DE102016102610A1 - laser scanner - Google Patents

Abstract

Disclosed is a multispectral laser scanner for the spatial and radiometric acquisition of data.

Description

The invention relates to a laser scanner according to the preamble of patent claim 1, in particular for acquiring spatial data.

For terrestrial acquisition of 3D geoinformation, e.g. For the creation of 3D city models, so-called terrestrial laser scanning (TLS) has been used for about 10 years, which, in contrast to photometric systems, works actively and therefore does not depend on the light conditions or the present object contrast. Laser scanners comprehensively record so-called point clouds which contain 3D coordinates of scanned object surfaces as well as their radiometric properties in the wavelength of the laser source used. These radiometric information (intensities) thus describe the respective local reflection behavior of an object surface.

In addition to the purely geometric detection of the object space, it is often necessary to obtain additional information about the detected objects, such as their structural or energetic properties. In this context, particularly material properties of interest, for their distinction, so-called spectral signatures are suitable, which have different reflectance depending on the wavelength used and can be detected for example by multi-spectral photographs. As a result, in addition to the assessment of geometric changes in the structural condition of buildings, old buildings or bridges, it is also possible to make statements about possibly present traces of vegetation (different moisture and chlorophyll contents) and to generally differentiate materials.

A fundamental problem in the separate collection of geometric (TLS) and radiometric data (multispectral photographs) by different sensors is the necessary merging of the data. A disadvantage is the different spatial and temporal resolution of said sensors. The latter is incidentally even contrary to each other: Cameras capture all information (pixels) simultaneously while laser scanners scan 3D points in the object space sequentially, which is why there is a temporal offset between the individual Measurements are available. The subsequent merger at the data level has per se disadvantages: the spatially and temporally different resolution during data acquisition can not be completely eliminated mathematically.

Another fundamental problem is the purely passive acquisition method of conventional spectral cameras operating at longer distances. Thus, the results obtained depend on the ambient lighting (daylight), which, however, can change significantly depending on the season, time of day and weather conditions.

In the pamphlets DE 10 2009 015 920 B4 and EP 2 097 715 B1 laser scanners are shown in which three laser diodes (RGB) are used to acquire color information, whose laser beams are directed onto the object to be measured via a 3D beam deflection system. The measuring beams reflected by the object are evaluated via photodiodes. At least one of the laser beams is modulated so that a distance to the object can be determined from the measured phase shift and its 3D measurement is possible.

In the US 2015/0043009 A1 a similar system is described in which three color channels (RGB), each with a laser diode and an additional radiating in the infrared laser diode are used for 3D measurement. The measuring beams are directed via a common optical beam path to the object to be measured. The measuring beams reflected by the object are each constructed using similar optoelectronic measuring channels (one measuring channel for each color) each consisting of a photodiode (APD and selective color filter), a preamplifier (transimpedance amplifier TIA), a bandpass filter (suitable for the respective modulation frequency), a driver Amplifier and an A / D converter supplied to all measurement channels evaluation processor. However, this configuration has significant disadvantages:
All channels have slightly different gains and run times due to component tolerances and temperature-dependent changes. This causes temporally and temperature-dependent variable color errors, which affects the quality of the color registration.

Particularly critical here are the bandpass filters, especially if they are tuned to different modulation frequencies of the different channels. This almost inevitably leads to different terms, which can be reasonably approximated only with great effort.

Even if the three (or more) channels are not used for the phase (= distance) measurement, but only for the intensity, even slightly different run times in the individual channels cause color errors in fast color transitions, since not all channels can change simultaneously. If slight color errors may still be tolerable in the case of simple acquisition of RGB color values, the evaluation requires multispectral Signatures highly accurate and stable measurements of the relative intensities of the measuring channels to each other, so that the above-mentioned errors are no longer acceptable.

The three (or more) fold electronic structure also requires a certain amount of space, which can be problematic with ever smaller implementations of today's devices.

It first seems obvious, by mapping all wavelengths on only one photodiode (APD), at the latest after the TIAs all signals together, but they have different modulation frequencies, by which they can be separated again in the evaluation processor by appropriate signal processing.

In fact, however, a significant disadvantage would be a multiplication of measurement noise, since with simple superimposition of all channels, the (very broadband) measurement noise of all channels would add up, which would lead to a dramatic deterioration of the signal-to-noise ratio (SNR), especially for the more as only 3 channels of a multispectral application.

For this reason, the measuring channels are kept separate from each other in the above-described known solutions.

In contrast, the invention has for its object to provide a laser scanner, with which the disadvantages are eliminated.

This object is achieved by a laser scanner having the features of patent claim 1.

Advantageous developments of the invention are the subject of the dependent claims.

On the one hand, the laser scanner according to the invention has sensors for acquiring spatial data - in that respect it does not differ from conventional 3D laser scanners. In addition, sensors for acquiring radiometric data / intensities, i. additional spectral channels provided. The sensor for recording the radiometric data has a plurality of laser diodes of different wavelengths whose laser beams are directed to the object to be measured via a 3D beam deflection system. The beams reflected from the object are processed via opto-electronic measuring channels with photodiodes, electronic signal processing and an assigned evaluation unit. According to the invention, a combiner is provided, via which at least all the radiometric measurement channels are added in sections and selectively to a signal path, wherein this signal path is assigned in each case a common amplifier, A / D converter and evaluation processor. It may also be advantageous to either integrate the additional channel for distance measurement in this signal path or to obtain the distance measurement without additional channel only from the phase evaluations of the radiometric channels.

Preferably, the combiner is designed to frequency-selectively add the measurement channels. In this case, preferably only the frequency ranges are cut out and added, in which the various measurement signals are located, so that a measurement noise of the individual channels is not superimposed and thus the SNR of the overall signal is not degraded.

By such a frequency selectivity and the many required in the previous solutions bandpass filter can be saved.

In one embodiment of the invention, the evaluation processor is designed to determine phase positions of the individual measurement frequencies and to determine and correct drifts / tolerances in the combiner therefrom.

The evaluation of the phase positions can also be used to determine the object distance, so that it is possible to dispense with an additional channel for distance measurement.

In this case, the combiner components with variable capacitance, such as Variocap diodes can be assigned, which can be controlled to compensate for the above drifts / tolerances on the common evaluation processor.

In a particularly preferred embodiment of the invention, at least one amplifier and one A / D converter are provided in the added signal path.

According to an advantageous development of the invention, all spectral sensors and also the distance meter have a common optical beam path within the laser scanner.

There is a simultaneous sampling of all spectral channels. Preferably, the same areas are simultaneously radiometrically and spatially surveyed, with the objects being actively illuminated, which makes the results independent of the ambient light.

The basic components of a laser scanner are - as stated above - a laser and a photodiode with which laser light of a wavelength emitted and the object backscattered light is received again, as well as a deflection system for three-dimensional scanning of the object space. For active detection in several spectral channels additional laser and photodiodes are to be used. As a result, in addition to the assessment of the structural condition, eg by means of relative moisture content and chlorophyll content, which makes statements about possible vegetation traces, materials can also be distinguished.

A peculiarity of the multispectral laser scanner can be the use of an identical optical path, which avoids parallaxes, so that all information layers for the same object areas can be detected synchronously in place and in time. The key problem in this context is the combination of the individual spectral channels into a coaxial measuring beam, for which fiber optic methods or, for example, dichroic mirrors or prisms are suitable. To determine suitable wavelengths for the multispectral sampling, spectral signatures of materials and substances of interest are determined. Based on these data, it is possible to select those wavelengths which have the greatest possible spectral differences between the characteristics of the materials investigated or of certain groups of materials.

In order to be able to use the system on kinematic platforms such as cars (mobile mapping) as far as possible, all the laser diodes used should work in a time- and space-synchronized manner, ie. measuring identical points in space at the same time. Also, when using the method, no user may be required to record the same scene multiple times for different spectral channels. A simultaneous scan in different spectral ranges also represents a considerable time advantage. Furthermore, the spectral information can significantly speed up and make much more reliable an automatic segmentation (differentiation of different objects) of the recorded data in an evaluation software. Since the use of the system in public space, for example, to capture entire city centers, is sought, it is necessary to take into account requirements of eye safety in the development. This means compliance with laser classes 1, 2 or 3R (according to BGV-B2 with visible laser radiation permissible for laser surveying equipment in public areas without further protective measures).

• • Technisch/Technologische Umsetzung der zu vereinigenden Strahlengänge
• • Mechanische Stabilität der einzelnen Strahlengänge – Abweichung der Ausrichtung zueinander
• • Trennung des Empfangssignals vom ambienten Licht
• • Vermeidung von Instabilitäten der Sendeleistung der Laserdioden – Abweichung von radiometrischen Kalibrierwerten
• • Verwendung mehrerer Laserdioden als Sender verschiedener Wellenlängen für die verschiedenen Spektralkanäle, wobei die empfangenen Wellenlängen nach schmalbandiger optischer Filterung entweder durch nur wenige / eine einzige Photodiode(n) erfasst werden können oder durch getrennte Photodioden erfasst werden, deren elektrische Signale aber bereits nach dem Eingangsverstärker (TIA) wieder zusammen geführt werden.
• • Unterscheidung der einzelnen Spektralkanäle im Empfangszweig durch deren unterschiedliche Modulations-Frequenzen.
• • Verwendung von Modulation / synchroner Demodulation im Sende- / Empfangs- Zweig der Spektralkanäle für hohe Empfindlichkeit und die Unterdrückung von Einflüssen der Umgebungsbeleuchtung.
• • Synchronisation aller Sende- und Empfangskomponenten
• • Softwaretechnische Verarbeitung sehr großer Datenmengen (Punktmengen > 30 Mio. 3D-Punkten mit zugehörigen Spektral-Kanälen) auf Standard-PCs
• • Datenhandling und Datenfluss der Multispektraldaten mittels geeigneter Datenstrukturen und Dateiformate
• • Die gemessenen Intensitätswerte sollen hinreichend korrigiert sein, um die Einflüsse hervorgerufen durch Objektdistanz und Auftreffwinkel zu kompensieren, was sich maßgeblich auf die Datenverarbeitung auswirkt
• • Punktwolkensegmentierung unter vollständiger Ausnutzung aller zur Verfügung stehenden geometrischen und radiometrischen Informationen

The following elements could be advantageous embodiments / aspects of the invention:

• • Technical / technological implementation of the beam paths to be combined
• • Mechanical stability of the individual beam paths - deviation of the alignment with each other
• • Separation of the received signal from the ambient light
• • Avoidance of laser diode transmission power instabilities - Deviation from radiometric calibration values
• Using multiple laser diodes as transmitters of different wavelengths for the different spectral channels, the received wavelengths can be detected by narrow-band optical filtering either by only a few / a single photodiode (s) or are detected by separate photodiodes, but their electrical signals already after the input amplifier (TIA) are brought together again.
• • Differentiation of the individual spectral channels in the reception branch due to their different modulation frequencies.
• • Use of modulation / synchronous demodulation in the transmit / receive branch of the spectral channels for high sensitivity and the suppression of ambient lighting effects.
• • Synchronization of all transmitting and receiving components
• • Software processing of very large amounts of data (point quantities> 30 million 3D points with associated spectral channels) on standard PCs
• • Data handling and data flow of multispectral data using suitable data structures and file formats
• • The measured intensity values should be corrected sufficiently to compensate for the influences caused by the object distance and the angle of incidence, which has a significant effect on the data processing
• • Point cloud segmentation, making full use of all available geometric and radiometric information

• • Unterscheidung / Separierung von verschiedenen Materialien (z.B. Teer, Stein, Holz, Kunststoff),
• • Automatisches Entfernen von Vegetation/Bewuchs wie etwa Bäumen, Hecken und Sträuchern aus 3D-Punktwolken von urbanen Szenen zur Vorbereitung der Gebäudemodellierung.
• • Detektion von Feuchtigkeit und biologischem Bewuchs (Moose, Flechten, etc.) an Bauwerken,
• • Weitere deutliche Verbesserung der Datenbasis für die Generierung fotorealistischer bzw. zweckgebunden strukturierter Gebäudemodelle.
• • Klassifizierung von Gestein im Bergbau, z.B. zur Verfolgung von Rohstoff-Adern unter Tage.
• • Klassifizierung von trennbaren Materialien in abzureißenden Anlagen, Gebäuden oder auf Deponien.
• • Unterscheidung verschiedener Spuren in der Forensik (Körperflüssigkeiten, Materialien, gefährliche Stoffe).
• • Einfachere und schnellere Segmentierung von 3D Punktewolken anhand der vorkommenden Oberflächen, Pflanzen, Straßen, Gebäude, Personen, Brücken, etc..

Based on the multi-sensor system, new application scenarios and evaluation options are opened in the TLS segment, such as:

• Differentiation / separation of different materials (eg tar, stone, wood, plastic),
• • Automatically remove vegetation / vegetation such as trees, hedgerows, and shrubs from 3D point clouds of urban scenes to prepare for building modeling.
• • detection of moisture and biological growth (mosses, lichens, etc.) on structures,
• • Further significant improvement of the database for the generation of photorealistic or earmarked structured building models.
• • Classification of rocks in mining, eg for tracking of underground resource veins.
• • Classification of separable materials in plants, buildings or landfills to be demolished.
• • Differentiation of different tracks in forensics (body fluids, materials, dangerous substances).
• • Easier and faster segmentation of 3D point clouds based on surfaces, plants, streets, buildings, people, bridges, etc.

The sensor system according to the invention also makes it possible for the first time to provide integrated data acquisition for answering current scientific questions in the fields of "urban system modeling" and "structural modeling of structures".

• • Simulation und Vergleich eines gemeinsamen optischen Strahlengangs nach verschiedenen Verfahren, da es für die erforderliche spektrale Breite keine Standardlösungen am Markt gibt.
• • Analyse zur Aufteilung des reflektierten Laserlichts in die einzeln emittierten Wellenlängen, wobei eine hohe Empfindlichkeit und die schmalbandige optische Filterung der einzelnen Kanäle wesentlich sind, und somit eine Messung bis auf mindestens 50m Distanz erlaubt.
• • Erzielen einer extrem kompakten Bauweise, die nach Möglichkeit in einem modifizierten Standard Laserscanner untergebracht werden kann, zumindest aber als Gesamtgerät tragbar (<15Kg) und Batterie betrieben gehalten sein muss.
• • Modularer Aufbau der Multispektral-Einheit, so dass diese möglichst einfach auf andere Spektralkanäle umgerüstet werden kann, ohne dass eine Umkonstruktion erforderlich wird.
• • Softwaretechnische Umsetzung eines Algorithmus zur Unterscheidung von Objekten oder Bauteilen an Gebäuden unter Ausnutzung des radiometrischen Segmentierungsergebnisses (aus externer Software). Es wird vorzugsweise eine sogenannte Segmentierungsgenauigkeit bzw. Klassifizierungsgüte von etwa 80% erreicht. Dies bedeutet, dass in einem bekannten Referenzszenario 80% aller erfassten Flächen segmentiert und schließlich korrekt klassifiziert wurden.
• • Nutzung von effizienten Datenstrukturen, Datenfluss und Algorithmen zum Handling sehr großer 3D-Datenmengen (Punktwolken > 30 Mio. Punkten) auf Standard-PCs
• • Nutzung eines Verfahrens zur radiometrischen und geometrischen Kalibrierung des Multisensorsystems
• • Auswertung der ausgesandten und empfangenen Signale und Ableitung von multispektralen Intensitäten bzw. Intensitätsunterschieden, die für die spektrale Klassifizierung erforderlich sind. Es gilt dabei eine Aufschlüsselung der einzelnen Kanäle mit einer Messgenauigkeit von 3% oder besser zu erreichen,
• • Verwendung eines Austauschformates zwischen 3D-Auswertesoftware und etablierten radiometrisch basierten Segmentierungsalgorithmen aus dem Bereich der Fernerkundung,
• • radiometrische und geometrische Kalibrierung des Multisensorsystems.

The following elements can also be advantageous developments:

• • Simulation and comparison of a common optical beam path using different methods, as there are no standard solutions on the market for the required spectral width.
• • Analysis of the distribution of the reflected laser light into the individually emitted wavelengths, whereby a high sensitivity and the narrow-band optical filtering of the individual channels are essential, and thus allows a measurement to at least 50m distance.
• • Achieving an extremely compact design, which can be accommodated in a modified standard laser scanner if possible, but at least as a portable device (<15Kg) and must be battery operated.
• • Modular design of the multispectral unit so that it can be easily converted to other spectral channels without the need for reconfiguration.
• • Software implementation of an algorithm for distinguishing objects or building components by exploiting the radiometric segmentation result (from external software). It is preferably achieved a so-called segmentation accuracy or classification quality of about 80%. This means that in a known reference scenario 80% of all recorded areas were segmented and finally classified correctly.
• • Use of efficient data structures, data flow and algorithms for handling very large amounts of 3D data (point clouds> 30 million points) on standard PCs
• • Use of a method for radiometric and geometric calibration of the multi-sensor system
• • Evaluation of the transmitted and received signals and derivation of multispectral intensities or intensity differences, which are required for the spectral classification. It is a breakdown of the individual channels with a measurement accuracy of 3% or better to achieve
• Use of an exchange format between 3D evaluation software and established radiometrically based segmentation algorithms in the field of remote sensing,
• • radiometric and geometric calibration of the multi-sensor system.

The inventive approach includes (any number) spectral channels and indicates the possibility to segment the scanned scene based on spectral differences. This would greatly facilitate the automatic detection of related surfaces or objects.

For example, the new approach requires essentially only one common signal path for three or more spectral channels, to which all measurement channels are connected after the preamplifiers (TIAs) of the photodiodes (APDs) via a so-called frequency-selective combiner. This not only minimizes component cost, but has the great advantage of minimizing differences in signal transmission (e.g., component tolerances or thermal drift) since all measurement signals are subjected to identical variations.

The variations occurring in the frequency-selective combiner can be compensated in a simple manner via variable capacitances (for example varactors), which are controlled by the evaluation processor or, if they are not too large, even without feedback, purely mathematically only in the evaluation processor.

This eliminates the individual, described in previous writings, bandpass filter whose drift - if at all, then only with great effort - could compensate.

Preferred embodiments of the invention are explained in more detail below with reference to schematic drawings. Show it:

1 a schematic representation of the beam path and the signal conditioning / processing of a laser scanner according to the invention and

2 Measurement channels of the laser scanner according to 1 ,

The basic structure of 3D laser scanners is from the above-mentioned prior art and for example from the DE 10 2012 105 027 A1 the Applicant known, so that in the following, only the essential for understanding the invention components are explained and incidentally in the DE 10 2012 105 027 A1 is referenced, whose Content should be included in the disclosure of the present application.

Accordingly, the laser scanner has 1 a measuring head, in which a plurality of laser diodes are arranged, which in the illustration according to 1 are labeled with IR, λ1 ... λn and are used for the radiometric measurement of the object. The laser diode labeled IR emits light in the infrared range. Such laser diodes are usually used for geometrical measurement of the object. The laser scanner is not limited to the above-described prior art to wavelengths in the red, green and blue, but the laser diodes for recording radiometric data (intensities) can be designed so that a much wider spectral signature, for example, from infrared to ultraviolet can be detected. This can lead to the differentiation of different substances and / or to the automatic classification of related objects within the recorded laser data. Of course, significantly more than three laser diodes can be used.

The control of the laser diodes IR, λ1 ... λn via a modulator unit 2 , The laser beams emitted by the laser diodes are coaxially aligned, for example via dichroic mirrors S or other optical elements, such as a system of prisms, as a coaxial bundle of laser beams 4 through a hole 12 a mirror 14 in the laser head and hit a rotating, tilted rotating mirror 6 on top of the coaxial bundle of laser beams 4 directed to the object to be measured, wherein the laser beams exit through an unillustrated exit window from the measuring head. In the illustrated embodiment, the rotating mirror rotates about a horizontal axis of rotation 8th , The entire measuring head rotates about a vertical axis, which in 1 coaxial with the exiting laser bundle 10 is drawn.

The reflected / backscattered from the object to be measured rays are transmitted through the rotating mirror 6 on the aforementioned mirror 14 deflected so that the beam path of the backscattered light (laser beams) via an optic 16 is converted into an image of the reception light. The beams deflected by the optics then in turn strike optical elements for the division of the individual wavelengths, for example dichroic mirrors S _IR , S ₁ ... S _n and are subsequently passed over optical bandpass filters 18a . 18b . 18c ... narrow band filtered, so that as little disturbing light on the optical receiver (photodiodes / APDs) of the individual spectral channels 20 . 22 . 24 ... arrived.

Three of these measuring channels 20 . 22 . 24 are in 2 illustrated in more detail by way of example. For a radiometric measuring system, however, significantly more channels would be required.

Accordingly, each measuring channel has 20 . 22 . 24 a photodiode (avalanche photodiode, APD) 26 . 28 . 30 , in which each of the laser beams of the over the bandpass filter 18a ... c separated wavelengths are converted into corresponding electrical signals. These electrical signals are then each a transimpedance amplifier (TIA) 32 . 34 . 36 fed and the amplified signals in sequence to a common combiner 38 guided. In this all involved measurement channels 20 . 22 . 24 ... added, which is not a simple addition, as for example in the well-known from high-frequency engineering combiners, but this addition is frequency-selective. Only those frequency ranges, in which the of the respective TIA 32 . 34 . 36 incoming measuring signal is located, cut out and added. For this reason, the measurement noise of the individual channels described above is not superimposed and, accordingly, the SNR of the overall signal is not degraded.

Another advantage over the known solutions described above is that the many bandpass filters required in conventional measuring channels are eliminated. The in the frequency-selective adaptive combiner 38 added measurement signals 40 then be in a common amplifier 42 amplified and finally via a common A / D converter 44 converted into digital electrical signals corresponding to the acquired radiometric / spectral data.

These signals will then be from one for all measurement channels 20 . 22 . 24 common evaluation processor 46 processed in a conventional manner.

As mentioned above, the combiner is 38 also exposed to variations due to thermal drift and component tolerances. To compensate for such measurement errors, the signal processing according to the invention can be improved to the effect that each measurement channel 20 . 22 . 24 ... is associated with a variable capacitance component, for example a variocap diode, by means of which such effects can be compensated. Through an additional evaluation of the individual phase positions of the measurement frequencies in the evaluation processor 46 can then be these drifts / tolerances of the combiner 38 determined mathematically and either in return 48 by controlling the respective Variocap diode (see the arrow in 2 ) in the combiner 38 or even mathematically in the evaluation processor 46 correct. However, the latter is preferably done only if these deviations are not too large. Of course you can Use the evaluation of the phase positions of the measurement frequencies also for the calculation of the object distance, so that under certain circumstances the separate IR channel for distance measurement can be omitted.

By the concept according to the invention, several measurement channels 20 . 22 . 24 ... at least in sections via a combiner 38 to a signal path 50 To add up, the measurement accuracy compared to conventional solutions can be significantly improved and also the circuit complexity can be reduced.

Disclosed is a multispectral laser scanner for the spatial and radiometric acquisition of data.

LIST OF REFERENCE NUMBERS

1

laser scanner

2

modulator unit

4

coaxial bundle of laser beams

6

rotating mirror

8th

the rotation axis

10

vertical axis

12

drilling

14

mirror

16

optics

18

Bandpass filter

20

measuring channel

22

measuring channel

24

measuring channel

26

APD

28

APD

30

APD

32

TIA

34

TIA

36

TIA

38

Assemblers

40

added measuring signals

42

amplifier

44

A / D converter

46

evaluation processor

48

return

50

signal path

IR

Laser diode (distance meter)

λ _1..N

Laser diodes (radiometric detection)

S _1..N

Dichroic mirrors

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102009015920 B4 [0006]
• EP 2097715 B1 [0006]
• US 2015/0043009 A1 [0007]
• DE 102012105027 A1 [0040, 0040]

Claims (11)

Laser scanner with a sensor for acquiring spatial data and, in addition, a plurality of multispectral sensors for acquiring radiometric data, each sensor having a laser diode whose laser beam is directed onto an object to be measured via a 3-D beam deflection system, whereby reflected radiation is transmitted through it optoelectronic measuring channels are processed with photodiodes and an associated evaluation unit, characterized by a combiner ( 38 ), over which at least some of the measuring channels ( 20 . 22 . 24 ) selectively to a signal path ( 50 ) are added, this a common evaluation processor ( 46 ) assigned. Laser scanner according to claim 1, wherein the combiner ( 38 ) is designed around the measuring channels ( 20 . 22 . 24 ) to add frequency selectively. Laser scanner according to claim 1 or 2, wherein the evaluation processor ( 46 ) is designed to determine phase angles of the individual radiometric measurement frequencies and from there drifts / tolerances in the combiner ( 28 ) to determine and correct. Laser scanner according to one of the claims 1 to 3, wherein the evaluation processor ( 46 ) are also used to determine the object distance Laser scanner according to claim 3 or 4, wherein at least some measuring channels ( 20 . 22 . 24 ) Components with variable capacitance, preferably variocap diodes, are assigned to compensate for drifts / tolerances via the evaluation processor ( 46 ) are controllable. Laser scanner according to one of the preceding claims, wherein the common signal path ( 50 ) of all radiometric channels and optionally also of the channel for 3D measurement (distance) only one amplifier ( 42 ) and an A / D converter ( 44 ) having. Laser scanner according to one of the preceding claims, having a common optical beam path of all laser diodes for 3D measurement and for radiometric measurement. Laser scanner according to one of the preceding claims, wherein it is controlled such that in each case identical surfaces in the object space are measured both 3D and radiometric. Laser scanner according to one of the preceding claims with at least one laser diode for 3D measurement and at least three further spectral channels with laser diodes for radiometric measurement. Laser scanner according to one of the preceding claims, wherein the distinction of the individual spectral channels in the receiving branch is also effected by their different modulation frequencies. Laser scanner according to claim 1 or 2, wherein the use of modulation / synchronous demodulation in the transmission / reception branch of the spectral channels for high sensitivity, as well as the suppression of ambient lighting.

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