KR20030092473A - Method for auto-align data page of holographic data storage system - Google Patents

Abstract

PURPOSE: A method of automatically aligning data pages in an apparatus for recording and reproducing holographic data is provided to control a reference beam angle control actuator to automatically adjust alignment of data pages. CONSTITUTION: An apparatus for recording and reproducing a holographic data reproduces holographic data page(S100). A column or a row in the data page is selected(S102). An align mark section of the selected column or row is approximated to a continuous function of the data value of the column or row(S104). The approximated function is second-order differentiated to obtain the first edge value or the second edge value(S106). A regression line of the first or second edge value is obtained(S112). When the position or slope of the regression line does not have a distance or slope set to a predetermined position of the data page, a servo controller of an actuator for controlling the angle of a reference beam is controlled to automatically align the holographic data page(S114).

Description

How to automatically align the data page of the holographic data recording and playback device {METHOD FOR AUTO-ALIGN DATA PAGE OF HOLOGRAPHIC DATA STORAGE SYSTEM}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an alignment method of a holographic data recording and reproducing apparatus, and more particularly, by using Fourier approximation of pixels to be inserted for alignment in a data page, a regression line of edges of each page is obtained, and the position of the pixel and the regression line of the page. And a data page automatic alignment method of a holographic data recording and reproducing apparatus for automatically adjusting the alignment of a data page by controlling an actuator for adjusting the reference light angle according to the inclination difference.

Currently, a holographic digital data storage system using semiconductor laser, charge coupled device (CCD), liquid crystal display (LCD), etc., is being actively researched and developed. Holographic digital data storage system has the advantages of large capacity and ultra-fast data transfer speed, so it is not only being used as a fingerprint reader and display device for storing and playing fingerprints, but also its application field is gradually expanding. .

Such a holographic digital data storage system interferes with the object light transmitted from the object and the reference light, and then reacts the interference fringe generated by the interference differently according to the amplitude and phase of the interference fringe. Three-dimensional holographic digital data in page units of binary data is stored by recording in a storage medium such as a refractive crystal or a polymer. The object light is blocked and only the reference light is provided to the storage medium to reproduce the stored three-dimensional data.

The holographic digital data is generally recorded and reproduced as square image data having the same form as a display screen in units of pages. However, since an alignment is required for accurate reproduction, an alignment mark is usually formed at the edge of the holographic data page. However, if the alignment marks of the data page form a pixel-to-pixel image on the CCD, if the alignment is not correct, the alignment mark may bleed to the pixel next to the CCD, thereby preventing accurate alignment.

To this end, U.S. Patent No. 6064586 proposes a new method of storing and reproducing holographic data on alignment, in which the marks related to alignment are displayed in bold in three columns on both vertical lines among the pixels of the holographic data page. However, due to the characteristics of the holographic data recording and reproducing apparatus which measures alignment within ± 0.5 pixels, there is a limitation in that alignment cannot be accurately measured using intra-pixel alignment marks.

An object of the present invention is to use the Fourier approximation of the pixels inserted for the alignment in the data page to solve the problems of the prior art as described above to obtain the regression line of the edges of each page and to the difference between the position and the slope of the page pixel and the regression line. Accordingly, the present invention provides a method of automatically aligning a data page of a holographic data recording and reproducing apparatus by controlling an actuator for adjusting the reference light angle to automatically adjust the alignment of a data page.

In order to achieve the above object, the present invention provides a method of adjusting the alignment of data pages in a holographic data recording and reproducing apparatus, the method comprising the steps of: reproducing the holographic data pages in the holographic data recording and reproducing apparatus; Selecting one row or one column and a continuous function of the row or column data values for the alignment mark interval of the selected row or column approximation with (x), and approximated function second derivative of (x) to find the first edge value or the second edge value, and each row from the next row selected in the data page to the last row or the next column to the last column, respectively. obtaining (x) and performing a second derivative to obtain each first edge value or second edge value, and obtaining a regression line of the first and second edge values of each row or column, and each regression line. And automatically aligning the holographic data page by controlling the servo control unit of the actuator for adjusting the angle of the reference light when the position or the slope of the control unit does not have the distance or the slope set to the predetermined position of the data page.

1 is a block diagram for explaining a data page automatic alignment method of the holographic data recording and reproducing apparatus of the present invention;

2 is a flowchart showing a method of automatically aligning a data page of a holographic data recording and reproducing apparatus;

3 shows a holographic data page with an alignment mark;

4A and 4B are diagrams showing a case where a data page is normally reproduced and a case where a data page is abnormally shifted and reproduced.

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

100: light source 102: optical separator

104, 110: shutters 106, 112: reflectors

108: actuator 114: spatial light modulator

116: storage medium 118: CCD

120: microcomputer 122: servo control unit

124: image compensation processing unit

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

1 is a block diagram illustrating a method of automatically aligning a data page of a holographic data recording and reproducing apparatus according to the present invention. The holographic data recording and reproducing apparatus includes a light source 100, an optical separator 102, and a shutter 104. 110, reflectors 106 and 112, spatial light modulator 114, actuator 108, storage medium 116, CCD 118, microcomputer 120, server controller 122, and And an image compensation processor 124.

2 is a flowchart showing a method of automatically aligning a data page of a holographic data recording and reproducing apparatus. 1 and 2, a data page automatic aligning method of the present invention will be described.

First, the holographic data recording and reproducing apparatus irradiates the storage medium 116 with only the reference light of the recording angle set when the data is reproduced to reproduce the holographic digital data page and transmit it to the CCD 118. (S100)

Then, the microcomputer 120 selects one row or one column from the data page transmitted from the CCD 118 and performs the automatic alignment method of the data page according to the present invention.

The microcomputer 120 continuously functions the row or column data values for the alignment mark interval of the selected row or column. Approximate to (x). (S104)

That is, the microcomputer 120 approximates a continuous function using row or column data values of a data page to process the holographic image at a sub pixel level. In this case, the approximation method is a Fourier approximation method, which is represented by Equation 1 below. However, the Fourier approximation should be noted that the number of harmonics should be less than half the number of data.

(J = 0, 1,…, m), , 2m + 1 ≦ n.

Also, when we want to measure the alignment mark on the vertical axis using the pixels in the row, the partial derivative for y must be removed because the angle is close to 90 °.

The microcomputer 120 then approximates the function The second derivative is used to find the first edge value or the second edge value of the data page. (S106) The second derivative is used to find the edge of the data page. The second derivative of (x) becomes zero and the inflection point is the edge. That is, the first edge value is (x) is the maximum The left edge LE is shown as a value of (x) = 0. The second edge value is (x) is the minimum The value of (x) = 0 indicates the right edge RE.

In the present invention, when the edge value of the data page is obtained, both the first edge value and the second edge value may be used, or only one of them may be used.

The microcomputer 120 determines whether i is the end in S106 (S108). If it is not the end as a result of the determination in S108, the microcomputer 120 changes to i → i + 1 (S110) and enters step S102. So each I incremented from the next row selected in the data page to the last row or next column to the last column, (x) is obtained and the second derivative is used to find the first edge value or the second edge value. (S108 to S110)

Next, the microcomputer 120 calculates a regression line using a fitting method in which the first and second edge values of these rows or columns are the least squares method (S112). If it is located in the middle of the edge RE, the alignment mark is an average of the left edge LE and the right edge RE.

The microcomputer 120 automatically controls the holographic data page by controlling the servo controller 122 of the actuator 108 that adjusts the angle of the reference light when the position or the slope of the regression line does not have the distance or the slope set to a predetermined position of the data page. (S114) For example, if the position of the measured regression line is 7 pixels apart by 0.5 pixel distance of the normal data page, the servo controller 122 moves the actuator 108 by -7 pixels. To control playback. The data page reproduced in the CCD 118 is then reproduced accurately in the 0.5 pixel range.

On the other hand, if the position or the slope of the regression line does not have the distance or the slope set to a predetermined position of the data page, the microcomputer 120 sends the data page to the image compensation processor 124 to digitally process the image of the holographic data page. In other words, the image compensation processing unit 124 may automatically align the image of the data page by moving the image of the data page by the difference of the position or the slope of the measured regression line to a predetermined position of the data page.

3 is a diagram illustrating a holographic data page having an alignment mark, and the alignment method of the present invention can be applied even when the alignment mark 202 is displayed at an edge around the holographic data page 200. The page shape can be applied to polygons in addition to rectangles.

4A and 4B are diagrams illustrating a case where a data page is normally reproduced and a case where a data page is abnormally shifted and reproduced.

4A shows that the holographic data page 200 with one row of left / right alignment marks is correctly pixel matched to a CCD Region of Interest (ROI). At this time, the lines 1 and 4 in the enlarged reference numerals a and b are both vertical boundaries of the CCD ROI. As shown in the figure, the center lines ② and ③ of the pixels are inward by 0.5 pixels from the boundary lines ① and ④. Therefore, the holographic data can be accurately aligned in the holographic data recording and reproducing apparatus which measures the alignment within ± 0.5 pixel.

However, as shown in FIG. 4B, when the holographic data page is matched with a position shifted by 0.7 pixels of the ROI of the CCD, the holographic data page may be aligned by the automatic alignment method of the present invention.

? And? Are obtained by approximating the column direction of the data page to Fourier to obtain the first and second edge lines of the pixel. Ideally, these two lines should be at the same position as the pixel center lines ⑥ and ⑧ on the data page, so we calculate the distance traveled in the x-axis direction by calculating the position distance of the two lines. The calculated distance is sent to the servo control unit to drive the actuator in the reverse direction by the calculated value so that the alignment of the holographic data page is precisely aligned. In the alignment method of FIG. 4B, the alignment mark in the vertical direction is taken into consideration, but the horizontal direction is also the same.

As described above, the present invention obtains the regression line of the edges of each page using Fourier approximation of the pixels inserted for alignment in the data page, and controls the actuator for adjusting the reference light angle according to the position of the page and the position and inclination of the regression line. This allows the alignment of data pages to be automatically adjusted.

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 (3)

A method of adjusting the alignment of data pages in a holographic data recording and reproducing apparatus, Reproducing the holographic data page in the holographic data recording and reproducing apparatus; Selecting one row or one column in the data page; Continuous function of the row or column data values for the alignment mark interval of the selected row or column approximating to (x); The approximated function second derivative of (x) to obtain a first edge value or a second edge value; From the next row selected in the data page to the last row or from the next column to the last column, respectively. (x) repeating the steps of obtaining each first edge value or second edge value by obtaining second derivatives; Obtaining a regression line of the first and second edge values of each row or each column; And Automatically aligning the holographic data page by controlling a servo control unit of an actuator that adjusts an angle of a reference light when the position or inclination of each regression line does not have a distance or inclination set to a predetermined position of the data page. And automatically aligning data pages of the holographic data recording and reproducing apparatus. The method of claim 1, wherein The step of second derivative of (x) to find the first edge value or the second edge value, (x) is the maximum The point at which (x) becomes zero is the first edge value (x) is the minimum A method for automatically aligning data pages of a holographic data recording and reproducing apparatus, wherein a point where (x) becomes zero is a second edge value. The image of the holographic data page of claim 1, wherein the image compensation processor controls the image compensation processor to digitally process the data page when the position or the slope of each regression line does not have a distance or slope set to a predetermined position of the data page. And automatically compensating for the automatic alignment of the data pages of the holographic data recording and reproducing apparatus.