Abstract:
A lens barrel and an optical device having small sizes by saving a space for inner components such as a moving group while stably retaining and moving the inner components are provided. The lens barrel retains lenses while allowing movement along an optical axis. The lens barrel includes: a first frame; a second frame positioned inside the first frame; and n linear guide structures configured to allow movement of the second frame relative to the first frame along the optical axis, wherein the n linear guide structures include: n linear guide concave parts spaced apart from each other in a circumferential direction around the optical axis and extending along the optical axis; and n linear guide convex parts engaging with the n linear guide concave parts in a relatively movable manner, wherein some of the n linear guide concave parts are provided on the first frame, and the others of the n linear guide concave parts are provided on the second frame (n is an integer equal to or greater than 2).

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
       [0001]    This application is a continuation application, claiming the benefit under §365(c), of an International application filed on Dec. 24, 2014 and assigned application number PCT/KR2014/012828, which claimed the benefit of a Japanese patent application filed on Feb. 28, 2014 in the Japanese Patent Office and assigned Serial number 2014-39651, and of a Japanese patent application filed on Aug. 18, 2014 in the Japanese Patent Office and assigned Serial number 2014-165842, the entire disclosure of which is hereby incorporated by reference. 
     
    
     TECHNICAL FIELD 
       [0002]    The present disclosure relates to a lens barrel and an optical device. 
       BACKGROUND 
       [0003]    A lens barrel including a barrel and a cam barrel is disclosed. In the lens barrel, a groove part is formed in a fixed frame, a linear groove is formed in a rotatable barrel, and a driving pin is formed on the cam barrel. The driving pin engages with the linear groove through the groove part. In the lens barrel disclosed in Patent document 1, the groove part, the linear groove, and the driving pin are arranged at angular positions approximately trisecting a circumference around an optical axis, and a movable group is linearly moved according to the rotation of the rotatable barrel. 
         [0004]    The above information is presented as background information only to assist with an understanding of the present disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art with regard to the present disclosure. 
       RELATED ART DOCUMENT 
       [0005]    [Patent Document 1] Japanese Patent Application Publication No. 2011-7938 
       SUMMARY 
       [0006]    However, in the lens barrel, the groove part formed in the fixed frame and the linear groove formed in the rotatable barrel are arranged across each other. Therefore, the driving pin should have a sufficient degree of strength so as to engage with both the groove part and the linear groove that cross each other, and thus it is necessary to form the driving pin to have a certain size. As a result, it is necessary to increase the width of the groove part or the linear groove for engagement with the driving pin, and thus a corresponding space is necessary in the fixed frame or the rotatable barrel. 
         [0007]    In addition, a member (the rotatable barrel), in which the linear groove is formed, should have a sufficient degree of strength to prevent deformation of the linear groove and guarantee linear movement of a moving group. To this end, it is preferable that a sidewall of the rotatable barrel be continuous throughout the circumference of the rotatable barrel. However, if a notch shape is formed in the sidewall of the rotatable barrel by removing a portion of the sidewall in a height direction, it may be difficult to guarantee a sufficient degree of strength for linear movement. 
         [0008]    Due to this reason, if a notch shape is not formed in the member, in which the linear groove is formed, because inner components such as a moving group are accommodated inside the member, it may be difficult to reduce the size of the lens barrel. 
         [0009]    Aspects of the present disclosure are to address at least the above-mentioned problems and/or disadvantages and to provide at least the advantages described below. Accordingly, an aspect of the present disclosure is to provide a lens barrel and an optical device having small sizes by saving a space for inner components such as a moving group while stably retaining and moving the inner components. 
         [0010]    An embodiment of the present disclosure provides a lens barrel retaining lenses while allowing movement along an optical axis, the lens barrel including: a first frame; a second frame positioned inside the first frame; and n linear guide structures configured to allow movement of the second frame relative to the first frame along the optical axis, wherein the n linear guide structures may include: n linear guide concave parts spaced apart from each other in a circumferential direction around the optical axis and extending along the optical axis; and n linear guide convex parts engaging with the n linear guide concave parts in a relatively movable manner, wherein some of the n linear guide concave parts may be provided on the first frame, and the others of the n linear guide concave parts may be provided on the second frame (n is an integer equal to or greater than 2). 
         [0011]    Another embodiment of the present disclosure provides a lens barrel retaining lenses while allowing movement along an optical axis, the lens barrel including: a first frame; a second frame positioned inside the first frame; a fixed frame positioned outside the first frame; and n linear guide structures configured to allow movement of the second frame relative to the first frame along the optical axis, wherein the n linear guide structures may include: n linear guide concave parts spaced apart from each other in a circumferential direction around the optical axis and extending along the optical axis; and n linear guide convex parts engaging with the n linear guide concave parts in a relatively movable manner, wherein the n linear guide concave parts may be provided on at least two of the first frame, the second frame, and the fixed frame (n is an integer equal to or greater than 2). 
         [0012]    Another embodiment of the present disclosure provides a lens barrel retaining lenses while allowing movement along an optical axis, the lens barrel including: a first frame; a second frame positioned inside the first frame; and n linear guide structures configured to allow movement of the second frame relative to the first frame along the optical axis, wherein n−1 linear guide structures of the n linear guide structures may include: n−1 linear guide concave parts spaced apart from each other in a circumferential direction around the optical axis and extending along the optical axis; and n−1 linear guide convex parts engaging with the n−1 linear guide concave parts in a relatively movable manner, and the other one of the n linear guide structures may include: a shaft spaced apart from the n−1 linear guide concave parts and the n−1 linear guide convex parts in the circumferential direction around the optical axis; and a sleeve engaging with the shaft, wherein the shaft may be positioned at one of the first and second frames, and the sleeve may be positioned at the other of the first and second frames (n is an integer equal to or greater than 3). 
         [0013]    An embodiment of the present disclosure provides a lens barrel retaining lenses while allowing movement along an optical axis, the lens barrel including: a first frame including a circumferential wall surrounding the optical axis; and a second frame including a circumferential wall surrounding the optical axis, the second frame being inserted into the first frame and movable relative to the first frame along the optical axis, wherein n linear guide concave parts and n linear guide convex parts are provided on the first and second frames, the n linear guide concave parts extending along the optical axis and being located at angular positions dividing a circumference around the optical axis into n approximately equal parts, the n linear guide convex parts engaging with the n linear guide concave parts in a relatively movable manner, wherein one to n−1 of the n linear guide concave parts are provided on the first frame, the other of the n linear guide concave parts is provided on the second frame, and each of the n linear guide convex parts is provided on one of the first and second frames on which the linear guide concave part engaging with the linear guide convex part is not provided (n is an integer equal to or greater than 2). 
         [0014]    In the above, n may be 3. 
         [0015]    In the lens barrel, the linear guide concave parts and the linear guide convex parts provided as guides for moving the second frame relative to the first frame along the optical axis are dispersed on the first and second frames. That is, all the linear guide concave parts are not provided on one of the first and second frames. Therefore, the strength of the first and second frames may be higher than a required value, and thus notch portions may be formed in the circumferential walls of the first and second frames. 
         [0016]    In addition, another embodiment of the present disclosure provides a lens barrel retaining lenses while allowing movement along an optical axis, the lens barrel including: a first frame including a circumferential wall surrounding the optical axis; a second frame including a circumferential wall surrounding the optical axis, the second frame being inserted into the first frame and movable relative to the first frame along the optical axis; and a fixed barrel into which the first frame is inserted, wherein n linear guide concave parts and n linear guide convex parts are provided on the first frame, the second frame, and the fixed barrel, the n linear guide concave parts extending along the optical axis and being located at angular positions dividing a circumference around the optical axis into n approximately equal parts, the n linear guide convex parts engaging with the n linear guide concave parts in a relatively movable manner, wherein one to n−1 of the n linear guide concave parts are provided on the first frame, the other of the n linear guide concave parts is provided on the second frame, and each of the n linear guide convex parts is provided on the fixed barrel or one of the first and second frames on which the linear guide concave part engaging with the linear guide convex part is not provided (n is an integer equal to or greater than 2). 
         [0017]    In the above, n may be 3. 
         [0018]    In the lens barrel, the linear guide concave parts and the linear guide convex parts provided as guides for moving the second frame relative to the first frame along the optical axis are dispersed on the first frame, the second frame, and the fixed barrel. That is, all the linear guide concave parts are not provided on one frame. Therefore, the strength of the first and second frames may be higher than a required value, and thus notch portions may be formed in the circumferential walls of the first and second frames. 
         [0019]    In addition, another embodiment of the present disclosure provides a lens barrel retaining lenses while allowing movement along an optical axis, the lens barrel including: a first frame including a circumferential wall surrounding the optical axis; a second frame including a circumferential wall surrounding the optical axis, the second frame being inserted into the first frame and movable relative to the first frame along the optical axis; and a fixed barrel into which the first frame is inserted, wherein n linear guide concave parts and n linear guide convex parts are provided on the first frame, the second frame, and the fixed barrel, the n linear guide concave parts extending along the optical axis and being located at angular positions dividing a circumference around the optical axis into n approximately equal parts, the n linear guide convex parts engaging with the n linear guide concave parts in a relatively movable manner, wherein one to n−1 of the n linear guide convex parts are provided on the first frame, the other of the n linear guide convex parts is provided on the second frame, and each of the n linear guide concave parts is provided on the fixed barrel or one of the first and second frames on which the linear guide convex part engaging with the linear guide concave part is not provided (n is an integer equal to or greater than 2). 
         [0020]    In the above, n may be 3. 
         [0021]    In the lens barrel, the linear guide concave parts and the linear guide convex parts provided as guides for moving the second frame relative to the first frame along the optical axis are dispersed on the first frame, the second frame, and the fixed barrel. That is, all the linear guide concave parts are not provided on one frame. Therefore, the strength of the first and second frames may be higher than a required value, and thus notch portions may be formed in the circumferential walls of the first and second frames. 
         [0022]    In addition, another embodiment of the present disclosure provides a lens barrel retaining lenses while allowing movement along an optical axis, the lens barrel including: a first frame including a circumferential wall surrounding the optical axis; and a second frame including a circumferential wall surrounding the optical axis, the second frame being inserted into the first frame and movable relative to the first frame along the optical axis, wherein n−1 linear guide concave parts and n−1 linear guide convex parts are provided on the first and second frames, the n−1 linear guide concave parts extending along the optical axis and being located at n−1 of angular positions dividing a circumference around the optical axis into n approximately equal parts, the n−1 linear guide convex parts engaging with the n−1 linear guide concave parts in a relatively movable manner, wherein a shaft provided as a cantilever on the first frame, and a sleeve provided on the second frame and engaging with the shaft are located at the other one of the angular positions at which the linear guide concave parts and the linear guide convex parts are not located (n is an integer equal to or greater than 3). 
         [0023]    In the above, n may be 3. 
         [0024]    In the lens barrel, the linear guide concave parts and the linear guide convex parts are provided as guides for moving the second frame relative to the first frame, and one of the linear guide concave parts and one of the linear guide convex parts are the sleeve and the shaft. Therefore, all the linear guide concave parts are not provided on one frame. Therefore, the strength of the first and second frames may be higher than a required value, and thus notch portions may be formed in the circumferential walls of the first and second frames. In addition, since the shaft is provided as a cantilever, the lens barrel may have a simple structure. 
         [0025]    In addition, another embodiment of the present disclosure provides a lens barrel retaining lenses while allowing movement along an optical axis, the lens barrel including: a first frame including a circumferential wall surrounding the optical axis; and a second frame including a circumferential wall surrounding the optical axis, the second frame being inserted into the first frame and movable relative to the first frame along the optical axis, wherein n−1 linear guide concave parts and n−1 linear guide convex parts are provided on the first and second frames, the n−1 linear guide concave parts extending along the optical axis and being located at n−1 of angular positions dividing a circumference around the optical axis into n approximately equal parts, the n−1 linear guide convex parts engaging with the n−1 linear guide concave parts in a relatively movable manner, wherein a shaft of which both ends are fixed to the first frame, and a sleeve provided on the second frame and engaging with the shaft are located at the other one of the angular positions at which the linear guide concave parts and the linear guide convex parts are not located (n is an integer equal to or greater than 3). 
         [0026]    In the above, n may be 3. 
         [0027]    In the lens barrel, the linear guide concave parts and the linear guide convex parts are provided as guides for moving the second frame relative to the first frame, and one of the linear guide concave parts and one of the linear guide convex parts are the sleeve and the shaft. Therefore, all the linear guide concave parts are not provided on one frame. Therefore, the strength of the first and second frames may be higher than a required value, and thus notch portions may be formed in the circumferential walls of the first and second frames. In addition, since both ends of the shaft are fixed, the shaft may be securely held. 
         [0028]    In addition, another embodiment of the present disclosure provides a lens barrel retaining lenses while allowing movement along an optical axis, the lens barrel including: a first frame including a circumferential wall surrounding the optical axis; and a second frame including a circumferential wall surrounding the optical axis, the second frame being inserted into the first frame and movable relative to the first frame along the optical axis, wherein n−1 linear guide concave parts and n−1 linear guide convex parts are provided on the first and second frames, the n−1 linear guide concave parts extending along the optical axis and being located at n−1 of angular positions dividing a circumference around the optical axis into n approximately equal parts, the n−1 linear guide convex parts engaging with the n−1 linear guide concave parts in a relatively movable manner, wherein a shaft provided as a cantilever on the second frame, and a sleeve provided on the first frame and engaging with the shaft are located at the other one of the angular positions at which the linear guide concave parts and the linear guide convex parts are not located (n is an integer equal to or greater than 3). 
         [0029]    In the above, n may be 3. 
         [0030]    In the lens barrel, the linear guide concave parts and the linear guide convex parts are provided as guides for moving the second frame relative to the first frame, and one of the linear guide concave parts and one of the linear guide convex parts are the sleeve and the shaft. Therefore, all the linear guide concave parts are not provided on one frame. Therefore, the strength of the first and second frames may be higher than a required value, and thus notch portions may be formed in the circumferential walls of the first and second frames. In addition, since the shaft is provided as a cantilever, the lens barrel may have a simple structure. 
         [0031]    In addition, another embodiment of the present disclosure provides a lens barrel retaining lenses while allowing movement along an optical axis, the lens barrel including: a first frame including a circumferential wall surrounding the optical axis; and a second frame including a circumferential wall surrounding the optical axis, the second frame being inserted into the first frame and movable relative to the first frame along the optical axis, wherein n−1 linear guide concave parts and n−1 linear guide convex parts are provided on the first and second frames, the n−1 linear guide concave parts extending along the optical axis and being located at n−1 of angular positions dividing a circumference around the optical axis into n approximately equal parts, the n−1 linear guide convex parts engaging with the n−1 linear guide concave parts in a relatively movable manner, wherein a shaft of which both ends are fixed to the second frame, and a sleeve provided on the first frame and engaging with the shaft are located at the other one of the angular positions at which the linear guide concave parts and the linear guide convex parts are not located (n is an integer equal to or greater than 3). 
         [0032]    In the above, n may be 3. 
         [0033]    In the lens barrel, the linear guide concave parts and the linear guide convex parts are provided as guides for moving the second frame relative to the first frame, and one of the linear guide concave parts and one of the linear guide convex parts are the sleeve and the shaft. Therefore, all the linear guide concave parts are not provided on one frame. Therefore, the strength of the first and second frames may be higher than a required value, and thus notch portions may be formed in the circumferential walls of the first and second frames. In addition, since both ends of the shaft are fixed, the shaft may be securely held. 
         [0034]    Furthermore, in any one of the lens barrels, an inner side notch portion may be formed in the circumferential wall of the second frame. 
         [0035]    In this case, particularly, even though an inner component of the second frame is placed in the inner side notch portion away from a center of the second frame, the inner component may not interference with the second frame because the circumferential wall of the second frame is not formed at the inner side notch portion. A second frame of the related art not including an inner side notch portion has to have a relatively large inner diameter because a circumferential wall of the second frame interferes with inner components. However, the lens barrel of the present disclosure includes an inner side notch portion, and thus even though the inner diameter of the lens barrel is decreased, inner components may be arranged in the lens barrel. That is, a space for inner components may be practically increased. Thus, the second frame of the lens barrel may have a smaller diameter that second frames of the related art. 
         [0036]    Furthermore, in any one of the lens barrels, an outer side notch portion may be formed in the circumferential wall of the first frame, and preferably, the outer side notch portion may communicate with the inner side notch portion. 
         [0037]    In this case, an inner component placed in the inner side notch portion away from the center of the lens barrel may be located close to the outer side notch portion of the first frame. Therefore, in addition to the second frame of the lens barrel, the first frame of the lens barrel may have a small diameter. 
         [0038]    Furthermore, both of the first and second frame may be movable along the optical axis, the first frame may be movable along the optical axis, or the second frame may be movable along the optical axis. 
         [0039]    Furthermore, in any one of the lens barrels, at least one anti-separation shape may be preferably provided on a linear guide convex part of the first frame. 
         [0040]    Furthermore, in any one of the lens barrels, at least one anti-separation shape may be preferably provided on a linear guide convex part of the second frame. 
         [0041]    Furthermore, in any one of the lens barrels, at least one anti-separation shape may be preferably provided on a linear guide concave part of the first frame. 
         [0042]    Furthermore, in any one of the lens barrel, at least one anti-separation shape may be preferably provided on a linear guide concave part of the second frame. 
         [0043]    Owing to the anti-separation shape, for example, even though the lens barrel is dropped and impacted, the first and second frames may not be dislocated and separated from each other. 
         [0044]    Furthermore, in any one of the lens barrels, at least one anti-separation shape may be preferably provided on a linear guide convex part of the fixed barrel. 
         [0045]    Furthermore, in any one of the lens barrels, at least one anti-separation shape may be preferably provided on a linear guide concave part of the fixed barrel. 
         [0046]    Owing to the anti-separation shape, for example, even though the lens barrel is dropped and impacted, the fixed barrel and the first frame may not be dislocated and separated from each other. 
         [0047]    An optical device of the present disclosure includes any one of the lens barrels. 
         [0048]    Since a notch portion is formed in the circumferential wall of the first frame or the second frame, a space for inner components may be practically increased in the optical device. 
         [0049]    According to the lens barrel and the optical device of the present disclosure, the circumferential wall of the first frame or the second frame is configured to form a notch portion, and thus a space for inner components may be practically increased. Therefore, parts such as the second frame may be reduced in size, and thus the lens barrel and the optical device may have small sizes. 
         [0050]    Other aspects, advantages, and salient features of the disclosure will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses various embodiments of the present disclosure. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0051]    The above and other aspects, features, and advantages of certain embodiments of the present disclosure will be more apparent from the following description taken in conjunction with the accompanying drawings, in which: 
           [0052]      FIG. 1  is a side sectional view illustrating an internal structure of an interchangeable lens (optical device) according to a first embodiment of the present disclosure. 
           [0053]      FIGS. 2A and 2B  are schematic views illustrating a cam frame,  FIG. 2A  being a front perspective view,  FIG. 2B  being a rear perspective view. 
           [0054]      FIGS. 3A and 3B  are schematic views illustrating a second lens group moving frame,  FIG. 3A  being a front perspective view,  FIG. 3B  being a rear perspective view. 
           [0055]      FIGS. 4A and 4B  are schematic views illustrating a fourth lens group moving frame,  FIG. 4A  being a front perspective view,  FIG. 4B  being a rear perspective view. 
           [0056]      FIG. 5  is a rear view illustrating a state in which the fourth lens group moving frame is inserted into the second lens group moving frame. 
           [0057]      FIGS. 6A and 6B  are schematic views illustrating a state in which the fourth lens group moving frame is inserted into the second lens group moving frame,  FIG. 6A  being a front perspective view,  FIG. 6B  being a rear perspective view. 
           [0058]      FIGS. 7A and 7B  are enlarged views illustrating modification examples of an anti-separation shape according to the present disclosure. 
           [0059]      FIG. 8  is a perspective view illustrating main parts of a lens barrel according to a second embodiment of the present disclosure. 
           [0060]      FIG. 9  is a perspective view illustrating main parts of the lens barrel according to the second embodiment of the present disclosure. 
           [0061]      FIG. 10  is a side view illustrating a modification example of the anti-separation shape according to the present disclosure. 
           [0062]      FIG. 11  is a perspective view illustrating main parts of a lens barrel according to a third embodiment of the present disclosure. 
       
    
    
       [0063]    Throughout the drawings, like reference numerals will be understood to refer to like parts, components, and structures. 
       DETAILED DESCRIPTION 
       [0064]    The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of various embodiments of the present disclosure as defined by the claims and their equivalents. It includes various specific details to assist in that understanding but these are to be regarded as merely exemplary. Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the various embodiments described herein can be made without departing from the scope and spirit of the present disclosure. In addition, descriptions of well-known functions and constructions may be omitted for clarity and conciseness. 
         [0065]    The terms and words used in the following description and claims are not limited to the bibliographical meanings, but, are merely used by the inventor to enable a clear and consistent understanding of the present disclosure. Accordingly, it should be apparent to those skilled in the art that the following description of various embodiments of the present disclosure is provided for illustration purpose only and not for the purpose of limiting the present disclosure as defined by the appended claims and their equivalents. 
         [0066]    It is to be understood that the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “a component surface” includes reference to one or more of such surfaces. 
         [0067]    Hereinafter, a lens barrel and an optical device will be described in detail according to the present disclosure with reference to the accompanying drawings. 
         [0068]    The optical device of the present disclosure may be an imaging device including a solid-state imaging element, such as an interchangeable lens system camera, a digital still camera, a video camera, or a surveillance camera. Alternatively, the optical device may be an interchangeable lens of such an imaging device. For example, the lens barrel of the present disclosure may constitute an interchangeable lens of the imaging device. 
       First Embodiment 
       [0069]      FIG. 1  is a side sectional view illustrating an internal structure of an interchangeable lens (optical device) according to a first embodiment of the present disclosure. In  FIG. 1 , reference numeral  1  denotes the interchangeable lens, and C denotes an optical axis. The interchangeable lens  1  includes a lens barrel  2  in which a plurality of lens groups G 1  to G 4  are arranged side by side along the optical axis C, and the lens groups G 1  to G 4  arranged in the lens barrel  2  constitute an inner focus-type zoom lens. 
         [0070]    The zoom lens may include four lens groups: a first lens group G 1 , a second lens group G 2 , a third lens group G 3 , and a fourth group G 4  that are sequentially arranged from an object side (a front side of the interchangeable lens  1 ). In addition, an aperture stop unit S may be placed in the second lens group G 2 . 
         [0071]    In the zoom lens, the first to fourth lens groups G 1  to G 4  may be individually moved along the optical axis C to adjust the magnification of the zoom lens (zooming), and the third lens group G 3  may be moved along the optical axis C to adjust the focus of the zoom lens (focusing). The structure of the zoom lens is not limited thereto. That is, for example, the number or combination of lenses of the zoom lens may be properly changed. 
         [0072]    The lens barrel  2  constituting the zoom lens includes: a fixed frame  3  shaped like a cylinder; a first lens group moving frame  4  inserted into the fixed frame  3  and movable in the fixed frame  3  along the optical axis C; a cam frame  5  inserted into the first lens group moving frame  4 , the cam frame  5  being movable in the first lens group moving frame  4  along the optical axis C and rotatable about the optical axis C; a second lens group moving frame (first frame)  6  inserted into the cam frame  5  and relatively movable in the cam frame  5  along the optical axis C; and a fourth lens group moving frame (second frame)  7  inserted into the second lens group moving frame  6  and relatively movable in the second lens group moving frame  6  along the optical axis C. 
         [0073]    A manipulation ring  8  shaped like a cylinder is installed around a front side (forward part) of the fixed frame  3  in a forward and backward rotatable manner, and an outer frame  9  is fixed behind the manipulation ring  8 . If the manipulation ring  8  is rotated by a control mechanism (not shown), a zoom motor unit  36  (described later) is operated. Three linear guide grooves (not shown) extending along the optical axis C may be formed in an inner surface of the fixed frame  3 , and three cam grooves (not shown) extending around the optical axis C may be formed in the inner surface of the fixed frame  3 . The linear guide grooves are arranged at angular positions approximately trisecting an approximately cylindrical circumferential wall in a circumferential direction around the optical axis C, and the cam grooves are also formed in the same manner. In the present disclosure, for example, the angular trisecting positions may refer to angular positions dividing 360° into angular intervals of 120°±10°. 
         [0074]    The first lens group moving frame  4  has an approximately cylindrical shape as a whole. A first lens group retaining part  12  having an approximately cylindrical shape may be formed on an inner front side of the first lens group moving frame  4 , and the first lens group G 1  may be retained in the first lens group retaining part  12 . Three linear guide convex parts (not shown) may be formed on an outer surface of the first lens group moving frame  4  and may be movably engaged with the linear guide grooves of the fixed frame  3 , and three linear guide grooves (not shown) and three cam pins (not shown) extending along the optical axis C may be formed on an inner surface of the first lens group moving frame  4 . The linear guide convex parts, the linear guide grooves, and the cam pins are respectively arranged at angular positions approximately trisecting approximately cylindrical circumferential walls in a circumferential direction around the optical axis C. 
         [0075]    Referring to  FIGS. 2A and 2B , the cam frame  5  has a cylindrical shape. The cam frame  5  includes: three cam pins  16  on an outer surface thereof; three first lens group moving frame cam grooves  17  in the outer surface thereof; three second lens group moving frame cam grooves  18  in an inner surface thereof; and three fourth lens group moving frame cam grooves  19  in the inner surface thereof. The cam pins  16  may be engaged with the cam grooves (not shown) of the fixed frame  3  in a relatively movable manner, and the first lens group moving frame cam grooves  17  may be engaged with the cam pins (not shown) of the first lens group moving frame  4  in a relatively movable manner. The cam pins  16 , the first lens group moving frame cam grooves  17 , the second lens group moving frame cam grooves  18 , and the fourth lens group moving frame cam grooves  19  may also be respectively arranged at angular positions approximately trisecting approximately cylindrical circumferential walls in a circumferential direction around the optical axis C. As illustrated in  FIG. 2B , a gear  20  is formed on a rear end portion of the cam frame  5 . 
         [0076]    Referring to  FIGS. 3A and 3B , the second lens group moving frame  6  includes a circumferential wall  6   a  having an approximately cylindrical, partially cut-away shape. Second lens group retaining parts  21   a  and  21   b  (refer to  FIG. 1 ) having an approximately cylindrical shape are formed inside the circumferential wall  6   a . Lenses are respectively retained in the second lens group retaining parts  21   a  and  21   b . In addition, a second lens group retaining frame  22  is installed at a rear side of the lens retained in the second lens group retaining part  21   b . The second lens group G 2  is retained by the second lens group retaining parts  21   a  and  21   b  and the second lens group retaining frame  22 . In addition, the aperture stop unit S is placed in the second lens group G 2 . 
         [0077]    Three linear guide protrusions  23  are formed on a front side end portion of an outer surface of the circumferential wall  6   a  of the second lens group moving frame  6 , and three cam pins  24  are formed on the outer surface of the circumferential wall  6   a  of the second lens group moving frame  6  in a center region along the optical axis C. The three linear guide protrusions  23  are engaged with the linear guide grooves (not shown) of the first lens group moving frame  4  in a relatively movable manner, and the cam pins  24  are engaged with the second lens group moving frame cam grooves  18  of the cam frame  5 . 
         [0078]    The three linear guide protrusions  23  and the cam pins  24  are respectively arranged at angular positions approximately trisecting the circumferential wall  6   a  having an approximately cylindrical shape in a circumferential direction around the optical axis C. 
         [0079]    As illustrated in  FIG. 3B , two linear guide grooves (linear guide concave parts)  25  extending along the optical axis C are formed in the outer surface of the circumferential wall  6   a . The linear guide grooves  25  are formed by removing portions of the circumferential wall  6   a  from a rear side edge to positions adjacent to a front side edge, and thus the linear guide grooves  25  are opened to the outside. 
         [0080]    A linear guide rib (linear guide convex part)  27  may be formed in a cut-away region of the circumferential wall  6   a , that is, between a first outer side notch portion  26   a  and a second outer side notch portion  26   b . The linear guide rib  27  has a narrow plate shape protruding outward in a radial direction from the second lens group retaining part  21   b  and extending along the optical axis C, and an anti-separation protrusion  27   a  may protrude outward in a radial direction from a rear side end portion of the linear guide rib  27 . The two linear guide grooves (linear guide concave parts)  25  and the linear guide rib (linear guide convex part)  27  may be respectively arranged at angular positions approximately trisecting the circumferential wall  6   a  having an approximately cylindrical shape in a circumferential direction around the optical axis C. 
         [0081]    Referring to  FIGS. 4A and 4B , the fourth lens group moving frame  7  includes a circumferential wall  7   a  having an approximately cylindrical, partially cut-away shape, and a lens group retaining part  28  (refer to  FIG. 1 ) having an approximately cylindrical shape is formed on a rear side of the circumferential wall  7   a . A third lens group retaining frame  28   a  is installed inside the lens group retaining part  28 , and the third lens group G 3  is retained in the third lens group retaining frame  28   a . In addition, the fourth lens group G 4  is retained on a rear side end portion of the lens group retaining part  28 . 
         [0082]    Three legs  29  extend from a front side end portion of the circumferential wall  7   a  of the fourth lens group moving frame  7  along the optical axis C and protrude outward in radial directions. Cam pins  30  are formed on outer surfaces of front side end portions of the legs  29 , respectively. The cam pins  30  are engaged with the fourth lens group moving frame cam grooves  19  of the cam frame  5  in a relatively movable manner. 
         [0083]    In addition, two of the three legs  29  include linear guide keys (linear guide convex parts)  31 . A narrow plate part  32  extending along the optical axis C is formed adjacent to the other of the three legs  29 , and a linear guide groove (linear guide concave part)  33  is formed in a length direction of the narrow plate part  32 . That is, the linear guide groove  33  extends along the optical axis C. The linear guide groove  33  is formed in an inner side of the narrow plate part  32  and opened at both sides of the narrow plate part  32 . A long hole  32   a  communicating with the linear guide groove  33  is formed in an outer side of the narrow plate part  32 . Here, the two linear guide keys (linear guide convex parts)  31  and the linear guide groove (linear guide concave part)  33  are respectively arranged at angular positions approximately trisecting the circumferential wall  7   a  having an approximately cylindrical shape in a circumferential direction around the optical axis C. In addition, the cam pins  30  are arranged in the same manner. 
         [0084]    In addition, cut-away portions, that is, first and second inner side notch portions  34   a  and  34   b  are formed in the circumferential wall  7   a  of the fourth lens group moving frame  7  at both sides of the narrow plate part  32 . A region of the first inner side notch portion  34   a  is formed by cutting a portion of the circumferential wall  7   a  entirely in a height direction (optical axis direction C) of the circumferential wall  7   a , and most of a region of the second inner side notch portion  34   b  is formed by cutting a portion of the circumferential wall  7   a  entirely in the height direction (optical axis direction C) of the circumferential wall  7   a.    
         [0085]    Referring to  FIGS. 5, 6A, and 6B , the fourth lens group moving frame  7  is inserted into the second lens group moving frame  6 . The first inner side notch portion  34   a  of the fourth lens group moving frame  7  communicates with the first outer side notch portion  26   a  of the second lens group moving frame  6 , and the second inner side notch portion  34   b  of the fourth lens group moving frame  7  communicates with the second outer side notch portion  26   b  of the second lens group moving frame  6 . 
         [0086]    In the current embodiment, inner components of the interchangeable lens  1  such as a focus motor  35  may be accommodated in a region in which such notch portions communicate with each other, specifically in a region in which the second inner side notch portion  34   b  and the second outer side notch portion  26   b  communicate with each other. 
         [0087]    Referring to  FIGS. 1 and 5 , the focus motor  35  is placed at a side of the optical axis C of the lens barrel  2 , that is, at a lateral side of the lens groups G 1  to G 4  arranged in a center region. Referring to  FIG. 5 , a portion of the focus motor  35  is outside a circular line  71  formed by an inner surface of the circumferential wall  7   a  of the fourth lens group moving frame  7 . In addition, a portion of the focus motor  35  is outside a circular line  61  formed by an inner surface of the circumferential wall  6   a  of the second lens group moving frame  6 . The second inner side notch portion  34   b  is formed in the circumferential wall  7   a  of the fourth lens group moving frame  7 , and the second outer side notch portion  26   b  is formed in the circumferential wall  6   a  of the second lens group moving frame  6 . Thus, the focus motor  35  may be placed without interference with the circumferential wall  6   a  of the second lens group moving frame  6  or the circumferential wall  7   a  of the fourth lens group moving frame  7 . 
         [0088]    As illustrated in  FIG. 5 , the linear guide keys  31  of the fourth lens group moving frame  7  are engaged with the linear guide grooves  25  of the second lens group moving frame  6  in a relatively movable manner, and as illustrated in  FIGS. 5, 6A, and 6B , the linear guide groove  33  of the fourth lens group moving frame  7  is engaged with the linear guide rib  27  of the second lens group moving frame  6  in a relatively movable manner. In a state in which the linear guide rib  27  is engaged with the linear guide groove  33  as described above, the anti-separation protrusion  27   a  of the linear guide rib  27  is engaged with the long hole  32   a  communicating with the linear guide groove  33  in a relatively movable manner. Owing to this structure, the linear guide rib  27  may not be dislocated from the linear guide groove  33 . Therefore, for example, even when the lens barrel  2  is unintentionally dropped and impacted, the fourth lens group moving frame  7  may not be dislocated from the second lens group moving frame  6  along the optical axis C, and thus the second lens group moving frame  6  and the fourth lens group moving frame  7  may not be separated from each other. That is, the anti-separation protrusion  27   a  functions as an anti-separation shape in the present disclosure. 
         [0089]    As illustrated in  FIG. 1 , the zoom motor unit  36  is installed in the fourth lens group moving frame  7 , and a light-blocking ring  37  is installed at a rear side of the lens group retaining part  28  of the fourth lens group moving frame  7 . The zoom motor unit  36  is engaged with the gear  20  (refer to  FIG. 2B ) formed on the inner surface of the cam frame  5 . In addition, a lens mount  38  having an approximately cylindrical shape is installed around the light-blocking ring  37 . 
         [0090]    The lens barrel  2  or the interchangeable lens  1  including the lens barrel  2  may be equipped with various components such as a manual or auto focusing mechanism. 
         [0091]    In the above-described structure of the lens barrel  2 , if the manipulation ring  8  is rotated, the lens groups G 1  to G 4  may be advanced or retreated (moved) along the optical axis C. That is, if the manipulation ring  8  is rotated in one direction or the other direction, an electric signal is transmitted to a camera body (not shown), and thus the zoom motor unit  36  is operated according to the amount of rotation of the manipulation ring  8 . Then, since the gear  20  formed on the inner surface of the cam frame  5  is engaged with the zoom motor unit  36 , the cam frame  5  is rotated. 
         [0092]    Since the cam pins  16  arranged on the outer surface of the cam frame  5  are engaged with the cam grooves (not shown) formed in the inner surface of the fixed frame  3 , the cam pins  16  are moved relative to the cam grooves as the cam frame  5  is rotated, and thus the cam frame  5  is moved forward (or backward) relative to the fixed frame  3 . That is, according to the shape of the cam grooves of the fixed frame  3 , the cam frame  5  is moved forward (or backward) while being rotated relative to the fixed frame  3 . In other words, the cam frame  5  is spirally operated. 
         [0093]    The cam pins (not shown) formed on the inner surface of the first lens group moving frame  4  are engaged with the first lens group moving frame cam grooves  17  of the cam frame  5 , and the linear guide convex parts (not shown) formed on the outer surface of the first lens group moving frame  4  are engaged with the linear guide grooves (not shown) of the fixed frame  3 . Thus, if the cam frame  5  is spirally operated as described above, the first lens group moving frame  4  is moved forward (or backward). Therefore, the first lens group G 1  is moved along the optical axis C. 
         [0094]    In addition, the cam pins  24  formed on the outer surface of the second lens group moving frame  6  are engaged with the second lens group moving frame cam grooves  18  of the cam frame  5 , and the linear guide protrusions  23  formed on the outer surface of the second lens group moving frame  6  are engaged with the linear guide grooves (not shown) of the first lens group moving frame  4 . Thus, when the cam frame  5  is spirally operated as described above, the second lens group moving frame  6  is moved forward (or backward). Therefore, the second lens group G 2  is also moved along the optical axis C. 
         [0095]    In addition, when the zoom motor unit  36  is operated, the operation amount of the zoom motor unit  36  is detected by a detection mechanism, and the control mechanism calculates a traveled distance based on the operation amount of the zoom motor unit  36 . Then, the focus motor  35  is operated by a proper amount according to the traveled distance, and thus the third lens group G 3  is moved forward (or backward). That is, the third lens group G 3  is also moved along the optical axis C. 
         [0096]    In addition, the cam pins  30  formed on the outer surface of the fourth lens group moving frame  7  are engaged with the fourth lens group moving frame cam grooves  19  of the cam frame  5 , the linear guide keys  31  are engaged with the linear guide grooves  25  of the second lens group moving frame  6 , and the linear guide groove  33  is engaged with the linear guide rib  27  of the second lens group moving frame  6 . Thus, when the cam frame  5  is operated, the fourth lens group moving frame  7  is moved forward (or backward). Therefore, the fourth lens group G 4  is also moved along the optical axis C. 
         [0097]    Therefore, in the interchangeable lens  1  including the lens barrel  2 , zooming-in/zooming-out may be performed by rotating the cam frame  5 . 
         [0098]    In the lens barrel  2  of the current embodiment, linear guide structures are provided to move the fourth lens group moving frame (second frame)  7  relative to the second lens group moving frame (first frame)  6  along the optical axis C. The linear guide structures include the linear guide concave parts (the linear guide grooves  25  and the linear guide groove  33 ) and the linear guide convex parts (the linear guide rib  27  and the linear guide keys  31 ). The linear guide structures are dispersed on both the second lens group moving frame  6  and the fourth lens group moving frame  7 . That is, since all the linear guide concave parts are not formed on one of the second lens group moving frame  6  and the fourth lens group moving frame  7 , the strength of the second lens group moving frame  6  or the fourth lens group moving frame  7  may be higher than a required value. Therefore, the notch portions (the first outer side notch portion  26   a , the second outer side notch portion  26   b , the first inner side notch portion  34   a , and the second inner side notch portion  34   b ) may be formed in the circumferential wall  6   a  of the second lens group moving frame  6  or the circumferential wall  7   a  of the fourth lens group moving frame  7 . Since inner components of the lens barrel  2  can be accommodated in the notch portions of the circumferential walls  6   a  and  7   a , an inner component installation space is practically increased. Therefore, the fourth lens group moving frame  7  or the second lens group moving frame  6  may have a smaller diameter than lens group moving frames of the related art, and thus the lens barrel  2  may have a small size. That is, while stably retaining and moving lenses, a space for inner components may be saved, thereby realizing size reduction. 
         [0099]    The first inner side notch portion  34   a  and the second inner side notch portion  34   b  are formed in the circumferential wall  7   a  of the fourth lens group moving frame  7 . Although inner components such as the focus motor  35  accommodated inside the fourth lens group moving frame  7  are placed in the second inner side notch portion  34   b  away from a center region including the optical axis C, since the circumferential wall  7   a  is not formed at the second inner side notch portion  34   b , the focus motor  35  may not interfere with the fourth lens group moving frame  7 . In the case of a moving frame of the related art not including a notch portion such as the second inner side notch portion  34   b , a circumferential wall of the moving frame interferes with the focus motor  35  (inner components), and thus the moving frame has to have a large inner diameter. However, in the lens barrel  2 , although the inner diameter of the fourth lens group moving frame  7  is decreased, the focus motor  35  may be placed in the second inner side notch portion  34   b . That is, a space for inner components such as the focus motor  35  may be practically increased. Therefore, the fourth lens group moving frame  7  of the lens barrel  2  may have a smaller diameter than moving frames of the related art. 
         [0100]    The first outer side notch portion  26   a  and the second outer side notch portion  26   b  are formed in the circumferential wall  6   a  of the second lens group moving frame  6 . Since the first outer side notch portion  26   a  and the second outer side notch portion  26   b  respectively communicate with the first inner side notch portion  34   a  and the second inner side notch portion  34   b  of the fourth lens group moving frame  7 , inner components such as the focus motor  35  placed in the first inner side notch portion  34   a  and the second inner side notch portion  34   b  away from the center region including the optical axis C may be placed adjacent to the first outer side notch portion  26   a  and the second outer side notch portion  26   b  of the second lens group moving frame  6 . Therefore, the second lens group moving frame  6  as well as the fourth lens group moving frame  7  of the lens barrel  2  may be reduced in size. 
         [0101]    In addition, since a space for inner components such as the focus motor  35  is practically increased owing to the notch portions formed in the circumferential wall  6   a  of the second lens group moving frame  6  or the circumferential wall  7   a  of the fourth lens group moving frame  7 , the size of the interchangeable lens (optical device)  1  including the lens barrel  2  may also be reduced. 
         [0102]    In the embodiment, the anti-separation protrusion  27   a  is formed on the linear guide rib  27  (the linear guide convex part of the first frame) as an anti-separation shape of the present disclosure. However, in the present disclosure, anti-separation shapes other than the anti-separation protrusion  27   a  may be used. 
         [0103]    For example, as illustrated in  FIGS. 4A and 4B , a pair of anti-separation protrusions  31   a  may be formed on an leading end portion of each of the linear guide keys (linear guide convex parts)  31  of the fourth lens group moving frame (second frame)  7  as anti-separation shapes of the present disclosure. That is, when the linear guide keys  31  are engaged with the linear guide grooves (linear guide concave parts)  25  of the second lens group moving frame (first frame)  6  as illustrated in  FIG. 5 , the anti-separation protrusions  31   a  extending from both sides of the leading end portion of each of the linear guide keys  31  are in contact with the outer surface of the circumferential wall  6   a  forming the linear guide grooves  25 . 
         [0104]    Therefore, for example, when the lens barrel  2  is unintentionally dropped, even though the linear guide keys  31  are impacted and pushed toward the inside of the circumferential wall  6   a  of the second lens group moving frame  6 , the linear guide keys  31  are not separated owing to the anti-separation protrusions  31   a . Therefore, the cam pins  30  may be not dislocated by separation of the linear guide keys  31 , and thus the fourth lens group moving frame  7  may not be dislocated from the second lens group moving frame  6  along the optical axis C. That is, the second lens group moving frame  6  and the fourth lens group moving frame  7  may not be separated from each other. That is, the anti-separation protrusions  31   a  also function as anti-separation shapes of the present disclosure. 
         [0105]    In addition, as illustrated in  FIG. 7A , anti-separation parts  25   a  may be provided on inner sides of each of the linear guide grooves  25 . The circumferential wall  6   a  in which the linear guide grooves  25  are formed, that is, portions of the circumferential wall  6   a  between which the linear guide grooves  25  are formed are bent toward the inside of the second lens group moving frame  6  and toward the linear guide grooves  25  so as to form the anti-separation parts  25   a  having an L-like sectional shape. Since the anti-separation parts  25   a  are provided at the linear guide grooves  25 , the linear guide keys  31  engaged with the linear guide grooves  25  may not be separated in a direction toward the inside of the circumferential wall  6   a . Therefore, the fourth lens group moving frame  7  may not be dislocated from the second lens group moving frame  6  along the optical axis C, and thus the second lens group moving frame  6  and the fourth lens group moving frame  7  may not be separated from each other. That is, the anti-separation parts  25   a  function as anti-separation shapes of the present disclosure. In addition, the pair of anti-separation parts  25   a  may be formed in one piece and provided as one anti-separation part. 
         [0106]    In addition, as illustrated in  FIG. 7B , anti-separation parts  33   a  having the same shape as the anti-separation parts  25   a  may be provided on inner sides of the linear guide groove  33  of the fourth lens group moving frame (second frame)  7 . In this case, an engagement protrusion  27   b  is provided on an upper end portion of the linear guide rib  27  engaging with the linear guide groove  33 , and the anti-separation parts  33   a  is engaged with the engagement protrusion  27   b . Since the anti-separation parts  33   a  are provided at the linear guide groove  33 , the linear guide rib  27  engaged with the linear guide groove  33  may not be separated toward the inside of the fourth lens group moving frame (second frame)  7 . Therefore, the fourth lens group moving frame  7  may not be dislocated from the second lens group moving frame  6  along the optical axis C, and thus the second lens group moving frame  6  and the fourth lens group moving frame  7  may not be separated from each other. That is, the anti-separation parts  33   a  function as anti-separation shapes of the present disclosure. 
       Second Embodiment 
       [0107]      FIG. 8  is a perspective view illustrating main parts of a lens barrel according to a second embodiment of the present disclosure. In  FIG. 8 , reference numeral  40  refers to the lens barrel. The lens barrel  40  is different from the lens barrel  2  described with reference to  FIGS. 1 to 6  in that one of three linear guide convex parts proposed in the present disclosure is provided on a fixed frame (fixed barrel)  3 . 
         [0108]    That is, as illustrated in  FIG. 8 , a linear guide key  41  is installed as a linear guide convex part on an end of the fixed frame  3  (a side facing the lens mount  38  in  FIG. 1 ) in an optical axis direction C. The linear guide key  41  is installed at a position corresponding to the linear guide rib  27  of the second lens group moving frame (first frame)  6  illustrated in  FIGS. 3A and 3B . That is, the linear guide key  41  is installed on the fixed frame  3  instead of the linear guide rib  27 . 
         [0109]    As illustrated in  FIG. 9 , the linear guide key  41  has a thin, long, narrow plate shape, and a mount part  41   a  having a screw hole is formed in one piece with an end of the linear guide key  41 . As illustrated in  FIG. 8 , the linear guide key  41  is fixed to the fixed frame  3  by screw coupling the mount part  41   a  to a mount member  42  formed on the end of the fixed frame  3 . 
         [0110]    In this structure, as illustrated in  FIG. 9 , the linear guide key  41  is movable engaged with a linear guide groove  33 . In addition, an anti-separation protrusion  41   b  is formed on the linear guide key  41 , and the anti-separation protrusion  41   b  movably engages with a long hole  32   a  of a narrow plate part  32  of a fourth lens group moving frame  7 . The anti-separation protrusion  41   b  has the same function as the anti-separation protrusion  27   a  of the linear guide rib  27  of the first embodiment. That is, for example, even when the lens barrel  40  is unintentionally dropped and impacted, a second lens group moving frame  6  may not be dislocated from the fixed frame  3  along the optical axis C, and thus the fixed frame  3  and the second lens group moving frame  6  may not be separated from each other. That is, the anti-separation protrusion  41   a  functions an anti-separation shape of the present disclosure. 
         [0111]    In the lens barrel  40  of the current embodiment having the above-described structure, guides for moving the fourth lens group moving frame (second frame)  7  relative to the second lens group moving frame (first frame)  6  along the optical axis C are constituted by linear guide concave parts (linear guide grooves  25  and the linear guide groove  33 ) and linear guide convex parts (the linear guide key  41  and linear guide keys  31 ), and the guides are dispersed on the second lens group moving frame  6 , the fourth lens group moving frame  7 , and the fixed frame  3 . That is, since all the linear guide concave parts are not formed on one frame, the strength of the second lens group moving frame  6  or the fourth lens group moving frame  7  may be higher than a required value. Therefore, notch portions (a first outer side notch portion  26   a , a second outer side notch portion  26   b , a first inner side notch portion  34   a , and a second inner side notch portion  34   b ) may be formed in circumferential walls  6   a  and  7   a , and owing to the notch portions formed in the circumferential walls  6   a  and  7   a , a space for inner components of the lens barrel  40  may be practically increased. Therefore, the fourth lens group moving frame  7  or the second lens group moving frame  6  may have a smaller diameter than lens group moving frames of the related art, and thus the lens barrel  40  may have a small size. That is, while stably retaining and moving the inner components, a space for inner components may be saved, thereby realizing size reduction. 
         [0112]    In addition, according to the second embodiment, one of three linear guide convex parts of the present disclosure is provided on the fixed frame  3 . However, one of three linear guide concave parts may be provided on the fixed frame  3 . In detail, the narrow plate part  32  having the linear guide groove  33  illustrated in  FIGS. 4A and 4B  may not be provided on the fourth lens group moving frame  7 . Instead, an independent member corresponding to the narrow plate part  32  may be provided on the fixed frame  3 . That is, like the linear guide key  41  illustrated in  FIG. 8 , the independent member may be mounted on the fixed frame  3  at a position corresponding to the narrow plate part  32  and may be movably engaged with the linear guide rib  27  of the second lens group moving frame  6 . 
         [0113]    In addition, as illustrated in  FIG. 10 , a linear guide groove member  43  may be provided as an independent member having a linear guide groove  33 , and a cover  43   a  may be formed on a leading end of the linear guide groove member  43  to close an opened side of the linear guide groove  33 . The cover  43   a  may be brought into contact with or separated from a leading end portion of the linear guide rib  27 . The linear guide rib  27  is a plate protruding outward in a radial direction of the second lens group moving frame  6 , and the leading end portion of the linear guide rib  27  may be brought into contact or separated from the cover  43   a.    
         [0114]    In this case, for example, even when the lens barrel  40  is unintentionally dropped and impacted, the second lens group moving frame  6  may not be dislocated from the fixed frame  3  along the optical axis C, and thus the fixed frame  3  and the second lens group moving frame  6  may not be separated from each other. That is, the cover  43   a  functions as an anti-separation shape of the present disclosure. 
         [0115]    In the lens barrel  40  in which the linear guide groove member  43  is provided on the fixed frame  3 , the fourth lens group moving frame  7  or the second lens group moving frame  6  may have a smaller diameter than lens group moving frames of the related art, and thus the lens barrel  40  may have a small size. That is, while stably retaining and moving lenses, a space for inner components may be saved, thereby realizing size reduction. 
       Third Embodiment 
       [0116]      FIG. 11  is a perspective view illustrating main parts of a lens barrel according to a third embodiment of the present disclosure. In  FIG. 11 , reference numeral  50  refers to the lens barrel. The lens barrel  50  is different from the lens barrel  2  described with reference to  FIGS. 1 to 6 , in that two of three linear guide convex parts and two of three linear guide concave parts of the present disclosure are provided on a second lens group moving frame (first frame)  6  or a fourth lens group moving frame (second frame)  7 , and the other linear guide convex part is provided as a shaft  51  and the other linear guide concave part is provided as a sleeve  52 . 
         [0117]    As illustrated in  FIG. 11 , the shaft  51  is installed on the second lens group moving frame  6  instead of the linear guide rib  27  at a position corresponding to the position of the linear guide rib  27  illustrated in  FIGS. 3A and 3B . The shaft  51  is formed of a metal or a hard resin and has a thin, long, cylindrical shape. In the current embodiment, an end portion of the shaft  51  is fixedly retained by a first retaining part  53 , and the other end portion is fixedly retained by a second retaining part  54 . That is, both end portions of the shaft  51  are fixed to the second lens group moving frame (first frame)  6 . 
         [0118]    In the current embodiment, the sleeve  52  is provided instead of the narrow plate part  32  including the linear guide groove  33  illustrated in  FIGS. 4A and 4B . As illustrated in  FIG. 11 , the sleeve  52  is formed in one piece with a leg  29 . The sleeve  52  includes: a base part  52   a  formed in one piece with the leg  29 ; a pair of retaining plate parts  52   b  formed in one piece with the base part  52   a ; and a connection part  52   c  connecting the retaining plate parts  52   b . The shaft  51  is inserted through penetration holes  52   d  formed in the retaining plate parts  52   b . That is, in a state in which the second lens group moving frame  6  and the fourth lens group moving frame  7  are attached to each other, the shaft  51  is inserted through the penetration holes  52   d  of the sleeve  52  and fixedly retained by the first retaining part  53  and the second retaining part  54 . In this manner, the shaft  51  and the sleeve  52  are engaged with each other. 
         [0119]    In the lens barrel  50  including the shaft  51  and the sleeve  52 , the fourth lens group moving frame  7  or the second lens group moving frame  6  may have a smaller diameter than lens group moving frames of the related art, and thus the lens barrel  50  may have a small size like the lens barrel  2 . That is, while stably retaining and moving lenses, a space for inner components may be saved, thereby realizing size reduction. 
         [0120]    In addition, since both end portions of the shaft  51  are fixed to the second lens group moving frame  6 , the shaft  51  may effectively maintain the shape of the second lens group moving frame  6 . 
         [0121]    Furthermore, in the third embodiment illustrated in  FIG. 11 , the shaft  51  is retained (positioned) by fixing both end portions of the shaft  51  to the second lens group moving frame (first frame)  6  using the first retaining part  53  and the second retaining part  54 . However, only one end portion of the shaft  51  may be fixedly retained. That is, like a cantilever, the shaft  51  may be fixedly retained by only the first retaining part  53 , and the second retaining part  54  may not be provided. 
         [0122]    In this case, the second lens group moving frame  6  may have a simple structure compared to the case in which both end portions of the shaft  51  are fixedly retained. 
         [0123]    Furthermore, in the third embodiment, the shaft  51  is provided instead of the linear guide rib  27  at a position corresponding to the position of the linear guide rib  27  illustrated in  FIGS. 3A and 3B , and the sleeve  52  is provided instead of the narrow plate part  32  at a position corresponding to the position of the narrow plate part  32  illustrated in  FIGS. 4A and 4B . However, this positional relationship may be reversed. That is, the sleeve  52  may be provided at a position corresponding to the position of the linear guide rib  27 , and the shaft  51  may be provided at a position corresponding to the position of the narrow plate part  32 . In other words, the sleeve  52  may be provided on the second lens group moving frame (first frame)  6 , and the shaft  51  may be provided on the fourth lens group moving frame (second frame)  7 . 
         [0124]    In detail, the sleeve  52  illustrated in  FIG. 11  may be used as a retaining part for fixedly retaining the shaft  51 , and the shaft  51  may be fixed to the retaining part. In this manner, the shaft  51  may be positioned at the fourth lens group moving frame (second frame)  7  using the retaining part. In this case, the pair of retaining plate parts  52   b  may be used to retain and fix the shaft  51 , and thus both end portions of the shaft  51  may be fixedly retained (positioned). Alternatively, the shaft  51  may be fixedly retained by only an outer one of the retaining plate parts  52   b  (the right retaining plate part  52   b  in  FIG. 11 ). That is, the shaft  51  may be retained (positioned) like a cantilever. 
         [0125]    In the case in which the sleeve  52  is provided on the second lens group moving frame (first frame)  6 , for example, the first retaining part  53  illustrated in  FIG. 11  may have a cylindrical shape so that the shaft  51  may be insertable into the first retaining part  53  and removable from the first retaining part  53 . In this manner, the first retaining part  53  may be used as a sleeve. 
         [0126]    Although the positions of the shaft  51  and the sleeve  52  are switched as described above, the fourth lens group moving frame  7  or the second lens group moving frame  6  may have a smaller diameter than lens group moving frames of the related art, and thus the lens barrel  50  may have a small size like in the third embodiment. That is, while stably retaining and moving lenses, a space for internal components may be saved, thereby realizing size reduction. 
         [0127]    In addition, if both end portions of the shaft  51  are fixed to the fourth lens group moving frame  7 , the shaft  51  may effectively maintain the shape of the fourth lens group moving frame  7 . 
         [0128]    If the shaft  51  is provided as a cantilever on the fourth lens group moving frame  7 , the fourth lens group moving frame  7  may have a simple structure compared to the case in which both end portions of the shaft  51  are fixed. 
         [0129]    While preferred embodiments of the present disclosure have been described with reference to the accompanying drawings, the present disclosure is not limited to the embodiments. Features such as shapes or combinations of constituent members described in the embodiments are examples, and these features may be variously modified according to conditions such as design requirements within the scope of the present disclosure. 
         [0130]    For example, in the first embodiment, two linear guide concave parts (the linear guide grooves  25 ) and a linear guide convex part (the linear guide rib  27 ) are formed on the first frame (the second lens group moving frame  6 ), and a linear guide concave part (the linear guide groove  33 ) and two linear guide convex parts (the linear guide keys  31 ) are formed on the second frame (the fourth lens group moving frame  7 ). However, a linear guide concave part and two linear guide convex part may be formed on the first frame (the second lens group moving frame  6 ), and two linear guide concave parts and a linear guide convex part may be formed on the second frame. 
         [0131]    Furthermore, in the first embodiment, three linear guide concave parts (the linear guide grooves  25  and the linear guide groove  33 ) and three linear guide convex parts (the linear guide rib  27  and the linear guide keys  31 ) are formed on the first frame (the second lens group moving frame  6 ) and the second frame (the fourth lens group moving frame  7 ) at angular positions approximately trisecting a circumference around the optical axis C. However, each of the number of the linear guide concave parts and the number of the linear guide convex parts may be two, four, or more. That is, each of the number of the linear guide concave parts and the number of the linear guide convex parts may be n (where n denotes an integer equal to or greater than 2). In this case, the linear guide concave parts are arranged at angular positions dividing a circumference around the optical axis C into n approximately equal parts, and the linear guide convex parts are arranged in the same manner. 
         [0132]    Furthermore, in the first embodiment, both the first frame (the second lens group moving frame  6 ) and the second frame (the fourth lens group moving frame  7 ) are movable in the fixed frame  3 . However, the present disclosure is not limited thereto. For example, one of the first and second frames may be movable, and the other of the first and second frames may be fixed. 
         [0133]    Furthermore, in the first embodiment, the fixed frame  3  is positioned outside the cam frame  5 . However, for example, the fixed frame  3  may be positioned between the second lens group moving frame  6  and the cam frame  5 . 
         [0134]    While the present disclosure has been shown and described with reference to various embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present disclosure as defined by the appended claims and their equivalents. 
       REFERENCE NUMERALS 
       [0135]      1  . . . interchangeable lens (optical device),  2  . . . lens barrel,  3  . . . fixed frame (fixed barrel),  5  . . . cam frame,  6  . . . second lens group moving frame (first frame),  6   a  . . . circumferential wall,  7  . . . fourth lens group moving frame (second frame),  7   a  . . . circumferential wall,  25  . . . linear guide grooves (linear guide concave parts),  26   a  . . . first outer side notch portion,  26   b  . . . second outer side notch portion,  27  . . . linear guide rib (linear guide convex part),  31  . . . linear guide keys (linear guide convex parts),  33  . . . linear guide groove (linear guide concave part),  34   a  . . . first inner side notch portion,  34   b  . . . second inner side notch portion,  35  . . . focus motor, C . . . optical axis, G 1  . . . first lens group, G 2  . . . second lens group, G 3  . . . third lens group, G 4  . . . fourth lens group,  40  . . . lens barrel,  41  . . . linear guide key,  43  . . . linear guide groove member,  50  . . . lens barrel,  51  . . . shaft,  52  . . . sleeve