JPH05281593A - Light quantity diaphragm device - Google Patents

Abstract

PURPOSE:To obtain an image of little dispersion by making the transmission factor of a filter region positioned at an opening part constant at the time of the diaphragm opening being smallest, and making the transmission factor continuously larger as the diaphragm opening becomes larger. CONSTITUTION:In an ND (neutral density) filter, a first region I positioned in the opening region at the time of a diaphragm device having the minimum opening is set in such a way that a transmission factor is constant, and a second region II positioned in the opening region at the time of the diaphragm opening becoming gradually larger than the minimum diaphragm opening is set in such a way that the transmission factor becomes continuously larger. It is also so formed that density dispersion is suppressed to the minimum in a diaphragm position of large probability of using the ND filter. As to density dispersion, only the density slippage from the viewpoint of photographic technique in each process of plate preparation, photographing and developing is to be taken account. The transmission factor of this filter is to be the same as the transmission factor of a boundary part between the uniform part and the continuously changed part so as to eliminate the step difference of the transmission factors.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art As shown in FIGS. 6 and 7, in a conventional diaphragm device, an ND filter 14 is used to cover a diaphragm aperture of about F8 to F11 in order to correct a small diaphragm.
Is attached or arranged by an adhesive 15 on the edge of the. On the other hand, the conventional ND filter 14 uses a uniform density filter. Therefore, in recent years, as the sensitivity of the image sensor has increased, the density of the ND filter is increased to reduce the amount of light transmission, and the minimum aperture of the diaphragm is increased even if the brightness of the subject is the same. But like this, N
When the density of the D filter becomes high, in the state as shown in FIG. 6, the light amount difference between the light a that has passed through the filter 14 and the light b that does not pass greatly differs, resulting in a drawback that the resolution decreases. In order to remedy 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 as shown in Japanese Patent Laid-Open No. 2-190833 as shown in FIG. 8 has been proposed. In this way, the N of the structure having various kinds of transmittance parts in one ND filter
As a method of manufacturing a D filter, Japanese Patent Application No. 3-3385
We have already proposed No. 95. This method is different from the conventional method of making a sheet of ND filter with rollers etc., which is a kneading type of dye and substrate,
This is a method of using as a filter and varying the density within the same filter by using a photography technique.

[0003]

In the case of such a filter having a portion having different density distribution in the same filter, the following drawbacks occur.

The problem is that the density arrangement accuracy in the aperture opening of the ND filter is greatly different from the conventional one. In the case of the conventional filter of uniform density, the placement accuracy in the aperture opening is determined by the attachment accuracy of the ND filter on the aperture blade as shown in FIG. 1, and the precision of ± 0.02 mm can be sufficiently maintained. It was However, if there is a change in concentration within the same filter, the ND on the blade
In addition to the accuracy of attaching the filter, a positional deviation occurs when the filter is created (in this case, the positional deviation indicates the position of the filter portion having a certain transmittance in the aperture opening). ). In the case of the method of Japanese Patent Application No. 3-338595, as the step of the producing method, the original edition is made →
It has the general process of taking a picture, developing, removing the outer mold, and attaching it to the blade. Among them, photography is a process for generating a positional deviation of a predetermined density. This causes a positional deviation due to the film feed accuracy for each frame. Also in the press punching, a position shift occurs depending on which part is punched out. Besides this,
There is a problem that the overall density deviates from the density determined by the photographic technique.

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

In FIG. 6, 1, 2, 3, 4, 5
Is an optical system, and 6 is an image plane.

[0007]

[Means and Actions for Solving the Problems] When the aperture opening is minimum, the transmittance of the filter at the portion corresponding to the aperture opening is made at least constant, and when the aperture is closed further, the transmittance is continuous. It is designed to be large.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention is an ND filter 2 shown in FIG.
0 is used instead of the ND filter 14 of 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 aperture region when the aperture device of FIGS. 6 and 7 has the minimum aperture aperture, and the aperture aperture gradually becomes larger than the minimum aperture aperture. The second region II located in the opening region at this time is set so that the transmittance continuously increases.

The positional deviation accuracy of the density cannot be improved by this method. In the case of a video lens, when the field of view exceeds a certain level of brightness, it is fixed at the smallest diaphragm part and it cannot be stopped any further. This is because the resolution is lowered when the size of the aperture is smaller than a certain size, and therefore the size is fixed. Therefore, in the case of outdoor shooting where the ND filter is most needed, the probability of being located at the minimum aperture opening increases greatly. Therefore, a feature of this embodiment is that the density variation is suppressed as much as possible at the stop position where the ND filter is most likely to be used. Since the density distribution is uniform 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 if there is a 0.2 mm shift in the continuously changing density portion, the density may change by as much as 10% even if the factors in terms of photography are excluded.

The second reason is that this is also a problem caused by density variations. As a method of setting the aperture value in the optics of a video camera, FNO is determined based on the amount of light on the image sensor. In the case of continuous transmittance change, the compatibility of the FNOs on the image sensor is greatly deviated by one device and the compatibility is lost for the above reason. On the other hand, if the method of the present embodiment is adopted, there is little variation if FNO is determined on the basis of the time of the minimum small aperture, so that compatible video cameras can be made.

The third reason is that the use efficiency is improved when the ND filter is pressed out of the microfilm. When all aperture openings change continuously, the filter press arrangement on the film is as shown in FIG.

On the other hand, the layout without press in the case of the present embodiment is as shown in FIG. 3, and it is possible to use the film with the maximum efficiency as compared with FIG. The reason for this is that since the adhesion margin on the blade and the minimum squeezing portion have the same density, the overlapping ratio of the upper and lower patterns is large, and the use efficiency is improved. The reason why the film density in the vertical direction was continuously connected to the aperture was to loosen the punching accuracy in the lateral direction. This is because the film frame feed accuracy is poor (± 0.2 mm), and even if one original plate is made for each filter, continuous drawing cannot be performed in the pressing process.

FIG. 4 shows another embodiment. The concentration distribution of FIG. 4 is shown in FIG. In this graph, it is shown that there is no step difference in the transmittance at the H concentration. This is necessary for smooth movement of the diaphragm. If the portion H is discontinuous, the diaphragm blades cannot move smoothly and the followability of the diaphragm deteriorates.

[0015]

According to the present invention, the transmittance of the light quantity adjusting filter, at least a part of which is located in the opening formed by the diaphragm blade, is set so that the area located in the opening portion at the minimum diaphragm opening has a constant transmittance. The transmittance is continuously and largely changed in the area located at the opening when the diaphragm aperture is opened, which suppresses the dispersion of the transmittance in the minimum diaphragm state where the usage probability is high. (EN) Provided is a light amount diaphragm device capable of obtaining a small amount of an image, simplifying individual adjustment of an optical device such as a camera, and further efficiently manufacturing a filter.

[Brief description of drawings]

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

FIG. 2 is a diagram for explaining a press-extracted state when manufacturing a conventional filter.

FIG. 3 is a view for explaining a press punching state at the time of manufacturing the filter used in the example.

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

5 is a graph showing the concentration 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.

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

[Explanation of symbols]

 20 ・ 20 'ND filter 13 Aperture blade

Claims (2)

[Claims] 1. A plurality of diaphragm blades that are relatively driven to change the size of the diaphragm opening, and a filter for adjusting the light amount, at least a part of which is arranged in the opening formed by the diaphragm blades. In the light quantity diaphragm device provided with the filter, when the diaphragm aperture of the light quantity diaphragm device is the minimum, the filter region applied to the opening portion has a uniform transmittance, and as the diaphragm opening becomes larger than the minimum opening, the transmittance is increased. A light amount diaphragm device characterized by being set so as to be continuously large. 2. The filter has the same transmittance at the boundary between the uniform portion and the continuously changing portion, and a filter having no transmittance step is used.
Light amount diaphragm device.