Laser surveying target

Abstract

To eliminate the need for replacing a prism target and a scanner target in three-dimensional laser scanner measurement using a laser measurement device which is provided with a total station and a laser scan device or the functions of these two.SOLUTION: A target plate 10 is held to an arm 12 so as to be rotatable around a revolving shaft 11, a first surface 10a of the target plate 10 being adopted as a prism target and a second surface 10b being adopted as a scanner target, with a prism 20 attached to the center of the first surface 10a. A prism target function and a scanner target function are switched by rotating the target plate 10 in the vertical direction.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a target used, for example, in three-dimensional laser scanner surveying. [Background technology]

[0002] In three-dimensional laser scanner surveying, a pulsed laser beam is irradiated while scanning the target or target area, and the light reflected from the target or objects in the target area is received. For each reflected light, the three-dimensional coordinates of the reflection points are calculated from the time it takes for the light to return and the irradiation angle of the laser beam, and the three-dimensional shape of the target or target area is obtained by connecting the three-dimensional coordinates of the many reflection points obtained. Since the range that can be scanned by a laser scanner device is limited, when surveying a wide area, multiple scanner targets are installed within the target area, the three-dimensional coordinates of each scanner target are measured, and each scanner target is used as the target for starting scanning, and the laser beam is scanned over a certain range to obtain three-dimensional coordinate data of many reflection points for each range. If there is an obstacle, the laser scanner device and the scanner target are moved, and the laser beam is irradiated again. Then, errors are corrected by software based on the three-dimensional coordinates of each scanner target to obtain the three-dimensional shape of the target or target area.

[0003] FIG. 4 shows a conventional scanner target 110 described in, for example, Patent Document 1. In FIG. 4, (a) shows a pattern drawn on one surface (front surface) of the target plate 111, and (b) shows a pattern drawn on the other surface (back surface) of the target plate 111. As shown in FIG. 4, the scanner target 110 is composed of a disk-shaped target plate 111, a substantially U-shaped arm 112 that holds the target plate 111 rotatably in the vertical direction around a horizontal axis 113, and a shaft part 114 that is attached to a leveling table 150 and holds the target plate 111 and the arm 112 rotatably in the horizontal direction around the vertical axis. As shown in FIG. 4(a), two orthogonal diameter lines 111a and 111b that form a predetermined angle (for example, 45 degrees) with respect to the horizontal axis 113 are drawn on one surface of the target plate 111, and the plate surface of the target plate 111 is divided into four by these diameter lines, and each of the four divided sections is colored alternately in white and black. 4(b), a small white circle 111c with a diameter of several centimeters is drawn in the center of the other side of the target plate 111, and the remaining part 111d is painted black. The target plate 111 is rotated according to the nature of the laser scan to use the side with high recognition efficiency for the laser scan. When painted black and white, almost no reflected light is returned from the black area because black absorbs light, but because white has a high reflectivity, the area near the boundary between the black area and the white area becomes a gray gradation, which is thought to make it difficult to recognize the center of the target plate 111.

[0004] However, the greater the distance between the laser scanner device and the scanner target, the more difficult it becomes to recognize the center of the scanner target, and the more difficult it becomes to accurately measure the three-dimensional coordinates of the reference point where the scanner target is to be placed. In addition, if the error in the three-dimensional coordinates of the reference point where the scanner target is to be placed is large, the three-dimensional shape of the object or target area obtained by piecing together the three-dimensional coordinate data of the reflection points obtained will be distorted. Therefore, a total station and a prism target are used to accurately measure the three-dimensional coordinates of the reference point where the scanner target is to be placed. In general, the laser scanner device and the total station are attached to a tripod via a leveling stand. For example, the total station and the prism target are first used to measure the three-dimensional coordinates of the reference point where the scanner target is to be placed, and then the total station is replaced with the laser scanner device and the prism target is replaced with the scanner target, and the three-dimensional shape of the object or target area is obtained by scanning with a laser beam.

[0005] Although a total station can measure the distance and angle to a target accurately (with an error of a few millimeters), it is necessary to use a prism target with a prism attached as the target. Fig. 5 shows a typical prism target 120 that is commercially available. This prism target 120 is removable from a leveling base 150 and is composed of a prism 121 held so as to be able to swing vertically around a horizontal axis 124, a target plate 122 attached to the back of the prism 121, and a base 123 for mounting the prism target 120 to the leveling base 150. The leveling base 150 is used by being attached to a tripod or the like, and is equipped with a screw for adjusting the horizontality, a rotation axis for rotating or swinging the prism target 120 in the horizontal direction, and the like (description of known methods will be omitted). On the surface of the target plate 122, approximately V-shaped or triangular marks 122a and 122b are provided symmetrically with respect to the center (optical axis) of the prism 121, and the optical axis of the prism 121 is adjusted from a total station provided at a distance by targeting the marks 122a and 122b provided on the target plate 122. The target plate 122 is fixed to a base 123, and the prism 121 performs a vertical swing motion around a horizontal axis 124, so that the adjustable range is narrow, and when the prism 121 is swung widely, there is a large deviation from the marks 122a and 122b on the target plate 122, making it difficult to adjust the optical axis. In addition, in the conventional prism target 120, the diameter D1 of the prism 121 is relatively large compared to the width W1 of the target plate 122 (for example, D1 / W1=about 2 / 3 to 1 / 2), so that it is difficult to adjust the optical axis of the prism 121 from a total station provided at a distance.

[0006] In general, the target mounting portion of the leveling table 150 is compatible, and even if it is a product of a different manufacturer, it can be mounted. However, as described above, the scanner target 110 and the prism target 120 have different structures, for example, the height of the shaft portion 114 of the scanner target 110 and the base 123 of the prism target 120, and even if the scanner target 110 is mounted on the same leveling table 150 after the prism target 120 is removed from the leveling table 150, the center of the target plate 111 does not necessarily coincide with the center (optical axis) of the prism 121. In addition, when replacing the scanner target 110 with the prism target 120, it is difficult to match the center of the scanner target 110 with the center of the prism target 120. In this regard, it is probably the same even if it is a product of the same manufacturer. Therefore, when replacing the prism target 120 with the scanner target 110, it is necessary to adjust the height. Similarly, since the heights of the laser scanner device and the total station are different, it is necessary to adjust the height by raising and lowering the elevator of the tripod.

[0007] Patent Document 2 describes a laser measurement device equipped with a total station function and a laser scanner function (hereinafter referred to as the "laser measurement device"). In a three-dimensional laser scanner survey using such a laser measurement device, prism targets are installed at multiple measurement target points, and the three-dimensional coordinate values ​​of each measurement target point are accurately measured using the total station function, and then the prism targets are replaced with scanner targets, and the laser scanner function is used to obtain three-dimensional coordinate data by targeting each scanner target. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] JP 2018-96855 A [Patent Document 2] Patent Publication No. 2021-43217 Summary of the Invention [Problem to be solved by the invention]

[0009] The present invention has been made to solve the problems of the conventional examples described above, and aims to provide a target for laser surveying used in three-dimensional laser scanner surveying using a total station and a laser scanner device, or a laser measuring device equipped with both functions, which has the functions of both a prism target and a scanner target in a single target, without the need to exchange the prism target and the scanner target. [Means for solving the problem]

[0010] The laser surveying target according to the present invention comprises: A target plate and an arm that holds the target plate rotatably around a predetermined rotation axis, A through hole is provided in the center of the target plate, and a prism is attached to a first surface of the target plate so as to be offset in the optical axis direction so that the prism constant is "0." And, The first surface of the target plate is divided into four regions by two color-separating lines that pass through the center of the first surface and are parallel and perpendicular to the rotation axis, and two adjacent regions are colored differently from each other; The second surface of the target plate is divided into four regions by two mutually perpendicular color dividing lines that pass through the center of the second surface and form a predetermined angle with respect to the rotation axis, and two adjacent regions are colored differently from each other.

[0012] The different colors applied to the first surface of the target plate may be yellow and black.

[0013] Also, a click-stop mechanism may be provided between the rotation shaft and the arm, allowing positioning at 90 degree intervals.

[0014] Furthermore, the diameter of the prism may be D, and the width of the target plate may be W, so that D / W is in the range of 1 / 4 to 1 / 10. Effect of the Invention

[0015] Thus, according to the present invention, in three-dimensional laser scanner surveying using a total station and a laser scanning device or a laser measuring device equipped with both functions, it is possible to accurately measure the three-dimensional coordinates of the reference point where the scanner target is to be installed using a single target without exchanging the prism target and the scanner target, and to continue with the three-dimensional laser scanner surveying by simply rotating the target plate vertically. [Brief description of the drawings]

[0016] [Figure 1] 1 is a perspective view of a laser surveying target according to an embodiment of the present invention, viewed from a first surface side of the target plate. [Diagram 2] FIG. 2 is a perspective view of the above-mentioned laser surveying target as viewed from the second surface side of the target plate. [Diagram 3] FIG. [Figure 4] FIG. 1 illustrates a conventional scanner target. [Diagram 5] FIG. 1 shows a conventional prism target. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] A laser surveying target according to an embodiment of the present invention will be described. FIG. 1 is a view of the laser surveying target 1 from a first surface side 10a of the target plate 10, showing a state in which it is used as a prism target. FIG. 2 is a view of the laser surveying target 1 from a second surface side 10b of the target plate 10, showing a state in which it is used as a scanner target. FIG. 3 shows a cross section of the target plate 10 and a prism 20, which will be described later. As can be seen from FIGS. 1 and 2, the laser surveying target 1 can be used as both a prism target and a scanner target by rotating the target plate 10, and in a three-dimensional laser scanner survey using a total station and a laser scanning device or a laser measuring device equipped with both functions, there is no need to exchange the prism target and the scanner target.

[0018] As shown in Figures 1 and 2, the laser surveying target 1 is composed of a target plate 10, an arm 12 that holds the target plate 10 rotatably around a predetermined rotation axis (horizontal axis) 11, and an axis portion 13 for attaching the target plate 10 and the arm 12 to a leveling table. As shown in Figure 1, a prism 20 is attached to a first surface 10a of the target plate 10 via a prism holder 21. The first surface 10a of the target plate 10 is divided into four areas by two colored lines 10c and 10d that pass through the center of the first surface 10a and are parallel and perpendicular to the rotation axis 11, and two adjacent areas are painted in different colors (e.g., yellow and black) as a mark for identifying the center. On the other hand, as shown in FIG. 2, the second surface 10b of the target plate 10 is divided into four regions by two mutually orthogonal colored dividing lines 10e and 10f that pass through the center of the second surface 10b and are set to form a predetermined angle (e.g., 45 degrees) with respect to the rotation axis 11, and the two adjacent regions are colored differently from each other (e.g., white and black) as a mark for identifying the center. The centers of the first surface 10a and the second surface 10b of the target plate 10 (the center of the target plate 10) are aligned, and a through hole 14 is provided in the center of the target plate 10. The target plate 10 is formed of, for example, a metal plate such as aluminum or a resin plate such as FRP (Fiber Reinforced Plastic). Although a rectangle is illustrated as an example of the planar shape of the target plate 10 in FIG. 1 and FIG. 2, it may be a circle.

[0019] The rotation shaft 11 is formed of, for example, FRP, and is a substantially cylindrical member in which the portion that contacts the target plate 10 is cut into a flat shape, and is attached, for example, by screws or the like to both ends of the paint separation line 10d of the first surface 10a of the target plate 10 from the second surface 10b side. The prism target is for accurately determining the coordinates of the reference point of the scanner target. Therefore, as shown in FIG. 3, the target plate 10 is rotatably attached to the arm 12 via the rotation shaft 11, and the center of the second surface 10b of the target plate 10, i.e., the scanner target side, is set to be located on the rotation center line of the rotation shaft 11 (in FIG. 3, the intersection 11b of the optical axis L of the prism 20 and the central axis C of the shaft portion 13: approximately the same position as the rear end 20c of the housing 20a of the prism 20). The first surface 10a of the target plate 10, i.e., the center on the prism target side, is offset from the rotation center line of the rotation axis 11 by the thickness of the target plate 10 (for example, 2 mm) in the direction perpendicular to the plate surface. Therefore, the center of the first surface 10a of the target plate 10 functioning as the prism target and the center of the second surface 10b functioning as the scanner target coincide with each other. When the laser surveying target 1 is attached to a leveling table and the horizontal is adjusted, the rotation axis 11 becomes horizontal. A click stop mechanism is provided between the rotation axis 11 and the arm 12. Specifically, a cross groove 11a is formed on the surface of the rotation axis 11 facing the arm 12, for example, parallel and perpendicular to the plate surface of the target plate 10, and a stopper 16 composed of, for example, a ball and a spring is provided on the arm 12. Therefore, the target plate 10 can be positioned horizontally and vertically every 90 degrees. When the laser surveying target 1 is attached to a leveling table and the horizontal is adjusted, the rotation axis 11 becomes horizontal, so that the target plate 10 can be easily held vertically and horizontally. A fixing screw 15 for fixing the rotating shaft 11 so as not to rotate is provided at the connection between the rotating shaft 11 and the arm 12. The outer periphery of the shaft 13 has an outer diameter that complies with a standard so that it can be attached to a commercially available leveling stand. Although not shown, the inner diameter of the shaft 13 has two stages of screw holes 13a and 13b of different sizes (standards) so that it can be directly attached to a tripod or the like.

[0020] As shown in FIG. 3, the prism holder 21 has a screw hole (female screw) 21a formed therein so as to face the through hole 14 of the target plate 10 when the prism holder 21 is attached to the target plate 10. A male screw 20b that screws into the screw hole 21a is also formed on the rear end side of the housing 20a of the prism 20, and the prism 20 can be attached to and detached from the prism holder 21 via these screws. Therefore, when the prism 20 is attached to the prism holder 21, the optical axis L of the prism 20 coincides with the center of the target plate 10, and the prism 20 is configured to be perpendicular to the first surface of the target plate 10. The prism holder 21 may be fixed to the target plate 10 using an adhesive or by screwing.

[0021] As is well known, each prism for a prism target has its own prism constant. The prism constant is defined by the refractive index of the material of the prism, the height of the prism, and the offset of the prism apex from the rotation axis. As described above, the through hole 14 is provided at the center of the target plate 10, and the prism 20 is attached with a shift (i.e., offset) in the optical axis direction (direction perpendicular to the plate surface of the target plate 10) so that the prism constant of the prism 20 is "0" so that correction based on the prism constant is not required. In the example shown in FIG. 3, the rear end 20c of the housing 20a of the prism 20 is attached with an offset so that it enters the through hole 14, and the second surface 10b of the target plate 10 and the rear end 20c of the housing of the prism 20 are almost flush with each other. Therefore, the three-dimensional coordinates of the reference point (second reference point described later) where the laser surveying target 1 is installed, measured using the total station function and the prism target function of the laser surveying target 1, can be used as is without correcting the prism constant.

[0022] Next, a method of using the laser surveying target 1 will be described. A tripod is installed at the location (first reference point) where the total station and the laser scanning device are installed, and the total station is attached to the tripod via a leveling stand to measure the three-dimensional coordinates of the first reference point. In addition, one or more laser surveying targets 1 are installed on the object or target area to be surveyed by the three-dimensional laser scanner so that the first surface 10a of the target plate 10 faces the total station, and the target plate 10 is viewed from the total station, and the optical axis L of the prism 20 is adjusted to face the total station, aiming at the marks (colored division lines 10c and 10d that are perpendicular to each other) provided on the first surface 10a. As described above, the four divided areas are colored yellow and black as marks on the first surface 10a of the target plate 10. As described above, when the first surface 10a of the target plate 10 is painted black and white, almost no reflected light is returned from the black area, but because white has a high reflectivity, the area near the boundary between the black area and the white area becomes a gray gradation, making it difficult to recognize the center of the target plate. On the other hand, yellow has a lower reflectivity than white, so the boundary between the black area and the yellow area, i.e., the painted lines 10c and 10d, are easy to recognize. Then, a total station is used to measure the three-dimensional coordinates of the installation location (second reference point) of the laser surveying target 1. When the three-dimensional coordinates of the second reference point are measured, the total station is replaced with a laser scanning device, and the target plate 10 of the laser surveying target 1 is rotated 180 degrees in the vertical direction as shown by arrow A, so that the second surface 10b of the target plate 10 faces the laser scanning device. The laser scanning device is used to scan a predetermined range based on the laser surveying target 1 with laser light to obtain the three-dimensional coordinates of the object or the target range.

[0023] As is well known, the beam system of laser light is very small, and the prism target reflects the laser light that is incident parallel to the optical axis in a parallel manner to the optical axis. Therefore, the reflected light from the prism enters the total station only when it is incident parallel to the optical axis of the prism from the total station. Therefore, even if the diameter of the prism of the prism target is made small, it does not affect the measurement accuracy. Comparing the first surface 10a that functions as the prism target of the laser surveying target 1 according to the present invention shown in FIG. 1 with the conventional prism target shown in FIG. 5, the diameter D of the prism 20 of the laser surveying target 1 is very small compared to the width W of the target plate 10 (for example, D / W=about 1 / 4 to 1 / 10), so that the intersection of the color division lines 10c and 10d that theoretically coincide with the optical axis of the prism 20 can be easily estimated, and the optical axis of the prism 20 can be easily adjusted even from a distant total station. For reference, the diameter of the conventional prism target shown in FIG. 5 is 1.5 to 2.5 inches (approximately 38 to 63.5 mm), but because the visibility of the target plate 10 has improved, the diameter of the prism 20 can be reduced to approximately 10 to 20 mm, and the height H of the prism 20 can be reduced accordingly. As a result, it is possible to correct the prism constant to "0" simply by penetrating the rear end 20c of the housing 20a of the prism 20 through the target plate 10, which has a plate thickness of approximately 2 mm. In addition, because the tip of the prism 20 protrudes only slightly from the first surface 10a of the target plate 10, it does not interfere with the vertical rotation of the target plate 10.

[0024] In addition, a click-stop mechanism is provided between the rotation axis 11 and the arm 12 of the laser survey target 1, and since it can be positioned every 90 degrees, the first surface 10a and the second surface 10b of the target plate can be selectively held horizontally upward. Therefore, for example, it is possible to perform three-dimensional laser scanner surveying using a drone from the sky. Furthermore, since the center of the first surface 10a of the target plate 10 functioning as a prism target and the center of the second surface 10b functioning as a scanner target coincide with each other, even if the target plate 10 is rotated to switch between the prism target function and the scanner target function, no height adjustment is required. Furthermore, if a somewhat lower measurement accuracy is acceptable, it is also possible to measure the three-dimensional coordinates of the target plate 1 using only the second surface 10b of the target plate 10 functioning as a scanner target. [Explanation of symbols]

[0025] 1 Laser survey target 10 Target Board 10a (target plate) first side 10b (target plate) second side 11 Rotation axis 11a Cross groove (click stop mechanism) 12 Arm 13 Shaft 13a, 13b screw holes 14 Through hole 15 (Click-stop mechanism) stopper 20 Prism 20a (Prism) Housing 20c (prism) rear end 21 Prism holder

Claims

1. A target plate and an arm that holds the target plate rotatably around a predetermined rotation axis, a through hole is provided at the center of the target plate, and a prism is attached to a first surface of the target plate so as to be offset in the optical axis direction thereof so that a prism constant is "0", The first surface of the target plate is divided into four regions by two color-separating lines that pass through the center of the first surface and are parallel and perpendicular to the rotation axis, and two adjacent regions are colored differently from each other; The second surface of the target plate is divided into four regions by two mutually orthogonal color-separating lines that pass through the center of the second surface and are set to form a predetermined angle with respect to the rotation axis, and two adjacent regions are colored differently from each other. A laser surveying target characterized by:

2. A laser surveying target as described in Claim 1, characterized in that the different colors applied to the first surface of the target plate are yellow and black.

3. A laser surveying target as described in claim 1 or claim 2, characterized in that a click-stop mechanism is provided between the rotation axis and the arm, allowing positioning every 90 degrees.

4. A laser surveying target described in any one of claims 1 to 3, characterized in that D / W is in the range of 1 / 4 to 1 / 10, where D is the diameter of the prism and W is the width of the target plate.

Images