Measurement device, measurement system, and measurement method

Abstract

One embodiment according to a technology of the present disclosure provides a measurement device, a measurement system, and a measurement method which can accurately calibrate a Doppler shift. Provided is a measurement device according to an aspect of the present invention, wherein a processor: acquires first scan data including information that is obtained by scanning a portion-to-be-measured of an object with a laser scanner in a first direction and indicates a first distance from the laser scanner to the portion-to-be-measured; acquires second scan data including information that is obtained by scanning the portion-to-be-measured of the object with the laser scanner in a second direction different from the first direction and indicates a second distance from the laser scanner to the portion-to-be-measured; and calculates calibrated data obtained by removing an effect of the Doppler shift from the first scan data and the second scan data by executing an averaging process on the first scan data and the second scan data.

Description

[Technical Field]

[0001] The present invention relates to a measurement device, a measurement system, and a measurement method, and more particularly to a technique for measuring an object using laser light. [Background technology]

[0002] In recent years, the inspection and maintenance (understanding the condition of structures and repairs according to the situation) of so-called "social infrastructure structures" such as roads, bridges, tunnels, dams, and buildings, specifically the presence and extent of defects (or damage) such as cracks, "lifting," and peeling, has become a major social issue. "Infra" is an abbreviation of "infrastructure."

[0003] In the past, defects in objects were checked by workers visually or by tapping, but this type of work takes time and effort, and it can sometimes be difficult to get close to the object being inspected.

[0004] To address this situation, researchers are studying the application of technology that uses laser light to measure objects non-contact and detect defects based on measuring minute irregularities (three-dimensional shapes).When measuring social infrastructure structures, high-speed scanning and high-precision detection are required depending on the type and size of the object.However, there is a problem in that the measurement accuracy (distance measurement accuracy) decreases due to Doppler shift when there is relative movement between the scanner and the object being measured.

[0005] One known technique for addressing this issue is that described in Patent Document 1. Patent Document 1 describes a technique for calibrating Doppler shift when a measurement head is fixed to a moving object. Specifically, the sample of the object to be measured is moved at multiple speeds, the difference between these speeds is calculated as the speed for calibration, and the difference in frequency of the reflected light at these speeds is calculated as the amount of frequency shift. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 2020-046368 Summary of the Invention [Problem to be solved by the invention]

[0007] When performing measurements using laser light, depending on the type and size of the measurement object (for example, when the measurement object is a social infrastructure structure), it may be difficult (virtually impossible) to move or rotate the measurement object itself. In this case, the optical axis direction changes as the scan proceeds, resulting in a change in the measurement angle. However, Patent Document 1 does not take such circumstances into consideration. Furthermore, depending on the measurement object, it may be difficult to perform a preliminary measurement of the entire measurement unit as in Patent Document 1 and measure the angle at each point in the obtained point cloud. Furthermore, depending on the measurement object, it may be difficult to accurately aim at the same location for two measurements at different speeds.

[0008] As described above, with conventional techniques, it has been difficult to calibrate the Doppler shift that accompanies changes in the scanning direction.

[0009] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a measurement device, a measurement system, and a measurement method that can accurately calibrate Doppler shift. [Means for solving the problem]

[0010] In order to achieve the above-mentioned object, a measuring device according to a first aspect of the present invention is a measuring device equipped with a processor, wherein the processor acquires first scan data obtained by scanning a measured portion of an object with a laser scanner in a first direction, the first scan data including information indicating a first distance, which is the distance from the laser scanner to the measured portion; acquires second scan data obtained by scanning a measured portion of the object with the laser scanner in a second direction different from the first direction, the second scan data including information indicating a second distance, which is the distance from the laser scanner to the measured portion; and calculates calibrated data from which the effects of Doppler shift in the first scan data and the second scan data have been removed by performing an averaging process on the first scan data and the second scan data.

[0011] In the first aspect, the first direction and the second direction may vary over time. That is, the first and second scan data are time-series data, and the measurement results include deviations from the true values ​​due to Doppler shift. Here, since the scan directions (first direction and second direction) are different between the first scan data and the second scan data, it is considered that the deviations from the true values ​​due to Doppler shift in the measurement results will have opposite signs. Therefore, averaging the first scan data and the second scan data can cancel out the effects of the Doppler shift. Note that in the first aspect and each of the following aspects, the first direction and the second direction may be opposite, but do not have to be completely opposite.

[0012] In this way, the measurement device according to the first aspect can calibrate the Doppler shift with high precision.

[0013] In the first aspect and each of the following aspects, the first and second scan data may include distance data and scan direction data (e.g., azimuth angle and elevation angle, or main scanning direction and sub-scanning direction), or may include three-dimensional position data. Distance and scan direction, and three-dimensional position are equivalent information that can be converted into each other.

[0014] Furthermore, the measurement device according to the first aspect can be realized, for example, as a processor part (a part that acquires and processes measurement data) of a measurement system, but is not limited to such an aspect.

[0015] In the measurement device according to the second aspect, the processor performs averaging processing according to the distance between the first measurement point where the first scan data was acquired and the second measurement point where the second scan data was acquired. For example, different averaging processing can be performed depending on whether the distance between the first measurement point and the second measurement point is close or far.

[0016] A measurement device according to a third aspect is the second aspect, wherein the processor averages the positions of the first measurement point and the second measurement point in the averaging process. In the third aspect, the "average" may be a simple average or a weighted average.

[0017] In the measuring device of the fourth aspect, in the first or second aspect, the processor acquires a first speed, which is the scanning speed, for each measurement point of the first measurement point group from which first scan data is obtained, by including it in the first scan data, and acquires a second speed, which is the scanning speed, for each measurement point of the second measurement point group from which second scan data is obtained, by including it in the second scan data, and performs averaging processing on the first scan data and the second scan data using the first speed and the second speed.

[0018] In the measurement device of the fifth aspect, in the fourth aspect, the processor calculates, as post-calibration data, the position obtained by dividing the position of a first point, which is a point selected from the first measurement point group, and the position of a second point, which is a point selected from the second measurement point group, by the ratio between the absolute value of the first velocity at the first point and the absolute value of the second velocity at the second point in the averaging process.

[0019] A measurement device according to a sixth aspect is the fifth aspect, in which the processor performs averaging processing with an internal division ratio of 1 to 1. The sixth aspect defines a specific method for the averaging processing.

[0020] A measurement device according to a seventh aspect is the fifth or sixth aspect, wherein the processor performs averaging processing on all pairs of first and second points where the difference in distance between the first and second points is equal to or less than a reference value. The seventh aspect specifies a method for selecting data to be subjected to averaging processing.

[0021] A measurement device according to an eighth aspect is the fifth or sixth aspect, wherein the processor performs averaging processing on pairs of a point in the first measurement point cloud and one or more second points selected from the second measurement point cloud in order of proximity to the first point. The eighth aspect defines another method for selecting data to be subjected to averaging processing.

[0022] A measurement device according to a ninth aspect is the fifth or sixth aspect, wherein the processor performs averaging processing on pairs of a second point and one or more first points selected from the first measurement point group in order of proximity to the second point. The ninth aspect defines yet another method for selecting data to be subjected to averaging processing.

[0023] A measuring device according to a tenth aspect is any one of the first to ninth aspects, wherein the processor measures the three-dimensional shape of the object using a plurality of pieces of post-calibration data. The processor may also evaluate damage (defects) such as lifting or peeling based on the measurement results.

[0024] In the measurement device according to the eleventh aspect, the processor extracts a damage candidate region of the object based on the measured three-dimensional shape, and outputs information indicating the extracted damage candidate region to an output device, which may be a display device or a recording device.

[0025] In the measurement device according to the twelfth aspect, the processor extracts, as a damage candidate region, an area where the deviation from design information of the three-dimensional shape of the object and / or previously acquired measurement results of the three-dimensional shape exceeds a standard. In the twelfth aspect, the "design information" may be, for example, data from a CAD system (CAD: Computer Aided Design), and the "previously acquired measurement results of the three-dimensional shape" may be, for example, past measurement results. Also, for example, a predetermined threshold value may be used as the "standard."

[0026] To achieve the above-mentioned object, a measurement system according to a thirteenth aspect of the present invention includes the measurement device according to any one of the first to twelfth aspects and a laser scanner. By including the measurement device according to any one of the first to twelfth aspects, the measurement system according to the thirteenth aspect can accurately calibrate the Doppler shift. In the thirteenth aspect, it is preferable that the laser scanner outputs information indicating the distance and information indicating the laser irradiation direction in association with each other. The measurement device can utilize this output.

[0027] A measurement system according to a fourteenth aspect is a measurement system according to the thirteenth aspect, wherein the laser scanner is a laser scanner that uses a frequency-modulated continuous wave laser beam. A "frequency-modulated continuous wave laser" (hereinafter sometimes referred to as an "FMCW laser") is a laser beam that transmits a frequency-modulated continuous wave, and can determine the distance to an object based on the frequency difference (beat frequency) between the transmitted wave and the reflected wave. In measurements using a frequency-modulated continuous wave laser beam, the distance resolution is determined by the "amount of frequency change per unit time (chirp rate) and the measurement resolution of the beat frequency."

[0028] A measurement system according to a fifteenth aspect is the measurement system according to the fourteenth aspect, in which the laser scanner is a laser scanner that uses a frequency-shifted feedback laser beam. A "Frequency-Shifted Feedback Laser (hereinafter sometimes referred to as an "FSF laser")" is a type of frequency-modulated continuous wave laser.

[0029] To achieve the above-mentioned object, a measurement method according to a sixteenth aspect of the present invention is a measurement method executed by a measurement device including a processor, wherein the processor acquires first scan data obtained by scanning a measurement portion of an object with a laser scanner in a first direction, the first scan data including information indicating a first distance, which is the distance from the laser scanner to the measurement portion, and second scan data obtained by scanning the measurement portion of the object with the laser scanner in a second direction different from the first direction, the second scan data including information indicating a second distance, which is the distance from the laser scanner to the measurement portion, and performs an averaging process on the first scan data and the second scan data to calculate calibrated data in which the influence of Doppler shift in the first scan data and the second scan data has been removed. According to the sixteenth aspect, as in the first aspect, Doppler shift can be calibrated with high accuracy.

[0030] The measurement method according to the sixteenth aspect may have the same configuration as the second to twelfth aspects. Also, a program that causes a measurement device equipped with a processor to execute the measurement method according to these aspects, and a non-transitory tangible recording medium (for example, various types of magneto-optical recording devices or semiconductor memories) on which computer-readable code of such a program is recorded, can also be cited as aspects of the present invention. Note that this "non-transitory tangible recording medium" does not include non-tangible recording media such as carrier signals or propagation signals themselves. [Effects of the Invention]

[0031] As described above, the measurement device, measurement system, and measurement method of the present invention make it possible to calibrate the Doppler shift with high precision. [Brief explanation of the drawings]

[0032] [Figure 1] FIG. 1 is a diagram showing the configuration of a measurement system according to the first embodiment. [Figure 2] FIG. 2 is an external view of the three-dimensional measuring apparatus according to the first embodiment. [Figure 3] FIG. 3 is a diagram showing the configuration of the three-dimensional measurement device. [Figure 4] FIG. 4 is a diagram showing an example of two-dimensional scanning. [Figure 5] FIG. 5 is a diagram showing another example of two-dimensional scanning. [Figure 6] FIG. 6 is a diagram showing the hardware configuration of the data processing device. [Figure 7] FIG. 7 is a flowchart (1 / 2) showing the process of the measurement method. [Figure 8] FIG. 8 is a flowchart (2 / 2) showing the process of the measurement method. [Figure 9] FIG. 9 is a diagram showing how calibration is performed using clockwise and counterclockwise measurement results. [Figure 10] FIG. 10 is a diagram showing how data is acquired at each measurement point by scanning. [Figure 11] FIG. 11 is a diagram showing how distance is calibrated using velocity data. [Figure 12] FIG. 12 is a diagram showing the radial velocity and the tangential velocity when the scanning direction is different. [Figure 13] FIG. 13 is a diagram showing how the influence of the Doppler shift is cancelled out by backward scanning. [Figure 14] FIG. 14 is a diagram showing an example of output of a damage candidate region. DETAILED DESCRIPTION OF THE INVENTION

[0033] [Effect of Doppler shift on measurements] In measurements using laser light, it is difficult to aim at the exact same point and measure multiple times, as described above. Furthermore, when an asymmetric mirror (see the examples in Figures 4 and 5) is used to change the irradiation direction of the laser light, the rotation speed may change slightly depending on the rotation position. Due to these circumstances, the relative distance and relative speed to the measurement object may change during the scanning process, and the distance measurement accuracy (measurement accuracy) may decrease due to the influence of Doppler shift. To address these issues, depending on the type, size, and other conditions of the object, it may be difficult to move the object, scan at multiple speeds, or measure the exact same point, as described above in Patent Document 1.

[0034] In light of these circumstances, the inventors of the present application have conducted extensive research and have come up with the idea that "since the sign of the deviation from the true value due to Doppler shift in measurement data should be opposite between forward and reverse scans, averaging the measurement results from the forward and reverse scans cancels out the influence of the Doppler shift, making it possible to measure distance (three-dimensional shape) with high accuracy." Below, we will explain embodiments of the present invention based on this idea.

[0035] [First embodiment] A first embodiment of a measurement device, a measurement system, and a measurement method according to the present invention will be specifically described.

[0036] 1 is a diagram showing the configuration of a measurement system according to the first embodiment. As shown in the figure, measurement system 1 (measurement system) is a system for measuring and inspecting railway tunnels, and includes a three-dimensional measurement device 10 (laser scanner), a data processing device 14 (measurement device, processor), and a power supply device 16.

[0037] In this example, the three-dimensional measuring device 10 is a LiDAR (Light Detection and Ranging), and in particular a frequency modulated continuous wave (FMCW) LiDAR that can measure distances with an accuracy on the order of several hundred microns, but the present invention is not limited to using distance measurement data (three-dimensional measurement data) measured by an FMCW LiDAR. Note that although the three-dimensional measuring device 10 is mounted on a tripod 12, it may also be mounted on a bogie 18 that runs or moves on a track.

[0038] [3D measurement device] FIG. 2 is an external view of a three-dimensional measuring device 10 according to the first embodiment. The three-dimensional measuring device 10 includes an FMCW (frequency modulated continuous wave) LiDAR. As shown in FIG. 2, the three-dimensional measuring device 10 is mounted on a bogie 18 that travels on a railroad track, and measures the distance to a wall surface 20A (object, portion to be measured) of a tunnel 20 (object). In addition to the three-dimensional measuring device 10, the bogie 18 is also equipped with a data processing device 14 (processor) and a power supply device 16. The power supply device 16 supplies power to the three-dimensional measuring device 10 and the data processing device 14.

[0039] In the measurement system 1, the distance and direction to the wall surface 20A, as well as the rate of change of these, can be measured using a three-dimensional measuring device 10, etc., and as will be described in detail later, the three-dimensional shape of the wall surface 20A (object) can be measured using multiple pieces of calibrated data.

[0040] In the example shown in FIG. 2, the three-dimensional measuring device 10 uses an FSF laser beam, which is a form of the FMCW laser beam, to scan a wall surface 20A shown in FIG. 2 in the left-right direction (main scanning direction) at high speed, while also moving the scanning line in the up-down direction (sub-scanning direction) of the wall surface 20A. This measures the distance from the laser scanner 15 (see FIG. 3) of the three-dimensional measuring device 10 to multiple measurement points on each scanning line of the laser beam. As will be described in detail later, the measurement results are averaged to remove the influence of Doppler shift, and post-calibration data is calculated. Then, three-dimensional data in a polar coordinate system, consisting of the irradiation direction of the laser beam and the measured distance, is converted into three-dimensional data in a Cartesian coordinate system, thereby obtaining three-dimensional measurement data indicating the three-dimensional shape of the wall surface 20A. In this example, three-dimensional measurement data (point cloud data) of multiple measurement points is obtained as the three-dimensional measurement data.

[0041] [FSF type laser device] 3 is a diagram showing the configuration of a three-dimensional measuring device 10. The three-dimensional measuring device 10 uses an FSF (Frequency Shifted Feedback) laser device, which is one aspect of the FMCW method, and includes a laser light source 11 that outputs frequency-shifted feedback laser light (FSF laser light), a control unit 13 for the laser light source 11, a laser scanner 15, and an encoder 17. The laser light source 11 includes a laser medium, a mirror, an AOM (Acousto-Optic Modulator), etc., but as described in JP 2021-096383 A, an optical SSB modulator (SSB: Single Side Band) may also be used as a frequency shifter.

[0042] [Scanning by rotating mirror] The laser scanner 15 scans the wall surface 20A (object) in the main scanning direction and sub-scanning direction (two-dimensional scanning) using the laser light output from the laser light source 11. FIG. 4 is a diagram showing an example of such two-dimensional scanning. As shown in the figure, the laser scanner 15 changes the irradiation direction of the laser light (the direction in which the laser light is reflected by the polygon mirror 15A) in the θ direction (main scanning direction) and the φ direction (sub-scanning direction) by rotating a polygon mirror 15A (an example of a scanning direction changing member) about two axes using a motor 15B. The laser scanner 15 is equipped with a light receiver (not shown) that receives the laser light reflected by the wall surface 20A.

[0043] In such two-dimensional scanning, for example, first scan data is obtained (first measurement) by scanning in the forward direction (first direction) in both the θ and φ directions, and then second scan data is obtained (second measurement) by scanning in the opposite direction (second direction) in both the θ and φ directions.

[0044] FIG. 5 shows another example of two-dimensional scanning. In the example shown in the figure, a monogon mirror 15C (a tilt mirror; another example of a scanning direction changing member) is rotated in a forward direction (first direction) or a reverse direction (second direction) by a motor 15B to change the irradiation direction of the laser light output from the laser light source 11. In this embodiment, if the tilt angle of the monogon mirror 15C can be changed around two axes, forward scanning and reverse scanning can be performed as in the example described above with reference to FIG. 4. Also, even if the tilt angle of the monogon mirror 15C can be changed only around one axis (for example, the φ direction), the entire wall surface 20A can be scanned by repeating one-dimensional scanning in accordance with the travel or movement of the cart 18.

[0045] [Obtaining data on distance, speed, and direction] The three-dimensional measuring device 10 also includes an encoder 17 (angle detector) that detects the rotation angle of the mirror. The data processing device 14 (or the measuring device 100) can calculate the irradiation direction (main scanning direction and sub-scanning direction) of the laser light from the output of the encoder 17, and can calculate the scanning speed (which may be a Cartesian coordinate system or a polar coordinate system) from the change in the irradiation direction and the measured distance. This allows the data processing device 14 (or the measuring device 100) to acquire the measured distance (first distance, second distance), scanning speed (first speed, second speed), and scanning direction (main scanning direction, sub-scanning direction) for each measurement point on the wall surface 20A in association with each other. Note that, because the three-dimensional position can be calculated from the distance and direction to the measurement point, acquiring the distance, direction, and speed in association with each other is equivalent to acquiring the three-dimensional position and speed in association with each other.

[0046] [Example of measurement conditions] The three-dimensional measuring device 10 may measure the minute uneven shape (three-dimensional shape) of the wall surface 20A under the following conditions, for example. Measurement accuracy: 50μm Measurement distance: 2-7m Measurement speed: 10m in area 2 / sec

[0047] The scanning speed of the laser light itself is, for example, about 4000 rpm, but the scanning speed when the scanning direction is reciprocated (scanning in the forward direction, then turning around and scanning in the reverse direction) is, for example, about 60 rpm. Furthermore, the three-dimensional measuring device 10 acquires three-dimensional data of the wall surface 20A at regular intervals while the carriage 18 is moving, for example, and it is preferable to acquire the three-dimensional data so that the measurement areas of the three-dimensional data acquired at each interval partially overlap. This is because the three-dimensional data acquired at each interval can be combined into a panoramic image.

[0048] The three-dimensional measuring device 10 can achieve the above measurement accuracy and the like by configuring it as a LiDAR of the FSF type (an example of the FMCW type).

[0049] It should be noted that the conditions such as the measurement accuracy of the three-dimensional measurement data required in the present invention are not limited to the above example, and the three-dimensional measurement device is not limited to the FSF type LiDAR, and various other types can be applied. For example, in addition to the FSF laser light, a DFB semiconductor laser (D F FMCW laser light can be generated using a distributed feedback (B) type, Fabry-Perot type semiconductor laser, surface-emitting semiconductor laser, etc. For example, if the drive current waveform of a semiconductor laser is controlled with a sawtooth or triangular wave, the frequency changes according to the change in current, so it operates as a frequency-modulated continuous wave laser.

[0050] The three-dimensional shape of wall surface 20A is preferably measured by 3D measuring device 10 at the start of measurement (construction) of the tunnel and at regular inspections after construction. The three-dimensional measurement data can be recorded in recording device 160 within data processing device 14 and / or an external recording device, along with the data at the start of measurement and at regular inspections. Design information (CAD data, etc.) of tunnel 20 (object) may also be recorded in recording device 160 and / or the external recording device. As will be described in detail below, such design information and past measurement results (previously acquired measurement results of the three-dimensional shape) can be used to extract potential damage areas.

[0051] [Hardware configuration of measurement device] FIG. 6 is a diagram showing the hardware configuration of a measurement device 100 (measurement device). As shown in the figure, the measurement device 100 functions as the data processing section (processor section) of the measurement system 1 and is configured, for example, by a personal computer, a workstation, or the like. The measurement device 100 includes a processor 110, a memory 120, a display device 130 (output device), an input / output interface 140, an operation unit 150, and a recording device 160 (output device). This measurement device 100 can be incorporated as one function of the data processing device 14 shown in FIGS. 1 to 3.

[0052] The processor 110 (processor) is composed of a CPU (Central Processing Unit) and the like, and controls the measurement device 100 and each part of the measurement system 1 in an integrated manner, and can execute a distance measurement program, a distance calibration program, a shape measurement program, a damage evaluation program, etc. Details of the various processes performed by the processor 110 will be described later.

[0053] The memory 120 includes a flash memory, a read-only memory (ROM), a random access memory (RAM), etc. The flash memory and the ROM are non-volatile memories (tangible and non-transitory recording media) that store an operating system and various programs including the measurement program according to the present invention.

[0054] The RAM functions as a work area for processing by the processor 110. It also temporarily stores various programs stored in a flash memory or the like, and three-dimensional measurement data of the surface of the wall surface 20A (object, building). Note that the processor 110 may have a part of the memory 120 (RAM) built in.

[0055] Display device 130 not only displays a screen for operating measuring device 100, but can also display measurement results calculated by measuring device 100, graphs and charts created based on these results, images of the surface properties of structures, etc. Display device 130 is also used as part of a GUI (Graphical User Interface) when accepting user input (such as designation of a point of interest on the surface of a structure) via operation unit 150. Note that display device 130 may be configured as a touch panel device, and user operations may be accepted via this device.

[0056] The input / output interface 140 includes a connection unit that can be connected to an external device and a communication unit that can be connected to a network. The connection unit that can be connected to an external device may be a Universal Serial Bus (USB), a High-Definition Multimedia Interface (HDMI) (HDMI is a registered trademark), or the like. The measuring device 100 can acquire scan data and the like required for measurement via this input / output interface 140 from external devices (other systems or recording devices) on the Internet or the cloud, or from recording media.

[0057] The measuring device 100 can also be configured as a device independent of the data processing device 14. In this case, the processor 110 acquires the 3D measurement data of the surface of the structure from the data processing device 14 via the input / output interface 140, or, if the 3D measurement data is stored in a database on the cloud or the like, acquires the 3D measurement data of the surface of the structure from the cloud via the input / output interface 140. The processor 110 can also record the 3D measurement data acquired in this way in the memory 120 or the recording device 160.

[0058] The operation unit 150 includes devices such as a mouse and a keyboard, and functions as part of a GUI that accepts instruction inputs by user operations using the display screen of the display device 130.

[0059] Recording device 160 is composed of a non-transitory, tangible recording medium such as a flash memory, a hard disk drive, or a magneto-optical recording device, and its control unit, and stores 3D measurement data (pre-acquired 3D shape measurement results) of the structure's surface measured by 3D measuring device 10 at the start of measurement of the structure and during periodic inspections, along with information indicating the measurement date and time. Design information (CAD data, etc.) of the 3D shape of tunnel 20 (object) may also be recorded in recording device 160. Recording device 160 can also record various data required for processing (such as a data selection method described below), measurement results at each measurement point (such as first and second scan data), data processing results (such as calibrated data, 3D shape measurement results, potential damage areas, etc.), etc.

[0060] [Measurement method processing] Next, a measurement method in the measurement system 1 configured as described above will be described. Figures 7 and 8 are flowcharts showing the processing of a measurement method according to one aspect of the present invention. In the following, a case will be described in which the measurement device 100 is incorporated as one function of the data processing device 14, and the processing is mainly performed by the processor 110. In addition, if the measurement device 100 is a device independent from the data processing device 14, the data processing device 14 and the measurement device 100 may share and execute the following processing.

[0061] [Processing condition settings] The processor 110 sets the processing conditions for the measurement (step S100). These processing conditions may include scan conditions (scan range, pitch, laser light irradiation pattern, etc.) for a new scan. Alternatively, when performing measurement using previously acquired data, the processing conditions may include designation of the data to be processed. The processing conditions may also include designation of a method (described later) for selecting points to be subjected to averaging processing from the measurement point cloud. The processor 110 may set the processing conditions based on a user operation via the operation unit 150, or may set the processing conditions according to conditions determined independently of a user operation. Note that some conditions, such as the method for selecting target points, may be set during the processing described below (for example, in step S130).

[0062] [Get scan data] The processor 110 acquires first scan data and second scan data (steps S110 and S120). The first scan data includes a first distance, which is a distance from the laser scanner 15 to the measured portion, obtained by scanning the measured portion of the wall surface 20A (object) with the laser scanner 15 in a first direction. The second scan data includes a first distance, which is a distance from the laser scanner 15 to the measured portion, obtained by scanning the measured portion of the wall surface 20A (object) in a first direction with the laser scanner 15. vinegar The scan data includes a second distance, which is the distance from the laser scanner 15 to the measured portion of the wall surface 20A, obtained by scanning the measured portion of the wall surface 20A in the second direction with the laser scanner 15. As described above, the processor 110 may perform a new scan to obtain the first and second scan data, or may obtain data that has been previously recorded in a recording device such as the recording device 160.

[0063] FIG. 9 is a diagram showing how calibration is performed using clockwise and counterclockwise measurement results. Part (a) of the figure shows how scanning is performed at a certain travel position (measurement point) in tunnel 20, and part (b) of the figure shows how scan data (measurement results) are acquired with clockwise (forward direction) as the first direction and counterclockwise, the opposite direction to clockwise, as the second direction, to obtain calibration results. Note that the scanning method is not limited to this example; it is sufficient that the first and second directions are different. Even if the second direction is not completely counterclockwise (even if the second direction is not completely opposite to the first direction), depending on the allowable calibration accuracy, such second direction can be considered to be "completely counterclockwise (completely opposite to the first direction)" and processed.

[0064] 10 is a diagram showing how data is acquired at each measurement point by scanning. In the example shown in the figure, for the i-th (i is an integer equal to or greater than 1) spot (measurement point), (distance L i , elevation angle Θ i , azimuth Φ i ) are correlated and acquired (acquisition of first scan data and second scan data). Note that the distance L i is the distance from the laser scanner 15 to the i-th spot (the portion to be measured on the wall surface 20A), and is the first distance in the case of the first scan, and the second distance in the case of the second scan.

[0065] The processor 110 acquires such data in each of the first direction scan and the second direction scan. The entire set of measurement points from which data is acquired in the first direction scan and the second direction scan are referred to as the first measurement point cloud and the second measurement point cloud, respectively.

[0066] The processor 110 can correlate and acquire the rate of change (first velocity, second velocity) of (distance, elevation angle, azimuth angle) for each measurement point of the first measurement point group and the second measurement point group. Note that (distance, elevation angle, azimuth angle) is equivalent to three-dimensional coordinates (x, y, z), and the rate of change of (distance, elevation angle, azimuth angle) is equivalent to three-dimensional velocity (Vx, Vy, Vz). Furthermore, the processor 110 can obtain the line-of-sight velocity V at each measurement point from these data. r and tangential velocity V t can be calculated.

[0067] [Select a pair of measuring points] Processor 110 selects a pair of measurement points to be calibrated (step S130). The selection can be performed by, for example, the following methods. Processor 110 may determine which method to use for selection based on a user operation via operation unit 150, or may determine the method without relying on a user operation. This determination may be performed in step S130, or may be performed in step S100 described above.

[0068] (Selection Method 1) Processor 110 performs averaging processing on all pairs of two points, each pair consisting of a first point (a point selected from the first measurement point cloud) and a second point (a point selected from the second measurement point cloud), where the difference in distance between the first point and the second point is equal to or less than a reference value. Pairs where the difference in distance is equal to or less than the reference value are considered to be likely to be corresponding points (points that should be measured as the same point), and therefore selection method 1 selects such pairs. Note that the "reference value" is a reference value for pair selection, and may be a value different from the "threshold value" described below.

[0069] (Selection Method 2) The processor 110 performs averaging processing on pairs of a point (first point) in the first measurement point cloud and one or more second points selected from the second measurement point cloud in order of proximity to the first point. In this way, in selection method 2, the second points are selected based on the first point.

[0070] (Selection Method 3) The processor 110 performs averaging processing on pairs of a second point and one or more first points selected from the first measurement point group in order of decreasing distance from the second point. In selection method 3, contrary to selection method 2, the first point is selected based on the second point.

[0071] [Calibration according to the distance between measurement points] In the first embodiment, as described below, calibration (averaging processing) is performed according to the distance between the selected measurement points (the distance between the first measurement point and the second measurement point). That is, if the distance between the measurement points is close, averaging processing is performed without using speed data, and if the distance is far, averaging using speed data is performed. This is because if the distance between the measurement points is close, calibration accuracy is good even without using speed data. Also, such processing allows calibration to be performed at high speed. However, the averaging processing in the present invention is not limited to this mode, and calibration can be performed with high accuracy by averaging using speed data for all pairs.

[0072] Specifically, processor 110 determines whether the distance between the measurement points is greater than or equal to a threshold value (step S140), and if the distance is close (less than the threshold value; NO in step S140), proceeds to step S155 to perform averaging processing without using the speed data.

[0073] [Averaging process when the distance between measurement points is less than the threshold] The position of the first measurement point is (x1, y1, z1), and the position of the second measurement point is (x2, y2, z2). The processor 110 calculates the distance L i , elevation angle Θ i , azimuth Φ i ) these positions can be calculated.

[0074] [Number 1] x i =L i ×sinΘ i ×cosΦ i y i =L i ×sinΘi ×sinΦ i z i =L i ×cosΘ i ···(1)

[0075] Then, the processor 110 can calculate the post-calibration position (x, y, z) by averaging (one aspect of averaging processing) the positions of the first and second measurement points using the following equation (2) (step S155). This post-calibration position corresponds to the post-calibration data.

[0076] [Number 2] x=(x1+x2) / 2 y=(y1+y2) / 2 z=(z1+z2) / 2 (2)

[0077] [Averaging process when the distance between measurement points is greater than or equal to the threshold] If the distance between the measurement points is equal to or greater than the threshold value (YES in step S140), averaging is performed using the velocity data. FIG. 11 is a conceptual diagram showing the averaging process using velocity data. In the figure, measurement points SP 11 ~SP 17 and then a counterclockwise scan (a second scan in the opposite direction to the first) is performed to obtain the measurement point SP 21 ~SP 26 In the first embodiment, the positions of these measurement points are divided internally by the ratio of the absolute values ​​of the velocities at the respective measurement points, and the resulting points are taken as post-calibration positions (point group indicated by reference symbol SPt).

[0078] The averaging process using velocity data will be specifically explained below. For simplicity, the explanation will be given in two dimensions, but the same process can be performed in three dimensions.

[0079] FIG. 12 is a diagram showing the relationship between the line-of-sight velocity and the tangential velocity. In the figure, the subscript "1" indicates a forward scan (clockwise, first scan), and the subscript "2" indicates a reverse scan (counterclockwise, second scan). Note that the angle θ is measured counterclockwise from the x-axis toward the y-axis. In this case, if the angular velocities acquired by the encoder 17 at measurement points P1 and P2 are ω1 and ω2, respectively, the tangential velocities obtained in the forward scan and the reverse scan are expressed by the following equation (3):

[0080] [Number 3] V t1 =r1×ω1 V t2 =r2×ω2 (3)

[0081] Here, V1 and V t1 The angle between V2 and V t2 The angle between and is considered to be equal under the condition that "the positions of measurement points P1 and P2 are sufficiently close," so the following equation (4) holds.

[0082] [Number 4] V r1 :V r2 ≒V t1 :V t2 ···(4)

[0083] That is, although the velocity in the line of sight direction and the velocity in the tangential direction have different values, the ratio of the two becomes equal.

[0084] Fig. 13 shows the internal division of the position based on the ratio of the absolute value of the velocity. The Doppler shift is expressed as Δf=2×V in the beat frequency domain. r / λ, and in the distance domain, it can be expressed as Δr=c×Δf / (2τ) (λ: wavelength of laser light, τ: chirp rate). Therefore, when the true values ​​of the distances at measurement points P1 and P2 are r1 and r2, respectively, the measured values ​​are r1+Δr1 and r2+Δr2, respectively. Also, from the above Doppler shift formula, Δr1=V r1 ×c / (λτ), Δr2=V r2× c / (λτ), where Δr1 and Δr2 indicate the influence of the Doppler shift, and “c / (λτ)” is a constant determined depending on the configuration of the laser scanner.

[0085] [Internal division of position by the ratio of absolute values ​​of velocity] From the above, if the true value of the position of the measurement point expressed in Cartesian coordinates is (x, y) and the measured value is (x', y'), the relationship between the true value and the measured value at measurement points P1 and P2 is expressed by the following equations (5) and (6).

[0086] [Number 5] x'1=x1+V r1 ×cosθ1×{c / (λτ)} y'1=y1+V r1 ×sinθ1×{c / (λτ)} ···(5) [Number 6] x'2=x2+V r2 ×cosθ2×{c / (λτ)} y'2=y2+V r2 ×sinθ2×{c / (λτ)} ···(6)

[0087] In equations (5) and (6), the second term represents the effect of the Doppler shift.

[0088] These measured values ​​(x'1, y'1) and (x'2, y'2) are V r By dividing internally by the ratio of the absolute values ​​of the above, the position of the measurement point (calibrated data) can be calculated with the influence of the Doppler shift removed, as shown in the following equation (7). Note that in equation (7), Δθ (the difference between θ1 and θ2) is assumed to be sufficiently small so that the slight first-order effect can be ignored.

[0089] [Number 7] x t =(|V r2 |×x'1+|V r1 |×x'2) / (|V r1 |+|V r2 |) ≒(|V r2 |×x1+|V r1 |×x2) / (|V r1 |+|Vr2 |) y t =(|V r2 |×y'1+|V r1 |×y'2) / (|V r1 |+|V r2 |) ≒(|V r2 |×y1+|V r1 |×y2) / (|V r1 |+|V r2 |) ···(7)

[0090] In addition, in equation (7), the ratio of the internal division is |V r1 |:|V r2 However, it is possible to divide it internally at other ratios. For example, if Δθ cannot be ignored, the ratio of internal division for x is |V r1 |cosθ1:|V r2 Weighting with cosθ as |cosθ2, and the ratio of the internal division for y is |V r1 |sinθ1:|V r2 It is possible to weight the coordinates with sinθ as |sinθ2. The same formula holds even if processing is performed using the polar coordinate system (r, θ) instead of the Cartesian coordinate system.

[0091] By performing such processing, the influence of the Doppler shift can be accurately calibrated and the position of the measurement point (the post-calibration position of the part to be measured; post-calibration data) can be obtained. Then, by repeating the processing of steps S130 to S155 (until step S160 returns YES), multiple pieces of position data (post-calibration data) of the wall surface 20A (object) can be obtained, and the three-dimensional shape of the wall surface 20A can be measured using these data (step S170).

[0092] [Extraction of potential damage areas] The processor 110 calculates the variation of the measured three-dimensional shape from the design information of the three-dimensional shape of the wall surface 20A (object) and / or previously acquired measurement results of the three-dimensional shape, and can extract areas where the magnitude of the variation exceeds a criterion as damage candidate areas (step S180). The "design information" can be, for example, three-dimensional data generated from CAD data, and the "previously acquired measurement results" can be past measurement results. The "criterion" can be, for example, a threshold value of the variation, and a threshold value set by the user can be used. The processor 110 can also display the extracted damage candidate areas on the display device 130 (display device, output device) and / or record them in the recording device 160 (recording device, output device).

[0093] FIG. 11 is a diagram showing how damage candidate regions are displayed. Specifically, it is a display example of the magnitude of the variation in the three-dimensional shape (the variation from the design information of the three-dimensional shape and / or the measurement results of the three-dimensional shape previously acquired, as described above). In the figure, the color intensity indicates the magnitude of the variation. The darker the color, the greater the variation, and the variation in regions 634 and 636 is greater than that in regions 630 and 632. In such a diagram, the processor 110 can overlay the magnitude of the variation based on the measurement with an image or design information of the wall surface 20A, thereby associating (correlating) the two. Note that the processor 110 may display the magnitude of the variation using saturation in addition to or instead of color intensity, or may display the color intensity in combination with letters, numbers, figures, symbols, graphs, etc.

[0094] In the measurement system 1, damage to the above-mentioned damage candidate region may be accurately measured or evaluated using some kind of measurement means (for example, a laser interferometer, non-contact acoustic excitation, image processing, etc.).

[0095] Processor 110 may display the 3D shape measurement results and damage assessment results in chronological order as charts, graphs, etc. on display device 130 and / or record them in recording device 160, or may make predictions based on past measurement results (step S190) and output (display, record, etc.) the results. Processor 110 may predict shape changes and damage by extrapolating past measurement results using a linear or nonlinear function, or may make predictions using a predictor developed by machine learning or a prediction model developed by other methods. Such predictions can be reflected in the evaluation of damage such as floating, and in the development of plans for inspection, repair, etc.

[0096] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described aspects and various modifications are possible. [Explanation of symbols]

[0097] 1. Measurement system 10. 3D measurement device 11 Laser light source 12 Tripod 13 Control Unit 14 Data Processing Device 15 Laser scanner 15A Polygon Mirror 15B motor 15C Monogon Mirror 16 Power supply 17 Encoder 18 Carts 20 Tunnel 20A Wall 100 Measuring Equipment 110 processors 120 memory 130 Display device 140 Input / Output Interface 150 Operation section 160 Recording Device 630 areas 632 areas 634 areas 636 areas P1 measurement point P2 measurement point

Claims

1. A measurement device including a processor, The processor: acquiring first scan data obtained by scanning a measurement portion of an object with a laser scanner in a first direction, the first scan data including information indicating a first distance, which is a distance from the laser scanner to the measurement portion; acquiring second scan data obtained by scanning the measurement portion of the object with the laser scanner in a second direction different from the first direction, the second scan data including information indicating a second distance, which is a distance from the laser scanner to the measurement portion; A measurement device that calculates calibrated data from which the influence of Doppler shift in the first scan data and the second scan data has been removed by performing an averaging process on the first scan data and the second scan data.

2. The measurement device according to claim 1 , wherein the processor performs the averaging process in accordance with a distance between a first measurement point at which the first scan data was acquired and a second measurement point at which the second scan data was acquired.

3. The measurement device according to claim 2 , wherein the processor averages the positions of the first measurement points and the second measurement points in the averaging process.

4. The processor: For each measurement point of the first measurement point group from which the first scan data is acquired, a first speed, which is a speed of the scan, is acquired by including the first scan data in the first scan data; For each measurement point of the second measurement point group from which the second scan data is acquired, a second speed, which is a speed of the scan, is acquired by including the second scan data in the second scan data; The measuring device according to claim 1 or 2, wherein the averaging process is performed on the first scan data and the second scan data using the first speed and the second speed.

5. In the averaging process, the processor 5. The measurement device according to claim 4, wherein the post-calibration data is calculated by dividing the position of a first point selected from the first measurement point cloud and the position of a second point selected from the second measurement point cloud by a ratio between the absolute value of the first velocity at the first point and the absolute value of the second velocity at the second point.

6. The measurement device according to claim 5 , wherein the processor performs the averaging process with the ratio of the internal division being 1:

1.

7. The measurement device described in claim 5, wherein the processor performs the averaging process for all pairs of the first point and the second point where the difference in distance between the first point and the second point is less than a reference value.

8. The processor: The measurement device according to claim 5, wherein the averaging process is performed on pairs of a point in the first measurement point cloud and one or more second points selected from the second measurement point cloud in order of proximity to the first point.

9. The processor: The measurement device according to claim 5 , wherein the averaging process is performed for pairs of the second point and one or more first points selected from the first measurement point group in order of proximity to the second point.

10. The measurement apparatus according to claim 1 , wherein the processor measures the three-dimensional shape of the object using a plurality of the post-calibration data.

11. The measurement device according to claim 10 , wherein the processor extracts a damage candidate region of the object based on the measured three-dimensional shape, and causes an output device to output information indicating the extracted damage candidate region.

12. The measurement device according to claim 11 , wherein the processor extracts, as the damage candidate region, a region where variation from design information of the three-dimensional shape of the object and / or previously acquired measurement results of the three-dimensional shape exceeds a standard.

13. The measurement device according to any one of claims 1 to 3; the laser scanner; A measurement system comprising:

14. 14. The measurement system according to claim 13, wherein the laser scanner is a laser scanner that uses a frequency-modulated continuous wave laser beam.

15. The measurement system according to claim 14, wherein the laser scanner is a laser scanner that uses a frequency-shifted feedback laser beam.

16. 1. A measurement method performed by a measurement device including a processor, comprising: The processor: acquiring first scan data obtained by scanning a measurement portion of an object with a laser scanner in a first direction, the first scan data including information indicating a first distance, which is a distance from the laser scanner to the measurement portion; acquiring second scan data obtained by scanning the measurement portion of the object with the laser scanner in a second direction different from the first direction, the second scan data including information indicating a second distance, which is a distance from the laser scanner to the measurement portion; A measurement method for calculating calibrated data from which the influence of Doppler shift in the first scan data and the second scan data has been removed by performing an averaging process on the first scan data and the second scan data.

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