Systems and methods for three-dimensional (3D) shape estimation of objects embedded in light-scattering media via polarimetry are provided. The systems and methods utilize polarization to exploit forward scattering in the light-scattering medium to mitigate backscatter interference (BSI).

Systems and methods for three-dimensional (3D) shape estimation of objects embedded in light-scattering media via polarimetry are provided. The systems and methods utilize polarization to exploit forward scattering in the light-scattering medium to mitigate backscatter interference (BSI).

A strain distribution measurement system includes a tensile tester that deforms a test piece to measure mechanical properties of a material of the test piece, and a strain distribution measuring device that measures a strain distribution of the test piece. The strain distribution measuring device measures the strain distribution of the test piece based on a distribution of at least one of a reflectance or a polarization characteristic on the main face of the test piece.

A multi-core fiber includes multiple optical cores, and for each different core of a set of different cores of the multiple optical cores, a total change in optical length is detected. The total change in optical length represents an accumulation of all changes in optical length for multiple segments of that different core up to a point on the multi-core fiber. A difference is determined between the total changes in optical length for cores of the set of different cores. A twist parameter and/or a bend angle associated with the multi-core fiber at the point on the multi-core fiber is/are determined based on the difference.

A multi-core fiber includes multiple optical cores, and for each different core of a set of different cores of the multiple optical cores, a total change in optical length is detected. The total change in optical length represents an accumulation of all changes in optical length for multiple segments of that different core up to a point on the multi-core fiber. A difference is determined between the total changes in optical length for cores of the set of different cores. A twist parameter and/or a bend angle associated with the multi-core fiber at the point on the multi-core fiber is/are determined based on the difference.

A method of measuring strain comprises providing laminated material comprising two or more ply layers and having a thickness along a direction orthogonal to a plane defined by the ply layers, and comprising a strain sensor embedded between adjacent ply layers, wherein: the strain sensor comprises a first planar optical waveguide and a second planar optical waveguide, each of the first planar optical waveguide and the second planar optical waveguide having a waveguiding core defining an optical propagation direction parallel to the plane of the laminated material and a Bragg grating in the waveguiding core, the optical propagation direction of the first planar optical waveguide being non-parallel to the optical propagation direction of the second planar waveguide; interrogating the Bragg grating of the first planar optical waveguide with transverse electric (TE) polarized light and with transverse magnetic (TM) polarized light to obtain a TE spectral response of the Bragg grating for the TE polarized light and a TM spectral response of the Bragg grating for the TM polarized light; interrogating the Bragg grating of the second planar optical waveguide with TE polarized light and with TM polarized light to obtain a TE spectral response of the Bragg grating for the TE polarized light and a TM spectral response of the Bragg grating for the TM polarized light; and processing the TE spectral response and the TM spectral response of the first planar optical waveguide and the TE spectral response and the TM spectral response of the second planar optical waveguide to extract at least a through-thickness component of strain within the laminated material which is aligned along the direction of the thickness of the laminated material.

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.

The hybrid measurement system includes an evanescent prism coupling spectroscopy (EPCS) sub-system and a light-scattering polarimetry (LSP) sub-system. The EPCS sub-system includes an EPCS light source optically coupled to an EPCS detector system through an EPCS coupling prism. The LSP sub-system includes an LSP light source optically coupled to an optical compensator, which in turn is optically coupled to a LSP detector system via a LSP coupling prism. A support structure supports the EPCS and LSP coupling prisms to define a coupling prism assembly, which supports the two prisms at a measurement location. Stress measurements made using the EPCS and LSP sub-systems are combined to fully characterize the stress properties of a transparent chemically strengthened substrate. Methods of processing the EPCS and LSP measurements to improve measurement accuracy are also disclosed.

A multi-core fiber includes multiple optical cores, and for each different core of a set of different cores of the multiple optical cores, a total change in optical length is detected. The total change in optical length represents an accumulation of all changes in optical length for multiple segments of that different core up to a point on the multi-core fiber. A difference is determined between the total changes in optical length for cores of the set of different cores. A twist parameter and/or a bend angle associated with the multi-core fiber at the point on the multi-core fiber is/are determined based on the difference.

Apparatus can comprise a cavity at least partially defined by a first major surface of a reference block and configured to receive a sample. The apparatus can comprise a first polarization-switching light source configured to emit a first polarization-switched light beam toward the cavity and a first detector configured to detect a corresponding signal. The apparatus can comprise a second polarization-switching light source configured to emit a second polarization-switched light beam toward the cavity and a second detector configured to detect a corresponding signal. The first reference block can be positioned between the second detector and the second reference block. Methods of determining an estimated stress profile can comprise determining a central tension from a measured retardation profile of the sample. Methods can comprise determining an initial stress profile from a refractive index profile of the sample. Methods can comprise scaling and adjusting stress profiles.