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Showing papers on "Interferometry published in 1989"


Journal ArticleDOI
TL;DR: In this article, a technique based on synthetic aperture radar (SAR) interferometry is described, which uses SAR images for measuring very small (1 cm or less) surface motions with good resolution (10 m) over swaths of up to 50 km.
Abstract: A technique is described, based on synthetic aperture radar (SAR) interferometry, which uses SAR images for measuring very small (1 cm or less) surface motions with good resolution (10 m) over swaths of up to 50 km. The method was applied to a Seasat data set of an imaging site in Imperial Valley, California, where motion effects were observed that were identified with movements due to the expansion of water-absorbing clays. The technique can be used for accurate measurements of many geophysical phenomena, including swelling and buckling in fault zones, residual displacements from seismic events, and prevolcanic swelling.

1,325 citations


Journal ArticleDOI
TL;DR: In this article, a high-sensitivity fiber-optic displacement sensor for atomic force microscopy is described based on the optical interference occurring in the micron-sized cavity formed between the cleaved end of a singlemode optical fiber and the microscope cantilever.
Abstract: A high‐sensitivity fiber‐optic displacement sensor for atomic force microscopy is described. The sensor is based on the optical interference occurring in the micron‐sized cavity formed between the cleaved end of a single‐mode optical fiber and the microscope cantilever. As a result of using a diode laser light source and all‐fiber construction, the sensor is compact, mechanically robust, and exhibits good low‐frequency noise behavior. Peak‐to‐peak noise in a dc to 1 kHz bandwidth is less than 0.1 A. Images are presented demonstrating atomic resolution of graphite and magnetic force imaging of bits written on a magnetic disk.

634 citations


Book ChapterDOI
TL;DR: In this paper, the authors discuss the theoretical and applicational aspects of the self-imaging phenomenon, that is, the property of the Fresnel diffraction field of some objects illuminated by a spatially coherent light beam.
Abstract: Publisher Summary This chapter describes the self-imaging phenomenon and its applications. The self-imaging phenomenon requires a highly spatially coherent illumination. It disappears when the lateral dimensions of the light source are increased. When the source is made spatially periodic and is placed at the proper distance in front of the periodic structure, a fringe pattern is formed in the space behind the structure. The chapter discusses the theoretical and applicational aspects of the self-imaging phenomenon—that is, the property of the Fresnel diffraction field of some objects illuminated by a spatially coherent light beam. The applications of self-imaging are summarized in four main groups—namely, (1) image processing and synthesis, (2) technology of optical elements, (3) optical testing, and (4) optical metrology. The chapter describes the double diffraction systems using spatially incoherent illumination. The first periodic structure plays the role of a periodic source composed of a multiple of mutually incoherent slits. Depending on whether the periods of two periodic structures are equal, the Lau or the generalized Lau effect is discussed. Various applications of incoherent double-grating systems are described in the fields of optical testing, image processing, and optical metrology. After examining some cases of coherent and incoherent illumination, the general issue of spatial periodicities of optical fields and its relevance to the replication of partially coherent fields in space is discussed.

457 citations


Journal ArticleDOI
TL;DR: In this article, the interaction geometry comprising four travelling laser waves which is used to obtain optical Ramsey fringes in atomic spectroscopy, is also well suited to build an atom interferometer based on the atomic recoil.

446 citations


Journal ArticleDOI
TL;DR: An experiment is described in which the step size of a stepper-motor-driven translation stage was measured by recording the spectrum of light output from an interferometer and performing a cross-correlation calculation with theoretical spectra.
Abstract: A technique is presented for measuring small displacements by observing the frequency of spectral modulation of white light in a Michelson interferometer. An experiment is described in which the step size of a stepper-motor-driven translation stage was measured by recording the spectrum of light output from an interferometer and performing a cross-correlation calculation with theoretical spectra. Measurements made using standard laboratory-quality optical equipment were accurate to within ~10 nm for a range of over 100 microm.

255 citations


Journal ArticleDOI
TL;DR: In this paper, a polarizing optical interferometer was developed for force microscopy, where the deflection of the force-sensing cantilever is measured by means of the phase shift of two orthogonally polarized light beams.
Abstract: We present a polarizing optical interferometer especially developed for force microscopy. The deflections of the force‐sensing cantilever are measured by means of the phase shift of two orthogonally polarized light beams, both reflected off the cantilever. This arrangement minimizes perturbations arising from fluctuations of the optical path length. Since the measured quantity is normalized versus the reflected intensity, the system is less sensitive to intensity fluctuations of the light source. The device is especially well suited to static force measurements. The total rms noise measured is ≲0.01 A in a frequency range from 1 Hz to 20 kHz.

200 citations


Journal ArticleDOI
TL;DR: This work demonstrates the potential of solitons as the natural bits in ultrafast optical processing by observing switching of 93% of the total reflected energy in a partially transmitting integrated fiber loop mirror that makes up the interferometer.
Abstract: We demonstrate, for the first time to our knowledge, the switching of optical solitons. We observe switching of 93% of the total reflected energy in a partially transmitting integrated fiber loop mirror that makes up the interferometer. This result demonstrates the potential of solitons as the natural bits in ultrafast optical processing.

193 citations


Journal ArticleDOI
TL;DR: In this article, the fundamental ideas of the recently opened field of two-particle interferometry, which employs spatially separated, quantum mechanically entangled twoparticle states, are discussed.
Abstract: An exposition is given of the fundamental ideas of the recently opened field of two-particle interferometry, which employs spatially separated, quantum mechanically entangled two-particle states. These ideas are illustrated by a realizable arrangement, in which four beams are selected from the output of a laser-pumped down-converting crystal, with two beams interferometrically combined at one locus and two at another. When phase shifters are placed in these beams, the coincident count rates at the two loci will oscillate as the phases are varied, but the single count rates will not.

187 citations


Journal ArticleDOI
TL;DR: In this paper, a sinusoidal grating structure is projected onto a diffuse three-dimensional surface, and the resulting deformed grating image is detected by a solid state array camera and processed by a microcomputer using interferometric phase measuring algorithms.

183 citations


Patent
15 Jun 1989
TL;DR: In this paper, a modulatable birefringent optical element is employed to divide a polarized light beam into two components, thereby producing a phase difference in two resulting light beams such that the two beams can be made to interfere with one another when recombined, the interference pattern providing the wavelength information required for the analysis of the incident light.
Abstract: An apparatus and method simultaneously measures a plurality of spectral wavelengths present in electromagnetic radiation. A modulatable birefringent optical element is employed to divide a polarized light beam into two components, thereby producing a phase difference in two resulting light beams such that the two beams can be made to interfere with one another when recombined, the interference pattern providing the wavelength information required for the analysis of the incident light. The interferometer thus created performs in a similar manner to a Michelson interferometer, but with no moving parts, and with a resolution dependent on the degree of phase shift introduced by the modulator.

146 citations


Journal ArticleDOI
TL;DR: In this paper, the authors consider fiber-optic interferometric sensors with a short coherence length and find that the minimum detectable phase is limited by the noise associated with incoherent interference.
Abstract: If a number of fiber-optic interferometric sensors are arranged so that their outputs are returned to the user via a common optical bus, then some method of distinguishing the returns from different sensors must be used to recover individual signals. One such method involves using light with a short coherence length, so that returns from different sensors will be mutually incoherent. The interferometric signal associated with each sensor can then be recovered via appropriate optical processing. The author considers sensors multiplexed using this technique and calculates their noise performance. It is found that for systems with only a few sensors, the minimum detectable phase is limited by the noise associated with incoherent interference; this can be minimized by using light with as short a coherence length as is practical. The maximum number of sensors that can be multiplexed is limited by optical power loss. A ladder topology is tentatively found to give the best performance. >

Journal ArticleDOI
TL;DR: Pion interferometry can provide a clear signal for the formation of high-density, moderate-pressure matter in ultrarelativistic collisions as discussed by the authors, which is shown by numerical simulations of various scenarios of the high density dynamics.

Journal ArticleDOI
TL;DR: An experiment to calibrate the effects of numerical aperture on objectives with good agreement with a theory developed by Ingelstam is described using four traceable step height standards and a computer-controlled interferometric optical profiler utilizing phase-measurement interferometry techniques.
Abstract: The numerical aperture (N.A.) of a microscope objective can affect the measurement of surface profiles. Large N.A. objectives measure smaller heights than the actual values. An experiment to calibrate these effects on objectives with N.A.s of 0.1–0.95 is described using four traceable step height standards and a computer-controlled interferometric optical profiler utilizing phase-measurement interferometry techniques. The measured N.A. scaling factors have good agreement with a theory developed by Ingelstam. N.A. scaling factors are determined to an uncertainty of ± 1% for N.A.s ≤0.5 and ± 2% for N.A.s ≥0.9.

Journal ArticleDOI
TL;DR: In this article, a multichannel far-infrared interferometer used on the Joint European Torus (JET) is described, with emphasis on features necessitated by remote handling requirements, fluctuations in atmospheric humidity, and unmanned automatic operation.
Abstract: A multichannel far‐infrared interferometer used on the Joint European Torus (JET) is described. The light source is a 195‐μm DCN laser. The instrument is of the Mach–Zehnder type, with a heterodyne detection system. The modulation frequency (100 kHz) is produced by diffraction from a rotating grating. There are six vertical and two oblique channels. The latter rely on retroreflection from mirrors mounted on the vessel wall. Their vibration is compensated by a second wavelength interferometer at 118.8 μm. The various subsystems are described, with emphasis on features necessitated by (a) large path lengths, (b) remote handling requirements, (c) fluctuations in atmospheric humidity, and (d) unmanned automatic operation. Typical measurements, along with real‐time and off‐line data analysis, are presented. The phase‐shift measurement is made with an accuracy of (1)/(20) of a fringe, corresponding to a line‐integrated electron density of 5×1017 m−2. Comparison with other electron density diagnostics are shown. The introduction of additional optics allows measurements of the Faraday effect and a determination of the poloidal magnetic field distribution. The signal processing and data analysis are described. Errors introduced by the calibration procedure, birefringence of the probing beams, toroidal field pickup, the flux geometry, and the density profile are considered. The Faraday angle is measured with an accuracy of 5% and a time resolution of 1–10 ms. The poloidal magnetic field is deduced with an accuracy of ±15%.

Journal ArticleDOI
TL;DR: The authors review noncoherent, frequency-tunable filter (receiver) technologies and describes three basic mechanisms of wavelength filtering: filters based on the wavelength dependence of interferometric phenomena, with emphasis on Fabry-Perot interferometer filters.
Abstract: The authors review noncoherent, frequency-tunable filter (receiver) technologies. They describe three basic mechanisms of wavelength filtering: filters that are based on the wavelength dependence of interferometric phenomena, with emphasis on Fabry-Perot interferometer filters; filters that are based on the wavelength dependence of coupling between optical fields (modes) induced by external perturbations (both acoustooptic and electrooptic filters are described); and filters that are based on resonant amplification of optical signals in semiconductor laser diode devices (these devices provide gain in addition to wavelength selectivity). For each technology the authors explain briefly the principles of operation and quantify the relevant system parameters: tuning range, channel separation, number of channels, crosstalk isolation, gain and distortion, speed of wavelength tuning, and complexity. They present a unified picture of filtering mechanisms in an appendix. >

Patent
24 Jan 1989
TL;DR: In this paper, the effect of variation in the birefringence in a bire-fringent optic fiber as a function of temperature was investigated using a Michelson interferometer, capable of being swept, associated with a detector.
Abstract: A multiple-point temperature sensor, with optic fibers, uses the effect of variation in the birefringence in a birefringent optic fiber as a function of temperature. This sensor has a plane polarized, wide spectrum source coupled to a monomode optic fiber for preservation of polarization, along one of the neutral axes, with weak coupling points distributed along this fiber. A polarizer at 45° to the neutral axes of the fiber is placed at the output of this sensing fiber. The output radiation is analyzed by spectroscopy, for example in a Michelson interferometer, capable of being swept, associated with a detector. The interferometer shifts needed to detect the extreme values of the transmission function are measurements of temperature deviations.

Journal ArticleDOI
TL;DR: A reflectively monitored optical-fiber Fabry-Perot interferometer was embedded in a graphite-epoxy composite material and its performance as a temperature sensor was demonstrated from 20 to 200 degrees C.
Abstract: A reflectively monitored optical-fiber Fabry-Perot interferometer was embedded in a graphite-epoxy composite material. Its performance as a temperature sensor was demonstrated from 20 to 200 degrees C. The change in relative phase shift with temperature, Deltao/oDeltaT, was measured to be 8.0 x 10(-6)/ degrees C for this embedded sensor. This value is 4% lower than for one employing a similar fiber in an air ambient. A thermal expansion coefficient for the composite material in the direction of the fiber axis is estimated from these data to be 2.1 x 10(-7)/ degrees C.

Journal ArticleDOI
TL;DR: It is shown that ``which-path'' (particle) information rules out interference (wave) effects due to the system-detector correlations and not due to a randomization of phase.
Abstract: We propose and analyze experiments designed to probe the way in which the measurement process (the presence of a detector) influences the investigated system. These experiments are based on the fact that number states of the radiation field can be generated by the use of the micromaser and cavity quantum electrodynamics. It is shown that ``which-path'' (particle) information rules out interference (wave) effects due to the system-detector correlations and not due to a randomization of phase. Specific experiments based on neutron interferometry and quantum-beat techniques taken together with the micromaser are suggested and analyzed.

Journal ArticleDOI
TL;DR: In this paper, a double beam laser interferometer is built up to study high-frequency piezoelectric and electrostrictive strains, which is capable of resolving a displacement of 10−2 A using lock-in detection and measuring the strain all the way to the resonance frequencies using a digital oscilloscope for detection.
Abstract: A double beam laser interferometer is built up to study high‐frequency piezoelectric and electrostrictive strains. The system is capable of resolving a displacement of 10−2 A using lock‐in detection and measuring the strain all the way to the piezoelectric resonance frequencies using a digital oscilloscope for detection. The interference of sample bending to the detected signal is effectively avoided.

Journal ArticleDOI
TL;DR: In this article, the power spectrum of the photocurrent resulting from two uncorrelated optical beams mixing on a photodetector is derived and a general rigorous theory of optical heterodyne and homodyne measurements is presented.
Abstract: A general rigorous theory of optical heterodyne and homodyne measurements is presented. The power spectrum of the photocurrent resulting from two uncorrelated optical beams mixing on a photodetector is derived. In particular, a rigorous analysis is presented for the delayed self-homodyne method which is used to characterize laser source linewidth by a Mach-Zehnder interferometer with a delay exceeding the source coherence length. Existing treatments are generalized to address non-Lorentzian laser sources of arbitrary lineshape. The analysis is further generalized to cover the case of modulated nonstationary sources. An example of the application of this theory is given. It is shown how the theory may be used to interpret an experimental result obtained using the gated delayed self-homodyne technique for characterizing the frequency chirp of laser sources under modulation. >

Journal ArticleDOI
TL;DR: In this paper, the simple optical nonpolarization heterodyne interferometer is tested experimentally to understand and reduce fringe distortion, achieving an accuracy of 0.1 nm for the 633-nm He-Ne laser interFERometer.
Abstract: Heterodyne laser interferometry and its accuracy at subnanometer levels are discussed. The simplest optical nonpolarization heterodyne interferometer is tested experimentally to understand and reduce fringe distortion. An accuracy of 0.1 nm for the 633-nm He-Ne laser interferometer is achieved. >

Journal ArticleDOI
TL;DR: A novel accelerometer in which the sensing element is a weighted diaphragm that is measured using a miniature hemispherical air-spaced Fabry-Perot interferometer, of which one mirror is mounted on the diphragm.
Abstract: We describe a novel accelerometer in which the sensing element is a weighted diaphragm. The displacement of the diaphragm produced by acceleration is measured using a miniature hemispherical air-spaced Fabry-Perot interferometer, of which one mirror is mounted on the diaphragm. The interferometer is illuminated by a diode laser and addressed through a monomode optical fiber.

Journal ArticleDOI
TL;DR: A new technique that provides linear measurement of dynamic phase change in a no-feedback, no-phase-bias fiber-optic interferometer is described and is unaffected by random changes in phase, source intensity, and fringe visibility.
Abstract: A new technique that provides linear measurement of dynamic phase change in a no-feedback, no-phase-bias fiberoptic interferometer is described. The phase measurement is unaffected by random changes in phase, source intensity, and fringe visibility. A minimum detectable phase shift of 0.1 rad has been measured for the configuration reported.

Proceedings ArticleDOI
29 Jan 1989
TL;DR: A long-trace optical profiling instrument is now in operation at Brookhaven National Laboratory measuring surface figure and macro-roughness on large optical components, principally long cylindrical mirrors for use in synchrotron radiation beam lines as discussed by the authors.
Abstract: A new long-trace optical profiling instrument is now in operation at Brookhaven National Laboratory measuring surface figure and macro-roughness on large optical components, principally long cylindrical mirrors for use in synchrotron radiation beam lines. The non-contact measurement technique is based upon a pencil-beam interferometer system. The optical head is mounted on a linear air bearing slide and has a free travel range of nearly one meter. We are able to sample surface spatial periods between 1 mm (the laser beam diameter) and 1 m. The input slope data is converted to surface height by a Fourier filtering technique which distributes the random noise error contributions evenly over the entire trace length. A number of optical components have been measured with the instrument. Results are presented for fused silica cylinders 900 mm and 600 mm in length and for a fused silica toroid and several electroless nickel-plated paraboloids. 9 refs., 8 figs.

Journal ArticleDOI
TL;DR: A novel fiber-optic humidity sensor is described, based on reversible sorption of water from the ambient atmosphere in a porous thin-film interferometer that sits on the tip of a fiber.
Abstract: A novel fiber-optic humidity sensor is described. It is based on reversible sorption of water from the ambient atmosphere in a porous thin-film interferometer that sits on the tip of a fiber. The sorbed water changes the refractive index of the thin films and thus the reflectivity of the interferometer; the resulting modulation of the reflected intensity is detected. The sensor is insensitive to electromagnetic interference and aggressive chemicals and is extremely small (micrometers).

Journal ArticleDOI
TL;DR: In this paper, a Michelson interferometer is used as a temporal reference level to map contour lines of equal propagation time on the plane pulse front surface, and the measured value of pulse-front distortion in a telescope (1.1 psec) is in good agreement with the calculated data.
Abstract: The pulse-front distortion occurring in lenses and lens systems has been measured by a Michelson interferometer. In this technique the plane pulse front from one arm of the interferometer is used as a temporal reference level to map contour lines of equal propagation time on the pulse-front surface. The experimental arrangement is capable of detecting pulse-front distortion with a resolution of 20 fsec, and this can be improved to approximately 1 fsec. The measured value of pulse-front distortion in a telescope (1.1 psec) is in good agreement with the calculated data.

BookDOI
01 Jan 1989
TL;DR: In this paper, an overview of phase closure imaging methods for high-angular resolution optical interferometry is presented, including the Papa Detector and the Knox-Thompson Algorithm.
Abstract: I: Basic principles.- to Fourier Optics and Coherence.- Optical Propagation and Image Formation Through the Turbulent Atmosphere.- Radio Telescopes: Basic Concepts.- Continuously Movable Telescopes for Optical Interferometry.- II: Module and phase estimation, image reconstruction.- Amplitude Estimation from Speckle Interferometry.- Notes on Noise Calibration of Speckle Imagery.- Amplitude Estimation from Diluted Array Interferometry.- First Order Imaging Methods: An Introduction.- Speckle Imaging with the Papa Detector and the Knox-Thompson Algorithm.- Phase Closure Imaging - Theory & Practice.- Speckle Masking, Speckle Spectroscopy, and Optical Aperture Synthesis.- Merits of Phase Restoration Methods.- Pupil-Plane Interferometry.- Real-Time Wavefront Sensing and Adaptive Optics.- Differential Interferometry.- Image Restoration.- Deconvolution Ancient and (Very) Modern.- III: Scientific and technical prospects.- Astrophysical Programs for High Angular Resolution Optical Interferometry.- Frontiers of Interferometry.- Perspectives in Optical Interferometry.- IV: Contributed seminars and posters.- Cophasing Telescope Arrays.- Some Thoughts on the Combination of Beams in Interferometers Using Telescopes of Unequal Size.- Real-Time Image Sharpening.- Scasis, Diffraction-Limited Imaging Using a Redundant Pupil Plane-Interferometer.- Aperture Synthesis in Space: Overview and Results from the Esa Study Group.- Estimation and Reconstruction from Aberrated Amplitude Interferometer Measurements.- Lunar Occultations or Milliarcsecond Resolution and Their Relation to Interferometric Techniques at Present and in Future.- List of posters.

Journal ArticleDOI
TL;DR: In this article, a pump-probe Mach-Zehnder interferometer was used to investigate the nonlinear-optical properties of CdSxSe1-x-doped glass channel waveguides.
Abstract: A pump–probe Mach–Zehnder interferometer was used to investigate the nonlinear-optical properties of CdSxSe1-x-doped glass channel waveguides. The technique is used in situ and may be used to determine the suitability of the material under investigation for all-optical switching. The saturation and dynamical properties of the material are readily determined by using the technique, as are thermal effects. Semiconductor-plasma theory was used to predict the nonlinear optical properties, and reasonable agreement with experiment was obtained.

Journal ArticleDOI
TL;DR: Several conventional methods for absolute sphericity testing of optical surfaces are reviewed and assessed for suitability in real time interferometry and a special subsequent digital spatial filtering technique for diminution of noise is described.
Abstract: Several conventional methods for absolute sphericity testing of optical surfaces are known. One method has been used previously for real time interferometry, but a detailed investigation has not been carried out so far. In this work the known conventional methods are reviewed and assessed for suitability in real time interferometry. One method has been applied to phase stepping interferometry and examined. Adjustment peculiarities, experimental results of deviation measurements on normal surfaces, and application of normals are reported. Measuring errors, especially coherent noise, are analyzed and a special subsequent digital spatial filtering technique for diminution of noise is described.

Journal ArticleDOI
TL;DR: In this paper, an out-of-plane and in-plane displacements at the surface of a specimen excited by ultrasound are measured using a heterodyne optical probe, and the principles at the basis of the two modes of operation are explained.
Abstract: An heterodyne optical probe, which permits one to measure out-of-plane and in-plane displacements at the surface of a specimen excited by ultrasound is presented. The principles at the basis of the two modes of operation are explained and the sensitivities for in-plane and out-of-plane detection are analyzed. The optical layout of the probe and the schematic of its demodulation circuitry are presented. Its accuracy is tested with Rayleigh surface waves. Examples of application to laser-generated Rayleigh and Lamb waves are also presented.