JPH03239209A - Lens barrel for zoom lens - Google Patents

Abstract

PURPOSE:To obtain high magnification by a compact lens barrel by providing a lens frame for moving forward and backward by the rotation of a cam cylinder, and a zoom ring fixed to the rear end of the cam cylinder. CONSTITUTION:A projecting piece of a zoom ring 26 is fitted into a notch of a cam cylinder 24 and fixed to the rear end part of the cam cylinder 24. By attaching directly the ring 26 for zoom driving to the rear end of the cam cylinder 24, a connecting pin is eliminated, and the lens barrel for a zoom lens can be constituted more compactly. In such a state, by driving the zoom ring 26 and rotating the cam cylinder 24, zoom lens groups 14, 16 move to execute zooming. In such a way, a zoom angle can be made large without enlarging the lens barrel, and high magnification zooming is obtained by a compact zoom lens barrel.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a zoom lens barrel, and particularly to a zoom lens &F suitable for a video camera.

[Conventional technology]

2. Description of the Related Art There is a zoom mechanism for a photographic lens in which a first zoom lens group and a second zoom lens group are moved back and forth to perform a zooming operation. In such a zoom lens barrel, a connecting pin is installed in a cam barrel that is rotatably supported inside a fixed barrel, the connecting pin is fitted with a zoom ring, and zooming is performed by rotating the zoom ring. . A gear that transmits the transmission force from the motor is integrally formed with the zoom ring. In this type of zoom lens barrel, a groove for relief must be formed in the fixed barrel that supports the cam barrel by the angle at which the connecting pin rotates.

On the other hand, when considering a zoom mechanism with high magnification, the amount of movement of the lens group moved by the cam barrel increases as the magnification increases. Generally, the relative positions of the first and second zoom lens groups are determined by optical design, and if a large amount of movement is to be achieved with the same cam barrel diameter, the rising angle of the cam groove must be set large. As this angle increases, the force for driving the lens increases, and the amount of deviation of the zoom lens group in the optical axis direction due to play between the groove and the pin that fits into the groove also increases.

[Problem to be solved by the invention]

Therefore, in the past, it was necessary to make the angle of the groove of the cam cylinder as small as possible. Therefore, in order to reduce the angle and obtain a large amount of movement, it is necessary to increase the zoom rotation angle or increase the diameter of the cam barrel and the length of the cam groove. It has the disadvantage of becoming larger.

The present invention has been made in view of the above circumstances, and an object of the present invention is to propose a zoom lens barrel that can obtain high magnification with a compact lens barrel.

[Means to solve problems]

In order to achieve the above object, the present invention provides a fixed cylinder, a cam cylinder having a first cam groove and a second cam groove and rotatably supported inside the fixed cylinder, and a first cam cylinder of the cam cylinder. a second lens frame having a first driven pin that fits into the cam groove and moves back and forth as the cam barrel rotates; and a second driven pin that fits into the second cam groove of the cam barrel; a second lens frame that moves back and forth as the lens rotates; a zoom ring that is fixed to the rear end of the cam barrel and is exposed from the outer fixed barrel;
It is characterized by consisting of.

[Effect]

The present invention eliminates the need for a connecting pin by attaching a zoom ring for direct zoom drive to the rear end of the cam barrel, making it possible to construct a zoom lens barrel more compactly.

Since it is not necessary to cut out the fixed cylinder, the angle of the cam grooves can be increased to the limit where the cam grooves interfere with each other.

〔Example〕

Preferred embodiments of the zoom lens barrel according to the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 shows a zoom lens barrel to which the present invention is applied. In FIG. 1, the fixed barrel 10 includes, from the front, a first fixed lens group 12, a first zoom movable lens group 14, a second zoom movable lens group 16, a focus movable lens group 18,
Five lens groups of the second fixed lens group 20 are arranged.

In addition, an aperture plate 17 is provided at the front of the second zoom movable lens group 16.
is provided.

The first fixed lens group 12 has a lens frame 2 at the front of the fixed barrel 10.
It is fixed via 2. A cam cylinder 24 is rotatably supported inside the center of the fixed cylinder 10. This cam tube 2
A zoom ring 26 is provided at the rear end of the camera 4.

In FIG. 7, a mounting structure for the zoom ring 26 is shown. A gear 26A is carved approximately halfway around the zoom ring 26. The gear 26A is connected to a motor (not shown) via a gear transmission mechanism (not shown). zoom ring 26
A protruding piece 26B is formed on the front surface of the cam cylinder 24, and a notch 24A corresponding to the protruding piece 26B is formed on the rear end of the cam cylinder 24.

The notch 24A serves as a reference for machining the cam grooves 32 and 38.

The zoom ring 26 is fixed to the rear end of the cam barrel 24 by fitting the projecting piece 26B into the notch 24A of the cam barrel 24. The zoom ring 26 may be attached by caulking, integrally molded with the cam cylinder 24, or the like. In either case, the zoom ring is exposed from the outer fixed barrel 10,
It is necessary to be able to operate externally.

The first zoom movable lens group 14 is mounted on a first lens frame 28, and a driven pin 3 is inserted from the top of the first lens frame 28.
0 is provided in a protruding manner, and this driven pin 30 is fitted into a cam groove 32 of the cam cylinder 24. On the other hand, the second zoom movable lens group 16 is mounted on a second lens frame 34 , and a driven pin 36 is protruded from the bottom of the second lens frame 34 , and this driven pin 36 is connected to a cam groove 36 of the cam barrel 24 . It is inserted inside.

A first guide bar 40 is provided at the upper part of the fixed barrel 10 in the axial direction of the fixed barrel 10, and a second guide bar 42 is further provided at the lower part of the fixed barrel 10.

The front end of the first guide bar 40 is inserted into a hole 46 of a support piece 44 provided at the upper front surface of the fixed cylinder 10 and is supported.
A rear end portion of the first guide bar 40 is inserted into a hole 48 formed in a stepped portion of the fixed cylinder 10 and is supported. Further, the front end of the second guide bar 42 is supported by a hole 52 of a support piece 50 formed at the front lower part of the fixed cylinder 10, and the rear end of the second guide bar 42 is formed at the rear end of the fixed cylinder 10. hole 5
Supported by 4. Support pieces 44.50 of the guide bar 40.42 formed on the fixed cylinder 10 are formed above and below the fixed cylinder 10, as shown in FIG. 2, and form fixed aperture pieces. This prevents unnecessary light from entering and reflection of so-called shiny objects such as the guide bar 40.42 and the driven bin 30.36.

FIG. 3 shows the relationship between the first zoom lens frame 28, the second zoom lens frame 34, and the first and second guide bars 40, 42. That is, the first guide bar 40 is fitted into the guide hole 56 formed at the upper part of the first run frame 28 and guided in the front-back direction, and the second guide bar 40 is inserted into the steady rest recess 58 formed at the lower part of the second run frame 26. The guide bar 42 is fitted to prevent the first zoom lens frame 28 from shaking. Therefore, when the cam barrel 24 rotates in this state, the first zoom lens frame 28 moves back and forth while being guided by the guide bars 40 and 42. On the other hand, a guide hole 60 is formed in the lower part of the second zoom lens frame 34, and the second guide bar 42 is fitted into this guide hole 60, and furthermore, in the upper part of the second zoom lens frame 34, there is a recess for preventing vibration. 62 is formed, and this recess 62
A first guide bar 40 is fitted into the hole. Therefore, when the cam barrel 24 rotates in this state, the second zoom lens frame 34
will move back and forth while being guided by guide bars 40 and 42. In this way, the first guide bar 40 is fitted into the guide hole 56 of the first zoom lens frame 28 to guide the first zoom lens frame 28, and is positioned in the recess 62 of the second zoom lens frame 34 to move the second zoom lens. It serves as a steady rest for the lens frame 34. The second guide bar 42 guides the hole 60 of the second zoom lens frame 34 and also serves as a steady rest for the first zoom lens frame 28, so the number of parts and processing steps are reduced compared to conventional zoom lens barrels. effective.

As shown in FIG. 1, the focus moving lens group 18 is mounted on a lens frame 63, and the second guide bar 42 is fitted into a guide hole 64 at the bottom of this lens frame 63. Further, a recess 66 is formed in the upper part of the focus lens frame 63, and the first guide bar 40 is fitted into the recess 66 to prevent the lens frame 63 from steadying. In this way, the focus lens frame 63 is attached to the guide bar 40 of the zoom lens system.
42 in common, it becomes easy to adjust the optical axes of the zoom lens system and the focus lens system, and the number of parts can be reduced.

Next, the drive mechanism of the focus lens will be explained.

As shown in FIG. 4, a pulley 70 is provided on the output shaft of the focus motor 68 attached to the fixed cylinder 10, a belt 72 is stretched around the pulley 70, and this belt 72 rotates a pulley 74. A screw shaft 76 is fixed to the pulley 74, and a nut member 78 is screwed onto the screw shaft 76. As shown in FIGS. 5 and 6, the nut member 78 is formed with a pair of forked locking portions 80. As shown in FIGS.

A pair of elongated holes 82.
82 is formed, and locking pieces 84, 84 are formed to be elastically deformable. This bifurcated locking portion 82 is engaged with a connecting piece 86 integral with the focus lens frame 63 shown in FIGS. 5 and 6. That is, the connecting piece 86 is formed from the bins 88, 88 on both sides and the spherical piece 9G. To attach the connecting piece 86, insert the pin 88.88 into the elongated hole 82.82 between the pair of forked locking parts 80, and insert the spherical piece 90 into the groove between the locking pieces 84.84. insert. The connection structure assembled in this way is shown in FIG.

In such a connection structure, the rotational force from the motor 68 is transmitted to the screw shaft 76, thereby causing the nut member 78 to move back and forth. When the nut member 78 moves back and forth, the nut member 78 and the focus lens frame 63 are connected through a spherical structure.

Therefore, the deviation in parallelism between the screw shaft 76 and the guide bar 40, 42 can be absorbed by this spherical contact portion, and the movement of the nut member 78 is not hindered.

Behind the focus moving lens 18, a second fixed lens group 20 is fixed to the fixed barrel 10 via a lens frame 79.

As shown in FIG. 1, a low-pass filter 92 is provided at the rear of the fixed cylinder 10, and further behind the low-pass filter 92, a CCD 94 is arranged.

In the lens barrel according to the present invention configured as described above, the zoom ring 26 is driven by a motor (not shown), and the cam barrel 24 is rotated, so that the zoom lens group 14 is rotated.
．． 16 moves as shown by the dashed line in FIG. 1 to perform zooming.

Also, the motor 68 rotates and the focus lens frame 6
3 moves to adjust the focus.

The photographed image light passes through a low-pass filter 92 and enters the CCD 94.
will be imaged.

〔Effect of the invention〕

According to the present invention, a large zoom angle can be obtained without increasing the size of the lens barrel, and high-magnification zoom can be obtained with a compact zoom lens barrel. Additionally, there is no need to create relief grooves on the fixed cylinder or create threaded holes for connecting pins on the cam cylinder.
Processing man-hours are also reduced.

[Brief explanation of drawings]

1 is a sectional view showing the structure of a zoom lens barrel to which the present invention is applied; FIG. 2 is a sectional view showing the shape of the front surface of the zoom lens barrel taken along the line ■-■ in FIG. 3 is a perspective view showing the relationship between the zoom lens frame and the guide bar, FIG. 4 is a sectional view showing the focus lens drive mechanism within the zoom lens barrel according to the present invention, and FIG. 5 is the same focus lens drive mechanism. FIG. 6 is a perspective view showing the structure of the coupling part of the focus lens drive mechanism, and FIG. 7 is a perspective view showing the mounting structure of the zoom ring. be. 10... Fixed tube, 24... Cam tube, 26.
...Zoom ring, 28...Second lens frame, 30...
・Followed pin, 32...Cam groove, 34...Second
Lens frame, 36...driven pin, 38...cam groove.

Claims (1)

[Claims] (1) A fixed cylinder, a cam cylinder having a first cam groove and a second cam groove and rotatably supported inside the fixed cylinder, and a first driven pin fitted into the first cam groove of the cam cylinder. a first lens frame that moves back and forth as the cam barrel rotates; and a second driven pin that fits into a second cam groove of the cam barrel, and a second lens frame that moves back and forth as the cam barrel rotates. A zoom lens barrel consisting of two lens frames, a zoom ring fixed to the rear end of a cam barrel and exposed from the outer fixed barrel.