Abstract:
A camera capable of stabilizing the open state and closed state of barrier blades is disclosed. The camera comprises a lens barrel which holds a lens; and a barrier unit placed closer to the end of the lens barrel than a flange which is formed on the lens barrel and extends in the direction orthogonal to the optical axis, wherein the barrier unit has: a barrier member which opens/closes the front of the lens through a rotation operation; a barrier driving mechanism which drives the barrier member according to the operation of the lens barrel; and a partition plate which separates the barrier member from the barrier driving mechanism in the direction of the optical axis, and a shaft which supports the barrier member in a rotatable manner is formed on the flange.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application is a divisional of application Ser. No. 10/777,256, filed Feb. 12, 2004, the entire disclosure of which is hereby incorporated by reference. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to a camera provided with a open/close type barrier mechanism which protects the lens front of a lens barrel and an optical apparatus.  
         [0004]     2. Description of the Related Art  
         [0005]     There are proposals of various types of a barrier mechanism which is provided in front of an image-pickup lens of a camera and causes barrier blades to perform an open/close operation in conjunction with operations (protruding and retracting) of the lens barrel in the direction of the optical axis. A basic structure of the barrier mechanism is shown in  FIG. 4 .  
         [0006]     Two barrier blades  101  are supported by rotation shafts  102  in a rotatable manner through engagement of hole portions  10   a  with the rotation shafts  102 . The rotation shafts  102  are provided on a base plate (not shown) (e.g., lens barrel, etc.). Then, driving pins  101   b  engage with notch portions  103   a  of a first driving ring  103 .  
         [0007]     The first driving ring  103  engages with a second driving ring  104  in a rotatable manner and is energized by an absorption spring  105  with respect to the second driving ring  104  in the direction indicated by arrow A (one turn direction). Here, since a hooking shaft  103   b  normally contacts a stopper  104   a  of the second driving ring  104  by spring force of the spring  105 , the first driving ring  103  normally operates together with the second driving ring  104  as one unit.  
         [0008]     The second driving ring  104  is held by a base plate (not shown) (e.g., lens barrel, etc.) in a rotatable manner and energized by an opening spring  106  in the direction indicated by arrow B.  
         [0009]     One end of the opening spring  106  is fixed to a hooking shaft  107  and the hooking shaft  107  is provided on a base plate (not shown) (e.g., lens barrel, etc.). The first driving ring  103  and second driving ring  104  are rotated by the opening spring  106  in the direction indicated by arrow B and cause the barrier blades  101  to rotate in the opening direction (direction indicated by arrow C) as a result. Since the barrier mechanism is held by a base plate (not shown) (e.g., lens barrel, etc.), the barrier blades  101  are in an open state when the lens barrel protrudes and it is an image-pickup state. On the other hand, when the lens barrel retracts and it is in a non-image-pickup state, a cam face  104   b  of the second driving ring  104  contacts a cam-shaped protrusion  108  inside the camera and moves along the cam-shaped protrusion  108  and thereby causes the first driving ring  103  and second driving ring  104  to rotate in the direction indicated by arrow A. In this way, the barrier blades  101  rotate in the direction opposite to the direction indicated by arrow C to close the lens front.  
         [0010]     When an external force in the direction indicated by arrow C is applied to the barrier blades  101  which are in a closed state, only the first driving ring  103  rotates in the direction indicated by arrow B against the spring force of the absorption spring  105 .  
         [0011]     In the above described structure, the structure in which the base plate and lens barrel house and hold the barrier mechanism will be explained using the cross-sectional views shown in  FIG. 5  to  FIG. 7 . In these figures, the same members as those explained in  FIG. 4  are assigned the same reference numerals.  
         [0012]     In the structure shown in  FIG. 5  (first conventional example), as disclosed in Japanese Patent Application Laid-Open No. H8 (1996)-234292 and Japanese Patent Application Laid-Open No. H10 (1998)-186453, the rotation shaft  102  and hooking shaft  107  (not shown) are directly provided in the lens barrel  109 . Furthermore, the barrier mechanism is housed in the lens barrel  109  and a barrier cover  110  covers the front of the lens barrel  109 .  
         [0013]     The structure shown in  FIG. 5  is simple and allows the barrier mechanism to be assembled from the front of the lens barrel  109 .  
         [0014]     The structure shown in  FIG. 6  (second conventional example), as is disclosed in Japanese Patent Application Laid-Open No. H9 (1997)-211536 (corresponding to U.S. Pat. No. 5,862,426 and EP 0 788 020 A1), is constructed in such a way that the barrier driving mechanism other than the barrier blade  101  is assembled from the inner side (right side in  FIG. 6 ) of the lens barrel  109 . In this structure, a plate  112  is used to house the first driving ring  103  and second driving ring  104  within the lens barrel  109 .  
         [0015]     The structure shown in  FIG. 7  (third conventional example) is a structure in which the barrier blades  101  and barrier driving mechanism are separated by a barrier base plate  113 . Thus, the rotation shaft  102  is provided on a barrier base plate  113 .  
         [0016]     However, in the structure shown in  FIG. 5 , when the barrier blades  101  moves to the closing position, the second driving ring  104  may be pushed forward (left side in  FIG. 5 ) in the lens barrel  109  by the cam-shaped protrusion  108 , thereby preventing the movement of the barrier blades  101  and producing insufficient closing of the barrier blades  101 .  
         [0017]     On the other hand, in the structure shown in  FIG. 6 , since the part of the lens barrel  109  is located between the barrier blades  101  and barrier driving mechanism (especially, second driving ring  104 ) other than the barrier blades  101 , even if the second driving ring  104  is pushed forward in the lens barrel  109  by the cam-shaped protrusion  108  as described above, the second driving ring  104  does not prevent the movement of the barrier blades  101 .  
         [0018]     However, since the barrier driving mechanism needs to be assembled from the inner side of the lens barrel  109  (right side in  FIG. 6 ), it is difficult to imbed the barrier mechanism in the lens barrel  109 .  
         [0019]     In the structure shown in  FIG. 7 , since the barrier base plate  113  is placed between the barrier blades  101  and barrier driving mechanism (especially, the second driving ring  104 ), even if the second driving ring  104  is pushed in by the cam-shaped protrusion  108  as described above, the movement of the barrier blades  101  is not blocked. Moreover, the barrier mechanism can be assembled from the front side (left side in  FIG. 7 ) of the lens barrel  109 , and therefore it is also easy to imbed the barrier mechanism in the lens barrel  109 .  
         [0020]     However, the structure shown in  FIG. 7  may make the open state and closed state of the barrier blades  101  unstable.  
         [0021]     That is, the closed state and open state of the barrier blades  101  are affected by the relative positional relationship between the rotation shaft  102  and driving pin  101   b , but if the rotation shaft  102  is provided on the barrier base plate  113 , the barrier base plate  113  moves within the plane orthogonal to the optical axis due to backlash of engagement between the lens barrel  109  and barrier base plate  113 , assembly error, part variations, etc., also causing the position of the rotation shaft  102  to change.  
         [0022]     Thus, when the position of the rotation shaft  102  changes, the relative positional relationship between the rotation shaft  102  and driving pin  101   b  is not constant and the opening position and the closing position of the barrier blades  101  are not fixed to a predetermined position, and therefore the open state and the closed state of the barrier blades  101  become unstable.  
       SUMMARY OF THE INVENTION  
       [0023]     One aspect of an optical apparatus of the present invention comprises a lens and a lens barrel which holds the lens. Here, the lens barrel has, in order from an object side, a barrier member which rotates around a first shaft and opens/closes the front of the lens, a partition plate and a barrier driving member which drives the barrier member through a second shaft, and the first shaft is united with the lens barrel.  
         [0024]     The features of the optical apparatus of the invention will become more apparent from the following detailed description of a preferred embodiment of the invention with reference to the drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0025]      FIG. 1  is an exploded perspective view of a barrier mechanism according to an embodiment of the present invention;  
         [0026]      FIG. 2  is a partial cross-sectional view of a lens barrel according to the embodiment;  
         [0027]      FIG. 3  is an external perspective view of a camera which is the embodiment;  
         [0028]      FIG. 4 (A) is an exploded perspective view of a conventional barrier mechanism viewed from the front and  FIG. 4 (B) is an exploded perspective view viewed from the back;  
         [0029]      FIG. 5  is a partial cross-sectional view of the conventional lens barrel;  
         [0030]      FIG. 6  is a partial cross-sectional view of the conventional lens barrel; and  
         [0031]      FIG. 7  is a partial cross-sectional view of the conventional lens barrel. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0032]      FIG. 1  and  FIG. 2  show a barrier mechanism of a camera which is an embodiment of the present invention.  FIG. 1  is an exploded perspective view of the barrier mechanism and  FIG. 2  is a partial cross-sectional view of a lens barrel provided with the barrier mechanism.  FIG. 3  is an external perspective view (schematic view) of the camera.  
         [0033]     In  FIG. 3 , reference numeral  21  denotes a camera body which contains various members necessary for image taking. Reference numeral  22  denotes a release button. An image-taking preparation operation (photometric operation or focusing operation, etc.) is started by a half-depressing operation of the release button  22  and an image-taking operation (exposure to a film or an image-pickup element such as CCD, etc.) is started by a full-depressing operation of the release button  22 .  
         [0034]     Reference numeral  23  denotes a view finder unit for observing an object image and  24  denotes a light projection unit which projects AF fill light, etc. Reference numeral  25  denotes an electronic flash unit which irradiates an object with illumination light.  
         [0035]     Reference numeral  26  denotes a lens barrel which holds an image-taking lens and can move (can protrude/retract) between a collapse state in which it is housed in the camera body  21  and an image-taking state in which it protrudes from the camera body  21 . On the front of the lens barrel  26 , a barrier mechanism which will be described later is provided.  
         [0036]     Then, the structure of the barrier mechanism of this embodiment will be explained using  FIG. 1  and  FIG. 2 .  
         [0037]     Hole portions  1   a  are formed at the one end of the barrier blades (barrier member)  1 . The barrier blades  1  are supported by rotation shafts  2   a  in a rotatable manner by allowing the hole portions  1   a  to engage with the rotation shafts  2   a  provided in a holding member  2  (part of the lens barrel  26 ). Furthermore, driving pins  1   b  are provided at positions closer to the optical axis than the hole portions  1   a  on the barrier blades  1  and engage with notch portions  3   a  of a first driving ring  3 .  
         [0038]     The first driving ring  3  engages with a second driving ring  4  in a rotatable manner. An absorption spring  5  energizes the first driving ring  3  with respect to the second driving ring  4  in the direction indicated by arrow A with one end of the absorption spring  5  engaging with a hooking shaft  3   c  of the first driving ring  3  and the other end engaging with a hooking shaft  4   c  of the second driving ring  4 .  
         [0039]     Here, by matching the phases of notch portions  3   b  formed in three parts in the circumferential direction of the first driving ring  3  and the phases of protrusions  4   b  formed in three parts in the circumferential direction of the second driving ring  4 , it is possible to assemble the first driving ring  3  into the second driving ring  4 .  
         [0040]     At this time, the first driving ring  3  is energized in the direction indicated by arrow A by the spring  5 , the end of the notch portions  3   b  are pressed against the end of the protrusions  4   b , and therefore the first driving ring  3  and second driving ring  4  operate together as one unit except when an opening/closing operation of the barrier blades  1  is performed by external force as will be described later.  
         [0041]     The second driving ring  4  is held by a lens holding portion  2   b  of the holding member  2  in a rotatable manner. An opening spring  6  energizes the second driving ring  4  in the direction indicated by arrow B with one end of the opening spring  6  engaging with a hooking shaft  4   d  of the second driving ring  4  and the other end engaging with the hooking shaft  2   c  of the holding member  2 .  
         [0042]     The first driving ring  3 , second driving ring  4 , absorption spring  5  and opening spring  6  are housed and held in the holding member  2  by being pressed by a barrier base plate (partition plate)  7  from the front of the lens barrel  26  (right side in  FIG. 2 ).  
         [0043]     Here, the barrier base plate  7  is fixed by bayonet lugs  2   d  provided in the holding member  2 . That is, in order to assemble the barrier base plate  7  into the holding member  2 , the barrier base plate  7  is attached to the holding member  2  by matching the phases of the bayonet lugs  2   d  and the phases of notch portions  7   a  provided in the barrier base plate  7  first and then the barrier base plate  7  is fixed to the holding member  2  by rotating the barrier base plate  7  clockwise (direction indicated by arrow A).  
         [0044]     At this time, the rotation shafts  2   a  of the holding member  2  penetrate through hole portions (recess portion)  7   b  formed in the barrier base plate  7  and support the barrier blades  1  in a rotatable manner. It is also possible to form notch portions (recess portion) obtained by notching the perimeter of the barrier base plate  7  instead of through hole portions  7   b.    
         [0045]     Furthermore, the barrier base plate  7  is provided with escape hole portions  7   c  so that the driving pins  1   b  of the barrier blades  1  can engage with the notch portions  3   a  of the first driving ring  3 . These escape hole portions  7   c  is formed like an elongated hole and secure an moving space of the driving pins  1   b  in a rotation operation of the barrier blades  1 .  
         [0046]     As the procedure for actually assembling the barrier mechanism into the holding member  2 , the second driving ring  4 , opening spring  6 , absorption spring  5  and first driving ring  3  are assembled into the holding member  2  sequentially and then the barrier base plate  7  is assembled into the holding member. Then, the barrier blades  1  are assembled and covered with the barrier cover  8 .  
         [0047]     Elastic lugs  8   a  are formed in the barrier cover  8  and the barrier cover  8  is fixed to the holding member  2  with the elastic lugs  8   a  engaging with the holding member  2 . At this time, the elastic lugs  8   a  engage with rotation stopper notch portions  7   d  formed on the perimeter of the barrier base plate  7 .  
         [0048]     Furthermore, protrusions  8   b  provided on the rear face of the barrier cover  8  engage with notch portions  2   e  provided in the front of the holding member  2 . This represses the barrier cover  8  from coming off the holding member  2  and also represses it from rotating around the optical axis. Then, the barrier cover  8  is fixed to the holding member  2 , which represses the barrier base plate  7  from rotating around the optical axis.  
         [0049]     In this embodiment, as shown in  FIG. 2 , the barrier mechanism is located closer to the end of the holding member  2  (left side in  FIG. 2 ) than an end  2   f  formed on the inner surface of the holding member  2 , and therefore it is possible to incorporate the barrier mechanism from the front of the holding member  2 . This makes it possible to easily assemble the barrier mechanism (lens barrel).  
         [0050]     Here, the end  2   f  is formed at an proximal position with respect to the barrier blades  1  in the lens barrel  26  and extends to the inner side of the holding member  2 , that is, extends toward the image-taking optical axis. Furthermore, the end  2   f  has a plane orthogonal to the optical axis.  
         [0051]     In the above described structure, the barrier mechanism incorporated from the front of the lens barrel  26  moves together with the holding member  2  as one unit according to the protruding/retracting operation of the lens barrel  26  in the direction of the optical axis.  
         [0052]     When the lens barrel  26  protrudes and is in an image-taking state, the barrier blades  1  are withdrawn from an opening  8   c  formed in the center of the barrier cover  8  and then remain open state. This allows a light flux from an object to go into the lens barrel  26 .  
         [0053]     On the other hand, when the lens barrel  26  retracts from the image-taking state into a collapse state, a cam face  4   a  of the second driving ring  4  contacts a cam-shaped protrusion  9  provided in the camera body  21  according to the retracting operation of the lens barrel  26 . Then, the second driving ring  4  rotates in the direction indicated by arrow A (direction opposite to the direction indicated by arrow B) against the spring force of the opening spring  6  through the engagement between the cam face  4   a  and cam-shaped protrusion  9 .  
         [0054]     When the second driving ring  4  rotates in the direction indicated by arrow A, the first driving ring  3  rotates in the direction indicated by arrow A by receiving the spring force of the absorption spring  5 , the barrier blades  1  rotate around the rotation shaft  2   a  through the engagement between the notch portions  3   a  and driving pins  1   b  and covers the opening  8   c.    
         [0055]     When the lens barrel  26  protrudes from a collapse state into an image-taking state, the engagement between the cam face  4   a  and cam-shaped protrusion  9  is released according to the protruding operation of the lens barrel  26 . At this time, the second driving ring  4  rotates in the direction indicated by arrow B by receiving the spring force of the opening spring  6  and the first driving ring  3  rotates in the direction indicated by arrow B (direction opposite to the direction indicated by arrow A).  
         [0056]     When the first driving ring  3  rotates in the direction indicated by arrow B, the barrier blades  1  rotate around the rotation shafts  2   a  through the engagement between the notch portions  3   a  and driving pins  1   b  and withdraw from the opening  8   c  into an open state.  
         [0057]     When the barrier blades  1  are in a closed state, if an external force is applied to the barrier blades  1  in the opening direction of the barrier blades  1 , only the first driving ring  3  rotates in the direction indicated by arrow B against the spring force of the absorption spring  5 .  
         [0058]     As shown in  FIG. 2 , in this embodiment, it is possible to incorporate the barrier mechanism from the front of the lens barrel  26  and thereby easily assemble the barrier mechanism.  
         [0059]     Furthermore, since the barrier blades  1  and barrier driving mechanism having the second driving ring  4 , opening spring  6 , absorption spring  5  and the first driving ring  3 , are placed sandwiching the barrier base plate  7 , even if the second driving ring  4  (cam face  4   a ) contacts the cam-shaped protrusion  9  and is pushed in to the front side of the lens barrel  26 , the movement (especially the closing operation) of the barrier blades  1  is not blocked.  
         [0060]     That is, since the displacements of the barrier base plate  7  and the barrier cover  8  in the direction of the optical axis are repressed, the space for the movement of the barrier blades  1  is secured.  
         [0061]     Furthermore, in this embodiment, the rotation shafts  2   a  are fixed to the holding member  2 , and therefore even if the barrier base plate  7  moves within the plane orthogonal to the optical axis with respect to the holding member  2  for reasons such as engagement backlash, assembly errors or parts variations, etc., the positions of the rotation shafts are never shifted and the open state and closed state of the barrier blades  1  never become unstable.  
         [0062]     In this embodiment, the hole portions  1   a  are formed in the barrier blades  1  and the rotation shafts  2   a  are formed in the holding member  2  to cause the hole portions  1   a  to engage with the rotation shafts  2   a , but the reverse structure may also be used. That is, it is also possible to form rotation shafts in the barrier blades  1  and form hole portions which engage with the above described rotation shafts in the holding member  2 .  
         [0063]     Furthermore, in this embodiment, the barrier blades  1  are driven using the barrier driving mechanism having the first driving ring  3 , second driving ring  4 , absorption spring  5  and opening spring  6 , but any structure may be used if it is at least the structure which causes the barrier blades  1  to move between the open position and the closed position. In this case, the barrier driving mechanism is separated from the barrier blades by the barrier base plate  7  and the rotation shafts of the barrier blades is provided in the lens barrel. Therefore, it is possible to achieve the same purpose as this embodiment.  
         [0064]     While preferred embodiment has been described, it is to be understood that modification and variation of the present invention may be made without departing from scope of the following claims.