A protective film thickness measuring method includes a step of applying light to a top surface of a wafer in a state in which no protective film is formed and measuring a first reflection intensity of the light reflected from the top surface, a step of forming the protective film including a light absorbing material, a step of irradiating the protective film with exciting light of a wavelength at which the light absorbing material fluoresces and measuring a second reflection intensity including fluorescence of the protective film and the light reflected from the top surface, and a step of excluding reflection intensity of patterns formed on the top surface, by subtracting the measured first reflection intensity from the measured second reflection intensity, and calculating fluorescence intensity of the protective film.

An inspection apparatus, including: an optical system configured to provide a beam of radiation to a surface to be measured and to receive redirected radiation from the surface; and a detection system configured to measure the redirected radiation, wherein the optical system includes an optical element to process the radiation, the optical element including a Mac Neille-type multilayer polarizing coating configured to produce a reduced chromatic offset of the radiation.

An apparatus for determining a characteristic of a photoluminescent (PL) layer comprises: a light source that generates an excitation light that includes light from the visible or near-visible spectrum; an optical assembly configured to direct the excitation light onto a PL layer; a detector that is configured to receive a PL emission generated by the PL layer in response to the excitation light interacting with the PL layer and generate a signal based on the PL emission; and a computing device coupled to the detector and configured to receive the signal from the detector and determine a characteristic of the PL layer based on the signal.

An inspection system for inspecting an object including a base and a coating layer includes: an emission unit configured to irradiate the object with a terahertz wave including at least a reference pattern; and a support unit configured to adjust a relative position between the emission unit and the object. The inspection system further includes: a detection unit configured to detect the terahertz wave reflected on the object and acquire a terahertz image; and a determination unit configured to determine, from a shape of the terahertz image, whether an incident angle of the terahertz wave on the object is a predetermined incident angle.

An optical interrogation system, e.g., an OFDR-based system, measures local changes, of index of refraction of a sensing light guide subjected to a time-varying disturbance. Interferometric measurement signals detected for a length of the sensing light guide are transformed into the spectral domain. A time varying signal is determined from the transformed interferometric measurement data set. A compensating signal is determined from the time varying signal which is used to compensate the interferometric measurement data set for the time-varying disturbance. Further robustness is achieved using averaging and strain compensation. The compensation technique may be applied along the length of the light guide.

Method of measuring the thickness of a layer by a light source irradiating the layer with a light beam, which light source is controlled by a sinusoidal control signal having a modulation frequency f.sub.m so that the light beam presents optical power that is sinusoidally modulated at the modulation frequency, the measurement method consisting in: using detector elements to determine a calibration phase shift (Δφ.sub.cal) between the optical power and the control signal; heating the layer with the light beam; using the detector elements to detect a sinusoidal component of a heat flux radiated by the layer; calculating a phase shift (Δφ.sub.th/opt) between the sinusoidal component of the radiated heat flux and the optical power of the light beam while taking account of the calibration phase shift; and determining the thickness of the layer of material as a function of the phase shift (Δφ.sub.th/opt).

Interferometric measurement signals are detected by a single optical interferometric interrogator for a length of a sensing light guide and an interferometric measurement data set corresponding to the interferometric measurement signals is generated. The interferometric measurement data set is transformed into a spectral domain to produce a transformed interferometric measurement data set. The transformed interferometric measurement data set is compared to a baseline interferometric data set to identify a time-varying signal corresponding to a time-varying disturbance. The baseline interferometric data set is representative of the sensing light guide not being subjected to the time-varying disturbance. A compensating signal is determined from the time-varying signal and used to compensate at least a portion of the interferometric measurement data set for the time-varying disturbance as part of producing a measurement of the parameter.

An article includes a substrate defining a surface, a bond coat on the surface of the substrate, a coating layer on the bond coat, and a wear indicator. The coating layer includes at least one of an environmental barrier coating (EBC) or an abradable coating. The wear indicator disposed in a first region of the coating layer and includes at least one chromophore dopant and a material of the EBC or the abradable coating. The wear indicator is configured to indicate wear of the coating layer.

An apparatus for determining a characteristic of a photoluminescent (PL) layer comprises: a light source that generates an excitation light that includes light from the visible or near-visible spectrum; an optical assembly configured to direct the excitation light onto a PL layer; a detector that is configured to receive a PL emission generated by the PL layer in response to the excitation light interacting with the PL layer and generate a signal based on the PL emission; and a computing device coupled to the detector and configured to receive the signal from the detector and determine a characteristic of the PL layer based on the signal.

An article includes a substrate defining a surface, a bond coat on the surface of the substrate, a coating layer on the bond coat, and a wear indicator. The coating layer includes at least one of an environmental barrier coating (EBC) or an abradable coating. The wear indicator disposed in a first region of the coating layer and includes at least one chromophore dopant and a material of the EBC or the abradable coating. The wear indicator is configured to indicate wear of the coating layer.