Abstract: A method, apparatus, and system are provided to monitor and characterize the dynamics of a phase change region (PCR) created during laser welding, specifically keyhole welding, and other material modification processes, using low-coherence interferometry. By directing a measurement beam to multiple locations within and overlapping with the PCR, the system, apparatus, and method are used to determine, in real time, spatial and temporal characteristics of the weld such as keyhole depth, length, width, shape and whether the keyhole is unstable, closes or collapses. This information is important in determining the quality and material properties of a completed finished weld. It can also be used with feedback to modify the material modification process in real time.

Abstract: A device and a method for characterizing the surface shape of a test object. The device for characterizing the surface shape of a test object has a test arrangement (130, 230) for determining the surface shape of a test object (111, 112, 113, 211, 212, 213) using a test wave. The test wave has a wavefront generated by diffraction at a diffractive optical element. The device additionally has a first vacuum chamber (110, 210) and a second vacuum chamber (120, 220), wherein the second vacuum chamber (120, 220) has a magazine for mounting at least two diffractive optical elements (121, 122, 123, 221, 222, 223).

Abstract: Disclosed is an OCT system, in particular a mid-IR OCT system, comprising: an upconversion module configured to frequency upconvert light received or receivable by the upconversion module and which is in a wavelength range between a first wavelength and a higher second wavelength, the difference between the second wavelength and the first wavelength being at least 300 nm or larger, and the wavelength range having a center wavelength at 2.8 ?m or larger, the center wavelength being defined by the average value between the first wavelength and the second wavelength.

Abstract: A clearance measurement device is a device for measuring a clearance between an inner peripheral surface of a casing and an outer peripheral surface of a rotary body. This device: emits light having a first wavelength and a second wavelength, respectively, towards the outer peripheral surface of the rotary body; receives the light reflected from the outer peripheral surface via a first filter having a transmission band corresponding to the first wavelength and via a second filter having a transmission band corresponding to the second wavelength; and measures the clearance based on a time difference of the moment to detect the rotary body.

Abstract: New and useful concepts for an autofocus system and method are provided. A basic concept uses fringe projection in an autofocus system and method. A further aspect provides spatial filtering concepts for the fringe projection concept. In yet another aspect, the fringe projection autofocus system and method is provided with temporal phase shifting using no moving parts. In a still further aspect, the fringe projection autofocus system and method is provided with unambiguous height measurement concepts.

Abstract: The invention provides a system and method for rapid validation of identity from tissue using registered two dimensional and optical coherence tomography (OCT) scan images. The preferred embodiment provides, for a human fingerprint, validation that the surface fingerprint matches the primary fingerprint. An alternate embodiment provides validation of “aliveness” by ascertaining blood flow. Various embodiments are taught.

Abstract: Disclosed are examples of hyperspectral imager-equipped lighting devices that provide general illumination supplied by artificial or natural light, and that also detect environmental conditions in the environment around the lighting device. The hyperspectral imager detects light within a contiguous data from the environment in the vicinity of the lighting device. In response, the hyperspectral imager generates image data representative of the spectral intensity distribution (e.g. intensities of a continuous range wavelengths in the optical spectrum) of the detected light. A controller may analyze the image data generated by the hyperspectral imager and may initiate action based on, or outputs a report indicating, an environmental condition detected by the analysis of the generated image data.

Abstract: The invention relates to a method of interrogating an interferometric optical fiber sensor system including a laser source configured to generate interrogation light and a sensor array with at least a first reflector and a second reflector.

Abstract: Holograms of colloidal dispersions encode comprehensive information about individual particles' three-dimensional positions, sizes and optical properties. Extracting that information typically is computation-ally intensive, and thus slow. Machine-learning techniques based on support vector machines (SVMs) can analyze holographic video microscopy data in real time on low-power computers. The resulting stream of precise particle-resolved tracking and characterization data provides unparalleled insights into the composition and dynamics of colloidal dispersions and enables applications ranging from basic research to process control and quality assurance.

Abstract: The present invention provides a gas measuring method based on photothermal effect in hollow-core optical fiber comprising: filling a target gas into the core of a hollow-core optical fiber; coupling a probe light and a periodically modulated pump light into the hollow-core optical fiber; absorbing the pump light by the target gas resulting in the periodic modulation of the phase of the probe light; demodulating the phase modulation information of the probe light to obtain the concentration of the target gas, wherein the pump laser is wavelength and/or amplitude modulated. In the present invention, two lasers including a pump laser and a probe laser are used for the measurement, this approach is simple and practical.

Abstract: A method and system described for sensing a displacement by receiving and propagating a laser light signal with an etched waveguide that is configured to enable an evanescent optical field above the waveguide surface. A movable perturber can be positioned so the perturber interacts with the evanescent optical field above the waveguide surface. An optical phase shift can be induced in the waveguide when the movable perturber is displaced in the evanescent optical field, and the optical phase shift can be measured with an optical readout circuit.

Abstract: A tomographic image generation apparatus includes a light source unit configured to emit light to be used for scanning an object; an optical control unit configured to control a direction of propagation of light; an optical coupler configured to divide and combine incident light; a plurality of optical systems optically connected to the optical coupler; and a modulation and correction device configured to modulate and correct the light to be used for scanning the object. The modulation and correction device may be disposed between the optical control unit and the optical coupler, or may be included in an optical system that irradiates light onto the object among the plurality of optical systems. The modulation and correction device may only modulate light that is reflected to the object.

Abstract: A system of computing surface reconstruction, in-plane and out-of-plane displacements and strain distribution utilizes the optical switching element to switch the reference beam to analyze the images of the test object before and after deformation, to measure the topography, in-plane and out-of-plane displacements and surface two-dimensional strain distribution on the test surface of the test object, and thus to increase the measurement range on the test surface of the test object with the use of image registration. Thereby, the complexity and error of scanning the test object can be reduced. Such a system need not to move the image capturing device or test object to generate relative displacement for reaching the measurement effect of the test surface of the test object in three-dimensional coordinates.

Abstract: Various methods and systems are provided for generation of a laser pulse with massive pulse-front tilt (PFT) and its use for measurement of laser pulses. In one embodiment, a method includes directing a laser pulse into an etalon and propagating the laser pulse through the etalon to form a tilted pulse. Another embodiment involves directing pulses into an etalon and propagating the pulses through the etalon in opposite directions to form a pair of massively tilted pulses that are tilted in opposite directions. In another embodiment, a system includes a Fresnel biprism configured to produce a pair of pulses from an input pulse and a lens configured to direct each pulse through an opening (or openings) in an input surface of an etalon, where the etalon is configured yield a pair of pulses tilted in opposite directions, each pulse having a massive PFT.

Abstract: The present application discloses a system comprising a compact curved grating (CCG) and its associated compact curved grating spectrometer (CCGS) or compact curved grating wavelength multiplexer/demultiplexer (WMDM) module and a method for making the same. The system is capable of achieving a very small (resolution vs. size) RS factor. In the invention, the location of the entrance slit and detector can be adjusted in order to have the best performance for a particular design goal. The initial groove spacing is calculated using a prescribed formula dependent on operation wavelength. The location of the grooves is calculated based on two conditions. The first one being that the path-difference between adjacent grooves should be an integral multiple of the wavelength in the medium to achieve aberration-free grating focusing at the detector or output slit (or output waveguide) even with large beam diffraction angle from the entrance slit or input slit (or input waveguide).

Abstract: A method for detecting a three dimensional object smaller than 300 nm includes providing a light source producing a first light beam (1), the light source being at least partially coherent; and splitting the first light beam (1) into an object beam (2) and a reference beam (6) by a first beam splitter (BS1). An image of the light source is produced in a light source image plane by a first microscope objective (L1), in the optical path of the object beam (2). The three dimensional object to be detected in an object cell (3) is positioned in the optical path of the object beam (2), between the first beam splitter (BS1) and the first microscope objective (L1). The object beam (2) and the reference beam (6) are recombined into a recombined beam (8) by use of optical devices. An optical stop (4) is placed in the light source image plane of the microscope objective (L1) on the optical axis of the microscope objective (L1).

Abstract: There is provided a method for referencing and correcting the beating spectrum generated by the interference of the components of a frequency comb source. The proposed method allows monitoring of variations of a mapping between the source and the beating replica. This can then be used to compensate small variations of the source in Fourier transform spectroscopy or in any other interferometry application in order to overcome the accuracy and measurement time limitations of the prior art. Constraints on source stability are consequently reduced.

Abstract: The present invention relates to a high-resolution scanning surface-plasmon microscope including a source (LG) of coherent light and a medium for coupling and confining a surface plasmon including an objective (O, OM) with a large numerical aperture, immersion oil (Hi), and a glass cover slip (GS). A metal layer (MS) covers a surface of the glass cover slip (GS). The microscope also includes a heterodyne-mode Twyman-Green interferometer placed between the light source and means (PL1, PL2, EC) for scanning the metal layer using a light beam and means (PD) for detecting the beam from the interferometer connected to processing means (S, F, DTec, COMP) for forming an image from that beam. According to the invention, at least one polarization converter (CP) for converting the light beams (L) emitted by the light source (LG) from linear polarization to radial polarization is disposed between the light source and the interferometer.

Abstract: A sensing coil for a Sagnac interferometer current sensor is disclosed, the sensing coil (14) being composed of an optical fiber (for example a spun polarizing Hi-Bi fiber) that is arranged in use to transmit a single elliptical polarization state and the sensing coil comprising at least two interconnected loops (15 and 16 or 26 and 27 or 28 and 29). At least one of the loops is arranged in use to enclose a current conductor (11, 12 or 25) and the loops are interconnected such that light propagating in a first direction (23 or 30) in the first loop will propagate in a second, opposite, direction (24 or 31) in the other or, if more than one, in each other loop, whereby the sensing coil provides minimal sensitivity to rotational movement. Also disclosed are a sensing unit (FIG. 5) that incorporates the sensing coil and a current sensor (FIG. 1) that incorporates the sensing unit.

Abstract: A sensor includes a sensor head with at least two surfaces separated by a gap. One surface is mechanically fixed, a second surface is free to move and deflections of the second surface relative to the first surface are monitored by optical interferometry. An optical fiber could be used to direct light from a light source to the sensor and collect light reflected by the sensor. Interaction of molecules or other objects in the sample with the second surface is detected as a change in amplitude and/or phase of deflection the second surface in response to an applied driving signal. A layer of binding molecules may be immobilized on the second surface and this surface exposed to a sample.