Patent Document

CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 11-156550, Jun. 3, 1999, the entire contents of which is incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     The present invention relates to an electronic still camera, and particularly to a camera shake proof electronic still camera being adapted to detect camera shake and to start an exposure operation at the timing of the camera shake becoming small. 
     In Jpn. Pat. Appln. KOKAI Publication No. 10-48681, a silver salt camera is disclosed which is adapted to monitor camera shake conditions after the release operation and to start film exposure when the quantity of camera shake has dropped below a predetermined value. 
     Further, in Jpn. Pat. Appln. KOKAI Publication No. 8-256289, a digital camera estimating the release time at which the result of shake detection falls within a predetermined permissible value and generating an image acquisition signal is disclosed. 
     However, since accidental camera shakes have no regularity, it is difficult to estimate them, and due to such error factors as response delay of a mechanical shutter, start delay of integration control of an imaging element or the like, a method of estimating camera shake conditions can not always produce a satisfactory result. 
     BRIEF SUMMARY OF THE INVENTION 
     Therefore, the object of the present invention is to provide an electronic still camera having an improved camera shake preventing performance without estimating future camera shake conditions and without involving an increase in cost or size. 
     In order to attain said object, an electronic still camera according to a first aspect of the present invention comprises: 
     an imaging device imaging an object; 
     a release section putting an imaging operation of said imaging device into effect; 
     a camera shake detection circuit detecting the quantity of camera shake during the imaging operation of said imaging device; and 
     a sequence control circuit evaluating the quantity of camera shake during the imaging operation detected by said camera shake detection circuit in response to a release operation by said release section and reading out an imaging signal when the result of camera shake detection is below a predetermined value. 
     Further, an electronic still camera according to a second aspect of the present invention comprises: 
     an imaging control circuit capable of repeating an imaging operation by an imaging device in response to a release operation; 
     a camera shake detection circuit detecting camera shake conditions in parallel with said imaging operation; and 
     a sequence control circuit evaluating the quantity of camera shake at a predetermined time of imaging operation by the imaging device, instructing the next imaging operation when the quantity of camera shake is below a predetermined value and terminating the imaging operation in order to read out picture data when the quantity of camera shake is below the predetermined value. 
     Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter. 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
     The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate presently preferred embodiments of the invention, and together with the general description given above and the detailed description of the preferred embodiments given below, serve to explain the principles of the invention. 
     FIG. 1 is a functional block diagram of an electronic still camera according to a first embodiment of the present invention; 
     FIG. 2 is a flowchart for illustrating the operation of the electronic still camera according to this embodiment; 
     FIGS. 3A and 3B are flowcharts showing an exposure processing in Step S 8  in detail; 
     FIG. 4 is a timing chart for illustrating the parts of the processing activities corresponding to Steps S 102  to S 115  in the flowcharts shown in FIGS. 3A and 3B; and 
     FIG. 5 is a part of a sequence showing the exposure according to a second embodiment of the present invention in detail. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Now, the embodiments of the present invention will be described in detail with reference to the drawings. 
     FIG. 1 is a functional block diagram of an electronic still camera according to a first embodiment of the present invention. CPU  1  is a sequence control means performing the sequence control of a camera. The camera shake detection sensor X 2  is a sensor detecting camera shake around the X-axis direction (yaw direction) on the image formation plane in the camera and comprises an oscillating gyro in this embodiment. The camera shake detection sensor Y 3  is a sensor detecting camera shake around the Y-axis direction (pitch direction) on the image formation plane in the camera and comprises an oscillating gyro. The X-Y composition circuit  4  is a circuit for composing an output voltage from the camera shake detection sensors X 2  and Y 2  analog and for finding an absolute value of the quantity of camera shake. Said camera shake detection sensors X 2  and Y 3  and said X-Y composition circuit  4  constitute a camera shake detection means. 
     Further, a photographing lens  5  for photographing an object  15  and an iris  6  for limiting the quantity of light from the object. The iris  6  is driven by means of an iris driving mechanism  7 . Further, the focusing mechanism  8  is a mechanism driving a part of the photographing lens  5  for focusing. 
     1RSW  9  is a switch put into ON by a first stroke (half push) of a release button. 2RSW is a switch put into ON by a second stroke (full push) of the release button. A focal-plane shutter  11  is provided in the vicinity of the film plane and is driven by means of a shutter driving mechanism  12 . 
     The CCD imaging device  13  is a device for obtaining a digital picture from the object image. The CCD driver  14  drives and controls the CCD imaging device  13  based upon control signals from CPU  1 . Said CPU  1  and CCD driver  14  constitute an imaging control means. 
     The picture processing circuit  15  is a circuit processing analog signals from the CCD imaging device  13 , and under the control of the CCD driver  14  it performs processing activities such as A/D conversion of analog picture signals, color conversion, compression of picture data and the like. The signals processed by means of the picture processing circuit  15  are recorded on a recording medium  16 . 
     FIG. 2 is a flowchart for illustrating the operation of the electronic still camera according to this embodiment. The operation starts by putting a power SW (not disclosed) into ON. First, the condition of 1RSW  9  is monitored, and when 1RSW  9  is in ON, the sequence proceeds to Step S 2 , and when it is not in ON, Step S 1  is repeated. In Step  2 , in-focus detection is performed by means of an in-focus detection (focusing condition detection) means (not shown). In next Step S 3  the lens is driven for focus adjustment corresponding to the quantity of defocus (the quantity of out-of-focus) obtained in Step S 2 . Here, a part of the photographing lens  5  is driven by the focusing mechanism  8  being driven and controlled. 
     In next Step S 4  photometry is performed by means of a photometric circuit (not shown). Subsequently, according to the result of said photometry, exposure calculations (Step S 5 ) are performed, and the set value of the iris  6  and the exposure time Tint of the CCD imaging device  13  are found. 
     In next Step S 6  the condition of 2RSW  10  is monitored, and when 2RSW  10  is in ON, the sequence proceeds to Step S 8 , and when it is not in ON, the sequence proceeds to Step S 7 . In Step S 7  the condition of 1RSW  9  is monitored, and when 1RSW is in ON, the sequence proceeds to Step S 6 , and when it is not in ON, the sequence returns to Step S 1 . 
     In Step  8  exposure is performed. This processing activity will be described in detail later. In next Step S 9  picture processing is performed with respect to the picture data obtained from the CCD imaging device  13  in the picture processing circuit  15 . Next, the sequence proceeds to Step  10 , and the processed data are recorded on the recording medium  16 . In Step  11  the shutter is charged. In the focal-plane shutter  11  the driving source is a spring, and as a preparatory operation prior to the operation it is necessary to charge the spring (to charge the shutter). 
     FIGS. 3A and 3B are flowcharts showing an exposure processing in Step S 8  in detail. First, in Step S 100  the iris driving mechanism  7  is controlled, and the iris  6  is driven and controlled. In next Step S 101 , a preceding scene is started with respect to the focal-plain shutter  11  by means of the shutter driving mechanism  12 . In next Step S 102  the electric charge accumulated in each photo diode PD in the CCD imaging device  13  is reset in order to be removed, and an integration operation is started. In next Step S 103  an exposure time is reset and started. In this embodiment the exposure time is controlled by an electronic shutter function of the CCD imaging device  13 . 
     In next Step S 104  it is judged whether the exposure time Tint determined in Step S 5  is longer than a predetermined time Tth or not, and according to the result thereof the following sequence is changed. When Tint is relatively long, that is, in case of Tint≧Tth, the sequence proceeds to Step S 105 , and when Tint is relatively short, that is, in case of Tint&lt;Tth, the sequence proceeds to Step S 112 . 
     In Step S 105  it is judged whether the count value of the exposure timer has reached Tint/2 or not, and when the count value has reached Tint/2, since it is in the middle point of the exposure time, the sequence proceeds to Step S 106 , and when it has not reached Tint/2, Step S 105  is repeated. 
     In Step S 106  the analog output voltage from the X-Y composition circuit  4  is inputted via an A/D conversion input terminal, and the quantity of camera shake is found. In next Step S 107  the found quantity of camera shake and a permissible value BUREth is compared, and in case of the quantity of camera shake&lt;BUREth, since the quantity of camera shake is permissible, the sequence proceeds to Step S 108 . And in case of the quantity of camera shake≧BUREth, since the quantity of camera shake is not permissible, the sequence proceeds to Step S 109 . In Step S 108  the camera shake flag is reset to 0. In Step S 109  the camera shake flag is reset to 1. 
     In Step S 110  it is judged whether the count value of the exposure timer has reached Tint or not, and when the timer count value is equal to Tint, the sequence proceeds to Step S 111 , and when the timer count value is not equal to Tint, Step S 110  is repeated. 
     On the other hand, in Step S 104 , when Tint is relatively short, that is, in case of Tint&lt;Tth, the sequence proceeds to Step S 1112 , however, in this step it is judged whether the count value of the exposure timer has reached Tint or not, and when the count value has reached Tint/2, the sequence proceeds to Step S 1113 , and when it has not reached Tint, Step S 1112  is repeated. Since the processing activities in Steps S 1113  to S 1116  are identical to those in said Steps S 106  to S 109 , the description thereof will be omitted here. 
     In Step S 111  it is judged whether the camera shake flag is equal to 1 or not, and in case of YES it is judged that the quantity of camera shake is impermissibly large, the sequence returns to Step S 102 , and the integration control of the CCD imaging device  13  is performed repeatedly. And when the camera shake flag is equal to 0, it is judged that the quantity of camera shake is permissibly large, and the sequence proceeds to Step S 112 . In this step the electric charge accumulated in PD is discharged to a CCD transfer pass. Next, in Step S 113  a following scene is started with respect to the focal-plane shutter  11  by means of the shutter driving mechanism  12 . The reason why the following scene is run in Step S 113  is that light must not enter the CCD transfer pass when the electric charge is transferred in the CCD transfer pass in order to prevent the generation of smear. 
     In next Step S 114  it is monitored by means of signals from a following scene run detection means whether the following scene has run or not, and when the following scene has run, the sequence proceeds to Step S 115 , and when it has not yet run, the judgement in Step S 114  is repeated. 
     In Step  115  the electric charge discharged in the CCD transfer pass is transferred by means of the CCD imaging device. At the same time, the analog picture signals outputted from the CCD imaging device  13  are converted to digital picture signals by means of the picture processing circuit  15 . Next, the sequence returns. 
     FIG. 4 is a timing chart for illustrating the parts of the processing activities corresponding to Steps S 102  to S 115  in the flowcharts shown in FIGS. 3A and 3B. The transverse axis represents the time lapsed, and the longitudinal axis represents the quantity of camera shake. The camera shake condition is detected in parallel with the imaging operation. According to this camera shake detection, the quantity of camera shake  101  which is represented by the output voltage of the X-Y composition circuit  4  varies with time as shown in the figure.  102  and  103  represent lines showing the permissible range (upper and lower limit) of the quantity of camera shake having a zero-point in the middle point. 
       104  represents the integration time of the electric charge of the CCD imaging device  13 .  104 - 1 ,  104 - 2 , . . . , and  104 -N represent the first, second, . . . , and N-th integration periods respectively. In  104 -N the quantity-of camera shake in the middle point of the integration period (exposure time) is  101 -N and falls within the permissible range of the quantity of camera shake for the first time.  105  represents the timing at which the electric charge accumulated in PD is discharged in the CCD transfer pass.  106  represents the running period of the following scene.  107  represents the electric charge transfer period of the CCD imaging device  13 . 
     According to the first embodiment, the imaging operation and the camera shake operation are performed repeatedly in parallel, and when the result of each camera shake detection is below the predetermined value, the imaging operation is stopped and the imaging data are read out, and therefore, an electronic still camera having an improved camera shake preventing performance without estimating future camera shake conditions and without involving an increase in cost or size can be provided. 
     Second Embodiment 
     Now, a second embodiment of the present invention will be described. FIG. 5 is a part of a sequence showing the exposure according to a second embodiment of the present invention in detail. The description of the parts in this figure having the same step numbers as in FIGS. 3A and 3B will be omitted because they are the same processes. In the second embodiment, camera shake detections are performed at the beginning, in the middle and at the end of the integration period of the CCD imaging device, and BURE 1 to 3 are found respectively (Steps S 200 , S 201  and S 202 ). And in Step  203  an average value of said BURE 1 to 3 is found, and in Step  204  the quantity of camera shake is judged. 
     According to the second embodiment, in addition to the advantages of the first embodiment, a more precise camera shake can be performed. 
     Moreover, from said concrete embodiments an invention having the following composition is extracted. 
     An electronic still camera being capable of repeating the imaging operation comprising: 
     an exposure means controlling the exposing operation of the pickup device; 
     a camera shake detection means detecting the quantity of camera shake during the operation of this exposure means; 
     a camera shake judgment means judging the result of camera shake detection during the particular exposure operation after the end of each exposure operation; and 
     an operation control means comparing the output of this camera shake judgment means with a predetermined level and starting said exposure operation again when the quantity of camera shake is above the predetermined level. 
     According to the present invention, an electronic still camera having an improved camera shake preventing performance without estimating future camera shake conditions and without involving an increase in cost or size can be provided. 
     Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the in its broadest aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.

Technology Category: h