Abstract: Interferometric method and apparatus for measuring aspheric surfaces and wavefronts by directing a spherical wavefront of known design at a wavelength &lgr;1 at a reference sphere with known measured surface properties to generate a first electronic signal containing information about the optical path differences between the reference and measurement wavefronts generated an interferometer and directing an aspherical wavefront of known design at a wavelength &lgr;2 at an aspherical surface or wavefront to be tested to generate a second electronic signal containing information about the optical path differences between the reference and measurement wavefronts generated by the interferometer.

Abstract: Interferometric apparatus and methods by which aspheric surfaces and wavefronts may be precisely measured. The apparatus is provided with two modes of operation. In one mode, the apparatus is configured generally as a Fizeau interferometer in which an aspheric reference surface is used to permit the rapid, robust measurement of the difference between the aspheric reference surface and an aspheric test optic or wavefront. In another mode of operation, the aspheric test surface itself is completely characterized through in-situ use of an interferometric scanning technique using a spherical reference surface.

Abstract: Conical surfaces (and other complex surface shapes) can be interferometrically characterized using a locally spherical measurement wavefront (e.g., spherical and aspherical wavefronts). In particular, complex surface shapes are measured relative to a measurement point datum. This is achieved by varying the radius of curvature of a virtual surface corresponding to a theoretical test surface that would reflect a measurement wavefront to produce a constant optical path length difference (e.g., zero OPD) between the measurement and reference wavefronts.

Abstract: Interferometric apparatus and methods by which the local surface characteristics of photolithographic mirrors or the like may be interferometrically measured in-situ to provide correction signals for enhanced distance and angular measurement accuracy. Surface characterizations along one or multiple datum lines in one or more directions may be made by measuring the angular changes in beams reflected off the surfaces during scanning operations to determine local slope and then integrating the slope to arrive at surface topology. The mirrors may be mounted either on the photolithographic stages or off the photolithographic stages on a reference frame.

Abstract: Interferometric apparatus and methods by which the local surface characteristics of photolithographic mirrors or the like may be interferometrically measured in-situ to provide correction signals for enhanced distance and angular measurement accuracy. Surface characterizations along one or multiple datum lines in one or more directions may be made by measuring the angular changes in beams reflected off the surfaces during scanning operations to determine local slope and then integrating the slope to arrive at surface topology. The mirrors may be mounted either on the photolithographic stages or off the photolithographic stages on a reference frame.

Abstract: Interferometric apparatus and methods by which the local surface characteristics of photolithographic mirrors or the like may be interferometrically measured in-situ to provide correction signals for enhanced distance and angular measurement accuracy. Surface characterizations along one or multiple datum lines in one or more directions may be made by measuring the angular changes in beams reflected off the surfaces during scanning operations to determine local slope and then integrating the slope to arrive at surface topology. The mirrors may be mounted either on the photolithographic stages or off the photolithographic stages on a reference frame.

Abstract: The invention features a nonlinear optical crystal assembly and a gas mixture that surrounds the nonlinear crystal. The gas mixture reduces photochemical degradation of the nonlinear crystal caused by exposure of the nonlinear crystal to a high power light source. For example, the nonlinear crystal may be a borate-based nonlinear crystal such as BBO and the gas mixture may include a hydrogen and oxygen to repair broken bonds in boron-oxygen rings of the borate-based crystal. The assembly may be incorporated into a light source, and applications requiring such a light source, such as, e.g., applications requiring ultraviolet light. Furthermore, the nonlinear crystal assembly may be placed inside an optical cavity.

Abstract: Interferometric apparatus for measuring changes in altitude between a surface and a datum line where the apparatus comprises a dimensionally stable metrology frame and the datum line is defined in an object mounted for nominally plane translation with respect to the metrology frame in at least two orthogonal directions while experiencing relatively smaller changes in altitude in a direction nominally normal to at least two orthogonal directions. An elongated reflector is mounted with respect to either the metrology frame or the object to provide the surface, and at least one interferometer system is mounted at least in part on object for movement therewith.

Abstract: A strain-isolated mirror is made from a substrate having first and second body portions. First and second connecting portions extend across a gap between the first body portion and the second body portion. A first flexural hinge on the first second connecting portion couples the second connecting portion to the first body portion.

Abstract: Interferometric apparatus and methods for reducing the effects of coherent artifacts in interferometers. Fringe contrast in interferograms is preserved while coherent artifacts that would otherwise be present in the interferogram because of coherent superposition of unwanted radiation generated in the interferometer are suppressed. Use is made of illumination and interferogrammetric imaging architectures that generate individual interferograms of the selected characteristics of a test surface from the perspective of different off-axis locations of illumination in an interferometer and then combine them to preserve fringe contrast while at the same time arranging for artifacts to exist at different field locations so that their contribution in the combined interferogram is diluted.

Abstract: The invention features an interferometry system which includes at least one dynamic beam steering assembly for redirecting one or more beams within the interferometry system in response to changes in the angular orientation or position of the measurement object. A control circuit controls the beam steering assembly based on a signal derived from one or more beams within the interferometry system. The dynamic beam steering assembly can be incorporated into interferometry systems that measure displacement, angle, and/or dispersion. The interferometry systems can be advantageously incorporated into lithography systems used to fabricate integrated circuits and other semiconducting devices and beam writing systems used to fabricate lithography masks.

Abstract: An apparatus for aligning a fiber to an optical device includes a base, a fiber holder mounted on the base, the fiber holder holding the fiber during operation of the apparatus, a first movable stage mounted on the base, the first movable stage holding the optical device during operation of the apparatus, a second movable stage mounted on the base, wherein the second movable stage is configured to move parallel to the first movable stage, a fiber positioner attached to the second movable stage, and a processor programmed to control the movement of the first movable stage and the second movable stage, wherein, during operation of the apparatus, the processor moves the first movable stage and the second movable stage towards the fiber.

Abstract: A fiber-locating structure for aligning an optical fiber includes opposed first and second faces. A first wall, defining a funnel, extends from the first face toward the second face; while a second wall, defining a tunnel, extends from the second face toward the first face. The first and second walls are disposed such that the funnel and the tunnel meet to form a continuous passageway between the first face and the second face.

Abstract: A method for compensating data age in measurement signals from an interferometer includes measuring a value of the measurement signal and adjusting the measured value based on the measurement signal with a data age adjustment value to correct for data age.

Abstract: The invention features a surface profiling method including: collecting interferometric data related to a surface profile of a measurement object; and calculating the surface profile based on the collected interferometric data and at least one value indicative of dispersion in the phase change on reflection (PCOR) of the profiled surface of the measurement object. The invention also features a surface profiling system including: an interferometry system which during operation provides interferometric data related to a surface profile of a measurement object; and an electronic processor coupled the interferometry system, wherein during operation the electronic processor calculates the surface profile based on the interferometric data and at least one parameter indicative of dispersion in the phase change on reflection (PCOR) of the profiled surface of the measurement object.

Abstract: Apparatus and method for interferometric measurement of a change in the relative directions of propagation of components of an optical beam, for interferometric measurement of a change in the direction of propagation of an optical beam, and for interferometric measurments of the change in orientation of an object. An interferometer is arranged to intercept light beams to produce an output beam from which a detector generates an electrical signal having a phase that varies in at least one plane in accordance with the angular separation between the beams. Electronic processing determines the phase and converts it to the angle separating the light beams.

Abstract: Apparatus and method for simultaneous interferometric measurements of angular orientation of and distance to a plane mirror measurement object using a multiple beam interferometer system. A first and second groups of the multiple beam interferometer systems have beams that contact the measurement object two times and three times, respectively, for simultaneous measurement of one or more of changes in the distance to and changes of the angular orientation in one plane or in two orthogonal planes of the measurement object.

Abstract: An interferometry system including: an interferometer which during operation directs a measurement beam along a measurement path contacting a measurement object and combines at least a portion of the measurement beam with another beam to form an overlapping pair of exit beams, the interferometer including a beam steering assembly having a beam steering element and a positioning system to orient the beam steering element, the beam steering element positioned to direct the measurement beam, the measurement beam contacting the beam steering element; a control circuit which during operation causes the positioning system to reorient the beam steering element in response to a change in at least one of angular orientation and position of the measurement object; a photodetector; and an optical fiber coupling an output beam derived from the overlapping pair of exit beams from the interferometer to the photodetector.

Abstract: An optical switching element for use in an optical cross-bar array, includes a magnetically responsive curtain that switches between an extended state and a deflected state in response to an applied switching-field. The switching element includes a curtain that moves in response to a magnetic field. The curtain has a fixed edge attached to a substrate and a free edge opposite the fixed edge. A first magnetic-field source magnetically coupled to the curtain generates a first magnetic field that urges the curtain into an extended position in which the curtain intercepts the optical beam. A second magnetic-field source, also magnetically coupled to the curtain, generates a second magnetic field that urges the curtain into a deflected position in which the curtain avoids intercepting the optical beam.

Abstract: Apparatus and methods particularly suitable for use in electro-optical metrology and other applications to measure and monitor the refractive index of a gas in a measurement path and/or the change in optical path length of the measurement path due to the gas while the refractive index of the gas may be fluctuating due to turbulence or the like and/or the physical length of the measuring path may be changing. More specifically, the invention employs electronic frequency processing to provide measurements of dispersion of the refractive index, the dispersion being substantially proportional to the density of the gas, and/or measurements of dispersion of the optical path length, the dispersion of the optical path length being related to the dispersion of the refractive index and the physical length of the measurement path.