Abstract: A sensing coil assembly and method for attaching a sensing coil to a support structure are provided for a fiber optic gyroscope. The method comprises affixing a preformed adhesive to a mating surface of a mounting structure, and coupling an inner surface of the sensing coil to the mating surface of the mounting structure via the preformed adhesive. The mating surface is substantially cylindrical or conical. The sensing coil assembly comprises a hub having a mating surface, an optical fiber coil having an inner surface encircling at least a portion of the mating surface, and a preformed adhesive pattern affixing the mating surface to the inner surface. The mating surface of the hub is substantially cylindrical or conical.

Abstract: A sensing coil is provided for optically guiding counter-propagating light beams in a fiber optic gyroscope. The sensing coil comprises a plurality of layers of an optical fiber having a winding direction. The plurality of layers comprises inner layers, middle layers, and outer layers. The middle layers comprise first and second input ends configured to receive the counter-propagating light beams. At least one of the inner layers, middle layers, and outer layers is coupled with a different one of the inner layers, middle layers, and outer layers while maintaining the winding direction. A method is provided for winding an optical fiber, having first and second connecting ends, to form a sensing coil for a fiber optic gyroscope having a winding direction.

Abstract: Methods and apparatus are provided for a low cost optical gyro with a free space closed optical path. A ring resonator comprises a substrate and reflectors formed or placed on the substrate. The reflectors comprise a closed optical path and are configured to direct each of first and second light beams in a different counter-propagating direction in the closed optical path. Each of the first and second light beams frequencies are tuned to the resonance frequency of the resonator in the direction of propagation for which the light beam is circulating in the closed optical path.

Abstract: A system for tomographic imaging includes a source of at least partially coherent radiation, a frequency-swept laser source and an interferometer. The radiation in the interferometer is phase modulated at a modulation frequency for elimination of DC and autocorrelation noises as well as the mirror image. The interference fringes of the radiation backscattered from the sample into the interferometer are detected to obtain a spectral signal. The spectral signal of the detected backscattered interference fringes is transformed to obtain a location dependent signal at each pixel location in a data window. A tomographic image of the fluid flow in the data window is generated for display and of the structure of the scanned fluid flow sample in the data window from the location dependent signal is generated.

Abstract: Included in this disclosure is a quantum positioning system (QPS) that includes a corner cube reflector and a plurality of baselines. Each baseline may include an interferometer, which may include a photon source, a beam splitter, and a photon detector. The interferometer is configured for creating a bi-photon pair and initiating communication of the bi-photon pair with the corner cube reflector. Also included in the QPS is a positioning device configured to calculate a user's position.

Abstract: An optical surface analysis system for scanning the surface of a (silicon) wafer and detect if any residual material is still on the wafer surface in order to determine an appropriate end-point in a polishing process. An Optical Surface Analyzer (OSA), of the present invention, is generally used to identify composition, measure surface area, and measure thickness variations of thin film layers of material. The difference in optical properties (index of refraction) of different materials on the surface allows the system of the present invention to separate different materials on the wafer surface using the histogram plots generated by the OSA. This method is used to detect and make a quantitative assessment regarding the amount of residual material to be removed by the polishing process and, therefore, when an appropriate end-point has been reached in the polishing process.

Abstract: The present invention provides an apparatus and method for determining displacement along the z-direction of an object, which is fixed in a holder of an apparatus and is illuminated by a beam of radiation, the beam being provided by the apparatus and having an optical axis extending in the z-direction. The method comprises arranging the measuring mirror(s) and/or measuring laser beam of an interferometer system such that no relevant part of the laser beam is parallel to the z-direction. This ensures that the interferometer system and its parts may be arranged away from the beam of radiation, allowing larger diameter projection systems for the beam of radiation, as well as more homogeneous air showers around the object. Thus the quality of the illumination of the object may be improved.

Abstract: A method of evaluating a device under test (DUT) includes detecting four interferograms of the DUT including two orthogonal detections and two orthogonal input polarizations, performing a Hilbert transformation to obtain transfer functions of the DUT on the basis of the detected interferograms, performing an Inverse Fourier transformation on the transfer functions of the DUT to get an impulse response matrix IR of the DUT, and determining impulse response eigenvalues of the DUT on the basis of the impulse response matrix of the DUT.

Abstract: An optical image measuring apparatus capable of speedily measuring a velocity distribution image of a moving matter.

Abstract: Scanning interferometer and method of using same providing for rapid, reliable detection of chemical compounds that are readily implemented in low-cost, portable configurations for application in a variety of monitoring and detection applications. A scanning double-beam interferometer, particularly a Michelson interferometer, in which the length of at least one of the optical paths (or arms) of the interferometer is selectively adjustable by use of an actuator in which rotational displacement of a rotatable element is converted into linear displacement of at least one reflective surface which forms an end of an optical path of the interferometer is employed to obtain interferograms of electromagnetic radiation attenuated, emitted, scattered or reflected from a sample. The length of the optical path that is adjusted is determined using an optical detection scheme, particularly where marking on the rotatable element are detected to determine linear displacement of the reflective surface.

Abstract: A device and a method are used for measuring the surface topography and a wave aberration of a lens system. The device is fitted with a first measuring system containing a light source radiating a first light beam of a first wavelength, and a detector which captures the first light beam which is reflected on the lens system. In addition the device has a second measuring system containing a light source for radiating a second light beam of a second wavelength and a detector for capturing the second light beam transmitted by the lens system. A diffractive optical element is disposed in a common beam path of the first measuring system and second measuring system. The optical element adapts the respective wave-front course of the first light beam and the second light beam in a wavelength-selective manner.

Abstract: An optical nulling apparatus for testing an optical surface includes an aspheric mirror having a reflecting surface for imaging light near or onto the optical surface under test, where the aspheric mirror is configured to reduce spherical aberration of the optical surface under test. The apparatus includes a light source for emitting light toward the aspheric mirror, the light source longitudinally aligned with the aspheric mirror and the optical surface under test. The aspheric mirror is disposed between the light source and the optical surface under test, and the emitted light is reflected off the reflecting surface of the aspheric mirror and imaged near or onto the optical surface under test. An optical measuring device is disposed between the light source and the aspheric mirror, where light reflected from the optical surface under test enters the optical measuring device.

Abstract: A system and method is provided for reducing the sensitivity of the rotation rate measurement to the frequency dependence of the feedback modulator. Specifically, the system and method uses a minimal bias switching technique to reduce rate errors associated with the low frequency 2? resets in a closed loop fiber optic gyroscope with a phase modulator with a different phase shift associated to low and high frequencies. In general, the minimal bias switching technique reduces the low frequency components of the feedback modulation drive by increasing the frequency of the 2? resets. As a consequence, the system and method reduces the low frequency component of the feedback modulator drive to avoid errors that occur with the low frequency 2? resets.

Abstract: A clock system for a fiber optic gyroscope is provided that includes a highly-tunable clock for the bias modulation and a separate asynchronous high-speed clock for the photodetector sampling. By separating the two clocks rather than using two derivatives of the same clock, the clock system and method can provide both the tunability objective of the bias modulation clock and the high-speed objective of the sampling clock, while using readily available, lower performance, radiation-hardened electronics parts.

Abstract: A resonant ellipsometer and method for determining ellipsometric parameters of a surface provide an efficient and low-cost mechanism for performing ellipsometric measurements. A surface of interest is included as a reflection point of a resonance optical path within a resonator. The intersection of the resonance optical path with the surface of interest is at an angle away from normal so that the complex reflectivity of the surface alters the phase of the resonance optical path. Intensity measurements of light emitted from a partially reflective surface of the resonator for orthogonal polarizations and for at least two effective cavity lengths provide complete information for computing the ellipsoidal parameters on the surface of interest. The resonator may be a Fabry-Perot resonator or a ring resonator. The wavelength of the illumination can be swept, or the cavity length mechanically or electronically altered to change the cavity length.

Abstract: An electromagnetic resonant sensor has a dielectric sensor body through which electromagnetic wave energy is propagated. The sensor body has a cavity, with surfaces facing one another to define a gap that varies as a function of a parameter to be measured. The resonant frequency of an electromagnetic standing wave in the body and the variable gap changes as a function of the gap dimension.

Abstract: A push-pull method of controlling a laser gyro. At least three mirrors form a closed-loop light path for two laser beams propagating in opposite directions, which is subjected to movement. At least two of the mirrors are associated with actuators connected to push-pull control members for controlling the positions of the mirrors to minimize the amplitude of the winking signal which occurs in a lased intensity signal of the laser beams. The method includes detecting the frequency of the winking signal of at least one laser beam, and of triggering the measurement of the amplitude of the winking signal when the frequency of the winking signal is less than a predetermined threshold corresponding to passing into a dead band of the gyro.

Abstract: Methods and apparatus are provided for sensing a rotation rate of a ring resonator in a transmission mode. A ring resonator for circulating light beams in counter-propagating directions comprises an optical fiber coil having a hollow core and first and second ends. A first optical element is configured to receive an input light beam and direct a portion of the input light beam in a counter-propagating direction of the ring resonator. A second optical element is configured to direct with the first optical element a majority of a circulating light beam in the counter-propagating direction of the ring resonator and derive a transmission mode component of the circulating light beam at one of the ends. The portion of the input light beam enters one of the first and second ends. The circulating light beam is based on the input light beam. The transmission mode component indicates a resonance peak of the counter-propagating direction of the ring resonator.

Abstract: A method of detecting non-uniform ellipsometric properties of a substrate surface involving: directing a measurement beam onto a spot at a selected location on or in the substrate; for each orientation of a plurality of different orientations of the reference beam relative to the scattered measurement beam, interfering the scattered measurement beam with the reference beam to produce a corresponding interference beam, wherein each of the different orientations of the reference beam is selected to produce a peak sensitivity for a portion of the scattered measurement beam that emanates from the object at a corresponding different diffraction angle of a plurality of diffraction angles; for each orientation of the reference beam, converting the interference beam into an interference signal; and using the interference signals to determine whether any non-uniform ellipsometric properties are present anywhere within a region on or in the substrate.

Abstract: In general, in one aspect, the invention features a method for determining the location of an alignment mark on a stage including measuring a location, x1, of a stage along a first measurement axis using an interferometer, measuring a location, x2, of the stage along a second measurement axis substantially parallel to the first measurement axis, and determining a location of the alignment mark along a third axis substantially parallel to the first measurement axis based on x1, x2, and a correction term, ?3, calculated from predetermined information including information characterizing imperfections in the interferometer.