JP2001311863A - Variable focal distance lens device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a variable focal distance lens device varying a focal distance without increasing the number of parts while keeping the accuracy of an interval between lens groups. SOLUTION: An interval between the 1st lens group 11 being a main moving side and a 2nd lens group 12 being a sub-moving side is changed by a cylindrical cam 34. The 2nd lens group side is brought into contact with the cam surface of the cam 34, and the cam 34 is driven at a rotational angle and in a rotating direction corresponding to the moving amount and the moving direction of the 1st lens group by a driving mechanism 23. The focal distance decided according to the interval between the 1st lens group being the main moving side and the 2nd lens group being the sub-moving side is regulated according to the distance of the step of the cam 34.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a variable focal length lens device having a variable focal length.

[0002]

2. Description of the Related Art In general, a variable focal length lens called a zoom lens is widely used in the field of photographing machines. This variable focal length lens has a variable focal length from a wide angle to a telephoto range, and usually includes a first lens group and a second lens group each movable along an optical axis. An arbitrary focal length is obtained by changing the distance between the second lens group and the second lens group.

An example of changing the distance between lens groups of such a variable focal length lens is disclosed in Japanese Patent Application No. 9-19 / 1997.
6739 (hereinafter referred to as "conventional example") discloses the configuration. In this conventional example, the distance between the front lens group and the rear lens group that can move along the optical axis direction is changed by a disk cam whose rotation center is an axis perpendicular to the optical axis. That is, the distance between the front group lens and the rear group lens is changed by moving the rear group lens along the cam surface formed on the outer peripheral surface of the disk cam that rotates with the movement of the front group lens, and the desired focal length I'm trying to get

[0004]

However, in this conventional method, it is necessary to secure a space for rotating the cam in one direction of the lens (downward in the specification). Since a rotating helicoid is used for feeding the lens, the lens has an eccentric optical center axis, and there is a problem that miniaturization is difficult.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide a variable focal length lens device that can change the focal length without increasing the number of components while maintaining the accuracy of the lens group interval.

[0006]

According to a first aspect of the present invention, there is provided a variable focal length lens apparatus comprising: a first lens group which is movable along an optical axis; A second lens group that is movable along the optical axis and is a driven side of the first lens group, and has a cam surface at one end of a cylinder that rotates around the optical axis; A second lens group side contacts and defines a focal length corresponding to a step in the optical axis direction, a cylindrical cam for varying the focal length provided on the first lens group side, and the cylindrical cam being the first cam. It has a drive mechanism for driving in a rotation angle and a rotation direction corresponding to the movement amount and the movement direction of the lens group. That is, the distance between the first lens group that is the driving side and the second lens group that is the driven side is changed by the cylindrical cam, and the second lens group side is brought into contact with the cam surface of this cylindrical cam, The cam is driven by a drive mechanism at a rotation angle and a rotation direction corresponding to the movement amount and the movement direction of the first lens group,
The focal length is determined by the distance between the step of the cylindrical cam and the distance between the first lens group on the driven side and the second lens group on the driven side.

According to a second aspect of the present invention, there is provided a variable focal length lens apparatus, wherein the first lens group is a driving side movable along an optical axis, and the first lens group is movable along the optical axis. A plurality of lens groups on the driven side of one lens group, and a cam surface at one end or both ends of a cylinder that rotates around an optical axis. The focal length is defined in accordance with the step, and the focal length variable cylindrical cam provided on the first lens group side, and the cylindrical cam corresponds to the moving amount and moving direction of the first lens group. It is provided with a drive mechanism for driving in a rotation angle and a rotation direction. That is, the distance between the first lens group on the driving side and the plurality of lens groups on the driven side is changed by a cylindrical cam, and the plurality of lens groups are brought into contact with the respective cam surfaces of the cylindrical cam. The cam is driven by a drive mechanism at a rotation angle and a rotation direction corresponding to the movement amount and the movement direction of the first lens group, and the first lens group and the driven side which are driven by the distance of each step of the cylindrical cam. And a focal length determined by an interval between the plurality of lens groups.

According to a third aspect of the present invention, there is provided a variable focal length lens apparatus according to the first or second aspect, wherein the cam surface of the cylindrical cam for varying the focal length varies when the focal length is varied by rotation. The focus is fixed at a specific distance, and the focus is fixed at a specific distance when the focal length is changed.

According to a fourth aspect of the present invention, there is provided a variable focal length lens device according to the first or second aspect, wherein the cam surface of the cylindrical cam for varying the focal length is rotated when the focal length is varied by rotation. The focal position is changed to a specific subject position according to the focal length. When the focal length is variable, the focal position is changed to a specific subject position according to the focal length.

According to a fifth aspect of the present invention, there is provided the variable focal length lens device according to the first or second aspect, wherein the cam surface of the cylindrical cam for varying the focal length varies when the focal length is varied by rotation. Stepped shape including a parallel surface enabling focusing at at least two focal lengths, wherein step zoom enabling focusing at at least two focal lengths becomes possible when the focal length is changed. It is characterized by.

[0011]

Embodiments of the present invention will be described below in detail with reference to the drawings.

In FIG. 1, FIG. 2 and FIG. 3, reference numeral 11 denotes a first lens group, and a second lens group 12 is disposed on the rear side along the optical axis X of the first lens group 11. ing. The first lens group 11 is held by the front frame 13, and the second lens group is held by the rear frame 14. Further, the front frame 13 is integrally attached to a front portion inside the front barrel 15, and an outer helicoid 15 a is provided at the rear end of the front barrel 15 with an inner helicoid 16 a of the middle barrel 16.
a. The rear end of the middle lens barrel 16 has an outer helicoid 16b, which meshes with a helicoid 17a in a rear lens barrel 17 integrally attached to the main body. When the middle lens barrel 16 is rotated by the drive gear 25 (see FIG. 4) of the drive mechanism 23, the middle lens barrel 16 can move in and out along the optical axis X direction. It should be noted that the shutter mechanism and the aperture mechanism are not shown.

In FIG. 4, a gear 16c is provided at the rear end of the middle lens barrel 16, and the gear 16c is engaged with the drive mechanism 23. This drive mechanism 23 allows the middle lens barrel 16
Is rotated, the middle lens barrel 16 moves in and out of the optical axis X direction by the outer helicoid 16b. At this time, since the front barrel 15 cannot be rotated by the groove 15b of the front barrel and the straight guide 18, the front barrel 15 enters and exits in the optical axis X direction without being rotated by the outer helicoid 15a.

The drive mechanism 23 is shown in FIGS.
As shown in the figure, the driving motor 24 and the driving gear 25
Further, it is constituted by a reduction gear train 26 meshed between the drive gear 25 and a motor gear 24a integrally attached to the rotation shaft of the motor 24. Here, as shown in FIG. 6, the motor 24 is mounted on the rear barrel 17 side, and forms a gear 26b forming a gear train 26.
And 26c are rotatably supported by the rear lens barrel 17, respectively.

The gear 26b is also meshed with a pulse gear 27, and the blade 27a of the pulse gear 27 is disposed so as to pass through the detecting section 28a of the photo interrupter 28. Accordingly, the pulse gear 27 also rotates with the rotation of the motor 24, and the blades 27 a pass through the detection unit 28 a of the photo-interrupter 28, so that the number of rotations of the motor 24 can be detected by the photo-interrupter 28.

As shown in FIG. 1, the rear frame 14 has a guide pin A31 which is integrally press-fitted at the upper portion thereof, and is slidably fitted in the guide hole 13a of the front frame 13 along the axial direction. . A guide pin B32 integrally press-fitted into the front frame 13 and a groove 14a formed in a lower portion of the rear frame 14 are fitted slidably in the axial direction. The guide pins A31 and B32 are provided in parallel with the optical axis X, and the rear frame 14 is also movably guided along the optical axis X.

A guide pin A31 provided on the upper part
3, a spring 32 is provided between the front frame 13 and the rear frame 14 as shown in FIG.
4 is always given a movement behavior toward the front frame 13 side by the spring 32.

In FIGS. 1 and 2, reference numeral 34 denotes a cylindrical cam, the front end face of which is in contact with the reference face 13d of the front frame 13, and the opposite face is a cam face having a step. The outer peripheral surface is in contact with the inside of the front lens barrel 16 and is rotatable around the optical axis. FIG. 5 is an exploded view of the cylindrical cam 34.
A cam lever 19 fixed to the middle lens barrel 16 by a screw 42 or the like is slidably inserted in the direction 4a in the direction of the optical axis X. When the middle lens barrel 16 rotates, the cylindrical cam 34 also rotates by the cam lever 19.

Reference numeral 18 denotes a straight guide, and screws 41 are attached to the rear plate 20.
Etc. are fixed. Outer peripheral portion 18a of the straight guide 18
Has a disk portion 16d of the middle lens barrel 16, and a rectilinear guide 18 is provided rotatably around the optical axis with respect to the middle lens barrel 16.

A gear 27 meshing with the gear portion 16c of the middle lens barrel 16 is attached to the rear plate 20 so as to be rotatable around a shaft 28, and meshes with a driving gear 25 of a reduction gear train 26.

Above the guide pin A31 of the rear frame 14, there is provided a portion 14d which comes into contact with the cam surface of the cylindrical cam 34. The portion 14d is always in contact with the cam surface by the spring 32.

Next, the operation of the above embodiment will be described.

First, when the drive motor 24 rotates under the control of an electric circuit (not shown) and the middle barrel 16 rotates via the reduction gear train 26 and the drive gear 25, the rear barrel 1
The middle lens barrel 16 advances in the optical axis direction by the helicoid 7. At this time, the rear plate 20 and the rectilinear guide 18 are
No. 7 advances without rotating by the rectilinear groove 17c of the portion without a helicoid. Since the front lens barrel 15 cannot be rotated by the rectilinear guide 18, it advances without being rotated by the helicoid of the middle lens barrel 16. Therefore, the middle lens barrel 16 rotates,
When the cylindrical cam 34 is rotated by the cam lever 19, the rear frame 14 changes the distance from the front frame 13 according to the step of the cam surface. Therefore, the distance between the first lens group 11 and the second lens group 12 changes, and the focal length changes. Therefore, the cylindrical cam 34 defines the focal length of the variable focal length lens according to the distance from the reference surface to the cam surface. At this time, since the number of rotations of the drive motor 24 is counted by the photo interrupter, when the predetermined pulse position is reached, it is controlled by an electric circuit (not shown) and can be kept at a predetermined focal length.

These operations are the same when the front frame 13 is driven backward.

Here, when the upper portion 14d of the rear frame 14 is in contact with the parallel portion of the cam surface 34b, the distance between the front frame 13 and the rear frame 14 is not changed, and the distance between the front frame 13 and the rear frame 14 is not changed. The frame 14 moves forward. That is, focusing is performed without changing the focal length. Therefore, the cam surface 34b
As a shape of, if a plurality of portions where the distance from the reference plane does not change within a certain range at different distances are provided,
Focusing at a plurality of focal lengths, so-called step zoom, can be used.

Although the example of the step zoom in which the cam surface 34b has a portion having the same distance from the reference surface as the shape of the cam surface 34b has been described above, the cam surface is not limited to such a shape. When the focal length moved along the optical axis X is variable, the focal point may be formed smoothly so as to fix the focal point at a specific distance. Similarly, when the focal length is variable, the focal length may be changed smoothly to a specific subject position according to the focal length.

Also, by changing the cylindrical cam 34 without changing the lens group, variable focal length lenses of various specifications can be produced.

Furthermore, in the above embodiment, an example of a combination of the first lens group 11 on the driving side and the second lens group 12 on the driven side has been described.
A plurality of lens groups on the driven side are provided with respect to the first lens group 11 on the driving side, and cylindrical cams are provided in correspondence with the plurality of lens groups. The zoom lens can be similarly configured.

[0029]

As described above, according to the first aspect of the present invention, the distance between the first lens group on the driving side and the second lens group on the driven side is changed by the cylindrical cam. The second lens group side is brought into contact with the cam surface of the cylindrical cam, and the cylindrical cam is driven by a driving mechanism at a rotation angle and a rotation direction corresponding to the moving amount and the moving direction of the first lens group. The first lens group is configured to define the focal length, which is the distance between the first lens group on the driving side and the second lens group on the driven side by the distance from the reference surface to the cam surface. The distance accuracy between the group and the second lens group is determined by the accuracy of only the cylindrical cam, and a high variable focal length accuracy can be easily obtained by increasing the distance accuracy of the cylindrical cam. Since the number of parts is reduced, the cost can be reduced.

Further, according to a second aspect of the present invention, the distance between the first lens group on the driving side and the plurality of lens groups on the driven side is changed by each of the cylindrical cams. The surfaces of the plurality of lens groups are brought into contact with each other, and these cylindrical cams are driven by a driving mechanism at a rotation angle and a rotation direction corresponding to the moving amount and the moving direction of the first lens group. The first lens group and the plurality of lenses are configured so as to respectively define the focal length, which is the distance between the first lens group on the driving side and the plurality of lens groups on the driven side depending on the distance to The distance accuracy between groups is determined by the accuracy of the cylindrical cam only,
As in the first aspect, by increasing the distance accuracy of the cylindrical cam, a high variable focal length accuracy can be easily obtained.
Since the number of parts can be reduced, the cost can be reduced.

According to a third aspect of the present invention, in addition to the variable focal length lens according to the first or second aspect, the cam surface of the cylindrical cam for varying the focal length is provided when the focal length is varied by rotation.
Since the focal point is fixed at a specific distance, the focal point can be fixed at a specific distance when the focal length is changed.

According to a fourth aspect of the present invention, in addition to the variable focal length lens according to the first or second aspect, the cam surface of the cylindrical cam for varying the focal length is provided when the focal length is varied by rotation.
Since the focus position is changed to the specific subject position by the focal length, the focal position can be changed to the specific subject position according to the focal length when the focal length is changed.

According to a fifth aspect of the present invention, in addition to the variable focal length lens according to the first or second aspect, the cam surface of the cylindrical cam for varying the focal length has at least two focal points when the focal length is varied by rotation. Since the distance from the reference plane that enables focusing at a distance is formed in steps including the same portion, step zoom that enables focusing at at least two focal lengths when the focal length is variable is possible. I do.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a main configuration of an embodiment of a variable focal length lens device according to the present invention.

FIG. 2 is a cross-sectional view from another angle in FIG. 1 and is a view as viewed from an angle focusing on a straight guide.

FIG. 3 is a cross-sectional view of FIG. 1 from another angle.

FIG. 4 is a longitudinal sectional view of a drive gear portion.

FIG. 5 is a developed view as viewed from the inside of the cylindrical cam.

FIG. 6 is a cross-sectional view of a drive gear portion.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 1st lens group 12 2nd lens group 13 Front frame 14 Rear frame 15 Front lens barrel 16 Middle lens barrel 17 Rear lens barrel 18 Straight guide 20 Rear plate 23 Drive mechanism 24 Motor 25 Drive gear 26 Gear train 27 pulse gear 28 photo interrupter 31 guide pin A 32 guide pin B 34 cylindrical cam

Claims (5)

[Claims] 1. A first lens group which is movable along an optical axis and is a driven side, and a second lens group which is movable along the optical axis and is a driven side of the first lens group. A first lens having a cam surface at one end of a cylinder rotating around an optical axis, the second lens group being in contact with the cam surface to define a focal length corresponding to a step in an optical axis direction; A cylindrical cam for varying the focal length provided on the group side; and a drive mechanism for driving the cylindrical cam at a rotation angle and a rotation direction corresponding to a moving amount and a moving direction of the first lens group. Characteristic variable focal length lens device. 2. A first lens group that is movable along the optical axis and is on the driving side, and a plurality of lens groups that are movable along the optical axis and is on the driven side of the first lens group; One end or both ends of a cylinder rotating around an optical axis has a cam surface, and the plurality of lens groups are in contact with the cam surface to define a focal length corresponding to a step in an optical axis direction, thereby defining the first focal length. A plurality of cylindrical cams for varying the focal length respectively provided on the lens group side of the lens group; and a drive mechanism for driving the cylindrical cam at a rotation angle and a rotation direction corresponding to a moving amount and a moving direction of the first lens group. A variable focal length lens device comprising: 3. The variable focal length lens device according to claim 1, wherein the cam surface of the variable focal length cylindrical cam fixes a focal point at a specific distance when the focal length is varied by rotation. . 4. The cam surface of the cylindrical cam for varying the focal length, wherein when the focal length is varied by rotation, the focal position is changed to a specific subject position by the focal length. Variable focal length lens device. 5. The cam surface of the variable focal length cylindrical cam includes a portion having the same distance from the first lens group that enables focusing at at least two focal lengths when the focal length is changed by rotation. 3. The variable focal length lens device according to claim 1, wherein the variable focal length lens device is formed in a step shape.