Abstract:
A lens barrel comprising bayonet type mount projections to detachably attach to a lens-fitting unit of a camera body having a photographic region, wherein mount projections are formed to avoid cross-section of light path area where object light is introduced in the camera body.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a lens barrel, a photographic device and production methods of the lens barrel and the photographic device. 
     2. Description of the Related Art 
     In the Japanese Unexamined Patent Publication (A) No. 2000-121904, a lens barrel is proposed to enable to change a diaphragm to cut off harmful rays in accordance with the size of the image circle. However, a prior lens barrel cannot reduce effects of catoptric light due to bayonet mounts. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide a lens barrel and a camera system enabling to reduce effects of catoptric light. 
     A lens barrel according to a first aspect of the present invention comprises 
     a barrel holding an optical system, and 
     a barrel-side mount fitting said barrel on a photographic device having an imaging unit, wherein 
     said imaging unit takes an image formed on a rectangular imaging plane by said optical system, and said barrel-side mount is placed in the position to avoid corners of said rectangular imaging plane. 
     A lens barrel according to a second aspect of the present invention comprises 
     a barrel holding an optical system, 
     a barrel-side mount to fit said barrel to a photographic device, and 
     two or more barrel-side electric contact groups, wherein 
     said photographic device comprises an imaging unit to take an image, number of said barrel-side mounts are present, and each of said barrel-side electric contact groups includes two or more electric contact points and is placed with a space between each other barrel-side electric contact groups. 
     A lens barrel according to a third aspect of the present invention comprises 
     a barrel holding an optical system, 
     a barrel-side mount to fit said barrel to a photographic device, and 
     two or more barrel-side electric contact points, wherein said photographic device comprises an imaging unit to take an image, and said barrel-side mount is placed between said barrel-side electric contact points. 
     A lens barrel according to a forth aspect of the present invention comprises 
     a barrel-side fitting unit placed detachably-attached to a body-side fitting unit of a camera body having a photographic region, and
         a barrel-side mount projection, which is formed at more than one point along the circumferential direction of said barrel-side fitting unit, set in opening site of said body-side fitting unit and engaged with a body-side mount projection formed at more than one point along the circumferential direction of said body-side fitting unit to prevent from releasing, wherein       

     at least said barrel-side mount projection is formed on said barrel-side fitting unit to avoid cross-section of light path area where object light is introduced in said camera body. 
     A lens barrel according to a fifth aspect of the present invention comprises 
     a bayonet unit arranged to a camera body having a photographic region to retain, wherein 
     said bayonet unit is arranged to avoid light flux entering in said photographic region among light flux going to the side of said photographic region. 
     A photographic device according to a first aspect of the present invention comprises 
     an imaging unit to take an image formed on a rectangular imaging plane by an optical system, and 
     a photographic device-side mount to fit a lens barrel to said photographic device, wherein 
     said lens barrel has said optical system, and said photographic device-side mount is placed to avoid corners of said rectangular imaging plane. 
     A photographic device according to a second aspect of the present invention comprises 
     an imaging unit to take an image by an optical system, 
     a photographic device-side mount to fit a lens barrel to said photographic device, and 
     two or more photographic device-side electric contact groups, wherein 
     said lens barrel has an optical system to form an image on said imaging plane, 
     each of said electric contact groups has two or more contact points, and is placed with a space between each other photographic device-side electric contact groups. 
     A photographic device according to a third aspect of the present invention comprises 
     an imaging unit to take an image by an optical system, 
     a photographic device-side mount to fit a lens barrel to the photographic device, and 
     two or more photographic device-side electric contact points, wherein 
     said lens barrel has said optical system to form an image on said imaging plane, and 
     said photographic device-side mount is placed between said photographic device-side electric contact points. 
     A production method of the lens barrel according to a first aspect of the present invention comprises the steps of: 
     providing a barrel holding an optical system, and 
     providing a barrel-side mount that fits a photographic device to said barrel, wherein 
     said photographic device comprises an imaging unit, 
     said imaging unit comprises a rectangular imaging plane, 
     said imaging unit takes an image formed on said rectangular imaging plane by said optical system, and 
     said barrel-side mount is placed to avoid corners of said rectangular imaging plane. 
     A production method of the lens barrel according to a second aspect of the present invention comprises the steps of: 
     providing a barrel holding an optical system, 
     providing multiple barrel-side mounts on said barrel to fit a photographic device having an imaging unit to take an image formed by said optical system, and 
     providing two or more barrel-side electric contact groups, each of which is placed with a space between each other and has two or more barrel-side electric contact points. 
     A production method of the lens barrel according to a third aspect of the present invention comprises the steps of: 
     providing a barrel holding an optical system, 
     providing a barrel-side mount on said barrel to fit a photographic device having an imaging unit to take an image formed by said optical system, and 
     providing two or more barrel-side electric contact points, said barrel-side mount being placed between said barrel-side electric contact points. 
     A production method of the photographic device according to the first aspect of the present invention comprises the steps of: 
     providing an imaging unit having a rectangular imaging plane to take an image formed on said rectangular imaging plane by an optical system, and 
     providing a photographic device-side mount to fit a lens barrel to the position to avoid corners of said rectangular imaging plane. 
     A production method of the photographic device according to the second aspect of the present invention comprises the steps of: 
     providing an imaging unit to take an image formed by an optical system, 
     providing multiple photographic device-side mounts to fit a lens barrel, and 
     providing two or more photographic device-side electric contact groups, each of which is placed with a space between each other and has two or more electric contact points. 
     A production method of the photographic device according to the third aspect of the present invention comprises the steps of: 
     providing an imaging unit to take an image formed by an optical system, 
     providing a photographic device-side mount to fit a lens barrel, and 
     providing two or more photographic device-side electric contact points, said photographic device-side mount being placed between said photographic device-side electric contact points. 
     A camera body according to the present invention comprises 
     a photographic region, 
     a mirror box to introduce subject light through light path area having predetermined cross-section to said photographic region, and 
     a body-side fitting unit to detachably attached to a barrel-side fitting unit of a lens barrel, wherein 
     a body-side mount projection to engage with said barrel-side mount projection formed at least on a part of the circumferential direction of opening site where a mount projection of said lens barrel is introduced in said body-side fitting unit, and 
     said body-side mount projection is formed to avoid the cross-section of said light path area. 
     A camera system according to the present invention comprises the above lens barrel. 
     The present invention can provide a lens barrel enabling to reduce effects of catoptric light and a camera system including said lens barrel. In the present invention, an object to reduce effects of catoptric light is achieved by changing the arranged position or the size of bayonet mount projections. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Below, the present invention will be explained in detail based on the embodiments illustrated in the figures, wherein 
         FIG. 1  is a perspective view of a lens barrel of an embodiment of the present invention. 
         FIG. 2  is a perspective view of a camera body of an embodiment of the present invention. 
         FIG. 3  is a cross-sectional view of the principal parts along an optical axis showing the inside of the camera body in  FIG. 2  where the lens barrel in  FIG. 1  is fitted, and a cross-sectional view of line III shown in  FIG. 4A . 
         FIG. 4A  is a cross-sectional view of the principal parts along line IVA-IVA in  FIG. 3 . 
         FIG. 4B  is a cross-sectional view of the principal parts along line IVB-IVB in  FIG. 4A . 
         FIG. 4C  is a view showing a frame format of a lens barrel and an imaging device, and an arranged position of mount projections. 
         FIG. 5  is a cross-sectional view of the principal parts along an optical axis showing the inside of the camera body where a lens barrel according to a comparative example of the present invention is fitted, and a cross-sectional view of line V in  FIG. 6 . 
         FIG. 6  is a cross-sectional view of the principal parts along line VI-VI in  FIG. 5 . 
         FIG. 7-FIG .  10  are cross-sectional views of the principal parts corresponding to  FIG. 4A  showing the inside of the camera body where each lens barrel according to other embodiments of the present invention is fitted. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     First Embodiment 
     As shown in  FIG. 1  and  FIG. 2 , a lens barrel-type imaging equipment represented by single-lens reflex camera typically includes a lens barrel  10  and a camera body  30 . A lens barrel-side fitting part  11  held on the back of the lens barrel  10  is detachably attached to a body-side fitting part  60  held on the front of the camera body  30 . 
     To the inside of a barrel body of a lens barrel  10  shown in  FIG. 1 , multiple optical lens groups (not shown in the figure) are attached movably in the direction of an optical axis. As shown in  FIG. 3 , a camera body  30  holds a low-pass filter  31  and an imaging device  32 . The imaging device  32  includes magnifying-type solid-state image sensing devices such as CMOS other than CCD. 
     A reason to provide a low-pass filter  31  is following. In the imaging device  32  of the camera body  30 , a phenomenon called a false color or a color moire can occur resulting in a different coloring from an actual one when a light with high spatial frequency enters in a single pixel of the imaging device  32 . This phenomenon can be reduced by setting the low-pass filter  31  at an object side of the imaging device  32 . 
     As shown in  FIG. 3 , to the inside of the camera body  30 , a mirror box  40  is attached at a predetermined position relative to body frames  30   a  and  30   b  of the body  30 . The imaging device  32  and the low-pass filter  31  are attached to the body frame  30   b  at a predetermined position. Note that a body frame  30   c  is attached to the back of the imaging device  32 . 
     A mirror not shown in figures is placed in the mirror box  40 , which leads an object light entering parallel to an optical axis in the direction of a finder when not taking pictures; and which leads an object light in the direction of the imaging device  32  by moving the mirror when taking pictures. 
     As shown in  FIG. 4A , the imaging device  31  is rectangular in shape when viewing vertically from an optical axis L 1 , which is smaller than a rectangular cross-section of an inner opening site  40   a  of the mirror box  40 . A cross section of an inner opening site of a body frame  30   b  shown in  FIG. 3  is rectangular as well as that of the inner opening site  40   a  of the mirror box  40 . On the other hand, a cross-section of an inner opening site of a body frame  30   a  positioned at the object side in the direction of the optical axis L 1  of the mirror box  40  is circular. To the front of the body frame  30   a , a ring-shaped body-side fitting part  60  is attached. 
     As shown in  FIG. 1  and  FIG. 4   b , the barrel-side fitting part  11  held on the back of the lens barrel  10  is ring-shaped in the whole to accommodate the shape of the lens barrel  10 . On the barrel-side fitting part  11 , a barrel-side fitting plane  14  is formed substantially vertical to an optical axis L 1  of an optical lens group. The barrel-side fitting plane  14  can be attached tightly to a body-side fitting plane  64  formed on a body-side fitting part  60  of a camera body  30 . The body-side fitting plane  64  is also substantially vertical to the optical axis L 1  of the optical lens group. 
     Both of the barrel-side fitting part  11  and the body-side fitting part  60  are made of metal, and can be detachably attached in the so-called style of a bayonet mount. That is, as shown in  FIG. 4A , three barrel-side mount projections  12  are formed at unequal intervals in the circumferential direction on the imaging surface side in the direction of the optical axis in the barrel-side fitting part  11 . 
     As shown in  FIG. 4B , barrel-side mount projections  12  are extended out radially from a cylindrical inner circumference face  15  of the barrel-side fitting part  11 . Three barrel-side mount projections  12  arranged along the circumference as shown in  FIG. 4A  are connected in the circumferential direction by a cylindrical stiffened member  16 . The radial thickness of the cylindrical stiffened member  16  is approximately a half or smaller of the radial width of the mount projections  12 . 
     As shown in  FIG. 2  and  FIG. 4B , body-side mount projections  62  are formed on the inner circumference face of the body-side fitting part  60  at the position corresponding to the barrel-side mount projections  12  at unequal intervals in the circumferential direction. The inner diameter of the body-side mount projection  62  is equal to or slightly larger than the outer diameter of the cylindrical stiffened member  16 . The outer diameter of the barrel-side mount projection  12  is slightly smaller than the inner diameter of the body-side fitting part  60  without body-side mount projections  62 . 
     The lens barrel  10  in  FIG. 1  is fitted to the camera body  30  in  FIG. 2  as follows: the mount projections  12  in the barrel-side fitting part  11  shown in  FIG. 1  are pressed into the inside of the body-side fitting part  60  at the position in the circumferential direction where body-side mount projections  62  shown  FIG. 2  are not formed. 
     After that, the lens barrel  10  is rotated around the optical axis L 1  to put the mount projections  12  of the barrel-side fitting part  11  in the imaging surface side of the body-side mount projections  62  of the body-side fitting part  60  where the lens barrel  10  is fitted to the camera body  30  in the bayonet-type. 
     As shown in  FIG. 4A  and  FIG. 4B , a circular-shaped electric contact holding member  70  is fixed on the imaging surface sides in the direction of the optical axis of the cylindrical stiffened member  16  of the barrel-side fitting part  11  and the mount projections  12 . The electric contact holding member  70  is comprised of an insulating member such as plastic, and two or more barrel-side electric contact points  72  may be placed on the outer circumferential face of the holding member  70  for example. These barrel-side electric contact points  72  are detachably connected by rotation to each body-side electric contact point  74  placed on the inner circumferential face of a body frame  30   a.    
     In the present embodiment, the electric contact holding member  70  is fixed at the barrel-side fitting part  11  as shown in  FIG. 4  so that the most of the holding member  70  is above the upper long side of an inner opening site  40   a  with a rectangular cross-section in the mirror box  40 . When fixing the electric contact holding member  70  at the barrel-side fitting part  11 , at least barrel-side electric contact points  72  has to be placed above the upper long side of the inner opening site  40   a  with a rectangular cross-section. 
     Further, as shown in  FIG. 4A , three barrel-side mount projections  12  are placed at unequal intervals in the circumferential direction so as to satisfy the following relationship: one of three barrel-side mount projections  12  is above (outside) the upper long side of the inner opening site  40   a  with a rectangular cross-section, another mount projection  12  is outside the right short side of the inner opening site  40   a , and the last mount projection  12  is below (outside) the lower long side of the inner opening site  40   a . It means that the mount projections  12  placed on the lens barrel  10  are not exposed at four corners  11   a ,  11   b ,  11   c  and  11   d  of the opening site  40   a  where only the cylindrical stiffened member  16  is exposed. 
     Note that the arranging position in the circumferential direction of the body-side mount projection  62 , which forms a bayonet structure in pairs with the barrel-side mount projection  12 , is same as that of the barrel-side mount projection  12 . 
     As shown in  FIG. 5  and  FIG. 6 , in a lens barrel  20  according to a comparative example of the invention, three barrel-side mount projections  22  are placed at equal intervals on the barrel-side fitting part  21  regardless of the shape of the cross-section of the inner opening site  40   a  in the mirror box  40 . Therefore, as shown in  FIG. 6 , a part of the mount projection  22  placed on the lens barrel  20  is exposed at four corners  21   a ,  21   b ,  21   c  and  21   d  of the opening site  40   a  when viewing the direction of the lens barrel  20  from a low-pass filter  31 . The mount projections  22  are exposed at two of the four corners,  21   a  and  21   b , and the exposed area is large. 
     The light  50  passing through the inside of the lens barrel  20  can pass through the low-pass filter  31  to enter an imaging device  32 , or can be reflected on the face of the low-pass filter  31  instead of passing through it. 
     Usually, this catoptric light hits the inner surface of the camera body  30  or the lens barrel  20 , diffuse to fade, or be absorbed, but in rare cases, it can enter the imaging device  32  after reflecting again on the end face of the bayonet-type mount projection  22  placed on the lens barrel  20 . This second catoptric light can hit at the inner surface of the camera body  30  if reflecting regularly on the end face of the bayonet-type mount projection  22 , but actually, it rarely reflects regularly since there is microasperity on the end face of the mount projection  22  due to machine process. 
     When the second catoptric light  52   b  and  52   c  enter the imaging device  32 , it is possible to become a ghost or a flare to deteriorate picture quality. Note that the light ray  50  can reflect on the imaging device  32 , and also in the case of a silver salt film camera, on the surface of the film. In the end face in the optical axis direction of the barrel-side fitting part  21 , the projection  22  has a broader width in the radial direction, where more catoptric light may hit to easily increase ghosts and flare. 
     Therefore, in the present embodiment, the above-described configurations of the bayonet-type mount projections  12  and  62  solve the above problems. Hereinbelow, the arranged position of the mount projections  12  will be explained. An explanation on the mount projections  62  will be skipped since they have the same arranged position as the mount projections  12 . 
     As shown in  FIG. 4C , the mount projections  12  are arranged to avoid the vicinity of four corners  11   a ,  11   b ,  11   c  and  11   d  of a light flux L with a rectangular cross-section that goes from the lens barrel  10  to enter the imaging device  32 . Actually as shown in  FIG. 4A , the mount projections  12  are arranged not to overlap four corners of the opening site  40   a . Therefore, the mount projections  12  are not on the diagonal line of the low-pass filter  31 , and not exposed on the inside of the opening site  40   a.    
     When viewing the lens barrel  10  from the low-pass filter  31 , four portions of the barrel-side fitting part  11  placed on the lens barrel  10  are exposed at four corners  11   a ,  11   b ,  11   c , and  11   d  of the opening site  40   a  as shown in  FIG. 4A . However, the exposed area is small and the effect of the catoptric light is low since the exposed portions are not the mount projections  12 . 
     As the mount projections  12  are not exposed on the inside of the opening site  40   a , the catoptric light  51  from the low-pass filter  31  does not enter the mount projection  12  as shown in  FIG. 3 . Therefore, the effect of catoptric light to reflect on the mount projection  12  can be reduced to prevent flares and ghosts and to minimize image degradation. 
     Further, when the lens barrel  10  is a bright optical lens barrel with F value of 2.8 or less, a telephoto lens barrel, or a large diameter lens barrel for instance, light passes right next to the barrel-side fitting part  11  causing that the catoptric light easily affects, and therefore, it is meaningful to prevent the catoptric light from entering the mount projection  12 . Also, the effects of the present embodiment are more significant when the distance between the imaging device and the mount projections are closer, e.g. when the imaging device is large (e.g. 24 mm×36 mm or larger), or when the diameters of the barrel-side fitting part  11  and the body-side fitting part  60  are small. 
     Also, a coating material is applied on components such as a lens holding rim inside the lens barrel  20  (See  FIG. 5  and  FIG. 6 ). However, the coating may peel off to adhere to the lens or the low-pass filter  31  if applying it on the exterior of the barrel-side fitting part  21  that is rubbed when fitting the lens barrel  20  and the camera body  30 . It is also unfavorable to apply a coating only on the mount projection  22  to prevent reflection, which is a protruding portion and may be easily rubbed and pealed off while removing the lens barrel  20  from the camera body. However, in this embodiment, it is possible to obtain good characteristics as the configuration of the mount projections  12  and  62  prevents reflection instead of applying any coating. 
     Second Embodiment 
     As shown in  FIG. 7 , in a lens barrel  10 - 2  according to the second embodiment in the invention, the bayonet-type mount projection  12  has the same arranged position as the mount projection  22  according to the comparative example shown in  FIG. 6 . However, a notch  13  is formed on the mount projection  12   a  so as to avoid the inner opening site  40   a  of the mirror box  40  in the lens barrel  10 - 2  in the present embodiment. 
     The second embodiment has advantages that it is easy to design and unnecessary to change in basic configuration of a bayonet-type mount projection  62  of the camera body  30  since the mount projections  12  can be arranged at equal intervals in the circumferential direction. Other configuration and effects in the present embodiment is same as in the above-described first embodiment. 
     Third Embodiment 
     As shown in  FIG. 8 , in a lens barrel  10 - 3  according to the third embodiment, each of two mount projections  12   b  are arranged on outside of the long sides in a cross-section of the inner opening site  40   a  of the mirror box  40 . This configuration results in no exposure of the mount projection  12   b  on the inside of the opening site  40   a . Other configuration and effects in the present embodiment is same as in the above-described first embodiment. 
     Forth Embodiment 
     As shown in  FIG. 9 , in a lens barrel  10 - 4  according to the forth embodiment, the diameters of the inner circumferences of the barrel-side mount projection  12   c  and the cylindrical stiffened member  16  are designed equal to or longer than the length of the diagonal line of the inner opening site  40   a  of the mirror box  40 . Also, both of a barrel-side mount projection  12   c  and a cylindrical stiffened member  16  are designed not to be exposed on the inside of the inner opening site  40   a . Other configuration and effects in the present is same as in the above-described first embodiment. 
     Fifth Embodiment 
     As shown in  FIG. 10 , in a lens barrel  10 - 5  according to the fifth embodiment, a barrel-side mount projection  12  is arranged similar to that in the first embodiment. Each of two electric contact holding members  70   a  and  70   b  is arranged on the outside of the long sides of the cross-section of the inner opening site  40   a  in the mirror box  40 . The outer circumferences of electric contact holding members  70   a  and  70   b  have barrel-side electric contact groups  72   a  and  72   b  respectively. 
     In the present embodiment, the number of the contact points at each of the electric contact groups  72   a  and  72   b  placed on the each of the electric contact holding members  70   a  and  70   b  can be reduced since the electric contact groups  72   a  and  72   b  are divided into two to exchange signals between the-lens barrel  10 - 5  and the camera body. As a result, the length in the circumferential direction can be reduced in each electric contact group  72   a  and  72   b , and they can be arranged in a smaller space. Further, it results in increasing the flexibility in design regarding the space between the electric contact groups  72   a  and  72   b  and becoming easier to arrange each of the electric contact holding members  70   a  and  70   b  to avoid the inner opening site  40   a  of the mirror box  40 . 
     Further, the arrangement to separate the electric contact groups  72   a  and  72   b  each other reduces interference between contacts, resulting in improving S/N ratio. For example, an electromagnetic ray may easily occur at a contact point for electric power supply where relatively large electric current passes. It can reduce an electric signal noise at a contact point for signal to separate a contact point for electric power supply from that for signal. Other configuration and effects in the present embodiment is same as in the above-described first embodiment. Note that the electric contact holding member where electric contact groups are placed is divided into four so that each can be arranged at the outside of four lines of the inner opening part  40   a  of the mirror box  40  respectively. 
     Other Embodiments 
     The following conversion is possible in each embodiment. 
     (1) As shown in  FIG. 4C , the mount projections  12  are described in the example to arrange all of them to avoid four corners  11   a  to  11   d  of the light flux L, but it is acceptable to arrange the mount projections  12  to avoid some of four corners  11   a  to  11   d . In this case, effects of catoptric light can be reduced as well. 
     (2) In the embodiment shown in  FIG. 8 , the mount projections  12  are arranged above and below the opening site  40   a , but it is acceptable to arrange them on the left and right of the opening site  40   a . Also, four mount projections  12  can be arranged on the left, right, top and bottom of the opening site  40   a . It is also acceptable to provide convexo-concave on the surface of the mount projections  12  for further prevention of reflection on the mount projections  12 . 
     (3) Each embodiment described above is an example to apply the configuration of the present invention in a lens barrel, but it is also possible to apply the invention in a camera system holding such a lens barrel, a video camera, and a TV camera, and other imaging equipments. 
     Note that the above-described embodiments can be used in combination, but detailed explanation is omitted here. Also, the invention is not limited to the embodiments explained above.