JP6751930B1 - Displacement measuring device and displacement measuring method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a displacement measuring device and a displacement measuring method capable of measuring a displacement of a marker (and thus an object) with a small processing load or a storage capacity. An internal marker creating unit creates a marker image having a predetermined inclination in the plane direction of an image as an internal marker image 35 with respect to a reference marker image captured by the imaging unit. The moire image creating unit has the same internal marker image as the measurement marker image 36 captured by the imaging unit at the first time point and the measurement marker image 36 captured by the imaging unit at the second time point. By superimposing 35, two moire images 37 are created respectively. The detection unit detects the phase difference of the phase of each moire fringe included in the two moire images, and the displacement amount of the marker generated between the first time point and the second time point based on the detected phase difference. Is detected. [Selection diagram] Fig. 5

Description

The present invention relates to a displacement measuring device and a displacement measuring method, and relates to, for example, a technique for measuring displacement by using a moire method.

Patent Document 1 discloses a displacement acquisition device that makes it possible to reduce an error due to the inclination of the target surface or the measurement direction when measuring the displacement of the measurement point on the target surface by using the sampling moire method. Patent Document 2 discloses a method of measuring in-plane displacement and out-of-plane displacement (displacement in the z (depth) direction) of an object by using a sampling moire method based on an image obtained from a single camera.

JP-A-2019-11984 International Publication No. 2017/0299005

For measuring the displacement of an object, in addition to the method using a classical surveying technique, a method using a laser or a light wave such as a total station for measuring the displacement in a non-contact or remote manner is known. Further, in recent years, a method is being used in which a marker having a periodic pattern such as a stripe pattern or a checker pattern is attached to an object, the marker is imaged by a camera, and computer analysis is performed on the marker image. .. As an analysis method at this time, a sampling moire method as shown in Patent Documents 1 and 2 is typically known.

In the sampling moiré method, a moiré image is formed by separately creating an image sampled by thinning out camera pixels based on a marker image. Further, by creating a similar image while sequentially shifting the sampling position, a plurality of moire images are formed. Then, based on the luminance distribution of the plurality of moire images, the phase of the moire fringes and the displacement amount of the object are calculated by performing an operation based on a predetermined calculation formula.

For example, by using such a sampling moiré method, it is possible to calculate the displacements generated at a plurality of measurement points in the mounting area of the marker on the object. However, in the sampling moiré method, since a complicated procedure is executed as described above, an increase in processing load and an increase in storage capacity may occur. Further, an analysis method with a small processing load has been proposed, but in this case, there may be a problem that the accuracy is different at each measurement point in the marker mounting area. On the other hand, for example, at a construction site such as a shaft construction, when measuring the displacement of the ground, the displacement information for each measurement point in the marker mounting area (and thus the deformation information in the object) is not particularly required. , The displacement information of the marker itself (and thus the movement information of the object itself) is often sufficient.

The present invention has been made in view of the above, and one of the objects thereof is to provide a displacement measuring device and a displacement measuring method capable of measuring the displacement of a marker (and thus an object) with a small processing load or storage capacity. To do.

A brief outline of the typical inventions disclosed in the present application is as follows.

Displacement measuring devices according to a typical embodiment of the present invention include an imaging unit that captures a marker on which a periodic pattern is written, and a displacement measuring unit that measures the displacement of the marker based on the marker image captured by the imaging unit. , Have. The displacement measurement unit includes an internal marker creation unit, a moire image creation unit, and a detection unit. The internal marker creating unit creates a marker image having a predetermined inclination in the plane direction of the image as an internal marker image with respect to the reference (measurement) marker image captured by the imaging unit. The moire image creation unit is an internal marker creation unit for the first marker image captured by the imaging unit at the first time point and the second marker image captured by the image pickup unit at the second time point. A first moire image and a second moire image are created by superimposing the same internal marker images created. The detection unit detects the phase difference between the phase of the moire fringes included in the first moire image and the phase of the moire fringes included in the second moire image, and based on the detected phase difference, the first time point and The amount of displacement of the marker generated between the second time point and the second time point is detected.

Among the inventions disclosed in the present application, the effects obtained by typical ones will be briefly described as follows. According to a typical embodiment of the present invention, the displacement of a marker (and thus an object) can be measured with a small processing load or storage capacity.

(A) is a schematic diagram showing a configuration example of a displacement measurement system according to an embodiment of the present invention, and (b) and (c) are schematic views showing different configuration examples of markers in (a). is there. It is a block diagram which shows the schematic structure example of the displacement measuring apparatus in FIG. It is a block diagram which shows the detailed structure example of the main part of the displacement measurement part in FIG. It is a figure explaining an example of the processing content of the internal marker creation part in FIG. It is a figure explaining an example of the processing content of the moire image creation part in FIG. It is a figure explaining an example of the processing content of the detection part in FIG. It is a figure explaining an example of the processing content following FIG. It is a flow chart which shows an example of the processing content in the displacement measurement method by one Embodiment of this invention. (A) and (b) are diagrams showing an example of the verification result obtained by the operation verification of the displacement measurement system of FIG. 1 (a).

Hereinafter, embodiments of the present invention will be described with reference to the drawings. It should be noted that the disclosure is merely an example, and those skilled in the art can easily conceive of appropriate changes while maintaining the gist of the invention are naturally included in the scope of the present invention. Further, in order to clarify the explanation, the drawings may schematically represent the width, thickness, shape, etc. of each part as compared with the actual embodiment, but this is just an example, and the interpretation of the present invention is used. It is not limited.

Further, in the present specification and each figure, the same elements as those described above with respect to the above-mentioned figures may be designated by the same reference numerals, and detailed description thereof may be omitted as appropriate.

<< Outline of displacement measurement system >>
1 (a) is a schematic view showing a configuration example of a displacement measurement system according to an embodiment of the present invention, and FIGS. 1 (b) and 1 (c) are markers in FIG. 1 (a), respectively. It is a schematic diagram which shows a different configuration example. The displacement measurement system shown in FIG. 1A includes a marker 1 mounted on an object 3 and a displacement measurement device 2 including an imaging unit such as a camera.

The object 3 is, for example, a building installed on the ground at a construction site such as a shaft construction, or the ground itself. The displacement measuring device 2 takes an image of the marker 1 mounted on such an object 3 and measures the displacement of the marker 1 (and thus the displacement of the ground) based on the captured marker image. As a result, the displacement state of the ground can be monitored, and for example, signs of an accident such as a landslide can be detected at an early stage. As a result, accidents can be prevented and the safety of workers can be ensured.

Here, in the specification, as shown in FIG. 1A, the optical axis direction of the camera (displacement measuring device 2) is the Z axis, and one direction (horizontal direction) is provided in the plane direction of the plane orthogonal to the Z axis. ) Is the X-axis, and the direction orthogonal to the one direction (vertical direction) is the Y-axis. The camera (displacement measuring device 2) is installed so that the surface of the marker 1 is the XY surface. A periodic pattern is written on the surface (XY surface) of the marker 1 as shown in FIG. 1 (b) or FIG. 1 (c).

The marker 1a shown in FIG. 1B is marked with a striped pattern extending in the Y direction and arranged at equal intervals at a pitch W along the X direction. However, instead of the striped pattern arranged in the X direction in this way, the striped pattern arranged in the Y direction may be used. Alternatively, a marker having a striped pattern arranged in the X direction and a marker having a striped pattern arranged in the Y direction may be used as a set of markers. These are used properly depending on the measurement direction of displacement.

The marker 1b shown in FIG. 1C is marked with a checker pattern in which only the intersections of black level lines installed at equal intervals at pitch W in an array are defined as black levels. In this case, for example, by performing averaging processing along the Y direction using image processing, a striped pattern arranged in the X direction (that is, a pattern as shown in FIG. 1B) can be generated, and the X direction can be generated. By performing the averaging process along the above, a striped pattern arranged in the Y direction can be generated. As a result, in image processing, the marker 1b can be regarded as a marker having a stripe pattern arranged in the X direction or a marker having a stripe pattern arranged in the Y direction.

<< Outline of displacement measuring device >>
FIG. 2 is a block diagram showing a schematic configuration example of the displacement measuring device in FIG. The displacement measuring device 2 shown in FIG. 2 includes an imaging unit 10 that captures the marker 1 and a displacement measuring unit 20 that measures the displacement of the marker 1 (and thus the object 3) based on the marker image captured by the imaging unit 10. Be prepared. The image pickup unit 10 is typically a digital camera or the like. The displacement measuring unit 20 is, for example, an information processing device such as a PC (Personal Computer), a dedicated image processing device, or the like. However, the imaging unit 10 and the displacement measuring unit 20 may be mounted in the same device in the form of, for example, an information processing device with a camera.

The imaging unit 10 includes a lens 11, an image sensor 12, a calculation unit 13, a data storage unit 14, and a communication interface 15. Of these, the arithmetic unit 13, the data storage unit 14, and the communication interface 15 are connected to each other by a bus. The arithmetic unit 13, the data storage unit 14, and the communication interface 15 may be mounted on, for example, one microcontroller.

The lens 11 collects the light from the marker 1 on the image sensor 12. The image sensor 12 is typically a CMOS (Complementary Metal Oxide Semiconductor) image sensor, a CCD (Charge Coupled Device) image sensor, or the like, and includes a plurality of pixels arranged in an array. Each pixel of the image sensor 12 generates an electric signal according to the amount of light focused by the lens 11. The image sensor 12 transmits the electric signal generated by each pixel to the calculation unit 13.

The data storage unit 14 is, for example, a non-volatile memory such as a flash memory, and corresponds to an internal memory in a microcontroller or an external memory such as a memory card. The calculation unit 13 receives an electric signal from the image sensor 12 to generate a marker image, and stores the generated marker image in the data storage unit 14. At this time, the calculation unit 13 may store the marker image in the data storage unit 14 after adding the information of the imaging time.

The arithmetic unit 13 includes a processor 13a such as a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), or a DSP (Digital Signal Processor), and a RAM (Random Access Memory) 13b. The processor 13a creates, for example, a marker image corresponding to an electric signal from the image sensor 12 by executing a predetermined program expanded from the data storage unit 14 to the RAM 13b.

The communication interface 15 transmits / receives data to / from the displacement measuring unit 20 (communication interface 21 in the communication interface 21). As one of them, the communication interface 15 transmits the marker image stored in the data storage unit 14 to the displacement measurement unit 20. The communication interface 15 and the communication interface 21 are connected by wire or wirelessly. In this case, for example, a form connected via an external network such as the Internet may be used.

When using an external network, for example, an imaging unit 10 provided with a communication interface 15 for wireless communication is fixedly installed at a construction site, and a displacement measuring unit 20 is mounted on an in-house server device of a construction company or the like. The morphology is beneficial. In this case, the imaging unit 10 sequentially transmits the captured marker images to the in-house server device via the external network, and the in-house server device performs displacement measurement based on the marker image.

The displacement measurement unit 20 includes a calculation unit 22, a data storage unit 23, and a communication interface 21. The calculation unit 22, the data storage unit 23, and the communication interface 21 are connected to each other by a bus. For example, when the displacement measuring unit 20 is configured by a dedicated image processing device or the like, the calculation unit 22, the data storage unit 23, and the communication interface 21 may be mounted on one microcontroller. The data storage unit 23 is, for example, a non-volatile memory such as a flash memory or a hard disk drive. The communication interface 21 receives, for example, a marker image from the communication interface 15 and stores it in the data storage unit 23.

The calculation unit 22 includes a processor 22a such as a CPU, GPU, or DSP, and a RAM 22b. The calculation unit 22 measures the displacement of the object 3 by executing a predetermined image process on the marker image stored in the data storage unit 23, for example. At this time, the processor 22a performs displacement measurement by, for example, executing a displacement measurement program expanded from the data storage unit 23 to the RAM 22b. The arithmetic unit 22 is not limited to the processor 22a, and a part or all of the arithmetic unit 22 may be composed of hardware such as an FPGA (Field Programmable Gate Array) or an ASIC (Application Specific Integrated Circuit). That is, the calculation unit 22 may be appropriately configured by a software method, a hardware method, or a combination thereof. This also applies to the calculation unit 13 in the imaging unit 10.

<< Details of displacement measurement unit >>
FIG. 3 is a block diagram showing a detailed configuration example of the main portion of the displacement measuring unit in FIG. FIG. 4 is a diagram illustrating an example of the processing content of the internal marker creating unit in FIG. FIG. 5 is a diagram illustrating an example of processing contents of the moire image creating unit in FIG. In the displacement measurement unit 20 of FIG. 3, the processor 22a includes an internal marker creation unit 31, a moire image creation unit 32, and a detection unit 33, which are implemented by executing a displacement measurement program. Further, here, as the marker 1, a case where a marker 1a having a striped pattern as shown in FIG. 1B is used is taken as an example.

As shown in FIG. 4, the internal marker creating unit 31 creates a marker image having a predetermined inclination θ in the plane direction (direction of the XY plane) of the reference marker image 30 imaged by the imaging unit 10. , Created as an internal marker image 35. The predetermined slope θ may be a value of non-zero [°], and may be a value in the positive direction or a value in the negative direction. The internal marker creation unit 31 stores the created internal marker image 35 in the data storage unit 23.

The reference marker image 30 is a marker image captured by the imaging unit 10 at any time point, and is typically the first time point at which the time-series displacement measurement of the marker 1 (and thus the object 3) is started. It is a marker image imaged by the imaging unit 10 in. However, as will be described in detail later, the displacement of the marker 1 that occurs between different time points can be measured as long as the same internal marker image 35 is used. Therefore, for example, when measuring the relative displacement of the marker 1 generated between the two time points, the marker image captured at the first time point may be used as the reference marker image 30. It is also possible to use the generated marker image as the reference marker image 30.

As an example of the method of creating the internal marker image 35, as shown in FIG. 4, the internal marker creating unit 31 rotates the reference marker image 30 by θ in the plane direction (XY plane direction) of the image by image processing. By doing so, the internal marker image 35 is created. Further, as another example, at a certain point in time, the imaging unit 10 is installed in a state of being rotated by θ in the plane direction (direction of the XY plane), and the internal marker creating unit 31 is imaged by the imaging unit 10 in this installed state. The created marker image may be defined as the internal marker image 35 as it is. However, in practice, since the image pickup unit 10 is fixedly installed at a predetermined location, for example, from this viewpoint, a method of using image processing that does not require changing the installation state of the image pickup unit 10 is desirable.

Further, the internal marker creating unit 31 can also create the internal marker image 35 without capturing the reference marker image 30. Specifically, the periodic pattern included in the reference marker image 30 can be calculated by performing a simulation or the like in advance without actually performing imaging. Therefore, the internal marker creating unit 31 may create an internal marker image 35 (that is, a computer graphics (CG) image) by performing rotation processing or the like on the calculated periodic pattern.

Returning to FIG. 3, in the data storage unit 23, the measurement marker image [1] 36a captured by the imaging unit 10 at the time point [1] and the measurement marker image captured by the imaging unit 10 at the time point [2] [2] 36b and the like are stored. The moire image creating unit 32 creates an internal marker for each of the measurement marker image [1] 36a and the measurement marker image [2] 36b (referred to as the measurement marker image 36) as shown in FIG. The moire image 37 (that is, the moire image [1] and the moire image [2]) is created by superimposing the same internal marker image 35 created in the unit 31.

The detection unit 33 detects the phase difference between the phase of the moire fringes included in the moire image [1] and the phase of the moire fringes included in the moire image [2], and based on the detected phase difference, the moire image [ The amount of displacement of the marker 1 (and thus the object 3) generated between the time point [1] corresponding to [1] and the time point [2] corresponding to the moire image [2] is detected. Specifically, when the detected phase difference is Δα [rad], the detection unit 33 uses the known pitch (period) W [mm] in the marker 1a shown in FIG. 1 (b) to formula (1). ) Is used to calculate the displacement amount Δu.
Δu = (Δα / 2π) × W… (1)

<< Details of detector >>
FIG. 6 is a diagram illustrating an example of the processing content of the detection unit in FIG. FIG. 7 is a diagram illustrating an example of processing contents following FIG. As described above, the detection unit 33 receives the moire image 37 created by the moire image creation unit 32 and performs processing. Here, as shown in FIG. 6, the moire fringes included in the received moire image 37 have a substantially rectangular wavy luminance distribution 41 when viewed with pixels arranged in the Y direction. It is possible to detect the phase of the moiré fringes using such a luminance distribution 41, but from the viewpoint of facilitating the phase detection process and improving the accuracy, the luminance distribution of the moiré fringes is sinusoidal (or cosine wavy). ) Is desirable.

Therefore, as shown in FIG. 6, the detection unit 33 approximates the luminance distribution 41 of the moire image 37 with a trigonometric function along the Y direction. Specifically, the detection unit 33 approximates the brightness I of each pixel arranged in the Y direction by a trigonometric function (cos function in this example) shown in the equation (2). For this approximation, for example, the least squares method is used. In equation (2), "A" is the amplitude, "y" is the Y coordinate of the pixels arranged in the Y direction, "λ" is the wavelength (period) [pixel] of the moire fringes, and "α1". Is the initial phase and "B" is the background brightness.
I = A × cos {(y / λ) × 2π + α1} + B… (2)

As a result, the luminance distribution 41 is approximated like the luminance distribution 42. Then, the detection unit 33 approximates the entire moire image 37 along the Y direction with a trigonometric function by performing the approximation in the Y direction based on the equation (2) while sequentially changing the pixels in the X direction, and as a result. An intermediate image 43 is created. The trigonometric function is not limited to the cos function and may be a sin function.

As shown in FIG. 7, the intermediate image 43 has a luminance distribution 45 in which the luminance distribution with a short period associated with the stripe pattern is modulated by the period (wavelength) of the moire fringes when viewed with pixels arranged in the X direction. Be prepared. Therefore, as shown in FIG. 7, the detection unit 33 approximates the luminance distribution 45 of the intermediate image 43 with a trigonometric function along the X direction. Specifically, for example, the detection unit 33 approximates the brightness I of each pixel arranged in the X direction at the specified Y coordinate (Y0) by the trigonometric function (sin function in this example) shown in the equation (3). To do. For this approximation, for example, the least squares method is used. In equation (3), "A" is the amplitude, "x" is the X coordinate of the pixels arranged in the X direction, "λ" is the wavelength (period) [pixel] of the moire fringes, and "α2". Is the initial phase and "B" is the background brightness.
I = A × sin {(x / λ) × 2π + α2} + B… (3)

As a result, the luminance distribution 45 is approximated like the luminance distribution 46. The detection unit 33 detects the phase of the moire fringes based on the approximate luminance distribution 46. Then, as described above, the detection unit 33 determines the phase difference between the phase of the moire fringes detected on the moire image 37 at a certain time point and the phase of the moire fringes detected on the moire image 37 at another time point. By detecting and performing the calculation of the equation (1) using this phase difference (Δα), the displacement amount (for example, the displacement amount in the X direction) Δu of the object 3 is detected.

The trigonometric function of the equation (3) is not limited to the sin function, but may be a cos function. Further, in the example of FIG. 7, the detection unit 33 detected the phase of the moire fringes at the specified Y coordinate (Y0). However, the detection unit 33, for example, moves the Y coordinate in the range of “Y0 ± ΔY”, detects the phase of the moire fringes for each Y coordinate in the same manner, and calculates the average value thereof to obtain the final value. The phase may be determined. Thereby, for example, the detection error due to the influence of noise and the like can be reduced.

<< Displacement measurement method >>
FIG. 8 is a flow chart showing an example of processing contents in the displacement measurement method according to the embodiment of the present invention. For example, at the initial time when the time-series displacement measurement is started, the imaging unit 10 images the marker 1 of FIG. 1A in the specified installation state, and the displacement measuring unit 20 images the marker imaged by the imaging unit 10. The image is acquired as the reference marker image 30 of FIG. 4 (step S101). Subsequently, as shown in FIG. 4, the internal marker creating unit 31 creates the internal marker image 35 by performing rotation processing or the like on the reference marker image 30 (step S102).

Next, the moire image creating unit 32 creates a reference moire image by superimposing the internal marker image 35 on the reference marker image 30 as in the case of FIG. 5 (step S103). The detection unit 33 detects the reference phase of the moire fringes on the reference moire image through image processing as shown in FIGS. 6 and 7 (step S104).

After that, it is in a standby state until the displacement measurement time is reached (step S105). The displacement measurement time point may be arbitrarily determined by the user, or may be periodically determined by the displacement measuring device 2 based on an internal timer or the like (for example, once a day). When the displacement measurement time point is reached in step S105, the imaging unit 10 images the marker 1 of FIG. 1 (a) in the same installation state as in step S101, and the displacement measuring unit 20 images the marker imaged by the imaging unit 10. The image is acquired as the measurement marker image 36 of FIG. 5 (step S106).

Subsequently, as shown in FIG. 5, the moire image creation unit 32 creates a measurement moire image by superimposing the internal marker image 35 created in step S102 on the measurement marker image 36 (step S107). .. The detection unit 33 detects the measurement phase of the moire fringes on the measurement moire image through image processing as shown in FIGS. 6 and 7 (step S108).

Then, the detection unit 33 detects the phase difference between the reference phase detected in step S104 and the measurement phase detected in step S108, and displaces the marker 1 using the equation (1) based on the detected phase difference. The amount is detected (step S109). After that, the processes of steps S105 to S109 are repeatedly executed until the displacement measurement becomes unnecessary (step S110). As a result, in this example, the displacement amount of the marker 1 (and thus the object 3) from the initial time point is detected at each displacement measurement time point.

Here, an example is shown in which a reference marker image (internal marker image) is created at the initial stage and is used continuously thereafter. However, in some cases, for example, when detecting the phase difference (and thus the displacement amount) between two time points, it is possible to appropriately create a reference marker image (internal marker image). That is, an internal marker image is created by using one of the measurement marker images acquired at the two time points as a reference marker image, and the internal marker image is superimposed on the two measurement marker images, so that between the two time points. The generated phase difference (and thus the amount of displacement) can be detected. Further, as described above, the internal marker image 35 may be a computer graphics (CG) image created without imaging.

<< Operation verification result >>
9 (a) and 9 (b) are diagrams showing an example of verification results obtained by the operation verification of the displacement measurement system of FIG. 1 (a). In this example, the marker 1a of FIG. 1B and the image sensor 12 (FIG. 2) of 640 × 360 pixels (pixels) are used. FIG. 9A shows how the phase of the moire fringes changes sequentially when the marker 1a is moved in the X direction in the range of 0 to 30 [mm] in units of 5 [mm]. In this example, when the displacement amount exceeds 20 [mm], the phase of the moire fringes changes by one cycle or more.

The detection unit 33 detects the displacement amount of the marker 1a based on the phase difference of the phases of the moire fringes as shown in FIG. 9A. FIG. 9B shows the relationship between the actual displacement amount of the marker 1a and the displacement amount (detected value) detected (calculated) based on the phase difference of FIG. 9A. In the example of FIG. 9B, a detected value close to the ideal value is obtained.

<< Various variants >>
Here, a case where the displacement amount of the marker 1a in the X direction is detected by using the marker 1a on which the stripe pattern arranged in the X direction is described as shown in FIG. 1B has been described as an example. On the other hand, for example, by using a marker having a striped pattern arranged in the Y direction, it is possible to detect the displacement amount of the marker in the Y direction in the same manner.

Further, when the marker 1b on which the checker pattern as shown in FIG. 1C is used, the displacement measuring unit 20 arranges the marker image including the checker pattern in the X direction by image processing. It may be converted into a striped pattern arranged in the Y direction. Further, the displacement measuring unit 20 may create an internal marker image by rotating the marker image converted into the stripe pattern, for example. As a result, the displacement measuring unit 20 can measure the displacement (displacement in the X direction, the Y direction, or both directions) of the marker 1b (and thus the object 3) in the same manner as when the marker 1a is used.

<< Main effects of the embodiment >>
As described above, by using the displacement measuring device and the displacement measuring method of the embodiment, it becomes possible to typically measure the displacement of the marker 1 itself with a small processing load or storage capacity. That is, the displacement amount of the marker 1 (and thus the object 3) as a whole can be detected without using a complicated process such as the sampling moire method. As a result, for example, at a construction site such as a shaft construction, the displacement state of the ground can be monitored, and the safety of workers can be ensured.

Although the invention made by the present inventor has been specifically described above based on the embodiment, the present invention is not limited to the above embodiment and can be variously modified without departing from the gist thereof.

1,1a, 1b ... Marker, 2 ... Displacement measuring device, 3 ... Object, 10 ... Imaging unit, 20 ... Displacement measuring unit, 30 ... Reference marker image, 31 ... Internal marker creation unit, 32 ... Moire image creation unit, 33 ... Detection unit, 35 ... Internal marker image, 36, 36a, 36b ... Measurement marker image, 37 ... Moire image, 43 ... Intermediate image

Claims (10)

An imaging unit that captures a marker with a periodic pattern and
A displacement measuring unit that measures the displacement of the marker based on the marker image captured by the imaging unit,
It is a displacement measuring device having
The displacement measuring unit
An internal marker creating unit that creates a marker image having a predetermined inclination in the plane direction of the image as an internal marker image with respect to the reference marker image captured by the imaging unit.
The same as the first marker image captured by the imaging unit at the first time point and the second marker image captured by the imaging unit at the second time point created by the internal marker creating unit. A moire image creation unit that creates a first moire image and a second moire image by superimposing the internal marker images of the above.
The phase difference between the phase of the moire fringes included in the first moire image and the phase of the moire fringes included in the second moire image is detected, and the first time point and the above are based on the detected phase difference. A detection unit that detects the total displacement of the marker generated between the second time point and the second time point.
Have
Displacement measuring device. In the displacement measuring device according to claim 1,
The periodic pattern is a striped pattern.
Displacement measuring device. In the displacement measuring device according to claim 1,
The periodic pattern is a checkered pattern.
The displacement measuring unit converts the checker pattern into a striped pattern by image processing.
Displacement measuring device. In the displacement measuring device according to claim 1,
The internal marker creating unit creates the internal marker image by rotating the reference marker image in the plane direction of the image by image processing.
Displacement measuring device. In the displacement measuring device according to claim 1,
The detection unit creates an intermediate image by approximating the brightness distribution of the moire image created by the moire image creation unit with a trigonometric function along a first direction, which is one of the plane directions of the image. The moire fringes are obtained by approximating the brightness distribution of the intermediate image with a trigonometric function along a second direction which is one of the plane directions of the image and is orthogonal to the first direction. Detect phase,
Displacement measuring device. A marker with a periodic pattern and
An imaging unit that captures the marker and
A displacement measuring unit that measures the displacement of the marker based on the marker image captured by the imaging unit,
This is a displacement measurement method for measuring the displacement of the marker using the above.
The first step in which the displacement measuring unit creates a marker image having a predetermined inclination in the in-plane direction of the reference marker image captured by the imaging unit as an internal marker image.
A second step of acquiring a first marker image by imaging the marker with the imaging unit at the first time point, and
A third step in which the displacement measuring unit superimposes the internal marker image created in the first step on the first marker image to create a first moire image.
A fourth step of acquiring a second marker image by imaging the marker with the imaging unit at a second time point.
A fifth step in which the displacement measuring unit superimposes the internal marker image created in the first step on the second marker image to create a second moire image.
The displacement measuring unit detects the phase difference between the phase of the moire fringes included in the first moire image and the phase of the moire fringes included in the second moire image, and the phase difference is based on the detected phase difference. A sixth step of detecting the total displacement of the marker between the first time point and the second time point, and the sixth step.
Have
Displacement measurement method. In the displacement measuring method according to claim 6,
The periodic pattern is a striped pattern.
Displacement measurement method. In the displacement measuring method according to claim 6,
The periodic pattern is a checkered pattern.
The displacement measuring method further includes a step in which the displacement measuring unit converts the checker pattern into a striped pattern by image processing.
Displacement measurement method. In the displacement measuring method according to claim 6,
In the first step, the displacement measuring unit creates the internal marker image by rotating the marker image for reference in the plane direction of the image by image processing.
Displacement measurement method. In the displacement measuring method according to claim 6,
In the sixth step, the displacement measuring unit approximates the brightness distribution of the moire image created in the fifth step with a trigonometric function along the first direction, which is one of the plane directions of the image. By doing so, an intermediate image is created, and the brightness distribution of the intermediate image is trigonometrically applied along a second direction which is one of the plane directions of the image and is orthogonal to the first direction. By approximating, the phase of the moire fringes is detected.
Displacement measurement method.