JPH01304417A - Variable transmittance distribution filter - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a filter whose transmittance changes continuously in the radial direction around the optical axis, and more specifically, to a filter whose transmittance continuously changes in a radial direction around an optical axis. The present invention relates to a variable transmittance distribution filter that allows for [Prior Art] As a filter whose transmittance changes continuously in the radial direction around the optical axis, a filter in which two glass plates having different transmittances are closely bonded is conventionally known. In this filter, the incident end face and the outgoing end face are parallel, and the interface between both glasses is a spherical surface, so by coating it with a material that has light absorption properties, it is possible to Transmittance changes continuously. When such a filter is used away from the pupil position of the lens, for example when attached to the front of a wide-angle lens, it is possible to increase or decrease the peripheral light intensity by setting the ratio of the peripheral light intensity to the central light intensity to a desired value. I can do it. Further, when it is provided at the pupil position of the photographic lens, the depiction characteristics can be changed. That is, it is possible to eliminate or emphasize ring blur and two-line blur caused by the convergence characteristics of the light beam. [Problem to be solved by the invention] However, in the above-mentioned conventional filter,
Since the transmittance characteristics of the filter are fixed, it is necessary to replace the filter in order to obtain different rendering characteristics, and even if the filter is replaced, there is a problem in that only stepwise adjustments can be made. [Purpose of the Invention] This invention has been made in view of the above-mentioned problems, and an object thereof is to provide a variable transmittance distribution filter whose transmittance characteristics can be continuously changed without the need for replacement. do. [Means for Solving the Problem] In order to achieve the above-mentioned object, the variable transmittance distribution filter according to the present invention forms a closed space between two transparent flat plates disposed opposite to each other. An elastic transparent film is stretched between flat plates to form two liquid chambers in a closed space, and each liquid chamber is filled with liquids that have the same refractive index and different light absorption characteristics, and the ratio of liquid volumes in each liquid chamber is changed. The present invention is characterized in that it is provided with a liquid amount adjusting means for adjusting the amount of liquid. [Operation] According to the above configuration, the transparent elastic membrane can be deformed by changing the liquid volume ratio in each liquid chamber, and thereby the transmittance distribution characteristics depending on the position where the light beam passes can be changed. can. [Embodiment] The present invention will be explained below based on the drawings. FIG. 1 shows an embodiment of a variable transmittance distribution filter according to the present invention. This variable transmittance distribution filter is generally composed of a filter part 10 that transmits a light beam, and a pump 20 as a liquid volume adjusting means that changes the liquid 1 ratio in a liquid chamber formed within this filter part. . The filter part 10 includes, for example, a cylindrical frame 11, colorless transparent flat plates 12 and 13, such as glass plates, which are provided at openings at both ends of the frame 11 and form a closed space inside the frame 11, and these transparent flat plates 12. , 13, a transparent elastic membrane 16 is fixed to the inner wall of the frame 11 and forms two liquid chambers 14, 15 in a closed space.
It is equipped with The liquid chambers 14 and 15 are respectively filled with liquids A and B having the same refractive index and different light absorption characteristics. In this example, a transparent silicone oil pre-colored with several kinds of dyes is used as the liquid A, and a colorless and transparent silicone oil is used as the liquid B to construct the filter. The transparent elastic film 16 is made of, for example, colorless and transparent silicone rubber, and is bonded along the inner circumferential wall of the frame 11 so as to form a flat surface in a free state without pressure. Then, due to a change in the pressure ratio within each liquid chamber 14, 15, the transparent elastic membrane 16 is deformed into a spherical surface having a radius of curvature according to the pressure ratio. In this example, the pump 20 is composed of one cylinder 21 and one piston 22, and the piston 2
Two spaces 2 in the cylinder 21 partitioned by 2
1a and 21b are respectively vibrators 23. It communicates with the liquid chambers 14 and 15 via 24. The vibrator 23 and the space 22a communicating with the liquid chamber 14 are filled with liquid A, and the vibrator 24 and the space 22b communicating with the liquid chamber 15 are filled with liquid B. Note that the configuration of the liquid amount adjusting means is not limited to this example, and two pumps may be provided corresponding to each liquid chamber. Driving rods 22a are connected to both ends of the piston 22, and when the rods 22a are moved to the right in the figure, the liquid A in the liquid chamber 14 is sucked into the space 21a, and the liquid A in the space 21b is sucked into the space 21b. Liquid B is injected into the liquid chamber 15, and the transparent elastic membrane 16 becomes convex toward the liquid chamber 14 side. If the rod 22a is moved to the left in the figure, a phenomenon opposite to that described in L will occur, but in either case, since the refractive indices of liquids A and B are equal, the convergence of the light beam, etc. is not affected. Note that in this example, only liquid A has optical attenuation characteristics, so when the rod 22a is moved to the right in the figure, the amount of attenuation is smaller for the light rays that pass through the center than for the rays that pass through the periphery. Conversely, when the rod 22a is moved to the left in the figure, the amount of attenuation of the light beam that passes through the center is greater than that of the light beam that passes through the periphery. Next, the operation of the variable transmittance distribution filter configured as described above will be explained based on a drawing in which the filter portion 10 is provided in a specific camera lens. This camera lens, as shown in Figure 2.4.6,
From the object side, a meniscus convex lens 30 and two laminated lenses 31 with strong concave surfaces facing each other. ．． 32 and a biconvex lens 33, the filter part 10 of the variable transmittance distribution filter described above is provided at a position that serves as an aperture stop between opposing strongly concave surfaces. As shown in FIG. 2, a transparent elastic film 16 is attached to each transparent plate 11.
．． When the pump is operated to adjust the ratio of liquid volumes in the liquid chambers 14 and 15 so as to form a plane parallel to the plane 12, the filter part 10 has the same attenuation characteristic for light rays passing through any position. demonstrate. In this state, the spot diagram on the defocus plane of the point image passing through the lens system and the point image intensity distribution are as follows.
It will look like the one shown in the figure. Figure 3 (A) is a spot diagram on the defocused surface, and Figure 3 (B) is a spot diagram on the defocused surface.
) (C) shows the point spread intensity distribution within the orthogonal cross section of the spot shown in (A). As shown in the figure, the intensity is stronger at the periphery than at the center. That is, this state is so-called ring blur, and the point images that are continuous in a line form become two-line blur. Next, when the pump 20 is operated to decrease the liquid A (shaded area) in the liquid chamber 14 and increase the liquid B in the liquid chamber 15, the transparent elastic membrane 16 becomes as shown in FIG. It is convex toward the object side, which is the left side in the diagram, and the transmittance at the center is higher than at the periphery. FIG. 5 shows a spot diagram and point spread intensity distribution similar to FIG. 3 in this state. Third
Comparing with the figure, the amount of light in the central area is increased, resulting in a flatter intensity distribution. Therefore, ring blur and two-line blur can be reduced. Furthermore, when the volume of the liquid chamber 14 is increased and the volume of the liquid chamber 15 is decreased, contrary to the example shown in FIG.
As shown in FIG. 6, it is convex toward the image side, which is the right side in the figure, and the transmittance of the central portion is lower than that of the peripheral portion. FIG. 7 shows a spot diagram and point spread intensity distribution similar to FIG. 3 in this state. Comparing with FIG. 3, the intensity at the center is lower than at the periphery. Therefore, it is possible to intentionally emphasize the two-line blur. In addition, in Fig. 2.4.6, the filter part 10 is provided at a position that serves as the aperture stop of the lens system, but it is also possible to provide it at a position away from the aperture stop, and in that case, the angle of view will change. Since the light flux passes through the filter at different locations depending on the filter, it is necessary to control the light m ratio between the center and the periphery. In addition, as shown in the table on page 10, the above-mentioned dyes are commercially available, and by using one or more of these dyes, it is possible to control the spectral transmittance. It can also be used as a play, or as a filter that targets only a specific wavelength range.
It is. In addition, in the above example, only the liquid A has light attenuation characteristics, but the liquids A and B may have different light attenuation characteristics. Furthermore, by setting the same degree of NVE between the transparent elastic membrane and each method, the elastic membrane will not be bent into an irregular shape due to the influence of gravity, and the elastic membrane will not become unstable due to the influence of vibration etc. There is no such thing as (Margin below)

【table】

[Effects] As explained above, according to the variable transmittance distribution filter of the present invention, the transmittance distribution can be continuously changed with one filter, so the filter can be replaced as usual. There's no need. Moreover, by taking advantage of these characteristics and attaching it to a camera lens, etc., the degree of freedom in drawing can be improved.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a variable transmittance distribution filter according to the present invention. FIG. 2, FIG. 4, and FIG. 6 are explanatory diagrams in which the variable transmittance distribution filter of the present invention is arranged within a camera lens system. Figures 3, 5, and 7 represent Figures 2, 4, and 7, respectively.
FIG. 7 is an explanatory diagram showing a spot diaphragm and a point spread intensity distribution corresponding to the configuration of FIG. 6; 12.13...Transparent flat plate 14.15...Liquid chamber 16...Transparent elastic membrane 20...Pump (liquid 1..I51'!I means) A, B
···liquid

Claims (1)

[Claims] A closed space is formed between two transparent flat plates provided facing each other, an elastic transparent film is stretched between the transparent flat plates, and two
The present invention is characterized by comprising two liquid chambers, each liquid chamber being filled with a liquid having the same refractive index and different light absorption characteristics, and a liquid volume adjusting means for changing the liquid volume ratio in each liquid chamber. Variable transmittance distribution filter.