Abstract: An optical apparatus for coherent detection of an input optical beam. The apparatus includes a beam splitter for splitting the input optical beam into a first component and a second component; an optical delay device arranged to receive the second component, the optical delay device imposing an intentional delay in the second component of the input optical beam; and an adaptive beam combiner coupled to receive the second component with a delay imposed thereon by the optical delay device; and the first component from the beam splitter. The adaptive beam combiner has two exiting components having the same wavefronts and propagating directions as the first and second components and being in quadrature. A detector arrangement is provided for receiving and detecting the first and second exiting components from the adaptive beam combiner.

Abstract: A spectrometer may include a radiant source configured to emit radiation and an optical amplifier configured to amply the radiation emitted by the radiant source to produce amplified radiation. A number of optical elements may be configured to produce an interference pattern from the amplified radiation. A detector may detect the interference pattern and generate data from the interference pattern. A processor may be configured to measure one or more from the data.

Abstract: An optoelectronic detector system is for generating a plurality of periodic, phase-shifted scanning signals from the scanning of a periodic fringe pattern. The fringe pattern extends in a detection plane with fringe-pattern period P in a fringe-displacement direction. The detector system is made up of a plurality of detector elements, the geometrical shape of the detector elements being selected such that a defined filtering of unwanted harmonics from the scanning signals thereby results. Within one fringe-pattern period P, a total of N detector elements of the same geometrical shape are arranged one immediately after the other in measuring direction x.

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: Interferometric two-dimensional displacement measuring system A measuring system for an apparatus having a bed, a first stage movable in a first direction relative to the bed, and a second stage movable in a second direction at right angles to the first direction, relative to the first stage. A first interferometer measures displacement in the first direction between a first reference reflector and a first target reflector fixed to the first stage. A second interferometer (a) measures displacement in the second direction between a second reference reflector and a second target reflector fixed to the second stage, (b) includes an intermediate reflector fixed to the first stage, (c) produces a beam that extends in the first direction from a position fixed to the bed to the intermediate reflector and in the second direction from the intermediate reflector to the second target reflector and (d) can therefore have a head that is mounted on the bed.

Abstract: A length measuring apparatus is provided that combines upper data with lower data and then outputs the composite data. The apparatus monitors taking down or up a digit of upper data or lower data and synchronization of lower data, thus preventing an occurrence of reading error. When an A/D area showing an area of lower data matches with an upper area quadrant showing an area of upper data (R2, R3), the upper count value outputting the upper data is output without any change. When the quadrant (0, 1, 2, 3) of the A/D area does not match with the quadrant (0, 1, 2, 3) of upper area because of an erroneous timing of a digit-taking-up of upper data (R1, R4), +1 or −1 is added to the upper count value. Thus, the continuity of a measured value can be obtained when the scale is being moved.

Abstract: An optical characteristic measurement device includes an optical path separation element to which a parallel laser beam is made incident through an aperture, a first face-type photo-detector that receives the laser beam transmitted through the optical path separation element and a second face-type photo-detector that receives the laser beam reflected by the optical path separation element. A length of an optical path from the aperture to the first face-type photo-detector is set to be different from a length of an optical path from the aperture to the second face-type photo-detector.

Abstract: An interferometric measuring method and device for measuring the shape of, or the distance to, surfaces are provided, in which light is generated, modulated with respect to its frequency, conducted to both an object surface and a reference surface, brought to interference, and conducted to a photodetector, and, to detect the particular distance, a phase of the photodetector signal is evaluated. A simple, rugged configuration, with the capability of taking a high-resolution measurements in the context of a large unambiguity range, is achieved in that the phase is considered in at least two different instants with the wavelengths that correspond on the basis of the frequency modulation, and the results are fed to the evaluation.

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 relates to microinterferometers. An embodiment of a microinterferometer for accurately measuring the distance to an object surface includes a substrate and a tunable, phase-sensitive, reflective diffraction grating formed atop said substrate. The diffraction grating is configured to reflect a first portion of an incident light and transmit a second portion of the incident light, such that the second portion of the incident light is diffracted. The diffraction grating is further configured to be controllably adjusted. The microinterferometer also includes a photo-detector for receiving interference patterns produced from the first portion of the incident light reflected from the diffraction grating and the second portion of the incident light reflected from the object surface. The microinterferometer also includes a controller coupled to the photo-detector and the diffraction grating for adjusting the diffraction grating, such that the interference patterns are altered.

Abstract: An apparatus including: a multi-axis interferometry system configured to receive an input beam and direct at least two beams derived from the input beam to contact different locations on a measurement object to monitor changes in an angular orientation of the measurement object; a beam steering assembly having a beam steering element positioned to direct the input beam into the interferometry system and a positioning system to selectively orient the beam steering element relative to the interferometry system; and a control circuit which during operation orients the beam steering element based on the changes in the angular orientation of the measurement object monitored by the interferometry system.

Abstract: The invention features a method for determining non-linear cyclic errors in a metrology system that positions a measurement object under servo-control based on an interferometrically derived position signal. The method includes: translating the measurement object under servo-control at a fixed speed; identifying frequencies of any oscillations in the position of measurement object as it is translated at the fixed speed; and determining amplitude and phase coefficients for sinusoidal components at the identified frequencies which when combined with the position signal suppress the oscillations. The invention also features a method for positioning a measurement object under servo-control based on an interferometrically derived position signal indicative of a position for the measurement object.

Abstract: A measuring device for detecting dimensions of bores has a light source emitting a light beam and a beamsplitter for splitting the light beam into a reference beam and a measuring beam. A reference mirror is arranged downstream of the beam splitter. The measuring beam is supplied to a measuring location of the bore and reflected on it. The reference beam is supplied to the reference mirror and reflected on it. The reflected beams are temporally incoherent and are recombined on the beamsplitter to form a recombined beam supplied to a receiver. Reference mirror and receiver have a lateral displacement relative to an optical axis of the measuring device, or the reference mirror is arranged laterally adjacent to the optical axis and the beam splitter at a slant to the optical axis. The measuring device is integrated into a tool or connected to a tool receptacle.

Abstract: A Cartesian scanning system for scanning a surface of a sample. The scanning system includes a light source assembly configured to produce at least one collimated beam of light, a light sensing system, a stage configured for mounting the sample thereon and a linear track having a direction of elongation. The linear track and the stage are configured to move relative to each other. The scanning system also includes a scanning head having a reflecting system which is configured to direct the collimated beam of light onto the surface and to direct a beam of light reflected from the surface to the light sensing system. The scanning head is slidably associated with the linear track so as to be moveable in a direction parallel to a direction of elongation of the linear track. Also included are a position determination system and a scan displacement correction system.

Abstract: A pattern inspecting apparatus includes an illuminating optical system for illuminating a pattern in a region subject to inspection on a workpiece from a substantially perpendicular direction; a detecting optical system for detecting regularly reflected light or transmitted light from the pattern illuminated by the illuminating optical system, the detecting optical system having a numerical aperture which does not allow the structure of the pattern in the region subject to inspection to be optically resolved; a wavelength-varying system for selectively rendering variable the wavelength of the light detected by the detecting optical system; and a measuring system for measuring the structure of the pattern on the basis of light intensity information of the detected light in correspondence with the wavelength varied by the wavelength-varying system.

Abstract: The invention features a method including: (i) providing an interference signal S(t) from two beams derived from a common source and directed along different paths, wherein the signal S(t) is indicative of changes in an optical path difference n{tilde over (L)}(t) between the different paths, where n is an average refractive index along the different paths, {tilde over (L)}(t) is a total physical path difference between the different paths, and t is time; (ii) providing coefficients representative of one or more errors that cause the signal S(t) to deviate from an ideal expression of the form A1 cos(&ohgr;Rt+&phgr;(t)+&zgr;1), where A1 and &zgr;1 are constants, &ohgr;R is an angular frequency difference between the two beams, and &phgr;(t)=nk{tilde over (L)}(t), with k=2&pgr;/&lgr; and &lgr; equal to a wavelength for the beams; (iii) calculating a quadrature signal {tilde over (S)}(t) based on the signal S(t); and (iv) reducing the deviation of S(t) from the ideal expression using an e

Abstract: A measurement interferometer (40) having a frame structure (43), a laser source (12), a detector (14), a beam splitter (18), a reference retroreflector (28), a reference holder (20) and a test retroreflector (30). The reference rertoreflector (28) and beam splitter (18) are disposed in fixed relation to the reference holder (20) to constitute a splitter-holder assembly (16). The test retroreflector (30) and the splitter-holder assembly (16) are movable relative to each other and both are movably mounted on the fine structure (43). Preferably, the test retroreflector (30) is situated between the reference holder (20) and the beam splitter (18). In a particular embodiment the beam splitter (18) is connected to the reference holder (20) by a carbon composite rod (22), and the test retroreflector (30) is mounted on a probe (34) made from a carbon composite. In one embodiment, the reference retroreflector (28) is integral with the beam splitter (18).

Abstract: A monolithic corrector plate for an interferometer, includes a substrate having an input face for intercepting a first beam emitted by the interferometer, and an output face opposite the input face. An aperture integral with the substrate is configured to transform a first beam intercepted by the input face into a second beam emerging from the output face.

Abstract: An absolute accuracy in the range from ±2 nm to ±1 nm for a displacement measurement value is provided by a laser interferometer displacement measuring system. A fluctuating error component that appears corresponding to the wave cycle of laser light is detected and subtracted from the measurement value while a stage is moving, thereby providing a high accuracy.

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

Abstract: The optical interferometer in which the incident light beam 3 is branched into 2 optical paths of the reflection light and the transmission light which cross at right angle with each other by the beam splitter 4, and on each optical path, the reflection light is totally reflected by the first reflection unit 5, and the transmission light is totally reflected by the second reflection unit 6, and the reflection lights by both reflection units 5 and 6 are wave-combined again by the beam splitter 4, and received by the light receiver 7. The beam splitter 4 by which the incident light beam is wave-separated and wave-combined, is arranged with a little inclination from the vertical to the incident light beam.

Abstract: A position sensor for movable body, which detects a position of a movable body which moves in a reciprocal direction, comprises; at least two portions to be detected, which are provided on one side surface of the movable body with respect to a moving direction of the movable body, and at least two detectors for detecting the portions to be detected, wherein one portion to be detected is not arranged on a line parallel to the moving direction, on which the other portion is disposed, nor arranged on a line perpendicular to the moving direction, on which the other portion is disposed, one detector corresponding to the one portion is arranged so that when the one detector detects the one portion by moving the movable body in one direction, the other portion is moved in the one direction beyond the one detector, and the other detector corresponding to the other portion is arranged so that when the other detector detects the other portion by moving the movable body in the other direction, the one portion is moved i

Abstract: In certain aspects, the invention features scanning interferometry systems and methods that can scan an optical measurement surface over distances greater than a depth of focus of imaging optics in the interferometry system, while keeping an optical measurement surface in focus (i.e., maintaining an image of the optical measurement surface coincident with the detector). The optical measurement surface refers to a theoretical test surface in the path of test light in the interferometer that would reflect the test light to produce an optical path length difference (OPD) between it and reference light that is equal to a constant across a detector.

Abstract: An optical moving information measuring apparatus comprising: light generating means for forming two light spots at a predetermined interval, on a surface of a moving object to be measured providing at least a light emitting source, a collimator lens for collimating light emitted from the light emitting source and an objective lens for irradiating the light passed through the collimator lens to the surface of the moving object; a beam splitter for rotating an optical axis of each of the two types of light reflected from the light spots and passed through the objective lens by a predetermined angle; a light receiving lens through which the two types of light from the beam splitter pass; a light receiving element for receiving the two types of light passed through the light receiving lens; and a processing part for calculating a time delay of one from the other of two types of output signals from the light receiving element obtained by movement of the moving object in order to obtain moving information of the m

Abstract: A method and apparatus for measuring particle motion using electromagnetic radiation uses beams of radiation modulated with a distinct frequency and/or phase. A particle traversing these beams scatters a portion of the radiation. Scattered radiation, which retains modulation information, is then detected, and a cross-correlation technique is used to quantify the particle's motion, for example, particle velocity.

Abstract: An absolute accuracy in the range from ±2 nm to ±1 nm for a displacement measurement value is provided by a laser interferometer displacement measuring system. A fluctuating error component that appears corresponding to the wave cycle of laser light is detected and subtracted from the measurement value while a stage is moving, thereby providing a high accuracy.

Abstract: The present invention provides a method and system to actively stabilize a probe, such as a microelectrode, relative to movement of the subject, utilizing laser interferometry. In the preferred embodiments, a probe is mounted on a manipulator such that the probe moveable in response to a control voltage. A laser interferometer is utilized to transmit a first light beam to the subject and to receive a reflected light beam, to modulate a second light beam with a radio frequency signal to form a reference light beam, and to combine the reflected light beam and the reference beam to form an interference pattern. A demodulator is utilized to quadrature demodulate a phase shift of a radio frequency component of the interference pattern to determine a displacement signal representative of an amount and direction of subject movement, and to convert the displacement signal to the control voltage.

Abstract: A position measuring system including a laser light source for radiating a laser beam, an optical lens system for generating an interference pattern on the basis of the laser beam having passed through different optical paths, a detector for detecting the interference pattern, and an arithmetic unit for calculating the position of at least one of the light source and the detector on the basis of a detection signal issued from the detector. For example, a spherical lens can be used as the optical lens system. In this case, the interference pattern is formed on the basis of spherical aberration of the lens. Alternatively, a multifocal lens may be used as the optical lens system.

Abstract: Techniques for compensating for geometric effects of beam misalignment in plane mirror interferometers are disclosed.

Abstract: The instant invention is a method and apparatus for the measurement, with low uncertainty, of the six degrees of freedom of a first structure relative to a second structure. The apparatus is comprised of compact, rigid, thermally stable structures. The invention uses linear displacement transducers which have no active pointing to maintain a desired orientation of the linear displacement transducers with other parts of the measurement system.

Abstract: Spatial filtering of beams in interferometry systems is used to reduce a displacement of the beams from an optical path corresponding to the path of the beams in an optimally-aligned system. By reducing beam displacement from the optical path, the system reduces the magnitude of beam shears and associated non-cyclic errors in linear and angular displacements measured by the interferometry systems.

Abstract: Several embodiments of a microinterferometer are disclosed. A first embodiment of a microinterferometer for measuring the absolute distance to an object surface includes a substrate. The microinterferometer also includes a phase-sensitive, reflective diffraction grating formed on the substrate. The diffraction grating is configured to reflect a first portion of an incident light and transmit a second portion of the incident light, such that the second portion of the incident light is diffracted. The microinterferometer further includes a lens formed on the substrate for focusing the second portion of the incident light to a predetermined local distance, and a photo-detector for receiving interference patterns produced from the first portion of the incident light reflected from the diffraction grating and the second portion of the incident light reflected from the object surface.

Abstract: An interferometer returns parallel beams that are subject to walk-off caused by reflector misalignment for an additional pass through the interferometer optics and thereby eliminates beam walk-off. A return reflector can be a plane mirror that directs returning beams to retrace paths through the interferometer optics to combine and exit along the axis of the input beam. Separation optics can separate the combined beam from the input beam. Alternatively, a return reflector such as an isosceles prism or a trapezoidal prism reflects and offsets returning beams so that the combined beam is offset from the input beam. The return reflector more generally responds to a shift in incident beam position with a matching shift of the reflected beam in contrast to a retroreflector, which shifts a reflected beam in a direction opposite to the shift in the incident beam.

Abstract: The optical interferometer in which the incident light beam 3 is branched into 2 optical paths of the reflection light and the transmission light which cross at right angle with each other by the beam splitter 4, and on each optical path, the reflection light is totally reflected by the first reflection unit 5, and the transmission light is totally reflected by the second reflection unit 6, and the reflection lights by both reflection units 5 and 6 are wave-combined again by the beam splitter 4, and received by the light receiver 7. The beam splitter 4 by which the incident light beam is wave-separated and wave-combined, is arranged with a little inclination from the vertical to the incident light beam.

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 capable of testing a displacement transducer having an extendable portion includes a slide capable of being moved along an axis and a measuring unit capable of determining a displacement of the slide along the axis. The extendable portion is connectible to the slide so that, when the extendible portion is connected and the slide is moved, the extendable portion is extended and retracted along a path. A method capable of testing a displacement transducer includes determining electrical signal values outputted from the transducer corresponding to displacements of the transducer and creating a statistical model based upon the electrical signal values and the displacements of the transducer. The method further includes determining a displacement error for each of the electrical signal values and the displacements of the transducer based upon the statistical model. Displacement errors that exceed a predetermined tolerance are determined.

Abstract: Systems and methods for characterizing and compensating non-cyclic errors in interferometers and interferometer components are disclosed.

Abstract: An optical encoder including a scale, a scanning device displaceable relatively to the scale in a measuring direction and having a scanning reticle with at least one transparent window limited by an opaque screen and a partial grit formed of an electrically conductive material and provided at least in a region of the window.

Abstract: Interferometry system including a multiple-pass interferometer having reflectors to reflect at least two beams along multiple passes through the interferometer. The multiple passes include a first set of passes and a second set of passes. The reflectors have first alignments that are normal to the directions of the paths of the beams that are reflected by the reflectors. The two beams provide information about changes in a first location on one of the reflectors after the first set of passes, and provide information about changes in the first location and changes in a second location on the reflector after the second set of passes. The paths of the beams are sheared during the first set of passes and during the second set of passes if at least one of the reflectors has an alignment other than the first alignment.

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: A method and system for determining range by correlating a relationship between one or more distances of a diffraction grating from an illuminated target surface with variations in the respective wavelengths of high order diffraction spectra. The high order diffraction spectra are observed through the diffraction grating. The high order diffraction spectra are derived from broadband radiation transmitted from the illuminated target surface.

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

Abstract: This specification discloses an apparatus comprising a first system for forming a composite light beam of two light beams to be made to interfere with each other, a splitting member for amplitude-splitting the composite light beam into three or more splitted light beams in the same area, and a second system for obtaining interference light beams of different phases from the plurality of splitted light beams.

Abstract: Methods and apparatus for reducing the effects of non-isotropic gas distributions on interferometry measurements are disclosed.

Abstract: A length of scale (1) which has a profile consisting of a sequence of troughs (18) and crests (16) is subjected to a process to make the shapes of the crests more regular, thus increasing and making more predictable the signal reflected from the crests on the scale. The process comprises passing a length of scale (1) between upper (20) and lower (22) cylindrical rollers. The lower roller (22) may be driven or the length of scale (1) may be pulled through. Reference marks or identification marks may be added to the scale by appropriately marking the upper roller (20). Alternatively, the marks may be added at an initial embossing step which imparts the troughs and crests profile to the scale or at a separate subsequent step.

Abstract: Apparatus and methodology by which the position, angular orientation, and departure of a moving body, such as a scanning head, can be measured with high accuracy with respect to a nominally straight line as the body translates along that line. Monolithic metrology and scanning heads with integrally formed metrology surfaces are provided and fabricated of preferably identical materials having low thermal coefficients and high temporal stability. Measuring systems operate in conjunction with the integral metrology surfaces to provide interferometric information by which the position and angular attitude of the moving body is constantly monitored. Calibration arrangements are provided for determining the absolute position and attitude of the moving body with respect to the metrology frame as the two move relative to one another so that any errors can be compensated with appropriate correction functions.

Abstract: A sensor has an interferometer which measures a change in an applied environmental condition relative to a reference environmental condition. The interferometer is operated under the applied environmental condition to generate an interference spectrum. Intensities of the interference spectrum are measured at first and second wavelengths, respectively. The first and second wavelengths correspond to first and second reference intensities that are separated from one another by an odd number of extrema in the interference spectrum when the interferometer is operated under the reference condition. Measurement of the change in the applied environmental condition is based on the measured intensities and the first and second reference intensities.

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

Abstract: In an optical interferometer, incident light 1 is divided into reflected light and transmitted light which travel along respective optical paths, which are orthogonal to each other. The reflected light is subjected to total reflection by means of a first reflector 3, and the transmitted light is subjected to total reflection by means of a second reflector 4. The light reflected by the first reflector 3 and the light reflected by the second reflector 4 are again merged by means of the beam splitter 2 into a single ray, and the thus-merged ray falls on a photodetector 5. The optical interferometer is equipped with a third reflector 6 which reflects the incident light 1 at right angles so as to fall on the beam splitter 2, and a fourth reflector 7 which reflects the light, having been transmitted through the beam splitter 2, at right angles so as to fall on the second reflector 4.