Abstract: The invention features an interferometry method including: directing two beams derived from a common source along different paths; producing a first output beam derived from a first portion of each of the two beams; producing a second output beam derived from a second portion of each of the two beams; and calculating a product of a first signal derived from the first output beam and a second signal derived from the second output beam.

Abstract: The present invention relates to a heterodyne interferometer system with a pre-processing of the target signal to isolate and remove self-interference signals using a known phase modulation of the carrier signal's frequency. Where self-interference signals do not include a time delay inherent in the target signal that travels to the target reflector, by selecting a modulation frequency tuned to the time delay and then filtering the resultant signal the target beam can be isolated and the self-interference signal can be effectively removed The system includes a modulation unit to apply a phase modulation to the carrier signal, and a mixing unit that demodulates the target signal at the modulation frequency to isolate the target beam.

Abstract: The invention features an interferometry system that uses a small angular difference in the propagation directions of orthogonally polarized components of an input beam to an interferometer. The orthogonally polarized components define reference and measurement beams for the interferometer. The angular difference allows one to distinguish between the reference and measurement beam components of the input beam and facilitates the suppression of at least some of the cyclic errors caused by interferometer imperfections.

Abstract: A distance detecting device for detecting a distance from objects with the use of wave signals determined by the distance measuring device and reflected from the objects, the distance detecting device comprising transmitter/receiver means for transmitting and receiving of wave signals with at least a first and a second transmitting/receiving unit which are spatially spaced from one another, with the first unit performing at least one transmitting functions and a second unit performing at least one receiving function, the both units being formed so that the second unit can receive wave signals emitted by the first unit as response signals, and either the function unit or the second unit can receive the wave signals emitted by the first unit as reflection signals, an interference determining device for determining at least one characteristic parameter of the response signal received in the second unit and for determining an interference based on the determined characteristic parameter.

Abstract: The invention is directed to the provision of a device and method for measurement of angle of rotation for measuring in a non-contacting fashion the concentration of an optically active substance such as a sugar, amino acid, vitamin, or the like dissolved in a sample.

Abstract: A near-field, interferometric optical microscopy system includes: a beam splitter positioned to separate an input beam into a measurement beam and a reference beam; a mask positioned to receive the measurement beam, the mask comprising at least one aperture having a dimension smaller than the wavelength of the input beam, wherein the mask aperture is configured to couple at least a portion of the measurement beam to a sample to define a near-field probe beam, the sample interacting with the near-field probe beam to define a near-field signal beam; a detector having an element responsive to optical energy; and optics positioned to direct at least a portion of the reference beam and at least a portion of the near-field signal beam to interfere at the detector element.

Abstract: A system and method for high speed and precision measurement of the distance between at least two near contact surfaces using heterodyne interferometry is disclosed. One of the surfaces is an optically transparent element and the other surface is a substantially non-transparent element. A laser source produces an output having two superimposed orthogonally polarized beams having S and P polarization, with a frequency difference between them. The polarized beams are split into measurement and reference beams without altering the characteristics of the polarized beams. The reference beams are caused to interfere, and a reference photo detector detects the reference beams and provides a reference signal. The measurement beam strikes the object of interest at an oblique angle after passing through a glass plate having a polarization coating on the bottom surface close to the object of interest.

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 interferometry system includes: i) a first polarizing beam splitter which during operation separates an input beam into a measurement beam and a reference beam; ii) a beam steering element positioned to direct the measurement beam, and not the reference beam, the measurement beam contacting the beam steering element; iii) an interferometer positioned to receive at least a portion of the measurement beam and direct it to a measurement object, which reflects it to define a return measurement beam, and wherein the interferometer is further positioned to receive at least a portion of the reference beam and direct it to a reference object, which reflects it to define a return reference beam; and (iv) an electronic control circuit coupled to the beam steering element. During operation the control circuit adjusts the orientation of the beam steering element in response to changes in the angular orientation of the measurement object.

Abstract: An apparatus includes a multi-axis interferometer for measuring a relative position of a reflective measurement object along multiple degrees of freedom, wherein the interferometer is configured to produce multiple output beams each comprising information about the relative position of the measurement object with respect to a different one of the degrees of freedom. Each output beam includes a beam component that contacts the measurement object at least one time along a common path, and at least one of the beam components further contacts the measurement object at least a second time along a first path different from the common path.

Abstract: The present invention is directed to a sensor system for monitoring metabolic activity of an anaerobic or aerobic microorganism. The present invention further relates to a sensor system that can individually and simultaneously monitor oxygen and carbon dioxide levels of a gas composition. Also provided is a sensor formulation for use with the sensor system of the present invention and a method of making the same.

Abstract: A signal having a low frequency fm is superposed on a signal having a high frequency f1. The light having the frequency fs is modulated and transmitted to a transmission line as a wavelength dispersion measurement light. A local oscillation light is multiplexed with the wavelength dispersion measurement light, and heterodyne-detected on a receiving side. Sideband components generated by modulating the frequency fs within the heterodyne-detected wavelength dispersion measurement light are extracted by bandpass filters, and the wavelength dispersion value of the transmission line is calculated by detecting the phase difference between the sideband components.

Abstract: A method and apparatus for enhancing the precision of distance or position measurements using a two-wavelength interferometer is disclosed. The invention provides for the direct measurement of air density fluctuations, thus allowing for correction of measurement errors, including those due to air turbulence and air thermal variations in a measurement path of a distance measuring interferometer. The invention can function both as a precision enhancement to an existing interferometric measuring system, or as a stand-alone system, measuring both “uncorrected” distance and air density and providing a corrected distance value. A novel measurement head design removes the constraint that a measurement and a reference component of the interferometer optical signals travel a shared path at any point in the interferometer, and thus substantially reduces errors due to polarization leakage.

Abstract: A non-contact, free-space method for determining the index of refraction of a thin film at a desired angular frequency. The method includes generating an input desired-frequency pulse and an optically detectable probe pulse. The thin film is moved in and out of the path of the input pulse, creating an output pulse that alternates between a transmitted signal, created when the film intercepts the input pulse path, and a reference signal, created when the sample is outside the input pulse path. The output pulse modulates the probe pulse, which is then detected with a photo detector, and the difference between the transmitted signal and the reference signal is calculated. The above steps are repeated over a plurality of delay times between the input pulse and the probe pulse until a complete field waveform of the differential signal is characterized. The index of refraction is calculated as a function of a ratio between the differential signal for the thin film and the reference signal.

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: A manufacturing method for rhomboid assemblies cuts stacks of glass plates that are glued together with coatings between the glass plates. The cuts are at an angle such as 45° and surfaces resulting from the cuts are finished to optical tolerances. These optical surfaces permit attachment of rhomboid assemblies directly to optical elements such as a polarizing beam-splitter (PBS) in a multi-axis interferometer. Further, elements such as quarter-wave plates, cube corner reflectors, and rhomboid elements that extend the separation of measurement beams can be attached to the PBS to provide integrated beam optics that are compact and thermally stable. Placing a reflective coating or other reference reflector on a quarter-wave plate for the reference beam can keep the entire beam path for the reference beam within the integrated structure. When rhomboid elements extend the separation between measurement beams, an extension to the PBS can match the optical path lengths of reference and measurement beams.

Abstract: An interferometer includes a two-frequency laser, a polarizing beam splitter that separates a beam from the laser into separate beams, and optical fibers that conduct the separate beams to a beam combiner for interferometer optics. The beam combiner uses a birefringent material to merge desired orthogonal polarization components of two separate beams into a combined beam that is input into the interferometer optics. Components of the two beams that lack the desired polarizations are directed away from the combined beam so that the combined beam contains highly orthogonal polarizations for frequency components.

Abstract: A laser interferometer system based on three design principles, the heterodyne frequency, the avoiding mixing, and the perfect symmetry, is described. These design principles give rise to the interferometer a high stable system with no periodic nonlinearity. This system is capable of providing both displacement and straightness measurements. The arrangement of invention employs a single frequency stabilized input beam from a laser source which is provided to a frequency-shifted means for converting the input beam into a pair of spatial-separated beams having the same optical properties but different optical frequencies. Two identical energy splitters further split the spatial-separated beams into a pair of measurement beams and a pair of reference beams respectively. The measurement beams are incident onto the measurement target and reference target respectively.

Abstract: An interferometric measuring system including a movable member having a measurement reflector attached thereto, a stationary member having a reference reflector attached thereto, a light source for providing a light beam, and an optical support block having first and second beam splitters mounted thereon. The first beam splitter is operable to convert the light beam into a first pair of orthogonally polarized beams and arranged to direct one of the first pair of beams along a reference path to the reference reflector and the other of the first pair of beams along a measurement path to the measurement reflector to create a measurement interference pattern between the first pair of beams for determining a position of the movable member. The second beam splitter is operable to form a second pair of orthogonally polarized beams and arranged to direct the second pair of beams along support block measurement paths to the reference reflector.

Abstract: The invention features an interferometry system that uses a small angular difference in the propagation directions of orthogonally polarized components of an input beam to an interferometer. The orthogonally polarized components define reference and measurement beams for the interferometer. The angular difference allows one to distinguish between the reference and measurement beam components of the input beam and facilitates the suppression of at least some of the cyclic errors caused by interferometer imperfections.

Abstract: A heterodyne interferometer and an associated interferometric method are provided that significantly reduce polarization crosstalk and that permit the target to translate to a limited extent in a direction orthogonal to the direction of interest and to be tilted to a limited extent without adversely affecting the resulting measurement. The heterodyne interferometer includes a beamsplitter for splitting each of a first beam and a coherent second beam into at least two partial beams. Advantageously, the first beam and the partial first beams propagate in a first plane, while the second beam and the partial second beams propagate in a second plane that is offset from the first plane by at least two beam diameters so as not to spatially overlap with the first beam and the partial first beams, thereby preventing polarization crosstalk. The heterodyne interferometer also includes a reference arm and a measurement arm that each receive a partial first beam and a partial second beam.

Abstract: An interferometric measuring system including a movable member having a measurement reflector attached thereto, a stationary member having a reference reflector attached thereto, a light source for providing a light beam, and an optical support block having first and second beam splitters mounted thereon. The first beam splitter is operable to convert the light beam into a first pair of orthogonally polarized beams and arranged to direct one of the first pair of beams along a reference path to the reference reflector and the other of the first pair of beams along a measurement path to the measurement reflector to create a measurement interference pattern between the first pair of beams for determining a position of the movable member. The second beam splitter is operable to form a second pair of orthogonally polarized beams and arranged to direct the second pair of beams along support block measurement paths to the reference reflector.

Abstract: The invention features systems and methods for generating optical beams having substantially orthogonal polarizations for use in distance measuring interferometry. In one embodiment, the invention features a system including a source which during operation generates two nonparallel propagating source beams; and a retarder element positioned to receive the two nonparallel propagating source beams and convert them into two nonparallel propagating output beams that are polarized substantially orthogonal to one another. The system can further include a birefringent prism positioned to receive the two nonparallel propagating output beams and produce two parallel output beams.

Abstract: A positioning stage system includes a first stage movable at least in one of a rotational direction and a tilt direction, a second stage movable at least in X and Y directions, a measurement mirror system fixed to the second stage, a reference mirror system disposed on the first stage, and a measuring system for measuring displacement of the measurement mirror system in the X or Y direction, while using the reference mirror system as a positional reference, wherein the reference mirror system is arranged so that laser light incident on the reference mirror system is reflected in the same direction as the incidence direction, substantially constantly.

Abstract: In an optical rotation angle polarimeter for investigating optical activity of a test object, a two-frequency laser source generates a laser beam with two eigen modes of two different temporal frequencies and two orthogonal linear polarized waves. The laser beam is to be passed through the test object. The polarized beam splitter is adapted to receive and split the laser beam, which exits the test object, into first and second orthogonal optical heterodyne interference X-axis and Y-axis components. Each of first and second photo detectors receives a respective one of the first and second orthogonal optical heterodyne interference X-axis and Y-axis components from the polarized beam splitter, and generates a corresponding optical heterodyne interference signal. A signal processor is connected to the first and second photo detectors, and combines the optical heterodyne interference signals therefrom so as to obtain an optical heterodyne interference output.

Abstract: An apparatus and method for using an acousto optic scanning laser vibrometer for measuring a dynamic parameter of micro and macro components is disclosed. A coherent source of a laser beam of single wavelength and of stabilized frequency is split into two orthogonal polarized beams. One of the beams strikes the surface of investigation and gets reflected back, and the other polarized beam impinges on the reference surface and gets reflected back. The beam reflected from the surface of investigation and the beam from the reference surface are combined, thereby causing them to interfere. At least one photo detector is positioned at the point of interference. The photo detector output signals are input to a signal processor or phase meter to obtain the dynamic parameter information. Information is provided that is based on the phase shift between the beam striking on the object of investigation and the beam striking the reference surface due to the difference in the optical path.

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: The invention features an interferometry system that measures changes in the angular orientation of a measurement object and that also includes at least one dynamic beam steering assembly. The dynamic beam steering assembly redirects one or more beams within the interferometry system in response to a change in the angular orientation of the measurement object. In many embodiments, the presence of the dynamic beam steering assembly permits the interferometry system to measure the angular orientation of the measurement object using only a single measurement beam to contact the measurement object. Furthermore, in many embodiments, a control signal derived from the measurement beam contacting the measurement object causes the beam steering assembly to redirect a measurement beam to contact the measurement object at normal incidence.

Abstract: Disclosed is a method for measuring the depth of the bottoms of craters under formation on a sample placed within an analysis chamber of a physico-chemical analyzer, by optical interferometry. The method consists in splitting an incident bi-frequency laser beam into two parallel paths, a measurement path and a reference path, focusing each of the two paths on the surface of the sample, respectively one in the crater and the other in the vicinity, along an incident direction inclined in relation to the surface of the sample, recombining the two beams reflected on the surface of the sample to form only one beam, and applying the recombined beam to an interferometric detector to measure the path difference between the two reflected beams. Application to ion analyzers.

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. For example, the control circuit can cause the beam steering assembly to redirect a measurement beam within the system such that exit measurement and reference beams used to generate an interferometric signal remain substantially parallel to one another over a range of angular orientations or translations of the measurement object. 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: The invention features interferometry systems and methods that quantify nonlinearities, e.g., cyclic errors, in an interference signal produced by an interferometry system. The systems and methods analyze interference signals for each of multiple Doppler shifts to thereby resolve nonlinearities that may otherwise overlap spectrally with a dominant interference signal, and also, to interpolate the contributions of the nonlinearities to measurements at different Doppler shifts. The time-varying interference signal or the phase extracted from the time-varying interference signal is Fourier transformed and at least some of the nonlinearities are associated with peaks in the square modulus of the Fourier transformed signal (i.e., the power spectrum). The amplitude and phase of the Fourier transform at the frequency of each such peak are used to quantify the associated nonlinearity. The quantified nonlinearities are used to correct optical path length measurements by the system.

Abstract: The invention features interferometry systems and methods that quantify nonlinearities, e.g., cyclic errors, in an interference signal produced by an interferometry system. The systems and methods analyze interference signals for each of multiple Doppler shifts to thereby resolve nonlinearities that may otherwise overlap spectrally with a dominant interference signal, and also, to interpolate the contributions of the nonlinearities to measurements at different Doppler shifts. The time-varying interference signal or the phase extracted from the time-varying interference signal is Fourier transformed and at least some of the nonlinearities are associated with peaks in the square modulus of the Fourier transformed signal (i.e., the power spectrum). The amplitude and phase of the Fourier transform at the frequency of each such peak are used to quantify the associated nonlinearity. The quantified nonlinearities are used to correct optical path length measurements by the system.

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 at least one 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 multiple pass interferometry 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.

Abstract: A laser interferometer for detecting the position of a moving object in a Y-direction when the object moves in an X-direction has a separating optical system that moves in the X-direction at a speed different from that of the moving object. A laser beam is separated by the separating optical system into a reference beam and a measurement beam, which are individually directed toward a reference mirror and a moving mirror on the moving object. The light of the measurement beam reflected from the moving mirror, and the light of the reference beam reflected from the reference mirror are received by a photodetector via the separating optical system, and the photoelectric conversion signal of the interference light is output as information concerning the position of the moving object in the Y-direction. A fixed mirror that is shorter than the moving object can be used because the separating optical system also moves in the X-direction.

Abstract: An improved interferometric system with reduced air turbulence error. The system includes an optical retarder that functions as a quarter wave plate for two harmonically related frequencies. The retarder may be formed by a pair of quartz disks cut so that the C axis lie in the plane of the disk and are oriented orthogonally relative to each other.

Abstract: An apparatus is disclosed for generating data representative of a three-dimensional distribution of the light backscattering potential of a transparent or semi-transparent object such as a human eye. The apparatus includes an interferometer, both the reference beam and measurement beam of which are directed toward the object and reflected by respective reference and measurement sites thereof, such that axial motion of the object during measurement affects both beams equally. The measurement beam is raster scanned transversely across each measurement site for which data is obtained. Also, the frequency of one of the beams is shifted by a non-moving frequency shifter, such that the reflected beams combine and are modulated by a heterodyne beat frequency, which is detected when the object path difference is matched with the interferometer path difference.