JP2006227432A - Manufacturing method of optical filter, and optical filter and light quantity adjusting device using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of optical filter capable of inexpensively manufacturing an optical filter which permits multistage concentration adjustment with a uniform light transmittance, without causing reflectance changes due to the difference in light wavelength, by using a simple method, and to provide the optical filter that uses the manufacturing method. <P>SOLUTION: A crucible (raw material storing part) for storing vapor deposition raw material and a substrate plate are arranged facing on prescribed positions in a vacuum vapor deposition chamber (tank). A first vapor deposition is performed, as follows: a first mask plate is disposed on the substrate plate so that the substrate plate and the mask plate become substantially parallel to each other and form a space with a prescribed interval. Subsequently, a second vapor deposition is performed as follows: a second mask plate having a masking region different from that of the masking plate having mentioned is disposed so that the substrate plate and the mask plate become substantially parallel to each other and form a space having a prescribed interval. As a result, a plurality of coating layers having different thickness are formed on the substrate plate. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method of manufacturing an optical filter in which a film having optical characteristics is formed on a plastic material or other light-transmitting substrate plate, and an optical filter or light amount adjusting device for various optical devices using the same.

In general, an optical filter used in a camera device, a projector device, a rear projection TV, or other optical equipment is widely known as a filter that is incorporated in a light-emitting portion of a device or a light-receiving portion such as an imaging tube and cuts light of a specific wavelength. Yes. In this optical filter, a film having optical characteristics is formed on a transparent plate such as plastic or glass by vapor deposition. For example, an ND filter (neutral density filter) incorporated in an imaging unit of a camera device forms a film by vapor-depositing a chromel film and a silicon dioxide film (SiO ₂ ) on a plastic sheet.

  Therefore, when a diaphragm device for adjusting the amount of light is incorporated into an imaging lens system such as a still camera or a video camera, there is a problem that the resolution decreases due to the hunting phenomenon or light diffraction phenomenon of the light amount adjusting blade when the aperture is small. In order to prevent the influence, an ND filter is provided at the tip of the blade, and the imaging light is taken in through this filter when the aperture is small. In recent years, especially when the resolution of a camera device has been increased and the size has been reduced, a filter having a uniform light transmittance on the entire surface of the filter cannot completely prevent the diffraction phenomenon due to a sudden change in the amount of light when the filter enters the aperture. Problems arise.

Therefore, for example, Patent Document 1 proposes a filter that can adjust the light transmittance in several steps. FIG. 7 shows a cross-sectional view of this filter, which has a thin film structure in which the density is adjusted stepwise depending on the position where the thin film is formed in a stepped manner and faced on the photographing optical path. In FIG. 7, a transparent dielectric layer 110 is formed of a material such as SiO ₂ , TiO ₂ , or Nb ₂ O ₅ on a transparent substrate 100, and a light absorber layer 120 is formed on the transparent dielectric layer 110 with TiNx, NbNx. And lower nitrides such as AlNx, and are alternately stacked. The light absorber layer 120 is formed so as to have different thicknesses in a stepped manner, and the latter becomes larger in the transmittances aa and bb in the drawing, and so on. The layers are formed so that the transmittance increases in the order of ee.

When forming a plurality of such transmittances in the form of a thin film, the one in FIG. 7 is formed in a staircase pattern, but as shown in FIG. It is disclosed in the same document. In FIG. 8, when forming the transparent dielectric layer 110 on the transparent substrate 100 and the light absorber layer 120 thereon, the light absorber layer 120 is inclined so that one end is thick and the other is thin. ing. A gradation filter in which the light transmittance gradually changes depending on the thickness of the light absorber layer 120 is known.
JP 2003-322709 A

  The following problems occur in the above optical filter. In the thin-film filter in which the layer cross-section shown in FIG. Diffraction may occur, and the image may be blurred due to the influence of this diffraction. In addition, in the filter formed of a thin film whose layer cross section is inclined as shown in FIG. 8, the flatness of the spectral transmittance at least on the red wavelength region side is easily broken due to the influence of the inclined multilayer film, and the effect is reddish. There was a problem that became an image.

  Accordingly, the present invention provides an optical filter that can adjust the concentration in multiple steps with a uniform light transmittance without changing the reflectance due to the difference in the wavelength of light, and at the same time does not cause light interference due to the thin film shape. The main problem is to provide a method for manufacturing an optical filter that can be manufactured stably and inexpensively by a simple method and an optical filter using the same.

  The present invention employs the following configuration in order to solve the above-described problems. A method of manufacturing an optical filter for forming a vapor deposition film having optical characteristics on a base plate made of a light-transmitting material, wherein a crucible (material storage portion) stores a vapor deposition material at a predetermined position in a vacuum vapor deposition chamber (tank) And a base plate, the first mask plate is placed on the base plate, and the base plate and the mask plate are substantially parallel to form a space with a predetermined interval, and then a first vapor deposition process is performed. A second mask plate having a masking area different from that of the mask plate is subjected to a second vapor deposition process by forming a substantially parallel space between the base plate and the base plate, and a plurality of the mask plates are formed on the base plate. Film layers having different thicknesses are formed.

  According to the present invention, using a base plate made of a plastic sheet and a plurality of mask plates having appropriate openings of different sizes for each plate, the base plate at an appropriate position in the vacuum deposition chamber, A plurality of mask plates, which are substantially parallel to the deposition surface of the base plate and spaced apart by a predetermined distance, are sequentially exchanged and supported by the mask plate having the largest opening for each deposition step, and vacuum deposition is performed on the surface of the base plate. By forming a vapor deposition film by the method, the vapor deposition film is divided into a plurality of regions in which a film layer is formed in a stepwise manner on the surface of the base plate, and each region has a uniform light transmittance. In addition, each region has a different light transmittance, and the side end portion of each region is formed on a lower film layer plane to form a gradation region in which the light transmittance increases and changes sequentially. Even though it is a multistage density filter, a part of the area between the multistage density areas is a gradation filter, so that the gradation part is slightly reflected and reddish, but the entire filter has uniform multistage density light transmission. It is possible to provide an optical filter that can obtain a high rate and that hardly causes image spots due to diffraction phenomenon.

  Embodiments of an optical filter (ND filter) and a method for manufacturing the same according to the present invention will be described below in detail with reference to the accompanying drawings. Here, FIG. 1 is a sectional view showing the structure of a deposited film laminated on a substrate plate (substrate plate), FIG. 2 is a schematic view of a vacuum deposition apparatus, and FIGS. 3 (a) to 3 (d) are depositions. It is a perspective view which shows the positional relationship of the base material plate and mask board with respect to the fixing jig in a manufacturing process.

First, the optical filter according to the present invention is shown in FIG. 1 (a) as an overall cross section and as shown in FIG. 1 (b) as an enlarged cross section. 11), transparent dielectric films and light absorber films are alternately formed on the base plate 11 in a laminated form, and the outermost surface is coated with a water repellent film CX. A transparent dielectric film (hereinafter referred to as a dielectric layer) 13 is formed of silicon dioxide (SiO ₂ ) or the like, and a light absorber film (hereinafter referred to as a light absorber layer) 12 is a metal film such as Ni, Cr, Ti, or the like. A metal oxide film is used. In the illustrated example, the light absorber layer 12 is formed of a chromel alloy of 90% nickel and 10% chromium. As shown in FIG. 1 (b), a light absorber layer 12 made of a chromel alloy is formed on a base plate 11 formed of a plastic sheet, and a dielectric layer 13 made of silicon dioxide is alternately laminated on the laminated structure. The film is formed stepwise with film thicknesses t ₁ , t ₂ , and t ₃ . The film thicknesses t ₁ , t ₂ , and t ₃ are all formed with uniform spectral characteristics, and the light transmittance is a portion where the film layers of T _1, T _2, and T ₃ are flat when T ₁ <T ₂ <T _3. Is formed with uniform transmittance.

Therefore, the ability to select multiple concentrations (three stages as shown), for example, the illustrated T ₁ parts transmittance 5%, T ₂ parts 20%, T ₃ parts concentration as 30% in three steps . The boundary between the ₂ parts shown T ₁ parts of T and T ₂ parts of T ₃ parts to match the thickness t ₂ of the ₂ parts of T gradually thinner from a thickness t ₁ of ₁ part T, T ₂ parts boundary of T ₃ parts also reduces gradually the thickness in the same manner as. That is, a plurality of film surfaces having different thicknesses with a uniform thickness are formed stepwise, and the film thickness is gradually reduced from a surface having a large thickness to a surface having a small thickness adjacent thereto.

  As shown in FIG. 1A, the base plate 11 serving as the base of the present invention has a thickness in the range of about 25 to 200 μm, and preferably in the range of 50 to 100 μm. This is because if the thickness is 25 μm or less, the film is too thin and the rigidity is insufficient, and the vapor deposition material includes a fragile dielectric material. On the other hand, when the thickness is 200 μm or more, turbidity increases and light scattering increases, which causes flare in the optical system when used as a filter.

  Further, it should be noted that the base plate 11 is made of a norbornene resin or a material containing a norbornene resin as the material of the base plate 11. The norbornene-based resin has an extremely low heat shrinkage rate, a light transmittance of 90% or more suitable for an optical filter, and a turbidity with a haze value of 0.5% or less. Furthermore, since norbornene-based resin has a glass transition temperature of 120 ° C. or higher and higher than the heating temperature of the base plate 11 in the vacuum deposition apparatus, it is possible to effectively prevent generation of wrinkles on the sheet surface. it can.

  In addition, by selecting the base plate 11 as a material formed into a sheet shape by casting in the norbornene-based resin or the material containing the norbornene-based resin, no stress is applied to the material itself at the time of molding. Like conventional PET (polyethylene terephthalate) or PEN (polyethylene naphthalate) material, it does not have anisotropic characteristics due to drawing and hardly causes birefringence. As a result, this optical filter (ND filter) was used. As an optical device equipped with a light amount adjusting device, it is possible to capture a clear image free from image blur and image spots.

Further, the remarkable point of the present invention is that, as shown in FIG. 1 (a), the optical filter (ND filter; the same shall apply hereinafter) 10 of the present invention has the light absorber layer 12 and the surface of the base plate 11. The dielectric layers 13 are alternately laminated, and the hard magnesium fluoride film (MgF ₂ ) 14 is coated on the uppermost layer, and finally the entire deposited layer is coated with the water-repellent film CX.

  The light absorber layer 12 is made of an alloy of 90% nickel and 10% chromium (chromel) as a vapor deposition material, and is formed as a colored vapor deposition film having light absorption characteristics. Therefore, the film is oxidized even when it is exposed to a high temperature for a long time in the vacuum deposition process or when the substrate plate 11 is exposed to the outside air several times in a series of deposition processes as will be described later. It is not easily affected and does not adversely affect optical properties.

  These deposited films are formed by a vacuum deposition method, and the thickness of each film is preferably about 0.5 to 1.0 μm. The light transmittance can be adjusted by the film thickness and the number of stacked layers. In addition to the chromel, a deposited film having characteristics similar to chromel can be formed from an alloy of nickel and chromium. In particular, it is desirable to use an alloy having a nickel ratio of 90% or more. Note that the deposited film may be formed by an ion plating method or a sputtering method other than the above-described vacuum deposition method.

  In addition, the dielectric layer 13 has an antireflection function, and can be reliably prevented from being reflected in the visible wavelength region by being alternately laminated with the light absorber layer 12. The filter surface is protected by a magnesium fluoride film 14 deposited on the uppermost surface. Furthermore, as described above, the water-repellent coating CX is a material that is resistant to oxidation as a vapor deposition film made of a nickel-chromium alloy as a vapor deposition material. Oxidation can be suppressed as much as possible by this coating treatment. The water-repellent coating CX is formed by vapor-depositing an organic resin compound such as an organic resin compound such as a fluorine resin, a silicone resin, or a polypropylene resin, or a copolymer containing these resin components.

Next, a method for manufacturing the above-described optical filter will be described.
In the present invention, the light absorber layer 12 and the dielectric layer 13 are formed on the base plate 11 by vacuum deposition. The vacuum deposition apparatus 15 shown in FIG. 2 includes a deposition tank 17 connected to a vacuum pump 16. A hemispherical turntable 18 is provided in the space above the vapor deposition tank 17, and a deposition target 19 is installed on the surface of the turntable 18. Above the turntable 18, a heater 20 for heating the deposition target 19 is disposed. On the other hand, a crucible 21 containing a vapor deposition material is provided on the bottom surface of the vapor deposition tank 17, and an electron gun 22 is provided in the vicinity thereof. Four recesses are provided on the upper surface of the crucible 21, and chromel 23, silicon dioxide 24, and magnesium fluoride 25, which are vapor deposition materials, are accommodated in the respective recesses in the form of granules.

  As shown in FIGS. 3A to 3D, the vapor deposition target 19 installed on the turntable 18 includes a plate-like fixing jig 26 that is directly fixed to the surface of the turntable 18, and this. The base plate 11 formed to be approximately the same size as the fixing jig 26 and a mask for sandwiching the base plate 11 with the base plate 11 being held at a predetermined appropriate distance L between the fixing jig 26. It is comprised with the board 27 (27a, 27b, 27c, 27d). Bolts 28 are erected on the fixing jig 26 at two opposite corners. On the other hand, the base plate 11 and the mask plate 27 are provided with insertion holes 29 and 30 for positioning at positions corresponding to the bolts 28, respectively. The mask plate 27 is provided with a large number of opening areas 31 in the vertical and horizontal directions that can be processed into the shape of an optical filter so that a large number of optical filters can be obtained from a single substrate plate 11.

  The base plate 11 and the mask plate 27 are placed on the fixing jig 26 in this order, and a nut (not shown) is fastened to the bolt 28 so that the mask plate 27 is spaced from the base plate 11 by a predetermined appropriate distance L. It is fixed in a state of being separated and held. As described above, the mask plate 27 is fixed to the base plate 11 while being held at a predetermined appropriate distance L, so that the vapor deposition film at the periphery of the opening area 31 diffuses outside, and vapor deposition is performed by this diffusion. Other than the side edge of the film, it has a uniform light transmittance, and the side edge part is a multistage density filter by forming a gradation region where the light transmittance gradually decreases and changes on each deposition plane. However, a part of the area between the multi-level density areas is a gradation filter, so that even though the gradation area is slightly reflected and reddish, the entire filter can obtain a uniform multi-level density light transmittance. In addition, it is possible to obtain an optical filter that hardly causes image spots due to diffraction phenomenon.

  As described above, when the dielectric layer 13 and the light absorber layer 12 are formed by vacuum deposition of the optical filter described in FIG. 1, the present invention provides a space having a predetermined interval between the base plate 11 and the mask plate 27. Is formed, and a vapor deposition process is performed, which will be described with reference to FIG.

  FIG. 9A shows the relationship between the base plate 11 and the mask plate 27 used in a normal vapor deposition method, and the two are in a state of complete contact. In this manner, in a state where the base plate 11 and the mask plate 27 are in close contact, a uniform thin film n is formed on the base plate. When the conventional step-like thin film shown in FIG. 7 is formed, the base plate and the mask plate are closely adhered as shown in FIG.

  In the present invention, as shown in FIG. 9 (b), a substantially parallel space L is formed between the base plate 11 and the mask plate 27. Then, in the film material constituting the light absorber layer 12 and the dielectric layer 13, molecular level fine particles scatter from the crucible 21 toward the base plate 11 and adhere to the plate surface. At this time, the film surface m1 having a substantially uniform thickness and the thickness in the vicinity of the masking region are gradually reduced by the space of the predetermined interval L, and an inclined boundary film surface m2 is formed. Thereby, the gradation layer shown in FIG. 1B is formed.

FIG. 10 shows the relationship between the distance L between the base plate 11 and the mask plate 27 and the gradation region G shown in FIG. When the film thickness is 300 nanometers (300 × 10 ⁻⁹ m) and the distance L is 0.5 mm, G = 0.4 mm. Similarly, when L = 1.0 mm, G = 0.8 mm, L = 2 A gradation region of G = 1.3 mm is formed when 0.0 mm, and G = 1.8 mm when L = 3.0 mm.

  After the deposition object 19 prepared as described above is set on the rotary table 18, the inside of the deposition tank 17 is sealed, and the vacuum pump 16 performs evacuation. At this time, the internal temperature is raised by the heater 20 at the same time, and the base plate 11 of the deposition target 19 is controlled to be heated to about 120 ° C. When the degree of vacuum inside the vapor deposition tank 17 reaches a predetermined level, the chromel 23 and the silicon dioxide 24 which are vapor deposition materials are alternately heated and melted by the electron beam 32 emitted from the electron gun 22 and vapor deposited on the vapor deposition target 19. Then, after repeating the deposition while replacing the mask plate 27 in the order shown in FIGS. 3A to 3C, the mask plate 27 is replaced and the magnesium fluoride 25 is heated and melted as shown in FIG. 3D. And deposit. The above-mentioned vapor deposition materials are laminated in the order as shown in FIG. 1 on the base plate 11 positioned on the deposition target 19 only in the region through the opening area 31 of the mask plate 27. Finally, the water-repellent coating material CX is applied to the vapor-deposited body 19.

Next, the process of forming a vapor deposition film on the base plate 11 by the above method will be described in detail below.
In the optical filter of the present invention, there are a case where a thin film is formed on one surface of a plastic sheet and a case where a thin film is formed on each of both surfaces.

[Step of forming a vapor deposition film on one surface of the substrate plate 11]
(1) The base plate 11 is fixed to a fixing jig 26 mounted in the vapor deposition tank. The base plate 11 is attached to the fixing jig 26, and the first mask plate 27a is attached at an interval L as shown in FIG. This mask plate 27a uses a mask plate having the largest opening area 31a. A plurality of the fixing jigs (hereinafter collectively referred to as vapor deposition body 19) are prepared.
(2) A predetermined number of vapor deposition bodies 19 are set on the turntable 18 of the vapor deposition tank 17 below.
(3) Formation of the first vapor deposition film.
The crucible 21 containing the chromel 23 is set at the vapor deposition position and vapor deposition is performed to form a chromel film (light absorber layer) 12. Next, the crucible 21 containing the silicon dioxide 24 is set at the vapor deposition position and the vapor deposition process is performed to form the silicon dioxide film (dielectric layer) 13.
After the deposition object 19 is taken out from the turntable 18 of the vapor deposition tank 17, the second mask plate 27 b is attached to the fixing jig 26. The second mask plate 27b is a mask plate having a second opening area 31b.
(4) Start of vapor deposition of the second vapor deposition layer.
The crucible 21 containing the chromel 23 is set at the vapor deposition position and vapor deposition is performed to form a chromel film (light absorber layer) 12. Next, the crucible 21 containing the silicon dioxide 24 is set at the vapor deposition position and the vapor deposition process is performed to form the silicon dioxide film (dielectric layer) 13.
After the deposition target 19 is taken out from the turntable 18 of the deposition tank 17, it is replaced with the third mask plate 27 c and attached to the fixing jig 26. The third mask plate 27c is a mask plate having a third opening area 31c.
(5) Start of vapor deposition of the third vapor deposition layer.
The crucible 21 containing the chromel 23 is set at the vapor deposition position and vapor deposition is performed to form a chromel film (light absorber layer) 12. Next, the crucible 21 containing the silicon dioxide 24 is set at the vapor deposition position and the vapor deposition process is performed to form the silicon dioxide film (dielectric layer) 13.
(6) Coating layer deposition.
The deposition object 19 is taken out from the turntable 18 of the vapor deposition tank 17 and set again after replacement with the first mask plate 27a. The crucible 21 is moved, the magnesium fluoride 25 is set at the vapor deposition position, and vapor deposition is performed to form the magnesium fluoride film 14. Next, the crucible 21 is moved, the water repellent coating CX is set at the vapor deposition position, and vapor deposition is performed to form a water repellent film.
(7) The object 19 is taken out from the turntable 18 of the vapor deposition tank 17.
(8) Formation of filter outer shape.
The object to be vapor-deposited 19 is hollowed into a predetermined shape with a press die.
(9) Drawing device assembly.
The optical filter 10 is attached to the first diaphragm blade 42, the first diaphragm blade 42 is attached to the base member 40 after the second diaphragm blade 43, and the diaphragm device 39 is assembled. At this time, the operation control of the vacuum pump 16, the heater 20, and the electron gun 22 is started in an optimum time such as a deposition time.

[Step of forming vapor deposition film on both surfaces of substrate plate 11]
(1) The base plate 11 is fixed to a fixing jig 26 mounted in the vapor deposition tank. The base plate 11 is attached to the fixing jig 26, and the first mask plate 27a is attached at an interval L as shown in FIG. This mask plate 27a uses a mask plate having the largest opening area 31a. A plurality of the fixing jigs (hereinafter collectively referred to as vapor deposition body 19) are prepared.
(2) A predetermined number of vapor deposition bodies 19 are set on the turntable 18 of the vapor deposition tank 17 below.
(3) Formation of the first vapor deposition film.
The crucible 21 containing the chromel 23 is set at the vapor deposition position and vapor deposition is performed to form a chromel film (light absorber layer) 12. Next, the crucible 21 containing the silicon dioxide 24 is set at the vapor deposition position and the vapor deposition process is performed to form the silicon dioxide film (dielectric layer) 13.
(4) After the deposition object 19 is taken out from the turntable 18 of the vapor deposition tank 17, the mounting surface of the base plate 11 is reversed, and after being replaced with the second mask plate 27b, it is mounted on the fixing jig 26 again. The second mask plate 27b is a mask plate having a second opening area 31b.
(5) Start of vapor deposition of the second vapor deposition layer.
The crucible 21 containing the chromel 23 is set at the vapor deposition position and vapor deposition is performed to form a chromel film (light absorber layer) 12. Next, the crucible 21 containing the silicon dioxide 24 is set at the vapor deposition position and the vapor deposition process is performed to form the silicon dioxide film (dielectric layer) 13.
(6) After the deposition object 19 is taken out from the turntable 18 of the vapor deposition tank 17, the mounting surface of the base plate 11 is reversed, replaced with the third mask plate 27 c, and mounted on the fixing jig 26 again. The third mask plate 27c is a mask plate having a third opening area 31c.
(7) Start of vapor deposition of the third vapor deposition layer.
The crucible 21 containing the chromel 23 is set at the vapor deposition position and vapor deposition is performed to form a chromel film (light absorber layer) 12. Next, the crucible 21 containing the silicon dioxide 24 is set at the vapor deposition position and the vapor deposition process is performed to form the silicon dioxide film (dielectric layer) 13. Thereafter, the mounting surface of the base plate 11 is reversed.
(8) Coating layer deposition.
The deposition object 19 is taken out from the turntable 18 of the vapor deposition tank 17 and set again after replacement with the first mask plate 27a. The crucible 21 is moved, the magnesium fluoride 25 is set at the vapor deposition position, and vapor deposition is performed to form the magnesium fluoride film 14.
(9) Next, the crucible 21 is moved, the water-repellent coating CX is set at the vapor deposition position, and vapor deposition is performed to form a water-repellent film.
(10) The deposition target 19 is taken out from the turntable 18 of the vapor deposition tank 17, the mounting surface of the base plate 11 is reversed, and then the mask plate 27a is set again. The crucible 21 is moved, the magnesium fluoride 25 is set at the vapor deposition position, and vapor deposition is performed to form the magnesium fluoride film 14.
(11) Next, the crucible 21 is moved, the water-repellent coating CX is set at the vapor deposition position, and vapor deposition is performed to form a water-repellent film.
(12) The object 19 is taken out from the turntable 18 of the vapor deposition tank 17.
(13) Formation of filter outer shape.
The object to be vapor-deposited 19 is punched into a predetermined shape with a press die.
(14) Assembling the throttle device.
The optical filter 10 is attached to the first diaphragm blade 42, the first diaphragm blade 42 is attached to the base member 40 after the second diaphragm blade 43, and the diaphragm device 39 is assembled. At this time, the operation control of the vacuum pump 16, the heater 20, and the electron gun 22 is started in an optimum time such as a deposition time.

  FIG. 4 shows the optical characteristics of the optical filter 10 obtained as described above. The vertical axis indicates the light transmittance in percentage, and the horizontal axis indicates the cross section of the deposited film of the optical filter 10. It is a graph which shows a relationship. According to FIG. 4, a three-stage density filter with light transmittances of approximately 0%, 30%, and 60% can be obtained, and a gradation region in which the light transmittance gradually decreases and changes is formed in the area portion of each curtain layer. is doing.

FIG. 5 shows a base plate 11 on which a large number of optical filters having three regions having different light transmittances are formed. As shown in FIG. 5, the portion where the deposited film is formed is punched out by pressing as shown in the drawing, and at the same time, the two optical filters 10 (10a, 10b) are completed. As shown in FIG. 4, the optical filter 10 has three regions T ₁ , T ₂ , T ₃ having different light transmittances, a substrate plate 11 and a gradation region G in which the light transmittance is successively reduced and changed between the regions. ₁ , G ₂ , and G ₃ are formed.

For example, three types of mask plates 27a, 27b, and 27c as shown in FIGS. 3A to 3C are used, and the mask plates 27a, 27b, and 27c are respectively set at predetermined intervals. It can be formed by being separated from the plate 11 and fixed to the fixing jig 26. That is, the first mask plate 27a is provided with opening areas 31a corresponding to the _three regions T ₁ , T ₂ , T ₃ , and the second mask plate 27b has the second region T ₂ and the third region T _1. open area 31b corresponding is provided, the third mask plate 27c open area 31c is provided corresponding to the third region T _1.

Then, the entire regions T ₁ , T ₂ , T ₃ are deposited in the _first deposition process using the first mask plate 27a, and the second deposition process is performed in the second deposition process using the second mask plate 27b. And the third regions T ₂ and T ₁ are vapor-deposited, and only the third region T ₁ is vapor-deposited in the third vapor-deposition process using the third mask plate 27c, so that the number of vapor-deposited films in the respective regions is increased. As a result, a plurality of regions having different light transmittances in stages can be formed. In this vapor deposition process, the mask plates 27a, 27b, and 27c are separated from the base plate 11 at predetermined intervals, so that the vapor deposition film diffuses between the gaps, and the light transmittance gradually decreases. Regions G ₁ , G ₂ and G ₃ are formed.

  As described above, when manufacturing an optical filter having regions with different light transmittances in stages, the above-described three types of mask plates 27a, 27b, and 27c need to be replaced during the vapor deposition process. Each time the vapor deposition tank 17 is opened and the vapor deposition target 19 is taken out and the mask plate is exchanged, it is exposed to the outside air. However, as described above, the light absorber layer 12 is not easily oxidized. The deposited film is hardly subjected to oxidation. Therefore, it hardly affects the optical characteristics of the optical filter, and exhibits the same characteristics as shown in FIG.

  FIG. 6 shows an example of an aperture device in which the above-described optical filter 10 is incorporated. An aperture device for exposure adjustment mounted on a small video camera, digital camera, or the like will be described. This diaphragm device includes a base member 40, an arm 41, a first diaphragm blade 42, a second diaphragm blade 43, a pair of magnets 44, a conductive coil 45 for excitation including a drive coil and a brake coil, and a drive coil and a brake coil externally. An electrode terminal 46 for electrical connection with the apparatus, and a magnetic sensor (not shown) for capturing the moving position of the magnet and detecting the aperture of the diaphragm, etc. The exposure hole 47 is provided, and guide pins 48 for guiding the slide of the diaphragm blades 42 and 43 are provided at several positions on both the left and right sides.

  The first diaphragm blade 42 and the second diaphragm blade 43 are formed with a long slot 49 into which a guide pin 48 is inserted and a diaphragm opening area 50 having substantially the same shape as the exposure hole 47. The optical filter 10 of the present invention is slidably disposed so as to cover a part of the aperture opening area 50. The amount of light passing through the exposure hole 47 can be adjusted by sliding the first diaphragm blade 42 and the second diaphragm blade 43 relative to each other, and the optical filter 10 is slid toward the exposure hole 47 when the aperture is small. By doing so, the light transmittance of the exposure hole 47 can be finely adjusted.

It is sectional drawing which shows the structure of the ND filter which concerns on this invention, and shows whole sectional drawing. It is sectional drawing which shows the structure of the ND filter concerning this invention, and shows an expanded sectional view. It is a schematic diagram of the vacuum evaporation system for manufacturing ND filter of the present invention. It is a perspective view which shows the positional relationship of the base material plate and mask board with respect to a fixing jig. It is a perspective view which shows the positional relationship of the base material plate and mask board with respect to a fixing jig. It is a perspective view which shows the positional relationship of the base material plate and mask board with respect to a fixing jig. It is a perspective view which shows the positional relationship of the base material plate and mask board with respect to a fixing jig. It is a graph which shows the optical characteristic of the optical filter which concerns on this invention. It is a perspective view which shows the optical filter provided with the area | region where light transmittance differs, and the base material plate in which many this optical filter was formed. It is a perspective view which shows one Example of the aperture_diaphragm | restriction apparatus incorporating the optical filter which concerns on this invention. It is sectional drawing which shows the structure of the conventional optical filter. It is sectional drawing which shows the structure of the conventional optical filter different from FIG. It is explanatory drawing which shows the vapor deposition method of an optical filter, (a) shows the relationship between a normal base-material plate and a mask board, (b) shows the relationship between the base-material plate concerning this invention, and a mask board. It is explanatory drawing which shows the relationship of the space | interval L of a base material plate and a mask board.

Explanation of symbols

10 Optical filter (ND filter)
11 substrate plate 12 light absorber film (light absorber layer)
13 Transparent dielectric film (dielectric layer)
14 Magnesium fluoride film CX Water-repellent coating 15 Vacuum deposition apparatus 17 Deposition tank 19 Deposition body 26 Fixing jig 27 Mask plate (27a, 27b, 27c, 27d)
31 Opening area

Claims (7)

An optical filter manufacturing method for forming a deposited film having optical characteristics on a base plate made of a light-transmitting material,
Place the crucible (material storage part) that stores the vapor deposition material in a predetermined position in the vacuum evaporation chamber (tank) and the base plate,
A first mask plate is formed on the base plate, and the base plate and the mask plate are substantially parallel to each other to form a space having a predetermined interval, and a first deposition process is performed. A second vapor deposition process is performed by forming a space at a predetermined interval between the mask plate and the base plate, and a plurality of coating layers having different thicknesses are formed on the base plate. An optical filter manufacturing method characterized by the above.   In the substantially parallel and predetermined space formed between the base plate and the mask plate in the first and second vapor deposition processes, the light transmittance gradually changes at the edge portion of the masking area of the mask plate. The method for manufacturing an optical filter according to claim 1, wherein the distance is set to form a gradation area.   Each of the first mask plate and the second mask plate is configured such that a masking region formed on each of the first mask plate and the second mask plate forms a plurality of coating layers having different light transmittances on the base plate stepwise. The optical filter according to claim 1, wherein a gradation layer having a uniform thickness and a uniform light transmittance is formed, and a gradation layer in which the light transmittance gradually changes is formed at the boundary of each coating layer. Manufacturing method. A base plate made of a translucent material;
A vapor-deposited film formed on the surface of the base plate, and
The deposited film is formed of a plurality of coating layers having different light transmittances in stages,
Each coating layer has a uniform light transmittance with a substantially uniform thickness,
An optical filter characterized in that the boundary between adjacent coating layers is connected by a gradation layer in which light transmittance gradually changes.   The gradation layer is formed by forming a substantially parallel space at a predetermined interval between the base plate and the mask plate and performing a vacuum evaporation process when forming the vapor deposition film layer on the surface of the base plate. The optical filter according to claim 4.   The optical filter according to claim 4, wherein the base plate is formed from a norbornene-based resin material in a sheet shape by casting. A main plate having an exposed opening;
A light amount adjusting means that is movably supported by the base plate and opens and closes the exposure opening to adjust the light amount;
In the light amount adjusting device comprising the light amount adjusting means and an ND filter that advances and retreats with respect to the exposure opening,
The ND filter is composed of a base plate made of a plastic sheet and a deposition material formed on the surface of the base plate,
The vapor deposition material is formed in a film layer that is stacked stepwise on the surface of the base plate and divided into a plurality of regions,
Each region has a uniform light transmittance, and each region is a deposited film having a different light transmittance,
A light amount adjusting device characterized in that the side end face of each vapor deposition film is formed with a gradation region in which the light transmittance is decreased and changed sequentially on each vapor deposition plane.

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