apply the grasping algorithm and perform data extraction accordingly.

Therefore, one megabyte or more of storage space is required to store one reproduction data image, and an algorithm for rotating an axis image is required.

Once the data images taken from the camera have been filled up in the temporary storage space, all the signal processing algorithms will be able to process the next data page immediately, which will slow down the overall holographic data storage system. do.

The present invention overcomes the above-mentioned limitations of the prior art and solves all the problems. When reproducing data from a hologram recorded on a rotating holographic disc, the data image is detected in consideration of the case where the reproduced data image is rotated. It is an object of the present invention to provide a method of detecting a reproduction data image in a holographic data storage system that can find an image that is not rotated at a time and signal-process only the image.

According to a preferred embodiment of the present invention for achieving the above object, a method of reproducing a data image in which the first and second marks are respectively inserted at positions corresponding to each other on the top of the data frame, the pixel data photographed through the camera Receiving and calculating a sum of 25 pixel data; determining if the pixel line is equally located at the first and second marks when the pixel lines reach the first and second marks; Performing signal processing on the data image when the first and second marks are located identically; skipping signal processing on the data image when the first and second marks are not located identically. A method of detecting a reproduction data image in a holographic data storage system is provided.

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

Prior to the description, the present embodiment is applied to the holographic data storage system of FIG. 3 described above, and the detailed description of the system configuration and operation of FIG. 3 will be omitted to avoid duplication.

In this embodiment, the holographic WORM system of FIG. 3 is equipped with a camera having a high frame rate, and the camera captures an image at the maximum speed.

The playback image is moved while rotating about the virtual center outside the camera as shown in FIGS. 4A to 4C, and the camera captures the moving playback data image every moment and transmits it to an external signal processing circuit in real time. At this time, the pixel data value transmitted from the camera to the outside is output at the timing shown in FIG.

6 is a timing diagram of a camera having a high speed camera interface. Normally, a camera transmits pixel data to the outside according to the pixel clock. In the case of a high-speed camera, a plurality of pixel data are transmitted in one pixel clock, and when one image is delivered, frame valid is delivered high and one line is delivered. Line Valid goes high during operation.

Therefore, in the hardware that handles the signal processing, data images reproduced by the holographic WORM system are not transmitted at once in units of frames, but are sequentially processed for each line of the camera sensor.

In this case, the data page to be applied to the present embodiment is as shown in FIG. 7.

In FIG. 7, the frame 700 plays a role of designating a location of a binary data image. The two marks 702a and 702b present in the forward direction of the image are lines of on-pixels of constant length. The present invention uses the two marks 702a and 702b to determine whether the captured image is rotated.

The data image reproduced after recording to the holographic storage device in the data format of FIG. 7 is captured by a camera as shown in FIG. 8.

As shown in FIG. 8, a frame 800 surrounding the data page exists and a line composed of 25 on-pixels on the left and right sides of the upper frame is reproduced. In the case of Figure 8 is the data photographed when there is no rotation of the image.

As illustrated in FIG. 8, when the data image reproduced in the holographic storage device is photographed by a camera, data is output to the outside for each camera line and each pixel. In the case of a camera having a timing diagram as shown in FIG. 6, 10 pixel data are transmitted to the outside at once, and the pixel at the top left is the first pixel and there are 1280 pixel data in each line (the camera used in the present invention). Has a 1280 × 1024 resolution, for example). When 1280 data of line 1 are output, data of the next line is output one after the other. At this time, the output of each line proceeds from left to right with reference to FIG.

9A and 9B illustrate a case where a data image is detected without rotation as shown in FIG. 8. In FIG. 9A, the Y axis represents the intensity sum of 25 pixel lines, and the X axis represents the initial position of the summed pixel lines. That is, in FIG. 9A, the pixel position representing the first peak value is 20 pixels, which means that the mark on the upper left of FIG. 7, that is, the first on-pixel mark 802a starts from 20 pixels.

First, FIG. 9A shows, for example, the intensity sum in the tenth pixel line, and FIG. 9B shows the intensity sum in the ninth pixel line, for example. As can be seen in FIGS. 9A and 9B, there is a point where the sum of the intensities is maximized at the left and right ends of the pixel line. That is, since the first on-pixel mark 802a and the second on-pixel mark 802b are both located at the tenth pixel line, the first on-pixel mark 802a and the second on-pixel mark 802b are located. The intensity sum of the pixel lines in E is the same, and when compared to the adjacent lines, that is, the sum of the intensities of the ninth pixel line, it can be seen that it is clearly distinguished from the pixel line in which there are 25 on-pixel lines.

Meanwhile, FIG. 10 illustrates a case where the image 1000 is rotated as a detection result of a reproduction data image in which an on-pixel mark is inserted according to the present invention.

The graphs of FIGS. 11A and 11B are graphs showing a result of a state in which rotation occurs and a data image about 1 pixel is distorted.

As can be seen from FIGS. 10, 11A, and 11B, the 25 pixel on data mark 1002a at the top left of the data image 1000 is located at the tenth pixel line and is located at the top right of the data image 1000. The present 25 pixel on data mark 1002b may be located on the ninth pixel line to determine that the data image 1000 is rotated.

Therefore, based on the result, it is possible to simply detect that the rotation of the image occurs, and it is possible to selectively process only the image that does not occur rotation of the data image continuously input.

Hereinafter, with reference to the above-described configuration, a process of detecting a reproduction data image in a holographic data storage system according to a preferred embodiment of the present invention will be described in detail with reference to the flowchart of FIG. 12.

First, in step S100, the DSP circuit unit 36 receives pixel data from the camera 34, and proceeds to step S102 to calculate the sum of 25 pixel data. In other words, the sum of intensities for each of 1 to 25 pixel lines is calculated.

As a result of this sum calculation, the DSP circuit unit 36 proceeds to step S104 to determine whether the pixel line reaches the first area, that is, the area of the first on-pixel mark 702a. That is, since the pixel line output proceeds from left to right, it is first determined whether the pixel line output reaches the first on-pixel mark 702a.

As a result of the determination in step S104, when the first on-pixel mark 702a is reached, the DSP circuit unit 36 proceeds to step S106 to determine whether the intensity sum of the current pixel line is greater than a preset maximum sum. .

If the intensity sum of the current pixel lines is greater than the maximum sum, the DSP circuit unit 36 proceeds to step S108 to update the intensity sum of the current pixel lines to the maximum sum.

Thereafter, in step S110, the DSP circuit unit 36 determines whether a peak value exists, and if there is a peak value, the process proceeds to step S112 and finally determines that the current pixel line is located at the first on-pixel mark 702a. do.

On the other hand, if the pixel line reaches the second on-pixel mark 702b as a result of the determination in step S104, the DSP circuit unit 36 proceeds to step S122 where the intensity sum of the current pixel line is preset. Determine if greater than the maximum sum.

If the intensity sum of the current pixel lines is greater than the maximum sum, the DSP circuit unit 36 proceeds to step S124 to update the intensity sum of the current pixel lines to the maximum sum.

Thereafter, in step S126, the DSP circuit unit 36 determines whether there is a peak value, and if there is a peak value, the process proceeds to step S128 and finally determines that the current pixel line is located at the second on-pixel mark 702b. do.

After this process, the DSP circuit unit 36 determines whether the pixel line exists in the data frame 700 as in step S114, and if the DSP circuit unit 36 exists in the data frame 700, the step is performed. Proceed to S116. This process is performed as the reproduction data image moves. When the pixel line does not reach the data frame 700, the process returns to step S102 to repeat the above processes.

In step S116, the DSP circuit unit 36 determines whether the position of the first on-pixel mark 702a and the position of the second on-pixel mark 702b are the same.

As a result of the determination in step S116, if the positions of the first on-pixel mark 702a and the second on-pixel mark 702b are the same, the DSP circuit unit 36 determines that the reproduced data image is not rotated. Signal processing is performed on the corresponding image (S118). At this time, the DSP circuit unit 36 waits for a new data image.

On the other hand, if the position of the first on-pixel mark 702a and the second on-pixel mark 702b is not the same as a result of the determination in step S116, the DSP circuit unit 36 indicates that the playback data image is rotated. In operation S120, the signal processing of the corresponding image is skipped. At this time, the DSP circuit unit 36 waits for a new data image.

As described above, the present invention implements to insert two marks composed of on-pixel on top of the image data, and to determine whether to rotate the reproduced image data according to the positions of the two marks in reproducing the image data. It is.

According to the present invention, it is possible to determine whether the image is rotated by detecting only a part of the lines of the pixel data of the camera, so that it is very simple to implement the rotation discrimination algorithm after all the images are stored as in the prior art. In addition, since data is input for each line, pixel data of a line where data is not yet input to the signal processing hardware is not input at the time when the image is rotated or not, so that signal processing is possible from an image captured in real time. Speed can also be improved.

As mentioned above, although this invention was demonstrated concretely based on the Example, this invention is not limited to such an Example, Of course, various deformation | transformation are possible for it within the technical idea and the scope of a claim mentioned later.

Claims (4)

delete A reproduction data image detection method in a holographic data storage system for reproducing a data image in which first and second marks are inserted at positions corresponding to each other on an upper end of a data frame, respectively. Receiving pixel data photographed through a camera and calculating a sum of 25 pixel data; Determining whether a pixel line reaches an area of the first mark; Determining whether an intensity sum of a current pixel line is greater than a preset maximum sum when reaching an area of the first mark; If the intensity sum of the current pixel lines is greater than the maximum sum, updating the intensity sum of the current pixel lines to the maximum sum; Determining whether a peak value exists, and finally determining that a current pixel line is located at the first mark if the peak value exists; When the pixel line reaches the region of the second mark, determining whether an intensity sum of a current pixel line is greater than the maximum sum; If the intensity sum of the current pixel lines is greater than the maximum sum, updating the intensity sum of the current pixel lines to the maximum sum; Finally determining that the current pixel line is located at the second mark if the peak value is present; Determining whether the position of the first mark and the position of the second mark are the same when the pixel line exists in the data frame; Performing signal processing on the data image when the positions of the first and second marks are the same; Skipping the signal processing of the data image when the positions of the first and second marks are not the same Playback data image detection method in a holographic data storage system comprising a. The method of claim 2, And the first and second marks are present in front of the rotational direction of the data image. The method of claim 2, And the first and second marks are lines consisting of on-pixels of a predetermined length.

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