Abstract:
An object, such as a robotically controlled television camera undergoes alignment with a reflective target by directing a coherent beam of radiation, e.g., a laser beam, into an opening in an enclosure having a reflective interior such that the radiation strikes a reflector in axial alignment with the enclosure opening. Upon striking the target, the beam undergoes reflection through the enclosure opening back to the object for detection. Alignment between the object and the target occurs when substantially all of the radiation undergoes reflection from the target to the object.

Description:
TECHNICAL FIELD 
       [0001]    This invention relates to a technique for aligning an object, such as a robotic television camera, in several dimensions. 
       BACKGROUND ART 
       [0002]    In many applications, a need exists to establish alignment of an object with a target. For example within a television studio, movement of a tripod or pedestal associated with a television camera to an alternate locations often occurs to better leverage the investment in such equipment. However, a change in the positioning of the tripod or pedestal with respect to the set often results a change in the camera position. As a consequence, the new position of the camera will likely differ by several centimeters, or even several meters from its previous position (referred to as a “preset”). In the case of a robotically operated camera, no mechanism typically exists for easily accomplishing re-alignment. Rather, the camera must undergo manual re-alignment and followed by time consuming re-programming of the location presets. 
         [0003]    Thus a need exists for a technique for simply and efficiently aligning a television camera. 
       BRIEF SUMMARY OF THE INVENTION 
       [0004]    Briefly, in accordance with a preferred embodiment of the present principles, there is provided a method for aligning an object, such as but not limited to, a robotically controlled television camera, with a target. The method commences by directing a coherent beam of radiation, e.g., a laser beam, into an opening in an enclosure having a reflective interior such that the radiation strikes the target which lies in axial alignment with the enclosure opening. Upon striking the target, the beam undergoes reflection through the enclosure opening back to the object for detection. Alignment between the object and the target occurs when substantially all of the radiation undergoes reflection from the target to the object. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]      FIG. 1  depicts a block schematic diagram of a system, in accordance with a preferred embodiment of the present principles, for aligning a robotically controlled camera with a target; 
           [0006]      FIGS. 2 and 3  depict front and side views, respectively, of the target of  FIG. 1 ; and 
           [0007]      FIG. 4  depicts a flow chart illustrating the steps of a method for aligning the robotically controlled camera with the target, both of  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION 
       [0008]      FIG. 1  depicts a block schematic of a system  10  in accordance with a preferred embodiment of the present principles for aligning an object, illustratively depicted as a television camera  12 , with a fixed target  14 , illustratively attached to a solid surface  16 , such as a wall. The alignment system  10  of the present principles includes the combination of a radiation source  18 , and a receiver  20 . In practice, the radiation source  18  comprises a laser for generating a beam  21  of coherent radiation (e.g., light) having a relatively small cross section. Typically, the receiver  20  comprises a photo detector, a photo diode or the like, in combination with a beam splitter (not shown), for detecting the radiation reflected from the target  14  along a path coaxial with the incident beam  21 . The radiation source  18  and the receiver  20  are both mounted to the camera  12  such that when the camera becomes aligned with the target  14  in the manner described hereinafter, the receiver will detect the beam  21  with little if any scattering. 
         [0009]    An interface  22  links both the radiation source  18  and the receiver  20  to a controller  24  that typically includes a programmed computer or the like (not shown). The interface  22  also links the controller  24  to a robotic motor control unit  26  that includes one or more motors (not shown) that serve to pan and tilt the camera  12 , thereby displacing the camera along the X and Y axes, respectively, which lie in a plane normal to axis of the beam  21  as seen in  FIG. 1 . In practice, the robotic motor controller  26  can also control a motorized pedestal (not shown) which serves to raise and lower the camera  12 . In addition, the controller  24  controls a camera lens control  28  coupled to the interface  22 . The camera lens control  28  includes one or more motors (not shown) that serve to adjust various functions of a camera lens (not shown), such as but not limited to, zoom, focus and iris. 
         [0010]      FIGS. 2 and 3  depict front and side views, respectively, of the target  14  associated with which is a hollow enclosure  30 , typically although not necessarily a tube, having a reflective surface. Referring to  FIG. 3 , the wall  16  supports the enclosure  30  of  FIG. 2  by way of a mounting mechanism (not shown) so that the enclosure has its central axis  34  normal to the wall. As best seen in  FIG. 2 , the enclosure  30  has an opening  31  through which a beam of radiation, such as beam  21  of  FIG. 1 , can enter. In practice, the target takes the form a reflector  32 , typically in the form of a circular mirror or the like, lies at the center of the enclosure opening  31  such that the central enclosure axis  34  lies coaxial with an axis normal to, and extending from the center of the reflector. Typically, the reflector  32  has a relatively small diameter (e.g., 0.1275 inches) as compared to the diameter of the enclosure opening  31  (e.g., 3 inches). 
         [0011]    The reflector  32  has its center at a fixed position in both along both the X and Y axes (typically 0, 0) known to the controller  24  of  FIG. 1 . Alignment of the camera  12  of  FIG. 1  with the target  14  will occur upon positioning of the camera such that the axis of the beam  21  of  FIG. 1  lies substantially coaxial with the central enclosure axis  34 , as determined by nearly complete reflection of the beam by the reflector  32  back to the camera with nearly no scattering. To better understand the alignment of the camera  12  in this manner, refer to  FIG. 3 . For purposes of discussion, assume that the camera  12  has a pedestal height such that the beam  21  can strike the reflector  32  when precisely aligned in X and Y. As seen in  FIG. 3 , a misalignment of the beam  21  along the Y axis will result in reflection of the beam along one of axes  36  or  38 , respectively, depending on whether the camera is tilted high or low, respectively. Indeed, the camera misalignment of the camera  12  depicted in  FIG. 3  is sufficiently great so that the beam  21  fails to enter the enclosure opening  31 . 
         [0012]    The alignment technique of the present principles can even detect a small misalignment between the camera  12  and the target  14 . Consider the circumstance when the camera  12  is roughly aligned with the target  14  to the degree that the beam  21  enters the enclosure opening  31  and even strikes the reflector  32 . However, presume that sufficient misalignment exists so that the beam  21  does not lie coaxial with the enclosure axis  34 . Under such circumstances, the reflector  32  will reflect the beam  21  off axis so that beam strikes the reflective interior surface of the enclosure  30 . Thus, the beam  21  will undergo scattering so that little if any portion of the beam will strike the receiver  20 . Thus, only when the camera  12  and target  14  are aligned such that the beam  21  enters the enclosure  30  and strikes the reflector  32  for reflection coaxial with the central enclosure axis  34  will the receiver  20  of  FIG. 1  detect the beam with little if any scattering. Providing the beam  21  with the relatively narrow cross section and marking the reflector  32  relatively small in diameter increases the precision of the alignment technique of the present principles. 
         [0013]    As described with respect to  FIG. 3 , the enclosure  30  is mounted to the support structure  16  to circumscribe the reflector  32 . However, the enclosure  30  could be mounted to the camera  12  to circumscribe the beam  21 . 
         [0014]      FIG. 4  depicts a flow chart showing the steps associated with camera set-up and camera alignment. Camera set-up commences by moving the camera  12  of  FIG. 1  and its associated tripod or pedestal (not shown) to a given position (step  100 ). Thereafter, the laser  18  of  FIG. 1  undergoes activation (step  102 ) to generate the beam  21  directed towards the target  14 . Assuming the camera  12  and the target  12  are aligned such that the laser beam  21  of  FIG. 1  will enter the enclosure  30  and undergo reflection by the reflector  32  with substantially no scattering, the receiver  20  of  FIG. 1  will detect the reflected beam during step  104  of  FIG. 3 . Using the controller  24  of  FIG. 1 , the user saves the camera  12 /laser  18  position as a “laser preset.” 
         [0015]    After initial alignment as described, the camera  12  and its tripod or pedestal can undergo repositioning during step  108 , thus prompting the need for alignment. Camera alignment commences by re-positioning the camera  12  during step  110  to a position close to its original X and Y position as in step  100 . Thereafter, the user activates the laser  18  of  FIG. 1  through the controller  24  of  FIG. 1 , during step  112  of  FIG. 4  to generate the beam  21  of  FIG. 1 . Assuming that the user did not perfectly align the camera  12  with the target  14  during step  110 , then the beam  21  will likely strike the support surface  16  (i.e., the wall) at a point outside of the enclosure opening  31  of  FIG. 1 . Thereafter, the user will recall the desired camera (and hence, laser) position during step  116  that was previously saved as a preset during step  106 . Assuming that the user positioned the camera during step  110  to a position reasonably close to the original position, then the recalling the preset position during step  116  will cause the beam  21  to enter the enclosure opening  31  to strike close to the target  14  during step  118 . Thereafter, the user will displace the camera  12 , either though manual movement or through slight jogs using the controller  24 , or a combination thereof, to precisely align the camera with the target, as signified by the reception of the reflected beam by the receiver  20 . 
         [0016]    The foregoing describes a technique for aligning an object with a target.