Abstract:
A zoom lens barrel having a macro-photographing mechanism including a main barrel carrying a control ring assembly which is divided into a first operating ring rotatable and slidable relative to the main barrel along the optical axis thereof, and a second operating ring movable with the first operating ring along the optical axis, the second operating ring being rotatable about the optical axis relative to the first operating ring. The rotation of the first operating ring effects the focusing of a lens system for ordinary photography, and the slide movement of the first operating ring effects zooming by causing a cam ring integral with the second operating ring to follow said movement, whereby when the cam ring is positioned at the wide-angle end or the telephoto end in zooming, the cam ring effects focusing of the lens system for macro-photography due to the rotation of the second operating ring relative to the first operating ring.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to improvements in zoom lenses and it relates more particularly to an improved zoom lens which may operate as an objective lens system for macro-photography of the type, in which an objective lens system includes at least two movable components which are movable so as to effect selective magnification. In this lens system, the focusing for macro-photography is effected by adjusting the position of one component relative to another into a position different from that taken upon zooming, with the order of arrangement of the aforesaid movable components within the system being maintained unchanged, or by moving the lens components which have been maintained stationary during zooming. 
     A zoom lens system having a macro-photographing mechanism of the type described above is known, such as in the Japanese Patent Publication No. SHO50-28829, in which a single operating ring is moved along the optical axis relative to a fixed lens barrel, either upon zooming or upon focusing for macro-photography. 
     The prior art zoom lens barrel has the following shortcomings: 
     (1) Fine adjustment is difficult in focusing for macro-photography. 
     (2) Because of a single operation, discrimination between the macro-focusing operation and the zooming operation is difficult, thus presenting the possibility of a faulty operation. 
     (3) Machining of the cam ring is difficult and the construction of the lens barrel is complex, so that its cost is increased and its reliability is reduced. 
     (4) Rapid switching from a zooming operation to a macro-focusing operation and vice-versa is difficult to achieve. 
     SUMMARY OF THE INVENTION 
     It is a principal object of the present invention to provide an improved zoom lens which may be focussed for macro-photography. 
     It is another object of the present invention to provide a zoom lens barrel which allows distinct discrimination in operation between a zooming and a macro-focusing mode, thereby eliminating any faulty operation. 
     It is still another object of the present invention to provide a zoom lens barrel which allows quick switching from a zooming operation to a macro-focusing operation. 
     It is yet another object of the present invention to provide a zoom lens barrel which is simple in construction, low in manufacture cost and high in precision. 
     A further object of the present invention is to provide a device of the above nature characterized by its high reliability, convenience of operation, ruggedness and high versatility and adaptability. 
     The above and other objects of the present invention will become apparent from a reading of the following description taken in conjunction with the accompanying drawing which illustrates preferred embodiments thereof. 
     In a sense, the present invention comtemplates the provision of a zoom lens which is adjustable to effect focusing for macro-photography, in which an operating ring is rotatable about and slidable along the optical axis relative to a fixed lens barrel; and the operating ring is divided into a first operating ring and a second operating ring; the movement of the first operating ring along the optical axis is transmitted to the second operating ring, while the second operating ring is allowed to rotate about the optical axis relative to the first operating ring; the rotation of the first operating ring about the optical axis effects focusing for normal photography; and the slide or longitudinal movement of the first operating ring along the optical axis causes a cam ring to follow the aforesaid movement for a zooming operation through the medium of the second operating ring, while the rotation of the second operating ring at the wider-angle end or telephoto end in zooming relative to the first operating ring causes the cam ring to cooperate with the second operating ring to follow the aforesaid rotation so as to effect focusing for macro-photography. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a medial longitudinal cross-sectional view, partly fragmented of one embodiment of a zoom lens barrel having a macro-photographing mechanism according to the present invention, showing the upper half thereof with respect to the optical axis; 
     FIG. 2 is a side view of the fixed lens barrel and the cam slots provided therein, in the embodiment of FIG. 1; 
     FIG. 3 is a side view of the cam ring used in the aforesaid embodiment and the cam slots provided therein; 
     FIG. 4 is a side view of the fixed lens barrel in the second embodiment of the present invention, and the cam slots provided therein; and 
     FIG. 5 is a side view of the cam ring used in the embodiment of FIG. 4 and the cam slots provided therein. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to FIGS. 1 to 3 which illustrates one embodiment of the present invention, a fixed lens barrel 1 mounted to a camera, as shown in FIG. 1, includes a master lens sleeve or frame 41 which is rigidly mounted therein and carries or retains a master lens group 42 coaxially within the inner periphery thereof. Provided in the inner peripheral surface of the fixed lens barrel 1, as shown in FIG. 2, are a cam slot 24z for use in zooming and a cam slot 24M for use in macro-focusing, which slot 24M joins and is continuous with the slot 24z, and a cam slot 34z for use in zooming and a cam slot 34M for use in macro-focusing joining cam slot 34z. In addition, formed in the front end of the fixed lens barrel 1 is a helicoid 3 which is in threaded engagement with a rotatable ordinary focus-adjusting cylinder 4. 
     The focus-adjusting cylinder 4 carries or retains a focus-adjusting lens group 12 on its front inner peripheral surface, and its outer wall extends rearwardly to loosely fit on the outer periphery of the fixed lens barrel 1. A follower defining pin 6 is anchored to the rear end of the outer wall of the focus-adjusting cylinder 4 and radially outwardly projects therefrom. 
     A first operating ring 7 includes in its forward inner peripheral surface an annular groove 8, in which an inwardly projecting annular member 5 is fitted, and a linear groove 10 which is longitudinally slidably engaged by the pin 6 and which extends parallel to the optical axis. The first operating ring 7 is fitted at its forward part on the outer peripheral surface of the focus-adjusting cylinder 4. The annular engaging member 5 is made of a friction cloth and softly contacts the outer peripheral surface of the focus-adjusting cylinder 4. An annular projection 9 is formed on the rear inner peripheral surface of the first operating ring 7, and rotatably matingly engages an annular groove 13 provided in the outer peripheral surface of the second operating ring 11, the annular groove 13 extending at a right angle to the optical axis. An annular groove 14 is provided in the rear inner peripheral surface of the second operating ring 11 and contains an annular engaging member 2 which is made of a friction cloth and softly contacts the outer surface of the fixed lens barrel 1. A click ball 15 is fitted in a radial bore provided in the inner peripheral surface of the second operating ring 11 and is urged against the outer peripheral surface of the barrel 1 under the action of a spring 16 housed in the bore. The front portion of the second operating ring 11 defines a cam ring 17 which is closely rotatably and slidably fitted on the outer peripheral surface of the fixed lens barrel 1. Provided in the peripheral surface of the cam ring 17 are a hole 25 and a cam slot 35, as shown in FIG. 3. 
     A first movable lens group frame 21 which carries or retains a first movable lens group 22 for use in zooming is closely fitted in the inner peripheral surface of the fixed lens barrel 1 in sliding relation thereto. A follower defining pin 23 is anchored to the outer peripheral surface of the first movable lens frame 21 and slidably engages the cam slot 24M for use in macro-photography as well as the cam slot 24z for use in zooming, the pin 23 matingly engaging the hole 25 provided in the cam ring 17 as well. 
     A second movable lens frame 31 carries or retains a second movable lens group 32 for use in zooming. The second movable lens group frame 31 is closely fitted in the inner peripheral surface of the fixed lens barrel 1 in sliding relation thereto. A follower defining pin 33 is anchored to the outer peripheral surface of the second movable lens frame 31 and engages in the cam slot 34z and cam slot 34M provided in the fixed lens barrel 1 in piercing relation, the pin 33 engaging cam slot 35 provided in the cam ring 17 as well. 
     In operation, when the first operating ring 7 is rotated about the optical axis, then the focus adjusting cylinder 4 having the follower pin 6 slidably engaging the linear groove 10 is also rotated so that the focus-adjusting cylinder 4 moves along the optical axis relative to the fixed lens barrel 1 with the aid of the helicoid 3 formed therein, with the result that the position of the focus-adjusting lens group 12 is adjusted along the optical axis relative to a master lens group 42, thereby adjusting the focusing for an object distance in ordinary photography. During this operation, rotation is not transmitted to the second operating ring 11 through the annular projection 9 and annular groove 13, and thus the second operating ring 11 is locked in position by means of the click mechanism. There thus results no movement of the first and second movable lens frames 21, 31 along the optical axis. 
     When the first operating ring 7 is longitudinally slid or moved along the optical axis with the follower pin 23 engaging the cam slot 24z and the pin 33 fitted in the cam slot 34z, then the cam ring 17 longitudinally slidably moves along the optical axis through the medium of the second operating ring 11 so that the first movable lens frame 21 moves longitudinally along the optical axis by the aid of the hole 25, and the pin 23 slidingly moves along the cam slot 24z. On the other hand, the follower pin 33 on the second movable lens frame 31 engages both the cam slot 34z and the cam groove 35 all the time, so that the pin 33 is slidably rotated so as to be positioned at an intersection of the slot 34z and groove 35, thereby adjusting the positions of the first movable lens group 22 and second movable lens group 32 relative to the lens group 12, 42 for effecting zooming. More particularly, upon zooming, the follower pin 23 provided on the first movable lens frame 21 moves along the cam slot 24z provided in the fixed lens barrel 1 under the influence of the cam ring 17, while the follower pin 33 provided on the second movable lens frame moves along the cam slot 34z provided in the fixed lens barrel 1 under the urging of the cam ring 17. In other words, when set to a telephoto position in zooming, the pin 23 is positioned at 23T in the cam slot 24z, and the pin 33 is positioned at 33T in the cam slot 34z. When set to a wide angle position, the follower pin 23 is positioned at 23W in the cam slot 23z, while the follower pin 33 is positioned at 33W in the cam slot 34z. 
     Upon focusing for macro-photography, when the follower pin 23 fitted in the hole 25 is at the wide angle end in the aforesaid zooming operation and is positioned at the bend or connecting portion of the cam slot 24z and the cam slot 24M, i.e., at 23W in FIG. 2, and the follower pin 33 is positioned at the connecting point of the cam slot 34z and the cam slot 34M, i.e., at 33W in FIG. 2, then the rotation of the second operating ring 11 in the direction of arrow A as shown in FIG. 3 relative to the first operating ring 7 causes the follower pin 23 to be guided by means of the hole 25 and cam slot 24M, and causes the follower pin 33 to be guided by the cam slot 34M and cam groove 35, with the result that the pin 23 is positioned at 23M, while the pin 33 is positioned at 33M as shown in FIG. 2. As a result, the second movable lens group 32 is moved along the optical axis as carried by the second movable lens frame 31 and as determined by the movement of the point of intersection of cam slots 34M and 35. 
     Meanwhile, in the case of the first embodiment, there is shown a lens barrel for use in a lens system of the type in which when the lens system is to be focused for macro-photography, the first movable lens group 22 does not move along the optical axis relative to the master lens group 42, while the second movable lens group 32 alone moves. In this case, it suffices that the cam slot 24M may be an arcuate linear slot provided along the barrel circumference and lying in a plane perpendicular to the optical axis, and the cam slot 24z may be a linear longitudinally slot intersecting at a right angle therewith. As a result, the provision of the cam slot 24M and cam slot 24z may be greatly facilitated. 
     FIGS. 4 and 5 show a second embodiment of the present invention, in which there are provided cam slots in a lens system of the type, that upon focusing for macro-photography, the first movable lens group 22 moves and, in addition, the second movable lens group 32 moves in a manner different from that in a zooming operation. 
     In this case of it suffices that a cam slot 44, the fixed lens barrel 1 with which the pin 23 on the first movable lens frame 21 within the fixed lens barrel 1 engages may be a linear slot extending parallel to optical axis and the hole 25 provided in the cam ring 17 is replaced by a cam slot 45 inclined relative to a circumferential groove perpendicular to the optical axis. On the other hand, the cam slot, which is slidably engaged by the follower pin 33 on the second movable lens frame 31 may be the combination of a cam slot 54M for use in macro-focusing and a cam slot 54z for use in zooming which slot 54M joins and is continuous with the slot 54M, while the cam slot provided in the cam ring 17 may be the combination of a cam slot 55M for use in macro-focusing, and a cam slot 55z for use in zooming. 
     As is clear from the foregoing, when the follower pin 33 on the second movable lens frame 31 is positioned in the cam slot 54z as well as in the cam slot 55z, zooming may be effected due to the movement of the first operating ring 7 along the optical axis. On the other hand, when the pin 33 is positioned at the connection point 33T of the cam slot 54z with the slot 55M, focusing for macro-photography may be effected due to rotation of the second operating ring 11 relative to the first operating ring 7. 
     While there has been described and illustrated preferred embodiments of the present invention, it is apparent that numerous alterations, additions and omissions may be made without departing from the spirit thereof.