Abstract:
The present invention offers a digital still camera capable of simply preventing blurring due to hand shake caused by holding down the shutter button of the digital still camera. When auto focus mode is in operation, the image capture unit  102  captures images of a subject after receiving directions from the control unit  105  to capture the images at predetermined time intervals, and outputs the image data to the control unit  105.  The control unit  105  sequentially stores, in the buffer  103,  the image data input from the image capture unit  102,  and displays the images in the display unit  104.  The control unit  105  reads image data stored most recently in the buffer  103  when a user operation of holding down the shutter button in the operation unit  101  is detected, and displays the image data in the display unit  104  while storing the image data in the image storage unit  106.  This allows to store image data captured right beforehand shake due to the operation of holding down the shutter button is made.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to a digital still camera, in particular to a technology for easily preventing hand shake made when the shutter button of a digital still camera is held down.  
         [0003]     2. Description of the Related Art  
         [0004]     Digital still cameras have gained in popularity immensely in recent years with an increase in resolution, which enables everyone to readily enjoy shooting. However, when beginners capture images, hand shake made when the shutter button is held down often becomes a problem.  
         [0005]     If captured with hand shake, images are blurring when displayed.  
         [0006]     A number of image stabilizing mechanisms have been proposed to eliminate blurring. One of the examples is discussed in Japanese Laid-Open Patent Application Publication No. H5-134287.  
         [0007]     However, to eliminate blurring, it is necessary to predict the amount of shaking and make compensation to thereby set the amount of shaking to “0” by using a complex mechanism.  
       SUMMARY OF THE INVENTION  
       [0008]     The object of the present invention is to offer a digital still camera preventing hand shake and producing images free from blurring without providing a complex mechanism. In addition, the image stabilizing mechanism of the digital still camera of the present invention is distinctly simple, and can therefore be easily applied to a digital still camera built in a mobile phone.  
         [0009]     The above-stated object is achieved by a digital still camera comprising: an operation unit operable to receive operations from the user; a detection unit operable to detect the operations; an image capture unit operable to capture image data pieces of a subject at a predetermined time interval when the detection unit detects a predefined operation; a buffer operable to store therein the image data pieces captured by the image capture unit in order of being captured; a display unit operable to display the image data pieces stored in the buffer; and a control unit operable to cause the display unit to display, from among the image data pieces stored in the buffer, the most recently stored piece when the detection unit detects an operation of holding down a shutter button.  
         [0010]     With such a structure, the present invention is capable of displaying a clear and sharp image free from blurring because, even if a blurring image is produced with hand shake caused when the user holds down the shutter button, it displays image data captured right before the shutter button is held down.  
         [0011]     Here, the minimum length of the predetermined time interval may be defined as the sum of (i) time required to store each piece of the image data pieces captured by the image capture unit into the buffer and (ii) time required to read the piece from the buffer and display the read piece in the display unit.  
         [0012]     With such a structure, the present invention is capable of preparing in advance image data free from blurring with hand shake associated with holding down the shutter button.  
         [0013]     The digital still camera may further comprise: an image data storage unit operable to store therein image data pieces. Here, the predefined operation is to set for auto focus mode. When the detection unit detects the operation of holding down the shutter button, the control unit reads the most recently stored piece displayed by the display unit and causes the image data storage unit to store therein the read most recently stored piece.  
         [0014]     With such a structure, the present invention is capable of providing image data corresponding to holding down the shutter button by using, for example, the auto focus mode set by holding down the shutter button halfway as a trigger.  
         [0015]     The digital still camera may further comprise: a motion detection unit operable to detect a motion of a body of the digital still camera. Here, the predefined operation is to turn on a power supply for starting to capture the image data pieces. If the motion detection unit detects the motion which is equal to or greater than a predetermined value at a moment when the detection unit receiving power supply in advance detects the operation of holding down the shutter button, the control unit causes the display unit to display the most recently stored piece.  
         [0016]     With such a structure, the present invention is capable of starting image capture by using the power supply of the digital still camera being turned on as a trigger, and using image data captured right before holding down the shutter button as image data for holding down the shutter button when the motion equal to or greater than the predetermined value is detected by the motion detection unit.  
         [0017]     Here, the predetermined value may be a value at which the image data pieces captured by the image capture unit become blurred from movements of the digital still camera due to hand shake.  
         [0018]     With such a structure, the present invention is capable of producing clear and sharp image data free from blurring caused by hand shake.  
         [0019]     The buffer may include: a 1st buffer used by the control unit to store therein the image data pieces captured by the image capture unit while sequentially updating; and a 2nd buffer used by the control unit, instead of the 1st buffer, to store therein the image data pieces captured by the image capture unit at a certain time interval when the motion detection unit does not detect the motion equal to or greater than the predetermined value for no less than a fixed period of time. Here, the control unit causes the display unit to display from among the image data pieces stored in the 2nd buffer, a most recently stored piece.  
         [0020]     With such a structure in which the 1st and 2nd buffers are provided, the present invention is capable of reducing the total amount of stored data and providing image data corresponding to holding down the shutter button.  
         [0021]     The digital still camera may further comprise: an image data storage unit operable to store image data pieces. Here, when the detection unit detects the operation of holding down the shutter button, the control unit reads the most recently stored piece displayed by the display unit and causes the image data storage unit to store therein the read most recently stored piece.  
         [0022]     With such a structure, the present invention is capable of storing blurring-free image data corresponding to holding down the shutter button.  
         [0023]     The motion detection unit may be composed of one of an angular velocity sensor and a three-dimensional velocity sensor.  
         [0024]     With such a structure, the present invention is capable of detecting the motion of the body of the digital still camera with precision.  
         [0025]     The above-stated object is also achieved by a mobile phone comprising the digital still camera.  
         [0026]     With such a structure, the present invention is capable of loading the digital still camera, able to handle hand shake with a simple mechanism, into a mobile phone.  
         [0027]     The above-stated object is also achieved by an image stabilizing method of a digital still camera comprises the steps of: an operation step of receiving operations from the user; a detection step of detecting the operations; an image capture step of capturing image data pieces of a subject at a predetermined time interval when a predefined operation is detected in the detection step; a storing step of storing, in a storage area, the image data pieces captured in the image capture step in order of being captured; a display step of displaying the image data pieces stored in the storage area; and a control step of causing, from among the image data pieces stored in the storage area, a most recently stored piece to be displayed in the display step when an operation of holding down a shutter button is detected in the detection step.  
         [0028]     With such a method, the present invention is capable of displaying a clear and sharp image free from blurring even if hand shake is made when the user holds down the shutter button. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0029]     These and other objects, advantages and features of the invention will become apparent from the following description thereof taken in conjunction with the accompanying drawings which illustrate specific embodiments of the invention. In the drawings:  
         [0030]      FIG. 1  shows a structure of Embodiment 1 of a digital still camera of the present invention;  
         [0031]      FIG. 2  shows appearance of the digital still camera of Embodiment 1;  
         [0032]      FIG. 3  is an explanatory diagram of image data stored in a buffer of Embodiment 1;  
         [0033]      FIG. 4  is a flowchart describing operation according to Embodiment 1;  
         [0034]      FIG. 5  shows a structure of Embodiment 2 of a digital still camera of the present invention;  
         [0035]      FIG. 6  illustrates shutter operation and image data stored according to Embodiment 2;  
         [0036]      FIG. 7  is a flowchart, part  1 , illustrating operation according to Embodiment 2; and  
         [0037]      FIG. 8  is a flowchart, part  2 , illustrating operation according to Embodiment 2. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0038]     Next are described embodiments of a digital still camera according to the present invention with the aid of drawings.  
       1. Embodiment 1  
       [0039]      FIG. 1  shows a structure of Embodiment 1 of the digital still camera according to the present invention.  
         [0040]     The digital still camera comprises: an operation unit  101 ; an image capture unit  102 ; a buffer  103 ; a display unit  104 ; a control unit  105 ; and an image storage unit  106 .  
         [0041]     The operation unit  101  receives user operation and sends a signal indicating the operation to the control unit  105 .  
         [0042]     The image capture unit  102  comprises a lens and an image capture device, such as CCD, CMOS or the like. The image capture unit  102  captures an image of a subject and outputs the image data to the control unit  105  according to the direction of the control unit  105 .  
         [0043]     The buffer  103  is composed of RAM and the like. Image data input to the control unit  105  from the image capture unit  102  is compressed by the control unit  105  and then stored in the buffer  103 .  
         [0044]     The display unit  104  is composed of a liquid crystal display and the like. Image data stored in the buffer  103  is read by the control unit  105 , and the image is then displayed in the display unit  104 .  
         [0045]     The control unit  105  has a CPU, and controls each unit of the digital still camera according to a control program stored in ROM. The control unit  105  receives power supply on a steady basis, even before the power supply of the body of the digital still camera is turned on.  
         [0046]     When receiving a signal indicating auto focus operation after the power supply is turned on in the operation unit  101 , the control unit  105  resets its own timer, and directs the image capture unit  102  to capture an image of a subject. The control unit  105  starts the timer with the direction of capturing an image, and directs the image capture unit  102  to capture an image of the subject at a predetermined time interval t-for example, every 100 ms, until receiving a signal indicating the shutter button being held down.  
         [0047]     The minimum of the predetermined time interval t is defined as the sum of the time required to store image data captured by the image capture unit  102  in the buffer  103  and the time required to read the image data stored in the buffer  103  and display the image in the display unit  104 .  
         [0048]     When receiving an input of image data from the image capture unit  102 , the control unit  105  compresses the image data according to JPEG standards for example; stores the compressed image data in the buffer  103 ; reads the stored image data; and displays the image in the display unit  104 .  
         [0049]     When receiving a signal indicating the shutter button being held down from the operation unit  101 , the control unit  105  reads image data stored most recently in the buffer  103 , and stores the image data in the image storage unit  106  at the same time as displaying the image in the display unit  104 .  
         [0050]     If receiving a signal indicating the shutter button being held down from the operation unit  101  without having received a signal indicating auto focus operation, the control unit  105  directs the image capture unit  102  to capture an image of a subject.  
         [0051]     When receiving an input of image data from the image capture unit  102 , the control unit  105  compresses the image data according to JPEG standards, and displays the image in the display unit  104  as well as storing the image data in the image storage unit  106 .  
         [0052]     The image storage unit  106  comprises a flash memory, such as a memory card. Image data corresponding to holding down the shutter button is stored by the control unit  105 , and the image storage unit  106  stores the image data.  
         [0053]      FIG. 2  shows appearance of the digital still camera viewed from an anterior perspective. At the front of a body  201 , a lens  202  constituting the image capture unit  102  is positioned. Equipped on the upper side of the lens  202  is a flash  204 . In addition, a shutter  203  constituting the operation unit  101  is provided on the top face of the body  201 . When the shutter  203  is held down halfway, a signal indicating auto focus operation is sent to the control unit  105 .  
         [0054]     At the back side of the body  201 , a power button and the display unit  104  are provided.  
         [0055]      FIG. 3  is a diagram for explaining image data stored in the image storage unit  106  at the time when operation of the shutter button being held down is performed after auto focus operation.  
         [0056]     The horizontal axis in  FIG. 3  is time. Images of a subject are captured at the predetermined time interval t from a time point  301  when auto focus operation is performed. Captured images are shown on the upper side of the figure. An image  302  captured at the time point  301  is displayed in the display unit  104  for the period of time indicated by an arrow  303 . Similarly, an image  305  captured at a time point  304  is displayed in the display unit  104  for the period of time indicated by an arrow  306 . An image  308  captured at a time point  307  is displayed in the display unit  104 .  
         [0057]     When operation of the shutter button being held down is performed at a time point  310  which is within the predetermined time interval t from the time point  307 , an image being displayed in the display unit  104 —that is, image data stored most recently in the buffer  103 —is read by the control unit  105 , and an image  311  is redisplayed in the display unit  104  after the period of time indicated by an arrow  309  which is shorter than the predetermined time interval t.  
         [0058]     Here, when no auto focus operation is performed, an image  312  with blurring, as shown on the lower side of  FIG. 3 , due to hand shake associated with holding down the shutter button is displayed in the display unit  104 .  
         [0059]     Note that focusing the lens  202  on a subject using auto focus operation and the like are well known technologies, and therefore, those descriptions are omitted here.  
         [0060]     Next is described operation of the present embodiment with the aid of a flowchart shown in  FIG. 4 .  
         [0061]     First, the control unit  105  waits for turning-on operation of the power supply from the operation unit  101  (Step S 402 ), and then, judges whether to have received a signal of auto focus operation (Step S 404 ). When having received a signal of auto focus operation, the control unit  105  resets the timer (Step S 406 ), and directs the image capture unit  102  to capture an image of a subject.  
         [0062]     The image capture unit  102  captures an image of the subject, and outputs the captured image data to the control unit  105  (Step S 408 )  
         [0063]     The control unit  105  starts the timer (Step S 410 ), and has the buffer  103  store the input image data therein while having the display unit  104  display the image (Step S 412 ).  
         [0064]     The control unit  105  judges whether the time indicated by the timer has exceeded  100  ms (Step S 414 ). Here, if NO, the control unit  105  further judges whether to have received a signal of holding down the shutter button from the operation unit  101  (Step S 416 ). If NO, the process returns to Step S 414 . At Step S 414 , the process returns to Step S 406  if the time indicated by the timer has exceeded 100 ms.  
         [0065]     At Step S 416 , when having received a signal of holding down the shutter button, the control unit  105  reads image data stored most recently in the buffer  103 , and displays the image in the display unit  104  (Step S 418 ). Then, the control unit  105  stores image data of the displayed image in the image storage unit  106  (Step S 420 ).  
         [0066]     The control unit  105  judges whether the image capture is finished according to the power supply being turned off (Step S 422 ). If YES, the process is terminated, while the process returns to Step S 404  if NO.  
         [0067]     When determining not to have received auto focus operation at Step S 404 , the control unit  105  further judges whether to have received a signal of holding down the shutter button (Step S 424 ). Then, when YES, the control unit  105  directs the image capture unit  102  to capture an image. If NO, the process moves to Step S 422 .  
         [0068]     The image capture unit  102  captures an image of the subject, and outputs the image data to the control unit  105  (Step S 426 ).  
         [0069]     The control unit  105  displays, in the display unit  104 , the image data input from the image capture unit  102  while at the same time storing this in the image storage unit  106  (Step S 428 ), and the process then moves to Step S 422 .  
         [0070]     The present embodiment assumes that beginners in handling a camera experience hand shake at the time of holding down the shutter button. In the present embodiment, image data captured right before the shutter button is held down is stored, and this stored image data is used as a replacement of blurry image data captured when the shutter button is held down with hand shake.  
       2. Embodiment 2  
       [0071]      FIG. 5  shows a structure of Embodiment 2 of the digital still camera according to the present invention. The digital still camera comprises a motion detection unit  501  in addition to the components of the digital still camera of Embodiment 1 above. Additionally, the digital still camera of the present embodiment has, in place of the buffer  103 , a buffer  504  comprising a 1st buffer  502  and a 2nd buffer  503 , and has a control unit  505  in place of the control unit  105 . The same components as those in Embodiment 1 above have the same numerals, and their descriptions are left out here.  
         [0072]     The motion detection unit  501  is implemented with a gyro sensor built into a body of the digital still camera, and detects the angular velocity of the digital still camera. Note that, instead of the angular velocity, the velocity of the camera body may be detected by using a three-dimensional velocity sensor, or alternatively, the acceleration of the camera body may be detected by an angular acceleration sensor or an acceleration sensor.  
         [0073]     The motion detection unit  501  notifies the control unit  505  of the detected angular velocity that represents the motion of the digital still camera.  
         [0074]     The buffer  504  comprises the  1 st buffer  502  for image display and the 2nd buffer  503  for temporary storage. Both of the 1st and 2nd buffers  502  and  503  are composed of, for example, RAM.  
         [0075]     The 1st buffer  502  has a storage area for at least two frames of image data. The 1st buffer  502  stores image data that has been captured by the image capture unit  102  and then compressed by the control unit  505  according to JPEG standards in order to display an image of the captured image data in the display unit  104 . The 1st buffer  502  stores image data captured by the image capture unit  102  alternatively in one of the two regions of the storage area, updating previously stored image data therein. Accordingly, image data stored most recently is stored in either one of the regions.  
         [0076]     The 2nd buffer  503  has a storage area for at least one frame of image data. The 2nd buffer  503  stores image data captured by the image capture unit  102  at a predetermined time interval (e.g. at an interval of 300 ms) when the control unit  505  is receiving a notice of a detection value less than a threshold (e.g. 1 degree/sec) from the motion detection unit  501  over a predefined period of time (e.g. 500 ms). When a detection value equal to or greater than the threshold is detected by the motion detection unit  501  at the time when the shutter button is held down, image data stored in the 2nd buffer  503  is stored in the image storage unit  106  as image data corresponding to the hold down of the shutter button.  
         [0077]     The control unit  505  has timers and counters. The control unit  505  has received power supply in advance, and directs the image capture unit  102  to capture images of a subject at a predetermined time interval upon receiving turning-on operation of the power supply from the operation unit  101 . The predetermined time interval is the same as in the case of Embodiment 1 above. When receiving an input of image data from the image capture unit  102 , the control unit  505  stores the image data in one of the two regions of the 1st buffer  502 . The control unit  505  displays an image of the stored image data in the display unit  104 . Then, next time when receiving an input of image data from the image capture unit  102 , the control unit  505  stores the image data in the other region of the  1 st buffer  502 . The control unit  505  stores the input image data alternately in the two regions of the 1st buffer  502 , overwriting previously stored image data therein.  
         [0078]     A 1st timer and a 1st counter are used for measuring the predefined period of time and for directing the image capture unit  102  to capture an image.  
         [0079]     Upon receiving a notice of the angular velocity detected by the motion detection unit  501 , the control unit  505  compares the angular velocity and a threshold (e.g. 1 degree/sec) that is a predetermined value stored in itself. When the informed angular velocity is less than the threshold, the control unit  505  determines that the digital still camera has not moved. On the other hand, when the informed angular velocity is equal to or greater than the threshold, the control unit  505  determines that the digital still camera has moved. Note that the threshold of the predetermined value is a value at which an image captured by the image capture unit  102  gets blurred due to hand shake.  
         [0080]     When determining that the digital still camera has not moved over a fixed time period (e.g. 500 ms) from the start of image capturing, the control unit  505  stores image data input from the image capture unit  102  in the 2nd buffer  503  at a certain interval-for example, every three frames (image data), updating the 2nd buffer  503 .  
         [0081]     The control unit  505  displays, in the display unit  104 , image data stored in the 2nd buffer  503 . In addition, image data not stored in the 2nd buffer  503  is stored in the 1st buffer  502 .  
         [0082]     The control unit  505  uses a 2nd timer and a 2nd counter for storing image data in the 2nd buffer  503 .  
         [0083]     Note that, when the angular velocity informed from the motion detection unit  501  for the above-mentioned fixed time period is equal to or greater than the threshold, the control unit  505  resets the 1st timer, and measures the fixed time period of 500 ms from the beginning. The fixed time period is defined on the assumption that the lens  202  is pointed at a subject and the digital still camera is not moved for a brief period.  
         [0084]     Also when receiving a signal indicating the shutter button being held down from the operation unit  101 , the control unit  505  displays, in the display unit  104 , an image of the latest image data stored in the 1st buffer  502  until the above-mentioned fixed time period elapses, as well as storing the image data in the image storage unit  106 .  
         [0085]     In the case where the angular velocity informed from the motion detection unit  501  is less than the predetermined value over a fixed time period and the control unit  505  then receives a signal indicating the shutter button being held down from the operation unit  101 , the control unit  505  reads image data stored in the 2nd buffer  503 , and stores the image data in the image storage unit  106  while displaying an image of the image data in the display unit  104 .  
         [0086]     Note that, at the time when the control unit  505  receives a signal of holding down the shutter button, if the angular velocity informed from the motion detection unit  501  is less than the predetermined value, the control unit  505  then stores, in the image storage unit  106 , image data captured in sync with the shutter button being held down, while displaying an image of the captured image data in the display unit  104 .  
         [0087]      FIG. 6  illustrates user&#39;s operation of holding down the shutter button together with image data stored in the image storage unit  106 .  
         [0088]     The horizontal axis in  FIG. 6  is time. A VSYNC signal  601  fulfilling the same function as a timer is output with a period of 100 ms. When the VSYNC signal  601  is in high level state  602 , the control unit  505  directs the image capture unit  102  to capture an image; receives an input of the image data from the image capture unit  102 ; and stores the image data in the 1st buffer  502  or the 2nd buffer  503 . When the VSYNC signal  601  is in low level state  603 , the control unit  505  reads an image from the 1st or 2nd buffer  502  or  503 , and displays the image in the display unit  104 .  
         [0089]     After the motion detection value informed from the motion detection unit  501  remains less than the predetermined value for a fixed time period of 500 ms, the control unit  505  stores one every three frames of image data (Frame 1 , Frame  2 , . . . , and Frame 7  in the figure) output from the image capture unit  102  in the 2nd buffer (Buff 2  in the figure).  
         [0090]     When the control unit  505  has received a signal of holding down the shutter button from the operating unit  101 , if the motion detection value informed from the motion detection unit  501  is equal to or greater than the predetermined value, the control unit  505  displays respectively, in the display unit  104 , Frame  1  in the case when Shutter 1  is held down, Frame  4  when Shutter  2  is held down, and Frame  7  when Shutter  3  is held down. At the same time, the control unit  505  stores each image data frame in the image storage unit  106 .  
         [0091]     Next is described operation of the present embodiment with the aid of flowcharts shown in  FIGS. 7 and 8 .  
         [0092]     First, the control unit  505  waits for turning-on operation of the power supply (Step S 702 ), and then initializes the 1st timer and resets the 1st counter n to “0” (Step S 704 ). Next, the control unit  505  directs the image capture unit  102  to capture an image, and starts the 1st timer (Step S 706 ). Then, the control unit  505  judges whether a detection value informed from the motion detection unit  501  is equal to or greater than a threshold (Step S 708 ). If YES, the control unit  505  determines that the body of the digital still camera has moved, and restarts the  1 st timer after resetting it while setting the 1st counter n to “0” (Step S 710 ), before the process moves to Step S 712 . If NO, the control unit  505  adds “1” to the counter n (Step S 712 ).  
         [0093]     The control unit  505  receives an input of image data captured by the image capture unit  102 ; stores the image data in the 1st buffer (Step S 714 ); and displays an image of the stored image data in the display unit  104  (Step S 716 ).  
         [0094]     Next, the control unit  505  judges whether to have received a signal indicating the shutter button being held down from the operation unit  101  (Step S 718 ). If YES, the control unit  505  displays an image of the image data stored in the 1st buffer in the display unit  104 , and stores the image data in the image storage unit  106  (Step S 724 ) before the process moves to Step S 828 . If there is no operation of holding down the shutter button, the control unit  505  judges whether the value indicated by the 1st timer is 100 ms×n (Step S 720 ). Here, if NO, the process returns to Step S 718 . If YES, the control unit  505  further judges whether the 1st counter n is “5” (Step S 722 ). Here, if NO, the process returns to Step S 708 . If YES, the control unit  505  initializes the 2nd timer and the 2nd counter m (Step S 802 ). Subsequently, the control unit  505  starts the 2nd timer (Step S 804 ), and judges whether the 2nd counter m is “0” (Step S 806 ). Here, if YES, the control unit  505  directs the image capture unit  102  to capture an image of a subject.  
         [0095]     The image capture unit  102  captures an image of the subject, and outputs the image data to the control unit  505 . The control unit  505  stores the input image data in the 2nd buffer  503  (Step S 808 ). The control unit  505  reads image data stored in the 1st or 2nd buffer  502  or  503 , and displays the read image in the display unit  104  (Step S 810 ). When determining that the 2nd counter m is not “0” at Step S 806 , the control unit  505  directs the image capture unit  102  to capture an image, and stores image data input from the image capture unit  102  (Step S 812 ) before the process moves to Step S 810 .  
         [0096]     Next, the control unit  505  adds “1” to the 2nd counter m (Step S 814 ), and judges whether there is operation of holding down the shutter button (Step S 816 ).  
         [0097]     Here, if NO, the control unit  505  further judges whether the value indicated by the 2nd timer is 100 ms×m (Step S 818 ). Here, if NO, the process returns to Step S 816 . If YES, the control unit  505  further judges whether the value of the 2nd counter m is “3” (Step S 820 ). Here, if YES, the control unit  505  sets the 2nd counter m to “0” (Step S 822 ), and judges whether the motion detection value informed from the motion detection unit  501  is equal to or greater than the threshold (Step S 824 ). Here, the process returns to Step S 710  if YES while returning to S 806  if NO.  
         [0098]     If YES at Step S 816 , the control unit  505  reads image data stored most recently in the 2nd buffer, and displays the image in the display unit  104  while storing the image data in the image storage unit  106  (Step S 826 ). Then, the control unit  505  judges whether there is operation of turning off the power supply (Step S 828 ). Here, if YES, the control unit  505  terminates the process, while the process returns to Step S 704  when NO.  
         [0099]     The motion detection unit  501  is implemented by using a detection sensor such as an angular velocity sensor in the present embodiment. However, it is a matter of course that software for detecting motion through image recognition can be used instead.  
         [0100]     In addition, the prevention of hand shake of the digital still camera described in the above embodiments can be realized with a simple mechanism, and therefore, the mechanism can be built in a mobile phone.  
         [0101]     Because allowing the prevention of hand shake with a simple mechanism, the digital still camera according to the present invention can be employed in the camera industry as a digital still camera achieving the prevention of hand shake at a low price.  
         [0102]     Although the present invention has been fully described by way of examples with reference to the accompanying drawings, it is to be noted that various changes and modifications will be apparent to those skilled in the art. Therefore, unless such changes and modifications depart from the scope of the present invention, they should be constructed as being included therein.