Patent Publication Number: US-6714362-B2

Title: Lens shutter mechanism

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a lens shutter mechanism. 
     2. Description of the Related Art 
     In a known lens shutter mechanism for opening and closing a photographing aperture, provided in a compact camera or the like, in general, the shutter mechanism is supported between front and rear support frames that are spaced apart in the optical axis direction. The lens shutter mechanism includes light intercepting members (sectors or blades), which are moved into and retracted from the photographing aperture, and a drive ring which drives the light intercepting members. 
     It is necessary to prevent leakage of harmful light from the periphery of the shutter mechanism toward the outer peripheral side of the support frames. In an arrangement in which drive force is transmitted from outside the support frames to the drive ring, an opening is formed on the outer peripheral portion of the support frames to transmit the drive force. This opening makes it difficult to intercept light completely. In a known light interception device for a lens-shutter unit, light interception tapes are attached or adhered to the outer peripheries of the support frames. However, there is a chance that the adhesive of the light interception tape sticks to the light interception members or the drive ring, etc., thus resulting in failure of correct operation thereof. 
     Moreover, in a known lens shutter mechanism in which a shutter and a diaphragm are provided adjacent to each other in the optical axial direction, the two separate light intercepting members provided in the support frames increase the number of movable members. Consequently, the adhesion of the light interception tapes without interfering with the operation of the movable members is more difficult. 
     Furthermore, a rotation support portion of the drive ring is supported by a support frame. If the shutter drive ring and the diaphragm drive ring are separately provided, the support structure of the respective drive rings is complicated, thus resulting in an increase in the size of the lens shutter mechanism. 
     SUMMARY OF THE INVENTION 
     The present invention provides a simple and small lens shutter mechanism in which the surrounding components of a shutter can be reliably intercepted from harmful light. 
     For example, in an embodiment, a lens shutter mechanism includes, between front and rear support frames spaced in an optical axis direction and having photographing apertures, shutter sectors which open and close the photographing apertures, a shutter drive ring which is rotatable about the optical axis to drive the shutter sectors, diaphragm sectors which change an aperture diameter of the photographing apertures independently of the shutter sectors, and a diaphragm drive ring which is rotatable about the optical axis to drive the diaphragm sectors. The shutter drive ring and the diaphragm drive ring are located at different radial positions and at the same position in the optical axis direction. One and the other of the shutter drive ring and the diaphragm drive ring is provided with an inner flange and an outer flange respectively, the inner flange and the outer flange projecting in a radial direction toward each other so as to overlap in the axial direction, and engaging so as to be relatively slidable in the circumferential direction. 
     An axial position of one of the shutter drive ring and diaphragm drive ring can be determined in accordance with an engagement thereof with the front and rear support frames. An axial position of the other of the shutter drive ring and diaphragm drive ring can determined in accordance with an engagement thereof with one of the front and rear support frames and in accordance with an engagement thereof between the inner flange and the outer flange. 
     The lens shutter mechanism can further include an opening between the front and rear support frames, which extends form the inner diameter side to the outer diameter side of the front and rear support frames. One of the shutter drive ring and the diaphragm drive ring, which is positioned at an outer radial position with respect to the other of the shutter drive ring and the diaphragm drive ring, can be provided with a fitting portion which is fitted in the opening in order to cover the opening, the fitting portion being movable in the circumferential direction. 
     One of the front and rear support frames can be provided on the outer peripheral edge thereof with an outer peripheral wall portion which projects in the optical axis direction close to the other of the front and rear support frames. The one of the shutter drive ring and the diaphragm drive ring, having the fitting portion, partly overlaps the outer peripheral wall portion in the radial direction to cover the opening together with the outer peripheral wall portion. 
     The lens shutter mechanism can further include a driven projection provided on the fitting portion of the one of the shutter drive ring and the diaphragm drive ring, the driven projection extending outwardly from the opening in the radial direction; and a rotational force providing device provided outside the front and rear support frames, which engages with the driven projection to cause the one of the shutter drive ring and the diaphragm drive ring to rotate. 
     The lens shutter mechanism can be provided in a zoom lens, and the rotational force providing device can provide rotation to the driven projection in accordance with a zooming operation of the zoom lens to thereby rotate the one of the shutter drive ring and the diaphragm drive ring which includes the driven projection. 
     One of the front and rear support frames can be provided with a motor drive gear which projects from a surface thereof opposed to the other of the front and rear support frames, the motor drive gear being driven by a motor. The other of the shutter drive ring and the diaphragm shutter drive ring, which is positioned at an inner radial position, is provided on the outer peripheral surface thereof with a gear which engages with the motor drive gear. A radial space in which the motor drive gear is accommodated can be provided between the shutter drive ring and the diaphragm drive ring. 
     The motor can be controlled by a controller, to change the angular displacement and the rotation speed of the drive ring having the gear which engages with the motor drive gear. 
     The diaphragm drive ring can be located at an outer radial position with respect to the shutter drive ring, the diaphragm drive ring being provided with the inner flange on an inner peripheral surface thereof, and the shutter drive ring being provided with the outer flange on an outer peripheral surface thereof. 
     In another embodiment, a lens shutter mechanism includes, between front and rear support frames spaced in an optical axis direction and having photographing apertures, shutter sectors which open and close the photographing apertures, a shutter drive ring which is rotated about the optical axis to drive the shutter sectors, diaphragm sectors which change an aperture diameter of the photographing apertures independently of the shutter sectors, and a diaphragm drive ring which is rotated about the optical axis to drive the diaphragm sectors. The shutter drive ring and the diaphragm drive ring are located at different radial positions and at the same position in the optical axis direction, so that the shutter drive ring is located at an inner radial position and the diaphragm drive ring is located at an outer radial position. The diaphragm drive ring is provided with an inner flange which projects inwardly in the radial direction, and the shutter drive ring is provided with an outer flange which projects outwardly in the radial direction, the inner flange and the outer flange overlapping in the axial direction and engaging so as to be relatively slidable in the circumferential direction. 
     An axial position of the diaphragm drive ring can be determined in accordance with an engagement thereof with the front and rear support frames. An axial position of the shutter drive ring can be determined in accordance with an engagement thereof with one of the front and rear support frames and in accordance with an engagement thereof between the inner flange and the outer flange. 
     The lens shutter mechanism can further include an opening between the front and rear support frames, which extends form the inner diameter side to the outer diameter side of the front and rear support frames. The diaphragm drive ring can be provided with a fitting portion which is fitted in the opening in order to cover the opening, the fitting portion being movable in the circumferential direction. 
     One of the front and rear support frames can be provided on the outer peripheral edge thereof with an outer peripheral wall portion which projects in the optical axis direction close to the other of the front and rear support frames. The diaphragm drive ring partly overlaps the outer peripheral wall portion in the radial direction to cover the opening together with the outer peripheral wall portion. 
     The lens shutter mechanism can further include a driven projection provided on the fitting portion of the diaphragm drive ring, the driven projection extending outwardly from the opening in a radial direction; and a rotational force providing device provided outside the front and rear support frames, which engages with the driven projection to cause the diaphragm drive ring to rotate. 
     The lens shutter mechanism can be provided in a zoom lens, and the rotational force providing device can provide rotation to the driven projection in accordance with a zooming operation of the zoom lens to thereby rotate the diaphragm drive ring. 
     One of the front and rear support frames can be provided with a motor drive gear which projects from a surface thereof opposed to the other of the front and rear support frames, the motor drive gear being driven by a motor. The shutter drive ring can be provided on the outer peripheral surface thereof with a gear which engages with the motor drive gear. A radial space in which the motor drive gear is accommodated can be provided between the shutter drive ring and the diaphragm drive ring. 
     The motor can be controlled by a controller, to change the angular displacement and the rotation speed of the shutter drive ring. 
     The present disclosure relates to subject matter contained in Japanese Patent Application No. 2001-81608 (filed on Mar. 21, 2001) which is expressly incorporated herein by reference in its entirety. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be discussed below with reference to the accompanying drawings, in which: 
     FIG. 1 is an exploded perspective view of components of a zoom lens barrel, according to the present invention; 
     FIG. 2 is a sectional view of an upper half of the zoom lens barrel in a retracted position; 
     FIG. 3 is a sectional view of an upper half of the zoom lens barrel in a wide-angle position; 
     FIG. 4 is a sectional view of an upper half of the zoom lens barrel in a telephoto position; 
     FIG. 5 is a perspective view of the zoom lens barrel in an advanced position; 
     FIG. 6 is an exploded perspective view of the zoom lens barrel shown in FIG. 5; 
     FIG. 7 is an exploded perspective view of the zoom lens barrel, showing a more detailed disassembly than FIG. 6; 
     FIG. 8 is a perspective view of first and second outer barrels; 
     FIG. 9 is a perspective view of a third linear guide ring; 
     FIG. 10 is an exploded perspective view of a third linear guide ring and a lens-shutter unit; 
     FIG. 11 is a developed view of a third linear guide ring, showing a diaphragm control cam groove thereof; 
     FIG. 12 is a developed view of an inner surface of a cam ring, showing a cam groove profile, by way of example; 
     FIG. 13 is an exploded perspective view of a lens-shutter unit; 
     FIG. 14 is an exploded perspective view of a rear unit of a lens-shutter unit; 
     FIG. 15 is a sectional view of an upper half of a rear unit of a lens-shutter unit; 
     FIG. 16 is a perspective view of a front unit of a lens-shutter unit and a lens-shutter unit FPC (annular FPC); 
     FIG. 17 is an exploded perspective view of a front holder ring and an annular FPC; 
     FIG. 18 is an exploded rear perspective view of a front unit and a rear unit, of a lens-shutter unit; 
     FIG. 19 is a rear perspective view of an assembly of a front and rear unit, of a lens-shutter unit; 
     FIG. 20 is an exploded perspective view of a first variable power lens group and surrounding components thereof; 
     FIG. 21 is an exploded perspective view of a lens-shutter unit and a lens support barrel; 
     FIG. 22 is an enlarged developed view of a front sub-lens group frame, a rear sub-lens group frame and a drive ring, in connection with a front hold ring; 
     FIG. 23 is an explanatory view showing a focusing operation using a drive ring; 
     FIG. 24 is an enlarged sectional view of an upper half of a lens-shutter unit and the surrounding components thereof when a lens barrier thereof is closed; 
     FIG. 25 is a sectional view similar to FIG. 24, when a lens barrier is open; 
     FIG. 26 is a block diagram of a control system of a zoom lens barrel shown in FIGS. 2 through 4; 
     FIG. 27 is a sectional view of an upper half of a rear unit, taken in a position different from that of FIG.  15 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The following embodiments are addressed to a lens shutter mechanism applied to a zoom lens barrel. The structure of the zoom lens barrel is discussed first, and is followed by an explanation of a lens shutter mechanism. 
     As shown in FIG. 1, a stationary barrel  12  secured to a camera body  11  is provided on its inner peripheral surface with a female helicoid  12   a  which is screw-engaged with a male helicoid  14   a  formed on an outer peripheral surface of a first helicoid ring  14 . A pinion  16  which is rotated by a zooming motor  15  is provided outside the stationary barrel  12 . The pinion  16  is in mesh with a gear  14   b  formed on the outer peripheral surface of the first helicoid ring  14  via a cut-out portion of the male helicoid  14   a . The gear  14   b  is inclined in the same direction as the lead of the male helicoid  14   a . The first helicoid ring  14  is connected at the front end thereof to a first outer barrel  17 . Consequently, when the first helicoid ring  14  is rotated in the forward or reverse direction by the zooming motor  15 , the first helicoid ring  14  and the first outer barrel  17 , integrally connected thereto, are moved in the optical axis direction in accordance with the engagement of the female helicoid  12  and the male helicoid  14   a.    
     A first linear guide ring  18  which is rotatable relative to, and movable together with, the first outer barrel  17  in the optical axis direction (i.e., not relatively movable with respect to the first outer barrel  17  in the optical axis direction) is supported in the inner periphery of the first outer barrel  17 . The first linear guide ring  18  has a projection  18   a  which is engaged in a linear guide groove  12   b  of the stationary barrel  12 , so that the first linear guide ring  18  is linearly movable only in the optical axis direction. The axial displacement of the first linear guide ring  18  is detected by a brush  19  and a code plate  20  secured to the first linear guide ring  18  and the stationary barrel  12 , respectively. 
     The first linear guide ring  18  is provided on the inner peripheral surface thereof with a female helicoid  18   b  which is engaged with a male helicoid  21   a  formed on an outer peripheral surface of a second helicoid ring  21 . The second helicoid ring  21  is provided on the outer peripheral surface thereof with a pair of guide portions  21   b  which are engaged in guide grooves  17   a  (see FIG. 8) formed in the inner peripheral surface of the first outer barrel  17  through guide through-grooves  18   c  formed in the first linear guide ring  18 . The guide through-grooves  18   c  are elongated through-holes inclined in the same direction as the female helicoid  18   b , and the guide grooves  17   a  are linear grooves parallel with the optical axis O of the zoom lens system. The second helicoid ring  21  is connected at the front end thereof to a second outer barrel  23 . Consequently, when the first outer barrel  17  is rotated in the forward or reverse direction by the zooming motor  15 , the second helicoid ring  21  and the second outer barrel  23 , integrally connected thereto, are rotated in accordance with the engagement between the guide portion grooves  17   a  and the guide portions  21   b , and accordingly, are moved in the optical axis direction with respect to the first linear guide ring  18  (and an assembly of the first outer barrel  17  and the first helicoid ring  14 ) in accordance with the female helicoid  18   b  and the male helicoid  21   a.    
     A second linear guide ring  25  which is rotatable relative to, and is movable in the optical axis direction together with, the second outer barrel  23  (i.e., not movable in the optical axis direction relative to the second outer barrel  23 ) is supported in the second outer barrel  23 . The second linear guide ring  25  has a projection  25   a  which is engaged in a linear guide groove  18   d  of the first linear guide ring  18 , so that the second linear guide ring  25  is linearly movable only in the optical axis direction. 
     Similar to the first linear guide ring  18 , the second linear guide ring  25  is provided on the inner peripheral surface thereof with a female helicoid  25   b  which is engaged with a male helicoid  30   a  formed on an outer peripheral surface of a rear end of a cam ring (third outer barrel)  30 . The cam ring  30  is provided on the outer peripheral surface thereof with a pair of guide portions  30   b  which are engaged in guide grooves  23   a  (see FIG. 8) formed in the inner peripheral surface of the second outer barrel  23  through guide through-grooves  25   c  formed in the second linear guide ring  25 . The guide through-grooves  25   c  are in the form of elongated through-holes inclined in the same direction as the female helicoid  25   b , and the guide grooves  23   a  are in the form of linear grooves parallel with the optical axis O. Consequently, when the second outer barrel  23  is rotated in the forward or reverse direction by the zooming motor  15 , the cam ring  30  is moved in the optical axis direction relative to the second linear guide ring  25  (and an assembly of the second outer barrel  23  and the second helicoid ring  21 ), in accordance with the engagement between the female helicoid  25   b  and the male helicoid  30   a.    
     A third linear guide ring  33  which is rotatable relative to, and is movable in, the optical axis direction together with the cam ring  30  (i.e., not movable in the optical axis direction relative to the cam ring  30 ) is supported in the cam ring  30 . The third linear guide ring  33  is provided on the outer peripheral surface thereof with a plurality of linear guide projections  33   a  which are engaged in a linear guide groove  25   d  formed on the inner peripheral surface of the second linear guide ring  25 , so that the third linear guide ring  33  is linearly movable only in the optical axis direction. 
     A lens support barrel (fourth outer barrel)  31  having a first variable power lens group L 1  (first sub-lens group S 1  and a second sub-lens group S 2 ) and a second lens group frame  32  having a second variable power lens group L 2  secured thereto are arranged in the cam ring  30 . The lens support barrel  31  and the second lens group frame  32  are guided to linearly move in the optical axis direction with the third linear guide ring  33 . Specifically, as shown in FIGS. 9 and 10, three arms  33   b,  which are provided on the periphery of an imaginary cylinder and constitute the third linear guide ring  33 , are each provided on the outer and inner surfaces (front and rear sides) thereof with linear guide grooves  33   c  and  33   d  which extend parallel with the optical axis O. Linear guide projections (not shown) provided on the inner peripheral surface of the lens support barrel  31  are movably fitted in the respective linear guide grooves  33   c,  and linear guide projections  32   a  provided on the outer peripheral surface of the second lens group frame  32  are movably fitted in the respective linear guide grooves  33   d.    
     The cam ring  30  is provided on the inner peripheral surface thereof with bottomed cam grooves  35  and bottomed cam grooves  36  for the lens support barrel  31  and the second lens group frame  32 , respectively. FIG. 12 shows a developed view of the bottomed cam grooves  35  and  36 . There are three sets of bottomed cam grooves  35  and  36 , respectively, and are spaced in the circumferential direction at equal pitches. The lens support barrel  31  and the second lens group frame  32  are provided with radially extending cam follower projections  31   a  and  32   b  which are fitted in the bottomed cam grooves  35  and  36 , respectively. 
     In FIG. 12, the bottomed cam grooves  35  and  36  have a range of usage between a telephoto extremity position and a retracted position. Upon photographing, the follower projections  31   a  and  32   b  are guided between the telephoto extremity position and a wide-angle extremity position within the range of usage of the bottomed cam grooves  35  and  36 . The bottomed cam grooves  36  are each provided with an intermediate interruption portion  36   a  between the telephoto extremity and the wide-angle extremity. The first variable power lens group L 1  held in the lens support barrel  31  which is guided by the bottomed cam grooves  35  has a switching function to move the first sub-lens group S 1  and the second sub-lens group S 2  to a mutually close position and a mutually distant position at an intermediate position between the telephoto extremity and the wide-angle extremity. Upon switching of the first variable power lens group L 1 , the second variable power lens group L 2  passes through the intermediate interruption portions  36   a  of the bottomed cam grooves  36 . The intermediate interruption portions  36   a  are not used as zooming areas during an actual zooming operation (i.e., the cam ring  30  is not stopped thereat). 
     In the zoom lens barrel constructed as above, when the pinion  16  is rotated in the forward or reverse direction by the zooming motor  15 , the cam ring  30  is moved in the optical axis direction while rotating, so that the lens support barrel  31  (first variable power lens group L 1 ) and the second lens group frame  32  (second variable power lens group L 2 ), guided in the cam ring  30  to linearly move in the optical axis direction, are linearly moved in the optical axis direction in accordance with predetermined profiles of the bottomed cam grooves  35  and  36 . For instance, in the retracted position of the lens barrel (accommodated position) shown in FIG. 2, the entire zoom lens barrel is substantially retracted in the camera body. When the zooming motor  15  is driven in the barrel advancing direction, the zoom lens barrel is moved to the wide-angle extremity position shown in FIG.  3 . The zoom lens barrel can be moved to the telephoto extremity position shown in FIG. 4 by further rotation of the zooming motor  15  in the barrel advancing direction. If the zooming motor  15  is rotated in the reverse direction, the zoom lens barrel is moved from the telephoto extremity position to the wide-angle extremity position and to the retracted position. The zooming operation is, in practice, controlled stepwise so that the focal length from the wide-angle extremity and the telephoto extremity is split into a plurality of focal length steps, wherein the zooming motor  15  is stopped at each focal length step to carry out focusing or an exposure. In the control therefor, the area corresponding to the switching of the first sub-lens group S 1  and the second sub-lens group S 2  between the mutually close position to the mutually distant position is not used for photographing and, hence, the focal length step does not exist in this area, wherein the cam ring  30  (zooming motor  15 ) does not stop thereat. 
     A lens-shutter unit  40  is provided in the lens support barrel  31 . As shown in FIGS. 13 and 18, the lens-shutter unit  40  includes a front support ring  41 , a rear support ring  42 , a gear retainer ring  43  and a sector retainer ring  44 . The lens-shutter unit  40  can be split into two units, i.e., a front unit  40 A having an assembly including the front support ring  41  and the gear retainer ring  43 , and a rear unit  40 B having an assembly including the rear support ring  42  and the sector retainer ring  44 . 
     The front unit  40 A will be discussed below. The front support ring  41  has a center opening  41   a  in which the front sub-lens group frame  45  and the rear sub-lens group frame  46  are fitted. The first sub-lens group S 1  is secured to the front sub-lens group frame  45  and the second sub-lens group S 2  is secured to the rear sub-lens group frame  46 . The relative axial position of the front sub-lens group frame  45  and the rear sub-lens group frame  46  (the first sub-lens group S 1  and the second sub-lens group S 2 ) between the telephoto extremity and the wide-angle extremity can be selectively moved to the mutually distant position for a short focal length and the mutually close position for a long focal length. The relative movement of the axial position of the front sub-lens group frame  45  and the rear sub-lens group frame  46 , and the focusing operation in which the front sub-lens group frame  45  and the rear sub-lens group frame  46  are moved together in the optical axis direction, can be performed by the drive ring  47 . 
     The rearward extremity of the drive ring  47  is restricted by the receiving surface  42   s  of the rear support ring  42  and is rotatably supported between the front support ring  41  and the rear support ring  42 . 
     The front sub-lens group frame  45  is cylindrical and is provided on the outer periphery thereof with diametrically opposed linear guide ribs  45   a , as shown in FIG.  20 . The linear guide ribs  45   a  are provided with guide holes  45   b  in which linear guide rods  48  are loosely fitted (inserted). The linear guide rods  48  are secured at the rear ends thereof to securing holes  43   a  formed in the bottom of the gear retainer ring  43 , and the front ends of the linear guide rods  48  are secured to a securing bracket  49 . The securing bracket  49  is secured to the front surface of the gear retainer ring  43  with securing screws  50 . Compression coil springs  51  which are provided between the securing bracket  49  and the linear guide ribs  45   a  surround the linear guide rods  48  to bias the front sub-lens group frame  45  toward the rear sub-lens group frame  46 . The gear retainer ring  43  is provided with generally U-shaped recesses  43   b  in which the linear guide rods  48  and the compression coil springs  51  are received. The recesses  43   b  are communicatively connected to the center opening  41   a  of the front support ring  41 . 
     The front sub-lens group frame  45  has four shift leading surfaces (shift cam surfaces)  45   c,  which are formed circumferentially at equi-angular intervals on the end-face of the front sub-lens group frame  45 , in order to move the front and rear sub-lens group frames to a mutually close position or a mutually distant position, in the optical axis direction. The shift leading surfaces  45   c  are provided at their opposed ends with follower engaging recesses  45   d  and  45   e  (FIG.  22 ). Note that only one shift leading surface  45   c  is shown in FIG.  22 . The rear sub-lens group frame  46  is provided with four follower projections  46   a  corresponding to the shift leading surfaces  45   c  of the front sub-lens group frame  45 . As shown in FIG. 20, the follower projections  46   a  are provided on the front end portions of inclined surfaces  46   b , corresponding to the shift leading surfaces  45   c  of the front sub-lens group frame  45 . The shift leading surfaces  45   c  formed on the front sub-lens group frame  45  and the follower projections  46   a  formed on the rear sub-lens group frame  46  constitute a shift cam mechanism for moving the front sub-lens group frame  45  and the rear sub-lens group frame  46  to a mutually close position or to a mutually distant position, in the optical axis direction. 
     The rear sub-lens group frame  46  is also provided with a pair of linear guide projections  46   c  which are located at the same circumferential positions as two of the four follower projections  46   a  that are diametrically opposed, and are provided behind the two follower projections  46   a  in the axial direction. Furthermore, three driven projections  46   d  are provided on the outer peripheral surface of the rear sub-lens group frame  46  and are spaced at equi-angular intervals in the circumferential direction and behind the linear guide projections  46   c  in the axial direction. 
     The front support ring  41  is provided on the inner peripheral surface thereof with a pair of rotation preventing surfaces  41   b  and  41   c  (see FIG. 22) which correspond to the linear guide projections  46   c  of the rear sub-lens group frame  46  and restrict the angular displacement of the rear sub-lens group frame  46  with respect to the front support ring  41 , which does no rotate. Namely, the rotation preventing surfaces  41   b  and  41   c  engage with the linear guide projections  46   c  to prevent further rotation of the rear sub-lens group frame  46  at the rotational movement extremities thereof when the rear sub-lens group frame  46  is rotated in the forward and reverse directions. Moreover, the rotation preventing surface  41   b  and the guide surface  41   d  opposed thereto constitute a wide-angle linear guide groove  41   e , and the rotation preventing surface  41   c  and the guide surface  41   f  opposed thereto constitute a telephoto linear guide groove  41   g.  The linear guide projections  46   c  are substantially snugly engaged in the guide grooves  41   e  and  41   g  at the wide-angle and telephoto extremities, respectively. 
     The drive ring  47  has three control recesses  47   a  (FIGS. 18 and 22) at the front end surface thereof, corresponding to the three driven projections  46   d  of the rear sub-lens group frame  46 . Note that only one or two control recesses  47   a  are shown in the drawings. As shown in FIG. 23, the control recesses  47   a  are symmetrical in the lateral direction with respect to a center line ‘c’ parallel with the optical axis, and each include a pair of effective surfaces  47   b  and  47   c  which engage with the driven projection  46   d , and telephoto and wide-angle focus leading surfaces (focus cam surfaces)  47   d  and  47   e  which abut against the arc end-surface of the driven projection  46   d . The telephoto focus leading surface  47   d  and the wide-angle focus leading surface  47   e  are defined by end cam surfaces having open ends between the effective surfaces  47   b  and  47   c.  The focus leading surfaces  47   d  and  47   e  are inclined with respect to the circumferential direction in opposite directions and at an equal inclination angle. The focus leading surfaces  47   d  and  47   e  of the drive ring  47  and the driven projections  46   d  formed on the rear sub-lens group frame  46  constitute a focus cam mechanism. 
     The compression coil springs  51 , which bias the front sub-lens group frame  45  rearwardly, cause the shift leading surfaces  45   c  of the front sub-lens group frame  45  to be always in contact with the follower projections  46   a  of the rear sub-lens group frame  46 , and cause the driven projections  46   d  of the rear sub-lens group frame  46  to be always in contact with the telephoto or wide-angle focus leading surfaces  47   d  and  47   e.  The drive ring  47  abuts at the rear end surface thereof against the receiving surface  42   s  of the rear support ring  42 , as mentioned above. The contact relationship of the front sub-lens group frame  45 , the rear sub-lens group frame  46 , the drive ring  47 , and the rear support ring  42  (receiving surface  42   s ) is maintained by the spring force of the compression coil springs  51 . In contacting state, as shown in FIGS. 24 and 25, the front end of the rear sub-lens group frame  46  is inserted inside the inner peripheral surface of the front sub-lens group frame  45 , and the drive ring  47  is fitted on the outer peripheral surface of the rear sub-lens group frame  46 . 
     At the mutually distant position at the wide-angle side of the first sub-lens group S 1  and the second sub-lens group S 2 , the effective surfaces  47   b  of the drive ring  47  abut against the driven projections  46   d , and the linear guide projections  46   c  are disengaged from the wide-angle linear guide grooves  41   e . In this state, if the drive ring  47  is moved in the right hand direction with respect to FIG. 22 (rotated in the clockwise direction), the effective surfaces  47   b  press against the driven projections  46   d  and rotate the rear sub-lens group frame  46  in the same direction, so that the linear guide projections  46   c  abut against the rotation preventing surfaces  41   c . During this movement, the front sub-lens group frame  45  (first sub-lens group S 1 ) comes close to the rear sub-lens group frame  46  (second sub-lens group S 2 ) in accordance with the engagement of the shift leading surfaces  45   c  and the follower projections  46   a  of the rear sub-lens group frame  46  and, consequently, the follower projections  46   a  are stably engaged in the follower engaging recesses  45   e.    
     Thus, the switching from the mutually distant position at the wide-angle side to the mutually close position at the telephoto side is completed. Consequently, the first sub-lens group S 1  is close to the second sub-lens group S 2  (mutually close extremity, i.e., at a mutually close position for a long focal length), and no further rotation of the drive ring  47  in the same direction is permitted. 
     When the switching to the mutually close position at the telephoto side is completed, the drive ring  47  is rotated in the reverse direction. Consequently, the driven projections  46   d  (rear sub-lens group frame  46 ) are moved rearwardly in accordance with the telephoto focus leading surfaces  47   d  and, hence, the linear guide projections  46   c  are engaged in the telephoto linear guide grooves  41   g,  so that the linear guide projections  46   c  are linearly movable only in the axial direction. The focusing operation on the telephoto side, from an intermediate focal length to the long focal length extremity (telephoto extremity), is carried out by the integral movement of the rear sub-lens group frame  46  and the front sub-lens group frame  45  at the mutually close extremity via the telephoto focus leading surfaces  47   d.  Namely, as shown in FIG. 23, when the drive ring  47  is rotated within the telephoto focus area ft (from the infinite object distance ∞ to the shortest object distance n) in a state that the driven projections  46   d  of the rear sub-lens group frame  46  abut against the telephoto focus leading surfaces  47   d,  the rear sub-lens group frame  46  whose rotation is restricted by the engagement of the telephoto linear guide grooves  41   g,  the linear guide projections  46   c , and the front sub-lens group frame  45  whose rotation is restricted by the engagement of the linear guide rods  48  in the guide holes  45   b  (i.e., the first sub-lens group S 1  and the second sub-lens group S 2 ) are integrally moved together in the optical axis direction to carry out the focusing operation. 
     When the drive ring  47  is rotated until the effective surfaces  47   c  come into contact with the driven projections  46   d , the linear guide projections  46   c  of the rear sub-lens group frame  46  are disengaged from the telephoto linear guide grooves  41   g.  In this state, when the drive ring  47  is moved in the left hand direction in FIG. 22 (rotated in the counterclockwise direction), the effective surfaces  47   c  press against the driven projections  46   d  to thereby rotate the rear sub-lens group frame  46  in the same direction. Consequently, the linear guide projections  46   c  abut against the rotation preventing surfaces  41   b.  During this movement, the front sub-lens group frame  45  comes close to the rear sub-lens group frame  46  in accordance with the engagement of the shift leading surfaces  45   c  and the follower projections  46   a  of the rear sub-lens group frame  46 , and the follower projections  46   a  become stably engaged in the follower engaging recesses  45   d.  Thus, the switching from the mutually close position at the telephoto side to the mutually distant position at the wide-angle side is completed, so that the first sub-lens group S 1  moves away from the second sub-lens group S 2  (mutually distant extremity, i.e., the mutually distant position for a long focal length), and no further rotation of the drive ring  47  in the same direction is permitted. 
     When the switching to the mutually distant position at the wide-angle side is completed, the drive ring  47  is rotated in the reverse direction. Consequently, the driven projections  46   d  (rear sub-lens group frame  46 ) are moved rearwardly in accordance with the wide-angle linear guide grooves  41   e , and accordingly, the linear guide projections  46   c  are engaged in the wide-angle linear guide grooves  41   e  and is linearly movable only in the optical axis direction. The focusing operation on the wide-angle side, from an intermediate focal length to the short focal length extremity, is carried out by the integral movement of the rear sub-lens group frame  46  and the front sub-lens group frame  45  at the mutually distant extremity by the wide-angle linear guide grooves  41   e . Namely, as shown in FIG. 23, when the drive ring  47  is rotated within the wide-angle focus area fw (from the infinite object distance ∞ to the shortest object distance n) in a state that the driven projections  46   d  abut against the wide-angle focus leading surface  47   e,  the rear sub-lens group frame  46  whose rotation is restricted by the engagement of the wide-angle linear guide grooves  41   e  and the linear guide projections  46   c , and the front sub-lens group frame  45  whose rotation is restricted by the engagement of the linear guide rods  48  in the guide holes  45   b  (i.e., the first sub-lens group S 1  and the second sub-lens group S 2 ) are moved together in the optical axis direction to carry out the focusing operation. 
     When the drive ring  47  is rotated until the effective surfaces  47   b  abut against the driven projections  46   d , the linear guide projections  46   c  of the rear sub-lens group frame  46  are disengaged from the wide-angle linear guide grooves  41   e  and are returned to the initial state. 
     As mentioned above, in the front unit  40 A of the lens-shutter unit  40 , the shifting operation for moving the first sub-lens group S 1  and the second sub-lens group S 2  to the mutually distant position for a short focal length, or to the mutually close position for a long focal length, and the focusing operation in which the first variable power lens group L 1  is entirely moved in the optical axis direction, can be carried out by controlling the rotation of the drive ring  47 . The focusing operations on the telephoto side and the wide-angle side are carried out by controlling the number of pulses counted by a pulser (encoder) of the driving system which drives the drive ring  47 , with reference to the position (the position in which the direction of the rotation of the drive ring  47  is reversed) in which the linear guide projections  46   c  of the rear sub-lens group frame  46  abut against the rotation preventing surfaces  41   b  or  41   c . For instance, the number of the pulses to move the focusing lens group (i.e., the first variable power lens group L 1  including the first sub-lens group S 1  and the second sub-lens group S 2 ) to the shortest object distance n, the infinite object distance ∞, or an object distance therebetween, from the reference position can be predetermined taking into account the lead angles of the telephoto and wide-angle focus leading surfaces  47   d  and  47   e.  Therefore, focusing can be carried out based on the object distance data by controlling the number of pulses. 
     The drive ring  47  is provided, on the entire outer peripheral surface of the rear end thereof, with a gear  47   f  which is in mesh with a terminal gear  52   a  (FIG. 18) of a reduction gear train  52 , so that the gear  47   f  can be rotated in the forward or reverse direction by a reversible drive motor  53  rotating in the forward and reverse directions (see FIGS.  13  and  18 ). 
     A pinion  53   a  of the reversible drive motor  53  is located on the front side of the front support ring  41  and a gear  47   f  of the drive ring  47  is located between the front support ring  41  and the rear support ring  42 , i.e., on the rear side of the front support ring  41 . Consequently, the reduction gear train  52 , shown in FIG. 13, which transmits the motor drive force from the pinion  53   a  to the gear  47   f,  is held between the front support ring  41  and the gear retainer ring  43  in such a way that the gears are arranged along the outer peripheral surface of the front support ring  41 . Moreover, a rotating slit disc  54 , which constitutes the pulser to detect the amount of rotation of the reversible drive motor  53 , is provided in the vicinity of the pinion  53   a  of the reversible drive motor  53 . A relay gear  55  is provided between the rotating slit disc  54  and the pinion  53   a.    
     The reversible drive motor  53  is held in a motor holding recess  41   h  of the front support ring  41 . The rotating slit disc  54  is held in the slit disc holding recess  41   i  of the front support ring  41  (shown best in FIG.  17 ). The front support ring  41  is provided with an interrupter holding recess  41   j  communicatively connected to the slit disc holding recess  41   i . A photo-interrupter  56  for detecting a drive amount of the reversible drive motor  53  for the switching operation of the sub-lens groups and for the focusing operation, is received in the interrupter holding recess  41   j  (see FIG.  17 ). The rotating slit disc  54  is arranged in the photo-interrupter  56  (between two components of the photo-interrupter), so that the rotation angle (amount of angular displacement) of the slit disc  54  can be detected by counting the number of pulses. In other words, the drive amount of the reversible drive motor  53  can be detected. 
     The rear unit  40 B will be explained below. A lens shutter and a diaphragm mechanism are provided between the rear support ring  42  and the sector retainer ring  44 . As shown in FIGS. 13 and 14, the rear support ring  42  and the sector retainer ring  44  are provided with front wall portions  42   a  and  44   a  in the form of circular discs extending in orthogonal planes, with respect to the optical axis, and three rear arms  42   b  and  44   b  extending rearwardly in the optical axis direction from the front wall portions  42   a  and  44   a , respectively. The lens shutter and the diaphragm mechanism are held between the front wall portions  42   a  and  44   a . The rear arms  42   b  and  44   b  are overlapped in the radial direction of the lens barrel (see FIG.  15 ). 
     The lens shutter has three shutter sectors  60  and a shutter drive ring  61  which opens and closes the shutter sectors  60 . The diaphragm mechanism has three diaphragm sectors  62  and a diaphragm drive ring  63  which opens and closes the diaphragm sectors  62 . A separation plate  64  is arranged between the shutter sectors  60  and the diaphragm sectors  62 , and a separation plate  65  is arranged between the diaphragm sectors  62  and the diaphragm drive ring  63 . The separation plate  64  prevents interference between the movable shutter sectors  60  and the movable diaphragm sectors  62 , and the separation plate  65  prevents interference of the diaphragm sectors  62  with the rotatable shutter drive ring  61  and the rotatable diaphragm drive ring  63 . The sector retainer ring  44 , the separation plate  64  and the separation plate  65  are provided with photographing circular openings  44   c,    64   a  and  65   a,  respectively, which have substantially in the same diameter about the optical axis O. The rear support ring  42  is provided with a center opening  42   c  whose diameter is greater than the diameter of the photographing circular openings  44   c,    64   a  and  65   a.    
     The shutter sectors  60  and diaphragm sectors  62  which are each made of three blades are rotatably supported by projecting pivots (support pivots)  66  (only one of which is shown in FIGS. 13 and 14) which extend rearward from the front wall portions  42   a  of the rear support ring  42 . The projecting pivots  66  extend through support holes  60   a  and  62   a  formed in the shutter sectors  60  and the diaphragm sectors  62 . Projecting pivot securing holes  44   d  (see FIG.  14 ), in which the front ends of the projecting pivots  66  are received, are formed in the front wall portions  44   a  of the sector retainer ring  44 . 
     The shutter drive ring  61  is provided with three rotation transmission dowels  61   a  which are engaged in rotational guide cam slots  60   b  formed in the shutter sectors  60 . The three shutter sectors  60  are rotated about the projecting pivots  66  in accordance with the relationship between the rotational guide cam slots  60   b  and the rotation transmission dowels  61   a  when the shutter drive ring  61  is reciprocally rotated, so that the front portion of the photographing circular opening  44   c  is opened and closed. The aperture of the shutter sectors  60  can be controlled by the angular displacement of the shutter drive ring  61 . The sector retainer ring  44  is provided with dowel receiving slots  44   e  in which the front ends of the rotation transmission dowels  61   a  are inserted. The shutter drive ring  61  is biased in the closing direction by a shutter drive ring biasing spring  74 , so that play (in the shutter drive ring  61 ) can be removed by the shutter drive ring biasing spring  74 . 
     Similar to the shutter drive ring  61 , the diaphragm drive ring  63  is provided with three rotation transmission dowels  63   a  which are engaged in rotational guide cam slots  62   b  formed in the diaphragm sectors  62 . The three diaphragm sectors  62  are rotated about the projecting pivots  66  in accordance with the relationship between the rotational guide cam slots  62   b  and the rotation transmission dowels  63   a  when the diaphragm drive ring  63  is reciprocally rotated, so that the front portion of the photographing circular opening  44   c  is opened and closed. The aperture of the diaphragm sectors  62  can be controlled by the angular displacement of the diaphragm drive ring  63 . The diaphragm sectors  62  are provided with through-holes  62   c  to prevent interference with the rotation transmission dowels  61   a  of the shutter drive ring  61  regardless of the angular position of the diaphragm sectors  62 . The front ends of the rotation transmission dowels  63   a  are in contact with, and held by, the front surface of the front wall portion  44   a . The diaphragm drive ring  63  is biased by a diaphragm drive ring biasing spring  72  which is engaged at one end thereof with the diaphragm drive ring  63  and at the other end thereof with the rear support ring  42  in a direction to open the diaphragm sectors  62 . 
     In the zoom lens barrel of the present invention, the shutter sectors  60  have a variable diaphragm function to determine a desired aperture value and a shutter function, and are electrically controlled so that the amount of opening (aperture value) and the opening time (shutter speed) of the shutter sectors  60  are varied in accordance with the exposure value when the shutter is released. The diaphragm sectors  62  are provided to restrict the maximum value of the aperture at a wide-angle object distance in particular, and the amount of opening thereof is varied in accordance with the feed amount of the zoom lens barrel as a whole. 
     The shutter drive ring  61  for opening and closing the shutter sectors  60  is provided on the outer peripheral surface thereof with a partial sector gear  61   b  which is in mesh with a reduction gear train  68  connected to a shutter drive motor  67  (see FIGS.  13  and  18 ). The shutter drive motor  67  is held in a motor holding recess  41   k  (see FIG. 17) of the front support ring  41 , and a pinion  67   a  of the shutter drive motor  67  is located in front of the front support ring  41 . The reduction gear train  68  transmits the drive force of the motor to the rear side of the front support ring  41 , and has a terminal gear  68   a  distant from the pinion  67   a  of the shutter drive motor  67  exposed to the rear portion of the front support ring  41  (front unit  40 A), as shown in FIG.  18 . The front wall portion  42   a  of the rear support ring  42  is provided with a through-hole  42   e  in which the terminal gear  68   a  of the reduction gear train  68  is inserted so as to engage with the sector gear  61   b.    
     When the shutter drive motor  67  is rotated in the forward or reverse direction, the shutter drive ring  61  is rotated in the same direction, so that the shutter sectors  60 , which are in a closed position, are instantaneously opened and closed. As mentioned above, the amount of opening, and the opening time of the shutter sectors  60  are variable and are controlled in accordance with the drive signal (electric current) supplied to the shutter drive motor  67 . Namely, if the rotation angle of the shutter drive ring  61  driven by the shutter drive motor  67  is increased, the amount of opening of the shutter sectors  60  is increased and the aperture value is reduced (approaches a fully open diaphragm position). If the rotation angle of the shutter drive ring  61  is decreased, the amount of opening of the shutter sectors  60  is decreased and the aperture value is increased (diaphragm closes). Moreover, if the time interval between the forward rotation and the reverse rotation of the shutter drive ring  61  driven by the shutter drive motor  67  is shortened, the opening time of the shutter sectors  60  is shortened, so that the shutter speed is increased. Conversely, if the time interval between the forward rotation and the reverse rotation is lengthened, the opening time of the shutter sectors  60  is prolonged, thus resulting in a slower shutter speed. 
     The shutter drive ring  61  has a slit plate  61   c  which is in the form of a small portion of a cylinder and protrudes forward in the optical axis direction. The slit plate  61   c  extends through an arc opening  42   d  (see FIG.  14 ), formed in the front wall portion  42   a  of the rear support ring  42 , and an arc opening  41   m  (see FIG. 17) formed in the rear surface of the front support ring  41 . The slit plate  61   c  is located in a photo-interrupter  69  (between two components of the photo-interrupter  69 ) shown in FIG. 17, so that the passing of slits of the slit plate  61   c  can be detected by the photo-interrupter  69  in order to detect the shutter operation. Namely, the opening and closing of the shutter sectors  60  can be detected by the operation of the shutter drive ring  61  via the slit plate  61   c  and the photo-interrupter  69 . 
     The front support ring  41  is provided with an interrupter holding recess  41   n  (see FIG. 17) for receiving the photo-interrupter  69 . The interrupter holding recess  41   n  is located adjacent to the interrupter holding recess  41   j  for receiving the photo-interrupter  56  for detecting the switching and focusing drive amount. The recesses  41   n  and  41   j  are covered by a common cover  70  in the form of a leaf spring. The two photo-interrupters  56  and  69  are held by the leaf spring cover  70 . 
     As can be understood from the foregoing, in the zoom lens barrel of the present embodiment, the exposure is controlled by the shutter sectors  60 . The purpose of the diaphragm sectors  62  is to restrict the size of the aperture so that the peripheral portion of the zoom lens system is not used for photographing at the short focal length. 
     The diaphragm drive ring  63 , for opening and closing the diaphragm sectors  62 , is provided on the outer peripheral surface thereof with a driven projection  63   b  which is engaged in a diaphragm control cam groove  71  (see FIG. 10) formed in the inner peripheral surface of the arm  33   b  of the third linear guide ring  33 . Upon zooming, the third linear guide ring  33  and the lens-shutter unit  40  (diaphragm drive ring  63 ) are relatively moved in the optical axis direction. Consequently, the driven projection  63   b  is moved in the circumferential direction in accordance with the diaphragm control cam groove  71  to rotate the diaphragm drive ring  63  to thereby vary the opening degree of the diaphragm sectors  62 . As shown in FIG. 11, the diaphragm control cam groove  71  includes a linear restriction portion  71   a  extending parallel with the optical axis O, an oblique restriction portion  71   b  which is inclined with respect to the optical axis O, and a restriction releasing portion  71   c  which opens into the front end of the third linear guide ring  33 . The width of the linear restriction portion  71   a  and the oblique restriction portion  71   b  is such that the driven projection  63   b  can be substantially snugly fitted therein. 
     When the zoom lens barrel is in the retracted position (accommodated position) shown in FIG. 2, the driven projection  63   b  is located in the linear restriction portion  71   a . When the zoom lens barrel is advanced to the wide-angle position, the driven projection  63   b  is still in the linear restriction portion  71   a . When the driven projection  63   b  is in the linear restriction portion  71   a , the driven projection  63   b  causes the aperture defined by the three diaphragm sectors  62  to be at a minimum aperture position. In the minimum aperture position, the diaphragm sectors  62  do not completely close the front portion of the photographing circular opening  44   c  but cover a predetermined width of the peripheral portion of the circular opening in the radial direction. Consequently, photographing is carried out at the wide-angle extremity without collecting unnecessary light. 
     When the zoom lens barrel is advanced toward the telephoto side and reaches the fourth focal length step from the wide-angle extremity, the driven projection  63   b  enters the oblique restriction portion  71   b  from the linear restriction portion  71   a . The oblique restriction portion  71   b  is inclined so that the diaphragm drive ring  63  is rotated in the diaphragm opening direction as the driven projection  63   b  is moved toward the restriction releasing portion  71   c . Therefore, when the lens barrel is advanced while the driven projection  63  in located in the oblique restriction portion  71   b , the diaphragm drive ring  63  is rotated in the diaphragm opening direction to gradually open the diaphragm sectors  62 . Specifically, a middle opening degree of the diaphragm sectors  62  is obtained at the fifth focal length step counting from the wide-angle extremity, and the diaphragm sectors  62  are fully opened at the sixth focal length step. 
     When further advancement of the zoom lens barrel takes place, the above-mentioned switching of the relative distance between the first sub-lens group S 1  and the second sub-lens group S 2  is carried between the sixth focal length step and the seventh focal length step, so that wide-angle photographing mode is transferred to the telephoto photographing mode. In the telephoto photographing mode, the driven projection  63   b  is located in the restriction releasing portion  71   c . The restriction releasing portion  71   c  is shaped so as to give less restriction on the relative position of the driven projection  63   b . When the driven projection  63   b  is in the restriction releasing portion  71   c , the diaphragm drive ring  63  is held at an angle position to open the diaphragm sectors  62  by the diaphragm drive ring biasing spring  72 . Therefore, in the telephoto photographing mode, a sufficient amount of light can be collected. 
     Conversely, when the zoom lens barrel is moved toward the wide-angle side from the telephoto side, the opening degree of the diaphragm sectors  62  is gradually reduced from the fifth focal length step counting from the wide-angle extremity. The diaphragm sectors  62  are closed in accordance with the relationship between the linear restriction portion  71   a  and the driven projection  63   b , from the fourth focal length step to the wide-angle extremity (first focal length step). Note that the restriction releasing portion  71   c  has an inclined guide surface  71   d  which is adapted to smoothly guide the driven projection  63   b  to the oblique restriction portion  71   b  when the photographing mode is transferred from the telephoto photographing mode to the wide-angle photographing mode. The inclined guide surface  71   d  ensures that the driven projection  63   b  is moved into the oblique restriction portion  71   b  without interfering with the diaphragm control cam groove  71 , even if the angular position of the diaphragm drive ring  63  which has been released at the telephoto photographing mode is slightly out of alignment. 
     In the rear unit  40 B constructed as above, the rotatable shutter drive ring  61  and the rotatable diaphragm drive ring  63  are located substantially in the same position in the axial direction. The shutter drive ring  61  is supported on the inner diameter side of the diaphragm drive ring  63  (see FIG.  15 ). The diaphragm drive ring  63  is provided on the inner peripheral surface thereof with three inner diameter thrust projections  63   c  that are spaced in the circumferential direction at equi-angular intervals to rotatably support the shutter drive ring  61 . The shutter drive ring  61  is provided on the outer peripheral surface thereof with three outer diameter thrust projections  61   d  that are spaced in the circumferential direction at equi-angular intervals to engage with the inner diameter thrust projections  63   c.  The diaphragm drive ring  63  is in contact with the rear surface of the front wall portion  42   a  of the rear support ring  42  and the rotation transmission dowels  63   a  are in contact with the front surface of the front wall portion  44   a  of the sector retainer ring  44 , so that the diaphragm drive ring  63  is supported between the rear support ring  42  and the sector retainer ring  44  so as not relatively move in the optical axis direction. The driven projection  63   b  of the diaphragm drive ring  63  supported between the rear support ring  42  and the sector retainer ring  44  (between the front wall portion  42   a  and the front wall portion  44   a ) is located between a pair of rear arms  42   b  and  44   b  in the circumferential direction, so that the driven projection  63   b  can be engaged by the diaphragm control cam groove  71  of the third linear guide ring  33  (see FIG.  10 ). The shutter drive ring  61  is supported between the rear support ring  42  and the sector retainer ring  44 , with the shutter drive ring  61  in contact with the rear surface of the front wall portion  42   a  and with the outer diameter thrust projections  61   d  being engaged with the inner diameter thrust projections  63   c.  The diaphragm drive ring  63  is shaped so that the sector gear  61   b  (see FIGS. 24 and 25) of the shutter drive ring  61 , located inside the diaphragm drive ring  63 , can engage with the reduction gear train  68 . 
     As can be understood from the above discussion, the lens-shutter unit  40  includes the front unit  40 A having the first variable power lens group L 1  (first sub-lens group S 1  and second sub-lens group S 2 ) and the drive mechanism therefore, and the rear unit  40 B having the lens shutter and the diaphragm mechanism. The front unit  40 A includes the reversible drive motor  53  for driving the first variable power lens group L 1 , and the shutter drive motor  67  for opening and closing the shutter sectors  60 . The front unit  40 A is also provided with the photo-interrupter  56  which detects the shift movement of the first sub-lens group S 1  and the second sub-lens group S 2  and the movement of the entire first variable power lens group L 1  during the focusing operation, and the photo-interrupter  69  which detects the opening and closing operation of the shutter sectors  60 . The reversible drive motor  53 , the shutter drive motor  67 , and the photo-interrupters  56  and  69  are connected to a control circuit  81  (see FIG. 2) in the camera body  11  via a lens-shutter unit FPC (flexible printed circuit)  80 . As shown in FIGS. 13 and 16, the lens-shutter unit FPC  80  is divided into an annular FPC  80 A extending around the outer peripheral surface of the front unit  40 A, and a foldable strip FPC  80 B which is elongated in the optical axis direction. The annular FPC  80 A is double-sided FPC having circuit patterns printed on upper and lower surfaces thereof. The foldable strip FPC  80 B is a one-sided FPC having a circuit pattern printed on only one of upper and lower surfaces thereof. 
     The foldable strip FPC  80 B is secured at a shutter securing end  80 B- 1  to the front support ring  41  by a securing screw  82 , as shown in FIG.  13 . An FPC support plate  83  is inserted between the shutter securing end  80 B- 1  and the securing screw  82 . A cylindrical press-contact support rubber  84  is inserted between the shutter securing end  80 B- 1  and the front support ring  41 . As shown in FIGS. 2 and 4, the foldable strip FPC  80 B is connected at the other end to the control circuit  81 . The foldable strip FPC  80 B can be freely deformed to vary the position of the bent portions and the linear portions thereof in accordance with the relative position of the lens-shutter unit  40  and the control circuit  81  which is changed in accordance with the advance or retraction of the zoom lens barrel, to prevent an interference of the FPC with other members of the lens barrel or the photographing light path. The foldable strip FPC  80 B is not connected to the motors (reversible drive motor  53  and the shutter drive motor  67 ) or the photo-interrupters  56  and  69  when the foldable strip FPC  80 B is solely mounted to the front support ring  41 . Namely, the motors and the photo-interrupters are connected to the control circuit  81  when the annular FPC  80 A is mounted. 
     As shown in FIG. 17, the annular FPC  80 A has two motor terminals  80 A- 1  and  80 A- 2  to supply power to the reversible drive motor  53  and the shutter drive motor  67 , and two interrupter terminals  80 A- 3  and  80 A- 4  to receive the pulses output from the photo-interrupters  56  and  69 , respectively. The wiring conductors extending from the terminals are gathered at a press-contact portion  8 OA- 5 . The press-contact portion  80 A- 5  is brought into press contact with the shutter securing end  80 B- 1  of the foldable strip FPC  80 B, so that the wiring conductors of the annular FPC  80 A and the foldable strip FPC  80 B are connected. Thus, the reversible drive motor  53 , the shutter drive motor  67 , and the photo-interrupters  56  and  69  are electrically connected to the control circuit  81 . The press-contact portion  80 A- 5  of the annular FPC  80 A is fastened together with the shutter securing end  80 B- 1  of the foldable strip FPC  80 B by the securing screw  82 , and are secured to the front support ring  41 . The annular FPC  80 A is also provided with four positioning holes  80 A- 6  in which front surface projections  43   c  (see FIGS. 20 and 21) of the gear retainer ring  43  are fitted to determine the position thereof. 
     The leaf spring cover  70 , which holds the photo-interrupters  56  and  69 , covers the portion of the annular FPC  80 A hatched in FIG. 17 to stably hold the annular FPC  80 A. 
     As shown in FIG. 26, the control circuit  81  controls the zooming motor  15  as well as the reversible motor  53  and the shutter drive motor  67 . Focal length information  81 A set by an operator (photographer) via a zoom switch (zoom operating device) etc., detected object distance information  81 B, object brightness information  81 C, angular position information of the cam ring  30  detected by a focal length detection device including the brush  19  and the code plate  20 , focusing drive amount information (position switching information of the first sub-lens group S 1  and the second sub-lens group S 2 ) detected by the photo-interrupter  56 , and opening and closing state information of the shutter sectors  60  detected by the photo-interrupter  69  are input to the control circuit  81 . The zooming motor  15 , the reversible drive motor  53 , and the shutter drive motor  67  are controlled so that the exposure is carried out under the correct exposure conditions at the set focal length, based on the input information. Note that although, in the illustrated embodiment, the shutter sectors  60  function as a shutter and a variable diaphragm, and the diaphragm sectors  62  restrict the aperture size at the wide-angle photographing position, it is possible to use a variable diaphragm mechanism in which the diaphragm sectors  62  are electrically driven by a motor. 
     The lens-shutter unit  40  is assembled with the members discussed above into a unit which is incorporated in the lens support barrel  31 . Namely, the front unit  40 A and the rear nit  40 B are assembled separately, the two units  40 A and  40 B are secured using three unit securing screws  39  (see FIG.  13 ), and the assembly of the units  40 A and  40 B is mounted into the lens support barrel  31 . 
     As shown in FIG. 21, the rear support ring  42  of the lens-shutter unit  40  is provided with engagement projections  42   f  provided on the outer surfaces of the three rear arms  42   b . The engagement projections  42   f  are engaged in the engagement holes  31   c  of the lens support barrel  31 . The engagement projections  42   f  are formed on resilient tongue portions  42   g  which are elastically deformable in the radial directions. When the lens-shutter unit  40  is inserted in the direction indicated by an arrow in FIG. 21 into the lens support barrel  31 , the engagement projections  42   f  are moved inwardly by the inner surface of the lens support barrel  31 , so that the elastic tongue portions  42   g  are elastically deformed inwardly. Further insertion o the lens-shutter unit  40  causes the engagement projections  42   f  to engage in the engagement holes  31   c , so that the elastic tongue portions  42   g  are returned to the initial state, or the inward deformation of the elastic tongue portions  42   g  is reduced. The cross sectional shape of the engagement projections  42   f  is such that the elastic tongue portions  42   g  can be easily deformed inwardly when the lens-shutter unit  40  is inserted forwardly in the optical axis direction, and the lens-shutter unit  40  cannot slip off the lens support barrel  31  in the rearward direction. Therefore, when the engagement projections  42   f  engage in the engagement holes  31   c , the lens-shutter unit  40  is held in the lens support barrel  31 . Three lens-shutter unit retainer springs  73  (see FIGS. 1 and 13) are provided between the lens-shutter unit  40  and the lens support barrel  31  to bias the lens-shutter unit  40  rearwardly in the optical axis direction. Accordingly, the axial position of the lens-shutter unit  40  can be accurately determined. 
     It is possible to adjust the position of the lens-shutter unit  40  in a direction perpendicular to the optical axis, during the assembly of the lens barrel. The lens support barrel  31  is provided on the inner peripheral surface thereof with a substantially annular front wall portion  31   b  in the vicinity of the front end of the lens support barrel  31 . The front wall portion  31   b  is provided with an insertion hole  31   e  (see FIG. 21) in which an eccentric member  85  and a direction member  86  are rotatably fitted. The eccentric member  85  is engaged in the gear retainer ring  43  of the lens-shutter unit  40 . The eccentric member  85  and the direction member  86  are relatively rotatable. When the direction member  86  is rotated from the front end of the lens support barrel  31 , the front end of the eccentric member  85  (the end of the eccentric member engaging with the lens-shutter unit  40 ) is moved in a plane perpendicular to the optical axis O. Consequently, the position of the lens-shutter unit  40  in the direction perpendicular to the optical axis within the lens support barrel  31  is varied, whereby the position of the first variable power lens group L 1  supported by the lens-shutter unit can be adjusted. 
     The lens support barrel  31  is provided on the front end thereof with a lens barrier mechanism which opens and closes the front opening of the first variable power lens group L 1 . As shown in FIG. 1, the lens barrier mechanism has a barrier unit including an outer decorative plate  90  secured to the front end of the lens support barrel  31 , a barrier retainer ring  96 , a pair of outer barrier blades  92  and a pair of inner barrier blades  93 which are rotatably mounted between the barrier retainer ring  96  and the decorative plate  90 , and barrier springs  94 . A barrier drive ring  91  is supported between the barrier unit and the front end  31   b  of the lens support barrel  31  so as to be rotatable about the optical axis O. The decorative plate  90  is provided with a projection (not shown) which rotatably supports the outer and inner barrier blades  92  and  93 . The outer and inner barrier blades  92  and  93  are rotated about this projection and are associated with each other to carry out the opening and closing operation. The barrier blades  92  and  93  are biased by the barrier springs  94  in a closing direction. 
     The barrier drive ring  91  is provided with diametrically opposed barrier engagement portions  91   a  and a driven arm  91   b  which extends rearwardly in the optical axis direction. The barrier engagement portions  91   a  engage with the inner barrier blades  93  to transmit the rotation of the barrier drive ring  91  to the inner barrier blades  93 . The inner barrier blades  93  are associated with the outer barrier blades  92 , and hence, the rotation of the barrier drive ring  91  is transmitted to the outer barrier blades  92  via the inner barrier blades  93 . The driven arm  91   b  extends through a center opening  31   d  of the front wall portion  31   b  (see FIG. 21) into the lens support barrel  31 . The driven arm  91   b  can be engaged with an inclined guide surface  33   e  formed on the front end of the partially cylindrical arm  33   b  of the third linear guide ring  33 . 
     The barrier drive ring  91  is biased by the drive ring biasing spring  95  in a direction to open the barrier blades  92  and  93 . The drive ring biasing spring  95  is stronger than the barrier biasing spring  94 , so that the biasing force of the drive ring biasing spring  95  is transmitted to the barrier blades  92  and  93  through the barrier engagement projections  91   a  to thereby open the barrier blades  92  and  93  against the barrier spring  94  when the barrier drive ring  91  is in a free state. At the wide-angle extremity shown in FIG.  3  and at the telephoto extremity shown in FIG. 4, the driven arm  91   b  and the inclined guide surface  33   e  do not come into contact with each other, so that the barrier drive ring  91  is free and, hence, the barrier blades  92  and  93  are open (see FIG.  25 ). When the zoom lens barrel is moved from the wide-angle extremity to the retracted position shown in FIG. 2, the inclined guide surface  33   e  of the third linear guide ring  33  engages with the driven arm  91   b  of the barrier drive ring  91 , so that the barrier drive ring  91  is forcedly rotated in a direction against the drive ring biasing spring  95 , i.e., in a direction to permit the barrier blades  92  and  93  to be closed, in accordance with the shape of the inclined guide surface  33   e.  Consequently, the barrier blades  92  and  93  which have been released from the restriction by the barrier drive ring  91  are closed by the spring force of the barrier spring  94  (see FIG.  24 ). 
     As mentioned above, in the zoom lens barrel of the present embodiment, the drive ring  47  is rotated to move the first variable power lens group L 1  in the optical axis direction to carry out the focusing operation. As indicated by two-dotted chain line in FIG. 25, when the first variable power lens group L 1  is moved to the front extremity of the movement for the focusing operation, the front end of the front sub-lens group frame  45  which supports the first sub-lens group S 1  is moved to a position located more forward than the axial positions of the barrier blades  92  and  93 . Note that FIG. 25 shows the telephoto photographing mode in which the first sub-lens group S 1  and the second sub-lens group S 2  are in the mutually close position. Likewise, at the wide-angle photographing mode in which the first sub-lens group S 1  and the second sub-lens group S 2  are in the mutually distant position, the front end of the front sub-lens group frame  45  is moved to a position located more forward than the axial positions of the barrier blades  92  and  93  at the front extremity of the movement for the focusing operation. 
     In the zoom lens barrel constructed as above, the shutter mechanism and the diaphragm mechanism are held between the rear support ring (support frame)  42  and the sector retainer ring (support frame)  44 , of the rear unit  40 B of the lens-shutter unit  40 . Namely, each of the front wall portion  42   a  of the rear support ring  42  and the front wall portion  44   a  of the sector retainer ring  44  is a circular plate portion provided in a plane normal to the optical axis, and the three shutter sectors (shutter member)  60  and the three diaphragm sectors (diaphragm member)  62  are rotatably supported by the projecting pivots  66  between opposed surfaces of the front wall portion  42   a  and the front wall portion  44   a . Also, the shutter drive ring (inner drive ring)  61  and the diaphragm drive ring (outer drive ring)  63  are coaxially supported to rotate about the optical axis O between opposed surfaces of the front wall portion  42   a  and the front wall portion  44   a . As mentioned above, when the shutter drive ring  61  is rotated in the forward and reverse direction, the three shutter sectors  60  are opened and closed. If the diaphragm drive ring  63  is rotated in the forward and reverse direction, the aperture diameter of the three diaphragm sectors  62  can be varied. 
     As can be seen in FIG. 27 which shows a sectional view of the rear unit  40 B in a position different from FIG. 15, the rear unit  40 B includes an opening  40 B- s  which extends radially, and is formed between the rear support ring  42  and the sector retainer ring  44  (between front wall portion  42   a  and the front wall portion  44   a ) and between each of the three rear arms  42   b  (and  44   b ) in a circumferential direction. The sector retainer ring  44  has overhang portions (outer peripheral wall portions)  44   f  which project forwardly in the optical axis direction from the outer peripheral edge of the front wall portion  44   a  and partly cover the opening  40 B- s  (see FIGS.  14  and  27 ). 
     As shown in FIGS. 15 and 27, the shutter drive ring  61  and the diaphragm drive ring  63  are located substantially at the same position in the axial direction and at different positions in the radial direction, i.e., so as to overlap each other in the radial direction. The diaphragm drive ring  63  is located more outwardly in the radial direction than the shutter drive ring  61 . 
     The diaphragm drive ring  63  is provided on the outer peripheral surface thereof with stepped portions  63   d  (see FIG. 27) and fitting portions  63   e  that extend radially and outwardly from the stepped portions  63   d . The stepped portions  63   d  overlap the overhang portions  44   f  in the radial direction and engage with the inner surfaces of the overhang portions  44   f.  The fitting portions  63   e  are inserted in a space (opening  40 B- s ) defined between the front ends of the overhang portion  44   f  and the front wall portion  42   a , and are located between the front surfaces of the overhang portions  44   f  and the rear surface of the front wall portion  42   a . The outward and radial position of the diaphragm drive ring  63  is restricted by the engagement of the stepped portions  63   d  and the overhang portions  44   f . Furthermore, the axial position of the diaphragm drive ring  63  is restricted when the fitting portions  63   e  are supported between the overhang portions  44   f  and the front wall portion  42   a . The main body of the diaphragm drive ring  63  contacts with the rear surface of the front wall portion  42   a  of the rear support ring  42 , and the front ends of the rotation transmission dowels  63   a  contact with the front surface of the front wall portion  44   a  of the sector retainer ring  44 . The axial position of the diaphragm drive ring  63  is also restricted by the engagement of the main body of the drive ring  63  and the rotation transmission dowels  63   a  with the front wall portions  42   a  and  44   a , respectively. 
     The shutter drive ring  61  is supported at the main body thereof by a stepped portion  42   h,  formed on the rear surface of the front wall portion  42   a  of the rear support ring  42 , and a small diameter cylindrical portion  42   i  projecting rearwardly in the axial direction from the front wall portion  42   a , so that the position of the shutter drive ring is restricted in the forward axial direction and in the radial direction. The position of the shutter drive ring  61  in the axial and rearward direction is restricted by the engagement of the outer diameter thrust projections (outer flange)  61   d  and the inner diameter thrust projections (inner flange)  63   c  provided on the diaphragm drive ring  63 . 
     The outer diameter thrust projections  61   d  and the inner diameter thrust projections  63   c  engage and overlap each other in the axial direction (optical axis direction) of the drive rings  61  and  63 , so that they are not relatively movable in the axial direction but are relatively slidable in the circumferential direction. The shutter drive ring  61 , which is located more inwardly than the diaphragm drive ring  63 , and the diaphragm drive ring  63  are coaxially rotatable relative to each other by the sliding contact between the outer diameter thrust projections  61   d  and the inner diameter thrust projections  63   c . Namely, the rotating support structure of the shutter drive ring  61  is partly formed by the diaphragm drive ring  63 , and the rotating support structure of the diaphragm drive ring  63  is partly formed by the shutter drive ring  61 , respectively. In particular, the position of the shutter drive ring  61  in the optical axis direction is determined by the engagement of the outer diameter thrust projections  61   d  and the inner diameter thrust projections  63   c.    
     The driven projection  63   b  of the diaphragm drive ring  63  supported as described above is provided on the fitting portion  63   e  and extends from the opening  40 B- s  in the radial and outward direction, so that the driven projection  63   b  can be actuated from the outside of the rear unit  40 B (FIG.  10 ). The driven projection  63   b  is engaged in the diaphragm control cam groove (rotational force providing device)  71  of the third linear movement guide ring  33 , so that the diaphragm drive ring  63  can be rotated via the engagement between the diaphragm control cam groove  71  and the driven projection  63   b  in accordance with the zooming operation. 
     The sector gear  61   b  of the shutter drive ring  61  is in mesh with the terminal gear  68   a  (see FIG.  18 ), of the reduction gear train (motor drive gear)  68 , which projects toward the rear surface of the front wall portion  42   a , so that the drive force of the shutter drive motor  67  is transmitted to the shutter drive ring  61 . The diaphragm drive ring  63  is provided on the inner peripheral surface thereof with a cut-away portion  63   f  (radial space) to prevent interference with the end gear of the reduction gear train  68  (see FIG.  14 ). 
     In the structure of the rear unit  40 B, the rotating support structure of the shutter drive ring and the diaphragm drive ring can be simplified. Namely, two drive rings, i.e., the shutter drive ring  61  and the diaphragm drive ring  63  are provided in the rear unit  40 B, however, the rotating support structure on the rear support ring  42  side or the sector retainer ring  44  side can be simplified because the shutter drive ring  61  and the diaphragm drive ring  63  overlap in the radial direction (i.e., are located at different positions in the radial direction) and the outer and inner diameter thrust projections  61   d  and  63   c  of the drive rings  61  and  63  which are opposed in the radial direction engage with each other, so that one of the drive rings  61  and  63  forms the rotating support structure of the other drive ring. Namely, it is necessary for the rear support ring  42  and the sector retainer ring  44  to restrict the radial positions of the drive rings  61  and  63 , and restrict the axial position of only one of the drive rings  61  and  63 . Consequently, no individual rotating supports for the rear support ring  42  and the sector retainer ring  44  are necessary, and thus the rear unit  40 B, and accordingly the lens-shutter unit  40 , can be made compact. 
     The rear unit  40 B is provided on the outer peripheral portion thereof with the opening  40 B- s,  through which the driven projection  63   b  of the diaphragm drive ring  63  extends outwardly. Therefore, it is necessary to prevent harmful light, which does not pass through the photographing circular opening (photographing aperture)  44   c , from leaking from, e.g., the inner diameter side (center opening (photographing aperture)  42   c ) to the outer diameter side (opening  40 B- s ) of the rear unit  40 B. In the lens shutter mechanism, such harmful light which would otherwise pass through the opening  40 B- s  in the rear unit  40 B can be effectively interrupted. Namely, since the shutter drive ring  61  and the diaphragm drive ring  63  are arranged in an overlapped state in the radial direction within a space through which the harmful light passes, it is difficult for harmful light to travel linearly therethrough. Furthermore, since the opening  40 B- s  is covered by the overhang portions  44   f  and the diaphragm drive ring  63  (fitting portions  63   e ) which partly overlaps the overhang portions  44   f , harmful light, which is not intercepted by the body portions of the shutter drive ring  61  and the diaphragm drive ring  63  and travels in the radial and outward direction, can be certainly intercepted. The overhang portions  44   f  and the fitting portions  63   e  engage with each other and form the rotating support structure of the diaphragm drive ring  63 . Namely, a plurality of functions including the light interception function can be provided. 
     Therefore, no troublesome operation in attaching light interception tapes to the outer periphery of the rear unit  40 B is necessary, and thus, the light interception structure can be simplified. Furthermore, there is no chance that the movable members in the rear unit  40 B are interfered with light interception tapes, since light interception tapes are not necessary. Note that the opening  40 B- s  is not formed at the portions of the rear support ring  42  and sector retainer ring  44  on which the rear arms  42   b  and  44   b  are provided since light interception thereat is performed by the rear arms  42   b  (FIG.  15 ). 
     As can be understood from the above discussion, according to the present invention, a small and simple lens shutter mechanism in which the surrounding components of the shutter can be reliably intercepted from harmful light can be attained. Namely, the arrangement of the shutter drive ring  61  and the diaphragm drive ring  63  is provided, so that the drive rings  61  and  63  have plural functions including the rotating support function thereof and the light interception function of the lens-shutter unit  40 , and hence, the lens-shutter unit  40  can be manufactured with less number of elements and can be made simple and compact. Moreover, since the drive rings, i.e., the movable members, constitute a portion of the light interception mechanism, there is no chance of the rotation of the shutter and diaphragm drive rings  61  and  63  being interrupted by other light interception members such as the light interception tapes, and thus, the shutter and the diaphragm can be reliably driven. 
     The present invention is not limited to the illustrated embodiments. For instance, the shutter sectors  60  have a variable stop function for the exposure control and the diaphragm sectors  62  restrict the aperture diameter on the wide-angle side in the illustrated embodiments. However, the present invention can be equally applied to a lens shutter mechanism in which the diaphragm sectors have a variable stop function to optionally vary the aperture value and the shutter sectors only have the shutter function. 
     Although the diaphragm drive ring  63  is located outside the shutter drive ring  61  to expose the driven projection  63   b  to the outer peripheral of the lens-shutter unit  40  in the illustrated embodiments, the positional relationship between the shutter drive ring and the diaphragm drive ring in the radial direction can be opposite if the drive mechanism to rotate the drive rings is different from that of the illustrated embodiments. For example, if both the shutter drive ring and the diaphragm drive ring are driven by a motor incorporated in the lens-shutter unit, it is possible to arrange the shutter drive ring on the outer side of the periphery of the diaphragm drive ring. 
     Obvious changes may be made in the specific embodiment of the present invention described herein, such modifications being within the spirit and scope of the invention claimed. It is indicated that all matter contained herein is illustrative and does not limit the scope of the present invention.