Abstract:
A guide bar used in a video lens barrel in the related art has problems of deterioration in supporting accuracy of the lens retaining frame, high manufacturing cost, and upsizing of the lens barrel. Also, in a cam pin type lens barrel, how the lens retaining frame is supported by the cam pins may not be clear. Therefore, by providing a plurality of guiding members on the inner surface of the fixed barrel of the lens barrel, and allowing a plurality of engaging portions on the lens retaining frames to engage the guiding members, the lens retaining frames are supported so as to be capable of moving in the direction of the optical axis. By differentiating the length of engagement of the respective engaging portions, the roles of the respective engaging portions on the lens retaining frames for supporting the lens unit in a space are clarified.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to a lens supporting mechanism in a lens barrel in a video camera or the like.  
         [0003]     2. Description of the Related Art  
         [0004]     There is a method of supporting a lens barrel in which a lens retaining frame is supported in a space with a thin shaft called “rod” or “guide bar” (for example, see Patent Document 1). There is also another method of supporting a lens barrel in the related art in which the lens retaining frame is supported in a space using three pins (cam followers) and cam grooves (for example, see Patent Document 2).  
         [0005]     As described in a first embodiment of the lens barrel (pp. 3, FIGS. 1, 2 and 3), there is a video lens barrel in which a lens retaining frame (movable lens frames 5 and 6) is supported with two guide bars3 and 4) fixed at both ends to a fixed barrel 1 and a fixed barrel 2 so as to be capable of moving in the direction of optical axis. Zooming is performed by driving the first movable lens frame 5 by a first stepping motor 11, and driving the second movable lens frame 6 by a second stepping motor 12.  
         [0006]     As described in the first embodiment of an optical apparatus, a general lens barrel using a cam includes three follower pins 1-a provided outside a moving first frame group 1 are fitted respectively into an elongated hole 4-a on a straight barrel 4 and a cam groove 5-a of a cam cylinder 5 (see FIG. 5 in Japanese Patent Application Laid-Open No. H07-120656). Likewise, three follower pins 2-a provided outside a second frame group 2 are fitted respectively into the elongated hole 4-a on the straight barrel 4 and a cam groove 5-b of the cam barrel 4 (see FIG. 5 in Japanese Patent Application Laid-Open No. H06-174998). When a zooming and focusing motor 8 is driven, the cam barrel 4 rotates, and hence the first frame group 1 and the second frame group 2 are driven in the direction of the optical axis (pp. 3, FIG. 1, FIG. 4, and FIG. 5).  
         [0007]     The lens barrel of a guide-bar type in the related art described above has following characteristics. (1) Since the guide bar is fixed at both ends to the fixed barrel or the like, it has a fixed beam structure, the midsection of the guide bar may be bent, and hence accuracy of eccentricity of the lens retaining frame is deteriorated, whereby quality of picture image may be deteriorated. (2) The guide bar, which is a single component, is required to have high degree of accuracy in its diameter or straightness, whereby the manufacturing cost is high, and thus the cost of the lens barrel may be increased. (3) The lens retaining frame is required to have a sufficient thickness for surrounding the guide bars to be fitted, whereby the lens barrel may be upsized.  
         [0008]     The lens barrel of a cam pin type in the related art as described above is characterized by its multifunction and compact design since the lens retaining frame is retained in the lens barrel and is driven only by three cam pins disposed outside the lens retaining frame. However, such multifunction may cause deterioration of the level of accuracy in eccentricity, which is difficult to improve.  
       SUMMARY OF THE INVENTION  
       [0009]     It is an object of the invention to provide a lens barrel which is lower in cost than the lens barrel in the related art with higher degree of accuracy and is capable of being downsized.  
         [0010]     Further objects, features and advantages of the present invention will become apparent from the following description of the preferred embodiments (with reference to the attached drawings).  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]      FIG. 1  is a drawing showing the configuration of a lens in a first embodiment.  
         [0012]      FIG. 2  is an appearance view of a lens barrel in the first embodiment.  
         [0013]      FIG. 3  is an exploded perspective view of the first embodiment.  
         [0014]      FIG. 4  is an enlarged view of the front side of the exploded perspective view in  FIG. 3 .  
         [0015]      FIG. 5  is an enlarged view of the back side of the exploded perspective view in  FIG. 3 .  
         [0016]      FIG. 6  is an exploded perspective view of the lens barrel viewed from the back side in the first embodiment.  
         [0017]      FIG. 7  is an enlarged view of the front side of the exploded perspective view in  FIG. 6 .  
         [0018]      FIG. 8  is an enlarged view of the back side of the exploded perspective view in  FIG. 6 .  
         [0019]      FIG. 9  is a perspective view of the internal structure of the first embodiment, illustrating a set-up state.  
         [0020]      FIG. 10  is a perspective view of the internal structure of the first embodiment, illustrating a state set for the short focal distance.  
         [0021]      FIG. 11  is a perspective view of the internal structure of the first embodiment, illustrating a state set for the long focal distance.  
         [0022]      FIG. 12  is an exploded perspective view of a second and fourth lens group retaining frames and a fixed barrel in the first embodiment.  
         [0023]      FIG. 13  is a front view of the first embodiment illustrating a state in which the second and fourth group lens retaining frame and the fixed barrel are built-in.  
         [0024]      FIG. 14  is a perspective view of the internal structure of the first embodiment (for describing the fourth lens group retaining frame).  
         [0025]      FIG. 15  is a perspective view of the internal structure of a second embodiment.  
         [0026]      FIG. 16  is an exploded perspective view of the second embodiment.  
         [0027]      FIG. 17  is an exploded perspective view of the second and fourth lens group retaining frames and the fixed barrel in the second embodiment.  
         [0028]      FIG. 18  is a front view of the second embodiment illustrating a state in which the second and fourth lens group retaining frames and the fixed barrel are built-in.  
         [0029]      FIG. 19  is a perspective view of the internal structure of a third embodiment.  
         [0030]      FIG. 20  is an exploded perspective view of the third embodiment.  
         [0031]      FIG. 21  is an exploded perspective view of the second and fourth lens group retaining frames in the third embodiment.  
         [0032]      FIG. 22  is a front view of the third embodiment in which the second and fourth lens group retaining frames are built-in.  
         [0033]      FIG. 23  is an enlarged view of a lens retaining frame fitting portion and a fixed barrel guiding member in a fourth embodiment.  
         [0034]      FIG. 24  is an enlarged view of the lens retaining frame fitting portion and the fixed barrel guiding member in a fifth embodiment.  
         [0035]      FIG. 25  is an enlarged view of the lens retaining frame fitting portion and the fixed barrel guiding member in a sixth embodiment.  
         [0036]      FIG. 26  is an enlarged view of the lens retaining frame fitting portion and the fixed barrel guiding member in a seventh embodiment.  
         [0037]      FIG. 27  is an enlarged view of the lens retaining frame fitting portion and the fixed barrel guiding member in an eighth embodiment.  
         [0038]      FIG. 28  is an enlarged view of the lens retaining frame fitting portion and the fixed barrel guiding member in a ninth embodiment.  
         [0039]      FIG. 29  is an enlarged view of the lens retaining frame fitting portion and the fixed barrel guiding member in a tenth embodiment.  
         [0040]      FIG. 30  is an enlarged view of the lens retaining frame fitting portion and the fixed barrel guiding member in an eleventh embodiment.  
         [0041]      FIG. 31  is an enlarged view of the lens retaining frame fitting portion and the fixed barrel guiding member in a twelfth embodiment.  
         [0042]      FIG. 32  is an enlarged view of the lens retaining frame fitting portion and the fixed barrel guiding member in a thirteenth embodiment. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0043]     Referring to the attached drawings, preferred embodiments of the invention will be described below.  
       First Embodiment  
       [0044]     A first embodiment of the invention will be described below.  FIG. 2  is a perspective view showing an appearance of the configuration of the entire lens barrel,  FIG. 9  is a perspective cross-sectional view of the outer fixed barrel, and  FIG. 3  is an exploded perspective view of the entire lens barrel.  
         [0045]     First, referring to  FIG. 1 , an optical system built in this lens barrel will be described.  
         [0046]      FIG. 1  is a drawing showing the change caused by zooming of an optical lens. A first lens group  102   a  which is fixed to the lens barrel and hence is not capable of moving, a second lens group  103   a  for adjusting variable power, a third lens group  106   a  as an a focal lens which is fixed to the lens barrel and hence is not capable of moving and a fourth lens group  107   a,  which corresponds to a relay lens, for adjusting variable power and focusing.  
         [0047]     The focal distance is changed by moving the second lens group  103   a  and the fourth lens group  107   a,  and the focusing is done by moving only the fourth lens group  107   a.    
         [0048]      FIG. 1  illustrates the positions of the respective lens groups when the lenses are in a short focal distance on the upper part, and the positions of the respective lens groups when the lenses are in the long focal distance on the lower part. Lines connecting the upper lens group and the lower lens group represent the movement of the respective lens groups. The maximum range of movement of the second lens group  103   a  is represented by A, and the maximum range of movement of the third lens group  106   a  is represented by B.  
         [0049]     After having zoomed, the fourth lens group  107   a  moves between the infinite position represented by a solid line and the close-in position represented by a broken lines in the drawing according to the position of a subject to achieve focusing.  
         [0050]     Referring now to  FIG. 2 , the appearance of the lens barrel will be described. In  FIG. 2 , a first lens group retaining frame  102  is fixed at the front of a fixed barrel  101  that supports the entire lens barrel, and a CCD holder  111  is fixed at the back of the fixed barrel  101 . A Flexible Printed Circuit (FPC)  112  for driving and controlling integrated two stepping motors is disposed on the upper surface of the fixed barrel  101 , and connected to a camera body (not shown yet) at a connecting portion  112   c,  so that the stepping motor is driven and controlled by a control unit in the camera body.  
         [0051]     Referring now to  FIG. 3 ,  FIG. 9 , and  FIG. 14 , the internal structure of the lens barrel will be described.  FIG. 9  is a drawing of the cross section of the fixed barrel  101  of the lens barrel cut vertically to make the internal structure visible. The first lens group retaining frame  102  is fixed to the front (the side where the subject exists) of the fixed barrel  101 , and then a second lens group retaining frame  103  is supported inside the fixed barrel  101  so as to be capable of moving forward and backward in the direction of the optical axis (how it is supported will be described later in detail).  
         [0052]     A second lens group stepping motor  108  is fixed to the upper inner surface of the fixed barrel  101  by motor fixing screws  113  shown in  FIG. 2 .  
         [0053]     A second lens group rack  115  rotatably fixed to the second lens group retaining frame  103  engages a lead screw  108   c  of the second lens group stepping motor  108  and moves the second lens group retaining frame  103  forward and backward in the direction of the optical axis by the rotation of the second lens group stepping motor.  
         [0054]     A second lens group photo interrupter (PR)  104  is fixed to the lower inner surface of the fixed barrel  101 , and optically detects penetration of a PR detector projection  103   g  of the second lens group retaining frame  103  in the direction of the optical axis.  
         [0055]     An aperture mechanism  105  is fixed inside the fixed barrel  101 , and controls the amount of light reaching the CCD adequately by moving an aperture blade, not shown, forward and backward in the optical path.  
         [0056]     In  FIG. 14 , a fourth lens group stepping motor  109  is fixed to the upper inner surface of the fixed barrel  101  by a motor fixing screw  114  shown in  FIG. 2 .  
         [0057]     A fourth lens group rack  116  rotatably fixed to a fourth lens group retaining frame  107  engages a lead screw  109   c  of a fourth lens group stepping motor  109 , and moves the fourth lens group retaining frame  107  forward and backward in the direction of the optical axis by the rotation of the fourth lens group stepping motor.  
         [0058]     A fourth lens group photo interrupter (PR)  110  is fixed to the lower inner surface of the fixed barrel  101 , and optically detects penetration of a PR detector projection  107   g  of the fourth lens group retaining frame  107  in the direction of the optical axis.  
         [0059]     The CCD holder  111  is fixed to the back of the fixed barrel  101 , and the CCD sensor  111   a  for converting a subject image formed by the lens group into electric signals is integrated in the CCD holder.  
         [0060]     Referring now to  FIG. 12  and  FIG. 13 , characteristic portions of the invention will be described in detail.  
         [0061]     The structure of the fixed barrel  101  will be described. In  FIG. 12 , there are provided a first guiding member  101   b  on the right side, a second guiding member  101   c  on the upper side, a third guiding member  101   d  on the left side, when viewed from the front of the lens barrel, in parallel with the optical axis in the fixed barrel  101 . These guiding members have a square shape of a uniform width. The second lens group stepping motor  108  is disposed at the upper right corner in the fixed barrel  101  (in  FIG. 12 , some of the components of the stepping motor are omitted so as to make the lead screw  108   c  visible for description).  
         [0062]     The supporting structure of the second lens group retaining frame  103  will be described. The second lens group  103   a,  which moves forward and backward in the direction of the optical axis for zooming and changes the magnification of an image, is built-in at the center of the second lens group retaining frame  103 . When viewed from the front, a first fitting arm  103   b  is disposed on the right side on the outer periphery of the second lens group retaining frame  103 , and is formed with a recessed groove at the center thereof and projections  103   b   1 ,  103   b   2  extending inwardly of the groove from the front and back sides of the groove. These projections  103   b   1 ,  103   b   2  fit the first guiding member  101   b  on the fixed barrel described above.  
         [0063]     A second fitting arm  103   c  is disposed on the upper portion of the outer periphery of the second lens group retaining frame  103  and is formed with a recessed groove at the center thereof and projections  103   c   1 ,  103   c   2  extending inwardly of the groove from the front and back side of the groove. These projections  103   c   1 ,  103   c   2  fit the second guiding member  101   c  on the fixed barrel described above. The distance between the two projections  103   c   1  and  103   c   2  of the second fitting arm is shorter than the distance between the two projections  103   b   1  and  103   b   2  of the first fitting arm.  
         [0064]     A third fitting arm  103   d  is disposed on the left side of the outer periphery of the second lens group retaining frame  103 , and is formed with a recessed groove at the center thereof. The thickness of the third fitting arm  103   d  in the direction of the optical axis is as thin as about 1 mm, and only the projection  103   d   1  fits the third guiding member  101   d  on the fixed barrel.  
         [0065]     For the convenience of description, coordinate axes are set as follows; the direction of the optical axis toward the subject is set to be a plus Z-axis, the upward direction in the drawing is set to be a plus Y-axis, and the rightward direction in the drawing is set to be a plus X-axis.  
         [0066]     In this manner, the translation in the direction of Y-axis and rotation about the X-axis of the second lens group retaining frame  103  is restricted by engagement of the first fitting arm  103   b,  which is the longest arm, and the first guiding member  101   b.  In addition, with additional engagement between the third fitting arm  103   d,  which is the shortest arm, and the third guiding member  101   d,  the rotation of the second lens group retaining frame  103  about the Z-axis is restricted.  
         [0067]     The rotation about the Y-axis of the second lens group retaining frame  103  is restricted by additional engagement between the second fitting arm  103   c  and the second guiding member  101   c.    
         [0068]     As described above, the second lens group retaining frame is restricted so that only the movement in the direction of the Z-axis (optical axis) is freely allowed, and the translation in the different directions or the rotational movement is restricted by the three arms  103   b,    103   c,    103   d  of the second lens group retaining frame.  
         [0069]     Subsequently, a mechanism for moving the second lens group retaining frame  103  forward and backward in the direction of the optical axis will be described. In  FIG. 12 , when viewing the lens barrel from the front, the rack fixing member  103   f  located on the upper right of the second lens group retaining frame  103  fixes the second group rack  115  so as to be capable of rotating about the axis extending in parallel with the optical axis.  
         [0070]     In  FIG. 13 , an engaging tooth  115   a  of the second lens group rack  115  engages a lead screw  108   c  of the second lens group stepping motor  108 , and a resilient tooth  115   b  having resiliency presses the lead screw  108   c  from the opposing direction toward the lead screw  108   c.  Consequently, the engaging tooth  115   a  and the resilient tooth  115   b  press against the lead screw  108   c  from the left and right sides, so that a state similar to fitting of generally used screw and nut is established. Therefore, when the second lens group stepping motor  108  rotates, the lead screw  108   c  connected directly to the motor rotates, and depending on the leading amount of the lead screw, the second lens group rack  115  is moved forward and backward in the direction of the optical axis, and the second lens group retaining frame  103  connected to the second lens group rack  115  is moved forward and backward in the direction of the optical axis, so that zooming operation is enabled.  
         [0071]     Referring now to  FIG. 12 , the supporting structure of the fourth lens group retaining frame  107  will be described. The fourth lens group  107   a  which moves forward and backward in the direction of the optical axis for changing the magnification of the image for zooming, and moves forward and backward in the direction of the optical axis for focusing, is built in at the center of the fourth lens group retaining frame  107 . When viewed from the front, a first fitting arm  107   b  is disposed on the left side of the outer periphery of the fourth lens group retaining frame  107  and is formed with a recessed groove at the center thereof and projections  107   b   1 ,  107   b   2  projecting inwardly of the groove from the front side and the back side of the groove. These projections  107   b   1 ,  107   b   2  fit the third guide member  101   d  on the fixed barrel described above.  
         [0072]     A second fitting arm  107   c  is disposed on the upper portion of the outer periphery of the fourth lens group retaining frame  107 , and is formed with a recess at the center thereof and projections  107   c   1 ,  107   c   2  projecting inwardly of the groove from the front side and the back side of the recess. These projections  107   c   1 ,  107   c   2  fit the second guiding member  101   c  of the fixed barrel described above. The distance between the two projections  107   c   1  and  107   c   2  of the second fitting arm is shorter than the distance between the two projections  107   b   1  and  107   b   2  of the first fitting arm.  
         [0073]     A third fitting arm  107   d  is disposed on the right side of the outer periphery of the fourth lens group retaining frame  107 , and is formed with a recess at the center thereof. The thickness of the third fitting arm  107   d  in the direction of the optical axis is as thin as about 1 mm, and only the projection  107   d   1  fits the first guide member  101   b  on the fixed barrel.  
         [0074]     In this manner, the translation in the direction of Y-axis and rotation about the X-axis of the third lens group retaining frame  107  is restricted by engagement of the first fitting arm  103   b,  which is the longest arm, and the third guiding member  101   d.  In addition, with additional engagement between the third fitting arm  107   d,  which is the shortest arm, and the first guiding member  101   b,  the rotation of the fourth lens group retaining frame  107  about the Z-axis is restricted.  
         [0075]     The rotation about the Y-axis of the fourth lens group retaining frame  107  is restricted by additional engagement between the second fitting arm  107   c  and the second guiding member  101   c.    
         [0076]     As described above, the fourth lens group retaining frame is restricted so that only the movement in the direction of the Z-axis (optical axis) is freely allowed, and the translation in the different directions or the rotational movement is restricted by the three arms  107   b,    107   c,    107   d  of the fourth lens group retaining frame.  
         [0077]     Subsequently, a mechanism for moving the fourth lens group retaining frame  107  forward and backward in the direction of the optical axis will be described. In  FIG. 14 , the fourth lens group rack  116  rotatably fixed about the axis extending in parallel with the optical axis of a rack fixing portion  107   f  of the fourth lens retaining frame  107  is shown.  
         [0078]     An engaging tooth  116   a  of the fourth lens group rack  116  engages a lead screw  109   c  of the fourth lens group stepping motor  109 , and a resilient tooth  116   b  having resiliency presses the lead screw  109   c  from the opposing direction toward the lead screw  109   c.  Consequently, the engaging tooth  116   a  and the resilient tooth  116   b  press against the lead screw  109   c  from the left and right sides, so that a state similar to fitting of generally used screw and nut is established. Therefore, when the fourth lens group stepping motor  109  rotates, the lead screw  109   c  connected directly to the motor rotates, and depending on the leading amount of the lead screw, the fourth lens group rack  116  is moved forward and backward in the direction of the optical axis, and the fourth lens group retaining frame  107  connected to the fourth lens group rack  116  is moved forward and backward in the direction of the optical axis, so that zooming operation or focusing operation are enabled.  
         [0079]     Subsequently, a mechanism for detecting the amount of movement of the second lens group retaining frame  103  and the fourth lens group retaining frame  107  from the infinite position will be described. For example, it is assumed that the lenses are in the shot focal distance, and the user turned off the power of the camera and then turned on the power of the camera for taking pictures again. The lens barrel is required to detect the initial positions of the second lens group retaining frame  103  and the fourth lens group retaining frame  107  for calculating the positions to be moved for subsequent zooming or focusing operation.  
         [0080]     At the moment when the power of the camera is turned on again, the second lens group retaining frame  103  and the fourth lens group retaining frame  107  are located at the positions of short focal distance as shown in  FIG. 10 .  
         [0081]     Therefore, the second lens group stepping motor  108  is driven to move the second lens group retaining frame  103  backward in the direction of the optical axis, and when the PR detector projection  103   g  of the second lens group retaining frame  103  passes over the second lens group PR (photo interrupter)  104  and the second lens group PR  104  detects its passage as shown in  FIG. 9 , the second lens group retaining frame  103  is stopped once. Immediately after this, the second lens group retaining frame  103  is moved forward, and when the second lens group PR  104  detects the passage of the PR detector projection  103   g  of the second lens group retaining frame  103  again, the control unit in the camera starts counting the number of steps of the second lens group stepping motor  108 . The counted number corresponds to the position of the optical axis of the second lens group retaining frame  103  from the position of the second lens group PR  104 . Then, when the counted number reaches a predetermined number which corresponds to the position of the short focal distance, the second lens group stepping motor  108  is stopped and the state shown in  FIG. 10  is achieved. This operation enables the second lens group retaining frame  103  to stop at the position of short focal distance accurately and makes the position of the second lens group retaining frame  103  controllable by the counted number even during subsequent forward and backward movement thereof.  
         [0082]     The fourth lens group retaining frame  107 , in the same manner as the second lens group retaining frame  103 , drives the fourth lens group stepping motor  109  to move the fourth lens group retaining frame  107  backward in the direction of the optical axis and, when the PR detector projection  107   g  of the fourth lens group retaining frame  107  passes over the fourth lens group PR (photo interrupter)  110  and the fourth lens group PR  110  detects its passage as shown in  FIG. 9 , the fourth lens group retaining frame  107  is stopped once. Immediately after this, the fourth lens group retaining frame  107  is moved forward, and when the fourth lens group PR  110  detects the passage of the PR detector projection  107   g  of the fourth lens group retaining frame  107  again, the control unit in the camera starts counting the number of steps of the fourth lens group stepping motor  109 . The counted number corresponds to the position of the optical axis of the fourth lens group retaining frame  107  from the position of the fourth lens group PR  110 . Then, when the counted number reaches a predetermined number which corresponds to the position of the short focal distance, the fourth lens group stepping motor  109  is stopped and the state shown in  FIG. 10  is achieved. This operation enables the fourth lens group retaining frame  107  to stop at the position of short focal distance accurately and makes the position of the fourth lens group retaining frame  107  controllable by the counted number even during subsequent forward and backward movement thereof.  
         [0083]     A characteristic effect of the first embodiment is that since the guiding member is unitary with the fixed barrel from the front end to the rear end, rigidity of the guiding member increases, and the supporting accuracy of the lens retaining frame increases.  
       Second Embodiment  
       [0084]     A second embodiment of the invention will be described below.  FIG. 15  is a perspective cross-sectional view obtained by cutting the fixed barrel on the outer side, and  FIG. 16  is an exploded perspective view of the entire lens barrel.  
         [0085]      FIG. 17  is an exploded perspective view of the second lens group retaining frame, the fourth lens group retaining frame, and the fixed barrel for explaining characteristics of the second embodiment.  
         [0086]      FIG. 18  is a front view of the second lens group retaining frame, the fourth lens group retaining frame, the fixed barrel, and the second lens group stepping motor for explaining characteristics of the second embodiment.  
         [0087]     Since the optical system built in the second embodiment is identical to the first embodiment shown in  FIG. 1 , and the operation during zooming and focusing is the same as in the first embodiment, the description will not be repeated again.  
         [0088]     Referring to  FIG. 17  and  FIG. 18 , the characteristic portions of the second embodiment will be described in detail. Here, only points which are different from the first embodiment will be described.  
         [0089]     The structure of a fixed barrel  201  will be described. In the fixed barrel  201 , a second guiding member  201   c  is disposed on the upper side in the fixed barrel  201 , a first guiding member  201   b  is disposed at a position turned clockwise by 120°, and a third guiding member  201   d  is disposed at a position turned clockwise further by 120° when viewing the lens barrel from the front, so as to extend in parallel with the optical axis and have a square shape of a uniform width. A second lens group stepping motor  208  is disposed on the upper right corner inside the fixed barrel  201  (in  FIG. 18 , some of the components of the stepping motor are omitted so as to make the lead screw  208   c  visible for description).  
         [0090]     The supporting structure of a second lens group retaining frame  203  will now be described. The second lens group  203   a  which moves forward and backward in the direction of the optical axis and changes the magnification of an image for zooming is built in at the center of the second lens group retaining frame  203 . When viewed from the front, a first fitting arm  203   b  is disposed at 120° on the lower right portion of the outer periphery of the second lens group retaining frame  203 , and is formed with a recessed groove at the center thereof and projections  201   b   1 ,  203   b   2  projecting inwardly of the groove from the front side and the rear side of the groove. These projections  203   b   1 ,  203   b   2  fit the first guiding member  201   b  of the fixed barrel described above. A second fitting arm  203   c  is disposed on the upper part of the outer periphery of the second lens group retaining frame  203 , and is formed with a recessed groove at the center thereof and projections  203   c   1  and  203   c   2  projecting inwardly of the groove from the front side and the back side of the groove. These projections  203   c   1 ,  203   c   2  fit the second guiding member  201   c  of the fixed barrel described above. The distance between the two projections  203   c   1  and  203   c   2  of the second fitting arm is shorter than the distance between the two projections  203   b   1  and  203   b   2  of the first fitting arm. A third fitting arm  203   d  is disposed at 120° on the lower left portion of the outer periphery of the second lens group retaining frame  103 , and is formed with a recessed groove at the center thereof. The thickness of the third fitting arm  203   d  in the direction of the optical axis is as thin as about 1 mm, and only a projection  203   d   1  fits the third guiding member  201   d  of the fixed barrel.  
         [0091]     For the convenience of description, coordinate axes are set as follows; the direction of the optical axis toward the subject is set to be a plus Z-axis, the upward direction in the drawing is set to be a plus Y-axis, and the rightward direction in the drawing is set to be a plus X-axis.  
         [0092]     In this manner, by the engagement between the first fitting arm  203   b,  which is the longest arm, and the first guiding member  101   b,  the second lens group retaining frame  203  is restricted in translation in a second direction which is vertical both to “a first direction directed from the optical axis to the first fitting arm” and “Z-axis”, and also in rotation about the first direction.  
         [0093]     Furthermore, rotation about the Z-axis of the second lens group retaining frame  203  is restricted by additional engagement between the third fitting arm  203   d,  which is the shortest arm, and the third guiding member  201   d.    
         [0094]     Rotation of the second lens group retaining frame  203  about the second direction is restricted by additional engagement between the second fitting arm  203   c  and the second guiding member  201   c.    
         [0095]     As described above, the second lens group retaining frame is restricted so that only the movement in the direction of the Z-axis (optical axis) is freely allowed, and the translation in the different directions or the rotational movement is restricted by the three arms  203   b,    203   c,    203   d  of the second lens group retaining frame.  
         [0096]     The supporting structure of a fourth lens group retaining frame  207  will be described. A fourth lens group  207   a  that moves forward and backward in the direction of optical axis to change the magnification of an image for zooming and moves forward and backward in the direction of optical axis for focusing is built in at the center of the fourth lens group retaining frame  207 . When viewed from the front, a first fitting arm  207   b  is disposed at 120° on the lower left portion of the outer periphery of the fourth lens group retaining frame  207 , and is formed with a recessed groove at the center thereof and projections  207   b   1 ,  207   b   2  projecting inwardly of the groove from the front side and the back side of the groove. These projections  207   b   1 ,  207   b   2  fit the third guiding member  201   d  of the fixed barrel described above. A second fitting arm  207   c  is disposed on the upper portion of the outer periphery of the fourth lens group retaining frame  207  and is formed with a recessed groove at the center thereof and projections  207   c   1 ,  207   c   2  projecting inwardly of the groove from the front side and the rear side of the groove. These projections  207   c   1 ,  207   c   2  fit the second guiding member  201   c  of the fixed barrel described above. The distance between the two projections  207   c   1  and  207   c   2  of the fourth fitting arm is shorter than the distance between the two projections  207   b   1  and  207   b   2  of the first fitting arm. A third fitting arm  207   d  is disposed at 120° on the lower right portion of the outer periphery of the second lens group retaining frame  107 , and is formed with a recessed groove at the center thereof. The thickness of the third fitting arm  207   d  in the direction of the optical axis is as thin as about 1 mm, and only a projection  207   d   1  fits the first guiding member  201   b  of the fixed barrel.  
         [0097]     For the convenience of description, coordinate axes are set as follows; the direction of the optical axis toward the subject is set to be a plus Z-axis, the upward direction in the drawing is set to be a plus Y-axis, and the rightward direction in the drawing is set to be a plus X-axis.  
         [0098]     In this manner, by the engagement between the first fitting arm  207   b,  which is the longest arm, and the third guiding member  101   d , the fourth lens group retaining frame  207  is restricted in translation in a second direction which is vertical both to “a first direction directed from the optical axis to the first fitting arm” and “Z-axis”, and also in rotation about the first direction.  
         [0099]     Furthermore, rotation about the Z-axis of the fourth lens group retaining frame  207  is restricted by additional engagement between the third fitting arm  207   d,  which is the shortest arm, and the first guiding member  201   b.    
         [0100]     Rotation of the fourth lens group retaining frame  207  about the second direction is restricted by additional engagement between the second fitting arm  207   c  and the second guiding member  201   c.    
         [0101]     As described above, the fourth lens group retaining frame is restricted so that only the movement in the direction of the Z-axis (optical axis) is freely allowed, and the translation in the different directions or the rotational movement is restricted by the three arms  207   b,    207   c,    207   d  of the fourth lens group retaining frame.  
         [0102]     A characteristic effect of the second embodiment is that since the guiding member is unitary with the fixed barrel from the front end to the rear end, rigidity of the guiding member increases, and the supporting accuracy of the lens retaining frame increases.  
       Third Embodiment  
       [0103]     A third embodiment of the invention will be described below.  FIG. 19  is a perspective cross-sectional view obtained by cutting the fixed barrel on the outer side, and  FIG. 20  is an exploded perspective view of the entire lens barrel.  
         [0104]      FIG. 21  is an exploded perspective view of the second lens group retaining frame, the fourth lens group retaining frame, and the fixed barrel for explaining characteristics of the third embodiment.  
         [0105]      FIG. 22  is a front view of the second lens group retaining frame, the fourth lens group retaining frame, the fixed barrel, and the second lens group stepping motor for explaining characteristics of the third embodiment.  
         [0106]     Since the optical system built in the third embodiment is identical to the first embodiment shown in  FIG. 1 , and the operation during zooming and focusing is the same as in the first embodiment, the description will not be repeated again.  
         [0107]     Referring to  FIG. 21  and  FIG. 22 , the characteristic portions of the third embodiment will be described in detail. Here, only points which are different from the first embodiment will be described.  
         [0108]     The structure of the fixed barrel  301  will be described. In  FIG. 21 , a first guiding member  301   b  is disposed on the right side, a second guiding member  301   c  is disposed on the upper side, a third guiding member  301   d  is disposed on the left side, and a fourth guiding member  301   e  is disposed on the lower side in the fixed barrel  301  when viewing the lens barrel from the front so as to extend in parallel with the optical axis and have a square shape of a uniform width. A second lens group stepping motor  308  is disposed on the upper right corner inside the fixed barrel  301  (in  FIG. 21 , some of the components of the stepping motor are omitted so as to make a lead screw  308   c  visible for description).  
         [0109]     The supporting structure of a second lens group retaining frame  303  will now be described. The second lens group  303   a  which moves forward and backward in the direction of the optical axis and changes the magnification of an image for zooming is built in at the center of the second lens group retaining frame  303 . When viewed from the front, a first fitting arm  303   b  is disposed on the right side of the outer periphery of the second lens group retaining frame  303 , and is formed with a recessed groove at the center thereof and projections  303   b   1 ,  303   b   2  projecting inwardly of the groove from the front side and the rear side of the groove. These projections  303   b   1 ,  303   b   2  fit the first guiding member  301   b  on the fixed barrel described above.  
         [0110]     A second fitting arm  303   c  is disposed on the upper portion of the outer periphery of the second lens group retaining frame  303 , and is formed with a recessed groove at the center thereof and projections  303   c   1 ,  303   c   2  projecting inwardly of the groove from the front side and the back side of the groove. These projections  303   c   1 ,  303   c   2  fit the second guiding member  301   c  of the fixed barrel described above. The distance between the two projections  303   c   1  and  303   c   2  of the second fitting arm is shorter than the distance between the two projections  303   b   1  and  303   b   2  of the first fitting arm.  
         [0111]     A third fitting arm  303   d  is disposed on the left side of the outer periphery of the second lens group retaining frame  303  and is formed with a recessed groove at the center thereof. The thickness of the third fitting arm  303   d  in the direction of the optical axis is as thin as about 1 mm, and only a projection  303   d   1  fits the third guiding member  301   d  of the fixed barrel. A fourth fitting arm  303   e  is disposed on the lower portion of the outer periphery of the second lens group retaining frame  303 , and is formed with a recessed groove at the center thereof. The thickness of the fourth fitting arm  303   e  in the direction of the optical axis is as thin as about 1 mm, and only the projection  303   e   1  fits the fourth guiding member  301   e  of the fixed barrel.  
         [0112]     For the convenience of description, coordinate axes are set as follows; the direction of the optical axis toward the subject is set to be a plus Z-axis, the upward direction in the drawing is set to be a plus Y-axis, and the rightward direction in the drawing is set to be a plus X-axis.  
         [0113]     In this manner by the engagement between the first fitting arm  303   b,  which is the longest arm, and the first guiding member  301   b,  and between the third fitting arm  303   d,  which is the shortest arm, and the third guiding member  301   d,  movement is restricted to a Z-X plane.  
         [0114]     Furthermore, by the engagement between the second fitting arm  303   c,  which is the second longest arm and the second guiding member  301   c,  and between the fourth fitting arm  303   e,  which is the shortest arm, and the fourth guiding member  301   e,  movement is restricted to a Z-Y plane.  
         [0115]     As described above, the second lens group retaining frame is restricted so that only the movement in the direction of the Z-axis (optical axis) is freely allowed, and the translation in the different directions or the rotational movement is restricted by the four arms  303   b,    303   c,    303   d,    303   e  of the second lens group retaining frame.  
         [0116]     The supporting structure of a fourth lens group retaining frame  307  will be described in  FIG. 21 . A fourth lens group  307   a  that moves forward and backward in the direction of optical axis to change the magnification of an image for zooming and moves forward and backward in the direction of optical axis for focusing is built in at the center of the fourth lens group retaining frame  307 . When viewed from the front, the first fitting arm  307   b  is disposed on the left side of the outer periphery of the fourth lens group retaining frame  307 , and is formed with a recessed groove at the center thereof, and projections  307   b   1 ,  307   b   2  projecting inwardly of the groove from the front side and the back side of the groove. These projections  307   b   1 ,  307   b   2  fit the third guiding member  301   d  of the fixed barrel described above.  
         [0117]     A second fitting arm  307   c  is disposed on the upper portion of the outer periphery of the fourth lens group retaining frame  307  and is formed with a recessed groove at the center thereof and projections  307   c   1 ,  307   c   2  projecting inwardly of the groove from the front side and the rear side of the groove. These projections  307   c   1 ,  307   c   2  fit the second guiding member  301   c  of the fixed barrel described above. The distance between the two projections  307   c   1  and  307   c   2  of the second fitting arm is shorter than the distance between the two projections  307   b   1  and  307   b   2  of the first fitting arm.  
         [0118]     A third fitting arm  307   d  is disposed on the right side of the outer periphery of the fourth lens group retaining frame  307 , and is formed with a recessed groove at the center thereof. The thickness of the third fitting arm  307   d  in the direction of the optical axis is as thin as about 1 mm, and only a projection  307   d   1  fits the first guiding member  301   b  of the fixed barrel.  
         [0119]     A fourth fitting arm  307   e  is disposed on the lower side of the outer periphery of the fourth lens group retaining frame  307 , and is formed with a recessed groove at the center thereof. The thickness of the fourth fitting arm  307   e  in the direction of the optical axis is as thin as about 1 mm, and only a projection  307   e   1  fits the fourth guiding member  301   e  of the fixed barrel.  
         [0120]     In this manner, by the engagement between the first fitting arm  307   b,  which is the longest arm, and the third guiding member  301   d,  and between the third fitting arm  307   d,  which is the shortest arm and the third guiding member  301   d,  movement is restricted to the Z-X plane.  
         [0121]     Furthermore, by the engagement between the second fitting arm  307   c,  which is the second longest arm, and the second guiding member  301 , and between the fourth fitting arm  307   e,  which is the shorter arm, and the fourth guiding member  301   e,  movement is restricted to the Z-Y plane.  
         [0122]     As described above, the fourth lens group retaining frame is restricted so that only the movement in the direction of the Z-axis (optical axis) is freely allowed, and the translation in the different directions or the rotational movement is restricted by the three arms  307   b,    307   c,    307   d,    307   e  of the fourth lens group retaining frame.  
         [0123]     A characteristic effect of the third embodiment is that since the guiding member is unitary with the fixed barrel from the front end to the rear end, rigidity of the guiding member increases, and the supporting accuracy of the lens retaining frame increases.  
       Fourth Embodiment  
       [0124]     Referring to  FIG. 23 , a fourth embodiment of the invention will be described below.  
         [0125]      FIG. 23  is an enlarged front view of the fourth embodiment characterized by the shape of the fitting portion of the lens retaining frame and the shape of the guiding member of the fixed barrel. A guiding member  401   c  on a fixed barrel  402  is shaped like an elongated rail extending in the direction of the optical axis with a uniform width and having flat portions  401   c   1 ,  401   c   2  on the left and right sides. A second fitting arm  403   c  of the second lens group retaining frame is formed with a recessed groove on top thereof, and with flat portions  403   h   1 ,  403   h   2  on the left and right sides thereof.  
         [0126]     The guiding member  401   c  and the second fitting arm  403   c  engage with each other by contact between the flat portion  401   c   1  of the guiding member  401   c  and the flat portion  403   h   1  of the fitting arm, and between the flat portion  401   c   2  of the guiding member  401   c  and the flat portion  403   h   2  of the fitting arm.  
         [0127]     In this manner, since contact between the flat surfaces is provided, engagement being resistant for destruction or deformation against the external force is established.  
       Fifth Embodiment  
       [0128]     Referring to  FIG. 24 , a fifth embodiment of the invention will be described below.  
         [0129]      FIG. 24  is an enlarged front view of the fifth embodiment characterized by the shape of the fitting portion of the lens retaining frame and the shape of the guiding member of the fixed barrel. A guiding member  501   c  on a fixed barrel  501  is formed into an elongated groove extending in the direction of the optical axis with a uniform width and having flat portions  501   c   1 ,  501   c   2  on the left and light sides. A second fitting arm  503   c  of the second lens group retaining frame is formed with a rail-shaped projection on top thereof, and with flat portions  503   h   1 ,  503   h   2  on the left and right sides thereof.  
         [0130]     Then, the guiding member  501   c  and the second fitting arm  503   c  engage with each other by contact between the flat portion  501   c   1  of the guiding member  501   c  and the flat portion  503   h   1  of the fitting arm, and between the flat portion  501   c   2  of the guiding member  501   c  and the flat portion  503   h   2  of the fitting arm.  
         [0131]     In this manner, since contact between the flat surfaces is established, engagement being resistant for destruction or deformation against the external force is established.  
       Sixth Embodiment  
       [0132]     Referring to  FIG. 25 , a sixth embodiment of the invention will be described below.  
         [0133]      FIG. 25  is an enlarged front view of the sixth embodiment characterized by the shape of the fitting portion of the lens retaining frame and the shape of the guiding member of the fixed barrel. A guiding member  601   c  on a fixed barrel  601  is shaped like an elongated rail as a base extending in the direction of the optical axis with a uniform width and having projections  601   c   1 ,  601   c   2  formed on the left and right sides and extending in the direction of the optical axis. A second fitting arm  603   c  of the second lens group retaining frame is formed with a recessed groove on top thereof and flat portions  603   h   1 ,  603   h   2  on the left and right sides.  
         [0134]     Then, the guiding member  601   c  and the second fitting arm  603   c  engage with each other by contact between the projection  601   c   1  of the guiding member  601   c  and the projection  603   h   1  of the fitting arm, and between the flat portion  601   c   2  of the guiding member  601   c  and the flat portion  603   h   2  of the fitting arm.  
         [0135]     In this manner, since contact between the projection and the flat portion is established, the contact portion is clarified and reduced in contact area. Therefore, engagement with high degree of accuracy is established, and a frictional force is reduced when the second lens group retaining frame moves.  
       Seventh Embodiment  
       [0136]     Referring to  FIG. 26 , a seventh embodiment of the invention will be described below.  
         [0137]      FIG. 26  is an enlarged front view of the seventh embodiment characterized by the shape of the fitting portion of the lens retaining frame and the shape of the guiding member of the fixed barrel. A guiding member  701   c  on a fixed barrel  701  is shaped like an elongated groove as a base extending in the direction of the optical axis with a uniform width and having projections  701   c   1 ,  701   c   2  formed on the left and right sides extending in the direction of the optical axis. A second fitting arm  703   c  of the second lens group retaining frame has a rail-shaped projection on top thereof, and flat portions  703   h   1 ,  703   h   2  on the left and right sides.  
         [0138]     Then, the guiding member  701   c  and the second fitting arm  703   c  engage with each other by contact between the flat portion  701   c   1  of the guiding member  701   c  and the flat portion  703   h   1  of the fitting arm, and between the flat portion  701   c   2  of the guiding member  701   c  and the flat portion  703   h   2  of the fitting arm.  
         [0139]     In this manner, since contact between the projection and the flat portion is established, the contact portion is clarified and reduced in contact area. Therefore, engagement with high degree of accuracy is established, and a frictional force is reduced when the second lens group retaining frame moves.  
       Eighth Embodiment  
       [0140]     Referring to  FIG. 27 , an eighth embodiment of the invention will be described below.  
         [0141]      FIG. 27  is an enlarged front view of the eighth embodiment characterized by the shape of the fitting portion of the lens retaining frame and the shape of the guiding member of the fixed barrel. A guiding member  801   c  on a fixed barrel  801  is shaped like an elongated rail extending in the direction of the optical axis with a uniform width and having flat portions  801   c   1 ,  801   c   2  on the left and right sides. A second fitting arm  803   c  of the second lens group retaining frame is formed with a recess on top thereof, and projections  803   h   1 ,  803   h   2  on the left and right inner surfaces.  
         [0142]     Then, the guiding member  801   c  and the second fitting arm  803   c  engage with each other by contact between the flat portion  801   c   1  of the guiding member  801   c  and the projection  803   h   1  of the fitting arm, and between the flat portion  801   c   2  of the guiding member  801   c  and the projection  803   h   2  of the fitting arm.  
         [0143]     In this manner, since contact between the projection and the flat portion is established, the contact portion is clarified and reduced in contact area. Therefore, engagement with high degree of accuracy is established, and a frictional force is reduced when the second lens group retaining frame moves.  
       Ninth Embodiment  
       [0144]     Referring to  FIG. 28 , a ninth embodiment of the invention will be described below.  
         [0145]      FIG. 28  is an enlarged front view of the ninth embodiment characterized by the shape of the fitting portion of the lens retaining frame and the shape of the guiding member of the fixed barrel. A guiding member  901   c  on a fixed barrel  901  is shaped like an elongated groove extending in the direction of the optical axis with a uniform width and having flat portions  901   c   1 ,  901   c   2  on the left and right sides thereof. A second fitting arm  903   c  of the second lens group retaining frame is formed with a rail-shaped projection on top thereof, and projections  903   h   1 ,  903   h   2  on the left and right sides.  
         [0146]     Then, the guiding member  901   c  and the second fitting arm  903   c  engage with each other by contact between the flat portion  901   c   1  of the guiding member  901   c  and the projection  903   h   1  of the fitting arm and between the flat portion  901   c   2  of the guiding member  901   c  and the projection  903   h   2  of the fitting arm.  
         [0147]     In this manner, since contact between the projection and the flat portion is established, the contact portion is clarified and reduced in contact area. Therefore, engagement with high degree of accuracy is established, and a frictional force is reduced when the second lens group retaining frame moves.  
       Tenth Embodiment  
       [0148]     Referring to  FIG. 29 , a tenth embodiment of the invention will be described below.  
         [0149]      FIG. 29  is an enlarged front view of the tenth embodiment characterized by the shape of the fitting portion of the lens retaining frame and the shape of the guiding member of the fixed barrel. A guiding member  1001   c  on the fixed barrel  1001  is shaped like an elongated rail extending in the direction of optical axis with a uniform width and having flat portions  1001   c   1 ,  1001   c   2  on the left and right sides. A second fitting arm  1003   c  of the second lens group retaining frame is formed with a recessed groove on top thereof, and flat portions  1003   h   1 ,  1003   h   2  on the left and right sides. A slit  1003   j  is formed between the flat portions, and hence the flat portion  1003   h   2  is apt to resiliently approach the flat portion  1003   h   1 .  
         [0150]     Then, the guiding member  1001   c  and the second fitting arm  1003   c  engage with each other by contact between the flat portion  1001   c   1  of the guiding member  1001   c  and the flat portion  1003   h   1  of the fitting arm and pressurization of the flat portion  1001   c   2  of the guiding member  1001   c  against the flat portion  1003   h   2  of the fitting arm.  
         [0151]     In this manner, since pressurization is established by a resilient force, engagement without rattling is enabled, and hence the lens retaining frame can be supported with high degree of accuracy.  
       Eleventh Embodiment  
       [0152]     Referring to  FIG. 30 , an eleventh embodiment of the invention will be described below.  
         [0153]      FIG. 30  is an enlarged front view of the eleventh embodiment characterized by the shape of the fitting portion of the lens retaining frame and the shape of the guiding member of the fixed barrel. A guiding member  1001   c  on a fixed barrel  1101  is shaped like an elongated groove extending in the direction of the optical axis with a uniform width and having flat portions  1101   c   1 ,  1101   c   2  on the left and right sides. A second fitting arm  1103   c  of the second lens group retaining frame is formed with a rail-shaped projection on top thereof, and flat portions  1103   h   1 ,  1103   h   2  on the left and right sides. A slit  1103   j  is formed between the flat portions and the flat portion  1103   h   2  is apt to move away from the flat portion  1103   h   1  by a resilient force.  
         [0154]     Then, the guiding member  1101   c  and the second fitting arm  1103   c  engage with each other by contact between the flat portion  1103   c   1  of the guiding member  1101   c  and the flat portion  1103   h   1  of the fitting arm and between the flat portion  1101   c   2  of the guiding member  1101   c  and the flat portion  1103   h   2  of the fitting arm.  
         [0155]     In this manner, since pressurization by a resilient force is established, engagement without rattling is enabled, and hence the lens retaining frame can be supported with high degree of accuracy.  
       Twelfth Embodiment  
       [0156]     Referring to  FIG. 31 , the twelfth embodiment 12 of the invention will be described below.  
         [0157]      FIG. 31  is an enlarged front view of the twelfth embodiment characterized by the shape of the fitting portion of the lens retaining frame and the shape of the guiding member of the fixed barrel. A guiding member  1201   c  on a fixed barrel  1201  is shaped like an elongated rail extending in the direction of the optical axis with a uniform width and having flat portions  1201   c   1 ,  1201   c   2  on the left and right sides. A slit  1201   f  is formed between the flat portions and the flat portion  1201   c   2  is apt to move away from the flat portion  1201   c   1  by a resilient force.  
         [0158]     A second fitting arm  1203   c  of the second lens group retaining frame is formed with a recessed groove on top thereof, and flat portions  1203   h   1 ,  1203   h   2  on the left and right sides.  
         [0159]     Then, the guiding member  1201   c  and the second fitting arm  1203   c  engage with each other by contact between the flat portion  1201   c   1  of the guiding member  1201   c  and the flat portion  1203   h   1  of the fitting arm and between the flat portion  1201   c   2  of the guiding member  1201   c  and the flat portion  1203   h   2  of the fitting arm.  
         [0160]     In this manner, since pressurization by a resilient force is established, engagement without rattling is enabled, and hence the lens retaining frame can be supported with high degree of accuracy.  
       Thirteenth Embodiment  
       [0161]     Referring to  FIG. 32 , a thirteenth embodiment of the invention will be described below.  
         [0162]      FIG. 32  is an enlarged front view of the thirteenth embodiment characterized by the shape of the fitting portion of the lens retaining frame and the shape of the guiding member of the fixed barrel. A guiding member  1301   c  in the fixed barrel  1301  is shaped like an elongated rail extending in the direction of optical axis with a uniform width and having flat portions  1301   c   1 ,  1301   c   2  on the left and right sides.  
         [0163]     A second fitting arm  1303   c  of the second lens retaining frame is formed with a recessed groove on top thereof, and projections  1303   h   1 ,  1303   h   2  are formed on the left and right sides. A slit  1303   j  is formed between the projections, and the projection  1303   h   2  is apt to resiliently approach the projection  1303   h   1 .  
         [0164]     Then, the guiding member  1301   c  and the second fitting arm  1303   c  engage with each other by contact between the flat portion  1301   c   1  of the guiding member  1301   c  and the projection  1303   h   1  of the fitting arm and pressurization of the flat portion  1301   c   2  of the guiding member  1301   c  against the projection  1303   h   2  of the fitting arm.  
         [0165]     In this manner, since pressurization is established by a resilient force, engagement without rattling is enabled, and hence the lens retaining frame can be supported with high degree of accuracy.  
         [0166]     In other words, in the lens barrel described above, since the lens retaining frame is supported in a space, support of the lens retaining frame with higher degree of accuracy than before is enabled by providing different supporting roles to the respective three supporting devices and adjusting and correcting the respective three supporting devices.  
         [0167]     In another lens barrel, since two directions are orthogonal to each other, the direction with less accuracy is clarified. Also, since the uniform accuracy can be maintained in any directions in 360°, support of the lens retaining frame with higher degree of accuracy than before is enabled.  
         [0168]     In still another lens barrel, since the lens retaining frame is supported in a space, support of the lens retaining frame with higher degree of accuracy than before is enabled by providing different supporting roles to the respective two supporting devices and adjusting and correcting the two respective supporting devices.  
         [0169]     In another lens barrel, since the two planes are orthogonal to each other, the direction with less accuracy is clarified. Also, since the uniform accuracy can be maintained in any directions in 360°, support of the lens retaining frame with higher degree of accuracy than before is enabled.  
         [0170]     In further lens barrel, since the guiding member is supported by the inner surface of the fixed barrel, rigidity of the guiding member increases, and hence support of the lens retaining frame with high degree of accuracy is enabled.  
         [0171]     By providing only three guiding members, downsizing of the lens barrel is enabled.  
         [0172]     Also, by differentiating the length of the respective guiding members, the first engaging portion serves as a first supporting device in the first aspect of the invention, the second engaging portion serves as a second supporting device in the first aspect of the invention, and the third engaging portion serves as a third supporting device in the first aspect of the invention. Accordingly, by providing different supporting roles to the respective three engaging portions and adjusting and correcting the respective three engaging-portions, support of the lens retaining frame with higher degree of accuracy than before is enabled.  
         [0173]     Also, by disposing the guiding member in contact with the inner surface of the fixed barrel, useless space is eliminated, and hence downsizing of the lens barrel is enabled.  
         [0174]     Since no additional component for supporting the lens retaining frame is necessary, a lens barrel with low cost is enabled.  
         [0175]     In another lens barrel, since the guiding members are positioned orthogonally to each other by 90°, or at equal angular intervals by 120°, the direction with less accuracy can be clarified, and hence the uniform accuracy in any directions in 360° can be maintained, whereby support of the lens retaining frame with higher degree of accuracy than before is enabled.  
         [0176]     In another lens barrel, since the guiding member is supported on the inner surface of the fixed barrel, rigidity of the guiding member increases, and hence the lens supporting frame can be supported with high degree of accuracy.  
         [0177]     Also, according to the third aspect of the invention, the first engaging portion and the third engaging portion achieves the first supporting device, the second engaging portion and the fourth engaging portion achieves the second supporting device, and adjustment and correction of the four respective engaging portions enables support of the lens retaining frame with higher degree of accuracy than before.  
         [0178]     Also, by disposing the guiding portion in contact with the inner surface of the lens barrel, the useless space is eliminated, and hence downsizing of the lens barrel is enabled.  
         [0179]     Also, since no additional component for supporting the lens retaining frame is necessary, a lens barrel with low cost is enabled.  
         [0180]     In another lens barrel, since the connecting portion which transmits force to move the lens retaining frame in the direction of the optical axis is located between the first engaging portion and the second engaged portion which provides a long length of engagement, the engaging portion which receives moment of rotation generated at the connecting portion is long, and hence rattling or deformation can hardly occur, whereby support of lens retaining frame with high degree of accuracy is enabled.  
         [0181]     In another lens barrel, by providing projections at the engaging portion, friction is reduced and the contact point is clarified, whereby support of the lens retaining frame with high degree of accuracy is enabled.  
         [0182]     In still another lens barrel, when a long engaging portion of the first lens retaining frame engages a certain one guiding member, the length of engagement can be increased effectively with respect to the limited length of the guiding member by engaging the second lens retaining frame with the short engaging portion. Therefore, support of the lens retaining frame with high degree of accuracy and downsizing of the lens barrel in the direction of the optical axis are enabled.  
         [0183]     In another lens barrel, since the guiding member and the engaging portion provide contact between the flat surfaces, engagement being resistant for destruction or deformation is established against the force from the outside, and hence support of the lens retaining frame with high degree of accuracy is enabled.  
         [0184]     In still another lens barrel, since the guiding member on the fixed barrel has a recess, no bulge is present and hence the size of the lens barrel in the diametrical direction can be reduced.  
         [0185]     In another lens barrel, by establishing a point contact between the guiding member and the connecting portion, friction is reduced and the contact position is clarified. Consequently, support of the lens retaining frame with high degree of accuracy is enabled.  
         [0186]     In still another lens barrel, since the contact between the guiding member and the connecting portion is a point contact between a straight line and an arcuate line, friction is reduced, the contact position is clarified, and the point contact can be maintained even when the connecting portion is inclined with respect to the guiding member. Consequently, support of the lens retaining frame with high degree of accuracy is enabled.  
         [0187]     In another lens barrel, by eliminating rattling between the guiding member and the connecting portion by a resiliently pressing device, support of the lens retaining frame with high degree of accuracy is enabled.  
         [0188]     Also, by generating resiliency by the shape of one of the guiding member of the connecting portion, necessity of additional components is eliminated, and hence the lens barrel with low cost is enabled.  
         [0189]     The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiment is therefore 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 and all changes which come within the meaning and range of equivalent of the claims are thereof intended to be embraced therein.  
         [0190]     This application claims priority from Japanese Patent Application No. 2003-393408 filed Nov. 25, 2003, which is hereby incorporated by reference herein.