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.

Abstract: This invention mainly provides a structure of high filtering precision optical signal interleaver. Herein the birefringent crystal is designed to lead the incident light having a suitable phase-delay and multi-pass to achieve a flattened filtering spectrum and to reduce the filtering spectrum error caused by unmatched component crystal length. Moreover, this invention will eliminate the element number and shorten the element length concurrently.

Abstract: An interferometry system includes an interferometer to split an input beam into a measurement beam and at least one other beam. The interferometer directs the measurement beam along a measurement path that includes at least two passes to a measurement object, and overlaps the measurement beam with the other beam after the measurement beam completes the at least two passes. The path of the measurement beam is sheared during the first and second passes when the measurement object moves along a direction orthogonal to a portion of the measurement path that contacts the measurement object. The interferometry system includes optics to redirect the measurement beam after the first pass and before the second pass so that shear imparted during the second pass cancels shear imparted during the first pass.

Abstract: Beam shear can be reduced in an interferometric system by conditioning an input beam prior to directing the input beam to an interferometer. Accordingly, apparatus and methods for conditioning an interferometer input beam are disclosed.

Abstract: An optical interference apparatus includes a light source, a beam splitter for splitting a light beam from the light source, a reference surface by which one split light beam from the beam splitter is reflected to propagate backward through the optical path. The light beam from the reference surface and the other split light beam (which emerges from the beam splitter, is reflected by an object to be detected, and returns) are combined by the beam splitter, and the combined light is used as interference light. The two split light beams emerge from the beam splitter as convergent light. An optical element has a function of converging a light beam or changing a divergent state of the light beam, and is inserted in an optical path of one of the split light beams emerging from the beam splitter. The convergent, reflected light beams are combined as spherical waves with curvature equal to each other owing to an effect of the optical element.

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: Electron beam lithography is used to make very small mechanical structures in single-crystal silicon. The structure may be a mesh having beam widths of less than 30 nm and suspended in a wafer, above a substrate. An rf drive voltage applied between the suspended structure and the underlying substrate produces vibration at or near the resonant frequency of the structure, and optical interference techniques are used to detect and measure the motion of the structure. The small dimensions of the structure provides a resonant frequency above 40 MHz. In one embodiment, the structure is a mesh formed of interconnected, very narrow, high aspect ratio parallel beams spaced about 315 nm apart. This results in a nanostructure having a low mass and a large relative surface area.

Abstract: Measurements on a sheet (12), for example measurement of the movement of the sheet in a printer, can be performed by directing a measuring beam (8) towards the sheet and utilizing the effects of self-mixing in a diode laser (2) and Doppler shift in the measuring beam caused by the movement. The measuring method and a dedicated, cheap and compact, sheet sensor (1) may be used for determining different parameters and in different sheet processing apparatus.

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: The degree of accuracy a machine tool or the like is moved along a given path is determined by a unique preferably laser beam directing measuring system directing simultaneously or in sequence a laser beam parallel to the orthogonal axes of the two or three dimensional space in which the spindle or other object is to be moved in a path which can diverge appreciably in directions other than the directions of these axes. The beam directing means includes means which provides a measure of the actual positions the object has at various sampling times relative to the axis along which the beam is directed. This actual path position data is compared to the desired path position data used to program the object moving machine to determine the path position error at the sampling times involved.

Abstract: Displacement detector 1 generates bi-phase sine wave signals S1A and S1B with a period of P1 in accordance with a displacement L to be detected. Another displacement detector 2 generates bi-phase sine wave signals S2A and S2B with a period of P2 different from the period P1 in accordance with the displacement L to be detected. Wavelength composing means 3 composes the sine wave signals S1A, S2A and the cosine wave signals S1B, S2B output from the displacement detectors 1 and 2 to generate bi-phase sine wave signals, SxA=S1A·S2B−S1B·S2A and SxB=S1B·S2B+S1A·S2A, with a period of Px equal to the least common multiple between the periods P1 and P2.

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

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

Abstract: An optical interference apparatus includes a light source, a beam splitter for splitting a light beam from said light source, a reference surface by which one split light beam from said beam splitter is reflected to propagate backward through the optical path, the light beam from said reference surface and the other split light beam which emerges from said beam splitter, is reflected by an object to be detected, and returns, being combined by said beam splitter and the combined light being finally used as interference light, and the two split light beams emerging from said beam splitter as convergent light, and an optical element having a function of converging a light beam or changing a divergent state of the light beam, said optical element being inserted in an optical path of one of the split light beams emerging from said beam splitter, and the reflected light beams from converging at said beam splitter positions of the two split light beams being combined as spherical waves with curvatures equal to each

Abstract: An optical signal transmission circuit for a probe is switched on by an optical switch-on signal comprising a burst 42 of pulses having a predetermined length. This is detected by a circuit which discriminates whether an input signal is a genuine switch-on signal or an interference burst 44, on the basis of the duration of the switch-on signal.

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: This invention relates to a method and apparatus for making absolute distance or ranging measurements using Fresnel diffraction. The invention employs a source of electromagnetic radiation having a known wavelength or wavelength distribution, which sends a beam of electromagnetic radiation through a screen at least partially opaque at the wavelength. The screen has an aperture sized so as to produce a Fresnel diffraction pattern. A portion of the beam travels through the aperture to a detector spaced some distance from the screen. The detector detects the central intensity of the beam as well as a set of intensities displaced from a center of the aperture. The distance from the source to the target can then be calculated based upon the known wavelength, aperture radius, and beam intensity.

Abstract: A measuring system for measuring the accuracy of the position and track of a machine element moved along a predetermined track. The system includes a predetermined track along which a machine element moves relative thereto and a measuring device for measuring the position of the machine element along the track. The track has a guide of the measuring device, on which a carriage is guided along the track, wherein the machine element can be fastened to the carriage. A component of the measuring device is fastened on the carriage and a drive integrated with the measuring device moves the carriage in a controlled manner along the guide into predetermined positions and at predetermined speeds.

Abstract: A position determining system (PDS)(100) or multiple parameters measurement system (MPMS)(300) particularly useful for translation and rotation measurement of objects having up to five degrees of freedom. A light source (122, 302) provides light beams (124, 304) into at least two channels. Each channel may include an interferometer (310), reflective target (110, 314), beam splitter (128, 312), detector (132, 316), and receiver (318). In concert, the detectors (132, 316) sense horizontal, vertical, and roll position and the receivers (318) sense longitudinal and yaw position change. Optionally, modulation can be imposed on the light beams (124, 304) and phase-sensitive synchronous demodulation used to enhance accuracy.

Abstract: In incremental detectors, measurement signals thereof are first corrected in graduation-specific fashion with respect to amplitude offsets, and phase displacement, and a rough angle is determined. The residual error of the rough angle is fine-corrected via rough-angle-specific, graduation-independent rough angle correction values and a position signal is determined in this way. The correction values for amplitudes offsets, and phase displacement are determined using regression, and the rough angle correction values are determined using high-precision reference angle measurements.

Abstract: A method for monitoring a device fabrication process. The method includes etching into a wafer disposed inside a chamber and detecting the intensity of a portion of a light reflected from a surface of the wafer and further scattered at a scattering inside surface of the chamber.

Abstract: A method and an apparatus are provided for contact-free optical displacement and/or vibration measurement of an object, in which the actual positions of the plurality of measurement points are selected and recorded. The display positions of the plurality of measurement points are displayed in the output unit based on a stored or video image of the object. Errors in congruency between the actual positions of the plurality of measurement points and the display positions of the plurality of measurement points are corrected.

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: A laser tracking interferometric length measuring instrument has a laser source and a tracking articulating optical lever provided on an optical path of an interferometric optical system. To track a retroreflector, the optical lever reflects a laser beam at the retroreflector, which reflects the beam back to the optical lever. This beam is reflected onto a quadrant photodiode. An attitude control means is used to control the attitude of the optical lever so that the laser beam reflected by the optical lever falls on the neutral point of the photodiode.

Abstract: An interference-type distance measuring device generates a reference beam having a first frequency and detection beam having a second frequency and directs these beams toward a moving detection unit which reflects these beams toward an interference system, where these beams are used to generate a detection interference wave. A reference interference wave generated by the interference system is converted into a first sine-wave signal, the interference detection wave is converted into a second sine-wave signal, first and second cosine-wave signals are generated from the first and second sine-wave signals, and the position of the motion detection unit is detected based upon these four signals.

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: A retroreflector has three mutually-orthogonal reflective surfaces arranged around an optical axis. The reflective surfaces stop short of the optical axis to provide a central region of the retroreflector which transmits incident light and a peripheral region of the retroreflector which retroreflects incident light. When the reflector is used in a Jamin-type interferometer with another reflector, this enables the interferometer to be used for measuring displacement between the reflectors.

Abstract: Disclosed is a position detecting method and position detecting system for measuring a position of a pattern formed on an object to be observed, for use in an exposure apparatus. The method includes providing incoherence-transformed illumination light for illuminating the pattern surface of the object by use of coherent light, and incoherence-transformed reference light, changing the quantity of the reference light in accordance with a reflection factor of the pattern surface, and imaging reflection light from the pattern surface and reference light reflected by a conjugate mirror, together, upon a photoelectric converting element, and measuring the position of the pattern on the basis of an interference image signal obtainable by the imaging.

Abstract: A stage apparatus on which a laser interferometer is mounted includes a reticle stage (1) movable in three, X-, Y-, and &thgr;-axes, laser heads (8a-8d) each for generating a laser beam, interferometers (9a-9d) each of which is mounted on the stage (1) and splits the laser beam into reference and measurement beams, bar mirrors (11a-11c) each of which is arranged outside the stage (1) and reflects the measurement beam, and detectors (10a-10c) each for detecting the interference beam of the reference and measurement beams.

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

Abstract: The present invention provides a method and apparatus for measuring both the linear displacement and angular displacement of an object using a linear interferometer system and an optical target comprising a lens, a reflective surface and a retroreflector. The lens, reflecting surface and retroreflector are specifically aligned and fixed in optical connection with one another, creating a single optical target which moves as a unit that provides multi-axis displacement information for the object with which it is associated. This displacement information is useful in many applications including machine tool control systems and laser tracker systems, among others.

Abstract: The invention features an interferometry system which includes at least one dynamic beam steering assembly for redirecting one or more beams within the interferometry system in response to changes in the angular orientation or position of the measurement object. A control circuit controls the beam steering assembly based on a signal derived from one or more beams within the interferometry system. The dynamic beam steering assembly can be incorporated into interferometry systems that measure displacement, angle, and/or dispersion. The interferometry systems can be advantageously incorporated into lithography systems used to fabricate integrated circuits and other semiconducting devices and beam writing systems used to fabricate lithography masks.

Abstract: An interferometer includes a beamsplitter for splitting a source beam into a test beam and a reference beam, an imaging device for detecting an interference pattern, a mirror disposed in a path of the test beam for reflection of the test beam toward the imaging device, a micromirror disposed in a path of the reference beam for reflection of a portion of the reference beam toward the imaging device, and a focusing mechanism disposed for focusing the reference beam on the micromirror. The micromirror has a lateral dimension not exceeding the approximate lateral dimension of a central lobe of the reference beam focused thereon by the focusing mechanism. A spatial filter for reducing effects of aberration in a beam includes a reflector disposed upon a transparent base wherein the reflector has a lateral dimension not exceeding the approximate lateral dimension of a central lobe of the spatial intensity distribution of the beam focused upon the reflector.

Abstract: An interferometer and method for performing preliminary and main measurements quickly and with high precision are provided. Laser light and white light are successively introduced to the same interferometer booth. Laser light is introduced from a laser light source, and the interference fringe with a reference mirror as a reference is detected using a CCD and a personal computer. By setting the interference fringe to a preset value, the position of a work is adjusted. White light from a halogen lamp is then introduced, a corner cube moving mount is moved, interference fringe with a reference mirror as a reference is detected, and preliminary measurement of the work is performed. Next, laser light is introduced, interference fringe with a reference mirror as a reference is detected, and the main measurement of the work is performed.

Abstract: A laser measuring method is provided, which suppress the shift or change of laser beams traveling toward an optical detector even if a displacement error (i.e., yawing and/or pitching) of an object to be measured occurs.

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

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

Abstract: An optical profiler is modified in a way which allows it to image a MEMS device at various points during the movement of the MEMS device. The light source is synchronized with a desired movement of the MEMS device. The light source produces pulse at each synchronization period. During each pulse, an interferometric measurement is carried out. So long as the pulse is short enough such that the device does not move significantly, a detection of the position of the device can be accurately obtained.

Abstract: Interferometric apparatus and method by which polarization effects and stage yaw and pitch are substantially reduced. A beam redirecting means selected from the group consisting of corner mirrors, prisms, diffractive elements, holographic elements, and combinations thereof are fixedly mounted on a body capable of rectilinear motion for movement therewith. The measurement beam path to and from the redirecting means is folded at least once so that incoming and outgoing beam segments are spatially separated and substantially parallel to one another and the reference beam.

Abstract: An interferometer includes a beamsplitter for splitting a source beam into a test beam and a reference beam, an imaging device for detecting an interference pattern, a mirror disposed in a path of the test beam for reflection of the test beam toward the imaging device, a micromirror disposed in a path of the reference beam for reflection of a portion of the reference beam toward the imaging device, and a focusing mechanism disposed for focusing the reference beam on the micromirror. The micromirror has a lateral dimension not exceeding the approximate lateral dimension of a central lobe of the reference beam focused thereon by the focusing mechanism. A spatial filter for reducing effects of aberration in a beam includes a reflector disposed upon a transparent base wherein the reflector has a lateral dimension not exceeding the approximate lateral dimension of a central lobe of the spatial intensity distribution of the beam focused upon the reflector.

Abstract: In a phase-shifting point diffraction interferometer, by sending the zeroth-order diffraction to the reference pinhole of the mask and the first-order diffraction to the test beam window of the mask, the test and reference beam intensities can be balanced and the fringe contrast improved. Additionally, using a duty cycle of the diffraction grating other than 50%, the fringe contrast can also be improved.