Method and arrangement for determining the orientation of a stationary laser scanner

Abstract

Landmark (40) for determining an orientation of a stationary laser scanner (10), wherein the landmark (40) is designed to generate characteristic distance and remission values ​​when scanned with the laser scanner (10), wherein the landmark (40) is designed in two colors and comprises two, in particular dark, vertical feet (42, 44), wherein the feet (42, 44) are connected by a vertically displaceable, in particular light, background (46), wherein the background (46) has a dark connecting line (48) running at an angle.

Description

State of the art

[0001] The invention relates to a device and a method for determining and adjusting the orientation of a stationary laser scanner. Such laser scanners are also referred to as LIDAR sensors.

[0002] A laser scanner for object recognition is known, for example, from DE 4340756 A1.

[0003] A laser surveying instrument is known from EP 1001250 A2. It comprises a rotating unit that scans the laser beam and a tilting mechanism that adjusts the angle of the beam, allowing data to be collected from multiple directions and heights without repositioning the main unit. It automatically detects and displays any misalignment or tilt and provides real-time corrections to ensure measurement accuracy.

[0004] US Pat. No. 5,844,679 A discloses a system for adjusting the orientation of a plane defined by a rotating laser beam. The laser beam is scanned over one or more multi-section targets.

[0005] EP1584946 A2 discloses methods for adjusting a monitor with a radar and a camera and for correcting the positions and orientations of their detection areas based on the intensity of reflected light from a target object. A single target with a specific pattern of bright and dark areas is placed in front of the monitor within the detection areas of the radar and the camera. The radar's detection area is first adjusted based on measurements of the target by the radar, and then the axial displacement of the camera's detection area is determined; a coordinate conversion parameter is obtained based on an image of the target captured by the camera.

[0006] DE 102012000831 A1 shows a target mark for determining a three-dimensional position and / or rotation parameters as spatial position parameters of terrestrial laser scanner point clouds, each consisting of a geometric body with a defined geometric center and an optical reflector with a clearly definable optical center or an antenna with an electromagnetic phase center for position determination, wherein the geometric center and the optical center or the phase center coincide and / or the relative positions of the centers to the geometric body are known.

[0007] DE 202015104802 U1 discloses a laser scanner mark with a body whose surface has at least one section with a predetermined color in a certain color space.

[0008] Due to the long range of laser scanners, even small deviations in the pitch angle result in the beam not being parallel to the ground, but hitting the ground or moving away from the ground with increasing distance. Similarly, small deviations in the roll angle result in a tilted plane. Traditionally, fine-tuning mounts for the laser scanner are used for horizontal alignment; these mounts are used to adjust the roll and pitch angles of the laser scanner. Since the laser beam is generally invisible to the human eye, its path must be measured by other means. Natural or artificial landmarks can be used for this purpose; these are then measured and displayed by the laser scanner. By knowing the position of these landmarks relative to the laser scanner, the orientation of the laser scanner can be deduced.

[0009] Another alignment option is artificial landmarks that detect laser beams and display them via an acoustic signal, such as a portable laser receiver ("scan finder") such as the Topcon LS-80L. This eliminates the need to evaluate laser scans.

[0010] To achieve the most accurate alignment possible, the position of the landmarks must be precisely determined. In particular, the height of the incident laser beam must be precisely measurable. This cannot be achieved with sufficient accuracy using either conventional landmarks or scan finders. Disclosure of the invention

[0011] The object of the invention is to provide a method and an arrangement whereby the orientation of a stationary laser scanner for monitoring the surroundings, in particular in a parking garage, can be determined with high accuracy and the laser scanner can thereby be aligned in particular so that a horizontal scanning plane is obtained.

[0012] The present invention particularly relates to an artificial landmark for determining the orientation of a stationary laser scanner intended for monitoring the surroundings in a parking garage. If the current orientation of the stationary laser scanner is known, according to a further aspect of the invention, the orientation of the laser scanner can be adjusted using at least one such landmark to result in a particularly horizontal scanning plane.

[0013] According to the invention, the landmark is designed in two colors and comprises two, particularly dark, vertical supports. The supports are connected by a vertically movable, particularly light, background, which has a connecting line, particularly dark, running at a 45° angle, for example. A connecting line is understood to be a line that is clearly visible in the measurement result (laser scan) and has a certain line thickness. For example, the line thickness can be similar to or the same as the thickness of the landmark's vertical supports.

[0014] Various materials, such as metal or paper, can be used to build the landmark.

[0015] Each landmark formed in this way and positioned at a defined distance from the laser scanner leaves characteristic distance and remission values ​​in the laser scan. These can be used to localize the landmark. The use of two of these artificial landmarks, in particular, enables fine adjustment of the laser scanner using the distance and remission values.

[0016] Remission is the diffuse (undirected) reflection of waves, especially visible light, also known as diffuse reflection. The remission value, or luminosity reference value, indicates the proportion of brightness a chromatic or achromatic shade has compared to a pure white surface. Thus, a pure white surface has a remission value of 100%, meaning all incident light is reflected. A perfectly black surface has a remission value of 0%.

[0017] The landmark therefore preferably has areas that differ significantly in their reflectance values. For example, the vertical feet and the connecting line are preferably dark, for example, black, while the background is light, for example, white.

[0018] In a preferred embodiment, a height scale is provided on the side of the landmark, which enables the height of the center point of the connecting line to be read.

[0019] The angle of the connecting line to the vertical feet is preferably 45°.

[0020] In a preferred embodiment of the invention, the landmark has a height scale that allows the height of the center point of the connecting line above the ground level to be read. This height can, in particular, correspond to a desired height of the scanning plane of the laser scanner. Particularly preferably, the height scale is arranged on the side of one of the vertical feet, thus providing easy reading for the user.

[0021] According to a further aspect of the invention, an arrangement for determining the orientation of a stationary laser scanner is proposed, which comprises at least one landmark configured as described above. Preferably, at least two landmarks are provided, which are positioned at a defined horizontal distance from one another and each have a defined distance, in particular the same distance, from the laser scanner.

[0022] In particular, the background of each of the landmarks is set in such a way that the center of the connecting line lies at a certain height above a ground plane.

[0023] According to a further aspect of the invention, a method for determining the orientation of a stationary laser scanner is proposed, using an arrangement designed as described above. The laser scanner determines characteristic distance and remission values ​​of the at least one landmark, and a scanning plane of the laser scanner is determined from the distance and remission values ​​of the at least one landmark.

[0024] In a preferred embodiment, the current orientation of the laser scanner is visually displayed to a user by displaying the remission values ​​of the landmark relative to a target marking, wherein the target marking corresponds to a target orientation of the laser scanner, in particular a scanning plane of the laser scanner that runs horizontally to a ground plane at a certain height.

[0025] According to a further aspect of the invention, a method for aligning a stationary laser scanner is proposed, wherein first a current alignment of the laser scanner is determined using the method described above and, based on this, a specific alignment of the laser scanner is set, in particular such that a scan plane of the laser scanner runs horizontally to a ground plane at a specific height. In particular, this takes advantage of the fact that, with a desired horizontal alignment of the scan plane of the laser scanner, a measurement result must be obtained when scanning the landmark in which three dark areas corresponding to the vertical feet of the landmark and the connecting line are present, wherein the dark area corresponding to the connecting line is the same distance from both dark areas corresponding to the vertical feet.

[0026] The invention has the advantage that the simple structure results in low costs for manufacturing the landmarks according to the invention. Furthermore, the use of the same landmarks for aligning different laser scanners is advantageously possible. Furthermore, there is advantageously no interference during measurement from other active laser scanners or laser scanners with multiple scan planes, as is the case with conventional "scan finders". The invention also enables simple adaptation to a desired calibration accuracy by adjusting the distance between the laser scanner and the landmark, as well as by adjusting the size (scaling) of the landmark. This simple and easily understandable principle allows user-related errors to be avoided. Furthermore, robust recognition of the landmark can be achieved by utilizing knowledge of the structure and material of the landmark.

[0027] The invention is intended for determining and adjusting the alignment of laser scanners. A laser scanner is understood to be a sensor that emits laser beams and receives light reflected back from objects, whereby, for example, the distance of the object can be determined via the light travel time. A single laser light source can be provided whose beam is deflected by means of corresponding optical elements, whereby a measuring plane (scan plane) is spanned. However, the invention is equally applicable to sensors that have a plurality of laser light sources arranged in a row or a matrix, whereby laser light sources arranged in a row each form a measuring plane (scan plane). The invention is therefore suitable, for example, for determining and adjusting the alignment of sensors that are usually referred to as laser scanners and that have, for example, a rotating deflecting mirror. Short description of the drawings Fig. Figure 1 shows a schematic side view of an arrangement of a stationary laser scanner on the wall of a parking garage with a horizontally aligned scanning plane. Fig. 2 a) shows a schematic side view of an arrangement of a stationary laser scanner on the wall of a parking garage with a scanning plane inclined to the ground. Fig. 2 b) shows a schematic side view of an arrangement of a stationary laser scanner on the wall of a parking garage with an upwardly inclined scanning plane. Fig. 2 c) shows schematically in perspective top view an arrangement of a stationary laser scanner on the wall of a parking garage with a scanning plane inclined to the right in top view. Fig. 2 d) shows schematically in perspective top view an arrangement of a stationary laser scanner on the wall of a parking garage with a scanning plane inclined to the left in top view. Fig. 3 a) shows a schematic arrangement of a stationary laser scanner on the wall of a parking garage with a horizontally aligned scan plane and two landmarks for determining the orientation of the scan plane. Fig. 3 b) shows a flow chart of a method according to the invention for horizontal alignment of the laser scanner by means of the arrangement of Fig. 3 a). Fig. 4 schematically shows a first embodiment of a landmark for determining the orientation of a stationary laser scanner. Fig. 5 a)-c) show schematically the landmark according to Fig. 4 for determining the alignment of a stationary laser scanner as well as displays for visualizing the alignment of the scan plane. Fig. 6 a) and b) schematically represent the corresponding displays for visualization according to two different orientations of the scanning plane. Fig. 5 c) the alignment of the scan plane. Implementation of the invention

[0028] In the following description of the exemplary embodiments of the invention, identical elements are designated by identical reference numerals, whereby a repeated description of these elements is omitted where appropriate. The figures only schematically illustrate the subject matter of the invention.

[0029] In Fig. Figure 1 schematically shows an arrangement of a stationary laser scanner 10 on a wall 20 of a parking garage. The laser scanner 10 has a scanning plane 15, which in this example is aligned horizontally with respect to the floor plane 30. Fig. 1 thus represents the target situation for the alignment of the scan plane 15 of the laser scanner 10.

[0030] In the Fig. 2 a)-d) show different situations in which the scanning plane 15 of the laser scanner is compared to the one in Fig. 1 is tilted or inclined relative to the target orientation shown. Fig. 2 a) shows a scanning plane 15 inclined relative to the horizontal 16 by the pitch angle δ towards the ground 30. Fig. 2 b) shows a scanning plane 15 inclined relative to the horizontal 16 by the pitch angle δ' away from the ground 30. Fig. 2 c) shows a top view of a scanning plane 15 inclined to the right relative to the horizontal 16 by the roll angle y. Fig. 2 d) shows a top view of a scanning plane 15 inclined to the left by the roll angle y' relative to the horizontal plane 16. In practice, any superpositions of the Fig. 2 a) - 2 d) shown orientations of the scan plane 15 occur.

[0031] Should the Fig. In order to create the ideal state of a scan plane 15 aligned horizontally and parallel to the ground plane 30 as shown in Figure 1, the current orientation of the scan plane must first be determined.

[0032] In Fig. Figure 3 a) shows an arrangement corresponding to a possible embodiment of the invention. Two identically designed landmarks 40 are positioned at a defined distance from the laser scanner 10. Each of the landmarks 40 is bicolored and comprises two dark, vertical supports, connected by a vertically movable, light background. The background has a dark connecting line running at a 45° angle. Each of the landmarks 40 is thus configured to generate characteristic distance and remission values ​​when scanned with the laser scanner 10, which allow conclusions to be drawn about the current orientation of the scan plane 15 of the laser scanner.

[0033] A method for aligning the laser scanner 10 can now be carried out, for example, as shown in Fig. 3b) shown as a flow chart: In a first step 201, the laser scanner 10 is set up and manually aligned roughly horizontally. In a second step 203, two landmarks 40' and 40" are set up. They are offset laterally at a distance d from each other at the same distance x' or x" from the laser scanner 10 (see Fig. 3 a)). The landmarks 40' and 40" are adjusted to the desired height so that the vertical center of the landmark, i.e. the center of the connecting line, corresponds to the height of the desired scan plane of the installed laser scanner. In a third step 205, a calibration mode of the laser scanner 10 is activated. The laser scanner 10 now measures distances and intensities. The dark areas, i.e., the vertical feet and the respective connecting lines of the landmarks 40' and 40", generate low intensities, while the bright areas, i.e., the respective background, generate high intensities. The distances between the individual measurement points correspond to the angular resolution of the laser scanner 10; their size depends on the beam expansion. Both values ​​are model-dependent and can be found in the laser scanner's data sheet. In a fourth step 207, the user can now change the pitch and / or roll angles of the scan plane 15 via a fine adjustment unit on the mount of the laser scanner 10 such that the remission values ​​of the measurement line are centered above a target value. As soon as this is the case for both landmarks 40' and 40", the scan plane 15 of the laser scanner is aligned horizontally.

[0034] Fig. 4 shows a landmark 40 designed according to the invention in detail. The landmark 40 is two-colored and comprises two dark, vertical feet 42 and 44, wherein the feet 42 and 44 are connected by a vertically movable, light, background 46. The background 46 has a dark connecting line 48 running at a 45° angle. The landmark 40 is thus designed to generate characteristic distance and remission values ​​when scanned with the laser scanner 10, which allow conclusions to be drawn about the current orientation of the scan plane 15 of the laser scanner. The landmark 40 also has a height scale 50 on one of the feet 44. When the background 46 is moved vertically, the current height of the center point 47 of the connecting line 48 is displayed on the height scale 50 by an indicator 55 connected to the background. The displayed height may, for example, represent the height of the center point 47 above the ground plane 30.Preferably, at the beginning of a measurement, the height is set to a certain height, for example, corresponding to the installation height of the laser scanner 10.

[0035] In Fig. 5 a) the landmark 40 is from Fig. 4 during a measurement. Furthermore, the Fig. 5 the scan plane is shown as the intersection line of the scan plane 15 with the plane of the landmark 40. The situation corresponds to that in Fig. 2 b) in which the scan plane 15 is tilted upward compared to a horizontal orientation. If the landmark 40 is now scanned with the laser scanner 10, a measurement result with characteristic distance and remission values ​​of the landmark 40 is obtained.

[0036] The remission values ​​can be measured in particular in the form of Fig. 5 b), which displays the remission values ​​along the intersection line of the scan plane 15 with the landmark 40. This can be achieved, for example, by the user selecting the area from the measurement data of the laser scanner 10. Alternatively, the area to be displayed can be automatically detected in the measurement data. Automatic detection requires that the size (width) of the landmark is known. The measurement result (laser scan) now displays a "route" with equal distance values ​​that can be detected. The length of the route corresponds to the width of the landmark 40.

[0037] The displayed first dark area 142 represents the first vertical base 42. Adjacent to the right of the first dark area 142 is a first bright area 146', which represents the background 46 of the landmark 40. Adjacent to the right of the first bright area 146' is a second dark area 147. The second dark area 147 represents the connecting line 48. Adjacent to the right of the second dark area 147 is a second bright area 146", which in turn represents the background 46 of the landmark 40. Adjacent to the right of the second bright area 146" is a third dark area 144. The third dark area 144 represents the second vertical base 44 of the landmark 40.It is immediately apparent from the arrangement that, in the case of a scan plane 15 already aligned parallel to the ground plane 30, at the height h of the center point 47, the distance a1 between the first dark area 142 and the second dark area 147 would have to be equal to the distance between the second dark area 147 and the third dark area 144. In the situation illustrated here as an example, the upwardly tilted scan plane 15 results in the distance a1 being greater than the distance a2. The display 64 also has a target marking 164. When the scan plane 15 is aligned horizontally, the second dark area 147, which represents the connecting line 48, is visible on the display 64 in such a way that the target marking 164 is centered above the second dark area 147. This corresponds to uniform or equal distances a1 and a2.

[0038] The display of the remission values ​​can be alternatively or additionally according to Fig. 5 c) by a vertical display 62. Display 62 corresponds to display 64, but is rotated by 90°. This allows the user to intuitively read the deviation of scan plane 15 from the desired horizontal alignment, comparable to a spirit level. The displayed dark areas can thus be intuitively interpreted in a similar way to the bubble level of a spirit level.

[0039] Fig. Figure 6 illustrates the advantages of using two landmarks when determining the orientation of the stationary laser scanner 10. The measurement setup corresponds to that shown in Fig. 3 a). The schematic view shows the landmarks 40' and 40" and the corresponding displays 62' and 62", which correspond to the remission values ​​of the laser scan of the respective landmarks 40' and 40" along the intersection line of the scan plane 15 with the plane of the landmarks 40' and 40". Furthermore, the intersection line of the scan plane 15 with the plane of the landmarks 40' and 40" is shown.

[0040] In the example after Fig. 6 a), the scan plane 15 deviates from the horizontal 16 by a certain roll angle y. In the setup shown, this results in no deviation from the horizontal being shown in the display 62", but in the display 62'. In this case, two landmarks are therefore necessary to detect and correct the deviation of the scan plane 15 from the horizontal.

[0041] That this does not have to be the case in all cases is illustrated by Fig. 6 b). In the example according to Fig.6 b), the scan plane 15 deviates by a pitch angle from the horizontal 16. With the illustrated arrangement of the landmarks 40' and 40", this results in a corresponding deviation from the respective target markings 164' and 164" being shown in both displays 62' and 62".

Claims

[1] Landmark (40) for determining an orientation of a stationary laser scanner (10), wherein the landmark (40) is designed to generate characteristic distance and remission values ​​when scanned with the laser scanner (10), wherein the landmark (40) is designed in two colors and comprises two, in particular dark, vertical feet (42, 44), wherein the feet (42, 44) are connected by a vertically displaceable, in particular light, background (46), wherein the background (46) has a dark connecting line (48) running at an angle. [2] Landmark (40) according to claim 1, wherein the angle of the connecting line (48) to the vertical feet (42, 44) is 45°. [3] Landmark (40) according to claim 1 or 2, wherein the landmark (40) has a height scale (50) which enables the height of the center point (47) of the connecting line (48) to be read. [4] Landmark (40) according to claim 3, wherein the height scale (50) is arranged laterally on one of the vertical feet (44). [5] Arrangement for determining the orientation of a stationary laser scanner (10) comprising at least one landmark (40) according to one of claims 1 to 4. [6] Arrangement according to claim 5, wherein at least two landmarks (40', 40") are provided, which are positioned at a horizontal distance (d) from each other and each have a defined distance (x', x"), in particular the same distance, from the laser scanner (10) [7] Arrangement according to claim 6, wherein the background (46) of each of the landmarks (40' 40") is set such that the respective center point (47) of the connecting line (48) lies at a certain height (h) above a ground plane (30). [8] Method for determining an orientation of a stationary laser scanner (10), wherein an arrangement according to one of claims 5 or 6 is used, wherein characteristic distance and remission values ​​of the at least one landmark (40, 40', 40") are determined with the laser scanner (10) and a scan plane (15) of the laser scanner (10) is determined from the distance and remission values ​​of the at least one landmark. [9] Method according to claim 8, wherein the current orientation of the laser scanner (10) is displayed to a user by displaying the remission values ​​(142, 146', 147, 146", 144) of the landmark (40) relative to a target marking (164), wherein the target marking (164) corresponds to a target orientation of the laser scanner (10), in particular a scanning plane (15) of the laser scanner (10) which runs horizontally to a ground plane (30) at a specific height (h). [10] Method for aligning a stationary laser scanner (10), wherein firstly a current alignment of the laser scanner (10) is determined by means of a method according to one of claims 8 or 9 and, on this basis, a specific alignment of the laser scanner (10) is set, in particular such that a scanning plane (15) of the laser scanner (10) runs horizontally to a ground plane (30) at a specific height (h).

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