Abstract: A super-resolution telescope. A target is illuminated with at least three laser beams, each beam having a slightly different frequency so as to produce an illumination pattern comprised of several sets of straight interference fringes which sweep across the target. The frequencies of the illumination beams are chosen so that each pair of beams has a unique beat frequency, and the corresponding fringe pattern for each pair sweeps over the target at a unique speed. By collecting a series of images, and demodulating them at the various beat frequencies, the downshifted spatial frequencies can be identified, correctly up-shifted, and fitted together with a set of special Fourier transform based algorithms to reconstruct high-resolution images. Applicants have performed laboratory experiments that this invention can provide resolution substantially better than diffraction limited resolution.

Abstract: Disclosed is a method of measuring a position of at least one substantially reflective layer surface on a substrate in a lithographic apparatus, and associated level sensor and lithographic apparatuses. The method comprises performing at least two interferometrical measurements using a broadband light source. Between each measurement, the component wavelengths and/or intensity levels over the component wavelengths of the broadband source beam is varied such that, where it is only the intensity levels that are varied, the intensity variation is different for at least some of the beam's component wavelengths. Alternatively, a single measurement and subsequent processing of the measurement to obtain measurement data whereby the component wavelengths and/or intensity levels over the component wavelengths are different can be applied as well to obtain the position.

Abstract: A lightwave interference measurement apparatus includes a wavelength-variable laser which periodically performs wavelength scanning between first and second reference wavelengths to emit light beam, a wavelength-fixed laser which emits light beam having a third reference wavelength, a light beam splitting element which splits the light beams into reference light beam and light beam under test, a phase detector which detects a phase based on an interference signal of the reference light beam and the light beam under test, and an analyzer which sequentially determines an interference order of the third reference wavelength based on the third reference wavelength, first and second synthetic wavelengths, an integer component of a phase change amount in the wavelength scanning, and interference orders of the first and second synthetic wavelengths, and calculates an absolute distance between the surface under test and the reference surface.

Abstract: The invention relates to a grinding machine for grinding a workpiece, which has been set on a chuck top surface, by moving a rotating grinding wheel in relation to the workpiece. The grinding machine includes: a microscope configured to be vertically movable; a CCD camera configured to take an image viewed through the microscope; and an image processor configured to process the image taken by the CCD camera to measure a vertical distance between a reference plane of the microscope and an object of the microscope. The image processor is adapted to measure the vertical distance between the reference plane of the microscope and the object of the microscope based on sharpness of the image, which corresponds to how clear the microscope is focused.

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

Abstract: Provided is an observation device which can obtain a phase image of a moving object rapidly with high sensitivity even when using a photodetector having a slow read-out speed per pixel. The observation device 1 comprises a light source 10, a first modulator 20, a second modulator 30, a lens 40, a beam splitter 41, a photodetector 46, and an arithmetic unit 50. The lens 40 receives scattered light generated by a moving object 2 and forms a Fourier transform image of the object 2. The photodetector 46 outputs data representing a sum in a v direction of data temporally changing at a frequency corresponding to a Doppler shift frequency of the light having reached each position on a light-receiving surface through the lens 40 at each position in a u direction at each time. The arithmetic unit 50 obtains an image of the object 2 according to the output of the photodetector 46.

Abstract: The present invention provides a measurement apparatus which measures a distance between a reference surface fixed on a fiducial surface and a test surface located on a test object, the apparatus including an optical frequency comb generation unit configured to generate a light beam with a plurality of optical frequency components, which have equal optical frequency separations therebetween, a detection unit configured to, for at least two of the plurality of optical frequency components, detect an interference signal between a light beam reflected by the reference surface and a light beam reflected by the test surface to detect a phase corresponding to an optical path length between the reference surface and the test surface, and a calculation unit configured to calculate a geometric distance between the reference surface and the test surface based on the phases detected by the detection unit.

Abstract: In a method for generating a synthetic wavelength, particularly for an interferometric distance measuring setup, with a primary laser source defining a primary frequency ?0 and at least a first sideband frequency ?1 of the primary frequency ?0, laser radiation with the first sideband frequency ?1 and a corresponding first wavelength is provided wherein the first sideband frequency ?1 is continuously shifted, particularly by modulating the primary laser source. The synthetic wavelength is generated by combining the first wavelength and a second wavelength which is defined by the primary laser source, particularly by superposition.

Abstract: A method for speckle mitigation in an interferometric distance meter comprises the steps of transmitting optical radiation with at least one wavelength ? to a target to be surveyed, receiving a portion of the optical radiation scattered back by the target in an optical axis (OA), wherein the optical radiation forms a speckle field, converting the received optical radiation into at least one received signal, determining a true distance to the target from the received signal by absolute or incremental interferometric distance measurements. In the method the true pointing direction relative to the optical axis (OA) is determined, wherein the distance error due to speckle effects is corrected.

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

Abstract: A measurement apparatus obtains a reference signal from reference light modulated at a first frequency and a measurement signal from measurement light reflected by a target object modulated at a second frequency along with movement of the target object in addition to the modulation at the first frequency, and processes the reference signal and the measurement signal to measure a position of the target object. Synchronized detection units multiply the measurement signal by a signal synchronized with the reference signal and output signals having the second frequency and harmonic components. Decimation filters filter, at a decimation frequency, the signals output from the synchronized detection units to attenuate the harmonic components.

Abstract: A fixed wavelength absolute distance interferometer including a first interferometer comprising a first light source transmitting a first light beam having a wavelength W toward a measurement target, a wavefront radius detector configured to provide a first measurement responsive to the wavefront radius at the wavefront radius detector, and a first path length calculating portion calculating a coarse resolution absolute path length measurement R; and a second interferometer comprising a beam transmitting device transmitting a second-interferometer light beam having a wavelength ?, a beam splitting/combining device separating the second-interferometer light beam into reference and measurement beams and combining the returning reference and measurement beams into a combined beam, a second-interferometer detector configured to receive the combined beam and provide signals of a phase ? of the combined beam, and a second path length calculating portion configured to determine a medium resolution absolute path leng

Abstract: An apparatus and method for non-determination of the surface velocity of a target using optical interference and Doppler shifting of the light reflected from the target are disclosed. It may be used to measure small-amplitude, acoustic frequency surface vibrations as well as non-periodic surface vibration.

Abstract: An object of this invention is to provide a charged particle beam apparatus that can easily evaluate the stability of a position that is irradiated with a charged particle beam. To achieve the above object, this invention includes a detector that scans a charged particle beam and detects secondary particles that originate from a substrate, and an image processer that displays an image of the substrate on a display based on the secondary particles that are detected by the detector. The image processer is configured to display on the display any two or more members of the group consisting of a scanning image produced by the charged particle beam of the substrate, a wave in time domain showing fluctuations of the irradiation position of the charged particle beam on the substrate, and a power spectrum of the wave in time domain.

Abstract: A fixed wavelength absolute distance interferometer including a first interferometer comprising a first light source transmitting a first light beam having a wavelength W toward a measurement target, a wavefront radius detector configured to provide a first measurement responsive to the wavefront radius at the wavefront radius detector, and a first path length calculating portion calculating a coarse resolution absolute path length measurement R; and a second interferometer comprising a beam transmitting device transmitting a second-interferometer light beam having a wavelength ?, a beam splitting/combining device separating the second-interferometer light beam into reference and measurement beams and combining the returning reference and measurement beams into a combined beam, a second-interferometer detector configured to receive the combined beam and provide signals of a phase ? of the combined beam, and a second path length calculating portion configured to determine a medium resolution absolute path leng

Abstract: A system for detecting and classifying a security breach may include at least one sensor configured to detect seismic vibration from a source, and to generate an output signal that represents the detected seismic vibration. The system may further include a controller that is configured to extract a feature vector from the output signal of the sensor and to measure one or more likelihoods of the extracted feature vector relative to set {bi} (i=1, . . . , imax) of breach classes bi. The controller may be further configured to classify the detected seismic vibration as a security breach belonging to one of the breach classes bi, by choosing a breach class within the set {bi} that has a maximum likelihood.

Abstract: An enhanced sensitivity laser vibrometer with increased output signal strength and more sensitive surface vibration detection, is provided by using a reflective mirror assembly to repeatedly bounce the sensing laser beam against the acoustic pressure-sensing diaphragm to magnify the acoustic incident pressure wave being detected. The enhancement in signal strength, in terms of power spectral density, is a function of the number of bounces squared and the detection of surface vibrations with a displacement of smaller than 4 picometers is demonstrated experimentally.

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

Abstract: A heterodyne interferometry displacement measurement apparatus includes a first optical system including a light source (LASER) and a diffraction grating (GT0) that generates two diffracted lights to combine the two diffracted lights to generate a combined light and that causes the two diffracted lights to interfere with each other to generate a first frequency difference signal, a second optical system that converts the combined light into two lights of which frequencies are different from each other by a second frequency difference in accordance with a displacement of an object and that causes the two lights to interfere with each other to generate a second frequency difference signal, and an output device that outputs information of a displacement amount of the object based on the first frequency difference signal and the second frequency difference signal.

Abstract: The present invention relates to a method and device for reducing the phase noise of a laser signal from a laser source. This device comprises a first current generator for supplying a driving current to the laser source in view of producing the laser signal. A phase noise detector is responsive to the laser wavelength for generating a phase error signal and a second current generator is responsive to the phase error signal for generating a compensation current added to the driving current supplied to the laser source for generating a phase-adjusted laser signal. The device therefore defines a phase stabilization loop formed by the phase noise detector and the second current generator, for reducing the phase noise of the laser signal.

Abstract: The apparatus and method for measuring displacement according to the present invention includes a first beam and a second beam. A first reflection structure reflects a first beam to the surface of an object under test; and a second reflection structure reflects a second beam to the surface of the object under test. The reflected first beam and the reflected second beam have an optical path difference. The object under test scatters a scattering beam of gathering the first and second beams. The scattering beam has an interference signal. A photodetector receives the interference signal of the scattering beam. Then an operational unit receives and computes the interference signal for producing a displacement value. By using the first and second reflection structures, the first and second beams split from an incident beam produce an optical path difference. Thereby, the structure of the apparatus for measuring displacement can be simplified.

Abstract: Non-contacting means of measuring the material velocities of harmonic acoustic telemetry waves travelling along the wall of drillpipe, production tubing or coiled tubing are disclosed. Also disclosed are contacting means, enabling measurement of accelerations or material velocities associated with acoustic telemetry waves travelling along the wall of the tubing, utilizing as a detector either a wireless accelerometer system or an optical means, or both; these may also be applied to mud pulse telemetry, wherein the telemetry waves are carried via the drilling fluid, causing strain in the pipe wall that in turn causes wall deformation that can be directly or indirectly assessed by optical means. The present invention enables detection of telemetry wave detection in space-constrained situations. The invention also teaches a substantially contactless method of determining the time-based changes of the propagating telemetry waves.

Abstract: A laser radar system using collocated laser beams to unambiguously detects a range of a target and a range rate at which the target is moving relative to the laser radar system. Another aspect of various embodiments of the invention may relate to a laser radar system that uses multiple laser radar sections to obtain multiple simultaneous measurements (or substantially so), whereby both range and range rate can be determined without various temporal effects introduced by systems employing single laser sections taking sequential measurements. In addition, other aspects of various embodiments of the invention may enable faster determination of the range and rate of the target, a more accurate determination of the range and rate of the target, and/or may provide other advantages.

Abstract: The present invention relates to absolute distance measurement method and system using an optical frequency generator. The absolute distance measurement method using the optical frequency generator includes (a) generating a plurality of different stabilized wavelengths by using the optical frequency generator; (b) obtaining an initial estimation value of a distance to be measured by using a frequency sweeping interferometer; (c) analyzing an uncertainty range of the obtained initial estimation value; (d) measuring excess fraction parts of the different wavelengths by analyzing interference signals for each of the wavelengths; (e) determining integer parts for each of the different wavelengths within the uncertainty range of the initial estimation value; and (f) measuring an absolute distance to be measured by using the excess fraction part and the integer parts for each of the different wavelengths.

Abstract: A vibration detection device that includes a light source that emits a laser beam; an interferometer, which includes two vibrating bodies that are capable of reflecting the laser beam, that splits the laser beam to cause interference patterns; and a detector that detects vibrations on the basis of the interference patterns.

Abstract: A laser interferometer includes: a laser source for emitting a laser beam while stabilizing a center wavelength of the laser beam by modulating the laser beam using a modulation signal of a predetermined frequency; and a reference mirror and a measurement mirror for reflecting the laser beam. The laser interferometer further includes: a sampling unit for acquiring a sampling value by sampling interference light reflected by the reference mirror and the measurement mirror with a sampling frequency that is a multiple by an integer of two or more of a frequency of the modulation signal; and an average calculator for calculating an average value by averaging a time-series sampling value acquired by the sampling unit in accordance with the sampling frequency. The laser interferometer calculates a displacement of the measurement mirror based on the average value calculated by the average calculator.

Abstract: Combination is disclosed for deriving and displaying the full complement of nine dynamic parameters associated with a mechanical motion transmission system; the parameters comprise: (1) angular displacement, (2) angular velocity, (3) angular acceleration, (4) moment of force (i.e. torque), (5) kinetic energy, (6) work, (7) power, (8) momentum and (9) impulse. Quasi-instantaneous, absolute measurements are derived from elapsed-time measurements between successive sensing of fixed, equal, position events such as electric pulses generated by an incremental shaft encoder. The parameters are displayed on the X and Y axes of a Cartesian or other suitable graph where the X-axis (i.e. the independent axis) indicates the angular displacement of the encoder expressed as a succession of fixed, equal position events in the units of radians. The Y-axis (i.e. the dependent axis) indicates the absolute value of the parameters.

Abstract: A device for the optic measuring of an object (1), including a signal processing unit (2) as well as an interferometer with a light source (3) and with at least one detector (4a, 4d). The interferometer is embodied such that a light beam (12) created by the light source (3) is split at least into a working beam (12a) and a reference beam (12b), with the working beam (12a) impinging the object (1) and the working beam (12a) is at least partially reflected by the object and interfered with the reference beam (12b) on the detector (4a, 4b). The signal processing unit (2) is connected to the detector (4a, 4b) and includes a vibrometer processing unit (2f), which detects the motion of the object (1) from the measuring signals of the detector (4a, 4d).

Abstract: In general, in one aspect, the invention features a system that includes a moveable stage, an interferometer configured to provide information about a first degree of freedom of the stage, an encoder configured to provide information about a second degree of freedom of the stage, and an electronic processor configured to monitor the position of the stage based on the information about the first and second degrees of freedom.

Abstract: A swept frequency laser ranging system having sub-micron accuracy that employs multiple common-path heterodyne interferometers, one coupled to a calibrated delay-line for use as an absolute reference for the ranging system. An exemplary embodiment uses two laser heterodyne interferometers to create two laser beams at two different frequencies to measure distance and motions of target(s). Heterodyne fringes generated from reflections off a reference fiducial XR and measurement (or target) fiducial XM are reflected back and are then detected by photodiodes. The measured phase changes ??R and ??m resulting from the laser frequency swept gives target position. The reference delay-line is the only absolute reference needed in the metrology system and this provides an ultra-stable reference and simple/economical system.

Abstract: A laser interferometer includes: a laser source for emitting a laser beam while stabilizing a center wavelength of the laser beam by modulating the laser beam using a modulation signal of a predetermined frequency; and a reference mirror and a measurement mirror for reflecting the laser beam. The laser interferometer further includes: a sampling unit for acquiring a sampling value by sampling interference light reflected by the reference mirror and the measurement mirror with a sampling frequency that is a multiple by an integer of two or more of a frequency of the modulation signal; and an average calculator for calculating an average value by averaging a time-series sampling value acquired by the sampling unit in accordance with the sampling frequency. The laser interferometer calculates a displacement of the measurement mirror based on the average value calculated by the average calculator.

Abstract: An apparatus for sensing the position of an object includes an irradiation portion for irradiating the object with continuous electromagnetic radiation, a detection portion for detecting electromagnetic radiation reflected by the object, and an output portion for supplying a change in an amplitude intensity or a phase of the electromagnetic radiation based on information obtained by the detection portion. The position of the object is detected based on information supplied from the output portion.

Abstract: In a method for generating a synthetic wavelength, particularly for an interferometric distance measuring setup, with a primary laser source defining a primary frequency U0 and at least a first sideband frequency U1 of the primary frequency U1, laser radiation with the first sideband frequency O1 and a corresponding first wavelength is provided wherein the first sideband frequency U1 is continuously shifted, particularly by modulating the primary laser source. The synthetic wavelength is generated by combining the first wavelength and a second wavelength which is defined by the primary laser source, particularly by superposition.

Abstract: A measuring device for the optic measuring of an object 13a is provided, in particular for measuring a motion of the object. The device includes an interferometer 20 with a measuring beam exit 12, a reflection beam entry 14, an interfering beam exit 15, and a light source 1 for creating a light beam 8, an optic detector 16, which is arranged at the interfering beam exit 15 of the interferometer 20 such that a light beam exiting the interfering beam exit 15 impinges the detector and a signal processing unit 17 connected to the detector 16 being embodied such that they can measure measuring signals of the detector 16.

Abstract: A position-measuring device for determining the positions of two objects movable with respect to each other along a measuring direction includes a first radiation source for emitting an electromagnetic beam of rays, a beam splitter, which splits each beam of rays emitted by the radiation source into at least one first and one second partial beam of rays, a reference reflector arranged in the beam path of the first partial beam of rays, a measuring reflector, movable with respect to the reference reflector along the measuring direction, which is arranged in the beam path of the second partial beam of rays, a device for superposing the two partial rays of beams after their reflecting at the respective reflector, for generating a measuring signal, a second radiation source for emitting additional electromagnetic beams of rays and a combining device for combining the additional electromagnetic beams of rays into the beam path of the electromagnetic beam of rays generated by the first radiation source.

Abstract: An optical perturbation sensing system includes a probing beam incident on a medium with perturbations and a sensing beam redirected from the medium and incident on a surface area of a photodetector. A reference beam directed onto the photodetector surface forms, with the sensing beam, an interference pattern on the photodetector surface and a phase patterner with at least two phase regions across its section, generates different phases in different regions of the interference pattern. An array of photodetector elements detects each phase region of the interference pattern and a constructive combiner subtract pairs of the detected signals, squares the subtracted signal squares, and sums the squared signals to form a stronger detected signal with reduced intensity noise, reduced background noise, and reduced sensitivity to phase drifts.

Abstract: A first portion of a beam including a first frequency component is directed along a first path. A second portion of the beam is frequency shifted to generate a shifted beam that includes a second frequency component different from the first frequency component and one or more spurious frequency components different from the first frequency component. At least a portion of the shifted beam is directed along a second path different from the first path. An interference signal S(t) from interference between the beam portions directed along the different paths is measured. The signal S(t) is indicative of changes in an optical path difference n{tilde over (L)}(t) between the paths, where n is an average refractive index along the paths, {tilde over (L)}(t) is a total physical path difference between the paths, and t is time.

Abstract: A laser radar system using collocated laser beams to unambiguously detects a range of a target and a range rate at which the target is moving relative to the laser radar system. Another aspect of various embodiments of the invention may relate to a laser radar system that uses multiple laser radar sections to obtain multiple simultaneous measurements (or substantially so), whereby both range and range rate can be determined without various temporal effects introduced by systems employing single laser sections taking sequential measurements. In addition, other aspects of various embodiments of the invention may enable faster determination of the range and rate of the target, a more accurate determination of the range and rate of the target, and/or may provide other advantages.

Abstract: A cantilever array having a simple structure and being able to reliably detect a surface of a sample, a method for fabricating the same, a scanning probe microscope, a sliding apparatus of a guiding and rotating mechanism, a sensor, a homodyne laser interferometer, a laser Doppler interferometer having an optically exciting function for exciting a sample, each using the same, and a method for exciting cantilevers. The cantilever array includes a large number of compliant cantilevers sliding on a surface of a sample.

Abstract: A lithographic apparatus is presented that includes a substrate holder configured to hold a substrate, an illuminator configured to condition a beam of radiation, a support structure configured to support a patterning device that imparts a desired pattern to the beam of radiation, a projection system that projects the patterned beam onto a target portion of the substrate, and an interferometer system configured to measure a position of the object to assist in positioning the object.

Abstract: A laser radar system using collocated laser beams to unambiguously detects a range of a target and a range rate at which the target is moving relative to the laser radar system. Another aspect of various embodiments of the invention may relate to a laser radar system that uses multiple laser radar sections to obtain multiple simultaneous measurements (or substantially so), whereby both range and range rate can be determined without various temporal effects introduced by systems employing single laser sections taking sequential measurements. In addition, other aspects of various embodiments of the invention may enable faster determination of the range and rate of the target, a more accurate determination of the range and rate of the target, and/or may provide other advantages.

Abstract: A multi-beam heterodyne vibrometer for analyzing vibration of an object includes an optical system and a combining element. The optical system generates a plurality of object beams and a plurality of reference beams where one of the plurality of beams has a frequency that is shifted from a frequency of the other plurality of beams. The optical system focuses each of the plurality of object beams on the object and transmits the plurality of focused object beams to the object. A portion of each of the plurality of focused object beams is reflected off of a surface of the object as a modulated object beam. The optical system collects the modulated object beams. The combining element combines each of the modulated object beams with a respective one of the reference beams into a plurality of beam pairs.

Abstract: A first portion of a beam including a first frequency component is directed along a first path. A second portion of the beam is frequency shifted to generate a shifted beam that includes a second frequency component different from the first frequency component and one or more spurious frequency components different from the first frequency component. At least a portion of the shifted beam is directed along a second path different from the first path. An interference signal S(t) from interference between the beam portions directed along the different paths is measured. The signal S(t) is indicative of changes in an optical path difference n{tilde over (L)}(t) between the paths, where n is an average refractive index along the paths, {tilde over (L)}(t) is a total physical path difference between the paths, and t is time.

Abstract: A method for non-linearity compensating interferometer position data generated from a measurement signal includes generating a first set of non-linearity parameters based on received digital position values. The method includes sensing whether a low velocity condition exists. A first one of the non-linearity parameters is updated based on an estimated magnitude of the measurement signal if the low velocity condition exists. At least one digital position value is compensated based on the updated non-linearity parameter if the low velocity condition exists.

Abstract: The aim of the invention is to determine the refractive index and/or compensation of the influence of the refractive index during interferometric length measurement with the aid of an interferometer (13, 13?) impinged upon by at least two measuring beams (v2, v3) having at least defined frequencies with an approximately harmonic ratio. Interferometric phases are evaluated for the at least two measuring beams (v2, v3) at the outlet of said interferometer. The interferometric phases corresponding to the harmonic ratio of the frequencies of the measuring beams (v2, v3) are multiplicated and at least one phase difference of the thus formed phase value is examined.

Abstract: An apparatus is provided for measuring a spacing between an object to be measured T and a transparent object 4. The transparent object 4 is disposed, facing a surface of the object to be measured T, light is emitted to impinge through the transparent object 4 onto the object to be measured T, and the spacing is calculated based on an intensity of interference light occurring in a facing portion between the surface of the object to be measured T and the transparent object 4. The apparatus comprises a light source 1 for emitting light, a modulator 2 for modulating an intensity of the emitted light with modulation waves having a predetermined frequency, a sensor 7 for converting the light intensity of the interference light into an electrical signal, and a synchronous demodulator 8 for subjecting the electrical signal to synchronous demodulation using the modulation waves as reference waves.

Abstract: The present invention concerns the discrimination of good measurement results measured by a computer vision system from bad results. By the method of the invention, values calculated from the observation vectors of several measuring devices can be discriminated into good and bad values by using a quality factor. The quality factor is calculated from the parameters of an error ellipsoid. The error ellipsoid is formed using the calculated value and the observation vectors. If the value calculated from the error ellipsoid parameters exceeds a threshold value that has been input, then the measurement result is rejected.

Abstract: In an optical movement information detector, light emitted from a laser diode (1) is split into a first beam (10), a second beam (11) and a third beam (12) by beam splitters (2a, 2b). The first, second and third beams are converged by a condenser lens (4) upon a surface of an object to be measured (5) to form a beam spot (13) thereon. Diffused light from the beam spot (13) is received by a photodiode (6) and an output signal of the photodiode (6) is processed by a signal processing circuit (20) including an analog-digital converter (8) and a Fourier transforming unit (9). A detecting section (21) obtains, for example, a moving velocity and a moving direction of the object based on spectrum peak frequencies obtained by the Fourier transform.

Abstract: Measurement systems that separate polarization components can use retroreflectors to preserve or transform polarization and avoid unwanted mixing of the polarization components. A suitable retroreflector can include a coated cube corner reflector with retardation plates having a slow axis set at a non-zero angle away from 45° with the directions of linearly polarized component beam. The non-zero angle can be set in situ to minimize polarization mixing in a measurement system. Alternatively, a cube corner reflector with one or more polarization manipulating elements controls the polarization of a reflected beam to preserve or transform the polarization of an incident beam.

Abstract: A heterodyne interferometer, adaptive optics system, method of measuring movement of a target and/or variations in a beam propagation medium, and method of controlling an adaptive optics system are provided. The heterodyne interferometer includes an acoustic-optical modulator that can superimpose a RF signal on a source signal, and output a zero order beam and a higher order beam. One of the beams comprises a target beam and the other beam comprises a local oscillator beam. A telescope can receive the target beam, and direct the target beam through the beam propagation medium to the target. A beam splitter can receive the local oscillator beam and the reflected beam from the target, and coherently combine the local oscillator beam and the reflected beam to produce a fringe pattern. A detector can receive the fringe pattern and generate an electrical beat signal, which can be demodulated based upon the RF signal.