JPS5926010B2 - Preset automatic aperture rebound prevention device for single-lens reflex cameras - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an aperture rebound prevention device for a lens barrel having an automatic aperture mechanism in a single-lens reflex camera.

In a single-lens reflex camera, light passing through the lens barrel is guided to the camera's viewfinder and formed into an image, and the photographer can use the image that appears in the viewfinder to align the pit with the subject or take a photo. When preparing to take a picture by deciding on the composition, it is desirable that the image of the subject formed in the viewfinder be bright.

Therefore, the more light that passes through the lens barrel, the better. Also, in so-called TTL metering, which measures the light that passes through the lens barrel to determine the appropriate exposure value for the subject, the more light that passes through the lens barrel, the more likely it is that other disturbances (for example, from the photographer's side to the viewfinder It is possible to reduce the influence of light rays, etc. that are incident oppositely on the TTL photometry value. For the above reasons, when preparing to take a picture by determining the composition or metering, it is recommended that the lens aperture be left open to allow as much light as possible to pass through the lens barrel. desirable.

However, when exposing film, the lens aperture is narrowed down to a predetermined aperture determined by TTL photometry, etc.
In addition, the opening must be stable. When the shutter opens, if the aperture is not stopped down to the specified aperture and stabilized, a focal plane shutter will cause uneven exposure in the vertical or horizontal direction of the screen, and a lens shutter will cause uneven exposure across the screen. This will manifest itself as improper exposure. In single-lens reflex cameras, an automatic aperture system is generally adopted in order to automatically perform the above-mentioned aperture operation, and when the photographer is preparing to take a picture, the aperture is open and the shutter button is pressed. The diaphragm starts to narrow down at the moment the aperture reaches a predetermined aperture, and the shutter opens only after the aperture has stabilized.

Therefore, even if the photographer presses the shutter button at the moment when he most wants to take a picture of the subject, the shutter does not actually open at the same time as the shutter release, but during that time the aperture is narrowed down from its open state to a predetermined aperture, and There is inevitably a time lag corresponding to the aperture stabilization time until the aperture stabilizes.

However, the condition of the subject changes from moment to moment,
It is quite possible that the subject will be in a different state from the photographer's intention after a moment, and the appropriate exposure value at that time will naturally change over time, so the appropriate exposure value determined by metering at the aperture is It is not always the case that the exposure value can be applied as is even after a moment, and if the above-mentioned time lag is long, an image of the subject will be taken that is contrary to the photographer's intention, and there is a risk that the proper exposure will not be given to the film. Therefore, in order to avoid missing out on a photo shoot opportunity, it is necessary that the time lag be as short as possible, which requires that the aperture stabilization time be as short as possible.

However, in general, the operation of the diaphragm is such that after the diaphragm is narrowed down from an open state to a predetermined aperture, the diaphragm blades repeat an oscillatory rebound around the predetermined aperture, and this rebound gradually attenuates until it finally stabilizes at the predetermined aperture. However, the duration of the rebound is long, and therefore the aperture stabilization time becomes long.

To explain this using diagrams, Figure 1 is a graph of diaphragm operation with time on the horizontal axis and aperture aperture on the vertical axis, and 1 shows the operating state of a general diaphragm using a conventional diaphragm action mechanism. This is the throttle operation curve.

According to this, the origin is the time when the shutter button is pressed and the diaphragm blades begin to narrow from open to a predetermined aperture, and the diaphragm diameter is rapidly accelerated from an initial velocity of zero, drawing an almost parabolic acceleration curve. However, after t1 seconds, the aperture is narrowed down to a predetermined aperture Z. However, at this time, due to the inertial mass of the diaphragm drive member, the diaphragm blades cannot suddenly stop at the predetermined aperture position, and vibratory rebound is repeated around the predetermined aperture, but this rebound gradually After attenuating and reaching a predetermined aperture, TR
The aperture z stabilizes at the predetermined aperture z at T2 seconds later. The aperture stabilization time does not refer to the time until t1 seconds when the aperture diameter is narrowed down to a predetermined aperture, but refers to the time until T2 seconds when the aperture diameter stabilizes at a predetermined aperture, so if the aperture rebound continues for a long time, the aperture stabilization time will decrease. It gets long. Furthermore, in the lens barrel, the aperture blades must operate at predetermined apertures that are arbitrarily set in the range from maximum aperture to the minimum aperture diameter, and each aperture stabilization time can be considered for each of these predetermined apertures. Generally, the closer the predetermined aperture is to the minimum aperture diameter, the longer the aperture stabilization time becomes.

To explain this with a diagram, in the aperture operation graph in Fig. 2, 2 and 3 are the same lens barrel, and the aperture is stopped to a predetermined aperture Z1 close to wide open and a predetermined aperture Z2 close to the minimum aperture diameter, respectively. This figure shows a typical throttle operation curve that appears when the diameter is set.

According to this, as shown in graph 2, when the aperture diameter is set to a predetermined aperture Z1 close to open, the aperture blades operate from an open state and reach the predetermined aperture Z1 after t1 (Z1) seconds. However, since the speed of the diaphragm blades has not yet been sufficiently accelerated, the required rebound time TR (z1) after T, (z1) seconds is
) seconds is short, and overall the aperture stabilization time T2 (z1) seconds is relatively short. However, when the predetermined aperture is set to Z2, which is close to the minimum aperture diameter, as shown in graph 3, the predetermined aperture Z2 is reached in t1 (Z2) seconds, which is longer than the aforementioned t1 (Z1) seconds. At that time, the speed of the diaphragm blades is high, and therefore the required rebound time TR (Z2) after t1 (Z2) seconds also becomes long, and the diaphragm stabilization time T as a whole becomes longer.
2 (Z2) seconds is a very long time. This aperture rebound is
Although it is possible to reduce the rebound to some extent by improving the precision of the parts of the diaphragm drive member or reducing the inertial mass, it is extremely difficult to meet the demand for reducing rebound using these methods. Implementation of these methods may also cause a decrease in productivity. In order to prevent such diaphragm rebound, the present invention adds a braking member to the conventional diaphragm mechanism, applies a brake to the operation of the diaphragm drive member at a position slightly before the automatic diaphragm reaches a predetermined opening, and It is therefore an object of the present invention to provide a device that greatly reduces the time required for rebound.

To explain the gist of the present invention with reference to the drawings below, FIG. 3 is a perspective view showing essential parts of an example of a lens barrel in which the present invention is implemented, and includes an index (not shown) attached to the lens barrel, When the photographer aligns the aperture scale (not shown) attached to the outer periphery of the aperture preset ring 4, the pin 5 embedded in the aperture preset ring 4 moves to a position corresponding to each predetermined aperture value. Since the cam surface 8 of the cam lever 7, whose one end is supported by the shaft pin 6 on the lens barrel (not shown), is always in contact with the pin 5, the aperture pin receiver formed at the tip of the cam lever 7 The hook portion 9 moves according to the set aperture value, and regulates the amount of movement of the pin 11 provided in the automatic diaphragm opening/closing ring 10.

The long groove 12 of the automatic diaphragm opening/closing ring 10 and the hole 14 of the support ring 13
Drive dowels 16 and 17 are installed in the aperture blades 15, respectively.
is inserted. On the other hand, the brake lever 19 whose one end is supported by the shaft 18 is provided with a brake hook portion 20 and a dowel 21, and the dowel 21 is attached to a dowel receiving edge 22 provided at the end of the cam lever 7 with a spring. etc. (not shown)
It is true. 4, 5, and 6 show the relative positions of the diaphragm preset ring 4, cam lever 7, pin 11, and brake lever 19 in FIG. 3, and the position of the diaphragm blade 15 corresponding to the position of the pin 11. 3, and for the sake of simplicity, the same parts as in FIG. 3 are given the same numbers.

When the pin 11 is in the position shown in FIG. 4, the opening of the diaphragm blade 15 is open, and at this time the dowel 21 of the brake lever 19 is in contact with the dowel receiving edge 22 of the cam lever 7, and the brake The hook portion 20 is configured to be located closer to the pin 11 with respect to the aperture pin receiving hook portion 9. One embodiment of the aperture rebound prevention device according to the present invention has the above structure, so that
In FIG. 4, when the photographer rotates the aperture preset ring 4 according to a predetermined aperture value, the cam surface 8 that contacts the pin 5 causes the cam lever 7 to rotate by a predetermined amount around the shaft pin 6. The aperture pin receiving hook portion 9 is then set at a predetermined position.

Next, when the camera is released, the pin 11 begins to rotate counterclockwise in the figure due to drive from the shutter button on the body side or the force of an elastic body (not shown) such as a spring attached to the pin 11. , the aperture blades 15 are driven via drive dowels 16 and 17, and the aperture of the aperture blades gradually becomes smaller.

The pin 11 is then gradually accelerated, but as shown in FIG. is applied, and the speed of the pin 11 is significantly reduced.

Therefore, the pin 11 finally comes into contact with the aperture pin receiving hook 9 and stops, and the rebound after the predetermined opening is achieved is small and quickly damps. If we look at this operation in the diaphragm operation curve in Fig. 8, we can see that the blades start moving from the open state and gradually accelerate while the aperture becomes smaller, and from the start of the movement T. Seconds later, when the aperture reaches ZO, the aperture pin collides with the brake hook and is braked to decelerate, resulting in rebound after the aperture pin hits the hook of the cam lever and reaches the predetermined aperture Z. is small and decays quickly. Therefore, as shown in the throttle operation curve 27 shown by the solid line in FIG. 8, the required rebound time Ts is short, and the throttle stabilization time t is short as a whole. On the other hand, in the case of a conventional mechanism in which there is no brake lever and the accelerated pin directly collides with the hook of the cam lever, the rebound time is long and The stabilization time is T2 seconds. Therefore, according to the device embodying the present invention, the aperture stabilization time that conventionally required T2 seconds can be reduced to t seconds, resulting in a significant reduction in the aperture stabilization time. FIG. 7 shows another embodiment of the present invention, which is an application of FIG. 21 is provided, and the dowel 2
1 is an elastic body (such as a spring) attached to the dowel receiving edge 22 of the cam lever 7.
(not shown).

Also, at this time, since the brake hook 20 is located closer to the iris pin 11 than the iris pin receiving hook 9, when the pin 11 rotates counterclockwise from the opening position of the iris 5 and is narrowed down. , just before the preset aperture value, first press the hook 20 of the brake lever.
When the pin 11 collides with the cam lever, sudden braking is applied, and the speed of the aperture pin 11 is greatly reduced.
The set opening is achieved, the rebound is small, and the effects of fast damping are the same as when the brake lever 19 of FIG. 3 is provided. As described above, according to the aperture rebound prevention device of the present invention, the aperture stabilization time is greatly shortened, which eliminates the conventional time lag caused by rebound, which delays the time until the shutter shutter opens after the camera release. It is possible to speed up the shutter speed, the photographer does not have to lose the shutter speed, and the structure is simple, requiring only the addition of a brake lever to the conventional aperture operating mechanism.

Therefore, by applying the present invention, the automatic diaphragm system can be adopted even for large-diameter lenses or long-focus lenses, for which it has been difficult to employ an automatic diaphragm mechanism in the past due to the large inertial mass of the diaphragm driving member. It is easy to process and assemble, which improves productivity and has a great effect.

[Brief explanation of the drawing]

FIGS. 1 and 2 are throttle operation curves showing general throttle operation conditions using a conventional throttle operation mechanism. FIG. 3 is a perspective view showing essential parts of an embodiment of the present invention. 4, 5, and 6 are front views of essential parts for explaining the operation of the embodiment shown in FIG. 3. FIG. 7 is a perspective view showing the main parts of another embodiment of the present invention. FIG. 8 is a throttle operation curve showing a general throttle operation state by the throttle rebound prevention device of the present invention. 1, 2,
3...Conventional aperture operation curve, 4...Aperture preset ring, 5...Pin, 6...Axis pin, 7... Cam lever, 8...cam surface, 9...diaphragm pin receiving hook part, 10...swing diaphragm opening/closing ring, 11...pin, 12... ... Long groove, 13 ... Support ring, 14 ... Hole, 15
...Aperture blade, 16, 17... Drive dowel, 18... Shaft, 19... Brake lever,
20...Brake hook, 21...Dowel, 2
2... Dowel receiving edge, 23... Braking ring.

Claims (1)

[Claims] 1 One end of the cam lever 7 that surrounds the lens optical path in a semicircular manner is pivoted and spring-biased toward the optical axis side, and the other end has a claw portion protruding inward, and the hook portion 9 of the claw has a separate Automatic diaphragm opening/closing ring 1
When the pin 11 installed at 0 is narrowed, it abuts in the same direction as the biasing force of the lever, and a concave cam part 8 is provided inside the intermediate part of the lever, and a separate aperture preset ring is provided. 4 is brought into contact with the implanted pin 5, and furthermore, a narrowing brake lever 19 (or ring 23) is provided overlapping the cam lever 7, and the two are engaged by a spring, so that the brake lever 19 (or ring 23) is brought into contact with the cam lever 7. The brake lever 19 (or ring) has a hook portion that is partially engaged with the tip so that it is biased in the opposite direction to the biasing direction of the cam lever, and that the pin 11 of the automatic throttle opening/closing ring collides with the brake lever 19 (or the ring) during the throttle operation. A preset automatic diaphragm bounce prevention device, in which the automatic diaphragm opening/closing ring is configured to tighten and stop at a preset value while obtaining a predetermined braking at the time of narrowing down.