JPS6349715A - Zoom lens barrel - Google Patents

Abstract

PURPOSE:To perform infinite-distance/close-up focusing with a single operation angle by forming cam grooves for focusing in a frame which rotates associatively with zooming operation, varying the use ranges of the cam grooves successively and interlockingly with the zooming, and moving the frame in the directions of the optical axis and then making corrections even at the infinite-distance position. CONSTITUTION:A focus group L4 is moved by the zooming between the infinite- distance position and a close-up photographic distance position. When a zooming ring 15 is rotated, a cam ring 5 is rotated by a zoom pin 21 and the power variation frame of a power variation group L2 is controlled by a cam groove 5a, so specific movement is performed in an optical-axis direction to perform the zooming. Further, when the cam ring 5 rotates, an F frame 8 also rotates in the same direction through a pin 23 and a pin 22 implanted in a correction frame 7 is controlled by the cam groove 5b of the cam ring 5, so when the cam ring 5 rotates, the correction frame 7 moves in the optical-axis direction and an interlocking frame 9 fixed integrally with the frame 7 also slides on the outer periphery of a fixed frame 1 in the optical-axis direction while holding the F frame 8 rotatably.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a zoom lens barrel, and more particularly to a rear focus type zoom lens barrel.

[Prior Art] Various so-called rear focus type zoom lens barrels are known, which have a single variable magnification group and a single focus group on the imaging plane side of the variable magnification group. In this type of zoom lens barrel, the focus group moves M from infinity to close-up, and the focus 7 at the same subject distance.
! The position of T changes with each focal length.

In particular, since the difference in the amount of movement of the focus group approximately corresponds to the square of the zoom magnification, the difference is significant in zoom lens barrels with high magnification.

[Problems to be solved by the invention] For this reason, the operating angle of the focusing ring changes at each focal length, and focus movement occurs due to zooming, so focusing is possible at any focal length with the same rotation angle. However, the operability was significantly worse than that of the so-called front lens focus type.

In view of these problems, the present invention corrects focus movement due to zooming and changes only the range of use of the cam groove that controls the movement of the focus group without changing the use angle, so that it can be adjusted to any focal length. It is an object of the present invention to provide a focusing type zoom lens barrel with good operability, which enables focusing at the same operating angle even in the case of the present invention.

[Means for Solving the Problems] In the zoom lens barrel of the present invention, a first cam groove is provided in a first cam ring that rotates in conjunction with zooming.
An interlocking frame that is movable only in the optical axis direction is engaged with the cam groove of the second cam ring, which is integral with the interlocking frame in the optical axis direction and is integral with the first cam ring in the rotational direction. A protrusion that is integrated with the focus group that rotates in conjunction with focusing is engaged with the cam groove of No. 2. The second cam groove is formed at an angle that is equal to or greater than the sum of the focusing operation angle and the zooming operation angle. The difference in the optical axis angle direction is approximately equal to the amount of movement of the focus group from infinity to the close shooting distance at the focal length.

[Operation] By cofocusing, the focus group is moved: By rotating the protrusion integrated with T, the protrusion moves in the optical axis direction according to the cam shape of the second cam groove, and the focus group moves. A focusing group in which the focusing operation angle of the protrusion moving on the second cam groove is the same at any focal length, and the amount of movement in the optical axis direction at both ends of the same operation angle is from infinity to close shooting distance at the focal length at that time. Since the amount of movement is equal to the amount of movement, focusing from infinity to close shooting distance can be performed at any focal length and at the same focusing operation angle.

Embodiment FIG. 1 is a sectional view of a zoom lens barrel showing an embodiment of the present invention. The state of this zoom lens barrel shown in FIG. 1 is the state at infinity in telephoto mode. The optical system consists of 4 groups, Ll and L3 are fixed 7! L L is a variable power group,
L4 is the focus 11T, so it is a rear focus type zoom lens barrel.

The fixed group L1 is held by the first group frame 16 and is screwed and fixed to the front fixed frame 2. A cam ring 5 is provided on the inner periphery of the front fixed frame 2.
A shaft 17 is rotatably fitted therein, and a shaft 17 arranged parallel to the optical axis direction is supported at one end by the front fixing frame 2 and by a shaft holder 18 at the other end. Here, the shaft presser 18 is fixed by fixing the presser frame 19 to the inner periphery of the end of the front fixed frame 2 with screws.
At the same time, the movement of the cam ring 5 in the optical axis direction is also restricted. Although only one shaft 17 is shown in FIG.
Actually, there are two to prevent rotation. That is, FIG. 4 shows a perspective view of the correction frame 7, and the fitting part 7d provided in the block 7c of this correction frame and the fitting part 7d and 180
The shafts 17 are fitted into fitting portions 7e provided at opposing positions, respectively. These 2 tons! ! By fitting with the shaft 17 at the i position, the correction frame 7 can move in the optical axis direction without rotation.

The variable magnification group L2 is supported by a variable magnification frame (not shown), and this variable magnification frame, like the hli regular frame 7 described above, has a fitting portion for two shutters, so that it can move parallel to the optical axis direction. It has become. A pin 22 is installed in the correction frame 7, and a similar pin is installed in the zoom frame (not shown), and these are the cam grooves 5b of the cam ring 5 shown in FIG.

5a, respectively. Further, a zoom pin 21 is implanted in the cam ring 5, and the zoom pin 21 is rotatably fitted into the groove 1 of the zoom ring 15 on the outer periphery of the front fixed frame 2.
It is inserted into 5a. Further, the zoom ring 15 is provided with a gear portion 15b that is an engaging portion with a zoom motor (not shown). Therefore, when the zoom ring 15 is rotated by the zoom motor or manually, the cam ring 5 rotates via the zoom pin 21, so the variable power group L2 follows the shape of the cam groove 5, and the correction frame 7 follows the shape of the cam groove 5b. Each moves only in the optical axis direction according to its shape.

Further, a focus ring 6 is rotatably held on the rear outer periphery of the front fixed frame 2. Furthermore, on the outer periphery of the front fixed frame 2, between the zoom ring 15 and the focus ring 6, there is an index ring 1 for reading the zooming position and the focusing position.
4 is fixed to the front fixed frame 2 by an index presser 20. The movement of the focus ring 6 in the optical axis direction is regulated by the intermediate frame 3, and the same-width frame 3 is fixed to the front fixed frame 2 with screws (not shown). The focus ring 6 is also provided with a gear portion 6a that is an engaging portion with a motor (not shown) (see FIG. 3).

Furthermore, a fixed group L corresponding to the third group is provided in the center of the intermediate frame 3.
3 is fixed. The fixed frame 1 that supports the focus group L4 is fixed to the intermediate frame 3 with screws (not shown). Further, at this time, an iris 4 is held between the intermediate frame 3 and the fixed frame 1. The focus group L4 is supported by a fourth group frame 13, and the fourth group frame 13 is slidable on the inner circumference of the fixed frame 1. An interlocking frame 9 fits into the outer periphery of the fixed frame 1, and this interlocking frame 9
On the outer periphery of the focus frame (hereinafter referred to as F
frame) 8 is rotatably held and the threaded portion 9 of the interlocking frame 9
d (see Fig. 4) with the presser frame 10 screwed onto F.
The frame 8 is regulated in the optical axis direction with respect to the interlocking frame 9. As shown in FIG. 4, the interlocking frame 9 is fixed at the threaded portions 9a, 9b by screws 25 and threaded portions 7f, 7g of the longitudinal portions 7a, 7b extending along the optical axis direction of the correction frame 7, When the correction frame 7 moves in the optical axis direction according to the shape of the cam groove 5b, the interlocking frame 9 also moves integrally with the correction frame 7.

As shown in FIG.
3 is implanted, and the pin 23 is fitted into a groove 5c (see FIG. 2) formed at the end of the longitudinal portion 5d of the cam ring 5.

The 4th group frame 13 has a focus pin (hereinafter referred to as F-bin)
12 is implanted, and this F pin 12 passes through the groove 1a provided in the fixed frame 1, the groove 9c provided in the interlocking frame 9, and the cam groove 8a provided in the F frame 8. As shown, a groove 11a of a focus lever (hereinafter referred to as F lever) 11 is fixed to the focus ring 6 with a screw 24.
is fitted.

In the zoom lens barrel shown in FIG. 1 configured as described above, the imaging plane of the zoom lens barrel exists on the right side of the focus group L4, and in actual use, an image pickup unit (not shown) is located at this position. A cord is provided.

Next, the operation of the zoom lens barrel having such a configuration will be explained.

In a rear focus type zoom lens barrel such as this zoom lens barrel, in which a single lens group L2 is moved to change the magnification and focusing is performed on the imaging plane side, the focus group L4 during zooming is The amount of movement from the infinity position to the closest shooting distance changes sequentially. FIG. 6 shows the moving state of the focus group L4 in the zoom lens barrel of this embodiment. In FIG. 6, a curve 101 shows the movement of the focus group L4 when zooming is performed at an infinity focusing position, and a curve 102 shows the movement of the focus group L4 when zooming is performed at a close position of 0.5 m. This shows that. The zooming lens barrel of this embodiment has a zoom ratio of 6 times, and the ratio of the amount of movement from infinity to a close distance of 0.5 m in wide and telephoto is 62, or about 36.

First, when the zoom ring 15 is rotated, the cam ring 5 is rotated by the zoom pin 21, but at this time, the variable power frame (not shown) of the variable power group L2 is regulated by the cam groove 5a shown in FIG. By doing so, a predetermined movement is performed in the optical axis direction, and zooming is performed. Also, when the cam ring 5 rotates, the pin 23
The F frame 8 also rotates in the same direction. Furthermore, at this time, since the pin 22 implanted in the correction frame 7 is regulated by the cam groove 5b of the cam ring 5, when the cam ring 5 rotates,
The correction frame 7 moves along the optical axis direction. Since the interlocking frame 9 is integrally fixed to the correction frame 7, the interlocking frame 9 also slides on the outer periphery of the fixed frame 1 in the optical axis direction while rotatably holding the F frame 8. That is, when the cam ring 5 rotates during zooming, the F frame 8 rotates on the interlocking frame 9 and moves in the optical axis direction together with the interlocking frame 9.

On the other hand, regarding focusing, the rotation of the focus ring 6 is transmitted to the F pin 12 by the F lever 11.
3 rotates. Since the F pin 12 is regulated by the cam groove 8a of the F frame 8, the rotation of the focus ring 5 causes the fourth group lens 13 to rotate along the cam groove 8a and move in the optical axis direction. In this embodiment, the magnification changing cam groove 5a of the cam ring 5 is linear, but the correction frame circumferential cam groove 5b and the F
The focusing cam groove 8a of the frame 8 is non-linear.

The shapes of the cam groove 8a and the cam groove 5b are respectively shown by a curve 103 shown in FIG. 7 and a curve 104 shown by a solid line in FIG. 8. In this embodiment, it is assumed that the rotation angle for zooming is 90'' and the rotation angle for focusing is 90''. First, to explain the shape of the cam groove 8a of the F frame 8, on the curve 103 shown in FIG. The point 0 on this curve 103 corresponds to the position where the F frame 8 has been rotated by 90'', and the amount of extension here is 0. This is the same as the amount of movement δV of the focus group L to the closest position of 5 m.

Next, considering the case of telephoto, the usable range of the cam groove 8a in telephoto is from point C on the curve 103 due to the characteristics of the zoom lens barrel. Here, the coordinates of the 0 point have already been determined, so the coordinates of the A point are the coordinates of the 0 point plus the amount of movement δT of the focus group L from infinity to the closest point of 0.5 m in Figure 6. . Similarly, in the standard position, the range of use is 90° from point D to point B, and the difference between the coordinates of point B and point D is the focus at standard time in Fig. 6? The amount of movement δS is j'f L 4.

Although the three focal length states have been explained above, the shape of the cam groove 8a shown by the curve 103 in FIG. The shape of the cam groove 5b around the correction frame of the cam ring 5 is shown in FIG. is the same as the curve 101, and the solid curve 104 is the shape of the cam?m5b.Curve 10
4 is a value corrected by taking into account the amount of movement from point E to point C of curve 105 in FIG. 7 above.

What about the behavior during focusing due to these? To explain in detail, first of all, at wide infinite speed, F bin 12
is located at point E, and pin 22 is located at point F. In this state, when the focus ring is rotated from infinity to close, the F lever 11 rotates and the F bin 12 is moved along the cam 8a, thereby moving the focus group L4 from point E to the close position of point 0. do.

Note that at this time, the F frame 8 does not rotate or move in the optical axis direction. When zooming from the wide infinity position, the cam ring 5 rotates, but the direction of rotation of the F pin 12 is restricted by the F lever 11, which does not rotate, so the focus group L4 rotates by the rotation of the cam ring 5. Only the cam groove 8a moves along the cam groove 8a.

At this time, the correction frame 7 is also moved by the cam groove 5b, but the cam form of the cam groove 5b is moved by the cam groove 8 as shown in FIG.
Since points F to H are provided in consideration of the cam shape of points E to C of a, focus J! The position of T L 4 is the same as F; 1 (limit curve 101) shown in FIG. It is.

By zooming, you can reach the standard infinite position, that is,
When the F pin 12 is present at point D and the pin 22 is present at point 6, the rotation angle of the focus ring 6 is always 90° when focusing, so the F pin 12 rotates from point D to point B. It moves within the cam groove 8a of the F frame 8 while being regulated by the F lever 11. Here, the difference between point B and point D is set equal to the difference δS between infinity and close range at the standard position in FIG. 6, so focusing from infinity to close range is possible.

In the telephoto state, pin 22 is at point H and F pin 12 is at point C.
Focusing is also possible by moving between points and points A.

Due to the above-described effects, arbitrary focusing is possible at any focal length.

[Effects of the Invention] As described above, according to the present invention, a focusing cam groove is provided in a frame that rotates in conjunction with zooming, and the usage range of the cam groove is sequentially changed in conjunction with zooming.
In addition, by moving the frame in the optical axis direction, the infinity position is corrected, so that focusing from infinity to close-up can be performed with a single operating angle at any focal length.

[Brief explanation of the drawing]

1 is a longitudinal sectional side view of a zoom lens barrel showing an embodiment of the present invention, FIG. 2 is a perspective view of a cam ring in FIG. 1, and FIG.
Figure 4 is a perspective view of the focus ring and F lever in the figure; Figure 4 is a perspective view of the correction frame and °-linked frame in Figure 1;
The figure is a perspective view of the F frame in Figure 1. Figure 6 is a characteristic curve diagram showing the relationship between the movement amount of the focus group and the focal length. Figure 7 is the shape of the cam groove formed in the F frame. FIG. 8 is a characteristic curve diagram showing the shape of the cam 1M formed in the cam ring. 5・・・・・・・・・・・・Cam ring (first cam ring) 5
b...Cam groove (first cam groove) 6...
......Focus ring 8...
...F frame (second cam ring) 8a...Cam groove (second cam groove) 9...Interlocking frame 12... ...F bottle (protrusion) 15...
...Zoom ring L2......Variable magnification group L4...Focus group is also 4th figure%5th figure,

Claims (3)

[Claims] (1) In a rear focus type zoom lens barrel in which the movement range and amount of movement of the focus group for the same shooting distance range changes depending on the focal length, the first cam groove rotates in conjunction with zooming. a first cam ring having a first cam ring; an interlocking frame that is regulated by the first cam groove and moves only in the optical axis direction when the first cam ring rotates; and an interlocking frame that is integral with the interlocking frame in the optical axis direction. a second cam ring which rotates integrally with the first cam ring in the rotational direction and has a second cam groove;
A zoom lens barrel comprising: a cam ring; and a protrusion that is integrally provided with the focus group while being engaged with the second cam groove and rotates in conjunction with focusing. (2) The second cam groove is formed with a set angle equal to or greater than the sum of a focusing operation angle and a zooming operation angle. zoom lens barrel. (3) The above-mentioned second cam groove is such that when the focusing operation angle is set at an arbitrary focal length position, the same operation angle is equal and the difference in position in the optical axis direction at both ends of the same operation angle is arbitrary. 2. The zoom lens barrel according to claim 1, wherein the focal length is approximately equal to the amount of movement of the focus group from infinity to close shooting distance.