JPS589214Y2 - Aperture mechanism of soft focus lens in single-lens reflex camera - Google Patents

Description

[Detailed Description of the Invention] This invention relates to an aperture mechanism for a soft-focus lens in a single-lens reflex camera that uses a soft-focus lens and allows easy focusing.

In single-lens reflex cameras, an automatic aperture mechanism is known that keeps the aperture fully open at all times and then narrows the aperture down to the required aperture value during shooting in order to brighten the viewfinder image and shallow the depth of focus to facilitate focusing. .

However, when using a soft-focus lens for portrait photography, flare becomes a nuisance when the aperture is wide open, making it extremely difficult to adjust the focus.

Figure 1 shows the spherical aberration of a certain type of soft focus lens.The spherical aberration increases rapidly and the softness increases when the aperture is smaller than F5.6, but when the aperture is smaller than F5.6, the spherical aberration increases. It can be seen that the aberrations are reduced and it can be used as a general lens without flare.

Now, if we draw a model of the line image intensity distribution in the open aperture state when the film surface is S in Figure 1, it will become as shown in Figure 2. It is roughly divided into a surrounding flare part F.

This portion C is formed by a light beam having a small spherical aberration near the optical axis, and a portion F outside thereof is formed by a light beam having a large aperture.

In Figure 3, the aperture is set at a constant aperture value - (F5 in the example in Figure 1) so that only the light beam effective for image formation is focused on the finder surface.
．． 6), at which point the flare disappears and the finder image becomes sharp.

Further, since the apparent depth of focus at a wide open aperture depends on the aperture of the light beam effective for imaging, the apparent depth of focus does not change even if the aperture is stopped down until flare disappears.

Therefore, in order to obtain a soft-tone image with a soft-focus lens, it is sufficient to stop down the aperture to a certain value, focus, and then open the aperture to the wide-open side and take a picture, so that only the light flux that is effective for image formation is transmitted. I understand.

In addition, even when shooting with a smaller aperture than the fixed aperture mentioned above, in order to make the viewfinder easier to see, focus at the brightest fixed aperture value mentioned above without flare, and then stop down to the desired aperture value when shooting. Just as with ordinary lenses, accurate focusing is also effective.

However, the aperture mechanism of soft focus lenses in conventional single-lens reflex cameras is exactly the same as that of ordinary lenses, and the aperture is always kept open, making it extremely difficult to obtain accurate focus. there were.

Therefore, when using a camera that has a diaphragm member on the lens or camera side that allows the aperture to be narrowed down to the set aperture value regardless of shutter operation, first set the aperture setting ring to the aperture value at which flare disappears. After narrowing down the aperture to a predetermined value using the aperture member and focusing on the viewfinder surface, the aperture setting ring is sometimes reset to the aperture value to be actually photographed, but this method takes a lot of time to focus. Not only is it unsuitable for photographing moving objects because it requires time and effort, but it is also likely that the user will often forget to set the aperture again and fail to obtain a soft contrast effect.

Note that with some lens shutters, the aperture can be fully opened (open) by manual operation regardless of shutter operation, but when using a soft focus lens, as mentioned above, flare gets in the way when the aperture is wide open, making it difficult to focus. Adjustments could not be made easily.

The purpose of this invention is to provide an aperture mechanism for a soft focus lens in a single-lens reflex camera that solves these problems, facilitates focus adjustment, and has good operability.

Therefore, the diaphragm mechanism of the soft focus lens invented by this invention is
A first annular member and a second annular member are arranged rotatably and concentrically with respect to the optical axis and are biased to rotate in opposite directions, and the bases of the plurality of aperture blades are attached to the first and second annular members. an externally operable aperture member that engages with one of these annular members and an aperture interlocking member that engages with the other; the first and second annular members are normally When the aperture blades are locked in a predetermined position and opened, and the aperture member is operated from the outside, one annular member is rotated within a predetermined range and the aperture blades are narrowed down to a predetermined aperture at which flare disappears. At the time of release, the other annular member is rotated by the diaphragm interlocking member to narrow down the diaphragm blades to a preset aperture value.

Embodiments of this invention will be described below with reference to FIGS. 4 to 7.

1 is a lens barrel; 2 is a first annular member disposed inside the lens barrel 1 so as to be rotatable about the optical axis; and 3 is a first annular member having a plurality of through holes 2a at equiangular positions; A second annular member is rotatably arranged concentrically with 2 and has a plurality of elongated holes 3a at equiangular positions corresponding to the through holes 2a; 4 is a pin 5 implanted in the same direction; 6 is the above-mentioned through hole 2a, long hole 3
A is a plurality of aperture blades that are loosely fitted into the aperture, and only one of them is shown in the figure for the sake of simplicity.

Although the aperture blades 4 are not actually visible in FIG. 4, they are shown by solid lines for convenience of explanation.

7 is a connecting pin implanted in the second annular member 3; 8 is pivotally attached to the lens barrel fixing portion with a shaft 9, has a long groove 8a into which the connecting pin 7 is inserted, and has a regulating pin 10 implanted therein; It's a bell crank.

Reference numeral 11 denotes an aperture regulating cam that rotates around the optical axis in conjunction with an externally adjustable aperture ring (not shown) and has a cam portion 11a with which the regulating pin 10 engages.

12.13 is engaged between the pins 14 and 15 implanted in the first annular member 2 and the second annular member 3, respectively, and the lens barrel fixing part, and holds the first and second annular members 2°3. The first spring and the second spring are biased to rotate in opposite directions, that is, clockwise and counterclockwise, respectively.

16 is a first locking member that is fixed to the lens barrel fixing part by a screw 17 and a long hole 16a, and locks the pin 14 to regulate the stopping position of the first annular member 2; 18 is a screw 19 and a long hole 18a; It is fixed to the lens barrel fixing part by locking the pin 15 and
This is a second locking member that regulates the stopping position of the annular member 3.

The first and second annular members 2 and 3 are connected to the first and second locking members 1.
6 and 18, the aperture blades 4 are kept open.

Reference numeral 20 denotes a narrowing lever that is rotatable about the optical axis, has a handle 20a and a protrusion 20b that engages with the pin 14 of the first annular member 2, and rotates between the stopper pins 21 and 22.

23 is rotatable around the optical axis and has a protrusion 23a that engages with the pin 15 of the second annular member 3. A mechanism (not shown) causes the spring 13 to move against the spring 13 before the shutter is activated by the release operation. This is an aperture interlocking lever on the camera body side that is driven in the direction of arrow A.

With the above configuration, the aperture interlocking lever 23 is normally disengaged from the pin 15 as shown in FIG. The locking members 16 and 1 are pulled and locked, and the aperture blades 4 are in an open state.

Therefore, flare occurs in the finder image, making it difficult to focus.

When the handle 20a is operated from this state and the narrowing lever 20 is rotated in the direction of arrow B against the biasing force of the spring 12 until it comes into contact with the stopper pin 21, the pin 14 is driven and the first annular member 2 rotates by a predetermined range in the same direction, the pin 5 is driven, and the aperture blades 4 rotate in the direction of arrow C using the pin 6 as a fulcrum, reaching the state shown in FIG. The aperture is narrowed down to make focusing easier.

When the pressure on the narrowing lever 20 is released, the first annular member 2 moves with the narrowing lever 20 to the pin 1 due to the spring 12.
4 is rotated clockwise until it comes into contact with the first locking member 16, and the diaphragm returns to the open state shown in FIG.

Next, when the aperture interlocking lever 23 is driven in the direction of arrow A in FIG. and rotates in the same direction, the bell crank 8 rotates to the left via the connecting pin 1, and when the restriction pin 10 comes into contact with the cam portion 11a of the aperture restriction cam 11, the rotation of the second annular member 3 also stops. Then, the aperture blades 4 are narrowed down to a preset aperture value by an aperture ring (not shown), resulting in the state shown in FIG.

Note that when the set aperture value is an open aperture, the regulation pin 10 opposes the circumferential portion of the aperture regulation cam 11, and rotation of the second annular member 3 is prevented and the aperture blades 4 are held in the open state. Ru.

In the above embodiment, the first annular member is rotated during focusing, and the second annular member is rotated during photographing, but it goes without saying that this may be reversed.

As described above, according to this invention, the viewfinder image is always kept in the open state to maintain maximum brightness, making viewfinder observation easy, and also enables wide-open photometry with a TTL exposure meter, allowing focus adjustment. Regardless of the set aperture value, by operating the aperture member, the aperture can be narrowed down to a predetermined aperture that eliminates flare during that operation, allowing accurate focusing with no flare. The aperture value can be narrowed down to a preset aperture value during shooting, making it possible to take soft contrast effects or sharp normal shots at any time.It has an excellent effect that greatly facilitates the use of soft focus lenses in reflex cameras. .

[Brief explanation of the drawing]

Figure 1 is a diagram showing an example of spherical aberration of a soft focus lens, Figure 2 is a diagram schematically showing the line image intensity distribution state when the aperture is wide open, and Figure 3 is a diagram when the aperture is stopped down to a predetermined aperture value. Fig. 4 is a schematic plan view showing the normal state of the automatic diaphragm mechanism according to this invention; Fig. 5 is a cross-sectional view taken along the line v-v in Fig. 4; 6 is a plan view similar to FIG. 4 showing the state when the aperture lever is operated, and FIG. 1 is a plan view similar to FIG. 4 showing the state when the camera is released. DESCRIPTION OF SYMBOLS 1... Lens barrel, 2... First annular member, 3... Second annular member, 4... Aperture blade, 7... ...Connecting pin, 8...Bell crank, 10...Regulation pin, 11...
Aperture regulation cam, 12...First spring, 13...
...Second spring, 20...Aperture lever 2
3...Aperture interlocking lever.

Claims (1)

[Scope of utility model registration request] A plurality of aperture blades whose bases are pivotally supported by a first annular member and a second annular member, which are rotatable and concentrically arranged with respect to the optical axis, and the first and second annular members are rotated in opposite directions. a spring that biases the first and second annular members to rotate; a locking member that restricts the stopping positions of the first and second annular members to keep the aperture blades in an open state; a diaphragm member that engages with one of the members to rotate the annular member within a predetermined range against the biasing force of the spring, and narrows the diaphragm blades to a predetermined aperture at which flare disappears; an aperture interlocking member that engages with the other of the first and second annular members to rotate the annular member against the biasing force of the spring to narrow down the aperture blades to a preset aperture value; An aperture mechanism for a soft focus lens in a single-lens reflex camera, characterized by the provision of an aperture mechanism.