Abstract: An optical filter includes a first substrate, a second substrate opposed to the first substrate, a first reflecting film provided to the first substrate, a second reflecting film provided to the second substrate, and opposed to the first reflecting film, a first electrode provided to the first substrate, a second electrode provided to the second substrate, and opposed to the first electrode, and a voltage control section adapted to control an electrical potential difference between the first electrode and a second electrode, and when switching a wavelength of a light beam to be dispersed by switching the electrical potential difference between the first electrode and the second electrode, and measuring an intensity of the light beam dispersed, the voltage control section switches the electrical potential difference from a first electrical potential difference to a second electrical potential difference larger than the first electrical potential difference.

Abstract: An environmental condition sensing device includes an interferometric modulator with optical properties, which change in response to being exposed to a predetermined environmental threshold or condition. The device includes an environmental reactive layer, which alters composition, in an optically-detectable manner, in response to being exposed to a predetermined environmental threshold or condition.

Abstract: Electrically tunable Fabry-Perot interferometers produced with micro-optical electromechanical (MOEMS) technology. Micromechanical interferometers of the prior art require high control voltage, their production includes complicated production phases, and the forms of the movable mirrors are restricted to circular geometries. In the inventive solution, there is a gap in the movable mirror, whereby mirror layers opposite to the gap are connected with anchoring. The anchoring is such that the stiffness of the mirror is higher at the optical area than at the surrounding area. This way it is possible keep the optical area of the mirror flat even if the control electrodes extend to the optical area. Due to large electrodes, lower control voltages are required.

Abstract: An integrated swept wavelength optical source uses a filtered ASE signal with an optical amplifier and tracking filter. This source comprises a micro optical bench, a source for generating broadband light, a first tunable Fabry Perot filter, installed on the bench, for spectrally filtering the broadband light from the broadband source to generate a narrowband tunable signal, an amplifier, installed on the bench, for amplifying the tunable signal, and a second tunable Fabry Perot filter, installed on the bench, for spectrally filtering the amplified tunable signal from the amplifier. A self-tracking arrangement is also possible where a single tunable filter both generates the narrowband signal and spectrally filters the amplified signal. In some examples, two-stage amplification is provided. The use of a single bench implementation yields a low cost high performance system. For example, polarization control between components is no longer necessary.

Abstract: The invention relates to controllable Fabry-Perot interferometers which are produced with micromechanical (MEMS) technology. The prior art interferometers have a temperature drift which causes inaccuracy and requirement for complicated packaging. According to the invention the interferometer arrangement has both an electrically tuneable interferometer and a reference interferometer on the same substrate. The temperature drift is measured with the reference interferometer and this information is used for compensating the measurement with the tuneable interferometer. The measurement accuracy and stability can thus be improved and requirements for packaging are lighter.

Abstract: The invention relates to an optical filter and a method for its production, and to a device for the examination of the spectral and spatial distribution of an electromagnetic radiation irradiated from an object. The invention is based on the task of providing an optical filter of the above described type that is inexpensive to produce, which can be used to detect a plurality of wavelengths, in which, however, tuning of the DBR mirrors by means of displacement is not necessary. Furthermore, a method for the production of such a filter is provided.

Abstract: A Fabry-Perot interferometer includes an input mirror and an output mirror arranged facing the input mirror via a gap. Each mirror includes a pair of high-refractive layers and a space layer arranged selectively between the high-refractive layers. At least one of an input-side bridge part and an output-side bridge part arranged crossing the gap, is movable as a membrane. Each bridge part includes a transmission portion and a periphery portion. Each transmission portions includes a mirror element in which the space layer is sandwiched by the pair of high-refractive layers. In a second direction perpendicular to the first direction, the mirror element of the input mirror has a width larger than seven times of a maximum wavelength of a transmission light output from the output mirror, and functions as a diffraction restriction mirror.

Abstract: The invention relates to controllable Fabry-Perot interferometers which are produced with micromechanical (MEMS) technology. The prior art interferometers have a temperature drift which causes inaccuracy and requirement for complicated packaging. According to the invention the interferometer arrangement has both an electrically tuneable interferometer and a reference interferometer on the same substrate. The temperature drift is measured with the reference interferometer and this information is used for compensating the measurement with the tuneable interferometer. The measurement accuracy and stability can thus be improved and requirements for packaging are lighter.

Abstract: An apparatus for position finding, including a light source to produce a wave field in a measurement section, a wave field variation device to generate a variation of a wavelength of the wave field over time, an interferometer to produce an interference pattern for the wave field which is dependent on the length of the measurement section, a detector to produce a measurement signal on the basis of the detected interference pattern, and an evaluation circuit to evaluate the measurement signal on the basis of the variation over time.

Abstract: An interference filter includes: a first substrate; a second substrate that faces one side of the first substrate and is bonded to the first substrate; a first reflection film formed on the side of the first substrate that faces the second substrate; and a second reflection film provided on the second substrate and faces the first reflection film, the first substrate including a first gap formation region in which the first reflection film is disposed and which is not contact with the second substrate, and wherein the first substrate and the second substrate are adhesively bonded to each other with the adhesive applied into the adhesive grooves with the first bonding region and the second bonding region bonded to each other.

Abstract: A low coherent light from a white light source is emitted to a sample surface. A detour distance in a detour section is adjusted such that an optical path difference between a reference light and a sample light is equal to or shorter than a coherence length of interference light. The interference light is incident on an image sensor only when an inclination angle of a diffraction grating plate and a wavelength of the interference light satisfy a predetermined condition. Thus, an interference fringe image is formed. Based on each of the interference fringe images taken on a wavelength-by-wavelength basis of the interference light and an optical distance between a reference surface and the sample surface along an optical path of a measuring light at the time of taking the interference fringe image, a shape of the sample surface is measured.

Abstract: An optical tomography imaging a tomogram by using a coherent light by a backscattering light of a measured object and a reflected light of a reference mirror, which has supercontinuum light sources, an optical system having group velocity dispersion connected to the supercontinuum light source, an optical detection element detecting a coherent light by a backscattering light of the measured object and a reflected light of the reference mirror, a timing detection element detecting a timing of each wavelength component in an output light from the optical system having the group velocity dispersion, and a unit sampling a signal from the optical detector by using a timing signal from the timing detection element with a signal from the supercontinuum light source as a trigger, and detecting an optical tomogram signal imaging a tomogram, thereby acquiring an optical tomogram at a higher speed than a conventional SS-OCT.

Abstract: An optical sensing device with multiple photodiode elements and multi-cavity Fabry-Perot ambient light filter structure to detect and convert light signal with different wavelength spectrum into electrical signal. In one embodiment, the optical sensing device capable of sensing color information of ambient light or sunlight and provides blocking of infrared (IR) light within the wavelength ranging from 700 nm to 1100 nm. Preferably, the optical sensing device senses not just the ambient light brightness but also the fundamental red, green and blue color components of the ambient light.

Abstract: A sensor assembly having an optical fiber, a lens in optical communication with the optical fiber, a reflective surface spaced from the lens, for reflecting light from the beam back to the lens, a partially reflective surface positioned between the reflective surface and the lens, the partially reflective surface for reflecting light from the beam back to the lens, and an alignment device for aligning the lens and reflective surface with respect to one another, such that light from the beam of light transmitted from the lens reflects from the reflective surface back to the lens. The alignment device can have a rotational component and a base component, where the rotational component rotates to align a beam of light transmitted from the lens. The rotational component can also cooperate with the base component to move axially with respect to the reflective surfaces to align the beam for optimum power.

Abstract: A method for inspecting a sandwich structure may comprise determining a reference frequency, directing first and second laser beams onto the structure, collecting reflected light, processing it using an interferometer, acquiring a time-dependent signal for a predetermined duration greater than a period corresponding to the reference frequency, processing the time-dependent signal to produce a frequency-dependent signal, and comparing characteristics of the processed frequency-dependent signal to the reference frequency.

Abstract: A Fabry-Perot interferometer includes a fixed mirror structure and a movable mirror structure. The fixed mirror structure has a fixed mirror in a spectral region. The movable mirror structure includes a membrane spaced from the fixed mirror structure. The membrane has a movable mirror in the spectral region and multiple springs arranged one inside the other around the spectral region. A spring constant of the inner spring is less than a spring constant of the outer spring. One of the fixed mirror structure and the membrane has multiple electrodes, and the other of the fixed mirror structure and the membrane has at least one electrode that is paired with the electrodes to form opposing electrode pairs arranged one inside the other around the spectral region. The number of the opposing electrode pairs is equal to the number of the springs.

Abstract: A fringe locking subsystem for an optical sensing cavity is provided. The subsystem comprises one or more photo detectors that detect a reference signal and a cavity signal; a first amplifier that generates a calculated differential between the reference signal and the cavity signal; a lock-in amplifier that generates a modulation signal based on the calculated differential; and a controller that adjusts a distance within the cavity based on the modulation signal.

Abstract: A plurality of Fabry-Perot interferometric sensors are optically coupled in series with each other to form an ordered optical series. Each Fabry-Perot interferometric sensor has a unique signalband and a passband. Each Fabry-Perot interferometric sensor has its unique signalband within the passbands of all of the next higher ordered Fabry-Perot interferometric sensors in the optical series so that a corresponding unique fringe signal from each of the Fabry-Perot interferometric sensors is a multiplexed output from the optical series.

Abstract: A method for estimating optical power in an optical channel includes determining a tunable filter full-width, FWF, by measuring a response of the tunable filter to a known signal and mapping the response to frequency. A portion of an optical channel is coupled to an input of the tunable optical filter. A peak power response, PR, and a full width tunable filter response, FWR, to the optical channel are determined by measuring a response of the tunable filter to the optical channel and mapping the response to frequency. A signal power, PS, is then calculated from the peak power response, PR, and a ratio of the full width tunable filter response, FWR, to the tunable filter full-width, FWF.

Abstract: A system is provided for improving the damage tolerance of a rotor assembly. The system includes one or more measurement subsystems for measuring the stresses in respective parts of the rotor assembly and issuing respective measurement signals. The system also includes a control subsystem for receiving the measurement signals from the measurement subsystems, determining a response to measured stresses indicative of crack growth, and issuing response signals. The system also includes one or more release subsystems for receiving respective response signals, and activating controlled release of material from respective parts of the rotor assembly to mitigate the effect of the crack growth.

Abstract: A system for assisting in spectrally characterizing or detecting a sample using radiation at a predetermined wavelength or in a predetermined wavelength range is disclosed. In one aspect, the system includes a substrate having a nanopore for excitation of plasmons. The nanopore provides a window through the substrate, wherein a smallest window opening of the window has an average length (L) and an average width (W) both being substantially smaller than 2 ?m. The nanopore supports highly confined surface plasmon polaritons and at specific wavelengths resonances are observed, when the conditions for a standing wave are fulfilled. This leads to strong field enhancements and enables single molecule spectroscopy.

Abstract: A projection system includes a display apparatus comprising a plurality of tunable Fabry-Perot filters, each of the filters being configured for shifting between a state in which the filter transmits radiation in a bandwidth in the visible range of the electromagnetic spectrum and a state in which the filter transmits radiation in a bandwidth outside the visible range of the electromagnetic spectrum. An illuminator provides light to the plurality of Fabry-Perot filters. A control system receives image data and controls the display apparatus to project an image onto an associated display surface. The control system includes a modulator which provides wavelength modulation signals to the plurality of Fabry-Perot filters to modulate a color of pixels in the image and causes selected ones of the Fabry-Perot filters to shift into the bandwidth outside the visible range to modulate the brightness of pixels in the image.

Abstract: The present invention relates to an actuator for moving a rigid element, e.g. an optical element such as mirror (1), the element being mechanically coupled to a frame (4) with a bendable coupling (2A), wherein actuator elements (3A, 3B) are mounted on said coupling between the frame and element, the coupling and actuator elements being adapted to provide a movement to the element when subject to signal from a signal generator.

Abstract: A gas concentration-measuring device makes it possible to measure gas components in a gas sample. An interferometer, based on a dual-band Fabry-Perot interferometer (1), is provided with a transmission spectrum that can be set by a control voltage (38). The control voltage (38) of the dual-band Fabry-Perot interferometer (1) is synchronized over the course of time with the activation and deactivation of the radiation sources (11, 12).

Abstract: An optical pressure sensor interrogation system is provided. The system includes a light source for providing an optical signal to an optical pressure sensor and an optical coupler for receiving a reflected signal from the optical pressure sensor. The optical coupler splits the reflected signal and provides a first portion of the reflected signal to a first optical detector. The system further includes a filter for receiving a second portion of the reflected signal and providing a filtered signal to a second optical detector and a processing circuitry configured to obtain pressure based on a division or a subtraction of light intensities of the first and the second optical detector output signals. The processing circuitry is further configured to provide a feedback signal to the light source to control a wavelength of the optical signal.

Abstract: Another embodiment has a method of driving a display device including an array of MEMS elements is disclosed. The MEMS elements are characterized by a preferred set of drive potential differences including preferred positive and preferred negative actuation potential differences, preferred positive and preferred negative hold potential differences, and a preferred release potential difference, where the preferred set of drive potential differences is symmetric about a voltage differing from 0V by an offset ?V. Another embodiment has a reduced set of supply voltages are used, while maintaining the charge balancing effects of applying potential differences of opposite polarity without visible artifacts.

Abstract: A frequency comb laser providing large comb spacing is disclosed. At least one embodiment includes a mode locked waveguide laser system. The mode locked waveguide laser includes a laser cavity having a waveguide, and a dispersion control unit (DCU) in the cavity. The DCU imparts an angular dispersion, group-velocity dispersion (GVD) and a spatial chirp to a beam propagating in the cavity. The DCU is capable of producing net GVD in a range from a positive value to a negative value. In some embodiments a tunable fiber frequency comb system configured as an optical frequency synthesizer is provided. In at least one embodiment a low phase noise micro-wave source may be implemented with a fiber comb laser having a comb spacing greater than about 1 GHz. The laser system is suitable for mass-producible fiber comb sources with large comb spacing and low noise. Applications include high-resolution spectroscopy.

Abstract: A Fabry-Perot interferometer includes a fixed mirror structure and a movable mirror structure. The fixed mirror structure has a fixed mirror in a spectral region. The movable mirror structure includes a membrane spaced from the fixed mirror structure. The membrane has a movable mirror in the spectral region and multiple springs arranged one inside the other around the spectral region. A spring constant of the inner spring is less than a spring constant of the outer spring. One of the fixed mirror structure and the membrane has multiple electrodes, and the other of the fixed mirror structure and the membrane has at least one electrode that is paired with the electrodes to form opposing electrode pairs arranged one inside the other around the spectral region. The number of the opposing electrode pairs is equal to the number of the springs.

Abstract: Embodiments of environmental stimulus sensors comprising multiple sources and detectors for interrogating one or more optically resonant cavities that are responsive to one or more environmental stimuli are disclosed. Such sensors have, among other advantages, improved immunity to source and/or detector noise.

Abstract: Even when only a few antigens exist in a specimen, a change in a dielectric constant and a change in an optical spectrum accompanied thereto in the periphery of a conductive member are made larger, so that sensing at high sensitivity can be performed. A structure including a protrusion including a dielectric material protruded on a substrate and a conductive member provided on a first surface of the protrusion, in which the maximum value of the cross-sectional area in the cross-section in parallel with a first surface of the conductive member is larger than the area of the first surface.

Abstract: A system and method for monitoring the structural integrity of a structure is provided. An optical fiber is acoustically coupled to one or more of the structural elements. A source of optical energy is configured to inject optical energy into the optical fiber, and an optical detector is configured to detect a first optical return signal having characteristics that are affected by vibrations of the structural elements. An analyzer measures characteristics of the optical return signal to determine information concerning the movement of the structural elements monitored by the fiber optic cable. The results of the analyzer can be stored and so that the analysis of the optical return signal can be compared to previously recorded signals to determine changes in structural integrity over time. Multiple fibers can be acoustically coupled to the monitored structural elements to obtain additional data concerning the structural integrity.

Abstract: In one embodiment, a system for determining information about an assay incorporates a filter assembly that includes an optical structure configured to be removably attachable to a laser resonating cavity of the system, the optical structure being configured to form a portion of the laser resonating cavity such that it reflects light propagating through a gain medium in the laser resonating cavity when attached thereto. The optical structure can include a first surface having an array of one or more sites, each site containing an assay, and a second surface configured such that the second surface is disposed within the laser resonating cavity forming a portion of the laser resonating cavity. The optical structure is configured to optically interact with the assay to change one or more characteristics of light in the laser resonating cavity based on a reaction that occurs in an assay on said first surface.

Abstract: An interferometer includes a cavity including a pair of mirrors defining a cavity length. An input beam and a counter-propagating reference beam are directed into the cavity. The interferometer generates a feedback control signal and an ultrasound signal for optimal performance and measurement of a target, respectively.

Abstract: The invention relates to controllable Fabry-Perot interferometers which are produced with micromechanical (MEMS) technology. Producing prior art interferometers includes a risk of deterioration of mirrors during the etching of the sacrificial layer (123). According to the solution according to the invention at least one layer (103, 105, 114, 116) of the mirrors is made of silicon-rich silicon nitride. In the inventive Fabry-Perot interferometer it is possible to avoid or reduce using silicon oxide in the mirror layers whereby the risk of deterioration of the mirrors is reduced. It is also possible to use mirror surfaces with higher roughness, whereby the risk of the mirrors sticking to each other is reduced.

Abstract: A fringe pattern from an interferometer is imaged onto a digital micromirror device containing an array of micromirrors in an associated pattern of pixel mirror rotational states that provide for sampling the circular fringe pattern in cooperation with one or more associated photodetectors, so as to provide for generate a corresponding set of associated complementary signals. A plurality of different sets of associated complementary signals generated for a corresponding plurality of mutually independent associated patterns of pixel mirror rotational states are used to determine at least one metric associated with the circular fringe pattern.

Abstract: Apparatus, methods, and other embodiments associated with monitoring combustion dynamics in a gas turbine engine environment are described herein. In one embodiment of a system for monitoring combustion dynamics in a gas turbine engine environment, the system includes a transducer and an optical fiber. The transducer is positioned within the gas turbine engine environment, and the transducer includes a diaphragm, a window, and a Fabry-Perot gap. The diaphragm has a reflective surface, and the window has a partially reflective surface. The Fabry-Perot gap is formed between the reflective surface of the diaphragm and the partially reflective surface of the window. The optical fiber is positioned proximate to the window and directs light into the Fabry-Perot gap and receiving light reflected from the Fabry-Perot gap.

Abstract: A tunable optical cavity can be tuned by relative movement between two reflection surfaces, such as by deforming elastomer spacers connected between mirrors or other light-reflective components that include the reflection surfaces. The optical cavity structure includes an analyte region in its light-transmissive region, and presence of analyte in the analyte region affects output light when the optical cavity is tuned to a set of positions. Electrodes that cause deformation of the spacers can also be used to capacitively sense the distance between them. Control circuitry that provides tuning signals can cause continuous movement across a range of positions, allowing continuous photosensing of analyte-affected output light by a detector.

Abstract: Apparatus, methods, and other embodiments associated with measuring multiple Fabry-Perot gaps to determine environmental parameters are described herein. In one embodiment, a system for measuring environmental parameters includes an optical fiber, a first reflective surface, a second reflective surface, a third reflective surface, and a light source. The first reflective surface is positioned proximate to a first end of the optical fiber. The second reflective surface is positioned to form a first Fabry-Perot gap between the first reflective surface and the second reflective surface. The third reflective surface is positioned to form a second Fabry-Perot gap between the second reflective surface and third reflective surface. The light source provides light to the optical fiber, wherein the optical fiber delivers light from the light source to the first Fabry-Perot gap and the second Fabry-Perot gap and the optical fiber receives reflected light from the first Fabry-Perot gap and the second Fabry-Perot gap.

Abstract: An environmental sensing device includes an interferometric modulator which permanently actuates, in a visually-detectable manner, in response to being exposed to a predetermined environmental threshold or condition. The device can include a reactive layer, coating, or proof mass disposed on a movable member of the interferometric modulator. The reactive layer, coating, or proof mass can expand, contract, bend, or otherwise move when exposed to a predefined chemical, level of humidity, temperature threshold, type of radiation, and/or level of mechanical shock, causing the interferometric modulator to collapse and permanently indicate such exposure.

Abstract: Electrically tunable Fabry-Perot interferometers which are produced with micromechanical (MEMS) technology. Producing interferometers with prior art processes includes costly and complicated production phases. Therefore, it has not been possible to apply interferometers in consumer mass products. According to the present solution, the Fabry-Perot cavity is made by removing a sacrificial layer (112) which has been polymer material. A mirror layer (113, 117-120) which is produced above the sacrificial layer can be made with atomic layer deposition technology, for example. According to a preferable embodiment, electrodes (106b, 115b) of the mirror structures are formed by using sputtering or evaporation. With the present solution it is possible to avoid the above mentioned problems related with prior art.

Abstract: The device includes two supports and a primary conductive strip. The primary conductive strip includes a neutral surface, a first side, and a second side. The primary conductive strip is connected one of directly and indirectly on the first side to the two supports such that the primary conductive strip is constrained in two dimensions and movable in one dimension. The device also includes a primary distributed feedback fiber laser. The primary distributed feedback fiber laser includes a fiber axis. The primary distributed feedback fiber laser is connected to the primary conductive strip along one of the first side and the second side such that there is a positive distance between the neutral surface of the primary conductive strip and the fiber axis of the primary distributed feedback fiber laser.

Abstract: The disclosure is directed at an interferometric localized surface plasmon resonance sensor (ILSPR) unit comprising an ILSPR sensor chip, the sensor chip including a localized surface plasmon resonance sensor (LSPR) layer; at least one light source for directing light through the ILSPR sensor chip at the LSPR layer; and a photodetector for sensing a level of light intensity after the light has struck the LSPR layer.

Abstract: An optical assembly for use in an interferometer is provided. The optical assembly includes first and second partially reflective surfaces positioned along an optical axis and oriented at different non-normal angles to the optical axis. The second partially reflective surface is configured to receive light transmitted through the first partially reflective surface along the optical path, transmit a portion of the received light to a test object to define measurement light for the interferometer and reflect another portion of the received light back towards the first partially reflective surface to define reference light for the interferometer. The reference light makes at least one round trip path between the second and first partially reflective surfaces.

Abstract: An implantable product includes an optical cavity structure with first and second parts, each of which can operate as an optical cavity. The first part includes a container with at least one opening through which bodily fluid can transfer between the container's interior and exterior when the product is implanted in a body. The second part includes a container that is closed and contains a reference fluid. The implantable product can also include one or both of a light source component and a photosensing component. Photosensed quantities from the first part's output light can be adjusted based on photosensed quantities from the second part's output light. Both parts can have their light interface surfaces aligned so that they both receive input light from a light source component and both provide output light to a photosensing component.

Abstract: An optical sensing probe includes a tube having a tip portion configured for placement in an environment in which conditions are to be sensed and an etalon having a known characteristic disposed proximate the tip portion. The tube also includes a head portion remote from the tip portion containing a light directing element for directing light beams at the etalon and receiving reflected light beams from the etalon wherein the received reflected light beams are used for determining an environmental condition proximate the tip portion. A method for measuring a thickness of the etalon may include directing a light beams at different frequencies at the etalon and receiving the light beams from the etalon. The method may also include identifying conditions of the respective light beams condition received from the etalon and then calculating a first thickness of the etalon responsive to the respective conditions and the known characteristic.

Abstract: A multi-beam interferometer, typically for use in Optical Coherence Tomography, comprising a multiple beam source, the source being arranged so as to provide, in use, a plurality of beams of light for use in the interferometer, the source comprising: a light source arranged to, in use, emit a beam of light; and a rattle plate comprising a first reflective surface and a second reflective surface facing one another, the second reflective surface being only partially reflective.

Abstract: Device and method for acquiring position with a confocal Fabry-Perot interferometer. In a general aspect, the device for acquiring position may include an arrangement for acquiring position where the acquiring arrangement has a confocal Fabry-Perot interferometer. In another general aspect, a method for acquiring position may include generating an interference pattern dependent on a position of an object by a confocal Fabry-Perot interferometer; detecting the interference pattern to obtain a measuring signal; and evaluating the measuring signal.

Abstract: A method for forming a structure comprising multiple parallel surfaces having a precise separation is disclosed. Precise separation and parallelism of the surfaces is achieved through the use of an adhesive mixture that comprises a plurality of spacers having a dimension substantially equal to the desired separation.

Abstract: A variable wavelength interference filter includes: a first substrate having a light transmissive property; a second substrate opposed to and bonded to one surface of the first substrate; a first reflecting film disposed on the one surface of the first substrate; a second reflecting film disposed on a first surface of the second substrate opposed to the first substrate, and opposed to the first reflecting film via a gap; and a variable section adapted to vary the gap, wherein the second substrate includes a light transmission opening disposed at a position opposed to the first reflecting film, and penetrating through the second substrate from the first surface to the second surface on the opposite side, and a planar transmissive member opposed to the first substrate and adapted to close the light transmission opening.

Abstract: In a tunable interference filter according to the invention, a second substrate includes a light transmission hole and alight transmissive member provided within the light transmission hole, and the light transmission hole is formed in a tapered shape having a diameter dimension of an inner circumferential surface increasing from the first surface toward the second surface, and the light transmissive member has a light incident surface in parallel to the first reflection surface and the second reflection surface, a light exiting surface in parallel to the first reflection surface and the second reflection surface, and a tapered side surface having a diameter dimension increasing from the first surface toward the second surface, and the tapered side surface is in contact with the inner circumferential surface of the light transmission hole.