JP2577259Y2 - Zoom lens barrel - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a zoom lens barrel having at least two front and rear lens groups, and more particularly, to a linear guide mechanism thereof.

"Prior art and its problems" In a zoom lens barrel, generally, at least two front and rear lens groups are guided straight in the optical axis direction, and these lens groups are moved in the optical axis direction while changing the air gap. , The focal length is changed.

Conventionally, the straight guide mechanism for the front and rear lens groups is
The rear lens group is guided to a fixed lens barrel or a linear member guided by the fixed lens barrel. That is,
Both the front group lens and the rear group lens were guided straight by the same guide member. However, according to this linear guide mechanism, tension, pressure,
When an external force such as torsion is applied, only the front group lens is displaced, and as a result, the positional relationship with the rear group lens is out of order, which may adversely affect focusing. In particular, a change in the distance between the front and rear groups has high sensitivity for focusing.

For example, consider a case in which the front group lens is pressed against a window glass to take a picture in order to prevent camera shake when the slow shutter is released. Since the front group lens is guided by the cam or the lead member, when pressed by a strong force in the optical axis direction, the front group lens moves by the clearance of the cam or the lead member and tries to rotate according to the cam or the lead member. At this time, if the entire structure supporting the front group is elastically deformed, the elastic deformation occurs in relation to the front group lens and independently of the rear group lens, which adversely affects the focus.

[Purpose of the Invention] The present invention aims to obtain a straight-ahead guide mechanism that has little effect on focusing even when an external force is applied to the front group lens.

"Outline of the invention" The present invention revises the straight guide mechanism of the front group lens and the rear group lens, which were conventionally guided straight independently of each other, and guides the rear group lens straight ahead for the front group lens guided straight. It was made based on the idea of.

That is, according to the present invention, when the front lens group and the rear lens group are rotated on the same annular member, and the front lens group and the rear lens group are rotated relative to the annular member in the same direction, the same lens in the optical axis direction is formed. The front group lens barrel supporting the front group lens, and a fixed lens barrel or a straight member guided straight to the fixed lens barrel, a straight guide mechanism for the front group lens is provided. A straight guide mechanism for the rear group lens is provided between the rear group lens frame supporting the rear group lens and the front group lens barrel.

According to this linear guide, when an external force is applied to the front lens group and the linear guide member is rotated by elastic deformation, the rotation is transmitted to the rear lens group. That is, since the rear lens unit rotates together with the rotation of the front lens unit,
The change in the lens interval between the front group and the rear group can be kept small.

"Embodiments of the Invention" The present invention will be described below with reference to the illustrated embodiments. In this embodiment, the present invention is applied to a zoom lens barrel proposed by the present applicant in Japanese Patent Application No. 1-281116. This zoom lens barrel has a small number of parts, but has excellent shock resistance when a shock is applied to the front group. The cam ring that is driven to rotate has an inner cam groove and a female helicoid (multi-thread). The female helicoid is screwed with the helicoid of the front lens barrel that is guided straight, and the cam groove is fitted with the cam roller of the rear lens frame that is also guided straight. . The inner cam groove of the cam ring and the female helicoid are such that when the front group lens and the rear group lens are relatively rotated in the same direction with respect to the cam ring, the movement amounts are different but the movement in the same direction in the optical axis direction occurs. Is formed.

A helicoid ring 12 is fixed to a fixed lens barrel 11 integrated with the camera body, and a male helicoid 10a formed on an outer peripheral surface of the cam ring 10 is fixed to a female helicoid 12a of the helicoid ring 12.
Is screwed. A female helicoid 10b and an inner cam groove 10c are formed inside the cam ring 10, and a male helicoid 13a of the front lens barrel 13 is screwed into the female helicoid 10b. As is apparent from FIG. 3, this female helicoid 10b
And the inner cam groove 10c is inclined macroscopically in the same direction. The front end of the inner cam groove 10c has a cam ring 1
0 is open to the end face. A rectilinear guide plate 14 is located at the rear end of the cam ring 10, and a radial projection 14 a of the rectilinear guide plate 14 is fitted in a rectilinear guide groove 11 a formed in the fixed lens barrel 11. A straight guide ring 15 is fixed to the straight guide plate 14, and the cam ring 10 is rotatable with respect to the straight guide ring 15.

The rectilinear guide ring 15 is a member whose rotation is restricted, and a linear key 15a having an arcuate cross section and an open front end and directed in a direction parallel to the optical axis is provided at the periphery thereof. Three are provided at angular intervals.

A shutter holding frame (guide member) 13c to which a rear end portion of an annular shutter unit 16 is fixed is fixed to the front lens barrel 13, and a helicoid ring 17 provided integrally with an inner peripheral portion of the shutter unit 16 is provided. The front group lens frame 18 holding the front group lens is screwed. The shutter unit 16 has its drive pin 16a engaged with a driven pin 18a integrated with the front lens frame 18. As is well known, the drive pin 16a is driven to rotate by an angle corresponding to the distance measurement signal from the distance measurement device, and this rotation is transmitted to the front group lens frame 18 via the driven pin 18a,
While the front group lens frame 18 (front group lens L1) rotates, the shutter unit 16 moves in the optical axis direction to perform focusing. Further, the shutter unit 16 opens and closes the shutter blade 16b according to the luminance signal of the subject.

As shown in FIGS. 1 and 2, the shutter holding frame 13c of the front lens barrel 13 has an annular shape as a whole, and has three front group rectilinear grooves 13d formed at equal angular intervals on its peripheral surface. have. The straight groove 13d for the front group is provided with the straight key 1 of the straight guide ring 15.
5a is slidably fitted, and the shutter holding frame 13c, that is, the front lens barrel 13 is guided straight in the optical axis direction by this fitting relationship. The shutter holding frame 13c is further provided with a rear group straight groove 13e located between the front group straight grooves 13d.

The rear lens group frame 19 supporting the rear lens group L2 has a cam roller 19a that protrudes in the radial direction.
The cam ring 10 is fitted in the cam groove 10c formed on the inner surface. The rear group lens frame 19 is formed with a rectilinear key 19b that fits into the rectilinear groove 13e for the rear group of the shutter holding frame 13c. The rectilinear key 19b, like the rectilinear key 15a of the rectilinear guide ring 15, has an arc-shaped cross section oriented in a direction parallel to the optical axis and has an open front end surface.

The cam roller 19a of the rear group lens frame 19 fits into a recess 13b formed on the rear end surface of the front lens barrel 13 during assembly. This is a structure for simultaneously fitting the cam roller 19a from the front open end of the inner cam groove 10c when screwing the male helicoid 13a on the outer periphery of the front lens barrel 13 with the female helicoid 10b of the cam ring 10. After the assembly, the rotation of the cam ring 10 causes the front lens barrel 13 to move independently in the optical axis direction according to the helicoids 10b and 13a, and the rear lens frame 19 to move independently according to the cam groove 10c. The direction of the movement is always the same when the cam ring 10 rotates in one direction, and the amount of the movement is different so as to satisfy the set zoom locus.

The zooming operation of the zoom lens barrel having the above configuration is as follows. When the cam ring 10 is rotationally driven, the male helicoid
The cam ring 10 itself moves in the optical axis direction according to the relationship between 10a and the female helicoid 12a. At the same time, the front group lens barrel 13 (front group lens L1) moves straight in the optical axis direction due to the screwing relationship between the female helicoid 10b and the male helicoid 13a, and the straight guide mechanism of the shutter holding frame 13c and the straight guide ring 15. Also cam ring 10
Is rotated, the cam groove 10c on its inner surface and the rear group lens frame 19
Of the rear group lens frame 1
The rear group lens frame 19 (rear group lens L2) moves in the optical axis direction by the rectilinear guide mechanism 9 and the rectilinear guide ring 15, and zooming is performed.

And in the above zoom lens barrel, the front group lens
It is assumed that an external force, for example, a pressing force in the optical axis direction is applied to the front lens barrel 13 supporting L1. Then, the front lens barrel 13
Since the front group lens barrel 13 is screwed to the cam ring 10, the front group lens barrel 13 tries to rotate, and as a result, a force is applied to deform the straight key 15a in the circumferential direction via the front group straight groove 13d. And straight key 1
When 5a is elastically deformed in the circumferential direction, the position of the front lens barrel 13 guided by the helicoid 13a in the optical axis direction changes.
However, even if the rectilinear key 15a is elastically deformed, the rear group lens frame 19 has its rectilinear key 19b fitted into the rectilinear groove 13e for the rear group of the shutter holding frame 13c. And moves in the same direction as the front group lens L1. That is, when the straight key 15a is bent, the change in the distance between the front lens group L1 and the rear lens group L2 is small, and the adverse effect on focusing is minimized. This effect is apparent when compared with the case where the rear group lens L2 is guided straight ahead independently of the front group lens L1. In this case, the rear lens group L2
Does not move, the change in the distance from the front group lens L1 changes greatly.

[Effects of the Invention] As described above, according to the present invention, the front lens group is guided straight by the rear lens group with respect to the front lens group guided straight by the fixed lens barrel, so that the front lens group is rotated by external force. However, the rotation is transmitted to the rear group lens. For this reason, the change in the lens interval between the front group and the rear group can be reduced, and the influence on the focus can be reduced.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view showing a zoom lens barrel according to an embodiment of the present invention, particularly around a shutter unit inside a front lens barrel. FIG. 2 is an exploded perspective view of the shutter unit and a shutter holding frame. FIG. 3 is an exploded perspective view of a main part, and FIG. 4 is a longitudinal sectional view of the entire lens barrel. The upper half shows a lens housed state, and the lower half shows a lens protruding state (telescopic state). FIG. 5 is an enlarged sectional view of a main part of the lens barrel shown in FIG. 10 cam ring, 11 fixed lens barrel, 11a straight guide groove, 1
2 Helicoid ring, 12a Female helicoid, 13 Front lens barrel, 13a Male helicoid, 13c Shutter holding frame (guide member), 13d Straight groove for front group, 13e Rear Straight groove for group, 14 ... Straight guide plate, 15 ... Straight guide ring, 15a ...
… Straight key, 16… Shutter unit, 17… Helicoid ring, 18… Front group lens frame, 19… Rear group lens frame, 19a
… Cam roller, 19b …… Straight key.

Claims (4)

(57) [Scope of request for utility model registration] 1. A zoom lens barrel having at least two front and rear movable lenses, wherein the two front and rear movable lens groups are respectively guided straight in the optical axis direction. The lens and the rear group lens are supported by the same annular member in such a manner that when the front group lens and the rear group lens are relatively rotated in the same direction with respect to the annular member, they move in the same optical axis direction. And a front-group lens linear guide mechanism provided between the front-group lens barrel supporting the front-group lens and the fixed barrel or a straight-moving member guided straight to the fixed barrel, and supporting the rear-group lens. A zoom lens barrel comprising a rear-group lens linear guide mechanism provided between the rear-group lens frame and the front-group lens barrel. 2. The zoom lens barrel according to claim 1, wherein the linear guide mechanism for the front lens group includes a linear key in a direction parallel to the optical axis, the key having an open front end. A zoom lens barrel comprising: a guide ring; and a front group straight groove formed in a guide member integrated with the front lens barrel, which fits into a straight key of the straight guide ring. 3. The zoom lens barrel according to claim 2, wherein the rectilinear guide mechanism of the rear group lens includes: a rectilinear groove for the rear group formed in the guide member; A straight-moving key formed in the group lens frame and having a front end opened in a direction parallel to the optical axis. 4. The zoom lens barrel according to claim 2, wherein the guide member is a shutter holding frame for fixing the shutter unit.