Abstract:
In an optical apparatus having a mount adapted to be rotated to be attached to and detached from a mount of another apparatus, the mount of the optical apparatus is molded by plastic material, and concave and convex portions are provided on an abutment surface of the mount of the optical apparatus to reduce the sliding area, thereby making the scratches caused by the sliding inconspicuous.

Description:
This is a continuation application under 37 CFR 1.62 of prior application Ser. No. 07/619,769, filed Nov. 29, 1990, now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to an optical apparatus such as a camera, lens, intermediate tube, etc., having mounts for coupling. 
     2. Description of the Related Art: 
     The conventional mounts for the camera and the lens have been made either by machining metal to the shape, or after having sintered stainless steel material, by applying treatments in portions. 
     For this reason, the conventional mounts for the camera and the lens require a long manufacturing process, thus being parts of very high price. 
     FIGS.  4 ( a ) and  4 ( b ) show an example of metallic mount for camera, with FIG.  4 ( a ) being a front view and FIG.  4 ( b ) being a back view. This mount is of the bayonet type. A plurality of pawl portions  4   a  are formed on the inner periphery of the mount  4 . Protuberances  4   b  are provided on the back side of these pawl portions  4   a.    
     Also, a plurality of screw-threaded holes  4   d  at which the mount  4  is to be fixedly secured to the camera body (not shown) are formed in the circumferential direction, and the abutment surface  4   e  at which the mount  4  abuts on a mount  3  of the photographic lens shown in FIG. 3 is formed to an even plane. The mount  4  for camera is provided with a mount spring  2  shown in FIG.  2 . When the photographic lens is attached to the camera body, the mount spring  2  abuts on portions of the lens mount  3  and functions to press the photographic lens against the camera body, as the spring portions  2   a  work as springs. The lens mount  3  has pawl portions  3   a  which are arranged to abut on the spring portions  2   a  of the mount spring  2  to receive the forces therefrom, a so-called abutment surface  3   b  which is arranged to abut on the abutment surface  4   e  of the camera mount to determine the axial position of the photographic lens, and a concave portion  3   c  formed therein. Incidentally, among the photographic lenses, there are some which do not have the concave portion  3   c.    
     The state in which the photographic lens has been attached to the mount  4  for camera made of metal constructed in such a way is shown in FIG.  5 . Coupling of the lens mount  3  of the photographic lens with the mount  4  for camera is to move the lens mount  3  from the left of FIG. 5 toward the mount  4  for camera to be fitted therein, adjust the pawls  3   a  of the lens mount  3  to the pawlless portions  4   g  of the mount  4 , move the lens mount  3  until the abutment surface  3   b  of the lens mount  3  abuts on the abutment surface  4   e  of the camera mount  4 , and rotate the lens mount  3  until it is stopped by a stopper member (not shown). At this time, the pawl portions  3   a  of the lens mount  3  are urged by the spring portions  2   a  of the mount spring  2 , and receive the bias force of direction to the left in FIG.  5 . The abutment surface  4   e  of the mount  4  for the camera abuts on the abutment surface  3   b  of the lens mount  3 , and the axial position of the photographic lens relative to the camera body is determined. 
     By the way, since the conventional mount for camera is made of metal, its manufacturing process is long, resulting in very expensive parts. 
     So, it may also be considered to mold the mount by using plastic material. However, the member molded of plastic material is weak in its surface hardness as compared with metallic material. When the photographic lens is attached to the camera, that surface which abuts on the metallic mount  3  of the lens side, particularly the force receiving surface, is apt to get scratches, which may extremely degrade the camera product. 
     That is, during the photographic lens attaching work, the lens mount  3  rotates, while receiving the force of the mount springs  2 . Because a large frictional force exists between the mount  4  for camera and the lens mount  3  made of metal, the mount  4  for camera, too, must be made of a material having an equal or higher surface hardness than that of the lens mount  3 . Otherwise, the mount  4  for camera would take large scratches. In the case of the lens mount not having the concave portion  3   c , the scratches occur at random. In the case of the lens mount having the concave portion  3   c , they occur in ring shapes. Thus, the state of scratches becomes conspicuous as differing from the non-contact portions. In either case, the camera product would be extremely degraded. 
     SUMMARY OF THE INVENTION 
     One aspect of this invention is to mold the mount for coupling with another apparatus from plastic material, and make the abutment surface which, when coupling, comes into sliding contact with the other apparatus, to be formed into convex and concave shape, thereby making the scratches inconspicuous. 
    
    
     BRIEF DESCRIPTION OF THE INVENTION 
     FIGS.  1 ( a ) and  1 ( b ) are respectively a front view and a back view of a first embodiment of the mount for camera. 
     FIG. 2 is a front view of the mount spring. 
     FIG. 3 is a front view of the lens mount of the photographic lens. 
     FIGS.  4 ( a ) and  4 ( b ) are respectively a front view and a back view of the conventional metallic mount for camera. 
     FIG. 5 is a sectional view illustrating the state in which the photographic lens is attached to the mount for camera shown in FIGS.  4 ( a ) and  4 ( b ). 
     FIG. 6 is a sectional view of the state in which the photographic lens is attached to the camera having the mount for camera shown in FIGS.  1 ( a ) and  1 ( b ). 
     FIGS.  7 ( a ) and  7 ( b ) are respectively a front view and a back view of a second embodiment of the mount for camera. 
     FIG. 8 is a sectional view of the state in which the photographic lens is coupled with the camera having the mount for camera of FIGS.  7 ( a ) and  7 ( b ). 
     FIGS.  9 ( a ) and  9 ( b ) are respectively a front view and a back view of a third embodiment of the mount for camera. 
     FIG. 10 is a sectional view of the state in which the photographic lens is coupled with the camera having the mount for camera of FIGS.  9 ( a ) and  9 ( b ). 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIGS.  1 ( a ) and  1 ( b ) show a first embodiment of the mount for camera according to the invention, with FIG.  1 ( a ) being a front view and FIG.  1 ( b ) being a back view. FIG. 6 is a sectional view illustrating the state in which the lens mount is attached to the mount for camera of the present embodiment. The mount for camera of the present embodiment is, similar to the conventional example, provided with the mount spring  2  shown in FIG.  2 . 
     The mount for camera of the present embodiment is of the bayonet type molded by plastic material. Similar to the conventional example, a plurality of pawl portions  1   a  and protuberances  1   b  extending from these pawl portions  1   a  toward the back side are molded in unison on the inner diameter side of the mount  1 . Also, in the mount  1 , there is formed a hole  1   c  into which a pin for lens lock is fitted and holes  1   d  for mount fastener screws. 
     Meanwhile, the mount surface  1   e  of the mount  1  for camera, while, in the conventional metallic mount for camera, being the even flat plane, is, in the present embodiment, made concave or provided with a circumferential groove  1   f  of cross-sectional concave shape. 
     That is, as shown in FIG. 6, when the photographic lens is attached to the mount  1  for camera according to the present embodiment, since the circumferential groove  1   f  is formed in the mount surface  1   e  of the mount  1  for camera to a concave shape in cross-section, the place at which the mount surface  1   e  abuts on the mount surface  3   b  of the lens mount  3  is the outer peripheral portion and inner peripheral portion of the open surface of the circumferential groove  1   f , i.e., only the portions of narrow width. Therefore, even if they are scratched, far smaller scratches are left than when the mount surface  1   e  is made to be the even flat plane. Accordingly, when the photographic lens is detached from the camera body, the scratches are inconspicuous and do not degrade the camera product. Incidentally, in FIG. 6, reference numeral  10  denotes the camera,  11  denotes a pentagonal prism,  12  denotes a mirror,  20  denotes the photographic lens, and  21  denotes a lens optical system. 
     Next, referring to FIGS.  7 ( a ) and  7 ( b ) and FIG. 8, a second embodiment is described. Incidentally, the parts similar to those of the first embodiment are not explained and are denoted by the same reference numerals. 
     A great number of minute protuberances  30   e  of semi-spheric shape are formed in the mount  1  for camera. Therefore, when the mount  1  for camera comes into sliding contact with the mount surface  3   b  of the lens mount  3 , the frictional force is applied only to top portions of the minute protuberances  30   e.    
     That is, the rub scratches which, when in the prior art, would be dispersed over the entire area of the mount surface  4   e , appear at only the tips of the minute protuberances  30   e . If microscopically observed, the scratches are present. However, to the human&#39;s eye, the scratches are not appreciable. So, they attract no attention at all. 
     Next, referring to FIGS.  9 ( a ) and  9 ( b ) and FIG. 10, a third embodiment is explained. Incidentally, the parts similar to those of the first embodiment are not explained and are denoted by the same reference numerals. 
     The mount  1  for camera has a plurality of ring-shaped protuberances  40   e  concentric with the mount  1 . Therefore, when the mount  1  for camera comes into sliding contact with the mount surface  3   b  of the lens mount  3 , the frictional force is applied only to summit portions of the ring-shaped protuberances  40   e.    
     That is, even if the mount  1  for camera is molded by plastic material, only the tips of the ring-shaped protuberances  40   e  abut on the mount surface  3   b  of the lens mount  3 . Therefore, the rub scratches which would be formed on the mount surface  4   e  when it is the even flat plane, if microscopically observed, are present on the tips of the ring-shaped protuberances  40   e  not appreciable to the human&#39;s eye. So they attract no attention at all. 
     It should be noted that though in the above described embodiments, the plastic mount has been used for the mount for camera, the mounts of the photographic lens, intermediate tube, extender, etc. may be made to be plastic mounts according to the present invention. Even in these cases, there are similar advantages.