JPH0440687B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an aperture correction mechanism for a zoom lens barrel.

Some standard zoom lenses and wide-angle zoom lenses maintain a constant F value by changing the aperture diameter in conjunction with zooming. This is because the brightness of the lens is determined by the ratio between the focal length and the diameter of the entrance pupil, and when the aperture moves along the optical axis during zooming, the aperture diameter is set to a constant size. This is because the F value changes even if A zoom lens with a built-in aperture correction mechanism that changes the aperture diameter in conjunction with the zooming operation and thereby keeps the F value constant is disclosed in Japanese Utility Model Application Publication No. 53-123933 and Japanese Patent Publication No. 52-29183.
Although these devices are already known as shown in the above publications, they have a complicated structure that changes the aperture diameter in conjunction with zooming, so they are not easy to assemble and have drawbacks such as high costs. It was hot.

The present invention has been made in view of the above-mentioned drawbacks, and provides an aperture correction mechanism for a zoom lens that has a simple structure and can always accurately set a desired F value without affecting the operability of zooming. This is what I am trying to do.

An embodiment of the present invention will be described below with reference to the drawings.

First, an overview of the zoom lens barrel equipped with an aperture correction mechanism according to the present invention will be explained.
In FIG. 1, reference numeral 1 denotes a mount ring that engages with the mount part on the camera body side, and the mount ring 1
An aperture preset ring 2 is fitted onto the outer circumferential surface of the mount ring 2 so as to be rotatable about the optical axis, and a connecting ring 3 is fixed to one end of the mount ring 1. Further, an index ring 4 having an index (not shown) engraved on the outer peripheral surface is integrally fixed to the connecting ring 3, and one end of the outer peripheral surface of the index ring 4 has a composite focal length of the lens system. A zooming ring 5 having a scale is fitted so as to be rotatable around the optical axis. 6 is a distance scale ring with an auxiliary distance scale engraved on its outer circumferential surface, and the distance scale ring 6 and the outer helicoid ring 7 rotate together, and the outer helicoid ring 7 has a focusing lens group L. Front frame 8 that holds ₁
is fixed. Further, the outer helicoid ring 7 is screwed into an inner helicoid ring 9 by a lead screw R, and when the zooming ring 5 is rotated and a zooming operation is performed, the inner helicoid ring 9 moves back and forth along the optical axis. As the lens moves, the outer helicoid ring 7 and the front frame 8 inevitably move back and forth, and as a result, the focusing lens group L ₁ moves back and forth on the optical axis in accordance with the rotation of the zooming ring 5. .

Furthermore, a drive ring 10 is slidably fitted into the inner peripheral surface of the inner helicoid ring 9, and the head 1 of the roller 10a implanted on the drive ring 10 in FIG.
0a' fits into a groove (not shown) drilled in the inner peripheral surface of the zooming ring 5, and as a result, when the zooming ring 5 is rotated, the drive ring 10 zooms while being regulated by the cam groove 9b. Rotates together with ring 5.

Further, a lens barrel 11 is fitted into the inner peripheral surface of the drive ring 10, and a roller 11a implanted in the lens barrel 11 as shown in FIG.
Since it is movably inserted into the guide groove 9c provided in the roller 11a, the cam groove 10c, and the inner helicoid ring 9, when the zooming ring 5 is rotated, the lens barrel 11 is moved between the roller 11a, the cam groove 10c, and the guide groove 9c. It moves on the optical axis while being regulated by the mutual relationship between the two. Next, an intermediate frame 12 that holds the master lens front group L ₂ is fixed to one end of the large diameter part of the lens barrel 11, and a rear frame 13 that holds the master lens rear group L ₃ is fixed to one end of the small diameter part. ing.

Further, a first fixed aperture ring 14 is slidably fitted on the inner circumferential surface of the drive ring 10, similar to the lens barrel 11, and a second fixed aperture ring 14 is fitted at one end of the first fixed aperture ring 14. An aperture ring 15 is fixed.

Further, as shown in FIG. 8, the roller 14a installed on the first fixed aperture ring 14 is movable into the cam groove 10b provided in the drive ring 10 and the guide groove 9d provided in the inner helicoid ring 9. When the zooming ring 5 is rotated, the first fixed aperture ring 14 is inserted into the roller 14a and the cam groove 10.
It moves on the optical axis while being regulated by the mutual relationship between the guide groove 9d and the guide groove 9d. The first and second fixed aperture rings 14 and 15 are provided to satisfy a predetermined optical performance of the zoom lens.

This zoom lens barrel is constructed as described above, and is shown schematically in FIGS. 3 and 10.
As shown in the figure, when the zooming ring ₅ is rotated from the telephoto L side in FIG. 10B to the wide-angle S side in FIG. It moves by l ₁ toward the subject along the optical axis, but due to the above zooming operation, the drive ring 10 also moves to the wide-angle S side (to the left in Fig. 11 A and B) via the head 10a' of the roller 10a. Cam groove 1 that rotates and is provided in the drive ring 10
Since 0b and 10c also rotate to the wide-angle S side, lens barrel 1
Both the roller 11a of the first fixed aperture ring 14 and the roller 14a of the first fixed aperture ring 14 move within the guide grooves 9c and 9d to the wide-angle S side while being regulated by the cam grooves 10b and 10c, and move toward the wide-angle S side in the direction of the lens barrel 11 and the middle frame 12. , the rear frame 13 and the master lens groups L ₂ and L ₃ move as a unit along the optical axis by l ₂ toward the film surface, and
The second fixed aperture rings 14, 15 also move in the same direction as the master lens groups _L2 , _L3 , but the amount of movement is _l3 . Therefore, the master lens groups L ₂ and L ₃ and the first and second fixed aperture rings 14,
15, the zooming operation from telephoto L to wide-angle S causes a difference in the amount of movement l ₂ -l ₃ as shown in FIG. 10B.

Next, the mechanism related to determining the aperture diameter will be explained according to FIGS. 1, 2, and 9.
is rotatably provided around the optical axis by a steel ball 20 and a presser ring 21, and one end of the release ring 17 is provided with a stopper lever (not shown) on the camera body side for determining the aperture diameter. A matching aperture release plate 18 is attached to the other end of the release ring 17, and a long aperture turning plate 19 is attached to the other end of the release ring 17 for transmitting the amount of rotation of the aperture release plate 18 to an opening/closing plate 32 of an aperture mechanism to be described later. The release ring 17 is always urged clockwise by an opening/closing spring 22 shown in FIGS. 2 and 9, and the opening/closing spring 22 has one end locked to the mount ring 1.
The other end is locked to the aperture release plate 18.

An aperture turning ring 16 that rotates together with the preset ring 2 is fitted on the inner peripheral surface of the mount ring 1.
A shaft 24 shown in FIG. 2 is embedded in the aperture ring 16, and an intermediate lever 23 is pivotally supported on the shaft 24. Further, the first dowel 26a fixed to one end of the intermediate lever 23 contacts the cam edge of the cam plate 25 fixed to the connecting ring 3, and the second dowel 26b fixed to the other end The aperture release plate 18 faces the rotation range of the aperture release plate 18 so as to function as a stopper when the aperture is stopped. Therefore, when the aperture preset ring 2 is rotated to a predetermined aperture value, the intermediate lever 23 is also cam plate 2
5 and the first dowel 26a and rotate by the same amount, thereby determining the stopping position of the aperture release plate 18 by the second dowel 26b, that is, the release ring 17 and the aperture The amount of rotation of the turning plate 19 is determined, and the aperture diameter of the aperture mechanism, which will be described later, is determined.

Next, the aperture correction mechanism, which is the gist of the present invention, will be explained in relation to the aperture mechanism.

The aperture mechanism includes a predetermined number of aperture blades 27, a support plate 28, an opening/closing ring 31, and an opening/closing plate 32.
The diaphragm mechanism consists of a master lens front group.
Located between L ₂ and master lens rear group L ₃ ,
It moves integrally with the master lens groups L ₂ and L ₃ . The aperture blade 27 is interposed between the support plate 28 and the opening/closing ring 31 as shown in FIG.
A pin 30 movably inserted into the aperture blade 8a and implanted on the other surface of the aperture blade 27 is loosely fitted into a hole drilled in the opening/closing ring 31.
The opening/closing ring 31 is fitted to the inner circumferential surface of the lens barrel 11 so as to be rotatable around the optical axis, and the opening/closing ring 31 is disposed within the lens barrel 11 so as to be rotatable around the optical axis. is always in engagement with the aforementioned aperture rotating plate 19 by the spring 32a, and from the above, the rotation angle of the opening/closing ring 31 corresponds to the rotation angle of the release ring 17 in a 1:1 ratio.

The shape of the cam groove 28a provided in the support plate 28 is such that, as shown in FIGS.
It is set so as to achieve linearity with the rotation angle θ ₁ of , and has a length that allows obtaining the minimum aperture diameter Dsmin on the wide-angle S side from the open aperture diameter DLmax on the telephoto L side. This is an angle corresponding to the opening/closing ring rotation angle θ ₀ .

Furthermore, a guide groove 2 cut into the edge of the support plate 28 is provided.
8b, the other end of a cam-shaped aperture correction plate 33 whose one end is fixed to the first fixed aperture ring 14 is engaged to be slidable in the optical axis direction. Therefore, when the zooming ring 5 is rotated from the telephoto L side to the wide angle S side, the support plate ₂₈ moves toward the film surface by an amount of movement l ₂ in the optical axis direction, similarly to the master lens groups L 2 and L ₃ . However, since the first fixed aperture ring 14 only moves toward the film surface by an amount l ₃ in the optical axis direction, the support plate 2 moves by an amount l ₂ −l ₃ as shown in FIG.
8 is rotated along the cam shape of the aperture correction plate 33 while moving on the optical axis. Therefore, if the cam shape of the aperture correction plate 28 is changed to a predetermined aperture diameter in accordance with the zooming operation, that is, the support plate 28 itself is configured to rotate by a predetermined amount θ ₂ , even when the zooming operation is performed, the aperture Aperture is corrected and always F
This makes it possible to keep the value constant.

That is, when the zooming ring 5 is in the telephoto L side as shown in FIGS. 2 and 4, the aperture release plate 18 on the lens side is pushed against the opening/closing spring 22 by the aperture lever (not shown) on the camera body side. When the aperture is rotated counterclockwise by θ _a , the opening/closing plate 32 fixed to the opening/closing ring 31 and the aperture turning plate 19 are rotated counterclockwise by the same angle θ _a , and the aperture preset ring 2 causes the aperture preset ring 2 to preset the aperture. The aperture blades 27 are narrowed down to the aperture diameter DLa. Next, rotate the zooming ring 5 to zoom to telephoto L.
When moving from the side to the wide-angle S side, the amount of movement of the support plate 28 relative to the aperture correction plate 33 is l ₂ −l ₃ , and the aperture correction plate 33 has a cam shape that corrects the aperture diameter in accordance with the zooming operation. The support plate 28 rotates clockwise by a predetermined amount θ ₂ about the optical axis during transition from the telephoto L side to the wide angle S side. Therefore, the pin 29 of the aperture blade 27 moves within the cam groove 28a, the aperture blade 27 is narrowed down, and the open aperture diameter changes from DLmax to Dsmax as shown in FIG. At this time, the opening/closing ring 31 does not rotate, but the support plate 28 rotates by θ ₂ , so relatively speaking, the opening/closing ring 31 rotates by θ ₂ , which is the same as the aperture blades 27 being narrowed down. .

In this state, if the aperture release plate 18 is rotated by the same angle θ _a as described above, the opening/closing ring 31 can be rotated by the same angle θ _a by the above-described procedure to obtain the predetermined aperture diameter Dsa. In this way, the aperture ratio during zooming can be kept constant. In the above case, the aperture correction plate 33 is attached to the first fixed aperture ring 14, but is not limited to the first fixed aperture ring 14, and is attached to the support plate 28.
The same effect can be obtained even if the support plate 28 is attached to another member having the same direction of movement along the optical axis and a different amount of movement than the support plate 28.

Furthermore, in order to correct the aperture aperture by the differential l ₂ −l ₃ between the support plate 28 and the first fixed aperture ring 14 during the zooming operation, the aperture correction plate 33 may be formed in a straight line. It is possible. In other words, as shown in FIGS. 11A and 11B, the guide groove 9d of the inner helicoid ring 9, which guides the roller 14a installed in the first fixed aperture ring 14 to which the aperture correction plate 33 is fixed, is used for zooming operations. The cam has a shape that corrects the aperture diameter accordingly, so by zooming
When changing from the wide-angle S side in Figure 1A to the telephoto L side in Figure 11B, the first fixed aperture ring 14 moves to the right in Figure 11, and when changing from the telephoto L side to the wide-angle S side, this time Conversely, since it rotates θ ₂ to the left, the aperture correction plate 33 fixed to the first fixed aperture ring 14 also moves θ ₂ as shown in FIG. The same effect as in Fig. 6) can be obtained.

As described above, according to the present invention, in order to keep the F value constant during zooming, the supporting member of the diaphragm blade is moved relative to another member that moves in the same direction as the supporting member and moves in a different amount. It is only necessary to rotate the support plate by a predetermined amount depending on the difference in amount and change the aperture diameter, so the members for rotating such a support member include an aperture correction plate, conventionally arranged rollers and guide grooves, etc. It can be manufactured in large quantities at low cost, and is easy to assemble, and the inertial mass of the support member rotated by the aperture correction plate is small, making it possible to reduce the rotational load. Since the influence on the rotational load of the zooming ring during zooming is almost negligible, operability is not impaired, and the support member rotated by the aperture correction plate only needs to be provided with a guide groove. It has advantages such as low cost.

[Brief explanation of drawings]

FIG. 1 is a side cross-sectional view of a zoom lens barrel equipped with an aperture correction mechanism according to the present invention, FIG. Figure 3 is a graph showing the movement of each lens group, Figure 4 is a graph showing the relationship between the aperture diameter and the rotation angle of the opening and closing ring at telephoto, and Figure 5 is a graph showing the relationship between the aperture diameter and the rotation angle of the opening and closing ring at wide-angle. graph, 6th
7 is a plan view showing the relationship between the aperture correction plate and the support plate, and FIG. 8 is an exploded view showing the mutual relationship between the inner helicoid ring, the drive ring, the lens barrel, and the first fixed aperture ring.
Figure 9 is an exploded view showing the aperture mechanism and related mechanisms, Figures 10A and 11A are wide-angle side S,
FIG. 0B and FIG. 11B are partially enlarged development views showing the rollers, cam grooves, and their movements on the telephoto side L. 5... Zooming ring, 9... Inner helicoid ring, 9d... Guide groove of inner helicoid ring 9, 14
...First fixed aperture ring, 14a...Roller installed in the first fixed aperture ring 14, 27...Aperture blade, 28...Support plate, 28a...Guide groove of support plate 28, 33... ...Aperture correction plate, _L1 ...Focusing lens group, _L2 , _L3 ...Master lens group.

Claims (1)

[Scope of Claims] 1. In a zoom lens barrel of second and third groups that performs zooming by moving a focusing group and a master lens group on the optical axis in conjunction with the rotational operation of a zooming ring, the zooming ring includes: an aperture blade support member that is fitted into the lens barrel for holding the master lens group and moves in the optical axis direction and is rotatable around the optical axis; One pin was inserted into a cam groove provided in the lens barrel, and the other pin was loosely fitted into a hole drilled in an opening/closing ring that rotates around the optical axis in accordance with the amount of aperture operation. an aperture blade, one end of which moves in conjunction with the support member or the zooming ring, whose movement direction in the optical axis direction is the same as that of the support member, and whose movement amount in the optical axis direction is different from that of the support member; an aperture correction plate that is slidably engaged with one of the other members in the optical axis direction and whose other end is fixed to one of the other member or the support member; An aperture correction mechanism comprising: a cam mechanism that rotates the support member by a predetermined amount around the optical axis based on a difference in relative movement amount in the optical axis direction with other members. 2. The aperture correction plate is a predetermined cam-shaped aperture correction plate with one end fixed to the fixed aperture ring as the other member, and the cam mechanism is connected to a guide groove cut in the support member and the cam. The aperture correction mechanism according to claim 1, wherein the aperture correction mechanism is configured to engage with the other end of a shaped aperture correction plate. 3. Claims in which the cam mechanism is constituted by an engagement relationship between a roller implanted in the fixed aperture ring as the other member and a predetermined cam-shaped guide groove provided in the inner helicoid ring. The aperture correction ring described in item 1.