Focal plane shutter and optical apparatus

This application is based upon and claims priority to Japanese Patent Application No. 2014-043284 filed on Mar. 5, 2014, subject matter of this patent document is incorporated by reference herein in its entirety.

(i) Technical Field

The present invention relates to focal plane shutters and optical apparatus.

(ii) Related Art

Japanese Examined Utility Model Application Publication No. 06-024821 discloses a focal plane shutter provided with: a coil spring for movement to move blades; and a spring for fine adjustment to finely adjust the movement speed of the blades.

In Japanese Examined Utility Model Application Publication No. 06-024821, the biasing direction of the spring for fine adjustment is the same as that of the coil spring for movement. Thus, the blades are biased in the same direction by the two springs, so that the large impact is applied to the blades when the moving blades are stopped. For this reason, the blades might be damaged. In particular, the high shutter speed type of the focal plane shutter needs high-speed blades, so that the large impact might be applied to the blades when the blades are stopped. Thus, there is a large possibility that the impact might damage the blades.

It is therefore an object of the present invention to provide a focal plane shutter including: a board including an opening; blades opening and closing the opening; an electromagnet supported by the board; a drive lever adsorbed to and held by the electromagnet, and swingably supported by the board; a drive arm connected to the drive lever, swingably supported by the board, and driving the blades; a first biasing member always biasing the drive lever away from the electromagnet and moving the blades; a first adjusting member that stepwisely adjusts a biasing force of the first biasing member; a second biasing member always biasing the drive arm in a direction opposite to a biasing direction of the first biasing member to such an extent that the blades are moved in accordance with the biasing force of the first biasing member; and a second adjusting member that steplessly adjusts a biasing force of the second biasing member.

FIG. 1 is front view of a focal plane shutter according to the present embodiment;

FIG. 2 is an explanatory view of an operation of the focal plane shutter;

FIG. 3 is an explanatory view of the operation of the focal plane shutter;

FIG. 4 is a sectional view around an electromagnet and a drive lever adsorbed to and held by the electromagnet;

FIG. 5 is a rear view of the focal plane shutter;

FIG. 6 is a view of a state of changing an angle of a swing lever;

FIG. 7A is a graph of changes in biasing forces of biasing members from the time when trailing blades start moving to the time when the trailing blades are stopped, and FIG. 7B is a graph of changes in biasing forces of biasing members from the time when trailing blades of an comparative example start moving to the time when the trailing blades are stopped;

FIGS. 8A to 8C are views of states of a drive arm from the time when trailing blades of a focal plane shutter according to a variation start moving to the time when the trailing blades are stopped; and

FIG. 9 is an explanatory view of adjusting speed of the trailing blades of a focal plane shutter according to a variation.

An embodiment will be described later with reference to the drawings. FIG. 1 is a front view of a focal plane shutter 1 . As illustrated in FIG. 1 , the focal plane shutter 1 includes: a board 10 ; blades 21 a to 24 a and 21 b to 24 b ; drive arms 31 a and 31 b ; support arms 32 a and 32 b ; and electromagnets 70 A and 70 B. The board 10 is made of a synthetic resin, and includes an opening 11 with a rectangular shape. Each of the blades 21 a to 24 a and 21 b to 24 b is made of a synthetic resin and is thinly formed. Also, although made of a synthetic resin, each of the blades 21 a to 24 a and 21 b to 24 b may be made of a metal or a fiber reinforced resin. Although being a metal thin plate, each of the drive arms 31 a and 31 b and the support arms 32 a and 32 b is made of a synthetic resin.

Four blades 21 a to 24 a configure leading blades 20 A. Four blades 21 b to 24 b configure trailing blades 20 B. The leading blades 20 A and the trailing blades 20 B open and close the opening 11 . FIG. 1 illustrates the leading blades 20 A in an overlapped state and the trailing blades 20 B in an expanded state. In FIG. 1 , the leading blades 20 A recedes from the opening 11 and the trailing blades 20 B close the opening 11 . Each of the leading blades 20 A and the trailing blades 20 B are movable between a closing position to close the opening 11 and a receding position to recede from the opening 11 .

The leading blades 20 A are connected to the drive arm 31 a and the support arm 32 a . The trailing blades 20 B are connected to the drive arm 31 b and the support arm 32 b . These drive arms 31 a and 31 b , and the support arms 32 a and 32 b are swingably supported by the board 10 .

Drive levers 40 A and 40 B for respectively driving the drive arms 31 a and 31 b are provided in the board 10 . The drive levers 40 A and 40 B are supported by the board 10 to be swingable in a predetermined range. Specifically, the drive lever 40 A is supported to swing about a spindle provided in the board 10 . This configuration is applied to the drive lever 40 B. The drive levers 40 A and 40 B correspond to drive members driving the leading blades 20 A and the trailing blades 20 B, respectively. The drive levers 40 A and 40 B are each made of a synthetic resin.

The drive arm 31 a is connected to the drive lever 40 A. The drive arm 31 b is connected to the drive lever 40 B. The swinging of the drive lever 40 A causes the drive arm 31 a to swing, thereby moving the leading blades 20 A. Likewise, the swinging of the drive lever 40 B causes the drive arm 31 b to swing, thereby moving the trailing blades 20 B.

Specifically, the drive levers 40 A and 40 B are provided with drive pins 43 a and 43 b fitted into the drive arms 31 a and 31 b , respectively. The board 10 is provided with arch-shaped escape slots 13 a and 13 b for respectively escaping the drive pins 43 a and 43 b . End portions of the escape slots 13 a and 13 b are provided with rubbers Ga and Gb for buffering the drive pins 43 a and 43 b , respectively.

The drive levers 40 A and 40 B each holds an iron piece which does not have a reference numeral. The drive lever 40 A can swing between the position where the iron piece abuts the electromagnet 70 A and the position where the iron piece recedes from the electromagnet 70 A. That is, the drive lever 40 A is movable such that the iron piece moves toward and away from the electromagnet 70 A. This is applied to the drive lever 40 B.

Also, the drive lever 40 A is biased by a spring, not illustrated, in such a direction that the iron piece moves away from the electromagnet 70 A. Likewise, the drive lever 40 B is biased by a spring, not illustrated, in such a direction that the iron piece moves away from the electromagnet 70 B. Additionally, FIG. 4 illustrates the iron piece and the spring of the drive lever 40 B, as will be described later.

Ratchet wheels 50 A and 50 B engage the drive levers 40 A and 40 B, respectively, through the springs mentioned above. One end of the spring, which biases the drive lever 40 A in such a direction as to move away from the electromagnet 70 A, engages the ratchet wheel 50 A. The other end of the spring engages the drive lever 40 A. The rotational amount of the ratchet wheel 50 A is adjusted, thereby adjusting the biasing force of the spring. The ratchet wheel 50 B also has a function similar to the ratchet wheel 50 A.

The electromagnet 70 A is energized, thereby adsorbing the iron piece of the drive lever 40 A against the biasing force of the above spring. Likewise, the electromagnet 70 B is energized, thereby adsorbing the iron piece of the drive lever 40 B against the biasing force of the above spring.

Next, the operation of the focal plane shutter 1 will be described. FIGS. 1 to 3 are explanatory views of the operation of the focal plane shutter 1 . Here, FIG. 2 illustrates the focal plane shutter 1 in an initial state. In this initial state, a set lever not illustrated is secured to an initial position, the leading blades 20 A are expanded to close the opening 11 , and the trailing blades 20 B are overlapped with each other to recede from the opening 11 . In this initial state, the iron pieces of the drive levers 40 A and 40 B abut the electromagnets 70 A and 70 B respectively, and are set to be adsorbed thereto.

In shooting, a release button of the camera is pushed to energize coils of the electromagnets 70 A and 70 B, whereby the iron piece of the drive lever 40 A is adsorbed to the electromagnet 70 A and the iron piece of the drive lever 40 B is adsorbed to the electromagnet 70 B. After that, the set lever moves away from the drive levers 40 A and 40 B. At this time, the drive levers 40 A and 40 B remain adsorbed to the electromagnets 70 A and 70 B, respectively.

Afterward, the energization of the coil of the electromagnet 70 A is stopped, thereby rotating the drive lever 40 A clockwise by the biasing force of the spring as illustrated in FIG. 3 . Therefore, the leading blades 20 A move away from the opening 11 to be in the overlapped state. Also, the energization of the coil of the electromagnet 70 B remains for a predetermined period, whereas the trailing blades 20 B remain away from the opening 11 . This causes the opening 11 to be in an opened state. FIG. 3 illustrates an exposed state.

After a predetermined period lapses from a time when the release button is pushed, the energization of the coil of the electromagnet 70 B is stopped, and then the drive lever 40 B rotates clockwise by the biasing force of the spring. Therefore, the trailing blades 20 B are expanded to close the opening 11 . The drive lever 40 B abuts an end portion of the slot formed in the board 10 . FIG. 1 illustrates the state just after the exposure operation is finished. In such a way, one cycle of shooting is finished.

Next, the drive lever 40 A and the drive lever 40 B are rotated counterclockwise by the set lever not illustrated. Therefore, the leading blades 20 A are expanded to close the opening 11 and the trailing blades 20 B are overlapped with each other to recede from the opening 11 , whereby the state is returned to the initial state illustrated in FIG. 2 .

Next, the electromagnet 70 B will be described in detail. FIG. 4 is a sectional view around the drive lever 40 B and the electromagnet 70 B in the state where the drive lever 40 B is adsorbed to and held by the electromagnet 70 B.

The drive lever 40 B includes: a board-shaped base portion 41 b ; a cylindrical portion 41 b 1 and a drive pin 43 b standing on the base portion 41 b ; a holding portion 42 b holding an iron piece 46 b ; and the like. Around the cylindrical portion 41 b 1 , there are provided the ratchet wheel 50 B and a spring 54 B for giving the drive lever 40 B a biasing force. One end of the spring 54 B is secured to the drive lever 40 B side, and the other end of the spring 54 B is secured to the ratchet wheel 50 B side. The rotational amount of the ratchet wheel 50 B is adjusted, thereby adjusting the biasing force of the spring 54 B. The spring 54 B biases the drive lever 40 B in such a direction as to move away from the electromagnet 70 B.

A spindle 11 b 1 provided in the board 10 is fitted into the cylindrical portion 41 b 1 . The drive lever 40 B rotates about the spindle 11 b 1 in a predetermined range. The spindle 11 b 1 is secured at its end with a holding board 120 by a pin 110 . A printed circuit board 100 is secured on an upper surface of the holding board 120 . The holding board 120 holds the electromagnets 70 A and 70 B. The printed circuit board 100 controls the energization of the electromagnets 70 A and 70 B.

The drive pin 43 b extends downwardly from the base portion 41 b . The drive pin 43 b is fitted onto the drive arm 31 b . A spindle 11 b 2 is coaxially formed with the spindle 11 b 1 in the board 10 . The drive arm 31 b rotatably fits onto the spindle 11 b 2 . The drive arm 31 b rotates about the spindle 11 b 2 in a predetermined range.

The holding portion 42 b has a wall shape standing upwardly on the base portion 41 b . A pin 45 b fitted into the iron piece 46 b penetrates through the holding portion 42 b . The pin 45 b penetrates through the holding portion 42 b in such a manner as to move in a given range in an axial direction of the pin 45 b . A spring 47 b biases the holding portion 42 b and the iron piece 46 b such that they move away from each other, and is arranged therebetween. The spring 47 b has a function to absorb an impact at the time when the iron piece 46 b abuts an iron core 76 b of the electromagnet 70 B as will be described later.

A rear board 18 faces the board 10 . The drive arm 31 b , the trailing blades 20 B, and the like are housed between the board 10 and the rear board 18 . The rear board 18 is formed with an escape slot 18 b 8 and an escape hole 18 b 2 for escaping the drive pin 43 b and the spindle 11 b 2 , respectively.

The electromagnet 70 B includes: the iron core 76 b ; a coil 79 b for exciting the iron core 76 b ; and a bobbin 72 b around which the coil 79 b is wound. The energization of the coil 79 b generates the magnetic attraction force between the iron core 76 b and the iron piece 46 b . The iron core 76 b has a letter U shape. The end surface of the end portion of the iron core 76 b is adsorbed with the iron piece 46 b . The coil 79 b is electrically connected to a pattern formed in the printed circuit board 100 by soldering. Therefore, the electromagnet 70 B and the printed circuit board 100 are electrically connected to each other.

The holding board 120 includes: a flat board portion 121 having a flat board shape; and a pair of sandwiching portions 122 b and 125 b standing on the flat board portion 121 . The holding board 120 is made of a metal and has a thin board shape elastically deformable. The flat board portion 121 is secured with the printed circuit board 100 . The sandwiching portions 122 b and 125 b stand on the flat board portion 121 to extend toward the board 10 side. The sandwiching portions 122 b and 125 b sandwich and hold the electromagnet 70 B.

FIG. 4 illustrates an engagement member 130 b engaging the ratchet wheel 50 B and stopping the rotation thereof. The engagement member 130 b is integrally provided in the holding board 120 . The engagement member 130 b is a leaf spring. An end portion of the engagement member 130 b engages a gear portion provided in the outer circumferential portion of the ratchet wheel 50 B, whereby the ratchet wheel 50 B is stopped at a predetermined position.

The biasing force of the spring 54 B is adjusted based on the stop position of the ratchet wheel 50 B. The spring 54 B always biases the drive lever 40 B and causes the trailing blades 20 B to move. As mentioned above, the engagement of the gear portion of the ratchet wheel 50 B with the engagement member 130 b permits the ratchet wheel 50 B to stop at a predetermined position. Thus, the stoppable positions of the ratchet wheel 50 B depend on the pitch of teeth of the gear portion thereof. Therefore, the stop position of the ratchet wheel 50 B can be stepwisely adjusted, but cannot be steplessly adjusted. Additionally, this configuration is applied to a spring 54 A the biasing force of which is adjusted by the ratchet wheel 50 A and which causes the leading blades 20 A to move. The spring 54 B is an example of a first biasing member. The ratchet wheel 50 B is an example of a first adjusting member.

An adjusting spring 80 and an adjusting mechanism 90 are arranged between the board 10 and the rear board 18 , as will be described later in detail.

FIG. 5 is a rear view of the focal plane shutter 1 . The rear board 18 is omitted in FIG. 5 . The support arms 32 a and 32 b are provided with rattle suppression springs Sa and Sb, respectively. The rattle suppression spring Sa is wound around a spindle portion supporting the support arm 32 a for swinging movement. An end of the rattle suppression spring Sa engages a hole 32 a H of the support arm 32 a , and the other end engages a projection 10 Sa formed on the board 10 . Likewise, the rattle suppression spring Sb is wound around a spindle portion supporting the support arm 32 b for swinging movement. An end of the rattle suppression spring Sb engages a hole 32 b H of the support arm 32 b , and the other end engages a projection 10 Sb formed on the board 10 . The rattle suppression springs Sa and Sb bias the support arms 32 a and 32 b to suppress rattling thereof, respectively. In addition, the rattle suppression springs Sa and Sb bias the support arms 32 a and 32 b respectively such that the leading blades 20 A and the trailing blades 20 B move away from the opening 11 , respectively. The support arms 32 a and 32 b are examples of support arms. The rattle suppression springs Sa and Sb are examples of third biasing members.

The drive pins 43 a and 43 b engage holes 31 a H and 31 b H of the drive arms 31 a and 31 b , respectively. The adjusting spring 80 is provided around the spindle 11 b 2 of the board 10 . Specifically, a coil portion 81 of the adjusting spring 80 is wound around the spindle 11 b 2 , an arm portion 83 continuous to the coil portion 81 and extending engages the hole 31 b H, and an arm portion 85 continuous to the coil portion 81 and extending engages a swing lever 91 of the adjusting mechanism 90 .

The adjusting spring 80 always biases the drive arm 31 b such that the trailing blades 20 B move away from the opening 11 . In contrast, the above described spring 54 B biases the drive lever 40 B such that the trailing blades 20 B move toward the opening 11 . Thus, the biasing directions of the adjusting spring 80 and the spring 54 B are opposite to each other. Further, this does not present a problem with the movement of the trailing blades 20 B trying to close the opening 11 , because the biasing force of the spring 54 B is greater than that of the adjusting spring 80 . Additionally, although the rattle suppression spring Sb biases the support arm 32 b such that the trailing blades 20 B move away from the opening 11 as mentioned above, this does not present a problem with the movement of the trailing blades 20 B trying to close the opening 11 , because the biasing force of the spring 54 B is greater than the total of the biasing forces of the rattle suppression spring Sb and the adjusting spring 80 .

The adjusting mechanism 90 includes the swing lever 91 and a securing screw 95 . The swing lever 91 has a rear end swingably supported by the board 10 and a front end engaging the arm portion 85 . The securing screw 95 secures the swing lever 91 unable to swing. The board 10 is provided thereon with projections 191 and 192 for restricting the swing range of the swing lever 91 . The angle of the swing lever 91 is adjusted and secured by the securing screw 95 , whereby the swing lever 91 is secured at an arbitrary angle on the board 10 .

FIG. 6 is a view of a state of changing an angle of the swing lever 91 . As illustrated in FIG. 6 , the securing screw 95 secures the swing lever 91 at an angle such that the swing lever 91 abuts the projection 192 . As illustrated in FIGS. 5 and 6 , a change in the position of the arm portion 85 of the adjusting spring 80 engaging the swing lever 91 changes the biasing force of the adjusting spring 80 . For example, the biasing force of the adjusting spring 80 is smaller in the state of FIG. 6 than in the state of FIG. 5 . In this way, the swing lever 91 is secured by the securing screw 95 in the present embodiment, so the angle of the swing lever 91 can be steplessly adjusted and secured. Therefore, the biasing force of the adjusting spring 80 can be steplessly adjusted. The adjusting spring 80 is an example of a second biasing member. The arm portions 83 and 85 are examples of the first and second arms, respectively. The adjusting mechanism 90 is an example of a second adjusting member. The swing lever 91 is an example of a swing member. The securing screw 95 is an example of a securing portion.

As mentioned above, the biasing force of the spring 54 B cannot be steplessly adjusted, but the biasing force of the adjusting spring 80 is steplessly adjusted, thereby finely adjusting the movement speed of the trailing blades 20 B.

FIG. 7A is a graph of changes in the biasing forces of the biasing members from the time when the trailing blades 20 B start moving to the time when the trailing blades 20 B are stopped. FIG. 7A illustrates changes in the biasing force 5 F of the spring 54 B, the biasing force 8 F of the adjusting spring 80 , and the total biasing force TF of these biasing forces. Additionally, to facilitate understanding, the same changing rates of the biasing forces 5 F and 8 F are illustrated. Further, a positive biasing force is illustrated as the biasing force causing the trailing blades 20 B to move in the direction from the receding position to recede from the opening 11 to the closing position to close the opening 11 . A negative biasing force is illustrated as the biasing force causing the trailing blades 20 B to move in the direction from the closing position to the receding position. Thus, the biasing force 5 F of the spring 54 B is illustrated as the positive value, and the biasing force 8 F of the adjusting spring 80 is illustrated as the negative value.

Although the biasing force 5 F decreases as the trailing blades 20 B come closer to the closing position, the biasing force 8 F opposite to the biasing force 5 F increases. Thus, the decrease rate of the total biasing force TF is greater than that of the biasing force 5 F, and the total biasing force TF further decreases as the trailing blades 20 B come closer to the closing position. In such a way, the total biasing force TF contributing to the movement of the trailing blades 20 B decreases as the trailing blades 20 B come closer to the closing position.

FIG. 7B is a graph of changes in the biasing forces of the biasing members from the time when trailing blades of an comparative example start moving to the time when the trailing blades are stopped. FIG. 7B illustrates changes in the biasing force 5 F of a spring, the biasing force 8 F′ of an adjusting spring, and the total biasing force TF′ of these biasing forces. Herein, unlike the adjusting spring 80 in the present embodiment, it is supposed that the adjusting spring in the comparative example biases a drive arm in the same direction as the biasing direction of the spring 54 B. It is also supposed that a value of the biasing force 5 F is the same in the present embodiment and in the comparative example. In this case, the biasing force 8 F′ of the adjusting spring has a positive value, and the total biasing force TF′ is greater than each of the biasing force 5 F and the total biasing force TF. Additionally, since the directions of the biasing forces 5 F and 8 F are the same in the comparative example, the decrease rate of the total biasing force TF′ is smaller than that of the total biasing force TF. For this reason, when the trailing blades are stopped, the impact and the impact sound are increased in the comparative example, as compared with that of the biasing force TF.

In the present embodiment, the biasing direction of the adjusting spring 80 is opposite to that of the spring 54 B, and the biasing force of the adjusting spring 80 increases as the trailing blades 20 B come closer to the closing position. Thus, the total biasing force TF can be further decreased as the trailing blades 20 B come closer to the closing position. That is, the speed of the trailing blades 20 B can be made smaller in the stepless manner as the trailing blades 20 B come closer to the closing position. Moreover, the decrease rate increases as they come closer to the closing position. It is therefore possible to suppress the impact and the impact sound when the trailing blades 20 B are stopped at the closing position.

Additionally, in the present embodiment, the biasing direction of the rattle suppression spring Sb is opposite to that of the spring 54 B, and the biasing force of the rattle suppression spring Sb increases as the trailing blades 20 B come closer to the closing position. Thus, actually, the total biasing force TF can be made much smaller as the trailing blades 20 B come closer to the closing position. It is therefore possible to suppress the impact and the impact sound when the trailing blades 20 B are stopped at the closing position.

Further, the swing lever 91 of the adjusting mechanism 90 adjusting the biasing force of the adjusting spring 80 swings about a predetermined position. Thus, the angle of the swing lever 91 is changed as illustrated in FIGS. 5 and 6 , so that the swingable range of the front end portion of the swing lever 91 can be ensured. Therefore, the angle of the arm portion 85 of the adjusting spring 80 engaging the front end portion of the swing lever 91 can be greatly changed. This ensures the adjustable range of the biasing force of the adjusting spring 80 .

Further, as illustrated in FIG. 4 , the spring 54 B and the ratchet wheel 50 B are arranged in one side of the board 10 , whereas the adjusting spring 80 and the adjusting mechanism 90 are arranged in the other side of the board 10 . Therefore, as compared with a case where these members are arranged in the same side of the board 10 , the focal plane shutter 1 according to the present embodiment is suppressed from increasing in its size in the plane direction.

Next, a variation will be described. FIGS. 8A to 8C are views of states of a drive arm 31 b ′ from the time when trailing blades of a focal plane shutter 1 ′ according to the variation start moving to the time when the trailing blades are stopped. Additionally, the similar components are designated with the similar reference numerals and the duplication description is omitted. The drive arm 31 b ′ is thin and made of a synthetic resin. A hole 31 b H′ of the drive arm 31 b ′ includes edges E 1 and E 2 facing each other. The edge E 1 is located at the movement start position side where the trailing blades start moving in the exposure operation, whereas the edge E 2 is located at the movement stop position side where the trailing blades are stopped in the exposure operation. A distance between the edges E 1 and E 2 is greater than the outer diameter of the drive pin 43 b . Thus, as illustrated in FIG. 8A , in the state where the trailing blades are stopped away from the opening, the adjusting spring 80 biases the drive arm 31 b ′ such that the edge E 2 abuts the drive pin 43 b.

After the trailing blades start moving, when the drive pin 43 b abuts the rubber Gb provided at the end portion of the escape slot 13 b as illustrated in FIG. 8B , the drive arm 31 b ′ tries to move further in accordance with the inertial force as illustrated in FIG. 8C . Therefore, the edge E 2 moves away from the drive pin 43 b , and the edge E 1 abuts the drive pin 43 b . After that, the inertial force exerting on the drive arm 31 b ′ decreases, so that the edge E 1 moves away from the drive pin 43 b and the edge E 2 abuts the drive pin 43 b in accordance with the biasing force of the adjusting spring 80 . As a result, the drive pin 43 b and the trailing blades 20 B are stopped.

As illustrated in FIGS. 8B and 8C , the direction of the biasing force of the adjusting spring 80 is opposite to that of the inertial force that exerts on the adjusting spring 80 just when the moving drive pin 43 b abuts the rubber Gb. Thus, the adjusting spring 80 can reduce the inertial force that exerts on the drive arm 31 b ′ just when the edge E 1 abuts the drive pin 43 b . Accordingly, for example, the deformation of the edge E 1 due to the strong abutment of the edge E 1 with the drive pin 43 b can be suppressed.

Next, a description will be given of an example of adjusting speed of the trailing blades of a focal plane shutter 1 a ′ according to a variation. FIG. 9 is an explanatory view of adjusting speed of the trailing blades of the focal plane shutter 1 a ′ according to the variation. The focal plane shutter 1 a ′ is secured on a measuring device T, each movement speed of the leading blades and the trailing blades are detected, and the movement speed of the trailing blades are adjusted. The measuring device T is equipped with an image pickup element. A lens is installed in the opposite side of the measuring device T with respect to the focal plane shutter 1 a ′. A board 10 ′ is provided with a drive mechanism DM for driving the leading blades and the trailing blades. The drive mechanism DM includes, for example, electromagnets as mentioned above, drive levers, ratchet wheels, and springs. FIG. 9 illustrates the simplified drive mechanism DM. The focal plane shutter 1 a ′ is secured to the measuring device T such that the board 10 ′ faces the lens side and the rear board 18 faces the measuring device T side. That is, the drive mechanism DM faces the lens side.

A swing lever 91 ′ of an adjusting mechanism 90 ′ is provided with an operating knob 97 projecting from the board 10 ′. An operator operates the rotation of the operating knob 97 , so that the angle of the swing lever 91 ′ can be adjusted. The operating knob 97 projects toward the lens side from the side where the drive mechanism DM is provided on the board 10 ′, that is, the side where the electromagnets are provided on the board 10 ′. Thus, the operator can operate the operating knob 97 in the state where the focal plane shutter 1 a ′ is attached to the T. Therefore, the biasing force of the adjusting spring 80 can be adjusted and the speed of the trailing blades can be adjusted in the state where the focal plane shutter 1 a ′ is attached to the T. In this way, the working property is improved. The operating knob 97 is an example of an operation portion.

Additionally, a securing screw is screwed into the operating knob 97 from the lens side, and this securing screw secures the adjusting mechanism 90 ′ to the board 10 ′. A head screw of this securing screw is located in the lens side. To adjust the angle of the swing lever 91 ′, the securing screw is loosened and the operating knob 97 is rotated by a desired amount, and the securing screw secures the adjusting mechanism 90 ′ to the board 10 ′ again.

While the exemplary embodiments of the present invention have been illustrated in detail, the present invention is not limited to the above-mentioned embodiments, and other embodiments, variations and modifications may be made without departing from the scope of the present invention.

The focal plane shutter according to the present embodiment can be employed in an optical apparatus such as a still camera or a digital camera.

At least one of the electromagnets 70 A and 70 B may be a self-holding type solenoid.

The swing lever 91 may be secured with an adhesive rather than by the securing screw 95 .

The adjusting spring 80 and the adjusting mechanism 90 may be provided for the drive arm 31 a . In this case, the adjusting spring 80 is arranged so as to bias the drive arm 31 a in the direction opposite to the direction of the biasing force of the spring adjusted by the ratchet wheel 50 A.