Abstract:
A method of optical data acquisition includes shaping a flexible reference system to be at least partially within a limited line of sight volume with respect to a workpiece.

Description:
[0001]    This application claims priority to U.S. Patent Appln. No. 61/807,563 filed Apr. 2, 2013. 
     
    
     BACKGROUND 
       [0002]    The present disclosure relates to an optical measurement system and, more particularly, to a flexible reference system therefor. 
         [0003]    Three-dimensional optical data acquisition systems optically acquire a multitude of X, Y, Z coordinates with small reference encoded dots randomly placed on or around a workpiece to form a reference system to match image acquisition from multiple angles. The system needs to image a minimum of three reference dots in any given measurement to collect and triangulate a point cloud for any feature. 
         [0004]    Conventional application of such data acquisition systems collect random reference point data but leave gaps where a reference could not be formed. Alternatively, custom reference frames specific to a single workpiece configuration locate the reference encoded dots within a field of view but may be relatively expensive and difficult to manufacture. 
       SUMMARY 
       [0005]    A method of optical data acquisition according to one disclosed non-limiting embodiment of the present disclosure includes shaping a flexible reference system to be at least partially within a limited line of sight volume with respect to a workpiece. 
         [0006]    In a further embodiment of the present disclosure, the limited line of sight volume is defined by a first and second image capture device. 
         [0007]    In a further embodiment of any of the foregoing embodiments of the present disclosure. the flexible reference system locates a multiple of encoded dots adjacent to the workpiece. 
         [0008]    A further embodiment of any of the foregoing embodiments of the present disclosure includes shaping the flexible reference system to follow a feature of the workpiece. 
         [0009]    A method of optical data acquisition of a gas turbine engine blade according to another disclosed non-limiting embodiment of the present disclosure includes shaping a flexible reference system to be at least partially within a limited line of sight volume with respect to an edge of the gas turbine engine blade. 
         [0010]    A further embodiment of any of the foregoing embodiments of the present disclosure includes shaping the flexible reference system around the edge. 
         [0011]    In a further embodiment of any of the foregoing embodiments of the present disclosure, the limited line of sight volume is defined by a first and second image capture device. 
         [0012]    In a further embodiment of any of the foregoing embodiments of the present disclosure, the flexible reference system locates a multiple of encoded dots adjacent to the workpiece. 
         [0013]    An optical data acquisition system according to another disclosed non-limiting embodiment of the present disclosure includes a flexible reference system. 
         [0014]    A further embodiment of any of the foregoing embodiments of the present disclosure includes a multiple of encoded dots on a flexible frame of the flexible reference system. 
         [0015]    In a further embodiment of any of the foregoing embodiments of the present disclosure, the flexible reference system locates the multiple of encoded dots adjacent to a workpiece. 
         [0016]    A further embodiment of any of the foregoing embodiments of the present disclosure includes a turntable that supports said flexible frame. 
         [0017]    The foregoing features and elements may be combined in various combinations without exclusivity, unless expressly indicated otherwise. These features and elements as well as the operation thereof will become more apparent in light of the following description and the accompanying drawings. It should be understood, however, the following description and drawings are intended to be exemplary in nature and non-limiting. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]    Various features will become apparent to those skilled in the art from the following detailed description of the disclosed non-limiting embodiment. The drawings that accompany the detailed description can be briefly described as follows: 
           [0019]      FIG. 1  is a schematic view of an optical data acquisition system; 
           [0020]      FIG. 2  is a schematic view of a limited sight volume with respect to a workpiece; 
           [0021]      FIG. 3  is a first perspective view of a flexible reference system; and 
           [0022]      FIG. 4  is a second perspective view of the flexible reference system. 
       
    
    
     DETAILED DESCRIPTION 
       [0023]      FIG. 1  schematically illustrates an optical data acquisition system  20  such as ATOM SO-4M provided by GOM mbH of Braunschweig, Germany. The optical data acquisition system  20  generally includes a light projector  22 , a first image capture device  24 , such as a digital camera, at a first location  26 , a second image capture device  28  at second location  30  and a control subsystem  32 . 
         [0024]    The optical data acquisition system  20  projects a light pattern onto a workpiece  100  such as, in the illustrated non-limiting embodiment, a fan blade. The two image capture devices  24 ,  28  provide a limited line of sight volume V ( FIG. 2 ) to acquire a multitude of encoded dots  34  randomly placed on or around the workpiece  100  to form a reference system to match measurements from multiple angles as the workpiece  100  is rotated on a turntable  36 . 
         [0025]    The optical data acquisition system  20  must image a minimum of three reference dots  34  within the limited line of sight volume V provided by the two image capturing device  24 ,  28  in any given measurement to determine a point cloud of X, Y, Z coordinates to provides three-dimensional data acquisition. The control subsystem  32  merges all the images of the encoded dots  34  to triangulate and generate a 3-dimensional relationship and location of all the encoded dots  34 . 
         [0026]    The limited line of sight volume V defined by the image capture device  24 ,  28  may typically be about 12×12×12 inches (300 cubic mm). Through triangulation, a surface map of the workpiece  100  is readily constructed by the control subsystem  32 . 
         [0027]    The workpiece  100  such as a fan blade has a very thin and sharp leading edge  102  and trailing edge  104  which may be at an angle where a portion of the respective edge  102 ,  104  is within the limited line of sight volume V, but the minimum of three encoded dots  34  are not. Also, the encoded dots  34  cannot be located on the edges  102 ,  104  without obscuring the edges  102 ,  104 . 
         [0028]    To assure the optical data acquisition system  20  images a minimum of three encoded dots  34  in the limited line of sight volume V a flexible reference system  40  is located adjacent each edge  102 ,  104 . The flexible reference system  40  generally includes a flexible frame  42  upon which a multiple of encoded dots  34  are located. The flexible frame  42  may be attached to the turntable  36  with a mount  44  such that the respective flexible frame  42  may, for example, be shaped to follow the contour of each edge  102 ,  104  to thereby locate at least three encoded dots  34  in the limited line of sight volume V ( FIG. 3 ). It should be appreciated that various flexible and articulable structures may be utilized as the flexible frame  92 . 
         [0029]    In conjunction with the encoded dots  34  located on the workpiece  100 , the flexible reference system  40  provides additional encoded dots  34  to orient the optical data acquisition system  20  at areas where there are otherwise not sufficient surface area for the encoded dots  34  (e.g., edges  102 ,  104 ). The flexible reference system  40  orients the optical data acquisition system  20  in such a manner as to permit the image of the edges  102 ,  104  because the encoded dots  34  are not physically located on the workpiece  100  but are still within the limited line of sight volume V. That is, the flexible frame  42  is shaped to follow a such as the edges  102 ,  104  of the workpiece  100  to locate the encoded dots  34  within the limited line of sight volume V of the image capture devices  24 ,  28 . 
         [0030]    It should be appreciated that although a fan blade is illustrated in a disclosed non-limiting embodiment, other application will benefit herefrom such as an inside surface of a fan blade sheath that has a narrow deep internal surface that slides on a blade body. The narrow passage has no surface area that can receive encoded dots  34 , so the sheath is supported at each end and the flexible reference system  40  allows the measurement of the internal surface. 
         [0031]    Still another application is the measurement of birds for use in bird ingestion finite element analysis. That is, the bird operates as a projectile that must be precisely measured for accurate analysis when fired into, for example, a gas turbine engine, aircraft canopy, etc. 
         [0032]    It should be understood that like reference numerals identify corresponding or similar elements throughout the several drawings. It should also be understood that although a particular component arrangement is disclosed in the illustrated embodiment, other arrangements will benefit herefrom. 
         [0033]    Although the different non-limiting embodiments have specific illustrated components, the embodiments of this invention are not limited to those particular combinations. It is possible to use some of the components or features from any of the non-limiting embodiments in combination with features or components from any of the other non-limiting embodiments. 
         [0034]    Although particular step sequences are shown, described, and claimed, it should be understood that steps may be performed in any order, separated or combined unless otherwise indicated and will still benefit from the present disclosure. 
         [0035]    The foregoing description is exemplary rather than defined by the limitations within. Various non-limiting embodiments are disclosed herein, however, one of ordinary skill in the art would recognize that various modifications and variations in light of the above teachings will fall within the scope of the appended claims. It is therefore to be understood that within the scope of the appended claims, the disclosure may be practiced other than as specifically described. For that reason the appended claims should be studied to determine true scope and content.