JP2754518B2 - Light intensity diaphragm device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diaphragm device provided in an optical apparatus such as a video camera, and more particularly to an improvement in a diaphragm device having a filter such as an ND (neutral density) filter for adjusting a light amount. It is.

[0002]

2. Description of the Related Art As shown in FIGS. 6 and 7, in a conventional aperture device, an ND filter 14 is provided with an aperture blade 13 so as to cover an aperture of about F8 to F11 for small aperture correction.
Is adhered or arranged on the edge portion of the substrate with an adhesive 15. On the other hand, the conventional ND filter 14 uses a uniform density filter. Therefore, in recent years, as the sensitivity of the image pickup device has increased, the density of the ND filter has been increased to reduce the amount of light transmission, and the minimum aperture of the diaphragm has been increased even if the brightness of the subject is the same. However, N
When the density of the D filter is increased, the light quantity difference between the light a passing through the filter 14 and the light b not passing in the state shown in FIG. In order to improve this drawback, a diaphragm device using an ND filter having a transmission characteristic in which the amount of transmitted light changes at a constant rate has been proposed as shown in Japanese Patent Application Laid-Open No. 2-190833 as shown in FIG. As described above, the ND filter having a structure having various types of transmittance portions in one ND filter
As a method for manufacturing a D filter, Japanese Patent Application No. Hei.
No. 95 has already been proposed. This method is different from the conventional method of making a ND filter sheet with a roller or the like by using a dye and a base material, and the microfilm is ND
This is a method in which the density is varied within the same filter by using a photography technique technique as a filter.

[0003]

In the case of such a filter having portions having different density distributions within the same filter, the following disadvantages have occurred.

As a problem, there is a problem that the arrangement accuracy of the density at the aperture opening of the ND filter greatly varies as compared with the related art. In the case of a conventional filter having a uniform density, as shown in FIG. 1, the placement accuracy at the aperture opening is determined by the attachment accuracy of the ND filter on the aperture blade, so that the accuracy of ± 0.02 mm can be sufficiently maintained. Was. However, if there is a density change in the same filter, ND on the blade
In addition to the accuracy of attaching the filter, misalignment occurs when the filter is created (in this case, misalignment indicates where the filter portion having a predetermined transmittance is located within the aperture opening. ). In the case of the method of Japanese Patent Application No. 3-338595, an original is created as a step of the creation method.
It has a general process of photographing → developing → removing the outer mold → attaching to the blade. In this process, there is a photographing process as a process for generating a positional deviation of a predetermined density. This causes a positional shift due to the accuracy of feeding the film for each frame. Also in the press blanking, a positional deviation occurs depending on which part is to be blanked. Besides this, ~
There is a problem that the overall density deviates from the determined density in photographic technology.

In consideration of all of the above problems, the accuracy of arranging the determined density line at a specific position with the aperture is degraded by about ± 0.1 mm.

[0006] In FIG. 6, 1 2 3 4 5
Is an optical system, and 6 is an imaging surface.

[0007]

According to the present invention, there is provided a diaphragm blade which changes the size of a diaphragm aperture by moving straight in a plane perpendicular to the optical axis, and a driving means for driving the diaphragm blade by moving an output member. Wherein a filter member attached to the diaphragm blade is attached to the diaphragm blade so as to be located in a diaphragm opening formed by the diaphragm blade, and each of the filter members is uniform. A small aperture having a first area set to a transmittance, and a second area where the transmittance changes continuously from the transmittance of the first area, wherein an aperture of the aperture device is set; When forming an aperture, only the first area of the filter member is located within the aperture formed by the aperture blade, and when the aperture becomes larger than the small aperture, In order to solve the above-described problem, the filter member is attached to the diaphragm blade so that the first region and the second region of the filter member are located within a diaphragm opening formed by the diaphragm blade. .

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention is an ND filter 2 shown in FIG.
0 is used in place of the ND filter 14 shown in FIGS.

That is, the ND filter 20 in this embodiment
Is set so that the transmittance is constant in the first region I located in the opening region when the diaphragm device of FIGS. 6 and 7 becomes the minimum diaphragm opening, and the diaphragm opening becomes gradually larger than the minimum diaphragm opening. The second region II located in the opening region at the time is set so that the transmittance continuously increases.

[0010] The position deviation accuracy of the density cannot be improved by this method. In the case of a video lens, when the field of view becomes brighter than a certain level, it is fixed at a minimum aperture portion and cannot be stopped further. This is because the resolution is reduced when the aperture becomes smaller than a certain aperture size, and thus the aperture is fixed. Therefore, in the case of outdoor photographing that requires the ND filter most, the probability that the ND filter is located at the minimum aperture is greatly increased. For this reason, a feature of the present embodiment is that the density variation is minimized at the stop position where the probability of using the ND filter is the largest. Because of the uniform density distribution at the minimum aperture position, the density variation is
It is only necessary to consider the density deviation in the photographic technology of the process. This is because, in the continuously changing density portion, if the density is shifted by 0.2 mm, the density may change by as much as 10% even if the photographic technology factor of-is removed.

As a second reason, which is also a problem due to the density variation, as a method of setting an aperture value optically of a video camera, the FNO is determined based on the amount of light on an image sensor. In the case of continuous transmittance change, the determination of FNO on the image sensor is greatly shifted one by one, and the compatibility is lost. On the other hand, according to the method of this embodiment, if the FNO is determined on the basis of the minimum aperture, there is little variation, so that video cameras compatible with each other can be produced.

The third reason is to improve the use efficiency when pressing an ND filter from a microfilm. When all the aperture openings continuously change, the arrangement of the press-released filters on the film is as shown in FIG.

On the other hand, the layout of the press punching in the case of the present embodiment is as shown in FIG. 3, and it is possible to use the film with maximum efficiency on the film as compared with FIG. The reason for this is that, since the margin for bonding to the blade and the minimum aperture portion have the same density, the ratio of the overlapping of the upper and lower patterns is increased, and the use efficiency is improved. The reason why the film density in the vertical direction is continuously connected to the aperture opening is to loosen the press-out accuracy in the horizontal direction. This is because, because the film frame feeding accuracy is poor (± 0.2 mm), even if one master is made for each filter, continuous punching cannot be performed in the pressing process.

FIG. 4 shows another embodiment. FIG. 5 shows the concentration distribution of FIG. This graph shows that there is no transmittance step when the concentration of H is high. This is necessary to make the movement of the aperture smooth. If this H portion becomes discontinuous, the diaphragm blades will not move smoothly, and the followability of the diaphragm will deteriorate.

[0015]

According to the present invention, there is provided a diaphragm having a diaphragm blade which changes the size of the diaphragm aperture by moving straight in a plane perpendicular to the optical axis, and a driving means for driving the diaphragm blade by moving an output member. In the apparatus, a filter member attached to the aperture blade is attached to the aperture blade so as to be located in an aperture opening formed by the aperture blade, and each of the filter members is set to have a uniform transmittance. And a second area in which the transmittance changes continuously from the transmittance of the first area, and the aperture of the aperture device becomes a set small aperture. When only the first region of the filter member is located within the aperture opening formed by the aperture blade and has a larger aperture than the small aperture,
The filter member is attached to the diaphragm blade so that the first region and the second region of the filter member are located within a diaphragm opening formed by the diaphragm blade, thereby reducing the variation in transmittance. It is possible to provide a suppressed and high-precision light amount aperture device.

[Brief description of the drawings]

FIG. 1 is an external view of a filter used in an embodiment.

FIG. 2 is a view for explaining a state of press punching at the time of manufacturing a conventional filter.

FIG. 3 is a diagram for explaining a press-cut state when manufacturing a filter used in an example.

FIG. 4 is an external view of a filter as another embodiment having a slightly different shape from the filter of FIG. 1;

FIG. 5 is a graph showing the density distribution of the filter of FIG.

FIG. 6 is a sectional view showing the entire diaphragm device.

FIG. 7 is a perspective view showing a main part of FIG. 6;

FIG. 8 is a graph showing a density distribution of a conventional filter.

[Explanation of symbols]

 13 Aperture blade 14 ・ 20 ・ 20 ′ ND filter I 1st area II 2nd area

────────────────────────────────────────────────── ─── Continued on the front page (56) References JP-A-2-311831 (JP, A) JP-A-2-190833 (JP, A) JP-A-3-35531 (JP, U) (58) Field (Int.Cl. ⁶ , DB name) G03B 9/00-9/07

Claims (1)

(57) [Claims] 1. A diaphragm device comprising: a diaphragm blade that changes the size of a diaphragm opening by moving straight in a plane perpendicular to an optical axis; and a driving unit that drives the diaphragm blade by moving an output member. A filter member attached to the aperture blade so as to be located within an aperture opening formed by the aperture blade, the filter member being attached to the aperture blade, wherein each of the filter members is set to have a uniform transmittance. And a second area in which the transmittance changes continuously from the transmittance of the first area. When the aperture of the aperture device becomes a set small aperture, the filter When only the first area of the member is located within the aperture formed by the aperture blades and becomes a larger aperture than the small aperture, the first area of the filter member is And the like second region is located in the aperture stop formed by the diaphragm blades, the diaphragm device wherein the filter element is characterized in that attached to the diaphragm blades.