Abstract:
In an image pickup apparatus comprising an optical finder for optically displaying an object image, an image pickup device for receiving the object image and converting it into an image signal for photographing, an electronic finder for displaying the object image received by the image pickup device on the basis of the image signal converted by the image pickup device, a focal plane shutter for shielding the image pickup device from light, and a beam guide device for guiding a beam from the object to the optical finder and the image pickup device, and a control method and a control program applied to the image pickup apparatus, the beam from the object guided by the beam guide device is changed over from the optical finder to the image pickup device and the focal plane shutter is rendered into its opened state so that before photographing, the image pickup device can receive the object image displayed by the electronic finder.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to an image pickup apparatus for taking an image, and particularly to an image pickup apparatus having a focal plane shutter. 
     2. Related Background Art 
     A conventional single-lens reflex digital still camera can effect optical finder display for a user to effect photographing after having visually confirmed an object image through the intermediary of a mirror, a pentaprism or the like. This digital still camera, however, opens a focal plane shutter only for a shutter time for photographing an object on an image pickup device such as a CCD and therefore, cannot effect electronic finder display for continuously displaying an object image on a liquid crystal monitor. 
     So, there has been proposed a digital still camera which can effect electronic finder display at all times through a focal plane shutter (for example, Japanese Patent Application Laid-Open No. 11-326992). This digital still camera has structure in which a leading vane moved to a light-intercepting position only during photographing and a trailing vane running after it are disposed forwardly of an image pickup device to thereby open the shutter at all times. 
     However, the above-described digital still camera has suffered from the inconvenience that it can effect electronic finder display at all times, but cannot effect optical finder display. 
     Also, it is of special structure in which in order to effect electronic finder display, the leading vane is moved in the same direction as the trailing vane to thereby open the shutter and therefore, it has suffered from the inconvenience that the structure becomes complicated and bulky. 
     SUMMARY OF THE INVENTION 
     It is a first object of the present invention to provide an image pickup apparatus having a focal plane shutter which can effect optical finder display and electronic finder display, and a control method and a control program applied to this image pickup apparatus. 
     It is a second object of the present invention to provide an image pickup apparatus having a focal plane shutter which can effect electronic finder display without being made complicated and bulky in structure, and a control method and a control program applied to this image pickup apparatus. 
     In order to achieve the first object, one aspect of the present invention is an image pickup apparatus comprising an optical finder for optically displaying an object image, an image pickup device for receiving the object image and converting it into an image signal for photographing, an electronic finder for displaying the object image received by the image pickup device on the basis of the image signal converted by the image pickup device, a focal plane shutter for shielding the image pickup device from light, and a beam guide device for guiding a beam from the object to the optical finder and the image pickup device, and a control method and a control program applied to this image pickup apparatus, and wherein the beam from the object guided by the beam guide device is changed over from the optical finder to the image pickup device and also, the focal plane shutter is opened so that before photographing, the image pickup device can receive the object image displayed by the electronic finder. 
     In order to achieve the second object, another aspect of the present invention is an image pickup apparatus comprising an image pickup device for receiving an object image and converting it into an image signal for photographing, an electronic finder for displaying the object image received by the image pickup device on the basis of the image signal converted by the image pickup device, and a focal plane shutter for shielding the image pickup device from light, and a control method and a control program applied to this image pickup apparatus, and wherein the image pickup device is exposed to light by the leading curtain after running and the trailing curtain before running of the focal plane shutter so that before photographing, the image pickup device can receive the object image displayed by the electronic finder and also, when shift is to be made from a state in which the object image before photographing is being displayed by the electronic finder to the photographing operation state, the leading curtain is moved into its state before running to thereby shield the image pickup device from light, whereafter the leading curtain is run to thereby expose the image pickup device to light and the trailing curtain is run to thereby shield the image pickup device from light, thus performing the photographing operation. 
     Other aspects of the present invention will become apparent from the description of a preferred specific embodiment shown below. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an illustration schematically showing the construction of a digital still camera according to an embodiment of the present invention, and shows the state of optical finder display. 
         FIG. 2  is an illustration schematically showing the construction of the digital still camera of  FIG. 1 , and shows the case of image pickup in the optical finder display mode. 
         FIG. 3  is an illustration schematically showing the construction of the digital still camera of  FIG. 1 , and shows the case of the termination of image pickup in the optical finder display mode. 
         FIG. 4  is an illustration schematically showing the construction of the digital still camera of  FIG. 1 , and shows the case of image pickup in the electronic finder mode. 
         FIG. 5  is an illustration schematically showing the construction of a shutter unit  8  in  FIG. 1 . 
         FIG. 6  is a block diagram of the electric circuit of the digital still camera of  FIG. 1 . 
         FIG. 7  is a flow chart of the photographing process by optical finder display executed by the digital still camera of  FIG. 1 . 
         FIG. 8  is a flow chart of the photographing process by electronic finder display executed by the digital still camera of  FIG. 1 . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     A preferred embodiment of the present invention will hereinafter be described in detail with reference to the drawings. 
       FIG. 1  is a typical view schematically showing the construction of a digital still camera according to an embodiment of the present invention. 
     Referring to  FIG. 1 , the digital still camera according to the embodiment of the present invention has a main body  1 . A pair of lenses  3  with a stop  2  interposed therebetween is disposed on the front face portion of the main body  1  of the camera. A pentaprism  4  and an eyepiece  5  (optical finder) are disposed on the eyepiece portion in the upper part of the main body  1  of the camera. A focusing plate  6  is disposed on the underside of the pentaprism  4 , and below it, there is disposed a quick return mirror  7  (deflecting means) for reflecting light from an object passed through the lenses  3  to the pentaprism  4 . This mirror  7  can be lifted up, and when lifted up, can pass therethrough the light from the object. 
     The shutter unit  8  of  FIG. 5  which will be described later, a low-pass filter  9  and an image pickup device  10  such as a CCD are disposed on the back portion of the main body  1  of the camera, and the shutter unit  8  contains therein a focal plane shutter comprising a shutter leading curtain  11  and a shutter trailing curtain  12 . A liquid crystal monitor  13  is also disposed on the back of the main body  1  of the camera. 
     In  FIG. 1 , the light from the object first enters through the front face portion of the main body  1  of the camera, and passes through the pair of lenses  3  with the stop  2  interposed therebetween and is focused, and is reflected by the mirror  7 , and enters the pentaprism  4  after the object image is formed on the focusing plate  6 . This light which has entered is visually confirmed as the object image by a user with the aid of the eyepiece  5 . At this time, some of the light is scattered and enters a light measuring element  14 . The light measuring element  14  detects the value of the luminosity of this scattered light as a voltage, and outputs the voltage and causes it to be converted into a digital signal. 
     The optical finder display mode will hereinafter be described with reference to  FIGS. 1 to 3 . 
     First, as shown in  FIG. 1 , the shutter leading curtain  11  of the shutter unit  8  is in its light-intercepting position and the shutter trailing curtain  12  is in its exposing position, and as previously described, optical finder display is effected. 
     Then, as shown in  FIG. 2 , exposing run in which the shutter leading curtain  11  is moved from its light-intercepting position to its exposing position is effected to thereby pass the light from the object therethrough, and image pickup is effected by the image pickup device  10 . After a shutter time, light-intercepting run in which the shutter trailing curtain  12  is moved from its exposing position to its light-intercepting position is effected, thus completing photographing ( FIG. 3 ). 
     The electronic finder display mode will hereinafter be described with reference to  FIG. 4 . 
     First, in  FIG. 4 , the mirror  7  is in its lifted-up position and the shutter leading curtain  11  and the shutter trailing curtain  12  are both in their exposing positions, and electronic finder display for effecting image pickup at all times is being effected. During photographing, light-intercepting charge in which the shutter leading curtain  11  is moved from its exposing position to its light-intercepting position is first effected, and the shutter leading curtain  11  again runs for exposure, and then, after the shutter time, the shutter trailing curtain  12  runs for light interception, thus completing photographing. Then, exposure charge in which the shutter trailing curtain  12  alone is moved from its light-intercepting position to its exposing position is effected to effect image pickup at all times. 
     The running/charging operations of the shutter leading curtain  11  and the shutter trailing curtain  12  as described above are performed by an operating mechanism (operating means) provided in the shutter unit  8  which will hereinafter be described. 
       FIG. 5  is an illustration schematically showing the construction of the shutter unit  8  in  FIG. 1 . 
     Referring to  FIG. 5 , the shutter unit  8  is provided with a leading curtain charge lever  15  for moving the shutter leading curtain  11  to its exposing position or its light-intercepting position, a leading curtain charge cam  19  for operating the leading curtain charge lever  15  through a leading curtain charge plate  17 , a trailing curtain charge lever  16  for moving the shutter trailing curtain  12  to its exposing position or its light-intercepting position, and a trailing curtain charge cam  20  for operating the trailing curtain charge lever  16  through a trailing curtain charge plate  18 . 
     The leading, curtain charge cam  19  and the trailing curtain charge cam  20  are disposed on the same shaft, but operate independently of each other.  FIG. 5  shows a state in which only the shutter trailing curtain  12  is exposure-charged, that is, is in its exposing position. 
       FIG. 6  is a block diagram of the electric circuit of the digital still camera of  FIG. 1 . 
     Referring to  FIG. 6 , the digital still camera of  FIG. 1  is comprised chiefly of a CPU  21  (operating means), a stop driving circuit  22  for driving the stop  2 , an A/D converter  23  for converting the voltage of the output of the image pickup device  10  into a digital signal, a storage medium  24  such as Compact Flash (R), an A/D converter  25  for photometry used in the photometric element  13 , a switch  26  for discriminating whether it is ON at the first stroke of a release button, not shown, a switch  27  for discriminating whether it is ON at the second stroke of the release button, a switch  28  for discriminating which of the optical finder display mode and the electronic finder display mode has been selected, a switch  29  for discriminating whether the mirror  7  is lifted up, a switch  30  for discriminating whether the mirror  7  is lowered, a switch  31  for discriminating whether the shutter trailing curtain  12  has been charged for exposure, that is, is in its exposing position, a switch  32  for discriminating whether the shutter leading curtain  11  has been charged for light interception, that is, is in its light-intercepting position, a motor  33  for bringing the mirror  7  into one of its lifted-up state and its lowered state, a transistor  34  for driving the motor  33 , a motor  35  for charging the shutter leading curtain  11  for light interception and charging the shutter trailing curtain  12  for exposure, a transistor  36  for driving the motor  35 , a magnet  37  for charging the shutter leading curtain  11  for light interception, a transistor  38  for driving the magnet  37 , a magnet  39  for charging the shutter trailing curtain  12  for exposure, and a transistor  40  for driving the magnet  39 . These constituent elements are connected to the CPU  21 . The image pickup device  10  is connected to the A/D converter  23 . 
       FIGS. 7 and 8  are flow charts of the photographing process executed by the digital still camera of  FIG. 1 . 
     In  FIG. 7 , when the switch  26  becomes ON at the first stroke of the release button (YES at a step S 1 ), whether the mode is the optical finder display mode is discriminated by the switch  28  (step S 2 ), and if it is the optical finder display mode, the processing of the optical finder display mode is executed by the processing of steps S 3  to S 13 . 
     In the processing of the optical finder display mode, light is first measured by the light measuring element  14  (step S 3 ), and the voltage of the output of the measured luminosity value is converted into a digital signal, and the shutter time and the aperture value of the stop  2  are calculated by the CPU  21  (step S 4 ) ( FIG. 7 ). 
     Then, whether photographing should be started is discriminated by the ON of the switch  27  by the second stroke of the release button (step S 5 ), and if it should be started, the mirror  7  is lifted up (step S 7 ), and at the next step S 8 , the shutter leading curtain  11  is run for exposure, and image pickup is effected by the image pickup device  10  (step S 9 ) ( FIG. 2 ), and after the shutter time, the shutter trailing curtain  12  is run for light interception and intercepts the light from the object (step S 10 ) ( FIG. 3 ). By the shutter trailing curtain  12  being run for light interception, smearing can be prevented. 
     The mirror  7  is lowered (step S 11 ), and one photographing process is terminated. Then, the stop  2  is opened, and the image taken at the step S 9  is read out, processed and recorded, and a photographed still picture is displayed on the liquid crystal monitor  13  (step S 12 ). 
     Further, the shutter leading curtain  11  is charged for light interception, and the shutter trailing curtain  12  is charged for exposure (step S 13 ), whereafter return is made to the processing after the selection of the optical finder display mode at the step S 3 . 
     When photographing is not started as the result of the discrimination at the step S 5 , whether the optical finder display should be continued is discriminated (step S 6 ), and if it should be continued, the processing of the steps S 3  to S 5  is repeated. 
     Also, when in the processing of the step S 13 , the shutter leading curtain  11  is charged for light interception after the shutter trailing curtain  12  has been charged for exposure, image pickup is effected by the image pickup device  10  and the object image is accumulated. However, this accumulated image, unlike exposed film, poses no problem because resetting for erasing an image accumulated before the next image pickup from the image pickup device  10  is effected. 
     When the optical finder display is not continued as the result of the discrimination at the step S 6 , it is judged that the optical finder display mode has been released, and return is made to the processing of the step S 2 , and the subsequent processing is repeated. 
     When as the result of the discrimination at the step S 2 , the mode is not the optical finder display mode, that is, it is the electronic finder display mode, the processing of the electronic finder display mode is executed by the processing of steps S 14  to S 29  in  FIG. 8 . 
     In the processing of the electronic finder display mode, in  FIG. 8 , the mirror  7  is first lifted up (step S 14 ), and the shutter leading curtain  11  is run for exposure, whereafter a still picture is taken by the image pickup device  10 , and the shutter trailing curtain  12  is run for light interception (step S 15 ) ( FIG. 5 ). The image taken at the step S 15  is read out, processed and recorded, and the still picture taken is displayed on the liquid crystal monitor  13  for a predetermined time (step S 16 ). Thereby, the user can confirm a composition or the like. At this time, light is measured from this still picture (step S 17 ), and the shutter time and the aperture value of the stop  2  are calculated by the CPU  21  (step S 18 ). 
     Then, only the shutter trailing curtain is charged for exposure (step S 19 ), and image pickup is effected at all times by the image pickup device  10 , and moving images are displayed (step S 20 ) ( FIG. 4 ). 
     At the next step S 21 , whether photographing should be started is discriminated by the ON of the switch  27  by the second stroke of the release button, and when it should be started, the shutter leading curtain  11  is charged for light interception (step S 22 ), and the shutter leading curtain  11  is run for exposure (step S 23 ), and a still picture is taken by the image pickup device  10  (step S 24 ), and after the shutter time, the shutter trailing curtain  12  is run for light interception (step S 25 ). The image taken at the step S 24  is read out, processed and recorded and the photographed still image is displayed on the liquid crystal monitor  13  for a predetermined time (step S 26 ), and return is made to the processing of the step S 19  and subsequent steps. 
     When photographing is not started as the result of the discrimination at the step S 21 , whether the electronic finder display should be continued is discriminated (step S 27 ), and when it should be continued, the processing of the steps S 20  to S 21  is repeated. 
     When the electronic finder display is not continued as the result of the discrimination at the step S 27 , it is judged that the photographing mode by the electronic finder display has been released, and the mirror  7  is lowered (step S 28 ), whereafter the shutter leading curtain  11  is charged for light interception (step S 29 ), and return is made to the processing of the step S 2  of  FIG. 7 , and the subsequent processing is repeated. 
     According to the processing of  FIGS. 7 and 8 , when the optical finder display mode has been selected (YES at step S 2 ), with the mirror  7  remaining lowered so that the light from the object may be measured by the light measuring element  14 , the mirror  7  is lifted up so that during the photographing by the digital still camera (steps S 7  to S 11 ), the light from the object may enter the image pickup device  10 , and then in order to effect the image pickup of the object (step S 9 ), the shutter leading curtain  11  is run for exposure and the shutter trailing curtain  12  is run for light interception, and when the electronic finder display mode has been selected (NO at step S 2 ), the mirror  7  is lifted up so that the light from the object may enter the image pickup device  10  (step S 14 ), whereafter only the shutter trailing curtain  12  is charged for exposure, and during the photographing by the digital still camera (steps S 22  to S 25 ), in order to effect the image pickup of the object (step S 24 ), the shutter leading curtain  11  is charged for light interception, whereafter the shutter leading curtain  11  is run for exposure and the shutter trailing curtain  12  is run for light interception and therefore, the optical finder display and the electronic finder display can be selectively effected almost without the construction of the conventional digital still camera being changed. 
     Of course, the present invention can also be applied to a case where a ROM  24  storing therein the program module of software for realizing the aforedescribed embodiment is achieved by supplying the program to a system or an apparatus. In this case, the program module itself read out from the ROM  24  realizes the novel function of the present invention, and the storage medium storing the program therein constitutes the present invention. 
     In the above-described embodiment, the program module is stored in the ROM  24  contained in the main body of the digital still camera, and as the ROM  24  for supplying the program module, there would occur to mind various ones such as a Floppy (registered trademark) disc, a hard disc, an optical disc, a magneto-optical disc, CD-ROM, MO, CD-R, DVD, a magnetic tape, a non-volatile memory card and Compact Flash (registered trademark), but it need not be restricted to a particular one, and can be any one capable of storing the above-described program therein. 
     The individual components shown in a schematic or block form in the drawings are all well-known in the camera art and their specific construction and operation are not critical to the operation or best mode for carrying out the invention. 
     While the present invention has been described with respect to what is presently considered to be the preferred embodiment, it is to be understood that the invention is not restricted to the disclosed embodiment. To the contrary, the invention is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions. 
     For example, in the above-described embodiment, the object light is selectively guided to the optical finder and image pickup device by the mirror, but the present invention can also be applied even if instead of the mirror, a half-mirror is used so that the object light may be guided to both of the optical finder and the image pickup device and the optical finder and the electronic finder can be used at a time.