JP2017207659A - Optical filter and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical filter and the like, having a structure for preventing foreign matter from intruding through a circumferential cavity communicating with a central cavity and the outside.SOLUTION: An etalon filter 10 comprises: a first light transmission body 11 including a first outside surface 11a and a first inside surface 11b; a second light transmission body 12 including a second outside surface 12a and a second inside surface 12b; metal layers 131-134 held between a circumferential side of the first inside surface 11b and a circumferential side of the second inside surface 12b, and bonding the first light transmission body 11 and the second light transmission body 12; a central cavity 14 between a center side of the first inside surface 11b and a center side of the second inside surface 12b; circumferential cavities 151-154 held between the circumferential side of the first inside surface 11b and the circumferential side of the second inside surface 12b, and communicating with the central cavity 14 and the outside; and translucent resin 23 filling the circumferential cavities 151-154 and the central cavity 14.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an optical filter that uses multiple interference between two opposing reflecting surfaces, and a method for manufacturing the same. In this specification, an etalon filter is taken as an example of such an optical filter.

  The etalon filter is used, for example, as a component for monitoring whether or not an optical wavelength is stably oscillated in a wavelength variable laser module indispensable for a large-capacity optical transmission system. 6 [A] is a front view of the related art 1 showing an etalon filter (see, for example, Patent Document 1) with a part cut away, and FIG. 6 [B] is a sectional view taken along line VIb-VIb in FIG. 6 [A]. 7 is a partially enlarged view of FIG. 6B. Hereinafter, description will be given based on these drawings.

  The etalon filter 80 of Related Art 1 includes a first light transmitting body 81 having a first outer surface 81a and a first inner surface 81b, and a second light transmitting body 82 having a second outer surface 82a and a second inner surface 82b. A metal layer 831 to 834 that is sandwiched between the peripheral side of the first inner side surface 81b and the peripheral side of the second inner side surface 82b and joins the first light transmitting body 81 and the second light transmitting body 82; A central gap 84 sandwiched between the central side of the side surface 81b and the central side of the second inner side surface 82b, and a central gap 84 sandwiched between the peripheral side of the first inner side surface 81b and the peripheral side of the second inner side surface 82b. Basically, peripheral gaps 851 to 854 communicating with the outside are provided.

  The first outer surface 81a is covered with the first reflective film 91a, the second outer surface 82a is covered with the second reflective film 92a, the first inner side surface 81b is covered with the first antireflection film 91b, and the second The inner side surface 82b is covered with a second antireflection film 92b. The laser beam L is incident from the first outer surface 81a, passes through the central gap 84, and is emitted from the second outer surface 82a. At this time, the laser beam L causes multiple interference between the first outer surface 81a and the second outer surface 82a, thereby obtaining a filter characteristic in which the transmittance periodically changes with respect to the optical frequency.

Japanese Patent Laying-Open No. 2015-132781

  One reason for the presence of the peripheral voids 851 to 854 is to use a metal mask when forming the metal layers 831 to 834. That is, the regions covered with the metal mask when the metal layers 831 to 834 are formed are the central gap 84 and the peripheral gaps 851 to 854. At this time, one circular central part of the metal mask corresponds to the central gap 84, and four rectangular peripheral parts supporting the central part correspond to the peripheral gaps 851 to 854.

  However, since the peripheral voids 851 to 854 communicate with the outside, foreign matter 931 to 934 may enter from the outside. In particular, when two substrates bonded through the metal layers 831 to 834 are cut by dicing to obtain a large number of etalon filters 80, oil and cleaning liquid used in the cutting are the foreign matters 931 to 934 as the peripheral gaps 851 to 851. From 854, it enters the central gap 84. As a result, the foreign matters 931 to 934 obstruct the progress of the laser light L, which adversely affects the characteristics and reliability of the etalon filter 80.

  Therefore, an object of the present invention is to provide an optical filter having a structure in which foreign matter does not enter from a peripheral gap communicating with a central gap and the outside, and a method for manufacturing the same.

The optical filter according to the present invention is:
A first light-transmitting body having a first outer surface as an incident surface and a first inner surface on the rear surface;
A second light-transmitting body having a second outer surface serving as an output surface and a second inner surface on the rear surface;
A metal layer sandwiched between the peripheral side of the first inner surface and the peripheral side of the second inner surface, and joining the first light transmitting body and the second light transmitting body;
A central gap sandwiched between the center side of the first inner surface and the center side of the second inner surface;
A peripheral gap sandwiched between a peripheral side of the first inner side and a peripheral side of the second inner side, and communicating with the central gap and the outside;
A translucent resin filled in the peripheral gap and the central gap;
It is equipped with.

The method for producing an optical filter according to the present invention includes:
A method for producing an optical filter according to the present invention, comprising:
One surface of the first substrate serving as the plurality of first light transmitting bodies and one surface of the second substrate serving as the plurality of second light transmitting bodies are covered with a metal mask, and are not covered with the metal mask. Forming a metal film to be the metal layer only in
Forming the metal layer, the central gap and the peripheral gap by abutting and joining the metal film formed on the first substrate and the metal film formed on the second substrate;
Solidifying the translucent resin after filling the central gap and the peripheral gap with the liquid translucent resin;
A step of obtaining a plurality of the optical filters by cutting the first substrate and the second substrate in which the light-transmitting resin is filled and solidified into the central space and the peripheral space;
including.

  According to the optical filter of the present invention, since the peripheral gap and the central gap are filled with the light-transmitting resin, it is possible to prevent foreign matter from entering the central gap from the outside through the peripheral gap. Can be improved.

  According to the method for manufacturing an optical filter according to the present invention, when the bonded first substrate and second substrate are cut into a plurality of pieces, the peripheral gap and the central gap are filled with a light-transmitting resin, so that a foreign matter is obtained. Can be prevented from entering the central gap from the outside through the peripheral gap, so that the yield and reliability can be improved.

The etalon filter of Embodiment 1 is shown, FIG. 1 [A] is the front view which notched one part, FIG. 1 [B] is the Ib-Ib sectional view taken on the line in FIG. 1 [A]. FIG. 2 is a partially enlarged view of FIG. 1 is a perspective view illustrating an etalon filter according to Embodiment 1. FIG. It is a top view which shows the manufacturing method of Embodiment 2, and a process progresses in order of FIG. 4 [A] and FIG. 4 [B]. It is the schematic which shows the manufacturing method of Embodiment 2, FIG.5 [A], FIG.5 [B], FIG.5 [C], FIG.5 [D], FIG.5 [E], FIG.5 [F] in order. The process proceeds. FIG. 6A is a front view with a part cut away, and FIG. 6B is a cross-sectional view taken along the line VIb-VIb in FIG. 6A. FIG. 7 is a partially enlarged view of FIG.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention (hereinafter referred to as “embodiments”) will be described with reference to the accompanying drawings. In the present specification and drawings, the same reference numerals are used for substantially the same components. Moreover, since the shape drawn on drawing is drawn so that those skilled in the art can understand easily, it does not necessarily correspond with an actual dimension and ratio.

  1A is a partially cutaway front view showing the etalon filter of Embodiment 1, FIG. 1B is a sectional view taken along line Ib-Ib in FIG. 1A, and FIG. 2 is FIG. 1B. FIG. 3 is a perspective view showing the etalon filter of the first embodiment. Hereinafter, description will be given based on these drawings.

  The etalon filter 10 according to the first embodiment includes a first translucent body 11 having a first outer surface 11a serving as an incident surface and a first inner surface 11b serving as a rear surface thereof, and a second outer surface 12a serving as an output surface and the rear surface thereof. The second translucent body 12 having the second inner side surface 12b, and the first translucent body 11 and the second translucent body are sandwiched between the peripheral side of the first inner side surface 11b and the peripheral side of the second inner side surface 12b. 12, the central gap 14 sandwiched between the central side of the first inner side surface 11 b and the central side of the second inner side surface 12 b, the peripheral side of the first inner side surface 11 b, and the second side The peripheral gaps 151 to 154 sandwiched between the peripheral side of the inner side surface 12b and communicated with the central gap 14 and the outside, and the translucent resin 23 filled with the peripheral gaps 151 to 154 and the central gap 14 are basically provided. I have.

  The first outer surface 11a is covered with the first reflective film 21a, the second outer surface 12a is covered with the second reflective film 22a, the first inner surface 11b is covered with the first antireflection film 21b, and the second The inner side surface 12b is covered with a second antireflection film 22b. The laser beam L is incident from the first outer surface 11a, passes through the central gap 14, and is emitted from the second outer surface 12a. At this time, the laser beam L causes multiple interference between the first outer surface 11a and the second outer surface 12a, thereby obtaining a filter characteristic in which the transmittance periodically changes with respect to the optical frequency. In FIG. 3, only the metal layers 131 to 134, the central gap 14, and the peripheral gaps 151 to 154 of the structure inside the etalon filter 10 are indicated by broken lines.

  Next, the configuration of the etalon filter 10 will be described in more detail.

  The etalon filter 10 has a rectangular parallelepiped shape as a whole. The rectangular parallelepiped mentioned here includes not only a cube but also a parallelepiped that can be handled substantially as a rectangular parallelepiped. When viewed from the front, the first outer surface 11a and the second outer surface 12a are square, the central gap 14 through which the laser light L is transmitted is circular, and the peripheral gaps 151 to 154 around the central gap 14 are rectangular. In addition, there are four metal layers 131 to 134 for bonding around the central gap 14. Each boundary of the metal layers 131 to 134 is a peripheral gap 151 to 154. The peripheral gaps 151 to 154 are holding marks of the metal mask used when the metal layers 131 to 134 are formed.

  The translucent resin 23 that fills the central gap 14 and the peripheral gaps 151 to 154 is commercially available as a liquid optical resin, and is preferably solidified by light or heat. Such optical resins are classified into epoxy-based, acrylic-based, vinyl-based, etc. depending on the main component, and are used for various applications such as optical path bonding adhesives and optical component sealing materials. The refractive index of the optical resin can be selected as a desired value by adjusting the components.

The first light transmitting body 11 is made of a material having a positive change in optical path length (a characteristic index is positive) with respect to a change in temperature. The second light-transmitting body 12 is made of a material whose change in the optical path length with respect to a change in temperature is negative (characteristic index is negative). In FIG. 1, a material having a positive characteristic index is arranged on the incident side, and a material having a negative characteristic index is arranged on the outgoing side. On the contrary, a material having a negative characteristic index is arranged on the incident side. A material having a positive characteristic index may be arranged on the emission side. An example of the material having a positive characteristic index is quartz (SiO ₂ ). Examples of the material having a negative characteristic index include strontium titanate (SrTiO ₃ ). As described above, the first light-transmitting body 11 and the second light-transmitting body 12 are bonded to form the etalon filter 10, so that the optical path length of the etalon filter 10 becomes constant with respect to the temperature change.

  The metal layers 131 to 134 include a metal film attached to the first inner side surface 11b (first antireflection film 21b) of the first light transmitting body 11 by sputtering and the second inner side surface 12b ( A metal film attached to the second antireflection film 22b) by sputtering or the like is abutted and joined. At the time of this bonding, an atomic diffusion bonding method is used in which sufficient bonding strength can be obtained even with a thin metal film. As a result, the metal layers 131 to 134 having sufficient bonding strength despite the thin film are formed.

  Each of these metal films is formed by laminating chromium (Cr) or tantalum (Ta) and gold (Au) from the first antireflection film 21b side or the second antireflection film 22b side, for example. The pair of metal films are bonded to each other by bonding Au to each other by atomic diffusion. In this way, the bonding between Cr and Ta, which strengthens the bonding between the first antireflection film 21b and the second antireflection film 22b (or the first light transmitting body 11 and the second light transmitting body 12), and the metal is bonded. The first light-transmitting body 11 and the second light-transmitting body 12 are preferably fixed by using a laminated structure with Au to be strengthened.

  The first antireflection film 21b suppresses reflection at the interface between the first light transmitting body 11 and the light transmitting resin 23, and the second antireflection film 22b reflects at the interface between the second light transmitting body 12 and the light transmitting resin 23. Suppress. The refractive index of the first antireflection film 21b is the geometric average of the refractive indexes of the first light transmitting body 11 and the light transmitting resin 23 located on both sides thereof, and the refractive index of the second antireflection film 22b is located on both sides thereof. It is preferable to match or approximate the geometric average of the refractive indexes of the second light transmitting body 12 and the light transmitting resin 23. When the refractive index of the translucent resin 23 is equal to the refractive index of the first translucent body 11, the first antireflection film 21 b can be omitted, and the refractive index of the translucent resin 23 is the refractive index of the second translucent body 12. , The second antireflection film 22b can be omitted.

The first antireflection film 21b and the second antireflection film 22b are, for example, a laminate of a plurality of thin films having different refractive indexes. The materials, the number of layers, and the thickness of the plurality of thin films are designed so that desired optical characteristics (for example, reflectance) can be obtained. The material of each thin film is, for example, a dielectric, and the dielectric is, for example, silicon dioxide (SiO ₂ ), titanium dioxide (TiO ₂ ), or tantalum pentoxide (Ta ₂ O ₅ ). The number of laminated thin films is, for example, 10 or less. The plurality of thin films are fixed in close contact with each other, the first antireflection film 21b is fixed in close contact with the first light transmitting body 11, and the second antireflection film 22b is fixed in close contact with the second light transmitting body 12. ing.

The first reflective film 21a and the second reflective film 22a are, for example, a laminate of a plurality of thin films having different refractive indexes. The materials, the number of layers, and the thickness of the plurality of thin films are designed so that desired optical characteristics (for example, reflectance) can be obtained. The material of each thin film is, for example, a dielectric, and the dielectric is, for example, silicon dioxide (SiO ₂ ), titanium dioxide (TiO ₂ ), or tantalum pentoxide (Ta ₂ O ₅ ). The number of laminated thin films is, for example, 10 or less. The plurality of thin films are fixed in close contact with each other, the first reflective film 21a is fixed in close contact with the first light transmitting body 11, and the second reflective film 22a is fixed in close contact with the second light transmitting body 12. .

  Next, the operation and effect of the etalon filter 10 will be described.

  According to the etalon filter 10, the peripheral gaps 151 to 154 and the central gap 14 are filled with the translucent resin 23, thereby preventing foreign matter from entering the central gap 14 from the outside through the peripheral gaps 151 to 154. Therefore, the yield and reliability can be improved.

  When the translucent resin 23 is an adhesive, the bonding force of the translucent resin 23 is added to the bonding force of the metal layers 131 to 134 so that the first translucent body 11 and the second translucent body 12 are bonded. The bonding strength can be improved. Moreover, since the thickness of the central gap 14 is determined by the film thickness of the metal layers 131 to 134, the first transparent body 11 and the second transparent body 12 are bonded using only the adhesive of the transparent resin 23. For example, variation in FSR (Free Spectral Range) characteristics can be suppressed.

  When the refractive index of the translucent resin 23 is equal to at least one of the first translucent body 11 and the second translucent body 12, at least one of the first antireflection film 21b and the second antireflection film 22b is omitted. Therefore, the etalon filter 10 can be easily manufactured and the manufacturing cost can be reduced.

  Next, an example of a method for manufacturing the etalon filter 10 will be described as a manufacturing method of the second embodiment. FIG. 4 is a plan view showing the manufacturing method of the second embodiment, and the process proceeds in the order of FIG. 4A and FIG. 4B. FIG. 5 is a schematic diagram illustrating a manufacturing method according to the second embodiment. FIG. 5 [A], FIG. 5 [B], FIG. 5 [C], FIG. 5 [D], FIG. The process proceeds in the order of F]. Hereinafter, description will be made by adding FIGS. 4 and 5 to FIGS.

  The manufacturing method of the second embodiment is a method of manufacturing the etalon filter 10 and includes the following steps.

  One surface 31 b of the first substrate 31 to be the plurality of first light transmitting bodies 11 and one surface 32 b of the second substrate 32 to be the plurality of second light transmitting bodies 12 are covered with the metal mask 40. 1st process of forming the metal films 51 and 52 used as the metal layers 131-134 only in the area | region which is not covered (FIG. 4 [A]-FIG. 4 [B]).

  The metal film 51 formed on the first substrate 31 and the metal film 52 formed on the second substrate 32 are abutted and joined to form the metal layers 131 to 134, the central gap 14 and the peripheral gaps 151 to 154. Second step (arrow in FIG. 4B).

  A third step of solidifying the translucent resin 23 after filling the central void 14 and the peripheral voids 151 to 154 with the liquid translucent resin 23 (FIGS. 5A to 5E).

  A fourth step of obtaining a plurality of etalon filters 10 by cutting the first substrate 31 and the second substrate 32 in which the central gap 14 and the peripheral gaps 151 to 154 are filled and solidified with the transparent resin 23 into a plurality of pieces (FIG. 5). [F]).

  Next, the first to fourth steps will be described in more detail. 4 and 5 show a process of simultaneously manufacturing a plurality of etalon filters 10 (three in the illustrated example, a total of nine in the vertical direction and three in the horizontal direction).

  <First Step> First, as shown in FIG. 4A, one surface 31b of the first substrate 31 and one surface 32b of the second substrate 32 are each covered with a metal mask 40. Then, as shown in FIG. 4B, the metal films 51 and 52 are only formed in the regions not covered with the metal mask 40 on the one surface 31b of the first substrate 31 and the one surface 32b of the second substrate 32, respectively. Form. For the formation, vacuum film forming methods such as vapor deposition and sputtering are suitable.

  At this time, the first substrate 31 and the second substrate 32 have an area where a plurality of etalon filters 10 can be formed, and those having already been coated with thickness polishing, an antireflection film, a reflection film, or the like are used. . The metal mask 40 is made of, for example, a thin stainless plate, and has a circular central portion 44, rectangular peripheral portions 451 to 454 that support the central portion 44, and a rectangular frame-shaped frame portion that holds the outer periphery of the metal mask 40. 46. One etalon filter has one central portion 44 and four peripheral portions 451-454. Thus, by using the metal mask 40, the patterns of the metal films 51 and 52 can be easily formed without using a complicated technique such as photolithography.

  <Second Step> Subsequent to the first step, as shown by the arrow in FIG. 4B, the metal film 51 and the metal film 52 are butted and joined. Thereafter, the metal films 51 and 52 are pressed through the first substrate 31 and the second substrate 32 so that the bonding surfaces are in close contact with each other. At the same time, the metal films 51 and 52 may be heated via the first substrate 31 and the second substrate 32 in order to promote atomic diffusion between metals. The heating temperature is preferably from room temperature to about 250 [° C.].

  <Third Step> Subsequent to the second step, as shown in FIGS. 5A to 5D, a liquid translucent resin 23 is filled into the central gap 14 and the peripheral gaps 151 to 154. Then, as shown in FIG. 5E, the translucent resin 23 is solidified. Here, what bonded the 1st board | substrate 31 and the 2nd board | substrate 32 at the 2nd process will be called the bonding board | substrate 33, and the filling process and the solidification process of the translucent resin 23 are demonstrated. 5A to 5E, the structures in the bonded substrate 33 (that is, the metal layers 131 to 134, the central gap 14, and the peripheral gaps 151 to 154) are not shown.

  First, as shown in FIG. 5A, among the four sides of the quadrangular bonded substrate 33, three sides are sealed with a sealing material 34, and the remaining one side is used as an injection port 35. Then, the bonded substrate 33 and the container 62 containing the liquid translucent resin 23 (ultraviolet solidification type) are placed in the vacuum chamber 61. Subsequently, the air 63 in the vacuum chamber 61 is discharged to make the inside of the vacuum chamber 61 have a predetermined degree of vacuum. Subsequently, the injection port 35 of the bonded substrate 33 is immersed in the liquid translucent resin 23 in the container 62 as shown in FIG. Subsequently, as shown in FIG. 5C, the air 63 is returned to the atmospheric pressure by introducing the air 63 into the vacuum chamber 61. Then, since the inside of the bonded substrate 33 is depressurized, the liquid translucent resin 23 is sucked into the bonded substrate 33. Subsequently, as shown in FIG. 5D, when the inside of the bonded substrate 33 is filled with the liquid transparent resin 23, the injection port 35 of the bonded substrate 33 is moved from the liquid transparent resin 23 in the container 62. Pull up. In order to shorten the filling time of the translucent resin 23, the translucent resin 23 having as low a viscosity as possible may be used.

  Subsequently, as shown in FIG. 5E, the ultraviolet lamp 65 irradiates the bonded substrate 33 taken out from the vacuum chamber 61 with ultraviolet rays 65. Thereby, the liquid translucent resin 23 in the bonded substrate 33 is solidified.

  <Fourth Step> Subsequent to the third step, as shown in FIG. 5F, a plurality of etalon filters 10 are obtained by cutting the bonded substrate 33 into a plurality of pieces by dicing.

  Next, the operation and effect of the manufacturing method of the second embodiment will be described. According to the manufacturing method of the second embodiment, the peripheral gaps 151 to 154 and the central gap 14 are filled with the transparent resin 23 when the bonded first substrate 31 and second substrate 32 are cut into a plurality of pieces. As a result, foreign substances such as oil and cleaning liquid used for cutting can be prevented from entering the central gap 14 from the outside through the peripheral gaps 151 to 154, so that the yield and reliability can be improved. Other configurations, operations, and effects of the second embodiment are the same as those of the first embodiment.

  Although the present invention has been described with reference to the above embodiments, the present invention is not limited to the above embodiments. For example, in each of the above-described embodiments, the case where the peripheral gap is generated by using the metal mask has been illustrated. However, the present invention is not limited thereto, and the present invention can be applied to the case where the peripheral gap is intentionally formed. Various changes that can be understood by those skilled in the art can be made to the configuration and details of the present invention. Further, the present invention includes a combination of some or all of the configurations of the above-described embodiments as appropriate.

  INDUSTRIAL APPLICABILITY The present invention is applicable to any optical filter using multiple interference between two opposing reflecting surfaces, such as a solid type or air gap type etalon filter or an etalon filter made of a transparent member other than quartz. Is possible.

<Embodiment 1>
10 Etalon filter (optical filter)
DESCRIPTION OF SYMBOLS 11 1st light transmission body 11a 1st outer surface 11b 1st inner surface 12 2nd light transmission body 12a 2nd outer surface 12b 2nd inner surface 131,132,133,134 Metal layer 14 Central space | gap 151,152,153 154 Peripheral gap 21a First reflection film 22a Second reflection film 21b First antireflection film 22b Second antireflection film 23 Translucent resin L Laser beam (optical axis)
<Embodiment 2>
31 First substrate 31b One side 32 Second substrate 32b One side 33 Bonded substrate 34 Sealing material 35 Inlet 40 Metal mask 44 Center part 451, 452, 453, 454 Peripheral part 46 Frame part 51, 52 Metal film 61 Vacuum chamber 62 Container 63 Air 64 UV lamp 65 UV <Related technology 1>
80 Etalon filter 81 First light transmitting member 81a First outer surface 81b First inner surface 82 Second light transmitting member 82a Second outer surface 82b Second inner surface 831, 832, 833, 834 Metal layer 84 Central gap 851, 852 , 853, 854 Peripheral gap 91a First reflection film 92a Second reflection film 91b First antireflection film 92b Second antireflection film 931, 932, 933, 934

Claims (4)

A first light-transmitting body having a first outer surface as an incident surface and a first inner surface on the rear surface;
A second light-transmitting body having a second outer surface serving as an output surface and a second inner surface on the rear surface;
A metal layer sandwiched between the peripheral side of the first inner surface and the peripheral side of the second inner surface, and joining the first light transmitting body and the second light transmitting body;
A central gap sandwiched between the center side of the first inner surface and the center side of the second inner surface;
A peripheral gap sandwiched between a peripheral side of the first inner side and a peripheral side of the second inner side, and communicating with the central gap and the outside;
A translucent resin filled in the peripheral gap and the central gap;
Optical filter with The translucent resin is an adhesive;
The optical filter according to claim 1. The refractive index of the translucent resin is equal to the refractive index of at least one of the first translucent body and the second translucent body.
The optical filter according to claim 1. A method for producing the optical filter according to any one of claims 1 to 3,
A region in which one surface of the first substrate serving as the plurality of first light transmitting bodies and one surface of the second substrate serving as the plurality of second light transmitting bodies are covered with a metal mask, and are not covered with the metal mask. Forming a metal film to be the metal layer only in
Forming the metal layer, the central gap and the peripheral gap by abutting and joining the metal film formed on the first substrate and the metal film formed on the second substrate;
Solidifying the translucent resin after filling the central gap and the peripheral gap with the liquid translucent resin;
A step of obtaining a plurality of the optical filters by cutting the first substrate and the second substrate in which the light-transmitting resin is filled and solidified into the central space and the peripheral space;
The manufacturing method of the optical filter containing this.

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