Abstract:
Provided are a focal plane shutter, which can offer a live view function, and improve a control velocity of a shutter speed to reduce a time interval between shootings, a photographing apparatus including the focal plane shutter, and a photographing method for the photographing apparatus. The focal plane shutter includes: a front curtain; a rear curtain; a support part coupled to one side of the front curtain and the rear curtain; and a movable part movably contacting one side of the support part, wherein either the front curtain or the rear curtain is independently moved by the motion of the movable part.

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATION 
       [0001]    This application claims the benefit of Korean Patent Application No. 10-2007-0079710, filed on Aug. 8, 2007, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a focal plane shutter, a photographing apparatus including the same, and a photographing method for the photographing apparatus, and more particularly, to a focal plane shutter, which can offer a live view function and improve a control velocity of a shutter speed to reduce a time interval between shootings, a photographing apparatus including the focal plane shutter, and a photographing method for the photographing apparatus. 
         [0004]    2. Description of the Related Art 
         [0005]    The rapid progress in electronics, computers, and the semiconductor technology has changed our daily lives. Personal computers (PCs), which are connected to the Internet and provide various content services, such as community, chatting, games, shopping, and news, are widely used in homes, schools, and offices. Not long ago, the most common way to see photographs was to take the film to a photo processor who would develop a film and print the photographs. With the rapid development in the semiconductor industry digital cameras were commercially introduced. 
         [0006]    Digital cameras using a charge coupled device (CCD), which is a semiconductor device, instead of a film are largely available, and mobile communication terminals are also equipped with digital cameras therein. Since digital cameras convert an image into data representing logic (e.g., 0 and 1), digital cameras can provide high robustness against noise, produce high quality signals at low cost, easily process information, compress information like an MPEG audio layer-3 (MP3), joint photographic coding experts group (JPEG), and moving picture experts group (MPEG), and reduce the size of a recording medium. 
         [0007]    Digital cameras can be roughly divided into rangefinder cameras and lens reflex cameras. 
         [0008]    Rangefinder cameras have a viewfinder in addition to a lens to look through to compose an image. Most of the current autofocus compact cameras and consumer-grade digital cameras are rangefinder cameras in which rangefinders (e.g., a pair of rangefinders) are used to focus a picture. 
         [0009]    A rangefinder, which measures a distance to a subject by eliminating parallax, has been used for artillery to measure a distance. When a camera is not focused, two images appear at the center of a viewfinder. Accordingly, the camera is focused by turning a lens rangefinder until the two images are perfectly superimposed. In general, the viewfinder is disposed over a left side of the lens. Because the viewfinder and the lens are placed at different positions, an apparent displacement of the subject occurs, i.e., parallax, as seen from the viewfinder and the lens. Since parallax increases as the subject approaches the camera, parallax correction is necessary when shooting close-up photographs. Since a rangefinder camera has a simple structure without using a mirror and employs a lens shutter, vibration and noise are low during shooting. Since the rangefinder camera has no mirror shock like a single lens reflex (SLR) camera, there is no risk of shaking the rangefinder camera. However, since a lens shutter is employed, the rangefinder camera does not have lens interchangeability, and has an iris and a shutter speed that are more limited than those of the SLR camera. 
         [0010]    Lens reflex cameras can be roughly divided into SLR cameras and twin lens reflex cameras. A conventional SLR camera  1 , which uses a mirror  20  to reflect an image incident through a lens  10  to a finder screen  34  and a viewfinder  40  to see the image, is shown in  FIGS. 1 and 2 . 
         [0011]    Most of the processional-grade cameras are SLR cameras.  FIG. 1  is a cross-sectional view of the conventional SLR camera  1  before a shutter is operated.  FIG. 2  is a cross-sectional view of the conventional SLR camera  1  after the shutter is operated. Referring to  FIG. 1 , an image introduced through the lens  10  of the conventional SLR camera  1  is reflected by the mirror  20  to the finder screen  34 , passes through a first objective lens  12 , is deviated by a pentaprism  32  by 90° to a second objective lens  14  and a third objective lens  16 , and is seen through the viewfinder  40 . 
         [0012]    The pentaprism  32  is a five-sided reflecting prism that reflects light several times therein and transmits the light through a right angle without inverting it. Since a plurality of optical elements, namely prisms and mirrors, are used in the conventional SLR camera  1 , the conventional SLR camera  1  is bulky and heavy. 
         [0013]    When the shutter is operated to photograph an image, the mirror  20 , disposed in front of an image pickup device  26 , is raised to allow an image incident through the lens  10  to enter the image pickup device  26 . 
         [0014]    In general, the image pickup device  26  is a charge coupled device (CCD) or a complementary metal-oxide semiconductor (CMOS). The shutter  24 , which is disposed in front of the image pickup device  26  and passes light for a predetermined period of time, is also called a focal plane shutter. 
         [0015]    In general, a focal plane shutter is a horizontal or vertical travel shutter which usually includes two cloths or metal curtains installed in front of a focal surface of a lens and allows a photosensitive material to be exposed to a proper amount of light by controlling a slit between a front curtain and a rear curtain or the speed of travel of the front curtain and the rear curtain. Focal plane shutters are widely used in cameras requiring the use of interchangeable lenses such as, for example SLR cameras. 
         [0016]    In particular, focal plane shutters are often used in cameras with a format of 6×6 cm or less. Focal plane shutters determine an exposure time by adjusting the width of a slit using a speed regulator or an electrically controlled electromagnet while maintaining a shutter blind speed constant. Focal plane shutters allow for use of interchangeable lenses and enable high speed photographing. 
         [0017]    Since the conventional SLR camera  1  can interchange the lens  10  or other lens designed exclusively for digital cameras, the conventional SLR camera  1  can selectively use lenses according to a preference or objective of a user. Also, since the image pickup device  26  is much bigger than that of other conventional digital cameras, noise can be prevented under low illumination conditions and a more precise image can be captured. 
         [0018]    However, since the mirror  20  is located to cover the image pickup device  26 , an image cannot be seen on a liquid crystal display (LCD)  28  during shooting such that a live view (also known as a preview) function is not offered and only an image review on the LCD  28  of the conventional SLR camera  1  is possible after taking a picture. That is, since an image should be seen through the optical viewfinder  40 , the field of view is limited and scenes at various angles including a low angle and a high angle are hidden. Also, when a subject, which is sensitive to any action, should be looked at furtively for a long time and instantaneously photographed, the conventional SLR camera  1  becomes inconvenient because the user must view the subject through the optical viewfinder  40  and because the camera  1  is too heavy to hold for a long time in the same position. 
         [0019]    Also, even when a conventional SLR camera  1  can offer a live view function, since a release time lag between the depression of a release button and the commencement of the movement of the shutter is long, an optimal shooting chance is gone and the release time lag is long. 
       SUMMARY OF THE INVENTION 
       [0020]    The present invention provides a focal plane shutter, which can offer a live view function, and improve a control velocity of a shutter speed to reduce a time interval between shootings, a photographing apparatus including the focal plane shutter, and a photographing method for the photographing apparatus. 
         [0021]    According to an aspect of the present invention, there is provided a focal plane shutter comprising: a front curtain; a rear curtain; a support part coupled to one side of the front curtain and the rear curtain; and a movable part movably contacting one side of the support part, wherein either the front curtain or the rear curtain is independently moved by the motion of the movable part. 
         [0022]    When the movable part is moved, the position of the support part contacting the one side of the movable part may be changed to move either the front curtain or the rear curtain. 
         [0023]    The focal plane shutter may further comprise an elastic member exerting a predetermined elastic force so that either the front curtain or the rear curtain is independently moved. 
         [0024]    The elastic member may exert an elastic force in a direction in which the focal plane shutter closes. 
         [0025]    When the movable part is raised, the front curtain may be lowered to open the focal plane shutter. 
         [0026]    When the movable part is lowered, the front curtain may be raised due to the elastic force provided by the elastic member to close the focal plane shutter. 
         [0027]    According to another aspect of the present invention, there is provided a focal plane shutter included in a photographing apparatus, the focal plane shutter comprising: a front curtain; a rear curtain disposed in parallel to the front curtain; a first front curtain support part comprising a first front curtain lever coupled to one side of the front curtain, a first front curtain arm coupled to one side of the first front curtain lever, and an elastic member interposed between the first front curtain lever and the first front curtain arm and exerting an elastic force between the first front curtain lever and the first front curtain arm; a second front curtain support part coupled to one side of the front curtain; a rear curtain support part coupled to the one side of the rear curtain; a first cam lever movably contacting one side of the first front curtain support part and one side of the rear curtain support part respectively and controlling the front curtain and the rear curtain to open and close; and a second cam lever movably contacting one side of the second front curtain support part and controlling the front curtain to open and close. 
         [0028]    In a live view mode of the photographing apparatus, the front curtain and the rear curtain may be separated from each other to open the focal plane shutter. 
         [0029]    When shooting is performed in a live view mode of the photographing apparatus, the focal plane shutter may close due to the elastic force exerted by the elastic member, and then an exposure may be started. 
         [0030]    The focal plane shutter may close when the front curtain is moved toward the rear curtain due to the elastic force provided by the elastic member. 
         [0031]    The first front curtain lever and the first front curtain may be pinned to each other to rotate together. 
         [0032]    The elastic member interposed between the first front curtain lever and the first front curtain arm may exert an elastic force so that the first front curtain lever rotates in a direction in which the focal plane shutter closes. 
         [0033]    The second front curtain support part may comprise: a second front curtain lever coupled to the one side of the front curtain; and a second front curtain arm coupled to one side of the second front curtain lever, wherein the second front curtain support part is rotatable about a junction between the second front curtain lever and the second front curtain arm. 
         [0034]    The rear curtain support part may comprise: a rear curtain lever coupled to one side of the rear curtain; and a rear curtain arm coupled to one side of the rear curtain lever, wherein the rear curtain support part is rotatable about a junction between the rear curtain lever and the rear curtain arm. 
         [0035]    A first front curtain control part and a rear curtain control part may be formed at one side of the first cam lever and respectively control the front curtain and the rear curtain to open and close. 
         [0036]    The first cam lever may be vertically movable so that when the first cam lever is lowered, the first front curtain control part and the rear curtain control part respectively press the first front curtain support part and the rear curtain support part to raise the front curtain and the rear curtain. 
         [0037]    The first cam lever may be vertically movable so that when the first cam lever is raised, the front curtain and the rear curtain are lowered due to their own weights. 
         [0038]    A second front curtain control part may be formed on one side of the second cam lever and control the front curtain to open and close. 
         [0039]    The second cam lever may be vertically movable so that when the second cam lever is raised, the second front curtain control part raises the second front curtain support part to lower the front curtain, and the elastic member is elastically deformed to some extent. 
         [0040]    The second cam lever may be vertically movable so that when the second cam lever is lowered, the front curtain is raised due to the elastic force provided by the elastic member. 
         [0041]    According to another aspect of the present invention, there is provided a photographing apparatus comprising: a lens through which light is incident; an image pickup device converting the incident light into an electrical signal; a display part displaying as an image signal the electrical signal received from the image pickup device; and an embodiment of the foregoing focal plane shutter that is interposed between the lens and the image pickup device for controlling the amount of light incident on the image pickup device. 
         [0042]    According to another aspect of the present invention, there is provided a photographing method for a photographing apparatus including a focal plane shutter, the method comprising: opening the focal plane shutter to perform a live view function; closing the shutter due to an elastic force exerted by an elastic member, when a shutter release button is depressed; moving a front curtain and a rear curtain of the focal plane shutter at a certain interval to perform an exposure; photographing an image; and closing the focal plane shutter for a next shooting. 
         [0043]    The opening of the focal plane shutter to perform the live view function may comprise moving the front curtain and the rear curtain apart from each other. 
         [0044]    When the opening of the focal plane shutter to perform the live view function is performed, the elastic member may be elastically deformed to some extent. 
         [0045]    The closing of the shutter due to the elastic member exerted by the elastic member may be performed by moving the front curtain toward the rear curtain. 
         [0046]    The closing of the shutter due to the elastic member exerted by the elastic member may be performed due to an elastic force exerted in a direction in which the elastically deformed elastic member returns to its initial state. 
         [0047]    Accordingly, a live view function can be preformed, and a control velocity of a shutter speed can be improved to reduce a time interval between shootings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0048]    The above and other features and advantages of the present invention will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings in which: 
           [0049]      FIG. 1  is a cross-sectional view of a conventional single lens reflex (SLR) camera before a shutter is operated; 
           [0050]      FIG. 2  is a cross-sectional view of the conventional SLR camera of  FIG. 1  after the shutter is operated; 
           [0051]      FIG. 3  is a cross-sectional view of a focal plane shutter according to an embodiment of the present invention; 
           [0052]      FIGS. 4 through 7  are cross-sectional views illustrating movements of various components of the focal plane shutter of  FIG. 3 ; 
           [0053]      FIG. 8  is a timing chart illustrating the operation of a photographing apparatus including a focal plane shutter according to an embodiment of the present invention; and 
           [0054]      FIG. 9  is a flowchart illustrating a photographing method according to an embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0055]    The present invention will now be described more fully with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown. 
         [0056]      FIG. 3  is a cross-sectional view of a focal plane shutter  100  according to an embodiment of the present invention. 
         [0057]    Referring to  FIG. 3 , the focal plane shutter  100  includes a front curtain  110 , a rear curtain  120 , a first front curtain support part  130 , a second front curtain support part  140 , a first rear curtain support part  150 , a second rear curtain support part  160 , a first cam lever  170 , and a second cam lever  180 . 
         [0058]    The front curtain  110  and the rear curtain  120  are cloths or metal curtains that are disposed generally in parallel to each other, and move relative to each other to expose or conceal an aperture  190 . That is, when the front curtain  110  and the rear curtain  120  are proximate to each other and there is no gap therebetween, the aperture  190  is concealed or closed. When the front curtain  110  and the rear curtain  120  are spaced apart from each other, the aperture  190  is exposed or opened. 
         [0059]    Although the front curtain  110  and the rear curtain  120  are shown in the Figures as moving relative to each other in a vertical direction, the present embodiment is not limited to vertically-moving curtains. That is, the front curtain  110  and the rear curtain  120  may move relative to each other in a horizontal direction. However, since most photographing apparatuses are normally configured to capture landscape images (i.e., a width of the image being greater than a height of the image), a vertical travel shutter travels a shorter side of a screen than a horizontal travel shutter does. Accordingly, the vertical travel shutter can have a shorter travel time and a higher shutter blind speed. To this end, a vertical travel shutter in which the front curtain  110  and the rear curtain  120  move relative to each other in a vertical direction will be explained hereinafter. 
         [0060]    The first front curtain support part  130  and the second front curtain support part  140  are respectively coupled to one side (e.g., the left side as shown) of the front curtain  110 . The first front curtain support part  130  and the second front curtain support part  140  support the front curtain  110 , and allow the front curtain  110  to be vertically moved to open and close the aperture  190 . 
         [0061]    The first front curtain support part  130  includes a first front curtain lever  131 , a first front curtain arm  132 , and an elastic member  135 . 
         [0062]    The first front curtain lever  131  is coupled at one end to the side of the front curtain  110 . That is, the first front curtain lever  131  substantially has a generally sideways L-shape with the end of the generally horizontal portion of the L-shape being coupled with a lower, left-hand corner of the front curtain  110 . An end of the generally vertical portion of the L-shape is coupled with an end of the elastic member  135 . 
         [0063]    The first front curtain arm  132  is also configured to have a generally sideways L-shape. The first front curtain arm  132  and the first front curtain lever  131  are generally mirror images of each other. One end of the first front curtain arm  132  that is most distal from the front curtain  110  contacts the first cam lever  170 . Corner portions of the first front curtain arm  132  and the first front curtain lever  131  are rotatably coupled together. The elastic member  135  is coupled between ends of the vertical portions of the L-shaped first front curtain arm  132  and first front curtain lever  131 . The elastic member  135  has a normal bias that urges the vertical portions of the first front curtain arm  132  and the first front curtain lever  131  to be proximate to each other so that the first front curtain arm  132  and the first front curtain lever  131  define a generally T-shaped first front curtain support  130 . The elastic member  135  may be an extension spring or the like that resists relative rotation of the first front curtain arm  132  and the first front curtain lever  131 , thereby causing the first front curtain arm  132  and the first front curtain lever  131  to return the first front curtain support  130  to its T-shaped configuration. 
         [0064]    Since corner portion of the first front curtain lever  131  and the first front curtain arm  132  are coupled to each other, the first front curtain lever  131  and the first front curtain arm  132  can rotate relative to each other. The elastic member  135 , which is interposed between the first front curtain lever  131  and the first front curtain arm  132 , provides a predetermined elastic force between the first front curtain lever  131  and the first front curtain arm  132 . In detail, referring to  FIG. 3 , the elastic force of the elastic member  135  resists relative rotation of the first front curtain lever  131  and the first front curtain arm  132  and urges the ends of the first front curtain lever  131  and the first front curtain arm  132  to be proximate to each other. In operation, when the first front curtain arm  132  is pressed downward and held in a downward orientation by the first cam lever  170  (e.g., as shown in  FIG. 3 ), lower ends of the first front curtain lever  131  and first front curtain arm  132  become separated. However, the elastic member  135  forces the first front curtain lever  131  to rotate counterclockwise to restore the normal, generally T-shaped configuration of the first front curtain support  130 , thereby raising the front curtain  110  (e.g., as shown in  FIG. 4 ). 
         [0065]    A front curtain spring  133  is coupled to the first front curtain arm  132  intermediate the corner portion of the arm  132  and the end that contacts the first cam lever  170 . One end of the front curtain spring  133  is coupled to the first curtain arm  132 , and the other end of the front curtain spring  133  is fixed. The front curtain spring  133  may be a compression spring so that it exerts an elastic force that resists compression of the front curtain spring  133 . Accordingly, the first front curtain arm  132  is forced to rotate counterclockwise to raise the front curtain  110 . 
         [0066]    A front curtain magnet  134  is configured to contact a lower portion of the first front curtain arm  132  intermediate the corner portion of the arm  132  and the end that contacts the first cam lever  170 . When electric current flows through the front curtain magnet  134 , the front curtain magnet  134  has a predetermined magnetic force and acts as an electromagnet. As shown in  FIG. 4 , the magnetic force provided by the front curtain magnet  134  causes the front curtain  110  to be fixedly supported instead of lowering by its own weight. 
         [0067]    The second front curtain support part  140  includes a second front curtain lever  141  and a second front curtain arm  142 . 
         [0068]    One end of the second front curtain lever  141  is coupled to the side of the front curtain  110  (e.g., the left side as shown, more particularly the upper left-hand corner). The second front curtain arm  142  is coupled to one side of the second front curtain lever  141 . The other end of the second front curtain arm  142  contacts the second cam lever  180 . 
         [0069]    The second front curtain lever  141  and the second front curtain arm  142  are firmly attached to each other and integrally moved (i.e., the second front curtain lever  141  and the second front curtain arm  142  are fixed to each other and do not move relative to each other). However, the second front curtain lever  141  and the second front curtain arm  142  can rotate or pivot about a junction therebetween. Because the second front curtain support part  140  rotates about the junction between the second front curtain lever  141  and the second front curtain arm  142 , the second front curtain support part  140  cooperates with the first front curtain support part  130  to raise or lower the front curtain  110 . As can be appreciated, the first and second front curtain support parts  130 ,  140  define a generally parallelogram-shaped linkage mechanism for moving the front curtain  110 . 
         [0070]    The first rear curtain support part  150  and the second rear curtain support part  160  are respectively coupled to one side of the rear curtain  120  (e.g., the left side as shown). The first rear curtain support part  150  and the second rear curtain support part  160  support the rear curtain  120 , and allow the rear curtain  120  to be vertically moved to open and close the aperture  190 . 
         [0071]    The first rear curtain support part  150  includes a rear curtain lever  151  and a rear curtain arm  152 . 
         [0072]    The rear curtain lever  151  is coupled to the side of the rear curtain  120 . The rear curtain lever  151  is configured to have a generally sideways L-shape that is generally a mirror image of the front curtain lever  131 . That is, a vertical portion of the L-shaped rear curtain lever  151  is oriented upward whereas a vertical portion of the L-shaped front curtain lever  131  is oriented downward. One end of the rear curtain lever  151  is coupled to the side of the rear curtain  120  (e.g., the left side, more particularly the upper left-hand corner). The other end of the rear curtain lever  151  and a corner portion thereof are coupled to the rear curtain arm  152 . That is, since the rear curtain lever  151  and the rear curtain arm  152  are coupled at two points, the rear curtain lever  151  and the rear curtain arm  152  are firmly attached to each other and integrally move. Another end of the rear curtain arm  152  (i.e., the end that is most distal from the rear curtain  120 ) contacts the first cam lever  170 . 
         [0073]    The rear curtain arm  152 , which is coupled with the rear curtain lever  151 , is configured to have a generally sideways L-shape so that the rear curtain arm  152  is generally a mirror image of the rear curtain lever  151 . Accordingly, the rear curtain lever  151  and the rear curtain arm  152  are coupled together to define an upside-down, generally T-shaped member. Also, the rear curtain lever  151  and the rear curtain arm  152  are pinned at a junction to each other (i.e., a location at which the corner portions are coupled together) and can rotate about the pinned junction. That is, the first rear curtain support part  150  rotates about the junction between the rear curtain lever  151  and the rear curtain arm  152  to raise or lower the rear curtain  120 . 
         [0074]    A rear curtain spring  153  is coupled to the rear curtain arm  152 . One end of the rear curtain spring  153  is coupled to the rear curtain arm  152  intermediate a corner portion of the arm  152  and the end that contacts the first cam lever  170 . The other end of the rear curtain spring  153  is fixed. The rear curtain spring  153  may be a compression spring that exerts an elastic force to resist compression of the spring  153 . When the spring  153  is compressed as shown in  FIG. 6 , the spring  153  forces the rear curtain arm  152  to rotate counterclockwise thereby raising the rear curtain  120  to an orientation shown in  FIG. 7 . 
         [0075]    A rear curtain magnet  154  is configured to contact a side of the rear curtain arm  152  intermediate the corner portion and an end that contacts the first cam lever  170 . When electric current flows through the rear curtain magnet  154 , the rear curtain magnet  154  has a predetermined magnetic force and acts as an electromagnet. In this case, due to a magnetic force provided by the rear curtain magnet  154 , the rear curtain  120  is not lowered by its own weight, but is fixedly supported. 
         [0076]    The second rear curtain support part  160  has a shape similar to that of the second front curtain lever  141 . One end of the second rear curtain support part  160  is coupled to the one side of the rear curtain  120 , and the other end of the second rear curtain support part  160  is coupled to an inside portion of the photographing apparatus (e.g., a portion of the focal plane shutter  100 ). Similar to the first and second front curtain support parts  130 ,  140 , the first and second rear curtain support parts  150 ,  160  define a generally parallelogram-shaped linkage mechanism for moving the rear curtain  120 . 
         [0077]    The first cam lever  170  includes a first front curtain control part  171  and a rear curtain control part  172 . The first cam lever  170  controls the front curtain  110  and the rear curtain  120  to open and close. 
         [0078]    In detail, the first cam lever  170  is formed beside the generally parallelogram-shaped linkage mechanisms defined by the first front curtain support part  130 , the second front curtain support part  140 , the first rear curtain support part  150 , and the second rear curtain support part  160 . The first cam lever  170  has a elongated bar shape and is vertically oriented. The first front curtain control part  171  and the rear curtain control part  172  respectively protrude from a middle portion and an upper portion of the first cam lever  170 . 
         [0079]    The protruding first front curtain control part  171  can contact the first front curtain arm  132 . In detail, the first front curtain arm  132  contacts a bottom surface of the first front curtain control part  171 . The protruding rear curtain control part  172  can contact the rear curtain arm  152 . In detail, the rear curtain arm  152  contacts a bottom surface of the rear curtain control part  172 . 
         [0080]    The first cam lever  170  is vertically moved, for example by a first cam, actuator, etc. (not shown). That is, when the first cam lever  170  is lowered, the first front curtain control part  171  and the rear curtain control part  172  respectively press downward on the first front curtain arm  132  and the rear curtain arm  152 , such that the first front curtain support part  130  and the first rear curtain support part  150  rotate counterclockwise about their pinned junctions, to raise the front curtain  110  and the rear curtain  120 . 
         [0081]    On the contrary, when the first cam lever  170  is raised, the first front curtain control part  171  and the rear curtain control part  172  respectively stop pressing on the first front curtain arm  132  and the rear curtain arm  152  such that the first front curtain support part  130  and the first rear curtain support part  150  rotate clockwise about their pinned junctions due to the weights of the front curtain  110  and the rear curtain  120 , thereby lowering the front curtain  110  and the rear curtain  120 . 
         [0082]    The second cam lever  180  includes a second front curtain control part  181 . The second cam lever  180  controls the front curtain  110  to open and close. 
         [0083]    In detail, the second cam lever  180  is formed behind the first cam lever  170  as shown in  FIG. 3 . One or more grooves  173  and  174 , and  183  and  184  are respectively formed in the first cam lever  170  and the second cam lever  180 . Pins  191  and  192  are inserted into the grooves  173 ,  174 ,  183 , and  184 . Accordingly, the first cam lever  170  and the second cam lever  180  are vertically moved along the pins  191  and  192  inserted into the grooves  173 ,  174 ,  183 , and  184 . 
         [0084]    The second cam lever  180  is formed beside the first front curtain support part  130 , the second front curtain support part  140 , the first rear curtain support part  150 , and the second rear curtain support part  160 . The second cam lever  180  has an elongated bar shape, which is similar to the first cam lever  170 , and the second front curtain control part  181  protrudes from a middle portion of the second cam lever  180 . 
         [0085]    The protruding second front curtain control part  181  can contact the second front curtain arm  142 . In detail, the second front curtain arm  142  contacts a top surface of the second front curtain control part  181 . 
         [0086]    The second cam lever  180  can be vertically moved by a second cam, actuator, etc. (not shown). That is, when the second cam  180  is raised, the second front curtain control part  181  of the second cam lever  180  raises the second front curtain arm  142 , such that the second front curtain support part  140  rotates clockwise about the pinned junction to lower the front curtain  110  (compare  FIG. 4  wherein the front curtain  110  is raised with  FIG. 3  wherein the front curtain  110  is lowered). 
         [0087]    On the contrary, when the second cam lever  180  is lowered, the second front curtain control part  181 , which supports the second front curtain arm  142 , is lowered such that the second front curtain support part  140  rotates counterclockwise about the pinned junction due to the elastic force of the elastic member  135 , to raise the front curtain  110 . 
         [0088]    The operation of the focal plane shutter  100  will now be explained in detail. 
         [0089]      FIGS. 3 through 7  are cross-sectional views illustrating the operation of the focal plane shutter  100  of  FIG. 3 .  FIG. 8  is a timing chart illustrating the operation of a photographing apparatus including a focal plane shutter according to an embodiment of the present invention. 
         [0090]      FIG. 3  illustrates the front curtain  110  and the rear curtain  120  being separated from each other thereby opening the focal plane shutter  100  so that the photographing apparatus operates in a live view mode. That is, the photographing apparatus is configured such that, in a live view mode, the front curtain  110  and the rear curtain  120  are separated from each other to open the focal plane shutter  100 , thereby enabling an image of a subject incident through a lens to be displayed on an LCD via an image pickup device. 
         [0091]    In the case of an SLR camera, it is natural that, in a live view mode, a mirror is automatically moved to enable light incident through a lens to be incident on a focal plane shutter and an image pickup device. 
         [0092]    Although it is described that the focal plane shutter  100  opens and a live view function is performed only in a live view mode of the photographing apparatus, the present embodiment is not limited thereto. That is, without a separate optical viewfinder, the focal plane shutter  100  may open and a live view function may be performed. In this case, since the separate optical viewfinder is not necessary, elements, such as a mirror and a pentaprism, for watching a subject using the optical viewfinder are not necessary, thereby making the photographing apparatus light and compact, reducing manufacturing costs, and simplifying a manufacturing process. In other words, the photographing apparatus can be made compact and light and have lens interchangeability. 
         [0093]    Referring to  FIG. 3  again, the first cam lever  170  and the second cam lever  180  are moved relative to each other so that the first cam lever  170  is in a lowered state and the second cam lever  180  is in a raised state. Accordingly, the second front curtain control part  181  is positioned between the first front curtain control part  171  and the rear curtain control part  172 . 
         [0094]    When the first cam lever  170  is lowered relative to the second cam lever  180  (as is illustrated by  FIGS. 6 and 7  in sequence), the first front curtain control part  171  and the rear curtain control part  172  of the first cam lever  170  respectively press the first front curtain arm  132  and the rear curtain arm  152 . Accordingly, the first front curtain support part  130  and the first rear curtain support part  150  rotate counterclockwise about their pinned junctions, thereby raising the front curtain  110  and the rear curtain  120 . 
         [0095]    However, in the state shown in  FIG. 7  (i.e., the first and second curtains  110 ,  120  being raised), when the second cam lever  180  is raised relative to the first cam lever  170 , the second front curtain control part  181  raises the second front curtain arm  142 , such that the second front curtain support part  140  rotates clockwise about the pinned junction and lowers the front curtain  110 . 
         [0096]    That is, since only the front curtain  110  is lowered while the rear curtain  120  is in the raised state, the focal plane shutter  100  opens, and a live view function can be performed by the open focal plane shutter  100 . 
         [0097]    In this state, since the elastic member  135  is longer than its initial length, an elastic force is exerted in a direction of the marked arrow, as illustrated in  FIG. 3 , such that the ends of the first front curtain lever  131  and the first front curtain arm  132  coupled to the elastic member  135  become closer to each other. To this end, the elastic member  135  urges the front curtain  110  to be raised for stopping the live view function. However, since the second front curtain control part  181  is moved upward for supporting the second front curtain support part  140 , the front curtain  110  remains in its lowered state to maintain the focal plane shutter  100  open. 
         [0098]    Also, in this state, since the front curtain spring  133  and the rear curtain spring  153  are longer than their initial lengths, an elastic force is exerted in a direction in which the front curtain spring  133  and the rear curtain spring  153  are compressed. That is, the first front curtain arm  132  and the rear curtain arm  152  are forced to be raised by the front curtain spring  133  and the rear curtain spring  153 . 
         [0099]    Also, in this state, the front curtain magnet  134  and the rear curtain magnet  154  are respectively in contact with the first front curtain arm  132  and the rear curtain arm  152 . However, since no current flows through the front curtain magnet  134  and the rear curtain magnet  154 , no separate magnetic force is formed. Flow of electric current through the front curtain magnet  134  and the rear curtain magnet  154  may be controlled by a controller of the photographing apparatus, for example a predetermined microprocessor (not shown). 
         [0100]      FIG. 4  illustrates that, the focal plane shutter  100  closes due to an elastic force provided by the elastic member  135 . 
         [0101]    In the state of  FIG. 3  where the live view function is performed, when a user depresses a shutter release button of the photographing apparatus, both the front curtain  110  and the rear curtain  120  are raised to close the focal plane shutter  100  for initiating an exposure. 
         [0102]    In the case of a conventional bulb shutter, in order to raise both a front curtain and a rear curtain and close a focal plane shutter, the rear curtain is lowered to close the focal plane shutter, and then the front curtain and the rear curtain are raised together. Since such a conventional focal plane shutter should undergo all the operations of lowering the rear curtain and raising both the front curtain and the rear curtain, a release time lag from the depression of a shutter release button to the start of an exposure is long. 
         [0103]    To solve the problem, the front curtain  110  can be independently raised by the elastic force provided by the elastic member  135 , thereby reducing a release time lag from the depression of a shutter release button to the start of an exposure. 
         [0104]    In detail, when a user depresses the shutter release button of the photographing apparatus, the second cam lever  180  is lowered, and thus the second front curtain control part  181  of the second cam lever  180 , which supports the second front curtain arm  142 , is lowered, and thus, the second front curtain arm  142  is no longer supported. Accordingly, the elastic member  135  (e.g., an extension spring that is extended) provides an elastic force in a direction in which the ends of the first front curtain lever  131  and the first front curtain arm  132  become closer to each other as described above, such that the first front curtain lever  131  of the first front curtain support part  130  and the second front curtain support part  140  rotate counterclockwise, to raise the front curtain  110  in a direction of the marked arrow as illustrated in  FIG. 3 . Thus, the shutter  100  becomes closed as shown in  FIG. 4 . 
         [0105]    In this configuration, since a control velocity of a shutter speed is improved and a preparation time for a next shooting is reduced, a time interval between shootings can be reduced. 
         [0106]    Also, in this state, since the front curtain spring  133  and the rear curtain spring  153  are extended longer than their initial lengths, an elastic force is exerted in a direction in which the front curtain spring  133  and the rear curtain spring  153  are compressed. That is, the first front curtain arm  132  and the rear curtain arm  152  are forced to be raised by the front curtain spring  133  and the rear curtain spring  153 . 
         [0107]    Also, in this state, the front curtain magnet  134  and the rear curtain magnet  154  are respectively in contact with the first front curtain arm  132  and the rear curtain arm  152 . Electric current flows through the front curtain magnet  134  and the rear curtain magnet  154 , and thus the front curtain magnet  134  and the rear curtain magnet  135  have a predetermined magnetic force and act as electromagnets. That is, since the front curtain magnet  134  and the rear curtain magnet  154  act as electromagnets and provide magnetic forces, the front curtain  110  and the rear curtain  120  are not lowered by their own weights, but are fixedly supported. Whether electric current flows through the front curtain magnet  134  and the rear curtain magnet  154  may be controlled by the microprocessor. 
         [0108]      FIG. 5  illustrates that an exposure is performed while the front curtain  110  and the rear curtain  120  of the focal plane shutter  100  are lowered at a predetermined interval. 
         [0109]    In the state of  FIG. 4  where both the front curtain  110  and the rear curtain  120  are raised, the focal plane shutter  100  closes and preparation for an exposure is completed. Once various values necessary for actual shooting, such as an exposure time, an auto focusing (AF) level, and an auto exposure (AE) level, are calculated, the front curtain  110  and the second curtain  120  are lowered at a predetermined interval to perform an exposure. 
         [0110]    Starting with the configuration shown in  FIG. 4 , first the first cam lever  170  is raised as shown in  FIG. 5  so that the first front curtain control part  171  and the rear curtain control part  172  are raised, thereby stopping the pressing on (i.e., releasing) the first front curtain arm  132  and the rear curtain arm  152 . At this time, if no force (e.g., electromagnetic force from one or both of the magnets  134 ,  154 ) is applied to the first front curtain support part  130  and the first rear curtain support part  150 , the front curtain  110  and the rear curtain  120  begin to lower simultaneously due to their own weights as is indicated in  FIG. 5  by the downward-pointing arrows. 
         [0111]    However, since electric current flows through the front curtain magnet  134  and the rear curtain magnet  154  and the front curtain magnet  134  and the rear curtain magnet  154  act as electromagnets as described above, the front curtain  110  and the rear curtain  120  are not lowered by their own weights, but are fixedly supported. 
         [0112]    In this state, when the front curtain magnet  134  and the rear curtain magnet  154  are turned off at predetermined instants (e.g., after a time interval (b) as shown in  FIG. 8 ), the front curtain  110  and the rear curtain  120  are respectively lowered at a predetermined interval due to their own weights and elastic forces provided by the front curtain spring  133  and the rear curtain spring  153 . As shown in  FIG. 8 , the first magnet (i.e., magnet  134 ) is first turned off at the beginning of interval (c) so that front curtain  110  can be lowered to expose the aperture  190 . Next as shown in  FIG. 8 , the second magnet (i.e., magnet  154 ) is turned off and the exposure takes place during interval (c). That is, due to the elastic forces and the weights, the first front curtain support part  130 , the second front curtain support part  140 , the first rear curtain support part  150 , and the second rear curtain support part  160  rotate clockwise about their pinned junctions, to lower the front curtain  110  and the rear curtain  120  in a direction of the marked arrow of  FIG. 5 . 
         [0113]    Accordingly, the focal plane shutter  100  opens in an instant to perform an exposure due to a difference between points of times when the front curtain  110  and the rear curtain  120  begin to be lowered. Here, the difference between the points of time when the front curtain  110  and the rear curtain  120  begin to be lowered, that is, a difference between points of time when the front curtain magnet  134  and the rear curtain magnet  154  are turned off, may be determined by the microprocessor considering light intensity, a distance to a subject and predefined values set by a user. 
         [0114]      FIG. 6  illustrates a configuration of the shutter  100  after an exposure is performed and the focal plane shutter  100  closes. 
         [0115]    When the front curtain  110  and the rear curtain  120  are completely lowered and the exposure is completed, the focal plane shutter  100  closes. The photographing apparatus converts an image of a subject introduced as a light beam through the focal plane shutter  100  into an electrical signal to obtain an image signal representing one still image, and converts the image signal into a digital signal. The photographing apparatus performs a process, such as a YC process, for the digital signal to obtain a predetermined digital image signal. The digital image signal representing the photographed image is recorded in a semiconductor memory. The recorded image signal may be read at any time and displayed on a display unit of a camera, reproduced as a printable signal, or output and displayed on a display device. 
         [0116]    Also, in this state, since the front curtain spring  133  and the rear curtain spring  153  return to their original lengths, no elastic force is applied. Also, in this state, no magnetic forces are applied by the front curtain magnet  134  and the rear curtain magnet  154 . 
         [0117]      FIG. 7  illustrates that one shooting is completed, and the front curtain  110  and the rear curtain  120  of the focal plane shutter  100  are raised for a next shooting. 
         [0118]    When one shooting is completed, the focal plane shutter  100  prepares for a next shooting. In detail, since the photographing apparatus is still in the live view mode, in order to enable an image of a subject incident through the lens to be displayed through the image pickup device on the LCD, the focal plane shutter  100  must open again. As shown in  FIG. 8 , the shooting is completed at the end of interval (d) and, subsequently, during interval (e) the front and rear curtains  110 ,  120  are raised together to be in the configuration shown in  FIG. 7 . 
         [0119]    To this end, the front curtain  110  and the rear curtain  120  are raised together. That is, when the first cam lever  170  is lowered, the first front curtain control part  171  and the rear curtain control part  172  of the first cam lever  170  respectively press the first front curtain arm  132  and the rear curtain arm  152 , such that the first front curtain support part  130  and the first rear curtain support part  150  rotate counterclockwise about their pinned junctions, to raise the front curtain  110  and the rear curtain  120 . At this time, since the front curtain  110  and the rear curtain  120  are raised simultaneously, the focal plane shutter  100  remains in its closed state. 
         [0120]    Also, in this state, since the front curtain spring  133  and the rear curtain spring  153  are extended longer than their initial lengths, an elastic force is exerted in a direction in which the front curtain spring  133  and the rear curtain spring  153  are compressed. That is, the first front curtain arm  132  and the rear curtain arm  152  are forced to be raised respectively by the front curtain spring  133  and the rear curtain spring  153 . 
         [0121]    Also, in this state, the front curtain magnet  134  and the rear curtain magnet  154  are respectively in contact with the first front curtain arm  132  and the rear curtain arm  152 . However, since current does not flow through the front curtain magnet  134  and the rear curtain magnet  154 , no separate magnetic force is formed. 
         [0122]    Finally, from the configuration shown in  FIG. 7 , the focal plane shutter  100  returns to the state of  FIG. 3  with the curtains  110 ,  120  being separated, thereby completing one cycle of one shooting. That is, after the curtains  110 ,  120  are raised during interval (e) of  FIG. 8 , the front curtain  110  is then lowered at the end of interval (e)/beginning of interval (a). 
         [0123]    In detail, when the second cam lever  180  is raised in order to open the focal plane shutter  100  again, the second front curtain control part  181  of the second cam lever  180  raises the second front curtain arm  142 , such that the second front curtain support part  140  rotates clockwise about the pinned junction, to lower the front curtain  110 . 
         [0124]    That is, since only the front curtain  110  is lowered while the rear curtain  120  is in the raised state, the focal plane shutter  100  opens so that a live view function is performed by the open focal plane shutter  100 , and preparation for a next shooting is finished, thereby completing the one cycle for one shooting. 
         [0125]    An SLR camera using the focal plane shutter  100  can have a live view function. Also, when the shutter release button is depressed, since the front raise curtain is raised independently to perform an exposure, unlike the conventional camera in which the rear curtain is lowered and then both the front curtain and the rear curtain are raised, a control velocity of a shutter speed can be improved drastically. As a result, in continuous shooting, a time interval between shootings can be reduced. 
         [0126]      FIG. 9  is a flowchart illustrating a photographing method according to an embodiment of the present invention. 
         [0127]    Referring to  FIG. 9 , in operation S 110 , a shutter opens to perform a live view function. In operation S 120 , a shutter release button is depressed to close the shutter. In operation S 130 , a front curtain and a rear curtain of the shutter are moved at a predetermined interval to perform an exposure (e.g., as shown in  FIG. 8 , first the front curtain  110  is moved and then the rear curtain  120  is moved after a predetermined period of time). In operation S 140 , an image is photographed. In operation S 150 , the shutter closes for a next shooting. 
         [0128]    In operation S 110 , a shutter opens to perform a live view function. In detail, in a live view mode, the first cam lever  170  of the focal plane shutter  100  is lowered and the second cam lever  180  is raised. Accordingly, the front curtain  110  is lowered and the rear curtain  120  is raised, such that the front curtain  110  and the rear curtain  120  are spaced apart from each other (see  FIG. 3 ). Accordingly, the focal plane shutter  100  opens, and an image of a subject incident through the lens is displayed through the image pickup device on the LCD. 
         [0129]    In operation S 120 , when a shutter release button is depressed, the shutter closes as shown in  FIG. 4 . In detail, in the state where the live view mode is performed, when a user depresses the shutter release button, both the front curtain  110  and the rear curtain  120  are raised so as to close the focal plane shutter  100 , thereby beginning an exposure. Accordingly, when the user depresses the shutter release button of the photographing apparatus, the second cam lever  180  is lowered, and thus the second front curtain control part  181  of the second cam lever  180  supporting the second front curtain arm  142  is lowered, and thus, the second front curtain arm  142  is no longer supported. The elastic member  135  provides an elastic force in a direction in which the ends of the first front curtain lever  131  and the first front curtain arm  132  become closer to each other, such that the first front curtain lever  131  of the first front curtain support part  130  and the second front curtain support part  140  rotate counterclockwise, to raise the front curtain  110 . 
         [0130]    In operation S 130 , the front curtain  110  and the rear curtain  120  of the shutter are moved at a predetermined interval to perform an exposure. In detail, in the state where the focal plane shutter  100  closes and preparation for an exposure is completed, once various values necessary for actual shooting, such as an exposure time, an AF level, and an AE level, are completely calculated, the front curtain  110  and the rear curtain  120  are lowered at a predetermined interval, to perform an exposure. 
         [0131]    That is, the first cam lever  170  is raised, and thus the first front curtain control part  171  and the rear curtain control part  172  of the first cam lever  170  respectively pressing the first front curtain arm  132  and the rear curtain arm  152  are raised. At this time, since electric current flows through the front curtain magnet  134  and the rear curtain magnet  154  and the front curtain magnet  134  and the rear curtain magnet  154  act as electromagnets, the front curtain  110  and the rear curtain  120  are not lowered by their own weights, but are fixedly supported. In this state, when the front curtain magnet  134  and the rear curtain magnet  154  are turned off at a predetermined interval, the front curtain  110  and the rear curtain  120  are respectively lowered at a predetermined interval due to their own weights and elastic forces provided by the front curtain spring  133  and the rear curtain spring  153 . Accordingly, the focal plane shutter  100  opens in an instant to perform an exposure due to a difference between points of time when the front curtain  110  and the rear curtain  120  begin to be lowered. 
         [0132]    In operation S 140 , an image is photographed. In detail, when the front curtain  110  and the rear curtain  120  are completely lowered (i.e., after interval (c) of  FIG. 8 ) and the exposure is finished, the focal plane shutter  100  closes. During one or more of intervals (d) and (e) shown in  FIG. 8 , the image pickup device converts an image of a subject introduced as a light beam by the focal plane shutter  100  into an electrical signal to obtain an image signal representing one still image, converts the image signal into a digital signal, and then records the digital signal as a certain image signal through a predetermined process. 
         [0133]    In operation S 150 , the shutter closes for a next shooting. In detail, when one shooting is completed, the focal plane shutter  100  prepares for the next shooting. That is, in order to enable an image of a subject incident through the lens to be displayed through the image pickup device on the LCD, the focal plane shutter  100  should open again. To this end, the front curtain  110  and the rear curtain  120  are raised together (e.g., interval (e) of  FIG. 8 ). That is, when the first cam lever  170  is lowered, the first front curtain control part  171  and the rear curtain control part  172  of the first cam lever  170  respectively press the first front curtain arm  132  and the rear curtain arm  152 , such that the first front curtain support part  130  and the first rear curtain support part  150  rotate counterclockwise about their pinned junctions, to raise both the front curtain  110  and the rear curtain  120 . At this time, since the front curtain  110  and the rear curtain  120  are raised simultaneously, the focal plane shutter  100  remains in its closed state. 
         [0134]    Finally, in operation S 160 , when a user wants to stop shooting, the photographing apparatus is turned off and shooting is stopped. However, when the user wants to take more photographs, the focal pane shutter  100  returns to operation S 110 , thereby completing one cycle for one shooting. In detail, when the second cam lever  180  is raised in order to open the focal plane shutter  100  again, the second front curtain control part  181  of the second cam lever  180  raises the second front curtain arm  142 , such that the second front curtain support part  140  rotates clockwise about the pinned junction, to lower the front curtain  110 . That is, since only the front curtain  110  is lowered while the rear curtain  120  is in the raised state, the focal plane shutter  100  opens (interval (a) shown in  FIG. 8 ), a live view function is performed by the open focal plane shutter  100 , and preparation for next shooting is finished, thereby completing one cycle for one shooting. 
         [0135]    While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by one of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims.