Abstract:
A camera is disclosed, in which it is possible to adjust the position of two mirrors easily for striking a balance between the focus detection performances in an optical viewfinder state and an electronic image display state. The optical apparatus includes a first mirror movable between a first position for an optical viewfinder and a second position for focus detection, a second mirror movable between a third position for focus detection and a fourth position where a light flux is not led to the second mirror, a first positioning member for positioning the first mirror at the second position, and a second positioning member for positioning the second mirror at the third position. The second positioning member is a member independent of the first positioning member.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Filed of the Invention  
         [0002]     The present invention relates to optical apparatuses having a mirror dividing an optical path.  
         [0003]     2. Description of the Related Art  
         [0004]     Conventionally, a camera has been disclosed in Japanese Patent Laid-Open Publication No. 2001-125173, which is switchable between an optical viewfinder state and an electronic image display state by moving a half mirror between a first position where the mirror leads light from a taking lens to the optical viewfinder and a second position where the mirror leads the light to an image-pickup device. In this camera, focus detection by the phase difference detection method can be performed in the optical viewfinder state. However, only focus detection by the contrast detection method can be performed in the electronic image display state because the image-pickup device takes images in a state in which the mirror has retreated from the optical path.  
         [0005]     In addition, a camera has been disclosed in U.S. patent Laid-Open Publication No. 2004-0155976, in which an optical path dividing system is switchable between a first optical path dividing state and a second optical path dividing state; a light flux from a taking lens is divided into a light flux directing to an optical viewfinder and another light flux directing to a focus detection device in the first optical path dividing state, and the light flux from the taking lens is divided into a light flux directing to an image-pickup device and another light flux directing to the focus detection device in the second optical path dividing state.  
         [0006]     According to this camera, the focus detection by the phase difference detection method can be performed not only in the optical viewfinder state (the first optical path dividing state) but also in the electronic image display state (the second optical path dividing state).  
         [0007]     In this camera, the focus detection by the phase difference detection method can be achieved in both the optical viewfinder state and the electronic image. However, the common positioning member is used for positioning a sub mirror that reflects the light flux to the focus detection device in the first optical path dividing state and positioning a half mirror that reflects the light flux to the focus detection device in the second optical path dividing state. Therefore, it is difficult to adjust the positioning member for striking a balance between the focus detection performances in the two states.  
       SUMMARY OF THE INVENTION  
       [0008]     One object of the present invention is to provide an optical apparatus in which it is possible to adjust the position of the two mirrors easily for striking a balance between the focus detection performances in the optical viewfinder state and the electronic image display state.  
         [0009]     An optical apparatus as an aspect of the present invention comprises: a viewfinder optical system; a focus detection device; a first mirror movable between a first position where the first mirror leads an incident light flux to the viewfinder optical system and a second position where the first mirror leads the incident light flux to the focus detection device; a second mirror movable between a third position where the second mirror leads an incident light flux to the focus detection device and a fourth position where the light flux does not make incident to the second mirror; a first positioning member, which positions the first mirror at the second position; and a second positioning member, which positions the second mirror at the third position. The second positioning member is a member independent of the first positioning member.  
         [0010]     An optical apparatus as another aspect of the present invention comprises: a viewfinder optical system; a focus detection device; a first mirror movable between a first position where the first mirror leads an incident light flux to the viewfinder optical system and a second position where the first mirror leads the incident light flux to the focus detection device; a first driving member, which drives the first mirror; a second mirror movable between a third position where the second mirror leads an incident light flux to the focus detection device and a fourth position where the light flux is not led to the second mirror; a second driving member, which drives the second mirror; a first positioning member, which contacts the first driving member to position the first mirror at the second position; and a second positioning member, which contacts the second driving member to position the second mirror at the third position. The second positioning member is a member independent of the first positioning member.  
         [0011]     Other objects and features of the present invention will become apparent from the following description and the attached drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]      FIG. 1  is a block diagram showing the electrical structure of the camera system of Embodiment 1 of the present invention.  
         [0013]      FIG. 2  is a construction drawing of the camera system of Embodiment 1 when the mirror mechanism is set to the OVF mode.  
         [0014]      FIG. 3  is a construction drawing of the camera system of Embodiment 1 when the mirror mechanism is set to the EVF mode.  
         [0015]      FIG. 4  is a construction drawing of the camera system of Embodiment 1 when the mirror mechanism is set to the image-taking mode.  
         [0016]      FIG. 5  is a perspective view of the mirror mechanism in the OVF mode.  
         [0017]      FIG. 6  is perspective view of the mirror mechanism in the EVF mode.  
         [0018]      FIG. 7  is a first perspective view of the mirror mechanism in the image-taking mode.  
         [0019]      FIG. 8  is a second perspective view of the mirror mechanism in the image-taking mode.  
         [0020]      FIG. 9  is a perspective view of the mirror mechanism in the OVF mode.  
         [0021]      FIG. 10  is a perspective view of the mirror mechanism in the middle of switching between the OVF mode and the image-taking mode.  
         [0022]      FIG. 11  is a perspective view of the mirror mechanism in the image-taking mode.  
         [0023]     FIGS.  12  to  15  are perspective views of the mirror mechanism in the middle of switching between the EVF mode and the image-taking mode.  
         [0024]      FIG. 16  is a perspective view of the mirror mechanism in the EVF mode.  
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0025]     A description will now be given of the preferred embodiment of the present invention by referring to the accompanying drawings.  
       Embodiment 1  
       [0026]      FIG. 1  is a block diagram showing the main electric structure of the camera constituting the camera system of Embodiment 1 of the present invention.  
         [0027]     In  FIG. 1 , reference numeral  2  denotes a microprocessor controlling the operation of a camera body  1 . Reference numeral  3  denotes a motor driving circuit. The motor driving circuit  3  receives a control signal from the microprocessor  2  to drive a motor, not shown in the figure provided in the camera body  1 . The motor is a drive source of movable members such as the after-mentioned half mirror and sub mirror, which are provided in the camera body  1 .  
         [0028]     Reference numeral  4  denotes a photometry sensor for measuring luminance of an object. The photometry sensor  4  outputs the photometry result to the microprocessor  2 . The microprocessor  2  calculates an exposure value (aperture value and shutter speed) by the photometry result from the photometry sensor  4 . Reference numeral  5  denotes a focus detection sensor for detecting a focus state of an image-taking optical system. The focus detection sensor  5  performs focus detection by the phase difference detection method.  
         [0029]     Reference numeral  6  denotes a shutter control circuit. The shutter control circuit  6  receives a control signal from the microprocessor  2  to control a shutter unit provided in the camera body  1 , thereby making it possible to adjust the amount of light reaching an image-pickup device from the image-taking optical system.  
         [0030]     Reference numeral  8  denotes a display unit. The display unit  8  displays image data generated from the output of the image-pickup device and predetermined information. Reference numeral  9  denotes a flash control circuit. The flash control circuit  9  receives a control signal from the microprocessor  2  to control a flash  16  built-in the camera body  1 .  
         [0031]     Reference numeral  10  denotes a storage circuit storing information on the setting state of the camera body  1  or the like. Reference numeral  11  denotes an image-pickup-device driving circuit for drive the image-pickup device. Reference numeral  12  denotes a lens communication circuit communicating with a lens apparatus mounted on the camera body  1 . The microprocessor  2  can communicate with a lens control circuit, not shown in the figure, provided in the lens apparatus via the lens communication circuit  12 .  
         [0032]     Concretely, the lens control circuit receives information on the drive amount of a focus lens, which is obtained from the detection result of the focus detection sensor  5 , from the microprocessor to move the focus lens provided in the lens apparatus in a direction of the optical axis, thereby performing focusing.  
         [0033]     In addition, the lens control circuit receives information on the aperture value from the microprocessor to control the drive of an aperture diaphragm via the diaphragm control circuit, thereby making it possible to adjust the amount of light taken in the camera body  1  from the lens apparatus.  
         [0034]     Reference numeral  13  denotes a communication circuit communicating with an accessory other than the lens apparatus such as an illumination apparatus or a recording medium, which is mounted on the camera body  1 .  
         [0035]     Reference numeral  14  denotes a SW1-switch for starting the image-taking preparation operation such as a photometry operation and focusing operation. Reference numeral  15  denotes a SW2-switch for starting the image-taking operation, which exposes the image-pickup device and records an image read out from the image-pickup device to the recording medium.  
         [0036]     Reference numeral  16  denotes the built-in flash. The built-in flash  16  illuminates an object when the external illumination apparatus is not mounted on the camera body  1  and irradiates AF (automatic focusing) fill light to the object when the AF is performed.  
         [0037]     FIGS.  2  to  4  are sectional views showing the outline configuration of the camera system of the present embodiment.  FIG. 2  shows a state in which an OVF mode (optical viewfinder mode), which is a mode for viewing an object image through an optical viewfinder, is set.  FIG. 3  shows a state in which an EVF mode (electronic viewfinder mode), which is a mode for viewing an object image through the display unit  8 ,is set.  FIG. 3  shows the camera system in an image-taking state.  
         [0038]     In FIGS.  2  to  4 , reference numeral  20  denotes a mirror box,  21  a half mirror unit (first mirror unit). The half mirror unit  21  is constituted by the half mirror  21   a  and a half mirror lever  21   b.    
         [0039]     The half mirror lever  21   b,  which holds the half mirror  21   a,  is attached rotatably around a rotation shaft  21   c  provided on the mirror box  20 .  
         [0040]     Reference numeral  23  denotes a sub mirror unit (second mirror unit). The sub mirror unit  23  is constituted by the sub mirror  23   a  and a sub mirror lever  23   b.  The sub mirror lever  23   b,  which holds the sub mirror  23   a,  is attached rotatably around a rotation shaft  23   c  provided on the mirror box  20 .  
         [0041]     The rotation of the sub mirror lever  23   b  around the rotation shaft  23   c  provided on the mirror box  20  moves the sub mirror  23   a  into and out of the image-taking optical path.  
         [0042]     Reference numeral  31  denotes the image-pickup device such as a CCD sensor or a CMOS sensor. The image-pickup device  31  converts an optical image formed by the image-taking optical system into electric charges by its photoelectrical converting function and accumulates the charge. The charge is read out as electronic signals. Reference numeral  30  denotes the shutter unit (focal plane shutter), which adjusts the amount of light entering the image-pickup device  31 .  
         [0043]     Reference numeral  32  denotes a display device included in the display unit  8 , which is provided on the exterior surface of the camera body  1 . A photographer can observe images and predetermined information displayed on the display device  32  from the outside of the camera body  1 .  
         [0044]     Reference numeral  40  denotes a finder optical system constituting the optical viewfinder. The finder optical system (optical viewfinder)  40  includes a penta prism  41 , a finder lens  42  and a focusing plate  43 . In the state shown in  FIG. 2 , the object light reflected by the half mirror unit  21  forms an object image on the focusing plate  43 .  
         [0045]     Further, the object image formed on the focusing plate  43  is converted into an erected image in the penta prism  41 . The photographer can observe the object image formed on the focusing plate  43  through the finder lens  42 .  
         [0046]     Reference numeral  60  denotes a focus detection unit including the focus detection sensor  5 , which detects the focus state of the image-taking optical system by the phase difference detection method. In the OVF mode shown in  FIG. 2 , the object light from the lens apparatus  50  is transmitted through the half mirror unit  21 , reflected by the sub mirror unit  23 , and then enters the focus detection unit  60 . In the EVF mode shown in  FIG. 3 , the object light from the lens apparatus  50  is reflected by the half mirror unit  21 , and then enters the focus detection unit  60 . The focus detection unit  60  detects the focus state based on the entered light.  
         [0047]     Reference numeral  50  denotes the lens apparatus mounted on the camera body  1 , the lens apparatus having an image-taking lens  50   a  constituting the image-taking optical system.  
         [0048]     Reference numeral  353  denotes a sub-mirror-lever positioning member (second positioning member), which is fixed to the mirror box  20 . The sub-mirror-lever positioning member  353  positions the sub mirror unit  23  at a third position in the image-taking optical path by contact with the sub mirror lever  23   b  in the OVF mode, as shown in  FIG. 2 .  
         [0049]     Reference numeral  354  denotes a sub-mirror positioning member (second positioning member), which is fixed to the mirror box  20 . The sub-mirror positioning member  354  positions the sub mirror unit  23  at the third position in the image-taking optical path by contact with the sub mirror  23   a  in the OVF mode. The sub mirror unit  23  located at the third position reflects the light coming from the image-taking lens  50   a  toward the focus detection unit  60 .  
         [0050]     Reference numeral  350  denotes a half-mirror positioning member (third positioning member), which is fixed to the mirror box  20 . The half-mirror positioning member  350  positions the half mirror unit  21  at a first position in the image-taking optical path by contact with the half mirror  21   a  in the OVF mode, as shown in  FIG. 2 .  
         [0051]     Reference numeral  355  denotes also a half-mirror positioning member (third positioning member), which is fixed to the mirror box  20 . The half-mirror positioning member  355  is arranged at substantially the same position of the half-mirror positioning member  350  when viewed from the direction vertical to the paper of  FIG. 2 .  
         [0052]     The half mirror unit  21  located at the first position reflects part of the light entering from the image-taking lens  50   a  toward the finder optical system  40 , and transmits the remaining part thereof. The transmitted light enters the sub mirror unit  23  located at the third position as described above.  
         [0053]     Reference numeral  352  denotes a half-mirror-lever positioning member (first positioning member), which is fixed to the mirror box  20 . The half-mirror-lever positioning member  352  positions the half mirror unit  21  at a second position in the image-taking optical path by contact with the half mirror lever  21   b  in the EVF mode, as shown in  FIG. 3 .  
         [0054]     Reference numeral  351  denotes a half-mirror positioning member (first positioning member), which is fixed to the mirror box  20 . The half-mirror positioning member  351  positions the half mirror unit  21  at the second position in the image-taking optical path by contact with the half mirror  21   a  in the EVF mode, as shown in  FIG. 3 .  
         [0055]     The half mirror unit  21  located at the second position reflects part of the light entering from the image-taking lens  50   a  toward the focus detection unit  60 , and transmits the remaining part thereof. The transmitted light forms an image on the image-pickup plane of the image-pickup device  31 , the image being photoelectrically converted and then output as electronic signals.  
         [0056]     In the EVF mode, the sub mirror unit  23  is located at a fourth position outside the image-taking optical path, as shown in  FIG. 4 .  
         [0057]     When SW 2  is operated, the half mirror unit  21  and the sub mirror unit  23  are moved out of the image-taking optical path as shown in  FIG. 4 , and then the image-taking operation of the camera is started.  
         [0058]     FIGS.  5  to  8  are external perspective views of the mirror unit including the half mirror unit  21  and the sub mirror unit  23 .  FIG. 5  is an external perspective view of the mirror unit in an object observation state in the OVF mode.  FIG. 6  is an external perspective view of the mirror unit in an object observation state in the EVF mode.  FIGS. 7 and 8  are external perspective views of the mirror unit in the image-taking state.  
         [0059]     The half mirror unit  21  includes the following members. Reference numeral  21   a  denotes the half mirror, which reflects part of the light transmitted through the image-taking lens  50   a  and transmits the remaining part thereof.  
         [0060]     Reference numeral  102  denotes a half-mirror holding plate, which holds the half mirror  21   a.  Reference numeral  104  denotes a half-mirror retaining pin, a plurality of the half-mirror retaining pins  107  being provided on the half-mirror holding plate  102 .  
         [0061]     Reference numeral  103  denotes a half-mirror retaining spring, which presses the half mirror  21   a  to the half-mirror holding plate  102 . The half-mirror retaining spring  103  is constituted so as to generate a pressing force by the half mirror retaining pins  104 .  
         [0062]     Reference numeral  105  denotes a half-mirror driving shaft. The half-mirror driving shaft  105  is fixed to the half-mirror holding plate  102 . Reference numeral  106  denotes a half-mirror camshaft. The half-mirror camshaft  106  is fixed to the half-mirror holding plate  102 . Reference numeral  107  denotes a half-mirror inversion shaft. A pair of the half-mirror inversion shafts  107  is provided on the half-mirror holding plate  102 .  
         [0063]     Reference numeral  110  denotes a half-mirror-holder lever. The half-mirror-holder lever  110  supports the half-mirror holding plate  102  rotatably around the half-mirror inversion shafts  107 . Reference numeral  110  denotes a half-mirror-holder positioning member. The half-mirror-holder positioning member  111  stabilizes the position of the half-mirror-holder lever  110  by contact with the half-mirror-lever positioning member  352  in the EVF mode. In other words, as shown in  FIG. 3 , the half-mirror-holder positioning member  111  positions the half mirror unit  21  in the image-taking optical path in the EVF mode.  
         [0064]     Reference numeral  120  denotes a half-mirror hinge shaft, which is attached to the mirror box  20 . The half-mirror hinge shaft  120  rotatably supports the half mirror  21   a.    
         [0065]     Reference numeral  108  denotes a half-mirror swinging spring. The half-mirror swinging spring  108  gives a spring force to the half-mirror holding plate  102  and the half-mirror-holder lever  110  around the half-mirror inversion shaft  107  so as to hold them in a predetermined state.  
         [0066]     The sub mirror unit  23  includes the following members. Reference numeral  201  denotes a sub-mirror holder. Reference numeral  23   a  denotes the sub mirror. The sub mirror  23   a  is fixed to the sub-mirror holder  201 . Reference numeral  203  denotes a sub-mirror camshaft. The operation of the sub mirror unit  23  is controlled by a cam member, not shown in the figure, which is provided on the mirror box, via the sub-mirror camshaft  203 .  
         [0067]     Reference numeral  204  denotes a sub-mirror swinging spring. The sub-mirror swinging spring  204  gives a spring force between the after-mentioned sub-mirror holder lever  210  and the sub-mirror holder  201 . The sub-mirror swinging spring  204  gives the spring force to the sub mirror unit  23  so that the sub mirror unit  23  may contact the sub-mirror positioning member  354  in the OVF mode. Reference numeral  205  denotes a sub-mirror-holder hinge shaft. The sub-mirror-holder hinge shaft  205  supports the sub-mirror holder  201  rotatably with respect to the after-mentioned sub-mirror holder lever  210 .  
         [0068]     Reference numeral  210  denotes the sub-mirror holder lever. The sub-mirror holder lever  210  supports the sub-mirror holder  201  rotatably with respect to the mirror box  20 . Reference numeral  211  denotes a sub-mirror driving shaft. The sub-mirror driving shaft  211  is fixed to the sub-mirror holder lever  210 . Reference numeral  212  denotes a sub-mirror hinge shaft. The sub-mirror hinge shaft  212  supports the sub mirror unit  23  rotatably with respect to the mirror box  20 .  
         [0069]     Reference numeral  213  denotes a sub-mirror driving spring. The sub-mirror driving spring  213  is arranged on the same axis with the sub-mirror hinge shaft  212 . One end of the sub-mirror driving spring  213  is fixed to the mirror box  20 , and the other end is fixed to the sub-mirror driving shaft  211 . Thereby, the sub-mirror driving spring  213  generates a spring force in a direction where the sub mirror unit  23  is moved into the image-taking optical path.  
         [0070]     The sub mirror unit  23  is positioned in the OVF mode by contact of the sub-mirror holder lever  210  biased by the sub-mirror driving spring  213  with the sub-mirror-lever positioning member  353 .  
         [0071]     The driving unit for the half mirror unit  21  and sub mirror unit  23  is constituted by the following members.  
         [0072]     Reference numeral  310  denotes a half-mirror driving lever. The half-mirror driving lever  310  engages with the half-mirror driving shaft  105  to drive the half mirror unit  21 . Reference numeral  311  denotes a sub-mirror driving lever. The sub-mirror driving lever  311  engages with the sub-mirror driving shaft  211  to drive the sub mirror unit  23 .  
         [0073]     Reference numeral  312  denotes a mirror driving gear. The mirror driving gear  312  interlocks the half-mirror driving lever  310  with the sub-mirror driving lever  311 .  
         [0074]     Reference numeral  313  denotes a mirror driving lever. The mirror driving lever  313  is arranged on the same axis with the mirror driving gear  312 . Reference numeral  314  denotes an absorbing spring. The absorbing spring  314  is arranged between the mirror driving gear  312  and the mirror driving lever  313  so as to be located on the same axis with them. One end of the absorbing spring  314  is fixed to the mirror driving gear  312 , and the other end is fixed to the mirror driving lever  313 .  
         [0075]     The absorbing spring  314  absorbs a deformation of the mirror driving lever  313  by an over-charging force and generates a force for moving the mirror down at the time of the mirror down.  
         [0076]     Reference numeral  314  denotes a mirror driving spring. One end of the mirror driving spring  315  is fixed to the mirror box  20 , and the other end is fixed to the mirror driving lever  313 . The force generated by the mirror driving spring  315  drives the half mirror unit  21  upward.  
         [0077]     Reference numeral  314  denotes an input portion of the mirror driving lever  313 . Inputting a driving force to the input portion  316  charges the mirror driving lever  315 , thereby making it possible to drive the half mirror unit  21  downward.  
         [0078]     Next, the description will be give of the shutter driving mechanism. Reference numeral  320  denotes a shutter driving lever. The shutter driving lever  320  is supported on the same axis with the mirror driving lever  313 . Reference numeral  321  denotes a shutter driving portion provided on the shutter driving lever  320 . The shutter driving portion  321  engages with the shutter unit  30  to charge it and release the charge.  
         [0079]     Reference numeral  322  denotes a half-mirror-unit driving cam provided on the shutter driving lever  320 . Driving the mirror driving lever  313  while keeping the shutter driving lever  320  at a predetermined position makes the half-mirror-unit driving cam  322  contact the half-mirror camshaft  106 , thereby driving the half mirror unit  21 .  
         [0080]     Reference numeral  323  denotes a shutter driving spring. One end of the shutter driving spring  323  is fixed to the mirror box  20 , and the other end is fixed to the shutter driving lever  320 . Reference numeral  324  denotes an input portion of the shutter driving lever  320 . Inputting a driving force to the input portion  324  charges the shutter driving spring  323 , thereby charging the shutter unit  30 .  
         [0081]     In each of FIGS.  5  to  8 , the mirror positioning member provided on the mirror box  20  is shown. As described above, reference numeral  350  denotes the half-mirror positioning member, which positions the half mirror unit  21  in the OVF mode. Reference numeral  351  denotes the half-mirror positioning member, which positions the half mirror unit  21  in the EVF mode. Reference numeral  352  denotes the half-mirror-lever positioning member, which positions the half mirror lever  21   b  in the EVF mode. Reference numeral  353  denotes the sub-mirror-lever positioning member, which positions the sub-mirror holder lever  210  in the OVF mode. Reference numeral  354  denotes the sub-mirror positioning member, which positions the sub mirror unit  23  in the OVF mode.  
         [0082]     Reference numeral  355  denotes the half-mirror positioning member, which assists the positioning of the half mirror unit  21  in the OVF mode. The half-mirror positioning member  355  is arranged at approximately the same position in the mirror box  20 . Reference numeral  356  denotes a half-mirror positioning member, which assists the positioning of the half mirror unit  21  in the EVF mode. The half-mirror positioning member  356  is arranged at approximately the same position in the half-mirror positioning member  351  in the mirror box  20 . In other words, the half-mirror positioning members  350  and  355  position the half mirror unit  21  in the OVF mode, and the half-mirror positioning members  351  and  356  position the half mirror unit  21  in the EVF mode.  
         [0083]     As shown in  FIG. 8 , of the half-mirror positioning members  350 ,  351 ,  355  and  356 , the half-mirror positioning members  350  and  351 , which are arranged on a side closer to the half-mirror driving lever  310  giving the driving force to the half mirror unit  21 , are the primary positioning members. On the other hand, the half-mirror positioning members  355  and  356 , which are not arranged on the side closer to the half-mirror driving lever  310 , are assistant positioning members.  
         [0084]     As described above, using the half-mirror positioning members  350  and  351  arranged on the side closer to the half-mirror driving lever  310  as the primary positioning members makes it possible to stabilize the position of the half mirror unit  21  after a position adjustment.  
         [0085]     Furthermore, the half-mirror positioning member  356  and sub-mirror positioning member  354  can function as a positioning member, respectively, by their different distances from the image-taking optical axis. Thereby, it is possible to increase the arrangement freedom of the positioning members.  
         [0086]     Each of the above-mentioned positioning members is constituted by a pin provided on the mirror box  20 . The pin is rotatably attached to the mirror box  20 , its rotation axis being eccentric. Therefore, rotating each positioning member around the rotation axis makes it possible to perform fine adjustment of each position of the half mirror unit  21  and sub mirror unit  23  in the OVF and EVF modes.  
         [0087]     Next, the description will be given of the mirror units with reference to FIGS.  5  to  7 .  
         [0088]     In  FIG. 5  that shows the OVF mode, the half mirror unit  21  is arranged obliquely in the image-taking optical path so as to divide the light flux from the image-taking optical system. The light flux from the image-taking optical system is divided by the half mirror unit  21  into a light flux directing to the finder optical system  40  and another light flux directing to the sub mirror unit  23 . The sub mirror unit  23  is arranged obliquely in the image-taking optical path so that the sub mirror  23   a  may reflect the light flux that has been transmitted through the half mirror  21   a  to lead it to the focus detection unit  60 .  
         [0089]     The mirror driving lever  313  and the shutter driving lever  320  are driven so as to charge the mirror driving spring  315  and the shutter driving spring  323 , respectively. The half mirror unit  21  is held so as to be pressed to the half-mirror positioning member  350  by the absorbing spring  314 . The sub mirror unit  23  is held so as to be pressed to the sub-mirror positioning member  354  and sub-mirror-lever positioning member  353  by the sub-mirror swinging spring  204  and sub-mirror driving spring  213 .  
         [0090]     In  FIG. 6  that shows the EVF mode, the sub mirror unit  23  is arranged at the retreat position outside the image-taking optical path, the reflective surface of the half mirror  21   a  in the half mirror unit  21  being arranged at approximately the same position as the sub mirror  23   a  shown in  FIG. 9 .  
         [0091]     Here, the reflective surface of the half mirror  21   a  is arranged at not completely the same position but approximately the same position because the incident light on the sub mirror  23   a  in the OVF mode refracts when it is transmitted through the half mirror  21   a  and its optical path is slightly different from that of the incident light on the half mirror  21   a  in the EVF mode.  
         [0092]     If the positioning member for the sub mirror  23   a  in the OVF mode and the positioning member for the half mirror  21   a  in the EVF mode are common (identical) member, it is not possible to make the positions of these mirrors  23   a  and  21   a  differ from each other. In contrast, according to the present embodiment, the half mirror unit  21  and the sub mirror unit  23  are positioned by the separate members, respectively, thereby making it possible to set the position of the sub mirror  23   a  in the OVF mode and the position of the half mirror  21   a  in the EVF mode individually. Therefore, it is possible to increase the detection accuracy of the focus detection unit  60 .  
         [0093]     The positioning of the half mirror unit  21  is performed by pressing the half-mirror-holder lever  110  to the half-mirror-lever positioning member  352  and pressing the half-mirror holding plate  102  to the half-mirror positioning member  351 , by the biasing force of the absorbing spring  314 .  
         [0094]     The shutter driving lever  320  is held in a state in which the charge of the shutter unit (not shown in the figure) is released. The mirror driving lever  313  is held in a state in which it is driven by an amount more than its charge amount shown in  FIG. 5 .  
         [0095]     In  FIG. 7  that shows the image-taking state, the half mirror unit  21  and the sub mirror unit  23  are retreated outside the image-taking optical path, the light from the image-taking lens  50   a  forming an image on the image-pickup plane of the image-pickup device  31 . The electronic signal corresponding to the image is output from the image-pickup device  31 .  
         [0096]     An external driving force does not act on the mirror driving lever  313  and the shutter driving lever  320 . Both the half mirror unit  21  and sub mirror unit  23  are set at the standby position by the spring forces of the mirror driving spring  315  and shutter driving spring  323 .  
         [0097]     Next, the description will be given of the operation of the mirror driving mechanism with reference to FIGS.  9  to  16 . FIGS.  9  to  11  are perspective views showing the operation of the mirror driving mechanism when operating between the object observation state and the image-taking state in the OVF mode.  
         [0098]      FIG. 9  is a perspective view of the mirror driving mechanism in the object observation state in the OVF mode, the figure being a perspective view of the mirror driving mechanism when viewed from a direction different from  FIG. 5 .  FIG. 10  is a perspective view of the mirror driving mechanism in the middle of the operation from the object observation state to the image-taking state in the OVF mode.  FIG. 11  is a perspective view of the mirror driving mechanism in the image-taking mode, the figure being a perspective view of the mirror driving mechanism when viewed from a direction different from  FIG. 7 .  
         [0099]     Now, the description will be given of the mirror driving operation from the object observation state to the image-taking state in the OVF mode.  
         [0100]     First, in the object observation state shown in  FIG. 9 , as described using  FIG. 5 , the mirror driving lever  313  and the shutter driving lever  320  are held in a state in which they have been charged by an external driving force.  
         [0101]     At this time, the half mirror unit  21  is pressed to the half-mirror positioning member  350  by the engagement of the half-mirror driving shaft  105  with a half-mirror driving portion  317 . The pressing force in this case is generated by the absorbing spring  314 .  
         [0102]     The contact of the half-mirror camshaft  106  with the half-mirror holder lever  110  makes it possible to stabilize the angle formed between the half-mirror holding plate  102  and the half-mirror holder lever  110 . Further, holding the half mirror unit  21  at three points of half-mirror hinge shaft  120  and the half-mirror positioning members  350  and  355  makes it possible to keep the angle of the half mirror unit  21  in the object observation state.  
         [0103]     As for the sub mirror unit  23 , an external driving force is not given directly to the sub-mirror driving shaft  211 , and the biasing force of the sub-mirror driving lever  311  is not given thereto, either. By the contact of the sub-mirror holder lever  210  with the sub-mirror-lever positioning member  353  by the biasing forces of the sub-mirror driving spring  213  and sub-mirror swinging spring  204 , and the contact of the sub-mirror holder  201  with the sub-mirror positioning member  354 , the sub mirror unit  23  is positioned in the image-taking optical path.  
         [0104]     From this state, when the mirror-up operation is started, the driving force that has been given to the mirror driving lever  313  and shutter driving lever  320  is released. Thereby, the mirror driving lever  313  and the shutter driving lever  320  are driven by the biasing forces of the mirror driving spring  315  and shutter driving spring  323 .  
         [0105]     When the drive of the mirror driving lever  313  and shutter driving lever  320  is started, the retreating operation of the half mirror unit  21  and sub mirror unit  23  from the image-taking optical path is started, as shown in  FIG. 10 . The half mirror unit  21  is driven by the half-mirror driving lever  310 , and the sub-mirror unit  23  is driven by the sub-mirror driving lever  311 .  
         [0106]     Then, the half mirror unit  21  and sub mirror unit  23  are completely retreated from the image-taking optical path, thereby becoming the image-taking state, as shown in  FIG. 11 . The operation from the image-taking state to the object observation state is performed in reverse order from the above-described operation in FIGS.  9  to  11 .  
         [0107]     In the image-taking state shown in  FIG. 11 , a driving force is given to the shutter driving lever  320  when the operation is started. When the drive of the shutter driving lever  320  is started, it contacts a shutter-driving-lever interlocking portion  318  provided on the mirror driving lever  313 . Thereby, the shutter driving lever  320  and the mirror driving lever  313  are simultaneously driven.  
         [0108]     Since the shutter driving lever  320  and the mirror driving lever  313  are simultaneously driven as described above, the half-mirror-unit driving cam  322  retreats simultaneously with the drive of the half mirror unit  21 , and do not drive the half-mirror camshaft  106 . Accordingly, the half-mirror holding plate  102  and the half-mirror holder lever  110  move into the image-taking optical path in a state in which they are held by the half-mirror swinging spring  108 , and reach the positions in the object observation state shown in  FIG. 9  through the state shown in  FIG. 10 . Thereby, it becomes possible to observe the object through the optical viewfinder  40 .  
         [0109]     FIGS.  11  to  16  are perspective views showing the operation of the mirror driving mechanism when operating between the object observation state and the image-taking state in the EVF mode. The description will hereinafter be given of the mirror driving operation between the object observation state and the image-taking state in the EVF mode with reference to FIGS.  11  to  16 .  
         [0110]      FIG. 16  is a perspective view of the mirror driving mechanism in the EVF mode, the figure being a perspective view of the mirror driving mechanism when viewed from a direction different from  FIG. 6 . FIGS.  12  to  15  are perspective views of the mirror driving mechanism in the middle of switching between the object observation state and the image-taking state in the EVF mode.  
         [0111]     Now, the description will be given of the mirror driving operation from the image-taking state to the object observation state. The drive from the image-taking state to the object observation state is performed by the input of an external driving force to the input portion  316  of the mirror driving lever  313 .  
         [0112]     When the external driving force is input to the input portion  316  of the mirror driving lever  313 , the mirror driving lever  313  is driven, and charges the mirror driving spring  315 . At the same time, the mirror driving gear  312  provided on the same axis with the mirror driving lever  313  is driven integrally with the mirror driving lever  313 . Since the mirror driving lever  313  and the mirror driving gear  312  are interlocked with each other by the absorbing spring  314 , the driving force is transmitted to the mirror driving gear  312  until the mirror driving gear  312  is stopped.  
         [0113]     The mirror driving gear  312  is connected to the half-mirror driving lever  310  and sub-mirror driving lever  311 , each lever driving the half mirror unit  21  and the sub mirror unit  23 .  
         [0114]     Here, in  FIG. 12 , when the half-mirror-unit driving cam  322  gives a rotational force to the half-mirror holding plate  102 , the angle formed between the half-mirror holding plate  102  and the half-mirror holder lever  110  changes. Since the rotation speed of the half-mirror holding plate  102  becomes larger than that of the half-mirror holder lever  110 , the drive trajectory of the half mirror unit  21  in the EVF mode is different from that in the OVF mode.  
         [0115]     When the drive further progresses, the mirror driving mechanism changes as shown  FIGS. 13, 14  and  15 . In  FIG. 13 , the half-mirror camshaft  106  is driven along the half-mirror-unit driving cam  322  in the half mirror unit  21 . Therefore, the moving trajectory of the mirror tip of the half mirror unit  21  is closer to the half-mirror hinge shaft  120  than that in the OVF mode, which was described using FIGS.  9  to  11 .  
         [0116]     Accordingly, the half mirror unit  21  passes on a side closer to the half-mirror hinge shaft  120  than the half-mirror positioning member  350 . Thereby, the half mirror unit  21  is driven without contacting the half-mirror positioning member  350 .  
         [0117]     When the mirror driving mechanism has been driven to the object observation state shown in  FIG. 16  from the states shown in  FIGS. 14 and 15  sequentially, the mirror driving lever  313  has been driven by an amount larger than the operation amount for driving the half mirror unit  21 . In this state, a rotational force generated in the mirror driving gear  312  by the charge of the absorbing spring  314  is transmitted to the half mirror unit  21 .  
         [0118]     The half mirror unit  21  is positioned so that its position can be adjusted by the half-mirror positioning member  351  and the half-mirror-lever positioning member  352 , which are fixed to the mirror box  20 .  
         [0119]     Moreover, the absorbing spring  314  has absorbed the over charged amount of the mirror driving lever  313 , and presses the half mirror unit  21  to the half-mirror positioning member  351  and the half-mirror-lever positioning member  352  to fix it. The half-mirror camshaft  106  is away from the half-mirror-unit driving cam  322  for preventing a change of the position and angle of the half mirror unit  21  in the EVF mode.  
         [0120]     The sub mirror unit  23  is retreated outside the image-taking optical path by the operation of the sub-mirror driving shaft  211  that the external driving force is input with the mirror driving lever  313 .  
         [0121]     Furthermore, the shutter lever  320  is driven to charge the shutter unit, not shown in the figure, and then the shutter lever  320  is released. Thereby, it is possible to take an image formed on the image-pickup device  31  and display it on the display device  32 .  
         [0122]     The switching operation from the object observation state to the image-taking state in the EVF mode is performed in reverse order from the above-described operation in FIGS.  11  to  16 .  
         [0123]     First, the shutter unit, which is opened for taking images in the object observation state shown in  FIG. 16 , is charged. Then, the shutter driving lever  320  is released as the shutter is held in the charged state. After that, the mirror-up operation is started.  
         [0124]     In the mirror-up operation, when the driving force that has been added to the input portion  316  of the mirror driving lever  313  is eliminated, the mirror driving lever  313  is driven by the biasing force of the mirror driving spring  315 . Thereby, the drive of the half mirror unit  21  and the sub mirror unit  23  is started.  
         [0125]     In this state, since the shutter driving lever  320  is released, the half mirror unit  21  is driven as the half-mirror camshaft  106  contacts the half-mirror-unit driving cam  322 . Therefore, the half mirror unit  21  is driven without contacting the half-mirror positioning member  350 . In actual operation, the mirror driving mechanism becomes the image-taking state shown in  FIG. 11  by the series of operation shown in FIGS.  15  to  12 .  
         [0126]     The mirror driving mechanism operates from the image-taking state to the object observation state shown in  FIGS. 6 and 16  by driving only the mirror driving lever  313  of the mirror driving lever  313  and the shutter driving lever  320 .  
         [0127]     The mirror driving lever  313  is configured so as to operate in conjunction with the drive of the shutter driving lever  320  via the shutter-driving-lever interlocking portion  318 . However, since the shutter driving lever  320  is not configured so as to operate in conjunction with the drive of the mirror driving lever  313 , the shutter driving lever  320  is driven freely in the object observation state of the EVF mode. Therefore, by repeating the charge operation of the shutter unit by the shutter driving lever  320  and the exposure operation, it is possible to take images in the object observation state without driving the mirror driving mechanism.  
         [0128]     In the above description, each operation of the mirror driving mechanism was explained with reference to FIGS.  9  to  16 . In addition to this, the operation of the camera system is as follows.  
         [0129]     (Image-Taking Operation from the OVF Mode)  
         [0130]     When an image-taking start signal is input to the camera system while observing an object in the OVF mode, the mirror driving mechanism is driven from the object observation state to the image-taking state, as described in FIGS.  9  to  11 . The exposure operation is performed in the image-taking state, and then the mirror driving mechanism is driven from the image-taking state to the object observation state in which the object image can be confirmed through the optical viewfinder  40 , as described in FIGS.  9  to  11 . Thus, a series of image-taking operation is performed.  
         [0131]     (Image-Taking Operation from the EVF Mode)  
         [0132]     When the image-taking start signal is input to the camera system while observing an object in the EVF mode, the mirror driving mechanism is driven from the object observation state to the image-taking state, as described in FIGS.  11  to  16 . The exposure operation is performed in the image-taking state, and then the mirror driving mechanism is driven from the image-taking state to the object observation state in which the object image can be confirmed through the display device  32 , as described in FIGS.  11  to  16 . Thus, a series of image-taking operation is performed.  
         [0133]     (Switching Operation from the OVF Mode to the EVF Mode)  
         [0134]     To switch from the OVF mode to the EVF mode, first, the mirror driving mechanism is driven from the object observation state in the OVF mode to the image-taking state, as described in FIGS.  9  to  11 . After that, the mirror driving mechanism is driven from the image-taking state to the object observation state in the EVF mode, as described in FIGS.  11  to  16 . Thereby, the camera system is set to the EVF mode, and it becomes possible to confirm an object image through the display device  32 .  
         [0135]     (Switching Operation from the EVF mode to the OVF Mode)  
         [0136]     To switch from the EVF mode to the OVF mode, first, the mirror driving mechanism is driven from the object observation state in the EVF mode to the image-taking state, as described in FIGS.  11  to  16 . After that, the mirror driving mechanism is driven from the image-taking state to the object observation state in the OVF mode, as described in FIGS.  9  to  11 . Thereby, the camera system is set to the OVF mode, and it becomes possible to confirm an object image through the optical viewfinder  40 .  
         [0137]     The description was given of the camera system in which the lens apparatus is detachably mounted on the camera body in the above embodiment, however the present invention can be applied to optical apparatuses such as an image-taking apparatus having a fixed lens.  
         [0138]     Further, the description was given of the mirror operation between three states, which are the object observation state in the OVF mode, the object observation state in the EVF mode and the image-taking state, in the above embodiment, however the present invention is not limited thereto.  
         [0139]     As described above, according to the above-mentioned embodiment, since a positioning member for positioning the sub mirror unit  23  in the object observation state in the OVF mode and a positioning member for positioning the half mirror unit  21  in the object observation state in the EVF mode are different from each other, it is possible to achieve the reduction of the adjustment time and the increase of the adjustment accuracy of the optical path dividing system in each mode.  
         [0140]     In addition, since the positioning members are provided in the vicinity of the mirror driving lever, deformation of the optical path dividing system is prevented, thereby making it possible to increase the stability of the optical path dividing system.  
         [0141]     This application claims foreign priority benefits based on Japanese Patent Application No. 2004-191318, filed on Jun. 29, 2004, which is hereby incorporated by reference herein in its entirety as if fully set forth herein.