LASER SCANNING DEVICE AND METHOD FOR THREE-DIMENSIONAL MEASUREMENT OF A SCENERY AT A LONG DISTANCE

Description

[0001] The invention relates to a laser scanning device and a method as known by generic terms from EP 2 182 377 B1.

[0002] Three-dimensional environmental measurement is becoming increasingly important in industrial and automotive environments. 3D cameras are being progressively replaced by laser scanning systems, which, depending on the intended application, require a wide field of view, high spatial resolution, long range, and / or a large dynamic range. These requirements are fundamentally contradictory. It is also essential that the parameters of the laser pulses emitted by the laser scanning system are selected to ensure that their energy remains within the range of eye safety.

[0003] Known laser scanning devices, such as those disclosed in the aforementioned EP 2 182 377 B1, and thus also a laser scanning device according to the invention, comprise a transmitter unit for emitting laser pulses, a receiver unit for receiving each portion of a laser pulse reflected from a target object, a storage and evaluation unit for determining distances from receiver signals generated by the receiver unit, and a movable deflection unit for one- or two-dimensional deflection of the direction of radiation of the laser pulses in the monitoring area.

[0004] To determine the distance to a target object based on the time-of-flight method, individual laser pulses are emitted sequentially at a frequency limited by the maximum expected travel time of a laser pulse. The travel time of each laser pulse corresponds to the time between the emission of the laser pulse and its reception. The reception time is determined by the occurrence of a specific characteristic of the useful signal component in the receiver signal caused by the received reflected portion of the laser pulse, for example, a maximum. From knowledge of the respective position of the deflection unit and the spatial orientation of the transmitting and receiving units at the time of emission of a laser pulse, and the correspondingly determined distance, a three-dimensional depth profile can be created over the monitored area.The position of the deflection unit is typically determined for a line scanner by a horizontal angle in a scan plane around a rotation axis, or for a matrix scanner by a horizontal angle in a scan plane around a rotation axis and a vertical angle in a cross-scan plane around a second rotation axis within a coordinate system. For a given laser pulse frequency, the spatial resolution decreases with increasing scan speed and increasing distance of the expected target objects in the scene. Simultaneously, depending on the scan speed, the reception divergence, or the size of the receiver unit's area in the scan direction, must be selected such that a portion of the laser pulse reflected from the target object is detected by the receiver unit, even though the receiver unit is moving relative to the target object at the scan speed.This problem is also addressed in patent EP 2 998 700 B1, which will be discussed in more detail below. However, a larger receiver area and greater reception divergence result in more ambient light (ambient light, extraneous light) striking the receiver area and increasingly influencing the receiver signal generated by the receiver unit. For the purposes of this description, a receiver signal is understood to be an amplitude signal formed over the receiver unit's reception time by the desired signal component and a noise signal component (caused, among other things, by ambient light). Recognizing the desired signal component, or a characteristic of the desired signal component, within a single receiver signal requires, at a minimum, that the amplitude caused by the desired signal component in the receiver signal is higher than the highest amplitude caused by the noise signal component, which is not the case for very long distances.

[0005] Typical measures to reduce the influence of ambient light include placing a narrowband optical filter in front of the receiver surface of the receiver unit, which has maximum transmission in the spectral range of the emitted laser pulse, selecting a receiver unit with a suitable spectral sensitivity, and matching the spectral bandwidth of the amplifier to the spectrum of the laser pulse. For greater distances, where a reflected signal component has a comparatively small amplitude, which can occur at distances as low as 50 m, these measures are often insufficient.

[0006] To improve the interpretability of a receiver signal, it is known for one-dimensional laser distance measuring devices, which are stationary at least during the measurement, to direct several laser pulses successively at the same target object and then accumulate the individual receiver signals. By adding the receiver signals, with practically identical amplitudes of the useful signal component and random amplitudes of the noise signal component that have different signs relative to a mean value, the accumulated receiver signal exhibits a clearly better signal-to-noise ratio than a single receiver signal.

[0007] German patent DE 10 2011 054 451 A1 discloses a method and a device for optical distance measurement over large distance ranges, in which second laser pulses suitable for evaluation using the sampling method are emitted when no reception times can be derived from the receiver signals using the threshold method caused by a first laser pulse. Thus, for distance measurements in the short range, the reception time can be determined from the receiver signals using the more accurate threshold method, even with high amplitudes of the useful signal components. For measurements in the long range, the reception time can be determined from the receiver signals using the sampling method by accumulating sampled receiver signals, even with small amplitudes of the useful signal components for which evaluation using the threshold method is not possible.

[0008] The requirement for a long range (large distance to the target objects) is not the same as the requirement for a large distance range (target objects at very different distances). A large distance range requires a large dynamic range, and measures to suppress ambient light are not necessarily required if the amplitude of the useful signal component is sufficiently high. Conversely, for a rangefinder with a long range, if all the expected target objects are located at a large measuring distance, a small dynamic range may suffice. However, it may then be necessary to take measures to minimize the influence of ambient light on the receiver signal or to improve the receiver signal's readability.

[0009] The evaluation of receiver signals using the sampling method and the improvement of their evaluability through the accumulation of receiver signals are described in the aforementioned DE 10 2011 054 451 A1. For evaluation, the analog receiver signal is sampled, and digitized samples are generated, each corresponding to one of the sampling points and collectively forming a digitized sample signal. Accumulation, i.e., repeated time-synchronous sampling and summation of corresponding digitized samples from successive receiver signals, creates an accumulated receiver signal. The accumulated receiver signal exhibits a better signal-to-noise ratio (SNR) than the individual receiver signals, thus increasing the range. The improvement in the SNR is proportional to the square root of the number of individual receiver signals comprising the accumulated receiver signal.

[0010] The possibility of accumulating receiver signals that are generated sequentially is known from the prior art, limited to stationary transmitting and receiving systems, since in systems with beam deflection and a receiver with a typically small reception divergence due to a desired high spatial resolution, the same target object is not measured multiple times in succession.

[0011] No prior art laser scanning device or method using a laser scanning device could be identified that provides improved evaluation of receiver signals through an accumulation of receiver signals.

[0012] A variety of laser scanning devices known from the state of the art are intended to cover a large dynamic range.

[0013] Typical applications for such laser scanning systems include monitoring technology in industry and vehicles, where objects within the monitoring area can be located at distances ranging from a few centimeters to several tens of meters. Accordingly, the dynamic range within which a receiver signal can be generated without overloading must be very large. This requirement for a large dynamic range also applies when the target objects have different surface finishes and thus very different reflection characteristics. Some prior art solutions that exhibit a large dynamic range also improve the signal-to-noise ratio between the actual useful signal component, caused by the portion of a laser pulse reflected from the target object, and the noise signal component superimposed on this useful signal component.

[0014] US Patent 5,311,353A discloses an optical receiver with a high dynamic range, comprising a first linear amplifier and a second logarithmic amplifier. The two amplifier signals are either summed or one of the two amplifier signals is selected for evaluation. Thus, weak receiver signals lie within the dynamic range of the first amplifier and are amplified linearly, while strong receiver signals lie within the dynamic range of the second amplifier and are amplified logarithmically. The combined dynamic range of both amplifiers constitutes the effective dynamic range of the receiver. Uniform light interference is not mentioned as a problem, which may be because even at the greatest expected target distances, a significantly higher signal-to-noise ratio is anticipated in the receiver signal.

[0015] The aforementioned EP 2 182 377 B1 also proposes a rangefinder, specifically a laser scanner capable of measuring distances, with the aforementioned features of known laser scanning devices. In this case, the effective dynamic range, which is too large for a single amplifier element, is divided by the use of two amplifiers. The receiver signal is fed in parallel to a more sensitive and a less sensitive amplification path, each connected to a first and a second amplifier, respectively. For digital signal processing and thus distance determination, the two amplification paths are routed to a common analog-to-digital converter for cost reasons. The two receiver signals from the amplification paths are reversibly combined beforehand.Besides the main objective of a large effective dynamic range, this solution should have the advantage that, due to the separate evaluation of weak and strong receiver signals, weak interference signals, such as from a windshield or fog droplets, which distort the measurement result by overlapping with the actual useful signal, can be suppressed.

[0016] The aforementioned EP 2 998 700 B1 addresses the fundamental problem regarding the quality of receiver signals and their evaluation for scanning laser rangefinders, in contrast to laser rangefinders with a stationary transmitter. This problem arises from the high scanning speed, which necessitates a receiver with a large field of view (FOV) to ensure that the received beam reflected from the target object strikes the receiver or its receiving surface. However, receivers with a large field of view have the disadvantage that a correspondingly large amount of daylight or ambient light (uniform light) also reaches the receiver. Simultaneously, an increasingly larger field of view leads to a progressively lower spatial resolution of the depth profile formed by the scene within the laser scanner's field of view.

[0017] The aforementioned EP 2 998 700 B1 proposes a distance measurement method and an optoelectronic distance meter suitable for scanning systems, comprising a detector that is improved not only with regard to its dynamic range but also with regard to its signal-to-noise ratio. The detector has two independent receiving segments, each designed to independently generate a resulting electrical receiver signal and configured to correspond to predefined, different distance ranges. In contrast to unsegmented detectors according to the prior art, the required effective dynamic range of the distance meter is divided into smaller dynamic ranges. The division of the detector into independent receiving segments is also intended to divide the amount of background light, thereby reducing its influence on the generated receiver signal.

[0018] German patent application DE 10 2007 030 823 A1 discloses a radar device that achieves an improved signal-to-noise ratio through the integration of received signals. The device is used to record the peak waveform of a reflecting object. For this purpose, a plurality of laser pulses are emitted within a specific angular range, and reflected signals are received. The scanned field of view is then divided into several overlapping areas, for each of which received signals are stored and integrated in parallel. Subsequently, a complex evaluation process takes place in which a peak waveform group is determined via peak search, and noise components are then removed to achieve a better signal-to-noise ratio and thus increase the accuracy of the distance calculation to the reflecting object.

[0019] In a LIDAR device and corresponding method disclosed in US 2017 / 0350967 A1, a scene to be captured is acquired in sections by scanning the scene horizontally. A receiver matrix is ​​used to acquire these sections, the pixels of which exhibit reduced receive divergence, at least in the scan direction. This reduced divergence is intended to increase the signal-to-noise ratio between the target signal and the background light. The lower divergence also leads to better spatial resolution, thereby reducing the influence of artifacts caused by glare from very bright light sources. The effect of the low divergence on the dynamic range of the distance measurement is not disclosed, especially since no measures are provided to improve the signal quality of weak target signals at long distances.

[0020] US patent 2018 / 284268 discloses a LiDAR device comprising a transmitter unit emitting a sequence of laser pulses, a receiver unit, an analog-to-digital converter (ADC), and a scanning unit with a control unit and a simple storage and evaluation unit. The beam cross-section of the emitted laser pulses is elliptical, which means the field of view cannot be divided into multiple equally sized receiver cells without overlap or information loss. This necessitates complex evaluation of the receiver signals when multiple receiver cells are scanned in parallel. The alignment of the receiver area and the laser beam is similar to that of other prior art devices where the transmission and reception divergence in the scan direction is smaller than in the cross-scan direction.

[0021] The object of the invention is to find a method for the three-dimensional measurement of a scene in a large field of view and at a great distance, which improves the evaluability of a receiver signal. At the same time, the method is intended to improve the spatial resolution of a depth profile (distance image) of the scene generated from the receiver signals.

[0022] It is also the object of the invention to find a laser scanning device suitable for carrying out the method.

[0023] This task is fulfilled for a laser scanning device with the features of claim 1.

[0024] Advantageous embodiments of the laser scanning device are specified in reverse claims 2 to 5.

[0025] The problem is further fulfilled for a method with the features of claim 6.

[0026] The invention will be explained in more detail below using exemplary embodiments and the accompanying drawings. The drawings show: Fig. 1 a schematic diagram of an embodiment of a laser scanning device according to the invention, Fig. 2 a representation of an exemplary arrangement of two receiver units and four transmitter units, each with two transmission channels, and Fig. 3 a simplified schematic representation of the process flow.

[0027] Fig. 1 Figure 1 shows an embodiment of a laser scanning device according to the invention for the three-dimensional measurement of a scene within a field of view (FOV) at a great distance. A great distance is defined as a distance at which a reflected and detected portion LP' of a laser pulse LP in a receiver signal S produces a useful signal portion SN that is not distinguished from a noise signal portion SR caused by uniform light. Depending on the reflectivity of the scene, this can occur at a distance of approximately 50 m.

[0028] The laser scanning device comprises at least one transmitter unit 1, with at least one transmitter channel 1.1, for emitting laser pulses LP in a sequence, and at least one receiver unit 2, with one receiver channel 2.1 and a receiver area 2.1.1, for receiving components LP' of the laser pulses LP reflected back from measurement fields M of the scene and for generating receiver signals S. The transmitter channels 1.1, which may be multiple, are arranged side by side in a cross-scan direction Rc.

[0029] The in Fig. 1 The laser scanning device shown in the schematic diagram features, for a simple description of the operating principle and a clear presentation, two transmitter units 1 each with a transmitter channel 1.1 and a receiver unit 2 as examples.

[0030] A laser scanning device according to the invention further comprises, like the laser scanning devices of the prior art of the same type, a basic analog-to-digital converter 3 for digitizing the receiver signals S, a deflection unit 4 for scanning the laser pulses LP in a scan direction Rs, a storage and evaluation unit 5 and a control unit 6.

[0031] It is essential to the invention that the transmitting channels 1.1 are designed such that the emitted laser pulses LP have a rectangular beam cross-section, and that the receiver area 2.1.1 is rectangular. Furthermore, it is essential to the invention that the radiation divergence of the transmitting channels 1.1 and the reception divergence of the receiver channels 2.1 in the scan direction Rs are each many times greater than the radiation divergence of the transmitting channels 1.1 and the reception divergence of the receiver channels 2.1 in the cross-scan direction Rc perpendicular to the scan direction Rs. As a result, a measurement field M in the field of view (FOV) illuminated by each of the laser pulses LP acquires a rectangular shape with a larger extent in the scan direction Rs.

[0032] It is also essential to the invention that the storage and evaluation unit 5 contains several storage and evaluation areas 5.1 for the parallel storage of digitized receiver signals SD and the formation of several accumulated receiver signals SA, from which a distance can be derived using algorithms known to those skilled in the art. Advantageously, the transmission and reception divergences in the scan direction RS are at least three times the transmission and reception divergences in the cross-scan direction Rc, in order to achieve a high overlap of the measurement fields M even at a high scan speed.

[0033] Since the radiation divergence and the reception divergence are equal in the scan direction Rs and the cross-scan direction Rc, the measurement field M is advantageously not restricted by the smaller divergence in either direction.

[0034] The added radiation divergence of all transmit channels 1.1 in the cross-scan direction Rc determines the size of the viewing angle of the field of view FOV in the cross-scan direction Rc, while the radiation divergence in the scan direction RS and the scan angle by which the deflection unit 4 can be deflected about a rotational axis determine the size of the viewing angle of the field of view FOV in the scan direction RS.

[0035] The size of the measurement fields M illuminated by each laser pulse LP depends on the emission and reception divergences of the transmit and receiver channels 1.1 and 2.1, and the distance of the scene within the limited angular range. All measurement fields M together constitute the field of view (FOV).

[0036] The number of transmission channels 1.1 determines the number of measurement fields M that lie one above the other in the cross-scan direction Rc. According to the in Fig. 1 In the illustrated embodiment, two transmitting units 1, each with a transmitting channel 1.1, are provided. Their transmission divergences are matched to the reception divergences of the receiver channel 2.1 of one receiver unit 2. The transmitting units 1 are continuously and alternately activated, so that during a scan (a single sampling of the field of view, FOV), the FOV is scanned virtually simultaneously in two lines. Since the two transmitting units 1 are activated sequentially, they can both be assigned to the single receiver channel 2.1, whereby the reception divergence of the single receiver channel 2.1 in the cross-scan direction Rc is equal to or greater than the resulting transmission divergence of the two transmitting channels 1.1 in the cross-scan direction Rc.

[0037] There can also be two or more receiver units 2 arranged next to each other in the cross-scan direction Rc, each of which is assigned one or more transmit channels 1.1, whereby in the case of multiple transmit channels 1.1 these belong to different transmit units 1.

[0038] Fig. 2 Figure 1 shows an example of an arrangement of two receiver units 2, represented by the receiver surfaces 2.1.1, and four transmitter units 1, each with two transmission channels 1.1, represented by eight measurement surfaces M projected onto the receiver surfaces 2.1.1. Each of the four transmitter units 1 assigns one transmission channel 1.1 to one of the receiver surfaces 2.1.1, so that the measurement surfaces M projected onto each receiver surface are illuminated by the four transmitter units 1. With this arrangement, a field of view (FOV) can be scanned virtually simultaneously, resolved into eight lines. The transmitter units 1 are addressed sequentially. After beam splitting, the emitted laser pulse LP is directed into the field of view (FOV) via two transmission channels 1.1, where different measurement fields M are illuminated, and the reflected components LP' of the laser pulse LP are received by one of the two receiver units 2.

[0039] The spatial resolution of the field of view (FOV) in the cross-scan direction RC is determined by the transmission and reception divergence in the cross-scan direction RC. In the scan direction Rs, the spatial resolution is determined by the signal processing of the receiver signals S according to the invention, largely independent of the scan speed and pulse frequency at which the laser pulses LP are emitted and scan the field of view (FOV).

[0040] Signal processing is a process step of the inventive method described below.

[0041] A method according to the invention performs a three-dimensional measurement of a scene within a field of view (FOV) at a great distance. As with similar methods from the prior art: 1. Laser pulses LP are emitted in a continuous sequence via at least one transmission channel 1.1, which exhibits a radiation divergence in both a scan direction Rs and a cross-scan direction Rc. 2. After reflection of the laser pulses LP in a measurement field M in the scene, the reflected components LP' of the laser pulses LP are received successively via at least one receiver channel 2.1, which exhibits a reception divergence in both the scan direction Rs and the cross-scan direction Rc. 3. A receiver signal S is generated, amplified, and digitized over the duration of each component LP' of the laser pulses LP, while the laser pulses LP are scanned in the scan direction RS, whereby a different measurement field M is captured with each laser pulse LP in the field of view FOV, depending on a scan speed and a pulse frequency.

[0042] It is essential to the invention that the field of view (FOV) is divided into a row or a matrix of virtual receiver cells (VE), each characterized by a virtual divergence angle about an imaginary central axis that is many times smaller than the transmission and reception divergence in the scan direction (Rs), such that several virtual receiver cells (VE) lie simultaneously within one of the measurement fields (M). The spatial positions of the central axes of the virtual receiver cells (VE) are each characterized by an angle (αS) in the scan direction (RS) and an angle (αC) in the cross-scan direction (Rc), as exemplified in Fig. 1 shown on a virtual receiver cell VE(α C α S ).

[0043] The digitized receiver signals SD are each assigned to each of the virtual receiver cells VE located within one of the measurement fields M, and the scan speed and pulse frequency are coordinated so that the measurement fields M overlap in the scan direction Rs, so that each virtual receiver cell VE is assigned several successive digitized receiver signals SD, from which an accumulated receiver signal SA with an accumulated useful signal component SA N is formed for each of the virtual receiver cells VE, from which a distance is derived.

[0044] Virtual receiver cells VE that are only partially located in the measurement field M are considered either to be located in the measurement field M or to be located outside the measurement field M.

[0045] In practice, the storage and evaluation unit 5 of a laser scanning device used to carry out the procedure can contain several storage and evaluation areas 5.1. These are at least as many as there are virtual receiver cells VE in each measurement field M.

[0046] Each storage and evaluation area 5.1 is then assigned to one of the virtual receiver cells VE. The digitized receiver signals SD are stored in parallel in those storage and evaluation areas 5.1 that are assigned to virtual receiver cells VE which lie within the measurement field M belonging to the digitized receiver signal SD. From the digitized receiver signals VE stored by each storage and evaluation unit 5, accumulated receiver signals SA are generated, from which a distance is derived that is assigned to one of the virtual receiver cells VE.

[0047] In Fig. 3 The field of view (FOV), which is divided here into a row of virtual receiver cells (VE), is shown at four consecutive time points TM1 - TM4, at each of which the position of the measurement field M has changed significantly for the sake of clarity. In practice, the scan speed is only such that preferably more than 20 digitized receiver signals (SD) are accumulated per virtual receiver cell (VE). By scanning the laser pulses (LP) in the scan direction Rs, a different measurement field (M1-M4) within the field of view (FOV) is illuminated at each of these time points.The receiver signals S(M1) - S(M4) derived from the reflected portion LP' of each laser pulse LP are converted into digitized receiver signals SD(M1) to SD(M4) and accumulated with further digitized receiver signals SD(M1) - SD(M4) to form an accumulated receiver signal SA(VE2) - SA(VE4) assigned to each of the virtual receiver cells VE2 - VE4. The in . Fig. 3The signal waveforms shown are for illustrative purposes only. Similarly, the number of virtual receiver cells VE covered by each measurement field M and the offset of successively generated measurement fields M in the scan direction RS are merely examples. The more digitized receiver signals SD can be accumulated, the better the signal-to-noise ratio between the accumulated noise signal component SA R and the accumulated useful signal component SA N. The narrower the virtual receiver cells VE are chosen, i.e., the smaller the angular field of view (FOV) assigned to them in the scan direction RS, the more the spatial resolution in the scan direction Rs is improved. Reference symbol list

[0048] 1 Transmitter unit 1.1 Transmit channel 2 Receiver unit 2.1 Receiver channel 2.1.1 Receiver area 3 Analog-to-digital converter 4 Deflection unit 5 Storage and evaluation unit 5.1 Storage and evaluation areas 6 Control unit LP Laser pulse LP' (back) reflected and detected portion of the laser pulse LP SE Receiver signal SD Digitized receiver signal SA Accumulated receiver signal SN Useful signal portion of the receiver signal S SA N Accumulated useful signal portion SR Noise signal portion of the receiver signal S SA R Accumulated noise signal portion FOV Field of view M Measurement field V Virtual receiver cell RS Scan direction Rc Cross-scan direction T Time points of laser pulse emission LP

Claims

1. A laser scanning device for the three-dimensional measurement of a setting in a field of view (FOV) from a great distance, comprising at least one transmitter unit (1), having at least one transmission channel (1.1), for transmitting laser pulses (LP) in a sequence, at least one receiver unit (2), having at least one receiver channel (2.1), which has a receiver surface (2.1.1), for receiving portions (LP') of the laser pulses (LP) reflected back from measurement fields (M) of the setting in a sequence and for forming receiver signals (S), an analog-to-digital converter (3) for digitizing the receiver signals (S), and a deflection unit (4) for scanning the transmitter unit (1) and the receiver unit (2), in a scanning direction (RS), the receiver unit (2) being arranged in a fixed relative position to the transmitter unit (1), a memory and evaluation unit (5), as well as a control unit (6), wherein the laser pulses (LP) have a rectangular beam cross-section, the receiver surface (2.1.1) is rectangular, an emission divergence of the at least one transmission channel (1.1) and a reception divergence of the at least one receiver channel (2.1) in the scanning direction (Rs) are in each case multiple times greater than an emission divergence of the at least one transmission channel (1.1) and a reception divergence of the at least one receiver channel (2.1) in a cross-scan direction (RC), and the memory and evaluation unit (5) includes a plurality of memory and evaluation areas (5.1) for parallel storage of digitized receiver signals (SD) and formation of accumulated receiver signals (SA) from which a distance can be derived in each case.

2. The laser scanning device according to claim 1, wherein the emission and reception divergences in the scanning direction (Rs) are at least three times the emission and reception divergences in the cross-scan direction (RC).

3. The laser scanning device according to claim 2, wherein the emission divergence and the reception divergence in the scanning direction (Rs) are equal.

4. The laser scanning device according to claim 1 or 3, wherein a plurality of transmission channels (1.1) is assigned to the at least one receiver unit (2), with the reception divergence of the at least one receiver channel (2.1) in the cross-scan direction (Rc) being equal to or greater than a resulting emission divergence of the plurality of transmission channels (1.1) in the cross-scan direction (Rc).

5. The laser scanning device according to claim 4, wherein at least two receiver units (2) are present, which are arranged next to each other in the cross-scan direction (RC).

6. A method for the three-dimensional measurement of a setting in a field of view (FOV) from a great distance, wherein laser pulses (LP), which have a rectangular beam beam cross-section, are emitted in a continuous sequence one after the other via at least one transmission channel (1.1) of at least one transmitter unit (1), which transmission channel (1.1) has an emission divergence in a scanning direction (RS) and a cross-scan direction (Rc) in each case, after reflection in the setting, reflected portions (LP') of the laser pulses (LP) are received via at least one receiver unit (2) with at least one receiver channel (2.1), which has a rectangular receiver surface (2.1.1.) and has a respective reception divergence in the scanning direction (Rs) and the cross-scan direction (RC), and are stored and evaluated in a storage and evaluation unit (5) comprising a plurality of storage and evaluation areas (5.1), a respective receiver signal (S) is formed and amplified over the travel time of each of the portions (LP') of the laser pulses (LP) and a digitized receiver signal (SD) is formed therefrom, while the laser pulses (LP) are scanned in the scanning direction (Rs) and a different measurement field (M) is detected with each laser pulse (LP) in the field of view (FOV), depending on a scanning speed and a pulse frequency, the emission divergence of the at least one transmission channel (1.1) and the reception divergence of the at least one receiver channel (2.1) in the scanning direction (RS) are in each case multiple times greater than the emission divergence of the at least one transmission channel (1.1) and the reception divergence of the at least one receiver channel (2.1) in a cross-scan direction (RC), the field of view (FOV) is divided into virtual receiver cells (VE) forming a row or a matrix, each of said virtual receiver cells (VE) being characterized by a virtual divergence angle about an imaginary center axis, which angle is multiple times smaller than the emission and reception divergence in the scanning direction (RS), so that a plurality of virtual receiver cells (VE) is located simultaneously within one of the measurement fields (M), and the digitized receiver signals (SD) are respectively assigned to each of the virtual receiver cells (VE) located within one of the measurement fields (M), and the scanning speed and the pulse frequency are matched to each other such that the measurement fields (M) overlap in the scanning direction (Rs) so that each virtual receiver cell (VE) is assigned a plurality of successive digitized receiver signals (SD), from which an accumulated receiver signal (SA) with an accumulated useful signal component (SAN), from which a distance is derived, is formed for each of the virtual receiver cells (VE).