Abstract:
A camera body includes a body mount adopted to detachably attach an interchangeable lens thereto, a body index mark which indicates a position of proper alignment of the interchangeable lens with respect to the body mount in order to attach the interchangeable lens to the camera body, and an illuminating device which illuminates the body index mark.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a camera body having a body mount to which an interchangeable lens is detachably attached. 
     2. Description of the Related Art 
     A conventional camera body (e.g., an SLR camera body) utilizing an interchangeable lens is generally provided on the front face with a body mount (body mount ring) to which a lens mount (lens mount ring) fixed at the rear end of an interchangeable lens is detachably attached. The body mount and the lens mount together constitute a lens mount device (or simply called “lens mount”) for coupling the lens to the camera body. Different types of lens mount devices are known. The most popular ones are the bayonet mount and the screw-type mount. 
     In a bayonet mount, when the lens is coupled to the camera body, firstly a body index mark on, or in the vicinity of, the body mount of the camera body and the corresponding index mark (lens index mark) on, or in the vicinity of, the lens mount of the lens are aligned, and then the lens mount is mounted onto the body mount. Subsequently, the lens is fully turned relative to the camera body in a predetermined rotational direction. 
     It is easy to attach the lens to the camera body while seeing the positions of the index marks under good light. However, in dim light or in the dark it is difficult to attach the lens to the camera body because the index marks cannot be clearly seen. Accordingly, formerly it is often necessary to carry a flashlight or an external light (which can be connected to a hot shoe on the camera body) together with the camera in case that the lens needs to be attached to the camera body in dim light or in the dark. 
     SUMMARY OF THE INVENTION 
     The primary object of the present invention is to provide a camera body having a device which makes it easy to attach the lens to the camera body even in dim light or in the dark. 
     To achieve the object mentioned above, according to an aspect of the present invention, a camera body is provided which includes a body mount adapted to detachably attach an interchangeable lens thereto, a body index mark which indicates a position of proper alignment of the interchangeable lens with respect to the body mount in order to attach the interchangeable lens to the camera body, and an illuminating device which illuminates the body index mark. 
     The body index mark is brought into alignment with a lens index mark of the interchangeable lens when the interchangeable lens is attached to the camera body. 
     Preferably, the body index mark includes a transparent member having a transparent projection fitted into a through hole formed on the body mount. The illuminating device includes a light source for lighting the transparent member from the inside of the camera body. Preferably, the transparent member is colored. 
     Preferably, the camera body further includes a lock mechanism for locking the interchangeable lens on the body mount after the interchangeable lens is properly coupled to the camera body, a lens-lock-release button which unlocks the lock mechanism when depressed, a switch which is open or closed in accordance with the operation of the lens-lock-release button, and a controller which turns the illuminating device ON or OFF in accordance with a change in an open/closed state of the switch. 
     Preferably, the controller turns the illuminating device ON at the time the open/closed state of the switch changes in accordance with a depression of the lens-lock-release button. 
     Preferably, the controller subsequently turns the illuminating device OFF after a predetermined period of time elapses. 
     Preferably, the camera body further includes a detector for detecting whether or not the interchangeable lens is attached to the body mount, wherein the controller controls the illuminating device such that the illuminating device remains OFF in the case where the detector detects that the lens mount is attached to the body mount even if the lens-lock-release button is depressed. 
     In an embodiment, the light source includes an LED positioned immediately behind the transparent member. 
     In an embodiment the camera body further includes a switch which can be manually turned ON and OFF, wherein the illuminating device includes a light source which is turned ON and OFF when the switch is turned ON and OFF, respectively. 
     In an embodiment, the body mount includes a bayonet type mount. 
     According to another aspect of the present invention, a camera body includes a body mount adopted to detachably attach an interchangeable lens thereto, a body index mark which indicates a position of proper alignment of the body mount with respect to the lens mount of the interchangeable lens when the interchangeable lens is attached to the camera body; an illuminating device which illuminates the body index mark, a detector adopted to detect whether or not the interchangeable lens is attached to the body mount, and a controller which prevents the illuminating device from turning ON when the detector detects that the lens mount is attached to the body mount. 
     According to another aspect of the present invention, a camera body includes a body mount adapted to detachably attach an interchangeable lens thereto, a lens-lock-release button which is manually depressed when the interchangeable lens is attached to the body mount, and a light source which is turned ON when the lens-lock-release button is depressed to attach the interchangeable lens to the body mount; the light source illuminating the body mount. 
     Preferably, a body index mark is further provided which is brought into alignment with a lens index mark of the interchangeable lens when the interchangeable lens is attached to the camera body; wherein the light source is turned ON to emit light towards the body index mark when the lens-lock-release button is depressed. 
     Preferably, the body index mark is made of a material which allows light to pass therethrough, the light source emitting light outwardly from inside the camera body via the body index mark. 
     The present disclosure relates to subject matter contained in Japanese Patent Application No.11-103843 (filed on Apr. 12, 1999) which is expressly incorporated herein by reference in its entirety. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will be described below in detail with reference to the accompanying drawings in which: 
     FIG. 1 is a front elevational view of a camera body to which the present invention is applied; 
     FIG. 2 is a side elevational view, partly in cross section, of an interchangeable lens which is detachably attached to the camera body shown in FIG. 1, a body mount of the camera body shown in FIG. 1, and fundamental elements of the camera body in the vicinity of the body mount; 
     FIG. 3 is a side elevational view, partly in cross section, of the fundamental elements of the camera body shown in FIG. 2, showing a state before a lens-lock-release button of the camera body is depressed; 
     FIG. 4 is a side elevational view, partly in cross section, of the fundamental elements of the camera body shown in FIG. 2, showing a state where the lens-lock-release button of the camera body is depressed; 
     FIG. 5 is a schematic circuit diagram of a control circuit provided in the camera body shown in FIG. 1; and 
     FIG. 6 is a rear elevational view of an interchangeable lens barrel. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 shows an embodiment of a camera body  10  to which the present invention is applied, while FIG. 2 shows a lens (interchangeable lens)  30  which is detachably attached to the camera body  10 . 
     The camera body  10  utilizes an SLR camera system and is provided on the front face thereof with a ring-shaped body mount  11 . This body mount  11  is a bayonet mount type. The body mount  11  is provided along an inner periphery thereof with three engaging blades  11   a . When the lens  30  is coupled to the camera body  10 , the three blades  11   a  are respectively engaged with corresponding three engaging blades (not shown) formed on a lens mount  31  fixed to the rear end of the lens  30 . 
     The camera body  10  is provided on the front left side thereof (as viewed in FIG. 1) with a grip portion  12  having a release button  13  at the top thereof. The camera body  10  is provided at the top center thereof with a retractable built-in flash  14 . The camera body  10  is provided, on an upper face thereof on right and left sides (as viewed in FIG. 1) of the built-in flash  14 , with an exposure-compensation-value select dial  16  and a shutter-speed select dial  15 , respectively. In FIG. 1 the built-in flash  14  is fully retracted into the camera body  10 . 
     The body mount  11  is fixed to the camera body  10  by a plurality of set screws  17 . The camera body  10  is provided on the body mount  11  with a set of body contact pins (lens information contacts)  18  which are arranged along a circle about the axis of the body mount  11  at substantially regular intervals. Each body contact pin  18  slightly projects from the front face of the body mount  11  which comes into closely contact with the rear face of the lens mount  31  when the lens  30  is coupled to the camera body  10 . Each body contact pin  18  is connected to a microcomputer  60  provided in the camera body  10 . As shown in FIG. 5, the microcomputer  60  of the camera body  10  data-communicates with the lens  30  via the set of body contact pins  18  and respective lens contact pins  38  (the camera body  10 , body and lens contact pins  18  and  38  are omitted from FIG.  5 ). As shown in FIG. 6, the lens contact pins  38  are provided on the lens mount  31  of the lens  30 . Each body contact pin  18  comes into contact with each respective lens contact pin  38  disposed on the lens mount  31  when the lens  30  has been properly attached to the camera body  10  so that the engaging blades  31   c  of the lens mount  31  have been inserted into the spaces between the engaging blades  11   c , and closely rotated, behind the engaging blades  11   c  of the body mount  11  by a predetermined angle of rotation. 
     The camera body  10  is provided with a male coupler  19  which projects from the front face of the body mount  11  at a predetermined position thereon. The male coupler  19  is engaged with a corresponding female coupler (not shown) when the lens  30  has been properly attached to the camera body  10 . The male coupler  19  is driven to rotate about the axis thereof by an AF motor (not shown) provided in the camera body  10  to drive the AF lens group provided in the lens  30  via the female coupler. The male coupler  19  and the female coupler together constitute a conventional AF coupler. 
     The camera body  10  is provided at the front thereof in the vicinity of the body mount  11  with a lens-lock-release button  20  which is manually depressed when the lens  30  is detached from the camera body  10 . 
     The body mount  11  is provided in the vicinity of the lens-lock-release button  20  with a first through hole  11   b . A lock pin (lock mechanism)  21  is fitted in the first through hole  11   b  from the rear side thereof (i.e., from within the camera body) to be movable forwardly and rearwardly. The lock pin  21  is interlocked with the lens-lock-release button  20  to move together with the lock release button  20  forwardly and rearwardly. In a free state, the tip of the lock pin  21  projects from the front face of the body mount  11  by a predetermined amount. In a state where the lens  30  is properly coupled to the camera body  10 , the tip of the lock pin  21  is engaged with a lock hole  31   a  formed on the lens mount  31  at a corresponding position thereon. The rear end (inner end) of the lock pin  21  is fixed to one end of a lock-pin mount member  22  which moves together with the lens-lock-release button  20  in the direction of an optical axis O of the lens  30 . Therefore, if the lens-lock-release button  20  is depressed, the lock pin  21  also moves rearwardly in the same direction to retreat in the camera body  10 . 
     The lock-pin mount member  22 , to which the lock pin  21  is fixed, is positioned in the camera body  10  and is guided in the direction of the optical axis O of the lens  30 . A shaft  20   a  which extends in the direction of movement of the lens-lock-release button  20  (the right/left direction as viewed in FIG. 2) in the camera body  10  is formed integral with the lens-lock-release button  20 . The tip of the shaft  20   a  normally comes into contact with an engaging portion  22   a  formed on the other end of the lock-pin mount member  22 . If the lens-lock-release button  20  is depressed, the shaft  20   a  moves together with the lens-lock-release button  20  to move the engaging portion  22   a  in the same direction (to the left as viewed in FIG.  2 ). Namely, if the lens-lock-release button  20  is depressed, the shaft  20   a  pushes the engaging portion  22   a  to thereby make the lock pin  21  retreat into the camera body  10 . 
     The lock-pin mount member  22  is provided with a shaft  26  which extends rearwardly from the engaging portion  22   a  in the direction of the optical axis O and coaxially to the shaft  20   a  of the lens-lock-release button  20 . The shaft  26  penetrates a fixed guide frame  23 , positioned in the camera body  10 , through a guide hole  23   a  formed on the fixed guide frame  23  so that the shaft  26  is guided in the direction of the optical axis O. 
     Accordingly, if the lens-lock-release button  20  is depressed, the shaft  26  also moves rearwardly in the direction of the optical axis O. A coil spring  24  is fitted on the shaft  26  to be positioned between the guide frame  23  and the engaging portion  22   a  of the lock-pin mount member  22  with the coil spring  24  being compressed therebetween. Therefore, the lock-pin mount member  22  and the lens-lock-release button  20 , which comes into contact with the lock-pin mount member  22 , are always biased forwardly (to the right as viewed in FIG. 2) in the direction of the optical axis O by the spring force of the coil spring  24 . 
     The camera body  10  is provided therein behind the guide frame  23  with a switch  25 . The switch  25  is provided with two spring leaves  25   a  and  25   b  which are apart from each other by a predetermined gap (distance) in a free state, with the free end of the spring leaf  25   b  facing the tip  26   a  of the shaft  26 . Each of the two spring leaves  25   a  and  25   b  is made of a resilient conductive material. The free end of the spring leaf  25   b  is pushed towards the spring leaf  25   a  to thereby come into contact with the spring leaf  25   b  if the lens-lock-release button  20  is depressed (see FIG.  4 ). Releasing the pushing force applied to the lens-lock-release button  20  causes the lens-lock-release button  20  to return to the initial position thereof by the spring force of the coil spring  24 . This further causes the shaft  26  to return to the initial position thereof so that the spring leaf  25   b  springs apart from the spring leaf  25   a  (see FIG.  3 ). 
     The body mount  11  is provided with a second through hole  11   c  at a predetermined position at which a body index mark (transparent projection)  50   a  which is aligned with a lens index mark  31   b  (see FIG. 6) formed on the lens mount  31  of the lens  30  when the lens  30  is coupled to the camera body  10  is to be formed. A window member (transparent member)  50  is fixed to the rear face of the body mount  11  so as to close the rear end of the second through hole  11   c . The window member  50  is formed integral with a transparent projection (body index mark)  50   a  which is snugly fitted into the second through hole  11   c . The window member  50  is made of red transparent plastic, so that the transparent projection which is fitted in the second through hole  11   c , functions as the body index mark  50   a , which is aligned with the lens index mark  31   b  formed on the lens mount  31  of the lens  30  when the lens  30  is coupled to the camera body  10 , since the red-colored transparent projection (body index mark)  50   a  can be seen as a red dot in the second through hole  11   c  from the outside the camera body  10 . The body index mark  50   a  and the lens index mark  31   b  indicate a position of proper alignment of the lens mount  31  with respect to the body mount  11  when attaching the lens  30  to the camera body  10 . 
     The camera body  10  is provided immediately behind the window member  50  with an LED (light source/illuminating device)  52  which is fixedly positioned in the camera body  10 . If the LED  52  lights up, the window member  50  is illuminated from the rear side thereof (i.e., illuminated outwardly from inside of the camera body  10 ) by the LED  52  so that red light is projected outwardly through the red-colored transparent projection (body index mark)  50   a . Accordingly, the LED  52  is provided as a light source for backlighting the transparent projection (body index mark)  50   a  from the inside of the camera body  10 . 
     The camera body  10  is provided therein with a microcomputer (controller)  60  in charge of the overall control of the camera body  10  (see FIG.  5 ). The switch  25 , the LED  52  and the set of body contact pins  18  are electrically connected to the microcomputer  60 . The microcomputer  60  is provided therein with an internal timer  61  for measuring the time from the commencement of lighting of the LED  52 . 
     The microcomputer  60  detects whether or not the lens  30  has been coupled to the camera body  10  in accordance with lens data sent from the lens  30  via the set of contacts  18 . The microcomputer  60  and the set of contacts  18  are fundamental elements of a detector for detecting whether or not the lens  30  has been coupled to the camera body  10 . 
     When the microcomputer  60  determines that the lens  30  has not been coupled to the camera body  10 , if the lens-lock-release button  20  is depressed to close the switch  25 , the microcomputer  60  starts supplying power to the LED  52  to turn the LED  52  on. Upon the commencement of power supply to the LED  52 , the microcomputer  60  starts the internal timer  61  to start measuring the time of lighting of the LED  52  and subsequently stops supplying power to the LED  52  to turn it OFF after a predetermined period of time (e.g., five seconds) elapses. 
     The microcomputer  60  does not supply power to the LED  52  even if the lens-lock-release button  20  is depressed to close the switch  25  in the case when it is determined by the microcomputer  60  that the lens  30  has been coupled to the camera body  10 . 
     The operation of the camera body  10  with respect to the attachment/detachment of the lens  30  will be hereinafter discussed. The operation of the camera body  10  when the lens  30  is attached to the camera body  10  will be discussed first. Firstly, the body index mark (transparent projection)  50   a  which is visible on the body mount  11  and the lens index mark  31   b  (see FIG. 6) on the lens mount  31  are aligned, and then the lens mount  31  is brought into contact with the body mount  11 . Due to the alignment of the body index mark  50   a  and the lens index mark  31   b , the engaging blades  31   c  of the lens mount  31  fit in between the engaging blades  11   a  of the body mount  11  so as not to collide with each other. Furthermore, when the lens mount  31  is brought into contact with the body mount  11 , the engaging blades  31   c  of the lens mount  31  are positioned behind the engaging blades  11   a  of the body mount  11  with respect to the optical axis of the lens  30 . Subsequently, the lens  30  is fully turned relative to the camera body  10  in a predetermined rotational direction (a direction that enables the coupling of the lens  30  to the camera body  10 ) by a predetermined angle of rotation. This causes each of the three engaging blades  11   a  of the body mount  11  to be engaged with the corresponding engaging blades  31   c  of the lens mount  31  wherein the engaging blades  31   c  are inserted behind the engaging blades  11   c  so that the lens mount  31  of the lens  30  can be supported by the body mount  11  of the camera body  10 . At the same time, the tip of the lock pin  21  is engaged with the lock hole  31   a  with a click. This completes the operation of attachment of the lens  30  to the camera body  10 . 
     As noted above, the body index mark (transparent projection)  50   a  on the body mount  11  is lit up to keep emitting red light for a predetermined period of time (e.g., five seconds) under the control of the microcomputer  60  if the lens-lock-release button  20  is depressed with no lens being mounted on the camera body  10 . Therefore, the index marks of the body mount  11  and the lens mount  31  can be easily aligned even in dim light or in the dark because the body index mark (red-colored transparent projection)  50   a  on the body mount  11  emits red light by simply depressing the lens-lock-release button  20 . Consequently, the lens  30  can be easily attached to the camera body  10  even in dim light or in the dark. 
     The operation of the camera body  10  when the lens  30  is detached from the camera body  10  will be hereafter discussed. Firstly the lens-lock-release button  20  is depressed to retreat the lock pin  21  from the lock hole  31   a , and then the lens  30  is turned relative to the camera body  10  in the reverse rotational direction (a direction of disconnecting the lens  30  from the camera body  10 ) opposite to the aforementioned predetermined rotational direction by a predetermined angle of rotation. This causes each of the three engaging blades  11   a  of the body mount  11  to be disengaged from the corresponding engaging blades of the lens mount  31 . This completes the operation of disconnection of the lens  30  from the camera body  10 . 
     When the lens  30  is disengaged (and subsequently removed) from the camera body  10 , the body index mark (transparent projection)  50   a  on the body mount  11  is not lit up via control of the microcomputer  60  even if the lens-lock-release button  20  is depressed. According to such control of the microcomputer  60 , the power consumption of the battery (not shown) accommodated in the camera body  10  as a power source thereof is reduced because the body index mark (transparent projection)  50   a  is not lit up when the lens  30  is disengaged from the camera body  10 . 
     As can be understood from the foregoing, according to the illustrated embodiment of the camera body  10  to which the present invention is applied, the lens  30  can be easily coupled to the camera body  10  even in dim light or in the dark. 
     In the illustrated embodiment, although the body index mark (transparent projection)  50   a  on the body mount  11  is backlit by the LED  52  from the inside of the camera body  10 , the present invention is not limited solely to this particular embodiment. For instance, the body index mark can be a conventional type of index mark formed on the body mount as a simple printed or engraved index mark. In this case, a light source such as an LED can be fixed to the camera body in the vicinity of the body index mark to illuminate the same. Alternatively, the light source (e.g., an LED) can be provided so as to illuminate the entire body mount  11  or a substantial portion thereof. This LED can be turned ON and OFF by control of the microcomputer  60 . 
     In the illustrated embodiment, although the LED  52  is turned OFF after a predetermined period of time (e.g., five seconds) elapses, from when the LED  52  is turned ON, the predetermined period of time may be set at less or more than five seconds. Furthermore, the LED  52  may be turned ON only during the time the lens-lock-release button  20  is held depressed (i.e., during the time the switch  25  is held closed). 
     In the illustrated embodiment, although the window member  50  provided with the transparent projection  50   a  which functions as a body index mark is made of a red transparent plastic, the window member  50  may be made of a transparent material of any other color. Alternatively, the window member  50  can be made of a translucent plastic, as long as it allows light to pass therethrough. 
     In the illustrated embodiment, although the body mount  11  is a bayonet mount type, the body mount  11  may be any other type, for example, a screw-type mount. 
     As can be understood from the foregoing, according to the camera body to which the present invention is applied, since the camera body is provided with a body mount to which the lens mount of an interchangeable lens is detachably attached, a body index mark which indicates the position of proper alignment of the body mount with respect to the lens mount of the interchangeable lens when the interchangeable lens is attached to the camera body, and a light source for lighting the body index mark; it is easy to attach the lens to the camera body even in dim light or in the dark. 
     Obvious changes may be made in the specific embodiment of the present invention described herein, such modifications being within the spirit and scope of the invention claimed. It is indicated that all matter contained herein is illustrative and does not limit the scope of the present invention.