DE102006006001B3 - Method and arrangement for inserting location-related information into a visual representation or view of a scene - Google Patents

Abstract

The invention relates to a method and an arrangement for fading in location-related information in a visual representation or view of a scene (1), in particular augmented reality. A distance measuring system is connected to a display device (10) for the visual display of the information displayed. The distance measuring system (11) radiates electromagnetic radiation onto the scene (1) so that the scene (1) reflects at least part of the electromagnetic radiation in the direction of the distance measuring system (11). The distance measuring system (11) repeatedly records images of the radiation reflected from the scene (1) and information is obtained from the images in each case about a distance between a plurality of elements of the scene (1). A position and orientation of the distance measuring system (11) and / or the display device (10) in relation to the scene (1) is determined from the distance information.

Description

The The invention relates to a method and an arrangement for fading location-related information in a visual representation or view a scene.

The The invention relates in particular to the technical field of augmented Reality (AR).

AR should e.g. as a new form of human-machine interaction be used. It can the user (human) information in his field of view so that they appear in the correct position in the viewed scene. The information is linked to the scene by location. For example can Parts of the scene (about individual components of a machine) in color be marked and / or associated Text will be presented. In a concrete application of the AR, e.g. while the execution of maintenance or installation work of the service technician or mechanic thereby support that information about the individual work steps appears become. A particular problem of AR applications lies in the so-called tracking of the movement of the person or the presentation device, which visualizes the displayed location-related information. The presentation device may be, for example, a partially transparent smart glasses or a portable display (e.g. a hand-held device) act. Tracking is required to get the location-related information dependent from the respective position and orientation (in particular depending on the viewing direction of the user or the orientation of the display) in the correct position to be able to show. The user and / or the presentation device should be moved can and yet the location-related information is displayed in the correct position can be.

For example Therefore, an AR arrangement may have a camera compatible with the Representation device is connected so that both during the application can not perform any significant movements relative to each other. Further For example, a small, portable computer unit may be provided which processes the signals recorded by the camera and the display of the information by the presentation device controls. In this case, the presentation device depending on the application be transparent (e.g., in the case of data glasses, by which the user watch the scene) or in addition to the location-based Additional information may also be an image of the scene (e.g. Case of the portable display). Such systems where the camera connected to the display device, make progress across from earlier Tracking systems using stationary cameras or other stationary sensors designed to track the movement of the presentation device were.

The Systems with moving cameras usually allow one much larger range of action and are less dependent that the action space in which the application is running should, is specially prepared. However, systems are also included still moving cameras not yet independent of their environment. Usually special markers are placed in the area, which are used by the Camera can be detected to enable tracking. Pure image-based Tracking methods that manage without markers in the scene and only from the captured two-dimensional image both position and Calculating orientation in space are still the subject of research. Currently, the calculation of the camera position and orientation usually still numerically unstable. Besides, the results are sensitive to noise and frequent inaccurate regarding the identification and localization of image features the scene.

The article entitled "Augmented Reality for Manufacturing Planning" by F. Doil et al., Published in: ACM International Conference Proceeding Series; Vol. 39, 2003, pages 71-76, available on the Internet at the URL: http: // portal .acm.org / citation.cfm? id = 769962 & jmp = citings & coll = & dl = acm & CFID = 15151515 & CFTOKEN = 6184618 (Retrieved December 12, 2006) describes an AR system for planning a factory, using an intuitive user interface to enable the planner to run various production systems or The visualization should be context-sensitive and congruent with the real environment, so an HMD (Head-Mounted Display) is used.A marker-based optical tracking system registers the necessary markers in the real environment Assigned by a simple menu to support the flexibility required. Moving a marker moves the virtual elements in the scene. As per section 5.5 The planner has to gather additional information while visiting the factory. An example is the task of measuring distances or positions of machines. To support this, a simple measuring routine is integrated into the system. To measure the desired distance, the user of the system selects two points in a live video. These points can either be points on the virtual content or in the real environment. The system determines the coordinates of the points with respect to the marker's coordinate system. Then it calculates the relative distance of the points. The implemented function can be used to rough Estimates of geometric proportions and distances in the factory environment.

DE 101 16 331 A1 describes an AR system with multiple interaction devices.

It is an object of the present invention, a method and a Arrangement for inserting location-related information into a visual representation or view a scene that is accurate and stable consideration a movement of the presentation device and / or the user with respect to the scene. It should focus on a special preparation of the scene for tracking preferably can be dispensed with.

The The object is achieved by a method having the features of the appended patent claim 1 and by an arrangement having the features of the attached patent claim 7 solved.

It It is suggested that the distance of elements of the scene to one Measuring device or the display device to measure and from the current position and orientation for showing the location-related To determine information. In particular, to measure the distance a specially designed camera can be used. Preferably enough for a single camera. The use of a stereotactic arrangement with at least two cameras is not required. At the elements the scene is e.g. around areas, the individual pixels a digital camera or an image of a digital camera correspond or to areas that are multiple pixels of the image or correspond to the camera.

In this way, an image with additional depth information of the scene can be obtained. In particular, the image data provided by the camera already contain (locally) three-dimensional position information about the scene. With this information, it is possible to determine the current position and orientation of the camera and / or of an object connected to the camera (in particular of the display device for the visual presentation of the displayed location-related information). In particular, it is proposed to use a so-called flight distance camera (time-of-flight camera) as the camera of the distance measuring system. Such cameras are known for example from US 2004/0008394 A1. The content of this US patent application is hereby incorporated by reference in its entirety as an exemplary embodiment of a flying distance camera in the present description. In particular, the flight distance camera as from paragraph 78 to paragraph 90 on page 6 of the US application. Furthermore, the depth information or information about the distance to the elements of the scene as in paragraph 95 , Paragraph 96 or paragraph 97 The US application described from the image obtained by the flight distance camera image data and additional information about the time dependence of the radiation used for the illumination of the scene are determined.

Farther becomes the content of the following document regarding the description of a potential embodiment a flying distance camera included in the present description: T. Oggier, M. Lehmann et al., "3D Time-of-Flight Camera Demonstrator ", published as CSEM Scientific and Technical Report 2003 on the Internet at http://www.csem.ch/corporate/Report2003/pdf/p45.pdf, released by CSEM, Rue Jaquet-Droz 1, CH-2007 Neuchâtel, Switzerland. Especially becomes the content of the one-page document regarding the construction of the camera Lighting unit and re the evaluation of the signals supplied by the camera in this description recorded with.

• – ein Abstands-Messsystem mit einer Darstellungseinrichtung zur visuellen Darstellung der eingeblendeten Informationen verbunden wird,
• – von dem Abstands-Messsystem elektromagnetische Strahlung auf die Szene eingestrahlt wird, sodass die Szene zumindest einen Teil der elektromagnetischen Strahlung in Richtung des Abstands-Messsystems reflektiert,
• – von dem Abstands-Messsystem wiederholt Bilder der von der Szene reflektierten Strahlung aufgenommen werden und aus den Bildern Informationen jeweils über einen Abstand einer Mehrzahl von Elementen der Szene gewonnen werden,

aus den Abstands-Informationen eine Position und Orientierung des Abstands-Messsystems und/oder der Darstellungseinrichtung in Bezug auf die Szene ermittelt wird.In particular, the following is proposed:
A method for inserting location-related information into a visual representation or view of a scene, in particular augmented reality method, wherein

• A distance measuring system is connected to a display device for the visual display of the displayed information,
• The electromagnetic radiation is radiated onto the scene by the distance measuring system so that the scene reflects at least part of the electromagnetic radiation in the direction of the distance measuring system,
• Images of the radiation reflected by the scene are repeatedly recorded by the distance measuring system and information is obtained from the images in each case over a distance of a plurality of elements of the scene,

from the distance information, a position and orientation of the distance measuring system and / or the display device with respect to the scene is determined.

The display of the location-related information in the visual representation or view of the scene can be done in any way. For example, when using smart glasses, the techniques common for fading information can be used. When using a display, the location-related information can be displayed directly through the display. In this case, the location-related information of the view of the scene can be superimposed, ie the scene and the superimposed location-related information in total form that image information that is displayed on the screen. When displaying the location-related information in By contrast, the user views the image of the scene through the semitransparent display device by using data glasses or another semitransparent display device. There are other, different presentation devices conceivable, for example display devices, of which the view of the scene is projected.

Together is the different types of presentation device that the location-related information in each case in the correct position to the visual representation or view of the scene can be represented, the location of the location-specific information of the current position and orientation the eyes of the beholder and / or the current position and orientation dependency of the presentation device relative to the scene.

The Distance measuring system (in particular a flight distance camera) is connected to the presentation device, so that at least during a Part-period the use no change of Relative position and relative orientation takes place.

Together is the above time-of-flight cameras that the scene is active is illuminated. In particular, electromagnetic radiation be irradiated to the scene, wherein a radiation flux density the radiation emitted by the distance measuring system is varied, is varied in particular periodically. Frequencies of this modulation the for the illumination used for illumination is e.g. In the range of 15 to 25 MHz.

Corresponding the variation of emitted radiation varies from that of the scene reflected radiation. From this, the distance can be determined in particular from a phase and / or intensity of the distance measuring system received radiation. In itself, the evaluation of the phase is already sufficient. However, additional information may also be the evaluation the strength the received reflected radiation, since the strength or radiation flux density proportional to the square of the distance between scene and distance measuring system decreases.

Preferably will be obtaining the distance information and the determination the position and orientation repeated continuously, so that the Show the location-related information in real time or quasi in real time according to a current position and orientation possible is. For this purpose, the user can use a computer of the distance measuring system carry with you. The user is therefore mobile and can therefore almost every possible position relative to the scene. Alternatively, however, the calculator can also be stationary and can transmit the data from the camera (in particular wirelessly) to the computer become. Conversely, the computer in this case supplies the for the correct position Representing the location-related information necessary data back to the Representation device that the user wears or in the area of User is arranged.

To the Comparison of the obtained from the distance measuring system three-dimensional information about the scene can be a three-dimensional model of the scene or a Part of the scene to be used. Such a three-dimensional Model can be created by means known per se, for example from the data of a CAD system, with which one or more objects the scene were constructed.

Especially if such planning data are not available, the distance measuring system can while an initialization phase to be used, a three-dimensional Model of the scene to win.

• – eine Darstellungseinrichtung, die ausgestaltet ist, zumindest die eingeblendeten Informationen darzustellen,
• – ein Abstands-Messsystem, das mit der Darstellungseinrichtung verbunden ist

wobei das Abstands-Messsystem eine Beleuchtungseinrichtung zur Erzeugung von elektromagnetischer Strahlung aufweist, die auf die Szene eingestrahlt werden kann, wobei das Abstands-Messsystem eine Bild-Aufnahmeeinrichtung zur Aufnahme von Bildern der Szene aufweist und wobei das Abstands-Messsystem eine Abstands-Ermittlungseinrichtung zur Ermittlung eines Abstandes einer Mehrzahl von Elementen der Szene zu der Darstellungseinrichtung und/oder zu der Bild-Aufnahmeeinrichtung aufweist.Also proposed is an arrangement for fading in location-related information into a visual representation or view of a scene, in particular an augmented reality arrangement, the arrangement comprising:

• A display device which is designed to display at least the information displayed,
• A distance measuring system connected to the display device

wherein the distance measuring system comprises an illumination device for generating electromagnetic radiation that can be irradiated onto the scene, wherein the distance measuring system has an image recording device for recording images of the scene, and wherein the distance measuring system comprises a distance determination device for detection a distance of a plurality of elements of the scene to the display device and / or to the image pickup device.

Because of the advantages and further developments of the arrangement is on referenced the previous description of the method and on the following description of the embodiments.

The embodiments will now be described with reference to the accompanying drawings. The individual figures of the drawing show:

1 schematically a scene that is viewed by a user

2 the arrangement according to 1 and to in addition, a transparent display device, through which the user views the scene, wherein the display device is connected to a flight distance camera,

3 schematically an arrangement with the positionally correct location information on the in 2 The display of the location-related information depends on the position and orientation of the camera relative to the scene,

4 a first flowchart illustrating a process flow for the correct position fading in of the location-related information and

5 a further flowchart illustrating steps for the positionally correct fading in of the location-related information.

The schematic in 1 represented scene 1 has a plurality of elements 5 . 6 . 7 . 8th . 9 on, which can be connected to each other and are usually arranged at least over a period of time in a fixed relative position to each other. An example of a scene is the arrangement of objects in the engine compartment of a road vehicle.

Some of the objects 5 - 9 the scene 1 have a greater distance from the eye 3 of a viewer (user 2 ) than others. For example, in the in 1 and 2 snapshot shown the distance between the eye 3 and the object 5 greater than the distance between the eye 3 and the object 6 ,

In the preferred embodiment of the invention, which here with reference to 1 to 5 However, not only distances to whole objects of the scene are taken into account, but under certain circumstances also subregions of the objects, that of a flying distance camera 11 ( 2 ) are visible from. Whether partial areas are taken into account depends solely on how the image resolution of the camera is designed and which partial areas or areas of the objects 5 to 9 in a given instantaneous position of the camera 11 are visible to them. In the 1 and 2 schematically illustrated arrangement is not to scale. Rather, the distance between the user 2 and the scene 1 in proportion to the extent of the scene 1 vary in practice.

As 2 shows is the flying distance camera 11 with a presentation device 10 connected, through which the eye 3 of the user 2 the scene 1 considered. On the presentation device 10 the location-related information can be displayed so that the user 2 sees the location-related information in the correct position for the view of the scene. By location is meant that the information is related to the location of an object or element of the scene. The location-relatedness thus exists eg in a coordinate system of the scene. A positionally correct representation of the location-related information is understood to mean that the respective location-related information is displayed at a given relative position between the user (in particular between the eye or the eyes of the user) on the one hand and the scene on the other hand and with a given orientation of the user's line of sight in that the location-related information appears or can be perceived by the user in such a way that it is assigned to the correct location of the scene. For example, the object 5 the scene 1 The color orange may be associated as additional color information to the object 5 towards other objects of the scene 1 especially to emphasize, though the object 5 has a different color, eg gray. In the correct position representation, therefore, an area on the presentation device would be colored orange, so that the object 5 for the viewer apparently has an orange color. However, other location-related information may also be displayed, for example font information associated with an associated object of the scene via an arrow, which informs the user that a specific action is to be performed in connection with the object.

In order to display the location-related information in the correct position, is now using the camera 11 the position of the presentation device 10 in terms of the scene 1 as well as the orientation of the presentation device 10 determined. The presentation device 10 is again in a fixed position in a coordinate system moved with the eye of the user. For such a display device is therefore particularly suitable a data glasses.

Different it is at a presentation device on which also a picture the scene is shown. This can be done by the flying distance camera generated (conventional) two-dimensional image can be used. The additional Three-dimensional (depth) information of the flying distance camera is then additionally for the Determination of the relative position and orientation used. The advantage such an arrangement is that the user relative to the Can move presentation device.

The in the 2 and 3 illustrated camera 11 For example, it is carried out as described in the above-mentioned Oggier, Lehmann et al. described. 3 shows schematically that the camera 11 with a lighting device 13 is connected to actively illuminate the scene. Preferred dimensions is that of Be illumination unit 13 emitted radiation in the visible wavelength range. However, this is not necessarily the case in order to determine the distance or the depth information of the scene. As in the cited publication by Oggier, Lehmann et al. described, the lighting device 13 and the camera 11 be arranged in a common housing or otherwise connected firmly together.

As 2 further shows, with the help of the camera 11 their distance to the different objects or areas of the scene 1 be determined. As an example of different distances are the distance d1 to the object 5 and the distance d2 to the object 6 shown. The difference of the viewing directions of the camera 11 and the eye 3 is exaggerated compared to practical embodiments.

3 further shows a computer 14 that the lighting device 13 drives and from the camera 11 receives and evaluates the image signals recorded by this. The connection to the lighting device 13 serves in particular to the fact that the computer 14 for the evaluation of the image signals, the phase and frequency of the illumination device 13 knows radiation emitted.

Also the calculator 14 can be in a common housing with the camera 11 be arranged. In a miniaturized version of the camera 11 However, the computer is preferably as in 3 shown executed as a separate component. In this case, the determination of the depth information and / or the determination of the position and orientation with respect to the scene to be described below can be carried out by the computer.

In principle, it is therefore possible that not only a computer is provided, but a first computer for determining the depth information from the image signals supplied by the camera and a second computer for determining the relative position and orientation. In addition, a further computer can be provided to display the correct position of the location-related information on the display device 10 to calculate and / or control. Schematically, therefore, is the representation of 3 in which all these arithmetic tasks from the calculator 14 be executed.

To refer to the embodiment according to the publication by Oggier, Lehmann et al. to come back, creates the lighting device 13 visible light of an arrangement with a plurality of light-emitting diodes whose radiation flux density is modulated at a frequency of 20 MHz. The camera receives the reflected light resolved for each pixel of the CCD / COMS technology camera sensor. A 12-bit A / D converter of the camera digitizes each of the analog output signals of the sensor pixels, and the data is transmitted to a FPGA (field programmable gate array) of the computer. There, the signals are processed and stored in a RAM memory. The FPGA controls the entire camera. It calculates the phase shift (to determine the distance to the respective element of the scene), the offset and the amplitude to determine the intensity or radiation flux density at the receiver.

Especially For example, depth determination may be as described in US 2004/0008394 A1 be executed. For further Details of the depth determination are referred to this document.

With respect to the flowchart of 4 corresponds to the determination of the three-dimensional image information about the scene (classic two-dimensional image information with additional depth information) step S1. According to this variant of the method according to the invention, three-dimensional data D of a model of the scene are also used. In step S2, an alignment of the 3D data obtained by the camera and the 3D data from the model takes place. In particular, the area of the 3D model that corresponds to the area covered by the camera is determined.

In Step S3 following step S2 becomes the two 3D data sets current position and orientation of the camera and thus also the presentation device determined. The transformation matrix is determined with which one of the two datasets (especially the record of the model) in the coordinate system the other record can be transformed. Such a process is commonly referred to as registration. Preferably is doing an ICP (iterative closest point) method applied. A preferred embodiment of the ICP method is described in the publication by Paul J. Besl and Neil D. McKay "A Method for Registration of 3-D Shapes "IEEE Transactions on Pattern Analysis and Machine Intelligence, Vol. 14, No. 2, February 1992, pages 239 to 256 described. The content of this publication, in particular of Section III from page 241 to the end of Section IV on page 246, is hereby incorporated in full in this description.

The ICP method is already, as the name implies, an iterative method that is used to optimize the registration of 3D datasets. As a result, a solution of the registration is obtained in which the deviation between the transformed first 3D data set and the second 3D data set is minimal. To those of the came ra gained image data for the ICP process, preferably a filtering (smoothing) of the 3D data obtained by the camera is made. The filtering serves, in particular, to compensate (smoothen) statistical fluctuations in the sensor signals of the individual pixels of the camera.

Regarding the further course of the basis of 4 described method follows step S3 step S4, in which the position of the location-related information to be displayed on the display device is calculated. In particular, the three-dimensional information from the model of the scene, which is now registered with the three-dimensional information obtained using the camera, on the two-dimensional display plane of the display device 10 projected. The projection can be done for selected objects, areas or parts thereof to which the location-related information is assigned. Furthermore, it can be determined in an optional additional step whether the object, the area or the part thereof to which the respective location-related information is assigned is hidden by other parts of the scene and is therefore not or only partially visible in the plane of the presentation device. In particular, it can then be decided that the location-related information on hidden parts of the scene is not displayed.

In the subsequent step S5 becomes the location-related information appears.

The method according to the flowchart of FIG 5 described. The method is one of many consecutive iterative procedures that are run during an AR application running over a period of time. In each case, the starting point for a method sequence is that registration of the data of the 3D model of the scene with the 3D data of the scene generated by the camera has already taken place for a past time.

In step S11, a 3D image of the scene is again taken by the camera for a new, later point in time 11 recorded and determined the associated depth information. Furthermore, again filtering can be performed.

In The following steps S12 and S13 again find the adjustment between two 3D datasets (Step S12) and the determination of the transformation matrix, preferably again according to the ICP procedure, instead of. This time, however, the adjustment or the transformation between the one in the previous step and the one in the current step present camera image made. As is the position and orientation usually between times that are in close proximity to each other follow, not changed significantly has, the transformation is at a much lower computational cost to investigate. Furthermore this has the advantage that with great certainty the right transformation matrix is found and not just a transformation matrix, the a side solution which corresponds to a local but not absolute minimum of distances equivalent.

In The next step S14 is then the current 3D image of the process run along with the associated Transformation information for the next Process flow saved.

In The following steps S15 and S16 again show the position of the one to be displayed Location-related information determined (step S15) and in step S16 appears.

If no 3D model of the scene to be considered exists at the beginning of an application, such a model can be constructed using the flying distance camera and using the associated further components of the arrangement (for example, the one based on FIG 3 described arrangement) are created. For this purpose, for a plurality of different relative positions and orientations of the camera with respect to the scene during an initialization, the 3D data record is determined and stored in each case for each position and orientation. In addition, in each case information is entered by the user, for example. Preferably, it is sufficient if the user establishes the association between the object or element of the scene and the location-related information for each object of the scene for which location-related information exists, and controls that the assignment is correct also for the most diverse relative positions and orientations is maintained. The latter is facilitated by the fact that the differences between two successive relative positions and / or orientations are not too great. The procedure corresponds to the basis of 5 explained iterative procedure. At the end, after step S16, it is then to be verified in each case that the assignment of the location-related information to the respective object or element of the scene is still correct.

Generally, solved by the specific embodiments, which have been explained with reference to the accompanying figures, the invention has the following advantages:
By using a camera connected to the display device, the mobile use of the display device is variable relative position and orientation with respect to the scene possible.

The additionally available to two-dimensional camera images depth information or 3D information makes the process independent of additional Facilities or measures at the scene, such as the placing of markers in the Scene. The computational effort for the determination of the relative position remains and orientation, compared to methods that are only two-dimensional camera images evaluate, low and leads to a stable solution for the optical tracking. Besides that is in the already high degree of miniaturization of Flight distance cameras and associated hardware for the evaluation of the camera signals possible, very handy, compact versions produce low weight, the presentation device and camera and optionally even the calculator included.

Claims (9)

Method for inserting location-related information into a visual representation or view of a scene ( 1 ), in particular augmented reality method, characterized in that - at least one part ( 11 ) of a distance measuring system ( 11 . 13 . 14 ) with a presentation device ( 10 ) is connected to the visual display of the displayed information, - by the distance measuring system ( 11 . 13 . 14 ) electromagnetic radiation on the scene ( 1 ), so that the scene ( 1 ) reflects at least part of the electromagnetic radiation in the direction of the distance measuring system, - by the distance measuring system ( 11 . 13 . 14 ) repeats pictures of the scene ( 1 ) reflected radiation and from the images information about a distance of a plurality of elements of the scene ( 1 ) to the presentation device ( 10 ) and / or to an image recording device ( 11 ), from the distance information a position and orientation of the distance measuring system ( 11 . 13 . 14 ) or part ( 11 ) thereof and / or the presentation device ( 10 ) in relation to the scene ( 1 ) is determined. Method according to the preceding claim, wherein a radiation flux density of the of the distance measuring system ( 11 . 13 . 14 ) emitted radiation is varied. Method according to the preceding claim, wherein a radiation flux density of the of the scene ( 1 ) is varied in accordance with the variation of the emitted radiation and wherein the distance from a phase and / or intensity of one of the distance measuring system ( 11 . 13 . 14 ) received radiation is determined. Method according to one of the preceding claims, wherein obtaining the distance information and identifying the Position and orientation is repeated continuously, so the fade in the location-related information in real time or quasi in real time according to a current position and orientation is possible. Method according to one of the preceding claims, wherein in determining the position and orientation with respect to the scene ( 1 ) a three-dimensional model (M) of the scene ( 1 ) or part of the scene ( 1 ) is used. Method according to the preceding claim, wherein the three-dimensional model (M) of the scene ( 1 ) is obtained using the distance measuring system during an initialization phase. Arrangement for inserting location-related information into a visual representation or view of a scene ( 1 ), in particular an augmented reality arrangement, the arrangement comprising a display device ( 10 ), which is designed to display at least the information displayed, characterized by a distance measuring system ( 11 . 13 . 14 ) associated with the presentation device ( 10 ), wherein the distance measuring system ( 11 . 13 . 14 ) a lighting device ( 13 ) for generating electromagnetic radiation incident on the scene ( 1 ), wherein the distance measuring system ( 11 . 13 . 14 ) an image recording device ( 11 ) for taking pictures of the scene ( 1 ) and wherein the distance measuring system ( 11 . 13 . 14 ) a distance determination device ( 14 ) for determining a distance of a plurality of elements of the scene ( 1 ) to the presentation device ( 10 ) and / or to the image recording device ( 11 ) having. Arrangement according to the preceding claim, wherein the distance measuring system ( 11 . 13 . 14 ), a radiation flux density of the illumination device ( 13 ), in particular to vary periodically. Arrangement according to the preceding claim, wherein the distance determination device ( 14 ), the distance from a phase and / or intensity of one of the image recording device ( 11 ) to determine radiation received.