Patent Publication Number: US-7907842-B2

Title: Collapsible lens barrel and optical instrument using the same

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a Continuation of application Ser. No. 12/370,366, which is a Division of application Ser. No. 11/978,429 filed Oct. 29, 2007, which is a Continuation of application Ser. No. 10/528,977, filed Mar. 22, 2005, which is a U.S. National Stage application of PCT/JP2003/012116, filed Sep. 22, 2003, which applications are incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present invention relates to a collapsible lens barrel for high-factor zooming. In particular, the present invention relates to a collapsible lens barrel capable of improving a zoom operability, miniaturizing a lens barrel and reducing an entire length of the lens barrel while maintaining its optical performance. Also, the present invention relates to an optical instrument using such a collapsible lens barrel. 
     BACKGROUND ART 
     In recent years, the use of a digital still camera (in the following, referred to as DSC) allowing a user to check a captured image immediately has been expanding rapidly. As a lens barrel for this DSC, a so-called collapsible lens barrel, which can be made shorter when not in use, generally is adopted in view of its portability when not in use. 
       FIG. 35  is an exploded perspective view showing a conventional collapsible lens barrel (see JP 2002-107598 A, for example). This collapsible lens barrel  60  is an optical system in which a single cam barrel  61  moves moving lens frames  62  and  63  back and forth so as to change a focal length. The inner peripheral surface of this cam barrel  61  is provided with cam grooves  64  and  65 , which determine moving paths of the moving lens frames  62  and  63 , respectively. Three cam pins  62   a  provided on the outer peripheral surface of the moving lens frame  62  and three cam pins  63   a  provided on the outer peripheral surface of the moving lens frame  63  mate with the cam grooves  64  and  65 , respectively, whereby the moving lens frames  62  and  63  move in an optical axis (Z-axis) direction. The cam barrel  61  is provided outside a fixed barrel  70  and can rotate freely around the optical axis. An outer periphery of the cam barrel  61  is provided with a gear  66 , which engages with a driving force transmitting gear  67 . The driving force transmitting gear  67  is connected to an output axis of a cam barrel driving actuator  69  via a reduction gear train  68 . Thus, when the cam barrel driving actuator  69  is driven, the driving force is transmitted via the reduction gear train  68  to the driving force transmitting gear  67 , thereby rotating the cam barrel  61 . This moves the moving lens frames  62  and  63  along respective shapes of the cam grooves  64  and  65 , so that zooming is carried out from a collapsed state via a wide angle end. 
       FIG. 36  is a development showing the cam grooves  64  and  65  formed on the inner peripheral surface of the cam barrel  61 . As shown in  FIG. 36 , the cam grooves  64  and  65  are formed in a circumferential direction of the cam barrel  61  so as to extend from a collapsed position through a wide angle end position to a telephoto end position. Accordingly, when the power of DSC is turned on, the moving lens frames  62  and  63  shift from the collapsed position to the wide angle end position, which is the next stop position, and stop there for an image capturing. 
     Further, with an increase in the optical zooming factor, the influence of camera shake has become conspicuous. In order to reduce this influence, a DSC including an image blurring correcting device is on its way to becoming commercialized. As this image blurring correcting device for DSC, there has been a suggested method of moving a correcting lens group in two directions that are perpendicular to the optical axis so as to correct the camera shake by a user, thereby obtaining a stable image (see JP 2001-117129 A, for example). 
     However, in the conventional collapsible lens barrel described above, since the reduction gear train  68  and the cam frame (cam barrel  61 ) are used for zooming, there have been problems in that an increase in a zoom speed and a reduction in a zoom noise are difficult to achieve. 
     DISCLOSURE OF INVENTION 
     Accordingly, the object of the present invention is to provide a collapsible lens barrel capable of increasing the zoom speed and reducing the zoom noise while being ready for a high zooming factor. Further, the object of the present invention is to provide an optical instrument including such a collapsible lens barrel. 
     In order to achieve the above-mentioned objects, a collapsible lens barrel according to the present invention includes a first holding frame for holding a first lens group, a second holding frame for holding a second lens group that is disposed on an image plane side with respect to the first lens group, an actuator for moving the second holding frame in an optical axis direction, and a tubular cam frame including a plurality of cam grooves that are formed at substantially equal intervals around a circumferential direction for moving the first holding frame in the optical axis direction. The actuator is attached to a portion in the cam frame where the cam grooves are not formed. 
     A first optical instrument according to the present invention is an optical instrument to which the above-described collapsible lens barrel according to the present invention is attached, and includes a storing system capable of storing an optical zooming factor at a time of turning off a power as an initial optical zooming factor information. In the case where the initial optical zooming factor information is stored in the storing system, the second lens group is moved to and stopped at an optical zooming factor position based on the initial optical zooming factor information when the power is turned on. 
     Further, a second optical instrument according to the present invention is an optical instrument to which the above-described collapsible lens barrel according to the present invention is attached, and includes an input system for inputting an optical zooming factor at a time of turning on a power, and a storing system for storing the optical zooming factor inputted from the input system as an initial optical zooming factor information. In the case where the initial optical zooming factor information is stored in the storing system, the second lens group is moved to and stopped at an optical zooming factor position based on the initial optical zooming factor information when the power is turned on. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is an exploded perspective view showing a collapsible lens barrel according to a first embodiment of the present invention. 
         FIG. 2A  is a half sectional view showing how to mold a fixing portion in a first group moving frame for fixing a guide pole in the collapsible lens barrel according to the first embodiment of the present invention.  FIG. 2B  is a half sectional view showing how the guide pole is press fitted and fixed into the fixing portion formed in the first group moving frame in the collapsible lens barrel according to the first embodiment of the present invention.  FIG. 2C  is a half sectional view showing how to fix a conventional guide pole. 
         FIG. 3  is an exploded perspective view for describing guide pole supporting portions in the collapsible lens barrel according to the first embodiment of the present invention. 
         FIG. 4A  shows a lens tilt in an ideal collapsible lens barrel,  FIG. 4B  shows a lens tilt in a conventional collapsible lens barrel, and  FIG. 4C  shows a lens tilt in the collapsible lens barrel according to the first embodiment of the present invention. 
         FIG. 5  is a development of cam grooves in the collapsible lens barrel according to the first embodiment of the present invention. 
         FIG. 6A  is a partially sectional view taken in a plane parallel with an optical axis, showing how a cam pin and a cam groove mate with each other in the collapsible lens barrel according to the first embodiment of the present invention.  FIG. 6B  is a partially sectional view taken in the plane parallel with the optical axis, showing how the cam pin and the cam groove mate with each other in a wide portion of the cam groove in the collapsible lens barrel according to the first embodiment of the present invention. 
         FIG. 7  is an exploded perspective view for describing a mounting position of a home position detecting sensor of a second group lens in the collapsible lens barrel according to the first embodiment of the present invention. 
         FIG. 8  is an exploded perspective view showing a configuration of an image blurring correcting device in the collapsible lens barrel according to the first embodiment of the present invention. 
         FIG. 9  shows the relationship between a displaced amount of a position detecting portion of the image blurring correcting device and a magnetic flux density in the collapsible lens barrel according to the first embodiment of the present invention. 
         FIG. 10  is a block diagram for describing an operation of the image blurring correcting device in the collapsible lens barrel according to the first embodiment of the present invention. 
         FIG. 11  is an exploded perspective view showing a cam frame in the collapsible lens barrel according to the first embodiment of the present invention. 
         FIG. 12  is a block diagram showing a configuration of an actuator driving circuit in an optical instrument according to the first embodiment of the present invention. 
         FIG. 13  a block diagram showing a hardware configuration of an image processing portion in the optical instrument according to the first embodiment of the present invention. 
         FIG. 14  is a schematic view showing an operating portion of the optical instrument according to the first embodiment of the present invention. 
         FIG. 15  is a flowchart showing a method for assembling the collapsible lens barrel according to the first embodiment of the present invention. 
         FIG. 16  is a perspective view for describing a first assembling step in the method for assembling the collapsible lens barrel according to the first embodiment of the present invention. 
         FIG. 17  is a perspective view for describing a second assembling step in the method for assembling the collapsible lens barrel according to the first embodiment of the present invention. 
         FIG. 18  is a perspective view for describing a third assembling step in the method for assembling the collapsible lens barrel according to the first embodiment of the present invention. 
         FIG. 19  is a perspective view for describing a fourth assembling step in the method for assembling the collapsible lens barrel according to the first embodiment of the present invention. 
         FIG. 20  is a sectional view for describing how the cam pin and the cam groove mate with each other in the fourth assembling step in the collapsible lens barrel according to the first embodiment of the present invention. 
         FIG. 21  is a perspective view for describing how to fix a flexible print cable in the method for assembling the collapsible lens barrel according to the first embodiment of the present invention. 
         FIG. 22  is a sectional view showing the collapsible lens barrel when it is collapsed according to the first embodiment of the present invention. 
         FIG. 23  is a sectional view showing the collapsible lens barrel when it is used at a telephoto end according to the first embodiment of the present invention. 
         FIG. 24  is a sectional view showing the collapsible lens barrel when it is used at a wide angle end according to the first embodiment of the present invention. 
         FIG. 25  is a sectional view showing the collapsible lens barrel when it is used at an intermediate position between the wide angle end and the telephoto end according to the first embodiment of the present invention. 
         FIGS. 26A to 26C  are drawings for describing images captured at predetermined zooming factors using the optical instrument according to the first embodiment of the present invention. 
         FIG. 27  is a sectional view showing a cam frame in a collapsible lens barrel according to a second embodiment of the present invention. 
         FIG. 28  is a sectional side view showing an arrangement of a front end of a second group lens driving actuator in a collapsible lens barrel according to a third embodiment of the present invention. 
         FIG. 29  is a block diagram showing a configuration of an actuator driving circuit in an optical instrument according to a fourth embodiment of the present invention. 
         FIG. 30  is a block diagram showing a configuration of an actuator driving circuit in an optical instrument according to a fifth embodiment of the present invention. 
         FIG. 31  is a schematic view showing an operating panel in a zoom initial position selecting system in the optical instrument according to the fifth embodiment of the present invention. 
         FIG. 32  is an exploded perspective view for describing the positional relationship between a driving gear and an image blurring correcting device in a collapsible lens barrel according to a sixth embodiment of the present invention. 
         FIG. 33  is a front view seen from a direction parallel with an optical axis, showing the driving gear and the image blurring correcting device in the collapsible lens barrel according to the sixth embodiment of the present invention. 
         FIG. 34  is an exploded perspective view for describing the positional relationship between a shutter unit and a second group moving frame in a collapsible lens barrel according to a seventh embodiment of the present invention. 
         FIG. 35  is an exploded perspective view showing a conventional collapsible lens barrel. 
         FIG. 36  is a development showing a cam groove formed on an inner peripheral surface of a cam barrel of the conventional collapsible lens barrel. 
     
    
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
     A collapsible lens barrel according to the present invention includes a first holding frame for holding a first lens group, a second holding frame for holding a second lens group that is disposed on an image plane side with respect to the first lens group, an actuator for moving the second holding frame in an optical axis direction, and a tubular cam frame including a plurality of cam grooves that are formed at substantially equal intervals around a circumferential direction for moving the first holding frame in the optical axis direction. The actuator is attached to a portion in the cam frame where the cam grooves are not formed. 
     In accordance with the collapsible lens barrel of the present invention described above, the first lens group is driven via the cam grooves, and the second lens group is driven via the actuator. Since the first lens group and the second lens group are driven separately in this manner, the first lens group does not have to be driven when driving the second lens group for zooming. Therefore, it is possible to achieve a collapsible lens barrel capable of increasing the zoom speed and reducing the zoom noise. Accordingly, a user can change the angle of view instantly, making it possible to chase a subject, capture a moving image, etc., which have been difficult in conventional DSCs. 
     Further, since the actuator for driving the second lens group is provided on the cam frame without interfering with the plurality of cam grooves, it is possible to reduce the number of components thanks to a high-density mounting, reduce the diameter of the lens barrel, simplify the configuration and lower costs. 
     The above-described collapsible lens barrel according to the present invention further may have a detecting member for detecting a position of the second holding frame, a substantially hollow cylindrical driving frame that is rotatable around an optical axis and moves together with the first holding frame in the optical axis direction, and a driving gear for rotating the driving frame. In this case, it is preferable that the cam grooves mate with the driving frame, and the driving frame moves in the optical axis direction along the cam grooves with a rotation of the driving frame. It also is preferable that the detecting member and the driving gear respectively are attached to the portion in the cam frame where the cam grooves are not formed. 
     With this preferable mode, since the position detecting member for the second lens group and the driving gear for rotating the driving frame are provided on the cam frame without interfering with the plurality of cam grooves, it is possible to reduce the number of components thanks to a high-density mounting, reduce the diameter of the lens barrel, simplify the configuration and lower costs. 
     In the above-described collapsible lens barrel according to the present invention, it is preferable that the cam frame is molded out of a resin by using a molding die, which is a combination of a plurality of molding die parts, and at least one of the plurality of cam grooves formed on the cam frame and at least one of mounting portions of the actuator, the detecting member and the driving gear are molded with a common molding die part. 
     With this preferable mode, since the number of molding die parts for resin-molding can be reduced, it is possible to reduce the costs of the molding die and thus lower the costs of the lens barrel. 
     The above-described collapsible lens barrel according to the present invention further may have at least two rod-like guide members parallel with each other whose one end is fixed to the first holding frame. In this case, it is preferable that the second holding frame is held slidably by the guide members. 
     With this preferable mode, when the first lens group tilts with respect to the optical axis, the second lens group also tilts in the same direction. Accordingly, the reduction of optical performance can be suppressed. 
     In this case, the collapsible lens barrel according to the present invention further may have an image blurring correcting member for holding a third lens group for correcting image blurring disposed on the image plane side with respect to the second holding frame. In this case, it is preferable that the guide members are supported in such a manner as to be slidable with respect to the image blurring correcting member substantially in parallel with the optical axis. 
     With this preferable mode, the directions in which the first and second lens groups tilt with respect to the third lens group for correcting image blurring, which have the greatest influence on the optical performance, can be aligned, thereby suppressing the reduction of optical performance further. 
     Also, it is preferable that each of the guide members is fixed to the first holding frame by being press-fitted into two through holes penetrating in the optical axis direction that are spaced from each other. 
     With this preferable mode, it is easy to adjust the degree of parallelization of the guide members with respect to the optical axis, so that the guide members can be fixed in parallel with the optical axis. Also, the number of assembling steps can be reduced compared with the conventional system of pre-fixing the guide member with a jig intended for this purpose and adhering it. 
     In the above-described collapsible lens barrel according to the present invention, it is preferable that a gap is provided between the first lens group and the first holding frame in a direction perpendicular to an optical axis, and the first lens group and the first holding frame move toward the image plane side and a front end of the actuator enters the gap at a time of non-capturing. 
     With this preferable mode, the entire length of a collapsed lens barrel can be reduced without increasing the diameter of the lens barrel. 
     The above-described collapsible lens barrel according to the present invention further may have a substantially hollow cylindrical driving frame that rotates around an optical axis relative to the cam frame, thereby moving together with the first holding frame in the optical axis direction. In this case, it is preferable that the driving frame includes mating members for mating with the cam grooves, and wide portions whose width along the optical axis direction is increased are formed in the cam grooves so that the mating members do not contact the cam grooves when the first lens group is moved furthest to the image plane side. 
     With this preferable mode, even when a compression load in the optical axis direction is applied in a collapsed state, the mating members do not contact the cam grooves. Therefore, it is possible to prevent damage to the lens barrel such as the deformation of the mating members or the damage to the cam grooves. 
     It is preferable that the above-described collapsible lens barrel according to the present invention further includes a detecting member disposed for detecting an absolute position of the second holding frame in the optical axis direction when the second holding frame is at a position furthest to the image plane side or in the vicinity thereof. 
     With this preferable mode, since the zooming position information after turning on the power can be detected and initialized instantly, it is possible to shorten the time required for shifting to the next zooming position. 
     Here, it is preferable that the position furthest to the image plane side substantially is a telephoto end position in an optical system. 
     With this preferable mode, the zooming position after turning on the power can be shifted instantly to the vicinity of the telephoto end position not through the wide angle end. This allows a user to scale up an image without missing an important shutter chance. 
     Also, the image blurring correcting member may include a pair of actuators for driving the third lens group in two directions perpendicular to the optical axis. In this case, it is preferable that the driving gear for rotating the driving frame is disposed between the pair of actuators. 
     With this preferable mode, since the driving gear is provided between the pair of actuators for correcting image blurring, it becomes possible to bring the driving gear toward the center of the optical axis without causing interference with the cam grooves. Consequently, the diameter of the lens barrel can be reduced. 
     The above-described collapsible lens barrel according to the present invention further may include a shutter unit between the image blurring correcting member and the second holding frame. In this case, it is preferable that the shutter unit includes a driving actuator on its surface on the side of the second holding frame, and the second holding frame is provided with a recessed portion that the driving actuator partially enters. 
     With this preferable mode, it is possible to reduce the clearance between the shutter unit and the second holding frame, thereby shortening the entire length of the collapsible lens barrel. 
     Although there is no particular limitation on a method for assembling the above-described collapsible lens barrel according to the present invention, this collapsible lens barrel can be assembled as follows, for example. That is, the method may include a first assembling step of assembling the first holding frame and the driving frame, a second assembling step of assembling the driving frame and the cam frame while allowing the mating members and the cam grooves to mate with each other, a third assembling step of moving the mating members of the driving frame to the wide portions of the cam grooves and a fourth assembling step of fixing a fixing frame to the cam frame. Here, the fixing frame is a frame on which a driving means for moving the first holding frame in the optical axis direction is mounted, though no driving means need be mounted yet in the fourth assembling step. In addition, all of the first to fourth assembling steps are carried out from the same direction. 
     With this method for assembling a collapsible lens barrel, since all the components are installed from the same direction, it is possible to reduce the number of assembling steps and lower the cost of the lens barrel. 
     Also, since the fourth assembling step fixes the fixing frame to the cam frame while the mating members are already moved to the wide portions of the cam grooves, the mating members and the cam grooves do not contact each other even when a compression load in the optical axis direction is applied to the barrel in the fourth assembling step, and problems such as deformation of the mating members or damages to the cam grooves are not caused. 
     Next, a first optical instrument according to the present invention is an optical instrument to which the above-described collapsible lens barrel according to the present invention is attached, and includes a storing system capable of storing an optical zooming factor at a time of turning off a power as an initial optical zooming factor information. In the case where the initial optical zooming factor information is stored in the storing system, the second lens group is moved to and stopped at an optical zooming factor position based on the initial optical zooming factor information when the power is turned on. 
     With this first optical instrument, when the power is turned off, a set value of the last zooming position used is stored automatically. Thus, the next time the power is turned on, it is possible to start capturing images at the same angle of view. 
     Further, a second optical instrument according to the present invention is an optical instrument to which the above-described collapsible lens barrel according to the present invention is attached, and includes an input system for inputting an optical zooming factor at a time of turning on a power, and a storing system for storing the optical zooming factor inputted from the input system as an initial optical zooming factor information. In the case where the initial optical zooming factor information is stored in the storing system, the second lens group is moved to and stopped at an optical zooming factor position based on the initial optical zooming factor information when the power is turned on. 
     With this second optical instrument, since the zooming factor at the time of turning on the power can be set freely by a user, it becomes possible to change the zooming factor depending on the scene or situation of image capturing. Consequently, it is less likely that a problem of missing a shutter chance is caused. 
     The following is a description of the present invention with reference to specific embodiments. However, the present invention is not limited to the embodiments described below. 
     First Embodiment 
     In the following, a collapsible lens barrel according to the first embodiment of the present invention will be described, with reference to  FIGS. 1 to 26 . 
     As shown in  FIG. 1 , an XYZ three-dimensional rectangular coordinate system is set, with an optical axis of a collapsible lens barrel  1  being a Z axis (an object side being a positive side). L 1  denotes a first group lens, L 2  denotes a second group lens that moves along an optical axis (Z axis) for zooming, L 3  denotes a third group lens for correcting an image blurring, and L 4  denotes a fourth group lens that moves along the optical axis for correcting an image plane fluctuation caused by zooming and for achieving focus. 
     A first group holding frame  2  holds the first group lens L 1  and is fixed to a tubular first group moving frame  3  with a screw or the like such that a center axis of the first group lens L 1  is parallel with the optical axis. One end of each of two guide poles (guide members)  4   a  and  4   b  parallel to the optical axis is fixed to this first group moving frame  3 . How to fix these guide poles  4  will be described later. 
     A second group moving frame  5  holds the second group lens L 2  and is supported by the above-mentioned two guide poles  4   a  and  4   b  so as to be slidable in the optical axis direction. Further, a feed screw  6   a  of a second group lens driving actuator  6  such as a stepping motor and a screw portion of a rack  7  provided in the second group moving frame  5  engage with each other, whereby the driving force of the second group lens driving actuator  6  causes the second, group moving frame  5  to move in the optical axis direction for zooming. 
     A third group frame  8  holds an image blurring correcting lens group L 3  (a third group lens) and constitutes an image blurring correcting device  31 , which will be described later. 
     A fourth group moving frame  9  is supported by two guide poles  11   a  and  11   b  that are parallel with the optical axis and interposed between the third group frame  8  and a master flange  10 , so that the fourth group moving frame  9  is slidable in the optical direction. Moreover, a feed screw  12   a  of a fourth group lens driving actuator  12  such as a stepping motor and a screw portion of a rack  13  provided in the fourth group moving frame  9  engage with each other, whereby the driving force of the fourth group lens driving actuator  12  causes the fourth group moving frame  9  to move in the optical axis direction for correcting the image plane fluctuation due to zooming and for achieving focus. 
     An imaging element (CCD)  14  is attached to the master flange  10 . 
     Herein, how to fix the guide poles  4   a  and  4   b  to the first group moving frame  3  will be described referring to  FIGS. 2A to 2C . Each of  FIGS. 2A to 2C  is a half sectional view showing one side alone with respect to the Z axis. Although the following description is directed to how to fix the guide pole  4   a  on one side with respect to the Z axis to a fixing portion  3   e , the same applies to the case of fixing the guide pole  4   b  on the other side to the fixing portion. 
       FIG. 2A  is a half sectional view showing a method for molding out of a resin the fixing portion  3   e  for fixing one end of the guide pole  4   a . As shown in  FIG. 2A , the fixing portion  3   e  for fixing one end of the guide pole  4   a  is formed on an inner surface of the first group moving frame  3  by molding. The fixing portion  3   e  substantially is parallel with the Z axis and formed of through holes  3   e   1  and  3   e   2  that are spaced from each other. These through holes  3   e   1  and  3   e   2  are molded out of a resin using three molding dies  29   a ,  29   b  and  29   c . The resin-molding is performed while keeping the columnar molding dies  29   a  and  29   b  in contact with both lateral surfaces of the molding die  29   c  having a substantially trapezoidal cross-section. Thereafter, the columnar molding dies  29   a  and  29   b  are pulled out in opposite directions A and B that are substantially parallel with the Z axis and the substantially trapezoidal molding die  29   c  is pulled out in a direction C approaching the Z axis, thereby obtaining the through holes  3   e   1  and  3   e   2 . At this time, the positions of the columnar molding dies  29   a  and  29   b  within a plane perpendicular to the Z axis are adjusted so that the guide pole  4   a  may be fixed in parallel with the Z axis when it is press-fitted into the through holes  3   e   1  and  3   e   2 . 
     Subsequently, as shown in  FIG. 2B , the guide pole  4   a  is press-fitted into the through holes  3   e   1  and  3   e   2  from the right side of the figure (the side of the imaging element  14 ). Although inner diameters d 1  and d 2  of the through holes  3   e   1  and  3   e   2  are set to be larger than an outer diameter D of the guide pole  4   a  by several micrometers, the guide pole  4   a  is fixed firmly by the two through holes  3   e   1  and  3   e   2  owing to a relative displacement or tilt of center axes  30   a  and  30   b  of the columnar molding dies  29   a  and  29   b  (see  FIG. 2A ) within the plane perpendicular to the Z axis. In this manner, the guide pole  4   a  is fixed to the first group moving frame  3  so as to be parallel with the Z axis. 
       FIG. 2C  is a half sectional view showing a conventional method for fixing the guide pole  4   a . The conventional fixing method is as follows. First, a fixing portion  3   d  formed of a single continuous through hole having an inner diameter d 3  that is sufficiently larger than the outer diameter D of the guide pole  4   a  is molded out of a resin. Next, the guide pole  4   a  is inserted into the fixing portion  3   d , pre-fixed with a jig intended for this purpose and fixed by filling an adhesive between the guide pole  4   a  and the fixing portion  3   d.    
     As described above, in the method for fixing the guide pole according to the present embodiment, the guide pole  4   a  can be fixed in parallel with the Z axis simply by press-fitting the guide pole  4   a  into the through holes  3   e   1  and  3   e   2 . Thus, unlike the conventional case, there is no need for a jig specifically for pre-fixing the guide pole  4   a  or an adhesive. Also, time and trouble in curing the adhesive are not needed. Consequently, it is possible to fix the guide pole  4   a  at a low cost and within a short time. Furthermore, simply by adjusting the positions of the molding dies  29   a  and  29   b  within the plane perpendicular to the Z axis, the guide pole  4   a  can be fixed precisely in parallel with the Z axis. 
     Next, how to support the guide poles  4   a  and  4   b  will be described referring to  FIG. 3 . 
     The third group frame  8  is provided with a supporting portion  8   a  (on a main axis side) and a supporting portion  8   b  (on a rotation stopper side). The guide poles  4   a  and  4   b  penetrate through the supporting portions  8   a  and  8   b , so that they are held in parallel with the optical axis. Since the guide poles  4   a  and  4   b  slide in the optical axis direction with respect to these two supporting portions  8   a  and  8   b , the first group lens L 1  held by the first group moving frame  3  fixed to one end of each of the guide poles  4   a  and  4   b  maintains its precision with respect to the image blurring correcting lens L 3  provided in the third group frame  8 . Furthermore, the guide poles  4   a  and  4   b  slidably penetrate through a supporting portion  5   a  (on the rotation stopper side) and a supporting portion  5   b  (on the main axis side) that are provided in the second group moving frame  5 , whereby the second group moving frame  5  is supported slidably in the optical axis direction by the guide poles  4   a  and  4   b . Consequently, the second group lens L 2  held by the second group moving frame  5  maintains its precision with respect to the image blurring correcting lens L 3  provided in the third group frame  8 . 
     Herein, the relationship among the first group lens L 1 , the second group lens L 2  and the third group lens L 3  mentioned above will be described referring to  FIGS. 4A to 4C . In these figures, arrows L 1   a  and L 2   a  indicate directions of center axes of the first group lens L 1  and the second group lens L 2 , respectively. 
       FIG. 4A  shows an ideal state of the three lens groups L 1 , L 2  and L 3 , in which the center axis L 1   a  of the first group lens L 1  and the center axis L 2   a  of the second group lens L 2  are parallel with the Z axis (which is the optical axis of the lens barrel and corresponds to the center axis of the third group lens L 3 ). 
       FIG. 4B  shows the case in which the first group lens L 1  and the second group lens L 2  are supported respectively by the cam pin  62   a  provided in the moving lens frame  62  and the cam pin  63   a  provided in the moving lens frame  63  shown in  FIG. 35  by a system similar to the conventional lens barrel shown in  FIG. 35 . In this case, because of a variation in precision of the cam pins  62   a  and  63   a  and the cam grooves  64  and  65 , the center axis L 1   a  of the first group lens L 1  and the center axis L 2   a  of the second group lens L 2  are neither parallel with each other nor parallel with the Z axis. Thus, it is likely that the optical performance will deteriorate. 
       FIG. 4C  shows the case according to the present embodiment. The first group lens L 1  and the second group lens L 2  are supported by the same guide poles  4   a  and  4   b . Therefore, even when the center axis L 1   a  of the first group lens L 1  and the center axis L 2   a  of the second group lens L 2  tilt with respect to the Z axis, the directions of these center axes Ma and L 2   a  always coincide with each other. In other words, since the first group lens L 1  and the second group lens L 2  always tilt in the same direction with respect to the image blurring correcting lens group L 3 , which has the greatest influence on the optical performance, it is possible to minimize the deterioration of the optical performance. 
     Next, the configuration of moving the first group lens L 1  in the optical axis direction will be described. 
     As shown in  FIG. 1 , a gear  15   a  is formed in a part of an inner peripheral surface of a substantially hollow cylindrical driving frame  15  on the side of the imaging element  14 . Also, three protruding portions  15   b  are formed at substantially 120° intervals on the inner peripheral surface thereof on the object side (the positive side of the Z axis). The protruding portions  15   b  mate with three circumferential groove portions  3   a  provided in an outer peripheral surface of the first group moving frame  3  on the side of the imaging element  14 , whereby the driving frame  15  can rotate relative to the first group moving frame  3  around the optical axis, and the driving frame  15  and the first group moving frame  3  move integrally in the optical axis direction. Furthermore, three cam pins  16   a ,  16   b  and  16   c  are press-fitted and fixed to the inner peripheral surface of the driving frame  15  at 120° intervals. 
     On an outer surface of a tubular cam frame  17 , three cam grooves  18   a ,  18   b  and  18   c  are formed at substantially 120° intervals.  FIG. 5  is a development of the outer peripheral surface of the cam frame  17 . The cam pins  16   a ,  16   b  and  16   c  of the driving frame  15  mate with the cam grooves  18   a ,  18   b  and  18   c  of the cam frame  17 , respectively. Each of the cam grooves  18   a ,  18   b  and  18   c  has a portion  19   a  that is substantially parallel with the circumferential direction of the cam frame  17  on the side of the imaging element  14  (the negative side of the Z axis), a portion  19   c  that is substantially parallel with the circumferential direction of the cam frame  17  on the object side (the positive side of the Z axis), a portion  19   b  that connects spirally the portion  19   a  and the portion  19   c  and a wide portion  19   d  whose width increases in the Z-axis direction at the end of the portion  19   a . When the cam pins  16   a ,  16   b  and  16   c  are located in the portion  19   a , the first group lens L 1  stops while being retracted toward the side of the imaging element  14  (a collapsed state). From this state, the driving frame  15  rotates around the optical axis, so that the cam pins  16   a ,  16   b  and  16   c  move through the portion  19   b  and reach the portion  19   c . When the cam pins  16   a ,  16   b  and  16   c  are located in the portion  19   c , the first group lens L 1  stops while being advanced toward the object side. 
     The cam grooves  18   a ,  18   b  and  18   c  are formed so as to have different widths along the optical axis direction depending on how far the driving frame  15  is advanced. This will be described referring to  FIG. 6 . 
       FIG. 6A  is a partially sectional view taken in a direction parallel with the Z axis, showing the cam pins  16   a ,  16   b  and  16   c  and the cam grooves  18   a ,  18   b  and  18   c  in the portions  19   a ,  19   b  and  19   c  of the cam grooves  18   a ,  18   b  and  18   c . As shown in the figure, in the portions  19   a ,  19   b  and  19   c , the cam grooves  18   a ,  18   b  and  18   c  are formed to be about several micrometers wider than the cam pins  16   a ,  16   b  and  16   c  along the Z-axis direction. As a result, the cam pins  16   a ,  16   b  and  16   c  can slide smoothly in the cam grooves  18   a ,  18   b  and  18   c.    
       FIG. 6B  is a partially sectional view taken in the direction parallel with the Z axis, showing the cam pins  16   a ,  16   b  and  16   c  and the cam grooves  18   a ,  18   b  and  18   c  in the wide portions  19   d  of the cam grooves  18   a ,  18   b  and  18   c . As shown in the figure, in the wide portions  19   d , the cam grooves  18   a ,  18   b  and  18   c  are formed to be wider than the cam pins  16   a ,  16   b  and  16   c  along the Z-axis direction so that the cam pins  16   a ,  16   b  and  16   c  do not contact the cam grooves  18   a ,  18   b  and  18   c  in the Z-axis direction. As a result, in the state where the driving frame  15  is retracted furthest to the image plane side (the state in  FIG. 22  described later), the cam pins  16   a ,  16   b  and  16   c  are located in the wide portions  19   d  and do not contact the cam grooves  18   a ,  18   b  and  18   c  as shown in  FIG. 6B . 
     On the outer peripheral surface of the cam frame  17 , a bearing portion  17   d  for holding driving gear shafts  20  at both ends of a spline-like driving gear  19  rotatably and a driving gear mounting portion (a recessed portion)  17   a  that is recessed in a hemicylindrical shape for avoiding an interference with the driving gear  19  are formed between the cam grooves  18   b  and  18   c , whereby the driving gear  19  is held rotatably on the outer peripheral surface of the cam frame  17 . The driving gear  19  transmits a driving force of a driving unit  21 , which will be described later, mounted to the master flange  10  to a gear portion  15   a  provided in the driving frame  15 . Accordingly, the rotation of the driving gear  19  causes the driving frame  15  to rotate around the optical axis. At this time, the cam pins  16   a ,  16   b  and  16   c  provided in the driving frame  15  move in the cam grooves  18   a ,  18   b  and  18   c  of the cam frame  17 , whereby the driving frame  15  moves also in the optical axis direction. Here, since the two guide poles  4   a  and  4   b  fixed to the first group moving frame  3  penetrate through the supporting portions  8   a  and  8   b  of the third group frame  8 , the rotation of the first group moving frame  3  around the optical axis is restricted, so that the first group moving frame  3  moves straight along the optical axis direction as the driving frame  15  moves along the optical axis direction. 
     The driving actuator  6  of the second group moving frame  5  is fixed to a mounting portion  17   b  of the cam frame  17 . Also, the driving actuator  12  of the fourth group moving frame  9  is fixed to a mounting portion  10   a  of the master flange  10 . The driving unit  21  for transmitting the driving force to the driving gear  19  includes a driving actuator  22  and a reduction gear unit  23  constituted by a plurality of gears and is fixed to a mounting portion  10   b  of the master flange  10 . 
     A shutter unit  24  is constituted by a diaphragm blade and a shutter blade that form a constant aperture diameter for controlling an exposure amount and an exposure time of the imaging element  14 . 
     A home position detecting sensor  25  for the second group moving frame  5  is a photo-detector sensor including a light-emitting element and a light-receiving element and detects the position of the second group moving frame  5  in the optical axis direction, namely, a home position (an absolute position) of the second group lens L 2 . As shown in  FIG. 7 , this home position detecting sensor  25  is mounted onto an mounting portion  17   c  of the cam frame  17  and detects the home position as follows: when the second group moving frame  5  moves to the position furthest to the side of the imaging element  14  (a −Z direction side) or the vicinity thereof, a blade  5   c  provided in the second group moving frame  5  passes in front of the home position detecting sensor  25  and blocks light, thereby allowing the home position to be detected. When the home position is detected, the second group moving frame  5  and the rack  7  mounted thereto are located furthest to the side of the imaging element  14  and close to the driving motor  6 . This state corresponds to that in  FIG. 22  described later. 
     A home position detecting sensor  26  for the fourth group moving frame  9  detects the position of the fourth group moving frame  9  in the optical axis direction, namely, a home position of the fourth group lens L 4 . A home position detecting sensor  27  for the driving frame  15  detects the position of the driving frame  15  in a rotational direction, namely, home positions of the first group moving frame  3  and the first group lens L 1  that move as one piece with the driving frame  15 . 
     The image blurring correcting device  31  moves the image blurring correcting lens group L 3  for correcting an image blurring at the time of image capturing in a pitching direction, which is a first direction (a Y direction) and a yawing direction, which is a second direction (an X direction). A first electromagnetic actuator  41   y  generates a driving force in the Y direction, and a second electromagnetic actuator  41   x  generates a driving force in the X direction, so that the image blurring correcting lens group L 3  is driven in the X and Y directions that are substantially perpendicular to the optical axis Z. 
     The image blurring correcting device  31  for correcting an image blurring using the image blurring correcting lens group L 3  will be described in detail, referring to  FIG. 8 . 
     The image blurring correcting lens group L 3  for correcting an image blurring at the time of image capturing is fixed to a pitching moving frame  32  that is movable in the pitching direction, which is the first direction (the Y direction) and the yawing direction, which is the second direction (the X direction). This pitching moving frame  32  has a bearing  32   a  on a −X direction side and a rotation stopper  32   b  on a +X direction side. A pitching shaft  33   a  parallel with the Y-axis direction is inserted into this bearing  32   a  and a pitching shaft  33   b  parallel with the Y-axis direction, which will be described later, is allowed to mate with the rotation stopper  32   b , so that the pitching moving frame  32  can slide in the first direction (Y direction). 
     A yawing moving frame  34  for moving the image blurring correcting lens group L 3  in the second direction (X direction) is provided on the −Z direction side with respect to the pitching moving frame  32 . The yawing moving frame  34  is provided with fixing portions  34   a  that fix both ends of the two pitching shafts  33   a  and  33   b  for sliding the above-described pitching moving frame  32  in the pitching direction (Y direction). Also, the yawing moving frame  34  has a bearing  34   b  on a +Y direction side and a yawing shaft  35   b  and a fixing portion  34   c  to which both ends of the yawing shaft  35   b  are press-fitted and fixed on a −Y direction side. A yawing shaft  35   a  parallel with the X direction is inserted into this bearing  34   b  and the yawing shaft  35   b  parallel with the X direction is allowed to mate with a rotation stopper portion  8   d  of the third group frame  8 , so that the yawing moving frame  34  can slide in the second direction (X direction). 
     The third group frame  8  provided on the −Z direction side with respect to the yawing moving frame  34  is provided with a fixing portion  8   c  that fixes the both ends of the yawing shaft  35   a  for sliding the above-described yawing moving frame  34  in the yawing direction (X direction) and the rotation stopper portion  8   d  with which the yawing shaft  35   b  mates. 
     A substantially L-shaped electric substrate  36  is attached to a −Z direction side surface of the pitching moving frame  32 . The electric substrate  36  is provided with a first coil  37   y  and a second coil  37   x  for driving the image blurring correcting lens group L 3  in the pitching direction and the yawing direction, respectively, and Hall elements  38   y  and  38   x  for detecting the position of the image blurring correcting lens group L 3  in the pitching direction and that in the yawing direction, respectively. These coils  37   y  and  37   x  are formed as layered coils in one piece with the electric substrate  36 . 
     Magnets  39   y  and  39   x  are two-pole magnetized on one side. These magnets  39   y  and  39   x  respectively are fixed to yokes  40   y  and  40   x  having a substantially U-shaped cross-section. The yoke  40   y  is fixed to a fitting portion  8   y  of the third group frame  8  by press-fitting from the Y direction. Similarly, the yoke  40   x  is fixed to a fitting portion  8   x  of the third group frame  8  by press-fitting from the X direction. 
     The first electromagnetic actuator  41   y  includes the first coil  37   y , the magnet  39   y  and the yoke  40   y . Similarly, the second electromagnetic actuator  41   x  includes the second coil  37   x , the magnet  39   x  and the yoke  40   x . The first electromagnetic actuator  41   y  constitutes a first driving means for driving the pitching moving frame  32  in the pitching direction (Y direction), which is the first direction, and the second electromagnetic actuator  41   x  constitutes a second driving means for driving the pitching moving frame  32  in the yawing direction (X direction), which is the second direction. 
     With the above-described configuration, when an electric current is passed through the first coil  37   y  of the electric substrate  36 , the magnet  39   y  and the yoke  40   y  generate an electromagnetic force along the pitching direction (Y direction), which is the first direction. In a similar manner, when an electric current is passed through the second coil  37   x  of the electric substrate  36 , the magnet  38   x  and the yoke  40   x  generate an electromagnetic force along the yawing direction (X direction), which is the second direction. In this way, the two electromagnetic actuators  41   y  and  41   x  drive the image blurring correcting lens group L 3  in the two directions, i.e., the X direction and the Y direction that are substantially perpendicular to the optical axis Z. 
     The following is a description of position detecting portions  42   y  and  42   x  for detecting the position of the image blurring correcting lens group L 3 . The Hall elements  38   y  and  38   x  for converting a magnetic flux into an electrical signal are positioned and fixed to the electric substrate  36 . The above-described magnets  39   y  and  39   x  of the electromagnetic actuators  41   y  and  41   x  also serve as detecting magnets. Accordingly, the Hall elements  38   y  and  38   x  and the magnets  39   y  and  39   x  constitute the position detecting portions  42   y  and  42   x . Here, referring to  FIG. 9 , the state of the magnetic fluxes of the magnets  39   x  and  39   y  will be described. The horizontal axis of the figure indicates a position in the pitching direction (the Y direction) or the yawing direction (the X direction) with the optical axis being the center, while the vertical axis indicates a magnetic flux density. The center of the horizontal axis corresponds to a boundary in the two-pole magnetized magnet  39   x  or  39   y , and the magnetic flux density is zero at this position. This position substantially coincides with the center of the optical axis of the image blurring correcting lens group L 3 . The Hall elements  38   y  and  38   x  move with respect to the magnets  39   y  and  39   x , whereby the magnetic flux density varies substantially linearly with the change in a displaced amount within the range that centers on the zero position of the displaced amount and is indicated by broken lines. Thus, by detecting the electric signal outputted from the Hall elements  38   y  and  38   x , it becomes possible to detect the position of the image blurring correcting lens group L 3  in the pitching direction (the Y direction) and the yawing direction (the X direction). 
     A flexible print cable  43  transmits signals between a circuit of a camera main body, which is not shown in the figure, and the coils  37   x  and  37   y  and the Hall elements  38   x  and  38   y  that are mounted on the electric substrate  36 . 
     The elements  32  to  43  described above constitute the image blurring correcting device  31 . 
     Now, the following description is directed to an operation of the image blurring correcting device  31  with reference to  FIG. 10 . 
     Image blurring is caused by displacement and vibrations of a camera due to hand movement. A camera incorporating the image blurring correcting device  31  detects these displacement and vibrations with two angular speed sensors  44   y  and  44   x  that are disposed so as to have a detecting direction of substantially 90°. Outputs of the angular speed sensors  44   y  and  44   x  are time-integrated. Subsequently, they are converted into an angle at which the camera main body has moved and then converted into target position information of the image blurring correcting lens group L 3 . In order to move the image blurring correcting lens group L 3  according to this target position information, a servo driving circuit  45  calculates a difference between the target position information and current positional information of the image blurring correcting lens group L 3  detected by the position detecting portions  42   y  and  42   x  and transmits a signal to the electromagnetic actuators  41   y  and  41   x . According to this signal, the electromagnetic actuators  41   y  and  41   x  drive the image blurring correcting lens group L 3 . 
     With respect to the driving in the pitching direction (Y direction), which is the first direction, the electromagnetic actuator  41   y  that has received an instruction from the servo driving circuit  45  passes an electric current through the first coil  37   y  via the flexible print cable  43  so as to generate a force in the pitching direction (Y direction), thereby driving the pitching moving frame  32  in the pitching direction (Y direction). 
     Also, with respect to the driving in the yawing direction (X direction), which is the second direction, the electromagnetic actuator  41   x  that has received an instruction from the servo driving circuit  45  passes an electric current through the second coil  37   x  via the flexible print cable  43  so as to generate a force in the yawing direction (X direction), thereby driving the yawing moving frame  34  and the pitching moving frame  32  mounted thereon in the yawing direction (X direction). 
     In this way, the image blurring correcting lens group L 3  can be moved as desired within a two-dimensional plane perpendicular to the optical axis by the pitching moving frame  32  and the yawing moving frame  34 , making it possible to correct the image blurring caused by camera shake. 
     Next, positions in the cam frame  17  to which the second group lens driving actuator  6 , the home position detecting sensor  25  and the driving gear  19  are mounted will be described. 
     As shown in  FIG. 11 , the second group lens driving actuator  6  is mounted to the mounting portion  17   b  of the cam frame  17 . The home position detecting sensor  25  of the second group lens L 2  is mounted onto the mounting portion  17   c  of the cam frame  17 , and the blade  5   c  provided in the second group moving frame  5  passes in front of the home position detecting sensor  25  and blocks light, thereby allowing the home position to be detected. Further, as described earlier, the driving gear  19  is mounted to the bearing portion  17   d  and the driving gear mounting portion (recessed portion)  17   a  of the cam frame  17 . 
       FIG. 5  shows the relationship of the three cam grooves  18   a ,  18   b  and  18   c  and the three mounting portions  17   a ,  17   b  and  17   c  when they are developed. In other words, the mounting portion  17   a  is provided between the cam grooves  18   b  and  18   c , the mounting portion  17   b  is provided between the cam grooves  18   a  and  18   b , and the mounting portion  17   c  is provided between the cam grooves  18   c  and  18   a . By providing the mounting portions  17   a ,  17   b  and  17   c  between these cam grooves in this way, it becomes possible to mount the driving gear  19 , the second group lens driving actuator  6  and the home position detecting sensor  25  to the cam frame  17  with the mounting portions  17   a ,  17   b  and  17   c  not interfering with the cam grooves  18   a ,  18   b  and  18   c.    
     An actuator driving circuit in an optical instrument (in this case, a DSC  80 ) including the collapsible lens barrel according to the present embodiment will be described with reference to  FIGS. 12 and 14 . 
     The DSC  80  includes a microcomputer  50  for controlling the DSC  80 . This microcomputer  50  drives and controls the first group lens driving actuator  22  via a driving control system  84  based on a signal from a power source button  81  provided in the DSC  80  and, after the home position detecting sensor  27  detects the home position of the first group lens L 1 , drives the first group lens L 1  to a predetermined position. Also, the microcomputer  50  drives and controls the second group lens driving actuator  6  via a driving control system  85  based on a signal from a zooming lever  82  and, after the home position detecting sensor  25  detects the home position of the second group lens L 2 , drives the second group lens L 2  to a predetermined zoom position. Furthermore, when a shutter button  83  is pressed down, the microcomputer  50  drives and controls the fourth group lens driving actuator  12  via a driving control system  86  and, after the home position detecting sensor  26  detects the home position of the fourth group lens L 4 , obtains focus. 
     Next, an image processing of the DSC  80  will be described referring to  FIGS. 13 and 14 . 
     The imaging element (CCD)  14  converts an image entering via the collapsible lens barrel  1  into an electric signal. An imaging element driving control system  143  controls the operation of the imaging element  14 . An analog signal processing system  144  performs an analog signal processing such as a gamma processing with respect to a video signal obtained by the imaging element  14 . An A/D converting system  145  converts the analog video signal outputted from the analog signal processing system  144  into a digital signal. A digital signal processing system  146  performs a digital signal processing such as a noise removal and an edge enhancement with respect to the video signal that has been converted into the digital signal by the A/D converting system  145 . A frame memory  147  temporarily stores an image signal that has been processed by the digital signal processing system  146 . An image recording control system  148  controls writing of the image stored temporarily in the frame memory  147  into an image recording system  149  such as an internal memory or a recording medium. According to a signal from an image display control system  150 , the captured image recorded in the image recording system  149  is displayed via a frame memory  151  on an image display system  152  such as a liquid crystal monitor mounted on the DSC  80 . 
     The collapsible lens barrel  1  constituted as above can be assembled by following steps S 1  to S 6  shown in  FIG. 15 . In the following, each of these steps will be described sequentially. 
     (First Assembling Step S 1 ) 
     As shown in  FIG. 16 , the guide poles  4   a  and  4   b  fixed to the first group moving frame  3  respectively are inserted into the supporting portions  5   a  and  5   b  of the second group moving frame  5 . Further, the protruding portions  15   b  provided in the driving frame  15  are allowed to mate with a groove portion  3   a  provided in the first group moving frame  3 , and then the driving frame  15  is rotated in a direction indicated by an arrow. 
     (Second Assembling Step S 2 ) 
     As shown in  FIG. 17 , the cam pins  16   a ,  16   b  and  16   c  protruding from an inner wall surface of the driving frame  15  are allowed to mate with the cam grooves  18   a ,  18   b  and  18   c  provided on the outer peripheral surface of the cam frame  17 . 
     (Third Assembling Step S 3 ) 
     As shown in  FIG. 18 , the driving frame  15  is rotated in a direction indicated by an arrow. Since the cam pins  16   a ,  16   b  and  16   c  and the cam grooves  18   a ,  18   b  and  18   c  mate with each other, the rotation of the driving frame  15  causes the cam frame  17  to move in the Z-axis direction and be received in the driving frame  15 . The rotation of the driving frame  15  moves the cam pins  16   a ,  16   b  and  16   c  to the positions of the wide portions  19   d  at terminal ends of the cam grooves  18   a ,  18   b  and  18   c . Next, the guide poles  4   a  and  4   b  are inserted into the supporting portions  8   a  and  8   b  of the third group frame  8  on which the image blurring correcting device  31  is mounted. 
     (Fourth Assembling Step S 4 ) 
     As shown in  FIG. 19 , after guide poles  11   a  and  11   b  and the fourth group moving frame  9 , which are not shown in the figure, are inserted behind the third group frame  8 , the master flange  10  is incorporated. Then, from behind the master flange  10 , the cam frame  17 , the third group frame  8  and the master flange  10  are fixed with three screws  135 . 
     Referring to  FIG. 20 , how the cam pins  16   a ,  16   b  and  16   c  mate with the cam grooves  18   a ,  18   b  and  18   c  in the fourth assembling step will be described. The lens barrel  1  is fastened with screws while keeping an end surface  3   b  on the object side of the first group moving frame  3  in contact with a placement surface  180  such that the first group lens L 1  faces downward. When fastening with screws, a downward load F acts on the cam frame  17 . At this time, the cam pins  16   a ,  16   b  and  16   c  are located in the wide portions  19   d  at terminal ends of the cam grooves  18   a ,  18   b  and  18   c . Therefore, even under the load F, the cam pins  16   a ,  16   b  and  16   c  do not contact the cam grooves  18   a ,  18   b  and  18   c . The load F is supported by the contact between an image-plane-side end surface  3   c  of a ring-shaped portion formed so as to protrude from the inner surface of the first group moving frame  3  and an object-side end surface  17   e  of the cam frame  17 . Consequently, the load F does not act on the cam pins  16   a ,  16   b  and  16   c  or the cam grooves  18   a ,  18   b  and  18   c  at the time of fastening with screws so as to cause problems such as deformation of the cam pins  16   a ,  16   b  and  16   c  or damage to the cam grooves  18   a ,  18   b  and  18   c.    
     (Fifth Assembling Step S 5 ) 
     The second group lens driving actuator  6  is fixed to the cam frame  17 , and the first group lens driving actuator  22  and the fourth group lens driving actuator  12  are fixed to the master flange  10 . 
     (Sixth Assembling Step S 6 ) 
     As shown in  FIG. 21 , the flexible print cable  43  for the image blurring correcting device  31  and a flexible print cable  138  for the shutter unit  24  are soldered to the electric substrate (a flexible printed circuit board)  36  attached to the master flange  10  so that soldering portions  36   a  and  43   a  are fixed to each other and soldering portions  36   b  and  138   a  are fixed to each other. Then, the imaging element  14  is fixed to a fixing portion  10   c  of the master flange  10 . 
     In the above manner, the assembly of the collapsible lens barrel  1  is completed. 
     In the following, the operation of the collapsible lens barrel  1  constituted as above will be explained. 
     First, in the operation of the collapsible lens barrel  1 , an operation of shifting from a non-capturing (non-use) state shown in  FIG. 22  via a state shown in  FIG. 23  to a capturing (wide angle end) state shown in  FIG. 24  will be described. 
     In the non-capturing state shown in  FIG. 22 , turning on a power source switch or the like of the DSC  80  starts a state ready for image capturing. First, the first group lens driving actuator  22  for driving the first group lens L 1  rotates, so that the driving gear  19  is rotated via the reduction gear unit  23 . The rotation of the driving gear  19  causes the driving frame  15 , which engages with the driving gear  19 , both to rotate around the optical axis and to move in the cam grooves  18   a ,  18   b  and  18   c  along the optical axis. After the home position detecting sensor  27  is initialized, the driving frame  15  moves in an object direction (the Z-axis direction), whereby the first group moving frame  3  also moves in the object direction. Then, when a rotation amount detecting sensor, which is not shown in the figure, detects that the first group lens driving actuator  22  has moved by a predetermined rotation amount, the first group moving frame  3  moves to a predetermined position, and then the rotation of the first group lens driving actuator  22  stops. At this stop position, the cam pins  16   a ,  16   b  and  16   c  already have reached the portion  19   c  that is substantially parallel with the circumferential direction of the cam frame  17  in the development of the cam grooves in  FIG. 5 .  FIG. 23  shows this state. 
     Next, in order to move the second group lens L 2  serving as a zooming lens to a predetermined position, the second group lens driving actuator  6  rotates and drives the rack  7  via the feed screw  6   a , so that the second group moving frame  5  starts moving along the Z axis. 
     First, the description is directed to the case where no initial position of a zooming factor after turning on the power source is set in the microcomputer  50  in the DSC  80 . 
     After initializing the home position detecting sensor  25 , the second group moving frame  5  moves in the object direction and stops at the wide angle end shown in  FIG. 24 , so that the camera main body is now able to capture an image. 
     On the other hand, in the case where the initial position of the zooming factor after turning on the power source is set to the vicinity of a telephoto end in the microcomputer  50  in the DSC  80 , after initializing the home position detecting sensor  25 , the second group moving frame  5  stops in the vicinity of the telephoto end shown in  FIG. 23 , so that the DSC  80  becomes ready for image capturing. If the shutter button  83  is pressed down in this state, the image to be captured shows a scaled-up subject as shown in  FIG. 26A . 
     Further, in the case where the initial position of the zooming factor after turning on the power source is set to substantially at the mid point between the telephoto end and the wide angle end in the microcomputer  50  in the DSC  80 , after initializing the home position detecting sensor  25 , the second group moving frame  5  stops in the vicinity of the mid point shown in  FIG. 25 , so that the DSC  80  becomes ready for image capturing. If the shutter button  83  is pressed down in this state, the image to be captured is as shown in  FIG. 26B . 
     In the case where the initial position of the zooming factor after turning on the power source is set to the vicinity of the wide angle end in the microcomputer  50  in the DSC  80 , after initializing the home position detecting sensor  25 , the second group moving frame  5  stops in the vicinity of the wide angle end shown in  FIG. 24 , so that the DSC  80  becomes ready for image capturing. If the shutter button  83  is pressed down in this state, the image to be captured is as shown in  FIG. 26C . 
     In any of the above cases, the first group moving frame  3  and the second group moving frame  5  move to a predetermined position while being supported by the same guide poles  4   a  and  4   b  held by the supporting portions  8   a  and  8   b  in the third group frame  8 . Accordingly, even when the first group lens L 1  and the second group lens L 2  tilt with respect to the optical axis, a certain optical performance can be secured because the directions of the tilt are the same with respect to the image blurring correcting lens group L 3 . 
     At the time of actual image capturing, the second group lens driving actuator  6  and the fourth group lens driving actuator  12  respectively perform a zooming operation and an operation of correcting an image plane fluctuation due to zooming and achieving focus. When zooming, an image is captured at the wide angle end in the state shown in  FIG. 24  and at the telephoto end in the state shown in  FIG. 23  in which the second group lens L 2  is moved in a −Z direction (at the end on the imaging element  14  side). Thus, it is possible to capture an image at an arbitrary position from the wide angle end to the telephoto end. 
     Next, an operation of shifting from each of the capturing states shown in  FIGS. 23 ,  24  and  25  to the non-capturing state shown in  FIG. 22  will be described. 
     In each of the capturing states, when the power source button  81  in the DSC  80  is switched off, the image capturing ends. The second group moving frame  5  first is moved to the side of the imaging element  14  by the second group lens driving actuator  6 , thus creating the state shown in  FIG. 23 . Subsequently, the first group lens driving actuator  22  rotates, thereby rotating the driving gear  19  in a direction opposite to the above via the reduction gear unit  23 . The rotation of the driving gear  19  causes the driving frame  15 , which is in engagement with the driving gear  19 , to rotate around the optical axis, and at the same time, the cam grooves  18   a ,  18   b  and  18   c  allow the driving frame  15  to move in the direction of the imaging element  14 , so that the first group moving frame  3  also moves. Thereafter, when the home position detecting sensor  27  detects the rotation of the driving frame  15 , the first group moving frame  3  moves to a predetermined position, and then the rotation of the first group lens driving actuator  22  stops. At this stop position, the cam pins  16   a ,  16   b  and  16   c  already have reached the portion  19   c  that is substantially parallel with the circumferential direction of the cam frame  17  in the development of the cam grooves in  FIG. 5 . In this way, a collapsed state shown in  FIG. 22  is achieved in which the length is reduced by a length C compared with the capturing state. 
     Here, in a collapsing operation of changing the length of the collapsible lens barrel  1  along the optical axis direction, the first group lens driving actuator  22  for driving the first group lens L 1  is used. In a zooming operation, the second group lens driving actuator  6  is used alone. Thus, since the zooming operation in an actual image capturing is carried out with the first group lens L 1  being advanced, there is no need to operate the first group lens driving actuator  22 , and the second group lens driving actuator  6  alone is driven to move the second group lens L 2  to a predetermined position between  FIG. 23  and  FIG. 24  for zooming. Accordingly, when conducting image capturing such as a zooming operation, it is not necessary to expand and retract a barrel according to a zooming factor unlike the conventional collapsible lens barrel shown in  FIG. 35 . In the conventional collapsible lens barrel shown in  FIG. 35 , in the zooming operation, one driving actuator  69  was rotated, and the cam barrel  61  was rotated via the reduction gear train  68 , thereby driving the moving lens frames  62  and  63  at the same time, leading to a low zooming speed and a large driving noise. On the other hand, in the collapsible lens barrel  1  according to the present invention, a stepping motor is used as the second group lens driving actuator  6 , and the second group moving frame  5  directly is driven via the feed screw  6   a  attached to this stepping motor, achieving a fast feed speed and a small operation noise. In this manner, even a collapsible lens barrel can achieve a faster zooming speed and a lower zooming noise. Thus, a user can change the angle of view instantly, making it possible to chase a subject, capture a moving image, etc., which have been difficult in conventional DSCs. 
     In the present embodiment, in order to move the second group lens L 2  for zooming to a position of a predetermined zooming factor after turning on the power, the first group lens L 1  has to be moved in advance from a position in the collapsed state to a predetermined position, and a certain time period is required therefor. However, instead of driving a plurality of the moving lens frames  62  and  63  by a single driving actuator  6  as in the conventional collapsible lens barrel shown in  FIG. 35 , the first group lens L 1  and the second group lens L 2  are driven by individual actuators. Thus, one actuator needs only a small driving force, and a driving speed (the number of revolutions of the actuator) can be increased, thus making it possible to shorten an entire time period. 
     As described above, according to the first embodiment, since the actuator  6  specifically for zooming can be attached without interfering with the cam grooves  18   a ,  18   b  and  18   c  of the cam frame  17 , even a collapsible lens barrel can achieve a faster zooming speed and a lower zooming noise. Thus, a user can change the angle of view instantly, making it possible to chase a subject, capture a moving image, etc., which have been difficult with conventional DSCs. 
     According to the present embodiment, the first group lens L 1  and the second group lens L 2  are driven individually. In other words, only the second group lens L 2  can be driven for zooming. Thus, it is possible to achieve a faster zooming speed and a lower zooming noise. Therefore, in a DSC in which sound is recorded using a microphone while capturing a moving image, for example, a level of recording a zooming noise, which is not preferable in itself, is lowered, thus improving a commercial value considerably. 
     Further, by disposing not only the actuator  6  for zooming but also the home position detecting sensor  25  and the driving gear  19  in a portion in the cam frame  17  where the cam grooves  18   a ,  18   b  and  18   c  are not formed, it becomes possible to achieve a high-density mounting that disposes all the components in the single cam frame  17 , thus miniaturizing the lens barrel, reducing the number of components thanks to a simplified configuration and lowering costs. 
     Also, in the DSC incorporating a lens ready for a high zooming factor, the home position detecting sensor  25  is disposed so that an absolute position of the lens group. L 2  for zooming can be detected when this lens is at a collapsed position, in particular, a telephoto end position or in the vicinity thereof, thus making it possible to move the lens group L 2  after turning on the power instantly to the vicinity of the telephoto end position not through the wide angle end. This produces a notable effect of preventing a user from missing an important shutter chance for scaled-up images. 
     Further, the structure in which the first group lens L 1  and the second group lens L 2  tilt at least the same direction with respect to the image blurring correcting lens L 3  allows the entire length in non use to be reduced while minimizing the reduction of optical performance. 
     Furthermore, the guide poles  4   a  and  4   b  are fixed by being press-fitted into two through holes penetrating in the optical axis direction that are spaced from each other, whereby the number of assembling steps can be reduced compared with the conventional system of pre-fixing the guide pole with a jig intended for this purpose and adhering it. Also, the relative positions of the molding dies  29   a  and  29   b  forming the through holes within the plane perpendicular to the Z axis are adjusted, so that the orientations of the guide poles  4   a  and  4   b  can be adjusted easily, making it possible to fix the guide poles  4   a  and  4   b  in parallel with the optical axis. 
     Moreover, in the collapsible lens barrel including the tubular cam frame  17  and the substantially hollow cylindrical driving frame  15  provided with the cam pins  16   a ,  16   b  and  16   c , the wide portions  19   d  are formed in the cam grooves so that the cam pins  16   a ,  16   b  and  16   c  do not contact the cam grooves  18   a ,  18   b  and  18   c  in the collapsed state. Consequently, even when a compression load in the optical axis direction is applied at the time of the assembly in the collapsed state, problems such as deformation of the cam pins  16   a ,  16   b  and  16   c  or damages to the cam grooves  18   a ,  18   b  and  18   c  are not caused. 
     Further, even in the collapsible lens barrel using the cam frame  17  whose assembly is complicated, by enabling the components to be installed and fastened with screws from one direction, it is possible to reduce the number of assembling steps and simplify the assembling work compared with a conventional method of assembling from both sides. 
     Although the first group frame  2  provided with the first group lens L 1  and the first group moving frame  3  are different members in the present embodiment, they also may be formed as one piece to which the guide poles may be fixed. 
     Additionally, in the image blurring correcting device  31  described in the present embodiment, the position detecting means using the Hall elements also may be provided in other places. Alternatively, a magnetic position detecting means may be replaced by an optical position detecting means including a light-emitting element and a light-receiving element, for example. 
     Although the third group lens L 3  can be moved in a direction perpendicular to the optical axis direction using the image blurring correcting device  31 , it is needless to say that even a general lens barrel in which the third group lens L 3  is fixed to the third group frame  8  and no image blurring correcting device is mounted can achieve a similar effect. 
     Although the first group moving frame  3  and the second group moving frame  5  are moved sequentially in the present embodiment, they also may be moved at the same time for shortening the time for expanding or collapsing. For example, when expanding the barrel, after the first group moving frame  3  starts moving and before it stops at a predetermined position, it may be possible to start moving the second group moving frame  5  from the collapsed position and stop it at the wide angle end position (or a desired zooming position). Also, when collapsing the barrel, after the second group moving frame  5  starts moving and before it stops at a predetermined position, it may be possible to start moving the first group moving frame  3  and stop it at the collapsed position. 
     Moreover, although the present embodiment has illustrated an example in which the actuator  6  for driving the second group lens L 2 , the position detecting sensor  25  of the second group lens L 2  and the driving gear  19  for rotating the driving frame  15  are attached to the cam frame  17 , the present invention is not limited to this configuration. Only the actuator  6  and the detecting sensor  25  or only the actuator  6  and the driving gear  19  may be attached to the cam frame  17 . 
     Second Embodiment 
     Hereinafter, a collapsible lens barrel in the second embodiment of the present invention will be described referring to  FIG. 27 .  FIG. 27  is a sectional view showing a cam frame  17  in the collapsible lens barrel of the present embodiment. The lens barrel of the present embodiment is similar to that in the first embodiment except for what is described below. The same elements as those in the first embodiment are given the same reference signs, and the description thereof will be omitted. 
       FIG. 27  is a sectional view of the cam frame  17  taken along a plane perpendicular to the optical axis. On an outer peripheral surface of the cam frame  17 , three cam grooves  18   a ,  18   b  and  18   c , a mounting portion  17   a  for a driving gear  19 , a mounting portion  17   b  for a driving actuator  6  of a second group moving frame  5  and a mounting portion  17   c  for a home position detecting sensor  25  of a second group lens L 2  are provided alternately so as not to interfere with each other. When molding this cam frame  17  out of a resin, it is necessary to combine a plurality of molding die parts to make one molding die, inject a resin into cavities in the molding die and, after resin-molding, pull out each of the molding die parts in a predetermined direction so as to obtain a molded article. 
     Generally conceivable molding dies and molding method are as follows. Since the three cam grooves  18   a ,  18   b  and  18   c  are provided at substantially 120° intervals, three molding die parts for molding the cam grooves  18   a ,  18   b  and  18   c  respectively are used, and after the resin-molding, these molding die parts are pulled out radially in three directions of A, B and C at 120° apart. Also, three molding die parts for molding the three mounting portions  17   b ,  17   c  and  17   a  respectively are used, and after the resin-molding, these molding die parts are pulled out radially in three different directions of D, E and F. Thus, in this method, it is necessary that at least six molding the parts respectively corresponding to the three cam grooves  18   a ,  18   b  and  18   c  and the mounting portions  17   a ,  17   b  and  17   c  should be used for resin molding and then pulled out radially in six different directions, thereby molding the cam frame  17 . 
     In the present embodiment, the directions A and F for pulling out the molding die parts are made parallel with each other, thereby molding the cam groove  18   a  and the mounting portion  17   c  of the home position detecting sensor  25  of the second group lens L 2  with one molding die part. This reduces the total number of the molding die parts. 
     As described above, according to the second embodiment, since the number of the molding die parts can be reduced when molding the cam frame  17 , it is possible to suppress the cost of molding dies. This makes it possible to reduce the cost of the collapsible lens barrel. 
     Although the above description has been directed to an example of molding the cam groove  18   a  and the mounting portion  17   c  with one molding die part, the present invention is not limited to this. By molding at least one of the three cam grooves  18   a ,  18   b  and  18   c  and at least one of the mounting portions  17   a ,  17   b  and  17   c  with a common molding die part, the effect described above can be obtained. 
     Third Embodiment 
     Next, a collapsible lens barrel in the third embodiment of the present invention will be described referring to  FIG. 28 .  FIG. 28  is a side sectional view showing an arrangement of a front end  6   b  of a second group lens driving actuator  6  in the collapsible lens barrel according to the present embodiment. The lens barrel of the present embodiment is similar to that in the first embodiment except for what is described below. The same elements as those in the first embodiment are given the same reference signs, and the description thereof will be omitted. 
       FIG. 28  shows a non-capturing state similar to  FIG. 22  in the first embodiment. Unlike the first embodiment, in the present embodiment, a gap  55  is provided between the first group lens L 1  and the tubular first group moving frame  3  in a direction perpendicular to the optical axis, and the front end  6   b  of the second group lens driving actuator  6  enters this gap  55  in the collapsed state. 
     In the configuration where the front end  6   b  of the second group lens driving actuator  6  is not made to enter this gap  55 , it is necessary for the second group lens driving actuator  6  to be disposed outside the first group moving frame  3  as in  FIG. 22  of the first embodiment or that the second group lens driving actuator  6  should be disposed inside the first group moving frame  3  and at a position on a −Z direction side (on the side of an imaging element  14 ). However, in the case where the second group lens driving actuator  6  is disposed outside the first group moving frame  3 , an outer diameter of the collapsible lens barrel increases. In the case where the second group lens driving actuator  6  is disposed inside the first group moving frame  3  and at the position shifted to the −Z direction side, the length L from the front end of the first group lens L 1  to an end portion of the second group lens driving actuator  6  on the side of the imaging element  14  increases. As a result, the entire length of the lens barrel  1  extends in the collapsed state. In contrast, according to the present embodiment, the outer diameter and the length L can be reduced. 
     As described above, in accordance with the third embodiment, with the configuration in which the gap  55  is provided between the first group lens L 1  and the first group moving frame  3  in the direction perpendicular to the optical axis and the front end  6   b  of the second group lens driving actuator  6  enters the gap  55  in the collapsed state, it becomes possible to reduce the outer diameter of the lens barrel  1  and shorten the entire length of the lens barrel  1  in the collapsed state. 
     Fourth Embodiment 
     In the following, an optical instrument using a collapsible lens barrel in the fourth embodiment of the present invention will be described referring to  FIG. 29 .  FIG. 29  is a block diagram showing a configuration of an actuator driving circuit in the optical instrument in the present embodiment. The optical instrument of the present embodiment is similar to that in the first embodiment except for what is described below. The same elements as those in the first embodiment are given the same reference signs, and the description thereof will be omitted. 
     The actuator driving circuit in the present embodiment shown in  FIG. 29  is obtained by adding a zoom initial position storing system  53  to the actuator driving circuit in the first embodiment shown in  FIG. 12 . This zoom initial position storing system  53  is configured by a nonvolatile memory such as EEPROM or the like and stores as initial optical zooming factor information a zoom position immediately before turning off the power after the completion of image capturing using the DSC  80 . In other words, when the power source button  81  is turned off in any of the capturing states shown in  FIGS. 23 ,  24  and  25 , the zooming position immediately before that is stored in the zoom initial position storing system  53 . 
     Thereafter, when the power source button  81  of the DSC  80  is turned on, the first group lens driving actuator  22  for driving the first group lens L 1  rotates and shifts to the state shown in  FIG. 23 . Next, the microcomputer  50  reads out the zooming position stored in the zoom initial position storing system  53  and, according to the read-out zoom initial position stored value, moves the second group lens L 2  serving as a zooming lens to a predetermined position. For example, if the zoom initial position stored value corresponds to the state at the wide angle end, the second group moving frame  5  is moved to the state shown in  FIG. 24  so as to achieve a state ready for image capturing. 
     As described above, according to the present embodiment, even after turning off the power of the DSC incorporating a lens ready for a high zooming factor, a set value of the zooming position before turning off is stored automatically. This is very useful for capturing images many times at the same angle of view. 
     It should be noted that a resetting function in which the initial value of the zooming position automatically can be set to, for example, a telephoto end when a user presses down a reset button (not shown) in the DSC also may be provided. 
     Fifth Embodiment 
     In the following, an optical instrument using a collapsible lens barrel in the fifth embodiment of the present invention will be described referring to  FIG. 30  and  FIG. 31 .  FIG. 30  is a block diagram showing a configuration of an actuator driving circuit in the optical instrument in the present embodiment, while  FIG. 31  is a schematic view showing an operating panel in a zoom initial position selecting system. The optical instrument of the present embodiment is similar to that in the first embodiment except for what is described below. The same elements as those in the first embodiment are given the same reference signs, and the description thereof will be omitted. 
     The actuator driving circuit in the present embodiment shown in  FIG. 30  is obtained by adding a zoom initial position selecting system  54  to the actuator driving circuit in the fourth embodiment shown in  FIG. 29 . The operating panel in the zoom initial position selecting system  54  is provided in an operating portion on an outer surface of a DSC  80  (see  FIG. 14 ), and its external appearance includes arrow keys  54   a  for selecting a zooming position and a display portion  54   b  for displaying a current zooming position by illumination as shown in  FIG. 31 . A user selects a zooming position by pressing down the arrow keys  54   a , thereby selecting freely the zooming positions after turning on the power. The selected zooming position is stored in the zoom initial position storing system  53  as the initial optical zooming factor information. 
     When the power source button  81  is pressed down to turn on the power, the first group lens L 1  moves to the position shown in  FIG. 23  similarly to the fourth embodiment described above. Subsequently, the microcomputer  50  reads out the zooming position of the zoom initial position storing system  53  set by the zoom initial position selecting system  54  and, based on this, the second group lens L 2  moves and automatically is set to the zooming position preset by a user. 
     As described above, in accordance with the present embodiment, the zooming factor at the time of turning on the power can be set freely by a user, thereby making it possible to change the zooming factor depending on the scene or situation of image capturing. Consequently, it is less likely that a problem of missing a shutter chance is caused. 
     It should be noted that the zoom initial position to be selected may be designed to be set continuously in the range from the wide angle end to the telephoto end. 
     Sixth Embodiment 
     Next, a collapsible lens barrel according to the sixth embodiment of the present invention will be described with reference to  FIGS. 32 and 33 .  FIG. 32  is an exploded perspective view for describing a positional relationship between the driving gear  19  and the image blurring correcting device  31  in the collapsible lens barrel in the present embodiment, while FIG.  33  is a front view, seen from a direction parallel with the optical axis, showing the driving gear  19  and the image blurring correcting device  31  in the collapsible lens barrel in the present embodiment. The lens barrel of the present embodiment is similar to that in the first embodiment except for what is described below. The same elements as those in the first embodiment are given the same reference signs, and the description thereof will be omitted. 
     Referring to  FIG. 32 , a mounting position of the driving gear  19  will be described. 
     The driving gear  19  transmits a driving force of the reduction gear unit  21  attached to the master flange  10  to the driving frame  15  and needs to have a predetermined length along the optical axis direction for the moving frame  15  to move in the optical axis direction. Also, in order to move the moving frame  15  in the optical axis direction, the cam frame  17  is provided with the cam grooves  18   a ,  18   b  and  18   c , and it is necessary that the driving gear  19  should be attached to the cam frame  17  so as not to interfere with the cam grooves. Furthermore, the image blurring correcting device  31  is provided between the master flange  10  and the cam frame  17 . Due to such restrictions, the driving gear  19  is disposed between the two electromagnetic actuators  41   y  and  41   x  that are placed at positions at 90° to the optical axis so as not to interfere with the image blurring correcting device  31 . As a result, the cam frame  17  is provided with the driving gear  19  and further with the cam grooves  18   b  and  18   c  on both sides thereof, so that in the collapsible lens barrel  1  having the image blurring correcting device  31 , the driving gear  19  can be disposed near to the center of the optical axis without causing interference between the image blurring correcting device  31  and the driving gear  19  for collapsing. 
     Furthermore, as shown in  FIG. 33 , the driving gear  19  is disposed between the two electromagnetic actuators  41   y  and  41   x , so that the third group frame  8  on which the image blurring correcting device  31  is mounted fits substantially within a circle of the cam frame  17  indicated by a double-dashed line. Accordingly, the diameter of the collapsible lens barrel  1  can be reduced. 
     As described above, according to the present embodiment, by providing the driving gear  19  for collapsing between the two actuators  41   y  and  41   x  for correcting image blurring, the driving gear  19  can be brought near to the center of the optical axis without causing interference with the cam grooves. Consequently, it is possible both to shorten the entire length of the lens barrel and to reduce the diameter thereof. 
     Seventh Embodiment 
     Now, a collapsible lens barrel according to the seventh embodiment of the present invention will be described referring to  FIG. 34 .  FIG. 34  is an exploded perspective view for describing a positional relationship between the shutter unit  24  and the second group moving frame  5  in the collapsible lens barrel in the present embodiment. The lens barrel of the present embodiment is similar to that in the first embodiment except for what is described below. The same elements as those in the first embodiment are given the same reference signs, and the description thereof will be omitted. 
     Referring to  FIG. 34 , where to place driving actuators  24   a  and  24   b  of the shutter unit  24  will be described. 
     The shutter unit  24  includes the diaphragm blade and the shutter blade that form a constant aperture diameter for controlling an exposure amount and an exposure time of the imaging element  14 . The diaphragm blade is driven by the driving actuator  24   a , and the shutter blade is driven by the driving actuator  24   b . The driving actuators  24   a  and  24   b  are provided so as to protrude from the surface of the shutter unit  24  opposite to the image blurring correcting device  31 , that is, the surface on the side of the second group moving frame  5 . In the surface of the second group moving frame  5  on the side of the shutter unit  24 , recessed portions  5   d  and  5   e  are provided at two positions corresponding to the driving actuators  24   a  and  24   b . As a result, when the distance between the second group moving frame  5  and the shutter unit  24  decreases, the driving actuators  24   a  and  24   b  partially enter the recessed portions  5   d  and  5   e  of the second group moving frame  5 , respectively, thereby preventing the interference between the driving actuators  24   a  and  24   b  and the second group moving frame  5 . 
     Therefore, for example, when the clearance between the second group lens L 2  and the image blurring correcting lens group L 3  decreases at the telephoto end shown in  FIG. 23 , a part of the driving actuator  24   a  of the shutter unit  24  enters the recessed portion  5   d  of the second group moving frame  5 . 
     As described above, in accordance with the present embodiment, the driving actuators  24   a  and  24   b  of the shutter unit  24  are provided on the surface of the shutter unit  24  on the side of the second group moving frame  5 , and the second group moving frame  5  is provided with the recessed portions that the driving actuators  24   a  and  24   b  partially enter. This can reduce the clearance between the shutter unit  24  and the second group moving frame  5 , thereby shortening the entire length of the collapsible lens barrel. 
     The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The embodiments disclosed in this application are to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, all changes that come within the meaning and range of equivalency of the claims are intended to be embraced therein.