Showing papers on "Interferometry published in 2001"

Permanent scatterers in SAR interferometry

Abstract: Temporal and geometrical decorrelation often prevents SAR interferometry from being an operational tool for surface deformation monitoring and topographic profile reconstruction. Moreover, atmospheric disturbances can strongly compromise the accuracy of the results. The authors present a complete procedure for the identification and exploitation of stable natural reflectors or permanent scatterers (PSs) starting from long temporal series of interferometric SAR images. When, as it often happens, the dimension of the PS is smaller than the resolution cell, the coherence is good even for interferograms with baselines larger than the decorrelation one, and all the available images of the ESA ERS data set can be successfully exploited. On these pixels, submeter DEM accuracy and millimetric terrain motion detection can be achieved, since atmospheric phase screen (APS) contributions can be estimated and removed. Examples are then shown of small motion measurements, DEM refinement, and APS estimation and removal in the case of a sliding area in Ancona, Italy. ERS data have been used.

Measurement of intraocular distances by backscattering spectral interferometry

Abstract: The diffraction tomography theorem is adapted to one-dimensional length measurement. The resulting spectral interferometry technique is described and the first length measurements using this technique on a model eye and on a human eye in vivo are presented.

Interferometric modulation of radiation

Abstract: An Interferometric Modulator (IMod) is a microelectromechanical device for modulating light using interference. The colors of these devices may be determined in a spatial fashion, and their inherent color shift may be compensated for using several optical compensation mechanisms. Brightness, addressing, and driving of IMods may be accomplished in a variety of ways with appropriate packaging, and peripheral electronics which can be attached and/or fabricated using one of many techniques. The devices may be used in both embedded and directly perceived applications, the latter providing multiple viewing modes as well as a multitude of product concepts ranging in size from microscopic to architectural in scope.

High-precision gravity measurements using atom interferometry

Abstract: We have built an atom interferometer that can measure g, the local acceleration due to gravity, with a resolution of Δg/g = 2 × 10−8 after a single 1.3 s measurement cycle, 3 × 10−9 after 1 min and 1 × 10−10 after two days of integration time. The difference between our value for g and one obtained by a falling corner-cube optical interferometer is (7 ± 7) × 10−9 g. The atom interferometer uses velocity-selective stimulated Raman transitions and laser-cooled caesium atoms in an atomic fountain. We extend previous methods of analysing the interferometer to include the effects of a gravitational gradient. We also present detailed experimental and theoretical studies of potential systematic errors and noise sources.

Possibility of direct measurement of the acceleration of the universe using 0.1-Hz band laser interferometer gravitational wave antenna in space

Abstract: It may be possible to construct a laser interferometer gravitational wave antenna in space with h(rms) approximately 10(-27) at f approximately 0.1 Hz in this century. Using this antenna, (1) typically 10(5) chirp signals of coalescing binary neutron stars per year may be detected with S/N approximately 10(4); (2) we can directly measure the acceleration of the universe by a 10 yr observation of binary neutron stars; and (3) the stochastic gravitational waves of Omega(GW) > or similar to 10(-20) predicted by the inflation may be detected by correlation analysis. Our formula for phase shift due to accelerating motion might be applied for binary sources of LISA.

Coherence radar and spectral radar —new tools for dermatological diagnosis

Abstract: "Coherence radar," an optical 3-D sensor based on short coherence interferometry, is used to measure skin surface topology. This method is called optical coherence profilometry (OCP) and it may be a useful tool for medical diagnosis in dermatology because different medical conditions show distinct alterations of the skin surface. The measuring uncertainty is less than 2 μm. The measuring time is about 4 s. in vivo 3-D mapping of naked skin was performed without preparation. For clinical application, a fiber optical implementation was introduced. Spectral radar is an optical sensor for the acquisition of skin morphology based on OCT techniques. The scattering amplitude a(z) along one vertical axis from the surface into the bulk can be measured within one exposure. No reference arm scanning is necessary. The theory of the sensor, including the dynamic range, is discussed and in vivo measurements of human skin by a fiber optical implementation of the sensor are demonstrated.

In vivo bidirectional color Doppler flow imaging of picoliter blood volumes using optical coherence tomography

Abstract: We describe a novel optical system for bidirectional color Doppler imaging of flow in biological tissues with micrometer-scale resolution and demonstrate its use for in vivo imaging of blood flow in an animal model. Our technique, color Doppler optical coherence tomography (CDOCT), performs spatially localized optical Doppler velocimetry by use of scanning low-coherence interferometry. CDOCT is an extension of optical coherence tomography (OCT), employing coherent signal-acquisition electronics and joint time-frequency analysis algorithms to perform flow imaging simultaneous with conventional OCT imaging. Cross-sectional maps of blood flow velocity with <50-μm spatial resolution and <0.6-mm/s velocity precision were obtained through intact skin in living hamster subdermal tissue. This technology has several potential medical applications.

Conversion of conventional gravitational-wave interferometers into quantum nondemolition interferometers by modifying their input and/or output optics

Abstract: The LIGO-II gravitational-wave interferometers (ca. 2006–2008) are designed to have sensitivities near the standard quantum limit (SQL) in the vicinity of 100 Hz. This paper describes and analyzes possible designs for subsequent LIGO-III interferometers that can beat the SQL. These designs are identical to a conventional broad band interferometer (without signal recycling), except for new input and/or output optics. Three designs are analyzed: (i) a squeezed-input interferometer (conceived by Unruh based on earlier work of Caves) in which squeezed vacuum with frequency-dependent (FD) squeeze angle is injected into the interferometer’s dark port; (ii) a variational-output interferometer (conceived in a different form by Vyatchanin, Matsko and Zubova), in which homodyne detection with FD homodyne phase is performed on the output light; and (iii) a squeezed-variational interferometer with squeezed input and FD-homodyne output. It is shown that the FD squeezed-input light can be produced by sending ordinary squeezed light through two successive Fabry-Perot filter cavities before injection into the interferometer, and FD-homodyne detection can be achieved by sending the output light through two filter cavities before ordinary homodyne detection. With anticipated technology (power squeeze factor e-2R=0.1 for input squeezed vacuum and net fractional loss of signal power in arm cavities and output optical train e*=0.01) and using an input laser power Io in units of that required to reach the SQL (the planned LIGO-II power, ISQL), the three types of interferometer could beat the amplitude SQL at 100 Hz by the following amounts μ≡sqrt[Sh]/sqrt[ShSQL] and with the following corresponding increase V=1/μ3 in the volume of the universe that can be searched for a given noncosmological source: Squeezed input —μ≃sqrt[e-2R]≃0.3 and V≃1/0.33≃30 using Io/ISQL=1. Variational-output—μ≃e*1/4≃0.3 and V≃30 but only if the optics can handle a ten times larger power: Io/ISQL≃1/sqrt[e*]=10. Squeezed varational —μ=1.3(e-2Re*)1/4≃0.24 and V≃80 using Io/ISQL=1; and μ≃(e-2Re*)1/4≃0.18 and V≃180 using Io/ISQL=sqrt[e-2R/e*]≃3.2.

High-speed phase- and group-delay scanning with a grating-based phase control delay line

Abstract: A rapid-scanning optical delay line that employs phase control has several advantages, including high speed, high duty cycle, phase- and group-delay independence, and group-velocity dispersion compensation, over existing optical delay methods for interferometric optical ranging applications. We discuss the grating-based phase-control delay line and its applications to interferometric optical ranging and measurement techniques such as optical coherence domain reflectometry and optical coherence tomography. The system performs optical ranging over an axial range of 3 mm with a scanning rate of 6 m/s and a repetition rate of 2 kHz. The device is especially well suited for applications such as optical coherence tomography that require high-speed, repetitive, linear delay line scanning with a high duty cycle.

New measurement system for fault location in optical waveguide devices based on an interferometric technique

Abstract: A new measurement system for fault location in optical waveguide devices is presented. The system consists of a fiber-optic Mach-Zehnder and a bulk-type Michelson interferometers. The spatial resolution of the scatter distribution is <380 μm, which is limited by the averaging time. The minimum detectable backscattered power is -116 dB relative to the light power propagating in the waveguides. Preliminary experimental results using single-mode fibers <10 cm long are demonstrated.

Method and apparatus for transmitting and receiving signals having a carrier interferometry architecture

Abstract: Principles of quantum interferometry are used to create a signal architecture (known as carrier interferometry) for wireless and waveguide electromagnetic-wave communications. Carrier interferometry provides unprecedented bandwidth efficiency and enables substantial improvements in interference rejection, power efficiency, and system versatility. The carrier interferometry architecture also enables simpler transceiver designs that facilitate digital up-conversion and down-conversion.

Interferometeric imaging with a grating based phase control optical delay line

Abstract: An apparatus for performing high speed scanning of an optical delay and its application for performing optical interferometry, ranging, and imaging, including cross sectional imaging using optical coherence tomography, is disclosed The apparatus achieves optical delay scanning by using diffractive optical elements in conjunction with imaging optics In one embodiment a diffraction grating disperses an optical beam into different spectral frequency or wavelength components which are collimated by a lens A mirror is placed one focal length away from the lens and the alteration of the grating groove density, the grating input angle, the grating output angle, and/or the mirror tilt produce a change in optical group and phase delay This apparatus permits the optical group and phase delay to be scanned by scanning the angle of the mirror In other embodiments, this device permits optical delay scanning without the use of moving parts

Phase-Coherent Optical Pulse Synthesis from Separate Femtosecond Lasers

Abstract: We generated a coherently synthesized optical pulse from two independent mode-locked femtosecond lasers, providing a route to extend the coherent bandwidth available for ultrafast science. The two separate lasers (one centered at 760 nanometers wavelength, the other at 810 nanometers) are tightly synchronized and phase-locked. Coherence between the two lasers is demonstrated via spectral interferometry and second-order field cross-correlation. Measurements reveal a coherently synthesized pulse that has a temporally narrower second-order autocorrelation width and that exhibits a larger amplitude than the individual laser outputs. This work represents a new and flexible approach to the synthesis of coherent light.

Transient strain accumulation and fault interaction in the eastern California shear zone

Abstract: Satellite synthetic aperture radar interferometry reveals transient strain accumulation along the Blackwater-Little Lake fault system within the Eastern California shear zone.

Single-shot measurement of carrier-envelope phase changes by spectral interferometry

Abstract: We demonstrated single-shot measurements of spectral interference between a white-light continuum generated in a hollow-fiber and its second harmonic. The interference has information on the carrier-envelope phase of an input pulse to the fiber and the time delay of the blue wing of the continuum. By analyzing the observed spectral interference, we estimated shot-by-shot changes of the carrier-envelope phase. This method is useful for determining the carrier-envelope phase changes of a low-repetition-rate, high-intensity laser.

Parametric Oscillatory Instability in Fabry-Perot (FP) Interferometer

Abstract: We present an approximate analysis of a nonlinear effect of parametric oscillatory instability in FP interferometer. The basis for this effect is the excitation of the additional (Stokes) optical mode and of the mirror's elastic mode when the optical energy stored in the FP resonator main mode exceeds the certain threshold. This effect is undesirable in laser gravitational wave antennae because it may create a specific upper limit for the value of energy stored in FP resonator. In order to avoid it the detailed analysis of the mirror's elastic modes and FP resonator optical modes structure is necessary.

Optical coherence topography based on a two-dimensional smart detector array

Abstract: A low-coherence reflectometer based on a conventional Michelson interferometer and a novel silicon detector chip with a two-dimensional array of pixels that allows parallel heterodyne detection is presented. We demonstrate acquisition of three-dimensional images with more than 100,000 voxels per scan at a sensitivity of -58 dB and a rate of 6 Hz.

A complementarity experiment with an interferometer at the quantum–classical boundary

Abstract: To illustrate the quantum mechanical principle of complementarity, Bohr1 described an interferometer with a microscopic slit that records the particle's path. Recoil of the quantum slit causes it to become entangled with the particle, resulting in a kind of Einstein–Podolsky–Rosen pair2. As the motion of the slit can be observed, the ambiguity of the particle's trajectory is lifted, suppressing interference effects. In contrast, the state of a sufficiently massive slit does not depend on the particle's path; hence, interference fringes are visible. Although many experiments illustrating various aspects of complementarity have been proposed3,4,5,6,7,8,9 and realized10,11,12,13,14,15,16,17,18, none has addressed the quantum–classical limit in the design of the interferometer. Here we report an experimental investigation of complementarity using an interferometer in which the properties of one of the beam-splitting elements can be tuned continuously from being effectively microscopic to macroscopic. Following a recent proposal19, we use an atomic double-pulse Ramsey interferometer20, in which microwave pulses act as beam-splitters for the quantum states of the atoms. One of the pulses is a coherent field stored in a cavity, comprising a small, adjustable mean photon number. The visibility of the interference fringes in the final atomic state probability increases with this photon number, illustrating the quantum to classical transition.

Land Subsidence Monitoring with Differential SAR Interferometry

Abstract: This article investigates whether differential synthetic aperture radar (SAR) interferometry can be used to monitor land subsidence. The principle of the technique and the approach used on a specific case are presented. The high potential of differential SAR interferometry to monitor a wide range of deformation velocities ranging from fast (m/year) to slow (mm/year) was demonstrated by the generation of subsidence maps for sites in Germany, Mexico, and Italy. The SAR interferometric displacement maps are validated with available leveling data. Differential SAR interferometry is suitable for operational monitoring of land subsidence due to the accuracy of the maps produced, the extensive SAR data archive over the past 10 years, the expected continued availability of SAR data, and the maturity of the required processing techniques. A strategy for the integration of leveling, global positioning systems, and SAR data is proposed in order to achieve an accurate, rational and cost-effective monitoring.

Self-calibrated interferometric-intensity-based optical fiber sensors

Abstract: This paper presents self-calibrated interferometric-intensity-based optical fiber sensors, which combine for the first time fiber interferometry and intensity-based devices into a single sensor system. The sensor involves an extrinsic Fabry-Perot (FP) interferometric cavity. The broadband light returned from the FP cavity is split into two channels in such a way that one channel has a coherence length much longer than the doubled air-gap separation in the sensor so the FP generates effective interference, while the coherence length in the other channel is so short that no effective interference takes place. As a result, the optical signal in the channel with a long coherence length yields information about the FP cavity length while the signal in the other channel is proportional only to the source power, fiber attenuation, and other optical loss factors in the optical path. To eliminate fringe direction ambiguity and relative measurement limitations associated with interferometric sensors, the sensor is designed such that it is operated over the linear range between a valley and a peak of one interference fringe in the first channel. Moreover, the ratiometric signal-processing method is applied for the signals in the two channels to obtain self-calibrating measurement to compensate for all unwanted factors, including source power variations and fiber bending losses. Various pressure and temperature sensors based on the self-calibrated interferometric/intensity-based scheme are designed, fabricated, and tested. Experimental results show that a resolution as high as 0.02% of full scale can be obtained for both the pressure and temperature measurements.

Pure optical contrast in scattering‐type scanning near‐field microscopy

Abstract: We have enhanced the apertureless scattering-type scanning near-field optical microscope by two improvements which together achieve a recording of the true near field without any height-induced artefact. These are the use of interferometric detection of the scattered light on one hand, and the use of higher-harmonic dither demodulation of the scattered signal on the other. Here we present the basic rationale for these techniques, and give examples measured with two different experiments, one in the infrared (10 microm wavelength), the other in the visible (633 nm). The latter operates in a fully heterodyne mode and displays simultaneous images of optical near-field phase and amplitude, at below 10 nm resolution.

Quantitative differential phase measurement and imaging in transparent and turbid media by optical coherence tomography.

Abstract: Differential phase-contrast optical coherence tomography allows one to measure the path-length differences of two transversally separated beams in the nanometer range. We calculate these path-length differences from the phase functions of the interferometric signals. Pure phase objects consisting of chromium layers containing steps of approximately 100–200-nm height were imaged. Phase differences can be measured with a precision of ±2°, corresponding to a path-difference resolution of 2–3 nm. To investigate the influence of scattering, we imaged the phase objects through scattering layers with increasing scattering coefficients. The limit of phase imaging through these layers was at approximately 8–9 mean free path lengths thick (single pass).

Jamin-type interferometers and components therefor

Abstract: A retroreflector (32) has three mutually-orthogonal reflective surfaces arranged around an optical axis (12). The reflective surfaces stop short of the optical axis to provide a central region of the retroreflector which transmits incident light (M,N) and a peripheral region of the retroreflector which retroreflects incident light (C,D). When the reflector is used in a Jamin-type interferometer (10) with another reflector (34), this enables the interferometer to be used for measuring displacement between the reflectors. In the interferometer, a projected beam (M) is disposed between a pair of return beams (D,N) and/or one of the return beams (N) is disposed between a pair of the projected beams (C,M). This enables a first contiguous area of a face of a beam splitter (22) to be provided with a phase-shifting coating (28) to produce a phase quadrature relationship between a pair of interferogram beams (G,I). This simplifies the masking required when applying the coating (28). In manufacture of the beam splitting member (22), a thin-film, beam-splitting, metal coating is applied to the member, and the member and coating are baked so as to modify the phase shift produced by the coating to enable the phase quadrature relationship. During baking a beam of light is projected at the coating with an angle of incidence of substantially π/4 radians so that the beam is split into a transmitted component and a reflected component. The intensities or phases of the transmitted and reflected components are monitored during baking, and the baking is terminated when the monitored intensities or phases have a predetermined relationship. This improves the reliability and/or accuracy of the resulting phase shift.

Femtosecond transillumination optical coherence tomography

Abstract: We describe a new technique, femtosecond transillumination optical coherence tomography, for time-gated imaging of objects embedded in scattering media. Time gating is performed with a fiber-optic interferometer with femtosecond pulses and coherent heterodyne detection to achieve a 130-dB dynamic range. A confocal imaging arrangement provides additional spatial discrimination against multiply scattered light. By time gating ballistic photons, we achieve 125-μm-resolution images of absorbing objects in media 27 scattering mean free paths thick. We derive a fundamental limit on ballistic imaging thickness based on quantum noise considerations.

Low-coherence optical tomography in turbid tissue: theoretical analysis

Abstract: On the basis of white-light interferometry and statistical optics, a theoretical model for low-coherence optical tomography is presented that establishes the relation of interference modulation with path-length-resolved reflectance and that can provide analytical expressions and numerical solutions by means of a Fourier transform. The Monte Carlo technique is used to simulate the path-length-resolved reflectance from different multilayer tissue phantoms. Theoretical analyses and preliminary experimental results suggest that, unlike time-resolved spectroscopy, low-coherence optical tomography detects the local relative variations of path-length-resolved reflectance from the turbid tissues.

Stable carrier generation and phase-resolved digital data processing in optical coherence tomography.

Abstract: We present a technique for improved carrier generation by eliminating the instability of a mechanical device in favor of an electro-optical phase modulator in the reference arm of an optical coherence tomography system. A greater than threefold reduction in the phase variance between consecutive A-line scans at a repetition rate of 1 kHz was achieved. Stable and reproducible interference fringe generation permits phase-resolved digital data processing. A correction algorithm was applied to the interferometric signal to compensate for the departure of the source spectrum from an ideal Gaussian shape, resulting in up to 8-dB sidelobe suppression at the expense of a 1-dB increase in the noise floor. In addition, we could eliminate completely the broadening effect of group-delay dispersion on the coherence function by introducing a quadratic phase shift in the Fourier domain of the interferometric signal.

Phase-referenced interferometer with subwavelength and subhertz sensitivity applied to the study of cell membrane dynamics

Abstract: We report a highly sensitive means of measuring cellular dynamics with a novel interferometer that can measure motional phase changes. The system is based on a modified Michelson interferometer with a composite laser beam of 1550-nm low-coherence light and 775-nm CW light. The sample is prepared on a coverslip that is highly reflective at 775 nm. By referencing the heterodyne phase of the 1550-nm light reflected from the sample to that of the 775-nm light reflected from the coverslip, small motions in the sample are detected, and motional artifacts from vibrations in the interferometer are completely eliminated. We demonstrate that the system is sensitive to motions as small as 3.6 nm and velocities as small as 1 nm/s. Using the instrument, we study transient volume changes of a few (approximately three) cells in a monolayer immersed in weakly hypotonic and hypertonic solutions.

Optical measurements : techniques and applications

Abstract: 1 Introduction.- 2 The Schlieren Technique.- 2.1 Introduction.- 2.2 Basic Principle.- 2.3 Optical and Thermodynamic Interrelations.- 2.3.1 Refraction Index and Temperature Field.- 2.3.2 The Deflection of Light in an Inhomogeneous Medium.- 2.4 Application of the Schlieren Technique.- 2.4.1 Application to Transient Combustion Research.- The Schlieren Cinematography.- The Color Schlieren Technique.- 2.4.2 Application to Fuel-Injection Systems.- 3 Fundamentals of Holography and Interferometry.- 3.1 Abstract.- 3.2 Introduction.- 3.3 Principle of Holography.- 3.4 Simple Holographic Arrangement.- 3.5 Holographic Interferometry.- 3.5.1 Double Exposure Technique.- 3.5.2 Real-Time Method.- 3.5.3 Evaluation of the Interferograms.- 3.5.4 Finite Fringe Method.- 3.6 An Interference Method for Simultaneous Heat and Mass Transfer.- 3.7 Comparison with Classical Methods.- 4 Holographic Interferometry.- 4.1 Introduction.- 4.2 Components of a Holographic Interferometer.- 4.2.1 Light Source.- 4.2.2 Optical Table.- 4.2.3 Shutter.- 4.2.4 Beam Splitter.- 4.2.5 Attenuation Filter.- 4.2.6 Beam Expander.- 4.2.7 Mirrors, Lenses.- 4.2.8 Recording Materials.- 4.2.9 Piezo Mirror.- 4.2.10 Test Facility.- 4.3 Evaluation of Interferograms.- 4.3.1 Theoretical Principles.- 4.3.2 Conclusions.- 4.3.3 Calculation of Temperature and Concentration Distributions.- 4.3.4 Determination of the Local Heat Transfer Coefficient.- 4.4 Examples.- 4.4.1 Determination of the Temperature Distribution in a Compact Plate Heat Exchanger with Plain Fins.- Description of the Test Section.- Description of the Interferograms.- 5 Short Time Holography.- 5.1 Introduction.- 5.1.1 Historical development of holography.- 5.1.2 The holographic image.- 5.1.3 Holography as an optical measurement method.- 5.2 Elements of holography.- 5.2.1 Recording materials.- 5.2.2 The pulsed laser.- 5.2.3 Optical set-up.- 5.2.4 Adjusting the holographic camera.- 5.2.5 Recording, development and reconstruction of holograms.- Amplitude hologram.- Phase hologram.- 5.3 Application example: Dispersion characteristics in stirred bubble columns.- 5.3.1 Statement of the problem.- 5.3.2 Recording the holograms.- 5.3.3 Reconstruction and evaluation of the holograms.- 5.3.4 Stereo matching of the two holograms.- 5.3.5 Results.- 6 Evaluation of holograms by digital image processing.- 6.1 Introduction.- 6.1.1 Digitization of a picture.- 6.1.2 Gray value pictures.- 6.1.3 Operations with gray value images.- 6.2 A digital image processing system for the evaluation of holographic reconstructions.- 6.2.1 Evaluation of holographic images.- Scanning of in-line holograms.- Scanning of off-axis holograms.- 6.2.2 set-up of a digital image processing system.- 6.3 Image processing.- 6.3.1 Evaluation of single pulsed holograms.- 6.3.2 Evaluation of double pulsed holograms.- 6.3.3 Stereo matching algorithm.- 6.3.4 Accuracy.- 6.4 Evaluation of interferograms.- 7 Light Scattering.- 7.1 Introduction.- 7.2 Scattering Processes.- 7.2.1 Interaction of Light and Matter.- 7.2.2 Elastic Scattering.- 7.2.3 Inelastic Scattering.- 7.3 Light Scattering Techniques in Heat Transfer.- 7.3.1 Mie-Scattering.- 7.3.2 Rayleigh-Scattering.- 7.3.3 Raman-Scattering.- 7.3.4 Laser Induced Fluorescence (LIF).- 7.3.5 Absorption.- 7.4 Concluding Remarks.- 8 Laser-Doppler Velocimetry.- 8.1 Introduction.- 8.2 Principles of LDV.- 8.3 Optics.- 8.4 Signal Processing.- 8.5 Seeding Particles.- 8.6 Determination of Characteristic Turbulence-Quantities.- 8.6.1 Fundamentals of Turbulent Flows.- 8.6.2 Measurement of Turbulence-Quantities.- 9 Phase Doppler Anemometry (PDA).- 9.1 Introduction.- 9.2 General considerations for the application of PDA.- 9.3 Principles of PDA.- 9.3.1 Light-scattering by particles.- 9.3.2 Optical parameters of a Phase Doppler Measurement System.- 9.3.3 Phase-diameter relationship.- 9.4 Measurement accuracy.- 9.5 Applications of PDA.- 10 Dynamic Light Scattering.- 10.1 Introduction.- 10.2 Overview.- 10.3 Light Scattering Theory.- 10.3.1 Scattering Geometry and Assumptions.- 10.3.2 Temporal and Spatial Behavior of Scattered Light.- 10.3.3 Correlation Functions.- 10.3.4 Hydrodynamic Fluctuation Theory.- 10.4 Experimental Methods.- 10.4.1 Homodyne Method.- 10.4.2 Heterodyne Method.- 10.5 Measurement of Thermal Diffusivity.- 11 Raman Scattering.- 11.1 Introduction.- 11.2 Theoretical Basics of Raman Spectroscopy.- 11.2.1 Concentration Measurements.- 11.2.2 Temperature Measurement.- General Considerations.- Thermometry by Rotational Raman Spectroscopy.- Thermometry by Vibrational Raman Spectroscopy.- 11.3 Experimental set-up.- 11.3.1 Laser.- 11.3.2 Focussing and Collection Lenses.- 11.3.3 Spectral Frequency Selection.- 11.3.4 Photon Converters.- 11.3.5 Data Acquisition and Control.- 11.4 Selected Applications.- 11.5 Concluding Remarks.- 12 Laser induced Fluorescence.- 12.1 Introduction.- 12.2 Basic Principles of Laser Induced Fluorescence.- 12.2.1 General Considerations.- 12.2.2 Concentration Measurement.- 12.2.3 Temperature Measurement.- 12.2.4 Tracer LIF.- 12.3 Experimental Setup and Procedures.- 12.3.1 Experimental Setup.- 12.3.2 Experimental and Evaluation Procedures.- 12.4 Selected Applications.- 12.5 Concluding Remarks.- 13 Absorption.- 13.1 Introduction.- 13.2 Line spectra.- 13.2.1 Position.- 13.2.2 Shape and width.- A. Natural line broadening.- B. Doppler broadening.- C. Collisional broadening.- D. Voigt function-Mixed line shapes.- 13.2.3 Line strength.- 13.3 Experimental techniques.- 13.3.1 Overview.- Techniques used in absorption spectroscopy.- 13.3.2 Experimental examples.- A. In situ measurements of ammonia concentration in industrial combustion systems.- B.Fast temperature measurements with tunable diode lasers.- C. Harmonic detection techniques for the measurement of small absorptions.- D. Simultaneous -situ detection of oxygen and water in a full scale waste incinerator with near infrared diode lasers.- E. In situ determination of free radicals in flames.- 14 Pyrometry and Thermography.- 14.1 Introduction.- 14.2 Temperature Radiation.- 14.3 Method of Transmission.- 14.4 Radiation Receiver (Detector).- 14.5 Thermal Cameras - Thermography Image Systems.- 14.6 Pyrometers.- 14.6.1 Classification According to Construction Types.- 14.6.2 Filament and Quotient Pyrometers.- 14.6.3 IR Recording Heads.- 14.7 Error Potential.- 14.7.1 Error Sources During Recording.- 14.7.2 Equipment Error.- 14.7.3 Problems with Thermograph Readings.- 14.8 Appendix.- 14.8.1 Important Constants.- 14.8.2 Further Information and Tables.- 15 Tomography.- 15.1 Introduction.- 15.2 Integral Measurement Methods.- 15.2.1 Absorption Methods.- 15.2.2 Interferometric Methods.- 15.3 Mathematical Reconstruction Methods.- 15.3.1 Algebraic Reconstruction Methods.- Matrix Methods.- Iterative Series Expansion.- 15.3.2 Explicit Reconstruction Methods.- Fourier Transform Method.- Analytical Solution of Integral Equations.- 15.3.3 Comparison of Reconstruction Methods.- 15.4 Implementations.- 15.4.1 Measurement of temperature fields in stirred vessels.- 15.4.2 Measurement of micro- and macromixing with the tomo-graphical dualwavelenght tomography.- 15.4.3 Tomographic measurements of flames with the Schlieren effect.- 15.4.4 Chemical species tomography by near infra-red absorption.- 16 Particle Image Velocimetry.- 16.1 Introduction.- 16.2 Hardware for the experimental set-up.- 16.3 Evaluation software.- 16.4 Three-dimensional flow.- 16.5 Applications.- Nomenclature.- References.