Abstract:
An imager comprising is provided having an image-capturing device, a display, and a view angle controller. The first in-focus detector is movable with respect to a stationary platform, and detects whether a subject image is in focus of an image sensor. The shake detector detects a shake transmitted to the first in-focus detector. The first driver repositions the first in-focus detector with respect to the stationary platform according to a shake detected by the shake detector. The first in-focus detector provided on an in-focus light path is different from a photographing light path on which light is directed to the image sensor, and detects whether a subject image is in focus using incoming light along the in-focus light path.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to an imager having an auto focus function. 
         [0003]    2. Description of the Related Art 
         [0004]    An imager, for example a digital camera, may comprise an auto focus function. The auto focus function virtually provides a distance measuring area on an imaging area of an imaging sensor, and automatically brings a subject into focus by using a subject image that is incident on the imaging area. Japanese Unexamined Patent Publication (KOKAI) No. 2006-343509 discloses that in the case that such camera has a shake reduction system, the shake reduction system performs so as to move the distance measuring area on the imaging area based on the amount of shaking a camera undergoes while the auto focus function is in effect. 
         [0005]    However, if a subject image is not incident on an imaging area, the effect that an imager experiences from shaking is not reduced during auto-focusing. This may make it impossible for a camera to automatically maintain a subject image in focus on an imaging sensor. 
       SUMMARY OF THE INVENTION 
       [0006]    An object of the present invention is to provide an imager that can maintain a subject image in focus on an imaging sensor, even if an imager is shaking. 
         [0007]    An imager comprising is provided having an image-capturing device, a display, and a view angle controller. The first in-focus detector is movable with respect to a stationary platform, and detects whether a subject image is in focus of an image sensor. The shake detector detects a shake transmitted to the first in-focus detector. The first driver repositions the first in-focus detector with respect to the stationary platform according to a shake detected by the shake detector. The first in-focus detector provided on an in-focus light path is different from a photographing light path on which light is directed to the image sensor, and detects whether a subject image is in focus using incoming light along the in-focus light path. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    The objects and advantages of the present invention will be better understood from the following description, with reference to the accompanying drawings in which: 
           [0009]      FIG. 1  is a perspective view of a rear surface of an imager according to the first embodiment of the present invention; 
           [0010]      FIG. 2  is a cross-sectional view of an imager; 
           [0011]      FIG. 3  is a block diagram of an imager; 
           [0012]      FIG. 4  is a perspective view of an image shake-reduction component; 
           [0013]      FIG. 5  is a perspective view of an AF sensor shake-reduction component; and 
           [0014]      FIG. 6  is a perspective view of an image sensor etc., according to the second embodiment. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0015]    An embodiment of a digital camera as an imager according to the present invention is described below with reference to the accompanying figures. 
         [0016]    The construction of a digital camera  100  according to the first embodiment is described with reference to  FIGS. 1 to 3 . 
         [0017]    An SWM button  111  that switches power of the digital camera  100  on and off, a shutter release button  112 , a shake reduction button  113 , a LCD monitor  114 , and a photographing lens  120  are provided on the digital camera  100 . 
         [0018]    The operation switch  110  comprises the SWM button  111 , the shutter release button  112 , and the shake reduction button  113 . 
         [0019]    The SWM button  111  is a momentary switch that projects from the rear surface of the digital camera  100 . When a user depresses the SWM button  111 , the main power of the digital camera is activated. When a user depresses the SWM button  111  while the main power of the digital camera is on, the main power of the digital camera is deactivated. 
         [0020]    The shutter release button  112  is a two-step momentary switch, and is provided on the top of the digital camera  100 . When a user depresses the shutter release button  112  halfway, a photometry operation, a distance surveying operation, and an in-focus operation are performed. Otherwise, a user fully depresses the shutter release button  112  and an imaging operation is performed. 
         [0021]    The shake reduction button  113  is a momentary switch that projects from the rear surface of the digital camera  100 . When a user depresses the shake reduction button  113 , the digital camera is set to a shake reduction mode. The shake reduction mode executes a shake reduction process that prevents blurring of a subject in a photographed image caused by movement of the digital camera  100  during exposure, and is described later. In the case that a user depresses the shake reduction button  113  when the digital camera  100  is in the shake reduction mode, the digital camera  100  is released from the shake reduction mode. 
         [0022]    The LCD monitor  114  is rectangular with an aspect ratio of three to four, which is the same as the aspect ratio of a photographed image. As illustrated in  FIG. 1 , the LCD monitor  114  is provided in the substantially central area of the rear surface of the digital camera  100  such that its longitudinal direction extends along the lateral direction of the digital camera  100 . A through image captured by the imaging sensor  231 , a photographed image, and various configuration data of the digital camera may be displayed on the LCD monitor  114 . 
         [0023]    The photographing lens  120  has a focusing lens  252  and an aperture diaphragm  253 , and projects from the front surface of the digital camera  100 . 
         [0024]    Hereinafter, an X axis is defined as the axis that is orthogonal to the optical axis LX, is parallel to the longitudinal direction of the LCD monitor  114 , and is positive in the direction toward the right when looking at the rear of the digital camera  100  from the perspective of  FIG. 1 . A Y axis is defined as the axis that is orthogonal to the optical axis LX, is parallel to the width direction of the LCD monitor  114 , and is positive in the direction toward the top of the digital camera  100  of  FIG. 1 . A Z axis is defined as the axis that is parallel to the optical axis LX, and is positive in the direction from the rear surface toward the front surface of the digital camera  100  of  FIG. 1 . 
         [0025]    A DSP  210 , a lens/aperture driver  251 , an AF sensor  280 , an AF stage driver  271 , a return mirror  262 , a shutter curtain  263 , a mirror/shutter driver  261 , an image sensor  231 , and a sensor stage driver  248  are provided in the digital camera  100 . 
         [0026]    The DSP  210  calculates the distance of movement of the focusing lens  252  based on a measured distance that is provided by the AF sensor  280 . The DSP  210  then sends a signal to the lens/aperture driver  251  based on the calculated distance of movement. The lens/aperture driver  251  moves the focusing lens  252  based on the received signal, and brings the photographing lens  120  into focus. Thereby, a subject image is in focus of the image sensor  231  provided in the digital camera  100 . 
         [0027]    The DSP  210  measures an amount of light that is reflected from a subject image passing through the photographing lens  120  when the release button  112  is depressed halfway. The DSP  210  calculates light exposure based on the measured amount of light, and calculates an aperture value and exposure time based on the measured amount of light. The aperture value and the exposure time are used for photographing. After that, the DSP  210  sends the calculated aperture value to the lens/aperture driver  251 , and the exposure time to the mirror/shutter driver  261 . 
         [0028]    The lens/aperture driver  251  is connected to the aperture diaphragm  253 . When the release button  112  is fully depressed, the lens/aperture driver  251  controls the aperture of the aperture diaphragm  253  based on the aperture value sent from the DSP  210 . 
         [0029]    The mirror/shutter driver  261  is connected to the shutter curtain  263 . When the release button  112  is fully depressed, the mirror/shutter driver  261  controls the speed of the shutter curtain  263  based on the exposure time sent from the DSP  210 . 
         [0030]    The return mirror  262  is connected to the mirror/shutter driver  261 . When the release button  112  is fully depressed, the DSP  210  sends a mirror-up signal to the mirror/shutter driver  261 . The mirror/shutter driver  261  raises the return mirror  262  based on the mirror-up signal. Thereby, the return mirror  262  is raised until the sweeping of the shutter curtain  263  is completed, so that a subject image is incident on the image sensor  231   
         [0031]    The DSP  210  receives a digital image signal, processes it and then generates image data. After that, the DSP  210  stores the image data in the SD card  133 , and displays it on the LCD monitor  114 . The memory  312  is used as a working memory that temporarily stores data while the DSP  210  processes these calculations and conducts image processing. 
         [0032]    The SD card  133  is detachably inserted into a card slot  116  that is provided on the side of the digital camera  100 . A user can easily replace the SD card  133  by accessing the SD card  133  from the outside of the digital camera  100 . 
         [0033]    The shake reduction system is described hereinafter. The shake reduction system comprises an angular velocity sensor  220  that measures the angular velocity of the digital camera  100  (i.e., it measures a shock that the digital camera  100  receives), the image sensor  231  that converts a subject image to analog image signal, a shake correction component  240  that moves the image sensor  231 , and the DSP  210  that controls the digital camera  100 . 
         [0034]    The angular velocity sensor  220  comprises an x-direction sensor  221  and a y-direction sensor  222  that are gyro sensors. The x-direction sensor  221  measures the angular velocity of the digital camera  100  in the x-direction. The x-direction angular velocity is the angular velocity in the direction parallel to the X axis, i.e. yawing motion that produces an angular velocity around the Y axis. The y-direction sensor  222  measures the angular velocity of the digital camera  100  in the y-direction. The y-direction angular velocity is the angular velocity in the direction parallel to the Y axis, i.e. a pitching motion that produces an angular velocity around the X axis. An output signal produced by the x-direction sensor  221  that indicates the x-direction angular velocity, and an output signal produced by the y-direction sensor  222  that indicates the y-direction angular velocity are input to the DSP  210 . 
         [0035]    The imaging sensor  231  is connected to the DSP  210  through an AFE (analog front end)  232  and a TG (timing generator)  233 . The imaging sensor  231  comprises a CCD or a CMOS image sensor, has an imaging surface on which the photographing lens  120  provides a subject image, and is provided in the digital camera  100  so that the optical axis LX passes through the center of the imaging sensor  231 . The TG  233  sends timing pulses to the imaging sensor  231  and the AFE  232  based on a signal from the DSP  210 . The imaging sensor  231  outputs an analog image signal, which is created based on a subject image provided on the imaging surface, according to the timing pulses from the TG  233 . The AFE  232  converts the analog image signal to a digital image signal based on the timing pulses from the TG  233 , according to instructions from the DSP  210 . After that, the digital image signal is sent to the DSP  210 . 
         [0036]    The imaging sensor  231  has an imaging area  234  that is used for imaging. A subject image passing through the imaging lens  120  is made incident on the imaging area  234 . 
         [0037]    The DSP  210  creates a virtual AF area  235  at the center of the imaging area  234 . The AF area  235  is rectangular and located at the center of the imaging area  234  in the vertical direction of the digital camera  100 , while extending in the horizontal direction, i.e., in the lengthwise direction of the imaging sensor  231 . The center of the imaging area  234  and the center of the AF area  235  overlap one another ( FIG. 4 ). The DSP  210  executes a contrast AF process so that the focusing lens  252  is moved into the in-focus position. 
         [0038]    The shake correction device  240  comprises a movable part  241  that is driven based on movement of the digital camera  100 , and a stationary platform  245  that is fixed with respect to the digital camera  100 . The shake correction device  240  is connected to the DSP  210  through a sensor stage driver  248 , which drives the movable part  241 . 
         [0039]    The image sensor  231  is connected to the movable part  241  so that the imaging surface is intersected by the path of light. The movable part  241  has two stepping motors: an x-direction motor  242  and a y-direction motor  243 . The drive axes of the x-direction motor  242  and y-direction motor  243  are respectively connected to the movable part  241 , so that the movable part  241  is driven in the X and Y directions. The x-direction motor  242  and the y-direction motor  243  are both connected to the sensor stage driver  248  with a flexible cable. 
         [0040]    An x-stage  250  is provided on the stationary platform  245  so as to be freely movable in the X direction. A y-stage  249  is provided on the x-stage  250  so as to be freely movable in the Y direction. Two cylindrical y-direction guide rods  247 , which extend in the Y direction, are connected to the x-x-stage  250 . Two cylindrical x-direction guide rods  246 , which extend in the X direction, are connected to the y-stage  249 . 
         [0041]    The movable part  241  comprises four guide holes that are aligned with the x-direction guide rods  246  and y-direction guide rods  247 . Two guide holes extend along the X direction while maintaining a constant distance between each other in the Y direction. The other two guide holes extend along the Y direction while maintaining a constant distance between each other in the X direction. The x-direction guide rods  246  and the y-direction guide rods  247  are inserted into these guide holes. Thereby, the x-direction guide rods  246  and the y-direction guide rods  247  guide the movable part  241  so that it moves in the X and Y directions. The movable part  241  is freely movable in the X direction and the Y direction by the workings of the x-direction motor  242 , y-direction motor  243 , x-direction guide rods  246 , and the y-direction guide rods  247 . 
         [0042]    The sensor stage driver  248  is connected to the DSP  210 , and applies voltage to the x-direction motor  242  and the y-direction motor  243  based on a signal from the DSP  210 . Thereby, the movable part  241  changes its position with respect to the stationary platform  245  in the X direction and the Y direction. 
         [0043]    The shake reduction operation of the imaging sensor  231  is carried out with these parts as described hereinafter. When the digital camera  100  moves, the x-direction sensor  221  and the y-direction sensor  222  measure angular velocities of the digital camera  100  in the X and Y directions. Then, the x-direction and y-direction angular velocities are input to the DSP  210 . The DSP  210  calculates an x-direction shake angle and a y-direction shake angle based on the x-direction angular velocity and the y-direction angular velocity. Then, it calculates an x-direction coordinate and a y-direction coordinate of the position of the movable part  241  based on the x-direction shake angle and the y-direction shake angle. The x-direction coordinate is the position to which the movable part  241  should be moved in the X direction. The y-direction coordinate is the position to which the movable part  241  should be moved in the Y direction. In this calculation, the focusing length of the photographing lens  120  etc., are considered. Then, the calculated x-direction position coordinate and y-direction position coordinate are sent to the sensor stage driver  248 . The sensor stage driver  248  calculates a voltage that to be applied to the x-direction motor  242  and the y-direction motor  243  based on the x-direction position coordinate and the y-direction position coordinate, and applies the calculated voltage to the x-direction motor  242  and the y-direction motor  243 . Thereby, the movable part  241  repositions itself with respect to the stationary platform  245  in the X direction and the Y direction so that the movement of the digital camera  100  is cancelled out. By repeating these processes every one millisecond, the unwanted effect of shaking on the imaging sensor  231  is reduced. Note that shake reduction processing is carried out for the imaging sensor  231  is when the digital camera  100  photographs a subject. 
         [0044]    Components that are used in the process of bringing a subject image into focus on the imaging sensor  231  are described hereinafter. 
         [0045]    The DSP  210  is connected to the lens/aperture driver  251  that controls the focusing lens  252  and the aperture diaphragm  253 , the mirror/shutter driver  261  that controls the return mirror  262  and the shutter curtain  263 , the AF sensor  280  that detects focusing of the photographing lens  120 , and the AF stage driver  271  that drives the AF stage  270  based on the movement of the digital camera  100 . 
         [0046]    The return mirror  262 , the shutter curtain  263 , and the AF sensor  280  are provided in a mirror box  150  of the digital camera  100 . 
         [0047]    The return mirror  262  includes a transparent part at the center of its light-receiving surface  265 . The transparent part is a half mirror that transmits a portion of light incident on the center of the light-receiving surface  265  to the backside of the light-receiving surface  265 . An auxiliary mirror  264  is provided on the backside of the light-receiving surface  265 . The auxiliary mirror  264  comprises a reflecting surface  266  that forms an angle of 90 degrees with the receiving light surface  265 , so that it reflects light. The light reflected by the auxiliary mirror  264  illuminates the AF sensor  280  as it passes through a condenser lens  182 , a first separator lens  282 , and a second separator lens  283 . 
         [0048]    An AF sensor shake reduction device  290  comprises the AF stage  270 , an AF stationary platform  275  that is fixed inside the digital camera  100 , an x-stage  279 , and a z-stage  278 . The AF sensor shake reduction device  290  is connected to the DSP  210  through an AF stage driver  271  that drives the AF stage  270 . 
         [0049]    The AF sensor  280  has a line sensor, and is provided on the bottom of the mirror box  150  so that the line sensor is exposed to the mirror box  150 . The condenser lens  182  directs subject images which respectively pass through different parts of the photographing lens  120 , to the first separator lens  282  and the second separator lens  283 . The subject images are made incident on the line sensor by the first separator lens  282  and the second separator lens  283 . Thereby, two subject images are made incident on the line sensor. The AF sensor  280  sends the positions of the two subject images incident on the line sensor to the DSP  210 . The DSP  210  determines whether the focusing lens  252  is in the in-focus position when the distance between the two subject images incident on the line sensor is a predetermined distance. If the distance between the two subject images is less than the predetermined value, the focusing lens  252  focuses on the front of a subject (front focus). However, if the distance between the two subject images is greater than the predetermined value, the focusing lens  252  focuses on the rear of a subject (rear focus). Therefore, the DSP  210  calculates the distance of movement of the focusing lens  252  according to the distance between two subject images. 
         [0050]    The AF sensor  280  is provided on the top surface of the AF stage  270  which is a rectangular solid. The AF stage  270  has two stepping motors, an x-direction stage motor  272  and a z-direction stage motor  273 . The drive axes of the x-direction stage motor  272  and the z-direction stage motor  273  are respectively connected to the side of the AF stage  270 , so that the motors drive the AF stage  270  in the X and Z directions. The x-direction stage motor  272  and the z-direction stage motor  273  are connected to the AF stage driver  271  through a flexible cable. 
         [0051]    An x-stage  279  is provided on the AF stationary platform  275  so as to be freely movable in the X direction. A z-stage  278  is provided on the X stage  279  so as to be freely movable in the Z direction. Two cylindrical z-direction AF guide rods  277  that extend along the Z direction are connected to the x-stage  279 . Two cylindrical x-direction AF guide rods  276  that extend along the X direction are connected to the z-stage  278 . 
         [0052]    The AF stage  270  comprises four guide holes so that it can slidably engage with the x-direction AF guide rods  276  and y-direction AF guide rods  277 . Two guide holes extend along the X direction while maintaining a constant distance between each other in the Z direction. The other two guide holes extend along the Y direction while maintaining a constant distance between each other in the X direction. The x-direction AF guide rods  276  and the y-direction AF guide rods  277  are inserted into these guide holes. Thereby, the x-direction AF guide rods  276  and the y-direction AF guide rods  277  guide the AF stage  270  when it moves in the X and Z directions. The AF stage  270  is freely movable in the X direction and the Z direction by the workings of the x-direction stage motor  272 , y-direction stage motor  273 , x-direction AF guide  276 , and the z-direction AF guide  277 . 
         [0053]    The AF stage driver  271  is connected to the DSP  210 , and applies voltage to the x-direction stage motor  272  and the z-direction stage motor  273  based on a signal received from the DSP  210 . Thereby, the AF stage  270  is repositioned with respect to the AF stationary platform  275  in the X and Z directions. 
         [0054]    The shake reduction operation of the AF sensor  280  is carried out with these parts as described hereinafter. When the digital camera  100  moves, the DSP  210  receives the x-direction angular velocity and the y-direction angular velocity from the x-direction sensor  221  and the y-direction sensor  222 . The plus and minus directions for the X axis of a subject image provided on the AF stage  270  correspond to the plus and minus directions of the X axis of the imaging sensor  231 . The plus and minus directions for the Z axis of a subject image provided on the AF stage  270  correspond to the plus and minus directions of the Y axis of the imaging sensor  231 . The DSP  210  calculates the x-direction coordinate and z-direction coordinate of the position of the AF stage  270  on the basis of the X-direction angular velocity and the Y-direction angular velocity, and sends the x-direction coordinate and z-direction coordinate of the position to the AF stage driver  271 . The AF stage driver  271  calculates the voltages to be applied to the x-direction stage motor  272  and the z-direction stage motor  273  based on the x- and z-direction position coordinates, and then applies the voltages to the x-direction stage motor  272  and the z-direction stage motor  273 . Thereby, the AF stage  270  is repositioned with respect to the AF stationary platform  275  in the X direction and the Z direction so that the movement of the digital camera  100  is cancelled out. By repeating these processes every one millisecond, the effects of shaking on the AF sensor  280  are reduced. Note that the shake reduction process for the AF sensor  280  is carried out when the photographing lens  120  focuses on a subject, i.e., before the digital camera  100  photographs a subject. 
         [0055]    According to this embodiment, the digital camera  100  can focus on a subject in a stable manner even if the digital camera  100  is shaking. 
         [0056]    Note that the shake reduction operation for the imaging sensor  231  may be carried out by the DSP  210  moving the AF area  235  relative to the imaging area  234 . In this case, a contrast AF process that moves the focusing lens  252  to the position that provides the highest contrast with respect to the subject image incident on the imaging sensor  231  may be used. The x-direction angular velocity and the y-direction angular velocity caused by movement of the digital camera  100  are measured by the x-direction sensor  221  and the y-direction sensor  222 . Then, the x-direction angular velocity and y-direction angular velocity are input to the DSP  210 . The DSP  210  receiving the x-direction angular velocity and the y-direction angular velocity calculates the distance of movement for the AF area  235  based on the x- and y-direction angular velocities. Then, according to the calculated distance of movement, the DSP  210  moves the AF area  235  relative to the imaging area  234 . The AF area  235  is moved relative to the imaging area  234  in the X and Y directions so that the effects of the digital camera  100  movements are cancelled out. Therefore, the contrast AF process can be carried out to mitigate the influence of shake on the digital camera  100 . 
         [0057]    The movable part  241  may comprise two driving coils, and a driving magnet may be provided on the stationary platform  245 , so that the movable part  241  can be repositioned with respect to the stationary platform  245 . In this case, an x-direction driving coil that drives the movable part  241  in the X direction, and a y-direction driving coil that drives the movable part  241  in the Y direction may be provided in the movable part  241 . The x-direction driving coil and the y-direction driving coil are connected to the sensor stage driver  248  through a flexible cable. The stationary platform  245  has an x-direction driving magnet and y-direction driving magnet. The x-direction driving magnet is provided in a magnetic field that is generated by the x-direction driving coil. The y-direction driving magnet is provided in a magnetic field that is generated by the y-direction driving coil. The stationary platform  245  supports the movable part  241  so that it can move freely in the X and Y directions. The sensor stage driver  248  is connected to the DSP  210 , and applies voltage to the x-direction driving coil and y-direction driving coil based on a signal received from the DSP  210 . Thereby, the movable part  241  moves relative to the stationary platform  245 . 
         [0058]    Two driving coils may be provided in the AF stage  270  and a driving magnet may be provided on the AF stationary platform  275 , so that the AF stage  270  can be repositioned relative to the stationary platform  245 . In this case, an x-direction driving coil that drives the AF stage  270  in the X direction and a z-direction driving coil that drives the AF stage  270  in the Z direction may be provided in the AF stage  270 . The x-direction driving coil and the z-direction driving coil are connected to the AF stage driver  271  through a flexible cable. The AF stationary platform  275  has an x-direction driving magnet and y-direction driving magnet. The x-direction driving magnet is provided in a magnetic field that is generated by the x-direction driving coil. The z-direction driving magnet is provided in a magnetic field that is generated by the z-direction driving coil. The AF stationary platform  275  supports the AF stage  270  so that it is freely movable in the X and Z directions. The AF stage driver  271  is connected to the DSP  210 , and applies voltage to the x-direction driving coil and z-direction driving coil based on a signal received from the DSP  210 . Thereby, the AF stage  270  moves relative to the AF stationary platform  275 . 
         [0059]    A second embodiment is described hereinafter with reference to  FIG. 6 . The constructions similar to those in the first embodiment are numbered the same and their explanations have been omitted. 
         [0060]    In this embodiment, the AF sensor  280  and the imaging sensor  231  are provided on the sheet-shaped AF stage plate  370 . The AF stage plate  370  forms a 90-degree angle from the bottom surface of the mirror box  150  to the side surface. The AF sensor  280  is provided on a part of the AF stage plate  370  located on the bottom surface of the mirror box  150 . The imaging sensor  231  is provided on a part of the AF stage plate  370  that is located on the side surface of the mirror box  150 . In the AF stage plate  370 , a flexible part is provided between the part on which the imaging sensor  231  is provided and the part on which the AF sensor  280  is provided, i.e., at the angled part or crease of the AF stage plate  370 . 
         [0061]    An AF stage stationary platform  375  is provided on the bottom surface of the mirror box  150 . The AF stage plate  370  is positioned on the top surface of the AF stage stationary platform  375 , i.e., the surface facing the return mirror  262  so as to be able to slide with the AF stage stationary platform  375 . A z-direction guide  376 , a first x-direction guide  377 , and a second x-direction guide  378  are provided on the top surface of the AF stage stationary platform  375  to restrict the movement of the AF stage plate  370  so that the movement of the AF stage plate  370  is restricted to a predetermined area. The z-direction guide  376 , the first x-direction guide  377 , and the second x-direction guide  378  have step-shaped cross-sections. One of their ends is fixed to the top of the AF stage stationary platform  375 . Their other ends are positioned slightly away from the top surface of the AF stage stationary platform  375  so that they create a space that is slightly wider than the thickness of the AF stage plate  370 . The AF stage plate  370  can slide between these other ends and the AF stage stationary platform  375 . 
         [0062]    The z-direction guide  376  prevents the AF stage plate  370  from moving away from the AF stage stationary platform  375 , and restricts the movable area of the AF stage plate  370  in the Z direction. 
         [0063]    The first x-direction guide  377  and the second x-direction guide  378  prevent that the AF stage plate  370  from moving away from the AF stage stationary platform  375 , and restrict the movable area of the AF stage plate  370  in the X direction. 
         [0064]    The angled part of the AF stage plate  370  is positioned between a first roller guide  381  and a second roller guide  384 . The first roller guide  381  and the second roller guide  384  are rotatable around each axis according to the movement of the AF stage plate  370 . A clearance that is slightly wider than the thickness of the AF stage plate  370  is provided between the first roller guide  381  and the second roller guide  384 . The AF stage plate  370  can slide in the X direction with the first roller guide  381  and the second roller guide  384 . 
         [0065]    The center of the AF sensor  280  and the imaging sensor  231  is positioned on the surface that passes through the center of the AF stage plate  370  in the X direction. 
         [0066]    When the x-direction motor  242  rotates in the positive direction, the movable part  241  moves along the X-axis in the positive direction. The AF stage plate  370  moves in the positive direction along the X axis with the movable part  241 , because it is fixed to the movable part  241 . Then, the AF sensor  280  provided on the AF stage plate  370  moves in the positive direction along the X axis. When the x-direction motor  242  rotates in the negative direction, the movable part  241  moves along the X axis in the negative direction, and the AF sensor  280  provided on the AF stage plate  370  moves in the negative direction along the X axis. 
         [0067]    When the y-direction motor  243  rotates in the positive direction, the movable part  241  moves in the positive direction along the Y axis. The end of the AF stage plate  370  moves in the positive direction along the Y axis with the movable part  241 , because the end of the AF stage plate  370  is fixed to the movable part  241 . The angled part of the AF stage plate  370  rotates about the first roller guide  381  and the second roller guide  384  and moves towards the bottom side of the mirror box  150 . The other end of the AF stage  270  that is near the bottom surface of the mirror box  150  moves along the Z axis in the positive direction. Thereby, the AF sensor  280  provided on the AF stage plate  370  moves along the Z axis in the positive direction. When the y-direction motor  243  rotates in the negative direction, the movable part  241  moves along the Y axis in the negative direction, and the AF sensor  280  provided on the AF stage plate  370  moves along the Z axis in the negative direction. 
         [0068]    Due to the construction of the return mirror  262  and the auxiliary mirror  264 , the reduction in shake of the imaging sensor  231  in the vertical direction is opposite to the direction of the reduction of shake of the AF sensor  280  in the vertical direction. However, because the shake reduction process for the AF sensor  280  is carried out when the photographing lens  120  focuses on a subject, i.e., before photographing, and the shake reduction process for the imaging sensor  231  is carried out when the digital camera  100  photographs a subject, these shake reduction processes are not carried out at the same time and therefore do not interrupt each other. 
         [0069]    According to the embodiment, the effect of a shake is easily reduced without increasing the number of driving parts because the effect of the shake on the imaging sensor  231  and the AF sensor  280  is reduces by the same parts. 
         [0070]    Note that the AF sensor  280  may be provided on the AF stage plate  370  so as to face in the same direction as the imaging sensor  231 . In this case, the AF stage plate  370  is not angled and does not have elastic properties. A light reflected by the auxiliary mirror  264  is directed toward the AF sensor  280  by a third mirror. The direction of reducing the effect of shake on the imaging sensor  231  in the vertical direction is the same as the direction for reducing the effect of shake on the AF sensor  280  in the vertical direction. 
         [0071]    The focusing lens  252  may not be moved to a focusing position based on a signal from the AF sensor  280 , but the focusing position of the contrast AF process may be in such a position to provide the highest contrast with respect to a subject image incident on the imaging sensor  231 . In this case, the effects of shake on the imaging sensor  231  or the AF area  235  may be reduced. 
         [0072]    Moreover, the focusing position of the focusing lens  252  may be determined based on a signal from the AF sensor  280  and the imaging sensor  231 . The effects of shake on the AF sensor  280 , the imaging sensor  231  the AF area  235  are reduced. The focusing lens  252  is moved to a nearby focusing position based on a signal from the AF sensor  280 , then, the focusing lens  252  is moved to a precise focusing position based on a signal from the imaging sensor  231  or the AF area  235 . 
         [0073]    The shake-detecting part may not be an angular velocity sensor  220 , it may instead be a different device that can detect shake, e.g. an acceleration sensor. 
         [0074]    Although the embodiment of the present invention has been described herein with reference to the accompanying drawings, obviously many modifications and changes may be made by those skilled in the art without departing from the scope of the invention. 
         [0075]    The present disclosure relates to subject matter contained in Japanese Patent Application No. 2009-037355 (filed on Feb. 20, 2009), which is expressly incorporated herein, by reference, in its entirety.