JPH0511169A - Zoom lens barrel - Google Patents

Abstract

PURPOSE:To prevent a focusing operating ring and a focusing ring from rotating at the time of zooming by making an angle formed by the crossing of the leading groove of the focusing operating ring and the guiding groove of a fixed barrel a specified angle. CONSTITUTION:The zooming is executed by rotating a zooming ring 5. The zooming ring 5 is integrated with a cam ring 3 through an interlocking pin 9 and an engaging groove 5a, so that the cam ring 3 similarly rotates through the rotation of the zooming ring 5. In this case, since a cam pin 7 is engaged to the cam groove 3a and the guiding groove 6a, a holding ring 2 for lens group goes straight along the guiding groove 6a when the cam ring 3 rotates. And focusing is executed by rotating the focusing operating ring 4, however, since the angle formed by the crossing of the leading groove 4A of the focusing operating ring 4 and the guiding groove 1d of the fixed barrel 1 is made to be the specified angle, the focusing ring 6 and the focusing operating ring 4 which rotate at the time of the focusing can be prevented from rotating at the time of the zooming.

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 having a lens group having both functions of zooming (also called zooming) and focusing (also called focusing).

[0002]

2. Description of the Related Art Focusing methods for a zoom lens include a front group moving-out method, an internal focusing method, a rear focus method, and a whole moving-out method. Of these, the front-group moving-out method can focus with almost the same moving-out amount at any focal length, so that the mechanism for focusing can have a simple structure. However, in a zoom lens including a wide angle range, the lens diameter of the first lens group becomes large in order to secure the peripheral light amount,
Since the lens weight becomes large, in the front group feeding method, A
Since a load for moving the first lens group when focusing on F is large, it is difficult to quickly focus.

On the other hand, the internal focusing method and the rear focusing method are advantageous for AF focusing because the load of the lens group to be moved is smaller than that of the front group feeding method. However, in the case of these methods, a change in the focal length causes a difference in the amount of movement of the lens group required for focusing, so it is necessary to provide a mechanism for correcting this. As a result, the structure becomes complicated and the lens barrel becomes large.

Therefore, in the technique disclosed in Japanese Patent Laid-Open No. 64-35516, the movement of the focusing lens group during zooming and the movement of the focusing lens group during focusing are performed. A simple structure has been proposed in which and can be performed with one cam curve.

[0005]

However, in the technique disclosed in Japanese Patent Laid-Open No. 64-35516, it is necessary to prevent the member that rotates during focusing from rotating during zooming. No means is disclosed.

[0006]

In order to solve the above problems in the present invention, a lens (L1) having both functions of zooming and focusing and a lens holding tube (L1) for holding the lens (L1) are provided. 2), a fixed barrel (1), a cam ring (3) that rotates about the optical axis and moves the lens holding barrel (2) in the optical axis direction, and a cam ring (3) that rotates about the optical axis. A zoom ring (5) for rotating and zooming 3) and a focusing ring (6) for rotating the lens holding barrel (2) in the optical axis direction by rotating about the optical axis.
And a focusing operation ring (4) which rotates about the optical axis to rotate the focusing ring (6) to perform focusing. In the zoom lens barrel, the zoom ring (5) is rotated to rotate the cam ring. (3) rotates, and further by rotation of the cam ring (3), the lens holding cylinder (2) that engages with the cam groove (3a) formed in the cam ring (3)
When the pin (8) implanted in the lens moves along the guide groove (6a) formed in the focusing ring (6) to move the lens holding barrel (2) in the optical axis direction, (6) and the focusing operation ring (4) are provided with a predetermined angle so as not to rotate due to the frictional force between the respective members, thereby forming a zoom lens barrel.

[0007]

As described above, the lead groove (4) of the focusing ring (4) is
Since the angle formed by the intersection of a) with the guide groove (1d) of the fixed barrel (1) is a predetermined angle, the focusing ring (6) and the focusing device ring (6) that rotate during focusing and that rotate during focusing. It is possible to prevent 4) from rotating during zooming.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a sectional view of a main part of the zoom lens barrel of this embodiment, FIG. 2 is a development view of a cam portion, FIG. 3 is a development view of a focus shield portion, and FIG. 4 is a focus suspension. It is a figure which shows the balance of the force of a part.

The inner barrel (1b) of the fixed barrel (1) is provided with a clearance groove (1c) for the cam pin (7), and the outer barrel (1a) has a guide groove through which the pin (8) penetrates. An escape groove (1e) for the (1d) and the interlocking pin (9) is provided.

A lens group holding ring (2) is fitted on the inner circumference of the inner barrel portion (1b) to hold the lens group (L1) which has both focusing and zooming functions. ing. A cam ring (3) is held on the outer periphery of the inner barrel portion (1b) so as to be rotatable only around the optical axis. Further, the cam ring (3) is provided with a cam groove (3a) through which the cam pin (7) penetrates.

A focusing operation ring (4) is held on the outer periphery of the outer body portion (1a) so as to be rotatable only around the optical axis, and a pin (8) is attached to the focusing operation ring (4). Penetrating lead groove (4
a) is provided. A zoom ring (5) is further held on the outer periphery of the outer body (1a) so as to be rotatable only around the optical axis, and an engaging groove (5a) for the interlocking pin (9) is provided. There is.

A focusing ring (6) is fitted on the inner circumference of the outer barrel portion (1a), and a guide groove (6a) into which a cam pin (7) penetrates is provided. The cam pin (7) is planted in the lens group holding ring (2), passes through the clearance groove (1c), and penetrates into the cam groove (3a) and the guide groove (6a).

The pin (8) is planted in the focusing ring (6) and penetrates the guide groove (1d) and the lead groove (4a). The interlocking pin (9) is planted in the cam ring (3),
The zoom ring (5) and the cam ring (3) rotate integrally as they penetrate the engagement groove (5a) through the escape groove (1e).

Next, the operation will be described. Zooming is performed by rotating the zoom ring (5). At this time, since the zoom ring (5) is integrated with the cam ring (3) by the interlocking pin (9) and the engaging groove (5a), the cam ring (3) is also rotated by the rotation of the zoom ring (5). It also rotates. As shown in FIG. 2, since the cam pin (7) is engaged with the cam groove (3a) and the guide groove (6a), the rotation of the cam ring (3) causes the lens group holding ring (2) to move into the guide groove (6a). ), Go straight. Fore
Casing is performed by rotating the focusing operation ring (4). As shown in FIG. 3, since the pin (8) is guided to the guide groove (1d) by the rotation of the focusing ring (4), when the focusing ring (4) rotates by θ, the focusing ring (4) is rotated. 6) moves forward while rotating by θ '. At this time, as shown in FIG. 2, the guide groove (6
Since the cam pin (7) penetrating into (a) moves along the cam groove (3a), the lens group holding ring (2) moves forward while rotating and moves to the in-focus position.

FIG. 4 is a view showing the force applied to the pin (8) and the focusing operation ring (4). Focusing ring during zooming (6)
Receives a force from the cam pin (7), which causes the pin (8) to rotate the focusing ring (4) by a force P.
Then, the following forces act on the pin (8) and the focusing ring (4). The friction coefficient is represented by μ. In the pin (8), the drag force R and the friction force μR received from the guide groove (1d)
The drag force N and the friction force μN received from the groove (4a) act.
It is assumed that the focusing operation ring (4) has a drag force N and a friction force μN with the pin (8), a drag force L and a friction force μL with the fixed barrel 1, and a weight of the focusing ring 4 is W. The frictional force μW acts on the sliding surface in the direction opposite to the direction in which it rotates.

A force indicated by Q is applied to the focusing operation ring 4 to prevent the focusing operation ring (4) from rotating.

Assuming that the inclination angle of the lead groove (4a) is θ ₁ and the inclination angle of the guide groove (1d) is θ ₂ , the following four equations are established from the balance of forces. P = Rsinθ ₂ + μRcosθ ₂ + Nsinθ ₁ -μNcosθ ₁ … Ncosθ ₁ + Nsinθ ₁ = Rcosθ ₂ -μRsinθ ₂ … Q = Nsinθ ₁ -μNcosθ ₁ -μL-μW… L = Ncosθ ₁ + μN sinθ ₁ …

By eliminating R, P / N = {( ₁ + μ ² ) sin (θ ₁ + θ ₂ )} / (cos θ ₂ −μsin θ ₂ ) ...

By eliminating L, (Q + μW) / N = (1-μ ² ) sin θ ₁ -2 μ cos θ ₁ ...

By eliminating N, Q = P {(1-μ ² ) sin θ ₁ -2 μcos θ ₁ } (cos θ ₂ -μsin θ ₂ ) / {( ₁ + μ ² ) sin (θ ₁ + θ ₂ )}-μW ……… is obtained.

In order that the focusing ring (4) does not rotate even if the force Q is not applied, Q ≦ 0 must be satisfied. Therefore, {(1 −μ ² ) sin θ ₁ −2 μ cos θ ₁ )} (cos θ ₂ -μsin θ ₂ ) / μ {( ₁ + μ ² ) sin (θ ₁ + θ ₂ )} ≦ W / P ……… is obtained.

Therefore, θ1 and θ2 are set so as to satisfy the above equation.
If is set, the focusing operation ring 4 does not rotate during zooming.

[0023]

According to the present invention, there is provided a structure in which the movement of the lens group during zooming and the movement of the lens group during focusing can be performed by one cam curve. Regardless of this, the angle formed by the lead groove (4a) of the focusing ring (4) and the guide groove (1d) of the fixed barrel (1) intersecting is a predetermined angle, so during focusing The rotating focusing ring (4) and focusing ring (6) do not rotate during zooming.

[Brief description of drawings]

FIG. 1 is a sectional view of an embodiment.

FIG. 2 is a development view of a cam portion according to an embodiment.

FIG. 3 is a development view of a focus shield unit according to an embodiment.

FIG. 4 is a diagram showing a balance of forces of a focus lead portion in one embodiment.

[Explanation of symbols]

1 ... Fixed cylinder, 2 ... Lens holding ring, 3 ... Cam ring, 4 ... Focusing ring, 5 ... Zoom ring, 6 ...
...... Focusing ring, 7 ………… Cam pin, 8 ………… Pin, 9 ……
… Interlocking pin

Claims (1)

Claim: What is claimed is: 1. A lens having both functions of zooming and focusing, a lens holding barrel for holding the lens, a fixed barrel, and a lens which rotates about an optical axis, A cam ring that moves the holding barrel in the optical axis direction, a zoom ring that rotates about the optical axis to rotate the cam ring to change the magnification, and a rotation about the optical axis to move the lens holding barrel to the optical axis. In a zoom lens barrel having a focusing ring that moves in the axial direction and a focusing operation ring that rotates about the optical axis to rotate the focusing ring, The cam ring rotates, and the rotation of the cam ring engages with the cam groove formed in the cam ring, and the pin planted in the lens holding cylinder engages with the guide groove formed in the focusing ring. When the lens holding cylinder is moved in the optical axis direction by moving along the optical axis, the focusing ring and the focusing operation ring generate frictional force between the members. The zoom lens barrel, wherein a predetermined angle so as not to rotate granted Ri.