JP2010038932A - Lens barrel and photographing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a compact lens barrel which avoids rupture of a gear in a drive transmitting device by absorbing load from the outside. <P>SOLUTION: The lens barrel includes: a lens holding member 1 holding a lens; a cam member 13 for moving the lens holding member in an optical axis direction; and the drive transmitting device 40 in which a worm gear 41 and a plurality of gears are arranged in this order from a driving source side in order to transmit driving force from the driving source to the cam member. The drive transmitting device 40 has a slip mechanism in a reduction gear 43 nearest to the driving source out of the plurality of gears 43 to 47 meshed with a gear integrally formed with a worm wheel 42 meshed with the worm gear. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a lens barrel that is mounted on a digital still camera, a video camera, an interchangeable lens, and the like and capable of zooming.

  In particular, the present invention relates to a lens barrel that uses a worm gear and a plurality of gears as a drive transmission mechanism of a lens holding member that holds a lens in the optical axis direction.

  Recently, a zoom lens camera in which a focal length of a photographing lens can be freely changed by a photographer's operation is generally used in a compact camera, and a subject can be framed to a desired size and photographed.

  In order to change the focal length of the photographing lens, first, the photographing lens needs to have a lens configuration of at least two groups.

  The focal length of the photographic lens changes by changing the positional relationship on the optical axis of each lens group constituting the photographic lens.

  In general, in order to extend the focal length of the taking lens, each lens group is extended to the subject side (collapse operation).

  As a result, the photographing lens moves to the subject side.

  Here, in order to extend the photographic lens to the subject side, a mechanism for moving the photographic lens is required.

  This mechanism uses many cylindrical parts (lens barrels), and when the photographic lens is extended toward the subject, these cylindrical parts extend in the direction of the optical axis and extend toward the subject. become.

  In this way, when the taking lens is in the extended state, the lens barrel may be damaged by the tip of the lens barrel hitting an object around the camera.

  That is, the lens barrel performs a drawing operation by receiving a driving force from a motor via a drive transmission device including a plurality of gears.

  Here, when an external impact is applied to the lens barrel, an excessive load is applied to the gear (gear) in the drive transmission device and the gear (gear) teeth are lost, and the lens barrel is stably fed and retracted. Can no longer do.

  In view of this, some drive transmission devices have a clutch mechanism for preventing gear breakage.

  This is for absorbing the impact when the lens barrel is impacted.

  This clutch mechanism is provided between the final gear of the reduction gear train that transmits the rotation of the motor and the gear mechanism that rotates the cam ring of the lens barrel. When a load of a predetermined value or more is applied in the rotation direction, the clutch mechanism It is said that the path through which the load is transmitted is opened.

  Further, the clutch mechanism is composed of two gears, and the gear 1 and the gear 2 which are integrally formed with the shaft have a mountain-and-valley-shaped meshing protrusion on one side surface facing each other.

  Further, a coil spring that urges the gear 2 in the direction in which the gear 2 is pressed against the gear 1, and a C-type retaining ring that serves to prevent the coil spring from coming off are held on the shaft of the gear 1.

  Thus, when the load applied to the clutch mechanism is equal to or greater than a predetermined value, the gear 2 rotates so as to ride on the mountain-shaped meshing protrusions in the gear 1 in order to release the load, and the gear 2 compresses the coil spring. That is, the gear shaft 1 moves in the direction of the C-shaped retaining ring.

  Then, after the mountain-shaped meshing protrusions ride on each other, they slide to the adjacent valley-shaped portions.

  This operation is repeated for a period in which the load applied to the clutch mechanism is a predetermined value or more.

Further, when the load applied to the clutch mechanism is equal to or less than a predetermined value, the gear 1 and the gear 2 in the clutch mechanism are integrally rotated by the urging force of the coil spring.
JP-A-8-110456

  The clutch mechanism described above is provided between the final gear of the reduction gear train that transmits the rotation of the motor and the gear mechanism that rotates the cam ring of the lens barrel.

  Further, when the load is below a predetermined value, the gear shaft is provided with a coil spring and a C-shaped retaining ring for urging the gear in the gear axis direction and rotating integrally.

  For this reason, there is a problem that the lens barrel is increased in size, for example, because it is necessary to increase the size of parts in order to increase the clutch torque or to increase the overall length of the clutch mechanism.

Therefore, in the present invention, a lens holding member holding a lens, a cam member for moving the lens holding member in the optical axis direction, and the driving source for transmitting a driving force from a driving source to the cam member. A lens barrel including a worm gear from the side and a drive transmission device arranged in order of a plurality of gears,
The drive transmission device includes a slip mechanism in a reduction gear of a gear closest to the drive source among the plurality of gears meshed with a gear integrally formed with a worm wheel meshed with the worm gear. The configuration.

  According to the present invention, an external load is absorbed to avoid gear destruction in the drive transmission device, and the entire length of the slip mechanism can be set short, so that the lens barrel can be downsized.

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

  FIG. 1 shows an outline of a configuration when the lens barrel of the present embodiment is applied to a video camera, a digital camera, an imaging device such as an interchangeable lens (hereinafter referred to as a camera).

  In FIG. 1, L represents a lens barrel capable of zooming, and B represents a camera body.

  In the camera body B, a silver salt film or an image sensor for recording a subject image formed by the photographing optical system in the lens barrel L is housed.

  In the present embodiment, the lens barrel L has a four-group variable magnification optical system (zoom lens), and in the non-use state (non-photographing state), the distance between the lens groups is normal (when photographing). It is shrinking.

  As a result, a so-called collapsible type that significantly shortens the overall lens length is used.

  2 to 5 are detailed views of the lens barrel at this time.

  2 is a cross-sectional view of the main part when retracted, FIG. 3 is a cross-sectional view of the main part at the widest angle (wide-angle end, WIDE end), and FIG. 4 is a cross-section of the main part at the maximum telephoto (telephoto end, TELE end). FIG. 5 is a rear view of the main part of the drive transmission device.

2 to 5, L1 is the first lens group which is the 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 Oa and performs an image blur correction operation.
L4 is a fourth lens group that performs a focusing operation (focus) by moving in the optical axis direction.
Reference numeral 1 denotes a lens holding member in the present embodiment, which is a first group barrel unit (first group barrel) holding the first lens group L1.
Reference numeral 2 denotes a second group barrel that holds the second lens group L2.
Reference numeral 3 denotes a shift unit (image blur correction device) that allows the third lens unit L3 to move in a plane perpendicular to the optical axis and performs a vibration-proof operation.
Reference numeral 4 denotes a fourth group barrel that holds the fourth lens unit L4.
Reference numeral 5 denotes an aperture shutter unit that adjusts the amount of light.
Reference numeral 11 denotes a rear lens barrel to which an image sensor such as a CCD is attached.
Reference numeral 12 denotes a fixed cylinder (fixed frame), which is fixed to the rear barrel 11 with three screws.
Reference numeral 13 denotes a cam cylinder, which is positionally restricted by the rear barrel 11 and the fixed cylinder 12 in the optical axis direction and is rotatably held on the outer periphery of the fixed cylinder 12.

  The cam cylinder 13 as a cam member has a driving first group cam groove 13a for driving the first lens group L1 in the optical axis direction and an impact cam groove 13b for impact receiving on the outer peripheral wall thereof.

  Further, the cam cylinder 13 has a second group cam groove 13c for driving the second lens group L2 and a third group cam groove 13d for driving the third lens group L3 in the optical axis direction on the inner peripheral wall thereof.

  Furthermore, it has an aperture shutter cam groove 13e for driving the aperture shutter unit 5 in the optical axis direction.

  A cam cylinder 13 as a cam member is fitted to a cam follower pin (not shown) provided integrally with each moving lens group.

Then, by rotating the cam cylinder 13 around the outer diameter of the fixed cylinder 12, the first lens group L1, the second lens group L2, the third lens group L3, and the aperture shutter unit 5 are advanced and retracted in the optical axis direction. It has a cam action for zooming, and the entire lens barrel is retracted.
Reference numeral 14 denotes a support frame fixed to the rear barrel 11 with three screws.
Reference numeral 15 denotes a focus motor unit which is a driving means for moving the fourth lens unit L4 in the optical axis direction to perform a focusing operation.

  In the focus motor unit 15, a lead screw coaxial with the rotating rotor meshes with a rack 35 attached to the fourth group barrel 4, and the fourth lens group L 4 is moved by the rotation of the rotor.

  Further, the backlash of each of the fourth group barrel 4, the guide bar (not shown), the rack 35, and the lead screw is offset by a torsion coil spring (not shown).

  The focus motor unit 15 is fixed to the support frame 14 with two screws.

  The driving means for rotating the cam ring 13 is a zoom motor unit 40.

  The zoom motor unit 40 engages with a gear portion 13f provided at the rear end portion of the cam cylinder 13 and rotates the cam cylinder 13 to perform a zooming operation.

  The zoom motor unit 40 is fixed to the rear barrel 11 with three screws.

  The position detection of the fourth group barrel 4 is performed using a photo interrupter (not shown).

  The photo interrupter electrically detects the switching between light shielding and light transmission due to movement of a light shielding portion (not shown) formed in the fourth group lens barrel in the optical axis direction, and detects the reference position of the fourth lens group L4.

The zoom (zoom position) reset switch also uses a photo interrupter (not shown) to electrically detect the switching between light shielding and light transmission caused by movement of the light shielding portion 13g formed at the rear end of the cam tube 13 in the rotational direction. Then, a plurality of reference positions of the cam cylinder 13 are detected.
Reference numeral 22 denotes an outer cylinder fixed to the rear barrel 11.

Next, the zoom motor unit 40 as a drive transmission device will be described with reference to FIG.
Reference numeral 41 denotes a worm gear fixed to a rotor shaft that is coaxial with the rotor of a zoom motor (not shown) that is a drive source. Reference numeral 42 denotes a worm wheel that meshes with the worm gear and is integrally formed with a spur gear.

The drive transmission device 40 is arranged in the order of the worm gear 42 and the plurality of gears 43 to 47 from the drive source side in order to transmit the driving force from the drive source to the cam cylinder 13.
Reference numeral 43 denotes a slip mechanism of the present embodiment, which meshes with a spur gear integrally formed with the worm wheel 42, and is arranged in a reduction gear of a spur gear closest to the zoom motor in the drive transmission device.
44 is a reduction gear of a spur gear that meshes with the slip mechanism 43, and 45 is an idler gear that meshes with the reduction gear 44 of a spur gear.
46 is a reduction gear of a spur gear meshing with the idler gear 45, and 47 is an output gear of the zoom motor unit 40 meshing with the reduction gear 46 of the spur gear.

  Here, the gears (gears) 42 to 47 are rotatably held on the outer periphery of a gear shaft (not shown).

  The output gear 47 meshes with a gear portion 13 f provided at the rear end portion of the cam cylinder 13.

  As described above, the driving force of the zoom motor (not shown) in the zoom motor unit 40 is amplified through the above-described many gears (gears) and transmitted to the cam barrel 13 to retract the entire lens barrel. Yes.

  Next, the configuration of the slip mechanism 43 will be described with reference to FIGS.

FIG. 7 is a view as seen from the direction A in FIG.
43a is a small gear that is the first rotating member of this embodiment, and includes a shaft portion 43a1.

  A washer 43b is fixed to the outer periphery of the shaft portion 43a1 of the first rotating member (small gear) 43a, and a compression coil spring 43c that is a biasing member that is compressed in the radial direction is held.

  The first rotating member (small gear) 43a may be made of metal, resin, or any other material, but is preferably made of metal.

A protrusion 43c1 is formed on the compression coil spring 43c.
43d is a large gear that is the second rotating member of the present embodiment, and an abutting portion 43d1 that abuts on the protruding portion 43c1 provided on the compression coil spring 43c is formed.

  The second rotating member (large gear) 43d may be made of metal, resin, or any other material, but is preferably made of resin.

  The winding direction of the compression coil spring 43c is a direction in which the abutting portion 43d1 abuts on the protrusion 43c1 of the compression coil spring 43c to apply a force, and in this embodiment, is the direction of arrow C3 (right-handed).

  Here, the first lens group L1, the second lens group L2, the third lens group L3, and the aperture shutter unit 5 advance and retract in the optical axis direction, the cam cylinder 13 rotates, and the slip mechanism 43 operates. The direction will be described.

  First, when a load is applied to the first group barrel unit 1 from the outside in the first direction in which the lens barrel is retracted, one of the cam barrels 13 fitted to a cam follower pin (not shown) provided in the first group barrel unit. A force is transmitted from the group cam groove 13 a in the direction in which the cam cylinder 13 rotates to the outer periphery of the fixed cylinder 12.

  At this time, the direction in which the cam cylinder 13 rotates is determined by the shape of the cam groove.

  In this embodiment, when a load is applied to the first group barrel unit 1 from the outside in the first direction in which the lens barrel is retracted, the cam barrel 13 rotates in the direction of the arrow C1 (FIG. 5).

  At this time, the rotation direction C1 of the cam cylinder 13 and the rotation direction of the first rotation member (small gear) 43a in the slip mechanism 43 are also determined by the gear configuration.

  In this embodiment, when the cam cylinder 13 rotates in the C1 direction, the first rotating member (small gear) 43a rotates in the direction of the arrow C2 (FIG. 5).

  That is, the first rotating member (small gear) 43a rotates in the direction of the arrow C2, so that the protrusion 43c1 of the compression coil spring 43c held by the first rotating member (small gear) 43a is rotated in the second direction. A force in the direction of arrow C3 (FIG. 7) is received from the contact portion 43d1 of the member (large gear) 43d.

  Here, when the force in the arrow C3 direction received by the projection 43c1 of the compression coil spring 43c from the contact portion 43d1 of the second rotating member (large gear) 43d becomes a predetermined value or more, the rotating member 1 (small gear) 43a. The inner periphery of the compression coil spring 43c expands with respect to the outer periphery of the shaft portion 43a1.

  Thereby, the frictional force generated between the inner periphery of the compression coil spring 43c and the outer periphery of the first rotating member (small gear) 43a is reduced.

  The compression coil spring 43c and the second rotating member (large gear) 43d are not rotated because they are in contact with the contact portion 43d1 of the second rotating member (large gear) 43d at the protrusion 43c1, and thus the first rotating member. The (small gear) 43a rotates in a slipping manner with respect to the compression coil spring 43c.

  By this series of operations, the above-described external load can be absorbed and the gear can be prevented from being broken.

  When the force in the direction of arrow C3 received by the protrusion 43c1 of the compression coil spring 43c from the contact portion 43d1 of the second rotating member (large gear) 43d is equal to or less than a predetermined value, the inner circumference of the compression coil spring 43c and the first circumference A frictional force is generated between the outer periphery of the rotating member (small gear) 43a.

  By this frictional force, the first rotating member (small gear) 43a and the second rotating member (large gear) 43d are connected by the compression coil spring 43c and rotate integrally.

  In the slip mechanism 43 of the present embodiment, the load absorption direction is set to the rotation direction instead of the axial direction.

  Further, the arrangement in the drive transmission device is a reduction gear of a spur gear closest to the zoom motor meshed with a spur gear integrally formed with the worm wheel 42.

  Thereby, the full length of the slip mechanism 43 can be set short, and a lens barrel can be reduced in size.

  Furthermore, in the embodiment of the present invention, the portion where the projection 43c1 of the compression coil spring 43c and the contact portion 43d1 of the second rotating member (large gear) 43d abut is one place, and the load is absorbed only during one-side rotation. I took the configuration.

  Here, in the case of adopting a configuration in which two contact portions are provided and the load is absorbed when rotating on both sides, two protrusion portions of the compression coil spring and two contact portions of the second rotating member are required.

  However, it is difficult to suppress the manufacturing variation at the two projecting portion angles provided on the compression coil spring, and considering this angular variation, a large amount of play in the rotational direction is set on the second rotating member side.

  This increases the variation of backlash in the slip mechanism, and there is a problem that the controllability of the lens barrel is deteriorated.

  Therefore, in this embodiment, a slip mechanism with good controllability of the lens barrel with reduced backlash is provided by adopting a configuration that absorbs a load only during one-side rotation (one contact portion).

  FIG. 8 is a system diagram of the driving of the lens barrel and the shake correction device in the photographing apparatus equipped with the lens barrel of the present embodiment.

In FIG. 8, 50 is an optical low-pass filter for removing a high frequency component of the spatial frequency of the subject.
Reference numeral 51 denotes a CCD, which is an image sensor for converting an optical image arranged on the focus surface into an electric signal.
The electrical signal a read from the CCD 51 is converted into an image signal b by the camera signal processing circuit 52.
A microcomputer 53 controls lens driving.

  When the power is turned on, the microcomputer 53 drives the focus motor drive circuit 56 and the zoom motor drive circuit 57 while monitoring the outputs of the focus reset circuit 54 and the zoom reset circuit 55.

  Thereby, each lens group is moved in the optical axis direction.

  The outputs from the focus reset circuit 54 and the zoom reset circuit 55 are reversed when the respective movable members reach predetermined positions.

  Here, the predetermined position is when the light shielding member provided on the movable member comes to a boundary portion where the light emitting portion of the photo interrupter provided on the fixed portion is shielded or transmitted.

  Then, the microcomputer can know the absolute position of each lens group by counting the number of subsequent motor drive steps in the microcomputer with the position as a reference.

  Thereby, accurate focal length information is obtained.

This series of operations is referred to as zoom and focus reset operation.
Reference numeral 58 denotes a diaphragm drive circuit for driving the diaphragm device, and the aperture diameter of the diaphragm is controlled based on the brightness information b of the video signal taken into the microcomputer 53.
Reference numerals 59 and 60 denote PITCH (vertical tilt angle) and YAW (horizontal tilt angle) angle detection circuits of the optical device. The angle is detected by, for example, an angular velocity sensor such as a vibration gyroscope fixed to the photographing apparatus. This is done by integrating the output of.

Outputs from both circuits 59 and 60, that is, information on the tilt angle of the photographing apparatus is taken into the microcomputer 53.
Reference numerals 61 and 62 denote PITCH (vertical direction) and YAW (horizontal direction) coil drive circuits for moving the third lens unit L3 perpendicularly to the optical axis in order to perform image blur correction.

The coil drive circuits 61 and 62 arrange a coil in a gap of a magnetic circuit including a magnet, and generate a drive force for shifting the third lens unit L3 by a so-called moving coil configuration.
Reference numerals 63 and 64 denote PITCH (vertical direction) and YAW (horizontal direction) position detection circuits for detecting the shift amount with respect to the optical axis of the third lens unit L3. The signal microcomputer 53 from the position detection circuits 63 and 64 Is taken in.

  When the third lens unit L3 moves perpendicularly to the optical axis, the passing light beam is bent and the position of the subject image formed on the CCD 51 moves.

  The microcomputer 53 controls the moving amount of the image at this time so that the moving amount is the same as the moving direction of the image when the photographing apparatus is actually tilted.

  Therefore, so-called image blur correction is realized in which the formed image does not move even when the photographing apparatus is tilted (image blur).

  In the microcomputer 53, the tilt signal of the photographing apparatus obtained by the PITCH angle detection circuit 59 and the YAW angle detection circuit 60 and the shift amount signal of the third lens unit L3 obtained from the PITCH position detection circuit 63 and the YAW position detection circuit 64 are obtained. Are subtracted respectively.

  Then, the third lens group L3 is driven by the PITCH coil drive circuit 61 and the YAW coil drive circuit 62 based on the signals obtained by amplifying the respective difference signals and performing appropriate phase compensation.

  By this control, positioning control is performed so that the above difference signal becomes smaller and the target position is maintained.

  Further, in this embodiment, the zooming operation is performed by relative movement of the first to third lens units L1 to L3.

  For this reason, the movement amount of the image with respect to the shift amount of the third lens unit L3 changes depending on the focal length.

  Therefore, the shift amount of the third lens unit L3 is not determined as it is based on the tilt signal of the photographing apparatus obtained by the PITCH angle detection circuit 59 and the YAW angle detection circuit 60, and correction is performed based on the focal length information.

  Thereafter, the image movement due to the tilt of the photographing apparatus is canceled by the shift of the third lens unit L3.

  According to the present embodiment, the slip mechanism configured in the drive transmission device includes a worm wheel that meshes with the worm gear, and a spur gear that is meshed with a spur gear integrally formed with the worm wheel and that is closest to the drive source. The configuration is arranged on the reduction gear.

  Further, in the slip mechanism, one first rotating member holds a biasing member that is provided with a protruding portion and is compressed in the radial direction, and the other second rotating member has a protrusion of the biasing member. The contact part which contact | abuts to a part was provided.

  Further, this slip mechanism is configured to absorb a load of a predetermined value or more only in the direction of rotation when a load is applied in the retracting (collapse) direction of the lens holding member.

  Thereby, while absorbing the load from the outside and avoiding the gear destruction in a drive transmission device, the full length of a slip mechanism can be set short, and the effect that the lens barrel can be reduced in size is acquired.

The perspective view of the imaging device which is an Example of this invention Sectional drawing of the lens barrel which is an embodiment of the present invention (when retracted) Sectional drawing (at the time of WIDE) of the lens barrel which is an Example of this invention Sectional drawing of the lens barrel which is an Example of this invention (at the time of TELE) The rear view of the drive transmission device which is an Example of this invention Exploded view of a slip mechanism according to an embodiment of the present invention Viewed from direction A in FIG. FIG. 3 is a system diagram of a lens barrel driving and blur correction apparatus according to an embodiment of the present invention.

Explanation of symbols

L Lens barrel B Camera body 1, 3, 5 Unit 2, 4, 11 Lens barrel 12, 13 Tube 13a, 13b, 13c, 13d, 13e Cam groove 14 Support frame 15, 40 Unit 43 Slip mechanism 43a, 43d Rotating member 43c Spring

Claims (5)

A lens holding member holding a lens, a cam member for moving the lens holding member in the optical axis direction, a worm gear from the drive source side to transmit the driving force from the drive source to the cam member, a plurality of A lens barrel having a drive transmission device arranged in the order of gears,
The drive transmission device includes a slip mechanism in a reduction gear of a gear closest to the drive source among the plurality of gears meshed with a gear integrally formed with a worm wheel meshed with the worm gear. Lens barrel. The slip mechanism includes a first rotating member and a second rotating member, and the first rotating member holds an urging member having a protruding portion that is compressed in the radial direction, and the second rotating member The rotating member includes a contact portion that contacts the protruding portion of the biasing member,
2. The structure according to claim 1, wherein the slip mechanism is configured to absorb the load in a direction in which the first rotating member rotates when a load is applied in a direction in which the lens holding member moves. Lens barrel.   The slip mechanism is configured to absorb the load only in a direction in which the first rotating member rotates when a load is applied in a first direction in which the lens holding member moves. 2. The lens barrel according to 2.   The urging member is a coil spring, and when the force received by the projection of the coil spring from the contact portion of the second rotating member becomes a predetermined value or more, the shaft portion of the first rotating member is 4. The lens barrel according to claim 2, wherein the inner circumference of the coil spring is widened.   An imaging apparatus comprising the lens barrel according to any one of claims 1 to 4.

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