Device and method for optically scanning and measuring an environment

A method for scanning and measuring an environment is provided. The method includes providing a three-dimensional (3D) measurement device having a controller. Images of the environment are recorded and a 3D scan of the environment is produced with a three-dimensional point cloud. A video image of the environment is recorded. The video image is displayed on a first portion of a display. A portion of the three-dimensional point cloud is displayed on a second portion of the display, the second portion of the display being arranged about the periphery of the first portion of the display. Wherein a portion of the 3D point cloud displayed in the second portion represents a portion of the environment outside of a field of view of the video image.

BACKGROUND OF THE INVENTION

The subject matter disclosed herein relates to a portable scanner, and in particular to a portable scanner having a display.

A portable scanner includes a projector that projects light patterns on the surface of an object to be scanned. The position of the projector is determined by means of a projected, encoded pattern. Two (or more) cameras, the relative positions and alignment of which are known or are determined, can record images of the surface with a further, uncoded pattern. The three-dimensional coordinates (of the points of the pattern) can be determined by means of mathematical methods which are known per se, such as epipolar geometry.

In video gaming applications, scanners are known as tracking devices, in which a projector projects an encoded light pattern onto the target to be pursued, preferably the user who is playing, in order to then record this encoded light pattern with a camera and to determine the coordinates of the user. The data are represented on an appropriate display.

A system for scanning a scene, including distance measuring, may include, in its most simplest form, a camera unit with two cameras, and illumination unit and a synchronizing unit. The cameras, which may optionally include filters, are used for the stereoscopic registration of a target area. The illumination unit is used for generating a pattern in the target area, such as by means of a diffractive optical element. The synchronizing unit synchronizes the illumination unit and the camera unit. Camera unit and illumination unit can be set up in selectable relative positions. Optionally, also two camera units or two illumination units can be used.

BRIEF DESCRIPTION OF THE INVENTION

According to one aspect of the invention, a method for optically scanning and measuring an environment is provided. The method includes providing a three-dimensional (3D) measurement device having at least one camera and a projector, the 3D measurement device further having a control and evaluation device operably coupled to the at least one camera and the projector. Images of the environment are recorded with the at least one camera. A 3D scan of the environment is produced with a three-dimensional point cloud. A video image of the environment is recorded. The video image is displayed on a first portion of a display. At least a portion of the three-dimensional point cloud is displayed on a second portion of the display, the second portion of the display being arranged about the periphery of the first portion of the display. Wherein the at least a portion of the three-dimensional point cloud displayed in the second portion represents a portion of the environment outside of a field of view of the video image.

According to another aspect of the invention, a device is provided. The device includes at least two first cameras arranged a predetermined first distance apart, each of the at least two cameras configured to record images of the environment. A projector is attached a predetermined second distance from the at least two first cameras. A second camera is arranged a predetermined distance from the projector, the second camera configured to record a video image of the environment. A controller is operably coupled to the at least two first cameras, the projector and the second camera, the controller being responsive to producing a three-dimensional point cloud in response to the images recorded in the environment. A display is operably coupled to the controller, the display having a first portion displaying the video image and a second portion displaying the three-dimensional point cloud, the second portion being arranged about the periphery of the first portion, wherein the portion of the point cloud displayed in the second portion represents areas of the environment outside of a field of view of the video image.

According to yet another aspect of the invention, a method for optically scanning and measuring an environment is provided. A three-dimensional (3D) measurement device is provided having at least two cameras, the 3D measurement device further having a control and evaluation device operably coupled to the at least two cameras. Images of the environment are recorded with the at least two cameras. A 3D scan of the environment is produced with a three-dimensional point cloud. A video image of the environment is recorded. The video image is displayed on a first portion of a display. At least a portion of the three-dimensional point cloud is displayed on a second portion of the display, the second portion of the display being arranged about the periphery of the first portion of the display. Wherein the at least a portion of the three-dimensional point cloud displayed in the second portion represents a portion of the environment outside of a field of view of the video image.

DETAILED DESCRIPTION OF THE INVENTION

In one embodiment, the carrying structure is stable mechanically and thermally, defines the relative distances and the relative alignments of a camera and of a projector. The arrangement on a front side of the 3D measuring device faces on the environment, has the advantage that these distances and alignments are not changed by a change of the shape of a housing.

The term “projector” is defined to generally refer to a device for producing a pattern. The generation of the pattern can take place by means of deflecting methods, such as generation by means of diffractive optical elements or micro-lenses (or single lasers), or by shading methods, for example the production by means of shutters, transparencies (as they would be used in a transparency projector) and other masks. The deflecting methods have the advantage of less light getting lost and consequently a higher intensity being available.

Depending on the number of assemblies provided for distance measuring, a corresponding number of arms of the carrying structure is provided, which protrude from a common center. The assemblies are provided in the area of the ends of the assigned arms. The assemblies may be arranged each on the reverse side of the carrying structure. Their respective optics is directed through an assigned aperture in the carrying structure, so that the assemblies face towards the environment from the front side. A housing covers the reverse side and forms the handle part.

In one embodiment, the carrying structure consists of a carbon-reinforced or a glass-fiber-reinforced matrix of synthetic material or ceramics (or of another material). The material provides for stability and a low weight and can, at the same time, be configured with viewing areas. A concave (spherical) curvature of the front side of the carrying structure does not only have constructive advantages, but it protects the optics of the assemblies provided for distance measuring, when the front surface of the 3D measuring device is placed on a work surface.

The projector produces the projected pattern, which may not be within the visible wavelength range. In one embodiment, the projected pattern has a wavelength in the infrared range. The two cameras have a corresponding sensitiveness in this wavelength range, while scattered light and other interferences may be filtered out in the visible wavelength range. A color or 2D camera can be provided as third camera for additional information, such as color for example. Such camera records images of the environment and of the object being scanned. In an embodiment where the camera captures color, the 3D-scan can be colored with the color information thus obtained.

The 3D measuring device generates multiple 3D scans of the same scene, from different positions. The 3D scans are registered in a joint coordinate system. For joining two overlapping 3D scans, recognizable structures are advantageous. Preferably, such recognizable structures are looked for and displayed continuously or, at least after the recording process. If, in a determined area, density is not at a desired level, further 3D scans of this area can be generated. A subdivision of the display used for representing a video image and the (thereto adjacent parts of the) three-dimensional point cloud helps to recognize, in which areas scan should still be generated.

In one embodiment, the 3D measuring device is designed as a portable scanner, i.e. it works at high speed and has little weight. It is, however, also possible to mount the 3D measuring device on a tripod (or on another stand), on a manually movable trolley (or another cart), or on an autonomously moving robot, i.e. that it is not carried by the user—optionally also by using another housing, for example without handle part. It should be appreciated that while embodiments herein describe the 3D measuring device as being hand-held, this is for exemplary purposes and the claimed invention should not be so limited. In other embodiments, the 3D measuring device may also be configured as a compact unit, which are stationary or mobile and, if appropriate, built together with other devices.

Referring toFIGS. 1-6, a 3D measuring device100is provided as portable part of a device for optically scanning and measuring an environment of the 3D measuring device100with objects O. As used herein, the side which faces the user of the 3D measuring device100shall be referred to as the reverse side, and the side which faces the environment as the front side. This definition extends to the components of the 3D measuring device100. The 3D measuring device100is provided (on its front side) visibly with a carrying structure102with three arms102a,102b,102c, which give the carrying structure102a T-shape or a Y-shape, i.e. a triangle arrangement. The area in which the three arms102a,102b,102care connected with each other, and from which the three arms102a,102b,102cprotrude, defines the center of the 3D measuring device100. From the user's view, the carrying structure102is provided with a left arm102a, a right arm102band a lower arm102c. In the present case, the angle between the left arm102aand the right arm102bis, for example, approximately 150°+20°, between the left arm102aand the lower arm102capproximately 105°+10°. The lower arm102cis, in most cases, somewhat longer than the two other arms102a,102b.

The carrying structure102preferably is configured from carbon-fiber-reinforced synthetic material (CFC). In another embodiment, the carrying structure102is made from carbon-fiber-reinforced ceramics or from glass-fiber-reinforced synthetic material. The material renders the carrying structure102mechanically and thermally stable and provides at the same time for a low weight. The measurement of the carrying structure102perpendicular to the arms102a,102b,102cis considerably smaller (for example 5 to 15 mm) than the length of the arms102a,102b,102c(for example 15 to 25 cm). The carrying structure102hence has a flat basic shape, in the present case at some sections of the arms102a,102b,102c, with a reinforced back in the center. It is, however, preferably not configured to be plane, but to be curved. Such curvature of the carrying structure102is adapted to the curvature of a sphere having a radius of approximately 1 to 3 m. The front side (facing the object0) of the carrying structure102is thereby configured to be concave, the reverse side to be convex. The curved shape of the carrying structure102is advantageous for the stability. The front side of the carrying structure102(and in the present case also the visible areas of the reverse side) is configured to be a viewing area, i.e. it is not provided with hiders, covers, cladding or other kinds of packaging. The preferred configuration from fiber-reinforced synthetic materials or ceramics is particularly suitable for this purpose.

On the reverse side of the carrying structure102, a housing104is arranged, which is connected with the carrying structure102within the area of the ends of the three arms102a,102b,102cin a floating way, by means of appropriate connecting means, for example by means of rubber rings and screws with a bit of clearance. Within the area of the left arm102aand of the right arm102b, the edge of the housing104extends into the immediate vicinity of the carrying structure102, while the housing104extends from the center of the 3D measuring device100within the area of the lower arm102c, at a distance to the carrying structure102, forming a handle part104g, bends off at the end of the handle part104gand approaches the end of the lower arm102c, where it is connected with it in a floating manner, and its edge extends into the immediate vicinity of the carrying structure102. As far as, in some sections of the carrying structure102, a reinforced back102ris provided, such back102rprotrudes into the interior of the housing104. The housing104acts as a hood.

The protective elements105may be attached to the housing104or to the carrying structure102, particularly at the ends of the arms102a,102b,102c, which protect from impacts and from damage resulting thereof. If not used, the 3D measuring device100can be put down with its front side to the bottom. Due to the concave curvature of the front side, it thus comes to lie on the ends of the arms102a,102b,102c. Here, too, the protective elements105at the ends of the arms102a,102b,102care advantageous, since the 3D measuring device100comes to lie on them. Furthermore, naps from a soft material for example from rubber, which provide for a good contact with the user's hand, can optionally be attached to the housing104, particularly to the handle part104g.

On the reverse side of the housing104, a control knob106, by means of which at least optical scanning and measuring, i.e. the scanning process, can be started and stopped, is arranged in the center of the 3D measuring device100. The control knob106may be multi-functional, for example by means of sequences which are structured in terms of time and/or by means of control devices which are distinguishable in terms of space, i.e. the control knob106cannot only be pressed in one direction, but be tilted in several directions in a distinguishable manner. In one embodiment, around the control knob106there are at least one status lamp107. In one embodiment, there may be a plurality of status lamps107. These status lamps107may be used to show the actual status of the 3D measuring device100and thus facilitate the operation thereof. The status lamps107can preferably show different colors (for example green or red) in order to distinguish several status'. The status lamps107may be light emitting diodes (LEDs).

On the carrying structure102, spaced apart from each other at a defined distance, a first camera111is arranged on the left arm102a(in the area of its end), and a second camera112is arranged on the right arm102b(in the area of its end). The two cameras111and112are arranged on the reverse side of the carrying structure102and fixed thereto, wherein the carrying structure102is provided with one aperture each, through which the respective camera111,112can view out of the front side of the carrying structure102. The two cameras111,112are preferably surrounded by the connecting means for the floating connection of the housing104with the carrying structure102.

The alignments of the first camera111and of the second camera112to each other are adjusted or adjustable in such a way that the fields of view overlap and stereoscopic images of the objects O are possible. If the alignments are fixed, there is a desired overlapping range, depending on the application. With regard to precision, an overlapping range similar to the dimension of the 3D measuring device100would be favorable. Depending on environment situations, also a range of several decimeters or meters may be desired. In another embodiment, the alignments can be adjusted by the user, for example by pivoting the cameras111and112in opposite directions. The alignment can be known to the hand scanner100at any time, if the adjusting process of the user is tracked, or the alignment is initially at random (and unknown), and is then made known to the 3D measuring device100, for example, by factory calibration.

The first camera111and the second camera112are preferably monochrome, i.e. sensitive to a narrow wavelength range, for example by being provided with corresponding filters, which then filter out other wavelength ranges, including scattered light. This narrow wavelength range may also be within the infrared range. In order to obtain color information on the objects O, the 3D measuring device100preferably is additionally provided with a 2D camera, such as color camera113which is preferably aligned symmetrically to the first camera111and to the second camera112, and arranged in the center of the 3D measuring device100, between those two. The 2D camera113is then sensitive in the visible wavelength range.

In order to illuminate the scene for the 2D camera, in the event of unfavorable lighting conditions, at least one, in the illustrated embodiment four (powerful) light-emitting diodes (LED)114are provided. One radiating element115each, by means of which the light of the light-emitting diode114is deflected in correspondence with the alignment of the 3D measuring device100, is assigned to the light-emitting diodes114. Such a radiating element115can, for example, be a lens or an appropriately configured end of a light guide. The (in the present case four) radiating elements115are arranged equally around the color camera113. Each light-emitting diode114is connected with the assigned radiating element115by means of one light guide each. The light-emitting diodes114therefore can be structurally arranged at a control unit118of the 3D measuring device100, such as by being fixed on a board thereof.

In order to later have a reference for the images recorded by the cameras111,112,113, preferably an inclinometer119is provided. In one embodiment, the inclinometer119is an acceleration sensor (with one or several sensitive axes), which is manufactured in a manner known per se, as MEMS (micro-electro-mechanical system). As inclinometer119, also other embodiments and combinations are possible. The data of the 3D measuring device100each have (as one component) a gravitation direction provided by the inclinometer119.

Basically, from the images recorded by the first camera111and by the second camera112, already three-dimensional data can be determined, i.e. 3D-scans of the objects O can be produced, for example by means of photogrammetry. The objects O, however, frequently have few structures and many smooth surfaces, so that generation of 3D-scans from the scattered light of the objects O is difficult.

A projector121is therefore provided, which is arranged at the lower arm102c(in the area of its end), on the reverse side of the carrying structure102and fixed thereto, corresponding to the cameras111,112,113, i.e. the carrying structure102is provided with an aperture, through which the projector121can view out of the front side of the carrying structure102. The projector121is preferably surrounded by the connecting means for the floating connection of the housing104with the carrying structure102. The projector121, the first camera111, and the second camera112are arranged in a triangle arrangement with respect to each other and aligned to the environment of the 3D measuring device100. The projector121is aligned in correspondence with the two cameras111and112. The relative alignment is preset or can be set by the user.

If the 3D measuring device100is laid down on its front side, i.e. with the front side to the bottom, on a storage area, the concave curvature of the front side provides for the cameras111,112,113and the projector121remaining spaced apart from the storage area, i.e. the respective lenses, for example, are protected from damage.

The cameras111,112,113, the projector121, the control knob106, the status lamps107, the light-emitting diodes114and the inclinometer119are connected with the common control unit118, which is arranged inside the housing104. This control unit118can be part of a control and evaluation device which is integrated in the housing. In an embodiment, the control unit118is connected with a standardized communication interface at the housing104, the interface being configured for a wireless connection (for example Bluetooth, WLAN, DECT) as an emitting and receiving unit, or for a cable connection (for example USB, LAN), if appropriate also as a defined interface, such as that described in DE 10 2009 010 465 B3, the contents of which are incorporated by reference herein. The communication interface is connected with an external control and evaluation device122(as a further component of the device for optically scanning and measuring an environment of the 3D measuring device100), by means of said wireless connection or connection by cable. In the present case, the communication interface is configured for a connection by cable, wherein a cable125is plugged into the housing104, for example at the lower end of the handle part104g, so that the cable125extends in prolongation of the handle part104g.

The control and evaluation device122may include one or more processors122ato carry out the methods for operating and controlling the 3D measuring device100and evaluating the measured data. The control and evaluation device122may be a portable computer (notebook) or a tablet (or smartphone) such as that shown inFIGS. 7 and 8, or any external or distal computer (e.g. in the web). The control and evaluation device122may also be configured in software for controlling the 3D measuring device100and for evaluating the measured data. However, the control and evaluation device122may be embodied in separate hardware, or it can be integrated into the 3D measuring device100. The control and evaluation device122may also be a system of distributed components, at least one component integrated into the 3D measuring device100and one component externally. Accordingly, the processor(s)122afor performing said methods may be embedded in the 3D measuring device100and/or in an external computer.

The projector121projects a pattern X, which it produces, for example by means of a diffractive optical element, on the objects to be scanned. The pattern X does not need to be encoded (that is to say single-valued), but it is preferably uncoded, for example periodically, that is to say multivalued. The multi-valuedness is resolved by the use of the two cameras111and112, combined with the available, exact knowledge of the shape and direction of the pattern.

The uncoded pattern X is preferably a point pattern, comprising a regular arrangement of points in a grid. In the present invention, for example, approximately one hundred times one hundred points are projected at an angle of approximately 50° to a distance of approx. 0.5 m to 5 m. The pattern X can also be a line pattern or a combined pattern of points and lines, each of which is formed by tightly arranged light points.

There is a relationship between the point density, the distance between the projector121and the object O and the resolution that can be obtained with the produced pattern X. With diffractive pattern generation, the light of one source is distributed over the pattern. In that case the brightness of the pattern elements depends on the number of elements in the pattern when the total power of the light source is limited. Depending on the intensity of the light scattered from the objects and the intensity of background light it may be determined whether it is desirable to have fewer but brighter pattern elements. Fewer pattern elements means the acquired point density decreases. It therefore seems helpful to be able to generate, in addition to pattern X, at least one other pattern. Depending on the generation of the patterns, a dynamic transition between the patterns and/or a spatial intermingling is possible, in order to use the desired pattern for the current situation. In an embodiment, the projector121may produce the two patterns offset to each other with respect to time or in another wavelength range or with different intensity. The other pattern may be a pattern which deviates from pattern X, such as an uncoded pattern. In the illustrated embodiment the pattern is a point pattern with a regular arrangement of points having another distance (grid length) to each other.

For reasons of energy efficiency and eye protection, the projector121produces the pattern X on the objects O only, when the cameras111and112(and if available113) record images of the objects O which are provided with the pattern X. For this purpose, the two cameras111,112and the projector121are synchronized, i.e. coordinated internally with each other, with regard to both, time and the pattern X used. Each recording process starts by the projector121producing the pattern X, similar to a flash in photography, and the cameras111and112(and, if available113) following with their records, more particularly their pairs of records (frames), i.e. one image each from each of the two cameras111,112. The recording process can comprise one single frame (shot), or a sequence of a plurality of frames (video). Such a shot or such a video is triggered by means of the control knob106. After processing of the data, each frame then constitutes a 3D-scan, i.e. a point cloud in the three-dimensional space, in relative coordinates of the 3D measuring device100.

The data furnished by the 3D measuring device100are processed in the control and evaluation device122, i.e. the 3D scans are generated from the frames. The 3D scans in turn are joined, i.e. registered in a joint coordinate system. For registering, the known methods can be used, i.e. natural or artificial targets (i.e. recognizable structures) can be localized and identified for example in overlapping areas of two 3D scans, in order to determine the assignment of the two 3D scans by means of corresponding pairs. A whole scene is thus gradually registered by the 3D measuring device100. The control and evaluation device122is provided with a display130(display device), which is integrated or connected externally.

One embodiment of the display130shown inFIG. 7illustrates a subdivided image or subdivided screen. In this embodiment, the display130is divided into a first display part130aand a second display part130b. In the present embodiment, the first display part130ais a (rectangular) central part of the display130, and the second display part130bis a peripheral area around the first display part130a. In another embodiment, the two display parts may be columns. In the embodiment illustrated inFIGS. 7-9, the first display part130ais shown as having a rectangular shape, however this is for exemplary purposes and the claimed invention should not be so limited. In other embodiments, the first display part130amay have other shapes, including but not limited to circular, square, trapezoid (FIG. 10), trapezium, parallelogram, oval, triangular, or a polygon having any number of sides. In one embodiment, the shape of the first display part130ais user defined or selectable.

In the first display part130aa video live image VL is displayed, such as that captured by 2D camera113for example. In the second display part130b, an image of the latest 3D scan (or a plurality of 3D scans that have been registered) is displayed as at least part of a view of the three-dimensional point cloud 3DP. The size of the first display part130amay be variable, and the second display part130bis arranged in the area between the first display part130aand the border131of the display130. As video live image VL changes, such as when the user moves the device100, the image of the three-dimensional point cloud 3DP changes correspondingly to reflect the change in position and orientation of the device100.

It should be appreciated that the placement of the image of the three-dimensional point cloud 3DP around the periphery of the video live image VL provides advantages in allowing the user to easily see where additional scanning may be required without taking their eyes off of the display130. In addition it may be desirable for the user to determine if the computational alignment of the current camera position to the already acquired 3D data is within a desired specification. If the alignment is outside of specification, it would be noticed as discontinuities at the border between the image and the three-dimensional point cloud 3DP. Referring now toFIG. 9, it can be seen that during a scanning operation some areas, such as areas140,142have a high density of points that allow for a representation of an object at a desired accuracy level. The user will be able to observe that other areas, such as areas144,146have lower point densities. The user may then determine whether additional scanning needs to be performed. For example, area144may be a table top where a generally low density of points may be acceptable. The user may determine that other areas, such as area146for example, may require additional scanning since the object has not been completely captured.FIG. 10illustrates a computer generated image of a scanning process, it should be appreciated that the image of the three-dimensional point cloud 3DP is variable and continuously changes, which could make it difficult for a user to determine when additional scanning is needed. Thus the video live image VL and the image of the three-dimensional point cloud 3DP cooperate to guide the user during the scanning process.

The image acquired by the camera113is a two-dimensional (2D) image of the scene. A 2D image that is rendered into a three-dimensional view will typically include a pincushion-shaped or barrel-shaped distortion depending on the type of optical lens used in the camera. Generally, where the field of view (FOV) of the camera113is small (e.g. about 40 degrees), the distortion is not readily apparent to the user. Similarly, the image of the three-dimensional point cloud data may appear distorted depending on how the image is processed for the display. The point cloud data 3DP may be viewed as a planar view where the image is obtained in the native coordinate system of the scanner (e.g. a spherical coordinate system) and mapped onto a plane. In a planar view, straight lines appear to be curved. Further, the image near the center-top and center-bottom edges (e.g. the poles) may be distorted relative to a line extending along the midpoint of the image (e.g. the equator). Further, there may also be distortions created by trying to represent a spherical surface on a rectangular grid (similar to the Mercator projection problem).

It should be appreciated that it is desired to have the images within the first display part130aappear to be similar to that in the second display part130bto provide a continuous and seamless image experience for the user. If the image of three-dimensional point cloud 3DP is significantly distorted, it may make it difficult for the user to determine which areas could use additional scanning. Since the planar image of the point cloud data 3DP could be distorted relative to the 2D camera image, one or more processing steps may be performed on the image generated from the point cloud data 3DP. In one embodiment, the field of view (FOV) of the second display part130bis limited so that only the central portion of the planar image is shown. In other words, the image is truncated or cropped to remove the highly distorted portions of the image. Where the FOV is small (e.g. less 120 degrees), the distortion is limited and the planar view of the point cloud data 3DP will appear as desired to the user. In one embodiment, the planar view is processed to scale and shift the planar image to provide to match the camera113image in the first display part130a.

In another embodiment, the three-dimensional point cloud data 3DP is processed to generate a panoramic image. As used herein, the term panoramic refers to a display in which angular movement is possible about a point in space (generally the location of the user). A panoramic view does not incur the distortions at the poles as is the case with a planar view. The panoramic view may be a spherical panorama that includes 360 degrees in the azimuth direction and +/−45 degrees ion the zenith. In one embodiment the spherical panoramic view may be only a portion of a sphere.

In another embodiment, the point cloud data 3DP may be processed to generate a 3D display. A 3D display refers to a display in which provision is made to enable not only rotation about a fixed point, but also translational movement from point to point in space. This provides advantages in allowing the user to move about the environment and provide a continuous and seamless display between the first display part130aand the second display part130b.

In one embodiment, the video live image VL in the first display part130aand the image of the three-dimensional point cloud 3DP in the second display part130bmatch together seamlessly and continuously (with respect to the displayed contents). A part of the three-dimensional point cloud 3DP is first selected (by the control and evaluation device122) in such a way, as it is regarded from the perspective of the 2D camera113or at least from a position aligned with the 2D camera113. Then, the selected part of the three-dimensional point cloud 3DP is selected in such a way that it adjoins continuously the video live image VL. In other words, the displayed image of the three-dimensional point cloud 3DP becomes a continuation of the video live image VL for the areas beyond the field of view of the 2D camera113on the left, on the right, top and bottom relative to the field of view of the 2D camera). As discussed above, the selected portion of the three-dimensional point cloud 3DP may be processed to reduce or eliminate distortions. In other embodiments, the representation may correspond to the representation of a fish-eye lens, but preferably it is undistorted. The part of the three-dimensional point cloud 3DP which is located in the area occupied by the first display part130a, in other words the portion beneath or hidden by the video live image VL, is not displayed.

It should be appreciated that the density of the points in the three-dimensional point cloud 3DP in the area where the first display part130ais located will not be visible to the user. Normally, the video live image VL is displayed using the natural coloring. However, in order to indicate the density of the points in the area covered/behind by the video live image VL, the coloring of the video live image VL may be changed artificially such as by overlaying for example. In this embodiment, the artificial color (and, if appropriate, the intensity) used for representing the artificially colored video live image VL corresponds to the density of the points. For example, a green coloring to the video live image VL may indicate a (sufficiently) high density while a yellow coloring may be used to indicate a medium or low point density (e.g. areas which still the scan data can be improved). In another embodiment, the distant-depending precision of the data points could be displayed using this color-coding.

To support the registration of the 3D scans, flags or marks133(FIG. 7andFIG. 8) may be inserted in the first display part130ato indicate structures (i.e. possible targets) recognized by the control and evaluation device122. The marks133may be a symbol, such as a small “x” or “+” for example. The recognizable structures can be points, corners, edges or textures of objects. The recognizable structures may be found by the latest 3D scan or the video live image VL being subjected to the beginning of the registering process (i.e. to the localization of targets). The use of the latest video live image VL provides advantages in that the registration process does not have to be performed as frequently. If the marks133have a high density, it is considered to be a successful registration of the 3D scans. If, however, a lower density of the marks133is recognized, additional 3D scans may be performed using a relatively slow movement of the 3D measuring device100. By slowing the movement of the device100during the scan, additional or higher density points may be acquired. Correspondingly, the density of the marks133may be used as a qualitative measure for the success of the registration. Similarly, the density of the points of the three-dimensional point cloud 3DP may be used to indicate a successful scan. As discussed above, the density of points in the scan may be represented by the artificial coloring of the video live image VL.

The movement of the 3D measuring device100and processing of the captured frames may also be performed by a tracking function, i.e. the 3D measuring device100tracks the relative movement of its environment with the methods used during tracking. If tracking gets lost, for example, if the 3D measuring device100has been moved too fast, there is a simple possibility of reassuming tracking. In this embodiment, the video live image VL as it is provided by the 2D camera113and the last video still image from tracking provided by it may be represented adjacent to each other in a side by side arrangement on the display130for the user. The user may then move the 3D measuring device100until the two video images coincide.

In one embodiment, the 3D measuring device100may be controlled based on movements of the device100. These movements or gestures by the user can also be used for controlling the representation of the video image VL or of the three-dimensional point cloud 3DP. In one embodiment, the scale of representation of the video image VL and/or of the three-dimensional point cloud 3DP on the display130may depend on the speed and/or acceleration of the movement of the 3D measuring device100. The term “scale” is defined as the ratio between the size (either linear dimension or area) of the first display part130aand the size of the complete display130, being denoted as a percentage.

A small field of view of the 2D camera113is assigned to a small scale. In the present embodiment with a subdivided display130with a central first display part130ashowing the video live image VL, this first display part130athen may be of smaller size than in the standard case, and the second display part130b(about the periphery of the first display part130a) shows a bigger part of the three-dimensional point cloud 3DP. A larger field of view is assigned to a large scale. In one embodiment, the video live image VL may fill the whole display130.

In the event of high speeds of movement of the 3D measuring device100are detected, the scale of the representation may be configured smaller than with low speeds and vice versa. Similarly, this may apply to accelerations of the movement of the 3D measuring device100. For example, the scale of the displayed image is reduced in the case of positive accelerations, and the scale is increased in the case of negative accelerations. The scale may also depend on a component of the speed and/or acceleration of the movement of the 3D measuring device100, for example on a component which is arranged perpendicular or parallel to the alignment of the 3D measuring device100. If the scale is determined based on a component of the movement, parallel to the alignment (i.e. in the direction of the alignment), the scale can also be made dependent on the change of an average distance to objects O from the 3D measuring device100.

In some embodiments, the change of the scale due to movement, a standstill of the movement of the 3D measuring device100or a threshold speed of movement value not being achieved can be used to record a sequence of still images of the camera113with a low dynamic range. These images may be captured at low dynamic range but with different exposure times or illumination intensities within the sequence to generate a high dynamic range image therefrom.

In some embodiments, the direction of gravity may be defined at the beginning of the registration process by a defined movement of the 3D measuring device100. This defined movement is carried out by the user by moving the device100in a vertical upward and downward movement for example. In other embodiments, the direction of gravity may be determined from a set of statistics of all movements during the registration process. A plane may be averaged from the coordinates of the positions taken by the device100while recording process along a path of movement through space. It is assumed that the averaged plane is located horizontally in space, meaning that the direction of gravity is perpendicular to it. As a result, the use of inclinometer119for determining the direction of gravity may be avoided.

The evaluation of the coordinates of the positions may also be used for determining the kind of scene and, if appropriate, to offer different representations or operating possibilities. A path of movement around a center location (with an alignment of the 3D measuring device100oriented towards the interior), suggests an image of a single object O (object-centered image). Similarly, a path of movement that orients the device100towards the outside (and particularly longer straight sections of the path of movements) makes reference to an image of rooms. Thus, where it is determined that a room is being scanned, an image of a floor plan (top view) may be inserted into the display130.