Tunable interference filter, optical module, and electronic apparatus

A tunable interference filter includes: first and second opposed substrates; a first reflection film provided on a first reflection film fixing surface of the first substrate; a second reflection film provided on a second reflection film fixing surface of the second substrate and separated from the first reflection film by a gap; and a first electrode provided on a first electrode surface of the first substrate facing the second substrate, wherein the first electrode surface is spaced apart from the second substrate by a different distance than the first reflection film fixing surface, and a layered part in which the first reflection film and the first electrode are stacked is provided on the first electrode surface, the layered part being spaced apart from the second substrate by a larger distance than the first reflection film fixing surface.

BACKGROUND

1. Technical Field

The present invention relates to a tunable interference filter, an optical module including the tunable interference filter, and an electronic apparatus including the optical module.

2. Related Art

A tunable interference filter in which reflection films are respectively oppositely provided across a predetermined gap on surfaces opposed to each other of a pair of substrates is known (for example, see JP-A-2002-277758).

In the tunable interference filter disclosed in JP-A-2002-277758, the reflection layers are respectively provided on the opposed surfaces of two optical substrates, and capacitance electrodes are provided at the outer sides in the radial direction of the reflection layers on the opposed surfaces of the optical substrates. In the tunable interference filter, the capacitance electrodes opposed to each other act as an electrostatic actuator, and a voltage is applied between the capacitance electrodes to vary the gap between the reflection layers by an electrostatic attractive force.

In the tunable interference filter, an electric charge may accumulate on the reflection layers, and, if the reflection layers opposed to each other are respectively charged, an electrostatic force is generated. Accordingly, even in the case where a predetermined set voltage is applied to the electrostatic actuator for setting the gap between the reflection layers to a set value, the gap may not be set to the desired set value due to the electrostatic force on the charged reflection layers. In this case, there is a problem that it is difficult to extract light having a desired wavelength from the tunable interference filter.

SUMMARY

An advantage of some aspects of the invention is to provide a tunable interference filter, an optical module, and an electronic apparatus that can extract light having a desired wavelength with high accuracy.

An aspect of the invention is directed to a tunable interference filter including a first substrate, a second substrate opposed to the first substrate, a first reflection film provided on a surface of the first substrate facing the second substrate, a second reflection film provided on a surface of the second substrate facing the first substrate and opposed to the first reflection film across a gap between the reflection films, and a first electrode provided on the surface of the first substrate facing the second substrate, wherein the first substrate has a first reflection film fixing surface provided with the first reflection film, and a first electrode surface provided with the first electrode, the first electrode surface being spaced apart from the second substrate by a different distance than the first reflection film fixing surface, and a layered part in which the first reflection film and the first electrode are stacked is provided on the first electrode surface and is spaced apart from the second substrate by a larger distance than the first reflection film fixing surface.

According to the aspect of the invention, the layered part formed by stacking the first reflection film and the first electrode is spaced apart from the second substrate more than the first reflection film fixing surface, and the first reflection film and the first electrode have surface contact so they are electrically connected at the layered part. Thereby, even when the first reflection film is charged, the accumulated charge may be released via the first electrode and generation of an electrostatic attractive force by charging between the first reflection film and the second reflection film may be prevented.

Here, it is conceivable that the edge of the first electrode and the edge of the first reflection film are brought into edge-to-edge contact for conduction. However, in this case, the contact area is smaller and conduction reliability is lower, and thus, the charge of the first reflection film may not be reliably released to the first electrode. On the other hand, as described above, by providing the layered part by stacking the first electrode and the first reflection film, the first electrode and the first reflection film may reliably be brought into surface contact and become electrically connected.

Further, in the aspect of the invention, the layered part is provided on the surface at a larger distance from the second substrate then the first reflection film fixing surface. Accordingly, the amount the gap between the reflection films and the gap between the electrodes may be varied is not suppressed by the presence of the layered part. Therefore, the wavelength range that can be extracted by the tunable interference filter is not narrowed.

In the tunable interference filter of the aspect of the invention, it is preferable that a second electrode is provided on the surface of the second substrate facing the first substrate and opposed to the first electrode via a larger gap between the first and second electrodes than exists between the reflection films, and the layered part is formed by extending the first reflection film from the first reflection film fixing surface over the first electrode surface and onto an inner peripheral edge of the first electrode.

In the tunable interference filter, a wavelength to be extracted by transmission or reflection is determined by the gap between the first reflection film and the second reflection film. Therefore, in the tunable interference filter, to acquire a transmitted or reflected wavelength in response to a wider wavelength range, it is desirable to widen the variation range of the gap between the reflection films. Here, in the case where a voltage is applied between the first electrode and the second electrode to vary the gap between the reflection films by an electrostatic attractive force, if the gap between electrodes is smaller than the gap between the reflection films, the gap between the reflection films may be varied only by the amount of the gap between electrodes. In the configuration, the variation range of the gap between the reflection films is smaller and the wavelength range that can be extracted by the tunable interference filter is narrower.

On the other hand, in the configuration described above, the gap between the electrodes is formed to be larger than the gap between the reflection films, and thus, the gap between the reflection films may be changed in a larger variation range, and the wavelength range that can be extracted by the tunable interference filter is made wider.

Further, generally, an electrostatic attractive force acting between the electrodes is inversely proportional to the square of distance, and, if the gap between the electrodes is smaller, control of the electrostatic attractive force becomes difficult and control of the gap between the reflection films becomes difficult. On the other hand, in the configuration described above, the gap between the electrodes is formed to be larger than the gap between the reflection films, and thus, the control of the electrostatic attractive force is easier and the gap between the reflection films may be set to a desired value with high accuracy.

In the tunable interference filter of the aspect of the invention, it is preferable that the layered part is formed by stacking the first reflection film on the first electrode.

In the configuration described above, the layered part has the configuration in which the first reflection film is stacked on the first electrode. That is, the first electrode is formed on the first substrate, and then, the first reflection film is formed partly thereon. Here, if the first reflection film is formed on the first substrate before the first electrode is formed, problems that the first reflection film is easily deteriorated when the first electrode is formed, and resolution of the tunable interference filter is lower, may arise. On the other hand, by first forming the first electrode on the first substrate, and then, forming the first reflection film thereon, the deterioration of the first reflection film in the manufacturing process may be suppressed. Therefore, the first reflection film having good reflection characteristics may be formed, and reduction of resolution in the tunable interference filter may be suppressed.

It is preferable that the tunable interference filter of the aspect of the invention includes a reflection film connection electrode connected to the second reflection film.

In the configuration described above, since the reflection film connection electrode is connected to the second reflection film, the charge accumulated in the second reflection film may be released from the reflection film connection electrode, and generation of an electrostatic force between the first reflection film and the second reflection film may be prevented more reliably. Therefore, the gap between the reflection films may be controlled with high accuracy by controlling the voltage applied to the first electrode and the second electrode.

Further, the reflection film connection electrode and the first electrode may be set at the same potential. In this case, no electrostatic attractive force is generated between the first reflection film and the second reflection film, and control of the gap between the reflection films may be performed easily with high accuracy.

Another aspect of the invention is directed to an optical module including the above described tunable interference filter, and a detection unit that detects light extracted by the tunable interference filter.

As described above, in the tunable interference filter of the aspect of the invention, even when the first reflection film is charged, the charge may be released from the first electrode and no electrostatic force is generated between the gap between the reflection films, and the dimension of the gap between the reflection films may accurately be controlled. Thereby, in the tunable interference filter, a light having a desired wavelength may be extracted by transmission or reflection with high accuracy. Further, in the optical module including the tunable interference filter, by detecting the amount of the light having the desired wavelength extracted by the tunable interference filter using the detection unit, the amount of the light having the desired wavelength may accurately be detected.

In the optical module of the aspect of the invention, it is preferable that the tunable interference filter includes a reflection film connection electrode connected to the second reflection film, and a voltage control unit is provided that controls the reflection film connection electrode and the first electrode at the same potential.

In the configuration described above, the voltage control unit sets the reflection film connection electrode connected to the second reflection film and the first electrode at the same potential. Thereby, the potential difference between the first reflection film and the second reflection film is zero, and no electrostatic attractive force is generated between the first reflection film and the second reflection film and the dimension of the gap between the reflection films may be controlled with high accuracy.

Still another aspect of the invention is directed to an electronic apparatus including the above described optical module.

According to the aspect of the invention, the electronic apparatus includes the optical module having the above described tunable interference filter, and thus, various kinds of electronic processing in the electronic apparatus may be performed based on the amount of the light having the desired wavelength detected with high accuracy.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Below, one embodiment according to the invention will be explained with reference to the drawings.

1. Overall Configuration of Colorimetric Instrument

FIG. 1is a block diagram showing a schematic configuration of a colorimetric instrument1(electronic apparatus) of the embodiment.

The colorimetric instrument1includes a light source unit2that outputs light to a test object A, a colorimetric sensor3(optical module), and a control unit4that controls the operation of the colorimetric instrument1as shown inFIG. 1. Further, the colorimetric instrument1is a device that imparts light output from the light source unit2onto the test object A, receives the reflected test object light in the colorimetric sensor3, and analyzes and measures the chromaticity of the test object light, i.e., the color of the test object A based on the detection signal output from the colorimetric sensor3.

2. Configuration of Light Source Unit

The light source unit2includes a light source21and plural lenses22(only one is shown inFIG. 1), and outputs white light to the test object A. Further, the plural lenses22may include a collimator lens, and, in this case, the light source unit2collimates the white light output from the light source21into parallel light by the collimator lens and outputs it from a projection lens (not shown) toward the test object A. Note that, in the embodiment, the colorimetric instrument1including the light source unit2is exemplified, however, for example, in the case where the test object A is a light emitting member such as a liquid crystal panel, the light source unit2may be omitted.

3. Configuration of Colorimetric Sensor

The colorimetric sensor3includes a tunable interference filter5, a detection unit31that receives light transmitted through the tunable interference filter5, and a voltage control unit32that varies the wavelength of the light to be transmitted through the tunable interference filter5as shown inFIG. 1. Further, the colorimetric sensor3includes an incidence optical lens (not shown) that guides the reflected light (test object light) reflected on the test object A inward in a location facing the tunable interference filter5. Furthermore, the colorimetric sensor3spectroscopically separates a light having a predetermined wavelength of the test object lights entering from the incidence optical lens by the tunable interference filter5, and receives the spectroscopically separated light by the detection unit31.

The detection unit31includes plural photoelectric conversion elements and generates electric signals in response to amounts of received light. Further, the detection unit31is connected to the control unit4, and outputs the generated electric signals as light reception signals to the control unit4.

3-1. Configuration of Tunable Interference Filter

FIG. 2is a plan view showing a schematic configuration of the tunable interference filter5, andFIG. 3is a sectional view showing the schematic configuration of the tunable interference filter5.

The tunable interference filter5is a plate-like optical member having a square shape in a plan view as shown inFIG. 2. The tunable interference filter5includes a fixed substrate51(a first substrate) and a movable substrate52(a second substrate) as shown inFIG. 3. The fixed substrate51and the movable substrate52are formed using various kinds of glass of soda glass, crystalline glass, quartz glass, lead glass, potassium glass, borosilicate glass, alkali-free glass, or quartz. Further, the fixed substrate51and the movable substrate52are integrally formed, in which a first bonding surface513and a second bonding surface523formed near the outer peripheral parts are bonded using a bonding film53formed by a plasma-polymerized film mainly containing siloxane, for example.

A fixed reflection film54forming a first reflection film is provided on the fixed substrate51and a movable reflection film55forming a second reflection film is provided on the movable substrate52. Here, the fixed reflection film54is fixed to the surface of the fixed substrate51facing the movable substrate52, and the movable reflection film55is fixed to the surface of the movable substrate52facing the fixed substrate51. Furthermore, the fixed reflection film54and the movable reflection film55are oppositely provided spaced across a gap G1between the reflection films.

In addition, an electrostatic actuator56for adjustment of the dimension of the gap G1between the reflection films between the fixed reflection film54and the movable reflection film55is provided in the tunable interference filter5. The electrostatic actuator56has a fixed electrode561(a first electrode) provided at the fixed substrate51side and a movable electrode562(a second electrode) provided at the movable substrate52side. Here, the fixed electrode561and the movable electrode562may be provided directly on the substrate surfaces of the fixed substrate51and the movable substrate52, respectively, or may be provided via another film member.

Further, in a plan view (hereinafter, referred to as “plan view of the filter”) of the tunable interference filter5as shown inFIG. 2as seen from a substrate thickness direction of the fixed substrate51(movable substrate52), the planar center point O of the fixed substrate51and the movable substrate52coincides with the center points of the fixed reflection film54and the movable reflection film55and coincides with the center point of a movable part521, which will be described later.

3-1-1. Configuration of Fixed Substrate

The fixed substrate51is formed by processing a glass base material formed in a thickness of 500 μm, for example. Specifically, on the fixed substrate51, an electrode formation groove511and a reflection film fixing part512are formed by etching as shown inFIG. 3. In the fixed substrate51, a thickness dimension is formed larger than that of the movable substrate52, and there is no electrostatic attractive force when a voltage is applied between the fixed electrode561and the movable electrode562or deflection of the fixed substrate51due to internal stress of the fixed electrode561.

The electrode formation groove511is formed in an annular shape around the planar center point O of the fixed substrate51in the plan view of the filter. The reflection film fixing part512is formed to project from the center part of the electrode formation groove511toward the movable substrate52side in a plan view. Here, a groove bottom surface of the electrode formation groove511is a fixed electrode surface511A (a first electrode surface) and a projecting end surface of the reflection film fixing part512is a reflection film fixing surface512A.

Further, three electrode lead grooves (not shown) extending from the electrode formation groove511toward the respective apexes C1, C2, C3of the outer peripheral edge of the fixed substrate51are provided on the fixed substrate51.

The fixed electrode561having the annular shape around the planar center point O is formed on a fixed electrode surface511A of the fixed substrate51. Here, it is more preferable that the fixed electrode561is formed in a circular ring shape. Further, the circular ring shape includes a configuration in which a fixed lead electrode563projects from a part of the circular ring shape, a configuration in which a part of the circular ring is lost, and a nearly C-shaped configuration in which a part of the circular ring is divided.

Note that insulating films (not shown) for preventing discharge between the fixed electrode561and the movable electrode562may be stacked on the fixed electrode561.

Further, the fixed lead electrode563extending from the outer peripheral edge of the fixed electrode561is formed on the fixed substrate51. Specifically, the fixed lead electrode563is formed from a location of the outer peripheral edge of the fixed electrode561nearest the apex C1along the electrode formation groove extending in the direction toward the apex C1to the apex C1. The end part of the fixed lead electrode563(the part located on the apex C1of the fixed substrate51) forms a fixed electrode pad563P.

Furthermore, a first opposed electrode581and a second opposed electrode582are provided in the electrode lead grooves formed from the electrode formation groove511toward the apexes C2, C3of the fixed substrate51, respectively. The first opposed electrode581and the second opposed electrode582are insulated from the fixed electrode561. The end parts of the first opposed electrode581and the second opposed electrode582(the parts located on the apexes C2, C3of the fixed substrate51) form a first opposed electrode pad581P and a second opposed electrode pad582P, respectively.

As described above, the reflection film fixing part512is formed in a nearly cylindrical shape having a diameter dimension smaller than that of the electrode formation groove511coaxially with the electrode formation groove511, and the surface (projection end surface) of the reflection film fixing part512facing the movable substrate52is a reflection film fixing surface512A.

Here, as described above, the reflection film fixing part512is formed to project from the electrode formation groove511toward the movable substrate52side. Therefore, the reflection film fixing surface512A is located nearer the movable substrate52than the fixed electrode surface511A. That is, in the embodiment, the dimension of the gap G2between electrodes is formed larger than the dimension of the gap G1between the reflection films.

Further, the electrode formation groove511and the reflection film fixing part512are formed by etching (wet etching) one surface side of the fixed substrate51, and thus, an outer circumference side surface512B of the reflection film fixing part512is not parallel to the substrate thickness direction of the fixed substrate51, but has a curved shape gently curved from the reflection film fixing surface512A toward the fixed electrode surface511A.

Furthermore, the fixed reflection film54is formed to cover the reflection film fixing surface512A, the outer circumference side surface512B, and the inner circumference part of the ring-shaped fixed electrode561provided on the fixed electrode surface511A. Here, the part in which the fixed reflection film54and the fixed electrode561are stacked forms a layered part57. The fixed reflection film54is formed in a circular shape around the planar center point O in the plan view of the filter as shown inFIG. 2. Therefore, the layered part57has a ring shape along a virtual circle around the planar center point O.

As the fixed reflection film54, a conductor material may be used. As a conductor material film, for example, a single-layer film of Ag or Ag alloy may be used. In the case of a dielectric multilayer film, for example, a dielectric multilayer film with a high-refractive-index layer of TiO2and a low-refractive-index layer of SiO2may be used.

The fixed reflection film54is in surface contact with the fixed electrode561by the layered part57and electric conduction with the fixed electrode561. Thereby, even when the fixed reflection film54is charged, the accumulated charge can be released to the fixed electrode561. Further, in the case where a film formed by stacking a dielectric film as an insulator and a multilayer film thereof on a metal film is used as the fixed reflection film54, the metal film and the fixed electrode561have direct contact and electric conduction at least in the surface contact part with the fixed electrode561in the layered part57. Thereby, even when the fixed reflection film54is charged, the charge accumulated near the metal film and the interface between the metal film and the insulating film can be released to the fixed electrode561.

Further, in the fixed substrate51, an anti-reflection film (not shown) is formed in a location corresponding to the fixed reflection film54on the opposite surface to the movable substrate52. The anti-reflection film is formed by alternately stacking a low-refractive-index film and a high-refractive-index film for reducing reflectance and increasing transmittance of visible light on the surface of the fixed substrate51.

3-1-2. Configuration of Movable Substrate

The movable substrate52is formed by processing a glass base material formed in a thickness of 200 μm, for example, by etching.

Specifically, the movable substrate52includes a movable part521having a circular shape around the planar center point O and a holding part522that is coaxial with the movable part521and holds the movable part521in the plan view of the filter as shown inFIG. 2.

Further, the movable substrate52has cutout parts524in correspondence with the respective apexes C1, C2, C3of the fixed substrate51, and the fixed electrode pad563P, the first opposed electrode pad581P, and the second opposed electrode pad582P are exposed on the surface of the tunable interference filter5as seen from the movable substrate52side as shown inFIG. 2.

The movable part521is formed to have a thickness dimension larger than that of the holding part522, and, for example, in the embodiment, formed to have the same dimension of 200 μm as the thickness dimension of the movable substrate52. Further, the movable part521is formed to have at least a larger radial dimension than the radial dimension of the outer peripheral edge of the fixed electrode561. The surface of the movable part521facing the fixed substrate51is a movable surface521A parallel to the reflection film fixing surface512A, and the movable reflection film55opposed to the fixed reflection film54via the gap G1between the reflection films and the movable electrode562opposed to the fixed electrode561via the gap G2between electrodes are fixed to the movable surface521A.

For the movable reflection film55, a reflection film having the same configuration as that of the above described fixed reflection film54is used. Further, a reflection film connection electrode551extending from the outer peripheral edge of the movable reflection film55is formed on the movable substrate52. The reflection film connection electrode551is formed from a location of the outer peripheral edge of the movable reflection film55nearest the apex C2toward the apex C2. As the reflection film connection electrode551, an electrode having conductivity may be used. If the movable reflection film55is made of a conducting metal such as a silver alloy, for example, the same material as that of the movable reflection film55may be used and the reflection film connection electrode551may be patterned at formation of the movable reflection film55. Further, a member that is different from the movable reflection film55may be used, and, in this case, the reflection film connection electrode551is formed by the same material as that of the movable electrode562, for example, and thus, the reflection film connection electrode551may be patterned at formation of the movable electrode562.

Further, the reflection film connection electrode551is electrically connected to the first opposed electrode581(first opposed electrode pad581P) formed in the location of the apex C2of the fixed substrate51near the outer peripheral edge of the movable substrate52by a conducting member58of Ag paste or the like, for example. Thereby, the charge of the movable reflection film55can be eliminated from the first opposed electrode pad581P located on the apex C2of the fixed substrate51.

The movable electrode562provided on the movable surface521A is formed in a region overlapping with the fixed electrode561and in a C shape having a part corresponding to the apex C2opening in a plan view of the filter. The reflection film connection electrode551is formed toward the apex C2in the C-shaped opening part. Further, the width dimension of the movable electrode562is formed in the same dimension as the ring width dimension (the difference between the radius of the inner circumferential edge and the radius of the outer circumferential edge) of the fixed electrode561.

Further, a movable lead electrode564extending from the outer circumferential edge of the movable electrode562is formed on the movable substrate52. The movable lead electrode564extends from a location of the movable electrode562nearest the apex C3toward the apex C3. The movable lead electrode564is electrically connected to the second opposed electrode582(second opposed electrode pad582P) formed in the location of the apex C3of the fixed substrate51near the outer peripheral edge of the movable substrate52by a conducting member of Ag paste or the like, for example.

Furthermore, in the movable part521, an anti-reflection film (not shown) is formed on the opposite surface to the fixed substrate51. The anti-reflection film has the same configuration as that of the anti-reflection film formed on the fixed substrate51and is formed by alternately stacking a low-refractive-index film and a high-refractive-index film.

The holding part522is a diaphragm surrounding the movable part521, and formed in a thickness dimension of 50 μm, for example, and having a stiffness that is smaller than that of the movable part521in the thickness direction.

Accordingly, the holding part522is more likely to deflect than the movable part521, and may be deflected toward the fixed substrate51side by a small electrostatic attractive force. In this regard, since the movable part521has a larger thickness dimension and larger stiffness than those of the holding part522, even when a force of deflecting the movable substrate52acts thereon by the electrostatic attractive force, there is little deflection of the movable part521and the deflection of the movable reflection film55formed in the movable part521may be prevented.

Note that, although the holding part522having the diaphragm shape is exemplified in the embodiment, the shape is not so limited. For example, a holding part having beam shapes provided at equal angular intervals around the planar center point O may also be employed.

3-2. Configuration of Voltage Control Unit

The voltage control unit32is connected to the fixed electrode pad563P, the first opposed electrode pad581P, and the second opposed electrode pad582P, sets the fixed electrode pad563P, the first opposed electrode pad581P, and the second opposed electrode pad582P at predetermined potentials based on the control signal input from the control unit4, and thereby, applies a voltage to the electrostatic actuator56for driving.

Specifically, the voltage control unit32grounds the first opposed electrode pad581P and the fixed electrode pad563P, and sets a potential for setting the gap G1between the reflection films to a predetermined dimension for the second opposed electrode pad582P. Thereby, a voltage is applied between the fixed electrode561connected to the fixed electrode pad563P and the movable electrode562connected to the second opposed electrode pad582P, the movable part521moves to the fixed substrate51side by the electrostatic attractive force, and the dimension of the gap G1between the reflection films is set to a predetermined value. In this regard, both the first opposed electrode pad581P and the fixed electrode pad563P are grounded, and thus, even when the fixed reflection film54and the movable reflection film55are charged, the charge may be released and no electrostatic attractive force acts between the fixed reflection film54and the movable reflection film55. Therefore, for setting the gap G1between the reflection films, the gap G1between the reflection films may be set to a desired target value with high accuracy only by setting the voltage between the fixed electrode561and the movable electrode562without consideration of the electrostatic attractive force acting between the fixed reflection film54and the movable reflection film55.

Note that, in the embodiment, the first opposed electrode pad581P and the fixed electrode pad563P are grounded, however, a configuration in which a predetermined potential can be set may be employed. In this case, the potential difference between the set potential of the second opposed electrode pad582P and the set potential of the fixed electrode pad563P is applied to the electrostatic actuator56as a drive voltage, and thereby, the dimension of the gap G1between the reflection films may be controlled. Further, in this case, by setting the first opposed electrode pad581P and the fixed electrode pad563P at the same potential, the fixed reflection film54and the movable reflection film55may be at the same potential and the electrostatic attractive force in the gap G1between the reflection films may be eliminated.

Further, the voltage control unit32may ground the second opposed electrode pad582P and set potentials for driving the electrostatic actuator56for the first opposed electrode pad581P and the fixed electrode pad563P. In this case, the voltage control unit32may drive the electrostatic actuator56by the applied voltage based on the potentials set for the first opposed electrode pad581P and the fixed electrode pad563P. In addition, the same potential is set for the first opposed electrode pad581P and the fixed electrode pad563P, and thereby, no electrostatic attractive force acts between the fixed reflection film54and the movable reflection film55, and the gap G1between the reflection films may be controlled with high accuracy by the potential set for the first opposed electrode pad581P and the fixed electrode pad563P.

4. Configuration of Control Unit

The control unit4controls the operation of the colorimetric instrument1.

As the control unit4, for example, a general-purpose personal computer, a portable information terminal, and additionally, a colorimetry-dedicated computer or the like may be used.

Further, the control unit4includes a light source control part41, a colorimetric sensor control part42, a colorimetric processing part43(an analytical processing unit) as shown inFIG. 1.

The light source control part41is connected to the light source unit2. Further, the light source control part41outputs a predetermined control signal to the light source unit2based on the setting input by a user, for example, and allows the light source unit2to output white light with predetermined brightness.

The colorimetric sensor control part42is connected to the colorimetric sensor3. Further, the colorimetric sensor control part42sets the wavelength of light to be received by the colorimetric sensor3based on the setting input by the user, for example, and outputs a control signal for detecting the amount of received light having the wavelength to the colorimetric sensor3. Thereby, the voltage control unit32of the colorimetric sensor3sets the voltage applied to the electrostatic actuator56so that only the wavelength of the light desired by the user may be transmitted based on the control signal.

The colorimetric processing part43analyzes the chromaticity of the test object A from the amount of received light detected by the detection unit31.

5. Advantages of Embodiment

As described above, in the tunable interference filter5according to the embodiment, the fixed substrate51has the fixed electrode surface511A and the reflection film fixing surface512A at different distances from the movable substrate52, and the fixed electrode561is provided on the fixed electrode surface511A, and the fixed reflection film54is provided from the reflection film fixing surface512A over part of the fixed electrode surface511A. Further, the outer circumference part of the fixed reflection film54is stacked on the inner circumference part of the fixed electrode561, and the stacked structure forms the layered part57. Accordingly, in the layered part57, the fixed reflection film54and the fixed electrode561have surface contact and the fixed reflection film54and the fixed electrode561are electrically connected, and, even when the fixed reflection film54is charged, the charge may be released from the fixed electrode561. Therefore, the generation of electrostatic force by the charging the fixed reflection film54and the movable reflection film55may be prevented, and adjustment of the dimension of the gap G1between the reflection films by the voltage control unit32may easily be performed with high accuracy.

In this regard, in the layered part57, by the surface contact between the fixed reflection film54and the fixed electrode561, conduction between the fixed reflection film54and the fixed electrode561may reliably be secured, and the charge of the fixed reflection film54may be released to the fixed electrode561. Further, the thickness dimension of the layered part57becomes larger than those of the fixed reflection film54and the fixed electrode561by stacking the fixed reflection film54and the fixed electrode561. However, the layered part57is provided on the fixed electrode surface511A at a larger distance from the movable substrate52, and thus, the variable range of the gap G1between the reflection films may not be hindered by the thickness of the layered part57and the variable region of the gap G1between the reflection films may sufficiently be secured.

Further, in the fixed substrate51, the reflection film fixing surface512A is formed to project from the fixed electrode surface511A toward the movable substrate52side and the dimension of the gap G2between electrodes is larger than the dimension of the gap G1between the reflection films. Accordingly, the variable region of the gap G1between the reflection films may be made larger, and the measurable wavelength range of the colorimetric instrument1may be made wider. In addition, the control of the electrostatic attractive force between the fixed electrode561and the movable electrode562may be easier and the dimension of the gap G1between the reflection films may be set to a desired value with higher accuracy.

Furthermore, in the layered part57, the fixed reflection film54is stacked on the fixed electrode561. During manufacturing, the tunable interference filter5may be easily formed by depositing the fixed electrode561, and then, depositing the fixed reflection film54. Since the fixed reflection film54is formed after the fixed electrode561, damage of the fixed reflection film54during manufacturing may be suppressed.

In addition, the reflection film connection electrode551is connected to the movable reflection film55and the reflection film connection electrode551is connected to the voltage control unit32from the first opposed electrode pad581P and grounded. Accordingly, even when the movable reflection film55is charged, the charge may be released from the reflection film connection electrode551and generation of the electrostatic force between the fixed reflection film54and the movable reflection film55may be prevented more reliably.

Further, the potential set for the first opposed electrode pad581P and the fixed electrode pad563P is not limited to the zero potential as long as the first opposed electrode pad581P and the fixed electrode pad563P are at the same potential by the voltage control unit32. In this case, the fixed reflection film54and the movable reflection film are at the same potential, and the generation of electrostatic attractive force between the fixed reflection film54and the movable reflection film55may be prevented.

Modifications of Embodiment

Note that the invention is not limited to the above described embodiment, but includes modifications, improvements, and the like within the range in which the purpose of the invention may be achieved.

For example, in the embodiment, the example in which the first substrate is the fixed substrate51and the fixed electrode surface511A and the reflection film fixing surface512A formed in different height locations are provided on the fixed substrate51has been shown, however, a configuration with the first substrate as the movable substrate52as shown inFIG. 4may be employed.

FIG. 4is a sectional view showing a schematic configuration of a tunable interference filter5A in another embodiment.

As shown inFIG. 4, the tunable interference filter5A includes the fixed substrate51and the movable substrate52.

The fixed substrate51includes the electrode formation groove511having the fixed electrode surface511A and the reflection film fixing part512having the reflection film fixing surface512A. Here, unlike the above described embodiment, the fixed electrode561and reflection film54are independently provided on the fixed electrode surface511A and the reflection film fixing surface512A, respectively. Further, although not illustrated, the fixed electrode561is formed in a nearly C-shape in the plan view of the filter, and the reflection film connection electrode connected to the fixed reflection film54is formed to extend toward the apex of the colorimetric instrument1of the fixed substrate51(for example, the apex C2inFIG. 2) in the C-shaped opening part.

On the other hand, the movable substrate52has a projection part525projecting from the movable part521toward the fixed substrate51side and an electrode formation concave part526. Here, the projection end surface (projection surface525A) of the projection part525forms a first reflection film fixing surface, a bottom surface526A of the electrode formation concave part526forms a first electrode surface, and a distance of the bottom surface526A from the fixed substrate51is formed larger than that of the projection surface525A.

Further, the movable electrode562opposed to the fixed electrode561via the gap G2between electrodes is provided in a location overlapping with the fixed electrode561in the plan view of the filter. Furthermore, the movable reflection film55opposed to the fixed reflection film54via the gap G1between the reflection films is provided on the projection surface525A, and the movable reflection film55is provided from the projection surface525A over a part of the bottom surface526A. The outer circumference part of the movable reflection film55is stacked on the inner circumference part of the movable electrode562and forms a layered part57A.

In the tunable interference filter5A, like the above described tunable interference filter5, even when the movable reflection film55is charged, the charge may be released to the movable electrode562. Further, even when the fixed reflection film54is charged, the charge may be released by the reflection film connection electrode. Therefore, no electrostatic attractive force acts between the fixed reflection film54and the movable reflection film55, and the dimension of the gap G1between the reflection films may be set with high accuracy by controlling the voltage applied between the fixed electrode561and the movable electrode562.

Further, in the embodiment and the example shown inFIG. 4, the example in which the pair of opposed electrodes (the fixed electrode561and the movable electrode562) form the electrostatic actuator56has been shown, however, as shown inFIG. 5, a configuration in which plural electrodes form the electrostatic actuator56may be employed.FIG. 5is a sectional view showing a schematic configuration of a tunable interference filter5B of another embodiment.

In the tunable interference filter5B shown inFIG. 5, an inner movable electrode562A and an outer movable electrode562B form the movable electrode562. In the tunable interference filter5B, by individually controlling the voltage applied between the inner movable electrode562A and the fixed electrode561and the voltage applied between the outer movable electrode562B and the fixed electrode561, the amount of displacement of the movable part521may be set with higher accuracy.

Further, in the embodiment, as shown inFIG. 3, the example in which the reflection film fixing surface512A of the reflection film fixing part512opposed to the movable substrate52is located nearer the movable substrate52than the fixed electrode surface511A and the dimension of the gap G2between electrodes is larger than the gap G1between the reflection films has been shown, however, the configuration is not so limited. The height locations of the fixed electrode surface511A and the reflection film fixing surface512A may be appropriately set depending on the wavelength range of the light to be transmitted by the tunable interference filter5(measurement wavelength range), i.e., the variable range of the gap G1between the reflection films, the dimension of the gap G2between electrodes, the thickness dimensions of the fixed reflection film54and the movable reflection film55. Therefore, for example, a configuration in which a reference film fixing groove having a cylindrical recessed groove shape is formed in the center part of the fixed electrode surface511A and a reference film fixing surface is formed on the bottom surface of the reference film fixing groove may be employed. In this case, the layered part57in which the fixed reflection film54and the fixed electrode561are stacked is provided in the bottom surface part of the reference film fixing groove at the larger distance from the movable substrate52, and thereby, the inconvenience that the variable amount of the gap G2between electrodes is restricted by the thickness dimension of the layered part57may be avoided.

Further, in the embodiment, the fixed electrode561forming the electrostatic actuator56has been exemplified as the first electrode, however, the configuration is not so limited. For example, a charge elimination electrode for eliminating the charge of the fixed reflection film54may be formed on the fixed electrode surface511A of the fixed substrate51and the fixed reflection film54may be stacked on the charge elimination electrode for eliminating the charge.

Furthermore, in the example shown inFIG. 4, the fixed reflection film54is connected to the reflection film connection wire (not shown) and the charge is eliminated from the reflection film connection wire, however, for example, a configuration in which a charge elimination electrode is formed on the fixed electrode surface511A of the fixed substrate51and the fixed reflection film54is stacked on the charge elimination electrode may be employed. In this case, a layered structure of the charge elimination electrode and the fixed reflection film54is formed on the fixed electrode surface511A at the larger distance from the movable substrate52than the reflection film fixing surface512A and the variable range of the gap G1between the reflection films does not become narrower by the thickness of the layered structure, and the charge may be released more reliably even when the fixed reflection film54is charged by surface contact between the charge elimination electrode and the fixed reflection film54.

In the embodiment and the examples shown inFIGS. 4 and 5, the configuration in which the gap G2between electrodes is larger than the gap G1between the reflection films has been exemplified, however, for example, a configuration in which the gap G2between electrodes is smaller than the gap G1between the reflection films may be employed. In this case, the variable range of the gap G1between the reflection films is restricted by the gap G2between electrodes, however, the restriction is not problematic when a sufficient dimension is secured for the wavelength range to be measured. Note that, as described above, the electrostatic attractive force is larger in inverse proportion to the square of distance, and, as the distance of the gap G2between electrodes is smaller, the control of the gap G1between the reflection films becomes difficult.

Further, the layered part57has been formed by stacking the fixed reflection film54on the fixed electrode561, however, a configuration in which the fixed electrode561is stacked on the fixed reflection film54may be employed.

In this case, if a material that easily deteriorates such as a silver alloy is used as a fixed reflection film54, for example, deterioration may occur during formation of the fixed electrode561after formation of the fixed reflection film54. For example, by masking the formed fixed reflection film54or otherwise, the number of steps increases, but the deterioration may be suppressed. Further, in the case where the fixed reflection film54is deteriorated, the deterioration usually progresses from the outer circumferential edge, however, in the configuration in which the outer circumferential edge of the fixed reflection film54is covered by the fixed electrode561, the progress of deterioration of the fixed reflection film54may be suppressed.

The colorimetric instrument1has been exemplified as an electronic apparatus according to the invention, however, the tunable interference filter, the optical module, and an electronic apparatus according to the invention may be used in other various fields.

For example, they may be used as a light-based system for detecting the presence of a specific material. As the system, for example, a gas detector such as a vehicle-mounted gas leak detector that detects a specific gas with high sensitivity by employing a spectroscopic measurement method using the tunable interference filter according to the invention or a photoacoustic gas detector for a breath test may be exemplified.

Below, an example of the gas detector will be explained according to the drawings.

FIG. 6is a schematic diagram showing an example of a gas detector including the tunable interference filter.

FIG. 7is a block diagram showing a configuration of a control system of the gas detector inFIG. 6.

This gas detector100includes a sensor chip110, a channel120having a suction port120A, a suction channel120B, an eject channel120C, and an eject port120D, and a main body part130as shown inFIG. 6.

The main body part130includes a detector (optical module) having a sensor part cover131having an opening in which the channel120is detachable, an ejecting unit133, a housing134, an optical unit135, a filter136, the tunable interference filter5, a light receiving device137(detection unit), a control unit138that processes a detected signal and controls the detection unit, a power supply unit139that supplies power, and the like. Further, the optical unit135includes a light source135A that outputs light, a beam splitter135B that reflects the light entering from the light source135A toward the sensor chip110side and transmits the light entering from the sensor chip side to the light receiving device137side, and lenses135C,135D,135E. Although the configuration using the tunable interference filter5is exemplified, configurations using the above described tunable interference filters5A,5B may be employed.

Further, as shown inFIG. 7, on the surface of the gas detector100, an operation panel140, a display unit141, a connection part142for interface with the outside, and the power supply unit139are provided. If the power supply unit139is a secondary cell, a connection part143for charging may be provided.

Furthermore, as shown inFIG. 7, the control unit138of the gas detector100includes a signal processing part144having a CPU, alight source driver circuit145for control of the light source135A, a voltage control part146for control of the tunable interference filter5, a receiver circuit147that receives a signal from the light receiving device137, a sensor chip detector circuit149that receives a signal from a sensor chip detector148that detects presence or absence of the sensor chip110, an eject driver circuit150that controls the ejecting unit133, and the like.

Next, an operation of the gas detector110will be explained.

Inside of the sensor part cover131in the upper part of the main body part130, the sensor chip detector148is provided and presence or absence of the sensor chip110is detected by the sensor chip detector148. When the signal processing part144detects the detection signal from the sensor chip detector148, the part determines that the state in which the sensor chip110is mounted, and outputs a display signal to the display unit141for displaying that a detection operation can be performed.

Then, for example, if the operation panel140is operated by a user and an instruction signal of starting detection processing is output from the operation panel140to the signal processing part144, first, the signal processing part144outputs a signal of light source activation to the light source driver circuit145and activates the light source135A. When the light source135A is driven, a stable laser beam of linearly-polarized light having a single waveform is output from the light source135A. Further, a temperature sensor and a light amount sensor are contained in the light source135A, and their information is output to the signal processing part144. Then, if the signal processing part144determines that the light source135A is in stable operation based on the temperature and the light amount input from the light source135A, the part controls the eject driver circuit150to activate the ejecting unit133. Thereby, a gas sample containing a target material (gas molecules) to be detected is guided from the suction port120A into the suction channel120B, the sensor chip110, the eject channel120C, and the eject port120D.

The sensor chip110has plural metal nanostructures incorporated therein and uses localized surface plasmon resonance. In the sensor chip110, when enhanced electric fields are formed between the metal nanostructures by the laser beam and the gas molecules enter the enhanced electric fields, Raman scattering light and Rayleigh scattering light containing information of molecule oscillation are generated.

The Raman scattering light and Rayleigh scattering light enter the filter136through the optical unit135, the Rayleigh scattering light is separated by the filter136, and the Raman scattering light enters the tunable interference filter5. Then, the signal processing part144controls the voltage control part146to adjust the voltage applied to the tunable interference filter5and allow the tunable interference filter5to spectroscopically separate the Raman scattering light in response to the gas molecules to be detected. Then, when the spectroscopically separated light is received by the light receiving device137, the light reception signal in response to the amount of received light is output to the signal processing part144via the receiver circuit147.

The signal processing part144compares spectrum data of the Raman scattering light in response to the gas molecules to be detected obtained in the above described manner and data stored in a ROM, determines whether or not they are the target gas molecules, and identifies the material. Further, the signal processing part144allows the display unit141to display the result information and outputs it to the outside from the connection part142.

InFIGS. 6 and 7, the gas detector100that performs gas detection from the spectroscopic separated Raman scattering light by spectroscopic separation of the Raman scattering light using the tunable interference filter5has been exemplified, however, it may be used as a gas detector that identifies a gas type by detecting absorbance unique to the gas. In this case, a gas sensor that takes a gas inside and detects light absorbed by the gas of the incident lights is used as the optical module according to the invention. Further, a gas detector that analyzes and discriminates the gas flowing into the sensor using the gas sensor is an electronic apparatus according to the invention. The configuration may even detect components of the gas using the tunable interference filter according to the invention.

Further, as a system for detection of the presence of a specific material, not limited to the gas detection, but also a material component analyzer such as a non-invasive measurement device of sugar using near-infrared spectroscopy or a non-invasive measurement device of information of foods, living organisms, minerals, or the like may be exemplified.

Below, a food analyzer as an example of the material component analyzer will be explained.

FIG. 8shows a schematic configuration of a food analyzer as an example of an electronic apparatus using the tunable interference filter5. Here, the tunable interference filter5is used, however, the tunable interference filters5A,5B may be used.

As shown inFIG. 8, this food analyzer200includes a detector210(optical module), a control unit220, and a display unit230. The detector210includes a light source211that outputs light, an imaging lens212that introduces light from an object to be measured, the tunable interference filter5that spectroscopically separates the light introduced from the imaging lens212, and an imaging unit213(detection unit) that detects the spectroscopically separated light.

Further, the control unit220includes alight source control part221that performs turn-on and turn-off control and brightness control when the light source211is turned on, a voltage control part222that controls the tunable interference filter5, a detection control part223that controls the imaging unit213and acquires spectroscopically separated images imaged by the imaging unit213, a signal processing part224, and a memory part225.

In the food analyzer200, when the system is driven, the light source211is controlled by the light source control part221, and the object to be measured is irradiated with light from the light source211. Then, the light reflected by the object to be measured passes through the imaging lens212and enters the tunable interference filter5. A voltage that enables spectroscopic separation of a desired wavelength is applied to the tunable interference filter5under the control of the voltage control part222, and the spectroscopically separated light is imaged in the imaging unit213including a CCD camera, for example. Further, the imaged light is accumulated as spectroscopically separated images in the memory part225. Furthermore, the signal processing part224controls the voltage control part222to change the voltage value applied to the tunable interference filter5, and acquires the spectroscopically separated images for the respective wavelengths.

Then, the signal processing part224performs computation processing on data of respective pixels in the respective images accumulated in the memory part225, and obtains spectra in the respective pixels. Further, for example, information on components of foods with respect to the spectra is stored in the memory part225. The signal processing part224analyzes the data of the obtained spectra based on the information on the foods stored in the memory part225, and obtains food components contained in the object to be detected and their contents. Further, from the obtained food components and contents, food calories, freshness, and the like may be calculated. Furthermore, by analyzing the spectrum distributions within the images, extraction of apart in which freshness has been deteriorated in the food of the object to be inspected or the like may be performed, and detection of foreign materials contained within the foods or the like may be performed.

Then, the signal processing part224performs processing to allow the display unit230to display the information on the components, contents, calories, freshness, and the like of the foods as the object to be inspected obtained in the above described manner.

FIG. 8shows the example of the food analyzer200, however, a device having nearly the same configuration may be used as the above described non-invasive measurement device of other information. For example, the device may be used as a living organism analyzer that performs analysis of living organism components such as measurement, analysis, or the like of body fluid components of blood or the like. The living organism analyzer as a device for measurement of the body fluid components of blood, for example, as a device for sensing ethyl alcohol, may be used as a drunk driving prevention device that detects the influence of alcohol of a driver. Further, the device may be used as an electronic endoscopic system including the living organism analyzer.

Furthermore, the device may be used as a mineral analyzer that performs component analyses of minerals.

In addition, the tunable interference filter, the optical module, and the electronic apparatus according to the invention may be applied to the following devices.

For example, by changing the intensity of the lights having respective wavelengths with time, data can be transmitted by the lights having respective wavelengths. In this case, a light having a specific wavelength is spectroscopically separated by the tunable interference filter provided in the optical module and received by the light receiving unit, and thereby, the data transmitted by the light having the specific wavelength may be extracted. Optical communications may be performed by processing the data of the lights having respective wavelengths using an electronic apparatus having the optical module for data extraction.

Further, as the electronic apparatus, the configuration may be applied to a spectroscopic camera, a spectroscopic analyzer, and the like that image spectroscopically separated images by spectroscopic separation of light using the tunable interference filter according to the invention. As an example of the spectroscopic camera, there is an infrared camera containing the tunable interference filter.

FIG. 9is a diagram showing a schematic configuration of a spectroscopic camera. As shown inFIG. 9, the spectroscopic camera300includes a camera main body310, an imaging lens unit320, and an imaging unit330(detection unit).

The camera main body310is a part grasped and operated by a user.

The imaging lens unit320is provided in the camera main body310and guides entering image light to the imaging unit330. Further, the imaging lens unit320includes an objective lens321, an image forming lens322, and the tunable interference filter5provided between these lenses as shown inFIG. 9.

The imaging unit330includes a light receiving device and images the image light guided by the imaging lens unit320.

In the spectroscopic camera300, a light having a wavelength to be imaged is transmitted through the tunable interference filter5, and thereby, a spectroscopically separated image of a light having a desired wavelength may be obtained.

Furthermore, the tunable interference filter according to the invention may be used as a bandpass filter, and, for example, may be used as an optical laser device that spectroscopically separates and transmits only lights in a narrow band around a predetermined wavelength of the lights in a predetermined wavelength range output by a light emitting device using the tunable interference filter.

Further, the tunable interference filter according to the invention may be used as a biometric identification device, and, for example, may be applied to an identification device of blood vessels, finger prints, retina, iris, or the like using lights in the near-infrared range and the visible range.

Furthermore, the optical module and the electronic apparatus may be used as a concentration detector. In this case, the concentration of an object to be detected in a sample is measured by spectroscopic separation and analysis of infrared energy (infrared light) output from a material using the tunable interference filter.

As shown above, the tunable interference filter, the optical module, and the electronic apparatus according to the invention may be applied to any device that spectroscopically separates a predetermined light from incident lights. Further, as described above, the tunable interference filter according to the invention may spectroscopically separate plural wavelengths by one device, and thus, measurement of spectra of the plural wavelengths and detection of plural components may be performed with high accuracy. Therefore, compared to the device in the past that extracts a desired wavelength using plural devices, downsizing of the optical module and the electronic apparatus may be promoted and the tunable interference filter may preferably be used as a portable or vehicle-mounted optical device, for example.

In addition, the specific structures when the invention is implemented may be appropriately changed to other structures within a range in which the purpose of the invention may be achieved.

The entire disclosure of Japanese Patent Application No. 2011-087225 filed Apr. 11, 2011 is expressly incorporated by reference herein.