Abstract:
A lens retraction mechanism slantways retracts a lens from a shooting position to a receiving space. The lens retraction mechanism includes a base body, which includes a substrate, a guide wall disposed on the substrate and the receiving space, a lens guiding frame moveable with respect to the base body in the direction of an optical axis of the lens group, a pair of guiding shafts having one end fixed to the guiding frame, and a lens holding frame that fixes a lens group and includes a pair of slippage portions moveable with respect to the guide wall. When the lens retracts, the guiding frame draws the guiding shaft to move towards the substrate in the direction of the optical axis, and the lens holding frame moves along the guide means and also along the guiding shaft, and finally falls into the receiving space. The lens retraction mechanism retracts the lens group stably and securely.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates generally to a zoom lens which is used with a camera or a digital video camera, and more particularly to a lens retraction mechanism of the zoom lens and the retracting method of the same. 
   2. Description of the Prior Art 
   In recent years, most photographic devices, such as digital cameras or digital video cameras, are equipped with zoom lenses. Users can photograph objects in different distances with one device by extending or retracting the zoom lens to adjust the lens focus. In shooting a distant object, the photographic device must have the lens extended by a zoom multiple. The larger the zoom multiple is, the longer the extended lens is. Users usually do not care about how long the lens can be extended in taking photographs, but they are more concerned about the overall weight and size of the photographic device when the lens of the device is retracted to a nonuse state. 
     FIG. 1  of the attached drawings shows a conventional lens retraction mechanism of a zoom lens. The conventional zoom lens comprises a lens barrel  9  and first, second and third lens groups  91 ,  92 ,  93  received in the lens barrel  9 . The lens groups  91 ,  92 ,  93  are sequentially and respectively received in a receiving space along an optical axis Z 0 . In the conventional retraction arrangement, the lens thickness inevitably exceeds the sum of the thickness of all lens groups  91 ,  92 ,  93 . Accordingly, the overall thickness of the photographic device is not satisfactory for general consumers. 
   In order to reduce the lens thickness, methods have been employed to retract the lens groups by deviating the lens away from the optical axis of the photographic device and retraction mechanisms working in this way are available in the market. An example is Ricoh Caplio R1 digital camera, in which when the lens begins to retract, a front lens group of the lens is drawn back along an optical axis of the lens, while a rear lens group of the lens is moved away from the optical axis, and finally positioned in either side space of the optical axis, to leave a space for accommodating backward moved front lens group. This arrangement allows the multiple lens groups to be stowed without stacking over each, and instead sideways positioned side by side, so as to reduce the overall thickness of the lens in a stowed condition. 
   Another example of lens retraction by sideways deviating lens from the optical axis is Pentax Optio S50 digital camera. When power supply is shut off, the lens is sequentially drawn back into the camera body, while a central lens group is moved upward, in a direction transverse to an optical axis of the lens, so as to leave a space for front and rear lens groups which are moved along the optical axis. 
   Such retraction structures and methods can also refer to the Japanese Patent Application Nos. 2004-317943, 2004-361657, 2004-361921, and US Patent Application Serial No. 20040228626. 
   The US Patent Application discloses a lens retraction mechanism for driving a lens barrel to move between an advanced state and a retracted state. The lens barrel comprises a front lens group, a rear lens group, and a focusing lens group. When the lens barrel is moved from the advanced state to the retracted state, the lens retraction mechanism moves at least one lens group sideways away from an optical axis to a receiving space sideways deviating from the optical axis; and when the lens barrel is moved from the retracted state to the advanced state, the lens retraction mechanism moves the sideways-deviated lens group back to the optical axis. The lens retraction mechanism comprises a stepping motor, and when the lens barrel starts to retract, a driving gear coupled to the stepping motor rotates at a predetermined timing and with this, a transmitting gear fixed to a rear lens group holding frame is forced to rotate and fiber transmitting its rotation force to a receiving gear. Therefore, the rear lens group is retracted with the rotation and retraction of the rear lens group holding frame, from the optical axis to the retracted state which is deviated from the optical axis. However, this known lens retraction mechanism has a complicated structure because it uses a lot of gears, which need to precisely mate each other and rotate synchronously. If one gear goes wrong, the whole lens retraction mechanism fails to work. Furthermore, in the retraction of the rear lens group, the rear lens group holding frame retracts by way of rotation, which increases the movement path of the rear lens group from the advanced state to the retracted state, thereby costing a lot of retraction time of the rear lens group. 
   Hence, an improved lens retraction mechanism and method for the mechanism are desired to overcome the above-mentioned disadvantages of the prior art. 
   SUMMARY OF THE INVENTION 
   Therefore, an object of the present invention is to provide a lens retraction mechanism which has a simple structure and reduced retraction time. 
   Another object of the present invention is to provide a lens retraction method for retracting a zoom lens from a shooting state to a non-use state steadily in a short period of time. 
   In order to achieve the objects and overcome the above-identified deficiencies in the prior art, a lens retraction mechanism in accordance with the present invention which retracts a zoom lens from a shooting position to a receiving space by slantways retracting comprises a base body having a substrate, a guide wall disposed on the substrate and the receiving space, a lens guiding frame moveable with respect to the base body, a pair of guiding shafts fixed to the guiding frame, and a lens holding frame that fixes a lens group and includes a pair of slippage portions moveable with respect to the guide wall. When the lens retracts, the guiding frame draws the guiding shaft to towards the substrate in the direction of the optical axis, and the lens holding frame moves along the guide means and also along the guiding shaft, and finally enters the receiving space. The lens retraction mechanism retracts the lens group stably and securely. 
   In order to achieve the objects of the present invention, a method for retracting a lens group by a lens retraction mechanism comprises: moving the lens guiding frame towards the base body along an optical axis of the lens group; and moving the lens holding frame towards the base body and away from the optical axis along a guiding track provided by the guiding device with driving of the lens guiding frame. 
   Other objects, advantages and novel features of the invention will become more apparent from the following detailed descriptions of preferred embodiments when taken in conjunction with the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention may be best understood through the following description with reference to the accompanying drawings, in which: 
       FIG. 1  is a cross-sectional schematic view showing a received state of a conventional zoom lens; 
       FIG. 2  is a cross-sectional schematic view of a zoom lens in accordance with the present invention in a use state, 
       FIG. 3  is a cross-sectional schematic view of the zoom lens in accordance with the present invention in a received state; 
       FIG. 4  is an exploded view of a lens retraction mechanism of a second lens group of the zoom lens in accordance with the present invention; 
       FIG. 5  is a simplified perspective view of the lens retraction mechanism of the second lens group of the zoom lens in accordance with the present invention; 
       FIG. 6  is a schematic view showing a retracting process from a shooting position to a receiving space of the zoom lens in accordance with the present invention, which mainly indicates positions A, B and C of a lens guiding frame during the retracting process; and 
       FIG. 7  is a schematic view similar to  FIG. 6 , showing the retracting process from a shooting position to a receiving space of the zoom lens in accordance with the present invention from another aspect of view. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   References will now be made in details to a preferred embodiment of the present invention. 
   A lens retraction mechanism in accordance with the present invention is used in an optical photographic device that has a zoom lens, such as a digital camera and a digital video camera. When the optical photographic device is powered on, the zoom lens is extended from a received state to a general shooting state. In the general shooting state, a focal length of the zoom lens can be adjusted by advancing the zoom lens to a tele-edge state having the longest focal length or retracting the zoom lens to a wide-edge state having the shortest focal length. In the following description, the general shooting state, the tele-edge state and the wide-edge state are all defined as a use state in which the camera can take a photo or obtain a video. Accordingly, the lens retraction mechanism in accordance with the present invention is provided for retracting the zoom lens from the shooting state to the received state.  FIG. 2  is a cross-sectional view showing the use state of the zoom lens, generally designated with reference numeral  10 , according to the present invention.  FIG. 3  is a cross-sectional view showing the received state of the zoom lens  10 . 
   Referring to  FIG. 2 , the zoom lens  10  comprises an optical system and a mechanical system for receiving, fixing, connecting or guiding the optical system. The optical system comprises an image component  120  (such as a CCD) arranged on the shooting axis Z 1 , and a first lens group  11 , a second lens group  12 , and a third lens group  13  sequentially arranged along the shooting axis Z 1  whose distances from the image component  120  are increased gradually. When the zoom lens  10  flexes among the general shooting state, the tele-edge state and wide-edge state, the second lens group  12  adjusts focal length of the zoom lens  10 , and the third lens group  13  sets the focus of the zoom lens  10 . In an embodiment of the present invention, when the optical photographic device is turned off, the first lens group  11  and the third lens group  13  are retracted in the direction of the shooting axis Z 1 , and the retraction of the lens groups  11 ,  13  is known in the art and constitutes no novel parts of the present invention. The second lens group  12  is retracted in the direction deviating from the shooting axis Z 1 , whose retraction mechanism will be detailedly described in the following. 
   Referring to  FIG. 4 , the lens retraction mechanism  130  of the second lens group  12  comprises a base body  131 , a lens holding frame  132  for holding the second lens group  12 , a shutter  133  assembled to the lens holding frame  132 , a lens guiding frame  134  which is movable towards or away from the base body  131  along the optical axis Z 1 , a guiding shaft  135  connecting with the lens holding frame  132  and the lens guiding frame  134 , a cap  136  for protecting the second lens group  112 , and a connecting assembly  138  for connecting the lens holding frame  132 , the lens guiding frame  134  and the base body  131 . 
   Referring to  FIG. 5 , the lens retraction mechanism  130  of the second lens group  112  is shown with the main components. The base body  131  comprises a substrate  1311  arranged perpendicular to the optical axis for fixing the image component  120  and a pair of guiding walls  1312  disposed on and perpendicular to the substrate  1311 . A receiving space  1315  is defined in an upper surface of the substrate  1311  for receiving the lens holding frame  132 . Each guiding wall  1312  has a slant track  1313  whose both ends have different heights relative to a bottom surface of the substrate  1311 , and a perpendicular track  1314  connecting the lowest end of the slant track  1313  and the bottom surface of the receiving space. 
   Referring to  FIGS. 4 and 7 , the lens holding frame  132  comprises a body portion  1321  and a hook portion  1322  extending from the body portion  1321 . A receiving cavity  1323  is defined in the body portion  1321  for receiving the second lens group  112 . When the zoom lens is in the shooting state, the receiving cavity  1323  aligns the image component  120 . The body portion  1321  defines a pair of grooves  1324  on both sides thereof for receiving the pair of guiding shafts  135 , respectively. The grooves  1324  are parallel to the substrate  1311 . A pair of slippage portions  1325  is respectively extended from flanges of both sides of the lens holding frame  132 , which are able to lean against the slant track  1313 . A pair of springs (not shown) is disposed under the lens holding frame  132  and adjacent to the respective slippage portions  1325 , which are used for providing elasticity in the direction of the optical axis. 
   The lens guiding frame  134  has a top wall  1348  and a annular side wall  1349 . The top wall  1348  defines therein a first light through hole  1341  corresponding to the shooting-stated second lens group  112  and a second light through hole  1342  corresponding to the retracted-stated second lens group  112 . The annular side wall  1349  defines an opening  1343  and a pair of fixing holes  1344  arranged adjacent to the opening  1343  for fixing a first end  1351  of the guiding shafts  135  to the lens guiding frame  134 . The guiding shafts  135  each is extended along a shaft axis, which is parallel to the substrate  1311 . 
     FIG. 5  generally illustrates connection between the lens holding frame  132  and the lens guiding frame  134 .  FIGS. 6 and 7  illustrate the movement of the lens holding frame  132  and the guiding shaft  135  towards the substrate  1311 . In the embodiment illustrated, the shutter  133  is separated from the lens holding frame  132  so that it is immovable when the lens holding frame  132  moves. In other embodiments, the shutter  133  can be fixed to the lens holding frame  132  to move together with the lens holding frame  132 . 
   When the zoom lens  10  is in the shooting state as shown in  FIG. 2 , the lens holding frame  132  and the guiding shaft  135  are located in an “A” position as shown in  FIGS. 6 and 7 . When they are is the position, the slippage portion  1325  leans against a highest end of the slant track  1313 , which has the furthest distance from the substrate  1311 . The second ends  1352  of the guiding shafts  135  are respectively received in the grooves  1324 . 
   Once the camera is turned off, the zoom lens  10  begins to retract from the shooting state. Referring to  FIGS. 5 to 7 , a retraction method of the lens retraction mechanism in accordance with the present invention comprises the following steps. 
   Firstly, the lens guiding frame  134  is driven to move towards the substrate  1311  in a direction parallel to the optical axis Z 1 , which forces the guiding shafts  135  to move towards the substrate  1311  too. Accordingly, the guiding shafts  135  draw the lens holding frame  132  to move downwardly. Meanwhile, the slippage portions  1325  are drawn to move downwardly and forwardly along the slant stack  1313  of the guiding wall  1312  under a resultant force combined with a downward force given by the lens holding frame  132  and a supporting force given by the slant track  1313 . The lens holding frame  132  moves downwardly together with the guiding shafts  135  and also forwardly relative to the guiding shafts  135 , which makes the second lens group  12  retreat away from the optical axis Z 1 . Then the slippage portions  1325  continuously to move to a lowest end of the slant track  1313  as shown in a B position. During this time, the lens holding frame  132  moves from adjacent to the second ends  1352  to adjacent to the first ends  1351  of the guiding shafts  135 . Then, the lens holding frame  132  is driven to move downwardly the with the direction of the lens guiding frame  134 , while the slippage portions  1325  glide along the perpendicular track  1314  of the guiding wall  1312 . During this time, the lens holding frame  132  doesn&#39;t move relative to the guiding shafts  135 . Finally, the lens guiding frame  134  and the lens holding frame  132  fall into the receiving space  1315  of the substrate  1311 , as indicated by a C position. During the time when the lens holding frame  132  moves from the B position to the C position, the springs connected with the lens holding frame  132  are compressed between the lens holding frame  132  and the substrate  1311 . 
   When the zoom lens  10  is zoomed to protrude from the retraction state to the shooting state, the springs firstly provide the lens holding frame  132  with a bounce force. Then the lens holding frame  132  is driven to move upwardly and backwardly towards the optical axis Z 1  by the lens guiding frame  134 , until a center of the second lens group  12  is located on the optical axis Z 1 . The extending process of the zoom lens  100  is reversed to the retraction process thereof. 
   The retraction method of the lens retraction mechanism according to the present invention is to provide a guiding device (including the slant track  1313 , the perpendicular track  1314  and the guiding shafts  135 ) for guiding the lens holding frame  132  to slide into the receiving space  1315 . Particularly, the slippage portions  1325  slide along the guiding track, and the lens holding frame  132  slides relative to the guiding shafts  135 . Accordingly, the retraction method simplifies the structure of the lens retraction mechanism of the second lens group  12  and ensures the retraction stable and secure. The retraction method according to the present invention can also be used to retract the other lens groups, such as the first lens group  11  and the third lens group  13 , in the zoom lens  10 , besides the second lens group  12 . 
   In other embodiments, the shutter  133  can be retracted together with the lens holding frame  132  so as to make the retracted zoom lens thinner 
   It is to be understood, however, that even though numerous characteristics and advantages of the present invention have been set forth in the foregoing description, together with details of the structure and function of the invention, the disclosure is illustrative only, and changes may be made in detail within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.