344 results about "Reflectometry" patented technology

A method and apparatus for mapping a wire network is disclosed. The method includes obtaining a reflectometry test signal of the wire network. An estimated network impulse response is estimated from the reflectometry response. A wire network model is then initialized, and iteratively improved by simulating an impulse response of the wire network model and adjusting the wire network model to reduce differences between the simulated impulse response and estimated network impulse response.

A guide wire assembly includes a guide wire, an optical fiber, and an insulating coating. The guide wire has a distal end, a proximal end, and a bore extending through the wire between the distal and proximal ends. The an optical fiber also includes a distal end and a proximal end and is located within the bore of the guide wire. The optical fiber extends at least between the distal and proximal ends of the guide wire. The insulating coating is around an outside diameter of the guide wire, and is applied such that the distal ends of the guide wire and optical fiber are exposed.

The present invention discloses simple and yet highly efficient configurations of optical coherence domain reflectometry systems. The combined use of a polarizing beam splitter with one or two polarization manipulator(s) that rotate the returned light wave polarization to an orthogonal direction, enables one to achieve high optical power delivery efficiency as well as fixed or predetermined output polarization state of the interfering light waves reaching a detector or detector array, which is especially beneficial for spectral domain optical coherence tomography. In addition, the system can be made insensitive to polarization fading resulting from the birefringence change in the sample and reference arms. Dispersion matching can also be easily achieved between the sample and the reference arm for high resolution longitudinal scanning.

This invention relates to a distributed disturbance sensing device based on polarization sensitive optical frequency domain reflectometry (OFDR) and the related demodulation thereof. The device, adopting OFDR, polarization controlling and analysis techniques, consists of a ultra-narrow linewidth tunable laser source module, polarization generating and polarization splitting balanced detecting module, laser source optical frequency and phase monitoring module, high-speed optical switch and so on to establish a large-scale and long-distance optical sensing network. The demodulation method consists of analysis the polarization information from sensing optical fiber, the method of suppressing and compensating of the non-linear optical frequency and the laser phase noise, super-resolution analyzing, advanced denoising method and the polarization information analysis method based on Jones and Mueller's matrices using distributed wave plate model of optical fiber.

The present invention provides apparatuses and methods for sample analysis, such as tissue analysis, that integrate high wavenumber (HW) Raman spectroscopy for chemical composition analysis and optical coherence tomography (OCT) to provide depth and morphological information. The invention also provides side-viewing optical probes that are based on a single double clad optical fiber for performing the combined HW Raman spectroscopy and OCT. Intravascular catheter embodiments and related vascular diagnostic methods are also provided.

Common path frequency domain optical coherence reflectometry / tomography devices include a portion of optical fiber with predetermined optical properties adapted for producing two eigen modes of the optical radiation propagating therethrough with a predetermined optical path length difference. The two replicas of the optical radiation outgoing from the portion of the optical fiber are then delivered to an associated sample by an optical fiber probe. The tip of the optical fiber serves as a reference reflector and also serves as a combining element that produces a combination optical radiation by combining an optical radiation returning from the associated sample with a reference optical radiation reflected from the reference reflector. The topology of the devices allows for registering a cross-polarized or a parallel-polarized component of the optical radiation reflected or backscattered from the associated sample. Having the optical path length difference for the two eigen modes of the optical radiation (which is an equivalent of an interferometer offset in previously known devices) differ from the reference offset in the devices of the present invention allows for relieving the requirements to the spectral resolution of the FD OCT engine and / or data acquisition and processing system, and substantially eliminates depth ambiguity problems.

The present invention relates to a non-contact, non-destructive measuring apparatus that measures thickness profile and refractive index distribution of a single or multiple layers of thin films by means of the principle of reflectometry. According to the present invention, by employing more than one narrow band-pass optical filters and a two-dimensional array of CCD sensors, and by finding an optimal solution for the nonlinear functional relationship between the thickness of said thin film or thin films and the corresponding refractive indexes by using an iterative numerical computation method, said apparatus simultaneously measures local area-wise thickness profile and refractive index distribution among others of said a single layer or multiple layers of thin films on a substrate.

An apparatus and method for high-resolution reflectometry that operates simultaneously in both the time and frequency domains, utilizing time-frequency signal analysis and a chirp signal multiplied by a Gaussian time envelope. The Gaussian envelope provides time localization, while the chirp allows one to excite the system under test with a swept sinewave covering a frequency band of interest. High resolution in detection of the reflected signal is provided by a time-frequency cross correlation function. The high-accuracy localization of faults in a wire / cable can be achieved by measurement of time delay offset obtained from the frequency offset of the reflected signal. The apparatus enables one to execute an automated diagnostic procedure of a wire / cable under test by control of peripheral devices.

A spectroscopy system is provided which operates in the vacuum ultra-violet spectrum. More particularly, a system utilizing reflectometry techniques in the vacuum ultraviolet spectrum is provided for use in metrology applications. The system may further include the use of an array detector in combination with an imaging spectrometer. In this manner data for multiple wavelengths may be simultaneously collected. Moreover, the multiple wavelengths of data may be collected simultaneously for a two dimensional sample area. The system may further include the use of a fixed diffraction grating and does not require the use of polarizing elements. To ensure accurate and repeatable measurement, the environment of the optical path is controlled. The optical path may include a controlled environmental chamber in which non-absorbing purge gases are present or in which vacuum evacuation techniques are utilized. The controlled environment may further include a separate instrument chamber and a separate sample chamber. The controlled environment limits in a repeatable manner the absorption of VUV photons.

A portion of a polarization maintaining (PM) optical fiber having two polarization states is analyzed. First and second spectral responses of the PM fiber portion are determined. In a preferred implementation, the spectral responses are determined using Optical Frequency Domain Reflectometry (OFDR). Each polarization state of the PM fiber portion has a corresponding spectral component in the first spectral response. First and second spectral analyses of the PM fiber portion are performed using the first and second spectral responses. Based on those spectral analyses of the PM fiber portion, a first physical characteristic affecting the PM fiber portion is determined that is distinct from a second different physical characteristic affecting the fiber portion. Example physical characteristics include temperature and strain. An output signal related to the first physical characteristics affecting the fiber portion is provided, e.g., for display, further processing, etc.

Common path frequency domain optical coherence reflectometry / tomography devices with an additional interferometer are suggested. The additional interferometer offset is adjusted such, that it is ether less than the reference offset, or exceeds the distance from the reference reflector to the distal boundary of the longitudinal range of interest. This adjustment allows for relieving the requirements to the spectral resolution of the frequency domain optical coherence reflectometry / tomography engine and / or speed of the data acquisition and processing system, and eliminates depth ambiguity problems. The new topology allows for including a phase or frequency modulator in an arm of the additional interferometer improving the signal-to-noise ratio of the devices. The modulator is also capable of substantially eliminating mirror ambiguity, DC artifacts, and autocorrelation artifacts. The interference signal is produced either in the interferometer or inside of the optical fiber probe leading to the sample.

Polarization sensitive common path OCT / OCR devices are presented. Optical radiation from a source is converted into two cross-polarized replicas propagating therethrough with a predetermined optical path length difference. The two cross-polarized replicas are then delivered to an associated sample by a delivering device, which is, preferably, an optical fiber probe. A combination optical radiation is produced in at least one secondary interferometer by combining a corresponding portion of an optical radiation returning from the associated sample with a reference optical radiation reflected from a tip of an optical fiber of the optical fiber probe. Subject to a preset optical path length difference of the arms of the at least one secondary interferometer, a cross-polarized component, and / or a parallel-polarized component of the combined optical radiation, are selected. The topology of the devices allows for time domain, as well as for frequency domain registration.

In common path time domain OCT / OCR devices optical radiation from a source is first split into two replicas, which are then delivered to an associated sample by an optical fiber probe. The tip of the optical fiber probe serves as a reference reflector and also serves as a combining element that produces a combination optical radiation by combining an optical radiation returning from the associated sample with a reference optical radiation reflected from the reference reflector. The topology of the devices eliminates the necessity of using Faraday mirrors, and also allows for registering a cross-polarized component of the optical radiation reflected or backscattered from the associated sample, as well as a parallel-polarized component.

Methods and systems for small angle CD metrology with a small spot size are introduced to increase measurement sensitivity while maintaining adequate throughput necessary for modern semiconductor manufacture. A small angle CD metrology system includes a small angle spectroscopic ellipsometry (SE) subsystem combined with a small angle spectroscopic reflectometry system, both operated at small angles of incidence. The small angle SE subsystem is configured to operate in a complete Mueller Matrix mode to further improve measurement sensitivity. The small angle CD metrology system includes an objective having all reflective surfaces in the light path. In some embodiments, the all-reflective objective is a Schwartzschild objective having an axicon mirror element to further reduce measurement spot size. In some embodiments, the small angle CD metrology system includes a dynamic aperture subsystem to isolate specific ranges of angles of incidence and azimuth for improved measurement sensitivity.

An apparatus and method for performing optical coherence domain reflectometry. The apparatus preferably includes a single output light source to illuminate a sample with a probe beam and to provide a reference beam. The reference beam is routed into a long arm of an interferometer by a polarizing beamsplitter. A reflected beam is collected from the sample. A 90.degree. double pass polarization rotation element located between the light source and the sample renders the polarizations of the probe beam and reflected beam orthogonal. The polarizing beamsplitter routes the reflected beam into a short arm of the interferometer. The interferometer combines the reference beam and the reflected beam such that coherent interference occurs between the beams. The apparatus ensures that all of the reflected beam contributes to the interference, resulting in a high signal to noise ratio.

An improved Optical Coherence Domain Reflectometry (OCDR) system is provided. One embodiment of this OCDR system outputs a detector signal carrying image depth information on multiple modulation frequencies, where each modulation frequency corresponds to a different image depth. The image depth information from the detector signal may be resolved by tuning to the desired modulation frequency. Another system for imaging body tissue uses multiple frequency modulators such that the light beam does not travel from an optical fiber to free space.

A CW lightwave modulated by a continuously reiterated binary pseudorandom code sequence is launched into an end of a span of ordinary optical fiber cable. Portions of the launched lightwave back propagate to the launch end from a continuum of locations along the span because of innate fiber properties including Rayleigh scattering. This is picked off the launch end and heterodyned to produce a r.f. beat signal. The r.f. beat signal is processed by a plurality (which can be thousands) of correlator type binary pseudonoise code sequence demodulators respectively operated in different delay time relationships to the timing base of the reiterated modulation sequences. The outputs of the demodulators provide r.f. time-domain reflectometry outputs representative of signals (e.g., acoustic pressure waves) incident to virtual sensors along the fiber at positions corresponding to the various time delay relationships.