Abstract:
A diaphragm device for a digital camera having an optical image input system including a photographing element for converting an optical image input by an optical system to electric signals and a signal processor for applying predetermined signal processing to the electric signals obtained by the photographing element. The diaphragm device adjusts an exposure time by controlling incident luminous flux to the photographing element and an electric charge storage time of the photographing element. The diaphragm device includes a diaphragm sheet rotatably arranged around a rotation central shaft which is set in parallel with a photographing optical axis of the optical system. The diaphragm sheet has a plurality of diaphragm apertures having different diameters arranged in a turret shape on a reference circle around the rotation central shaft. The diaphragm device includes a rotary ring arranged rotatably in forward and reverse directions around the photographing optical axis and a click member is retained by the rotary ring rotatably only in one direction so as to rotate the diaphragm sheet in one direction. A rotation driving device drives the rotary ring to rotate, and a positioning mechanism fastens the diaphragm sheet in a position setting a selected diaphragm aperture.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a diaphragm mechanism and a shutter mechanism for a camera, and more particularly to a diaphragm device and a shutter device for an electronic camera, such as a digital video camera and a digital still camera, which photographs an object by converting an optical image of an object into electric signals using a solid photographing element including a charge coupled device (CCD) or the like. 
     2. Discussion of the Background 
     In a video camera for photographing a dynamic image, generally a solid photographing element such as a solid photographing element including a charge coupled device (CCD) is used as a photographing light receiving element. Furthermore in recent years, digital still cameras have come in widespread use. Such digital still cameras photograph an object image by using a solid photographing element to obtain image data of a still image of the object and record it digitally into an integrated circuit (IC) card or a floppy disk. Among these digital cameras, some are capable of photographing not only a still image but also a dynamic image (a movie image). 
     As methods of reading out photoelectric-converted pixels in a solid photographing element such as, for example, a CCD solid photographing element, there are a field read-out method and a frame read-out method. For photographing a still image, there are increasing cases of using the frame read-out method which is advantageous in resolution and the like. 
     In the frame read-out method, an odd number of field transfer read-out operations and an even number of field transfer read-out operations must be performed sequentially. Further, physical light shielding is generally required to the CCD solid photographing element immediately after completion of an appropriate exposure in order to prevent a defective phenomenon such as a smear caused by an exposure during the read-out operation. 
     In a CCD solid photographing element of a total pixel read-out type, the light shielding after the exposure as described above is not required. However, the above total pixel read-out type CCD solid photographing element is hard to enhance in the number of pixels for manufacturing reasons. Therefore, from the viewpoint of difficulties in manufacturing, an interlace-type CCD solid photographing element is still advantageous though it requires physical light shielding. 
     The following is general process of photographing a still image with an electronic camera having an electronic finder with a monitor display of a liquid crystal display (LCD) and a zoom lens in which light shielding is performed after completion of an exposure in the frame read-out method. 
     (1) Turn on the camera. 
     (2) Set the camera to a photographing (i.e., recording) mode. 
     (3) Measure luminance of an outside world, particularly that of a field of photographing. Then, a diaphragm is automatically set according to the measured value. 
     (4) A through image captured by the CCD solid photographing element is displayed, for example on an LCD monitor screen. 
     (5) Set a zoom position, if necessary. 
     (6)Determine the composition and depress a release button. 
     (7) An auto-focus (AF) mechanism is actuated and the photographing lens is moved to a focal position. 
     (8) An exposure for the CCD solid photographing element is commenced. 
     (9) The CCD solid photographing element is shielded from the exposure light after an appropriate time period. 
     (10) The CCD solid photographing element reads out data by an odd number field transfer and by an even number field transfer. 
     (11) A signal processing device performs display, recording, or other processing appropriately onto image information read out from the CCD solid photographing element. 
     (12) Start the next photographing operation, or stop the photographing and turn off the camera. 
     When using a single-focus lens or a fixed-focus lens instead of the zoom lens or in photographing with an electric flash, a process partially different from the above is applied. In every case, however, two different operations, diaphragm setting and light shielding, are required in the photographing process as above, and various improvements have been attempted. 
     For example, Japanese Patent Publication No. 2622296 discloses accomplishing a diaphragm function and a light shielding function by providing a plurality of diaphragm apertures and a shielding portion adjacent to each of the diaphragm apertures. 
     Additionally, Japanese Unexamined Patent Publication No. 7-11616 discloses accomplishing a diaphragm function and a light shielding function in almost the same manner as the above Japanese Patent Publication No. 2622296 by providing a turret-type diaphragm sheet having a plurality of diagram apertures and a shielding sheet having a double-sheet configuration arranged separately from the diaphragm sheet with the diaphragm sheet and shielding sheet coupled with each other. 
     As described above, generally, two separate types of operations, diaphragm setting  5  and light shielding, have been required in a still image photographing process, and therefore, as disclosed in the Japanese Patent Publication No. 2622296 and Japanese Unexamined Patent Publication No. 7-11616, the diaphragm function and the light shielding function are achieved by providing diaphragm apertures and shielding members, each operated independently. 
     In the Japanese Patent Publication No. 2622296, however, because the exposure and light shielding operations are performed by simply sliding a diaphragm sheet having a plurality of diaphragm apertures, there is a problem that light shielding is performed by a shift of a diaphragm aperture itself having a diaphragm aperture size selected during an exposure. In other words, the exposure operation is generally continued until the diaphragm aperture selected during the exposure is covered behind any end portion of a peripheral portion of an opened diaphragm aperture of the optical system, and therefore an irregular exposure occurs on a surface of the image obtained. In addition, when a moving object is photographed, an unfavorable phenomenon may occur, such as a blurred image, or a deformed object image depending upon a moving direction of the diaphragm aperture and that of the object for photographing even if the camera has a shutter speed (an exposure time between a commencement of the exposure and completion of the light shielding) at which an image can be captured normally. 
     In addition, because the shielding operation is started from an end of the diaphragm aperture, particularly when a large aperture size is selected, time is consumed from a commencement of light shielding to a completion thereof, which causes the same results as caused by a low shutter speed and a long exposure time, thus causing a problem that blurring easily occurs from an unsteady hold on the camera. 
     Furthermore, in the Japanese Unexamined Patent Publication No. 7-11616, a shielding sheet having a double-sheet configuration is arranged separately from the turret-type diaphragm sheet. As a result, it is further needed to arrange a coupling member and an energizing spring for opening or closing the shielding sheet, by which the mechanism is complicated. 
     Still further, because there is no arrangement of a positioning device on the shielding sheet, when the diaphragm aperture is positioned with a stepping motor, due to a step position precision of the stepping motor itself or the like, a diaphragm aperture cannot be set in an accurate position. 
     Furthermore, when a desired diaphragm aperture size is selected with a turret-type diaphragm sheet, diaphragm apertures having other diaphragm aperture sizes pass the opened diaphragm aperture of the optical system. Therefore, there is a problem that the shielding sheet is opened and closed on all such occasions wastefully, which causes a deterioration of durability of the mechanism or some failure and also generates uncomfortable mechanical sounds when the mechanism is operated. 
     More recently, there are various improved constitutions in which the shutter is operated after the diaphragm aperture is set by a single motor. However, in such constitutions, because a series of operations is generally treated as a single sequence, it is hard to arbitrarily change the diaphragm aperture after the diaphragm aperture has been once set. Therefore, these constitutions have a tendency to have a disadvantage such as a need for re-executing the sequence from the beginning to change the diaphragm aperture or involving an unnecessary shutter operation. 
     SUMMARY OF THE INVENTION 
     The present invention has been made in view of the above-discussed and other problems and addresses the above-discussed and other problems. 
     Preferred embodiments of the present invention provide a novel diaphragm device in which a reliable diaphragm performance and a high diaphragm precision are achieved and respective functions are performed independently from each other and stably. 
     Preferred embodiments further provide a novel diaphragm device in which a diaphragm sheet can be small in its external size so as to achieve downsizing of the entire camera and reliable positioning of the diaphragm sheet can be achieved in a simple constitution. 
     Further, preferred embodiments provide a novel diaphragm device in which a positioning member for positioning a diaphragm sheet is integrated with a position detecting member for detecting a position of the diaphragm sheet so as to detect the position reliably without error in a simple constitution and in which a specific diaphragm aperture position can be detected reliably, very precisely, and durably. 
     Furthermore, preferred embodiments provide a novel diaphragm device in which a diaphragm sheet can be set reliably in a predetermined position. 
     Preferred embodiments of the present invention provide a novel shutter device in which an identical rotary ring can be used to control opening or closing of a shutter independently of diaphragm aperture setting and thereby multi-functions, space saving, and low cost are achieved with a small number of members. 
     Preferred embodiments further provide a novel shutter device in which a high-precision control of the shutter device can be achieved in relation with a diaphragm setting. 
     Preferred embodiments further provide a novel shutter device in which a series of opening and closing operations of the shutter device can be performed simply with forward and reverse rotation of a rotary ring without a need for a fastening release actuator and the like and which is therefore superior in cost, space, and reliability. 
     Further, preferred embodiments provide a novel shutter device in which there is no interference between the shutter open-close operation and the diaphragm aperture setting operation and each operation can be adjusted independently. 
     Furthermore, preferred embodiments provide a novel shutter device that allows photographing repeatedly at a high speed, and that thereby extends the photographing functions. 
     Furthermore, preferred embodiments provide a novel shutter device in which a light volume is adjustable at monitoring and a degree of freedom is high in a program diagram so as to reduce smear or other defects at high luminance which have been frequently found in background art. 
     Preferred embodiments further provide a novel shutter device in which regular shutter operations are achieved by reducing contact friction between shutter blades moving in opposite directions and in which a variable diaphragm aperture is achieved with a high exposure precision. 
     According to a preferred embodiment of the present invention, a digital camera has an optical image input system including a photographing element for converting an optical image input by an optical system to electric signals, a signal processor for applying predetermined signal processing to the electric signals obtained by the photographing element, and a diaphragm device adjusting an exposure time by controlling incident luminous flux to the photographing element and an electric charge storage time of the photographing element. According to the present invention, a novel diaphragm device includes a diaphragm sheet rotatably arranged around a rotation central shaft thereof which is set in parallel with a photographing optical axis of the optical system. The diaphragm sheet has a plurality of diaphragm apertures having different diameters arranged in a turret shape on a reference circle around the rotation central shaft having a radius equal to a distance from the rotation central shaft to the photographing optical axis. The diaphragm device includes a rotary ring arranged rotatably in forward and reverse directions around the photographing optical axis and a click member is retained by the rotary ring rotatably only in one direction so as to rotate the diaphragm sheet in one direction. A rotation driving device drives the rotary ring to rotate, and a positioning mechanism fastens the diaphragm sheet in a position setting a selected diaphragm aperture. 
     According to the present invention, rotation of the click member in a first direction is regulated by the rotary ring so that a tip of the click member is engaged with a protruding portion of the diaphragm sheet at rotation of the rotary ring in a predetermined direction, and the click member rotates in a second direction different from the first rotation direction while leaving the diaphragm sheet behind in the selected diaphragm aperture setting position at rotation of the rotary ring in a direction reverse to the predetermined direction after completion of setting the selected diaphragm aperture. 
     According to the present invention, the positioning mechanism may include recess portions formed on an outer periphery of the diaphragm sheet correspondingly to the diaphragm apertures, respectively, and a positioning member energized substantially toward the center of the diaphragm sheet and pushing the recess portion corresponding to the selected diaphragm aperture so that the diaphragm sheet is fastened and positioned in the selected diaphragm aperture setting position. 
     Further, the positioning member may include a positioning lever rotatable around the rotation central shaft set in parallel with the photographing optical axis. The positioning lever has a first protruding portion having a boss for fastening the diaphragm sheet and extending in a radial direction from a rotation axis of the positioning lever and a second protruding portion extending in a different radial direction for detecting a position of the diaphragm sheet. 
     According to the present invention, one of the recess portions may have a different shape from those of the other recess portions such that a rotation angle of the positioning lever when the boss of the positioning lever is engaged with the recess portion having the different shape is discriminated from rotation angles of the positioning lever when the boss of the positioning lever is engaged with the other recess portions. As a result, the diaphragm sheet is detected to be in a reference position setting one of the plurality of diaphragm apertures by a moving amount of the second protruding portion of the positioning lever for position detection. An optical sensor may be used for detecting the diaphragm sheet to be in the reference position with the second protruding portion of the positioning lever. 
     According to the present invention, each of the recess portions of the outer periphery of the diaphragm sheet may have a form such that the boss of the positioning lever drops from an outmost periphery of the diaphragm sheet toward a center thereof immediately before an arbitrary diaphragm aperture reaches the selected diaphragm aperture setting position and prevents rotation of the diaphragm sheet in a direction reverse to the predetermined rotation direction of the diaphragm sheet. Further, each part of the recess portions closest to the center of the diaphragm sheet may be formed so as to be symmetrical about a straight line connecting the center of the diaphragm sheet and that of the boss and to extend in a substantially radial direction from the center of the diaphragm sheet in order to balance a spring force of the boss toward the center of the diaphragm sheet. 
     Another preferred embodiment of the present invention provides a novel shutter device for a digital camera having an optical image input system including a photographing element for converting an optical image input by an optical system to electric signals and a signal processor for applying predetermined signal processing to the electric signals obtained by the photographing element. The shutter device has a diaphragm function of adjusting an exposure time by controlling incident luminous flux to the photographing element and an electric charge storage time of the photographing element and includes a diaphragm sheet rotatably arranged around a rotation central shaft set in parallel with a photographing optical axis of the optical system. The diaphragm sheet has a plurality of diaphragm apertures having different diameters arranged in a turret shape on a reference circle around the rotation central shaft having a radius equal to a distance from the rotation central shaft to the photographing optical axis. A rotary ring arranged rotatably in forward and reverse directions around the photographing optical axis includes a click member retained by the rotary ring rotatably only in one direction so as to rotate the diaphragm sheet in the one direction. A rotation driving device drives the rotary ring to rotate and a positioning mechanism fastens the diaphragm sheet in a position setting a selected diaphragm aperture. In addition, a shutter mechanism has a shutter blade for light shielding, and the light shielding shutter blade in a closed state is put in a release state in the middle of rotation of the rotary ring from an initial position of the rotary ring in a diaphragm aperture setting direction and, after completion of a diaphragm aperture setting, the light shielding shutter blade is closed in the middle of rotation of the rotary ring in a reverse direction for returning to the initial position. 
     According to the present invention, the rotary ring may have a member retaining the click member and a member controlling a releasing and closing operation of the shutter blade of the shutter mechanism, which are integrated with the rotary ring, respectively. 
     Further, the shutter mechanism may have an open-close lever energized so as to drive the shutter blade in a closing direction and a fastening lever energized to fasten the open-close lever in a released state, and a series of operations including pushing the open-close lever with the rotary ring, releasing the shutter blade, dropping the fastening lever, separating the rotary ring from the open-close lever, and fastening the open-close lever with the fastening lever are performed with rotation of the rotary ring from the initial position of the rotary ring. Another series of operations including kicking the fastening lever with the rotary ring, releasing the open-close lever fastened with the fastening lever, and closing the shutter blade by rotation of the open-close lever are performed with rotation of the rotary ring in a direction for returning to the initial position. 
     According to the present invention, the shutter blade may be released and closed by the shutter mechanism while the rotary ring rotates from the initial position to an intermediary rotated position before a maximally rotated position of the rotary ring and a selected diaphragm aperture may be set while the rotary ring rotates from the intermediary rotated position to the maximally rotated position, such that interference is not caused between operations of releasing and closing the shutter blade and setting the selected diaphragm aperture. 
     Furthermore, the rotary ring may be driven so as to repeatedly rotate from the initial position to the intermediary rotated position so that the shutter blade is repeatedly released and closed for repeatedly photographing at high speed. 
     Also, the rotary ring may be driven to rotate from the intermediary rotated position to the maximally rotated position so as to change the selected diaphragm aperture for adjusting a light volume at monitoring. 
     Further, the shutter mechanism may include two pieces of the shutter blade, and the two shutter blades may be arranged such that the diaphragm sheet is put between the two shutter blades in a direction of the photographing optical axis. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A more complete appreciation of the present invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein: 
     FIG. 1 is an exploded perspective view illustrating a main portion of an electronic camera in which a shutter device according to the present invention is mounted; 
     FIGS. 2 through 6 are diagrams illustrating operation conditions of the shutter device for assisting explanation of the operation of the shutter device, FIG. 2 illustrating an initial condition, FIG. 3 a shutter blade setting condition, FIG. 4 an intermediate condition of changing a diaphragm aperture, FIG. 5 a condition immediately after the diaphragm aperture has been changed, and FIG. 6 an intermediate condition of a rotary ring returning to the initial position with reverse rotation; 
     FIG. 7 is a timing chart illustrating operation timings and operation amounts of the rotary ring, the diaphragm sheet, a positioning lever, an open-close lever, a fastening lever and shutter blades, an exposure status, and timings of odd number field read-out and even number field read-out operations in a CCD solid photographing element; 
     FIG. 8 is a cross-sectional view taken on a line of an optical axis to indicate a positional relationship between the diaphragm sheet and the shutter blades; 
     FIG. 9 is a flowchart of an exemplary photographing operation in a normal photographing mode of the electronic camera in which the shutter device according to the present invention is mounted; 
     FIG. 10 is a exemplary program diagram for use in controlling a program exposure; and 
     FIG. 11 is an exemplary block diagram of a control part of the camera relating to the program exposure. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to the drawings, wherein like reference numerals designate identical or corresponding parts throughout the several views, preferred embodiments of the present invention are now described. 
     FIG. 1 is an exploded perspective view illustrating a main portion of an electronic camera in which a shutter device having a diaphragm function according to the present invention is mounted. FIGS. 2 to  6  illustrate operation conditions of the shutter device for assistance in explaining the operation of the shutter device in FIG.  1 . The shutter device illustrated in FIGS. 1 to  6  includes a shutter base  1 , a stepping motor  2 , a motor setscrew  3 , an idler gear  4 , a rotary ring  5 , a click member  6 , a shaft  7 , a C-ring  8 , an energizing spring  9 , an open-close lever  10 , a spring  11 , a fastening lever  12 , a spring  13 , a C-ring  14 , a positioning lever  15 , a spring  16 , a photo-interrupter  17 , a diaphragm sheet  18 , shutter blades  19  and  20 , a supporting sheet  21 , a press sheet  22 , spacers  23  and  24 , and a set-screw  25 . 
     The stepping motor  2  is fastened to the shutter base  1  by the motor setscrew  3 . The idler gear  4  is mated with a boss la formed on the shutter base  1  so as to engage with a pinion gear  2   a  which is pressed into a shaft of the stepping motor  2 . 
     The rotary ring  5  has an arm  5   a  extending in a radial direction, and the click member  6  is retained by the arm  5   a  rotatably with the energizing spring  9 , the shaft  7 , and the C-ring  8 . 
     The open-close lever  10  is mated with a boss  1   b  pressed into the shutter base  1  and is energized in a counterclockwise direction by the spring  11 . The fastening lever  12  is, in the same manner, mated with a boss  1   c  pressed into the shutter base  1 , energized by the spring  13  in the counterclockwise direction, and fastened by the C-ring  14  for preventing the lever  12  from falling off. 
     The positioning lever  15  which is a positioning member is, in the same manner, mated with a boss  1   d  pressed into the shutter base  1  and is energized by the spring  16  in the counterclockwise direction. The photo-interrupter  17  generates ON/OFF signals appropriately according to a rotation amount of the positioning lever  15 . 
     The diaphragm sheet  18  is mated with a boss  1   e  formed on the shutter base  1  and is rotated in the counterclockwise direction by the click member  6 . The shutter blades  19  and  20  are mated with a boss  1   f  and a boss  1   g  formed on the shutter base  1 , respectively, and are actuated to be opened or closed by a boss  10   a  at a tip of an arm of the open-close lever  10  extending in one direction. 
     The supporting sheet  21  receives the diaphragm sheet  18  and the shutter blades  19  and  20  and also serves as a lift preventer for the idler  4 , the rotary ring  5 , the open-close lever  10 , and the positioning lever  15 . The press sheet  22  forms a blade chamber for housing the diaphragm sheet  18  and the shutter blades  19  and  20  by inserting the spacers  23  and  24  between the press sheet  22  and the supporting sheet  21 . The setscrew  25  is used to fix the blade chamber portion to the shutter base  1 . The diaphragm sheet  18  has two or more (four in this embodiment) diaphragm apertures having different diameters (F 2 , F 4 , F 8 , and F  11 , for example) in a turret shape on a reference circle around a rotation center of the diagram sheet  18  having a radius equal-to a distance from the rotation center to a photographing optical axis  26 . The diaphragm sheet  18  is configured to rotate in a predetermined single direction by using the click member  6 . 
     The click member  6  is retained on the rotary ring  5  which can rotate in forward and reverse directions as described above around the photographing optical axis  26 , so that the diaphragm apertures can be sequentially varied by rotating the diaphragm sheet  18  in a single direction with the forward and reverse rotation of the rotary ring  5 . Furthermore, a rotary driving force is given by the stepping motor  2  via an idler gear  4  and a pinion gear  2   a  engaging with a gear portion  5   c  formed on an outer periphery of the rotary ring  5 . 
     Next, diaphragm setting and shutter operations are described below with reference to front views of related main components illustrated in FIGS. 2 to  6 . FIGS. 2,  3 ,  4 ,  5 , and  6  illustrate an initial condition, a shutter blade setting (charging) condition, an intermediate condition of changing the diaphragm aperture, a condition immediately after the diaphragm aperture is completed to be changed, and an intermediate condition of the rotary ring returning to the initial position with reverse rotation, respectively. 
     In FIG. 4, one arm  6   b  of the click member  6  is regulated with respect to rotation in a counterclockwise direction by the boss  5   d  provided on the rotary ring  5 , and therefore in a rotation of the rotary ring  5  in the counterclockwise direction. A tip of another arm  6   a  of the click member  6  is rotated around the optical axis while pushing straight line portions  18   a  of four projecting portions of the diaphragm sheet  18 . In a condition in FIG. 5, a new diaphragm aperture of the diaphragm sheet  18  is set, and therefore the rotary ring  5  starts reverse rotation from the condition in FIG. 5 to progress to the condition in FIG.  6 . At this time, the diaphragm sheet  18  is regulated by the positioning lever  15  with respect to rotation in the clockwise direction. Therefore, a single-direction ratchet mechanism is formed, by which the click member  6  turns around against a spring force of the energizing spring  9  along an outer periphery  18   b  of the protruding portion of the diaphragm sheet  18  and rotates in the clockwise direction around the optical axis with the diaphragm sheet  18  left behind. 
     Further, in FIG. 5, a recess portion on the outer periphery of the diagram sheet  18  (formed at four places in this embodiment) is pushed by the boss  15   a  formed on a first protruding portion of the positioning lever  15  by a force indicated by an arrow F toward the center of the diaphragm sheet  18 , and thereby the diaphragm sheet  18  is fastened and positioned. 
     The positioning lever  15  also has a second protruding portion  15   b  extending in a different radial direction for detecting the position of the diaphragm sheet  18 . 
     Furthermore, one of the recess portions on the outer periphery of the diaphragm sheet  18  is different from others in shape. When the boss  15   a  of the positioning lever  15  is engaged with this recess portion by pressing this portion, the position detecting protruding portion  15   b  rotates by an angle different from angles by which the position detecting protruding portion  15   b rotates when the boss  15   a  of the positioning lever  15  is engaged with the other recess portions, so that a reference position of the diaphragm sheet  18  can be detected. 
     As a detecting device for the reference position, a photo-interrupter  17 , which is an optical sensor, is arranged in a position opposite to the position detecting protruding portion  15   b  without contacting the protruding portion  15   b.    
     Furthermore, as indicated by dashed lines in FIG. 5, the diaphragm sheet  18  has a form such that the boss  15   a  of the positioning lever  15  drops from the outer periphery of a protruded portion of the diaphragm sheet  18  toward the center thereof immediately before setting an arbitrary diaphragm aperture and such that after the drop it prevents reverse rotation of the diaphragm sheet  18 . The shape of a part of the recess portion closest to the center of the diaphragm sheet  18  is formed so as to be symmetrical about a line between the center of the diaphragm sheet  18  and that of the boss  15   a  and to extend in a radial direction, and the diaphragm sheet  18  rocks repeatedly with a force of the boss  15   a  oriented toward the center of the diaphragm sheet  18  and finally settles into a steady state at a position closest to the center of the diaphragm sheet  18 . 
     Next, operations of the shutter blades  19  and  20  will be described below. First, in the initial condition shown in FIG. 2, the fastening lever  12  is pushed up in the clockwise direction by a boss  5   g  extending to the rear of the rotary ring  5  which is coupled with the stepping motor  2  by a gear via the idler  4 . 
     While the fastening lever  12  is given a spring force in the counterclockwise direction by the spring  13 , the rotary ring  5  is held at the initial position, in other words, in a condition that a tip of the rotary ring  5  is in contact with a-stopper boss  1   h  formed on the shutter base  1  by a detention torque of the stepping motor  2 . Therefore, the fastening lever  12  is pushed up against the spring force of the spring  13  so as not to be put into contact with the open-close lever  10 . 
     A stopper  1   i  illustrated in FIG. 2 regulates the fastening lever  12  not to rotate in the counterclockwise direction when the rotary ring  5  releases the push-up of the fastening lever  12  with rotation in the counterclockwise direction. 
     Referring to FIG. 3, there is illustrated a condition where the shutter blades  19  and  20  are set, in other words, a charge condition. With the rotation of the rotary ring  5  in the counterclockwise direction from the initial position, a cam  5   f  at the tip of a protruding portion  5   b  of the rotary ring  5  pushes up a tip protruding portion  10   b  of one arm of the open-close lever  10 , so that the open-close lever  10  rotates in the clockwise direction, and thereby the shutter blades  19  and  20  are released. Simultaneously therewith a tip  12   b  of one protruding portion  12   a  of the fastening lever  12  enters the inside of the open-close lever  10 . 
     At the condition in FIG. 4, the cam portion  5   f  of the rotary ring  5  completely separates from the open-close lever  10 , and therefore the protruding portion  10   b  at the tip of the lever  10  is put into contact with the tip  12 b of the fastening lever  12  to enter the condition where the shutter blades  19  and  20  are set due to a spring force in the counterclockwise direction given by the spring  11  (FIG.  1 ). 
     Thereafter, during the rotation of the rotary ring  5  in the clockwise direction for returning to the initial position, in contrast to the setting process of the shutter blades  19  and  20 , when the boss  5 g extending to the rear of the rotary ring  5  kicks the tip  12   c  of the fastening lever  12 , the other tip portion  12   a  releases the open-close lever  10 . Therefore, the open-close lever  10  rapidly rotates in the clockwise direction by a force of the spring  11  to close the shutter blades  19  and  20 , and the rotary ring  5  returns to the initial position, and thereby photographing is completed for one time. 
     The rotary ring  5  has a portion retaining the click member  6  for setting the diaphragm aperture and a member for controlling the shutter release and closing operations, which are integrated with the rotary ring  5 , respectively. 
     The releasing and closing operation of the shutter blades  19  and  20  is performed by the operations of the rotary ring  5 , the open-close lever  10 , and the fastening lever  12 . Specifically, the releasing and setting operations of the shutter blades  19  and  20  are performed with counterclockwise rotation of the rotary ring  5  from the initial condition of the rotary ring  5  illustrated in FIG. 2, through the intermediate condition illustrated in FIG. 3, to the setting condition illustrated in FIG. 4, and the closing operation is performed with the rotation of the rotary ring  5  in the direction for returning to the initial position from the condition in FIG. 4 to the condition in FIG.  2 . In addition, as apparent from an operation timing chart illustrated in FIG. 7, the rotary ring  5  is configured so as to release or close the shutter blades  19  and  20  while the rotary ring  5  rotates from the initial position (corresponding to the initial position  27  in FIG. 7) to an intermediary rotated position (corresponding to the standby or home position  28  in FIG.  7 ), and to set a diaphragm aperture while the rotary ring  5  rotates from the intermediary rotated position (the standby or home position  28 ) to the maximally rotated position (corresponding to the maximally rotated position  29  in FIG.  7 ), such that no interference is caused between the operations of releasing and closing the shutter blades  19  and  20  and setting a selected diaphragm aperture. 
     In the operation timing chart in FIG. 7, there are illustrated, accompanied by a pulse step of the stepping motor  2  (“pulse step” in FIG.  7 ), operation timings and operation amounts of the rotary ring  5 , the diaphragm sheet  18 , the positioning lever  15 , the open-close lever  10 , the fastening lever  12 , and the shutter blades  19  and  20 . Also, an exposure status and timings of odd number field read-out and even number field read-out operations in the CCD solid photographing element are illustrated. 
     When the rotary ring  5  in the initial position in the power-off condition (corresponding to the initial position  27  in FIG. 7) is driven by the stepping motor  2  and reaches a position immediately before the intermediary rotated position (corresponding to the standby or home position  28 ), the open-close lever  10  and the shutter blades  19  and  20  are actuated to set the rotary ring  5  in the intermediary rotated position by the fastening lever  12 . 
     If a diaphragm switching operation is performed in this condition, the rotary ring  5  is further driven by the stepping motor  2  so as to actuate the diaphragm sheet  18  and the positioning lever  15 , so that the diaphragm sheet  18  is fastened by the positioning lever  15  in the maximally rotated position (corresponding to the maximally rotated position  29 ), and thereby the subsequent diaphragm aperture is set. 
     The rotary ring  5  is then driven to rotate in reverse by the stepping motor  2  to return to the intermediary rotated position. The diaphragm aperture can be further changed by repeating the above driving operation of the rotary ring  5  for the forward and reverse rotation by the stepping motor  2 . Respective diaphragm apertures of the diaphragm sheet  18  are thus set sequentially. 
     When the rotary ring  5  is rotated in reverse by the stepping motor  2 , while commencing an exposure of the CCD solid photographing element at a timing according to an exposure amount, to a predetermined position from the intermediary rotated position, the fastening lever  12  is actuated to close the shutter blades  19  and  20 , and after the blades  19  and  20  are completed to be closed, that is, after the exposure is completed, the odd number field read-out and the even number field read-out operations are performed. 
     By driving the rotary ring  5  to rotate from the initial position (corresponding to the initial position  27 ) or the intermediary rotated position (corresponding to the standby or home position  28 ) to the maximally rotated position (corresponding to the maximally rotated position  29 ) again, the diaphragm sheet  18  is fastened by the positioning lever  15  in the same manner as above and the next diaphragm aperture is set. 
     When photographing is continued with the diaphragm aperture which has been set in the intermediary rotated position of the rotary ring  5  after the rotation from the first initial position, the rotary ring  5  is immediately driven to rotate in reverse and an exposure of the CCD solid photographing element is commenced at a timing according to an exposure amount, and thereby the photographing is performed. 
     Furthermore, the shutter blades  19  and  20  can be released and closed in succession by repeating a reciprocating motion of the rotary ring  5  between the initial position and the intermediary rotated position. Therefore, it is possible to take pictures in succession at high speed. 
     In addition, a desired diaphragm aperture can be set and be changed to another desired diaphragm aperture by a reciprocating motion of the rotary ring  5  between the intermediary rotated position (the standby or home position  28 ) and the maximally rotated position (the maximum rotated position  29 ) once or a plurality of times. Therefore, a light volume can be adjusted, for example, at monitoring without performing any shutter operation. 
     Referring to FIG. 8, there is illustrated a cross-sectional view taken on a line of the optical axis  26  to indicate a positional relationship between the diaphragm sheet  18  and the shutter blades  19  and  20 . As apparent from FIG. 8, the diaphragm sheet  18  is put in a position between the shutter blade  19  and the shutter blade  20  and is in contact with respective tip portions  19   a  and  20   a  of the shutter blades  19  and  20 . 
     FIG. 9 illustrates a flowchart of an exemplary photographing operation in a normal photographing mode of the electronic camera in which the shutter device according to the above embodiment is mounted. FIG. 10 illustrates an exemplary program diagram for use in controlling a program exposure, and FIG. 11 illustrates a block diagram of a control part of the camera relating to the program exposure. 
     Referring to FIG. 9, when the electronic camera is turned on to start the photographing operation, the stepping motor  2  is rotated in the forward direction by “m” pulses, for example, to drive the rotary ring  5  up to the intermediary rotated position (corresponding to the standby or home position in FIG. 7) in step S 11 . By this operation, the shutter blades  19  and  20  are released (step S 12 ) to enter the standby condition. In this condition, the first photometric operation is performed (step S 13 ) and a diaphragm value is set on the basis of the program diagram of FIG.  10 . An initial diaphragm value of the diaphragm sheet  18 , in other words a reference position, is assumed to be set to a second diaphragm aperture corresponding to the focal number F 4  from a maximum diaphragm aperture corresponding to the focal number F 2  for a condition in which a light value (LV) of a luminance of an outside world (i.e., a field of photographing) is more than 10 and less than 12.5. 
     Then, whether or not the LV value of the luminance of the outside world (the field of photographing) is greater than a specific value, e.g. 15.5 or greater, is judged (step S 14 ). If the LV value is determined to be 15.5 or greater, Yes in step S 14 , forward and reverse rotation of the stepping motor  2  each by “n” pulses is repeated twice to set a minimum diaphragm aperture corresponding to a focal number, e.g. F 11  (step S 15 ). If the LV value is determined to be less than 15.5 in step S 14 , then whether or not the LV value is greater than a second value, e.g. 12.5 or greater, is judged (step S 16 ). If the LV value is 12.5 or greater, Yes in step S 16 , forward and reverse rotation of the stepping motor  2  each by “n” pulses is repeated three times and the diaphragm aperture is set to a second diaphragm aperture from the minimum diaphragm aperture corresponding to a focal number, e.g. F 8  (step S 17 ). If the LV value is determined to be less than 12.5 in step S 16 , then whether or not the LV value is less than a third value, e.g. 10 or smaller, is judged (step S 18 ). If the LV value is 10 or smaller, Yes in step S 18 , forward and reverse rotation of the stepping motor  2  each by “n” pulses is performed once and the diaphragm aperture is set to the maximum diaphragm aperture corresponding to a focal number, e.g. F 2  (step S 19 ). 
     If the LV value is determined to exceed 10, No in step S 18  or after the diaphragm aperture setting has been completed in step S 15 , S 17 , or S 19 , a desired image angle is set by a zooming operation (step S 20 ). 
     In this condition, the operation awaits for a first stage of a release button to be activated (step S 21 ). If the first stage is activated, the focusing operation is performed (step S 22 ). 
     Next, the operation awaits for a second stage of the release button to be activated in this condition (step S 23 ). If the second stage is activated, an exposure is commenced (step S 24 ), the stepping motor  2  is driven to rotate in reverse by “m” pulses (step S 25 ), and the shutter blades  19  and  20  are closed (step S 26 ) to complete the photographing operation. 
     If the second stage of the release button is determined not to be activated in step S 23 , the photometric operation is performed again (step S 27 ) and it is judged whether or not the luminance is changed (step S 28 ). Unless the luminance is changed, the operation directly returns to step S 23  to await the second stage of the release button to be activated. If a luminance change is detected in step S 28 , the stepping motor  2  is driven for forward and reverse rotation according to a focal number corresponding to a luminance change (step S 29 ), and then the operation returns to step S 23  to await the second stage of the release button to be activated. 
     Referring to FIG. 11, a schematic exemplary block diagram of an electronic camera operating as described above is illustrated. The electronic camera illustrated in FIG. 11 has a lens group  101 , a diaphragm/shutter  102 , a lens group  103 , a CCD solid photographing element  104 , a signal processing circuit  105 , an output circuit  106 , a central processing unit (CPU)  111 , a zoom control circuit  112 , a diaphragm/shutter control circuit  113 , a CCD control circuit  114 , a photometric circuit  115 , and an auto-focus (AF) circuit  116 . 
     The lens groups  101  and  103  constitute a zoom lens which is a photographing lens. The diaphragm/shutter  102  includes a shutter device according to the embodiment of the present invention. The CCD solid photographing element  104  converts an object image formed by the lens groups  101  and  103  to electric image signals. The signal processing circuit  105  applies predetermined signal processing to image signals output from the CCD solid photographing element  104 . The output circuit  106  outputs video signals output from the signal processing circuit  105  for output processing such as displaying to a liquid crystal display (LCD) or recording to a memory card. 
     The central processing unit  111  controls operations of the electronic camera. The zoom control circuit  112  drives the lens groups  101  and  103  for a zooming operation. The diaphragm/shutter control circuit  113  drives the above stepping motor  2  or the like to control a focal number and a shutter operation of the diaphragm/shutter  102 . 
     The CCD control circuit  114  controls an operation of the CCD solid photographing element  104  to control an exposure and a field read-out operation of image signals. The photometric circuit  115  measures a luminance of the outside world (the field of photographing). The auto-focus circuit  116  measures a distance to the object for focusing by driving at least one of the CCD solid photographing element  104  and the lens groups  101  and  103  via the central processing unit  111 . 
     The central processing unit  111  controls the operations of the CCD solid photographing element  104 , the signal processing circuit  105 , the zoom control circuit  112 , the diaphragm/shutter control circuit  113 , the CCD control circuit  114 , the photometric circuit  115 , and the auto-focus circuit  116 . 
     Numerous additional modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the present invention may be practiced otherwise than specifically described herein. 
     This document claims priority and contains subject matter related to Japanese patent applications No. 11-026788 and No. 10-360030 filed in the Japanese Patent Office on Feb. 3, 1999, and Dec. 2, 1998, respectively, and the entire contents of which are hereby incorporated herein by reference.