JP2012127917A - Wavelength selective infrared detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wavelength selective infrared detector for selectively detecting light of prescribed wavelength in a wider wavelength area than before with a single Fabry-Perot filter.SOLUTION: The wavelength selective infrared detector includes: a first filter of a variable Fabry-Perot type having a mirror placed opposite; a second filter which has a bandpass part for selectively transmitting light of a prescribed band and the bandpass part is provided in correspondence with the mirror; and an infrared detector for detecting light transmitting the bandpass part with an infrared detection element. A plurality of orders of interfering light are transmitted through the first filter. The bandpass part has light transmission in accordance with a modulation bandwidth in which an arbitrary order of the interfering light can obtain as a gap length changes. The second filter has many kinds of bandpass parts corresponding to different orders of the interfering light respectively. The infrared detector has a plurality of infrared detection elements for detecting the interfering light transmitted through the second filter by the infrared detection elements different every kind of the bandpass part.

Description

  The present invention relates to a wavelength-selective infrared detection apparatus integrally including a wavelength selection filter and an infrared detector.

  2. Description of the Related Art Conventionally, as shown in Patent Document 1, for example, a wavelength-selective infrared detection device that is integrally provided with a variable Fabry-Perot filter and an infrared detector is known.

  Further, as the above-described variable Fabry-Perot filter, for example, those shown in Patent Documents 2 and 3 are known. This Fabry-Perot filter includes a pair of mirror structures (a fixed mirror structure and a movable mirror structure) in which a low refractive index layer is disposed between high refractive index layers made of polysilicon. These mirror structures are arranged to face each other through an air gap. In Patent Document 2, a silicon dioxide layer as a low refractive index layer is arranged in a transmission region to form a mirror. On the other hand, in Patent Document 3, an air layer as a low refractive index layer is arranged in a transmission region to form a mirror.

  Further, the high refractive index layer of each mirror structure is doped with impurities to form electrodes. Therefore, the electrostatic force generated by applying a voltage to the electrodes of each mirror structure displaces the movable mirror structure membrane located on the gap, thereby changing the gap length and changing the gap length between the mirrors. It is possible to selectively transmit light having a wavelength corresponding to the wavelength.

Japanese Patent No. 4158076 Japanese Patent No. 3457373 JP 2008-134388 A

  In recent years, from the viewpoint of reducing the number of components and multi-component detection in an infrared gas detector, a single wavelength selection filter that can selectively transmit (spectroscope) light in a wider wavelength range is desired. . That is, a wavelength selective filter having a wide transmission spectrum modulation band is desired.

  Here, the wavelength λ of the spectrum (interference light) transmitted through the Fabry-Perot filter is expressed by λ = 2 × d / m. d is the gap length between the mirrors, and m is a positive integer indicating the order of the interference light.

  In fact, among the various orders of interference light, those having peaks in the spectral band of the Fabry-Perot filter (wavelength range where light can be selectively transmitted) corresponding to the reflection band of the mirror (band showing high reflectance), Selectively passes through a Fabry-Perot filter. Further, the gap length d changes with the displacement of the membrane MEM. Therefore, the interference light having a peak in the spectral band described above is selectively transmitted through the Fabry-Perot filter in a range in which the gap length d can be taken with the displacement of the membrane MEM. Accordingly, the wavelength range in which light is selectively transmitted within the range of the gap length d is the modulation band of the transmission spectrum.

  In the Fabry-Perot filters disclosed in Patent Documents 1 to 3, the electrostatic force generated by applying a voltage to the electrodes of each mirror structure is inversely proportional to the square of the opposing distance of the electrodes, and the spring is restored due to the displacement of the membrane. The force is directly proportional to the amount of change in the facing distance of the electrodes. Therefore, when the amount of change in the opposing distance of the electrode is larger than 1/3 of the opposing distance of the electrode in the initial state where no electrode is applied, the electrostatic force exceeds the spring restoring force, and both mirror structures are drawn by the electrostatic force. Even if the voltage is removed by sticking, the original state is not restored (a pull-in phenomenon occurs). Therefore, if the gap length between the mirrors in the initial state where no voltage is applied is di and the opposing distance of the electrodes is also di, the range from di to di × 2/3 is a possible range of the gap length d. .

  Therefore, the modulation band of the widest primary interference light (m = 1) is ideally 2di to di × 4/3, and the primary interference light is selectively detected by the infrared detector. However, the modulation spectrum of the transmission spectrum is not wide enough. For this reason, for example, it is difficult to configure a multi-component detection gas detector with one Fabry-Perot filter.

  SUMMARY OF THE INVENTION In view of the above problems, the present invention provides a wavelength selective infrared detecting device capable of selectively detecting light of a predetermined wavelength in a wider wavelength range than the prior art while having only one Fabry-Perot filter. With the goal.

In order to achieve the above object, the invention described in claim 1
A variable Fabry-Perot type first filter that can change a gap length between mirrors arranged opposite to each other and selectively transmits light having a wavelength corresponding to the gap length in the infrared region;
A second filter having a bandpass portion that selectively transmits light in a predetermined band, the bandpass portion being provided corresponding to the mirror;
An infrared detector that detects light transmitted through the bandpass portion with an infrared detector;
The light transmitted through the first filter includes a plurality of orders of interference light,
The bandpass unit has a light transmission characteristic corresponding to a modulation band that interference light of an arbitrary order can take with a change in gap length,
The second filter has a plurality of types of bandpass units corresponding to different orders of interference light,
The infrared detector has a plurality of infrared detection elements so that the interference light transmitted through the second filter is detected by a different infrared detection element for each type of bandpass unit.

  In the present invention, the first filter (variable Fabry-Perot filter) transmits a plurality of orders of interference light according to the gap length, and each bandpass section of the second filter transmits a plurality of orders of interference light. Among them, light having a wavelength corresponding to its own light transmission characteristic is selectively transmitted. And the interference light which permeate | transmitted the band pass part is detected by the infrared detection element which differs for every light transmission characteristic of a band pass part. For example, light transmitted through a bandpass unit having a light transmission characteristic corresponding to the modulation band of the primary interference light is detected by an infrared detection element for the bandpass unit, and is light corresponding to the modulation band of the secondary interference light The light transmitted through the bandpass part having the transmission characteristic is detected by the infrared detection element for the bandpass part.

  Therefore, the sum of the modulation bands of the interference light that can be transmitted through each bandpass unit becomes the modulation band of the transmission spectrum by the first filter and the second filter. For this reason, according to the present invention, in a configuration having only one first filter (Fabry-Perot filter), it is possible to selectively detect light of a predetermined wavelength in a wider wavelength range than in the past.

  According to a second aspect of the present invention, the second filter may be configured to have a bandpass unit for a plurality of successive orders of interference light.

  Here, in the case of a mirror having an optical multilayer structure in which a low refractive index layer is interposed between high refractive index layers, the optical film thickness of each layer is 1/4 times the center wavelength. In other words, the center wavelength is determined by the optical film thickness of each layer. This center wavelength determines the center position of the reflection band of the mirror. The reflection band is determined based on the refractive index ratio of the high refractive index layer to the low refractive index layer with the center wavelength at the center. For this reason, the larger the refractive index ratio, the wider the width of the reflection band. Further, the mirror exhibits a reflection action (high reflectance) with respect to light having a wavelength in the reflection band, and has a low reflectance with respect to light having a wavelength outside the reflection band, and does not exhibit a reflection action. In the Fabry-Perot filter configured using this mirror, the spectral band capable of selectively transmitting light corresponds to the reflection band of the mirror.

  Therefore, with the configuration described in claim 2, since the modulation bands of the interference light are close to each other, it is easy to adjust so that the modulation bands of each interference light are located within the spectral band. That is, it is easy to configure the first filter. Further, depending on the order of the interference light, a plurality of modulation bands can be made one continuous modulation band.

For example, as described in claim 3, the first filter has a pair of mirror structures in which the mirror and the electrode are integrally formed, and the forming portions of the mirror and the electrode are arranged to face each other with a gap therebetween. In the initial state where no voltage is applied, the gap length between the mirrors is set to be equal to or less than the opposing distance between the electrodes, and the gap in one mirror structure is bridged by electrostatic force generated based on the voltage applied between the pair of electrodes. The amount of change in the facing distance between the electrodes is 1/3 of the facing distance between the electrodes in the initial state where no voltage is applied, and the electrostatic force is balanced with the spring restoring force of the membrane. And
The second filter may employ a configuration having a bandpass unit corresponding to at least two successive interference lights of the second, third, and fourth orders as a plurality of successive orders of interference light.

  The wavelength λ of the spectrum (interference light) transmitted through the Fabry-Perot filter is expressed by λ = 2 × d / m. d is the gap length between the mirrors, and m is a positive integer indicating the order of the interference light. In the case of the first filter in which 1/3 of the facing distance between the electrodes in the initial state is the pull-in limit, the lower limit of the modulation band of the second-order interference light (wavelength at the pull-in limit) and the upper limit of the third-order interference light (initial Wavelength in the state). That is, there is no gap between the secondary interference light and the tertiary interference light between the modulation bands. Therefore, when the secondary interference light and the tertiary interference light are included as targets, these modulation bands can be set as one continuous modulation band.

  In addition, the lower limit (wavelength at the pull-in limit) of the third-order interference light is lower than the upper limit (wavelength in the initial state) of the fourth-order interference light. In other words, there is no gap between the third-order interference light and the fourth-order interference light between the modulation bands. Therefore, even when the third-order interference light and the fourth-order interference light are included as targets, these modulation bands can be made one continuous modulation band. In addition, even when second-order, third-order, and fourth-order interference light is targeted, these modulation bands can be made one continuous modulation band.

According to a fourth aspect of the present invention, in the first filter, the pair of mirrors has a low refractive index air between the high refractive index layers made of a silicon semiconductor thin film and a lower refractive index air than the material constituting the high refractive index layer. It has an optical multilayer structure in which a refractive index layer is interposed, and the initial gap length before displacement is the same length as the upper limit of the spectral band of the first filter,
The second filter has a bandpass unit corresponding to each of the second, third, and fourth order interference lights as a plurality of successive interference lights,
In the band where the third order interference light and the fourth order interference light pass through one of the band pass part corresponding to the third order interference light and the band pass part corresponding to the fourth order interference light, the third order interference light and 4 Based on the output of the infrared detection element corresponding to the bandpass part through which the third-order interference light and one of the fourth-order interference light are transmitted, based on the output of the infrared detection element corresponding to the bandpass part through which the next interference light passes. A configuration including a correction processing unit that performs correction processing is preferable.

  According to this, since the upper limit of the modulation band of the secondary interference light substantially coincides with the upper limit of the spectral band of the first filter in the air mirror structure in which silicon is a high refractive index layer and air is a low refractive index layer, Almost the entire spectral band of the first filter can be used as the modulation band of the transmission spectrum by the first filter and the second filter. It should be noted that the gap length between the mirrors in the initial state is not limited to the exact same as the upper limit of the spectral band, but may be approximately the same. In addition, since air is employed as the low refractive index layer, the refractive index ratio of the high refractive index layer to the low refractive index layer can be increased. Thereby, the spectral band of the first filter can be widened.

  As described above, the lower limit (wavelength at the pull-in limit) of the third-order interference light is lower than the upper limit (wavelength in the initial state) of the fourth-order interference light. Therefore, the modulation bands partially overlap, and the third-order interference light and the fourth-order interference light are transmitted from the bandpass unit corresponding to the third-order interference light in some wavelength regions. However, at this time, only the fourth-order interference light is transmitted from the bandpass unit corresponding to the fourth-order interference light. In the present invention, the influence of the fourth-order interference light on the output of the infrared detection element corresponding to the third-order bandpass unit is determined by the correction processing unit based on the output of the infrared detection element corresponding to the fourth-order bandpass unit. Can be corrected. Thereby, the third order interference light can be detected.

  Similarly, the third-order interference light and the fourth-order interference light are transmitted from the bandpass unit corresponding to the fourth-order interference light in some wavelength regions. However, at this time, only the third-order interference light is transmitted from the bandpass unit corresponding to the third-order interference light. In the present invention, the influence of the third-order interference light on the output of the infrared detection element corresponding to the fourth-order bandpass unit is determined by the correction processing unit based on the output of the infrared detection element corresponding to the third-order bandpass unit. Can be corrected. Thereby, the fourth-order interference light can be detected.

  From the above, even when the second-order, third-order, and fourth-order interference light is targeted, the entire modulation band can be set as one continuous modulation band. Therefore, the wavelength range in which light of a predetermined wavelength can be selectively detected can be made wider.

According to a fifth aspect of the present invention, in the first filter, the pair of mirrors is made of silicon dioxide having a lower refractive index than a material constituting the high refractive index layer between the high refractive index layers made of a silicon semiconductor thin film. It has an optical multilayer structure in which a low refractive index layer is interposed, and the gap length in the initial state before displacement is the same length as the upper limit of the spectral band of the first filter,
The second filter may employ a configuration having a bandpass unit corresponding to each of the second-order and third-order interference light as a plurality of successive orders of interference light.

  According to this, since the upper limit of the modulation band of the secondary interference light substantially coincides with the upper limit of the spectral band of the first filter in the mirror structure in which silicon is a high refractive index layer and silicon dioxide is a low refractive index layer. The substantially entire spectral band of the first filter can be used as the modulation band of the transmission spectrum by the first filter and the second filter. It should be noted that the gap length between the mirrors in the initial state is not limited to the exact same as the upper limit of the spectral band, but may be approximately the same.

According to a sixth aspect of the present invention, the first filter has a pair of mirror structures in which a mirror and an electrode are integrally formed, and a portion including the mirror and the electrode is disposed to face each other with a gap interposed therebetween. The part that bridges the gap in one mirror structure is a displaceable membrane, and the length twice as long as the gap length in the initial state before displacement is the same length as the upper limit of the spectral band of the first filter. The amount of change in the gap length between the mirrors arranged opposite to each other can be set to 1/2 or more of the gap length in the initial state before displacement,
The second filter may employ a configuration having a bandpass unit corresponding to each of the first and second order interference lights as a plurality of successive orders of interference light.

  For example, if the amount of change in the gap length is 1/2 of the gap length in the initial state, the lower limit of the modulation band of primary interference light (wavelength at the pull-in limit) and the upper limit of secondary interference light (in the initial state) Of the same wavelength). Further, when the amount of change in the gap length is made larger than 1/2 of the gap length in the initial state, the lower limit (wavelength at the pull-in limit) of the primary interference light is set to the upper limit of the secondary interference light ( Less than the wavelength in the initial state). Therefore, according to the present invention, a plurality of modulation bands can be made one modulation band continuous without a gap. That is, light of a predetermined wavelength can be selectively detected in one continuous wide wavelength range. The interference light has a wider modulation band as the order is smaller. Therefore, according to the present invention, it is possible to further widen the wavelength range in which light having a predetermined wavelength can be selectively detected.

  According to a seventh aspect of the present invention, the first filter has a configuration in which a length twice as long as the gap length in the initial state before the displacement is the same as the upper limit of the spectral band of the first filter. It is preferable. According to this, since the upper limit of the modulation band of the primary interference light substantially coincides with the upper limit of the spectral band of the first filter, almost the entire spectral band of the first filter is transmitted by the first filter and the second filter. It can be a spectrum modulation band. Note that the same length as the upper limit of the spectral band is not limited to a perfect match, but may be the same length.

  Note that a first filter having a pair of mirror structures in which a mirror and an electrode are integrally formed and having a gap length change amount of 1/2 or more of the initial gap length ( As the Fabry-Perot filter, the configuration described in the previous applications (Japanese Patent Application Nos. 2010-261490, 2010-258028, and 2009-170310) filed by the present applicant can be employed.

For example, as described in claim 8, in the first filter, the peripheral region excluding the mirror formation region in the membrane is a spring deformation portion provided in a multiple manner so as to surround the mirror formation region. A first spring deforming portion provided over the first spring deforming portion, and a second spring deforming portion which is provided on the inner side of the first spring deforming portion and has a spring constant set smaller than that of the first spring deforming portion,
When the spring constant of the first spring deforming portion is k ₁ and the spring constant of the second spring deforming portion is k ₂ , the spring deforming portion is configured to satisfy k ₁ / k ₂ ≧ 7,
In the peripheral region excluding the mirror formation region at the membrane-facing portion of the membrane and the fixed mirror structure, electrodes are provided so as to face each other to form an electrode pair,
The electrode pairs are provided in the same number of multiples corresponding to the plurality of spring deforming portions while surrounding the mirror forming region, and the first electrode pairs deforming the first spring deforming portions by electrostatic force generated by applying a voltage; The second electrode pair is provided on the inner side of the second electrode pair, and mainly deforms the second spring deformation portion by electrostatic force generated by application of voltage,
It is possible to adopt a configuration in which a period in which a voltage is applied to each electrode pair is at least partially overlapped, and the membrane is displaced by electrostatic force generated in each electrode pair in the overlapping period.

  According to the present invention, by applying a voltage to the first electrode pair corresponding to the first spring deforming portion, the electrostatic force generated in the first electrode pair is positioned on the outermost periphery among the plurality of spring deforming portions. The first spring deforming portion can be deformed. As a result, the entire membrane is displaced. In addition, by applying a voltage to the second electrode pair located inside the first electrode pair, the first spring deforming portion is hardly deformed from the relationship of the spring constant due to the electrostatic force generated in the second electrode pair. Moreover, the 2nd spring deformation | transformation part located inside can be deformed.

  For this reason, by applying a voltage to the second electrode pair located inside while applying a voltage to the first electrode pair and displacing the mirror forming region portion of the membrane, the mirror forming region portion of the membrane is further increased. Can be displaced. By this multistage displacement, the membrane can be displaced beyond the conventional pull-in limit without causing a pull-in phenomenon. As described above, according to the present invention, at least a part of the period during which voltage is applied to each electrode pair is overlapped, and the membrane is displaced beyond the conventional pull-in limit by the electrostatic force generated in each electrode pair during the overlap period. be able to.

  Here, the wavelength λ of transmitted light is represented by λ = 2 × d / m. m is a positive integer indicating the order of the interference light, and d is the gap length between the mirrors. Therefore, the modulation band of the primary interference light is approximately twice the amount of change in the gap length between the mirrors. However, in the conventional Fabry-Perot filter, 1/3 of the initial length of the electrode facing distance is the pull-in limit, and this makes it impossible to increase the displacement of the membrane. Between the modulation bands of the secondary interference light, there was a wavelength band that could not be dispersed. This non-spectral region is an obstacle to widening the bandwidth.

On the other hand, according to the present invention, the change amount of the gap length can be made larger than 1/2 of the initial length of the gap from the relationship between the spring constants k ₁ and k ₂ . Then, by applying a voltage so that the amount of change in the gap length between the mirrors arranged opposite to each other is 1/2 or more of the gap length in the initial state before displacement, the modulation band of the primary interference light is applied. The modulation band of the primary interference light and the modulation band of the secondary interference light can be made continuous. As described above, according to the present invention, a plurality of modulation bands can be made one modulation band continuous without a gap. That is, light of a predetermined wavelength can be selectively detected in one continuous wide wavelength range.

Further, as described in claim 9, in the first filter, in the initial state where no voltage is applied, the gap length between the mirrors is equal to or less than the facing distance between the electrodes,
In at least one of the pair of mirror structures, the electrode and the other part of the mirror structure excluding the electrode are electrically separated,
The membrane is provided between the high-rigidity portion surrounding the mirror, the first spring deformation portion provided at the outer end of the membrane and connected to the high-rigidity portion, and the high-rigidity portion and the mirror. A second spring deformation part connected to
The two spring deformed portions provided in multiple so as to surround the mirror are less rigid than the other mirrors and high-rigidity portions constituting the membrane,
The part of the electrode formed on the membrane facing the other electrode occupies only a part of the highly rigid part in the direction from the center of the membrane toward the outer end,
In the direction from the center of the membrane toward the outer end, the distance between the center of the opposed portion of the pair of electrodes and the end of the high rigidity portion on the first spring deforming portion side is L1, and the length of the high rigidity portion is L2.
L2 / L1 ≧ 3/2
It may be configured to satisfy.

  In the present invention, the first spring deformed portion, the highly rigid portion including the electrode, the second spring deformed portion, and the mirror are provided in this order from the outer end of the membrane toward the center. That is, apart from the first spring deforming portion and the second spring deforming portion, a highly rigid portion having higher rigidity than these spring deforming portions is provided. Therefore, when a voltage is applied between the electrodes and the membrane electrode tries to displace toward the other electrode due to the electrostatic force generated between the electrodes, the connection portion with the second spring deforming portion is connected to the first spring. It displaces while inclining so that it may approach a fixed mirror structure rather than a connection end with a deformation | transformation part. Further, the high-rigidity part having higher rigidity than the spring deformation part can be displaced while being inclined in a flat state without being bent like the spring deformation part.

  Focusing on the position of the electrode facing portion (hereinafter simply referred to as the electrode facing portion) in the high-rigidity portion, the distance L1 between the center of the electrode facing portion and the end of the high-rigidity portion on the first spring deforming portion side The length L2 of the highly rigid portion is configured to satisfy L2 / L1 ≧ 3/2. The length of the high-rigidity portion is sufficiently longer than the length of the first spring deformation portion, and the opposing distance of the electrodes when no voltage is applied is de, and the end on the first spring deformation portion side in the high-rigidity portion is The displacement amount of the pull-in limit at the electrode facing portion with respect to the reference end is de × 1/3, and the displacement amount at the end of the high-rigidity portion on the second spring deformed portion side is de × 1/2. And As described above, since the highly rigid portion is displaced while being inclined in a flat state, L2 / L1 = 3/2 from a proportional relationship. Therefore, by satisfying L2 / L1 ≧ 3/2, the amount of displacement at the end portion on the second spring deformed portion side in the highly rigid portion becomes de × 1/2 or more. Since the mirror is connected via the high-rigidity part and the second spring deforming part, the displacement amount of the gap length between the mirrors is also ½ or more of the initial gap length.

  For this reason, the modulation of the primary interference light is performed by applying a voltage so that the amount of change in the gap length between the mirrors arranged opposite to each other is 1/2 or more of the gap length in the initial state before the displacement. The band can be lengthened, and the modulation band of the primary interference light and the modulation band of the secondary interference light can be made continuous. As described above, according to the present invention, a plurality of modulation bands can be made one modulation band continuous without a gap. That is, light of a predetermined wavelength can be selectively detected in one continuous wide wavelength range.

  In the present invention, the high-rigidity part and the mirror are mechanically (structurally) separated by the high-rigidity part and the second spring deformation part that has lower rigidity (small spring constant) than the high-rigidity part and the mirror. Therefore, even when a voltage is applied between the electrodes and the highly rigid portion including the electrodes is displaced, the displaced mirror can be held substantially parallel to the mirror structure (mirror) on the other side. In addition, in at least one of the pair of mirror structures, the electrode and the other part of the mirror structure excluding the electrode are electrically separated, so that an electrostatic force is generated between the mirrors even when a voltage is applied between the electrodes. Each mirror can be held flat with little (or no) occurrence. Thereby, the half value width (FWHM) of a transmission wavelength can be reduced.

Moreover, as described in claim 10,
In the first filter:
In at least one of the pair of mirror structures, the mirror and the electrode are electrically insulated and separated,
In an initial state where no voltage is applied, the opposing distance dei between the electrically coupled portion including the electrode in one mirror structure and the electrically coupled portion including the electrode in the other mirror structure Longer than the facing distance dmi between,
dei ≧ dmi × 3/2
It may be configured to satisfy.

  In the present invention, the mirror and the electrode are electrically insulated and separated in at least one of the pair of mirror structures. Therefore, even if a voltage is applied between the electrodes to change the gap, the mirror on the side that is insulated from the electrode does not have the same potential as the electrode. As a result, there is little or no electrostatic force between the mirrors, and the pull-in limit is the electrically coupled portion including the electrode in one mirror structure (in other words, the same as the electrode). It depends on the opposing distance de between the potential portion) and the electrically coupled portion including the electrode in the other mirror structure (in other words, the portion having the same potential as the electrode).

  Further, among the facing distance de, the facing distance dei in the initial state where no voltage is applied is longer than the facing distance dmi between the mirrors (dei> dmi). Therefore, dei × 1/3> dmi × 1/3. Accordingly, the initial length dmi between the mirrors can be displaced by exceeding dmi × 1/3. In particular, in the present invention, it is set so as to satisfy dei ≧ dmi × 3/2. Therefore, the amount of change in the facing distance between the mirrors can be set to 1/2 or more of the initial gap length dmi.

  For this reason, the modulation of the primary interference light is performed by applying a voltage so that the amount of change in the gap length between the mirrors arranged opposite to each other is 1/2 or more of the gap length in the initial state before the displacement. The band can be lengthened, and the modulation band of the primary interference light and the modulation band of the secondary interference light can be made continuous. As described above, according to the present invention, a plurality of modulation bands can be made one modulation band continuous without a gap. That is, light of a predetermined wavelength can be selectively detected in one continuous wide wavelength range.

  In addition, as a first filter (Fabry-Perot filter) having a configuration in which the amount of change in the gap length can be ½ or more of the gap length in the initial state, an earlier application (patent application) filed by the applicant of the present application. 2010-280814) can also be employed.

As recited in claim 11, the first filter comprises:
A fixed mirror structure having a fixed mirror in a transmission region that transmits light;
A movable mirror structure having a movable portion disposed opposite to the fixed electrode and the first electrode on the membrane, wherein the portion facing the fixed mirror structure via the first gap is displaceable.
An electrode structure that is disposed on the opposite side to the front fixed mirror structure with respect to the movable mirror structure and has a second electrode in a portion facing the membrane via the second gap;
In an initial state where no voltage is applied between the first electrode and the second electrode, the length dei between the electrodes in the second gap and the length dmi between the mirrors in the first gap satisfy dei ≧ 3 × dmi. Meets
The membrane of the movable mirror structure and the membrane facing portion of the fixed mirror structure including the fixed mirror have the same potential at the portions facing each other.
By applying a voltage between the first electrode and the second electrode and displacing the membrane in a direction approaching the electrode structure, the length de between the electrodes in the second gap becomes shorter than the initial length dei. And the length dm between the mirrors in the first gap is configured to be longer than the length dmi in the initial state,
A 2nd filter is good also as a structure which has a band pass part corresponding to each interference light of 1st order and 2nd order as interference light of a plurality of continuous orders.

  Thus, in the present invention, three structures are arranged via two gaps, and the structure located in the middle is a movable mirror structure having a movable mirror and a first electrode on a displaceable membrane. In addition, one of the structures at both ends has a fixed mirror structure having no fixed electrode and a fixed mirror, and the other of the structures at both ends has an electrode structure having no second mirror and having a second electrode. . Therefore, when a voltage is applied between the first electrode of the movable mirror structure and the second electrode of the electrode structure to generate an electrostatic force (electrostatic attractive force), the membrane of the movable mirror structure is placed on the electrode structure side. Although the length of the second gap is shortened by being pulled, the length of the first gap between the fixed mirror structure and the movable mirror structure is increased.

  Thus, since the length between the mirrors is increased as the length between the electrodes is shortened, the possible range of the length dm between the mirrors is the initial length between the mirrors as in the prior art. Rather than being determined only by the length dmi, the upper limit value is determined based on the initial length dei between the electrodes. Specifically, it is dmi to (dmi + dei × 1/3). The initial length dei between the electrodes is longer than the initial length dmi between the mirrors. Therefore, the change amount Δdm (dei × 1/3) of the length between the mirrors from the initial state to the pull-in limit of the membrane (first electrode) is changed to the change amount Δdm (dmi × 1) of the length between the mirrors of the conventional configuration. / 3).

  In the present invention, the membrane of the movable mirror structure and the membrane facing portion of the fixed mirror structure including the fixed mirror are set to the same potential at the portions facing each other. Accordingly, it is possible to suppress the occurrence of a potential difference between the membrane of the movable mirror structure and the membrane facing portion of the fixed mirror structure, and the influence of the electrostatic force based on the potential difference on the displacement of the membrane. In other words, the membrane facing portion of the fixed mirror structure is not displaced, and only the membrane of the movable mirror structure is displaced.

  As described above, according to the present invention, the membrane can be displaced so that the change amount Δdm is larger than 1/3 of the initial length dmi.

  Particularly, in the present invention, in order to satisfy dei ≧ 3 × dmi, the upper limit value of the modulation band of the second order interference light is equal to or greater than the lower limit value of the modulation band of the first order interference light. That is, the modulation band of the primary interference light and the modulation band of the secondary interference light can be made one modulation band continuous without a gap. That is, light of a predetermined wavelength can be selectively detected in one continuous wide wavelength range. The interference light has a wider modulation band as the order is smaller. Therefore, according to the present invention, it is possible to further widen the wavelength range in which light having a predetermined wavelength can be selectively detected.

  In addition, since the effect of the invention of Claim 12 is the same as the effect of the invention of Claim 7, the description is omitted.

Further, as described in claim 13, the first filter can make the amount of change in the gap length between the mirrors larger than 1/2 of the initial gap length before displacement,
In the band where the primary interference light and the secondary interference light pass through one of the band pass part corresponding to the primary interference light and the band pass part corresponding to the secondary interference light, the primary interference light and 2 Based on the output of the infrared detection element corresponding to the bandpass part through which the first interference light and the second one of the interference light are transmitted, based on the output of the infrared detection element corresponding to the bandpass part through which the next interference light is transmitted. A configuration including a correction processing unit that performs correction processing is preferable.

  As described above, the lower limit (wavelength at the pull-in limit) of the primary interference light is lower than the upper limit (wavelength in the initial state) of the secondary interference light. Accordingly, the modulation bands partially overlap, and the primary interference light and the secondary interference light are transmitted from the bandpass unit corresponding to the primary interference light in some wavelength regions. However, at this time, only the secondary interference light is transmitted from the bandpass unit corresponding to the secondary interference light. In the present invention, the influence of the secondary interference light on the output of the infrared detection element corresponding to the primary bandpass unit based on the output of the infrared detection element corresponding to the secondary bandpass unit by the correction processing unit. Can be corrected. Thereby, the primary interference light can be detected.

  Similarly, the primary interference light and the secondary interference light are transmitted from the bandpass unit corresponding to the secondary interference light in a part of the wavelength range. However, at this time, only the primary interference light is transmitted from the bandpass unit corresponding to the primary interference light. In the present invention, the influence of the primary interference light on the output of the infrared detection element corresponding to the secondary bandpass unit based on the output of the infrared detection element corresponding to the primary bandpass unit by the correction processing unit. Can be corrected. Thereby, the secondary interference light can be detected.

  From the above, even when primary and secondary interference light are targeted, the entire region of these modulation bands can be made one continuous modulation band. Therefore, the wavelength range in which light of a predetermined wavelength can be selectively detected can be made wider.

  According to a fourteenth aspect of the present invention, the plurality of band pass portions are configured such that the shape of the light receiving surface and the light receiving area are equal to each other and are arranged concentrically with respect to the center of the mirror in a direction perpendicular to the gap length direction. And good.

  According to this, variation in intensity of light detected by each infrared detection element can be suppressed. That is, the sensitivity can be made substantially the same for each infrared detecting element.

  According to a fifteenth aspect of the present invention, the second filter is made of a material that does not transmit the light transmitted through the first filter, and the plurality of bandpass portions are integrally formed so that the light is transmitted through each bandpass portion. The first filter, the second filter, and the infrared detection unit have a non-transmission portion to be held, and spacers are interposed between the first filter and the second filter and between the second filter and the infrared detector, respectively. It is good also as a structure with which the vessel was integrated. According to this, since the first filter, the second filter, and the infrared detector are stacked via the spacer, the configuration is easy.

  In addition, as described in claim 16, the band-pass part constituting the second filter may be laminated on the corresponding infrared detection element of the infrared detector. According to this, since the infrared detection element exists immediately below the band pass portion, the size can be reduced in the stacking direction while improving the sensitivity of the infrared detection element.

It is sectional drawing which shows schematic structure of the wavelength selection type infrared detection apparatus which concerns on 1st Embodiment. It is a top view which shows schematic structure of a 2nd filter. The figure which shows the reflective band of the mirror which comprises a 1st filter, (b) is a figure which shows the spectral band of a 1st filter. It is a figure which shows the modulation band of each interference light. In this embodiment, it is a figure which shows the modulation band of the interference light which permeate | transmits a 2nd filter. It is sectional drawing which shows a modification. It is sectional drawing which shows a modification. In the wavelength selective infrared detecting device according to the second embodiment, the first filter is a simplified model of a spring deformable portion and an electrode. It is a figure which shows the relationship between a spring constant ratio and the displacement ratio with respect to the gap length of an initial state. It is a figure which shows schematic structure of a 1st filter, and shows the state which applied the voltage to two electrode pairs, respectively, and produced the electrostatic force. It is a figure which shows the modulation band of each interference light. (A) is a figure which shows the spectral band of the 1st filter shown in 1st Embodiment, (b) is a figure which shows the spectral band when the spring constant ratio is set to 7 in the 1st filter which concerns on 2nd Embodiment. is there. In the wavelength selective infrared detection device concerning a 3rd embodiment, it is a figure showing the schematic structure of the 1st filter, and shows the state where the voltage was impressed. FIG. 14 is a diagram for explaining the positions of the opposed portions of the movable electrode and the fixed electrode in the high rigidity portion and the effects thereof in the first filter shown in FIG. 13. In the wavelength selective infrared detecting device according to the fourth embodiment, it is a diagram showing a schematic configuration of the first filter, (a) is an initial state where no voltage is applied, (b) is a maximum displacement Δdmax from the state of (a). It shows the state that was made to. It is a figure which shows the relationship between ratio dei / dmi of the distance between electrodes dei and the distance between mirrors dmi in an initial state, and maximum displacement (DELTA) dmax. In the wavelength-selective infrared detecting device according to the fifth embodiment, it is a diagram showing a schematic configuration of a first filter, where (a) shows an initial state and (b) shows a state where a voltage is applied. It is a figure which shows the modulation band of a transmission spectrum when the initial length dei between electrodes is 3 times the initial length dmi between mirrors.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following, common or related elements are given the same reference numerals. Further, an example in which the gap between the pair of mirrors M1 and M2 constituting the first filter is an air gap AG (air gap) is shown. Further, the length direction of the air gap, in other words, the displacement direction of the membrane MEM is simply referred to as the length direction, and the direction perpendicular to the length direction is simply referred to as the vertical direction.

(First embodiment)
As shown in FIG. 1, the wavelength selective infrared detection device 10 according to the present embodiment includes a variable Fabry-Perot first filter 11 and a second filter 12 having a bandpass unit 60 as a wavelength selective filter. An infrared detector 13 having an infrared detection element 70 is provided. Furthermore, in the present embodiment, when one infrared detection element 70 detects two orders of interference light (specifically, third order interference light and fourth order interference light) whose modulation bands partially overlap. The correction processing unit 14 for correcting the output of the infrared detection element 70 is provided.

  Further, a spacer 15 is interposed between the first filter 11 and the second filter 12 in a region different from the transmission region S1 that transmits light, and between the second filter 12 and the infrared detector 13. The spacer 16 is interposed in a region different from the transmission region S1. The first filter 11, the second filter 12, and the infrared detector 13 are stacked and integrated through the spacers 15 and 16. As described above, when the spacers 15 and 16 are used, the configuration is easy.

  First, the first filter 11 will be described.

  The first filter 11 can change the gap length of the mirrors M1 and M2 arranged opposite to each other, and is a variable Fabry-Perot that selectively transmits light in the infrared region and having a wavelength corresponding to the gap length. It is a filter. In this embodiment, an electrostatic drive type Fabry-Perot filter is employed.

  As an example, the first filter 11 (Fabry-Perot filter) configured as shown in FIG. 1 is basically the same as that disclosed in Patent Document 1 (Japanese Patent Laid-Open No. 2008-134388) by the applicant. A brief description will be given below.

  The first filter 11 is formed using the MEMS technology, and is disposed on the substrate 20 and has a fixed mirror structure 30 having a fixed mirror M1 in the transmission region S1, and a fixed mirror structure through a support member 40. 30 and a movable mirror structure 50 having a movable mirror M2 in the transmission region S1. A portion of the movable mirror structure 50 that bridges the air gap AG is a displaceable membrane MEM. The membrane MEM is displaced by the electrostatic force (electrostatic attractive force) generated based on the voltage applied between the electrode 34 of the fixed mirror structure 30 and the electrode 54 of the movable mirror structure 50, and the length of the air gap AG is reduced. It is going to change. Due to the displacement of the membrane MEM, the distance between the mirrors M1 and M2 in the air gap AG, that is, the gap length is changed, and light having a desired wavelength according to the gap length can be selectively transmitted.

  The fixed mirror structure 30 is disposed on one surface of the substrate 20 via an insulating film 22. In the present embodiment, a planar rectangular semiconductor substrate made of, for example, single crystal silicon is employed as the substrate 20. An insulating film 22 such as a silicon oxide film or a silicon nitride film is formed on the one surface of the substrate 20 with a substantially uniform thickness. A fixed mirror structure 30 is disposed on one surface of the substrate 20 with the insulating film 22 interposed therebetween. Further, in the present embodiment, an absorption region 21 doped with impurities is selectively provided in a region excluding the transmission region S1 in the vertical direction on the surface layer of the one side of the substrate 20, and thereby, outside the transmission region S1. The transmission of light is suppressed. A configuration without the absorption region 21 may be employed.

  The fixed mirror structure 30 is made of, for example, polysilicon, and a high refractive index lower layer 31 laminated on the insulating film 22, and a high refractive index upper layer 32 made of, for example, polysilicon and laminated on the high refractive index lower layer 31. And having. A portion where an air layer as a low refractive index layer 33 is interposed between the high refractive index lower layer 31 and the high refractive index upper layer 32 is a fixed mirror M1 having an optical multilayer structure. The fixed mirror M1 is divided (subdivided) into a plurality of parts by a connecting part in which a portion of the high refractive index upper layer 32 is in contact with the high refractive index lower layer 31, and each fixed mirror M1 is connected by the connecting part. ing. Further, in a region excluding the transmission region S1 (a region where the fixed mirror M1 is formed), the high refractive index upper layer 32 is in contact with the high refractive index lower layer 31, and is a peripheral region T1 that is a portion facing the membrane MEM and surrounds the transmission region S1. An electrode 34 is formed in the region. Reference numeral 35 denotes a pad for the electrode 34, and reference numeral 36 denotes a through hole for forming an air layer as the low refractive index layer 33 by etching.

  On the other hand, the movable mirror structure 50 is made of, for example, polysilicon and bridges the air gap AG to be disposed on the support member 40. The movable mirror structure 50 is made of, for example, polysilicon and is formed on the high refractive index lower layer 51. And a high refractive index upper layer 52 laminated. A portion where an air layer as a low refractive index layer 53 is interposed between the high refractive index lower layer 51 and the high refractive index upper layer 52 is a movable mirror M2 having an optical multilayer structure. The movable mirror M2 is divided into a plurality of parts (divided) by a connecting portion in which a portion of the high refractive index upper layer 52 is in contact with the high refractive index lower layer 51, and each movable mirror M2 is connected by the connecting portion. ing. The movable mirror M2 faces the fixed mirror M1. Further, in the region excluding the transmission region S1 (region where the movable mirror M2 is formed), the high refractive index upper layer 52 is in contact with the high refractive index lower layer 51, and the peripheral region T1 region surrounding the transmission region S1 is the membrane MEM. The electrode 54 is formed. Reference numeral 55 denotes a pad for the electrode 54, and reference numeral 56 denotes a through hole for forming an air layer as the low refractive index layer 53 by etching. Reference numeral 57 denotes a through hole that penetrates the membrane MEM and communicates the air gap AG with the outside. The through hole 57 is a through hole for removing a part of the support member 40 by etching to form an air gap AG.

  Further, reference numeral 41 shown in FIG. 1 is an opening as a contact hole that penetrates the support member 40 and reaches the high refractive index upper layer 32, and a pad 35 for the electrode 34 is formed in the opening 41.

  As described above, when polysilicon is employed as the high refractive index layers 31, 32, 51 and 52 constituting the mirror structures 30 and 50, since it is transparent to infrared light having a wavelength of about 2 to 10 μm, infrared gas is used. It is suitable as a wavelength selection filter for a detector. If a semiconductor thin film containing at least one of silicon and germanium, such as polygermanium or polysilicon germanium, is employed in addition to polysilicon, the same effect can be expected.

  In addition, as described above, when an air layer is employed as the low refractive index layers 33 and 53 of the mirrors M1 and M2, the refractive index nH (for example, 3.45 for Si and 4 for Ge) of the high refractive index layer is low. The n ratio (nH / nL) to the refractive index nL (1 in the air) of the refractive index layer is increased (for example, 3.3 or more) to selectively transmit the infrared light having the wavelength of about 2 to 10 μm. A Fabry-Perot filter that can be used can be realized at low cost.

  Here, in the first filter 11 described above, when the amount of change in the facing distance between the electrodes 34 and 54 is larger than 1/3 of the initial length of the facing distance, the electrostatic force exceeds the spring restoring force of the membrane MEM. Both mirror structures 30 and 50 are pulled in by electrostatic force, and even if the voltage is removed, they do not return to their original state (a pull-in phenomenon occurs). For this reason, 1/3 of the initial length of the opposing distance between the electrodes 34 and 54 is the pull-in limit.

  Moreover, as described above, the fixed mirror M1 and the movable mirror M2 have an optical multilayer structure. The optical film thickness of the layers 31 to 33 and 51 to 53 constituting each mirror is ¼ of the center wavelength λc, and the center wavelength λc is equal between the fixed mirror M1 and the movable mirror M2. ing. As described above, the center wavelength λc is determined by the optical film thickness of each of the layers 31 to 33 and 51 to 53. This center wavelength λc forms the center position of the reflection bands of the mirrors M1 and M2, as shown in FIG. The reflection band is centered on the center wavelength λc, and its width is determined by the refractive index ratio of the high refractive index layers 31, 32 (51, 52) to the low refractive index layer 33 (53). Even with the same refractive index ratio, the longer the center wavelength λc, the wider the width.

  As shown in FIG. 3A, the fixed mirror M1 and the movable mirror M2 exhibit a reflection effect (high reflectance) with respect to light with a wavelength in the reflection band, and reflect with respect to light with a wavelength outside the reflection band. The rate is low and does not show a reflection effect. In the first filter 11 (Fabry-Perot filter) formed by arranging the mirrors M1 and M2 so as to face each other, the spectral band capable of selectively transmitting light corresponds to the reflection band of the mirror as shown in FIG. . In this embodiment, it has a spectral band of approximately 3 to 8 μm.

Further, the wavelength λ of the transmission spectrum (interference light) selectively transmitted through the first filter 11 is expressed by the following equation. d is the gap length between the mirrors, and m is a positive integer indicating the order of the interference light.
(Equation 1) λ = 2 × d / m
Actually, among the interference lights of various orders, those having peaks in the above-described spectral band selectively pass through the first filter 11. Further, the gap length d changes with the displacement of the membrane MEM. Therefore, the interference light having a peak in the spectral band described above is selectively transmitted through the first filter 11 within a range in which the gap length d can be taken with the displacement of the membrane MEM. Accordingly, in the range that the gap length d can take, the wavelength range in which light is selectively transmitted is the modulation band of the interference light as illustrated in FIG. 2B.

  Assuming that the gap length between the mirrors M1 and M2 and the facing distance between the electrodes 34 and 54 are equal in the initial state where no voltage is applied (the state before the membrane MEM is displaced), the modulation bands of the respective orders are expressed by the following equation (1). As shown. The modulation band of the primary interference light (m = 1) is ideally 2di to di × 4/3. The modulation band of the secondary interference light (m = 2) is ideally di to di × 2/3. The modulation band of the third-order interference light (m = 3) is ideally di × 2/3 to di × 4/9. The modulation band of the fourth-order interference light (m = 4) is ideally di × 1/2 to di × 1/3. Therefore, as shown in FIG. 4, there is a wavelength band (non-spectral band) that cannot be dispersed between the modulation band of the primary interference light and the modulation band of the secondary interference light. Further, the lower limit (pull-in limit) of the second order interference light and the upper limit (initial state) of the third order interference light coincide with each other, so that the modulation band of the second order interference light and the modulation band of the third order interference light are changed. , There is no gap and no overlapping bands are connected as one wavelength region. Further, the lower limit (pull-in limit) of the third order interference light is lower than the upper limit (initial state) of the fourth order interference light, so that the modulation band of the second order interference light and the modulation band of the third order interference light are reduced. , While being partially overlapped, they are connected as one wavelength region.

  In the present embodiment, the gap length di in the initial state is set to substantially the same length as the upper limit of the spectral band of the first filter 11 (8 μm in the present embodiment). Therefore, the modulation bands of the second order interference light, the third order interference light, and the fourth order interference light are located within the spectral band of the first filter 11, and the second order interference light is transmitted from the first filter 11. Three orders of interference light, that is, third order interference light and fourth order interference light, are transmitted.

  Next, the remaining second filter 12, infrared detector 13, and correction processing unit 14 will be described.

  The second filter 12 includes a bandpass unit 60 that selectively transmits light in a predetermined band (light corresponding to a modulation band of interference light of an arbitrary order). The bandpass unit 60 is a so-called bandpass filter having an optical multilayer structure, and is provided corresponding to the formation region of the mirrors M1 and M2, that is, the transmission region S1 of the first filter 11, as shown in FIGS. It has been. The bandpass unit 60 includes a plurality of types of bandpass units 60a to 60c corresponding to different orders of interference light. Each of the bandpass units 60a to 60c has a light transmission characteristic corresponding to the modulation band of the corresponding order of interference light.

  In the present embodiment, the bandpass unit 60a has a characteristic of selectively transmitting light in the modulation band of the second order interference light, and the bandpass unit 60b selects light in the modulation band of the third order interference light. It has the characteristic of transmitting light. In addition, the bandpass unit 60c has a characteristic of selectively transmitting light in the modulation band of the fourth-order interference light. Accordingly, among the interference light transmitted through the first filter 11, secondary interference light is transmitted from the bandpass unit 60a. Further, the third-order interference light is mainly transmitted from the band pass unit 60b. Further, the fourth-order interference light is mainly transmitted from the band pass unit 60c. In FIG. 1, for convenience, one band pass unit 60 is illustrated so as to correspond to one (a pair) of the subdivided mirrors M1 and M2. However, one bandpass unit 60 may be provided corresponding to the plurality of pairs of mirrors M1 and M2. When one mirror M1 and M2 is provided in the transmission region S1 instead of the subdivided mirrors M1 and M2, a plurality of bands are provided so as to correspond to different parts of the one mirror M1 and M2. What is necessary is just to provide the pass parts 60a-60c.

  As described above, the modulation bands of the third-order interference light and the fourth-order interference light partially overlap. For this reason, when the third-order interference light is located in the region A that can be taken when the gap length is within a predetermined range from the initial state di, not only the third-order interference light but also the fourth-order interference light from the bandpass unit 60b. Transparent. Further, when the fourth-order interference light is located in the region B that can be taken when the gap length is within the predetermined range from the pull-in limit, not only the fourth-order interference light but also the third-order interference light is transmitted from the bandpass unit 60c. The Regions A and B will be described later.

  In the present embodiment, as shown in FIG. 2, the plurality of bandpass portions 60a to 60c have the same light receiving surface shape and light receiving area, and the center C1 of the mirrors M1 and M2 (transmission region S1) in the vertical direction. Are arranged on a concentric circle. With such an arrangement, it is possible to suppress variations in the intensity of light detected by each of the infrared detection elements 70a to 70c provided corresponding to the bandpass portions 60a to 60c. That is, the sensitivity can be made substantially the same in each of the infrared detection elements 70a to 70c. In addition, although the example of a perfect circle is shown in FIG. 2 as a shape of a light-receiving surface, a shape in particular is not limited.

  Moreover, in this embodiment, the band pass parts 60a-60c are hold | maintained at the base material 61 which consists of metals, and the 2nd filter 12 is a band pass filter array. The base material 61 functions as a mask (non-transmissive portion) that does not transmit the interference light transmitted through the first filter 11. A through hole is provided in a portion corresponding to the transmission region S1 in the base material 61 corresponding to the arrangement portion of the band pass portions 60a to 60c. The inner wall of the through hole in the vicinity of the opening opposite to the first filter 11 has a reduced diameter as shown in FIG. 1, and bandpass portions 60a to 60c are mounted on the reduced diameter portion.

  The infrared detector 13 has a plurality of infrared detection elements 70 so that the interference light transmitted through the second filter 12 is detected by different infrared detection elements 70 for each type of the bandpass unit 60. In this embodiment, it has three infrared detection elements 70a-70c corresponding to the three band pass parts 60a-60c. The number of infrared detection elements 70 is not limited to the same number as the number of bandpass units 60. For example, a plurality of band-pass portions 60a for secondary interference light may be provided, and one infrared detection element 70a may be provided corresponding to the plurality of band-pass portions 60a. A plurality of infrared detection elements 70a may be provided corresponding to one band pass unit 60a.

  As the infrared detecting element 70, a bolometer, a thermopile (thermopile), a pyroelectric element, a quantum element, or the like can be employed. In the present embodiment, the infrared detector 13 is provided so as to cover a thermopile formed on one surface of the substrate 71 made of, for example, silicon or germanium on the second filter 12 side, and at least a part of the thermopile. The thermal infrared detecting elements 70a to 70c having the infrared absorbing film are provided.

  Further, interference light (secondary interference light) transmitted through the bandpass unit 60a enters the infrared detection element 70a, and interference light (mainly third order interference light) transmitted through the bandpass unit 60b enters the infrared detection element 70b. Incident. Further, interference light (mainly fourth-order interference light) that has passed through the bandpass unit 60c is incident on the infrared detection element 70c.

  The correction processing unit 14 transmits two consecutive orders of interference light in a band in which two consecutive orders of interference light pass through one of the two bandpass sections corresponding to the two consecutive orders of interference light. The output of the infrared detection element corresponding to the transmitting bandpass part is corrected based on the output of the infrared detection element corresponding to the bandpass part through which only one of the two consecutive orders of interference light is transmitted.

  In this embodiment, since the modulation bands of the third-order interference light and the fourth-order interference light partially overlap, the third-order interference light is present when the wavelength of the third-order interference light is in the region A shown in FIG. The fourth-order interference light is transmitted together with the third-order interference light from the band-pass unit 60b corresponding to. For this reason, the third-order interference light and the fourth-order interference light are incident on the infrared detection element 70b corresponding to the bandpass unit 60b, and the output thereof is affected by the two interference lights.

  However, when the wavelength of the third-order interference light is in the region A shown in FIG. 5, only the fourth-order interference light is transmitted from the bandpass unit 60c corresponding to the fourth-order interference light. For this reason, the output of the infrared detection element 70c corresponding to the fourth-order bandpass unit 60c is only affected by the fourth-order interference light. When the wavelength of the third-order interference light is in the region A shown in FIG. 5, the correction processing unit 14 calculates the influence of the fourth-order interference light on the output of the infrared detection element 70b based on the output of the infrared detection element 70c. to correct. For example, the difference between the output of the infrared detection element 70b and the output of the infrared detection element 70c is defined as the influence of the third-order interference light by the infrared detection element 70b.

  Similarly, when the wavelength of the fourth-order interference light is in the region B shown in FIG. 5, the third-order interference light is transmitted together with the fourth-order interference light from the bandpass unit 60c corresponding to the fourth-order interference light. The On the other hand, only the third-order interference light is transmitted from the bandpass unit 60b corresponding to the third-order interference light. When the wavelength of the fourth-order interference light is in the region B shown in FIG. 5, the correction processing unit 14 calculates the influence of the third-order interference light on the output of the infrared detection element 70c based on the output of the infrared detection element 70b. to correct. For example, the difference between the output of the infrared detection element 70c and the output of the infrared detection element 70b is set as the influence of the fourth-order interference light by the infrared detection element 70c.

  As a result, the third-order interference light and the fourth-order interference light can be detected while the modulation areas of the third-order interference light and the fourth-order interference light have overlapping regions. As for the secondary interference light, the modulation band does not overlap with other interference light, so that the correction processing unit 14 does not perform correction and outputs the output of the infrared detection element 70a as it is.

  Next, the effect of the characteristic part of the wavelength selective infrared detecting device 10 provided with the first filter 11 whose pull-in limit is 1/3 of the facing distance between the electrodes 34 and 54 in the initial state will be described.

  In the present embodiment, the pair of mirrors M1 and M2 constituting the first filter 11 has the low refractive index layers 33 and 53 made of air interposed between the high refractive index layers 31, 32, 51 and 52 made of silicon. It is an air mirror. For this reason, the spectral band of the first filter 11 can be widened. Further, the gap length in the initial state is the same as the upper limit of the spectral band of the first filter 11, and the second filter 12 is a bandpass unit corresponding to each of the second, third, and fourth order interference light. 60a-60c. For this reason, almost the entire spectral band of the first filter 11 can be used as the modulation band of the transmission spectrum by the first filter and the second filter. Further, in the regions A and B where the third-order interference light and the fourth-order interference light are transmitted through one of the band-pass portion 60b corresponding to the third-order interference light and the band-pass portion 60c corresponding to the fourth-order interference light. The output of the infrared detecting element corresponding to the bandpass part through which the third-order interference light and the fourth-order interference light are transmitted corresponds to the bandpass part through which the third-order interference light and one of the fourth-order interference lights are transmitted. A correction processing unit 14 that performs correction processing based on the output of the infrared detection element is provided. Therefore, the third-order interference light and the fourth-order interference light can be detected substantially while the modulation areas of the third-order interference light and the fourth-order interference light have overlapping areas. Therefore, light having a predetermined wavelength can be selectively detected in a range from the upper limit of the modulation band of the second-order interference light to the lower limit of the modulation band of the fourth-order interference light, in other words, in the entire spectral band.

  In the present embodiment, an example in which the second filter 12 includes the bandpass units 60a to 60c for second-order to fourth-order interference light is shown. However, the order of the interference light passing through the second filter 12 is not limited to the above example. At least the variable Fabry-Perot type first filter 11 transmits a plurality of orders of interference light according to the gap length, and each bandpass unit 60 of the second filter 12 itself among the plurality of orders of interference light. The light of the wavelength according to the light transmission characteristic is selectively transmitted. Then, the interference light transmitted through the bandpass unit 60 may be detected by the infrared detection element 70 that is different for each light transmission characteristic of the bandpass unit 60. For example, the first to fourth order interference light is transmitted from the first filter 11, and the second filter 12 transmits the first, second, and fourth order interference light among the first to fourth order interference light. As described above, the configuration may include three band pass units 60 corresponding to the first, second, and fourth order interference light. In the configuration having only one first filter 11, the sum of the modulation bands of the interference light that can pass through each bandpass unit 60 becomes the modulation band of the transmission spectrum of the wavelength selection filter by the first filter and the second filter. Thus, light having a predetermined wavelength can be selectively detected in a wider wavelength range than in the past.

  In particular, as shown in the present embodiment, the second filter 12 is preferably configured to include the bandpass unit 60 for a plurality of successive orders of interference light. Since the modulation bands of the interference light are close to each other, it is easy to adjust so that the modulation bands of each interference light are located within the spectral band. That is, it is easy to configure the first filter 11. Further, depending on the order of the interference light, a plurality of modulation bands can be made one continuous modulation band.

  Further, in the present embodiment, the second filter 12 has the bandpass portions 60a to 60c for the second to fourth order interference light as a plurality of successive orders of interference light, but the second and third order interference light. A configuration having only the bandpass portions 60a and 60b for interference light and a configuration having only the bandpass portions 60b and 60c for third and fourth order interference light may be employed. When only the secondary and tertiary interference light bandpass units 60a and 60b are provided, the correction processing unit 14 can be omitted.

  For example, as an example having only the bandpass units 60a and 60b for secondary and tertiary interference light, the configuration shown in FIG. 6 can be adopted. In the wavelength selective infrared detecting device 10 shown in FIG. 6, in the first filter 11, the pair of mirrors M <b> 1 and M <b> 2 is interposed between the high refractive index layers 31, 32, 51, and 52 made of silicon semiconductor thin film, rather than silicon. It has an optical multilayer structure in which low refractive index layers 33 and 53 made of low refractive index silicon dioxide are interposed. The gap length in the initial state is almost the same as the upper limit of the spectral band of the first filter 11. The second filter 12 has bandpass portions 60a and 60b corresponding to the second and third interference light, and the infrared detector 13 corresponds to the infrared detection element 70a corresponding to the bandpass portions 60a and 60b. , 70b.

  With such a configuration, in the mirrors M1 and M2 in which silicon is the high refractive index layers 31, 32, 51, and 52 and silicon dioxide is the low refractive index layers 33 and 53, the upper limit of the modulation band of the secondary interference light is Thus, the upper limit of the spectral band (approximately 3 to 6 μm) of the first filter 11 is substantially coincident, and the lower limit of the modulation band of the third-order interference light is substantially coincident with the lower limit of the spectral band. Therefore, almost the entire spectral band of the first filter 11 can be set as the modulation band of the transmission spectrum by the first filter 11 and the second filter 12.

  Further, in the present embodiment, an example in which the second filter 12 and the infrared detector 13 are stacked and disposed via the spacer 16 is shown. However, for example, as illustrated in FIG. 7, the bandpass units 60 a to 60 c configuring the second filter 12 may be stacked on the corresponding infrared detection elements 70 a to 70 c of the infrared detector 13. With such a configuration, since the infrared detection element 70 exists directly below the bandpass unit 60, the size of the wavelength selective infrared detection device 10 can be reduced in size in the stacking direction while improving the sensitivity of the infrared detection element 70. Can do. In the example shown in FIG. 7, as the infrared detecting element 70, a bolometer is formed by injecting p-conductivity type or n-conductivity type impurities into the surface layer on the second filter 12 side of the substrate 71 made of silicon or germanium, for example. Has been. In this case, by applying a predetermined detection voltage to a bolometer as the infrared detection element 70, infrared rays can be detected based on a resistance change of the infrared detection element 70 due to a temperature change of infrared absorption. Reference numeral 17 shown in FIG. 7 is a spacer interposed between the substrate 71 of the infrared detector 13 and the first filter 11.

(Second Embodiment)
In the present embodiment, the first filter 11 has a pair of mirror structures 30 and 50 as in the first embodiment. And the part which bridge | crosslinks the air gap AG of the movable mirror structure 50 is the membrane MEM which can be displaced. In addition, twice the gap length di in the initial state is almost the same as the upper limit of the spectral band of the first filter 11, and the amount of change in the gap length between the mirrors M1 and M2 arranged opposite to each other. Can be set to 1/2 or more of the gap length di in the initial state. The main feature is that the second filter 12 has a bandpass unit 60 corresponding to the first order interference light and a bandpass unit 60 corresponding to the second order interference light as a plurality of successive orders of interference light. And

  An example of the first filter 11 that can change the gap length variation between the mirrors M1 and M2 to be 1/2 or more of the gap length di in the initial state will be described. The first filter 11 shown in the present embodiment is the one described in Japanese Patent Application No. 2010-261490 previously filed by the present applicant, so please refer to the details.

  FIG. 8 is a diagram in which the first filter 11 according to the present embodiment is simply modeled with a spring deforming portion and electrodes. In FIG. 8, an electrode E2 (corresponding to the electrode 54 of the first embodiment) is disposed opposite to the electrode E1 (corresponding to the electrode 34 of the first embodiment), and the electrodes E1, E2 are connected by a spring deforming part B1. Yes. In addition, the electrode E3 is disposed opposite to the electrode E1, and the electrode E3 is connected to the electrode E2 at the spring deformation portion B2. That is, it has two spring deformation parts B1 and B2 and two electrode pairs. Of the three electrodes E1 to E3, the position of the electrode E1 is fixed, and the electrodes E2 and E3 can be displaced.

Here, the spring constant of the spring deformation portion B1 _{k 1,} the spring constant _{k 2} of the spring deformation portion B2, _{V 1} the voltage applied to the electrode pair E1, E2, the voltage applied to the electrode pair E1, E3 _{V 2} The opposing distance between the electrodes E1 and E2 and the initial length of the electrodes E1 and E3 (the length when no voltage is applied) are both di. Further, x ₁ the absolute amount of displacement of the electrode E2 when a voltage is applied to V1, _V2, also the absolute amount of displacement x ₂ electrodes E3 upon application of voltages V1, _V2, the dielectric constant in the air epsilon, electrode E1, E2 facing area of _{S 1,} the opposing area of the electrodes E1, E3 and _{S 2.}

Balance of forces acting on the electrode E2 is the electrostatic force generated by application of the voltage V1 of the restoring force of the spring deformation portion B1 of the displacement x ₁ of the electrode E2 by application of voltages V1, V2, the displacement x ₁ of the electrode E2 And is shown by the following formula 2.
(Expression 2) k ₁ x ₁ = k ₂ (x ₂ −x ₁ ) + εS ₁ V ₁ ² / {2 (di−x ₁ ) ² }
On the other hand, the balance of forces acting on the electrode E3 is by applying a voltage V1, V2, and the restoring force of the spring deformation portion B2 of the displacement _{x 2} of the displacement _{x 1} and the electrode E3 of the electrode E2, the displacement _{x 2} electrodes E3 Is determined by the balance with the electrostatic force generated by the application of the voltage V2, and is expressed by the following formula 3.
(Expression 3) k ₂ (x ₂ −x ₁ ) = εS ₂ V ₂ ² / {2 (di−x ₂ ) ² }
Pull limit, in these formulas 2 and 3, the displacement x ₁ and x ₂ is a state with the largest contact solution can be calculated by numerical calculation.

9, the maximum value of the displacement x ₂ of the calculated electrode E3, a diagram showing the dependence on the spring constant ratio k _{1 /} k _2. When the spring constant ratio k ₁ / k ₂ is made larger than 1, that is, the spring constant k ₂ is made smaller than the spring constant k ₁ , the displacement amount of the electrode E3 is calculated from 1/3 (0.33) of the initial length di. Can also be increased. If the spring constant ratio k ₁ / k ₂ is infinite, x ₂ = 5 di / 9. In other words, it can be ideally displaced to 5/9 (0.56) of the initial length di.

  Next, the first filter 11 to which the simple model configuration shown in FIG. 8 is applied will be described. The first filter 11 shown in FIG. 10 includes a fixed mirror structure 30 having a fixed mirror M1 in the transmission region S1, and a movable mirror structure 50 having a movable mirror M2 in the transmission region S1. The movable mirror structure 50 includes a movable mirror M2, and a portion facing the fixed mirror structure 30 via the air gap AG is a displaceable membrane MEM. At least a part of the portion excluding the membrane MEM is supported. The member 40 is supported on the fixed mirror structure 30. Note that the movable mirror M2 configured in the membrane MEM is disposed to face the fixed mirror M1.

Further, in the peripheral region T1 excluding the transmission region S1 (formation region of the movable mirror M2) in the membrane MEM, a plurality of spring deforming portions are provided in a multiple manner so as to surround the transmission region S1. The spring constants of these spring deformed portions are set to be smaller as the spring deformed portions are closer to the center of the membrane MEM in the direction from the outer peripheral end of the membrane MEM toward the center of the membrane MEM. In the example shown in FIG. 10, two spring deformable portions B <b> 1 and B <b> 2 are provided as a plurality of spring deformable portions as in the model of FIG. 8. Then, the spring constant k ₂ of the spring deformation portion B2 closer to the center of the membrane MEM is, is smaller than the spring constant k ₁ of the spring deformation portion B1 closer to the outer peripheral edge of the membrane MEM, further two spring deformation portion B1 , B2 has a spring constant ratio k ₁ / k ₂ of 7 or more.

  Further, in the peripheral region T1 of the membrane facing part of the membrane MEM and the fixed mirror structure 30, electrodes are provided so as to face each other to form an electrode pair. The electrode pairs are provided in the same number of multiples as the spring deformed portions so as to surround the transmissive region S1 and correspond to the plurality of spring deformed portions, and the plurality of electrode pairs can be electrically applied so that voltages can be applied independently of each other. It is separated. In the example shown in FIG. 10, a plurality of electrodes E2 and E3 are formed on the membrane MEM of the movable mirror structure 50 so as to surround the transmission region S1 and correspond to the plurality of spring deformation portions B1 and B2 and the spring deformation portions B1 and B2. The same number of multiplexes are provided. More specifically, from the outer peripheral end side of the membrane MEM, the spring deformation portion B1, the electrode E2, the spring deformation portion B2, the electrode E3, and the movable mirror M2 are arranged in this order. Further, the electrode E1 is provided on the fixed mirror structure 30 so as to face the electrodes E2 and E3. That is, the spring deformed portion B1 is provided at the outer peripheral end of the membrane MEM, and in the direction from the outer peripheral end of the membrane MEM toward the center of the membrane MEM, a plurality of spring deformable portions B1, B2 and a plurality of electrode pairs (electrode pairs E1, E2 And electrode pairs E1, E3) are provided alternately. Further, in the membrane MEM, the rigidity of the electrodes E2 and E3 constituting each electrode pair is higher than that of any of the spring deformation portions B1 and B2.

In the first filter 11 having such a configuration, the voltage V1 is applied to the outermost electrode pair E1 and E2 (first electrode pair) corresponding to the outermost spring deformed portion B1, whereby the electrode pair E1 and E2 is applied. The outermost spring deformable portion B1 of the plurality of spring deformable portions B1 and B2 can be deformed by the electrostatic force generated in the. By applying this voltage V1, the entire membrane MEM is displaced. Further, for example, by applying a voltage V2 to the electrode pair E1, E3 (second electrode pair) located inside the outermost electrode pair E1, E2, the spring is generated by the electrostatic force generated in the electrode pair E1, E3. From the constant relationship (k ₁ > k ₂ ), it is possible to deform the spring deformed portion B2 located on the inner side without substantially deforming the outermost spring deformed portion B1. In the present embodiment, the electrostatic force generated in the electrode pair E1, E3 is made smaller than the electrostatic force generated in the electrode pair E1, E2 from the relationship of the spring constant (k ₁ > k ₂ ).

  For this reason, the voltage V2 is applied to the inner electrode pair E1, E3 in a state where the transmission region S1 portion (movable mirror M2) of the membrane MEM is displaced by applying the voltage V1 to the outermost electrode pair E1, E2. By applying, the transmission region S1 portion of the membrane MEM located inside the electrode E3 can be further displaced as shown in FIG. Ideally, assuming that the gap length in the initial state of the mirrors M1 and M2 is di as in the facing distance of the electrodes E1 and E3, the mirror length of the mirror M2 in the initial state is caused by the electrostatic force generated in the electrode pair E1 and E2. 1/3 displacement. Thereby, the gap length of the mirrors M1 and M2 becomes 2/3 of the initial length di. The mirror M2 is further displaced by 1/3 with respect to 2/3 of the gap length di in the initial state by electrostatic force generated in the electrode pair E1, E3. In other words, ideally, the mirror M2 can be displaced 5/9 of the initial gap length di in total. In this manner, at least part of the period in which the voltage is applied to each electrode pair is overlapped, and the membrane MEM is made to have a conventional pull-in limit (the opposing distance between the electrodes in the initial state) by the electrostatic force generated in each electrode pair during the overlap period. 1/3) can be displaced.

  In this embodiment, in the initial state, the facing distance between the electrodes E1 and E2 and the facing distance between the electrodes E1 and E3 are equal, and the gap length between the mirrors M1 and M2 is equal to the facing distance between the electrodes E1 and E2 and the electrode E1. , E3 or less. Therefore, the amount of change in the gap length between the mirrors M1 and M2 can be made larger than 1/3 of the gap length di in the initial state.

Further, in the present embodiment, the spring constant ratio k ₁ / k ₂ between the two spring deformation portions B1 and B2 is 7 or more. Therefore, as shown in FIG. 9, the amount of change in the facing distance between the electrodes E1 and E3 can be made larger than 1/2 of the gap length di in the initial state. It should be noted that the spring constant ratio k ₁ / k ₂ is 6, the amount of change in the facing distance between the electrodes E 1 and E 3 is slightly smaller than 1/2 of the initial length di, and the spring constant ratio k ₁ / k ₂ is 7. The amount of change in the facing distance between the electrodes E1 and E3 is larger than ½ of the gap length di in the initial state.

  Here, in the initial state in which no voltage is applied, the gap length di between the mirrors M1 and M2, the opposing distance between the electrodes E1 and E2, and the opposing distance between the electrodes E1 and E3 are equal, and the mirror M2 is in the initial gap length di. If it can be displaced by 1/2, the modulation band of each order is as shown below from Equation 1. The modulation band of the primary interference light (m = 1) is ideally 2di to di. The modulation band of the secondary interference light (m = 2) is ideally di to di × 1/2. The modulation band of the third-order interference light (m = 3) is ideally di × 2/3 to di × 1/3. The modulation band of the fourth-order interference light (m = 4) is ideally di × 1/2 to di × 1/4. Therefore, as shown in FIG. 11, the lower limit (pull-in limit) of the first order interference light and the upper limit (initial state) of the second order interference light coincide with each other. The modulation bands of the interference light are connected as one wavelength band without gaps and without overlapping bands. If the mirror M2 can be displaced by ½ of the gap length di in the initial state, the lower limit (pull-in limit) of the primary interference light is lower than the upper limit (initial state) of the secondary interference light. As a result, the modulation band of the primary interference light and the modulation band of the secondary interference light are connected as one wavelength region while partly overlapping.

FIGS. 12A and 12B show the modulation bands of the primary interference light and the secondary interference light. 12A and 12B, in the initial state, as in this embodiment, the gap length di between the mirrors M1 and M2, the opposing distance between the electrodes E1 and E2, and the opposing distance between the electrodes E1 and E3 are the same. Shows the results. In FIG. 12A shown as a comparative example, the movable mirror M2 can be displaced only up to the pull-in limit of 2800 nm (di × 1/3) with respect to the initial length di (4200 nm). The modulation band is narrow, and there is a non-spectral region between the modulation band of the primary interference light and the modulation band of the secondary interference light. On the other hand, in the configuration in which the spring constant ratio k ₁ / k ₂ of the two spring deformable portions B1 and B2 is 7 or more, as shown in FIG. The modulation band of the interference light is continuously one band. FIG. 12B shows a state in which the air gap 4200 nm is the initial length di and the air gap 2100 nm has displaced the movable mirror M2 by 1/2 of the initial length di.

As described above, when the spring constant ratio k ₁ / k ₂ of the two spring deformation portions B 1 and B ₂ is 7 or more, the modulation band of the primary interference light is widened, and the modulation band of the primary interference light and 2 The modulation band of the next interference light can be made continuous. That is, it is possible to eliminate the non-spectral region.

  In the present embodiment, the length twice as large as the gap length di in the initial state is substantially the same as the upper limit of the spectral band of the first filter 11 (for example, 8 μm as in the first embodiment). Therefore, the upper limit of the modulation band of the first order interference light substantially coincides with the upper limit of the spectral band of the first filter 11, and the lower limit of the modulation band of the second order interference light is almost equal to the lower limit of the spectral band of the first filter 11. Match. For this reason, the modulation bands of the primary interference light and the secondary interference light are located in the spectral band of the first filter 11. From the first filter 11, the primary interference light and the secondary interference light are located. The two orders of interference light are transmitted.

  Although not shown, the second filter 12 has a bandpass unit 60 corresponding to the first order interference light and a bandpass unit 60 corresponding to the second order interference light as a plurality of successive orders of interference light. ing. Further, the infrared detector 13 has an infrared detection element 70 corresponding to each of the bandpass units 60.

  From the above, according to the wavelength selective infrared detection device 10 according to the present embodiment, in one continuous wide wavelength range from the upper limit of the modulation band of the primary interference light to the lower limit of the modulation band of the secondary interference light. , It is possible to selectively detect light of a predetermined wavelength. In addition, since the interference light has a wider modulation band as the order is smaller, according to the present embodiment using the first order interference light and the second order interference light, the wavelength capable of selectively detecting light of a predetermined wavelength. The area can be made wider. In addition, light having a predetermined wavelength can be selectively detected in almost the entire spectral band.

When the spring constant ratio k ₁ / k _{2 of} the spring deformed portions B1 and B2 is 7, the lower limit (pull-in limit) of the first order interference light and the upper limit (initial state) of the second order interference light match, and the modulation Since the bands do not overlap, the correction processing unit 14 shown in the first embodiment is unnecessary. On the other hand, if the spring constant ratio k ₁ / k _{2 of} the spring deformed portions B1 and B2 is larger than 7, the lower limit (pull-in limit) of the first order interference light is lower than the upper limit (initial state) of the second order interference light, and modulation is performed. Bands overlap. In this case, the correction processing unit 14 shown in the first embodiment may be provided. In the correction processing unit 14 of the present embodiment, the primary interference light and the secondary interference light are transmitted through one of the bandpass unit 60 corresponding to the primary interference light and the bandpass unit 60 corresponding to the secondary interference light. In the transmission band, the primary interference light and one of the secondary interference lights are transmitted through the output of the infrared detection element 70 corresponding to the bandpass unit 60 through which the primary interference light and the secondary interference light are transmitted. Correction processing is performed based on the output of the infrared detection element 70 corresponding to the bandpass unit 60. Therefore, while the modulation band of the primary interference light and the modulation band of the secondary interference light overlap, the entire region of these modulation bands can be made one continuous modulation band. Therefore, the wavelength range in which light of a predetermined wavelength can be selectively detected can be made wider.

  In the first filter 11 shown in FIG. 10, the electrodes E2 and E3 have higher rigidity than the spring deformed portions B1 and B2, and the electrodes E2 and E3 and the spring deformed portions B1 and B2 are electrically separated. . That is, the electrodes E2, E3 and the spring deformation parts B1, B2 are structurally separated. Therefore, it is possible to displace the membrane MEM by deforming the spring deformation portions B1 and B2 while keeping the electrodes E2 and E3 forming the electrode pair in parallel. Thereby, the controllability of the facing distance between the movable mirror M2 connected to the electrode E3 and the fixed mirror M1 can be improved. Then, the half-value width (FWHM) of the transmission wavelength can be reduced, that is, the resolution can be improved. However, in the membrane MEM, the electrodes E2 and E3 constituting the electrode pair may also serve as the spring deformed portions B1 and B2. Specifically, the electrode E2 may also serve as the spring deformation portion B1, and the electrode E3 may also serve as the spring deformation portion B2. According to this, as compared with the configuration in which the electrodes E2 and E3 and the spring deformation portions B1 and B2 are structurally separated, the configuration can be simplified and the size of the first filter 11 can be reduced in the vertical direction. It is.

  In addition, the movable mirror structure 50 includes a plurality of electrodes E2 and E3 that are electrically separated from each other, and the fixed mirror structure 30 includes a single electrode E1 that is disposed to face the plurality of electrodes E2 and E3. showed that. However, the fixed mirror structure 30 has a plurality of electrodes E2 and E3 that are electrically separated from each other, and the movable mirror structure 50 has a single electrode E1 disposed to face the plurality of electrodes E2 and E3. May be. Moreover, both the fixed mirror structure 30 and the movable mirror structure 50 may have the same number of electrodes (two electrodes) to form a plurality of electrode pairs.

(Third embodiment)
In the present embodiment as well, as in the second embodiment, the first filter 11 sets the amount of change in the gap length between the mirrors M1 and M2 disposed so as to be 1/2 or more of the initial gap length di. The second filter 12 includes a bandpass unit 60 corresponding to the first order interference light and a bandpass unit 60 corresponding to the second order interference light as a plurality of successive orders of interference light. Such a configuration is characterized in that the configuration is different from that of the first filter 11 shown in the second embodiment. Since the present applicant has previously filed the first filter 11 in Japanese Patent Application No. 2010-258028, please refer to the details.

  In the following, the opposing distance between the fixed electrode E1 and the movable electrode E2 is de, the opposing distance in the initial state where no voltage is applied is dei, the opposing distance at the pull-in limit is dep, and the amount of change in the opposing distance is Δde, especially the pull-in Let Δdep be the amount of change at the limit. Further, the facing distance between the fixed mirror M1 and the movable mirror M2 is dm (corresponding to the gap length d), the facing distance in the initial state where no voltage is applied is dmi (corresponding to the gap length di), and the pull-in limit. Let dmp be the facing distance, Δdm the amount of change in the facing distance, and especially Δdmp the amount of change at the pull-in limit.

  As shown in FIG. 13, the first filter 11 according to this embodiment also includes a fixed mirror structure 30 and a movable mirror structure 50 that are arranged to face each other via an air gap AG. A portion that bridges the air gap AG is a membrane MEM that can be displaced by applying a voltage between electrodes E1 and E2, which will be described later. Further, the fixed mirror structure 30 includes a fixed mirror M1 and a fixed electrode E1 as opposed portions via the air gap AG. On the other hand, the movable mirror structure 50 includes a movable mirror M2 disposed to face the fixed mirror M1 through the air gap AG, and a movable electrode E2 at least partially disposed to face the fixed electrode E1 through the air gap AG. Have. In the example illustrated in FIG. 1, the movable mirror structure 50 is supported (fixed) on one surface of the fixed mirror structure 30 via the support member 40.

  When an electrostatic force is generated based on the voltage V applied between the fixed electrode E1 and the movable electrode E2, the membrane MEM of the movable mirror structure 50 is displaced, and the length of the air gap AG changes. Thereby, it is possible to selectively transmit light having a wavelength corresponding to the facing distance dm between the fixed mirror M1 and the movable mirror M2 in the air gap AG.

  Note that the initial length dmi between the mirrors M1 and M2 is set to be equal to or smaller than the initial length dei between the electrodes E1 and E2 in order to make the variation Δdm of the facing distance between the mirrors M1 and M2 as large as possible. In FIG. 13, dmi = dei.

  In the present embodiment, the fixed electrode E1 and other portions of the fixed mirror structure 30 excluding the fixed electrode E1 (such as the fixed mirror M1), and the movable electrode structure 50 excluding the movable electrode E2 and the movable electrode E2 are provided. At least one of the other parts (such as the movable mirror M2) is electrically separated. Therefore, the fixed mirror M1 and the movable mirror M2 can be set to substantially the same potential or completely the same potential while applying a voltage between the fixed electrode E1 and the movable electrode E2 to change the air gap AG. For this reason, there is little or no electrostatic force between the fixed mirror M1 and the movable mirror M2, and the pull-in limit depends on the facing distance de between the fixed electrode E1 and the movable electrode E2. As such an electrical isolation structure, pn junction isolation or trench insulation isolation in which polysilicon is patterned by etching and spatially isolated can be employed.

  Further, as shown in FIGS. 13 and 14A and 14B, the membrane MEM is provided at the movable mirror M2, the high-rigidity portion H1 surrounding the movable mirror M2, and the outer end of the membrane MEM. A first spring deformation part B1 connected to the part H1, and a second spring deformation part B2 provided between the high rigidity part H1 and the movable mirror M2 and connected to the high rigidity part H1 and the movable mirror M2. Have. That is, the first spring deformed portion B1, the high rigidity portion H1 including the movable electrode E2, the second spring deformed portion B2, and the movable mirror M2 are provided in this order from the outer end of the membrane MEM toward the center.

  The high-rigidity portion H1 is a portion that is set to have higher rigidity than the spring deformation portions B1 and B2 so that the membrane MEM does not bend when it is displaced and remains flat, and includes the movable electrode E2 at least partially. 14A to 14C, the outer end of the high-rigidity portion H1, that is, the end connected to the first spring deforming portion B1, is denoted as H1a, and the inner end, ie, the first end. An end portion on the side connected to the two spring deformable portion B2 is denoted as H1b. The high-rigidity portion H1 has the same opposing distance in the initial state with the fixed mirror structure 30 in the direction from the center of the membrane MEM toward the outer end. That is, the initial length is dei throughout the high-rigidity portion H1.

  The two spring deformable portions B1 and B2 are provided in multiple (double) so as to surround the movable mirror M2, and have lower rigidity than the other parts constituting the membrane MEM, that is, the movable mirror M2 and the high-rigidity portion H1. This is a part that is easily deformed. More specifically, a portion of the movable mirror structure 50 that is fixed to the fixed mirror structure 30 (a portion that is supported by the support member 40 in FIG. 13) and a highly rigid portion H1 (a portion other than the first spring deformation portion B1 in the membrane MEM). ) Is mechanically (structurally) separated so that the membrane MEM can be displaced. The first spring deforming part B1 is located outside the movable electrode E2, and has a low rigidity (a low spring constant) so as to displace the membrane MEM when a voltage is applied. Further, the length of the first spring deforming portion B1 is set to a sufficiently short length with respect to the length of the high-rigidity portion H1. On the other hand, the second spring deforming portion B2 is located on the inner side of the movable electrode E2 (highly rigid portion H1), and is rigid so as to mechanically (structurally) separate the highly rigid portion H1 and the movable mirror M2. Is set low (spring constant is low).

  Furthermore, in the present embodiment, the fixed electrode E1 and the movable electrode E2 are such that the portion of the movable electrode E2 facing the fixed electrode E1 (in other words, the portion facing the movable electrode E2 and the fixed electrode E1) is the center of the membrane MEM. Is provided so as to occupy only a part of the high-rigidity portion H1 in the direction from the outer end to the outer end. Then, in the direction from the center of the membrane MEM toward the outer end, the center Ec of the movable electrode E2 facing the fixed electrode E1 (in other words, the portion facing the movable electrode E2 and the fixed electrode E1) and the highly rigid portion H1. The distance L1 from the end H1a on the first spring deformed portion B1 side and the length of the high-rigidity portion H1 (length from the end H1a to the end H1b) L2 satisfy at least L2 / L1 ≧ 3/2. It is configured as follows. In the direction from the center of the membrane MEM toward the outer end, the relationship between the dimensions of the fixed electrode E1 and the movable electrode E2 is not particularly limited. The fixed electrode E1 may be longer, or the movable electrode E2 may be longer. Further, the lengths of the fixed electrode E1 and the movable electrode E2 may be equal.

  Next, the effect of the feature point of the first filter 11 will be described.

  From the relationship shown in Formula 1, the modulation band of the first-order interference light is ideally 2 dmi to 2 (dmi−Δdmp). Also, the modulation band of the secondary interference light is ideally dmi to (dmi−Δdmp). In order to eliminate the spectral non-spectral region between the primary interference light and the secondary interference light, the lower limit value [2 (dmi−Δdmp)] of the wavelength variable band of the primary interference light is set to the wavelength of the secondary interference light. It may be less than the upper limit [dmi] of the variable band. When the amount of change Δdmp at the pull-in limit is equal to or greater than ½ of the initial length dmi, the lower limit value of the modulation band of the primary interference light is equal to or less than the upper limit value dmi of the modulation band of the secondary interference light.

  On the other hand, in the present embodiment, the length of the first spring deformation part B1 is set to a sufficiently short length with respect to the length of the high rigidity part H1, thereby the first spring deformation part B1. Hardly affects the length in the displacement direction. For this reason, when the voltage V is applied and the membrane MEM is displaced from the initial state shown in FIG. 2 (a) to the state shown in FIG. 2 (b), the outer end H1a (first spring) of the high rigidity portion H1. The amount of change in the deformed portion B1 side end) can be regarded as almost zero. The amount of change of the center Ec of the portion of the movable electrode E2 facing the fixed electrode E1 with respect to the reference end when the voltage V is applied is the above-described Δde, and the amount of change relative to the reference end is the end H1a outside the high-rigidity portion H1. Let Δd1 be the amount of change in the end H1b inside the rigid portion H1.

  Here, in the present embodiment, a high-rigidity part H1 is provided separately from the first spring deformation part B1 and the second spring deformation part B2, and the movable electrode E2 is provided on at least a part of the high-rigidity part H1. Therefore, when the voltage V is applied and the movable electrode E2 tries to be displaced toward the fixed electrode E1 by the electrostatic force generated between the electrodes E1 and E2, as shown in FIG. The end portion H1b is displaced while being inclined so as to be closer to the fixed mirror structure 30 than the outer end portion H1a. Further, the high-rigidity portion H1 having higher rigidity than the spring deformation portions B1 and B2 is displaced while being inclined in a flat state without being bent like the spring deformation portions B1 and B2.

Thus, the highly rigid part H1 is displaced while inclining in a flat state. Therefore, the following proportional relationship is established between the distances L1 and L2 and the change amounts Δde and Δd1.
(Expression 4) L2 / L1 = Δd1 / Δde
The movable mirror M2 is connected to the end portion H1b of the high-rigidity portion H1 through the second spring deformation portion B2. Therefore, when the change amount Δde of the facing distance between the electrodes is the pull-in limit Δdep (= dei × 1/3), the change amount Δd1 of the inner end portion H1b of the high-rigidity portion H1 is expressed by the following equation. .
(Expression 5) L2 / L1 = 3Δd1 / dei
As described above, when the amount of change Δdmp at the pull-in limit is ½ or more of the initial length dmi, the lower limit value of the modulation band of the primary interference light is less than or equal to the upper limit value dmi of the modulation band of the secondary interference light. It becomes. The initial length dmi between the mirrors M1 and M2 is equal to or shorter than the initial length dei between the electrodes E1 and E2. Therefore, if the change amount Δd1 of the end portion H1b of the high-rigidity portion H1 is ½ or more of the initial length dei between the electrodes E1 and E2, the change amount Δdmp at the pull-in limit between the mirrors M1 and M2 is the initial value. It becomes 1/2 or more of the length dmi. As shown in the present embodiment, when the initial length dei and the initial length dmi are equal, Δd1 is ½ of the initial length dei and the change amount Δdmp is ½ of the initial length dmi. A formula satisfying this is as follows from Formula 5.
(Expression 6) L2 / L1 ≧ 3/2
In this way, when the relationship of Expression 6 is satisfied, the movable mirror M2 is displaced by more than 1/2 of the initial length dmi, and thereby, the modulation band of the primary interference light and the modulation band of the secondary interference light are continuous. Can be made. That is, it is possible to eliminate the non-spectral region.

  Further, in the present embodiment, the opposing distance in the initial state is twice the length of dmi (gap length di in the initial state) as the upper limit of the spectral band of the first filter 11 (for example, 8 μm as in the first embodiment). It is almost the same length. Therefore, the upper limit of the modulation band of the first order interference light substantially coincides with the upper limit of the spectral band of the first filter 11, and the lower limit of the modulation band of the second order interference light is almost equal to the lower limit of the spectral band of the first filter 11. Match. For this reason, the modulation bands of the primary interference light and the secondary interference light are located in the spectral band of the first filter 11. From the first filter 11, the primary interference light and the secondary interference light are located. The two orders of interference light are transmitted.

  Although not shown, the second filter 12 has a bandpass unit 60 corresponding to the first order interference light and a bandpass unit 60 corresponding to the second order interference light as a plurality of successive orders of interference light. ing. Further, the infrared detector 13 has an infrared detection element 70 corresponding to each of the bandpass units 60.

  From the above, also in the wavelength selective infrared detection device 10 according to the present embodiment, in one continuous wide wavelength range from the upper limit of the modulation band of the primary interference light to the lower limit of the modulation band of the secondary interference light, Light of a predetermined wavelength can be selectively detected. In addition, since the interference light has a wider modulation band as the order is smaller, according to the present embodiment using the first order interference light and the second order interference light, the wavelength capable of selectively detecting light of a predetermined wavelength. The area can be made wider. In addition, light having a predetermined wavelength can be selectively detected in almost the entire spectral band.

  In the case of L2 / L1 = 3/2, the lower limit (pull-in limit) of the first order interference light and the upper limit (initial state) of the second order interference light coincide with each other, and the modulation bands do not overlap. The correction processing unit 14 shown in FIG. On the other hand, when L2 / L1> 3/2, the lower limit (pull-in limit) of the primary interference light is lower than the upper limit (initial state) of the secondary interference light, and the modulation bands overlap. In this case, the correction processing unit 14 shown in the first embodiment may be provided. In the correction processing unit 14 of the present embodiment, the primary interference light and the secondary interference light are transmitted through one of the bandpass unit 60 corresponding to the primary interference light and the bandpass unit 60 corresponding to the secondary interference light. In the transmission band, the primary interference light and one of the secondary interference lights are transmitted through the output of the infrared detection element 70 corresponding to the bandpass unit 60 through which the primary interference light and the secondary interference light are transmitted. Correction processing is performed based on the output of the infrared detection element 70 corresponding to the bandpass unit 60. Therefore, while the modulation band of the primary interference light and the modulation band of the secondary interference light overlap, the entire region of these modulation bands can be made one continuous modulation band. Therefore, the wavelength range in which light of a predetermined wavelength can be selectively detected can be made wider.

  In the present embodiment, the high-rigidity portion H1 and the movable mirror M2 are mechanically (structurally) separated by the second spring deformation portion B2 having a rigidity lower than that of the high-rigidity portion H1 and the movable mirror M2. Therefore, even if the voltage V is applied between the electrodes E1 and E2 and the high-rigidity portion H1 including the movable electrode E2 is displaced, the movable mirror M2 is fixed to the fixed mirror structure 30 (fixed mirror M1) as shown in FIG. It can be held substantially parallel to. Further, at least one of the other part of the fixed mirror structure 30 excluding the fixed electrode E1 and the fixed electrode E1 and the other part of the movable mirror structure 50 excluding the movable electrode E2 and the movable electrode E2 is electrically connected. Therefore, while the voltage is applied between the electrodes E1 and E2, the fixed mirror M1 and the movable mirror M2 can be set to substantially the same potential or completely the same potential. For this reason, almost no electrostatic force is generated between the mirrors M1 and M2 (or at all), and the movable mirror M2 and the fixed mirror M1 can be held flat. Thereby, the half value width (FWHM) of transmitted light (interference light) can be reduced.

(Fourth embodiment)
In the present embodiment, similarly to the second embodiment and the third embodiment, the first filter 11 changes the amount of change in the gap length between the mirrors M1 and M2 arranged to face each other to 1 / of the initial gap length di. The second filter 12 includes a band-pass unit 60 corresponding to the first-order interference light and a band-pass unit 60 corresponding to the second-order interference light as a plurality of successive orders of interference light. Have. Such a configuration is characterized in that the form is different from the first filter 11 shown in the second embodiment and the third embodiment. Regarding the first filter 11, the present applicant has previously filed an application in Japanese Patent Application No. 2009-170310, so please refer to the details for details.

  In FIG. 15, the movable mirror M2 is shown thicker than the fixed mirror M1, but this is because the movable mirror M2 is more convex than the movable electrode E2 toward the fixed mirror structure 30. , Dei> dmi, and does not particularly define the thickness of both mirrors M1 and M2. Further, in FIG. 15, as the mirror structures 30 and 50, only the facing portions via the air gap AG are shown.

  As shown in FIGS. 15A and 15B, the first filter 11 according to the present embodiment also includes a fixed mirror structure 30 and a movable mirror structure 50 that are arranged to face each other via an air gap AG. . In addition, as an opposing portion through the air gap AG, the fixed mirror structure 30 has a fixed mirror M1 and a fixed electrode E1 into which impurities are introduced, and the movable mirror structure 50 has an air gap AG interposed therebetween. And a movable mirror M2 facing the fixed mirror M1 and a movable electrode E2 into which impurities are introduced. The membrane MEM of the movable mirror structure 50 is displaced by the electrostatic force generated based on the voltage applied between the electrodes E1 and E2, thereby changing the air gap AG. Then, light having a wavelength corresponding to the facing distance dm between the fixed mirror M1 and the movable mirror M2 in the air gap AG is selectively transmitted.

  In particular, in the present embodiment, in the fixed mirror structure 30, an insulating separation region F1 is provided between the fixed mirror M1 and the fixed electrode E1, and thereby the fixed mirror M1 and the fixed electrode E1 are electrically separated. Yes. On the other hand, the movable mirror M2 and the movable electrode E2 constituting the movable mirror structure 50 are electrically coupled, and the movable mirror M2 has the same potential as the movable electrode E2.

  Thus, in the first filter 11 according to the present embodiment, the fixed mirror M1 and the fixed electrode E1 constituting the fixed mirror structure 30 are electrically insulated and separated. Therefore, even if a voltage is applied between the fixed electrode E1 and the movable electrode E2 to change the air gap AG, the fixed mirror M1 that is insulated from the fixed electrode E1 does not have the same potential as the fixed electrode E1. As a result, little or no electrostatic force is generated between the fixed mirror M1 and the movable mirror M2, and the pull-in limit is a region electrically connected to the fixed electrode E1 (hereinafter referred to as the fixed electrode E1). It depends on the facing distance de between the region having the same potential and the region electrically connected to the movable electrode E2 (hereinafter, the region having the same potential as the movable electrode E2). 15A and 15B, only the fixed electrode E1 is included as a region having the same potential as the fixed electrode E1, and the movable electrode E2 and the movable mirror M2 are included as regions having the same potential as the movable electrode E2. .

  Further, in an initial state where no voltage is applied between the electrodes E1 and E2, as shown in FIG. 15A, in the movable mirror structure 50, the movable mirror M2 is closer to the fixed mirror structure 30 than the movable electrode E2. It is convex. Further, the insulating isolation region F1 is at least opposed to a portion (movable electrode E2 in the case of FIG. 15) excluding the convex portion including the movable mirror M2 in the movable mirror structure 50. In other words, the region having the same potential as the fixed electrode E1 is not opposed to the convex portion including the movable mirror M2 in the movable mirror structure 50, and is opposed to only the portion excluding the convex portion. By adopting such a structure, the opposing distance dei between the region having the same potential as the fixed electrode E1 and the region having the same potential as the movable electrode E2 is larger than the opposing distance dmi between the mirrors M1 and M2 in the initial state. It is longer (dei> dmi).

  Note that the facing distance dei is the distance of the shortest portion of the facing distance de between the region having the same potential as the fixed electrode E1 and the region having the same potential as the movable electrode E2 in the air gap AG in the initial state. In the present embodiment, the insulating separation region F1 is provided on the fixed mirror structure 30 side instead of the convex movable mirror structure 50 side, and the region having the same potential as the fixed electrode E1 and the region having the same potential as the movable electrode E2 are provided. As shown in FIG. 15A, not only the facing distance de1 between the fixed electrode E1 and the movable electrode E2, but also the facing distance de2 between the fixed electrode E1 and the movable mirror M2 (convex portion). Must also be considered.

  In the present embodiment, the opposing distance de1 is the opposing distance dei in the initial state, and even when a voltage is applied (displaced state), the region having the same potential as the fixed electrode E1 and the region having the same potential as the movable electrode E2 The protruding length of the movable mirror M2 from the movable electrode E2 and the vertical width of the insulating isolation region F1 are set so as to be the shortest portion. As described above, when the facing distance de1 between the fixed electrode E1 and the movable electrode E2 is set to the facing distance dei, the changing direction of the facing distance de and the facing distance dm substantially coincides with the above displacement direction. Therefore, it is possible to simplify the design of the first filter 11 than to set the facing distance de2 that is an oblique distance to the facing distance dei.

Here, the facing distance de between the region having the same potential as the fixed electrode E1 and the region having the same potential as the movable electrode E2 is displaced from the initial state (dei) by Δdmax (= dei × 1/3) of the pull-in limit, Assuming that the facing distance dep at the pull-in limit shown in the following formula 7 is obtained, the facing distance dm (= dmp) between the fixed mirror M1 and the movable mirror M2 at this time is a value represented by the following formula 8.
(Expression 7) dep = dei × 2/3
(Equation 8) dmp = dmi− (dei × 1/3)
In the first filter 11 according to the present embodiment, since dei> dmi as described above, dei × 1/3> dmi × 1/3 in the parentheses shown in Expression 8. Therefore, according to the present embodiment, the membrane MEM of the movable mirror structure 5 is displaced beyond dmi × 1/3 with respect to the facing distance dmi between the fixed mirror M1 and the movable mirror M2 in a state where no voltage is applied. be able to.

The maximum displacement Δdmax up to the pull-in limit described above can be expressed by the following equation.
(Equation 9) Δdmax / dmi = (dei / dmi) × 1/3
FIG. 16 shows the relationship between the maximum displacement Δdmax and dei / dmi shown in Equation 9. As is clear from FIG. 16, when dei / dmi = 3/2, Δdmax / dmi = 1/2 can be obtained. That is, the movable mirror M2 is displaced by more than 1/2 of the initial length dmi, so that the modulation band of the primary interference light and the modulation band of the secondary interference light can be made continuous. That is, it is possible to eliminate the non-spectral region described above. Therefore, it is more preferable that the facing distance dei between the region having the same potential as the fixed electrode E1 and the region having the same potential as the movable electrode E2 is set so as to satisfy the following expression.
(Equation 10) dei ≧ dmi × 3/2
As described above, when the relationship of Expression 10 is satisfied, the movable mirror M2 is displaced by more than 1/2 of the initial length dmi, and thereby, the modulation band of the primary interference light and the modulation band of the secondary interference light are continuous. Can be made. That is, it is possible to eliminate the non-spectral region.

  Further, in the present embodiment, the length of the opposing distance in the initial state twice as long as dmi is substantially the same as the upper limit of the spectral band of the first filter 11 (for example, 8 μm as in the first embodiment). Therefore, the upper limit of the modulation band of the first order interference light substantially coincides with the upper limit of the spectral band of the first filter 11, and the lower limit of the modulation band of the second order interference light is almost equal to the lower limit of the spectral band of the first filter 11. Match. For this reason, the modulation bands of the primary interference light and the secondary interference light are located in the spectral band of the first filter 11. From the first filter 11, the primary interference light and the secondary interference light are located. The two orders of interference light are transmitted.

  Although not shown, the second filter 12 has a bandpass unit 60 corresponding to the first order interference light and a bandpass unit 60 corresponding to the second order interference light as a plurality of successive orders of interference light. ing. Further, the infrared detector 13 has an infrared detection element 70 corresponding to each of the bandpass units 60.

  From the above, also in the wavelength selective infrared detection device 10 according to the present embodiment, in one continuous wide wavelength range from the upper limit of the modulation band of the primary interference light to the lower limit of the modulation band of the secondary interference light, Light of a predetermined wavelength can be selectively detected. In addition, since the interference light has a wider modulation band as the order is smaller, according to the present embodiment using the first order interference light and the second order interference light, the wavelength capable of selectively detecting light of a predetermined wavelength. The area can be made wider. In addition, light having a predetermined wavelength can be selectively detected in almost the entire spectral band.

  In the case of dei = dmi × 3/2, the lower limit (pull-in limit) of the first order interference light and the upper limit (initial state) of the second order interference light match, and the modulation bands do not overlap, so the first embodiment The correction processing unit 14 shown in FIG. On the other hand, when dei> dmi × 3/2, the lower limit (pull-in limit) of the primary interference light is lower than the upper limit (initial state) of the secondary interference light, and the modulation bands overlap. In this case, the correction processing unit 14 shown in the first embodiment may be provided. In the correction processing unit 14 of the present embodiment, the primary interference light and the secondary interference light are transmitted through one of the bandpass unit 60 corresponding to the primary interference light and the bandpass unit 60 corresponding to the secondary interference light. In the transmission band, the primary interference light and one of the secondary interference lights are transmitted through the output of the infrared detection element 70 corresponding to the bandpass unit 60 through which the primary interference light and the secondary interference light are transmitted. Correction processing is performed based on the output of the infrared detection element 70 corresponding to the bandpass unit 60. Therefore, while the modulation band of the primary interference light and the modulation band of the secondary interference light overlap, the entire region of these modulation bands can be made one continuous modulation band. Therefore, the wavelength range in which light of a predetermined wavelength can be selectively detected can be made wider.

  In the present embodiment, an example in which a convex portion is provided only on the movable mirror structure 50 among the mirror structures 30 and 50 has been described. However, dei> dmi may be satisfied by providing a configuration in which only the fixed mirror structure 30 is provided with a convex portion or a configuration in which both mirror structures 30 and 50 are provided with a convex portion. good.

  In the present embodiment, the example in which the insulating isolation region F <b> 1 is provided only in the fixed mirror structure 30 among the mirror structures 30 and 50 has been described. However, it is also possible to provide a configuration in which only the movable mirror structure 50 is provided with an isolation region, or a configuration in which both mirror structures 30 and 50 are provided with an isolation region. If both mirrors M1 and M2 are set to the same potential, no electrostatic force acts between the mirrors M1 and M2, so that the amount of displacement can be controlled with high accuracy.

(Fifth embodiment)
In the present embodiment as well, in the same way as in the second to fourth embodiments, the first filter 11 changes the amount of change in the gap length between the mirrors M1 and M2 arranged to face each other to 1 / of the initial gap length di. The second filter 12 includes a band-pass unit 60 corresponding to the first-order interference light and a band-pass unit 60 corresponding to the second-order interference light as a plurality of successive orders of interference light. Have. Such a configuration is characterized in that the configuration is different from that of the first filter 11 shown in the second to fourth embodiments. Since the present applicant has previously filed the first filter 11 in Japanese Patent Application No. 2010-280814, the details thereof should be referred to.

  As shown in FIGS. 17A and 17B, the first filter 11 according to this embodiment includes a fixed mirror structure 30 having a fixed mirror M1, and a fixed mirror structure 30 via a first air gap AG1. Is a membrane MEM that is displaceable in the length direction. The membrane MEM has a movable mirror structure 50 having a movable mirror M2 and a movable electrode E2, and a movable mirror structure 50 in the length direction. An electrode structure 80 disposed on the opposite side of the fixed mirror structure 30 and having a fixed electrode E3 at a portion facing the membrane MEM via the second air gap AG2.

  Thus, in this embodiment, the movable mirror structure 50 is disposed between the fixed mirror structure 30 and the electrode structure 80 in the length direction. Further, the fixed mirror structure 30 does not have the fixed electrode E1, and instead the fixed electrode E3 is provided on the electrode structure 80. Also in this embodiment, the fixed mirror M1 and the movable mirror M2 are opposed to each other, and the formation region of the mirrors M1 and M2 in the first filter 11 is a transmission region S1 that selectively transmits light. Yes. Further, the correspondence with the description in the claims is that the first air gap AG1 is the first gap, the second air gap AG2 is the second gap, the movable electrode E2 is the first electrode, and the fixed electrode E3 is the first gap. It corresponds to two electrodes.

  In the example shown in FIGS. 17A and 17B, the movable mirror structure 50 is disposed on the electrode structure 80 via the support member 42, and on the movable mirror structure 50 via the support member 40. A fixed mirror structure 30 is arranged.

  Further, in the initial state where no voltage is applied between the movable electrode E2 and the fixed electrode E3, as shown in FIG. 17A, the length dei between the electrodes in the second air gap AG2 (hereinafter referred to as the initial between the electrodes). The length dei) is longer than the length dmi between the mirrors in the first air gap AG1 (hereinafter referred to as the initial length dmi between the mirrors) (dei> dmi). In the present embodiment, in the initial state, the facing distance between the membrane facing portion of the fixed mirror structure 30 and the membrane MEM of the movable mirror structure 50 is substantially equal throughout the first air gap AG1. That is, the initial length dmi between the mirrors is equal to the length d1max of the maximum length portion in the first air gap AG1. For this reason, the initial length dei between the electrodes is longer than the maximum length d1max in the first air gap AG1 (dei> d1max).

  Further, the membrane MEM of the movable mirror structure 50 and the membrane facing portion of the fixed mirror structure 30 are set to the same potential at the portions facing each other. As such a configuration, for example, the entire membrane MEM and the entire membrane facing portion may be set to the same potential. In addition, the mirror M1 and M2 formation region (transmission region S1) and the peripheral region T1 have different potentials in the mirror structures 30 and 50, and the mirror M1 and M2 formation regions and the peripheral region T1 The potentials may be the same.

  When the first filter 11 applies a voltage between the movable electrode E2 and the fixed electrode E3, the membrane MEM approaches the electrode structure 80 as shown in FIG. 17B (FIG. 17B). Displacement in the direction of the white arrow). Due to this displacement, the length de between the electrodes becomes shorter than the initial length dei, and the length dm between the mirrors becomes longer than the initial length dmi.

  Next, the effect of the main characteristic part of the 1st filter 11 which concerns on this embodiment is demonstrated.

  In the present embodiment, the movable mirror structure 50 is disposed between the fixed mirror structure 30 and the electrode structure 80 in the length direction. Further, the fixed mirror structure 30 does not have the fixed electrode E1, and instead the fixed electrode E3 is provided on the electrode structure 80. Therefore, when a voltage is applied between the movable electrode E2 and the fixed electrode E3 to generate an electrostatic force (electrostatic attractive force), the membrane MEM is pulled toward the electrode structure 80, and the length de between the electrodes is initially set. It becomes shorter than the length dei. On the other hand, the length dm between the mirrors is longer than the initial length dmi.

  In this way, the length dm between the mirrors is increased as the length de between the electrodes E2 and E3 that generate an electrostatic force for displacing the membrane MEM is shortened. Therefore, the possible range of the length dm between the mirrors is not determined only by the initial length dmi between the mirrors as in the prior art, but the upper limit value is determined based on the initial length dei between the electrodes. The Specifically, the possible range of the length dm between the mirrors is dmi to (dmi + dei × 1/3). The initial length dei between the electrodes is longer than the initial length dmi between the mirrors (dei> dmi). Therefore, the change amount Δdm (= dei × 1/3) of the length dm between the mirrors up to the pull-in limit of the electrodes E2, E3 is changed to the change amount Δdm (= dmi × 1/3) of the length between the mirrors of the conventional configuration. ) Can be larger.

  In the present embodiment, the membrane MEM of the movable mirror structure 50 and the membrane facing portion of the fixed mirror structure 30 are set to the same potential at the portions facing each other. Therefore, a potential difference is generated between the membrane MEM of the movable mirror structure 50 and the membrane facing portion of the fixed mirror structure 30, and the influence of the electrostatic force based on the potential difference on the displacement of the membrane MEM is suppressed. Can do. For this reason, the membrane facing portion of the fixed mirror structure 30 is not displaced, and only the membrane MEM of the movable mirror structure 50 is displaced.

  As described above, according to the first filter 11 according to the present embodiment, the membrane MEM of the movable mirror structure 50 can be displaced so that the variation Δdm is larger than 1/3 of the initial length dmi. That is, the modulation band of the transmission spectrum can be made wider than before.

  Further, in the conventional first filter 11, the length de between the electrodes is d1max at the maximum regardless of whether the electrode is provided at any position of the membrane MEM and the membrane facing portion facing each other through the air gap AG. That is, the maximum amount of change Δde between the electrodes is d1max × 1/3. On the other hand, in the present embodiment, the initial length dei between the electrodes is longer than the maximum length d1max in the first air gap AG1 (dei> d1max). For this reason, the membrane MEM of the movable mirror structure 50 can be displaced so that the change amount Δde is larger than d1max × 1/3. As a result, it is possible to widen the modulation band of the transmission spectrum more securely than in the past.

In the present embodiment, the initial length dei between the electrodes and the initial length dmi between the mirrors are configured to satisfy the relationship of the following formula.
(Equation 11) dei ≧ 3 × dmi
From Equation 1 above, the modulation band of the primary interference light is ideally 2 dmi to 2 (dmi + dei × 1/3). Also, the modulation band of the secondary interference light is ideally dmi to (dmi + dei × 1/3). Therefore, there is no gap (non-spectral region) between the modulation band of the primary interference light and the modulation band of the secondary interference light, and these modulation bands are set as one continuous modulation band. It is sufficient that the upper limit value of the modulation band of the secondary interference light is equal to or greater than the lower limit value of the modulation band of the primary interference light.

  When the relationship of Equation 11 described above is satisfied, the upper limit value of the modulation band of the second order interference light is equal to or greater than the lower limit value of the modulation band of the first order interference light. For example, when dei = 3 × dmi, the state in which the movable mirror M2 is displaced by dmi is the pull-in limit of the electrodes E2 and E3. Therefore, as shown in FIG. 18, the modulation band of the primary interference light is ideally 4 to 2 dmi. Also, the modulation band of the secondary interference light is ideally 2 dmi to dmi. Note that the modulation band of the third-order interference light is ideally dmi × 4/3 to dmi × 2/3. In this way, the lower limit value of the modulation band of the primary interference light matches the upper limit value of the modulation band of the secondary interference light. Further, when dei> 3 × dmi, Δdm can be made larger than dmi. Therefore, the upper limit value of the modulation band of the secondary interference light exceeds the lower limit value of the modulation band of the primary interference light.

  In this way, when the relationship of Expression 11 is satisfied, the modulation band of the primary interference light and the modulation band of the secondary interference light can be made one modulation band continuous without a gap. Therefore, it is possible to selectively detect light of a predetermined wavelength in one continuous wide wavelength range. Since the interference band has a wider modulation band as the order is smaller, using a plurality of orders of interference light (for example, primary to tertiary interference light) including the primary interference light and the secondary interference light, the modulation band is reduced. Can be effectively widened.

  Further, in the present embodiment, the spectral band of the first filter 11 (for example, the first embodiment) is twice as long as the length dm between the mirrors in a state where the membrane MEM is displaced to the pull-in limit of the electrodes E2 and E3. Similarly, the length is almost the same as the upper limit of 8 μm). Therefore, the upper limit of the modulation band of the first order interference light substantially coincides with the upper limit of the spectral band of the first filter 11, and the lower limit of the modulation band of the second order interference light is almost equal to the lower limit of the spectral band of the first filter 11. Match. For this reason, the modulation bands of the primary interference light and the secondary interference light are located in the spectral band of the first filter 11. From the first filter 11, the primary interference light and the secondary interference light are located. The two orders of interference light are transmitted.

  Although not shown, the second filter 12 has a bandpass unit 60 corresponding to the first order interference light and a bandpass unit 60 corresponding to the second order interference light as a plurality of successive orders of interference light. ing. Further, the infrared detector 13 has an infrared detection element 70 corresponding to each of the bandpass units 60.

  From the above, also in the wavelength selective infrared detection device 10 according to the present embodiment, in one continuous wide wavelength range from the upper limit of the modulation band of the primary interference light to the lower limit of the modulation band of the secondary interference light, Light of a predetermined wavelength can be selectively detected. In addition, since the interference light has a wider modulation band as the order is smaller, according to the present embodiment using the first order interference light and the second order interference light, the wavelength capable of selectively detecting light of a predetermined wavelength. The area can be made wider. In addition, light having a predetermined wavelength can be selectively detected in almost the entire spectral band.

  In the case of dei = 3 × dmi, the lower limit (pull-in limit) of the first-order interference light and the upper limit (initial state) of the second-order interference light match, and the modulation bands do not overlap. Further, the correction processing unit 14 is unnecessary. On the other hand, when dei> 3 × dmi, the lower limit (pull-in limit) of the primary interference light is lower than the upper limit (initial state) of the secondary interference light, and the modulation bands overlap. In this case, the correction processing unit 14 shown in the first embodiment may be provided. In the correction processing unit 14 of the present embodiment, the primary interference light and the secondary interference light are transmitted through one of the bandpass unit 60 corresponding to the primary interference light and the bandpass unit 60 corresponding to the secondary interference light. In the transmission band, the primary interference light and one of the secondary interference lights are transmitted through the output of the infrared detection element 70 corresponding to the bandpass unit 60 through which the primary interference light and the secondary interference light are transmitted. Correction processing is performed based on the output of the infrared detection element 70 corresponding to the bandpass unit 60. Therefore, while the modulation band of the primary interference light and the modulation band of the secondary interference light overlap, the entire region of these modulation bands can be made one continuous modulation band. Therefore, the wavelength range in which light of a predetermined wavelength can be selectively detected can be made wider.

  Further, in the present embodiment, the electrode structure 80 has a fixed electrode E3 as the second electrode in a region (peripheral region T1) different from the transmission region S1, but is a region different from the formation region of the fixed electrode E3. And at least a light transmission portion in a region corresponding to the transmission region S1. Although it is possible to provide a fixed electrode E3 formed by impurity ion implantation or metal vapor deposition in the transmission region S1, a part of light (infrared rays) transmitted through the pair of mirrors M1 and M2 is absorbed by the fixed electrode E3. Will be. On the other hand, when the fixed electrode E3 is provided in the peripheral region T1 and the region including the transmissive region S1 where the fixed electrode E3 is not provided is used as the light transmitting portion, the transmittance can be improved.

  Preferably, as shown in FIG. 17, a through hole H1 is provided in the electrode structure 80 (the substrate constituting the electrode structure 80), and a region where the through hole H1 is formed is used as a light transmission portion. According to this, light absorption by the substrate and reflection of light on the substrate surface can be suppressed, thereby improving the transmittance. Further, it is not necessary to use an expensive substrate (for example, a low oxygen concentration substrate) in order to suppress light absorption by the substrate, so that the cost can be reduced. It is also possible to suppress reflection of light on the substrate surface by providing an antireflection film (AR coating) on the substrate surface, but it is difficult to form an antireflection film corresponding to a wide modulation band (wavelength range). It is. On the other hand, when the through-hole H1 is provided, an antireflection film can be made in the first place, so that the cost can be reduced while suppressing the reflection of light on the substrate surface in a wide wavelength range.

  More preferably, in the through hole H1 provided in the substrate, the position of the smallest opening portion having the smallest opening area (area along the vertical direction) may coincide with the transmission region S1 in the vertical direction. According to this, the board | substrate which has the through-hole H1 can be used as a shielding board with a vacant aperture (opening). For this reason, transmission of light in the peripheral region T1 can be suppressed, and light can be selectively transmitted only in the transmission region S1. Further, since it is not necessary to separately implant impurities or form a metal thin film in order to form the aperture, the manufacturing process can be simplified.

  The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention.

  In the present embodiment, as the substrate 20 of the first filter 11, an example of a semiconductor substrate provided with an insulating film 22 on one surface is shown. However, the substrate 20 is not limited to the above example, and an insulating substrate such as glass can also be adopted. In that case, the insulating film 22 is unnecessary.

  In the present embodiment, the example in which the movable mirror structure 50 configuring the first filter 11 is supported on the fixed mirror structure 30 via the support member 40 has been described. However, it is also possible to adopt a configuration in which the movable mirror structure 50 located outside the membrane MEM is in contact with the fixed mirror structure 30 and functions as a support member that supports the membrane MEM. That is, a configuration without the support member 40 can also be adopted. Similarly, in the configuration shown in the fifth embodiment, at least one of the support members 40 and 42 may be omitted.

DESCRIPTION OF SYMBOLS 10 ... Wavelength selection type infrared detector 11 ... 1st filter 12 ... 2nd filter 13 ... Infrared detector 14 ... Correction processing part 60, 60a-60c ... Band pass part 70 , 70a to 70c ... infrared detection elements M1, M2 ... mirror MEM ... membrane S1 ... transmission region AG ... air gap (gap)

Claims (16)

A variable Fabry-Perot type first filter that can change the gap length between the mirrors arranged opposite to each other and selectively transmits light having a wavelength corresponding to the gap length in the infrared region;
A second filter provided with a bandpass portion that selectively transmits light in a predetermined band, the bandpass portion corresponding to the mirror;
An infrared detector that detects light transmitted through the bandpass unit with an infrared detection element;
The light passing through the first filter includes a plurality of orders of interference light,
The bandpass unit has a light transmission characteristic according to a modulation band that interference light of an arbitrary order can take with a change in gap length,
The second filter includes a plurality of types of the bandpass units corresponding to different orders of interference light,
The infrared detector includes a plurality of the infrared detection elements so that the interference light transmitted through the second filter is detected by the infrared detection elements that are different for each type of the bandpass unit. Wavelength selective infrared detector.   2. The wavelength selective infrared detection device according to claim 1, wherein the second filter includes the bandpass unit for a plurality of successive orders of interference light. The first filter is:
The mirror and the electrode are integrally formed, and a part including the mirror and the electrode has a pair of mirror structures disposed to face each other through the gap,
In an initial state where no voltage is applied, the gap length between the mirrors is equal to or less than the facing distance between the electrodes,
Due to the electrostatic force generated based on the voltage applied between the pair of electrodes, the portion of the membrane that bridges the gap in one of the mirror structures is displaced,
The amount of change in the facing distance between the electrodes is 1/3 of the facing distance between the electrodes in the initial state where no voltage is applied, and the electrostatic force is balanced with the spring restoring force of the membrane.
3. The second filter has a bandpass unit corresponding to at least two consecutive interference lights of the second, third, and fourth orders as a plurality of successive interference lights. 2. A wavelength-selective infrared detecting device according to 1. In the first filter, the pair of mirrors includes a low refractive index layer made of air having a lower refractive index than a material constituting the high refractive index layer interposed between high refractive index layers made of a silicon semiconductor thin film. The gap length in the initial state before displacement is the same length as the upper limit of the spectral band of the first filter,
The second filter has the bandpass unit corresponding to each of the second-order, third-order, and fourth-order interference light as a plurality of successive orders of interference light,
Third-order interference light in a band where the third-order interference light and the fourth-order interference light pass through one of the band-pass portion corresponding to the third-order interference light and the band-pass portion corresponding to the fourth-order interference light. And the output of the infrared detection element corresponding to the bandpass part through which the fourth-order interference light is transmitted, and the output of the infrared detection element corresponding to the bandpass part through which the third-order interference light and one of the fourth-order interference lights are transmitted. The wavelength selective infrared detection apparatus according to claim 3, further comprising a correction processing unit that performs correction processing based on the output. In the first filter, in the pair of mirrors, a low refractive index layer made of silicon dioxide having a lower refractive index than that of a material constituting the high refractive index layer is interposed between high refractive index layers made of a silicon semiconductor thin film. The gap length in the initial state before displacement is the same length as the upper limit of the spectral band of the first filter,
4. The wavelength selective infrared detection according to claim 3, wherein the second filter includes the bandpass unit corresponding to each of the second-order and third-order interference light as a plurality of successive orders of interference light. apparatus. The first filter has a pair of mirror structures in which the mirror and the electrode are integrally formed, and a portion including the mirror and the electrode is disposed to face each other through the gap, and one of the mirror structures The part of the body that bridges the gap may be a displaceable membrane, and the amount of change in the gap length between the opposed mirrors may be 1/2 or more of the initial gap length before displacement. Can
The wavelength-selective infrared detection device according to claim 2, wherein the second filter has a bandpass unit corresponding to each of the first-order and second-order interference light as a plurality of successive orders of interference light. .   The wavelength according to claim 6, wherein the first filter has a length that is twice the gap length in the initial state before displacement as the upper limit of the spectral band of the first filter. Selective infrared detector. In the first filter,
In the peripheral region excluding the mirror formation region in the membrane, as a spring deformation portion provided in multiple surrounding each of the mirror formation regions, a first spring deformation portion provided over a predetermined range from the outer peripheral end of the membrane, A second spring deformation portion provided inside the first spring deformation portion and having a spring constant set smaller than that of the first spring deformation portion;
When the spring constant of the first spring deformation portion is k ₁ and the spring constant of the second spring deformation portion is k ₂ , the spring deformation portion is configured to satisfy k ₁ / k ₂ ≧ 7,
In the peripheral region excluding the mirror formation region, which is the membrane and the membrane facing part in the pair of mirror structures, electrodes are provided so as to face each other, and an electrode pair is configured.
The electrode pairs are provided in the same number of multiples corresponding to the plurality of spring deforming portions while surrounding the mirror forming region, and the first electrodes deform the first spring deforming portions by electrostatic force generated by applying a voltage. A pair and a second electrode pair that is provided inside the first electrode pair and deforms the second spring deformed portion mainly by electrostatic force generated by application of a voltage;
The period of applying a voltage to each electrode pair is at least partially overlapped, and the membrane is displaced by electrostatic force generated in each electrode pair during the overlapping period. Wavelength selective infrared detector. In the first filter,
In an initial state where no voltage is applied, the gap length between the mirrors is equal to or less than the facing distance between the electrodes,
In at least one of the pair of mirror structures, the electrode and the other part of the mirror structure excluding the electrode are electrically separated,
The membrane is provided between a high-rigidity portion surrounding the mirror, a first spring deformed portion provided at an outer end of the membrane and connected to the high-rigidity portion, and the high-rigidity portion and the mirror. A second spring deformation portion connected to the high-rigidity portion and the mirror,
The two spring deformed portions provided in a multiple manner so as to surround the mirror have a lower rigidity than the other mirrors and the high-rigidity portion constituting the membrane,
The facing part of the electrode formed on the membrane with the other electrode occupies only a part of the high-rigidity part in the direction from the center of the membrane toward the outer end,
In the direction from the center of the membrane toward the outer end, the distance between the center of the opposed portion of the pair of electrodes and the end of the high rigidity portion on the first spring deformation portion side is L1, and the length of the high rigidity portion is L2
L2 / L1 ≧ 3/2
The wavelength-selective infrared detection device according to claim 6 or 7, wherein the wavelength-selective infrared detection device is configured to satisfy the above. In the first filter,
The mirror and the electrode are electrically insulated and separated in at least one of the pair of mirror structures.
In an initial state where the voltage is not applied, an opposing distance dei between an electrically coupled portion including an electrode in one of the mirror structures and an electrically coupled portion including an electrode in the other mirror structure Is longer than the facing distance dmi between the mirrors,
dei ≧ dmi × 3/2
The wavelength-selective infrared detecting device according to claim 6, wherein the wavelength-selective infrared detecting device is set to satisfy the above. The first filter is:
A fixed mirror structure having a fixed mirror in a transmission region that transmits light;
A movable mirror structure having a portion that can displace the fixed mirror structure through the first gap, and having a movable electrode provided on the membrane so as to face the fixed mirror. ,
An electrode structure that is disposed on the opposite side to the fixed mirror structure with respect to the movable mirror structure and has a second electrode in a portion facing the membrane via a second gap;
In an initial state where no voltage is applied between the first electrode and the second electrode, a length dei between the electrodes in the second gap and a length dmi between the mirrors in the first gap are:
dei ≧ 3 × dmi
Meets
The membrane of the movable mirror structure and the membrane facing portion of the fixed mirror structure including the fixed mirror have the same potential at the portions facing each other.
By applying a voltage between the first electrode and the second electrode and displacing the membrane in a direction approaching the electrode structure, the length de between the electrodes in the second gap is the initial length. And the length dm between the mirrors in the first gap is longer than the initial length dmi,
The wavelength-selective infrared detection device according to claim 2, wherein the second filter has a bandpass unit corresponding to each of the first-order and second-order interference light as a plurality of successive orders of interference light. .   The first filter is formed between the mirrors in the first gap in a state where the membrane is displaced to a position where an electrostatic force generated by applying a voltage between the electrodes in the second gap and a spring restoring force of the membrane are balanced. 12. The wavelength selective infrared detection device according to claim 11, wherein the length twice as long as the length dm is the same as the upper limit of the spectral band of the first filter. The first filter can make the amount of change in the gap length between the mirrors larger than 1/2 of the initial gap length before displacement,
The primary interference light in a band in which the primary interference light and the secondary interference light pass through one of the band pass portion corresponding to the primary interference light and the band pass portion corresponding to the secondary interference light. And the output of the infrared detection element corresponding to the bandpass part through which the second order interference light is transmitted, and the output of the infrared detection element corresponding to the bandpass part through which the first order interference light and one of the second order interference light are transmitted. The wavelength selective infrared detection device according to claim 6, further comprising a correction processing unit configured to perform correction processing based on the output.   The plurality of band-pass portions have a light-receiving surface shape and a light-receiving area that are equal to each other, and are arranged concentrically with respect to the center of the mirror in a direction perpendicular to the gap length direction. The wavelength selective infrared detection device according to any one of 1 to 13. The second filter is made of a material that does not transmit light that passes through the first filter, and includes a non-transmission portion that integrally holds the plurality of bandpass portions so that light is transmitted through each bandpass portion. Have
Spacers are interposed between the first filter and the second filter and between the second filter and the infrared detector, respectively, and the first filter, the second filter, and the infrared detector are The wavelength selective infrared detection device according to claim 1, wherein the wavelength selection infrared detection device is integrated.   The wavelength selective infrared according to any one of claims 1 to 14, wherein the band-pass part constituting the second filter is laminated on a corresponding infrared detection element of the infrared detector. Detection device.

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