Abstract:
Apparatus operable to change direction of an optic axis of a camera, the apparatus comprising: a sphere configured so that at least one camera is mountable therein and having a region through which light may enter the sphere and be collected by the at least one camera; and at least one motor operable to rotate the sphere about the center of the sphere to orient the optic axis in a desired direction.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
       [0001]    The present application claims benefit under 35 U.S.C. §119(a)-(d) of British Application GB0805843.0 filed Apr. 1, 2008, the entire content of which is incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    Embodiments of the invention relate to an “omni-directional” camera system operable to orient an optical axis of a camera in a substantially 4π steradian solid angle of directions. 
       BACKGROUND 
       [0003]    Omni-directional camera systems that are operable to orient a camera to image scenes in a relatively wide range of different directions are relatively common and are used in many different applications. They may be used for example for surveillance and/or alarm systems and for robotic vision. 
         [0004]    Generally, these systems comprise an electromagnetic motor coupled to a camera by a relatively complicated transmission system. The motor and transmission system are controllable to point an optic axis of the camera in a relatively wide range of directions so that the camera can image scenes in an extended field of view that is substantially larger than the camera field of view. 
         [0005]    U.S. Pat. No. 7,274,805 describes an omni-direction camera system that comprises “a rotary electric machine for horizontally rotating (panning)” a camera. The electric machine is coupled to the camera using a relatively complicated set of shafts and a reduction gear. 
         [0006]    U.S. Pat. No. 7,268,819 describes a “scanning camera comprising: an imaging device for capturing an image having an image pickup element, a support shaft attached to the imaging device for changing a photographing direction, a frame for supporting the imaging device through the support shaft, a driver attached to the frame for rotating the imaging device, and a flexible connector electrically connected to the image pickup element and having two planar portions, said two planar portions extending to the frame from at least two positions of the imaging device at opposite sides relative to an axis of the support shaft diagonally away from each other such that the two planar portions of the flexible connector are arranged parallel to the axis of the support shaft.” 
         [0007]    Some surveillance and scanning systems use an optical system for providing an extended field of view for a camera. U.S. Pat. No. 7,190,259 descries a surveillance system for use on a mobile body that has an optical system for providing an extended field of view. The system has “an omnidirectional vision sensor comprising an optical system for reflecting light incident from a maximum surrounding 360-degree visual field area toward a predetermined direction and an imaging section for imaging light reflected from the optical system to obtain image data”. 
       SUMMARY 
       [0008]    An aspect of some embodiments of the invention relate to providing a relatively simple omni-directional camera system operable to orient a camera to image a scene in a relatively large range of different directions. 
         [0009]    According to an aspect of some embodiments of the invention, the omni-directional camera system is configured to point an optical axis of a camera comprised in the system in substantially any direction in a solid angle substantially equal to 4π steradians. 
         [0010]    An aspect of some embodiments of the invention relates to providing a relatively small omni-directional camera system. 
         [0011]    An aspect of some embodiments of the invention relates to providing a relatively simple transmission system for coupling a motor to a camera optionally comprised in an omni-directional camera system so that the motor is operable to change direction of the optic axis of the camera. Optionally, the transmission system couples at least one piezoelectric motor to the camera. 
         [0012]    According to an aspect of an embodiment of the invention, the transmission system, hereinafter referred to as a “sphere transmission” system, comprises a sphere that may be rotated through substantially any angle of rotation about substantially any given axis passing through the center of the sphere. Rotation of the sphere about a given axis may be performed by directly rotating the axis about the given axis or by rotating the sphere about a plurality of other axes that result in a rotation of the sphere about the given axis. Optionally, the sphere is friction coupled to at least one piezoelectric motor operable to rotate the sphere about an axis passing through the sphere&#39;s center. A camera is mounted inside the sphere so that its optical axis is collinear with the center of the sphere and passes through a region of the surface of the sphere through which light may enter the camera. 
         [0013]    In an embodiment of the invention, a support frame having features or comprising elements that contact the surface of the sphere in at least three regions supports the sphere. The support frame is moveable so that coordinates of contact regions relative to a fixed coordinate system having an origin at the center of the sphere may be changed. The contact regions may therefore be changed so that they do not block a direction along which it is desired to point the optic axis of the camera. 
         [0014]    For convenience of presentation an omni-directional camera system comprising a sphere transmisison system is referred to as a “Seeing-Eye” camera system. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES  
         [0015]    Examples illustrative of embodiments of the invention are described below with reference to figures attached hereto. In the figures, identical structures, elements or parts that appear in more than one figure are generally labeled with a same numeral in all the figures in which they appear. Dimensions of components and features shown in the figures are generally chosen for convenience and clarity of presentation and are not necessarily shown to scale. The figures are listed below. 
           [0016]      FIGS. 1A and 1B  schematically show an omni-directional Seeing-Eye camera system, in accordance with an embodiment of the invention; and 
           [0017]      FIG. 2  schematically shows an omni-directional Seeing-Eye camera system comprising a sphere transmission system in accordance with an embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       [0018]      FIGS. 1A and 1B  schematically show an omni-directional camera system  200 , “a Seeing-Eye camera system  200 ”, in accordance with an embodiment of the invention. 
         [0019]    Seeing-Eye camera system  200  comprises a sphere  202 , having mounted inside the sphere a camera  204 , shown in dashed lines, having an optic axis  206  optionally collinear with the center of the sphere. Optic axis  206  passes through a region  208  of sphere  202  through which light that camera  204  images passes. Optionally, region  208  comprises a collecting lens that is a component of an optical system of the camera. By way of example, in  FIGS. 5A and 5B  region  208  is shown having a collecting lens  210  that collects light which camera  204  images. 
         [0020]    Camera  204  is mounted inside sphere  202  using any of various methods and devices. For example, assuming sphere  202  is a substantially hollow spherical shell, camera  204  may optionally be held in place by a configuration of struts attached to the camera and an inside wall of the shell. Optionally, the camera is held in place by a lightweight material such as Styrofoam that is shaped to at least partially fill the sphere and hold the camera. If sphere  202  is substantially solid, optionally camera  204  is held in place in a cavity formed in the sphere. 
         [0021]    Sphere  202  is optionally supported by at least one piezoelectric motor  220 . By way of example, sphere  202  is shown supported by three piezoelectric motors  220 , of which only two are shown in  FIG. 5A . An inset  100  schematically shows an enlarged view of a motor  220 . Optionally, each piezoelectric motor  220  comprise a relatively thin planar piezoelectric vibrator  221  having front and back planar face surfaces  53 , relatively long edge surfaces  54  and relatively short top and bottom edge surfaces  55  and  56  respectively. A friction nub  222  that contacts sphere  202  is located on short edge  55  of the motor. Optionally, four quadrant electrodes  58  are located in a symmetric checkerboard pattern on front face surface  53 . A single large electrode (not shown) is located on back surface  53 . A controller, not shown, electrifies quadrant electrodes  58  to generate vibrations in piezoelectric motor  220  and thereby in friction nub  222  to apply force to sphere  202 . 
         [0022]    In an embodiment of the invention, at least one motor  220  is controllable to generate vibrations in its friction nub  222  to apply force to sphere  202  selectively in either direction along a tangent to the sphere parallel to the motor&#39;s vibrator  221  and in either direction along a tangent to the sphere perpendicular to the vibrator. Motors suitable for the practice of the invention that are controllable to provide such forces are described in U.S. Pat. Nos. 5,453,653, 7,075,211 or 6,384,515, the disclosures of which are incorporated herein by reference. All three motors  220  are shown in  FIG. 5B  discussed below. 
         [0023]    Each piezoelectric motor  220  is optionally held in a “U” shaped motor mounting frame  230 , which is fixed to a support ring  240  and has arms  231 . U-frames  230  and their piezoelectric motors  220  are optionally symmetrically positioned on support ring  240 . The support ring is optionally connected to a beam  242  by a connecting arm  244 . 
         [0024]    Any of various methods known in the art may be used to mount and hold a piezoelectric motor  220  in its U-frame  230 . Optionally, the U-frame has “buttons”  232  that contact and grasp piezoelectric motor  220 . A resilient element  234  comprised in U-frame  230  urges piezoelectric motor  220  so that friction nub  221  of the motor presses against sphere  202 . Optionally, each arm  231  of a U-frame  230  has a bearing  236  at its end on which sphere  202  is supported that allows the sphere to rotate relatively freely about any axis through the center of the sphere. Bearing  236  may be any type of bearing or configuration of bearing known in the art. Optionally, the bearing is a low friction surface along which sphere  202  is free to slide easily. Optionally, as shown in  FIGS. 1A and 1B  bearing  236  comprises a single ball bearing  237 . 
         [0025]    In some embodiments of the invention, an opposing bearing  250  is located on a side of sphere  202  opposite to that contacted by piezoelectric motors  220 . Opposing bearing  250  is connected to beam  242  by a connecting arm  246  and operates to apply force to sphere  202  that maintains the sphere pressed against bearings  236  of U-frames  230  and piezoelectric motors  220 . Optionally, the force is generated by suitably configuring connecting arms  244  and  246  and providing the arms with appropriate elasticity, and/or by directly spring loading bearing  236  and  250 . 
         [0026]    Opposing bearing  250  may be any bearing or bearing arrangement known in the art that allows sphere  202  to rotate freely about any axis through the center of the sphere and to be positioned securely seated on bearings  236  of U-frames  220 . For example, bearing  250  may comprise a low friction surface along which sphere  202  can relatively easily slide, a single bearing or a plurality of ball bearings held in a suitable bearing housing. In  FIGS. 1A and 1B , opposing bearing  250  is shown, by way of example, comprising a single ball bearing  251  held by cylindrical housing  252 . Ball bearing  251  has its center coincident with a line (not shown) passing through the center of sphere  202  and a center of support ring  232 . 
         [0027]    A controller, not shown, controls piezoelectric motors  220  to apply a suitable combination of forces substantially tangent to sphere  202  and parallel to and/or perpendicular to a plane of at least one piezoelectric motor  220  so as to rotate the sphere  202  about any axis through the center of the sphere by a desired angle. The controller can therefore control the motors to orient optic axis  206  of camera  20  along any direction in which it is desired to have the camera acquire an image of a scene. 
         [0028]    It is noted that it is possible to have one motor  220  apply force to sphere  202  while the other motors  220  are operated so that they are substantially disengaged from the sphere. A motor  220  is disengaged from the sphere by exciting the motor so that its friction nub  221  vibrates substantially only along a direction perpendicular to the spheres surface. When operated so that its friction nub  221  vibrates perpendicular to the sphere&#39;s surface friction between the motors&#39; friction nub and sphere  202  is relatively small and contact of the nub and sphere does not substantially resist motion of the sphere. Piezoelectric motors controllable to selectively vibrate substantially only perpendicular to a surface of a body to which it is coupled to move the body are described in U.S. Pat. No. 7,075,211 referenced above. Methods of disengaging a piezoelectric motor from a load to which it is coupled by exciting the motor to vibrate its friction nub perpendicular to a surface to which the nub is pressed, is described in U.S. Patent Publication 2007138910, the disclosure of which is incorporated herein by reference. 
         [0029]    It is noted that for directions in which optic axis  206  intersects or passes near to an element, such as a connecting arm  244  or  246 , ring  232  or a motor  220 , of the structure supporting sphere  202 , the field of view of camera  204  is expected to be at least partially obstructed. For example, in  FIG. 1A , if motors  220  are controlled to orient optic axis  206  to point optic in a direction indicated by a block arrow  256 , the field of view of camera  202  would at least partially be obstructed by opposing bearing  250 . 
         [0030]    In accordance with an embodiment of the invention, to enable camera  204  to image a scene that might be obstructed by an element of the support structure of sphere  202 , beam  242  is rotatable about an axis  243  of the beam so that the obstructing element can be rotated out of the camera&#39;s field of view. For example, to provide an unobstructed field of view for camera  202  in a direction indicated by block arrow  256  beam  242  is optionally rotated by 180°. Following rotation of beam  202 , as schematically shown in  FIG. 1B  the positions of opposing bearing  250  and motors  220  are reversed, with the opposing bearing on the “bottom” and the motors on the top and the field of view in direction  256  is no longer obstructed. Motors  220  may then be controlled to orient sphere  220  so that optic axis  221  points in the direction  256  and camera  204  has an unobstructed view in direction  256 . It is of course understood that a rotation of beam  242  about axis  243  by an angle other than 180°, for example, a rotation of 90° or 45°, could of course be used to unclutter the field of view in direction  256 . 
         [0031]    Beam  242  may be rotated using any of various methods and devices known in the art. In some embodiments of the invention, at least one piezoelectric motor is used to rotate beam  242 . Optionally, an electromagnetic motor is used to rotate the beam. Whereas beam  242  in  FIGS. 1A and 1B  is shown as a single uniform beam, in some embodiments of the invention, beam  242  is articulated so that the beam may be bent about an axis perpendicular to axis  243  and the location of the center of sphere  202  changed. 
         [0032]    Whereas in Seeing-Eye camera system  200 , three piezoelectric motors  220  are used to orient sphere  202 , the present invention is not limited to rotating sphere  202  using three piezoelectric motors that contact the sphere. U.S. Pat. No. 6,284,515, the disclosure of which is incorporated herein by reference, describes a method of rotating a sphere using a single piezoelectric motor in contact with the sphere. 
         [0033]      FIG. 2  schematically shows an omni-directional camera system  260  comprising a single piezoelectric “driving” motor  262  in contact with a sphere  202  having a camera  204  mounted inside the sphere. Camera  204  has an optic axis  206  optionally collinear with the center of the sphere. Optionally, driving motor  262  is similar to motors  50  and  60  shown in  FIGS. 1A-1D  and comprises a relatively thin piezoelectric vibrator  263  having a friction nub  264 . 
         [0034]    Sphere  202  seats on friction nub  264  of piezoelectric driving motor  262  and is held in place on the friction nub optionally by a support bearing  270 , which enables the sphere to rotate freely about any axis through the center of the sphere. Support bearing  270  may be any suitable bearing known in the art and is optionally a ring bearing comprises an annular ball bearing housing  271  comprising a plurality of ball bearings (not shown). An arm  272  optionally connects annular ring housing  271  to a beam  242  rotatable about an axis  243 . 
         [0035]    Driving motor  262  is optionally mounted inside a rotation frame  266 . Rotation frame  266  has an axis of rotation  267  and optionally comprises a rotation collar  268 . The rotation collar is held by a bearing collar  280  that extends from a motor mounting frame  281  so that the rotation collar is substantially freely rotatable about axis  267 . Motor mounting frame  281  holds a piezoelectric steering motor  290 . Steering motor  290  is optionally similar to piezoelectric motors  50  and  60  ( FIGS. 1A-1D ) and has a piezoelectric vibrator  291  and a friction nub  292 . Mounting frame  281  urges piezoelectric motor towards rotation collar  268  so that friction nub  291  resiliently presses against the collar. Any method known in the art may be used to resiliently press steering motor  290  to collar  268 . Optionally, as shown in  FIG. 2 , mounting frame  281  comprises a spring  282  that urges the motor to the collar. 
         [0036]    In an embodiment of the invention, driving motor  262  is controllable to apply force to rotate sphere  202  selectively in either direction along a tangent, schematically indicated by a double arrowhead line  300 , to the sphere at the region where the sphere contacts friction nub  264 , which tangent is parallel to piezoelectric vibrator  263 . Depending on its direction along tangent  300 , the force rotates sphere  202  clockwise or counterclockwise about a rotation axis  302  that passes through the center of the sphere and is perpendicular to tangent  300  and axis  267 . 
         [0037]    Steering motor  290  is controllable to rotate rotation collar  268  and thereby piezoelectric motor  262  about axis  267  so that tangent  300  and therefore axis of rotation  302  points in any desired direction perpendicular to axis  267 . Driving motor  262  is then controllable to rotate sphere  202  clockwise or counterclockwise about rotation axis  302 . A suitable controller, not shown, controls steering motor  290  to rotate driving motor  262  about axis  267  and motor  262  to rotate sphere  202  about rotation axis  302  through appropriate angles to point optic axis  206  in any desired direction. As in Seeing-Eye camera  200 , beam  242  is rotatable to provide camera  204  with a clear field of view in substantially any direction. 
         [0038]    It is noted that the above configurations of a Seeing-Eye camera in accordance with an embodiment of the invention, comprise a support structure for supporting a sphere, which has a bearing configuration opposed by an opposing bearing or a piezoelectric motor. The opposing bearing or piezoelectric motor applies a force to the sphere that aids in maintaining the sphere seated in the bearing configuration. Practice of the invention is not limited to any particular support structure for holding a sphere so that it is rotatable about axes that pass through the sphere&#39;s center. For example, in some embodiments of the invention, a Seeing-Eye camera does not comprise an opposing bearing or opposing piezoelectric motor that applies a force that operates to seat the sphere in a bearing configuration. Optionally, the sphere of the camera rests and is held in place on an at least one piezoelectric motor and/or a suitable bearing configuration by gravity. Optionally, the sphere is held in place by magnetic force between the sphere and a suitable permanent or electromagnet magnet. For example, the sphere is optionally held in place by magnetic force between a magnet and magnetic moment induced in material of the sphere by the field of the magnet. 
         [0039]    It is further noted that whereas in the described embodiments of the invention the camera mounted in the sphere has an optic axis collinear with the sphere center, in some embodiments of the invention the camera may have an optic axis displaced from the sphere center. It is also noted that in some embodiments of the invention a Seeing-Eye camera may comprise more than one camera mounted inside a sphere. For example a Seeing-Eye camera, in accordance with some embodiments of the invention, comprises two cameras mounted inside a sphere. Optionally, the cameras have their optic axes parallel and are displaced one from the other to provide binocular vision and depth perception. 
         [0040]    In the description and claims of the present application, each of the verbs, “comprise” “include” and “have”, and conjugates thereof, are used to indicate that the object or objects of the verb are not necessarily an exhaustive listing of members, components, elements or parts of the subject or subjects of the verb. 
         [0041]    The invention has been described with reference to embodiments thereof that are provided by way of example and are not intended to limit the scope of the invention. The described embodiments comprise different features, not all of which are required in all embodiments of the invention. Some embodiments of the invention utilize only some of the features or possible combinations of the features. Variations of embodiments of the described invention and embodiments of the invention comprising different combinations of features than those noted in the described embodiments will occur to persons of the art.