JPS5946369B2 - Interchangeable lens aperture device - Google Patents

Description

[Detailed description of the invention] The present invention relates to an aperture device for a photographic interchangeable lens.

In conventional aperture devices for general photographic lenses, one pin of the aperture blades is rotatably supported on a fixed part, and the other pin is inserted into a straight groove in the aperture blade drive plate (arrow wheel). A structure is known in which an aperture lever that engages with an aperture setting lever can be rotated integrally with an aperture blade drive plate.
According to this device, when the aperture diameter is narrowed down from the maximum aperture diameter to the minimum aperture diameter, the aperture diameter decreases by a factor of 1/V in response to each stage of aperture reduction. In the opposite case, as the aperture approaches its opening, the aperture diameter increases by a factor of 1 for each change in aperture. In other words, the diameter of the aperture changes geometrically, and the stroke of the aperture lever changes proportionally accordingly. In the stroke characteristics of the aperture lever shown in Fig. 1, this conventional photographic lens has a curve represented by the broken line A. As this curve shows, in the conventional configuration, when controlling the aperture with the aperture lever, the aperture diameter As the aperture becomes smaller, the aperture lever stroke per aperture step becomes smaller, and the control accuracy becomes worse.

Therefore, we installed cams on the aperture blades and drive plate, and straight line B in Figure 1 was used.
A device is known in which the stroke of the aperture lever is changed arithmetically with respect to a change in each aperture step.

However, with this configuration, as mentioned above, the amount of change in the aperture diameter per aperture stage is large, especially near the opening of the aperture.
Therefore, since the amount of displacement of the aperture blades is large, the efficiency of the cam deteriorates near the first stage of aperture due to friction loss on the cam surface, and the start-up speed of the aperture decreases, causing poor followability of the aperture blades near the opening of the aperture. The drawback is that it takes a long time to stop down to the desired aperture value. To solve this drawback, a cam means for controlling the displacement of the aperture lever (for example, a cam groove is formed on the aperture blade drive plate, and As shown by the solid line C in Fig. 1, in the region X near the first stage of the aperture where the change in the aperture diameter is particularly large, the amount of displacement of the aperture lever relative to the change in the number of stages of the aperture is geometrically proportional. The reference setting curve may be determined so that the amount of displacement changes arithmetically after that, that is, in the region y, and the shape of the cam is determined based on this curve so that the aperture lever operates.

Although this eliminates the above-mentioned drawbacks, inconveniences arise when this technology is used as is in zoom lenses and macro lenses.

Many standard zoom lenses, wide-angle zoom lenses, and macro lenses maintain a constant open F-number by changing the aperture diameter in conjunction with zooming or focusing.

The zoom lens shown in FIG. 2 is composed of a first lens group and a second lens group, and zooming is accomplished by relatively moving both lens groups. A diaphragm 1 is provided in the second lens group, and its position changes with the lens. In the same figure, the solid line indicates the telephoto position, and the aperture 1 at this time
Assuming that (aperture diameter φT) is in the open state, when each lens group 1'1' is moved to the wide-angle position shown by the imaginary line, in order to keep the F number constant, the aperture blades must be driven as the movement is made. It is necessary to rotate the plate and reduce the diameter of the aperture 1' to φW. Therefore, when the above-mentioned cam means is provided on the aperture blade drive plate of such a zoom lens, when the aperture is in the telephoto position shown by 1 in Fig. 2, the relationship between the number of aperture stages and the stroke of the aperture lever is as shown in Fig. 3. However, when the aperture moves to the wide-angle position shown by V in Figure 2 due to zooming, the aperture blade drive plate rotates and the aperture blade pins rotate. Because it slides on the cam groove, the relationship between the number of aperture stages and the stroke of the aperture lever is the third.
As shown by the imaginary line C in the figure, an error of Δ will occur with respect to the reference setting curve.

For example, when this lens is attached to a camera with a shutter-priority automatic aperture, and the metering circuit instructs to close the aperture by two stops to obtain the correct exposure, the camera body will close down the aperture by two steps. The setting lever stops at the position where the lens aperture lever moves by a stroke a. At this time, at the telephoto position of the lens, the aperture lever will stop down by two steps to reach an appropriate value, but at the wide-angle position, an error Δ will occur and the aperture will be stopped down too much. Furthermore, with some lenses, the position of the aperture remains fixed and only the diameter of the aperture changes in conjunction with zooming, and similar problems occur in such lenses as well.

It is an object of the present invention to solve the above-mentioned drawbacks, and to solve this problem, the aperture lever changes proportionally to the change in the number of stages of the aperture in the vicinity of the first stage of the aperture in either the zooming or focusing position, and after that, the aperture lever changes proportionally. An object of the present invention is to obtain an aperture device for a photographic lens barrel such as a zoom lens, which is configured to change the diaphragm.

Examples of the present invention will be described in detail below.

The embodiment shown in FIG. 4 is for a zoom lens in which both the aperture diameter and the aperture position change in conjunction with zooming.

In the figure, reference numeral 11 indicates a predetermined number of aperture blades, each of which has a pin 1 inserted into a hole in a fixed ring (not shown).
1b and a pin 11a that is fitted into the cam groove 12a of the aperture blade drive plate 12. The aperture blade drive plate 12 is rotatable around the optical axis and has a protrusion 12b on its outer periphery.
The shape of the cam groove 12a of the drive plate 12 is determined so that the characteristic of the relationship between the stroke of the aperture lever 13 and the change in the number of aperture stages, which will be described later, is a reference setting curve C shown in FIG. That is, in region X near the first stage of aperture, the aperture lever is displaced geometrically with respect to changes in the number of aperture stages, and in the subsequent region y, the aperture lever is displaced arithmetic with respect to changes in the number of aperture stages, and The shape of this cam is determined so that the aperture lever can be smoothly displaced even at the boundary between the nearby area and the subsequent area, and this boundary point is set to be near one aperture stage. Reference numeral 13 denotes an aperture lever that engages with an aperture setting lever 14 on the camera side and is rotatably provided on a shaft 15. The aperture lever 13 has a transmission pin 16 and is biased downward in the drawing by a spring 17.

Reference numeral 18 denotes an auxiliary lever that is rotatably mounted on the shaft 15 and has an arm 19 at one end extending in the optical axis direction, and has a groove 18a into which the transmission pin 16 of the aperture lever is inserted, and a spring 20 with a smaller urging force than the spring 17. is biased upward in the figure.

The arm 19 is formed with an inclined groove 19a that engages with the protrusion 12b of the aperture blade 1 drive plate 12 described above, and a sloped surface 19b having a slope of height γ with respect to the stroke L in the optical axis direction. Reference numeral 21 denotes a protrusion that slides linearly parallel to the optical axis together with the aforementioned first lens group, and engages with the inclined surface 19b.

The state shown in FIG. 4 shows a state in which the zoom lens is at the telephoto position, and the transmission pin 16 is located at the lowest point of the groove 18a of the auxiliary lever 18. During shooting, when the camera's metering circuit determines the aperture value to obtain the appropriate exposure based on subject brightness, shutter speed, film sensitivity, etc., the aperture is set by an amount corresponding to that value just before the front shutter curtain runs. The lever 14 moves in the direction of the arrow.

When the aperture setting lever moves in the telephoto position shown in the figure, the aperture lever 13 rotates counterclockwise around the shaft 15 by the spring 17, and at the same time, the auxiliary lever 18 also moves with the arm 19 via the pin 16 and the groove 18a. Since the aperture blade drive plate 12 is rotated by a predetermined amount counterclockwise via the inclined groove 19a1 and the protrusion 12b, the aperture blade 11 is narrowed down. At this time, the relationship between the stroke of the aperture lever 13 and the number of aperture stages becomes the standard setting curve shown in FIG. 5C. Next, when the second lens is moved to the wide-angle position, the aperture blade 11, the aperture blade drive plate 12, and the protrusion 21 slide together by a distance L toward the right in the figure.

Therefore, the aperture blade drive plate 12 rotates counterclockwise by the sum of the slope of the inclined groove 19a and the slope γ of the slope surface 19b, and the pin 11a of the aperture blade moves in the cam groove 12a, so that the aperture diameter becomes the second As the pin 16 changes from φT to φW in the figure, the pin 16 is located at the uppermost point of the groove 18a. When the aperture setting lever 14 moves in this position, the pin 16 moves from the uppermost point of the groove 18a to the lowermost point by the rotation of the aperture lever 13 in the initial stage, and then the auxiliary lever 18 and the arm 19 are displaced and the aperture blades 1 The drive plate 12 is rotated to operate the aperture blades 11. Here,
If the stroke of the narrowing lever corresponding to the sliding distance of the pin 16 in the groove 18a is δ, then the narrowing lever does not participate in the actual narrowing down at the initial stage δ, as shown by the broken line C2 in FIG. Errors can be eliminated in practical aperture stages of one or more stages. When implementing the present invention in a lens that performs aperture correction by fixing the aperture position and changing only the aperture diameter during zooming,
It is also possible to realize it based on the principle shown in FIG.

That is, a gear 120 that is interlocked with an aperture blade drive plate having a cam groove similar to that shown in FIG. 4, a gear 180 that is also interlocked with a similar auxiliary lever, and a shaft 60 that slides in the direction of the arrow in conjunction with lens zooming. A differential mechanism consisting of a gear 61 that is rotatably fitted to the lens displaces the aperture blades by sliding the gear 120 through the gear 61 when the lens is extended, while the aperture lever rotates. However, when the auxiliary lever rotates via the pin 16 and groove 18a in FIG. 4, the sliding of the gear 180 that is interlocked with the dirt slides the gear 120 via the gear 61, and the aperture blades are displaced. As described above, according to the present invention, in an interchangeable lens such as a zoom lens or a macro lens, in which the aperture aperture is changed in accordance with lens movement operations such as zooming and focusing, and the aperture aperture is kept constant, the aperture stop is one stop or more. It is possible to obtain an aperture device that does not have an error in the number of aperture stages with respect to a reference setting curve within a practical range.

It goes without saying that the present invention can also be used for macro lenses, etc., which change the aperture position and diameter during focusing.

[Brief explanation of drawings]

1, 3, and 5 are stroke curve diagrams of the aperture lever, FIG. 2 is a schematic diagram showing the optical system and diaphragm of the zoom lens, and FIG. 4 is a perspective view showing an embodiment of the present invention. FIG. 6 is a schematic diagram showing the principle of another embodiment. Explanation of symbols of main parts, 13... Aperture lever, x... Area near the first stage of aperture, y...
...Area after x, 11...Aperture blade, 12
...Aperture blade, drive plate, 12a...Cam groove, 19...Arm, 19a...Slanted groove, 18...Auxiliary lever , 16...Transmission pin of the aperture lever.

Claims (1)

[Scope of Claims] 1 Aperture lever; an aperture blade drive member interlocked with the aperture lever; a region in which the amount of displacement of the aperture lever relative to the number of aperture stages corresponds to the vicinity of the first stage of aperture according to the operation of the aperture blade drive member; A cam means that controls the aperture blades so that the blades change geometrically in the first region and arithmetic in the subsequent region; the cam means is operated in conjunction with the movement of the lens to correct the aperture aperture and adjust the aperture aperture. an opening F-number correcting means for keeping the aperture constant; and a first stage of stopping down by setting a non-interlocking region between the aperture lever and the aperture drive member corresponding to the amount by which the aperture aperture is narrowed down by the opening F-number correcting means. A lens aperture device characterized by comprising an aperture step number correction means for correcting an aperture step number error after the vicinity of the aperture step. 2. The aperture step number correction means has an auxiliary lever between the aperture lever and the aperture blade drive member that interlocks the two, and a non-interlocking area corresponding to the amount of correction of the aperture opening is determined by the auxiliary lever. The diaphragm device according to claim 1, wherein the diaphragm device is set by the operation of the diaphragm device. 3. A patent characterized in that a gap of a predetermined size is formed in the engagement portion between the auxiliary lever and the aperture lever, and the size of the gap is changed according to the amount of correction of the aperture opening. A diaphragm device according to claim 2.