JP2010276654A - Light quantity adjusting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a light quantity adjusting device capable of decreasing gear noise caused by an influence of backlash even if a stepping motor is used as a drive source. <P>SOLUTION: The light quantity adjusting device includes: three or more diaphragm blades; a ring member having a blade drive pin, and driving to open and close the diaphragm blade by rotating centering an optical axis; a drive source coupled with the ring member through a gear to drive the ring member; and an energizing gear meshed with the ring member through the gear, and energizing the backlash of the ring member. The energizing gear comprises a gear, and is energized in a rotating direction and an optical axis direction by an energizing member. The energizing gear is meshed with the gear of the ring member, thereby energizing the ring member in two directions, that is, the optical axis direction and the rotating direction. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a light amount adjusting device that drives a plurality of aperture blades and adjusts the aperture diameter of an aperture, and an imaging device such as a digital still camera or a video camera that has an interchangeable lens detachable or an integrated lens body. It is suitable for.

  Conventionally, a guillotine diaphragm and an iris diaphragm are mainly used for a light amount adjusting device (aperture device) used in a video camera, a digital camera, or the like. The guillotine diaphragm is configured such that two diaphragm blades are movably sandwiched between a base plate having an opening on the optical axis and a cover. The two diaphragm blades move relatively in the same direction and in the opposite direction in a plane orthogonal to the optical axis, and the aperture shape of the diaphragm can be freely changed to adjust the amount of light passing through (see Patent Document 1). ). Since the guillotine diaphragm has two diaphragm blades, the configuration is simple, but the diaphragm aperture shape on the small diaphragm side is substantially diamond-shaped. As a result, there is a problem in that the shape of the bokeh shape / surface reflection ghost emitted from the point light source appears to be a diamond. For this reason, it is mounted on an inexpensive imaging device for consumers. Similarly to the guillotine diaphragm, the iris diaphragm is configured such that a plurality of three or more diaphragm blades are movably sandwiched between a base plate having an opening on the optical axis and a cover. In general, a galvanometer is used as a driving source for the diaphragm blades. The diaphragm blades are connected to a windmill (ring member) that rotates about the optical axis via an arm member from a galvanometer. A plurality of three or more diaphragm blades are arranged on the windmill so as to overlap in a clockwise or counterclockwise direction.

  Further, the aperture blade hole is rotatably fitted to a rotating shaft provided in the fixed portion, the drive pin is fitted to the elongated hole portion of the aperture blade, and the other aperture blades are also supported by the same structure. As the windmill rotates about the optical axis, a plurality of diaphragm blades are interlocked to swing, and the amount of light passing therethrough is adjusted by changing the aperture shape. In an iris diaphragm, since the aperture shape is determined by a plurality of diaphragm blades, the aperture shape at the time of small aperture is substantially circular. For this reason, the shape of a blur / surface reflection ghost emitted from a point light source is substantially circular and has little influence on image quality, and is often used in high-end and high-precision imaging devices. 2. Description of the Related Art Conventionally, an electromagnetic drive diaphragm in which a stepping motor is mounted on an iris diaphragm drive source is known (see Patent Document 2).

JP 05-005926 A JP-A-62-240942

  When a stepping motor is used as the driving source for the diaphragm blades, the rotation range of the driving source is not restricted, so that the operating angle of the windmill for driving the diaphragm blades can be increased. In particular, the amount of movement of the diaphragm blades with respect to the rotation angle of the windmill is reduced, and high control is possible up to a highly sensitive small diaphragm.

  However, since the stepping motor is gear-coupled with the windmill, noise tends to increase due to the influence of backlash. In addition, due to vibration during driving of the stepping motor, vibration is transmitted from the gear coupling portion of the windmill, and so-called chatter noise that is vibration noise of the windmill is generated. For this reason, there is no problem in shooting a still image like a digital still camera, but noise is a problem in moving image shooting (especially a high-precision lens). As a result, an imaging apparatus that performs moving image shooting often employs a galvanometer that can continuously control the drive source of the aperture device (light quantity adjustment device) and that can easily perform position feedback control by a sensor.

  However, a diaphragm device using a galvanometer has a restriction on the angle at which the rotation angle of the meter can be rotated by about 60 degrees at maximum because of the configuration of the galvanometer. For this reason, the iris diaphragm is configured to link from an arm member driven at the center of the meter axis to a windmill that rotates about the optical axis. Therefore, the operating rotation angle of the windmill is further reduced, the rotation angle of the drive pin of the aperture blade is also restricted, and it is difficult to make a cam shape that reduces the amount of oscillation of the aperture blade on the small aperture side. Therefore, there has been a problem that the change in the F value of the diaphragm blades on the small diaphragm side becomes very large as compared with that at the time of opening, and the control sensitivity becomes high.

  An object of the present invention is to provide a light amount adjusting device that can reduce gear noise due to the influence of backlash even when a stepping motor is used as a drive source.

  The light amount adjusting device of the present invention has three or more diaphragm blades, a blade driving pin, a ring member that drives and opens and closes the diaphragm blade by rotating around the optical axis, and a gear connection with the ring member, A driving source for driving the ring member; and a biasing gear that meshes with the ring member by a gear and biases the play of the ring member. The biasing gear is formed of a gear and is rotated in the direction of rotation by the biasing member. Further, the biasing gear is biased in the optical axis direction, and the biasing gear meshes with the gear of the ring member to bias the ring member in two directions of the optical axis direction and the rotation direction.

  According to the present invention, it is possible to obtain a light amount adjusting device that can reduce gear noise due to the influence of backlash even when a stepping motor is used as a drive source.

1 is an exploded perspective view of a lens barrel that incorporates a light amount adjusting device according to a first embodiment of the present invention. 1 is an exploded perspective view of a light amount adjusting apparatus according to a first embodiment of the present invention. (A) is the figure which looked at the windmill 32 and biasing gear 36 part of Example 1 of this invention from the side, (B) is the figure which expanded the windmill 32 and biasing gear 36 part of (A). The figure explaining the structure of the light quantity adjustment apparatus of Example 1 of this invention. Explanatory drawing of the light quantity adjustment apparatus of Example 2 of this invention Explanatory drawing of the example which eliminates the harmful effect by the urging of the present invention

  Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. The light quantity adjusting device of the present invention will be described as follows using reference numerals attached to members described later for reference. The light quantity adjusting device of the present invention has three or more diaphragm blades 33 and blade driving pins 32c for transmitting the driving force from the driving source 35 to drive the three or more diaphragm blades 33 and driving the optical axis. And a ring member 32 that drives the aperture blade to open and close by rotating at the center.

  Further, a driving source 35 comprising a stepping motor that drives the ring member 32 by being gear-connected by the ring member 32 and the gear portion 32b, the gear portion 36b, and the gear portion 35a is used. The ring member 32 is engaged with the gear portions 32b and 36b, and has a biasing gear 36 made of a rotating body that biases the play of the ring member 32. The urging gear 36 is a stepped gear or a bevel gear, and the urging gear 36 is urged by an urging member 37 in the rotation direction (C direction) and the optical axis direction (A direction). At this time, the urging gear 36 meshes with the gear 32b of the ring member 32, thereby urging the ring member 32 in two directions of the optical axis direction (A direction) and the rotation direction (B direction). When the connecting portion 36b 'of the urging gear 36 is composed of a bevel gear 36b' having an arbitrary vertical angle, the urging gear 36 is urged by the urging member 37 in the rotation direction and the optical axis direction. The Further, the urging gear 36 meshes with the gear 32 b ′ of the ring member 32, thereby urging the ring member 32 in three directions including the optical axis direction, the rotation direction, and the radial direction. And by using the biasing gear which consists of a rotary body, the biasing force is given to the ring member 32 in the tangential direction, and the play of the ring member 32 is taken.

[Example 1]
FIG. 1 is an exploded perspective view of a lens barrel incorporating a light amount adjusting device according to a first embodiment of the present invention. L1 is a fixed first lens group. L2 is a second lens group that performs a zooming operation by moving in the optical axis direction. L3 is a third lens group that moves in a plane perpendicular to the optical axis and performs an image blur correction operation that occurs when a camera (imaging device) having a lens barrel vibrates. L4 is a fourth lens group that performs zooming and focusing operations by moving in the optical axis direction. The first to fourth lens groups L1 to L4 constitute a zoom lens. Reference numeral 11 denotes a front lens barrel unit that holds the first lens unit L1. A moving frame 12 holds the second lens unit L2 and moves in the optical axis direction. Reference numeral 13 denotes a shift unit that allows the third lens unit L3 to move in a plane perpendicular to the optical axis. Reference numeral 14 denotes a moving frame that holds the fourth lens unit L4 and moves in the optical axis direction. Reference numeral 15 denotes a rear lens barrel to which an image sensor such as a CCD is attached. The front lens barrel unit 11 and the rear lens barrel 15 are positioned and fixed by two guide bars 16 and 17. Further, the shift unit 13 and the rear barrel 15 are positioned by the guide bar 18. The moving frame 12 is supported by guide bars 16 and 17 so as to be movable in the optical axis direction. The moving frame 14 is supported by the guide bars 16 and 18 so as to be movable in the optical axis direction. The shift unit 13 is positioned on the rear barrel 15 and fixed with screws by three screws from the front. Reference numeral 19 denotes a light amount adjusting device that changes the aperture diameter of the stop of the optical system (zoom lens). The light amount adjusting device is a so-called iris diaphragm device that moves six diaphragm blades to change the aperture diameter of the diaphragm. Three or more aperture blades may be used.

  In this embodiment, the lens unit is disposed immediately before the third lens unit L3 and is fixed to the shift unit 13. The rear lens barrel 15 is positioned on the front lens barrel unit 11 and fixed with screws by three screws from the rear. Reference numeral 20 denotes a lead screw which is a part of driving means for moving the fourth lens unit L4 in the optical axis direction to perform a focusing operation. The lead screw 20 has a front and rear bearing shape, and a rotor magnet 20a magnetized in multiple poles is fixed to the rear part. 21 is a stepping motor stator unit for rotating the rotor magnet 20a. The lead screw 20 meshes with a rack 14a attached to the moving frame 14, and moves the fourth lens unit L4 by the rotation of the rotor magnet 20a. Further, the play of the moving frame 14, the guide bars 16, 18, the rack 14a, and the lead screw 20 is offset by the torsion coil spring 14b.

  Reference numeral 22 denotes a lead screw which is a part of driving means for moving the second lens unit L2 in the optical axis direction to perform a zooming operation. The lead screw 22 has a front and rear bearing shape, and a rotor magnet 22a magnetized in multiple poles is fixed to the rear part. Reference numeral 23 denotes a stepping motor stator unit for rotating the rotor magnet 22a. The lead screw 22 is supported by bearings provided in the shift unit 13 and the stepping motor stator unit 23. The lead screw 22 meshes with the rack 12a attached to the moving frame 12, and moves the second lens group L2 by the rotation of the rotor magnet 22a. Further, the play of the moving frame 12, the guide bars 16, 17 and the rack 12a lead screw 22 is offset by the torsion coil spring 12b. The stepping motor stator units 21 and 23 are each fixed to the rear barrel 15 with two screws. Reference numeral 24 denotes a photo interrupter, which electrically detects the switching between light shielding and light transmission due to movement of the light shielding portion 14c formed in the moving frame 14 in the optical axis direction. Thus, a focus reset switch for detecting the reference position of the fourth lens unit L4 is configured. The photo interrupter 24 is fixed to the rear barrel 15 with a screw through a substrate. Reference numeral 25 denotes a photo interrupter, which electrically detects the switching between light shielding and light transmission due to movement of the light shielding portion 12c formed in the moving frame 12 in the optical axis direction. This constitutes a zoom reset switch for detecting the reference position of the second lens unit L2. The photo interrupter 25 is fixed to the front lens barrel unit 11 with a screw through a substrate.

  FIG. 2 is an exploded perspective view of the light amount adjusting device 19 according to the first embodiment of the present invention. In FIG. 2, reference numeral 31 denotes a fixed base member of the light amount adjusting device, which has a fixed opening 31a centered on the optical axis. Reference numeral 32 denotes a windmill (ring member) for driving the diaphragm blades 33. There are six diaphragm blades 33 forming the aperture opening shape, but three or more diaphragm blades may be used. The aperture blades 33 are sequentially arranged in the clockwise direction or counterclockwise in the optical axis direction. In each diaphragm blade 33, a hole 33a formed in the diaphragm blade 33 is rotatably fitted to a rotation pin 31b provided in the base member 31 of the fixed portion. A drive pin 32c of the wind turbine 32 is fitted in a slot 33b formed in the aperture blade 33 so as to be movable in the slot 33b. Reference numeral 34 denotes a pressing member for restricting the diaphragm blade 33 to a space formed between the base blade 31 and a fixed opening 34 a centered on the optical axis. The pressing member 34 is positioned and fixed to the base member 31 with four screws (not shown). Reference numeral 35 denotes a stepping motor (drive source) for driving the diaphragm blade 33, and a pinion gear 35a is fixed to the output shaft (not shown) by press fitting or bonding. The driving stepping motor 35 is coupled to the base member 31 with screws.

  The driving stepping motor 35 transmits driving force to the windmill 32 by meshing with a gear 32a configured in the windmill 32 by a pinion gear 35a. As a result, the windmill 32 rotates about the optical axis, and the aperture diameter of the diaphragm is made variable by the diaphragm blades 33 through the elongated holes 33b fitted to the drive pins 32c provided on the windmill 32. Reference numeral 36 denotes an urging gear for reducing the play of the windmill 32. Reference numeral 37 denotes a torsion compression coil spring (biasing member) which is hooked by a hook portion (hook) 31d formed on the base member 31 and a hook portion (hook) 36a formed on the biasing gear 36. Reference numeral 38 denotes a rotating shaft of the urging gear 36, which has a flange shape for preventing it from coming off. The rotating shaft 38 is fixed together with the biasing gear 36 by pressing the torsion compression coil spring 37 in the thrust direction (optical axis direction) and press-fitting or bonding to the base member 31. At that time, the urging gear 36 is urged in the optical axis direction by the torsion compression coil spring 37. A gear portion 36 b provided on the urging gear 36 meshes with a gear portion 32 b formed on the windmill 32. The wind turbine 32 is biased in the rotational direction by the biasing gear 36 biased in the rotational direction by the torsion compression coil spring 37. Further, at that time, the gear portion 32b of the wind turbine 32 and the meshing portion of the urging gear portion 36b press the wind turbine 32 in the optical axis direction by the stepped flange portion 36c provided in the urging gear 36. As a result, the wind turbine 32 is urged in two directions, ie, the rotational direction and the optical axis direction, with a single configuration.

  FIG. 3 is a side view of the meshing portion of the wind turbine 32 of the light amount adjusting device 19 for explaining the embodiment of the present invention, the pinion gear 35a of the driving step motor (driving source) 35, and the gear portion 36b of the urging gear 36. It is explanatory drawing seen from. The urging gear 36 is urged in the A direction (optical axis direction) by a torsion compression coil spring 37. A meshing portion of the gear portion 32 b of the wind turbine 32 and the biasing gear portion 36 b of the biasing gear 36 b is biased in the A direction by a flange portion 36 c formed in the biasing gear 36. Here, the A direction is the optical axis direction.

  FIG. 4 is an enlarged view of the gear portion 32b of the wind turbine 32 and the meshing portion (biasing gear portion) 36b of the urging gear 36. As shown in FIG. Thereby, the rampage by the play of the gear part 32b of the windmill 32 in the optical axis direction is reduced.

  FIG. 5 is a development view of the light amount adjusting device 19 illustrating the embodiment of the present invention with the pressing member 34 removed. The driving force is transmitted to the wind turbine 32 by meshing with the gear 32a configured in the wind turbine 32 by the pinion gear 35a configured in the driving stepping motor 35. Thereby, the windmill 32 rotates around the optical axis, and the aperture blades 33 can change the aperture diameter. When the pinion gear 35a rotates clockwise as indicated by an arrow F, the aperture blade 33 is rotated in the B direction, which is the closing direction, by the windmill 32 rotating in the B direction. Since the gear portion 32b and the biasing gear portion 36b of the windmill 32 are engaged with each other, when the windmill 32 rotates in the B direction, the biasing gear 36 rotates in the C direction. An end of the torsion compression coil spring 37 is held by a hook (hanging portion) 31 d formed on the base member 31. When the urging gear 36 rotates in the C direction, the urging force is always applied in the opposite direction (B direction) to the C direction by being pushed by a hook 36a configured to the urging gear 36 (hanging portion). As a result, the wind turbine 32 is always biased in the direction opposite to the B direction (the reverse direction to the C direction), and the backlash generated between the pinion gear 35a and the gear portion 32a of the wind turbine 32 can be reduced. it can. Therefore, according to the description of the first embodiment, the wind turbine 32 is moved in the optical axis direction (A direction) and the rotational direction (reverse direction of the B direction) (tangential direction) by one urging mechanism (36, 37). It can be biased in one direction, and the noise of the stepping motor can be reduced.

[Example 2]
FIG. 6 is a diagram showing means for further improvement of the light amount adjusting apparatus according to the first embodiment of the present invention. The shape of the gear portion 36b of the urging gear 36 described in the first embodiment is a shape having an inclination having an arbitrary standing angle such as a bevel gear 36 '. At the same time, the gear connecting portion (windmill gear) 32b ′ of the windmill 32 that meshes with the urging gear 36 is also shaped to have an inclination that meshes with the gear portion 36b ′ of the urging gear 36. Since the urging gear 36 is urged in the A direction (optical axis direction) by the torsion compression coil spring 37 as in the example described in the first embodiment, the windmill gear portion 32b meshing with an inclination. The urging force in the D direction is applied to 'and the urging gear portion 36b'. In the first embodiment, the biasing in two directions of the optical axis direction (A direction) and the rotation direction (reverse direction of the B direction) can be performed by one mechanism.

  According to the present embodiment, the direction perpendicular to the optical axis, which is the direction in which the backlash generated in the rotating shaft 31c provided on the base member 31 which is the fitting portion between the base member 31 and the windmill 32 described in FIG. Radial direction) is also possible. Therefore, according to the description of the second embodiment, the optical axis direction (A direction) of the windmill 32 and the rotation direction (the reverse direction of the B direction) are performed by one urging mechanism (the urging gear 36 and the torsional compressor 37). ) In the radial direction (radial direction). Then, noise generated from each member when driven by the stepping motor 35 can be reduced. FIG. 7 is an explanatory view of a structure (configuration) for preventing the windmill 32 from being lifted, for example, in the E direction by the biasing mechanism (37, 36 ') according to the present invention. As in the windmill gear 32b 'and the urging gear 36b' described above, the meshing between the windmill gear 32a 'and the pinion gear 35a' is, for example, an inclined meshing like a bevel gear. As described above, the urging gear 36 ′ suppresses the floating of the windmill 32 due to the engagement between the windmill gear 32 a ′ and the pinion gear 35 a ′. At this time, the first connecting structure which is a connecting portion between the gear portion 35a ′ on the drive source 35 side and the gear portion 32a ′ of the windmill (ring member) 32 for preventing the windmill 32 from being lifted, and the gear of the biasing gear 36 The second connection configuration between the portion 36b ′ and the gear portion 32b ′ of the windmill 32 has the following pattern. Both the first and second coupling configurations are bevel gears. Both the first and second connection configurations are stepped gears. One is a bevel gear and the other is a stepped gear.

  As described above, according to each embodiment, the urging gear made of the rotating body is used to urge the windmill in the direction of looseness. Thereby, it is possible to reduce windmill backlash and noise in the optical axis direction, which are noise generation sources. In particular, the windmill 32 is urged by the urging gear 36 in a direction opposite to the rotation direction B of the windmill 32, thereby causing backlash between the pinion gear 35 a of the stepping motor 35 and the gear coupling portion of the gear portion 32 a of the windmill 32. Can be reduced. Further, when a flange portion 36c such as a stepped gear is provided in the biasing gear 36 and a structure capable of biasing in the optical axis direction A is adopted, it can be further pressed in the optical axis direction by vibration of the stepping motor 35. The chatter sound of the windmill 32 can be reduced. Further, since the connecting portion between the urging gear 36 and the gear portion 32b of the windmill 32 is a combination of bevel gears, the urging gear 36 can be further urged in the radial direction (radial direction). Noise during rotation can be reduced. Therefore, it is possible to reduce the noise caused by the connection between the gear portion 35a of the stepping motor 35 and the gear portion 32a of the windmill 32 with one urging structure (36, 37), and the stepping motor that can be used even when shooting moving images. Thus, a light amount adjusting device using the light source as a drive source can be obtained. In addition, with regard to the deviation of the aperture due to the play of the windmill, by adopting the biasing gear, the cause of the play is reduced, and the optical characteristics such as aperture accuracy and hysteresis are improved.

  31 base member, 32 windmill, 33 aperture blade, 34 holding member, 35 stepping motor for driving, 36 biasing gear, 37 torsion compression coil spring, 38 biasing gear rotating shaft

Claims (6)

  Three or more diaphragm blades, a blade driving pin, a ring member that drives and opens and closes the diaphragm blade by rotating around the optical axis, and a drive source that drives the ring member by gear coupling with the ring member And an urging gear that meshes with the ring member by a gear and urges the backlash of the ring member, and the urging gear is composed of a gear, and is urged by the urging member in the rotation direction and the optical axis direction. And the biasing gear meshes with the gear of the ring member to bias the ring member in two directions of the optical axis direction and the rotation direction.   The light amount adjusting device according to claim 1, wherein the connecting portion of the urging gear includes a stepped gear.   The connecting portion of the urging gear includes a bevel gear having an arbitrary vertical angle, and the urging gear is urged in the rotation direction and the optical axis direction by the urging member. The light amount adjusting device according to claim 1, wherein the gear biases the ring member in three directions of an optical axis direction, a rotation direction, and a radial direction by meshing with the gear of the ring member.   The light quantity according to claim 1, 2, or 3, wherein an urging force is applied to the ring member in a tangential direction by using an urging gear made of the rotating body, thereby taking play of the ring member. Adjustment device.   The connecting portion between the gear portion of the driving source and the gear portion of the ring member and the connecting portion between the biasing gear and the gear portion of the ring member are configured to prevent the ring member from lifting. The light amount adjusting device according to claim 1, wherein the light amount adjusting device is a light amount adjusting device.   An image pickup apparatus comprising the light amount adjusting apparatus according to claim 1.