JP2018060087A - Lens barrel and imaging apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lens barrel capable of achieving at least one of the suppression of the increase of the number of components, the reduction of restriction in the cam groove layout of a cam mechanism, and the achievement of a focus mechanism capable of widening a focus stroke range by making a transmission part or a lead screw long.SOLUTION: The lens barrel includes an optical element 30 which is movable in an optical axis direction, a first frame body 31 which is movable in the optical axis direction together with the optical element 30, a motor with a lead screw 33 which moves the optical element 30 in the optical axis direction, an engagement member 23, a second frame body 21, and a cam mechanism 40. The engagement member 23 is engaged with the lead screw, the second frame body 21 holds the engagement member 23 and is movable in the optical axis direction, and the cam mechanism 40 supports the second frame body 21 movably in the optical axis direction. The first frame body 31 supports the motor, so that the motor and the optical element are integrally moved, when the motor 33 is driven.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a lens barrel and an imaging apparatus, for example, a lens barrel and an imaging apparatus having a focus adjustment function.

  As an image pickup apparatus having a focus adjustment function, an image pickup apparatus using a motor having a lead screw on an output shaft is known. Here, the lead screw is rotated by a motor, and a nut or a rack engaged with the lead screw is driven in the optical axis direction. As a result, the lens holder attached to the rack and the lens holder biased in the axial direction so as to come into contact with the nut screwed with the lead screw in the optical axis direction are moved in the optical axis direction. Also known is a mechanism that moves in the optical axis direction together with the motor in order to extend the focus stroke range.

  In the mechanism described in Patent Document 1, the lead screw is extended toward the image sensor side, and a focusing motor is mounted on the second lens holding frame. The guide shaft is also attached to the second lens holding frame toward the image sensor side, and the moving table is screwed to the lead screw. A holding frame of a third lens that is a focusing lens is guided in the optical axis direction by the guide shaft and abuts on the moving table. In this configuration, when the focusing motor is driven, the third lens holding frame moves in the optical axis direction together with the moving table. When the zooming operation or the collapsing / retracting operation is performed, the focusing motor moves together with the second lens holding frame, so that the focus stroke range also moves.

  Patent Document 2 discloses a mechanism that uses a focus frame that moves in the optical axis direction by the rotation of a cam ring and a focus motor that is fixed to the focus frame. Similar to the mechanism described in Patent Document 1, the focus frame holding the focus motor is moved by the collapsing / feeding-out operation or the zooming operation, so that the focus stroke range is also moved.

JP 2003-98418 A JP 2006-276464 A

  However, in the mechanism of Patent Document 1, if the lead screw is extended for a long time, the leading end portion of the lead screw tends to interfere with the fixed cylinder holding the image sensor. Also, if the motor body is moved closer to the subject side while maintaining the lead screw tip position, the motor body and the subject side lens are likely to interfere with each other when the diameter of the subject side lens is large. Therefore, it is a mechanism that is not easy to extend the length of the lead screw.

  In the mechanism of Patent Document 2, since it is necessary to separately provide a focus frame that moves with a cam ring, the number of parts is likely to increase, and it is necessary to provide a cam groove for the focus frame on the cam ring. Restrictions are likely to occur on the degree of freedom.

In view of the above problems, a lens barrel according to one aspect of the present invention includes an optical element that is movable in the optical axis direction, a first frame that is movable in the optical axis direction together with the optical element, and the optical element that emits light. A motor with a lead screw that moves in the axial direction, an engagement member that engages with the lead screw,
A first frame that holds the engaging member and is movable in the optical axis direction; and a cam mechanism that supports the second frame so as to be movable in the optical axis direction. When the body drives the motor, the body supports the motor so that the motor and the optical element move together.

  In view of the above problems, a lens barrel according to another aspect of the present invention includes an optical element movable in the optical axis direction, a first frame movable in the optical axis direction together with the optical element, and the optical element. An actuator including a drive source section and a transmission section for moving the drive source section in the optical axis direction, a second frame body holding one of the drive source section and the transmission section and movable in the optical axis direction, and the second And a cam mechanism for movably supporting the frame body in the optical axis direction, and the first frame body, when driving the actuator, the other of the drive source section, the transmission section, and the optical element. Supports the drive source unit, the other of the transmission unit, and the optical element so that the transmission unit moves integrally, and the transmission unit engages with the drive source unit and extends over a predetermined stroke length. In response to the driving force from the driving source unit, the first frame and the second frame are combined. To move,

  According to the present invention, suppression of an increase in the number of parts, reduction of cam groove layout restrictions of the cam mechanism, realization of a focus mechanism that makes it possible to extend the focusing stroke range by lengthening the transmission part or the lead screw, At least one of the following can be achieved.

Sectional drawing which shows the retracted state of a lens-barrel. Sectional drawing which shows the imaging state of infinity. Sectional drawing which shows the near imaging | photography state. The perspective view of an imaging device which has a lens barrel.

  According to one aspect of the present invention, in a focus mechanism that moves together with an actuator such as a motor by a collapsing / feeding-out operation or a variable magnification operation, the focus mechanism can be used without increasing the number of parts or restricting the cam groove layout. Can be realized. Further, it is possible to provide a focus mechanism that can take a wider focus stroke range by appropriately arranging an actuator or a motor with a lead screw and taking the transmission portion or the lead screw sufficiently long.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, these do not limit the scope of the invention, and various changes and modifications can be made within the scope of the gist of the invention. FIG. 1 is a sectional view of the lens barrel in the retracted state. The retracted state refers not only to the state in which the lens is housed in the camera body, but also to the state in which the lens enters the lens hood provided on the front surface of the camera body. Further, when the lens barrel is an interchangeable lens, the lens is stored in the interchangeable lens main body. FIG. 2 is a cross-sectional view of a state in which the focus adjustment lens is adjusted and the focus is adjusted to infinity in a state where the lens is extended to a shootable position. FIG. 3 is a cross-sectional view of a state in which the focus adjustment lens is adjusted and the focus is adjusted to the closest position in a state in which the lens is extended to a shootable position. In FIG. 1 to FIG. 3, the left is drawn as the subject side (front side of the lens barrel).

  In the figure, reference numeral 10 denotes a first lens group, and 11 denotes a first lens holder that holds the first lens group 10 so that it can be retracted and extended (can be retracted and extended). The first lens holder 11 is formed in a cylindrical shape, holds the first lens group 10 at the subject side end of the cylindrical portion, and has a cam follower 12 at the image plane side end of the cylindrical portion. The cam follower 12 engages with the first lens cam groove of the rotating cam ring 40.

  Reference numeral 20 denotes a second lens group, and reference numeral 21 denotes a second lens holder that holds the second lens group 20 so that it can be retracted and extended. A cam follower 22 is provided at the image plane side end of the second lens holder 21. The rotation of the first lens holder 11 and the second lens holder 21 is restricted by a straight guide cylinder (not shown), and reciprocates linearly only in the optical axis direction along a predetermined cam locus by the rotation of the rotating cam ring 40. Then retracted. The rotation of the rotating cam ring 40 is executed by, for example, a driving force from a not-illustrated zooming motor. A cam mechanism is constituted by the cam follower 22, the rotating cam ring 40, the second lens cam groove, and the like.

  Reference numeral 30 denotes a third lens group for focus adjustment, which adjusts the focus by moving in the optical axis direction. Reference numeral 31 denotes a third lens holder that holds the third lens group 30. The third lens holder 31 is provided with a rectilinear guide bar 32. The rectilinear guide bar 32 is fitted to the sleeve of the second lens holder 21 and is guided so as to be movable in the optical axis direction with respect to the second lens holder 21. A focus motor 33 is fixed to the third lens holder 31. A lead screw 34 is provided on the output shaft of the focus motor 33, and the lead screw 34 rotates when the focus motor 33, which is a drive source unit, is driven. The lead screw 34 extends from the motor 33 toward the subject side. Since the third lens holder 31 is not engaged with the rotating cam ring 40, the third lens holder 31 does not directly receive the rotational force of the rotating cam ring 40, but the light of the second lens holder 21 due to the rotation of the rotating cam ring 40. Along with the movement in the axial direction, it moves in the optical axis direction. Such a movement is performed when the retracted state described later is used.

  A nut or rack 23 that is an engaging member is engaged with the lead screw 34. The nut or rack 23 is installed in the second lens holder 21, and the movement in the optical axis direction and the rotation of the second lens holder 21 are restricted. Reference numeral 41 denotes a base plate, which rotatably holds the rotating cam ring 40. In the present embodiment, the image pickup element 42 is held on the ground plane 41. In the case of an interchangeable lens, the image sensor 42 is usually provided on the camera body side.

  In the above configuration, when the focus motor 33 is driven in the lens barrel extended state, the second lens holder 21 and the third lens holder 31 relatively move in the optical axis direction according to the advance angle of the lead screw 34. At this time, the second lens holder 21 is cam-engaged with the rotating cam ring 40 as described above, and the position in the optical axis direction is determined by the cam groove. Accordingly, when the focus motor 33 is driven, the third lens holder 31 moves together with the focus motor 33 and the guide bar 32 in the optical axis direction with respect to the second lens holder 21. When the third lens group 30 is set to the infinity position, the state shown in FIG. 2 is obtained, and when the third lens group 30 is set to the close position, the state shown in FIG. 3 is set.

  When the lens barrel is retracted, first, the focus motor 33 is driven to extend the third lens group 30 to approach the second lens group 20, and then the rotating cam ring 40 is rotated by the zooming motor. The first lens group 10 and the second lens group 20 are retracted. The first lens holder 11 and the second lens holder 21 are cam-engaged with the cam ring 40. When the cam ring 40 is rotated, the first lens holder 11 and the second lens holder 21 move in the optical axis direction. They are determined by the first lens cam locus and the second lens cam locus, respectively.

  FIG. 4 is a perspective view of the imaging device 50 having the lens barrel 1. As shown in FIG. 4, the imaging device 50 according to the present embodiment includes an imaging device main body 51 and a lens barrel 1 attached to the main body 51. A finder objective lens 57 for determining the composition of the subject, an auxiliary light means 52 for assisting a light source when performing a photometry operation and a distance measurement operation, a strobe 53, and the lens barrel 1 are provided in front of the imaging device 50. Yes. On the upper surface of the main body 51, a release button 54, a zoom changeover switch 55, and a power supply changeover button 56 are provided. Further, a liquid crystal display device (not shown) is provided on the back surface of the imaging device main body 51. In the present embodiment, the lens barrel 1 is movable between a retracted state (the state shown in FIG. 4) and a extended state (the photographing state).

  The effect of this embodiment will be described. In the configuration described in Patent Document 1, the focus motor is provided in the second lens holder (intermediate lens holder), and the lead screw is extended toward the image plane side. When the main body of the focus motor overlaps the lens or lens holder of the first lens group (subject lens group) in front projection, it is necessary to prevent the focus motor from interfering with the first lens group. There is. Therefore, it is necessary to dispose the first lens unit on the image plane side in both the retracted state and the extended state. Therefore, the length of the focus motor main body and the lead screw is easily limited.

  In the present embodiment, as shown in FIG. 1, the main body of the focus motor 33 (the main body that houses the coil and the rotor) and the lens holder 11 of the first lens group 10 overlap each other by the amount X in front projection. In addition, the tip of the lead screw 34 is disposed outside (in the radial direction) outside the outer diameter of the lens or lens fitting portion of the first lens group 10, and the tip of the lead screw 34 is in the optical axis direction in the retracted state. The length overlaps with one lens group 10. Of the screw length, the length of the area closer to the image plane than the first lens group 10 is A, and the length of the area overlapping the first lens group 10 in the optical axis direction is B. In the configuration described in Patent Document 1, the screw length is only A, but in the configuration of the present embodiment, the lead screw 34 can be A + B. Therefore, it is possible to obtain effects such as a wide focusing stroke range and an increased degree of freedom in optical design. In the present embodiment, since the motor 33 is supported by the third lens holder 31, a part corresponding to the focus frame of the motor base plate described in Patent Document 2 is unnecessary. Further, with respect to the third lens holder 31, it is not necessary to provide a cam groove for the focus frame in the cam ring 40, and the number of cam grooves is reduced correspondingly, so that restrictions on the cam groove layout are reduced.

  In the present invention, in addition to the above-described embodiment, the following changes or modifications are possible. The motor can also be installed on the frame of the intermediate second lens group. However, in this case, it is not easy to sufficiently extend the focus stroke of the focus lens behind the intermediate frame where the motor is installed. In this regard, if the motor is installed in the frame of the third lens group on the image sensor side as in the above embodiment, the rear focus lens can be driven in a wide focusing stroke range without increasing the number of components.

  Moreover, the motor with a lead screw can be replaced with an actuator including a large-diameter portion having a relatively large diameter as a driving source and a transmission portion for transmitting the driving force of the driving source over the length of the stroke. As such an actuator, there is a linear ultrasonic motor including a drive source unit in which vibrators of piezoelectric elements are stacked and a slider that engages with the drive source unit and slides relatively in the optical axis direction. In this case, the second frame body holds one of the drive source part (piezoelectric element part) and the transmission part (slider). The first frame (corresponding to the third lens holder 31) has a drive source section and a transmission section so that when the actuator is driven, the other of the drive source section, the transmission section, and the optical element move integrally. And the other optical element. Even with such a configuration, the same effects as those of the above embodiment can be obtained. For example, in a configuration in which a first frame (corresponding to the third lens holder 31) holds a transmission unit (slider), the transmission unit extends from the first frame toward the subject side to increase the lens stroke. You can earn. In this case, the driving source unit and the lens holder 11 of the first lens group 10 overlap each other by the amount X in front projection. In addition, the tip of the slider is disposed outside (in the radial direction outside) the outer diameter of the lens or lens fitting portion of the first lens group 10, and the tip of the slider is in the optical axis direction in the retracted state. And set to overlap length.

  Moreover, it is not necessary to install an optical element in the second intermediate frame in practice. However, in order to increase the lens stroke while reducing the number of parts, it is preferable to provide an optical element as in the above embodiment.

  1: lens barrel, 20: second lens group, 21: second lens holder (second frame), 23: engagement member (nut or rack), 30: third lens group (optical element, focus adjustment) Lens), 31: third lens holder (first frame), 33: focus motor (motor with lead screw), 34: lead screw, 40: rotating cam ring (cam mechanism)

Claims (12)

An optical element movable in the optical axis direction;
A first frame movable in the optical axis direction together with the optical element;
A motor with a lead screw that moves the optical element in the optical axis direction;
An engaging member that engages with the lead screw;
A second frame that holds the engaging member and is movable in the optical axis direction;
A cam mechanism that supports the second frame so as to be movable in the optical axis direction;
The first frame supports the motor so that when the motor is driven, the motor and the optical element move integrally.
A lens barrel characterized by that. An optical element movable in the optical axis direction;
A first frame movable in the optical axis direction together with the optical element;
An actuator including a drive source unit and a transmission unit for moving the optical element in the optical axis direction;
A second frame that holds one of the drive source section and the transmission section and is movable in the optical axis direction;
A cam mechanism that supports the second frame so as to be movable in the optical axis direction;
Have
When the actuator is driven, the first frame is configured so that the other of the drive source unit, the transmission unit, and the optical element move integrally, and the other of the drive source unit, the transmission unit, and the optical unit. The transmission portion engages with the drive source portion, receives the driving force from the drive source portion over a predetermined stroke length, and receives the driving force from the drive source portion. Move relative to the frame of
A lens barrel characterized by that. The drive source section includes a piezoelectric element vibrator, the transmission section includes a slider extending in the optical axis direction, and the actuator is a linear ultrasonic motor.
The lens barrel according to claim 2. The second frame is provided on the subject side in the optical axis direction with respect to the first frame, the first frame supports the slider, and the slider extends from the first frame. Extending towards the subject,
The lens barrel according to claim 3. The second frame is provided on the subject side in the optical axis direction with respect to the first frame, and the lead screw extends from the motor toward the subject.
The lens barrel according to claim 1. Having another optical element closer to the subject than the first frame and the second frame;
The lens barrel according to any one of claims 1 to 5, wherein: The lead screw or the slider is disposed radially outside the other optical element and overlaps the other optical element in the optical axis direction in a retracted state.
The lens barrel according to claim 6. The lens mirror according to claim 6 or 7, wherein a main body portion or the drive source portion for housing the motor coil and rotor overlaps the other optical element in a front projection. Tube. The optical element that is movable in the optical axis direction together with the first frame is a focus adjustment lens.
The lens barrel according to claim 1, wherein the lens barrel is a lens barrel. The first frame is not engaged with the cam mechanism;
The lens barrel according to claim 1, wherein the lens barrel is a lens barrel. The second frame can be retracted and extended in the optical axis direction,
The cam mechanism supports the second frame so that it can be retracted and extended in the optical axis direction.
The lens barrel according to any one of claims 1 to 10, wherein: An imaging apparatus comprising the lens barrel according to claim 1.