Tracking method, laser scanner and tracking program

Abstract

To enable a laser scanner to more easily track and to enable the scanner to track a measuring object with no retroreflective characteristics.SOLUTION: A laser scanner comprises a distance measuring section 23 for irradiating the pulse distance measuring light 31, receiving reflected light 31', and performing distance measurement; an optical axis deflecting section 21 for scanning a predetermined scan range with the pulse distance measuring light at a predetermined cycle; a tracking section 13 for performing tracking on the basis of a distance measurement result of the distance measuring section; and a control section 16 for controlling the distance measuring section, the optical axis deflecting section, and the tracking section. The control section is configured to acquire point group data of the predetermined scan range, compare the distance measurement results of the point group data for every cycle, detect a moving measuring object on the basis of the comparison, set a local scan area including the measuring object, locally scan the local scan area, acquire local point group data, calculate a center of gravity position of the local point group data, and cause the tracking section to track the measuring object on the basis of the calculated center of gravity position.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a tracking method, a laser scanner, and a tracking program having a tracking function. [Background technology]

[0002] A laser scanner scans with pulsed ranging light to obtain point cloud data.

[0003] Typically, laser scanners are surveying instruments that rotate and emit distance-measuring light all around to acquire point cloud data, so they do not have the function of tracking the object being measured.

[0004] Patent Document 1 discloses a laser scanner that scans a predetermined range two-dimensionally, and indicates that this laser scanner has a tracking function. The laser scanner in Patent Document 1 is provided with a tracking optical system, and the object to be tracked is an object with retroreflective properties, such as a prism.

[0005] Therefore, the optical system becomes complicated and the target to be tracked is limited. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2020-51818 [Patent Document 2] Japanese Patent Application Laid-Open No. 2016-151423 [Patent Document 3] Japanese Patent Application Laid-Open No. 2016-161411 [Patent Document 4] Japanese Patent Application Laid-Open No. 2017-106813 [Patent Document 5] Japanese Patent Application Publication No. 2018-66571 Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention enables a laser scanner to more easily perform tracking and to track a measurement object that does not have retroreflective properties. [Means for solving the problem]

[0008] The present invention relates to a tracking method including the steps of: scanning a predetermined range at a predetermined cycle with a laser scanner to acquire point cloud data; comparing the point cloud data for each cycle; calculating a deviation by comparing the point cloud data; setting a local area including measurement points for which the deviation has been calculated; locally scanning the local area to acquire local point cloud data; calculating the center of gravity position of the local point cloud data; and performing tracking based on the center of gravity position.

[0009] The present invention also relates to a laser scanner having a distance measuring unit that irradiates pulsed distance measuring light and receives reflected light to measure distance, an optical axis deflection unit that scans the pulsed distance measuring light over a predetermined scan range at a predetermined cycle, a tracking unit that performs tracking based on the distance measurement results of the distance measuring unit, and a control unit that controls the distance measuring unit, the optical axis deflection unit, and the tracking unit, wherein the control unit is configured to acquire point cloud data of the predetermined scan range, compare the distance measurement results of the point cloud data at each cycle, detect a moving measurement target based on the comparison, set a local scan area including the measurement target, locally scan the local scan area, acquire local point cloud data, calculate the center of gravity position of the local point cloud data, and cause the tracking unit to track the measurement target based on the calculated center of gravity position.

[0010] The present invention also relates to a laser scanner in which the optical axis deflection unit has a pair of disk prisms, and is configured so that deflection and scanning of distance measuring light is performed by the independent rotation of each disk prism, and local scanning is performed by controlling the rotation of each of the disk prisms.

[0011] The present invention also relates to a laser scanner that further comprises an imaging unit having an angle of view larger than the maximum deflection range of the optical axis deflection unit, and a display unit on which an image acquired by the imaging unit is displayed, and the local scan area is displayed on the display unit.

[0012] The present invention also relates to a laser scanner having a horizontal rotation drive unit and a vertical rotation drive unit, and configured so that the position of a pixel relative to the image center of the imaging unit corresponds to the angle of deviation relative to the reference optical axis of the optical axis deflection unit, the angle of deviation of the measurement object is detected from the image, and the laser scanner is rotated by the horizontal rotation drive unit and the vertical rotation drive unit so that the measurement object is at the center of the image.

[0013] Furthermore, the present invention relates to a tracking program for causing a control unit in a laser scanner to execute each of the above steps. [Effects of the Invention]

[0014] According to the present invention, the method includes the steps of using a laser scanner to scan a predetermined range at a predetermined cycle to obtain point cloud data, comparing the point cloud data for each cycle, calculating the deviation by comparing the point cloud data, setting a local area including the measurement point for which the deviation was calculated, locally scanning the local area to obtain local point cloud data, calculating the center of gravity position of the local point cloud data, and performing tracking based on the center of gravity position, thereby making it possible to perform tracking easily without having to equip the laser scanner with a tracking optical system or provide a retroreflector on the object to be measured.

[0015] In addition, according to the present invention, there is provided a distance measuring unit that irradiates pulsed distance measuring light and receives reflected light to measure distance, an optical axis deflection unit that scans the pulsed distance measuring light over a predetermined scan range and at a predetermined cycle, a tracking unit that performs tracking based on the distance measurement results of the distance measuring unit, and a control unit that controls the distance measuring unit, the optical axis deflection unit, and the tracking unit, and the control unit is configured to acquire point cloud data of the predetermined scan range, compare the distance measurement results of the point cloud data at each cycle, detect a moving measurement target based on the comparison, set a local scan area including the measurement target, locally scan the local scan area, acquire local point cloud data, calculate the center of gravity position of the local point cloud data, and cause the tracking unit to track the measurement target based on the calculated center of gravity position, thereby providing the excellent effect of enabling simple tracking without the need for a tracking optical system or for providing a retroreflector on the measurement target. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a schematic diagram of a laser scanner according to an embodiment of the present invention; [Figure 2] FIG. 2 is a schematic diagram of the laser scanner. [Figure 3] 10(A) and 10(B) are explanatory diagrams showing the operation of the optical axis deflection unit of the laser scanner. [Figure 4] 3 is an explanatory diagram showing an example of a scan pattern formed by the optical axis deflection unit. FIG. [Figure 5] 4 is a flowchart showing the operation of the laser scanner of the present embodiment. [Figure 6] 10A and 10B are explanatory diagrams of the tracking operation of the laser scanner, in which (A) shows the n-1th scan pattern, (B) shows the nth scan pattern, and (C) shows the state in which the deviation between scan patterns is calculated. [Figure 7] FIG. 10 is an explanatory diagram showing a state in which a scan pattern is shifted to a local pattern. [Figure 8] 10A and 10B are diagrams illustrating the case where a local pattern is moved to the center of an image. [Figure 9] FIG. 10 is an explanatory diagram showing an application example of the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0018] First, a laser scanner according to an embodiment of the present invention will be described with reference to FIGS.

[0019] In FIG. 1, 1 indicates a laser scanner and 2 indicates a tripod as a support device.

[0020] The laser scanner 1 is mounted on the support device 2 via a stand 3. The laser scanner 1 also has a display unit 4 such as a liquid crystal display on the back, and an operation unit 5 consisting of a group of switches. The display unit 4 may also serve as an operation unit as a touch panel. Furthermore, the display unit and operation unit may be a wirelessly connected tablet or a PC connected via the Internet, etc.

[0021] The base 3 is equipped with a vertical rotation drive unit (not shown) and a horizontal rotation drive unit (not shown), and the vertical rotation drive unit is configured to rotate the laser scanner 1 vertically around a vertical rotation axis V, and the horizontal rotation drive unit is configured to rotate the laser scanner 1 horizontally around a horizontal rotation axis H. In addition, the vertical rotation drive unit is capable of detecting the amount of vertical rotation, and the horizontal rotation drive unit is capable of detecting the amount of horizontal rotation.

[0022] The vertical rotation drive unit and the horizontal rotation drive unit are controlled by a control unit 16, which will be described later.

[0023] The laser scanner 1 mainly comprises an imaging unit 8, an imaging control unit 9, a distance measurement light emitting unit 11, a light receiving unit 12, a tracking unit 13, a distance measurement control unit 15, a control unit 16, a memory unit 17, an optical axis deflection control unit 18, an attitude detection unit 19, and an optical axis deflection unit 21, which are housed and integrated in a housing 40. The distance measurement light emitting unit 11, the light receiving unit 12, the distance measurement control unit 15, the optical axis deflection unit 21, etc. constitute a distance measurement unit 23 that functions as an optical distance meter.

[0024] A CPU specialized for this embodiment, or a general-purpose CPU, an embedded CPU, a microprocessor, etc., is used as the distance measurement control unit 15 and the control unit 16. Furthermore, a semiconductor memory such as RAM, ROM, Flash ROM, or DRAM, a magnetic recording memory such as HDD, or an optical recording memory such as CD-ROM is used as the storage unit 17.

[0025] The storage unit 17 stores various programs for executing this embodiment, such as a distance measurement program for executing and controlling distance measurement, an optical axis deflection program for calculating the optical axis direction, controlling the optical axis deflection, and measuring the horizontal and vertical angles of the optical axis, a calculation program for calculating three-dimensional data based on the distance measurement results and the calculation results of the optical axis direction, a tracking program for performing tracking based on the measurement results, an image processing program for controlling the imaging unit 8 and processing images, etc. The storage unit 17 also stores various data such as measurement data, direction angle, attitude detection data, and image data.

[0026] The distance measurement control section 15 and the control section 16 each develop the stored program and execute required operations and controls at required timings.

[0027] The control unit 16 controls the optical axis deflection unit 21 via the optical axis deflection control unit 18. Furthermore, the control unit 16 controls the deflection of the distance measurement optical axis via the optical axis deflection unit 21, and performs integrated control of the distance measurement control unit 15 and the tracking unit 13, synchronous control of distance measurement, imaging, and tracking, etc.

[0028] The control unit 16 also controls the vertical rotation drive unit (not shown) and horizontal rotation drive unit (not shown) equipped on the stand 3 to set the orientation of the laser scanner 1, adapt it to the measurement situation, and change the orientation of the laser scanner 1.

[0029] The control unit 16 is also configured to execute a measurement mode in which a distance measurement program, an optical axis deflection program, etc. are deployed to scan the measurement area with distance measurement light and acquire point cloud data of the measurement area, and further to execute a tracking mode in which a tracking program is deployed to track a specific measurement target within the measurement area.

[0030] The attitude detection unit 19 detects the tilt of the laser scanner 1 relative to the horizontal or vertical, and the detection result is input to the control unit 16. A tilt detector such as a tilt sensor is used as the attitude detection unit 19, and further, the attitude detection device disclosed in Patent Document 2 can be used. The attitude detection device of Patent Document 2 can detect tilts of 360° or more in all directions in real time.

[0031] The control unit 16 acquires the tilt angle and tilt direction of the laser scanner 1 relative to the horizontal during measurement from the attitude detection unit 19. Furthermore, the control unit 16 corrects the measurement results based on the tilt angle and tilt direction acquired from the attitude detection unit 19. Therefore, there is no need to level the laser scanner 1 during measurement.

[0032] The distance measuring light emitting unit 11 has an emission optical axis 25, and a light emitting element 26, for example, a laser diode (LD), is provided on the emission optical axis 25. A light projecting lens 27 is also provided on the emission optical axis 25. The emission optical axis 25 is deflected by mirrors 28 and 29 so as to coincide with a light receiving optical axis 33 (described later).

[0033] The light-emitting element 26 emits a pulsed laser beam or a burst laser beam. The distance-measuring light emitting unit 11 emits the pulsed laser beam (or the burst-emitted laser beam) emitted from the light-emitting element 26 as distance-measuring light 31. Note that burst emission is disclosed in Patent Document 4.

[0034] The distance measuring light 31 is converted into a parallel beam by the light projecting lens 27 and is irradiated via the optical axis deflecting unit 21 .

[0035] The light receiving unit 12 will now be described. Reflected distance measuring light 31' from the measurement target is incident on the light receiving unit 12 via the optical axis deflection unit 21. The light receiving unit 12 has the light receiving optical axis 33, and the light receiving optical axis 33 coincides with the emission optical axis 25 deflected by the mirrors 28 and 29.

[0036] The state in which the emission optical axis 25 and the light receiving optical axis 33 coincide is referred to as the distance measurement optical axis (see FIG. 1).

[0037] The optical axis deflection unit 21 is disposed on the distance measurement optical axis. A straight optical axis that passes through the center of the optical axis deflection unit 21 is a reference optical axis O. The reference optical axis O coincides with the emission optical axis 25, the light receiving optical axis 33, and the distance measurement optical axis when not deflected by the optical axis deflection unit 21.

[0038] An imaging lens 35 is disposed on the light receiving optical axis 33 that has passed through the optical axis deflection unit 21. Also, a light receiving element 36 is provided on the light receiving optical axis 33. The light receiving element 36 is, for example, an avalanche photodiode (APD) or an equivalent photoelectric conversion element.

[0039] The imaging lens 35 forms an image of the reflected distance measuring light 31' on the light receiving element 36. The light receiving element 36 receives the reflected distance measuring light 31' and generates a light receiving signal. The light receiving signal is input to the distance measurement control unit 15. The distance measurement control unit 15 measures the distance to the measurement target (optical distance measurement) based on the timing of emitting the distance measuring light, the timing of receiving the reflected distance measuring light, and the speed of light.

[0040] The measurement may be a prism measurement in which the measurement object has retroreflectivity, or a non-prism measurement in which the measurement object does not have retroreflectivity.

[0041] The light receiving section 12 is composed of the optical axis deflection section 21, the imaging lens 35, the light receiving element 36, and the like.

[0042] As will be described later, the tracking unit 13 is configured to recognize a portion of the point cloud data where a change in the distance measurement value is detected as a tracking target and track it.

[0043] The optical axis deflection unit 21 will be described with reference to FIG.

[0044] The optical axis deflection unit 21 has a pair of disk prisms 41, 42, each of which is a circular plate of the same diameter and is composed of multiple prism pillars. By changing the relative rotation angle of the two disk prisms 41, 42, the optical axis can be deflected in the required direction.

[0045] The disk prisms 41 and 42 are rotated independently by motors 43 and 44, respectively, and the motors 43 and 44 are driven and controlled by the optical axis deflection control unit 18. The rotation angle and rotation position of the disk prisms 41 and 42 are detected by the optical axis deflection control unit 18.

[0046] The optical axis deflection unit 21 is disclosed in Patent Document 3.

[0047] By combining the rotational positions of the disk prism 41 and the disk prism 42, the deflection angle and deflection direction of the emitted distance measuring light 31 with respect to the reference optical axis O can be changed arbitrarily.

[0048] When the positional relationship between the disk prism 41 and the disk prism 42 is fixed (when the deflection angle obtained by the disk prism 41 and the disk prism 42 is fixed), and the disk prism 41 and the disk prism 42 are rotated together by the motors 43, 44, the trajectory of the distance measurement light 31 that passes through the distance measurement light deflection unit becomes a circle centered on the reference optical axis O.

[0049] Also, as shown in Figure 3(A), if the deflection direction of the optical axis deflected by the disk prism 41 is deflection A and the deflection direction of the optical axis deflected by the disk prism 42 is deflection B, the deflection of the optical axis by the disk prisms 41 and 42 becomes a composite deflection C, with the angle difference θ between the disk prisms 41 and 42.

[0050] Therefore, by rotating the disk prism 41 and the disk prism 42 in opposite directions at a constant speed, the distance measuring light 31 can be scanned back and forth along a linear locus 45 in the direction of the combined deflection C.

[0051] 3B, if the disk prism 42 is rotated at a rotation speed slower than that of the disk prism 41, the angular difference θ gradually increases while the distance measuring light 31 rotates. Therefore, the scanning locus of the distance measuring light 31 becomes spiral.

[0052] Furthermore, by individually controlling the rotation direction and rotation speed of the disk prism 41 and the disk prism 42, various two-dimensional scan patterns can be obtained by scanning the distance measuring light 31 with the reference optical axis O as the center.

[0053] For example, by rotating one of the disk prisms 41 and 42 forward at 17.5 Hz and rotating the other disk prism 42 backward at 5 Hz, a petal-shaped two-dimensional closed-loop scan pattern (petal pattern 46 (hypotrochoid curve)) as shown in Figure 4 is obtained.

[0054] Furthermore, the distance measuring light 31 is emitted in pulses, and the point where each pulse of light is irradiated is the measurement point. Distance measurement (distance) and angle measurement (horizontal angle, vertical angle) are performed for each pulse of light, and three-dimensional point cloud data along the scanning trajectory can be obtained.

[0055] When scanning with the petal pattern 46, the point cloud density increases if the pattern is rotated by a predetermined angle for each scan pattern.

[0056] Furthermore, by individually controlling the rotation of the disk prisms 41 and 42, it is possible to form and scan a scan pattern within the maximum deflection range of the optical axis deflection unit 21, form and scan a scan pattern within a specified range set within the maximum deflection range, and even scan within a limited local range within the maximum deflection range or the specified range (hereinafter referred to as local scanning).

[0057] The imaging unit 8 will now be described.

[0058] The imaging unit 8 has an optical axis 48 parallel to the reference optical axis O, and an imaging lens 49 and an imaging element 50 are provided on the optical axis 48. The imaging unit 8 is capable of acquiring an image at an angle of view larger than the maximum deflection angle of the optical axis deflection unit 21. The acquired image is displayed on the display unit 4. The imaging element 50 uses a CCD, CMOS sensor, or the like, which is composed of a collection of pixels, and the position of each pixel on the imaging element 50 can be identified.

[0059] The optical axis 48 passes through the center of the image sensor 50, and the position of the pixel can be identified on the image sensor 50. For example, each pixel has pixel coordinates in a coordinate system (XY coordinate system) with the center of the image sensor 50 as the origin, and the light receiving signal from each pixel contains pixel coordinates (position information).

[0060] Furthermore, the center of the image sensor 50 is the position of the reference optical axis O, and the horizontal and vertical angles with respect to the reference optical axis are set to correspond to the pixel coordinates (x, y). Therefore, the horizontal and vertical angles with respect to the reference optical axis O can be calculated from the position on the image.

[0061] The measurement and tracking operations of this embodiment will be described below with reference to FIGS.

[0062] STEP 01: Install the laser scanner 1 in a required position. Use the stand 3 to point the laser scanner 1 in the direction to be measured. Check the image displayed on the display unit 4 to see if the measurement direction includes the object to be measured.

[0063] STEP 02: Set the measurement conditions. The measurement conditions include the scan area, point cloud density, scan speed, and scan pattern. The scan area can be set by referring to the image. For example, the scan area is set to the maximum deflection range, and the scan pattern is set to the petal pattern 46 shown in FIG. 4. Regarding the point cloud density, if the measurement object is formed by a surface, the point cloud density is set to a low value, and if the object has a complex shape, the point cloud density is set to a high value. The control unit 16 may automatically change the density of the point cloud data based on the measurement results. The scan pattern is arbitrary, as long as it is a pattern obtained by two-dimensional scanning.

[0064] STEP:03 Once the measurement conditions have been set, measurement will begin in measurement mode. Scanning will begin in the set scan area, and point cloud data will be acquired along the scanning trajectory. The data for each point in the point cloud is 3D data (x, y, z) consisting of horizontal angle, vertical angle, and distance measurement value.

[0065] STEP 04: Once the point cloud data of the measurement area has been acquired, the tracking mode is selected. In the tracking mode, the direction of the laser scanner 1 is fixed, and a scan pattern 46 is first executed within the measurement area. The completion of one scan pattern is considered one pattern scan, and the pattern scans may be executed continuously or at predetermined time intervals. In other words, the pattern scan is executed at a predetermined cycle.

[0066] STEP 05: Compare the 3D data for each measurement point between the previous (n-1th cycle) single pattern scan and the next (nth cycle) single pattern scan (see Figure 6). If there is nothing moving within the scan range, there will be no change in the measurement data for all measurement points. In particular, there will be no change in the distance measurement data.

[0067] If there is a moving object 52 within the scan area, taking the difference between the pattern scan in the n-1th period and one pattern scan in the nth period will result in a deviation in the measurement data for the measurement point corresponding to the moving object 52. Therefore, the deviation of the measurement point is calculated.

[0068] STEP 06: The measurement point where deviation occurred is extracted, and the moving measurement target is detected. The area including the measurement point where deviation occurred is calculated, and a local area 53 is calculated by setting a required margin for that area.

[0069] The shape of the local area 53 is appropriately selected from rectangles, circles, ellipses, etc., that fit the shape of the extracted measurement points.

[0070] STEP: 07 An optimal pattern for scanning the local area 53 (hereinafter referred to as local scan) is calculated and set as the local scan pattern 54. Once the local scan pattern 54 is set, the control unit 16 controls the optical axis deflection unit 21 via the tracking unit 13 to locally scan the local area 53 at a predetermined cycle. The set local area 53 is displayed on the display unit 4.

[0071] STEP: 08 Local scans are performed, and point cloud data is acquired for each local scan. The point clouds included in the local scan pattern 54 are treated as local point clouds, and the centroid position (x, y, z) of the local point cloud data is calculated for each local scan pattern. The tracking unit 13 moves the local area 53 to follow the movement of the measurement target based on the calculated centroid position, and performs tracking. The tracking status and the local area 53 moving due to tracking are displayed on the display unit 4 in real time.

[0072] STEP: 09 The center of gravity position of the local point cloud data in the (n-1th cycle) and the center of gravity position of the local point cloud data in the (nth cycle) are compared to calculate the direction and amount of movement of the center of gravity.

[0073] STEP 10: If tracking mode is continued, local scans are continuously performed at each cycle, local point cloud data is acquired, and the center of gravity position, direction of movement of the center of gravity, and amount of movement of the local point cloud data are calculated in three dimensions. During tracking, the scan range is limited to a local area, so tracking can be performed in a short time with a small amount of data.

[0074] Since a local area is scanned intensively, the shape, orientation, etc. of the measurement object can be detected accurately.

[0075] Therefore, according to this embodiment, it is possible to identify an object moving within the scan area, and further to measure the direction and amount of movement in three dimensions. Furthermore, when performing tracking, it is not necessary to provide a retroreflector such as a prism on the measurement target.

[0076] Furthermore, by storing and setting a sample image of the measurement object and specifying a specific measurement object (sample image), the measurement object can be automatically recognized from the image acquired by the imaging unit 8 through image recognition such as image matching between the image acquired by the imaging unit 8 and the sample image, and local scanning can be performed around objects moving in the image.

[0077] Alternatively, the operator may designate a local area on the display unit 4, execute a local scan, and start tracking.

[0078] Next, if the object to be measured moves significantly or moves at a high speed that exceeds the deflection range of the optical axis deflection unit 21, the laser scanner 1 can be rotated horizontally and vertically by the mount 3 while performing tracking, so that the object to be measured is always positioned near the reference optical axis O or at the center of the image acquired by the imaging unit 8.

[0079] In FIG. 8, 56 indicates an image acquired by the imaging unit 8, and also shows a schematic representation of the relationship with the laser scanner 1, where 1 indicates the measurement center (reference position) of the laser scanner.

[0080] O indicates the center of the image. The image center coincides with the reference optical axis O. Point 57 in image 56 indicates the center of gravity position obtained based on the local scan. If the coordinates of point 57 in the image are (x1, y1), then (x1) corresponds to the horizontal angle θH with respect to the reference optical axis O, and (y1) corresponds to the vertical angle θV with respect to the reference optical axis O. The distance to the measurement target is represented by (z).

[0081] To bring point 57 to the center of image 56, the laser scanner 1 is rotated clockwise by θH, so that it can be positioned at the center of the image in the horizontal direction. Furthermore, to bring point 57 to the center of the image, the laser scanner 1 is further rotated vertically upward by θV. measurement If the start time is used as the reference, θH and θV should be added to the horizontal and vertical angles of the measurement results, respectively.

[0082] Therefore, the position (three-dimensional coordinates) of the moving measurement target can be known from the measurement results of the local scan, making it possible to track the target in a range exceeding the maximum deflection angle of the optical axis deflection unit 21.

[0083] Furthermore, if the target object is lost during tracking operation, it is possible to return to tracking by repeating STEP: 01 to STEP: 09.

[0084] FIG. 9 shows an application example of this embodiment.

[0085] In FIG. 9, 59 denotes a crane, and 60 denotes a structural member of a building, such as a concrete pillar.

[0086] A laser scanner 1 is installed near an assembly position 61 of the structural member 60. Position information of the assembly position 61, the shape of the installation location, etc. are input into the laser scanner 1. Furthermore, if the shape of the tracking target is known from BIM (Building Information Modeling) or design data, the shape is fitted to the point cloud data and the position of the tracking target is displayed.

[0087] The laser scanner 1 is directed toward the structural member 60 and scans a two-dimensional pattern at the maximum deflection range to detect the moving structural member 60. A local area is set based on the detection result, a local scan pattern is generated according to the shape of the local area, a local scan is performed, and tracking is performed.

[0088] In local scanning, a local range is scanned intensively, resulting in a high point cloud density, which makes it possible to recognize the shape, posture, and tilt of the structural member 60 based on the point cloud data. Furthermore, the data obtained is three-dimensional data, and by acquiring three-dimensional data (x, y, z) in real time and analyzing changes in the three-dimensional data, the moving speed and moving direction of the structural member 60 can be calculated.

[0089] It goes without saying that the local scan pattern is not fixed, but an optimal local scan pattern is generated as needed in accordance with changes in the posture, orientation, tilt, etc. of the structural member 60.

[0090] Furthermore, based on the position information of the assembly position 61 and the measurement results when tracking the structural member 60, it is possible to accurately instruct the crane operator on movement to the target point and the orientation of the structural member 60. [Explanation of symbols]

[0091] 1. Laser scanner 2 Support device 3 Mounting stand 8. Imaging unit 9. Imaging control section 11 Distance measurement light emission section 12 Light receiving section 13 Tracking part 15 Distance control section 16 Control Unit 17 Memory section 18 Optical axis deflection control section 19 Attitude detection unit 21 Optical axis deflection section 23 Ranging section 46 Petal Pattern 53 Local Area 54 Local Scan Pattern

Claims

1. a step of setting a predetermined range within a maximum deflection range as a scan area in a laser scanner, and scanning the scan area at a predetermined cycle to acquire point cloud data; a step of comparing three-dimensional data for each measurement point between the point cloud data acquired in the latest scan for each cycle and the point cloud data acquired in the scan one cycle prior; a step of extracting measurement points where a deviation has occurred in the comparison of point cloud data and detecting a moving measurement target; a step of calculating an area including the measurement points where a deviation has occurred and setting a local area in which a required margin has been set for the area; a step of setting a local scan pattern for scanning the local area; a step of locally scanning the local area intensively using the local scan pattern to acquire local point cloud data; a step of calculating a center of gravity position of the local point cloud data;

2. The tracking method according to claim 1 , further comprising the step of detecting a shape and a posture of a measurement target based on the local point cloud data, and measuring a moving direction, a moving speed, and a moving amount.

3. a distance measuring unit that irradiates a pulse distance measuring light and receives a reflected light to measure distance; an optical axis deflection unit that scans the pulse distance measuring light in a predetermined scan range at a predetermined cycle; a tracking unit that performs tracking based on a distance measuring result from the distance measuring unit; and a control unit that controls the distance measuring unit, the optical axis deflection unit, and the tracking unit; The control unit a scanning area obtained by scanning the scan area at a predetermined period, comparing the three-dimensional data for each measurement point between the point cloud data obtained in the latest scan and the point cloud data obtained in the scan one cycle prior to the current scan for each period, extracting measurement points where a deviation has occurred in the comparison of the point cloud data, and detecting a moving measurement object; and calculating an area including the measurement points where a deviation has occurred, setting a local area with a required margin set for the area, setting a local scan pattern for scanning the local area, locally scanning the local area intensively using the local scan pattern, obtaining local point cloud data, calculating the center of gravity of the local point cloud data, and causing the tracking unit to track the measurement object based on the center of gravity position.

4. The laser scanner according to claim 3, wherein the optical axis deflection unit has a pair of disk prisms, and is configured so that deflection and scanning of the distance measurement light are performed by independent rotation of each disk prism, and local scanning is performed by controlling the rotation of each disk prism.

5. 4. The laser scanner according to claim 3, further comprising an imaging unit having an angle of view larger than a maximum deflection range of the optical axis deflection unit, and a display unit on which an image acquired by the imaging unit is displayed, and the local area is displayed on the display unit.

6. 4. The laser scanner according to claim 3, further comprising a horizontal rotation drive unit and a vertical rotation drive unit, and a pixel position relative to an image center of the imaging unit is configured to correspond to a deviation angle relative to a reference optical axis of the optical axis deflection unit, a deviation angle of the measurement object is detected from an image, and the laser scanner is rotated by the horizontal rotation drive unit and the vertical rotation drive unit so that the measurement object is located at the image center.

7. A tracking program for causing a control unit of a laser scanner to execute each of the steps of claim 1.

Images