JPS589213Y2 - Aperture mechanism of interchangeable camera lenses - Google Patents

Description

[Detailed Description of the Invention] This invention relates to an improvement of the aperture mechanism of an interchangeable lens for a camera.

In zoom-type interchangeable lenses for cameras, the diaphragm mechanism is generally placed behind the zooming lens group, that is, on the image point side, so if you try to increase the zoom ratio, the aperture of the objective lens will increase due to thermal and thermal reasons. The lens barrel also becomes long and quite large.

For this reason, it is desirable to place the diaphragm mechanism between the lens groups that zoom However, in order to keep the aperture ratio constant, the actual aperture diameter of the aperture blades must be changed each time.

Therefore, this idea placed the diaphragm mechanism between the zooming lens groups to make the interchangeable lens smaller and more compact.
Moreover, the camera can change the actual aperture when the aperture is open according to zooming without using a complicated mechanism, and can also keep the ratio of the actual aperture of a predetermined aperture to the actual aperture of each open aperture as constant as possible. This provides an aperture mechanism for interchangeable lenses.

An example of this invention will be explained with reference to a drawing. The zoom lens shown in Fig. 1 has a distance adjustment and zoom lens group (not shown) located at the frontmost position on the subject side (left side of the figure), and a second lens group 2.
3. The third lens group 24, the fourth lens group 25, and the fixed master lens group 26 should be used.
Although the fourth lens group moves back and forth together, the second lens group and the fourth lens group move together while changing the relative distance with the third lens group disposed therebetween.

The holding cylinders 15 of the second and fourth lens groups and the holding cylinder 14 of the third lens group both slide inside the lens barrel body 16, and are moved by different amounts of movement as the zoom cam 11 rotates.

20 indicates a ring or knob for zoom operation, and 18 and 19 indicate cam follower pins for movement.

The diaphragm mechanism housing 14a is formed as an extension of the holding cylinder 14.

The rear rotating ring 4 is supported by the housing 14a from the front, with the front rotating ring 9, the fixed ring 7, and the aperture blade 1 interposed therebetween.

The fixed ring 7 is fixedly attached to the housing 14a, and both the front rotating ring 9 and the rear rotating ring 4 are rotatably supported with respect to the housing 14a.

Similar to the conventional iris diaphragm rotating ring, the rear rotating ring 4 has radially linear long grooves 5 (Fig. 3) bored at equal intervals, and a rotating arm 6 is attached to a part of the periphery, and the rotating arm 6 is attached to the housing. It extends rearwardly through a portion of the body 14a and is linked with the aperture scale adjustment mechanism 21,22.

Although the illustrated example shows a manual adjustment mechanism, it is also possible to link it with a known automatic diaphragm mechanism.

A fixed ring γ is fixedly attached to the housing 14a in front of the rear rotary ring 4, sandwiching a required number of aperture blades 1 therebetween.

As shown in FIG. 3, the aperture blade 1 has a protruding pin 2 on the front side and a pin 3 on the rear side, and the pin 3 is engaged with the radial linear groove 5 of the rear rotating ring 4, and the pin 2 will be described later. Since it is inserted into the through hole formed by the intersection of the long groove 8 of the stationary ring γ and the long groove 10 of the front rotary ring 9, it is made relatively long.

The fixed ring 1 has the same number of long grooves 8 as the diaphragm blades and is equally spaced from the center hole, and in this example, the long grooves 8 are straight grooves, and are formed so that their axes are slightly deviated from the radial direction. do.

In front of the fixed ring 7, a front rotary ring 9 is rotatably supported by the housing 14a in contact with the fixed ring 7.

The front rotating ring 9 has the same number of aperture blades 1 at equal intervals,
A long groove 10 is bored leading to the center hole.

The long groove 10 is a pseudo-arc curved groove.

Since the fixed ring T and the front rotary ring 9 are arranged so that their surfaces are in contact with each other, the straight long groove 8 of the fixed i7 and the curved long groove 10 of the front rotary ring 9 are arranged so as to intersect with each other to form a through hole. When the pin 2 of the aperture blade 1 is inserted into this through hole, the aperture blade 1 remains pivoted at that position unless there is relative rotation between the fixed ring 7 and the front rotating ring 9. becomes.

When the front rotary ring 9 is rotated relative to the fixed ring 1, the long groove 8
Since the relative position of the aperture blade 1 and the long groove 10 changes and the position of the through hole changes, the pivot position of the aperture blade 1 by the pin 2 changes, and the attitude of the aperture blade 1 becomes different from the previous state as shown in Fig. 6. , the actual caliber changes.

The front rotating ring 9 has an arc-shaped cam plate 11 on a part of its periphery.
The cam plate 11 penetrates a part of the holding cylinder 14 and extends rearward, and a cam groove 12 is provided in the part of the cam plate 11.
A pin 13 attached to a holding cylinder 15 of the fourth lens group is slidably fitted into this cam groove 12.

During the zoom operation of this embodiment, the second lens group, the third lens group, and the fourth lens group each move in three ways. The amount of movement of the fourth lens group, that is, each holding tube 1
4 and 15 are different, the relative position between the cam groove 12 and the pin 13 is changed by using the relative movement between the two, giving rotational motion to the cam plate 11, and rotating the front rotating ring 9. Rotate.

Figures 1 and 2 show the states of the zoom lens group before and after operation, and Figures 4 and 6 show the changes in the support position of the aperture blades of the aperture mechanism at that time. This will be explained.

Fig. 1 shows the state in which the second, third, and fourth lens groups are respectively at their extreme rear positions, and in this case, the state in which the aperture blades of the aperture mechanism are supported is shown in Fig. 4, and the actual aperture is It is the largest.

. The actual diameter is γ1, and the straight line connecting the pin 3 fitted in the radially linear long groove 5 of the rear rotating ring 4 and the center O of each rotating ring is 90Y, which is fixed to the curved long groove 10 of the front rotating ring 9. It is assumed that the pin 2 fitted into the through hole formed at the intersection with the linear long groove 8 of i7 is on the OY twill line.

Note that the state shown in FIG. 4 shows the state where the aperture is opened at the focal length of the state shown in FIG.

Now, when zooming is performed to change the focal length, the cam plate 11 is rotated and the front rotating ring 9 is rotated as described above.

The state of the lens group after movement at that time is shown in FIG. 2, and the state of support of the aperture blades at that time is shown in FIG.

As shown in FIG. 2, the third lens group, the second lens group, and the fourth lens group all move forward with respect to the lens barrel 16, but since the amount of movement of the holding cylinder 14 is smaller than that of the holding cylinder 15, The relative distances between the lens group and the third lens group, and between the third lens group and the fourth lens group are different from those in FIG. 1, and the focal length changes accordingly.

Pin 13 and holding tube 14 attached to holding tube 15 at the same time
Due to the cam engagement of the cam plate 11 with the cam groove 12, which moves forward as a result of this movement, the cam plate 11 rotates, and the front rotating ring 9 rotates.

As shown in FIG. 6, when the four front rotating rings 9 are rotated counterclockwise by an angle β with respect to the fixed ring T, the linear long grooves 8
Since the intersection position of the curved long groove 10 changes and the position of the through hole changes, the pin 2 of the aperture blade 1 also changes its position with the movement of the through hole, and the pin 3 also moves into the radial linear long groove of the rear rotating ring 4. 5, that is, on the OY line, toward the center.

Since the linear long groove 8 of the fixed ring 1 is slightly deviated from the radial direction, the pin 2 moves to a position deviated counterclockwise by Δα with respect to the OY line.

As the positions of pin 2 and pin 3 move as described above,
The position and attitude of the aperture blades 1 change as shown in FIG. 6, and the radius of the actual aperture becomes γ3.

This actual aperture is the aperture when the aperture is opened at the focal length changed by this zooming operation.

Next, the aperture operation at each focal length is shown in FIG. 5 in the case of stopping down from the open position in FIG. 4, and in FIG. 7 in the case of stopping down from the open position in FIG.

When the aperture is manually or automatically narrowed down to a predetermined aperture value from the open position shown in FIG.
The rear rotary ring 4 is rotated by an angle α corresponding to a predetermined aperture value.

Then, as the radial long groove 5 moves, the pin 3 fitted therein also moves from the line of OY to the line of rotation angle α, but since the pin 2 remains in that position, the aperture blade 1 ends up moving the pin 2. It is rotated around the center.

Therefore, the aperture blade 1 changes its attitude, and the actual aperture formed thereby has a radius γ2.

Even when the aperture is manually or automatically narrowed down to a predetermined aperture value from the open position shown in FIG. Due to the engagement relationship between the long groove 5 and the pin 3, the aperture blade 1 rotates around the pin 2 and assumes the attitude shown in FIG.

The actual diameter at this time is the radius γ4.

In the above aperture operation, in order to make the aperture rotation angle α the same when the aperture ratio is the same, γ, /γ2 = γ3/γ
Must be 4.

However, between the aperture rotation angle α and the actual aperture diameter (more precisely, the area of the pseudo-polygonal aperture formed by multiple aperture blades),
Since there is no simple linear proportional relationship, in the case of this proposal, the curve of the cam groove 12, the curve of the pseudo-arc-shaped long groove 10 of the front rotating ring 9, the inclination angle of the long groove 8 of the fixed ring γ with respect to the radial direction, etc. are designed carefully. By adjusting γ1/γ2 and γ3/γ4, it is possible to make γ1/γ2 and γ3/γ4 approximately equal within an error range of several percent or less.

Figure 8 shows the error between the measured value and the theoretical value for the zoom lens that was actually designed.The horizontal axis shows the aperture value F1 and the vertical axis shows the actual aperture diameter.
．． The error at 85 mm is shown at the F-g intersection, and the intersection without a numerical value is the error O.

As shown in this graph, the error remains within ±2%, and a larger error is allowed in practice, so the proposed mechanism can be fully put to practical use.

In the embodiment described above, the differential relationship between the third lens group and the second and fourth lens groups is used in order to give the rotation angle β to the front rotating ring 9. The zoom cam may be moved back and forth and rotated by a separate cam groove provided in the zoom cam.

Also, regarding the engagement relationship between the aperture blades and the pins and long grooves of the rear rotary ring, contrary to the above embodiment, the long grooves may be provided on the aperture blades and the pins protrude from the rear rotary ring. is advantageous.

As described above, in this invention, as an interchangeable lens for cameras, the aperture mechanism is placed between the second and fourth zoom lens groups, so the lens barrel does not become large, and the aperture mechanism is fixed to support the aperture blades. It consists of a rotating ring before and after the ring groove, so
The configuration is simple and compact, and the actual aperture when the aperture is opened can be changed according to the zoom operation, and the ratio of the actual aperture of a predetermined aperture value to each open actual aperture is always kept constant. This has practical effects such as the ability to

[Brief explanation of drawings]

Fig. 1 is a side sectional view of a part of the zoom lens equipped with the aperture mechanism of the present invention, Fig. 2 is a side sectional view showing the state of zoom operation of the same zoom lens, and Fig. 3 is the aperture diaphragm of the present invention. Exploded perspective views of the parts of the mechanism. Figures 4 to 7 are views showing the operating status of the diaphragm mechanism as seen from the front rotating ring side. Figures 4 and 6 show the state when the diaphragm is open, and Figures FIG. 7 shows a state in which the aperture is narrowed down to a predetermined aperture value, and FIG. 8 is a graph showing the relationship between the aperture value and the actual aperture diameter in a design example. 1... Aperture blade, 2... Pin, 3...
... Pin, 4 ... Rear rotation ring, 5 ...
...Long groove, 1...Fixed ring, 8...Long groove, 9...Front rotating ring, 10...Long groove,
11...Cam plate, 12...Long groove, 13
...Pin, 14...Third lens holding cylinder, 14a...Aperture mechanism housing, 15...
・Second and fourth lens holding tube, 16... lens barrel body,
17...Zoom cam, 23...2nd lens group, 24...3rd lens group, 25...
...Fourth lens group.

Claims (1)

[Scope of utility model registration request] A housing 14a is provided close to the third lens group 24 disposed between the second lens group 23 and the fourth lens group 25, and the fixed ring 1 is attached to the housing 14a, and the front surface thereof is rotated forward. A rear rotating ring 4 with a plurality of aperture blades 1 sandwiched between the ring 9 and the back side of the ring 9
are rotatably supported on the housing 14a, the fixed ring T has a long groove 8, the front rotating ring 9 has a long groove 10, and both long grooves intersect to form a through hole in the axial direction. Each aperture blade 1 has a pin 2 planted near its front end engaged with the through hole, and a fixed ring 7 and a front rotating ring 9.
The aperture blade 1 and the rear rotary ring 4 are engaged with each other by a pin 3 planted on one of them and a long groove 5 bored in the other, and the front rotary ring 9 is The holding cylinders 15 of the second lens group 23 and the fourth lens group 25 are rotated by the zoom cam 17 together with each other or separately, and the rotating arm 6 provided on the rear rotating ring 4 is linked to the aperture scale adjustment mechanism to adjust the aperture. An aperture mechanism for an interchangeable camera lens, characterized in that the ratio of the actual aperture when opened and the actual aperture when stopped down is always constant.