Abstract:
A digital camera can retain its optical performance and has a particularly slim closed status. The digital camera ( 1 ) includes two lens groups ( 51, 52 ) installed in a collapsible lens barrel ( 3   a ), a focus lens ( 44 ), and a CCD ( 42 ) generating an image. An evading mechanism carries the front parts of the lens groups to rotate about a rotary axis parallel to the optical axis and placing the front parts beside the image sensor. When the collapsible lens barrel ( 3   a ) is retracted in the housing of the digital camera ( 1 ), the first lens group ( 51 ) and the second lens group ( 52 ) are rotated around a central axis J( 2 ) parallel to the optical axis J( 1 ) and are located beside the CCD ( 42 ). Thus, the axes of the first, second lens groups ( 51, 52 ) are prevented from being offset, and a thin digital camera ( 1 ) is obtained.

Description:
BACKGROUND OF THE INVENTION  
   1. Field of the Invention 
   The present invention relates to a digital camera with a collapsible lens barrel. 
   2. Description of Related Art 
   Recently, in addition to the promotion of pixel quantity and zoom ratio, digital cameras have become even thinner than before. An effective means to minimize the thickness of the digital camera is to reduce clearances between lens sets and a picture pick-up device when the digital camera is switched off. Thus, the digital camera is generally provided with a telescopic lens frame which can extend out and retract into a camera body. 
   In the prior art, a non-patent document (titled “Digital CAPA”, page 20-22, No. 3, Vol. 19, Mar. 1, 2003, published by Study &amp; Research Institute, Japan,) discloses a digital camera with a collapsible lens barrel. The method for minimizing the thickness of the digital camera is to move the second lens set beside the picture pick-up device while the lens barrel is retracted. 
   However, the performance of the digital camera not only depends on the pixels of image sensor and the zoom ratio, but also depends on the performance of the optical system. For the optical system of general digital cameras, the alignment of the first and second lens sets is greatly related to the optical performance. The method disclosed in the non-patent document will cause the optical axis of the second lens set tilt or misalignment, when the second lens set is moved beside the image sensor. Therefore, the prior art still has some problem, which can not be solved. 
   Therefore, the invention provides a compact digital camera and obviates the aforementioned problems. 
   SUMMARY OF THE INVENTION  
   The main objective of the invention is to provide a digital camera with a minimized thickness and high optical performance. 
   The invention provides a digital camera, which includes a plurality of lens groups moving in an optical axis to change their relative positions; a collapsible lens barrel loaded with the lens groups; an image sensor receiving beams traveling through the lens groups, and outputing image signals; and an evading mechanism carrying front parts of the lens groups to rotate about a rotary axis parallel to the optical axis and locating front parts beside the image sensor when the collapsible lens barrel is retracted in the housing of the digital camera. 
   The invention provides a digital camera, wherein the lens groups includes a first lens group, a second lens group and a third lens group sequentially, and the front parts of the lens groups is composed of the first and second lens groups. 
   The invention provides a digital camera, wherein the third lens group is a focus lens. 
   The invention provides a digital camera, wherein the rotary axis is the central axis of the collapsible lens barrel, and the first and second lens groups are rotated about the rotary axis when the collapsible lens barrel is retracted in the housing of the digital camera. 
   The invention provides a digital camera further including a motor, which drives the lens groups to move back and forth in the optical axis during operation, and retracts the collapsible lens barrel in the housing of the digital camera by rotating about the rotary axis after turning off the digital camera. 
   The invention provides a digital camera further including a fixed barrel to support the collapsible lens barrel. In addition, the evading mechanism is a barrel-cam mechanism between the collapsible lens barrel and the fixed barrel. 
   The invention provides a digital camera, wherein the collapsible lens barrel has a first barrel containing the first lens group, a second barrel containing the second lens group and the first barrel, and a third barrel containing the second barrel and held by the fixed barrel. 
   The digital camera of the invention provides the desired optical performance and has a minimized thickness. 
   The digital camera of the invention prevents the optical axes of the first and second lens groups from misalignment. 
   The digital camera of the invention has a simple structure. 
   The digital camera of the invention has a minimized thickness. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a cross-sectional view of a digital camera disclosed in the invention; 
       FIG. 2  schematically shows the periphery and interior of a lens unit of the digital camera disclosed in the invention; 
       FIG. 3  is an enlarged view partially showing the cross-section of the lens unit; 
       FIG. 4  is a schematic view showing the lens unit positioning at telephoto end (TELE); 
       FIG. 5  is a schematic view showing the position of a first lens group and a second lens group while the lens unit is retracted; 
       FIG. 6  is a schematic view showing the position of a first lens group and a second lens group after the lens unit is completely sunk in the housing of the digital camera; and 
       FIG. 7  is a cross-sectional view of the digital camera after sinking the lens unit in the housing of the digital camera. 
   

   DESCRIPTION OF THE INVENTION  
     FIG. 1  is a cross-sectional view of a digital camera  1  disclosed in an embodiment of the invention. After the beams from an object (namely, the opposite direction of Z axis in  FIG. 1 ) travel through a plurality of movable lens groups, the digital camera  1  takes a picture of the object (not shown) by an image sensor receiving beams from the object (namely, the opposite direction of the Z axis in  FIG. 1 ). 
   Along the Z axis shown in  FIG. 1 , the digital camera  1  has a housing  2 , and a fixed barrel  34  with a central axis J 2  is mounted in the housing  2 . An image sensor arranged in two-dimension, such as a charge-coupled device (CCD)  42 , is located at rear end  35  of the fixed barrel  34 . A low pass filter  43  is positioned between the CCD  42  and the fixed barrel  34 . 
   From the object side, a first lens group  51 , a second lens group  52  and a third lens group (namely focus lens group)  44  are sequentially installed in the digital camera  1 . Along the Z axis, the first lens group  51 , second lens group  52 , focus lens  44  and CCD  42  are sequentially arranged in the optical axis J 1 . The zoom ratio is altered by moving the first lens group  51  and the second lens group  52  in the optical axis J 1 . The focus lens  44  is also moved in the optical axis J 1  so as to fit the focal plane to the sensing surface of the CCD  42 . The CCD  42  receives the beams from the object and outputs electronic signals, and then the electronic signals are stored in a memory (not shown). 
   From the object side, the digital camera  1  further has a first barrel  31 , a second barrel  32  and a third barrel  33 , and the first  31 , second  32  and third barrels  33  are concentric and has a central axis J 2  parallel with the optical axis J 1 . In addition, the first lens group  51  and the second lens group  52  are contained in the first  31 , second  32  and third barrels  33 . The first barrel  31  is held by the second barrel  32 , the second barrel  32  is held by the third barrel  33 , and the third barrel  33  is held by the fixed barrel  34 . The first barrel  31 , second barrel  32  and third barrel  33  (further including the fixed barrel  34  or not) constitute a collapsible lens barrel  3  to sink the first lens group  51 , second lens group  52  and focus lens  44  in the housing  2 . The second barrel  32  is composed of a first outer tube  32   a  and a first inner tube  32   b , and the third barrel  33  is composed of a second outer tube  33   a  and a second inner tube  33   b.    
     FIG. 1  schematically illustrates an interior structure of a collapsible lens barrel  3 . The structure including the collapsible lens barrel  3  and the fixed barrel  34  are named as lens unit  3   a.    
   A shelter  36  of objective side is mounted at a front end of the first barrel  31 , and the first lens group  51  is mounted on an interior portion of the shelter  36 . The second lens group  52  is mounted on a lens support  37  in the second barrel  32 . A shutter  53  is provided in front of the second lens group  52 . 
     FIG. 2  schematically shows the periphery and interior of lens unit  3   a , viewing from (−Z) to (+Z). The shelter  36 , lens support  37  and shutter  53  shown in  FIG. 1  are ignored, and the lens groups  51 ,  52  are represented by the dashed lines. 
   As shown in  FIG. 2 , a focus motor  46  is positioned in the fixed barrel  34  and drives the focus lens  44  through a transmission (not shown). With reference to  FIG. 1 , when the focus motor  46  is actuated, the focus lens  44  is moved along the optical axis J 1  back and forth. 
   As shown in  FIGS. 1 and 2 , a zoom motor  38  and a decelerating gear set  381  for zooming and collapsing are coupled with the fixed barrel  34 . The decelerating gear set  381  decelerates the rotary speed of the zooming motor  38  and engages the gear  331  at the second outer tube  33   a  of the third barrel  33 , as shown in  FIG. 1 . The driving gear (not numbered) of the decelerating gear set  381  engages with the second outer tube  33   a  of the third barrel  33  by using the opening of the fixed barrel  34 . Thus, the third barrel is moved along the optical axis J 1  while collapsing the lens. 
   In the digital camera  1  of the invention, the CCD  42 , the shutter  53 , the zoom motor  38  and the focus motor  46  are connected with a control unit (not shown in the figures) for controlling these components. For example, when a user operates the control unit to drive the zoom motor  38 , the lens groups  51 ,  52  are moved along the optical axis J 1  to alter the zoom ratio. Thereafter, the focus motor  46  is actuated to move the focus lens  44  so as to focus the image on the CCD  42 . Finally, the image is captured by the CCD  42 . 
   When the user turns off the digital camera  1 , the first barrel  31 , second barrel  32  and third barrel  33  are collapsed in the fixed barrel  34  by the zoom motor  38 . 
   The motions of the lens unit  3   a  driven by the zoom motor  38  will be described more detail hereinafter.  FIG. 3  shows an enlarged cross sectional view of an upper part of the lens unit  3   a  including elements related to the motions. 
   The first barrel  31  has a first protrusion  611  formed at a rear end thereof, and adjacent the CCD  42  and extending outward. The first protrusion  611  is movably received in a first linear slot  622  parallel to the optical axis J 1  and defined in the first inner tube  32   b . Similarly, the second barrel  32  has a second protrusion  621  formed at a rear end of the first inner tube  32   b , and adjacent the CCD  42  and extending outwards. The second protrusion  621  is movably received in a second linear slot  632  parallel to the optical axis J 1  and defined in the second inner tube  33   b . The third barrel  33  has a third protrusion  631  formed at a rear end of the second inner tube  33   b  and extending outwards. The third protrusion  631  is received in a first cam slot  642  defined in the fixed barrel  34 . 
   The first cam slot  642  is composed of a curved segment adjacent the CCD  42  and a linear segment away from the CCD  42 . The third protrusion  631  and the first cam slot  642  constitute a first barrel-cam means  663   a  to enable the third barrel  33  to slide along the central axis J 2  with respect to the fixed barrel  34 , and the second inner tube  33   b  to rotate about the central axis J 2  with respect to the fixed barrel  34 . Thus, by the first protrusion  611  received in the first linear slot  622  and the second protrusion  621  received in the second linear slot  632 , the first barrel  31  and the first inner tube  32   b  of the second barrel  32  can be rotated about the central axis J 2  along with the second inner tube  33   b  of the third barrel  33 . 
   Furthermore, the third barrel  33  has a first pin  653  formed on the second outer tube  33   a  and received in a second cam slot (not numbered) in the fixed barrel  34 . The first pin  653  and the fixed barrel  34  constitute a second barrel-cam means  663 . The decelerating gear set  381  and the gear  331  are mounted on the outer periphery of the second outer tube  33   a  of the third barrel  33 . When the zooming motor  38  drives the second outer tube  33   a  to rotate, the third barrel  33  is slid along the central axis J 2  with respect to the fixed barrel  34  by the second barrel-cam means  663 . 
   The second outer tube  33   a  of the third barrel  33  is connected with the first outer tube  32   a  of the second barrel  32  by a second pin  652   a  to enable the second outer tube  33   a  to rotate about the central axis J 2  along with first outer tube  32   a  of the second barrel  32 . Moreover, the second pin  652   a  is fitted into a third linear slot (not numbered) of the second outer tube  33   a  of the third barrel  33 , so the first outer tube  32   a  of the second barrel  32  can be slid along the central axis J 2  with respect to the second outer tube  33   a  of the third barrel  33 . 
   The first outer tube  32   a  of the second barrel  32  further has a third pin  652  formed thereon and fitted into a third cam slot (not numbered) defined in the second outer tube  33   a  of the third barrel  33 . The third pin  652  and the second outer tube  33   a  constitute a third barrel-cam means  662 . When the rotation of the second outer tube  33   a  of the third barrel  33  drives the first outer tube  32   a  of the second barrel  32  to rotate with respect to the second inner tube  33   b  of the third barrel  33 , the second barrel  32  is slid along the central axis J 2  with respect to the third barrel  33  by the third barrel-cam means  662 . 
   The first barrel  31  has a fourth pin  651  formed thereon and received in a fourth cam slot (not numbered) defined in the first outer tube  32   a  of the second barrel  32 . The first outer tube  32   a  and the fourth pin  651  constitute a fourth barrel-cam means  661 . Because the first barrel ( 31 ) is slidable relative to the first inner tube ( 32   b ) of the second barrel ( 32 ) along a straight line, the first barrel  31  is slid along the central axis J 2  with respect to the second barrel  32  by the fourth barrel-cam means  661  when the first outer tube  32   a  of the second barrel  32  is rotated about the first inner tube  32   b.    
   As illustrated in  FIG. 1 , the lens support  37  has a fifth pin  372  fitted into the fourth cam slot of the first outer tube  32   a  of the second barrel  32 . The first outer tube  32   a  and the fifth pin  372  constitute a fifth barrel-cam structure  664 . The fifth pin  372  is also guided by a fourth linear slot  623  defined in the first inner tube  32   b . Thus, in a situation of the first inner tube  32   b  of the second barrel  32  being fixed, when the first outer tube  32   a  is rotated, the second lens group  52  will be slid along the central axis J 2  with respect to the second barrel  32 . 
     FIGS. 1 and 3  illustrate the multiple barrel-cam means as described above and respectively provided at multiple positions (such as three positions) about the central axis J 2 , so the first barrel  31 , second barrel  32 , the third barrel  33  and the lens support  37  can be steadily slid. 
     FIG. 4  is a cross sectional view without hatched lines of the lens unit  3   a  telephoto end, and  FIG. 1  is a cross sectional view of the lens unit  3   a  at wide-photo end. 
   As illustrated in  FIGS. 1 ,  3  and  4 , when the third barrel  33  is in the outermost position with respect to the fixed barrel  34  (the shoot position), the second inner tube  33   b  of the third barrel  33  is guided in the linear segment of the first cam slot  642  by the first barrel-cam means  663   a . Thus, when the zoom motor  38  is actuated to zoom in on an object to be captured, the first barrel  31 , the first inner tube  32   b  of the second barrel  32  and the second inner tube  33   b  of the third barrel  33  can not be rotated, and the first outer tube  32   a  of the second barrel  32  and the second outer tube  33   a  of the third barrel  33  are rotated along the central axis J 2  to slide the third barrel  33  about the fixed barrel  34 , the second barrel  32  about the third barrel  33  and the first barrel  31  about the second barrel  32 . At the same time, the lens support  37  is slid about the second barrel  32 , and the first lens group  51  and second lens group  52  are slid along the optical axis J 1 . 
     FIGS. 5 and 6  illustrate the rotation of the first lens group  51  and second lens group  52  while the lens unit  3   a  is retracted, and  FIG. 7  is a cross sectional view of the digital camera  1  after sinking the lens unit  3   a  in the housing  2  of the digital camera  1 . As illustrated in  FIGS. 5 and 6 , by the rotation of the first barrel  31  and the first inner tube  32   b  of the second barrel  32 , the first lens group  51  and the second lens group  52  are rotated around the central axis J 2  at an angle of 180°. Referring to  FIG. 7 , the second lens group  52  is retracted to a position beneath the CCD  42 . 
   In detail, as shown in  FIG. 2 , the zoom motor  38  drives the second outer tube  33   a  of the third barrel  33  to rotate. As shown in  FIG. 3 , the third barrel  33  is retracted into the fixed barrel  34  by the second barrel-cam means  663  between the third barrel  33  and the fixed barrel  34 , and the second inner tube  33   b  is rotated at the angle of 180° to approach the CCD  42  by means of the first pin  653  of the second inner tube  33   b  of the third barrel  33  being moved along the curved segment of the first cam slot  642  (e.g. by the first barrel-cam means  663   a ). Thus, the first inner tube  32   b  of the second barrel  32  and the first barrel  31  moved along with the inner tube  32   b  of the third barrel  33  are also rotated around the central axis J 2  at the angle of 180° degree. 
   The rotation of the second outer tube  33   a  of the third barrel  33  drives the first outer tube  32   a  of the second barrel  32  to rotate by the second pin  652   a , and the second barrel  32  is retracted into the third barrel  33  by the third barrel-cam means  662  between the first outer tube  32   a  of the second barrel  32  and the second inner tube  33   b  of the third barrel  33 . Furthermore, the rotation of the first outer tube  32   a  of the second barrel  32  drives the first barrel  31  to retract into the second barrel  32  by a fourth barrel-cam means  661  between the first barrel  31  and the first outer tube  32   a  of the second barrel  32 . Therefore, the first lens group  51  and second lens group  52  are retracted together and rotated around the central axis J 2  from the optical axis J 1  to the position beneath the CCD  42  and the focus lens  44 . 
   After sinking in the camera body, an overall length of the lens unit  3   a  along the central axis J 2  (or the lens frame  3 ) is shortened to the length sum of the first lens group  51  and second lens group  52 . Namely, the switched-off digital camera  1  achieves its slimmest condition. According to the sizes of the lens groups and the CCD  42 , the method, which rotates the first lens group  51  and second lens group  52  without moving the focus lens  44  as described above, is a preferable way to achieve the slimmest condition of the digital camera  1 . 
   The conventional method moves only the second lens group  52  to a position beside the CCD  42 . However, referring to  FIG. 1  of the present invention, the first lens group  51  and second lens group  52  have the synchronous movement to maintain the optical axes of the lens groups  51 ,  52  in alignment with each other at all time, and the optical performance of the digital camera  1  is always great. Even after long term use of the camera whereby the retracting motion of the lens frame  3  may have caused the components to have become worn, the first lens group  51  and second lens group  52  still maintain their optical axes coaxial, and the optical performance of the digital camera  1  is also maintained. 
   Because the first barrel-cam means  663   a  is driven by the zoom motor  38  as a power source to retract the lens frame and rotate the first lens group  51  and second lens group  52  (e.g. the lens frame ( 3 )), the digital camera  1  does not need to have another power source, and thus has a simple structure. 
   While the preferred embodiment of the present invention has been described, it is to be understood that modifications will be apparent to those skilled in the art without departing from the spirit of the invention. 
   The invention does not limit the optical system of the digital camera  1  to three lens groups. No matter how many lens groups the optical system includes, the digital camera can maintain the optical performance. For example, by moving the objective lens group(s) (e.g. the first lens group  51  and second group  52  in the preferred embodiment described above) beside the CCD  42 , the digital camera is particularly slim. 
   In addition, the objective lens group may not rotate with other lens groups. If the lens frame has enough space to contain other actuating means, the objective lens group will be moved along the optical axis J 1  and rotated around a central axis J 2 . Moreover, the objective lens set can also be located above the CCD  42  (along the direction of the Y reference axis), or at the left or right side of the CCD  42  (along the direction of the X reference axis or the opposite thereof). 
   The lens frame preferably has a simple structure including three movable barrels or two movable barrels. 
   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, especially in matters of shape, size, and arrangement of parts 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.