U.S. patent application number 13/038587 was filed with the patent office on 2011-09-22 for optical filter and analytical instrument.
This patent application is currently assigned to SEIKO EPSON CORPORATION. Invention is credited to Susumu SHINTO, Seiji YAMAZAKI.
Application Number | 20110228396 13/038587 |
Document ID | / |
Family ID | 44260891 |
Filed Date | 2011-09-22 |
United States Patent
Application |
20110228396 |
Kind Code |
A1 |
SHINTO; Susumu ; et
al. |
September 22, 2011 |
OPTICAL FILTER AND ANALYTICAL INSTRUMENT
Abstract
An optical filter includes: a lower substrate; a lower mirror
provided to the lower substrate; a lower electrode provided to the
lower substrate; an upper substrate disposed so as to be opposed to
the lower electrode; an upper mirror provided to the upper
substrate, and opposed to the lower mirror; and an upper electrode
provided to the upper substrate, and opposed to the lower
electrode, wherein the upper substrate has a groove surrounding the
upper mirror in a plan view, the groove includes a first side
surface section, a second side surface section, a bottom surface
section, a first end section located between the first side surface
section and the bottom surface section, and a second end section
located between the second side surface section and the bottom
surface section, in a cross-sectional view, and the first end
section and the second end section each have a curved surface.
Inventors: |
SHINTO; Susumu; (Suwa,
JP) ; YAMAZAKI; Seiji; (Fujimi, JP) |
Assignee: |
SEIKO EPSON CORPORATION
Tokyo
JP
|
Family ID: |
44260891 |
Appl. No.: |
13/038587 |
Filed: |
March 2, 2011 |
Current U.S.
Class: |
359/578 |
Current CPC
Class: |
G02B 26/001 20130101;
G01J 3/26 20130101; G02B 5/284 20130101; G02F 1/21 20130101; G02F
1/213 20210101; G03F 7/70575 20130101 |
Class at
Publication: |
359/578 |
International
Class: |
G02B 5/28 20060101
G02B005/28 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 19, 2010 |
JP |
2010-063923 |
Claims
1. An optical filter comprising: a lower substrate; a lower mirror
provided to the lower substrate; a lower electrode provided to the
lower substrate; an upper substrate disposed so as to be opposed to
the lower substrate; an upper mirror provided to the upper
substrate, and opposed to the lower mirror; and an upper electrode
provided to the upper substrate, and opposed to the lower
electrode, wherein the upper substrate has a groove surrounding the
upper mirror in a plan view, the groove includes a first side
surface section, a second side surface section, a bottom surface
section, a first end section located between the first side surface
section and the bottom surface section, and a second end section
located between the second side surface section and the bottom
surface section, in a cross-sectional view, and the first end
section and the second end section each have a curved surface.
2. The optical filter according to claim 1, wherein the bottom
surface section is flat, and the upper electrode is disposed on the
upper substrate within a region located under the bottom surface
section in the plan view.
3. The optical filter according to claim 1, wherein the first end
section is located nearer to the upper mirror, and the first end
section fails to overlap the upper mirror in the plan view.
4. The optical filter according to claim 1, wherein the lower
substrate and the upper substrate each have a light transmissive
property.
5. The optical filter according to claim 1, wherein the groove is
formed by performing a wet-etching process after performing a
dry-etching process.
6. An analytical instrument comprising the optical filter according
to claim 1.
7. An analytical instrument comprising the optical filter according
to claim 2.
8. An analytical instrument comprising the optical filter according
to claim 3.
9. An analytical instrument comprising the optical filter according
to claim 4.
10. An analytical instrument comprising the optical filter
according to claim 5.
Description
BACKGROUND
[0001] 1. Technical Field
[0002] The present invention relates to an optical filter and an
analytical instrument.
[0003] 2. Related Art
[0004] In the past, as an optical filter for selecting a light beam
having a target wavelength from the incident light beams and then
emitting the light beam, there has been known an optical filter of
an air-gap type and of an electrostatic-drive type, in which a pair
of substrates are disposed so as to be opposed to each other, each
of the surfaces of the substrates opposed to each other is provided
with a mirror, electrodes are respectively disposed in the
peripheries of the mirrors, a diaphragm section is disposed in the
periphery of one of the mirrors, and the diaphragm section is
displaced due to electrostatic force generated between the
electrodes to thereby vary the gap (air gap) between the mirrors,
thus taking out the light beam having a desired wavelength (e.g.,
JP-A-2003-57438).
[0005] In such an optical filter, it is required to control a gap
between the pair of mirrors in an extremely narrow range such as a
sub-micron range through a range of several microns in the
manufacturing process, and moreover, it is important to keep the
gap between the mirrors with accuracy, and at the same time, to
control the gap to have a desired gap amount.
[0006] Incidentally, in the optical filter of the air-gap type and
of the electrostatic-drive type, the diaphragm is moved by
electrostatic attractive force to thereby vary the gap between the
mirrors. Therefore, it results that the applied voltage for
generating the electrostatic attractive force necessary for the
displacement of the gap varies in accordance with the thickness of
the diaphragm section. Therefore, it is desirable for the diaphragm
section to be as thin as possible in order for holding down the
applied voltage. However, thinning the diaphragm section causes
degradation of strength, and in the optical filter repeatedly
varying the gap stress is applied to the diaphragm section every
time the gap is varied, and therefore, there arises a problem that
the degradation of strength directly causes breakage of the
diaphragm section.
SUMMARY
[0007] An advantages of some aspects of the invention is to provide
an optical filter and an optical module equipped with the optical
filter each capable of preventing the degradation of strength of
the diaphragm section even in the case of thinning the diaphragm
section on the ground of holding down the applied voltage, and as a
result, enhancing the strength of the diaphragm section while
reducing the maximum applied voltage, varying the gap stably, and
being driven preferably.
[0008] According to an aspect of the invention, there is provided
an optical filter including a lower substrate, a lower mirror
provided to the lower substrate, a lower electrode provided to the
lower substrate, an upper substrate disposed so as to be opposed to
the lower substrate, an upper mirror provided to the upper
substrate, and opposed to the lower mirror, and an upper electrode
provided to the upper substrate, and opposed to the lower
electrode, wherein the upper substrate has a groove surrounding the
upper mirror in a plan view, the groove has a first side surface
section, a second side surface section, a bottom surface section, a
first end section located between the first side surface section
and the bottom surface section, and a second end section located
between the second side surface section and the bottom surface
section, in a cross-sectional view, and the first end section and
the second end section each have a curved surface.
[0009] The optical filter according to this aspect of the invention
has a curved surface in each of the end sections of the groove.
Thus, the stress concentration to the end sections of the groove
caused when varying the gap can be eased to thereby enhance the
strength of the diaphragm section. As a result, a stable gap
variation becomes possible, and it becomes possible to preferably
drive the gap.
[0010] According to another aspect of the invention, in the optical
filter described above, the bottom surface section is flat, and the
upper electrode is disposed on the upper substrate within a region
located under the bottom surface section in the plan view.
[0011] Thus, it becomes possible to prevent a crack or the like in
the upper electrode due to the distortion of the groove from
occurring.
[0012] According to another aspect of the invention, in the optical
filter described above, the first end section is located nearer to
the upper mirror, and the first end section fails to overlap the
upper mirror in the plan view.
[0013] Thus, it is possible to prevent the propagation of the light
beam entering the upper mirror from being blocked by the side
surface sections of the diaphragm, thereby making preferable
sensing possible.
[0014] According to another aspect of the invention, in the optical
filter described above, the lower substrate and the upper substrate
each have a light transmissive property.
[0015] By arranging that the first and second substrates each have
a light transmissive property as described above, the transmittance
of the light beam in the substrate is improved, and the strength of
the light beam taken out is also raised. Therefore, the efficiency
of taking out the light beam is improved.
[0016] According to another aspect of the invention, in the optical
filter described above, the groove is formed by performing a
wet-etching process after performing a dry-etching process.
[0017] By using the wet-etching process in the manufacturing
process, it becomes easy to provide a curved surface shape to the
end section, thereby making it possible to ease the stress
concentration to the end sections, and thus the strength of the
diaphragm section can be improved. Further, by combining the
dry-etching process and the wet-etching process with each other, it
becomes possible to reduce the time necessary for forming the
groove, and at the same time to provide a structure in which the
end sections of the groove each have a curved surface, thus the
stress concentration to the end sections can be eased to thereby
improve the strength of the diaphragm section. As a result, a
stable gap variation becomes possible, and preferable drive becomes
possible.
[0018] According to another aspect of the invention, there is
provided an analytical instrument using any one of the optical
filters described above.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] The invention will be described with reference to the
accompanying drawings, wherein like numbers reference like
elements.
[0020] FIG. 1 is a plan view of an optical filter according to an
embodiment of the invention.
[0021] FIG. 2 is a cross-sectional view of the optical filter
according to the embodiment.
[0022] FIG. 3 is a diagram showing a relationship between the
wavelength and the transmittance in the case of applying no voltage
in the optical filter according to the embodiment.
[0023] FIG. 4 is a diagram showing a relationship between the
wavelength and the transmittance in the case of applying a voltage
in the optical filter according to the embodiment.
[0024] FIGS. 5A through 5C are diagrams for explaining a method of
manufacturing the optical filter according to the embodiment.
[0025] FIGS. 6A and 6B are diagrams for explaining the method of
manufacturing the optical filter according to the embodiment.
[0026] FIGS. 7A through 7C are diagrams for explaining the method
of manufacturing the optical filter according to the
embodiment.
[0027] FIGS. 8A through 8C are diagrams for explaining the method
of manufacturing the optical filter according to the
embodiment.
[0028] FIGS. 9A and 9B are diagrams for explaining the method of
manufacturing the optical filter according to the embodiment.
DESCRIPTION OF AN EXEMPLARY EMBODIMENT
[0029] Hereinafter, an optical filter according to an embodiment of
the invention will be explained. Here, as the optical filter, an
optical filter of an air-gap type and of an electrostatic-drive
type will be explained.
[0030] In FIGS. 1 and 2, the reference numeral 1 denotes an optical
filter of the air-gap type and of the electrostatic-drive type. The
optical filter 1 is composed of an upper substrate 2, a lower
substrate 3 bonded (or joined with an adhesive) to the upper
substrate 2 in the state of being opposed thereto, a mirror 4A (an
upper mirror) having a circular shape disposed at a central portion
of an opposed surface 2a of the upper substrate 2, the opposed
surface 2a being opposed to the lower substrate 3, a mirror 4B (a
lower mirror) having a circular shape disposed at a central portion
of a bottom surface of a first recessed section 5 formed at a
central portion of a surface of the lower substrate 3, the surface
being opposed to the upper substrate 2, so as to be opposed to the
mirror 4A via a first gap G1, an electrode 6A (an upper electrode)
having a ring shape disposed in the periphery of the mirror 4A of
the upper substrate 2, an electrode 6B (a lower electrode) having a
ring shape disposed in a second recessed section 7 having a ring
shape formed in the periphery of the first recessed section 5 of
the lower substrate 3 so as to be opposed to the electrode 6A via a
second gap G2, and a thin-wall and ring-shaped diaphragm section 8
provided to an opposite surface of the upper substrate 2 to the
opposed surface 2a thereof, and formed at the position roughly
corresponding to the electrode 6A using an etching (selectively
removing) process.
[0031] The diaphragm section 8 is composed of a first side surface
section 8c, a second side surface section 8e, a bottom surface
section 8a, a first end section 8b located between the first side
surface section 8c and the bottom surface section 8a, and a second
end section 8d located between the second side surface section 8e
and the bottom surface section 8a. Further, the first side surface
section 8b located near to the mirror 4A in the diaphragm section 8
is formed so as not to overlap the mirror 4A in a plan view. By
adopting such a structure as described above, it is possible to
prevent the propagation of the light beam entering the mirror 4A
from being blocked by the first side surface section 8c of the
diaphragm section 8.
[0032] Further, the electrodes 6A, 6B disposed so as to be opposed
to each other via the second gap G2 and the diaphragm 8 constitute
an electrostatic actuator.
[0033] As the material of the upper substrate 2 and the lower
substrate 3, glass can be used. As the glass, specifically, soda
glass, crystallized glass, quartz glass, lead glass, potassium
glass, borosilicate glass, sodium borosilicate glass, alkali-free
glass, and so on are preferably used.
[0034] By using a material having a light transmissive property for
both of the upper substrate 2 and the lower substrate 3,
electromagnetic waves in a desired wavelength band or visible light
can be used as the incident light.
[0035] Further, by forming both of the upper substrate 2 and the
lower substrate 3 using a semiconductor material such as silicon,
near infrared light can be used as the incident light.
[0036] The mirrors 4A, 4B are disposed so as to be opposed to each
other via the first gap G1, and are each composed of a dielectric
multilayer film having high-refractive index layers and
low-refractive index layers stacked alternately to each other. It
should be noted that the mirrors 4A, 4B are not limited to the
dielectric multilayer films, but alloy films having silver as a
principal constituent or multilayer films thereof, for example, can
also be used.
[0037] Out of these mirrors 4A, 4B, one 4A of the mirrors is
provided to the upper substrate 2, which is deformable, and is
therefore called a movable mirror, and the other 4B of the mirrors
is disposed to the lower substrate 3, which is undeformable, and is
therefore called a fixed mirror in some cases.
[0038] In the case of using the optical filter 1 in the visible
light region or the infrared light region, as the material of
forming the high-refractive index layers in the dielectric
multilayer film, titanium oxide (Ti.sub.2O), tantalum oxide
(Ta.sub.2O.sub.5), niobium oxide (Nb.sub.2O.sub.5), and so on can
be used. Further, in the case of using the optical filter 1 in the
ultraviolet light region, as the material of forming the
high-refractive index layers, aluminum oxide (Al.sub.2O.sub.3),
hafnium oxide (HfO.sub.2), zirconium oxide (ZrO.sub.2), thorium
oxide (ThO.sub.2), and so on can be used.
[0039] On the other hand, as the material for forming the
low-refractive index layer in the dielectric multilayer film,
magnesium fluoride (MgF.sub.2), silicon oxide (SiO.sub.2), and so
on can be used.
[0040] The number of layers and thickness of the high-refractive
index layers and the low-refractive index layers are appropriately
set based on the necessary optical characteristics. In general, in
the case of forming a reflecting film (a mirror) with a dielectric
multilayer film, the number of layers necessary for obtaining the
optical characteristics is equal to or larger than 12.
[0041] The electrodes 6A, 6B are disposed so as to be opposed to
each other via the second gap G2, and for constituting a part of
the electrostatic actuator for generating electrostatic force
between the electrode 6A, 6B in accordance with the drive voltage
input thereto to thereby move the mirrors 4A, 4B relatively to each
other in the state in which the mirrors are opposed to each
other.
[0042] Thus, the electrodes 6A, 6B are arranged to displace the
diaphragm section 8 in a vertical direction in FIG. 2 to vary the
first gap G1 between the mirrors 4A, 4B, thereby emitting the light
beam with a wavelength corresponding to the first gap G1.
[0043] Further, as shown in FIG. 2, the electrode 6A is disposed
within a region located under the bottom surface section 8a, which
is a flat plane. If the electrode 6A is formed to overlap the first
end section 8b and the second end section 8d each having a curved
surface, when driving the diaphragm section 8, the diaphragm
section 8 is distorted to cause large stress in the electrode 6A
located under the first end section 8b and the second end section
8d. Thus, there is a possibility that a problem such as a crack
arises in the electrode 6A. However, by forming the electrode 6A
within the region under the bottom surface section 8a which is a
flat plane, the crack and so on of the electrode 6A due to the
distortion of the diaphragm section 8 can be prevented.
[0044] It should be noted that since in the present embodiment the
opposed surface 2a of the upper substrate 2 and the second recessed
section 7 provided to the lower substrate 3 are arranged to be
parallel to each other, the electrodes 6A, 6B are also parallel to
each other.
[0045] It is sufficient for the material for forming the electrodes
6A, 6B to be conductive, and the material is not particularly
limited. However, metal such as Cr, Al, Al alloy, Ni, Zn, Ti, or
Au, resin having carbon or titanium dispersed, silicon such as
polycrystalline silicon (polysilicon) or amorphous silicon, or a
transparent conductive material such as silicon nitride or ITO can
be used as the material.
[0046] As shown in FIG. 1, wiring lines 11A, 11B are connected
respectively to the electrodes 6A, 6B, and the electrodes 6A, 6B
are connected to a power supply (not shown) via the wiring lines
11A, 11B.
[0047] It should be noted that the wiring lines 11A, 11B are formed
in a wiring groove 12A provided to the upper substrate 2 or a
wiring groove 12B provided to the lower substrate 3. Therefore, it
is arranged that the wiring lines do not interfere the bonding
between the upper substrate 2 and the lower substrate 3.
[0048] The power supply is for applying a voltage to the electrodes
6A, 6B as a drive signal to thereby drive the electrodes 6A, 6B,
thus generating desired electrostatic force between the electrodes
6A, 6B. It should be noted that a control device (not shown) is
connected to the power supply, and it is arranged that by
controlling the power supply using the control device, the
electrical potential difference between the electrodes 6A, 6B can
be adjusted.
[0049] The diaphragm section 8 has a smaller thickness compared to
a portion of the upper substrate 2 where the diaphragm section 8 is
not formed. The portion of the upper surface 2 with a smaller
thickness compared to the other portion of the upper substrate 2 as
described above is arranged to be deformable (displaceable) with
elasticity (flexibility), and thus, the diaphragm section 8 is
arranged to have a wavelength selection function for varying the
first gap G1 to change the distance between the mirrors 4A, 4B to a
distance corresponding to a light beam with a desired wavelength,
thereby outputting the light beam with the desired wavelength.
[0050] The shape and the thickness of the diaphragm section 8 are
not particularly limited providing the light beams having
wavelengths within a desired wavelength range can be output, and
are specifically set in accordance with the wavelength range of the
output light beam required for the optical filter 1 taking the
variation amount, the variation speed, and so on of the distance
between the mirrors 4A, 4B into consideration.
[0051] In the optical filter 1 according to the present embodiment,
in the case in which the control device and the power supply are
not driven, and therefore, no voltage is applied between the
electrodes 6A, 6B, the mirror 4A and the mirror 4B are opposed to
each other via the first gap G1. Therefore, when a light beam
enters the optical filter 1, it results that the light beam with
the wavelength corresponding to the first gap G1, for example, the
light beam with the wavelength of 720 nm is output as shown in FIG.
3.
[0052] Here, when driving the control device and the power supply
to apply a voltage between the electrodes 6A, 6B, the electrostatic
force corresponding to the level of the voltage (electrical
potential difference) is generated between the electrodes 6A, 6B.
As described above, the control device controls the power supply to
thereby apply a desired voltage between the electrodes 6A, 6B, thus
making it possible to generate desired electrostatic force between
the electrodes 6A, 6B. When the desired electrostatic force is
generated between the electrodes 6A, 6B in such a manner as
described above, the electrodes 6A, 6B are attracted to each other
due to the electrostatic force to thereby deform the upper
substrate 2 toward the lower substrate 3, and thus the first gap G1
between the mirrors 4A, 4B is narrowed compared to the case in
which no voltage is applied.
[0053] On this occasion, the stress is caused in the first end
section 8b and the second end section 8d by the movement of the
diaphragm section 8 due to the electrostatic force. However,
according to the present embodiment, since the first end section 8b
and the second end section 8d each have a shape with a large
curvature radius, it becomes difficult to cause the stress
concentration, the breakage is hardly caused even by repeated drive
of the diaphragm section 8, and thus preferable drive is
repeated.
[0054] Therefore, when a light beam enters the optical filter 1, it
results that the light beam with the wavelength corresponding to
the displaced first gap G1, for example, the light beam with the
wavelength of 590 nm is output, and the transmission wavelength is
shifted toward a shorter wavelength as shown in FIG. 4.
[0055] Then, a method of manufacturing the optical filter 1
according to the present embodiment will be explained with
reference to the accompanying drawings. FIGS. 5A through 5C, 6A,
6B, 7A through 7C, 8A through 8C, 9A, and 9B are cross-sectional
views showing a method of manufacturing the optical filter 1
according to the present embodiment.
[0056] The manufacturing method includes a manufacturing process of
the upper substrate and a manufacturing process of the lower
substrate. Hereinafter, each of the processes will sequentially be
described.
1. Manufacturing Process of Upper Substrate
[0057] A shown in FIG. 5A, a mask layer 51 is deposited on the
entire surface of the upper substrate 2. As a material for
composing the mask layer 51, for example, a metal film made of
Cr/Au or the like can be used. The thickness of the mask layer 51
is not particularly limited, but is preferably set to about 0.01
through 1 .mu.m, further preferably about 0.1 through 0.3 .mu.m. If
the mask layer 51 is too thin, the upper substrate 2 may not
sufficiently be protected, and if the mask layer 51 is too thick,
the mask layer 51 may become easy to be peeled off due to the
internal stress of the mask layer 51. In the present embodiment, a
Cr/Au film is deposited as the mask layer 51 by a sputtering
process to have a thickness of the Cr layer of 0.01 .mu.m and a
thickness of the Au layer of 0.3 .mu.m.
[0058] Subsequently, as shown in FIG. 5B, an opening section 51a
for forming the diaphragm section 8 is provided to the mask layer
51. The opening section 51a can be formed by, for example, a
photolithography process. Specifically, a resist layer (not shown)
having a pattern corresponding to the opening section 51a is formed
on the mask layer 51, and then the mask layer 51 is removed
partially using the resist layer as a mask, and then the resist
layer is removed to thereby form the opening section 51a. It should
be noted that the partial removal of the mask layer 51 is performed
by a wet-etching process or the like.
[0059] Subsequently, as shown in FIG. 5C, the upper substrate 2 is
etched by a wet-etching process to thereby form the diaphragm
section 8. As an etching fluid, hydrofluoric acid or buffered
hydrofluoric acid (BHF), for example, can be used. Further,
alternatively, the diaphragm section 8 can be formed by performing
a wet-etching process after performing a dry-etching process.
According to this configuration, it is possible to reduce the time
necessary for processing the groove, and at the same time to form
the structure in which the first end section 8b and the second end
section 8d of the groove each have a curved surface, which makes it
possible to ease the stress concentration to the end sections to
thereby enhance the strength of the diaphragm section 8.
[0060] Subsequently, as shown in FIG. 6A, the electrode 6A and the
wiring line 11A are formed. As a material for forming the electrode
6A and the wiring line 11A, a metal film made of, for example, Cr,
Al, or a transparent conductive material such as ITO can be used.
The thickness of the electrode 6A and the wiring line 11A is
preferably set to, for example, 0.1 through 0.2 .mu.m.
[0061] In order for forming the electrode 6A and the wiring line
11A, the metal film or the like is deposited by a vapor deposition
process, a sputtering process, an ion-plating process or the like,
and then the film is patterned by a photolithography process and an
etching process.
[0062] Subsequently, the mirror 4A is formed at a position 2a' on
the opposed surface 2a surrounded by the diaphragm section 8. For
example, titanium oxide (Ti.sub.2O) as a material for forming the
high-refractive index layer and silicon oxide (SiO.sub.2) as a
material for forming the low-refractive index layer are stacked to
each other, and then these layers are patterned by a liftoff
process to thereby obtain the mirror 4A.
2. Manufacturing Process of Lower Substrate
[0063] As shown in FIG. 7A, a mask layer 61 is deposited on the
opposed surface 3a of the lower substrate 3 opposed to the upper
substrate 2. As a material for forming the mask layer 61, a typical
resist material is used.
[0064] Subsequently, as shown in FIG. 7B, an opening section 61a
for forming the second recessed section 7 is provided to the mask
layer 61. The opening section 61a can be formed by a
photolithography process.
[0065] Subsequently, as shown in FIG. 7C, the lower substrate 3 is
etched by a wet-etching process to form the second recessed section
7. As an etching fluid, hydrofluoric acid or buffered hydrofluoric
acid (BHF), for example, can be used. It should be noted that the
method of forming the second recessed section 7 is not limited to
the wet-etching process, but other etching processes such as a
dry-etching process can also be used.
[0066] Subsequently, after removing the mask layer 61 by the
etching process, the first recessed section 5 is then formed in the
same manner as the formation of the second recessed section 7.
Specifically, a mask layer 62 is deposited on the lower substrate
3, as shown in FIG. 8A, to thereby form an opening section 62a for
forming the first recessed section 5. Subsequently, as shown in
FIG. 8B, the lower substrate 3 is etched by a wet-etching process
to form the first recessed section 5. Then, as shown in FIG. 8C, by
removing the mask layer 62 by the etching process, the lower
substrate 3 provided with the first and second recessed sections 5,
7 can be obtained.
[0067] Subsequently, as shown in FIG. 9A, the electrode 6B and the
wiring line 11B are formed. As a material for forming the electrode
6B and the wiring line 11B, a metal film made of, for example, Cr,
Al, or a transparent conductive material such as ITO can be used.
The thickness of the electrode 6B and the wiring line 11B is
preferably set to, for example, 0.1 through 0.2 .mu.m.
[0068] In order for forming the electrode 6B and the wiring line
11B, the metal film or the like is deposited by a vapor deposition
process, a sputtering process, an ion-plating process or the like,
and then the film is patterned by a photolithography process and an
etching process.
[0069] Then, the mirror 4B is formed at a position opposed to the
mirror 4A disposed on the upper substrate 2. For example, titanium
oxide (Ti.sub.2O) as a material for forming the high-refractive
index layer and silicon oxide (SiO.sub.2) as a material for forming
the low-refractive index layer are stacked to each other, and then
these layers are patterned by a liftoff process to thereby obtain
the mirror 4B.
[0070] As explained hereinabove, according to the optical filter of
the present embodiment, when varying the first gap G1 in order for
selectively taking out the wavelength, the stress is caused in the
first end section 8b and the second end section 8d by the movement
of the diaphragm section 8. However, according to the present
embodiment, since the first end section 8b and the second end
section 8d each have a shape with a large curvature radius, it
becomes difficult to cause the stress concentration, the breakage
is hardly caused even by repeated drive of the diaphragm section 8,
and thus preferable drive is repeated.
[0071] It should be noted that the optical filter according to the
invention can be applied to an analytical instrument such as a
colorimeter for measuring colors or a gas detector for measuring
gasses.
[0072] The entire disclosure of Japanese Patent Application No.
2010-063923, filed Mar. 19, 2010 is expressly incorporated by
reference herein.
* * * * *