Abstract: Presented is an optical coherence tomography system and method to increase imaging depth of optical coherence tomography (OCT) by selective amplification. In a swept-source OCT system with periodically linear wavenumber-vs-time characteristic, the signal in principle is summation of various sinusoidal signals with different frequencies. Each frequency component of the recorded signal carries reflectivity information for a certain depth of the analyzed object. At greater depth inside the analyzed object, the reflectivity information is generally weak due absorption and scattering. An analog or digital electronic circuit selectively filters and amplifies frequencies above some threshold, possibly up to another threshold. In this way, even small signals for relatively larger depths become detectable.

Abstract: Inspecting a multilayer sample. In one example embodiment, a method may include receiving, at a beam splitter, light and splitting the light into first and second portions; combining, at the beam splitter, the first portion of the light after being reflected from a multilayer sample and the second portion of the light after being reflected from a reflector; receiving, at a computer-controlled system for analyzing Fabry-Perot fringes, the combined light and spectrally analyzing the combined light to determine a value of a total power impinging a slit of the system for analyzing Fabry-Perot fringes; determining an optical path difference (OPD); recording an interferogram that plots the value versus the OPD for the OPD; performing the previous acts of the method one or more additional times with a different OPD; and using the interferogram for each of the different OPDs to determine the thicknesses and order of the layers of the multilayer sample.

Abstract: An optical pen for an optical measurement system includes a probe body arranged to be adjustably mounted in a measuring machine for optically measuring a test object. A single mode fiber optically coupled within the pen body transmits a source beam having an instantaneous or sequentially established bandwidth spanning a range of wavelengths to the pen body and also transmits a measurement beam from the pen body toward a detector. A combination and configuration of optics within the pen body provides a more compact and efficient optical pen.

Abstract: A force detector and method for using the same includes a lens. A cantilever is below the movable lens. A laser above the movable lens emits a beam of light through the movable lens, such that light reflects from the lens and the cantilever. A camera is configured to capture images produced by the light reflected from the lens and the light reflected from the cantilever. A processor is configured to determine a force between the movable lens and the cantilever based on a change in phase of the interference rings.

Abstract: An embodiment provides an optical image measuring apparatus capable of acquiring images with high lateral resolution and global sharpness. An optical image measuring apparatus of an embodiment includes an optical system, image forming part, controller and composite-cross-sectional-image forming part. The optical system includes a scanner that changes an irradiation position of signal light on an object and a focus position changing part that changes a focus position of the signal light. The optical system detects interference light of returned light of the respective signal light from the object and reference light. The image forming part forms a cross-sectional image based on detection results of a plurality of interference light corresponding to a plurality of irradiation positions of the signal light. The controller controls the optical system to irradiate the signal light onto the plurality of irradiation positions repeatedly while changing the focus position.

Abstract: An optical system having an optical sensor with an ultra-short FP cavity, and a low-resolution optical interrogation system coupled to the optical sensor and operational to send light signals and receive light signals to and from the optical sensor is disclosed. The optical system may operate in a wavelength range including the visible and near-infrared range. Optical assemblies and methods of interrogating optical sensors are provided, as are numerous other aspects.

Abstract: An apparatus and method for the accurate and non-invasive measurement of the volume of liquid samples by optical interferometry. Small volumes of liquid samples are often contained in and partially fill the wells of a microplate. A low-coherence interferometric ranging system is used to determine the topography of the sample surface exposed by each well. The surface topography, together with the measured, or otherwise known, dimensions of the well, determine the volume of the liquid sample. Embodiment options include confining the optical beams of the interferometer to optical fiber and varying the optical-path length by piezo-electric stretching of a portion of the fiber. Other embodiment options include automation of data collection by stepping the microplate beneath the interferometer, pixelating the optical beam of the interferometer and scanning the microplate by scanning the sample beam of the interferometer with a mirror. Uniformity of the microplate wells is not required.

Abstract: In one embodiment, a method is provided. The method comprises generating a waveform; measuring signals representative of angular rotation rate in a linear region of the waveform; and diminishing bias error about at least one of a waveform's maxima and minima.

Abstract: A signal processing device is provided for acquisition of predetermined information. The signal processing device includes a light source unit configured to radiate beams of coherent light having a plurality of wavelengths; an imaging unit configured to capture a speckle image representing an interference state of reflected light caused by the light radiated from the light source unit to an object; and a processing unit configured to process, for each of the wavelengths, the speckle image captured by the imaging unit. The processing unit acquires the predetermined information by analyzing a variation amount of the speckle image acquired for each of the wavelengths. The light source unit radiates beams of light having different wavelengths to a plurality of respective objects. The present technology can be applied to a sensor.

Abstract: In an in situ interrogation system for multiple wavelength interferometers a fringe spectrum that includes non-quadrature-spaced radiation-intensity samples is analyzed to obtain a high resolution relative phase measurement of the optical path length difference associated with the fringe spectrum. The fringe spectrum can be analyzed to obtain a fringe number and a quadrant as well, which can be combined with the relative phase measurement to obtain a high precision measurement of the absolute optical path length difference. An environmental condition corresponding to the absolute optical path length difference can be measured using the measurement of the absolute optical path length difference including salinity, pressure, density, and refractive index of a medium.

Abstract: A photostimulation apparatus includes an objective lens arranged to face a biological object, a light source configured to output light to be radiated toward the biological object via the objective lens, a shape acquisition unit configured to acquire information about a shape with a refractive index difference in the biological object, a hologram generation unit configured to generate aberration correction hologram data for correcting aberrations due to the shape with the refractive index difference on the basis of the information acquired by the shape acquisition unit, and a spatial light modulator on which a hologram based on the aberration correction hologram data is presented and which modulates the light output from the light source.

Abstract: An optical inner-surface measurement device includes: an optical fiber included inside a tube, the optical fiber being configured to be inserted into a hole of an inspection object; at least two optical-path converting elements disposed in a forward-end of the optical fiber; and a motor for rotationally driving at least one of the at least two optical-path converting elements. The at least two optical-path converting elements emit a light beam, guided thereto through the optical fiber, to an inner peripheral surface of the hole of the inspection object three-dimensionally in a circumferential direction and an axial direction of the hole.

Abstract: Some embodiments are directed to a multiplexed fiber sensor for a fiber optic hydrophone array, including a signal receiver configured to receive a signal from the fiber optic hydrophone sensor array and an interferometer. The interferometer is configured to produce a first signal component and a second signal component from the signal received from the hydrophone array, and also provided with a first polarization controller configured to control the polarization of the first signal component and a second polarization controller configured to control the polarization of the second signal component. A modulated carrier signal generator configured to generate a modulated carrier signal component based on the first signal component is also provided. A detector configured to output a demodulated output signal from the modulated signal component and the second signal component is included, wherein the modulated signal component and the second signal component output separately from the interferometer.

Abstract: Aspects of the disclosure relate to an integrated spectral unit including a micro-electro-mechanical systems (MEMS) interferometer fabricated within a first substrate and a light redirecting structure integrated on a second substrate, where the second substrate is coupled to the first substrate. The light redirecting structure includes at least one mirror for receiving an input light beam propagating in an out-of-plane direction with respect to the first substrate and redirecting the input light beam to an in-plane direction with respect to the first substrate towards the MEMS interferometer.

Abstract: An interferometer is provided that includes a single retroreflector arranged at a target plane and a plurality of retroreflectors arranged at a reference plane of the interferometer. The single retroreflector and the plurality of retroreflectors are positioned such that a measurement beam provided to the interferometer makes a plurality of passes between the single retroreflector and the plurality of retroreflectors. One of the plurality of retroreflectors is positioned as a terminal retroreflector that reflects the measurement beam back on itself such that an output of the interferometer is coaxial with an input to the interferometer.

Abstract: The present disclosure provides apparatus and methods for overlay measurement. An exemplary overlay measurement apparatus includes an illuminating unit, configured to generate light to illuminate a first overlay marker having a first sub-overlay marker along a first direction and a second overlay marker along a second direction; a first measuring unit, configured to receive light reflected from the first overlay marker to cause the reflected light to laterally shift and shear to generate interference light, to receive the interference light to form a first image and to determine existence of overlay offsets along the first direction and the second direction and values of the overlay offset; and a first drive unit connected to the first measuring unit, and configured to drive the first measuring unit to rotate from a first position to a second position to measure the first sub-overlay marker and the second sub-overlay marker, respectively.

Abstract: A method for analyzing stress in an object according to spectrum data is provided. The spectrum data is obtained from an interference fringe pattern of the object that results from performing photoelasticity. The method includes: analyzing the spectrum data to obtain three sets of intensity data related respectively to different wavelengths of light used in photoelasticity; calculating wrapped phases according to the three sets of intensity data, respectively; calculating preliminary stress values according to the wrapped phases, respectively; determining a system of stress equations according to a relation among the preliminary stress values; and calculating an estimated stress value using the system of stress equations.

Abstract: Aspects of the present disclosure involve a system and method for performing radio frequency interferometry using optical fiber sensing. Optical fiber sensing is performed as a reference signal is defined and compared, in the optical domain, to incoming signals to obtain interference fringe patterns that can be used to decode phase shift offsets with respect to the designated reference signal. The phase shift offsets can be determined by first optically modulating the reference and incoming signals using a laser source as the carrier. In the optical domain, the reference and incoming signals are combined using an optical coupler and then converted back to the electrical domain for processing.

Abstract: By removing remaining components of Rayleigh scattered light, control is sufficiently performed of polarization states even when the wavelength of scattered light has changed. A light source unit configured to generate probe light, a wavelength control unit configured to receive backscattered light emitted from an optical fiber to be tested by the probe light and to output Brillouin backscattered light included in the backscattered light, and a self-delayed heterodyne interferometer to which the Brillouin backscattered light is input are included. The wavelength control unit includes a wavelength separation filter, a variable wavelength filter, an optical intensity measurement unit, and a control unit. The wavelength separation filter has two output ports, outputs and transmits, from one of the two output ports, the Brillouin backscattered light to the variable wavelength filter, and outputs and transmits, from the other output port, Rayleigh scattered light to the optical intensity measurement unit.

Abstract: A method performs phase shift interferometry to detect irregularities of a surface of a wafer after the wafer has been placed into an interferometer and while the wafer is vibrating. Additionally, a system and a non-transitory computer-readable storage medium have computer-executable instructions embodied thereon for performing phase shift interferometry to detect irregularities of a surface of a wafer after the wafer has been placed into an interferometer and while the wafer is vibrating.