JP6173023B2 - Mirror drive device and imaging device provided with the same - Google Patents

Description

  The present invention relates to a mirror driving device.

  Conventionally, in a quick return mirror mechanism such as a single-lens reflex camera, a main mirror and a sub mirror are rotated at high speed in and out of an optical path (imaging optical path) of an imaging optical system.

  As a quick return mirror mechanism, a spring charge mechanism has been proposed in which the main mirror is retracted from the mirror-up position to the mirror-down position by releasing the charging force of the spring. However, the spring charge mechanism requires a large driving force to charge the spring.

  Therefore, Patent Document 1 proposes a direct drive mechanism that rotates the main mirror by the driving force of the actuator.

Japanese Patent Laid-Open No. 11-95317

  FIG. 7 is a diagram for explaining the rotation operation of the main mirror and the sub mirror in the conventional spring charge mechanism. As shown in FIG. 7A, as a method of rotating the sub mirror 302, a cam dowel pin 303 fixed in the mirror box follows a cam surface 302a formed on the sub mirror 302 in accordance with the rotation of the main mirror 301. A method has been proposed.

  However, in the direct drive mechanism as in Patent Document 1, when the sub mirror is rotated by the cam, the load applied to the drive lever for rotating the sub mirror varies during the rotation of the main mirror depending on the shape of the cam.

  In particular, as shown in FIGS. 7A and 7B, when the contact surface of the cam dowel pin 303 is switched from the cam portion 302a of the sub mirror 302 to the cam portion 302b, the sub mirror is reversed and the drive lever A large load is applied instantaneously. In the spring charge mechanism, such a change in load is not a big problem. However, in the direct drive mechanism, when a stepping motor is used as a drive source, it causes a step-out of the stepping motor. If it is driven safely as a step-out measure, the speed cannot be increased.

  In the mirror down position, the light beam reflected by the sub-mirror is guided to the focus detection sensor. However, in order to improve the focus detection accuracy, it is necessary to adjust the angle of the sub-mirror with respect to the light beam after assembly. That is, while the main mirror is urged by the restricting portion, the restricting portion of the sub mirror is required to be able to move a minute amount for adjustment.

  In view of such problems, an object of the present invention is to provide a mirror driving device capable of high-speed driving and high-precision positioning with a simple configuration.

A mirror driving device according to one aspect of the present invention has a shaft portion that is pivotally supported by an imaging device, and is rotationally driven between a mirror-down position and a mirror-up position, and a part of a light beam is transmitted at the mirror-down position. A main mirror to be transmitted; a sub-mirror that is pivotally supported by the main mirror and reflects a light beam that has passed through the main mirror; a stepping motor that performs rotational driving; and a lead screw that rotates by transmission of the rotational motion of the stepping motor; A moving portion that moves along the lead screw by engaging with the lead screw, and that rotates the main mirror about the shaft portion by energizing the main mirror during movement, and the main mirror Is positioned at the mirror down position, the first position restricting portion for restricting the position of the sub mirror, and the main mirror Is positioned at the mirror up position, the second position restricting portion for restricting the position of the sub mirror, and the first gear portion that is pivotally supported coaxially with the main mirror and that is formed on the sub mirror. And a biasing portion that biases the coupling portion so that the first and second position regulating portions regulate the position of the sub-mirror. .

  According to the present invention, high-speed driving and high-accuracy positioning are possible with a simple configuration.

It is a center section schematic diagram of a camera system concerning an embodiment of the present invention. It is a perspective view of a mirror drive device. It is a figure explaining a main mirror drive mechanism. It is a figure explaining operation | movement of a sub mirror and a sun gear at the time of main mirror rotation. It is a figure explaining the sun gear in which the buffer member was formed. It is a figure explaining the other shape of the gear part of a sun gear. It is a figure explaining the rotation operation | movement of the conventional main mirror and a submirror.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In each figure, the same members are denoted by the same reference numerals, and redundant description is omitted.

  First, the mirror driving device according to the present embodiment will be described with reference to FIGS.

  FIG. 1A is a schematic cross-sectional view of the center of the camera system according to the present embodiment. FIG. 1B is a schematic cross-sectional view seen from the opposite side of FIG. 1A, and portions not necessary for description are omitted for the sake of simplicity.

  FIG. 2A is an external perspective view of the mirror driving device, and FIG. 2B is an exploded perspective view of the mirror driving device viewed from the opposite side of FIG. In FIG. 2B, only a part of the wall surface is shown for the mirror box 201.

  The camera system according to the present embodiment includes a photographing lens (lens device) 100 and a digital single-lens reflex camera (hereinafter referred to as a camera) 200.

  The taking lens 100 is attached to the camera 200 in an exchangeable manner. The lens unit 101 that is an imaging optical system is composed of a focus lens group and a zoom lens group.

  An imaging element 202 including a photoelectric conversion element including an optical low-pass filter, an infrared cut filter, and a CMOS sensor is disposed in the vicinity of a planned imaging plane on which a light beam guided from the photographing lens 100 in the camera 200 is imaged. Is done.

  The mirror box 201 is a box-shaped member having a main mirror 203 and a sub mirror 204 inside, and a mirror driving unit and a focus detection sensor described later are attached in addition to the main mirror 203 and the like.

  The main mirror 203 and the sub mirror 204 are disposed obliquely with respect to the optical axis 102a of the photographing lens 100. The main mirror 203 is pivotally supported by the shaft portion 201 c of the mirror box 201, and the sub mirror 204 is pivotally supported by the shaft portion 203 e of the main mirror 203.

  A state in which the main mirror 203 is in contact with the down stopper 201a is defined as a mirror down position. At this time, the sub mirror 204 is in contact with the sub mirror dowel portion (first position restricting portion) 209a and the position thereof is restricted.

  A state in which the main mirror 203 is in contact with the up stopper 201b and the main mirror 203 and the sub mirror 204 are retracted from the optical axis 102a is defined as a mirror up position (second position). At this time, the sub mirror 204 is in contact with the back surface portion (second position restricting portion) 203d of the main mirror 203, and the position thereof is restricted. A configuration for regulating the position may be provided on the back surface of the main mirror 203.

  The down stopper 201a and the up stopper 201b are configured in the mirror box 201. The up stopper 201b may be configured as a rigid body as a part of the mirror box 201, or may be configured as another elastic member such as urethane foam.

  When the main mirror 203 is positioned at the mirror down position, the light beam 102b reflected by the main mirror 203 forms an image on the mat surface of the focusing plate 205 having the mat surface and the Fresnel surface, and the pentaprism 206 and the eyepiece optical system 207 Through the eyes of the photographer. The light beam 102c transmitted through the half mirror unit 203a attached to the main mirror 203 is reflected by the mirror unit 204a of the sub mirror 204 and received by a focus detection sensor (focus detection unit) 208 that detects the focal length of the subject.

  When the main mirror 203 is located at the mirror-up position, the light beam 102c that has passed through the photographing lens 100 is directly imaged on the image sensor 202.

  Here, a mirror driving unit that rotates the main mirror 203 will be described. FIG. 3 is a diagram illustrating the main mirror driving mechanism. Parts that are not necessary for the description of the rotation operation of the main mirror 203 are omitted for the sake of simplicity.

  The mirror drive unit that drives the main mirror 203 includes a movable element 211, a mirror drive torsion spring 212, a stepping motor (hereinafter referred to as a motor) 213, a lead screw 214, an angle 215, and a guide shaft 216.

  The mover 211 has a rack portion 211 a that meshes with the lead screw 214 and is slidably attached to the guide shaft 216.

  The mirror drive torsion spring 212 is attached to the dowel 211b of the mover 211, and is restricted from rotating about the dowel 211b by a spring rotation stopper 211c. The mirror drive torsion spring 212 sandwiches the main mirror drive lever 203b formed on the main mirror 203.

  The lead screw 214 is connected to a rotating shaft of a motor 213 that is a rotation driving unit, and can be rotated integrally by a rotating motion of the motor 213.

  The angle 215 is inclined with respect to the main mirror 203, and a lead screw 214 and a guide shaft 216 are attached thereto.

  FIG. 3A shows the state of the mirror down position. At this time, the main mirror drive lever 203b is urged by the end 212a of the mirror drive torsion spring 212, and the position of the main mirror 203 is regulated while being in contact with the down stopper 201a. The mover 211 is held by the cogging force of the motor 213.

  When the motor 213 is driven, the mover 211 is linearly driven parallel to the lead screw 214. At this time, since the main mirror drive lever 203b is held by the mirror drive torsion spring 212, the main mirror 203 rotates.

  The main mirror 203 rotates to the mirror up position in FIG. 3B and contacts the up stopper 201b. At this time, the sub mirror 204 is in contact with the back surface portion 203 d of the main mirror 203.

  Further, when the mover 211 moves from the state shown in FIG. 3B in the direction D in FIG. 3C, the main mirror drive lever 203b moves to the end of the mirror drive torsion spring 212 as shown in FIG. Energized by the portion 212b, the position of the main mirror 203 is regulated.

  As described above, the main mirror 203 is restricted to the respective position restricting portions at the mirror down position and the mirror up position by the charging force of the mirror drive torsion spring 212. As a result, even when the posture of the camera 200 is changed or when vibration is applied, the main mirror 203 is maintained in a position-controlled state at the mirror-down position or the mirror-up position.

  The sub mirror 204 is formed with a sub mirror gear portion (first gear portion) 204b which is a sector gear. The sub mirror gear portion 204b meshes with a gear portion (second gear portion) 221a of a sun gear (connecting portion) 221 that is pivotally supported by the shaft portion 201c of the mirror box 201. As the sun gear portion 221 a and the sub mirror gear portion 204 b mesh with each other, the sub mirror 204 rotates in conjunction with the rotation operation of the main mirror 203.

  The adjustment unit 209 is pivotally supported by the shaft 201e of the mirror box 201 so as to be rotatable in the C direction shown in FIG. The sub mirror 204 can also rotate in the direction A shown in FIG. 1B in accordance with the rotation of the adjusting unit 209. That is, the adjustment unit 209 can adjust the direction of the light beam 102 b reflected by the sub-mirror 204 to guide the light beam to an appropriate position of the focus detection sensor 208. Therefore, in the present embodiment, a highly accurate focus detection operation can be performed. After adjusting the direction of the light beam 102 b, the adjustment unit 209 is fixed to the mirror box 201.

  The sun gear (connection portion) 221 is pivotally supported by the shaft portion 201c of the mirror box 201 coaxially with the main mirror 203, and is rotatable in the B direction shown in FIG.

  The sun gear biasing spring (biasing portion) 222 has a torsion spring shape, and the sun gear 221 rotates clockwise by contacting the sun gear protrusion 221b and the spring hooking dowel portion 201d formed on the mirror box 201. Or, it is biased counterclockwise.

  The rotation operation of the main mirror 203, the sub mirror 204, and the sun gear 221 will be described with reference to FIG. FIG. 4 is a diagram for explaining the operation of the sub mirror 204 and the sun gear 221 when the main mirror 203 is rotated.

  FIG. 4A shows the state of the mirror down position. At this time, the end 222a of the sun gear biasing spring 222 is in contact with the spring hooking dowel 201d, and the sun gear 221 is biased in the counterclockwise direction. As a result, the sub mirror 204 is urged clockwise around the shaft 203e, and the position of the sub mirror 204 is regulated while being in contact with the sub mirror dowel 209a.

  By driving the motor 213 from the state of FIG. 4A, the main mirror 203 starts to rotate counterclockwise.

  FIG. 4B is a state immediately after the main mirror 203 is rotated by a small angle from the state of FIG. 4A and the charge of the sun gear biasing spring 222 is released. When the sun gear biasing spring 222 is released, the sun gear 221 stops rotating. Then, the main mirror 203 and the sub mirror 204 rotate in the direction of the mirror up position in the state shown in FIG. During the rotation operation of the main mirror 203, the sub mirror 204 rotates through the sun gear 221, so that the driving load on the main mirror drive lever 203b due to the inversion of the sub mirror 204 is smoothed. Therefore, the load on the motor 213 is smoothed, and the occurrence of step-out during the driving of the motor 213 can be suppressed. The driving load at this time is determined by the moment of inertia caused by the rotation of the sub mirror 204 and the gear ratio between the sun gear portion 221a and the sub mirror gear portion 204b.

  When the main mirror 203 is rotated and the main mirror 203 is rotated by a small angle as shown in FIG. 4D, the position reaches the mirror up position. At this time, the sun gear biasing spring 222 is just before starting to be charged. The sub mirror 204 comes into contact with the back surface portion 203d of the main mirror 203 and is closed.

  When the main mirror 203 further rotates counterclockwise from this state, the sun gear 221 receives rotational torque from the sub mirror gear portion 204b of the sub mirror 204, and rotates counterclockwise. When the main mirror 203 is driven to a position where it comes into contact with the up stopper 201b, that is, the mirror up position shown in FIG. 4E, the main mirror 203 and the sun gear 221 stop rotating.

  At the position of FIG. 4 (e), the end 222b of the sun gear biasing spring 222 abuts on the spring hooking dowel portion 201d, and biases the sun gear 221 in the clockwise direction. As a result, the sub mirror 204 is urged in the counterclockwise direction, and is restricted to a position in contact with the back surface portion 203 d of the main mirror 203. Thereby, the sub-mirror 204 can be reliably retracted to the mirror-up position during the exposure with the image sensor 202, and the light beam 102c can be prevented from being prevented from being guided to the image sensor 202.

  The rotation operation from the mirror-up position to the mirror-down position is only the reverse of the rotation operation from the mirror-down position to the mirror-up position, and the description thereof is omitted. That is, the main mirror 203, the sub mirror 204, and the sun gear 221 operate in order from the state of FIG. 4 (e) to the state of FIG. 4 (a).

  As described above, in this embodiment, the sub mirror 204 is rotated in accordance with the rotation operation of the main mirror 203 by meshing the sub mirror gear portion 204b of the sub mirror 204 and the sun gear portion 221a of the sun gear 221. . That is, by rotating the sub mirror 204 by gear interlocking, the load on the drive unit including the mover 211 and the motor 213 due to the rotation operation of the sub mirror 204 can be smoothed.

  Further, at the mirror down position and the mirror up position, the sun gear 221 is urged by the sun gear urging spring 222, so that the position is regulated while the sub mirror 204 is in contact with the position regulating portion at each position. . Thus, even when the main mirror 203 is in contact with the down stopper 201a at the mirror down position, the direction of the light beam reflected by the sub mirror 204 can be adjusted by moving the adjustment unit 209. Therefore, a highly accurate focus detection operation can be performed.

  Further, the setting of the spring charge of the sun gear biasing spring 222 may be made different between the mirror up position and the mirror down position.

  For example, the position of the main mirror 203 at the mirror down position shown in FIG. Then, the position of the main mirror 203 at the mirror-up position shown in FIG. 4E is set to a position rotated by 50 degrees from the initial position.

  In order to urge the sub mirror 204 toward the back surface portion 203d of the main mirror 203 at the mirror up position, the charge of the sun gear urging spring 222 as shown in FIG. 4D is before the angle α of the mirror up position (50 degrees). Let's start with This angle α is set in consideration of component and assembly tolerances so that the sub mirror 204 is surely brought into contact with the back surface portion 203d of the main mirror 203.

  On the other hand, in order to urge the sub mirror 204 to the sub mirror dowel 209a in the mirror down position, the angle at which the charging of the sun gear urging spring 222 as shown in FIG. 4B is started is changed from the mirror down position (0 degree). The position is rotated by an angle β. As described above, the position of the adjustment unit 209 is adjusted in order to improve the accuracy of the focus detection operation at the mirror down position. Therefore, the angle β is set so that the sub mirror 204 is surely brought into contact with the sub mirror dowel 209a in the adjustment scale of the adjustment unit 209 in addition to the tolerance of parts and assembly.

  Therefore, when designing the charge amount (bias amount) of the sun gear urging spring 222 at the mirror up position and the mirror down position, it is desirable to set the angles α and β as follows.

α <β (1)
By setting in this way, the sub-mirror 204 can be reliably urged to the position restricting portion at each position at the mirror-up position and the mirror-down position, while reducing the charge amount of the sun gear urging spring 222. .

  Next, the shape of the sun gear 221 will be described. The sun gear 221 has been described in the shape as shown in FIGS. 1 to 4, but as shown in FIG. 5 in order to alleviate the bounce that occurs when the main mirror 203 moves to the mirror down position and the mirror up position. It may be configured.

  FIG. 5 is a diagram illustrating the sun gear 221 in which the buffer member is formed. As shown in the enlarged perspective view of FIG. 5A, the sun gear side surfaces 221c and 221d of the sun gear 221 are formed with buffer members (buffer portions) 223a and 223b indicated by diagonal lines. The buffer members 223a and 223b are made of a material that is compressed by receiving a load, and preferably have a damping effect such as urethane, elastomer rubber, or silicone.

  FIG. 5B shows a state where the main mirror 203 is being rotated from the mirror-up position to the mirror-down position. Only a part of the mirror box 201 is shown in FIG. As shown in FIG. 5B, when the sun gear biasing spring 222 is not charged, the mirror box window 201f and the buffer members 223a and 223b are not in contact with each other, or the buffer members 223a and 223b are almost compressed. Not in a state.

  FIG. 5C shows a state at the moment when the main mirror 203 reaches the mirror down position. When the main mirror 203 rotates from the state of FIG. 5B to the state of FIG. 5C, the sub mirror 204 collides with the sub mirror dowel 209a to generate a bounce. At this time, the reaction force due to the bounce of the sub mirror 204 is transmitted to the sun gear portion 221a via the sub mirror gear portion 204b. However, the shock absorbing member 223a is compressed between the sun gear side surface portion 221c and the mirror box window portion 201f, so that the shock can be absorbed and the bounce of the sub mirror 204 can be reduced.

  FIG. 5D shows a state at the moment when the main mirror 203 reaches the mirror up position. When the main mirror 203 is rotated from the mirror-down position to the state shown in FIG. 5D, the sub mirror 204 collides with the back surface portion 203d of the main mirror 203 and a bounce occurs. However, the shock absorbing member 223b is compressed between the sun gear side surface part 221d and the mirror box window part 201f, so that the shock can be absorbed and the bounce of the sub mirror 204 can be reduced.

  By reducing the bounce of the sub-mirror 204 at the mirror-down position, the light beam 102b to the focus detection sensor 208 is stabilized, and an accurate focus detection operation can be performed. Furthermore, it is possible to shorten the time until the bounce of the sub mirror 204 is settled, and to quickly move to the focus detection operation. Further, by reducing the bounce of the sub-mirror 204 at the mirror-up position, it is possible to quickly move to the exposure operation in the image sensor 202 and to shorten the release time lag.

  In addition, although the buffer member was formed in the sun gear 221 side in FIG. 5, you may form a buffer member in the mirror box 201f.

  Next, another shape of the sun gear portion 221a of the sun gear 221 will be described with reference to FIG. FIG. 6 is a diagram illustrating a shape in which a part of the tooth width of the sun gear portion 221a of the sun gear 221 is increased. 6A is a front view of the sun gear 221, and FIG. 6B is a right side view of FIG. 6A.

  When the main mirror 203 is moved to the mirror up position and the mirror down position by the rotation operation of the main mirror 203, the sub mirror 204 collides with each position restricting portion, and gives an impact load to the sun gear portion 221a via the sub mirror gear portion 204b.

  Therefore, the tooth width (second tooth width) of the gear portion (second region) 241 and 242 that meshes with the sub mirror gear portion 204b at the mirror up position and the mirror down position of the sun gear portion 221a is the range of the other gear portion. It is made thicker than the tooth width (first tooth width) of (first region). Therefore, it is possible to improve the durability of the sun gear portion 221a with respect to an impact caused by the rotation operation of the main mirror 203 to the mirror up position and the mirror down position. Similarly, by setting the tooth width in the range of the gear portion meshing with the sun gear portion 221a at the mirror up position and the mirror down position of the sub mirror gear portion 204b to be larger than the tooth width in the range of the other gear portions, the sub mirror gear portion The durability of 204b can be improved.

  In this embodiment, the mirror drive torsion spring 212 and the movable element 211 that engage with the main mirror drive lever 203b that rotates the main mirror 203 are separate components, but the mirror drive movable that is configured by integrating two components. It is good also as a child. For example, two projections that are elastically deformed in a thin plate shape are formed on a mirror drive movable element made of resin, and the main mirror drive lever 203b is sandwiched between the two projections. The elastic deformation of the plate-like protrusion may be used in place of the mirror drive torsion spring 212.

  In this embodiment, the mirror drive unit is driven straight by using the lead screw 214, but other methods may be used. For example, it is conceivable to rotate the main mirror 203 by sandwiching the main mirror drive lever 203b with a cam or the like that is rotated for driving the rotation drive unit.

  Further, the shaft of the motor as a rotation drive unit is directly connected to the rotation shaft 203c of the main mirror 203, or a gear unit is formed on the rotation shaft 203c and the main mirror 203 is rotated from the rotation drive unit via the reduction gear unit. It is also possible.

  As mentioned above, although preferable embodiment of this invention was described, this invention is not limited to these embodiment, A various deformation | transformation and change are possible within the range of the summary.

203 Main mirror 203d Back part 204 Sub mirror 204b Sub mirror gear part 209a Sub mirror dowel 221 Sun gear 221a Gear part 222 Sun gear biasing spring

Claims (9)

A main mirror that has a shaft portion that is pivotally supported by the imaging device, is driven to rotate between a mirror-down position and a mirror-up position, and transmits a part of a light beam at the mirror-down position;
A sub-mirror that is pivotally supported by the main mirror and reflects a light beam transmitted through the main mirror;
A stepping motor for rotational driving;
A lead screw that rotates by transmitting the rotational motion of the stepping motor; and
A moving part that moves along the lead screw by engaging with the lead screw, and that rotates the main mirror around the shaft part by urging the main mirror when moving;
A first position restricting portion for restricting a position of the sub mirror when the main mirror is located at the mirror down position;
A second position restricting portion for restricting the position of the sub mirror when the main mirror is located at the mirror up position;
A coupling portion having a second gear portion that is pivotally supported coaxially with the main mirror and meshes with a first gear portion formed on the sub-mirror;
A mirror driving device comprising: a biasing portion that biases the coupling portion so that the first and second position regulating portions regulate the position of the sub-mirror.   The mirror driving device according to claim 1, wherein the second position restricting portion is one surface of the main mirror. The biasing part is
After the sub mirror comes into contact with the first position restricting portion, the connecting portion is urged,
3. The mirror driving device according to claim 1, wherein after the sub mirror comes into contact with the second position restricting portion and overlaps the main mirror, the connecting portion is biased. 4. The biasing portion does not bias the connecting portion in a state where the sub mirror is not in contact with the first position restricting portion and a state in which the sub mirror is not in contact with the second position restricting portion. The mirror driving device according to claim 3. Mirror driving apparatus according to any one of 4 from claim 1, further comprising a focus detection unit which receives the light beam reflected by the sub-mirror to detect the focal length of the object.   6. The mirror drive according to claim 1, wherein an urging amount of the urging unit at the mirror down position is larger than an urging amount of the urging unit at the mirror up position. apparatus. It said connecting portion is any one of claims 1 to 6, characterized in that the main mirror buffer unit to mitigate the impact when reaching the mirror-up position and the mirror-down position is formed The mirror drive device described in 1. At least one of the first gear portion and the second gear portion has a first region in which teeth having a first tooth width are formed and a tooth having a second tooth width that is thicker than the first tooth width. A formed second region is formed;
Said first and second gear portions, in the mirror-up position and the mirror-down position, the mirror according to any one of claims 1 7, characterized in that are engaged with each other in the second region Drive device. Imaging apparatus characterized by comprising a mirror drive device according to any one of claims 1 to 8.