Patent Publication Number: US-2015062708-A1

Title: Optical device, optical module, electronic apparatus, optical housing, and method of manufacturing optical housing

Description:
BACKGROUND 
     1. Technical Field 
     The present invention relates to an optical device, an optical module, an electronic apparatus, an optical housing, and a method of manufacturing an optical housing. 
     2. Related Art 
     An optical device in which an optical element, such as an interference filter or a mirror device, is housed in a hermetically sealed housing is known (for example, refer to JP-A-2005-93675). 
     The optical device disclosed in JP-A-2005-93675 includes a container-like substrate, a metal frame body that blocks an opening of the substrate and has an opening for light transmission, and a glass member that blocks the opening of the metal frame body. A bonding material of low melting point glass is provided in a region of the metal frame body facing the glass member, and the metal frame body and the glass member are bonded to each other by the bonding material. In a region of the metal frame body not facing the glass member, a metal layer for anti-corrosion of the metal frame body is provided using a plating method. 
     Incidentally, in order to ensure satisfactory bonding strength and airtightness by bonding the glass member and the metal frame body to each other through the low melting point glass, it is preferable to form a fillet of low melting point glass along the outer periphery of the glass member. 
     On the other hand, in JP-A-2005-93675, the bonding material is provided only in a region of the metal frame body surface facing the glass member. For this reason, there is a problem in that bonding strength and airtightness are not sufficient. 
     In addition, in JP-A-2005-93675, when a fillet is formed, a metal layer is formed in a region of the metal frame body not facing the glass member using the plating method. Accordingly, a fillet of low melting point glass is formed on the metal layer. In this case, due to the difference in thermal expansion coefficient between the metal frame body and the metal layer according to the plating method, cracking occurs in the metal layer according to the plating method. The low melting point glass also cracks due to the cracking of the metal layer. In this case, there is a problem in that the bonding strength or airtightness between the glass member and the metal frame body is reduced. 
     SUMMARY 
     An advantage of some aspects of the invention is to provide an optical device with high bonding strength and airtightness, an optical module, an electronic apparatus, an optical housing, and a method of manufacturing an optical housing. 
     An aspect of the invention is directed to an optical device including: an optical element; a first member that is disposed so as to cover the optical element and has an opening; a second member that is disposed so as to face the first member with the optical element interposed therebetween and that houses the optical element together with the first member; a third member that covers the opening so as to transmit light; and a metal layer that covers the first member. When a side of the opening is viewed from the third member, the metal layer does not overlap the third member on a side of the first member facing the third member. 
     The optical device according to the aspect of the invention includes an optical element having a light receiving surface or a light emitting surface, a first member having an opening, a second member that forms a receiving space capable of housing the optical element together with the first member, a light transmissive member that is bonded to the first member so as to cover the opening, and a metal layer provided on the first member, and the metal layer is provided at a position separated from the outer peripheral edge of the light transmissive member by a predetermined distance toward a side away from the opening in plan view when viewed from the normal direction with respect to the opening surface of the opening. 
     In the aspect of the invention, the light transmissive member is bonded to the first member. In addition, in the first member, the metal layer is provided so as to be separated from the outer peripheral edge of the light transmissive member outward by the predetermined distance. The metal layer can be formed using a plating method. That is, the metal layer is not provided in a region (hereinafter, referred to as a first region in some cases) from a position, which is away from the outer peripheral edge of the light transmissive member outward by the predetermined distance, to the opening edge of the opening, and the metal layer is provided in a region (hereinafter, referred to as a second region in some cases) other than the first region. In addition, the metal layer may not be provided in the first region. For example, the metal layer may be formed in the entire second region, or may be provided in a part of the second region. 
     In such a configuration, the metal layer and a bonding material for bonding the light transmissive member to the first member are not in contact with each other. Therefore, even if adhesion between the metal layer and the bonding material is poor or the thermal expansion coefficients of the metal layer and the bonding material are different, it is possible to suppress deterioration or cracking in the metal layer. As a result, it is possible to maintain the corrosion resistance of the first member by using the metal layer. In addition, since the cracking of the bonding material due to cracking of the metal layer does not occur either, it is possible to bond the first member and the light transmissive member to each other with high bonding strength and high airtightness. 
     In addition, since the first region reaches the position of the line separated from the outer peripheral edge of the light transmissive member by the predetermined distance, it is possible to form a fillet of the bonding material along the outer peripheral edge of the light transmissive member in the first region. By forming such a fillet, it is possible to further improve the bonding strength and airtightness of the first member and the light transmissive member. 
     In the optical device according to the aspect of the invention, it is preferable that the light transmissive member is bonded to the first member through low melting point glass. 
     With this configuration, the light transmissive member is bonded to the first member through the low melting point glass. By the bonding using the low melting point glass, it is possible to improve the airtightness of the light transmissive member and the first member. 
     In the optical device according to the aspect of the invention, it is preferable that the optical device further includes a resin member that covers a surface of the low melting point glass that is not in contact with the light transmissive member and the first member. 
     With this configuration, the surface of the low melting point glass that is not in contact with the light transmissive member or the first member is covered by the resin member, in addition to the bonding using the low melting point glass. Therefore, it is possible to further improve the bonding strength and airtightness of the low melting point glass. 
     In addition, by providing the resin member so as to also be in contact with the light transmissive member and the first member, the light transmissive member can be pressed toward the first member side due to contraction of the resin member at the time of curing. Accordingly, it is also possible to improve the bonding strength. 
     In the optical device according to the aspect of the invention, it is preferable that, in plan view when viewed from the normal direction with respect to the opening surface of the opening, the metal layer is provided so as to cover a region other than a region from the line, which is separated from the outer peripheral edge of the light transmissive member by the predetermined distance toward a side away from the opening and is disposed along the outer peripheral edge of the light transmissive member, to the opening edge of the opening, and the resin member covers a region, in which the low melting point glass is not provided, of the region between the line and the opening edge of the opening. 
     With this configuration, the first member is covered by the metal layer in the second region, and is covered by the resin member in a region where the low melting point glass is not in contact with the first member in the first region. That is, the entire first member is covered by any of the low melting point glass, the metal layer, and the resin member. By adopting such a configuration, it is possible to improve corrosion resistance without the surface of the first member being exposed to the outside. 
     In the optical device according to the aspect of the invention, it is preferable that the light transmissive member has a flat surface portion facing the first member and an inclined surface portion that is continuous with an outer peripheral edge side of the light transmissive member from the flat surface portion and is inclined in a direction away from the first member toward the outer peripheral edge of the light transmissive member, the low melting point glass is disposed between the flat surface portion and the first member, and the resin member is in contact with the inclined surface portion of the light transmissive member. 
     With this configuration, the low melting point glass is provided between the first member and the flat surface portion. In such a configuration, a fillet of the low melting point glass can be formed toward the first member from the end of the flat surface portion. Therefore, as described above, it is possible to improve the bonding strength and airtightness of the first member and the light transmissive member. 
     The resin member is in contact with the inclined surface portion of the light transmissive member. That is, the resin member is provided between the inclined surface portion of the light transmissive member and the first member or between the inclined surface portion of the light transmissive member and a surface (non-bonding surface) of the low melting point glass that is not in contact with the first member and the light transmissive member. In such a configuration, since the resin member contracts at the time of curing, the light transmissive member can be pressed toward the first member side where the light transmissive member is interposed therebetween. Therefore, it is possible to further improve bonding strength and airtightness. 
     In the optical device according to the aspect of the invention, it is preferable that the light transmissive member is formed of glass, the first member is formed of Kovar, and the metal layer contains nickel. 
     With this configuration, Kovar is used as the first member, and a plating material containing nickel can be used as the metal. In this case, since the adhesion of nickel to Kovar is high, it is possible to suppress the peeling of the metal. As a result, it is possible to maintain the corrosion resistance of Kovar satisfactorily. 
     In addition, by using the light transmissive member formed of glass and the first member formed of Kovar having thermal expansion coefficients close to each other, it is possible to reduce disadvantages, such as cracking that occurs in the low melting point glass due to a thermal expansion coefficient difference at the time of bonding using the low melting point glass as a bonding member. Therefore, it is possible to improve bonding strength and airtightness. 
     In the optical device according to the aspect of the invention, it is preferable that the optical element is an interference filter including a pair of reflective films facing each other. 
     With this configuration, when the reflective film used in the interference filter is deteriorated due to, for example, oxidation, the resolution of light emitted from the interference filter is reduced. Therefore, in particular, it is necessary to maintain the inside of the optical device in a decompressed state (more preferably, in a vacuum state) to maintain it hermetically. In addition, when the interference filter is configured so as to be able to change the size of a gap between reflective films, for example, by an electrostatic actuator, it is preferable to maintain the inside of the optical device in a decompressed state (more preferably, in a vacuum state) to maintain it hermetically in order to improve responsiveness at the time of driving. 
     In contrast, in the optical device according to the aspect of the invention with the configuration described above, the light transmissive member and the first member are bonded to each other with high bonding strength and high airtightness as described above. Therefore, since the inside of the optical device can be maintained under an appropriate environment (decompressed or vacuum state), it is possible to suppress the performance degradation of the interference filter. 
     Another aspect of the invention is directed to an optical module including: an optical device that includes an interference filter including a pair of reflective films facing each other, a first member having an opening, a second member that is disposed so as to face the first member with the interference filter interposed therebetween and that houses the interference filter together with the first member, a third member that covers the opening so as to transmit light, and a metal layer that covers the first member; and a light receiving unit that receives light emitted from the interference filter. When a side of the opening is viewed from the third member, the metal layer does not overlap the third member on a side of the first member facing the third member. 
     The optical module includes an optical device, which includes an interference filter including a pair of reflective films facing each other, a first member having an opening, a second member that forms a receiving space capable of housing the interference filter together with the first member, a light transmissive member that is bonded to the first member so as to cover the opening, and a metal layer provided on the first member, and a light receiving unit that receives light emitted from the interference filter. The metal layer is provided at a position separated from the outer peripheral edge of the light transmissive member by a predetermined distance toward a side away from the opening in plan view when viewed from the normal direction with respect to the opening surface of the opening. 
     With this configuration, since the bonding strength and airtightness of the first member and the light transmissive member in the optical device can be improved as described above, it is possible to maintain the inside of the optical device under an appropriate environment. Therefore, since it is possible to suppress the performance degradation of the interference filter, light having a desired wavelength can be emitted from the interference filter with high resolution. As a result, also in the optical module, the light receiving unit can accurately detect the amount of light having a desired wavelength. 
     Still another aspect of the invention is directed to an electronic apparatus including: an optical device that includes an interference filter including a pair of reflective films facing each other, a first member having an opening, a second member that is disposed so as to face the first member with the interference filter interposed therebetween and that houses the interference filter together with the first member, a third member that covers the opening so as to transmit light, and a metal layer that covers the first member; and a control unit that controls the interference filter. When a side of the opening is viewed from the third member, the metal layer does not overlap the third member on a side of the first member facing the third member. 
     The electronic apparatus includes an optical device, which includes an interference filter including a pair of reflective films facing each other, a first member having an opening, a second member that forms a housing space capable of housing the interference filter together with the first member, a light transmissive member that is bonded to the first member so as to cover the opening, and a metal layer provided on the first member, and a control unit that controls the interference filter. The metal layer is provided at a position separated from the outer peripheral edge of the light transmissive member by a predetermined distance toward a side away from the opening in plan view when viewed from the normal direction with respect to the opening surface of the opening. 
     With this configuration, since the bonding strength and airtightness of the first member and the light transmissive member in the optical device can be improved as described above, it is possible to maintain the inside of the optical device under an appropriate environment. Therefore, when the control unit controls the interference filter, it is possible to perform highly accurate control. As a result, it is possible to improve the performance of the electronic apparatus. 
     Yet another aspect of the invention is directed to an optical housing including: a first member that has an opening; a second member that houses an optical element together with the first member; a third member that covers the opening so as to transmit light; and a metal layer that covers the first member. When a side of the opening is viewed from the third member, the metal layer does not overlap the third member on a side of the first member facing the third member. 
     The optical housing includes a first member having an opening, a light transmissive member that is bonded to the first member so as to cover the opening, and a metal layer provided on the first member, and the metal layer is provided at a position separated from the outer peripheral edge of the light transmissive member by a predetermined distance toward a side away from the opening in plan view when viewed from the normal direction with respect to the opening surface of the opening. 
     With this configuration, as described above, the light transmissive member is bonded in the first region of the first member using a bonding material, and the metal layer is provided in the second region. For this reason, neither the cracking of the metal layer nor the cracking of the bonding material due to contact between the bonding material and the metal layer occurs. In addition, since a fillet of the bonding material can also be provided in the first region, the fillet does not come in contact with the metal layer even if the fillet is formed. Therefore, it is possible to maintain the corrosion resistance of the first member by the metal layer and to improve the bonding strength and airtightness of the first member and the light transmissive member. 
     Still yet another aspect of the invention is directed to a method of manufacturing an optical housing which includes a first member having an opening, a second member for housing an optical element together with the first member, a third member that covers the opening so as to transmit light, and a metal layer that covers the first member and in which the metal layer does not overlap the third member on a side of the first member facing the third member when a side of the opening is viewed from the third member. The method of manufacturing an optical housing includes: plating a metal layer in a second region of the first member; and bonding the third member to a first region of the first member. When the side of the opening is viewed from the third member, the first region includes a region between an outer peripheral edge of the third member and an opening edge of the opening, and the second region is a region other than the first region. 
     The method of manufacturing an optical housing is a method of manufacturing an optical housing including a first member having an opening, a light transmissive member that covers the opening and is bonded to the first member, and a metal layer provided on the first member. The first member has a first region and a second region other than the first region. The first region is a region between a line, which is separated from the outer peripheral edge of the light transmissive member by a predetermined distance toward a side away from the opening and is disposed along the outer peripheral edge of the light transmissive member in plan view when viewed from the normal direction with respect to the opening surface of the opening, and the opening edge of the opening. The manufacturing method includes plating the metal layer in the second region of the first member and bonding the light transmissive member, which covers the opening, to the first region of the first member. 
     With this configuration, the metal layer is formed in the second region in the plating step. As such a metal layer forming method, for example, a metal layer may be formed on the entire first member and then the metal layer in the first region may be removed using various methods, such as etching or polishing, or the metal layer may be formed after masking a portion corresponding to the first region. Then, in the bonding process, the light transmissive member and the first member are bonded to each other through the bonding material in the first region. Here, the first region is set as a region from the line, which is separated from the outer peripheral edge of the light transmissive member outward by the predetermined distance, to the opening edge of the opening. Accordingly, even if a fillet is formed along the outer peripheral edge of the light transmissive member, the fillet does not come in contact with the metal. For this reason, there is no cracking of the bonding material due to contact between the fillet and the metal. As a result, it is possible to bond the first member and the light transmissive member to each other with high bonding strength and high airtightness. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be described with reference to the accompanying drawings, wherein like numbers reference like elements. 
         FIG. 1  is a plan view schematically showing an optical filter device of a first embodiment. 
         FIG. 2  is a cross-sectional view of the optical filter device of the first embodiment. 
         FIG. 3  is a plan view of the wavelength tunable interference filter of the first embodiment. 
         FIG. 4  is a cross-sectional view of the wavelength tunable interference filter of the first embodiment. 
         FIG. 5  is an enlarged cross-sectional view of a part of a lid of the first embodiment. 
         FIG. 6  is a flowchart showing the process of manufacturing the optical filter device of the first embodiment. 
         FIG. 7  is an enlarged cross-sectional view of a part of a lid of a second embodiment. 
         FIG. 8  is an enlarged cross-sectional view of a part of a lid of a third embodiment. 
         FIG. 9  is a diagram showing a change in the internal pressure of the optical filter device of each embodiment. 
         FIG. 10  is a block diagram showing the schematic configuration of a colorimetric apparatus of a fourth embodiment. 
         FIG. 11  is a diagram showing the schematic configuration of a gas detector that is an example of an electronic apparatus. 
         FIG. 12  is a block diagram showing the configuration of a control system of the gas detector shown in  FIG. 11 . 
         FIG. 13  is a diagram showing the schematic configuration of a food analyzer that is an example of an electronic apparatus. 
         FIG. 14  is a diagram showing the schematic configuration of a spectral camera that is an example of an electronic apparatus. 
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     First Embodiment 
     Hereinafter, a first embodiment of the invention will be described with reference to the accompanying diagrams. 
     Configuration of Optical Filter Device 
       FIG. 1  is a plan view showing the schematic configuration of an optical filter device  600  that is an embodiment of an optical device according to the invention.  FIG. 2  is a cross-sectional view of the optical filter device  600 . 
     The optical filter device  600  is a device that extracts light having a predetermined target wavelength from incident test target light and emits the extracted light, and includes a housing  610  (optical housing according to the invention) and a wavelength tunable interference filter  5  housed in the housing  610 . The optical filter device  600  can be assembled into an optical module, such as a colorimetric sensor, or an electronic apparatus, such as a colorimetric apparatus or a gas analyzer, for example. The configuration of an optical module or an electronic apparatus including the optical filter device  600  will be described in detail later. 
     Configuration of Wavelength Tunable Interference Filter 
     The wavelength tunable interference filter  5  is an example of the optical element according to the invention. 
       FIG. 3  is a plan view showing the schematic configuration of the wavelength tunable interference filter  5  housed in the housing  610 , and  FIG. 4  is a cross-sectional view taken along the line IV-IV of  FIG. 3  and shows the schematic configuration of the wavelength tunable interference filter  5 . 
     As shown in  FIG. 3 , the wavelength tunable interference filter  5  includes a fixed substrate  51  and a movable substrate  52  corresponding to a substrate according to the invention. Each of the fixed substrate  51  and the movable substrate  52  is formed of various kinds of glass, such as soda glass, crystalline glass, quartz glass, lead glass, potassium glass, borosilicate glass, and alkali-free glass, and crystal, for example. As shown in  FIG. 4 , the fixed substrate  51  and the movable substrate  52  are integrally formed by being bonded to each other through a bonding film  53  (first and second bonding films  531  and  532 ). Specifically, a first bonding portion  513  of the fixed substrate  51  and a second bonding portion  523  of the movable substrate  52  are bonded to each other through the bonding film  53  that is formed of a plasma-polymerized film containing siloxane as a main component, for example. 
     In the following description, a plan view when viewed from the substrate thickness direction of the fixed substrate  51  or the movable substrate  52 , that is, a plan view when the wavelength tunable interference filter  5  is viewed from the lamination direction of the fixed substrate  51 , the bonding film  53 , and the movable substrate  52  is referred to as a filter plan view. 
     As shown in  FIG. 4 , a fixed reflective film  54  that forms one of a pair of reflective films according to the invention is provided on the fixed substrate  51 . A movable reflective film  55  that forms the other one of the pair of reflective films according to the invention is provided on the movable substrate  52 . The fixed reflective film  54  and the movable reflective film  55  are disposed so as to face each other with an inter-reflective film gap G 1  interposed therebetween. 
     In addition, an electrostatic actuator  56  used to adjust the size of the inter-reflective film gap G 1  is provided in the wavelength tunable interference filter  5 . This electrostatic actuator  56  includes a fixed electrode  561  provided on the fixed substrate  51  and a movable electrode  562  provided on the movable substrate  52 , and is formed such that the electrodes  561  and  562  face each other. The fixed electrode  561  and the movable electrode  562  face each other with an inter-electrode gap interposed therebetween. Here, the electrodes  561  and  562  may be directly provided on the surfaces of the fixed substrate  51  and the movable substrate  52 , or may be provided with another film member interposed therebetween. 
     In the present embodiment, the configuration is exemplified in which the inter-reflective film gap G 1  is formed so as to be smaller than the inter-electrode gap. For example, depending on a wavelength range to be transmitted by the wavelength tunable interference filter  5 , the inter-reflective film gap G 1  may be formed so as to be larger than the inter-electrode gap. 
     In filter plan view, a side C 1 -C 2  of the fixed substrate  51  protrudes outward from a side C 1 ′-C 2 ′ of the movable substrate  52 , and forms a fixed side electrical portion  514 . In addition, a side C 3 ′-C 4 ′ of the movable substrate  52  protrudes outward from a side C 3 -C 4  of the fixed substrate  51 , and forms a movable side electrical portion  524 . 
     Configuration of Fixed Substrate 
     In the fixed substrate  51 , an electrode arrangement groove  511  and a reflective film arrangement portion  512  are formed by etching. The fixed substrate  51  is formed in a larger thickness than the movable substrate  52 . Accordingly, there is no bending of the fixed substrate  51  due to the internal stress of the fixed electrode  561  or electrostatic attraction when applying a voltage between the fixed electrode  561  and the movable electrode  562 . 
     The electrode arrangement groove  511  is formed in an annular shape, which has a filter center point O of the fixed substrate  51  as its center, in filter plan view. The reflective film arrangement portion  512  is formed so as to protrude from the center of the electrode arrangement groove  511  to the movable substrate  52  side in the plan view. The groove bottom surface of the electrode arrangement groove  511  is an electrode arrangement surface  511 A on which the fixed electrode  561  is disposed. The protruding distal surface of the reflective film arrangement portion  512  is a reflective film arrangement surface  512 A. 
     On the fixed substrate  51 , a connection electrode groove  511 B is provided in a region from the electrode arrangement groove  511  to the fixed side electrical portion  514  and a region from the electrode arrangement groove  511  to the side C 3 -C 4 . In the present embodiment, the electrode arrangement surface  511 A, the bottom portion of the connection electrode groove  511 B, and the surface of the fixed side electrical portion  514  are the same plane. 
     The fixed electrode  561  that forms the electrostatic actuator  56  is provided on the electrode arrangement surface  511 A. More specifically, the fixed electrode  561  is provided in a region of the electrode arrangement surface  511 A facing the movable electrode  562  of a movable portion  521  to be described later. In addition, an insulating film for ensuring the insulation between the fixed electrode  561  and the movable electrode  562  may be laminated on the fixed electrode  561 . 
     A fixed connection electrode  563  connected to the outer peripheral edge of the fixed electrode  561  is provided on the fixed substrate  51 . The fixed connection electrode  563  is provided over the fixed side electrical portion  514  and the connection electrode groove  511 B toward the fixed side electrical portion  514  from the electrode arrangement groove  511 . The fixed connection electrode  563  forms a fixed electrode pad  563 P, which is electrically connected to an inside terminal portion to be described later, in the fixed side electrical portion  514 . 
     In addition, although the configuration in which one fixed electrode  561  is provided on the electrode arrangement surface  511 A is shown in the present embodiment, it is possible to adopt a configuration (double electrode configuration) in which two electrodes as concentric circles having the filter center point O as their center are provided, for example. In addition, a configuration may be adopted in which a transparent electrode is provided on the fixed reflective film  54 , or a connection electrode may be formed in the fixed side electrical portion  514  from the fixed reflective film  54  using a conductive fixed reflective film  54 . In this case, a part of the fixed electrode  561  may be notched according to the position of the connection electrode. 
     As described above, the reflective film arrangement portion  512  is formed in an approximately cylindrical shape, which has a smaller diameter than the electrode arrangement groove  511 , on the same axis as the electrode arrangement groove  511 , and includes the reflective film arrangement surface  512 A facing the movable substrate  52  of the reflective film arrangement portion  512 . 
     As shown in  FIG. 4 , the fixed reflective film  54  is provided in the reflective film arrangement portion  512 . As the fixed reflective film  54 , it is possible to use a metal film, such as Ag, and an alloy film, such as an Ag alloy, for example. In addition, it is also possible to use a dielectric multilayer film having a high refractive layer of TiO 2  and a low refractive layer of SiO 2 , for example. In addition, it is also possible to use a reflective film in which a metal film (or an alloy film) is laminated on a dielectric multilayer film, a reflective film in which a dielectric multilayer film is laminated on a metal film (or an alloy film), a reflective film in which a single refractive layer (for example, TiO 2  or SiO 2 ) and a metal film (or an alloy film) are laminated, and the like. 
     On the light incidence surface (surface on which the fixed reflective film  54  is not provided) of the fixed substrate  51 , an anti-reflection film may be formed at a position corresponding to the fixed reflective film  54 . The anti-reflection film can be formed by laminating a low refractive index film and a high refractive index film alternately, and reduces the reflectance of visible light on the surface of the fixed substrate  51 . As a result, the transmittance is increased. 
     In addition, a portion of the surface of the fixed substrate  51  facing the movable substrate  52 , on which the electrode arrangement groove  511 , the reflective film arrangement portion  512 , and the connection electrode groove  511 B are not formed by etching, forms the first bonding portion  513 . The first bonding film  531  is provided in the first bonding portion  513 , and the first bonding film  531  is bonded to the second bonding film  532  provided on the movable substrate  52 . Thus, the fixed substrate  51  and the movable substrate  52  are bonded to each other, as described above. 
     Configuration of Movable Substrate 
     The movable substrate  52  includes the movable portion  521 , which is formed in a circular shape having a filter center point O as its center, and a holding portion  522 , which is coaxial with the movable portion  521  and holds the movable portion  521 . 
     The movable portion  521  is formed in a larger thickness than the holding portion  522 . The movable portion  521  is formed so as to have a larger diameter than at least the diameter of the outer peripheral edge of the reflective film arrangement surface  512 A in filter plan view. The movable electrode  562  and the movable reflective film  55  are provided in the movable portion  521 . 
     Similar to the fixed substrate  51 , an anti-reflection film may be formed on a surface of the movable portion  521  not facing the fixed substrate  51 . The anti-reflection film can be formed by laminating a low refractive index film and a high refractive index film alternately, and reduces the reflectance of visible light on the surface of the movable substrate  52 . As a result, the transmittance can be increased. 
     The movable electrode  562  faces the fixed electrode  561  with a gap G 2  interposed therebetween, and is formed in an annular shape that is the same shape as the fixed electrode  561 . The fixed electrode  561  and the movable electrode  562  form the electrostatic actuator  56 . A movable connection electrode  564  connected to the outer peripheral edge of the movable electrode  562  is provided on the movable substrate  52 . The movable connection electrode  564  is provided from the movable portion  521  to the movable side electrical portion  524  so as to face the connection electrode groove  511 B provided on the side C 3 -C 4  of the fixed substrate  51 , and forms a movable electrode pad  564 P, which is electrically connected to an inside terminal portion, in the movable side electrical portion  524 . 
     The movable reflective film  55  is provided in the center of the movable surface  521 A of the movable portion  521  so as to face the fixed reflective film  54  with the gap G 1  interposed therebetween. As the movable reflective film  55  described above, a reflective film having the same configuration as the fixed reflective film  54  is used. 
     Although the example where the gap G 2  is larger than the gap G 1  is shown as described above in the present embodiment, the invention is not limited thereto. For example, when infrared light or far-infrared light is used as measurement target light, the gap G 1  may be larger than the gap G 2  according to the wavelength band of the measurement target light. 
     The holding portion  522  is a diaphragm surrounding the periphery of the movable portion  521 , and is formed in a smaller thickness than the movable portion  521 . The holding portion  522  bends more easily than the movable portion  521  does. Accordingly, it is possible to displace the movable portion  521  to the fixed substrate  51  side by slight electrostatic attraction. In this case, since the movable portion  521  is thicker than the holding portion  522 , the rigidity of the movable portion  521  is large. Therefore, even if the holding portion  522  is pulled to the fixed substrate  51  side due to electrostatic attraction, no change in the shape of the movable portion  521  is caused. Accordingly, since the bending of the movable reflective film  55  provided in the movable portion  521  does not occur either, it is possible to maintain the fixed reflective film  54  and the movable reflective film  55  in a parallel state continuously. 
     In addition, although the diaphragm-like holding portion  522  is exemplified in the present embodiment, the invention is not limited thereto. For example, beam-shaped holding portions, which are disposed at equal angular intervals around the filter center point O, may also be provided. 
     In the movable substrate  52 , a region facing the first bonding portion  513  is the second bonding portion  523 . The second bonding film  532  is provided in the second bonding portion  523 , and the second bonding film  532  is bonded to the first bonding film  531  as described above. Thus, the fixed substrate  51  and the movable substrate  52  are bonded to each other. 
     Configuration of Housing 
     As shown in  FIGS. 1 and 2 , the housing  610  includes a base  620  corresponding to a second member according to the invention and a lid  630  corresponding to a first member according to the invention. The base  620  and the lid  630  are bonded to each other to form a receiving space therebetween, and the wavelength tunable interference filter  5  is housed in the receiving space. 
     Configuration of Base 
     The base  620  is formed of ceramic, for example. The base  620  includes a pedestal portion  621  and a side wall portion  622 . 
     The pedestal portion  621  is formed, for example, in a flat plate shape having a rectangular outer shape in filter plan view, and the side wall portion  622  rises toward the lid  630  from the outer periphery of the pedestal portion  621 . 
     The pedestal portion  621  includes a first opening  623  passing therethrough in the thickness direction. The first opening  623  is provided so as to include a region, which overlaps the reflective films  54  and  55 , in plan view when viewed from a normal direction with respect to the opening surface of the first opening  623  in a state where the wavelength tunable interference filter  5  is housed in the pedestal portion  621 . 
     A first glass member  627  that covers the first opening  623  is bonded to the surface (base outside surface  621 B) of the pedestal portion  621  not facing the lid  630 . In order to bond the pedestal portion  621  and the first glass member  627  to each other, it is possible to use low melting point glass bonding using a glass frit (low melting point glass) which is a piece of glass obtained by dissolving a glass material at high temperature and quenching the glass material, bonding using an epoxy resin, and the like. In the present embodiment, the receiving space is hermetically maintained in a state where the inside of the receiving space is maintained in a decompressed state. Accordingly, it is preferable to bond the pedestal portion  621  and the first glass member  627  to each other by low melting point glass bonding. 
     An inside terminal portion  624  connected to the electrode pads  563 P and  564 P of the wavelength tunable interference filter  5  is provided on the inside surface (base inside surface  621 A) of the pedestal portion  621  facing the lid  630 . The inside terminal portion  624  and each of the electrode pads  563 P and  564 P are connected to each other through a wire, such as Au, by wire bonding, for example. Although wire bonding is exemplified in the present embodiment, for example, a flexible printed circuit (FPC) may be used. 
     In the pedestal portion  621 , a through hole  625  is formed at a position where the inside terminal portion  624  is provided. The inside terminal portion  624  is connected to an outside terminal portion  626 , which is provided on the base outside surface  621 B of the pedestal portion  621 , through the through hole  625 . 
     The side wall portion  622  rises from the edge of the pedestal portion  621 , and covers the periphery of the wavelength tunable interference filter  5  placed on the base inside surface  621 A. The surface (bonding end surface  622 A) of the side wall portion  622  facing the lid  630  is a flat surface parallel to the base inside surface  621 A, for example. 
     The wavelength tunable interference filter  5  is fixed to the base  620 , for example, using a fixing material, such as an adhesive. In this case, the wavelength tunable interference filter  5  may be fixed to the side wall portion  622 , or may be fixed to the pedestal portion  621 . A fixing material may be provided at a plurality of places. However, in order to suppress the stress of the fixing material from being transmitted to the wavelength tunable interference filter  5 , it is preferable to fix the wavelength tunable interference filter  5  at one place. 
     Configuration of Lid 
       FIG. 5  is an enlarged cross-sectional view of a part of the lid  630 . 
     The lid  630  is a plate-shaped member having a rectangular shape, which is the same as the pedestal portion  621 , in plan view when viewed from the thickness direction of the lid  630 . The lid  630  can be formed of, for example, an alloy, such as Kovar, or metal. In the present embodiment, the lid  630  is formed of Kovar. 
     As shown in  FIGS. 1 and 2 , the lid  630  has a second opening  631  (corresponding to an opening according to the invention) passing therethrough in the thickness direction of the lid  630 . The second opening  631  is provided so as to include a region, which overlaps the reflective films  54  and  55 , in plan view when viewed from a normal direction with respect to the opening surface of the second opening  631  in a state where the wavelength tunable interference filter  5  is placed in the base  620 . 
     On the outer peripheral surface of the lid  630 , a second glass member  632  (corresponding to a light transmissive member according to the invention) is bonded so as to cover the second opening  631 . 
     A metal layer  633  is coated and formed on the surface of the lid  630 . The metal layer  633  can be formed using a plating method. 
     In  FIG. 1 , a line L is a virtual line that is separated from the outer peripheral edge of the second glass member  632  outward (toward a side away from the second opening  631 ) by a predetermined distance and is disposed along the outer peripheral edge of the second glass member  632  in plan view when the lid  30  is viewed from a normal direction with respect to the opening surface of the second opening  631  in a state where the second glass member  632  is bonded to the lid  630 . In the present embodiment, in a region (first region Ar 1 ) from the line L to the second opening  631 , the second glass member  632  is bonded to the lid  630 . In the first region Ar 1 , the metal layer  633  is not provided. The metal layer  633  is provided in a region (second region Ar 2 ) other than the first region Ar 1 . Preferably, the metal layer  633  is provided in the entire second region Ar 2 . 
     Here, it is preferable that the metal layer  633  cover the lid  630  as much as possible. Therefore, it is preferable that the distance (the predetermined distance) between the line L and the outer peripheral edge of the second glass member  632  be as small as possible (the line L is located as close to the outer peripheral edge of the second glass member  632  as possible) and be a distance, which does not allow the metal layer  633  and low melting point glass  634  to be in contact with each other, even if the fillet of the low melting point glass  634  is formed when bonding the second glass member  632  using the low melting point glass  634 . That is, the line L is set at a position closest to the outer peripheral edge of the second glass member  632  to the extent that the line L is not in contact with the fillet of the low melting point glass. 
     The second glass member  632  is bonded to the lid  630  in the first region Ar 1  through the low melting point glass  634 . 
     As shown in  FIG. 5 , the low melting point glass  634  is in contact with a portion of the second glass member  632  from a facing surface  632 A of the second glass member  632 , which faces the lid  630 , to a side surface  632 B (surface perpendicular to the facing surface  632 A) along the outer peripheral edge of the second glass member  632 . That is, in the first region Ar 1 , a fillet  634 A of the low melting point glass  634  is provided over the outer peripheral edge of the second glass member  632 . 
     As described above, since the metal layer  633  is provided in the second region Ar 2 , the low melting point glass  634  provided in the first region Ar 1  does not come in contact with the metal layer  633 . 
     As described above, the metal layer  633  is provided so as to cover the second region Ar 2 . As the metal layer  633 , a material having a high adhesion property for the lid  630  is selected. In the present embodiment, the metal layer  633  containing nickel is used for the lid  630  formed of Kovar. 
     The lid  630  is bonded to the bonding end surface  622 A of the base  620 . For this bonding, for example, not only bonding based on metal brazing but also seam, laser welding, and the like can be used. In this case, since the base  620  and the lid  630  are bonded to each other, the receiving space in which the wavelength tunable interference filter  5  is housed is hermetically sealed. 
     Manufacturing of Optical Filter Device 
     A method of manufacturing the optical filter device  600  will be described. 
       FIG. 6  is a flowchart showing the process of manufacturing the housing  610  of the optical filter device  600  of the present embodiment. 
     As shown in  FIG. 6 , in the present embodiment, the housing  610  of the optical filter device  600  is manufactured by a base forming step, a filter fixing step, a lid forming step, and a housing bonding step. 
     In the base forming step, a ceramic sheet in which the first opening  623  and the through hole  625  are formed is laminated, a ceramic sheet corresponding to the side wall portion  622  is laminated, and these are baked. As a result, the basic shape of the base  620  including the pedestal portion  621  and the side wall portion  622  is formed. 
     Then, the through hole  625  is embedded using a conductive member (for example, metal paste), the inside terminal portion  624  is formed on the base inside surface  621 A of the pedestal portion  621 , and the outside terminal portion  626  is formed on the base outside surface  621 B. As a result, airtightness in the through hole  625  is maintained. 
     Then, the first glass member  627  that covers the first opening  623  is bonded to the base outside surface  621 B through low melting point glass. 
     In the filter fixing step, a fixing material, such as an adhesive, is applied onto the base inside surface  621 A of the base  620  or the side wall portion  622 . Then, the wavelength tunable interference filter  5  is fixed by a fixing material while performing alignment so that the reflective films  54  and  55  of the wavelength tunable interference filter  5  are disposed in the opening region of the first opening  623 . In this case, by fixing the fixed substrate  51  of the wavelength tunable interference filter  5  with the fixing material, it is possible to suppress the inclination of the movable portion  521  and the like due to the stress of the fixing material. 
     Then, each of the electrode pads  563 P and  564 P of the wavelength tunable interference filter  5  and the inside terminal portion  624  of the base  620  are connected to each other by wire bonding. 
     In the lid forming step, first, the metal layer  633  is formed on the lid  630  formed of Kovar, in which the second opening  631  is provided, using a plating method (plating step). 
     In this case, in the lid  630 , the metal layer  633  is formed in the second region Ar 2  other than the first region Ar 1  from the line L to the opening edge of the second opening  631 . Specifically, the metal layer  633  is applied onto the entire surface of the lid  630  after masking the first region Ar 1  of the lid  630 , and then the mask is removed. 
     The plating method is not limited to this. For example, only the metal layer  633  of the first region Ar 1  may be removed by etching, polishing, or the like after forming the metal layer  633  on the entire surface of the lid  630 . 
     Then, the low melting point glass  634  in a molten state is provided on the surface of the lid  630  facing the second glass member  632  of the first region Ar 1 , and is bonded to the second glass member  632  (bonding step). 
     In this case, by pressing the second glass member  632  against the lid  630  side, the low melting point glass  634  protrudes outward from the outer peripheral edge of the second glass member  632  (in the first region Ar 1 ) and rises along the side surface  632 B, and the fillet  634 A is formed. 
     As described above, the lid  630  is formed. 
     In the housing bonding step, the base  620  and the lid  630  are bonded to each other. For example, bonding between the base  620  and the lid  630  is performed by the seam under the environment set as a vacuum atmosphere by a vacuum chamber device or the like. As the bonding method, it is possible to use various bonding methods, such as bonding based on metal brazing and laser welding, as described above. 
     As described above, the optical filter device  600  is manufactured. 
     Operations and Effects of First Embodiment 
     In the present embodiment, the metal layer  633  is not provided in the first region Ar 1  on the surface of the lid  630 , and the metal layer  633  is provided in the second region Ar 2 . For this reason, when bonding the second glass member  632  to the lid  630  through the low melting point glass  634 , even if the fillet  634 A of the low melting point glass  634  is formed along the outer peripheral edge of the second glass member  632 , the metal layer  633  and the low melting point glass  634  do not come in contact with each other. Therefore, deterioration or cracking of the metal layer  633 , cracking of the low melting point glass  634 , and the like due to contact between the low melting point glass  634  and the metal layer  633  do not occur. 
     In addition, since the fillet  634 A is formed at the time of bonding using the low melting point glass  634 , the bonding strength between the lid  630  and the second glass member  632  can be further increased, and airtightness can also be increased. Therefore, it is possible to maintain the airtightness of the receiving space formed by the base  620  and the lid  630 . 
     In the present embodiment, the wavelength tunable interference filter  5  is housed in the receiving space. 
     When driving the wavelength tunable interference filter  5  by applying a voltage to the electrostatic actuator  56 , if air is present between the reflective films  54  and  55 , the responsiveness of the wavelength tunable interference filter  5  is reduced. When the reflective films  54  and  55  are metal films, there is a problem, such as oxidation. In contrast, in the present embodiment, since the airtightness inside the housing  610  is high as described above, it is possible to maintain the vacuum state for a long period of time. Therefore, it is possible to suppress a reduction in the driving responsiveness of the wavelength tunable interference filter  5  and to suppress the deterioration of the reflective films  54  and  55 . 
     Second Embodiment 
     Next, a second embodiment of the invention will be described with reference to the diagrams. 
     In the first embodiment described above, only the low melting point glass  634  is used to bond the lid  630  and the second glass member  632  to each other. In contrast, the present embodiment is different from the first embodiment in that a resin member is further used. 
       FIG. 7  is an enlarged cross-sectional view of a part of a lid  630  in an optical filter device  600 A of the second embodiment. In explaining the subsequent embodiments, the same components as in the embodiments described above are denoted by the same reference numerals, and explanation thereof will be omitted or simplified. 
     In the optical filter device  600 A of the present embodiment, as shown in  FIG. 7 , a bonding portion between the lid  630  and the second glass member  632  is covered by further using a resin adhesive (resin member  635 ), thereby improving the bonding strength. 
     Specifically, the resin member  635  covers a region from an outer peripheral portion of a top surface  632 C of the second glass member  632  to the surface of the fillet  634 A of the low melting point glass  634  and the first region Ar 1  of the lid  630 . Accordingly, the lid  630  is covered by the metal layer  633  in the second region Ar 2 , and is covered by the low melting point glass  634  or the resin member  635  in the first region Ar 1 . In this case, as shown in  FIG. 7 , the peeling of the metal layer  633  can be suppressed by covering the end of the metal layer  633  along the line L using the resin member  635 . 
     Operations and Effects of Second Embodiment 
     In the present embodiment, a surface of the low melting point glass  634  (surface of the fillet  634 A) that is not in contact with the second glass member  632  and the lid  630  is covered by the resin member  635 . Therefore, it is possible to further improve the airtightness of the bonding of the low melting point glass  634 . 
     The resin member  635  covers from the top surface of the second glass member  632  to the first region Ar 1  of the lid  630 . Therefore, since the second glass member  632  is biased to the lid  630  side by the contraction force during the curing of the resin member  635 , it is possible to increase the bonding strength. 
     Furthermore, the resin member  635  covers the first region Ar 1 . That is, the surface of the lid  630  is covered by any of the metal layer  633 , the low melting point glass  634 , and the resin member  635 . Therefore, it is possible to increase the corrosion resistance of the lid  630 . 
     Third Embodiment 
     Next, a third embodiment of the invention will be described with reference to the diagrams. 
     In the second embodiment described above, the example is illustrated in which the fillet  634 A is formed from the side surface  632 B of the second glass member  632  and the surface of the fillet  634 A is covered by the resin member  635 . In contrast, in the third embodiment, it is possible to further improve the bonding strength by providing the resin member  635  between the second glass member  632  and the lid  630 . 
       FIG. 8  is an enlarged cross-sectional view of a part of a lid  630  in an optical filter device  600 B of the third embodiment. 
     As shown in  FIG. 8 , in the first region Ar 1 , the second glass member  632  of the present embodiment is configured to include a facing surface  632 D (flat surface portion) that faces the lid  630 , an inclined surface  632 E (inclined surface portion) that is continuous with an end  632 D 1  of the facing surface  632 D and is inclined in a direction away from the lid  630  toward the outer peripheral edge of the second glass member  632 , a side surface  632 B, and a top surface  632 C. 
     As shown in  FIG. 8 , the low melting point glass  634  is provided between the facing surface  632 D and the lid  630 , forms a fillet  634 B toward the outside from the end  632 D 1 , and bonds the lid  630  and the second glass member  632  to each other. That is, a gap is formed between the inclined surface  632 E of the second glass member  632  and the lid  630 . 
     The resin member  635  of the present embodiment covers a region from an outer peripheral portion of the top surface  632 C of the second glass member  632  to the side surface  632 B, the inclined surface  632 E, the surface of the fillet  634 B of the low melting point glass  634 , and the first region Ar 1  of the lid  630 . 
     That is, the resin member  635  is provided in a region, in which the low melting point glass  634  is not provided, between the second glass member  632  and the lid  630 . 
     Operations and Effects of Third Embodiment 
     In the present embodiment, the inclined surface  632 E is interposed between the resin member  635  and the top surface  632 C of the second glass member  632 , and a biasing force that biases the second glass member  632  to the lid  630  side is increased by the contraction force at the time of resin curing. Therefore, compared with the second embodiment, it is possible to obtain stronger bonding strength and higher airtightness. 
     Bonding Strength in Each Embodiment 
       FIG. 9  is a diagram showing a change in the internal pressure of each of the optical filter devices  600 ,  600 A, and  600 B in the embodiments described above. In  FIG. 9 , data A shows a change in the internal pressure of an optical filter device that is obtained by forming a metal layer on the entire surface of the lid and then bonding the second glass member to the metal layer through low melting point glass. Data B shows a change in the internal pressure of the optical filter device  600  of the first embodiment, data C shows a change in the internal pressure of the optical filter device  600 A of the second embodiment, and data D shows a change in the internal pressure of the optical filter device  600 B of the third embodiment. 
     As shown in  FIG. 9 , when a metal layer is formed on the entire surface of the lid using a plating method and the second glass member is bonded to the metal layer through the low melting point glass, cracking occurs in the metal layer. Due to the cracking, airtightness is significantly reduced. For this reason, the internal pressure changed at a rate of 10 Pa/day over time. In contrast, the amount of change in the internal pressure was 0.2 Pa/day in the optical filter device  600 , 0.1 Pa/day in the optical filter device  600 A, and 0.05 Pa/day in the optical filter device  600 B, and airtightness was maintained satisfactorily. 
     Fourth Embodiment 
     Next, a fourth embodiment of the invention will be described with reference to the accompanying diagrams. 
     In the fourth embodiment, a colorimetric sensor  3 , which is an optical module in which the optical filter device  600  of the first embodiment is provided, and a colorimetric apparatus  1 , which is an electronic apparatus in which the optical filter device  600  is provided, will be described. Instead of the optical filter device  600 , the optical filter devices  600 A and  600 B of the second and third embodiments may also be provided. 
     Schematic Configuration of Colorimetric Apparatus 
       FIG. 10  is a block diagram showing the schematic configuration of the colorimetric apparatus  1 . 
     The colorimetric apparatus  1  is an electronic apparatus according to the invention. As shown in  FIG. 10 , the colorimetric apparatus  1  includes a light source device  2  that emits light to a test target X, the colorimetric sensor  3  (optical module), and a control device  4  that controls the overall operation of the colorimetric apparatus  1 . The colorimetric apparatus  1  receives test target light, which is emitted from the light source device  2  and is reflected by the test target X, using the colorimetric sensor  3 . In addition, the colorimetric apparatus  1  is an apparatus that analyzes and measures the chromaticity of the test target light, that is, the color of the test target X, based on a detection signal output from the colorimetric sensor  3  that has received the test target light. 
     Configuration of Light Source Device 
     The light source device  2  includes a light source  21  and a plurality of lenses  22  (only one lens is shown in  FIG. 10 ), and emits white light to the test target X. A collimator lens may be included in the plurality of lenses  22 . In this case, the light source device  2  forms the white light emitted from the light source  21  as parallel light using the collimator lens and emits the parallel light from a projection lens (not shown) toward the test target X. Although the colorimetric apparatus  1  including the light source device  2  is exemplified in the present embodiment, the light source device  2  may not be provided, for example, when the test target X is a light emitting member, such as a liquid crystal panel. 
     Configuration of Colorimetric Sensor 
     The colorimetric sensor  3  forms the optical module according to the invention, and includes the optical filter device  600  of the first embodiment described above. As shown in  FIG. 10 , the colorimetric sensor  3  includes the optical filter device  600 , a detection section  31  that receives light transmitted through the optical filter device  600 , and a voltage control section  32  that changes the wavelength of light transmitted through the wavelength tunable interference filter  5 . 
     In addition, the colorimetric sensor  3  includes an incident optical lens (not shown) that is provided at a position facing the wavelength tunable interference filter  5  and that guides reflected light (test target light), which is reflected by the test target X, to the inside. The colorimetric sensor  3  separates light having a predetermined wavelength, from the test target light incident from the incident optical lens, using the wavelength tunable interference filter  5  in the optical filter device  600 , and receives the separated light using the detection section  31 . 
     The detection section  31  is formed by a plurality of photoelectric conversion elements, and generates an electrical signal corresponding to the amount of received light. The detection section  31  is connected to the control device  4 , for example, through a circuit board  311 , and outputs the generated electrical signal to the control device  4  as a light receiving signal. 
     In addition, the outside terminal portion  626  formed on the base outside surface  621 B of the housing  610  is connected to the circuit board  311 . The outside terminal portion  626  is connected to the voltage control section  32  through a circuit formed on the circuit board  311 . 
     In such a configuration, the optical filter device  600  and the detection section  31  can be integrally formed through the circuit board  311 . Therefore, the configuration of the colorimetric sensor  3  can be simplified. 
     The voltage control section  32  is connected to the outside terminal portion  626  of the optical filter device  600  through the circuit board  311 . The voltage control section drives the electrostatic actuator  56  by applying a predetermined step voltage between the fixed electrode pad  563 P and the movable electrode pad  564 P based on the control signal input from the control device  4 . Then, electrostatic attraction occurs in the inter-electrode gap, and the holding portion  522  is bent. Accordingly, since the movable portion  521  is displaced to the fixed substrate  51  side, it is possible to set the inter-reflective film gap G 1  to a desired size. 
     Configuration of Control Device 
     The control device  4  controls the overall operation of the colorimetric apparatus  1 . 
     As the control device  4 , for example, a general-purpose personal computer, a personal digital assistant, and a computer dedicated to color measurement can be used. 
     In addition, as shown in  FIG. 10 , the control device  4  is configured to include a light source control section  41 , a colorimetric sensor control section  42 , and a colorimetric processing section  43 . 
     The light source control section  41  is connected to the light source device  2 . In addition, the light source control section  41  outputs a predetermined control signal to the light source device  2 , for example, based on setting input from the user and emits white light with predetermined brightness from the light source device  2 . 
     The colorimetric sensor control section  42  is connected to the colorimetric sensor  3 . In addition, the colorimetric sensor control section  42  sets the wavelength of light received by the colorimetric sensor  3 , for example, based on a setting input from the user and outputs to the colorimetric sensor  3  a control signal indicating the detection of the amount of received light with the wavelength. Then, the voltage control section  32  of the colorimetric sensor  3  sets a voltage, which is applied to the electrostatic actuator  56 , based on the output control signal such that only light with a wavelength that the user desires is transmitted. 
     The colorimetric processing section  43  analyzes the chromaticity of the test target X from the amount of received light detected by the detection section  31 . 
     Operations and Effects of Fourth Embodiment 
     The colorimetric apparatus  1  of the present embodiment includes the optical filter device  600  described in the first embodiment. As described above, the optical filter device  600  has high airtightness in the receiving space, and can suppress a change in the internal pressure. Therefore, since the installation environment of the wavelength tunable interference filter  5  can be maintained in a decompressed state, it is possible to maintain high responsiveness when driving the wavelength tunable interference filter  5 . In addition, since the deterioration of the reflective films  54  and  55  can be suppressed, it is also possible to suppress a reduction in resolution. 
     Therefore, also in the colorimetric sensor  3  and the colorimetric apparatus  1  including the optical filter device  600  described above, it is possible to suppress performance degradation. As a result, since light having a target wavelength extracted with high resolution can be detected for a long period of time, it is possible to perform accurate color analysis processing. 
     Modifications of Embodiments 
     The invention is not limited to the embodiments described above, and various modifications or improvements may be made without departing from the scope and spirit of the invention. 
     For example, although the example where the metal layer  633  is provided in the entire second region Ar 2  of the lid  630  is illustrated in each of the embodiments described above, the invention is not limited thereto. For example, the metal layer  633  may be provided in a part of the second region Ar 2 . 
     In the embodiment described above, the first member is the lid  630 , and the second member is the base  620 . However, the invention is not limited to this. For example, the first member may be a base on which an optical element is provided, and may be formed of metal or an alloy, such as Kovar. In this case, the first glass member that blocks the first opening provided in the first member becomes a light transmissive member, and the invention can be applied in the bonding. 
     In the embodiment described above, the example is illustrated in which the lid  630  as the first member is formed of Kovar, the second glass member  632  as a light transmissive member is formed of glass, and the metal layer  633  is formed of nickel using a plating method. However, the invention is not limited to the example. As the light transmissive member and the first member, it is possible to appropriately select and use materials having approximately the same thermal expansion coefficient. As the metal, it is possible to appropriately select and use a metal having good adhesion to the first member. 
     For example, when infrared light is used as light to be analyzed, silicon allowing infrared light to be transmitted therethrough may be used as the light transmissive member. The lid  630 , which is the first member, may be formed of, for example, an alloy or aluminum as well as Kovar. As the metal layer  633 , for example, zinc according to the plating method may be used, in addition to the nickel according to the plating method. 
     In the embodiment described above, the example is illustrated in which the lid  630  as the first member and the second glass member  632  as a light transmissive member are bonded to each other through the low melting point glass. However, the invention is not limited to the example. For example, the first member and the light transmissive member may also be bonded to each other through a bonding material, such as an epoxy resin. As the bonding material, it is preferable to select a material having approximately the same thermal expansion coefficient as the first member or the light transmissive member. 
     In the third embodiment, the configuration has been exemplified in which the second glass member  632  has the planar inclined surface  632 E that is continuous with the end  632 D 1  of the facing surface  632 D. However, the invention is not limited to the configuration. For example, the inclined surface  632 E may be a curved surface, or may have a plurality of inclined surfaces  632 E. Alternatively, for example, a plurality of flat surfaces, which are parallel to the facing surface  632 D and have different distances from the lid  630 , may be provided in a stepped shape. In all of the configurations, the resin member  635  can be filled between the second glass member  632  and the lid  630 . As a result, it is possible to improve bonding strength and airtightness. 
     In each of the embodiments described above, the configuration has been exemplified in which the second glass member  632 , which is a light transmissive member, has a rectangular shape in plan view when viewed from the normal direction with respect to the opening surface of the second opening  631 . However, the shape of the second glass member  632  is not limited to the rectangular shape. For example, the second glass member  632  may be formed in other shapes, such as a circular shape or a polygonal shape, and any shape that can cover the second opening  631  may be used. The second opening  631  is not limited to being formed in a rectangular shape either, and may be formed in other shapes, such as a circular shape or a polygonal shape. 
     In addition, the virtual line L may be set according to the shape of the second glass member  632 . For example, the virtual line L may include a curve. 
     Although the wavelength tunable interference filter or the interference filter has been exemplified as the optical element according to the invention in each of the embodiments described above, the invention is not limited thereto. For example, a mirror device that can accurately change the light reflection direction can be exemplified as the optical element. 
     In addition, although the wavelength tunable interference filter  5  has been exemplified as an optical element, it is also possible to use an interference filter in which the electrostatic actuator  56  is not provided and the size of a gap between the reflective films  54  and  55  is fixed. 
     In the fourth embodiment, the colorimetric apparatus  1  has been exemplified as the electronic apparatus according to the invention. However, the optical device, the optical module, and the electronic apparatus according to the invention can be applied in various fields. 
     For example, the optical device, the optical module, and the electronic apparatus according to the invention can be used as a light-based system for detecting the presence of a specific material. As examples of such a system, an in-vehicle gas leak detector that detects a specific gas with high sensitivity by adopting a spectroscopic measurement method using the wavelength tunable interference filter provided in the optical device according to the invention or a gas detector, such as a photoacoustic rare gas detector for mammography, can be exemplified. 
     An example of such a gas detector will now be described with reference to the accompanying drawings. 
       FIG. 11  is a schematic diagram showing an example of a gas detector including the wavelength tunable interference filter. 
       FIG. 12  is a block diagram showing the configuration of a control system of the gas detector shown in  FIG. 11 . 
     As shown in  FIG. 11 , a gas detector  100  is configured to include a sensor chip  110 , a flow path  120  including a suction port  120 A, a suction flow path  120 B, a discharge flow path  120 C, and a discharge port  120 D, and a main body  130 . 
     The main body  130  is configured to include: a detection device including a sensor unit cover  131  having an opening through which the flow path  120  can be attached or detached, a discharge unit  133 , a housing  134 , an optical unit  135 , a filter  136 , the optical filter device  600 , and a light receiving element  137  (detection unit); a control unit  138  that processes a detected signal and controls the detection unit; and a power supply unit  139  that supplies electric power. Instead of the optical filter device  600 , the optical filter devices  600 A and  600 B in the second and third embodiments may also be used. In addition, the optical unit  135  is configured to include a light source  135 A that emits light, a beam splitter  135 B that reflects light incident from the light source  135 A toward the sensor chip  110  side and transmits light incident from the sensor chip side toward the light receiving element  137  side, and lenses  135 C,  135 D, and  135 E. 
     In addition, as shown in  FIG. 11 , an operation panel  140 , a display unit  141 , a connection unit  142  for interface with the outside, and the power supply unit  139  are provided on the surface of the gas detector  100 . When the power supply unit  139  is a secondary battery, a connection unit  143  for charging may be provided. 
     As shown in  FIG. 12 , the control unit  138  of the gas detector  100  includes a signal processing section  144  formed by a CPU or the like, a light source driver circuit  145  for controlling the light source  135 A, a voltage control section  146  for controlling the wavelength tunable interference filter  5  of the optical filter device  600 , a light receiving circuit  147  that receives a signal from the light receiving element  137 , a sensor chip detection circuit  149  that reads a code of the sensor chip  110  and receives a signal from a sensor chip detector  148  that detects the presence or absence of the sensor chip  110 , and a discharge driver circuit  150  that controls the discharge unit  133 . 
     Next, the operation of the gas detector  100  will be described below. 
     The sensor chip detector  148  is provided inside the sensor unit cover  131  located in the upper portion of the main body  130 , and the presence or absence of the sensor chip  110  is detected by the sensor chip detector  148 . When a detection signal from the sensor chip detector  148  is detected, the signal processing section  144  determines that the sensor chip  110  has been mounted, and outputs a display signal to display that “detection operation is executable” on the display unit  141 . 
     Then, for example, when the operation panel  140  is operated by the user and an instruction signal indicating the start of detection processing is output from the operation panel  140  to the signal processing section  144 , the signal processing section  144  first outputs a signal for operating the light source to the light source driver circuit  145  to operate the light source  135 A. When the light source  135 A is driven, linearly-polarized stable laser light with a single wavelength is emitted from the light source  135 A. A temperature sensor or a light amount sensor is provided in the light source  135 A, and the information is output to the signal processing section  144 . When it is determined that the light source  135 A is stably operating based on the temperature or the amount of light input from the light source  135 A, the signal processing section  144  controls the discharge driver circuit  150  to operate the discharge unit  133 . Then, a gas sample containing a target material (gas molecules) to be detected is guided from the suction port  120 A to the suction flow path  120 B, the inside of the sensor chip  110 , the discharge flow path  120 C, and the discharge port  120 D. 
     A dust filter  120 A 1  is provided on the suction port  120 A in order to remove relatively large dust particles, water vapor, and the like. 
     The sensor chip  110  is a sensor in which a plurality of metal nanostructures are included and which uses localized surface plasmon resonance. In such a sensor chip  110 , an enhanced electric field is formed between the metal nanostructures by laser light. When gas molecules enter the enhanced electric field, Rayleigh scattered light and Raman scattered light including the information of molecular vibration are generated. 
     Such Rayleigh scattered light or Raman scattered light is incident on the filter  136  through the optical unit  135 , and the Rayleigh scattered light is separated by the filter  136  and the Raman scattered light is incident on the optical filter device  600 . Then, the signal processing section  144  controls the voltage control section  146  to adjust a voltage applied to the wavelength tunable interference filter  5  of the optical filter device  600 , and separates the Raman scattered light corresponding to gas molecules to be detected using the wavelength tunable interference filter  5  of the optical filter device  600 . Then, when the separated light is received by the light receiving element  137 , a light receiving signal corresponding to the amount of received light is output to the signal processing section  144  through the light receiving circuit  147 . 
     The signal processing section  144  determines whether or not the gas molecules to be detected obtained as described above are target gas molecules by comparing the spectral data of the Raman scattered light corresponding to the gas molecules to be detected with the data stored in the ROM, and specifies the material. In addition, the signal processing section  144  displays the result information on the display unit  141 , or outputs the result information to the outside through the connection unit  142 . 
     In  FIGS. 11 and 12 , the gas detector  100  that performs gas detection from the Raman scattered light separated by the wavelength tunable interference filter  5  of the optical filter device  600  is exemplified. In addition, as a gas detector, it is also possible to use a gas detector that specifies the type of gas by detecting the gas-specific absorbance. In this case, a gas sensor that detects light absorbed by gas, among incident light, after making gas flow into the sensor is used as the optical module according to the invention. In addition, a gas detector that analyzes and determines gas flowing into the sensor using a gas sensor is used as the electronic apparatus according to the invention. Also in such a configuration, it is possible to detect components of gas using the wavelength tunable interference filter. 
     In addition, as a system for detecting the presence of a specific material, a material component analyzer, such as a non-invasive measuring apparatus for obtaining the information regarding sugar using near-infrared spectroscopy or a non-invasive measuring apparatus for obtaining information regarding food, minerals, living bodies, and the like can be exemplified without being limited to the gas detection described above. 
     Hereinafter, a food analyzer will be described as an example of the material component analyzer. 
       FIG. 13  is a drawing showing the schematic configuration of a food analyzer that is an example of an electronic apparatus using the optical filter device  600 . 
     As shown in  FIG. 13 , a food analyzer  200  includes a detector  210  (optical module), a control unit  220 , and a display unit  230 . The detector  210  includes a light source  211  that emits light, an imaging lens  212  to which light from a measurement target is introduced, the optical filter device  600  that can separate the light introduced through the imaging lens  212 , and an imaging unit  213  (detection section) that detects the separated light. Instead of the optical filter device  600 , the optical filter devices  600 A and  600 B in the second and third embodiments may also be used. 
     In addition, the control unit  220  includes a light source control section  221  that performs ON/OFF control of the light source  211  and brightness control at the time of lighting, a voltage control section  222  that controls the wavelength tunable interference filter  5  of the optical filter device  600 , a detection control section  223  that controls the imaging unit  213  and acquires a spectral image captured by the imaging unit  213 , a signal processing section  224 , and a storage section  225 . 
     In the food analyzer  200 , when the system is driven, the light source control section  221  controls the light source  211  so that light is emitted from the light source  211  to the measurement target. Then, light reflected by the measurement target is incident on the optical filter device  600  through the imaging lens  212 . By the control of the voltage control section  222 , a voltage by which light having a desired wavelength can be separated is applied to the wavelength tunable interference filter  5  of the optical filter device  600 . The separate light is imaged by the imaging unit  213  formed by a CCD camera, for example. The imaged light is stored in the storage section  225  as a spectral image. The signal processing section  224  changes the value of a voltage applied to the wavelength tunable interference filter  5  by controlling the voltage control section  222 , thereby obtaining a spectral image for each wavelength. 
     Then, the signal processing section  224  calculates a spectrum in each pixel by performing arithmetic processing on the data of each pixel in each image stored in the storage section  225 . For example, information regarding the components of the food for the spectrum is stored in the storage section  225 . The signal processing section  224  analyzes the data of the obtained spectrum based on the information regarding food stored in the storage section  225 , and calculates food components contained in the detection target and the content thereof. In addition, food calories, freshness, and the like can be calculated from the obtained food components and content. By analyzing the spectral distribution in the image, it is possible to extract a portion, of which freshness is decreasing, in the food to be examined. In addition, it is also possible to detect foreign matter contained in the food. 
     Then, the signal processing section  224  performs processing for displaying the information obtained as described above, such as the components or the content of the food to be examined and the calories or freshness of the food to be examined, on the display unit  230 . 
     Although an example of the food analyzer  200  is shown in  FIG. 13 , the invention can also be used as a non-invasive measuring apparatus for obtaining other information, as described above by applying substantially the same configuration. For example, the invention can be used as a biological analyzer for the analysis of biological components involving the measurement and analysis of body fluids, such as blood. For example, if an apparatus that detects ethyl alcohol is used as the apparatus for measuring the body fluids, such as blood, the biological analyzer can be used as a drunk driving prevention apparatus that detects the blood alcohol level of the driver. In addition, the invention can also be used as an electronic endoscope system including such a biological analyzer. 
     In addition, the invention can also be used as a mineral analyzer for analyzing the components of minerals. 
     The wavelength tunable interference filter, the optical module, and the electronic apparatus according to the invention can be applied to the following apparatuses. 
     For example, it is possible to transmit data with light of each wavelength by changing the intensity of light of each wavelength with time. In this case, data transmitted by light having a specific wavelength can be extracted by separating the light having a specific wavelength using a wavelength tunable interference filter provided in the optical module and receiving the light having a specific wavelength using a light receiving unit. By processing the data of light of each wavelength using an electronic apparatus including such an optical module for data extraction, it is also possible to perform optical communication. 
     The electronic apparatus can also be applied to a spectral camera, a spectral analyzer, and the like for capturing a spectral image by separating light using a wavelength tunable interference filter. As an example of such a spectral camera, an infrared camera including a wavelength tunable interference filter can be exemplified. 
       FIG. 14  is a schematic diagram showing the configuration of a spectral camera. As shown in  FIG. 14 , a spectral camera  300  includes a camera body  310 , an imaging lens unit  320 , and an imaging unit  330  (detection unit). 
     The camera body  310  is a portion held and operated by the user. 
     The imaging lens unit  320  is provided on the camera body  310 , and guides incident image light to the imaging unit  330 . In addition, as shown in  FIG. 14 , the imaging lens unit  320  is configured to include an objective lens  321 , an imaging lens  322 , and the optical filter device  600  provided between these lenses. Instead of the optical filter device  600 , the optical filter devices  600 A and  600 B in the second and third embodiments may also be used. 
     The imaging unit  330  is formed by a light receiving element, and images image light guided by the imaging lens unit  320 . 
     In the spectral camera  300 , a spectral image of light having a desired wavelength can be captured by transmitting the light having a wavelength to be imaged using the wavelength tunable interference filter  5  of the optical filter device  600 . 
     In addition, it is also possible to use an optical device that uses the wavelength tunable interference filter as a band pass filter. For example, the optical device according to the invention can also be used as an optical laser device that separates and transmits only light in a narrow band having a predetermined wavelength at the center, of light in a predetermined wavelength band emitted from a light emitting element, using the wavelength tunable interference filter. 
     In addition, the wavelength tunable interference filter housed in the optical device according to the invention may be used as a biometric authentication device. For example, the wavelength tunable interference filter according to the invention can also be applied to authentication devices of blood vessels, fingerprints, retinas, irises, and the like using light in a near infrared region or a visible region. 
     In addition, the optical module and the electronic apparatus can be used as a concentration detector. In this case, using a wavelength tunable interference filter, infrared energy (infrared light) emitted from a material is separated and analyzed, and the object concentration in a sample is measured. 
     As described above, the optical device, the optical module, and the electronic apparatus according to the invention can also be applied to any apparatus that separates predetermined light from incident light. In addition, since the optical device described above can separate light beams with a plurality of wavelengths using one device as described above, measurement of the spectrum of a plurality of wavelengths, and detection of a plurality of components can be accurately performed. Accordingly, compared with a known apparatus that extracts a desired wavelength using a plurality of devices, it is possible to make an optical module or an electronic apparatus small. Therefore, the optical device according to the invention can be appropriately used in a portable electronic apparatus or an in-vehicle electronic apparatus, for example. 
     In addition, the specific structure when implementing the invention may be formed by appropriately combining the respective embodiments described above and modification examples in a range where the object of the invention can be achieved, or may be appropriately changed to other structures or the like. 
     The entire disclosure of Japanese Patent Application No. 2013-183796, filed Sep. 5, 2013 is expressly incorporated by reference herein.