Micro-displacement measurement system

Abstract

To provide a microdisplacement measurement system capable of securely obtaining a fixed point when measuring microdisplacement of a structure by image measurement so as to correct an influence such as a shake of a camera and perform the highly-accurate measurement.SOLUTION: A microdisplacement measurement system 1 for measuring microdisplacement of a structure by image measurement includes: a video camera 2 for imaging a surface of the structure in oder to perform the image measurement; a laser irradiation device 3 which is provided at a position adjacent to the video camera so as to display a laser fixed point on the surface of the structure; a self-oscillation measurement device 4 attached to the laser irradiation device; and a calculation processing part for calculating displacement of a measurement object from a moving image captured by the video camera.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a micro-displacement measurement system and a micro-displacement measurement method for measuring micro-displacement of a structure by image measurement.

Background Art

[0002] As disclosed in Patent Document 1, a technique is known that uses a laser Doppler vibrometer to measure extremely minute vibrations of structures such as bridges with high accuracy in a non-contact manner in outdoor environments. When performing inspection by this non-contact vibration measurement, data from vibration and inclination angle measurement sensors mounted inside the housing of the laser Doppler vibrometer is used to correct measurement errors caused by shaking and tilting of the laser Doppler vibrometer itself due to external disturbances such as wind and ground vibration.

[0003] On the other hand, as disclosed in Non-Patent Document 1, as a new technology alternative to laser measurement, vibration measurement technology based on image measurement using a video camera has come to be used. In the vibration measurement using the laser Doppler vibrometer described above, only the vibration at one laser irradiation point is measured, whereas vibration measurement by image measurement has advantages such as being able to simultaneously measure vibrations at multiple points in a captured image.

[0004] Here, in addition to the structure to be measured, if an object that can be regarded as a fixed point or a reference point can be simultaneously captured within the imaging field of view, the influence of camera shake can be corrected by calculating the relative displacement between the fixed point or the like and the measurement object. For example, when measuring the deflection of a bridge girder, the center of the girder span is taken as the measurement object, an object with obviously smaller displacement compared to the girder such as an abutment is assumed as a fixed point (reference point), and by obtaining the relative displacement between the center of the span and the fixed point on the abutment, the influence of camera shake can be eliminated even if the camera shakes.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

[0006] [Non-Patent Document 1] Two external researchers, Development of structural inspection technology using video cameras and drones, Railway Technical Research Institute Report, Vol. 35, No. 9, pp. 41-46, 2021.9 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] However, when taking close-up photos of a part of a structure to measure minute vibrations, it may not be possible to keep the stationary object within the field of view, making it impossible to compensate for the effects of camera shake and tilt caused by external disturbances.

[0008] The accuracy (resolution) of image measurement using a video camera depends on the resolution of the pixels in the image. Therefore, when it is necessary to measure extremely minute vibrations of a structure, it is necessary to take close-up shots of the object to be measured and cover a narrow area with a large number of pixels. In such cases, it becomes more difficult to include a separate stationary point within the field of view of the image.

[0009] Therefore, the present invention aims to provide a micro-displacement measurement system and a micro-displacement measurement method that can reliably secure a fixed point when measuring minute displacements of structures by image measurement, and can perform highly accurate measurements by correcting for the effects of camera shake and other factors. [Means for solving the problem]

[0010] To achieve the above objective, the present invention provides a micro-displacement measurement system for measuring the micro-displacement of a structure by image measurement, comprising: a video camera for capturing images of the surface of the structure for the purpose of image measurement; a laser irradiation device installed adjacent to the video camera for displaying a laser fixed point on the surface of the structure; a self-vibration measurement device attached to the laser irradiation device; and a calculation processing unit for calculating the displacement of the object to be measured from a video captured by the video camera, wherein the laser fixed point is also captured in the image of the object to be measured, and the calculation processing unit calculates the actual displacement of the object to be measured by determining the relative displacement amount between the object to be measured and the laser fixed point in the video, and by incorporating the amount of movement of the laser fixed point obtained from the measurement results of the self-vibration measurement device.

[0011] Alternatively, a minute displacement measurement system for measuring minute displacements of a structure by image measurement, comprising: a video camera for photographing the surface of the structure in order to perform the image measurement; a laser irradiation device installed adjacent to the video camera for displaying a fixed laser point on the surface of the structure; a camera laser irradiation device attached to the video camera so as to irradiate a laser that is the same as or parallel to the optical axis of the video camera; and a calculation processing unit for calculating the displacement of the object to be measured from the video footage captured by the video camera, wherein the image of the object to be measured captures both the fixed laser point and the camera laser point from the camera laser irradiation device, and the calculation processing unit determines the amount of camera movement based on the change in the relative distance between the camera laser point and the fixed laser point, and calculates the actual displacement of the object to be measured based on the amount of displacement of the object in the video footage and the amount of camera movement.

[0012] Furthermore, the invention of the minute displacement measurement method is a minute displacement measurement method for measuring minute displacements of a structure by image measurement, characterized by comprising the steps of: installing a laser irradiation device at a position adjacent to a video camera that photographs the surface of the structure in order to perform the image measurement, such that a laser fixed point is displayed in the image of the object to be measured; photographing the object to be measured and the laser fixed point with the video camera; and calculating the displacement of the object to be measured based on the positions of the object to be measured and the laser fixed point in the captured video. [Effects of the Invention]

[0013] The present invention, configured in this way, involves installing a laser irradiation device adjacent to a video camera to display a laser fixed point on the surface of a structure, thereby capturing the laser fixed point in the image of the object to be measured.

[0014] Therefore, when measuring minute displacements of a structure by zooming in on the object to be measured using image measurement, it is possible to reliably secure a fixed point and perform highly accurate measurements by correcting for the effects of camera shake and other factors. [Brief explanation of the drawing]

[0015] [Figure 1] This is a schematic diagram illustrating the configuration of the minute displacement measurement system of this embodiment. [Figure 2] This is an explanatory diagram illustrating the structures that will be measured. [Figure 3] This is an explanatory diagram illustrating a laser fixed point captured in an image. [Figure 4] This is an explanatory diagram illustrating the method for calculating the relative displacement between the laser fixed point and the object being measured. [Figure 5] This diagram illustrates the movement of the laser fixed point when the mounting surface of a micro-displacement measurement system is displaced, with (a) being an explanatory diagram for parallel displacement of the mounting surface and (b) being an explanatory diagram for rotational displacement of the mounting surface. [Figure 6]It is an explanatory diagram illustrating an example of a method for calculating the actual displacement of a measurement object. [Figure 7] It is a flowchart explaining the procedure of the micro-displacement measurement method according to the present embodiment. [Figure 8] It is an explanatory diagram schematically showing the configuration of the micro-displacement measurement system of Example 1. [Figure 9] It is a diagram for explaining the positional relationship of irradiation points of two laser irradiation devices when the installation surface of the micro-displacement measurement system of Example 1 is displaced, wherein (a) is an explanatory diagram when the installation surface undergoes parallel displacement, and (b) is an explanatory diagram when the installation surface undergoes rotational displacement. [Figure 10] It is an explanatory diagram illustrating an example of a method for calculating the actual displacement of a measurement object of Example 1. [Figure 11] It is a flowchart explaining the procedure of the micro-displacement measurement method of Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Fig. 1 is an explanatory diagram schematically showing the configuration of a micro-displacement measurement system 1 according to the present embodiment. Fig. 2 is an explanatory diagram illustrating a bridge B as an example of a structure to be measured.

[0017] As shown in Fig. 1, the micro-displacement measurement system 1 according to the present embodiment includes a video camera 2 for performing image measurement, a laser irradiation device 3 installed at a position adjacent to the video camera 2, a self-vibration measurement device 4 attached to the laser irradiation device 3, and an arithmetic processing unit (not shown) that calculates the displacement of the measurement object from a moving image captured by the video camera 2.

[0018] The video camera 2 is an imaging device that images the surface of a structure such as a bridge B for image measurement. For example, a video camera with high resolution and a high frame rate (4K: 266 fps, FHD: 935 fps, HD: 1384 fps, etc.) can be used.

[0019] To perform image measurement with video camera 2, the dynamic behavior of the object to be measured is calculated from the captured video using the digital image correlation method, as described in Non-Patent Document 1, for example. In the digital image correlation method, the surface pattern is treated as a pattern of brightness information based on the digital image information of the object to be measured, and the magnitude and direction of displacement of any point in the image are determined by searching for the position between two images before and after movement or deformation.

[0020] To explain in more detail, a small N×N pixel region around an arbitrary displacement calculation point is extracted from images before and after movement or deformation. The magnitude and direction of the displacement are then calculated by detecting the position corresponding to that small region on an integer coordinate system corresponding to the number of pixels in the image after the movement or deformation has occurred, based on the degree of correlation.

[0021] Thus, vibration measurement using video camera 2 detects vibration from the displacement of the measurement point in the captured image due to vibration. The amplitude can be determined by using the dimensions of an object with known dimensions in the captured image as a leveling rod, by measuring the dimensions of an object on a leveling rod, or by the geometric relationship between the distance from video camera 2 to the measurement point and the shooting system.

[0022] In the case of image measurement using video camera 2, if there is a fixed point (immovable point) in the image of the subject that is actually stationary, the movement of the immovable point obtained from image analysis can be judged as an apparent movement due to vibration of video camera 2, etc., and the displacement of the object being measured can be corrected. That is, by calculating the relative movement of the point being measured with respect to the immovable point and subtracting the component corresponding to the movement of the immovable point from that movement, the influence of vibration of video camera 2, etc. can be eliminated.

[0023] For example, when measuring the deflection of the girder of bridge B shown in Figure 2, it is difficult to capture a fixed point such as a bridge abutment within the field of view when taking a close-up photograph of the measurement range B1, which is the center of the girder span.

[0024] Therefore, the minute displacement measurement system 1 of this embodiment uses a laser irradiation device 3 that displays a laser fixed point on the surface of the structure. The laser irradiation device 3 is a device that sets a virtual fixed point (laser fixed point) near the measurement target by laser projection from a remote position on the structure.

[0025] By determining the relative displacement between the fixed laser point irradiated by the laser irradiation device 3 and the object being measured, it becomes possible to correct for measurement errors caused by external disturbances such as wind in the video camera 2.

[0026] Figure 3 is an explanatory diagram illustrating a fixed laser point captured in image P of the video from video camera 2. The shape of the projected laser is preferably a distinctive shape such as a circle or rectangle, so that when there are irregularities or inclinations on the plane being measured, the shape of the projected laser will be distorted, and the degree of that distortion can be determined.

[0027] Furthermore, the projection laser shape is large enough to span multiple pixels when captured by video camera 2. That is, it is larger than one pixel of the video image and larger than two pixels.

[0028] Furthermore, the projected laser shape is designed to allow for the definition of a reference line for the direction of motion (displacement direction) of the points being analyzed during image data analysis. For example, if the projected laser shape is rectangular, the four orthogonal sides can be defined as reference lines. Similarly, if the projected laser shape is circular, the tangent lines of the circle can be defined as reference lines.

[0029] The laser irradiation device 3 is lighter than the video camera 2 and can be rigidly fixed to a tripod 31 or the like. For example, if the laser irradiation device 3 is rod-shaped with a small surface area exposed to wind, it can be fixed to the tripod 31 so as not to sway due to wind.

[0030] In short, when a laser irradiation device 3 is installed near a video camera 2 mounted on a tripod 21, it is preferable that the laser irradiation device 3 only tolerates extremely small vibrations even if the video camera 2 is shaken by external disturbances such as wind.

[0031] Furthermore, the laser irradiation device 3 is equipped with a self-vibration measuring device 4 that can measure its own horizontal and rotational displacement and vibration. The self-vibration measuring device 4 can utilize vibration sensors, gyro sensors, etc.

[0032] As shown in Figure 1, if the laser irradiation device 3 is installed adjacent to the video camera 2 on the same mounting surface G, then when the video camera 2 experiences horizontal or rotational vibrations due to ground vibrations, the laser irradiation device 3 will also experience similar horizontal and rotational vibrations. The displacement caused by these ground vibrations can then be measured by the self-vibration measuring device 4 attached to the laser irradiation device 3.

[0033] The processing unit calculates the displacement of the object to be measured from the video captured by the video camera 2 based on the digital image correlation method. Figure 4 is an explanatory diagram illustrating the method for calculating the relative displacement between the laser fixed point 30 and the vibration measurement point T that is the object to be measured.

[0034] When a vibration measurement point T on the surface of the structure being measured vibrates in-plane, the laser stationary point 30 does not move in conjunction with the vibration of the vibration measurement point T. By determining the relative displacement between the vibration measurement point T and the laser stationary point 30 through image correlation analysis, the vibration of the vibration measurement point T to be calculated is determined. In short, by determining the change in the relative distance D between the vibration measurement point T and the laser stationary point 30, which changes in conjunction with the vibration of the vibration measurement point T, the displacement (vibration) of the vibration measurement point T in the video can be calculated.

[0035] On the other hand, if the ground on which the micro-displacement measurement system 1 is installed (installation surface G) vibrates or rotates, the position of the laser fixed point 30 displayed on the surface of the structure (measurement target surface B2) will also change. Figure 5 is a diagram illustrating the amount of movement of the laser fixed point 30 when the installation surface G of the micro-displacement measurement system 1 is displaced.

[0036] As shown in Figure 5(a), when the installation surface G moves in a parallel direction vertically or horizontally, the amount of parallel displacement h of the ground (laser irradiation device 3) recorded by the self-vibration measuring device 4 becomes the amount of movement h of the laser fixed point 30 on the measurement target surface B2.

[0037] Furthermore, as shown in Figure 5(b), when the installation surface G undergoes rotational displacement, L·tanθ represents the amount of movement of the fixed laser point 30 on the measurement target surface B2, where θ is the rotation angle indicating the amount of rotational displacement of the ground (laser irradiation device 3) and L is the distance between the measurement target surface B2 and the laser irradiation device 3.

[0038] When the installation surface G of the micro-displacement measurement system 1 is displaced in this manner, it is necessary to determine the actual displacement of the object being measured by adding the amount of movement of the laser fixed point 30 to the relative displacement amount in the video between the laser fixed point 30 and the vibration measurement point T.

[0039] Figure 6 is an explanatory diagram illustrating a method for calculating the actual displacement of the object being measured. In this example, for simplicity of explanation, only the X-direction component of the displacement is shown. The laser fixed point 30A shown in this figure indicates the irradiation position when there is no displacement in the installation surface G. If the installation surface G is displaced in the X direction by a displacement of X2, the laser fixed point 30 will be captured in image P. Here, the displacement X2 is the same as the distance between the reference line 301A of the laser fixed point 30A and the reference line 301 of the laser fixed point 30.

[0040] On the other hand, the displacement of vibration measurement point T in the video can be determined by calculating the relative displacement, which is the change in the relative distance X1 between the laser stationary point 30 and the reference line 301. However, the actual displacement of vibration measurement point T is the change in the relative distance X3 (relative displacement) between the laser stationary point 30A and the reference line 301A, without any movement X2 of the installation surface G.

[0041] Therefore, the calculation processing unit calculates the actual displacement of the vibration measurement point T (relative displacement of X3) by obtaining the relative displacement amount of the vibration measurement point T and the laser fixed point 30 in the video, and by incorporating the amount of movement X2 of the laser fixed point 30 obtained from the measurement results of the self-vibration measurement device 4.

[0042] Next, the procedure for measuring minute displacements in this embodiment will be explained with reference to the flowchart in Figure 7.

[0043] First, in step S1, the micro-displacement measurement system 1 is installed at a location away from the bridge B, for example, as shown in Figure 1. For example, when measuring the micro-vibrations of the bridge B's girder when a train passes over it, a tripod 21 is set up and a video camera 2 is attached to a stable ground surface G that is far enough away from the train's influence and where the girder is clearly visible and observation is easy.

[0044] Furthermore, a tripod 31 is installed adjacent to the video camera 2 on the same mounting surface G, and the laser irradiation device 3 is attached to it. The video camera 2 is oriented in a direction that allows the measurement range B1 shown in Figure 2 to be captured, and the laser irradiation device 3 is oriented in a direction that the fixed laser point 30 is irradiated onto the same measurement range B1.

[0045] In step S2, after the measurement preparations are complete, video recording is started so that the object to be measured and the laser fixed point 30 are in the same image P. The measurement using video recording by video camera 2 is performed for any desired amount of time, and the captured image data is recorded in a data logger connected to video camera 2.

[0046] Meanwhile, the amount of movement of the laser irradiation device 3 during video recording by the video camera 2 is measured by the self-oscillation measuring device 4 and recorded in a data logger connected to the self-oscillation measuring device 4. Therefore, in step S3, the amount of movement of the laser fixed point 30 at each time is calculated from the measurement results by the self-oscillation measuring device 4.

[0047] Step S3 is performed regardless of the order. In Step S4, the relative displacement between the vibration measurement point T and the laser fixed point 30 in the video is calculated by performing a correlation analysis on the video image data.

[0048] Then, in step S5, the actual displacement of the vibration measurement point T to be measured is calculated based on the amount of movement of the laser fixed point 30 calculated in steps S3 and S4 and the relative displacement of the vibration measurement point T on the video (relative displacement of X1).

[0049] Next, the operation of the minute displacement measurement system 1 and minute displacement measurement method of this embodiment will be described. The micro-displacement measurement system 1 of this embodiment, configured in this way, includes a video camera 2 for image measurement, a laser irradiation device 3 installed adjacent to the video camera to display a laser fixed point 30 on the surface of the structure, and a self-vibration measurement device 4 attached to the laser irradiation device 3.

[0050] When video camera 2 captures a video of the object to be measured, the laser stationary point 30 is also captured within the same image P. Furthermore, the amount of movement of the laser stationary point 30 due to the displacement of the mounting surface G is measured by the self-vibration measuring device 4.

[0051] Therefore, when measuring minute displacements of a structure by image measurement with a close-up view of the object being measured, it is possible to reliably secure a fixed point for determining the relative displacement with respect to the object being measured, and to perform high-precision measurements that eliminate the effects of vibrations caused by external disturbances such as wind on the video camera 2.

[0052] For example, it becomes possible to measure minute vibrations, such as constant tremors (very small vibrations during normal operation), from a remote location using video camera 2 for structures such as bridge B. Furthermore, because the camera can zoom in on the object being measured, it becomes possible to measure minute vibrations of structures without using expensive high-resolution cameras. As a result, structural inspections using vibration measurement can be made more cost-effective and sophisticated. [Examples]

[0053] Hereinafter, an embodiment different from the micro-displacement measurement system 1 and micro-displacement measurement method of the above-described embodiment will be described with reference to Figures 8-11. In addition, the same terms or reference numerals will be used to describe parts that are the same as or equivalent to those described in the above embodiment.

[0054] In the above embodiment, a micro-displacement measurement system 1 in which a self-vibration measuring device 4 is attached to a single laser irradiation device 3 was described. However, in this embodiment 1, a micro-displacement measurement system 1A using two laser irradiation devices (3,22) will be described.

[0055] As shown in Figure 8, the minute displacement measurement system 1A of this embodiment 1 comprises a video camera 2 for image measurement, a laser irradiation device 3 installed adjacent to the video camera 2, a camera laser 22 attached to the video camera 2, and a calculation processing unit (not shown) that calculates the displacement of the object to be measured from the video captured by the video camera 2.

[0056] The camera laser 22 is a laser irradiation device attached to the video camera 2 so as to emit a laser that is the same as or parallel to the optical axis of the video camera 2. The configuration of the camera laser 22 is the same as that of the laser irradiation device 3 described in the above embodiment.

[0057] For example, the camera laser 22 is positioned so that its optical axis is parallel to the video camera 2, and the camera laser point 220 is displayed by laser projection at a position adjacent to the display of the fixed laser point 30 which is within the shooting angle of view.

[0058] Then, the relative displacement between the fixed laser point 30 and the camera laser point 220 is used to detect errors (apparent displacement) caused by shaking or tilting of the video camera 2 due to wind, etc., and the effects of shaking or tilting of the video camera 2 are corrected by subtracting these errors from the measurement results of the object being measured by image analysis.

[0059] In this embodiment 1, the laser irradiation device 3 that irradiates the fixed laser point 30 is lighter and more rigidly fixed than the video camera 2, and is designed not to be shaken by wind or other factors during measurement.

[0060] Figure 9 illustrates the positional relationship between the irradiation points (30, 220) of the two laser irradiation devices (3, 22) when the installation surface G of the micro-displacement measurement system 1A of Example 1 is displaced. Figure 9(a) is an explanatory diagram when the installation surface G is displaced parallel to itself, and Figure 9(b) is an explanatory diagram when the installation surface G is displaced rotationally.

[0061] When a laser irradiation device 3 that irradiates a fixed laser point 30 and a video camera 2 are installed in close proximity, and both are shaken by the same ground vibration (horizontal and rotation) on the same installation surface G, the effect is equal to that on the fixed laser point 30 and the camera laser point 220. For this reason, in the minute displacement measurement system 1A of Example 1, there is no need to install a self-vibration measurement device 4 for measuring the displacement of the installation surface G.

[0062] Figure 10 is an explanatory diagram illustrating the method for calculating the actual displacement of the object being measured in Example 1. In this example, as in the previous embodiment, only the X-direction component of the displacement is shown to simplify the explanation.

[0063] The relative displacement between the fixed laser point 30 and the camera laser point 220 is due to the shaking and tilting of the video camera 2 caused by external disturbances such as wind. Therefore, the relative displacement between the fixed laser point 30 and the camera laser point 220 is considered as the apparent displacement due to the shaking of the video camera 2.

[0064] Then, the actual displacement of vibration measurement point T is calculated by subtracting the apparent displacement due to the shaking of video camera 2 from the displacement calculation result of the vibration measurement point T obtained from the image correlation analysis. The displacement calculated in this way is a value corrected for the effect of the shaking of video camera 2.

[0065] In detail, the camera laser point 220A shown in Figure 10 indicates the irradiation position before the video camera 2 is shaken. When the video camera 2 shakes due to wind or other factors, the camera laser point 220 will be captured in image P. Here, the apparent displacement (camera movement R2) due to the shaking of the video camera 2 is the distance between the reference line 221A of the camera laser point 220A and the reference line 221 of the camera laser point 220. This can be calculated by subtracting the distance between the reference lines 301 and 221A before the shaking from the distance between the reference lines 301 and 221 after the shaking.

[0066] On the other hand, the displacement R1 of the vibration measurement point T on image P is obtained from correlation analysis of the video image data. However, the actual displacement of the vibration measurement point T is obtained after removing the effects of wind, etc., on the video camera 2. Therefore, the actual displacement R3 of the object being measured is obtained by subtracting the camera movement R2 from the displacement R1 of the vibration measurement point T on the video.

[0067] Therefore, the processing unit calculates the camera movement R2 based on the change in the relative distance between the camera laser point 220 and the laser stationary point 30, and calculates the actual displacement R3 of the vibration measurement point T, which is the target of measurement, based on the displacement R1 obtained from the video of the vibration measurement point T and the camera movement R2.

[0068] Next, the procedure for measuring minute displacements in this embodiment 1 will be explained with reference to the flowchart in Figure 11.

[0069] First, in step S11, the video camera 2 and laser irradiation device 3 are installed on a stable ground surface G that allows for clear observation of the object to be measured. The installed video camera 2 is fitted with a camera laser 22, and its irradiation direction is parallel to the optical axis of the video camera 2.

[0070] In step S12, after the measurement preparations are complete, video recording is started so that the object to be measured, the laser fixed point 30, and the camera laser point 220 are all included in the same image P. If the video camera 2 shakes due to wind or other factors during video recording, the amount of camera movement R2 is calculated as the relative displacement between the camera laser point 220 and the laser fixed point 30 by performing a correlation analysis of the video image data (step S13).

[0071] Step S13 is performed regardless of the order. In step S14, the displacement R1 of the vibration measurement point T on the video is calculated by performing a correlation analysis on the video image data.

[0072] Then, in step S15, the actual displacement of the vibration measurement point T to be measured is calculated based on the camera movement amount R2 calculated in steps S13 and S14 and the displacement amount R1 of the vibration measurement point T on the video.

[0073] Next, the operation of the minute displacement measurement system 1A and the minute displacement measurement method of this embodiment 1 will be described. The minute displacement measurement system 1A of this embodiment 1, configured in this way, includes a video camera 2 for image measurement, a laser irradiation device 3 installed adjacent to the video camera to display a laser fixed point 30 on the surface of the structure, and a camera laser 22 attached to the video camera 2.

[0074] Then, when recording a video of the object to be measured with video camera 2, both the fixed laser point 30 and the camera laser point 220 are captured within the same image P. Here, even if the fixed laser point 30 moves due to the displacement of the mounting surface G, the camera laser 22 also moves by the same amount, so there is no need to correct for the horizontal or rotational displacement of the mounting surface G.

[0075] Therefore, when measuring minute displacements of a structure by image measurement with a close-up view of the object to be measured, a fixed point can be reliably secured, and the vibration of the video camera 2 due to wind, etc., can be eliminated by the camera movement amount R2 calculated based on the camera laser point 220 and the laser fixed point 30, thereby enabling highly accurate measurements.

[0076] The other configurations and effects are substantially the same as those of the above-described embodiment, so their explanation will be omitted.

[0077] While embodiments of the present invention have been described in detail above with reference to the drawings, the specific configuration is not limited to these embodiments or examples, and any design modifications that do not depart from the spirit of the present invention are included in the present invention. [Explanation of Symbols]

[0078] 1,1A: Micro-displacement measurement system 2: Video camera 22: Laser for cameras (laser irradiation device) 220: Camera laser point 221: Reference line 3: Laser irradiation device 30: Laser fixed point 301: Reference line 4: Self-oscillation measuring device B:Bridge (structure) B2: Surface to be measured (surface of the structure) T: Vibration measurement point (object to be measured) P: Image

Claims

1. A micro-displacement measurement system for measuring minute displacements of structures by image measurement, A video camera for taking pictures of the surface of the structure in order to perform the aforementioned image measurement, A laser irradiation device installed adjacent to the video camera and used to display a fixed laser point on the surface of the structure, A self-oscillation measuring device attached to the laser irradiation device, The system includes a calculation processing unit that calculates the displacement of the object to be measured from the video captured by the aforementioned video camera, The image of the object to be measured also includes the laser stationary point. The minute displacement measurement system is characterized in that the calculation processing unit determines the relative displacement amount on the video between the object to be measured and the laser stationary point, and incorporates the amount of movement of the laser stationary point obtained from the measurement results of the self-vibration measuring device to calculate the actual displacement of the object to be measured.

2. A micro-displacement measurement system for measuring minute displacements of structures by image measurement, A video camera for taking pictures of the surface of the structure in order to perform the aforementioned image measurement, A laser irradiation device installed adjacent to the video camera and used to display a fixed laser point on the surface of the structure, A camera laser irradiation device attached to the video camera such that a laser is emitted that is the same as or parallel to the optical axis of the video camera, The system includes a calculation processing unit that calculates the displacement of the object to be measured from the video captured by the aforementioned video camera, The image of the object to be measured captures both the fixed laser point and the camera laser point from the camera laser irradiation device. The aforementioned calculation processing unit determines the amount of camera movement based on the change in the relative distance between the camera laser point and the laser stationary point, and calculates the actual displacement of the object to be measured based on the amount of displacement of the object in the video and the amount of camera movement, thereby providing a minute displacement measurement system.

3. The minute displacement measurement system according to claim 1 or 2, characterized in that the laser fixed point is of a size that spans multiple pixels in the image and has a shape that can define a reference line in the displacement direction of the object to be measured.

4. The minute displacement measurement system according to claim 1 or 2, characterized in that the laser irradiation device is formed in a shape that is less susceptible to wind.

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