Abstract:
An object is to provide a lens system that can change the magnitude of torque required to rotate an operation ring according to the attachment/detachment of a drive unit to/from a lens barrel, the lens barrel, and the drive unit. When the drive unit is not mounted on the lens barrel, a torque adjustment mechanism works and a friction member presses the operation ring by a biasing force of a biasing member. When the drive unit is mounted on the lens barrel, a release member provided on the drive unit releases a bias, which is performed by the biasing member, by acting on the torque adjustment mechanism through a passage formed in a fixed ring.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a Continuation of PCT International Application No. PCT/JP2013/072957 filed on Aug. 28, 2013, which claims priority under 35 U.S.C. §119(a) to Japanese Patent Application No. 2012-190739 filed on Aug. 31, 2012. Each of the above application(s) is hereby expressly incorporated by reference, in its entirety, into the present application. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a lens system, a lens barrel, and a drive unit. 
         [0004]    2. Description of the Related Art 
         [0005]    Optical systems, such as a zoom lens, a focus lens, and an iris, are built in a lens barrel of a movie camera, or the like. Operation rings, such as a zoom ring, a focus ring, and an iris ring, are rotatably provided on the outer peripheral surface of the lens barrel. When the operation rings are manually operated, the positions of the optical systems (the zoom lens and the like) corresponding to the operation rings are adjusted. 
         [0006]    Meanwhile, a drive unit, which electrically drives an operation ring, is mounted on a lens barrel of a broadcasting camera, and a cameraman adjusts an optical system by rotating the operation ring through the operation of the drive unit. There are also a lens barrel on which a drive unit can be detachably mounted and the drive unit so that a camera is used for both a movie and broadcasting. Since an operation ring is rotated by hand when the drive unit is not mounted, it is desirable that torque required to rotate the operation ring be relatively large. It is preferable that the operation ring not move due to only contact by mistake. Meanwhile, when the drive unit is mounted, it is preferable that torque required to rotate the operation ring be small for the reduction in power consumption. 
         [0007]    JP2001-147362A discloses a structure that allows a friction member to come into contact with an operation ring to prevent the position of an optical system from being changed by the weight of a lens, but there is provided a switching switch for switching a position where the friction member works and a position where the friction member is released. The structure disclosed in JP2001-147362A is not provided with a drive unit. 
         [0008]    A lens barrel disclosed in JP2009-276468A switches a load, which is applied to an operation ring, by motor driving and manual driving while a drive unit is mounted on the lens barrel. A load applied to the operation ring is given using frictional resistance, but a technical object that torque required to rotate the operation ring is not changed according to the attachment/detachment of the drive unit is not provided. 
       SUMMARY OF THE INVENTION 
       [0009]    An object of the invention is to change the magnitude of torque, which is required to rotate an operation ring, according to the attachment/detachment of a drive unit to/from a lens barrel. 
         [0010]    More particularly, an object of the invention is to change torque required to rotate an operation ring so that the torque is relatively reduced when a drive unit is mounted on a lens barrel and the torque is relatively increased when a drive unit is detached. 
         [0011]    A lens system according to the invention includes a lens barrel on which an operation ring used to adjust an optical system provided in the lens barrel is rotatably provided, and a drive unit that is detachably mounted on the lens barrel and rotates the operation ring when being mounted on the lens barrel. 
         [0012]    The lens barrel includes a lens barrel body in which the optical system is built, the operation ring that is provided on an outer peripheral side of the lens barrel body, a fixed ring that is disposed and fixed to the outer peripheral side of the lens barrel body and guides the rotation of the operation ring, and a torque adjustment mechanism that is provided in a space between an outer peripheral surface of the lens barrel body and a part of the operation ring and the fixed ring. 
         [0013]    The torque adjustment mechanism includes a friction member, a holding member that is provided on the fixed ring and holds the friction member so that the friction member freely approaches or is freely separated from the operation ring or a member interlocking with the operation ring, and a biasing member that biases the friction member in a direction where the friction member comes into contact with the operation ring or a member interlocking with the operation ring. 
         [0014]    A passage, which communicates with the torque adjustment mechanism from the outside, is formed in the fixed ring. 
         [0015]    The drive unit includes a release member that separates the friction member from the operation ring or the member interlocking with the operation ring by acting on the torque adjustment mechanism through the passage when the drive unit is mounted on the lens barrel. 
         [0016]    When the drive unit is not mounted on the lens barrel, the torque adjustment mechanism works and the friction member comes into contact with and presses the operation ring or the member interlocking with the operation ring by a biasing force of the biasing member. Accordingly, a frictional force of the friction member acts on the operation ring. For this reason, torque required to rotate the operation ring is relatively large. 
         [0017]    When the drive unit is mounted on the lens barrel, the release member provided on the drive unit releases a bias, which is performed by the biasing member, by acting on the torque adjustment mechanism through the passage formed in the fixed ring. Accordingly, the friction member is separated from the operation ring or the member interlocking with the operation ring, so that a frictional force is not applied. Torque required to rotate the operation ring is relatively reduced. 
         [0018]    As described above, according to the invention, it is possible to change the magnitude of torque required to rotate the operation ring according to the attachment/detachment of the drive unit to/from the lens barrel. 
         [0019]    The invention also provides the lens barrel that forms the lens system. 
         [0020]    An operation ring used to adjust an optical system provided on a lens barrel is rotatably provided on the lens barrel according to the invention. The lens barrel includes a lens barrel body in which the optical system is built, the operation ring that is provided on an outer peripheral side of the lens barrel body, a fixed ring that is disposed and fixed to the outer peripheral side of the lens barrel body and guides the rotation of the operation ring, and a torque adjustment mechanism that is provided in a space between an outer peripheral surface of the lens barrel body and a part of the operation ring and the fixed ring. The torque adjustment mechanism includes a friction member, a holding member that is provided on the fixed ring and holds the friction member so that the friction member freely approaches or is freely separated from the operation ring or a member interlocking with the operation ring, and a biasing member that biases the friction member in a direction where the friction member comes into contact with the operation ring or the member interlocking with the operation ring. Further, a passage, through which a release member provided on the drive unit acts on the torque adjustment mechanism when a drive unit is mounted on the lens barrel, is formed in the fixed ring. 
         [0021]    In the lens barrel, the friction member comes into contact with and presses the operation ring or the member interlocking with the operation ring by the work of the torque adjustment mechanism. For this reason, since the frictional force of the friction member is applied, torque required to rotate the operation ring is relatively large. 
         [0022]    The invention provides a drive unit that is suitable for the lens barrel. The drive unit is detachably mounted on the lens barrel, and includes a drive that rotates the operation ring when the drive unit is mounted on the lens barrel and the release member that acts on the torque adjustment mechanism through the passage. 
         [0023]    Accordingly, when the drive unit according to the invention is mounted on the lens barrel, the release member releases the bias of the friction member, which is performed by the biasing member, by acting on the torque adjustment mechanism through the passage formed in the fixed ring of the lens barrel. Accordingly, a frictional force, which is caused by the friction member, is not applied to the operation ring or the member interlocking with the operation ring. As a result, torque required to rotate the operation ring is relatively reduced. 
         [0024]    In the embodiment of the invention, the release member acts on the holding member or the biasing member of the torque adjustment mechanism. 
         [0025]    In one embodiment of the torque adjustment mechanism, the holding member and the biasing member are formed by one leaf spring. In another embodiment, the holding member is a link member of which a part is rotatably supported, the friction member is provided at one end portion of the link member, and the other portion of the link member is pulled or pushed by the biasing member, so that the friction member comes into contact with and presses the operation ring or the member interlocking with the operation ring. In still another embodiment, the holding member and the biasing member are formed by a combination of a first support member that is fixed to the fixed ring, a rectangular parallelepiped elastic body that is fixed to the first support member, and a second support member that is fixed to the elastic body, and the friction member is mounted on the second support member. 
         [0026]    As described above, it is possible to change the magnitude of torque required to rotate an operation ring according to the attachment/detachment of a drive unit to/from a lens barrel. Further specific embodiments of the invention will become more apparent in the description of an example with reference to the following drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0027]      FIG. 1  is a perspective view of a lens barrel on which a drive unit is mounted. 
           [0028]      FIG. 2  is a cross-sectional view of the lens barrel on which the drive unit is not mounted. 
           [0029]      FIG. 3  is a cross-sectional view of the lens barrel on which the drive unit is mounted. 
           [0030]      FIG. 4  is a view showing a modification of a torque adjustment mechanism and is a cross-sectional view of the lens barrel on which the drive unit is not mounted. 
           [0031]      FIG. 5  is a view showing the modification of the torque adjustment mechanism and is a cross-sectional view of the lens barrel on which the drive unit is not mounted. 
           [0032]      FIG. 6  is a view showing another modification of the torque adjustment mechanism and is a cross-sectional view of the lens barrel on which the drive unit is not mounted. 
           [0033]      FIG. 7  is a view showing another modification of the torque adjustment mechanism and is a cross-sectional view of the lens barrel on which the drive unit is mounted. 
           [0034]      FIG. 8  is a view showing a still another modification of the torque adjustment mechanism and shows a state in which the drive unit is not mounted. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0035]      FIG. 1  is a perspective view of a lens barrel  20  (a lens system), and shows a state in which a drive unit  1  driving a zoom lens or the like built in the lens barrel  20  is mounted. 
         [0036]    A focus ring  22 , a zoom ring  23 , and an iris ring  24  are rotatably provided on the outer peripheral surface of the lens barrel  20  in this order from a front end side toward a rear end side. A lens cover  21  is mounted on the front end portion of the lens barrel  20 . A mount portion  25 , which is mounted on a camera body (not shown), is formed at the rear end portion of the lens barrel  20 . 
         [0037]    An optical system (an imaging lens), such as a focus lens (not shown), a zoom lens (of which one example is denoted in  FIG. 2  and the like by reference numeral  100 ), and an iris (not shown), is held in the lens barrel  20 . When a user manually rotates the focus ring  22  (when the drive unit  1  is not mounted) or rotates the focus ring  22  by using the drive unit  1  that is mounted on the lens barrel  20 , the focus lens moves in a direction of an optical axis. When a user manually rotates the zoom ring  23  or rotates the zoom ring  23  by using the drive unit  1 , the zoom lens moves in the direction of the optical axis. Further, when the iris ring  24  is rotated, the aperture diameter is changed (the adjustment of the optical system). 
         [0038]    An iris mode switching switch  2 , an automatic switch  3 , a zoom seesaw switch  4 , and a return switch  5 , which are operated by a user, are provided on the side surface of the drive unit  1 . The iris mode switching switch  2  is a switch used to switch a mode to a mode in which the adjustment of the iris is automatically performed and a manual mode in which the adjustment of the iris is manually performed. The automatic switch  3  is a switch that is used to temporarily switch a mode to the automatic mode when the adjustment of the iris is performed in the manual mode. The zoom seesaw switch  4  is a switch that is used to give a command for moving the position of the zoom lens by rotating the zoom ring  23  by the drive unit  1 . The return switch  5  is a switch that is used to switch an image displayed on a view finder (not shown). In addition, a focus switch (not shown) that is used to rotate the focus ring  22  by the drive unit  1  and an iris switch (not shown) that is used to rotate the iris ring  24  are provided at the rear end portion of the drive unit  1 . 
         [0039]    Mounting legs  6  and  7  are formed at four positions on the drive unit  1  (only two mounting legs  6  and  7  are shown in  FIG. 1 , and the other two mounting legs are not shown). Holes are formed at these mounting legs  6  and  7  and fixing screws  8  and  9  pass through these holes and are screwed into screw holes formed at a barrel body of the lens barrel  20  (a portion of the lens barrel  20  except for the rings  22 ,  23 , and  24 ), so that the drive unit  1  is mounted on the lens barrel  20 . When these screws  8  and  9  are removed, the drive unit  1  is detached from the lens barrel  20 . 
         [0040]      FIG. 2  is a cross-sectional view including the optical axis and as seen from the side a cross section cut in the vertical direction (corresponding to a cross-sectional view taken along line II-II) of a portion that is necessary for the description of the lens barrel  20  (particularly, a mechanism for moving the zoom lens). The upward direction in the vertical direction is the direction of the side on which the drive unit  1  is installed and the downward direction is the opposite direction of the upward direction. The drive unit  1  is detached from the lens barrel  20 , and the appearance of the drive unit  1  is schematically shown. 
         [0041]    The basic structure of the lens barrel  20  is a cylindrical lens barrel body  31 . A cylindrical cam barrel  35  is rotatably fitted to the outer peripheral surface of the lens barrel body  31 . The zoom ring  23  is provided on the outside (outer periphery) of the cam barrel  35 , and the zoom ring  23  and the cam barrel  35  are integrally fixed to each other by a screw  42 . When the zoom ring  23  is rotated, the cam barrel  35  is also rotated. A spiral cam groove  36  is formed on the inner peripheral surface of the front end portion of the cam barrel  35 , and the head of a cam pin  41  is movably fitted to the cam groove  36 . Meanwhile, the zoom lens  100  (only one of a zoom lens group is shown) is held on an annular moving frame  60  by a holding member  62  that is integrated with the moving frame  60 . The moving frame  60  is movable in the lens barrel body  31  in the axial direction of the lens barrel body  31 . The cam pin  41  stands on the moving frame  60  in a radial direction. The cam pin  41  passes through a long hole (guide hole)  32 , which is formed in the lens barrel body  31  along the axial direction, so as to be movable in the long hole. A groove, a long hole, and a cam pin, which are the same as the spiral groove  36  of the cam barrel  35 , the long hole  32  of the lens barrel body  31 , and the cam pin  41 , are also provided at positions that are point-symmetric with respect to the center axis of the lens barrel body  31  (on the opposite side corresponding to a phase difference of) 180°. When the zoom ring  23  is rotated by the above-mentioned mechanism, the cam barrel  35  is rotated and the cam pin  41  moves in the axial direction that is restricted by the spiral groove  36  and the long hole  32 . Accordingly, the zoom lens  100  moves in the axial direction. 
         [0042]    Fixed rings  50  and  80  are fixed to the outer periphery of the lens barrel body  31  at positions on both sides of the zoom ring  23 . A screw, which is used to fix the fixed ring  50 , is denoted by reference numeral  52 . Annular stepped portions  54  and  81  are formed at end edges of the fixed rings  50  and  80 , which respectively come into contact with the zoom ring  23 . The zoom ring  23  is fitted to the annular stepped portions, so that the annular stepped portions guide the rotation of the zoom ring  23  (the zoom ring  23  does not move in the axial direction). Teeth (gear)  23 A are formed on a part of the peripheral surface of the zoom ring  23 . When the drive unit  1  is mounted on the lens barrel  20 , a driving gear  14 , which is rotationally driven by a motor (not shown) provided in the drive unit  1 , meshes with the teeth  23 A. Accordingly, the zoom ring  23  is electrically driven. Meanwhile, the iris ring  24  is rotatably provided between the fixed ring  80  and the mount portion  25 . 
         [0043]    A small annular space is formed between the fixed ring  50  and the cam barrel  35  and between a portion of the zoom ring  23  corresponding to the inner peripheral side of the teeth  23 A and the cam barrel  35 . A torque adjustment mechanism  90  is provided at a position in the space that corresponds to a position at which the drive unit  1  is mounted. The torque adjustment mechanism  90  includes a leaf spring  91  and a friction member  96 . One end of the leaf spring  91  is fixed to the inner peripheral surface of the fixed ring  50  by a pin  95 , the leaf spring  91  is slightly bent toward the lens barrel body  31  and extends to the inner peripheral side of the zoom ring (the inside of a portion of the zoom ring where the teeth  23 A is formed), and the friction member  96  is fixed to the other end of the leaf spring  91 . The friction member  96  has only to generate sliding friction having appropriate magnitude in consideration of a biasing force of rubber (elastic body), a synthetic resin, or the other leaf spring  91 . The friction member  96  comes into contact with the inner surface of the zoom ring  23  due to the spring force (biasing force) of the leaf spring  91 , and slightly presses the inner surface (a state shown in  FIG. 2 ). The leaf spring  91  has functions of the holding member and the biasing member for the friction member  96 . 
         [0044]    Since the friction member  96  comes into contact with the inner surface of the zoom ring  23  due to the force of the leaf spring  91  and slightly presses the inner surface of the zoom ring  23  when the drive unit  1  is not mounted on the lens barrel  20 , a frictional force acts. For this reason, torque required to rotate the zoom ring  23  is relatively large. 
         [0045]    A hole  53 , which serves as a passage through which a release member passes, is formed at a portion of the fixed ring  50  that exactly corresponds to the leaf spring  91 . This passage is not limited to a hole and may be a notch. Further, the shape of a hole or a notch may be a desired shape, such as a circular shape, a quadrangular shape, or a U shape. 
         [0046]    Meanwhile, protrusions  11  and  13  are formed at the drive unit  1  so that the drive unit  1  comes into close contact with the lens barrel  20 . When the drive unit  1  is mounted on the lens barrel  20  as shown in  FIG. 3 , these protrusions  11  and  13  come into contact with the surfaces of the fixed rings  50  and  80 . One protrusion  11  is further provided with a release member  12  that protrudes outward. The release member  12  enters the lens barrel  20  through the passage  53  and pushes the leaf spring  91  to the inside when the drive unit  1  is mounted. Accordingly, the friction member  96  fixed to the leaf spring  91  is separated from the inner surface of the zoom ring  23 . Since a frictional force does not act by the friction member  96 , torque required to rotate the zoom ring  23  is relatively reduced. 
         [0047]      FIGS. 4 and 5  show a modification of the torque adjustment mechanism. The same members as the members shown in  FIGS. 2 and 3  are denoted by the same reference numerals, and the repeated description thereof will be omitted. The same is true in other modifications to be described below. 
         [0048]    In  FIG. 4 , a torque adjustment mechanism  91 A includes a link member  111 . One end of the link member  111  is rotatably mounted on a support arm  112 , which is provided on the inner surface of the fixed ring  50 , by a pin  113 . A friction member  96  is fixed to the other end of the link member  111 . The link member  111  is also biased in a direction, in which the friction member  96  comes into contact with the inner surface of the zoom ring  23 , by a pull spring  114  that is mounted on the inner surface of the fixed ring  50 . Accordingly, a force required to rotate the zoom ring  23  is relatively large. 
         [0049]    When the drive unit  1  is mounted on the lens barrel  20  as shown in  FIG. 5 , the release member  12  enters the lens barrel  20  through the passage  53  and pushes the link member  111  to the inside. Accordingly, since the friction member  96  is separated from the inner surface of the zoom ring  23 , torque required to rotate the zoom ring  23  is reduced. 
         [0050]      FIGS. 6 and 7  show a still another modification of the torque adjustment mechanism. 
         [0051]    An L-shaped support member (first support member)  124  is fixed to the inner peripheral surface of the fixed ring  50 . The support member  124  extends in a direction of the passage  53 , and a support plate  120  (second support member) is fixed to the surface of the support member  124  through a rectangular parallelepiped elastic body  123  (for example, rubber) at a position exactly corresponding to the passage  53 . A friction member  122 , which comes into contact with the inner peripheral surface of the zoom ring  23 , is fixed to the front end portion of the support plate  120 . 
         [0052]    When the drive unit  1  is not mounted on the lens barrel  20  as shown in  FIG. 6 , the support plate  120  is pushed toward the zoom ring  23  by an elastic force of the elastic body  123  and the friction member  122  comes into contact with the inner peripheral surface of the zoom ring  23 . For this reason, torque required to rotate the zoom ring  23  is relatively large. 
         [0053]    In contrast, since the elastic body  123  is crushed (compressed) by the release member of the drive unit  1  when the drive unit  1  is mounted on the lens barrel  20  as shown in  FIG. 7 , the support plate  120  is displaced toward the center of the lens barrel  20 . Accordingly, the friction member  122  having come into contact with the inner peripheral surface of the zoom ring  23  is separated from the inner peripheral surface of the zoom ring  23 , so that torque required to rotate the zoom ring  23  is reduced. 
         [0054]    As described above, it is possible to relatively increase torque required to rotate the zoom ring  23  when the drive unit  1  is not mounted on the lens barrel  20 , and to reduce torque required to rotate the zoom ring  23  when the drive unit  1  is mounted on the lens barrel  20 . 
         [0055]      FIG. 8  is a view showing a still another modification of the torque adjustment mechanism. In a torque adjustment mechanism  90 C, a link member  111  is rotatably mounted on a substantially middle of a support arm  112 , which is fixed to the inner surface of the fixed ring  50 , by a pin  113 . One end portion of the link member  111  extends to a position corresponding to the passage  53 , and a friction member  96  is fixed to the surface, which faces the cam barrel  35 , of the other end portion thereof extending to the side opposite to the passage  53 . The other end portion of the link member  111  is biased by a push spring  115  mounted on the inner surface of the fixed ring  50 , so that the friction member  96  comes into contact with the cam barrel  35  and is slightly pressed. The cam barrel  35  is joined to the zoom ring  23  as described above. Accordingly, torque required to rotate the zoom ring  23  is relatively large. 
         [0056]    When the drive unit  1  is mounted on the lens barrel  20 , the release member  12  of the drive unit  1  enters the lens barrel  20  through the passage  53  and pushes the other end portion of the link member  111 . Accordingly, the friction member  96  is separated from the surface of the cam barrel  35  as shown by a chain line. Torque required to rotate the zoom ring  23  is reduced. 
         [0057]    The zoom ring  23  has been described in the above-mentioned example. However, it goes without saying that the focus ring  22  or the iris ring  24  may be provided with the same torque adjustment mechanism, torque required to rotate the focus ring  22  or the iris ring  24  can be increased when the drive unit  1  is not mounted on the lens barrel  20 , and torque required to rotate the focus ring  22  or the iris ring  24  can be reduced when the drive unit  1  is mounted on the lens barrel  20 .