Abstract: The present invention relates to a interferometric measuring device for measuring the shape especially of rough surfaces of a measured object (O), having a radiation-producing unit (SLD) emitting short-coherent radiation, a beam splitter (ST1) for forming a first and a second beam component (T1, T2), of which the first is directed via an object light path to the measured object (O), and the second is directed via a reference light path to a reflecting reference plane (RSP), having a superposition element at which the radiation coming from the measured object (O) and the reference plane (RSP) are brought to superposition, and an image converter (BS), which receives the superposed radiation and sends corresponding signals to a device for evaluation, for the measurement to be taken, the optical path length of the object light path being changed relative to the optical path length of the reference light path.

Abstract: A lens evaluation method includes diffracting light derived from a lens so that two diffracted rays of different orders (e.g., a 0th-order diffracted ray and a +1st-order diffracted ray) interfere with each other, thereby obtaining a shearing interference figure, and changing phases of the diffracted rays. The method also includes in the shearing interference figure, determining phases of light intensity changes at a plurality of measuring points on a measuring line which passes through a midpoint of a line segment interconnecting optical axes of the two diffracted rays, and determining characteristics (defocus amount, coma, astigmatism, spherical aberration and a higher-order aberration) of the lens based on the phases.

Abstract: A device for the inspection of one or more movable surfaces (8), more in particular for the inspection of a rotating surface (8) of a wafer, which device includes at least one light source (1), notably a laser light source, and a beam splitter (4) for splitting a light beam that is emitted by said laser light source into at least one reference beam (6) that is applied to a detector (16) and at least one measuring beam (5) that is applied to the surface (surfaces) and contains at least one component in the direction of movement (U) of the respective surface or in the opposite direction, the light (15) that is reflected by the surface (8) having, upon detection of a defect (14), a frequency (&ugr;′) that has been shifted relative to the measuring beam (5) and on which the reference beam (6) can be superposed.

Abstract: The invention features an interferometry method including: directing two beams derived from a common source along different paths; producing a first output beam derived from a first portion of each of the two beams; producing a second output beam derived from a second portion of each of the two beams; and calculating a product of a first signal derived from the first output beam and a second signal derived from the second output beam.

Abstract: A multi-axis interferometer uses a combined beam for a first pass through the interferometer optics. Measurement and reference components of the combined beam that exit the interferometer optics are subject to walk-off that measurement or reference reflector misalignment can cause. A return reflector and non-polarizing beam splitter system split the combined beam into separated input beams for the various axes of the interferometer and return the separated beams for respective second passes through the interferometer optics. Walk-off for the separated beams in the interferometer optics cancels the walk-off for the combined beam to eliminate beam walk-off in separated output beams. Sharing a combined beam for a first pass through the interferometer optics reduces the sizes required for the interferometer optics and reference and measurement mirrors. The multi-axis interferometer may have a single return reflector.

Abstract: An optical recording and/or reproduction apparatus includes: a light source for emitting a first light beam; an optical system for outputting first and second diffracted light beams and a second light beam; and a controlling section for controlling the optical system, wherein the first and second diffracted light beams interfere with each other to generate interference fringes which extend in a direction substantially perpendicular to a recording layer of an recording medium, the optical recording and/or reproduction apparatus further includes a detection section for detecting the interference fringes reflected by the guiding portion so as to output a detection signal, and the control section controls the optical system based on the detection signal such that the optical spots follow at least either of concave portions and convex portions of the guiding portion.

Abstract: An interoferometric fiber optic sensing system uses three optical fibers. A sensing optical fiber is applied to a structure to be monitored to detect displacement or the like by changing its optical path length. A reference optical fiber has a fixed optical path length. An adjustable length optical fiber is controllably adjusted in its optical path length. The three optical fibers form optical paths whose light outputs are caused to interfere. The adjustable length optical fiber is adjusted until an interference fringe appears. The quantity to be detected is derived from the maximum of the interference fringe. Several sensing optical fibers can be multiplexed; by staggering their optical path lengths, their interference fringes can be separated sufficiently to resolve them.

Abstract: Interferometric apparatus and methods for reducing the effects of coherent artifacts in interferometers. Fringe contrast in interferograms is preserved while coherent artifacts that would otherwise be present in the interferogram because of coherent superposition of unwanted radiation generated in the interferometer are suppressed. Use is made of illumination and interferogrammetric imaging architectures that generate individual interferograms of the selected characteristics of a test surface from the perspective of different off-axis locations of illumination in an interferometer and then combine them to preserve fringe contrast while at the same time arranging for artifacts to exist at different field locations so that their contribution in the combined interferogram is diluted.

Abstract: A test media in the form of a disk for use in an apparatus for performing interferometric measurement/testing of fly heights of read-write head sliders, the disk having a central opening for use with a spindle for rotation about a central axis, comprising: a disk-shaped substrate comprised of a light transmissive material and including a pair of opposed, smooth, major surfaces; an optical underlayer in contact with one major surface; and a wear-resistant, protective overcoat layer on the optical underlayer for improving the tribological properties of the media; wherein the thickness of the optical underlayer is selected for enhancing the sensitivity of testing by increasing the intensity of reflected light of pre-selected wavelength received by a detector for fly heights within a pre-selected fly height region-of-interest.

Abstract: A Wollaston prism phase-stepping point diffraction interferometer for testing a test optic. The Wollaston prism shears light into reference and signal beams, and provides phase stepping at increased accuracy by translating the Wollaston prism in a lateral direction with respect to the optical path. The reference beam produced by the Wollaston prism is directed through a pinhole of a diaphragm to produce a perfect spherical reference wave. The spherical reference wave is recombined with the signal beam to produce an interference fringe pattern of greater accuracy.

Abstract: This invention provides a method and an optical system for sensing and controlling the frequency for a laser with respect to an optical cavity and for sensing and controlling the length difference of interferometer paths in a two beam interferometer. A misalignment is introduced in the incident laser radiation to produce a fundamental mode (TEM00) in the cavity or interferometer and the reflection of a least one higher order mode (TEM01). A split photodetector (10) allows the interference between these two modes to be measured separately by detecting two spatially distinct portions of the single reflected beam. An error signal indicative of the difference between the fundamental mode frequency and the cavity resonant frequency is obtained by substracting the outputs from the two parts of the photodetector.

Abstract: Apparatus and methodology by which the radius of curvature of individual optics may be determined through the interferometric measurement of the optical length of a spherical cavity established from null tests of combinations of the individual optics and an algorithm that mutually intercompares the measured cavity lengths and radii of curvature of the individual optics.

Abstract: A method or apparatus for measuring lateral variations of a property such as thickness or refractive index of a transparent film on a semiconductor, in a region of repeated patterning comprises: illuminating over the patterned area with a beam of light of multiple wavelengths, the beam having dimensions to include repeated patterning; detecting the intensity of light reflected over the patterned area for each wavelength; producing a signal defining the variation of the intensity of the detected light as a function of the wavelength of the detected light; decomposing the signal into principal frequencies thereof, determining from the principal frequencies, values of the thickness etc. of the transparent film; and applying the values to repetitions within the repeated patterning.

Abstract: A fiber optic gyroscope (FOG) including a depolarizer having substantially equal first and second fiber segments of polarization maintaining (PM) fiber coupled to a single mode (SM) fiber loop. The first PM fiber segment includes sections of fiber connected together via a splice having an angle from about 35° to 55° between major axes of polarization of the sections which it connects. Similarly, the second PM fiber segment includes sections of fiber connected together via a splice having an angle from about 35° to 55° between major axes of polarization of the sections which it connects. The length of each fiber section is chosen to maintain the thermal and mechanical symmetry of the SM fiber loop.

Abstract: An apparatus and method to measure optical intensity and phase of one or several light pulses is described. The apparatus combines a spectrally resolved interferometric asymmetric single-shot optical autocorrelator and imaging spectrograph. The asymmetric design of the optical autocorrelator based on second harmonic generation eliminates time-direction ambiguity, while a spectrally resolved interferometric pattern allows the performance of self-check and self-calibration of the apparatus and substantially improves convergence, robustness and reliability of the computational retrieval algorithm.

Abstract: The invention relates to a method for measuring a required feature of a thin layer (4) used in a polishing process that is carried out by a polish head by producing a localized temperature rise on the surface of the layer (4) by focusing a short pump laser pulse (11) on the surface of the layer, as to generate a sound wave (13) that propagates into the layer; repeated measuring the surface reflection properties of the layer, by passing a probe laser pulse (21) and focusing it on the surface of the layer and by monitoring the portion of the probe laser pulse that is reflected (22) by the surface, as to detect a change in surface reflection properties caused by a boundary echo (32) that is a reflected part of the sound wave (13); measuring the elapsed time between the generation of the sound wave and the change in surface reflection properties; and calculating the required layer feature. Furthermore the invention relates to a measuring apparatus, which is able to perform the above-mentioned method.

Abstract: A fiber optic fault detector and generic fiber optic sensor system for detecting breaks in an optical fiber using a low coherence interferometric technique. The system comprises a light source configured to produce light traveling along the optical path, a modulator optically coupled to the light source configured to modulate at least a portion of the light as a function of a modulation signal, a detector optically coupled to the modulator configured to produce a detector output based upon a sensed intensity of the light, and an electronic array configured to receive the detector output and determine the optical fault. The low coherence interferometric technique allows for detection of a fault in the fiber with a minimal amount of test equipment and with higher measurement sensitivity and resolution. The system may alternatively include a transducer, positioned in place of the fiber under test, having a response which changes in reflective or optical path length.

Abstract: A phase difference calculation method, a device (34), and a system (38) are disclosed. In an optical fiber ring interference sensor (37) using a 3×3 optical splitting coupler (30) and an optical splitting coupler (12), linear sections are determined in advance, where a relationship between a phase difference &thgr; of propagation lights and an intensity Ppdn (n=1, 2, 3) outputted from each photo detector (15-1, 15-2, 15-3) becomes approximately linear. The intensity Ppdn of an interference light, between propagation lights in CW and CCW directions in an optical fiber loop (13), having a difference non-reciprocal phase bias is measured not less than two times. A phase difference &thgr; is then calculated based on the intensity Ppdn in the linear sections.

Abstract: A wavelength-determining unit for determining the wavelengths of a plurality of successive optical signals &lgr;(t) includes a wavemeter unit for determining first wavelength values &lgr;1(t) for the optical signals &lgr;(t). An absolute-measuring unit having unambiguous wavelength properties at known absolute wavelength values determines second wavelength values &lgr;2(t) as such of the known absolute wavelength values covered by the optical signals &lgr;(t). An evaluation unit receives the determined first &lgr;1(t) and second &lgr;2(t) wavelength values and provides forcorrected wavelength values &lgr;1′(t) based on a comparison of the determined first &lgr;1(t) and second &lgr;2(t) wavelength values.

Abstract: Interferometric apparatus and methodology for monitoring the relative motion among objects, preferably that of mask and wafer stages in photolithographic processes. The apparatus comprises a plurality of interferometers with each operating to provide a mixed optical interference signal containing phase information indicative of the motion of a corresponding object. Electrical interference signals are generated from the optical interference signals, and one of these is modified to compensate for any Doppler shift differences among the electrical interference signals caused by differences in preferred relative rates of motion in the objects. A mixer receives the electrical interference signals and the modified electrical interference signal and generates an output electrical interference signal containing information about the relative motion between objects.