Patent Publication Number: US-2005129392-A1

Title: Image blur correction apparatus and optical apparatus

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to an image blur correction apparatus which is mounted on an optical apparatus such as a camera to correct image blur.  
      2. Related Background Art  
      In a camera, nowadays, since operations such as exposure determination and focusing important for photographing are all automated, a possibility that those unskilled in camera operation will fail in photographing has greatly been reduced. Additionally, studies have recently been conducted on a system which corrects image blurs caused by hand shakes applied to the camera. Accordingly, there are now almost no factors to cause photographers to fail in photographing.  
      Now, the system that corrects image blurs caused by hand shakes will be described briefly. A hand shake of the camera during photographing is normally a vibration with a frequency 1 Hz to 12 Hz. To enable photographing free of image blur even when the hand shake occurs at the time of shutter release operation, a camera shake (i.e., acceleration, a speed, or the like) due to the hand shake must first be detected accurately. Then, an optical axis change caused by the camera shake needs to be corrected by displacing a correction lens in accordance with a result of the detection.  
       FIG. 5  is a perspective view showing a schematic configuration of a conventional system for correcting image blurs (image blur correction apparatus including a correction optical unit, a vibration detection sensor, and the like), i.e., the system that corrects image blues caused by a camera vertical vibration indicated by an arrow  81   p  in  FIG. 5  and a camera horizontal vibration indicated by an arrow  81   y  (see Japanese Patent Application Laid-Open No. 5-215992).  
      Specifically, according to the conventional system, a correction optical device  85  (including coils  87   p ,  87   y  for applying thrusts to a correction lens, and position detection elements  86   p ,  86   y  for detecting a position of the correction lens) is driven toward outputs of vibration detection sensors  83   y ,  83   p  for detecting the vertical and horizontal vibration of the camera, respectively, (vibration detection directions are indicated by arrows  84   p ,  84   y ) as target values to correct image blurs on an image plane  88 .  
       FIG. 6  is a conceptual block diagram illustrating conventional image blur correction control.  
      In  FIG. 6 , when a target positional signal (vibration signal) dIN is input, force factors K containing amplification gains are integrated by an operation unit, and a result is output as a driving signal F to drive the correction optical system to a target position to the correction optical device. When the correction optical system is driven by the driving signal F, a mechanical integration operation in the correction optical device generates an acceleration signal a, a speed signal v, and a displacement signal dOUT.  
      In the correction optical device, a viscous force C corresponding to a frictional force and a speed is reversed and input to an addition point P 2  to form a feedback loop. In the operation unit, the displacement signal dOUT is reversed and input to an addition point P 1  to form a feedback loop. In other words, it is possible to change driving characteristic of the correction optical system by changing the amplification gain to change the force factor K and changing the driving signal F.  
      Now, from the conceptual block diagram of  FIG. 6 , a gain (amplitude ratio of the output signal dOUT to the input signal dIN) and a phase (phase delay of the output signal dOUT to the input signal dIN) are represented by the following equations.  
               Gain   :          G   ⁡     (     j   ⁢           ⁢   ω     )              =     K           (     K   -     m   ⁢           ⁢     ω   2         )     2     +       (     C   ⁢           ⁢   ω     )     2                   (   1   )                 Phase   :     ∠G   ⁡     (     j   ⁢           ⁢   ω     )         =       tan     -   1       ⁢         -   C     ⁢           ⁢   ω       K   -     m   ⁢           ⁢     ω   2                     (   2   )             
 
      As apparent from the equations (1) and (2), a gain becomes smaller and a phase delay becomes larger as the viscous force C corresponding to the frictional force and the speed in the correction optical device become larger. Additionally, when an amplification gain is increased to increase the force factor K, a resonance frequency is shifted toward a high frequency side, a gain becomes larger, and a phase delay becomes small. In other words, driving characteristic is improved.  
       FIGS. 7A and 7B  are diagrams illustrating characteristics of the conventional image blur correction apparatus in which  FIG. 7A  shows a gain (amplitude ratio of the output signal dOUT to the input signal dIN), and  FIG. 7B  shows a phase (phase delay of the output signal dOUT with respect to the input signal dIN).  
      In  FIG. 7A , reference numeral  101  denotes gain characteristic when the image blur correction apparatus is in a horizontal state (state in which a gravity direction is orthogonal to an optical axis), and reference numeral  102  denotes gain characteristic when the image blur correction apparatus is in an upward facing state (state in which a gravity direction is the same as an optical axial direction). In  FIG. 7B , reference numeral  103  denotes phase characteristic when the image blur correction apparatus is in the horizontal state, and reference numeral  104  denotes phase characteristic when the image blur correction apparatus is in the upward facing state.  
      As apparent from the drawings, driving characteristic is worse in the upward facing state of the image blur correction apparatus than those in the horizontal state.  
      That is, in the upward facing state of the image blur correction apparatus, a frictional force between a support pin for supporting the correction optical system and a member engaged with the support pin is increased. Thus, a force (viscous force C) reversed to a driving force and input in the correction optical system is increased. Thus, as apparent from the equations (1) and (2), driving characteristic of the correction optical system is deteriorated.  
      Accordingly, to improve the driving characteristic, the amplification gain may be increased to increase the driving force applied to the correction optical device.  
       FIGS. 8A and 8B  are diagrams illustrating characteristics of a gain (amplitude ratio of the output signal dOUT to the input signal dIN) ( FIG. 8A ) and characteristics of a phase (phase delay of the output signal dOUT with respect to the input signal dIN) ( FIG. 8B ) when amplification gains are uniformly increased in the horizontal state of the image blur correction apparatus.  
      In  FIG. 8A , gain characteristic denoted by reference numeral  101  are equivalent to the gain characteristic of  FIG. 7A , and reference numeral  105  denotes gain characteristic when the amplification gain is increased in the horizontal state of the image blur correction apparatus. In  FIG. 8B , phase characteristic denoted by reference numeral  103  are equivalent to the phase characteristic of  FIG. 7B , and reference numeral  106  denotes phase characteristic when the amplification gain is increased in the horizontal state of the image blur correction apparatus.  
      As apparent from the drawings, irrespective of whether the image blur correction apparatus is in the horizontal state or upward facing state, when the amplification gain is increased, in the horizontal state in which the frictional force is small between the support pin for supporting the correction optical system and the member engaged with the support pin, the force factor K is increased while a term C of the frictional force is small as can be understood from the equations (1) and (2). Thus, the resonance frequency is shifted toward the high frequency side, and a peak of a gain in a resonance frequency band becomes excessively high, causing a problem of oscillation.  
     SUMMARY OF THE INVENTION  
      It is therefore an object of the present invention to provide an image blur correction apparatus which can improve driving characteristic of a correction optical system in a hand shake frequency domain irrespective of a direction in which a force of gravity is applied.  
      According to one aspect of the invention, an image blur correction apparatus for correcting an image blur caused by a vibration by driving an optical element, includes: a vibration detector for detecting the vibration; a diving mechanism for driving the optical element; a controller for controlling the driving mechanism based on an output of the vibration detector; and a posture detector for detecting a posture of the apparatus, in which the controller changes a driving characteristic of the driving mechanism in accordance with an output of the posture detector.  
      In further aspect of the invention in the image blur correction apparatus, the posture detector detects the posture of the apparatus in a gravity direction.  
      In further aspect of the invention in the image blur correction apparatus, the controller generates a driving signal for driving the driving mechanism based on a vibration signal obtained from the output of the vibration detector and amplification gain data, and changes a value of the amplification gain data in accordance with the output of the posture detector.  
      In further aspect of the invention in the image blur correction apparatus, the controller increases a value of amplification gain data as a resistance force generated in the driving mechanism against driving of the optical element is larger with respect to the output of the posture detector.  
      In further aspect of the invention in the image blur correction apparatus, the apparatus further includes a memory which stores an amplification gain value according to the posture of the apparatus, and the controller reads the amplification gain value according to the output of the posture detector from the memory.  
      In further aspect of the invention in the optical apparatus for correcting an image blur caused by a vibration by driving an optical element, the apparatus further includes: a driving mechanism which drives the optical element; a controller which controls the driving mechanism based on an output of a vibration detector which detects the vibration; and a posture detector which detects a posture of the optical apparatus, and the controller changes a driving characteristic of the driving mechanism in accordance with an output of the posture detector.  
      Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.  
       FIG. 1  is a block diagram showing circuitry of an interchangeable lens and a camera on which an image blur correction apparatus according to a first embodiment of the invention is mounted;  
       FIG. 2  is comprised of  FIGS. 2A and 2B  showing flowcharts illustrating a series of operations in a camera system according to the first embodiment of the present invention;  
       FIGS. 3A and 3B  are diagrams illustrating characteristics of the image blur correction apparatus according to the first embodiment of the present invention;  
       FIG. 4  is a sectional view showing a schematic configuration of a correction optical unit;  
       FIG. 5  is a perspective view showing a schematic configuration of a conventional image blur correction system;  
       FIG. 6  is a conceptual block diagram of conventional image blur correction control;  
       FIGS. 7A and 7B  are diagrams illustrating characteristics of a conventional image blur correction apparatus;  
       FIGS. 8A and 8B  are diagrams illustrating characteristics when amplification gains are uniformly increased in the conventional image blur correction apparatus;  
       FIG. 9  is a view showing a structure of an acceleration sensor for detecting a gravity direction according to the first embodiment of the present invention; and  
       FIG. 10  is a view showing a relation between a detection axis of the acceleration sensor and a force of gravity. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      Next, preferred embodiments of the present invention will be described.  
     First Embodiment  
       FIG. 1  is a block diagram showing circuitry of a camera system which includes an interchangeable lens, on which an image blur correction apparatus of a first embodiment of the invention is mounted, and a camera having the interchangeable lens detachably attached thereto.  FIGS. 2A and 2B  are flowcharts showing a series of operations (photographing operations) in the camera system of this embodiment.  FIGS. 3A and 3B  are diagrams illustrating characteristics of the image blur correction apparatus of this embodiment.  
      In  FIG. 1 , reference numeral  200  denotes a camera, and  300  denotes an interchangeable lens. First, a configuration of the camera  200  will be described.  
      Reference numeral  201  denotes a camera CPU constituted by a microcomputer. As described later, the camera CPU  201  controls operations of various circuits integrated in the camera  200 , and communicates with a lens CPU  301  through a camera contact group  202  when the interchangeable lens  300  is mounted on the camera  200 .  
      The camera contact group  202  includes a signal transmission contact  202   a  for transmitting and receiving a signal to and from the interchangeable lens  300 , a power supply contact  202   b  for supplying power from a power source  209  on the camera  200  side to the interchangeable lens  300  side, and a ground contact  202   c  connected to the interchangeable lens  300  side and grounded.  
      Reference numeral  203  denotes a power supply switch operable from the outside. When the power supply switch  203  is switched on, the camera CPU  201  is started to supply power to actuators, sensors, circuits, and the like in the camera system, whereby the camera system becomes operable.  
      Reference numeral  204  is a 2-stage stroke type releasing operation member operable from the outside, and an output signal thereof is input to the camera CPU  201 .  
      The camera CPU  201  carries out a photographing preparation operation when a switch SW 1  that responds to a first stroke operation of the releasing operation member  204  is ON. For the photographing preparation operation, for example, the camera CPU  201  controls driving of a photometric circuit  205  to measure a luminance of a subject, and calculates an exposure value based on a result of the measurement. The camera CPU  201  controls driving of a focus detection circuit  208  (described later) to detect a focus adjustment state of a photographing optical system, and controls driving of a focusing lens disposed in the interchangeable lens  300  based on a result of the detection to set the photographing optical system in a focused state.  
      On the other hand, when a switch SW 2  that responds to a second stroke operation is switched on, the camera CPU  201  transmits a signal regarding an aperture stop operation command (described later) to the lens CPU  301  (the lens that controls operations of various circuits and units disposed in the interchangeable lens  300  and communicates with the camera CPU  201  through a lens contact group  302  when the interchangeable lens  300  is mounted on the camera  200 ) in the interchangeable lens  300 . The camera CPU  201  transmits a signal regarding an exposure starting command (i.e., a shutter speed or the like) to an exposure circuit  206  to execute an exposure operation (exposure to a film by an opening/closing operation of a shutter (not shown)). Upon reception of an exposure end signal from the exposure circuit  206 , the camera CPU  201  transmits a feed starting command to a feeding circuit  207  to wind the film by one frame.  
      This embodiment has been described by way of the camera  200  which uses the film. In place of the film, however, an imaging device such as a CCD or a CMOS image sensor can be used.  
      Reference numeral  208  is a focus detection circuit. The focus detection circuit  208  detects a focus adjustment state of the photographing optical system with respect to the subject corresponding to a focus detection area disposed in a photographing screen in accordance with the focus detection starting command sent from the camera CPU  201  when the switch SW 1  is switched on, and determines a moving amount of the focusing lens necessary for setting the photographing optical system in a focused state based on a result of the detection. Information regarding the moving amount of the focusing lens is transmitted to the camera CPU  201 .  
      Next, a configuration of the interchangeable lens  300  will be described.  
      Reference numeral  302  is a lens contact group disposed in the interchangeable lens  300 . The lens contact group  300  includes a signal transmission contact  302   a  for transmitting and receiving a signal to and from the camera  200 , a power supply contact  302   b  for receiving power from the camera  200  side, and a ground contact  302   c  connected to the camera  200  side and grounded.  
      Reference numeral  303  denotes an IS switch operable from the outside which selects whether an image blur correcting operation (or IS operation) (described later) is executed or not, and can set the IS operation in an ON state.  
      Reference numeral  304  denotes a vibration detection unit (vibration detection means). The vibration detection unit  304  includes a vibration detection portion  304   a  which detects a vertical vibration (vibration in a pitch direction) and a horizontal vibration (vibration in a yaw direction) of the camera  200  (camera system) as an acceleration, a speed, or the like in accordance with a command from the lens CPU  301 , and an operation output portion  304   b  which outputs a vibration signal indicating a displacement obtained by electrically and mechanically integrating an output signal of the vibration detection portion  304   a  to the lens CPU  301 .  
      Reference numeral  305  denotes a posture sensor (posture detection means) which consists of, for example, an acceleration sensor, and detects a gravity direction of the camera (camera system). The posture sensor  305  detects the gravity direction of the camera in accordance with a command from the lens CPU  301 , and outputs a result thereof to the lens CPU  301 . A method of detecting a posture by the acceleration sensor will be described later with reference to  FIGS. 9 and 10 .  
      Reference numeral  306  denotes an amplification gain variable circuit. The amplification gain variable circuit  306  reads an amplification gain value corresponding to a gravity detection value (output of the posture sensor  305 ) from an amplification gain table prestored in a memory  301   a  of the lens CPU  301 , and sets this value as an amplification gain in a force factor when generating a driving signal input to a correction optical unit  307  ( FIG. 6 ).  
      According to this embodiment, the memory  301   a  is incorporated in the lens CPU  301 . However, the memory  301   a  may be disposed separately from the lens CPU  301 . According to this embodiment, the amplification gain value corresponding to the gravity detection value is read from the amplification gain table prestored in the memory  301   a . However, an amplification gain value corresponding to the gravity detection value may be obtained therefrom by calculation. However, the processing speed can be increased by reading the amplification gain value corresponding to the gravity detection value from the amplification gain table.  
      A controller  310  equivalent to control means described in the claims is constituted by the lens CPU  301  and the amplification gain variable circuit  306 .  
      Reference numeral  307  denotes a correction optical unit. As shown in  FIG. 4 , the correction optical unit  307  includes a correction lens L, a support frame  1 , and permanent magnets  7  and  8 , yokes  0 . 5  and  6 , and a coil  2  for driving the correction lens L in pitch and yaw directions. Now, a configuration of the correction optical unit  307  will be descried with reference to  FIG. 4 .  FIG. 4  is a sectional view showing a schematic configuration of the correction optical unit  307 .  
      Referring to  FIG. 4 , symbol L denotes a correction lens (optical element) arranged in the photographing optical system. Reference numeral  1  denotes the support frame for supporting the correction lens L, and the coil  2  is fixed to the support frame  1  through adhesion or the like. In the support frame  1 , for example, support pins  3  are fixed to three positions at equal angular intervals in a circumferential direction of the support frame  1  by a fixing method such as press fitting.  
      Each support pin  3  is engaged with a cam hole  4   a  formed in a base board  4  (described later) to prevent displacement of a unit constituted by the correction lens L, the support frame  1 , and the coil  2  in an optical axis direction, and to support the unit to be operable within a plane orthogonal to an optical axis. As it is supported by the support frame  1 , the correction lens L is supported on the base board  4  through the support pins  3  disposed in the support frame  1 . Then, by a driving mechanism constituted of the permanent magnets  7  and  8 , the yokes  5  and  6 , and the like, the correction lens L and the support frame  1  are driven in the pitch and yaw directions to correct an image blurs.  
      Reference numeral  4  denotes the base board, on which the yokes  5  and  6  attracted by the permanent magnets  7  and  8  are fixed by screws or the like to surfaces opposed to the coil  2 . Reference numeral  9  denotes a lock ring rotatably supported on the base board  4 . A coil  1   b  is fixed to the lock ring  9  through adhesion or the like.  
      Reference numerals  11   a  and  11   b  denote an adsorption yoke and an adsorption coil which are fixed to the base board  4  by screws or the like. When no power is supplied to the coil  10  and the adsorption coil  11   b , the lock ring  9  is rotated in a direction for locking the support frame  1  spring-biased by a charge spring (not shown). A locking projection portion (not shown) disposed on the lock ring  9  and a locking projection portion of the support frame  1  are engaged with each other, whereby the support frame  1  is locked in position (positioned) with respect to the base board  4 .  
      On the other hand, when power is supplied to the coil  10 , the yokes disposed in the surface opposed to the coil  10  and attracted by permanent magnets (not shown), and the like, the lock ring  9  is rotated in a direction for unlocking the locked state with respect to the support frame  1 , whereby the locking projection portion (not shown) in the lock ring  9  and the locking projection portion of the support frame  1  are disengaged from each other. Thus, the support frame  1  becomes operable.  
      In this case, when power is supplied to the adsorption coil  11   b , the adsorption yoke  11   a  adsorbs a metal piece (not shown) disposed in the lock ring  9 , whereby the lock ring  9  is maintained in an unlocked state.  
      Reference numeral  12  denotes a printed board, on which a PSD for detecting a position of the correction lens L and various electric elements are mounted.  
      Referring to  FIG. 1 , reference numeral  308  denotes a focusing unit. The focusing unit  308  includes a focusing lens  308   b  movable in the optical axis direction, and a control circuit  308   a  which controls driving of the focusing lens  308   b  based on an output (corresponding to the moving amount of the focusing lens sent from the camera CPU  201 ) of the lens CPU  301 .  
      Reference numeral  309  denotes a stop unit. The stop unit  309  includes a stop member  309   b  which forms an opening area of light passage in the interchangeable lens  300 , and a control circuit  309   a  which controls driving of the stop member  309   b  based on an output (corresponding to stop information sent from the camera CPU  201 ) of the lens CPU  301 .  
      Next, an operation of the camera system of this embodiment (operations of the camera CPU  201  and the lens CPU  301 ) will be described with reference to the flowchart of  FIG. 2 .  
      First, in a step S 5001 , the camera CPU  201  judges whether the power supply switch  203  is on or not. If the result shows that the power supply switch  203  is on, power is supplied from the power source  209  of the camera  200  to the electric components in the camera  200  and to the interchangeable lens  300 , and communication is started between the camera  200  and the interchangeable lens  300 .  
      In this case, when a new battery is mounted on the camera  200  or when the interchangeable lens  300  is mounted on the camera  200 , power is supplied from the power source  209  of the camera  200  to the interchangeable lens  300 , and communication is started between the camera  200  and the interchangeable lens  300 .  
      Upon the start of the communication between the camera  200  and the interchangeable lens  300  as described above, in a step S 5002 , the camera CPU  201  stands by until the switch SW 1  becomes on by the first stroke of the releasing operation member  204 , and proceeds to a step S 5003  after the switch SW 1  switched on.  
      In the step S 5003 , the lens CPU  301  judges whether the IS switch  303  is on (IS operation selected) or not. If the IS operation has been selected, the process proceeds to a step S 5004 . If the IS operation has not been selected, the process proceeds to a step S 5020 .  
      In the step S 5004 , the lens CPU  301  starts an internal timer. In a step S 5005 , a gravity direction of the camera system is detected through the posture sensor  305 .  
      In a step S 5006 , an amplification gain is determined based on the gravity direction obtained in the step S 5005 . Specifically, based on the output (gravity detection value) of the posture sensor  305 , an amplification gain value corresponding to the gravity detection value is read from the amplification gain table prestored in the memory  301   a  of the lens CPU  301 , and this value is set as an amplification gain in a force factor when generating a driving signal input to the correction optical unit  307 .  
      In other words, as the influence of a force of gravity applied on the correction optical unit  307  is increased (e.g., when the camera system is shifted from the horizontal state to the upward facing state), an amplification gain is increased stepwise, and a driving force of the correction optical unit  307  is increased stepwise. Thus, according to this embodiment, the amplification gain is increased stepwise in accordance with the influence of the force of gravity applied on the correction optical unit  307 , whereby it is possible to prevent an increase of a gain peak value which occurs when amplification gains are uniformly increased as in the conventional case. Furthermore, by stepwise increasing the amplification gain in accordance with the influence of the force of gravity, gain characteristic and phase characteristic can be obtained in accordance with the influence of the force of gravity, and good driving characteristics can be obtained.  
      In a step S 5007 , the camera CPU  201  drives the photometric circuit  205  and the focus detection circuit  208  to obtain photometric information and focus adjustment information of the photographing optical system. The lens CPU  301  communicates with the camera CPU  201  to receive the focus adjustment information described above, and drives the focusing unit  308  based on the focus adjustment information to execute a focusing operation.  
      Further, the lens CPU  301  starts vibration detection for the camera system through the vibration detection unit  304 . The lens CPU  301  also drives the correction optical unit  307 , making it ready for the shake operation. In other words, the engagement between the lock ring  9  and the support frame  1  is released by supplying power to the coil  10  and the adsorption coil  11   b  as shown in  FIG. 4 , whereby the correction lens L becomes operable within the plane orthogonal to the optical axis.  
      In a step S 5008 , the lens CPU  301  judges whether the time clocked by the timer has reached a predetermined time T 1  or not, and stands by in this step until the time T 1  is reached. This is for the purpose of securing a time until an output of the vibration detection unit  304  is stabilized.  
      After a passage of the predetermined time T 1 , in a step S 5009 , based on a target value signal from the output of the vibration detection unit  304  (operation output portion  304   b ) and an output of the position detection sensor (PSD or the like described above) disposed in the correction optical unit  307 , the lens CPU  301  starts control of driving of the correction optical unit  307  within a current value range set for each driving direction (pitch direction or yaw direction) by the amplification gain variable circuit  306 , i.e., shake correction control by driving of the correction lens L.  
      In a step S 5010 , the camera CPU  201  judges whether the switch SW 2  that responds to the second stroke operation of the releasing operation member  204  is on or not. The process proceeds to a step S 5011  if the switch SW 2  is in an on state, and to a step S 5012  if it is in an off state.  
      In the step S 5011 , the lens CPU  301  controls driving of the stop unit  309  to set the diameter of an opening formed by the stop member  309   b , and the camera CPU  201  controls driving of the exposure circuit  206  to execute an exposure operation on a film. Incidentally, in the case of using an imaging device, the light of a subject is received by the imaging device, electric charges corresponding to the amount of the received light are stored, and then the stored electric charges are read. The read signal is subjected to predetermined processing (e.g., color processing) by a signal processing circuit disposed in the camera  200 , and displayed as a photographed image in a display portion disposed in the camera  200 , or recorded in a recording medium.  
      In this case, during the exposure operation of the step S 5011 , the correction lens L moves in the plane orthogonal to the optical axis in the shake correction optical unit  307 , whereby an image blurs caused by a vibration applied to the camera system is corrected.  
      In the step S 5012 , judgment is made again as to whether the switch SW 1  is on or not. The process returns to the step S 5010  if the switch SW 1  is in an on state, and to a step S 5013  if it is in an off state.  
      In the step S 5013 , the lens CPU  301  stops the shake correction control. In a step S 5014 , the power supplied to the coil  10  and the adsorption coil  11  is cut off to engage the lock ring  9  with the support frame  1 , and to hold the correction lens L of the correction optical unit  307  in a predetermined position (optical axis center position).  
      Upon completion of the exposure operation in the aforementioned manner, in the step S 5012 , the camera CPU  201  judges an on/off state of the switch SW 1 , and the process proceeds to the step S 5013  if the switch SW 1  is off as described above. Then, the lens CPU  301  stops the shake correction control. In the step S 5014 , the power supplied to the coil  10  and the adsorption coil  11  is cut off to hold the correction optical unit  307  (correction lens L) in the predetermined position (optical axis center position).  
      After the end of the foregoing operation, the process proceeds to a step S 5015 , in which the lens CPU  301  resets the internal timer to start the operation again. In steps S 5016  and S 5017 , judgment is made as to whether the switch SW 1  becomes on again or not within a predetermined time T 2 . If the switch SW 1  becomes on again within the predetermined time T 2  after the stop of the shake correction, the process proceeds to a step S 5018 .  
      In the step S 5018 , the camera CPU  201  controls driving of the photometric circuit  205  to detect a luminance of the subject, and controls driving of the focus detection circuit  208  to detect a focus adjustment state of the photographing optical system. The lens CPU  301  controls driving of the driving circuit  308   a  of the focusing unit  308  based on a command from the camera CPU  201  to move the focusing lens  308   b  to a predetermined focusing position. Further, the lens CPU  301  controls driving of the correction optical unit  307  to unlock the correction lens L as described above.  
      In this case, since the vibration detection by the vibration detection unit  304  continues, the process proceeds to the step S 5009  to immediately drive the correction lens L based on a target value signal and an output (data regarding a current position of the correction lens L) of the position detection sensor, thereby starting the shake correction operation again. Thereafter, an operation similar to the above is repeated.  
      By the aforementioned process, when the switch SW 1  becomes on again after it becomes off from on by photographer&#39;s operation of the releasing operation member  204 , the vibration detection unit  304  is started each time the switch SW 1  becomes on. Accordingly, it is possible to eliminate the problem in that the process must stand by until the output of the vibration detection unit  304  is stabilized.  
      On the other hand, if the switch SW 1  does not become on within the predetermined time T 2  after the stop of the shake correction operation in the step S 5016 , the process proceeds to a step S 5019  to stop the vibration detection (stop the operation of the vibration detection unit  304 ). Subsequently, the process returns to the step S 5002 , and stand by until the switch SW 1  becomes on.  
      If an IS operation is not selected in the step S 5003 , the process proceeds to a step S 5020 , and the camera CPU  201  executes a photometric operation and detects a focus adjustment state through the photometric circuit  205  and the focus detection circuit  208 . Then, the lens CPU  301  executes a focusing operation to move the focusing lens  308   b  to a focusing position in accordance with a detection result of the focus adjustment state.  
      Then, in a step S 5021 , the camera CPU  201  judges whether the switch SW 2  is on or not. If the switch SW 2  is in an off state, the process proceeds to a step S 5023  to judge whether the switch SW 1  is on or not again. If the switch SW 1  is not on, the process returns to the step S 5002 , and stands by until the switch SW 1  becomes on.  
      On the other hand, if the switch SW 2  is not on in the step S 5021  while the switch SW 1  is on in the step S 5023 , the process returns to the step S 5021 . Then, upon detection of the on state of the switch SW 2  in the step S 5021 , the process proceeds to a step S 5022 , and the lens CPU  301  controls the stop unit  309  (drives the stop member  309   b ), and the camera CPU  201  drives the exposure circuit  206  to execute an exposure operation.  
      Preceding to the step S 5023 , the camera CPU  201  judges an on/off state of the switch SW 1 , and the process returns to the step S 5002  or the step S 5021  based on a result of the judgment.  
      According to the camera system of this embodiment, the aforementioned series of operations are repeated until the power supply switch  203  becomes off. When the switch becomes off, the communication between the camera CPU  201  and the lens CPU  301  is stopped, and the power supply from the camera  200  to the interchangeable lens  300  is stopped.  
       FIGS. 3A and 3B  are diagrams illustrating characteristics of the image blur correction apparatus according to this embodiment:  FIG. 3A  showing a gain (amplitude ratio of the output signal dOUT to the input signal dIN), and  FIG. 3B  showing a phase (phase delay of the output signal dOUT to the input signal dIN).  
      Referring to  FIG. 3A , reference numeral  101  denotes an example of gain characteristic in case of a small influence of a force of gravity applied on the correction optical unit  307 , showing gain characteristic when an amplification gain value corresponding to a gravity detection value is set from the amplification gain table prestored in the memory  301   a  of the lens CPU  301  based on the output (gravity detection value) of the posture sensor  305  in the horizontal state (state in which a gravity direction is a direction A in  FIG. 4 ) of the image blur correction apparatus (camera system).  
      Reference numeral  102  denotes an example of gain characteristic in case of a large influence of a force of gravity applied to the correction optical unit  307 , showing gain characteristic in the case of a conventional amplification gain in the upward facing state (state in which a gravity direction is a direction B in  FIG. 4 ) of the image blur correction apparatus.  
      Reference numeral  107  denotes an example of gain characteristic in case of a large influence of a force of gravity applied to the correction optical unit  307 , showing gain characteristic when amplification gain value corresponding to the gravity detection value is set from the amplification gain table prestored in the memory  301   a  of the lens CPU  301  based on the output (gravity detection value) of the posture sensor  305  in the upward facing state (state in which the gravity direction is the direction B in  FIG. 4 ) of the image blur correction apparatus.  
      Referring to  FIG. 3B , reference numeral  103  denotes an example of phase characteristic in case of a small influence of a force of gravity applied on the correction optical unit  307 , showing phase characteristic when an amplification gain value corresponding to a gravity detection value is set from the amplification gain table prestored in the memory  301   a  of the lens CPU  301  based on the output (gravity detection value) of the posture sensor  305  in the horizontal state (state in which the gravity direction is the direction A in  FIG. 4 ) of the image blur correction apparatus.  
      Reference numeral  104  denotes an example of phase characteristic in case of a large influence of a force of gravity applied to the correction optical unit  307 , showing phase characteristic in the case of a conventional amplification gain in the upward facing state (state in which the gravity direction is the direction B in  FIG. 4 ) of the image blur correction apparatus. Incidentally, characteristic in a downward facing state of the image blur correction apparatus are similar to those in the upward facing state.  
      Reference numeral  108  denotes an example of phase characteristic in case of a large influence of a force of gravity applied to the correction optical unit  307 , showing phase characteristic when amplification gain value corresponding to the gravity detection value is set from the amplification gain table prestored in the memory  301   a  of the lens CPU  301  based on the output (gravity detection value) of the posture sensor  305  in the upward facing state (state in which the gravity direction is the direction B in  FIG. 4 ) of the image blur correction apparatus.  
      As apparent from the drawings, when the amplification gain value corresponding to the gravity detection value is set, a fictional force is increased between the support pins  3  for supporting the correction optical system (correction lens L and support frame  1 ) and the cam hole  4   a  disposed in the base board  4 . Thus, as can be understood from the equations (1) and (2), by increasing a force factor K by an amount corresponding to an increase of a term C of the frictional force, a resonance frequency is shifted toward a high frequency side, and a gain is suppressed. Therefore, driving characteristic of the image blur correction apparatus in a normal use area become similar to those in the case of a small influence of a force of gravity, and good driving characteristics can be obtained.  
       FIG. 9  is a view showing a structure of an acceleration sensor as an example of the posture sensor  305  for detecting a gravity direction.  FIG. 10  is a view showing a relation between a detection axis of the acceleration sensor of  FIG. 9  and a force of gravity. Here, the acceleration sensor is used to detect a posture.  
      According to a principle of the acceleration sensor, generally, a weight is mounted to a sensor base through proper spring and damper systems, and a displacement of the weight with respect to the sensor base is converted into an electric signal. Depending on mechanisms of converting weight displacements into electric signals, there are a piezoelectric method, a dynamic electric method, a photoelectric method, a strain resistance method, a capacitance method, a servo method, and the like. Acceleration sensors of various sizes, structures, and characteristics have conventionally been developed in accordance with application purposes.  
      The acceleration sensor shown in  FIG. 9  is a semiconductor acceleration sensor  401  of a strain resistance type, and manufactured by processing a silicon wafer or the like through a semiconductor process. A weight  402  is supported in cantilever on a frame  404  by a beam  403 . A piezoelectric resistance element  405  is disposed on the beam  403 , and glass substrates  406  and  407  are bonded to both surfaces of the frame  404 . A displacement of the weight  402  is converted into an electric signal by the piezoelectric resistance element  405 , and output from a circuit (not shown).  
      Displacement directions of weights in many acceleration sensors are almost linear, and such a displacement direction is referred to as a detection axis or a maximum sensitivity axis. As long as the detection axis is not arranged to be completely orthogonal to a gravity acceleration direction (arrangement in which the detection axis is horizontal), a DC component by gravity acceleration is output. In other words, when the detection axis of the acceleration sensor  401  is at an angle θ which is not 90° to a direction of a force of gravity G as shown in  FIG. 10 , the acceleration sensor  401  becomes sensitive to a gravity component (Gcosθ) parallel to the detection axis, and a sensor output becomes a DC component corresponding to the angle θ in accordance with tilting of the sensor  401 .  
      By using the acceleration sensor  401 , it is possible to finely detect the posture of the camera (camera system).  
      The configuration of the camera system of this embodiment has been described. However, the present invention is not limited to the configuration of this embodiment, and it is needless to say that configurations capable of achieving functions described in claims and functions of this embodiment can be employed.  
      That is, according to the embodiments described above, the semiconductor acceleration sensor of the strain resistance type is used as the sensor for detecting the gravity direction of the correction optical unit  307 . However, the present invention is not limited to this sensor, and the acceleration sensors of the other types described above can be used. Software and hardware configurations of this embodiment can be properly replaced by others.  
      The present invention can be applied to an optical apparatus such as a single lens reflex camera, a lens shutter camera, or a video camera. Further, the invention according to aspects of the present invention or the configurations of this embodiment may constitute one device as a whole, be separated from/connected to other devices, or be elements which constitute a device. For example, a vibration detection unit may be disposed in the camera, and components of the other shake correction apparatus may be disposed in the interchangeable lens.  
      Additionally, the correction optical system of this embodiment has been described by way of the shift optical system which moves the correction lens L (optical member) in a plane vertical to the optical axis. However, light beam changing means such as a variable apex angle prism for correcting an image blur by changing a titling angle of the prism with respect to an optical axis of optical members positioned in both ends may be used.  
      According to the invention, by changing the driving characteristics (e.g., gain characteristic and phase characteristic) of the driving mechanism in accordance with the output of the posture detection means, it is possible to prevent deterioration of the driving characteristic of the apparatus caused by a uniform increase of the amplification gains irrespective of the posture of the image blur correction apparatus as in the conventional case.  
      In other words, the driving signal for driving the driving mechanism is generated based on the shake signal obtained from the output of the vibration detection means and the amplification gain data, and the value of the amplification gain data is changed according to an output of the posture detection means. Thus, it is possible to obtain good driving characteristic.  
      Specifically, good driving characteristic can be obtained by increasing the value of the amplification gain data as the resistance force generated in the driving mechanism against the driving of the optical element is larger with respect to the output of the posture detection means. When the resistance force is small, the value of the amplification gain data needs not be increased, and it is possible to suppress an increase of a gain peak caused by the increased value of the amplification gain data in the horizontal state (state in which the resistance force is small) of the image blur correction apparatus which occurs in the conventional case.  
      The memory is disposed to store the amplification gain value in accordance with the posture, and the amplification gain value is read from the memory by the control means in accordance with the output of the posture detection means. Thus, it is possible to easily generate a diving signal in accordance with the image blur correction apparatus.  
      As many apparently widely different embodiments of the present invention can be make without departing from the spirit and scope thereof, it is to be understood that the invention is not limited to the specific embodiments thereof except as defined in the claims.  
      This application claims priority from Japanese Patent Application No. 2003-412525 filed Dec. 10, 2003, which is hereby incorporated by reference herein.