JPWO2019082528A1 - Measurement method, computer program and measurement system - Google Patents

Abstract

It enables the displacement or vibration of the measurement area to be measured more appropriately. The measurement method is a measurement method in a measurement system having an image pickup device and an information processing device, and the image pickup device includes a longitudinal direction of a rectangular measurement region that is a part of a sample and a longitudinal direction of a rectangular diagonal lattice. The images before and after the deformation of the measurement area to which the diagonal grid is pasted are taken so that they match, and the information processing device calculates the phase difference in the longitudinal direction of the diagonal grid from the shot images before and after the deformation by the moire method analysis. , Includes calculating the displacement or vibration in the lateral direction before and after deformation of the measurement area based on the calculated phase difference in the longitudinal direction.

Description

The present disclosure relates to a technique for measuring displacement or vibration in a measurement area.

As a technique for measuring in-plane or out-of-plane displacement or vibration of an object, a one-dimensional sine wave lattice as shown in FIGS. 1A and 1B or a two-dimensional dot lattice as shown in FIGS. 1C and 1D is used. The moiré image displacement measurement method (sampling moiré method) used has been developed. With these techniques, it is possible to measure the minute displacement distribution with an accuracy of 1/1000 of the lattice pitch (Patent Documents 1 and 2).

On the other hand, when an oblique lattice is used, by applying the two-dimensional sampling moire method, it is possible to significantly reduce the random noise of the camera and the periodic measurement error due to the thinning process and the luminance interpolation. Therefore, it is expected that the measurement accuracy will be improved by using the oblique grid (Patent Document 3).

Japanese Patent No. 4831703 Japanese Patent No. 6120459 Japanese Patent No. 5818218

However, in the above method, a marker size that is at least twice the lattice pitch is required to calculate the displacement. Therefore, it is difficult to measure an extremely elongated object such as a columnar structure or a thin structure having a small surface area.

The purpose of the measuring method, computer program and measuring system is to make it possible to more appropriately measure the displacement or vibration of the measuring area.

The measurement method according to one aspect of the embodiment is a measurement method in a measurement system including an image pickup device and an information processing device, wherein the image pickup device has a longitudinal direction of a rectangular measurement region that is a part of a sample and a rectangular shape. The images before and after the deformation of the measurement area where the diagonal grid is pasted so as to match the longitudinal direction of the diagonal grid are taken, and the information processing device takes the images before and after the deformation, and the length of the diagonal grid is analyzed by the Moire method. This includes calculating the phase difference in the direction and calculating the displacement or vibration in the lateral direction before and after the deformation of the measurement region based on the calculated phase difference in the longitudinal direction.

The measurement method according to the other aspect of the embodiment is a measurement method in a measurement system including an image pickup device and an information processing device, wherein the image pickup device is a rectangular measurement region that is a part of a sample and has a rectangular shape. The images before and after the deformation of the measurement area to which the two diagonal grids are attached so that the stretching directions of the lines in the two diagonal grids are different from each other are taken, and the information processing apparatus takes the images before and after the deformation, and the moire method is used. By analysis, the phase difference in the longitudinal direction of each of the two diagonal grids is calculated, and based on the calculated phase difference in the longitudinal direction, the two-dimensional in-plane displacement or vibration before and after the deformation of the measurement region is calculated. Including.

The computer program according to one aspect of the embodiment is a computer program of an information processing device included in a measurement system having an image pickup device, and is a longitudinal direction of a rectangular measurement region that is a part of a sample taken by the image pickup device. The phase difference in the longitudinal direction of the diagonal grid was calculated from the images before and after the deformation of the measurement area where the diagonal grid was pasted so as to match the longitudinal direction of the rectangular diagonal grid, and the calculated longitudinal length was calculated by the Moire method analysis. The information processing apparatus is made to calculate the displacement or vibration in the lateral direction before and after the deformation of the measurement region based on the phase difference in the directions.

The computer program according to the other aspect of the embodiment is a computer program of the information processing device included in the measurement system having the image pickup device, and is a rectangular measurement area which is a part of the sample photographed by the image pickup device. From the images before and after the deformation of the measurement area where the two diagonal grids are pasted so that the stretching directions of the lines in the two rectangular grids are different from each other, the length of each of the two diagonal grids is analyzed by the Moire method analysis. The information processing apparatus is made to calculate the phase difference in the direction and calculate the two-dimensional in-plane displacement or vibration before and after the deformation of the measurement region based on the calculated phase difference in the longitudinal direction.

The measurement system according to one aspect of the embodiment is a measurement system including an image pickup device and an information processing device, and the image pickup device includes a longitudinal direction of a rectangular measurement region that is a part of a sample and a rectangular diagonal lattice. The images before and after the deformation of the measurement area to which the diagonal grid is pasted so as to match the longitudinal direction of the image are taken, and the information processing device uses the images before and after the taken deformation to analyze the position of the diagonal grid in the longitudinal direction. It has a first calculation unit that calculates the phase difference, and a second calculation unit that calculates the displacement or vibration in the lateral direction before and after the deformation of the measurement region based on the calculated phase difference in the longitudinal direction.

The measurement system according to the other aspect of the embodiment is a measurement system having an image pickup device and an information processing device, and the image pickup device is a rectangular measurement area that is a part of a sample and has two rectangular shapes. The images before and after the deformation of the measurement area where the two diagonal grids are pasted so that the stretching directions of the lines in the diagonal grid are different from each other are taken, and the information processing apparatus uses the moire method analysis from the shot images before and after the deformation. Based on the first calculation unit that calculates the phase difference in the longitudinal direction of each of the two diagonal grids and the calculated phase difference in the longitudinal direction, the two-dimensional in-plane displacement or vibration before and after the deformation of the measurement region is calculated. It has a second calculation unit.

According to this embodiment, the measuring method, the computer program and the measuring system can more appropriately measure the displacement or vibration of the measuring area.

The objects and effects of the present invention will be recognized and obtained specifically by using the components and combinations pointed out in the claims. Both the general description described above and the detailed description below are exemplary and descriptive and do not limit the invention as described in the claims.

It is a schematic diagram which shows the conventional lattice. It is a schematic diagram which shows the conventional lattice. It is a schematic diagram which shows the conventional lattice. It is a schematic diagram which shows the conventional lattice. It is a figure which shows an example of the schematic structure of the measurement system 100. It is a flowchart which shows the example of the operation of the measurement process. It is a schematic diagram which shows an example of an oblique lattice. It is a schematic diagram which shows an example of an oblique lattice. It is a schematic diagram which shows an example of an oblique lattice. It is a schematic diagram which shows an example of an oblique lattice. It is a schematic diagram which shows an example of a sample, a measurement area and an oblique lattice. It is a schematic diagram for demonstrating the definition of a coordinate system. It is a schematic diagram for demonstrating the definition of a coordinate system. It is a schematic diagram for demonstrating the definition of a coordinate system. It is a schematic diagram for demonstrating the definition of a coordinate system. It is a schematic diagram for demonstrating an oblique grid and a coordinate system. It is a schematic diagram for demonstrating an oblique grid and a coordinate system. It is a schematic diagram for demonstrating an oblique grid and a coordinate system. It is a schematic diagram for demonstrating the displacement of an oblique lattice. It is a schematic diagram for demonstrating the displacement of an oblique lattice. It is a schematic diagram for demonstrating the displacement analysis of an oblique lattice. It is a schematic diagram for demonstrating the displacement analysis of an oblique lattice. It is a schematic diagram for demonstrating the displacement analysis of an oblique lattice. It is a schematic diagram for demonstrating the displacement analysis of an oblique lattice. It is a schematic diagram for demonstrating the displacement analysis of a set of lattice pairs. It is a schematic diagram for demonstrating the displacement analysis of a set of lattice pairs. It is a schematic diagram which shows the setup of a laboratory experiment. It is a schematic diagram which shows the graph of displacement. It is a schematic diagram which shows the graph of displacement. It is a schematic diagram which shows the graph of displacement. It is a schematic diagram which shows the graph of displacement. It is a schematic diagram which shows the graph of displacement. It is a schematic diagram which shows the graph of displacement. It is a schematic diagram which shows the graph of displacement. It is a schematic diagram which shows the graph of displacement. It is a schematic diagram for demonstrating the laboratory experiment using a set of lattice pairs. It is a schematic diagram which shows the graph of displacement. It is a schematic diagram which shows the graph of displacement. It is a schematic diagram which shows the graph of displacement. It is a schematic diagram which shows the graph of displacement. It is a schematic diagram which shows the setting of a grid marker. It is a schematic diagram which shows the measurement result of displacement. It is a schematic diagram which shows the measurement result of displacement. It is a schematic diagram which shows the setup of measurement. It is a schematic diagram which shows the measurement result of displacement. It is a schematic diagram which shows the measurement result of displacement. It is a schematic diagram which shows the measurement result of vibration. It is a schematic diagram which shows the measurement result of vibration. It is a schematic diagram which shows the measurement result of vibration. It is a schematic diagram which shows the measurement result of vibration. It is a schematic diagram which shows the measurement result of vibration. It is a schematic diagram which shows the measurement result of vibration. It is a schematic diagram for demonstrating the displacement measurement on a road surface. It is a schematic diagram for demonstrating the displacement measurement on a road surface. It is a schematic diagram for demonstrating the displacement measurement of a columnar structure. It is a schematic diagram for demonstrating the displacement measurement of a columnar structure.

Hereinafter, the measurement system according to one aspect of the present disclosure will be described with reference to the drawings. However, it should be noted that the technical scope of the present disclosure is not limited to those embodiments, but extends to the inventions described in the claims and their equivalents.

The present embodiment is a technique for measuring in-plane and out-of-plane displacement and vibration of an object from an obliquely arranged and repeating regular pattern on the object taken by an optical camera equipped with an image sensor. Regarding.

In the displacement measurement method based on the conventional sampling moire method, images before and after deformation of a regularly repeating pattern (for example, a lattice pattern) on an object taken by an optical camera equipped with an image sensor are analyzed. In this displacement measurement method, a one-dimensional line-shaped grid marker or a two-dimensional dot grid marker as shown in FIGS. 1A to 1D is used. In this displacement measurement method, the displacement amount of the vertical grid (FIG. 1A) is measured and analyzed for the horizontal displacement measurement, and the displacement amount of the horizontal grid (FIG. 1B) is measured for the vertical displacement measurement. The amount of displacement is measured and analyzed. On the other hand, in order to perform sufficient displacement measurement in both the horizontal and vertical directions at the same time using the two-dimensional grid marker, the grid including both the horizontal and vertical grids is rectangular (Fig. 1C) or square. It is necessary to have the mesh shape of (FIG. 1D) or the pattern of two-dimensional dots (the shape of the inverted mesh).

Further, in this displacement measurement method, the marker needs to have a width and a height of at least twice the lattice pitch. Therefore, when performing a mechanical test of a nano-micro structure or a measurement of displacement on a road surface such as a bridge, the place where a marker is installed is limited. In addition, it is difficult to install markers on columnar structures such as utility poles, street lamps, and space structures, which are curved objects.

When using a one-dimensional sine wave or square wave marker, it is necessary to use a marker whose line is orthogonal to the displacement measurement direction.

In the following, a new method for measuring the displacement or vibration of an object using an oblique grid will be described in order to relax the limitation on the installation size of the marker as described above or to realize more accurate displacement analysis.

In this embodiment, diagonal grids are used instead of horizontal grids, vertical grids or orthogonal grids arranged parallel to either the horizontal or vertical direction as is commonly used. As a result, the following can be realized.

The horizontal grid is a grid in which each of a plurality of lines (parallel lines) extending in the horizontal direction of the spatial coordinates are arranged at regular intervals. A vertical grid is a grid in which a plurality of lines extending in the vertical direction of spatial coordinates are arranged at regular intervals. The orthogonal grid is a grid in which each of the plurality of lines extending in the horizontal direction is arranged at regular intervals, and each of the plurality of lines extending in the vertical direction is arranged at regular intervals. In the present embodiment, the grid direction means a direction orthogonal to the direction in which regular changes in the grid appear. An oblique grid is a grid whose grid direction is diagonal with respect to the horizontal or vertical direction. That is, in the diagonal lattice, each of a plurality of lines inclined and extending in the longitudinal direction or the lateral direction of the oblique lattice are arranged at regular intervals.

The diagonal grid may be provided by arranging the horizontal grid and the vertical grid at an angle with respect to the horizontal direction or the vertical direction in the rectangular measurement area. Further, when the diagonal grid is provided in a rectangular shape, the diagonal grid may be provided by inclining the horizontal grid with respect to the lateral direction of the diagonal grid.

(1) The two-dimensional sampling moire method (Patent Document 3) can be used instead of the conventional one-dimensional sampling moire method, and phase analysis can be performed with higher accuracy. In the two-dimensional sampling moire method, a two-dimensional discrete Fourier transform is executed on the phase-shifted moiré fringes obtained by the thinning process and the brightness interpolation process in both the x direction and the y direction.
(2) By setting the direction orthogonal to the direction in which the displacement is measured as the analysis direction (displacement in the x direction is analyzed in the y direction, and displacement in the y direction is analyzed in the x direction), the marker size can be adjusted. It is possible to greatly relax the restrictions.
(3) The two-stage moire method can be used more easily. In the two-stage moire method, the moire fringes are regarded as a grid, and the two-stage moire fringes are further calculated from the calculated moire fringes by appropriate thinning processing and brightness interpolation processing, and a wide-field and highly sensitive deformation measurement is executed. Will be done.

FIG. 2 is a diagram showing an example of a schematic configuration of the measurement system 100 according to the embodiment.

The measurement system 100 includes a sample 200, an image pickup device 300, and an information processing device 400.

Sample 200 is a columnar structure such as a utility pole, a street lamp, or a space structure (rocket or the like). The sample 200 includes a rectangular measurement area 201 that is a part of the sample 200. The measurement area 201 may have at least one pixel on each side when imaged by the image pickup apparatus 300, and may be, for example, a linear shape (horizontal or vertical line shape). A rectangular diagonal grid 202 is attached to the measurement area 201. In the diagonal grid 202, each of a plurality of lines inclined and extending in the longitudinal direction or the lateral direction of the diagonal grid 202 are arranged at regular intervals. The diagonal grid 202 is formed as a tape having glue or the like adhered to the back surface, and is attached to the measurement region 201 by the measurer so that the longitudinal direction of the measurement region 201 and the longitudinal direction of the diagonal grid 202 are aligned with each other.

The image pickup device 300 is, for example, an optical camera. The image pickup device 300 is output from an image pickup device such as a CCD (Charge Coupled Device) element or a C-MOS (Complementary Metal Oxide Semiconductor) element, an imaging optical system that forms an image on the image pickup device, and an image pickup device. It has an A / D converter that amplifies the electric signal and converts it into analog / digital. The image pickup apparatus 300 is fixedly installed so as to periodically image the measurement area 201 of the sample 200. When the measurement area 201 to which the oblique grid 202 is attached is deformed, the image pickup apparatus 300 captures images before and after the deformation of the measurement area 201. The image pickup device 300 is connected to the information processing device 400, converts the captured image into a digital image in which each pixel has a brightness value in the range of 0 to 255 (in the case of an 8-bit image sensor), and outputs the captured image to the information processing device 400. To do.

The information processing device 400 is, for example, a personal computer. The information processing device 400 includes an interface device 401, a communication device 402, an input device 403, a display device 404, a storage device 405, and a CPU (Central Processing Unit) 410.

The interface device 401 has an interface circuit similar to a serial bus such as USB (Universal Serial Bus), and is electrically connected to the image pickup device 300 to transmit and receive image data and various information.

The communication device 402 has a wired communication interface circuit such as TCP / IP (Transmission Control Protocol / Internet Protocol), and communicates with an external device according to a communication method such as Ethernet (registered trademark). The communication device 402 may communicate with an external device via an access point (not shown) according to a wireless LAN (Local Area Network) communication method.

The input device 403 includes a touch panel type input device, an input device such as a keyboard and a mouse, and an interface circuit for acquiring a signal from the input device. The input device 403 receives the input data input by the measurer, and outputs a signal corresponding to the received input data to the CPU 410.

The display device 404 includes a display composed of a liquid crystal, an organic EL (Electro-Luminescence), or the like, and an interface circuit for outputting image data or various information to the display. The display device 404 is connected to the CPU 410 and displays the image data output from the CPU 410 on the display.

The storage device 405 includes a memory device such as a RAM (Random Access Memory) and a ROM (Read Only Memory), a fixed disk device such as a hard disk, or a portable storage device such as a flexible disk and an optical disk. Further, the storage device 405 stores computer programs, databases, tables, etc. used for various processes of the information processing device 400. The computer program may be installed from a computer-readable portable recording medium such as a CD-ROM (compact disk read only memory) or a DVD-ROM (digital versatile disk read only memory). The computer program is installed in the storage device 405 using a known setup program or the like. Further, in the storage device 405, as data, the pitch of the diagonal grid 202 (interval between lines adjacent to each other), the angle of each line, the resolution of the image captured by the imaging device 300, the frame rate, and the imaging device 300 capture the data. The number of pixels and the like between the lines adjacent to each other of the diagonal grid 202 in the image are stored.

The CPU 410 operates based on a program stored in the storage device 405 in advance. The CPU 410 may be a general-purpose processor. Even if a GPU (Graphics Processing Unit), DSP (digital signal processor), LSI (large scale integration), ASIC (Application Specific Integrated Circuit), FPGA (Field-Programmable Gate Array), etc. are used instead of the CPU 410. Good.

The CPU 410 is connected to the interface device 401, the communication device 402, the input device 403, the display device 404, and the storage device 405, and controls each of these parts. The CPU 410 reads each program stored in the storage device 405 and operates according to each read program. As a result, the CPU 410 functions as an acquisition unit 411, a first calculation unit 412, and a second calculation unit 413.

FIG. 3 is a flowchart showing an example of the operation of the measurement process by the image pickup apparatus 300 and the information processing apparatus 400.

Hereinafter, an example of the operation of the measurement process will be described with reference to the flowchart shown in FIG. The operation flow described below is mainly executed by the CPU 410 in cooperation with each element of the information processing device 400 based on the program stored in the storage device 405 in advance.

In the present embodiment, a method of measuring displacement or vibration in the horizontal or vertical direction from a single grid by arranging a grid 202 in the diagonal direction as shown in FIG. 4A in the measurement region 201 of the sample 200 will be described. To do.

When the information processing apparatus 400 wants to measure the displacement or vibration of the rectangular measurement area 201 of the sample 200 in the lateral direction, it measures the displacement or vibration in the longitudinal direction thereof. As a result, the information processing apparatus 400 is displaced in the horizontal direction with respect to a sample in which it is difficult to attach a grid whose grid direction is vertical, such as a columnar structure such as a street lamp, a utility pole, or a space structure. It becomes possible to analyze the vibration. Similarly, the information processing apparatus 400 has a lattice direction in the horizontal direction, such as a structure such as a road surface in which it is necessary to measure the displacement of the central portion by using a flat plate-shaped marker having a sufficiently low height. It is possible to analyze vertical displacement or vibration with respect to a sample for which it is difficult to attach a certain lattice.

For example, when the lateral direction of the rectangular measurement region 201 of the sample 200 is the horizontal direction, the information processing apparatus 400 may be displaced in the longitudinal direction (vertical direction) in which the size of the lattice 202 is sufficiently large by the moire method analysis. Analyze the vibration. The information processing apparatus 400 calculates the displacement or vibration in the horizontal direction in which the size of the lattice 202 is small by performing a numerical correction calculation on the calculated displacement value (displacement value). As a result, the information processing apparatus 400 can correctly measure the displacement or the vibration by using the diagonal grid.

It is not necessary that the horizontal and vertical directions and the vertical and horizontal arrangement directions of the image pickup devices of the image pickup device 300 match, but it is desirable that they match in order to simplify the process. If the horizontal and vertical directions do not match the vertical and horizontal arrangement directions of the image pickup devices of the image pickup device 300, a level provided by the image pickup device 300, a level provided separately from the image pickup device 300, or the like. The deviation angle is measured by. Then, the information processing apparatus 400 corrects the captured image by using the measured deviation angle.

First, the image pickup apparatus 300 takes an image before and after the deformation of the measurement area 201 to which the oblique grid 202 is attached (step S101).

Next, the acquisition unit 411 of the information processing device 400 acquires images before and after the deformation of the measurement area 201 from the image pickup device 300 via the interface device 401 (step S102).

Next, the first calculation unit 412 calculates the phase difference in the longitudinal direction of the diagonal grid 202 from the acquired images before and after the deformation by moire method analysis (step S103). For example, the first calculation unit 412 calculates the phase difference in the longitudinal direction of the diagonal grid 202 by the one-dimensional sampling moiré method.

Hereinafter, the phase change of the moire fringes before and after the deformation of the measurement region 201 when the one-dimensional sampling moire method is applied will be described using the diagonal grid shown in FIG. 4A. Assuming that the pitches of the grid 202 in the x-direction and the y-direction are Px and Py, respectively, the brightness I of the grid 202 in the image before deformation is represented by the equation (1).

Here, x and y are horizontal and vertical positions (coordinates) in the image before deformation, respectively, and A and B are the modulation amplitude and background brightness of the grid 202, respectively. The angle in the cos function of equation (1) represents the phase φ of the grid 202. That is, the phase φ is represented by the equation (2).

On the other hand, the phase φ'of the grid 202 corresponding to the brightness I in the deformed image is represented by the equation (3). However, the deformation is assumed to be a mere rigid body displacement. Alternatively, the amount of strain due to deformation is sufficiently small and can be ignored.

Here, x'and y'are the positions (coordinates) in the horizontal direction and the vertical direction corresponding to the brightness I in the deformed image, respectively. From the formulas (2) and (3), the phase change (phase difference) Δφ of the grid 202 caused by the deformation of the sample 200 (measurement region 201) is represented by the formula (4).

The moire fringes before and after deformation obtained by downsampling the phase φ of equation (2) and the phase φ'of equation (3) with the thinning number T _x in the x direction by applying the one-dimensional sampling moire method. The phase φ _mx and the phase _φ'mx are represented by the equations (5) and (6), respectively. For a detailed explanation of the method of calculating the phase of the moire fringes by the one-dimensional sampling moire method, refer to, for example, Japanese Patent No. 5818218.

From the equations (5) and (6), the phase difference Δφ _mx of the moire fringes caused by the deformation of the sample 200 (measurement region 201) obtained by the analysis in the x direction is expressed by the equation (7).

Further, the phase phi 'expression phases phi and formula (2) (3), 1-dimensional sampling moire method by applying the moire before and after modification obtained by downsampling at a thinning number T _y in the y-direction represented by the phase phi _my and the phase phi _my 'each type stripe (8) and (9).

From the equations (8) and (9), the phase difference Δφ _mx of the moire fringes caused by the deformation of the sample 200 (measurement region 201) obtained by the analysis in the y direction is expressed by the equation (10).

As shown in the formulas (4), (7) and (10), the phase difference of the grid 202, which is the displacement of the sample 200 (measurement region 201), is analyzed in the x direction and the y direction. And the result is the same. That is, the phase difference Δφ of the grid 202 is represented by the equation (11).

As described above, when the diagonal grid 202 is used, the phase difference is theoretically the same regardless of whether the analysis is performed in the x direction or the y direction. Therefore, the information processing apparatus 400 can calculate the displacement in the horizontal direction by analyzing the diagonal grid 202 in the vertical direction. Similarly, the information processing apparatus 400 can calculate the displacement in the vertical direction by analyzing the diagonal grid 202 in the horizontal direction.

Next, the second calculation unit 413 calculates the displacement or vibration in the lateral direction before and after the deformation of the measurement region 201 based on the phase difference in the longitudinal direction calculated by the first calculation unit 412 (step S104).

(Definition of coordinate system)
First, the spatial coordinate system in the displacement measurement by the one-dimensional sampling moiré method is defined. As shown in FIG. 5A, xy coordinates are defined with the horizontal direction as the x-axis and the vertical direction as the y-axis. Let u _x be the displacement in the horizontal direction, that is, the x direction, and let u _y be the displacement in the vertical direction, that is, the y direction.

Next, the coordinate system for analysis by the one-dimensional sampling moiré method is defined. As shown in FIG. 5B, the XY coordinates are defined. The horizontal direction in the analysis by the one-dimensional sampling moiré method is the X coordinate, and the vertical direction in the analysis by the one-dimensional sampling moiré method is the Y coordinate.

In the conventional vertical grid, horizontal grid, and orthogonal grid, the xy coordinates and the XY coordinates are the same. As shown in FIG. 5C, when each line in the grid is parallel to the Y axis, the displacement in the X direction is calculated by analyzing in the X direction (horizontal direction). Further, as shown in FIG. 5D, when each line in the grid is parallel to the X axis, the displacement in the Y direction is calculated by analyzing in the Y direction (vertical direction).

(Calculation of displacement in the case of a single diagonal grid)
On the other hand, as shown in FIG. 6A, each line in the diagonal grid 202 is arranged at an angle θ (counterclockwise is positive) with respect to the x-axis in the xy coordinate system. For the sake of simplicity, only one grid is displayed in the figure. In this case, as shown in FIGS. 6B and 6C, the X-axis and the Y-axis in the XY coordinate system are arranged at an angle −φ with respect to the x-axis and the y-axis in the xy coordinate system, respectively. .. Here, the angle φ formed by the x-axis and y-axis and the X-axis and Y-axis is −90 ° <φ ≦ 90 °.

When the displacement is analyzed in the X direction, as shown in FIG. 6B, each line of the diagonal grid 202 is analyzed in a state parallel to the Y axis, so that the x-axis and the y-axis are formed by the X-axis and the Y-axis. The angle φ is expressed by the equation (12).
Therefore, when the displacement is analyzed in the X direction, the lattice angle θ is 0 ° <θ ≦ 180 °.

When the displacement is analyzed in the Y direction, as shown in FIG. 6C, each line of the diagonal grid 202 is analyzed in a state parallel to the X-axis, so that the x-axis and the y-axis are connected to the X-axis and the Y-axis. The angle φ is expressed by the equation (13).
Therefore, when the displacement is analyzed in the Y direction, the lattice angle θ is −90 ° <θ ≦ 90 °.

Here, as shown in FIG. 7A, consider a case where the diagonal grid 202 is displaced by a specific displacement amount in a specific direction. In this case, when the displacement of the diagonal lattice 202 is represented by the displacement vector u, the displacement vector u is represented by the sum of the displacement vector u _x in the x direction and the displacement vector u _{y in} the y direction, as shown in FIG. 7B. Displacement. That is, the displacement vector u is represented by the equation (14).

(Calculation of displacement amount when displacement analysis is performed in the X direction)
Here, as shown in FIG. 6A, consider the displacement amount of the diagonal grid 202 in which each line is arranged at an angle θ (counterclockwise is positive) with respect to the x-axis of the xy coordinate system. .. As shown in FIG. 8A, the displacement vector u of the diagonal grid 202 is represented by the XY coordinate system. When the displacement is analyzed in the X direction by the one-dimensional sampling moiré method, the analysis value u _X is calculated. Vector u _X with an analysis value u _X, as shown in FIG. 8B, the vector u _Xx for x-direction displacement u _x, is resolved into a vector u _Xy against displacement u _y in the y-direction. That is, the vector u _X is represented by the equation (15).

As shown in FIG. 8B, the analysis value u _Xx for x-direction displacement amount u _x, and the analysis value u _Xy for displacement u _y in the y-direction is represented by the respective formulas (16) and (17) ..

From the equations (15), (16) and (17), the analysis value u _X is expressed by the equation (18) using the displacement amount u _{x in the x} direction and the displacement amount u _y in the y direction.

Here, in the case of displacement only in the x direction, that is, in the case of u _x >> u _y , the second term on the right side of the equation (18) can be regarded as zero. Therefore, as in Eq. (19), the displacement amount u _x in the x direction is calculated from the analysis value u _X of the diagonal lattice.

Similarly, when displaced only in the y direction, that is, when u _y >> u _x , the first term on the right side of equation (18) can be regarded as zero. Therefore, as in equation (20), the displacement amount u _y in the y direction is calculated from the analysis value u _X of the diagonal lattice.

As described above, when the displacement direction is only one of the x direction and the y direction, the information processing apparatus 400 analyzes u _X in the X direction by the one-dimensional sampling moire method, thereby performing the x direction or the y direction. The displacement in the y direction can be calculated. Here, u _X is calculated by multiplying the phase difference of the moire fringes in the X direction by the lattice pitch P (FIG. 4A) and dividing by (-2π) on the same principle as the displacement measurement of the conventional one-dimensional sampling moire method. Is calculated by.

(Calculation of displacement amount when displacement analysis is performed in the Y direction)
Similarly, as shown in FIG. 9A, the displacement vector u of the diagonal grid 202 can be represented by the XY coordinate system. When displacement analysis is performed in the Y direction by the one-dimensional sampling moiré method, the analysis value u _Y is calculated. Vector u _Y having analysis value u _Y, as shown in FIG. 9B, the vector u _Yx for x-direction displacement u _x, is resolved into a vector u _Yy against displacement u _y in the y-direction. Equations (21) to (24) hold for this vector u _Y in the same manner as in the case of displacement analysis in the X direction.

Here, in the case of displacement only in the x direction, that is, in the case of u _x »u _y , the second term on the right side of the equation (24) can be regarded as zero. Therefore, as in Eq. (25), the displacement amount u _x in the x direction is calculated from the analysis value u _Y of the diagonal lattice.

Similarly, when displaced only in the y direction, that is, when u _y >> u _x , the first term on the right side of equation (24) can be regarded as zero. Therefore, as in Eq. (26), the displacement amount u _y in the y direction is calculated from the analysis value u _Y of the diagonal lattice.

As described above, when the displacement direction is only one of the x direction and the y direction, the information processing apparatus 400 analyzes u _Y in the Y direction by the one-dimensional sampling moire method, thereby performing the x direction or the y direction. The displacement in the y direction can be calculated. Here, u _Y is based on the same principle as the displacement measurement of the conventional one-dimensional sampling moiré method, by multiplying the phase difference of the moiré fringes in the Y direction by the lattice pitch P (FIG. 4A) and dividing by (-2π). It is calculated.

In addition, the second calculation unit 413 performs frequency conversion on the waveform in which the displacements calculated for each acquired image are arranged in time series by using the fast Fourier transform (FFT). The second calculation unit 413 detects peak frequencies in one or a plurality of predetermined frequency bands from the frequency-converted waveform, and sets the detected peak frequencies in the lateral direction before and after the deformation of the measurement region 201 or in the lateral direction. Calculated as longitudinal vibration (number).

(Calculation of phase difference by two-dimensional sampling moire method)
In step S103, the first calculation unit 412 may calculate the phase difference in the longitudinal direction of the diagonal lattice 202 by using the two-dimensional sampling moire method instead of the one-dimensional sampling moire method as the moire method analysis. Good. For a detailed description of the method of calculating the phase of moire fringes by the two-dimensional sampling moire method, refer to, for example, Japanese Patent No. 5818218.

As described in Japanese Patent No. 5818218, when the two-dimensional sampling moiré method is applied to the diagonal grid before deformation, the grid pitches in the x and y directions are thinned out close to P _x and P _y. The phase φ _{mxy of the} moire fringes calculated by downsampling with the numbers T _x and T _y is expressed by Eq. (27).

Similarly, when the two-dimensional sampling moire method is applied to the deformed diagonal lattice, the phase _φ'mxy of the moire fringes is expressed by the equation (28).

Therefore, the phase difference Δφ _mxy of the moire fringes before and after the deformation is expressed by the equation (29).

As shown in the equation (30), the phase difference of the moire fringes calculated by the two-dimensional sampling moire method is equivalent to the phase difference calculated by the one-dimensional sampling moire method shown in the equation (4). That is, the analysis result by the two-dimensional sampling moire method and the analysis result by the one-dimensional sampling moire method are the same. However, the two-dimensional sampling moiré method requires a longer measurement time than the one-dimensional sampling moiré, but is resistant to random noise of the camera, and is therefore suitable for displacement analysis using a noisy image.

That is, in the two-dimensional sampling moiré method as well, the phase difference of the lattice caused by the deformation of the object can be used for the displacement measurement of the oblique lattice, as in the one-dimensional sampling moiré method. The displacement and vibration in each direction are calculated from the phase difference Δφ _mxy of the moire fringes before and after the deformation in the same manner as when the one-dimensional sampling moire method is used.

(Calculation of phase difference by two-stage moire method)
In step S103, the first calculation unit 412 may calculate the phase difference in the longitudinal direction of the diagonal grid 202 by using the two-stage moire method instead of the one-dimensional sampling moire method as the moire method analysis. For a detailed explanation of the method of calculating the phase of moire fringes by the two-stage moire method, refer to, for example, International Publication WO2018 / 061321A.

As described in International Publication WO2018 / 061321, when the two-stage moiré method is applied to the x-direction analysis of the diagonal lattice before deformation, first, the x-direction is the same as the one-dimensional sampling moiré method. Moire fringes are calculated by downsampling with a thinning number T _x close to P _x , which is the lattice pitch of. Then, the calculated moire fringes are regarded as a grid, and downsampling is performed again with a thinning number T _x ⁽²⁾ close to the pitch of the grid to calculate two-stage moire (moire moire) fringes. The phase φ _mx ⁽²⁾ of this two-stage moire fringe is expressed by Eq. (31).

Similarly, when the two-stage moiré method is applied to the analysis in the x direction for the deformed diagonal lattice, the phase _φ'mx ⁽²⁾ of the two-stage moiré fringes is expressed by Eq. (32).

Therefore, the phase difference Δφ _mx ⁽²⁾ of the moire fringes in the x direction before and after the deformation is expressed by the equation (33).

In this way, the phase difference of the moire fringes calculated by applying the two-stage moire method in the x direction of the diagonal lattice is equivalent to the phase difference calculated by the one-dimensional sampling moire method shown in the equation (4). Become. That is, the analysis result by the two-stage moire method and the analysis result by the one-dimensional sampling moire method are the same. However, the two-stage moire method has a lower spatial resolution than the one-dimensional sampling moire method, but it is possible to measure the displacement with a wide field of view and high accuracy.

Similarly, when the two-stage moiré method is applied to the analysis in the y direction for the diagonal lattice before deformation, the thinning number T close to P _y , which is the lattice pitch in the y direction, is the same as the one-dimensional sampling moiré method. Moire fringes are calculated by downsampling with _y . Then, the calculated moire fringes are regarded as a grid, and downsampling is performed again with a thinning number T _y ⁽²⁾ close to the pitch of the grid to calculate two-stage moire (moire moire) fringes. The phase φ _my ⁽²⁾ of this two-stage moire fringe is expressed by the equation (34).

Similarly, with respect to diagonal grid after deformation, if the two-step moire method is applied in the y-direction of the analysis, the two-stage moire fringe phase phi _'my ⁽²⁾ is represented by the formula (35).

Therefore, the phase difference Δφ _my ⁽²⁾ of the moire fringes in the y direction before and after the deformation is expressed by the equation (36).

In this way, the phase difference of the moire fringes calculated by applying the two-stage moire method in the y direction of the diagonal lattice is equivalent to the phase difference calculated by the one-dimensional sampling moire method shown in the equation (4). Become. That is, the analysis result by the two-stage moire method and the analysis result by the one-dimensional sampling moire method are the same.

That is, in the two-stage moire method as well as the one-dimensional sampling moire method, the phase difference of the lattice caused by the deformation of the object can be used for the displacement measurement of the oblique lattice. The displacement and vibration in each direction are calculated from the phase difference Δφ _mx ⁽²⁾ or Δφ _my ⁽²⁾ of the moire fringes before and after the deformation in the same manner as when the one-dimensional sampling moire method is used.

When the equation (4), the equation (11), the equation (30), the equation (33) and the equation (36) are put together, the equation (37) is established.

That is, in any of the one-dimensional sampling moiré method capable of high-speed processing, the two-dimensional sampling moiré method resistant to noise, and the two-stage moiré method having high accuracy and wide field of view, the phase difference of the lattice caused by the deformation of the object is oblique. It can be used to measure the displacement of a lattice.

(Calculation of displacement using a set of diagonal grid pairs)
If the displacement is only in the x or y direction, the displacement can be calculated by using a single diagonal grid. However, when the displacement is in any direction other than the x direction or the y direction, that is, when the displacement has both the x component and the y component, the information processing apparatus 400 calculates two variables, u _x and u _y. There is a need. In this case, the information processing apparatus 400 cannot calculate the displacement only by using a single diagonal grid.

Therefore, as shown in FIG. 4B or FIG. 4C, not a single diagonal grid 202 but two rectangular diagonal grids 202 (a set of diagonal grid pairs) are attached to the measurement area 201 of the sample 200. May be good. Alternatively, as shown in FIG. 4D, a mesh-like grid in the diagonal direction in which two diagonal grids are overlapped may be attached to the measurement region 201 of the sample 200. In this case, two different diagonal grids are extracted in advance by image processing such as Fourier transform and low-pass filter processing. Also in this case, in each of the two diagonal grids 202, a plurality of lines that are inclined and extended with respect to the longitudinal direction or the lateral direction of the diagonal grid 202 are arranged at regular intervals. Each of the two diagonal grids 202 is formed as a tape having glue or the like adhered to the back surface, and the measurer sets the measurement area 201 so that the stretching directions of the lines in the two diagonal grids 202 are different from each other (alternately). It can be pasted. In particular, as shown in FIG. 4E, the two diagonal grids 202 are attached to the rectangular measurement region 201 of the sample 200 so that the longitudinal direction of the measurement region 201 and the longitudinal direction of each diagonal grid 202 are aligned with each other. However, it is assumed that the displacement amounts of the two diagonal grids 202 are the same. That is, it is assumed that each line changes in the same manner in the two diagonal grids 202 (rigid body displacement). The two diagonal grids 202 may be formed separately as two markers or sheet grids, or may be integrally formed as one marker or sheet grid.

The information processing apparatus 400 calculates the displacement of the two diagonal grids 202 in an arbitrary direction by regarding the points Q ₁ and Q ₂ on the two diagonal grids 202 as one point.

The information processing apparatus 400 analyzes the displacement in a direction different from the direction in which the displacement is measured (for the displacement measurement in the horizontal direction, the displacement analysis is performed in the vertical direction). As a result, the information processing apparatus 400 can individually measure the displacement in the horizontal direction or the vertical direction. Alternatively, the information processing apparatus 400 can simultaneously measure displacements in the horizontal direction and the vertical direction.

In this case, in step S101, the image pickup apparatus 300 captures images before and after the deformation of the measurement area 201 to which the two diagonal grids 202 are attached.

In step S102, the acquisition unit 411 acquires images before and after the deformation of the measurement area 201 from the image pickup apparatus 300.

In step S103, the first calculation unit 412 performs the phase difference in the longitudinal direction of the two diagonal grids 202 from the acquired images before and after the deformation by the moire method analysis in the same manner as when a single diagonal grid 202 is used. Is calculated. For example, the first calculation unit 412 calculates the phase difference in the longitudinal direction of each diagonal grid 202 by the one-dimensional sampling moiré method. The first calculation unit 412 may calculate the phase difference in the longitudinal direction of each diagonal grid 202 by the two-dimensional sampling moire method. Alternatively, the first calculation unit 412 may calculate the phase difference in the longitudinal direction of each diagonal grid 202 by the two-stage moire method.

In step S104, the second calculation unit 413 deforms the measurement region 201 based on the phase difference in each longitudinal direction calculated by the first calculation unit 412 in the same manner as when a single diagonal grid 202 is used. Calculate the front-back two-dimensional in-plane displacement or vibration.

As shown in FIG. 10A, the angles of the two diagonal grids 1 and 2 with respect to the horizontal direction are θ ₁ and θ ₂ , respectively. When the displacement analysis is performed in the X direction by the one-dimensional sampling moire method, θ ₁ and θ ₂ are 0 ° <θ ₁ ≤ 180 ° and 0 ° <θ ₂ ≤ 180 °, respectively, and the displacement analysis is performed in the Y direction. In the case, −90 ° <θ ₁ ≦ 90 °, −90 ° <θ ₂ ≦ 90 °.

Hereinafter, as shown in FIG. 10B, processing when the two diagonal grids 202 are moved by the displacement u in an arbitrary direction will be described. Hereinafter, a case where the displacement analysis is performed in the X direction by the one-dimensional sampling moiré method and a case where the displacement analysis is performed in the Y direction by the one-dimensional sampling moiré method will be described.

(Calculation of displacement when displacement analysis is performed in the X direction)
When the two diagonal grid 202 is moved by displacement u in any direction, when the displacement analyzer in the X direction one-dimensional sampling moire method, u _X1 is calculated as the amount of displacement of the point to Q ₁ on diagonal grid 1, u _X2 is calculated as the amount of displacement of the point Q ₂ on the diagonal grid 2. u _X1 and u _X2 are represented by the formulas (38) and (39), respectively, according to the formula (18).

Equation (38) and the formula by solving (39) as simultaneous equations, the amount of displacement of the displacement u _x and y directions in the x direction of the two diagonal grid 202 u _y are each formula (40) and (41) It is calculated as.

Here, K ₁ and K ₂ are represented by the formulas (42) and (43), respectively.

As described above, when the two diagonal grids 202 are used, the displacements in the x direction and the displacement in the y direction are calculated by analyzing in the X direction by the one-dimensional sampling moire method.

(Calculation of displacement when displacement analysis is performed in the Y direction)
When the two diagonal grid 202 is moved by displacement u in any direction, when the displacement analyzer in the Y direction by a one-dimensional sampling moire method, u _Y1 is calculated as the amount of displacement of the point to Q ₁ on diagonal grid 1, u _Y2 is calculated as the amount of displacement of the point Q ₂ on the diagonal grid 2. u _Y1 and u _Y2 are represented by the formulas (44) and (45), respectively, according to the formula (24).

Equation (44) and formula by solving (45) as simultaneous equations, the amount of displacement of the displacement u _x and y directions in the x direction of the two diagonal grid 202 u _y are each formula (46) and (47) It is calculated as.

Here, K ₁ and K ₂ are represented by the above equations (42) and (43), respectively.

In this way, when the two diagonal grids 202 are used, the displacements in the x-direction and the y-direction are calculated by analyzing in the Y direction by the one-dimensional sampling moire method.

[Measurement Example 1]
(Displacement measurement with a single diagonal grid when displaced only in the horizontal direction)
The results of laboratory experiments to demonstrate horizontal (x-direction) displacement measurements with a single diagonal grid are shown below.

FIG. 11 shows a laboratory experiment setup. In this experiment, an oblique grid 6 having a grid pitch of 4 mm and each line having various angles is used. The grid angles are 45 °, 60 °, −45 ° (135 °), −60 ° (120 °). The grid 6 is photographed by the digital camera 5 while being displaced by the moving stage 7 in the horizontal direction (x direction) 8 by 0.1 mm within a range of 0 to 1 mm. The camera 5 is installed so that the grid pitch on the captured image is 10 pixels.

A continuous frame (still image) in the captured moving image is subjected to displacement analysis by the one-dimensional sampling moire method as an image before and after deformation. The displacement analysis of the captured image is performed in each of the X direction and the Y direction.

The method of the present invention was applied to the analysis results, and the effectiveness of the present embodiment was confirmed. FIG. 12A shows a graph of the amount of displacement when displacement analysis is performed in the X direction by the one-dimensional sampling moire method using the lattice pattern 6 having lattice angles of 45 ° and 60 °. FIG. 12B shows a graph of the displacement amount corrected by the equation (19) by applying the method of the present embodiment. In each graph, the horizontal axis shows the given displacement amount, and the vertical axis shows the displacement amount calculated as a result of the displacement analysis. By applying the correction by the method of this embodiment to the displacement amount shown in FIG. 12A, it was confirmed that the displacement amount was accurately calculated at any of the grid angles as shown in FIG. 12B. ..

Similarly, FIG. 12C shows a graph of the amount of displacement when displacement analysis is performed in the Y direction by the one-dimensional sampling moire method. FIG. 12D shows a graph of the displacement amount calculated by the equation (25) by applying the method of the present embodiment. It was confirmed that the displacement amount was calculated accurately even in the case of the displacement analysis in the Y direction by the one-dimensional sampling moiré method, as in the case of the displacement analysis in the X direction by the one-dimensional sampling moiré method.

[Measurement example 2]
(Displacement measurement with a single diagonal grid when displaced only in the vertical direction)
The results of a laboratory experiment of displacement measurement when the grid is displaced in the vertical direction (y direction) under the same conditions and procedures as in Measurement Example 1 are shown below.

The grid 6 is photographed by the digital camera 5 while being displaced by the moving stage 7 by 0.1 mm in the range of 0 to 1 mm in the vertical direction.

FIG. 13A shows a graph of the amount of displacement when displacement analysis is performed in the X direction by the one-dimensional sampling moire method using the lattice pattern 6 having lattice angles of 45 ° and 60 °. FIG. 13B shows the value of the displacement amount calculated by the equation (20) by applying the method of the present embodiment. In each graph, the horizontal axis shows the given displacement amount, and the vertical axis shows the displacement amount calculated as a result of the displacement analysis. By applying the method of this embodiment to the displacement amount shown in FIG. 13A, it was confirmed that the displacement amount was accurately calculated at any of the lattice angles as shown in FIG. 13B.

Similarly, FIG. 13C shows a graph of the amount of displacement when displacement analysis is performed in the Y direction by the one-dimensional sampling moire method. FIG. 13D shows a graph of the displacement amount corrected by the equation (26) by applying the method of the present embodiment. It was confirmed that the displacement amount was calculated accurately even in the case of the displacement analysis in the Y direction by the one-dimensional sampling moiré method, as in the case of the displacement analysis in the X direction by the one-dimensional sampling moiré method.

[Measurement example 3]
(Displacement measurement with a set of diagonal grid pairs when displaced simultaneously in the horizontal and vertical directions)
The results of a laboratory experiment to demonstrate the displacement measurement when displaced in any direction with a pair of diagonal grids are shown below.

In Measurement Example 3, the setup shown in FIG. 11 is used as in Measurement Example 1 and Measurement Example 2. When performing displacement analysis in the X direction using the one-dimensional sampling moiré method as the grid angle of the diagonal grid pair, the combination of θ ₁ = 45 ° and θ ₂ = 135 ° and θ ₁ = 60 ° and θ ₂ = 120 ° The combination of was used. When performing displacement analysis in the Y direction using the one-dimensional sampling moiré method as the lattice angle of diagonal lattice pairs, the combination of θ ₁ = 45 ° and θ ₂ = −45 °, and θ ₁ = 60 ° and θ ₂ = − A 60 ° combination was used. As shown in FIG. 14, the diagonal lattice pair 6 is displaced by the moving stage 7 in the arbitrary direction 10 by 0.1 mm in the horizontal direction (x direction) within a range of 0 to 1 mm, and in the vertical direction (y). A moving image is taken by the digital camera 5 while being displaced by 0.2 mm in the range of 0 to 2 mm in the direction).

FIG. 15A shows a graph of the amount of displacement when displacement analysis is performed in the X direction by the one-dimensional sampling moire method. FIG. 15C shows a graph of the displacement amount calculated by the equations (40) to (43) by applying the method of the present embodiment. In the graph of FIG. 15A, the horizontal axis shows the given displacement amount, and the vertical axis shows the displacement amount calculated as a result of the displacement analysis. In the graph of FIG. 15C, the horizontal axis represents the displacement amount u _x in the x direction calculated as a result of the displacement analysis, and the vertical axis represents the displacement amount u _y in the y direction calculated as a result of the displacement analysis. As shown in FIG. 15C, it was confirmed that the displacement amount was accurately calculated at any of the lattice angles.

Similarly, FIG. 15B shows a graph of the amount of displacement when displacement analysis is performed in the Y direction by the one-dimensional sampling moire method. FIG. 15D shows a graph of the displacement amount calculated by the formulas (46) to (47) and the formulas (42) to (43) by applying the method of the present embodiment. It was confirmed that the displacement amount was calculated accurately even when the displacement was analyzed in the Y direction by the one-dimensional sampling moire method.

From the results of laboratory experiments, the displacement in the x direction and the amount of displacement in the y direction are appropriately separated and accurately measured when the displacement is analyzed in either the X direction or the Y direction by the one-dimensional sampling moire method. It was confirmed that.

[Measurement example 4]
(Measurement of displacement of the bridge on the bridge)
The results of displacement measurement for demonstrating displacement measurement in an actual structure are shown below.

FIG. 16 shows the setting of the grid markers in this experiment. The pitch of the grid 11 of the conventional method is set to 40 mm, and the pitch of the grid 12 of the present embodiment is set to 10 mm. The grid angles of the diagonal grid 12 of the present embodiment are set to θ ₁ = 45 ° and θ ₂ = 135 °. In this measurement, the displacement in the y direction was analyzed in the X direction.

The displacement of the bridge when the truck passed over the bridge was measured by the conventional method and the method of the present embodiment, respectively, and the measurement results of the displacement were compared and verified.

FIG. 17A shows the displacement measurement result by the conventional method, and FIG. 17B shows the displacement measurement result by the method of the present embodiment. From the measurement result of this displacement, it was confirmed that the displacement is measured by the method of this embodiment as well as the conventional method.

[Measurement Example 5]
(Measurement of displacement and vibration of columnar structure)
The results of displacement measurement and vibration measurement of the columnar structure are shown below.

FIG. 18 shows the setup of this measurement. In this measurement, a grid marker 14 according to the method of the present embodiment and a grid marker 15 according to the conventional method are attached to a columnar structure having a columnar shape having a diameter of 50 mm at a height of 1.5 m from the ground. .. Then, the measurement results of the displacement and the frequency of the columnar structure 16 in the horizontal direction by the method of the present embodiment and the conventional method are compared. As a reference point, a marker according to the conventional method and a marker according to the method of the present embodiment are attached to the columnar structure at the position of the columnar structure at the ground surface height.

Vibration in the horizontal direction 16 was applied 30 seconds after the start of measurement, vibration in the front-back direction 17 was applied 60 seconds after the start of measurement, and a moving image was shot with a cinema camera 13 having a sampling rate of 24 fps (Frame Per Sec). ..

The distance between the columnar structure and the camera is 3 m. The grid pitch of the diagonal grid 14 according to the method of the present embodiment is set to 10 mm, and the grid angle is set to 45 °. As the grid marker 15 according to the conventional method, a grid in the vertical direction having a grid pitch of 10 mm is used.

Vibration analysis was performed by performing FFT frequency analysis processing on the displacement measurement results. As the vibration analysis, the method of Example 3 of International Publication WO2018 / 061321 was used.

As the analysis of the displacement amount, the analysis is performed in the X direction in the conventional method, whereas the analysis is performed in the Y direction in the method of the present embodiment.

FIG. 19A shows the displacement measurement result by the conventional method, and FIG. 19B shows the displacement measurement result by the method of the present embodiment. From the displacement measurement results, it was confirmed that the displacement of the present embodiment is also measured with an accuracy of 0.3 mm or less, which is the same as the conventional method.

FIG. 20A shows the measurement result of the vibration at rest (30 seconds from the start of measurement) by the conventional method, and FIG. 20B shows the measurement result of the vibration at rest (30 seconds from the start of measurement) by the method of the present embodiment. .. From the measurement result of this vibration, it was confirmed that the frequency component is calculated by the method of this embodiment as well as the conventional method.

FIG. 21A shows the measurement result of the vibration when the vibration in the horizontal direction 16 is applied by the conventional method (between 30 seconds and 60 seconds after the start of measurement), and FIG. 21B shows the vibration in the horizontal direction 16 by the method of the present embodiment. The measurement result of the vibration at the time of application (from 30 seconds to 60 seconds after the start of measurement) is shown. From this measurement result, it was confirmed that when the vibration in the horizontal direction 16 is applied, the frequency component is calculated by the method of the present embodiment as well as the conventional method.

FIG. 22A shows the measurement result of the vibration when the vibration in the front-rear direction 17 is applied by the conventional method (after 60 seconds have passed from the start of the measurement), and FIG. 22B shows the measurement result when the vibration in the front-rear direction 17 is applied by the method of the present embodiment (measurement). The measurement result of the vibration (after 60 seconds from the start) is shown. From the measurement result of this vibration, it was confirmed that the frequency component was calculated by the analysis method in the longitudinal direction of the columnar structure of the present embodiment even when the vibration in the front-rear direction 17 was applied, as in the conventional method.

In this measurement example, since a grid having a pattern with a relatively fine grid pitch was used, displacement and vibration were correctly measured even by the conventional method. However, if a vertical grid with a coarser grid pitch pattern is used, such as that used when the camera is installed farther away, the displacement and the influence of the circumferential curvature of the tubular structure will cause displacement and Vibrations may not be analyzed correctly. For example, when the lattice pitch in one round of the tubular structure is 2, only one change point of the lattice is shown in the captured image, and the displacement and vibration are not analyzed correctly. On the other hand, in the method of the present embodiment, since the longitudinal direction of the tubular structure can be regarded as a part of a plane (straight line), displacement and vibration are calculated with high accuracy.

According to this embodiment, the restrictions on the grid mounting in the displacement analysis by the sampling moiré method are relaxed, so that the grid can be mounted on the measurement target of various shapes. Therefore, the measurement system 100 can measure the displacement without being restricted by the shape of the structure or the measurement target.

As shown in FIG. 23A, for example, when measuring the displacement on the road surface, the conventional method can measure the displacement only at the end of the road surface. On the other hand, as shown in FIG. 23B, in the method of the present embodiment, by attaching the diagonal grid 22 to a thin box-shaped block or hump, it is possible to measure the displacement at various places such as the central part of the road. ..

Further, as shown in FIG. 24A, it is difficult to attach a grid of a size required for displacement measurement to a thin columnar structure by the conventional method, and it is possible to perform displacement measurement with high accuracy. It was difficult. On the other hand, as shown in FIG. 24B, in the method of the present embodiment, a grid 25 having a size required for displacement measurement can be attached to a thin columnar structure, so that the columnar structure can be attached. It is possible to measure the displacement of the above with high accuracy.

As described in detail above, the method of the present embodiment makes it possible to measure in-plane or out-of-plane displacement or vibration of structures having various shapes without being restricted by the shape of the structure. ..

In particular, in the method of the present embodiment, from microstructures such as MEMS (Micro Electro Mechanical Systems) machines to large structures such as bridges, tunnels or high-rise buildings which are social infrastructures, more accurately and more easily. It is possible to measure displacement or vibration.

100 Measurement system 200 Sample 201 Measurement area 202 Diagonal grid 300 Imaging device 411 Acquisition unit 412 First calculation unit 413 Second calculation unit

Claims (12)

It is a measurement method in a measurement system having an image pickup device and an information processing device.
The image pickup apparatus captures images before and after deformation of the measurement area to which the diagonal grid is attached so that the longitudinal direction of the rectangular measurement region that is a part of the sample and the longitudinal direction of the rectangular diagonal grid are aligned with each other. Take a picture
The information processing device
From the images before and after the deformation taken, the phase difference in the longitudinal direction of the diagonal lattice was calculated by the moire method analysis.
Based on the calculated phase difference in the longitudinal direction, the displacement or vibration in the lateral direction before and after the deformation of the measurement region is calculated.
A measurement method characterized by including. The measurement method according to claim 1, wherein the moire method analysis is a one-dimensional sampling moire method. The measurement method according to claim 1, wherein the moire method analysis is a two-stage moire method. The diagonal grid is formed as a tape
The measurement method according to any one of claims 1 to 3, wherein each of a plurality of lines inclined and extending in the lateral direction of the diagonal lattice are arranged at regular intervals. It is a measurement method in a measurement system having an image pickup device and an information processing device.
The imaging device is a rectangular measurement area that is a part of a sample, and is a measurement area to which the two diagonal grids are attached so that the stretching directions of the lines in the two rectangular grids are different from each other. Take images before and after deformation,
The information processing device
From the images before and after the deformation taken, the phase difference in the longitudinal direction of each of the two diagonal lattices was calculated by the moire method analysis.
Based on the calculated phase difference in each longitudinal direction, the two-dimensional in-plane displacement or vibration before and after the deformation of the measurement region is calculated.
A measurement method characterized by including. The measurement method according to claim 5, wherein the moire method analysis is a one-dimensional sampling moire method or a two-dimensional sampling moire method. The measurement method according to claim 5, wherein the moire method analysis is a two-stage moire method. The two diagonal grids are formed as tape and
The invention according to any one of claims 5 to 7, wherein a plurality of lines inclined and extending with respect to the lateral direction of the diagonal grid are arranged at regular intervals in each of the two diagonal grids. Measurement method. It is a computer program of an information processing device of a measurement system having an image pickup device.
Before and after deformation of the measurement area to which the diagonal grid is attached so that the longitudinal direction of the rectangular measurement area which is a part of the sample and the longitudinal direction of the rectangular diagonal grid, which are photographed by the imaging device, match. The phase difference in the longitudinal direction of the diagonal lattice was calculated from the image of the above by the moire method analysis.
Based on the calculated phase difference in the longitudinal direction, the displacement or vibration in the lateral direction before and after the deformation of the measurement region is calculated.
A computer program characterized by causing the information processing apparatus to execute the above. It is a computer program of an information processing device of a measurement system having an image pickup device.
The two diagonal grids are attached so that the stretching directions of the lines in the two rectangular grids are different from each other in the rectangular measurement area which is a part of the sample photographed by the imaging device. From the images before and after the deformation of the measurement area, the phase difference in the longitudinal direction of each of the two diagonal grids was calculated by the moire method analysis.
Based on the calculated phase difference in each longitudinal direction, the two-dimensional in-plane displacement or vibration before and after the deformation of the measurement region is calculated.
A computer program characterized by causing the information processing apparatus to execute the above. A measurement system that has an imaging device and an information processing device.
The imaging device captures images before and after deformation of the measurement area to which the diagonal grid is attached so that the longitudinal direction of the rectangular measurement region that is a part of the sample and the longitudinal direction of the rectangular diagonal grid are aligned with each other. Take a picture
The information processing device
The first calculation unit that calculates the phase difference in the longitudinal direction of the diagonal grid by the moire method analysis from the images before and after the deformation taken.
Based on the calculated phase difference in the longitudinal direction, the second calculation unit that calculates the displacement or vibration in the lateral direction before and after the deformation of the measurement region, and
A measurement system characterized by having. A measurement system that has an imaging device and an information processing device.
The image pickup apparatus is a rectangular measurement region that is a part of a sample, and is a measurement region to which the two diagonal grids are attached so that the stretching directions of the lines in the two rectangular grids are different from each other. Take images before and after deformation,
The information processing device
The first calculation unit that calculates the phase difference in the longitudinal direction of each of the two diagonal grids by the moire method analysis from the images before and after the deformation taken.
A second calculation unit that calculates the two-dimensional in-plane displacement or vibration of the measurement region before and after deformation based on the calculated phase difference in each longitudinal direction.
A measurement system characterized by having.