JPH10133253A - Light quantity stopping device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plastic filter which has sufficient strength of its surface to sliding and has the performance as an ND filter by using the filter formed with inorg. hard films on one or both surfaces of a plastic base plate. SOLUTION: The filter formed with the inorg. hard films on one or both surfaces of the plastic base plate is used for the light quantity stopping device having plural diaphragm vanes and the plastic ND filter for light quantity adjustment to be arranged in at least part within the aperture formed by these diaphragm vanes. The hard film forming materials are preferably SiOx (x=1 to 2), MgF2 , Al2 O3 , etc. The methods of forming the hard films are preferably vacuum vapor deposition, ion plating, etc. The film thicknesses of the hard films are generally preferably 1.0 to 0.5μm. As a result, the light quantity stopping device has the sufficient strength to sliding contact and can maintain the performance as the ND filter in a wavelength region of 400 to 700nm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a light amount aperture device suitable for use in photographing equipment such as a video camera.

[0002]

2. Description of the Related Art N light used in a conventional light amount diaphragm device
As a D (neutral density) filter, a material in the form of a film [cellulose acetate,
PET (polyethylene terephthalate), vinyl chloride, etc.], a type in which an organic dye or pigment that absorbs light is mixed and kneaded, and a type in which a dye or pigment that absorbs light is applied to the material are used. I have. The ND filter 1 and the aperture blade 2, which are main parts of the light quantity aperture device, have a configuration as shown in FIG. The main reason for using a plastic film is that the light amount aperture device shown in FIG. As a result, in the optical sectional view shown in FIG.
The distance between A and the lens 2B can be shortened, and a higher magnification image can be obtained.

In FIG. 2, 1A, 1B, 1C and 1D
1A is an ND filter, 1B and 1C are relatively driven (here, opposed to each other) diaphragm blades, and two diaphragm blades are substantially rhombic. An opening having a variable size is formed. The ND filter is
It is bonded to one of the aperture blades. 1D is an aperture blade support plate. Reference numerals 2A, 2B, 2C, and 2D denote component lenses constituting the photographing optical system 2, 3 denotes a low-pass filter, and 4 denotes a solid-state image sensor.

[0004]

However, since the surface of the plastic ND filter attached to the diaphragm blade is made of plastic, the diaphragm blade and the diaphragm blade when the light amount diaphragm slides in accordance with the brightness of the field of view. The support plate and the ND filter rub against each other, causing scratches on the ND filter surface. In recent years, as the sensitivity of the image sensor has increased, there has been a problem that the resolution is reduced due to the scratch.

Accordingly, it is an object of the present invention to provide a diaphragm device having a sufficient strength of the surface of the plastic filter against sliding, and having a performance as an ND filter.

[0006]

SUMMARY OF THE INVENTION The present invention comprises a plurality of aperture blades which are relatively driven to change the size of an aperture opening;
A light-aperture stop device including a plastic ND filter for adjusting a light amount disposed at least in a part of an opening formed by the diaphragm blade, wherein the filter has an inorganic hard film on one or both surfaces of a plastic substrate. A light amount diaphragm device characterized by being a formed filter.

The inorganic hard film formed on the surface of the plastic substrate is desirably formed on only one side from the viewpoint of cost. However, due to the design of the drawing device, if scratches occur on both sides of the ND filter due to sliding, both sides are required. Need to be formed.

In the light amount diaphragm device of the present invention, the surface of the ND filter has a sufficient strength against sliding contact with the blade portion when the diaphragm device is opened and closed, and the visible light wavelength region 400n.
It has sufficient performance as an ND filter at m to 700 nm.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION As a hard film forming substance, SiO _x
(X = 1 to 2), MgF _2, Al ₂ O _{3 and the} like are preferable, and as a method for forming the hard film, vacuum deposition and ion plating are preferable. Generally, the thickness of the hard film is preferably from 1.0 μm to 0.05 μm.

(Example 1) First, an inorganic hard film having a thickness of 0.1 μm was formed on a 100 μm-thick ND filter into which an organic dye was kneaded by a vacuum evaporation method. The vapor deposition method was selected because the film thickness can be controlled relatively easily, the optical characteristics can be controlled, and the film formation method is excellent as a method capable of forming a film at a low temperature. FIG. 3 shows the obtained film structure. The material of the ND filter is heat resistant temperature (T _g )
PET or PEN (polyethylene naphthalate) having high moisture absorption and low moisture absorption was selected. As a hard film forming material, MgF ₂ having much higher hardness than plastic film and having sufficient strength for sliding of a drawing device.
Alternatively, SiO ₂ was selected. Since these thin films do not absorb light, they also have the advantage of maintaining the transmittance characteristics of the ND filter.

The shape of the filter is made asymmetrical in order to make it easy to determine the bonding surface when the manufactured ND filter is bonded to the aperture blade. In addition, in order to ensure sufficient adhesion between the ND filter and the aperture blade, a hard film was not formed on the bonded portion of the ND filter, and the plastic surface was exposed.

In order to check the strength of the surface of the ND filter produced by the above method, the ND filter was actually mounted on a light amount diaphragm device, and the diaphragm was opened and closed 250,000 times and slid. As a result, it was confirmed that no scratch was generated on the hard thin film surface of the ND filter having the hard film formed by the vapor deposition method (FIG. 4A). When the same test was performed on a plastic ND filter on which a hard film was not formed, it was confirmed that a large scratch was generated on the contact orbit between the diaphragm blade and the ND filter (FIG. 4).
(B)). From the above results, it was possible to manufacture a light amount diaphragm device having sufficient strength against sliding contact by the hard film formed by the vapor deposition method.

Example 2 Next, in order to simplify the ND filter manufacturing process, a hard film forming substance was selected, and a hard film having a function as an ND filter was formed on a transparent PET or PEN substrate having a thickness of 100 μm. Was formed. According to this method, the process of fabricating the ND filter can be shortened from two processes of kneading the organic dye and depositing the hard film to a single process of depositing the hard film only.

FIG. 5 shows the obtained film structure. All the film-forming substances were selected because their hardness was sufficiently higher than the plastic surface. Further, the second, fourth and sixth layers of TiO _y (y =
For the layers 1 and 2), a substance having a function of lowering the transmittance was selected. The transmittance changes depending on the total thickness of the three layers, and the transmittance decreases as the thickness increases. Also, 400 nm to 70
The neutrality of the transmittance in the wavelength range of 0 nm changes depending on the y of the TiO _y film composition. In order to make the transmittance neutral within the above wavelength range, it is desirable to set the value of y to 1.2 and form the film. When the value of y is smaller than 1.2, the transmittance particularly in the wavelength range of 400 to 550 nm tends to decrease. If it is larger than 1.2, the transmittance increases in the wavelength range of 400 to 550 nm, and the neutrality tends to deteriorate.
The first, third and fifth layers are Al ₂ O ₃ and are selected because they have a property of reducing the reflectance in the wavelength range of 400 nm to 700 nm when laminated with TiO _y at an appropriate thickness. As described above, a hard film having a function as an ND filter is formed.
gF ₂ or SiO ₂ was formed. Here, the thickness of each layer is 0.095 μm for the first layer and 0.053 μm for the second layer.
m, third layer: 0.035 μm, fourth layer: 0.047 μm
m, fifth layer: 0.053 μm, sixth layer: 0.018 μm
And the seventh layer: 0.096 μm.

Example 1 Regarding the ND Filter Produced
A sliding test was performed in the same manner as described above. As a result, the hard film surface of the ND filter was free of scratches and had sufficient strength against sliding contact (FIG. 6).

The transmittance of the fabricated ND filter is 400 nm to 700 nm as shown in FIG.
Shows a constant transmittance and is excellent in flatness. As shown in FIG. 8, the reflectivity shows a sufficiently low value in the above wavelength range, and is sufficiently acceptable as an ND filter.

As described above, by forming an inorganic hard film on a plastic substrate, the present invention has sufficient strength against sliding contact with the blade portion when opening and closing the diaphragm device, and has a wavelength range of 400 nm to 400 nm. It is possible to provide a light amount diaphragm device having a performance as an ND filter at 700 nm.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a main part of a light quantity stop device.

FIG. 2 is an optical cross-sectional view showing an operation when an ND filter is provided in a photographing system.

FIG. 3 is a diagram showing a hard film structure according to the first embodiment of the present invention.

FIG. 4 is a schematic diagram of an ND filter surface after a sliding test performed in Example 1 of the present invention.

FIG. 5 is a diagram showing a hard film structure of a vapor deposition ND filter in Embodiment 2 of the present invention.

FIG. 6 is a schematic view of an ND filter surface after a sliding test performed in Example 2 of the present invention.

FIG. 7 shows a result of measurement of spectral transmittance measured in Example 2 of the present invention.

FIG. 8 shows a result of measuring spectral reflectance measured in Example 2 of the present invention.

Claims (7)

[Claims] 1. A plurality of aperture blades which are relatively driven to change the size of an aperture opening, and a plastic ND for adjusting a light amount disposed in at least a part of an opening formed by the aperture blades. A light amount diaphragm device comprising a filter, wherein the filter is a filter in which an inorganic hard film is formed on one or both surfaces of a plastic substrate. 2. The light amount stop device according to claim 1, wherein the inorganic hard film is a film formed by a vapor deposition method. 3. The material for forming the outermost layer of the inorganic hard film is S
iO_x Or MgF _Two 2. The light amount aperture device according to claim 1, wherein
Place. 4. The plastic substrate is made of PET.
The light amount diaphragm device according to claim 1, wherein the light amount diaphragm device is PEN. 5. The method according to claim 1, wherein the inorganic hard film comprises a TiO _y layer and Al ₂
The light amount stop device according to claim 1, wherein the light amount stop device is a film having an O ₃ layer. 6. The light amount stop device according to claim 1, wherein the shape of the filter is left-right asymmetric. 7. The light amount stop device according to claim 1, wherein the filter is a filter in which an inorganic hard film is not formed on a plastic substrate at a portion where the filter is bonded to the stop blade.