Abstract: An exemplary method generally includes reflecting, by a movable reflector, electromagnetic radiation from a field of view in a region of interest of an additive manufacturing machine to an optics assembly; splitting, by a beam splitter of the optics assembly, the electromagnetic radiation into a plurality of beams; directing the plurality of beams to a plurality of optical sensors such that each optical sensor of the plurality of optical sensors receives a corresponding and respective beam of the plurality of beams; generating, by the plurality of optical sensors, a plurality of outputs, each output including information related to a corresponding and respective beam; and controlling, by a controller, the movable reflector to move the field of view to maintain a predetermined relationship between the field of view and a moving build point within the region of interest.

Abstract: Embodiments of the present disclosure relate to optical devices for augmented, virtual, and/or mixed reality applications. In one or more embodiments, an optical device metrology system is configured to measure a plurality of see-through metrics for optical devices.

Abstract: Disclosed are methods of detecting an analyte of interest comprising introducing a sample comprising an analyte of interest to an antibody or antibody fragment; incubating the sample and antibody or antibody fragment under conditions sufficient to allow binding of the analyte of interest to the antibody or antibody fragment; and detecting the binding of the analyte of interest to the antibody or antibody fragment using a label-free second harmonic detection system. Also disclosed are methods of screening and diagnosing using antibodies or antibody fragments and a label-free second harmonic detection system.

Abstract: Disclosed herein are systems and methods capable of identifying, tracking, and sorting particles or droplets flowing in a channel, for example, a microfluidic channel having a fluid medium. The channel and the fluid medium can have a similar refractive index such that they appear translucent or transparent when illuminated by electromagnetic radiation. The particles or droplets can have a refractive index substantially different from that of the channel and the medium, such that the particles or droplets interfere with the electromagnetic radiation. A sensor can be disposed adjacent to the channel to record the electromagnetic radiation. The sensor can be attached to a system for identifying, tracking, and sorting the droplets.

Abstract: An OCT signal processing device has an acquisition unit for acquiring three or more OCT signals being temporally different from each other with respect to the same position on a subject, from an OCT device that detects an OCT signal based on reflection light of measurement light applied to a subject and reference light corresponding to the measurement light, and a calculation unit for calculating motion contrast based on a plurality of OCT signals. The calculation unit selects two or more sets of OCT signals having different time interval between the OCT signals among sets obtained by extracting a plurality of OCT signals out of the three or more OCT signals, and calculates motion contrast for each of the selected two or more sets.

Abstract: An imaging system uses polarized light to illuminate the target and then uses a polarization filter to remove the light that is reflected from the target without modification. The target can include one or more anisotropic objects that scatter the light and alter the polarization state of the reflected light and causing it to be selectively transmitted to the imaging device which can record the transmitted light through the filter. The illuminating light can be circularly polarized and the filter can remove the circularly polarized light. The target can include asymmetric nanoparticles, such as nanorods that alter the amplitude or phase of the scattered light enabling pass through the filter to be detected by the imaging device.

Abstract: Proposed are a three-dimensional (3D) optical tomography method and apparatus using a partially coherent light and a multi-illumination pattern. The 3D optical diffraction tomography method based on low coherence light and a multi-illumination pattern using a 3D optical diffraction tomography apparatus may include making light incident on a sample using a plurality of patterns, measuring, by an image measurement unit, different locations at different depth locations of the sample and measuring two-dimensional (2D) images of the sample, and reconstructing 3D refractive index information of the sample based on the different patterns and the 2D images obtained at the different depth locations.

Abstract: An impairment detection system is provided and includes an emitter, first and second beam selectors, a reference reflector, a sensor and a control module. The emitter is configured to emitter a first light signal. The first beam selector is configured to forward the first light signal to a touch probe. The reference reflector is configured to reflect the first light signal received from the first beam selector to generate a second reflected signal. The second beam selector is configured to receive (i) a first reflected signal from the touch probe based on reflection of the first light signal on an area of a person, and (ii) the second reflected signal. The sensor is configured to receive from the second beam selector the first reflected signal and the second reflected signal. The control module is configured to determine an impairment level of the person based on an output of the sensor.

Abstract: Provided are a refractive index measuring device and a refractive index measuring method. A detector (2) detects an intensity of a measuring beam transmitted through the sample. A camera (200) images a color image of the measuring beam which is dispersed into multiple colors by transmitting through the sample. A scanning processing portion (101) carries out scanning by changing an angle of receiving the measuring beam transmitted through the sample or an angle of the measuring beam incident on the sample. A wavelength specifying processing portion (102) specifies, based on the detected intensity of the detector (2) varying with the scanning by the scanning processing portion (101) and color information corresponding to a position of the measuring beam incident on the detector (2) in a color image which is imaged by the camera (200), the wavelength corresponding to each peak of the detected intensity.

Abstract: A method and apparatus for adjusting a modulation index of an analog optical signal using an interference phenomenon of a coherent light, the method including dividing an analog optical signal for a first path and a second path, extracting an optical carrier from an analog optical signal divided for the first path, controlling an intensity and a phase of the optical carrier, and controlling a modulation index of the analog optical signal by combining an analog optical signal divided for the second path and the optical carrier of which the intensity and the phase are controlled.

Abstract: The system and methods are made to apply interferometry to ophthalmic applications. The system makes use of a low-coherence interferometer to obtain a plurality of measurements of a contacts lens. The system and methods characterizes the surface profile of both surfaces of a contact lens, a thickness profiles, and combines these measurements with an index information to reconstruct a complete model of the contact lens.

Abstract: Provided are improved optical detection systems and methods for using same, which systems and methods comprise single channel interferometric detection systems and methods for determining a characteristic property of samples. Such interferometric detection systems and methods employ a light beam that impinges two or more discrete zones along a channel, thereby avoiding variations that can result in increases in detection limits and/or measurement errors.

Abstract: A virtual image phase array (VIPA) includes two parallel surfaces, a first highly-reflective surface with a highly-reflective coating, and a second partially-reflective surface. The first highly-reflective surface also requires an input zone with an anti-reflection coating, which abuts the highly-reflective coating, with a transition zone therebetween. Light enters the VIPA through the input zone, and reflects back and forth between the highly and partially reflective surfaces, gradually leaking out through the partially reflective surface. To minimize the transition zone and thereby minimize the input angle of incidence and maximize the number of reflections per unit of length, the substrate coated with the highly-reflective coating is subsequently polished at an acute angle resulting in the transition zone having the same sharp angle.

Abstract: An interferometric holographic instrument enables the generation of digital data for testing and enabling 2-dimensional and 3-dimensional analysis of “live” and real-time semiconductor or anisotropic devices and materials. The digitally recorded interferometric data can be displayed, stored or connected to a live data stream for transmission to digital processing devices. A digital electric processor or analyzer connected to the recording device, or live data stream, enables the interferometric data to be utilized to test, develop, and shape semiconductor and anisotropic microelectronic processing, wireless and microwave devices.

Abstract: A method for evaluating the condition of a ceramic coating deposited on a substrate comprising illuminating the ceramic coating with light, measuring the intensity of light returned from the ceramic coating as function of depth in the coating and transverse position on the coating, and analyzing the measured light intensities to obtain one or more of intensity of the light returned from the exposed coating surface relative to the intensity of light returned from the coating/substrate interface, intensity of the light returned from the coating/substrate interface relative to the intensity of light returned from the bulk of the ceramic coating, determination of roughness at the exposed surface of the ceramic coating, and determination of roughness of the interface between the ceramic coating and underlying bond coat or substrate.

Abstract: A terahertz spectrometer includes: a terahertz-wave emitter and a terahertz receiver elements. The terahertz wave generated by means of generating beat frequency corresponding to the difference between two rapidly tunable continuous wave lasers. Having a difference in time between the interrogating signal and the reference signal at the receiver end side, which corresponds to intermediate frequency (IF), not centered around the baseband, i.e. zero Hertz. The offset step size of the intermediate frequency from zero Hertz is linearly correlated to the position of the interrogated object position.

Abstract: Improved methods and systems for inspection imaging for holographic or interferometric semiconductor test and evaluation through all phases of device development and manufacture. Specifically, systems and methods are disclosed for extending the range of optical holographic interferometric inspection for testing and evaluating microelectronic devices and determining the interplay of electromagnetic signals and dynamic stresses to the semiconductor material are provided in which an enhanced imaging method provides continuous and varying the magnification of the optical holographic interferometric images over a plurality of interleaved optical pathways and imaging devices. Analysis of one or more holographic interference patterns displays internal and external stresses and the various effects of such stresses upon the operating characteristics of features within the features, interior structures or within the internal surfaces of the semiconductor device at any stage of development or manufacture.

Abstract: A method of controlling the gain or sensitivity of a test and measurement system. The test and measurement system includes a host, a controller with an optical transmitter and an optical receiver, optical-to-electrical converter, an accessory head, and a device under test. The method includes determining whether a gain or sensitivity adjustment of the test and measurement system is required, determining the amount of gain or sensitivity adjustment, and adjusting the output power of a laser of the optical transmitter in response to the determination of the gain or sensitivity adjustment of the test and measurement system.

Abstract: A method is disclosed of detecting the presence of an organism in a medium. In some embodiments, the method includes: obtaining a series of optical coherence tomography measurements of a region of the medium; processing the series of optical coherence tomography measurements to determine information indicative of translational and rotational motion of an object in the region of the medium; identifying the object as organism based on the information indicative of translational and rotational motion of the object; and outputting information indication of the presence of the organism.

Abstract: An apparatus and method for detecting refractive index variations in a sample is disclosed. The apparatus includes a multi frequency laser source configured to generate a mixed laser beam having at least two optical frequencies. A sinusoidal function generator is configured to modulate the optical frequencies to generate a chirp-modulated mixed laser beam. The chirp-modulated mixed laser beam being configured to pass through the sample. A detector is configured to detect the chirp-modulated mixed beam. A signal processer is configured to process the detected chirp-modulated mixed beam to measure refractive index variations in the sample.

Abstract: Disclosed is a system and method for characterizing optical materials, using steps and equipment for generating a coherent laser light, filtering the light to remove high order spatial components, collecting the filtered light and forming a parallel light beam, splitting the parallel beam into a first direction and a second direction wherein the parallel beam travelling in the second direction travels toward the material sample so that the parallel beam passes through the sample, applying various physical quantities to the sample, reflecting the beam travelling in the first direction to produce a first reflected beam, reflecting the beam that passes through the sample to produce a second reflected beam that travels back through the sample, combining the second reflected beam after it travels back though the sample with the first reflected beam, sensing the light beam produced by combining the first and second reflected beams, and processing the sensed beam to determine sample characteristics and properties.

Abstract: A system (10) for controlling an optical surface to be measured relatively to an optical reference surface, the control system (10) including a first optical element (36) provided with a first optical axis and able to introduce a first phase function into the phase of an incident beam, and a second optical element (38) provided with a second optical axis and able to introduce a second phase function into the phase of a beam transmitted through or reflected by the first optical element (36). The first phase function and the second phase function each correspond to the same optical aberration and at least one from among the first optical element (36) and the second optical element (38) is rotary around the optical axis specific to the relevant optical element (36, 38).

Abstract: A method for determining information about a test object includes combining two or more scanning interference signals to form a synthetic interference signal; analyzing the synthetic interference signal to determine information about the test object; and outputting the information about the test object. Each of the two or more scanning interference signals correspond to interference between test light and reference light as an optical path length difference between the test and reference light is scanned, wherein the test and reference light are derived from a common source. The test light scatters from the test object over a range of angles and each of the two or more scanning interferometry signals corresponds to a different scattering angle or polarization state of the test light.

Abstract: The present invention relates to systems and methods for quantitative three-dimensional mapping of refractive index in living or non-living cells, tissues, or organisms using a phase-shifting laser interferometric microscope with variable illumination angle. A preferred embodiment provides tomographic imaging of cells and multicellular organisms, and time-dependent changes in cell structure and the quantitative characterization of specimen-induced aberrations in high-resolution microscopy with multiple applications in tissue light scattering.

Abstract: An optical tomographic image forming method including: splitting low coherence light emitted from a light source is split into a measuring light and a reference light; forming an optical tomographic image of a measured object by detecting an interference light that is obtained by superposing reflected light, reflected from the measured object when the measuring light is irradiated onto the measured object via a condenser lens, and reflected light, reflected from a reference mirror, which is positioned a predetermined length of optical path away from the splitting position, when the reference light is irradiated onto the reference mirror, wherein the method further includes: inputting a refractive index of the measured object; correcting the tomographic image in accordance with the inputted refractive index of the measured object; and outputting the corrected tomographic image.

Abstract: The invention relates to a method and an apparatus for measuring the thickness of a transparent film by broad band interferometry, comprising the steps of preparing a correlogram of the film by an interferometer, applying a Fourier transformation to said correlogram to obtain a Fourier phase function, removing a linear component thereof, applying a second integral transformation to the remaining non-linear component to obtain an integral amplitude function of said non-linear component, identifying the peak location of said integral amplitude function and determining the thickness of the film as the double value of the abscissa at said peak location considering a refractive index of a film which is dependent on wavelength. The last two steps may be replaced by identifying the peak locations of said integral amplitude function and determining the thickness of the films as the double values of the abscissas at the peak locations.

Abstract: Measuring of an electro-optic coefficient and a thermo-optic coefficient of an optical device and an optical material, and more specifically, to measurement systems and methods of evaluating the electro-optic and thermo-optic coefficients by using interference fringe measurement techniques, wherein those optical characteristics can be precisely measured over a wide wavelength intended without using a complicated measuring equipment.

Abstract: A method for an automated inline determination of the refractive power of an ophthalmic lens (5) including providing an inspection cuvette having an optically transparent bottom (21) and having a concave inner surface (210) and containing the ophthalmic lens (5) immersed in a liquid, and providing a light source (42) and a wavefront sensor (6) including a detector. The light coming from the light source (42) and having passed the ophthalmic lens (5) contained in the inspection cuvette and impinging on the detector generates signals at the detector. By comparing the signals generated at the detector with predetermined signals representative of a reference refractive power, the refractive power of the ophthalmic lens (5) is thereby determined.

Abstract: A method and apparatus for measuring refractive index of an object are disclosed. The method includes, acquiring a number of first fringes of a first interference pattern formed by interference of a first beam of light transmitted through the object with a second beam of light not transmitted through the object; acquiring a number of second fringes of a second interference pattern formed by interference of a third beam of light reflected from a first surface of the object with a fourth beam of light transmitted through the object and reflected from a second surface of the object; and calculating the refractive index of the object based on the number of first fringes and the number of second fringes. The method may further include calculating the Abbe number of the object based on the refractive indices of the object measured at different wavelengths.

Abstract: An optical device suitable for forming a pixel in a video display. The optical device includes a first layer having a first refractive index; a second layer over the first layer, the second layer having a second refractive index less than the first refractive index; and a third layer over the second layer, the third layer having a third refractive index larger than the second refractive index; and a fourth layer that is at least partially optically absorptive, wherein the optical stack and the fourth layer are a first distance from one another when the device is in a first state and are a second distance from one another when the device is in a second state, the first distance different from the second distance.

Abstract: Measuring refractive index of air based on laser synthetic wavelength interferometry. The Apparatus includes a dual-frequency laser that emits orthogonal linear polarized light of wavelengths ?1 and ?2, a beamsplitter, two polarizing beamsplitters, two corner-cube retroreflectors, a quartz vacuum cavity of length L disposed in the measuring optical path in parallel to the light propagation direction, and two detectors. The apparatus is used to measure the refractive index of air using the dual-frequency laser to emit orthogonal linear polarized light with wavelengths ?1 and ?2, using the beamsplitters, corner-cube retroreflectors, quartz vacuum cavity, and detectors. The integer N and fraction ? of interference fringes of wavelength ?2 are determined. The refractive index of air n is obtained by using the length L of the vacuum cavity, integer N and fraction ? of the interference fringes of wavelength ?2.

Abstract: A method of measuring a refractive index distribution includes steps of setting a plurality of different arrangements by a translation movement in a state where an object is arranged in first and second media having refractive indices different from a refractive index of the object, measuring transmissive wavefront of the object for each of media and each of the plurality of arrangements by reference light entering the object (S400), obtaining wavefront aberration corresponding to a difference between each transmissive wavefront and a reference transmissive wavefront (S500), obtaining refractive index distribution of the object by removing an influence of a shape error of the object using wavefront aberration of two media in which the object is arranged at the same position (S70), and obtaining refractive index distribution information of the object based on a plurality of refractive index distributions corresponding to the plurality of arrangements (S80).

Abstract: By using two probe optical systems for measurement by disposing the probe optical systems with a test object sandwiched therebetween, an optical path length of light transmitted through the test object which is identified locally is calculated using an interference signal thereof. In addition, a geometrical thickness of the same part is calculated by measuring positions of the probe optical systems, whereby two calculated values are obtained. Based on the values and a calculated value for a reference object, a refractive index distribution of the test object is obtained.

Abstract: An optical device suitable for forming a pixel in a video display. The optical device includes a first layer having a first refractive index; a second layer over the first layer, the second layer having a second refractive index less than the first refractive index; and a third layer over the second layer, the third layer having a third refractive index larger than the second refractive index; and a fourth layer that is at least partially optically absorptive, wherein the optical stack and the fourth layer are a first distance from one another when the device is in a first state and are a second distance from one another when the device is in a second state, the first distance different from the second distance.

Abstract: The present invention provides a measuring apparatus for measuring an absolute distance between a reference surface an d a test surface, including a phase detection unit configured to detect an interference signal between light reflected by the reference surface and light reflected by the test surface, and detect, from the interference signal, a phase corresponding to an optical path length between the reference surface and the test surface, and a processing unit configured to perform processing of obtaining the absolute distance by controlling the phase detection unit so as to detect the phase corresponding to the optical path length between the reference surface and the test surface for each of a first reference wavelength and a second reference wavelength while changing the wavelength of light to be emitted by a first light source continuously from the first reference wavelength to the second reference wavelength.

Abstract: A measuring method includes measuring a sum of an optical path length of a test object and a first medium in a first container, introducing light into an area that includes the first medium but does not include the test object and measuring the optical path length of the first medium, measuring a sum of the optical path length of the test object and a second medium in a second container, the second medium having a refractive index different from that of the first medium, introducing the light into an area that includes the second medium but does not include the test object and of measuring the optical path length of the second medium, and calculating a refractive index of the test object based on the measured optical path lengths and an actual distance of an optical path for which each optical path length is measured.

Abstract: The measuring method includes a step of causing reference light to enter an object placed in a first medium to measure a first transmitted wavefront, a step of causing the reference light to enter the object placed in a second medium to measure a second transmitted wavefront, a step of measuring first and second placement positions where the object is placed in the first and second media, and a calculating step of calculating an internal refractive index distribution of the object by using measurement results of the first and second transmitted wavefronts. The calculating step calculates the internal refractive index distribution from which a shape component of the object is removed by using the measurement results of the first and second transmitted wavefronts, and first and second reference transmitted wavefronts of a reference object to be placed at positions identical to the first and second placement positions.

Abstract: A method for contactless measurement of the density of a porous material, using a measurement of the refractive index of the material by optical coherence tomography. In the optical coherence tomography technique, the optical path corresponding to the crossing of an object made of the material by a light beam used in the technique, is determined, the thickness of the object is determined, the refractive index of the material is determined from the optical path and from the thickness, and the density of the material is determined from the refractive index.

Abstract: In an interferometer system and a method for its operation, the interferometer system includes an interferometer having an interferometer light source whose emitted radiation is able to be split into a measuring arm and a reference arm, an object to be measured being disposed in the measuring arm, and the interferometer delivering interferometer signals as a function of the position of the object to be measured. In addition, a detecting device is provided for detecting fluctuations in the refractive index of the air in the measuring arm and/or reference arm. The detecting device includes a spectrometer unit; the spectrometer unit has at least one spectrometer light source, as well as at least one spectrometer detector unit.

Abstract: The method measures first transmitted wavefronts and second transmitted wavefronts by respectively causing reference light to enter an object placed in plural placement states in a first medium and a second medium, calculates an aberration sensitivity with respect to changes of the placement state of the object, and calculates an alignment error of the object in each placement state by using the aberration sensitivity and the first and second transmitted wavefronts measured in each placement state. The method further calculates first and second reference transmitted wavefronts respectively acquirable when causing the reference light to enter the reference object placed in placement states including the alignment errors in the first medium and the second medium, and calculates a refractive index distribution of the object which a shape component thereof is removed, by using the first and second transmitted wavefronts and the first and second reference transmitted wavefronts.

Abstract: A refractive index distribution measurement method includes the steps of measuring a first transmission wavefront of a test object by introducing reference light to the test object immersed in a first medium having a first refractive index lower than that of the test object by 0.01 or more, measuring a second transmission wavefront of the test object by introducing the reference light to the test object immersed in a second medium having a second refractive index lower than that of the test object by 0.01 or more and different from the first refractive index, and obtaining a refractive index distribution of the test object based on a measurement result of the first transmission wavefront and a measurement result of the second transmission wavefront.

Abstract: Methods and/or systems are disclosed herein for use in imaging an object including using interferometry while modifying at least one characteristic of the object (e.g., refractive index of the object).

Abstract: Quantifying a refractive index of a test medium by obtaining spectral data representative for an optical signal being modulated with an optical transfer characteristics of a photonic sensor, the modulation being obtained by combining modulation of a first electromagnetic wave component in an optical filter element with a first periodic transfer spectrum having a first free spectral range and modulation of a second electromagnetic wave component in an optical filter element with a second periodic transfer spectrum having a second free spectral range being different from the first free spectral range. A relative is change induced in the second periodic transfer spectrum by bringing the test medium in proximity with the optical filter element with the second periodic transfer spectrum. The refractive index of the test medium is quantified by determining a wavelength offset of an envelope signal in said spectral data.

Abstract: Subject matter disclosed herein relates to measuring optical fibers or measuring devices comprising optical fibers and, in particular, to measuring a variation of refractive index of an optical fiber as a function of position and wavelength.

Abstract: A method and system that enable the measurement of a second-harmonic-generation-forward/backward (SHG F/B) ratio from an object by performing only a single image scan using via epi-imaging using an epi-detection technique. Two simultaneous SGH images (a forward propagating SHG “F” image and a back propagating SHG “B” image) are generated during the single image scan. A pinhole mirror can be used to separate the F-SHG and the B-SHG, which are detected by separate detectors.

Abstract: Method and apparatus for determining dielectric function of liquid solutions and thereby concentrations of substances in aqueous solution or the volatile/non-volatile nature of the liquid by self-referenced reflection THz spectroscopy. Having the aqueous solution in any container with a window allows irradiating coherent THz radiation with frequencies within the range 0.05-2 THz on the front of the window, and recording both a reference signal reflected from the front of the window and a sample signal reflected from the back of the window in contact with the aqueous solution. From these signals, the complex index of refraction, (I) or the complex reflection coefficient (II), can be calculated. The calculated components are compared with previously determined components from samples with known concentrations, whereby a concentration of the substance in the mixture can be estimated.

Abstract: The method includes first and second steps of placing an object in first and second media whose refractive indices are lower than that of the object, and of causing the reference light to enter the object to measure first and second transmitted wavefronts. When light rays entering a peripheral portion of the object and passing through a same point of the object are defined as first and second light rays, the method causes these light rays to proceed in directions mutually different to change an NA of the reference light such that the reference light after being transmitted through the object is brought closer to collimated light than that before entering the object. The method calculates an effective thickness of the object using geometric thicknesses thereof and calculates a refractive index distribution thereof using the first and second transmitted wavefronts and the effective thickness.

Abstract: An apparatus and method for detecting refractive index variations in a sample is disclosed. The apparatus includes a multi frequency laser source configured to generate a mixed laser beam having at least two optical frequencies. A sinusoidal function generator is configured to modulate the optical frequencies to generate a chirp-modulated mixed laser beam. The chirp-modulated mixed laser beam being configured to pass through the sample. A detector is configured to detect the chirp-modulated mixed beam. A signal processer is configured to process the detected chirp-modulated mixed beam to measure refractive index variations in the sample.

Abstract: A method and apparatus for measuring refractive index of an object are disclosed. The method includes, acquiring a number of first fringes of a first interference pattern formed by interference of a first beam of light transmitted through the object with a second beam of light not transmitted through the object; acquiring a number of second fringes of a second interference pattern formed by interference of a third beam of light reflected from a first surface of the object with a fourth beam of light transmitted through the object and reflected from a second surface of the object; and calculating the refractive index of the object based on the number of first fringes and the number of second fringes. The method may further include calculating the Abbe number of the object based on the refractive indices of the object measured at different wavelengths.

Abstract: An optoacoustic convolver includes: a light source; a first acoustic waveguide filled with a light-transmissive first acoustic medium; a second acoustic waveguide filled with a light-transmissive second acoustic medium; an optical system whereby light emitted from the light source is split into a first light beam and a second light beam, the first light beam entering the first acoustic waveguide, and the second light beam entering the second acoustic waveguide, thereby generating interference light between the first light beam having passed through the first acoustic waveguide and the second light beam having passed through the second acoustic waveguide; a light-receiving section for receiving the interference light and outputting an electric signal based on an intensity of the received light; and a correlation determination section for determining whether the received signal is correlated with the reference signal by observing the electric signal output from the light-receiving section.