JPH0625816B2 - Camera zoom lens barrel - Google Patents

Description

TECHNICAL FIELD The present invention relates to a zoom lens barrel of a camera, and in particular,
The present invention relates to improvement of a mechanism for moving a lens group to perform zooming.

[Prior Art] To perform zooming, it is necessary to separately move the two lens groups in the optical axis direction. Therefore, conventionally, as shown in FIG. 14, for example, a first support frame 52 for supporting the first lens group 51 and a second support frame 54 for supporting the second lens group 53 are respectively provided with guide rods. The drive ring 5 is formed by engaging with 55 and 56 so as to be movable only in the optical axis direction, and projecting guide pins 57 and 58 on the support frames 52 and 54.
The guide pins are engaged with the two cam grooves 60 and 61 formed in the optical disc 9 and the drive ring 59 thereof is rotated, so that the first and second lens groups 51 and 53 are independently provided on the optical axes. I was trying to move in the direction.

[Problems to be Solved by the Invention] However, in the conventional zoom lens barrel of the camera as described above, since the two lens groups are separately driven by the drive ring, the two cam grooves 60, 61 and Guide pins 57, 58
The distance between the two lens groups 51 and 53 varies from time to time due to the clearance existing between the lens group and the lens group, and the focal plane fluctuates, and the apparatus is large and the lens barrel is compact. There was a drawback that I could not put together. Especially when the boom ratio of the lens increases,
The fluctuation error of the distance between each lens group sensitively affects the focus position and the reduction of the focusing accuracy becomes unacceptable, and the moving amount of each lens group becomes large and the lens barrel becomes large. However, there are some major drawbacks that cannot be ignored.

The present invention eliminates such drawbacks of the prior art, allows each lens group to be moved while controlling the distance between each lens group with high accuracy during zooming, and can also make the lens barrel compact. It is an object to provide a zoom lens barrel for a camera.

[Means for Solving Problems] A zoom lens barrel of a camera according to the present invention for solving the above problems includes a front first lens group having a small movement amount and a rear lens group having a large movement amount. The first lens group is supported in a zoom lens barrel of a camera that has two moving lens groups of the second lens group, and moves these lens groups in the optical axis direction to perform zooming. First
Lens group support frame, a second lens group support frame which is provided in the first support frame and supports the second lens group, and the first lens group support frame is moved back and forth in the optical axis direction. The first driving means for driving and the movement of the first lens group supporting frame actuate to move the second lens group supporting frame in the optical axis direction relative to the first lens group supporting frame. A second drive means for driving the lens barrel is provided, and the retracting means for retracting the first lens group support frame further into the lens barrel from the maximum retracted position during zooming when the lens barrel is housed is used as the first drive. And a stopper for restricting the second lens group support frame from further retracting into the lens barrel from the maximum retracted position during zooming.

[Operation] The first lens group support frame is driven to move back and forth in the optical axis direction by the first driving means, and the first lens group is extended or retracted. Then, the movement of the first lens group support frame actuates the second driving means to drive the second lens group support frame, so that the second lens group support frame moves relative to the first lens group support frame. And moves back and forth relatively in the optical axis direction. Zooming is performed in this way, during which the distance between the first and second lens groups is determined only by the operation of the second driving means.

[Embodiment] An embodiment of the present invention will be described with reference to FIGS. 1 to 13.

1 and 2 show the lens barrel in a state where the focal length is minimized by zooming, and FIG. 3 is a front sectional view showing the positional relationship between the cam grooves and the guide pins in a combined manner. is there. Incidentally, FIG. 1 shows the AO cross section and the BO cross section in FIG. 3 in a combined manner. FIG. 2 shows a C-O cross section in FIG. Further, FIG. 4 and FIG. 5 are development views showing the positional relationship between each of the plurality of cam grooves and the guide pins formed in the mechanism.

In the figure, 1 is a first lens group having a small movement amount, and 2 is a second lens group having a large movement amount. Although each of the lens groups 1 and 2 is schematically shown as one lens in the drawing, each of them may be composed of a plurality of lenses. Reference numeral 3 is a first lens group support frame that supports the first lens group, and 4 is a second lens group support frame that supports the second lens group. An autofocus unit 5 is fixed to the first lens group support frame 3, and the first lens group 1 is fixed in a helicoid ring 6 screwed with the autofocus unit 5. The first lens group 1 is driven by the autofocus unit 5 in the optical axis direction for focusing. That is, the autofocus unit 5
Rotates the operation pin 5a around the optical axis by a predetermined amount according to the photographing distance, and the first lens group 1 is rotationally extended by the engagement piece 6a that engages with it. In this embodiment, as described above, the first lens group 1 includes the autofocus unit 5
Although it is supported by the first lens group support frame 3 via the and the helicoid ring 6, the first lens group 1 may be directly supported by the support frame 3.

Reference numeral 7 is a cover fixed to the first lens group support frame 3 with screws, and reference numeral 8 is a barrier device that moves to the front surface of the first lens group 1 to protect the lens surface when the camera is not used.

An axial linear groove 9 is formed in the peripheral surface of the rear half of the first lens group support frame 3, and a cam cylinder 10 is fitted to the inner peripheral side of the linear groove 9 rotatably around the optical axis. There is. As shown in FIG. 4, the cam groove 11 formed in the cam cylinder 10 has a straight groove 11a formed on one end side along an axial direction with a sharp bend, and the other end side 11b in the opposite direction. It is formed by bending an obtuse angle into a dogleg shape.

In FIG. 1, reference numeral 12 is a holding plate fixed to the rear end surface of the first lens group support frame 3 so that the cam cylinder 10 does not move in the axial direction.

The second lens group supporting frame 4 is loosely fitted on the inner peripheral side of the cam barrel 10, and the guide pin 13 protruding from the second lens group supporting frame 4 is provided with the linear groove 9 and the cam groove. 11 is engaged with. The linear groove 9, the cam groove 11, and the guide pin 13 are provided in three sets on the circumference at 120 ° intervals. A rotatable guide roller or the like may be used as the guide pin 13.

A coil spring 14 is interposed between the first and second lens group support frames 3 and 4 so as to always bias the second lens group support frame 4 rearward. Reference numeral 15 denotes a rod inserted in the coil spring 14 so as to guide the expansion and contraction of the coil spring 14, and its head portion 15a is pressed and fixed by the coil spring 14 to the first lens group support frame 3. There is. Further, the second lens group support frame 4 is provided with an escape hole 16 so that the rod 15 does not hit when the coil spring 14 is compressed.

A fixed frame 17 is fixed to the camera body and has a cam groove 18 and a linear groove 19 in the axial direction. Then, the cam groove 18 is provided with 1
The guide pin 20 of the book is engaged. This cam groove 18
Has a linear portion 18a along the axial direction near the rear end as shown in FIG. Reference numeral 3a denotes a relief portion that is cut out so that the guide pin 20 does not interfere with the first lens group support frame 3.

The spacer 3 is provided on the outer surface of the rear end of the first lens group support frame 3.
b is fixed at intervals of 120 degrees, and the guide pin 21 is projectingly provided there. Therefore, the guide pin 21 is integrated with the first lens group support frame 3 via the spacer 3b. The spacer 3b is loosely fitted to the inner peripheral surface of the fixed frame 17, and the drive ring 22 is fitted to the outer periphery of the fixed frame 17 so as to be rotatable around the optical axis. And spacer 3
The guide pin 21 protruding from b is used for the linear groove 19 of the fixed frame.
And the cam groove 23 of the drive ring 22. As shown in FIG. 5, the cam groove 23 has a circumferential groove portion 23a at its rear end portion.

Further, the tooth portion 22 fixed to the outer periphery of the drive ring 22 with screws is fixed.
The pinion 24 is biting in a, and this pinion 2
4 is rotationally driven by a drive motor (not shown). Of course, the drive ring 22 may be manually rotated by a manually operated ring or the like. Reference numeral 25 denotes a stopper that comes into contact with the rear end surface of the second lens group support frame 4 and restricts the rearward movement of the second lens group support frame 4, and is provided on the fixed frame 17 so as to project. Reference numeral 26 is a lens barrel cover.

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

When the pinion 24 is driven by a drive motor (not shown) from the shortest focal length state shown in FIGS. 1 and 2, the drive ring 22 rotates around the optical axis. Then, the guide pin 21 projecting from the spacer 3b is connected to the drive ring 22.
It is guided by the cam groove 23 formed on the front side and moves forward.
The development view of FIG. 6 shows the state. As a result, the first lens group support frame 3 is moved forward, and together with this, the first lens group 1 is moved forward.

When the first lens group support frame 3 is extended to the front, the guide pins 20 projecting from the cam barrel 10 are moved to the position 20 in FIG.
As indicated by a, it moves forward and is guided by the cam groove 18 of the fixed frame 17 to rotate around the optical axis. Then, since the cam cylinder 10 rotates about the optical axis, the guide pin 13 projecting from the second lens group support frame 4 resists the urging force of the coil spring 14 as shown in FIG. To move forward. As a result, as shown in FIG. 7, the second lens group support frame 4 moves forward, and the second lens group 2 approaches the first lens group 1. That is, the distance between the first and second lens groups 1 and 2 is set so that the cam groove 1 formed in the cam barrel 10 that operates when the first lens group support frame 3 moves back and forth.
Determined by 1. In this way, the second lens group 2 moves forward by a distance obtained by adding the moving amount of the first lens group supporting frame 3 to the moving amount of the second lens group supporting frame 4.

The state shown in FIG. 7 is the state where the focal length is the longest, and if the rotation of the pinion 24 is stopped on the way to this point, the lens groups 1 and 2 will stop at that position and the intermediate focus point will be reached. When the distance is obtained and the pinion 24 is reversed, the state returns to the state shown in FIG. 1 where the focal length is short. In the present invention, in this way, the second lens group support frame 4 is actuated by the movement of the first lens group support frame 3 to determine the distance between the first and second lens groups 1 and 2. Therefore, the occurrence of the spacing error is very small as compared with the conventional mechanism in which the first and second lens groups are independently operated.

In the present embodiment, the second lens group support frame 4 is further added.
Is always biased rearward by the coil spring 14, so that the guide pin 13 is always pressed to the rear surface side of the cam groove 11. Therefore, the cam groove 11 and the guide pin 1
There is no play between the first and second lens groups 1 and 2 due to clearance, and the distance between the first and second lens groups 1 and 2 can be controlled with extremely high accuracy without variation. Further, since the second lens group support frame 4 and the cam cylinder body 20 for driving the same are housed in the first lens group support frame 3, the lens barrel can be made compact and small.

The zoom lens barrel of this embodiment is also capable of so-called macro photography. When performing macro photography, a macro photography switch (not shown) is turned on, and the pinion 24 is further rotated in the feeding direction from the long focus state shown in FIG. 7 by a drive motor (not shown). Then, the drive ring 22 further rotates around the optical axis, and the guide pin 21 integral with the first lens group support frame 3 moves further to the tip side as shown in FIG. As a result, the first lens group support frame 3 is further extended forward, and the guide pin 20 projecting from the cam barrel 10 also moves forward as indicated by 20b in FIG. 4, resulting in the rotation around the optical axis. Rotate. Therefore, the cam barrel 10 is rotated around the optical axis, and the guide pin 13 projecting from the second lens group support frame 4 as shown in FIG. Entering the end portion 11b, as a result, the second lens group support frame 4 moves in a direction away from the first lens group 1. In this way, while the entire lens system is extended forward, the distance between the first and second lens groups is widened, and macro photography can be performed with a small extension amount for the entire lens system.

When the main switch (not shown) is turned off when the lens barrel is stored, the pinion 24 is rotated by a drive motor (not shown), and from the state of the shortest focal length shown in FIG.
Further, the drive ring 22 rotates in the retracting direction. As shown in FIG. 11, the guide pin 21 moves to the rear end of the cam groove 23, and the first lens group support frame 3 is retracted. At this time, the guide pin 30 projecting from the cam barrel 10 enters the straight portion 18a at the rear end of the cam groove 18 as shown by 20c in FIG. 4, so that the guide pin 20 does not rotate. . Therefore, the cam cylinder 10 also does not rotate.

The second lens group support frame 4 also tries to move rearward together with the first lens group support frame 3, but the second lens group support frame 4 is restricted from moving rearward by the stopper 25. On the other hand, the guide pin 13 projecting from the second lens group support frame 4 is provided with the cam barrel 10 as shown in FIG.
Into the axial straight portion 11a of the cam groove 11 formed in
Therefore, only the cam barrel 10 can move rearward with the guide pin 13 kept at the same position. A state in which this storing operation is completed is shown in FIG. 13, in which the coil spring 14 is compressed and the end portion of the rod 15 enters into the escape hole 16. In this way, the position of the second lens group 2 closer to the camera body is not moved, and only the first lens group 1 at the tip portion is further moved from the state of the shortest focal length,
The size of the lens barrel during storage can be reduced to facilitate portability.

A circumferential groove portion 23a is further formed in the cam groove 23 formed in the drive ring 22 of the present embodiment, and this portion operates an opening / closing mechanism (not shown) of the barrier device 8 during storage. It is provided in order to obtain an operating force, and the drive ring 22 continues to rotate within the range of the circumferential groove 23a even after the lens system is completely stored.

When returning from the housed state to the used state shown in FIG. 1, an operation reverse to the above is performed by turning on a main switch (not shown).

[Effects of the Invention] According to the zoom lens barrel of the camera of the present invention, the distance between the first lens group and the second lens group is determined only by the second driving means during the zooming operation. The error in the variation of the distance between the lens groups is extremely small.
Therefore, even in a zoom lens having a large zoom ratio, in which the variation error of the interval sensitively affects the focus position, there is an excellent effect that stable and good focus accuracy can always be obtained.

Further, when the lens barrel is stored, the two lens groups are maximally retracted into the lens barrel during zooming, and then only the first lens group on the front side is further retracted into the lens barrel to accommodate the lens barrel during storage. The size can be reduced to make it easier to carry.

[Brief description of drawings]

FIG. 1 is a side sectional view showing a lower half portion of an embodiment of the present invention, FIG. 2 is a side sectional view taken along a different section of the embodiment, and FIG. 4 to 6 are development views showing the positional relationship between the cam grooves and the guide pins, FIG. 7 is a side sectional view of the embodiment in which the lens group is extended, and FIGS. Is a development view showing the positional relationship between the cam grooves and the guide pins, FIG. 13 is a side sectional view of the embodiment in the stored state, and FIG. 14 is a side sectional view of a conventional zoom lens barrel. 1 ... First lens group, 2 ... Second lens group, 3 ...
1st lens group support frame, 4 ... 2nd lens group support frame,
9 ... Straight groove, 10 ... Cam cylinder, 11 ... Cam groove, 1
2 ... Presser plate, 13 ... Guide pin, 14 ... Coil spring, 17 ... Fixed frame, 18 ... Cam groove, 19 ... Straight groove, 20 ... Guide pin, 21 ... Guide pin, 22 ...
... drive ring, 23 ... cam groove, 24 ... pinion.

Claims (2)

[Claims] 1. A front lens group having a small moving amount and a second lens group having a large moving amount on a rear side are provided, and these lens groups are respectively moved in the optical axis direction. In a zoom lens barrel of a camera adapted to perform zooming, a first lens group supporting frame for supporting the first lens group, and the second lens group provided in the first supporting frame.
Second lens group support frame for supporting the first lens group support frame, first driving means for driving the first lens group support frame forward and backward in the optical axis direction, and operation by movement of the first lens group support frame. And a second drive means for driving the second lens group support frame to move back and forth in the optical axis direction relative to the first lens group support frame, and the first lens when the lens barrel is housed. Retracting means for retracting the group supporting frame further into the lens barrel from the maximum retracting position during zooming is provided in the first drive means, and the second lens group supporting frame is moved from the maximum retracting position during zooming. Further, a zoom lens barrel for a camera is provided with a stopper for restricting the lens from being pulled into the barrel. 2. A cam groove, wherein the second driving means is rotated by advancing / retreating the first lens group support frame, and a projection provided on the second lens group support frame to engage with the cam groove. 2. The zoom lens barrel for a camera according to claim 1, further comprising a guide pin for driving the second lens group supporting frame and a biasing means for constantly biasing the second lens group supporting frame in the optical axis direction.