Abstract: This paper describes a method to enhance the capability of two-wavelength phase-shifting interferometry. By introducing the phase data of a third wavelength, one can measure the phase of a very steep wave front. Experiments have been performed using a linear detector array to measure surface height of an off-axis parabola. For the wave front being measured the optical path difference between adjacent detector pixels was as large as 3.3 waves. After temporal averaging of five sets of data, the repeatability of the measurement is better than 25-A rms (λ = 6328 A).

Abstract: This paper describes some practical methods to calibrate the phase shifter in phase-shifting interferometry (PSI). The phase shifter used in the experiment is a piezoelectric transducer (PZT) that has a nonlinearity of <1%. Using the quantitative method described in this paper, the repeatability in the measurement of the phase-shifting angle is ~0.046° rms, and the 3σ value is 0.139°. A calibration-insensitive phase calculation algorithm is discussed and compared with other synchronous detection equations (e.g., the three-bucket or the four-bucket method). Experimental results verify the calibration-insensitive mechanism of the self-calibrating algorithm.

Abstract: When a sinusoidal grating is projected on either a reference plane or a diffuse object to be measured, every point along a line normal to the grating lines, on the reference plane as well as the object, can be characterized by a unique phase value. By measuring this phase accurately using phase modulation methods and by determining points on the reference plane and the object having identical phases, it is shown that the object height can be computed. A working system requires a projector, a translatable sinusoidal grating, and a detector array interfaced to a microcomputer. Results of measurements on diffuse test objects are described and errors are analyzed.

Abstract: This article identifies the description of OD phases as one of the fundamental theoretical problems in the field of organization de velopment. Although phase models have been proposed for over 30 y...

Abstract: An important practical limitation to the sensitivity of frequency-modulation spectroscopy arises because of imperfect phase modulation of the laser beam. This imperfection manifests itself as residual amplitude modulation (RAM), and we present data from a careful series of experiments designed to elucidate its origin. Experimentally, we find two components to the RAM, one that depends for its intensity on the laser frequency and one that does not. We present a model that correctly accounts for the intensity and rf phase and frequency behavior of the laser-frequency-dependent component. We are unable to offer a plausible explanation for the laser-frequency-independent component.

Abstract: En appliquant la methode d'integrale de parcours a 2 systemes en interaction, on montre que la phase specifique Γ apparaissant dans le processus adiabatique quantique recemment trouve par Berry et Simon s'obtient comme une action additive a la fonctionnelle d'action dynamique conventionnelle

Abstract: Publisher Summary There are two major analytic procedures for direct phasing from anomalous scattering. One of these uses the normal scattering contributions from the anomalous scatterers to resolve the ambiguity inherent in phase information from anomalous scattering at a single wavelength. The resolved anomalous phasing methods presented derive from procedures developed in the structural analysis of crambin. The second major category of direct anomalous phasing is based on measurements at multiple wavelengths. Such measurements cart be made with the tunable radiation from synchrotron sources and can in principle lead to a definitive solution of the phase problem. A third category of procedures for the analysis of anomalous scattering data is advanced recently. The theory for integrating classic direct methods with anomalous scattering measurements has developed but practical implementation is not yet in place. The atomic scattering factor decreases with scattering angle due to diffuseness of the electron cloud, but it is “normally” independent of the X-ray frequency (or wavelength).

Abstract: Encoding the Precession phase angle of proton nuclei for Fourier analysis has produced accurate measurement of fluid velocity vector components by MRI. A Pair of identical gradient pulses separated in time by exactly ½ TE, are used to linearly encode the phase of flow velocity vector components without changing the phase of stationary nuclei, Two-dimensional Fourier transformation of signals gave velocity density images of laminar flow in angled tubes which were in agreement with the laws of vector addition. These Velocity profile images provide a quantitative method for the investigation of fluid dynamics and hemodynamics.© 1985 Academic Press,Inc.

Abstract: Two-wavelength holography and phase-shifting interferometry are combined to measure the phase contours of deep wavefronts and surfaces, such as those produced by aspherics, with a variable sensitivity. When interference fringes are very closely spaced, the phase data contain high frequencies where 2 ~ ambiguities cannot be resolved. In this technique, the surface is tested at a synthesized longer equivalent wavelength. The phase of the wavefront is calculated modulo 2φ using phase-shifting techniques at each of two visible wavelengths. The difference between these two phase sets is the phase of the wavefront as it would be measured at λeq=λ1λ2/|λ1 − λ2 |, assuming that 2π ambiguities can be removed at λeq. This technique enables surfaces to be contoured to an accuracy of λeq/100.

Abstract: An optical profiler includes a two-beam interferometer. An interference pattern produced thereby is focused onto an array of photocells. Phase shift in a reference beam of the interferometer is produced by accelerating a piezoelectric transducer supporting the interferometer mirror to a constant velocity. The velocity is maintained constant for at least 360° of phase shift, during which four integrated buckets are obtained from each photocell. The outputs of the photodetector array are continuously integrated and effectively read out every 90° of phase shift of the reference beam by a computer that computes a first value of phase corresponding to each photocell output from the first, second, and third integrated buckets produced by that photocell and a second phase value from the second, third, and fourth integrated bucket values obtained from that photocell. The two phase values are averaged, eliminating the effects of sinusoidal noise produced by inaccuracies in the reference beam phase at which integrated buckets are initiated and terminated. Data points at which intensity modulation produced by the reference beam phase variation is less than a noise threshold are masked from phase calculations. The intensity of the interferometer light source is automatically controlled by averaging intensity of the intereference pattern at angles that differ by 180° to cancel out the effects of the interference and obtain an average intensity. The lamp voltage is automatically adjusted to maintain the average intensity.

Abstract: We have used data obtained from measurements of ionic and gating currents to study the process of K+ channel activation in squid giant axons. A marked improvement in the recording of K+ channel gating currents (IKg) was obtained by total replacement of Cl- in the external solution by NO-3, which eliminates approximately 50% of the Na+ channel gating current with no effect on IKg. The midpoint of the steady state charge-voltage (Qrel - V) relationship is approximately 40 mV hyperpolarized to that of the steady state activation (fo - V) curve, which is an indication that the channel has many nonconducting states. Ionic and gating currents have similar time constants for both ON and OFF pulses. This eliminates any Hodgkin-Huxley nx scheme for K+ channel activation. An interrupted pulse paradigm shows that the last step in the activation process is not rate limiting. IKg shows a nonartifactual rising phase, which indicates that the first step is either the slowest step in the activation sequence or is voltage independent. These data are consistent with the following general scheme for K+ channel activation: (formula; see text)

Abstract: Wider use of hologram interferometry for quantitative measure-ments has been delayed by the fact that interpolation between the fringe maxima and minima to obtain the optical path difference at a particular point in the field is laborious and inaccurate. A solution to this problem is quasi-hetero-dyne interferometry, which permits rapid and accurate measurements simultaneously at a number of points distributed over the interference pattern. In this technique a television camera is used in conjunction with digital electronics to measure and store the irradiance values at points on a rectangular sampling grid covering the real-time interference fringes. The phase difference between the interfering wavefronts at each point is then calculated from the irradiance values obtained from successive scans of the camera made while the phase of one of the wavefronts is shifted either continuously or in steps. A practical system is described with which values of the optical path difference for 10,000 data points can be obtained with an accuracy of ± A/200 in less than 10 s. The application of quasi-heterodyne hologram interferometry to the measurement of vector displacements and to holographic contouring is discussed.

Abstract: We present initial results from the investigation of a surface field phase perturbation method for the calculation of the wave field scattered by a rough surface. This technique is based on the extinction theorem and uses a perturbation expansion of a function closely related to the complex phase of the surface field. This approach was suggested earlier, but we use the expansion in a different way. In the present work we consider only deterministic periodic surfaces, rough in one dimension, on which the total field is zero. We find that, for surfaces with modest slope and curvature, this technique can be used to calculate scattered fields even when surface relief is significant compared to the wavelength of the incident radiation.

Abstract: The paper considers the random phase errors in the phase shifters which are used in an antenna array to steer the beam in the look direction, and analyzes the effect of these errors on the performance of the optimal processor which maximizes the output SNR by deriving the expressions for the output signal power, residual interference power, output SNR, and the array gain as a function of the variance of these errors. The paper also considers the phase quantization error which arises in the digital phase shifters and shows how the performance of the optimal processor depends on the number of bits of the digital phase shifters.

Abstract: A scheme for recovering phase using irradiance data alone, without interferometric techniques, is developed using the transport equations for phase and irradiance. For the case of one transverse dimension a general solution, for an arbitrary irradiance distribution, of the transport equation for the optical phase is already given by an application of the divergence theorem. Numerical simulation results are given that indicate that the phase-recovery scheme works well even in the presence of large pupil-plane aberrations if the signal-to-noise ratio is sufficiently high. In particular, pupil-plane phase aberrations may be determined from irradiance measurements in two planes that are near the image plane.

Abstract: A procedure is proposed for obtaining coupling constants from phase-sensitive H,H-COSY spectra. For this purpose, firstly pseudo-one-dimensional spectra are created by co-addition of individual traces of cross-peaks, and by a similar addition of diagonal peaks in a spectrum which is phase corrected to pure-absorption line shapes. The sum and difference of the pseudo-one-dimensional spectra of a cross-peak and its diagonal peak give two spectra, with a pattern in which the active coupling ceases to exist (‘spin decoupling’) but is shifted by half the value of the same. If diagonal peaks are not available owing to overlapping signals, sums and differences of the pseudo-one-dimensional spectra of two cross-peaks can be applied to simplify spectral patterns for the evaluation of J values. The procedure is demonstrated with the example of the AMXY spin system of a tyrosine, and the complex pattern of the Pro8 spin system of the cyclic decapeptide antamanide. The conformation of the Pro8 ring, derived from the coupling constants thus obtained, is of the γE type.

Abstract: A light modulator for generating a beam of phase modulated light including a source of polarized light, at least one and preferably two liquid crystal cells having a thin layer of nematic liquid crystals of positive dielectric anistropy through which the polarized light is directed to produce a beam of light having a phase shift corresponding to a modulating electrical signal which is applied to each of the liquid crystal cells. The liquid crystal cells in addition have a continuing electrical bias applied across the layers in order to achieve the rapid response times necessary to achieve modulation of the polarized light. Demodulation of the polarized light occurs by splitting the modulated light beam into its quadrature components and developing an electrical signal corresponding to the phase difference between the two quadrature components. A communication system involving its modulators and demodulators delivers communication through light as a transmission medium.

Abstract: The conventional beam‐forming technique cannot be used for source location in a waveguide because of the modal interference structure of the field. In this paper a new method of passive source ranging in a layered waveguide is proposed. The mode filtering processor was used to process the field data of a vertical array to obtain individual modes. The source range information can be extracted by measurement of three individual mode phases. The source range was expressed in terms of the ‘‘mode interference distance’’ as follows: r=Li j*Di j+Δri j; Δri j=Di j ×(δφi j/2π), where Li j is a certain integer, δφi j is the phase difference of the ith and jth modes, Di j is the ‘‘mode interference distance’’ defined by Di j=2π/(ki−k j), and ki is the wavenumber of the ith mode given by a numerical mode code. The information of Li j can be estimated by means of comparison with the phase of the jth mode with another mode, say the mth mode, and then Li j would be estimated by solving the following equation: (δφ jm/2π)...

Abstract: A new fiber-optic device designed to steer the radiation beam of a phased-array antenna has been demonstrated. A radiofrequency (RF) signal at 125 MHz is generated via photomixing at the output of a single-mode fiber-optic interferometer. The phase of the electrical signal is shifted over several cycles in direct proportion to a voltage applied to an optical controller. The controller consists of a Pockels-type optical phase modulator located in one arm of the heterodyne interferometer. Rapid changes in RF phase are feasible. A miniature low-voltage version of the device, based upon integrated optics, is proposed.

Abstract: A double‐pass image transmission through a single multimode fiber is demonstrated, using a passive phase conjugate mirror. An application to interferometry based on phase sensing is demonstrated, by implementing the multimode fiber and the passive phase conjugate mirror as one arm of a Michelson interferometer. Due to the unique properties of the self‐pumped conjugator, nonuniform distortions caused by modal dispersion in the fiber and other aberrations are cancelled out, while uniform phase changes are detected.

Abstract: Theoretical and experimental investigations of a closed-loop fiber-optic gyroscope are reported. Phase nulling is accomplished by applying a sawtooth modulation to an integrated-optic phase modulator located at one side of the sensing loop. The frequency of the phase modulation is proportional to the rotation rate, thus permitting a digital readout. The influence of a finite flyback period on the scale factor is investigated.

Abstract: A new optical rotation sensor is described. It is a ring passive phase conjugator in which the ring may consist of a multimode fiber. A nonreciprocal phase shift in the ‘‘passive’’ like fiber ring activates a grating movement and subsequent frequency detuning of the beams in a photorefractive four‐wave mixer. This device has the advantages of natural reciprocal behavior of phase conjugate beams (essential for rotation sensing) and has several adjustable controlling parameters. It reveals a new class of interferometry in which changes in the ring’s optical phases, the beam’s intensities and losses, and the mixing crystal’s efficiency and electric field modulate a frequency detuning of the oscillating beams.

Abstract: The magnitude and phase of the small-signal injection current-to-frequency modulation transfer function in GaAlAs semiconductor diode lasers has been measured over the frequency range 100 Hz-1300 MHz using network analyzers. Channeled substrate planar (CSP), buried heterostructure (BH), and crank transverse junction stripe (TJS) laser structures were investigated and will be compared. Approximately 180, 180, and 90° phase differences between the low frequency, thermal frequency modulation (FM), and the high-frequency carrier-density FM was observed for BH, TJS, and CSP laser structures, respectively. The origin of this phase difference and its implications for FM optical communications will be discussed, A rate equation analysis for small-signal injection current modulation (using Mason's flowgraph representation) indicates the presence of a real-axis left half-plane zero in the carrier-density small-signal frequency modulation response. Experimental evidence for this feature has been observed in the measured injection current-to-FM transfer functions.