JPH0625817B2 - Macro shooting mechanism of zoom lens barrel - Google Patents

Description

The present invention relates to a macro photographing mechanism of a zoom lens barrel in a camera or the like.

[Prior Art] A conventional zoom lens barrel includes a first support frame 5 for supporting a first lens group 51, as shown in FIG. 14, for example.
2 and a second support frame 54 that supports the second lens group 53 are arranged so as to be movable only in the optical axis direction by engaging guide rods 55 and 56, respectively, and guide pins are attached to the support frames 52 and 54. 57 and 58 projectingly formed on the drive ring 59
Engage the guide pins in the two cam grooves 60, 61,
By rotating the drive ring 59, the first and second lens groups 51 and 53 are independently moved in the optical axis direction. In order to perform macro photography with such a zoom lens barrel, it is possible to widen the distance between the two lens groups 51, 53 at the position of the longest focal length in which the two lens groups 51, 53 are brought close to each other and extended forward. Cam grooves 60,6
1 may be formed.

[Problems to be Solved by the Invention] However, when the two lens groups 51 and 53 are separately driven by the two cam grooves 60 and 61 thus formed in one driving ring, the two cam grooves 60 and 61 and the guide pin 57,
Due to the clearance existing between the lens group 51 and the lens group 58, the distance between the lens groups 51 and 53 varies from time to time, and there is a drawback in that the focus surface fluctuates. In particular, when the zoom ratio of the lens becomes large, the error in the variation of the distance between the lens groups sensitively affects the focus position, and the reduction of the focus accuracy becomes unacceptable.

In order to eliminate such a defect, the first lens group arranged on the front side of the lens barrel is driven to move back and forth in the optical axis direction, and
It is conceivable to adopt a structure in which the second lens group is moved back and forth in the optical axis direction by moving the lens group back and forth.
By doing so, the second lens group advances and retreats directly in conjunction with the movement of the first lens group, and therefore the error in the variation in the distance between the lens groups becomes extremely small, which is also favorable for zoom lenses with a large zoom ratio. Focus accuracy can be obtained.

If a macro photography function is simply added to the zoom lens barrel having such a structure, in order to obtain a driving force that widens the distance between the lens groups, from the position of the longest focal length where the lens groups are most extended, The first lens group must be extended further forward. However, this causes a drawback that the lens barrel becomes long due to the addition of the macro photographing function.

The present invention eliminates such drawbacks, and always provides good focusing accuracy during zooming, and further provides a macro photography mechanism for a zoom lens barrel that can be equipped with a macro photography function in a compact barrel. The purpose is to provide.

[Means for Solving Problems] A macro photography mechanism of a zoom lens barrel according to the present invention for solving the above problems includes a first lens group disposed on the front side of the lens barrel and a rear portion thereof. And a second lens group disposed in the first lens group, the first lens group supporting the first lens group in a zoom lens barrel in which each of the lens groups is moved in the optical axis direction to perform zooming. A lens group support frame, a second lens group support frame supported in the first lens group support frame to support the second lens group, and the first lens group support frame in the optical axis direction. First driving means for driving the first lens group supporting frame to move forward and backward and to rotate the first lens group supporting frame around the optical axis at the position of the longest focal length, and to operate by the movement of the first lens group supporting frame. Attach the second lens group support frame to the first lens group. And a second drive means for moving the second lens group support frame rearward by driving the first lens group support frame forward and backward relative to the lens group support frame in the optical axis direction. It is characterized by that.

[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.

When performing macro photography, the first drive means
The lens group support frame rotates about the optical axis, and the rotation causes the second driving unit to move the second lens group support frame rearward so that the distance between the lens groups widens, and the macro photographing state is set.

[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, reference numeral 1 denotes a first lens group having a small movement amount, which is arranged on the front side of the lens barrel. Reference numeral 2 denotes a second lens group that is arranged behind the second lens group and has 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, a straight groove 11a that is bent at an acute angle and extends along the axial direction is formed at one end of the cam groove 11 formed in the cam cylinder 10.

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. The cam groove 18 is provided with a projection 51 on the cam cylinder 10.
The guide pin 20 of the book is engaged. This cam groove 18
Has linear portions 18a and 18b along the axial direction at both ends as shown in FIG. 3a is a guide pin 2
Reference numeral 0 is a relief portion cut out so as not to 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 straight groove 19 is bent at a right angle on the front end side thereof and is continuous with the circumferential groove portion 19a.
3 is continuous with the groove 23a in the circumferential direction on the rear end side.

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 in and moves forward.
The developed view of FIG. 6 shows the state, and the guide pin 2
1 stops just before the bent portion of the front end of the linear groove 19.
(The length of the linear groove 19 is set as such. It is sufficient if it is longer than the radius of the guide pin 21 from the stop position.) Therefore, the guide pin 21 does not move by slipping into the circumferential groove portion 19a, The guide pin 21 is always stable and stops at this position. As a result, the first lens group support frame 3
Is forwarded, and the first lens group 1 is forwarded together with this.

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.

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 state of FIG. 7 by a drive motor (not shown). Then, the drive ring 22 further rotates around the optical axis, and the guide pin 21 integrated with the first lens group support frame 3 enters the circumferential groove portion 19a of the fixed frame 17 as shown in FIG. , Move in the circumferential direction. As a result, the first lens group support frame 3 rotates around the optical axis.
On the other hand, the guide pin 20 projecting from the cam barrel 10 enters the straight portion 18b at the front end of the cam groove 18 formed in the fixed frame 17 as shown at 20b in FIG.
Does not rotate. As a result, the linear groove 9 of the first lens group support frame 3 rotates around the optical axis with respect to the cam groove 11 of the cam barrel body 10, and as shown in FIG. The guide pin 13 projecting from 4 moves rearward.
In this way, the first lens group 1 only rotates around the optical axis and does not move forward, but the second lens group 2 moves backward and the distance between the lens groups 1 and 2 increases. Then, it becomes a macro photography state.

In the above embodiment, as described with reference to FIG. 6, the first lens group support frame 3 is moved by about the radial dimension of the guide pin 21 in order to set the macro photographing state from the position of the longest focal length. Although it is necessary to extend it forward, it can be considered that its length is extremely small. Further, if necessary, the feeding amount may be completely set to zero.

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 retracted 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 macro photography mechanism of the zoom lens barrel of the present invention,
Since the support frame that supports the rear lens group is supported in the support frame that supports the front lens group, a large amount of movement of the rear lens group can be secured without increasing the overall length of the lens barrel. Since it is not necessary to extend the lens group on the front side of the lens barrel when performing macro photography, there is an excellent effect that the macro photography function can be compactly equipped without lengthening the lens barrel.

Further, during the zooming operation, since the distance between the first lens group and the second lens group is determined only by the second driving means, the variation error of the distance between the lens groups is extremely small and always stable. Thus, good focusing accuracy can be obtained.

[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, 18b ... Straight portion, 19 ... Straight groove, 19a ... Circumferential groove portion, 20
...... Guide pin, 21 …… Guide pin, 22 …… Drive ring, 23 …… Cam groove, 24 …… Pinion.

Claims (1)

[Claims] 1. A first lens group disposed on the front side of a lens barrel, and a second lens group disposed behind the lens group, each of which is moved in the optical axis direction for zooming. In a zoom lens barrel configured to perform, a first lens group support frame that supports the first lens group, and the first lens group support frame.
Second lens group support frame which is supported in the lens group support frame and supports the second lens group, and the first lens group support frame which is moved forward and backward in the optical axis direction and which has the longest focal length position. In the first lens driving method, the first lens group supporting frame can be driven to rotate about the optical axis, and the second lens group supporting frame is operated by the movement of the first lens group supporting frame. A second drive for driving the second lens group support frame backward and forward relative to the first lens group support frame in the optical axis direction, and for rotating the first lens group support frame backward. A macro photographing mechanism for a zoom lens barrel, characterized in that: