SPECTROSCOPE, WAVELENGTH VARIABLE INTERFERENCE FILTER, OPTICAL FILTER DEVICE, OPTICAL MODULE, AND ELECTRONIC DEVICE

A spectrometer includes a first reflective film, a second reflective film facing the first reflective film with a gap interposed therebetween, a gap change portion that changes the amount of the gap by changing the relative position of the second reflective film with respect to the first reflective film, and a processing unit that outputs optical characteristic data at a predetermined first wavelength interval on the basis of light of a plurality of the wavelengths to be measured which are extracted by the first reflective film and the second reflective film by changing the gap amount using the gap change portion, wherein a full width at half maximum of a spectrum of at least one component of light among the light of the plurality of wavelengths to be measured which are extracted by the first reflective film and the second reflective film is larger than the first wavelength interval.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

First Embodiment

Hereinafter, a first embodiment of the invention will be described with reference to the accompanying drawings.

Configuration of Spectrometer

FIG. 1is a block diagram illustrating a schematic configuration of a spectrometer (spectroscope) according to a first embodiment of the invention.

A spectrometer1is equivalent to a spectroscope and an electronic device according to the invention, and is a device that measures a spectrum of light to be measured on the basis of the light to be measured reflected from a measuring object X. Meanwhile, in the present embodiment, an example of measuring the light to be measured which is reflected from the measuring object X is illustrated, but as the measuring object X, for example, when an illuminant such as a liquid crystal panel is used, light emitted from the illuminant may be used as light to be measured.

As shown inFIG. 1, the spectrometer1includes an optical module10and a control unit20.

Configuration of an Optical Module

Next, the configuration of the optical module10will be described below.

As shown inFIG. 1, the optical module10includes a wavelength variable interference filter5, a detector11(detection unit), an I-V converter12, an amplifier13, an A/D converter14, and a voltage control unit15(gap control unit).

The detector11receives light passing through the wavelength variable interference filter5, and outputs a detection signal (current) in accordance with the light intensity of the received light.

The I-V converter12converts a detection signal which is input from the detector11into a voltage value, and outputs the converted value to the amplifier13.

The amplifier13amplifies a voltage (detection voltage) in accordance with the detection signal which is input from the I-V converter12.

The A/D converter14converts a detection voltage (analog signal) which is input from the amplifier13into a digital signal, and outputs the converted signal to the control unit20.

The voltage control unit15applies a voltage to an electrostatic actuator56, described later, of the wavelength variable interference filter5, and transmits light of a target wavelength according to the applied voltage from the wavelength variable interference filter5.

Configuration of Wavelength Variable Interference Filter

FIG. 2is a cross-sectional view illustrating a schematic configuration of the wavelength variable interference filter5.

The wavelength variable interference filter5of the present embodiment is a so-called Fabry-Perot etalon. As shown inFIG. 2, the wavelength variable interference filter5includes a fixed substrate51and a movable substrate52. The fixed substrate51and the movable substrate52are formed of, for example, various types of glass, quartz crystal, silicon, or the like. The fixed substrate51and the movable substrate52are integrally formed through the bonding of a first bonding portion513of the fixed substrate51to a second bonding portion523of the movable substrate52using a bonding film53which is constituted by, for example, a siloxane-based plasma polymerized film and the like.

The fixed substrate51is provided with a fixed reflective film54(first reflective film), and the movable substrate52is provided with a movable reflective film55(second reflective film). The fixed reflective film54and the movable reflective film55are disposed so as to face each other with a gap G1(gap) between reflective films interposed therebetween. The wavelength variable interference filter5is provided with an electrostatic actuator56(gap change portion) used for adjusting (changing) the amount of the gap G1between the reflective films. The electrostatic actuator56is constituted by a fixed electrode561provided on the fixed substrate51and a movable electrode562provided on the movable substrate52. The fixed electrode561and the movable electrode562face each other with an inter-electrode gap interposed therebetween, and function as the electrostatic actuator56(gap change portion). Here, the fixed electrode561and the movable electrode562may be provided directly on the surfaces of the fixed substrate51and the movable substrate52, respectively, and may be provided through another film member. Meanwhile, inFIG. 2, an example is shown in which the amount of the inter-electrode gap is larger than the amount of the gap G1between the reflective films, but a configuration may be used in which the inter-electrode gap is smaller than the gap G1between the reflective films.

Hereinafter, the configuration of the wavelength variable interference filter5will be described in more detail.

An electrode installing groove511and a reflective film installing portion512are formed on the fixed substrate51by etching. The fixed substrate51is formed so as to have a thickness larger than that of the movable substrate52, and thus there is no electrostatic attractive force when a voltage is applied to the electrostatic actuator56, or no bending of the fixed substrate51due to internal stress of the fixed electrode561.

The electrode installing groove511is formed, for example, in a circular shape centered on the planar center point of the fixed substrate51. In the above-mentioned planar view, the reflective film installing portion512is formed so as to protrude from the central portion of the electrode installing groove511to the movable substrate52side. The groove bottom of the electrode installing groove511is an electrode installing surface511A on which the fixed electrode561is disposed. In addition, the protruding apical surface of the reflective film installing portion512is a reflective film installing surface512A.

In addition, although not shown in the drawing, the fixed substrate51is provided with an electrode extraction groove extending from the electrode installing groove511toward the outer circumferential edge of the fixed substrate51, and is provided with an extraction electrode of the fixed electrode561provided in the electrode installing groove511.

The fixed electrode561is provided on the electrode installing surface511A of the electrode installing groove511. More specifically, the fixed electrode561is provided on a region facing the movable electrode562of the movable portion521, described later, in the electrode installing surface511A. In addition, an insulating film for securing insulating properties between the fixed electrode561and the movable electrode562may be laminated on the fixed electrode561. In addition, a fixed extraction electrode is connected to the fixed electrode561. The fixed extraction electrode is extracted from the above-mentioned electrode extraction groove to the outer circumferential portion of the fixed substrate51, and is connected to the voltage control unit15.

Meanwhile, in the embodiment, the configuration is shown in which one fixed electrode561is provided on the electrode installing surface511A, but a configuration (double electrode configuration) or the like may be formed, for example, in which two electrodes having a concentric circle centered on the planar center point are provided.

As mentioned above, the reflective film installing portion512is formed coaxially with the electrode installing groove511and in a substantially cylindrical shape having a diameter smaller than that of the electrode installing groove511, and includes the reflective film installing surface512A that faces the movable substrate52of the reflective film installing portion512.

The fixed reflective film54is installed on the reflective film installing portion512.

The fixed reflective film.54is formed of an optical film having reflectance and transmittance with respect to light of a wavelength region (measurement wavelength region) serving as an object for measuring an optical spectrum using the spectrometer1. Specifically, the fixed reflective film54is constituted by an optical film having optical characteristics in which the minimum value of reflectance is equal to or less than 75% and the maximum value thereof is equal to or more than 30% with respect to the measurement wavelength region. Here, when the minimum value of reflectance exceeds 75%, the full width at half maximum of the wavelength variable interference filter5becomes small, and the amount of light received in the detector11deteriorates. In addition, when the minimum value of reflectance is less than 30%, a wavelength selection function in the wavelength variable interference filter5deteriorates. That is, light of each wavelength for the wavelength to be measured is nearly transmitted, and thus the accuracy of measurement of the optical spectrum deteriorates without receiving the amount of light for a predetermined wavelength. On the other hand, as mentioned above, when the fixed reflective film54has optical characteristics in which the minimum value of reflectance is equal to or less than 75% and equal to or more than 30%, it is possible to transmit light having a sufficient amount of light and receive the light in the detector11while suppressing a deterioration in a wavelength selection function in the wavelength variable interference filter5, and to achieve an improvement in the accuracy of measurement.

As such a fixed reflective film54, any optical film may be used as long as the fixed reflective film has optical characteristics as mentioned above. For example, a metal film such as Ag, an alloy film such as an Ag alloy, a single-layer refractive layer (such as, for example, TiO2single-layer film, SiO2single-layer film, or ITO single-layer film), a dielectric multilayer film, a reflective film in which a metal film (or alloy film) is laminated on a dielectric multilayer film, a reflective film in which a dielectric multilayer film is laminated on a metal film (or alloy film), a reflective film in which a single-layer refractive layer (such as TiO2or SiO2) and a metal film (or alloy film) are laminated, or the like can be used.

Particularly, when an Ag metal film or an Ag alloy film is used as the fixed reflective film54, this film is preferably formed to have a film thickness of equal to or less than 40 nm and equal to or more than 15 nm. The Ag metal film or the Ag alloy film shows reflection characteristics with respect to a wavelength band having a large width, particularly, in a metal, and can satisfy optical characteristics as mentioned above (the minimum value of reflectance is equal to or less than 75% and equal to or more than 30%) when the film thickness thereof is equal to or less than 40 nm and equal to or more than 15 nm.

In addition, when a TiO2single-layer film, a SiO2single-layer film, or an ITO single-layer film is used as the fixed reflective film54, it is possible to suppress a deterioration in a film, and to achieve the lifetime duration of the wavelength variable interference filter5, with respect to a case where the Ag metal film or the Ag alloy film is used. Further, when the fixed reflective film54is formed of an ITO single-layer film, and the fixed electrode561is also formed of an ITO single-layer film, it is possible to simultaneously form the fixed reflective film54and the fixed electrode561using one process, and to achieve an improvement in manufacturing efficiency.

Meanwhile, a description will be given later of the optical characteristics of the wavelength variable interference filter5in a case where the fixed reflective film54is configured to have optical characteristics (reflectance characteristics) as mentioned above.

In addition, on the light incidence plane (plane on which the fixed reflective film54is not provided) of the fixed substrate51, an anti-reflective film may be formed at a position corresponding to the fixed reflective film54. Since this anti-reflective film can be formed by alternately laminating a low refractive index film and a high refractive index film, the reflectance of visible light from the surface of the fixed substrate51is reduced, and the transmittance thereof is increased.

The movable substrate52includes the circle-shaped movable portion521centered on the planar center point, a holding portion522which is coaxial with the movable portion521and holds the movable portion521, and a substrate outer circumferential portion525provided outside the holding portion522.

The movable portion521is formed so as to have a thickness larger than that of the holding portion522, and is formed so as to have the same thickness as that of the movable substrate52, for example, in the embodiment. In the planar view of the filter, the movable portion521is formed so as to have a diameter larger than at least the diameter of the outer circumferential edge of the reflective film installing surface512A. The movable portion521is provided with the movable electrode562and the movable reflective film55.

Meanwhile, similarly to the fixed substrate51, an anti-reflective film may be formed on the surface of the movable portion521on the opposite side to the fixed substrate51. Such an anti-reflective film can be formed by alternately laminating a low refractive index film and a high refractive index film, thereby allowing the reflectance of visible light from the surface of the movable substrate52to be reduced, and allowing the transmittance thereof to be increased.

The movable electrode562faces the fixed electrode561with the inter-electrode gap interposed therebetween, and is formed in a circular shape having the same shape as that of the fixed electrode561. In addition, although not shown in the drawing, the movable substrate52is provided with a movable extraction electrode extending from the outer circumferential edge of the movable electrode562toward the outer circumferential edge of the movable substrate52. The movable extraction electrode is connected to the voltage control unit15, similarly to the fixed extraction electrode.

On the central portion of a movable surface521A of the movable portion521, the movable reflective film55is provided facing the fixed reflective film54with the gap G1between the reflective films interposed therebetween. As the movable reflective film55, a reflective film having the same configuration as that of the above-mentioned fixed reflective film54is used.

The holding portion522is a diaphragm that surrounds the periphery of the movable portion521, and is formed so as to have a thickness smaller than that of the movable portion521. Such a holding portion522is more likely to be bent than the movable portion521, and thus can cause the movable portion521to be displaced to the fixed substrate51side due to slight electrostatic attractive force. At this time, the movable portion521has a thickness larger than that of the holding portion522, and has a rigidity larger than that. Thus, even when the holding portion522is pulled to the fixed substrate51side due to electrostatic attractive force, a change in the shape of the movable portion521is not caused. Therefore, the movable reflective film.55provided on the movable portion521is not only bent, but also the fixed reflective film54and movable reflective film55can always be maintained to the parallel state.

Meanwhile, in the embodiment, the diaphragm-shaped holding portion522is illustrated by way of example, but without being limited thereto, for example, beam-shaped holding portions which are disposed at equiangular intervals centered on the planar center point may be provided.

As mentioned above, the substrate outer circumferential portion525is provided outside the holding portion522in the planar view of the filter. The surface of the substrate outer circumferential portion525facing the fixed substrate51includes the second bonding portion523which faces the first bonding portion513, and the second bonding portion523is bonded to the first bonding portion513by the bonding film53.

Configuration of Control Unit

Returning toFIG. 1, the control unit20of the spectrometer1will be described.

The control unit20is equivalent to a processing unit according to the invention, is configured by a combination of, for example, a CPU, a memory and the like, and controls the entire operation of the spectrometer1. As shown inFIG. 1, the control unit20includes a filter driving unit21, a light amount acquisition unit22, and a spectroscopic measurement unit23. In addition, the control unit20includes a storage unit30constituted by a ROM (Read Only Memory), a RAM (Random Access Memory) and the like. Various types of data are stored in the storage unit30, and V-λ data for controlling the electrostatic actuator56is stored in the storage unit30.

A voltage value applied to the electrostatic actuator56with respect to the peak wavelength of light passing through the wavelength variable interference filter5is recorded in the V-λ data.

The filter driving unit21outputs a command signal for causing light within a predetermined measurement wavelength region to pass through the wavelength variable interference filter5at a predetermined measurement wavelength interval. Specifically, the filter driving unit21outputs a control signal to the voltage control unit15so as to read a voltage value corresponding to a wavelength λn to be measured (n=0, 1, 2, 3 . . . ) for each measurement wavelength interval λc (for example, λc=20 nm) on the basis of the V-λ data and sequentially apply a voltage corresponding to the voltage value to the electrostatic actuator56of the wavelength variable interference filter5. Thereby, the voltage control unit15applies a commanded voltage to the electrostatic actuator56, and the gap G1between the reflective films is sequentially switched, so that the peak wavelength (center wavelength) of light transmitted from the wavelength variable interference filter5is sequentially changed.

The light amount acquisition unit22acquires the amount (intensity) of light received in the detector11, on the basis of a signal (voltage) which is input from the A/D converter14.

The spectroscopic measurement unit23measures spectral characteristics of light to be measured, on the basis of the amount of light acquired by the light amount acquisition unit22.

Here, in the present embodiment, in the optical characteristics of the wavelength variable interference filter5, even when the full width at half maximum is large, the following spectrum estimation process is performed in order to accurately calculate the optical spectrum of measurement light reflected from the measuring object X.

That is, as shown in the following Expression (1), the spectroscopic measurement unit23estimates an optical spectrum S of the light to be measured (light reflected from the measuring object X) by causing an estimation matrix Ms (transformation matrix) stored in a storage unit (not shown) such as, for example, a memory to act on a measurement spectrum (amount of light for each wavelength to be measured) D obtained by the light amount acquisition unit22.

Meanwhile, the spectrometer1measures reference light in which a precise optical spectrum S0is measured in advance, and thus the estimation matrix Ms is calculated from a measurement spectrum D0obtained by the measurement, and the precise optical spectrum S0.

In the above Expression (1), “t” denotes a transposed vector. In Expression (1), the optical spectrum S and the measurement spectrum D are denoted as a “row vector”, and thus the transposed vector becomes a “column vector”.

When the above Expression (1) is represented in a state where each element is specified, the expression is represented as Expression (2).

In the above Expression (2), the measurement spectrum D is constituted by elements of a number equivalent to the number of wavelengths (number of bands) to be measured in the spectrometer1. In addition, in the present embodiment, the measurement wavelength region (400 nm to 700 nm) is measured at a pitch of 20 nm. In this case, in the above Expression (2), the measurement wavelength region is constituted by sixteen elements of d1 to d16. Meanwhile, these elements of d1 to d16 become the amount of light acquired by the light amount acquisition unit22with respect to each wavelength to be measured.

In addition, the optical spectrum S is constituted by elements of a number equivalent to the number of wavelengths (number of spectra) to be estimated. For example, in the above Expression (2), the optical spectrum S is estimated by setting a target wavelength region of 400 nm to 700 nm to a wavelength having a data output wavelength interval λd (for example, λd=pitch of 5 nm). Therefore, the number of elements of the row vector of the optical spectrum S is sixty-one. That is, the data output wavelength interval λd is equivalent to a first wavelength interval according to the invention.

Therefore, the estimation matrix Ms for estimating the optical spectrum S from the measurement spectrum D becomes a matrix of 61 rows×□16 columns as shown in Expression (2).

Here, the number of elements of the measurement spectrum D is sixteen, whereas the number of elements of the optical spectrum S is sixty-one. Therefore, it is not possible to determine the estimation matrix Ms of 61 rows×16 columns simply by a set of measurement spectrum D and optical spectrum S. Therefore, the estimation matrix Ms is determined by measuring a plurality of sample light (reference light in which the optical spectrum S0is measured in advance) using the spectrometer1.

Such an estimation matrix Ms is determined as follows. That is, the plurality of sample light (reference light) in which the optical spectrum S is measured in advance is measured using the spectrometer1, and the measurement spectrum D0for each sample light is acquired. At this time, the measurement spectrum D0may be transformed into a measurement spectrum corresponding to spectral reflectance divided by a measurement spectrum Dw of a standard white plate.

Here, when the optical spectrum S is assumed to have elements of the number k of spectra (sixty-one in the case of Expression (2)), and the sample light of the number n of samples are measured, the optical spectrum S0can be represented in the form of a matrix Stas shown in the following Expression (3). In addition, the measurement spectrum D0has elements of the number b of bands (16 in the case of Expression (2)), and measurement results are obtained with respect to the sample light of the number n of samples, respectively. Therefore, the measurement spectrum D0can be represented in the form of a matrix Dtas shown in the following Expression (4).

An evaluation function F (Ms)=|St−Ms·Dt|2is set indicating a deviation between the matrix Stand the inner product (Ms·Dt) of the matrix Dtand the estimation matrix Ms, and the estimation matrix Ms is determined so that the evaluation function F (Ms) is minimized. That is, since a value obtained by partially differentiating the evaluation function F (Ms) by the estimation matrix Ms is equal to 0, the estimation matrix Ms can be determined by the following Expression (5).

Meanwhile, in the above description, an error is assumed not to be present in the optical spectrum S0of the sample light which is reference light, but the estimation matrix Ms considering an error of the optical spectrum S0of the sample light may be determined. That is, the optical spectrum S0of the sample light is measured using a measuring device such as a multi-spectral colorimeter. However, in the measuring device, the optical spectrum S0is measured by extracting light in an extremely narrow wavelength range of several nm or so. In this manner, when the extremely narrow wavelength range is extracted, the amount of light decreases, and an SN ratio lowers, which leads to a tendency for errors to be superimposed. In such a case, when a principal component analysis method is used, a matrix Snkcan be represented as “Snk=anj·vjk” by setting a principal component number to j, setting a principal component value to a, and setting a principal component vector to v, and the estimation matrix Ms considering the error of the sample light can also be calculated.

Meanwhile, other estimation processes may be performed without being limited to the above-mentioned spectrum estimation process, and, for example, a Wiener estimation method or the like may be used.

Optical Characteristics of Wavelength Variable Interference Filter5

FIGS. 3 and 4are diagrams illustrating outlines of a measurement method of an optical spectrum of the related art.FIG. 3shows the amount of light (current value from the detector11) of each wavelength to be measured which is obtained by measurement.FIG. 4is a diagram illustrating an optical spectrum estimated by a method of the related art and an actual optical spectrum. The broken line shows the optical spectrum estimated by the method of the related art, and the solid line shows the actual optical spectrum.

In addition,FIG. 5is a diagram illustrating optical characteristics (transmittance characteristics) of the wavelength variable interference filter5of the present embodiment, andFIG. 6is a diagram illustrating a full width at half maximum of each wavelength in the optical characteristics ofFIG. 5.FIG. 7is a diagram illustrating optical characteristics of a wavelength variable interference filter of the related art, andFIG. 8is a diagram illustrating a full width at half maximum for each wavelength in the optical characteristics ofFIG. 7.

Hitherto, in an electronic device such as a spectrometer, when a precise optical spectrum is analyzed, the amount of light of the wavelength λn to be measured (n=0, 1, 2, 3 . . . ) for each measurement wavelength interval λc has been acquired by sequentially switching the gap between the reflective films of the wavelength variable interference filter, as shown inFIG. 3. The amount of light for each wavelength to be measured is plotted on a graph indicating, for example, a relationship between the wavelength and the amount of light, and the optical spectrum of measurement light has been measured by connecting these amounts as shown inFIG. 4. In such a configuration of the related art, it is necessary to transmit light of a desired wavelength to be measured at a high resolution using the wavelength variable interference filter, and to suppress the transmission of light of other wavelength regions. Therefore, as shown inFIGS. 7 and 8, the full width at half maximum is set to be small with respect to the measurement wavelength interval of each wavelength to be measured. For example, when a spectral curve having a wavelength of 440 nm inFIG. 7is adopted by way of example, a full width at half maximum W440′ is smaller than the measurement wavelength interval λc.

That is, when the amount of light detected by the detector is set to the amount of light for the wavelength to be measured, the full width at half maximum has been required to be set to be small so that light other than the wavelength to be measured is not mixed to the utmost in order to measure a high-precision optical spectrum. In addition, in the related art, when the full width at half maximum is equal to or more than the data output wavelength interval (first wavelength interval) λd, the amount of light of multiple wavelengths to be measured is included in one piece of data, and thus it is considered that a measurement error of the optical spectrum becomes large. For this reason, when the optical spectrum is measured by the method of the related art, the full width at half maximum of the wavelength variable interference filter is preferably made smaller than the data output wavelength interval λd.

However, as mentioned above, in the wavelength variable interference filter of the related art for making the full width at half maximum smaller, the amount of light passing through the wavelength variable interference filter is also reduced.FIG. 9is a diagram illustrating a relationship between a full width at half maximum in the optical characteristics of the wavelength variable interference filter5and a current (PD current) which is output at the time of receiving light in the detector11.

As shown inFIG. 9, the full width at half maximum and the PD current which is output from the detector11have a substantially proportional relationship, and as the full width at half maximum increases, the PD current which is output from the detector11linearly increases. Therefore, in the wavelength variable interference filter of the related art as mentioned above, it is not possible to obtain the sufficient amount of light received in the detector11. Accordingly, there is a tendency to be influenced by a noise component due to light or the like (such as, for example, stray light) of wavelengths other than wavelength to be measured, and there is also a tendency for a measurement error to be generated.

In addition, in the optical characteristics of the wavelength variable interference filter, even when the full width at half maximum is set to be extremely small, it is difficult to completely narrow down the width to light of one wavelength. For example, in the wavelength region in which the optical spectrum of measurement light drastically changes like a wavelength λ1ofFIG. 4, an error occurs between the actual optical spectrum and the amount of light (current value I1′ inFIG. 3) obtained by measurement.

On the other hand, in the present embodiment, as shown inFIGS. 5 and 6, the full width at half maximum of the wavelength variable interference filter5is set to be larger. Specifically, the full width at half maximum of the wavelength variable interference filter5of the present embodiment is set to be equal to or more than the data output wavelength interval λd (first wavelength interval) and equal to or more than the measurement wavelength interval (second wavelength interval) λc. For example, inFIG. 5, the full width at half maximum W440in spectral curves in which a wavelength of 440 nm is used as a peak wavelength is appropriately 80 nm, and has a sufficiently large value as compared to the measurement wavelength interval λc (=20 nm) or the data output wavelength interval λd (=5 nm).

Accuracy of Optical Spectrum Estimation Process of Spectroscopic Measurement Unit23

In the present embodiment as mentioned above, light of a wide wavelength region centered on the wavelength to be measured is mixed in the light passing through the wavelength variable interference filter5. Even in such a case, the spectroscopic measurement unit23estimates the optical spectrum S by causing the estimation matrix Ms to act on the measurement spectrum D acquired by the detector11. Therefore, it is possible to extract the amount of light of a principal component of the wavelength λn to be measured by cutting the amount of light of components other than the wavelength λn to be measured, and to calculate the precise optical spectrum S closer to the actual optical spectrum.

That is, in the present embodiment, even when noise components are mixed, it is possible to accurately cut these noise components. In addition, even when the optical spectrum of measurement light drastically changes, it is possible to accurately cut unnecessary wavelength components. Therefore, in the related art, it is possible to measure an optical spectrum having a high level of measurement accuracy only in a range to which the full width at half maximum of the wavelength variable interference filter is limited. However, in the present embodiment, it is possible to perform a high-accuracy optical spectrum estimation in a range in which the full width at half maximum is larger.

FIG. 10is a diagram illustrating an optical spectrum estimated by the spectroscopic measurement unit23using the wavelength variable interference filter5of the present embodiment. InFIG. 10, the solid line indicates an actual optical spectrum of measurement light, and the plotted point indicates an estimation value of the optical spectrum for each data output wavelength interval λd. In addition,FIG. 11is a diagram illustrating an optical spectrum measured by a measurement method of the related art as shown inFIGS. 3 and 4using the wavelength variable interference filter5of the present embodiment. Meanwhile, inFIG. 11, the solid line indicates an actual optical spectrum of measurement light, and the plotted point indicates a point obtained by setting a curved line through a measured value for each measurement wavelength interval (λc), and dividing the curved line for each data output wavelength interval λd.

In addition,FIG. 12is a diagram illustrating a difference (solid line) between the optical spectrum estimated by the spectroscopic measurement unit23of the present embodiment and the actual optical spectrum and a difference (broken line) between the optical spectrum measured by the measurement method of the related art and the actual optical spectrum, when the full width at half maximum of the wavelength variable interference filter5is changed.

As shown inFIG. 11, when the value of the amount of light detected by the detector11as in the related art is set to the amount of light of the wavelength to be measured which passes through the wavelength variable interference filter, there is a great divergence from the actual optical spectrum, and the accuracy of measurement deteriorates. In order to reduce the difference between the actual optical spectrum and the spectrum obtained by measurement, as shown inFIG. 7, it becomes necessary to use a wavelength variable interference filter having a small full width at half maximum.

On the other hand, when an optical spectrum estimation process is performed by the spectroscopic measurement unit23of the present embodiment, as shown inFIG. 10, the optical spectrum S which is substantially consistent with the actual optical spectrum can be estimated with a high degree of accuracy. In addition, as shown inFIG. 5, even when the full width at half maximum is large, the accuracy does not deteriorate.

Operations and Effects of First Embodiment

In the spectrometer1of the present embodiment, the full width at half maximum in the optical characteristics (spectral curve of the wavelength to be measured) of the wavelength variable interference filter5is larger than the data output wavelength interval λd or the measurement wavelength interval λc of the optical spectrum S in the spectroscopic measurement unit23.

For this reason, not only the light of one wavelength to be measured, but also the light of the wavelength region of equal or more than the data output wavelength interval λd centered on the wavelength to be measured and equal to or more than the measurement wavelength interval λc passes through the wavelength variable interference filter5. Therefore, since the amount of light passing through the wavelength variable interference filter5increases, and a detection signal (current) from the detector11also increases, it is possible to reduce the influence of noise components, and to improve the accuracy of measurement.

On the other hand, in the configuration in which the light of a plurality of wavelengths centered on the peak wavelength is extracted by the wavelength variable interference filter5as mentioned above, when the amount of light detected by the detector11is set to the amount of light for the peak wavelength (wavelength to be measured) as it is, an error becomes large. On the other hand, in the present embodiment, the amount of light of a component corresponding to the wavelength to be measured is extracted from a measurement spectrum obtained by the detector11by performing a spectrum estimation using the spectroscopic measurement unit23, and the amount of light of other wavelength regions is cut. By performing such a process, even when the wavelength variable interference filter5having a large full width at half maximum is used, it is possible to perform a high-precision optical spectrum estimation process.

More specifically, in the present embodiment, a measurement result of the measurement spectrum for multiple wavelengths to be measured is set to a matrix Dt, and the estimation matrix Ms is caused to act on the above matrix, to thereby estimate the optical spectrum S. The estimation matrix Ms is a matrix in which sample light having the optical spectrum S0being known is measured using the spectrometer1, and which is calculated on the basis of the obtained spectrum D0and the optical spectrum S0. Therefore, as mentioned above, it is possible to estimate the higher-precision optical spectrum S by causing the estimation matrix Ms to act on the measurement spectrum D.

In addition, as in the related art, when the measurement spectrum obtained by the detector11is set to an optical spectrum, an error becomes large in a case where the optical spectrum of measurement light drastically changes in the vicinity of a specific wavelength region. Even when an attempt or the like to enhance the accuracy is performed by reducing the full width at half maximum of the wavelength variable interference filter5, it is difficult to extract only light of a predetermined one wavelength, and thus it is difficult to eliminate the error as mentioned above. In addition, as mentioned above, when the full width at half maximum of the wavelength variable interference filter5is reduced, the amount of light received in the detector11is reduced, and thus a measurement error due to the lack of the amount of light (noise component or the like) is generated. On the other hand, as in the present embodiment, the spectrum estimation of the spectroscopic measurement unit23is performed, and thus it is possible to estimate a high-precision optical spectrum at the predetermined data output wavelength interval λd even when the optical spectrum of measurement light drastically changes in the vicinity of a specific wavelength region.

In the present embodiment, the minimum value of the reflectance of the fixed reflective film54and the movable reflective film55in the measurement wavelength region is equal to or less than 75% and equal to or more than 30%.

When the minimum value of the reflectance of the fixed reflective film54and the movable reflective film55in the measurement wavelength region exceeds 75%, in the optical characteristics of the wavelength variable interference filter5, the full width at half maximum for the peak wavelength is made small, and the amount of light passing through the wavelength variable interference filter5is reduced. On the other hand, when the minimum value of the reflectance of the fixed reflective film54and the movable reflective film55in the measurement wavelength region falls below 30%, the amount of light increases, but an effect of the multiple interference of light by the fixed reflective film54and the movable reflective film55is not obtained. That is, a wavelength selection function of the wavelength variable interference filter5deteriorates, and light of each wavelength of the measurement wavelength region passes through the wavelength variable interference filter5uniformly.

On the other hand, as mentioned above, when the minimum value of the reflectance of the fixed reflective film54and the movable reflective film55is equal to or less than 75% and equal to or more than 30%, it is possible to suitably achieve an increase in the amount of light while maintaining the wavelength selectivity of the wavelength variable interference filter5.

In the present embodiment, as the fixed reflective film54and the movable reflective film55, an Ag metal film or an Ag alloy film having reflection characteristics with respect to the wide wavelength region may be preferably used. In this case, the film thickness thereof is preferably set to equal to or more than 40 nm and equal to or less than 15 nm. In such a configuration, the minimum value of the reflectance of the fixed reflective film54and the movable reflective film55can be set to equal to or less than 75% and equal to or more than 30%.

In addition, as the fixed reflective film54and the movable reflective film55, a single-layer film such as TiO2, SiO2, or ITO may be used. When such reflective films54and55are used, the deterioration of the reflective films54and55can be further suppressed than in a case where the Ag metal film or the Ag alloy film is used. In addition, when an ITO single-layer film is used as the fixed electrode561and the movable electrode562constituting the electrostatic actuator using an ITO single-layer film, it is possible to simultaneously perform the formation of electrodes and the formation of reflective films, and to achieve an improvement in manufacturing efficiency.

As mentioned above, in a configuration in which the full width at half maximum of the wavelength variable interference filter5is increased, a lot of options are given to the reflective films54and55, and the degree of design freedom in the wavelength variable interference filter5is improved. Thereby, it is also possible to manufacture the lower-cost wavelength variable interference filter5, and to reduce the cost of the electronic device such as the optical module10or the spectrometer1.

Second Embodiment

In the above-mentioned first embodiment, as shown inFIG. 5, an example is illustrated in which the minimum value of transmittance in the measurement wavelength region (for example, 400 to 700 nm) is appropriately 0%, as the optical characteristics of the wavelength variable interference filter5. On the other hand, in the second embodiment, an example is illustrated in which the minimum value of transmittance is not 0%.

FIG. 13is a diagram illustrating the optical characteristics of the wavelength variable interference filter5of the present embodiment.

InFIG. 13, the wavelength variable interference filter5of the present embodiment has the minimum transmittance of 20% or so in the wavelength to be measured. That is, even when the gap G1between the reflective films is set to any values, equal to or more than 20% light of all the wavelengths within the measurement wavelength region is set to be transmitted, the entire spectral curve has a floating form. Meanwhile, as shown inFIG. 13, a region in which the spectral curve floats in the optical characteristics is called a spectrum floating region U.

The wavelength variable interference filter5having such optical characteristics can be formed by using a single-layer film such as TiO2, SiO2, or ITO, a metal film having a small thickness size, or a metal alloy film as the reflective films54and55.

In addition, inFIG. 13, an example is illustrated in which the minimum value of reflectance becomes appropriately 20% with respect to the spectrum floating region U, but the value may be set to equal to or more than 5% and less than 45%.

FIG. 14is a diagram illustrating results when the optical spectrum estimation process is performed using the wavelength variable interference filter5in which the minimum value of transmittance is set to 45%, as the spectrum floating region U.

As can be seen by comparingFIG. 10withFIG. 14, when the spectrum floating region exceeds 45% (when the minimum value of transmittance exceeds 45%), it is difficult to accurately split light of the wavelength serving as a principal component (light corresponding to the peak wavelength) from light passing through the wavelength variable interference filter5, and the accuracy of the optical spectrum estimation process deteriorates.

In addition, the spectrum floating region may be less than 5% (the minimum value of transmittance is less than 5%). However, in this case, a great difference between such a value and the optical characteristics of the wavelength variable interference filter5in the first embodiment does not occur, and thus an effect of an increase in the amount of light by the spectrum floating region is not much obtained.

Therefore, when the spectrum floating region U is provided, as mentioned above, the spectrum floating region U is set so that the minimum value of transmittance is equal to or more than 5% and less than 45%. By providing such a spectrum floating region U, it is possible to further improve the amount of light in the wavelength to be measured, and to further improve the accuracy of the estimation process of the optical spectrum in the spectrometer1.

Alternatively, as the optical characteristics of the wavelength variable interference filter5, as shown inFIG. 13, two peak wavelengths (for example, 400 nm and 680 nm) may appear within the wavelength region to be measured. In this manner, the amount of light passing through the wavelength variable interference filter5increases by providing a plurality of peak wavelengths, and thus the accuracy of measurement can be improved. Meanwhile, even when the plurality of peak wavelengths are provided, the optical spectrum S of which the component value of each peak wavelength is accurately analyzed can be estimated by the spectrum estimation process of the spectroscopic measurement unit23, and thus the accuracy of measurement does not deteriorate.

Operations and Effects of Second Embodiment

In the present embodiment, the optical characteristics of the wavelength variable interference filter5have (have the floating region U of the spectrum) the minimum transmittance of equal to or more than 5% and less than 45% with respect to each wavelength within the measurement wavelength region. That is, when the gap G1between the reflective films is changed in accordance with a predetermined wavelength to be measured, the most of light of the wavelength to be measured is transmitted as the peak wavelength depending on the gap G1between the reflective films, but light of other wavelengths is also transmitted at the transmittance of equal to or more than 5% and less than 45%.

In the optical characteristics having such as floating region U of the spectrum, since the amount of light passing through the wavelength variable interference filter5can be increased, and a detection current which is output from the detector11also increases, it is possible to effectively suppress an influence of noise or the like.

In addition, as shown in the present embodiment, a plurality of peak wavelengths may be present within the measurement wavelength region, and other peak wavelengths different from the wavelength to be measured may be present in the vicinity of the upper limit and the lower limit of the measurement wavelength region. In such a case, light corresponding to the peak wavelength different from the wavelength to be measured is transmitted, thereby the amount of light can be further increased.

As mentioned above, even when light other than the wavelength to be measured passes through the wavelength variable interference filter5, the spectrum estimation of the spectroscopic measurement unit23is performed, thereby the high-precision optical spectrum S can be estimated.

Third Embodiment

Next, a third embodiment of the invention will be described with reference to the accompanying drawings.

In the spectrometer1of the above-mentioned first embodiment, the optical module10is configured to be directly provided with the wavelength variable interference filter5. However, an optical module may often have a complicated configuration, and particularly, it may be difficult that a small-size optical module is directly provided with the wavelength variable interference filter5. In the present embodiment, an optical filter device capable of easily installing the wavelength variable interference filter5with respect to such an optical module will be described below.

FIG. 15is a cross-sectional view illustrating a schematic configuration of an optical filter device according to the third embodiment of the invention.

As shown inFIG. 15, an optical filter device600includes a wavelength variable interference filter5and a housing601that houses the wavelength variable interference filter5. Meanwhile, in the present embodiment, the wavelength variable interference filter5of the first embodiment is illustrated as an example, but the wavelength variable interference filter5provided with the spectrum floating region U of the second embodiment may be used.

The housing601includes a base substrate610, a lid620, a glass substrate630on the base side, and a glass substrate640on the lid side.

The base substrate610is formed of, for example, a single-layer ceramic substrate. A movable substrate52of the wavelength variable interference filter5is installed on the base substrate610. The installation of the movable substrate52on the base substrate610may be performed through, for example, an adhesion layer or the like, or may be performed by fitting to another fixed member or the like. In addition, a light passing hole611is formed in the base substrate610in an opening state. The glass substrate630on the base side is bonded so as to cover the light passing hole611. As a bonding method of the glass substrate630on the base side, for example, glass frit bonding using a glass frit which is a fragment of glass obtained by dissolving a glass raw material at a high temperature and then performing rapid cooling thereon, bonding using an epoxy resin, or the like can be used.

A base inside surface612of the base substrate610facing the lid620is provided with an inside terminal portion615corresponding to an extraction electrode connected to a fixed electrode561of the wavelength variable interference filter5and an extraction electrode connected to a movable electrode562. Meanwhile, the connection of each extraction electrode to the inside terminal portion615can be performed using, for example, an FPC615A. For example, this connection is performed using an Ag paste, an ACF (Anisotropic Conductive Film), an ACP (Anisotropic Conductive Paste) or the like. In addition, wiring connection using, for example, wire bonding or the like may be performed without being limited to the connection using the FPC615A.

In addition, on the base substrate610, a through-hole614is formed corresponding to a position provided with each inside terminal portion615. Each inside terminal portion615is connected to an outside terminal portion616, provided on a base outside surface613on the opposite side to the base inside surface612of the base substrate610, through a conductive member filled in the through-hole614.

The outer circumferential portion of the base substrate610is provided with a base bonding portion617bonded to the lid620.

As shown inFIG. 15, the lid620includes a lid bonding portion624bonded to the base bonding portion617of the base substrate610, a side wall portion625, continuous from the lid bonding portion624, which stands up in a direction away from the base substrate610, and a ceiling portion626, continuous from the side wall portion625, which covers the fixed substrate51side of the wavelength variable interference filter5. The lid620can be formed of, for example, an alloy such as Kovar or a metal.

The lid620is closely bonded to the base substrate610by the bonding of the lid bonding portion624to the base bonding portion617of the base substrate610.

Bonding methods include, for example, soldering using a silver solder or the like, sealing using an eutectic alloy layer, welding using low-melting-point glass, glass adhesion, glass frit bonding, adhesion using an epoxy resin, and the like, in addition to laser welding. These bonding methods can be appropriately selected depending on materials of the base substrate610and the lid620, a bonding environment or the like.

The ceiling portion626of the lid620is parallel to the base substrate610. A light passing hole621is formed in the ceiling portion626in an opening state. The glass substrate640on the lid side is bonded so as to cover the light passing hole621. As a bonding method of the glass substrate640on the lid side, similarly to the bonding of the glass substrate630on the base side, for example, glass frit bonding, adhesion using an epoxy resin or the like can be used.

Operations and Effects of Third Embodiment

In the optical filter device600of the present embodiment as mentioned above, since the wavelength variable interference filter5is protected by the housing601, it is possible to prevent the wavelength variable interference filter5from being broken due to external factors.

Other Embodiments

Meanwhile, the invention is not limited to the above-mentioned embodiment, but changes, modifications and the like within the range capable of achieving the object of the invention are included in the invention.

For example, in the above-mentioned first and second embodiments, the measurement wavelength region is set to be 400 nm to 700 nm, but other wavelength regions may be used as the measurement wavelength region without being limited thereto.

In addition, an example is illustrated in which all the full width at half maximums of the optical characteristics (spectral curve) for each wavelength to be measured (wavelength of measurement wavelength interval λc=20 nm) within the measurement wavelength region are set to equal to or more than 30 nm. However, without being limited thereto, for example, optical characteristics may be used in which the full width at half maximum has a size of equal to or more than 30 nm with respect to at least one light out of light of multiple wavelengths to be measured, and the full width at half maximum is set to appropriately 20 nm in other wavelengths to be measured.

Further, inFIGS. 5 and 13, an example of the optical characteristics of the wavelength variable interference filter5according to the invention is illustrated, but is not limited thereto. In the invention, the full width at half maximum in characteristics considering the optical characteristics of not only the wavelength variable interference filter5, but also a plurality of optical members disposed on the wavelength variable interference filter5, that is, the optical characteristics of the entire optical module may be set to equal to or more than the measurement wavelength interval.

For example, in the optical module10as shown inFIG. 1, a detection signal (current) having characteristics obtained by combining the optical characteristics of the wavelength variable interference filter5with sensitivity characteristics in the detector11is output from the detector11. Therefore, in order to acquire the sufficient amount of light, the characteristics obtained by combining the optical characteristics of the wavelength variable interference filter5with the sensitivity characteristics in the detector11become optical characteristics as shown inFIGS. 5 and 13, and the full width at half maximum in each wavelength may be set to equal to or more than the measurement wavelength interval λc.

In addition, when a light source that emits light to an object to be measured is further included as the optical module10, the configuration of the wavelength variable interference filter5and the optical members are set so that the full width at half maximum in the optical characteristics of the entire optical module10obtained by combining the optical characteristics of the wavelength variable interference filter5and the sensitivity characteristics in the detector11with the emission intensity characteristics of the light source is set to equal or more than the measurement wavelength interval. Meanwhile, as the optical module10, when a filtering element such as a lens, a transmission glass plate, or a band pass filter, a mirror member and the like are provided on the light path of the wavelength variable interference filter5, in consideration of the optical characteristics (transmittance characteristics and reflectance characteristics) of these optical members, the characteristics of each optical member and the reflective films54and55of the wavelength variable interference filter5may beset so that the full width at half maximum for each wavelength in the characteristics obtained by combining these optical characteristics is equal to or more than the measurement wavelength interval.

InFIGS. 5 and 13, an example is illustrated in which the full width at half maximum is equal to or more than the measurement wavelength interval λc (data output wavelength interval λd) in each spectral curve for each wavelength to be measured, but is not limited thereto. For example, a configuration may formed in which the full width at half maximum is equal to the measurement wavelength interval λc in the optical characteristics of any one wavelength to be measured of multiple wavelengths to be measured within the measurement wavelength region, and the full width at half maximum is smaller than the measurement wavelength interval λc in the optical characteristics of other wavelengths to be measured.

In the above-mentioned embodiment, as the gap change portion, the electrostatic actuator56constituted by the fixed electrode561and the movable electrode562is illustrated, but is not limited thereto.

For example, an inductive actuator constituted by a first inductive coil provided in the fixed substrate51and a second inductive coil or a permanent magnet provided in the movable substrate52may be used.

Further, a piezoelectric actuator may be used instead of the electrostatic actuator56. In this case, for example, a lower electrode layer, a piezoelectric film, and an upper electrode layer are laminated on the holding portion522, and a voltage applied between the lower electrode layer and the upper electrode layer is made available as an input value, thereby allowing the holding portion522to be bent by expanding and contracting the piezoelectric film.

Further, a configuration or the like in which the amount of the gap G1between the reflective films is adjusted can also be used, for example, by changing air pressure between the fixed substrate51and the movable substrate52, without being limited to the configuration in which the amount of the gap G1between the reflective films is changed by voltage application.

In addition, as the spectroscope and the electronic device according to the invention, the spectrometer1is illustrated in each of the above-mentioned embodiments. However, besides, the spectroscope, the optical module, and the electronic device using the wavelength variable interference filter according to the invention can be applied to various fields.

For example, as shown inFIG. 16, the spectroscope and the electronic device according to the invention can also be applied to a colorimeter for measuring a color.

FIG. 16is a block diagram illustrating an example of a colorimeter400including a wavelength variable interference filter.

As shown inFIG. 16, the colorimeter400includes a light source device410that emits light to a test object A, a colorimetric sensor420(optical module), and a control device430(processing unit) that controls the entire operation of the colorimeter400. The colorimeter400is a device that reflects light emitted from the light source device410in the test object A, receives the reflected light to be tested in the colorimetric sensor420, and analyzes and measures the chromaticity of the light to be tested, that is, the color of the test object A, on the basis of a detection signal which is output from the colorimetric sensor420.

Including the light source device410, a light source411, and a plurality of lenses412(only one is shown inFIG. 16), for example, reference light (for example, white light) is emitted to the test object A. In addition, a collimator lens may be included in the plurality of lens412. In this case, the light source device410changes the reference light emitted from the light source411to parallel light using the collimator lens, and emits the parallel light from a projection lens, not shown, toward the test object A. Meanwhile, in the present embodiment, the colorimeter400including the light source device410is illustrated, but when the test object A is, for example, a light-emitting member such as a liquid crystal panel, the light source device410may not be provided.

As shown inFIG. 16, the colorimetric sensor420includes the wavelength variable interference filter5, the detector11that receives light passing through the wavelength variable interference filter5, and the voltage control unit that controls a voltage applied to the electrostatic actuator56of the wavelength variable interference filter5. In addition, the colorimetric sensor420includes an incident optical lens, not shown, which guides reflected light (light to be tested) reflected from the test object A into the inside, at a position facing the wavelength variable interference filter5. The colorimetric sensor420spectroscopically disperses light of a predetermined wavelength out of the light to be tested which is incident from the incident optical lens by the wavelength variable interference filter5, and receives the spectroscopically dispersed light in the detector11.

The control device430controls the entire operation of the colorimeter400.

As the control device430, for example, a general-purpose personal computer, a portable information terminal, other special computers for colorimetry, or the like can be used. As shown inFIG. 16, the control device430includes a light source control unit431, a colorimetric sensor control unit432, a colorimetry processing unit433, and the like.

The light source control unit431is connected to the light source device410, outputs a predetermined control signal to the light source device410, for example, on the basis of a user's setting input, and emits white light of predetermined brightness.

The colorimetric sensor control unit432is connected to the colorimetric sensor420, sets the wavelength of light received by the colorimetric sensor420, for example, on the basis of a user's setting input, and outputs a command signal for detecting the amount of received light of the wavelength to the colorimetric sensor420. Thereby, the voltage control unit15of the colorimetric sensor420applies a voltage to the electrostatic actuator56on the basis of the control signal, and drives the wavelength variable interference filter5.

The colorimetry processing unit433is a processing unit according to the invention, and analyzes the chromaticity of the test object A from the amount of received light detected by the detector11. Specifically, similarly to the first and the second embodiments mentioned above, the colorimetry processing unit433analyzes the chromaticity of the test object A by using the amount of light obtained by the detector11as the measurement spectrum D, and estimating the optical spectrum S using the estimation matrix Ms.

In addition, another example of the electronic device according to the invention includes a light-based system for detecting the presence of a specific substance. As such a system, for example, a spectroscopic measurement system using a wavelength variable interference filter according to the invention is adopted, and a gas leak detector for a vehicle that detects a specific gas with a high degree of sensitivity, or a gas detector such as a photoacoustic rare gas detector for a breath test can be used.

An example of such a gas detector will be described below with reference to the accompanying drawings.

FIG. 17is a schematic diagram illustrating an example of a gas detector including a wavelength variable interference filter.

FIG. 18is a block diagram illustrating a configuration of a control system of the gas detector ofFIG. 17.

As shown inFIG. 17, the gas detector100includes a sensor chip110, a flow channel120provided with a suction port120A, a suction flow channel120B, an exhaust flow channel120C, and an exhaust port120D, and a main body130.

The main body130is constituted by a detector including a sensor cover131having an opening capable of attaching and detaching the flow channel120, an exhaust unit133, a housing134, an optical portion135, a filter136, a wavelength variable interference filter5, a light receiving element137(detection unit) and the like, a control unit138that processes a detected signal and controls the detection unit, a power supply portion139that supplies power, and the like. In addition, the optical portion135is constituted by a light source135A that emits light, a beam splitters135B that reflects light incident from the light source135A to the sensor chip110side and transmits light incident from the sensor chip side to the light receiving element137side, and lenses135C,135D, and135E.

In addition, as shown inFIG. 18, the surface of the gas detector100is provided with an operation panel140, a display unit141, a connection portion142for an interface with the outside, and a power supply portion139. When the power supply portion139is a secondary battery, a connection portion143for charge may be included.

Further, as shown inFIG. 18, the control unit138of the gas detector100includes a signal processing unit144constituted by a CPU and the like, a light source driver circuit145for controlling the light source135A, a voltage control unit146for controlling the wavelength variable interference filter5, a light receiving circuit147that receives a signal from the light receiving element137, a sensor chip detection circuit149that receives a signal from a sensor chip detector148for reading a code of the sensor chip110and detecting the presence or absence of the sensor chip110, an exhaust driver circuit150that controls the exhaust unit133, and the like. In addition, the gas detector100includes a storage unit (not shown) that stores the V-λ data. The voltage control unit146controls a voltage applied to the electrostatic actuator56of the wavelength variable interference filter5on the basis of the V-λ data stored in the storage unit.

Next, operations of the gas detector100as mentioned above will be described below.

The sensor chip detector148is provided inside the sensor cover131located at the upper portion of the main body130, and the presence or absence of the sensor chip110is detected by the sensor chip detector148. When a detection signal from the sensor chip detector148is detected, the signal processing unit144determines that the sensor chip110is mounted, and emits a display signal for displaying an executable detection operation on the display unit141.

When the operation panel140is operated by, for example, a user, and an instruction signal for starting a detection process is output from the operation panel140to the signal processing unit144, first, the signal processing unit144causes the light source driver circuit145to operate the light source135A by outputting a light source operation signal. When the light source135A is driven, stable laser light of linearly polarized light having a single wavelength is emitted from the light source135A. In addition, the light source135A has a temperature sensor or a light amount sensor built-in, and its information is output to the signal processing unit144. When it is determined that the light source135A is stably operated on the basis of the temperature or the amount of light which is input from the light source135A, the signal processing unit144controls the exhaust driver circuit150and brings the exhaust unit133into operation. Thereby, a gaseous sample including a target substance (gas molecules) to be detected is induced from the suction port120A to the suction flow channel120B, the inside of the sensor chip110, the exhaust flow channel120C, and the exhaust port120D. Meanwhile, the suction port120A is provided with a dust filter120A1, relatively large dust particles, some vapor and the like are removed.

In addition, the sensor chip110is a sensor, having a plurality of metal nanostructures built-in, in which localized surface plasmon resonance is used. In such a sensor chip110, an enhanced electric field is formed between metal nanostructures by laser light, and gas molecules gain entrance into the enhanced electric field, Raman scattering light including information of a molecular vibration and Rayleigh scattering light are generated.

The Rayleigh scattering light and the Raman scattering light are incident on the filter136through the optical portion135, the Rayleigh scattering light is split by the filter136, and the Raman scattering light is incident on the wavelength variable interference filter5. The signal processing unit144outputs a control signal to the voltage control unit146. Thereby, as shown in the above-mentioned first embodiment, the voltage control unit146reads a voltage value corresponding to the wavelength to be measured from the storage unit, applies the voltage to the electrostatic actuator56of the wavelength variable interference filter5, and spectroscopically disperses the Raman scattering light corresponding to gas molecules to be detected using the wavelength variable interference filter5. Thereafter, when the spectroscopically dispersed light is received in the light receiving element137, a light receiving signal according to the amount of light received is output to the signal processing unit144through the light receiving circuit147. Here, the measurement spectrum D for each predetermined measurement wavelength interval is acquired with respect to the measurement wavelength region by changing the gap G1between the reflective films of the wavelength variable interference filter5, and the signal processing unit144estimates the optical spectrum S by causing the estimation matrix to act on the measurement spectrum D. The signal processing unit acquires spectrum data of Raman scattering light on the basis of the estimated optical spectrum S, compares the spectrum data with data stored in a ROM, and determines whether the targeted gas molecules are present, to specify the substances. In addition, the signal processing unit144causes the display unit141to display result information thereof, or outputs the result information from the connection portion142to the outside.

Meanwhile, inFIGS. 17 and 18, the gas detector100is illustrated in which the Raman scattering light is spectroscopically dispersed by the wavelength variable interference filter5and a gas is detected from the spectroscopically dispersed Raman scattering light, but the gas detector may be used as a gas detector that specifies a gas type by detecting absorbance inherent in a gas. In this case, a gas sensor that causes a gas to flow into a sensor and detects light absorbed by a gas in the incident light is used as the optical module according to the invention. A gas detector that analyzes and discriminates the gas flowing into the sensor using such a gas sensor is used as the electronic device according to the invention. In such a configuration, it is also possible to detect gas components using the wavelength variable interference filter.

In addition, as a system for detecting the presence of a specific substance, a substance component analyzer such as a noninvasive measurement device of saccharide using near-infrared spectroscopy, or a noninvasive measurement device of information such as food, a living body, and a mineral can be used without being limited to the gas detection as mentioned above.

Hereinafter, a food analyzer will be described as an example of the above-mentioned substance component analyzer.

FIG. 19is a diagram illustrating a schematic configuration of a food analyzer which is an example of the electronic device using the wavelength variable interference filter5.

As shown inFIG. 19, a food analyzer200includes a detector210(optical module), a control unit220, and a display unit230. The detector210includes a light source211that emits light, an imaging lens212into which light from an object to be measured is introduced, the wavelength variable interference filter5that spectroscopically disperses light introduced from the imaging lens212, and an imaging unit213(detection unit) that detects spectroscopically dispersed light.

In addition, the control unit220includes a light source control unit221that performs turn-on and turn-off control of the light source211and brightness control at the time of turn-on, a voltage control unit222that controls the wavelength variable interference filter5, a detection control unit223that controls the imaging unit213and acquires a spectroscopic image which is imaged by the imaging unit213, a signal processing unit224(processing unit), and a storage unit225.

The food analyzer200is configured such that when the system is driven, the light source211is controlled by the light source control unit221, and light is applied from the light source211to an object to be measured. Light reflected from the object to be measured is incident on the wavelength variable interference filter5through the imaging lens212. The wavelength variable interference filter5is controlled by the voltage control unit222, and the wavelength variable interference filter5is driven by the driving method as shown in the first embodiment or the second embodiment mentioned above. Thereby, light of the wavelength region centered on a target wavelength is extracted from the wavelength variable interference filter5. The extracted light is imaged by the imaging unit213which is constituted by, for example, a CCD camera and the like. In addition, the imaged light is accumulated in the storage unit225as a spectroscopic image. In addition, the signal processing unit224changes a voltage value applied to the wavelength variable interference filter5by controlling the voltage control unit222, and acquires a spectroscopic image for each wavelength.

The signal processing unit224arithmetically processes data of each pixel in each image accumulated in the storage unit225, and obtains a spectrum in each pixel. That is, an optical spectrum is estimated from a measurement spectrum for each pixel in a plurality of spectroscopic images obtained by performing the same process as that in the spectroscopic measurement unit23of the above-mentioned first embodiment.

In addition, for example, information on components of food regarding the spectrum is stored in the storage unit225. The signal processing unit224analyzes data of the obtained spectrum on the basis of the information on the food stored in the storage unit225, and obtains food components included in the object to be detected and the content thereof. In addition, food calorie, freshness and the like can be calculated from the obtained food components and content. Further, by analyzing a spectral distribution within the image, it is possible to extract a portion in which freshness deteriorates in food to be tested, and to detect foreign substances or the like included in the food.

The signal processing unit224performs a process of displaying information such as the components, the content, calorie, freshness and the like of the food to be tested which are obtained as mentioned above, on the display unit230.

In addition, inFIG. 19, an example of the food analyzer200is illustrated, but the food analyzer can also be used as the above-mentioned noninvasive measurement device of other information using substantially the same configuration. For example, the food analyzer can be used as a living body analyzer that analyzes living body components, for example, measures and analyzes body fluid components such as blood. Such a living body analyzer is used as a device that measures, for example, body fluid components such as blood. When the analyzer is used as a device that detects ethyl alcohol, the analyzer can be used as an anti-drunk-driving device that detects the drinking condition of a driver. In addition, the analyzer can also be used as an electronic endoscope system including such as living body analyzer.

Further, the analyzer can also be used as a mineral analyzer that performs a component analysis of a mineral.

Further, the wavelength variable interference filter, the optical module, and the electronic device according to the invention can be applied to the following devices.

For example, it is also possible to transmit data using the light of each wavelength by temporally changing the intensity of the light of each wavelength. In this case, light of a specific wavelength is spectroscopically dispersed by the wavelength variable interference filter provided in the optical module, and is received in the light receiving unit, thereby allowing data transmitted by the light of a specific wavelength to be extracted. The data of the light of each wavelength is processed by the electronic device including such an optical module for data extraction, and thus it is also possible to perform optical communication.

In addition, the electronic device can also be applied to a spectroscopic camera, a spectroscopic analyzer and the like that image a spectroscopic image by spectroscopically dispersing light using the wavelength variable interference filter according to the invention. An example of such a spectroscopic camera includes an infrared camera having a wavelength variable interference filter built-in.

FIG. 20is a schematic diagram illustrating a schematic configuration of a spectroscopic camera. As shown inFIG. 20, a spectroscopic camera300includes a camera body310, an imaging lens unit320, and an imaging unit330(detection unit).

The camera body310is a portion which is held and operated by a user.

The imaging lens unit320is provided in the camera body310, and guides incident image light to the imaging unit330. In addition, as shown inFIG. 20, the imaging lens unit320includes an objective lens321, an imaging lens322, and the wavelength variable interference filter5provided between these lenses.

The imaging unit330is constituted by a light receiving element, and images image light guided by the imaging lens unit320.

In such a spectroscopic camera300, it is possible to image a spectroscopic image of light having a desired wavelength by transmitting light of a wavelength serving as an imaging object using the wavelength variable interference filter5.

In addition, the optical module and the electronic device can be used as a concentration detector. In this case, infrared energy (infrared light) emitted from a substance is spectroscopically dispersed and analyzed by the wavelength variable interference filter, and the concentration of a test object in a sample is measured.

As mentioned above, the wavelength variable interference filter, the optical module, and the electronic device according to the invention can also be applied to any device that spectroscopically disperses predetermined light from incident light. As mentioned above, since the wavelength variable interference filter according to the invention can spectroscopically disperse multiple wavelengths using one device, it is possible to accurately perform the measurement of a spectrum of multiple wavelengths, and the detection of a plurality of components. Therefore, as compared to a device of the related art that extracts a desired wavelength using a plurality of devices, the optical module and the electronic device can be facilitated to be reduced in size, and can be suitably used as, for example, a portable or in-car optical device.

Besides, a specific structure at the time of carrying out the invention can be appropriately changed to other structures in a range capable of achieving an object of the invention.

The entire disclosure of Japanese Patent Application No. 2012-205346 filed on Sep. 19, 2012 is expressly incorporated by reference herein.