A metrology apparatus has an illumination source that directs collimated light to a reference surface and to an optical component having a test surface that is in parallel with the reference surface. A first imaging lens defines a Fourier transform plane for light reflected from the reference surface and the test surface. A spatial filtering element is actuable to a blocking position that blocks specular light at the transform plane. A second imaging lens forms, at an image plane, an image of the test surface. A sensor array generates image data from received light at the image plane.

There is provided a system and method of a method of detecting a local shape deviation of a structural element in a semiconductor specimen, comprising: obtaining an image comprising an image representation of the structural element; extracting, from the image, an actual contour of the image representation; estimating a reference contour of the image representation indicative of a standard shape of the structural element, wherein the reference contour is estimated based on a Fourier descriptor representative of the reference contour, the Fourier descriptor being estimated using an optimization method based on a loss function specifically selected to be insensitive to local shape deviation of the actual contour; and performing one or more measurements representative of one or more differences between the actual contour and the reference contour, the measurements indicative of whether a local shape deviation is present in the structural element.

An ellipsometer includes a first separation unit configured to separate a first reflected light into two reflected lights, a first polarizing optical element configured to separate each of the two reflected lights into two linearly polarized lights, a first interference device configured to form an interference fringe by allowing components of the two linearly polarized lights to interfere with each other, a second separation unit configured to separate a second reflected light into two reflected lights, a second polarizing optical element configured to separate each of the two reflected lights into two linearly polarized lights, and a second interference device configured to form an interference fringe by allowing components of the two linearly polarized lights to interfere with each other.

A swept source OCT system and related method are disclosed. The system comprises a control device for operating a tunable light source in response to an electronic sweep control signal such that the tunable light source carries out wave length sweeps with a repetition rate f.sub.sweep, which depends on the frequency of the sweep control signal. The system further comprises a detection device for the time-resolved detection of an interference signal from a sample beam and a reference beam with the help of a detection cycle signal. The sweep control signal and the detection cycle signal are phase-locked, or means for creating a signal or signal sequence are provided, said signal or signal sequence being characterising for the frequency relationship and/or the relative phase position of the sweep control signal and detection cycle signal.

An imaging system can include of a plurality of pairs of lenslets and a respective plurality of two-dimensional arrays of photonic waveguides arranged in a respective plurality of photonic integrated circuits. Each waveguide can collect light in an airy-disk-size bin to cover a full field of view of the lenslet. Light from each pair of respective waveguides from each pair of lenslets can be demultiplexed into wavelength bins and combined with appropriate phase shifts to enable a measurement of the complex visibility. The complex visibilities from all of the measurements then can be processed to form an image.

An optical coherence tomograph includes a wavelength tunable illuminating device, an illumination and measurement beam path with a dividing element and a scanner and a front optical unit and a reference beam path, a detection beam path and a flat panel detector. A beam splitter conducts the separated measurement radiation to the detection beam path and an optical element acts only on the illumination radiation. The optical element sets the numerical aperture of the illumination of the illumination field in the eye. An optical element acts only on the measurement radiation and sets the numerical aperture with which measurement radiation is collected in the eye. An aperture is arranged in front of the flat panel detector in an intermediate image plane and defines the size of an object field. The flat panel detector has a spatial resolution of 4 to 100 pixels in a direction.

An overlay metrology system may include, an illumination sub-system, a collection sub-system and a controller. The illumination sub-system may include one or more illumination optics configured to direct an illumination beam to an overlay target on a sample as the sample is scanned along a stage-scan direction by a translation stage, where the overlay target includes one or more cells having a grating-over-grating structure with periodicity along the stage-scan direction. The collection sub-system may include an objective lens, a first photodetector located in a pupil plane at a location of overlap between 0-order diffraction and +1-order diffraction, and a second photodetector located in a pupil plane at a location of overlap between 0-order diffraction and −1-order diffraction. The controller may receive time-varying interference signals from the first and second photodetectors and determine an overlay error between the first and second layers of the sample along the stage-scan direction.

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.

An optical coherence tomography apparatus includes a branching and merging device that branches a light beam emitted from a wavelength sweeping laser light source into an object light beam and a reference light beam, a balanced photodetector that generates information about a change in an intensity ratio of interference light beams, which are generated by the interference between the object light beam and the reference light beam, wherein the object light beam is scattered from the measurement object after being transmitted through the transparent substrate including a structure that changes a thickness, and a control unit that acquires structural data of the measurement object in a depth direction based on the information about the change in the intensity ratio of the interference light beams and connects the structural data while moving an irradiation position of the object light beam with a position of the above structure as a reference.

A swept-source OCT imaging system for imaging a region of an object, comprising: a swept light source which generates a beam of varying wavelength; a scanning element which scans the beam across the object; an interferometer which generates interference light by combining light scattered by the object (owing to the scan) with reference light; a photodetector which generates an electrical signal (S) having frequency components spanning a frequency band and caused by interference of the scattered light with the reference light; a band-pass filter module which band-pass filters the electrical signal; and a sample acquisition module which samples the filtered electrical signal. The band-pass filter module extracts at least some of the frequency components spanning the frequency band from the electrical signal. The sample acquisition module band-pass samples the filtered electrical signal.