JP2013029693A - Light amount control device and optical apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the number of light shielding blades in a light amount control device without enlargement of the device in a radial direction.SOLUTION: A light amount control device 19 includes: a base member 32 having a fixed aperture 31a; a driving member 32 rotated around the fixed aperture relative to the base member; and light shielding blades 33 and 34 which are arranged in plural in a circumferential direction of the fixed aperture and are turned relative to the base member by the rotating driving member to change the size of a light amount control aperture. The plurality of light shielding blades include a plurality of first light shielding blades 33 turning in a first direction due to rotation in one direction of the driving member and a plurality of second light shielding blades 34 turning in a second direction opposite to the first direction due to rotation in the one direction of the driving member.

Description

  The present invention relates to a light amount adjusting device mounted on an optical apparatus such as a camera or an interchangeable lens.

  In the light amount adjusting device (aperture), a large number of light shielding blades (aperture blades) are arranged around a fixed opening formed in a base member, and the diaphragm blades are respectively rotated by a drive ring that rotates around the fixed opening. There is a so-called iris diaphragm that changes the size of the diaphragm aperture. In conventional iris diaphragms, five, six, or eight diaphragm blades are often used. Patent Document 1 discloses such an iris diaphragm.

  The drive ring and each diaphragm blade are formed with cam pins and cam grooves for rotating the diaphragm blade relative to the base member by rotation of the drive ring. These diaphragm blades rotate in the same direction with respect to the rotation of the drive ring in the same direction, thereby changing the size of the diaphragm opening.

A diaphragm aperture (particularly a small diaphragm aperture) formed by such a large number of diaphragm blades has an opening shape close to a circle as compared with a diaphragm aperture formed by a smaller number of diaphragm blades. For this reason, the shape of the blur or ghost formed on the image including the light from the point light source becomes close to a circle, which is advantageous for improving the image quality. In order to make the small aperture opening closer to a circle for further improvement in image quality, the number of aperture blades may be increased.

JP 2002-318403 A

  However, when the number of diaphragm blades is simply increased in the iris diaphragm, it is necessary to increase the diameter of the base member and the drive ring to secure a space for holding and driving the increased number of diaphragm blades. In order to avoid such an increase in the size of the apparatus, there is a method of narrowing the width of each diaphragm blade. However, this causes a problem such as a gap being formed in a portion to be shielded in a small aperture state. Thus, it is difficult to increase the number of aperture blades while avoiding an increase in the size of the apparatus in the radial direction.

  Therefore, the present invention provides a light quantity adjusting device that can increase the number of light shielding blades without increasing the size of the device in the radial direction.

  A light amount adjusting device (iris-type light amount adjusting device) according to one aspect of the present invention includes a base member having a fixed opening, a driving member that rotates around the fixed opening with respect to the base member, and a circumferential direction of the fixed opening. A plurality of light-amount adjusting openings that are arranged to face the fixed opening are formed, and a light-shielding blade that is rotated with respect to the base member by a rotating drive member to change the size of the light-amount adjusting opening. The plurality of light shielding blades are rotated in a second direction opposite to the first direction by the plurality of first light shielding blades rotating in the first direction by the rotation of the driving member in the same direction. And a plurality of second light shielding blades.

  According to the present invention, by including a plurality of light shielding blades that rotate in opposite directions by rotation of the drive member in the same direction, the device can be compared with a case where all the light shielding blades rotate in the same direction. The number of light shielding blades can be increased without increasing the size in the radial direction. Thereby, the aperture shape of the small aperture can be made closer to a circle easily.

The front view which shows the structure of the iris diaphragm which is an Example of this invention. FIG. 3 is an exploded perspective view of a lens barrel portion of an imaging apparatus equipped with the iris diaphragm according to the embodiment. The disassembled perspective view which shows the structure of the iris diaphragm of an Example. The front view explaining the movement of the 1st aperture blade group in the iris diaphragm of an Example. The front view explaining the motion of the 2nd aperture blade group in the iris diaphragm of an Example. The front view explaining a motion of a pair of 1st and 2nd aperture blade in the iris diaphragm of an Example. The enlarged view which shows the opening shape of the small aperture opening in the iris diaphragm of an Example.

  Embodiments of the present invention will be described below with reference to the drawings.

  First, FIG. 2 shows a configuration of a lens barrel portion of an imaging apparatus (optical apparatus) such as a video camera equipped with an iris diaphragm as an iris-type light amount adjusting apparatus which is Embodiment 1 of the present invention. In order from the subject side (hereinafter referred to as the front side), L1 is a fixed first lens group, and L2 is a second lens group that moves in the optical axis direction and performs zooming. L3 is a third lens group that moves in a plane orthogonal to the optical axis and performs image blur correction. L4 is a fourth lens group that moves in the optical axis direction and performs focus adjustment. The first to fourth lens groups L1 to L4 and the iris diaphragm 19 of the present embodiment constitute a photographing optical system.

  Reference numeral 11 denotes a front lens barrel unit that holds the first lens unit L1. Reference numeral 12 denotes a zoom movement frame that holds the second lens unit L2, and reference numeral 13 denotes a shift unit that moves the third lens unit L3 within a plane orthogonal to the optical axis. Reference numeral 14 denotes a focus movement frame that holds the fourth lens unit L4. Reference numeral 15 denotes a rear barrel that holds an image pickup element (not shown) that is a photoelectric conversion element such as a CCD sensor or a CMOS sensor.

  The front lens unit 11 and the rear lens barrel 15 hold both ends of the two guide bars 16 and 17. Further, both ends of the guide bar 18 are held by the fixed portion of the shift unit 13 and the rear barrel 15.

  The zoom movement frame 12 is supported by the guide bars 16 and 17 so as to be movable in the optical axis direction, and the focus movement frame 14 is supported by the guide bars 16 and 18 so as to be movable in the optical axis direction.

  The fixing portion of the shift unit 13 is positioned on the rear barrel 15 and is fastened and fixed by three screws.

  An iris diaphragm (hereinafter simply referred to as a diaphragm) 19 adjusts the amount of light passing through the diaphragm aperture by changing the size of the diaphragm aperture (diaphragm aperture diameter) as the light amount adjustment aperture. In this embodiment, the diaphragm 19 is disposed immediately before the third lens unit L3 and is fixed to the fixing portion of the shift unit 13.

  The rear lens barrel 15 is positioned with respect to the front lens barrel unit 11 and is fastened and fixed from behind by three screws.

  Reference numeral 20 denotes a lead screw that meshes with a rack 14 a attached to the focus movement frame 14. The lead screw 20 has a rotor magnet 20a fixed to the rear end thereof so as to be integrally rotatable.

  Reference numeral 21 denotes a stepping motor unit for rotating the rotor magnet 20a, which rotates the rotor magnet 20a by energizing an internal coil to move the focus moving frame 14 in the optical axis direction via the rack 14a. Further, the play between the focus moving frame 14, the guide bars 16, 18, the rack 14a, and the lead screw 20 is removed by the spring force of the torsion coil spring 14b.

  Reference numeral 22 denotes a lead screw that meshes with a rack 12 a attached to the zoom movement frame 12. The lead screw 22 has a rotor magnet 22a fixed to the rear end thereof so as to be integrally rotatable.

  Reference numeral 23 denotes a stepping motor unit for rotating the rotor magnet 22a. The rotor magnet 22a is rotated by energization of an internal coil, and the zoom moving frame 12 is moved in the optical axis direction via the rack 12a. Further, the play between the zoom moving frame 12, the guide bars 16, 17, the rack 12a, and the lead screw 22 is removed by the spring force of the torsion coil spring 12b.

  The stepping motor units 21 and 23 are fixed to the rear barrel 15 with two screws, respectively.

  Reference numeral 24 denotes a focus reset switch, which includes a photo interrupter. The focus reset switch 24 has a light shielding portion 14c formed on the focus moving frame 14 moving in the optical axis direction between the light emitting portion and the light receiving portion, so that the focus moving frame 14 is set to the focus reference position. Detect position. The focus reset switch 24 is fixed to the rear barrel 15 with screws through the substrate.

  Reference numeral 25 denotes a zoom reset switch, which includes a photo interrupter. The zoom reset switch 25 has a light blocking portion 12c formed on the zoom moving frame 12 moving in the optical axis direction between the light emitting portion and the light receiving portion, so that the zoom moving frame 12 is at the zoom reference position. Detect position. The zoom reset switch 25 is fixed to the front lens barrel unit 11 with a screw through a substrate.

  FIG. 3 shows the diaphragm 19 in an exploded manner. 31 is a base member, and a circular fixed opening 31a is formed in the center thereof. The center of the fixed opening 31a is located on the optical axis of the photographing optical system. Further, support shaft portions 31b are formed at a plurality of (6) circumferential positions in the portion of the base member 31 around the fixed opening 31a. In the following description, the circumferential direction of the base member 31 (fixed opening 31a) is referred to as the circumferential direction of the diaphragm 19, and the radial direction of the base member 31 (fixed opening 31a) is referred to as the radial direction of the diaphragm 19.

  Reference numeral 32 denotes a blade drive ring (drive member), which is held so as to be rotatable around the fixed opening 31 a with respect to the base member 31. Drive pin portions 32 b are formed at a plurality of (6) locations in the circumferential direction of the blade drive ring 32. Further, a gear portion 32 a is formed in a range of a part in the circumferential direction of the outer peripheral portion of the blade drive ring 32.

  Reference numeral 33 denotes a first diaphragm blade group including a plurality of first diaphragm blades (first light shielding blades) 33a arranged in the circumferential direction of the fixed opening 31a. In the present embodiment, the first diaphragm blade group 33 includes six first diaphragm blades 33a.

  Each first aperture blade 33a has a proximal end portion having a support hole 33b into which the support shaft portion 31b of the base member 31 is inserted, and a distal end portion for forming an aperture opening facing the fixed opening 31a. Further, a cam groove portion (cam portion) 33c that is inserted into and engages with the drive pin portion 32b of the blade drive ring 32 is inserted between the base end portion and the tip end portion of each first diaphragm blade 33a. Is formed.

  FIG. 4 shows the arrangement of the first aperture blade group 33 when viewed from the side opposite to the base member 31 in the optical axis direction (that is, from the front side). Each first diaphragm blade 33a has a tip end portion in the clockwise direction in the circumferential direction when viewed from the front side at the position where the diaphragm opening shown in FIG. It arrange | positions so that it may overlap on the base end part of 33a. The aperture opening (diameter) shown in FIG. 4A is called an open aperture opening (diameter), and the position or state of each first aperture blade 33a shown in FIG. 4 is called an open position or an open state.

  In each first aperture blade 33a, the blade drive ring 32 rotates in the clockwise direction (first direction) CW from the open position shown in FIG. 4A, and the drive pin portion 32b moves in the cam groove portion 33c. Thus, the support shaft portion 31b inserted into the support hole 33b rotates around the support shaft portion 31b in the clockwise direction. Thereby, as shown in FIG.4 (b), the aperture opening diameter formed by the 1st aperture blade group 33 becomes small. The aperture opening (diameter) shown in FIG. 4B is called a small aperture opening (diameter), and the position or state of each first aperture blade 33a shown in FIG. 4 is called a small aperture position or a small aperture state.

  Each first diaphragm blade 33a is rotated counterclockwise around the support shaft portion 31b by rotating the blade drive ring 32 counterclockwise and moving the drive pin portion 32b in the cam groove portion 33c. To turn. Thereby, the aperture diameter of the aperture formed by the first aperture blade group 33 is increased (FIG. 4A).

  Reference numeral 34 denotes a second diaphragm blade group including a plurality of second diaphragm blades (second light shielding blades) 34a arranged in the circumferential direction of the fixed opening 31a. In the present embodiment, the second diaphragm blade group 34 also includes six second diaphragm blades 34a.

  Each second aperture blade 34a has a base end portion having a support hole 34b into which the support shaft portion 31b of the base member 31 is inserted, and a distal end portion for forming an aperture opening facing the fixed opening 31a. Further, a cam groove portion (cam portion) 34c that is inserted into and engages with the drive pin portion 32b of the blade drive ring 32 is inserted between the base end portion and the tip end portion of each second diaphragm blade 34a. Is formed.

  FIG. 5 shows the arrangement of the second aperture blade group 34 when viewed from the front side. Each of the second diaphragm blades 34a is in the counterclockwise direction of the circumferential direction when viewed from the front side (the direction opposite to the first diaphragm blade group 33) at the position where the diaphragm opening shown in FIG. ), The tip end portion of the second diaphragm blade 34a is disposed so as to overlap the base end portion. The aperture opening (diameter) shown in FIG. 5A is called an open aperture opening (diameter), and the position or state of each second aperture blade 34a shown in FIG. 5 is called an open position or open state.

  Each of the second diaphragm blades 34a has a support hole 34b when the blade drive ring 32 rotates in the clockwise direction CW from the open position shown in FIG. 5A and the drive pin portion 32b moves in the cam groove portion 34c. It rotates in the counterclockwise direction (second direction) around the support shaft portion 31b inserted into the center. Thereby, as shown in FIG.5 (b), the aperture opening diameter formed by the 2nd aperture blade group 34 becomes small. The aperture opening (diameter) shown in FIG. 5B is called a small aperture opening (diameter), and the position or state of each second aperture blade 34a shown in FIG. 5 is called a small aperture position or a small aperture state.

  Each of the second diaphragm blades 34a rotates in the clockwise direction around the support shaft portion 31b as the blade drive ring 32 rotates counterclockwise and the drive pin portion 32b moves in the cam groove portion 34c. Rotate. Thereby, the aperture diameter of the aperture formed by the second aperture blade group 34 is increased (FIG. 5A).

  In this manner, the first diaphragm blade group 33 and the second diaphragm blade group 34 are mutually rotated in the clockwise and counterclockwise directions by the rotation of the blade drive ring 32 in the same direction in the clockwise and counterclockwise directions. It rotates in the opposite direction to change the size of the aperture diameter.

  Note that the overlapping direction (clockwise direction and counterclockwise direction) and the rotation direction of the first and second aperture blade groups 33 and 34 may be opposite to the above.

  An aperture stepping motor 35 is fixed to the base member 31 with a screw (not shown). A pinion gear 35 a is fixed to the output shaft of the aperture stepping motor 35. The pinion gear 35 a meshes with the gear portion 32 a of the blade drive ring 32. For this reason, the rotation of the aperture stepping motor 35 is transmitted to the blade drive ring 32 to rotate it.

  The rotation of the aperture stepping motor 35 is controlled by a controller such as a CPU (not shown). Specifically, the controller controls the rotation of the aperture stepping motor 35 in accordance with the change in the luminance of the video signal generated using the output signal from the image sensor, and changes the aperture diameter.

  Reference numeral 36 denotes a cover member for partitioning the space for housing the first and second aperture blade groups 33 and 34 together with the base member 31, and has a fixed opening 36a centered on the optical axis. The cover member 36 is fixed to the base member 31 with screws (not shown).

  FIG. 1 shows a state in which the first diaphragm blade group 33 and the second diaphragm blade group 34 are combined (superposed) in the optical axis direction. FIG. 1A shows an open state, and FIG. 1B shows a small aperture state. FIG. 6 shows one first diaphragm blade 33a combined in the optical axis direction and one second diaphragm blade 34a adjacent to the first diaphragm blade 33a in the circumferential direction. 6A shows an open state, and FIG. 6B shows a small aperture state.

  As can be clearly understood from FIG. 6, the first diaphragm blade 33a and the second diaphragm blade 34a adjacent to the first diaphragm blade 33a in the counterclockwise direction are formed in the base member 31 in the support hole portions 33b and 34a. A (common) support shaft portion 31b is inserted. Further, the second diaphragm blade 34a shown in FIG. 6 and the first diaphragm blade 33a (not shown) adjacent to the second diaphragm blade 34a in the counterclockwise direction are provided in the cam groove portions 34c and 33c (indicated by a two-dot chain line). The same (common) drive pin portion 32b formed in the blade drive ring 32 is inserted.

  By using the common support shaft portion 31b for the first and second diaphragm blades 33a and 34a in this way, the drive pin portion 32b is engaged with the first drive shaft portion 32b as compared with the case where the common support shaft portion is not used. The design of the cam groove portions 33c, 34c of the first and second aperture blades 33a, 34a is facilitated. Further, by engaging the common drive pin portion 32b with the cam groove portions 33c and 34c of the first and second aperture blades 33a and 34a, the drive for engaging one aperture blade with the cam groove portion of the other aperture blade. It is possible to eliminate the need to form a relief shape (such as a long hole) with respect to the pin portion. For this reason, it is possible to avoid an increase in size and complexity of each aperture blade, and it is possible to arrange a large number (as many as 12) aperture blades in a limited radial space.

  In the present embodiment, the support shaft portion 31b and the drive pin portion 32b are each formed in a simple cylindrical shape having a constant diameter. However, each of the support shaft portion 31b and the drive pin portion 32b has a stepped portion in which the diameter of the portion inserted into the first aperture blade 33a and the diameter of the portion inserted into the second aperture blade 34a are different from each other. You may form in a cylindrical shape. Alternatively, in each of the support shaft portion 31b and the drive pin portion 32b, the portion inserted into the first aperture blade 33a and the portion inserted into the second aperture blade 34a may be eccentric from each other. In these cases as well, there is no difference in that the support shaft portion 31b and the drive pin portion 32b are integrally formed, so that they are common (identical) to the first and second aperture blades 33a and 34a. It can be said that there is.

  As shown in FIG. 6, as described above, the first and second diaphragm blades 33a and 34a support the rotation of the blade drive ring 32 in the same direction in the clockwise direction CW and the counterclockwise direction CCW. Rotate in opposite directions around the shaft portion 31b.

  In the present embodiment, the first and second aperture blades 33a and 34a rotate at the same angular velocity between the open position and the fully closed position where the aperture opening is fully closed. That is, the rotational speed of the blade drive ring 32 and the angular speed of rotation of the first and second diaphragm blades 33a and 34a vary according to the change speed of the subject brightness. In either case, the first and second diaphragms The angular velocity of rotation is the same between the blades 33a and 34a.

  4B and FIG. 5B, the first and second aperture blade groups 33 and 34 each independently form a small aperture opening shape that is close to a hexagon, but is similar to FIG. As shown in the drawing, a combination of the first and second aperture blade groups 33 and 34 provides a small aperture opening shape close to a circle. FIG. 7 shows an enlarged view of a small stop aperture having a dodecagonal opening shape (opening shape in which each side of the dodecagon is formed as a convex arc toward the outside).

  Thus, the present embodiment includes a plurality of diaphragm blades 33a and 33b that rotate in opposite directions by rotation of the blade drive ring 32 in the same direction. Thereby, compared with the case where all the aperture blades rotate in the same direction, the number of aperture blades 33a and 33b can be increased without enlarging the aperture 19 in the radial direction. As a result, the aperture shape of the small aperture can be easily made closer to a circle, which is effective for obtaining a captured image with good image quality.

  In the present embodiment, the fixed opening 31a of the base member 31, the support shaft portion 31b serving as the rotation center of the first and second diaphragm blades 33a and 34a, and the first and second diaphragm blades 33a and 34a. The drive pin portion 32b for driving the motor is disposed within a narrow range in the radial direction. This is to make the size of the diaphragm 19 in the radial direction as small as possible. For this reason, the width of each of the first and second aperture blades 33a and 34a cannot be increased. For this reason, in the small aperture state shown in FIGS. 4B and 5B, portions (cam groove portions 33c and 34c) other than the aperture openings formed by the first and second aperture blade groups 33 and 34 are formed. There is a possibility that light enters from the gap to the position facing the fixed opening 31a. If there is light leakage, good light intensity adjustment cannot be performed.

  However, in the present embodiment, the first and second diaphragm blades 33a and 34a are rotated in opposite directions with respect to the same direction rotation of the blade drive ring 32, so that the first and second diaphragms in the small diaphragm state. A gap formed in one of the blade groups 33 and 34 can be covered by the other. That is, according to this embodiment, even if the widths of the first and second diaphragm blades 33a and 34a are narrow in order to reduce the size of the diaphragm 19 in the radial direction, a gap other than the diaphragm opening is generated in the small diaphragm state. Can be prevented, and good light quantity adjustment can be performed.

  Further, in this embodiment, as shown in FIG. 7, the 12 first and second diaphragm blade groups 33 and 34 that form a polygonal small aperture that is nearly circular are respectively (polygonal). 6 aperture blades corresponding to the number of sides / 2). As a result, as compared with the case where all the diaphragm blades rotate in the same direction (overlapped in the same direction), the diaphragm blades are overlapped by overlapping portions of the diaphragm blades that form the small diaphragm aperture in the small diaphragm state. Deformation (swelling) in the optical axis direction can be suppressed. As a result, the thickness of the stop 19 in the optical axis direction can be reduced.

  In the present embodiment, the first and second aperture blade groups 33 and 34 always rotate between the open position and the fully closed position. However, only one of the first and second aperture blade groups 33 and 34 is rotated between the small aperture position (the position before the aperture opening is fully closed) and the fully closed position, and the other is stopped. You may make it leave. As a result, deformation due to overlapping of the portions of the diaphragm blades that form the small aperture opening is less likely to occur, and the thickness of the diaphragm 19 in the optical axis direction can be reduced.

  In the above-described embodiment, the case where the number of the first and second diaphragm blade groups is 6 has been described. However, the number of the respective diaphragm blade groups is another number such as 4 or 5. Also good. In the above embodiment, the case where the number of first and second diaphragm blade groups is the same (the first and second diaphragm blades make a pair) has been described. However, these numbers are different from each other. May be. For example, the number of first diaphragm blade groups may be eight and the number of second diaphragm blade groups may be four.

  In the above-described embodiment, the case where the first and second diaphragm blades arranged adjacent to each other in the circumferential direction rotate around the same support shaft portion provided on the base plate has been described. Moreover, the case where the 1st and 2nd aperture blade arrange | positioned adjacently in the circumferential direction has a cam groove part engaged with the same drive pin part provided in the drive ring was demonstrated. In the above embodiment, the case where the first and second diaphragm blades rotate at the same angular velocity between the open position and the fully closed position has been described. However, these features are not necessarily features that should be provided, and may be selectively given as necessary.

  Furthermore, in the above-described embodiment, the imaging optical system-integrated image pickup apparatus having the diaphragm 19 is described. However, as another embodiment, the diaphragm 19 may be mounted on the interchangeable lens.

  Each embodiment described above is only a representative example, and various modifications and changes can be made to each embodiment in carrying out the present invention.

  It is possible to provide a light amount adjustment device effective for obtaining a photographed image with good image quality.

31 Base member 31a Fixed opening 32 Blade drive ring 33 First diaphragm blade group 34 Second diaphragm blade group

Claims (6)

A base member having a fixed opening;
A drive member that rotates about the fixed opening relative to the base member;
A plurality of light adjustment holes arranged in the circumferential direction of the fixed opening are formed to face the fixed openings, and are rotated with respect to the base member by the rotating driving member to change the size of the light quantity adjustment openings. An iris-type light amount adjusting device having a light shielding blade,
The plurality of light shielding blades rotate in a second direction opposite to the first direction and a plurality of first light shielding blades that rotate in a first direction by rotation of the driving member in the same direction. A light quantity adjusting device comprising a plurality of second light-shielding blades that move.   Of the plurality of first and second light shielding blades, the first and second light shielding blades arranged adjacent to each other in the circumferential direction rotate around the same support shaft provided on the base member. The light amount adjusting device according to claim 1, wherein the light amount adjusting device moves.   Of the plurality of first and second light shielding blades, the first and second light shielding blades arranged adjacent to each other in the circumferential direction engage with the same drive pin portion provided on the drive member. The light amount adjusting device according to claim 1, further comprising a cam portion.   The first light shielding blade and the second light shielding blade rotate at the same angular velocity between a position at which the light amount adjustment opening is opened and a position at which the light amount adjustment opening is fully closed. Item 4. The light amount adjusting device according to any one of Items 1 to 3.   2. Only one of the first and second light shielding blades rotates between a position before the light amount adjustment opening is completely closed and a position where the light amount adjustment opening is fully closed. 5. The light quantity adjusting device according to any one of items 1 to 4. An optical apparatus comprising an optical system including the light amount adjusting device according to claim 1.