Abstract:
The present invention provides an optical option attachment ring comprising: a ring body into which a lens barrel is inserted; a clamping ring rotatably fastened on the periphery of the ring body; an elastic member arranged between the ring body and the clamping ring; and an abutting portion which is provided on the clamping ring and abuts on the elastic member according to the rotational position of the clamping ring to elastically deform the elastic member to cause at least a part of the elastic member to project further inwards than the inner peripheral surface of the ring body and to be positioned in a groove formed in the lens barrel.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to an optical option attachment ring, and in particular, to an optical option attachment ring which has the same substantially cylindrical contour as a lens barrel and no projection. 
   2. Description of the Related Art 
   An optical option attachment ring for mounting a wide-angle converter and teleconverter on a lens barrel has been known hitherto (refer to, for example, Japanese Patent Application Laid-Open No. 2004-271892). 
   An optical option attachment ring according to Japanese Patent Application Laid-Open No. 2004-271892 is described below with reference to a drawing. As illustrated in  FIG. 7 , the optical option attachment ring  10 ′ includes one end  21 ′ and the other end  22 ′ arranged at predetermined spaced intervals, a ring body  20 ′ which couples the one end  21 ′ to the other end  22 ′ and into which a lens barrel (not shown) is inserted, and a fixing screw  23 ′ which is inserted into screw holes  21   a ′ and  22   a ′ causing the one end  21 ′ to communicate with the other end  22 ′. In the optical option attachment ring  10 ′, the fixing screw  23 ′ is fastened to cause the one end  21 ′ to be close to the other end  22 ′ to decrease the ring body  20 ′ in diameter, fixing the ring body  20 ′ to the lens barrel and the fixing screw  23 ′ is loosened to cause the one end  21 ′ to be apart from the other end  22 ′ to increase the ring body  20 ′ in diameter, releasing the fixing. 
   As illustrated in  FIG. 7 , the one end  21 ′ and the other end  22 ′ of the optical option attachment ring  10 ′ are slanted. Fastening the fixing screw  23 ′ causes a portion  22   b ′ of the other end  22 ′ to move along the slant face of the one end  21 ′ and project inside the inner surface  20   a ′ of the ring body  20 ′ and be positioned in (be engaged with) a groove (not shown) formed in the lens barrel. This prevents the optical option attachment ring  10 ′ from falling off the lens barrel even if the fixing screw  23 ′ loosens. 
   SUMMARY OF THE INVENTION 
   However, in the optical option attachment ring  10 ′ according to Japanese Patent Application Laid-Open No. 2004-271892, the one end  21 ′ and the other end  22 ′ protrude from the cylindrical contour, which causes a problem in that the protruding one end  21 ′ and the other end  22 ′ may be caught on or hit something around the periphery. 
   In view of the above, the present invention has been made and has its purpose to provide an optical option attachment ring which has the same substantially cylindrical contour as a lens barrel and no projection. 
   The present invention has been made to solve the above problems. An optical option attachment ring according to a first aspect of the present invention comprises a ring body into which a lens barrel is inserted, a clamping ring rotatably fastened on the periphery of the ring body, an elastic member arranged between the ring body and the clamping ring and an abutting portion which is provided on the clamping ring and abuts on the elastic member according to the rotational position of the clamping ring to elastically deform the elastic member to cause at least a part of the elastic member to project further inwards than the inner peripheral surface of the ring body and to be positioned in a groove formed in the lens barrel. 
   According to the first aspect of the present invention, the rotation of the clamping ring causes at least a part of the elastic member (for instance, the curved portion of the leaf spring) to project further inwards than the inner peripheral surface of the ring body according to the rotational position of the clamping ring and to be positioned in a groove formed in the lens barrel. In other words, at least a part of the elastic member is engaged with the groove. Unlike a conventional mounting ring, there is no need to provide a portion (the one end and the other end) projected from a cylindrical contour because the elastic member is engaged with the groove. Accordingly, it is enabled to provide the optical option attachment ring which has the same substantially cylindrical contour as the lens barrel and no projection. 
   Furthermore, a conventional fixing screw has been so small in diameter to make it difficult to tighten. According to the first aspect of the present invention, the clamping ring is comparatively larger in diameter, which make it relatively easy to tighten. 
   According to a second aspect of the present invention, in the first aspect, the ring body includes an opening causing the periphery and the inner peripheral surface of the ring body to communicate with each other, the elastic member is a leaf spring with a fixed end fixed to the ring body, a free end movable between the inner peripheral surface of the clamping ring and the periphery of the ring body in the radial direction and a curved portion formed between the fixed end and the free end and positioned in the opening, and the clamping ring is provided with relatively thin and thick portions on the inner peripheral surface thereof and rotated to cause the thick portion to abut on the free end of the elastic member to elastically deform the elastic member to cause the curved portion to project further inwards than the inner peripheral surface of the ring body from the opening and to be positioned in a groove formed in the lens barrel. 
   According to the second aspect of the present invention, the rotation of the clamping ring causes the curved portion of the leaf spring to project further inwards than the inner peripheral surface of the ring body from the opening according to the rotational position of the clamping ring and to be positioned in a groove formed in the lens barrel. In other words, the curved portion of the leaf spring is engaged with the groove. Unlike a conventional mounting ring, there is no need to provide a portion (the one end and the other end) projected from a cylindrical contour because the curved portion of the leaf spring is engaged with the groove. Accordingly, it is enabled to provide the optical option attachment ring which has the same substantially cylindrical contour as the lens barrel and no projection. 
   Furthermore, a conventional fixing screw has been so small in diameter to make it difficult to tighten. According to the second aspect of the present invention, the clamping ring is comparatively larger in diameter, which makes it relatively easy to tighten. 
   According to a third aspect of the present invention, in the first or the second aspect, the clamping ring is rotated to cause the thick portion to abut on the free end of the elastic member to elastically deform the elastic member to cause the curved portion to project further inwards than the inner peripheral surface of the ring body from the opening and to abut on the bottom of the groove formed in the lens barrel. 
   According to the third aspect of the present invention, slightly rotating the clamping ring allows the optical option attachment ring to be fixed to the lens barrel (hitherto, a fixing screw needs to be given a few turns to fix a mounting ring to a lens barrel). 
   According to a fourth aspect of the present invention, in any of the first to the third aspect, the optical option attachment ring further comprises a rotation regulating projection provided on the inner peripheral surface of the clamping ring and projecting into the opening. 
   According to the fourth aspect of the present invention, the effect of the rotation regulating projection causes the clamping ring not to rotate any more, thereby a user is enabled to be informed that the optical option attachment ring is closely fitted to the lens barrel (or that the optical option attachment ring can be removed from the lens barrel). 
   According to the present invention, it is enabled to provide an optical option attachment ring which has the same substantially cylindrical contour as a lens barrel and no projection. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  describes the configuration of an optical option attachment ring according to the present invention; 
       FIG. 2  describes the configuration of an optical option attachment ring according to the present invention; 
       FIG. 3  describes a configuration to elastically deform a leaf spring; 
       FIG. 4  describes a configuration to elastically deform a leaf spring; 
       FIG. 5  describes the modification example of a configuration to elastically deform a leaf spring; 
       FIGS. 6A and 6B  are examples of configuration to keep the relationship between a ring body  20  and a clamping ring  30 ; 
       FIG. 7  describes the configuration of a conventional optical option attachment ring; 
       FIG. 8  describes an example of modification of a rotation regulating projection  34 ; and 
       FIG. 9  describes an example of modification of the rotation regulating projection  34 . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Referring to the accompanying drawings, preferred embodiments of the optical option attachment ring according to the present invention are described below. 
     FIGS. 1 and 2  describe the configuration of an optical option attachment ring according to the present invention. 
   As illustrated in  FIGS. 1 and 2 , the optical option attachment ring  10  is used to mount optical accessories OP such as a wide-angle converter and teleconverter on a lens barrel  50 . It basically includes a ring body  20  into which the lens barrel  50  is inserted and a clamping ring  30  rotatably mounted on the periphery of the ring body  20 . 
   As illustrated in  FIG. 3 , a leaf spring  40  is arranged between the ring body  20  and the clamping ring  30  (three leaf springs are illustrated as examples in  FIG. 2 ). The one end  41  of the leaf spring  40  is fixed to the ring body  20  using screws and the other end  42  thereof is a free end which is movable in the radial direction. The leaf spring  40  is provided with a curved portion  43  which has a ridge, a groove and a ridge in this order between the one end  41  and the other end  42  thereof. The curved portion  43  is positioned in an opening  23  which causes a periphery  21  of the ring body  20  to communicate with an inner peripheral surface  22  thereof. The leaf spring  40  may be formed of a metallic plate or synthetic resin. 
   The clamping ring  30  is provided with portions  31  and  32  which are relatively thin and thick in thickness respectively on its inner peripheral surface. The other end  42  of the leaf spring  40  is positioned in a space K defined by the thin portion  31  and the periphery  21  of the ring body  20 . The thin and the thick portion  31  and  32  continue through a slope  33 . 
   In  FIG. 3 , the counterclockwise rotation of the clamping ring  30  causes the other end  42  of the leaf spring  40  to relatively move along the thin portion  31  and the slope  33  and soon reach the thick portion  32  as illustrated in  FIG. 4 . At this point, a rotation regulating projection  34  which is provided on the inner peripheral surface (on the thick portion  32 ) of the clamping ring  30  and projects into the opening  23  abuts on the other end  42  of the leaf spring  40 , causing the clamping ring  30  not to rotate any more. 
   As illustrated in  FIG. 4 , when the thick portion  32  is reached by the other end  42  of the leaf spring  40  (in other words, when the clamping ring  30  does not rotate any more), the thick portion  32  abuts on the other end  42  of the leaf spring  40  to elastically deform the leaf spring  40  (in other words, to displace the other end  42  of the leaf spring  40  downward). For this reason, the curved portion  43  projects further inwards than the inner peripheral surface  22  of the ring body  20 . That is to say, the curved portion  43  is positioned a groove  51  formed in the lens barrel  50  (or, the curved portion  43  abuts on the bottom of the groove  51  formed in the lens barrel  50  depending on projections) and engaged with the groove  51 . This closely fits the optical option attachment ring  10  to the lens barrel  50 . 
   As illustrated in  FIG. 5 , a thin portion is provided on the ring body  20  and the thick portion  32  of the clamping ring  30  is further increased in thickness, whereby the curved portion  43  may be projected further inwards than the inner peripheral surface  22  of the ring body  20 . This enables the optical option attachment ring  10  to be more closely fitted to the lens barrel  50 . 
   On the other hand, in  FIG. 4 , the clockwise rotation of the clamping ring  30  causes the other end  42  of the leaf spring  40  to relatively move along the thick portion  32  and the slope  33  and soon reach the thin portion  31  as illustrated in  FIG. 3 . At this point, the rotation regulating projection  34  which is provided on the inner peripheral surface (on the thick portion  32 ) of the clamping ring  30  and projects into the opening  23  abuts on the one end  41  of the leaf spring  40 , causing the clamping ring  30  not to rotate any more. 
   As illustrated in  FIG. 3 , when the thin portion  31  is reached by the other end  42  of the leaf spring  40  (in other words, when the clamping ring  30  does not rotate any more), the other end  42  of the leaf spring  40  is displaced upward by a force recovering to its original shape before the elastic deformation of the leaf spring  40 . For this reason, the curved portion  43  is positioned further outwards than the inner peripheral surface  22  of the ring body  20 . That is to say, the curved portion  43  is positioned again in the opening  23 . 
   An example of application of the optical option attachment ring  10  thus configured is briefly described below. 
   First, it is described how the optical option attachment ring  10  works when mounted. 
   As illustrated in  FIG. 3 , the curved portion  43  is positioned further outwards than the inner peripheral surface  22  of the ring body  20  (in other words, the curved portion  43  is positioned in the opening  23 ). For this purpose, the clamping ring  30  is rotated clockwise in  FIG. 4  to such an extent that the rotation regulating projection  34  abuts on the one end  41  of the leaf spring  40  not to rotate the clamping ring  30  any more. 
   Second, as illustrated in  FIG. 1 , the lens barrel  50  (end portion thereof) is inserted into the ring body  20 . An end face  24  of the ring body  20  abuts on a projecting portion  52  (extending in the circumferential direction) of the lens barrel  50 , enabling the ring body to be easily located when the lens barrel is inserted. 
   In the next place, as illustrated in  FIG. 4 , the curved portion  43  is caused to project further inwards than the inner peripheral surface  22  of the ring body  20 . For this purpose, the clamping ring  30  is rotated counterclockwise in  FIG. 3  to such an extent that the rotation regulating projection  34  abuts on the other end  42  of the leaf spring  40  not to rotate the clamping ring  30  any more. This rotation causes the other end  42  of the leaf spring  40  to relatively move along the thin portion  31  and the slope  33  and soon reach the thick portion  32  as illustrated in  FIG. 4 . The thick portion  32  abuts on the other end  42  of the leaf spring  40  to elastically deform the leaf spring  40  (in other words, to displace the other end  42  of the leaf spring  40  downward). For this reason, the curved portion  43  projects further inwards than the inner peripheral surface  22  of the ring body  20 . That is to say, as illustrated in  FIG. 4 , the curved portion  43  is positioned in a groove  51  formed in the lens barrel  50  (or, the curved portion  43  abuts on the bottom of the groove  51  formed in the lens barrel  50  depending on projections) and engaged with the groove  51 . This enables the optical option attachment ring  10  to be closely fitted to the lens barrel  50 . That is to say, slightly rotating the clamping ring  30  allows the optical option attachment ring  10  to be fixed to the lens barrel  50  (hitherto, a fixing screw needs to be given a few turns to fix a mounting ring to a lens barrel). 
   The positional relationship illustrated in  FIG. 3  is kept by a frictional force caused between the inner peripheral surface of the clamping ring  30  and the periphery of the ring body  20 . 
   The rotation regulating projection  34  abuts on the other end  42  of the leaf spring  40  not to rotate the clamping ring  30  any more, thereby a user is enabled to be informed that the optical option attachment ring  10  is closely fitted to the lens barrel  50 . 
   In the following, it is described how the optical option attachment ring  10  works when demounted. 
   As illustrated in  FIG. 3 , the curved portion  43  is positioned further outwards than the inner peripheral surface  22  of the ring body  20  (in other words, the curved portion  43  is positioned in the opening  23 ). For this purpose, the clamping ring  30  is rotated clockwise in  FIG. 4  to such an extent that the rotation regulating projection  34  abuts on the one end  41  of the leaf spring  40  not to rotate the clamping ring  30  any more. This rotation causes the other end  42  of the leaf spring  40  to relatively move along the thick portion  32  and the slope  33  and soon reach the thin portion  31  as illustrated in  FIG. 3 . The other end  42  of the leaf spring  40  is displaced upward at the thin portion  31  by a force recovering to its original shape before the elastic deformation of the leaf spring  40 . For this reason, the curved portion  43  is positioned further outwards than the inner peripheral surface  22  of the ring body  20 . That is to say, the curved portion  43  is positioned again in the opening  23 . This allows the optical option attachment ring  10  to be demounted from the lens barrel  50 . 
   The positional relationship illustrated in  FIG. 4  is kept by a frictional force caused between the inner peripheral surface of the clamping ring  30  and the periphery of the ring body  20 . 
   The rotation regulating projection  34  abuts on the one end  41  of the leaf spring  40  not to rotate the clamping ring  30  any more, thereby a user is enabled to be informed that the optical option attachment ring  10  can be demounted from the lens barrel  50 . 
   As described above, according to the optical option attachment ring  10  of the present embodiment, the rotation of the clamping ring  30  causes the curved portion  43  of the leaf spring  40  to project further inwards than the inner peripheral surface  22  of the ring body  20  according to the rotational position of the clamping ring  30  and to be positioned in the groove  51  formed in the lens barrel  50  (or, the curved portion  43  abuts on the bottom of the groove  51  formed in the lens barrel  50  depending on projections). That is, the curved portion  43  of the leaf spring  40  is engaged with the groove  51 . Unlike a conventional mounting ring, there is no need to provide a portion (one end and the other end) protruded from a cylindrical contour because the curved portion of the leaf spring is engaged with the groove formed in the lens barrel. As a result, it is enabled to provide the optical option attachment ring  10  which has the same substantially cylindrical contour as the lens barrel  50  and no projection. 
   Furthermore, a conventional fixing screw has been so small in diameter to make it difficult to tighten. According to the optical option attachment ring  10  of the present embodiment, the clamping ring  30  is comparatively larger in diameter, which make it relatively easy to tighten. 
   An example of a modification is described in the following. 
   In the embodiment described above, although the positional relationship illustrated in  FIG. 3  (or in  FIG. 4 ) is kept by a frictional force caused between the inner peripheral surface of the clamping ring  30  and the periphery of the ring body  20 , the present invention is not limited to the above. 
   For instance, as illustrated in  FIG. 6A , the ring body  20  is provided with a depression  25  and the clamping ring  30  is provided with an engaging portion  35  capable of entering the depression  25  and a spring B urging the engaging portion  35 . When the clamping ring  30  is rotated counterclockwise in  FIG. 3  (or counterclockwise in  FIG. 4 ) to such an extent that the rotation regulating projection  34  abuts on the other end  42  (or the one end  41 ) of the leaf spring  40  not to rotate the clamping ring  30  any more, the engaging portion  35  is caused to enter the depression  25  by the urging force of the spring B as illustrated in  FIG. 6B . This may be used to keep the positional relationship illustrated in  FIG. 3  (or in  FIG. 4 ). 
   Incidentally, the clamping ring  30  may be provided with the depression  25  and the ring body  20  may be provided with the engaging portion  35  capable of entering the depression  25  and the spring B urging the engaging portion  35 . 
   Although three leaf springs  40  are exemplified in the above embodiments, the present invention is not limited to this. For example, one, two, or four leaf springs  40  may be provided. 
   Although the rotation regulating projection  34  provided on the inner peripheral surface of the clamping ring  30  and projecting into the opening  23  abuts on the other end  42  (or on the one end  41 ) of the leaf spring  40  to cause the clamping ring  30  not to rotate any more in the embodiment described above, the present invention is not limited to this. For example, as illustrated in  FIG. 8 , the rotation regulating projection  34  may be provided on the inner peripheral surface of the clamping ring  30  and a depression  26  (for example, a groove) in which the projection  34  is positioned is provided in the ring body  20  to regulate the rotation of the clamping ring  30  by using the relationship of the projection  34  and the depression  26 . Alternatively, on the contrary, a projection (equivalent to the rotation regulating projection  34 ) may be provided on the periphery of the ring body  20  and a depression (equivalent to the depression  26 ) in which the projection is positioned is provided in the clamping ring  30  to regulate the rotation of the clamping ring  30  by using the relationship of the projection and the depression. 
   Alternatively, as illustrated in  FIG. 9 , depressions  27  and  28  may be provided in the ring body  20  at predetermined spaced intervals and a ball BO capable of entering depressions  27  and  28  and a spring B urging the ball BO are provided on the clamping ring  30  to regulate the rotation of the clamping ring  30 . This allows the ball BO to enter the depression  27  when the clamping ring  30  is rotated counterclockwise, regulating the rotation in the direction, and the ball BO to enter the depression  28  when the clamping ring  30  is rotated clockwise, regulating the rotation in the direction. Incidentally, slopes  27   a  and  28   a  are provided on the inner walls of the depressions  27  and  28  to make the ball BO easy to pull out of the depressions  27  and  28 . That is to say, the clamping ring  30  can be rotated between the depressions  27  and  28  with a weaker force. 
   The present embodiments are in all respects merely illustrative and not to be construed as restrictive by the above description. The present invention can be implemented in other various forms without departing from its spirit and principal features.