JPS61143728A - Aperture correcting mechanism for zoom lens - Google Patents

Abstract

PURPOSE:To execute the adjustment of a full-aperture diameter independently from the adjustment of the aperture diameter in the stage of automatic diaphragm by providing integrally a cam face for correcting the full-aperture diameter and a cam face for correcting the previous running quantity to an aperture blade open/shut member. CONSTITUTION:The cam face 25b for correcting the full-aperture diameter is provided to part to the left lower side of an interlocking plate 25 of an aperture correcting mechanism for a zoom lens and the cam face 25c for correcting the previous running quantity is provided to the upper part of a hole 25a to be fitted with a driving pin 6. The plate 25 is fixed to an open/shut plate 8 and is given with the energizing force by a lower open spring 26. A pin 28 for controlling the open diameter fixed to an attaching plate 27 is slidingly attached to the cam face 25b. The plate 27 is fixed to a lens frame moving only in the optical axis direction as a result of zooming. The adjustment of the full-aperture diameter is executed independently from the adjustment of the aperture diameter in the state of automatic diaphragm by which the operability of the aperture mechanism is improved.

Description

[Detailed Description of the Invention] Technical field The camera has an automatic preset aperture mechanism that keeps the aperture fully open before shooting and narrows it down to a preset comparison value during shooting, and is also configured to allow aperture control from the camera body side. This invention relates to an aperture correction mechanism for zoom lenses that is compatible with shutter-priority automatic exposure and program automatic exposure.

Prior art and its problems Conventionally, in a zoom lens in which the aperture aperture is corrected according to zooming, as shown in Fig. 4, the aperture block held in the mirror dust moves in the optical axis direction due to zooming. The aperture diameter was corrected by rotating the aperture blade support part of the aperture block using a cam groove provided in the fixed part.

The structure and operation of the conventional example shown in FIG. 4 will be explained below.

1 is an aperture lever on the camera body, 2 is a lens-side aperture drive lever, 3 is a restoring position regulating member for the aperture drive lever 2 provided on the lens side, and 4 is a restoring spring. The aperture drive lever 2 is pivotally connected to a fixed member by a lever shaft 5. Reference numeral 6 denotes an aperture drive pin that engages with the interlocking plate 7. 8
is an opening/closing plate rotatably supported by the lens barrel 9, and the aperture blades 1
The number of cam grooves 11 corresponds to the number of 0 sheets. Fourth
Other cam grooves 11 are not shown in the figure. The interlocking plate 7 is fixed to the opening/closing plate 8 so as to move integrally with the opening/closing plate 8. Reference numeral 12 is an aperture stopper pin fixed to the opening/closing plate 8. Reference numeral 13 denotes an aperture drive dowel, which is fixed to the aperture blade 10 and fitted into the cam groove 11. 14 is a support dowel fixed to the aperture blade 10. Reference numeral 15 denotes a support plate, which has a support hole 16 into which the support dowel 14 is fitted, and which is fitted into the lens barrel 9 to compensate for the diameter adjustment amount (unlike the aperture diameter correction amount associated with zooming, and absorbs errors in component precision). ) can be rotated around the optical axis.

17 is a bell crank lever, which is pivotally connected to the lens barrel 9. 18 is a cam follow pin that moves in unison with the bell crank lever 17. A cam member 19 is rotatably fitted to the lens barrel 9. 20 is a cam turning pin and the cam member 19
and move in unison.

21 is a cam rotating plate that moves integrally with an aperture preset ring (not shown). In addition, in this configuration, by rotating the lens barrel 9 around the optical axis during zooming, the support plate 15
Since the aperture diameter is corrected by rotating the cam member 19, the axial position of the bell crank lever 17, which is pivotally attached to the lens barrel 9, is also rotated. A cam groove 22 is required in the cam turning plate 21 to prevent the positional relationship from changing. 23 is lens barrel 9
24 is a cam groove for correcting the aperture diameter provided in the fixed member.

Next, the operation of this conventional example will be explained. First, along with the shutter release, the aperture lever 1 on the camera body
However, the lens-side aperture drive lever 2 is pushed down against the force of the restoring spring 4. Next, the aperture drive pin 6 fixed to the aperture drive lever 2 rotates the opening/closing plate 8 clockwise via the interlocking plate 7. The opening/closing plate 8 is a bell crank lever 1 to which a cam member 19 and a cam follower pin 18 are fixed.
The aperture stopper pin 12 is rotated until it hits the position determined by 7 to determine a predetermined aperture diameter. When zooming, the lens barrel 9 is rotated by the cam groove 24 for aperture correction, and the support plate 15 attached to it is rotated.
The aperture aperture is also rotated as a unit to correct the aperture diameter. Since the opening/closing plate 8 is rotatably fitted to the lens barrel 9, it remains in a position regulated by the diaphragm drive pin 6 even if it moves in the optical axis direction during zooming. The aperture drive pin 6 is fitted into the linear hole 7a provided in the interlocking plate 7 so as to be movable in the thrust direction and without play in the circumferential direction.

In the above configuration, at the focal length on the side where the aperture aperture is not restricted by the aperture blades, the aperture blades are always open unless they are located radially above the member that restricts the aperture aperture (opening/closing plate 8 or support plate 15). This will cause an error during photometry.

In order to prevent the above-mentioned error from occurring, it is necessary to raise the aperture blades above a predetermined aperture at a focal length on the side where the aperture aperture is not restricted by the aperture blades. In that case, in the conventional configuration shown in Fig. 4, the aperture blade support part (support plate 15) must be rotated by a predetermined amount or more, so this influence not only affects the open aperture but also the aperture of each F number during automatic aperture. This tends to make the aperture diameter larger than the predetermined aperture diameter, which is undesirable from a functional standpoint, and also requires delicate adjustment during assembly in order to bring the aperture diameter of each F number within a certain tolerance range.

Furthermore, in addition to the above-mentioned problems, in a zoom lens of a normally open aperture type that always maintains an open state unless an external load is applied to the aperture drive member on the lens side, as shown in FIG. No. and Japanese Patent Publication No. 57-49931
If an attempt is made to enable aperture control from the camera side using the forward travel amount correction method disclosed in No. 1, it becomes extremely difficult to provide a difference in the amount of correction for each focal length.

Here, the amount of forward travel referred to in the two prior art examples will be briefly explained. In the aperture comparison value, the amount that is corrected in the relay operation system of the diaphragm blade control is called the forward travel amount, which is the amount that corresponds to the difference between the illuminance error of the film surface and light receiving surface, which differs for each interchangeable lens, and that of the reference lens. I'm here. The above-mentioned correction is necessary for single-limit reflex cameras and the like that have program control and aperture control functions.

the purpose The present invention has the following objectives.

In other words, in a zoom lens that corrects the aperture aperture during zooming, the aperture can be adjusted independently of the aperture adjustment during automatic aperture to improve functionality and ease of assembly. This is intended to be implemented in a simpler manner than the conventional forward movement correction method in a normally open aperture type zoom lens that always maintains an open state when no external load is applied to the drive member.

Structure of Embodiment FIG. 1 shows an embodiment of the present invention. The same parts as in the conventional example are indicated by the same reference numerals.

As shown in the conventional example of FIG. 4, the interlocking plate 7 in FIG.
had a rectangular shape with a straight hole 7a in the middle.

In one embodiment of the present invention, as shown in the first diagram, a partially open diameter correction cam surface 25b is provided at the lower left side of the interlocking plate 25, and a forward travel amount is provided at the upper part of the hole 25a into which the drive pin 6 fits. This is provided as a correction cam surface 25c.

The interlocking plate 25 is fixed to the opening/closing plate 8, and is biased downward by an opening spring 26. Therefore, the opening/closing plate 8 is also always biased counterclockwise. Similarly, the drive pin 6 is always in sliding contact with the forward travel amount correction cam surface 25c.

On the other hand, an open diameter regulating pin 28 fixed to a mounting plate 27 is attached in sliding contact with the open diameter correcting cam surface 25b. Although not shown here, the mounting plate 27 is fixed to a lens frame that is movable only in the optical axis direction by zooming and cannot be rotated.

Note that the aperture correction pin and the cam groove for aperture diameter correction shown in FIG. 4 of the conventional example are not required in this embodiment.

As in the above configuration, the cam surface for correcting the open aperture and the cam surface for correcting the forward travel distance are integrally provided on the member that opens and closes the aperture blades.

Effects of the Embodiment First, in explaining the effects of the embodiment, the focal length on the side where the aperture is regulated by the diaphragm blades is S, and the opening/closing plate 8. in FIG. The focal length on the side where the aperture is regulated by members such as the support plate 15 is set.

FIG. 1 shows the state at the S end, where the restoring position of the opening/closing plate 1° is regulated by an open diameter regulating pin 28, and a predetermined open diameter is formed by the aperture blades.

First, we will explain the operation of automatic aperture when a predetermined aperture is preset on the lens side. First, when the shutter is released, the aperture lever 1 on the camera body begins to move downward, and the aperture drive lever 2 begins to rotate clockwise against the force of the restoring spring 4. The aperture drive pin 6, which moves integrally with the aperture drive lever 2, is connected to the interlocking plate 2.
5, the riJrJ5 plate 8 is rotated clockwise against the force of the release spring 26. Then, it rotates to a position determined by the cam member 19, cam follower pin 18, and bell crank lever 17, and a predetermined aperture diameter is determined.

Furthermore, when zooming to the L end, there is a lens frame (not shown) that moves in unison with the opening regulation pin 28 and another lens frame (not shown) that moves in unison with the diaphragm mechanism.
Due to the difference in zooming movement between the
5 is moved to the position 28' by the force of the release spring 26. The opening/closing plate 8, which rotates together with the interlocking plate 25, rotates counterclockwise, and the aperture blades 10 are pulled up, so that the opening diameter is regulated by the inner diameter of the opening/closing plate 8.

Regarding the aperture during automatic aperture, the cam rotation pin 20 moves to the <20' position as shown in FIG. .

Next, the operation when controlling the aperture on the lens side from the camera body side will be explained.

First, in the S end state shown in FIG. 1, the restoring position of the aperture drive lever is regulated by the restoring position regulating member 3.
Further, the restored position of the opening/closing plate 8 is regulated by an open diameter regulating pin 28. At that time, the aperture drive pin 6 and the interlocking plate 2
The positional relationship with 5 is as shown in Figure 2. Therefore, during actual photographing, the aperture lever 1 on the camera body first pushes down the lens-side aperture drive lever 2 by a predetermined amount based on the calculation result. Furthermore, the aperture lever 1 is
Since it is constantly pushed downward with a biasing force smaller than the restoring force of the restoring spring 4 and is in contact with the aperture drive lever 2, the aperture drive lever 2 can be reliably pushed down by a predetermined amount. In this case, the positional relationship between the diaphragm drive pin 6 and the interlocking plate 25 is as shown in FIG.
The movement of the aperture drive lever 2 does not participate in the narrowing operation of the aperture blades until it comes into contact with the forward travel amount correction cam surface 25b. By providing this air section ΔS of the aperture drive lever, it is possible to correct errors based on the open aperture difference and errors caused by delays in the drive system. In addition, when controlling the aperture on the lens side from the camera body side as described above, it is necessary to set the cam member 21 in a position where the aperture is reliably narrowed down to the minimum aperture. 6 Next, the state is set to the L end by zooming. In FIG. 2, the aperture drive pin 6 is in the state 6', and the open diameter regulating pin 28 is in the state 6'.
is in the state of 28', and the interlocking plate 25 is in the state of 25'.

In this case, the idle running section of the aperture drive lever becomes ΔL as shown in FIG. In other words, by setting the forward travel amount correction cam surface 25b so that an appropriate free travel section is obtained according to each focal length, highly accurate aperture control becomes possible.

In the embodiment, the opening/closing plate 8. Assuming that the lens frame including the aperture block such as the support plate 15 is the lens frame A, the lens frame B to which the aperture regulating pin 28 is attached and the plate 27 is attached moves linearly with zooming. The amount of movement is shown in FIGS. 2 and 3 as χ, , χB.

Also, the aperture diameter adjustment during assembly is performed as follows.

First, regarding the adjustment of the open aperture, the mounting plate 27 attached to the lens frame B is installed by shifting the position in the circumferential direction to adjust the circumferential position of the open aperture regulating pin 28 around the optical axis. Adjust to adjust the opening aperture. At this time, after adjusting the open aperture so as to secure the idle running section ΔS shown in FIG. 2, the position of the restoring position regulating member 3 is adjusted to determine the positional relationship between the diaphragm drive pin 6 and the interlocking plate 25. The aperture during automatic aperture is adjusted by rotating the support plate 15 around the optical axis.

In conventional zoom lenses that correct the aperture aperture during zooming, the adjustment of the aperture is the same as the adjustment of the aperture during automatic aperture, and the focal length on the side where the aperture is not regulated by the aperture blades. In this case, the aperture blades must be pulled upward in the R direction from the open aperture regulating member, so the aperture during automatic aperture tends to increase accordingly, which is not only functionally undesirable, but also difficult to assemble. It was also not easy to keep the aperture diameter of each F number within a certain tolerance range during adjustment.

In the present invention, the open aperture is adjusted by the position of the open aperture regulating pin, and the aperture during automatic aperture is adjusted by the support plate, so each can be adjusted independently, which is advantageous in terms of both functionality and work. It's large.

In a zoom lens with a normally open aperture that keeps the aperture open unless an external load is applied to the aperture drive member on the lens side, a conventional example shown in Fig. 4 has a diaphragm drive member that runs idly according to each focal length. It has been difficult to enable aperture control from the camera body side by providing a section, but in the present invention, highly accurate control can be performed with a simple structure.

[Brief explanation of the drawing]

FIG. 1 is an exploded perspective view showing one embodiment of the present invention, FIGS. 2 and 3 are explanatory views of main parts of the embodiment, and FIG. 4 is an exploded perspective view showing a conventional example. 1... Aperture lever 2... Aperture drive lever 7... Interlocking plate 8... Opening/closing plate 15-Support plate 21... Cam turning plate 25... Interlocking plate 25b
...Cam surface for correcting open diameter 25c...Cam surface for correcting forward travel distance Patent applicant Asahi Kogaku Kogyo Co., Ltd. ηZ Fig. 3 Fig.

Claims (1)

[Claims] An aperture correction mechanism for a zoom lens, characterized in that an aperture blade opening/closing member is integrally provided with a cam surface for correcting the aperture aperture and a cam surface for correcting the forward travel amount.