Abstract:
Systems and methods of reproducing images onto surfaces are disclosed. In one embodiment, the system includes an image file that digitally produces a planar surface normal to a surface of a master model. The planar surfaces are referenced to a coordinate system of the master model through a series of points. A tracker surfacing system, comprising a tracking instrument, generates and emits a signal as the tracking instrument crosses the planar surface. An output device is actuated by the tracking device as it crosses the planar surface, reproducing the series of points as an image onto a surface, including a flat, curved or compound surface. Both the spatial position and orientation of the output device are detected and adjustments are made so that the image is precisely applied to intended locations on the surface being imaged.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation-in-part of U.S. patent application Ser. No. 11/112,698, filed Apr. 21, 2005 now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention generally relates to systems that reproduce images, and more specifically, to systems that reproduce images onto surfaces, including compound curved surfaces. 
     2. Description of the Related Art 
     Complex surfaces, including small components such as mechanical parts or large objects such as buildings, have traditionally been mapped using standard methods, including mylar transfer templates, theodolites laser trackers, and more recently, laser projectors. Generally, these methods are time consuming, tedious and may lack accuracy. For example, a laser projector may be used to project two-dimensional images onto a contoured surface. The projected images are used as patterns for manufacturing products and locating an image onto a desired location. For example, an image may be projected onto a ply manufactured for airplane fuselages, and the like. To be effective, the laser emitter must generally be positioned in an accurate and precise manner. The projector&#39;s designated points and angles, however, may not be accurately controlled. It becomes necessary to use multiple laser projector heads to accurately project the lines in their proper location, the larger the projected image and the more complex the surface it is to be projected upon. In addition, the focal length of the laser may be hindered by physical objects, i.e. floors, walls, support posts, &amp; ceilings. If the projection head can not be placed far enough away from the object, it will be unable to project over the entire surface thus requiring more equipment or additional set-ups. 
     Recently, theodolites have been employed to provide for greater accuracy in determining the coordinates of the reference marks. A theodolite is a mounted optical instrument, which measures horizontal and vertical angles in space. Though it may accurately define a point from the horizontal and vertical angles of a surface relative to a given coordinate system, it typically does not indicate the object geometry, including shape, dimension, and location. Generally, a theodolite is fairly expensive, time consuming and labor intensive. Moreover, current methods of mapping complex surfaces lack the ability to print images onto complex contoured surfaces that have no physical points of reference. 
     A further problem in mapping and marking surfaces relates to the need to properly position surface marking devices such as a printer, so that the markings are precisely applied at the correct locations on the marking surface. An error in marking the surface can result in scrap and/or production delays. It would be desirable to automatically verify that the marking device is in the correct location before it is actuated, and to control the verification process as well as the firing process automatically. 
     Accordingly what is needed is a system and method for reproducing images onto surfaces in which the spatial position an image producing device, such as a printer, is automatically verified as being correct before the surface is marked. The invention is directed toward satisfying this need. 
     BRIEF SUMMARY OF THE INVENTION 
     The invention is directed to systems and methods of reproducing images onto surfaces, in which the position of a marking device such as a printer is verified as correct before the image is reproduced onto the surface. Embodiments of the invention generally provide a method of outputting images, including-lines, cross hairs and text, onto complex surfaces, including complex contoured surfaces. 
     In accordance with one aspect of the invention, a system is provided for reproducing an image on a surface. The system comprises a model containing a feature to be reproduced as an image on the surface. An imaging device is movable over the surface for reproducing the feature as an image on the surface at a location based on the location of the feature in the model. A tracker is used to track the three dimensional position of the imaging device, and a computer program is provided for correlating the position of the imaging device determined by the tracker with the three dimensional position of the feature in the model. A controller controls the operation of the imaging device based on the correlated position of the tracker. 
     In accordance with another aspect of the invention, a method is provided for reproducing an image on a surface, comprising the steps of: determining the position of features on a three dimensional model; moving an imaging device over the surface; determining the position of the imaging device; correlating the position of the features in the model with the position of the imaging device; and, reproducing an image of the features on the surface at a location on the surface based on the results of the correlation. 
     According to still another aspect of the invention, a method is provided for reproducing an image on a surface, comprising the steps of: obtaining the three dimensional location of a feature in a model; obtaining the three dimensional location of an imaging device; correlating the obtained three dimensional location of the feature with the obtained three dimensional location of the imaging device based on a common, three dimensional coordinate system; determining the location on the surface where an image of the feature should be reproduced based on the results of the correlation; and, reproducing an image of the feature at the determined location imaging device. 
     Other features, benefits and advantages of the invention will become apparent from the following description of the invention, when viewed in accordance with the attached drawings and appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       Preferred and alternate embodiments of the invention are described in detail below with reference to the following drawings. 
         FIG. 1  is a schematic view of the system for reproducing images onto surfaces, according to one embodiment of the invention. 
         FIG. 2  is a schematic view of the system for reproducing images onto surfaces, according to another embodiment of the invention. 
         FIG. 3  is a schematic view of a system for reproducing images onto surfaces, according to yet another embodiment of the invention. 
         FIG. 4  is a block diagrammatic view of a method of reproducing images onto surfaces, according to an embodiment of the invention. 
         FIG. 5  is a block diagrammatic view of a method of reproducing images onto surfaces according to yet another embodiment of the invention. 
         FIG. 6  is a side cross-sectional view of a tracking instrument in accordance with an embodiment of the invention. 
         FIG. 7  is an enlarged, perspective view showing the tracking instrument on a surface relative to a fence file and a laser tracker beam. 
         FIG. 8  is a broad block diagram of the system for controlling the output device. 
         FIG. 9  is a flow diagram of a program for controlling the operation of the output device. 
         FIG. 10  is a flow diagram of a program for communicating with a tracker position correlation program. 
         FIG. 11  is a combined block diagram and flow diagram of a program for communicating with the output device. 
         FIG. 12  is a screen capture of a graphical user interface display, showing the variances between the tracker location and the feature location 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The invention relates to systems and methods for reproducing images onto surfaces. Many specific details of certain embodiments of the invention are set forth in the following description and in  FIGS. 1-12  to provide a thorough understanding of such embodiments. One skilled in the art, however, will understand that the invention may have additional embodiments, or that the invention may be practiced without one or more of the details described in the following description. 
     In general, embodiments of methods and systems in accordance with the invention may be used for reproducing images onto a variety of surfaces. The surfaces may include relatively simple contoured surfaces, or compound contoured surfaces, including surfaces encountered in aeronautical, automotive, and marine applications. In further embodiments, the surfaces may include relatively flat surfaces, including, for example, signs, billboards, and any other suitable surfaces. 
       FIG. 1  is a schematic view of a system for reproducing images onto surfaces  100 , including compound contoured surfaces. The system may include an operating interface  110  comprising a computer, such as a desktop, laptop, or any other suitable interface device. The operating interface  110  may be used to produce and store an image file  112 . In one embodiment, the image file  112  may comprise a digitally produced igs (image grayscale system) file, or other suitable digital file. An igs file may display a full range of black and white images, including various shades of gray. The image file  112  may then be adapted to digitally produce a planar surface  114  normal to a surface of a master model by extruding the line created from the intersection of the edge of a modeled part and the digital master model surface  116 . 
     The planar surface  114  may be extruded from the surface of a master model  116 , such as a mechanical part like an aircraft stiffener, for example, to a plane  118  normal to the outer mold of the master model. The resulting extruded planar surface  114  may be referred to as a “fence file”. The extruded planar surface (i.e. fence file)  114  may appear to look like a ribbon, following the contours of the master model  116  created by extruding the lines normal to the surface of the master model  116 . These surfaces  114  may be referenced to a coordinate system  120  of the master model  116  through a series of points (not shown). In one particular embodiment, the coordinate system  120  may comprise a Cartesian coordinate system. In alternate embodiments, the coordinate system  120  may include a two-intersecting planar system, a three-intersecting planar system, or any other suitable coordinate system. 
       FIG. 2  is a schematic view of another embodiment of the invention. In addition to producing and storing the image file  112 , the operating interface  110  may comprise a tracker surfacing system  220 , which includes a design program  212 . In one embodiment, the design program  212  includes a computer aided design program (CAD) that can model surfaces via a computer. The CAD program may, for example, be a commercially available program, including the Unigraphics program available from Electronic Data Systems Corporation of Plano, Tex., the CATIA® program available from Dassault Systems Corporation of Suresnes, France, or any other suitable CAD program. The CAD program may be adapted to convert the “blueprint” drawings to create two-dimensional (2-D) drawings or three-dimensional (3-D) models. The design program  212  may further include a Computer-Aided Inspection Program, including, for example, the VERISURF® Computer Aided Inspection Program commercially-available from Verisurf Software, Inc. of Anaheim, Calif. The Computer Aided Inspection Program may compare actual readings from an actual device to theoretical designed model surfaces. 
     Still referring to  FIG. 2 , the tracker surfacing system  220  may also include a tracking instrument  224 . The design program  212  may be adapted to generate and emit a signal  226  as the tracking instrument  224  crosses the extruded plane (or fence file)  114 . In one particular embodiment, the tracking instrument  224  includes a tracker ball  225  and uses software that samples how close the center (0,0,0) of the tracker ball  225  is to the extruded fence file  114 . As the center of the ball  225  crosses the extruded plane  114 , the tracking instrument  224  may emit an electrical signal. In one embodiment, the signal  226  may be transmitted via a cable  227  to an output device  228 . In another embodiment, the signal  226  may be transmitted via electromagnetic waves, acoustic signals, optical signals, or any other suitable means. In operation, the crossing of the tracking instrument  224  over the planar surface  114  may actuate the output device  228 . More specifically, in one particular embodiment, the output device  228  may include an ink jet printer, and the tracking instrument  224  may emit an electrical signal that triggers the ink jet to fire. If necessary, the ink jet may be set to fire numerous shots in quick succession. The output device  228  may be used to reproduce the series of points of the master model  116  onto a surface (not shown). The output device  228  may include a printer, scanner, facsimile, laser, electron beam, computer display, and other suitable devices. 
     In an alternate embodiment, the output device  228  may be mechanically coupled to the tracking instrument  224 . For example,  FIG. 6  is a side cross-sectional view of a tracking instrument  224  in accordance with an embodiment of the invention. In this embodiment, the tracking instrument  224  may include a housing member  230  that operatively supports a tracking ball  225  and an output device  228 . In alternate embodiments, the tracking instrument  224  may include a laser tracking ball, a laser tracker projector, or any other suitable tracker surfacing instruments. The output device  228  includes an ink jet head  232  coupled to an ink reservoir  233 . A power lead  235  provides power to the output device  228 , and feet (or rollers)  237  support the housing  230 . As further shown in  FIG. 6 , a center point  239  of the tracking ball  225  is aligned with the ink jet head  232  along a tracking axis  241 . 
     Referring to  FIG. 3 , a tracking instrument  224  may track the extruded plane  114 , as previously described with reference to  FIG. 2 . As the tracking instrument  224  tracks the planar surface  114 , the tracking instrument  224  may actuate the output device  228  to reproduce the series of points  330  of the master model. In one particular embodiment, as the tracking instrument  224  is passed over the planar surface  114  at different locations, a point  330  may be produced at each intersection (not shown). The series of points  330  may then be reproduced as an image  332  onto a surface  334 , including onto a flat, curved, or compound surface. 
       FIG. 4  is a block diagrammatic view of a method of reproducing images onto surfaces. At block  440 , an image file comprising planar surfaces normal to a surface of a master model is digitally produced. The image file may be digitally produced by an interface operator  110 , as previously described with reference to  FIG. 1 . The master model may then be referenced, at a block  442 , in a coordinate system through a series of reference points that are coordinated between the actual part and the digital model. At block  443 , the actual points are imported into the digital model, and at block  444 , a best fit between the two sets of reference points is determined. At block  445 , the series of reference points may be used to track the planar surface extruded from the master model. A tracking instrument  224 , as previously described with reference to  FIG. 2  and  FIG. 3 , may be employed to track the planar surface. As the series of reference points are tracked, a signal may be generated and emitted at block  446  by a design program, such as a CAD program. An output device (e.g. a printer) may be actuated, at block  448 , by the tracking instrument  224  to reproduce the series of reference points as an image onto a surface. In particular embodiments of the invention, the surfaces may include contoured surfaces and compound contoured surfaces, including aeronautical, automotive, and marine surfaces. In alternate embodiments, the surfaces may include relatively flat surfaces, including, for example, signs, billboards, stadium grounds art and layouts, and any other suitable applications. 
       FIG. 5  is a block diagrammatic view of a method of reproducing images onto surfaces, according to another embodiment of the invention. At block  550 , an image file comprising planar surfaces normal to a surface of a master model is digitally produced. The master model may then be referenced, at block  552 , in a coordinate system through a series of points. At block  554 , the series of points may be used to track the planar surface extruded from the master model. A tracking instrument, as previously described with reference to  FIG. 2  and  FIG. 3 , may be employed to track the planar surface. As the series of points are tracked, a signal may be generated and emitted at block  556  by a design program, such as a CAD program. An output device may be actuated, at block  558 , by the tracking device  224  to provide an image onto a surface, such as a surface of a vehicle. In alternate embodiments, as described above with respect to the method  400  shown in  FIG. 4 , a series of actual points may be imported into the digital model (block  443 ), and a best fit between the two sets of points may be determined (block  444 ). 
     In accordance with the invention, a system and method are provided for assuring that the spatial position of the output device  228  is correct when the markings are applied so that the markings may be reproduced at the correct locations on the marking surface  242 .  FIG. 7  shows the tracking instrument  224  supported on a surface, marking surface  242 , to be marked by feet  237  on the bottom of the body  230 . A laser beam  702  from a laser tracker  706  may be reflected from the tracking ball  225  so that the position of the tracking instrument  224  can be continuously tracked. As previously described, when the tracking instrument  224  traverses a fence file  114 , the output device  228  can be fired to produce a marking corresponding to a feature at the reference location of the feature in the model, which, as previously explained, may be a CAD file. Accordingly, it is important that the exact location of the tracking device  224  be known so that firing signals are delivered to the output device  228  only when the tracking instrument  224  is in a position that will result in the markings being reproduced at the correct location. The invention achieves marking location precision using a system that employs software programs. These software programs can correlate the three dimensional location of the tracking instrument  224  with the three dimensional location of the model features, using a common coordinate system. 
     Referring to  FIG. 8 , the laser tracker  706  may monitor the exact three dimensional position of the tracking instrument  224 , using the tracking ball  225  ( FIG. 7 ). The laser tracker  706  may continuously transmit the exact three dimensional location of the tracking instrument  224  based on a chosen coordinate system, such as a Cartesian system in which a location is defined in terms of x, y and z coordinates. A model whose features are to be marked on the marking surface  242  may be stored in CAD files  802 . This stored information may include the location of the model features in terms of the coordinate system used by the laser tracker  706 . The feature location information is delivered to a computer  804 , which may comprise the previously described operating interface  110 , or a separate computer. 
     The computer  804  may include a correlation program  806  and a control program  808 . The correlation program  806  may comprise the previously described VERISURF© Computer Aided Inspection Program which is a commercially available software package that compares actual readings from an actual device to theoretical, designed model surfaces. Thus, the correlation program  806  may correlate the three dimensional position of the tracking instrument  224  with the physical component or feature stored in the CAD files  802 . Once the correlation program  806  establishes a correlation, the program may generate difference values between the tracking instrument location and specified features in the CAD file  802 . These differences may be broadcast on an IP address by the computer  804 . The position difference values generated by the correlation program  806  may be displayed for viewing by an operator by using a graphical user interface (GUI)  818 .  FIG. 12  is a typical screen display provided by the GUI  818  in which the position variances in the x, y and z directions are shown in windows  1202 ,  1204  and  1206  respectively. The three dimensional position differences are shown at window  1208 . The size of the marking window is shown as a value at window  1210 , which may correspond to the size of the area on the marking surface  242  within which the markings must be reproduced. An off delay value is displayed at window  1212 . 
     The control program  808  may monitor the difference values shown in  FIG. 12  and compare them against location tolerances, input values and/or reference conditions which collectively form a set of preconditions. Providing that the difference values satisfy the preconditions, the control program  808  may output fire command signals that actuate the output device  228 . In the embodiment illustrated in  FIG. 8 , the output device  228  may comprise an ink jet printer  820  mounted on the tracking instrument  224  ( FIG. 7 ). The printer  820  may include a controller  810 , a relay  812 , a valve  814  and a print head  816 . The fire command signals from the computer  804  are delivered to controller  810  which may comprise an R25/210 dual relay controller, for example. The R25/210 dual relay controller is an RS-232 programmable relay controller that is commercially available from a variety of suppliers. Controller  810  is responsive to the fire command signals issued by the control program  808  to activate relay  812  which opens valve  814 . The valve  814  allows compressed air to actuate a pneumatic cylinder (not shown) which forces print head  816  to contact the marking surface  242 , thereby causing one or more ink dots to be reproduced on the marking surface  242 . The relay  812  is closed by the controller  810  when the control program  808  issues a stop command signal. 
       FIG. 9  is a flow chart of the steps performed in carrying out a method for accurately reproducing images on a marking surface  242 . As previously described, the three dimensional position of tracker target (tracking ball  225 ) within a chosen coordinate system may be acquired at  902 . The three dimensional coordinates of components or features on the model may be retrieved from a CAD file at  904 . Based on the coordinates of the tracker target and the model feature, a correlation may be made between the position of the target and the position of the component features at  906 . A calculation may then be made at step  908  to determine the difference values between the target location and the feature location, in terms of the chosen coordinate system. Next at step  910 , the difference values may be compared to the each of the preconditions, and at step  912 , a determination may be made of whether the difference values satisfy the preconditions. If the difference values satisfy the preconditions, a fire command signal is issued at step  916 , otherwise if the difference values do not satisfy the preconditions, the process is stopped at  914 , and the fire command signal may not be issued. 
       FIG. 10  is a flow chart for the control program  808 . At  1002  the correlation program  806  may be polled to obtain the difference values using an interface device (not shown) which may form part of the commercially available VERISURF® software. The difference values obtained at  1002  are used to update the GUI delta values at  1004 , for the x,y,z coordinates as well as the overall three dimensional values. A determination may be made at  1006  of whether the change in the x value is within a preset tolerance. If the answer is yes, then the x value may be displayed with a green background in window  1202  of the GUI screen display  1200  shown in  FIG. 12 . If the change in the x value is not within tolerance, then the value may be shown in window  1202  with a different color background, for example a grey background. 
     Next, a determination may be made at  1012  of whether the change in the y difference value is within a preset tolerance. If the answer is yes, then change in the y difference value may be displayed with a green background in window  1204  ( FIG. 12 ) as shown at step  1014 . If the change in the y difference value is not within tolerance, then at step  1016 , the change in the y difference value may be displayed with a grey background in window  1204 . Next, at step  1018 , a determination is made of whether the change in the z difference value is within tolerance. If the change in the z difference is within tolerance, then at step  1020  the change in the z value may be displayed in window  1208  with a green background. Otherwise, if the change in the z difference value is not within tolerance, the value may be displayed with a grey background, at  1022 . Finally, a determination is made at whether the change in the 3-D difference is within tolerance. If the change in the 3-D difference is within tolerance, then at step  1026 , the difference value may be displayed in window  1208  with a green background. If the 3-D difference is not within tolerance, then at step  1028  the change in the 3-D difference value may be displayed with a grey background. 
       FIG. 11  is a combined block diagram and flow chart of an additional portion of the control program  808  shown in  FIG. 8 . A determination may be made at  1102  as to whether the preconditions have been met that would result in a fire command signal being issued to produce a marking. If a marking event has been triggered at  1102 , then at step  1104 , an “on” or fire command signal may be sent to an RS-232 serial port  1110  at step  1104  which connects computer  804  to the controller  810 . Next, at  1106 , the program waits for a predetermined period, referred to as the “off delay time” which may be selected by an operator using the GUI  818 . This off delay time, which is shown in the window  1212  in  FIG. 12 , may comprise the period of time that the output device  228  must remain off before being actuated by a subsequent fire command signal. At  1108 , an off command signal may be generated and sent via the serial port  1110  from the computer  804  to the controller  810 , which causes the relay  812  to remain off for during the off delay time. 
     From the forgoing, it can be appreciated that the location at which markings or images are reproduced on the marking surface  242  are closely controlled. In the event that the tracking instrument  224  is not within a specified range of the exact location to be marked, the printer or other output device  228  may be prevented from marking the surface  242 . 
     While preferred and alternate embodiments of the invention have been illustrated and described, as noted above, many changes can be made without departing from the spirit and scope of the invention. Accordingly, the scope of the invention is not limited by the disclosure of these preferred and alternate embodiments. Instead, the invention should be determined entirely by reference to the claims that follow.