Abstract:
One end of an FPC ( 21 ) for supplying power to the driving section of a light amount control section provided in a shutter unit ( 20 ) is disposed between a second lens holder ( 17 ) and the shutter unit ( 20 ) secured to this second lens holder ( 17 ) and is held between the second lens holder ( 17 ) and the shutter unit ( 20 ). Thus, the FPC ( 21 ) is prevented from being spaced apart from the shutter unit ( 20 ), and a member for securing the FPC ( 21 ) to the shutter unit ( 20 ) is eliminated, reducing the number of part items. Further, the second lens holder ( 17 ) and the shutter unit ( 20 ) blocks unwanted light toward the FPC ( 21 ), so that a ghost image is prevented from appearing on an image due to unwanted light reflected on the FPC ( 21 ).

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a lens unit to be mounted on optical instruments such as cameras. 
       BACKGROUND ART 
       [0002]    Conventionally, cameras and others including an image pickup optical system composed of plural lenses are in widespread use. In such a camera or the like, an image of a subject based on a light pencil incident on the image pickup optical system is formed on image sensors such as CCDs (Charge Coupled Devices) placed at specified positions. For such cameras, there is a desire for their further downsizing with a view to facilitating their incorporation into portable terminal equipment in addition to enhancements in zoom function, autofocus function or other higher functions and higher resolutions. 
         [0003]    Furthermore, cameras having the zoom function are, in general, so designed that a zoom lens group and a shutter unit are integrally moved so as to provide a smaller aperture. That is, the shutter unit is secured on a subject side of the integrally driven lens group, with an FPC (Flexible Printed Circuit) provided for supplying power to the shutter unit. The FPC goes deformed with the moving lens group. 
         [0004]    Among lens tubes equipped with such an FPC as shown above is one disclosed in JP 2006-3458 A (Patent Literature 1). An example of FPC placement and routing disclosed in Patent Literature 1 is shown in FIG. 7. 
         [0005]    In FIG. 7, the FPC 1 is placed on an image pickup side of the shutter unit (not shown), and an L-shaped hooking holder 4 is integrally formed with an annular lid member 3 of a shutter holding frame 2 for routing of the FPC 1. Then, on a subject side of the FPC 1, a U-shaped portion 5 is formed by bending the FPC 1, and the U-shaped portion 5 is hooked to the hooking holder 4, with the FPC 1 drawn out on the image pickup side. 
         [0006]    However, the conventional lens tube disclosed in Patent Literature 1 has the following problems. That is, since the shutter unit is placed more on the subject side than the lens group that is movably supported by the shutter holding frame 2, there arises a need for the annular lid member 3 to support the shutter unit on the shutter holding frame 2. Thus, members count increases as a problem. 
         [0007]    Also, since the FPC 1 on the shutter unit side needs to be hooked to the hooking holder 4 provided in the annular lid member 3, the assembling work becomes more complex as another problem. 
         [0008]    There is also a problem that since the FPC 1 undergoes an abrupt bending stress applied to the U-shaped portion 5 hooked to the hooking holder 4, disconnection may occur to conductive portions of the FPC 1. 
       SUMMARY OF INVENTION 
     Technical Problem 
       [0009]    Accordingly, an object of the present invention is to provide a lens unit which allows the shutter unit to be driven along with the lens group and in which its optical system is not affected by routing of the FPC for supplying power to the shutter unit. 
       Solution to Problem 
       [0010]    A lens unit according to the present invention includes: 
         [0011]    a lens group arrayed in an optical-axis direction; 
         [0012]    a lens holder on which the lens group is mounted and which is movable along a shaft parallel to the optical axis; 
         [0013]    a shutter unit which is secured to the lens holder and which moves along with the lens holder; 
         [0014]    a driving section which is mounted on the shutter unit and which drives a light amount control section provided on the shutter unit so that the light amount control section performs a light amount control operation; and 
         [0015]    an interconnection which has flexibility and which supplies power to the driving section, wherein 
         [0016]    one end, which is a driving section-side end, of the interconnection is placed between the lens holder and the shutter unit. 
         [0017]    According to this invention, the driving-section side end of the interconnection for supplying power to the driving section of the light amount control section is held between the lens holder and the shutter unit, which is secured to the lens holder and which moves along with the lens holder. Therefore, the interconnection is prevented from being separated from the shutter unit, eliminating the need for any member for securing the interconnection to the shutter unit so that the parts count can be reduced. 
         [0018]    Further, the one end of the interconnection is placed between the lens holder and the shutter unit. Therefore, unwanted light for the interconnection can be blocked by the lens holder and the shutter unit, so that formation of ghosts in images due to reflection of unwanted light by the interconnection is prevented. 
         [0019]    In one embodiment, the interconnection is bent at an end portion of the shutter unit toward a subject side of the lens unit so as to extend toward the subject side, and is then curved halfway so as to extend toward an image pickup side of the lens unit, while an other end portion of the shutter unit opposite to the one end portion is secured to a side wall of a casing of the lens unit. Also, a power supply terminal of a position detection sensor for detecting a position of the lens holder is connected to an other end of the interconnection. 
         [0020]    According to this embodiment, the interconnection undergoes no restraints during a process from when being bent toward the subject side until when being secured to the side wall of the casing. Therefore, unlike the case of the conventional lens tube disclosed in Patent Literature 1, no abrupt bending stress due to catching by the hooking holder is applied to the interconnection, so that the interconnection can be prevented from undergoing undue stress during movement of the lens holder. As a consequence, it becomes possible to form a conductor only on one side of the base material of the interconnection, which will lead to the reduction of the thickness of the interconnection. 
         [0021]    Furthermore, connected to the other end of the interconnection is the power supply terminal of the position detection sensor. Therefore, there is no need for additionally providing any exclusive interconnection for supplying power to the position detection sensor, so that the parts count can be reduced. 
         [0022]    In one embodiment, the interconnection is band-shaped and allows a position of the curvature to move along with movement of the lens holder and the shutter unit. And, in the interconnection, at least a width of a region over which the position of the curvature moves along with movement of the shutter unit is narrower than a width of the other end portion of the interconnection. 
         [0023]    According to this embodiment, the width of the band-shaped interconnection in the region in which the interconnection is curved is narrower than the width of the other regions of the interconnection. Therefore, the force that the lens holder receives from the curved portion of the interconnection along with the movement of the lens holder is made smaller. As a consequence, it becomes possible to decrease changes of an angle of the interconnection with respect to the optical axis of the lens holder to lessen effects of curvature of the interconnection on the image quality. 
         [0024]    In one embodiment, the interconnection is band-shaped, and the lens holder has a slit-like cutout near a position in which the interconnection is bent toward the subject side, and the interconnection is inserted into the cutout so that the interconnection is held by the lens holder. 
         [0025]    According to this embodiment, the interconnection is held by the lens holder at a place where the interconnection is bent toward the subject side. Therefore, position and angle of the interconnection at which the interconnection is bent toward the subject side are prevented from varying along with movement of the lens holder and the shutter unit, so that the interconnection can be prevented from intruding to the optical path side. 
         [0026]    In one embodiment, the cutout is defined by a body of the lens holder and a protruding portion of the lens holder that protrudes from a side face of the lens holder. 
         [0027]    According to this embodiment, the interconnection, which is bent toward the subject side at the place of the cutout defined by the protruding portion of the lens holder and the body of the lens holder, is curved halfway so as to extend toward the image pickup side, passing outside the protruding portion, i.e., through between the protruding portion and the side wall of the casing, thus being secured to the side wall of the casing. Therefore, the protruding portion is enabled to move while thrusting out the interconnection to the side-wall side along with the lens holder. As a consequence, the interconnection can more effectively be prevented from intruding to the optical path side along with the movement of the lens holder and the shutter unit. 
       ADVANTAGEOUS EFFECTS OF INVENTION 
       [0028]    As is apparent from the above, in the lens unit according to the present invention, because the one end of the interconnection for supplying power to the driving section of the light amount control section is disposed and held between the lens holder and the shutter unit, the interconnection is prevented from being separated from the shutter unit, which eliminates the need for any member for securing the interconnection to the shutter unit so that the parts count can be reduced. 
         [0029]    Furthermore, the one end of the interconnection is placed between the lens holder and the shutter unit. Therefore, unwanted light directed to the interconnection is blocked by the lens holder and the shutter unit, so that formation of ghosts in images due to reflection of unwanted light by the interconnection is prevented. 
         [0030]    If the interconnection is routed so as not undergo restraints during a process from when being bent toward the subject side until when being secured to the side wall of the casing, the interconnection is prevented from undergoing undue stress during movement of the lens holder. 
         [0031]    When the width of the band-shaped interconnection in the region in which the interconnection is curved is narrower than the width of the other regions of the interconnection, the force that the lens holder receives from the curved portion of the interconnection along with the movement of the lens holder is made smaller. As a consequence, it becomes possible to decrease changes of an angle of the interconnection with respect to the optical axis of the lens holder to lessen effects of curvature of the interconnection on the image quality. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0032]      FIG. 1  is a perspective view showing a schematic construction of an optical unit on which a lens unit of the invention is mounted; 
           [0033]      FIG. 2  is a perspective view of the optical unit shown in  FIG. 1 , as viewed in a direction different from that of  FIG. 1 ; 
           [0034]      FIG. 3  is a view showing a second lens holder in  FIG. 1  and members mounted thereon; 
           [0035]      FIG. 4  is a developed view of the FPC in  FIG. 1 ; 
           [0036]      FIG. 5  is a plan view of the optical unit shown in  FIG. 1 , in which the second lens holder has moved most to an image sensor side; 
           [0037]      FIG. 6  is a plan view of the optical unit shown in  FIG. 1 , in which the second lens holder has moved most to a subject side; and 
           [0038]      FIG. 7  is an explanatory view of the routing of a conventional FPC in the lens tube. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0039]    Hereinbelow, the present invention will be described in detail by way of embodiments thereof illustrated in the accompanying drawings.  FIGS. 1 and 2  are perspective views showing a schematic construction of an optical unit in which a lens unit of this embodiment is incorporated. In  FIGS. 1 and 2 , the optical unit  11  is formed in a generally rectangular-parallelepiped shape. Hereinbelow, a Z axis is set along an optical-axis direction while X and Y axes are set along two sides, respectively, of the rectangular parallelepiped of the optical unit  11  orthogonal to the optical axis. 
         [0040]    The optical unit  11  is so constructed that optical components are mounted on an optical base  12  composed of a subject-side wall  12   a , an image pickup-side wall  12   b  and a side wall  12   c  which is a Y-Z plane. Therefore, light coming incident from the subject-side wall  12   a  is thrown onto image sensors (not shown) provided on the image pickup-side wall  12   b  side. 
         [0041]    Also in the optical unit  11 , cylindrical guide shafts  13 ,  14 ,  15  are provided between the subject-side wall  12   a  and the image pickup-side wall  12   b  so as to be parallel to the Z axis and supported by the subject-side wall  12   a  and the image pickup-side wall  12   b . Then, the guide shafts  13 ,  15  are inserted into a first lens holder  16 , the first lens holder  16  being movable parallel to the Z axis along the guide shafts  13 ,  15 . Similarly, the guide shafts  14 ,  15  are inserted into a second lens holder  17 , the second lens holder  17  being movable parallel to the Z axis along the guide shafts  14 ,  15 . It is noted that driving means for driving the first lens holder  16  and the second lens holder  17  in the Z-axis direction is not shown. 
         [0042]    The first lens holder  16 , on which a first lens group  18  is mounted, moves in the Z-axis direction to make focus adjustment. The second lens holder  17  has a second lens group  19  mounted thereon and a shutter unit  20  secured thereto on its image sensor side. An FPC  21  for supplying power to the shutter unit  20  has one end placed between a subject side of the shutter unit  20  and an image sensor side of the second lens holder  17 . Then, the FPC  21  running out from between the shutter unit  20  and the second lens holder  17  extends from an end portion of the second lens holder  17  toward the subject, further being bent in an arc-shaping form toward the image sensor side, and set at an outside portion of the side wall  12   c  of the optical base  12 . Further in the optical unit  11 , as shown in  FIG. 2 , a first position detector  22  for detecting a position of the first lens holder  16  and a second position detector  23  for detecting a position of the second lens holder  17  are set up. Power supply to the first position detector  22  and the second position detector  23  is fulfilled by the FPC  21 . 
         [0043]      FIG. 3  shows the second lens holder  17  and members mounted on the second lens holder  17 . A guide hole  24 , which is a through hole, is formed in the second lens holder  17 , and the guide shaft  14  is inserted into the guide hole  24 . Also, an inverted U-shaped guide shaft receiver  25  is formed on a side wall  12   c  side of the optical base  12  opposite to the guide hole  24  side with the optical axis therebetween. The guide shaft  15  is inserted into the inverted U-shaped portion of the guide shaft receiver  25 . 
         [0044]    A light amount restricting section (not shown) for restricting light that goes incident on the image sensors is placed on a face  26  which is located on the image pickup side of the shutter unit  20  and which is vertical to the Z axis and parallel to the X-Y plane. On a face  27  of the shutter unit  20  which is located on the subject side of the shutter unit  20  and which is vertical to the Z axis and parallel to the X-Y plane, one end portion of the FPC  21  is placed along the face  27 , and one end of the FPC  21  is soldered to the face  27  for supplying power to the driving section for the light amount restricting section. The FPC  21 ′ has electroconductive members formed on only one surface of its base material, and the electroconductive members are formed on the subject side of the base material. 
         [0045]    Fixation between the second lens holder  17  and the shutter unit  20  is done by screws  28 ,  29  tightened to the subject-side face  27  of the shutter unit  20  through the second lens holder  17 . That is, the one end portion of the FPC  21  is placed between the second lens holder  17  and the shutter unit  20 , and tightened by the screws  28 ,  29 . Therefore, the FPC  21  can be prevented from being partly separated from the shutter unit  20 . Further, unwanted light for the FPC  21  is blocked by the second lens holder  17  and the shutter unit  20 . Therefore, it can be prevented that unwanted light impinges on the FPC  21  and is reflected therefrom to be a cause of ghosts in image pickup. 
         [0046]    A protruding portion  30  is formed on an FPC  21 -side end face of the second lens holder  17 . The protruding portion  30  is provided so as to extend from an upper portion of the guide shaft receiver  25  of the second lens holder  17  to an upper side in the Y-axis direction, while a gap  31  is formed in the X-axis direction of the protruding portion  30 . The FPC  21 , which extends from the shutter unit  20 , is inserted into the gap  31 , and the FPC  21  is bent at a position of the gap  31  so as to be drawn out toward the subject side. Accordingly, the FPC  21  can be set up without being fixed to the second lens holder  17  with adhesive or double-sided tape or any fixing member or the like. Moreover, the gap  31  is positioned upper in the Y direction than the guide shaft receiver  25 , thus facilitating guidance of the FPC  21  in assembling process, conveniently. 
         [0047]      FIG. 4  shows a developed view of the FPC  21 . Under a portion  21   a  of the FPC  21  that is placed outside the optical base  12  (hereinafter, the portion will be referred to as outer portion), four holes  32  are provided on the subject side, and four holes  33  are provided on the image pickup side. Into these holes  32  and holes  33 , as shown in  FIG. 2 , metallic legs are inserted for conduction to the first position detector  22  and the second position detector  23 , and the metallic legs are later electrically connected to the outer portion  21   a  of the FPC  21  by soldering or the like. Thus, it becomes possible to supply power to the first position detector  22  and the second position detector  23  by the FPC  21 . 
         [0048]    According to the routing of the FPC  21  as shown above, since electroconductive members are formed only on the subject-side surface of the base material of the FPC  21 , it becomes possible to achieve a manufacturability and a cost cut of the FPC  21 . Furthermore, since a portion  21   b  of the FPC  21  in which a curvature position of the FPC  21  moves along with movement of the second lens holder  17  and the shutter unit  20  can be made smaller in thickness, it becomes possible to smoothly move the second lens holder  17 . 
         [0049]    Since the portion  21   b  of the FPC  21  in which the curvature position moves is narrower in width than a portion  21   c  of the FPC  21  in which the curvature position does not move, it becomes possible to smoothly move the second lens holder  17  as in the foregoing case. Furthermore, since the portion  21   b  in which the curvature position moves is narrower in width than the portion  21   c  in which the curvature position does not move, a force that the second lens holder  17  receives from the curved portion of the FPC  21  along with the movement of the second lens holder  17  becomes smaller. Therefore, it becomes possible to decrease changes of an angle of the FPC  21  with respect to an optical axis of the second lens holder  17  to lessen effects of curvature of the FPC  21  on the image quality. 
         [0050]      FIG. 5  is a plan view of  FIG. 1 , showing a case in which the second lens holder  17  has moved most toward the image sensor side. A position of the first lens holder  16  in this state is as shown in  FIG. 5 . The FPC  21 , which is drawn out from the shutter unit  20  so that its thicknesswise direction is along a direction in which the Z-X plane extends, passes through the gap  31  formed by the protruding portion  30  of the second lens holder  17 , further being guided toward the subject side. Then, the FPC  21  is curved near the first lens holder  16  so as to be directed toward the image pickup side, coming out from a cutout  34  of the side wall  12   c  of the optical base  12 . 
         [0051]      FIG. 6  shows a case in which the second lens holder  17  has moved most toward the subject side. The FPC  21  passes through the gap  31  of the protruding portion  30 , and is curved at near the subject-side wall  12   a  of the optical base  12  so as to be directed toward the image pickup side and further guided to between the protruding portion  30  and the side wall  12   c  of the optical base  12 , coming out from the cutout  34  of the side wall  12   c  of the optical base  12 . 
         [0052]    In this case, the protruding portion  30  is enabled to move along with the second lens holder  17  while the FPC  21  guided toward the image pickup side is kept pressed against the side wall  12   c  of the optical base  12 . Therefore, it becomes possible to prevent the FPC  21  from being held between the first lens holder  16  and the second lens holder  17 . It also becomes possible to prevent the occurrence that as the FPC  21  approaches the optical path, reflected light from the FPC  21  becomes ghosts in image pickup. 
         [0053]    As described above, according to this embodiment, the FPC  21  for supplying power to the shutter unit  20  secured on the image pickup side of the second lens holder  17  has one end placed between the shutter unit  20  and the second lens holder  17  so as to be held by the second lens holder  17  and the shutter unit  20 . Therefore, the FPC  21  can be prevented from being separated from the shutter unit  20 , eliminating the need for a member for securing the FPC  21  to the shutter unit  20  so that the parts count can be reduced. 
         [0054]    Furthermore, the one end of the FPC  21  is placed between the second lens holder  17  and the shutter unit  20 . Therefore, unwanted light for the FPC  21  can be blocked by the second lens holder  17  and the shutter unit  20 , so that formation of ghosts in images due to reflection of unwanted light by the FPC  21  can be prevented. 
         [0055]    The FPC  21  undergoes no restraints during a process from when being bent toward the subject side at an end portion of the shutter unit  20  until when being secured to the side wall  12   c  of the optical base  12 . Therefore, as in the case of the conventional lens tube disclosed in Patent Literature 1, no abrupt bending stress due to catching by the hooking holder is applied to the interconnection, so that the FPC  21  can be prevented from undergoing undue stress during movement of the second lens holder  17 . As a consequence, it becomes possible to form the conductor only on one side of the base material of the FPC  21  to reduce its thickness. 
         [0056]    Furthermore, to the other-side outer portion  21   a  of the FPC  21 , power supply terminals of the first position detector  22  and the second position detector  23  are connected. Therefore, there is no need for additionally providing any exclusive FPC for supplying power to the first position detector  22  and the second position detector  23 , so that the parts count can be reduced. 
         [0057]    The band-shaped FPC  21  is so formed that its portion  21   b  in which the curvature of the FPC  21  moves is set narrower in width than its portion  21   c  in which the curvature does not move. Therefore, the force that the second lens holder  17  receives from the curvature portion of the FPC  21  along with the movement of the second lens holder  17  can be made smaller. As a consequence, changes of the angle of the FPC  21  to the optical axis of the second lens holder  17  can be decreased, so that effects of the curvature of the FPC  21  on the image quality can be reduced. 
         [0058]    A portion of the FPC  21  at which the FPC  21  is bent toward the subject side is held by the gap  31  provided in the protruding portion  30  of the second lens holder  17 . Therefore, position and angle of the FPC  21  at which the FPC  21  is bent toward the subject side never vary along with movement of the second lens holder  17  and the shutter unit  20 , so that the FPC  21  can be prevented from intruding to the optical path side. 
         [0059]    The FPC  21 , which is bent toward the subject side at the place of the gap  31  provided in the protruding portion  30 , is curved halfway so as to extend toward the image pickup side, passing outside the protruding portion  30 , i.e., through between the protruding portion  30  and the side wall  12   c  of the optical base  12 , thus being fitted and secured to the side wall  12   c . Therefore, the protruding portion  30  is enabled to move while thrusting out the FPC to the side wall  12   c  side along with the second lens holder  17 . As a consequence, the FPC  21  can more effectively be prevented from intruding to the optical path side along with the movement of the second lens holder  17  and the shutter unit  20 .