Flexible printed circuit board for a camera

Abstract: The invention relates to a flexible printed circuit board assembly for a camera, comprising an annular lens guide ring (24) adapted to be moved linearly along the optical axis of the lens. The annular guide ring (24) has at least one elongated groove (82) for retaining a flexible printed circuit board (81) positioned within said groove (82).

Description: This invention relates to a flexible printed circuit board assembly as described in the generic part of the independent claim. An assembly of this kind is known from WO-A-87/07038 which describes a camera having a zoom lens with a rotatable cam ring encompassing the flexible printed circuit board assembly. The zoom lens also comprises an annular ring adapted to be moved in optical axis direction within the cam ring. The problem to be solved by the present invention is to provide a flexible printed circuit board assembly connecting camera components between a position inside and a fixed position outside said annular ring without having an adverse influence on the operation of other components and the optical system. The invention solves this problem by the features given 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 a developed or plan view of a cam ring, a lens guide ring, and an inner helicoid ring; and Fig. 6 is a partially cut away or broken prospective view of a mechanism for housing a flexible printed circuit board connected to the shutter unit of a zoom lens barrel, as shown in Figs. 1-4. 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 plate 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. 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 11a 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. As shown in Fig. 5, the section ℓ 1 of the front lens group cam groove 41 and the rear lens group cam groove 42 represents the normal photographing range (i.e., the zooming section), section ℓ 2 represents the MACRO transferring section, which is connected to the TELE extremity position of zooming section ℓ 1, and section ℓ 3 represents a lens accommodating or retracted section connected to the WIDE extremity position of zooming section ℓ 1, respectively. MACRO transferring section ℓ 2 has a lead angle which is opposite to the angle of inclination of zooming section ℓ 1, with respect to a direction which is parallel to the optical axis. Specifically, assuming that the lead angle of the zooming section ℓ 1 is positive (+), then the lead angle of the MACRO transferring section ℓ 2 will be negative (-). 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. Movement of the two lens groups is best illustrated in Figure 6. As shown, rings 22 and 24 move over substantially the same distance along the optical axis direction. Thus, 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 lla of the camera body or from the cylindrical lens cover 38. Specifically, cam ring 22 rotates and moves along the optical axis direction in accordance with the lead angle of helicoid teeth 20a. Accordingly, the axial lengths of cam grooves 41 and 42 can be shorter than the largest axial displacement L1 of lenses 15 and 16, by an amount which corresponds to the axial displacement L2 of cam ring 22. In other words, the total length of cam ring 22 can be shorter than the largest displacement L1 of the lenses by an amount which corresponds to the axial displacement L2 of cam ring 22. On the other hand, known cam ring 50 does not move along the optical axis direction. Consequently, in such a known cam ring 50, the axial lengths of cam grooves 51 and 52 correspond to the axial displacement of the moving lenses (i.e., to the movement of cam pins 53 and 54), and, accordingly, the axial length of cam ring 50 must be equal to or greater than the largest displacement of the lenses. In the present structure, even if lens displacement effected by cam grooves 41 and 42 is decreased by reducing the lead angles of cam grooves 41 and 42, axial displacement effected by the lead angle of the helicoid teeth 20a will not change. Specifically, assuming that the lead angles of cam grooves 41 and 42 are zero, the displacement of lenses 15 and 16 with respect to cam ring 22 will also become zero, but lenses 15 and 16 will be finally moved by a displacement which corresponds to the lead angle of helicoid teeth 20a, insofar as cam ring 22 will axially move in accordance with the lead angle of helicoid teeth 20a. Thus, even if the rear lens group cam groove 42 is provided in a plane which is perpendicular to the optical axis, lens 16 can be retracted into the accommodation position by rotating cam ring 22. This means that the lead or inclination angles of the rear lens group cam groove 42 and the lens guide groove 44 formed on cam ring 22 can be significantly reduced, so that the axial lengths of rear lens group cam groove 42 and lens guide groove 44 can be reduced in order to shorten the cam ring 22 and so as to increase the resulting accuracy of movement of moving lenses 15 and 16. The relationship between the lead angles and the cam grooves 41 and 42 becomes clear when looking at accommodation section ℓ 3 of rear lens group cam groove 42. section ℓ 3 of groove 42, as seen in Fig. 5, is oriented so that it is perpendicular to the optical axis of cam ring 22. If cam ring 22 could only rotate, and could not also move in the optical axis direction, moving lenses 15 and 16 could not be retracted. However, in accordance with the present invention, since cam ring 22 can move along the optical axis direction, it is possible to retract moving lenses 15 and 16 even when the groove (i.e., slot) is perpendicular to the optical axis, unlike the situation with the illustrated prior art structure. It is important to remember that the necessary displacement of lenses 15 and 16 from the TELE extremity position to the macro-photographing range is very small in a zoom lens barrel as used in accordance with the present invention. In order to decrease the displacement of lenses 15 and 16, yet still achieve necessary displacement of the lenses, excess displacement is eliminated by the disclosed configuration of cam grooves 41 and 42. Specifically, the lead angles of macro-transferring section 2 of cam grooves 41 and 42 are negative (-) to provide a negative (-) lead angle. This results in the shorter displacement L4 of rear lens group 16 (i.e., of guide pin 36) with respect to the axial displacement of cam ring 22 in the macro-transferring section ℓ 2, than occurs in the zooming section ℓ 1. That is, the displacement of moving lenses 15 and 16 with respect to angular displacement of cam ring 22 can be reduced. With such an arrangement, since the displacement of lenses 15 and 16 relative to the angular displacement of cam ring 22 is very small, it is possible to provide a sufficient angular displacement of cam ring 22 so as to result in highly precise movement of the lenses. Further, since the lead angle of the macro-transferring section ℓ 2 is minus (e.g., a negative), the total length of cam ring 22 can be reduced. In the illustrated embodiment referred to above, guide groove 27, as well as lens guide grooves 43 and 44, are all straight grooves. However, it should be appreciated that the present invention is not limited to the use of such straight grooves. Specifically, the present invention does not exclude, prevent, nor eliminate the possibility of providing guide groove 27 and lens guide grooves 43 and 44 of shapes which are other than straight, e.g., of an angled configuration. To summarize, the shapes of guide groove 27, cam grooves 41 and 42, and lens guide grooves 43 and 44 are determined so that the lens guide ring 24 will move along the optical axis direction, together with the cam ring 22, in accordance with rotation of the cam ring, and so that lenses 15 and 16 will move in the optical axis direction, along a predetermined track, in accordance with relative rotation (and axial movement) of cam ring 22 and lens guide ring 24. It should be noted that lens guide ring 24 could be provided to rotate if desired. This could be accomplished, e.g., by forming lens guide groove 27 at a predetermined angle of inclination with respect to the optical axis, rather than parallel thereto, as is shown in Fig. 5. Even if ring 24 is rotatable, however, rings 22 and 24 can still be rotatable with respect to each other, since they can be formed so as to rotate over different angular amounts with respect to each other. At least three guide pins 35 and at least three guide pins 36 are provided (in engageable association with cam grooves 41, 42 and lens guide grooves 43, 44) in order to prevent rear lens group frame 31 and front lens group moving frame 34 from being inclined with respect to the optical axis, which might occur due to the otherwise insufficient length of engagement with respect to lens guide ring 24. Thus, if a sufficient engagement length can be provided, or if there is the possibility that the incline of rear lens group frame 31 and front lens group moving frame 34 can be eliminated by providing additional guide poles or similar structure, the number of guide pins can be reduced to either one or two. Although the male helicoid ring 20 and the cam ring 22 are formed of separate members which are interconnected by set screws 21, in the illustrated embodiment, they could alternatively be molded as a single integral piece of synthetic resin or similar material. The following discussion is directed to a guide mechanism for the flexible printed circuit board 81, which supplies an operating signal to shutter block 32. As illustrated in Fig. 3, the flexible printed circuit board 81 is connected to control circuit board 54, and is positioned or introduced within a space defined by stationary barrel 12 and cam ring 22 through a window formed in stationary barrel 12. The flexible PC board 81 is then extended rearwardly within the space located substantially along the inner surface of stationary barrel 12, so that it is introduced rearwardly through the gap which exists between projections 26a of the linear movement guide plate 26. The flexible PC board 81 is then bent forwardly, at a first bent portion 81a, and extends along the outer surface of guide plate 26 and along the inner circumference thereof, in a generally forward direction. Lens guide ring 24 is provided, along its inner periphery, with a substantially linear (flexible PC board) guide groove 82 having a bottom or base extending along (i.e., parallel to) the optical axis direction, as shown in Fig. 6. The flexible PC board 81, which extends along the inner side face of guide plate 26, extends forwardly through guide groove 82. Board 81 is bent backwardly or rearwardly at a second bent portion 81b, in the vicinity of the front end of guide groove 82 of lens guide ring 24, so that it will be superimposed onto the remaining portion of flexible PC board 81. The flexible PC board 81 extends beyond the rear ends of shutter unit 32, the lens guide cylinder 38, and the front lens groove frame 30, and is then bent forwardly at a third bent portion 81c so that it will be connected to shutter block 32. The flexible PC board 81 includes contact sections al, a2, and a3. Portion al comes into contact with the rear side face of guide plate 26 and portion a2 comes into contact with the bottom of guide groove 82. Portion a3 is located in the vicinity of the second bent portion 81b. Flexible board 81 is connected along at least the above-mentioned portions al, a2, and a3, to respective contacting members by a suitable adhesive or mechanical connector. Of course, the board can be connected to any adjacent camera components, as long as the board retains its flexibility, yet remains secured to the camera; similarly, a greater or lesser number of sections can be so adhered. Flexible board 81 is deformable, in accordance with zooming operation of the zoom lens, as detailed hereinafter. When the zoom lens is moved from its accommodation position, as shown in Fig. 1, to the WIDE extremity position shown in Fig. 2, and thereafter to the TELE extremity position as shown in Fig. 3, by the zooming motor, cam ring 22 moves along the optical axis direction while rotating, so that lens guide ring 24 will move, without rotating, together with cam ring 22. As a result, the space behind guide plate 26 is expanded, and the loop formed by the bent or deformed portion 81a of board 81 becomes relatively large. However, the extent of the expansion of the loop of bent portion 81a is relatively small, since the expansion of the loop occurs while the flexible board 81 moves in the direction of movement of lens guide ring 24. Further, because moving lens 15 and, accordingly, shutter block unit 32, are moved forward relative to lens guide ring 24 by the relative rotation of cam ring 22 and lens guide ring 24, which occurs at the same time as axial movement of cam ring 22, lens guide ring 24 and shutter block unit 32, the space between the front lens group frame 30 and the guide plate 26 is expanded during such forward movement of the cam ring. Simultaneously, the loop diameter of flexible PC board 81 expands while the third bent portion 81c moves forwardly, with the extent of expansion being small. Accordingly, movement and deformation of bent portions 81a and 81c caused by axial movement of shutter unit 32 causes the flexible PC board 81 to extend without having an adverse influence on the operation of other components and the optical system, i.e., the relatively small loop expansion does not interfere with the operation of other camera elements. Since the second bent portion 81b is bonded, at its periphery, to guide groove 82, no relative displacement of the second bent portion 81b with respect to the lens guide ring 24 will occur. Even when in the MACRO or TELE extremity positions, in which the loop of bent portions 81a and 81c is the largest, because the upper portions of these bent portions are adhered to plate 26 (or, alternatively, to stationary barrel 12) and to flexible PC board guide groove 82, respectively, neither inclination of the bent portions 81a and 81b with respect to the optical axis, nor the entrance of bent portions 81a and 81b into the light path, will occur, thereby resulting in a lack of interference with other camera components. To the contrary, when the zoom lens is returned from the TELE extremity to the WIDE extremity or the accommodation position, the space between shutter unit 32 and guide plate 26, and the space behind guide plate 26, are both reduced. Simultaneously, the length of the portions of the flexible board 81 that are superimposed on each other increases, so that the bent portions 81a and 81c are moved rearwardly to decrease their loop diameters. Specifically, the length of superimposition of the flexible PC board 81 increases and the loop diameter of the bent portions 81a and 81c decreases in accordance with rearward movement of shutter block unit 32. Accordingly, there is no possibility that the flexible PC board will interfere with other moving members, or will enter into the light path.

Claims: A flexible printed circuit board assembly for a camera lens, comprising an annular ring (24) adapted to be moved along the optical axis of the lens and a flexible printed circuit board (81) adapted to electrically connect camera components (32, 54) between a position inside said annular ring (24) and a fixed position outside said annular ring (24), said flexible printed circuit board (81) being bent back upon itself to form several bent portions (81a, 81b), characterized in that said annular ring (24) is a lens guide ring linearly movable along said optical axis and being provided along its inner periphery with a substantially linear retaining groove (82) having a bottom extending parallel to the optical axis direction, said flexible printed circuit board (81) being attached to said guide groove bottom at a portion (a2) between two of its bent portions (81a, 81b). An assembly in accordance with claim 1, characterized by an annular ring movement guide plate (26) attached to a rear surface of said lens guide ring (24), said plate (26) including an extension (45) for preventing light from reaching the film plane of said camera. An assembly in accordance with claim 1 or 2, characterized by a first flexible printed circuit board portion adapted to extend rearwardly along the inner surface of a stationary outer barrel (12), a second portion extending generally forwardly along an inner surface of said lens guide ring (24), a third portion extending rearwardly to be partially superimposed upon said second portion, and a fourth portion flexibly connected to a shutter block (32) in said lens guide ring (24). An assembly in accordance with claim 3, characterized in that said fourth portion extends forwardly within said barrel (12) and is partially superimposed upon said third flexible printed circuit board portion. An assembly in accordance with any of claims 2 to 4, characterized in that an additional portion of said flexible printed circuit board plate (81) extends rearwardly of said guide plate (26), between said first and second portions. An assembly in accordance with any of the foregoing claims, characterized in that said flexible printed circuit board (81) is secured to said rear end of said lens guide ring (24). An assembly in accordance with any of the foregoing claims, characterized in that said flexible printed circuit board (81) is secured to the front end of said lens guide ring (24). An assembly in accordance with any of the foregoing claims, characterized in that said flexible printed circuit board (81) is adhered to said flexible printed circuit board guide groove (82) at least along a portion of said flexible printed circuit board (81) that extends forwardly from said lens guide ring (24).

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