Displacement Measuring Device

Abstract

To provide a displacement measurement device and a displacement measurement method that, with a small processing load, can measure displacement of a marker, that is, a measurement point, while reflecting displacement of an imaging apparatus itself.SOLUTION: A displacement measurement instrument 20 calculates the amount of displacement of a reference marker generated between a time point #1 and a time point #2 based on reference marker images 27r#1, 27r#2 obtained at the time point #1 and the time point #2. Similarly, the displacement measurement instrument 20 calculates the amount of displacement of a measurement marker generated between the time point #1 and the time point #2 based on measurement marker images 27m#1, 27m#2 obtained at the time point #1 and the time point #2. The displacement measurement instrument 20 calculates a correct amount of displacement Dm (x, y) of the measurement marker with the value of difference from the amount of displacement of the reference marker.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a displacement measuring device and a displacement measuring method. [Background technology]

[0002] Patent Document 1 discloses a method for measuring the displacement of a measurement object with high accuracy. In this method, an image captured at a first time point, including a reference position and a measurement position, and an image captured at a second time point, including the reference position and the measurement position, are acquired, and the displacement of the measurement position relative to the reference position that occurred between the first time point and the second time point is calculated based on these images. In this case, the positional relationship between the reference position and the measurement position is associated with association information such as a homogeneous transformation matrix, and the measurement position that appears in the image captured at the second time point is estimated based on the reference position in the image and the association information. The displacement of the measurement position is calculated based on the difference between the estimated measurement position and the actual measurement position that appears in the image.

[0003] Patent Document 2 discloses a method for determining the state of a columnar structure based on time-series image data of a predetermined pattern attached to the columnar structure, determining the displacement occurring in the columnar structure from the time-series image data, determining the natural frequency of the columnar structure from the displacement, and judging the state of the columnar structure based on the natural frequency. The digital image correlation method or the moire fringe phase analysis method is used to determine the displacement occurring in the columnar structure.

[0004] Patent Document 3 discloses a method for reducing errors due to the tilt of the target surface or the measurement direction when measuring the displacement of a measurement point on the target surface using the sampling moiré method. Patent Document 4 discloses a method for measuring the in-plane displacement and out-of-plane displacement of an object using the sampling moiré method based on an image obtained from a single camera. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2018 / 56206 [Patent Document 2] Japanese Patent Application Publication No. 2018-141663 [Patent Document 3] Japanese Patent Application Publication No. 2019-11984 [Patent Document 4] International Publication No. 2017 / 029905 Summary of the Invention [Problem to be solved by the invention]

[0006] In recent years, technology for measuring the displacement of an object based on images captured by an imaging device has been developed. This technology involves capturing an image of a marker attached to an object and then performing various image processing on the captured image to calculate the displacement of the marker and, ultimately, the object. Compared to using dedicated surveying equipment such as a total station, this technology can reduce equipment costs and improve work efficiency through automation. Furthermore, various advantages are achieved, such as the ability to record measurement results not only as numerical values ​​but also in the form of images, the ability to perform continuous measurements using an infrared camera, and the ability for the imaging device to double as a surveillance camera.

[0007] For example, at a construction site or the like, it may be necessary to measure displacement at multiple measurement points on a single or multiple objects. In this case, for example, images of multiple markers attached to the multiple measurement points may be captured. Furthermore, by using one of the multiple markers as a reference marker attached to a fixed point, it becomes possible to measure the displacement of the imaging device itself, which can be a problem particularly during long-term measurements. However, capturing images of multiple markers generally requires a long imaging distance. In this case, there is a risk that the angle of view will become narrower or the resolution of the imaging surface will decrease.

[0008] Therefore, for example, it is possible to use the method disclosed in Patent Document 1. Patent Document 1 describes capturing images of the reference position and the measurement position with separate cameras. However, using the method of Patent Document 1 requires complex arithmetic processing associated with association information such as a homogeneous transformation matrix. This could increase the processing load.

[0009] The present invention has been made in consideration of the above, and one of its objectives is to provide a displacement measurement device and a displacement measurement method that can measure the displacement of a marker, and ultimately a measurement point, while reflecting the displacement of the imaging device itself, with a small processing load. [Means for solving the problem]

[0010] Among the inventions disclosed in this application, the outline of representative inventions will be briefly explained as follows.

[0011] A displacement measurement device according to a representative embodiment of the present invention includes a first imaging device and a second imaging device that capture images of markers attached to measurement points of one or more objects, and a displacement measuring instrument that measures the displacement of the markers based on images captured by the first imaging device and the second imaging device. The first imaging device captures images of a reference marker attached to a measurement point treated as a fixed point at a first time point and a second time point to create a first reference marker image and a second reference marker image, respectively. The second imaging device captures images of a measurement marker attached to a predetermined measurement point at the first time point and the second time point to create a first measurement marker image and a second measurement marker image, respectively. The displacement measuring instrument calculates the amount of displacement of the reference marker that occurred between the first and second time points based on the first reference marker image and the second reference marker image, calculates the amount of displacement of the measurement marker that occurred between the first and second time points based on the first measurement marker image and the second measurement marker image, and calculates the correct amount of displacement of the measurement marker as the difference value from the amount of displacement of the reference marker. [Effects of the Invention]

[0012] To briefly explain the effect obtained by a representative invention among those disclosed in this application, it becomes possible to measure the displacement of the marker, and therefore the measurement point, while reflecting the displacement of the imaging device itself, with a small processing load. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a schematic diagram showing an example of the configuration of a displacement measuring system according to a first embodiment. [Figure 2] 2 is a schematic diagram showing an example of a marker image created by the imaging device in FIG. 1. FIG. [Figure 3] FIG. 2 is a block diagram showing a schematic configuration example of the displacement measuring device in FIG. [Figure 4] FIG. 4 is a block diagram showing an example of a schematic configuration of a main part of the displacement measuring instrument shown in FIG. 3. [Figure 5A] 5 is a schematic diagram illustrating an example of processing details of a displacement amount calculation unit in FIG. 4. FIG. [Figure 5B] 5 is a schematic diagram illustrating an example of processing details of a displacement amount calculation unit in FIG. 4. FIG. [Figure 5C] 5 is a schematic diagram illustrating an example of processing details of a displacement amount calculation unit in FIG. 4. FIG. [Figure 6] FIG. 5 is a block diagram showing an example of the configuration of a sampling moiré unit in FIG. 4. [Figure 7] 7 is a schematic diagram illustrating an example of processing content of a phase detection unit in FIG. 6. FIG. [Figure 8] 10 is a schematic diagram showing an example of a marker image created by the imaging device in FIG. 1 in the displacement measuring device according to the second embodiment. FIG. [Figure 9] FIG. 4 is a block diagram showing a schematic configuration example of a main part of the displacement measuring device in FIG. 3 in the displacement measuring device according to the second embodiment. [Figure 10] 10 is a block diagram showing an example of the configuration of a phase-only correlation unit in FIG. 9. FIG. [Figure 11] 10 is a schematic diagram showing an example of a marker image created by the imaging device in FIG. 1 in the displacement measuring device according to the third embodiment. FIG. [Figure 12] FIG. 4 is a block diagram showing a schematic configuration example of a main part of the displacement measuring device in FIG. 3 in the displacement measuring device according to the third embodiment. [Figure 13] 13 is a conceptual diagram illustrating an example of processing details of a displacement amount calculation unit in FIG. 12. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, each embodiment of the present invention will be described with reference to the drawings. Note that the disclosure is merely an example, and any appropriate modifications that a person skilled in the art can easily conceive while maintaining the gist of the invention are naturally included within the scope of the present invention. Furthermore, in order to clarify the explanation, the drawings may show the width, thickness, shape, etc. of each part schematically compared to the actual embodiment, but these are merely examples and do not limit the interpretation of the present invention.

[0015] Furthermore, in this specification and each drawing, elements similar to those previously described with respect to the preceding drawings are given the same reference numerals, and detailed descriptions thereof may be omitted as appropriate.

[0016] (Embodiment 1) <Outline of the displacement measurement system> Fig. 1 is a schematic diagram showing an example of the configuration of a displacement measurement system according to a first embodiment. Fig. 2 is a schematic diagram showing an example of a marker image created by the imaging device in Fig. 1. The displacement measurement system shown in Fig. 1 has multiple markers 1r, 1m attached to one or multiple objects 3[1], 3[2], and a displacement measurement device 2. In this specification, the multiple markers 1r, 1m are collectively referred to as markers 1. The objects 3[1], 3[2] are, for example, structures installed on the ground at a construction site such as a shaft construction site, or the ground itself.

[0017] The displacement measurement device 2 comprises multiple imaging devices 10[1], 10[2] and a displacement measuring instrument 20. The displacement measurement device 2 captures an image of a marker 1 using the imaging devices 10[1], 10[2] and measures the displacement of the marker 1, and therefore the displacement of structures, the ground, etc., based on the captured image. This allows for continuous monitoring of the displacement status of structures, the ground, etc., and enables early detection of signs of accidents such as the collapse of structures or landslides. As a result, accidents can be prevented before they occur, and the safety of workers can be ensured.

[0018] Marker 1r is a reference marker attached to a measurement point treated as a fixed point. On the other hand, markers 1m other than reference marker 1r are measurement markers attached to actual measurement points. For example, displacement may occur not in marker 1 but in the installation angle of the imaging devices 10[1] and 10[2]. By providing reference marker 1r, it becomes possible to detect displacement of such imaging devices 10[1] and 10[2] themselves.

[0019] Here, the imaging device 10[1] captures images of the reference marker 1r at time #1 and time #2, thereby creating two reference marker images. Meanwhile, the imaging device 10[2] captures images of the measurement marker 1m at time #1 and time #2, thereby creating two measurement marker images. The imaging devices 10[1] and 10[2] are installed, for example, on a common support 4 via a highly rigid mounting member or the like. In this case, the relative displacement between the imaging devices 10[1] and 10[2] is zero, and if the imaging device 10[1] is displaced, a similar displacement will also occur in the imaging device 10[2].

[0020] The displacement measuring instrument 20 calculates the amount of displacement of the reference marker 1r that occurred between time #1 and time #2 based on the two reference marker images created by the imaging device 10[1]. Similarly, the displacement measuring instrument 20 calculates the amount of displacement of the measurement marker 1m that occurred between time #1 and time #2 based on the two measurement marker images created by the imaging device 10[2]. Then, the displacement measuring instrument 20 calculates the correct amount of displacement of the measurement marker 1m as the difference value from the amount of displacement of the reference marker 1r. This makes it possible for the displacement measuring instrument 20 to calculate the correct amount of displacement of the measurement marker 1m after reflecting the displacement of the imaging device 10[2] itself.

[0021] The number of imaging devices is not limited to two, and may be three or more. In this case, for example, a third imaging device is attached to the common support 4 shown in FIG. 1 in addition to the imaging devices 10[1] and 10[2]. The third imaging device images a measurement marker different from that of the imaging device 10[2]. The displacement measuring instrument 20 then calculates the correct displacement amount of the measurement marker as a difference value from the displacement amount of the reference marker 1r.

[0022] In the specification, as shown in Figure 1, the approximate optical axis direction of the imaging devices 10[1] and 10[2] is defined as the Z axis, and in the plane direction perpendicular to the Z axis, one direction, here the horizontal direction, is defined as the X axis, and the direction perpendicular to that one direction, here the vertical direction, is defined as the Y axis. Multiple markers 1r and 1m are attached so that the XY plane is imaged. The imaging devices 10[1] and 10[2] respectively image the markers 1r and 1m, which have patterns written on the XY plane, to create a marker image 27 as shown in Figure 2.

[0023] The marker image 27 shown in FIG. 2 includes a marker 1A corresponding to the reference marker 1r or the measurement marker 1m. A periodic pattern is inscribed on the marker 1A. By using the periodic pattern, the displacement of the marker 1 can be measured using a sampling moiré method, which will be described later. In this example, the periodic pattern is a lattice pattern, in which black level squares are arranged at equal intervals in the X-axis direction and the Y-axis direction, sandwiching white level squares. The pitch of the black level or white level squares in the X-axis direction is Wx [mm], and the pitch in the Y-axis direction is Wy [mm], and the pitches Wx and Wy may be, for example, several mm to several tens of mm.

[0024] Furthermore, the grid pattern shown in FIG. 2 is essentially equivalent to a stripe pattern aligned in the X-axis direction or the Y-axis direction. That is, by performing image processing on the grid pattern, specifically averaging processing along the Y-axis direction, it can be converted into a stripe pattern aligned in the X-axis direction. Similarly, by performing image processing on the grid pattern, specifically averaging processing along the X-axis direction, it can be converted into a stripe pattern aligned in the Y-axis direction. Note that the periodic pattern is not limited to a grid pattern, and may be such a stripe pattern.

[0025] <Outline of displacement measurement device> Fig. 3 is a block diagram showing a schematic configuration example of the displacement measuring device in Fig. 1. The displacement measuring device 2 shown in Fig. 3 includes two imaging devices 10[1] and 10[2] and a displacement measuring instrument 20 realized by an information processing device such as a PC (Personal Computer) or a dedicated image processing device. These can be realized in various forms, for example, each being configured as a stand-alone device, or by mounting the imaging device 10[1] and the displacement measuring instrument 20 in the same device in the form of an information processing device with a camera, and providing the imaging device 10[2] separately from that.

[0026] The imaging device 10[1] includes a lens 11, an image sensor 12, a computing unit 13, an internal memory 14, and a communication interface 15. The computing unit 13, the internal memory 14, and the communication interface 15 are connected to one another via a bus. The computing unit 13, the internal memory 14, and the communication interface 15 may be implemented in, for example, a single microcontroller.

[0027] The lens 11 focuses light from the imaging area onto the image sensor 12. The image sensor 12 is typically a CMOS (Complementary Metal Oxide Semiconductor) image sensor or a CCD (Charge Coupled Device) image sensor, and includes a plurality of pixels arranged in an array. Each pixel of the image sensor 12 generates an electrical signal corresponding to the amount of light focused by the lens 11. The image sensor 12 transmits the electrical signal generated by each pixel to the computing unit 13. The internal memory 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.

[0028] The computing unit 13 includes a processor 13a, such as a central processing unit (CPU), a graphics processing unit (GPU), or a digital signal processor (DSP), and a random access memory (RAM) 13b. The processor 13a executes, for example, a program loaded from the internal memory 14 to the RAM 13b. As a result, the processor 13a creates a marker image 27, such as that shown in FIG. 2, based on the electrical signal from the image sensor 12. In this case, the marker image 27 includes the reference marker 1r, and stores the created marker image in the internal memory 14.

[0029] The communication interface 15 transmits and receives data to and from the displacement measuring instrument 20, specifically the communication interface 21 therein. As one of the transmissions, the communication interface 15 transmits the marker image 27 stored in the internal memory 14 to the displacement measuring instrument 20. The configuration of the imaging device 10[2] is the same as that of the imaging device 10[1]. The imaging device 10[2] creates a marker image 27 including the measurement marker 1m and transmits the marker image 27 stored in the internal memory 14 to the displacement measuring instrument 20.

[0030] The communication interface 15 and the communication interface 21 are connected by wire or wirelessly. In this case, for example, a connection via an external network such as the Internet may be used. When an external network is used, it is useful to install the imaging devices 10[1], 10[2] equipped with the communication interface 15 for wireless communication permanently at the construction site, and to implement the displacement measuring device 20 in an in-house server device of the construction company. In this case, the imaging devices 10[1], 10[2] sequentially transmit the created marker images 27 to the in-house server device via the external network, and the in-house server device can perform displacement measurement based on the marker images 27.

[0031] The displacement measuring instrument 20 includes a computing unit 22, an internal memory 23, and a communication interface 21. The computing unit 22, the internal memory 23, and the communication interface 21 are connected to one another via a bus. For example, if the displacement measuring instrument 20 is configured using a dedicated image processing device or the like, the computing unit 22, the internal memory 23, and the communication interface 21 may be implemented in a single microcontroller. The internal memory 23 is, for example, a non-volatile memory such as a flash memory or a hard disk drive. The communication interface 21 receives a marker image 27 from the communication interface 15 of the imaging devices 10[1] and 10[2], and stores it in the internal memory 23.

[0032] The calculator 22 includes a processor 22a such as a CPU, a GPU, or a DSP, and a RAM 22b. The calculator 22 calculates the amount of displacement for each of the plurality of markers 1, for example, by performing predetermined image processing on the marker images 27 stored in the internal memory 23. In this case, the processor 22a calculates the amount of displacement by, for example, executing a displacement measurement program loaded from the internal memory 23 to the RAM 22b.

[0033] The computing unit 22 is not limited to the processor 22a, and may be partially or entirely configured with hardware such as an FPGA (Field Programmable Gate Array) or an ASIC (Application Specific Integrated Circuit). That is, the computing unit 22 may be configured as appropriate using software, hardware, or a combination thereof. The same applies to the computing units 13 in the image capture devices 10[1] and 10[2].

[0034] <Outline of displacement measuring instrument> Fig. 4 is a block diagram showing a schematic configuration example of the main parts of the displacement measuring instrument in Fig. 3. The displacement measuring instrument 20 shown in Fig. 4 includes a marker image analysis unit 28a. The marker image analysis unit 28a is realized, for example, by the processor 22a executing a displacement measurement program. Furthermore, the internal memory 23 of the displacement measuring instrument 20 stores marker images 27 at each time point, including a reference marker image 27r#1 and a measurement marker image 27m#1 obtained by imaging at time point #1, and a reference marker image 27r#2 and a measurement marker image 27m#2 obtained by imaging at a subsequent time point #2.

[0035] In the present specification, the reference marker images 27r#1 and 27r#2 are collectively referred to as reference marker images 27r or simply as marker images 27r. Similarly, the measurement marker images 27m#1 and 27m#2 are collectively referred to as measurement marker images 27m or simply as marker images 27m.

[0036] The marker image analysis unit 28a calculates the amount of displacement of the reference marker 1r that occurred between time points #1 and #2 based on the reference marker image 27r#1 and the reference marker image 27r#2. Similarly, the marker image analysis unit 28a calculates the amount of displacement of the measurement marker 1m that occurred between time points #1 and #2 based on the measurement marker image 27m#1 and the measurement marker image 27m#2. Then, the marker image analysis unit 28a calculates the correct amount of displacement of the measurement marker 1m as a difference value from the amount of displacement of the reference marker 1r.

[0037] In detail, the marker image analysis unit 28a includes a marker region setting unit 30, a sampling moiré unit 31, and a displacement amount calculation unit 32. The marker region setting unit 30 sets a known marker region in which the marker 1 exists for each of the multiple marker images 27r#1, 27m#1, 27r#2, and 27m#2 stored in the internal memory 23. That is, the marker region in which the marker 1 exists within the marker image 27 is fixedly determined in advance based on the positional relationship at the stage when the displacement measurement system shown in FIG. 1 is constructed. In the example shown in FIG. 2, a pixel range slightly inside the outer frame of the marker 1A is fixedly determined as the marker region 26a.

[0038] The sampling moiré unit 31 detects the phases of the moiré fringes (PHr#1 and PHr#2 in this case) using the sampling moiré method for the reference marker image 27r#1 and the reference marker image 27r#2, specifically the marker region 26a therein. Then, the sampling moiré unit 31 calculates the phase difference ΔPHr(x,y) of the reference marker image 27r that occurred between time #1 and time #2 based on the difference between the detected phases PHr#1 and PHr#2. The phase difference ΔPHr(x,y) includes a phase difference ΔPHr(x) in the X-axis direction and a phase difference ΔPHr(y) in the Y-axis direction.

[0039] Similarly, the sampling moiré unit 31 detects the phases of the moiré fringes (here, PHm#1 and PHm#2) using the sampling moiré method for the measurement marker images 27m#1 and 27m#2, specifically the marker region 26a therein. Then, the sampling moiré unit 31 calculates the phase difference ΔPHm(x,y) of the measurement marker image 27m that occurred between time #1 and time #2 based on the difference between the detected phases PHm#1 and PHm#2. The phase difference ΔPHm(x,y) includes a phase difference ΔPHm(x) in the X-axis direction and a phase difference ΔPHm(y) in the Y-axis direction.

[0040] The displacement amount calculation unit 32 calculates the displacement amount of the marker 1, for example, the displacement amount Dm(x,y) of the measurement marker 1m, based on the phase difference ΔPHr(x,y) of the reference marker image 27r and the phase difference ΔPHm(x,y) of the measurement marker image 27m calculated by the sampling moiré unit 31. The displacement amount Dm(x,y) includes the displacement amount Dm(x) in the X-axis direction and the displacement amount Dm(y) in the Y-axis direction.

[0041] Specifically, for example, for measurement marker 1m, the phase difference ΔPHm(x) [rad] in the X-axis direction and the phase difference ΔPHm(y) [rad] in the Y-axis direction from sampling moiré unit 31, and the displacement amount Dm(x) [mm] in the X-axis direction and the displacement amount Dm(y) [mm] in the Y-axis direction calculated by displacement amount calculation unit 32 have the relationship shown in equations (1) and (2). In equations (1) and (2), Wx [mm] and Wy [mm] are the pitches on marker 1A shown in FIG. 2, respectively. The displacement amount calculation unit 32 calculates the displacement amount Dm(x, y) of measurement marker 1m using equations (1) and (2). Dm(x)=(ΔPHm(x) / 2π)×Wx …(1) Dm(y)=(ΔPHm(y) / 2π)×Wy…(2)

[0042] However, at this time, the displacement amount calculation unit 32 calculates the displacement amount Dm(x, y) of the measurement marker 1m as a difference value from the displacement amount of the reference marker 1r. In detail, the displacement amount calculation unit 32 regards, for example, the difference value "ΔPHm(x, y) - ΔPHr(x, y)" between the phase difference ΔPHm(x, y) occurring in the measurement marker 1m and the phase difference ΔPHr(x, y) occurring in the reference marker 1r as the phase difference occurring in the measurement marker 1m. Then, the displacement amount calculation unit 32 calculates the correct displacement amount Dm(x, y) of the measurement marker 1m by substituting the regarded phase difference into equations (1) and (2).

[0043] 5A, 5B, and 5C are schematic diagrams illustrating an example of the processing contents of the displacement amount calculation unit in FIG. 4. FIG. 5A shows an example in which no displacement occurs in the imaging devices 10[1] and 10[2], but displacement occurs in the measurement marker 1m. Due to the lack of displacement of the imaging devices 10[1] and 10[2], the reference marker 1r in the reference marker images 27r#1 and 27r#2 does not have a phase difference, and thus no displacement amount dr, and dr=0. Furthermore, the measurement marker 1m in the measurement marker images 27m#1 and 27m#2 has a phase difference in the X-axis direction, and thus a displacement amount dm in the X-axis direction. The displacement amount calculation unit 32 calculates "dm," which is the correct displacement amount Dm(x) of the measurement marker 1m, using the difference value "dm-dr" between the displacement amount dm of the measurement marker 1m and the displacement amount dr of the reference marker 1r.

[0044] 5B shows an example in which displacement occurs in the imaging devices 10[1] and 10[2], and furthermore, displacement also occurs in the measurement marker 1m. A phase difference in the X-axis direction, and therefore a displacement amount dr in the X-axis direction, occurs in the reference marker 1r in the reference marker images 27r#1 and 27r#2. Furthermore, a phase difference in the X-axis direction, and therefore a displacement amount dm in the X-axis direction, occurs in the measurement marker 1m in the measurement marker images 27m#1 and 27m#2. The displacement amount calculation unit 32 calculates "dm-dr," which is the correct displacement amount Dm(x) of the measurement marker 1m, from the difference value "dm-dr" between the displacement amount dm of the measurement marker 1m and the displacement amount dr of the reference marker 1r.

[0045] 5C shows an example in which displacement occurs in the imaging devices 10[1] and 10[2] but not in the measurement marker 1m. The reference marker 1r in the reference marker images 27r#1 and 27r#2 has a phase difference in the X-axis direction, and thus a displacement amount dr in the X-axis direction. Furthermore, the measurement marker 1m in the measurement marker images 27m#1 and 27m#2 has the same phase difference as the reference marker 1r, and thus a displacement amount dm, where dm = dr, due to the displacement of only the imaging devices 10[1] and 10[2]. The displacement amount calculation unit 32 calculates the correct displacement amount Dm(x) of the measurement marker 1m, 0, from the difference value "dm-dr" between the displacement amount dm of the measurement marker 1m and the displacement amount dr of the reference marker 1r.

[0046] In this way, by calculating the phase difference, and therefore the displacement amount, of the measurement marker 1m as the difference value between the phase difference, and therefore the displacement amount, of the reference marker 1r, as described in FIG. 1, the displacement of the imaging device 10[2] can be detected, and the displacement of the measurement marker 1m can be measured while reflecting the displacement of the imaging device 10[2]. Note that although FIGS. 5A, 5B, and 5C show an example in which the marker 1 is displaced in the X-axis direction, the same applies when the marker 1 is displaced in the Y-axis direction. Furthermore, by separately calculating the displacement amount in the X-axis direction and the displacement amount in the Y-axis direction, the displacement amount can be calculated in the same way even when the marker 1 is displaced in both the X-axis direction and the Y-axis direction.

[0047] <Details of the sampling moire section> FIG. 6 is a block diagram showing an example of the configuration of the sampling moiré unit in FIG. 4. FIG. 7 is a schematic diagram illustrating an example of the processing content of the phase detection unit in FIG. 6. The sampling moiré unit 31 shown in FIG. 6 includes a phase detection unit 35 and a phase difference calculation unit 36. The phase detection unit 35 detects the phase PH(x,y)#1 of the moiré fringes using the sampling moiré method for the marker image 27#1 at time #1, specifically, for the marker region 26a therein. Similarly, the phase detection unit 35 detects the phase PH(x,y)#2 of the moiré fringes for the marker image 27#2 at time #2, specifically, for the marker region 26a therein. The marker image 27#1 corresponds to either the reference marker image 27r#1 or the measurement marker image 27m#1 at time #1, and the marker image 27#2 corresponds to either the reference marker image 27r#2 or the measurement marker image 27m#2 at time #2.

[0048] Here, each of the phases PH(x,y)#1 and PH(x,y)#2 includes a phase PH(x) in the X-axis direction and a phase PH(y) in the Y-axis direction. The phase PH(x) in the X-axis direction is obtained from a periodic pattern aligned in the X-axis direction, and the phase PH(y) in the Y-axis direction is obtained from a periodic pattern aligned in the Y-axis direction. As described with reference to FIG. 2, when detecting the phase PH(x) in the X-axis direction, the phase detection unit 35 converts the grid pattern included in the marker image 27 into a stripe pattern aligned in the X-axis direction as a preprocessing. Similarly, when detecting the phase PH(y) in the Y-axis direction, the phase detection unit 35 converts the grid pattern included in the marker image 27 into a stripe pattern aligned in the Y-axis direction as a preprocessing.

[0049] Figure 7 shows the principle of the sampling moiré method used in the phase detection unit 35. In Figure 7, imaging devices 10[1] and 10[2], which have multiple pixels P arranged at a pitch p, capture an image of a marker 1A to create a marker image 27 containing a periodic pattern. The phase detection unit 35 detects the phase of the moiré fringes by performing the following processing based on the sampling moiré method on this periodic pattern.

[0050] First, the phase detection unit 35 samples pixels P at predetermined intervals, typically every four pixels, of the periodic pattern in the marker image 27 to create a sampled image. At this time, the phase detection unit 35 shifts the positions of the pixels to be sampled in order to create four sampled images 40[0] to 40[3].

[0051] Next, the phase detection unit 35 performs interpolation on each of the four sampling images 40[0] to 40[3] to create four moiré images 41[0] to 41[3] containing moiré fringes. Next, the phase detection unit 35 calculates equation (3) for each of the multiple pixels P to determine the phase of the moiré fringes contained in the moiré image 41[0], more specifically, the phase PH for each pixel P in the moiré fringe luminance distribution 42. In equation (3), I0, I1, I2, and I3 are the luminance values ​​of the moiré images 41[0], 41[1], 41[2], and 41[3] at each pixel P, respectively. tan(PH)=-(I3-I1) / (I2-I0) …(3)

[0052] Here, the luminance value In of each pixel P in a moiré image 41[n] (n=0, 1, 2, 3) can generally be expressed by equation (4) using luminance amplitude A0, phase PH, and background luminance B0. In equation (4), if the unknowns A0 and B0 are known, it is possible to calculate the phase PH. Therefore, in the sampling moiré method, as shown in FIG. 7, for example, four moiré images 41[0] to 41[3] are created, each with a phase shifted by π / 2, so that four luminance values ​​I0 to I3 can be obtained for each pixel P. Once the four luminance values ​​I0 to I3 are obtained, four simultaneous equations can be created based on equation (4). Equation (3) is an equation used to calculate the phase PH from these four simultaneous equations. In=A0×cos(PH+(n×π / 2))+B0 …(4)

[0053] Using this sampling moiré method, the phase detection unit 35 detects a phase PH(x,y)#1 for each marker image 27#1 at time #1 for each of multiple pixels P, and detects a phase PH(x,y)#2 for each marker image 27#2 at time #2. As shown in FIG. 7, a method of creating multiple grid images (here, moiré images) with sequentially shifted phases and calculating the phase PH of the grid (here, moiré fringes) using equation (3) or the like is also called a phase shifting method. The sampling moiré method utilizes this phase shifting method and applies a moiré image created by sampling pixels P as the grid image.

[0054] Returning to FIG. 6, the phase difference calculation unit 36 ​​includes an average value calculation unit 37. The phase difference calculation unit 36 ​​receives an input from the phase detection unit 35 and calculates the phase difference between a phase PH(x,y)#1 at time point #1 and a phase PH(x,y)#2 at time point #2. Specifically, the phase difference calculation unit 36 ​​calculates such a phase difference for each of a plurality of pixels P using equation (3). The average value calculation unit 37 calculates the average value of the phase differences obtained from the plurality of pixels P and outputs the calculated phase difference ΔPH(x,y) to the displacement amount calculation unit 32 shown in FIG. 4.

[0055] The sampling moiré method is generally used to measure the in-plane displacement in the area where the marker 1 is attached, in other words, the deformation state of an object, based on the phase difference for each pixel P. On the other hand, for example, at a construction site such as a shaft construction site, when measuring the displacement of a building, the ground, etc., information on the in-plane displacement of the marker 1 is not particularly required, but rather information on the displacement of the marker 1 as a whole, and ultimately information on the movement of the object itself, etc. is often required. In order to measure the displacement of the marker 1 as a whole in this way, in this example, an average value is calculated using the average value calculation unit 37.

[0056] Furthermore, since the accuracy and resolution of displacement measurement decrease as the resolution of the marker 1A in the marker image 27 decreases, the marker image 27 must have a relatively high resolution. For this reason, it is beneficial to create two marker images 27 using two imaging devices 10[1] and 10[2] instead of one, as shown in Figure 1.

[0057] <Major Effects of the First Embodiment> As described above, by using the method of the first embodiment, it is possible to measure the displacement of the marker 1, and therefore the measurement point, with a small processing load, while reflecting the displacement of the imaging device 10 [2] itself. Specifically, in the method of the first embodiment, the displacement amount of the reference marker 1r and the displacement amount of the measurement marker 1m are calculated, and the displacement amount of the measurement marker 1m is calculated as the difference value from the displacement amount of the reference marker 1r. This makes it possible to calculate the correct displacement amount Dm(x, y) of the measurement marker 1m without performing complex arithmetic processing associated with association information such as a homogeneous transformation matrix, as shown in Patent Document 1.

[0058] In addition, by using two imaging devices 10[1], 10[2] to individually create a reference marker image 27r and a measurement marker image 27m, the displacement measuring instrument 20 can measure the displacement of the marker 1 based on the marker image 27 with sufficient resolution. As a result, high-resolution or high-precision displacement measurement becomes possible. Furthermore, by using two imaging devices 10[1], 10[2], the imaging distance can be longer compared to when imaging multiple markers 1 with a single imaging device, which can further improve safety when applied to disaster areas or large-scale structures.

[0059] (Embodiment 2) <Outline of displacement measuring instrument> FIG. 8 is a schematic diagram showing an example of a marker image created by the imaging device in FIG. 1 in the displacement measuring device according to the second embodiment. Marker image 27 shown in FIG. 8 includes marker 1B, which corresponds to reference marker 1r or measurement marker 1m. A geometric pattern is printed on marker 1B. By using the geometric pattern, it is possible to measure the displacement of the marker using a phase-only correlation method, which will be described later. In this example, the geometric pattern is six circles arranged at 60° intervals. However, the geometric pattern is not limited to this, and may be any of various commonly known patterns, particularly as long as it does not contain periodic components in the X-axis and Y-axis directions.

[0060] Fig. 9 is a block diagram showing a schematic configuration example of the main parts of the displacement measuring instrument in Fig. 3 in the displacement measuring device according to embodiment 2. The displacement measuring instrument 20 shown in Fig. 9 includes a marker image analysis unit 28b different from that in Fig. 4. As in Fig. 4, the internal memory 23 in the displacement measuring instrument 20 stores marker images 27 at each time point, including a reference marker image 27r#1 and a measurement marker image 27m#1 obtained by imaging at time point #1, and a reference marker image 27r#2 and a measurement marker image 27m#2 obtained by imaging at a subsequent time point #2.

[0061] 4, the marker image analysis unit 28b calculates the amount of displacement of the reference marker 1r that occurred between time points #1 and #2 based on the reference marker image 27r#1 and the reference marker image 27r#2. Similarly, the marker image analysis unit 28b calculates the amount of displacement of the measurement marker 1m that occurred between time points #1 and #2 based on the measurement marker image 27m#1 and the measurement marker image 27m#2. Then, the marker image analysis unit 28b calculates the correct amount of displacement of the measurement marker 1m as a difference value from the amount of displacement of the reference marker 1r.

[0062] However, unlike the case of Fig. 4, marker image analysis unit 28b includes, in addition to marker region setting unit 30 similar to that of Fig. 4, a phase-only correlation unit 45 and a displacement amount calculation unit 46. As in the case of Fig. 4, marker region setting unit 30 sets a known marker region in which marker 1 exists for each of multiple marker images 27r#1, 27m#1, 27r#2, and 27m#2 stored in internal memory 23. In the example shown in Fig. 8, a pixel range slightly inside the outer frame of marker 1B is fixedly defined as marker region 26b.

[0063] The phase-only correlation unit 45 calculates the correlation between the reference marker images 27r#1 and 27r#2, specifically, the correlation of the marker region 26b therein, using the phase-only correlation method, to calculate the shift amount ΔSFr(x, y) of the reference marker image 27r that occurred between time points #1 and #2. The shift amount ΔSFr(x, y) includes a shift amount ΔSFr(x) in the X-axis direction and a shift amount ΔSFr(y) in the Y-axis direction.

[0064] Similarly, the phase-only correlation unit 45 calculates the correlation between the measurement marker image 27m#1 and the measurement marker image 27m#2, specifically, the correlation of the marker region 26b therein, using the phase-only correlation method, to calculate the shift amount ΔSFm(x,y) of the measurement marker image 27m that occurred between time point #1 and time point #2. The shift amount ΔSFm(x,y) includes a shift amount ΔSFm(x) in the X-axis direction and a shift amount ΔSFm(y) in the Y-axis direction.

[0065] The displacement amount calculation unit 46 calculates the displacement amount of the marker 1, for example, the displacement amount Dm(x, y) [mm] of the measurement marker 1m, based on the shift amount ΔSFr(x, y) [pixels (px)] of the reference marker image 27r and the shift amount ΔSFm(x, y) [px] of the measurement marker image 27m calculated by the phase-only correlation unit 45. The displacement amount Dm(x, y) includes the displacement amount Dm(x) in the X-axis direction and the displacement amount Dm(y) in the Y-axis direction.

[0066] Specifically, for example, for the measurement marker 1m, the X-axis direction shift amount ΔSFm(x) [px] and Y-axis direction shift amount ΔSFm(y) [px] from the phase-only correlation unit 45 and the X-axis direction displacement amount Dm(x) [mm] and Y-axis direction displacement amount Dm(y) [mm] calculated by the displacement amount calculation unit 46 have the relationship shown in equations (5) and (6). In equations (5) and (6), Lx [mm] and Ly [mm] are the X-axis direction length and Y-axis direction length on the marker 1 corresponding to one pixel of the image sensor 12, and are fixedly determined based on the number of pixels of the image sensor 12, the optical magnification setting at the time of image capture, etc. The displacement amount calculation unit 46 calculates the displacement amount Dm(x, y) of the measurement marker 1m using equations (5) and (6). Dm(x) = ΔSFm(x) × Lx … (5) Dm(y) = ΔSFm(y) × Ly … (6)

[0067] However, at this time, the displacement amount calculation unit 46 calculates the displacement amount Dm(x,y) of the measurement marker 1m as a difference value from the displacement amount of the reference marker 1r, as in the case of Fig. 4. In detail, the displacement amount calculation unit 46 regards the difference value "ΔSFm(x,y)-ΔSFr(x,y)" between the shift amount ΔSFm(x,y) occurring in the measurement marker 1m and the shift amount ΔSFr(x,y) occurring in the reference marker 1r as the shift amount occurring in the measurement marker 1m. Then, the displacement amount calculation unit 46 calculates the correct displacement amount Dm(x,y) of the measurement marker 1m by substituting the regarded shift amount into equations (5) and (6).

[0068] <Details of the phase-only correlation section> FIG. 10 is a block diagram showing an example of the configuration of the phase-only correlation unit in FIG. 9. A method is known in which the degree of coincidence of multiple images is determined by the correlation of the frequency components of the images. When the frequency components of an image are determined, information about the shape of the image within the image is generally retained by the phase spectrum rather than the amplitude spectrum. Taking advantage of this, the phase-only correlation method normalizes the amplitude spectrum of the frequency components of the image to, for example, 1, and then determines the correlation mainly based on the phase spectrum.

[0069] The phase-only correlation unit 45 shown in FIG. 10 includes a Fourier transform unit 50, a composite function calculation unit 51, and a correlation function calculation unit 52. Marker image 27#1 at time #1, specifically image data f1(m,n) of marker region 26b therein, and marker image 27#2 at time #2, specifically image data f2(m,n) of marker region 26b therein, are input to the Fourier transform unit 50. Marker image 27#1 corresponds to either reference marker image 27r#1 or measurement marker image 27m#1 at time #1, and marker image 27#2 corresponds to either reference marker image 27r#2 or measurement marker image 27m#2 at time #2. Here, where marker region 26b in marker image 27 is M×N pixels, m is one of M integers, and n is one of N integers.

[0070] The Fourier transform unit 50 calculates the Fourier transform values ​​F1(u,v) and F2(u,v) shown in equations (7) and (8) by, for example, performing a two-dimensional discrete Fourier transform on the image data f1(m,n) and f2(m,n). In equations (7) and (8), u is one of M integers, and v is one of N integers. Furthermore, A(u,v) and B(u,v) are amplitude spectra, and e jθ1(u,v) and e jθ2(u,v) is the phase spectrum. F1(u,v)=A(u,v)×e jθ1(u,v) …(7) F2(u,v)=B(u,v)×e jθ2(u,v) …(8)

[0071] The composite function calculation unit 51 calculates the composite function C12(u,v) shown in equation (9) by multiplying the phase spectrum of the Fourier transform value F1(u,v) by the complex conjugate of the phase spectrum of the Fourier transform value F2(u,v). The correlation function calculation unit 52 calculates the correlation function c12(m,n) by performing a two-dimensional inverse discrete Fourier transform on the composite function C12(u,v) of equation (9). C12(u,v)=e j(θ1(u,v)-θ2(u,v)) …(9)

[0072] Here, for example, assume that the image positions of image data f1(m,n) and image data f2(m,n) are the same. In this case, the correlation function c12(m,n) between image data f1(m,n) and image data f2(m,n) is close to a delta function with a peak value at the origin position (0,0). On the other hand, assume that image data f2(m,n) is image data in which the image position is shifted by Δm in the m direction relative to image data f1(m,n). In this case, when the correlation function c12(m,n) between image data f1(m,n) and image data f2(m,n) (= f1(m-Δm,n)) is calculated, the position of the peak value shifts by Δm in the m direction from the origin position. The same is true for the n direction.

[0073] In this way, by using the phase-only correlation unit 45, it is possible to calculate the shift amounts in the m and n directions of the marker image 27 that occurred between time #1 and time #2, i.e., the shift amounts ΔSF(x,y) in the X-axis and Y-axis directions, based on the positions where the peak values ​​occurred. The phase-only correlation unit 45 outputs the calculated shift amounts ΔSF(x,y) to the displacement amount calculation unit 46 shown in FIG. 9. Note that the lower the resolution of the marker 1B in the marker image 27, the lower the accuracy and resolution of the displacement measurement. Therefore, the marker image 27 needs to have a relatively high resolution. For this reason, it is beneficial to create two marker images 27 using two imaging devices 10[1] and 10[2] instead of one, as shown in FIG. 1.

[0074] <Major Effects of the Second Embodiment> As described above, the method of the second embodiment can also achieve the same effects as those described in the first embodiment. Typically, it becomes possible to measure the displacement of the marker 1, and in turn the displacement of the measurement point, while reflecting the displacement of the imaging device 10 [2] itself, with a small processing load. Comparing the sampling moiré method and the phase-only correlation method, the sampling moiré method is superior in terms of resolution, while the phase-only correlation method is superior in terms of processing load, cost, etc. Therefore, for example, when high resolution is required for displacement measurement, the method of the first embodiment should be applied, and when not, the method of the second embodiment should be applied.

[0075] That is, while the resolution is in pixel units in the phase-only correlation method, the sampling moiré method effectively measures displacement in sub-pixel units by enlarging the periodic pattern shown in marker image 27 in Figure 7 to the periodic pattern shown in moiré image 41[0]. Also, while the phase-only correlation method can measure displacement using simple arithmetic processing as described in Figure 10, the sampling moiré method requires somewhat complex image processing as described in Figure 7. Furthermore, since the phase-only correlation method does not usually require high resolution, it does not require a high-performance, i.e., expensive, image sensor 12, etc., as compared to the sampling moiré method.

[0076] (Embodiment 3) <Outline of displacement measuring instrument> FIG. 11 is a schematic diagram showing an example of a marker image created by the imaging device in FIG. 1 in the displacement measuring device according to the third embodiment. Marker image 27 shown in FIG. 11 includes marker 1C, which corresponds to reference marker 1r or measurement marker 1m. Marker 1C is a combination of marker 1A shown in FIG. 2 and marker 1B shown in FIG. 8. That is, marker 1C has a geometric pattern and a periodic pattern written side by side, for example, in the X-axis direction, so that they do not overlap each other. The geometric pattern is used in the phase-only correlation method, and the periodic pattern is used in the sampling moiré method.

[0077] FIG. 12 is a block diagram showing a schematic configuration example of the main parts of the displacement measuring instrument in FIG. 3 in the displacement measuring device according to the third embodiment. The displacement measuring instrument 20 shown in FIG. 12 includes a marker image analysis unit 28c. As in the cases of FIGS. 4 and 9, the marker image analysis unit 28c calculates the amount of displacement of the reference marker 1r that occurred between time #1 and time #2 based on the reference marker images 27r#1 and 27r#2 stored in the internal memory 23. Similarly, the marker image analysis unit 28c calculates the amount of displacement of the measurement marker 1m that occurred between time #1 and time #2 based on the measurement marker images 27m#1 and 27m#2 stored in the internal memory 23. The marker image analysis unit 28c then calculates the correct amount of displacement of the measurement marker 1m as a difference value from the amount of displacement of the reference marker 1r.

[0078] 4 and 9, marker image analysis unit 28c includes marker region setting unit 30, sampling moiré unit 31, phase-only correlation unit 45, and displacement amount calculation unit 55. As in the cases of FIGS. 4 and 9, marker region setting unit 30 sets known marker regions 26a and 26b, in which periodic patterns and geometric patterns exist, for marker image 27 shown in FIG. 11, i.e., for each of multiple marker images 27r#1, 27m#1, 27r#2, and 27m#2 stored in internal memory 23.

[0079] When using markers 1C such as those shown in Fig. 11, the known marker areas 26a and 26b can be large, so if an image including two such markers 1C is created using a single imaging device, it can be difficult to maintain the resolution of the periodic pattern and geometric pattern in each marker 1C. On the other hand, if the two markers 1C are captured separately using two imaging devices 10[1] and 10[2] as shown in Fig. 1, it becomes possible to ensure a certain degree of sufficient resolution for each of the geometric pattern and the periodic pattern.

[0080] 4 and 6, and calculates the phase difference ΔPHr(x, y) occurring in the reference marker image 27r and the phase difference ΔPHm(x, y) occurring in the measurement marker image 27m using the sampling moiré method. The phase-only correlation unit 45, which has the same configuration as shown in Figures 9 and 10, and calculates the shift amount ΔSFr(x, y) occurring in the reference marker image 27r and the shift amount ΔSFm(x, y) occurring in the measurement marker image 27m using the phase-only correlation method.

[0081] The sampling moiré method uses a periodic pattern, so if a displacement of the marker 1 exceeds the length of one period of the periodic pattern, i.e., if a periodic shift occurs, it becomes difficult to detect the periodic shift. On the other hand, the phase-only correlation method uses a geometric pattern, so such a periodic shift problem does not occur. Therefore, the displacement amount calculation unit 55 determines the magnitude of the periodic shift added to the phase difference ΔPHr(x,y) of the reference marker image 27r calculated by the sampling moiré unit 31 based on the shift amount ΔSFr(x,y) of the reference marker image 27r calculated by the phase-only correlation unit 45. The displacement amount calculation unit 55 then calculates the displacement amount of the reference marker 1r based on the phase difference ΔPHr(x,y) and the determined magnitude of the periodic shift.

[0082] Similarly, the displacement amount calculation unit 55 determines the magnitude of the periodic shift added to the phase difference ΔPHm(x,y) of the measurement marker image 27m calculated by the sampling moiré unit 31, based on the shift amount ΔSFm(x,y) of the measurement marker image 27m calculated by the phase-only correlation unit 45. Then, the displacement amount calculation unit 55 calculates the displacement amount of the measurement marker 1m, based on the phase difference ΔPHm(x,y) and the determined magnitude of the periodic shift.

[0083] 13 is a conceptual diagram illustrating an example of the processing performed by the displacement amount calculation unit in FIG. 12. FIG. 13 shows the phase of a luminance distribution 42#1 of moiré fringes at time point #1 and the phase of a luminance distribution 42#2 of moiré fringes at time point #2, both of which are detected by the sampling moiré unit 31. The sampling moiré unit 31 calculates the phase difference ΔPH [rad] between the phase of the luminance distribution 42#1 and the phase of the luminance distribution 42#2 in the range of −π to +π. Therefore, the actual phase difference is not necessarily ΔPH+0, but may be ΔPH+2π, ΔPH+4π, or the like. The value of 0, 2π, 4π, etc. is determined based on the shift amount ΔSF(x, y) from the phase-only correlation unit 45.

[0084] As a specific example, assume that the pitch Wx of the periodic pattern in the marker 1C shown in FIG. 11 is 5 mm, the resolution using the phase-only correlation method, i.e., Lx in equation (5), is 5 mm or less, and the actual displacement is 12 mm. When the sampling moiré method is used, the displacement result is, for example, 2 mm, 7 mm, 12 mm, 17 mm, etc. On the other hand, when the phase-only correlation method is used, the displacement result is, for example, within the range of 10 mm to 15 mm. The displacement amount calculation unit 55 can calculate the actual displacement of 12 mm based on the overlapping portion of these results.

[0085] In this way, the displacement amount calculation unit 55 calculates the actual displacement amount of the reference marker 1r and the actual displacement amount of the measurement marker 1m. Furthermore, similar to the case of Fig. 4, the displacement amount calculation unit 55 calculates the correct displacement amount Dm(x, y) of the measurement marker 1m after reflecting the displacement of the imaging device 10[2], based on the difference value between the actual displacement amount of the measurement marker 1m and the actual displacement amount of the reference marker 1r.

[0086] <Major Effects of the Third Embodiment> As described above, by using the method of the third embodiment, it is possible to obtain the same effects as those described in the first and second embodiments, typically making it possible to measure the displacement of the marker 1, and in turn the displacement of the measurement point, while reflecting the displacement of the image capture device 10 [2] itself, with a small processing load. Furthermore, the magnitude of the periodic shift that occurs in the sampling moiré method can be detected using the phase-only correlation method, making it possible to achieve high-resolution measurements based on the sampling moiré method over a wide measurement range.

[0087] The invention made by the inventor has been specifically described above based on the embodiments, but the present invention is not limited to the above-described embodiments and can be modified in various ways without departing from the spirit of the invention. [Explanation of symbols]

[0088] 1, 1A to 1C... marker, 1r... reference marker, 1m... measurement marker, 2... displacement measurement device, 3[1], 3[2]... object, 10[1], 10[2]... imaging device, 20... displacement measurement instrument, 27... marker image, 27r... reference marker image, 27m... measurement marker image, 28a to 28c... marker image analysis unit, 31... sampling moiré unit, 32, 46, 55... displacement amount calculation unit, 45... phase-only correlation unit

Claims

1. A first imaging device and a second imaging device for capturing images of markers attached to measurement points of one or more objects; a displacement measuring instrument that measures the displacement of the marker based on images captured by the first imaging device and the second imaging device; A displacement measuring device having the first imaging device captures images of a reference marker attached to a measurement point treated as a fixed point at a first time point and a second time point to create a first reference marker image and a second reference marker image, respectively; the second imaging device captures images of measurement markers attached to predetermined measurement points at the first time point and the second time point to create first measurement marker images and second measurement marker images, respectively; The displacement measuring instrument is calculating a displacement of the reference marker that occurred between the first time point and the second time point based on the first reference marker image and the second reference marker image; calculating a displacement of the measurement marker that occurred between the first time point and the second time point based on the first measurement marker image and the second measurement marker image; Calculating the correct displacement amount of the measurement marker as a difference value between the displacement amount of the reference marker and the measurement marker; a periodic pattern is marked on each of the reference marker and the measurement marker; The displacement measuring instrument is detecting a first phase and a second phase of Moiré fringes for the first reference marker image and the second reference marker image using a sampling Moiré method, and calculating a phase difference between the reference marker images that occurred between the first time point and the second time point based on a difference between the first phase and the second phase; detecting a third phase and a fourth phase of Moire fringes using the sampling Moire method for the first measurement marker image and the second measurement marker image, respectively, and calculating a phase difference between the measurement marker images occurring between the first time point and the second time point based on a difference between the third phase and the fourth phase; Displacement measuring device.

2. A first imaging device and a second imaging device for imaging markers attached to measurement points of one or more objects; a displacement measuring instrument that measures the displacement of the marker based on images captured by the first imaging device and the second imaging device; A displacement measuring device having the first imaging device captures images of a reference marker attached to a measurement point treated as a fixed point at a first time point and a second time point to create a first reference marker image and a second reference marker image, respectively; the second imaging device captures images of measurement markers attached to predetermined measurement points at the first time point and the second time point to create first measurement marker images and second measurement marker images, respectively; The displacement measuring instrument is calculating a displacement of the reference marker that occurred between the first time point and the second time point based on the first reference marker image and the second reference marker image; calculating a displacement of the measurement marker that occurred between the first time point and the second time point based on the first measurement marker image and the second measurement marker image; Calculating the correct displacement amount of the measurement marker as a difference value between the displacement amount of the reference marker and the measurement marker; a geometric pattern is marked on each of the reference marker and the measurement marker; The displacement measuring instrument is calculating a correlation between the first reference marker image and the second reference marker image using a phase-only correlation method to calculate a shift amount of the reference marker image that occurred between the first time point and the second time point; calculating a correlation between the first measurement marker image and the second measurement marker image using the phase-only correlation method, thereby calculating a shift amount of the measurement marker image that has occurred between the first time point and the second time point; Displacement measuring device.

3. A first imaging device and a second imaging device for imaging markers attached to measurement points of one or more objects; a displacement measuring instrument that measures the displacement of the marker based on images captured by the first imaging device and the second imaging device; A displacement measuring device having the first imaging device captures images of a reference marker attached to a measurement point treated as a fixed point at a first time point and a second time point to create a first reference marker image and a second reference marker image, respectively; the second imaging device captures images of measurement markers attached to predetermined measurement points at the first time point and the second time point to create first measurement marker images and second measurement marker images, respectively; The displacement measuring instrument is calculating a displacement of the reference marker that occurred between the first time point and the second time point based on the first reference marker image and the second reference marker image; calculating a displacement of the measurement marker that occurred between the first time point and the second time point based on the first measurement marker image and the second measurement marker image; Calculating the correct displacement amount of the measurement marker as a difference value between the displacement amount of the reference marker and the measurement marker; a periodic pattern and a geometric pattern are marked on each of the reference marker and the measurement marker; The displacement measuring instrument is a sampling moiré unit that uses a sampling moiré method to detect first and second phases of moiré fringes for the periodic patterns of the first reference marker image and the second reference marker image, respectively, and calculates a phase difference of the reference marker images that occurred between the first time point and the second time point based on a difference between the first phase and the second phase; and that uses the sampling moiré method to detect third and fourth phases of moiré fringes for the periodic patterns of the first measurement marker image and the second measurement marker image, respectively, and calculates a phase difference of the measurement marker images that occurred between the first time point and the second time point based on a difference between the third phase and the fourth phase; a phase-only correlation unit that calculates the correlation between the geometric pattern of the first reference marker image and the geometric pattern of the second reference marker image using a phase-only correlation method to calculate the amount of shift of the reference marker image that occurred between the first time point and the second time point, and that calculates the correlation between the geometric pattern of the first measurement marker image and the geometric pattern of the second measurement marker image using the phase-only correlation method to calculate the amount of shift of the measurement marker image that occurred between the first time point and the second time point; a displacement amount calculation unit that determines the magnitude of periodic shift added to the phase difference of the reference marker image calculated by the sampling moiré unit based on the shift amount of the reference marker image calculated by the phase-only correlation unit, calculates the displacement amount of the reference marker based on the phase difference and the magnitude of the periodic shift, determines the magnitude of periodic shift added to the phase difference of the measurement marker image calculated by the sampling moiré unit based on the shift amount of the measurement marker image calculated by the phase-only correlation unit, and calculates the displacement amount of the measurement marker based on the phase difference and the magnitude of the periodic shift; Equipped with Displacement measuring device.

4. The displacement measuring device according to any one of claims 1 to 3, the first imaging device and the second imaging device are installed on a common support. Displacement measuring device.

Images