DEVICE FOR SURVEYING AN ENVIRONMENT

Description

[0001] The present invention relates to a device for measuring an environment moving relative thereto by measuring the time of flight of laser pulses reflected from the environment in a coordinate system, comprising a first scanning unit for emitting a first pulse train of laser pulses over successive deflection periods at a pulse repetition rate, wherein the laser pulses falling in each deflection period are emitted in first scanning directions fanned out around a first scanning axis and thus form a first scanning fan per deflection period, which they traverse with a predeterminable angular velocity profile, and for receiving the associated laser pulses reflected from first scanning points of the environment.

[0002] Devices of this type are described, for example, in EP 3 182 159 B1 and are carried on board an aircraft or ship, for example, to topographically survey environments such as the ground or seabed. It is also possible to mount such a device on a land vehicle, for example, to survey building facades, urban canyons, or tunnels as they pass by. The device can also be installed stationary, for example, in an open-pit or underground mine to survey its workings, above a conveyor belt to survey objects moving on it, etc.

[0003] The scanning unit emits laser pulses from a variety of scanning directions to numerous scanning points in the environment. Time-of-flight measurements of the target reflections are used to determine the target distances. From this, a point model ("3D point cloud") of the environment is created—based on the position of the scanning unit and the respective scanning direction. In mobile, vehicle-mounted devices, the scanning fan spanned by the scanning directions of the laser pulses of a deflection period is moved across the environment by the vehicle's movement. In stationary devices, the scanning fan is pivoted around, for example, by rotating the scanning unit, in order to scan the environment. Likewise, the environment to be measured can be moved relative to the scanning fan, for example, to measure objects on conveyor belts.

[0004] In order to create meaningful 3D point clouds, it is desirable to measure a wide variety of sample points and environments as accurately as possible. However, there are limitations to this.

[0005] For example, the sensitivity of a laser receiver and the transmission power of a laser transmitter in the scanning unit cannot be designed simultaneously for weakly reflecting and strongly reflecting, or for distant and near scanning points in the environment. If high sensitivity and / or high transmission power are used to measure weakly reflecting or distant scanning points, the laser receiver will saturate at strongly reflecting or near scanning points and, during a dead time, will be unable to detect the intensity curve of the laser pulse being received or subsequent laser pulses. If, on the other hand, lower sensitivity and / or lower transmission power are used to measure strongly reflecting or near scanning points, weakly reflecting or far scanning points cannot be measured at all because the received signal from laser pulses reflected from them is drowned out by the ever-present receiver noise.

[0006] Similarly, the pulse width of the emitted laser pulses cannot be optimally selected for all types of sampling points. With a constant laser pulse intensity, shorter pulse widths could be used to more accurately determine the laser pulse propagation time – e.g., through curve fitting – and thus distinguish between multiple target reflections in the received signal, e.g., a water surface above shallow bottom could be separated from it. However, for weakly reflecting or distant sampling points, this leads to weak received signals that are lost in the receiver noise. With longer pulse widths, on the other hand, more transmitted energy could be emitted to improve the signal-to-noise ratio. However, for close or strongly reflecting sampling points, this leads to less accurate propagation time measurements and an inseparable mixing of multiple target reflections in the received signal.

[0007] Last but not least, the divergence of the laser pulses and thus the size of the sampling points also place contradictory demands. For example, with larger sampling points, inhomogeneous environments such as trees with foliage can be measured in a single step due to multiple target reflections per laser pulse ("multi-target capability"), e.g., the foliage and the ground simultaneously, but with a scan direction that can only be determined imprecisely. With smaller sampling points, however, the scan direction can be determined more precisely, but multi-target capability is impossible, for example, if the laser pulse only hits a single leaf.

[0008] On the one hand, static multi-beam laser scanners, as described in US 2019 / 0196020 A1 and US 2020 / 0142061 A1, are designed for multiple scanning of sample points, but they cannot be used variably. On the other hand, movable multi-beam laser scanners, as known from DE 10 2004 050 682 A1, are designed for multiple scanning of sample points, but not for multiple scanning of sample points.

[0009] The invention aims to create a device for laser scanning which enables a particularly meaningful creation of a 3D point cloud of the environment.

[0010] This aim is achieved with a device of the type mentioned in the introduction, which is characterized according to the invention by at least one further scanning unit for emitting a further pulse train of laser pulses over successive deflection periods with the same pulse repetition rate, wherein the laser pulses falling in each deflection period are emitted in further scanning directions fanned out around a further scanning axis and thus form a further scanning fan per deflection period, which they scan with the same predeterminable angular velocity profile, and for receiving the associated laser pulses reflected from further scanning points in the environment,wherein all scanning compartments substantially overlap when viewed in the direction of one of the scanning axes, and in the overlapping region of the scanning compartments, an area of ​​the surroundings already scanned by a front scanning compartment viewed in the direction of the scanning axis is scanned again by a rear scanning compartment viewed in this direction of the scanning axis, and a control device connected to the at least one further scanning unit, which is designed to pivot the scanning compartments of each further scanning unit relative to the scanning compartments of a respective adjacent scanning unit in a predetermined sequence of scanning units by a pivot angle dependent on the pulse repetition rate and the angular velocity profile such that the further scanning points coincide with the first scanning points.

[0011] The laser scanning device of the invention, thanks to its plurality of scanning units, can emit two or more scanning fans simultaneously, whereby one and the same scanning points of the environment can be measured multiple times and thus more accurately in the same time, e.g. by averaging the multiple distance measured values ​​of a scanning point. If the device and the environment are additionally moved relative to one another in the scan axis direction of a scanning fan, an area of ​​the environment already scanned by a front scanning fan as seen in the scan axis direction can be scanned again in the overlapping area of ​​the scanning fans by a rear scanning fan as seen in this scan axis direction. The inventive pivoting of the scanning fans enables the laser pulses of the rear scanning fan to again hit the scanning points of the area already scanned by the front scanning fan, i.e. the scanning points of the front and rear scanning fans coincide.

[0012] Because each sampling point is scanned multiple times, sampling points with very different properties can be measured with the same device, meaning that both weakly reflective or distant and highly reflective or near-surface points can be measured. For example, one scanning unit can use a high-sensitivity laser receiver and / or a high-power laser transmitter to measure weakly reflective or distant sampling points with a good signal-to-noise ratio, while another scanning unit can use a lower-sensitivity laser receiver and / or a lower-power laser receiver to measure highly reflective or near-surface points without saturating the laser receiver.In particular, for this purpose, the first scanning unit can be designed to emit its laser pulses each with a first intensity, and the at least one further scanning unit can be designed to emit its laser pulses each with a further intensity different from the first intensity.

[0013] Likewise, different scanning units can emit their laser pulses with different pulse widths, firstly to determine the laser pulse propagation time more accurately with shorter pulse widths and / or to better distinguish between multiple target reflections in the received signal, and secondly to emit more transmission energy with longer pulse widths and thus achieve a better signal-to-noise ratio. For this purpose, the first scanning unit is preferably configured to each emit its laser pulses with a first pulse width, and the at least one further scanning unit is configured to each emit its laser pulses with a further pulse width that differs from the first pulse width.

[0014] In order to scan each scanning point of the environment once as a larger scanning point for the above-mentioned multi-target capability and once as a smaller scanning point for a precise scanning direction determination, the first scanning unit can preferably be designed to emit its laser pulses in each case with a first beam divergence, and the at least one further scanning unit can be designed to emit its laser pulses in each case with a further beam divergence different from the first beam divergence.

[0015] In further preferred embodiments of the invention, the laser pulses from different scanning units can also differ in other optical properties such as wavelengths, polarizations, etc., e.g. in that the first scanning unit is designed to emit its laser pulses each with a first wavelength and / or polarization, and the at least one further scanning unit is designed to emit its laser pulses each with a further wavelength different from the first wavelength and / or a further polarization different from the first polarization. On the one hand, different wavelengths can be used for the above-mentioned multi-target capability, e.g. in bathymetry, to measure the water surface with a first wavelength that is reflected by water and the waterbed with a second wavelength to which water is permeable.On the other hand, different wavelengths can be used to measure the material properties of one and the same sampling point, e.g. in vegetation analysis, in order to determine a vegetation index from the ratio of the received signals of different wavelengths, from which the water or chlorophyll content in plants can be determined, such as the Green Normalized Difference Vegetation Index (GNDVI).

[0016] The pulse repetition rate and angular velocity can be fixed for a specific measurement task or can change during the measurement. The inventive dependence of the swivel angle on the pulse repetition rate and the angular velocity profile of the control unit enables automatically adjusted operation. The control unit can, for example, measure these values ​​itself or receive them from a measuring unit or a control value transmitter, which the measurement technician uses to adjust these values ​​during operation.

[0017] Last but not least, each scanning unit only receives the laser pulses reflected from the environment in the respective scanning direction of its own scanning fan, which geometrically separates the laser pulses emitted by different scanning units on the receiver side. This allows the number of processed laser pulses per unit of time to be multiplied according to the number of scanning units.

[0018] As a result, the device of the invention achieves a particularly precise measurement of the environment and a particularly meaningful 3D point cloud.

[0019] As already briefly discussed, a preferred application of the device according to the invention is that it is mounted on a vehicle designed for a main direction of movement, preferably an aircraft, with its scanning axes each non-normal to the main direction of movement. This ensures that the main direction of movement has a component in the direction of the scanning axis, in which the scanning fan beams overlap. As a result, a rearward scanning fan beam, as seen in this direction, can rescan an environmental area already scanned by a frontward scanning fan beam, as seen in this direction, in order to measure the scanning points therein more accurately and increase the informative value of the 3D point cloud.

[0020] In a preferred embodiment, the control device is configured to specify the angular velocity profile depending on at least one past distance measurement of the environment. This allows, on the one hand, the distances between the sampling points within a scanning fan and, on the other hand, the distances between two consecutive scanning fans of a scanning unit to be equalized. For example, the device could be mounted on an aircraft, and the control device could specify the angular velocity profile depending on the flight altitude such that a higher flight altitude is associated with higher angular velocities and a lower flight altitude with lower angular velocities, in order to achieve, as far as possible, the same sampling point distances within the scanning fans and the same scanning fan distances across the entire environment to be measured, with a constant pulse repetition rate.

[0021] In principle, the scanning compartments of different scanning units can be arranged in any position relative to each other, provided they overlap in the direction of one of the scanning axes. In an advantageous embodiment, however, all scanning axes coincide. This means that the scanning compartments are parallel and radiate from a single scanning axis. The tilt angle applied to the scanning compartments of a scanning unit is therefore no longer dependent on any possible tilt angle between the different scanning axes.

[0022] Coincident scan axes also allow the sweep angle to be determined independently of the distance to the surroundings. This makes it particularly easy to determine the sweep angle required for the scanning points to coincide and to use it for different environmental topographies. Furthermore, the use of a common scan axis maximizes the overlap area of ​​the scan bays and thus the width of the scan strip, allowing the environment to be scanned more accurately.

[0023] In the case of coincident scanning axes, it is particularly advantageous if the control device is further designed to pivot the scanning compartments of each further scanning unit relative to the scanning compartments of a respective adjacent scanning unit in a predetermined sequence of scanning units such that the scanning directions of the scanning compartments coincide when they occupy substantially the same plane in the coordinate system. The scanning compartments can occupy the same plane in the coordinate system if the device is moved relative to the environment and a rear scanning unit, viewed in the direction of movement, emits its scanning compartment into the plane into which a front scanning unit, viewed in the direction of movement, already emitted a scanning compartment, so that these scanning compartments, emitted at a time offset, occupy the same plane. This applies vice versa if the environment is moved relative to the device.By merging the scanning directions in the angular range, it is possible to align the scanning points of different scanning fans in the environment regardless of their distance, thus constantly increasing the informative value of the 3D point cloud regardless of the topography.

[0024] In particular, it is advantageous if the pivot angle between the scanning compartments of two scanning units adjacent to one another in the series, when the scanning compartments essentially occupy the same plane in the coordinate system, increased by the angle difference between the scanning directions first traveled in these two scanning compartments, results in a multiple of the angle between two scanning directions successively traveled in a scanning compartment.

[0025] The invention provides two embodiments of scanning fan pivoting by the control device—which can optionally be combined with one another. In a first embodiment, this pivoting is achieved electronically in that the control device is configured to pivot the scanning fans of said at least one further scanning unit by controlling a temporal offset in the transmission of its pulse train of laser pulses. The control pulses of the laser sources of the scanning units are phase-shifted, e.g., by delay elements, which enables particularly fast and precise pivoting of their scanning fans. Furthermore, the control software or hardware can be reproduced cost-effectively, thus facilitating industrial production of the device.

[0026] In a second embodiment, the pivoting is achieved optically, in that the control device is configured to pivot the scanning fans of said at least one further scanning unit by controlling optical elements in the beam path of its laser pulses. The use of controlled optical elements, e.g., electro-optical elements, pivoting or rotating mirrors, prisms, etc., in the beam path allows the scanning fans to be pivoted without curtailing the fan angle.

[0027] The scanning units of the device can be constructed, for example, with oscillating mirrors, rotating mirrors, Palmer scanners, or the like. In a particularly preferred device configuration, each scanning unit comprises a deflection device with a mirror prism rotatable about its prism axis, the outer sides of which each form a mirror surface and the prism axis of which is the scanning axis, and a laser transmitter for emitting the respective pulse train of laser pulses in a respective transmission direction to the deflection device. With such a rotating mirror prism, a constant angular velocity profile can be achieved when scanning the scanning fan and subsequently returning to the beginning of the scanning fan in the next deflection period, i.e., a line-by-line scanning of the surroundings at high speed.

[0028] If the deflection devices of all scanning units are preferably formed by one and the same deflection device, the scanning units are particularly compact, and separate drives for each mirror prism are eliminated. Furthermore, the scanning directions of different scanning fans can be coordinated particularly easily by referencing them to the single common mirror prism. Furthermore, due to its design, a single mirror prism results in the same angular velocity profile for the scanning fans of all scanning units, eliminating the need for separate synchronization.

[0029] In the preferred device design of the invention, the scanning directions of different scanning compartments can be arranged to coincide in the angular range, in particular by selecting the pivot angle between the scanning compartments of two scanning units adjacent to each other in the row as λ k , k − 1 = i ⋅ ω PRR − 2 ⋅ ϑ k − ϑ k − 1 + ω ⋅ D k , k − 1 ν mod 360 ° ⋅ 2 J mod ω PRR with λ k,k-1 is the tilt angle of the k-th scan fan relative to the (k-1)-th scan fan, i is an integer, ω is the average angular velocity of the angular velocity profile, PRR is the pulse repetition rate, ϑ k is the transmission direction of the k-th laser transmitter, D k,k-1 is the distance between the k-th and (k-1)-th scan fans along the prism axis, v is the relative velocity between the device and the environment, J is the number of mirror surfaces, and mod is the modulo operator.

[0030] In the said preferred device structure of the invention, in particular three advantageous variants - which can optionally also be combined with one another - for pivoting the scanning compartments by means of optical elements can be provided.

[0031] In a first variant, the laser transmitter has an adjustable deflecting mirror located in the beam path of the laser pulses, and the control device is designed to pivot the scanning compartments of said at least one further scanning unit by adjusting the deflecting mirror. The position of the deflecting mirror defines the respective transmission direction and can be adjusted, for example, by an actuator connected to the control device. A lightweight deflecting mirror can be adjusted particularly quickly due to its low mass inertia, so that a pivoting required, for example, due to a change in the angular velocity profile can be carried out quickly. In addition, a deflecting mirror can be adjusted over a large angular range and can therefore also effect large changes in the transmission direction and the pivot angle.

[0032] In a second variant, the laser transmitter is mounted so as to be adjustable relative to the deflection device, and the control device is designed to pivot the scanning compartments of said at least one additional scanning unit by controlling the position of the associated laser transmitter. In this variant, the laser transmitters are adjusted, e.g., pivoted or shifted, by actuators connected to the control device, so that large pivot angles can be achieved even without a deflection mirror.

[0033] In the first and second variants, to receive the laser pulses from pivoted scanning fans, the receiving aperture of the laser receiver of each additional scanning unit could be enlarged so that the reflected laser pulses from the pivoted corresponding scanning fan still lie within this receiving aperture. Alternatively, the laser receivers of the additional scanning units can maintain their receiving aperture if the viewing direction of the laser receivers is pivoted along with the corresponding scanning fan, e.g., by the control device controlling adjustable optical elements in the beam path of the reflected laser pulses or the position of the laser receivers themselves.

[0034] In a third variant, the control device is designed to pivot the scanning fans of the at least one additional scanning unit by controlling the phase position of the rotational movement of the mirror prism. This allows the existing mirror prisms to be used directly for scanning fan pivoting—e.g., by appropriately controlling their rotational axis drives—thus eliminating the need for additional optical elements.

[0035] In a further preferred embodiment of the invention, all scanning fans originate from the same point, eliminating the need to consider the spacing of the scanning fan vertices when pivoting the scanning fans. This also allows for a particularly compact design because a short mirror prism can be used for transmission.

[0036] In particular, in the case of coincident scan axes, the regular arrangement of the scan directions of all scan compartments, if they essentially occupy the same plane in the coordinate system, can be achieved by selecting the swivel angle between the scan compartments of each two scan units adjacent to each other in the sequence as λ k , k − 1 = i ⋅ ω PRR − R k , 1 , p − R k − 1,1 , p mod ω PRR with λ k, k-1 is the sweep angle of the k-th scan fan relative to the (k-1)-th scan fan (k = 1 ... K), i is an integer, ω is the average angular velocity of the angular velocity profile, PRR is the pulse repetition rate, R k,1,p is the first-stepped scan direction of the k-th scan unit in a reference deflection period, R k-1,1,p' is the first-stepped scan direction of the (k-1)-th scan unit in that deflection period in which its scan fan occupies essentially the same plane in the coordinate system as the scan fan of the k-th scan unit in the reference deflection period, and mod is the modulo operator.

[0037] As can be seen from equation (2), only the first scan directions of the scanning units in the respective deflection periods, the pulse repetition rate and the angular velocity profile are taken into account in determining the swivel angle, so that the swivel angle is independent of the topography of the environment to be measured and the relative velocity between the device and the environment.

[0038] The invention is explained in more detail below with reference to exemplary embodiments illustrated in the accompanying drawings. In the drawings: Fig. 1 a laser scanning device mounted on an aircraft and one of its scanning units emitting its scanning fan to measure an environment in a schematic perspective view; Fig. 2 a transmitting and receiving channel of the device of Fig. 1 in a block diagram with schematically drawn beam paths; the Fig. 3a und 3c two different embodiments of the laser scanning device of the invention and the Fig. 3b und 3d Laser scanning devices not according to the invention, each mounted on an aircraft during the measurement of an environment with three scanning units, each emitting a scanning fan and each forming a transmission and reception channel, in a schematic perspective view; Fig. 4 an exemplary intensity / time diagram of pulse trains of laser pulses generated by the scanning units of the laser scanning devices of the Fig. 3a - 3d be sent out; Fig. 5 an example of a sample point distribution on the environment, as it is achieved with the scanning compartments of Fig. 3a , but without the inventive pivoting for the impulse trains of Fig. 4 would receive, in a plan view; Fig. 6 the inventive pivoting of the scanning compartments of the embodiment of the Fig. 3a - 3d seen in the direction of the scan axes; Fig. 7 an example of a sampling point distribution on the environment, as it is achieved with the tilted scanning fans of Fig. 6 obtained, in a plan view; Fig. 8 an intensity / time diagram of temporally offset pulse trains of laser pulses, which in a first, electronically realized embodiment for scanning fan pivoting in the laser scanning devices of the Fig. 3a - 3d be used; Fig. 9 the first electronically realized embodiment of the laser scanning devices of the Fig. 3a - 3d in a block diagram with schematically drawn beam paths; the Fig. 10 und 11 different variants of a second, optically realized embodiment of the laser scanning device of the Fig. 3a or 3b once in a perspective view ( Fig. 10 ) and once seen in the scan axis direction ( Fig. 11 ) each with schematically drawn beam paths.

[0039] In Fig. 1 1 shows a device 1 for measuring an environment 2 from a vehicle 3. The environment 2 to be measured can be, for example, a landscape (terrain), but also the road surface and the facades along a street, the interior surface of a hall, a tunnel, or a mine, or the sea surface and / or the seabed, etc. The vehicle 3 can be a land, air, or water vehicle, manned or unmanned. Alternatively, the device 1 could also be stationary and measure either a stationary environment 2 or an environment 2 that is moving relative to the device 1, e.g., objects moving on a conveyor belt, workpieces, etc.

[0040] The device 1 scans the environment 2 by means of an emitted pulse train 4 of laser pulses 5 n (n = 1, 2, ...) for the purpose of measuring the environment. For this purpose, the laser pulses 5 n are emitted by a scanning unit 6 in scanning directions R n that are oriented around a scanning axis 7 with a deflection period AP (see later). Fig. 4 ). As a result, the scanning directions R n of the laser pulses 5 n fan out a scanning fan 8 within a deflection period AP between a first scan direction R 1 and a last scan direction R Ω, ​​which they scan with an angular velocity profile ω. The angular velocity profile ω is determined by the specific structure of the scanning unit 6 and can either be constant over the deflection period AP, ie ω = const, or change within the deflection period AP or for scan directions R n, ie ω = ω (t) or ω = ω(R n ).

[0041] In addition, the device 1 is moved forward in the direction of travel F of the vehicle 3 at a relative speed v to scan the environment 2 essentially in a scan strip 9. If the vehicle 3 is an aircraft, the direction of travel F is the main flight direction of the aircraft for which it is designed. The direction of travel F is therefore not in the plane of the scan fan 8. In the case shown, the direction of travel F is normal to the plane of the scan fan 8, so that the scan fan 8 lies in the nadir direction of the vehicle 3 and is directed downwards toward the environment 2. However, the scan fan 8 can also be rotated, for example, about a vertical axis g of the vehicle 3, so that its intersection lines 10 with the environment 2, the "scan lines," in the scan strip 9 lie obliquely to the projected direction of travel F. Similarly, the scan fan 8 could be rotated about a pitch axis p and / or roll axis r of the vehicle 3.

[0042] Each laser pulse 5 n is emitted by the device 1 to the environment 2, reflected back to the device 1 at a sampling point ("target point") P n of the environment 2, and received by the scanning unit 6. From a time-of-flight measurement of the laser pulses 5 n, distance measurement values ​​dn from the respective current position pos n of the device 1 to the respective sampling point P n of the environment 2 can be calculated using the known relationship d n = c ⋅ ΔT n / 2 = c ⋅ t E , n − t S , n / 2 with ts,n transmission time of the laser pulse 5 n , t E,n reception time of the laser pulse 5 n and cspeed of light.

[0043] Knowing the respective position pos n of the device 1 when the laser pulse 5 n is emitted in a local or global x / y / z coordinate system 11 of the environment 2, the respective orientation ori n of the device 1 in the coordinate system 11, specified, for example, by the tilt, roll, and yaw angles of the vehicle 3 about its transverse, longitudinal, and vertical axes p, r, g, and the respective angular position ang n of the laser pulse 5 n in the direction of the point P n with respect to the vehicle 3, the position of the sampling point P n in the coordinate system 11 can then be calculated from the respective distance measurement value dn. A plurality of such measured and calculated sampling points P n maps the environment 2 in the form of a "3D point cloud" in the coordinate system 11.

[0044] Fig. 2 shows the propagation time measuring principle of the device 1 in a transmit / receive channel of the device 1, which is used for the Fig. 1 the scanning compartments 8 of the scanning unit 6 shown as examples.

[0045] According to Fig. 2 The laser pulses 5 n are emitted in each transmit / receive channel of the device 1 by a laser transmitter 12 via a deflection mirror 13 and a deflection device 14. In Fig. 2 The deflection device 14 is a mirror prism 16 rotating about its prism axis 15 at a predeterminable angular velocity ω A , the outer sides of which each form a mirror surface 17 j (j = 1, 2, ..., J), and the prism axis 15 of which is the scanning axis 7. The constant or variable angular velocity ω A and the number J of mirror surfaces 17 j specify the aforementioned angular velocity profile ω and the duration T AP of a deflection period AP according to the formulas ω = 2•ω A and T AP = 360° / (ω A, d •J), where ω A, d denotes the average angular velocity ω A . Alternatively, the deflection device 14 could be implemented by any other deflection device known in the art, e.g., as an oscillating mirror, rotating mirror pyramid, etc.Likewise, the laser transmitter 12 could also transmit non-normally to the prism axis 15 onto the deflection device 14, whereby, for example, the angular velocity profile ω is calculated according to the formula ω = G•ω A, where G is a geometric projection factor G ≠ 2.

[0046] The emitted laser pulses 5 n are received back after reflection at the respective environmental point P n along the same path via the deflection device 14 and impinge on a laser receiver 18, i.e., the current viewing direction of the laser receiver 18 is equal to the current scanning direction R n . The transmission times t S,n of the laser pulses 5 n and the reception times t E,n of the ambient-reflected laser pulses 5 n are fed to a distance calculator 19, which calculates the respective distance dn therefrom using equation (3).

[0047] The pulse repetition rate (PRR) of the laser pulses 5 n is constant or can be modulated, for example, to resolve MTA (multiple time around) ambiguities within a deflection period AP in order to facilitate the assignment of transmitted and received laser pulses 5 n to each other, as is known in the art.

[0048] Alternatively, for a time-of-flight measurement and assignment of the transmitted and received laser beam 4, it could also be modulated, as is known in the prior art.

[0049] Optionally, the angular velocity ω and thus the deflection period T AP of the deflection device 14 and / or the relative velocity v can be adapted to a measured or expected distance dn, e.g. in order to obtain regular distances of the sampling points P n within each scan line 10 and between successive scan lines 10 over an environment 2 with a strongly variable topography.

[0050] In the Fig. 1 und 2 To explain the measuring principle, only the scanning compartments 8 of a scanning unit 6 of the device 1 or the associated transmit / receive channel were shown. Fig. 3a - 3d show, however, the laser scanning device 1 carried on the aircraft 3 with several (here: three) as in connection with the Fig. 1 und 2 described scanning units 6 k (k = 1, 2, ..., K; here K = 3), ie in a predetermined sequence of a "first", "second", and "third" scanning unit 6 1 , 6 2 , 6 3 . It is understood that the device 1 can have any number K > 1 of scanning units 6 k .

[0051] Each of the three scanning units 6 k repeatedly emits its respective pulse train 4 k of laser pulses 5 k,n at the same pulse repetition rate PRR in scanning directions R k,n, which are fanned out around a respective scanning axis 7 k. For each deflection period AP, the scanning directions R k,n of a scanning unit 6 k thus each span a corresponding scanning fan 8 k and traverse this fan with the same angular velocity profile ω.

[0052] In the embodiment of Fig. 3a The scanning axes 7 k of the scanning compartments 8 k lie on a common straight line 21, ie they coincide, and are spaced apart from each other in the direction of the straight line 21 by mutual distances D k,k-1. As a result, the scanning compartments 8 k of the scanning units 6 k are parallel. In the embodiment of Fig. 3b Both the scanning axes 7 k of the scanning compartments 8 k and their vertices 22 k coincide, ie the scanning compartments 8 k lie in a common plane and emanate from a common vertex 22 1, 2, 3. In the embodiment Fig. 3c the scanning compartments 8 k originate from a common vertex 22 1,2,3, but are not parallel but diverge from each other, ie their scanning axes 7 k do not coincide, but intersect at the common vertex 22 1,2,3 . In the embodiment of Fig. 3d the scanning compartments 8 k are arranged parallel and in one plane, but their vertices 22 k are spaced apart from each other.

[0053] In each of these embodiments of the Fig. 3a - 3d the scanning compartments 8 k overlap each other in the direction of one of the scanning axes 7 k essentially in a common overlapping area 20 (hatched), in which the scanning points P k,n of several scanning compartments 8 k come to lie in the direction of this scanning axis 7 k. As a result, those scanning compartments 8 k which lie in one plane ( Fig. 3b und 3d ), the overlap area 20 by design in the same deflection period AP; and for those scanning compartments 8 k which are not in the same plane ( Fig. 3a und 3c ), a trailing scanning fan 8 k-1 seen in the direction of one of the scanning axes 7 k follows a leading scanning fan 8 k seen in this direction due to the relative movement between device 1 and environment 2 and rescans its already measured part of the common scanning strip 9. For example, in the Fig. 3a und 3c the rear scanning compartment 8 1 scans the scan lines 10 2 , 10 3 of its two front scanning compartments 8 2 , 8 3 , and the rear scanning compartment 8 2 scans the scan lines 10 3 of its front scanning compartment 8 3 again.

[0054] The 8 k scanning trays are not necessarily flat. For example, in the Fig. 3c The scanning fans 8 1 , 8 3 , which are inclined forwards and backwards in the direction of travel F—e.g., due to the deflection mechanism of the laser pulses 5 k,n—lie on slightly curved conical surfaces. This can be disregarded for the purposes of the present invention.

[0055] Instead of as in the Fig. 3a - 3d As shown, the scanning compartments 8 k could also be in any other position relative to each other, as long as they overlap each other at least in pairs in an overlap area 20.

[0056] The Fig. 4 und 5 illustrate an uncoordinated transmission of the pulse trains 4 k of each individual scanning unit 6 k , ie without taking into account the other scanning units 6 k . For this purpose, Fig. 4 the intensities I k of the laser pulses 5 k,n for each scanning unit 6 k are plotted against time t for several deflection periods AP k,p (p = 1, 2, ...) of its deflection device 14 k. In Fig. 5 the resulting scan lines 10 k,p of the scan units 6 k are shown for several deflection periods AP k,p.

[0057] In the example shown, the pulse trains 4 k are emitted synchronously with the same pulse repetition rate PRR, i.e. with a pulse spacing τ = 1 / PRR. Depending on the size of the pulse spacing τ, the deflection period AP k,p , the relative speed v and the position of the scanning fans 8 k, different distributions of the sampling points P k,n arise: If the deflection period T AP is a multiple of the pulse spacing τ, i.e. T AP = m • τ (m ... a natural number), the laser pulses 5 k,n are in the same position within each deflection period AP k,p. As a result, the scanning directions R k,n of different deflection periods AP k,p of a scanning unit 6 k coincide and are located one behind the other as seen in the direction of travel F.If the angular velocity ω A of the deflection device 14 k and / or the relative velocity v is / are adapted to a measured or expected distance dk,n, it may happen, depending on the size of these values ​​and the topography of the environment 2, that the sampling points P 1,n (shown as diamonds) and P 2,n (shown as circles) of the rear scanning fans 8 1 , 8 2 never coincide with the already scanned sampling points P 3,n (shown as triangles) of the front scanning fan 8 3 .

[0058] If the deflection period T AP is not a multiple of the pulse spacing τ, i.e. T AP ≠ m • τ, the laser pulses 5 k,n shift from deflection period AP k,p to deflection period AP k,p+1 by a temporal drift D ( Fig. 4 ), which pivots the scanning compartments 8 k of consecutive deflection periods AP k,p of one and the same scanning unit 6 k around the corresponding scanning axis 7 k, so that, for example, the first scanned points P k,1 of consecutive deflection periods AP k,p , AP k,P+1 of a scanning unit 6 k, viewed in the direction of travel F, have a corresponding spatial offset S ( Fig. 5 ) suffer. If, due to the joint movement of the scanning units 6 k in the direction of movement F, the scanning lines 10 k of a "rear" scanning unit 6 k begin to shift over previous scanning lines 10 k+1 of a "front" scanning unit 6 k+1, as shown in Fig. 4 und 5 for three exemplary scanning units 6 1 , 6 2 , 6 3 is shown, then the following usually happens: When scanning a scan line 10 multiple times, e.g. once as the first scan line 10 3,1 of the third ("front") scanning unit 6 3 in its first deflection period AP 3,1 , once as the fourth scan line 10 2,4 of the second ("middle") scanning unit 6 2 in its fourth deflection period AP 2,4 and once as the seventh scan line 10 1,7 of the first ("rear") scanning unit 6 1 in its seventh deflection period AP 1,7 , the first scan directions R 1,1 , R 2,1 , R 3,1 of the scanning units 6 1 , 6 2 , 6 3 when scanning this scan line 10 are offset from each other by an angular difference Δ ϕ21 , Δ ϕ31 , Δ ϕ32 are offset so that the scanning directions R k,n of all scanning units 6 k scan the overlap area 20 in the multiply scanned scan line 10 or (here:) 10 3,1 , 10 2,4 , 10 1,7 at irregular angular intervals.As a result, different spatial distances Δs 21 , Δs 31 , As 32 occur between the associated sampling points P 1,n , P 2,n , P 3,n of the scanning units 6 1 , 6 2 , 6 3 , and the sampling points P 3,n , P 2,n and P 1,n , respectively, within this scanning line 10 and 10 3,1 , 10 2,4 , 10 1,7 do not generally coincide.

[0059] The Fig. 6 und 7 illustrate how a coincidence of the sampling points P k,n of different scanning compartments 8 k is achieved and how the sampling points P k,n can be scanned several times and thus more accurately and / or more meaningfully.

[0060] For this purpose, as in Fig. 6 As shown, the scanning compartments 8 2 of the second scanning unit 6 2 are pivoted relative to the scanning compartments 8 1 of the adjacent first scanning unit 6 1, and the scanning compartments 8 3 of the third scanning unit 6 3 are pivoted relative to the scanning compartments 8 2 of the adjacent second scanning unit 6 2, each by a pivot angle λ 21 or λ 32 about their respective scanning axis 7 k. It should be noted that the sequence of the scanning units 6 k is arbitrary, i.e., which of the scanning units 6 k is referred to as "first," "second," "third," etc., is arbitrary. The term "adjacent" scanning unit 6 k is therefore not to be understood in a spatial sense, but in a numerical sense in this arbitrarily predetermined sequence.

[0061] For example, the swivel angles λ 21 and λ 32 in Fig. 6 chosen such that, with the associated angular difference Δϕ 21 , Δϕ 32 caused by the drift D, they result in a 0-fold or 1-fold of the angle Δϕ between two consecutively paced scanning directions R k,n of a scanning fan 8 k . As a result, the scanning directions R k,n of all scanning fans 8 1 , 8 2 , 8 3 coincide there when they have traversed ("occupied") one and the same plane 23 in the coordinate system 11 with respect to the environment 2. In particular, the swivel angle λ k,k-1 , increased by the angle difference Δϕ k,k-1 between the scanning directions R k,1 and R k-1,1 first stepped in these two scanning compartments 8 k , 8 k-1 , corresponds to a multiple of the angle Δϕ between two scanning directions R k,n successively stepped in a scanning compartment 8 k , e.g. an i-fold i·Δϕ = i·ω / PRR, where i is an integer.

[0062] If, in addition, the pulse repetition rate PRR is selected depending on a measured or expected distance dk,n to the environment 2 and is changed within the deflection period AP k,p, the sampling points P k,n in each scan fan 8 k can be arranged at regular intervals over the entire scan line 10 k, as in Fig. 7 shown.

[0063] According to Fig. 7 The sampling points P k,n of different scanning units 6 k can optionally be of different sizes by having the laser pulses 5 k,n of different scanning units 6 k with different beam divergences. For example, each sampling point P k,n can be measured once as a larger sampling point P 2,n (shown as a circle) with multiple target reflections per laser pulse 5 2,n and once as a smaller sampling point P 1,n , P 3,n (shown as a rhombus or triangle) with a precisely definable scanning direction R k,n.

[0064] As in Fig. 8 As shown, the laser pulses 5 k,n of different scanning units 6 k can optionally also have different pulse intensities PI k and / or pulse widths PW k in order to measure both strongly and weakly reflecting, near and far scanning points P k,n.

[0065] Likewise, the laser pulses 5 k,n from different scanning units 6 k can optionally differ in other or further optical properties and, for example, have different wavelengths (not shown), polarizations (not shown), etc., in order to obtain additional information about the scanning points P k,n. For example, for the joint survey of the sea floor and seabed, the laser pulses 5 1,n from the first scanning unit 6 1 could have a wavelength that is reflected by water, and the laser pulses 5 k,n from another scanning unit 6 k could have a wavelength for which water is transparent.

[0066] The Fig. 8 und 9 show a first practical embodiment for pivoting the scanning compartments 8 k to the Fig. 6 und 7 described manner, i.e. by means of an electronically generated time offset V k of the pulse trains 4 k of the scanning units 6 k .

[0067] Fig. 8 shows the thus offset pulse trains 4 k and Fig. 9 the block diagram of such an electronic implementation of a three-channel device 1 according to the embodiments 3a - 3d. Each scanning unit 6 k comprises a laser transmitter 12 k and an associated laser receiver 18 k , which are connected to the laser beams 12 k by a deflection device 14 common to all scanning units 6 k - each as shown in Fig. 2 shown for one channel - interact and are connected to a common distance calculator 19 which calculates the respective distances dk,n to the sampling points P k,n. A clock generator 24 generates a control pulse train 25 1 for the laser transmitter 12 1 of the first scanning unit 6 1 , which generates the first pulse train 4 1 therefrom. Delay elements 26 2 , 26 3 delay the control pulse train 25 1 in cascade by a time offset V 21 or V 32 and feed the control pulse trains 25 2 , 25 3 delayed in this way to the laser transmitters 12 2 , 12 3 , which generate the pulse trains 4 2 , 4 3 of the second and third scanning units 6 2 , 6 3 therefrom.

[0068] The time offset V 21 , V 32 to be applied in the delay elements 26 2 , 26 3 is specified by an offset calculator 27. The offset calculator 27 receives, for example, the control pulse train 25 1 from the clock generator 24 and the angular velocity ω A of the deflection device 14 from an angular velocity sensor 28 and uses this to determine the pulse repetition rate PRR or the current angular velocity profile ω and, depending thereon, the time offsets V 21 , V 32 .

[0069] The offset computer 27 with the delay elements 26 2 , 26 3 can thus also be regarded as a control device 29 which offsets the pulse trains 4 k of the scanning units 6 k with respect to one another in time and thus pivots the scanning compartments 8 k about their scanning axes 7 k , namely the second scanning compartments 8 2 relative to the first scanning compartments 8 1 by the angular offset λ 21 and the third scanning compartments 8 3 relative to the second scanning compartments 8 2 by the angular offset λ 32 .

[0070] The control device 29 can be implemented together with the distance calculator 19 in a processor system 30, i.e. in hardware and / or software.

[0071] In particular, the offset calculator 27 can calculate the time offsets V 21 , V 32 for the embodiment of Fig. 3b for an angle equalization of Fig. 6 according to the following formula: V k , k − 1 = i ⋅ 1 PRR − 1 ω R k , 1 , p − R k − 1,1 , p mod ω PRR with V k,k-1 temporal offset of the k-th pulse train compared to the (k-1) -th pulse train (k = 1 ... K), i an integer, ω average angular velocity of the angular velocity profile, PRR pulse repetition rate, R k,1,p first scan direction of the k-th laser transmitter 12 k in a reference deflection period AP k,p , v relative velocity between device 1 and environment 2, mod modulo operator.

[0072] Optionally, the offset calculator 27 can also determine the applicable temporal offset V 21 , V 32 depending on further values, e.g. the relative speed v, a measured or expected distance dk,n or the positions of the scanning units 6 k , ie their positions and orientations, etc. In this case, the offset calculator 27 can determine the temporal offsets V 21 , V 32 for the embodiment of Fig. 3a for an angle equalization of Fig. 6 according to the following formula: V k , k − 1 = i ⋅ 1 PRR − 1 ω R k , 1 , p − R k − 1,1 , p + ω ⋅ D k , k − 1 ν mod ω ⋅ T AP mod ω PRR with V k,k-1 temporal offset of the k-th pulse train compared to the (k-1) -th pulse train (k = 1 ... K), i an integer, ω average angular velocity of the angular velocity profile, PRR pulse repetition rate, R k,1,p first scan direction of the k-th laser transmitter 12 k in a reference deflection period AP k,p , D k,k-1 distance between the k-th and (k-1) -th scan fan 8 k, v relative velocity between device 1 and environment 2, T AP deflection period duration and mod modulo operator.

[0073] Alternatively, the control device 29 can also assign fixed transmission times ts,k,n related to the deflection period AP k,p to each scanning unit 6 k within each deflection period AP k,p, e.g., by shifting the pulse trains 4 k of each scanning unit 6 k per deflection period AP k,p by a time offset V k corresponding to the drift D between two consecutive deflection periods AP k,p , AP k,p+1. For this purpose, the control device 29 could also be connected to the first scanning unit 6 1 in order to also pivot its scanning fans 8 1 .

[0074] The Fig. 10 und 11 show a second practical embodiment for pivoting the scanning compartments 8 k by means of a control device 29, which, instead of delay elements 26 2 , 26 3 for temporal offsets, now contains adjustable optical elements, e.g. electro-optical elements, mirrors, prisms, etc. in the beam path of the laser pulses 5 k,n of the respective scanning compartments 8 k. This is explained below in three exemplary variants based on the Fig. 10 und 11 each showing a possible mechanical structure of the embodiments of Fig. 3a and 3b respectively.

[0075] In a first, in Fig. 10 In the variant shown, the control device 29 contains an actuator 31 k for each scanning unit 6 k , which actuator is controlled by the offset computer 27 and can adjust the position of its deflection mirror 13 k . This changes the respective transmission direction ϑ k to the common mirror prism 16 or the respective mirror prism 16 k normal to the scanning axis 7 k .

[0076] In a second, also in Fig. 10 as well as in Fig. 11 In the variant shown, the laser transmitters 12 k are adjustably mounted and the offset computer 27 controls actuators 32 k , which can change the position and / or orientation, ie the position, of the respective laser transmitter 12 k relative to the common or respective mirror prism 16 k and thus the transmission direction ϑ k .

[0077] It is understood that, in order to measure the time of flight, the laser pulses 5 k,n of the pivoted scanning fans 8 k must also be received by the associated laser receivers 18 k in the first and second variants. For this purpose, these laser receivers 18 k in one embodiment have a receiving aperture which is large enough that the reflected laser pulses 5 k,n pass through them despite the pivoting of the associated scanning fan 8 k. In an alternative embodiment, these laser receivers 18 k retain their, for example, optimally adjusted receiving aperture and the viewing directions of these laser receivers 18 k are pivoted along with the associated scanning fan 8 k. For this pivoting, the control device 29 could - as described in the first or second variant for the transmission channel - control adjustable optical elements in the receiving channel by means of actuators or the position of these laser receivers 18 k themselves.

[0078] In a third, also in Fig. 10 In the variant shown, the offset computer 27 controls actuators 34 k mounted on a common drive shaft 33 of the mirror prisms 16 k , with which actuators the mirror prisms 16 k can each be individually rotated relative to the drive shaft 33 in order to adjust the phase position ϕ k, k-1 = ϕ k - ϕ k-1 = λ k, k-1 / 2 between two mirror prisms 16 k , 16 k-1. This again pivots the scanning compartments 8 k of different scanning units 6 k against each other.

[0079] In the variants mentioned, the offset computer 27 together with the actuators 31 k , 32 k , 34 k forms the control device 29, which pivots the scanning compartments 8 k of the scanning units 6 k about their scanning axes 7 k .

[0080] For a coincidence of the scanning directions R k,n of different scanning compartments 8 k in the overlapping area 20, if these essentially occupy the same plane 23, the swivel angle λ k,k-1 can be determined in each of the three variants mentioned, for example, as λ k , k − 1 = i ⋅ ω PRR − 2 ⋅ ϑ k − ϑ k − 1 + ω ⋅ D k , k − 1 ν mod 360 ° ⋅ 2 J mod ω PRR or in the embodiment of Fig. 11 with D k,k-1 =0 as λ k , k − 1 = i ⋅ ω PRR − 2 ⋅ ϑ k − ϑ k − 1 mod ω PRR or generally for parallel scanning fans 8 k , even if the transmission directions ϑ k are not normal to the prism axis 15, as λ k , k − 1 = i ⋅ ω PRR − R k , 1 , p − R k − 1,1 , p ′ mod ω PRR with λ k,k-1 swivel angle of the k-th scanning fan 8 k relative to the (k-1)-th scanning fan 8 k-1 (k = 1 ... K), i an integer, ω average angular velocity of the angular velocity profile, PRR pulse repetition rate, ϑ k transmission direction of the k-th laser transmitter 12 k , R k,1,p first scan direction of the k-th scanning unit 6 k in a reference deflection period AP k,p , R k-1,1,p' first scan direction of the (k-1)-th scanning unit 6 k-1 in that deflection period AP k-1,p' in which its scanning fan 8 k-1 essentially occupies the same plane 23 in the coordinate system 11 as the scanning fan 8 k of the k-th scanning unit 6 k in the reference deflection period AP k,p , D k,k-1 distance between the k-th and (k-1)-th scan fans 8 k along the prism axis 15 k , vRelative velocity between device 1 and environment 2, JNumber of mirror surfaces 17 j and modModulo operator.

[0081] It is understood that in equations (1) and (2) or (4), (5) and (6) a representation of the transmission directions ϑ k , the angle Δϕ or the first scan directions R k,1,p is to be chosen as a scalar, e.g. as a direction angle in a projection plane common to all scan fans 8 k , for example in the case of parallel scan fans 8 k projected onto a common scan fan plane, as in Fig. 11 shown.

[0082] Of course, further optical elements upstream or downstream of the deflection device 14 can also be present in the beam path of the laser pulses 5 k,n, which can be controlled by the offset computer 27 to pivot the scanning fans 8 k around and / or along the scanning axes 7 k.

[0083] The invention is not limited to the embodiments shown, but includes all variants, modifications and combinations thereof that fall within the scope of the appended claims.

Claims

1. Apparatus for measuring an environment (2) moving relative thereto by means of time-of-flight measurement of laser pulses (5k,n) reflected thereon in a coordinate system (11), comprising: a first scanning unit (61) for emitting a first pulse train (41) of laser pulses (51,n) over successive deflection periods (AP1,p) at a pulse repetition rate (PRR), wherein the laser pulses (51,n) which respectively fall within one deflection period (AP1,p) are emitted in first scan directions (R1,n) fanned out about a first scan axis (71) and thus respectively form, for each deflection period (AP1,p), a first scanning fan (81) which they traverse with a predeterminable angular velocity profile (ω), and for receiving the corresponding laser pulses (51,n) reflected from first scan points (P1,n) of the environment (2), at least one further scanning unit (6k) for emitting an further pulse train (4k) of laser pulses (5k,n) over successive deflection periods (APk,p) with the same pulse repetition rate (PRR), wherein the laser pulses (5k,n) which respectively fall within one deflection period (APk,p) are emitted in further scan directions (Rk,n) fanned out about an further scan axis (7k) and thus respectively form, for each deflection period (APk,p), an further scanning fan (8k) which they traverse with the same predeterminable angular velocity profile (ω), and for receiving the corresponding laser pulses (5k,n) reflected from further scan points (Pk,n) of the environment (2), wherein all scanning fans (8k), seen in the direction of one of the scan axes (7k), substantially overlap and an area of the environment in the overlap area (20) of the scanning fans (8k) that has already been scanned by a front scanning fan (81), seen in the direction of the scan axis, is scanned again by a rear scanning fan (8k), seen in the direction of this scan axis, and a control unit (29) connected to the at least one further scanning unit (6k), which is configured to pivot the scanning fans (8k) of each further scanning unit (6k) relative to the scanning fans (8k-1) of a scanning unit (6k-1) which is respectively adjacent in a predetermined sequence of scanning units (6k), by a pivot angle (λk,k-1) depending on the pulse repetition rate (PRR) and the angular velocity profile (ω) in such a way, that the further scan points (Pk,n) coincide with the first scan points (P1,n).

2. Apparatus according to claim 1, characterized in that the first scanning unit (6k) is configured to respectively emit its laser pulses (51,n) with a first intensity (PI1), and the at least one further scanning unit (6k) is configured to respectively emit its laser pulses (5k,n) with a further intensity (PI2) different from the first intensity (PI1).

3. Apparatus according to claim 1 or 2, characterized in that the first scanning unit (6k) is configured to respectively emit its laser pulses (51,n) with a first pulse width (PW1), and the at least one further scanning unit (6k) is configured to respectively emit its laser pulses (5k,n) with a further pulse width (PW2) different from the first pulse width (PW1).

4. Apparatus according to one of claims 1 to 3, characterized in that the first scanning unit (61) is configured to respectively emit its laser pulses (51,n) with a first beam divergence and the at least one further scanning unit (6k) is configured to respectively emit its laser pulses (5k,n) with a further beam divergence different from the first beam divergence.

5. Apparatus according to one of claims 1 to 4, characterized in that the first scanning unit (6k) is configured to respectively emit its laser pulses (51,n) with a first wavelength and / or polarization and the at least one further scanning unit (6k) is configured to emit its laser pulses (5k,n) respectively with a further wavelength different from the first wavelength and / or a further polarization different from the first polarization.

6. Apparatus according to one of claims 1 to 5, characterized in that it is mounted on a vehicle (3) which is configured for a main direction of movement (F), preferably on an aerial vehicle, with its scan axes (7k) respectively non-normal to the principle direction of movement (F).

7. Apparatus according to one of claims 1 to 6, characterized in that the control unit (29) is configured to predetermine the angular velocity profile (ω) depending on at least one previous distance measurement value (dk,n) of the environment (2).

8. Apparatus according to one of claims 1 to 7, characterized in that all scanning fans (8k) originate from the same point (221,2,3).

9. Apparatus according to one of claims 1 to 7, characterized in that all scan axes (7k) coincide.

10. Apparatus according to claim 9, characterized in that the control unit (29) is configured to pivot the scanning fans (8k) of each further scanning unit (6k) relative to the scanning fans (8k-1) of a scanning unit (6k-1) which is respectively adjacent in a predetermined sequence of scanning units (6k) in such a way, that the scan directions (Rk,n) of the scanning fans (8k) coincide when they substantially occupy the same plane (23) in the coordinate system (11).

11. Apparatus according to claim 9 or 10, characterized in that the pivot angle (λk,k-1) between the scanning fans (8k, 8k-1) of each two scanning units (6k, 6k-1) which are adjacent to one another in the sequence, when the scanning fans (8k, 8k-1) substantially occupy the same plane (23) in the coordinate system (11), increased by the angular difference (Δϕ21, Δϕ32) between the scan directions (Rk,1, Rk-1,1) that are respectively traversed first in these two scanning fans (8k, 8k-1), yields a multiple of the angle (Δϕ) between two consecutively traversed scan directions (Rk,n, Rk,n+1) in one scanning fan (8k).

12. Apparatus according to one of claims 1 to 11, characterized in that the control unit (29) is configured to pivot the scanning fans (8k) of said at least one further scanning unit (6k) by controlling a temporal offset (V21, V32) when emitting its pulse train (4k) of laser pulses (5k,n).

13. Apparatus according to one of claims 1 to 12, characterized in that the control unit (29) is configured to pivot the scanning fans (8k) of said at least one further scanning unit (6k) by controlling optical elements in the beam path of their laser pulses (5k,n).

14. Apparatus according to one of claims 1 to 13, characterized in that each scanning unit (6k) comprises: a deflection unit (14) with a mirror prism (16k) rotatable about its prism axis (15k), the lateral sides of which each form a respective mirror surface (17j) and the prism axis (15k) of which is the scan axis (7k), and a laser emitter (12k) for emitting the respective pulse train (4k) of laser pulses (5k,n) in a respective emission direction (ϑk) onto the deflection unit (14).

15. Apparatus according to claim 14, characterized in that the deflection units (14) of all scanning units (6k) are formed by one and the same deflection unit (14).

16. Apparatus according to claim 14 or 15, in combination with claim 9 respectively, characterized in that the pivot angle (λk,k-1) between the scanning fans (8k, 8k-1) of each two scanning units (6k, 6k-1) which are in the sequence adjacent to one another is chosen as λ k , k − 1 = i ⋅ ω PRR − 2 ⋅ ϑ k − ϑ k − 1 + ω ⋅ D k , k − 1 ν mod 360 ∘ ⋅ 2 J mod ω PRR with λk,k-1 pivot angle of the kth scanning fan 8k relative to the k-1th scanning fan 8k-1 (k = 1 ... K), i an integer, ω average angular velocity of the angular velocity profile, PRR pulse repetition rate, ϑk emission direction of the kth laser emitter 12k, Dk,k-1 distance between the kth and k-1th scanning fan (8k) along the prism axis (15k), v relative velocity between the Apparatus (1) and the environment (2), J number of mirror surfaces, and mod modulo operator.

17. Apparatus according to one of claims 14 to 16, characterized in that the laser emitter (12k) further comprises an adjustable deflection mirror (13k) located in the beam path of the laser pulses (5k,n), and the control unit (29) is configured to pivot the scanning fans (8k) of said at least one further scanning unit (6k) by adjusting the deflection mirror (13k).

18. Apparatus according to one of claims 14 to 17, characterized in that the laser emitter (12k) is mounted to be adjustable relative to the deflection unit (14), and the control unit (29) is configured to pivot the scanning fans (8k) of said at least one further scanning unit (6k) by controlling the position of the respective laser emitter (12k).

19. Apparatus according to one of claims 14 to 18, characterized in that the control unit (29) is configured to pivot the scanning fans (8k) of said at least one further scanning unit (6k) by controlling the phase position (ϕk) of the rotative movement of the mirror prism (16k).

20. Apparatus according to one of claims 1 to 19, in combination with claim 9 respectively, characterized in that the pivot angle (λk,k-1) between the scanning fans (8k, 8k-1) of each two scanning units (6k, 6k-1) which are in the sequence adjacent to one another is chosen as λ k , k − 1 = i ⋅ ω PRR − R k , 1 , p − R k − 1,1 , p ′ mod ω PRR with λk,k-1 pivot angle of the kth scanning fan (8k) relative to the k-1th scanning fan (8k-1) (k = 1 ... K), i an integer, ω average angular velocity of the angular velocity profile, PRR pulse repetition rate, Rk,1,p first traversed scan direction of the kth scanning unit (6k) in a reference deflection period (APk,p), Rk-1,1,p' first traversed scan direction of the (k-1)th scanning unit (6k-1) in that deflection period (APk-1,p') in which its scanning fan (8k-1) occupies substantially the same plane (23) in the coordinate system (11) as the scanning fan (8k) of the kth scanning unit (6k) in the reference deflection period (APk,p), and mod modulo operator.