JP2020165893A - Displacement measurement device, displacement measurement method, and program - Google Patents

Abstract

To improve measurement accuracy of out-of-plane displacement of an object.SOLUTION: A displacement measurement device includes: an image acquisition part which acquires an image obtained by imaging a marker, in which predetermined patterns are repeatedly drawn with a predetermined pitch, formed on a surface of an object whose displacement is calculated, with an imaging part; a pitch information acquisition part which acquires pitch information indicating the pitch of the marker; an angle information acquisition part which acquires angle information indicating an angle formed by a direction of an optical axis of the imaging part and a direction of the object to the imaging part; an in-plane displacement calculation part which calculates in-plane displacement that is apparent displacement in the image and is displacement in a predetermined direction among directions parallel to an imaging surface where the marker is imaged, based on the imaged image and the pitch indicated by the pitch information; and an out-of-plane displacement calculation part which calculates out-of-plane displacement that is displacement in a direction vertical to the imaging surface based on the angle indicated by the angle information and in-plane displacement.SELECTED DRAWING: Figure 1

Description

The present invention relates to a displacement measuring device, a displacement measuring method, and a program.

Conventionally, non-contact displacement sensors using a mechanical displacement meter or laser light have been widely used as a technique for measuring the displacement of an object, but there is a problem that installation work for mounting these sensors is laborious and costly. There was a point.

On the other hand, as a measurement method using an image, a moire image displacement measurement method (sampling moire method) using a regular pattern in which a predetermined pattern is repeatedly drawn at a predetermined pitch has been developed (Patent Document 1). And Patent Document 2). In the sampling moiré method, a minute in-plane displacement distribution can be measured with an accuracy of 1/1000 of the pitch.

FIG. 16 is a diagram showing an example of a method of measuring displacement of an object by a conventional sampling moire method. Generally, in the method of measuring the displacement of an object by the sampling moire method, a camera 102 (an optical camera equipped with an image pickup element) is used from the direction facing the object 103 to be measured with a regular pattern (lattice marker 101) attached to the surface. The object 103 before and after the deformation is photographed, and the displacement amount is calculated from the photographed image.
Displacement of an object includes in-plane displacement and out-of-plane displacement. The in-plane displacement is a displacement in a direction (x direction or y direction) parallel to the element surface of the camera 102. The out-of-plane displacement is a displacement in the direction (z direction) perpendicular to the element surface of the camera 102.

However, in the case of displacement measurement from the direction facing the object, when there is an obstacle between the object and the camera, the camera cannot capture the regular pattern of the grid markers attached to the surface of the object, which makes measurement difficult. There is.

Further, when the displacement of a structure is measured by the sampling moire method, there may be a river, the sea, etc. between the camera and the structure, and the camera may not be installed at an appropriate distance from the structure. Further, when measuring the displacement of a structure by the sampling moire method, if the structure is a bridge that straddles a river or a valley, the camera may not be installed at a position facing the bridge.

On the other hand, as a method of measuring the displacement of an object, there is a method of measuring the out-of-plane displacement. A laser Doppler type displacement meter is mainly used for measuring out-of-plane displacement. Laser Doppler displacement gauges are often used to measure bridge deflection as a measure of out-of-plane displacement, but laser Doppler displacement gauges are expensive and can only measure one point at a time.

As a method of measuring the out-of-plane displacement by image measurement, a method of measuring the out-of-plane displacement from a change in the lattice pitch of a regular pattern on the surface of an object is known. In this method, as in FIG. 16, a regular pattern on the surface of an object placed on the surface facing the camera is photographed, the pitch of the photographed regular pattern is analyzed by the moire method, and the pattern is out of plane due to a change in the lattice pitch. This is a method of measuring displacement.

JP-A-2009-264852 Republished WO2015 / 008404

However, in the above-mentioned measurement of out-of-plane displacement by pitch, when the distance between the object and the camera is large, the change in the pitch of the regular pattern cannot be sufficiently captured, and the out-of-plane displacement cannot be measured with sufficiently high accuracy. The measurement accuracy of out-of-plane displacement is generally about one tenth of the measurement accuracy of in-plane displacement, and the greater the distance between the object and the camera, the lower the measurement accuracy.

An object of the present invention has been made in view of the above points, and an object of the present invention is to provide a method capable of improving the measurement accuracy of out-of-plane displacement of an object.

The present invention has been made to solve the above problems, and one aspect of the present invention is a marker in which a predetermined pattern is repeatedly drawn at a predetermined pitch, and the surface of an object whose displacement is to be calculated. An image acquisition unit that acquires an image captured by the image pickup unit, a pitch information acquisition unit that acquires pitch information indicating the pitch of the marker, a direction of the optical axis of the image pickup unit, and the above. The angle information acquisition unit that acquires angle information indicating the angle formed by the direction of the object with respect to the imaging unit, the image acquired by the image acquisition unit, and the pitch information acquired by the pitch information acquisition unit indicate. In-plane displacement calculation that calculates the apparent displacement in the image based on the pitch, which is the displacement in a predetermined direction among the directions parallel to the imaging surface on which the marker is imaged. In terms of displacement in the direction perpendicular to the imaging surface, based on the unit, the angle indicated by the angle information acquired by the angle information acquisition unit, and the in-plane displacement calculated by the in-plane displacement calculation unit. It is a displacement measuring device including an out-of-plane displacement calculation unit for calculating a certain out-of-plane displacement.

Further, in one aspect of the present invention, in the displacement measuring device, the predetermined direction is the direction in which the displacement of the object is the smallest among the directions parallel to the imaging surface.

Further, in one aspect of the present invention, in the displacement measuring device, the out-of-plane displacement calculation unit obtains the in-plane displacement calculated by the in-plane displacement calculation unit by the angle information acquisition unit. The out-of-plane displacement is calculated by dividing by the tangent of the angle indicated by the information.

Further, one aspect of the present invention is a marker in which a predetermined pattern is repeatedly drawn at a predetermined pitch, and an image in which a marker formed on the surface of an object for which displacement is calculated is captured by an imaging unit is acquired. Image acquisition process, pitch information acquisition process for acquiring pitch information indicating the pitch of the marker, angle information indicating an angle formed by the direction of the optical axis of the imaging unit and the direction of the object with respect to the imaging unit. It is an apparent displacement in the image based on the angle information acquisition process for acquiring the image, the image acquired by the image acquisition process, and the pitch indicated by the pitch information acquired by the pitch information acquisition process. The in-plane displacement calculation process for calculating the in-plane displacement, which is the displacement in a predetermined direction among the directions parallel to the imaging surface on which the marker is imaged, and the angle information acquired by the angle information acquisition process are An out-of-plane displacement calculation process for calculating an out-of-plane displacement, which is a displacement in a direction perpendicular to the imaging surface, based on the indicated angle and the in-plane displacement calculated by the in-plane displacement calculation process. It is a displacement measuring method to have.

Further, one aspect of the present invention is a marker in which a predetermined pattern is repeatedly drawn on a computer at a predetermined pitch, and a marker formed on the surface of an object for which displacement is calculated is imaged by an imaging unit. An image acquisition step for acquiring an image, a pitch information acquisition step for acquiring pitch information indicating the pitch of the marker, an angle formed by the direction of the optical axis of the imaging unit and the direction of the object with respect to the imaging unit. The apparent displacement in the image is based on the angle information acquisition step for acquiring the indicated angle information, the image acquired by the image acquisition step, and the pitch indicated by the pitch information acquired by the pitch information acquisition step. The displacement is acquired by the in-plane displacement calculation step for calculating the in-plane displacement, which is the displacement in a predetermined direction among the directions parallel to the imaging surface on which the marker is imaged, and the angle information acquisition step. An out-of-plane displacement calculation step that calculates an out-of-plane displacement, which is a displacement in a direction perpendicular to the imaging surface, based on the angle indicated by the angle information and the in-plane displacement calculated by the in-plane displacement calculation step. It is a program to execute.

According to the present invention, it is possible to improve the measurement accuracy of the out-of-plane displacement of an object.

It is a figure which shows an example of the measuring method of the out-of-plane displacement which concerns on embodiment of this invention. It is a figure which shows an example of the marker which concerns on embodiment of this invention. It is a figure which shows an example of the structure of the measurement system which concerns on embodiment of this invention. It is a figure which shows an example of the out-of-plane displacement measurement processing which concerns on embodiment of this invention. It is a figure which shows an example of the out-of-plane displacement calculation process which concerns on embodiment of this invention. It is a figure which shows an example of the repeating pattern which concerns on embodiment of this invention. It is a figure which shows an example of the repeating pattern in an oblique direction which concerns on embodiment of this invention. It is a figure which shows an example of the installation position of the camera which concerns on embodiment of this invention. It is a figure which shows an example of the measurement point which concerns on embodiment of this invention. It is a figure which shows an example of the bridge to be measured which concerns on embodiment of this invention. It is a figure which shows an example of the setup of the displacement measurement which concerns on embodiment of this invention. It is a figure which shows an example of the installation position of the marker which concerns on embodiment of this invention. It is a figure which shows an example of the setting of the displacement measurement in the y direction which concerns on embodiment of this invention. It is a figure which shows an example of the measurement result of the out-of-plane displacement which concerns on embodiment of this invention. It is a figure which shows an example of the measurement result of the out-of-plane displacement which concerns on embodiment of this invention. It is a figure which shows an example of the displacement measurement method of the object by the conventional sampling moire method.

(Embodiment)
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram showing an example of a method for measuring out-of-plane displacement according to the present embodiment. In this embodiment, the out-of-plane displacement of the object 3 which is a structure is measured. The out-of-plane displacement of the object 3 is measured as the out-of-plane displacement of the marker 1 placed on the surface of the object 3. The camera 2 is installed far away from the object 3 and photographs the marker 1 installed on the surface of the object 3.

Let the distance D be the distance between the camera 2 and the object 3. The angle of view between the camera 2 and an arbitrary point on the object 3 is defined as the angle θ. The out-of-plane displacement when the point P1 on the object 3 is displaced to the point Q1 due to the out-of-plane displacement is defined as the out-of-plane displacement Δz.

In the method for measuring the out-of-plane displacement according to the present embodiment, the in-plane displacement Δy is first calculated. Here, the in-plane displacement Δy is an apparent displacement in the image captured by the camera 2 in a direction in which the in-plane displacement is not displaced or the displacement is negligibly small.
In the method for measuring the out-of-plane displacement according to the present embodiment, the out-of-plane displacement Δz of the object is measured by converting the calculated in-plane displacement Δy into the out-of-plane displacement Δz based on the angle θ.

Here, a predetermined pattern is repeatedly drawn on the marker 1 at a predetermined pitch. In the present embodiment, the in-plane displacement Δy obtained from the phase difference before and after the displacement of the captured grid image is calculated by the displacement analysis based on the predetermined pattern repeatedly drawn on the marker 1.
In the present embodiment, a case where the sampling moire method is used will be described as an example of the displacement analysis method for calculating the in-plane displacement Δy. As another example of the displacement analysis method, various Fourier transform methods such as a general Fourier transform method, a Fourier transform method with a window, and a wavelet transform method may be used.

Here, the marker 1 will be described with reference to FIG. FIG. 2 is a diagram showing an example of the marker 1 according to the present embodiment. In the marker 1a shown in FIG. 2A, a rectangular wave grid is repeatedly drawn at a predetermined pitch. In the marker 1b shown in FIG. 2B, the letter "A" of the alphabet is repeatedly drawn at a predetermined pitch. In the marker 1c shown in FIG. 2C, diagonal lines are repeatedly drawn at a predetermined pitch.
As the marker 1, any of the marker 1a, the marker 1b, and the marker 1c may be used. Further, another example of the regular pattern drawn on the marker 1 will be described later with reference to FIGS. 6 and 7.

FIG. 3 is a diagram showing an example of the configuration of the measurement system MS according to the present embodiment. The measurement system MS includes an out-of-plane displacement measuring device 10 and an imaging unit 20.

The imaging unit 20 images the marker 1. The image capturing unit 20 supplies the captured image of the marker 1 as image data PD to the out-of-plane displacement measuring device 10. The image pickup unit 20 is, for example, an optical camera such as a CCD (Charge Coupled Device) camera or a CMOS (Complementary metal-oxide-semicondutor) camera. The imaging unit 20 corresponds to the camera 2 in FIG.

The out-of-plane displacement measuring device 10 calculates the out-of-plane displacement Δz based on the image data PD, the pitch information PI, and the angle information AI. The out-of-plane displacement measuring device 10 includes a parameter input unit 11, an arithmetic processing unit 12, and a display unit 13. The out-of-plane displacement measuring device 10 is, for example, a personal computer (PC: Personal Computer).

The parameter input unit 11 accepts an operation of inputting a parameter used for measuring the out-of-plane displacement. The parameters used for measuring the out-of-plane displacement include, for example, the pitch p, which is the pitch of the checkered pattern repeatedly drawn on the marker 1, the direction of the optical axis of the imaging unit 20, and the direction of the object 3 from the imaging unit 20. There is an angle θ formed by. The parameter input unit 11 includes a keyboard, a mouse, and the like as an example.

The parameter input unit 11 may acquire a parameter stored in advance in the storage device as a parameter used for measuring the out-of-plane displacement. This storage device may be provided integrally with the out-of-plane displacement measuring device 10 or may be provided independently of the out-of-plane displacement measuring device 10.

The parameter input unit 11 supplies the pitch information PI and the angle information AI to the arithmetic processing unit 12. Here, the pitch information PI is information indicating the pitch p of the marker 1. The angle information AI is information indicating an angle θ formed by the direction of the optical axis of the imaging unit 20 and the direction of the object 3 with respect to the imaging unit 20.

The arithmetic processing unit 12 executes an out-of-plane displacement calculation process, which is a process for calculating the out-of-plane displacement Δz. The calculation processing unit 12 includes an image acquisition unit 120, a pitch information acquisition unit 121, an angle information acquisition unit 122, a phase calculation unit 123, an in-plane displacement calculation unit 124, and an out-of-plane displacement calculation unit 125.

The arithmetic processing unit 12 is realized by a CPU (Central Processing Unit), and the arithmetic processing unit 12 includes an image acquisition unit 120, a pitch information acquisition unit 121, an angle information acquisition unit 122, a phase calculation unit 123, and an in-plane. The displacement calculation unit 124 and the out-of-plane displacement calculation unit 125 are modules realized by the CPU reading a program from a ROM (Read Only Memory) and executing processing, respectively.

The image acquisition unit 120 acquires the image data PD supplied from the image pickup unit 20.
The pitch information acquisition unit 121 acquires the pitch information PI supplied from the parameter input unit 11.
The angle information acquisition unit 122 acquires the angle information AI supplied from the parameter input unit 11.

The phase calculation unit 123 executes the phase analysis process. In the phase analysis process, the phase calculation unit 123 samples the image data PD based on the image data PD acquired by the image acquisition unit 120 and the pitch information PI acquired by the pitch information acquisition unit 121. Calculate the phase of the image.

The in-plane displacement calculation unit 124 calculates the in-plane displacement Δy based on the phase calculated by the phase calculation unit 123.
The out-of-plane displacement calculation unit 125 calculates the out-of-plane displacement Δz based on the in-plane displacement Δy calculated by the in-plane displacement calculation unit 124 and the angle information AI acquired by the angle information acquisition unit 122.

The display unit 13 displays the calculation result output by the arithmetic processing unit 12. The result of the arithmetic processing of the arithmetic processing unit 12 includes the out-of-plane displacement Δz. The display unit 13 is, for example, a display.

FIG. 4 is a diagram showing an example of the out-of-plane displacement measurement process according to the present embodiment. In the out-of-plane displacement measurement process according to the present embodiment, the in-plane displacement Δy in the y direction is assumed to be non-displaceable or small enough that the displacement can be ignored.

Step S10: The imaging unit 20 images the marker 1. Here, the imaging unit 20 images the marker 1 as a moving image. The image capturing unit 20 supplies the captured image of the marker 1 as image data PD to the out-of-plane displacement measuring device 10. The image data PD includes images of markers 1 in a plurality of frames.

Step S20: The parameter input unit 11 accepts an operation of inputting a parameter used for measuring the out-of-plane displacement. When the pitch p is input as a parameter, the parameter input unit 11 generates a pitch information PI indicating the input pitch p. When the angle θ is input as a parameter, the parameter input unit 11 generates the angle information AI indicating the input angle θ.
The parameter input unit 11 supplies the generated pitch information PI and angle information AI to the arithmetic processing unit 12.

The angle θ is calculated from the angle of view of the lens of the camera 2 used as an example. The calculation method of the angle θ is not limited to this. The angle θ may be calculated from the relationship between the number of pixels of the captured image and the size of the object 3. The angle θ may be calculated by equipping the camera 2 with a surveying sensor. If there is a design drawing for the object 3, the angle θ may be calculated from the geometrical relationship of the measurement points.

Step S30: The arithmetic processing unit 12 executes the out-of-plane displacement calculation process.
Here, the details of the out-of-plane displacement calculation process will be described with reference to FIG. FIG. 5 is a diagram showing an example of the out-of-plane displacement calculation process according to the present embodiment. Each process from step S100 to step S160 in FIG. 5 corresponds to the process in step S30 in FIG.

Step S100: The image acquisition unit 120 acquires the image data PD supplied from the image pickup unit 20. The image acquisition unit 120 supplies the acquired image data PD to the phase calculation unit 123.
As described above, the image acquisition unit 120 acquires the image data PD in which the marker 1 formed on the surface of the object 3 whose displacement is to be calculated is captured by the image pickup unit 20.

Step S110: The pitch information acquisition unit 121 acquires the pitch information PI supplied from the parameter input unit 11. The pitch information acquisition unit 121 supplies the acquired pitch information PI to the phase calculation unit 123.

Step S120: The angle information acquisition unit 122 acquires the angle information AI supplied from the parameter input unit 11. The angle information acquisition unit 122 supplies the acquired angle information AI to the out-of-plane displacement calculation unit 125.

Step S130: The phase calculation unit 123 executes the phase analysis process. In the phase analysis process, the phase calculation unit 123 samples the image data PD based on the image data PD acquired by the image acquisition unit 120 and the pitch information PI acquired by the pitch information acquisition unit 121. Calculate the phase of the image.

(Example of calculating the phase of a moire image)
Here, the details of the phase analysis process in which the phase calculation unit 123 calculates the phase of the moire image will be described.
As an example, the phase calculation unit 123 uses the known sampling moire method described in Patent Document 1. By using the sampling moiré method, the phase calculation unit 123 analyzes the displacement distribution of the object 3 to be measured by using the single frequency component included in the marker 1 in which a predetermined pattern is repeatedly drawn at a predetermined pitch. can do.

FIG. 6 is a diagram showing an example of a repeating pattern according to the present embodiment.
As the repeating pattern drawn on the marker 1, for example, the striped grid shown in FIG. 6 (b) and the two-dimensional grid shown in FIGS. 6 (c) and 6 (d) can be used. The center point U indicates the center point of the repeating pattern. The brightness of the striped grid shown in FIG. 6B changes at a constant pitch in the vertical direction. The brightness of the striped grid shown in FIGS. 6 (c) and 6 (d) changes at a constant pitch in the vertical direction and the horizontal direction, respectively.

As described above, in the present embodiment, the in-plane displacement Δy is not displaced or is small enough that the displacement can be ignored. Therefore, in the present embodiment, as the repeating pattern drawn on the marker 1, the striped grid shown in FIG. 6A whose brightness changes with a pitch in the horizontal direction (x direction) is not adopted.

Next, a known sampling moire method will be described. The luminance distribution f (i, j) of the repeating pattern of the marker 1 captured in the image data PD acquired by the phase calculation unit 123 is represented by the equation (1).

In the formula (1), f (i, j) indicates the luminance value at the coordinates (i, j). i and j indicate coordinate values in the horizontal direction and the vertical direction, respectively. a, b, φ ₀ , and φ are the amplitude of the repeating pattern, the background brightness, the initial phase of the repeating pattern, and the phase of the repeating pattern, respectively. P is the pitch on the image.

A predetermined thinning interval T is set as a parameter in the phase calculation unit 123. The thinning interval T may be an integer of 2 or more. The unit of the thinning interval T is the number of pixels. The thinning interval T may be equal to or different from P. The phase calculation unit 123 performs thinning in the vertical direction for each of 0 to T-1 as the start point k of thinning, and generates T thinned images. Here, the process of generating the thinned image corresponds to spatial downsampling.

The phase calculation unit 123 interpolates the brightness values of the thinned-out pixels adjacent to each other for each of the T thinned-out images, and creates a moire image having the brightness values of each pixel arranged at the same intervals as before the thinning-out. Generate. A method for generating a thinned image and a method for generating a moire image are described in Patent Document 1, respectively.
The brightness value f _M (i, j; k) of the generated moire image is represented by the equation (2).

The phase calculation unit 123 performs a discrete Fourier transform on each of the T moire images, and has a phase distribution φ _M (i, j; ω) and an amplitude distribution a _M (i, j; ω) in a component of an arbitrary spatial frequency ω. ) And is calculated. The phase distribution φ _M (i, j; ω) is expressed by Eq. (3).

The amplitude distribution a _M (i, j; ω) is expressed by Eq. (4).

The phase calculation unit 123 performs the same processing for each marker for each frame, and calculates the phase distribution φ _M (i, j; ω) and the amplitude distribution a _M (i, j; ω) of the moire image. This phase distribution φ _M (i, j; ω) corresponds to the phase of the above moire image. The phase calculation unit 123 acquires in advance the phase distribution φ _M (i, j; ω) and the amplitude distribution a _M (i, j; ω) of the moire image for each marker for the frame of the reference time. ..

The phase calculation unit 123 has a phase difference Δφ _M (i, j;) which is a difference between the phase distribution φ _M (i, j; ω) in each frame and the phase distribution φ _M (i, j; ω) at the reference time. ω) is calculated.

Step S140: The in-plane displacement calculation unit 124 calculates the in-plane displacement. Here, as shown in the equation (5), the in-plane displacement calculation unit 124 has a displacement distribution Δy based on the phase difference Δφ _M (i, j; ω) calculated by the phase calculation unit 123 and the pitch p of the repeating pattern. (I, j; ω) is calculated.

In equation (5), p represents the actual length of the pitch of the pattern represented on the object to be measured. The unit of p is millimeters, meters, and the like. The phase calculation unit 123 presets some of the parameters used for calculating the displacement amount. The above-mentioned pitch P is a parameter that is different from p, which indicates an actual pitch value, in that it is the pitch of the pattern on the image. Here, P, which is the pitch of the pattern on the image, is in units of the number of pixels.

The phase calculation unit 123 multiplies the calculated displacement distribution Δy (i, j; ω) by the amplitude distribution a _M (i, j; ω), synthesizes the multiplication values obtained between frequencies, and synthesizes the multiplication values between frequencies. The averaged displacement distribution Δy (i, j) is calculated. Here, the phase calculation unit 123 uses a weighting coefficient proportional to the power of the amplitude distribution a _M (i, j; ω) instead of the amplitude distribution a _M (i, j; ω) as a displacement distribution Δy (i, j; It may be multiplied by ω).

In steps S130 and 140 described above, an example of analyzing the displacement distribution of the object to be measured using a single frequency component has been described, but the present invention is not limited to this. The displacement distribution of the object to be measured may be analyzed using a plurality of frequency components in steps S130 and 140.

Here, a known sampling moire method for analyzing the displacement distribution of the measurement object using a plurality of frequency components included in the repeating pattern will be described. Therefore, in addition to the repeating pattern illustrated in FIGS. 6 (b)-(d), any repeating pattern having regularity in the fluctuation of the brightness in the vertical direction can be used.
The luminance distribution g (i, j) of the repeating pattern represented by one marker indicated by the image data acquired by the phase calculation unit 123 is represented by the equation (6).

In the formula (6), g (i, j) indicates the luminance value at the coordinates (i, j). w, a _w , φ _w , and b are the order of the frequency component, the amplitude of the w-th order frequency component, and the initial phase of the w-th order frequency component, respectively. w is an integer greater than or equal to 1 and less than or equal to W. W indicates the maximum order of the frequency component. W may be an integer smaller than P / 2 and 2 or more according to the sampling theorem. P indicates the pitch of the regular pattern represented in the image. Here, P, which is the pitch of the pattern on the image, is in units of the number of pixels. The phase calculation unit 123 presets the maximum degree W.

The phase calculation unit 123 thins out the acquired image of the regular pattern in the vertical direction at the thinning interval T to generate a thinned image. The phase calculation unit 123 generates T thinned-out images for each of 0 to T-1 as the thinning start point k. The phase calculation unit 123 interpolates the brightness values of the pixels after thinning out adjacent to each other for each of the T thinned-out images, and shifts the phase having the brightness values of each pixel arranged at the same intervals as before the thinning out. Generates a moire image. The luminance value g _M (i, j; m) of each moire image is represented by the equation (7).

The phase calculation unit 123 performs a discrete Fourier transform on each of the T moire images to calculate the phase distribution φ _M (i, j; ω) in the component of an arbitrary frequency ω. The phase calculation unit 123 substitutes the frequency components g _{w, M} (i, j; m) of the luminance values of each order in place of the luminance values f _M (i, j; m) shown in the equation (3). The phase distribution φ _{w, M} (i, j; w, ω) of each order is calculated.

The in-plane displacement calculation unit 124 substitutes the phase difference Δφ _{w, M} (i, j; w, ω) into the phase difference Δφ _M (i, j; ω) in the equation (5), and the w-th order pitch P The displacement distribution Δy (i, j; w, ω) is calculated by substituting / w for the pitch p in the equation (5). Here, the phase difference Δφ _{w, M} (i, j; w, ω) is the phase at the reference time from the phase distribution φ'w _{, M} (i, j; w, ω) in each frame calculated by the phase calculation unit 123. It is obtained by subtracting the distribution φ _M (i, j; w, ω).

The in-plane displacement calculation unit 124 multiplies the calculated displacement distribution Δy (i, j; w, ω) by the order and the amplitude distribution a _M (i, j; w, ω) for each frequency. May be combined between the order and the frequency to calculate the displacement distribution Δy (i, j) averaged between the order and the frequency. Here, the in-plane displacement calculation unit 124 uses a weight proportional to the power of the amplitude distribution a _M (i, j; w, ω) instead of the amplitude distribution a _M (i, j; w, ω) for each frequency. You may multiply the coefficients.

In addition, the in-plane displacement calculation unit 124 averages the displacement amount at the representative point of each marker or the displacement amount in each marker or in each region in the markers in the calculated displacement distribution Δx (i, j). The value may be adopted as the displacement amount for each marker. Here, the representative points of each marker are, for example, a center point U, a center point U ₁ , and a center point U ₂ , which will be described later.

The phase calculation unit 123 may use the two-stage moire method as a method for calculating the phase of the moire image from the image data PD acquired from the image pickup unit 20. The two-stage moiré method is a method having a two-stage moiré analysis process.
The first-stage process is a process of generating a phase distribution of the first-stage moire image by using the sampling moire method for the acquired image. The second-stage process is a process of generating the phase distribution of the second-stage moire image by using the sampling moire method for the phase distribution of the first-stage moire image as the repeating pattern of the second stage.

When the phase calculation unit 123 uses the two-stage moiré method, the in-plane displacement calculation unit 124 generates a displacement distribution of each marker from the phase distribution of the second-stage moiré image, and obtains a displacement amount based on the generated displacement distribution. ..

The changing direction of the repeating pattern is not limited to the vertical direction as long as it intersects the horizontal direction, and may be an oblique direction. The diagonal direction is a direction that intersects both the vertical direction and the horizontal direction.

FIG. 7 is a diagram showing an example of a repeating pattern in an oblique direction according to the present embodiment.
In the repeating pattern illustrated in FIG. 7A, the brightness is repeated at a constant pitch in the upper left direction with respect to the drawing. The repeating pattern illustrated in FIGS. 7B and 7C each has two regions, and the repeating direction of the luminance is different for each region.

The repeating pattern illustrated in FIG. 7B is divided into two regions in the vertical direction, and the center point of the region R1b above and the center point of the region R2b below with respect to the drawing are the center points U ₁ and U ₁ , respectively. It becomes the center point U ₂ . The repeating direction of the pattern in the upper region R1b with respect to the drawing is the upper left direction, whereas the repeating direction of the pattern in the lower region R2b is the upper right direction.

The repeating pattern illustrated in FIG. 7C is divided into two regions in the horizontal direction, and the center point of the left region R1c and the center point of the right region R2c with respect to the drawing are the center points U, respectively. _1. It becomes the center point U ₂ . The repeating direction of the pattern in the left region R1c with respect to the drawing is the upper right direction, whereas the repeating direction of the pattern in the right region R2c is the upper left direction.
The repeating pattern illustrated in FIG. 7D is a two-dimensional lattice in which the brightness is repeated at a constant pitch in both the upper left direction and the upper right direction with respect to the drawing.

Therefore, even repeating pattern repetition direction is an oblique direction, the in-plane displacement calculating section 124 can pitch p in the vertical direction, as a repeating pattern comprising a p s _/ cos, and calculates the amount of displacement. Here, p _s denotes the pitch of the repetitive pattern in the repeat direction, [psi indicates the angle between the vertical and repeat direction.

Further, by using a repeating pattern in which the repeating direction is an oblique direction, the in-plane displacement calculation unit 124 can perform the phase difference of the moire image in the longitudinal direction even if the sample is elongated in one direction smaller than the longitudinal direction. It is possible to obtain the displacement amount in one direction without sacrificing the measurement accuracy based on the above. Therefore, the degree of freedom in the shape and installation location of each marker can be increased. For example, the vertical height of the marker may be smaller than the horizontal width. The shape of the marker may be flat or columnar. Therefore, the conditions for the marker installation location are relaxed. However, it is desirable that the repeating direction is an angle sufficiently distant from the horizontal direction (for example, the angle θ is −75 ° to 75 °).

As described above, the in-plane displacement calculation unit 124 calculates the in-plane displacement based on the phase difference calculated by the phase calculation unit 123 and the pitch p. Here, the phase calculation unit 123 calculates the phase difference based on the pre-displacement image and the post-displacement image acquired by the image acquisition unit 120.
That is, the in-plane displacement calculation unit 124 is imaged by the image pickup unit 20 based on the image data PD acquired by the image acquisition unit 120 and the pitch P indicated by the pitch information PI acquired by the pitch information acquisition unit 121. The in-plane displacement, which is the apparent displacement in the image and is the displacement in a predetermined direction among the directions parallel to the imaging surface on which the marker 1 is imaged, is calculated.
Further, as described above, the in-plane displacement calculation unit 124 calculates the in-plane displacement Δy based on the moire method.

Here, the predetermined direction is a direction in which the displacement is not displaced or the displacement is negligible among the in-plane displacements. The predetermined direction may be the direction in which the displacement of the object 3 is the smallest among the directions parallel to the imaging surface.

Returning to FIG. 5, the description of the out-of-plane displacement measurement process will be continued.
Step S150: The out-of-plane displacement calculation unit 125 calculates the out-of-plane displacement Δz based on the in-plane displacement Δy calculated by the in-plane displacement calculation unit 124 and the angle information AI acquired by the angle information acquisition unit 122. Here, the out-of-plane displacement calculation unit 125 calculates the out-of-plane displacement Δz by converting the in-plane displacement Δy calculated by the in-plane displacement calculation unit 124 using the equation (8).

Due to the relationship of equation (8), when the in-plane displacement in either the x-direction or the y-direction is zero, the image before and after the displacement of the structure is in the direction in which the in-plane displacement is zero using the sampling moire method. The out-of-plane displacement Δz can be obtained from the in-plane displacement Δx or the in-plane displacement Δy obtained by the in-plane displacement analysis.

Further, from the relation of the equation (8), the larger the angle θ, the higher the measurement sensitivity of the out-of-plane displacement Δz, and the more accurate the measurement can be performed.

As described above, the out-of-plane displacement calculation unit 125 is based on the angle θ indicated by the angle information AI acquired by the angle information acquisition unit 122 and the in-plane displacement Δy calculated by the in-plane displacement calculation unit 124. The out-of-plane displacement Δz, which is the displacement in the direction perpendicular to the imaging surface, is calculated.

Here, the out-of-plane displacement calculation unit 125 calculates the out-of-plane displacement Δz based on the equation (8). That is, the out-of-plane displacement calculation unit 125 divides the in-plane displacement Δy calculated by the in-plane displacement calculation unit 124 by the tangent of the angle θ indicated by the angle information AI acquired by the angle information acquisition unit 122. The outer displacement Δz is calculated.

Step S160: The arithmetic processing unit 12 outputs the out-of-plane displacement Δz to the display unit 13 as a result of the out-of-plane displacement calculation processing.
With the above, the calculation processing unit 12 ends the out-of-plane displacement calculation process.

Returning to FIG. 4, the description of the out-of-plane displacement measurement process will be continued.
Step S40: The display unit 13 displays the calculation result output by the arithmetic processing unit 12. The display unit 13 displays the out-of-plane displacement Δz as a calculation result.
This completes the out-of-plane displacement measurement process of the measurement system MS.

(Installation position of imaging unit)
FIG. 8 is a diagram showing an example of the installation position of the camera 2 according to the present embodiment. For comparison, FIG. 8A shows the camera installation position by the conventional out-of-plane displacement measurement method, and FIG. 8B shows the camera installation position by the out-of-plane displacement measurement of the present embodiment.

FIG. 8 describes an example in which the deflection of the bridge 3B is measured as the out-of-plane displacement Δz of the object 3. In the bridge 3B, the center is the most flexible, and it is particularly required to measure the deflection at this center. Markers as shown in FIGS. 2, 6 and 7 are pre-attached to the lower part of the central floor slab of the bridge 3B.

Instead of attaching the marker, a regular pattern may be applied as a marker to the lower part of the floor slab in the center of the bridge 3B. That is, the marker is formed on the surface of the object for which the displacement is calculated.

In the conventional out-of-plane displacement measurement method, the out-of-plane displacement is calculated from the change in the lattice pitch. In the conventional out-of-plane displacement measurement method, the camera 2a is often installed directly below the center, which is the most flexible position of the bridge 3B. However, when the distance Da from the camera 2a to the floor slab of the bridge 3B becomes long, the change in the lattice pitch in the image captured by the camera 2a is slight, and it is difficult to measure a minute out-of-plane displacement.

On the other hand, in the present embodiment, the camera 2b is installed near the pier of the bridge 3B. Therefore, the central direction of the bridge 3B as seen from the camera 2b is tilted by an angle θ with respect to the optical axis of the camera lens. That is, the camera 2b photographs the center of the bridge 3B from an angle.

As shown in FIG. 1 above, when the object is deformed from P1 to Q1, that is, when the object is displaced by Δz in the out-of-plane direction, the image captured by the camera 2b is imaged as if it is deformed from P1 to P'1. Will be done. This means that the out-of-plane displacement Δz that is originally desired to be measured is imaged as the apparent in-plane displacement Δy. In other words, the conventional out-of-plane displacement measurement is performed by measuring the in-plane displacement Δy with high accuracy and considering the angle θ formed by the measurement point from the optical axis of the lens due to the angle of view of the camera 2b and the geometric arrangement. With this method, out-of-plane displacement, which was difficult to measure, can be measured accurately.
Here, the measurement point is a point on the surface of the object for which the displacement is measured. The marker is placed at the measurement point.

However, in this method, when in-plane displacement and out-of-plane displacement occur at the same time at the measurement point of the object, the sum of the displacement amounts of both the in-plane displacement and the out-of-plane displacement is apparent. It is an in-plane displacement.
Therefore, in the present embodiment, it is assumed that the object to be measured does not deform in either of the two-dimensional in-plane directions (x direction and y direction), or the amount of deformation thereof is negligibly small. In the present embodiment, under this assumption, the apparent in-plane displacement of the grid in the non-deformable direction is calculated, and the out-of-plane displacement is corrected by considering the angle θ as shown in the equation (8). To measure.

Therefore, when the out-of-plane displacement measuring method according to the present embodiment is applied to the measurement of the out-of-plane displacement of an object that can be freely deformed three-dimensionally in a three-dimensional space, either direction is in the two-dimensional in-plane direction. It is considered that the measurement accuracy is lower than that in the case where the deformation is not considered or the amount of the deformation is considered to be negligibly small. The out-of-plane displacement measuring method according to the present embodiment is effective when measuring out-of-plane displacement in an object that is considered to be constrained in one direction, such as an infrastructure structure such as a bridge or a tunnel.

In the case of the example of FIG. 8B, the bridge 3B deforms in the traveling direction (y direction) and the vertical direction (z direction) of the train as the train passes, but the direction (x) perpendicular to the traveling direction of the train. In the direction), it is considered that it will not deform unless a strong external force such as an earthquake or strong wind is applied.

Taking advantage of this, the two-dimensional marker 1 is photographed, the in-plane displacement Δy calculated from the y direction is calculated as it is as the in-plane displacement in the y direction, and the in-plane displacement dx calculated from the x direction is calculated. By converting to the out-of-plane displacement Δz, which is the deflection of the bridge 3B due to the weight of the train, the out-of-plane displacement Δz is more accurate than before even if the distance from the camera 2b to the center of the bridge 3B to be measured is long. Will be able to measure at.

Here, with reference to FIG. 9, an example of another method of selecting the measurement point will be described. FIG. 9 is a diagram showing an example of measurement points according to the present embodiment. A plurality of measurement points may be selected at any point of the object to be measured. In FIG. 9, measurement points M1-2, measurement points M1-3, and reference points A1 are shown as measurement points for the out-of-plane displacement of the bridge 3B.

When selecting a plurality of measurement points, a marker 1 is installed for each of the plurality of measurement points. The marker 1-1 is installed at the reference point A1. Markers 1-2 are placed at measurement point M1-2. Markers 1-3 are placed at measurement points M1-3.
The plurality of measurement points are located within the range of the angle of view V of the camera 2b as viewed from the camera 2b. Therefore, the markers 1-1, the markers 1-2, and the markers 1-3 installed at each of the plurality of measurement points are simultaneously imaged in one frame by the camera 2b.

When selecting a plurality of measurement points, the displacement distribution of the object to be measured may be calculated. Further, when a plurality of measurement points are selected, the influence of the shake of the camera 2b can be reduced by taking a relative displacement between a point having no displacement or a small displacement amount and the displacement amount at the reference point A1 in the same captured image. , The accuracy of displacement measurement can be expected to improve.

(Measurement of out-of-plane displacement by shooting from directly below the bridge)
With reference to FIGS. 10 to 15, out-of-plane displacement measurement by photographing from directly below the bridge will be described.
The deflection (out-of-plane displacement) of the bridge was measured by measuring the out-of-plane displacement by photographing from directly below the bridge by the method for measuring the out-of-plane displacement according to the present embodiment. The effectiveness of the out-of-plane displacement measuring method according to the present embodiment is confirmed by comparing with the measurement result by the conventional out-of-plane displacement measuring method as described in Patent Document 1.

FIG. 10 is a diagram showing an example of the bridge 3C to be measured according to the present embodiment. In the bridge 3C, the distance between the bridge girders is 30 meters, and the height from the floor slab of the bridge 3C to the ground is about 16 meters. A digital camera 2c is provided at the base of the pier of the bridge 3C.

FIG. 11 is a diagram showing an example of a displacement measurement setup according to the present embodiment.
In this embodiment, the marker 1c is used as a regular pattern of the grid marker for measurement. The marker 1c is a marker in which a set of diagonal grid pairs as shown in FIGS. 2 (c) and 7 (b) are repeatedly drawn at a predetermined pitch. The pitch and angle of the marker 1c are 71 mm, 45 degrees and 88 mm, -45 degrees, respectively.

FIG. 12 is a diagram showing an example of the installation position of the marker 1c according to the present embodiment. As the marker 1c, the marker 1c-1, the marker 1c-2, the marker 1c-3, the marker 1c-4, the marker 1c-A, and the marker 1c-B are installed at six positions on the bottom surface of the bridge 3C. In FIG. 12, as the marker 1c, an image in which the marker 1c-1, the marker 1c-2, the marker 1c-3, the marker 1c-4, the marker 1c-A, and the marker 1c-B are imaged is shown.

Of the 6 points on the bottom, 2 points on the pier side were used as reference points, and the remaining 4 points were used as measurement points for measurement. Markers 1c-1 and 1c-3 were installed at measurement points M1 and measurement points M3 located at the center of the bridge (1/2 point), respectively. Markers 1c-2 and 1c-4 were installed at measurement points M2 and measurement points M4 located at intermediate points (1/4 points) between the center of the bridge and the piers, respectively. Markers 1c-A and 1c-B were installed at reference points A and B located near the piers, respectively. The measurement point M1, the measurement point M2, and the reference point A are located directly below the up line of the train. The measurement point M3, the measurement point M4, and the reference point B are located directly below the down line of the train.

A digital camera 2c is installed directly under the bridge 3C, and a video is taken when the train passes the up line of the bridge with a lattice marker attached in advance to the floor slab of the bridge about 16 meters away from the digital camera 2c. , The out-of-plane displacement is measured by the sampling moire method. The shooting frame rate of the moving image is 24 fps as an example.

Since the train TR passes through the up line, the train TR passes directly above the measurement point M1, the measurement point M2, and the reference point A. In the bridge 3C, since in-plane displacement occurs in the x direction, it is assumed that in-plane displacement does not occur in the y direction, and the displacement in the out-of-plane direction is analyzed. Here, the x direction is the passing direction of the train TR. The y direction is a direction perpendicular to the passing direction of the train TR.

FIG. 13 is a diagram showing an example of a setting for displacement measurement in the y direction according to the present embodiment. The angle of view in the out-of-plane displacement calculation was calculated from the number of pixels on the image of FIG. 12 described above. The angles of view θ1 and θ2 in FIG. 13 were both 15 °.

In order to compare the out-of-plane displacement measurement method according to this embodiment with the conventional measurement method (displacement measurement from the facing direction), at the same time as the measurement by the out-of-plane displacement measurement method according to this embodiment, the distance from the bridge is 30 m. The side surface of the bridge (the side surface on the up line side) was photographed from the position, and the vertical displacement of the bridge was measured. The relationship between the measurement positions corresponds to the measurement point M1 of the out-of-plane displacement measurement method according to the present embodiment. In other words, a grid marker was installed on the up line side of the center of the bridge. Also in the conventional measurement method, a moving image was taken with a cinema camera in the same manner as in the out-of-plane displacement measurement method according to the present embodiment, and a two-dimensional dot grid marker having a grid pitch of 50 mm was used as the grid marker.

14 and 15 are diagrams showing an example of the measurement result of the out-of-plane displacement according to the present embodiment. FIG. 14A shows a graph of the amount of displacement under the same conditions by the conventional measurement method for comparison. FIG. 14B shows a graph of the displacement amount of the bridge when the out-of-plane displacement of the measurement point M1 is analyzed by the out-of-plane displacement measuring method according to the present embodiment. Further, FIG. 15A shows the measurement results of the measurement point M2 in FIG. 12, FIG. 15B shows the measurement results of the measurement point M3, and FIG. 15C shows the measurement results of the out-of-plane displacement at the measurement point M4.

Comparing FIGS. 14 (a) and 14 (b), the out-of-plane displacement measuring method and the conventional measuring method according to the present embodiment have obtained peak values of substantially the same amount of displacement, which is 10% as a whole. It was confirmed that the error was within. In the out-of-plane displacement measuring method according to the present embodiment, further improvement in accuracy can be expected by appropriately selecting the size, pitch and shape of the regular pattern.

From the measurement results of FIGS. 14 (b) and 15, it was confirmed that the out-of-plane displacement measuring method according to the present embodiment can simultaneously measure the displacements of a plurality of measurement points when the train TR passes. This is an advantage not found in conventional measurement methods. Comparing FIG. 14 (b) and FIG. 15 (a), that is, comparing the measurement point M1 and the measurement point M2, the peak value of the waveform is almost half, and the measurement point M2 (1/4 of the bridge). It was confirmed that a reasonable value was obtained as the displacement amount of the point).

Comparing the analysis results shown in FIGS. 14 and 15, the difference between the displacement on the side through which the train TR has passed and the displacement on the side through which the train TR has not passed can be seen. That is, it can be confirmed that the displacements of the measurement points M3 and the measurement points M4 are smaller than those of the measurement points M1. From the above results, it was confirmed that a single camera can measure highly accurate out-of-plane displacement in the entire field of view even if it is far away from the object.

As described above, the displacement measuring device according to the present embodiment (in this example, the out-of-plane displacement measuring device 10) includes an image acquisition unit 120, a pitch information acquisition unit 121, an angle information acquisition unit 122, and a surface. It includes an internal displacement calculation unit 124 and an out-of-plane displacement calculation unit 125.
The image acquisition unit 120 is an image in which a predetermined pattern is repeatedly drawn at a predetermined pitch p, and the marker 1 formed on the surface of the object 3 for which the displacement is calculated is captured (in this example, in this example). Image data PD) is acquired.
The pitch information acquisition unit 121 acquires the pitch information PI indicating the pitch p of the marker 1.
The angle information acquisition unit 122 acquires the angle information AI indicating the angle θ formed by the direction of the optical axis of the imaging unit 20 and the direction of the object 3 with respect to the imaging unit 20.
The phase calculation unit 123 uses the image acquisition unit 20 based on the image acquired by the image acquisition unit 120 (image data PD in this example) and the pitch p indicated by the pitch information PI acquired by the pitch information acquisition unit 121. The in-plane displacement Δy, which is the apparent displacement in the image captured by the image, and is the displacement in a predetermined direction among the directions parallel to the imaging surface on which the marker 1 is imaged, is calculated.
The out-of-plane displacement calculation unit 125 is perpendicular to the imaging surface based on the angle θ indicated by the angle information AI acquired by the angle information acquisition unit 122 and the in-plane displacement Δy calculated by the in-plane displacement calculation unit 124. The out-of-plane displacement Δz, which is the displacement in the direction, is calculated.

With this configuration, in the displacement measuring device according to the present embodiment (in this example, the out-of-plane displacement measuring device 10), the in-plane displacement Δy higher than the measurement accuracy of the out-of-plane displacement Δz is calculated and the in-plane displacement Δy is calculated. Since it can be converted into the out-of-plane displacement Δz, the measurement accuracy of the out-of-plane displacement Δz of the object 3 can be improved.

With the conventional method of measuring out-of-plane displacement, when the distance between the object and the camera is large, the change in the pitch of the regular pattern cannot be sufficiently captured, and it is difficult to measure the out-of-plane displacement with sufficiently high accuracy. there were. The measurement accuracy of the out-of-plane displacement is generally 10 times lower than the measurement accuracy of the in-plane displacement and is about 1/100 of the pitch, and the measurement accuracy decreases as the distance increases.
The displacement measuring device according to the present embodiment (in this example, the out-of-plane displacement measuring device 10) is particularly effective when measuring the out-of-plane displacement Δz of the object 3 located at a position away from the imaging unit 20. The displacement measuring device according to the present embodiment (in this example, the out-of-plane displacement measuring device 10) can measure a minute in-plane displacement distribution with an accuracy of 1/1000 of the pitch.

Further, in the displacement measuring device according to the present embodiment (in this example, the out-of-plane displacement measuring device 10), when the installation of the camera and the lattice marker is restricted and it is difficult to measure the displacement of the object, the camera and the lattice marker are used. It can give flexibility to the installation and relax the restrictions in measuring the displacement of an object.

In the conventional method of measuring out-of-plane displacement, when the object to be measured is a bridge, when the pier is several meters or tens of meters and the pier is high like a viaduct, not only sufficient accuracy cannot be obtained. Since it is necessary to install the camera directly under the center of the bridge, it is difficult to install the camera when the bridge straddles a river or valley.

On the other hand, in the displacement measuring device according to the present embodiment (in this example, the out-of-plane displacement measuring device 10), it is not necessary to arrange the camera at a position facing the measurement position, so that the camera is installed in the measurement of the structure. Since the displacement and vibration of the structure can be measured even in a difficult place, the displacement and vibration of various structures can be measured with less restrictions on the place in the measurement as compared with the conventional case. For this reason, it is particularly effective for measuring the deflection of bridges such as viaducts and highways through which trains pass.

Further, in the displacement measuring device according to the present embodiment (in this example, the out-of-plane displacement measuring device 10), the predetermined direction is the direction in which the displacement of the object 3 is the smallest among the directions parallel to the imaging surface (in this example). , Y direction).
With this configuration, the displacement measuring device according to the present embodiment (in this example, the out-of-plane displacement measuring device 10) can minimize the error of the apparent in-plane displacement Δy used for calculating the out-of-plane displacement Δz. The measurement accuracy of the out-of-plane displacement Δz can be improved as compared with the case where the predetermined direction is parallel to the imaging surface and the displacement of the object 3 is not the smallest. Here, the error of the apparent in-plane displacement Δy is an error with respect to the case where the in-plane displacement Δy is zero.

Further, in the displacement measuring device according to the present embodiment (in this example, the out-of-plane displacement measuring device 10), the out-of-plane displacement calculation unit 125 obtains the in-plane displacement Δy calculated by the in-plane displacement calculation unit 124 as angle information. The out-of-plane displacement Δz is calculated by dividing by the tangent of the angle θ indicated by the angle information AI acquired by the acquisition unit 122.
With this configuration, in the displacement measuring device according to the present embodiment (in this example, the out-of-plane displacement measuring device 10), the angle is when the measurement point of the object 3 is located at a position deviated by an angle θ from the optical axis of the imaging unit 20. Since the out-of-plane displacement Δz can be calculated by correcting the deviation of θ, the measurement accuracy of the out-of-plane displacement Δz can be improved as compared with the case where the out-of-plane displacement Δz is not calculated by dividing the in-plane displacement Δy by the tangent of the angle θ. Can be improved.

A part of the displacement measuring device in the above-described embodiment, for example, the image acquisition unit 120, the pitch information acquisition unit 121, the angle information acquisition unit 122, the phase calculation unit 123, the in-plane displacement calculation unit 124, and the out-of-plane displacement calculation. The unit 125 may be realized by a computer. In that case, the program for realizing this control function may be recorded on a computer-readable recording medium, and the program recorded on the recording medium may be read by the computer system and executed. The "computer system" referred to here is a computer system built in the out-of-plane displacement measuring device 10, and includes hardware such as an OS and peripheral devices. Further, the "computer-readable recording medium" refers to a portable medium such as a flexible disk, a magneto-optical disk, a ROM, or a CD-ROM, or a storage device such as a hard disk built in a computer system. Furthermore, a "computer-readable recording medium" is a medium that dynamically holds a program for a short period of time, such as a communication line when a program is transmitted via a network such as the Internet or a communication line such as a telephone line. In that case, a program may be held for a certain period of time, such as a volatile memory inside a computer system serving as a server or a client. Further, the above-mentioned program may be a program for realizing a part of the above-mentioned functions, and may be a program for realizing the above-mentioned functions in combination with a program already recorded in the computer system.
Further, a part or all of the out-of-plane displacement measuring device 10 in the above-described embodiment may be realized as an integrated circuit such as an LSI (Large Scale Integration). Each functional block of the out-of-plane displacement measuring device 10 may be made into a processor individually, or a part or all of them may be integrated into a processor. Further, the method of making an integrated circuit is not limited to LSI, and may be realized by a dedicated circuit or a general-purpose processor. Further, when an integrated circuit technology that replaces an LSI appears due to advances in semiconductor technology, an integrated circuit based on this technology may be used.

Although one embodiment of the present invention has been described in detail with reference to the drawings, the specific configuration is not limited to the above, and various design changes and the like are made without departing from the gist of the present invention. It is possible to do.

Since the present invention can analyze the out-of-plane displacement of an object even when photographed from a long distance based on a phase analysis method such as the sampling moire method, restrictions on the image capturing location are relaxed and the range in which the displacement of the structure can be measured is expanded. It can be expanded.

For example, when a bridge straddles a river, a valley, the sea, or the like, a camera can be installed at the base of the pier for measurement, so that displacement can be measured in a place that was difficult with the conventional method.

In addition, since the camera is installed under the bridge, the effect on rain and snow measurements can be reduced.

Since the present invention obtains the out-of-plane displacement from the amount of in-plane displacement obtained by a phase analysis method such as the sampling moire method, the conventional measurement method can be used even when the distance between the camera and the object to be measured is large. Compared to this, it is possible to measure displacement with higher accuracy.

In the above-described embodiment, the deflection measurement of the bridge structure is shown as an example, but the present invention can also be applied to the out-of-plane displacement measurement of a small-scale structure.

10 ... Out-of-plane displacement measuring device, 120 ... Image acquisition unit, 121 ... Pitch information acquisition unit, 122 ... Angle information acquisition unit, 124 ... In-plane displacement calculation unit, 125 ... Out-of-plane displacement calculation unit, 20 ... Imaging unit, 1 ... marker, 3 ... object

Claims (5)

An image acquisition unit in which a predetermined pattern is repeatedly drawn at a predetermined pitch, and a marker formed on the surface of an object for which displacement is calculated acquires an image captured by the imaging unit.
A pitch information acquisition unit that acquires pitch information indicating the pitch of the marker, and
An angle information acquisition unit that acquires angle information indicating an angle formed by the direction of the optical axis of the imaging unit and the direction of the object with respect to the imaging unit.
Based on the image acquired by the image acquisition unit and the pitch indicated by the pitch information acquired by the pitch information acquisition unit, which is an apparent displacement in the image and the marker is imaged. An in-plane displacement calculation unit that calculates in-plane displacement, which is a displacement in a predetermined direction among the directions parallel to the surface,
Out-of-plane displacement, which is a displacement in a direction perpendicular to the imaging surface, based on the angle indicated by the angle information acquired by the angle information acquisition unit and the in-plane displacement calculated by the in-plane displacement calculation unit. Out-of-plane displacement calculation unit that calculates displacement,
Displacement measuring device. The displacement measuring device according to claim 1, wherein the predetermined direction is a direction in which the displacement of the object is the smallest among the directions parallel to the imaging surface. The out-of-plane displacement calculation unit divides the in-plane displacement calculated by the in-plane displacement calculation unit by the tangent of the angle indicated by the angle information acquired by the angle information acquisition unit, thereby causing the out-of-plane displacement. The displacement measuring device according to claim 1 or 2. An image acquisition process in which a predetermined pattern is a marker repeatedly drawn at a predetermined pitch, and a marker formed on the surface of an object for which displacement is calculated acquires an image captured by an imaging unit.
A pitch information acquisition process for acquiring pitch information indicating the pitch of the marker, and
An angle information acquisition process for acquiring angle information indicating an angle formed by the direction of the optical axis of the imaging unit and the direction of the object with respect to the imaging unit.
Based on the image acquired by the image acquisition process and the pitch indicated by the pitch information acquired by the pitch information acquisition process, which is an apparent displacement in the image and the marker is imaged. The in-plane displacement calculation process for calculating the in-plane displacement, which is the displacement in a predetermined direction among the directions parallel to the plane, and
Out-of-plane displacement, which is a displacement in a direction perpendicular to the imaging surface, based on the angle indicated by the angle information acquired by the angle information acquisition process and the in-plane displacement calculated by the in-plane displacement calculation process. Out-of-plane displacement calculation process to calculate displacement and
Displacement measurement method having. On the computer
An image acquisition step in which a predetermined pattern is a marker repeatedly drawn at a predetermined pitch, and a marker formed on the surface of an object for which displacement is calculated acquires an image captured by an imaging unit.
A pitch information acquisition step for acquiring pitch information indicating the pitch of the marker, and
An angle information acquisition step for acquiring angle information indicating an angle formed by the direction of the optical axis of the imaging unit and the direction of the object with respect to the imaging unit.
Based on the image acquired by the image acquisition step and the pitch indicated by the pitch information acquired by the pitch information acquisition step, the image is an apparent displacement in the image and the marker is imaged. An in-plane displacement calculation step that calculates an in-plane displacement, which is a displacement in a predetermined direction among the directions parallel to the surface, and
Out-of-plane displacement, which is a displacement in a direction perpendicular to the imaging surface, based on the angle indicated by the angle information acquired by the angle information acquisition step and the in-plane displacement calculated by the in-plane displacement calculation step. Out-of-plane displacement calculation step to calculate displacement and
A program to execute.