Laser scanner and mirror pyramid, and methods for their manufacture.

Description

[0001] The present invention relates to a laser scanner according to claim 6.

[0002] The invention further relates to a mirror pyramid according to claim 1 and a method for producing a mirror pyramid according to claim 8.

[0003] Laser scanners are known, for example, from EP 3 792 653 A1 by the same applicant. The transmitted beam directed at the rotating mirror pyramid is periodically scanned by the pyramid over a scanning angle range ("scanning fan"), and the received beam reflected by the surroundings is received back in the same direction. This means that the mirror facet currently being used for transmission is simultaneously used to redirect the received beam received from the same direction to the laser receiver.

[0004] The present invention relates to a type of laser scanner in which at least one mirror facet has a different inclination relative to the rotation axis than the other mirror facets, as is known, for example, from documents AT 510 045 A4 and EP 3 982 150 A1. This allows a single transmission beam to generate not just a single scanning fan, but, depending on the number of different inclinations, two, three, or more scanning fans that diverge from one another. Laser scanners of this type are required for a variety of applications, for example, to detect undercuts in the surrounding area, for compensation or differential measurements by scanning the surrounding area twice, or similar.

[0005] The invention aims to improve laser scanners of this type so that they have a better range and lower error rate.

[0006] This object is achieved in a first aspect of the invention with a mirror pyramid according to claim 1 and in a second aspect of the invention with a laser scanner according to claim 6.

[0007] With the laser scanner or mirror pyramid according to the invention, several diverging scanning fans with equal fan angles can be generated with a single transmission beam. If the laser scanner is moved across the environment in a direction of travel that is different from the scanning plane, e.g., perpendicular to one of the scanning fans, the scanning lines generated by the individual scanning fans on the environment—i.e., the intersection lines of the scanning fans with the environment—overlap as closely as possible in the direction of travel. This can be used, for example, to scan the same points in the environment multiple times or to create a particularly dense, regular network of scanning points across the environment.

[0008] According to the invention, the laser scanner or the mirror pyramid has at least four mirror facets, wherein among all sequences of mirror facets obtainable by permuting around the axis of rotation, the sequence is selected which results in minimal scattering of the receiving surfaces of all mirror facets, wherein the receiving surface of a mirror facet is its surface projected in the direction of a transmission beam reflected by it, the point of incidence of which lies in the middle of the said arc angle.

[0009] By minimizing the area dispersion of the receiving surfaces of the mirror facets according to the invention and thus homogenizing the receiving sensitivity of the laser scanner in the various scanning fan-outs (its "receiving channels"), optimal control of the single laser receiver responsible for all scanning fan-outs can be achieved. As a result, the mirror pyramid according to the invention can be used to construct a laser scanner with several diverging scanning fan-outs generated by a single transmit beam, which on average has improved measurement sensitivity without the risk of measurement errors due to overloading in individual receiving channels. A laser scanner constructed in this way has a better range and a lower error rate.

[0010] In a third aspect, the invention provides a specialized method for producing a mirror pyramid with a rotation axis for a laser scanner, during the operation of which a transmission beam impinges on the rotating mirror pyramid non-normally to the rotation axis, which mirror pyramid has at least four pyramid sides inclined relative to the rotation axis at a predetermined inclination, each forming a mirror facet, wherein at least two mirror facets have different inclinations, comprising: in a computer, generating a group of data sets, each of which represents a different sequence of mirror facets around the axis of rotation, obtainable by permutation, wherein in each sequence the mirror pyramid is designed such that, when the laser scanner is in operation, the point of incidence of the transmitted beam on the mirror pyramid sweeps out an equally large arc angle on each mirror facet, viewed in the direction of the axis of rotation; during or after generation, for each data set, in the computer: calculating a scattering of the receiving surfaces of all mirror facets, wherein the receiving surface of a mirror facet is its surface projected in the direction of a transmitted beam reflected by it, the point of incidence of which lies in the middle of the said arc angle; in the computer, selecting the data set with the minimum scattering; and producing the mirror pyramid with the sequence of mirror facets represented by the selected data set, each with a predetermined inclination.

[0011] The method of the invention is particularly suitable for mirror pyramids or laser scanners, where the transmitted beam impinges on the mirror pyramid parallel to the rotation axis during operation of the laser scanner. For example, if a mirror facet is tilted at 45° to the rotation axis, it creates a flat scanning fan that can produce particularly straight scanning lines on the surrounding area.

[0012] The invention can be used, in particular, to manufacture mirror pyramids or laser scanners in which all mirror facets are inclined differently relative to the axis of rotation, preferably also with five or more mirror facets.

[0013] In a preferred embodiment of the invention, production is carried out using a 3D printer, to which the data set is fed from the computer. Furthermore, the mirror pyramid is preferably manufactured as a hollow pyramid, in which each mirror facet has an individual wall thickness, whereby the wall thicknesses of the mirror facets are selected such that the mirror pyramid is dynamically balanced around the axis of rotation. If a 3D printer is used to produce the mirror pyramid, each mirror facet is printed by the 3D printer with an individual wall thickness, whereby the wall thicknesses are calculated by the computer and fed to the 3D printer such that the manufactured mirror pyramid is dynamically balanced around the axis of rotation. The mirror pyramid is preferably manufactured from a 3D-printable sintered material.

[0014] The invention is explained in more detail below with reference to exemplary embodiments illustrated in the drawings. In the drawings: Fig. 1 the laser scanner of the invention (without carrier) in a schematic perspective view; Fig. 2 the laser scanner from Fig. 1 in a block diagram with schematically drawn beam paths; the Fig. 3a - 3c the mirror pyramid and a housing window of the laser scanner of the Fig. 1 and 2 in three different rotational positions of the mirror pyramid, each in relation to the transmitting and receiving apertures of the laser transmitter and receiver in a top view of the mirror pyramid in the direction of its rotational axis; Fig. 4 und 5 another embodiment of the mirror pyramid of the invention in a plan view ( Fig.4 ) and on average ( Fig. 5 ); the Fig. 6a bis 6l twelve permutations of the sequence of mirror facets around the rotation axis of the mirror pyramid of Fig. 4 each in a top view; Fig. 7 a table of the permutations of the mirror facet sequences of the Fig. 6a bis 6l ; Fig. 8 an apparatus for producing the mirror pyramid of the invention; and Fig. 9 a flow chart of the process for manufacturing the mirror pyramid of the invention.

[0015] Fig. 1 shows schematically a laser scanner 1 comprising a mirror pyramid 2, which is mounted on a shaft 3 and rotated by a motor 4 about a rotation axis 5. A rotation angle encoder or sensor 4' is flanged to the motor 4, which measures or encodes the current position of the mirror pyramid 2 and transmits it to an electronic unit 6 ( Fig. 2 ) signaled.

[0016] The mirror pyramid 2 has the shape of a multi-sided (in Fig. 1 : four-sided) pyramid whose pyramid axis is its rotation axis 5. The pyramid sides inclined to the rotation axis 5 form the mirror facets 7 i (i = 1 ... I) of the mirror pyramid 2. The number I of mirror facets is 4, 5 or more.

[0017] It is understood that in the present description, the term "pyramid shape" or "mirror pyramid" refers to any type of pyramid with any polygonal base, including straight and "oblique" pyramids (pyramid axis not perpendicular to the base), regular and irregular pyramids, pointed or "blunt" pyramids ("truncated pyramids"), as well as pyramids that are truncated at their apex and / or base, such as those in the Fig. 1 and 5 The pyramids shown here have a circularly truncated lower section 8 to reduce air resistance during rotation. A "blunt" mirror pyramid 2, or one truncated at its apex, has a top surface 9 that is generally parallel to the bottom surface 10 of its lower section 8. If necessary, the top surface 9 and the bottom surface 10 could also be non-parallel to each other.

[0018] A laser transmitter 11 is directed at the mirror pyramid 2, which emits a transmission beam 12 onto the mirror facets 7 i , specifically onto one (the "active") mirror facet 7 i at a time during their rotation, so that the transmission beam 12 is periodically pivoted through a scanning angle β by the rotational movement of the mirror pyramid 2 in order to form several scanning fans 13 j (j = 1 ... J). With each scanning fan 13 j , for example, a surface 14 of the environment U can be scanned "line by line" if the scanning fan 13 j , e.g., the entire laser scanner 1, is moved over the surface 14 in a direction R that is foreign to the scanning plane, e.g., normal to one or the middle of the scanning fans 13 j .

[0019] The reflections of the transmitted beam 12 or scanning fan 13j from the surface 14 are detected by a laser receiver 16, which receives them back as a received beam 15—again via the path of the mirror pyramid 2—converts them into electrical signals, and feeds them to the electronics unit 6 for evaluation. The electronics unit 6 controls the laser transmitter 11 accordingly, e.g., by triggering, pulsing, modulating, etc., as is known in the art.

[0020] The mirror pyramid 2 considered here is of a special type, namely at least one of the pyramid sides 7 i has a different inclination α i relative to the rotation axis 5 than the other pyramid sides 7 i . As a result, when the mirror pyramid 2 rotates, not just a single scanning fan is produced, but, depending on the number of different inclinations α i , two, three or more scanning fans 13 j , which diverge from one another. The respective divergence angle γ between two scanning fans 13 j and 13 j+1 corresponds to twice the difference between the inclinations α i , α i+m (m > 0) of two mirror facets 7 i , 7 i+m producing these two scanning fans 13 j , 13 j+i . Laser scanners of this type are required for different applications, for example for detecting undercuts on the surface 14, for compensation or difference measurements by scanning the same surface 14 twice, or the like.

[0021] The laser transmitter 11 could be located directly in the beam path of the receiving beam 15 between the mirror pyramid 2 and the laser receiver 16, for example, if it is a very small semiconductor laser. In the example shown, however, the laser transmitter 11 consists of a larger laser 18 outside the receiving beam path and a small deflecting mirror 19, which is located in the receiving beam path between the mirror pyramid 2 and the laser receiver 16 and directs the laser beam 12 emerging from the laser 18 onto the mirror pyramid 2 approximately parallel (or slightly obliquely, if desired) to the rotation axis 5.

[0022] The laser receiver 16 could, in principle, be of any type known in the art, for example, a large-format photosensitive element, a CCD chip, etc. In the example shown, the laser receiver 16 has (at least) a converging lens 20 and a receiving element 21 arranged downstream of the converging lens 20 in the receiving beam path and at the focal point of the converging lens 20. The receiving element 21 is highly sensitive, for example, a photomultiplier or an avalanche photodiode.

[0023] A (here: semicircular) aperture 22 is arranged upstream of the converging lens 20 in the receiving beam path. The optical axis of the converging lens 20 coincides with the rotation axis 5 of the mirror pyramid 2. The size of the converging lens 20 in conjunction with the aperture 22, i.e., less the portion thereof blocked by the aperture 22, and the size of the currently active mirror facet 7 i , i.e., the smaller of the two sizes, determines the receiving aperture of the laser receiver 16. Instead of the combination of the converging lens 20 and the upstream aperture 22, the converging lens 20 could also simply be cropped, i.e., the portion of the converging lens 20 previously defined by the aperture 22 could be "cut away," giving the converging lens 20 a circular sector shape or (here:) a semicircular shape.

[0024] As in Fig. 2 The transmission beam 12 is shown, for example, as a pulsed laser beam with individual transmission pulses, each of which is emitted at a transmission pulse time t S,n , is reflected after deflection by the mirror pyramid 2 from a point U n of the surface 14 of the environment U and is received after redirection via the mirror pyramid 2 in the laser receiver 16 at a reception time t E,n . From the transit time ΔT n = t E,n - t S,n of a pulse, the known relationship D n = c ⋅ ΔT n / 2 = c ⋅ t S , n − t E , n / 2 , with t S,n ... transmission time of the transmitted laser pulse S n , t E,n ... reception time of the received laser pulse E n , and c ......... speed of light. the target distance D n of the laser scanner 1 in the respective transmission direction to the scanning point U n the environment U.

[0025] Fig. 2 shows the laser scanner 1 of Fig. 1 - simplified two-dimensionally - installed in a housing 23 that supports all components of the laser scanner 1. For the transmission and reception beams 12, 15, the housing 23 has a window 24 made of a transparent material, e.g., plastic or glass. The window 24 could, for example, be a large, flat glass pane or have the shape of a cylindrical segment, or be composed of several flat, mutually angled sections 25, 26, 27, for example, glued together.

[0026] In the Fig. 3a - 3c Three rotational positions of an "active" mirror facet 7 i , that is, the mirror facet 7 i which is currently hit by the transmitted beam 12, here the mirror facet 7 1 (thinly hatched), are shown with respect to the point of impact C (the "transmission aperture", thickly hatched) of the transmitted beam 12 of the laser transmitter 11 and the receiving aperture E (dotted) of the laser receiver 16, namely: in Fig. 3a that angular position of the active mirror facet 7 1 in which the point of incidence C has just crossed the edge 28 between the mirror facet 7 4 and the active mirror facet 7 1 and thus lies entirely on the active mirror facet 7 1; in Fig. 3b the middle position, in which the active mirror facet 7 1 has been rotated so far that the point of impact C, seen in the circumferential direction U, lies in the middle of the active mirror facet 7 1; and in Fig. 3c the position in which the point of impact C just lies entirely on the active mirror facet 7 1, ie just before it crosses the edge 29 between the active mirror facet 7 1 and the adjacent playing facet 7 2 and thus makes it "active".

[0027] As can be seen, the laser transmitter 11 is directed toward the edge region 30 of the mirror pyramid 2, i.e., the radial distance r of its point of impact C relative to the rotation axis 5 is maximized to such an extent that the point of impact C, in the radial direction, just lies on the respective active mirror facet 71. Furthermore, the diameter DS of the point of impact C should be as small as possible in relation to the circumferential extent LU of the active mirror facet 71 in the edge region 30. For example, the diameter DS of the point of impact C is less than a quarter, in particular less than an eighth, of the circumferential extent LU of the respective active mirror facet 71 in its edge region 30.

[0028] According to the Fig. 3a - 3c the receiving aperture E (dotted line) of the laser receiver 16 is approximately as large as twice one of the mirror facets 7 i (thinly hatched) viewed in the direction of the rotation axis 5, i.e. in each case in a projection in the direction of the rotation axis 5 onto a projection plane normal to the rotation axis 5 (here: the drawing plane). Since the mirror facets 7 i of the mirror pyramid 2 have different inclinations α i in order to generate different scanning fans 13 j, they are generally of different sizes viewed in the direction of the rotation axis 5. In this case, the receiving aperture E of the laser receiver 16 is preferably approximately as large as twice the largest of all the mirror facets 7 i viewed in the direction of the rotation axis 5.

[0029] By using such a large receiving aperture E, the laser receiver 16 can be used in any of the Fig. 3a - 3c shown positions of the mirror pyramid 2 each utilize and receive the entire reception beams 15 received back and deflected by an active mirror facet, such as the mirror facet 7 1 here.

[0030] In principle, the receiving aperture E (viewed in the direction of the rotation axis 5) could also be larger than twice the largest mirror facet 7 i, for example, covering the entire mirror pyramid 2, ie, the aperture 22 could be omitted. However, this does not further increase the receiving sensitivity of the laser scanner 1, because only receiving beams 15 that strike the active mirror facet 7 i and are incident from the relevant outgoing direction of the transmit beam 12 are useful beams.

[0031] On the other hand, the receiving aperture E could also be in a range between the single area of ​​a mirror facet 7 i (in particular the largest of these) viewed in the direction of the rotation axis 5 and the aforementioned double area, with a corresponding reduction in the receiving sensitivity of the laser scanner 1 near the end positions of the Fig. 3a und 3c .

[0032] In the example of Fig. 4 und 5 The mirror pyramid 2 has five mirror facets 7 i , 7 2 , 7 3 , 7 4 and 7 5 , i.e., I = 5, and is trimmed ("blunt") on its top surface 9, parallel to its bottom surface 10. Each of the mirror facets 7 i is inclined at a different angle α i relative to the rotation axis 5, for example, α i = 45°, α 2 = 45° + 10°, α 3 = 45° + 5°, α 4 = 45° - 5°, α 5 = 45° - 10°. This allows five scanning fans 13 j (J = 5) to be emitted.

[0033] The mirror facets 7 i are now arranged around the rotation axis 5 with their respective predetermined inclinations α i such that the point of incidence C of the transmitted beam 12 on each mirror facet 7 i describes an arc bi upon rotation of the mirror pyramid 2 about the rotation axis 5, the arc angle δ i of which is approximately the same for each mirror facet 7 i. This ensures that the scanning fans 13 j each have the same fan angle β j .

[0034] Since the mirror facets 7 i each have a predetermined inclination α i , the shape of the mirror pyramid 2 results from the fact that the plane in which the respective mirror facet 7 i lies passes through the two end points A i and B i of the arc bi , on which the point of impact C moves, and this plane forms the angle α i with respect to the rotation axis 5. If the mirror facets 7 i are delimited on their underside by a base surface 10 which runs, for example, perpendicular to the rotation axis 5 and are delimited on their upper side by a cover surface 9 which runs, for example, parallel thereto, then the shape shown in Fig. 5 The truncated pyramid shape shown in section, with the top surface 9 forming an irregular pentagon, which is usually located off-center to the axis of rotation 5, and the bottom surface 10 as well, unless the entire lower area 8 of the mirror pyramid 2 is as in Fig. 1 shown is circularly trimmed; in this case the bottom surface 10 is circular, as also in Fig. 4 shown.

[0035] It is understood that the top and bottom surfaces 9, 10 may also be non-parallel and non-normal to the rotation axis 5. The trimming at the top, i.e., the top surface 9, may also be omitted, so that the mirror pyramid 2 is "pointed."

[0036] As in Fig. 5 As shown, the mirror pyramid can be designed as a hollow pyramid, ie with a hollow interior 31, and each mirror facet 7 i then has a wall thickness W i assigned to it. The base of such a hollow pyramid could be omitted and the shaft 3 could, for example, only act on the top surface 9 or the intersecting mirror facets 7 i.

[0037] In order to dynamically balance the mirror pyramid 2 around the rotation axis 5, the wall thicknesses W i of the mirror facets 7 i can be varied accordingly to symmetrically distribute the mass of the mirror pyramid 2 around the rotation axis 5. If the mirror pyramid 2 is manufactured, for example, by 3D printing a sinterable material, which is subsequently sintered and ground and polished to form the mirror facets 7 i, the mirror facets 7 i can be 3D printed in their respective wall thicknesses W i, as explained in more detail later.

[0038] The reception sensitivity of the laser scanner 1 via the respective active mirror facet 7 i (thinly hatched in the Fig. 3a - 3c ) is defined not only by the receiving aperture E of the laser receiver 16, but - in the case of the mirror pyramid 2 presented here with differently inclined and therefore generally differently sized mirror facets 7 i - also by the receiving surface AR i of the respectively active mirror facet 7 i . The receiving surface AR i of a mirror facet 7 i is the surface which a receiving beam 15 coming from a surrounding point U n "sees". Since the receiving beam 5 comes from exactly the opposite direction from which the transmitting beam 12 was emitted by the active mirror facet 7 i, the receiving surface AR i is thus the surface (surface) of the mirror facet 7 i projected in the direction (or opposite direction, this is the same thing) of the transmitting beam 12 emitted via the mirror facet 7 i.However, since the emission direction of the transmitted beam 12 progressively changes over the fan angle β during the rotation of the mirror pyramid 2, the received beam 15 also "sees" a correspondingly varying receiving surface AR i of the active mirror facet 7 i , according to the directional cosine of the respective viewing angle of the received beam 15 onto the passing mirror facet 7 i . The maximum receiving surface AR i of a mirror facet 7 i that is "visible" to the received beam 15 is the (top) surface of the mirror facet 7 i projected in the direction of that transmitted beam 12 whose point of incidence C lies precisely in the center of the arc angle δ i (provided that the transmitted beam 12 is emitted onto the mirror pyramid 2 in a plane containing the rotation axis 5; otherwise, the receiving surface AR i must be calculated accordingly).

[0039] The maximum receiving area AR i of a mirror facet 7 i that is "visible" to the receiving beam 15 simultaneously determines the maximum receiving sensitivity of the laser scanner 1 in the scanning fan 13 j = i . To equalize the receiving sensitivities of the various diverging scanning fans 13 j and thereby prevent overloading of the laser receiver 16, the receiving areas AR i of the mirror facets 7 i and thus the geometric shape of the mirror pyramid 2 are optimized as follows.

[0040] The sequence of the mirror pyramids 7 i around the rotation axis 5 is used as a design parameter. Fig. 6a bis 6l show twelve different permutations P k (k = 1 ... K, K = 12) of sequences of mirror facets 7 i around the rotation axis 5 for the five-faceted mirror pyramid 2 of Fig. 4 , if each mirror facet 7 i has a different inclination α i, as shown in the table of Fig. 7 The number K of possible permutations P k is due to the rotatability of the mirror pyramid I! / I = (I - 1)!. Moreover, since it usually does not matter whether the mirror pyramid 2 is rotated clockwise or counterclockwise, the number K of practically useful permutations is (I - 1)! / 2. If some of the mirror facets 7 i have the same inclination α i , the number K of practically different permutations P k is reduced accordingly.

[0041] Each of the possible sequences P k , which can be obtained by correspondingly permuting the mirror facets 7 i in their sequence around the axis of rotation 5, leads to a differently shaped mirror pyramid 2 under the premises that the mirror facets 7 i have predetermined inclinations α i , that the point of incidence C on each mirror facet 7 i sweeps out an equally large arc angle δ i and that thus each mirror facet 7 i passes through the end points A i and B i of the respective arc bi. This is because other sequences P k lead to other intersection lines S1 i and S2 i of a mirror facet 7 i with its neighboring mirror facets 7 i-1 , 7 i+1 and thus to a different surface and thus ultimately reception surface AR i of this mirror facet 7 i .

[0042] By determining the permutation or sequence P k in which the receiving surfaces AR i of the mirror facets 7 i scatter the least among each other, ie deviate the least from each other, the optimized shape of the mirror pyramid 2 can be found in which the laser scanner 1 has the most uniform reception sensitivity and thus overload security in its various reception channels formed by the scanning compartments 13 j. Fig. 9 shows the steps of a method for producing a mirror pyramid 2 optimized in this way in the form of a flow chart and Fig. 8 a suitable device 32 for producing the mirror pyramid 2.

[0043] According to Fig. 8 The device 32 for producing the mirror pyramid 2 comprises a computer 33, to which the desired number I of mirror facets 7 i and their respective desired inclinations α i are specified at an input 34. The computer 33 controls a 3D printer 35, which deposits hardenable, for example sinterable, material onto a conveyor 36 in order to build a blank 37 for the mirror pyramid 2. The blank 37 of the mirror pyramid 2 is transferred from the conveyor 36 to a hardening station 38, e.g., an oven, a UV irradiation system, or the like, where it is hardened or sintered. Then, in a grinding and polishing station 39, the surfaces of the pyramid sides are ground and polished to form the mirror facets 7 i. It is understood that the 3D printer 35 could also form the mirror pyramid 2 in other ways, e.g. by milling and grinding from a solid block, ie the 3D printer 35 is then, for example, a CNC milling machine.

[0044] The computer 33 calculates according to the subsequently with reference to Fig. 9 The method described determines the optimal sequence (permutation) P opt of the mirror facets 7 i with the specified inclinations α i and (optionally) the wall thicknesses W i of the mirror facets 7 i and uses this data to control the 3D printer 35 via an interface 40. It is understood that the interface 40 could be an offline interface, i.e., the computer 33 could store the control data for the 3D printer 35 on a data carrier, which is then transferred to the 3D printer 35 and read by it. Typically, however, the 3D printer 35 is connected directly ("online") to the output of the computer 33. The interface 40 between the computer 33 and the 3D printer 35 can also contain other process parameters necessary for the production of the mirror pyramid 2, such as the absolute dimensions (height, diameter, etc.).) of the mirror pyramid 2, the data of the top and bottom surfaces 9, 10, data for mounting openings, nozzles or bearings for mounting the mirror pyramid 2 on the shaft 3, etc.

[0045] With reference to Fig. 9 To produce the mirror pyramid 2, in a first step 41 the number I of mirror facets 7 i to be produced and their desired inclinations α i are specified, e.g. fed into the input 34 of the computer 33.

[0046] In a subsequent step 42, the computer 33 now generates a group 43 ( Fig. 7 ) of data sets 44, each of which represents a different possible sequence (permutation) P k of the mirror facets 7 i around the rotation axis 5, for example the first sequence P 1 of Fig. 6a , the second sequence P 2 of Fig. 6b , the third sequence P 3 of Fig. 6c , etc. In the example shown, for each value in the table of Fig. 7For the permutation P k (k = 1 ... K) shown, a data set 44 is generated. If all inclinations α i are different from each other, there are K = (I - 1)! permutations P k ; taking into account the de facto equivalence of clockwise and counterclockwise rotating mirror pyramids K = (I - 1)! / 2 permutations P k ; and correspondingly fewer if some of the inclinations α i are equal to each other.

[0047] In a subsequent step 45, a scatter measure S k of the reception areas AR i of all mirror facets 7 i of this permutation P k is calculated for each permutation P k , i.e. for each data set 44. The reception area AR i of a mirror facet 7 i considered in each case is, as explained above, the area (surface) of the mirror facet 7 i projected in the direction of the transmission beam 12 emanating from the mirror pyramid 2, if the point of incidence C of the transmission beam 12 is, for example, currently located in the center M i of the arc angle δ i of the mirror facet 7 i. Alternatively, instead of the center M i, another division point of the arc angle δ i could also be considered, for example at a third of the arc length bi , a quarter or the like.

[0048] For the scatter measure S k , any scatter measure known in the art can be used, which is a measure of the mutual deviations of the receiving surfaces AR i of the mirror facets 7 i , e.g. their variance, standard deviation, mean absolute deviation from the mean value, range between minimum and maximum value, or the like.

[0049] It is understood that steps 42 and 45 could also be combined, ie immediately upon generation of a permutation P k , its control measure S k could also be calculated.

[0050] Subsequently, in a step 46, the data set 44 or P k with the minimum scatter measure S k is selected, ie the index min = k of the minimum scatter measure S k of all scatter measures {S k} is simultaneously the index opt = min of the permutation P opt , which represents the optimal sequence of the mirror facets 7 i around the rotation axis 5.

[0051] In a subsequent (optional) step 47, a wall thickness W i can now additionally be calculated for each mirror facet 7 i - in the selected optimal sequence P opt - which leads to a dynamic balancing of the mirror pyramid 2 during its rotation about the rotation axis 5. As a rule, different wall thicknesses W i result for the individual mirror facets 7 i , and the wall thickness W i could also vary over the surface extension of a mirror facet 7 i, ie a mirror facet 7 i could also have a wedge-shaped wall thickness, for example.

[0052] Subsequently, in step 48, the mirror pyramid 2 is manufactured using the data {α i}, P opt and optionally {W i} generated in step 46 (and optionally step 47), e.g., by means of the 3D printer 35 and its (optional) downstream processing stations 38, 39. The output data of steps 46 and 47 are fed to the 3D printer 34 via the interface 40.

[0053] The invention is not limited to the embodiments shown, but includes all variants, modifications and combinations thereof that fall within the subject matter of the appended claims.

Claims

1. Mirror pyramid with an axis of rotation(5) for a laser scanner (1), during operation of which a transmission beam (12) hits the rotating mirror pyramid (2) at a non-normal angle to the axis of rotation(5), which mirror pyramid (2) has pyramid faces that are inclined, each at a respective predetermined inclination (αi) relative to the axis of rotation(5), and respectively form a mirror facet (7i), wherein at least two mirror facets (7i) have different inclinations (αi), wherein the mirror pyramid (2) is configured in such a manner that, during operation of the laser scanner (1), the hit point (C) of the transmission beam (12) from the laser transmitter (11) on the mirror pyramid (2) sweeps over an equally large arc angle (δi) on each mirror facet (7i) when viewed in a direction of the axis of rotation, wherein the mirror pyramid (2) has at least four mirror facets (7i), characterized in that from all sequences (Pk) of mirror facets (7i) around the axis of rotation (5) obtainable by permutation that sequence (Popt) is chosen in which a minimal dispersion (Smin) of the receiving areas (ARi) of all mirror facets (7i) is obtained, wherein the receiving area (ARi) of a mirror facet (7i) is considered as its area projected in the direction of a transmission beam (12) reflected therefrom, the hit point (C) of which lies in the centre of said arc angle (δi).

2. Mirror pyramid according to claim 1, characterized in that all mirror facets (7i) have different inclinations (αi).

3. Mirror pyramid according to claim 1 or 2, characterized in that the mirror pyramid (2) has at least five mirror facets (7i).

4. Mirror pyramid according to any one of claims 1 to 3, characterized in that the mirror pyramid (2) is a hollow pyramid, in which each mirror facet (7i) has an individual wall thickness (Wi), wherein the wall thicknesses (Wi) of the mirror facets (7i) are chosen such that the mirror pyramid (2) is dynamically balanced around the axis of rotation (5).

5. Mirror pyramid according to any one of claims 1 to 4, characterized in that it is made of a 3D-printed sinter material.

6. Laser scanner for scanning an environment, comprising: a carrier (23), a laser transmitter (11) supported by the carrier (23) for transmitting a transmission beam (12), a laser receiver (16) supported by the carrier (23) for receiving the transmission beam (12) reflected by the environment (U) as a receiving beam (15), and a mirror pyramid (2) according to one of claims 1 to 5, arranged in the beam path of the transmission and the receiving beam (12, 15) and rotatably mounted on the carrier (23) for rotating about an axis of rotation(5).

7. Laser scanner according to claim 6, characterized in that the transmission beam (12) hits the mirror pyramid (2) parallel to the axis of rotation (5) during operation of the laser scanner (1).

8. Method for producing a mirror pyramid (2) with an axis of rotation (5) for a laser scanner (1), during operation of which a transmission beam (12) hits the rotating mirror pyramid (2) at a non-normal angle to the axis of rotation (5), which mirror pyramid (2) has at least four pyramid faces that are inclined, each at a respective predetermined angle (αi) relative to the axis of rotation (5), and respectively form a mirror facet (7i), wherein at least two mirror facets (7i) have different inclinations (αi), comprising: in a computer (33), generating (42) a group (43) of data sets (44), each representing a different sequence (Pk) of mirror facets (7i) around the axis of rotation (5) obtainable by permutation, wherein in each sequence (Pk) the mirror pyramid (2) is configured such that during operation of the laser scanner (1), the hit point (C) of the transmission beam (12) on the mirror pyramid (2) sweeps over an equally large arc angle (δi) on each mirror facet (7i) when viewed in the direction of the rotational axis; during or after generating (42), for each data set (44), in the computer (33): calculating (45) a dispersion (Sk) of the receiving areas (ARi) of all mirror facets (7i), wherein the receiving area (ARi) of a mirror facet (7i) is considered as its area projected in the direction of a transmission beam (12) reflected therefrom, the hit point (C) of which lies in the centre of said arc angle (δi); in the computer (33), selecting (46) the data set (44) with the minimal dispersion (Smin); and producing (48) the mirror pyramid (2) with the sequence (Popt) of mirror facets (Sk) of respective predetermined inclination (αk) represented by the selected data set (44).

9. Method according to claim 8, characterized in that the producing (48) is carried out by means of a 3D printer (35), to which the selected data set (44) is fed from the computer (33).

10. Method according to claim 9, characterized in that the mirror pyramid (2) is a hollow pyramid and each mirror facet (7i) is printed by the 3D printer (35) with an individual wall thickness (Wi), wherein the wall thicknesses (Wi) are calculated by the computer (33) and fed to the 3D printer (35) in such a manner that the produced mirror pyramid (2) is dynamically balanced around the axis of rotation (5).