JPH07120662A - Zoom lens tube using varifocal optical system - Google Patents

Abstract

PURPOSE:To realize a zoom lens tube using a varifocal optical system where zooming and focusing are never interfered with each other while keeping the operability of focusing at the same level as a conventional zoom lens level. CONSTITUTION:A fixed cylinder 1 has a zoom cam ring 2 only rotatable and regulated in optical axial movement, and a focus cam ring 3 movable on in the optical axial direction and regulated in rotation. The zoom cam ring 2 is rotated at zooming, and the focus cam ring 3 is longitudinally moved in the optical axial direction at focusing, thereby, the mutual interference in lens group movement between zooming and focusing is avoided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a zoom lens barrel using a varifocal optical system, and more particularly to improvement of a driving mechanism for a focusing block of the zoom lens barrel.

[0002]

2. Description of the Related Art In a zoom lens barrel using a varifocal optical system, each lens group mounted in the lens barrel is divided into a zooming lens group and a focusing lens group, and the roles of the zoom lens group are not fixed. The zoom lens can also be used for focusing at the same time, so that the zoom ratio can be increased and focusing to a close range can be performed.

However, in such a zoom lens barrel of a varifocal optical system, the extension amount of the focusing block when focusing is changed according to the change of the focal length for the same subject on the tele side and the wide side during zooming. Therefore, in the case where the manual focusing function is installed, the rotation angle at the time of operating the range ring changes depending on the focal length, which causes a problem in operability.

As a means for solving such a problem,
Conventionally, there is, for example, a prior art for correcting the focus by changing the range of use of the focusing cam that contributes to the extension of the focusing block in accordance with the change in the focal length due to the zooming operation, for example, Japanese Patent Laid-Open No. 57-37307.
No. 63-49715 or 4-18
It is proposed in Japanese Patent No. 4406.

However, in any of the above-mentioned prior art examples, it is unavoidable that the focusing mechanism is simultaneously operated during zooming, that is, so-called mutual interference occurs. In the case of adopting a method of changing the range of use of the focusing cam, in order to prevent mutual interference between the zooming mechanism and the focusing mechanism, by using an ultrasonic motor as a drive means for autofocus, during manual focusing, Although a mechanism that locks the mechanism in a state where focus correction is performed to prevent mutual interference has been developed, it is not a drastic solution such as a complicated device.

In order to mechanically prevent the mutual interference between the zooming mechanism and the focusing mechanism, Japanese Patent Laid-Open No. 3-101707 discloses a combination of a zoom cam and a focus cam for focus correction. A one-hand zoom type zoom lens barrel is disclosed.

In this prior art example, the lens groups that contribute to zooming and focusing are regulated by the intersections of the zoom cam and focus cam, zooming is performed by relative rotation of both cams, and focusing is achieved by relative movement in the optical axis direction. During focusing, the relative movement amount of both cams is kept substantially constant for a predetermined subject regardless of the focal length.
Further, the zoom cam is formed on a fixed barrel, and the focus cam is formed on a cam ring fitted to the fixed barrel so as to be rotatable and movable in the optical axis direction.

Zooming is performed by moving the zoom ring provided on the outermost periphery of the lens barrel in the optical axis direction, and focusing is performed by rotating the distance ring also provided on the outermost periphery of the lens barrel. During focusing, the operating angle of the range ring is kept constant from the wide side to the tele side.

[0009]

However, in the above prior art example, since the zoom cam is formed in the fixed cylinder, there are the following problems. That is, the fixed barrel is usually formed integrally with the bayonet portion for mounting on the camera body, and is equipped with a movable ring frame for holding the cam ring and lens group inside and outside, so that it is a big one. Since it is a component and its shape is complicated, the manufacturing cost is inevitably high.

Therefore, when the fixed cylinder is a metal part,
In order to process a zoom cam that requires high precision, a high level of processing technology is required, and the rate of defective products is expected to increase considerably. Further, when the fixed cylinder is used as a molded part, the structure of the molding die provided with the zoom cam is very complicated and the cost becomes high, so that there is a problem that it is difficult to implement.

The present invention has been made to solve such a problem, and improves the operability of manual focusing while improving the operability of manual focusing in a structure using a varifocal optical system in which mutual interference between zoom and focus does not occur. It is an object of the present invention to provide a zoom lens barrel which can be made compact and which can be manufactured relatively easily and can effectively reduce the cost.

[0012]

To achieve the above object, a zoom lens barrel using a varifocal optical system of the present invention comprises a plurality of lens groups that are driven in the optical axis direction and contribute to zooming and focusing. A fixed barrel, a zoom cam ring that is restricted from moving in the optical axis direction relative to the fixed barrel and is only rotatable, a zoom ring for rotating the zoom cam ring, and a rotation limited to the fixed barrel. A focus cam ring that can move only in the axial direction, a focus ring for moving the focus cam ring in the direction of the optical axis, and a rotational drive of an autofocus motor provided on the camera side of the focus cam ring. Convert to movement along the optical axis A
F drive transmission means.

A zoom cam is formed on the zoom cam ring, a focus cam is formed on the focus cam ring, and movement of each lens group in the optical axis direction is restricted by an intersection of the zoom cam and the focus cam. Each of the lens groups is linked to a zoom cam and a focus cam.

Further, during zooming, by rotating the zoom ring to rotate the zoom cam ring,
While rotating the zoom cam and the focus cam relative to each other, during focusing, the focus ring is rotatably operated or the autofocus motor is rotationally driven to move the zoom cam and the focus cam in the optical axis direction of the focus cam ring. The relative movement in the optical axis direction is performed, and the necessary amount of linear movement of the focus cam ring is kept substantially constant for a predetermined subject during this focusing.

[0015]

According to the structure of the present invention, a cam ring for zooming,
The zoom cam ring is separated from the focusing cam ring, and the zoom cam ring is held so as to rotate only with respect to the fixed barrel and the focus cam ring only moves straight with respect to the fixed barrel.

Therefore, although a rotational force is applied to the focusing cam ring during zooming, it does not rotate because it is guided in the optical axis direction. Further, a rotational force is also applied to the zoom cam ring during focusing, but since the load on the zoom system is large and the cam ring does not rotate, mutual interference between zooming and focusing does not occur.

Further, since the zoom cam having a complicated and precise shape is not formed on the fixed barrel, the structure of the fixed barrel does not become complicated. Therefore, since the fixed cylinder can have a relatively simple shape, it can be formed of a molded product, and the mold thereof can be manufactured at low cost.

[0018]

Embodiments of the present invention will now be described in detail with reference to the drawings. 1 to 7 show a first embodiment of the present invention.
1 shows a state in which the focal length of the lens is set to the wide end, and FIG. 2 shows a state in which the focal length of the lens is set to the tele end. Further, FIG. 3 shows a focus drive unit, and FIG. 4 shows a zoom drive unit.
Further, FIG. 5 shows essential parts of the fixed barrel 1, the zoom cam ring 2 and the focus cam ring 3 which form the lens barrel.

In these figures, the fixed barrel 1 is integrally formed with a bayonet portion 1d for mounting the lens barrel on the camera body at the rear end portion. Zoom cam ring 2 is fixed cylinder 1
Is provided on the outer diameter side, and is held by the fixed barrel 1 in a state in which movement is restricted in the optical axis direction and only rotatable.

A focus cam ring 3 is provided on the inner diameter side of the fixed barrel 1 so as to be movable only in the optical axis direction and restricted in rotation. That is, a projection 3b is formed on the outer diameter side of the focus cam ring 3, and the projection 3b is engaged with the inner diameter straight groove 1c formed in the fixed barrel 1, whereby the focus cam ring 3 is formed. Is driven straight without rotating.

A helicoid cylinder 4 is held so as to be rotatable only with respect to the zoom cam ring 2, and a helicoid screw provided on the inner diameter side is screwed with the focus cam ring 3. A zoom cam ring 5 for the fourth group is linked to the zoom cam ring 2 through a lever-shaped protrusion 2d extending from the zoom cam ring 2 toward the inner diameter side. Reference numeral 3c is an escape hole formed in the focus cam ring 3 for penetrating the lever-shaped protrusion 2d.

Reference numeral 6 denotes a manual focus ring for rotating operation when performing manual focusing.
It is provided on the outermost front side of the lens barrel and is engaged with a focus interlocking pin 13 projecting on the outer diameter side of the helicoid cylinder 4. Reference numeral 7 denotes a manual zoom ring for rotating operation during manual zooming, which is provided on the rear side of the outermost periphery of the lens barrel and is provided on the outer diameter side rear end of the zoom cam ring 2 to project from the zoom. It is engaged with the interlocking pin 12.

Reference numerals 8 to 11 denote lens frames of the first to fourth groups, which fix and hold the corresponding lens groups G1 to G4, respectively. A lead protrusion 8a is formed on the inner diameter side of the first group lens frame 8, and a protrusion 8b is formed on the outer diameter side rear end portion thereof. The lead protrusion 8a is formed on the outer diameter side of the zoom cam ring 2. The protrusion 8b is engaged with the crab scissors protrusion 2a, and the protrusion 8b is fixed to the fixed cylinder 1.
Engages with the straight groove 1a formed on the inner diameter side.

The second lens group frame 9 is provided with a second lens group guiding pin 14 at the rear end portion on the outer diameter side, and the second lens group guiding pin 14 forms a cam groove 2b as a zoom cam formed in the zoom cam ring 2. ,
It protrudes over a cam groove 3a as a focus cam formed on the focus cam ring 3. 15 is 2
A second group guide roller rotatably fitted to the group guide pin 14 and a second group guide spring 16 interposed between the peripheral surfaces of the second group guide pin 14 and the second group guide roller 15.

On the outer diameter side of the third lens group frame 10, the third lens group guiding pin 1 is provided.
7 is projected, and the third group guide pin 17 projects through a cam groove 2c as a zoom cam formed in the zoom cam ring 2 and a rectilinear groove 1b formed in the fixed barrel 1.
Reference numeral 18 denotes a third group guide roller rotatably fitted to the third group guide pin 17.

A fourth group guide pin 2 is provided on the outer diameter side of the fourth group lens frame 11.
1 is projectingly provided, and the fourth group guide pin 21 is formed in the fourth group zoom cam ring 5 as a cam groove 5a as a zoom cam.
And a straight-ahead groove 10a formed on the outer diameter side of the third group lens frame 10. 22 is the fourth group guide pin 21.
A fourth-group guide roller rotatably fitted to the second-group guide roller 23 is a fourth-group guide spring interposed between the peripheral surfaces of the fourth-group guide pin 21 and the fourth-group guide roller 22.

In the zoom lens barrel of the present embodiment having the above structure, the movement loci of the respective lens groups G1 to G4 during zooming are as shown in FIG. 6, and the second lens group G2 is Contributes mainly to focus. Further, the third group lens frame 10 is equipped with a diaphragm mechanism 28. In the figure, the optical axis direction (horizontal axis) and the angle θ direction (vertical axis) are set so that the locus of movement of the first lens group G1 during zooming is a straight line forming an angle of 45 ° with respect to the optical axis. is doing.

Reference numeral 19 denotes a focus stopper fixed to the fixed barrel 1 with a screw, and reference numeral 20 denotes a focus stopper ring fixed to the manual focus ring 6 with a screw for restricting the rotation range of the manual focus ring 6. FIG. 3 shows an infinity state, and in order to change the state from this state to the closest state, the helicoid tube 4 is rotated counterclockwise by the focus stopper ring 20.
Rotate until it touches.

In FIG. 3, reference numeral 27 denotes a focus reduction gear, which is used to drive the rotation of an autofocus motor (not shown) provided on the camera body side to the focus cam ring 3.
Function as an AF drive transmission unit that converts the movement into a movement in the optical axis direction. The small diameter gear 27a of the focus reduction gear 27
Is attached to the output end of a lens coupler driven by the coupler on the camera body side during autofocus, and the large diameter gear 27b meshes with the transmission gear 4a formed on the outer diameter side of the helicoid cylinder 4. .

Next, the operation of the above configuration will be described. First,
Prior to the operation of the specific configuration, mechanical correction of varifocal will be described. In the zoom lens barrel of the present embodiment, since the internal focus (second group focus) is adopted as described above, it is a varifocal optical system, which is mechanically corrected by devising a cam shape. By doing so, it is configured as a normal zoom lens.

In a general zoom lens barrel, a mechanical structure is adopted which is a combination of a normal zoom cam z'and a rectilinear groove g as shown in FIG. 7 (A). In the example, the zoom cam z as shown in FIG.
And a focus cam f are combined to adopt a mechanical structure, in which zooming is performed by rotating the zoom cam z, and focusing is performed by moving the focus cam f in the optical axis direction.

When performing this focusing, as shown in the conceptual diagram of the zoom cam and the focus cam of FIG. 8, the amount of extension of the second lens group G2 from infinity to a certain subject varies depending on the zoom position, but the focus cam ring 3 moves. The cam shape is determined so that the feeding amount is constant. As a result, the range ring rotation angle for feeding out the focus cam ring 3 is constant regardless of the zoom position, as in a normal zoom lens. Regarding the burr correction error, the method of obtaining the above-mentioned cam shape is approximate because of design considerations.
The burr correction error cannot be zero over the entire zoom and focus areas.

Next, the specific operation of this embodiment will be described. First, during zooming, the manual zoom ring 7 is manually rotated. This rotation is transmitted to the zoom cam ring 2 via the zoom interlocking pin 12. When the zoom cam ring 2 rotates, the rotational force is transmitted by the engagement between the claw scissors protrusion 2a and the lead protrusion 8a of the first group lens frame 8, and the protrusion 8b of the first group lens frame 8 is fixed to the fixed barrel 1. Straight groove 1
The rotation is restricted by a, and the first group lens frame 8 is driven straight forward.

The rotation of the zoom cam ring 2 is caused by the cam groove 2b.
Is transmitted from the second group guide pin 14 to the second group guide pin 14, the second group guide pin 14 moves in the optical axis direction while being guided by the cam groove 3a of the focus cam ring 3, and the second group lens frame 9 is driven while rotating. It Further, the rotation of the zoom cam ring 2 is caused by the rotation of the cam groove 2c.
Is transmitted to the third group guide pin 17, and the third group guide pin 17 linearly moves in the optical axis direction while being guided by the straight groove 1b of the fixed barrel 1, whereby the third group lens frame 10 is linearly driven.

Furthermore, the rotation of the zoom cam ring 2 is transmitted to the fourth group zoom cam ring 5 from the lever-shaped protrusion 2d.
When the zoom cam ring 5 for the fourth group rotates, the fourth group guide pin 21
Receives the rotational force from the cam groove 5a of the fourth group zoom cam ring 5 and moves straight in the optical axis direction while being guided by the rectilinear groove 10a of the third group lens frame 10, and accordingly the fourth group lens frame 11 moves straight. Driven. In this case, since the fourth group zoom cam ring 5 is held so as to be rotatable only in the optical axis direction with respect to the third group lens frame 10, the cam groove 5a is held in the third group lens frame 10.
And a cam shape having a movement amount difference of the fourth group lens frame 11.

FIG. 4 shows a wide state of the zoom drive section. When zooming to the tele side, the zoom cam ring 2 is rotated counterclockwise.

Next, the operation during focusing will be described. First, at the time of manual focus, if the manual focus ring 6 is manually rotated,
This rotation is transmitted to the helicoid cylinder 4 via the focus interlocking pin 13. Since the helicoid cylinder 4 is held so as to be rotatable only with respect to the zoom cam ring 2, when the helicoid cylinder 4 rotates, the focus cam ring 3 is driven by the helicoid screw.

At this time, the focus cam ring 3 is driven straight without rotating because the protrusion 3b is engaged with the inner diameter straight groove 1c of the fixed barrel 1. The linear drive of the focus cam ring 3 is transmitted from the cam groove 3a to the second group guide pin 14, and the second group guide pin 14 is connected to the cam groove 2 of the zoom cam ring 2.
While being guided by b, it moves in the optical axis direction while rotating, and along with this, the second group lens frame 9 is driven while rotating.

During autofocus, the rotational force of the lens coupler driven by the body side coupler shown in FIG. 3 is transmitted to the helicoid cylinder 4 by the gear train focus reduction gear 27, and thereafter, the same as during manual focus. Helicoid cylinder 4-> focus interlocking pin 13-> focus cam ring 3-> second group guide pin 14 and second group lens frame 9
Is driven.

9 to 11 show the second embodiment of the present invention. 9 shows a state in which the focal length of the lens is set to the wide end, and FIG. 10 shows the shapes of cams formed on the fixed barrel 1, the zoom cam ring 2 and the focus cam ring 3.
In the present embodiment, parts having the same configurations as those of the first embodiment are designated by the same reference numerals, and the description thereof will be omitted to avoid duplication.

In this embodiment, among the lens groups G1 to G4,
The third and fourth lens groups are mainly configured to contribute to focusing. Further, the diaphragm mechanism 28 is provided in the third group lens frame 10 as in the above embodiment, but in this case, when the focusing third and fourth group lens frames 10 and 11 rotate, the diaphragm control on the camera body side. Since mechanical linkage with the system is hindered, these third and fourth group lens frames 10 and 11 are devised so as not to rotate.

That is, in this embodiment, the third group moving frame 24 is interposed between the focus cam ring 3 and the third group lens frame 10, and the third group guide pin 17 is provided so as to project from the third group moving frame 24. There is. As a result, the third-group moving frame 24 is extended in the optical axis direction while being rotated by the cam groove 2c of the zoom cam ring 2 and the cam groove 3a 'of the focus cam ring 3, and the third-group lens frame 10 includes the third group lens frame 10. The movable frame 24 is held so that it can only rotate.

Further, a cam 10b is formed on the outer diameter side front end of the third group lens frame 10, and this cam 10b is engaged with a rectilinear groove 9a formed on the inner diameter side of the second group lens frame 9. Therefore, the third lens group frame 10 is guided straight with respect to the second lens group frame 9 by the cam 10b engaging with the straight groove 9a, whereby the third lens group frame 10 rotates. It is driven straight ahead.

The manual zoom ring 7 and the zoom cam ring 2 are interlocked by a zoom interlocking gear 26 interposed between gears provided at the inner diameter side rear end of the manual zoom ring 7 and the outer diameter side rear end of the zoom cam ring 2. It is connected. The manual focus ring 6 and the helicoid cylinder 4 are interposed between a focus gear train (not shown) provided at the inner diameter side rear end of the manual focus ring 6 and the outer diameter side rear end of the helicoid cylinder 4. The focus interlocking ring 25 is interlockingly connected.

Further, as shown in FIG. 10, the zoom cam ring 2 has a cam groove 2 corresponding to the claw scissor protrusion 2a of the first embodiment.
a'is formed. On the other hand, a protrusion 8 corresponding to the lead protrusion 8a of the first embodiment is provided on the outer diameter side rear end portion of the first group lens frame 8.
a'is formed, and the first group guide pin 30 is provided on the inner diameter side so as to project from the first group guide pin 30.
The protrusion 8a 'engages with the straight groove 1a of the fixed barrel 1. Reference numeral 31 is a first group guide roller rotatably fitted to the first group guide pin 30.

The second group guide pin 14 projecting from the second group lens frame 9 is a straight groove 3d formed in the focus cam ring 3.
Through a cam groove 2b formed in the zoom cam ring 2 and a straight groove 1a formed in the fixed barrel 1. Also,
Third-group guide pin 17 protruding from the third-group moving frame 24
Is projected into a cam groove 2c formed in the zoom cam ring 2, a clearance groove 1f formed in the fixed barrel 1 and a cam groove 3a 'formed in the focus cam ring 3.

Next, the specific operation of this embodiment will be described. First, during zooming, the manual zoom ring 7 is manually rotated. This rotation is transmitted to the zoom cam ring 2 via the zoom interlocking gear 26. In this way, the rotation of the manual zoom ring 7 is controlled by the zoom interlocking gear 26.
If the transmission is performed by a gear train having
It is possible to reduce the size of the notch hole 29 (see FIG. 10) that needs to be provided in the space as small as possible.

By the way, in the first embodiment, since the zoom interlocking pin 12 is used, the notch of the fixed barrel 1 has to be enlarged by the moving range of the zoom interlocking pin 12, and the size reduction is realized accordingly. It can be said that there is a disadvantage in doing so.

When the zoom cam ring 2 rotates, the rotation is transmitted to the first-group guide pin 30 via the cam groove 2a ', and the projection 8a' of the first-group ball frame 8 is directly moved into the straight groove 1 of the fixed barrel 1.
The rotation is regulated by a, so that the first group lens frame 8 is driven straight in the optical axis direction. Further, the rotation of the zoom cam ring 2 is transmitted from the cam groove 2b to the second group guide pin 14 and is transmitted to the second group guide pin 1.
Reference numeral 4 moves in the optical axis direction while being restricted in rotation by the rectilinear groove 1b of the fixed barrel 1, and accordingly the second lens group frame 9 is driven rectilinearly.

Further, the rotation of the zoom cam ring 2 is caused by the rotation of the cam groove 2
The third group guide pin 17 is transmitted from c to the third group guide pin 17.
Moves while moving while being guided by the cam groove 3a 'of the focus cam ring 3 in the optical axis direction, whereby the third group moving frame 24 is rotated and fed out. At this time, the third group moving frame 2
The third group lens frame 10 which is held rotatably with respect to 4 is guided linearly with respect to the second group lens frame 9 by the cam 10b and the straight groove 9a, whereby the third group lens frame 10 rotates. Drive straight ahead without driving.

Further, the rotation of the zoom cam ring 2 is transmitted to the fourth group zoom cam ring 5 from the lever-shaped protrusion 2d.
When the zoom cam ring 5 for the fourth group rotates, the fourth group guide pin 21
Receives the rotational force from the cam groove 5a of the fourth group zoom cam ring 5 and moves straight in the optical axis direction while being guided by the rectilinear groove 10a of the third group lens frame 10, and accordingly the fourth group lens frame 11 moves straight. Driven.

Next, the operation during focusing will be described. First, when the manual focus ring 6 is manually rotated, this rotation is caused by the focus interlocking ring 25.
To the helicoid cylinder 4 via the focus gear train.
Be transmitted to. When the helicoid cylinder 4 rotates, the helicoid screw drives the focus cam ring 3.

At this time, the focus cam ring 3 is moved in the straight groove 3d.
Since it is guided by the engagement of the second group guide roller 15 with the second group guide roller 15, it is driven straight ahead without rotating with respect to the fixed cylinder 1. The linear drive of the focus cam ring 3 is transmitted from the cam groove 2c and the cam groove 3a 'of the zoom cam ring 2 to the third group guide pin 17, whereby the third group moving frame 24 is extended while being rotated.

Since the third group lens frame 10 is held so as to be rotatable only with respect to the third group moving frame 24, it is guided straight to the second group lens frame 9 by the cam 10b and the rectilinear groove 9a. There is. Therefore, the third group lens frame 10 is driven straight without rotating.

During autofocus, as shown in FIG. 11, the rotational force of the lens coupler driven by the body side coupler causes the focus reduction gear 2 of the gear train to rotate.
It is transmitted to the helicoid cylinder 4 by 7, and thereafter it is driven in the same manner as in the manual focus.

12 and 13 show a third embodiment of the present invention. FIG. 12 shows a state in which the focal length of the lens is set to the wide end. In addition, in the present embodiment, the same reference numerals are given to the portions having the same configurations as those of the respective embodiments, and the description thereof will be omitted to avoid duplication.

This embodiment is similar in basic structure to the second embodiment, but as shown in FIG. 13, the drive of the focus cam ring is a feed screw 27a provided coaxially with the focus reduction gear 27. The difference is that it is done by. The feed screw 27a is screwed with a female screw portion 3e provided at the rear end of the focus cam ring 3. Since the movement during zooming in this embodiment is the same as that in the second embodiment, the description of the operation is omitted.

The operation during focusing in the above configuration will be described. First, when the manual focus ring 6 is manually rotated, this rotation is transmitted to the focus interlocking ring 25 to rotate the focus reduction gear 27. The rotation of the focus reduction gear 27 is transmitted to the focus cam ring 3 because the feed screw 27a and the female screw portion 3e of the focus cam ring 3 are screwed together.

At this time, the focus cam ring 3 moves in the straight groove 3d.
Since it is guided by the engagement of the second group guide roller 15 with the second group guide roller 15, it is driven straight ahead without rotating with respect to the fixed cylinder 1. The linear drive of the focus cam ring 3 is transmitted from the cam groove 2c and the cam groove 3a 'of the zoom cam ring 2 to the third group guide pin 17, whereby the third group moving frame 24 is extended while being rotated.

Further, since the third group lens frame 10 is held so as to be rotatable only with respect to the third group moving frame 24, it is guided straight to the second group lens frame 9 by the cam 10b and the rectilinear groove 9a. There is. Therefore, the third group lens frame 10 is driven straight without rotating.

During autofocus, the rotational force of the lens coupler driven by the body side coupler is transmitted to the focus reduction gear 27, and the focus reduction gear 27 rotates accordingly. After that, it is driven in the same manner as in manual focusing. The autofocus motor may be provided not only on the camera body but also on the lens side.

[0062]

As described above, according to the zoom lens barrel of the present invention, in the one using the varifocal optical system, the zoom cam ring and the focus cam ring are separated and the zoom cam ring is separated. Holds only the rotation with respect to the fixed member, and the focus cam ring so as to go straight with respect to the fixed barrel. It can be eliminated and excellent operability can be realized.

Further, since the zoom cam having a complicated and precise shape is not formed on the fixed barrel, the structure of the fixed barrel does not become complicated. Therefore, since the fixed cylinder can be formed in a relatively simple shape, it can be formed of a molded product, and its die can be manufactured at low cost. It has been demonstrated.

[Brief description of drawings]

FIG. 1 is a sectional view of a first embodiment of the present invention in a wide state.

FIG. 2 is a sectional view of the telephoto state.

FIG. 3 is a front view showing the focus driving unit.

FIG. 4 is a front view showing the zoom drive unit.

FIG. 5 is a main-part perspective view showing the fixed barrel, the zoom cam ring, and the focus cam ring in a disassembled state.

FIG. 6 is a diagram showing a movement locus of each lens unit during zooming.

FIG. 7 is a diagram schematically showing the shapes of guide grooves in a general example and this embodiment.

FIG. 8 is a development view conceptually showing a zoom cam and a focus cam.

FIG. 9 is a sectional view of a second embodiment of the present invention in a wide state.

FIG. 10 is a view conceptually showing the cam shapes of the fixed barrel, zoom cam ring, and focus cam ring.

FIG. 11 is a cross-sectional view of an essential part showing a lens coupler part.

FIG. 12 is a sectional view of a third embodiment of the present invention in a wide state.

FIG. 13 is a cross-sectional view of essential parts showing a lens coupler part.

[Explanation of symbols]

 1 Fixed cylinder 2 Zoom cam ring 3 Focus cam ring 4 Helicoid cylinder 5 4 group zoom cam ring 6 Manual focus ring 7 Manual zoom ring 8 1 group lens frame 9 2 group lens frame 10 3 group lens frame 11 4 group lens frame 12 Zoom interlocking Pin 13 Focus interlocking pin 14 2nd group guide pin 15 2nd group guide roller 16 2nd group guide spring 17 3rd group guide pin 18 3rd group guide roller 19 Focus stopper 20 Focus stopper ring 21 4th group guide pin 22 4th group guide roller 23 4th group Guide spring 24 Third group moving frame 25 Focus interlocking ring 26 Zoom interlocking gear 27 Focus deceleration gear

Claims (1)

[Claims] 1. A plurality of lens groups that are driven in the optical axis direction to contribute to zooming and focusing, a fixed barrel, a zoom cam ring that is restricted from moving in the optical axis direction with respect to the fixed barrel, and is only rotatable. A zoom ring for rotating the zoom cam ring, a focus cam ring whose rotation is restricted with respect to the fixed barrel and which can only move in the optical axis direction, and a moving operation for moving the focus cam ring in the optical axis direction. A focus ring and AF drive transmission means for converting the rotational drive of the autofocus motor into movement of the focus cam ring in the optical axis direction are provided, and a zoom cam is formed on the zoom cam ring and a focus cam is provided on the focus cam ring. And each of the lens groups is configured so that movement of each of the lens groups in the optical axis direction is restricted by the intersection of the zoom cam and the focus cam. And a focus cam, and the zoom ring and the focus cam are rotated relative to each other by rotating the zoom ring and rotating the zoom cam ring during zooming, while rotating the focus ring during focusing. The autofocus motor is rotationally driven to move the focus cam ring in the optical axis direction to relatively move the zoom cam and the focus cam in the optical axis direction, and
A zoom lens barrel using a varifocal optical system, characterized in that a necessary amount of straight movement of the focus cam ring is kept substantially constant with respect to a predetermined subject during focusing.