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.

Apparatus include a polarization state generator situated to provide an interferometer source beam with a region of polarized source light with a polarization state that is in-plane as subsequently incident on a sample and a region of polarized source light with a polarization state that is perpendicular to in-plane as subsequently incident on the sample, and an interferometer unit configured to split the interferometer source beam into test and reference arm beams, to direct the test arm beam to the sample and the reference arm beam to a reference surface, and to recombine the test and reference arm beams to produce an interferometer output beam. Methods use a polarization state generator to produce an interferometer source beam and use an interferometer unit which splits the interferometer source beam into test and reference arm beams.

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.

A cascaded interferometric system for Fourier domain optical coherence tomography (OCT) in which the output of one sub-system interferometer is directed through a second sub-system interferometer for performing the Fourier transform in hardware.

A physical parameter estimating method, a physical parameter estimating device, and electronic apparatus are disclosed. The method includes: reading a Newton's rings fringe pattern obtained by performing an interferometric measurement on a unit to be measured; downsampling the Newton's rings fringe pattern to obtain a downsampled Newton's rings fringe pattern; calculating a magnitude spectrum of an intensity distribution signal of at least one first-direction pixel set in the downsampled Newton's rings fringe pattern under each fractional Fourier transform (FRFT) order in a searching range of FRFT orders, the first-direction direction pixel set including a line of pixels in a first direction, the first direction being one of a row direction and a column direction of the downsampled Newton's rings fringe pattern; determining a matched order of the intensity distribution signal according to the calculated magnitude spectrums; and estimating a physical parameter involved in the interferometric measurement according to at least the matched order. Therefore, physical parameters of the unit to be measured can be estimated with high accuracy even in presence of noise and obstacles in the fringe pattern.

A 3-D imaging system including a computer determining a plurality of coherence factors measuring an intensity contrast between a first intensity of a first region of an interference comprising constructive interference between a sample wavefront and a reference wavefront, and a second intensity of a second region of the interference comprising destructive interference between the sample wavefront and the reference wavefront, wherein the interference between a reference wavefront and a reflection from different locations on a surface of an object. From the coherence factors, the computer determines height data comprising heights of the surface with respect to an x-y plane perpendicular to the heights and as a function of the locations in the x-y plane. The height data is useful for generating a three dimensional topological image of the surface.

Systems and methods for improved interferometric imaging are presented. One embodiment is a partial field frequency-domain interferometric imaging system in which a light beam is scanned in two directions across a sample and the light scattered from the object is collected using a spatially resolved detector. The light beam could illuminate a spot, a line or a two-dimensional area on the sample. Additional embodiments with applicability to partial field as well as other types of interferometric systems are also presented.

Systems and methods for improved interferometric imaging are presented. One embodiment is a partial field frequency-domain interferometric imaging system in which a light beam is scanned in two directions across a sample and the light scattered from the object is collected using a spatially resolved detector. The light beam could illuminate a spot, a line or a two-dimensional area on the sample. Additional embodiments with applicability to partial field as well as other types of interferometric systems are also presented.

Retinal imaging systems and related methods employ a user specific approach for controlling the reference arm length in an optical coherence tomography (OCT) imaging device. A method includes restraining a user's head relative to an OCT imaging device. A reference arm length adjustment module is controlled to vary a reference arm length to search a user specific range of reference arm lengths to identify a reference arm length for which the OCT image detector produces an OCT signal corresponding to the retina of the user. The user specific range of reference arm lengths covers a smaller range of reference arm lengths than a reference arm length adjustment range of the reference arm length adjustment module.

A device for determining the water content in the atmosphere comprising: a laser transmitter suitable for transmitting a laser beam for illuminating particles of water and/or ice present in the atmosphere, a first out-of-focus imager having a first collection angle suitable for capturing at least one first representative image of the particles, and processing unit in communication connection with the first image. The device further comprises a second out-of-focus imager having a second collection angle suitable for capturing at least one second image. The processing unit is in communication connection with the second imager, the processing unit being suitable for processing the first and second images in order to determine the water content in the atmosphere.