JPH0618326Y2 - Zoom lens barrel - Google Patents

Description

[Technical Field] The present invention relates to a zoom lens barrel, and particularly to a zoom lens barrel capable of remarkably shortening a storage length.

“Prior Art and Its Problems” Recently, demands for miniaturization of cameras have been extremely strong, and the width and the height have reached a limit which is limited by the size of the film and the aperture. However, with regard to thickness, the shorter the lens storage length, the more the lens group moves, and when the length of the long cam ring is unbalanced, the lens retracts, but the cam ring There is an inconvenience that the bulge does not become thin as a whole.

The purpose of the present invention is to provide a zoom lens barrel which can reduce the thickness especially when the lens is housed and can effectively cut harmful rays that do not contribute to image formation on the film. To aim.

[Outline of Device] In the conventional zoom lens barrel, the present inventor moves a lens between a use position including zooming and a storage position by a cam ring that rotates at a fixed position, which is thin. The present invention was made by solving the problem by discovering the fact that it obstructs the above.

The present invention provides a fixed barrel, a cam ring rotatably supported by the fixed barrel so as to move in the optical axis direction while rotating; a means for applying a driving torque to the cam ring; A lens guide ring that moves integrally in the optical axis direction and that rotates relative to the cam ring when the cam ring moves in the optical axis direction; and a cam for at least two front and rear movable lens groups formed on the cam ring. A groove; a lens guide groove formed on the lens guide ring corresponding to these cam grooves; and a guide pin inserted across both the lens guide groove and the cam groove to move at least two groups in front and rear. Further, the cam groove and the lens guide groove move the front and rear moving lens groups along a predetermined locus by a combined movement of the cam groove and the lens guide ring moving in the optical axis direction and relative rotation. Shape And have it; and, at the rear end of the lens guide ring, the light shielding plate that is provided for blocking the harmful rays; are characterized.

According to this zoom lens barrel, the cam ring and the lens guide ring that rotate relative to each other move forward and backward in the optical axis direction while holding the moving lens, and the relative rotation of both moves the moving lens in the optical axis direction. Even if the lengths of the cam ring and the lens guide ring in the optical axis direction are short, the moving distance of the moving lens can be made large, and thus the lens storage length can be shortened. Further, since the light shielding plate cuts harmful rays that are not involved in the image formation on the film surface, it is possible to prevent a situation in which the contrast of the image is lowered or the coloring of the color film is impaired.

INDUSTRIAL APPLICABILITY The zoom lens barrel of the present invention can be used for a lens shutter type camera in which a fixed barrel is fixed to a camera body, and an interchangeable lens type camera which can be attached to and detached from the camera body.

"Embodiment of the Invention" The present invention will be described below with reference to illustrated embodiments. In the illustrated embodiment, the zoom lens barrel of the present invention is applied to a zoom lens having a macro photographing function, and FIGS. 1 to 3 show a storage position, a wide end position, and a tele end position, respectively. From these three figures, it is obvious that the zoom lens barrel of the present invention has a short storage length.

A fixed barrel 12 is fixed to a camera body 11 of the lens shutter type camera. Reference numerals 13 and 14 denote an outer rail and an inner rail formed on the camera body 11 as film guides. According to the present invention, two front and rear movable lenses 15,
16 can be retracted and stored to a state of being extremely close to the outer rail 13 and the inner rail 14, and the annular member such as the cam ring is also short and the storage length is short.

The fixed barrel 12 has an outer helicoid (inner helicoid) 1
8 is fixed via a fixing screw 19. The outer helicoid 18 has an inner helicoid (outer peripheral helicoid).
20 is screwed together, and the cam ring 22 is fixed to the inner circumference 20 of the inner helicoid via fixing screws 21 (see FIG. 4). As shown in FIG. 4, the inner helicoid 20 is formed with a gear 20b that is inclined at the same angle as the inclination of the helicoid crest 20a. A pinion that meshes with the gear 20b and a motor that rotationally drives this The cam ring 22 is rotationally driven in the forward and reverse directions via a not shown).
Therefore, when the cam ring 22 is rotationally driven, it moves in the optical axis direction according to the lead of the helicoid crest 20a.

A lens guide ring 24 is fitted on the inner circumference of the cam ring 22. A straight guide plate 26 is fixed to the rear end of the lens guide ring 24 by a fixing screw 25. The straight guide plate 26 has a part of the outer circumference formed on the inner surface of the fixed barrel 12. It is engaged with the groove 27. The lens guide ring guide groove 27 is a linear groove parallel to the optical axis in this embodiment. And this straight guide plate 26
And an annular groove 28 formed between the lens guide ring 24 and the rear end of the lens guide ring 24.
An inward flange 29 formed at the rear end of the cam ring 22 is fitted in the cam ring 22 so as to be relatively rotatable.

Therefore, the lens guide ring 24 has the lens guide ring guide groove 27.
Although rotation is restricted by the cam ring 22, the cam ring 22 always moves integrally with the cam ring 22 in the optical axis direction, and the cam ring 22 can rotate with respect to the lens guide ring 24.

The front and rear two groups of movable lenses 15 and 16 include a lens guide ring 24.
The front lens group frame 30 and the rear lens group frame 31 located inside
It is fixed to each. The front lens group frame 30 is helicoidally coupled to a helicoid ring 33 fixed to a shutter block 32. The shutter block 32 is fixed to the front group moving frame 34, and at least three guide pins 35 are provided on the outer peripheral portion of the front group moving frame 34. Similarly, at least three guide pins 36 are provided on the outer periphery of the rear lens group frame 31. Note that the guide pins 35 and 36 are drawn overlapping in FIGS. 1 and 3 for convenience of illustration.

As is well known, the shutter block 32 has a drive pin 32a at an angle corresponding to a distance signal from a distance measuring device to a subject.
Is rotated to rotate the front lens group frame 30 coupled to the drive pin 32a and move it in the optical axis direction according to the helicoid to adjust the focus. Further, the shutter blade 32b is operated according to the brightness signal of the subject.

Reference numeral 38 denotes a lens cover cylinder provided integrally with the front group moving frame 34,
Reference numeral 39 is a decorative cylinder that covers the outer circumferences of the lens guide ring 24 and the cam ring 22 protruding from the main body shell 11a.

A front group cam groove 41 and a rear group cam groove 42, through which the guide pins 35 and 36 are inserted, project from the cam ring 22, respectively, and the lens guide ring 24 has each of the front group cam groove 41 and the rear group cam groove. Lens guide grooves 43 corresponding to the grooves 42, respectively.
And 44 are drilled. In this embodiment, the lens guide grooves 43 and 44 are both linear grooves parallel to the optical axis. The guide pin 35 is inserted across the front group cam groove 41 and the lens guide groove 43, and the guide pin 36 is inserted across the rear group cam groove 42 and the lens guide groove 44.

The shapes of the front group cam groove 41 and the lens guide groove 43, and the rear group cam groove 42 and the lens guide groove 44 are respectively the movements of the cam ring 22 and the lens guide ring 24 in the optical axis direction as the cam ring 22 rotates. The relative rotation of the cam ring 22 and the lens guide ring 24 allows the movable lenses 15 and 16 to be given a predetermined movement path in the optical axis direction. In FIG. 4, the section 1 of the front group cam groove 41 and the rear group cam groove 42 is a zooming section, 2 is a macro transition section following the tele end of the zooming section 1, and 3 is a storage section following the wide end of the zooming section 1. Is.

A light blocking plate 45 is also provided at the rear end of the lens guide ring 24. The light shielding plate 45 cuts off harmful rays that enter the inner wall surface of the lens barrel from the peripheral edge of the moving lens 16 and are not involved in image formation on the film surface. The peripheral portion is formed so as to extend in a direction orthogonal to the optical axis, and its inner end extends to a position corresponding to the peripheral portion of the moving lens 16. When harmful rays enter the inner wall surface of the lens barrel from the peripheral portion of the moving lens 16, they are reflected by the inner wall surface of the lens barrel and reach the film surface from the aperture 46. It has a bad effect such as poor coloring of the film. This phenomenon is likely to occur when the lens is at the tele end position. That is, at the tele end position, the moving lens 15,
Since 16 is extended to the maximum forward, the internal space of the lens barrel is expanded. Therefore, the harmful rays that have passed through the peripheral portion of the moving lens 16 spread to the entire expanded internal space and are reflected on the inner wall surface of the lens barrel in a complicated manner before reaching the film surface. The light blocking plate 45 effectively cuts the incoming harmful light rays at the tele end side position. This shading plate 45 is
It can also be formed separately from the linear guide plate 36.

The guide pins 35 and 36 (hence the cam grooves 41, 42,
And the lens guide grooves 43 and 44) are at least three because the lengths of the rear lens group frame 31 and the front lens group moving frame 34 to be fitted to the lens guide ring 24 cannot be long, and therefore the tilting with respect to these optical axes is not possible. This is to prevent Therefore, the guide pin may be one or two when there is no risk of falling, such as when the fitting length can be long or the structure in which the lens group is guided by the guide pole.

The present zoom lens barrel having the above-described configuration includes the inner helicoid 20.
When the inner helicoid 2 is rotated, the outer helicoid 18 meshing with the inner helicoid 2 is fixed.
0, that is, the cam ring 22 moves in the optical axis direction while rotating according to the lead of the helicoid crest 20a, and the lens guide ring 24
Both move in the optical axis direction. With this movement in the optical axis direction,
Due to the relationship between the cam grooves 41 and 42 and the lens guide grooves 43 and 44, the cam ring 22 rotates with respect to the lens guide ring 24, and the relative rotation causes the movable lenses 15 and 16 to move in the optical axis direction. This allows the moving lenses 15 and 16
Can be moved from the housed state of FIG. 1 to the telephoto end state of FIG. 3, and even in the housed state, the cam ring 22 and the lens guide ring 24 do not project, and the housed length is extremely short. When the movable lenses 15 and 16 are extended to the telephoto end position, the internal space of the lens barrel expands and the harmful light rays easily enter the peripheral space of the movable lens 16 into the expanded space. Cut by. Therefore, only the effective rays necessary and sufficient for forming a correct image reach the film surface.

The effect of shortening the storage length is that the cam ring 22 advances and retreats in the optical axis direction as it is driven to rotate, the lens guide ring 24 moves in the optical axis direction together with the cam ring 22, and the moving lens 15 moves.
And 16 are supported by the cam ring 22 and the lens guide ring 24, and the relative movement of the cam ring 22 and the lens guide ring 24 causes the movable lenses 15 and 16 to move in the optical axis direction. This is because the shapes of 41 and the rear group cam groove 42, and the lens guide grooves 43 and 44 can be determined. The cam ring 22 and the lens guide ring 24 can be shorter than the moving amounts of the moving lenses 15 and 16, and the overall thickness can be reduced.

In other words, according to the present invention, the amount of movement of the movable lenses 15 and 16 in the optical axis direction is first secured by the amount of movement of the cam ring 22 in the optical axis direction, that is, the lead of the helicoid crest 20a of the inner helicoid 20. It is possible to compensate for the shortage of the movement amount due to the lead by the front group cam groove 41 and the rear group cam groove 42. Or helicoid mountain 20a
If the movement amount due to the lead is larger, the excess movement amount may be subtracted by the front group cam groove 41 and the rear group cam groove 42.

The relationship between the lead of the helicoid crest 20a and the front group cam groove 41 and the rear group cam groove 42 is particularly clear with reference to the storage section 3 of the rear group cam groove 42. This storage section 3
Is oriented in a direction orthogonal to the optical axis on the cam ring 22, and if the cam ring 22 only rotates, the moving lens 16 cannot be retracted. However, according to the present invention, since the cam ring 22 itself moves in the optical axis direction with rotation and the moving lens 16 is supported by the cam ring 22, the rear group cam groove 42 is in a plane orthogonal to the optical axis. However, the movable lens 16 can be retracted to the storage position as the cam ring 22 rotates. This means that the front group cam groove 41 and the rear group cam groove 42 formed on the cam ring 22 can be laid down as a whole (the inclination angle from the optical axis direction can be increased), and thus the front group cam groove 41. The length of the rear group cam groove 42 in the optical axis direction can be shortened to shorten the cam ring 22, and the moving accuracy of the moving lenses 15 and 16 can be improved.

The macro transition section 2 of the cam grooves 41 and 42 is inclined in the same direction as the inclination direction of the helicoid crest 20a, but this is because the lens movement amount from the tele end is small.

In the above embodiment, the lens guide ring guide groove 27 and the lens guide grooves 43 and 44 are all formed as straight grooves. Forming them from straight grooves has the advantage of facilitating the machining of these grooves and the setting of the shapes of the front group cam groove 41 and the rear group cam groove 42. However, the present invention provides the lens guide ring guide groove 27 and It does not prevent forming the lens guide grooves 43 and 44 into a shape other than a straight groove. In short, the rotation of the cam ring 22 causes the lens guide ring 24 to move together in the optical axis direction (including rotation at this time), and the relative rotation of the cam ring 22 and the lens guide ring 24 causes the moving lens 15 to move. These lens guide ring guide grooves 2 are arranged so that 16 moves along the optical axis in a predetermined locus.
The shapes of 7, the lens guide grooves 43 and 44, the front group cam groove 41, and the rear group cam groove 42 may be determined.

In the embodiment, the inner helicoid 20 and the cam ring 22 are composed of separate members, and they are fixed by the fixing screws 21, but they can be integrally molded with a resin material.
Further, in the embodiment, the moving lenses are the front and rear two groups, but the present invention can of course be applied to a zoom lens barrel having three or more moving lenses. In this case, a cam groove for each moving lens may be formed in the cam ring 22. Such a zoom lens barrel can be used, for example, as an interchangeable lens for a higher-grade single-lens reflex camera.

[Advantage of Invention] As described above, in the zoom lens barrel of the present invention, the cam ring that holds the moving lens and the lens guide ring move in the optical axis direction, respectively, and the cam ring and the lens guide ring move relative to each other. Since the moving lens moves in the optical axis direction due to the rotation, the storage length of the moving lens can be shortened, and the camera (lens) can be miniaturized, especially thin. In addition, since a light shield plate is provided at the rear end of the lens guide ring, harmful rays that enter the lens barrel are cut by this, and the effective rays necessary and sufficient to form a correct image on the film surface. Can only be reached.

[Brief description of drawings]

1 to 3 are upper half sectional views showing an embodiment of a zoom lens barrel of the present invention. FIG. 1 is a retracted state, FIG. 2 is a wide end state, and FIG. 3 is a tele end state. FIG. 4 and FIG. 4 are development views of the cam ring, the lens guide ring, and the cam ring helicoid. 11 ... Camera body, 12 ... Fixed tube, 15, 16 ...
… Moveable lens, 18 …… Outside helicoid (inner circumference helicoid), 20 …… Inside helicoid (outer circumference helicoid), 2
2 ... Cam ring, 24 ... Lens guide ring, 26 ... Straight guide plate, 27 ... Lens guide ring guide groove, 30 ... Front group lens frame, 31 ... Rear group lens frame, 32 ... Shutter block , 33 ... helicoid ring, 34 ... front group moving frame, 35, 36 ... guide pin, 41 ... front group cam groove,
42 ... Rear group cam grooves, 43, 44 ... Lens guide grooves.
45 ... Shading plate.

Claims (2)

[Scope of utility model registration request] 1. A fixed barrel; a cam ring rotatably supported by the fixed barrel so as to move in the optical axis direction while rotating; a means for applying a driving torque to the cam ring; And a lens guide ring that moves integrally in the optical axis direction and that rotates relative to the cam ring when the cam ring moves in the optical axis direction; at least two front and rear movable lens groups formed on the cam ring. A cam groove; a lens guide groove formed on the lens guide ring in correspondence with these cam grooves; and a movement of at least two groups, front and rear, having guide pins inserted over both the lens guide groove and the cam groove. Further, the cam groove and the lens guide groove move the front and rear moving lens groups along a predetermined locus by a combined movement of the cam groove and the lens guide ring in the optical axis direction and relative rotation. Shape And a light-shielding plate that blocks harmful rays at the rear end of the lens guide ring. 2. The lens guide ring according to claim 1, wherein the lens guide ring includes a straight guide plate which is guided by the fixed cylinder so as to be able to move straight in the optical axis direction, and the light shielding plate extends the straight guide plate inward. The formed zoom lens barrel.