Abstract:
An auto focus module of an image capture device is provided. The auto focus module comprises at least one gear, a nut, a lead screw and a driver. The gear has at least one first extension and a first through hole. The nut has at least one second extension and a second through hole. The lead screw penetrates the first through hole and the second through hole. The driver drives the lead screw and the gear so that the lead screw and the gear move relatively along the axis of the lead screw. The nut and the gear terminate approaching toward each other after the first extension and the second extension lean against each other.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention generally relates to an auto focus (AF) module of an image capture device, and more particularly to an auto focus module which can prevent lens jamming resulting from malfunction. 
         [0003]    2. Description of Related Art 
         [0004]    Modern digital image capture devices are widely applied in digital cameras, digital video cameras, video lenses for home use or conference use etc. image sensors on a circuit board are integrated with a lens module to receive optical image signals and to transfer the optical image signals to electronic signals via photoelectric technologies to render optical images suitable for storage, identification and processing. Conventional auto focus lens module uses a stepping motor to drive a lens into a focus position. In order to proceed auto focus action, the lens must move in directions along a lens axis. In some unusual circumstances, such as malfunctions of the auto focus lens module or failures of lens position detectors, the lens of the auto focus lens module would continue moving over the predetermined stop position until the lens jams such that even the stepping motor driving the lens in a reverse direction can not release the lens from jamming resulting in malfunction of the auto focus lens module and render the auto focus lens module unable to focus. 
         [0005]    The invention provide an auto focus module which can prevent the lens from jamming resulting from malfunction to resolve the problem of lens jamming caused by the malfunctions or unstable condition of lens position sensors and controller 
       SUMMARY OF THE INVENTION 
       [0006]    An object of the present invention is to provide an auto focus module which can prevent the lens from being jammed due to malfunction through altering the direction of the contact force so as to avoid the lens frame being stuck owing to the snaps between the screw threads of the components of the auto focus module. 
         [0007]    According to the object set forth, one embodiment of the present invention provides an auto focus module of an image capture device, the auto focus module of the image capture device comprises at least one gear, a nut, a lead screw and a driver. The gear has at least one first extension and a first through hole. The nut has at least one second extension and a second through hole. The lead screw passes through the first through hole of the gear and the second through hole of the nut. The driver drives the gear to drive the lead screw so as to move the nut along an axis of the lead screw, wherein the nut and the gear stop approaching to each other through the contact between the first and second extensions. 
         [0008]    Another embodiment of the present invention provides an auto focus lens module, the auto focus lens module comprises a lead screw, a gear set and a nut. The gear set includes a gear having at least one first extension configured to the lead screw. The nut is disposed on the lead screw and has at least one second extension configured toward the first extension. The gear set drives the lead screw and the gear to move the nut along an axis of the lead screw, 
         [0009]    the nut stops approaching the gear through the contact between the first and second extensions along tangent directions of the rotation circles of the gear or the nut. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    The accompanying drawings illustrate various embodiments of the present invention and are a part of the specification. The illustrated embodiments are merely examples of the present invention and do not limit the scope of the invention. 
           [0011]      FIG. 1  shows a partial exploded view of an auto focus module of an image capture device according to one embodiment of the invention. 
           [0012]      FIG. 2  shows a schematic view of the auto focus module shown in  FIG. 1  after assembling according to one embodiment of the invention. 
           [0013]      FIG. 3  shows a schematic view of the auto focus module during a normal operation condition according to one embodiment of the invention. 
           [0014]      FIG. 4  shows a schematic view of the auto focus module during a malfunction operation condition according to one embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0015]    The detailed description of the present invention will be discussed in the following embodiments in accordance with corresponding drawings which are not intended to limit the scope of the present invention, but can be adapted for other applications. Beside the detailed description, the invention can be made and performed by other replacement, modified and equivalent embodiments which are included in the scopes of the invention and the claims. In the description of the present invention, a plurality of detailed features are provided to enable one with ordinary skill in the art to make and use the invention. However, the invention can still be performed while some detailed features are omitted. Furthermore, well-known process steps or elements are not described in detail. While drawings are illustrated in details, it is appreciated that the scale of each component may not be expressly exactly. 
         [0016]    Referring to  FIG. 1 , a partial exploded view of an auto focus module  100  of an image capture device according to one embodiment of the invention is shown. The image capture device comprises digital cameras, and digital video cameras, but not limited to digital cameras and digital video cameras, any electronic device having auto focus lens module is included. 
         [0017]    As shown in  FIG. 1 , the auto focus module  100  includes a driver  102 , a nut  104 , gears  106  and  110 , a lead screw  108 , a lens axis  112 , a lens frame  114  and a base  116 . The driver  102  may be a stepping motor, while the nut  104  and the gear  106  have extensions  120  and  122  and through holes  107  and  105  respectively. The extension  120  of the gear  106  and the extension  122  of the nut  104  are toward each other. The lead screw  108  is through the through holes  107  and  105  of the gear  106  and the nut  104 , wherein the lead screw  108  and the gear  106  can be combined through any known configuration to rotate synchronously. The lead screw  108  has a screw thread matching with an inside screw thread (not shown) of the nut  104  so that the lead screw  108  rotates synchronously with the gear  106  when the gear  106  is drove by the driver  102 , while the nut  104  moves along the axis of the lead screw  108 . In a preferred embodiment, the driver  102  drive the gear  106  so that the gear  106  and the lead screw  108  rotates synchronously to move the nut  104  along the axis of the lead screw  108 . The moving directions of the nut  104  depend on the directions of rotation of the gear  106  and the lead screw  108 . The lens frame  114  has a first extending portion  115  with a first opening  119  and a second extending portion  117  with a second opening  121 . The lead screw  108  is also through the first opening  119  of the first extending portion  115  of the lens frame  114  so that the driver can drive the lens frame  114 . The lens axis  112  is through the second opening  121  of the second extending portion  117  of the lens frame  114  so that the lens frame  114  can move along the axis of the lens axis  112 . Therefore, the lens frame  114  will also synchronously move along the axis of the lens axis  112  and the lead screw  108  when the nut  104  moves along the axis of the lead screw  108 . The lens of the auto focus module  100  is on the lens frame  114 . The bear  116  bears the rotations of a rotational axis  103  of the driver  102 , the lead screw  108  and a gear set  101  including the gears  106  and  110  and a gear  111 . The lead screw  108  is parallel to the lens axis  112 . It is to be appreciated that many well-known elements of the auto focus module  100  shown in  FIG. 1  are omitted and the components in the figure are not arranged in the sequence of assembling. The omitted well-known features can be practiced by any related art and anyone with ordinary skill in the art can make and use the invention based on ordinary level of skill in the art. 
         [0018]    In another embodiment, as mentioned above, the lead screw and the gear are combined as a single component (not shown) to rotate synchronously. The nut  104  and the gear of the component also have extensions respectively. The extension of the gear and the extension  122  of the nut  104  are also toward each other. As the driver  102  drives the component, the nut  104  moves along the axis of the lead screw of the component. The lead screw of the component is also through the first opening  119  of the first extending portion  115  of the lens frame  114  so that the driver can drive the lens frame  114 . The lens frame  114  will synchronously move along the axis of the lens axis  112  and the lead screw of the component when the nut  104  moves along the axis of the lead screw. 
         [0019]      FIG. 2  shows a schematic view of the auto focus module  100  shown in  FIG. 1  after assembling according to one embodiment of the invention. As shown in  FIG. 2 , one end of the rotational axis  103  of the driver  102  connects to the gear  111  so that the gears  106  and  110  of the gear set  101  will synchronously rotate to drive the lead screw  108  when the rotational axis  103  of the driver  102  rotates. The extension  120  of the gear  106  and the extension  122  of the nut  104  extend toward each other. The first extending portion  115  of the lens frame  114  is above the nut  104 , and the nut  104  comprises a circular structure. The lead screw  108  is through the center of the circular structure so that the lens frame  114  will simultaneously move along the axis of the lead screw  108  and the lens axis  112  when the nut  104  moves along the axis of the lead screw  108 . The second extending portion  117  of the lens frame  114  comprises a hollow cylindrical structure, and the lens axis  112  is through the center of the hollow cylindrical structure. 
         [0020]      FIG. 3  shows a schematic view of the auto focus module  100  during a normal operation condition according to one embodiment of the invention. As shown in  FIG. 3 , the driver  102  will drive the gear set  101  to rotate the lead screw  108  so that the nut  104  moves along the axis of the lead screw  108  during the auto focus operation of the auto focus module  100 . During a normal operation condition of the auto focus module  100 , the extension  120  of the gear  106  and the extension  122  of the nut  104  will not contact or rub with each other, and there will be gaps between the extensions  120  and  122  so that the lens frame  114  will not be jammed resulting from the contact between the nut  104  and the gear  106 . During a normal operation condition of the auto focus module  100 , the moving status or position of the lens frame  114  along the axis of the lens axis  112  are detected by a photo interrupter (not shown) or other detector device. Moreover, the photo interrupter or detector device will emit signals when the lens frame  114  moves to a predetermined position of the photo interrupter or detector device along the lens axis  112  to interrupt the photo signal of the photo interrupter. Then the control unit of the image capture device will control the driver  102  according to the signals of the photo interrupter or detector device to stop driving the gear set  101  to rotate the lead screw  108  so as to stop the nut  104  and the lens frame  114  moving downward or toward the gear  106  and the base  116  to prevent the lens frame  114  from jamming due to the gear  106  contacting and rubbing with the nut  104 . 
         [0021]      FIG. 4  shows a schematic view of the auto focus module  100  during a malfunction operation condition according to one embodiment of the invention. As shown in  FIG. 4 , when improper setting of sensitivity or malfunction of the photo interrupter or detector device occur, the control unit of the image capture device will control the driver  102  to continually drive the gear set  101  to rotate the lead screw  108  so as to drive the nut  104  and the lens frame  114  moving downward or toward the gear  106  and the base  116  until the extension  120  of the gear  106  contacts and rubs with the extension  122  of the nut  104 . In one embodiment, the extensions  120  and  122  have incline surfaces  124 , contact surfaces  126  and top portions  128  respectively. The extensions  120  and  122  rotationally contact with each other through the contact surfaces  126 . The contact surfaces  126  preferably comprising a plane and can be vertical to the nut  104  and the gear  106  respectively. The incline surfaces  124  can be parallel to the screw thread of the lead screw  108 . The incline surfaces  124  can be parallel to each other. The top portions  128  comprise arcs top portions, but are not limited to arcs top portions. Since the gear  106  and the nut  104  will be close to each other with contrary rotational directions and the extensions  120  and  122  will rotationally contact with each other through the contact surfaces  126 , the nut  104  will not continually move toward the gear  106  even if the driver  102  continually drive the gear set  101  to rotate the lead screw  108  due to the side contact between the extensions  120  and  122 . Since the nut  104  will move toward the gear  106  for a distance of a thread pitch when the nut  104  rotates for one circle, the incline surfaces  124  of the extensions  120  and  122  parallel to the screw thread of the lead screw  108  or the angles between the incline surfaces  124  and the surfaces of the gear  106  and the nut  104  smaller than the incline angle of the screw thread can prevent the incline surfaces  124  of the extensions  120  and  122  from contact or being stuck due to contact. The arc top portions of the extensions  120  and  122  can further prevent the top portions  128  of the extensions  120  and  122  from being stuck due to contact. The numbers of the extensions  120  and  122  could be the same or not. That is, the number of the extension  120  could be more than that of the extension  122 , or the amount of the extension  122  could be larger than that of the extension  120 . Particularly, if more than two extensions  120  are configured, the minimum height of the extension  120  can be decreased as the number of the extension  120  increase so as to meet the requirement of minimizing the volume occupied. Similarly, if more than two extensions  122  are provided, the minimum height of the extension  122  can be reduced as the number of the extension  122  increase so as to meet the requirement of minimizing the space occupied. The heights or lengths of the extensions  120  and  122  could be the same or different. That is, the lengths of the extensions  120  could be larger than those of the extensions  122 , or the heights of the extensions  122  could be higher than that of the extension  120 . Moreover, the lengths of the extensions  120  and  122  could be, but not limited to, multiples of the thread pitch of the lead screw  108 . Regardless of the lengths, amount and shape of the extensions  120  and  122 , the top portion  128  of the extension  120  can not contact the surface of the nut  104  perpendicular to the extension  122 , while the top portion  128  of the extension  122  can not contact the surface of the gear  106  perpendicular to the extension  120 . Since the extensions  120  and  122  of the gear  106  and the nut  104  will rotationally approach with each other as the nut  104  advances to the gear  106 , the extensions  120  and  122  will contact laterally or along tangent directions of the rotation circles of the gear  106  or the nut  104  so as to convert the direction of the contact force between the gear  106  and the nut  104  from along axial direction of the lead screw  108  to along tangent directions of the rotation circles of the gear  106  or the nut  104 , and thus the contact surfaces  126  of the extensions  120  and  122  will contact and apply forces against each other. The contact force will be transferred from the driver  102  to the gear  106  of the gear set  101  and the nut  104 , and then finally to the lens axis  112  so that the screw threads of the nut  104  and the lead screw  108  will not “snap” with each other and the nut  104  and the lead screw  108  will not be stuck due to the axial applied force. Therefore, when the driver  102  reversely drives the gear set  101  to reversely rotate the lead screw  108 , the gear  106  and the nut  104  can rotate in reverse directions respectively and render the nut  104  and the lens frame  114  gradually away from the gear  106  and the base  116  so as to prevent the lens frame  114  from being jammed resulting from the axial contact between the gear  106  and the nut  104 . 
         [0022]    The invention utilizes the extensions of the gear and the nut of an auto focus module to prevent the contact of the nut and the gear along the moving direction of the lens frame when the nut approaches the gear. Through the lateral contact or the contact along the tangent directions of the rotation circles of the gear or the nut so as to convert the direction of the force provided by the driver so that the lens frame will not be jammed owing to the snaps between the screw threads of the nut and the lead screw caused by the axial force from the nut against the gear. 
         [0023]    Although specific embodiments have been illustrated and described, it will be appreciated by those skilled in the art that various modifications may be made without departing from the scope of the present invention, which is intended to be limited solely by the appended claims.