Abstract:
A lens body tube including at least one component to be fixed therein is provided with at least one first recessed portion, each of which is recessed outward along the radial direction of the lens body tube on a part of the inner circumferential surface of the lens body tube, at least one second recessed portion, each of which is recessed inward along the radial direction of the lens body tube on a part of the outer circumferential surface of a corresponding one of the at least one component which is located such that the outer circumferential surface thereof faces the inner circumferential surface of the lens body tube, and at least one insertion member. Each pair of the at least one first recessed portion and the at least one second recessed portion forms an opening recessed along the axial direction of the lens body tube. A corresponding one of the at least one insertion member is inserted into the opening along the axial direction of the lens body tube.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The present invention relates to a lens body tube in which components such as a lens and an aperture diaphragm are incorporated, and especially relates to a lens body tube capable of adjusting angular positions of the components incorporated therein with respect to the axis of the lens body tube.  
         [0002]     A lens body tube provided in an optical apparatus such as a camera is configured with components such as at least one lens and an aperture diaphragm being incorporated therein. Such a lens body tube, for example, as disclosed in Japanese Unexamined Patent Publication No. 2004-191558, generally has a structure configured such that lens frames supporting lenses are fixed to a main body tube with screws. Japanese Unexamined Patent Publication No. 2004-191558 discloses the following structure of a lens body tube. A fixed lens that is not moved during a zooming operation is fixed to a body tube or a lens frame, and the body tube or the lens frame is fixed to an outside body tube thereof with screws.  FIG. 1 , which shows an example of such a lens body tube as provided with a fixed lens frame therein, is a half cross-sectional view of the lens body tube along an optical axis of the lens body tube, the lens body tube being an object to which the present invention will be applied. It is noted that the optical axis is indicated by a horizontal dashed line in  FIG. 1 . In this case, the lens body tube is configured as a zoom lens, and is provided with a cylindrical main body tube  1 , a zoom ring  2  that is manually rotatably attached to the outer circumferential surface of the main body tube  1 , and a cam tube  3  that is located on the inner circumferential surface of the main body tube  1  and is rotatable integrally with the above zoom ring  2 . A first lens frame  41  is attached to the inner circumferential surface at the distal end of the main body tube  1 . A second lens frame  51  and a third lens frame  61  are attached to the inner circumferential surface of the above-mentioned cam tube  3 . The first, second, and third lens frames  41 ,  51 , and  61  support a first lens  4 , a second lens  5 , and a third lens  6 , respectively. The aforementioned first and second lens frames  41  and  51  are supported such that they can move along the optical axis inside the main body tube  1  according to rotation of the cam tube  3 . In other words, the cam tube  3  is formed with two cam grooves (which are not shown in  FIG. 1 ), and cam protrusions  42  and  52 , which are integrally formed with the first and second lens frames  4  and  5 , respectively, are inserted into the respective cam grooves. When the cam tube  3  is rotated, the first and second lens frames  41  and  51  are translated along the optical axis direction of the lens body tube due to engagement of the cam protrusions  42  and  52  with the respective cam grooves. It is noted that the optical axis direction is defined as a direction from the left side to the right side along the optical axis in  FIG. 1 .  
         [0003]     On the other hand, the third lens frame  61  is fixed to the aforementioned main body tube  1 .  FIG. 7  is an enlarged cross-sectional view showing a conventional structure for fixing the third lens frame  61 A to the main body tube  1 A, and corresponds to a cross-sectional view along an A-A line shown in  FIG. 1 . The third lens frame  61 A is integrally provided with an aperture diaphragm driving portion  7 , which has to be located at a predetermined angular position with respect to the axis of the main body tube  1 A, i.e., the optical axis of the lens body tube. Therefore, when the third lens frame  61 A is fixed to the main body tube  1 A inside the main body tube  1 A, the angular position of the third lens frame  61 A with respect to the axis of the main body tube  1 A has to be determined. In order to fix the third lens frame  61 A to the main body tube  1 A in a state of the third lens frame  61 A being located at a predetermined angular position in this way, in the constitution shown in  FIG. 7 , the third lens  61 A is attached to the main body tube  1 A such that the outer circumferential surface thereof has contact with the inner circumferential surface of the main body tube  1 A. The main body tube  1 A is formed with a screw hole  101  that penetrates through the main body tube  1 A in the radial direction, and a screw  102  is inserted into the screw hole  101  to pass completely through the main body tube  1 A. The third lens frame  61 A is fixed to the main body tube  1 A with the screw  102  being tightened in the third lens frame  61 A.  
         [0004]     In the case of the fixing structure of the third lens frame  61 A shown in  FIG. 7 , when fastening the screw  102  to fix the third lens frame  61 A, a fastening force of the screw  102  is applied to the main body tube  1 A. Consequently, the main body tube  1 A is likely to be partially deformed, so that the cam tube  3 , which is connected to the outer circumferential surface of the main body tube  1 A, cannot smoothly rotate. In addition, there is a problem that grease with which the cam tube  3  is lubricated, as indicated by a thick arrow in  FIG. 7 , leaks inside the main body tube  1 A via a joint portion between the screw hole  101  and the third lens frame  61 A, and thereby, the grease adheres to a lens surface and/or comes to the aperture diaphragm driving portion  7  to contaminate them. Especially, since it is necessary to fix the third lens frame  61 A with screws at a plurality of positions in the circumferential direction in order to fix the third lens frame  61 A stably, the grease is easier to leak as the number of the screws increases. Moreover, it is hard to downsize the main body tube  1 A or the lens body tube, since it is necessary to use the screw  102  with a certain level of strength, i.e., the screw  102  that has a required length and a required diameter, in order to keep the angular position of the third lens frame  61 A with respect to the axis of the main body tube  1 A.  
       SUMMARY OF THE INVENTION  
       [0005]     The present invention is advantageous in that a lens body tube, which is capable of fixing parts such as lenses inside a body tube at a predetermined angular position without a screw hole being opened in a radial direction through the body tube, is provided.  
         [0006]     According to an aspect of the invention, there is provided a lens body tube including at least one component to be fixed therein that is provided with at least one first recessed portion, each of which is recessed outward along the radial direction of the lens body tube on a part of the inner circumferential surface of the lens body tube, the at least one first recessed portion being arranged in the circumferential direction of the lens body tube, at least one second recessed portion, each of which is recessed inward along the radial direction of the lens body tube on a part of the outer circumferential surface of a corresponding one of the at least one component which is located such that the outer circumferential surface thereof faces the inner circumferential surface of the lens body tube, the at least one second recessed portion being arranged in the circumferential direction of the lens body tube, and at least one insertion member. Each pair of the at least one first recessed portion and the at least one second recessed portion forms an opening recessed along the axial direction of the lens body tube. A corresponding one of the at least one insertion member is inserted into the opening along the axial direction of the lens body tube.  
         [0007]     Optionally, the lens body tube may further include at least one ring member, each of which is configured to be attached to the inner circumferential surface of the lens body tube to grip a corresponding one of the at least one component in the axial direction of the lens body tube inside the lens body tube.  
         [0008]     Further optionally, the lens body tube may have a female screw portion on the inner circumferential surface thereof. Optionally, each of the at least one ring member may be configured to be screwed together with the female screw portion on the inner circumferential surface of the lens body tube.  
         [0009]     Optionally, each of the at least one ring member may be configured to have contact with a corresponding one of the at least one insertion member in the axial direction of the lens body tube to prevent the one of the at least one insertion member from dropping out of the opening into which the one of the at least one insertion member is inserted.  
         [0010]     Optionally, each of the at least one insertion member may be configured to be fastened to the lens body tube along the axial direction of the lens body tube.  
         [0011]     Still optionally, each of the at least one insertion member may have a screw portion on the bottom face thereof to be screwed together with the lens body tube along the axial direction of the lens body tube.  
         [0012]     Optionally, each of the at least one first recessed portion may be formed to have substantially a semicircular cross section. In this case, each of the at least one second recessed portion may be formed to have substantially a semicircular cross section. Thereby, each pair of the at least one first recessed portion and the at least one second recessed portion may form substantially a circular opening. Preferably, each of the at least one insertion member may be formed of substantially a cylinder solid.  
         [0013]     Optionally, one of the at least one component may be a lens frame that is configured to support a lens and integrally include an aperture diaphragm driving portion. 
     
    
     BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS  
       [0014]      FIG. 1  is a half cross-sectional view of a lens body tube to which the present invention is applied, along an optical axis of the lens body tube;  
         [0015]      FIG. 2  is an enlarged cross-sectional view of a relevant part of a lens body tube of a first embodiment;  
         [0016]      FIGS. 3A and 3B  are cross-sectional views of the lens body tube of the first embodiment along an A-A line shown in  FIG. 1  and a B-B line shown in  FIG. 2 , respectively;  
         [0017]      FIG. 4  is an exploded perspective view of a relevant part of the lens body tube of the first embodiment;  
         [0018]      FIG. 5  is an enlarged cross-sectional view of a relevant part of a lens body tube of a second embodiment;  
         [0019]      FIGS. 6A and 6B  are cross-sectional views of the lens body tube of the second embodiment along the A-A line shown in  FIG. 1  and a C-C line shown in  FIG. 5 , respectively; and  
         [0020]      FIG. 7  is a cross-sectional view of a conventional lens body tube along the A-A line shown in  FIG. 1 . 
     
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS  
     First Embodiment  
       [0021]     A first embodiment according to the present invention will be explained with reference to accompanying drawings. In the first embodiment, there will be shown an example where the present invention is applied to a structure for fixing a third lens frame  61 , which supports a third lens  6 , to a main body tube  1  in a lens body tube shown in  FIG. 1 .  FIG. 2  is an enlarged cross-sectional view of a relevant part, and  FIGS. 3A and 3B  are cross-sectional views of the lens body tube along an A-A line shown in  FIG. 1  and a B-B line shown in  FIG. 2 , respectively. The third lens frame  61  supports the third lens  6 , and, at an adjacent position in an axial direction, is integrally provided with an aperture diaphragm driving portion  7  for driving a diaphragm. The aperture diaphragm driving portion  7 , of which a detailed explanation will be omitted, drives the diaphragm provided in the third lens frame  61  to control an aperture, and is required to be located at a predetermined angular position with respect to the axis of the main body tube  1  so as to enable appropriate power distribution.  
         [0022]     At a part on the inner circumferential surface of the main body tube  1 , an annular step portion  13  is formed by making the inside diameters of an adjacent couple of parts different from one another, to one of which the third lens frame  61  is attached. A female screw portion  14  is formed at a place that is a required distance away from the step portion  13  in the axial direction of the main body tube  1 . The third lens frame  61  is inserted into the main body tube  1  in the axial direction, and one end face, which is on the right side of the third lens frame  61  in  FIG. 2 , has contact with the step portion  13 . In addition, the female screw portion  14  is screwed together with an annular locking ring  8  that has a male screw portion  81  on the outer circumferential surface thereof. The other end face, which is on the left side of the third lens frame  61  in  FIG. 2 , has contact with the locking ring  8 . The third lens frame  61  is fixed inside the main body tube  1  with the third lens frame  61  being gripped between the locking ring  8  and the step portion  13  in the axial direction of the main body tube  1 .  
         [0023]     Moreover, as an exploded perspective view is schematically shown in  FIG. 4 , a location groove  62  that has a semicircular cross section with a predetermined diameter is formed on a portion of the outer circumferential surface of the third lens frame  61 . On the other hand, a reference groove  15  that has a semicircular cross section with the same diameter as the location groove  62  is also formed on a portion of the inner circumferential surface of the main body tube  1 . When the reference groove  15  and the location groove  62  are located at the same angular position with respect to the axis of the main body tube  1 , both of the grooves are arranged opposite one another to form a circular recessed portion  9  between the main body tube  1  and the third lens frame  61 . In the circular recessed portion  9 , there is inserted a cylindrical circular pin  10  with substantially the same diameter and length in the optical axis direction of the lens body tube as the circular recessed portion  9 . The circular pin  10  is inserted in a state where it has contact with each inner circumferential surface of the location groove  62  and the reference groove  15 , and is fixed by the locking ring  8  such that the circular pin  10  does not drop out of the circular recessed portion  9 . In such a way, by making the circular pin  10  have close contact with the inner circumferential surface of the circular recessed portion  9 , backlash between the main body tube  1  and the third lens frame  61  in the circumferential direction and the optical axis direction can be restrained. In addition, the circular pin  10  may be configured to be slotted in the axial direction of the body tube such that the circular pin can deform in the radial direction and the outer circumferential surface thereof can have close contact with the inner circumferential surface of the circular recessed portion  9 .  
         [0024]     The assembling method of the third lens  6  in the lens body tube will be described as follows. The third lens frame  61 , which previously supports the third lens  6  and is integrally provided with the aperture diaphragm driving portion  7 , is inserted into the main body tube  1  from the distal end thereof, and one end face of the third lens frame  61  is made contact with the step portion  13 . Next, rotating the third lens frame  61  around the axis of the main body tube  1 , the angular position thereof is set such that the location groove  62  faces the reference groove  15  in the radial direction of the main body tube  1 . The circular pin  10  is then inserted from the distal end of the main body tube  1  to be put in the circular recessed portion  9  that is configured with the location groove  62  and the reference groove  15 . Thereby, the third lens frame  61  is locked in the rotation direction around the axis of the main body tube  1  with the circular pin  10  being in contact with the location groove  62  and the reference groove  15 , and the angular position thereof is determined. The locking ring  8  is then inserted from the distal end of the main body tube  1 , and the male screw portion  81  of the locking ring  8  is screwed together with the female screw portion  14  of the main body tube  1 . Thereby, the locking ring  8  has contact with the other end face of the third lens frame  61  to grip the third lens frame  61  in the axial direction of the main body tube  1  between the step portion  13  and itself.  
         [0025]     In this way, the angular position of the third lens frame  61  with respect to the axis of the main body tube  1  is determined with the circular pin  10  being inserted into the circular recessed portion  9  that is configured with the reference groove  15  on the inner circumferential surface of the main body tube  1  and the location groove  62  on the outer circumferential surface of the third lens frame  61 . Further, the third lens frame  61  is fixed in the main body tube  1  with the locking ring  8  being tightened in the main body tube  1 . Thereby, the third lens frame  61  is fixed inside the main body tube  1  by the circular pin  10  in a state where the angular position thereof with respect to the axis of the main body tube  1  is determined. In this case, since the circular pin  10  is in contact with the reference groove  15  and the location groove  62  in respect of the circular surface thereof, when a stress is applied to the circular pin  10  in the rotation direction around the axis of the main body tube  1 , the stress is less likely to concentrate at a part of the contact surface, and the stable positioning of the third lens frame  61  is allowed.  
         [0026]     In addition, since a screw hole  101  is not required to be opened from the outer circumferential surface of a main body tube  1  to the inside thereof and to be screwed together with a screw  102 , as a lens body tube shown in  FIG. 7 , the main body tube  1  is not deformed by the screw  102 . Further, since grease with which a cam tube  3  is lubricated does not leak inside the main body tube  1  via the screw hole  101 , the grease does not contaminate a lens and/or the aperture diaphragm driving portion  7 . At the same time, since it is not necessary to use a screw with a predetermined length and diameter to determine the angular position of the third lens frame  61  with respect to the axis of the main body tube  1 , the aforementioned features of this embodiment are advantageous in respect of downsizing the lens body tube. Moreover, in the constitution of this embodiment, since the locking ring  8  is attached to cover a part of the circular recessed portion  9 , the locking ring  8  prevents the circular pin  10  inserted into the circular recessed portion  9  from dropping out, and the angular position of the third lens frame  61  can be stably maintained.  
       Second Embodiment  
       [0027]      FIG. 5  shows a variation of a circular pin for determining the angular position of a third lens frame  61  with respect to the axis of a main body tube  1 , and is an enlarged cross-sectional view of a relevant part of a lens body tube in a second embodiment in a similar fashion to  FIG. 2  in the first embodiment. In addition,  FIGS. 6A and 6B  are cross-sectional views along the A-A line shown in  FIG. 1  and a C-C line shown in  FIG. 5 , respectively. In the second embodiment, the circular pin has a function of fixing the third lens frame as well as the aforementioned function in the first embodiment, and each of equivalent parts to the first embodiment is labeled with the same reference number. A circular pin  10  is integrally formed with a small diameter screw  10   a  at the distal end thereof Further, corresponding to the circular pin  10  with the screw  10   a,  a reference groove  15  is formed of a circular arc with a large center angle on the inner circumferential surface, and is formed with a screw hole  15   a  to be screwed together with the screw  10   a  on an end face of the reference groove  15 . On the other hand, a location groove  62  of the third lens frame  61  is formed of a circular arc with a small center angle. A pair of the location groove  62  and the reference groove  15  forms a circular recessed portion  9 . Each of the reference groove  15  and the location groove  62  is formed at a plurality of places in the circumferential direction, in this case, at three places that are located at intervals of a center angle of 120 degrees. It is noted that in the second embodiment, a female screw portion is not formed as described in the first embodiment, and a locking ring is not employed.  
         [0028]     In the second embodiment, the third lens frame  61  is inserted into the main body tube  1  until one end face of the third lens frame  61  has contact with a step portion  13 . Rotating the third lens frame  61  around the axis of the main body tube  1 , the angular position thereof is set such that the location groove  62  faces the reference groove  15 , that is, a pair of the location groove  62  and the reference groove  15  forms the circular recessed portion  9 . Then, the circular pin  10  is inserted into each of the circular recessed portions  9  that are formed at three places inside the main body tube  1 . The screw  10   a  of the circular pins  10  is screwed together with the screw hole  15   a,  so that the circular pins  10  is fixed to the main body tube  1 . Since the circular pin  10  is fixed to the main body tube  1  in this way, the bottom face of the circular pin  10  has contact with the bottom wall of the location groove  62 , i.e., with the third lens frame  61 , so that the third lens frame  61  is gripped in the axial direction of the main body tube  1  between the circular pin  10  and the step portion  13 . In addition, the circumferential surface of the circular pin  10  has contact with each inner circumferential surface of the location groove  62  and the reference groove  15 , so that the angular position of the third lens frame  61  with respect to the axis of the main body tube  1  in the similar fashion to the first embodiment. In this case, preferably, the length of the third lens frame  61  in the optical axis may be determined such that the bottom face of the location groove  62  is slightly protruded backward in the optical axis direction from the bottom face of the reference groove  15 . Thereby, backlash of the third lens frame  61  in the optical axis direction can be restrained. Moreover, in the same way as the first embodiment, backlash thereof in the circumferential direction can be restrained if the circular pin  10  is designed such that the diameter thereof is substantially equal to the inside diameter of the circular recessed portion  10 .  
         [0029]     In the second embodiment as well as the first embodiment, since a screw hole is not required to be opened from the outer circumferential surface of a main body tube  1  to the inside thereof and to be screwed together with a screw, as a lens body tube shown in  FIG. 7 , the main body tube  1  is not deformed by the screw or the screw hole. Further, since grease with which a cam tube  3  is lubricated does not leak inside the main body tube  1  via the screw hole, the grease does not contaminate a lens and/or the aperture diaphragm driving portion  7 . In addition, since it is unnecessary to prepare such a locking ring and a screw portion to be screwed together therewith as described in the first embodiment, the invention of the second embodiment is advantageous in simplifying the constitution of the main body tube.  
         [0030]     Hereinabove, there are presented in the first and second embodiment the examples of the lens body tube in which the third lens is fixed inside the main body tube. It is noted that when an aperture diaphragm driving portion and/or other parts are fixed inside a main body tube independently of lenses, the present invention can be applied to the above portion and/or parts. In particular, if the present invention is applied to a part that is required to be fixed with the angular position thereof with respect to the optical axis of a lens body tube being specified, deformation of the main body tube and/or leakage of contaminated material such as external grease inside the main body tube are prevented.  
         [0031]     The present invention can be applied to lens body tubes of various kinds of optical apparatuses, each of which is provided with lenses and/or various components being fixed in a body tube as well as a lens body tube of a camera.  
         [0032]     The present disclosure relates to the subject matter contained in Japanese Patent Application No. P2004-294507, filed on Oct. 7, 2004, which is expressly incorporated herein by reference in its entirely.