Abstract:
A lens apparatus capable of efficiently arranging a stop blade, an optical filter and a shutter blade to reduce the size of the apparatus is disclosed. The lens apparatus comprising a lens, a lens holding member which holds the lens, a stop blade which changes an area of a light-passing aperture, an optical filter which inserts and removes with respect to a region opposed to the light-passing aperture and a shutter blade which opens and closes the light-passing aperture. Here, at least one member of the stop blade, the optical filter and the shutter blade is arranged at one end side of the lens holding member and the other member is arranged at the other end side of the lens holding member.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a structure of a lens apparatus of camera which takes an object image. 
   2. Description of the Related Art 
   The number of pixels of an image pickup element (CCD, etc.) for an electronic camera represented by a digital camera is significantly increasing in recent years and its pixel pitch has a tendency to reduce rapidly. On the other hand, there is a lens barrel of a camera having an iris diaphragm having a stop blade with an opening or a plurality of stop blades, gradually changing the stop diameter to restrict the quantity of light incident on an image plane and arranged in an optical path. 
   Light has properties of a wave and it is a well-known fact that these properties become conspicuous when the diameter of the aperture stop falls below a certain value, that is, a phenomenon of diffraction takes place. Here, when the pixel pitch of the image pickup element is reduced, the image pickup element can even capture a high frequency area, but in this high frequency area it receives strong influences of diffraction and resolution (image quality) deteriorates drastically. 
   For this reason, for the purpose of suppressing deterioration of the image quality, it is not possible to reduce the aperture of the stop when the pixel pitch of the image pickup element is small. 
   Therefore, when the aperture is small, a structure in which an ND (Neutral Density) filter structured integral with the stop blade is moved into the optical path is used. The ND filter has an effect of restricting the amount of transmitted light and can thereby perform effective light quantity control without the need to reduce the aperture of the stop and suppress aforementioned deterioration of the image quality. 
   Restricting the light quantity is not simply limited to the effect of appropriate exposure, but also has the effect of actually adding various effects to photographic expressions by a photographer, which constitutes an important factor. For example, photographic expressions using various image taking methods are required such as highlighting an object by fully opening the stop, clearly describing all parts of scenery with the stop stopped down, increasing the shutter speed with an increased light quantity, slowing down the shutter speed with a reduced light quantity or the like. 
   However, the stop provided with an ND filter as an integral part is subject to many restrictions on photographic expressions such that there is only one diameter of a reduced aperture to adjust the light quantity with the ND filter or it is not possible to reduce the light quantity with the stop fully opened. That is, the conventional ND filter is used to suppress deterioration of the image quality in a small aperture state and not intended to actively create or edit pictures. 
   Thus, there is a demand for a lens barrel having an iris diaphragm capable of a multi-stage setting of the stop diameter and a ND filter adjusting the quantity of transmitted light respectively, but it is difficult to arrange a driving unit for the stop and a driving unit for the ND filter within the limited space in the lens barrel. 
   Furthermore, when the stop unit, shutter unit and ND unit are held in the same lens holding frame for a purpose of reducing a size of the lens barrel, the overall weight of the lens holding frame increases, which causes a problem that when external shock is given to the lens barrel, the lens holding frame is tilted with respect to the optical axis because of this weight. 
   SUMMARY OF THE INVENTION 
   One aspect of the lens apparatus of the present invention comprises a lens, a lens holding member which holds the lens, a stop blade which changes an area of a light-passing aperture, an optical filter which inserts and removes with respect to a region opposed to the light-passing aperture and a shutter blade which opens and closes the light-passing aperture. Here, at least one member of the stop blade, the optical filter and the shutter blade is arranged at one end side of the lens holding member and the other member is arranged at the other end side of the lens holding member. 
   One aspect of the camera of the present invention comprises a lens, a lens holding member which holds the lens, a stop blade which changes an area of a light-passing aperture, an optical filter which inserts and removes with respect to a region opposed to the light-passing aperture, a shutter blade which opens and closes the light-passing aperture and an image pickup element which photoelectrically converts an object image formed by the lens into an electric signal. Here, at least one member of the stop blade, the optical filter and the shutter blade is arranged at one end side of the lens holding member and the other member is arranged at the other end side of the lens holding member. 
   One aspect of the camera system of the present invention comprises the above described lens apparatus and a camera comprising an image pickup element which photoelectrically converts an object image formed by the lens in the lens apparatus into an electric signal. 
   A detailed configuration of the lens apparatus, camera and camera system of the present invention, the above and other objects and features of the invention will be apparent from the embodiment, described below. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIGS. 1A and 1B  are a top view and a front view of a camera; 
       FIG. 2  is a sectional view of a lens barrel; 
       FIG. 3  is an inner exploded view of a movable cam ring; 
       FIG. 4  is a front view of a stop shutter unit when a shutter cover is removed; 
       FIG. 5  is a front view of the stop shutter unit when a shutter base plate is removed from the state shown in  FIG. 4 ; 
       FIG. 6  is a front view of the stop shutter unit when five stop blades are removed from the state shown in  FIG. 5 ; 
       FIG. 7  is a front view of an ND unit when an ND cover is removed; 
       FIG. 8  is a rear view of the stop shutter unit; 
       FIG. 9  is a sectional view along a line A-A in  FIG. 2 ; and 
       FIG. 10  is a sectional view of a camera system. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   A lens barrel which is an embodiment of the present invention will be explained.  FIG. 1  shows an external view of a camera provided with the lens barrel which is this embodiment. In  FIG. 1A  is a top view of a camera and  FIG. 1B  is a front view of the camera. 
   In  FIGS. 1A and 1B , a lens barrel  101  is provided substantially at the center viewed from the front of a camera body  100  and a finder  102  is provided at the upper left of the lens barrel  101 . Reference numeral  103  denotes a power switch, which sets a replay mode (mode to replay and display a captured image) when turned clockwise in  FIG. 1A  and sets an image-taking mode when turned counterclockwise in  FIG. 1A . 
   Reference numeral  104  denotes a mode dial, which is a dial to select various image-taking modes. Reference numeral  105  denotes a release button, on the circumference of which a zoom key  107  is provided in a manner rotatable with respect to the camera body  100  and it is possible to change the focal length of the image-taking optical system to the telephoto side or wide-angle side according to the rotation direction of the zoom key  107 . Reference numeral  106  denotes an electronic dial, which allows, when turned, various operations such as changing an aperture value or shutter speed. 
     FIG. 2  shows a sectional view of the lens barrel  101 . 
   In  FIG. 2 , reference numerals  1 ,  2  and  3  denote a first lens unit, a second lens unit and a third lens unit respectively, which move in the direction of the optical axis to perform a variable power operation. Reference numeral  4  denotes a fourth lens unit which is responsible for focusing and image plane correction,  5  denotes a low pass filter and  6  denotes an image pickup element (CCD or CMOS sensor, etc.) arranged on the image forming plane of a light flux from an object. 
   Reference numerals  11 ,  12 ,  13  and  14  denote a first holding barrel, a second holding barrel, a third holding barrel and a fourth holding barrel which hold the lens units  1  to  4  respectively. The first holding barrel  11 , second holding barrel  12  and third holding barrel  13  are arranged inside a movable cam ring  21  and engage with cam groove portions formed in the inner surface of the movable cam ring  21 . 
   Reference numeral  22  denotes a fixed barrel and the movable cam ring  21  engages with a cam groove portion formed in the inner surface thereof. The movable cam ring  21  is movable in the direction of the optical axis through the engagement with the cam groove portion of the fixed barrel  22 . Reference numeral  24  denotes a holder to which the fixed barrel  22  is fixed. The holder  24  holds the low pass filter  5  and the image pickup element  6 . 
   Reference numeral  25  denotes a driving ring which rotates the movable cam ring  21  around the optical axis. Reference numeral  26  denotes a rectilinear propagation guide ring which blocks the rotation of the first holding barrel  11 , second holding barrel  12  and third holding barrel  13  around the optical axis and moves these holding barrels  11  to  13  in the direction of the optical axis. Reference numeral  27  denotes a focus motor which drives the fourth holding barrel  14 ,  28  denotes a zoom motor which drives the driving ring  25  and these motors  27  and  28  are fixed to the holder  24 . 
   Reference numeral  71  denotes a flexible printed wiring board (hereinafter referred to as “FPC”) which transmits an output signal of the image pickup element  6  to the camera body side. A signal processing circuit (not shown) provided on the camera body side receives an image signal from the image pickup element  6  through the FPC  71 , performs predetermined processing and then displays this image on a display section provided in the camera body or records it in a recording medium housed in the camera body. 
   Reference numeral  72  denotes an FPC which transmits a driving signal from the camera body side to the stop shutter unit and the ND unit. Reference numerals  73  and  74  denote FPCs which supply power to the focus motor  27  and the zoom motor  28 , respectively. 
   The operation of the lens barrel with the above described structure will be explained. In a camera provided with the lens barrel of this embodiment, when power is OFF, the lens barrel is housed inside the camera body (in a collapse state). When power is turned ON, the lens barrel moves in the direction of the optical axis from the collapse state into an image-taking state. In the image-taking state, it is possible to perform a zooming operation by moving the lens barrel forward or backward in the direction of the optical axis. 
   The driving force of the zoom motor  28  is transmitted to a driving gear (not shown) through a gear system (not shown). Here, the driving gear engages with an inner gear  25   a  formed on the inner surface of the driving ring  25 , and therefore the driving ring  25  receives a driving force from the zoom motor  28  and rotates around the optical axis. 
   An outer gear  25   c  is formed on the external surface of the driving ring  25  and the outer gear  25   c  is at a position shifted from the position of the inner gear  25   a  in the direction of the optical axis (object side). Forming the outer gear  25   c  at a position shifted from the inner gear  25   a  in the direction of the optical axis makes it possible to set the thickness of the driving ring  25  to such a thickness that allows one gear (outer gear  25   c  or inner gear  25   a ) to be formed and reduce the thickness of the driving ring  25  compared to a case where the two gears  25   c  and  25   a  are formed at the same position in the direction of the optical axis. 
   Here, shifting the two gears  25   a  and  25   c  away from each other in the direction of the optical axis makes it possible to substantially equalize a pitch circle diameter of the inner gear  25   a  to that of the outer gear  25   c  irrespective of the thickness of the driving ring  25  or increase either one of the two gears  25   a  and  25   c  depending on the module setting of the gears  25   a  and  25   c  and the thickness of the driving ring  25 . 
   The driving ring  25  is coupled with a driven unit arranged in the camera body, for example, a finder unit through a gear train. More specifically, the outer gear  25   c  engages with one gear of the gear train coupled with the finder unit and when the driving ring  25  rotates around the optical axis, this rotational force is transmitted to the finder unit. In the finder unit, the transmitted force allows zooming in the finder optical system. 
   The driving ring  25  is provided with three rectilinear propagation guide groove portions  25   b  which extend in the direction of the optical axis with a uniform width. Three cam followers  21   a  are provided on the external surface of the movable cam ring  21 . These cam followers  21   a  engage with the three inner cam groove portions formed on the inner surface of the fixed barrel  22  respectively. The cam followers  21   a  move along the inner cam groove portions of the fixed barrel  22  respectively, according to the rotation of the driving ring  25  around the optical axis. In this way, the movable cam ring  21  rotates around the optical axis. 
   A guide portion  21   b  formed integral with the movable cam ring  21  is provided in the vicinity of the cam followers  21   a  and the guide portion  21   b  engages with the rectilinear propagation guide groove portion  25   b  of the driving ring  25  in a slidable manner. 
   When the driving ring  25  receives a driving force from the zoom motor  28  and rotates around the optical axis, the movable cam ring  21  rotates around the optical axis through the engagement between the rectilinear propagation guide groove portion  25   b  and the guide portion  21   b . As shown above, when the movable cam ring  21  rotates around the optical axis, the cam followers  21   a  move along the inner cam groove portions of the fixed barrel  22 , and therefore the movable cam ring  21  moves in the direction of the optical axis while rotating around the optical axis. 
   On the other hand, in the movable cam ring  21 , a pin  21   c  is provided in the vicinity of the cam followers  21   a  and the pin  21   c  is fitted in a groove portion  22   a  formed on the inner surface of the fixed barrel  22  with a certain gap. In this structure, when the lens barrel receives external shock, the pin  21   c  contacts the end surface of the groove portion  22   a  and absorbs the shock and thereby prevents the cam followers  21   a  from disengaging from the inner cam groove portions of the fixed barrel  22 . 
   A guide groove portion  21   d  having a uniform width is formed on the circumference of the inner surface of the movable cam ring  21  and a projection  26   d  provided on the external surface of the rectilinear propagation guide ring  26  engages with the guide groove portion  21   d  in a slidable manner. This causes the rectilinear propagation guide ring  26  to slide in response to the rotation of the movable cam ring  21 . 
   The rectilinear propagation guide ring  26  is prevented from rotating around the optical axis by rotation prevention keys  61  and  62  (see  FIG. 9 ) which extend in the direction of the optical axis as will be described later and is movable only in the direction of the optical axis. For this reason, when the movable cam ring  21  moves in the direction of the optical axis while rotating around the optical axis, the rectilinear propagation guide ring  26  only moves in the direction of the optical axis without rotating around the optical axis. 
   Cam followers  11   a ,  12   a  and  13   a  formed on the external surface of the first holding barrel  11 , second holding barrel  12  and third holding barrel  13  respectively engage with the cam groove portions formed on the inner surface of the movable cam ring  21 . 
   Here, the cam followers  11   a  are formed integral with the external surface of the first holding barrel  11  and are provided at three locations in the circumferential direction of the first holding barrel  11 . The cam followers  12   a  are formed integral with the external surface of the second holding barrel  12  and consist of cam followers provided at two locations in the circumferential direction of the second holding barrel  12  and a movable cam follower pressed against the cam groove portion of the movable cam ring  21  by means of a spring force. The cam followers  13   a  is formed integral with the external surface of the third holding barrel  13  and consists of cam followers  13   a   1  provided at two locations in the circumferential direction of the third holding barrel  13  and a movable cam follower  13   a   2  pressed against the cam groove portion of the movable cam ring  21  by means of a spring force. 
   Rectilinear propagation guide groove portions  26   a ,  26   b  and  26   c  extending in the direction of the optical axis with a predetermined width are formed in the rectilinear propagation guide ring  26 . Part of the first holding barrel  11 , part of the second holding barrel  12  and a rib  13   c  formed on the third holding barrel  13  engage with these rectilinear propagation guide groove portions  26   a ,  26   b  and  26   c  respectively in a slidable manner. 
   As described above, since part of the first holding barrel  11 , part of the second holding barrel  12  and the rib  13   c  of the third holding barrel  13  engage with these rectilinear propagation guide groove portions  26   a ,  26   b  and  26   c  extending in the direction of the optical axis respectively, the holding barrels  11 ,  12  and  13  do not rotate around the optical axis but can move only in the direction of the optical axis. Then, the holding barrels  11 ,  12  and  13  move in the direction of the optical axis through the engagement between the cam followers  11   a ,  12   a ,  13   a  and the cam groove portions of the movable cam ring  21 . This structure allows the first lens unit  1 , second lens unit  2  and third lens unit  3  to move to a position according to a desired focal length. 
   In this embodiment, the cam followers  11   a  have a plane perpendicular to the optical axis. Furthermore, as shown in the inner exploded view of the movable cam ring  21  in  FIG. 3 , the cam groove portions  21   f  of the movable cam ring  21  which engages with the cam followers  11   a  has no gradient between the WIDE position and the TELE position. That is, the area between WIDE and TELE of the cam groove portion  21   f  is located within the plane perpendicular to the optical axis. 
   When the lens barrel is in a state capable of image-taking (between the WIDE state and TELE state), the above described structure prevents the cam followers  11   a  from coming off the cam groove portions  21   f  when external shock is added to the lens barrel by the cam followers  11   a  contacting the cam groove portions  21   f  in the direction perpendicular to the cam groove portions  21   f  (direction of the optical axis). 
   In  FIG. 3 , reference numerals  21   f ,  21   g  and  21   h  denote cam groove portions with which the cam followers  11   a ,  12   a  and  13   a  of the first holding barrel  11 , second holding barrel  12  and third holding barrel  13  engage respectively. Reference numerals  21   j  and  21   k  denote guide groove portions which guide the cam followers  11   a ,  12   a  and  13   a  into the cam groove portions  21   f ,  21   g  and  21   h  when the lens barrel is assembled. Reference numeral  21   m  denotes a coupling groove portion which couples the cam groove portion  21   g  with the cam groove portion  21   h.    
   As described above, since one of the cam followers  12   a  and  13   a  (including three cam followers) is a movable cam follower energized by means of a spring, it can stabilize the driving loads of the second holding barrel  12  and third holding barrel  13 , eliminate play between the cam groove portions  21   g  and  21   h , and the cam followers  12   a  and  13   a  to prevent the lens units  2  and  3  from decentering with respect to the optical axis. 
   In this embodiment, the cam groove portions  21   g  and  21   h  have a sharp gradient between the collapse position and the WIDE position or between the WIDE position and TELE position, and therefore the width of the movable cam ring  21  (length in the direction of the optical axis) needs to be wide enough to form the cam groove portions  21   g  and  21   h . Here, to reduce the size of the movable cam ring  21  (lens barrel) in the direction of the optical axis, the cam groove portion  21   g  and cam groove portion  21   h  need to be arranged close to each other as shown in  FIG. 3 . 
   In this way, arranging the cam groove portion  21   g  and cam groove portion  21   h  close to each other eliminates the area in the movable cam ring  21  for forming a guide groove portion to guide the cam follower  12   a  of the second holding barrel  12  into the cam groove portion  21   g . Furthermore, when the first holding barrel  11 , second holding barrel  12  and third holding barrel  13  are incorporated in the movable cam ring  21 , attempting to incorporate the first holding barrel  11  from the same direction as that in which the second holding barrel  12  and third holding barrel  13  are incorporated eliminates the area for forming the guide groove portions to guide the cam followers  11   a  of the first holding barrel  11  into the cam groove portions  21   f.    
   In this embodiment, as shown in  FIG. 3 , the guide groove portions  21   j  of the first holding barrel  11  (cam followers  11   a ) are formed at one end (object side) of the movable cam ring  21  and the guide groove portions  21   k  of the second holding barrel  12  (cam followers  12   a ) and third holding barrel  13  (cam followers  13   a ) are formed at the other end (image plane side) of the movable cam ring  21 , therefore the second holding barrel  12  and the third holding barrel  13  are incorporated into the movable cam ring  21  from a direction different from the direction in which the first holding barrel  11  is incorporated into the movable cam ring  21 . 
   In correspondence with the above described incorporation directions, the rectilinear propagation guide groove portion  26   a  is formed up to one end (end on the object side) of the rectilinear propagation guide ring  26  and the rectilinear propagation guide groove portions  26   b  and  26   c  are formed up to the other end (end on the image plane side) of the rectilinear propagation guide ring  26  (see  FIG. 2 ). This allows the first holding barrel  11  to be incorporated from the one end of the rectilinear propagation guide ring  26  and the second holding barrel  12  and the third holding barrel  13  to be incorporated from the other end of the rectilinear propagation guide ring  26 . 
   Furthermore, the cam groove portion  21   g  and cam groove portion  21   h  are coupled by the coupling groove portion  21   m  and the second holding barrel  12  and the third holding barrel  13  are incorporated from one guide groove portion  21   k  into the movable cam ring  21 . That is, when the second holding barrel  12  and the third holding barrel  13  are incorporated into the movable cam ring  21 , the cam follower  12   a  of the second holding barrel  12  is first allowed to pass through the cam groove portion  21   h  and coupling groove portion  21   m  and then guided into the cam groove portion  21   g  and thereby the second holding barrel  12  is incorporated in the movable cam ring  21 . Then, the cam follower  13   a  of the third holding barrel  13  is introduced into the cam groove portion  21   h  and thereby the third holding barrel  13  is incorporated into the movable cam ring  21 . 
   As described above, by adopting a structure capable of forming the cam groove portion  21   h  and the cam groove portion  21   g  close to each other and incorporating the holding barrels  11 ,  12  and  13  from both ends of the movable cam ring  21 , it is possible to reduce the diameter of the movable cam ring  21  (lens barrel) and the length in the direction of the optical axis. 
   Then, the driving mechanism of the fourth lens unit  4  which performs a focusing operation by moving in the direction of the optical axis will be explained. 
   In  FIG. 2 , the fourth holding barrel  14  which holds the fourth lens unit  4  is supported by a main guide bar (not shown) arranged in parallel to the optical axis and is movable along this main guide bar. Furthermore, a sub-guide bar is arranged in parallel to the optical axis on the substantially opposite side of the main guide bar across the optical axis and a rotation stopper provided on the external surface of the fourth holding barrel  14  engages with the sub-guide bar in a slidable manner. 
   A nut bearing portion whose cross section is horseshoe-shaped is provided in the vicinity of the main guide bar of the fourth holding barrel  14 , and this nut bearing portion is provided with a nut  15  which engages with a lead screw portion  27   a  of the focus motor  27 . The rotation of the nut  15  is blocked by a rotation stopper (not shown), and therefore when the focus motor  27  (lead screw portion  27   a ) rotates, the nut  15  moves along the lead screw portion  27   a . This allows the fourth holding barrel  14  (fourth lens unit  4 ) to move in the direction of the optical axis and stop at a predetermined in-focus position. 
   The one ends of the above described main guide bar and sub-guide bar are fixed to a CCD holder  24  and the other ends are fixed to a fourth cap  29 . Furthermore, the end of the lead screw portion  27   a  of the focus motor  27  is fixed to the fourth cap  29 . 
   Then, the structure of the stop shutter unit and ND unit will be explained. 
   In  FIG. 2 , reference numeral  31  denotes a stop blade,  32  denotes a pinwheel which drives the stop blade  31 ,  33  denotes a stop base plate. Reference numeral  34  denotes a shutter blade,  35  denotes a shutter base plate,  36  denotes a shutter cover and  52  denotes a shutter yoke. The stop shutter unit is made up of these members. Reference numeral  41  denotes an ND base plate,  42  denotes an ND blade and  43  denotes an ND cover. The ND unit is made up of these members. 
   The structure of the stop shutter unit will be explained using  FIGS. 4 ,  5  and  6 . 
     FIG. 4  is a front view of the stop shutter unit when the shutter cover  36  is removed.  FIG. 4  shows the state in which the two shutter blades  34  have moved away from the opening  35   b  serving as a hole portion for light passage formed in the shutter base plate  35 . 
   Each shutter blade  34  is supported to the rotation shaft  35   a  formed on the shutter base plate  35  in a rotatable manner and a driving pin  38   a  formed at the end of the driving lever  38  (shown by a dotted line in  FIG. 4 ) engages with a long hole portion  34   a  formed at the end (rotation shaft side) of each shutter blade  34 . The driving lever  38  receives a driving force from a driving unit which will be described later and can rotate and through this rotation, each shutter blade  34  rotates around each rotation axis  35   a . In this way, the two shutter blades  34  open/close the opening  35   b.    
     FIG. 5  is a front view of the stop shutter unit when shutter blades  34  and shutter base plate  35  are removed from the state shown in  FIG. 4 . In  FIG. 5 , six stop blades  31  of the same shape are supported to the rotation shafts  33   a  formed on the stop base plate  33  in a rotatable manner. 
     FIG. 6  is a front view of the stop shutter unit when the five stop blades  31  are removed from the state shown in  FIG. 5 . 
   In  FIG. 6 , reference numeral  39  denotes a driving lever which drives (rotates) a pinwheel  32  and is rotatable around a shaft  39   b . A pin  39   a  is provided at the end of the driving lever  39  and the pin  39   a  engages with a long hole portion (shown with a dotted line in  FIG. 6 )  32   a  formed on the back of the pinwheel  32 . 
   When the driving lever  39  rotates, the pinwheel  32  rotates around the optical axis (direction shown by an arrow in the figure) through the engagement between the pin  39   a  and long hole portion  32   a . Six pins  32   b  are formed on the pinwheel  32  and these pins  32   b  engage with the cam groove portions  31   a  formed in the stop blades  31 . 
   In the above described structure, when the pinwheel  32  rotates, the stop blades  31  rotate around the rotation shafts  33   a  through the cam engagement between the pin  32   b  and cam groove portion  31   a  and move forward or backward to/from the opening  33   b  formed in the stop base plate  33 . This operation changes the area of the opening of light passage (aperture diameter). 
   Then, the structure of the ND unit will be explained using  FIG. 7 .  FIG. 7  is a front view of the ND unit when the ND cover  43  is removed. 
   In  FIG. 7 , reference numeral  42   a  denotes an opening formed in the ND blade  42 . Reference numeral  44  denotes an ND filter (optical filter shown by a dotted line in the figure) which is attached to the ND blade  42  and covers the opening  42   a . Reference numeral  41   a  denotes a rotation shaft formed on the ND base plate  41  and supports the ND blade  42  in a rotatable manner. Reference numeral  45   a  denotes a driving pin formed on a rotatable driving lever  45  (see  FIG. 8 ), the driving pin  45   a  engages with a long hole portion  42   b  formed in the end side (rotation shaft  41   a  side) of the ND blade  42 . 
   In the above described structure, when the driving lever  45  rotates, the ND blade  42  rotates around the rotation shaft  41   a  through the engagement between the driving pin  45   a  and long hole portion  42   b . That is, when the ND blade  42  moves with respect to the opening (shown with a dotted line in  FIG. 7 )  41   b  formed in the ND base plate  41 , the opening  41   b  can be covered with the ND filter  44 . At this time, the amount of light incident on the image plane is restricted by the action of the ND filter  44 . Furthermore, when the ND blade  42  moves to the position shown by a two-dot dashed line in  FIG. 7 , the ND filter  44  can be moved away from the opening  41   b . The stop shutter unit and the ND unit are fixed to the third holding barrel  13  with screws (not shown). 
   Then, the driving unit for driving the stop blade  31 , shutter blade  34  and ND blade  42  will be explained using  FIG. 8 .  FIG. 8  is a rear view of a stop shutter unit. 
   In  FIG. 8 , reference numeral  50  denotes a stepping motor constituting a driving unit which drives the stop blade  31  and a driving lever  39  is connected to the output shaft of the stepping motor. In this embodiment, the stepping motor  50  is driven in micro steps to perform finer position control and thereby improve the stopping-down accuracy. 
   Reference numerals  51 ,  52  and  53  denote a coil, yoke and magnet, respectively which constitute the driving unit which drives the shutter blade  34 . The magnet  53  rotates in a predetermined direction through a magnetic force generated when power is supplied to the coil  51 . Here, since the driving lever  38  is attached to the magnet  53  as an integral part, the driving lever  38  also rotates together with the rotation of the magnet  53 . 
   Reference numerals  54 ,  55  and  56  denote a coil, yoke and magnet, respectively which constitute the driving unit which drives the ND blade  42 . The magnet  56  rotates in a predetermined direction through a magnetic force generated when power is supplied to the coil  54 . Here, since the driving lever  45  is attached to the magnet  56  as an integral part, the driving lever  45  also rotates together with the rotation of the magnet  56 . 
   In this embodiment, as shown in  FIG. 2 , the above described driving units which drive the stop blade  31 , shutter blade  34  and ND blade  42  are arranged in the space which is in the periphery of the third lens unit  3  and formed between the stop blade  31  and the ND blade  42 . 
   By arranging the respective driving units using a dead space formed between the stop blade  31  and the ND blade  42 , it is possible to shorten (make thinner) the length of the third holding barrel  13  in the direction of the optical axis. Furthermore, since each driving unit is arranged in substantially the same position in the direction of the optical axis with respect to the third holding barrel  13 , it is possible to shorten wiring of an FPC  72  which supplies power to the stepping motor  50 , coils  51  and  54  compared to the case where the driving units are arranged in different positions in the direction of the optical axis with respect to the third holding barrel  13  and thereby reduce the cost or reduce power loss. 
   Here, when the three types of blades; stop blade  31 , shutter blade  34  and ND blade  42  and the driving units to drive these blades are arranged on one side (object side or image plane side) of the lenses (third holding barrel  13 ), another movable area for other blades needs to be provided in a area other than the movable area of one of the blades  31 ,  34  and  42 . Thus, arranging the stop blade  31 , shutter blade  34  and ND blade  42  altogether in the lens barrel will result in an increase of side of the lens barrel because the movable areas for the blades  31 ,  34  and  42  need to be secured. 
   Thus, in this embodiment, the stop blade  31  and shutter blade  34  are arranged on the object side with respect the third holding barrel  13  (third lens unit  3 ) and the ND blade  42  is arranged on the image plane side with respect to the third holding barrel  13  (third lens unit  3 ). A space which serves as the movable areas for three kinds of blades  31 ,  34  and  42  are formed at both ends of the third holding barrel  13 , thereby increases the degree of design freedom in forming the movable areas for the blades  31 ,  34  and  42  compared to the above described case where three kinds of blades  31 ,  34  and  42  are arranged together on one side of the third holding barrel  13  and can thereby efficiently arrange the blades and driving units which drive them in the lens barrel taking into account the movable areas of the blades  31 ,  34  and  42  and repress the size of the lens barrel size from increasing. 
   Then, in the above described structure, by arranging the driving units of the blades  31 ,  34  and  42  in the dead space formed between the stop blade  31  and ND blade  42 , it is possible to reduce the size of the lens barrel compared to the case where the space for the arrangement of the driving units is separately secured in the lens barrel. 
   In this embodiment, the stop blade  31  and shutter blade  34  are arranged at one end of the third holding barrel  13  and the ND blade  42  is arranged at the other end, but this arrangement (structure) can take any other forms. That is, any one of the stop blade  31 , shutter blade  34  and ND blade  42  can be arranged at one end of the third holding barrel  13  and the other blades can be arranged at the other end. Then, the driving units can be arranged in the space between the blades arranged at both ends of the third holding barrel  13 . 
   Furthermore, in this embodiment, as shown in  FIG. 8 , the driving units are arranged on substantially the same circumference centered on the optical axis. This allows the driving units to be more efficiently arranged in the diameter direction on the lens barrel, compared to the arrangement of the driving units in the diameter direction of the lens barrel, and can thereby reduce the size in the diameter direction of the third holding barrel  13  and reduce the size in the diameter direction of the lens barrel. 
   Then,  FIG. 9  shows a sectional view along a line A-A in  FIG. 2 . 
   In  FIG. 9 , reference numerals  61  and  62  denote the aforementioned rotation blocking keys. Reference numeral  13   c  denotes ribs (second engaging portion) formed on the external surface of the third holding barrel (lens holding member)  13  as integral parts, which extend in the direction of the optical axis. These ribs  13   c  are fitted in the rectilinear propagation guide groove portion  26   c  (first engaging portion) that extends in the direction of the optical axis and is formed in the rectilinear propagation guide ring  26  (second member) with a certain gap. The ribs  13   c  are provided in three locations (can be any number of locations) in the circumferential direction of the third holding barrel  13  with substantially the same distance. 
   Here, the third holding barrel  13  holds the stop shutter unit and the ND unit, and therefore the third holding barrel  13  has large weight. As is apparent from  FIG. 2 , the center of gravity of the third holding barrel  13  is located distant from the cam follower  13   a  serving as a support portion of the third holding barrel  13  in the direction of the optical axis. Because of this, when external shock is given to the lens barrel, the third holding barrel  13  is tilted with respect to the optical axis, which may cause the cam follower  13   a  to come off the cam groove portion of the movable cam ring  21  (first member). 
   In this embodiment, the ribs  13   c  extending in the direction of the optical axis are fitted in the rectilinear propagation guide groove portion  26   c  of the rectilinear propagation guide ring  26  so that when the third holding barrel  13  is tilted, the ribs  13   c  contact the end surface of the rectilinear propagation guide groove portion  26   c  to prevent the third holding barrel  13  from tilting. On the other hand, because a sufficient clearance is provided between the ribs  13   c  and the rectilinear propagation guide groove portion  26   c  of the rectilinear propagation guide ring  26 , when the lens barrel is driven, the ribs  13   c  do not contact the rectilinear propagation guide groove portion  26   c  and do not constitute any driving load on the lens barrel due to frictional resistance between the ribs  13   c  and the rectilinear propagation guide groove portion  26   c.    
   In this embodiment, the ribs  13   c  are formed in the third holding barrel  13  which has large weight and the third holding barrel  13  is prevented from tilting through the contact between the ribs  13   c  and the rectilinear propagation guide groove portion  26   c , but it is also possible to form the above described ribs in other holding barrels  11 ,  12  and  14  to prevent these holding barrels from tilting. In this embodiment, the rib  13   c  is formed on the third holding barrel and the rectilinear propagation guide groove portion  26   c  is formed in the rectilinear propagation guide ring  26 , but a groove portion (corresponding to the rectilinear propagation guide groove portion  26   c ) can be formed in the third holding barrel and a projection portion (corresponding to the rib  13   c ) can be formed on the rectilinear propagation guide ring  26 . 
   The above described embodiment has described a lens-integral type camera, but as shown in  FIG. 10 , the present invention is also applicable to a camera system comprising a camera  100 ′ and a lens apparatus  101 ′ which is mounted on a camera mount  100   a ′ of the camera  100 ′ through a lens mount  101   a ′. In  FIG. 10 , the same members as those explained in the above-described embodiment are assigned the same reference numerals and explanations thereof will be omitted. In this camera system, a low pass filter  5  and an image pickup element  6  are provided inside the camera  100 ′.