The present disclosure relates to the field of measuring three-dimensional shapes of 3D structures, in particular wind turbine structures like wind turbine blades, using optical fibre strain sensors, namely Fibre Bragg Gratings, FBGs. It is disclosed a device and corresponding method for measuring a three-dimensional shape of a structure by being slidably coupled to the structure such that the deformation of the structure, except lengthening or shortening, causes a corresponding deformation of the device, the device comprising: a pliant beam; three or more optical fibres arranged lengthwise in parallel within said beam and having a transversal distance between said fibres in at least two different transversal directions; wherein said optical fibres comprise a plurality of sensor regions distributed along said optical fibres, wherein each said sensor region comprises a Fibre Bragg Grating in each of the optical fibres.

Methods and systems for measuring optical properties of transistor channel structures and linking the optical properties to the state of strain are presented herein. Optical scatterometry measurements of strain are performed on metrology targets that closely mimic partially manufactured, real device structures. In one aspect, optical scatterometry is employed to measure uniaxial strain in a semiconductor channel based on differences in measured spectra along and across the semiconductor channel. In a further aspect, the effect of strain on measured spectra is decorrelated from other contributors, such as the geometry and material properties of structures captured in the measurement. In another aspect, measurements are performed on a metrology target pair including a strained metrology target and a corresponding unstrained metrology target to resolve the geometry of the metrology target under measurement and to provide a reference for the estimation of the absolute value of strain.

An optical fiber sensing system, method and apparatus for simultaneously measuring temperature, strain, and pressure are provided and belong to the field of optical fiber sensors. A distributed optical fiber temperature sensor is configured to monitor the temperature, and transmit the monitored temperature to a fiber grating strain and pressure sensor; the fiber grating strain and pressure sensor performs self temperature compensation based on received temperature; and the fiber grating strain and pressure sensor monitors the strain and the pressure. The distributed optical fiber temperature sensor is used to replace a temperature compensation function of the fiber grating strain sensor, and sense temperature distribution of each point along a route. Further, the fiber grating strain and pressure sensor is simplified inside, temperature demodulation is no longer required and speed of obtaining values of the strain and the pressure has been accelerated.

A method, system and devices for optical structural health monitoring that implements digital image correlation (DIC) by applying an invisible pattern comprising a random dot pattern and/or codes, which is applied using a coating containing a dye or substance that is not visible during the normal lighting conditions. The structure is imaged at different time intervals by capturing images of the pattern and codes using a camera and suitable light source. The captured images of the pattern and codes are stored in a CAD file that represents the structure or part to which the pattern and codes are applied, and includes the locations of the pattern and codes. Comparative measurements of the pattern and codes (e.g., using DIC) determine one or more structural health parameters, such as strain, deformation, and other stresses or averse conditions that may be detected from one interval to another (e.g., between measurements).

A system for mechanical testing a specimen includes a 3D printed mechanical testing fixture; a linear actuator having an axis of movement; a controller configured to control the linear actuator; two cameras; a data-acquisition system configured to acquire data from the linear actuator, the controller, and the two cameras; and the specimen. The specimen is marked in two locations with tracking markers to provide indication to the data acquisition system via at least one camera of movement and change in length of the specimen. The fixture includes force-sensing beams extending perpendicular to the axis of force.

In order to provide a detection device that can accurately detect thermal deformation in any state including a case where thermal deformation has already occurred, there is provided a detection device which includes: a scale with a strained grating; and two sensor heads mounted on a pedestal at a predetermined distance, the sensor heads detecting positions on the scale based on the grating. Thermal deformation of the pedestal or the scale is detected based on a change in a difference between the positions detected by the two sensor heads.

An apparatus, and related method, relates generally to a fiber-optic sensing system. In such a system, fiber-optic sensors are in a rosette or rosette-like pattern. An optical circulator is coupled to receive a light signal from a broadband light source, to provide the light signal to the fiber-optic sensors, and to receive a returned optical signal from the fiber-optic sensors. A spectral engine is coupled to the optical circulator to receive the returned optical signal and configured to provide an output signal.

A measuring method includes the following. An image to be tested of an object to be tested with a first characteristic pattern is formed and is copied to form multiple images to be tested. The multiple images to be tested are superimposed to form a to-be-tested overlapped image which has the multiple first characteristic patterns. A reference image of a reference object with a second characteristic pattern is formed and is copied to form multiple reference images. The multiple reference images are superimposed to form a reference overlapped image which has the multiple second characteristic patterns. The to-be-tested overlapped image and the reference overlapped image are superimposed to generate a virtual moiré image having a moiré pattern different from the multiple first characteristic patterns and the multiple second characteristic patterns.

A surface shape determination system includes a surface shape sensor in the form of a flexible and stretchable elastomeric substrate with strain/displacement sensing elements embedded in it. The sensor may be a single-core optical fiber with a series of fiber Bragg Gratings (FBGs) located at predetermined positions along its length. A light source provides an incident light spectrum at one end of the fiber. Each grating of the fiber has index modulation which causes particular wavelengths of the light spectrum that do not satisfy the Bragg condition to be reflected back in the fiber. The refractive index of each grating changes with strain on the substrate due to deflection of it. An interrogator captures the reflected wavelengths and retrieves signal information therefrom. A processor receives the output of the interrogator and performs non-linear regression analysis on the information using a neural network to reconstruct the surface morphology in real-time.

An apparatus has a cassette configured to hold optical fiber comprising one or more optical sensors. The cassette has a spool configured to one or more of extract and retract the optical fiber from the cassette. A pre-strain mechanism is configured to apply a predetermined pre-strain to the one or more optical sensors. An optical fiber installation tool is configured to mount the optical fiber comprising the one or more pre-strained optical sensors to a surface.