JPH04134408A - Lens barrel - Google Patents

Abstract

PURPOSE:To decrease the number of parts and to reduce the size, weight and cost of the above lens barrel by extending the respective revolving shafts of motors and freely rotatably supporting these shafts via bearings in the lens barrel and providing 1st and 2nd lead screw parts varying in pitch on the respective revolving shafts thereby freely movably constituting moving lens frames. CONSTITUTION:The lens barrel 1 is constituted of the cylindrical front lens barrel 2 which is fixed and semi-cylindrical main lens barrels 3, 4 which are bisected longitudinally to the right and left. The front ends of the respective revolving shafts 22, 22 of the stepping motors 10, 10 fixed to the rear side of the main lens barrel 3 are freely rotatably supported on the thrust bearings. The respective revolving shafts 11, 11 of the motors 10, 10 are so disposed as to parallel with an optical axis C and the 1st, 2nd lead screw parts 11a, 11a varying in pitch are respectively formed before and behind these shafts. A variator lens 12 for zooming having a variable power function is held in the screw parts 11a, 11a and is supported on the 1st moving lens frame 13. The dealing with the different moving strokes of the moving lens frames 13, 15 is executed by maintaining the rotating speeds of the motors 10, 10 at the same speed and changing the moving speeds of the 1st, 2nd moving lens frames 13, 15.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an inner focus type lens barrel used for example in a video camera.

[Summary of the Invention] The invention as set forth in claim 1 provides a lens barrel for a camera, in which rotating shafts of a pair of motors extend parallel to the optical axis within the lens barrel, and are rotatable through bearings. A first rotor with a different pitch is mounted on each rotary shaft. A pair of movable lens frames holding a lens via one of the lead screw parts can be moved along the optical axis by the rotation of each of the second lead screw parts. , The number of parts can be reduced to reduce size, weight, and cost, and the moving speed of each moving lens frame can be varied using the same type (type) of motor and rotating shaft to achieve the optimal speed. It was made so that it could be done.

In addition, the invention according to claim 2 is configured such that the lens barrel can be freely divided into two in the vertical direction parallel to the optical axis, and a pair of motors is attached to one of the divided lens barrels. This makes it possible to assemble the tube extremely easily and with high precision.

[Prior Art] For example, a video camera uses an inner focus lens barrel in which element lenses such as a compensator lens group and a master lens group are slightly moved along the optical axis to adjust the focus. To explain this in detail with reference to FIG. 7, 100 is a lens barrel;
The lens barrel of this lens barrel 100 has a cylindrical front barrel 101.
and a cylindrical rear lens barrel 10 connected to this front lens barrel 101.
It consists of 2. Front flange 1 of this front lens barrel 101
A focusing lens group (hereinafter referred to as focusing lens) 103 as a front lens is fitted in the center of the inner peripheral surface of the front lens barrel 101, and a focusing lens group (hereinafter referred to as focusing lens) 103 as a front lens is fitted in the center of the inner peripheral surface of the n section 101b on the rear side of the front lens barrel 101. A compensator lens group (hereinafter referred to as a compensator lens) 104 is fitted.

A pair of guide shafts 105 and 105 are interposed between the front flange 101a and the rear flange 101b of the front lens barrel 101 so as to be parallel to the optical axis C. A pair of guide shafts 106 and 106 are also interposed between the rear flange 101b of 101 and the rear flange 102b of the rear lens barrel 102 so as to be parallel to the optical axis C.

A pair of guide shafts 105.1 of the front lens barrel 101
05, a ring plate-shaped first movable lens frame 108 holding a zoom variator lens group (hereinafter referred to as variator lens) 107 having a variable magnification function is inserted through and slidably supported. At the same time, the pair of guide shafts 106 and 106 of the rear lens barrel 102 are focused and corrected.

A second movable lens frame 110 in the shape of an annular plate holding a focusing master lens group (hereinafter referred to as master lens) 109 having an imaging function is slidably supported through the lens frame.

An engagement pin 111 as a cam follower is provided protruding from the first movable lens frame 108 . This engagement pin 1
11 is a cam barrel 1 that slides on the inner peripheral surface of the front lens barrel 101;
The cam slot 112a is slidably inserted into the cam slot 112a, which is formed obliquely in the cam slot 112. This cam barrel 112 is connected via a pin 114 to a cylindrical zoom ring 113 that rotates around the rear side of the outer circumferential surface of the front lens barrel 101, so that the zoom ring 113 does not rotate. The inner circumferential surface of the front lens barrel 101 is rotated clockwise and counterclockwise. The rotation of the zoom ring 113 causes the cam barrel 112 to rotate around the inner peripheral surface of the front lens barrel 101, so that the first movable lens frame 108 moves back and forth along the pair of guide shafts 105 and 105. Move to. As a result, the variator lens 107 held by the first movable lens frame 108 is moved in the front-rear direction along the optical axis C.

Further, the second movable lens frame 110 is connected to the rear lens barrel 102.
It is screwed into a lead screw 116 that is integrally formed on the tip side of the rotating shaft of the motor 115 that passes through the rear flange 102b. By driving this motor 115 and rotating the lead screw 116, the second movable lens frame 110 moves the optical axis C in the front-rear direction along the pair of guide shafts 106°106. As a result, the second
The master lens 10 held in the movable lens frame 110 of
9 is adapted to move in the front-back direction along the optical axis C. Incidentally, in FIG. 7, reference numeral 117 is a reduction gear for the motor 115.

[Problems to be Solved by the Invention] However, in the conventional lens barrel 100, guide shafts 105 and 106 for guiding the movement of the variator lens 107 and the master lens 109 are provided separately, and the guide shafts 105 and 106 are provided separately. In addition to 106, a lead screw 116 for moving the master lens 109 is provided, which has the disadvantage of increasing the number of parts, increasing costs, and making the structure complex and large.

The lens barrel of the lens barrel 100 is composed of a front lens barrel 101 and a rear lens barrel 102, and includes a variator lens 107.
and a guide shaft 105.1 that guides the master lens 109.
06 are also provided separately, so each lens 103, 104, 107, 109 can be decentered with respect to the optical axis C,
It is difficult to position it without tilting it,
For example, after assembling the front lens barrel 101, the rear lens barrel 1
When assembling 02, it was necessary to change the reference, which increased the overall cumulative error and complicated the assembly process.

Therefore, the present invention provides a lens barrel that can solve the above problems.

[Means for Solving the Problems] The lens barrel according to claim 1 is provided with rotating shafts of a pair of motors extending parallel to the optical axis within the lens barrel and rotatably supported through bearings. , each rotating shaft has a first
．． Second lead screw parts are respectively provided, and a pair of movable lens frames holding lenses via one of the lead screw parts can be moved along the optical axis by rotation of each of the rotation axes.

Further, in the lens barrel according to a second aspect of the present invention, the lens barrel is configured to be freely splittable in a vertical direction parallel to the optical axis, and a pair of motors is attached to one of the split lens barrels.

[Function] The pair of guide shafts that move the pair of movable lens frames that hold the zoom and focus lenses along the optical axis also serve as the rotation axes of the pair of motors, which reduces the number of parts. , the lens barrel can be made smaller, lighter, and lower in cost. In addition, first and second lead screw parts having different pitches are provided on each rotating shaft of the pair of motors, and the rotation of each rotating shaft causes the pair of movable lens frames to move through one of the lead screw parts. Since each movable lens frame is made movable along the optical axis, each movable lens frame is moved at an optimum speed by the same rotation speed of the pair of motors of the same type.

In addition, since the lens barrel is configured to be splittable and a pair of motors etc. are attached to one of the split lens barrels, fully automatic assembly, which was almost impossible with conventional lens barrels, has been realized, and the lens barrel can be assembled easily. Assembling the tube becomes significantly easier and assembly accuracy improves.

[Example] Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings.

In FIGS. 1 and 2, reference numeral 1 indicates an inner focus type lens barrel used in a video camera.

The lens barrel of this lens barrel 1 includes a cylindrical front barrel 2, and this front barrel 2 is fixed to the front side via screws 5, and has left and right sides as shown in FIG. A pair of approximately semi-cylindrical primary lens barrels 3 that are vertically divided into two (in a direction parallel to the optical axis C);
It consists of 4.

A focusing lens 6 as a front lens is fixed to the center of the inner peripheral surface of the front lens barrel 2 by thermal caulking or the like.

Above the front and rear sides of the primary lens barrel 3 on the one side (front left side),
Each pair of lower flanges 3a, 3a and 3b, 3b protrudes in a disc shape, and each pair of upper and lower flanges on the front and rear sides of the other (front right) main lens barrel 4 The portions 4a, 4a and 4b, 4b are circularly curved and protrude into the disk shape of each pair of flange portions 3a, 3a and 3b of the one main lens barrel 3,
3b is fitted. A pair of annular bearing metals 7.7 are press-fitted into the center of the pair of front flanges 3a, 3a of one of the main lens barrels 3, and are opposed to the pair of bearing metals 7.7. A pair of thrust receivers 8.8 are press-fitted into the annularly projecting flange 2a of the front lens barrel 2. These bearing metal 7 and thrust bearing 8 constitute a thrust bearing. and a pair of flange portions 3b on the rear side of the one main lens barrel 3.

The tip portions of the rotating shafts 11 of the pair of stepping motors 10 and 10 fixed to the motor 3b by screws 9 are rotatably supported by the pair of thrust bearings.

Each rotating shaft 1 of this pair of stepping motors 10.10
1.11 are respectively arranged parallel to the optical axis C, and in front and behind (base) there are a first lead screw part 11a and a second lead screw part 11b with different pitches. are formed respectively. Each of the lead screw portions 11a, 11a formed in a predetermined area on the front side of the pair of rotating shafts 11.11 has a substantially annular plate-shaped lens holding a zoom variator lens 12 having a variable power function. Above the first movable lens frame 13.

The pair of rotating shafts 11. are supported by passing through the lower side thereof.・Focusing, correction,
The second movable lens frame 15, which has a substantially annular plate shape and holds a focusing master lens 14 having an image forming function, is supported by passing through the upper and lower sides thereof.

As shown in FIG. 5, the 1.2 movable lens frame 13
．． A pair of guide holes 13b, 1 having a diameter one size larger than the diameter of each rotating shaft 11 are provided in the upper portions 13a, 15a of the rotating shafts 11.
3b, 15b, and 15b, respectively, and each rotating shaft 1
1 is inserted through.

Moreover, the upper part 13a of the first and second movable lens frames 13.15
, 15a has a molded spring 16.1 made of synthetic resin.
7 is fixed by press-fitting or heat welding. At the center of each molded spring 16, 17 are guide holes 13b, 15.
The rack portions 16a and 17a curved to approximately the center of b are integrally protruded. Then, the screw 16b formed inside the rack part 16a of the first movable lens frame 13 is connected to the first lead screw part 11a of the rotating shaft 11 of the stepping motor 10 fixed to the upper side of the main lens barrel 3. Part 1
6a, the first movable lens frame 13 reciprocates a predetermined distance along the optical axis C, and the rack portion 17a of the second movable lens frame 15 A screw 17b formed inside the rack part 1 is connected to the second lead screw part 11b of the rotating shaft 11 of the stepping motor 10 fixed to the lower side of the main lens barrel 3.
The second movable lens frame 15 is configured to reciprocate a predetermined distance along the optical axis C by meshing with each other through the elastic biasing force of the second movable lens frame 7a.

Further, approximately U-shaped guide grooves 13c and 15c are formed at the lower part of the 1.2 movable lens frame 13.15, respectively. Guide groove 13 of this first movable lens frame 13
c is a stepping motor 1 fixed to the lower side of the main lens barrel 3
The first movable lens frame 13 is inserted into the first lead screw portion 11a side of the rotation shaft 11 of
is prevented from rotating, and the guide groove 15c of the second movable lens frame 15 is inserted into the second lead screw portion 11b side of the rotating shaft 11 of the stepping motor 10 fixed to the upper side of the main lens barrel 3. By being, the above second
The movable lens frame 15 is prevented from rotating.

Further, a fixed lens frame 18 is fixed to a predetermined position on the inner peripheral surface between the first and second movable lens frames 13 and 15 of the left and right main barrels 3 and 4 by heat caulking or the like. A relay lens 19 is fitted into the center of the inner peripheral surface of the fixed lens frame 18. Furthermore, the left and right main lens barrels 3 and 4 on the front side of the relay lens 19 have built-in iris 20 that open and close a diaphragm 21 by a motor 22.

In addition, the flanges 3b and 4 on the rear side of the left and right main lens barrels 3 and 4 are
A CCD unit 23 is coupled to the openings 3c and 4c formed at the base end of b. An optical low-pass filter unit 24 is mounted inside the openings 3c and 4c at the center of the front side of the CCD unit 23.

In addition, the left and right main lens barrels 3 and 4 are located on their outer peripheral surfaces,
It is assembled by fastening each pair of bracket parts 3d, 3d and 4d, 4d, which are integrally molded on the lower part, with respective screws 25. Further, each stepping motor 10 is connected to a motor drive circuit (not shown) via a lead wire 10a to be driven.

According to the lens barrel 1 of the above embodiment, the zoom variator lens 12. The first lens holds the master lens 14 for focusing. The second moving lens frame 13.15 is moved by a pair of stepping motors 10. \10 each rotation axis 11.1
1, and the rotating shaft 11 of each stepping motor 10 serves both as a sliding shaft and a rotation prevention shaft, so that each rotating shaft 11 serves as a motor shaft and a drive transmission shaft.

Since the four functions of the sliding shaft rotation prevention shaft are provided, the number of parts can be reduced accordingly, and cost and volume savings can be achieved. This makes it possible to further reduce the size and weight of the lens barrel 1 as a whole.

In addition, a thrust bearing that rotatably supports the tip of the rotating shaft 11 of each stepping motor 10 is provided on the pair of upper and lower flanges 3a, 3a on the front side of the main lens barrel 3, and the main lens barrel 3 itself is connected to each stepping motor. 10, there is no need for a motor unit such as a U-shaped sheet metal or a separate bearing, which was conventionally required to support the rotating shafts 11. This enables stable driving with less deformation and the like. Thereby, the loss of transmission torque of each rotating shaft 11 can be reduced, and the efficiency of each stepping motor 10 can be increased.

Further, each rotating shaft 11.11 of the pair of stepping motors 10.10 has a first motor having a different pitch. Second lead screw parts 11a and 11b are provided respectively, and rotation of one of the rotating shafts 11 causes the first lead screw part 11a to
The first movable lens frame 13 holding the variator lens 12 was moved along the optical axis C, and the master lens 14 was held via the second lead screw portion 11b of the other rotating shaft 11. Second moving lens frame 15
Since the first . The moving speed of the second moving lens frame 13.15 can be changed, and the moving speed of the second moving lens frame 13.15 can be changed. Second moving lens frame 1
3.15 different travel strokes can be accommodated. In this case, while keeping the number of rotations of each of the stepping motors 10 low to reduce noise and vibration, the first. The moving speeds of the second moving lens frames 13 and 15 are varied respectively, and the moving speeds of the second moving lens frames 13 and 15 are varied. The second movable lens frames 13, 15 can each be moved at optimum fast speeds. Note that the first. The second lead screw parts 11g and 11b do not form independent lead screw parts before and after each rotating shaft 11, but rather
．． The middle part of the second lead screw part 118.11b is connected to the first lead screw part 118.11b with a different pitch. Second lead screw part 11a
, llb as a transition region and connect them continuously. second lead screw part 11a,
llb can be formed continuously by gear cutting or rolling, and the rotating shaft 11 can be provided at low cost.

In addition, the main lens barrel 3°4 that constitutes the lens barrel of the lens barrel 1 is
Since a pair of stepping motors 10, 10, etc. are attached to one lens barrel 3, after assembling the main lens barrel 4 to the main lens barrel 3, The lens barrel 1 can be easily assembled by simply assembling the front lens barrel 2, and completely automatic assembly, which is almost impossible with conventional lens barrels, becomes possible. As a result, the time for assembling the lens barrel 1 can be significantly shortened, and
A highly accurate lens barrel 1 can be provided at low cost.

Incidentally, according to the embodiment described above, the front lens barrel 2 and the main lens barrel 3.4 are each separate bodies, but as in another embodiment shown in FIG. may be integrally formed (indicated by reference numeral 3' in FIG. 6), and the bearing that rotatably supports the tip of the rotating shaft 11 may be replaced by a ball bearing 8' instead of the thrust bearing in the embodiment described above. The same effect can be achieved.

Further, although the lens barrel used in a video camera has been described, it goes without saying that the lens barrel can be applied to a still camera.

[Effects of the Invention] As described above, according to the lens barrel of the present invention, the rotating shafts of the pair of motors are provided within the lens barrel in parallel with the optical axis, and are rotatably supported via bearings. A first rotary shaft with a different pitch is attached to each rotating shaft. A second lead screw part is provided, and the lens is held through one of the lead screw parts by rotation of each rotation axis, and the pair of movable lens frames are made movable along the optical axis. Therefore, it is possible to reduce the number of parts and achieve a reduction in size, weight, and cost, and the moving speed of each moving lens frame can be varied using the same type of motor and rotating shaft, so that each moving lens frame can be moved at an optimal speed. It can be moved with.

In addition, because the lens barrel is configured to be splittable and a pair of motors are attached to one of the split lens barrels, fully automated assembly, which is almost impossible with conventional lens barrels, can be achieved, allowing for high efficiency. A precision lens barrel can be assembled extremely easily and in a short time.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a lens barrel showing an embodiment of the present invention.
Fig. 2 is a plan view of the same, Fig. 3 is a front view of the same, Fig. 4 is an explanatory diagram of the lens barrel divided into sections, and Fig. 5 is a perspective view of a movable lens frame used in the lens barrel. , FIG. 6 is a sectional view of a main part of another embodiment, and FIG. 7 is a sectional view of a conventional lens barrel. 1... Lens barrel, 3.4... Lens barrel, 7, 8...
Bearing, 10... Motor, 11... Rotating shaft, lla.
...First lead screw part, llb...Second lead screw part, 12.14...Lens, 13.1
5...Moving lens frame, C...Optical axis. Figure 3: Explanatory diagram of τ・1 Figure 4

Claims (2)

[Claims] (1) Rotating shafts of a pair of motors are installed in the lens barrel parallel to the optical axis and supported rotatably via bearings, and first and second leads with different pitches are attached to each rotating shaft. A lens characterized in that a pair of movable lens frames holding a lens via one of the lead screw parts are respectively movable along the optical axis by the rotation of the respective rotation axes, each having a screw part. lens barrel. (2) The lens barrel according to claim 1, wherein the lens barrel is configured to be freely splittable in a vertical direction parallel to the optical axis, and a pair of motors is attached to one of the split lens barrels. lens barrel.