CROSS-REFERENCE TO RELATED APPLICATION 
   This is a complete patent application based on Provisional Patent Application No. 60/438,797, filed Jan. 9, 2003. 


   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a method of and an apparatus for the inspection of vehicle wheel alignment and, more particularly, to methods and apparatus using cameras for the inspection of vehicle wheel alignment. 
   2. Description of the Related Art 
   In U.S. Pat. No. 5,535,522, issued Jul. 16, 1996 to Bernie F. Jackson, there is disclosed an apparatus for determining the alignment of a motor vehicle&#39;s wheels which comprises optical sensing means such as a pair of video cameras, an electronic processing means connected to the optical sensing mean, targets which either form parts of the wheels or are attached thereto and a display for indicating the detected alignment. In operation of this prior art system, the cameras are employed to provide images of the targets on the wheels, and the images are processed by the electronic processing means to provide an indication of the alignment or misalignment of the wheels. 
   Such inspection requires the targets to be kept within the fields of view of the cameras. However, during the correction of the alignment of the wheels of a vehicle, it is usually necessary to perform work underneath the vehicle and also at e.g. waist height. Consequently, it is necessary to raise and lower the vehicle. This has required corresponding raising and lowering of the cameras. For this purpose, the cameras were normally mounted on a boom provided with a hydraulic or other means for raising and lowering the boom and, therewith, the cameras. 
   This arrangement has a number of disadvantages. Firstly, the provision of the cameras with a camera boom and the means for raising and lowering the camera boom are relatively expensive, and considerable energy is utilized in raising and lowering the boom. Also, when the camera boom is in a lowered position, it becomes a hazard for people who risk walking into the boom and knocking their heads on the boom. Lowering of the camera boom produces the hazard that something or someone might be accidentally crashed below the boom. In addition, since it is necessary to leave an area free below the boom, that area is wasted. 
   BRIEF SUMMARY OF THE INVENTION 
   It is accordingly an object of the present invention to provide a novel and improved method of and apparatus for the inspection of vehicle wheel alignment which avoids the use of a camera boom which has to be raised and lowered. 
   According to the present invention, there is provided a vehicle wheel alignment inspection apparatus which comprises at least one camera, and preferably a pair of cameras, for generating image information by viewing one or more optical targets mounted on one or more wheels of a vehicle, a data processing apparatus responsive to the image information from the camera or cameras for generating wheel alignment information, and a camera tilt mechanism connected to the or each camera. 
   In operation of the present apparatus, the vehicle is raised and lowered on a vehicle lift to enable work to be performed under the vehicle and at e.g. waist height, and the or each camera is correspondingly tilted such that the field of view always includes the optical targets mounted to the vehicle wheels. 
   The camera tilt mechanism may be manually operable or, alternatively, may be pneumatically, hydraulically or electrically driven. 
   In a preferred embodiment of the invention, the camera tilt mechanisms is pneumatically operated, and uses compressed air lines which are commonly available in vehicle service bays. 
   Means for pneumatically tilting the cameras may be linked to a pneumatic system for operating the vehicle lift used to raise and lower the vehicle under test, so that operation of the vehicle lift automatically and simultaneously operates the camera tilting mechanism. 
   A pair, or two pairs, of the cameras may be mounted on a camera boom so as to be movable laterally of the cameras, i.e. in the longitudinal direction of the camera boom, from one service bay to another. In this way, the apparatus according to the present invention can be readily adapted for use in a plurality of different service bays in side-by-side applications. Also, the apparatus can be mounted to a support beam that pivots about the vertical axis. In this way, the apparatus according to the present invention can be readily adapted for use in face-to-face service bay applications. 
   The present invention also provides a method of vehicle wheel alignment inspection which employs at least one camera for generating image information by viewing a target mounted on a wheel of a vehicle and, in response to the image information from the cameras, generating wheel alignment information, and which includes the step of tilting or pivoting the camera or cameras in accordance with raising and lowering of the vehicle to maintain the target in a filed of view of the camera. 


   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be more readily understood from the following description of preferred embodiments thereof, which are given by way of example only, and which are illustrated in the accompanying drawings, in which: 
       FIG. 1  shows a view in side elevation of a pneumatically operated vehicle wheel alignment apparatus according to the present invention in use with a vehicle elevated into a raised position on a vehicle lift; 
       FIG. 2  shows a view corresponding to that of  FIG. 2 , but with the vehicle lift retracted to move the vehicle into a lowered position; 
       FIG. 3  shows a perspective view of an optical target mounted on a motor vehicle wheel during wheel alignment inspection; 
       FIG. 4  shows a side view of the vehicle wheel alignment apparatus of  FIGS. 1 and 2  with the camera in a home or raised position; 
       FIG. 5  shows a side view of the vehicle wheel alignment apparatus corresponding to that of  FIG. 4  with the camera in a tilted position; 
       FIG. 6  shows a perspective view of a pair of cameras mounted on a camera boom supported by a camera tilt mechanism and forming parts of the apparatus of  FIG. 1 ; 
       FIG. 7  shows a block diagram of a pair of cameras and an associated data processor and display. 
       FIGS. 8 and 9  show views in side elevation of a manually operated camera tilt mechanism with a camera in two different positions; and 
       FIG. 10  shows a view in front elevation of a camera boom mounted on an overhead. 
   


   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Referring now to the accompanying drawings,  FIGS. 1 and 2  show a motor vehicle, indicated generally by reference numeral  10 , carried on a vehicle lift system, indicated generally by reference numeral  12 , for inspection by a pneumatically operated vehicle wheel alignment inspection apparatus indicated generally by reference numeral  14 . 
   The inspection apparatus comprises a support in the form of a post  15  extending vertically downwardly from a ceiling  16  and carrying a horizontal camera boom  46  (FIG.  6 ), on opposite ends of which are mounted a pair of video cameras  18 . The camera boom  46  is connected to the lower end of the post  15  by a hinge  20  which has a horizontal axis of pivotation and which therefore allows the boom  46  and therewith the cameras  18  to pivot vertically. A pneumatic cylinder  22  is connected between the post  15  and the camera boom  46  for effecting such vertical pivotation. 
   As shown in  FIG. 1 , the vehicle lift  12  is extended to raise the vehicle  10  into an elevated position, and the pneumatic cylinder  22  is in a retracted, or home position, such that fields of view  24 , indicated by chain-dot lines, of the cameras  18  include optical targets  26  and wheels  28  of the vehicle  10 . As shown in  FIGS. 1 and 2 , the optical targets  26  are on the front and rear wheels  28  at one side of the vehicle, within the field of view of one of the cameras  18 , and it is to be understood that similar optical targets (not shown) are mounted on the front and rear wheels at the opposite side of the vehicle  10  within the field of view of the other camera  18 . 
   In  FIG. 2 , the vehicle lift  12  has been contracted to lower the vehicle  10 . A piston rod  30  ( FIGS. 4 and 5 ) has been correspondingly extended along the longitudinal axis of the pneumatic cylinder  22  so as to deflect the field of view  24  in  FIG. 1  of the camera  18  downwardly in order to maintain the targets  26  and wheels  28  within the field of view  24 . 
     FIG. 3  shows an expanded view of one of the optical targets  26  mounted on a motor vehicle wheel  28  by an adaptor indicated generally by reference numeral  32 . The camera  18  forms a perspective image of this optical target  26  and translates this into an electrical signal. 
   As can be seen in  FIGS. 4 and 5 , the camera  18  is pivotally connected to the lowermost end of the post  15  by means of a metal plate  34  attached to camera  18  and a metal plate  36  attached to the post  15 , the hinge  20  being attached to the metal plates  34  and  36 . The pneumatic cylinder  22  is mounted on and fixed to the metal plate  36  and the piston rod  30  is fixed to the metal plate  34 . The pneumatic cylinder  22  has two compressed pneumatic inlets  38  and  40  attached to compressed pneumatic lines  42  and  44 , respectively. The compressed pneumatic lines  42  and  44  are attached to a compressed pneumatic source (not shown) by means of valves (not shown). 
     FIG. 4  shows the pneumatic cylinder  22  in a neutral position with the piston rod  30  fully retracted so as to raise the boom  47  and therewith the cameras  18  into raised positions corresponding to the raised elevation of the vehicle  10  on the lift  12  as shown in FIG.  1 . 
   When the vehicle  10  is lowered by the lift  12 , the camera  18  must be adjusted to maintain the optical targets  26  within the fields of view  24 . To accomplish this, compressed air is supplied through the pneumatic inlet  38 , causing piston  30  to extend along the longitudinal axis of the pneumatic cylinder  22 , and simultaneously air is exhausted through the pneumatic inlet  40 , causing a low pressure and allowing the extension to take place. The piston rod  30  is allowed to reach its maximum stroke, at which point the pneumatic cylinder  22  and piston rod  30  are again in a rest position. The cameras  18  are now adjusted so that their fields of view include the optical targets  26  of the lowered vehicle  10 . 
   When the vehicle  10  is raised by the lift  12 , a corresponding adjustment needs to be made to the cameras  18 . In this situation, compressed air is supplied though the inlet  40  while air is exhausted through the inlet  38 , forcing the piston rod  30  to contract into the pneumatic cylinder  22 . Again, the piston rod  30  is allowed to reach it&#39;s maximum bore at which point the piston rod  30  is in a rest position with pneumatic cylinder  22 . 
   In the above-described embodiment of the invention, the cameras  18  are connected to a data processor  47  (FIG.  7 ), at which image information generated by the cameras  18  from the targets  26  is analyzed to provide wheel alignment information which, in turn, is displayed on a display  48 . The cameras  18 , the data processor  47 , software employed by the data processor  47  and the display  48  are components of a commercially available wheel alignment system sold as the V3D Wheel Alignment System by John Bean Company, of Arkansas, and are therefore not described herein in greater detail. Alternatively, the wheel alignment system sold by Hunter Engineering Company, of St. Louis, Mo. as DSP 400 or DSP 600 Wheel Alignment System, or any other suitable system, may be employed. 
   The above-described pneumatic camera tilting system may be connected to the pneumatic system of the vehicle lift  12  so that the cameras are automatically tilted when the vehicle is raised or lowered. 
   Instead of employing a pneumatically operated tilting device as described above, it is alternatively possible to employ an hydraulically or electrically operable device for tilting the cameras  18 . 
   Another method and apparatus for tilting cameras  118 , (only one of which is shown), mounted on opposite ends of a camera boom  116  which is supported on the top of a post  117 , makes use of a manually operated handle  49 , as shown in  FIGS. 8 and 9 . The handle  49  is connected to the boom  116 , which is pivotally mounted on its post  117  so as to be vertically pivotable, i.e. pivotable about a horizontal axis, by a lever linkage, which is indicated generally by reference numeral  50 . 
     FIG. 8  shows the position of one of the cameras  118  during inspection of a vehicle which has been raised by a lift (not shown), corresponding to the situation of the vehicle  10  in FIG.  1 . The handle  49  has been correspondingly pivoted upwardly to tilt the boom  116  and the cameras  118  so that targets (not shown) are within the fields of view of the cameras. 
   In  FIG. 9 , the handle  49  has been lowered to tilt the boom  116  and the cameras  118  so as to deflect the fields of view  24  of the cameras  118  downwardly when the vehicle is lowered by the lift. 
     FIG. 10  shows a further modified wheel alignment inspection apparatus. In  FIG. 10 , a boom  130  carrying a pair of cameras  134  is suspended from the lower end of a horizontally displaceable vertical member  132  by a hinge and pneumatic cylinder arrangement which is similar to that of  FIGS. 4 and 5 . 
   More particularly, the boom  130  is connected to the lower end of the vertical member  132  by a hinge  136  between a pair of plates  146  and  148 , with a pair of pneumatic cylinders  138  for causing relative pivotation of the plates  146  and  148 , and thereby tilting of the boom  130  and the cameras  134 . 
   The upper end of the vertical member  132  is connected to a trolley indicated generally by reference numeral  160 , which can run to and from along a track  162  in a direction parallel to the longitudinal axis of the boom  130  in order to move the boom  130  and its cameras  134  from one service bay to another. 
   In this embodiment of the invention, the track  162 , the trolley  160 , the vertical member  132  all serve as components of a support for the cameras  134 . 
   As will be apparent from the above description of the preferred embodiments of the present invention, the present apparatus and method have the advantage that they enable the field of view of the cameras to be varied vertically without the expense or hazards of prior art systems employing vertically displaceable camerabooms requiring camera lifting devices, this being achieved according to the present invention by tilting the cameras. 
   As will be apparent to those skilled in the art, various modifications may be made to the above-described embodiments of the present invention. 
   For example, the present method and apparatus may be modified to employ two pairs of cameras, at opposite ends of the vehicle under test, and may alternatively employ three cameras or only a single camera. 
   Also, the tilting of the camera or cameras or of the camera boom may be controlled automatically, in accordance with the raising and lowering of the vehicle, by the use of image seeking technology.
An apparatus and a method for inspecting wheel alignment employ an optical target mounted on a wheel of a motor vehicle, a support mounting a camera above ground for generating image information of the optical target that falls within the camera's field of view, and a pivotal connection between the camera and the support,. The pivotal connection allows vertical pivotation of the camera through a range of pivotation sufficient to maintain the target in the field of view of the camera during displacement of the vehicle between raised and lowered positions of a vehicle lift carrying the vehicle. Images of the target captured by the camera are analysed to generate wheel alignment information.