Abstract:
An eye cup moving mechanism of an optical device includes: an eyepiece lens holding barrel that houses and holds an eyepiece lens; an eyepiece outer casing that is capable of sliding against an external circumferential portion of the eyepiece lens holding barrel; and an eye cup cover provided at the eyepiece outer casing. The eyepiece lens holding barrel includes a first regulating member provided at the external circumferential portion thereof; and the eyepiece outer casing includes a second regulating member that comes in contact with the first regulating member to regulate a movement of the eye cup cover along an optical axis of the eyepiece lens.

Description:
INCORPORATION BY REFERENCE 
     The disclosure of the following priority application is herein incorporated by reference: 
     Japanese Patent Application No. 2000-175186 filed Jun. 12, 2000 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an eye cup moving mechanism of an optical device having an eye cup, such as a telescope, a binocular or a microscope. 
     2. Description of the Related Art 
     The eye cup of an optical device, which is mounted at the eyepiece unit, is moved along the direction of the optical axis of the eyepiece lens to offer a comfortable visual field to both a user wearing glasses and a user who does not wear glasses. An eye cup in the prior art is rotated around the optical axis of the eyepiece lens to travel along the direction of the optical axis, and its traveling distance is regulated by a cam mechanism. 
     FIG. 5 is a longitudinal sectional view of the structure adopted in an eye cup moving mechanism in the prior art. An eye cup  20  is constituted by securing an eye cup cover  11  around the external circumference of an eyepiece outer casing  12 . The eyepiece outer casing  12  is formed in a cylindrical shape, and its internal circumferential surface is allowed to slide against the external circumferential surface of an eyepiece lens holding barrel  14 . The external circumferential surface “s” of the eyepiece lens holding barrel  14  is formed to extend straight along the direction of the optical axis. With the eyepiece outer casing  12  moving relative to the eyepiece lens holding barrel  14  along the external circumferential surface “s”, the distance between an eye cup front end  20   a  and the outer end surface of the eyepiece lens is varied. 
     In FIG. 5, the eye cup front end  20   a  is at position d 1  which sets the eye cup in an driven-out state. When the eye cup front end  20   a  is at position d 2  indicated by the dotted line in the figure, the eye cup is in a driven-in state. The eye cup front end is set at position d 1  or d 2  by employing a cam mechanism constituted of camshafts  15   a  and  15   b  provided at the eyepiece lens holding barrel  14  and a cam groove (not shown) formed at the eyepiece outer casing  12 . It is to be noted that the eyepiece lens holding barrel  14  normally holds a plurality of eyepiece lenses and is mounted at the optical device main unit on the objective lens side. 
     FIG. 6A is a top view, FIG. 6B is a side elevation, FIG. 6C is a bottom view and FIG. 6D is a side elevation of the half cylinder obtained by slicing the top view in FIG.  6 A through line X—X, all provided to illustrate the structure of the eyepiece outer casing  12  in the prior art. 
     Simply put, the eyepiece outer casing  12  is a cylinder having two cam grooves  16   a  and  16   b  set at 180° relative to each other at the cylinder surface. The camshafts  15   a  and  15   b  in FIG. 5 engage with the two cam grooves  16   a  and  16   b  respectively. When the camshafts  15   a  and  15   b  are each at position d 1 , the eye cup  20  is set in a driven-out state, whereas when the camshafts  15   a  and  15   b  are at position d 2 , the eye cup  20  is set in a driven-in state. When the eye cup  20  is retained at either position d 1  or d 2 , the camshafts  15   a  and  15   b  are each pressed at an end of the cam groove  16   a  or  16   b.  In other words, the movement of the eye cup is regulated by the cam mechanism. 
     When the camshafts are retained to set the position of the eye cup, the camshafts are pressed against the cam grooves, and thus, the greatest force is applied where the camshafts are mounted at the eyepiece holding barrel. In an optical device having a compact eyepiece unit, in particular, small camshafts that are mounted (e.g., screwed in) over a small screwing diameter are naturally used. 
     The eye cup cover for the eye cup is often constituted of rubber, and when it is rotated, a large moment is generated to result in an impact force manifesting upon the camshafts becoming pressed against the ends (position d 1  or d 2 ) of the cam grooves. In a worst case, the areas over which camshafts are mounted that are most greatly affected by the impact force may become damaged. The ends of the cam grooves, too, are subject to the impact force. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide an eye cup moving mechanism that prevents camshafts and cam grooves from becoming damaged even when a great force is applied. 
     In order to attain the above object, an eye cup moving mechanism of an optical device according to the present invention, comprises: an eyepiece lens holding barrel that houses and holds an eyepiece lens; an eyepiece outer casing that is capable of sliding against an external circumferential portion of the eyepiece lens holding barrel; and an eye cup cover provided at the eyepiece outer casing. The eyepiece lens holding barrel includes a first regulating member provided at the external circumferential portion thereof; and the eyepiece outer casing includes a second regulating member that comes in contact with the first regulating member to regulate a movement of the eye cup cover along an optical axis of the eyepiece lens. 
     In this eye cup moving mechanism of an optical device, it is preferred that the eyepiece lens holding barrel and the eyepiece outer casing are relatively moved along an optical axis of the eyepiece lens by a cam mechanism constituted of a cam shaft provided at either the eyepiece lens holding barrel or the eyepiece outer casing and a cam groove formed at either the eyepiece lens holding barrel or the eyepiece outer casing at which the camshaft is not provided; and the first regulating member at the eyepiece lens holding barrel and the second regulating member at the eyepiece outer casing are provided so as to come into contact with each other before an end of the cam groove comes in contact with the camshaft. 
     Also, it is preferred that the first regulating member comprises a third regulating member and a fourth regulating member; the second regulating member comprises a fifth regulating member and a sixth regulating member; the third regulating member at the eyepiece lens holding barrel and the fifth regulating member at the eyepiece outer casing come in contact with each other when the eye cup cover is driven-out furthest toward a user; and the fourth regulating member at the eyepiece lens holding barrel and the sixth regulating member at the eyepiece outer casing come in contact with each other when the eye cup cover is driven in furthest from the user. In this case, it is preferred that the third regulating member and fourth regulating member are formed so as to project outward at the external circumferential portion of the eyepiece lens holding barrel; the fifth regulating member is formed so as to project inward at an internal circumferential portion of the eyepiece outer casing; and the sixth regulating member is constituted of an end of the eyepiece outer casing located on a side opposite from the user. Furthermore, it is preferred that a cutting portion is provided at a portion of at least either the third regulating member or the fifth regulating member so as to ensure that the third regulating member and the fifth regulating member do not come in contact with each other. 
     Also, it is preferred that the first regulating member at the eyepiece lens holding barrel and the second regulating member at the eyepiece outer casing come in contact with each other when the eye cup cover is driven-out furthest toward a user. In this case, it is preferred that the first regulating member is formed so as to project outward at the external circumferential portion of the eyepiece lens holding barrel; and the second regulating member is formed so as to project inward at an internal circumferential portion of the eyepiece outer casing. Furthermore, it is preferred that a cutting portion is provided at a portion of at least either the first regulating member or the second regulating member so as to ensure that the first regulating member and the second regulating member do not come in contact with each other. 
     Also, it is preferred that the first regulating member at the eyepiece lens holding barrel and the second regulating member at the eyepiece outer casing come in contact with each other when the eye cup cover is driven in furthest from a user. In this case, it is preferred that the first regulating member is formed so as to project outward at the external circumferential portion of the eyepiece lens holding barrel; and the second regulating member is constituted of an end of the eyepiece outer casing located on a side opposite from the user. 
     A telescope according to the present invention comprises at least one eye cup moving mechanism. The eye cup moving mechanism comprises: an eyepiece lens holding barrel that houses and holds an eyepiece lens; an eyepiece outer casing that is capable of sliding against an external circumferential portion of the eyepiece lens holding barrel; and an eye cup cover provided at the eyepiece outer casing. The eyepiece lens holding barrel includes a first regulating member provided at the external circumferential portion thereof; and the eyepiece outer casing includes a second regulating member that comes in contact with the first regulating member to regulate a movement of the eye cup cover along an optical axis of the eyepiece lens. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a longitudinal sectional view illustrating the structure adopted in the eye cup moving mechanism in conjunction with the eyepiece unit in an embodiment of the present invention; 
     FIG. 2A is a side elevation of the eyepiece lens holding barrel adopted in conjunction with the eye cup moving mechanism in the embodiment of the present invention; 
     FIG. 2B is a top view of the eyepiece lens holding barrel; 
     FIGS.  3 A˜ 3 C are a top view, a side elevation and a bottom view, provided to illustrate the structure of the eyepiece outer casing adopted in conjunction with the eye cup moving mechanism in the embodiment of the present invention; 
     FIG. 3D is a side elevation of the half cylinder obtained by slicing FIG.  3 A through line X—X; 
     FIG. 4 is an overall view of a telescope having the eye cup moving mechanism according to the present invention; 
     FIG. 5 is a longitudinal sectional view of the structure adopted in an eye cup moving mechanism in the prior art in conjunction with a specific eyepiece unit; 
     FIGS.  6 A˜ 6 C are a top view, a side elevation and the bottom view, provided to illustrate the structure of the eyepiece outer casing adopted in conjunction with the eye cup moving mechanism in the prior art; and 
     FIG. 6D is a side elevation of the half cylinder obtained by slicing the top view in FIG.  6 A through line X—X. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The eye cup moving mechanism according to the present invention includes an eyepiece lens holding barrel  4 , an eye cup  10  constituted by securing an eye cup cover  1  around the external circumference of an eyepiece outer casing  2  and a mechanism that allows the eyepiece outer casing  2  to slide against the eyepiece lens holding barrel  4 . This eye cup moving mechanism features a mechanism that prevents damage to the camshafts and the cam grooves by providing an additional regulating member without stopping movement with a cam mechanism. 
     The following is an explanation of the eye cup moving mechanism according to the present invention, given in reference to the drawings. 
     FIG. 4 is an overall view of a telescope provided with the eye cup moving mechanism according to the present invention. FIG. 1 is a longitudinal sectional view illustrating the eye cup moving mechanism adopted in the telescope in FIG. 4 in conjunction with the eyepiece unit. FIG. 2A is a side elevation and FIG. 2B is a top view, both showing a state in which the eye cup in the longitudinal sectional view in FIG. 1 is removed. FIG. 3A is a top view, FIG. 3B is a side elevation, FIG. 3C is a bottom view and FIG. 3D is a side elevation of the half cylinder obtained by slicing the top view in FIG.  3 A through line X—X, all provided to illustrate the structure of the eyepiece outer casing adopted in the eye cup moving mechanism in the embodiments of the present invention. The X—X sectional plane passes through the center of the eyepiece outer casing. It is to be noted that in the explanation given in reference to FIGS. 1 through 3, members and mechanisms that are identical to those employed in the prior art explained in reference to FIGS.  5 ˜ 6 D earlier may not be explained again. In FIG. 1, the eye cup  10  is in a driven-out state when the eye cup front end  10   a  is at position D 1 , whereas the eye cup  10  is in a driven-in state when the eye cup front end  10   a  is at position D 2  indicated by the dotted line in the figure. The interval between D 1  and D 2  represents the distance over which the eye cup  10  travels. 
     The following two features differentiate the eye cup moving mechanism according to the present invention from those in the prior art. Firstly, the eye cup moving mechanism according to the present invention includes a ring-like (toroidal, brim shaped or flange shaped) projecting portion  4   a  which extends out around the circumference of the eyepiece lens holding barrel  4 , located near the center of the eyepiece lens holding barrel  4 . Secondly, the eye cup moving mechanism according to the present invention includes a similar ring-like projecting portion  3  ( 3   a  and  3   b  in the figure) extending around the circumference of the eyepiece lens holding barrel  4 , located toward the observer (toward the user) at the eyepiece lens holding barrel  4 . Thus, a structure having stages at the external circumferential surface S of the eyepiece lens holding barrel  4  is achieved. These features are easily discerned when one compares the longitudinal sectional view in FIG. 1 with the longitudinal sectional view in FIG.  5 . 
     FIG. 2A is a side elevation and FIG. 2B is a top view of the eyepiece lens holding barrel  4  employed in the eye cup moving mechanism according to the present invention. It is to be noted that FIGS. 2A and 2B show the eyepiece lens holding barrel  4  rotated by 90° around the optical axis of the eyepiece lens relative to FIG.  1 . FIGS. 2A and 2B even more clearly show the two features described above, i.e., the projecting portion  4   a  and the projecting portion  3  (constituted of  3   a ˜ 3   d ). The projecting portion  4   a  and the projecting portion  3  together achieve a function as a regulating member. In addition, screw holes  5   a   1  and  5   b   1  at which camshafts  5   a  and  5   b  are to be mounted are formed at projecting portions  3   a  and  3   b.    
     The projecting portion  3  is formed in a circular shape having  4  cutting portions  3   e,  as is clearly shown in the top view in FIG.  2 B. The reason for providing such cutting portions at the projecting portion  3  is to be explained later. It is to be noted that the eyepiece lens holding barrel  4 , which must achieve a high degree of both dimensional accuracy and strength, is normally an integrated unit constituted of metal. 
     FIGS.  3 A˜ 3 D show the structure of the eyepiece outer casing employed in the eye cup moving mechanism according to the present invention. The side elevation presented in FIG. 3D is a side elevation of the half cylinder obtained by slicing the top view in FIG.  3 A through line X—X. As becomes obvious when FIGS. 3A and 3D are compared with FIGS. 6A and 6D respectively, the eyepiece outer casing  2  is characterized in that four distended (or projected) portions  2   a ˜ 2   d  are provided on the lower side of its inner surface (toward the objective lens). These distended portions provide a function as a regulating member provided at the eyepiece outer casing. 
     Now, the reason for providing the cutting portions at the projecting portion  3  is explained, in reference to FIGS. 2B and 3A. The eye cup is mounted at the eyepiece unit by inserting the eyepiece outer casing  2  at the eyepiece lens holding barrel  4 . This process is facilitated by aligning the distended portions  2   a ˜ 2   d  at the eyepiece outer casing  2  with the positions of the cutting portions  3   e.  Then, by turning the eyepiece outer casing  2  by 45°, the alignment of the projecting portions  3   a ˜ 3   b  with the distended portions  2   a ˜ 2   d  is completed. 
     Next, the specific manner in which the eye cup moving mechanism according to the present invention operates is explained. 
     Two cam grooves  6   a  and  6   b  are set at 180° relative to each other at the cylinder surface of the eyepiece outer casing  2  (see FIGS.  3 B and  3 D). The camshafts  5 A and  5 B shown in FIG. 1 are respectively engaged with these cam grooves, so that the eye cup is set in a driven-out state when the camshafts  5   a  and  5   b  are each at position D 1  and the eye cup is set in a driven-in state when the camshafts  5 A and  5 B are each at position D 2 . The system explained so far is identical to that in the mechanism in the prior art. 
     As described earlier in reference to FIG. 5, the camshafts  15   a  and  15   b  are respectively pressed against the ends of the cam grooves  16   a  and  16   b  when the eye cup is retained at position d 1  or d 2  by utilizing the eye cup moving mechanism in the prior art. However, this does not happen in the eye cup moving mechanism according to the present invention. 
     In the eye cup moving mechanism according to the present invention, at least one regulating member is provided both at the eyepiece lens holding barrel  4  and the eyepiece outer casing  2 . In the embodiment, two regulating members, i.e., the regulating member  4   a  and the regulating member  3  (which is constituted of  3   a ˜ 3   d ) are provided at the eyepiece lens holding barrel  4 , as shown in FIGS. 1 and 2. In addition, the regulating members  2   a ˜ 2   d  are provided at the eyepiece outer casing  2 , as shown in FIG.  3 . 
     As the eye cup  10  is driven-out to reach position D 1 , regulating members  2   a ˜ 2   d  at the eyepiece outer casing  2  are placed in contact with the regulating member  3  ( 3   a ˜ 3   d ) of the eyepiece lens holding barrel  4 , thereby stopping the eye cup  10 . If, on the other hand, the eye cup  10  is driven in to reach position D 2 , the end surface of the eyepiece outer casing  2  toward the objective lens is placed in contact with the regulating member  4   a  of the eyepiece lens holding barrel  4 , thereby stopping the eye cup  10 . The eyepiece outer casing  2  stop positions (D 1  and D 2 ) are set slightly inward relative to the positions at which the camshafts  5   a  and  5   b  would come in contact with the ends of the cam grooves  6   a  and  6   b  respectively, to ensure that the camshafts  5   a  and  5   b  are never pressed against the ends of the cam grooves  6   a  and  6   b.  As a result, damage to the camshafts and cam grooves is prevented. 
     In addition, since the regulating members are formed at the existing eyepiece lens holding barrel and eyepiece outer casing, the number of components required to constitute the eye cup moving mechanism does not need to increase compared to that in the prior art. 
     While the eye cup moving mechanism in the embodiment is explained above by using an example in which it is adopted in a telescope, the present invention is not limited to this example, and it may be adopted in all types of optical devices having an eye cup moving mechanism including binoculars, microscopes and the like.