Abstract: A laser interferometric measuring instrument includes: a light source that emits a laser beam of 1064 nm and another laser beam of 532 nm; a polarizing beam splitter; a dichroic mirror that splits a long-wavelength laser beam provided in a measurement optical path; a long-wavelength corner cube that reflects the split laser beam; a measurement corner cube that is displaceable along the measurement optical path; a reference corner cube that is displaceable along a reference optical path; a optical path changing unit that changes an optical path length of the long-wavelength laser beam; a phase detector that outputs interference signals; a sum signal computer that calculates a sum signal; a displacement controller that displaces the reference corner cube so as not to change a phase of the sum signal; a reference displacement detector that detects a displacement of the reference corner cube; and a measurement displacement computer that calculates a displacement of the measurement corner cube.

Abstract: In a displacement measurement apparatus using light interference, a probe light path is spatially separated from a reference light path. Therefore, when a temperature or refractive index distribution by a fluctuation of air or the like, or a mechanical vibration is generated, an optical path difference fluctuates between both of the optical paths, and a measurement error is generated. In the solution, an optical axis of probe light is brought close to that of reference light by a distance which is not influenced by any disturbance, a sample is irradiated with the probe light, a reference surface is irradiated with the reference light, reflected light beams are allowed to interfere with each other, and a displacement of the sample is obtained from the resultant interference light to thereby prevent the measurement error from being generated by the fluctuation of the optical path difference.

Abstract: A stage configuration is provided, wherein a ceramic plate is used as the z-stage body to decrease the use of the metal plates in the conventional configuration, so that the compact structure of the z-stage may decrease the vibrational movements of the z-stage. Further, two Laser interferometer are used to detect a movement of different points along a vertical line of the z-stage sidewall to calculate a movement of the specimen surface, so that a horizontal movement of the specimen surface can be detected more accurately.

Abstract: A laser beam emitted by an encoder main body enters a wafer table via a PBS from the outside, and reaches a grating at a point that is located right under exposure area, and is diffracted by the grating. Then, by receiving interference light of a first polarized component that has returned from the grating and a second polarized component reflected by the PBS, positional information of the wafer table is measured. Accordingly, because the first polarized component, which has passed through PBS passes through the wafer table until it is synthesized with the second polarized component again, does not proceed through the atmosphere outside, position measurement of the wafer table can be performed with high precision without the measurement beam being affected by the fluctuation of the atmosphere around the wafer table.

Abstract: A method and system for positioning by using optical speckle are disclosed in this invention. A highly coherent laser light irradiates a positioning template in advance to record optical speckles caused by interference by scattered light beams from the positioning template for establishing a speckle database. Furthermore, a reference point is defined to position each recorded speckle. Therefore, a coordinate with respect to the reference point corresponding to a specified speckle can be used to position a target or applied to distance measurement by the speckle database. The precision of the speckles according to the present invention is within several micrometers. Hence, it can provide high precision positioning.

Abstract: An apparatus and method for using a counter-propagating signal method for locating events is disclosed. The apparatus and method uses a Mach Zehnder interferometer through which counter-propagating signals can be launched. If the sensing zone of the Mach Zehnder interferometer is disturbed, modified counter-propagating signals are produced and the time difference between receipt of those signals is used to determine the location of the event. A microcontroller receives feedback signals which adjusts polarization controllers so that the polarization states of the counter-propagating signals can be controlled to match the amplitude and/or phase of the output signals. Detectors are provided for detecting the modified signals.

Abstract: The present invention provides a measuring apparatus for measuring an absolute distance between a reference surface and 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: 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 tilting angle measuring device includes an optical device, a four-quadrant optical detector and a computing unit. By the optical device, a light beam emitted by the coherent light source is processed into a reference beam and a test beam. The four-quadrant optical detector has four photoelectric converting units arranged in an array for respectively receiving the reference and test beams. The computing unit is electrically connected to the four-quadrant optical detector for computing a tilting angle of the object with respect to a predetermined position according to four intensity values of the test beam.

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: Optical coherence tomography (OCT) is an imaging method which can image with micrometer-scale resolution up to a few millimeters deep into, for example, living biological tissues and preserved tissue samples. An improved apparatus and image reconstruction algorithm for parallel Fourier Domain OCT which greatly eases requirements for interferometer stability and also allows for more efficient parallel image acquisition is provided. The apparatuses and algorithms reconstruct images from interfered, low-coherence, multiwave length signals having a .pi. radian phase difference relative to one another. Other numbers of signals and other phase differences may be alternatively used, with some combinations resulting in higher resolution and image stability. The apparatus also eliminates a need for bulk optics to modulate a phase delay in a reference arm of the optical path. Images may be reconstructed using two spectrometers, where each is coupled to a detector array such as a photodiode array.

Abstract: Systems and methods are disclosed for an interferometer system. An interferometer system may comprise a plurality of light sources, wherein each light source of the plurality is configured to transmit a source beam. The interferometer system may also include an interferometer including a polarizing beam splitter and a reference reflector. The interferometer is configured to receive the source beam and transmit a measurement beam to a target reflector and a reference beam to the reference reflector. Additionally, the interferometer system may include a plurality of receivers, wherein each receiver of the plurality is associated with a light source and configured to receive a mixed beam comprising a reflected measurement beam and a reflected reference beam. Moreover, the interferometer is configured to receive at least one source beam at an angle with respect to an axis perpendicular to a side of the interferometer configured to receive the source beam.

Abstract: An interference contrast imaging system images phase objects. The system includes an illumination source, illumination optics, polarizing optics for splitting the illumination into orthogonal polarizations and for recombining the polarizations, objective optics that form an image at a detector, a wavefront coding element and a post processor for processing the image by removing a phase shift imparted by the wavefront coding element. The wavefront coding element has an aperture, is between the phase object and the detector, and provides an altered optical transfer function of the imaging system by imparting the phase shift to the illumination transmitted through the wavefront coding element. The altered optical transfer function is insensitive to an object distance between the phase object and the objective optics over a greater range of object distances than would be provided by an optical transfer function of a corresponding interference contrast imaging system without the wavefront coding element.

Abstract: A method of detecting a movement of a measuring probe provided between an objective lens adapted to image an object plane on a predetermined image plane and the object plane is disclosed. Additionally, a measuring instrument comprising an objective lens and a measuring probe is disclosed. An input beam of light is split into a measurement beam and a reference beam. The measurement beam is focused on a reverse focal plane of the objective lens such that the measurement beam is collimated by the objective lens. The collimated measurement beam is reflected at the measuring probe. The reflected measurement beam is directed towards the objective lens such that the objective lens focuses the reflected measurement beam on the reverse focal plane. The reflected measurement beam is collimated. The collimated reference beam and the reference beam are superimposed to form a superimposed beam and an interference between the reflected measurement beam and the reference beam is detected.

Abstract: In a displacement measurement apparatus using light interference, a probe light path is spatially separated from a reference light path. Therefore, when a temperature or refractive index distribution by a fluctuation of air or the like, or a mechanical vibration is generated, an optical path difference fluctuates between both of the optical paths, and a measurement error is generated. In the solution, an optical axis of probe light is brought close to that of reference light by a distance which is not influenced by any disturbance, a sample is irradiated with the probe light, a reference surface is irradiated with the reference light, reflected light beams are allowed to interfere with each other, and a displacement of the sample is obtained from the resultant interference light to thereby prevent the measurement error from being generated by the fluctuation of the optical path difference.

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 laser interferometer (10) comprises: a first beam splitter (22) which splits a laser beam emitted from a light source (3) into a first beam (L2) and a second beam; a second beam splitter (24) which splits the second beam into a third beam (L1) and a fourth beam (L3), and which causes reflected beams, produced by reflection of the split beams (L1, L3) and incident from reverse directions to the directions of the split beams, to exit in a reverse direction to the direction of the second beam; and a beam selecting unit (50, 51, 60, 66, 68) which, from among the reflected beams produced by reflection of the third and fourth beams (L1, L3) and caused to exit the second beam splitter (24) in the reverse direction to the direction of the second beam, selects a beam to be combined in the first beam splitter (22) with a reflected beam produced by reflection of the first beam (L2) and incident on the first beam splitter from a reverse direction to the direction of the first beam (L2).

Abstract: An interferometer has a first reflective surface having a nominal orientation; a second reflective surface having a nominal orientation orthogonal to the nominal orientation of the first reflective surface; a retroreflector facing the first reflective surface; a double polarizing beam splitter (DPBS) between the first reflective surface and the retroreflector; and a respective quarter-wave plate between the DPBS and each of the reflective surfaces. The DPBS has first and second beam-splitting surfaces each having a nominal orientation with respect to the first reflective surface. At least part of at least one of the first reflective surface, the second reflective surface and the beam-splitting surfaces is effectively tilted relative to the respective nominal orientation of such surface, and constitutes a respective tilted surface.

Abstract: An optical coupling apparatus for a dual column charged particle beam tool allowing both optical imaging of an area of an integrated circuit, as well as localized heating of the integrated circuit to form silicide. In one embodiment, optical paths from a whitelight source and a laser source are coupled together by way of first and second beam splitters so that a single optical port of the dual column tool may be utilized for both imaging and heating. In another embodiment, a single laser source is employed to provide both illumination for standard microscopy-type imaging, as well as localized heating. In a third embodiment, a single laser source provides heating along with localized illumination for confocal scanning microscopy-type imaging.

Abstract: In a displacement measurement apparatus using light interference, a probe light path is spatially separated from a reference light path. Therefore, when a temperature or refractive index distribution by a fluctuation of air or the like, or a mechanical vibration is generated, an optical path difference fluctuates between both of the optical paths, and a measurement error is generated. In the solution, an optical axis of probe light is brought close to that of reference light by a distance which is not influenced by any disturbance, a sample is irradiated with the probe light, a reference surface is irradiated with the reference light, reflected light beams are allowed to interfere with each other, and a displacement of the sample is obtained from the resultant interference light to thereby prevent the measurement error from being generated by the fluctuation of the optical path difference.

Abstract: An optical axis polarization type laser interferometer including a reference sphere which forms a reference of measurement, a retro-reflecting means disposed at a measurement object, a laser interference measuring apparatus for outputting a measurement value corresponding to an increase or a decrease in the distance to and from the retro-reflecting means; and a two-axis turning mechanism for turning an emission beam of the corresponding laser interference measuring apparatus centering around the reference sphere, which measures, with the center coordinates of the reference sphere used as the reference, the distance to and from the retro-reflecting means where the optical axes of the emission beam from the laser interference measuring apparatus mounted on the two-axis turning mechanism and a return beam become parallel to each other, wherein the fixing portion of the first axis turning mechanism installed at the base part of the apparatus is disposed at the inner circumference thereof, the reference sphere is

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: An apparatus includes an interferometer having a polarizing beam splitter to split an input beam into a measurement beam and a reference beam, the measurement beam contacting a measurement object, the reference beam contacting a reference object. The interferometer includes at least one thin retarder on a surface of the interferometer.

Abstract: A first beam having high coherence and a second beam having low coherence and having a central wavelength difference from that of the first beam are multiplexed onto the same optical axis. First and second multiplexed beams obtained by beam splitting are emitted at a measurement reflection plane and a reference plane, respectively. The reflected first and second multiplexed beams are multiplexed and interfere with each other. The interference generates a first interference signal that is obtained from the first beams at the interference unit and that relates to information on the distance to the measurement reflection plane and a second interference signal that is obtained from the second beams. The first and second interference signals are used to carry out calculations for determining the position of a measurement origin for the measurement reflection plane.

Abstract: A first beam having high coherence and a second beam having low coherence are multiplexed onto the same optical axis. This multiplexed beam is split into first and second multiplexed beams. The first multiplexed beam is directed towards a measurement reflection plane of an object to be measured, and the second multiplexed beam is directed towards a reference plane. The first and second multiplexed beams that are reflected from the measurement reflection plane and the reference plane, respectively, are multiplexed to cause the first beams to interfere with each other and the second beams to interfere with each other. Calculations are carried out to determine a measurement origin on the basis of the first and second interference signals obtained from the first and second beams, respectively.

Abstract: An optical assembly of an interferometer that includes a beam splitter for dividing the beams emitted by a radiation source into at least one measuring and one reference beam and at least one measuring and one reference mirror, on which the measuring and the reference beams impinge, wherein at least one of the mirrors can be displaced along a measuring axis. The optical assembly further includes a beam deflector, as well as a retro-reflector, wherein the measuring and the reference beams reflected at the measuring and the reference mirrors via the beam deflector and the retro-reflector are guided at least a second time in the direction toward the measuring and the reference mirrors and wherein the beam deflector is embodied as a plane-parallel plate.

Abstract: Methods and systems for determining information about the incident angle of a beam are disclosed, the method including directing a beam having an s-polarized component and a p-polarized component to reflect from an interface at a non-normal angle, where the non-normal reflection introduces for each component a phase change upon reflection that is different for each component, and measuring an optical interference signal related to the phase change between the components of the reflected beam.

Abstract: In general, in a first aspect, the invention features a method that includes using an interferometry assembly to provide three different output beams, each output beam including an interferometric phase related to an optical path difference between a corresponding first beam and a corresponding second beam, each first beam contacting a measurement object at least once, monitoring the interferometric phases for each of the three different output beams, and deriving information about variations in the optical properties of a gas in the first beam paths from the three monitored phases.

Abstract: A polarising double-passed interferometer comprises a polarising beamsplitter (16), a reference mirror (20) in the path of a reference beam (14) and a movable measurement mirror (26) in the path of a measurement beam (12). The reference and measurement beams have different polarisations. An angular beam deflection device such a glass wedge or prism (32) acts to remove or separate out an error beam (30) caused by leakage of light of one polarisation into the path of light of the other polarisation.

Abstract: A tilting angle measuring device includes an optical device, a four-quadrant optical detector and a computing unit. By the optical device, a light beam emitted by the coherent light source is processed into a reference beam and a test beam. The four-quadrant optical detector has four photoelectric converting units arranged in an array for respectively receiving the reference and test beams. The computing unit is electrically connected to the four-quadrant optical detector for computing a tilting angle of the object with respect to a predetermined position according to four intensity values of the test beam.

Abstract: An apparatus and method for using a counter-propagating signal method for locating events is disclosed. The apparatus and method uses a Mach Zehnder interferometer through which counter-propagating signals can be launched. If the sensing zone of the Mach Zehnder interferometer is disturbed, modified counter-propagating signals are produced and the time difference between receipt of those signals is used to determine the location of the event. A microcontroller receives feedback signals which adjusts polarisation controllers so that the polarisation states of the counter-propagating signals can be controlled to match the amplitude and/or phase of the output signals. Detectors are provided for detecting the modified signals.

Abstract: An apparatus and method for using a counter-propagating signal method for locating events is disclosed. The apparatus and method uses a Mach Zehnder interferometer through which counter-propagating signals can be launched. If the sensing zone of the Mach Zehnder interferometer is disturbed, modified counter-propagating signals are produced, and the time difference between receipt of those signals is used to determine the location of the event. Polarisation controllers receive feedback signals so that the polarisation states of the counter-propagating signals can be controlled to match the amplitude and/or phase of the signals. Detectors are provided for detecting the modified signals.

Abstract: An optical axis polarization type laser interferometer including a reference sphere which forms a reference of measurement, a retro-reflecting means disposed at a measurement object, a laser interference measuring apparatus for outputting a measurement value corresponding to an increase or a decrease in the distance to and from the retro-reflecting means; and a two-axis turning mechanism for turning an emission beam of the corresponding laser interference measuring apparatus centering around the reference sphere, which measures, with the center coordinates of the reference sphere used as the reference, the distance to and from the retro-reflecting means where the optical axes of the emission beam from the laser interference measuring apparatus mounted on the two-axis turning mechanism and a return beam become parallel to each other, wherein the fixing portion of the first axis turning mechanism installed at the base part of the apparatus is disposed at the inner circumference thereof, the reference sphere is

Abstract: Position detection apparatus comprises: an incident unit that forms a parallel beam from a light beam of a light source and supplies the parallel beam to a beam splitter in a way that the separated beams, obtained from the parallel beam by the beam splitter, are respectively incident upon the reference surface and the measurement target surface at an angle; and a reflection unit that reflects the separated beams, which have been reflected by the reference surface and the measurement target surface and integrated to a light path by the beam splitter, to be supplied to the beam splitter as a parallel beam along the light path, and generates a signal corresponding to a phase difference of the separated beams by interfering a light beam that has been supplied from the reflection unit, separated by the beam splitter, reflected by the reference surface and the measurement target surface, and integrated again to a light path by the beam splitter.

Abstract: An optical component has a coating including one or more layers at each reflecting surface. The coating causes the optical component to have polarization eigenstates that are substantially linear and to have the properties of a half-wave plate. The coated optical component can be used in interferometry and microlithography system.

Abstract: A phase difference detector generates a plurality of signals from an input beam including orthogonal, linearly polarized object and reference beam components. The detector may be configured such that as the reference and object beam components traverse the detector, phase shifts due to surface interactions are made as similar as possible between the s-components of the reference object beams, and between the p-components of the reference and object beams. Various outputs may be formed by interfering p-components exclusively, or s-components exclusively, negating errors that may otherwise arise due to differential phase shifts between p- and s-components. Phase-shifting elements in the detector may receive beams from beam splitting surfaces where the transmissive differential phase shift between p- and s-components is adjusted to insignificance.

Abstract: Spatially-separated heterodyne interferometer architecture is combined with monolithic glass construction techniques to provide a monolithic, spatially-separated, common-path interferometer. The monolithic interferometer includes multiple optical components bonded together into a monolithic structure. The bonded components provide both optics and structure for the interferometer, thereby producing a small, compact, and light-weight interferometry system. Beam splitters and combiners are provided on the interfaces between the optical components to direct and combine signal measurement, signal reference and local oscillator beams used in the interferometry system. The spatially-separated architecture reduces cyclic error values below those of polarization-separated interferometers. In addition, the monolithic architecture of the interferometer minimizes the impact of mechanical, thermal, and optical variations within the system.

Abstract: A system and a method for determining a position of two objects relative to each other is suggested, comprising: a source 43 of coherent radiation, a beam guidance for providing a measuring branch 49 for a measuring beam, which has an optical path length dependent on the position of the two objects, a radiation intensity sensor 65 for measuring an intensity of an interfering superposition of radiation, which include radiation at least after passing through the measuring branch 49, and a calculator 67 which responds to a measuring signal from the radiation intensity sensor 65, in order to detect optical path lengths of the measuring branch 49 and therefrom to detect the position of the two objects relative to each other, wherein the measuring branch 49 includes: at least one emitter fixedly mountable on a first of the two objects for emitting radiation supplied to the measuring branch 49 in a space between the two objects, at least three retroreflectors 19 mountable on the second one of the two objects, such t

Abstract: An interferometer provides a large dynamic range for perpendicular displacement measurements. In operation, a measurement reflector on an object reflects a measurement beam to an overlying Porro prism, and a reference reflector on the object returns a reference beam to the interferometer. A second Porro prism in the interferometer can return the reference beam for a second pass to the reference reflector, while the measurement beam complete only one pass. Reductions in beam walk-off result from retroreflections in the Porro prisms and the matching effects that some object rotations have on measurement and reference beams. Perpendicular motion of the object relative to the first Porro prism causes a Doppler shift only in the measurement beam. Accordingly, a beat frequency found when combining the measurement and reference beams can indicate a residual Doppler shift associated with the motion in the perpendicular direction.

Abstract: A detector for interferometric distance or displacement measurement. The detector may receive orthogonally polarized object and reference path output beams, which are directed to a polarization-sensitive beam deflecting element. The beam deflecting element deflects one or both orthogonally polarized beams to provide a desired divergence angle between the beams. The diverging beams are input to a mixing polarizer. The beams exiting the mixing polarizer are similarly polarized and therefore interfere. The interfering diverging beams form interference fringes. The spatial phase of the fringes relative to a photodetector array characterizes the phase difference between the object and reference beams of the interferometer.

Abstract: At least two discrete quarter wave plates are provided for use as plane mirrors or reflectors in a displacement measuring interferometer, where the plates share common or substantially common reflecting surface geometries. A plurality of geometrically matched discrete matched quarter wave plates reduces the amount of tilt between an input beam provided to, and an output measurement beam provided by, an interferometer, resulting in increased interferometer dynamic range.

Abstract: An exposure apparatus includes a projection optical system for projecting an exposure pattern, onto an object to be exposed, and a measuring apparatus for measuring, as an interference fringe, optical performance of the projection optical system, wherein the measuring apparatus includes an optical element having opposing first and second surfaces, wherein the first surface has a first measurement pattern, and the second surface has a second measurement pattern and is closer to the projection optical system than the first measurement pattern, and wherein the measuring apparatus introduces light into the projection optical system via first and second measurement patterns.

Abstract: The invention relates to a polarizing beam splitter device, an interferometer module system, a lithographic apparatus, and a device manufacturing method. The polarizing beam splitter device includes an optical element and a polarizing beam splitter layer. The optical element includes a retroreflector surface having three mutually perpendicular faces of high optical quality, a radiation beam passage surface and a handling surface. By designing the optical element, in particular the handling portion, to the shape of a beam splitter element, such as a prism, the handling portion, and thus the polarizing optical beam splitter device etc. itself, may be made more compact and with fewer surfaces to be polished and/or antireflection-coated. The positioning of the parts in a beam splitter is more reliable.

Abstract: A compact monolithic quadrature detector generates four signals from an input beam including orthogonally polarized object and reference beam components provided by an interferometer. The single input beam may be split into four output beams using a first beam splitting interface between two prisms, reflections at two air interface surfaces of the prisms, and a second beam splitting element. Different respective predetermined phase shifts may be imposed on the respective output beams by coatings on the beam splitting surfaces, which impart a different phase shift to the components of a transmitted beam as compared to a reflected beam. The four relatively phase shifted output beams may be directed through polarizers onto respective detectors to provide four signals usable to eliminate many common mode errors and determine the phase difference between the components of the original input beam with high accuracy.

Abstract: A laser interferometer is disclosed comprising a housing capable of being substantially repeatably mounted to a wall of an environmental chamber, the housing including a laser source, a reflector attached to an object located within the environmental chamber, and a light passage provided through the wall of the environmental chamber enabling passage of a laser beam from the laser source to the reflector. At least one beam steerer may be provided for adjusting direction of passage of a laser beam through the light passage. Also disclosed is a column laser interferometer.

Abstract: In general, in one aspect, the invention features apparatus that include an interferometer including a main assembly having two laterally displaced polarizing beam splitter interfaces, wherein the interfaces are positioned to receive two spatially separated beams and direct them each to make at least two passes to one or more remote objects. Each interface reflects and transmits each beam at least once, and the interferometer is configured to combine the two beams after they make the at least two passes to the one or more remote objects to produce an output beam including information about an optical path length difference between paths traveled by the two beams.

Abstract: In general, in one aspect, the invention features assemblies that include a first polarizing beam splitter positioned in the paths of a pair of initial beams, the polarizing beam splitter being configured to combine the pair of initial beams to form an input beam. The assemblies further include an interferometer positioned to receive the input beam and configured to produce an output beam that includes information about an optical path difference between the paths of two component beams derived from the input beam. A second polarizing beam splitter is positioned in the path of the output beam and configured to split the output beam into a pair of secondary output beams that each include information about the optical path difference between the component beam paths.

Abstract: In general, in one aspect, the invention features an apparatus including a multi-axis interferometer configured to produce at least three output beams each including interferometric information about a distance between the interferometer and a measurement object along a corresponding measurement axis, wherein at least three of the measurement axes are in a common plane, wherein the output beams each include a component that makes a pass to the measurement object along a common beam path.

Abstract: Beam shearing apparatus for introducing a lateral shear between the components of a light beam. The apparatus is an optical assembly having a polarizing interface and input and output facets and two reflecting surfaces one of which is arranged at an angle generally opposite the input facet and the other of which is arranged at an angle generally opposite the output facet.

Abstract: Disclosed herein is a method and apparatus for simultaneously measuring a displacement and angular variations. The method and apparatus of the present invention allows light radiated from a single light source to be placed along a light axis so as to simultaneously measure a distance (displacement) and angular variations that are different physical quantities, so that the displacement and angular variations of the measuring device of a precision measuring apparatus or machining device of a machine tool moved by a stage can be simultaneously measured without an Abbe error.