Abstract:
A mount for directional devices such as cameras, optical devices or laser devices, providing independent orthogonal adjustment of panning alignment of such devices in a horizontal plane in combination with independent adjustment of rotation alignment of such devices about a vertical axis parallel to the optical axis. In a preferred embodiment, a CCD camera is aligned over a Liquid Crystal Display under test. Threaded adjustment screws angularly separate opposing plates disposed along each of x-, y- and z-axes. This angular separation generates a moment about the axis of rotation, causing a corresponding shift in the camera&#39;s alignment. Structure is also provided to compensate for differential thermal behavior of opposing plates. The inventive mount is advantageously designed to be reversible so that left-handed and right-handed embodiments can be nested to facilitate a multi-camera deployment.

Description:
TECHNICAL FIELD OF THE INVENTION 
     This invention relates generally to mounts for directional devices such as cameras, optical devices or laser devices, and specifically to a mount that provides independent orthogonal adjustment of panning alignment of such devices in a horizontal plane in combination with independent adjustment of rotation alignment of such devices about a vertical axis parallel to the optical axis. 
     BACKGROUND OF THE INVENTION 
     It is known in the art to use cameras having charge-coupled device (“CCD”) arrays to test the operation of liquid crystal displays (“LCDs”) such as may be found on many cellular telephones. As information is fed from the telephone to be displayed on the LCD, testing generally requires that the LCD actually displays the information in the way designed. A technique to enable such testing is to view the LCD with a CCD camera as the information is sent to the LCD. The signal from the camera can be compared with the information sent to the LCD to verify accuracy to a high degree of resolution. 
     It will be understood that it is important for the CCD array in the camera to be able to be accurately aligned with the LCD array to enable precise testing. If the scan lines on the camera can be lined up accurately with the pixels on the LCD, the testing software generally works much more predictably. Camera mountings in the art generally allow fine adjustment of the camera&#39;s field of view by “sweeping” or “panning” along both X and Y directions in the plane of the arrays, but do not allow fine adjustment of rotation about a Z-axis orthogonal to the plane of the arrays and parallel to the optical axis of the camera. Hereinafter, such rotational adjustment about the Z-axis shall also be referred to “Theta” adjustment, or adjustment in the “Theta axis”. 
     Prior art mounting devices are known to use translational stages to adjust position in X and Y directions. These stages consume significant space. Such prior art mounts also offer no Theta axis adjustment as a built-in feature, so that X, Y and Theta adjustment can be accomplished independently in a single device. 
     In addition to being large, prior art mounts tend to be very expensive. The large size and prohibitive expense of prior art mounts can be explained to some extent in that such mounts are almost universally designed for optical applications. There is a need in the art for a camera mount addressing the problems of digital testing in a confined space. In particular, it is sometimes desirable to place two or more CCD cameras in close proximity to test LCDs. The extravagant use of physical space by prior art mounts makes such multi-camera deployments very challenging. 
     Prior art mounts typically also lack locking mechanisms for holding the camera in place during and after adjustment and alignment. It is often desirable to move the entire testing assembly without upsetting the alignment. 
     There is therefore a need in the art for a camera mount independently adjustable in X, Y and Theta axes. A solution also providing compactness and cost economy will also provide measurable advantage, especially if multi-camera deployments are also enabled. A locking mechanism will provide further advantage towards preventing loss of alignment. 
     SUMMARY OF THE INVENTION 
     These and other objects, features and technical advantages are achieved by a three axis camera mount that provides rotational adjustment in X, Y, and Theta axes. All axes of rotation consist of two plates rotationally attached using spherical contact surfaces and adjusted by a fine pitch screw. X and Y rotation is required to pan the camera to align its field of view precisely. The Theta rotation is to compensate for the camera&#39;s inherent misalignment in the CCD position, which is often out of position by up to 3 degrees. 
     Each adjustable axis consists of two plates, a ball bearing and another spherical surface for the hinge, one or more spring-loaded retaining screws, and a fine pitch adjustment screw with a lock nut. 
     The invention has a locking capability. Using lock nuts on the adjustment screws means that there will not be any movement of the device during use or drifting over time. 
     The invention combines the three needed axes of adjustment in one device. The design further controls differential thermal behavior of the cooperating elements of the mount so as to minimize the effect of such thermal behavior on the alignment. In a preferred embodiment, thermal behavior is controlled by guiding differential thermal displacement via slots retaining one point of contact in each of the horizontal and vertical planes. Displacement is contained to axial directions (X, Y or Z) that are easily compensated for by adjustment. 
     The invention is very low cost. Ball bearings are used for the precise rotation axes. Machined features in the various plates serve as the other bearing surfaces. 
     Each camera is attached to a 3-axis mount that allows the maintenance technician to adjust the camera&#39;s field of view along X and Y axes independently. The mount further allows the operator to align the Theta axis independent of other adjustments. 
     In a preferred embodiment, the angular range of camera motion for each adjustment is approximately plus or minus 5 degrees. The threads on the adjustment screws are selected to give an approximate resolution of 0.358 degrees of camera rotation per turn of the screw. This corresponds to a panning motion for the camera&#39;s field of view of 1.5 mm to 2.5 mm per turn of the screw (depending on the distance of the mount from LCD). 
     The camera is connected to the mount using a camera-specific mounting plate. This enables the mount to be used with different cameras. 
     Each mount contains a baseplate rigidly mounted to the fixture. The horizontal motion plate (providing X and Y adjustments) is attached to the baseplate. The vertical support plate is fixed to the horizontal motion plate. The vertical motion plate (providing Theta adjustment) is attached to the vertical support plate. The camera-specific mounting plate is fixed to the vertical motion plate, and the camera is mounted to it. 
     The mount is also designed to accommodate multi-camera deployment with minimal adaptation. In a preferred embodiment, the L-shaped base plate is reversible. The mount may be assembled on the base plate whether the base plate is disposed “right side up” or “upside down,” thus allowing two cameras to be placed side by side in within a “U” configuration formed by adjacent L-shaped base plates. This feature makes the invention extremely compact. Its nested design conserves space to the highest degree possible, while still allowing very fine, precision adjustment. 
     Reversibility of the base plate is enhanced still further in a preferred embodiment where the design is selected to keep the optical axis of the camera a constant distance from the vertical mounting surface regardless of whether the base plate is disposed “right side up” or “upside down.” In this way, cameras can be nested in a multi-camera deployment where the optical axes of the cameras are co-planar and parallel to the plane of the vertical mounting surface. 
     It is therefore a technical advantage of the present invention to provide a camera mount that is independently adjustable in X, Y and Theta axes. 
     A further technical advantage of the present invention is to contain thermal displacement of the mount to directions that are easily adjustable. 
     A still further technical advantage of the present invention is to be able to lock in an adjustment of the mount to preserve alignment. 
     Another technical advantage of the present invention is to provide a light and compact mount that is relatively low in cost to manufacture. 
     Another technical advantage of the present invention is to facilitate camera nesting in multi-camera deployments. A reversible base plate allows the same mount to be assembled on the base plate whether the base plate is disposed “right side up” or “upside down.” As a result, two cameras may be nested side-by-side in a within a combined “U” frame, advantageously also maintaining a constant separation between the optical axes of the camera and the plane of the vertical mounting surface. 
     The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and the specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a more complete understanding of the present invention, and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which: 
     FIG. 1 is a frontal perspective view of inventive mount  100  holding a camera pointing down; 
     FIG. 2 is a rear perspective view of inventive mount  100  as depicted in FIG. 1; 
     FIG. 3 is an exploded view of inventive mount  100  as depicted in FIG. 1; and 
     FIG. 4 is plan view of a multi-camera deployment using right-handed and left hand assemblies  401 L and  401 R. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 is a perspective view of the inventive mount  100  holding camera assembly  180  in preparation for alignment. In FIG. 1, camera assembly  180  comprises lens  181  (pointing down) awaiting alignment over, for example, an LCD (not illustrated). It will be appreciated that in accordance with the invention, it is desired to adjust the field of view of lens  181  by independently (1) sweeping (panning) along an X-axis orthogonal to the optical axis of lens  181 , (2) sweeping (panning) along a Y-axis also orthogonal to the optical axis of lens  181  and further orthogonal to the X-axis, and (3) rotating about a Z-axis parallel to the optical axis of lens  181 . As noted earlier, for purposes of this disclosure, rotation of about the Z-axis is termed “Theta rotation” or “Theta adjustment.” 
     In FIG. 1, base plate  101  is disposed to be fixed to an immobile vertical mounting surface (fixation to surface not illustrated for clarity). As shown on FIG. 1, base plate  101  is advantageously an L shape with legs extending along X- and Y-axes. In the X- and Y-axis convention according to FIG. 1, mounting leg  102  of base plate  101  extends along the X-axis and is fixed to the vertical mounting surface so that cantilevering leg  103  cantilevers out from the vertical mounting surface. Thrust plate  110  comprises an L-shaped horizontal motion portion  112  with a horizontal planar surface  113  also disposed in the X-Y plane and positioned to oppose base plate  101 . Thrust plate  110  further comprises a vertical support portion  114  with a vertical planar surface  115  disposed to extend along the Z-axis. 
     With further reference to FIG. 1, vertical motion plate  120  is planar, its plane extending along the Z-axis and its reverse face positioned to oppose vertical planar surface  115 . Mounting plate  130  attaches to the averse side of vertical motion plate  120 , and camera assembly  180  in turn attaches to mounting plate  130 . In a preferred embodiment, inventive mount  100  may be disposed to accommodate a range of mounting plates  130 , each mounting plate  130  customized to the particular attachment requirements of various different types and models of camera assembly  180 . 
     FIG. 2 is a further perspective view of inventive mount  100 , this time from behind vertical support portion  114 . FIG. 2 shows holes  201  in mounting leg  102  of base plate  101 . Holes  201  receive fasteners (not illustrated) to fix inventive mount  100  to a vertical mounting surface (omitted for clarity) in the manner described above with reference to FIG.  1 . 
     FIG. 3 is an exploded view of FIG.  1 . With reference now to FIG. 3, base plate  101  and horizontal motion portion  112  are held together by screws  303 H and are separated by ball bearing  305 H. Screws  303 H pass through plain holes  307 H in base plate  101  and engage into threaded holes  309 H in horizontal motion portion  112 . Recesses  311 H in the underside of base plate  101  receive springs  313 H as retained over screws  303 H threaded into threaded holes  309 H. When compressed by tightening of screws  303 H, springs  313 H thus hold base plate  101  and horizontal motion portion  112  adjustably apart on opposing sides of ball bearing  305 H. 
     FIG. 3 further shows that vertical support portion  114  and vertical motion plate  120  are held together by screws  303 V and separated by ball bearings  305 V. Analogous to the separation of base plate  101  and horizontal motion portion  112 , screws  303 V pass through plain holes  307 V in vertical support portion  114  and engage into threaded holes  309 V in vertical motion plate  120 . Recesses  311 V in the back of vertical support portion  114  receive springs  313 V as retained over screws  303 V threaded into threaded holes  309 V. When compressed by tightening of screws  303 V, springs  313 V thus hold vertical support portion  114  and vertical motion plate  120  adjustably apart on opposing sides of ball bearings  305 V. 
     With continuing reference to FIG. 3, ball bearing  305 H sits, when assembled, in a recess  321 H in each of opposing faces of base plate  101  and horizontal motion portion  112  (recess  321 H in horizontal planar surface  113  hidden). Recesses  321 H may advantageously, although not mandatorily, be undersized holes in said opposing faces. 
     Similarly, one of ball bearings  305 V sits, when assembled, in a recess  321 V in each of opposing faces of vertical support portion  114  and vertical motion plate  120  (recess  321 V in vertical planar surface  115  again hidden). Again, recesses  321 V may advantageously, although not mandatorily, be undersized holes in said opposing faces. In a preferred embodiment, however, one side of the other ball bearing  305 V sits, when assembled, in a slotted recess  323 V in one of the opposing faces of vertical support portion  114  and vertical motion plate  120  (FIG. 3 illustrating slotted recess  323 V in vertical support portion), while the other side of the other ball bearing  305 V sits in a plain recess  321 V (hidden in FIG.  3 ). Again, slotted recess  323 V may advantageously, although not mandatorily, be an undersized slotted hole. The inventive significance of this slotted recess  323 V feature is described further below in connection with the control of thermal behavior. 
     FIG. 3 also depicts adjustment screws  151 X,  151 Y and  151 T. Adjustment screws  151 X and  151 Y are disposed, when threaded through threaded holes  331 H in base plate  101 , to adjustably separate base plate  101  and horizontal motion portion  112  at the point of contact of adjustment screws  151 X and  151 Y with horizontal planar surface  113 . In this way, referring now to FIG. 1, it will be seen that the adjustable separation caused by rotation of adjustment screw  151 X causes a moment to be exerted about the Y-axis along a line between ball bearing  305 H and the point of contact between adjustment screw  151 Y and horizontal planar surface  113 . This moment causes camera assembly  180  to sweep or pan along the X-axis. Similarly, the adjustable separation caused by rotation of adjustment screw  151 Y causes a moment to be exerted about the X-axis along a line between ball bearing  305 H and the point of contact between adjustment screw  151 X and horizontal planar surface  113 . This moment causes camera assembly  180  to sweep or pan along the Y-axis. 
     Referring back to FIG. 3, adjustment screw  151 T is disposed, when threaded through threaded hole  331 V in vertical motion plate  120 , to adjustably separate vertical support portion  114  and vertical motion plate  120  at the point of contact between adjustment screw  151 T and vertical planar surface  115 . In this way, referring now again to FIG. 1, it will be seen that the adjustable separation caused by rotation of adjustment screw  151 T causes a moment to be exerted about the Z-axis along a line between ball bearings  305 V. This moment causes the desired Theta adjustment of camera assembly  180 . 
     The foregoing X, Y and Theta adjustment is further facilitated in a preferred embodiment where, advantageously, plain holes  307 H and  307 V are oversized in receiving screws  303 H and  303 V respectively. A loose fit of screws  303 H and  307 V in holes  307 H and  307 V enables “sloppiness” therein, whereby the retention of screws  303 H and  303 V in holes  307 H and  307 V does not impede or interfere with enablement of X-, Y- or Theta adjustment of camera assembly  180 . 
     With continuing reference to FIG. 3, adjustment screws  151 X,  151 Y and  151 T each also optionally include locking nuts  341  to lock adjustment screws  151 X,  151 Y and  151 T in place once alignment is complete. 
     In a preferred embodiment, adjustment screws  151 X,  151 Y and  151 T are advantageously ball-tipped M5×0.4 screws. This thread pitch gives an approximate resolution of 0.358 degrees of camera rotation per turn of the screw, which in turn corresponds to a panning motion for the camera&#39;s field of view of 1.5 mm to 2.5 mm per turn of the screw (depending on the distance of the mount from LCD). The ball-tipped feature of adjustment screws  151 X,  151 Y and  151 T ensures that highly localized points of contact are made with opposing surfaces during adjustment, allowing incremental displacement to be exerted on the opposing surfaces as precisely as possible. 
     As described above with reference to FIG. 3, a preferred embodiment disposes one ball bearing  305 V to sit, when assembled, in a slotted recess  323 V in one of the opposing faces of vertical support portion  114  and vertical motion plate  120 . In this embodiment, the three points of contact in the interface between vertical support portion  114  and vertical motion plate  120  comprise one fixed (one ball bearing  305 V sitting in recesses  321 V), one free (ball-tip of adjustment screw  151 T on vertical planar surface  115 ), and one guided (other ball bearing  305 V constrained by one side thereof received into slotted recess  323 V). With the three points of contact disposed in this way (one fixed, one free, one guided), differential thermal behavior of vertical support portion  114  and vertical motion plate  120  is now controlled to displacement in either Z- or X-directions, both of which can be directly compensated for by adjustment. 
     Thermal behavior in the horizontal (X-Y) plane is similarly controlled by an analogous mechanism. Ball bearing  305 H as received in recesses  321 H is a fixed point of contact in the interface between opposing faces of base plate  101  and horizontal motion portion  112 . The ball-tip of a selected one of adjustment screws  151 X or  151 Y is a free point of contact against horizontal planar surface  113 . In a preferred embodiment, however, the ball-tip of the other adjustment screw is received into a slot provided into horizontal planar surface  113  along an axis parallel to the portion of base plate  101  directly opposing beneath (slot not illustrated). Again, with the three points of contact disposed in this way (one fixed, one free, one guided), differential thermal behavior of base plate  101  and horizontal motion portion  112  is now controlled to displacement in either Xor Y- directions, both of which can be directly compensated for by adjustment. 
     Further reference to FIG. 3 shows that in a preferred embodiment, base plate  101  is disposed to be reversible. Base plate  101  may be separated from the rest of the assembly by releasing screws  303 H, whereupon base plate  101  may be flipped “upside down” so that what was formerly the underside of base plate  101  now opposes horizontal planar surface  113 . It will be appreciated that to enable this reversibility, adjustment screws  151 X and  151 Y must be unscrewed all the way out and screwed in again from the other side. Also, to be reversible, base plate  101  must (1) provide recesses  311 H and a recess  321 H on both sides, in order to receive springs  313 H and ball bearing  305 H from either side; and (2) provide holes  307 H equidistantly along mounting leg  102  and cantilevering leg  103 . 
     Reversibility of base plate  101  as described immediately above enables two cameras to be nested adjacently within a combined “U”-shape as shown on FIG.  4 . Assemblies  401 L and  401 R differ only in that the base plate  101  in one assembly is reversed, and that mounting leg supports vertical support portion  114  in one assembly while cantilevering leg  103  supports it in the other. Significant further advantage is gained in the multi-camera deployment illustrated in FIG. 4 when the dimensions, diameters, hole placements and thicknesses of the components of assemblies  401 L and  401 R are selected to keep a constant cantilevered distance D from the optical axis of camera assemblies  180  to a common vertical mounting surface. 
     The foregoing disclosure describes the inventive mount in use in conjunction with holding and aligning a CCD camera. It will be appreciated, however, that the invention is not limited solely to CCD camera applications, and that the invention may be used with equivalent enabling effect for adjustment and alignment advantage in conjunction with other devices, such as optical or laser devices. 
     Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims.