Apparatus for selectively opening and closing a photographic opening in a lens cover

Abstract: The invention relates to an apparatus for selectively opening and closing a photographic opening in a lens cover (38) adapted for use with a lens in a camera having an optical axis. The apparatus comprises at least one movable barrier (140) and means for selectively covering said opening with said barrier (140), said selectively covering means (38, 24) comprising first and second elements (38, 24) which are relatively movable along said optical axis.

Description: This invention relates to a zoom lens comprising a barrier apparatus. A zoom lens of this kind is known from WO-A-87/07038 and is described in the generic part of the independent claim. The barrier mechanism comprises a movable member positioned in a peripheral opening of a lens support frame. The movable member engages with at least one barrier plate and can be selectively moved within the frame to close the lens opening when the lens is moved into an accomodation position. This driving principle of the barrier mechanism can be adversely influenced by errors which occurred during the manufacture and/or assembly of camera components. The problem to be solved by the invention is to provide a zoom lens having a barrier apparatus, the mechanism of which is driven so that errors occurred during manufacture and/or assembly cannot influence its function. The invention solves the problem by the features indicated in the independent claim. Advantageous further developments are described in the dependent claims. The invention will be discussed in greater detail hereinafter with specific reference to the drawings which are attached hereto, in which like reference numerals are used to represent similar parts throughout the several views, and wherein: Fig. 1 is a longitudinal sectional view of the upper half of a zoom lens barrel capable of macro-photography, shown in a position in which the lenses are retracted or accommodated, according to one embodiment of the present invention; Fig. 2 is a view which is similar to Fig. 1, with the apparatus shown at a WIDE extremity position; Fig. 3 is a view similar to Fig. 1, with the apparatus shown at a TELE extreme position; Fig. 4 is a view similar to Fig. 1, with the apparatus shown at a MACRO photographing position; Fig. 5 is an exploded perspective view of the zoom lens barrel illustrated in Figs. 1-4, in combination with a light barrier mechanism; Figs. 6A and 6B are longitudinal sectional views of a zoom lens barrel having a barrier mechanism as shown in Fig. 5, and is shown in a closed position in which the barriers are closed and an open position in which the barriers are open, respectively; and Figs. 7A and 7B are front elevational views of the barrier mechanism illustrated in Fig. 5, corresponding to the views of Figs. 6A and 6B, respectively. In the illustrated embodiment, the present invention is used in a zoom lens barrel having a macro photographic function; although many of the features can equally well be used in a camera without such a function. Figs. 1, 2, 3 and 4 illustrate the lens in a retracted position, a WIDE extremity position, a TELE extremity position, and a MACRO photographing position, respectively. It can thus be easily understood from the drawings of Figs. 1-4 (and particularly Fig. 1) that the accommodation or retracted length of the lens barrel in accordance with the present invention is small. As illustrated in Fig. 1, a stationary barrel 12 is secured to a camera body 11, preferably of a lens shutter type of zoom lens camera. The camera body 11 includes an outer rail 13 and an inner rail 14, respectively, which serve as a film guide. Inner and outer rails 13 and 14 further define a film holding plane. In the illustrated embodiment, front and rear lens groups 15 and 16, respectively, can be retracted to, and accommodated within, a position which is very close to the film holding plane. Additionally, annular members such as cam ring 22 are relatively small, and, accordingly, the accommodation length of the camera can be decreased. A female helicoid ring 18 having inner peripheral helicoid teeth or threads 18a is secured to, and inside of, stationary barrel 12 by set screws 19. The female helicoid ring 18 is screw/ threadably engaged by a male helicoid ring 20 having outer peripheral helicoid teeth or threads 20a. Cam ring 22 is secured to male helicoid ring 20 by set screws 21, as illustrated in Fig. 5. A gear 20b is formed on the outer periphery of male helicoid ring 20; the gear has threads or teeth, each of which extends parallel to the optical axis, as illustrated in Fig. 5. Gear 20b extends at the same angle of inclination as the lead angle of helicoid teeth 20a of male helicoid ring 20, i.e., it is parallel to the direction of each of the teeth or threads 20a, as shown in Figure 5. Cam ring 22 is rotated in both forward and reverse directions by a driving motor, described in detail hereinafter, through a pinion which meshes with gear 20b, so that when the male helicoid ring 20 is rotated, cam ring 22 is moved in the optical axis direction in accordance with the lead angle of helicoid teeth 20a, all while the cam ring is rotating. Lens guide ring 24 is fitted into the inner periphery of cam ring 22 so as to move together with cam ring 22 along the optical axis direction, and so that it will rotate relative to cam ring 22. Lens guide ring 24 includes a linear movement guide plate 26 which is secured to the rear end of the lens guide ring 24 by set screws 25. Linear movement guide plate 26 includes at least one outer projection which are each engaged in a respective lens guide ring guide groove 27 formed on the interior surface of stationary barrel 12. Each guide groove 27 is provided in the form of a straight groove, which extends along (i.e., parallel to) the optical axis direction in the embodiment which is shown in the figures. An annular groove 28 is provided between the linear movement guide plate 26 and the rear end of lens guide ring 24; an inner flange 29 on the rear end of cam ring 22 is relatively rotatably fitted within annular groove 28, so that lens guide ring 24 can move along the optical axis direction together with movement of cam ring 22. Guide ring 24 cannot, however, rotate, due to the presence of guide groove(s) 27, which engages plate 26 to prevent rotation. Cam ring 22 can, of course, rotate relative to (and about) lens guide ring 24. Front and rear lens groups 15 and 16 are secured to front lens group frame 30 and rear lens group frame 31, respectively, which are both located inside the lens guide ring 24. Front lens group frame 30 is connected to helicoid ring 33, which is itself secured to shutter block 32. The shutter block is secured to a front lens group moving frame 34, which is provided along its outer periphery with at least three guide pins 35. Rear lens group frame 31 is provided along its outer periphery with at least three guide pins 36. As illustrated in Figs. 1 and 3, the guide pins are shown at the same axial positions, thereby making it possible to show only one such pin; Figures 2 and 4, however, illustrate the pins at axially spaced positions (as does, e.g., Fig. 5). Shutter block 32 rotates driving pin 32a over an angular displacement corresponding to an object distance which is detected by an object distance measuring device (not illustrated) in order to rotate the front lens group frame 30, which is associated with driving pin 32a, via pin 30a. In this fashion, front lens group frame 30 is moved along the optical axis direction in accordance with movement of the helicoid in order to effect focusing, in a well-known fashion. Shutter block 32 also operates shutter blades 32b in accordance with a signal representing the brightness of an object which has been detected. A cylindrical lens cover 38 is provided which is integral with front lens group moving frame 34, and a decorative cylinder 39 is provided which covers the outer peripheries of lens guide ring 24 and cam ring 22, which are adapted to respectively project from the outer shell lla of the camera body. Cam ring 22 is provided with a front lens group cam groove 41 and a rear lens group cam groove 42 within which guide pins 35 and 36, respectively, are fitted. Lens guide ring 24 is provided with lens guide grooves 43 and 44 which, respectively, correspond to the front lens group cam groove 41 and the rear lens group cam groove 42. As shown in the embodiment of Figs. 1-4, lens guide grooves 43 and 44 are straight grooves which extend in the direction of the optical axis. Guide pin 35 extends through both the front lens group cam groove 41 and the lens guide groove 43, and guide pin 36 extends through both the rear lens group cam groove 42 and the lens guide groove 44. The profiles of front lens group cam groove 41, lens guide groove 43, and rear lens group cam groove 42, as well as lens guide groove 44, are determined such that movable lenses or lens groups 15 and 16 are moved along a predetermined axial track in accordance with the axial movement of cam ring 22 and lens guide ring 24 effected by rotation of the male helicoid ring 20, and by relative rotation of cam ring 22 with respect to lens guide ring 24. The zoom lens as constructed operates as detailed hereinafter. When male helicoid ring 20 is rotated in forward and reverse directions, the male helicoid ring 20 will move along the optical axis direction while rotating, in accordance with the lead angle of helicoid teeth 20a, since the female helicoid ring 18 which is engaged by the male helicoid ring 20 is secured to stationary barrel 12. Namely, cam ring 22, which is secured to male helicoid ring 20, is rotated together with the male helicoid ring 20 and will be moved along the optical axis direction in accordance with the lead angle of the helicoid teeth 20a. Further, lens guide ring 24, which is mounted to cam ring 22 so that the two rings will rotate with respect to each other and move together along the optical axis direction, is moved along the direction of the optical axis, without rotating, in accordance/association with axial movement of cam ring 22. Relative rotation of cam ring 22 and lens guide ring 24 causes axial movement of moving lenses 15 and 16 in accordance with the relationship between cam groove 41 and lens guide groove 43, as well as in accordance with the relationship between cam groove 42 and lens guide groove 44. Lenses 15 and 16 can be moved from the accommodation position, as shown in Fig. 1, to the macro-photographing position, which is illustrated in Fig. 4, as a result of the movement of cam ring 22 and lens guide ring 24. Thus, it should be appreciated that when in the accommodation position, the accommodation length of the lens is extremely small, since the cam ring 22 and lens guide ring 24 do not protrude outwardly from the outer shell 11a of the camera body or from the cylindrical lens cover 38. Figs. 5-7 illustrate a barrier mechanism which can be advantageously incorporated into the zoom lens barrel referred to above, e.g. The barrier mechanism is notable in that its barriers are closed and opened by relative axial displacement of a cylindrical lens cover, including the barriers, and the lens guide ring 24. A pair of lens barriers 140 are provided on the front end of cylindrical lens cover 38. Lens barriers 140 are opened and closed in such a way that they will be closed in the accommodation position of the lens and such that they will be maintained in an open position whenever the lens is located between the accommodation position and the macro position. Although two barriers 140 are shown, one (or more than two) could also be used. Barriers 140 are pivoted to a surface of a flange portion 38a provided on the inner periphery of the front end of lens cover barrel 38, via respective pivot pins 141. Barriers 140, which are symmetrically opposed to each other, have barrier plate portions 140a which can be moved into the light path, and driving arm portions 140b which extend in opposite directions from barrier plate portions 140a, with respect to pins 141. Driving arm portions 140b are provided at their ends with pins 142 which extend rearwardly, along the optical axis direction, through the inner space, i.e., opening, in flange portion 38a. A circular disk-like intermediate ring 143 and a circular disk-like driving ring 145 for operating barriers 140 are rotatably mounted on the back of flange portion 38a. Intermediate ring 143 is provided along its inner periphery with grooves or notches 143a, within which pins 142 are engaged; and, along its outer periphery, with a projection 143b and intermediate engaging piece 143c, both of which extend rearwardly along the optical axis direction. A closing spring 144, which continuously biases lens barriers 140 to close the barriers, is provided between projection 143b and pin 145c, which itself is provided on driving ring 145. Driving ring 145 has an outer periphery with a driving arm 145a attached thereto which extends rearwardly along the optical axis direction. Driving arm 145a extends through the gap which exists between cam ring 22 and lens guide ring 24, and includes a pin 146 provided on the front end of driving arm 145a. Pin 146 is fitted into barrier opening and closing cam groove 24c which is formed in lens guide ring 24. Recess 145b is formed on the outer periphery of driving ring 145 so that the intermediate engaging piece 143c of intermediate ring 143 will be fitted into recess 145b. Driving ring 145 is continuously biased by an opening spring 147 which is provided between driving arm 145a and cylindrical lens cover 38 in order to open barriers 140. As a result, pin 146 of driving ring 145 is brought into abutment with barrier opening and closing cam groove 24c by the rotational spring force of opening spring 147. Intermediate engaging piece 143c of intermediate ring 143 is brought into contact with the inner wall of recess 145b of driving ring 145 under the rotational biasing force of closing spring 144; in this fashion, intermediate ring 143 rotates together with driving ring 145. A barrier cover 148, which covers lens barriers 140 and which includes a photographing opening 148a, is attached to the front end of lens cover barrel 38. In a barrier mechanism constructed as detailed above, pin 146 rides on an inclined portion (i.e., a barrier opening and closing drive portion) 24d of the barrier opening and closing cam groove 24c, when the zoom lens is positioned in the accommodation position illustrated in Fig. 6A. In this fashion, driving ring 145 is rotated against the force of opening spring 147 so as to close barriers 140. Consequently, intermediate ring 143 rotates in the closing direction, together with driving ring 145, so as to rotate barriers 140 so that barrier plate portions 140a will close the light path (see Figs. 6A and 7A). When motor 270 rotates, cam ring 22 also rotates and moves along the optical axis direction, as noted above, so that the front lens group moving frame 34 will move forward (with lens cover 38) relative to lens guide ring 24. Since lens cover 38, the driven or intermediate ring 143, and driving ring 145 move forward together with front lens group moving frame 34, pin 146 will move towards the portion of the barrier opening and closing cam groove 24c that extends, parallel to the optical axis, from the inclined portion 24d of the groove 24c. As a result, driving ring 145 is rotated in the barrier opening direction under the rotational biasing force of opening spring 147 so as to rotate the intermediate ring 143 in the same direction, thereby rotating barriers 140 so as to open them (see Figs. 6B and 7B). Thereafter, even if cam ring 22 is rotated from the zooming range into the macro position, pin 146 will come into slidable contact with the portion of the barrier opening and closing cam groove 24c that extends parallel to the optical axis and will thus maintain its rotational or angular position; accordingly, barriers 140 will thus be maintained in their open position. In the embodiment which is illustrated, intermediate ring 143 is positioned between barriers 140 and driving ring 145, and closing spring 144 is positioned between intermediate ring 143 and driving ring 145 to bias the driven intermediate ring 143 towards the barrier closing direction with respect to the driving ring, so that some play (i.e., space) will be provided between the intermediate engaging piece 143c, which functionally connects intermediate ring 143 and driving ring 145, and recess 145b. Thus, when driving ring 145 is rotated in the closing direction, intermediate ring 143 is rotated in the same direction, maintaining abutment of the intermediate engaging piece 143c with one of the inner walls of recess 145b, all under the biasing spring force of closing spring 144. In this fashion, barriers 140 can be rotated into the closed position. When opposed edges of the barrier plate portions 140a of barriers 140 come into contact with each other to stop rotation of barriers 140, intermediate ring 143 will stop rotating. However, driving ring 145 continues rotating further in the closing direction, thus tensing opening spring 144, since the aforementioned play does exist between recess 145b and intermediate engaging piece 143c (due to their relative sizes). The further or excess rotation of driving ring 145, as referred to above, absorbs (i.e., compensates for) possible dimensional or tolerance type errors which arise during manufacturing and assembly of components, in order to completely close barriers 140. It should be appreciated that, as an alternative structure, it will be possible to provide spring members which bias the respective barriers 140 to open the barriers in order to provide play between the pin and the recess which functionally connect barriers 140 and driving ring 145, instead of using intermediate ring 143.

Claims: A zoom lens comprising a barrier apparatus, a stationary barrel (12) adapted to be secured to a camera body (11) having an optical axis, a rotatable cam ring (22) which is supported by said stationary barrel (12); at least two movable front and rear lens groups (15, 16) which are supported on said cam ring (22) for movement in said optical axis direction along a predetermined track in association with rotation of said cam ring (22) so as to constitute means for changing the focal length of said lens groups (15, 16) within a zoom photographing range, said lens groups (15, 16) being movable between a lens accommodation position, in which said movable lens groups (15, 16) are completely retracted, and a photographing position, in which a picture is to be taken; and a cylindrical lens cover (38) which is adapted to move, in association with said lens groups (15, 16) along said optical axis direction; said barrier apparatus comprising barriers (140) in said lens cover (38) which are adapted to open and close a photographic opening located forwardly of said movable lens groups (15, 16); and a barrier opening and closing mechanism (145, 146) positioned in said lens cover (38) and comprising means for opening and closing said barriers (140) in association with movement of said lens cover (38); characterized by a lens guide ring (24) which is arranged to move together with said cam ring (22) along said optical axis direction, wherein said cam ring (22) and said lens guide ring (24) are arranged to rotate relative to each other in association with axial movement of said cam ring (22) such as to move said front and rear lens groups, and by a driving ring (145) having a driving arm (145a), said lens guide ring (24) having a cam groove (24c) with an inclined portion (24d) for actuating said driving ring (145) by means of said driving arm (145a) coupled with said inclined portion (24d) such as to move said barriers, said driving ring (145) being biased such that said barriers are kept open when said driving ring (145) is not actuated by said inclined portion. A zoom lens in accordance with claim 1, wherein said barriers comprise a pair of barriers (140) which are rotatably mounted on said lens cover (38) via respective pivot pins (141) positioned on said lens cover (38) on a plane which is perpendicular to said optical axis. A zoom lens in accordance with claim 2, wherein said driving ring (145) is arranged to rotate in a plane which is perpendicular to said optical axis in order to open and close said pair of barriers (140), and wherein said driving arm is engaged with said inclined portion by an association member (146) which effects rotation of said driving ring (145) in association with relative movement of said lens cover (38) and said lens guide ring (24) along the optical axis direction.

Inventors: NOMURA HIROSHI, NOMURA, HIROSHI, NOMURA, HIROSHI, C/O ASAHI KOGAKU KOGYO K.K.
Applicants: ASAHI OPTICAL CO LTD, ASAHI KOGAKU KOGYO KABUSHIKI KAISHA
Application year: 1989
Main classification: G02B7
IPC codes: G02B7, G03B17