Structural displacement measuring device and method capable of measuring at high speed and having robustness to noise

Abstract

Disclosed are a structural displacement measuring device and method capable of measuring at high speed and having robustness to noise. A marker, provided according to one aspect of the present embodiment, is installed on one position of a civil structure and has patterns with continuous and repeated brightness or chroma changes, such that displacement occurring in the civil structure is measured numerically.

Description

Structural displacement measurement device and method with high-speed measurement and noise robustness

[0001] The present invention relates to a displacement measuring device and method that can measure displacement of a structure at high speed and is robust to noise.

[0002] The content described in this section merely provides background information for the present embodiment and does not constitute prior art.

[0003] For various civil engineering structures, such as bridges, tunnels, and railways, safety diagnosis and monitoring are essential to prevent damage or collapse. Displacement measurement is a representative safety diagnosis and monitoring method. This method measures the amount of displacement occurring at the most flexible point within the civil engineering structure. For example, in the case of bridges, safety diagnosis and monitoring is conducted by measuring displacement at the center of the bridge, the point with the greatest flexibility.

[0004] Traditionally, various contact-type sensors have been utilized to measure displacement. Linear Variable Displacement Transducer (LVDT) sensors have been used to measure displacement (mainly sagging displacement) of civil engineering structures. Contact-type sensors, while economical and highly accurate, require a supporting structure beneath for measurement. In other words, when a contact-type sensor makes contact with a civil engineering structure, a supporting structure must be provided on the opposite side of the contact surface (with the civil engineering structure) to support the contact sensor. If the civil engineering structure is a bridge, the installation of contact-type sensors can be quite difficult, as rivers or the sea may exist beneath the bridge. Similarly, when the civil engineering structure is located at a very high elevation, the installation of contact sensors can be quite difficult.

[0005] To address the shortcomings of conventional contact sensors, methods utilizing strain gauges or remote measurement sensors, such as laser sensors, have been employed to measure displacement. However, because the strain values ​​provided by strain gauges require linked analysis with a model of the target civil engineering structure to be converted into displacement, conventional methods utilizing strain gauges have the disadvantage that, even if the measurement is performed correctly, the accuracy of the final measured value can be significantly reduced if the model's accuracy is low or the analysis is incorrect.

[0006] Long-distance measurement sensors, such as the Laser Doppler Vibrometer (LDV), have excellent measurement accuracy and precision, but they can only measure one point at a time and are expensive, making them difficult to use in the field.

[0007] Due to these issues, image sensor-based displacement measurement methods have emerged. These methods capture images of civil engineering structures and then measure displacement through image processing. However, these existing methods require image processing, which generally requires considerable time and makes them highly susceptible to noise that can occur during the shooting process.

[0008] One embodiment of the present invention aims to provide a displacement measuring device and method that can measure displacement of a structure at high speed and is robust to noise.

[0009] According to one aspect of the present invention, a marker capable of measuring a displacement value occurring in a civil engineering structure is provided, wherein the marker is mounted at a location of the civil engineering structure and is characterized by including a pattern in which brightness or saturation changes continuously and repeatedly.

[0010] According to one aspect of the present invention, the pattern is characterized in that it is formed to be repeated in a horizontal direction.

[0011] According to one aspect of the present invention, the pattern is characterized in that it is formed to be repeated in a vertical direction.

[0012] According to one aspect of the present invention, the pattern is characterized in that it is formed to be repeated in each of the horizontal and vertical directions.

[0013] According to one aspect of the present invention, a displacement measuring device that photographs a marker including a pattern and measures displacement occurring in a civil engineering structure from the photographed image, the displacement measuring device comprising: a photographing unit that photographs a marker installed in the civil engineering structure; a frame extraction unit that extracts each frame of the image photographed by the photographing unit; an FFT transformation unit that performs a two-dimensional FFT (Fast Fourier Transform) on each frame extracted by the frame extraction unit; a phase extraction unit that extracts a phase for the pattern of the marker based on a result transformed by the FFT transformation unit; a memory unit that stores information on the marker and information on the image photographed by the photographing unit; and a displacement value calculation unit that calculates a displacement value occurring in the civil engineering structure using information extracted from the phase extraction unit and information stored in the memory unit.

[0014] According to one aspect of the present invention, the photographing unit is characterized in that it photographs an area that is the same as the marker or smaller by a preset ratio.

[0015] According to one aspect of the present invention, the memory unit is characterized in that it stores wave number information (WN) of a pattern formed on the marker as information of the marker.

[0016] According to one aspect of the present invention, the memory unit is characterized in that it stores size information for each direction of the marker as information of the marker.

[0017] According to one aspect of the present invention, the memory unit is characterized in that it stores information on the area of ​​the image being photographed as image information photographed by the photographing unit.

[0018] According to one aspect of the present invention, the memory unit is characterized in that it stores information on the number of pixels of the image being photographed as image information photographed by the photographing unit.

[0019] According to one aspect of the present invention, a displacement measurement system for measuring a displacement value occurring in a civil engineering structure is provided, comprising: a marker mounted at a location of the civil engineering structure and including a pattern in which brightness or saturation changes continuously and repeatedly; and a displacement measurement device for photographing the marker and measuring a displacement occurring in the civil engineering structure from the photographed image; wherein the displacement measurement device comprises: a photographing unit for photographing a marker mounted in the civil engineering structure; a frame extraction unit for extracting each frame of an image photographed by the photographing unit; an FFT transformation unit for performing a two-dimensional FFT (Fast Fourier Transform) on each frame extracted by the frame extraction unit; a phase extraction unit for extracting a phase for a pattern of the marker based on a result transformed by the FFT transformation unit; a memory unit for storing information on the marker and information on an image photographed by the photographing unit; and a displacement value calculation unit for calculating a displacement value occurring in the civil engineering structure using information extracted from the phase extraction unit and information stored in the memory unit.

[0020] According to one aspect of the present invention, the pattern is characterized in that it is formed to be repeated in a horizontal direction.

[0021] According to one aspect of the present invention, the pattern is characterized in that it is formed to be repeated in a vertical direction.

[0022] According to one aspect of the present invention, a displacement measuring device photographs a marker including a pattern, and a method for measuring displacement occurring in a civil engineering structure from the photographed image comprises: a photographing process of photographing the marker;

[0023] A displacement measurement method is provided, characterized by including an extraction process for extracting each frame in an image captured in the above-described shooting process, a performance process for performing a two-dimensional FFT on each frame extracted in the above-described extraction process, a first calculation process for calculating the phase of a pattern of a marker in each frame from the FFT result value performed in the above-described performance process, and a second calculation process for calculating a displacement value generated in a civil engineering structure using the phase of the marker calculated in the above-described calculation process and previously stored information.

[0024] As described above, according to one aspect of the present invention, there is an advantage in that the displacement of a structure can be measured at high speed while being robust to noise.

[0025] FIG. 1 is a diagram illustrating the configuration of a displacement measurement system according to one embodiment of the present invention.

[0026] FIG. 2 is a drawing illustrating an example of a marker according to an embodiment of the present invention.

[0027] FIG. 3 is a drawing illustrating the configuration of a displacement measuring device according to one embodiment of the present invention.

[0028] FIG. 4 is a diagram illustrating a result converted by an FFT conversion unit according to one embodiment of the present invention.

[0029] FIG. 5 is a flowchart illustrating a method for measuring displacement occurring in a civil engineering structure by a displacement measuring device according to one embodiment of the present invention.

[0030] The present invention is susceptible to various modifications and embodiments. Specific embodiments are illustrated and described in detail in the drawings. However, this is not intended to limit the present invention to specific embodiments, but rather to encompass all modifications, equivalents, and alternatives falling within the spirit and technical scope of the present invention. Throughout the description of each drawing, similar reference numerals have been used to designate similar components.

[0031] Terms such as first, second, A, and B may be used to describe various components, but these components should not be limited by these terms. These terms are used solely to distinguish one component from another. For example, without departing from the scope of the present invention, a first component may be referred to as a second component, and similarly, a second component may also be referred to as a first component. The term "and / or" includes a combination of multiple related items described herein or any of multiple related items described herein.

[0032] When a component is referred to as being "connected" or "connected" to another component, it should be understood that it may be directly connected or connected to that other component, but that there may be other components intervening. Conversely, when a component is referred to as being "directly connected" or "connected" to another component, it should be understood that there are no other components intervening.

[0033] The terminology used in this application is solely for the purpose of describing specific embodiments and is not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly dictates otherwise. It should be understood that terms such as "comprise" or "have" in this application do not preclude the presence or possibility of addition of features, numbers, steps, operations, components, parts, or combinations thereof described in the specification.

[0034] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs.

[0035] Terms defined in commonly used dictionaries should be interpreted to have a meaning consistent with their meaning in the context of the relevant technology, and will not be interpreted in an idealized or overly formal sense unless expressly defined in this application.

[0036] In addition, each configuration, process, procedure or method included in each embodiment of the present invention may be shared within a scope that is not technically inconsistent with each other.

[0037] FIG. 1 is a diagram illustrating the configuration of a displacement measurement system according to one embodiment of the present invention.

[0038] Referring to FIG. 1, a displacement measurement system (100) according to one embodiment of the present invention includes a marker (110) and a displacement measurement device (120).

[0039] A displacement measurement system (100) measures displacement occurring in a civil engineering structure (130) that is a measurement target. Various types of civil engineering structures can be measured by the displacement measurement system (100), and in particular, structures that may cause significant safety problems when displacement occurs, such as bridges, can be the target. The displacement measurement system (100) uses a marker (110) that can be easily mounted on a civil engineering structure, and can measure displacement occurring in a civil engineering structure simply by photographing and analyzing the mounted marker. In particular, since the displacement measurement system (100) measures displacement by photographing a marker, it can be relatively robust against unavoidable noise, and at the same time, it can secure real-time performance by significantly shortening the image processing process (which takes a relatively considerable amount of time).

[0040] The marker (110) is mounted at a location of the civil engineering structure. The marker (110) is mounted at a location of the civil engineering structure, particularly, at a location that is most vulnerable to displacement or changes the most due to displacement when displacement occurs in the civil engineering structure.

[0041] The marker (110) has a preset structure, which will be described later with reference to FIG. 2. Since the marker (110) has a preset structure, the displacement measuring device (120) can smoothly measure displacement occurring in a civil engineering structure simply by photographing the marker (110) and performing simple image processing. Since the marker (110) has a preset structure, it is sufficient to simply install it regardless of the method, and there is no need to have a separate support structure to support it, unlike a conventional contact sensor. Accordingly, the marker (110) can be installed without being affected by the shape or installation location of the civil engineering structure, unlike a conventional contact sensor.

[0042] The displacement measuring device (120) photographs the marker (110) at a position a preset distance away from the marker (110) and measures the displacement occurring in the civil engineering structure from the photographed image.

[0043] The displacement measuring device (120) photographs the marker (110) at a position a preset distance away from the marker (110). The displacement measuring device (120) includes a photographing unit that photographs the marker (110) and photographs the marker (110). The displacement measuring device (120) photographs the marker (110) at a preset distance away from the marker (110), for example, several tens of meters.

[0044] A displacement measuring device (120) measures displacement occurring in a civil engineering structure from a captured image. The displacement measuring device (120) analyzes the captured image to extract the phase of the marker, and measures the displacement occurring in the civil engineering structure through a simple calculation process from the extracted phase. The displacement measuring device (120) can measure the displacement occurring in the civil engineering structure simply by extracting the phase of the marker and performing a calculation process from the extracted phase, thereby ensuring (almost) real-time performance in displacement measurement. In addition, depending on the structural characteristics of the marker (110), measurement can be performed almost simultaneously without repetitive processes for displacement occurring in both directions as well as displacement occurring in one direction. A specific description of the displacement measuring device (120) will be described below with reference to FIG. 3.

[0045] FIG. 2 is a drawing illustrating an example of a marker according to an embodiment of the present invention.

[0046] As illustrated in FIG. 2, the marker (110) has a pattern in which brightness and / or saturation continuously and repeatedly changes. As illustrated in FIG. 2a or FIG. 2b, brightness and / or saturation may continuously and repeatedly change only in one direction (vertically or horizontally), or, as illustrated in FIG. 2c, brightness and / or saturation may continuously and repeatedly change in both vertical and horizontal directions. As illustrated in FIG. 2, in order for brightness and / or saturation within the marker (110) to continuously and repeatedly change, it is preferable to have a sinusoidal pattern, but is not necessarily limited thereto, and may have various continuous and repetitive patterns such as a triangular waveform, a square waveform, and a sawtooth waveform.

[0047] The marker (110) can be implemented with a preset size or area. In addition, since the marker (110) has a form in which brightness and / or saturation continuously and repeatedly changes, it has wave number (WN) information for the brightness and / or saturation that changes repeatedly.

[0048] FIG. 3 is a drawing illustrating the configuration of a displacement measuring device according to one embodiment of the present invention.

[0049] Referring to FIG. 3, a displacement measuring device (120) according to one embodiment of the present invention includes a photographing unit (310), a frame extraction unit (320), an FFT conversion unit (330), a phase extraction unit (340), a displacement value calculation unit (350), and a memory unit (360).

[0050] The camera unit (310) photographs a marker (110) installed in a civil engineering structure. The camera unit (310) photographs the marker (110) and an area that is identical or similar to the marker (110) (smaller by a preset ratio). However, when photographing an area similar to the marker (110), the camera unit (310) photographs the pattern of the marker (110) so that it is as visible as possible. Accordingly, the process of tracking and editing the marker (110) in a separately photographed image is minimized.

[0051] The frame extraction unit (320) extracts each frame of the video captured by the camera unit (310). For example, the camera unit (310) can capture video at 30 frames per second or 60 frames per second. The frame extraction unit (320) extracts images corresponding to each frame within the video captured by the camera unit (310).

[0052] The FFT conversion unit (330) performs a two-dimensional FFT (Fast Fourier Transform) on each frame extracted by the frame extraction unit (320). The FFT conversion unit (330) performs a two-dimensional FFT on each frame, and the results are illustrated in FIG. 4.

[0053] FIG. 4 is a diagram illustrating a result converted by an FFT conversion unit according to one embodiment of the present invention.

[0054] As shown in FIGS. 4a and 4b, if the pattern within the marker (110) is formed vertically and is repeated horizontally, the result of performing the 2D FFT shows wave components symmetrically on the horizontal axis passing through the center point with the center point as the reference. Here, the wave components are components determined according to the wave number of the pattern within the marker (110), and as the wave number increases, they move away from the center.

[0055] Conversely, as shown in FIGS. 4c and 4d, if the pattern within the marker (110) is formed horizontally and is repeated in the vertical direction, the result of performing the two-dimensional FFT shows the wave components symmetrically on the vertical axis passing through the center point with the center point as the reference.

[0056] Additionally, as shown in FIGS. 4e and 4f, if the pattern within the marker (110) is formed in both the horizontal and vertical directions and is formed to be repeated in the vertical and horizontal directions, the result of performing the two-dimensional FFT shows wave components that are symmetrical on both the horizontal and vertical axes passing through the center point with the center point as the reference.

[0057] Referring back to FIG. 3, the FFT conversion unit (330) performs a two-dimensional FFT on each of the frames extracted in this manner. The FFT conversion unit (330) can obtain the results even if it is performed only once, regardless of the direction in which the marker pattern is formed on the frames. That is, even if the pattern within the marker (110) is formed to be repeated in both the horizontal and vertical directions, the desired results can be obtained even if it is performed only once without having to perform the two-dimensional FFT according to the horizontal direction and the two-dimensional FFT according to the vertical direction separately.

[0058] The phase extraction unit (340) extracts the phase for the pattern of the marker (110) based on the result converted by the FFT conversion unit (330). When each frame is two-dimensionally FFT converted by the FFT conversion unit (330), the converted result has a complex number form. Accordingly, the phase extraction unit (340) extracts the phase for the pattern of the marker (110) based on the result having a complex number form. When a displacement occurs in a civil engineering structure, the marker (110) moves according to the displacement and the phase value changes. In order to utilize this characteristic, the phase extraction unit (340) extracts the phase from the result converted by the FFT conversion unit (330).

[0059] The displacement value calculation unit (350) derives motion information and marker length conversion constants within the frame from information extracted from the phase extraction unit (340) and information stored in the memory unit (360), and calculates displacement values ​​generated in civil engineering structures using them.

[0060] The displacement value calculation unit (350) derives the motion information within the frame and the marker length conversion constant using the following formula.

[0061]

[0062] Here, the number of pixels of the captured frame corresponds to the number of pixels in the direction in which the pattern of the marker (110) is repeated. That is, when the pattern of the marker (110) is repeated in the horizontal direction as shown in FIG. 4A, the number of pixels of the captured frame refers to the number of pixels in the horizontal direction, and in the case of FIG. 4C, the number of pixels of the captured frame refers to the number of pixels in the horizontal direction. As shown in FIG. 4E, when the pattern of the marker (110) is repeated in both directions, the calculation is performed for each of the number of pixels in the horizontal direction and the number of pixels in the vertical direction. The displacement value calculation unit (350) calculates the motion information within the frame and converts the phase change that occurs in proportion to the motion of the marker into a pixel unit.

[0063] Meanwhile, the displacement value calculation unit (350) derives the length conversion constant of the marker as follows.

[0064]

[0065] The number of pixels of a marker captured within a frame refers to the total number of pixels in the portion corresponding to the marker within the captured image (frame). Both the actual size of the marker and the number of pixels of the marker captured within the frame correspond to information measured with respect to the direction of the frame corresponding to the number of pixels in the captured frame.

[0066] The displacement value calculation unit (350) uses information stored in the memory unit (360) such as frequency information, pixel count information of the captured frame, marker actual size information, and pixel count information of the captured marker within the frame. The displacement value calculation unit (350) uses the value extracted from the phase extraction unit (340) as the phase value for the marker pattern.

[0067] The displacement value calculation unit (350) can calculate the displacement value that occurred in the civil engineering structure by multiplying the derived intra-frame movement information and the marker length conversion constant. As shown in FIG. 4a or FIG. 4c, if the displacement value that occurred in one direction for the civil engineering structure is to be measured, the above-described calculation only needs to be performed once. On the other hand, as shown in FIG. 4e, if the displacement value that occurred in both directions for the civil engineering structure is to be measured, the above-described calculation (derived intra-frame movement information and marker length conversion constant derivation) can be performed twice to measure the displacement that occurred in each direction.

[0068] As described above, the displacement measuring device (120) can measure displacement by performing a two-dimensional FFT on the extracted frame and calculating the phase from the FFT result value, thereby using the calculated phase and the information stored in the memory unit (360) to calculate the displacement value. That is, the displacement measuring device (120) can measure displacement with only the FFT process and a simple (multiplication) operation, and thus can measure displacement occurring in a civil engineering structure quite quickly. In particular, since it does not include an image processing process, an image analysis process, or an image editing process as in the prior art, the displacement measuring device (120) can measure displacement at a significantly faster speed than in the prior art.

[0069] In addition, depending on the structural characteristics of the marker (110), the displacement measuring device (120) can be considerably robust to noise. Since the displacement measuring device (120) measures displacement by photographing the marker (110), noise generated by foreign substances being placed (between the displacement measuring device (120) and the marker (110)) in the image photographed by the displacement measuring device (120) or noise generated in the form of haze due to various causes may occur. In the conventional image sensor-based displacement measuring method, even if such noise occurs only in a part of the photographed area, it has a fatal impact on the reliability of the result, and therefore, a process for removing such noise had to be additionally included. However, the marker (110) has the characteristic of having a continuous and repetitive pattern as described above. Accordingly, even if noise occurs in a part of the photographed image, the noise portion that occurs according to the repetitive characteristics can be quickly and easily supplemented. In particular, since the structural characteristics of the marker (110) are stored within the memory unit (360) described below, noise occurring in a portion can be removed or supplemented without difficulty and quickly. The supplementation can be processed visually, but can also be quickly performed during the calculation process since the structural characteristics of the marker (110) are already recognized.

[0070] The memory unit (360) stores information about the marker (110) and information about the image captured by the photographing unit (310). The memory unit (360) stores information about the frequency of the pattern formed on the marker (110) and information about the actual size of the marker (110) in each direction. The memory unit (360) stores information about the area of ​​the image captured by the photographing unit (310) and information about the number of pixels in the image captured by the photographing unit (310). The memory unit (360) stores the corresponding information so that the displacement value calculation unit (350) can calculate the displacement value generated in the civil engineering structure.

[0071] FIG. 5 is a flowchart illustrating a method for measuring displacement occurring in a civil engineering structure by a displacement measuring device according to one embodiment of the present invention.

[0072] The filming unit (310) films the marker (110) (S510).

[0073] The frame extraction unit (320) extracts each frame in the captured image (S520).

[0074] The FFT conversion unit (330) performs a two-dimensional FFT on each extracted frame (S530).

[0075] The phase extraction unit (340) calculates the phase for the pattern of markers in each frame from the FFT result value (S540).

[0076] The displacement value calculation unit (350) calculates the displacement value generated in the civil engineering structure using the phase of the calculated marker and the information stored in the memory unit (360) (S550).

[0077] Although FIG. 5 describes each process as being executed sequentially, this is merely an illustrative description of the technical idea of ​​one embodiment of the present invention. In other words, a person of ordinary skill in the art to which one embodiment of the present invention pertains can modify and apply various modifications and variations, such as changing the order described in each drawing and executing the process, or executing one or more of the processes in parallel, without departing from the essential characteristics of one embodiment of the present invention. Therefore, FIG. 5 is not limited to a chronological order.

[0078] Meanwhile, the processes illustrated in FIG. 5 can be implemented as computer-readable code on a computer-readable recording medium. A computer-readable recording medium includes all types of recording devices that store data that can be read by a computer system. That is, a computer-readable recording medium includes storage media such as magnetic storage media (e.g., ROM, floppy disks, hard disks, etc.) and optical reading media (e.g., CD-ROMs, DVDs, etc.). In addition, a computer-readable recording medium can be distributed across network-connected computer systems, so that the computer-readable code can be stored and executed in a distributed manner.

[0079] The above description is merely an example of the technical idea of ​​the present embodiment, and those skilled in the art will appreciate that various modifications and variations can be made without departing from the essential characteristics of the present embodiment. Therefore, the present embodiments are not intended to limit the technical idea of ​​the present embodiment, but rather to explain it, and the scope of the technical idea of ​​the present embodiment is not limited by these embodiments. The scope of protection of the present embodiment should be interpreted by the claims below, and all technical ideas within a scope equivalent thereto should be interpreted as being included in the scope of rights of the present embodiment.

[0080]

[0081] This patent is the result of research conducted with the support of the Korea Institute of Industrial Technology Planning and Evaluation with funding from the government of the Republic of Korea (Ministry of Trade, Industry and Energy) (Project ID: 2410005255, Subproject ID: 20021979, Project Name: Development of an abnormal operation detection system based on optical sensing for gas-insulated switches) and

[0082] This is the result of research conducted with the support of the Korea Institute of Industrial Technology Planning and Evaluation (Project ID: 2410004075, Subproject ID: 20022843, Project Name: Development of automated inspection equipment capable of high-speed and high-precision analysis of large-diameter SiC bare and Epi wafers and defect detection and classification technology) funded by the Ministry of Trade, Industry and Energy of the Republic of Korea.

[0083]

[0084] CROSS-REFERENCE TO RELATED APPLICATION

[0085] This patent application claims priority under 35 USC § 119(a) of U.S. Patent Application No. 10-2024-0004738, filed in Korea on January 11, 2024, the entire contents of which are incorporated by reference herein. Furthermore, this patent application claims priority in countries other than the United States for the same reasons, the entire contents of which are incorporated by reference herein.

Claims

1. In a marker that can measure displacement values occurring in civil engineering structures, A marker mounted at a location of the above civil engineering structure and characterized by including a pattern in which brightness or saturation changes continuously and repeatedly.

2. In paragraph 1, The above pattern is, A marker characterized by being formed to be repeated in a horizontal direction.

3. In paragraph 1, The above pattern is, A marker characterized by being formed to repeat in a vertical direction.

4. In paragraph 1, The above pattern is, A marker characterized by being formed to be repeated in each of the horizontal and vertical directions.

5. A displacement measuring device that photographs a marker including a pattern and measures displacement occurring in a civil engineering structure from the photographed image. A photographing unit for photographing a marker installed in the above civil engineering structure; A frame extraction unit that extracts each frame of the video shot by the above shooting unit; An FFT transform unit that performs a two-dimensional FFT (Fast Fourier Transform) on each frame extracted by the above frame extractor; A phase extraction unit that extracts the phase of the pattern of the marker based on the result converted by the FFT conversion unit; A memory unit storing information on the marker and information on images captured by the camera unit; and A displacement value calculation unit that calculates the displacement value that occurred in a civil engineering structure using the information extracted from the phase extraction unit and the information stored in the memory unit. A displacement measuring device characterized by including a .

6. In paragraph 5, The above filming department, A displacement measuring device characterized by photographing an area equal to or smaller than the above marker by a preset ratio.

7. In paragraph 5, The above memory section, A displacement measuring device characterized in that it stores wave number information (WN) of a pattern formed on the marker as information of the marker.

8. In paragraph 5, The above memory section, A displacement measuring device characterized by storing size information for each direction of the marker as information of the marker.

9. In paragraph 5, The above memory section, A displacement measuring device characterized in that it stores information about the area of the image being photographed as image information photographed by the above photographing unit.

10. In paragraph 5, The above memory section, A displacement measuring device characterized in that it stores information on the number of pixels of an image captured by the above-mentioned shooting unit.

11. In a displacement measurement system that measures displacement values occurring in civil engineering structures, A marker mounted at a location of the above civil engineering structure and including a pattern in which brightness or saturation changes continuously and repeatedly; and It includes a displacement measuring device that photographs the marker and measures the displacement that occurs in the civil engineering structure from the photographed image. The above displacement measuring device, A photographing unit for photographing a marker installed in the above civil engineering structure; A frame extraction unit that extracts each frame of the video shot by the above shooting unit; An FFT transform unit that performs a two-dimensional FFT (Fast Fourier Transform) on each frame extracted by the above frame extractor; A phase extraction unit that extracts the phase of the pattern of the marker based on the result converted by the FFT conversion unit; A memory unit storing information on the marker and information on images captured by the camera unit; and A displacement measurement system characterized by including a displacement value calculation unit that calculates a displacement value occurring in a civil engineering structure using information extracted from the phase extraction unit and information stored in the memory unit.

12. In paragraph 11, The above pattern is, A displacement measuring system characterized by being formed to be repeated in a horizontal direction.

13. In paragraph 11, The above pattern is, A displacement measuring system characterized by being formed to be repeated in a vertical direction.

Images