JP2001074997A - Variable focal lens barrel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a variable focal lens barrel where a focus cam and a zoom cam do not interfere with each other. SOLUTION: This lens barrel is provided with an intermediate moving frame 22 supporting a focus lens frame 12 fitted relatively movably in a focus operation ring 30; a zoom cam ring 21 moving a variable power lens group and the moving frame 22 by the rotating operation of a zoom operation ring 20; a focus cam ring 24 integrally turning with the ring 21 in a rotating direction and having the focus cam 26. Then, cam followers formed on the frames 12 and 22 are engaged with the cam 26, and when the frame 22 is moved in the optical axis direction by the rotation of the ring 21, the ring 30 is guided by the cam 26 and relatively moved in the optical axis direction while relatively rotating to the frames 12 and 22, and the cam 26 changes the engaging position with the cam follower of the frame 12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a varifocal lens barrel.

[0002]

2. Description of the Related Art Varifocal lenses
It is defined as a lens whose focal plane moves when the focal length is changed. For this reason, if the focal length is changed, the extension position of the focus lens group for focusing on an object at the same distance changes. In an autofocus camera, the extension position (movement amount from the standby position) of the focus lens group may be determined in consideration of (to compensate for) movement of the focal plane when the focal length changes. Even with a single-lens reflex camera, the movement of the focal plane (blur) when the focal length is changed can be viewed through a finder, and the distance ring (focus ring) can be rotated so that the blur does not occur. No problem.

However, in the case of a single-lens reflex camera, it is necessary to engrave (display) a photographing distance scale on a distance ring. At any focal length, an object at the distance indicated by the photographing distance scale must be focused. No. In other words, when focusing on a subject at the same distance, the focus lens group must be moved by different distances at the same rotation angle of the distance ring from the infinity shooting position, for example, according to different focal lengths to focus on the subject. Must. That is, in terms of operation, the same operability as a zoom lens in which the focal plane does not move even if the focal length is changed is required. In this sense, there is no practical difference between the varifocal lens barrel and the zoom lens barrel. As used herein, the terms zoom or zooming are
It is used to mean variable power of a varifocal lens.

[0004] Such a varifocal lens barrel is
Various types have already been proposed and put to practical use, but in general, not only the structure is complicated, but also a focus cam that changes the extension position of the focus lens group per unit rotation angle of the distance ring according to a change in the focal length, There is a problem that it is difficult to remove mutual interference (effect) with the zoom cam for performing zooming.

[0005]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a varifocal lens barrel that allows zooming without interference between a focus cam and a zoom cam.

[0006]

SUMMARY OF THE INVENTION The present invention has a plurality of zooming lens groups movable in the direction of the optical axis for changing the focal length, one of which has both functions of zooming and focusing. A zoom operation ring that is rotated in a varifocal lens barrel that is a focus lens group in which the focus extension position for the same subject distance changes at different focal lengths;
A focus operation ring that is rotated independently of the zoom operation ring; a focus lens frame that supports the focus lens group and is driven to rotate by the rotation operation of the focus operation ring; this focus lens is guided in the optical axis direction. An intermediate moving frame supporting the frame; a zoom cam ring for moving the plurality of variable power lens groups and the intermediate moving frame along a predetermined locus in the optical axis direction by rotating the zoom operation ring; A focus cam ring having a focus cam that rotates integrally and is capable of relative movement in the optical axis direction and that compensates for image plane movement at a focal length determined by the rotational position of the zoom cam ring; and the focus of the focus cam ring A cam follower formed on each of the focus lens frame and the intermediate moving frame, the cam followers being simultaneously engaged with a cam; When the intermediate moving frame moves in the optical axis direction due to the rotation of the zoom cam ring, the cam ring is guided by the focus cam and relatively moves in the optical axis direction while rotating relative to the focus lens frame and the intermediate moving frame, The focus cam changes an engagement position of the focus lens frame with a cam follower.

The intermediate moving frame and the focus lens frame are integrally moved without changing their relative positions during zooming via a focus cam of a focus cam ring in a state of focusing on an object at infinity. Is preferred.

The focus cam may be in the form of a groove or a projection.

[0009]

FIG. 1 to FIG. 7 show a first embodiment of a varifocal lens barrel 10 according to the present invention. The lens configuration includes, in order from the object side, a first lens group A, a second lens group B, a third lens group C, and a fourth lens group D, each of which has a first group frame 11, a second group frame (focus lens frame). It is fixed to frames 12, 13, and 4. The first lens group A to the fourth lens group D are respectively variable power lens groups, of which the second lens group B
Is a focus lens group having both a variable power function and a focus adjustment function.

A fixed barrel 15 which is connected and fixed to the body of the single-lens reflex camera has a zoom operation ring 20 which can be rotated independently from the outside, and a focus operation ring 30 which is rotatable and does not move in the axial direction. Have been. The zoom operation ring 20 is connected via a radial connecting arm 20a (FIG. 1).
It is coupled to a zoom cam ring 21 supported on the inner peripheral surface of the fixed cylinder 15 so as to be rotatable and not to move in the axial direction,
The zoom operation ring 20 and the zoom cam ring 21 always rotate equally.

The first cam groove 21 is provided on the zoom cam ring 21.
A, a second group cam groove 21B and a third group cam groove 21C are formed, and a first group cam groove 21A and a third group cam groove 21C are formed.
A cam follower 11C formed integrally with the first group frame 11
And a cam follower 13C integrally formed with the third group frame 13 is fitted. On the other hand, the second group frame 12 has no cam follower that fits in the second group cam groove 21B of the zoom cam ring 21. Instead, the second group cam groove 21B is formed integrally with the intermediate moving frame 22. The cam follower 22C is fitted. The intermediate moving frame 22 is fitted on the outer periphery of the second group frame 12 so as to be relatively movable in both the optical axis direction and the circumferential direction. Are rotatably fitted to both.
The second group frame 12 (second lens group B) includes the focus cam ring 2
4 and is supported by the intermediate moving frame 22.

The fixed cylinder 15 has a straight guide groove 15s parallel to the optical axis in which the cam follower 11C, the cam follower 13C and the cam follower 22C are fitted. This straight guide groove 15s is composed of a plurality of grooves having different circumferential positions as shown in FIGS. 2 and 3, but in FIG.
It is represented by one groove.

The zoom cam ring 21 is connected to a fourth group cam ring 25 via a radial connecting pin 21p (FIG. 1). The fourth group cam ring 25 always rotates the same as the zoom cam ring 21. A cam groove (not shown) for the fourth lens group D is formed in the fourth group cam ring 25, and a follower pin (not shown) formed integrally with the fourth group frame 14 is fitted in this cam groove. The fourth group frame 14 is guided linearly by the third group frame 13, and when the zoom cam ring 21 (the fourth group cam ring 25) rotates, the fourth lens group D moves in the optical axis direction according to the cam groove locus of the fourth group cam ring 25. Go to

That is, when the zoom operation ring 20 is rotated, the zoom cam ring 21 and the fourth group cam ring 25 are integrally rotated via the connecting arm 20a and the connecting pin 21p. As a result, the first group cam groove 21A, the second group cam groove 21B,
The first group frame 11 (first lens group A), the second group frame 12 (second lens group B), and the third group frame 13 (third lens group C) move in the optical axis direction based on the group cam groove 21C. The fourth group frame 14 (fourth lens group D) moves in the optical axis direction according to the cam groove of the fourth group cam ring 25 to perform zooming.

The above-described zooming is described in the description of the intermediate moving frame 2.
2, the relationship between the focus cam ring 24 and the second group frame 12 (second lens group B) is neglected. The varifocal lens is a lens whose image plane position changes when zooming is performed. In order to compensate for this change in the image plane position, the second lens group B is used for an object having the same object distance at different focal lengths. Therefore, it is necessary to bring out different amounts of feeding to focus. The constraints at that time are, as described above,
When focusing on a subject at the same distance, the condition is that the focus lens group must be moved by a different distance at the same rotation angle of the distance ring according to different focal lengths to focus on the subject.

Next, a configuration for obtaining this function will be described. On the inner surface of the zoom cam ring 21, a straight guide groove 21s parallel to the optical axis is formed.
A radial pin 24p provided integrally with the focus cam ring 24 is slidably fitted in 1s. Therefore, the focus cam ring 24 always rotates integrally with the zoom cam ring 21 in the rotation direction, and can move relatively in the axial direction.
2 and 3 show the zoom cam ring 21 and the intermediate moving frame 2.
FIG. 2 is a diagram in which main parts are developed in the axial direction to make the relationship between the focus cam ring 24 and the second group frame 12 easy to understand.

The focus cam ring 24 has a penetrating focus cam groove 26 formed therein. A cam follower 26C (12) formed integrally with the second group frame 12 and a cam follower 26C (22) formed integrally with the intermediate moving frame 22 are fitted on the front and back sides of the focus cam groove 26 at the same time.

A focus lever 31 is fixed to the rear end of the focus operation ring 30. The focus lever 31 extends forward inside the zoom cam ring 21 and has a pin 31a at its distal end. (See FIG. 11). The transmission bar 32 is fixed to the second group frame 12, and the pin 31 a is slidably fitted in a groove 32 a formed in the transmission bar 32 in a direction parallel to the optical axis. Due to this interlocking relationship, when the focus operation ring 30 is rotated, the second group frame 12 always rotates integrally. The second group frame 12 is relatively movable in the optical axis direction with respect to the focus operation ring 30 (focus lever 31).

The varifocal lens barrel 10 operates as follows. When the zoom operation ring 20 is rotated between the telephoto end and the wide end, the zoom cam ring 21 that rotates integrally with the zoom operation ring 20 is moved between the upper telephoto end position and the lower wide end position in FIGS. Rotate between This maximum rotation angle is defined as ΔθL. Even if the zoom cam ring 21 rotates, its axial position does not change, and the intermediate moving frame 22 (cam follower 22C) that is guided straight ahead moves the optical axis by ΔZ _L according to the second group cam groove 21B of the zoom cam ring 21. Move in the direction. At this time, the rotational position of the focus cam ring 24 is always the same as that of the zoom cam ring 21 due to the relationship between the straight guide groove 21s and the radial pin 24p. In the focus cam groove 26 of the focus cam ring 24, the second group frame 12
And the cam follower 26C (12) integrated with the
When the second group frame 12 is rotated via the focus lever 31 and the transmission bar 32 by rotating the focus operation ring 30, the focus cam ring 24 does not rotate. Moves in the optical axis direction while rotating. The maximum rotation angle of the focus operation ring 30 from the infinity shooting position to the shortest shooting position is Δθ shown in FIG.
Is F _N, it is constant regardless of the rotational position of the zoom operation ring 20.

Now, the zoom operation ring 20 (zoom cam ring 2)
When 1) is at the wide end position, a state is considered in which the second group frame 12 (second lens group B) is at the infinity shooting position. At this time, the cam followers 26C (12) of the second group frame 12 and the cam followers 26C of the intermediate moving frame 22 are provided at the upper end of the focus cam groove 26 of the focus cam ring 24 shown in the lower part of FIG.
C (22) is fitted at the same circumferential position (two cam followers are fitted on the front and back). When the focus operation ring 30 is rotated in the wide-end infinity shooting state, the second group frame 12 (cam follower 26C (12)) rotates with respect to the fixed focus cam ring 24 (focus cam groove 26). Therefore, the second group frame 12 moves in the optical axis direction according to the focus cam groove 26 while rotating. When the zoom operation ring 20 is at the wide end position and the focus operation ring 30 has moved from the infinity shooting position to the shortest shooting position by an angle ΔθF _N , the amount of movement in the optical axis direction of the second group frame 12 is ΔF _S.

When the zoom operation ring 20 is turned from the wide end position to the tele end position, the zoom cam ring 21 is turned to rotate as shown in FIG.
From the lower position to the upper position of the first group cam groove 21
A, according to the cam groove 21B for the second group and the cam groove 21C for the third group,
The first group frame 11 (first lens group A), the intermediate moving frame 22 (second
The lens group B) and the third group frame 13 (the third lens group C and the fourth lens group D) move (forward) in the optical axis direction. When the zoom cam ring 21 rotates, the focus cam ring 24 rotates at the same angle as the zoom cam ring 21 by the fitting relationship between the radial direction pin 24p and the straight guide groove 21s. Cam follower 2 engaging with groove 21B
The intermediate moving frame 22 having 2C moves (moves forward) in the optical axis direction according to the second group cam groove 21B. At this time, the cam follower 26C (12) of the second group frame 12 is also fitted into the focus cam groove 26 of the focus cam ring 24 at the same time, so that the second group frame 12 advances by the same amount as the intermediate moving frame 22. The advance amount of the intermediate moving frame 22 and the second group frame 12 at this time due to the rotation of the zoom cam ring 21 is defined as ΔZ _L. The movement amount ΔZ _L of the second group frame 12 (second lens group B) due to the rotation of the zoom cam ring 21 is determined only by the shape of the second group cam groove 21B (not affected by the focus cam groove 26). In other words, the shape of the second group cam groove 21B is set on an infinity basis for focusing on an object at infinity.

On the other hand, when the focus cam ring 24 rotates by the same amount as the zoom cam ring 21, it retreats by ΔF _{0 with} respect to the intermediate moving frame 22 according to the focus cam 26. That is, with respect to the fixed barrel 15, the intermediate moving frame 22 and the second group frame 12
Moves forward by ΔZ _L whereas the focus cam ring 24
It will move forward by Z _L -ΔF ₀ . As described above, at this time, the second group frame 12 and the intermediate moving frame 22 do not change their relative positions.

When the focus cam ring 24 rotates, the focus cam groove 2 of the cam follower 26C (12)
6, the relative position within the focus operation ring 30 changes.
Is rotated, the maximum rotation range (maximum rotation angle ΔθF _N ) of the cam follower 26C (12) in the focus cam groove 26 when performing focusing is changed. (FIG. 3).
Therefore, by appropriately setting the shape of the focus cam groove 26, the second group frame 12 (the second lens group B) is moved forward and backward by different distances by the same rotation angle of the focus operation ring 30, and the focus shift accompanying zooming is performed. And an operation of focusing on the subject can be given at the same time.

The above is the operation in the case where the zoom operation ring 20 is rotated from the wide end to the telephoto end. Similarly, at the intermediate focal length, the focus at the time of focusing is performed by rotating the focus operation ring 30. The maximum rotation angle ΔθF _N of the cam groove 26 can be changed. The shape of the focus cam groove 26 is determined so that the above operation can be obtained.

The above description is for the case of focusing on an object at infinity, and the positions of the cam followers 26C (12) and 26C (22) in the circumferential direction coincide with each other. on the other hand,
When focusing on a finite distance, the cam follower 26C (1
Since only 2) moves in the focus cam groove 26, the cam followers 26C (12) and 26C (2) in the circumferential direction
The position 2) is shifted. When zooming is performed by rotating the zoom operation ring 20 in this state, the focus cam ring 24 rotates as described above, but the cam follower 26C
Since there is a shift in the circumferential positions of (12) and 26C (22), the operation is slightly different from the above-mentioned operation. During zooming, the cam follower 26C (22) moves by 2 in the optical axis direction.
The cam follower 2 is restricted by the group cam groove 21B.
6C (12) has no such regulation. Therefore, the focus cam ring 24 moves the cam follower 26 during zooming.
C (22), the cam follower 26C (1
2) is guided by the focus cam groove 26 of the focus cam ring 24 and moves in the optical axis direction. As a result, the relative position between the intermediate moving frame 22 and the focus lens frame 12 changes,
The second group frame 12 (second lens group B) moves to a focus position corresponding to a focal length determined by a rotational position of the zoom operation ring 20 with respect to the fixed barrel 15. In other words, even if zooming is performed while focusing on a subject at a finite distance,
The focal length can be changed while maintaining the in-focus state for the subject.

A specific example of a method for determining the shape of the focus cam groove 26 will be described with reference to FIGS. The rotation angles (ΔθF _{1 to} ΔθF _N ) of the focus operation ring 30 and the extension amounts (infinity to close distance) (ΔF _S , ΔF _{1 to} ΔF ₄ , ΔF _L ) of the second group frame 12 (second lens group B) The relationship, Z _S ~
For each focal length of Z _L , shooting position at infinity (extending amount: 0)
Is obtained with respect to the origin, a change curve as shown in FIG. 4 is obtained. In this graph, Z _S and Z _L are the focal lengths at the wide end and the tele end, respectively, and Z ₁ through Z
₄ is an arbitrary intermediate focal length suitable for determining the shape of the focus cam groove 26. FIG. 6 shows the arrangement of the variation curves of the feeding amount for each focal length obtained in FIG. 4 corresponding to the rotation angle (Δθ _{S to} Δθ _L ) of the zoom operation ring 20 corresponding to the focal length. . FIG. 6 shows the relationship between the rotation angle of the zoom operation ring 20 and the amount of extension of each lens group, that is, the movement trajectory (T2 to T2) of each lens group during zooming.
4) is also drawn at the same time. T2 is the movement locus of the second lens group B, T3 is the movement locus of the third lens group C, and T4 is the first
6 is a movement locus of a lens group A. The arrangement method of the change curves at this time is, for example, when the change amount curves P and Q at the focal lengths Z _S and Z ₁ are arranged, as shown in FIG. Rotation angle Δθ _S of operation ring 20
(Origin), and then the change curve Q
Is located at the corresponding position of the same rotation angle Δθ1. Hereinafter, when such an arrangement is performed for all the graphs of the respective focal lengths, a set graph R0 of the extension amount of the second group frame 12 (the second lens group B) is obtained. By connecting the origin of the set graph R0, a continuous curve R shown in FIG. 7 is obtained. 6 and 7, the horizontal axis indicating the rotation angle of the zoom operation ring 20 is scaled so that the continuous curve R becomes a smooth curve.

If the continuous curve R obtained in FIG. 7 is formed into the shape of the focus cam groove 26, the above-described operation can be performed by the second group frame 12 (the second lens group B). Continuous curve R
Is obtained by connecting the origin of the above-mentioned change curve (that is, the infinity shooting position of the second group frame 12 (the second lens group B)).
An accurate in-focus position of 2 (second lens group B) can be secured.
On the other hand, at the finite distance, since the continuous curve R is approximately drawn, the extension amount of the second group frame 12 (the second lens group B) at the finite shooting distance has an error. Therefore, by changing the maximum rotation angle ΔθF _N of the focus operation ring 30, the shape of the focus cam groove 26 is set so that this error falls within an allowable error range (within the depth of field). Therefore, by changing the maximum rotation angle ΔθF _N of the focus cam groove 26 in accordance with zooming according to the shape of the focus cam groove 26, the second group frame 12
The (second lens group B) can be moved to an accurate focusing position with no error at an infinite distance, and to a position within the depth of field at a finite distance.

In the AF lens, the focus operation ring 30 may be electrically driven by a rotation angle based on the defocus amount. If the defocus amount is the same, the rotation angle is constant at each focal length.

In the above embodiment, the focus cam ring 2
4 shows a configuration in which the focus cam groove 26 is formed.
It is also possible to use a cam projection instead of the cam groove. FIG.
FIG. 10 to FIG. 10 show the embodiment. The configuration other than the periphery of the cam projection is substantially the same as that of the embodiment of FIG. 1, and the same elements are denoted by the same reference numerals and description thereof will be omitted.

As shown in FIG. 9, the focus cam ring 33 shown in FIG.
A and 34B are integrally formed three each. The shape of the focus cam protrusion 34A is a shape corresponding to the shape of the above-described focus cam groove 26, as shown in FIG. Since only the range of the maximum rotation angle ΔθL of the zoom cam ring 21 at the end (the hatched portion in FIG. 10) is used, only that range is formed. The focus cam projection 34A is slidable on a pair of pin followers 35 integrally formed inside the second group frame 12, and the focus cam projection 34B is slidable on a pair of pin followers 36 integrally formed outside the intermediate moving frame 22. The pin follower 35 and the pin follower 36 are held by the second group frame 12 and the intermediate moving frame 22 at intervals of 120 °, respectively.
Are arranged. Therefore, the pin followers 35 and 36 of the second group frame 12 and the intermediate moving frame 22 are guided by the focus cam protrusions 34A and 34B, respectively, and the same operations as the second group frame 12 and the intermediate moving frame 22 by the focus cam groove 26 are performed. I do.

According to the aspect of the cam projection, the focus cam 33 can be formed as a molded product using a resin or the like. With such a configuration, variation between products can be minimized, and since it can be formed with a simple mold configuration, it is advantageous for cost reduction.

[0032]

According to the present invention, a varifocal lens barrel in which the focus cam and the zoom cam do not interfere with each other can be obtained.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing an embodiment of a varifocal lens barrel according to the present invention.

FIG. 2 is a development view illustrating a relationship between a zoom cam ring, an intermediate moving frame, and a focus cam ring of the lens barrel in FIG.

FIG. 3 is a development view for explaining another relationship.

FIG. 4 is a graph showing a relationship between a rotation angle of a focus operation ring and an amount of extension of a second group frame (second lens group) (from infinity to a close distance) for each focal length.

FIG. 5 is a diagram showing a method of arranging the curves for each focal length obtained in FIG. 4 such that the origin thereof coincides with the rotation angle of the zoom operation ring for each focal length.

6 is a diagram showing a set graph in which the relationship between the amount of extension of the second group frame and the rotation angle of the zoom operation ring for each focal length is arranged by the method shown in FIG. 5;

FIG. 7 is a graph showing a continuous curve obtained by connecting the origin of the set graph of FIG. 6;

FIG. 8 is a longitudinal sectional view showing another embodiment of the varifocal lens barrel according to the present invention.

9 is a cross-sectional view of the focus cam ring of FIG. 8 as viewed from the optical axis direction.

FIG. 10 is a developed view showing a relationship between a focus cam and a cam follower of the lens barrel in FIG. 8;

FIG. 11 is a view taken in the direction of the arrow XI in FIG. 1, showing a connection structure between the focus lever and the transmission bar.

[Explanation of symbols]

A First lens group B Second lens group (focus lens group) C Third lens group D Fourth lens group 11 First group frame 12 Second group frame (focus lens frame) 13 Third group frame 14 Fourth group frame 15 Fixed cylinder 15s Straight guide groove 20 Zoom operating ring 30 Focus operating ring 20a Connecting arm 21 Zoom cam ring 21A First group cam groove 21B Second group cam groove 21C Third group cam groove 11C Cam follower 13C Cam follower 21p Coupling pin 21s Straight guiding groove 22 Intermediate moving frame 22C Cam follower 24 Focus cam ring 24p Radial pin 25 Fourth group cam ring 26 Focus cam groove (Focus cam) 26C Cam follower 31 Focus lever 32 Transmission bar 33 Focus cam ring 34A 34B Focus cam projection (Focus cam) 35 36 Pin follower (Cam follower) A)

Claims (4)

[Claims] 1. A zoom lens system comprising: a plurality of variable power lens groups movable in an optical axis direction for changing a focal length, one of which has both functions of zooming and focusing; In a vari-focal lens barrel, which is a focus lens group in which the focus extension position changes for the same object distance, a zoom operation ring that is rotated; a focus operation ring that is rotated independently of the zoom operation ring; A focus lens frame that supports the focus lens group and is driven to rotate by a rotation operation of the operation ring; an intermediate moving frame that is guided in the optical axis direction and supports the focus lens frame; A zoom cam ring for moving the plurality of zoom lens groups and the intermediate moving frame in a predetermined locus in the optical axis direction; Rotates integrally, the relative movement of the optical axis direction can be,
A focus cam ring having a focus cam for compensating an image plane movement at a focal length determined by a rotation position of the zoom cam ring; and a focus lens frame and an intermediate moving frame which are simultaneously engaged with the focus cam of the focus cam ring. The focus cam ring is guided by the focus cam and rotated relative to the focus lens frame and the intermediate moving frame when the intermediate moving frame moves in the optical axis direction by rotation of the zoom cam ring. A varifocal lens barrel wherein the focus cam moves relative to the optical axis while changing the position of engagement of the focus cam with a cam follower of the focus lens frame. 2. The vari-focal lens barrel according to claim 1, wherein the intermediate moving frame and the focus lens frame are moved through a focus cam of a focus cam ring during zooming in a state of focusing on an object at infinity. A varifocal lens barrel that moves together without changing its relative position. 3. The varifocal lens barrel according to claim 1, wherein the focus cam is formed from a focus cam groove. 4. The varifocal lens barrel according to claim 1, wherein the focus cam is formed from a focus cam projection.