Patent ID: 12204031

DETAILED DESCRIPTION

FIG.1shows a typical laser scanner1according to the prior art, here with two rotational axes, for example mounted on a tripod2, wherein the laser scanner1comprises a slow (vertical) axis of rotation—also referred to as the support axis of rotation3—for an azimuthal rotation of the laser scanner1, or a rotation of a support4of the laser scanner about a base5of the laser scanner1, and a fast (horizontal) axis of rotation—also referred to as the beam axis of rotation6—with respect to a fast rotating beam deflection element7, mounted in the support4of the laser scanner1.

For a sensing of linear or linearly movable structures and environments, such as, for example, railway track systems, roads, tunnels systems or air fields, a base or azimuth rotational axis is often dispensed with and instead, the laser scanner is mounted on a means of locomotion, such as a land-based or airborne carrier vehicle. Such laser scanners with just one beam axis of rotation6are also called profilers.

In particular profilers, but also two-axis laser scanners for a contiguous measurement of a large area, often also have a position and orientation system, which is, for example, directly integrated in the laser scanner to automatically reference local sensing data with a global 3D coordinate system.

The laser scanner1here also has a camera8, for example, for recording RGB data, wherein the camera images of the environment can be associated with the sensing data generated by means of the rotating distance measurement beam9and associated angle encoder data for the direction of the distance measurement beam9. The camera can in particular be individually movable, in order, for example, to record different fields of view and/or to orient the camera images and the scanning data with respect to a common reference surface or a common coordinate system.

FIG.2shows typical principal components of a common laser scanner1′, here for example with two axes of rotation, wherein the laser scanner1′ is based on a design using a base5and a support4, wherein the support5is rotatably mounted13on the base5about a support axis of rotation3, in particular a slow rotation axis. Often, the rotation of the support4about the support axis of rotation3is also called azimuthal rotation, regardless of whether the laser scanner1′, or the support axis of rotation3, is exactly vertically aligned.

The core component of the laser scanner1′ is formed by an optical distance measuring device10arranged in the support4for recording distance measurement data, with a transmitter unit for emitting a distance measurement radiation9, for example pulsed laser radiation, and a receiver unit with a receiver optics, in particular a lens11, and a light-sensitive sensor for receiving returning parts of the distance measurement radiation9, wherein an echo is received from a back-scattering surface point of the environment and, for example, based on the propagation time, the shape and/or the phase of the pulse, a distance to the surface point is derived.

A scanning of the environment is carried out by a variation of the orientation of the emission direction of the distance measurement beam9by means of a rotating beam steering unit7for the distance measurement radiation, which is mounted13in the support4such that it can rotate about a beam axis of rotation6, in particular a fast rotation axis, substantially orthogonal to the support axis of rotation3. Using angle encoders12for detecting angle data, for example fixed angle angular positions and/or relative angular changes with respect to a rotation of the support4about the support axis of rotation3and angle data with respect to a rotation of the beam steering unit7about the beam axis of rotation6, the emission direction of the distance measurement beam9is detected and associated with correspondingly acquired distance measurement data. By using a plurality of such measurement points essentially the entire environment can therefore be spatially measured, wherein, for example, a desired point-to-point resolution is set by adjusting the pulse rate of the distance measurement beam9and/or by adjusting the rotational speed of the beam steering unit7. A subsequent display of the data can be based, for example, on common data processing steps and/or display methods, for example, for displaying the acquired data in the form of a 3D point cloud.

The beam steering unit7has a mirrored surface14for a deflection of the distance measurement radiation9, in particular, a mirrored surface which is tilted with respect to the beam axis of rotation6, such as a plane or parabolic mirrored surface, which on account of the fast rotation of the beam steering unit7and the resulting large centrifugal forces is typically designed to be integral with the rotating body of the beam steering unit7, or less commonly by attaching a separate optical component such as a separate mirror.

A defined scanning motion of the distance measurement beam9with a minimal tolerance for the guidance of the distance measurement beam9with a high angular accuracy typically requires a mounting13of the support4and the beam steering unit7with the minimum possible amount of play, that is to say, with a minimum tolerance for a tilting of the support4with respect to the support axis of rotation3, respectively for a tilting of the beam steering unit7with respect to the beam axis of rotation6. In addition, the mirrored surface14typically has a high surface accuracy to ensure, for example, an optimal beam collimation and intensity sensitivity.

To ensure a zero-play mounting13with a minimum tilting of the beam steering unit7and the support4, the mounting13is typically implemented in each case along an effective stabilization region15with a maximum axial extent. Due to the weight of the support4, in the prior art the mounting13of support4about the support axis of rotation3is typically based on designing a vertical axis16to be as long (or high) as possible relative to the total volume of the support4, which in combination with the mounting13of the support4defines a stabilization region15with a maximum axial extent.

FIG.3shows an inventive system17for optical measurement and for imaging an environment, here for example in the area of interior room measurement, wherein a laser scanner1″, for example to minimize possible shadowing and/or dead angles, can be placed anywhere in the room, here on a table18in the room. The system17comprises the laser scanner1″ for detecting measurement data, i.e. distance measurement data and angle data, provided by a distance measuring unit and angle encoders for determining the emission direction of the distance measurement beam. The measurement data also comprise surface sensor data, provided by a sensor arranged on the support4and co-rotating with the support4, for example a camera8, in particular an RGB camera or an infrared camera.

The measurement data is recorded by the laser scanner1″ as part of a measurement process, defined by a scanning sensing using the distance measuring device with a defined continuous rotation of the support4about the support axis of rotation3, a defined continuous rotation of the beam steering unit7about the beam axis of rotation6and a continuous emission of the distance measurement radiation and a continuous reception of returning parts of the distance measurement radiation, as well as a repeated reading of the surface sensor8with respect to different azimuthal viewing directions of the sensor8.

The inventive system17also comprises a processing unit, arranged on a separate computing device19from the laser scanner1″, in particular a computer or tablet, for processing parts of the measurement data with respect to an association of the surface sensor data with the distance measurement data and the angle data, wherein the inventive system17is designed in such a way that already during the data acquisition of the measurement data as part of the measurement process, at least an initial processing of portions of the measurement data is carried out in relation to an association of the surface sensor data with the distance measurement data and the angle data, in particular with the minimum possible delay, in other words substantially temporally in parallel with the data recording, and is continuously displayed for a user20, for example as a continuously growing colored 3D point cloud, for example by means of a display coupled to or integrated with the computing device19. In particular, the laser scanner1″ and the computing device19are configured in such a way that the transfer of the measurement data from the laser scanner1″ to the computing device19, which is carried out substantially parallel to the measurement process by means of a data streaming which is started simultaneously with respect to the measurement process, for example using a WLAN or Bluetooth connection. In particular, the laser scanner1″ and the computing device19are configured in such a way that monitoring and control signals are transferred from the computing device19to the laser scanner1″ and therefore the laser scanner1″ is monitored by the external processing unit19and, for example, a defined measurement process of the laser scanner1″ can be started, stopped, interrupted and/or adjusted from the computing device19.

In laser scanners the scanning by means of the distance measuring device is central and in the state of the art, camera data are therefore typically only recorded after a complete room scan (360 degrees of azimuth rotation) by the distance measuring device, for example, as supplementary information and often only for selected regions of the environment, for example to provide an improved display of a region of interest for a user.

Distance measurement modules used in laser scanners for spatial measurement typically have no color sensitivity, which means the 3D point cloud generated can be displayed in grayscale levels without the need to use additional data. As a result of the lack of color effect and the lack of depth effect supported by the presence of colors, many details remain hidden to a human observer. Using RGB data from a color camera, for example, a “colored” 3D point cloud can be generated, which, for example, makes its display to the human eye considerably easier. Such a referencing of different data and data sets is nowadays carried out, for example, using common data processing algorithms in an increasingly standardized manner.

In the prior art laser scanners are often designed in such a way that the field of view of a camera, for example an RGB camera, essentially records a scanning plane of the distance measurement radiation defined by a virtual 360-degree rotation of the beam steering unit about the beam axis of rotation, for example by means of parallel alignment of the optical axis of the camera with respect to the scanning plane or using appropriate coaxial coupling of the beam path of the camera into the beam path of the distance measuring device. This has the advantage, for example, that at least for the viewing range of the camera, directly corresponding camera and distance measurement data can be recorded. This allows, for example, a simultaneous recording of the camera data with the distance measurement data corresponding to the camera field of view, which can facilitate the referencing of the camera data with the distance measurement data. Thus, for example, any interference effects in the environment that occur during the measurement process can then be identified both in the camera data and in the distance measurement data.

Such an integration and alignment of the camera field of view, however, is often associated with a certain level of integration effort and in particular in the case of a highly compact construction of the laser scanner is only possible to a limited extent.

One aspect of the invention relates to an integration of the surface sensor8, and in particular an RGB camera, in the laser Scanner1″, so that the viewing direction of the surface sensor differs significantly from the scanning plane, wherein, for example, a virtual backward extension of the optical axis of the surface sensor intersects with the scanning plane under a cutting angle of at least degrees, in particular under an angle of 90 degrees, in particular wherein the scanning plane is not captured by the field of view of the surface sensor.

This arrangement of the camera8in the laser scanner allows, for example, a compact design of the laser scanner1″ but has the disadvantage that a simultaneous recording of the camera data with distance measurement data corresponding to the camera field of view may not be possible. The inventive arrangement, by contrast, enables a parallel reading of the surface sensor8, for example the RGB camera, with the scanning with the distance measuring device, which means, for example, a full-dome measurement can be carried out by the scanning distance measuring device and the camera8in one action, is thus accelerated, wherein, for example, the distance measurement data, the angle data and the camera data then can be computationally referenced with respect to one another accordingly.

A complete room scan (360 degrees azimuthal rotation) by means of the distance measuring device takes a relatively long time compared with a 360-degree recording of the camera data. In order nevertheless to ensure a display of the environment started directly with the measurement process, in particular as a colored 3D point cloud, one aspect of the invention relates to the fact that color camera data of the environment are recorded first, and the scanning by means of the distance measuring device is only carried out afterwards. An at least initial processing is thus carried out already based on the relatively quickly recorded camera data, which are displayed to a user20, for example as a 2D panoramic view; and an association of the distance measurement data and the angle data with the recorded camera data can be carried out virtually in real-time with the acquisition of the distance measurement data, allowing a steadily growing colored 3D point cloud to be displayed to the user20substantially in real-time. This allows, for example, a rapid assessment of the recorded data by the user20and, if necessary, an immediate adjustment or change to the settings of the laser scanner1″, for example, a defined measuring mode with a different point density.

Since the laser scanner1″ in the context of the system according to the invention can be controlled by means of an external computer unit19, in particular a tablet wirelessly connected to the laser scanner1″, which, in particular, also performs the computationally intensive association of the distance measurement data with the camera data and the angle data as well as the display of the measurement data, the laser scanner1″ may designed to be very compact.

In particular, the laser scanner1″ itself requires only a minimal number of control elements integrated in the laser scanner1″. For example, a laser scanner1″ according to the invention has only a single integrated control element21, which has an active and an inactive state, and can be switched by way of an external action in order to occupy the active or inactive state. The two states, respectively, a change of the state of the control element21from the inactive to the active state, a change of the state of the control element21from the active to the inactive state, a switching of the control element21by means of a persistent external action during a defined time interval (e.g., continued pressing of a control knob), a coded sequence of state changes of the control element21between the active and inactive state and/or a coded sequence of temporally continuing external actions on the control element21over defined periods of time, are assigned, for example, individual measurement programs and/or actions of the laser scanner1″, for example, activation/deactivation of the laser scanner1″, starting a defined measurement process, or interruption/aborting/restarting a measurement process.

For example, the laser scanner1″ can also be designed with a position and orientation system, for example using an inertial system, tilt sensors or a receiver for a global satellite navigation system, which is transferred into an active state by the control element21, whereupon the position and/or orientation of the laser scanner1″ are determined continuously and stored in the measurement data continuously. In this mode, the laser scanner1″ can then be moved within the room and, for example, local scanning data can be automatically referenced with a global 3D coordinate system.

The laser scanner1″ may also be designed in such a way that defined measurement programs and actions are stored on the laser scanner1″ and/or that new measurement programs and actions, for example, via a corresponding input functionality of the external computing device19, can be defined and assigned to the states/state changes of the control element21.

A further aspect of the invention relates to a status indicator22for indicating a device status, for example, indicating a status of a current measurement process, wherein the status indicator22is arranged on the support4, in other words co-rotates about the support axis of rotation3during the rotation of the support4. The status indicator22is then designed in such a way that it appears substantially identical around its circumference with respect to the support axis of rotation3in all azimuthal directions. For example, a user20of the laser scanner1″ regardless of their direction of view of the laser scanner1″ (seen from the scanner regardless of an azimuth angular position of the user20) can be provided with the same information, in particular, even when a measurement process is running and the scanner1″ is rotating.

For example, the status indicator22is designed by means of a fiber-optic ring with two opposite located coupling inputs for light, wherein with increasing distance from the coupling position along the fiber-optic ring the ratio of radiation emission (radial light extraction) to transmission of light increases, wherein the device status is revealed to a user20by means of a visual coding, for example, a defined color coding of the status indicator22and/or by means of a defined flash coding of the status indicator22.

FIG.4shows a further embodiment of an inventive system17′ for optical measurement and for imaging an environment, for example in the area of interior room measurement, wherein the laser scanner1′ is mounted on a tripod. As before (seeFIG.3), the laser scanner1′″ is wirelessly controlled via an external computing device19′, here, for example, by means of a tablet, wherein data as well as monitoring and control signals are transferred in both directions (laser scanner1′″ to tablet19′ and vice versa).

In this embodiment the tablet19′ is also equipped with an inertial measurement system and/or tilt sensors, so that the laser scanner1′″ can be controlled on the basis of a location (position, orientation) of the computing device19′, for example substantially synchronously with the change of position of the computing device19′.

The tablet19′ also has a display23on which, for example, a current live stream from the camera8is displayed, so that for different azimuthal angles of the support4of the laser scanner1′″ a user can observer the environment from the point of view of the position and orientation of the laser scanner1′″. This means, for example, it can be checked prior to the measurement whether the current position of the laser scanner1′″ in the room needs to be adjusted in order to avoid dead angles.

The user20can also, for example via the tablet19′, for example using a touch screen functionality, define different areas of interest24in the environment for various azimuth positions of the laser scanner1′″, and allocate to these areas of interest24settings defined prior to the measurement process for the recording of measurement data (e.g. camera resolution, distance measurement accuracy, scanning resolution) and/or defined settings for the display of parts of the processed measurement data (e.g. color setting, highlighting).

In addition, the tablet19′ (or the laser scanner1′″) can, for example, access data for an augmented reality, so that for example further details of the surrounding area, hidden to the human eye, are displayed to the user20from the point of view of the scanner1′″, such as electricity cables or water pipes concealed in the walls, mounting points, items of furniture, etc.

FIG.5shows a laser scanner according to the invention with a plurality of cameras8integrated on the support, in particular wherein the cameras8are arranged in such a way that their optical axes25all lie in the same azimuthal plane—here, for example, perpendicular to the scanning plane of the distance measurement radiation defined by a virtual 360-degree rotation of the beam steering unit7about the beam axis of rotation6—and the cameras8therefore have the same azimuthal viewing direction.

The laser scanner has a central reference point26as the origin for the distance and angle measurement of the distance measuring device, for example, the point of intersection of the optical axis of the lens with the beam steering unit7. Alternatively, the distance measurement data can also be corrected by computation with respect to a central reference point defined elsewhere.

The cameras8are now arranged in accordance with the invention on the support4in such a way that a virtual backward extension of each of their optical axes25passes through the central reference point26, the cameras8are thus arranged in a parallax-free manner with respect to the central reference point26. This facilitates, for example, the referencing of the camera data with distance and angle data for displaying the measurement data as a 3D point cloud.

In addition, the parallax-free arrangement ensures that the optical axis25of the camera8is always substantially coaxial to an orientation (azimuth and elevation angle) of the distance measurement beam, namely, in the sense that during the measurement process (as part of the azimuthal rotation of the support4) the camera8is sooner or later rotated into a past or future viewing direction of the distance measurement radiation, depending on whether the camera8is looking “ahead” or “backwards” with respect to the azimuth direction of rotation and the azimuthally rotating scanning plane of the distance measurement radiation. Due to the parallax-free arrangement the camera8thus “sees” the same view as the distance measurement radiation and is subject to substantially the same (generated by the environment) shadowing and field of view blockages as the distance measuring device, and so essentially captures the same sampling points as the distance measurement radiation. As a result, for example, corners and edges are detected substantially identically by the camera8and the distance measuring device, which, in turn, improves their referencing and/or modeling based on the camera and scanning data.

In the specific case the cameras8can be designed and positioned in such a way that they cover different elevational fields of view, for example, three cameras, wherein their visual field cones27intersect above a minimum radius28around the central reference point26.

In particular if the camera with the steepest elevational alignment of the optical axis is designed such that its visual field cone27intersects the support axis of rotation3, for example, at a distance of the above minimum radius28from the central reference point26, the arrangement of the cameras from the minimum radius28and greater enables a full-dome measurement (measurement of the hemisphere defined by the support axis of rotation3and the beam axis of rotation6across the plane which is defined perpendicular to the support axis of rotation3and perpendicular to the beam axis of rotation6).

Also shown in the figure is a camera29with parallax with respect to the central reference point26, for example, an infrared camera for recording heat data.

FIG.6shows another embodiment of a laser scanner according to the invention with parallax-free cameras8arranged in the support4with respect to a central reference point26of the laser scanner as the origin for the distance and angle measurement of the distance measuring device (seeFIG.5). The support4here additionally has a plurality of lamps30, each illuminating the field of view of individual cameras, wherein the lamps30are designed and arranged in such a way that they are used for a selectively controllable illumination, substantially targeted at the field of view of a specific camera.

The lamps30are typically designed in such a way that the divergence of their light cone31is smaller than the field of view angle of the cameras, wherein each camera is assigned, for example, two or four lamps30arranged immediately at its side. The lamps30are implemented, for example, as LEDs to emit white light, or in each case as a dual LED, i.e. as LED couplets with two LEDs with distinct emitted spectral ranges, in order to achieve color representations of the camera images as realistic as possible to the human eye.

In order to achieve an optimal (individual) illumination of the individual cameras, for example, a 360-degree (azimuth rotation) preliminary scanning can be first carried out using the cameras, for example with lamps switched off or wherein the lamps are adjusted to a uniform intensity in order to derive optimized exposure times and illumination intensities for different azimuth positions for each of the individual cameras, which are then taken into account in an effective measurement scanning process.

FIG.7shows a further embodiment of a laser scanner according to the invention with a biaxial arrangement with respect to the outgoing distance measurement beam9and the optical axis of the lens11or the receiver of the distance measuring device10, wherein the outgoing distance measurement beam9and the returning parts32of the distance measurement beam are deflected into the surroundings via the same optical rotating element7, or into the lens11respectively. This enables, for example, a compact, simple and robust design of the distance measuring device10. In the example shown the outgoing distance measurement radiation9is arranged in such a way that it exits directly next to the lens11of the receiving unit of the distance measuring device10.

In contrast to the frequently used coaxial arrangement between distance measurement beam and lens no central shadowing occurs, caused for example by a deflection mirror arranged in the center of the lens for the distance measurement radiation. However, in particular for parts of the distance measurement radiation returning from a near field, a parallax effect does occur, caused by the lateral offset of the beam outlet with respect to the optical axis of the lens. As a result, a vertical wall for example is therefore scanned by the distance measurement beam with sinusoidal scanning sections instead of substantially vertical scanning sections.

However, on the one hand this effect can be compensated with a suitable corrective optics in the lens11, for example a cylindrical lens, and/or on the other hand, compensated computationally using a compensation algorithm as part of a referencing of the measurement data with respect to a common coordinate system, based on the angular position of the beam steering unit7and the distance detected stored at the time of recording the distance measurement radiation.

FIG.8shows a further embodiment of a laser scanner according to the invention with a biaxial arrangement with respect to the outgoing distance measurement beam9and the optical axis of the lens11or the receiver of the distance measuring device10, wherein here the distance measurement radiation9exits through an outlet area33arranged in the lens11, for example through a cutout portion or a window in the lens11. This will reduce, on the one hand, the parallax effect caused by the lateral offset between the outgoing distance measurement beam9and the optical axis of the receiver unit and, on the other hand, the effective light collection area is better exploited by the beam steering unit7and the lens11.

FIG.9shows a front view of a lens unit11for an inventive biaxial arrangement with respect to the outgoing distance measurement beam9and the optical axis of the lens11of the distance measuring device, wherein the distance measurement radiation9exits through an outlet region33arranged in the lens11(seeFIG.8), here, for example arranged directly radially at the edge of the lens11. In addition, a corrective optics34for compensating the parallax effect for parts of the distance measurement radiation returning from a near-range of the distance measurement radiation9.

The outlet region33is typically dimensioned and oriented such that the geometry of the outlet region33substantially only just covers the minimum35and the maximum 36 extension of the beam waist of the outgoing distance measurement radiation9—for example, depending on the geometry, arrangement and orientation of a diode generating the distance measurement radiation9, in particular wherein the geometry and orientation of the outlet region are adjusted with regard to the geometry and orientation of the beam cross section, for example in the form of an oval window.

FIG.10shows a schematic drawing of a receiver circuit37according to the invention of a laser distance measuring module according to the invention, suitable for deriving a distance to a target object based on the signal propagation-time method, which here is coupled to a pulser38.

For example, the receiver circuit37comprises a receiver element39, such as a receiver diode, a transimpedance amplifier40and an amplifier unit41for adjusting a signal amplitude, in particular by means of amplification or attenuation of an input signal, for example by means of a Variable Gain Amplifier (VGA). The receiver circuit37also comprises a comparator stage42for deriving a signal amplitude of a detected received signal, here arranged after the amplifier unit41, wherein the comparator stage42can also alternatively be arranged in front of the amplifier unit41. The circuit37also has a first43A and a second43B analog-to-digital conversion stage, as well as a control unit44, for example a microprocessor or an FPGA (Field Programmable Gate Array).

The comparator stage42, the amplifier unit41and the first43A and second43B analog-to-digital conversion stage are arranged in such a way that a continuous sequence of distance measurements comprises a first distance measurement by means of the first analog-to-digital conversion stage43A, for example based on a first signal packet of successive received signals, and a second distance measurement by means of the second analog-to-digital conversion stage43B, for example, based on a second packet of successively received signals. This process involved an alternating use of the first43A and second43B analog-to-digital conversion stage, wherein a first received signal is used as a test signal and a second signal as a measurement signal. The test signal is fed to the comparator stage42, by means of which a signal amplitude of the test signal is derived, wherein an adjustment of the amplifier unit41is carried out for at least parts of the received signals containing the measurement signal based on the derived signal amplitude of the test signal, so that at least the measurement signal is present as an input signal in the control range of the analog-to-digital conversion stages43A,B.

In the example shown, the receiver circuit37also has an activation unit45, by means of which, for example, a setting is applied according to which the test signal is either additionally taken into account or discarded for the derivation of the distance to the target object. Specifically, the activation unit45can be configured in such a way that, for example, with appropriate storage of the detected received signals, a range of values for a usable signal amplitude of the test signal is defined and the signal amplitude of the sample signal derived by the comparator stage is compared with the range of values; wherein the activation unit45is controlled based on the comparison of the signal amplitude with the range of values, so that if the signal amplitude of the test signal is within the range of values, the test signal is taken into account for the derivation of the distance to the target object, and if the signal amplitude of the test signal is outside the value range, the test signal is discarded for the derivation of the distance to the target object.

FIG.11shows an example drawing of pulse packets46of transmitted signals47and received signals48used as test and measurement signals within a receiver circuit37according to the invention (seeFIG.10) with two analog-to-digital conversion stages43A,B (seeFIG.10), wherein each analog-to-digital conversion stage has a sampling phase49for receiving an incoming signal and an output phase50for an evaluation of the incoming signal, wherein as part of the alternating use of the first51A and second51B analog-to-digital conversion stage the output phase50of the first analog-to-digital conversion stage takes place simultaneously or almost simultaneously with the sampling phase49of the second analog-to-digital conversion stage, and the output phase50of the second analog-to-digital conversion stage takes place simultaneously or almost simultaneously with the sampling phase49of the first analog-to-digital conversion stage.

This means that, for example, as part of a single distance measurement by the second analog-to-digital conversion stage, a received signal52of a received packet of an immediately preceding distance measurement can be used by the first analog-to-digital conversion stage as the current test signal53for the distance measurement of the second analog-to-digital conversion stage (and vice versa). As a result, a suitable input signal in the control range of the analog-to-digital conversion stages can be set after only a few iterations, wherein the alternating use of the analog-to-digital conversion stages allows high distance measurement rates to be achieved.

FIG.12shows a laser scanner according to the invention with a “passive” base5′ with regard to scanning and data acquisition, here with a short axial vertical axis54compared to the radial extent and with the motor55for the rotation of the support4integrated in the support4.

The base5′ is passive to the extent that all active electronics required for the motorization of the rotation around the support axis of rotation3—for example, for a direct drive, piezoelectric drive or friction-wheel drive—is arranged exclusively in the support4and co-rotates with the support4about the support axis of rotation3, wherein, for example, an active drive element55for the rotation of the support4about the support axis of rotation3, here a rotary motor with a drive shaft56coupled to the motor, and a power supply unit for the active drive element55are each arranged entirely in the support4.

In the example shown, the drive for the rotation of the support4about the support axis of rotation3is designed as a friction wheel drive, wherein a drive shaft56of a rotary motor55extends to the base5′ parallel to the support axis of rotation3with an offset relative to the support axis of rotation3, wherein on the output section of the drive shaft56, for example, an idle wheel57implemented with a rubber ring is arranged, which rolls off along a circular symmetric bearing surface58of the base5′.

Due to the compact design, in particular the short axial vertical axis54, here the radial extension59of the vertical axis is chosen as large as possible and the drive shaft56, respectively the idle wheel57, runs on a bearing surface58defined by the inside of a base ring. Alternatively, the drive can also be designed in such a way that the drive shaft56is arranged outside of a base ring, so that it rolls off on an outer side of the base ring of the base.

In a specific embodiment, the laser scanner has a total of only one power supply unit, namely the power supply unit for the active drive element55, which is arranged in the support4, wherein the base5′ is permanently and irreversibly electrically decoupled from the support4and no electrical power transmission takes place between the support4and the base5′.

TheFIGS.13a,bshow two embodiments of a mounting according to the invention of an axially compact vertical axis, in other words of an axial vertical axis which is short compared to the radial extension59. In each of the examples shown the laser scanner is placed, for example, on a table18.

Due to the axially compact (short) design the vertical axis along the support axis of rotation3has exclusively one short overall effective stabilization region15, by means of which a stabilization of the support4is obtained with respect to a tilting of the support4relative to the base5, or the support axis of rotation3. In order to prevent a tilting of the support4relative to the base5therefore, according to the invention the substantially radially symmetric extension59of the vertical axis, perpendicular to the support axis of rotation3, is greater than its axial extension.

In accordance with one aspect of the invention, the support4is also mounted on the stabilization region15of the base5with a single bearing rim such that it can rotate about the support axis of rotation, the stabilization being obtained exclusively by the single bearing rim.

The bearing rim can be designed as a single-row four-point roller bearing60with a rolling body66(FIG.13a) or as a single-row sliding bearing61with an outer62A and inner ring62B (FIG.13b), wherein the outer ring with the inner ring forms two contact bearings63A,B axially spaced apart with respect to the support axis of rotation3. For example, one contact bearing63A can be arranged elastically67, to ensure sufficient play for the rotation around the support axis of rotation3.

The stabilization can then be generated, for example, by means of a spring tension acting radially on the bearing rim with respect to the support axis of rotation3.

A further aspect of the invention is aimed at ensuring that bearing lubricants cannot escape from the bearing into other parts of the laser scanner. This is important, for example, in a drive unit according to the invention designed as a rotary motor55with a drive shaft56offset with respect to the support axis of rotation3and with an idle wheel57implemented with a rubber ring (see description forFIG.12) for the rotation of the support4about the support axis of rotation3, because due to lubricants, for example, the adhesion of the idle wheel57on the base ring58is reduced (seeFIG.12).

On the one hand, this can be achieved by, for example, the mounting being implemented as a four-point roller bearing in the form of a dry-running ring bearing with ceramic roller elements.

On the other hand, for example, along a boundary region substantially parallel to a contact bearing a lubricant-repellent emulsion can be applied, so that any dispersion of a lubricant due to the surface tension of the lubricant-repellent emulsion is substantially limited by the boundary region.

FIGS.14a,bshow a mounting13according to the invention and a compact drive unit according to the invention of the beam steering unit7about the fast axis by means of a bell-shaped element68.

FIG.14ashows the beam steering unit7, which is connected to a shaft69mounted13in the support4along the beam axis of rotation, in particular wherein the shaft69penetrates into the beam steering unit7with a defined penetration depth or is designed integrally with the beam steering unit7. The shaft69is also connected to a bell-shaped element68, wherein the bell-shaped element68defines a bell-shaped body70and a bell-shaped back71(seeFIG.14b). In the bell-shaped body70a passive magnetic element72is arranged, which is connected to the bell-shaped element68, and an active drive element73is arranged on the support4to generate an electromagnetic interaction with the passive magnetic element72, for example an electrical coil element, wherein the active drive element73protrudes at least partly into the bell-shaped body70, so that by a radial interaction between the active drive element73and the passive magnetic element72the beam steering unit7can be set into a defined rotational movement about the beam axis of rotation.

For a maximally compact design, for example the whole of the active drive element73and at least part of the mounting bush74for the mounting13of the shaft69in the support4are arranged in the bell-shaped body70, in particular wherein the bearing is implemented as a roller bearing and rolling bodies66of the rolling bearing protrude at least partially into the bell-shaped body70. In addition, a part of the mounting bush74can protrude into the beam steering unit7, in particular wherein parts of the rolling bodies66of the roller bearing at least partially protrude into the beam steering unit7.

A further aspect of the invention relates, for example, to the fact that the shaft69comprises only one single effective stabilization region15′ axially along the beam axis of rotation, which is used to stabilize the support against a tilting of the shaft69relative to the support4, or to the beam axis of rotation, wherein the beam steering unit7, the bell-shaped element68and the shaft69are designed and arranged with respect to each other (for example, including by means of balancing elements) in such a way that their common center of gravity75axially along the beam axis of rotation is located in the stabilization region15′, in particular wherein the stabilization is achieved exclusively by a bearing which substantially axially-symmetrically surrounds the center of gravity75.

FIG.15shows a further embodiment of the inventive bell element68′, wherein here an encoder disc76is arranged on the bell-shaped back, in particular integrated or forming a single piece with the bell-shaped element68′, for recording angle encoder data with respect to the rotation of the beam steering unit7about the beam axis of rotation by means of an angle encoder12′ arranged in the support4.

TheFIGS.16a,bshow an inventive coupling of a beam steering unit7to the shaft69along the beam axis of rotation by means of compressible stabilization elements77in the coupled and uncoupled state.

FIG.16ashows the uncoupled beam steering unit7, which comprises a mirrored surface14for deflecting the distance measurement radiation, in particular a tilted mirrored surface with respect to the beam axis of rotation. Typically, on account of the high centrifugal forces induced by the rapid rotation of the beam steering unit7, the mirrored surface14is implemented integrally with the beam steering unit.

The beam steering unit7has an enclosure region78for a penetration of the shaft69during a coupling of the beam steering unit7to the shaft69, so that in the coupled state between the shaft69and the enclosure region78of the beam steering unit7a gap79with a defined width is present (seeFIG.16b, which shows the beam steering unit7in the state where it is coupled to the shaft69). The enclosure region78also has a stabilization element77that can be compressed in the gap79for tolerance compensation and for the stable connection of the beam steering unit7to the shaft69, wherein in the uncoupled state the stabilization element77has a thickness that is greater than the width of the gap79and in the coupled state surrounds the shaft69, for example in a continuous annular manner.

In accordance with one aspect of the invention, the beam steering unit7, the shaft69and the stabilization element77are designed and interact in such a way that during the coupling of the beam steering unit7with the shaft69the stabilization element77arranged between the enclosure region78and the shaft69is compressed and in the coupled state is present in the gap79in such a deformed state, in particular wherein at least a portion of the stabilization element77is plastically deformed, that only small residual elastic forces act on the beam steering unit7and the shaft69radially to the beam axis of rotation; and the beam steering unit7and the shaft69are stabilized in relation to each other in the axial direction with respect to the beam axis of rotation, the beam steering unit7is stabilized against a tilting relative to the shaft69over a stabilization region15″ defined by the length of the penetration region, and the residual elastic forces do not act on the mirrored surface14apart from a defined tolerance range, to the extent that the residual elastic forces on the mirrored surface14are so small that a high surface accuracy of the mirrored surface14is maintained.

The stabilization element77can be implemented, for example, in an annular shape and from a material with homogeneous plastic properties, for example, a homogeneous plastic flow range, wherein the stabilization element77is integrated into the beam steering unit7, for example injection molded on the beam steering unit7.

In addition, the beam steering unit7and the shaft69are typically glued80to each other as part of their coupling, wherein for excess adhesive or for applying the adhesive, defined openings81or access ports are provided in the beam steering unit7.

TheFIGS.17a,bshow an arrangement according to the invention of a laser scanner using a skeletal, three-part support4′ and a base5, wherein the support4′ here is formed by means of a skeletal structure consisting of three separately detachable support structures82,83A,B, which are coupled to each other, for example, by means of a connection based on normal pins.FIG.17ashows the individual elements of the support4′ and the base5, whereasFIG.17bshows the assembled elements.

A central support structure82is mounted on the base5coaxially with the support axis of rotation3and two further separate support structures83A,B are connected to the central support structure82, but not to the base5, wherein the beam steering unit7is arranged exclusively in one of the other support structures83A. In particular, the central support structure82defines a vertical axis84with an effective stabilization region15′″, by means of which a stabilization of the further support structures83A,B is obtained against tilting of the support structures83A,B relative to the vertical axis84and thus to the support axis of rotation3. The vertical axis84further comprises two holders85A,B for receiving and coupling the further, in particular, plate-like support structures83A,B.

Such a design of the support4′ allows, for example, a modular deployment of the laser scanner, in particular with regard to servicing, in other words, maintenance or replacement of individual modular parts, or in terms of upgrade capabilities of the laser scanner. For example, the support structures can be designed in such a way that one support structure83A receives the beam steering unit and another support structure83B receives the distance measuring device10, so that these two core elements of the laser scanner are each interchangeable in a modular fashion.

In order to ensure sufficient axial positional stability despite the skeletal structure, in particular in terms of tilting of the support structure83A carrying the beam steering unit7with respect to the support axis of rotation3, the support structures82,83A,B, and in particular the two further support structures83A,B, are each formed, for example, by means of an all-aluminum housing86A,B (indicated by the dashed line inFIG.17b), which additionally rests, for example, directly on a horizontal surface87of the central support structure82.

FIG.18shows a typical reference element88in the support4″ for the adjustment and/or calibration of the distance measuring device, for example, for an intensity, contrast and/or distance reference. Typically, the reflectivity and/or color of the reference element88can vary with the beam direction of rotation defined by the rotating beam steering unit7, for example, to enable a dynamic distance and intensity calibration. In the example shown the reflectivity of the reference element88varies in three fixed levels. Alternatively, a reference element unit with a reflectivity gradient and/or with a color gradient can also be used.

The distance measuring unit and the scanning can be based both on a single distance measurement beam and on a plurality of distance measurement beams emitted at the same time.

FIG.19aandFIG.19bshow a laser scanner according to the invention, wherein the distance measuring unit and the scanning are based on a multi-beam scanning pattern89,89′, for example of a plurality of distance measurement beams emitted at the same time. This has the advantage, for example, that with a lower rotation speed of the beam steering unit about the fast axis a higher point rate and/or a higher point density is achieved. For example, instead of a single distance measurement beam a beam fan9′ can be used consisting, for example, of four adjacently arranged single beams, each with a small divergence.

For example, the individual beams are generated by an electronic distance measuring module arranged in the support4with a plurality of transmission beams and aimed at the beam steering unit7, for example with a divergence of less than 15 degrees between the individual beams. For example, the beams are aligned in such a way that during the scanning process, in a scanning region near to the horizontal scanning plane (the plane perpendicular to the beam axis of rotation3and support axis of rotation6), substantially similarly oriented scanning patterns89,89′ are generated in each case by the individual beams, for example, a scanning line, in particular, a smooth horizontal scanning line89(FIG.19a) or a substantially—formed inFIG.19bby six scanning points—horizontal scanning line89′ (FIG.19b) with alternating vertically offset scanning points. Alternatively, the individual beams can be emitted in such a way that they form complex two-dimensional scanning patterns.

At least in a defined scanning region, for example near the horizontal plane, the beam fans89,89′ can be emitted in such a way that, during the rotation of the support4and the beam steering unit7, for example complementary scanning lines or overlapping scanning lines are generated. The point density rises toward the zenith, where, for example, the individual scanning points, respectively scanning lines, increasingly overlap. The rotation of the scanning pattern (90 degrees of rotation with respect to alignment to the horizon) and over-determination of the 3D point cloud in the zenith can be allowed for by means of appropriate data reduction and/or data selection, for example. In addition, the rotation speeds of the support4about the support axis of rotation3and of the beam steering unit7about the beam axis of rotation6can be synchronized, for example to optimize the scanning with respect to scan traces.

FIG.20a,bshows a receiving element90for receiving the base5″ of a laser scanner, for example, for attaching the laser scanner to a tripod, wherein the receiving element90can be detached from the base5″ by means of a latching device.FIG.20ashows the receiving element90in the state uncoupled to the base5″ andFIG.20bshows the receiving element90in the state coupled to the base5″.

The latching device comprises a cutout portion91on the base5″, into which a ring92is recessed, which ring92in its interior has a circumferentially continuous cavity, and on the receiving element90comprises a spigot93, wherein the spigot93comprises at least three latching bodies94, which in a basic position of a release device comprising a radial pin95A, an axial pin95B and a spring96push radially outwards, for example by means of a tensioning spring, in order to block the detachability of the receiving element90from the base5″ by the fact that the latching bodies94engage in the cavity of the ring92. In order to release the receiving element90from the base5″, activating the release device enables the latching bodes94to radially escape into the spigot93.

It goes without saying that these figures illustrated only show possible exemplary embodiments in schematic form. The different approaches can also be combined with methods from the prior art.