Abstract:
A camera assembly may include an autofocus assembly that selectively imparts a first displacement between a lens assembly and an imaging sensor and a second displacement between the lens assembly and the imaging sensor. The autofocus assembly includes at least one positioner and an actuator. The actuator is configured to move the positioner between a first position in which the positioner contacts a first surface that is in a first plane corresponding to the first displacement and second position in which the positioner contacts a second surface that is in a second plane corresponding to the second displacement. The first and second planes may be offset so that a distance between the first displacement and the second displacement directly corresponds to a distance between the first and second planes.

Description:
TECHNICAL FIELD OF THE INVENTION 
       [0001]    The technology of the present disclosure relates generally to an autofocus assembly for a camera and, more particularly, to a precision autofocus assembly that establishes two or more subject distance ranges for a camera. 
       DESCRIPTION OF THE RELATED ART 
       [0002]    Mobile and/or wireless electronic devices are becoming increasingly popular. For example, mobile telephones, portable media players and portable gaming devices are now in wide-spread use. In addition, the features associated with certain types of electronic devices have become increasingly diverse. For example, many mobile telephones now include cameras. 
         [0003]    Due to size and power constraints in a mobile telephone, many camera phones have used a fixed focus camera assembly. But as the resolution of the imaging sensor for these cameras increases (e.g., three to five megapixels or more), it becomes more difficult to achieve acceptable sharpness using a fixed focus arrangement. It has been proposed to add an autofocus system to camera phones to assist in taking sharp photographs at various subject distances, thereby leading to better image quality compared to a fixed focus camera. But adding an autofocus system may increase the cost of the camera system beyond the expectations of many users. 
         [0004]    Also, autofocus systems rely on complex and sensitive component assemblies that are not generally practical for camera phones. For example, conventional autofocus systems rely on a mechanical activator that displaces a lens relative to an imaging sensor. The various types of activators that have been used include piezoelectric activators, electromechanical activators implemented with a voice coil acting against a magnet, and stepper motor actuators. Each of these types of activators has advantages and disadvantages. For instance, some actuators are more accurate and/or faster than others, but the better performing actuators are typically more expensive and are harder to control than less accurate and/or slower actuators. The less accurate and/or slower actuators tend to be more economical and easier to manufacture. 
       SUMMARY 
       [0005]    To improve focusing of a camera assembly, the present disclosure describes an improved autofocus assembly. The autofocus assembly is particularly well suited for use with camera phones and other miniature cameras. Not only is the disclosed autofocus system cost effective, it achieves a high degree of performance without using a complicated assembly of components. In one embodiment, displacement of a lens assembly is changed by rotating a control member. Positioners (e.g., spherical bearings) may be disposed in through holes in the control member. When the control member is in a first position, the positioners may be received in corresponding receptacles (e.g., apertures or indents) of a displacement member that is located adjacent the control member. In the first position, the lens assembly may have a first optical displacement with respect to an imaging sensor. As the control member is rotated from the first position to a second position with respect to the displacement member, the balls may leave the apertures and ride on a surface of the displacement member. This has the effect of positioning the lens assembly at a second optical displacement with respect to the imaging sensor. The different optical displacements impart different subject distance ranges to the camera system such that actuation between the first and second positions results in changes to the focus of the camera assembly. 
         [0006]    A high degree of precision in positioning of the lens assembly with respect to the imaging sensor may be achieved with very little electronic control and, in at least one embodiment, without the use of position sensors and/or a feedback system. In the above-described exemplary embodiment, a high degree of accuracy in the displacement of the lens assembly with respect to the imaging sensor may be readily achieved by controlling the physical thickness of the displacement member, which is a relatively simple task. At the same time, the amount of rotation of the control member need not be precisely controlled since over-rotation of the control member will have little or no impact on the amount of displacement of the lens assembly. Therefore, in the exemplary embodiment, a relatively unsophisticated actuator to effectuate rotation of the control member may be employed. In one embodiment, the actuator may be a shape memory allow (SMA), such as a “muscle wire.” Also, at the time of manufacturing of the camera assembly, little or no calibration and/or adjustment of the autofocus components may be required. In addition, a relatively simple controller may be employed to control the focus of the camera assembly. Furthermore, the autofocus assembly may be bi-stable (e.g., may not move from the first position to the second position or vice versa without actuation) and, therefore, will consume very little or no power between position changes. 
         [0007]    According to one aspect of the disclosure, a camera assembly includes an imaging sensor; a lens assembly; and an autofocus assembly that selectively imparts a first displacement between the lens assembly and the imaging sensor and a second displacement between the lens assembly and the imaging sensor, wherein the autofocus assembly includes at least one positioner and an actuator, the actuator configured to move the positioner between a first position in which the positioner contacts a first surface that is in a first plane corresponding to the first displacement and second position in which the positioner contacts a second surface that is in a second plane corresponding to the second displacement, the first and second planes being offset so that a distance between the first displacement and the second displacement directly corresponds to a distance between the first and second planes. 
         [0008]    According to one embodiment of the camera assembly, the actuator applies force to a control member that moves the positioner between the first and second positions. 
         [0009]    According to one embodiment of the camera assembly, the control member traps the positioner in a receptacle of the control member. 
         [0010]    According to one embodiment of the camera assembly, the receptacle of the control member is a through hole. 
         [0011]    According to one embodiment of the camera assembly, the first surface is a surface of a displacement member that includes a receptacle into which the positioner is received so that the positioner contacts the second surface. 
         [0012]    According to one embodiment of the camera assembly, the receptacle of the displacement member is a through hole. 
         [0013]    According to one embodiment of the camera assembly, the second surface is a surface of a camera module housing located adjacent the displacement member, and the camera module housing retains the autofocus assembly and the lens assembly. 
         [0014]    According to one embodiment of the camera assembly, the positioner is spherical. 
         [0015]    According to one embodiment of the camera assembly, a thickness of the displacement defines the distance between the first displacement and the second displacement. 
         [0016]    According to one embodiment of the camera assembly, the positioner further contacts a contact surface of the lens assembly to force the lens assembly between the first and second displacements. 
         [0017]    According to one embodiment of the camera assembly, force is applied to the lens assembly to maintain contact between the lens assembly and the positioner. 
         [0018]    According to one embodiment of the camera assembly, the force is applied by one or more springs. 
         [0019]    According to one embodiment of the camera assembly, the second surface is part of a member other than the displacement member. 
         [0020]    According to one embodiment of the camera assembly, force is applied to the lens assembly to maintain contact between the positioner and the first surface when the positioner is in the first position and between the positioner and the second surface when the positioner is in the second position. 
         [0021]    According to one embodiment of the camera assembly, the actuator includes a shape memory alloy (SMA) member attached to the control member such that contraction of the SMA member achieves the movement of the control member to move the positioner from the first position to the second position. 
         [0022]    According to one embodiment of the camera assembly, the actuator applies counter-force to the control member to return the positioner from the second position to the first position. 
         [0023]    According to one embodiment of the camera assembly, the force and the counter-force are applied by contracting different portions of the same SMA member. 
         [0024]    According to one embodiment of the camera assembly, the camera assembly is part of a mobile telephone. 
         [0025]    These and further features will be apparent with reference to the following description and attached drawings. In the description and drawings, particular embodiments of the invention have been disclosed in detail as being indicative of some of the ways in which the principles of the invention may be employed, but it is understood that the invention is not limited correspondingly in scope. Rather, the invention includes all changes, modifications and equivalents coming within the scope of the claims appended hereto. 
         [0026]    Features that are described and/or illustrated with respect to one embodiment may be used in the same way or in a similar way in one or more other embodiments and/or in combination with or instead of the features of the other embodiments. 
         [0027]    The terms “comprises” and “comprising,” when used in this specification, are taken to specify the presence of stated features, integers, steps or components but do not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0028]      FIGS. 1 and 2  are respectively a front view and a rear view of an exemplary electronic device that includes a camera assembly having an autofocus assembly; 
           [0029]      FIG. 3  is an exploded view of an exemplary autofocus assembly for the camera assembly; 
           [0030]      FIG. 4  is a perspective view of an assembled control member and an actuator member for the autofocus assembly of  FIG. 3 ; 
           [0031]      FIG. 5  is a schematic block diagram of the electronic device of  FIGS. 1 and 2 ; and 
           [0032]      FIG. 6  is a schematic diagram of a communications system in which the electronic device of  FIGS. 1 and 2  may operate. 
       
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       [0033]    Embodiments will now be described with reference to the drawings, wherein like reference numerals are used to refer to like elements throughout. It will be understood that the figures are not necessarily to scale. 
         [0034]    Described below in conjunction with the appended figures are various embodiments of an improved autofocus assembly. In the illustrated embodiments, the autofocus assembly has two positions that correspond to two subject distance ranges, but other embodiments of the autofocus assembly may have more than two subject distance ranges. The disclosed autofocus assembly differs from many conventional high performance autofocus assemblies that typically position a lens among twenty to thirty discrete positions. While the conventional high performance autofocus assemblies may facilitate taking sharp pictures at subject distances from about ten centimeters to infinity, the disclosed approach may assist in taking photographs that are acceptable to most camera phone users. 
         [0035]    A fixed focus solution, on the other hand, has a fixed subject distance. In a fixed focus system, the camera relies on a depth of field of the lens to obtain a fairly large subject distance range. The exact range for a particular fixed focus camera will depend on the lens focal length, the aperture, the pixel count and the optical format of the imaging sensor. As the pixel count of the sensor increases, the depth of field becomes shallower (assuming the other parameters stay the same). 
         [0036]    A fixed focus camera is usually focused at its hyperfocal distance (LH), meaning that an acceptable image may be captured at subject distances from a near distance (L NEAR ) of about half the hyperfocal distance (LH divided by 2) to a far distance (L FAR ) equaling infinity. The hyperfocal distance may be calculated using equation 1 where f is the focal length of the lens assembly, N is the aperture (F-number) and C is the blur circle (largest permissible circle for a light bundle incident on the imaging sensor, also known as the largest permissible circle of confusion). 
         [0000]    
       
         
           
             
               
                 
                   
                     Hyperfocal 
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                      
                     Distance 
                      
                     
                         
                     
                      
                     
                       L 
                       H 
                     
                   
                   = 
                   
                     
                       f 
                       2 
                     
                     NC 
                   
                 
               
               
                 
                   Eq 
                   . 
                   
                       
                   
                    
                   1 
                 
               
             
           
         
       
     
         [0037]    As an example, a camera may have an imaging sensor with three million pixels and a pixel pitch of 1.75 microns, and a lens with a focal length of 3.7 millimeters to achieve a horizontal field of view of about fifty two degrees. If the blur circle is double the pixel pitch, the blur circle for the camera would be about 3.5 microns. Solving equation 1 would determine that the hyperfocal distance is about 1.4 meters. Therefore, the near focus distance (L NEAR ) of this exemplary camera would be about seventy centimeters. 
         [0038]    If the user is interested in taking pictures of objects closer than seventy centimeters, blurry photographs would likely result. The autofocus solution described herein lowers the available near distance. In one embodiment, the disclosed autofocus solution adds a second focus setting. Following the foregoing example for the three megapixel camera, the first focus setting may be about 1.4 meters to provide a first subject range of about seventy centimeters to infinity. The second focus setting may be set to about forty seven centimeters, or about one third of the exemplary hyperfocal distance. In the second setting, the near distance would be about thirty five centimeters, or about one quarter the hyperfocal distance, and the far distance would be about seventy centimeters. Therefore, by switching between the first setting and the second setting in accordance with the proximity of an object to be photographed with the camera, an effective focus range of about thirty five centimeters to infinity may be established with just the two lens positions. In the example, the displacement of the lens assembly between the first focus setting and the second focus setting is about twenty microns. 
         [0039]    The autofocus assembly will be primarily described in the context of positioning a lens assembly for a digital camera (e.g., a digital still camera and/or a digital video camera) for a mobile telephone. It will be appreciated that the autofocus assembly may be used in other operational contexts such as, but not limited to, a dedicated camera, another type of electronic device that has a camera (e.g., a personal digital assistant (PDA), a media player, a gaming device, a “web” camera, a computer, etc.), a projector, and so forth. It is further noted that the interchangeable terms “electronic equipment” and “electronic device” include portable radio communication equipment. The term “portable radio communication equipment,” which hereinafter is referred to as a “mobile radio terminal,” includes all equipment such as mobile telephones, pagers, communicators, electronic organizers, PDAs, smartphones, portable communication apparatus or the like. 
         [0040]    Referring initially to  FIGS. 1 and 2 , an electronic device  10  is shown. The illustrated electronic device  10  is a mobile telephone. The electronic device  10  includes a camera assembly  12  for taking digital still pictures and/or digital video clips. Therefore, it is highlighted that the electronic device  10  need not be a mobile telephone, but could be a dedicated camera or some other device as indicated above. 
         [0041]    With additional reference to  FIG. 3 , the electronic device  10  may include an autofocus assembly  14 . In the illustrated embodiment, the autofocus assembly  14  moves a lens assembly  16  between a first position and a second position. In the first position, the lens assembly  16  has a first displacement with respect to an imaging sensor  18  and, in the second position, the lens assembly  16  has a second displacement with respect to the imaging sensor  18 . The first and second positions respectively impart a first focus range and a second focus range to the camera assembly  12 . 
         [0042]    The autofocus assembly  14 , the lens assembly  16  and the imaging sensor  18  may be collectively assembled to form a camera module  20  that may be mounted within a housing  22  of the electronic device  10 . The lens assembly  16  may include one or more lenses  24  that are retained by a lens retainer  26 . The imaging sensor  18  captures images of a scene contained within a field of view of the camera assembly  12  while the lens assembly  16  focuses light from the field of view onto the imaging sensor  18 . A window  28  may be present over an opening in the housing  22  to serve as a protective cover for the camera module  20 . The window  28  may also function as a lens and/or a filter. In another embodiment, the window  28  may be omitted or formed as part of the lens assembly  16 . The camera module  20  may include other optical components, such as filters, prisms, mirrors, optical zooming mechanics, a lens or lenses that remain stationary relative to the imaging sensor  18 , etc. 
         [0043]    It will be appreciated that the camera assembly  12  may include additional components that may form part of the camera module  20  or that may be retained by the electronic device  10  separately from the camera module  20 . For instance, the camera assembly  12  may include an electronic controller (not illustrated) that controls operation of the camera module  20  and other camera assembly  12  operations. Other components of the camera assembly  12  include, for example, a flash  30 , a light meter  32 , a display  34  for functioning as an electronic viewfinder and as part of an interactive a user interface, a keypad  36  and/or buttons  38  for accepting user inputs, an optical viewfinder (not shown), and any other components commonly associated with cameras. 
         [0044]    Referring now to  FIGS. 3 and 4 , details of the illustrated embodiment of the autofocus assembly  14  will be described. The autofocus assembly  14  of the illustrated embodiment is configured to impart movement of the lens assembly  16 . It will be appreciated that the operative principles of the autofocus assembly  14  instead may be applied to impart movement to the imaging sensor  18 , or both the imaging sensor  18  and the lens assembly  16 . 
         [0045]    The autofocus assembly  14  may include a stack of components, including a platform  40 , a displacement member  42 , a control member  44 , a plurality of positioners  46 , and a spring  48 . The lens assembly  16  may be located between the spring  48  and the control member  44 . The platform  40  may form part of a housing for the camera module  20 . 
         [0046]    Using directional and relational terms that correspond to the illustrated vertical arrangement of components, the interaction of the components will be described. It will be appreciated that different directional and relational terms may be used depending on the orientation of the components, changes in the order of components, and/or the addition and/or subtraction of components. 
         [0047]    As illustrated, many of the components may include a central through hole to create an optical pathway for light to travel from an opening in the housing  22  (which may be covered by the window  28 ), through the lens assembly  16  and onto an operative portion of the imaging sensor  18 . 
         [0048]    An upper end of the spring  48  may contact a lower surface of the housing  22 . In other embodiments, the upper end of the spring  48  may contact another surface, such as a dedicated housing member (not illustrated) for the camera module  20 . A lower end of the spring  48  may contact an upper surface of the lens retainer  26 . The lens retainer  26  may have a stepped radius along the longitudinal axis of the lens retainer. The stepped radius may be arranged such that the upper portion of the lens retainer  26  includes a flange  50  that has a lower surface that serves as a contact surface  51  for the positioners  46 . The lower portion of the lens retainer  26  may fit in the central through hole of one or more of the control member  44 , the displacement member  42  and the platform  40 . Also, while the flange  50 , the control member  44  and the displacement member  42  are shown and described as being annular in nature (e.g., round), these components may have other geometries. Also, other structures that are shown and/or described as being circular and/or spherical may have other geometries. 
         [0049]    When the autofocus assembly  14  is assembled, each positioner  46  may fit within a receptacle of the control member  44  so that the positioners  46  are laterally trapped by the control member  44 . In the illustrated embodiment, each positioner  46  fits within a corresponding through hole  52  of the control member  44  such that the control member  44  surrounds a vertically central portion of the positions  46 . In this manner, the positioners  46  are laterally trapped by the control member  44  and rotation of the control member  44  causes corresponding circumferential movement of the positioners  46  about a longitudinal axis of the autofocus assembly  14 . The upper portion of the positioners  46  may contact the contact surface  51  of the flange  50 . The control member  44  may include a radially projecting lever  54 . Applying circumferentially directed force to the lever  54  may result in rotation of the control member  44  and corresponding movement of the positioners  46 . 
         [0050]    The positioners  46  of the illustrated embodiment are spheres. For instance, the positioners  46  may be ball bearings. In another embodiment, the positioners  46  may be located in and trapped by recesses in a lower surface of the control member  44 . Alternatively, the positioners  46  may be bumps or detents that are formed on or integral with a lower surface of the control member  44 . In these embodiments the positioners  46  do not contact the contact surface  51 . Instead, an upper surface of the control member  44  may contact the contract surface  51 . Also, even when the positioners  46  extend through an upper surface of the control member  44 , the upper surface of the control member  44  may contact the contact surface  51  in one or both of the positions of the autofocus assembly  14 . 
         [0051]    The control member  44  may rest over (and possibly contact) the displacement member  42 , which may have receptacles in which lower portions of the positioners  46  may be received when the receptacles (e.g., holes  52 ) of the control member are vertically aligned with the receptacles of the displacement member  42 . In the illustrated embodiment, the receptacles of the displacement member  42  are through holes  56 . In this embodiment, when the autofocus assembly  14  is in the second position so that the displacement of the lens assembly  16  is closer to the imaging sensor  18  relative to the first position, the through holes  52  of the control member  44  and the through holes  56  of the displacement member  42  may be vertically aligned. In this position, the lower portions of the positioners  46  may contact an upper surface of the platform  40 . Therefore, the distance between the upper surface of the platform  40  and contact surface  51  will be about the diameter of the positioners  46 . 
         [0052]    Application of circumferentially directed force on the lever  54  may urge the control member  44  in a corresponding rotational direction. Under this force, the positioners  46  may ride up and out of the through holes  56 , and onto the upper surface of the displacement member  42  to achieve the first position of the autofocus assembly  14 . Also, the lens assembly  16  will be forced upward against the spring  48 , which may compress in reaction to the upward force. In this position, the distance between the upper surface upper surface of the platform  40  and contact surface  51  will be about the diameter of the positioners  46  plus the thickness of the displacement member  42 . The autofocus assembly  14  may be moved from the first position back to the second position by applying force to the lever  54  to urge the control member  44  in a direction to achieve alignment of the through holes  52  and the through holes  56 . While the illustrated spring  48  is shown as a coil spring, one or more leaf springs or other resilient members may be positioned to apply downward pressure on the lens assembly  16 . Also, one or more coil springs may be positioned between the platform  40  and the lens assembly  16  to pull the lens assembly  16  downward. 
         [0053]    It will be appreciated that the difference in the displacement of the lens assembly  16  with respect to the imaging sensor  18  will change by the thickness of the displacement member  42  when the autofocus assembly  14  moves between the first and second positions. The thickness of the displacement member  42  and the thickness of the positioners  46  may be controlled so that when the autofocus assembly  14  is in the first position, objects in a first focus range of the camera assembly  12  may be satisfactorily imaged. As indicated above, the first focus range may be about half the hyperfocal distance to infinity. Also, the thickness of the displacement member  42  and the positioners  46  may be controlled so that when the autofocus assembly  14  is in the second position, the second focus range may be about a quarter of the hyperfocal distance to about half of the hyperfocal distance. It will be appreciated that other thicknesses can be used to achieve other focus ranges. Following the above-described example of the three megapixel camera, the thickness of the displacement member  42  may be about twenty microns to achieve a first focus range of about seventy centimeters to infinity and a second focus range of about thirty five centimeters to about seventy centimeters. 
         [0054]    To assist in accurately controlling the displacement of the lens assembly  16 , the applicable upper and lower surfaces of the lens assembly  16 , the control member  44 , the displacement member  42  and the platform  40  may be in generally parallel planes. 
         [0055]    In another embodiment, the displacement member  42  may be omitted and recesses with controlled depths may be formed in the upper surface of the platform  40  to receive the positioners  46  when the autofocus assembly  14  is in the second position. In another embodiment, the platform may have raised steps (e.g., rectangular blocks). The positioners  46  may rest on the platform  40  in areas between the steps when the autofocus assembly  14  is in the second position and the positioners  46  may rest on the steps when the control member  44  is rotated so that the autofocus assembly  14  is in the first position. In these embodiments, the platform  40  may be considered a displacement member. 
         [0056]    In another embodiment, the control member  44  may be omitted in favor of pockets that trap the positioners  46  in the contact surface  51  of the lens assembly  16 . In this embodiment, displacement of the lens assembly  16  may be achieved by rotation of the lens assembly  16  or the displacement member  42 . Also, in this embodiment, the lens retainer  26  may be considered a control member. 
         [0057]    In still another embodiment, the control member  44  may be omitted in favor of positioners  46  that are formed as part of the lens retainer  26 . For instance, the positioners  46  may take the form of detents that are formed on the under side of the flange  50 . The detents may be, for example, polygons with beveled or rounded corners. Also, the displacement member  42  may be omitted in favor of receptacles formed in the platform  40 . The receptacles may have a cross-sectional profile the approximates a cross-sectional profile of the positioners  46 . For instance, the receptacles may be indents that have bottom surfaces that contact bottom surfaces of the positioners  46  when the autofocus assembly  14  is in the second position. When the autofocus assembly  14  is moved to the first position, the detents may slide out of the indents so that the bottom surfaces of the detents rest on the upper surface of the platform  40 . In this manner, the vertical distance between the bottom of the indents and the surface of the platform  40  may control the displacement of the lens assembly  16 . To facilitate movement from the second position to the first position and vice versa, the edges of the detents and the sidewalls of the indents may be made at corresponding angles (e.g., the sidewalls of the indents may be angled to act as a ramp for the detents). In this embodiment, the platform  40  may be considered a displacement member and the lens retainer  26  may be considered a control member. In a similar embodiment, the detents may be placed on the platform  40  and the indents may be formed in the lens retainer  26 . 
         [0058]    In still another embodiment, a spacer member may be positioned between the displacement member  42  and the platform  40  and/or a spacer member may be positioned between the upper portion of the positioners  46  and the contact surface  51 . The spacer member(s) may be used to assist in establishing a desired optical displacement between the lens assembly  16  and the imaging sensor  18 . Even with the presence of a spacer member(s), the optical displacement between the lens assembly  16  and the imaging sensor  18  may be controlled by the thickness of the displacement member  42 . 
         [0059]    In yet another embodiment, the components may be placed in a different order. For instance, the spring  48  may be positioned under the contact surface  51  and the control member  44 , the displacement member  42  and the positioners  46  may be located above the lens assembly  16 . 
         [0060]    In another embodiment, the autofocus assembly  14  may have more than two positions. For instance, the displacement member  42  may not have an upper surface and a lower surface that are in parallel planes. Rather, the upper surface of the displacement member  42  may be stepped, sloped, beveled, have cam surfaces, have recesses of varying depths, etc. Rotation of the control member  44  may be controlled to bring the positioner  46  into alignment with various points of the displacement member  42  so as to effectuate a corresponding number of displacements of the lens assembly  16 . 
         [0061]    The general operation of the autofocus assembly  14  for the illustrated embodiment may be summarized as follows. When the components are aligned so that the positioners  46  pass through the through holes  52  in the control member  44  and the through holes  56  the displacement member  42 , the spring  48  pushes the lens assembly  16  to establish contact between the lens assembly  16  and the positioners  46  and to establish contact between the positioners  46  and the platform  40 . As the control member  44  is rotated, the positioners  46  are forced to leave the through holes  56  in the displacement member  42  and climb upward and on to the upper surface of the displacement member  42 . In the rotated configuration, the spring  48  pushes the lens assembly  16  downward to establish contact between the lens assembly  16  and the positioners  46  and to establish contact between the positioners  46  and the displacement member  42 . The upward travel of the positioners  46  also results in upward movement of the lens assembly  16 . In this manner, the distance between the lens assembly  16  and the platform  40  is elevated an amount equal to (or a function of) the thickness of the displacement member  42 . Thus, the displacement of the lens assembly  16  with respect to the imaging sensor  18  also is changed an amount commensurate with the thickness of the displacement member  42 . Rotation of the control member  44  to re-establish alignment of the through holes  52  and  56  allows the positioners  46  to leave the surface of the displacement member  42  and, under the force of the spring  48 , move into the holes  56 . In this manner, the positioners  46  and the lens assembly  16  move optically closer to the imaging sensor  18  a distance that is commensurate with the thickness of the displacement member  42 . 
         [0062]    As will be appreciated, the autofocus assembly  14  provides very accurate displacement of the lens assembly  16  that is not dependent on the accuracy of the amount of rotation of the control member  44 . So long as the control member  44  is rotated a threshold amount, displacement of the lens assembly  16  may be achieved. The threshold amount may be, for example, at least the radius of the positioners  46 , but is preferably a little more. An appropriate range for the threshold amount in an exemplary embodiment may be about three quarters of the diameter of the positioners  46  to about twice the diameter of the positioners  46 . 
         [0063]    The control member  44  may be rotated by an actuator  58 . As indicated, the precision of actuator  58  need not be high to achieve a high degree of precision in the displacement of the lens assembly  16 . Exemplary actuators  58  may include one or more motors, one or more electromagnetic actuators, and one or more piezoelectric actuators. 
         [0064]    As shown in the illustrated embodiment, the actuator  58  may include a member  60  that is made from a shape memory alloy (SMA). In the illustrated embodiment, the member  60  is a wire SMA member, which is commonly known as a “muscle wire.” Wire SMA members exhibit the property of shrinking in length when heated to a suitable temperature, which is typically about eighty degrees Celsius to about ninety degrees Celsius. For instance, many SMA wires will contract in length about three percent to about eight percent when heated to a temperature of about ninety degrees Celsius. Heating of the wire may be achieved by passing a current through the wire to create resistive heating. When the wire cools by a few degrees it may soften and may be expanded to its original length by applying a relatively weak mechanical force. Suitable wire SMA members are sold by Nitinol Devices and Components of Fremont, Calif., USA, and under the designation FLEXINOL by Dynalloy, Inc. of Costa Mesa, Calif., USA, as well as other manufacturers and vendors. 
         [0065]    With continued reference to  FIGS. 3 and 4 ,  FIG. 3  shows the member  60  assembled with retaining components of the camera module  20  and  FIG. 4  shows the member  60  assembled with the control member  44 . When the camera assembly  12  is fully assembled, the member  60  will be assembled with both the retaining components of the camera module  20  and the control member  44 . 
         [0066]    The member  60  may have a first end that is mechanically secured and electrically connected to a first electrical terminal  62  (shown schematically in  FIG. 4  as a node). A second end of the member  60  may be mechanically secured and electrically connected to a second electrical terminal  64  (shown schematically in  FIG. 4  as a node). A point of the member  60  between the first and second ends of the member  60  may be in at least electrical connection with a third terminal  66 . In the illustrated embodiment, the member  60  is mechanically and electrically connected to the third terminal  66  at about a midpoint between the first and second ends. In an alternative embodiment, a first SMA member may be connected between the first terminal  62  and the third terminal  66  and a second SMA member may be connected between the second terminal  64  and the third terminal  66  (or a fourth terminal). 
         [0067]    Connected to the platform  40  or integrally formed with the platform  40  may be posts that are used to support and guide the member  60 . The posts may be non-conductive so as not interfere with current that is passed through the member  60 . In one embodiment, the posts may be replaced by sidewalls of a housing for the camera module  20 . 
         [0068]    In the illustrated embodiment, the terminals  62 ,  64  and  66  are centrally mounted to the platform  40  along a rear edge of the platform  40 . Proceeding from the first terminal, the member  60  may be threaded through a first post  68  that is located at the rear, left-hand corner of the platform  40  and then through a second post  70  that is located at the front, left-hand corner of the platform  40 . Then, the member  60  is threaded vertically through a first hole  72  in the lever  54  and returns to the third terminal  66  through the second post  70  and the first post  68 . Proceeding from the third terminal  66 , the member  60  may be threaded through a third post  74  that is located at the rear, right-hand corner of the platform  40  and then through a fourth post  76  that is located at the front, right-hand corner of the platform  40 . Then, the member  60  is threaded vertically through a second hole  78  in the lever  54  and returns to the second terminal  64  through the fourth post  76  and the third post  74 . 
         [0069]    The third terminal  66  may function as a common ground for a first portion  80  of the member  60  that is connected between the first terminal  62  and the third terminal  66  and for a second portion  82  of the member  60  that is connected between the second terminal  64  and the third terminal  66 . When a control signal is applied to the first portion  80  (e.g., by passing current between the first terminal  62  and the third terminal  66  and through the first portion  80 ), the control member  44  may be rotated in a clockwise direction by contraction of the first portion  80  of the member  60 . Similarly, when a control signal is applied to the second portion  82  (e.g., by passing current between the second terminal  64  and the third terminal  66  and through the second portion  82 ), the control member  44  may be rotated in a counter-clockwise direction by contraction of the second portion  82  of the member  60 . In one embodiment, the control member  44  may be rotated clockwise to dislodge the positioners  46  from the holes  56  in the displacement member  42  and may be rotated counter-clockwise to return the positioners  46  to the holes  56 . In another embodiment, the control member  44  may be rotated counter-clockwise to dislodge the positioners  46  from the holes  56  in the displacement member  42  and may be rotated clockwise to return the positioners  46  to the holes  56 . Directing the member  60  around the perimeter of the control member  44  may provide enough length to the member  60  so that the member  60  may be contracted enough to result in sufficient rotational movement of the control member  44 . 
         [0070]    In one embodiment, the coil spring  48  of the illustrated embodiment may be replaced by clips, leaf springs, resilient members or elastic members that are retained by the posts. For instance, a first resilient strap may be retained by two adjacent posts (e.g., posts  68  and  70 ) and a second resilient strap may be retained by another pair of adjacent posts (e.g., posts  74  and  76 ). The straps may engage an upper surface of the lens retainer  26  to apply downward pressure to the lens assembly  16 . In another embodiment, downward force on the lens assembly may be indirectly exerted on the lens assembly  16 . For instance, force may be exerted on a supplemental ring that, in turn, acts upon the lens assembly  16 . 
         [0071]    As indicated, the illustrated electronic device  10  shown in  FIGS. 1 and 2  is a mobile telephone. Features of the electronic device  10 , when implemented as a mobile telephone, will be described with additional reference to  FIG. 5 . The electronic device  10  is shown as having a “brick” or “block” form factor housing, but it will be appreciated that other housing types may be utilized, such as a “flip-open” form factor (e.g., a “clamshell” housing) or a slide-type form factor (e.g., a “slider” housing). 
         [0072]    As indicated, the electronic device  10  may include the display  34 . The display  34  displays information to a user such as operating state, time, telephone numbers, contact information, various menus, etc., that enable the user to utilize the various features of the electronic device  10 . The display  34  also may be used to visually display content received by the electronic device  10  and/or retrieved from a memory  84  ( FIG. 5 ) of the electronic device  10 . The display  34  may be used to present images, video and other graphics to the user, such as photographs, mobile television content and video associated with games. 
         [0073]    The keypad  36  and/or buttons  38  may provide for a variety of user input operations. For example, the keypad  36  may include alphanumeric keys for allowing entry of alphanumeric information such as telephone numbers, phone lists, contact information, notes, text, etc. In addition, the keypad  36  and/or buttons  38  may include special function keys such as a “call send” key for initiating or answering a call, and a “call end” key for ending or “hanging up” a call. Special function keys also may include menu navigation and select keys to facilitate navigating through a menu displayed on the display  34 . For instance, a pointing device and/or navigation keys may be present to accept directional inputs from a user. Special function keys may include audiovisual content playback keys to start, stop and pause playback, skip or repeat tracks, and so forth. Other keys associated with the mobile telephone may include a volume key, an audio mute key, an on/off power key, a web browser launch key, a camera key, etc. Keys or key-like functionality also may be embodied as a touch screen associated with the display  34 . Also, the display  34  and keypad  36  and/or buttons  38  may be used in conjunction with one another to implement soft key functionality. 
         [0074]    The electronic device  10  may include call circuitry that enables the electronic device  10  to establish a call and/or exchange signals with a called/calling device, which typically may be another mobile telephone or landline telephone. However, the called/calling device need not be another telephone, but may be some other device such as an Internet web server, content providing server, etc. Calls may take any suitable form. For example, the call could be a conventional call that is established over a cellular circuit-switched network or a voice over Internet Protocol (VoIP) call that is established over a packet-switched capability of a cellular network or over an alternative packet-switched network, such as WiFi (e.g., a network based on the IEEE 802.11 standard), WiMax (e.g., a network based on the IEEE 802.16 standard), etc. Another example includes a video enabled call that is established over a cellular or alternative network. 
         [0075]    The electronic device  10  may be configured to transmit, receive and/or process data, such as text messages, instant messages, electronic mail messages, multimedia messages, image files, video files, audio files, ring tones, streaming audio, streaming video, data feeds (including podcasts and really simple syndication (RSS) data feeds), and so forth. It is noted that a text message is commonly referred to by some as “an SMS,” which stands for simple message service. SMS is a typical standard for exchanging text messages. Similarly, a multimedia message is commonly referred to by some as “an MMS,” which stands for multimedia message service. MMS is a typical standard for exchanging multimedia messages. Processing data may include storing the data in the memory  84 , executing applications to allow user interaction with the data, displaying video and/or image content associated with the data, outputting audio sounds associated with the data, and so forth. 
         [0076]    The electronic device  10  may include a primary control circuit  86  that is configured to carry out overall control of the functions and operations of the electronic device  10 . The control circuit  86  may be responsible for controlling actuation of the autofocus assembly  14 . Alternatively, control of the autofocus assembly  14  may be handled by a separate controller (not shown) of the camera assembly  12 . The control circuit  86  may include a processing device  88 , such as a central processing unit (CPU), microcontroller or microprocessor. The processing device  88  executes code stored in a memory (not shown) within the control circuit  86  and/or in a separate memory, such as the memory  84 , in order to carry out operation of the electronic device  10 . 
         [0077]    Among other data storage responsibilities, the memory  84  may be used to store images captured by the camera assembly  12 . Alternatively, the images may be stored in a separate memory. The memory  84  may be, for example, one or more of a buffer, a flash memory, a hard drive, a removable media, a volatile memory, a non-volatile memory, a random access memory (RAM), or other suitable device. In a typical arrangement, the memory  84  may include a non-volatile memory (e.g., a NAND or NOR architecture flash memory) for long term data storage and a volatile memory that functions as system memory for the control circuit  86 . The volatile memory may be a RAM implemented with synchronous dynamic random access memory (SDRAM), for example. The memory  84  may exchange data with the control circuit  86  over a data bus. Accompanying control lines and an address bus between the memory  84  and the control circuit  86  also may be present. 
         [0078]    The processing device  88  may execute code that implements the various functions of the electronic device  10 . It will be apparent to a person having ordinary skill in the art of computer programming, and specifically in application programming for mobile telephones or other electronic devices, how to program a electronic device  10  to operate and carry out various logical functions. 
         [0079]    Continuing to refer to  FIGS. 1 ,  2 , and  5 , the electronic device  10  includes an antenna  90  coupled to a radio circuit  92 . The radio circuit  92  includes a radio frequency transmitter and receiver for transmitting and receiving signals via the antenna  90 . The radio circuit  92  may be configured to operate in a mobile communications system and may be used to send and receive data and/or audiovisual content. Receiver types for interaction with a mobile radio network and/or broadcasting network include, but are not limited to, global system for mobile communications (GSM), code division multiple access (CDMA), wideband CDMA (WCDMA), general packet radio service (GPRS), WiFi, WiMax, digital video broadcasting-handheld (DVB-H), integrated services digital broadcasting (ISDB), etc., as well as advanced versions of these standards. It will be appreciated that the antenna  90  and the radio circuit  92  may represent one or more than one radio transceivers. 
         [0080]    The electronic device  10  further includes a sound signal processing circuit  94  for processing audio signals transmitted by and received from the radio circuit  92 . Coupled to the sound processing circuit  94  are a speaker  96  and a microphone  98  that enable a user to listen and speak via the electronic device  10  as is conventional. The radio circuit  92  and sound processing circuit  94  are each coupled to the control circuit  86  so as to carry out overall operation. Audio data may be passed from the control circuit  86  to the sound signal processing circuit  94  for playback to the user. The audio data may include, for example, audio data from an audio file stored by the memory  84  and retrieved by the control circuit  86 , or received audio data such as in the form of streaming audio data from a mobile radio service. The sound processing circuit  94  may include any appropriate buffers, decoders, amplifiers and so forth. 
         [0081]    The display  34  may be coupled to the control circuit  86  by a video processing circuit  100  that converts video data to a video signal used to drive the display  34 . The video processing circuit  100  may include any appropriate buffers, decoders, video data processors and so forth. The video data may be generated by the control circuit  86 , retrieved from a video file that is stored in the memory  84 , derived from an incoming video data stream that is received by the radio circuit  92  or obtained by any other suitable method. 
         [0082]    The electronic device  10  may further include one or more I/O interface(s)  102 . The I/O interface(s)  102  may be in the form of typical mobile telephone I/O interfaces and may include one or more electrical connectors. As is typical, the I/O interface(s)  102  may be used to couple the electronic device  10  to a battery charger to charge a battery of a power supply unit (PSU)  104  within the electronic device  10 . In addition, or in the alternative, the I/O interface(s)  102  may serve to connect the electronic device  10  to a headset assembly (e.g., a personal handsfree (PHF) device) that has a wired interface with the electronic device  10 . Further, the I/O interface(s)  102  may serve to connect the electronic device  10  to a personal computer or other device via a data cable for the exchange of data. The electronic device  10  may receive operating power via the I/O interface(s)  102  when connected to a vehicle power adapter or an electricity outlet power adapter. The PSU  104  may supply power to operate the electronic device  10  in the absence of an external power source. 
         [0083]    The electronic device  10  also may include a system clock  106  for clocking the various components of the electronic device  10 , such as the control circuit  86  and the memory  84 . 
         [0084]    The electronic device  10  also may include a position data receiver  108 , such as a global positioning system (GPS) receiver, Galileo satellite system receiver or the like. The position data receiver  108  may be involved in determining the location of the electronic device  10 . 
         [0085]    The electronic device  10  also may include a local wireless interface  110 , such as an infrared transceiver and/or an RF interface (e.g., a Bluetooth interface), for establishing communication with an accessory, another mobile radio terminal, a computer or another device. For example, the local wireless interface  110  may operatively couple the electronic device  10  to a headset assembly (e.g., a PHF device) in an embodiment where the headset assembly has a corresponding wireless interface. 
         [0086]    With additional reference to  FIG. 6 , the electronic device  10  may be configured to operate as part of a communications system  112 . The system  112  may include a communications network  114  having a server  116  (or servers) for managing calls placed by and destined to the electronic device  10 , transmitting data to the electronic device  10  and carrying out any other support functions. The server  116  communicates with the electronic device  10  via a transmission medium. The transmission medium may be any appropriate device or assembly, including, for example, a communications tower (e.g., a cell tower), another mobile telephone, a wireless access point, a satellite, etc. Portions of the network may include wireless transmission pathways. The network  114  may support the communications activity of multiple electronic devices  10  and other types of end user devices. As will be appreciated, the server  116  may be configured as a typical computer system used to carry out server functions and may include a processor configured to execute software containing logical instructions that embody the functions of the server  116  and a memory to store such software. 
         [0087]    Although certain embodiments have been shown and described, it is understood that equivalents and modifications falling within the scope of the appended claims will occur to others who are skilled in the art upon the reading and understanding of this specification.