JPH03216610A - Driving device for zoom lens - Google Patents

Abstract

PURPOSE:To simplify camera structure and to improve the operability by moving a negative movable lens group among three positive, negative, and positive relay lens groups between two positions along the optical axis. CONSTITUTION:The fixed lens group IV with positive refracting power, the movable lens group V which has negative refracting power and is moved to vary the focal length, and the fixed lens group VI with positive refracting power are arranged as the relay lens groups in order from the object field side. Then a cam 50 and an arm 52 are used to shift the movable lens V in position. The cam 50 is provided nearby the movable lens group V rotatably by a motor on an axis 54 as shown by the arrow B and the movable lens group V is moved as shown by the arrow C by the arm 52 extended from the cam 50. Consequently, the movable lens group can be moved by the simple device to obtain excellent operability.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a zoom lens driving device, and more specifically, the present invention relates to a zoom lens driving device, and more specifically, a zoom lens driving device that moves some lens groups of a zoom lens while keeping the image plane position unchanged. The present invention relates to a zoom lens driving device having a function of changing the focal length range of a zoom lens.

(Prior art) Changes in the focal length of a zoom lens, for example, when the focal length is lO
The following methods are known for changing the focal length from 100mm to 15mm to 150mm.

(1) A method in which an attachment lens is attached and detached between the zoom lens body and the image plane.

(2) A method in which parts of the zoom lens that are not involved in focusing and zooming, the so-called relay part of the zoom lens, are replaced. (3) A method of attaching and detaching an afocal lens system whose absolute value of angular magnification is not 1 to the subject side of the zoom lens body.

(4) A method of attaching and detaching an attachment lens to a part of the zoom lens relay. These methods (1) to (4) require a mechanism to attach and detach the attachment lens from the side to the zoom lens body, which complicates the structure of the lens barrel of the zoom lens body and makes it prone to failure. There is a problem with this.

In contrast to this type of system, there is a so-called double zoom system in which a zoom system is further provided in a portion of the relay of the zoom lens.

(Problem to be Solved by the Invention) In the double zoom method, the focal length range can be continuously changed while keeping the image plane position unchanged, and the total optical length does not change. It's a useful tool.

However, this system has problems in that the zoom mechanism is also included in the relay of the zoom lens, which makes the structure extremely complicated, the size is large, and the price is high.

In order to solve these problems, the applicant of the present application previously proposed a zoom lens shown in FIGS. 4 and 5 in Japanese Patent Application No. 1-301444.

Such a zoom lens has, from the object world side, a focusing lens group (2), a zooming lens group (2), (2), and a relay lens group. It is composed of three lens groups ■, V1■, and the three lens groups ■,
Of V and VI, lens group V having a negative refractive power is provided in a movable lens group that can be moved on the optical axis between two positions that are the same image plane position (2). According to this zoom lens, by moving the lens group V, which is a movable lens group, on the optical axis so that it is located at two positions, the position shown in FIG. 4 and the position shown in FIG. You can change the zoom area instantly.

Furthermore, since the optical axis of one of the lens groups making up part of the relay is moved, the structure is simpler and easier to operate than a conventional double zoom type zoom lens. However, the drive device that drives the movable lens group has a simple structure and good operability, which simplifies the camera structure and improves the operability using the zoom lens shown in Figs. 4 and 5. It is important for

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to be able to instantly drive a lens group V having negative refractive power, which constitutes a part of the zoom lens relay shown in FIGS. 4 and 5, to two predetermined positions, and to An object of the present invention is to provide a zoom lens driving device that can simplify the structure of a camera using a zoom lens and improve operability.

(Means for Solving the Problems) The present inventor considered that it would be effective to drive the lens group V shown in FIGS. Achieved an invention.

That is, in the present invention, from the object world side, the focusing lens group,
In a zoom lens having a zooming lens group and a relay lens group, a lens having a negative refractive power among the three lens groups that make up the relay lens group and whose refractive powers are positive, negative, and positive from the object world side. A cam rotatably provided near the lens group and a lens group extending from the cam and having negative refractive power of the relay lens group are aligned on the optical axis between two positions that are the same image plane position. The zoom lens driving device is characterized in that it includes an arm whose distal end is connected to the lens group having negative refractive power so as to be movable above the lens group.

In the present invention having such a configuration, since the arm is an elastic member, it is possible to bias the lens group having negative refractive power of the relay lens group in the direction of a predetermined position, regardless of the orientation of the camera. The lens group can be held in place.

(Function) In the present invention, the lens group having a negative refractive power of the relay lens group which is a movable lens group is an arm extending from a rotatable cam provided near the movable lens group. connected to the tip.

Therefore, the movable lens group can be instantly moved to a predetermined position by rotating the cam.

Further, the moving speed of the movable lens group can be easily controlled by adjusting the rotating speed of the cam, the length of the arm, etc.

As described above, in the present invention, since the movement and control of the movable lens group can be performed by a simple drive device consisting of a cam and an arm, a zoom lens having a movable lens group in the relay lens group is used. The structure of the camera can be simplified and the operability can be improved.

(Example) The present invention will be explained in more detail using the drawings.

FIG. 1 is a partial cross-sectional view showing an example of the present invention, and shows lens groups 1 to 10 constituting a zoom lens in a camera case A.
(2) is incorporated so that the image is formed at the image plane position (2).

FIG. 4 shows the basic arrangement of lens groups 1 to 2 that constitute such a zoom lens.

This zoom lens has two movable focusing lens groups for focusing, two movable zooming lens groups for zooming, and a fixed relay lens for focusing and zooming. The group is arranged.

In addition, the relay lens group consists of, from the object world side, a fixed lens group (■) with positive refractive power, a movable lens group (V) that has negative refractive power and is moved when changing the focal length, and a positive refractive lens group (V). Powerful fixed lens groups ■ are arranged in sequence.

Note that a zoom lens in which such a lens group is arranged forms an image at the position of the image plane (■).

In the zoom lens shown in Fig. 4, the focal length can be changed from 1 to 7 by moving the zooming lens groups ■ and ■.
．． It changes up to 6009.

Table 1 shows standardized data for the lens shown in FIG.

Table ■ In Table 1, Ri is the radius of curvature of the i-th surface, Di is the axial wall thickness or axial air gap between the i-th surface and the i+1-th surface, ν is the dispersion value, and N is the refractive index (d-line). are shown respectively.

Further, dLd2 and d3 indicate the inter-lens spacing that changes due to zooming, and an example of data is shown at the bottom of Table 1. The total sum is, of course, constant.

Furthermore, d4 and d5 indicate the distance between the fixed lens group ■ and the movable lens group V, and the distance between the movable lens group V and the fixed lens group ■, respectively. When the zoom lens is at the spacing position shown in Table 1, the zoom lens is connected to the zooming lens group ■. , ■, the focal length changes from 1 to 7.6009 as described above.

In this embodiment, as will be described later, the movable lens group V is moved from the position shown in FIG. 4 (Table 1) to the image field side (backward), and is moved on the optical axis to the position shown in FIG. It is provided in

In the case of the lens system shown in FIG. 4 and Table 1, the movable lens group V is placed on the image field side. 80886 When moving (Figure 5)
, the image is formed at the position of the image plane ■. The focal length of the entire system at this time takes a value from 1.4602 to 11.0991, and the focal length changes within a range that is 1.4602 times the focal length of the zoom lens shown in FIG.

In addition, the distance between the final surface (33 surfaces) of the lens system and the image surface ■ before and after the movement of the movable lens group V (back focus)
is unchanged at 2.6742, and the total optical length also does not change.

In such a lens system, the amount of movement of the movable lens group V is D
and the focal length at the wide-angle end by basic zooming is fs
If mo and the focal length at the wide-angle end after changing the zoom area are fwe, then the zoom area changing magnification R is R=five/fw
It is expressed as o. In addition, fixed lens group ■, movable lens group V
, the focal lengths of the fixed lens group ■ are fL1 and fL2, respectively.
, fL3, the focal length of the movable lens group V is: When the movable lens group V is moved by a distance D, images are formed on the same image plane (2). In this case, the back focus also remains unchanged.

Here, instead of the movable lens group V, it is possible to provide a fixed lens group (2) having a positive refractive power so as to be movable back and forth, but it is not easy to correct various aberrations.

It is also possible to make the front group of the relay lens group have negative refractive power, the middle group positive, and the rear group positive refractive power, and move the front group with negative refractive power back and forth, but the entire lens system cannot be adopted because it becomes too large.

In this embodiment, the cam 50 and arm 52 shown in FIG. 1 are used to move the movable lens group V from the position shown in FIG. 4 to the position shown in FIG. 5.

The cam 50 is provided near the movable lens group V so as to be rotatable about a shaft 54 in the direction of an arrow B by a motor (not shown).

The arm 52 extending from the cam 50 moves the movable lens group V in the direction of arrow C.

That is, the tip 60 of the arm 52 is connected to a protrusion 62 provided on the outer peripheral surface of the lens case 56 that holds the movable lens group V, as shown in FIG. Therefore, by rotating the cam 50, the lens case 56 can be moved while coming into sliding contact with the inner peripheral surface of the camera case A.

Furthermore, a groove 68 is formed in the outer peripheral surface of the lens case 56. The end surfaces 64 and 66 of this groove 68 are the stopper 68.
The lens case 56, which moves while being in sliding contact with the inner peripheral surface of the camera case A, can be stopped at a predetermined position.

Note that the arm 52 extending from the cam 50 is an elastic member made of a spring material.

In such a drive device for the movable lens group V shown in FIG. 2, the cam 50 is rotated to the right, and the movable lens group V is moved in the direction of the fixed lens group (2) as shown in FIG. 3(a). do. At this time, when the end surface 64 of the groove 68 comes into contact with the stopper 5, the movement of the lens case 56 is stopped.

At this time, the arm 52 is curved because it is an elastic member,
The lens case 56 is urged in the direction of arrow D.

On the other hand, when moving the movable lens group V from the position shown in FIG. 3(a) in the direction of the fixed lens group (2), the cam 50 is rotated to the left.

In this case, when the movable lens group V moves to a predetermined position and stops, the direction of curvature of the arm 52 is opposite to that in FIG. 3(a), as shown in FIG. 3(b), and the movable lens group The direction in which group V is energized is also in the direction of arrow E, which is opposite to the direction of arrow D in FIG. 3(a).

The movable lens group V is urged by this curvature of the arm 52, and is pressed toward the fixed lens group (2) or (2) with a constant force. Therefore, no matter what direction the camera faces, the movable lens group V can be held at a predetermined position.

Further, the impact exerted on the movable lens group V when the stopper comes into contact with the end surface 64 or 66 of the groove 68 can also be absorbed by the curvature of the arm 52. In this embodiment, the moving speed of the movable lens group V can be adjusted by the rotating speed of the cam 50 or the length of the arm 52.

That is, when the length of the arm 52 is increased, the amount of movement of the cam 50 per unit rotation angle can be increased compared to an arm with a short length.

In this embodiment, the cam 50 is rotated by a motor, but the moving distance of the movable lens group V is usually
Since the distance is approximately several tens of millimeters, the cam 50 may be rotated manually.

(Effects of the Invention) According to the present invention, the movable lens group having negative refractive power of the relay lens group consisting of three groups having positive, negative, and positive refractive powers is moved between two positions along the optical axis. By simply moving the lens across the area, the zoom area can be instantly changed between two areas while keeping the image plane position unchanged, providing excellent operability.

Furthermore, since the movable lens group can be moved by a simple device consisting of a cam and an arm, the camera structure is simple and provides good operability. Therefore, it is possible to provide a high-performance zoom lens with fewer failures at a low cost, making it suitable for consumer video cameras and the like.

[Brief explanation of drawings]

FIG. 1 is a partial sectional view showing one embodiment of the present invention, and FIG.
3 is an explanatory diagram for explaining the structure and operation state of the drive device of the present invention, FIG. 4 is a sectional view of the lens at the wide-angle end in the basic state before the movable lens group moves, and FIG. 5 is a sectional view of the lens at the wide-angle end.
Each of the lens cross-sectional views at the wide-angle end after moving the movable lens group and changing the focal length by zooming in the zoom lens shown in the figure is shown. In the figure, ■... Focusing lens group, ■, ■... Zooming lens group, ■... Fixed lens group, ■... Movable lens group, ■...
...Fixed lens group, ■...Image surface position, 50...Cam, 52...Arm. Figure 2 Figure B 3 Drafting procedure amendment dated November 17, 1990

Claims (1)

[Claims] 1. In a zoom lens having a focusing lens group, a zooming lens group, and a relay lens group from the object world side, the refractive power of the relay lens group is positive from the object world side,
Of the three negative and positive lens groups, a cam is rotatably provided near the lens group with negative refractive power, and a relay lens group with negative refractive power extends from the cam. The arm includes an arm whose tip end is connected to the lens group having negative refractive power so that the lens group can be moved on the optical axis between two positions that are the same image plane position. A zoom lens drive device featuring: 2. The zoom lens driving device according to claim 1, wherein the arm is an elastic member.