Abstract: An apparatus for measuring at least one parameter associated with a fluid flowing within a pipe comprises an optical measurement device and a signal processor. The optical measurement device provides output signals indicative of unsteady pressures within the fluid at two or more axial locations along the pipe in response to light reflected from an outer surface of the pipe. The signal processor provides an output signal indicative of at least one parameter associated with the fluid in response to the output signals. The optical measurement device may include, for example, an electronic speckle pattern interferometer, a Fabry-Perot device, and/or a laser vibrometer. The at least one parameter may include at least one of: density of the fluid, volumetric flow rate of the fluid, mass flow rate of the fluid, composition of the fluid, entrained air in the fluid, consistency of the fluid, size of particles in the fluid, and health of a device causing the unsteady pressures to be generated in the pipe.

Abstract: An optical system provides information about tangential vibration components of a surface at remote location. The optical system includes a light source assembly that emits first and second beams, each having one or more wavelengths and one or two polarizations. The first and second beams are directed to the interrogated surface. A detector system is positioned to detect a third beam formed by at least a portion of the first and second beams being reflected from the interrogated surface. The first, second and third beams having incident and reflection angles relative to the interrogated surface that do not lay in a same plane. The detector system positioned remotely from the interrogated surface, and providing information on a phase change in the third beam relative to the first and second beam. The phase change is indicative of at least one surface vibration vector component of the interrogated surface. The detector system is a 90 degree optical hybrid balanced detector with four photodiodes.

Abstract: A device designed to apply uniaxial pressure to the surface of an electro-active material while simultaneously applying a current to the material under controlled temperature conditions and then measuring the displacement of the material by means of a laser interferometer. The device involves a housing with a chamber in which a sample of material is secured. The chamber has an aperture with a quartz window that allows the laser beam from the interferometer to pass. The sample is connected to electrodes and the chamber is filled with dielectric oil that applies the uniaxial pressure to one side of the sample. The device is placed onto a thermal control system. When the appropriate thermal and pressure conditions are established, current is applied to the sample and the interferometer measures the displacement.

Abstract: A specialized containment cell with optically transparent apertures, in conjunction with a laser interferometer system provides the means for non-contact displacement measurements of electro-active (piezoelectric and electrostrictive) materials to be performed under controlled conditions of pressure, temperature and applied voltage. A sample of electro-active material is placed inside the cell. Electrical connections are made from a high voltage power source to the sample through the cell. Thermoelectric heaters/coolers and a cooling water heat sink built into the cell control the temperature of the sample. The cell is flooded with a dielectric oil pressurizing the interior of the cell to a desired pressure. The cell is optically aligned to the interferometer, and with the cell heated to the proper temperature, a voltage is applied to the sample as the interferometer measures the displacement of the sample.

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

Abstract: In general, in one aspect, the invention features an interferometer assembly for use in a lithography tool used for fabricating integrated circuits on a wafer, wherein the lithography tool includes a support structure and a stage for positioning the wafer relative to the support structure, the interferometer assembly including an interferometer configured to direct a measurement beam between the stage and the support structure and combine the measurement beam with another beam to form an output beam which includes a phase related to a position of the stage relative to the support structure, wherein the interferometer is mechanically secured to the lithography tool through an interferometer surface selected to cause the phase of the output beam to be insensitive to thermal changes of the interferometer over a range of temperatures.

Abstract: An method and device suitable for navigation on a wide variety of surfaces is introduced. Specular reflection is used to determine relative motion over typical surfaces. A specific application is a computer mouse.

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: An optical displacement sensor is provided, in which an optical fiber is disposed between a light source and a light receiving means so that light emitted from the light source is conducted therethrough so as to be duly received by the light receiving means whereby a beam diameter can be controlled and a uniform intensity distribution of emitted light can be ensured without providing a pinhole aperture. Also, a six-axis force sensor incorporating such an optical displacement sensor is provided.

Abstract: An optical navigation system for determining movement relative to a navigation terrain includes a first source and a second source of optical radiation for illuminating the navigation terrain, the first source differing from the second source in at least one operating parameter. The system further includes means to select the first source and the second source independently based on decision criteria. The system further includes a detector for capturing patterns in the optical radiation subsequent to illuminating of the navigation terrain.

Abstract: The present invention relates to micron-scale displacement measurement devices. A first embodiment is a device that includes a substrate and a rigid structure suspended above the substrate to form a backside cavity. Formed in the rigid structure is a reflective diffraction grating positioned 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 device also includes a membrane positioned a distance d above the reflective diffraction grating and at least a first 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 membrane.

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: A laser beam is irradiated onto a moving object, and scattered light reflected from the moving object is split into two beams, which are then received through respective spatial filters that are 90° out of phase with each other, thereby providing two signals. The signals are processed to determine the movement direction of the moving object.

Abstract: Multidirectional retroreflectors and methods of reflecting light beams from multiple directions are provided. The multidirectional retroreflectors utilize a four-mirror retroreflector with a common virtual reflection point.

Abstract: An interferometry apparatus comprises one or more beam generators, a detector, and a plurality of optical paths along which one or more beams of light propagate. Disposed along at least one of the optical paths is an apodization mask to shape one of the beams.

Abstract: A first polarizing beam splitter splits the light emitted by a light source into a measurement beam and a reference beam. The reference beam is returned by a second polarizing beam splitter and an optical member which is constituted by a right angle prism and a pentaprism, reenters the first polarizing beam splitter via a half wavelength plate and guided to a detector. On the other hand, the measurement beam is reflected by a corner mirror, is returned by the second polarizing beam splitter and the optical member, is reflected by the corner mirror again, reenters the first polarizing beam splitter via a half wavelength plate and guided to the detector. The optical member returns the measurement beam such that the measurement beam exits at the different point from the incident point and that light rays incident thereon in a state shifted from each other are returned with the shifted direction and shifted amount between each light rays kept unchanged.

Abstract: An optical profile determining apparatus includes an optical detector and an optical source. The optical source generates a transmit beam including a plurality of wavelengths, and generates a reference beam including the plurality of wavelengths. Optical elements direct the transmit beam to a target, direct a resulting reflected transmit beam back from the target to the optical detector, and combine the reference beam with the reflected transmit beam so that a profile of the target is based upon fringe contrast produced by the plurality of wavelengths in the reference beam and the plurality of wavelengths in the reflected transmit beam.

Abstract: 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 interferometer that has no moving parts and can acquire an interferogram in a single exposure is disclosed. Embodiments according to the invention can be used for polychromatic and/or monochromatic detection and include a fixed-position element that divides a beam segment into a plurality of parallel sub-beams of successively increasing path lengths. Embodiments according to the invention can be constructed from separate elements or can be combined into a one-piece device to provide increased stability and ruggedness.

Abstract: One embodiment relates to an optical displacement sensor for sensing transverse displacement of a data input device relative to a surface by determining displacement of optical features in a succession of frames. The sensor includes at least a coherent light source, illumination optics to illuminate a portion of the surface, imaging optics, and a first array of photosensitive elements having a periodic distance. The illuminator and the detector are configured to produce on the first array of photosensitive elements an intensity pattern of light reflected from the illuminated portion of the surface. The intensity pattern comprises a plurality of speckles having an average speckle diameter which is between one half and two times the periodic distance of the array.

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

Abstract: Methods and apparatus for characterizing and compensating non-cyclic errors in fiber optic pickups in interferometry systems are disclosed.

Abstract: A chuck having a high specific stiffness and high thermal conductivity compared to conventional chucks, with an apparatus for measuring thermal expansion in the chuck. High specific stiffness allows for a higher control bandwidth and improved scanning performance. High thermal conductivity enables excellent positioning accuracy because thermal expansion and strain may be accurately measured or predicted, and thus compensated.

Abstract: An optical measurement system increases the number of translational and angular measurements made with a single laser beam by combining an optical interferometer with an optical autocollimator. Translational measurements are made with an optical interferometer and yaw and pitch measurements are made with an autocollimator. In a preferred embodiment, angular deviations in the reflected measuring beam are minimized with a reverse telescopic lens assembly, allowing a wider range of angular measurements without significant degradation of interferometer accuracy.

Abstract: A system includes an optical interferometer, an interference detector, and a controller. The optical interferometer includes a measurement arm, a reference arm, and an optical splitter. The measurement arm has a probe. The arms are coupled to receive light from the optical splitter and to cause light outputted by the arms to interfere. The interference detector is coupled to receive a portion of the interfering light to determine information representative of a location, an orientation, or a velocity of a portion of the patient or animal from the received light. The controller is coupled to receive the information and to adjust data collection on the animal or patient in a manner responsive to a change in a relative location, orientation, or velocity between the probe and the portion of the animal or patient.

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: An optical component especially suited for common path heterodyne interferometry comprises a symmetric dual-periscope configuration. Each periscope is substantially identical to the other with regard to certain design aspects. The resulting design is an optical component that is highly stable with variations in temperature and angular deviations.

Abstract: A position measurement system optically measures a position of an object in a simple manner at low cost. The position measurement system includes: a light source; an optical lens with a large spherical aberration which transmits light from the light source and forms a light ring due to its spherical aberration; a light receiving device (CCD sensor) which detects the light ring as formed by the optical lens; and a calculator which measures a position of the light source according to detected information on the light ring as detected by the CCD sensor. An optical mirror with a large spherical aberration may be used instead of the optical lens.

Abstract: An interferometer has a source for generating a first beam and a second beam of a coherent monochromatic light having a wavelength ?, optical elements for directing the beams through two different optical paths having a path-length difference, a detector for detection of an interference signal of the beams, and a modulator for additionally varying the path-length difference periodically to allow the interference signal be detected near a path-length difference of ?/4 periodically. A maximum intensity change in the interference signal caused by a small period change of the path-length difference is thus detectable. The maximum intensity change caused by varying the path-length difference by at least ?/2 may also be detectable. The interferometer may be used to measure small vibrations, without pre-calibration and/or a feedback servo system for keeping the path-length difference near ?/4.

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

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: 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(?Rt+?(t)+?1), where A1 and ?1 are constants, ?R is an angular frequency difference between the two beams, and ?(t)=nk{tilde over (L)}(t), with k=2?/? and ? 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 error signal S?(t) generated from the coefficients and error basi

Abstract: Interferometric apparatus and method for measuring changes in distance to an object are compensated for the presence of undesirable phase shifts in measurement beams that result from their interacting with non-polarization preserving optical elements in at least one interferometer measurement leg. Compensation is provided by phase plates, multi-order phase plates set at a predetermined angle with respect to beam components, coatings on reflecting surfaces, or a segmented phase plate at least part of which is rotated with respect to polarized beam components, and combinations thereof. Compensation is provided in interferometers having measurement legs folded with reflecting surfaces that cause relative phase shifts in propagating polarized beams because of non-normal incidence. Compensation is also provided in upward and downward looking interferometers for measuring altitude and changes in altitude to a surface such as a translating wafer stage of a photolithographic exposure apparatus.

Abstract: A method for determining relative movement between an optical navigation device and a navigation terrain includes generating two overlapping coherent optical beams, and generating a pattern of interference fringes between the two overlapping optical beams. The method further includes illuminating a surface portion of the navigation terrain with the pattern of interference fringes, imaging a fringe-illuminated surface portion, and generating a pattern of signals in response to the imaged fringe-illuminated surface portion.

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: In one aspect, the invention features an angle-measuring interferometry system that includes an interferometer which during operation directs a measurement beam to contact a measurement object, the interferometer comprising a beam steering assembly having a beam steering element positioned to contact and direct the measurement beam and an electronic positioning system to selectively orient the beam steering element within the interferometer. The angle-measuring interferometry system also includes an angle measurement system which during operation calculates a change in angular orientation of the measurement object based on a measurement signal derived from the measurement beam, wherein the measurement signal is derived from at least one interferometric signal produced by combining at least a portion of the measurement beam with a second beam after the measurement beam contacts the measurement object.

Abstract: A multiple degree-of-freedom ultra-precision (DOF) robotic system yielding either rigid body guidance or large deformation analysis (LDRS, i.e. semi-flexible and flexible robotics) is developed based on the technology of integrating a multiple DOF ultra-precision shadow robotic measurement system with a multiple DOF robot for form a closed-loop linkage chain to establish a corresponding closed-loop feedback control of end-effecter of said robotic system without the use and limitation of any target or artificial marker in work-cell as the reference. In this way, the major degrading problems that greatly drag down the positioning accuracy of a robot have been fairly resolved. The embodiment conducts the details of the development of such a multiple DOF ultra-precision robotic system for the general applications in precision engineering.

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 multi-axis interferometer includes a multiplexer portion and a beam splitter portion integrated into the same optically transmissive monolith. The multiplexer portion is configured to split an input beam into a corresponding plurality of intermediate beams, each of which is directed toward the beam splitter portion through a corresponding output port of the multiplexer portion. The beam splitter portion is configured to separate the intermediate beam into a measurement component and a reference component.

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: 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: In one embodiment, a method of and apparatus for self-calibrating a motion control system is provided. The method includes the steps of receiving a test parameter, ensuring a reasonable test can be executed based on the test parameter, generating a part program based upon the test parameter, instructing a user of the motion control system regarding set up of a device capable of acquiring data associated with the test, and executing the test, wherein the part program is executed as part of the test.

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: A device for the non-contacting measurement of an object to be measured, particularly for distance and/or vibration measurement, has at least one laser light source, optical devices for splitting the light into object light (4) and reference light (5) for interacting with the object to be measured and for superimposing object light and reference light following the interaction of the object light with the object to be measured, preferably a frequency shift device in the form of a Bragg cell for producing a frequency shift between the object light and the reference light and a detecting device (15) for converting reference light and object light into electrical signals suitable for further processing. The detecting device has at least two series-connected optoelectronic transducers in the form of photodiodes (30, 31). Between the transducers is located a tap (32) for tapping a difference signal which, for further processing, is supplied to a transimpedance circuit (33) associated with one of the transducers.

Abstract: The present invention relates to an inspection apparatus for tires having a positioning device for the tire to be inspected and a laser inspection device. In accordance with the invention, the inspection device comprises several measuring heads, in particular laser measuring heads in order to reduce the inspection time. In accordance with one aspect of the invention, several observation units and associated lighting sources are integrated in each measuring head.

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: In general, in one aspect, the invention features a method, including interferometrically measuring first and second optical path lengths to a measurement object along respective first and second paths, wherein the measurement of the optical path lengths includes directing first and second measurement beams to reflect from the measurement object, measuring propagation directions of the first and second measurement beams, compensating the first measured optical path length for time-varying optical properties of gas in the first path based on the first and second measured optical path lengths and the first and second measured propagation directions.

Abstract: An apparatus for optically detecting rotational position information of a rotating object, includes a light source, a detector which is located at a position to receive scattered light from the rotating object when the rotating object is irradiated with a light beam from the light source, and outputs a frequency signal based on the scattered light, a signal processing system for detecting rotational position information by performing signal processing for the frequency signal from the detector, and a rotation control system for controlling rotation of the rotating object. The rotation control system preliminarily rotates the rotating object in detecting the rotational position information.

Abstract: A z-movement detector utilises an optical interferometer with a laser diode as a light source (301) and an optical interference detector (302) which detects changes in the speckle pattern of the light from the laser as a result of movements of a target (307) in the z-direction. Key element of the interferometer is the use of a single block of glass (318) which physically integrates the beam splitting functions and some of the reflection functions of the interferometer.

Abstract: An optical navigation device for determining movement relative to an object includes a source of optical radiation for illuminating the object, and a detector for capturing phase patterns in the optical radiation returning from the object. The phase patterns are correlated with optical nonuniformities of the object. A system is provided for controlling a positional pointer on a computer screen using a mouse to detect movement relative to an object. The system creates interferograms, each such interferogram being unique to a portion of the object over which the mouse moves, and converts successive pairs of unique interferograms into signals corresponding to relative movement between the mouse and the object. The source of optical radiation may be selected from a list including diode emitters, LEDs, multimode vertical-cavity surface-emitting lasers (VCSELs), laser diodes, and white light.