Showing papers on "Interference (wave propagation) published in 1973"

Expanding the tactual field of view

Abstract: Can tactual information be acquired simultaneously by several different fingers? Blind and sighted Ss were asked to scan vertical displays of braille (consisting of either one or two dots) with the index and middle fingers on each hand-using one, two, or four fingers at the same time. Stimuli were recognized most rapidly when the displays were scanned by two fingers on different hands and least rapidly when two fingers on the same hand were used; performance was similar with one finger and with four fingers. The results indicated some parallel perceptual processing of the inputs to the two hands and mutual interference in processing inputs from fingers on the same hand.

Interference effects in sequential decay

Abstract: In this paper we utilize the Green's function method to study sequential decay processes which involve interference effects. The model system involves a zero-order discrete state coupled to a set of continua, which are themselves coupled together, while the coupling matrix elements are energy independent. Interference effects in parallel and consecutive decay involving two continua result in the retardation of the decay rate of the initial state and in the reversal of the branching ratio for the population of the two continua. Finally, a general solution was provided for the problem of sequential decay involving multiple continua.

Optical Contour Mapping of Surfaces

Abstract: A precise nondestructive optical contour mapping method with adjustable sensitivity for noncontact testing of surface deformations up to 30 μm/cm is described. The method employs an optical grating that is placed in front of the test surface. Illumination of the grating by a monochromatic plane wave generates an interference pattern between the beam components of two different diffraction orders. Reflection at the test surface and superposition with the fixed grating generate a fringe pattern that resembles the surface contours of the test object. This fringe pattern consists of a superposition of an interference line system and a moire line system. Whereas the distance between two adjacent contour lines of the interference pattern corresponds to a surface deformation of a half-wavelength of the illuminating light the distance between two lines of the moire system is determined by the grid constant and the direction of the grid illumination. Therefore, the scale of measurement can be chosen according to the problem. Applications for surface flatness testing of semiconductor wafers and photomasks are presented.

Multiple-channel information translation system and method

Abstract: A multiple-channel information translation system includes a Bragg light-sound interaction cell interposed in the path of a spatially coherent input light beam. Carrier generating means generates a plural number greater than two of electrical carriers each having a different RF frequency. The carriers are respectively amplitude modulated by information-bearing input signals to produce a like plural number of amplitude-modulated carrier signals used to drive the Bragg cell. The cell Bragg-diffracts the input beam into a corresponding plural number of primary output light beams respectively amplitude-modulated in accordance with the input signals. The carrier generating means causes the frequencies, or frequencies and relative phase, of the carriers to be such that random, signal-related spurious amplitude modulation of the primary output light beams which might otherwise result from cross-channel interference effects in the cell is suppressed. In one disclosed embodiment the carrier frequencies are selected such that the frequency differences between each carrier frequency and all others are equally spaced in the frequency domain. In a second disclosed embodiment the carriers are phase-locked in order to effect the said suppression of spurious amplitude modulation of the primary output beams.

Coupling device for optical waveguide

Abstract: An optical coupling system comprises a prism or diffraction grating coupling element in combination with a film waveguide or the like affording high selectivity and high coupling coefficient. A prism when used has a coated, partially reflective and interference inducing face arranged parallel to the film waveguide along a coupling interval wavelength of the latter. The coated face coating includes a partially transparent mirror layer and an interference film. When a grating coupling element is used, multiple interfering beams ordinarily produced are reduced to one output beam per diffraction order. Light beams may be propagated on one or both sides of the film.

A quantitative study of cochlear potentials along the scala media of the guinea pig.

Abstract: The relationship between the parameters of pure‐tone acoustic stimuli and those of the cochlear microphonics (CM) and summating potentials (SP) was studied for measurements from scala media in each of the four turns of the guinea‐pig cochlea. For each turn similarities in the shapes of the input‐output functions over a wide range of frequencies permitted adequate quantitative description of these functions by a single third‐degree polynomial equation. Therefore, the properties of both cochlear potentials (CM and SP) can be described by a nonlinear transfer curve over the specified frequency range. These results imply the SP should not be regarded as being generated by a process different from the CM but as an expression of the nonlinear characteristics of the generator of cochlear potentials. At frequencies where the measuring electrode is near the peak of the mechanical traveling wave envelope, the transfer curve no longer described the cochlear potentials. Calculations based upon phase measurements and upon theoretical considerations indicate that this is due to interference effects from the out‐of‐phase generators in the vicinity of the electrode.

Apparatus and method for analyzing surface contour

Abstract: Surface contour is analyzed by providing a plurality of surface contact members in a housing. A first portion of the members contacts the surface. A second portion serves as a diffraction wave producing means. The housing also includes a second diffraction wave producing means spaced from the first. Electromagnetic radiation is directed at the first and second diffraction wave producing means to form a plurality of discrete interference patterns each caused by the interaction of waves produced from said first and second diffraction wave producing means.

Justification of the Model for Electron Interference Produced by an Electrostatic Biprism

Abstract: The wave function describing the electron interference produced by an electrostatic biprism derived from the perturbation theory involves an integral which is not easy to evaluate numerically. Using the method of stationary phase it is shown in the paper that the expression of this integral in terms of the Fresnel integrals considerably facilitates the calculations. Physically this expression corresponds to the superposition of two waves emerging from two virtual images of the source diffracted by two opaque half-planes of opposite orientation. In such a way the model widely used for discussions of the interference of this type is justified.

Three beam interferometer for the observation of kinetic cooling in air.

Abstract: A three beam interferometer, which has recently been used to measure the time constant associated with kinetic cooling, is described in detail. Design features necessitated by operation of the device over a 5-m path are discussed, as well as system response to vibrational noise and drift, and means used for their monitoring and control. The effective working length resolution of the system, dL/L, was 1 part in 2.6 x 10(9) with a He-Ne laser source operating at 0.63 microm.

Interferometer apparatus incorporating a spherical element of index of refraction of two

Abstract: An interferometer arrangement of either the transmission or reflection type incorporating at least a pair of partially spherical or spherical elements having an index of refraction of approximately two is disclosed. In a preferred embodiment, the spherical or radiation directing elements are glass spheres having an index of refraction of approximately two at the wavelength of a light source being utilized. In a transmission type interferometer, both the spherical or radiation directing elements are utilized as beam splitters and collimators while, in the reflection type interferometer, one of these spheres is used as a beam splitter and collimator while the other is utilized as a retroreflector. The complete spherical symmetry of such radiation directing elements permits them to function with any orientation relative to the optical path between them. Mechanisms in which desired motions are controlled with high precision by applying mechanical feedback to position a movable body relative to a fixed reference body, using the above described interferometer arrangement are also disclosed. The same mechanisms are capable of being controlled from a programmed computer causing the movable body to exhibit a desired motion using interference fringe detection schemes to both monitor and accurately position the movable body relative to a reference body. Also disclosed is an actuator based on a hollow hydraulic cylinder having a given longitudinal axis which includes an interferometer arrangement incorporating at least a pair of spherical elements which have an optical axis substantially coincident with the longitudinal axis of the actuator. Also disclosed are transducer arrangements disposed in series with the actuator which are utilized to meet high frequency stability requirements.

Diffraction and Interference of Partially Coherent Light Traversing Two Superposed Sound Fields

Abstract: The diffraction and interference of a light wave passing through two superposed sound waves have been studied theoretically on the basis of Huygens' principle. As a result of frequency shifts in every deflected light ray caused by the sound waves, the instantaneous intensity resulting from linear superposition of the deflected light rays consists of the d.c. component as well as the a.c. component as a sum of beating signals among those rays, provided that the coherence time of the light is long enough compared with the period of a beating signal under consideration. A general formula for diffraction is derived and two-beam interference is considered as a special case. The resultant formula illustrates that the complex degree of coherence is modulated, after traversing the sound field, with a form of the Bessel function of zeroth-order which varies with Raman-Nath parameters as well as with the separation of two points on the wavefront of the light. This validity will hold so long as the inclination facto...

Effects of Measurement Devices on Conducted Interference Levels

Abstract: Measurements of power line conducted interference voltages are commonly made throughout the 150 kHz to 30 MHz frequency range on military, industrial, and consumer equipment using line impedance stabilization networks (LISN) and, more recently, current probe techniques. This paper presents some brief background information concerning power line conducted interference measurements and the results of a study to assess the effects of LISN and current probe measurement devices on the level of measured conducted interference. A model is defined which facilitates prediction of the effects. The model concept allows the procedures described in this paper to be extended to equipment of other impedance definitions. A comparison of the calculated and empirical differences is made and suggests an analytical approach in sizing the effects upon the conducted interference levels.

Simple optical interference method for the inspection of solid surfaces.

Abstract: Measuring methods based on optical interference are used to evaluate the surface roughness of solids. This article gives an example of a simple and accurate method.

Analysis of Radio Paging Errors in Multitransmitter Mobile Systems

Abstract: Many mobile telephone and personal paging systems require signaling simultaneously from multiple transmitters. This paper analyzes the factors that cause paging errors due to interference when the signaling format consists of audio tones sent simultaneously from two FM transmitters. The factors considered are: drift in carrier and modulation frequencies, and misequalization of land-line amplitude and audio delay. The following results are shown: 1) the interference errors are eliminated if the land lines are amplitude and phase equalized, 2)if the lines are not equalized but the modulation frequencies are equal, then the interference errors can be decreased by an order of magnitude if the transmitters are mistuned such that their difference carrier frequency is just greater than the modulation tone filter bandwidth in the receiver, and 3) if the modulation frequencies are slightly different, then the interference errors can be decreased somewhat by misequalizing the modulation indicies. It is then concluded that if the land lines are not equalized and the signaling tones are not exactly equal, the interference errors cannot be eliminated, but can be decreased by properly aligning the system.

Block defocused spherical fabry-perot interferometer.

Abstract: A solid Fabry-Perot interferometer with a quasi-confocal resonator has been constructed. The essential characteristics of this interferometer are discussed in relation to its advantages for spectral analysis. These advantages include high resolving power (>107) with satisfactory instrumental finesse (>30) in static mode. Experimental results show that this instrument can be used for analysis of spatial coherence along the cross section of the incoming light beam.

Multi-purpose real-time holographic polariscope

Abstract: A modification of a real-time holographic interferometer to permit the observation of a complete set of interference patterns from a single reference hologram. The apparatus consists of a conventional off-axis transmission holographic set-up with the addition of several polarization optical elements to alter the polarization of the light at various stages of a procedure to study an object. These elements are adjusted so as to produce circularly polarized light for recording the reference hologram. After producing the hologram these elements are readjusted to any desired state of polarization and the corresponding interference pattern is observed in real-time and may be changed at any time to view a different type of interference pattern.

Analysis of radio paging errors in multitransmitter mobile systems

Abstract: Many mobile telephone and personal paging systems require signaling simultaneously from multiple transmitters. This paper analyzes the factors that cause paging errors due to interference when the signaling format consists of audio tones sent simultaneously from two FM transmitters. The factors considered are: drift in carrier and modulation frequencies, and misequalization of land-line amplitude and audio delay. The following results are shown: 1) the interference errors are eliminated if the land lines are amplitude and phase equalized, 2)if the lines are not equalized but the modulation frequencies are equal, then the interference errors can be decreased by an order of magnitude if the transmitters are mistuned such that their difference carrier frequency is just greater than the modulation tone filter bandwidth in the receiver, and 3) if the modulation frequencies are slightly different, then the interference errors can be decreased somewhat by misequalizing the modulation indicies. It is then concluded that if the land lines are not equalized and the signaling tones are not exactly equal, the interference errors cannot be eliminated, but can be decreased by properly aligning the system.

Internal waves in llyn Tegid

Abstract: The paper deals with the formation of internal waves of periods of about 12 hours, 24 hours, and in one case 48 hours on Lake Tegid (Bala) in North Wales. It was possible to isolate these waves by means of a numerical filter, applied to the outputs of 30 thermistors place below each other on a chain suspended from a buoy. The wave characteristics are very closely related to those of the wind and a high correlation can be found in most cases with the internal waves lagging behind the corresponding filtered components in the wind stress by about a third of a period. The movement of the waves round the lake was investigated by using two buoys, one of which was moved round the lake perimeter and then after using the filter, obtaining the phase difference between the two for the various components. The results indicated a clockwise movement which is contrary to what one would expect of simple Kelvin waves. The effect can be caused, however, by the interference of several waves of approximately the same frequency but of different mode and wavelength. The filter was also used to examine the vertical profile of the water movement. The profiles indicated, as expected, that there is a mixture of many modes present but some of these can be identified by comparison with the theoretical mode profiles.

Observation of Interference Effects in the Reaction π + p-->π + pπ 0

Abstract: In the reaction tr+p-+ tr+ptr at 2.67 GeV/c, the central value of the p mass peak and its width are found to vary as a function of position in the Dalitz plot. The major variations are associated with the crossover regions of pp with diffractively produced tr+(ptr ) and tr~ N* final states, and so have a natural interpretation in terms of interferences among these final states. >:C Work done under the auspices of the U.S. Atomic Energy Commission. -2+ In a study of P production in the reaction + + 0 '11' p -+'11' p '11' (1) at 2.67 GeV/c, the central value of the p mass peak and its width ar~ found to vary as a function of position in the Dal itz plot. (1) These · variations are associated with the cross-over regions of the pp final state with ~'11', N*'ll', and diffractively produced '11'+(p'11' ) states, and so have a possible interpretation in terms of interferences among these final states. Such an interference of pp with diffractive dissocation of the proton has been suggested by J. MacNaughton et. al., (2) as a means of accounting for a mass-dependent asymmetry in the di-pion t-channel helicity (or Gottfried-Jackson) angular distribution, or, alternatively, a shift in the p mass as a function of this angle. Such effects have long been studied in terms of '11''11' scattering phase shifts, where this behavior is attributed to interference of an S-wave, I = 2 amplitude with the resonant P-wave I = 1 state.( 3,4) However, since the known exchanges in p production include, in addition to the pion quantum numbers, both isoscalar and isovector, natural and unn'atural parity,· non-zero spin states, (l ,J) and since the changes in apparent mass and width reported here are associated with the cross-over in the Dalitz * ---·· -· -.-.. -~----.. plot of pp and 'II'N states, it appears desirable to consider an interpretation in the context of the overall '~~'+P '11' production reaction. The· analysis of Reference · 2 falls in this category. Those authors emphasize that their interpretation may well be equivalent to the OPE approach at the pion pole, and hence does not necessarily invalidate the deterniination of ~'11' phase shifts, provided the extrapolations involved are from a region of small enough momentum transfer. On the other hand, their model t

The behaviour of large-angle pd → dp scattering with energy

Abstract: We present a discussion of the energy-dependent behaviour of the proton-deuteron elastic scattering atϑ c.m.=180°. We show that the interference betweenS andP waves is mainly responsible for the low-energy peak. It is also pointed out that the present-day experimental information is not sufficient to support or rule out the alternative explanations for the higher-energy peak.

Phase Variation and Amplitude Fading of NWC-22.3kHz Signal at Dawn

Abstract: The diurnal variation of phase and amplitude of NWC-22.3kHz signal is investigated. Typical pattern of the phase variation and amplitude fading during sunrise transition, for the case of the summer season in the northern hemisphere, is interpreted in terms of waveguide modes interference. By considering the second mode propagation besides the first in daylight, a good agreement between theoretical and experimental results is obtained.

A Maximum-Likelihood Multiple-Hypothesis Testing Algorithm, with an Application to Monopulse Data Editing

Abstract: : A simple algorithm for multiple-hypothesis testing, based on a generalization of likelihood ratio testing between pairs of hypotheses, is developed and applied to a specific problem. The problem arises in connection with an amplitude comparison monopulse system in an air traffic control application. In particular, it is desired to measure target azimuth in a beacon system in the presence of interference and multipath. The multiple hypotheses relate to the presence or absence of a desired signal, with or without either of two kinds of interfering signal. The analysis leads to a new technique of data editing, or processing, to detect the presence of interference.