Abstract:
A target system and method for photogrammetry using a target holder with an aperture at least partially therethrough to precisely position a target assembly therein for use in determining geometric properties of an object.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation-in-part to co-pending U.S. application Ser. No. 12/612,565, filed Nov. 4, 2009 and which claims priority pursuant to 35 U.S.C. 119(e) to U.S. Provisional Patent Application Ser. No. 61/111,243, filed Nov. 4, 2008, the entire disclosures of which are incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present general inventive concept relates to a target system and method to be used in photogrammetry, and in one particular embodiment, to a target holder having an aperture at least partially therethrough to precisely position a target assembly therein for use in determining geometric properties of an object. In another embodiment, the general inventive concept relates to a target holder including an annular protruding rim and a generally flat surface for placement of a target piece (such as a target paper material). In still another embodiment, the general inventive concept relates to a method of placing a target piece on a target holder. 
     2. Description of the Related Art 
     A large number of industries require precise and accurate measuring for a number of applications such as production, manufacturing, and process control. In many such applications, measurement errors on the order of even one ten-thousandth of an inch can be critical. Instruments such as laser trackers, scanners, associated targets and the like are particularly well suited for such applications because they provide extreme precision and accuracy. 
     Retro-reflective photogrammetric target systems have been designed, such as the system disclosed by U.S. Pat. No. 5,073,005, the entire disclosure of which is incorporated herein by reference, for precise measurement application. Nevertheless, the target structure of U.S. Pat. No. 5,073,005 provides significant challenges during manufacturing, as minor imprecision during the assembly of a single component (such as a mask over a reflective material of the target) can result in significant inaccuracy of the target during usage Therefore, it would be desirable to provide a target structure that can be assembled with less possibility of resulting in inaccuracies of the target during usage. 
     SUMMARY OF THE INVENTION 
     The present general inventive concept provides an improved target system and method to be used in photogrammetry. In one particular embodiment the general inventive concept provides a target holder having an aperture therethrough to precisely position a target assembly therein for use in determining geometric properties of an object. In another embodiment, the general inventive concept relates to a target holder including an annular protruding rim and a generally flat surface for placement of a target piece. In still another embodiment, the general inventive concept relates to a method of placing a target piece on a target holder. 
     The present general inventive concept further provides a target assembly with improved accuracy. 
     The present general inventive concept further provides a target assembly that protects a target piece by recessing the target piece into the target assembly. 
     The present general inventive concept further provides, in a preferred embodiment, a target assembly with elements that magnetically engage each other thereby eliminating the need to handle elements that are sensitive to touch such as reflective paper. 
     The present general inventive concept further provides, in a preferred embodiment, a target assembly having a flat disk to receive a removable target piece. 
     The present general inventive concept further provides a target paper that is attached to a flat disk via an adhesive, static, and/or magnetic attachment means. 
     The present general inventive concept further provides, in a preferred embodiment, a target having a mask that is attached by means that prevent creep or other undesired movement of the mask, which overcomes the problem of traditional vinyl masks that are attached by an adhesive that results in eventual creep and inaccuracy of the target. 
     The present general inventive concept further provides, in a preferred embodiment, a target assembly having a flat disk to support a target paper that is made of a material other than vinyl and preferably made from paper to yield a crisp, clean edge about a circumference of the target paper. 
     The present general inventive concept further provides, in a preferred embodiment, a target assembly having a plug or flat disk to support a target paper, the flat disk being insertably mounted into a target holder such that the flat disk face and target paper are slightly recessed into the target holder from a face surface of the target holder to protect the target paper from fingerprints, debris, and the like. 
     The present general inventive concept further provides, in a preferred embodiment, a plug or flat disk to support a target paper, the flat disk having a magnetic cover to magnetically engage the flat disk for the purpose of trapping the target paper between the magnetic cover and the flat disk thereby protecting and/or securing the target paper. 
     The present general inventive concept further provides, in a preferred embodiment, a target system having an easily removable target assembly design to ensure correct positioning and accuracy of a target. 
     The present general inventive concept further provides, in a preferred embodiment, a target assembly having a plug or target body that can be removed from a hole in the target system such that the target body can be disassembled to replace one or more pieces of the target body such as a target paper if it becomes worn or damaged, and then reassembled and installed back into the target system in the exact same pre-removal position thereby ensuring accuracy of the target assembly. 
     The present general inventive concept further provides, in a preferred embodiment, a target system having a target assembly with a tubular base that is insertable into a receiver and rotatable therein. 
     Additional aspects and utilities of the present general inventive concept will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the general inventive concept. 
     The foregoing and/or other aspects and utilities of the present general inventive concept may be achieved by providing a target system having a elongated body with an aperature at an upper end opposite to a insertable stand lower end, the aperture sized and shaped to accommodate a ring therein, the ring sized and shaped to accommodate a disk therein, the disk having a surface to mount a target. 
     The foregoing and other objects are intended to be illustrative of the present general inventive concept and are not meant in a limiting sense. Many possible embodiments of the present general inventive concept may be made and will be readily evident upon a study of the following specification and accompanying drawings comprising a part thereof. Various features and subcombinations of present general inventive concept may be employed without reference to other features and subcombinations. Other objects and advantages of this present general inventive concept will become apparent from the following description taken in connection with the accompanying drawings, wherein is set forth by way of illustration and example, an embodiment of this present general inventive concept. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and/or other aspects and utilities of the present general inventive concept will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which: 
         FIG. 1  is a front elevation view of an embodiment of the present general inventive concept illustrating an assembled target system. 
         FIG. 2  is an exploded cross view of embodiment of  FIG. 1  illustrating a target system with target assembly including a target disc support, a target perimeter ring, and a target adhesive piece. 
         FIG. 3  is a perspective view of an embodiment of the present general inventive concept illustrating an exploded target system. 
         FIG. 4  is a perspective view of an embodiment of the present general inventive concept illustrating an exploded target system. 
         FIG. 5  is a perspective view of an embodiment of the present general inventive concept illustrating an exploded target system. 
         FIG. 6  is a perspective view of another embodiment of a target system of the present general inventive concept. 
         FIG. 7  is a front sectional view of the target system of  FIG. 6 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Reference will now be made in detail to the embodiments of the present general inventive concept, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. The embodiments are described below in order to explain the present general inventive concept by referring to the figures. 
     As illustrated in  FIG. 1 , a target system  1  includes an elongated body  10  with a flat face surface  15  adjacent to a top surface  16 , a convex rear surface  17  opposite to the face surface  15  that extends from the top surface  16  to a lower surface  18 , and a base  20  extending from the lower surface  18 . 
     The elongated body  10  is generally tubular except for the face surface  15  that is machined therein. An intermediate portion  21  subtly connects the face surface  15  to the generally tubular elongated body  10 . 
     A circular aperture  30  extends through the face surface  15  to the rear surface  17  and is sized and shaped to accommodate a target perimeter ring  40 . 
     The target perimeter ring  40  has a front surface  42  and a rear surface  43  with a cavity  44  therein. The cavity  44  is opened at an end adjacent to the front surface  42  to receive a disc  50  and has an abutment surface with aperture therein. In the exemplary embodiment, the perimeter ring  40  is magnetic and the disc  50  is metal such that the two elements may be easily assembled without additional connection means. It is foreseen, however, that the perimeter ring  40  and/or disc  50  may be made of other like materials such as plastic, metal etc., and may be assembled within aperture  30  using glue, epoxy, welding, etc. 
     The disc  50  is circular and has a flat face surface  52  and an opposite-facing rear surface  54 . The flat face surface  52  is sized and shaped to receive a target paper  60 . 
     The target paper  60  is circular and has a textured front surface  62  and an adhesive back surface  64 , the adhesive back surface  64  provided to facilitate attachment of the target paper  60  to the disk  50  face surface  52 . 
     In use, the target paper  60  back surface  52  is adhered to the face surface  52  of the disc  50 . The perimeter ring  40  is inserted into the body  10  by sliding the front surface  42  through the aperture  30  from the rear surface. 
     Once the perimeter ring  40  is installed, the disc  50  is inserted into the cavity  44  by sliding the face surface  52  into the cavity  44  until the target paper  60  abuts an interior of the cavity  45 . 
     In another embodiment, the disc  50  is inserted into the body  10  first, then glued or otherwise attached within the aperture  30  and then target paper  60  is adhered to face surface  52  of the disc  50 . The ring  40  is then installed and glued, or other wise attached, in place within the aperture  30 . 
     In another embodiment, as illustrated by  FIG. 3 , the circular aperture  30  may be replaced with simply a recessed portion  100  such that the target paper  60  nests within the recessed portion  100 . Additionally, the target paper  60  may be covered by a circular plate  110  having an aperture  120  therethrough. The circular plate  110  fits tightly within the recessed portion  100 . In this manner, the target paper  60  abuts both a rear surface of the recessed portion  100  and the circular plate  110 , and the circular plate  110  acts to secure the target paper  60  within the recessed portion  100 . 
     While the face surface  15  of the above embodiments extends at zero degrees with respect to the base  20 , it is foreseen that the face surface  15  may extend at other various angles including but not limited to forty-five degrees, as illustrated by  FIG. 4 , or ninety degrees, as illustrated by  FIG. 5 , with respect to the base  20 . In these embodiments, the target paper  60  nests within the recessed portion  100  and may be covered by the circular plate  110  having an aperture therethrough. The circular plate  110  fits tightly within the recessed portion  100  such that the target paper  60  abuts both a rear surface of the recessed portion  100  and the circular plate  110 . In this manner, the circular plate  110  acts to secure the target paper  60  within the recessed portion  110 . 
     Referring to  FIGS. 6 and 7 , another embodiment of the inventive concept is shown in which target system  1  includes a generally cylindrical body  10  with a flat face surface  15  that is also the top surface of the body  10 . The flat face surface  15 , of the embodiment shown in  FIGS. 6 and 7 , is surrounded by an annular protruding lip  616  that extends upward from the surface around the perimeter of the body  10 . Target paper  60  is adhered to face surface  15 . In a preferred embodiment, target paper  60  is sized to cover approximately the entire surface of face  15 . A lathe and razor blade is then used to cut a circle having a diameter less than the diameter of face surface  15  at the center of face surface  15 . The excess material of target paper  60  is removed from around the perimeter of the central circle, leaving a centered circle of target paper  60  as is shown in  FIG. 6 . 
     It will be appreciated that although body  10  is shown in the embodiment of  FIGS. 1-5  as generally elongated, and in the embodiment of  FIGS. 6 and 7  as generally cylindrical, that the shape of the body  10  of any embodiment of the instant inventive concept may be elongated, cylindrical, or any other shape desired without departing from the spirit and scope of the instant inventive concept. 
     Although a few embodiments of the present general inventive concept have been illustrated and described, it will be appreciated by those skilled in the art that changes may be made in these exemplary embodiments without departing from the principles and spirit of the general inventive concept, the scope of which is defined in the appended claims and their equivalents.