1497results about "Force measurement by measuring optical property variation" patented technology

Systems and methods for measuring the stress profile of ion-exchanged glass are disclosed, based on the TM and TE guided mode spectra of the optical waveguide formed in the ion-exchanged glass. The method includes digitally defining from the TM and TE guided mode spectra positions of intensity extrema, and calculating respective TM and TE effective refractive indices from these positions. The method also includes calculating TM and TE refractive index profiles n_TM(z) and n_TE(z) using either an inverse WKB calculation or a fitting process that employs assumed functions for n_TM(z) and n_TE(z). The method also includes calculating the stress profile S(z)=[n_TM(z)−n_TE(z)]/SOC, where SOC is a stress optic coefficient for the glass substrate. Systems for performing the method are also disclosed.

A fiber optic force sensing assembly for detecting forces imparted at a distal end of a catheter assembly. The structural member may include segments adjacent each other in a serial arrangement, with gaps located between adjacent segments that are bridged by flexures. Fiber optics are coupled to the structural member. In one embodiment, each fiber optic has a distal end disposed adjacent one of the gaps and oriented for emission of light onto and for collection of light reflected from a segment adjacent the gap. The optical fibers cooperate with the deformable structure to provide a change in the intensity of the reflected light, or alternatively to provide a variable gap interferometer for sensing deformation of the structural member. In another embodiment, the gaps are bridged by fiber Bragg gratings that reflect light back through the fiber optic at central wavelengths that vary with the strain imposed on the grating.

The present invention concerns movement facilitation devices for facilitating movement between a first portion of a first object and a second portion of the first object. One or more of the movement facilitation devices may be combined to form a movement device for facilitating movement of at least one joint or limb of a patient's body. One form of a movement device according to the invention is a glove which at least partially encloses the joint or limb. The invention also encompasses systems for applying Continuous Passive Motion therapy to a joint or limb of a patient using the devices of the invention. The invention also encompasses the use of shape memory materials and of conducting polymers in the devices and systems of the invention, as well as the design of force transducers and actuators that may be used in the devices.

The invention discloses a device for monitoring the state of a power transmission line tower-line system, which fully utilizes the advantages of corrosion resistance, wide operation temperature range, anti-electromagnetic interference, passivity, long measuring distance, reliable operation and long service life and the like of optical fiber sensors to configure the optical fiber sensors on a transmission conductor and a tower in a quasi-distributed structure for detecting the temperature, the strain and the acceleration of the transmission conductor and the multipoint stress variation on the tower which are transmitted to an optical modulator demodulator for demodulating and are sent to a computer analyzing and processing system for calculating to obtain the icing quality, the waving amplitude, the breeze vibration amplitude and frequency and the sag of the transmission conductor, and the inclination angle of the tower, thus realizing the simultaneous monitoring on the icing, the waving, the breeze vibration and the sag of the transmission conductor, and the inclination angle state of the tower, and being capable of finishing long-time reliable operation under the on-site severe environment conditions.

The invention relates to an instrumented tubular device for transporting a pressurized fluid notably in the field of oil exploration and in that of the transport of gas or hydrocarbons. This device comprises a tube (20) in which this fluid flows, with which are associated means for measuring the main deformations of this tube, and means for measuring the temperature of the fluid in the tube. This tube is equipped with measurement means integral with its surface and offset by at least one remote optical cable towards an electronic measurement system. These measurement means are means for assembling at least two non-parallel optical fibers which comprise at least three assemblies (B1, B2, B3) of at least two optical gages with Bragg gratings attached to at least three measurement locations (22) and connected to the remote optical cable (23) via optical fibers. At least one assembly further comprises a temperature gage.

The invention relates to a system for distributed or dispersed measurement of axial and bending deformations of a structure including at least one threadlike device (10) equipped for the distributed or dispersed measurement of these axial and bending deformations, and means for processing measurement signals generated by said device, in which each device includes a cylindrical reinforcement (11) supporting, at its periphery, at least three optical fibres (12) locally parallel to the axis of the reinforcement, and in which the processing means implement means for spectral or time division multiplexing of signals coming from optical fibres.

A fiber optic acoustic sensor system including an optical conductor having low reflectivity mirrors is provided. Optical sensors are provided by sections of the optical conductor bounded by pairs of the low reflectivity mirrors. Pulses of light are injected into the optical conductor and reflected by the low reflectivity mirrors. The reflected pulses of light are processed using a compensating interferometer to generate interference patterns representative of the environmental conditions acting upon the optical conductor.

A technique facilitates the monitoring of elongate structures. An elongate structure is combined with an optical fiber deployed along the structure. An interrogation system is operatively joined with the optical fiber to input and monitor optical signals to determine any changes in parameters related to the structure.

A distributed fiber sensor based on spontaneous Brillouin scattering uses a single-frequency fiber laser as a source and a cw Brillouin fiber ring laser as an OLO to optically shift the frequency of the OLO to set the Brillouin/OLO beat frequency within the bandwidth of a conventional heterodyne receiver. The distributed fiber sensor is capable of real-time measurement of both temperature and strain.

The present invention provides a sensor system for sensing a parameter, comprising an optical source, coupler and signal processor system in combination with multiple structured fiber Bragg gratings. The optical source, coupler and signal processor system provide an optical source signal to the multiple structured fiber Bragg gratings. The optical source, coupler and signal processor system also responds to multiple structured fiber Bragg grating signals, for providing an optical source, coupler and signal processor system signal containing information about a sensed parameter. The multiple structured fiber Bragg gratings respond to the optical source signal, and further respond to the sensed parameter, for providing the multiple structured fiber Bragg grating signals containing information about a complex superposition of spectral responses or codes related to the sensed parameter. Each of the multiple structured fiber Bragg gratings includes a respective broadband spectral response or code related to the sensed parameter.

Disclosed herein is an accelerometer and/or displacement device that uses a mass coupled to a rhomboidal flexure to provide compression to an optical sensing element preferably having a fiber Bragg grating (FBG). The transducer includes a precompressed optical sensor disposed along a first axis between sides of the flexure. The top portion of the flexure connects to the mass which intersects the flexure along a second axis perpendicular to the first axis. When the mass experiences a force due to acceleration or displacement, the flexure will expand or contract along the second axis, which respectively compresses or relieves the compression of the FBG in the optical sensing element along the first axis. Perturbing the force presented to the FBG changes its Bragg reflection wavelength, which is interrogated to quantify the dynamic or constant force. A temperature compensation scheme, including the use of additional fiber Bragg gratings and thermal compensators axially positioned to counteract thermal effects of the optical sensing element, is also disclosed.

An optical sensor (10) that provides for concurrent pressure and temperature measurements at substantially the same location includes at least one launch fiber (22) and at least one temperature sensitive material (52) having a refractive index that changes with a change in temperature. The launch fiber and temperature sensitive material are spaced from each other across a gap (21) having length (L). A reflecting fiber (26) can be provided adjacent the temperature sensitive material. The optical sensor (10) also includes a sealed cavity (20). The launch fiber (22) and reflecting fiber (26) can be attached to the tube and at least partially disposed within the cavity. Changes in pressure change the length (L) of the gap (21).

According to embodiments of the present invention, a distributed pressure and shear stress sensor includes a flexible substrate, such as PDMS, with a waveguide formed thereon. Along the waveguide path are several Bragg gratings. Each Bragg grating has a characteristic Bragg wavelength that shifts in response to an applied load due to elongation/compression of the grating. The wavelength shifts are monitored using a single input and a single output for the waveguide to determine the amount of applied pressure on the gratings. To measure shear stress, two flexible substrates with the waveguide and Bragg gratings are placed on top of each other such that the waveguides and gratings are perpendicular to each other. To fabricate the distributive pressure and shear sensor, a unique micro-molding technique is used wherein gratings are stamped into PDMS, for example.

An electric cable includes a strain sensor longitudinally extending along the cable and including a strain optical fibre arranged within a bending neutral region surrounding and including a bending neutral longitudinal axis of the electric cable, and at least two longitudinal structural elements, at least one of the at least two longitudinal structural elements being a core including an electrical conductor, wherein the strain sensor is embedded in a strain-transferring filler mechanically coupling at least one of the at least two longitudinal structural elements with the strain sensor. With the disclosed cable construction, the strain experienced by the at least one of the at least two longitudinal structural elements is transferred to the strain sensor at least in a strained condition. In the preferred embodiments, the electric cable is a heavy-duty cable.

A garment and system includes a monitoring fabric that exhibits a light reflection property and substantially no light transmission property when the fabric is illuminated with light having wavelength(s) in the range of 400 to 2200 nanometers. The amount of useful light reflected by the fabric into an aperture of acceptance defined with respect to an axis extending from the fabric relative to the amount of light lost to the aperture of acceptance detectably changes when the fabric stretches in response to motion, as the motion induced by physiological activity (e.g., heart rate). The system includes at least one radiation source and at least one radiation detector, with the detector disposed in the aperture of acceptance. The source and detector may be attached to the fabric in relative positions such that the reception of incident radiation by the detector is directly affected by a change in the amount of useful light reflected by the fabric into the aperture of acceptance as the fabric stretches in response to motion.

Broadband energy incident on a transducer having partially or fully reflective surfaces separated by a gap which is greater than the coherence length of the broadband energy but smaller than one-half a coherence length of a band of energy within said broadband energy causes a portion of the spectral content of the broadband energy corresponding to a coherence length greater than twice the gap length to exhibit interference effects while the average power of the broadband energy remains unaffected. Splitting energy reflected from the transducer into two beams which are filtered at preferably similar center frequencies but with different pass bands yields beams which are radically different in sensitivity to changes in gap length. Analyzing the beams to derive a ratio of powers (since source intensity and fiber attenuation in a common fiber are thus self-cancelling) allows high accuracy and high resolution absolute measurement of temperature, pressure or strain. Effects of any of these physical parameters which are not of interest in a measurement can be fully compensated or made arbitrarily insignificant in a simple transducer structure of extremely small size. Use of broadband energy permits measurement over greater lengths of optical fiber.

The fiber optic pressure sensing system includes a sensor housing formed using MEMS processing. The sensor housing has ribs and grooves in both horizontal and vertical directions relative to the surface to allow the membrane to flex in a consistent manner. The flexing of the membrane allows the pedestal to be repeatedly positioned in response to pressure acting on the extension of the sensor head and membrane.

The invention relates to a method and a system for monitoring and warning a pipeline landslide based on a fiber Bragg grating and a method for constructing the system. The monitoring is performed on four parts including landslide depth displacement, landslide surface displacement, thrust of landslide on a pipeline and pipeline strain, and comprises the steps of: firstly, inserting an inclinometerpipe (1) pasted with a fiber Bragg grating sensor from the landslide (13) to all potential sliding surfaces (15); secondly, embedding a slender concrete ground beam (2) of which two ends are fixedly restrained and the axial direction of a central reinforced bar (17) is stuck to a ground beam fiber Bragg grating sensor (20) in a direction vertical to the deformation direction of the landslide (13)below the surface of the landslide (13); thirdly, measuring the thrust of the landslide (13) on the pipeline by using an earth pressure cell fiber Bragg grating sensor (4) fixed on the pipeline (14);and fourthly, arranging monitoring sections on edges on two sides and the pipeline (14) in the center of the landslide (13), and uniformly arranging three pipe strain fiber Bragg grating sensors (3) on each monitoring section to monitor the axial strain of the pipeline (14).

Described is an anomaly detector apparatus 10 for detecting an anomaly in a tire comprising: a source of coherent light 18 to shine the light 27 directly onto the tire surface 24 and the light being reflected 32 from the tire; a stressing apparatus 12 which can stress the tire; a reflected light receiving apparatus 40 for receiving the light 32 reflected directly from the tire surface 24 when the tire is in a stressed and unstressed condition; a processor 44 which compares images of reflected light from the reflected light receiving apparatus 40 when the tire is stressed and unstressed thereby ascertaining an anomaly in the tire and generates an output from the comparison; and a display apparatus 46 electronically connected to the processor for displaying the output from the processor.

Fiber optical gages that impart physical strain to an optical fiber by varying the tension applied axially to the fiber, which causes a change in the optical property of the light transmitted through the fiber. A gage carrier which provides the benefits of a metal carrier for ease of handling and mounting without degrading gage performance. At least a portion of the gage carrier is elastic with respect to expansion, compression or both along its longitudinal axis, thereby allowing for variation of the distance between the two points at which the gage carrier is attached to a test specimen. In a specific embodiment, the gage carrier functions as two independent rigid fiber fastening elements separated by a compliant or flexible member. The invention further provides fiber Bragg grating strain gages, which are particularly useful for monitoring ambient conditions and measuring physical properties and mechanical phenomena.

A pressure sensor (100) and system for measuring pressure changes, especially in harsh environments, is described. The pressure sensor has a Fabry-Perot optical cavity formed within a tube (115) with a partial reflective mirror (130) provided by an end of an optical fiber (105) and a reflective mirror (135) provided by an end of a plug (120), with a gap (125) formed between. The pressure sensor may be disposed within a sensing chamber of a housing having an opening into the environment to be monitored. Alternatively, an isolator means may be used to isolate the sensor from the environment while communicating pressure changes to the sensing chamber. In another embodiment, the sensing chamber is filled with a compressible non-flowing material.

A strain isolated optical fibre Bragg grating sensor (1) has an optical fibre (2) provided at or adjacent one end (2a) with the Bragg grating (3). An open mouth cap (4) surrounds the fibre end (2a) and region provided with the Bragg grating (3) at a spacing from the fibre, fibre end and Bragg grating. The cap (4) is sealed to the fibre (2) at the open mouth at a side of the grating (3) remote from the fibre end (2a). The cap (4) is made from a low Young's modulus material and is operable to isolate the grating (3) from strain.

The invention relates to a system for testing heart valve leaflets. The system includes a leaflet support assembly with a support post for receiving and supporting a leaflet to be tested, the post being disposed in a target region of the support assembly. The system also has a transmitter assembly that includes a light source and is configured and arranged to direct light from the light source onto the target region. The system further includes a receiver assembly that has an image sensor configured and arranged to sense an image of the target region and generate image information indicative of the sensed image, such as leaflet droop.

An ablation catheter system configured with a compact force sensor at a distal end for detection of contact forces exerted on an end effector. The force sensor includes fiber optics operatively coupled with reflecting members on a structural member. In one embodiment, the optical fibers and reflecting members cooperate with the deformable structure to provide a variable gap interferometer for sensing deformation of the structural member due to contact force. In another embodiment, a change in the intensity of the reflected light is detected to measure the deformation. The measured deformations are then used to compute a contact force vector. In some embodiments, the force sensor is configured to passively compensate for temperature changes that otherwise lead to erroneous force indications. In other embodiments, the system actively compensates for errant force indications caused by temperature changes by measuring certain local temperatures of the structural member.

The invention relates to a method for monitoring the stress of a casing in a well by applying optical-fiber sensors, which mainly solves the problem that the existing research field of the casing erosion of an oil field and oil-water well does not have a direct method for monitoring the stress loading process of the casing in the well and the morphological characters of the casing erosion. The method is characterized in that: optical-fiber grating sensors are circumferentially arranged along the outer surface of the casing; a ground optical-fiber grating demodulation instrument connected with the optical-fiber grating sensors is utilized to monitor the circumferential strain Epsilon Theta of the casing and obtain the circumferential strain data of the casing; meanwhile, Brilliouin optical-fiber sensors are axially arranged along the outer surface of the casing; a ground Brilliouin optical-fiber demodulation instrument connected with the Brilliouin optical-fiber sensors is utilized to monitor the axial strain Epsilon Z of the casing and obtain the axial stain data of the casing; and the obtained circumferential strain Epsilon Theta and the axial strain Epsilon Z of the casing are utilized to obtain the stress of the outer layer of the casing in the well according to a ground stress explanation model. The method is characterized by being capable of permanently monitoring the deformation of the casing and obtaining corresponding stratum pressure under the condition without knowing the casing erosion and the stratum pressure.

A method is described using optical fiber technology to measure the vibration characteristics of long slender structures subjected to dynamic disturbances imposed by water or wind generated loads. The method is based on making bending strain measurements at selected locations along the length of long slender structures such as marine risers or large ropes using fiber optics technology including Optical Time Domain Reflectometry and Bragg diffraction gratings. Engineering interpretation of information obtained from bending strains determines the vibration characteristics including frequency, amplitude, and wave length. Maximum bending strain measurements assess pending structural damage. One application is measurement of vortex induced vibrations (VIV) response of marine risers. The fiber optics based method is also applicable to the measurement of the bending characteristics of spoolable pipe using plastic optical fibers which can be interpreted to assess the pipe structural integrity and to prevent lock-up during deployment into a small diameter annulus.

An apparatus for varying the gain of a fiber optic sensor that non-intrusively senses the strain response of a pipe is provided. The apparatus includes a circumferential strain attenuator that has an annular land portion that mechanically couples the attenuator to the pipe. An annular web extends coaxially from the land portion and has a reduced cross sectional area relative to the land, and an annular mandrel portion extends coaxially from the web portion and forms a gap between the pipe and the mandrel. The fiber optic sensor is wound on the circumferential strain attenuator. The web and mandrel cooperate to reduce the strain response of the fiber optic sensor relative to the strain response of the pipe.

A fiber Bragg grating (FBG) sensor is mounted to a rotating body, which is supported by a rotating shaft mounted rotatably with respect to a fixed element. The FBG sensor extends along the rotating shaft, one end of which is disposed at the center of the end of the rotating shaft. An optical fiber is mounted to the fixed element, one end of which is disposed opposite to the end of the FBG sensor, apart from the FBG sensor. Light emitted from a broadband light source passes through the optical fiber and is transmitted to the FBG sensor across a gap between the optical fiber and the FBG sensor. The FBG sensor reflects light with frequencies corresponding to deformation of the rotating body. A data processing unit receives the reflected light and calculates the deformation of the rotating body based thereupon.

A method and apparatus for monitoring changes in temperature or strain, using fiber Bragg gratings (FBG). The Method and apparatus is advantageously useful for the measurement under harsh conditions, such as by combustion turbines. The invention uses the wavelength shift which is caused by temperature or strain changes at the FBG and the changing of the refraction index of the fiber.

An apparatus and method for continuous, passive detection and measurement of tensile and compressional strain in a structure utilizing a shielded optic fiber, the optic fiber having one or more Bragg gratings thereon, the gratings and shield being disposed in a curved path on the structure and a baseline response for the grating is made using an optical source and detector. Changes in tensile or compressional forces on the structure will result in changes in the curve of the grating, resulting in a frequency shift for the returned light.