JPH01107222A - Cam structure for driving zoom lens - Google Patents

Abstract

PURPOSE:To eliminate the trouble required to adjust focal length initially by coupling a driving member with a driven member through a cam and providing the shortest-focal-length part and longest-focal-length part of the cam with blind sectors. CONSTITUTION:The driving member 22 which is driven by receiving an external driving force and a moving lens barrel 4 which moves lens groups 1 and 2 in specific relation in the direction of the optical axis are coupled with each other by the cam 9 and the shortest-focal-length side end (W-end) part 9b and longest-focal-length side end (T-end) part 9c of this cam 9 are provided with the blind sectors wherein the moving lens barrel 4 does not move even during the operation of the driving member 22. Therefore, when the lens groups 1 and 2 are positioned at the W-end part 9b and T-end part 9c, the lens groups 1 and 2 do not move away from the W-end part 9b and T-end part 9c unless they are driven for longer than a specific time even if the external driving force for moving the lens groups 1 and 2 is applied. Consequently, the initial adjusting operation for the focal length is facilitated.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention is directed to the shortest focal length of a photographing lens (hereinafter referred to as
It is abbreviated as "W end". ) and the longest edge (
Hereinafter, it will be abbreviated as "T end". ), if it is around
This invention relates to a cam structure for driving a zoom lens, in which the shortest focal length and the longest focal length can be maintained without moving the photographic lens even if power is applied to the driving member of the photographic lens to change the focal length.

[Conventional technology]

2. Description of the Related Art There are zoom lenses that can take photographs by continuously changing the focal length by appropriately moving a lens group. In recent years, so-called compact cameras have become popular so that people can easily take photos, but compact cameras with zoom lenses have also been developed.

I! of conventional zoom lenses of this type. l! The movement mechanism is a double lens barrel in which an outer lens barrel is fitted into an inner lens barrel.One lens barrel is fixed to the camera body and the other is rotatable around the optical axis. By rotating the lens group, the lens group is moved in the optical axis direction.

In other words, a linear groove along the optical axis is formed on either the inner or outer barrel, and a spiral cam groove corresponding to the number of lens groups is formed on the other lens barrel. The pin implanted in the mount is inserted into both the linear groove and each cam groove. When one lens barrel is rotated, the pin is guided by both the linear groove and the cam groove, so the linear groove restricts the direction of movement, and the cam groove restricts the distance of movement, allowing the lens group to move. . The focal length is changed by moving this lens group.

[Problem that the invention seeks to solve]

By the way, since a zoom lens continuously changes its focal length, it is necessary to maintain a predetermined optical relationship as the lens group moves.This optical relationship is as described above. This is maintained by the shape and position of the cam grooves.

In order to maintain this optical relationship as specified, the linear groove and the cam groove must be machined with high precision, and the focal length at the W end position and the focal length at the T end position must be If not properly adjusted, the optical relationship will be disrupted at intermediate focal lengths.

Therefore, when initially adjusting the focal length, the lens must be reliably stopped at the W end and the T end.

However, because the cam grooves are machined with high precision,
In order to stop each lens group at the W end or T end, high precision is also required in the position adjustment work. Therefore, this adjustment work is laborious and requires a considerable amount of time.

Therefore, when the lens group is located at the W end and the T end, even if a driving force is applied from outside to move this lens group, if the lens group is not driven for a predetermined time or more, the W end and It is an object of the present invention to provide a cam structure for driving a zoom lens, which prevents a lens group from coming off from the T end and facilitates adjustment of the focal length at the W end and the T end.

[Means for solving problems]

In order to achieve the above object, the cam structure according to the present invention provides a zoom lens that changes the focal length by applying a driving force from the outside and moving an appropriate number of lens groups in a predetermined relationship in the optical axis direction. A driving member driven by receiving an external driving force and a movable lens barrel that moves the lens group in the optical axis direction in a predetermined relationship are connected by a cam, and the shortest focus side end and the longest focus side end of this cam are connected by a cam. It is characterized by providing a dead zone in which the movable lens barrel does not move even when the drive member is in operation.

[For production]

Even if the above-mentioned driving member operates in response to an external driving force,
When the focal length of the photographic lens is on the short focal length side or the long focal length side, the driving member and the movable lens barrel are linked by the dead zone, so the movable lens barrel does not operate and the lens group does not move. When the driving member rotates beyond a predetermined angle, it leaves the dead zone, power is transmitted from the driving member to the movable lens barrel, and the lens group begins to move.

〔Example〕

EMBODIMENT OF THE INVENTION Hereinafter, the cam structure for driving a zoom lens according to the present invention will be specifically explained based on the illustrated embodiment.

First, based on FIG. 3, the structure of a lens driving section of a compact camera equipped with a zoom lens in which a lens group is moved by this cam structure will be explained.

This zoom lens is a two-group zoom consisting of a front group lens 1 and a rear group lens 2. The front lens group 1 is housed in a shutter unit 3, and this shutter unit 3 is moved to a movable lens barrel 4.
It is fixed to the front part of the body with three setscrews 3a. In addition,
The inclination of the front group lens 1 in the optical axis direction can be adjusted by interposing spring washers 3b between two of the set screws 3a.

The movable lens barrel 4 has a substantially rectangular parallelepiped frame-like member with a mounting plate 4a for fixing the shutter unit 3 thereon. A guide hole 4b is provided at the rear of the upper surface of the movable lens barrel 4 by forming a substantially rectangular through hole parallel to the optical axis.
b, by inserting the protrusion 5a formed at the upper end of the lens mount 5 of the rear group lens 2 into the rear group lens 2.
is arranged at the rear of the movable lens barrel 4.

A guide portion 5b is provided by forming a through hole in a direction parallel to the optical axis at the lower side end portion of the lens mount 5, and a bushing 5c is fitted into the guide portion 5b. A rear group guide rod 6a is inserted into this bushing 5c, and the tip end of the rear group guide bar 6a on the side of the movable lens barrel 4 is supported by a support provided within the movable lens barrel 4. A presser plate 6b is brought into contact with the rear end of the rear group guide rod 6a, and the presser plate 6b is fixed to the movable lens barrel 4 with a set screw 6c. A push spring 6d is wound between the lens mount 5 of the rear group guide shaft 6a and the support part in the movable lens barrel 4, and the lens mount 5 transfers the restoring force between the guide hole 4b and the rear group. It is biased so that it is guided by the guide bar 6a and moves rearward. A suitable recess is formed on the lower surface of the lens mount 5, the eccentric pin 7a of the focus adjustment pin 7 and the flange 7b are fitted into the recess, and the holding plate 7c is fixed to the lens mount 5 with a set screw 7d. By doing so, the focus adjustment pin 7 is fixed to the lens mount 5.

A circular fulcrum pin 7e is formed on the focus adjustment pin 7 fixed to the lens mount 5, and this fulcrum pin 7e is inserted into the interlocking hole 8a of the interlocking lever 8 by passing through the through hole 7f of the holding plate 7c. Insert loosely. The interlocking lever 8 is approximately L-shaped, and the interlocking hole 8a is formed at the tip of one arm thereof. A through hole 8b is formed in the bent portion of the L-shape, and a support screw 8c passing through the through hole 8b is tightened to the lower surface of the movable lens barrel 4, and the interlocking lever 8 is attached to the movable lens barrel 4 with this support. It is provided so as to be rotatable around the screw 8c. Further, at the tip of the other arm of the interlocking lever 8, there is provided an interlocking pin 8d that projects in a direction opposite to the movable lens barrel 4.

A cam portion 9 having a through hole formed in a shape described later is provided at the rear side of the movable lens barrel 4.

Further, a main guide shaft having a through hole formed in the optical axis direction is provided at the side end portion of the upper surface of the movable lens barrel 4, and a bushing 4d is fitted into the main guide portion 4c. A cam plate 10 having a cam surface 10a is fixed to the side of the main guide portion 4c. Note that this cam plate 10 may be made in common with the main guide section 4c, and the cam surface 10a may be formed on the side surface of the main guide section 4c. At the lower part of the side surface of the movable lens barrel 4 opposite to the side surface on which the cam portion 9 is provided, there is provided a sub-guide portion 4e whose tip portion is cut out into a substantially U-shape, as shown by a broken line.

As described above, the movable lens barrel 4 with the front group lens 1, the rear group lens 2, the interlocking lever 8, etc. attached is attached to the camera body A (the fourth
(Illustrated) is housed in a fixed frame 11 fixed to At this time,
The main guide bar 4f is inserted into the main guide part 4c, and the support part 1a above the rear end of the fixed frame 11 is made to support the rear end of the main guide bar 4f.

Further, the sub-guide bar 4g is inserted into the notch at the tip of the sub-guide part 4e, and its rear end is supported by the support part 11b provided on the inner side surface of the fixed frame 11. And the fixed frame 11
A frame-shaped lid 12 is secured to the front peripheral edge of the housing by tightening with a set screw 12a.

As shown in FIGS. 3 and 4, the lower surface of the fixed frame 11 is provided with a cam hole 13 in which a cam surface 13a is formed, with which the side surface of the interlocking pin 8d of the interlocking lever 8 comes into contact.

Further, a worm 14 having a rotation axis in the vertical direction is disposed on the side surface of the fixed frame 11. The rotation axis of this worm 14 is made to protrude above the upper surface of the fixed frame 11, and a drive gear is attached to this protrusion. 15 is fitted. On the upper surface of the fixed frame 11, a gear train 16 including an appropriate number of gears such as a gear 16a and having an appropriate reduction ratio is arranged, and the rotation of a motor (not shown) is transmitted to the drive gear 15 via this gear train 16. . A worm wheel 17 pivotally supported on the side surface of the fixed frame 11 meshes with the worm 14, and a transmission gear 18 is provided coaxially with the worm wheel 17. These worm wheels 1
7 and the transmission gear 18 are mutually rotatable, and by applying an appropriate frictional force between their sides, when the load applied to these gears exceeds a predetermined value, one of the gears stops. However, the other gear is set to idle.

The transmission gear 18 includes an intermediate gear 1 pivotally supported on the fixed frame 11.
9 are in mesh with each other, and a gear for driving an encoder 20 and a fan-shaped gear 21 are in mesh with this intermediate gear 19.

The rotating shaft 21a of the sector-shaped gear 21 passes through a through hole 11c formed on the side surface of the fixed frame 11, and the tip of the rotating shaft 21a is connected to a notch 4 formed at the rear lower end of the movable lens barrel 4.
h and is located inside the movable lens barrel 4 housed in the fixed frame 11. Then, the base end of an input lever 22 as a driving member is fixed to the tip of the rotation shaft 21a with a set screw 22a, so that the input lever 22 and the fan-shaped gear 21 rotate in synchronization. be. °This input lever 2
A drive pin 22b is provided at the free end of the movable lens barrel 2 and protrudes toward the sector gear 21, and the drive pin 22b is loosely inserted into the cam portion 9 formed on the side surface of the movable lens barrel 4.

The upper surface of the fixed frame 11, and the movable lens barrel 4 accommodated therein.
A through hole lid having a shape corresponding to the cam surface 10a is formed in a portion located substantially above the cam plate 10.

Further, an interlocking plate 23 is provided on the upper surface of the fixed frame 11, and a set screw 2
3a, it is pivotably supported approximately at the center thereof. A downwardly directed engagement pin 23b is protruded from one end of the interlocking plate 23, and this engagement pin 23b passes through the through hole lid and comes into contact with the cam surface 10a of the cam plate 10. . An upwardly directed input pin 23c is protruded from the other end of the interlocking plate 23, and this input pin 23c is interlocked with a magnification change mechanism (not shown) of the finder. In addition, the interlocking plate 23 is.

It may be supported pivotably on the camera body A or the finder case.

Next, details of the cam portion 9 formed on the movable lens barrel 4 will be explained based on FIG. 1 and FIGS. 2(a) to 2(c). −
The cam part 9 has a zoom part 9a having a long through hole formed in the vertical direction.
, an arcuate W end portion 9b continuous with the upper end of the zoom portion 9a and centered on the rotation shaft 21a of the input lever 22;

The rotation shaft 2 of the input lever 22 is continuous with the lower end of the zoom section 9a.
An arc-shaped T end 9c centered on 1a, and a W end 9
It consists of a storage section 9d that continues vertically upward from the upper end of the storage section b. Note that the W end 9b regulates when the focal length of the photographing lens is at its shortest, and the T end 9c regulates when it is at its longest.

The operation of the cam structure according to the present invention configured as described above is as follows.
This will be explained together with the movement operations of the front group lens 1 and the rear group lens 2.

When the motor (not shown) rotates, the drive gear 15 rotates via the gear train 16, and the worm 14 rotates.

When the worm 14 rotates, the transmission gear 18 rotates due to the frictional force between the worms meshed with the worm. The rotation of the transmission gear 18 is transmitted to the sector gear 21 via the intermediate gear 19, and the sector gear 21 rotates counterclockwise in FIG. 1 about the rotation shaft 21a. Note that the rotation of the motor when rotating the fan-shaped gear 21 in this direction is assumed to be forward rotation.

When the sector gear 21 rotates, the input lever 22 coaxially with the sector gear 21 swings in the same direction in synchronization. Therefore, the drive pin 22b of the input lever 22 pivots in the counterclockwise direction in FIG. 1 about the pivot shaft 21a. In the figure, since this drive pin 22b is located in the storage part 9d of the cam part 9,
The cam portion 9 is pushed by the rotation of the drive pin 22b. Therefore, the movable lens barrel 4 forming the cam part 9 is guided by the main guide part 4C and the sub guide part 4g, and the fixed frame 11
Move forward toward the subject. A shutter unit 3 including a front lens group 1 is fixed to the front part of the movable lens barrel 4, and the front lens group 1 also moves forward. Note that since the length of the storage section 9d is short, the movable lens barrel 4 only moves forward slightly.

When the motor further rotates forward and the sector gear 21 rotates,
As shown in FIG. 2(a), the drive pin 22b of the input lever 22 is located at the W end 9b. Since this W end portion 9b is formed in an arc shape with the rotation axis 21a as the center, when the drive pin 22b is located at this W end portion 9b, even if the input lever 22 swings, the movement ar544 is In other words, this W end portion 9b constitutes a dead zone in which the movable lens barrel 4 does not operate even if the input lever 22 as a drive member operates.

When the input lever 22 further swings and the drive pin 22b is positioned at the zoom section 9a as shown in FIG. Move forward with 4.

When the movable mirror JIM4 moves forward, the interlocking lever 8 that is pivotally supported by the movable mirror JIM4 also moves in the same way. Since the interlocking pin 8d of the interlocking lever 8 is in contact with the cam surface 13a of the cam hole 13 formed in the fixed frame 11, when the interlocking lever 8 moves forward with respect to the fixed frame 11, the interlocking lever 8 is moved against the cam surface 13a. It is guided and rotates counterclockwise in FIG. 4 about the support screw 8c. On the other hand, the lens mount 5 of the rear group lens 2 is connected to the interlocking lever 8 via the focus adjustment pin 7.
are connected to each other, the rotation of the interlocking lever 8 causes the lens mount 5 to move against the restoring force of the push spring 6d.
move forward against. Therefore, the rear group lens 2 moves forward with respect to the movable lens barrel 4, and the distance between it and the front group lens 1 is narrowed. Therefore, zooming is performed by continuously changing the focal length.

Note that the optical positional relationship between the front group lens 1 and the rear group lens 2 when zooming is to be ensured.

The cam surface 13a may be designed to have a predetermined cam curve.

Then, the input lever 22 further swings and the drive pin 22
When b is located at the T end 9c as shown in FIG. 2(c), the movable lens barrel 4 will not move even when the input lever 22 swings. This means that the T end 9c is similar to the W end 9b,
This is because it is formed in an arc shape centered on the rotation shaft 21a, that is, a dead zone is also formed at the T end portion 9c. Note that when the drive pin 22b is located at the T end 9c, the tip of the movable lens barrel 4 is in a position protruding from the fixed frame 11.

To move the movable lens barrel 4 backward from the state where the drive pin 22b is located at the T end 9C of the cam portion 9 and the movable lens barrel 4 is located at the forefront, a motor (not shown) must be rotated in the opposite direction. Bye. Due to the reverse rotation of the motor, the fan-shaped gear 21 moves as shown in Fig. 2 (Q
) Since it rotates in the upper clockwise direction, the drive pin 22b also rotates in the same direction. Therefore, contrary to the above, the movable lens barrel 4 retreats while being accommodated in the fixed frame 11.

A push spring 6 is used to keep the lens mount 5 always moving backwards.
d, and the interlocking lever 8 receives a force to rotate clockwise in FIG.
It is in contact with 3a. Therefore, the interlocking pin 8d is guided by the cam surface 13a and rotates clockwise in FIG. 4 about the support screw 8c. Therefore, the fulcrum pin 7e also rotates in the same direction, and the lens mount 5 retreats with respect to the movable lens barrel 4.

As a result, the rear group lens 2 moves backward, and in cooperation with the retreat of the front group lens 1 accompanied by the movable lens barrel 4, the focal length is continuously changed to the shortest distance.

When initially adjusting the focal length, drive pin 2
The movable lens barrel 4 is positioned so that the drive pin 22b is located at the W end 9b to adjust the shortest focal length, and the movable lens barrel 4 is positioned so that the drive pin 22b is located at the T end 9c to adjust the shortest focal length. Just adjust the focal length. At this time, since there is a dead zone at the W end 9b and the T end 9C, there is no need to stop each lens group with high precision.

In this embodiment, a telephoto type zoom lens in which the front group lens 1 and rear group lens 2 move forward to create a long focal point has been described, but this is also a retrofocus type zoom lens in which each lens group moves backward to create a long focal point. I don't mind. In this case, the arrangement of the W end 9b and the T end 9C of the cam portion 9 is reversed.

Furthermore, although the input lever 22 has been described as a driving member, a rotary plate is provided in place of the input lever 22, and the outer circumferential surface of this rotary plate forms a dead zone (an arc-shaped portion centered around its rotation center). An appropriate cam curve may be used, and the movable lens barrel 4 may be provided with a pin or the like that is in constant contact with the outer peripheral surface of the rotary plate.

In addition, according to the structure of the input lever 22 and the cam part 9 as in this embodiment, the cam part 9 can be formed of a circular arc part and a straight part, so it is relatively easy to process and the accuracy can be easily increased. .

〔Effect of the invention〕

As explained above, according to the cam structure for driving a zoom lens according to the present invention, the driving member and the driven member are connected with the cam, and the dead zone is provided at the shortest focal length part and the longest focal length part of the cam. If either the member or the driven member is located within this dead zone, the shortest focal length and longest focal length can be adjusted. Therefore, it is not necessary to accurately stop the photographic lens at a predetermined position to adjust the focus, so that the effort required for initial adjustment of the focal length can be saved as much as possible. Further, the processing accuracy of the cam does not need to be higher than that of conventional cams, and the photographic lens can be maintained in a predetermined optical relationship.

Furthermore, when photographing, it is easy to photograph at a known focal length when the focal length is the shortest and when the focal length is the longest. Moreover, since it has a simple structure, the cost of processing and parts can be reduced, making it possible to provide an inexpensive zoom lens.

[Brief explanation of the drawing]

FIG. 1 is a front view of the cam part showing the cam structure according to the present invention, and FIGS. 2(a) to (Q) show a state in which the movable lens barrel is housed in a fixed frame provided with an input lever. 2(a) is a front view of the cam section, FIG. 2(a) shows the case at the W end, FIG. 2(b) shows the case at the zoom section, and FIG. 2(c) shows the case at the T end. FIG. 1 is an exploded perspective view showing an embodiment of a zoom lens equipped with a cam structure according to the present invention. FIG. 4 is a partial cross-sectional view taken along a horizontal line in which the movable lens barrel is housed in the fixed frame. 1...Front group lens 2...Rear group lens 4...
・Moving lens barrel 9...Cam part 9a...Zoom part 9b...W end 9c...T end
9d... Storage section 11... Fixed frame
21... Sector gear 21a... Rotation shaft 22... Input lever (drive part #) 22a... Set screw 22b... Drive bin A
・・・Camera body patent applicant Fuji Photo-Koki Co., Ltd. Figure 1 Rei Figure 4

Claims (1)

[Claims] A zoom lens that changes the focal length by applying an external driving force to move an appropriate number of lens groups in a predetermined relationship in the optical axis direction, the zoom lens being driven by receiving the external driving force. A driving member and a movable lens barrel that moves the lens group in the optical axis direction in a predetermined relationship are connected by a cam, and a cam is attached to the end of the shortest focus side and the end of the longest focus side of the cam during operation of the driving member. A cam structure for driving a zoom lens characterized by a dead zone in which the movable lens barrel does not move.