Abstract: An optical system includes: a beam splitter system configured to split an input beam into a plurality of output beams including a first output beam, a second output beam, and a third output beam; a first polarizing filter having a first polarization angle and configured to filter the first output beam to produce a first filtered output beam; a second polarizing filter having a second angle of polarization and configured to filter the second output beam to produce a second filtered output beam; and a third polarizing filter having a third angle of polarization and configured to filter the third output beam to produce a third filtered output beam, the first, second, and third angles of polarization being different from one another.

Abstract: A LIDAR system includes a waveguide array configured to output a LIDAR output signal such that the LIDAR output signal is reflected by an object located off the LIDAR chip. The system also includes electronics configured to tune a wavelength of the LIDAR output signal such that the direction that the LIDAR output signal travels away from the LIDAR chip changes in response to the tuning of the wavelength by the electronics.

Abstract: Disclosed herein are systems and methods for linearizing frequency chirp in a frequency-modulated continuous wave (FMCW) coherent LiDAR system. Exemplary methods can include generating a continuous wave laser signal having a frequency characteristic, in which the frequency characteristic can include a frequency chirp over a frequency band in at least one period; and receiving a signal based on the generated laser signal. The methods can further include mixing the received signal with a local oscillator signal, the local oscillator signal having the frequency characteristic; determining at least one beat frequency based on the mixed signal; sampling the mixed signal at a rate equal to at least two times the beat frequency; determining a correction signal based on the sampled signal; and applying the correction signal to the laser signal.

Abstract: An interferometer system including: an optical system arranged to split a radiation beam from a laser source into a first beam along a first optical path and a second beam along a second optical path, and recombine the first beam and the second beam to a recombined beam, a detector to receive the recombined beam and to provide a detector signal based on the received recombined beam, and a processing unit, wherein a first optical path length of the first optical path and a second optical path length of the second optical path have an optical path length difference, and wherein the processing unit is arranged to determine a mode hop of the laser source on the basis of a phase shift in the detector signal.

Abstract: An integrated optical assembly is provided, with enhancements that are particularly useful when the integrated optical assembly forms part of a laser radar system. The integrated optical assembly produces a reference beam that is related to the optical characteristics of a scanning reflector, or to changes in position or orientation of the scanning reflector relative to a source. Thus, if the scanning reflector orientation were to shift from its intended orientation (due e.g. to thermal expansion) or if characteristics of the scanning reflector (e.g. the index of refraction of the scanning reflector) were to change on account of temperature changes, the reference beam can be used to provide data that can be used to account for such changes. In addition, if the scanning reflector were to be positioned in an orientation other than the orientation desired, the reference beam can be used in identifying and correcting that positioning.

Abstract: Methods and apparatus are provided for imaging a response of a sample to radiative heating. A method in accordance with one embodiment has steps of: illuminating a first area of the sample with a radiative heating beam; illuminating a portion of the first area with a probe beam; collecting light exiting the sample due to interaction of the probe beam with the sample; superimposing the light exiting the sample with a reference beam derived from the probe beam, wherein the reference is characterized by an optical phase relative to the probe beam; detecting a spatial portion of the light exiting the sample and the reference beam with at least one detector to generate an interference signal; and processing the interference signal to obtain an image of the sample associated with absorption of the radiative heating beam.

Abstract: A distance measurement device (2000) generates transmission light by modulating an optical carrier wave. The distance measurement device (2000) transmits the generated transmission light, and receives reflected light acquired by the transmission light being reflected by a measured object (10). The distance measurement device (2000) generates a first beat signal by causing the transmission light to interfere with reference light. The distance measurement device (2000) generates a second beat signal by causing the reflected light to interfere with the reference light. The distance measurement device (2000) calculates a distance to the measured object (10), based on a difference between the first beat signal and the second beat signal.

Abstract: The invention pertains to a contactless measurement method for detecting rotation of an object over an axis coinciding with an optical axis of a probe beam. The probe beam is comprised of two monochromatic wavelengths with circular polarizations of opposite chirality, having a frequency difference for providing a heterodyne probe beam. A neutral beam splitter is provided that directs a reflected beam via a polarizer filter towards a first photodetector and that directs a transmitted beam toward a quarter wave plate attached to a rotatable object. A mirror reflects the probe beam, via the same quarter wave plate, back into the neutral beam splitter, which directs the reflected beam via a polarizer filter toward a second photodetector. The rotation is derived from the relative phase difference between the first and second photodetector signals.

Abstract: A laser interference device includes a measurement laser that outputs a laser beam, a beam splitter that divides the laser beam into a measurement laser beam and a frequency monitor laser beam, a reference laser that outputs a reference laser beam, a frequency detector that detects a beat frequency resulting from interference between the reference laser beam and the frequency monitor laser beam, a wavelength calculator that calculates a wavelength of the frequency monitor laser beam (a wavelength measurement value) on the basis of the beat frequency, a light detector that detects an interference light of the measurement light and the reference light of the measurement laser beam and outputs a light detection signal, and a displacement calculator that calculates a displacement of the measurement mirror by performing an arithmetic process based on the wavelength measurement value and the light detection signal.

Abstract: The optical distance measurement device is configured in such a manner that the frequency-swept light output unit outputs frequency-swept light during a time period from when frequency sweeping of frequency-swept light being output is completed to when the next frequency sweeping becomes possible, the frequency-swept light output during the time period being frequency swept at a different frequency from the frequency-swept light being output.

Abstract: A measuring assembly for the frequency-based determination of the position of a component, in particular in an optical system for microlithography, includes at least one optical resonator, which has a stationary first resonator mirror, a movable measurement target assigned to the component, and a stationary second resonator mirror. The second resonator mirror is formed by an inverting mirror (130, 330, 430, 530), which reflects back on itself a measurement beam coming from the measurement target.

Abstract: An optical module includes a mirror unit and a beam splitter unit. The mirror unit includes a base with a main surface, a movable mirror, a first fixed mirror, and a drive unit. The beam splitter unit constitutes a first interference optical system for measurement light along with the movable mirror and the first fixed mirror. A mirror surface of the movable mirror and a mirror surface of the first fixed mirror follow a plane parallel to the main surface and face one side in a first direction perpendicular to the main surface. The movable mirror, the drive unit, and at least a part of an optical path between the beam splitter unit and the first fixed mirror are disposed in an airtight space.

Abstract: Systems and methods which provide a compact spectrometer using static Fourier transform interferometer (SFTI) cube configurations, such as are suitable for use with respect to mobile and portable electronic devices, are described. A SFTI cube of embodiments comprises a monolithic dual mirrored wedge beam splitter structure wherein mirrored wedge surfaces provide two reflective mirrors that are slightly tilted away from the orthogonal directions so that the resultant beams of light cross over one another and form an interference pattern. SFTI cube implementations of embodiments facilitate highly compact spectrometer configurations having a wide wavelength range, high resolution, high throughput, and low cost.

Abstract: An airborne vehicle includes a positioning system to acquire information relating to a position of the airborne vehicle, and a measurement system to transmit signals to and receive signals from survey sensors of a survey arrangement used to survey a target structure, the received signals indicating positions of the respective survey sensors.

Abstract: An optical interferometer includes a branching-combining unit, a first optical system, a second optical system, and a drive unit. The branching-combining unit includes a branching surface, an incident surface, a first output surface, a combining surface, and a second output surface on an interface of a transparent member, the branching surface partially reflects incident light and outputs as first branched light, and transmits the rest of the incident light into the interior as second branched light, the combining surface partially combines the first branched light and the second branched light to be output to the outside as first combined light, and combines the rest of the first branched light and the second branched light to be propagated into the interior as second combined light, and the second output surface partially outputs the second combined light to the outside.

Abstract: The phase shift interferometer is configured to measure the shapes of measurement objects by acquiring a plurality of images of interference fringes while shifting the phases of the interference fringes. The interference fringes are provided with a phase difference of 90° relative to each other utilizing polarization of light. Images of the interference fringes are captured by two respective cameras while, in accordance with a conventional phase shift method, mechanically displacing a reference surface or a reference optical path to shift the phases. The phases of the interference fringes are calculated independently from the respective images acquired by the cameras and an average of the two phase calculation results is calculated.

Abstract: Provided is a method, system, and apparatus for inspecting a substrate. The method comprises illuminating the substrate with a singular laser beam, the singular laser beam forming an illuminated spot on the substrate and a bright fringe at a surface of the substrate, the bright fringe extending over at least a portion of the illuminated spot, and detecting, by an optical detection system, scattered light from nano-defects present on the substrate within the illuminated spot.

Abstract: An apparatus for measuring acceleration includes: a reference cavity having a first fixed reflecting surface and a second fixed reflecting surface; a sense cavity having a fixed reflecting surface and a non-fixed reflecting surface, the non-fixed reflecting surface being configured to be displaced when subject to an acceleration force; a light source to illuminate the reference and sense cavities; a controller to vary a wavelength of light emitted by the light source and/or an index of refraction of an optical medium of the cavities; a photodetector to detect light emitted by the reference and sense cavities; an interferometer sensor to measure using the detected light, for each variation of the wavelength of light and/or the index of refraction a reference displacement of the reference cavity and a sense displacement of the sense cavity; and a processor to calculate the acceleration using each of the reference displacements and the sense displacements.

Abstract: A measurement system comprising: a radiation source arranged to generated a detection beam; a probe; and a probe positioning system arranged to move the probe from an un-aligned position in which it is not illuminated by the detection beam, to an aligned position in which it is illuminated by the detection beam and the detection beam is reflected by the probe to generate a reflected detection beam. A scanner generates a relative scanning motion between the probe and a sample, the sample being aligned with the probe and interacting with the probe during the relative scanning motion. A sensor detects the reflected detection beam during the relative scanning motion to collect a first data set from the sample. A second device is provided for modifying the sample or obtaining a second data set from the sample. A sample stage is arranged to move the sample in accordance with an offset vector stored in a memory so that it becomes un-aligned from the probe and aligned with the second device.

Abstract: An optical layer system for a position-measuring device includes at least first, second and third functional surfaces disposed on a surface of a transparent substrate. Each of the functional surfaces have a different optical function. The functional surfaces are composed of a first layer stack and a second layer stack.

Abstract: The invention relates to a method and a corresponding apparatus for measuring distance and optionally speed, in particular for multiscale distance measurement.

Abstract: A gravimeter, a gravimeter system, and a method for measuring gravitational acceleration within a borehole are described herein. The gravimeter includes a proof mass that is constrained by springs and an optical interferometer for measuring displacement of the proof mass. The optical interferometer generates a light path from a light source to a reflective surface on the proof mass. Spatial displacement of the proof mass from a reference position to a position of gravitational equilibrium is determined by measuring a change in length of the light path. In turn, gravitational acceleration can be determined from the spatial displacement of the proof mass. A number of such gravimeters can be used in a gravimeter system to make measurements of gravitational acceleration in variety of different directions.

Abstract: A displacement measurement system of heterodyne grating interferometer, comprises a reading head, a measurement grating and an electronic signal processing component. Laser light emitted from the laser tube is collimated, passes through the first polarization spectroscope, and then emits two light beams with an orthogonal polarization direction and an orthogonal propagation direction; the two light beams pass through two acousto-optic modulators and respectively generate two first-order diffraction light beams with different frequencies, which are later divided into reference light and measurement light; two parallel reference light beams form a beat frequency electric signal with positive and negative first-order diffraction measurement light respectively after passing through a measurement signal photo-electric conversion unit; the beat frequency signals are transmitted to the electronic signal processing component for signal processing, thus the output of linear displacement in two directions is realized.

Abstract: A laser heterodyne interferometric straightness measurement apparatus and method with six DOFs determination includes a part for determining the straightness and its position based on laser heterodyne interferometry and a part for error determination and compensation. The optical path for determination of four DOFs errors including three common beam-splitters, a polarizing beam-splitter, a planar mirror, a convex lens, a position-sensitive detector and two quadrant detectors is added in the optical configuration of the part for determining the straightness and its position based on laser heterodyne interferometry.

Abstract: A method distributing data in a network is provided. The method comprises measuring the path lengths between a reference clock and a plurality of remote destinations and sending a timing signal from the reference clock to the plurality of remote destinations. The method further comprises measuring the phase between the reference clock and a return signal from each of the plurality of remote destinations and adjusting the phase of the data such that each remote destination receives the data within a skew tolerance.

Abstract: Methods and systems of sensing conditions in a fiber includes launching a light beam into a fiber. A first branch of scattered light is set to a mode other than a fundamental mode. A second branch of scattered light is optically filtered to remove unscattered input light. Brillouin scattered light is coherently detected on the first branch to produce a combined temperature/strain profile of the fiber. Raman scattered light on the second branch is directly detected to produce a temperature profile of the fiber. A strain profile of the fiber is determined, using a processor, based on the combined temperature/strain profile and the temperature profile.

Abstract: An off-axis alignment system includes, sequentially along a transmission path of a light beam, an illumination module (10), an interference module (20) and a detection module (30). The interference module (20) includes: a polarization beam splitter (21) having four side faces, the illumination module (10) and the detection modules (30) both located on a first side of the polarization beam splitter (21); a first quarter-wave plate (22) and a first reflector (23), sequentially disposed on a second side opposite to the first side; and a second quarter-wave plate (24) and a cube-corner prism (25), sequentially disposed on a third side of the polarization beam splitter (21); and a third quarter-wave plate (26), a second reflector (27) and a lens (28), sequentially disposed on a fourth side of the polarization beam splitter (21). The second reflector (27) is located on a rear focal plane of the lens (28). A center of a bottom of the cube-corner prism (25) is situated on an optical axis of the lens (28).

Abstract: A wind energy power plant optical vibration sensor is described, using two light sources 15, 16 that emit light at different respective frequencies. The light from the first light source falls on a surface 44 of the wind energy power plant at a detection site. Movements in the surface result in changes to the phase of the light reflected back from the surface which can be detected by mixing the first light with the light emitted from the second light source. The difference in frequencies between the two light sources results in a beating of the resulting interference signal, whereas movements in the sensor surface result in changes in the phase timing and frequency of the beats.

Abstract: A beam emitted from a light source is split into a probe beam that irradiates a measurement object and a reference beam that does not irradiate the measurement object. A signal beam obtained by the reflection of the probe beam is split into first and second split signal beams, which are mutually orthogonal polarized components. The first split signal beam and the reference beam are inputted to a first coherence optical system to cause the beams to interfere with each other to generate at least three coherence beams differing in phasic relationship. The second split signal beam and the reference beam are inputted to a second coherence optical system to cause the beams to interfere with each other to generate at least three coherence beams differing in phasic relationship. The coherence beams are then detected.

Abstract: A measuring apparatus for measuring a position or a shape of a surface to be inspected includes a multi-wavelength interferometer and a control unit. The multi-wavelength interferometer includes an optical system that causes light to be inspected, which enters the surface to be inspected and is reflected by the surface to be inspected, and reference light to interfere with each other, a spectroscopic unit that divides interference light between the light to be inspected and the reference light into each wavelength, and a detector that detects the interference light and is provided for each divided interference light and an optical member that can adjust a position of a light guide portion that guides light from the spectroscopic unit to the detector. The control unit controls the optical member by using information related to inclination of the surface to be inspected to adjust the position of the light guide portion.

Abstract: A spatial frequency reproducing apparatus includes a light source, a first means for modulating a light emitted from the light source into two lights having different frequencies and separately irradiated adjacently, a second means for two-dimensionally scanning the two lights, a third means for irradiating an object under measurement with the two lights, a fourth means for receiving and converting into an electrical signal at least two or more divided lights from the object under measurement with a boundary line being interposed therebetween in a direction substantially perpendicular to the direction separating the two lights, a fifth means for amplifying respective photoelectrically converted electrical signals while varying a degree of amplification according to frequencies thereof and generating a difference signal or a summation signal of the amplified signals, and a sixth means for obtaining a phase difference or an intensity difference of these signals to obtain a measurement value.

Abstract: Robust terahertz time-domain spectrometer has a reflective surface arrangement that renders the sensor insensitive to x or y displacement. The apparatus includes: (a) first scanner head; (b) a first reflective surface; (c) emitter; (d) beam splitter to yield reference radiation pulses and sample radiation pulses; (e) first reflector to reflect sample radiation pulses that have been transmitted through the sample to generate reflected sample radiation pulses that are directed towards a web; (f) second reflector that reflects the reference radiation pulses to generate reflected reference radiation pulses that are directed towards the beam splitter which in turn transmits a portion of the reflected references radiation pulses towards the web; and (g) a detector that receives (i) the reflected sample radiation pulses that have interacted with the sample a plurality of times and (ii) reflected reference radiation pulses that have interacted with the sample a plurality of times.

Abstract: A multi-wavelength interferometer includes a beam splitter configured to split plural light fluxes into a reference beam and a measurement beam, a frequency shifter configured to shift a frequency of at least one of the reference beam and the measurement beam to make the frequencies of the reference beam and the measurement beam different from each other, an optical system configured to cause the measurement beam to be incident on a measurement surface and to cause the measurement beam reflected from the measurement surface to interfere with the reference beam to obtain interference light, a dividing unit configured to divide the interference light into a plurality of light beams, and a detection unit configured to detect the plurality of light beams divided by the dividing unit.

Abstract: Four-axis four-subdividing interferometer comprising a four-axis light splitting module and an interference module which are sequentially arranged along the incident direction of polarization orthogonal double-frequency laser. The four-axis light splitting system comprises three 50% plane beam splitters and three 45-degree plane reflecting mirrors. The invention comprises a four-axis four-subdividing plane mirror interferometer and a four-axis four-subdividing differential interferometer. In the differential interferometer, an adjustable 45-degree reflecting mirror is used to guide the reference light to a reference reflecting mirror which is arranged in the same direction as a measurement mirror and fixed on the moving object.

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.

Abstract: A high speed high resolution heterodyne interferometric method and system are provided. The invention uses two spatially separated beams with slightly different frequencies and has two measurement signals with opposite Doppler shift. The switching circuit selects one of the two measurement signals for displacement measurement according to the direction and speed of the target movement. In this invention, the measurement is insensitive to the thermal variation; the periodic nonlinearity is essentially eliminated by using two spatially separated beams; the measurable target speed of the interferometer is no longer limited by the beat frequency of the laser source.

Abstract: The present invention relates to an optical position-measuring device for generating a plurality of phase-shifted scanning signals regarding the relative position of a fiber optic scanning head and a reflection measuring standard movable relative thereto in at least one measuring direction. In the fiber optic scanning head, a scanning reticle is disposed before the measuring standard end of an optical fiber. The scanning signals are coded in a wavelength-dependent manner. To this end, a beam incident on the scanning reticle is split into at least two sub-beams which strike the reflection measuring standard and are subsequently recombined to interfere with each other so as to generate the phase-shifted scanning signals. The sub-beams travel different optical path lengths between splitting and recombination.

Abstract: Four-axis four-subdividing interferometer comprising a four-axis light splitting module and an interference module which are sequentially arranged along the incident direction of polarization orthogonal double-frequency laser. The four-axis light splitting system comprises three 50% plane beam splitters and three 45-degree plane reflecting mirrors. The invention comprises a four-axis four-subdividing plane mirror interferometer and a four-axis four-subdividing differential interferometer. In the differential interferometer, an adjustable 45-degree reflecting minor is used to guide the reference light to a reference reflecting minor which is arranged in the same direction as a measurement minor and fixed on the moving object.

Abstract: In a distance-measuring method comprising a distance-measuring apparatus having at least one frequency-modulatable laser source for producing chirped laser radiation. The laser radiation has radiation components with opposite chirp as time dependency of the modulated wavelengths, the simultaneous oppositeness of the frequency curve being realized via an optical delay path (3) for one of the two radiation components. The radiation produced is passed in a measuring interferometer (5) to a target (6) and parallel via a local Oscillator. After reception of the laser radiation scattered back from the target (6) and passed via the local oscillator path, the laser radiation received is converted into signals and the distance to the at least one target (6) is determined from the signals on the basis of interferometric mixing.

Abstract: A displacement measurement method, an apparatus thereof, and a probe microscope. which enable stable measure an amount of displacement and a moving distance of an object under measurement with an accuracy of the sub-nanometer order or below without being affected by disturbances such as fluctuations of air and mechanical vibration. A pulsed beam is split into two; one beam is reflected by an object under measurement and then inputted to a delay optical path equivalent to one pulse period; and the other beam is sent through the same delay optical path in the opposite direction up to the object under measurement with a delay of one pulse period, and then reflected by the object under measurement. An optical phase variation caused by the movement of the object under measurement is obtained by subjecting the two pulsed beams to interference.

Abstract: A distance measuring apparatus and method that enable high-precision and high-speed measurement by canceling variations of a delay circuit in the apparatus are provided. Pulsed light is branched into first and second reference light, and transmitted measurement light, and the difference in detection time among the first reference light along a first path with no optical variations, the second reference light along a second path with an optical delay, and received measurement light from an object to be measured is measured. The received measurement light and the first reference light are temporally separate, distance is calculated from the difference in detection time between the received measurement light and the first reference light.

Abstract: The present invention relates to a high-resolution scanning surface-plasmon microscope including a source (LG) of coherent light and a medium for coupling and confining a surface plasmon including an objective (O, OM) with a large numerical aperture, immersion oil (Hi), and a glass cover slip (GS). A metal layer (MS) covers a surface of the glass cover slip (GS). The microscope also includes a heterodyne-mode Twyman-Green interferometer placed between the light source and means (PL1, PL2, EC) for scanning the metal layer using a light beam and means (PD) for detecting the beam from the interferometer connected to processing means (S, F, DTec, COMP) for forming an image from that beam. According to the invention, at least one polarization converter (CP) for converting the light beams (L) emitted by the light source (LG) from linear polarization to radial polarization is disposed between the light source and the interferometer.

Abstract: The present invention provides a measuring apparatus for measuring an absolute distance between a reference surface an d a test surface, including a phase detection unit configured to detect an interference signal between light reflected by the reference surface and light reflected by the test surface, and detect, from the interference signal, a phase corresponding to an optical path length between the reference surface and the test surface, and a processing unit configured to perform processing of obtaining the absolute distance by controlling the phase detection unit so as to detect the phase corresponding to the optical path length between the reference surface and the test surface for each of a first reference wavelength and a second reference wavelength while changing the wavelength of light to be emitted by a first light source continuously from the first reference wavelength to the second reference wavelength.

Abstract: An optical interference measuring apparatus comprises a first multiple-wavelength light source 200a emitting a light beam having a plurality of spectra, a second multiple-wavelength light source 200b emitting a light beam having a wavelength different from that of the light beam from the first multiple-wavelength light source, a polarizing beam splitter 6 separating the light beams, a reference surface 7 reflecting the light beam from the second multiple-wavelength light source 200b, a test surface 8 reflecting the light beam from the first multiple-wavelength light source 200a, spectral optical elements 9a, 9b dividing interference signals of the light beams, detecting devices 10a, 10b which detect interference signals having single wavelengths of the light beams for a plurality of frequencies, and an analyzer 11 processing the signals from the detecting devices 10a, 10b to calculate an optical path difference between the reference surface 7 and the test surface 8.

Abstract: A laser interferometer system for measuring roll angle around the direction of linear displacement comprises a light source of a frequency stabilized input beam (15) with two linear orthogonally polarized components which may or may not be of the same frequency, a polarizing beam splitting prism, two quarter-wave retardation plates, a corner cube retroreflector, a prism assembly, attached to the mechanical apparatus whose roll angle of travel is to be measured, a wedge mirror assembly, a polarizer, a photoelectric detector, and a phase meter; the light source emits a frequency-stable incident beam and generates a stable electric reference signal; under the actions of the polarizing beam splitting prism, quarter-wave plate and corner cube retroreflector, the incident beam travels twice through and then reflected twice by the wedge mirror assembly, and finally exits from the polarizing beam splitting prism.

Abstract: The present invention provides a displacement measurement method, an apparatus thereof, a probe microscope. which make it possible to stably measure an amount of displacement and a moving distance of an object under measurement with an accuracy of the sub-nanometer order or below without being affected by disturbances such as fluctuations of air, mechanical vibration. Specifically, with the present invention, a pulsed beam is split into two; one beam is reflected by an object under measurement and then inputted to a delay optical path equivalent to one pulse period; and the other beam is sent through the same delay optical path in the opposite direction up to the object under measurement with a delay of one pulse period, and then reflected by the object under measurement. Then, an optical phase variation caused by the movement of the object under measurement is obtained by subjecting the two pulsed beams to interference.

Abstract: The invention relates to a differential interferometer module adapted for measuring a direction of displacement between a reference mirror and a measurement mirror. In an embodiment the differential interferometer module is adapted for emitting three reference beams towards a first mirror and three measurement beams towards a second mirror for determining a displacement between said first and second mirror. In a preferred embodiment the same module is adapted for measuring a relative rotation around two perpendicular axes as well. The present invention further relates to a lithography system comprising such a interferometer module and a method for measuring such a displacement and rotations.

Abstract: A The local probe microscopy apparatus (1) comprises a probe (3) with translation stages (5a, 5b) for controlling the position of the probe (3) relative to a sample surface. The probe (3) has a feedback mechanism (6, 5 7) for maintaining the deflection of the probe and a height measuring system (9) which includes means for compensating for environmental noise. The local probe microscopy apparatus is particularly suitable for use as a wafer inspection tool in a wafer fabrication plant where the inspection tool is liable to be exposed to significant mechanical vibration.

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 are disclosed wherein the structural health of a civil structure, such as, but not limited to, a bridge or the like is measured by electronic distance measurement (EDM) from a plurality of stable locations to a plurality of cardinal points on the structure in a methodical manner. By measuring the coordinates of the cardinal points, the dynamic and long-term static behavior of the structure provide an indication of the health of the structure. Analysis includes: comparison to a Finite Element Model (FEM); comparison to historical data; and modeling based on linearity, hysteresis, symmetry, creep, damping coefficient, and harmonic analysis.