Image pickup device and focal plane shutter

This application is a continuation of and claims priority to International Patent Application No. PCT/JP2014/074897 filed on Sep. 19, 2014, which claims priority to Japanese Patent Application No. 2013-253507 filed on Dec. 6, 2013, subject matter of these patent documents is incorporated by reference herein in its entirety.

(i) Technical Field

The present invention relates to image pickup devices and focal plane shutters.

(ii) Related Art

Japanese Unexamined Patent Application Publication Nos. 2010-181522 and 2008-256844 disclose a focal plane shutter driving a shutter by use of an electromagnet.

In a case of using the actuator as a drive source for driving the shutter, a change in temperature of a coil of the actuator also changes the resistance value of the coil. This might cause an exposure period to vary.

It is therefore an object of the present invention to provide an image pickup device and a focal plane shutter that suppress variations in an exposure period.

According to an aspect of the present invention, there is provided an image pickup device including: an image pickup element; a board including an opening through which light entering the image pickup element passes; a shutter opening and closing the opening; an actuator driving the shutter, and including: a rotor; a stator; and first and second coils wound around the stator and not electrically connected to each other; and a drive circuit including plural terminal portions to which the first and second coils are individually connected.

According to another aspect of the present invention, there is provided an image pickup device including: an image pickup element; a board including an opening through which light entering the image pickup element passes; a shutter opening and closing the opening; an actuator driving the shutter, and including: a rotor; a stator; and first and second coils wound around the stator and not electrically connected to each other; and drive circuits to which the first and second coils are individually connected.

According to another aspect of the present invention, there is provided an image pickup device including: an image pickup element; a board including an opening through which light entering the image pickup element passes; a shutter opening and closing the opening; an actuator driving the shutter, and including: a rotor; a stator; and first and second coils wound around the stator and electrically connected to each other in parallel; and a drive circuit to which the first and second coils are connected.

According to another aspect of the present invention, there is provided a focal plane shutter including: a board including an opening; a shutter opening and closing the opening; and an actuator driving the shutter, and including: a rotor; a stator; and first and second coils wound around the stator and not electrically connected to each other.

According to another aspect of the present invention, there is provided a focal plane shutter including: a board including an opening; a shutter opening and closing the opening; and an actuator driving the shutter, and including: a rotor; a stator; and first and second coils wound around the stator and electrically connected to each other in parallel.

FIG. 1 is a block diagram of a camera including a focal plane shutter;

FIG. 2 is a front view of the focal plane shutter;

FIG. 3 is an explanatory view of an actuator;

FIG. 4 is an explanatory view of a comparative example of an actuator;

FIG. 5A is a graph indicating a change in a current value after a coil of the actuator starts being energized, and FIG. 5B is a graph indicating a change in a current value after a coil of the actuator of the comparative example starts being energized;

FIGS. 6A and 6B are explanation views of variations of actuators; and

FIGS. 7A and 7B are block diagrams of cameras in variations of the actuators.

In the following, a description will be given of embodiments.

First Embodiment

FIG. 1 is a block diagram of a camera (image pickup device) A including a focal plane shutter 1 . The camera A includes the focal plane shutter 1 , a control portion 110 , an image pickup element 130 , and a drive circuit 170 b . The focal plane shutter 1 includes a trailing shutter actuator (hereinafter, referred to as actuator) 70 b.

The control portion 110 gives a predetermined instruction to the drive circuit 170 b . The drive circuit 170 b controls the drive of the actuator 70 b in accordance with this instruction from the control portion 110 . The control portion 110 controls the operation of the whole camera, and includes a CPU, a ROM, and a RAM. The image pickup element 130 is a CMOS. The image pickup element 130 is a light receiving element that converts subject images into electric signals on the basis of photoelectric conversion. Moreover, the camera A includes lenses, not illustrated in FIG. 1 , for adjusting a focal length.

The control portion 110 sequentially starts storing charges by sequentially resetting the stored charges in the image pickup element 130 for every pixel line in a predetermined direction. Specifically, the charges sequentially start being stored in the image pickup element 130 at predetermined timing for every pixel line, perpendicular to the movement direction of the trailing shutter 20 B, of the image pickup element 130 . Therefore, the electronic leading shutter moves from an exposure start position to an exposure end position in a simulated manner. After that, the trailing shutter 20 B is moved to close the opening 11 after a predetermined period elapses, so that the charges sequentially finish being stored for every pixel line of the image pickup element 130 and the exposure operation is finished. The camera A is an image pickup device with a so-called electronic leading shutter function.

FIG. 2 is a front view of the focal plane shutter 1 . In FIG. 2 , the actuator 70 b is omitted. The focal plane shutter 1 includes a board 10 , a trailing shutter 20 B, arms 31 b and 32 b , and the actuator 70 b . The board 10 is provided with a rectangular opening 11 . FIG. 2 illustrates an imaging surface of the image pickup element 130 within the opening 11 . The light entering the image pickup element 130 passes through the opening 11 .

The trailing shutter 20 B includes three blades 21 b to 23 b . In FIG. 2 , the trailing shutter 20 B is in an overlapped state and recedes from the opening 11 . The trailing shutter 20 B is connected to the arms 31 b and 32 b . These arms 31 b and 32 b are each rotatably supported by the board 10 .

The board 10 is provided with a trailing shutter drive lever 55 b (hereinafter, referred to as drive lever) for each driving the arm 31 b . The drive lever 55 b is connected with a gear 50 b . The gear 50 b engages a gear 40 b . The gears 40 b and 50 b include pipe portions 41 b and 51 b respectively, and are rotatably supported around spindles 42 b and 52 b fitting into the pipe portions by the board 10 , respectively. Additionally, the spindles 42 b and 52 b do not have to be always formed on the board 10 in which the opening 11 is formed, and have only to be positionally fixed with respect to the opening 11 .

The gear 40 b is connected with a rotor of the actuator 70 b . The driving of the actuator 70 b drives the gears 40 b and 50 b , thereby driving the drive lever 55 b . The driving of the drive lever 55 b drives the arm 31 b . Thus, the trailing shutter 20 B moves. The trailing shutter 20 B is movable between a receded position to recede from the opening 11 and a closed position to close the opening 11 .

Next, operation of the focal plane shutter 1 will be described. In a wait state, as illustrated in FIG. 2 , the trailing shutter 20 B is positioned at the receded position, and the opening 11 is maintained in a fully opened state. When a release switch of the camera A is pushed, the control portion 110 performs sensor reset so as to erase the charges stored in the image pickup element 130 at predetermined timing for every pixel line of the image pickup element 130 perpendicular to the movement direction of the trailing shutter 20 B from the exposure start position to the exposure end position. In other words, the charges are stored at predetermined timing for every pixel line of the image pickup element 130 perpendicular to the movement direction of the trailing shutter 20 B. After a predetermined period elapses from the time when the charges start being stored in the image pickup element 130 , the control portion 110 energizes the actuator 70 b to cause the trailing shutter 20 B to move and close the opening 11 . Thus, the charges finish being stored for every pixel line of the image pickup element 130 . Additionally, in the present embodiment, the storage of the charges from the exposure start position to the exposure end position for every pixel line of the image pickup element 130 at predetermined timing is referred to as the movement of the electronic leading shutter. After that, when the trailing shutter 20 B fully closes the opening 11 , the energization of the coil of the actuator 70 b is stopped. In such a way, the exposure operation is finished. Herein, the period from the time when the electronic leading shutter starts moving to the time when the trailing shutter 20 B closes the opening 11 is referred to as an exposure period. After the exposure operation is finished, the data are output to the RAM of the control portion 110 or a memory of the camera side.

After that, a charging operation starts. In the charging operation, the control portion 110 energizes the actuator 70 b to move the trailing shutter 20 B away from the opening 11 . This brings the opening 11 into the fully opened state as illustrated in FIG. 2 , so the wait state is shifted.

FIG. 3 is an explanatory view of the actuator 70 b . The actuator 70 b is supported by the board 10 . The actuator 70 b includes: a rotor 71 b rotatably supported by the board 10 ; a stator 74 b energized to exert a magnetic force between the stator 74 b and the rotor 71 b ; and coils 76 b and 77 b for energizing the stator 74 b . The rotor 71 b is a permanent magnet magnetized to different polarities in the circumferential direction. The rotor 71 b is fixed with the gear 40 b . The energization of the coils 76 b and 77 b rotates the rotor 71 b to rotate the gear 40 b and the gear 50 b . The rotation of the gear 50 b causes a drive lever 55 b to swing, so the trailing shutter 20 B moves. In addition, the reverse energization of the coils 76 b and 77 b reversely rotates the rotor 71 b , so the trailing shutter 20 B moves in the opposite direction to the above-mentioned one.

The stator 74 b includes: a base portion 74 b 1 ; and arm portions 74 b 2 and 74 b 3 extending substantially in parallel with each other from respective ends of the base portion 74 b 1 in substantially the same direction. Distal end portions of the arm portions 74 b 2 and 74 b 3 are respectively formed with magnetic pole portions 74 b 4 and 74 b 5 facing the rotor 71 b . In addition, the two coils 76 b and 77 b are wound around the arm portion 74 b 3 through a coil bobbin 79 b . Ends of the two coils 76 b and 77 b are individually connected to terminal portions 171 b to 174 b of the drive circuit 170 b.

The coils 76 b and 77 b are the same in diameter and also in length. The coils 76 b and 77 b are not electrically connected to each other. The coils 76 b and 77 b , wound around the arm portion 74 b 3 side of the stator 74 b , are substantially the same in the number of turns. The coils 76 b and 77 b may be wound around the arm portion 74 b 3 in the same direction or in the opposite direction, as long as the energization directions in energizing both the coils 76 b and 77 b does not offset polarities that are generated in the magnetic pole portions 74 b 4 and 74 b 5 by energization. In the present embodiment, the directions in which each current flowing through the coils 76 b and 77 b are set so as to flow in the same direction around the arm portion 74 b 3 . Additionally, the position where the two coils 76 b and 77 b are wound is not limited to the arm portion 74 b 3 . For example, any one of the coils 76 b and 77 b may be wound around the arm portion 74 b 2 , the other may be wound around the arm portion 74 b 3 .

FIG. 4 is an explanatory view of an actuator 70 x of a comparative example. As for the actuator 70 x , similar components of the actuator 70 b are designated with similar reference numerals and a description of those components will be omitted. In the actuator 70 x , a single coil 76 x is wound around the arm portion 74 b 3 side of the stator 74 b . Both ends of the coil 76 x are respectively connected to terminal portions 171 x and 172 x of a drive circuit 170 x . The number of turns of the coil 76 x is the same as the total number of turns of the coils 76 b and 77 b . In addition, the resistance value of the coil 76 x is the same as the total resistance value of the coils 76 b and 77 b . In addition, the voltage applied to the coil 76 x is adjusted such that the value of the current flowing through the coil 76 x is the same as each value of the current flowing through the coils 76 b and 77 b . Specifically, the voltage applied to the coil 76 x is twice as high as each voltage applied to the coils 76 b and 77 b . Thus, the ampere-turn of the coil 76 x is the same as the total ampere-turn of the coils 76 b and 77 b . Therefore, the actuator 70 x is substantially the same as the actuator 70 b in torque.

FIG. 5A is a graph illustrating a change in a current value from the time when the coil 76 b of the actuator 70 b starts being energized. FIG. 5B is a graph illustrating a change in a current value from the time when the coil 76 x of the actuator 70 x of the comparative example starts being energized. A curve B 1 indicates a value of the current flowing through the coil 76 b . Incidentally, the coil 77 b is the same as the coil 76 b in the number of turns, in the resistance value, in the applied current value, and in the applied voltage value. For this reason, a value of the current flowing through the coil 77 b is also changed as indicated by the curve B 1 . A curve X 1 indicates a value of the current flowing through the coil 76 x . As indicated by the curves B 1 and X 1 , there are time lags from when the energization starts to when a current value reaches the desired current value. The time lag in the actuator 70 b is shorter than that in the actuator 70 x . This is because the resistance value of the coil 76 b is smaller than that of the coil 76 x and it is easier to cause the current to flow through the coil 76 b than the coil 76 x . Therefore, as compared with the case of the actuator 70 x using the coil 76 x , in the case of the actuator 70 b using the coils 76 b and 77 b , the torque at the desired current value is reached for short time. This reduces the period from the time when the energization starts to the time when the trailing shutter 20 B starts moving.

B 2 and X 2 illustrated in FIGS. 5A and 5B respectively indicate values of current flowing through the coils 76 b and 76 x of the actuators 70 b and 70 x in a high temperature environment. As illustrated in FIGS. 5A and 5B , in each case, a time lag from when the energization starts to when a current value reaches the desired current value is increased after high temperature. This is because, in general, an increase in temperature of a coil increases a resistance value, so the current hardly flows.

Here, the change amount ΔB illustrated in FIG. 5A indicates the change amount of the rising period from when the current starts being applied to the coil 76 b to when a current value flowing through the coil 76 b reaches the desired current value. Similarly, the change amount ΔX illustrated in FIG. 5B indicates the change amount of the rising period from when the current starts being applied to the coil 76 x to when a current value flowing through the coil 76 x reaches the desired current value. The change amount ΔB is smaller than the change amount ΔX. This reason is supposedly as follows. Since the resistance value of the coil 76 b is smaller than that of the coil 76 x by the number of turns of the coil 76 x , the change amount of the resistance value of the coil 76 b due to the change in the temperature is smaller than that of the resistance value of the coil 76 x , when both temperatures of the coils 76 b and 76 x change to the same degree.

The temperatures of the coils 76 b and 76 x also change in such a way, when the actuators 70 b and 70 x are driven multiple times. Thus, for example, the actuators 70 b and 70 x are driven multiple times by continuous shooting or the like, the temperatures of the coils 76 b and 76 x supposedly increase to the same degree. In this case, the change amount ΔB of the rising period of the current flowing through the coil 76 b is smaller than the change amount ΔX. For this reason, as compared with the comparative example, the present embodiment suppresses the change in the period from the time when the energization starts to the time when the trailing shutter 20 B starts moving.

Thus, the present embodiment can suppress the variations in the exposure period caused by the temperature change. When using the electronic leading shutter, the moving speed of the electronic leading shutter is not changed by the temperature change in use environment. For this reason, the main cause of the variations in the exposure period might be the change in the period from when the energization starts to when the trailing shutter 20 B starts moving. However, the actuator 70 b uses two coils 76 b and 77 b in the present embodiment, thereby suppressing the change in the moving speed of the trailing shutter 20 B and the variations in the exposure period even when using the electronic leading shutter.

Additionally, although the control portion 110 energizes both the coils 76 b and 77 b in the exposure operation, the control portion 110 may energize one of the coils 76 b and 77 b in the charging operation. This is because the exposure operation requires the fast moving speed of the trailing shutter 20 B, but the charging operation does not require the moving speed of the trailing shutter 20 B. This can suppress the power consumption. In addition, in the continuous shooting mode, the coils 76 b and 77 b may both be energized even in the charging operation.

FIGS. 6A and 6B are explanatory views of variations. As illustrated in FIG. 6A , the coils 76 b and 77 b are respectively connected to individual drive circuits 170 b 1 and 170 b 2 . Specifically, both ends of the coil 76 b are respectively connected to the terminal portions 171 b and 172 b of the drive circuit 170 b 1 , and both ends of the coil 77 b are respectively connected to the terminal portions 173 b and 174 b of the drive circuit 170 b 2 . Also, the drive circuits 170 b 1 and 170 b 2 are controlled by the control portion 110 . Such a configuration can also suppress the change in the moving speed of the trailing shutter 20 B and the variations in the exposure period.

Incidentally, one end and the other end of the coil 76 b may be respectively wound around two projecting portions formed in the coil bobbin 79 b , and one end and the other end of the coil 77 b are respectively wound around the other two projecting portions formed in the coil bobbin 79 b . In this case, through the single focal plane shutter 1 , it can be confirmed that the two coils 76 b and 77 b not electrically connected to each other are wound around the stator 74 b.

As illustrated in FIG. 6B , the coils 76 b and 77 b wound around the stator 74 b of an actuator 70 b 1 are connected to each other in parallel and to a drive circuit 170 b 3 . Therefore, the drive circuit 170 b 3 is provided with only the two terminal portions 171 b and 172 b . One ends of the coils 76 b and 77 b are connected to the terminal portion 171 b , and the other ends of the coils 76 b and 77 b are connected to the terminal portion 172 b . Such a configuration can also suppress the change in the moving speed of the trailing shutter 20 B and the variations in the exposure period.

Incidentally, one ends of the coils 76 b and 77 b , wound around the projecting portion or the like of the coil bobbin 79 b , may be electrically connected to each other, and the other ends of the coils 76 b and 77 b , wound around the other projecting portion or the like of the coil bobbin 79 b , may be electrically connected to each other. In this case, through the single focal plane shutter 1 , it can be confirmed that the two coils 76 b and 77 b electrically connected in parallel are wound around the stator 74 b.

FIG. 7A is a block diagram of a camera Aa according to a variation. The camera Aa includes a focal plane shutter 1 a , a control portion 110 a , and a drive circuit 170 a . The focal plane shutter 1 a includes a leading shutter 20 A and a leading shutter actuator 70 a (hereinafter referred to as actuator) for driving the leading shutter 20 A. The drive circuit 170 a controls the drive of the actuator 70 a in accordance with the instruction from the control portion 110 a . The camera Aa does not use the electronic leading shutter, but uses the mechanical leading shutter 20 A. Such a case of using the leading shutter 20 A and the actuator 70 a can also suppress the change in the moving speed of the trailing shutter 20 B caused by the changes in the temperatures of the coils 76 b and 77 b , thereby suppressing the variations in the exposure period.

Incidentally, like the actuator 70 b , a case where the actuator 70 a uses two coils can also suppress the variations in the exposure period. In this case, the two coils of the actuator 70 a are not always the same as the two coils 76 b and 77 b of the actuator 70 b in temperature. Thus, even in such a case, the exposure period might vary somewhat. However, it is possible to suppress the change amount of each moving speed of the leading shutter 20 A and the trailing shutter 20 B caused by the changes in the temperatures, thereby suppressing the variations in the exposure period. Also, it is possible to suppress a decrease in the moving speed for both the leading shutter 20 A and the trailing shutter 20 B, thereby suppressing a decrease in the shutter speed.

Further, the actuator 70 a may use the two coils as described above, and the actuator 70 b may use a single coil. This case can also suppress the variations in the moving speed of the leading shutter 20 A and the variations in the exposure period.

FIG. 7B is a block diagram of a camera Ab according to a variation. The camera Ab includes a focal plane shutter 1 b , and a control portion 110 b . The focal plane shutter 1 b includes the leading shutter 20 A, a spring S, and a leading shutter magnet (hereinafter, referred to as electromagnet) 80 a . The leading shutter 20 A is biased by the spring S in such a direction as to recede from the opening 11 . The electromagnet 80 a maintains the leading shutter 20 A in a state of closing the opening 11 based on the electromagnetic force, in a state where the leading shutter 20 A closes the opening 11 . Specifically, a drive lever for driving the leading shutter 20 A is biased by the spring S. Further, the drive lever is provided with an iron piece capable of being adsorbed on the electromagnet 80 a.

When the electromagnet 80 a is energized, the iron piece of the drive lever is adsorbed on and held by the electromagnet 80 a against the biasing force of the spring S. When the energization of the electromagnet 80 a is stopped, the leading shutter 20 A is moved away from the opening 11 by the biasing force of the spring S. Also, the focal plane shutter 1 b is provided with a non-illustrated set lever that drives the drive lever to cause the iron piece of the drive lever to come into contact with the electromagnet 80 a . Such a configuration can also suppress the change in the moving speed of the trailing shutter 20 B and the variations in the exposure period.

Further, the above-described cameras Aa and Ab may use the configuration illustrated in FIG. 6A or the configuration illustrated in FIG. 6B .

The coils 76 b and 77 b may be different in at least one of length, diameter, and resistance value. This is because this case can also suppress the variations in the exposure period, as compared with the case of driving the shutter only by a single coil.

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 used in an optical apparatus such as a still camera or a digital camera.

Although blades that are made of a synthetic resin has been described in the present embodiment, blades may be made of a thin-shaped metal.

In the above embodiment, the trailing shutter is composed of three blades, but not limited to this.