An optical frequency domain reflectometer according to the invention includes: a swept light source that outputs wavelength-swept light; an auxiliary interferometer that has a the auxiliary interference signal generating delay fiber and outputs an auxiliary interference signal from the wavelength-swept light; a measurement interferometer that has a measurement target optical fiber and outputs a measurement interference signal from the wavelength-swept light; a plurality of linearization units that have different delay times, compensate non-linearity in a wavelength sweep of the swept light source for the measurement interference signal, using the auxiliary interference signal, and output compensated signals as output signals; and a weighted addition and Fourier transform unit that outputs a frequency domain signal as a result of addition and Fourier transformation of weighted signals which are multiplying the output signals from the plurality of linearization units by different weights.

Exemplary apparatus and method are provided. In particular, an electromagnetic radiation can be emitted with, e.g. a light source arrangement. For example, the light source arrangement can include a cavity and a filter, and a spectrum of the electromagnetic radiation can be controlled, e.g., with such cavity and filter, to have a mean frequency that changes (i) at an absolute rate that is greater than about 100 terahertz per millisecond, and (ii) over a range that is greater than about 10 terahertz. Additionally or alternatively, the light source arrangement can include a frequency shifting device which can shift the mean frequency of the electromagnetic radiation.

This application relates to an optical refractometer. In one aspect, the optical refractometer includes a prism, a light source and a sensor. The prism includes a first surface to which light is incident, a second surface to which the incident light is refracted when it contacts a substance, and a third surface reflecting the light refracted at the second surface toward the first surface. The light source emits light onto the first surface of the prism to be refracted toward the second surface. The sensor receives the light reflected from the third surface and output from the first surface. The light projected from the light source travels an optical path that directs the light to pass through the first surface of the prism, refract on the second surface, reflect on the third surface, and emit and condense to the first surface.

Systems and methods are disclosed for dynamic addressing of optical fiber sensors in fiber optic interferometry systems. Events that occur along the optical fiber span have defining attributes such as location along the optical fiber span, type, magnitude, time of occurrence, and duration. The event attributes may be used to dynamically form a unique address that fully defines and identifies the event. Other information, such as the corresponding identifier for one or more of the optical fiber span and the corresponding fiber optic interrogator may be included as part of the unique address.

A method for calibrating electromagnetic radiation-based three-dimensional imaging includes: obtaining (501) a calibration imaging result at least partly on the basis of electromagnetic waves received from a calibration artifact, forming (502) calibration data on the basis of the calibration imaging result and a known thickness profile of the calibration artifact, and correcting (503), with the aid of the calibration data, an imaging result obtained at least partly on the basis of electromagnetic waves received from a sample to be imaged. The calibration artifact includes layers, for example Langmuir-Blodgett films, having pre-determined thicknesses and stacked on each other so as to achieve the pre-determined thickness profile of the calibration artifact. A three-dimensional imaging system configured to carry out the method.

A system and method are described for performing tear film structure measurement. A broadband light source illuminates the tear film. A spectrometer measures respective spectra of reflected light from at least one point of the tear film. A color camera performs large field of view imaging of the tear film, so as to obtain color information for all points of the tear film imaged by the color camera. A processing unit calibrates the camera at the point measured by the spectrometer so that the color obtained by the camera at the point matches the color of the spectrometer at the same point. The processing unit determines, from the color of respective points of the calibrated camera, thicknesses of one or more layers of the tear film at the respective points. Other applications are also described.

A method for optical inspection includes illuminating a patterned polymer layer on a semiconductor wafer with optical radiation over a range of infrared wavelengths, measuring spectral properties of the optical radiation reflected from multiple points on the patterned polymer layer over the range of infrared wavelengths, and based on the measured spectral properties, computing a complex refractive index of the patterned polymer layer.

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.

A method for imaging of an object includes, for each of a plurality of surface-regions of the object, determining a corresponding image-sensor pixel group of a camera illuminated by light propagating from the surface-region via a lens of the camera. The method also includes, after the step of determining and for each surface-region: (i) changing a distance between the object and the lens such that the surface region intersects an in-focus object-plane of the camera and the lens forms an in-focus surface-region image on the corresponding image-sensor pixel group; (ii) capturing, with the corresponding image-sensor pixel group, the in-focus surface-region image of the surface-region; and (iii) combining the in-focus surface-region images, obtained by performing said capturing for each surface-region, to yield an all-in-focus image of the object.

An apparatus comprising: a double path interferometer comprising a sample path for an object and a reference path; a source of linearly polarized light for the double path interferometer, a phase plate positioned in the sample path; means for superposing the sample path and reference path to create a beam of light for detection; means for spatially modulating the beam of light to produce a modulated beam of light; means for dispersing the modulated beam of light to produce a spatially modulated and dispersed beam of light; a first detector, a second detector, and means for splitting the spatially modulated and dispersed beam of light, wherein light of a first linear polarization is directed to the first detector and light of a second linear polarization, orthogonal to the first linear polarization, is directed to the second detector.