Abstract:
A laser scanner or a laser tracker includes a light source that emits a light beam within an environment, and a data capture component that captures the light beam reflected back to the laser scanner or tracker from the environment. The laser scanner or tracker also includes a projector integrated within a body of the laser scanner or tracker or mounted to the body of the laser scanner or tracker at a predetermined location, the projector being operable to project visible information onto an object located within the environment, the projected visible information being indicative of images, data or information, the projected visible information being at least one of design intent information, information acquired by the laser scanner or tracker, or guidance to an operator.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to U.S. Provisional Application No. 61/380,869, filed on Sep. 8, 2010; and to U.S. Non-Provisional application Ser. No. 13/006,507, filed on Jan. 14, 2011; which claims the benefit of priority to U.S. Provisional Application No. 61/296,555 filed on Jan. 20, 2010, to U.S. Provisional Application No. 61/351,347 filed on Jun. 4, 2010 and to U.S. Provisional Application No. 61/355,279 filed on Jun. 16, 2010. The present application also claims priority to U.S. Non-Provisional application Ser. No. 13/006,468, filed on Jan. 14, 2011; which claims the benefit of priority to U.S. Provisional Application No. 61/296,555 filed on Jan. 20, 2010, to U.S. Provisional Application No. 61/351,347 filed on Jun. 4, 2010 and to U.S. Provisional Application No. 61/355,279 filed on Jun. 16, 2010. The present application also claims priority to U.S. Non-Provisional application Ser. No. 13/006,524, filed on Jan. 14, 2011; which claims the benefit of priority to U.S. Provisional Application No. 61/296,555, filed on Jan. 20, 2012; the entire contents of each which are incorporated herein by reference. 
     FIELD OF THE INVENTION 
     The present invention relates to coordinate measurement devices, for example, laser scanners, laser trackers, and total stations, and more particularly to laser scanners and laser trackers having one or more relatively small projectors integrated therewith or added thereto by, e.g., mounting thereon, for projecting visual information in the form of images and/or data (e.g., CAD data or scanned point cloud data) onto various surfaces. The projected visual information may, for example, be of a type such as to provide guidance to an operator, such as written instructions, highlighted points to be measured, indicated areas where data are to be taken, and real time feedback on the quality of the data. 
     BACKGROUND 
     A laser scanner is one type of coordinate measurement device typically used for non-contact optical scanning of many different types of relatively large closed or open spaces or objects, for example, interior spaces of buildings, industrial installations and tunnels, or exterior shapes of planes, automobiles or boats. Laser scanners can be used for many different purposes, including industrial applications and accident reconstruction. A laser scanner optically scans and measures the environment around the laser scanner by emitting a rotating laser beam and detecting the laser beam as it is reflected back from the various objects in its path. Laser scanners typically collect a variety of data points with respect to the environment, including distance information for each object in its surrounding environment, a grey scale value (i.e., a measure of the intensity of light) for each distance measurement value, and coordinates (e.g., x, y, and z) for each distance measurement value. This scan data is collected, stored and sent to a processor that is typically remote from the laser scanner, where the data is processed to generate a three dimensional (3D) scanned image of the scanned environment with measurements. In order to generate the 3D scanned image, at least four values (x, y, z coordinates and grey scale value) are collected for each scanned data point. 
     Many contemporary laser scanners also include a camera mounted on the laser scanner for gathering digital images of the environment and for presenting the digital images to an operator of the laser scanner. The images can be oriented together with the scanned data to provide a more realistic image of the object being scanned. By viewing the images, the operator of the scanner can determine the field of view of the scanned data, and can adjust the settings on the laser scanner if the field of view needs adjusting. In addition, the digital images may be transmitted to the processor to add color to the 3D scanned image. In order to generate a 3D color scanned image, at least six values (x, y, z coordinates; and red value, green value, blue value or “RGB”) are collected for each data point. Examples of laser scanners are disclosed in U.S. Pat. No. 7,193,690 to Ossig et al.; U.S. Pat. No. 7,430,068 to Becker et al.; and U.S. Published Patent Application No. US2010/0134596 to Becker; each being incorporated by reference herein. 
     Another type of coordinate measurement device is a laser tracker, which measures the 3D coordinates of a certain point by sending a laser beam to the point, where the laser beam is typically intercepted by a retroreflector target. The laser tracker finds the coordinates of the point by measuring the distance and the two angles to the target. The distance is measured with a distance-measuring device such as an absolute distance meter (ADM) or an interferometer. The angles are measured with an angle-measuring device such as an angular encoder. A gimbaled beam-steering mechanism within the instrument directs the laser beam to the point of interest. The retroreflector may be moved manually by hand, or automatically, over the surface of the object. The laser tracker follows the movement of the retroreflector to measure the coordinates of the object. Exemplary laser trackers are disclosed in U.S. Pat. No. 4,790,651 to Brown et al., incorporated by reference herein; and U.S. Pat. No. 4,714,339 to Lau et al. The total station, which is most often used in surveying applications, may be used to measure the coordinates of diffusely scattering or retroreflective targets. The total station is closely related to both the laser tracker and the scanner. 
     A common type of retroreflector target is the spherically mounted retroreflector (SMR), which comprises a cube-corner retroreflector embedded within a metal sphere. The cube-corner retroreflector comprises three mutually perpendicular mirrors. The apex of the cube corner, which is the common point of intersection of the three mirrors, is located at the center of the sphere. It is common practice to place the spherical surface of the SMR in contact with an object under test and then move the SMR over the surface of the object being measured. Because of this placement of the cube corner within the sphere, the perpendicular distance from the apex of the cube corner to the surface of the object under test remains constant despite rotation of the SMR. Consequently, the 3D coordinates of the object&#39;s surface can be found by having a tracker follow the 3D coordinates of an SMR moved over the surface. It is possible to place a glass window on the top of the SMR to prevent dust or dirt from contaminating the glass surfaces. An example of such a glass surface is shown in U.S. Pat. No. 7,388,654 to Raab et al., incorporated by reference herein. 
     A gimbal mechanism within the laser tracker may be used to direct a laser beam from the tracker to the SMR. Part of the light retroreflected by the SMR enters the laser tracker and passes onto a position detector. The position of the light that hits the position detector is used by a tracker control system to adjust the rotation angles of the mechanical azimuth and zenith axes of the laser tracker to keep the laser beam centered on the SMR. In this way, the tracker is able to follow (track) the SMR as it is moved. 
     Angular encoders attached to the mechanical azimuth and zenith axes of the tracker may measure the azimuth and zenith angles of the laser beam (with respect to the tracker frame of reference). The one distance measurement and two angle measurements performed by the laser tracker are sufficient to completely specify the three-dimensional location of the SMR. 
     As mentioned, two types of distance meters may be found in laser trackers: interferometers and absolute distance meters (ADMs). In the laser tracker, an interferometer (if present) may determine the distance from a starting point to a finishing point by counting the number of increments of known length (usually the half-wavelength of the laser light) that pass as a retroreflector target is moved between the two points. If the beam is broken during the measurement, the number of counts cannot be accurately known, causing the distance information to be lost. By comparison, the ADM in a laser tracker determines the absolute distance to a retroreflector target without regard to beam breaks, which also allows switching between targets. Because of this, the ADM is said to be capable of “point-and-shoot” measurement. Initially, absolute distance meters were only able to measure stationary targets and for this reason were always used together with an interferometer. However, some modern absolute distance meters can make rapid measurements, thereby eliminating the need for an interferometer. Such an ADM is described in U.S. Pat. No. 7,352,446 to Bridges et al., incorporated by reference herein. The distances measured by interferometers and absolute distance meters are dependent on the speed of light through air. Since the speed of light varies with air temperature, barometric pressure, and air humidity, it is common practice to measure these quantities with sensors and to correct the speed of light in air to obtain more accurate distance readings. The distances measured by total stations and scanners also depend on the speed of light in air. 
     In its tracking mode, the laser tracker automatically follows movements of the SMR when the SMR is in the capture range of the tracker. If the laser beam is broken, tracking will stop. The beam may be broken by any of several means: (1) an obstruction between the instrument and SMR; (2) rapid movements of the SMR that are too fast for the instrument to follow; or (3) the direction of the SMR being turned beyond the acceptance angle of the SMR. By default, following the beam break, the beam may remain fixed at the point of the beam break, at the last commanded position, or may go to a reference (“home”) position. It may be necessary for an operator to visually search for the tracking beam and place the SMR in the beam in order to lock the instrument onto the SMR and continue tracking. 
     Some laser trackers include one or more cameras. A camera axis may be coaxial with the measurement beam or offset from the measurement beam by a fixed distance or angle. A camera may be used to provide a wide field of view to locate retroreflectors. A modulated light source placed near the camera optical axis may illuminate retroreflectors, thereby making them easier to identify. In this case, the retroreflectors flash in phase with the illumination, whereas background objects do not. One application for such a camera is to detect multiple retroreflectors in the field of view and measure each retroreflector in an automated sequence. Exemplary systems are described in U.S. Pat. No. 6,166,809 to Pettersen et al., and U.S. Pat. No. 7,800,758 to Bridges et al., incorporated by reference herein. 
     Some laser trackers have the ability to measure with six degrees of freedom (DOF), which may include three coordinates, such as x, y, and z, and three rotations, such as pitch, roll, and yaw. Several systems based on laser trackers are available or have been proposed for measuring six degrees of freedom. Exemplary systems are described in U.S. Pat. No. 7,800,758 to Bridges et al., U.S. Pat. No. 5,973,788 to Pettersen et al., and U.S. Pat. No. 7,230,689 to Lau. 
     It is desirable to provide a laser scanner or a laser tracker with one or more projectors, with each projector projecting visual information in the form of images and/or data (e.g., CAD data or scanned point cloud data) onto various surfaces. The projected visual information may, for example, be of a type such as to provide guidance to an operator, such as written instructions, highlighted points to be measured, indicated areas where data are to be taken, and real time feedback on the quality of the data. 
     SUMMARY OF THE INVENTION 
     According to an aspect of the present invention, a laser scanner includes a light source that emits a light beam within an environment, and a data capture component that captures the light beam reflected back to the laser scanner from the environment. The laser scanner also includes a projector integrated within a body of the laser scanner or mounted to the body of the laser scanner at a predetermined location, the projector being operable to project visible information onto an object located within the environment, the projected visible information being indicative of images, data or information, the projected visible information being at least one of design intent information, information acquired by the laser scanner, or guidance to an operator. 
     According to another aspect of the present invention, a laser tracker includes a light source that emits a light beam towards a target located within an environment, and a data capture component that captures the light beam reflected back to the laser scanner from the target located within the environment. The laser tracker also includes a projector integrated within a body of the laser tracker or mounted to the body of the laser tracker at a predetermined location, the projector being operable to project visible information onto an object located within the environment, the projected visible information being indicative of images, data or information, the projected visible information being at least one of design intent information, information acquired by the laser tracker, or guidance to an operator. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Referring now to the drawings, exemplary embodiments are shown which should not be construed to be limiting regarding the entire scope of the disclosure, and wherein the elements are numbered alike in several FIGURES: 
         FIG. 1  is a front cross sectional view of a head portion of a laser scanner having a projector integrated therein in accordance with embodiments of the present invention; 
         FIG. 2  is an optical schematic view of the head portion of a laser scanner of  FIG. 1  having a projector integrated therein in accordance with embodiments of the present invention; 
         FIG. 3  is a front cross sectional view of a head portion of a laser scanner having a projector externally mounted to the head portion in accordance with embodiments of the present invention; 
         FIG. 4  are two views showing visualization of movement over time of the Tower of Pisa using a projected image of the Tower of Pisa earlier in time utilizing the laser scanner having the projector according to the embodiments of  FIGS. 1-3 ; 
         FIG. 5  shows a laser scanner with a projector according to embodiments of the present invention projecting “hidden features” onto a surface such as a wall; 
         FIG. 6  is a perspective view of a laser tracker having a projector integrated therein in accordance with embodiments of the present invention; 
         FIG. 7  is a perspective view of the laser tracker of  FIG. 6  having computing and power supply elements attached thereto; 
         FIG. 8  is a perspective view of the laser tracker of  FIG. 6  projecting a pattern onto a surface of an object or workpiece according to embodiments of the present invention; 
         FIG. 9  is a block diagram of various components including a projector within a portion of the laser tracker of  FIG. 6  according to embodiments of the present invention; 
         FIG. 10  is a block diagram of various components including a projector within a portion of the laser tracker of  FIG. 6  according to other embodiments of the present invention; and 
         FIG. 11  is a perspective view of alternative embodiments of the laser tracker of  FIG. 6  with an external projector projecting a pattern onto a surface of an object or workpiece. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to  FIG. 1 , in accordance with embodiments of the present invention, there illustrated is a rotating scanning head portion  10  of a laser scanner  12  having a commercially available, relatively small or “miniature,” “ultraminiature,” or “pico” projector  14  integrated directly within the optical components (“optics”) located within the scanner head  10 . The projector  14  may contain some amount of processing capability, as is known. The projector  14  may be connected with, or in communication with, a first computer or processor  15  of the laser scanner  12 , where the computer or processor may be integral with the scanner  12  (e.g., located within the scanner head  10 ) or may be a second separate computer or processor  17  therefrom (e.g., a laptop computer). The scanner head  10  is typically mounted to a supporting tripod (not shown), which sits on the ground or other surface during laser scanner use. As described in more detail with respect to  FIG. 2 , the projector  14  sends various images, data or other information through the optics within the scanner head  10  and onto a rotating scanning mirror  16  that typically rotates relatively quickly through 360 degrees about a horizontal axis through the head  10 , wherein the mirror  16  projects the images, data or other information towards a surface (not shown) for viewing. The scanner head  10  itself may rotate relatively more slowly through 360 degrees about a vertical axis through the head  10 . 
     Various embodiments of the present invention include the integration or addition of such a relatively small image or data projector into equipment generally used for 3D measurement or metrology, including but not limited to, a laser scanner, laser tracker, white light scanner or similar type technological device or instrument. In embodiments of the present invention, the projector may be integrated within the laser scanner  12  or laser tracker, and the projected images, data or other information are controlled using data or information from the measurement equipment  12  itself, data or information previously captured by the measurement equipment  12 , or data or information from some other source. As described in detail hereinafter, the projected images or data provide visualization of various types of information that is useful during a measurement session, or the projected images or data can assist in visualization of data previously taken by the equipment  12 . The projected visual information may, for example, be of a type such as to provide guidance to an operator, such as written instructions, highlighted points to be measured, indicated areas where data are to be taken, and real time feedback on the quality of the data. This visual information provided to the operator may, for example, be in the form of visual cues, text or some other visual form of information. 
     Further, the projector may comprise one or more commercially available galvanometers or polygon scanners rather than one of the types of projectors mentioned herein above, for example, a miniature, ultraminiature, or pico-projector which might be based, for example, on microelectromechanical systems (MEMS) technology, liquid crystal display (LCD) or liquid crystal on silicon (LCOS) technology. For example, typically two galvanometers or two polygon scanners are used with associated mirrors to project the desired image, data, or information, in a desired pattern in two dimensions onto the surface of interest. In the case of a laser scanner  12 , the galvanometer mirrors project the images or other information onto the rotating mirror where they are reflected off of towards the object of interest. The rotation of the main mirror in the laser scanner  12  and the rotation of the galvanometer mirror also in the laser scanner  12  creating the image or other projected information would be synchronized. As such, the laser scanner creates the images in the same way that images are generated for laser light shows. In the case of a laser tracker (discussed in more detail hereinafter), the galvanometer mirrors would project the images or other information directly onto the target of interest. The size of the pattern projected by a projector disposed on the tracker may be expanded by moving the tracker head to cover a relatively large area while, at the same time, dynamically changing the pattern from the projector to produce the desired image over a relatively large region of space. This way, the head of the laser tracker acts like a galvanometer mirror. When used, the galvanometers or polygon scanners may provide a relatively more powerful, brighter and more efficient laser beam for image or data projection purposes as compared to the light from a pico projector. 
     In many cases, it is advantageous to provide a focusing mechanism to make the projected image as sharp as possible on the surface of the object to which the two-dimensional pattern is projected. The focusing mechanism will generally include a mechanical actuator for moving one or more lenses. 
     With MEMS, LCD, LCOS, and other types of pico-projectors, it is common today to provide color projection patterns. Color may be used advantageously in providing information about an object. 
     Laser scanners and laser trackers frequently employ optics, sensors, mirrors, and/or laser sources mounted to motors and/or gimbals such that the scanner or tracker instrument or device  12  can automatically scan a large area or object or track a movable target (e.g., a retroreflector) within the working volume of the device  12  without the need to manually aim or move the sensor modules of the device  12 . 
     Referring to  FIG. 2 , in some embodiments of a laser scanner  10 , the laser light emitted from a laser light source  18  can be directed through use of a mirror  20 . Techniques are known that allow the reflective surface of a mirror  20  to be coated in such a way (e.g., “dichroic” coating) as to reflect light at the wavelength of the source laser  18  while passing light of other wavelengths. Such embodiments allow a miniature projector  14  to be mounted behind an angled mirror  20  that reflects the laser beam emitted from the laser  18  to the rotating scanning mirror  16  ( FIG. 1 ). In the embodiment shown in  FIG. 2 , the motors, encoders and drive circuitry used to point the laser beam also simultaneously direct the beam of the projector  14  via the scanning mirror  16  ( FIG. 1 ). 
     Thus, in some embodiments, the computer or processor associated with the laser scanner  12  may be required to perform some mathematical calculations to correctly locate the image or data from the projector  14  onto the rotating scanning mirror  16 . These calculations should be apparent to one of ordinary skill in the art. That is, the projected image or data is compensated for to account for the rotation of the mirror  16  so that the image or data is not distorted or smeared. For example, the image projected by the projector  14  onto the mirror  16  may be changed dynamically to provide an image that is stationary on a projection surface (e.g., a wall). The mirror  16  typically is made to rotate, in part, for laser safety reasons. In alternative embodiments, the laser that provides the laser beam to the rotating scanning mirror  16  for metrology purposes may be turned off, the mirror  16  may be held in a stationary position, and then the projector  14  may provide the relatively weaker light that comprises the image or data to the mirror  16 . In these embodiments, no mathematical corrections for the now stationary mirror  16  are typically needed. In some cases, the size of the image projected onto the reflective surface of the mirror  16  is adjusted according to the distance from the scanner to the projection surface. This would be the case, for example, if the projector were to emit a diverging pattern of light and if the image on the projection surface were intended to have a fixed size. In this case, the distance measuring capability of the scanner may provide the information needed to enable the projector  14  to correctly size the projected image. 
     The image, data or other information projected from the projector  14  onto the surface of interest may have its timing controlled such that the image, data or other information may be mechanically or electronically strobed to coincide with certain angles of the rotating scanning mirror  16 . Also, the laser beam used by the scanner  12  for metrology purposes may be provided in a mutually exclusive manner (e.g., multiplexed) with respect to the image, data or other information provided from the projector  14 . That is, the laser beam and the projected light pattern or data may not be “on” (i.e., projected) at the same time, as that condition may not be necessary. Alternatively, the laser beam and the projected light pattern may be on at the same time. Typically, the projecting mode of the laser scanner  12 , according to embodiments of the present invention, is not tied to or dependent upon the scanning mode of the scanner  12 . 
     Referring to  FIG. 3 , in other embodiments of the present invention, the projector  14  can be mounted to multi-axis, motorized gimbals  22 , for example, on top of the laser scanner head  10 , as an alternative to being installed in-line with the measurement optics of the laser scanner  12  as in the embodiments of  FIGS. 1 and 2 . This allows the projection system  14  to be added to existing laser scanner equipment  12  that may not support the full integration embodiments of  FIGS. 1 and 2 . The embodiment of  FIG. 3  may in some situations be simpler and less expensive to implement. In such an embodiment, the gimbals  22  upon which the projector  14  is mounted may be driven and aimed in synchronization with the optics of the 3D measurement device  12 , thus assuring that the projector image is pointed to the same area that is of interest in taking measurements by the laser scanner  12 . This has advantages when using the projector  12  for guidance or data presentation. Alternately, the independently mounted projector  14  may be commanded to project images in an area different than the primary device optics. 
     The position and orientation of a 3D metrology device such as a 3D laser scanner  12  or laser tracker relative to an object, part or structure to be measured may be established by identification of reference points or part or object features using known techniques. Once the coordinate system has been established, both the 3D metrology device (e.g., the laser scanner)  12  and the projector  14  can be synchronized and controlled with a relatively high degree of precision by an external computer connected to the device  12  as part of the device  12 , or an on-board computer as part of the device  12  that can process the device position and control the orientation of the device optics. This allows the projected image to be shaped, scaled and controlled to match the surface onto which it projected, and it allows the image to update as the direction of the projector  14  changes such that it is always synchronized and locked to the environment. 
     Various implementations or usages of a projector  14  integrated within, or mounted to, a computer controlled 3D measurement device such as a laser scanner  12  according to embodiments of the present invention include, but are not limited to, projecting data, text, instructions, images or guidance in the form of, for example, visual cues or text or other forms of information on the surface of a part to be measured. They may also include providing a projected overlay of previously scanned/measured data or CAD data showing design intent for visualization of changes to a part or parameters. For 3D scanned data this may include: (1) comparison of a car body before and after an accident or before and after repair; (2) comparison of the CAD design of a planned equipment installation compared to the actual completed installation; (3) visualization of a proposed change to a part, equipment set-up, assembly line, wall, or building; (4) visualization of a part design compared to a drawing as a method of inspection; (5) visualization of hidden features ( FIG. 5 ) such as studs, piping, electrical wiring and duct works behind a wall, ceiling or floor by projecting CAD data of the design, or scans taken during construction, onto the visible surface; (6) visualization of elements beneath the skin of the human or animal body by projecting an image of a 3D CAT scan, 3D X-ray or other 3D diagnostic data onto the body, which can provide visual assistance in locating organs, tumors, blood vessels, bones, or other physiological features as part of a surgical procedure; (7) visualization of crime scenes, before and after; (8) projection of contour maps onto a part, thereby indicating regions of the part that need to be removed, for example, by filing, sanding, or lapping, or filled in, for example, with epoxy filler; (9) projection of marks indicating areas in which subcomponents should be attached to the object, for example, with bolts, screws, or adhesive; (10) projection of lines, curves, marks, or fiducial features for aid in aligning of components; and (11) visualization of degradation or movement over time (via sequential scans) of archaeological sites, historic buildings, bridges, railways, roads, and other facilities that are subject to wear, settling, decomposition, weathering, or general deterioration over time, as illustrated, for example, in  FIG. 4 , which can be extended to the examination and visualization of wear and damage to large vehicles like ships, aircraft, spacecraft (e.g. space shuttle tiles). Specifically, the sole view  400  in  FIG. 4A  and the right hand leaning view  400  in  FIG. 4  shows the Tower of Pisa tilted to the right side as viewed in  FIGS. 4A and 4B , and also having a upright vertical image  410  of the Tower (shown in dotted lines in  FIG. 4B ) projected (in part) onto the leaning tower view  400  in  FIG. 4B  by the laser scanner  12  having the projector  14 , according to various embodiments of the present invention. This illustrates the amount of movement or “tilt” to the right of the Tower of Pisa over time. Note that normally one would not see the left-hand (dotted line) portion of the upright vertical image  410  of the Tower since it would not be projected onto the tilted Tower nor would be projected onto any other surface. That is, this dotted line left-hand portion of the upright vertical image  410  of the Tower would be projected in free space. Instead, one would normally only see the shaded or filled in right-hand portion of the upright vertical image  410  projected onto the Tower  400 . In  FIG. 4B  the entire upright vertical image  410  of the Tower is shown for exemplary purposes only. 
     To further extend the usefulness of the controlled projected image, multiple projectors  14  may be incorporated into a single device such as a laser scanner  12 . This allows for a potential increase in the range of image coverage, ultimately to 360 degrees around the scanning device, with the possible exception of relatively small areas blocked by the laser scanner itself (e.g., at the location where the scanner head  10  attaches to the tripod). 
     In other embodiments of the present invention, synchronized images may be generated by multiple projectors  14  mounted independently of the laser scanner  12  or laser tracker, for example, on gimbaled computer controlled mounts or in fixed positions measured and known to the laser scanner  12  or tracker. In these embodiments, each projector  14  may be controlled by the laser scanner  12  or tracker, or by a computer attached to the laser scanner  12  or tracker and used to establish the coordinate system of the area. These embodiments may provide for relatively broader simultaneous coverage by the projected images while also supporting image projection in areas that might otherwise be blocked by equipment or features, including by the laser scanner  12  itself. Images projected by this array of projectors  14  can then be managed and controlled by the central computer or laser scanner  12  or other metrology device such that the projected images or data or other information is scaled, sized and properly aligned to the objects in the environment. For example, the projector  14  projects images, data or other information that is related to the direction and/or orientation that the laser scanner  14  is currently pointed to. As an example, the movement of a person or other object may be tracked by the laser scanner  14  and then images or data may be projected by the laser scanner  12  with the projector  14  according to the position and/or orientation of that person or object. 
     Embodiments of the present invention may be applied to any computer controlled aiming system that can establish a baseline coordinate system on a part or in an environment such that projected images can be aligned with the surface onto which they are projected. Other embodiments of the present invention may be utilized for entertainment purposes and may comprise, for example, projecting a movie on the surrounding walls of a room. For example, if a moving object (e.g., a person) can be tracked within a stationary environment, then the projected images within the environment can be automatically adjusted as a function of, for example, the person&#39;s movement, actions, or head orientation. This involves console gaming and virtual reality technologies. However, the 3D space reconstruction is different than the 2D gaming technologies. As an example, a system may have a laser scanner or tracker detect and follow a person walking around building, all the while projecting information on the wall that a person looks at. The projector cannot cover 360 degrees of space, but it can selectively project where someone is looking at, which gives the perception of projection over 3D space. 
     Referring to  FIG. 5 , there illustrated is a laser scanner  12  having a projector  14  according to embodiments of the present invention in which the projector  14  projects “hidden features”  24  onto a surface such as a wall  26 . The hidden features may include objects such as, for example, studs, piping, electrical wiring and duct works that are located behind the wall  26 , ceiling, floor or other visible surface. A worker may not know what is exactly positioned behind the wall surface  26  and/or does not know the exact positioning of these items behind the wall surface  26 . It would be beneficial to provide the worker with an image of the items behind the wall surface  22  and the exact location of those items. Generally, this information about the hidden features is available as, e.g., CAD design data. 
     The projection of hidden features according to embodiments of the present invention may come about, for example, by first scanning a building such as a home using a laser scanner  12  during various construction phases (e.g., framing, wiring, plumbing, HVAC, etc.) to obtain scanned point cloud data of various structural details of the building. After completion of certain phases of the scanning to collect images and data, the laser scanner  12  with the projector  14  may then be used to project various “real” images and/or data obtained from the scanning process onto the walls, ceiling, floors, etc. Alternatively, CAD design “intent” data of the various surfaces of the building may be projected onto the surfaces. Regardless of whether real or intended images and/or data are projected, the projection of the hidden features onto these surfaces may assist someone in carrying out tasks, such as, for example, drilling a hole in a precise location of a stud behind a wall. These embodiments of the present invention allow a user of the laser scanner  12  with the projector  14  to identify the precise location of these objects or features such that no harm is caused to other objects or that no time is wasted trying to locate these hidden objects or features. 
     Similar to the embodiments illustrated in  FIG. 5 , the hidden features may comprise those within a human body that are covered by skin. For example, the projector  14  may project data onto the patient&#39;s skin to assist a doctor or surgeon in precisely locating internal human body parts to be accessed and/or surgically operated on. In an operating room, for example, a doctor may use a laser scanner  12  having a projector  14  to determine a precise location for making an incision or finding a tumor, correlating this location with 3D Computer Axial Tomography (CAT) data. In this case, the projector  14  may project an image on the patient, providing markers or actual replication of CAT scan imagery to guide the surgeon. Surgery performed remotely by manually operated robots may use such projection systems  14  in the same way as described above. 
     Besides displaying hidden components, for example, in a construction area or in an engineering device, the projector may display regions as they would appear following attachment. For example, before the wall surface  26  was in place in  FIG. 5  and before the pipes and other construction elements were installed behind the wall surface  26 , a scanner could display the desired appearance of the area, thereby providing guidance to the builder. 
     Referring now to  FIGS. 6-11 , there illustrated are embodiments of a laser tracker  30  having a projector integrated therein or mounted thereto, according to another aspect of the present invention. In  FIG. 6 , the laser tracker  30  includes a gimbaled beam-steering mechanism  32  that comprises a zenith carriage  34  mounted on an azimuth base  36  and rotated about an azimuth axis  38 . A payload  40  is mounted on the zenith carriage  34  and is rotated about a zenith axis  42 . The zenith mechanical rotation axis  42  and the azimuth mechanical rotation axis  38  intersect orthogonally, internally to the tracker  30 , at a gimbal point  44 , which is typically the origin for distance measurements. A laser beam  46  virtually passes through the gimbal point  44  and is pointed orthogonal to the zenith axis  42 . In other words, the laser beam  46  is in the plane normal to the zenith axis  42 . The laser beam  46  is pointed in the desired direction by motors located within the tracker  30  that rotate the payload  40  about the zenith axis  42  and the azimuth axis  38 . Zenith and azimuth angular encoders (not shown) or transducers  41 ,  43 , located internal to the tracker  30 , are attached to the zenith mechanical axis  42  and to the azimuth mechanical axis  38 , and indicate, to a relatively high degree of accuracy, the angles of rotation. The laser beam  46  travels to an external retroreflector  48  such as a spherically mounted retroreflector (SMR). By measuring the radial distance between the gimbal point  44  and the retroreflector  48  and the rotation angles about the zenith and azimuth axes  42 ,  38 , the position of the retroreflector  48  is found within the spherical coordinate system of the tracker  30 . 
     The laser beam  46  may comprise one or more laser wavelengths. For the sake of clarity and simplicity, a steering mechanism of the type shown in  FIG. 6  is assumed in the following discussion. However, other types of steering mechanisms are possible. For example, it may be possible to reflect a laser beam off a mirror rotated about the azimuth and zenith axes  38 ,  42 . An example of the use of a mirror in this way is disclosed in U.S. Pat. No. 4,714,339 to Lau et al. The techniques described here are applicable, regardless of the type of steering mechanism utilized. 
     In the laser tracker  30 , one or more cameras  50  and light sources  52  are located on the payload  40 . The light sources  52  illuminate the one or more retroreflector targets  48 . The light sources  52  may be LEDs electrically driven to repetitively emit pulsed light. Each camera  50  may comprise a photosensitive array and a lens placed in front of the photosensitive array. The photosensitive array may be a CMOS or CCD array. The lens may have a relatively wide field of view, for example, thirty or forty degrees. The purpose of the lens is to form an image on the photosensitive array of objects within the field of view of the lens. Each light source  52  is placed near a camera  50  so that light from the light source  52  is reflected off each retroreflector target  48  onto the camera  50 . In this way, retroreflector images are readily distinguished from the background on the photosensitive array as their image spots are brighter than background objects and are pulsed. In an embodiment, there are two cameras  50  and two light sources  52  placed symmetrically about the line of the laser beam  46 . By using two cameras  50  in this way, the principle of triangulation can be used to find the three-dimensional coordinates of any SMR  48  within the field of view of the camera  50 . In addition, the three-dimensional coordinates of the SMR  48  can be monitored as the SMR  48  is moved from point to point. A use of two cameras for this purpose is described in U.S. Published Patent Application No. US20100128259 to Bridges. 
     Other arrangements of one or more cameras  50  and light sources  52  are possible. For example, a light source  52  and a camera  50  can be coaxial or nearly coaxial with the laser beams  46  emitted by the tracker  30 . In this case, it may be necessary to use optical filtering or similar methods to avoid saturating the photosensitive array of the camera  50  with the laser beam  46  from the tracker  30 . 
     Another possible arrangement is to use a single camera  50  located on the payload or base  40  of the tracker  30 . A single camera  50 , if located off the optical axis of the laser tracker  30 , provides information about the two angles that define the direction to the retroreflector  48  but not the distance to the retroreflector  48 . In many cases, this information may be sufficient. If the 3D coordinates of the retroreflector  48  are needed when using a single camera  50 , one possibility is to rotate the tracker  30  in the azimuth direction by 180 degrees and then to flip the zenith axis  42  to point back at the retroreflector  48 . In this way, the target  48  can be viewed from two different directions and the 3D position of the retroreflector  48  can be found using triangulation. 
     Another possibility is to switch between measuring and imaging of the target  48 . An example of such a method is described in international application WO 03/062744 to Bridges et al. Other camera arrangements are possible and can be used with the methods described herein. 
     As shown in  FIG. 7 , an auxiliary unit  60  is usually a part of the laser tracker  30 . The purpose of the auxiliary unit  60  is to supply electrical power to the laser tracker body and in some cases to also supply computing and clocking capability to the system. It is possible to eliminate the auxiliary unit  60  altogether by moving the functionality of the auxiliary unit  60  into the tracker body. In most cases, the auxiliary unit  60  is attached to a general purpose computer  62 . Application software loaded onto the general purpose computer  62  may provide application capabilities such as reverse engineering. It is also possible to eliminate the general purpose computer  62  by building its computing capability directly into the laser tracker  30 . In this case, a user interface, preferably providing keyboard and mouse functionality is built into the laser tracker  30 . The connection between the auxiliary unit  60  and the computer  62  may be wireless or through a cable of electrical wires. The computer  62  may be connected to a network, and the auxiliary unit  60  may also be connected to a network. Plural instruments, for example, multiple measurement instruments or actuators, may be connected together, either through the computer  62  or the auxiliary unit  60 . 
     Referring to  FIG. 8 , there illustrated is a laser tracker  30  having an internal projector  94  (not shown) integrated within the tracker  30  ( FIGS. 9-10 ) and projecting a pattern  70  onto a surface  72  of an object  74 , such as a workpiece. Such a pattern  70  may be used, for example, to highlight the features  76  where measurements with the tracker  30  are to be taken through use of a circle  78 , while also overlaying indicators  80  where the measurement device  30  would acquire the measurement points. 
     Referring to  FIG. 9 , there illustrated are various internal components within the laser tracker  30  of  FIG. 6 . The components include one or more distance meters  80 , which may comprise an interferometer (IFM), an absolute distance meter (ADM), or both. Emitted from the distance meter  80  is one or more laser beams  82 , which might be visible or infrared or both. The outgoing laser beam  82  passes through a first beam splitter  84 . If the outgoing laser beam  82  is directed to a retroreflector  48  ( FIG. 6 ), then on the return path this retroreflected laser beam  86  bounces off this first beam splitter  84  and travels to a position detector  88 . The position of the light on the position detector  88  is used by the control system of the laser tracker  30  to keep the laser outgoing beam  82  centered on the retroreflector  48 , thereby enabling the tracking function. If the outgoing laser beam  82  is directed to the workpiece  74  ( FIG. 8 ) rather than a retroreflector  48 , then the position of the returning laser beam  86  on the position detector  88  is not important. After passing through the first beam splitter  84 , the outgoing laser beam  82  passes through a beam expander  90 , which causes the diameter of the outgoing laser beam  82  to increase when the beam is traveling in the forward direction (out toward the retroreflector  48 ). The outgoing laser beam  82  then passes though a second beam splitter  92 . Light from a projector  94  (similar to the projector  14  in the embodiments of  FIGS. 1-5 ) sends a pattern of laser light  96  onto the second beam splitter  92 . The reflected light  96  off of the second beam splitter  92  combines with the outgoing laser beam  82  from the distance meters  80 , and the combined light  98  travels to either the retroreflector  48  or to the workpiece  74 . In the case where the laser beam  98  is directed toward the workpiece  74 , it may be possible to turn off the any visible light contained within the beam  82 . This may allow the projected beam  98  to be more clearly seen. 
     Referring to  FIG. 10 , there illustrated is an embodiment of the various components of the laser tracker  30  similar to that of  FIG. 9 , except that the second beam splitter  92  and the projector  94  are both placed in front of the beam expander  90 . The advantage of this approach is that the second beam splitter  92  can be made smaller than for the embodiment of  FIG. 9 . The disadvantage is that it may be more difficult to obtain proper alignment of the projector  94 . 
     In the embodiments illustrated in  FIGS. 6-10  and described herein, the laser tracker  30  has the projector  94  integrated within the internal components of the laser tracker  30 . However, in other embodiments, it is possible for the projector  94  to be mounted on or otherwise attached to the laser tracker  30 . For example,  FIG. 11  illustrates such an embodiment in which the laser tracker  30  has the projector  14  mounted on top of the tracker body. The projector  14  may be mounted rigidly to the tracker body or the projector  14  may be mounted using a gimbal mechanism  22  similar to that of the embodiment of the laser scanner  12  shown in  FIG. 3 . 
     In another embodiment, the projector is offset from the optical axis that carries the laser beams  82  and  86 . By moving the projector from the optical axis, the optical system that carries the light beam  82  may be made more compact and the distance from the projector to the region outside the tracker made smaller, thereby enabling creation of two-dimensional patterns having larger divergence angles. In this embodiment, it is not necessary to provide an independent axis for zenith (horizontal axis) rotation. 
     In the various embodiments of the present invention described hereinabove with respect to the laser tracker  30  of  FIGS. 6-11 , the projector  94 , in a similar manner to the projector  14  of the laser scanner embodiments of the present invention described hereinabove with respect to  FIGS. 1-5 , may project images, data or other information. Such projected information provides visualization to an operator of various types of information that is useful during a measurement session using the laser tracker  30 , or the projected images or data can assist in visualization of data previously taken by the equipment  12 . The projected visual information may, for example, be of a type such as to provide guidance to an operator, such as written instructions, highlighted points to be measured, indicated areas where data are to be taken, and real time feedback on the quality of the data. This visual information provided to the operator may, for example, be in the form of visual cues, text or some other visual form of information. The uses to which the projected images may be put are generally the same as for a laser scanner. Of particular importance for laser trackers are (1) projections in which marks indicate where material is to be removed from or added to a structure and (2) projections in which marks indicate where components are to be added to a structure. 
     While preferred embodiments have been shown and described, various modifications and substitutions may be made thereto without departing from the spirit and scope of the invention. Accordingly, it is to be understood that the present invention has been described by way of illustrations and not limitation. 
     The presently disclosed embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims, rather than the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.