Abstract:
Provided is a zoom lens barrel including a plurality of lens groups, each having at least one lens arranged in an optical axis direction, an actuating mechanism capable of moving the lens groups in an optical axis direction, and a shutter unit including an opening portion for exposure, a blade capable of adjusting the degree of opening of the opening portion, and an electronic actuating apparatus capable of actuating the blade to adjust the degree of opening of the opening portion according to the distance between the shutter unit and one of the lens groups adjacent to the shutter unit when the distance is shorter than a predetermined distance.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     This application claims the priority of Korean Patent Application No. 2003-89367, filed on Dec. 10, 2003, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.  
         [0002]     1. Field of the Invention  
         [0003]     The present invention relates to a zoom lens barrel for a camera such as a digital camera, and more particularly, to a zoom lens barrel having a total length which is remarkably reduced.  
         [0004]     2. Description of the Related Art  
         [0005]     In general, a lens barrel used for a camera such as a digital camera, capable of zooming and having an accommodation function, includes a first lens group, a second lens group, and a third lens group arranged in an optical axis direction from an object to be photographed, and an actuating mechanism to move the lens groups in the optical axis direction. The zoom lens barrel further includes a shutter unit having an opening portion for exposure, a blade capable of adjusting a degree of opening of the opening portion, and an electronic drive source to drive the blade. Recently, it is a trend to make a camera such as a digital camera thinner and smaller.  
         [0006]     In a conventional film camera, however, since the opening portion needs to be shielded by closing the blade of the shutter unit to prevent film from being exposed to light when the camera is in a zoom state or in an accommodation state, the shutter unit and the lens groups cannot be overlapped. Accordingly, there is a limit in reducing the total length of the lens barrel so that it is difficult to make the camera thinner and smaller.  
         [0007]     In the conventional typical digital camera, since the inner diameter of the opening portion of the shutter unit is less than the outer diameter of a lens frame, the shutter unit and the second lens group cannot be overlapped and the shutter unit is fixed by being separated a predetermined distance from the second lens group. In the accommodation state as in the zoom state, the shutter unit needs to maintain a predetermined distance from the second lens group. Thus, there is a limit in making the camera thinner and smaller by reducing the total length of the lens barrel.  
         [0008]     Japanese Patent Publication No. 2003-121720 discloses a structure of a lens barrel of a camera in which the shutter unit is fixed to the first lens group. In the lens barrel, since the inner diameter of the opening portion of the shutter unit is less than the lens frame of the second lens group, even if they are overlapped at their maximum, only a very small portion of a leading end of the second lens group overlaps the opening portion of the shutter unit so that there is a limit in reducing the total length of the lens barrel. Furthermore, in the accommodation state as in the zoom state, since the maximum open size of the blade of the shutter unit remains the same, it is difficult to make the shutter unit and the second lens group completely overlapping each other.  
       SUMMARY OF THE INVENTION  
       [0009]     To solve the above and/or other problems, the present invention provides a zoom lens barrel in which a shutter unit is operated in engagement with the movement of lens groups so that the shutter unit and the lens groups are overlapped at their maximum. Thus, the total length of the lens barrel is remarkably reduced so that a camera can be made thinner and smaller.  
         [0010]     The present invention provides a zoom lens barrel in which the inner diameter of an opening portion of the shutter unit is larger than the outer diameter of a lens frame of the lens groups so that, in an accommodation state, the lens frame of the lens groups is completely inserted in the opening portion of the shutter unit. Thus, the total length of the lens barrel is remarkably reduced so that a camera can be made thinner and smaller.  
         [0011]     According to an aspect of the present invention, a zoom lens barrel comprises a plurality of lens groups, each having at least one lens arranged in an optical axis direction, an actuating mechanism actuating the lens groups capable of moving in the optical axis direction, and a shutter unit including an opening portion for exposure, a blade capable of adjusting a degree of opening of the opening portion, and an electronic actuating apparatus actuating the blade to adjust a degree of opening of the opening portion according to the distance between the shutter unit and one of the lens groups adjacent to the shutter unit when the distance is shorter than a predetermined distance.  
         [0012]     During a zoom operation, the blade of the shutter unit is actuated, capable of adjusting a degree of opening of the opening portion to be large or small according to a degree of necessary exposure. During an accommodation operation, the blade of the shutter unit opens the opening portion so that a lens of at least one lens group adjacent to the opening portion lens group is inserted in the opening portion of the shutter unit. The blade of the shutter unit is actuated to open the opening portion larger during an accommodation operation than during a zoom operation. In an accommodation state, a lens of at least one lens group adjacent to the opening portion of the shutter unit is inserted in the opening portion of the shutter unit.  
         [0013]     An elastic unit is provided between the shutter unit and a lens frame which arranges the lens of one of the lens groups adjacent to the shutter unit in the optical axis direction. In a zoom state, the elastic unit is in a non-compression state. When a camera is in an operation state, the elastic unit is in a non-compression state. In an accommodation state, while the elastic unit is compressed, the shutter unit is located at a position more towards one of the lens groups adjacent to the shutter unit. When a camera is in a non-operation state, while the elastic unit is compressed, the shutter unit is located at a position more towards one of the lens groups adjacent to the shutter unit.  
         [0014]     During a zoom operation, the shutter unit moves toward an object to be photographed in the optical axis direction in engagement with operation of the actuating mechanism, and one of the lens groups adjacent to the shutter unit moves toward the object to be photographed in the optical axis direction in engagement with the movement of the shutter unit.  
         [0015]     During an accommodation operation, the shutter unit moves away from an object to be photographed in the optical axis direction in engagement with operation of the actuating mechanism, and one of the lens groups adjacent to the shutter unit moves away from the object to be photographed in the optical axis direction in engagement with the movement of the shutter unit.  
         [0016]     According to another aspect of the present invention, a zoom lens barrel comprises a plurality of lens groups including at least a first lens group and a second lens group arranged in order from an object to be photographed, each lens group having at least one lens arranged in an optical axis direction, an actuating mechanism capable of moving the lens groups in the optical axis direction, and a shutter unit including an opening portion for exposure, a blade capable of adjusting a degree of opening of the opening portion, and an electronic actuating apparatus actuating the blade to adjust a degree of opening of the opening portion according to a distance between the shutter unit and the second lens group when the distance is shorter than a predetermined distance.  
         [0017]     The shutter unit is interposed between the first lens group and the second lens group. In a non-accommodation state, the blade of the shutter unit is capable of adjusting a size of opening of the opening portion so that a lens of the second lens group is inserted therein. During an accommodation operation, the blade of the shutter unit opens the opening portion so that a lens of the second lens group is inserted therein. The shutter unit is actuated to approach the second lens group as the second lens group is shifted from a non-accommodation state to an accommodation state.  
         [0018]     An elastic unit is interposed between the shutter unit and a second lens frame which maintains a lens of the second lens group to be arranged in the optical axis direction. In a non-accommodation state, the elastic unit is in a non-compression state. In an accommodation state, as the elastic unit is compressed, the shutter unit is located at a position moved toward the second lens group.  
         [0019]     During a zoom operation, the shutter unit moves toward the object to be photographed in the optical axis direction in engagement with operation of the actuating mechanism, and the second lens group moves toward the object to be photographed in the optical axis direction in engagement with the movement of the shutter unit.  
         [0020]     During an accommodation operation, the shutter unit moves away from the object to be photographed in the optical axis direction in engagement with operation of the actuating mechanism, and the second lens group moves away from the object to be photographed in the optical axis direction in engagement with the movement of the shutter unit.  
         [0021]     According to another aspect of the present invention, a zoom lens barrel comprises a plurality of lens groups including at least a first lens group and a second lens group arranged in order from an object to be photographed, each lens group having at least one lens arranged in an optical axis direction, an actuating mechanism actuating the lens groups capable of moving in the optical axis direction, and a shutter unit including an opening portion for exposure, a blade capable of adjusting a degree of opening of the opening portion, and an electronic actuating apparatus actuating the blade, and actuating the blade, and in an accommodation state, overlapping the second lens group so that a lens of the second lens group is inserted in the opening portion. The shutter unit is interposed between the first lens group and the second lens group. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0022]     The above and other features and advantages of the present invention will become more apparent by describing in detail preferred embodiments thereof with reference to the attached drawings in which:  
         [0023]      FIG. 1  is a front view illustrating a lens barrel according to an embodiment of the present invention;  
         [0024]      FIG. 2  is a sectional view taken along line I-I of  FIG. 1  which shows the lens barrel when the lens groups are in an accommodation state;  
         [0025]      FIGS. 3 through 6  are exploded perspective views illustrating the respective constituent elements;  
         [0026]      FIG. 7  is a sectional view taken along line I-I of  FIG. 1  which shows the lens barrel when the lens groups are arranged at a wide angle photographing position; and  
         [0027]      FIG. 8  is a sectional view taken along line I-I of  FIG. 1  which shows the lens barrel when the lens groups are arranged at a telescopic photographing position.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0028]      FIGS. 1 through 5  show a lens barrel according to an embodiment of the present invention. As shown in  FIGS. 1 and 2 , the lens barrel according to the present embodiment includes a filter  11  and an imaging device  12  arranged in order from an object to be photographed along an optical axis in an optical axis direction L, a base  10  fixed to a main body (not shown) of a camera on which a charge coupled device (CCD), for example, is installed, a fixed barrel  20  fixed to the base  10 , an outer guide frame  30  coupled to an outer surface of the fixed barrel  20  and capable of rotating around the optical axis and along an outside surface of the fixed barrel  20 , a cam barrel  40  coupled to an inner surface of the fixed barrel  20  and capable of linearly moving while rotating around the optical axis along an inner surface of the fixed barrel  20 , an inner guide frame  70  coupled to an inner surface of the can barrel  40  and capable of linearly moving along the optical axis while rotating around the optical axis with respect to the cam barrel  40  along an inner surface of the cam barrel  40 , a first lens group  50  disposed between the inner surface of the cam barrel  40  and the outer surface of the inner guide frame  70  and capable of moving in the optical axis direction, a shutter unit  90  actuated in engagement with the cam barrel  40  moving in the optical axis direction, a second lens group  60  disposed inside the inner guide frame  70  and capable of moving in the optical axis direction in engagement with-the actuation of the shutter unit  90 , and a third lens group  80  supported by the base  10  and capable of moving in the optical axis direction.  
         [0029]     The fixed barrel  20 , as shown in  FIG. 3 , includes at least one, for example, three, cam barrel guide slot  21  penetrating the fixed barrel  20  to guide rotation and linear movement of the cam barrel  40 ; at least one, for example, three, inner guide frame guide groove  22  formed in an inner circumferential surface of the fixed barrel  20  to guide a linear motion of the inner guide frame  70 ; and at least one, for example, three, cam barrel guide groove  23  formed in the inner circumferential surface of the fixed barrel  20  to guide the cam barrel  40  to an accurate position when the cam barrel  40  rotates and linearly moves.  
         [0030]     The outer guide frame  30 , as shown in  FIG. 3 , includes a drive gear portion  31  partially formed at an edge of a rear side of an outer circumferential surface thereof, a drive slot  32  penetrating the outer guide frame  30  to drive a finder, and a cam barrel drive groove  33  formed in an inner circumferential surface thereof in the optical axis direction to drive the cam barrel  40 .  
         [0031]     The cam barrel  40 , as shown in  FIG. 3 , includes at least one, for example, three, cam barrel driving protrusion  41  formed at an edge of a rear side of an outer circumferential surface of the cam barrel  40  in a predetermined interval, for example, a particular interval in a radial direction, and a cam barrel pin  42  formed at the edge of the rear side of the outer circumferential surface of the cam barrel  40  to limit the position of the cam barrel  40  such that the cam barrel  40  is arranged at an accurate position on the optical axis. In an assembled state, the cam barrel driving protrusion  41  passes through the cam barrel guide slot  21  of the fixed barrel  20  and inserted in the cam barrel drive groove  33  of the outer guide frame  30 . The cam barrel pin  42  is inserted in the cam barrel guide groove  23 . In the assembled state, the cam barrel driving protrusion  41  is moved by receiving a rotation force from the outer guide frame  30  that is rotated by power transferred from an external drive source  110  via the drive gear portion  31 . Then, the cam barrel driving protrusion  41  rotates around the optical axis along the cam barrel guide slot  21  of the fixed barrel  20  and simultaneously advances or retreats in the optical axis direction. Accordingly, the cam barrel  40  coupled to the cam barrel driving protrusion  41  rotates around the optical axis and simultaneously advances or retreats in the optical axis direction. At this time, as the cam barrel pin  42  moves along the cam barrel guide groove  23  of the fixed barrel  20 , when the cam barrel  40  rotates and moved forward and backward, the motion of the cam barrel  40  is restricted such that the cam barrel  40  can move to an accurate position on the optical axis.  
         [0032]     The cam barrel  40  includes a shutter unit guide groove  43  formed in an inner circumferential surface of the cam barrel  40  to guide movement in the optical axis direction and rotation with respect to the optical axis of the shutter unit  90 , a first lens group guide groove  44  formed in the inner circumferential surface thereof to guide movement in the optical axis direction and rotation with respect to the optical axis of the first lens group  50 , a cam barrel step portion  45  formed along an edge of a rear side of the inner circumferential surface of the cam barrel  40  to guide a relative rotation motion of the inner guide frame  70  with respect to the cam barrel  40  around the optical axis, and a cam barrel step portion protrusion  46  that is at least one protrusion formed at an edge of a rear side of the cam barrel step portion  45  at a particular interval in a radial direction to guide a relative rotation motion of the inner guide frame  70  with respect to the cam barrel  40  with respect to the optical axis.  
         [0033]     The inner guide frame  70 , as shown in  FIG. 3 , includes a shutter unit guide slot  71  formed in the optical axis direction by penetrating the inner guide frame  70  to guide a linear motion of the shutter unit  90  in the optical axis direction, a first lens group guide groove  72  formed in an outer circumferential surface of the inner guide frame  70  in the optical axis direction to guide a linear motion of the first lens group  50  in the optical axis direction, an inner guide frame guide groove  74  formed between two flanges  73   a  and  73   b  protruding from an edge of a rear side of the outer circumferential surface of the inner guide frame  70  in a radial direction and coupled to the cam barrel step portion protrusion  46 , to guide a rotation motion of the inner guide frame  70  around the optical axis, and an inner guide step portion protrusion  75  protruding outwardly in a radial direction from an outer circumferential surface from the flange  73   a  located at a rear side of the flanges  73   a  and  73   b  and inserted in the inner guide frame guide groove  22  of the fixed barrel  20 , to guide a linear motion of the inner guide frame  70  in the optical axis direction. Since the flange  73   a  at the rear side of the two flanges  73   a  and  73   b  of the inner guide frame  71  protrudes further than the flange  73   b  at the front side, in the radial direction of the outer circumferential surface thereof, the inner guide frame  70  is not inserted in the cam barrel  40  and contacts an end portion of the rear side of the cam barrel  40  so as to be coupled to the fixed barrel  20 .  
         [0034]     The first lens group  50 , as shown in  FIG. 4 , includes a plurality of lenses consisting of a G1 lens and a G2 lens and a first lens frame  51  which fixes the G1 and G2 lenses, is disposed between the inner circumferential surface of the cam barrel  40  and the outer circumferential surface of the inner guide frame  70 , and is capable of moving in the optical axis direction. A first lens group guide pin  52  is formed at an edge of a rear side of an outer circumferential surface of the first lens frame  51  and inserted in the first lens group guide groove  44  so that, during a zoom operation, the first lens group  50  is moved in the optical axis direction in engagement with the movement of the cam barrel  40 . An inner guide frame insertion slot  54  is formed at an edge of a lens fixing portion  53  of the first lens frame  51  in which a protruding portion  76  formed by extending the shutter unit guide slot  71  and the first lens group guide groove  72  of the inner guide frame  70  is inserted during an accommodation operation. A front panel  120  is installed in front of the first lens frame  51 , as shown in  FIG. 4 . At least one, for example, three, panel fixing portions  121  to fix the front panel  120  to the first lens frame  51  protrude at an edge of the front panel  120 . A panel fixing groove  122  is formed at the panel fixing portion  121 . As a panel fixing protrusion.  55  formed at a portion of the edge of a front side of the inner circumferential surface of the first lens frame  51  is inserted in the panel fixing groove  122 , the front panel  120  is coupled to the first lens group  50 .  
         [0035]     The second lens group  60 , as shown in  FIG. 5 , includes a plurality of lenses consisting of a G3 lens and a G4 lens, a lens fixing portion  61  protruding from a center portion thereof to fix the G3 and G4 lenses, an extension portion  62  extending outwardly in a radial direction from the lens fixing portion  61 , and a support portion  63  extending from the extension portion  62  to the front and rear sides of the optical axis direction. The support portion  63 , as shown in  FIG. 5 , includes a shutter unit coupling groove  64  which guides the shutter unit  90  to linearly move in the optical axis direction and is coupled to the shutter unit  90 . A shutter unit coupling protrusion  65  that is used when the second lens group  60  is coupled to the shutter unit  90  is formed on the shutter unit coupling groove  64 .  
         [0036]     The shutter unit  90 , as shown in  FIG. 5 , includes a front cover  92  and a rear cover  93  having an opening portion  91  for exposure at the center thereof, a blade  94  arranged between the front cover  92  and the rear cover  93  to open the opening portion  91 , an electronic actuator  95  to actuate the blade  94 , and a shutter unit coupling portion  96  extending from edges of the front and rear covers  92  and  93  in the optical axis direction and inserted in the shutter unit coupling groove  64  of the second lens group  60 .  
         [0037]     The electronic actuator  95  is accommodated in the front and rear covers  92  and  93 . During the accommodation operation, as the shutter unit  90  approaches the second lens group  60 , the electronic actuator  95  actuates the blade  94  such that the second lens frame  61  of the second lens group  60  is inserted in the opening portion  91  of the shutter unit  90 . By doing so, since the opening portion  91  of the shutter unit  90  in the accommodation state is open larger than that in a zoom state, the second lens frame  61  of the second lens group  60  can be inserted therein so that the shutter unit  90  and the second lens group  60  is completely overlapped.  
         [0038]     A shutter unit groove  97  and a shutter unit guide pin groove  99  are formed in the shutter unit coupling portion  96 . The shutter unit coupling protrusion  65  of the second lens group  60  is inserted in the shutter unit groove  97 . By the above structure, during the zoom operation, when the shutter unit  90  moves toward an object in the optical axis direction, the unit coupling protrusion  65  is caught in the shutter unit groove  97  so that the second lens group  60  in engagement with the shutter unit  90  moving forward in the optical axis direction maintains a particular distance from the shutter unit  90  and moves forward in the optical axis direction along the second lens group  60 . During the accommodation operation, as the shutter unit  90  moves backward in the optical axis direction, since the shutter unit  90  moves without interference from the shutter unit coupling protrusion  65 , it prevents the second lens group  60  from moving in the optical axis direction and simultaneously approaches the second lens group  60  while compressing an elastic unit  66  to be described later. The shutter unit guide pin  98  is coupled to the shutter unit guide pin groove  99 . The shutter unit guide pin  98  is formed with the shutter unit coupling portion  96  or in other portion of the shutter unit  90 . The shutter unit guide pin  98  penetrates the shutter unit guide slot  71  of the inner guide frame  70 , is inserted in the shutter unit guide groove  43  of the cam barrel  40 , and moves forward and backward in the optical axis direction in engagement with the cam barrel  40 .  
         [0039]     As shown in  FIGS. 2 and 5 , the elastic unit  66 , for example, a spring, is interposed between the shutter unit  90  and the second lens group  60 . The elastic unit  66  is arranged encompassing the second lens frame  61  so that the second lens frame  61  penetrates the elastic unit  66 . In the zooming state, the elastic unit  66  that is not compressed maintains a particular distance between the shutter unit  90  and the second lens group  60 . In the accommodation state, the shutter unit  90  moves toward the second lens group  60  while compressing the elastic unit  66 , part of the second lens group  60 , for example, the second lens frame  61 , is inserted in the opening portion  91  of the shutter unit  90  so that the second lens group  60  and the shutter unit  90  are completed overlapped. At this time, as the shutter unit  90  approaches the second lens frame  60 , the blade  94  of the shutter unit  90  opens the opening portion  91  larger compared to a case in which the opening portion  91  is open to adjust brightness in the zooming state, so that the second lens frame  60  can be inserted in the opening portion  91  of the shutter unit  90 . Such operation is performed by actuating the blade  94  so that the electronic actuator  95  inserts the second lens frame  60  in the opening portion  91  of the shutter unit  90  as the shutter unit  90  approaches the second lens group  60  in engagement of the movement of the cam barrel  40 .  
         [0040]     In a state in which the shutter unit guide pin  98  penetrates the shutter unit guide slot  71  of the inner guide frame  70  and is inserted in the shutter unit guide groove  43 , the shutter unit  90  can approach the second lens group  60  in the accommodation state as the cam barrel  40  is rotated by receiving a rotational force from the outer guide frame  30  that is rotated by the external drive source  110 .  
         [0041]     The third lens group  80 , as shown in  FIG. 6 , includes a G5 lens, a third lens frame  81  arranging and fixing the G5 lens in the optical axis direction, a third lens group drive motor  82  moving the third lens frame  81  forward and backward in the optical axis direction, and three guide bars  83 ,  84 , and  85  guiding the movement of the third lens frame in the optical axis direction. Among the three guide bars  83 ,  84 , and  85 , one is arranged in the upper portion of the third lens frame  81  and two are arranged in the lower portion thereof, as shown in  FIG. 6 . The three guide bars  83 ,  84 , and  85  are guided by being inserted in holes  83   a  and  85   a  formed in the third lens frame  81  and a hole  84   a  formed in an additional guide plate  87 , respectively. The third lens frame  81  is moved in the optical axis direction as a guide screw portion  89  extending from the third lens group drive motor  82  and passing through a guide screw hole  88  formed in the guide plate  87  rotates along a screw formed in an inner circumferential surface of the guide screw hole  88  by receiving power of the third lens group drive motor  82 . A third lens group elastic unit  86  is installed around an outer circumferential surface of the guide screw portion  89  and performs an elastic function between the third lens group drive motor  82  and the third lens frame  81  to make the third lens frame  81  closely contact the guide plate  87 . By providing the third lens group elastic unit  86 , the driving force of the third lens group drive motor  82  is transferred to the third lens frame  81  via the guide screw portion  89  and the guide screw hole  88  so that the G5 lens moves in the optical axis direction.  
         [0042]     The base  10 , as shown in  FIG. 6 , includes an external drive motor  111  forming the external drive source  110  and a series of gears  112   a,    112   b,    112   c,    112   d,    112   e,  and  112   f.    
         [0043]     The operation of the lens barrel is described with reference to  FIGS. 2, 7 , and  8 . In a state in which the a camera is not in use, as shown in  FIG. 2 , the first lens group  50 , a second lens group  60 , and a third lens group  80  retreat to the rearmost position in the optical axis direction. That is, the third lens group  80  is located close to the filter  11  and the second lens group  60  is located close to the third lens group  80 . The shutter unit  90  overlaps the second lens group  60  in a state in which the opening portion  91  is open at its maximum so that the second lens frame  61  of the second lens group  60  is inserted in the opening portion  91 . The first lens group  50  is located close to the second lens group  60 .  
         [0044]     When the camera is in use, the external drive source  110  rotates in one direction, the outer guide frame  30  is rotated by the drive gear portion  31 . Accordingly, the cam barrel driving protrusion  41  of the cam barrel  40  penetrating the cam barrel guide slot  21  of the fixed barrel  20  and inserted in the cam barrel drive groove  33  of the outer guide frame  30  is moved along the cam barrel drive groove  33  and the cam barrel  40  is moved in the optical axis direction while rotating around the optical axis. The cam barrel  40  can be guided to an accurate position by the cam barrel pin  42  inserted in the cam barrel guide groove  23 . As the cam barrel  40  is driven as above, the shutter unit  90  and the first lens group  50  are actuated by the shutter unit guide pin  98  and the first lens group guide pin  52  inserted in the shutter unit guide groove  43  and the first lens group guide groove  44  of the cam barrel  40 , respectively. As the shutter unit  90  is actuated, the second lens group  60  is actuated in the optical axis direction by the shutter unit coupling protrusion  65  inserted in the shutter unit groove  97  of the shutter unit  90 . Also, the third lens group  80  is moved in the optical axis direction by the driving of the third lens group drive motor  82 . Thus, by the above movements, the camera is in a wide angle photographing position.  
         [0045]     When the external drive source  110  further rotates in the wide angle photographing position, as shown in  FIG. 8 , the outer guide frame  30  further rotates and the cam barrel  40  further rotates. Accordingly, the shutter unit  90  engaged with the driving of the cam barrel  40  rotates around the optical axis and further moves in the optical axis direction. Thus, the second lens group  60  that is moved in the optical axis direction as the shutter unit  90  moves in the optical axis direction further moves in the optical axis direction toward the object to be photographed. Consequently, the camera achieves a telescopic photographing position by the above movements.  
         [0046]     When the external drive source  110  rotates in the opposite direction, the outer guide frame  30  and the cam barrel  40  moving in engagement with the outer guide frame  30  are rotated in the opposite direction by the drive gear portion  31 . The first lens group  50  and the shutter unit  90  are moved in a reverse path so as to retreat to the initial accommodation state. The shutter unit coupling portion  96  is moved backward by the shutter unit coupling groove  64  of the second lens group  50  without being restricted by the shutter unit coupling protrusion  65  of the second lens group  60  that is caught by the shutter unit groove  97 . Accordingly, the shutter unit  90  compresses the elastic unit  66  and approaches the second lens group  60 . Furthermore, as the shutter unit  90  operates the blade  94  so that the opening portion  91  can be open larger than in the zoom state, the second lens frame  61  can be inserted in the opening portion  91 . The third lens group  80  retreats by the driving of the third lens group drive motor  82  in the opposite direction for accommodation. The third lens group  80  moves toward the object to be photographed in the optical axis direction by the driving of the third lens group drive motor  82  in the opposite direction during the zoom operation.  
         [0047]     According to the present embodiment, during the accommodation operation, the shutter unit  90  can approach closer to the second lens group  60  than during the zoom operation. As the shutter unit  90  approaches the second lens group  60 , the blade  94  of the shutter unit  90  is operated to allow complete insertion into the opening portion  91  of the shutter unit  90 . Thus, the total length of the lens barrel can be remarkably reduced compared to a case in which only a part of a leading end portion of the second lens frame  61  of the second lens group  60  overlaps a part of the opening portion  91  of the conventional shutter unit  90 .  
         [0048]     Although in the above embodiment the first lens group  50  through the third lens group  80  are described as the plurality of lens groups, the lens barrel according to the present invention is not limited thereto and different numbers of lens groups can be employed.  
         [0049]     As described above, the present invention having the above structure has the following effects.  
         [0050]     In the lens barrel according to the present invention, during the accommodation operation, the shutter unit approaches closer to an adjacent lens group than that during the zoom operation so that the shutter unit is moved in the optical axis direction in engagement with the adjacent lens group that moves in the optical axis direction. Also, during the accommodation operation, the opening portion is sufficiently open such that at least a part of the adjacent lens group can be completely inserted in the opening portion so that the total length of the lens barrel is remarkably reduced. Thus, the camera can be made thinner and smaller.  
         [0051]     While this invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.