JP3837792B2 - Zoom lens barrel - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a zoom lens barrel of a camera that holds a zoom lens, and is particularly suitable for a zoom lens barrel used in a construction camera.
[0002]
[Prior art]
In the conventional zoom lens barrel, as shown in FIG. 4, a male helicoid 31a is screwed on a lens frame 31 that holds a predetermined lens group, and a female helicoid that is screwed with the male helicoid 31a is shown. The lens frame 31 was advanced and retracted by a non-external cylinder. The portion of the lens frame 31 where the male helicoid 31a is screwed is the rear end in the optical axis direction.
[0003]
Further, in the conventional zoom lens barrel, when the lens frame 31 is linearly slid in the optical axis direction, the lens frame 31 is provided with a sliding groove 31b, and a linear guide plate 32 in which a metal plate is bent in the sliding groove 31b. The guide portion 32a was slid, but was longer than the length of the slide groove 31b in the optical axis direction than the length of the guide portion 32a in the optical axis direction.
[0004]
[Problems to be solved by the invention]
As described above, in the conventional technology, the male helicoid of the lens frame is screwed at the rear end, so that when the lens frame is screwed with the female helicoid of the outer cylinder, the lens frame is in a cantilever state, so that the heavy lens group Is unstable. Therefore, when the camera is struck or dropped, the lens frame is tilted by the impact force, and as a result, the held lens group is tilted with respect to the optical axis, resulting in one-sided blur on the focus surface. .
[0005]
The present invention is directed issues to solve such a problem.
[0008]
[Means for Solving the Problems]
Upper Symbol challenges includes a sliding frame holding a predetermined plurality of lens groups in's Murenzu, in the zoom lens barrel provided with a drive cylinder for driving so as to advance and retreat the slide frame in the optical axis direction, the In the zooming range of the zoom lens, the distance between the groups of the plurality of lens groups held by the sliding frame changes, and the virtual plane passes through the approximate center of gravity of the sliding frame and is orthogonal to the optical axis of the lens group. This is solved by a zoom lens barrel characterized in that it always crosses a fitting portion of a predetermined length that is provided on the outer periphery of the sliding frame and fits with the drive cylinder.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of a zoom lens barrel using the present invention will be described in detail with reference to FIGS.
[0011]
First, members constituting the zoom lens barrel will be described with reference to FIGS.
[0012]
FIG. 1 is a cross-sectional view of a zoom lens barrel when the zoom lens is short-focused, and FIG. 2 is a cross-sectional view of the zoom lens barrel when the zoom lens is long-focused, both in the upper half from the optical axis. Only drawn. FIG. 3 is an exploded perspective view showing main members of the zoom lens barrel.
[0013]
Reference numeral 1 denotes a front base plate which carries all members described below and is fixed to a camera body (not shown). Reference numeral 2 denotes an ff adjustment ring, and the outer periphery thereof is fitted to the inner periphery of the front base plate 1. Further, a protrusion (not shown) provided on the inner periphery of the front base plate 1 and parallel to the optical axis K engages with a long groove 2a provided on the outer periphery of the ff adjustment ring 2, so that the ff adjustment ring 2 can only move linearly. Is possible.
[0014]
Reference numeral 3 denotes a cam cylinder whose outer periphery is fitted to the inner periphery of the ff adjustment ring 2. Further, since the front end 3 a of the cam cylinder 3 is sandwiched between the front end 2 b of the ff adjustment ring 2 and the cam cylinder holding plate 5 fixed via the spacer 4, the cam cylinder 3 is attached to the ff adjustment ring 2. On the other hand, it can rotate freely, but in the case of movement in the optical axis direction, it moves integrally with the ff adjustment ring 2.
[0015]
Accordingly, after a cam cylinder 3 carrying a lens group, which will be described later, is moved by a small amount in the optical axis direction together with the ff adjustment ring 2, the ff adjustment ring 2 is fixed to the front base plate 1 with screws 6.
[0016]
Reference numeral 7 denotes a sliding frame, and a male helicoid 7 a screwed on the outer periphery is screwed with a female helicoid 3 b provided on the inner periphery of the cam cylinder 3. A long groove 7b is provided across the male helicoid 7a from the rear of the sliding frame 7, and a straight guide plate 8 bent in an L shape by a metal plate is screwed to the front base plate 1 by a set screw 9. The guide portion 8a parallel to the optical axis K of the rectilinear guide plate 8 is engaged with the long groove 7b of the slide frame 7, and the rotation of the slide frame 7 is prevented in the thickness direction of the guide portion 8a.
[0017]
The sliding frame 7 and the cam cylinder 3 are not limited to the above-described helicoid coupling, but may be a cam coupling using a cam groove and a cam pin. At this time, a cam groove may be provided on the outer peripheral wall of the sliding frame 7 to provide a cam pin on the cam cylinder 3, or a cam pin may be provided on the outer peripheral wall of the sliding frame 7 to provide a cam groove on the cam cylinder 3. That is, as long as the sliding frame 7 can be driven, the portion of the sliding frame 7 that fits with the cam cylinder 3 may be any of a male helicoid, a cam groove, and a cam pin. It replaces with the cylinder 3 and is called a drive cylinder, and the part of the sliding frame 7 fitted with a drive cylinder is called the fitting part.
[0018]
Further, the straight guide plate 8 may be fixed to the camera main body or a fixing member connected to the camera main body (not shown) without being fixed to the front base plate 1.
[0019]
Reference numeral 23 denotes a ring-shaped dustproof sheet made of flocked paper or the like, which is fixed to the front base plate, and dust or the like enters the male helicoid 7a through the gap between the front base plate 1 and the outer peripheral wall 7d of the sliding frame 7. Is preventing.
[0020]
Reference numeral 24 denotes a strip-shaped dustproof sheet made of flocked paper or the like, and is screwed to the front ground plate 1 together with the linear guide plate 8 by a set screw 9, so that the bottom portion of the long groove 7b and the surface portion of the guide portion 8a Dust and the like are prevented from entering the male helicoid 7a through the gap.
[0021]
Here, the zoom lens according to the present embodiment is a two-group zoom, and includes a first lens Fc in the front group and a second lens Rc in the rear group, and the first lens Fc is attached to the first lens frame 11. Inserted and held by a retaining ring 12 screwed into the first lens frame 11 in the optical axis direction.
[0022]
A shutter unit 13 is fixed to the sliding frame 7, and the first lens frame 11 is screwed to the shutter unit 13. Accordingly, the first lens Fc moves integrally with the sliding frame 7.
[0023]
Reference numeral 14 denotes a flexible substrate that drives and controls the shutter unit 13 from the camera body.
[0024]
On the other hand, the second lens Rc is inserted into the second lens frame 15 and is held by a retaining ring 16 screwed into the second lens frame 15 in the optical axis direction. The second lens frame 15 is fitted to the inner periphery of the sliding frame 7 at the outer periphery, and protrusions 15a parallel to the optical axis K are provided at three locations on the outer periphery, so that the optical axis of the inner periphery of the sliding frame 7 is provided. It is engaged with a long groove (not shown) provided in a direction parallel to K. Therefore, the second lens frame 15 does not rotate with respect to the sliding frame 7 and only moves linearly in the optical axis direction.
[0025]
Further, the cam pin 17 is fixed to the second lens frame 15 by a set screw 18 through a long hole 7 c formed in the sliding frame 7. A cam groove 3c is provided along with a female helicoid 3b on the inner periphery of the cam cylinder 3, and a cam pin 17 is engaged with the cam groove 3c.
[0026]
Note that the cam pin 17 is loose with respect to the cam groove 3c in a direction parallel to the optical axis K in terms of processing accuracy. Therefore, a tension spring 21 is applied between the light shielding plate 22 provided at the rear end of the sliding frame 7 and the rear end portion 15 b of the second lens frame 15, and the cam pin 17 is urged rearward together with the second lens frame 15. As a result, the cam pin 17 abuts only on the rear side wall of the cam groove 3c, and there is no backlash in a direction parallel to the optical axis K.
[0027]
Next, the zooming operation in the zoom lens barrel having the above configuration will be described.
[0028]
Although not shown, a lens driving motor and a reduction gear are arranged around the front base plate 1, and the final stage gear of the reduction gear is notch of the front base plate 1 (not shown). It meshes with a large gear 3d provided at the outer peripheral rear end. Accordingly, when the lens driving motor rotates, the cam cylinder 3 rotates. The sliding frame 7 is engaged with the male helicoid 7a of the cam cylinder 3 and the female helicoid 3b of the cam cylinder 3 and is prevented from rotating by the rectilinear guide plate 8 fixed to the front base plate 1. Therefore, the rotation of the cam cylinder 3 Move straight according to the helicoid lead. On the other hand, the cam pin 17 erected on the second lens frame 15 engages with the cam groove 3c of the cam barrel 3, and the second lens frame 15 is formed so as not to rotate with respect to the sliding frame 7. The second lens frame 15 moves linearly according to the cam groove 3 c of the cam cylinder 3.
[0029]
Accordingly, the rotation of the cam cylinder 3 causes the sliding frame 7 and the second lens frame 15, that is, the first lens Fc and the second lens Rc held in each, to move straight in the optical axis direction, for example, as shown in FIG. The lens is extended from the short focus state to the long focus state shown in FIG.
[0030]
As described above, the sliding frame 7 carries a number of members including heavy members such as the shutter unit 13, the first lens frame 11, the first lens Fc, the second lens frame 15, and the second lens Rc. The male helicoid 7a is screwed into the female helicoid 3b of the cam cylinder 3 with a helicoid. From the short focus state shown in FIG. 1 to the long focus state shown in FIG. 2, if the center of gravity position of the sliding frame 7 carrying each member is G, the virtual position passing through the center of gravity position and orthogonal to the optical axis K is assumed. The plane always crosses the male helicoid 7a.
[0031]
Therefore, the sliding frame 7 is a zoom lens barrel that stably supports each member with good balance and is strong against impact. Even if the above condition is not strictly satisfied, the same effect as described above can be obtained if the virtual plane passing through the approximate vicinity of the gravity center position G crosses the male helicoid 7a.
[0032]
Further, the length of the guide portion 8 a parallel to the optical axis of the rectilinear guide plate 8 is much shorter than the length of the long groove 7 b of the sliding frame 7. Therefore, the sliding frame 7 can operate smoothly even if the bending accuracy of the linear guide plate 8 by pressing is not high as in the prior art.
[0033]
[Length of the guide portion 8a of the linear guide plate 8] + [Length of the long groove 7b of the sliding frame 7] = [Movement amount of the sliding frame 7 between the short focus and the long focus] + [Guide portion 8a And the length in which the long groove 7b is fitted] + [allowance].
[0034]
Further, since the sliding frame 7 is integrally assembled with the first lens frame 11 that holds the first lens Fc and carries the second lens frame 15 that holds the second lens Rc, When the first lens Fc is tilted, the second lens Rc is tilted in the same manner, and no one-side blur occurs on the focus surface.
[0035]
In addition, after the first lens Fc is inserted into the first lens frame 11, the retaining ring 12 is screwed and held. After the second lens Rc is inserted into the second lens frame 15, the retaining ring is retained. Since 16 is screwed and held, the lens is more resistant to impact than the fixing by caulking.
[0036]
In the above embodiment, the zoom lens has a two-group configuration. However, the zoom lens can also be implemented in a three-group configuration. In this case, a third lens frame that is cam-driven in the same manner as the second lens frame 15 is used. What is necessary is just to make it fit to the sliding frame 7. FIG.
[0037]
【The invention's effect】
According to the zoom lens barrel according to claim 1 to 4, sliding frame so holds a plurality of lens groups, such as well-balanced stable lens group even impact is applied is the one-sided blur in the focal plane tilted It is hard to happen .
[0038]
According to the zoom lens barrel of the fifth aspect, when one lens tilts due to an impact, the other lens also tilts in the same manner. In addition to the above effect, a zoom lens barrel that hardly causes one-side blur on the focus surface is realized. it can.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a zoom lens barrel when a zoom lens has a short focal point.
FIG. 2 is a cross-sectional view of a zoom lens barrel when the zoom lens has a long focal point.
FIG. 3 is an exploded perspective view showing main members of a zoom lens barrel.
FIG. 4 is a diagram of a lens frame in a conventional zoom lens barrel.
[Explanation of symbols]
Fc First lens Rc Second lens 1 Front base plate 3 Cam cylinder 7 Sliding frame 8 Straight guide plate 11 First lens frame 13 Shutter unit 15 Second lens frame 17 Cam pin

Claims (5)

A sliding frame for holding a plurality of predetermined lens groups in the zoom lens;
In a zoom lens barrel provided with a drive cylinder that drives the sliding frame to advance and retract in the optical axis direction ,
In the zooming range of the zoom lens, the distance between the groups of the plurality of lens groups held by the sliding frame changes, and passes through the approximate center of gravity of the sliding frame and is orthogonal to the optical axis of the lens group. A zoom lens barrel characterized in that a surface always crosses a fitting portion of a predetermined length that is provided on the outer periphery of the sliding frame and engages with the drive cylinder.   The zoom lens barrel according to claim 1, wherein the fitting portion is a male helicoid.   The zoom lens barrel according to claim 1, wherein the fitting portion is an outer peripheral surface provided with a cam groove.   The zoom lens barrel according to claim 1, wherein the fitting portion is an outer peripheral surface provided with a cam pin.   The sliding frame is integrally assembled with a first lens frame that holds a first lens group, and carries a second lens frame that holds a second lens group. Item 5. The zoom lens barrel according to any one of Items 1 to 4.

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