JPH087312B2 - Cam structure for driving zoom lens - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to the case where the focal length of the taking lens is around the shortest end (hereinafter abbreviated as “W end”) and the longest end ( (Hereinafter, abbreviated as "T end"), the shortest focal length and the longest focal length do not move even if power is applied to the driving member of the photographing lens in order to change the focal length. The present invention relates to a cam structure for driving a zoom lens that can maintain the distance.

[Conventional technology]

There is a zoom lens capable of taking a photograph by continuously changing the focal length by appropriately moving the lens group. In recent years, so-called compact cameras have become widespread so that a photograph can be taken easily, and a compact camera with a zoom lens in which a zoom lens is attached has been developed.

The conventional driving mechanism for this type of zoom lens is a double lens barrel in which the outer lens barrel is fitted to the inner lens barrel, one lens barrel is fixed to the camera body, and the other lens is rotatable around the optical axis. By rotating the other lens barrel, the lens group is moved in the optical axis direction.

That is, a straight groove along the optical axis is formed on either the inner lens barrel or the outer lens barrel, and a spiral cam groove corresponding to the number of lens groups is formed on the other lens barrel, and each lens group is formed. The pins planted in the mount are inserted into both the straight groove and the respective cam grooves. When one of the lens barrels is rotated, the pin is guided in both the linear groove and the cam groove, so that the linear groove regulates the movement direction and the cam groove regulates the movement distance, and the lens group moves. To do. The movement of this lens group changes the focal length.

[Problems to be solved by the invention]

By the way, since the zoom lens continuously changes the focal length, its optical relationship must be kept to a predetermined level according to the movement of the lens group. This optical relationship is maintained by the shape and positional relationship of the cam grooves.

In order to maintain this optical relationship at a predetermined level, the linear groove and the cam groove must be processed with high accuracy, and the focal length at the W end position and the focal length at the T end position must be the same. If not properly adjusted, the optical relationship will be lost at the intermediate focal length. Therefore, it is necessary to surely stop the lens at the W end and the T end at the initial adjustment of the focal length.

However, since the cam groove is processed with high precision, in order to stop the lens groups at the W end and the T end, respectively, high precision is required for the position adjustment work. Therefore, this adjustment work is time-consuming and requires a considerable amount of time.

Therefore, according to the present invention, when the lens groups are located at the W end and the T end, even if a driving force is applied from the outside to move the lens groups, the W end should be driven for a predetermined time or more. (EN) It is an object of the present invention to provide a cam structure for driving a zoom lens, in which the lens group is not detached from the T end and the focal length at the W end and the T end can be easily adjusted.

[Means for solving problems]

In order to achieve the above object, the cam structure according to the present invention is a zoom lens in which a focal length is changed 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 that receives a driving force from the outside and drives the lens group, moves in the optical axis direction by the operation of the driving member, and one or more of the lens groups moves in accordance with this movement. A moving lens barrel for moving the held lens group while maintaining a predetermined optical relationship at a speed different from the speed, and the driving means and the moving lens barrel are connected to each other in the optical axis direction of the moving lens barrel. And a dead zone in which the movable lens barrel does not move even during operation of the drive member, provided at the shortest focus side end and the longest focus side end of the cam of the cam means. I am trying.

[Work]

Even if the driving member operates by receiving a driving force from the outside, when the focal length of the taking lens is on the short focal side and the long focal side, the driving member and the movable lens barrel are linked by the dead zone. Therefore, the movable lens barrel does not operate and the lens group does not move. Then, when the driving member rotates by a predetermined angle or more, the driving member is separated from the dead zone, power is transmitted from the driving member to the movable lens barrel, and the lens group starts moving.

〔Example〕

Hereinafter, the driving cam structure of the zoom lens according to the present invention will be specifically described based on the illustrated embodiments.

First, the structure of the lens drive unit of a compact camera equipped with a zoom lens in which the lens group moves by this cam structure will be described with reference to FIG.

This zoom lens is a two-group zoom including a front group lens 1 and a rear group lens 2. The front lens group 1 is housed in a shutter unit 3, and the shutter unit 3 is fixed to the front part of the movable lens barrel 4 by three setscrews 3a. In addition,
By interposing a spring washer 3b between two setscrews 3a of the setscrews 3a, the tilt of the front lens group 1 in the optical axis direction can be adjusted.

The movable lens barrel 4 has a shape in which a mounting plate 4a for fixing the shutter unit 3 is formed on a substantially rectangular frame member. A guide hole 4b is formed in the rear of the upper surface of the movable lens barrel 4 in a substantially rectangular shape in parallel with the optical axis to provide a guide hole 4b.
Then, the rear group lens 2 is arranged at the rear portion of the movable lens barrel 4 by inserting the protrusion 5a formed on the upper end portion of the lens mount 5 of the rear group lens 2.

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 bush 5c is fitted to the guide portion 5b. The rear group guide rod 6a is inserted through the bush 5c, and the tip of the rear group guide rod 6a on the side of the movable lens barrel 4 is supported by a support portion provided in the movable lens barrel 4. A pressing plate 6b is brought into contact with the rear end of the rear group guide rod 6a, and the pressing plate 6b is fixed to the movable lens barrel 4 by a set screw 6c. A pushing spring 6d is wound between the lens mount 5 of the rear group guide rod 6a and the above-mentioned supporting portion in the movable lens barrel 4, and the restoring force of the pushing spring 6d is adjusted by the lens mount 5 to the guide hole 4b and the rear group. It is urged to move backward by being guided by the guide rod 6a. An appropriate depression is formed on the lower surface of the lens mount 5, the eccentric pin 7a and the flange portion 7b of the focus adjustment pin 7 are fitted into the depression, and the pressing plate 7c is fixed to the lens mount 5 with the 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 the fulcrum pin 7e is passed through the through hole portion 7f of the pressing plate 7c to form the interlocking hole 8a of the interlocking lever 8. Insert loosely. The interlocking lever 8 is substantially L-shaped, and the interlocking hole 8a is formed at the tip of one arm portion thereof. A through hole 8b is formed in the substantially L-shaped bent portion, a support screw 8c penetrating the through hole 8b is fastened to the lower surface of the movable lens barrel 4, and the interlocking lever 8 is attached to the movable lens barrel 4. It is rotatably provided around 8c. An interlocking pin 8d is provided at the tip of the other arm of the interlocking lever 8 so as to project in a direction opposite to the direction of the movable lens barrel 4.

At the rear of the side surface of the movable lens barrel 4, there is provided a cam portion 9 which constitutes a cam means having a through hole formed in a shape described later.

Further, a main guide portion 4c having a through hole formed in the optical axis direction is provided at a side end portion of the upper surface of the movable lens barrel 4, and a bush 4d is fitted into the main guide portion 4c. A cam plate 10 having a cam surface 10a is fixed near the side of the main guide portion 4c. In addition,
The cam plate 10 may be common to the main guide portion 4c, and the cam surface 10a may be formed on the side surface of the main guide portion 4c. As shown by a broken line, a sub-guide portion 4e having a U-shaped tip is cut out 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.

As described above, the movable lens barrel 4 on which the front lens group 1, the rear lens group 2, the interlocking lever 8 and the like are mounted is housed in the fixed frame 11 fixed to the camera body A (shown in FIG. 4). At this time,
The main guide rod 4f is inserted into the main guide portion 4c, and the rear end portion of the main guide rod 4f is supported by the support portion 11a above the rear end portion of the fixed frame 11. Further, the auxiliary guide bar 4g is inserted into the notch at the tip of the auxiliary guide portion 4e, and the rear end portion is supported by the support portion 11b provided on the inner side surface of the fixed frame 11. Then, the frame-shaped lid body 12 is fastened and fixed to the front peripheral edge of the fixed frame 11 with the 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 having a cam surface 13a with which the side surface of the interlocking pin 8d of the interlocking lever 8 abuts.

Further, a worm 14 having a rotation axis in the vertical direction is arranged on the side surface of the fixed frame 11, and the rotation axis of the worm 14 is projected above the upper surface of the fixed frame 11, and the drive gear is attached to this projection. 15 is fitted. On the upper surface of the fixed frame 11, a gear train 16 having an appropriate reduction ratio, which is composed of an appropriate number of gears such as a gear 16a, 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. The worm wheel 17 and the transmission gear 18 are rotatable with respect to each other, and when an appropriate frictional force is applied between these side surfaces so that the load applied to these gears exceeds a predetermined magnitude, one of the The gear is stopped and the other gear is allowed to idle.

An intermediate gear 19 pivotally supported by the fixed frame 11 meshes with the transmission gear 18, and a gear for driving the encoder 20 and a sector gear 21 mesh with the intermediate gear 19.

The rotation shaft 21a of the fan-shaped gear 21 penetrates a through hole 11c formed in the side surface of the fixed frame 11, and the tip end of the rotation shaft 21a has a notch 4h formed at the rear lower end of the movable lens barrel 4. It is located inside the movable lens barrel 4 which has passed through and is accommodated in the fixed frame 11. Then, the base end portion of the input lever 22 as a driving member is fixed to the tip end portion of the rotating shaft 21a with a setscrew 22a so that the input lever 22 and the sector gear 21 rotate in synchronization. is there. A drive pin 22b is provided on the free end of the input lever 22 so as to be oriented in the direction of the fan 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. There is.

The movable lens barrel 4 which is the upper surface of the fixed frame 11 and is accommodated in the fixed frame 11.
The portion of the cam plate 10 located substantially above the cam plate 10 has a cam surface
A through hole 11d having a shape corresponding to 10a is formed. An interlocking plate 23 is rotatably supported on the upper surface of the fixed frame 11 by a set screw 23a so that the interlocking plate 23 can rotate about the center thereof. This interlocking board 23
An engaging pin 23b directed downward is projected from one end of the cam plate 10 through the through hole 11d.
Is in contact with the cam surface 10a. An input pin 23c directed upward is provided at the other end of the interlocking plate 23 so as to project upward, and the input pin 23c is interlocked with a variable magnification mechanism (not shown) of the finder. The interlocking plate 23 may be pivotally supported on the camera body A or the case of the finder.

Next, details of the cam portion 9 formed on the movable lens barrel 4 will be described with reference to FIGS. 1 and 2 (a) to (c). The cam portion 9 is a zoom portion 9a in which a long through hole is formed in the vertical direction, an arcuate W end portion 9b that is continuous with the upper end of the zoom portion 9a and has the rotation shaft 21a of the input lever 22 as the center, and the zoom portion 9a. An arcuate T-end portion 9 which is continuous with the lower end and which is centered on the rotation shaft 21a of the input lever 22
c, and further comprises a storage portion 9d which is vertically continuous from the upper end of the W end portion 9b. The W end 9b regulates the case where the taking lens has the shortest focal length, and the T end 9c regulates the case where it has the longest focal length.

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

When a motor (not shown) rotates, the drive gear 15 rotates via the gear train 16 and the worm 14 rotates. Warm 14
When the worm rotates, the worm wheel 17 meshed with the worm rotates, and the frictional force between the worm wheel 17 and the worm wheel 17 causes the transmission gear 18 to rotate. The rotation of the transmission gear 18 is the rotation of the intermediate gear 19
It is transmitted to the fan-shaped gear 21 via the rotary shaft 21a, and the fan-shaped gear 21 rotates counterclockwise in FIG. The rotation of the motor when rotating the fan gear 21 in this direction is defined as normal rotation.

When the fan-shaped gear 21 rotates, the input lever 22 that is coaxial with the fan-shaped gear 21 synchronously swings in the same direction. Therefore, the drive pin 22b of the input lever 22 pivots counterclockwise in FIG. 1 about the pivot shaft 21a. Since the drive pin 22b is located in the storage portion 9d of the cam portion 9 in the figure, the cam portion 9 is pushed by the turning of the drive pin 22b. Therefore, the movable lens barrel 4 forming the cam portion 9 is guided by the main guide portion 4c and the sub guide rod 4g and advances toward the subject side with respect to the fixed frame 11. A shutter unit 3 including the 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. Since the length of the storage portion 9d is short, the movable lens barrel 4 only slightly moves forward.

When the motor further rotates forward and the fan gear 21 rotates,
As shown in FIG. 2 (a), the drive pin 22 of the input lever 22
b is located at the W end 9b. Since this W end 9b is formed in an arc shape centering on the rotation shaft 21a, when the drive pin 22b is located at this W end 9b, even if the input lever 22 swings, the movable lens barrel is moved. 4 does not move forward. That is, this W end
In 9b, even if the input lever 22 as a drive member operates,
A dead zone is formed in which the movable lens barrel 4 does not operate.

When the input lever 22 further swings and the drive pin 22b is positioned on the zoom portion 9a as shown in FIG. 2 (b), the front lens group 1 is moved by the rotation of the input lever 22 as described above. Go forward with 4.

When the movable lens barrel 4 moves forward, the interlocking lever 8 pivotally supported on the movable lens barrel 4 also moves. 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 moves to the cam surface 13a. It is guided and rotates counterclockwise in FIG. 4 about the support screw 8c. On the other hand, since the lens mount 5 of the rear group lens 2 is connected to the interlocking lever 8 via the focus adjustment pin 7,
The rotation of the interlocking lever 8 moves the lens mount 5 forward with respect to the movable lens barrel 4 against the restoring force of the push spring 6d. Therefore, the rear lens group 2 moves forward with respect to the movable lens barrel 4, and the space between the rear lens group 2 and the front lens group 1 is narrowed.
Therefore, zooming is performed by continuously changing the focal length. In order to secure the optical positional relationship when the front lens group 1 and the rear lens group 2 perform zooming, the cam curve of the cam surface 13a may be designed to have a predetermined cam curve.

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

In order to retract the movable lens barrel 4 from the state in which 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) is reversely rotated. Good. Since the fan gear 21 rotates clockwise in FIG. 2 (c) by the reverse rotation of the motor, the drive pin 22b also rotates in the same direction. For this reason, the movable lens barrel 4 is, contrary to the above, fixed frame.
Retreat while accommodated in 11.

The lens mount 5 is a push spring so that it always moves backward.
Since the interlocking lever 8 receives the restoring force of 6d and the force of rotating clockwise through the focus adjusting pin 7 in FIG. 4, the interlocking pin 8d receives the force of the cam surface 13a.
Is in contact with Therefore, the interlocking pin 8d becomes the cam surface 13a.
And is rotated clockwise around the support screw 8c in FIG. Therefore, the fulcrum pin 7e also turns in the same direction, and the lens mount 5 retracts with respect to the movable lens barrel 4.
As a result, the rear lens group 2 retreats, and in cooperation with the retreat of the front lens group 1 accompanying the movable lens barrel 4, the focal length is continuously changed to the shortest distance.

And for the initial adjustment of the focal length, the drive pin
Position the movable lens barrel 4 so that 22b is located at the W end 9b, and adjust the shortest focal length, and position the movable lens barrel 4 so that the drive pin 22b is located at the T end 9c. Adjust the focal length. At this time, since the W end portion 9b and the T end portion 9c have a dead zone, it is not necessary to stop each lens group with high accuracy.

In this embodiment, the telephoto type zoom lens in which the front lens group 1 and the rear lens group 2 move forward to form a long focus has been described, but it is a retrofocus type zoom lens in which each lens group moves backward to form a long focus. It doesn't matter. In this case, the positions of the W end 9b and the T end 9c of the cam portion 9 are reversed.

Further, although the input lever 22 has been described as a driving member, a rotary plate is provided instead of the input lever 22, and the outer peripheral surface of the rotary plate has a dead zone (an arc-shaped portion centered on the rotation center).
Alternatively, the movable lens barrel 4 may be provided with a pin or the like that is always in contact with the outer peripheral surface of the rotary plate.

According to the configuration of the input lever 22 and the cam portion 9 as in the present embodiment, the cam portion 9 can be formed by the circular arc portion and the straight portion, so that the machining is relatively easy and the accuracy can be easily increased. .

〔The invention's effect〕

As described above, according to the drive cam structure for a zoom lens according to the present invention, the drive member and the movable lens barrel are connected to each other by the cam, and the dead zone is provided in the shortest focal length portion and the longest focal length portion of the cam. If either the drive member or the movable lens barrel is located within this dead zone, the shortest focal length and the longest focal length can be adjusted. Therefore, it is not necessary to stop the taking lens at a predetermined position with high accuracy to perform focus adjustment, and the labor 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 the conventional one, and the photographing lens can be maintained in a predetermined optical relationship.

Further, also at the time of photographing, if the focal length is the shortest and the focal length is the longest, it is possible to easily photograph with the known focal length. Moreover, since it has a simple structure, the cost required for processing and parts can be small, and an inexpensive zoom lens can be provided.

[Brief description of drawings]

FIG. 1 is a front view of a cam portion showing a cam structure according to the present invention, showing a state in which a movable lens barrel is housed in a fixed frame provided with an input lever. 2 (a) to 2 (c) are front views of the cam portion. FIG. 2 (a) is at the W end, FIG. 2 (b) is at the zoom portion, and FIG. Indicates the case at the T end. FIG. 3 is an exploded perspective view showing an embodiment of the zoom lens provided with the cam structure according to the present invention. FIG. 4 is a partial cross-sectional view taken along the horizontal line in a state where the movable lens barrel is housed in the fixed frame. 1 ... front lens group, 2 ... rear lens group 4 ... moving lens barrel, 9 ... cam section 9a ... zoom section, 9b ... W end section 9c ... T end section, 9d ... storage section 11 ...... Fixed frame, 21 ...... fan gear 21a …… Rotary shaft 22 …… Input lever (driving member) 22a …… Set screw, 22b …… Drive pin A …… Camera body

Front page continued (72) Inventor Kazuhiko Onda 1-324 Uetakecho, Omiya-shi, Saitama Fuji Photo Optical Co., Ltd. Incorporated (56) References Japanese Patent Laid-Open No. 63-169620 (JP, A) Actually developed 63-39206 (JP, U)

Claims (1)

[Claims] 1. A zoom lens in which an appropriate number of lens groups are moved in the optical axis direction in a predetermined relationship to change the focal length by applying a driving force from the outside, and the driving is performed by receiving the driving force from the outside. And a lens group that holds the lens group, moves in the optical axis direction by the operation of the driving member, and holds one or more of the lens groups at a speed different from the moving speed in accordance with the movement. A movable lens barrel that moves while maintaining an optical relationship of a predetermined value, and a cam unit that connects the drive unit and the movable lens barrel and that moves the movable lens barrel in the optical axis direction, A drive cam structure for a zoom lens, characterized in that a dead zone is provided at the shortest focus side end and the longest focus side end of the cam of the cam means so that the movable lens barrel does not move even during operation of the drive member.