JPH07287157A - Zoom lens barrel - Google Patents

Abstract

PURPOSE:To realize the small diameter of the zoom lens barrel and to reduce the cost thereof low by disusing an expensive cam barrel in a zoom lens barrel which changes a focal distance by moving in the parallel direction with at least the optical axes of two lens groups. CONSTITUTION:Interlocked with moving the 1st lens group 5 out of two lens groups 5 and 7 in the parallel direction with the optical axis, the 2nd lens group 7 is moved in the parallel direction with the optical axis and positioned; and a cam groove 2c obtained by synthesizing the zoom loci of the 1st and the 2nd lens groups 5 and 7 is provided on the lens barrel which holds the 2nd lens group 7 or a member 2 which is engaged with the lens barrel.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a zoom lens barrel which changes a focal length by moving at least two lens groups in a direction parallel to an optical axis.

[0002]

2. Description of the Related Art Currently, as a standard interchangeable lens for a single-lens reflex camera, a zoom lens covering a wide-angle to a medium-telephoto range is mainly used. Among them, two lens groups are moved (hereinafter referred to as two-group movement) The number of short zoom type lens configurations is increasing.

FIG. 5 is a view showing a zoom mechanism of a conventional two-group moving short zoom lens. In FIG.
Reference numeral 1 is a fixed barrel fixed to a camera body (not shown) by a bayonet portion 21a, and 22 is a cam barrel. This cam barrel 22 engages with a convex portion 21b of the fixed barrel 21 at a recess 22a and rotates about the optical axis. Supports possible. Reference numeral 23 denotes a front lens group moving cylinder, and the front lens group moving cylinder 23 is radially fitted to the inner peripheral surface of the fixed cylinder 21 at the outer peripheral portion thereof.
A helicoid screw portion 23a for focusing is provided.

Reference numeral 24 denotes a concave portion 23b on the outer peripheral surface of the front group moving barrel 23.
The front group roller 24 is fixed to the front group roller 24. The front group roller 24 is engaged with a straight groove 21c provided in the fixed barrel 21 and extending in the optical axis direction, and is restricted from rotating around the optical axis. 22
It engages with the front group moving cam groove 22b provided on the front lens group, and is restricted from moving in the optical axis direction.

Reference numeral 25 denotes a rear group lens barrel, and this rear group lens barrel 25
Is radially engaged with the inner periphery of the fixed cylinder 21 at the outer peripheral portion, holds the rear group lens 2b on the inner peripheral side, and is arranged in the outer peripheral surface concave portion 25a.
7 is stuck. Like the front group roller 24, the rear group roller 27 is engaged with the rectilinear groove 21c of the fixed barrel 21 and the rear group moving cam groove 22c of the cam barrel 22 and is restricted from moving in the optical axis direction. Reference numeral 28 denotes a front group lens barrel, which holds the front group lens 29 on the inner peripheral side, and is attached to the inner peripheral surface of the front group moving barrel 23 by a helicoid screw portion 28a provided on the outer peripheral surface. It is positioned by being screwed into the provided helicoid screw portion 23a.

Reference numeral 30 denotes a focus key that rotates around the optical axis. The focus key 30 is connected to a focus driving unit (not shown), and one end of the focus key 30 is a key groove 28 of the front lens barrel 28.
engaged with b. Reference numeral 31 denotes a zoom operation ring, which has a bayonet portion 31a that is rotatably supported by the fixed barrel 21, and is integrally connected to the cam barrel 22 in the rotational direction by a zoom key 32. The zoom operation ring 3 is fixed to the tip of the zoom operation ring 31.
It is a reinforcing ring that prevents the bending of No. 1.

Next, the zooming operation of the zoom lens barrel having the above structure will be described. First, the zoom operation ring 31
When the is rotated around the optical axis, the rotational force is
Is transmitted to the cam barrel 22 and the cam barrel rotates. Due to the rotation of the cam barrel 22, the front group roller 24 and the rear group roller 27, which are respectively engaged with the front group moving cam groove 22b and the rear group moving cam groove 22c provided in the cam barrel, are the straight grooves of the fixed barrel 21. 21c moves in the optical axis direction while being restricted in rotation.

Therefore, the front lens barrel 23 and the rear lens barrel 25, to which these rollers are fixed, similarly move in the optical axis direction. The front lens barrel 28 has a focus key 30 during zooming.
Since the rotation around the optical axis is restricted by the optical axis, it moves in the optical axis direction together with the front group moving barrel 23. As a result, each lens barrel 2
The lenses 26, 29 held by 5, 28 move in the optical axis direction by the respective cam loci, and zooming is achieved.

During focus driving, the front lens barrel 28 is moved to the front lens barrel 2 by rotating the focus key 30 around the optical axis with a focus lens driving device (not shown).
Due to the helicoid engagement with 3, the lens is moved in the direction parallel to the optical axis while rotating around the optical axis, and focus adjustment is performed.

Many of the above-described two-group-moving short zooms have a locus in which one of the lens groups makes a U-turn during zooming in one direction. In that case,
The configuration of the lens barrel described above is essential.

[0011]

However, in the above-mentioned conventional example, it is indispensable to use the cam barrel, and the cam barrel must be made of metal with high precision.
Therefore, there is a problem that the cost is high, and it is difficult to reduce the size and cost by reducing the number of constituent parts and thinning.

An object of the present invention is to obtain a zoom lens barrel which solves the above problems.

[0013]

According to the present invention, in a zoom lens barrel in which the focal length is changed by moving at least two lens groups in a direction parallel to the optical axis, the first lens group of the two lens groups is used. Or a holding member for holding the second lens group by moving the second lens group in the direction parallel to the optical axis and positioning the second lens group in conjunction with moving the second lens group in the direction parallel to the optical axis. By providing a cam that combines the zoom loci of the first and second lens groups in a member that engages with the expensive cam barrel, the diameter of the zoom lens barrel can be reduced and the cost can be reduced. Can be converted.

[0014]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a sectional view in the optical axis direction of a zoom lens barrel of the present invention, in which the lower side from the center shows a wide state and the upper side shows a tele state.

In FIG. 1, reference numeral 1 denotes a fixed barrel which is fixed by engaging with a mount portion of a camera body by a bayonet portion 1a. The fixed barrel 1 has a straight groove 1b extending in a direction parallel to the optical axis. It has a front group moving cam 1c portion.

Reference numeral 2 denotes a front group moving cylinder whose outer circumferential surface is slidably supported by being radially fitted to the inner circumferential surface of the fixed cylinder 1. The front group moving cylinder 2 has an inner circumferential surface on which the front group is mounted. The lens barrel 4 has a female helicoid portion 2a that engages with the helicoid and a cam groove 2c. Three
Is a front group roller, and this front group roller 3 is the front group moving barrel 2
It is fixed to the surface portion 2b of the above and is also engaged with the front group moving cam 1c portion provided on the fixed barrel 1.

The front group lens barrel 4 as a holding member holds the front group lens group 5 on the inner circumference thereof, and the front group moving barrel 2 on the outer circumference side thereof.
It has a male helicoid 4a for helicoid engagement with the female helicoid 2a.

Reference numeral 6 denotes a rear group lens barrel as a holding member for holding the rear group lens group 7 on the inner peripheral side, and a fitting portion 6a for radially fitting the inner peripheral surface of the fixed barrel 1 and the fixed barrel 1. And a linear groove 6b provided on the front group moving barrel 2 and a linear key 6b for restricting the rear group lens barrel so as to be movable only in the optical axis direction. It has a roller portion 6c.

Reference numeral 9 denotes a zoom operation ring, which has a bayonet portion 9a rotatably supported with respect to the fixed barrel 1 and has a rear lens group 7 on the inner peripheral side in the optical axis direction. A rear group moving cam 9b for moving is provided, and a roller portion 6d provided on the rear group lens barrel 6 is engaged with the rear group moving cam 9b.

Reference numeral 8 denotes a focus key. One end of the focus key 8 is engaged with a key groove 4b provided in the front lens barrel 3 and the other end is connected to a focus lens driving device (not shown). The focus lens driving device is driven to rotate about the optical axis. Reference numeral 10 is a reinforcing ring that is fixed to the tip of the zoom operation ring 9 and prevents the zoom operation ring 9 from bending.

2 and 3, the front group roller 3 provided on the front group moving barrel 2 in the rectilinear groove 1b on the fixed barrel 1 and the front group moving cam 1c.
2 is a development view showing the movement of the cam groove 2c, the linearly moving key portion 6b provided on the rear lens barrel 6 and the roller portion 6c during zooming. FIG. 2 shows a tele state and FIG. 3 shows a wide state.

Next, the zooming operation of the zoom lens barrel having the above structure will be described. When changing from the wide state to the tele state, first, by manually rotating the zoom operation ring 9 about the optical axis, the rear group cam 9b on the inner periphery of the zoom operation ring and the straight groove 1b of the fixed barrel 1 are formed. By the engagement of the rectilinear key 6b and the roller portion 6d of the rear lens barrel 6 engaged with
The rear lens barrel 6 starts moving in the optical axis direction.

At this time, due to the engagement between the roller portion 6c of the rear lens barrel 6 and the cam groove 2c provided in the front lens barrel 2, the front lens barrel 2 receives a force that rotates about the optical axis. Due to this rotation force, the front group moving barrel 2 rotates along the curve of the cam 1c portion by the engagement of the front group roller 3 fixed to the surface portion 2b and the front group moving cam 1c portion provided on the fixed barrel 1. While moving in the direction of the optical axis.

The front lens barrel 4 is in a helicoidal engagement with the front lens barrel 2 and is prevented from rotating around the optical axis by a fixed focus key 8 during zooming. It moves in the direction parallel to the optical axis without rotating (or while rolling).

Next, at the time of focus driving, the focus key 8 is rotated around the optical axis by a focus lens driving device (not shown), so that the front lens barrel 4 and the front lens barrel 2 engage with each other by helicoid engagement. While rotating around the axis, the focus can be adjusted by moving in the direction parallel to the optical axis.

Next, the relationship between the optical zoom loci of the front and rear groups and the shape of each cam groove will be described. FIG. 4 shows the above relationship due to zooming. In FIG. 4, it is assumed that the O point is located at the reference position in the wide state and the front group and the rear group are located. And the change amount of the cam shape are shown.

In the figure, a indicates the zoom locus of the front lens group, and b indicates the zoom locus of the rear lens group. In zooming, the front lens barrel 4 is rotated by the focus key 8 in the lens barrel structure of this embodiment. The front lens barrel 4 and the front lens barrel 2 are regulated.
There is an extension (zoom locus c in the figure) due to the helicoid engagement by the amount of the rotation of the front group moving barrel caused by zooming. Therefore, the cam shape of the front group moving cam 1c provided on the fixed barrel 1 is a zoom locus d obtained by subtracting the extension c by the helicoid engagement from the optical front group movement amount a.
become.

The shape of the cam groove 2c provided on the front lens group moving cylinder 2 is such that the front lens group moving cylinder moves along the zoom locus d in the figure, whereas the rear group must move along the zoom locus b. Therefore, the difference of the loci is calculated as the zoom locus b of the rear group.
It suffices that the zoom locus e added to is obtained.

[0029]

As described above, according to the present invention,
Of the two lens groups, the second lens group is moved and positioned in parallel with the movement of the first lens group in the direction parallel to the optical axis, and the second lens group is positioned. Since the holding member that holds the holding member or the member that engages with the holding member is provided with the cam in which the zoom loci of the first and second lens groups are combined, it is possible to eliminate the conventionally required cam barrel. Since the outer diameter of the lens barrel can be reduced by the amount of the cam barrel, and the cost for the cam barrel can be reduced, a compact and low-cost zoom lens barrel can be obtained. As a result, it is extremely effective for simplification of the zoom lens barrel by applying it to the lens barrel having a complicated lens group structure and a part thereof.

Also, since the rear lens barrel does not rotate during zooming as in the embodiment, there is an effect that wiring is easy when an electromagnetic diaphragm or the like is arranged on the rear lens barrel.

[Brief description of drawings]

FIG. 1 is a sectional view in an optical axis direction of an interchangeable lens to which a zoom lens barrel of the present invention is applied.

FIG. 2 is a development view of the zoom lens barrel in FIG. 1 in a telephoto state.

3 is a development view of the zoom lens barrel of FIG. 1 in a wide state.

FIG. 4 is a diagram showing the relationship between the movement of each group and each cam shape due to zooming of the interchangeable lens of FIG.

FIG. 5 is a sectional view showing a conventional interchangeable lens in an optical axis direction.

[Explanation of symbols]

 1 Fixed barrel 1b Straight advance groove 1c Front group moving cam 2 Front group moving barrel 2c Cam groove 4 Front group lens barrel 5 Front group lens 6 Rear group lens barrel 7 Rear group lens 9 Zoom operation ring 9b Rear group cam

Claims (1)

[Claims] 1. A zoom lens barrel in which a focal length is changed by moving at least two lens groups in a direction parallel to an optical axis, wherein a first lens group of the two lens groups is parallel to the optical axis. In conjunction with the movement, the second lens group is moved in a direction parallel to the optical axis for positioning, and the holding member for holding the second lens group or the member engaging with the holding member has the first and the second members. A zoom lens barrel comprising a cam in which a zoom locus of the second lens group is combined.