JPH08313784A - Zoom lens barrel - Google Patents

Abstract

(57) [Summary] [Object] To provide a lens barrel of a double helicoid type lens barrel having a small number of parts and excellent stability of a lens group frame. [Structure] A fixed frame 7 fixed to a camera body and having a helicoid screw in its inner diameter, and a movable frame (2) screwed with the inner diameter of the fixed frame and provided with a helicoid screw or a cam groove in the inner diameter so as to be movable back and forth in the optical axis direction. 2, a moving frame (1) 1 screwed with the inner diameter of the moving frame (2) and integrated with the first group lens frame, and a cam having a one-sided cam 6a on the inner diameter which receives a rotational force directly from the moving frame (2). Rotation is constrained by a frame 6 and a straight key groove having an inner diameter of a fixed frame, and is moved forward and backward integrally with the moving frame (2), and has a straight frame 5 having a cam hole 5a for guiding a cam frame.

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 plurality of lens frames.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 7, in order to perform zooming, it is necessary to independently move three lens groups in the optical axis direction. That is, the movable frame 1 holding the first lens group, the shutter frame 3c holding the second lens group and provided with guide pins at three positions, and the shutter frame 3c holding the third lens group 3
By rotating and driving the moving frame 2 with the three-group frame provided with the guide pin at a position, the three lens groups are independently moved in the optical axis direction by being guided by the helicoid and the cam groove inside the moving frame 2. I was trying to do it.

[0003]

However, in the zoom lens barrel of the conventional camera as described above, the three lens groups are separately driven by the moving frame 2, so that the two cam grooves and the guide pins are formed. Due to the clearance existing between them, the distance between the lens groups of the first and second groups and the distance between the lens groups of the second and third groups fluctuate from time to time, and there is a drawback that the focus surface fluctuates. Not only the accuracy but also the zoom accuracy is degraded.

The present invention solves the conventional drawbacks described above, and provides a zoom lens barrel for a camera capable of moving each lens group while controlling the distance between the lens groups with high accuracy during zooming. With the goal.

[0005]

In order to solve these problems, the present invention has a zoom of a camera having at least three lens groups, each of which is independently moved in the optical axis direction to perform zooming. In the lens barrel, the second lens group moves by the forced rotation of the cam frame while the cam frame guide pin determines the amount of movement in the optical axis direction by the guide of the rectilinear frame cam hole by the rotation of the moving frame 2. And then the third
Provided is a zoom lens barrel characterized in that the lens group is controlled by a relative movement amount with respect to the cam frame by a one-sided cam having an inner diameter of the cam frame.

Further, it has at least three lens groups,
In a zoom lens barrel of a camera that is independently moved in the optical axis direction for zooming, a fixed frame that is fixed to the camera body and has a helicoid screw on the inner diameter, and a helicoid that is screwed into the inner diameter of the fixed frame A movable frame 2 provided with a screw and a cam groove, which can be driven from the outside and can be moved back and forth in the optical axis direction, a movable frame 1 screwed with an inner diameter of the movable frame 2 and integrated with the first lens group, and a movable frame. 2 has a cam frame that receives a rotational force directly from 2 and has a one-sided cam on its inner diameter, and a cam hole for guiding the cam frame, which is constrained from rotating by a straight-moving key groove of the fixed frame inner diameter and moves back and forth integrally with the moving frame 2. Provided is a zoom lens barrel characterized by having a straight-moving frame.

[0007]

The cam frame is rotated by the operation of the moving frame 2 and guided by the rectilinear frame cam hole to move the second lens group in the optical axis direction. Further, the inner diameter cam of the cam frame moves the third lens group forward and backward in the optical axis direction by the relative movement amount with respect to the second lens group.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an exploded perspective view of a lens barrel unit, FIG. 2 is a vertical cross-sectional view in which the focal length is minimized by zooming, and FIG. 3 shows the positional relationship between the cam grooves and guide pins of each component in a composite manner. FIG. 4 and FIG. 5 are front elevational sectional views showing the positional relationship between the cam grooves and the guide pins.

In the figure, 1 is a moving frame (1) for fixing the first lens group 1a, and 3 is 2 for supporting the second lens group 3b.
The group unit 4 is a third group frame that holds the third lens group 4a.

An electric drive system composed of a motor and a gear train (not shown) transmits the rotational force to the moving frame (2) 2 via the zoom gear. A male helicoid screw 2c is provided on the outer diameter of the moving frame (2) 2 in addition to a gear (not shown) and is screwed with a female helicoid screw 7a having an inner diameter of the fixed frame 7.

The first lens group 1a is integrated with the moving frame (1) 1 and is moved by the male helicoid screw 1b.
The female helicoid screw 2a of 2 is screwed, and the back-and-forth movement is guided. At that time, the rotation of the moving frame (1) 1 is restricted by the rectilinear frame key groove 5b. The second lens group 3b uses the AF
-Built into the shutter unit 3a, it delivers a movement amount according to the shooting distance. The shutter unit 3a is fixed to the shutter frame 3c with screws, and the cam frame 6
And move back and forth together. At this time, rotation of the second group unit 3 including the shutter unit 3a is restricted by the inner diameter keyway 5c of the rectilinear frame 5, and at the same time when the shutter is released, the distance measurement calculation circuit causes the shutter unit to move in accordance with the shooting distance at that time. Only the second lens group 3b is extended inside.

The rectilinear frame 5 is screwed and fixed by sandwiching the rectilinear frame fixing plate 8 and the flange portion of the movable frame (2) 2 so as to be paid out together with the movable frame (2) 2.
The straight-movement key portion of the straight-movement frame fixing plate 8 is the straight-movement key groove 7 of the fixed frame 7.
Since it is engaged with b, the rotation of the rectilinear frame 5 is restricted. The outer diameter of the rectilinear frame 5 is provided with three key grooves 5b in order to prevent the rotation of the moving frame (1) 1, and the inner diameter of the straight frame 5 is set to 3 in order to prevent the rotation of the second group unit 3. A key groove 5c is provided at a location.

In addition to the key groove, the rectilinear frame 5 includes a cam frame 6 (second lens group 3b and third lens group 4a) and a first lens group 1.
Cam holes 5a for controlling the group interval with a are provided at three locations, and the cam frame guide pins 6b are guided in the cam holes 5a.

The cam frame 6 is provided with cam frame guide pins 6b at three locations in the radial direction with respect to the optical axis, and the moving frame (2)
It fits in the cam groove 2b of 2 inner diameter and receives forced rotation. At the same time, the cam frame guide pin 6b is connected to the cam hole 5 of the rectilinear frame 5.
By a, the forward and backward movement of the cam frame 6 is guided, that is, the second group unit 3 including the second lens group 3b is guided. FIG. 4 is a development view of the inner diameter showing the positional relationship among the cam groove of the movable cylinder, the cam hole of the rectilinear frame, and the guide pin of the cam frame.

A third group frame 4 supported by a shutter frame 3c
Is engaged with a one-sided cam 6a having an inner diameter of the cam frame 6, and is moved by the cam frame 6 relative to the second group unit 3 in the optical axis direction. FIG. 5 is a development view of the inner diameter showing the positional relationship between the one-sided cam having the inner diameter of the cam frame and the guide pins of the third group frame.

Coil springs 9 and 10 are mounted between the moving frame (1) 1 and the second group unit 3 and between the second group unit 3 and the third group frame 4, respectively. ) 1
Is always in front of the second group unit 3 and the third group frame 4 is always 2
The load is set so that the group unit 3 is biased rearward.

[0017]

According to the lens extension mechanism of the camera lens barrel of the present invention, the movement guide of the third group frame (third lens group) is controlled by the relative movement amount with respect to the movement of the second group unit (second lens group). Therefore, the variation error of the interval between the lens groups is extremely small.

Therefore, even in a high-magnification zoom lens in which the variation error of the interval sensitively affects the focus position, stable focus accuracy and zoom accuracy can always be obtained.

[Brief description of drawings]

FIG. 1 is an exploded perspective view of a lens barrel unit that is an embodiment of the present invention.

FIG. 2 is a longitudinal sectional view showing a state in which a focal length is minimized by zooming a lens barrel which is an embodiment of the present invention.

FIG. 3 is a front sectional view showing a combined positional relationship between cam grooves and guide pins of each component of the lens barrel that is an embodiment of the present invention.

FIG. 4 is an inner diameter development view showing the positional relationship between the cam groove of the movable barrel, the cam hole of the rectilinear frame, and the guide pin of the cam frame.

FIG. 5 is an inner diameter development view showing the positional relationship between the one-sided cam of the cam frame and the guide pins of the third group frame.

FIG. 6 is a vertical sectional view of a conventional lens barrel.

[Explanation of symbols]

 1 Moving frame (1) 1a 1st lens group 1b Male helicoid 2 Moving frame (2) 2a Female helicoid 2b Cam groove 2c Male helicoid 3 2nd group unit 3a AF / Shutter unit 3b 2nd lens group 3c Shutter frame 3d Straight key 4 3rd group frame 4a 3rd lens group 4b Straight advance key 4c Guide pin 5 Straight advance frame 5a Cam hole 5b Straight advance key groove 5c Straight advance key groove 6 Cam frame 6a Single contact cam 6b Guide pin 7 Fixed frame 7a Female helicoid 7b Straight advance key groove 7c Zoom Gear holder 8 Straight frame fixing plate 9, 10 Coil spring

Claims (2)

[Claims] 1. In a zoom lens barrel of a camera having at least three lens groups, each of which is independently moved in an optical axis direction for zooming, a second lens group is formed by rotating a moving frame 2. The cam frame guide pin moves by the forced rotation of the cam frame while determining the amount of movement in the optical axis direction by guiding the straight frame cam hole, and the third lens group moves by the one-sided cam having the inner diameter of the cam frame. A zoom lens barrel characterized by being controlled by a relative movement amount with respect to a frame. 2. A zoom lens barrel of a camera having at least three lens groups, each of which is independently moved in the optical axis direction for zooming, and fixed to a camera body and having a helicoid screw on an inner diameter. The frame and the inner diameter of the fixed frame are screwed together, the helicoid screw and the cam groove are provided in the inner diameter, and the movable frame 2 that can be driven from the outside and is movable back and forth in the optical axis direction is screwed into the inner diameter of the movable frame 2. A movable frame 1 that is integrated with the first lens group, a cam frame that receives a rotational force directly from the movable frame 2 and has a one-sided cam on its inner diameter, and rotation is constrained by a straight key groove of the fixed frame inner diameter, and the movable frame 2 And a rectilinear frame having a cam hole for guiding a cam frame, the zoom lens barrel.