U.S. patent application number 14/215510 was filed with the patent office on 2014-09-18 for interference filter, optical filter device, optical module, and electronic apparatus.
This patent application is currently assigned to Seiko Epson Corporation. The applicant listed for this patent is Seiko Epson Corporation. Invention is credited to Akira Sano.
Application Number | 20140268345 14/215510 |
Document ID | / |
Family ID | 50396862 |
Filed Date | 2014-09-18 |
United States Patent
Application |
20140268345 |
Kind Code |
A1 |
Sano; Akira |
September 18, 2014 |
INTERFERENCE FILTER, OPTICAL FILTER DEVICE, OPTICAL MODULE, AND
ELECTRONIC APPARATUS
Abstract
A wavelength tunable interference filter includes a fixed
substrate, a fixed reflection film that is provided on the fixed
substrate, reflects part of incident light, and transmits at least
part of the incident light, a movable reflection film that faces
the fixed reflection film, reflects part of incident light, and
transmits at least part of the incident light, and a fixed
electrode that surrounds the fixed reflection film and has a light
absorbing layer and a metal layer, and the light absorbing layer is
disposed closer to the fixed substrate than the metal layer.
Inventors: |
Sano; Akira; (Shiojiri,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Seiko Epson Corporation |
Tokyo |
|
JP |
|
|
Assignee: |
Seiko Epson Corporation
Tokyo
JP
|
Family ID: |
50396862 |
Appl. No.: |
14/215510 |
Filed: |
March 17, 2014 |
Current U.S.
Class: |
359/584 |
Current CPC
Class: |
G02B 26/001 20130101;
G01J 3/26 20130101; G02B 5/28 20130101; G02B 26/0841 20130101; G02B
6/29358 20130101; G01J 3/51 20130101 |
Class at
Publication: |
359/584 |
International
Class: |
G02B 5/28 20060101
G02B005/28 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 18, 2013 |
JP |
2013-054678 |
Claims
1. An interference filter comprising: a substrate; a first
reflection film provided on the substrate; a second reflection film
facing the first reflection film; and a first electrode provided in
an area surrounding the first reflection film, the first electrode
having a light absorbing layer and a metal layer, wherein the light
absorbing layer is disposed closer to the substrate than the metal
layer.
2. The interference filter according to claim 1, wherein at least
part of an inner circumferential edge of the first electrode is in
direct contact with the first reflection film.
3. The interference filter according to claim 1, wherein the first
electrode has a frame shape that surrounds the first reflection
film.
4. The interference filter according to claim 1, further comprising
a movable portion on which the second reflection film is disposed
and which is movable in a thickness direction of the second
reflection film, wherein a shortest distance between outer
circumferential edges of the first reflection film and the first
electrode is greater than a shortest distance between the outer
circumferential edges of the first reflection film and the movable
portion in a plan view of the interference filter.
5. The interference filter according to claim 1, further comprising
a stress relaxation film provided on a second surface of the
substrate that faces away from a first surface of the substrate on
which the first electrode is provided, the stress relaxation film
opposing the first electrode through the substrate, wherein the
stress relaxation film has two light absorbing layers and a metal
layer provided between the two light absorbing layers.
6. The interference filter according to claim 1, wherein the first
reflection film is electrically conductive, and the first electrode
is electrically connected to the first reflection film.
7. The interference filter according to claim 6, wherein the second
reflection film is electrically conductive, and the interference
filter further comprises a mirror electrode connected to the second
reflection film.
8. The interference filter according to claim 4, further comprising
a second electrode provided on the movable portion and facing at
least part of the first electrode.
9. The interference filter according to claim 8, wherein the second
electrode is formed of a plurality of partial electrodes that are
electrically independent of each other, and the first electrode is
an electrode common to the plurality of partial electrodes.
10. The interference filter according to claim 1, wherein the
substrate is made of a glass material, the light absorbing layer is
made of at least one of TiW, TiN, NiCr, TiO.sub.2, Al.sub.2O.sub.3,
MgF.sub.2, Nd.sub.2O.sub.3, and Ta.sub.2O.sub.5 and formed on the
substrate, and the metal layer is formed on the light absorbing
layer.
11. The interference filter according to claim 1, wherein the metal
layer is made of at least one of Au, Al, Ti, Ag, W, Nb, Ta, Mo, Cu,
Ni, Co, Fe, Pt, and Zn.
12. An interference filter comprising: a first reflection film; a
second reflection film that faces the first reflection film; and a
first electrode surrounding the first reflection film, the first
electrode including a light absorbing layer and a metal layer,
wherein the light absorbing layer is disposed farther away from the
second reflection film than the metal layer in a direction
extending from the first reflection film toward the second
reflection film.
13. An optical filter device comprising: an interference filter
including a substrate, a first reflection film provided on the
substrate, a second reflection film facing the first reflection
film, and a first electrode provided on the substrate and
surrounding the first reflection film, the first electrode having a
light absorbing layer and a metal layer; and an enclosure that
accommodates the interference filter, wherein the light absorbing
layer is disposed closer to the substrate than the metal layer.
14. An optical module comprising: the interference filter of claim
1; and a detector that detects light extracted by the first
reflection film and the second reflection film.
15. An electronic apparatus comprising: the interference filter of
claim 1; and a control unit that controls the interference filter.
Description
BACKGROUND
[0001] 1. Technical Field
[0002] The present invention relates to an interference filter, an
optical filter device, an optical module, and an electronic
apparatus.
[0003] 2. Related Art
[0004] A known wavelength tunable interference filter has a pair of
reflection films facing each other and changes a distance between
the reflection films is changed to extract light of a predetermined
wavelength from light under measurement (see JP-A-2003-57571, for
example). The pair of reflection films disposed in the wavelength
tunable interference filter face each other and cause incident
light to undergo an interference process to transmit light of a
given wavelength according to the dimension of the gap between the
reflection films.
[0005] In the thus configured wavelength tunable interference
filter, when light that does not pass through the area where the
pair of reflection films are disposed so that they face each other,
that is, light that is not separated by the wavelength tunable
interference filter exits out thereof and is received with a light
receiver, spectroscopic precision decreases.
[0006] To reduce the decrease in spectroscopic precision, in
JP-A-2003-57571, a metal electrode provided to change the dimension
of the gap between the reflection films is used as an aperture.
[0007] In JP-A-2003-57571, however, the metal electrode used as an
aperture is made of a metal material having a relatively high
reflectance (aluminum, gold, chromium, or titanium, for example).
When used as an aperture, the thus formed metal electrode may
undesirably reflect light incident thereon to produce reflected
light. The reflected light may then undesirably be reflected off an
enclosure that seals the wavelength tunable interference filter or
the inner wall and other portions of an optical module or any other
apparatus that accommodates the wavelength tunable interference
filter to form stray light. The stray light is then received by a
light receiver, undesirably resulting in a decrease in
spectroscopic precision.
SUMMARY
[0008] An advantage of some aspects of the invention is to provide
an interference filter, an optical filter device, an optical
module, and an electronic apparatus capable of suppressing the
generation of stray light.
[0009] An aspect of the invention is directed to an interference
filter including a substrate, a first reflection film that is
provided on the substrate, reflects part of incident light, and
transmits at least part of the incident light, a second reflection
film that faces the first reflection film, reflects part of
incident light, and transmits at least part of the incident light,
and a first electrode that is provided in an area around the first
reflection film and has a light absorbing layer and a metal layer,
and the light absorbing layer is disposed in a position closer to
the substrate than the metal layer.
[0010] In the aspect of the invention, the first electrode is
disposed in an area around the first reflection film. In the first
electrode, the light absorbing layer is disposed on the side facing
the substrate, and the metal layer is disposed on the opposite side
of the light absorbing layer to the substrate.
[0011] The thus configured first electrode functions as an aperture
because the inner circumferential edge of the first electrode
defines a light incident range through which light is incident on
the first reflection film. Defining the light incident range
through which light is incident on the first reflection film as
described above prevents light from being incident on areas other
than the area where the reflection films face each other, whereby a
decrease in spectroscopic precision can be reduced.
[0012] Further, in the first electrode, since light that passes
through the substrate and enters the light absorbing layer of the
first electrode is absorbed by the light absorbing layer, the
amount of light reflected off the metal layer and directed toward
the substrate again can be reduced. As a result, stray light
generated by reflection at the metal layer of the first electrode
can be suppressed, whereby a decrease in spectroscopic precision
can be reduced.
[0013] In the interference filter according to the aspect of the
invention, it is preferable that at least part of an inner
circumferential edge of the first electrode is in contact with the
first reflection film.
[0014] With this configuration, at least part of an inner
circumferential edge of the first electrode is in contact with the
first reflection film. As a result, the first electrode and the
first reflection film partially overlap with each other, whereby no
gap is created between the first reflection film and the first
electrode, and hence light passing through a possible gap is not
present.
[0015] In the interference filter according to the aspect of the
invention, it is preferable that the first electrode has a
frame-like shape that surrounds the first reflection film.
[0016] With this configuration, the first electrode has a
frame-like shape that surrounds the first reflection film and the
first electrode is disposed so that it surrounds the first
reflection film. The configuration allows the first electrode as an
aperture to have improved light blocking performance, whereby a
decrease in spectroscopic precision can be further effectively
reduced.
[0017] In the interference filter according to the aspect of the
invention, it is preferable that the interference filter further
includes a movable portion on which the second reflection film is
disposed and which is capable of moving in a thickness direction of
the second reflection film, and the shortest distance between outer
circumferential edges of the first reflection film and the first
electrode is greater than the shortest distance between outer
circumferential edges of the first reflection film and the movable
portion when the interference filter is viewed in the thickness
direction.
[0018] With this configuration, when the interference filter is
viewed in the thickness direction of the second reflection film
(that is, in a plan view viewed in the thickness direction of the
substrate), the shortest distance between the outer circumferential
edges of the first reflection film and the first electrode is
greater than the shortest distance between the outer
circumferential edges of the first reflection film and the movable
portion. In other words, the first electrode is disposed so that it
is present on both the inner and outer sides of the outer
circumferential edge of the movable portion, and the outer
circumferential edge of the first electrode is located in a
position outside the outer circumferential edge of the movable
portion. As a result, no light will be incident on the outer
circumferential edge of the movable portion, whereby stray light
can be suppressed.
[0019] In the interference filter according to the aspect of the
invention, it is preferable that the interference filter further
includes an stress relaxation film provided on a surface of the
substrate that faces away from the surface on which the first
electrode is provided with the stress relaxation film facing the
first electrode through the substrate, and the stress relaxation
film has two light absorbing layers and a metal layer provided
between the two light absorbing layers.
[0020] With this configuration, a stress relaxation film is
provided on a surface of the substrate that faces away from the
surface on which the first electrode is provided with the stress
relaxation film facing the first electrode through the substrate,
and the stress relaxation film has two light absorbing layers and a
metal layer provided between the light absorbing layers.
[0021] Since the stress relaxation film has the same metal layer as
that of the first electrode, the stress relaxation film produces
internal stress having substantially the same magnitude of internal
stress produced in the metal layer of the first electrode, whereby
the overall internal stress that acts on the substrate can be
canceled and hence deformation of the substrate can be
prevented.
[0022] Further, the stress relaxation film has a pair of light
absorbing layers that sandwich the metal film. The light absorbing
layer facing the substrate can absorb light incident through the
substrate, and even when part of light incident on the interference
filter is incident on the stress relaxation film, the other light
absorbing layer can absorb the incident light.
[0023] As described above, the stress relaxation film of the aspect
of the invention can not only reduce the stress produced by the
first electrode but also reliably suppress stray light.
[0024] In the interference filter according to the aspect of the
invention, it is preferable that the first reflection film is
electrically conductive, and that the first electrode is
electrically connected to the first reflection film.
[0025] With this configuration, since the first reflection film and
the first electrode are electrically connected to each other, the
first reflection film can be used as an electrode via the first
electrode. Further, setting the first electrode at, for example, a
ground potential allows removal of charge accumulated on the first
reflection film.
[0026] In the interference filter according to the aspect of the
invention, it is preferable that the second reflection film is
electrically conductive, and that the interference filter further
includes a mirror electrode connected to the second reflection
film.
[0027] With this configuration, since the second reflection film is
connected to the mirror electrode, the second reflection film is
allowed to function as an electrode. In this case, for example,
setting the first electrode and the mirror electrode at the same
potential (ground potential, for example) prevents generation of
electrostatic attractive force between the first reflection film
and the second reflection film. Further, the first reflection film
and the second reflection film are allowed to function as
electrodes for capacitance detection. Moreover, a drive voltage can
be applied between the first reflection film and the second
reflection film. In this case, the first reflection film and the
second reflection film are also allowed to function as drive
electrodes for changing the dimension of the gap between the first
reflection film and the second reflection film.
[0028] In the interference filter according to the aspect of the
invention, it is preferable that the interference filter further
includes a second electrode provided on the movable portion and
facing at least part of the first electrode.
[0029] With this configuration, the first electrode and the second
electrode can form a gap changer that changes the dimension of the
gap between the reflection films. It is therefore unnecessary to
separately provide a drive electrode and the first electrode as an
aperture, whereby the size of the interference filter can be
reduced.
[0030] In the interference filter according to the aspect of the
invention, it is preferable that the second electrode is formed of
a plurality of partial electrodes electrically independent of each
other, and that the first electrode is an electrode common to the
plurality of partial electrodes.
[0031] With this configuration, using the first electrode as an
electrode common to the partial electrodes and setting the partial
electrodes at different potentials allow electrostatic attractive
forces having different magnitudes to be produced between the
partial electrodes and the first electrode. That is, the plurality
of partial electrodes and the first electrode that faces them can
form a plurality of electrostatic actuators, whereby the dimension
of the gap between the reflection films can be controlled with high
precision.
[0032] In the interference filter according to the aspect of the
invention, it is preferable that the substrate is made of a glass
material, that the light absorbing layer is made of at least one of
TiW, TiN, NiCr, TiO.sub.2, Al.sub.2O.sub.3, MgF.sub.2,
Nd.sub.2O.sub.3, and Ta.sub.2O.sub.5 and formed on the substrate,
and that the metal layer is formed on the light absorbing
layer.
[0033] With this configuration, the substrate is made of a glass
material. The light absorbing layer is made of at least one of TiW,
TiN, NiCr, TiO.sub.2, Al.sub.2O.sub.3, MgF.sub.2, Nd.sub.2O.sub.3,
and Ta.sub.2O.sub.5 and formed on the substrate. The metal layer is
formed on the light absorbing layer. The thus formed light
absorbing layer is in intimate contact with the metal layer and the
substrate, which is made of a glass material, whereby the metal
layer and the substrate can be reliably connected to each other.
Further, the light absorbing layer can suppress reflection at the
interface between the light absorbing layer and the substrate,
which is made of a glass material, whereby generation of stray
light can be more effectively suppressed.
[0034] In the interference filter according to the aspect of the
invention, it is preferable that the metal layer is made of at
least one of Au, Al, Ti, Ag, W, Nb, Ta, Mo, Cu, Ni, Co, Fe, Pt, and
Zn.
[0035] With this configuration, the metal layer is made of at least
one of Au, Al, Ti, Ag, W, Nb, Ta, Mo, Cu, Ni, Co, Fe, Pt, and
Zn.
[0036] The metal layer can therefore be formed by using a highly
electrically-conductive, light-blocking material, whereby the metal
layer can be preferably used both as an electrode and an
aperture.
[0037] Another aspect of the invention is directed to an
interference filter including a first reflection film that reflects
part of incident light and transmits at least part of the incident
light, a second reflection film that faces the first reflection
film, reflects part of incident light, and transmits at least part
of the incident light, and a first electrode that is provided in an
area around the first reflection film and has a light absorbing
layer and a metal layer, and the light absorbing layer is disposed
in a position farther away from the second reflection film than the
metal layer in a direction from the first reflection film toward
the second reflection film.
[0038] In the aspect of the invention, the first electrode is
disposed in an area around the first reflection film and functions
as an aperture, as in the aspect of the invention described above.
Further the first electrode has the light absorbing layer. The
amount of light reflected off the metal layer can therefore be
reduced. As a result, stray light generated by reflection at the
metal layer of the first electrode can be suppressed, whereby a
decrease in spectroscopic precision can be reduced.
[0039] Still another aspect of the invention is directed to an
optical filter device including an interference filter including a
substrate, a first reflection film that is provided on the
substrate, reflects part of incident light, and transmits at least
part of the incident light, a second reflection film that faces the
first reflection film, reflects part of incident light, and
transmits at least part of the incident light, and a first
electrode that is provided in an area around the first reflection
film and has a light absorbing layer and a metal layer; and an
enclosure that accommodates the interference filter, and the light
absorbing layer is disposed in a position closer to the substrate
than the metal layer.
[0040] In the aspect of the invention, the first electrode is
disposed in an area around the first reflection film and functions
as an aperture, as in the aspect of the invention described above.
Further, the first electrode has the light absorbing layer.
Therefore, in the area where the first electrode is formed, light
having passed through the substrate can be blocked, and stray light
generated by reflection at the metal layer of the first electrode
can be suppressed, whereby a decrease in spectroscopic precision
can be reduced.
[0041] Further, since the interference filter is accommodated in
the enclosure, degradation of the reflection films due to gases and
other substances contained in the atmosphere and adherence of
foreign matter to the reflection films can be prevented.
[0042] Yet another aspect of the invention is directed to an
optical module including a substrate, a first reflection film that
is provided on the substrate, reflects part of incident light, and
transmits at least part of the incident light, a second reflection
film that faces the first reflection film, reflects part of
incident light, and transmits at least part of the incident light,
a first electrode that is provided in an area around the first
reflection film and has a light absorbing layer and a metal layer;
and a detector that detects light extracted by the first reflection
film and the second reflection film, and the light absorbing layer
is disposed in a position closer to the substrate than the metal
layer.
[0043] In the aspect of the invention, the first electrode is
disposed in an area around the first reflection film and functions
as an aperture, as in the aspect of the invention described above.
Further, the first electrode has the light absorbing layer. The
optical module therefore allows, in the area where the first
electrode is formed, light having passed through the substrate to
be blocked and stray light generated by reflection at the metal
layer of the first electrode to be suppressed, whereby a decrease
in spectroscopic precision can be reduced.
[0044] Still yet another aspect of the invention is directed to an
electronic apparatus including a substrate, a first reflection film
that is provided on the substrate, reflects part of incident light,
and transmits at least part of the incident light, a second
reflection film that faces the first reflection film, reflects part
of incident light, and transmits at least part of the incident
light, a first electrode that is provided in an area around the
first reflection film and has a light absorbing layer and a metal
layer; and a control unit that controls the interference filter,
and the light absorbing layer is disposed in a position closer to
the substrate than the metal layer.
[0045] In the aspect of the invention, the first electrode is
disposed in an area around the first reflection film and functions
as an aperture, as in the aspect of the invention described above.
Further, the first electrode has the light absorbing layer. The
electronic apparatus therefore allows, in the area where the first
electrode is formed, light having passed through the substrate to
be blocked and stray light generated by reflection at the metal
layer of the first electrode to be suppressed, whereby a decrease
in spectroscopic precision can be reduced.
BRIEF DESCRIPTION OF THE DRAWINGS
[0046] Embodiments of the invention will be described with
reference to the accompanying drawings, wherein like numbers
reference like elements.
[0047] FIG. 1 is a block diagram showing a schematic configuration
of a spectroscopic measurement apparatus of a first embodiment.
[0048] FIG. 2 is a plan view showing a schematic configuration of a
wavelength tunable interference filter of the first embodiment.
[0049] FIG. 3 is a cross-sectional view of the wavelength tunable
interference filter taken along the line III-III in FIG. 2.
[0050] FIG. 4 is a cross-sectional view showing a schematic
configuration of a wavelength tunable interference filter of a
second embodiment.
[0051] FIG. 5 is a cross-sectional view showing a schematic
configuration of a wavelength tunable interference filter of a
third embodiment.
[0052] FIG. 6 is a cross-sectional view showing a schematic
configuration of a wavelength tunable interference filter of a
fourth embodiment.
[0053] FIG. 7 is a plan view showing a schematic configuration of a
wavelength tunable interference filter of a fifth embodiment.
[0054] FIG. 8 is a cross-sectional view showing the schematic
configuration of the wavelength tunable interference filter of the
fifth embodiment.
[0055] FIG. 9 is a cross-sectional view showing a schematic
configuration of an optical filter device of a sixth
embodiment.
[0056] FIG. 10 is a cross-sectional view showing a schematic
configuration a variation of the optical filter device.
[0057] FIG. 11 shows a schematic configuration of a colorimetry
apparatus (electronic apparatus) including any of the wavelength
tunable interference filters according to the embodiments of the
invention.
[0058] FIG. 12 shows a schematic configuration of a gas detection
apparatus (electronic apparatus) including any of the wavelength
tunable interference filters according to the embodiments of the
invention.
[0059] FIG. 13 is a block diagram showing a control system of the
gas detection apparatus shown in FIG. 12.
[0060] FIG. 14 shows a schematic configuration of a food analyzer
(electronic apparatus) including any of the wavelength tunable
interference filters according to the embodiments of the
invention.
[0061] FIG. 15 shows a schematic configuration of a spectroscopic
camera (electronic apparatus) including any of the wavelength
tunable interference filters according to the embodiments of the
invention.
DESCRIPTION OF EXEMPLARY EMBODIMENTS
First Embodiment
[0062] A first embodiment will be described below with reference to
the drawings.
Configuration of Spectroscopic Measurement Apparatus
[0063] FIG. 1 is a block diagram showing a schematic configuration
of a spectroscopic measurement apparatus of a first embodiment
according to the invention.
[0064] A spectroscopic measurement apparatus 1 is an electronic
apparatus of an embodiment according to the invention and an
apparatus that receives light under measurement reflected off an
object X under measurement and measures the spectrum of the light
under measurement. In the present embodiment, the light under
measurement reflected off the object X under measurement is
measured by way of example, whereas when the object X under
measurement is a light emitting object, such as a liquid crystal
panel, light emitted from the light emitting object may be the
light under measurement.
[0065] The spectroscopic measurement apparatus 1 includes an
optical module 10 and a control unit 20, as shown in FIG. 1.
Configuration of Optical Module
[0066] The optical module 10 includes a wavelength tunable
interference filter 5, a detector 11, an I-V converter 12, an
amplifier 13, an A/D converter 14, and a voltage controller 15.
[0067] In the optical module 10, light under measurement is guided
via an optical system for incident light (not shown) to the
wavelength tunable interference filter 5, which transmits light of
a predetermined wavelength out of the light under measurement, and
the detector 11 receives the transmitted light. A detection signal
from the detector 11 is outputted via the I-V converter 12, the
amplifier 13, and the A/D converter 14 to the control unit 20.
Configuration of Wavelength Tunable Interference Filter
[0068] The wavelength tunable interference filter 5 incorporated in
the spectroscopic measurement apparatus 1 will now be described
below. FIG. 2 is a plan view showing a schematic configuration of
the wavelength tunable interference filter. FIG. 3 is a
cross-sectional view of the wavelength tunable interference filter
taken along the line III-III in FIG. 2.
[0069] The wavelength tunable interference filter 5 of the present
embodiment is what is called a Fabry-Perot etalon. The wavelength
tunable interference filter 5 includes a fixed substrate 51, which
correspond to the substrate in an embodiment according to the
invention, and a movable substrate 52, as shown in FIGS. 2 and 3.
Each of the fixed substrate 51 and the movable substrate 52 is
made, for example, of any of a variety of glass materials, quartz,
or silicon. A first bonding portion 513 of the fixed substrate 51
and a second bonding portion 523 of the movable substrate 52 are
bonded to each other via a bonding film 53 formed, for example, of
a plasma polymerization film primarily made, for example, of
siloxane so that the fixed substrate 51 and the movable substrate
52 form an integrated unit.
[0070] A fixed reflection film 54 (first reflection film) is
provided on the fixed substrate 51, and a movable reflection film
55 (second reflection film) is provided on the movable substrate
52. The fixed reflection film 54 and the movable reflection film 55
are disposed so that they face each other with an
inter-reflection-film gap G1 (gap) therebetween. The wavelength
tunable interference filter 5 is provided with an electrostatic
actuator 56, which is used to adjust (change) the size of the
inter-reflection-film gap G1. The electrostatic actuator 56 is
formed of a fixed electrode 561 provided on the fixed substrate 51
and a movable electrode 562 provided on the movable substrate 52.
The fixed electrode 561 and the movable electrode 562 face each
other with an inter-electrode gap therebetween and function as the
electrostatic actuator 56.
[0071] In the following description, a plan view viewed in the
substrate thickness direction of the fixed substrate 51 or the
movable substrate 52, that is, a plan view in which the wavelength
tunable interference filter 5 is viewed in the direction in which
the fixed substrate 51, the bonding film 53, and the movable
substrate 52 are layered on each other is referred to as a filter
plan view.
Configuration of Fixed Substrate
[0072] The fixed substrate 51 has an electrode placement groove 511
and a reflection film attachment portion 512 formed therein in an
etching process, as shown in FIG. 3. The fixed substrate 51 is
formed to be thicker than the movable substrate 52 and is therefore
not bent by an electrostatic attractive force produced when a
voltage is applied between the fixed electrode 561 and the movable
electrode 562 or internal stress produced in the fixed electrode
561.
[0073] Further, a cutout 514 is formed at a vertex C1 of the fixed
substrate 51 and a movable electrode pad 564P, which will be
described later, is exposed on the side of the fixed substrate 51
of the wavelength tunable interference filter 5, as shown in FIG.
2.
[0074] The electrode placement groove 511 is formed so that it has
an annular shape around a plan-view center point O of the fixed
substrate 51 in the filter plan view. The reflection film
attachment portion 512 is formed so that it has a substantially
cylindrical shape and protrudes from a central portion of the
electrode placement groove 511 in the plan view described above
toward the movable substrate 52. A groove bottom surface of the
electrode placement groove 511 forms an electrode attachment
surface 511A, on which the fixed electrode 561 (corresponding to
the first electrode according to an embodiment of the invention) is
disposed. Further, the front end surface of the thus protruding
reflection film attachment portion 512 forms a reflection film
attachment surface 512A.
[0075] Further, electrode drawing grooves 511B, which extend from
the electrode placement groove 511 toward the vertices C1 and C2 at
the outer circumferential edge of the fixed substrate 51, are
provided in the fixed substrate 51.
[0076] The fixed electrode 561 is disposed on the electrode
attachment surface 511A of the electrode placement groove 511.
[0077] More specifically, the fixed electrode 561 is formed so that
it has a frame-like shape (annular shape in the present embodiment)
that surrounds the fixed reflection film 54. Further, the fixed
electrode 561 overlaps with the following two areas of the
electrode attachment surface 511A: an area facing a movable portion
521 of the movable substrate 52, which will be described later; and
an area facing a holding portion 522. That is, the fixed electrode
561 is disposed so that it covers the position corresponding to a
sidewall portion 521B (corresponding to the outer circumferential
edge of the movable portion according to an embodiment of the
invention) of the movable portion 521, which will be described
later, in the filter plan view. Further, in other words, the fixed
electrode 561 is configured so that the shortest distance between
the outer circumferential edges of the fixed reflection film 54 and
the fixed electrode 561 is greater than the shortest distance
between the outer circumferential edges of the fixed reflection
film 54 and the sidewall portion 521B of the movable portion 521 in
the filter plan view.
[0078] The fixed electrode 561 has a light absorbing layer 571 and
a metal layer 572, which are sequentially layered on the fixed
substrate 51.
[0079] The metal layer 572 is made of an electrically conductive,
light blocking metal material and hence does not transmit light.
Examples of the metal material of which the metal layer 572 is made
include Au, Al, Ti, Ag, W, Nb, Ta, Mo, Cu, Ni, Co, Fe, Pt, and
Zn.
[0080] The light absorbing layer 571 suppresses reflection of light
incident through the fixed substrate 51. That is, the light
absorbing layer 571 not only functions as an antireflection layer
that suppresses reflection at the interface between the fixed
substrate 51 and the light absorbing layer 571 but also has a
function of attenuating (absorbing) light incident on the light
absorbing layer 571. Examples of the material of which the light
absorbing layer 571 is made include TiW, TiN, NiCr, TiO.sub.2,
Al.sub.2O.sub.3, MgF.sub.2, Nd.sub.2O.sub.3, and
Ta.sub.2O.sub.5.
[0081] The fixed electrode 561 is formed, for example, by
depositing a film (TiW film, for example) that forms the light
absorbing layer 571 on the fixed substrate 51, further depositing a
film (Au film, for example) that form the metal layer 572, and
patterning the films (TiW film and Au film) in a photolithography
process. Each of the light absorbing layer 571 and the metal layer
572 has a thickness ranging, for example, from 30 to 100 nm.
[0082] A fixed drawn electrode 563 is provided on the fixed
substrate 51 and extends from the outer circumferential edge of the
fixed electrode 561 toward the vertex C2. A front end portion of
the thus extending fixed drawn electrode 563 (portion located at
vertex C2 of fixed substrate 51) forms a fixed electrode pad 563P,
which is connected to the voltage controller 15. The fixed
electrode pad 563P is connected, for example, to GND (ground) in
the voltage controller 15.
[0083] An insulating film for ensuring insulation between the fixed
electrode 561 and the movable electrode 562 may be layered on the
fixed electrode 561.
[0084] The reflection film attachment portion 512 is coaxial with
the electrode placement groove 511, has a substantially cylindrical
shape having a diameter smaller than that of the electrode
placement groove 511, and has the reflection film attachment
surface 512A facing the movable substrate 52, as described
above.
[0085] The fixed reflection film 54 is disposed on the reflection
film attachment surface 512A, as shown in FIG. 3.
[0086] The fixed reflection film 54 disposed on the reflection film
attachment surface 512A extends onto the electrode placement groove
511 in the filter plan view, as shown in FIG. 3. Part of an outer
circumferential portion of the fixed reflection film 54 covers an
inner circumferential portion of the fixed electrode 561 (area
within predetermined dimension from inner circumferential edge
thereof).
[0087] In the configuration described above, an effective diameter
of light incident on the fixed reflection film 54 is defined by the
inner circumferential edge of the fixed electrode 561. That is, the
fixed electrode 561 functions as an aperture.
[0088] An area where the fixed electrode 561 and the fixed
reflection film 54 overlap with each other (overlapping area) is
formed on the electrode attachment surface 511A. Since the
electrode attachment surface 511A is disposed in a position farther
away from the movable substrate 52 than the reflection film
attachment surface 512A in the substrate thickness direction, the
fixed reflection film 54 in the overlapping area will not come into
contact with the movable substrate 52 or any other film on the
movable substrate 52 when the movable substrate 52 is displaced
toward the fixed substrate 51.
[0089] The fixed reflection film 54 is electrically conductive and
can be formed, for example, of a metal film made, for example, of
Ag, Bi, or Nd or an alloy film made, for example, of an Ag alloy.
The fixed reflection film 54 is in contact with the fixed electrode
561, which is a GND electrode, and hence serves as GND.
[0090] The fixed reflection film 54 may instead be formed of a
reflection film formed of a metal film (or alloy film) layered on a
dielectric multilayer film, for example, having a high refractive
layer made of TiO.sub.2 and a low refractive layer made of
SiO.sub.2, a reflection film formed of a dielectric multilayer film
layered on a metal film (or alloy film), or a reflection film that
is a laminate of a single-layer refractive layer (made, for
example, of TiO.sub.2 or SiO.sub.2) and a metal film (or alloy
film).
[0091] An antireflection film may be formed on a light incident
surface of the fixed substrate 51 (surface on which fixed
reflection film 54 is not provided) in a position corresponding to
the fixed reflection film 54. The antireflection film can be formed
by alternately layering a low refractive index film and a high
refractive index film on each other, and the thus formed
antireflection film decreases visible light reflectance of the
surface of the fixed substrate 51 whereas increasing visible light
transmittance thereof.
[0092] Part of the surface of the fixed substrate 51 that faces the
movable substrate 52, specifically, the surface where the electrode
placement groove 511, the reflection film attachment portion 512,
or the electrode drawing grooves 511B are not formed in the etching
process forms the first bonding portion 513. A first bonding film
531 is provided on the first bonding portion 513 and bonded to a
second bonding film 532 provided on the movable substrate 52,
whereby the fixed substrate 51 and the movable substrate 52 are
bonded to each other as described above.
Configuration of Movable Substrate
[0093] The movable substrate 52 has the movable portion 521, which
has a circular shape around the plan-view center point O, the
holding portion 522, which is coaxial with the movable portion 521
and holds the movable portion 521, and a substrate outer
circumferential portion 525, which is provided in an area outside
the holding portion 522, in the filter plan view as shown in FIG.
2.
[0094] Further, the movable substrate 52 has a cutout 524 formed in
correspondence with the vertex C2, and the cutout 524 exposes the
fixed electrode pad 563P when the wavelength tunable interference
filter 5 is viewed from the side where the movable substrate 52 is
present, as shown in FIG. 2.
[0095] The movable portion 521 is formed to be thicker than the
holding portion 522. In the present embodiment, for example, the
movable portion 521 is formed to be as thick as the movable
substrate 52. The movable portion 521 is formed so that it has a
diameter greater than at least the diameter of the outer
circumferential edge of the reflection film attachment surface 512A
in the filter plan view. The movable electrode 562 and the movable
reflection film 55 are disposed on the movable portion 521.
[0096] An antireflection film may be formed on the surface of the
movable portion 521 that faces away from the fixed substrate 51, as
in the case of the fixed substrate 51. The antireflection film can
be formed by alternately layering a low refractive index film and a
high refractive index film on each other, and the thus formed
antireflection film decreases visible light reflectance of the
surface of the movable substrate 52 whereas increasing visible
light transmittance thereof.
[0097] The movable reflection film 55 is disposed on a central
portion of a movable surface 521A of the movable portion 521 so
that the movable reflection film 55 faces the fixed reflection film
54 via the inter-reflection-film gap G1. The movable reflection
film 55 has the same configuration as that of the fixed reflection
film 54 described above.
[0098] The movable reflection film 55 is connected to GND with a
wiring line that is not shown and hence has the same potential as
the potential at the fixed reflection film 54. The movable
electrode 562 is disposed on the movable surface 521A in an area
around the movable reflection film 55 and has an annular shape
around the plan-view center point O. The movable electrode 562
faces part the fixed electrode 561 via the inter-electrode gap G2.
The area where the fixed electrode 561 and the movable electrode
562 face each other forms the electrostatic actuator 56, which
corresponds to the gap changer according to an embodiment of the
invention.
[0099] The movable electrode 562 has alight absorbing layer 581 and
a metal layer 582, which are sequentially layered on the movable
substrate 52, as in the case of the fixed electrode 561. The light
absorbing layer 581 and the metal layer 582 are made of the same
materials as those of the light absorbing layer 571 and the metal
layer 572 of the fixed electrode 561, respectively.
[0100] A movable drawn electrode 564 is provided on the movable
substrate 52 and extends from the outer circumferential edge of the
movable electrode 562 toward a vertex C1 of the movable substrate
52. A front end portion of the thus extending movable drawn
electrode 564 (portion located at vertex C1 of movable substrate
52) forms the movable electrode pad 564P, which is connected to the
voltage controller 15. The voltage controller 15 applies a drive
voltage to the movable electrode 562.
[0101] In the present embodiment, the size of the inter-electrode
gap G2 is greater than the size of the inter-reflection-film gap G1
as described above by way of example, but the dimensions of the
gaps are not necessarily set this way. For example, when the light
under measurement is infrared light or far infrared light, the size
of the inter-reflection-film gap G1 may be greater than the size of
the inter-electrode gap G2 depending on the wavelength region of
the light under measurement.
[0102] An insulating film for ensuring insulation between the fixed
electrode 561 and the movable electrode 562 may be layered on the
movable electrode 562.
[0103] The holding portion 522 is a diaphragm that surrounds the
movable portion 521 and is formed to be thinner than the movable
portion 521. The thus configured holding portion 522 is more
readily bent than the movable portion 521 and can therefore
displace the movable portion 521 toward the fixed substrate 51
under a small amount of electrostatic attractive force. Since the
movable portion 521 is thicker and therefore more rigid than the
holding portion 522, the movable portion 521 is not deformed when
the holding portion 522 is attracted toward the fixed substrate 51
under an electrostatic attractive force. The movable reflection
film 55 disposed on the movable portion 521 will therefore not be
bent, whereby the fixed reflection film 54 and the movable
reflection film 55 can be consistently maintained parallel to each
other.
[0104] In the present embodiment, the diaphragm-shaped holding
portion 522 is presented by way of example, but the holding portion
522 is not necessarily formed of a diaphragm. For example,
beam-shaped holding portions disposed at equal angular intervals
may be provided around the plan-view center point O.
[0105] The substrate outer circumferential portion 525 is disposed
in an area outside the holding portion 522 in the filter plan view,
as described above. The surface of the substrate outer
circumferential portion 525 that faces the fixed substrate 51 forms
the second bonding portion 523, which faces the first bonding
portion 513. The second bonding film 532 is disposed on the second
bonding portion 523 and bonded to the first bonding film 531,
whereby the fixed substrate 51 and the movable substrate 52 are
bonded to each other as described above.
Configurations of Detector, I-V Converter, Amplifier, A/D
Converter, and Voltage Controller
[0106] Referring back to FIG. 1, the detector 11 receives (detects)
light having passed through a light interference area where the
reflection films 54 and 55 of the wavelength tunable interference
filter 5 face each other and outputs a detection signal based on
the amount of received light.
[0107] The I-V converter 12 converts the detection signal inputted
from the detector 11 into a voltage value and outputs the voltage
value to the amplifier 13.
[0108] The amplifier 13 amplifies the voltage according to the
detection signal (detected voltage) inputted from the I-V converter
12.
[0109] The A/D converter 14 converts the detected voltage (analog
signal) inputted from the amplifier 13 into a digital signal and
outputs the digital signal to the control unit 20.
[0110] The voltage controller 15 is connected to the fixed drawn
electrode 563 (fixed electrode pad 563P) and the movable drawn
electrode 564 (movable electrode pad 564P) of the wavelength
tunable interference filter 5. The voltage controller 15 applies a
voltage to the fixed electrode pad 563P and the movable electrode
pad 564P and hence applies the voltage to the electrostatic
actuator 56 under the control of the control unit 20. Specifically,
the voltage controller 15 connects the fixed electrode pad 563P to
a ground circuit to set the fixed electrode pad 563P at a ground
potential. On the other hand, the voltage controller 15 sets the
movable electrode pad 564P at a drive potential under the control
of the control unit 20. As a result, an electrostatic attractive
force is produced between the fixed electrode 561 and the movable
electrode 562 of the electrostatic actuator 56 and displaces the
movable portion 521 toward the fixed substrate 51. The dimension of
the inter-reflection-film gap G1 is thus set at a predetermined
value.
Configuration of Control Unit
[0111] The control unit 20 is, for example, a combination of a CPU,
a memory, and other components and controls the overall action of
the spectroscopic measurement apparatus 1. The control unit 20
includes a filter drive section 21, a light amount acquisition
section 22, and a spectroscopic measurement section 23, as shown in
FIG. 1.
[0112] The control unit 20 further includes a storage section 30
that stores a variety of data. The storage section specifically
stores V-.lamda. data according to which the electrostatic actuator
56 is controlled.
[0113] The recorded V-.lamda. data contains a voltage and a peak
wavelength of light that passes through the wavelength tunable
interference filter 5 when the voltage is applied to the
electrostatic actuator 56.
[0114] The filter drive section 21 sets a target wavelength of
light to be extracted through the wavelength tunable interference
filter 5 and reads a target voltage value corresponding to the set
target wavelength from the V-.lamda. data stored in the storage
section 30. The filter drive section 21 then outputs a control
signal to the voltage controller 15 to cause it to apply the read
target voltage value. As a result, the voltage controller 15
applies a voltage having the target voltage value to the
electrostatic actuator 56.
[0115] The light amount acquisition section 22 acquires the amount
of light of the target wavelength having passed through the
wavelength tunable interference filter 5 based on the amount of
light acquired with the detector 11.
[0116] The spectroscopic measurement section 23 measures spectral
characteristics of the light under measurement based on the amount
of light acquired by the light amount acquisition section 22.
[0117] A spectroscopic measurement method used in the spectroscopic
measurement section 23 is, for example, a method for measuring an
optical spectrum by using the amount of light detected for a
wavelength under measurement with the detector 11 as the amount of
light of the wavelength under measurement or a method for
estimating an optical spectrum based on the amounts of light of a
plurality of wavelengths under measurement.
[0118] An example of the method for estimating an optical spectrum
includes producing a measured spectrum matrix in which the amounts
of light of a plurality of wavelengths under measurement are the
matrix elements and operating a predetermined conversion matrix on
the measured spectrum matrix to estimate an optical spectrum of the
light under measurement. In this case, a plurality of types of
sample light having known optical spectra are measured by using the
spectroscopic measurement apparatus 1, and the conversion matrix is
set so that a matrix produced by operating the conversion matrix on
a measured spectrum matrix produced based on the measured amounts
of light minimally deviates from the known optical spectra.
Advantageous Effects of First Embodiment
[0119] In the wavelength tunable interference filter 5 according to
the present embodiment, the fixed electrode 561, which has an
annular (frame-like) shape that surrounds the fixed reflection film
54, is provided on the fixed substrate 51. The fixed electrode 561
is formed by sequentially layering the light absorbing layer 571
and the optically opaque metal layer 572.
[0120] The thus configured fixed electrode 561 can function as an
aperture because the inner circumferential edge of the fixed
electrode 561 can define an effective diameter of light incident on
the fixed reflection film 54. Further, even when part of light
incident on the fixed substrate 51 passes therethrough and impinges
on the fixed electrode 561, the antireflection capability of the
light absorbing layer 571 prevents the incident light from being
reflected off the light absorbing layer 571 but causes the incident
light to enter the light absorbing layer 571. The light absorbing
layer 571 then absorbs part of the incident light and can hence
attenuate the incident light. Further, even when the light having
entered the light absorbing layer 571 is reflected off the metal
layer 572, the reflected light passes again through the light
absorbing layer 571, whereby the reflected light is further
absorbed and hence attenuated.
[0121] ***As described above, the fixed electrode 561 of the
present embodiment can not only function as an aperture but also
attenuate any light possibly incident on the fixed electrode 561,
preventing generation of stray light. Therefore, a decrease in
spectroscopic precision of the wavelength tunable interference
filter 5 can be suppressed, and the amount of light of a target
wavelength can be received with high precision in the optical
module 10. The spectroscopic measurement apparatus 1 can therefore
perform accurate spectroscopic measurement on the object X under
measurement.
[0122] In the wavelength tunable interference filter 5 of the
present embodiment, the inner circumferential portion of the fixed
electrode 561 overlaps with the outer circumferential portion of
the fixed reflection film 54. No gap is therefore created between
the fixed electrode 561 and the fixed reflection film 54, avoiding
an inconvenient situation in which light through a possible gap
between the fixed electrode 561 and the fixed reflection film 54
forms stray light.
[0123] In the present embodiment, in particular, the
inter-substrate distance in the area where the fixed electrode 561
and the fixed reflection film 54 overlap with each other
(overlapping area) is greater than the inter-substrate distance at
the center (plan-view center point O) of the area where the fixed
reflection film 54 and the movable reflection film 55 face each
other (film-facing area).
[0124] Therefore, driving the electrostatic actuator 56 will not
lead to an inconvenient situation in which the movable electrode
562 on the movable portion 521 comes into contact with the fixed
reflection film 54 on the fixed electrode 561.
[0125] In the wavelength tunable interference filter 5 of the
present embodiment, the fixed electrode 561 overlaps with both the
movable portion 521 and the holding portion 522 in the filter plan
view. That is, the fixed electrode 561 is disposed so that it
covers the sidewall portion 521B of the movable portion 521 or the
boundary between the outer circumferential edge of the movable
portion 521 and the holding portion 522. The configuration can
prevent light from being incident on the sidewall portion 521B and
can hence prevent stray light from being generated when light
incident on the sidewall portion 521B is irregularly reflected off
the sidewall portion 521B.
[0126] In the wavelength tunable interference filter 5 of the
present embodiment, the fixed reflection film 54 is electrically
conductive and electrically connected to the fixed electrode 561.
Any electrostatic charge accumulated on the fixed reflection film
54 can therefore be removed. Therefore, when the size of the gap
between the reflection films is changed, no undesirable
electrostatic attractive force acts on the reflection films,
whereby a decrease in reflection film drive precision due to a
possible electrostatic attractive force can be avoided.
[0127] In the wavelength tunable interference filter 5 of the
present embodiment, the fixed electrode 561 functions not only as a
drive electrode that forms the electrostatic actuator 56 but also
as an aperture. The configuration eliminates a need to provide the
drive electrode and the aperture separately, whereby the size of
the wavelength tunable interference filter 5 can be reduced.
[0128] In the wavelength tunable interference filter 5 of the
present embodiment, the fixed substrate 51 is made of a glass
material. On the other hand, the light absorbing layer 571 is made,
for example, of TiW, TiN, NiCr, TiO.sub.2, Al.sub.2O.sub.3,
MgF.sub.2, Nd.sub.2O.sub.3, or Ta.sub.2O.sub.5 and formed on the
fixed substrate 51. Further, the metal layer 572 is formed on the
light absorbing layer 571.
[0129] The thus formed light absorbing layer 571 is in intimate
contact with the metal layer 572 and the fixed substrate 51, which
is made of a glass material, whereby the metal layer 572 and the
fixed substrate 51 can be reliably connected to each other.
Further, the light absorbing layer 571 can suppress reflection at
the interface between the light absorbing layer 571 and the fixed
substrate 51, whereby generation of stray light can be more
effectively suppressed.
[0130] In the wavelength tunable interference filter 5 of the
present embodiment, the metal layer 572 is made of a highly
electrically-conductive, light-blocking material, such as Au, Al,
Ti, Ag, W, Nb, Ta, Mo, Cu, Ni, Co, Fe, Pt, or Zn. The metal layer
572 can therefore be preferably used as an electrode and an
aperture.
Second Embodiment
[0131] A second embodiment according to the invention will next be
described with reference to the drawings.
[0132] The present embodiment differs from the first embodiment
described above in that the fixed electrode covers the sidewall of
the reflection film attachment portion 512.
[0133] FIG. 4 is a cross-sectional view showing a schematic
configuration of a wavelength tunable interference filter 5A of the
second embodiment according to the invention. The wavelength
tunable interference filter 5A basically has the same configuration
as that of the wavelength tunable interference filter 5 of the
first embodiment except the difference described above. In the
following description of the present embodiment, the components
having been already described have the same reference characters
and descriptions thereof will be omitted or simplified.
[0134] A fixed electrode 561A has an inner circumferential edge
located on the reflection film attachment surface 512A and covers a
sidewall portion 512B of the reflection film attachment portion
512, as shown in FIG. 4.
[0135] Further, a fixed reflection film 54A is provided so that an
outer circumferential portion thereof covers an inner
circumferential portion of the fixed electrode 561A, which is
provided on the electrode attachment surface 511A, in the filter
plan view.
Advantageous Effect of Second Embodiment
[0136] In the wavelength tunable interference filter 5A of the
present embodiment, the fixed reflection film 54A located inside
the inner circumferential edge of the fixed electrode 561A is
uniformly separated from the movable reflection film 55. The
wavelength tunable interference filter 5A can therefore transmit
light of a desired target wavelength more precisely, whereby the
spectroscopic precision can be further improved.
Third Embodiment
[0137] A third embodiment according to the invention will next be
described with reference to the drawings.
[0138] The present embodiment differs from the first embodiment
described above in that the fixed electrode 561 is provided on one
surface of the fixed substrate 51 and a stress relaxation film is
provided on the other surface of the fixed substrate 51 with the
stress relaxation film facing the fixed electrode 561 through the
fixed substrate 51.
[0139] FIG. 5 is a cross-sectional view showing a schematic
configuration of a wavelength tunable interference filter 5B of the
third embodiment according to the invention.
[0140] In the wavelength tunable interference filter 5B of the
present embodiment, a stress relaxation film 59 is provided on the
surface of the fixed substrate 51 that faces away from the surface
on which the fixed electrode 561 is provided and is located so that
the stress relaxation film 59 coincides with the fixed electrode
561 in the filter plan view, as shown in FIG. 5. The stress
relaxation film 59 has a first light absorbing layer 591, a metal
layer 592, and a second light absorbing layer 593, which are
sequentially layered on the fixed substrate 51.
[0141] The metal layer 592 is made of the same material as that of
the metal layer 572 and has the same thickness as that of the metal
layer 572. The metal layer 592 therefore exerts internal stress
having the following magnitude and direction on the fixed substrate
51: The magnitude is the same as that of internal stress exerted on
the fixed substrate 51 by the metal layer 572: but the direction is
opposite to that of the internal stress exerted by the metal layer
572, whereby the overall internal stress exerted on the fixed
substrate 51 is relaxed (canceled)
[0142] The first light absorbing layer 591, which is made of the
same material as that of the light absorbing layer 571, suppresses
reflection of light incident through the fixed substrate 51 and
attenuates the incident light.
[0143] The second light absorbing layer 593, which is also made of
the same material as that of the light absorbing layer 571, and
when part of incident light incident on the wavelength tunable
interference filter is incident on the stress relaxation film 59,
the second light absorbing layer 593 suppresses reflection of the
incident light and attenuates the incident light.
Advantageous Effects in Third Embodiment
[0144] In the wavelength tunable interference filter 5B of the
present embodiment, the stress relaxation film 59 is provided on
the surface of the fixed substrate 51 that faces away from the
surface on which the fixed electrode 561 is provided with the
stress relaxation film 59 facing the fixed electrode 561 through
the fixed substrate 51, and the stress relaxation film 59 has the
two light absorbing layers 591 and 593 and the metal layer 592
disposed between the light absorbing layers 591 and 593. The metal
layer 592 has the same configuration as that of the metal layer 572
of the fixed electrode 561, and each of the two light absorbing
layers 591 and 593 has the same configuration as that of the light
absorbing layer 571.
[0145] The metal layer 592 can therefore cancel the internal stress
in the metal layer 572 of the fixed electrode 561 and hence
suppress deformation of the fixed substrate 51.
[0146] Further, the first light absorbing layer 591 can suppress
reflection of light incident through the fixed substrate 51 and
attenuate the incident light. Therefore, even when part of light
incident on the fixed electrode 561 is not sufficiently attenuated
but reflected off the fixed electrode 561, the reflected light is
incident on the stress relaxation film 59 and attenuated therein,
whereby stray light can be further suppressed.
[0147] Moreover, even when part of the light incident on the
wavelength tunable interference filter 5B is incident on the stress
relaxation film 59, the second light absorbing layer 593 can
attenuate light reflected off the metal film 592 and hence suppress
stray light.
[0148] As described above, the stress relaxation film 59 can relax
stress produced by the fixed electrode 561 and can more reliably
suppress generation of stray light.
[0149] In the present embodiment, since the metal layer 592 is made
of the same material as that of the metal layer 572 and has the
same shape as that of the metal layer 572, the metal layer 592 can
be readily formed so that it has a stress relaxation capability.
However, the metal layer 592 is not necessarily made of the same
material as that of the metal layer 572 or does not necessarily
have the same shape as that of the metal layer 572 but may be made
of an arbitrary material and may have an arbitrary shape as long as
the resultant metal film can exert stress that relaxes the stress
produced by the metal layer 572 on the fixed substrate 51. In
particular, the diameter of the inner circumferential edge of the
stress relaxation film 59 may be set to be smaller than the
diameter of the reflection film attachment surface 512A. In this
case, the range through which light is incident on the reflection
film 54 is defined so that the light is incident only on an area
where the dimension of the gap G1 between the reflection films 54
and 55 is substantially the same.
Fourth Embodiment
[0150] A fourth embodiment according to the invention will next be
described with reference to the drawings.
[0151] The present embodiment differs from the first embodiment
described above in that the movable electrode is formed of a
plurality of partial electrodes.
[0152] FIG. 6 is a cross-sectional view showing a schematic
configuration of a wavelength tunable interference filter 5C of the
fourth embodiment according to the invention.
[0153] The wavelength tunable interference filter 5C of the present
embodiment includes the following two movable electrodes on the
movable surface 521A of the movable substrate 52 as shown in FIG.
6: a first movable electrode 562A having a substantially C-like
shape around the plan-view center point O; and a second movable
electrode 562B having a substantially C-like shape and provided in
an area outside the first movable electrode 562A in the filter plan
view.
[0154] The first movable electrode 562A and the second movable
electrode 562B are spaced apart from each other. That is, in the
present embodiment, a dual-electrode structure in which inner and
outer two movable electrodes are disposed in the filter plan view
is provided.
[0155] Although not shown, the first movable electrode 562A is
provided with a movable drawn electrode extending from the outer
circumferential edge of the first movable electrode 562A toward one
of the vertices of the movable substrate 52, and a front end
portion of the thus extending movable drawn electrode (a portion
located at the vertex of the movable substrate 52) forms a movable
electrode pad connected to the voltage controller 15.
[0156] Similarly, the second movable electrode 562B is provided
with a movable drawn electrode extending from the outer
circumferential edge of the second movable electrode 562B toward
another vertex of the movable substrate 52, and a front end portion
of the thus extending movable drawn electrode forms a movable
electrode pad connected to the voltage controller 15.
[0157] The fixed electrode 561 is an electrode common to the first
movable electrode 562A and the second movable electrode 562B and is
connected, for example to the GND circuit in the voltage controller
15. The area where the fixed electrode 561 and the first movable
electrode 562A face each other forms a first electrostatic actuator
56A, and the area where the fixed electrode 561 and the second
movable electrode 562B face each other forms a second electrostatic
actuator 56B.
[0158] In the thus configured wavelength tunable interference
filter 5C, different voltages can be applied to the first movable
electrode 562A and the second movable electrode 562B.
Advantageous Effects of Fourth Embodiment
[0159] In the wavelength tunable interference filter 5C of the
present embodiment, the movable electrode 562 is formed of the
first movable electrode 562A and the second movable electrode 562B,
that is, a plurality of partial electrodes, and the fixed electrode
561 serves as an electrode common to the partial electrodes. As a
result, the fixed electrode 561 is allowed to function as an
aperture and can suppress stray light, as in the first to third
embodiments. In addition, setting the first movable electrode 562A
and the second movable electrode 562B at different potentials
allows the first electrostatic actuator 56A and the second
electrostatic actuator 56B to produce different electrostatic
attractive forces, whereby the dimension of the gap between the
reflection films can be more precisely controlled for
high-precision spectroscopy.
Fifth Embodiment
[0160] A fifth embodiment according to the invention will next be
described with reference to the drawings.
[0161] The present embodiment differs from the first embodiment
described above in that a mirror electrode 551 is connected to the
movable reflection film 55.
[0162] FIG. 7 is a plan view showing a schematic configuration of a
wavelength tunable interference filter 5D of the present
embodiment.
[0163] FIG. 8 is a cross-sectional view of the wavelength tunable
interference filter taken along the line VIII-VIII in FIG. 7.
[0164] In the wavelength tunable interference filter 5D of the
present embodiment, the movable electrode 562 has a substantially
C-like shape. On the movable substrate 52 is provided a mirror
electrode 551 connected to the movable reflection film 55, passing
through the opening of the C-shaped movable electrode 562, and
extending to a vertex C3. When the movable reflection film 55 is
formed of a metal film made, for example, of an Ag alloy, the
mirror electrode 551 can be formed simultaneously with the movable
reflection film 55.
[0165] Further, a front end portion of the mirror electrode 551
(portion located at vertex C3 of movable substrate 52) forms a
mirror electrode pad 551P, which is connected to the voltage
controller 15.
[0166] The voltage controller 15 connects the fixed electrode pad
563P and the mirror electrode pad 551P to the ground circuit to set
the two pads at the ground potential (0 V).
[0167] The fixed substrate 51 has a cutout 515 formed at the vertex
C3, and the cutout 515 exposes the mirror electrode pad 551P.
Advantageous Effect of Fifth Embodiment
[0168] In the present embodiment, the mirror electrode 551, which
is connected to the movable reflection film 55, is set at the
ground potential. The movable reflection film 55 will therefore not
be charged. As a result, generation of an electrostatic attractive
force between the reflection films 54 and 55 can be more reliably
prevented, whereby the electrostatic actuator 56 can be driven more
precisely.
[0169] The present embodiment has been described with reference to
the case where the voltage controller 15 connects the pads 551P and
563P to the ground circuit to set them at the ground potential, but
the pads 551P and 563P are not necessarily set at the ground
potential. For example, the pads 551P and 563P may be set at a
predetermined common potential. In this case as well, the fixed
reflection film 54 and the movable reflection film 55 can have the
same amount of charge, whereby no electrostatic attractive force
will be generated.
Variation of Fifth Embodiment
[0170] The above fifth embodiment has been described with reference
to the case where the voltage controller 15 connects the pads 551P
and 563P to the ground circuit to set the fixed reflection film 54
and the movable reflection film 55 at the ground potential, but the
pads 551P and 563P are not necessarily connected to the ground
circuit.
[0171] For example, the voltage controller 15 may connect the pads
551P and 563P to a capacitance detection circuit the voltage
controller 15.
[0172] In this case, the capacitance detection circuit can apply a
high-frequency voltage between the fixed reflection film 54 and the
movable reflection film 55 to detect the capacitance between the
reflection films 54 and 55, that is, the dimension of the gap G1
between the reflection films 54 and 55.
Sixth Embodiment
[0173] A sixth embodiment according to the invention will next be
described with reference to the drawings.
[0174] In the spectroscopic measurement apparatus 1 of the first
embodiment described above, the wavelength tunable interference
filter 5 is directly accommodated in the optical module 10. Some
optical modules have complicated configurations, and it is in some
cases difficult to directly accommodate the wavelength tunable
interference filter 5 particularly in a compact optical module. In
the present embodiment, a description will be made of an optical
filter device that allows the wavelength tunable interference
filter 5 to be readily accommodated in such a compact optical
module.
[0175] FIG. 9 is a cross-sectional view showing a schematic
configuration of an optical filter device of the sixth embodiment
according to the invention.
[0176] An optical filter device 600 includes an enclosure 610,
which accommodates the wavelength tunable interference filter 5, as
shown in FIG. 9.
[0177] The enclosure 610 has a bottom 611, a lid 612, a
light-exiting-side glass window 613 (light guide portion), and a
light-incident-side glass window 614 (light guide portion).
[0178] The bottom 611 is formed, for example, of a single-layer
ceramic substrate. The movable substrate 52 of the wavelength
tunable interference filter 5 is disposed on the bottom 611.
Further, a light exiting hole 611A is formed as an opening through
the bottom 611 in an area facing the reflection films (fixed
reflection film 54 and movable reflection film 55) of the
wavelength tunable interference filter 5. The light exiting hole
611A is a window through which light separated and extracted by the
wavelength tunable interference filter 5 passes, and the
light-exiting-side glass window 613 is bonded to the bottom 611 in
a portion around the light exiting hole 611A. The
light-exiting-side glass window 613 can be bonded to the bottom
611, for example, in a glass frit bonding process in which a glass
raw material is melted at a high temperature and the molten glass
material is rapidly cooled to produce glass frit that is formed of
rapidly cooled glass pieces.
[0179] Terminals 616 are provided on the upper surface of the
bottom 611 (inside enclosure 610), and the number of terminals 616
corresponds to the electrode pads 563P and 564P of the wavelength
tunable interference filter 5. A through hole 615 is formed through
the bottom 611 in a position where each of the terminals 616 is
disposed, and each of the terminals 616 is connected via the
through hole 615 to a connection terminal 617, which is provided on
the lower surface of the bottom 611 (outside enclosure 610).
[0180] The bottom 611 has a sealer 619 provided along the outer
circumferential edge thereof, and the sealer 619 is boned to the
lid 612.
[0181] The lid 612 has a sealer 620, which is bonded to the sealer
619 of the bottom 611, a sidewall 621, which continuously extends
from the sealer 620 upward in a direction away from the bottom 611,
and a top plate 622, which covers the fixed substrate 51 of the
wavelength tunable interference filter 5, as shown in FIG. 9. The
lid 612 can be made of an alloy, such as kovar, or a metal.
[0182] The lid 612 is boned to the bottom 611 by bonding the sealer
620 to the sealer 619 of the bottom 611, for example, in a laser
sealing process. A light incident hole 612A is formed as an opening
through the top plate 622 of the lid 612 in correspondence with the
area where the reflection films 54 and 55 of the wavelength tunable
interference filter 5 face each other. The light incident hole 612A
is a window through which light that is desired to undergo
spectroscopic operation performed by the wavelength tunable
interference filter 5 (light under measurement) passes, and the
light-incident-side glass window 614 is bonded to the lid 612 in a
portion around the light incident hole 612A.
Advantageous Effects of Sixth Embodiment
[0183] In the optical filter device 600 of the present embodiment,
light having passed through the fixed substrate 51 will not be
reflected off the area where the fixed electrode 561 is formed, and
no stray light will therefore be generated from any possible light
reflected off the inner wall of the enclosure 610, as in the first
embodiment described above.
[0184] Further, in the optical filter device 600 of the present
embodiment, since the enclosure 610 protects the wavelength tunable
interference filter 5, the wavelength tunable interference filter 5
will not be damaged due to external factors. The wavelength tunable
interference filter will therefore not be damaged due to impact and
other types of interaction with other members when the wavelength
tunable interference filter 5 undergoes installation and
maintenance.
[0185] Moreover, for example, when the wavelength tunable
interference filter 5 manufactured in a factory is transported, for
example, to an assembly line where an optical module or an
electronic apparatus is assembled, the wavelength tunable
interference filter 5 protected by the optical filter device 600
can be safely transported.
[0186] Further, since the optical filter device 600 is provided
with the exposed connection terminals 617 disposed on the outer
circumferential surface of the enclosure 610, wiring can be readily
performed when the optical filter device 600 is incorporated in an
optical module or an electronic apparatus.
Variation of Sixth Embodiment
[0187] FIG. 10 is a cross-sectional view showing a schematic
configuration of an optical filter device according to a variation
of the sixth embodiment described above.
[0188] An optical filter device 600A includes a ceramic substrate
631, which has a filter accommodation portion 631C, which is a
recess that accommodates the wavelength tunable interference filter
5, and a glass lid 632, which covers the filter accommodation
portion 631C, as shown in FIG. 10. The optical filter device 600A
is configured so that the glass lid 632 is bonded to the ceramic
substrate 631 to seal an internal space 634 with the wavelength
tunable interference filter 5 accommodated in the filter
accommodation portion 631C.
[0189] A light exiting hole 631A is formed as an opening in the
ceramic substrate 631, which faces the glass lid 632, and extends
in the thickness direction of the substrate. A light-exiting-side
glass window 633 is bonded to the ceramic substrate 631 in a
portion around the light exiting hole 631A.
[0190] Further, the ceramic substrate 631 is provided with a
terminal 616, through which electric power is supplied to the
wavelength tunable interference filter 5. A through hole 631B is
further formed through the ceramic substrate 631 in a position
where the terminal 616 is disposed, and the terminal 616 is
connected through the through hole 631B to a connection terminal
617 provided on the lower surface of the ceramic substrate 631.
[0191] In the optical filter device 600A of the present variation,
light incident through the glass lid 632 is incident on the
wavelength tunable interference filter 5, and light separated by
the wavelength tunable interference filter 5 exits through the
light exiting hole 631A. The present variation can also provide the
same advantageous effects as those provided in the sixth embodiment
described above.
[0192] In the optical filter device 600A, the lid on the light
incident side is made of a glass material and can hence transmit
light. Therefore, even when part of incident light is reflected off
the fixed electrode 561 provided in the wavelength tunable
interference filter 5, the reflected light passes through the glass
lid 632 toward the light incident side. No stray light is therefore
generated due to reflection at the fixed electrode 561.
Other Embodiments
[0193] The invention is not limited to the embodiments described
above, but variations, improvements, and other modifications fall
within the scope of the invention to the extent that they can
achieve the advantage of the invention.
[0194] For example, the fixed electrode 561 has a two-layer
configuration in which the light absorbing layer 571 and the metal
layer 572 are sequentially layered on the fixed substrate 51, but
the invention is not necessarily configured this way. The fixed
electrode 561 may have a configuration which has three or more
layers and in which other layers are provided between the fixed
substrate 51 and the light absorbing layer 571 and between the
light absorbing layer 571 and the metal layer 572. For example, a
transparent electrode layer made, for example, of ITO may be
provided between the fixed substrate 51 and the light absorbing
layer 571.
[0195] In each of the embodiments described above, the
configuration in which the inner circumferential portion of the
fixed electrode 561, which serves as an aperture, overlaps with the
outer circumferential portion of the fixed reflection film 54 is
presented by way of example, but the invention is not necessarily
configured this way. For example, the side surface of the inner
circumferential edge of the fixed electrode 561 may be in contact
with the side surface of the outer circumferential edge of the
fixed reflection film 54 so that the portion inside the fixed
electrode 561 forms the fixed reflection film 54.
[0196] Instead, for example, the inner circumferential portion of
the fixed electrode 561, which serves as an aperture, may overlap
with at least part of the outer circumferential portion of the
fixed reflection film 54. In this case as well, the fixed electrode
561 and the fixed reflection film 54 that overlap with each other
produce no portion between the fixed electrode 561 and the fixed
reflection film 54 through which light transmits.
[0197] In each of the embodiments described above, the fixed
electrode 561, which is an aperture electrode, is present on both
sides of the sidewall portion 521B of the movable portion 521,
which is the boundary between the outer circumferential edge of the
movable portion 521 and the holding portion 522, but the invention
is not necessarily configured this way. That is, the fixed
electrode 561 may be provided so that it covers at least an area
around the fixed reflection film 54 or may be provided only in an
area inside the portion facing the holding portion 522 in the
filter plan view.
[0198] Further, the fixed electrode 561 may be provided at least in
an area around the fixed reflection film 54. For example, the fixed
electrode 561 may be provided so that it surrounds part of the
circumference of the fixed reflection film 54. In this case as
well, in the area where the fixed electrode 561 is disposed, the
range of incident light can be defined and generation of stray
light resulting from light reflected off the metal layer 572 of the
fixed electrode 561 can be suppressed.
[0199] The above fifth embodiment has been described with reference
to the case where the movable reflection film 55 is set at the GND
potential for charge removal and the case where the fixed
reflection film 54 and the movable reflection film 55 are allowed
to function as electrodes for electrostatic capacitance detection.
Further, the fixed reflection film 54 and the movable reflection
film 55 may be allowed to function as an electrostatic actuator for
driving themselves.
[0200] In each of the embodiments described above, each of the
reflection films 54 and 55 is electrically conductive but may be
made of a non-electrically-conductive material. For example, each
of the fixed reflection film 54 and the movable reflection film 55
may be formed, for example, of a dielectric multilayer film having
no electrically conductive layer.
[0201] In each of the embodiments described above, the fixed
electrode 561 provided on the fixed substrate 51 serves as an
aperture electrode, but the invention is not necessarily configured
this way. That is, the movable electrode 562 provided on the
movable substrate 52 may serve as an aperture electrode, or each of
the fixed electrode 561 and the movable electrode 562 may serve as
an aperture electrode.
[0202] In each of the embodiments and the variations described
above, the electrostatic actuator is presented as the gap changer
by way of example, but the gap changer is not limited to an
electrostatic actuator. For example, the gap changer may be an
induction actuator having a first induction coil provided in place
of the fixed electrode 561 and a second induction coil or a
permanent magnet provided in place of the movable electrode 562.
The gap changer may instead be any driver capable of changing the
inter-reflection-film gap G1, such as a configuration in which a
piezoelectric device is used to displace the movable portion 521
and a configuration in which the inter-reflection-film gap is
changed based on air pressure.
[0203] In the embodiments and the variations described above, the
wavelength tunable interference filters 5, 5A, 5B, 5C, and 5D, each
of which is a wavelength tunable Fabry-Perot etalon, have been
described, but the invention is not necessarily configured this
way. That is, each of the wavelength tunable interference filters
may be a wavelength-fixed Fabry-Perot etalon including no
electrostatic actuator 56 (gap changer). In this case, the aperture
electrode in each of the embodiments of the invention can be used
as the electrostatic capacitance detection electrode described
above, the charge prevention electrode described above, or other
electrodes for other purposes.
[0204] In the embodiments and the variations described above, each
of the wavelength tunable interference filters 5, 5A, 5B, 5C, and
5D is configured by way of example so that the fixed reflection
film 54, which is a first reflection film, is provided on the fixed
substrate 51 and the movable reflection film 55, which is a second
reflection film, is provided on the movable substrate 52, but the
invention is not necessarily configured this way. For example, each
of the reflection films may not be provided on a substrate. In this
case, for example, after a first electrode and the first reflection
film are provided on one surface of a parallel glass substrate, and
a second electrode and the second reflection film are provided on
the other surface, which is parallel to the one surface, the
parallel glass substrate is etched away, for example, in an etching
process. In this configuration, in which no substrate is provided,
the thickness of the spectroscopic device can be further reduced.
In this case, the dimension of the gap between the reflection films
can be maintained by providing a spacer or any other component
interposed between the first reflection film and the second
reflection film.
[0205] In each of the embodiments described above, the
spectroscopic measurement apparatus 1 is presented as the
electronic apparatus according to an embodiment of the invention by
way of example. The wavelength tunable interference filter 5, the
optical module, and the electronic apparatus according to the
embodiments of the invention are applicable to a variety of fields
as well as the example described above.
[0206] For example, the electronic apparatus according to the
embodiment of the invention is applicable to a colorimetry
apparatus for color measurement.
[0207] FIG. 11 is a block diagram showing an example of a
colorimetry apparatus 400 including the wavelength tunable
interference filter 5.
[0208] The colorimetry apparatus 400 includes a light source
section 410, which outputs light toward an object X under
measurement, a colorimetry sensor 420 (optical module), and a
control section 430 (control unit), which controls overall action
of the colorimetry apparatus 400, as shown in FIG. 11. The
colorimetry apparatus 400 operates as follows: The light outputted
from the light source section 410 is reflected off the object X
under measurement; the colorimetry sensor 420 receives the
reflected light under measurement; and the chromaticity of the
light under measurement, that is, the color of the object X under
measurement is analyzed and measured based on a detection signal
outputted from the colorimetry sensor 420.
[0209] The light source section 410 includes alight source 411 and
a plurality of lenses 412 (FIG. 11 shows only one of them) and
outputs, for example, reference light (white light, for example)
toward the objet X under measurement. The plurality of lenses 412
may include a collimator lens. In this case, in the light source
section 410, the collimator lens parallelizes the reference light
emitted from the light source 411 and outputs the parallelized
reference light through a projection lens (not shown) toward the
objet X under measurement. In the present embodiment, the
colorimetry apparatus 400 including the light source section 410 is
presented by way of example, but the light source section 410 may
not be provided, for example, when the objet X under measurement is
a liquid crystal panel or any other light emitting member.
[0210] The colorimetry sensor 420 includes the wavelength tunable
interference filter 5, the detector 11, which receives light having
passed through the wavelength tunable interference filter 5, and
the voltage controller 15, which controls the voltage applied to
the electrostatic actuator 56 in the wavelength tunable
interference filter 5, as shown in FIG. 11. The colorimetry sensor
420 further includes an optical lens for incident light (not shown)
that is located a position facing the wavelength tunable
interference filter 5 and guides the reflected light reflected off
the objet X under measurement (light under measurement) into the
colorimetry sensor 420. In the colorimetry sensor 420, the
wavelength tunable interference filter 5 separates light of a
predetermined wavelength from the light under measurement incident
through the optical lens for incident light and the detector 11
receives the separated light.
[0211] The control section 430 is the control unit in an embodiment
of the invention and controls overall action of the colorimetry
apparatus 400.
[0212] The control section 430 can, for example, be a
general-purpose personal computer, a personal digital assistant, or
a computer dedicated for colorimetry. The control section 430
includes a light source controller 431, a colorimetry sensor
controller 432, and a colorimetry processor 433, as shown in FIG.
11.
[0213] The light source controller 431 is connected to the light
source section 410 and outputs a predetermined control signal
based, for example, on a user's setting input to the light source
section 410 to cause it to emit white light of predetermined
luminance.
[0214] The colorimetry sensor controller 432 is connected to the
colorimetry sensor 420 and sets the wavelength of light to be
received by the colorimetry sensor 420 based, for example, on a
user's setting input and outputs an instruction signal to the
colorimetry sensor 420 to cause it to detect the amount of light of
the thus set wavelength. The voltage controller 15 in the
colorimetry sensor 420 then applies a voltage to the electrostatic
actuator 56 based on the control signal to drive the wavelength
tunable interference filter 5.
[0215] The colorimetry processor 433 analyzes the chromaticity of
the objet X under measurement based on the received amount of light
detected with the detector 11. The colorimetry processor 433 may
instead analyze the chromaticity of the objet X under measurement
by using the amount of light obtained from the detector 11 as a
measured spectrum D and estimating an optical spectrum S by using
an estimated matrix Ms, as in the first and second embodiments
described above.
[0216] Another example of the electronic apparatus according to the
embodiment of the invention may be a light-based system for
detecting presence of a specific substance. Examples of such a
system may include an on-vehicle gas leakage detector that employs
a spectroscopic measurement method using the wavelength tunable
interference filter 5 according to any of the embodiments of the
invention, an optoacoustic rare gas detector for respiratory
detection, and other gas detection apparatus.
[0217] An example of such a gas detection apparatus will be
described below with reference to the drawings.
[0218] FIG. 12 is a schematic view showing an example of a gas
detection apparatus including the wavelength tunable interference
filter 5.
[0219] FIG. 13 is a block diagram showing the configuration of a
control system of the gas detection apparatus shown in FIG. 12.
[0220] A gas detection apparatus 100 includes a sensor chip 110, a
channel 120 having a suction port 120A, a suction channel 120B, a
discharge channel 120C, and a discharge port 120D, and a main body
130, as shown in FIG. 12.
[0221] The main body 130 includes a sensor unit cover 131 having an
aperture through which the channel 120 can be attached and
detached, a discharge unit 133, an enclosure 134, an optical unit
135, a filter 136, the wavelength tunable interference filter 5, a
detection unit including a light reception device 137 (detector), a
control unit 138, which processes a detected signal and controls
the detector, and an electric power supply 139, which supplies
electric power. The optical unit 135 includes a light source 135A,
which emits light, a beam splitter 135B, which reflects the light
incident from the light source 135A toward the sensor chip 110
whereas transmitting light incident from the sensor chip side
toward the light reception device 137, and lenses 135C, 135D, and
135E.
[0222] On the exterior surface of the gas detection apparatus 100
are provided an operation panel 140, a display section 141, a
connector 142 for external interfacing, and the electric power
supply 139, as shown in FIG. 13. When the electric power supply 139
is a secondary battery, a connector 143 for charging purposes may
be further provided.
[0223] Further, the control unit 138 in the gas detection apparatus
100 includes a signal processor 144, which is formed, for example,
of a CPU, alight source driver circuit 145, which controls the
light source 135A, a voltage controller 146, which controls the
wavelength tunable interference filter 5, a light reception circuit
147, which receives a signal from the light reception device 137, a
sensor chip detection circuit 149, which receives a signal from a
sensor chip detector 148, which reads a code of the sensor chip 110
and detects whether or not the sensor chip 110 is present, and a
discharge driver circuit 150, which controls the discharge unit
133, as shown in FIG. 13. The gas detection apparatus 100 further
includes a storage section (not shown) that stores the V-.lamda.
data.
[0224] The action of the thus configured gas detection apparatus
100 will next be described.
[0225] The sensor chip detector 148 is disposed inside the sensor
unit cover 131 in an upper portion of the main body 130, and the
sensor chip detector 148 detects whether or not the sensor chip 110
is present. The signal processor 144, when it detects a detection
signal from the sensor chip detector 148, determines that the
sensor chip 110 has been attached and provides the display section
141 with a display signal that causes the display section 141 to
display information representing that detection action is
ready.
[0226] For example, when a user operates the operation panel 140
and the operation panel 140 outputs an instruction signal
representing start of detection to the signal processor 144, the
signal processor 144 first outputs a light source activation signal
to the light source driver circuit 145 to activate the light source
135A. Having been driven, the light source 135A emits
single-wavelength, linearly polarized, stable laser light. Further,
the light source 135A has a built-in temperature sensor and light
amount sensor, which output information on the temperature and the
amount of light to the signal processor 144. When the signal
processor 144 determines that the light source 135A is operating in
a stable manner based on the temperature and the amount of light
inputted from the light source 135A, the signal processor 144
controls the discharge driver circuit 150 to activate the discharge
unit 133. As a result, a gaseous specimen containing a target
substance to be detected (gas molecule) is guided through the
suction port 120A through the suction channel 120B, the sensor chip
110, and the discharge channel 120C to the discharge port 120D. The
suction port 120A is provided with a dust removal filter 120A1,
which removes relatively large dust, part of water vapor, and other
substances.
[0227] The sensor chip 110 is a sensor that has a plurality of
metal nano-structures incorporated therein and operates based on
localized surface plasmon resonance. In the thus configured sensor
chip 110, the laser light incident thereon forms an enhanced
electric field among the metal nano-structures. When a gas molecule
enters the enhanced electric field, Raman scattered light carrying
information on molecular vibration and Rayleigh scattered light are
produced.
[0228] The Rayleigh scattered light and the Raman scattered light
are incident through the optical unit 135 on the filter 136, which
separates the Rayleigh scattered light out, and the Raman scattered
light is incident on the wavelength tunable interference filter 5.
The signal processor 144 then outputs a control signal to the
voltage controller 146. The voltage controller 146 then reads a
voltage value corresponding to a wavelength under measurement from
the storage section and applies the voltage to the electrostatic
actuator 56 in the wavelength tunable interference filter 5 to
cause the wavelength tunable interference filter 5 to separate
Raman scattered light corresponding to the gas molecule under
detection, as described in the above first embodiment. Thereafter,
having received the separated light, the light reception device 137
outputs a light reception signal according to the amount of
received light to the signal processor 144 via the light reception
circuit 147. In this case, target Raman scattered light can be
precisely extracted through the wavelength tunable interference
filter 5.
[0229] The signal processor 144 compares data on the spectrum of
the thus obtained Raman scattered light corresponding to the gas
molecule under detection with data stored in a ROM and determines
whether or not the detected gas molecule is the target gas molecule
to identify the substance. The signal processor 144 further
displays information on the result of the identification on the
display section 141 and outputs the information via the connector
142 to an external apparatus.
[0230] In FIGS. 12 and 13 described above, the gas detection
apparatus 100, which performs gas detection based on Raman
scattered light separated from initial Raman scattered light by the
wavelength tunable interference filter 5, is presented byway of
example, but a gas detection apparatus that identifies the type of
gas by detecting the absorbance specific to the gas may instead be
used. In this case, a gas sensor that receives a gas flowing
therein, separates light absorbed by the gas from incident light,
and detects the separated light is used as the optical module
according to the embodiment of the invention. A gas detection
apparatus that includes the gas sensor and analyzes and identifies
a gas that flows into the sensor can be the electronic apparatus
according to the embodiment of the invention. The configuration
described above also allows gas component detection by using the
wavelength tunable interference filter 5.
[0231] The system for detecting presence of a specific substance is
not limited to the gas detection system described above. Another
system for detecting presence of a specific substance can, for
example, be a substance composition analyzer, such as a noninvasive
measurement apparatus for measuring sugars based on near-infrared
spectroscopy and a noninvasive measurement apparatus for acquiring
information on food, biological body, mineral, and other
substances.
[0232] A food analyzer will be described below as an example of the
substance composition analyzer described above.
[0233] FIG. 14 shows a schematic configuration of a food analyzer
that is an example of the electronic apparatus using the wavelength
tunable interference filter 5.
[0234] A food analyzer 200 includes a detection unit 210 (optical
module), a control unit 220, and a display unit 230, as shown in
FIG. 14. The detection unit 210 includes a light source 211, which
emits light, an imaging lens 212, which introduces light from an
object under measurement, the wavelength tunable interference
filter 5, which separates desired light from the light introduced
through the imaging lens 212, and an imager 213 (detector), which
detects the separated light.
[0235] The control unit 220 includes a light source controller 221,
which performs light-on/off control on the light source 211 and
luminance control when the light source 211 is emitting light, a
voltage controller 222, which controls the wavelength tunable
interference filter 5, a detection controller 223, which controls
the imager 213 and acquires a spectroscopic image captured with the
imager 213, a signal processor 224, and a storage section 225.
[0236] In the food analyzer 200, when the system thereof is driven,
the light source controller 221 controls the light source 211 to
cause it to emit light toward an object under measurement. Light
reflected off the object under measurement then passes through the
imaging lens 212 and enters the wavelength tunable interference
filter 5. The wavelength tunable interference filter 5 is driven
under the control of the voltage controller 222 based on the drive
method shown in the first or second embodiment described above. The
wavelength tunable interference filter 5 can thus precisely
extracts light of a target wavelength. The extracted light is then
captured as an image with the imager 213 formed, for example, of a
CCD camera. The captured image light is accumulated as a
spectroscopic image in the storage section 225. The signal
processor 224 controls the voltage controller 222 to change the
value of the voltage applied to the wavelength tunable interference
filter 5 to acquire spectroscopic images of a variety of
wavelengths.
[0237] The signal processor 224 then computes data from the pixels
of each of the images accumulated in the storage section 225 to
determine a spectrum at each of the pixels. The storage section 225
has further stored, for example, information on the composition of
food corresponding to a spectrum, and the signal processor 224
analyzes data on the obtained spectra based on the information on
food stored in the storage section 225 to determine food components
contained in the object under detection and the contents of the
food components. Further, the calorie, the degree of freshness, and
other factors of the food can be calculated based on the resultant
food components and contents thereof. Moreover, the spectral
distribution in each image can be analyzed, for example, to extract
a portion of the food under inspection where freshness has lowered
and even detect foreign matter and other undesirable objects
contained in the food.
[0238] The signal processor 224 then displays information on the
thus obtained components, contents, calorie, freshness, and other
factors of the food under inspection on the display unit 230.
[0239] In addition to the example of the food analyzer 200 shown
FIG. 14, substantially the same configuration can be used as
noninvasive measurement apparatus described above that measure
other types of information. For example, a bioanalyzer that
analyzes biological components, for example, measures and analyzes
blood or other bodily fluid components, can be provided. A
bioanalyzer of this type, for example, an apparatus that measures
blood and other bodily fluid components, can be an apparatus that
senses ethyl alcohol, which can be used as a drunk-driving
prevention apparatus that detects the state of a drunk driver.
Further, an electronic endoscope system including a bioanalyzer of
this type can be provided.
[0240] Moreover, a mineral analyzer that analyzes mineral
components can be provided.
[0241] Further, the wavelength tunable interference filter, the
optical module, and the electronic apparatus according to the
embodiments of the invention are applicable to the following
apparatus.
[0242] For example, changing the intensity of light of a variety of
wavelengths over time allows the light of the variety of
wavelengths to transmit data. In this case, the wavelength tunable
interference filter 5 provided in an optical module separates light
of a specific wavelength and a light receiver receives the light
for extraction of the data transmitted by the light of the specific
wavelength. An electronic apparatus including the data extraction
optical module can process the data carried by the light of the
variety of wavelengths for optical communication.
[0243] Further, an electronic apparatus including the wavelength
tunable interference filter according to any of the embodiments of
the invention that separates light is applicable to a spectroscopic
camera that captures a spectroscopic image, a spectroscopic
analyzer, and other apparatus. An example of a spectroscopic camera
of this type may include an infrared camera in which the wavelength
tunable interference filter 5 is incorporated.
[0244] FIG. 15 is a diagrammatic view showing a schematic
configuration of a spectroscopic camera. A spectroscopic camera 300
includes a camera body 310, an imaging lens unit 320, and an imager
330 (detector), as shown in FIG. 15.
[0245] The camera body 310 is a portion grasped and operated by a
user.
[0246] The imaging lens unit 320 is attached to the camera body 310
and guides incident image light to the imager 330. The imaging lens
unit 320 includes an objective lens 321, an image forming lens 322,
and the wavelength tunable interference filter 5 disposed between
the two lenses, as shown in FIG. 15.
[0247] The imager 330 is formed of a light reception device and
captures the image light guided through the imaging lens unit
320.
[0248] The thus configured spectroscopic camera 300, in which the
wavelength tunable interference filter 5 transmits light of a
wavelength to be captured as an image, can capture a spectroscopic
image formed by the light of a desired wavelength.
[0249] Further, the wavelength tunable interference filter
according to any of the embodiments of the invention may be used as
a bandpass filter. For example, the wavelength tunable interference
filter can be used as an optical laser apparatus in which the
wavelength tunable interference filter 5 receives light within a
predetermined wavelength region emitted from a light emitting
device, separates only narrow-band light around a predetermined
wavelength, and transmits the separated light.
[0250] Moreover, the wavelength tunable interference filter
according to any of the embodiments of the invention may be used as
a biometrics authentication apparatus. For example, the wavelength
tunable interference filter is also applicable to an authentication
apparatus based on blood vessels, fingerprints, retina, iris, or
any other body part by using near-infrared light or visible
light.
[0251] Further, the optical module and the electronic apparatus
according to the embodiments of the invention can be used as a
concentration detection apparatus. In this case, the wavelength
tunable interference filter 5 separates infrared energy (infrared
light) radiated from an object, and the energy is analyzed for
measurement of the concentration of a subject in a sample.
[0252] As described above, the wavelength tunable interference
filter, the optical module, and the electronic apparatus according
to the embodiments of the invention are applicable to any apparatus
that separates predetermined light from incident light. Since the
wavelength tunable interference filter according to any of the
embodiments of the invention can by itself separate light of a
plurality of wavelengths from incident light as described above,
spectral measurement based on the plurality of wavelengths and
detection of a plurality of components can be performed with
precision. Therefore, each of the optical module and the electronic
apparatus has a size further smaller than the size of an apparatus
of related art that extracts light of a desired wavelength by using
a plurality of devices and can, for example, be preferably used as
a portable or on-vehicle optical device.
[0253] In addition, the specific structure according to an
embodiment of the invention may be an appropriate combination of
the embodiments and the variations described above or may be
changed as appropriate to any other structure in actual
implementation of the invention to the extent that the advantage of
the invention is achieved.
[0254] The entire disclosure of Japanese Patent Application No.
2013-054678 filed Mar. 18, 2013 is expressly incorporated by
reference herein.
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