Abstract: Disclosed herein is a system for determining information about one or more defects on or in a test object. The system includes a light source configured to illuminate a test object with spatially coherent light; a multi-element detector positioned to detect an interference pattern of light associated with one or more defects on or in the illuminated test object; and an electronic control module in communication with the multi-element detector and configured to process the interference pattern to determine information about the one or more defects on or in the test object.

Abstract: Systems and methods for generating 3D representations of shape and color texture of a test surface are described. In one aspect, surface topography interferometers are equipped with a multi-element detector and an illumination system to produce a true-color image of the measured object surface. Color information can be presented as a true-color two-dimensional image or combined with topography information to form a three-dimensional representation of the shape and color texture of the object, effectively creating for a human observer the impression of looking at the actual part.

Abstract: An imaging interferometer includes optics defining an interferometric cavity, in which the optics include a first beam-splitting optic positioned to separate an input beam into a test beam and a reference beam, a second beam-splitting optic positioned to transmit the test beam to the test surface, receive the test beam back from the test surface, and thereafter recombine the test beam with the reference beam, and a third optic positioned to direct the reference beam from the first optic to the second optic. The interferometric cavity defines a virtual reference surface positioned along a path for the reference beam between the second and third optics. The interferometer also includes an imaging channel positioned to receive the recombined test and reference beams, where the imaging channel includes an imaging detector, and at least one imaging element configured to image the test surface and the virtual reference surface onto the detector.

Abstract: Determining a height profile of a test object surface includes obtaining, from a scanning interferometry device, scanning interferometry data for the test object surface, calculating a coherence profile of the test object surface and a phase profile of the test object surface based on the scanning interferometry data, calculating an phase gap map based on the coherence profile and the phase profile, modifying the coherence profile based on the phase gap map to obtain a corrected coherence profile, and determining a height of the test object surface based on the corrected coherence profile.

Abstract: Determining spatial information about a part includes positioning the part in a fixture having two reference surfaces, where the part is positioned between the two reference surfaces, imaging the two reference surfaces and opposing surfaces of the part to different locations of a multi-element detector, simultaneously acquiring images of the opposing sides of the part and the two reference surfaces using the multi-element detector, and determining spatial information about the part based on the simultaneously acquired images.

Abstract: A method for determining information about changes along a degree of freedom of an encoder scale includes directing a first beam and a second beam along different paths and combining the first and second beams to form an output beam, where the first and second beams are derived from a common source, the first and second beams have different frequencies, where the first beam contacts the encoder scale at a non-Littrow angle and the first beam diffracts from the encoder scale at least once; detecting an interference signal based on the output beam, the interference signal including a heterodyne phase related to an optical path difference between the first beam and the second beam; and determining information about a degree of freedom of the encoder scale based on the heterodyne phase.

Abstract: A method for determining information about changes along a degree of freedom of an encoder scale includes directing a first beam and a second beam along different paths and combining the first and second beams to form an output beam, where the first and second beams are derived from a common source, the first and second beams have different frequencies, where the first beam contacts the encoder scale at a non-Littrow angle and the first beam diffracts from the encoder scale at least once; detecting an interference signal based on the output beam, the interference signal including a heterodyne phase related to an optical path difference between the first beam and the second beam; and determining information about a degree of freedom of the encoder scale based on the heterodyne phase.

Abstract: Methods for forming a three-dimensional image of a test object include directing light to a surface of best-focus of an imaging optic, where the light has an intensity modulation in at least one direction in the surface of best-focus, scanning a test object relative to the imaging optic so that a surface of the measurement object passes through the surface of best-focus of the imaging optic as the test object is scanned, acquiring, for each of a series of positions of the test object during the scan, a single image of the measurement object using the imaging optic, in which the intensity modulation of the light in the surface of best-focus is different for successive images, and forming a three-dimensional image of the test object based on the acquired images.

Abstract: A method includes obtaining, from a detector of an interferometry system, an interference signal based on a combination of a first beam and a reference beam, subsequent to the first beam being diffracted by an encoder scale, obtaining, through an electronic processor, an error compensation signal based on a non-harmonic cyclic error that modifies the interference signal, and outputting information about a change in a position of the encoder scale relative to an optical assembly of the interferometry system based on the interference signal and the error compensation signal.

Abstract: A system includes an interference microscope having one or more optical elements arranged to image a test object to an image plane by combining test light from the test object with reference light from a reference object to form an interference pattern at the image plane, wherein the test and reference light are derived from a common broadband light source.

Abstract: Deformations of a surface of a test object can be measured by attaching mirrors to a surface of a test object, each mirror having a reflective surface with a dimension and a radius of curvature smaller than those of the surface of the test object. Light is directed towards the mirrors and a reference surface, and interference patterns are generated using light reflected from the mirrors and the reference surface. Changes in the surface of the test object are determined based on the interference patterns.

Abstract: Disclosed is an apparatus including a mechanical reference frame and a rigid object mechanically coupled to the reference frame by two or more constraints. The stiffnesses of at least two of the constraints are different from one another, and the relative locations and stiffnesses of the constraints cause a designated point on the rigid object to remain stationary with respect to the reference frame during thermal expansion of the rigid object over a range of temperatures.

Abstract: Metrology system, apparatus and method used to implement measurements inside a lithography tool are described, such that the disclosed measurements can be performed without contributing outgassed effluent within the lithography tool. Disclosed is a system including: an objective for projecting an image of an object positioned at an object plane to an image plane; a stage to execute motions relative to the objective while supporting the wafer at the image plane; an optical sensor for producing an optical monitoring signal associated with the motions of the stage; and a glass optical fiber having a metal outer coating, the metal-coated glass optical fiber being arranged to provide light to, or collect light from, the optical sensor.

Abstract: An encoder head includes one or more components arranged to: i) direct a first incident beam to the diffractive encoder scale at a first incident angle with respect to the encoder scale; ii) receive a first return beam from the encoder scale at a first return angle, the first return angle being different from the first incident angle; iii) redirect the first return beam to the encoder scale as a second incident beam at a second incident angle; and iv) receive a second return beam back from the encoder scale at a second return angle, the second return angle being different from the second incident angle, in which a difference between the first incident angle and second incident angle is less than a difference between the first incident angle and the first return angle and less than a difference between the second incident angle and the second return angle.

Abstract: A method for determining information about changes in a position of an encoder scale includes separating, in a first interferometry cavity, a low coherence beam into a first beam propagating along a first path of the first interferometry cavity and a second beam propagating along a second path of the first interferometry cavity, combining the first beam and the second beam to form a first output beam, separating, in a second interferometry cavity, the first output beam into a measurement beam propagating along a measurement path of the second interferometry cavity and a reference beam propagating along a reference path of the second interferometry cavity, combining the measurement beam and the reference beam to form a second output beam, detecting an interference signal based on the second output beam, and determining the information about changes in the position of the encoder scale based on phase information from the interference signal.

Abstract: An encoder system includes an encoder scale and an encoder head, in which the encoder head is configured to combine each twice-diffracted measurement beam of multiple twice-diffracted measurement beams with a corresponding reference beam to form multiple output beams, where the encoder head includes a monolithic optical component having multiple facets, the multiple facets being arranged to: receive multiple once-diffracted measurement beams from a surface of the encoder scale; and redirect the multiple once-diffracted measurement beams back towards the surface of the encoder scale, the encoder scale being positioned in a path of the once-diffracted measurement beams to produce the twice-diffracted measurement beams.

Abstract: In-situ calibration of an interferometer includes making a sequence of phase measurements of a test object using the interferometer, each of the measurements having a same carrier fringe frequency, where at least some of the measurements are made at three or more different orientations of carrier fringes, and determining information about the test object based on at least some of the phase measurements, in which determining the information includes reducing errors in the measurements arising from imperfections in the interferometer based on the measurements made at the three or more different orientations.

Abstract: Apparatus include a microscope including an objective and a stage for positioning a test object relative to the objective, the stage being moveable with respect to the objective, and a sensor system, that includes a sensor light source, an interferometric sensor configured to receive light from the sensor light source, to introduce an optical path difference (OPD) between a first portion and a second portion of the light, the OPD being related to a distance between the objective lens and the stage, and to combine the first and second portions of the light to provide output light, a detector configured to detect the output light from the interferometric sensor, a fiber waveguide configured to direct light between the sensor light source, the interferometric sensor and the detector, a tunable optical cavity in a path of the light from the sensor light source and the interferometric sensor, and an electronic controller in communication with the detector, the electronic controller being configured to determine in

Abstract: A method for determining information about changes along a degree of freedom of an encoder scale includes directing a first beam and a second beam along different paths and combining the first and second beams to form an output beam, where the first and second beams are derived from a common source, the first and second beams have different frequencies, where the first beam contacts the encoder scale at a non-Littrow angle and the first beam diffracts from the encoder scale at least once; detecting an interference signal based on the output beam, the interference signal including a heterodyne phase related to an optical path difference between the first beam and the second beam; and determining information about a degree of freedom of the encoder scale based on the heterodyne phase.

Abstract: Determining spatial information about a part includes positioning the part in a fixture having two reference surfaces, where the part is positioned between the two reference surfaces, imaging the two reference surfaces and opposing surfaces of the part to different locations of a multi-element detector, simultaneously acquiring images of the opposing sides of the part and the two reference surfaces using the multi-element detector, and determining spatial information about the part based on the simultaneously acquired images.