Abstract: An interferometric optical system for measuring a test object, including: i) a reference object comprising a partially reflective reference surface; ii) a light source module configured to direct first and second input beams through the reference surface to the test object at an angle to one another; iii) a detector positioned to detect light reflected from the reference surface and one or more surfaces of the test object; and iv) an aperture positioned to selectively block light from reaching the detector, wherein the angle between the first and second input beams causes the aperture to block light from the first input beam reflected by the reference surface and pass light from second input beam reflected by the reference surface, wherein the two input beams have a mutual coherence length smaller than twice an optical distance between the reference surface and the test object.

Abstract: An interferometric optical system for measuring a test object, including: i) a reference object comprising a partially reflective reference surface; ii) a light source module configured to direct first and second input beams through the reference surface to the test object at an angle to one another; iii) a detector positioned to detect light reflected from the reference surface and one or more surfaces of the test object; and iv) an aperture positioned to selectively block light from reaching the detector, wherein the angle between the first and second input beams causes the aperture to block light from the first input beam reflected by the reference surface and pass light from second input beam reflected by the reference surface, wherein the two input beams have a mutual coherence length smaller than twice an optical distance between the reference surface and the test object.

Abstract: Techniques for removing interferometry signal phase variations caused by distortion and other effects in a multi-layer stack include: providing an electronic processor sample interferometry data acquired for the stack using a low coherence imaging interferometry system; transforming, by the electronic processor, the sample interferometry data to a frequency domain; identifying a non-linear phase variation from the sample interferometry data in the frequency domain, in which the non-linear phase variation is a result of dispersion introduced into a measurement beam by the test sample; and removing the non-linear phase variation from the sample interferometry data thereby producing compensated interferometry data.

Abstract: An optical method for determining an orientation of surface texture of a mechanical part includes: i) acquiring data for a first areal surface topography image using a surface topography measurement instrument, wherein the first image corresponds to a first field of view of the mechanical part for the surface topography measurement instrument; ii) rotating the mechanical part with respect to a rotation axis provided by a rotatable mount used to secure the mechanical part to provide a second field of view of the mechanical part for the surface topography measurement instrument, wherein the first and second fields of view overlap to provide image information about a common region of the mechanical part; iii) acquiring data for a second areal surface topography image using the surface topography measurement instrument, wherein the second image corresponds to the second field of view; and iv) processing the data from the images.

Abstract: Techniques for removing interferometry signal phase variations caused by distortion and other effects in a multi-layer stack include: providing an electronic processor sample interferometry data acquired for the stack using a low coherence imaging interferometry system; transforming, by the electronic processor, the sample interferometry data to a frequency domain; identifying a non-linear phase variation from the sample interferometry data in the frequency domain, in which the non-linear phase variation is a result of dispersion introduced into a measurement beam by the test sample; and removing the non-linear phase variation from the sample interferometry data thereby producing compensated interferometry data.

Abstract: An optical method for determining an orientation of surface texture of a mechanical part includes: i) acquiring data for a first areal surface topography image using a surface topography measurement instrument, wherein the first image corresponds to a first field of view of the mechanical part for the surface topography measurement instrument; ii) rotating the mechanical part with respect to a rotation axis provided by a rotatable mount used to secure the mechanical part to provide a second field of view of the mechanical part for the surface topography measurement instrument, wherein the first and second fields of view overlap to provide image information about a common region of the mechanical part; iii) acquiring data for a second areal surface topography image using the surface topography measurement instrument, wherein the second image corresponds to the second field of view; and iv) processing the data from the images.

Abstract: Calibrating a scanning interferometry imaging system includes: configuring the scanning interferometry imaging system for operation with an interference objective using light having a narrowband wavelength spectrum; using the scanning interferometry imaging system to direct measurement light and reference light along different paths and to overlap the measurement and reference light on a detector, the measurement and reference light having the narrowband wavelength spectrum; scanning an optical path length difference between the measurement light and the reference light at the detector while acquiring intensity data using the detector, the detector acquiring the intensity data at a frame rate and the scanning being performed at a scan speed; determining information about the scan speed based on the acquired intensity data, geometric information about the scanning interferometry imaging system, and the narrowband wavelength spectrum; and calibrating the scanning interferometry imaging system based on the infor

Abstract: Generating a composite image of a non-flat surface includes: acquiring, using a microscope, multiple images of different areas of the non-flat surface, where each image includes a region of overlap with at least one adjacent image, the microscope having sufficient resolution to image in three dimensions a microstructure on the non-flat surface having a lateral dimension of 10 microns or less and a height of 10 nm or less; determining, for each of the images, a set of rigid body parameters relating a position and orientation of the test object in the image to a common coordinate system, where the set of rigid body parameters is determined by fitting the resolved microstructure in the overlap region in the image with the corresponding microstructure in the overlap region of the adjacent image; and combining the images based on the sets of rigid body parameters to generate a composite image.

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 a transparent optical element including a lens portion and a plane parallel portion, the lens portion having at least one curved surface and the plane parallel portion having opposing first and second surfaces, includes: directing measurement light to the transparent optical element; detecting measurement light reflected from at least one location on the first surface of the plane parallel portion; detecting measurement light reflected from the second surface of the plane parallel portion at a location corresponding to the at least one location on the first surface; determining, based on the detected light, information about the plane parallel portion; and evaluating the transparent optical element based on the information about the plane parallel portion.

Abstract: A method for determining information about an object including a curved portion and a planar portion, the curved portion having a first curved surface having an apex and defining an axis of the object, includes: directing measurement light to the object; detecting measurement light reflected from the first curved surface of the curved portion; detecting measurement light reflected from at least one other surface of the object; and determining, based on the detected light, information about the apex of the first curved surface of the curved portion.

Abstract: An interferometry system includes: a light source, defining a coherence length, an interferometer configured to combine measurement and reference beams to form an output beam, where the interferometer includes a dispersion imbalance between measurement and reference paths large enough to produce a coherence envelope for the system having a width more than twice the coherence length; a phase modulation device configured to introduce a variable phase between the measurement and reference beams; a detector; imaging optics to direct the output beam to the detector and produce an image of the measurement surface; and an electronic processor electronically coupled to the phase modulation device and the detector and configured to record multiple interference signals corresponding to different locations on the measurement surface, in which the interference signals are based on the intensity of the output beam as a function of the variable phase for the different locations of the measurement surface.

Abstract: Calibrating a scanning interferometry imaging system includes: configuring the scanning interferometry imaging system for operation with an interference objective using light having a narrowband wavelength spectrum; using the scanning interferometry imaging system to direct measurement light and reference light along different paths and to overlap the measurement and reference light on a detector, the measurement and reference light having the narrowband wavelength spectrum; scanning an optical path length difference between the measurement light and the reference light at the detector while acquiring intensity data using the detector, the detector acquiring the intensity data at a frame rate and the scanning being performed at a scan speed; determining information about the scan speed based on the acquired intensity data, geometric information about the scanning interferometry imaging system, and the narrowband wavelength spectrum; and calibrating the scanning interferometry imaging system based on the infor

Abstract: A method for determining information about a transparent optical element including a lens portion and a plane parallel portion, the lens portion having at least one curved surface and the plane parallel portion having opposing first and second surfaces, includes: directing measurement light to the transparent optical element; detecting measurement light reflected from at least one location on the first surface of the plane parallel portion; detecting measurement light reflected from the second surface of the plane parallel portion at a location corresponding to the at least one location on the first surface; determining, based on the detected light, information about the plane parallel portion; and evaluating the transparent optical element based on the information about the plane parallel portion.

Abstract: A method for determining information about an object including a curved portion and a planar portion, the curved portion having a first curved surface having an apex and defining an axis of the object, includes: directing measurement light to the object; detecting measurement light reflected from the first curved surface of the curved portion; detecting measurement light reflected from at least one other surface of the object; and determining, based on the detected light, information about the apex of the first curved surface of the curved portion.

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: An encoder interferometry system includes a beam splitting element positioned to receive an input beam from a light source, in which the beam splitting element is configured to direct a first portion of the input beam along a measurement path to define a measurement beam and a second portion of the input beam along a reference path to define a reference beam, an encoder scale positioned to diffract the measurement beam at least once, one or more optical components configured and arranged to alter a direction of a first diffracted portion of the measurement beam and a direction of a second diffracted portion of the measurement beam such that beam paths of the first diffracted portion and the second diffracted portion are non-parallel subsequent to the first diffracted portion and the second diffracted portion passing through the beam splitting element, and a detector positioned to receive the first diffracted portion.

Abstract: Generating a composite image of a non-flat surface includes: acquiring, using a microscope, multiple images of different areas of the non-flat surface, where each image includes a region of overlap with at least one adjacent image, the microscope having sufficient resolution to image in three dimensions a microstructure on the non-flat surface having a lateral dimension of 10 microns or less and a height of 10 nm or less; determining, for each of the images, a set of rigid body parameters relating a position and orientation of the test object in the image to a common coordinate system, where the set of rigid body parameters is determined by fitting the resolved microstructure in the overlap region in the image with the corresponding microstructure in the overlap region of the adjacent image; and combining the images based on the sets of rigid body parameters to generate a composite image.

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: An encoder interferometry system includes an interferometer positioned to receive first and second beams having different frequencies, in which the interferometer has at least one polarizing beam splitting element for directing the first beam along a measurement path to define a measurement beam and the second beam along a reference path to define a reference beam. The encoder interferometry system further includes a encoder scale positioned to diffract the measurement beam at least once, a detector positioned to receive the measurement and reference beams after the measurement beam diffracts from the encoder scale, and an output component positioned to receive the measurement and reference beams before they reach the detector and deflect spurious portions of the first and second beam away from the detector.