Analytical device and analytical method

Abstract

To provide an analyzer for irradiating a sample with light and analyzing a plurality of measurement target components on the basis of its transmitted light, in which the entire device size is reduced while using a light source whose luminous energy is large.SOLUTION: Provided is an analyzer that irradiates a sample with light, detects light having passed through the sample, and analyzes measurement target components in the sample, the analyzer comprising a light source that irradiates the sample with light, a light detector that detects light having passed through the sample, and a first optical filter and a second optical filter that are arranged between the light source and the light detector. The first optical filter and second optical filter are arranged on the same optical path, and are constructed using a periodic structure having a peak wavelength for analysis whose transmissivity changes by application of a voltage, the peak wavelength for analysis of the first optical filter and the peak wavelength for analysis of the second optical filter being made different from each other.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an analytical device and an analytical method used for analyzing the components of, for example, gases. [Background technology]

[0002] For example, some analyzers use the NDIR method to measure the concentration of a component to be measured contained in a sample gas such as exhaust gas from an internal combustion engine.

[0003] Conventional analytical instruments using the NDIR method include a light source, an optical chopper, a sample cell, an optical filter, and a photodetector. The light source irradiates the sample cell with infrared light, and the transmitted wavelength of the infrared light is limited by the optical filter and detected by the photodetector. This type of analytical instrument uses an optical chopper to chop and modulate the infrared light emitted from the light source at a desired frequency, creating an AC signal of the desired frequency. The photodetector then extracts only signals with the frequency components that coincide with the timing of the optical chopper (see Patent Document 1). This eliminates noise components that oscillate at different frequencies or timings (e.g., those due to the surrounding environment, such as ambient temperature changes or mechanical noise). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-226097 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the modulation method using an optical chopper as described above, i.e., a method in which a motor rotates a disk to mechanically interrupt and modulate light, requires the use of a high-speed rotating motor and the need to control the rotation speed with high precision, which results in a large device configuration.

[0006] It is also possible to modulate light by turning the light source itself on and off without using an optical chopper, but because the light source itself has heat capacity, it is difficult to follow changes by turning it on and off when using a light source with a large light output.If a small light source is used, it is possible to follow changes by turning it on and off, but in that case there is the problem of reduced light output.

[0007] Another problem is that in order to analyze multiple components to be measured, multiple optical filters corresponding to the absorption wavelengths of each component and multiple corresponding photodetectors must be arranged in parallel, which makes the device configuration large.

[0008] The present invention has been made to solve all of the above-mentioned problems at once, and its main objective is to reduce the size of the entire analytical device, which irradiates a sample with light and analyzes multiple components to be measured based on the transmitted light, while using a light source with a large light output. [Means for solving the problem]

[0009] That is, the analytical device of the present invention is an analytical device that irradiates a sample with light, detects the light that has passed through the sample, and analyzes the components to be measured in the sample, and is equipped with a light source that irradiates the sample with light, a photodetector that detects the light that has passed through the sample, and a first optical filter and a second optical filter that are arranged between the light source and the photodetector, and is characterized in that the first optical filter and the second optical filter are arranged on the same optical path and are constructed using a periodic structure having an analytical peak wavelength whose transmittance changes when a voltage is applied, and the analytical peak wavelength of the first optical filter and the analytical peak wavelength of the second optical filter are different from each other.

[0010] With this configuration, an optical filter is used that is constructed using a periodic structure having a peak wavelength for analysis whose transmittance changes when a voltage is applied, so that by changing the voltage applied to the optical filter, it is possible to control and modulate the transmission and blocking of light corresponding to the absorption wavelength of the component to be measured. This eliminates the need for an optical chopper equipped with a motor, disk, etc., and allows the entire device to be made smaller. Furthermore, since two optical filters with different analytical peak wavelengths are placed on the same optical path, a common photodetector can be used to detect the light transmitted through each optical filter, enabling the analysis of multiple target components while miniaturizing the overall device. Furthermore, since there is no need to turn the light source on and off to modulate the light, it is possible to use a light source with a large amount of light. Furthermore, since the first optical filter and the second optical filter have different analytical peak wavelengths, the transmittance in wavelength regions other than the analytical peak wavelength can be reduced compared to when only one optical filter is used, and the background can also be reduced.

[0011] Furthermore, in the analysis device, it is preferable that the first optical filter and the second optical filter each have a side peak wavelength at which transmittance peaks in a wavelength range other than the peak wavelength for analysis, and that one of the first optical filter and the second optical filter has the peak wavelength for analysis near the side peak wavelength of the other of the first optical filter and the second optical filter. In this way, light of the peak wavelength for analysis that has passed through one of the first optical filter and the second optical filter can also be efficiently passed through the other of the first optical filter and the second optical filter and detected by the photodetector.

[0012] It is preferable that the other of the first optical filter and the second optical filter has the analytical peak wavelength in the vicinity of the side peak wavelength of one of the first optical filter and the second optical filter. In this way, the light of the peak wavelengths for analysis of the first optical filter and the second optical filter can be efficiently detected by the photodetector.

[0013] A specific example of a mode in which the light detected by the photodetector in the analytical device is modulated is one in which the analytical device further includes a filter control unit that controls the transmittance of the first optical filter and the second optical filter by controlling the voltage applied to the first optical filter and the second optical filter, and the filter control unit periodically changes the voltage value applied to the first optical filter and the second optical filter, thereby modulating the intensity of the light detected by the photodetector. In this way, by inputting different voltage signals to each optical filter, the light transmitted through each optical filter can be detected as independent light intensity signals at the photodetector. This makes it possible to analyze two types of target components and also allows one optical filter to be used as a reference for light source drift correction. Furthermore, by changing the frequency of the voltage applied to each optical filter, it is possible to set the frequency to match the detector being used.

[0014] A specific example of a method for detecting signals for each wavelength of each optical filter in a photodetector is to have the filter control unit change the voltage values ​​applied to the first optical filter and the second optical filter at different frequencies, or change the voltage values ​​so as to create a phase difference between them.

[0015] As a specific embodiment of the analytical device, it is preferable that the light transmitted through the sample is detected by a single photodetector. In this way, a common photodetector can be used to detect light transmitted through each optical filter.

[0016] In a specific embodiment of the analysis device, the periodic structure constituting the first optical filter and the periodic structure constituting the second optical filter have different lattice constants or hole radii. In this way, by making the lattice constants or hole radii of the periodic structures different from each other, the first optical filter and the second optical filter can have different analytical peak wavelengths.

[0017] A specific example of the periodic structure is a photonic crystal.

[0018] The analytical method of the present invention is also an analytical method for analyzing a component to be measured in a sample by irradiating a sample with light from a light source and detecting the light that has transmitted through the sample with a photodetector, characterized in that a first optical filter and a second optical filter having different analytical peak wavelengths are arranged on the same optical path between the light source and the photodetector, the first optical filter and the second optical filter being configured using a periodic structure having an analytical peak wavelength whose transmittance changes when a voltage is applied thereto. Such an analysis method can achieve the same effects as the above-described analysis device of the present invention. [Effects of the Invention]

[0019] According to the present invention described above, in an analytical device that irradiates a sample with light and analyzes multiple components to be measured based on the transmitted light, the entire device can be made smaller even while using a light source that generates a large amount of light. [Brief explanation of the drawings]

[0020] [Figure 1] 1 is a diagram showing the overall configuration of an analysis device according to an embodiment of the present invention. [Figure 2] FIG. 2 is a diagram showing an example of the configuration of an optical filter according to the embodiment. [Figure 3] FIG. 2 is a diagram schematically showing the structure of a photonic crystal that constitutes the optical filter of the embodiment. [Figure 4] 3A to 3C are diagrams illustrating optical characteristics of the optical filter according to the embodiment. [Figure 5] FIG. 2 is a diagram showing the arrangement of a first optical filter and a second optical filter in the embodiment. [Figure 6]FIG. 3 is a diagram showing optical characteristics of a first optical filter and a second optical filter according to the embodiment. [Figure 7] 4 shows a transmission spectrum obtained by modulating the first optical filter and the second optical filter of the same embodiment. [Figure 8] FIG. 10 is an overall schematic view of an analysis device according to another embodiment of the present invention. [Figure 9] FIG. 10 is an overall schematic view of an analysis device according to another embodiment of the present invention. [Figure 10] FIG. 10 is an overall schematic view of an analysis device according to another embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0021] An analysis device 100 according to one embodiment of the present invention will be described below with reference to the drawings.

[0022] The analytical device 100 of this embodiment analyzes a plurality of components to be measured (e.g., CO, CO2, NO, N2O, HC, etc.) contained in a sample such as exhaust gas using the NDIR method (non-dispersive infrared absorption method).

[0023] Specifically, as shown in FIG. 1, this analytical device 100 includes a sample cell 1 into which a sample is introduced and extracted, a light source 2 that irradiates the sample in the sample cell 1 with infrared light, a photodetector 3 that detects the infrared light that has passed through the sample, an optical filter unit 4 disposed between the light source 2 and the photodetector 3, and an information processing device 5 that receives a light intensity signal that is an output signal from the photodetector 3 and calculates the concentration of the component to be measured based on the value of the light intensity signal.

[0024] The sample cell 1 has light entrance and exit ports formed of a transparent material such as quartz, calcium fluoride, or barium fluoride, which has almost no light absorption in the absorption wavelength band of the component to be measured. The sample cell 1 is provided with an inlet port 11 for introducing gas into the inside and an outlet port 12 for discharging the gas inside. The sample is introduced into the sample cell 1 from the inlet port 11.

[0025] The light source 2 emits infrared light in a wavelength range from the near-infrared region to the mid-infrared region, and is, for example, an incandescent lamp using a tungsten filament.

[0026] The photodetector 3 may be a thermal element such as a thermoelectric element (such as a thermopile), a pyroelectric element (such as PZT, TGS), a resistive element, or a pneumatic element, or a quantum element such as a photovoltaic element (e.g., HgCdTe, InGaAs, PbSe, InAsSb, etc.).

[0027] The optical filter section 4 transmits light in a wavelength range corresponding to the absorption wavelength range of the component to be measured, and is disposed on the optical path between the sample cell 1 and the photodetector 3 in this example.

[0028] The information processing device 5 is a dedicated or general-purpose computer equipped with a CPU, memory, an input / output interface, an AD converter, etc. The information processing device 5 performs at least the function of a concentration calculation unit 51 by the CPU and its peripheral devices working together in accordance with a predetermined program stored in a predetermined area of ​​the memory.

[0029] This concentration calculation unit 51 acquires the output signal (light intensity signal) from the photodetector 3 and uses the light intensity signal to calculate the concentration of the component to be measured based on the Beer-Lambert law, which is expressed by the following equation (1). TIFF0007814027000001.tif10169Here, A: absorbance, I0: incident light intensity, I: transmitted light intensity, ε: molar absorption coefficient, c: molar concentration, and l: optical path length. More specifically, the concentration calculation unit 51 calculates the concentration of the component to be measured based on the logarithm of the ratio between the light intensity when the component to be measured is not present in the sample cell 1 and the light intensity when the component to be measured is present.

[0030] In the analytical device 100 of this embodiment, the optical filter unit 4 has a first optical filter 41 and a second optical filter 42 that have different optical properties, and the first optical filter 41 and the second optical filter 42 are configured using a periodic structure having a peak wavelength whose transmittance changes when a voltage is applied. In this embodiment, the periodic structure used is a photonic crystal 4P, which is an artificial crystal (structure) having a periodic structure in which materials with different refractive indices are arranged at intervals approximately the same as the wavelength of light.

[0031] The following describes a first optical filter 41 and a second optical filter 42 that are configured using a photonic crystal 4P. As shown in Figures 2 and 3, the first optical filter 41 and the second optical filter 42 are generally plate-shaped, and have an incident surface 4a onto which light enters and an exit surface 4b from which transmitted light exits, respectively, formed on the front and back surfaces. The first optical filter 41 and the second optical filter 42 have a p-type semiconductor layer 4c, a multiple quantum well layer 4d, and an n-type semiconductor layer 4e that are stacked in this order from the incident surface 4a side toward the exit surface 4b side.

[0032] In this embodiment, the p-type semiconductor layer 4c is made of p-GaAs, which is GaAs doped with Be, a p-type impurity. The n-type semiconductor layer 4e is made of n-GaAs, which is GaAs doped with Si, an n-type impurity. The multi-quantum well layer 4d is made of many layers of GaAs and AlGaAs stacked alternately. Note that the materials constituting the p-type semiconductor layer 4c, the n-type semiconductor layer 4e, and the multi-quantum well layer 4d are not limited to these and may be other materials.

[0033] A plurality of holes 4f are formed in each of the first optical filter 41 and the second optical filter 42 along their thickness direction. The holes 4f are cylindrical and open to the incident surface 4a, which is the surface of the p-type semiconductor layer 4c, and are formed so as to penetrate the p-type semiconductor layer 4c and the multiple quantum well layer 4d. When the incident surface 4a is viewed from above, the plurality of holes 4f are formed in a triangular lattice shape. The plurality of holes 4f, the p-type semiconductor layer 4c, the multiple quantum well layer 4d, and the n-type semiconductor layer 4e form a triangular lattice two-dimensional photonic crystal 4P.

[0034] The first optical filter 41 and the second optical filter 42 are each provided with a p-type electrode 4g and an n-type electrode 4h for applying a voltage to the photonic crystal 4P. The p-type electrode 4g and the n-type electrode 4h are formed on the surfaces of the p-type semiconductor layer 4c and the n-type semiconductor layer 4e, respectively, so that a voltage can be applied between the p-type semiconductor layer 4c and the n-type semiconductor layer 4e with the multiple quantum well layer 4d sandwiched between them. The p-type electrode 4g and the n-type electrode 4h of each optical filter 41, 42 are connected to different voltage sources.

[0035] The first optical filter 41 and the second optical filter 42 configured using such a photonic crystal 4P have an optical characteristic in which, when a voltage is applied between the p-type semiconductor layer 4c and the n-type semiconductor layer 4e, the electron density in the multiple quantum well layer 4d changes, and the transmittance of light in a specific wavelength region R changes according to the lattice constant of the photonic crystal 4P and the hole diameter of the holes 4f. More specifically, as shown in FIG. 4(a), the first optical filter 41 and the second optical filter 42 have an optical characteristic in which, as the applied voltage increases (10 V in this case), the electron density in the multiple quantum well layer 4d decreases, thereby increasing the transmittance in the specific wavelength region R, and as the applied voltage decreases (0 V in this case), the electron density in the multiple quantum well layer 4d increases, thereby decreasing the transmittance in the specific wavelength region R. On the other hand, the first optical filter 41 and the second optical filter 42 have an optical characteristic in which, in wavelength regions other than the specific wavelength region R, the transmittance is substantially constant regardless of the applied voltage (i.e., the transmittance does not change significantly even when the applied voltage value is changed). Therefore, as shown in (b) of Figure 4, the first optical filter 41 and the second optical filter 42 function as optical filters in which the transmittance of the portion of the difference spectrum, which is the difference between the transmittance when a relatively large voltage is applied and the transmittance when a relatively small voltage is applied, is modulated by voltage.

[0036] In the analytical device 100 of this embodiment, the first optical filter 41 and the second optical filter 42 having such optical properties are arranged in this order on the same optical path between the sample cell 1 and the photodetector 3. Specifically, as shown in Fig. 5, the first optical filter 41 and the second optical filter 42 are arranged in series on the optical path with their incident surfaces 4a facing the same direction. Light that has passed through the sample cell 1 is transmitted in order through the first optical filter 41 and the second optical filter 42, and then detected by the single (i.e., common) photodetector 3.

[0037] The first optical filter 41 and the second optical filter 42 are configured such that, by adjusting the lattice constant of the photonic crystal 4P and the diameter of the holes 4f, the peak wavelengths Pa1 and Pa2 (also referred to as analytical peak wavelengths) at which the transmittance peaks in the respective specific wavelength ranges R1 and R2, where the transmittance changes with the application of voltage, correspond to the absorption wavelengths of the components to be measured. Specifically, the first optical filter 41 and the second optical filter 42 are configured using photonic crystals 4P with different lattice constants or hole diameters of the holes 4f. As shown in Figures 6(a) and 6(b), the analytical peak wavelengths Pa1 and Pa2 are configured to be different from each other, and the specific wavelength ranges are configured so that they do not overlap. Note that Figures 6(a) and 6(b) show the transmittance of the first optical filter 41 and the second optical filter 42 when a voltage is applied.

[0038] 6(a) and 6(b), the first optical filter 41 and the second optical filter 42 each have one or more side peak wavelengths Ps1 and Ps2 at which light transmittance reaches a peak in a wavelength range other than the analytical peak wavelengths Pa1 and Pa2 (more specifically, a wavelength range other than the specific wavelength range). The first optical filter 41 is configured to have its analytical peak wavelength Pa1 near the side peak wavelength Ps2 of the second optical filter 42, and the second optical filter 42 is configured to have its analytical peak wavelength Pa2 near the side peak wavelength Ps1 of the first optical filter 41. Here, "near the side peak wavelength" means a continuous wavelength range that includes the side peak wavelength Ps and has a transmittance of 50% or more at the side peak wavelength Ps. In Figure 6, the first optical filter 41 and the second optical filter 42 have side peak wavelengths Ps1 and Ps2 on both sides (long wavelength side and short wavelength side) of the specific wavelength region, respectively, but they may also have side peak wavelengths Ps1 and Ps2 on only one side, either the long wavelength side or the short wavelength side.

[0039] In this way, by setting one analytical peak wavelength Pa1, Pa2 and the other side peak wavelength Ps1, Ps2 of each optical filter 41, 42 to overlap with each other, the optical filter unit 4 as a whole can have two different analytical peak wavelengths Pa1, Pa2 (first analytical peak wavelength, second analytical peak wavelength), as shown in Fig. 6(c). In this optical filter unit 4, the transmittance at these two analytical peak wavelengths Pa1, Pa2 can be individually changed by individually changing the voltages applied to the first optical filter 41 and the second optical filter 42.

[0040] In the analytical device 100 of this embodiment, the information processing device 5 further functions as a filter control unit 52 that controls the light transmittance of the optical filter unit 4. This filter control unit 52 individually controls the transmittance at multiple (here, two) analytical peak wavelengths Pa1 and Pa2 that the optical filter unit 4 has. More specifically, this filter control unit 52 is configured to individually output voltage control signals to the voltage sources of the optical filters 41 and 42 to control the applied voltages, thereby individually changing the transmittance at the first analytical peak wavelength Pa1 and the second analytical peak wavelength Pa2.

[0041] Specifically, the filter control unit 52 is configured to apply AC voltages to the first optical filter 41 and the second optical filter 42, respectively, and periodically change the values ​​of the applied voltages to periodically change the intensities of light corresponding to the analytical peak wavelengths Pa1 and Pa2 detected by the photodetector 3. As a result, the first optical filter 41 functions as an optical filter whose transmittance in a specific wavelength region R1 (specifically, the difference spectrum of the first optical filter 41 in two states where different voltage values ​​are applied) is modulated by the voltage, as shown in Fig. 7(a). Also, the second optical filter 42 functions as an optical filter whose transmittance in a specific wavelength region R2 (specifically, the difference spectrum of the second optical filter 42 in two states where different voltage values ​​are applied) is modulated by the voltage, as shown in Fig. 7(b).

[0042] Here, the filter control unit 52 is configured to input different voltage signals to the first optical filter 41 and the second optical filter 42 so that the light transmitted through each optical filter 41, 42 can be detected as independent light intensity signals in the photodetector 3. More specifically, the filter control unit 52 is configured to change the voltage values ​​applied to each optical filter at different frequencies or to change the voltages so as to create a phase difference between them. The filter control unit 52 is configured to change the frequency and phase of the AC voltage applied to each optical filter 41, 42. Here, "changing the voltage value so as to create a phase difference between them" means, for example, shifting the timing at which voltage is applied to each optical filter 41, 42 or the timing at which the voltage value reaches its peak.

[0043] The concentration calculation unit 51 then acquires from the photodetector 3 the light intensity signals of the light transmitted through the first optical filter 41 and the light intensity signals of the light transmitted through the second optical filter 42, and calculates the concentrations of the components to be measured that have absorption wavelengths at the respective analytical peak wavelengths Pa1 and Pa2 based on the principle of the Beer-Lambert law.

[0044] The analytical device 100 of this embodiment configured as described above uses the first optical filter 41 and the second optical filter 42 configured using periodic structures having analytical peak wavelengths Pa1 and Pa2 whose transmittance changes when a voltage is applied, and therefore can control and modulate the transmission and blocking of light corresponding to the absorption wavelength of the component to be measured by changing the voltage applied to each optical filter 41, 42. This eliminates the need for an optical chopper equipped with a motor, disk, etc., and allows the overall device to be made smaller. Furthermore, since two optical filters with different analytical peak wavelengths Pa1 and Pa2 are arranged on the same optical path, the photodetector 3 that detects light transmitted through each optical filter 41 and 42 can be shared, making it possible to analyze multiple target components while still miniaturizing the entire device. Furthermore, since there is no need to turn the light source 2 on and off to modulate the light, it is possible to use a light source 2 with a large amount of light. Furthermore, since the analytical peak wavelengths Pa1 and Pa2 of the first optical filter 41 and the second optical filter 42 are different from each other, the transmittance in wavelength regions other than the analytical peak wavelength can be reduced compared to when only one optical filter is used, and the background can also be reduced.

[0045] The present invention is not limited to the above-described embodiment. For example, in the above embodiment, the first optical filter 41 and the second optical filter 42 are configured using the photonic crystal 4P as the periodic structure, but this is not limiting. In other embodiments, the first optical filter 41 and the second optical filter 42 may be any periodic structure other than the photonic crystal 4P, as long as they have optical properties with analytical peak wavelengths Pa1 and Pa2 whose transmittance changes when a voltage is applied.

[0046] In addition, in the above embodiment, both the first optical filter 41 and the second optical filter 42 are disposed on the optical path between the sample cell 1 and the photodetector 3, but this is not limited to this. In other embodiments, for example, as shown in FIG. 8 , one of the first optical filter 41 and the second optical filter 42 may be disposed between the light source 2 and the sample cell 1, and the other may be disposed between the sample cell 1 and the photodetector 3.

[0047] In other embodiments, both the first optical filter 41 and the second optical filter 42 may be disposed between the light source 2 and the sample cell 1, as shown in FIG.

[0048] In still another embodiment of the analysis device 100, the optical filter unit 4 may include three or more optical filters configured using a periodic structure. For example, as shown in Fig. 10, the analysis device 100 of another embodiment may further include a third optical filter 43 configured with a periodic structure between the light source 2 and the photodetector 3. This third optical filter 43 may be arranged on the same optical path as the first optical filter 41 and the second optical filter 42, or may be arranged on a different optical path.

[0049] In the above embodiment, the light source 2 is an incandescent bulb, but this is not limiting. In other embodiments, the light source 2 may be an LED. In addition, the light source 2 emits infrared light, but this is not limiting and the light source may emit light in other wavelength ranges.

[0050] Furthermore, although the analytical device 100 in the above embodiment is of the NDIR type, the analytical device 100 is not limited to this type. The analytical device 100 in other embodiments may be of any type as long as it irradiates a sample with light and analyzes the sample based on the transmitted light.

[0051] In the above embodiment, the sample to be analyzed is exhaust gas, but this is not limited to this. In other embodiments, the sample to be analyzed may be the atmosphere, gas during combustion, or process gas generated in a chemical plant, etc., and may be a liquid or solid. In this sense, the present invention is applicable to measuring components that are not only gases but also liquids and solids.

[0052] In another embodiment, "near the side peak wavelength" may refer to a wavelength range that includes the side peak wavelength and is within ±20% of the side peak wavelength Ps.

[0053] In addition, various modifications and combinations of the embodiments may be made as long as they do not go against the spirit of the present invention. [Explanation of symbols]

[0054] 100...Analyzer 1. Sample cell 2...Light source 3. Photodetector 41 First optical filter 42 Second Optical Filter 4P Photonic Crystal R...specific wavelength range Pa: Peak wavelength for analysis Ps: Side peak wavelength

Claims

1. An analytical device that irradiates a sample with light, detects light transmitted through the sample, and analyzes a component to be measured in the sample, a light source that irradiates the sample with light; a photodetector that detects light transmitted through the sample; a first optical filter and a second optical filter disposed between the light source and the photodetector; the first optical filter and the second optical filter are arranged on the same optical path and are configured using a periodic structure having a peak wavelength for analysis whose transmittance changes when a voltage is applied, the analytical peak wavelength of the first optical filter and the analytical peak wavelength of the second optical filter are different from each other, a filter control unit that controls the transmittance of the first optical filter and the second optical filter by controlling a voltage applied to the first optical filter and the second optical filter, the filter control unit periodically changes a voltage value applied to the first optical filter and the second optical filter, thereby modulating the intensity of light detected by the photodetector; The filter control unit changes the voltage values ​​applied to the first optical filter and the second optical filter at different frequencies, or changes the voltage values ​​so as to generate a phase difference between the first optical filter and the second optical filter.

2. the first optical filter and the second optical filter each have a side peak wavelength at which transmittance peaks in a wavelength range other than the peak wavelength for analysis, The analytical device according to claim 1 , wherein one of the first optical filter and the second optical filter has the analytical peak wavelength in the vicinity of the side peak wavelength of the other of the first optical filter and the second optical filter.

3. The analytical device according to claim 2 , wherein the other of the first optical filter and the second optical filter has the analytical peak wavelength in the vicinity of the side peak wavelength of one of the first optical filter and the second optical filter.

4. 4. The analytical device according to claim 1, wherein the light transmitted through the sample is detected by a single photodetector.

5. The analytical device according to any one of claims 1 to 4, wherein the periodic structure constituting the first optical filter and the periodic structure constituting the second optical filter have different lattice constants or hole radii.

6. The analytical device according to any one of claims 1 to 5, wherein the periodic structure is a photonic crystal.

7. 1. An analytical method for analyzing a component to be measured in a sample by irradiating a sample with light from a light source and detecting the light transmitted through the sample with a photodetector, comprising: a first optical filter and a second optical filter configured using a periodic structure having a peak wavelength for analysis whose transmittance changes when a voltage is applied thereto, the first optical filter and the second optical filter having different peak wavelengths for analysis are disposed on the same optical path between the light source and the photodetector; An analytical method in which, when modulating the intensity of light detected by the photodetector by periodically changing the voltage values ​​applied to the first optical filter and the second optical filter, the voltage values ​​applied to the first optical filter and the second optical filter are changed at different frequencies or so as to create a phase difference between them.

8. An analytical device that irradiates a sample with light, detects light transmitted through the sample, and analyzes a component to be measured in the sample, a light source that irradiates the sample with light; a photodetector that detects light transmitted through the sample; a first optical filter and a second optical filter disposed between the light source and the photodetector; the first optical filter and the second optical filter are arranged on the same optical path and are configured using a periodic structure having a peak wavelength for analysis whose transmittance changes when a voltage is applied, the analytical peak wavelength of the first optical filter and the analytical peak wavelength of the second optical filter are different from each other, the first optical filter and the second optical filter each have a side peak wavelength at which transmittance peaks in a wavelength range other than the peak wavelength for analysis, An analytical device, wherein one of the first optical filter and the second optical filter has the analytical peak wavelength in the vicinity of the side peak wavelength of the other of the first optical filter and the second optical filter.

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