Abstract:
A lens apparatus is disclosed, which is capable of keeping the engagement of a protruding portion of a first member and a cam groove portion of a second member even if an external force acts on the apparatus. The lens apparatus comprises: a first member including first and second protruding portions; and a second member including a first groove portion with which the first protruding portion engages, and a second groove portion into which the second protruding portion is inserted. The second protruding portion and the second groove portion are away from each other in a case where the first and second members are located in a specified positional relationship, and come into contact with each other in a case where the first and second members are located in another positional relationship.

Description:
FIELD OF THE INVENTION 
   The present invention relates to a lens apparatus which includes a member having a protruding portion and a member having a groove portion that the protruding portion engages with, the members being moved relatively by their relative rotation, and an image-taking apparatus with the same. 
   BACKGROUND OF THE INVENTION 
   In compact film cameras and digital still cameras equipped with an image-pickup element such as a CCD sensor, a so-called collapsible lens apparatus is provided for good portability, which is housed in the camera body in a non-image-taking state. 
   In such a collapsible lens barrel, a barrel member is movable in a direction of the optical axis by the engagement of a cam groove portion and a cam follower pin. 
   When the lens barrel is in a protruded state (image-taking state), there is a possibility that the front barrel will receive a strong impact in a case where the camera is dropped or collides with something in a state in which the camera is hung with a strap. Therefore, a lens barrel has been disclosed in Japanese Patent Laid-Open application 2002-90611, which has a structure capable of preventing the disengagement of the cam groove portion and cam follower pin. 
   In the lens barrel disclosed in Japanese Patent Laid-Open application 2002-90611, the disengagement of a tapered roller for cam driving from the cam groove portion is prevented by the contact of a cylindrical roller, which is provided separately from the tapered roller, with a disengagement preventing groove portion. 
   However, in the lens barrel disclosed in Japanese Patent Laid-Open application 2002-90611, the tapered roller and the cylindrical roller are arranged in the optical axis direction. In this case, when an external force acts on the lens barrel, the lens barrel is deformed, and thereby the tapered roller is displaced along the sidewall of the cam groove portion and the cylindrical roller is also displaced. Consequently, the contact area of the cylindrical roller and the disengagement preventing groove portion is reduced. This is not preferable for ensuring the strength of the lens barrel. 
   BRIEF SUMMARY OF THE INVENTION 
   One object of the present invention is to provide a lens apparatus capable of keeping the engagement of a protruding portion provided in a first member and a cam groove portion provided in a second member even if an external force acts on the lens barrel, and to provide an image-taking apparatus with the same. 
   A lens apparatus that is one aspect of the present invention is a lens apparatus which comprises: a first member which includes a first protruding potion and a second protruding portion; and a second member which includes a first groove portion with which the first protruding portion engages, and a second groove portion into which the second protruding portion is inserted. The second protruding portion and the second groove portion are away from each other in a case where the first and second members are located in a specified positional relationship in a direction orthogonal to an optical axis, and come into contact with each other in a case where the first and second members are located in a positional relationship other than the specified positional relationship. 
   A lens apparatus that is another aspect of the present invention is a lens apparatus which comprises: a first member which includes a first protruding potion having a tapered shape; and a second member which includes a first groove portion that is a cam groove portion with which the first protruding portion engages, the first and second members being moved relatively in a direction of an optical axis by their relative rotation. The first member includes a second protruding portion having one of a tapered shape with a taper angle smaller than that of the first protruding portion and a non-tapered shape, and the second member includes a second groove portion into which the second protruding portion is inserted. 
   Other objects and further features of the present invention will become readily apparent from the following description of the preferred embodiments with reference to accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is an exploded perspective view showing the structure of a lens barrel that is an embodiment of the present invention. 
       FIG. 2  is a sectional view showing the lens barrel of the embodiment in a collapsed state. 
       FIG. 3  is a sectional view showing the lens barrel of the embodiment in a wide-angle state. 
       FIG. 4  is a sectional view showing the lens barrel of the embodiment in a telephoto state. 
       FIG. 5  is an exploded perspective view showing the supporting structure of a first and second barrel in the lens apparatus of the embodiment. 
       FIGS. 6A to 6D  are enlarged view showing the supporting part of the second barrel. 
       FIG. 7  is an exploded perspective view showing a unit including the first barrel. 
       FIGS. 8A to 8E  are explanatory drawings showing the behavior of the first barrel when an external force acts on it. 
       FIG. 9  is a block diagram showing a camera equipped with the lens barrel of the embodiment. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Preferred embodiments of the present invention will hereinafter be described with reference to the drawings. 
   The description will be given of a lens barrel (lens apparatus) that is an embodiment of the present invention. The image-taking optical system in the lens barrel of this embodiment is constituted by four lens units including a convex lens unit, a concave lens unit, a convex lens unit and a convex lens unit in order from an object side. Further, the lens barrel of this embodiment is a collapsible lens barrel whose total length becomes shorter by shortening the distances between the four lens units in a non-use state (non-image-taking state) than in an in-use state (image-taking state). 
     FIG. 1  is an exploded perspective view showing the structure of the lens barrel of this embodiment,  FIG. 2  is a sectional view showing the lens barrel in a collapsed state.  FIG. 3  is a sectional view showing the lens barrel in a wide-angle state, and  FIG. 4  is a sectional view showing the lens barrel in a telephoto state. 
   In these figures, L 1  denotes a first lens unit, L 2  a second lens unit. L 3  denotes a third lens unit for correcting an image blurring by its movement in a direction substantially orthogonal to the optical axis. L 4  denotes a fourth lens unit for performing focusing by its movement in the optical axis direction. 
     1  denotes a first barrel which is a first member and holds the first lens unit L 1 ,  2  a second barrel holding the second lens unit L 2 .  3  denotes a shift unit holding the third lens unit L 4  and moving the third lens unit L 4  in the direction substantially orthogonal to the optical axis. 
     3   a  denotes a cam pin having a tapered surface and being fixed to the rear end portion of the shift unit  3  by press fitting or the like.  4  denotes a movable frame holding the fourth lens unit  4 . 
     5 ,  6  and  7  denote guide bars extending in the optical axis direction. The guide bars  5  and  6  support the shift unit  3  so that it can move in the optical axis direction. The guide bars  7  and  6  support the movable frame  4  so that it can move in the optical axis direction. 
     8  denotes a supporting frame for positioning and fixing one end (front side end in the lens barrel) of each of the guide bars  5 ,  6  and  7 .  9  denotes a rear barrel for positioning and fixing the other end (rear side end in the lens barrel) of each of the guide bars  5 ,  6  and  7 . An image-pickup element such as a CCD sensor or CMOS sensor is fixed to the rear barrel  9 . The supporting frame  8  is fixed to the rear barrel  9  with three screws. 
     10  denotes a fixed barrel whose position in the optical axis direction is fixed.  11  denotes a cam barrel positioned in the optical axis direction by the rear barrel  9  and held rotatably around the optical axis with respect to the outer circumference of the fixed barrel  10 . 
   In the inner circumferential wall surface and outer circumferential wall surface of the cam barrel that is a second member, a plurality of cam groove portions are formed. Cam follower pins engage with these cam groove portions, as described later. 
     12  denotes a stopper stopping the rotation of the cam barrel  11 , and the stopper  12  is fixed to the rear barrel  9  with screws. When the cam barrel  12  rotates by a predetermined amount around the optical axis, the cam barrel  11  contacts the stopper  12  to stop a further rotation of the cam barrel  11 . 
     13  denotes a diaphragm unit (iris diaphragm) having a plurality of light-shielding blades. Moving these light-shielding blades with respect to a fixed-light-passing aperture, which is formed in the diaphragm unit  13 , changes the diameter of the light-passing aperture formed by the light-shielding blades, thereby making it possible to change the amount of light directing an image plane. Further, by switching the position of the light-shielding blades between an open position and the close position, the diaphragm unit functions as a shutter. 
     14  denotes a focus motor that is the driving source of the fourth lens unit L 4 , and has a lead screw  14   a  rotating together with its rotor. The lead screw  14   a  engages with a rack  4   a  provided on the movable frame  4 , and the rack  4   a  is moved in the optical axis direction (longitudinal direction of the lead screw  14   a ) according to the rotation of the lead screw  14 . Thereby the fourth lens unit L 4  is moved in the optical axis direction. 
   A torsion coil spring  4   b  biases the rack  4   a  and movable frame  4  to one side to eliminate backlashes between the rack  4   a  and the lead screw  14   a , and between the movable frame  4  and the guide bars  6  and  7 . The focus motor  14  is fixed on the supporting frame  8  with two screws. 
     15  denotes a zoom motor that is a driving source for rotating the cam barrel  11 . The zoom motor  15  is interlocked with a gear portion  11   a  formed at the rear end of the cam barrel  11  via a reduction mechanism (not shown in the figure). The driving force of the zoom motor  15  is transmitted to the cam barrel, thereby rotating the cam barrel  11  around the optical axis. 
   A zoom operation is performed by the rotation of the cam barrel  11  around the optical axis, as described later. The zoom motor  15  is fixed on the rear barrel  9  with two screws. 
     16  denotes a photoelectric detector having a light-emitting portion and a light-receiving portion that receives light from the light-emitting portion. A light-shielding portion  4   c  provided on the movable frame  4  is moved into and out of the gap between the light-emitting portion and the light-receiving portion according to the movement of the movable frame  4  in the optical axis direction, and the movement of the light-shielding portion  4   c  switches the state of the photoelectric detector  16  between a light-shielding state and a light-receiving state. 
   The photoelectric detector  16  is used for detecting the reference position of the fourth lens unit L 4  and functions as a focus reset switch since it outputs a signal according to the switching between the light-shielding state and the light-receiving state. 
     17  denotes a photoelectric detector, and its state switches between a light-receiving state and a light-shielding state according to the rotation of a lever  18  as described later. The photoelectric detector  17  is used for detecting the reference position of the zoom operation and functions as a zoom reset switch since it outputs a signal according to the switching between the light-receiving state and the light-shielding state. 
   The lever  18  engages rotatably with a pin  9   a  provided on the rear barrel  9 . The lever  18  contacts a cam portion  11   b  shown in  FIGS. 2 and 3  by receiving a biasing force from a torsion coil spring  19 . The cam portion  11   b  is formed on the inner circumferential surface of the cam barrel  11 , and extends inward in a direction of the barrel&#39;s diameter. 
   When the cam barrel  11  rotates around the optical axis, the lever  18  is rotated around the pin  9   a  by being pushed by the cam portion  11   b . A light-shielding portion  18   a  formed on the lever  18  is moved with respect to the photoelectric detector  17 . 
   Using an output signal from the photoelectric detector  17  at the time of switching from the light-receiving state to the light-shielding state makes it possible to detect the rotation angle of the cam barrel  11 . 
   Next, the description will be given of the supporting structure of the first and second lens unit L 1  and L 2 . 
     FIG. 5  is an exploded perspective view showing the supporting structure of the first and second lens unit L 1  and L 2  when viewed from the rear side of the lens barrel. 
   At the front end of the fixed barrel  10 , three splines  10   a  are formed equiangularly in the circumferential direction of the fixed barrel  10 . On the inner circumferential wall surface of the first barrel  1 , three straight groove portions  1   a  extending in the optical axis direction are formed. The straight groove portions  1   a  engage with the splines  10   a.    
   The engagement of the three splines  10   a  and the three straight groove portions  1   a  permits the first barrel  1  to move with respect to the fixed barrel  10  only in the optical axis direction without rotating around the optical axis. 
   At the rear end of the first barrel  1 , three cam follower pins  1   b  that are first protruding portion and three impact-resistant pins  1   c  that are second protruding pins are fixed by press fitting or the like. These cam follower pins  1   b  and impact-resistant pins  1   c  are arranged alternately and equiangularly in the circumferential direction of the first barrel  1 . Each of the cam follower pins  1   b  and impact-resistant pins  1   c  has a taper surface at the tip thereof. 
   The three cam follower pins  1   b  engage with three cam groove portions  11   c , respectively, and the three impact-resistant pins  1   c  engage with three cam groove portions  11   d , respectively, the cam groove portions  11   c  and  11   d  being formed on the outer circumferential surface of the cam barrel  11 . The cam groove portion  11   c  has a shape corresponding to the shape of tip of the cam follower pins  1   b , and the cam groove portion  11   d  has a shape corresponding to the shape of tip of the impact-resistant pin  1   c . In other words, the sidewalls of the cam groove portions  11   c  and  11   d  have a tapered surface. 
   Engaging the cam follower pins  1   b  and impact-resistant pins  1   c  with the cam groove portions  11   c  and  11   d  makes it possible to prevent the first lens unit from tilting with respect to the optical axis. 
   Further, when the cam barrel  11  rotates around the optical axis, the first barrel  1  is moved with respect to the cam barrel  11  in the optical axis direction by a camming action of the cam groove portions  11   c  and  11   d  engaging with the cam follower pin  1   b  and impact-resistant pin  1   c , respectively. 
   The cam tracks of the cam groove portions  11   c  and  11   d , which are formed at different phase positions on the outer circumferential surface of the cam barrel  11 , substantially coincide with each other. 
   The cam follower pin  1   b  consistently engages with the cam groove portion  11   c  regardless of whether the lens barrel is in the collapsed state (non-image-taking state) or the protruding state (image-taking state). The tip of the impact-resistant pin  1   c  (portion that engages with the cam groove portion  11   d ) is formed in a generally cylindrical shape. 
   The tip of the impact-resistant pin  1   c  is located in the cam groove portion  11   d , and away from the sidewall of the cam groove portion  11   d  without engaging with the cam groove portion  11   d  in a state in which an external force does not act on the lens barrel (first barrel  1 ), that is, a state in which the first barrel  1  and the cam barrel  11  are located in a specific positional relationship. 
   When an external force (impact) acts on the first barrel  1  as in the case where the camera equipped with the lens barrel of this embodiment is dropped, the cam follower pin  1   b  is moved along the sidewall of the cam groove portion  11   c  in a direction in which the cam follower pin  1   b  may disengage from the cam groove portion  11   c . However, at this time, the impact-resistant pin  1   c  engages with the cam groove portion  11   d , thereby preventing the cam follower pin  1   b  from disengaging from the cam groove portion  11   c.    
   In other words, according to this embodiment, since the impact-resistant pin  1   c , which is the second protruding portion, contact the cam groove portion  11   d  when the external force acts on the lens barrel, it is possible to keep the engaging state of the cam follower pin  1   b , which is the first protruding portion, and the cam groove portion  11   c.    
   Next, the detailed description will be given of the behavior of the first barrel  1  on which the external force acts with reference to  FIG. 8 . 
     FIG. 8A  shows the first barrel  1  when viewed from the rear side. The cam follower pins  1   b  and impact-resistant pins  1   c  are arranged alternately and equiangularly in the circumferential direction of the first barrel  1 . 
     FIG. 8B  is a sectional view of the first barrel  1  and cam barrel  11  in the optical axis direction, and shows a state of the engagement of the cam follower pin  1   b  and impact-resistant pin  1   c  with the cam groove portions  11   c  and  11   d.    
     FIG. 8C  is a partially sectional view showing the impact-resistant pin  1   c  and the cam groove portion  11   d  in a state in which the external force does not act on the first barrel  1 . As shown in this figure, though the impact-resistant pin  1   c  is located in the cam groove portion  11   d , the impact-resistant pin  1   c  does not contact the sidewall of the cam groove portion  11   d.    
     FIG. 8D  is a partially sectional view showing the cam follower pin  1   b  and the cam groove portion  11   c . As shown in this figure, the cam follower pin  1   b  contact a part of the sidewall of the cam groove portion  11   c.    
   As shown in  FIGS. 8C and 8D , the taper angle of the cam follower pin  1   b  is larger than that of the impact-resistant pin  1   c . The taper angle is an angle θ of the tapered surface with respect to the central axis of the pin, as shown in  FIG. 8E . 
   Although the impact-resistant pin  1   c  has a tapered surface in this embodiment, the impact-resistant pin may be formed in a non-tapered shape, that is, a substantially cylindrical shape. 
   As shown in  FIG. 8B , when the external force acts on the front end of the first barrel  1  in the direction shown by the arrow F, the cam follower pin  1   b  is moved along the sidewall of the cam groove portion  11   c  because they have the tapered surfaces. Thereby, the cam follower pin  1   b  is displaced outward in the diameter direction of the first barrel  1 , as shown by the arrow D 1 . 
   Then, the first barrel  1  deforms elastically with the displacement of the cam follower pin  1   b , and its shape of cross section in the direction orthogonal to the optical axis thereby becomes a generally triangular shape. 
   At this time, the three impact-resistant pins  1   c , which are arranged respectively between the three cam follower pins  1   b , are displaced in the direction shown by the arrow D 2 , or inward in the diameter direction of the first barrel  1 , and contact the cam groove portion  11   d.    
   As described above, when the external force shown by the arrow F in  FIG. 8B  acts on the first barrel  1 , the contact area of the cam follower pin  1   b  and the cam groove portion  11   c  is reduced by the outward displacement of the cam follower pin  1   b  in the diameter direction of the first barrel  1 . On the other hand, the impact-resistant pin  1   c  is displaced inward in the diameter direction of the first barrel  1  and contacts the cam groove portion  11   d.    
   Therefore, since the impact-resistant pin  1   c  contacts the cam groove portion  11   d  even if the contact area of the cam follower pin  1   b  and the cam groove portion  11   c  reduces, it is possible to receive the external force by the contact area of the impact-resistant pin  1   c  and the cam groove portion  11   d.    
   Consequently, it is possible to prevent the disengagement of the cam follower pin  1   b  from the cam groove portion  11   c , which is caused by the action of the external force only on the cam follower pin  1   b . Further, the contact of the impact-resistant pin  1   c , which has been displaced inward in the diameter direction of the first barrel  1 , with the cam groove portion  11   d  ensures a sufficient total contact area, thereby making it possible to increase the strength of the lens barrel. 
   As shown in  FIG. 5 , the second barrel  2  has three arm portions  2   b  extending in the optical axis direction. A cam follower pin  20  and two pins  21  are fixed on the tip of the arm portions  2   b  by press fitting or the like. The three arm portions  2   b  are provided equiangularly in the circumferential direction of the second barrel  2 . 
   The fixed barrel  10  has three straight groove portions  10   b  extending in the optical axis direction. These straight groove portions  10   b  engage with the cylindrical portions of the pins  20  and  21 . The three straight groove portions  10   b  and the pins  20  and  21  are provided with the same phase positional relationship. The pins  20  and  21  extend through the straight groove portion  10   b  and engage with a cam groove portion  11   e  formed on the inner circumferential surface of the cam barrel  11 . 
   The engagement of the pins  20  and  21  with the straight groove portion  10   b  permits the second barrel  2  to move with respect to the fixed barrel  10  in the optical axis direction without rotating around the optical axis. 
   Three splines  2   a  are formed in the front end (object side end) of the second barrel  2 , the spline  2   a  extending outward in the diameter direction of the second barrel  2 . The three splines  2   a  are formed equiangularly in the circumferential direction of the second barrel  2 . 
   The three splines  2   a  engage with the three straight groove portions  1   a  formed on the inner circumferential wall surface of the first barrel  1 . Thereby, the rotation of the second barrel  2  with respect to the first barrel  1  around the optical axis is prevented, and thereby the second barrel  2  is positioned with respect to the first barrel  1  around the optical axis. 
   In the configuration described above, since the second barrel  2  engages with the fixed barrel  10  and first barrel  1  via the spline  2   a  and pins  20  and  21 , the second barrel  2  is prevented from tilting with respect to the optical axis. 
   Here, when the first barrel  1  is displaced in the direction orthogonal to the optical axis due to backlashes of the engagement between the first barrel  1  and other members, unevenness of the shape of the groove portion and the like, the front side portion of the second barrel  2  follows to the first barrel  1 . Thereby, it is possible to minimize the relative positional deviation of the first lens unit L 1  held by the first barrel  1  and the second lens unit L 2  held by the second barrel  2 . 
   The cam follower pin  20  has a cone-shaped cam follower portion  20   a  having a tapered surface at its tip. The cam follower portion  20   a  engages constantly with one of the three cam groove portions  11   e  formed on the inner circumferential wall surface of the cam barrel  11 . 
   When the cam barrel  11  rotates around the optical axis, the second barrel  2  is moved with respect to the cam barrel  11  and fixed barrel  1  in the optical axis direction by the engagement of the cam follower portion  20   a  and the cam groove portion  11   e.    
   A leaf spring biases the cam follower pin  20  outward in the diameter direction of the second barrel  2  to make the cam follower portion  20   a  contact the cam groove portion  11   e , thereby eliminating a backlash between the cam follower pin  20  and the cam groove portion  11   e.    
     FIGS. 6A to 6D  are enlarged views showing the engaging part of the second barrel  2  and cam barrel  11 . 
     FIG. 6A  is a partially sectional view of the lens barrel of this embodiment, showing the engaging state of the cam follower pin  20 , the cam groove portion  11   e  and the straight groove portion  10   b . In this embodiment, the pin  21  does not have a portion corresponding to the cam follower portion  20   a  of the cam follower pin  20  as shown in  FIG. 5 , and the position of the second barrel  2  in the optical axis direction is determined only by the engagement of the cam follower portion  20   a  of the cam follower pin  20  and the cam groove portion  11   e.    
   When an external force (impact) due to the camera&#39;s drop or the like acts on the second barrel  2 , there is a possibility that the external force will act only on the cam follower pin  20 , and thereby the cam follower portion  20   a  will disengage from the cam groove portion  11   e.    
   Here, a pin  200  having a shape shown in  FIG. 6B  can be used instead of the pin  21 . The pin  200  has a tapered pin portion  200   a  which is located in the cam groove portion  11   e  in a normal in-use state in which an external force do not act on the second barrel  2 . In other words, the tapered pin portion  200   a  does not contact the sidewall of the cam groove portion  11   e  in the normal in-use state. 
   The cam groove portion  11   e  engaging with the pin  200  has the same cam track as the cam groove portion  11   e  engaging with cam follower pin  20 , and these cam groove portions  11   e  are formed at positions (phases) different from each other on the cam barrel  11 . 
   In the configuration including the pin  200 , when the cam follower portion  20   a  of the cam follower pin  20  comes close to disengaging from the cam groove portion  11   e  by the external force, the tapered pin portion  200   a  of the pin  200  contacts the cam groove portion  11   e.    
   Consequently, it is possible to receive the external force evenly at the one cam follower pin  20  and two pins  200 , thereby making it possible to increase the durability of the second barrel  2  against external impacts. 
   Further, as shown in  FIGS. 6C and 6D , a step portion  10   c  can be formed in the straight groove portion  10   b  of the fixed barrel  10 , and a cam follower pin  210  can be used instead of the pin  21 , the pin  210  having a cam follower portion  210   a  engaging with the cam groove portion  11   e  and a flange portion  210   b  engaging with the step portion  10   c.    
   In the configuration shown in  FIGS. 6C and 6D , the external force can be received by the contact of the cam follower portion  20   a  of the cam follower pin  20  and the cam groove portion  11   e , the contact of the cam follower portion  210   a  of the cam follower pin  210  and the cam groove portion  11   e , and the contact of the flange portion  210   b  and the step portion  10   c.    
   In this case, since the external force is received by the above-mentioned plural contact portions, it is possible to distribute the external force to the plural contact portions, thereby making it possible to increase the durability of the second barrel  2 . 
   The three splines  2   a  formed at the front end of the second barrel  2  and the pins  20  and  21  are provided on the three arm portions  2   b . In other words, the spline  2   a  and the pin  20  or  21  are provided at the same phase. The spline  10   a  and straight groove portion  10   b  formed on the fixes barrel  10  are provided at the same phase position in the circumferential direction of the fixed barrel  10 . 
   In this embodiment, the spline  2   a  of the second barrel  2  and the spline  10   a  of the fixed barrel  10  are provide at the same phase position, and they engage with the same straight groove portion  1   a . Therefore, it is possible to increase the mechanical strength of the first barrel  1  compared to the case where the splines  2   a  and  10   a  are formed at different phase positions on the inner circumferential surface of the first barrel  1  and a plurality of straight groove portions are formed in accordance with the phases of the splines  2   a  and  10   a . In addition, making a flange portion (including the spline  10   a ) formed at the front end of the fixed barrel  10  thicker than a predetermined thickness makes it possible to increase the mechanical strength of the interlocking part of the fixed barrel  10  and the first barrel  1 . 
   Next, the description will be given of the structure of the unit including the first barrel  1  and the first lens unit L 1  with reference to  FIG. 7 .  FIG. 7  is an exploded perspective view of the above-mentioned unit. 
     23  denotes a lens holding frame holding the first lens unit L 1 .  25  denotes a intermediate ring fixed with three screws  26  by sandwiching between screw clamp portions  1   d  formed at the vicinity of the front end of the first barrel  1  and screw clamp portions  23   a  formed on the lens holding frame  23 . The screw clamp portions  1   d  and  23   a  are formed equiangularly in the circumferential direction of the first barrel  1  and the lens holding frame  23 , respectively. 
   The intermediate ring  25  has flange portions  25   a  contacting the screw clamp portions  23   a  formed on the lens the first barrel  1 . The thickness of the flange portion  25   a  in the optical axis direction reduces gradually toward the direction shown by the arrow A in  FIG. 7 . In other words, of the flange portion  25   a , the surface contacting the screw clamp portions  23   a  is a surface substantially orthogonal to the optical axis, and the surface contacting the screw clamp portions  1   d  is a tapered surface tilting with respect to a plane orthogonal to the optical axis. 
   In the above-mentioned configuration, rotating the intermediate ring  25  changes the position of the first lens unit L 1  with respect to the first barrel  1  in the optical axis direction. 
   Further, there is a backlash between the screw  26  and a hole portion formed in the screw clamp portion  23   a  in the direction orthogonal to the optical axis (the diameter direction of the lens holding frame  23 ). Consequently, it is possible to slide the lens holding frame  23  with respect to the intermediate ring  25  in the direction orthogonal to the optical axis, thereby making it possible to adjust the position of the first lens unit L 1  in the direction orthogonal to the optical axis 
   Since the magnification varying optical system in the lens barrel of this embodiment is constituted by the four lens units, the variable magnification factor thereof is larger than a predetermined factor. Consequently, high position accuracy is required for each lens unit. Therefore, this embodiment adopts the structure in which the position of the first lens unit L 1  is adjustable in the optical axis direction and the direction orthogonal thereto, as described above, for ensuring a predetermined optical performance. 
   The first barrel  1 , lens holding frame  23  and intermediate ring  25  are fixed with the three screws  26  after the adjustment of their positions. 
     27  denotes a front mask having an opening. The front mask  27  is fixed to the first barrel  1  with screws.  28  denotes a decorative plate covering the screws for fixing the front mask  27 . The decorative plate  28  is fixed to the front mask  27  by adhesion or the like. 
   In the lens barrel with the above-mentioned structure, as shown in  FIGS. 2 to 4 , the focal length of the image-taking optical system can be changed by changing the distances between the four lens units L 1  to L 4 . Further, as shown in  FIG. 2 , the lens barrel can be housed into a camera body by minimizing the distances between the four lens units L 1  to L 4 . 
     FIG. 9  is a block diagram showing a camera equipped with the lens barrel of this embodiment. 
   In  FIG. 9 ,  50  denotes an optical filter eliminating a high spatial frequency component of the luminous flux from an object and cutting an infrared light. The optical filter  50  is fixed to the lens barrel of this embodiment. 
     51  denotes an image-pickup element such as a CCD sensor or a CMOS sensor. The image-pickup element  51  photoelectrically converts an object image (optical image) formed by the image-taking optical system in the lens barrel into electronic signals. A camera signal processor  52  performs predetermined processing such as color correction and gamma correction on the electronic signals ‘a’ read out from the image-pickup element  51  to generate image signals ‘b’. 
   The image signals ‘b’ are recorded on a recording medium, and are output to a display unit to display a taken image. 
     53  denotes a microcomputer controlling the whole operation of the camera including the operation of the lens barrel. After the power of the camera is on, the microcomputer  53  moves each lens unit in the optical axis direction while monitoring the output of the focus reset switch  54  corresponding to the photoelectric detector  16  and the output of the zoom reset switch  55  corresponding to the photoelectric detector  17 . 
   The microcomputer  53  can move each lens unit in the optical axis direction by controlling the drive of the focus motor  14  and zoom motor  15  via a focus motor driving circuit  56  and a zoom motor driving circuit  57 . 
   When the fourth lens unit L 4  reaches its reference position, in other words, the photoelectric detector  16  is changed from the light-receiving state to the light-shielding state by the light-shielding portion  4   c  formed on the fourth barrel  4 , the output of the focus reset switch  54  is changed. The microcomputer  53  determines that the fourth lens unit L 4  has reached the reference position by detecting the change of the output of the focus reset switch  54 . 
   When the first to third lens units L 1  to L 3  reach their reference positions, in other words, the photoelectric detector  17  is changed from the light-receiving state to the light-shielding state by the light-shielding portion  18   a  formed on the lever  18 , the output of the zoom reset switch  55  is changed. The microcomputer  53  determines that the first to third lens units L 1  to L 3  have reached the reference position by detecting the change of the output of the zoom reset switch  55 . 
   In a case where stepping motors are used as the focus motor  14  and zoom motor  15 , the microcomputer  53  can detect an absolute position of each of the lens units L 1  to L 4  by counting driving pulses input to the stepping motor after the determination of the reference position. Thereby, it is possible to obtain accurate focal length information and focus information of the image-taking optical system. 
   On the other hand, the microcomputer  53  controls the diaphragm unit  13  via a diaphragm driving circuit  58 . In other words, the microcomputer  53  controls the aperture diameter of the diaphragm unit  13  based on luminance information included in the image signals ‘b’ generated by the camera signal processor  52 . 
     59  and  60  denote a PITCH angle detector detecting a tilt angle in a pitch direction (vertical direction) and a YAW angle detector detecting a tilt angle in a yaw direction (horizontal direction), respectively. The detection of the tilt angles is performed by integrating the output of an angular speed sensor such as a vibration gyro, which is fixed in the camera. 
   The microcomputer  53  loads the output of the PITCH angle detector  59  and YAW angle detector  60 , or the tilt angle information of the camera. 
     61  and  62  denote a PITCH coil driving circuit and a YAW coil driving circuit, respectively, the circuits  61  and  62  being for driving the third lens unit L 3  in a plane orthogonal to the optical axis. The shift unit  3  has a so-called moving magnet structure in which a magnet is fixed on the base of the shift unit  3  and a coil is moved together with the third lens unit L 3 . The coil and magnet generate driving force for shifting the third lens unit L 3  in the plane orthogonal to the optical axis. 
     63  and  64  denote a PITCH position detector detecting a shift amount of the third lens unit L 3  in the pitch direction and a YAW position detector detecting a shift amount of the third lens unit L 3  in the yaw direction, respectively. The output of the position detectors  63  and  64  are input to the microcomputer  53 . 
   The shift of the third lens unit L 3  in the plane orthogonal to the optical axis bends the luminous flux passing through the third lens unit L 3 , and thereby the position of the object image formed on the image-pickup element  51  is shifted. 
   When the camera is shaken, by controlling the drive of the third lens unit L 3  so that the object image may be shifted by an amount corresponding to the tilt angle detected by the angle detectors  59  and  60  in a direction opposite to the direction detected by them, the movement of the object image on the pickup surface of the image-pickup element  51  is suppressed. Thereby, it is possible to achieve so-called image stabilization which stabilizes the object image on the image plane even if the camera is shaken. 
   The microcomputer  53  calculates the difference between tilt signals indicating the camera&#39;s tilt, which are obtained from the PITCH and YAW angle detectors  59  and  60 , and shift amount signals indicating the position of the third lens unit L 3 , which are obtained from the PITCH and YAW position detectors  63  and  64 , respectively. Then, the microcomputer  53  performs amplification and phase compensation on the difference signals to generate driving signals, and controls the drive of the third lens unit L 3  based on the driving signals via the PITCH and YAW coil driving circuits  61  and  62 . 
   According to this, the positioning control is performed so that the difference signal may reduce, thereby driving the third lens unit L 3  continuously to target positions for correcting image vibration. 
   On the other hand, in this embodiment, since the magnification varying operation is performed by the relative movement of the first to third lens units L 1  to L 3 , the movement amount of the object image to the shift amount of the third lens units L 3  changes according to the focal length. 
   Therefore, in this embodiment, the shift amount (correction amount) of the third lens units L 3  is determined after the tilt signals are corrected based on the focal length information without determining the shift amount of the third lens units L 3  directly from the tilt signals detected by the PITCH and YAW angle detectors  59  and  60 . Thereby, it is possible to perform the image stabilization according to the focal length of the image-taking optical system. 
   In the above-mentioned embodiment, the description of the camera with lens was made. However, the present invention can be applied to a lens apparatus included in a camera system constituted by a camera and the lens apparatus mounted on the camera. 
   This application claims foreign priority benefits based on Japanese Patent Application No. 2004-229034, filed on Aug. 5, 2004, which is hereby incorporated by reference herein in its entirety as if fully set forth herein.