Abstract:
An optical apparatus includes a barrier member disposed in front of a lens and arranged to be openable and closable, an urging member arranged to exert an urging force on the barrier member, and an abutting member arranged to be capable of abutting on the urging member, wherein, when the abutting member abuts on the urging member, the urging member exerts on the barrier member an urging force acting in a direction of closing the barrier member, and, when the abutting member does not abut on the urging member, the urging member exerts on the barrier member an urging force acting in a direction of opening the barrier member.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention mainly relates to a zoom lens camera, and more particularly to a barrier opening-and-closing device and to a lens barrel and a camera having the barrier opening-and-closing device. 
     2. Description of Related Art 
     In a camera disclosed in Japanese Laid-Open Patent Application No. HEI 7-191380, a pair or a plurality of barrier members are arranged at the fore end part of a lens barrel to be opened and closed within a plane perpendicular to an optical axis by utilizing drawing-in and drawing-out motions of the lens barrel. 
     In another camera disclosed in Japanese Laid-Open Utility Model Application No. HEI 04-091341, a door-like barrier member is arranged at the fore end of a lens barrel to be manually opened toward an object of photo-taking. 
     However, the camera disclosed in Japanese Laid-Open Patent Application No. HEI 7-191380 necessitates use of a complex mechanism for driving the barrier members within the lens barel and also necessitates a large space for retracting the barrier members into the lens barrel in opening them. 
     In the barrier mechanism of the camera disclosed in Japanese Laid-Open Utility Model Application No. HEI 04-091341, the fore end of the barrier member is in a pointed shape when it is in an open state, and thus can not be used as a hood. Therefore, the camera necessitates a hood member to be arranged separately from a barrier member. This, however, causes an increase in the number of parts. 
     BRIEF SUMMARY OF THE INVENTION 
     In accordance with an aspect of the invention, there is provided a camera or an optical apparatus, which comprises a barrier member disposed in front of a lens and arranged to be openable and closable, an urging member arranged to exert an urging force on the barrier member, and an abutting member arranged to be capable of abutting on the urging member, wherein, when the abutting member abuts on the urging member, the urging member exerts on the barrier member an urging force acting in a direction of closing the barrier member, and, when the abutting member does not abut on the urging member, the urging member exerts on the barrier member an urging force acting in a direction of opening the barrier member, so that the structural arrangement of a barrier can be simplified. 
     The other and further aspects and features of the invention will become apparent from the following detailed description of preferred embodiments thereof taken in connection with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
     FIGS.  1 ( a ) to  1 ( d ) show the appearance of a camera having a barrier opening-and-closing device according to a first embodiment of the invention, FIG.  1 ( a ) being a top view showing the camera in a state of having its lens barrel at a wide-angle end position, FIG.  1 ( b ) being a front view showing the camera in the same state, FIG.  1 ( c ) being a side view showing the camera in the same state, and FIG.  1 ( d ) being a side view showing the camera in a state of having its lens barrel at a telephoto end position. 
     FIGS.  2 ( a ) to  2 ( c ) show the camera having the barrier opening-and-closing device according to the first embodiment, FIG.  2 ( a ) being a top view of the camera in a state of having the lens barrel at a stowed position, FIG.  2 ( b ) being a front view of the camera in the same state, and FIG.  2 ( c ) being a side view of the camera in the same state. 
     FIGS.  3 ( a ) to  3 ( d ) are enlarged views showing the fore end of a lens barrel of the camera according to the first embodiment, FIG.  3 ( a ) being a perspective view showing a barrier in a closed state, FIG.  3 ( b ) being a perspective view showing the barrier in an open state, FIG.  3 ( c ) being a front view showing the barrier in the closed state, and FIG.  3 ( d ) being a front view showing the barrier in the open state. 
     FIGS.  4 ( a ) and  4 ( b ) are partly-broken enlarged perspective views of the fore end of the lens barrel of the camera according to the first embodiment, FIG.  4 ( a ) showing the barrier in a closed state, and FIG.  4 ( b ) showing the barrier in an open state. 
     FIGS.  5 ( a ) and  5 ( b ) are partly-broken enlarged views of the fore end of the lens barrel of the camera according to the first embodiment, FIG.  5 ( a ) being a front view showing the barrier in a closed state, and FIG.  5 ( b ) being a side view showing the barrier in the closed state. 
     FIGS.  6 ( a ) and  6 ( b ) are partly-broken enlarged views of the fore end of the lens barrel of the camera according to the first embodiment, FIG.  6 ( a ) being a front view showing the barrier in an open state, and FIG.  6 ( b ) being a side view showing the barrier in the open state. 
     FIGS.  7 ( a ) to  7 ( c ) are enlarged views of the fore end of a lens barrel of a camera according to a second embodiment of the invention, FIG.  7 ( a ) being a front view showing a barrier in an open state, FIG.  7 ( b ) being a side view showing the barrier in the open state, and FIG.  7 ( c ) being a top view showing the barrier in the open state. 
     FIGS.  8 ( a ) to  8 ( c ) are enlarged views of the fore end of the lens barrel of the camera according to the second embodiment, FIG.  8 ( a ) being a front view showing the barrier in a closed state, FIG.  8 ( b ) being a side view showing the barrier in the closed state, and FIG.  8 ( c ) being a top view showing the barrier in the closed state. 
     FIG. 9 is a vertical sectional side view showing a camera according to a third embodiment of the invention in a state of having a lens barrel at a stowed position. 
     FIG. 10 is a vertical sectional side view showing the camera according to the third embodiment in a state of having the lens barrel at a wide-angle end position. 
     FIG. 11 is a vertical sectional side view showing the camera according to the third embodiment in a state of having the lens barrel at a telephoto end position. 
     FIG. 12 is a vertical sectional side view showing a camera according to a fourth embodiment of the invention in a state of having a lens barrel at a stowed position. 
     FIG. 13 is a vertical sectional side view showing the camera according to the fourth embodiment in a state of having the lens barrel at a wide-angle end position. 
     FIG. 14 is a vertical sectional side view showing the camera according to the fourth embodiment in a state of having the lens barrel at a telephoto end position. 
     FIG. 15 is a block diagram of a control arrangement of the camera according to the third embodiment of the invention in respect to focusing and zooming actions of the camera. 
     FIG. 16 is an exploded perspective view of a lens barrel of a camera having a barrier device according to a fifth embodiment of the invention. 
     FIG. 17 is a partly cutaway view showing the lens barrel of the camera according to the fifth embodiment in a state of having the barrier (device) opened. 
     FIGS.  18 ( a ) to  18 ( d ) show the open state of the barrier in the fifth embodiment, FIG.  18 ( a ) being a front view showing the lens barrel in a state of having its fancy cover removed, FIG.  18 ( b ) being a sectional side view of the lens barrel including a YZ plane and excluding a lower barrier member, FIG.  18 ( c ) being a side view of the lens barrel with a sectional view including the YZ plane showing only the fancy cover and a fore end tube, and FIG.  18 ( d ) being a front view showing the fancy cover. 
     FIG. 19 is a partly cutaway view showing the lens barrel of the camera according to the fifth embodiment in a state of having the barrier thereof closed. 
     FIGS.  20 ( a ) and  20 ( b ) show the lens barrel in the fifth embodiment in a state of having the barrier closed, FIG.  20 ( a ) being a front view showing the lens barrel with the fancy cover removed, and FIG.  20 ( b ) being a side view showing the lens barrel with a sectional view including the YZ plane showing only the fancy cover and the fore end tube. 
     FIG. 21 is a side view for explaining a situation in which, in the fifth embodiment, after a rectilinear motion tube is moved in the direction of parting from each spring and each barrier member is opened, an upper barrier member is forcibly pushed from the open position in the direction of an arrow toward a closed position. 
     FIG. 22 is a side view for explaining a situation in which, in the fifth embodiment, after the rectilinear motion tube is moved in the direction of pushing each spring and each barrier member is closed, the upper barrier member is forcibly pushed from the closed position in the direction of an arrow toward the open position. 
     FIG. 23 is a perspective view showing the appearance of the lens barrel of the camera according to the fifth embodiment in a state of having the barrier at an open position. 
     FIG. 24 is a perspective view showing the appearance of the lens barrel of the camera according to the fifth embodiment in a state of having the barrier at a closed position. 
     FIGS.  25 ( a ) to  25 ( c ) show a barrier device according to a sixth embodiment of the invention, FIG.  25 ( a ) being a front view showing the barrier device in a state of having a barrier at an open position with a fancy cover excluded from the illustration, FIG.  25 ( b ) being a side view showing the barrier device in a state of having the barrier at the open position with a sectional view including the YZ plane showing only the fancy cover and a fore end tube, and FIG.  25 ( c ) being a side view showing the barrier device in a state of having the barrier at a closed position. 
     FIGS.  26 ( a ) to  26 ( c ) show a barrier device according to a seventh embodiment of the invention, FIG.  26 ( a ) being a front view showing the barrier device in a state of having a barrier at an open position with a fancy cover excluded from the illustration, FIG.  26 ( b ) being a side view showing the barrier device in a state of having the barrier at the open position with a sectional view including the YZ plane showing only the fancy cover and a fore end tube, and FIG.  26 ( c ) being a side view showing the barrier device in a state of having the barrier at a closed position. 
     FIGS.  27 ( a ) to  27 ( d ) show a barrier device according to an eighth embodiment of the invention, FIG.  27 ( a ) being a front view showing the barrier device in a state of having a barrier at an open position with a fancy cover excluded from the illustration, FIG.  27 ( b ) being a side view showing the barrier device in a state of having the barrier at the open position with a sectional view including the YZ plane showing only the fancy cover and a fore end tube, FIG.  27 ( c ) being a side view showing the barrier device in a state of having the barrier at a closed position, and FIG.  27 ( d ) being a top view showing springs in the barrier device in a look-through manner. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Hereinafter, preferred embodiments of the invention will be described in detail with reference to the drawings. 
     (First Embodiment) 
     The appearance of a camera having a barrier opening-and-closing device according to a first embodiment of the invention is first described. 
     FIGS.  1 ( a ) to  1 ( d ) show the appearance of the camera having the barrier opening-and-closing device according to the first embodiment in a state of having its lens barrel at a wide-angle end position. The camera permits photo-taking when barrier members  401  and  411  disposed at the fore end of the lens barrel open to expose a lens surface. 
     FIGS.  2 ( a ),  2 ( b ) and  2 ( c ) show the camera in a state of having the lens barrel at a stowed position where the barrier members  401  and  411  disposed at the fore end of the lens barrel are closed. With the camera in the state of having the lens barrel at the stowed position, the lens surface is covered with the barrier members  401  and  411 . A front face plate  406  is arranged around the barrier members  401  and  411  as an external fancy cover. The external faces of the barrier members  401  and  411  and the front face plate  406  are in cylindrical surface shapes having the same curvature. The upper boundary line between the front face plate  406  and the barrier member  401  has about the same curvature as the external face curvature of the barrier member  401  in a state where the barrier members  401  and  411  are closed. Therefore, even when the barrier members  401  and  411  are in an open state as shown in FIGS.  3 ( b ) and  3 ( d ), no large clearance is brought about at the boundary between the front face plate  406  and the barrier member  401 . 
     The barrier opening-and-closing device according to the first embodiment is next described. FIGS.  4 ( a ) and  4 ( b ) are perspective views clearly showing a feature of the first embodiment. FIG.  4 ( a ) shows the barrier opening-and-closing device in a state of having the barrier members  401  and  411  at their closed positions. 
     The barrier member  401  has a curved surface having the curvature of a cylinder and is provided with rotation shaft parts  401   a  and hole parts  401   b  at its two ends. The rotation shaft parts  401   a  are arranged to enable the barrier member  401  to open and close in front of the lens barrel by swinging thereon. The hole parts  401   b  are arranged to have two ends of a spring  402  fitted therein. An antireflection coating material is applied to the inner surfaces of the barrier member  401 . 
     The spring  402  is composed of fore end parts  402   a  which are arranged to be fitted into the hole parts  40   b  of the barrier member  401 , projections  402   b  which are arranged to come into contact with a rectilinear motion tube (to be described later), and a fixing part  402   c  where the spring  402  is fixed by a screw  403 . 
     A fore end tube  404  is located at the fore end of the lens barrel. The fore end tube  404  is provided with bearing parts  404   a  where the rotation shaft parts  401   a  of the barrier member  401  are respectively rotatably secured, a spring receiving part  404   c  where the spring  402  is secured in place, hole parts  404   b  where the projections  402   b  of the spring  402  are allowed to escape, and a bonding face  404   d  where the front face plate  406  is secured by bonding thereto. The screw  403  secures the spring  402  to the spring receiving part  404   c  of the fore end tube  404 . 
     Referring to FIGS.  4 ( a ) and  4 ( b ), the front face plate  406 , which is shown only at the lower left end part thereof in FIGS.  4 ( a ) and  4 ( b ), is provided with bearing parts  406   a  (shown in FIG.  5 ( b )) arranged to rotatably secure thereto the rotation shaft parts  401   a  of the barrier member  401 , a barrel-shaped aperture part  406   b  arranged to allow a light flux necessary for forming an image to pass there, a hole part  406   c  arranged to allow the barrier member  401  to escape, and a bonding face  406   d  at which the front face plate  406  is bonded to the fore end tube  404 . The surface of the front face plate  406  is in a cylindrical surface shape, as described in the foregoing. 
     A rectilinear motion tube  405  is disposed on the inner side of the fore end tube  404 . The rectilinear motion tube  405  has projections  405   b  arranged to push the projections  402   b  of the spring  402  toward an object to be photographed when the lens barrel is in a stowed state. 
     When the lens barrel is at a position between a wide-angle end position and a telephoto end position in a photo-taking state, a shown in FIG.  4 ( b ), the two fore end parts  402   a  of the spring  402  are trying to flex toward a film which is on an image forming plane, while each of the fitting hole parts  401   b  for the spring  402  is located on the periphery of each of the rotation shaft parts  401   a.  Therefore, the barrier member  401  is urged to swing in the direction of opening, as shown in FIG.  6 ( b ). The elastic force of the spring  402  thus urges the barrier member  401  to be always opened upward. 
     Next, when a switch of the camera is turned off, the state of the lens barrel comes to change into a stowed state. The rectilinear motion tube  405  then approaches the fore end tube  404 . The projections  405   b  of the rectilinear motion tube  405  come to push the projections  402   b  of the spring  402  toward the front of the fore end tube  404 . As a result, the fore end parts  402   a  of the spring  402  are pushed toward the front of the fore end tube  404 . 
     Since the spring fitting hole parts  401   b  for the spring  402  are located on the periphery of the rotation shaft parts  401   a,  the barrier member  401  swings in the direction of closing and the barrier member  401  is thus closed as shown in FIG.  5 ( b ). The barrier members  401  and  411  may be made of an elastic material such as hard rubber. 
     The above-stated arrangement of the first embodiment gives the following advantages. 
     Use of a thin wire spring for the urging means requires only a small space for it, so that it contributes to reduction in size and cost of parts. 
     The antireflection coating applied to the inner surfaces of the barrier members effectively lessens light reflection from the inner surfaces to permit taking a high-quality picture. 
     Since the barrier members are arranged to have some curvature, the curved barrier members give a larger hood effect in the neighborhood of the upper and lower diagonal parts than flat barrier members. 
     The boundary lines of the front face plate and the barrier members which are in parallel and near to the rotation shafts of the barrier members have approximately the same curvature as the external surface curvature of the barrier members. Therefore, the gap at the boundary is always small irrespective as to whether the barrier members are open or closed, so that the amount of stray light incident on the inside of the lens barrel coming through the boundary gap can be minimized. As a result, it is possible to reduce leakage of light to a film surface at the time of non-photo-taking or to reduce flare ghost at the time of photo-taking. Further, the arrangement for vertically opening the barrier members enables the upper barrier member to prevent the incident rays of sunlight from above on the fore end lens surface, so that flare ghost can be prevented. 
     Further, the upper barrier member also serves to prevent raindrops or snowflakes from sticking to the lens surface to degrade the picture quality. The lower barrier member serves to prevent unnecessary incident rays of light from below on the fore end lens surface, such as sunlight reflected by a water surface or the like, so that flare ghost can be prevented. In a case where the barrier members are made of an elastic material such as hard rubber, if the camera accidentally falls on the ground to have the lens barrel first hit the ground, the barrier members first come into contact with the ground. Then, the fall impact is first absorbed by the deformation of the urging means and that of the barrier members taking place when the barrier member close, so that damages of the lens barrel and the camera body can be mitigated. 
     (Second Embodiment) 
     FIGS.  7 ( a ) to  7 ( c ) and FIGS.  8 ( a ) to  8 ( c ) show a barrier opening-and-closing device according to a second embodiment of the invention. 
     Referring to FIGS.  7 ( a ) to  7 ( c ), a pair of upper and lower barrier members  701  and  711  are arranged alike to be openable and closable in front of a lens barrel. The barrier member  711  is shown in a full line and the other barrier member  701  is shown in a dotted line. Since the barrier members  701  and  711  are arranged alike, the following description covers only the barrier member  711 . 
     The barrier member  711  has a flat barrier face part and is arranged to open and close vertically in a pair with the barrier member  701  in front of the lens barrel by swinging on a rotation shaft part  711   a  which is disposed at the center of a root of the barrier member  711 . The rotation shaft part  711   a  has a gear part  711   b  formed on its periphery to be in mesh with a rack part  702   a  of a spring  702  (to be described later). Light-blocking lines  711   c  are carved in the inner face of the barrier member  711  for the purpose of preventing reflection. 
     The spring  702  is made of an elastic material in its entirety and is approximately in an elliptic shape as viewed from on the front side. The spring  702  has a pair of upper and lower rack parts  702   a  and  702   b  formed along the minor axis of the elliptic shape and arranged to open and close the barrier member  711  in mesh with the gear part  711   b  of the barrier member  711 . The spring  702  further has a pair of right and left hole parts  702   c  and  702   d  which are arranged along the major axis of the elliptic shape to have ball parts  714   c  and  715   c  of links  714  and  715  fitted therein. 
     A fore end tube  704  is located at the fore end of the lens barrel. The fore end tube  704  has bearing parts  704   a  and  704   b  to which the rotation shaft part  711   a  of the barrier member  711  is secured in a ratable manner, and also has holding parts  704   c  and  704   d  which are arranged to rotatably hold the links  714  and  715 . 
     The link  714  has a rotation center  714   a  arranged to be rotatably held by the holding parts  704   c  and  704   d  of the fore end tube  704 , the ball part  714   c  which is fitted in the hole part  702   c  of the spring  702 , and a contact part  714   b  which is arranged to be pushed by the fore end  705   a  of a rectilinear motion tube  705  (to be described later). The other link  715  is also arranged in the same manner as the link  714 . 
     The rectilinear motion tube  705  has the fore end  705   a  which is arranged to come into contact with the contact parts  714   b  and  715   b  of the links  714  and  715 . 
     Next, the operation of the barrier opening-and-closing device according to the second embodiment to bring the barrier member  711  from an open state into a closed state is described with reference to FIGS.  7 ( a ) to  7 ( c ) and FIGS.  8 ( a ) to  8 ( c ). 
     When a switch of the camera is turned off, the rectilinear motion tube  705  approaches the fore end tube  704  as shown in FIG.  8 ( c ). The fore end  705   a  of the rectilinear motion tube  705  then pushes the contact parts  714   b  and  715   b  of the links  714  and  715 . 
     The thus-pushed links  714  and  715  rotate on their centers of rotation  714   a  and  715   a.  The ball parts  714   c  and  715   c  then come closer to an optical axis. The holes  702   c  and  702   d  of the spring  702  in which the ball parts  714   c  and  715   c  of the links  714  and  715  are fitted also come close to the optical axis. Therefore, the right and left parts of the spring  702  are compressed along the major axis of the elliptic shape. This causes the spring  702  to vertically expand along the minor axis of the elliptic shape thereof. 
     As a result, the rack part  702   a  which is located on the lower side of the spring  702  moves downward to cause the gear part  711   b  of the barrier member  711  which is in mesh with the rack part  702   a  to rotate. The rotation of the gear part  711   b  causes the barrier member  711  to close. The other barrier member  701  also comes to close in the same manner. 
     When the switch of the camera is turned on, the rectilinear motion tube  705  comes to part from the fore end tube  704  as shown in FIG.  7 ( c ). Then, the contact parts  714   b  and  715   b,  which have been pushed by the fore end  705   a  of the rectilinear motion tube  705 , are freed. 
     At this time, the spring  702  tries to resume its original free shape shown in FIG.  7 ( a ). This causes the hole parts  702   c  and  702   d  to horizontally spread to bring the links  714  and  715  back to their positions shown in FIG.  7 ( c ). 
     The spring  702  then becomes vertically narrower in the direction of the minor axis of the elliptic shape to cause the rack part  702   a  of the spring  702  to move upward. The upward movement of the rack part  702   a  causes the gear part  711   b  of the barrier member  711  which is in mesh with the rack part  702   a  to rotate. The rotation of the gear part  711   b  causes the barrier member  711  to open. The other barrier member  701 , which is indicated with a dotted line, also comes to open in the same manner. 
     The advantages of the second embodiment described above lie in the following points. 
     The upper and lower barrier members  711  and  701  are arranged to be under the urging force of one spring to move in the direction of opening the barrier. The arrangement permits reduction in number of parts. 
     The elasticity of the spring prevents the barrier opening-and-closing device from being damaged, by absorbing an external force even when the external force happens to be applied to the barrier opening-and-closing device in the direction of closing the barrier. 
     The light-blocking (or flare-blocking) lines provided on the inner surfaces of the barrier members effectively lessen reflection by the inner surfaces, so that pictures can be taken with a high picture quality. 
     (Third Embodiment) 
     FIGS. 9 to  11  and FIG. 15 relate to a third embodiment of the invention. 
     Referring to FIG. 11, the structural arrangement of a camera according to the third embodiment is described as follows. A lens barrel of the camera is a three-step lens barrel including a two-group zoom lens arranged to be drawn out by means of a zoom motor for zooming. As for focusing, a first lens group is arranged to be drawn out for focusing by means of a focus motor (not shown) disposed within a fore end tube  904 . 
     The fore end tube  904  is located at the fore end. of the three-step lens barrel which is arranged to be drawn out by means of a cam-and-pin arrangement. 
     A fixed tube  929  is secured to a camera body  930 . A third tube  927  which is arranged to be rotatively drawn out by the zoom motor fittingly engages the inner surface of the fixed tube  929 . A third rectilinear motion tube  928  fittingly engages the inner surface of the third tube  927  and is arranged to be drawn out in a nonrotating manner together with the third tube  927 . 
     A second tube  925  is arranged on the front side of the third tube  927  to be rotatively drawn out with respect to the third tube  927 . A rectilinear motion tube  926  is arranged on the inner side of the second tube  925  to be drawn out in a nonrotating manner together with the second tube  925 . 
     The fore end tube  904  is arranged at the fore end of the second tube  925  to be drawn out in a nonrotating manner. The barrier opening-and-closing device which is described above in the description of the first embodiment is disposed in front of the fore end tube  904 . 
     The operation of the camera according to the third embodiment which is arranged as described above is next described below with reference to FIG. 15, which is a block diagram. 
     When the lens barrel is in its stowed state, as shown in FIG. 9, with the switch of the camera in its off-state, the barrier opening-and-closing device is closed by the pressure of the rectilinear motion tube  926 . Now, when the switch of the camera is turned on, the zoom motor  931  rotates to cause the position of the lens barrel to change to a wide-angle end position. The rectilinear motion tube  926  relatively moves away from the fore end tube  904 . Then, the barrier opening-and-closing device is opened by the restoration of the shapes of upper and lower springs  902  and  912 . 
     The rotation of the zoom motor  931  also causes a second-lens-group frame  922  to come to a wide-angle end position optically designed. Meanwhile, a first-lens-group frame  921  is moved to an incompletely drawn-out position which is located away from the optical design position on the side of a film surface. 
     At this time, a focal length detecting means  1101  detects that the lens barrel is at the wide-angle end position. A storage means  1102  then informs a first-lens-group control means  1105  of an amount of deficiency of drawing out the first-lens-group frame  921  for the wide-angle end position. 
     Under this condition, when a shutter release is made for taking a picture, information on a distance to an object of shooting measured by a distance measuring means  1104  is sent to the first-lens-group control means  1105 . A first-lens-group position detecting means  1103  detects the current position of the first-lens-group frame  921  within the fore end tube  904  and sends the information to the first-lens-group control means  1105 . 
     The first-lens-group control means  1105  then computes and obtains an amount of drawing out the first-lens-group frame  921  for focusing, on the basis of the current position of the first lens group, the deficiency amount for drawing out the first-lens-group frame  921  and the information on the object distance. 
     The computed amount of drawing out the first-lens-group frame  921  is transmitted to a first-lens-group driving means  1106 . The first-lens-group driving means  1106  then draws out the first-lens-group frame  921 . 
     Then, the film surface is exposed to light, and the film is wound up. The first-lens-group driving means  1106  brings the first-lens-group frame  921  back to its initial position. 
     FIG. 10 shows the lens barrel in its infinity distance shooting state obtained at the wide-angle end position. In this state, the first-lens-group frame  921  is drawn out on the side of the object with respect to the barrier opening-and-closing device. Therefore, an edge SW of incident light forming an image is allowed to pass very near the fore ends of the barrier members  901  and  911  but without being eclipsed by the fore ends of the barrier members  901  and  911 . 
     Next, when the lens barrel is operated for zooming to a telephoto end position, the position of the lens barrel is changed by the rotation of the zoom motor  931  from the position shown in FIG. 10 to the telephoto end position as shown in FIG.  11 . The first-lens-group frame  921  and the second-lens-group frame  922  are moved for zooming to their optically designed telephoto end positions. 
     The position of the first-lens-group frame  921  relative to the barrier opening-and-closing device is drawn in further toward the film surface when the lens barrel is at the telephoto end position than when the lens barrel is at the wide-angle end position. An edge ST of incident light, therefore, passes nearby the fore ends of the barrier members  901  and  911  when the lens barrel is at the telephoto end position. 
     The third embodiment arranged as described above has the following advantages. 
     The position of the first lens group relative to the barrier members is drawn out toward the object when the lens barrel is at the wide-angle end position and drawn in toward the film surface when the lens barrel is at the telephoto end position. Further, an effective length, as a hood, from the fore ends of the barrier members to the first lens surface of the lens barrel is arranged to be shorter to prevent an effective image-forming incident light flux from being eclipsed by the fore ends of the barrier members when the lens barrel is at the wide-angle end. The effective length as a hood is arranged to be longer to cut a larger amount of harmful rays included in the image-forming incident light flux for taking a high-quality picture when the lens barrel is at the telephoto end position. 
     The barrier members are arranged to be driven for only two purposes of opening and closing them. That arrangement, therefore, permits simplification of the barrier opening-and-closing mechanism and reduction in size of the barrier opening-and-closing device. 
     (Fourth Embodiment) 
     FIGS. 12,  13  and  14  show a camera according to a fourth embodiment of the invention. The camera according to the fourth embodiment has a lens barrel, which is a three-step lens barrel including a two-group zoom lens arranged to alternately perform zooming and focusing actions with one and the same motor. 
     The barrier opening-and-closing device in the fourth embodiment is arranged in about the same manner as that of the first embodiment. The following description, therefore, covers only a different point of the fourth embodiment from the first embodiment. 
     A ring member  1031  is slide-fitted to the front inner side of a fore end tube  1004  and is arranged to be pushed forward by a rectilinear motion tube  1026  and a projection  1022   a  of a second-lens-group frame  1022 . 
     The second-lens-group frame  1022  has the above-stated projection  1022   a  arranged on its periphery to push the ring member  1031 . 
     In zooming the lens barrel from a stowed position to a wide-angle end position and then to a telephoto end position, the camera operates as described below. 
     When the lens barrel is in a stowed state as shown in FIG. 12 with a switch of the camera in an off-state, the rectilinear motion tube  1026  is pushing the ring member  1031  toward the object of shooting. The ring member  1031  is in turn pushing a projection  1012   b  of a spring  1012  toward the object. A barrier member  1011  is thus caused to be at its closed position while another barrier member  1001  is also at its closed position under this condition. 
     When the switch of the camera is turned on, the lens barrel comes to take a wide-angle end position as shown in FIG.  13 . The rectilinear motion tube  1026  then moves rearward relative to the fore end tube  1004  to allow the spring  1012  which has been deformed to resume its original shape. Then, the projection  1012   b  of the spring  1012  pushes the ring member  1031  toward a film surface. After that, the ring member  1031  comes to a stop at a position where the ring member  1031  receives no pressure from other parts. 
     The recovery of the spring  1012  to its original shape causes the barrier members  1011  and  1001  to open to a full extent. 
     With the barrier members  1011  and  1001  fully opened, their fore ends allow the edge SW of an image-forming incident light flux to pass nearby there without being eclipsed. 
     When the position of the lens barrel is shifted by a zooming operation to a telephoto end position as shown in FIG. 14, the second-lens-group frame  1022  comes closest to a first-lens-group frame  1021 . Then, the projection  1022   a  of the second-lens-group frame  1022  pushes the ring member  1031  toward the object. 
     The projection  1012   b  of the spring  1012  is pushed to move toward the object by the pressure of the ring member  1031 . The amount of this movement is smaller than the amount of movement of the ring member  1031  caused by the pushing pressure of the rectilinear motion tube  1004 . The barrier members  1011  and  1001 , therefore, come to a stop at a half-open position. 
     With the barrier members  1011  and  1001  at the half open positions, the edge part ST of image-forming incident light passes nearby the fore ends of the barrier members  1011  and  1001 . 
     After that, when the lens barrel is reversely zoomed from the telephoto end position toward the wide-angle end position, the projection  1022   a  of the second-lens-group frame  1022  moves relative to the ring member  1031  toward the film surface to free the ring member  1031  from pressure. Then, the righting moment of the spring  1012  causes the ring member  1031  to be pushed and moved by the projection  1012 b of the spring  1012  toward the film surface. The barrier members  1011  and  1001  are then fully opened by the righting moment of the spring  1012 . The image forming incident light is thus never eclipsed by the barrier members  1011  and  1001 . 
     The fourth embodiment arranged as described above has the following advantages. 
     The barrier members of the barrier opening-and-closing device are arranged to fully open when the lens barrel is between the wide-angle end position and an intermediate focal length position. This prevents the effective image forming light from being eclipsed by a hood part. The barrier members are arranged to be half opened when the position of the lens barrel is in the neighborhood of the telephoto end position. That permits cutting harmful rays of light in a larger amount to ensure taking a high-quality picture. 
     Further, since the opening angle of the barrier member is mechanically controlled within the lens barrel, an electrical control circuit disposed within the camera can be operated without any load of control over the opening angle, so that the arrangement of electrical control can be simplified. 
     (Fifth Embodiment) 
     A barrier opening-and-closing device of a lens barrel according to a fifth embodiment of the invention is described below with reference to FIGS. 16 to  24 . 
     FIG. 16 is an exploded perspective view of the lens barrel  100  having the barrier opening-and closing device according to the fifth embodiment. The feature of the fifth embodiment is best shown in FIG.  16 . The appearance of the lens barrel  100  is shown in FIGS. 23 and 24. 
     As shown in FIG. 16, the lens barrel  100  according to the fifth embodiment has a rectilinear motion tube  110 , a fore end tube  109 , a base seat  108 , a fancy cover  101 , a pair of upper and lower barrier members  102  and  103 , springs  104  and  105  arranged to urge the barrier members  102  and  103 , and screws  106  and  107  arranged to secure the springs  104  and  105  to the base seat  108 . 
     The rectilinear motion tube  110  of the lens barrel  100  has an optical lens disposed therein as a photo-taking lens. A flange part  110  formed on the base end side of the rectilinear motion tube  110  is arranged to be used in mounting the lens barrel on a camera body. The rectilinear motion tube  110  functions as a pushing member to push the springs  104  and  105  with a pushing face  110   a  which is formed on the fore end side of its inner circumferential surface. 
     In the lens barrel  100 , the inside diameter of the fore end tube  109  is arranged to be approximately the same as the outside diameter of the rectilinear motion tube  110 . The fore end tube  109  and the rectilinear motion tube  110  are thus arranged to be movable relative to each other through the sliding contact of the inner circumferential surface of the fore end tube  109  and the outer circumferential surface of the rectilinear motion tube  110 . The rectilinear motion tube  110  is fitted into the fore end tube  109  by rectilinearly or rotatively sliding over the inner circumferential surface of the fore end tube  109 . 
     The fore end tube  109  is thus fitted on the rectilinear motion tube  110  on its base end side. A ring-shaped inner flange part  109   c  is formed on the inner fore end side of the fore end tube  109 . A projection  109   j  is formed at an inner part further on the fore end side than the inner flange part  109   c  for the purpose of positioning the base seat  108 . A circumferential groove part  109   a  is formed in the fore end tube  109  further on the fore end side than the projection  109   j  for the purpose of fitting the fancy cover  101  therein. Further, hole parts  109   g  and  109   b  are formed in the inner flange part  109   c  of the fore end tube  109  for the purpose of inserting projections  104   b  and  105   b  of the springs  104  and  105  therein. 
     The base seat  108  is formed in a shape to be fitted onto the inner circumferential face of the fore end part of the fore end tube  109 . An aperture part  108   f  is formed in the middle of the main face of the base seat  108 . The base seat  108  has a raised wall part  108   p  which is formed around the aperture part  108   f.  The raised wall part  108   p  is provided with grooves, stoppers, etc., for mounting the barrier members  102  and  103  in a swingable manner. 
     More specifically, various parts are arranged around the aperture part  108   f  as follows. Groove-shaped stopper parts  108   i  are arranged on the upper and lower sides of the aperture part  108   f  as viewed in FIG. 16 to allow the rear end parts of the barrier members  102  and  103  to enter there and to stop them from swinging. Stopper parts  108   j  are arranged on the right and left sides of the aperture part  108   f,  as viewed in FIG. 16, to have the fore end inner faces of the barrier members  102  and  103  respectively abut thereon. On the right and left inner sides of the stopper parts  108   j,  there are wall face parts  108   l  arranged to house the springs  104  and  105 , hole parts (not shown) arranged to have about the same shape as the hole parts  109   g  and  109   b  of the fore end tube  109 , and female screw parts  108   m  and  108   n  arranged to have screws  106  and  107  screwed therein. Further, on the two end sides in the longitudinal direction of each stopper part  108   i,  there are formed upper bearing parts  108   b  and  108   c  and lower bearing parts  108   g  and  108   h  which are arranged in an arcuate groove shape to hold the barrier members  102  and  103  in a swingable manner. 
     A cutaway part  108   a  is arranged in the upper end part of the base seat  108  to be used for positioning the base seat  108  with respect to the fore end tube  109 . The base seat  108  is positioned by inserting it into the inner circumferential part of the fore end tube  109  while fitting a Y face  108   d  and an X face  108   e  of the cutaway part  108   a  respectively onto a Y face  109   d  and an X face  109   e  of the projection  109   j  of the fore end tube  109 . The cutaway part  108   a  is thus caused to abut on the inner flange part  109   c  of the fore end tube  109 . In this state, the base seat  108  is secured to the fore end tube  109  by bonding. 
     The barrier members  102  and  103  are in a plate-like shape and are made of an elastic material, such as hard rubber or the like. The barrier members  102  and  103  are provided respectively with rotation shaft parts  102   b,    102   c,    103   b  and  103   c,  which are disposed on the base end side of the barrier members  102  and  103 . 
     The upper barrier member  102 , i.e., a first barrier member, is mounted in a swingable manner on the base seat  108  which is in one body with the fore end tube  109  by fitting its rotation shaft parts  10   b  and  102   c  into the upper bearing parts  108   b  and  108   c  of the base seat  108 . The lower barrier member  103 , i.e., a second barrier member, is likewise mounted in a swingable manner on the base sear  108  by fitting its rotation shaft parts  103   b  and  103   c  into the lower bearing parts  108   g  and  108   h  of the base seat  108 . The barrier member  102  is thus arranged to swing at a part above an optical axis of the optical lens disposed inside of the rectilinear motion tube  110 . The other barrier member  103  is arranged to swing at a part below the optical axis. Further, the axes of swing of the barrier members  102  and  103  are in parallel with each other. 
     The rotation shaft part  102   b  of the barrier member  102  is provided with a hole part  102   a  which has the fore end part  105   a  of the spring  105  fitted therein. The rotation shaft part  103   b  of the barrier member  103  is likewise provided with a hole part  103   a  which has the fore end part  104   a  of the spring  104  fitted therein, as shown in FIG.  18 ( a ). 
     To avoid irregular reflection of light, light-blocking grooved parts  103   j,  each composed of a plurality of grooves, are provided on the inner surfaces of the barrier members  102  and  103 , as shown in FIG.  16 . 
     Each of the springs  104  and  105  is formed by three-dimensionally bending a wire-like elastic member. In the case of the fifth embodiment, one-end parts of the springs  104  and  105  are arranged to interlink the barrier members  102  and  103  with each other. The other-end parts of the springs  104  and  105  are formed as ring-like fixing parts  104   d  and  105   d  which are arranged to permit screws  106  and  107  to be inserted therein. In each of the springs  104  and  105 , an intermediate part between the two end parts is formed into a projection  104   b  or  105   b  which is arranged to be pushed by the pushing face  110   a  of the rectilinear motion tube  110 . The two springs  104  and  105  are in the same shape. Therefore, for the sake of expedience, details of these springs are described below mainly covering only the spring  105 . 
     The fore end part  105   a  of the spring  105  is connected to the barrier member  102  by fitting the fore end part  105   a  into the hole part  102   a  formed in the rotation shaft part  102   b  of the barrier member  102 . 
     The fixing part  105   d  of the spring  105  is secured to the base seat  108  with the screw  107  inserted therein and screwed into the female screw part  108   n  of the base seat  108 . At this time, the spring  105  has its projection  105   b  inserted into the above-stated hole part of the base seat  108  and also into a hole part  109   b  of the fore end tube  109 . 
     As shown in FIGS.  18 ( b ),  18 ( c ),  21 , etc., the diameter of the fancy cover  101  is a little smaller than that of the fore end tube  109 . The fancy cover  101  is secured to the fore end side of the fore end tube  109  with its rear face  101   a  attached by bonding to the circumferential groove part  109   a  of the fore end tube  109 . The front (outer) surface of the fancy cover  101  is in a spherical shape. As shown in FIG. 17, the fancy cover  101  has an aperture part  101   b  formed in an approximately rectangular shape corresponding to the raised wall part  108   p  of the base seat  108 . A cover part  101   j  which is in a flange-like shape is formed to extend from the aperture part  101   b  to a rear face  101   a,  as shown in FIG.  18 ( d ). In this cover part  101   j  are included, as shown in FIGS. 17 and 23, side edge parts  101   f  and  101   h  formed in positions being opposed to the wall face parts  108   l  and other side edge parts  101   i  formed in positions opposed to the bearing parts  108   b,    108   c,    108   g  and  108   h  of the base seat  108 . The springs  104  and  105  are set in positions by means of these parts. Further, as shown in FIG. 16, bearing parts having arcuate grooves are formed in the side edge parts  101   i  at positions which are opposed to the bearing parts  108   b,    108   c,    108   g  and  108   h  of the base seat  108 . For the sake of expedience, FIG. 16 shows only the left half of the fancy cover  101 . As to the bearing parts of the fancy cover  101 , only the bearing parts  101   c  and  101   k  which correspond to the bearing parts  108   c  and  108   h  are shown. The right half of the fancy cover  101  is arranged in the same manner as the left half. 
     In the lens barrel  100 , with the fancy cover  101  secured to the fore end of the fore end tube  109  as described above, one of the rotation shaft parts ( 102   c ) of the barrier member  102  is rotatably carried jointly by the bearing part  101   c  of the fancy cover  101  and the bearing part  108   c  of the base seat  108 . The other rotation shaft parts ( 102   b ) of the barrier member  102  is also rotatably carried jointly by a bearing part (not shown) of the fancy cover  101  and the bearing part  108   b  of the base seat  108 . With regard to the other barrier member  103 , its rotation shafts  103   b  and  103   c  are also carried in a rotatable manner by the bearing parts  108   g  and  108   h  of the base seat  108  and the bearing parts of the fancy cover  101  including the bearing part  101   k  and another which is not shown. 
     Further, with the fancy cover  101  secured to the fore end side of the fore end tube  109 , the cover part  101   j  which includes the side edge parts  101   f,    101   h  and  101   i  of the fancy cover  101  abuts on the raised wall part  108   p  which includes the wall face  108   l  of the base seat  108  in such a way as to cover and hide the springs  104  and  105 . The springs  104  and  105  in the lens barrel  100  are thus encompassed with the inner wall part  109   f  of the fore end tube  109 , the wall face  108   l  of the base seat  108 , the front surface of the base seat  108  and the back surface of the fancy cover  101 . Since no external light reaches the spring  105 , no light comes toward the rectilinear motion tube  110  through the hole parts of the base seat  108  and the hole part  109   b  of the fore end tube  109 . The inside of the lens barrel  100  is, therefore, completely shielded from light. Besides, the springs  104  and  105  are effectively prevented from deteriorating as external light and dust are blocked from coming to the part where these springs are located. 
     The shape and allocation of the spring  105  are described further in detail with reference to FIG. 17 as follows. FIG. 17 shows in a perspective view the barrier members  102  and  103  in an open state. For the sake of expedience, the illustration of FIG. 17 omits the fancy cover  101  and shows the fore end tube  109  in a sectional state with the right half thereof excluded from the illustration. The spring  105  is located further outward than the barrier members  102  and  103  and also on the outside of the wall face part  108   l  of the base seat  108 . The spring  105  is, as mentioned above, encompassed with the inner wall part  109   f  of the fore end tube  109 , the wall face  108   l  of the base seat  108 , the front surface of the base seat  108  and the back surface of the fancy cover  101 . 
     As shown in FIG. 17, the spring  105  has a bent part  105   c  which extends from a fixed part  105   d  along the shape of the base seat  108  in the direction of −Y (downward), and turns at the lower end of the wall face part  108   l  of the base seat  108  to extend in the opposite direction. The spring  105  further extends from the bent part  105   c  in the direction of +Y (upward), turns in the direction of +X at a point where it passes the head part of the screw  107 , and further turns in the direction of −Z, forming the projection  105   b.    
     The projection  105   b  passes through the hole part of the base seat  108  and the hole part  109   b  of the fore end tube  109  to face the pushing face  110   a  of the rectilinear motion tube  110  and turns back to pass again the hole part of the base seat  108  and the hole part  109   b  of the fore end tube  109 . The spring  105  is then bent in the direction of −X at a point where it has passed the hole part of the base seat  108 . The spring  105  is further bent at the wall face part  108   l  of the base seat  108  in the direction of +Y. After that, the spring  105  is lastly bent in the direction of −X to form a fore end part  105   a  where it is inserted into the hole part  102   a  of the barrier member  102 . The direction in which the fore end part  105   a  of the spring  105  is inserted into the hole part  102   a  of the barrier member  102  is in parallel with the rotation shaft of the barrier member  102 . 
     With the spring  105  formed in the above-stated shape, when the barrier member  102  is in its open state as shown in FIG. 17, the fore end part  105   a  of the spring  105  tries to further move in the composite direction of −Z and +X. However, a component of the moving force in the direction of −Z is nullified by receiving it at the hole part  102   a  of the barrier member  102 . Another component of the force in the direction of +X is nullified by sliding of the fore end part  105   a  within the hole part  102   a  of the barrier member  102 . Meanwhile, the projection  105   b  also tries to further move in the composite direction of −Z and +X. However, since the spring  105  is restricted at the fore end part  105   a  and the fixed part  105   d,  a component of the moving force in the direction of −Z is converted into a flexion in the direction of −Z. Another component in the direction of +X causes a displacement of the projection  105   b  until the projection  105   b  comes into contact with the inner wall part  109   f  of the fore end tube  109 . 
     The shape and arrangement of the other spring  104  are the same as those of the spring  105  described. 
     The barrier opening and closing actions in the fifth embodiment are as follows. FIGS.  18 ( a ) to  18 ( d ) show the lens barrel in a state of having the barrier opened. FIG.  18 ( a ) is a front view showing the lens barrel with the fancy cover  101  excluded from the illustration. FIG.  18 ( b ) is a sectional side view showing the lens barrel, excluding the barrier member  103  and including a YZ plane. FIG.  18 ( c ) is a side view with a sectional view including the YZ plane showing only the fancy cover  101  and the fore end tube  109 . FIG.  18 ( d ) is a front view of the fancy cover  101 . 
     The spring  105  has its fixed part  105   d  secured to the base seat  108  with the screw  107  while its fore end part  105   a  is fitted into the hole part  102   a  of the barrier member  102 . Therefore, in the state in which the pushing face  110   a  of the rectilinear motion tube  110  is not pushing the projection  105   b  of the spring  105  as shown in FIG.  18 ( c ), a force is exerted to move the fore end part  105   a  toward the rectilinear motion tube  110  (in the direction of −Z). This force causes the barrier member  102  to swing on its rotation shaft  102   b  to its open position. Then, as shown in FIG.  18 ( b ), the swing of the barrier member  102  is brought to a stop where the rear end part  102   e  collides with a stopper  108   i  of the base seat  108 . At this time, the hole part  102   a  of the barrier member  102  in which the fore end part  105   a  of the spring  105  is fitted is at an angle of 45 degrees to the center of swing, i.e., with respect to the XY plane passing through the center of swing, as shown in FIG.  18 ( c ). 
     The other barrier member  103  is also arranged to be caused to swing in the same manner and to come to a stop at an angle of 45 degrees with respect to the XY plane which passes through the center of swing. 
     Next, when the rectilinear motion tube  110  is drawn out toward the object (in the direction of +Z), the projection  105   b  of the spring  105  is pushed by the pushing face  110   a  of the rectilinear motion tube  110 . This causes the fore end part  105   a  of the spring  105  to move toward the object (in the direction of +Z) against the force of moving it toward the rectilinear motion tube  110  (in the direction of −Z). Then, the spring  105  elastically deforms to cause the barrier member  102  to swing on its rotation shaft  102   b.  As a result, the barrier member  102  comes to a closed position as shown in FIGS. 19,  20 ( a ) and  20 ( b ). Meanwhile, the other barrier member  103  which is in connection with the other spring  104  also swings in the same manner to come to a closed position as shown in FIGS. 19,  20 ( a ) and  20 ( b ). 
     FIG. 19 shows the lens barrel in the state of having the barrier, i.e., the barrier members, in the closed state. FIG. 19 shows, for the sake of expedience, the lens barrel with the fancy cover  101  excluded from the illustration and the fore end tube  109  in a sectional view. FIGS.  20 ( a ) and  20 ( b ) also show the lens barrel in the state of having the barrier closed. FIG.  20 ( a ) is a front view showing the barrier with the fancy cover  101  excluded from the illustration. FIG.  20 ( b ) is a side view with a sectional view including the YZ plane showing only the fancy cover  101  and the fore end tube  109 . 
     The barrier members  102  and  103  are closed in the following manner. When the rectilinear motion tube  110  is moved toward the object, the pushing face  110   a  of the rectilinear motion tube  110  pushes the projection  105   b  of the spring  105  toward the object, i.e., in the direction of +Z. This causes the fore end part  105   a  of the spring  105  to try to flex or deflect toward the object, i.e., in the direction of +Z. 
     The spring  105  is secured to the base seat  108  with the screw  107  while its fore end part  105   a  fitted in the hole part  102   a  of the barrier member  102 . When the projection  105   b  of the spring  105  is pushed by the pushing face  110   a  of the rectilinear motion tube  110 , therefore, the spring  105  moves its fore end part  105   a  toward the object (in the direction of +Z) by spreading the root part of the projection  105   b.  The movement of the fore end part  105   a  of the spring  105  then causes the barrier member  102  to swing on its rotation shaft  102   b  to its closed position. 
     Then, as shown in FIG.  20 ( b ), the barrier member  102  stops its swing when its side end part  102   h  comes to collide against the stopper part  108   j  of the base seat  108 . At this time, the hole part  102   a  of the barrier member  102  in which the fore end part  105   a  of the spring  105  is fitted is at an angle of −45 degrees to the center of swing, i.e., with respect to the XY plane passing through the center of swing, as shown in FIG.  20 ( b ). 
     The other barrier member  103  is also arranged to be caused to swing in the same manner and to come to a stop at an angle of −45 degrees with respect to the XY plane which passes through the center of swing. 
     When the rectilinear motion tube  110  moves from its position at which the barrier is closed as shown in FIG.  20 ( b ) toward the camera body, i.e., in the direction of −Z, the spring  105  moves its fore end part  105   a  by spreading the root part of the projection  105   b  to cause the barrier member  102  to swing to its open state as shown in FIGS. 17,  18 ( a ) to  18 ( d ) and  23 . The other spring  104  and the other barrier member  103  also act in the same manner. 
     FIG. 21 shows how the barrier member  102  is closed from the state of having the barrier members  102  and  103  at their open positions. The barrier member  102  is closed with the rectilinear motion tube  110  moved in the direction of −Z to cause the fore end part  102   d  of the barrier member  102  to be forcibly pushed in the direction of an arrow. 
     At this time, the fore end part  105   a  of the spring  105  which is fitted in the hole part  102   a  of the barrier member  102  is forcibly displaced in the direction of Z. Since the spring  105  is secured to the base seat  108  at its fixed part  105   d,  the displacement of the fore end part  105   a  is converted into elasticity (positional energy) mainly by the deformation of a part of the spring  105  between the fore end part  105   a  and the projection  105   b.    
     When the side end part  102   h  of the barrier member  102  comes to abut on the stopper part  108   j  of the base seat  108 , the barrier member  102  comes to a stop and the positional energy reaches a maximum energy. Under this condition, the spring  105  is compressed to have its projection  105   b  become vertically shorter than in its initial state. As a result, there is developed a force to bring the projection  105   b  back to its initial state. Further, there is also developed another force to move back the fore end part  105   a  in the directions of +Y (upward as viewed in FIG. 21) and −Z (toward the rectilinear motion tube  110 ). Therefore, upon removable of the forcible power exerted to move the barrier member  102  in the direction of the arrow as shown in FIG. 21 in this state, the elastic force of the spring  105  causes the barrier member  102  to open again to bring about the state shown in FIGS. 17,  18 ( a ) to  18 ( d ) and  23 . 
     FIG. 22 shows a state in which the rectilinear motion tube  110  is located in the direction of +Z, and the barrier member  102  is opened by forcibly pushing the fore end part  102   d  of the barrier member  102  in the direction of an arrow from its position obtained with both the barrier members  102  and  103  closed. 
     In this instance, as apparent from comparison with FIG.  18 ( b ), the fore end part  105   a  of the spring  105  which is fitted in the hole part  102   a  of the barrier member  102  is forcibly displaced in the direction of −Z. Then, since the spring  105  is secured to the base seat  108  at its fixed part  105   d,  the displacement of the fore end part  105   a  is converted into an elasticity (positional energy) mainly by the deformation of a part of the spring  105  between the fore end part  105   a  and the projection  105   b.    
     Then, when the rear end part  102   e  of the barrier member  102  abuts on the stopper part  108   i  of the base seat  108 , the barrier member  102  comes to a stop and the positional energy reaches a maximum energy as mentioned in the foregoing with reference to FIG.  18 ( b ). Therefore, upon removable of the forcible power exerted to move the barrier member  102  in the direction of the arrow, the elastic force of the spring  105  causes the barrier member  102  to close again to bring about the state shown in FIG.  24 . 
     The lens barrel is arranged to have the fitting direction in which the fore end parts  104   a  and  105   a  of the spring  104  and  105  are fitted into the holes  102   a  and  103   a  of the barrier members  102  and  103  to be parallel respectively with the rotation shafts of the barrier members  102  and  103 . This arrangement ensures that no component force in the direction of X of the springs  104  and  105  is transmitted to the barrier members  102  and  103 . Only the forces in the directions of Y and Z that are necessary for swinging the barrier members  102  and  103  are transmitted to the barrier members  102  and  103  so that the barrier members  102  and  103  can be smoothly swung. Further, the barrier members  102  and  103  are connected to the spring  104  and  105  at the end faces of the approximately cylindrical rotation shafts  102   b  and  101   c  of the barrier members  102  and  103 . That arrangement permits reduction in thickness of the whole barrier opening-and-closing device. 
     Further, the projections  104   b  and  105   b  of the springs  104  and  105  are urged in the direction of the outside diameter of the fore end tube  109 . This keeps the projections  104   b  and  105   b  in contact with the inner. surface of the fore end tube  109 . The projections  104   b  and  105   b,  therefore, can be brought into contact with the front circumferential face of the rectilinear motion tube  110  without fail. 
     The shapes, etc., of the fancy (decorative) cover  101  and the barrier members  102  and  103  are described below with reference to FIGS. 23 and 24, which are perspective views showing the appearance of the lens barrel  100 . 
     In the lens barrel  100 , the front surface of the fancy cover  101  has a spherical surface. The outside surfaces of the barrier members  102  and  103  are also in spherical shapes having about the same curvature as the spherical surface of the fancy cover  101 . 
     The edge parts  102   f  and  102   h  on the fore end side of the barrier member  102  are arranged to be wider than the edge parts  102   g  and  102   i  on the base end side located near to the rotation shaft part. The barrier member  103  is also in the same shape. This shape enables the lens barrel  100  to allow a light flux from the object to be led to the lens without any restriction on size in the horizontal direction necessary for forming an image. 
     When the barrier members  102  and  103  are in an open state as shown in FIG. 23, a boundary line between the upper end part  101   e  of the fancy cover  101  and the rear end part  102   e  of the barrier member  102  is about equal to an arc which is formed by geometrical crossing of the front spherical surface of the fancy cover  101  and the outer spherical surface of the barrier member  102 . 
     As mentioned above, in the lens barrel  100 , the curvature of the front spherical surface of the fancy cover  101  is about the same as that of each of the outer spherical surfaces of the barrier members  102  and  103 . Therefore, when the barrier members  102  and  103  are closed, as shown in FIG. 24, the front surface of the fancy cover  101  and the outer surfaces of the barrier members  102  and  103  form a smooth spherical shape, so that external matters, dust or the like can be prevented from sticking to the surface. Further, with the lens barrel in this shape, when the barrier is opened, the fore ends of the barrier members  102  and  103  come to show an arcuate shape which effectively cuts unnecessary rays of incident light to give a higher hooding effect. 
     Further, according to the arrangement of the lens barrel described, the barrier members  102  and  103  vertically open to give a hooding effect by themselves. The upper barrier member  102  prevents the incidence of sunlight on the fore end lens surface from above and thus effectively prevents flare ghost. The upper barrier member  102  also prevents rainwater or snowflake from sticking to the lens surface, so that the quality of pictures can be prevented from degrading. The lower barrier member  103  prevents incidence of unnecessary light, such as sunlight reflected by a water surface, from below, so that the quality of pictures can be also prevented from degrading. Besides, the arrangement of the barrier members permits the barrier opening-and-closing device to be formed in a compact size with a fewer number of parts. 
     The boundary line between the fancy cover  101  and each of the barrier members  102  and  103  which is nearly in parallel with and close to the rotation shaft of the barrier member  102  or  103  is approximately in an arcuate shape when the barrier members are closed. By virtue of this shape, clearances between the fancy cover  101  and the barrier members  102  and  103  can be minimized to effectively prevent external light or dust from entering into the barrier opening-and-closing device from outside. This gives a high hooding effect to lessen the possibility of having ghost flare. 
     In the lens barrel  100  in the fifth embodiment, the springs  104  and  105  are arranged to constantly urge the barrier members  102  and  103  in the opening direction. Therefore, the barrier members  102  and  103  close to prevent a finger print or the like from sticking to the lens surface and thus to prevent picture quality from degrading when the barrier members  102  and  103  are pushed by a finger or the like. Further, in the event of an impact caused by a fall of the camera while the camera is in a photo-taking state, the barrier members  102  and  103  close and the impact can be absorbed in part by the springs  104  and  105  to minimize a possible damage of the barrier members  102  and  103 . Further, in a case where the barrier members  102  and  103  are formed with an elastic material such as hard rubber, the barrier members  102  and  103  first come into contact with the ground in the event of an impact caused by a fall while the camera is in the photo-taking state. Then, the impact is. absorbed by the deformation of the barrier members  102  and  103  themselves as well as by that of the springs  104  and  105  taking place when the barrier members  102  and  103  close. Such absorbing actions effectively lessen possible damages of the lens barrel and the camera body. 
     Further, the springs  104  and  105  are arranged to come into contact with the rectilinear motion tube  110  in the lens barrel  100  at their projections  104   b  and  105   b  which extend toward the rectilinear motion tube  110  along the optical axis. The projections  104   b  and  105   b  are in a state of being urged toward the outer side of the fore end tube  109 . The base seat  108  and the rectilinear motion tube  110  have hole parts arranged to allow these projections  104   b  and  105   b  to pass therethrough. This arrangement enables the pushing force of the rectilinear motion tube  110  to be efficiently transmitted to the springs  104  and  105  with a few number of parts. Further the barrier members  102  and  103  are connected to the springs  104  and  105  at the end faces of the rotation shafts  102   b  and  103   b  of the barrier members  102  and  103 . That arrangement permits reduction in thickness of the barrier opening-and-closing device. Further, since each of the barrier members  102  and  103  is connected to the spring  104  or  105  only at one part, the barrier opening-and-closing device can be assembled without difficulty. 
     Further, each of the springs  104  and  105  is arranged to be connected to the barrier members  102  or  103  only at its one end and to the rectilinear motion tube  110  at the other end while the projection  104   b  or  105   b  is formed at its intermediate part to be pushed by the rectilinear motion tube  110 . The arrangement ensures that the movement of each projection is transmitted directly to the part where the spring is connected to the barrier member  102  or  103 , so that the barrier opening and closing actions can be quickly carried out. 
     (Sixth Embodiment) 
     A barrier opening-and-closing device according to a sixth embodiment of the invention is described below. FIGS.  25 ( a ) to  25 ( c ) show essential parts of a lens barrel  200  having the barrier opening-and-closing device according to the sixth embodiment. FIG.  25 ( a ) is a front view showing a barrier in an open state with a fancy cover excluded from the illustration. FIG.  25 ( b ) is a side view showing the barrier in the open state with a sectional view including a YZ plane showing only the fancy cover and a fore end tube. FIG.  25 ( c ) is a sectional side view showing the barrier in a closed state. 
     Referring to FIGS.  25 ( a ) to  25 ( c ), the lens barrel  200  has a fore end tube  209 , a rectilinear motion tube  210  arranged to be rectilinearly slidable in a state of being fitted in the fore end tube  209 , a base seat  208  secured by bonding to the front face of the fore end tube  209 , a pair of barrier members  202  and  203 , springs  204  and  205  arranged to urge the barrier members  202  and  203 , screws  206  and  207  arranged to secure the springs  204  and  205  to the base seat  208 , and a fancy cover  201 . The fore end tube  209 , the rectilinear motion tube  210 , the base seat  208 , the fancy cover  201 , the barrier members  202  and  203  and the screws  206  and  207  are arranged in approximately the same manner as those of the fifth embodiment described above and, therefore, the details of them are omitted from the following description. 
     The sixth embodiment differs from the fifth embodiment in the arrangement of the springs  204  and  205 . Therefore, the positions of the screws  206  and  207  which are screwed into the base seat  208  also differ from those in the fifth embodiment. Since the springs  204  and  205  are in the same shape, the following describes in detail only the arrangement of the spring  205 . 
     The spring  205  has a fore end part  205   a  fitted into a hole part  202   a  of the barrier member  202 , and a projection  205   b  which protrudes toward the pushing face  210   a  of the rectilinear motion tube  210 . The shapes of these parts are approximately the same as those of the corresponding parts of the fifth embodiment. Further, the spring  205  has a fixed part  205   d  at which the screw is secured to the base seat  208 . The position and the shape of the fixed part  205   d  differ from those in the fifth embodiment. In addition to this difference, an end part opposite to the fore end part  205   a  of the spring  205  is a bent end part  205   c  which is bent approximately in the direction of an X axis. 
     The fixed part  205   d  of the spring  205  is secured to the base seat  208  with the screw  207 . The fore end part  205   a  of the spring  205  is fitted into the hole part  202   a  of the barrier member  202 . The fixed part  205   d  and the fore end part  205   a  of the spring  205  are nearly on one and the same XY plane. The projection  205   b  which is an intermediate part of the spring  205  extends from the XY plane in the direction of −Z in parallel with an optical axis toward the rectilinear motion tube  210  through a first hole part  209   b  of the fore end tube  209 . The bent part  205   c  extends further from the fixed part  205   d  in the direction of −X through a penetrating groove  208   k  of the base seat  208 . A clearance between the penetrating (through) groove  208   k  and the spring  205  is sufficiently small to prevent any leak of light. 
     The other spring  204  is likewise secured to the base seat  208  with a screw  208 . A fore end part  204   a  of the spring  204  is fitted in a hole part  203   a  of the barrier member  203 . In the state shown in FIG.  25 ( b ), the fore end part  205   a  of the spring  205  is trying to flex toward the camera body (in the direction of −Z). Therefore, in this state, the barrier member  202  swings on its rotation shaft  202   b  to come to a stop at a barrier opened position. At this time, the hole part  202   a  of the barrier member  202  in which the fore end part  205   a  of the spring  205  is fitted is at an angle of 30 degrees with respect to the XY plane. Meanwhile, the other barrier member  203  opens in the same manner and has its hole part  203   a  also at the angle of 30 degrees with respect to the XY plane. 
     When the rectilinear motion tube  210  is drawn out toward the object (in the direction of +Z), as shown in FIG.  25 ( c ), a pushing face  210   a  of the rectilinear motion tube  210  pushes the projection  205   b  of the spring  205  and the projection  204   b  of the spring  204  upward. The fore end part  205   a  of the spring  205  is displaced in the direction of +Z. This displacement causes the barrier member  202  to swing on the rotation shaft  202   b.  The fore end of the barrier member  202  collides against a stopper part  208   j  of the base seat  208 . This brings the swinging motion of the barrier member  202  to a stop at its closed position. The other barrier member  203  likewise comes to a stop at its closed position. At this time, the hole part  202   a  of the barrier member  202  in which the fore end part  205   a  of the spring  205  is fitted is at an angle of −60 degrees with respect to the XY plane. Then, the other barrier member  203  closes in the same manner and has its hole part  203   a  also at the angle of −60 degrees with respect to the XY plane. 
     With the lens barrel  200  in the sixth embodiment arranged as described above, the sixth embodiment has the following advantages, in addition to the same advantages of the fifth embodiment. 
     Each of the springs  204  and  205  has their parts other than the projection  204   b  or  205   b  arranged to be within one and the same plane and the flexing angle to be not exceeding 90 degrees. This arrangement facilitates machining work on the springs  204  and  205  to permit reduction in cost of manufacture. 
     Further, the angles of the hole parts  202   a  and  203   a  of the barrier members  202  and  203  are arranged to be a small angle of 30 degrees when the barrier is open. By virtue of that arrangement, the flexing force in the direction of −Z of the fore end of each of the springs  205  and  204  can be efficiently converted into a force of opening the barrier member, and a force required for holding the barrier in its open state becomes large. Therefore, the barrier cannot be easily moved by an accidental external force such as the force of a finger inadvertently exerted while the barrier is open during a photo-taking operation. Therefore, a trouble such as an accidental eclipse of a necessary image forming light flux by the barrier can be avoided. 
     (Seventh Embodiment) 
     A barrier opening-and-closing device according to a seventh embodiment of the invention is next described with reference to FIGS.  26 ( a ) to  26 ( c ). 
     FIGS.  26 ( a ) to  26 ( c ) show essential parts of a lens barrel  300  having the barrier opening-and-closing device according to the seventh embodiment. FIG.  26 ( a ) is a front view showing a barrier in an open state with a fancy cover excluded from the illustration. FIG.  26 ( b ) is a side view showing the barrier in the opened state with a sectional view including a YZ plane showing only the fancy cover and a fore end tube. FIG.  26 ( c ) is a sectional side view showing the barrier in a closed state. 
     Referring to FIGS.  26 ( a ) to  26 ( c ), the lens barrel  300  has a fore end tube  309 , a rectilinear motion tube  310  arranged to be rectilinearly slidable in a state of being fitted in the fore end tube  309 , a base seat  308  secured by bonding to the front face of the fore end tube  309 , a pair of barrier members  302  and  303 , springs  304  and  305  arranged to urge the barrier members  302  and  303 , screws  306  and  307  arranged to secure the springs  304  and  305  to the base seat  308 , and a fancy cover  301 . 
     The fore end tube  309 , the rectilinear motion tube  310 , the base seat  308 , the fancy cover  301 , the barrier members  302  and  303  and the screws  306  and  307  are arranged in approximately the same manner as these of the fifth and sixth embodiments described above and, therefore, the details of them are omitted from the following description. 
     The seventh embodiment differs from the fifth and sixth embodiments in the arrangement of the springs  304  and  305 . Therefore, the positions of the screws  306  and  307  which are screwed into the base seat  308  differ from those in the fifth embodiment but are about the same as those in the sixth embodiment. Since the springs  304  and  305  are in the same shape, the following describes in detail only the arrangement of the spring  305 . 
     The spring  305  has a fore end part  305   a  connected to the barrier member  302 , and another end part on the opposite side is formed as a projection  305   b  which is to be pushed by the rectilinear motion tube  310 . A part between the fore end part  305   a  and the projection  305   b  is bent backward into a U-shaped part as a fixed part  305   d.  The U-shaped fixed part  305   d  is secured to the base seat  308  and the fore end tube  309 . 
     The fixed part  305   d  of the spring  305  is secured to the base seat  308  which is mounted on the fore end tube  309 . The fore end part  305   a  of the spring  305  is fitted into a hole part  302   a  of the barrier member  302 . 
     The spring  305  has the fixed part  305   d  and the fore end part  305   a  located approximately within one and the same XY plane. As shown in FIGS.  26 ( a ) to  26 ( c ), the spring  305  is bent back approximately into the U shape from the fixed part  305   d  within the XY plane to extend in the direction of +Y and is then bent in the direction of +X at a point lower than the fore end part  305   a.  The spring  305  is further bent to extend in the direction of −Z in parallel with an optical axis in such a way as to extend toward the rectilinear motion tube  310  through a hole part  309   b  of the fore end tube  309 . The fore end of the spring  205  in this direction is bent in the direction of −Y to form the projection  305   b.    
     The other spring  304  is also secured to the base seat  308  with the screw  306 . The fore end part  304   a  of the spring  304  is fitted into a hole part  303   a  of the barrier member  303 . 
     When the rectilinear motion tube  310  is not pushing the projection  305   b  of the spring  305 , the fore end part  305   a  tries to flex toward the camera body (in the direction of −Z). This causes the barrier member  302  to swing on its rotation shaft  302   b  and to come to a stop at an open position as shown in FIG.  26 ( b ). At this time, the hole part  302   a  of the barrier member  302  in which the fore end part  305   a  of the spring  305  is fitted is at an angle of 45 degrees with respect to the center of swing and with respect to the XY plane which passes the center of swing. Then, the other barrier member  303  opens in the same manner and has its hole part  303   a  also at the angle of 45 degrees. 
     Further, the barrier member  303  is caused to swing by a similar mechanism and comes to a stop at the angle of 45 degrees relative to the XY plane which passes the center of swing. 
     The projection  305   b  of the spring  305  is arranged to flex toward the camera body (in the direction of −Z) and in the direction of the outer diameter (in the direction of +X). As shown in FIGS.  26 ( a ) and  26 ( b ), the projection  305   b  is displaced toward the rectilinear motion tube  310  while being in contact with the inner wall part of the fore end tube  309  until the projection  305   b  comes to a stop retaining a predetermined clearance between the projection  305   b  and the fore end  305   a.    
     The projection  304   b  of the other spring  304  is likewise displaced toward the rectilinear motion tube  310  while being in contact with the inner wall part of the fore end tube  309  until the projection  304   b  comes to a stop. 
     When the rectilinear motion tube  310  is drawn out toward the object (in the direction of +Z), the pushing face  310   a  of the rectilinear motion tube  310  causes the projection  305   b  of the spring  305  to move in the direction of +Z. Then, as shown in FIG.  26 ( c ), the projection  305   b  comes into contact with another part of the spring  305  on the side of the fore end part  305   a  to displace the fore end part  305   a  in the direction of +Z. The displacement of the fore end part  305   a  causes the barrier member  302  to swing on its rotation shaft  302   b.  The fore end of the barrier member  302  then collides against a stopper part  308   j  of the base seat  308  to bring the barrier member  302  to a stop at a closed position. The other barrier member  303  likewise comes to a stop at its closed position. At this time, the hole part  302   a  of the barrier member  302  in which the fore end part  305   a  of the spring  305  is fitted is at an angle of −45 degrees with respect to the center of swing and with respect to the XY plane which passes the center of swing. Then, the other barrier member  303  closes in the same manner and has its hole part  303   a  also at the angle of −45 degrees. 
     With the lens barrel  300  in the seventh embodiment arranged as described above, the seventh embodiment gives the following advantages, in addition to advantages which are the same as the advantages of the fifth embodiment: 
     The part of the spring  305  extending from the fixed part  305   d  to the fore end part  305   a  and another part extending from the fixed part  305   d  to the projection  305   b  are separately arranged. Therefore, the movement of a connection part between the spring  305  and the barrier member  302  and the movement on the XY plane of a contacting part between the spring  305  and the rectilinear motion tube  310  do not interfere with each other, to permit transmission of only such forces that are required for opening and closing the barrier member  302 . Further, since the projection  305   b  of the spring  305  is in the state of being urged in the direction of the outside diameter of the lens barrel, the projection  305   b  comes into contact with the pushing face  310   a  of the rectilinear motion tube  310  without fail when the projection  305   b  is pushed by the rectilinear motion tube  310 . The arrangement precludes the occurrence of such a trouble that the projection  305   b  of the spring  305  comes outside of the pushing face  310   a  of the rectilinear motion tube  310  by slipping in the direction of the inside diameter of the lens barrel. 
     (Eighth Embodiment) 
     A barrier opening-and-closing device according to an eighth embodiment of the invention is next described below with reference to FIGS.  27 ( a ) to  27 ( d ). 
     FIGS.  27 ( a ) to  27 ( d ) show essential parts of a lens barrel  500  having the barrier opening-and-closing device according to the eighth embodiment. FIG.  27 ( a ) is a front view showing a barrier in an open state with a fancy cover excluded from the illustration. FIG.  27 ( b ) is a side view showing the barrier in the open state with a sectional view including a YZ plane showing only the fancy cover and a fore end tube. FIG.  27 ( c ) is a sectional side view showing the barrier in a closed state. FIG.  27 ( d ) is a look-through view showing springs as viewed from above with the barrier in the open state. 
     Referring to FIGS.  27 ( a ) to  27 ( d ), the lens barrel  500  has a fore end tube  509 , a rectilinear motion tube  510  arranged to be rectilinearly slidable in a state of being fitted in the fore end tube  509 , a pair of barrier members  502  and  503 , a spring  511  arranged as a first urging member to urge the barrier members  502  and  503 , a spring  512  arranged as a second urging member to be pushed by the rectilinear motion tube  510 , a screw  507  arranged to secure the springs  511  and  512  to the rectilinear motion tube  510 , and a fancy cover  501 . The rectilinear motion tube  510  is arranged to be in one body with a base seat part which is arranged in the same manner as described in the foregoing embodiments. The springs  511  and  512  and the barrier members  502  and  503  are thus mounted directly on the rectilinear motion tube  510 . 
     Further, the rectilinear motion tube  510 , the fancy cover  501 , the barrier members  502  and  503  and the screw  507  are arranged approximately in the same manner as in each of the foregoing embodiments disclosed. 
     The barrier member  502  has rotation shafts  502   b  and  502   c  fitted in the bearing parts  509   h  and  509   i  of the fore end tube  509  and is swingably secured to a bearing part  501   c  of the fancy cover  501 . Further, as shown in FIG.  27 ( c ), the barrier member  502  has its fore end part  502   d  in a so-called tapered shape which is arranged to have the fore end part  503   d  of the other barrier member  503  inserted there on the inner circumferential side of the fore end part  502   d.    
     In the eighth embodiment, the arrangement of the springs  511  and  512 , the positions and number of screws to be screwed into the rectilinear motion tube  510  differ from those in each of the other embodiments described above. 
     The spring  512  which is the second urging member is disposed in front of the fore end tube  509 . As shown in FIG.  27 ( a ), the spring  512  is formed approximately in a C shape as a whole. The two ends of the C shape of the spring  512  extend toward the rectilinear motion tube  510  (in the direction of −Z) in parallel with an optical axis, as shown in FIGS.  27 ( b ) to  27 ( d ). More specifically, the first (upper) fore end part  512   a  which is shown in FIG.  27 ( a ) extends toward the rectilinear motion tube  510  through a first hole part  509   b  of the fore end tube  509 . The second (lower) end part  512   d  extends toward the rectilinear motion tube  510  through a second hole part  509   g  of the fore end tube  509 . 
     The spring  511  which is the first urging member is formed approximately in a C shape as a whole as shown in FIG.  27 ( a ). The spring  511  is arranged to overlap the spring  512 . The two ends of the spring  511  are a first end part  511   a  which is provided for connection to the barrier member  502  and a second end part  511   e  which is for connection to the barrier member  503 . The spring  511  has an intermediate part  511   c  secured to the fore end tube  509  with the screw  507 . 
     The spring  511  has the first end part  511   a  fitted in a hole part  502   a  of the upper barrier member  502  and the second end part  511   e  fitted in a hole part  503   a  of the lower barrier member  503 . The intermediate part  512   c  of the spring  512  is interposed in between the front face of the fore end tube  509  and the other spring  511  in such a way as to prevent the springs  511  and  512  from coming off their positions. The first fore end part  512   a  and the second fore end part  512   e  of the spring  512  are urged toward the outside diameter of the lens barrel in a state of being constantly in contact with the inner face  509   f  of the rectilinear motion tube  510 . 
     When the spring  512  is not pushed by the rectilinear motion tube  510 , the first and second fore end parts  511   a  and  511   e  of the other spring  511  try to flex toward the rectilinear motion tube  510  (in the direction of −Z). Therefore, with the spring  512  not pushed as shown in FIG.  27 ( b ), the spring  511  causes the barrier members  502  and  503  to swing on their rotation shafts  502   b  and  503   b.  As a result, the barrier is open. Further, under this condition, as shown in FIG.  27 ( a ), the two springs  511  and  512  are in contact with each other at predetermined parts to have the spring  512  pushed by the spring  511  toward the rectilinear motion tube  510  (in the direction of −Z). 
     More specifically, the spring  511  is in contact with the first (upper) contact part  512   b  and the second (lower) contact part  512   d  of the spring  512  at its first (upper) contact part  511   b  and its second (lower) contact part  511   d.  When the spring  512  is pushed toward the rectilinear motion tube  510  under this condition, the first and second fore end parts  512   a  and  512   e  of the spring  512  come to be pushed out toward the rectilinear motion tube  510 . At this time, as shown in FIG.  27 ( d ), the second (lower) fore end part  512   e  of the spring  512  comes to protrude further toward the rectilinear motion tube  510  than the first (upper) fore end part  512   a.    
     When the rectilinear motion tube  510  moves toward the barrier members  502  and  503  as shown in FIG.  27 ( c ), the pushing face  510   a  of the rectilinear motion tube  510  first pushes the second fore end part  512   e  of the spring  512  in the direction of +Z. Then, the second contact part  512   d  of the spring  512  pushes up the second contact part  511   d  of the spring  511 . This causes the second fore end part  511   e  of the spring  511  to be displaced in the direction of +Z, and causes the lower barrier member  503  to sing in the direction of closing. The barrier member  503  thus first begins to close. After that, the first fore end part  512   a  of the spring  512  is pushed by the pushing face  510   a  of the rectilinear motion tube  510 . That causes the first contact part  512   b  of the spring  512  to push up the first contact part  511   b  of the spring  511 . The first fore end part  511   a  of the spring  511  is displaced in the direction of +Z to cause the barrier member  502  to swing in the direction of closing. The barrier member  502  thus also begins to close. The barrier members  503  and  502  eventually completely close, as shown in FIG.  27 ( c ). 
     Further, when the rectilinear motion tube  510  moves from this position shown in FIG.  27 ( c ) in the direction of −Z, the elastic force of the spring  511  causes the first and second fore end parts  511   a  and  511   d  of the spring  511  to be displaced toward the rectilinear motion tube  510 . Then, the upper barrier member  502  first begins to open. Following this, the lower barrier member  503  begins to open. Both the barrier members  503  and  502  eventually open to a full extent, as shown in FIG.  27 ( b ). 
     With the lens barrel  500  in the eighth embodiment arranged as described above, the eighth embodiment gives the following advantages in addition to advantages which are the same as the advantages of the fifth embodiment. 
     Without increasing the number of springs which are urging means from two, one spring  512  is arranged to be used solely for contact with the rectilinear motion tube  510  while the other spring  511  is arranged to be used solely for connection to the barrier members. When the spring  512  is pushed by the rectilinear motion tube  510 , the spring  512  pushes the spring  511  to open the barrier members. Therefore, the wire diameters of these springs  512  and  511  can be selected separately according to their roles, so that a barrier opening-and-closing device can be arranged to smoothly perform its opening and closing actions. The arrangement also permits omission of parts such as a screw otherwise necessary for fixing the spring  512  as a second urging member. The reduction of the number of necessary parts permits reduction in cost. 
     One of the barrier members, i.e., the barrier member  502  is arranged to open and close prior to the other barrier member  503 , and the impact of contact of the protrusions of the barrier members which otherwise takes place once is divided into two times, so that the force and sound of the collision can be lessened to make the rectilinear motion tube  510  drivable by a smaller force. 
     When the barrier is closed, the two barrier members  502  and  503  overlap each other at their fore end parts. Therefore, dust, external light, etc., can be prevented from intruding into the lens barrel. 
     In each of the fifth, sixth and seventh embodiments disclosed, the length of projection of one spring extending toward the rectilinear motion tube is arranged to be equal to that of the other spring. This arrangement may be changed to have these projections differ in length from each other, as in the case of the eighth embodiment. Such a modification also has the same advantages as those of the eighth embodiment. 
     The lens barrel having the barrier opening-and-closing device arranged as described in the foregoing enables a camera to take pictures with a higher quality.