Showing papers on "Interference (wave propagation) published in 1970"

Reduction of polarization effects in interference coatings.

Abstract: A design procedure is developed which yields layer combinations having a polarization independent effective index of refraction. A method of transforming massive media to nonpolarizing effective massive media is shown. These two design techniques are then applied to the problem of making polarization independent metal–dielectric–metal interference filters and polarization independent beam splitters.

Phase-Difference Amplification by Nonlinear Holograms

Abstract: Bryngdahl pointed out that a photographic plate, exposed to fine interference fringes and processed with high gamma, can record an amplification of the original phase difference. Interferograms obtained with this technique are shown. With a Mach-Zehnder two-beam interferometer, 14-fold phase-difference amplification was observed. Sources of experimental errors encountered in practice are discussed.

Optical Image Synthesis (Complex Amplitude Addition and Subtraction) in Real Time by a Diffraction-Grating Interferometric Method

Abstract: A coherent processing system for obtaining complex addition of two or more patterns in real time is described. In this system, a sinusoidal diffraction grating is used in the spatial-frequency plane. The input patterns to be added are displayed symmetrically about the optical axis in the object plane. The complex amplitude addition appears in th zero-order location in the output plane. Complex amplitude subtraction may be obtained by adding a 180° phase plate behind one of the input patterns. Displacing the sinusoidal diffraction grating by half a line pitch is also shown to change the performance of the system from addition to subtraction for two input functions, without the need for a phase plate. Experimental verification of the performance is presented. Analysis of the system for two input patterns is first given, then extended to the complex addition of multiple inputs.

Optical excitation of high‐amplitude surface waves

Abstract: A new scheme for optically exciting high‐amplitude Rayleigh waves is described. The interference of two high‐power laser beams on a metallic surface produces periodic heating and a Rayleigh wave. The surface motions diffract the two laser beams, and ID∝ IL3. These surface motions were as high as 200 A at 30 MHz. Rayleigh waves have also been observed at 800 MHz, using a modulated laser for excitation.

Variable phase-contrast and interference microscope

Abstract: An interference system for qualitative and quantitative investigation of micro-objects in transmitted light by means of the variable phase-contrast and variable shear interference methods. The system is located between an microscope objective and eyepiece. It resembles the Michelson interferometer in which a standard light beam splitter is replaced by an interference polarizer (Banning type), giving two orthogonally polarized beams, and two quarter-wave plates inserted in the split beams, and a common linear polarizer placed in the recombined beams. The interferometer mirrors are located in the planes conjugated with an aperture diaphragm of a microscope condenser. For interference investigation a slit condenser diaphragm is used. The optical path difference between the object under investigation and the surrounding medium is measured by the Senarmont method. Image shear is varied by tilting one of the interferometer mirrors. For phase contrast observation a ring-shaped condenser aperture is used together with an annular stop located close to one interferometer mirror and annular opening located close to the other mirror. The annular stop absorbs the direct (undiffracted) light and the annular opening absorbs the diffracted light, thus the first said mirror reflects the diffracted light and the second mirror reflects the direct light. Both light beams are recombined by the interference polarizer and brought to the vibrations in the same polarisation plane by a common linear polarizer. These light beams interfering with each other produce interference images of objects under investigation. The image contrast and contrast sign is changed with the Senarmont compensator.

Intercollisional Interference Effects in Collision-Induced Light Scattering

Abstract: A general kinetic theory of intercollisional interference effects has been developed. Applied to collision-induced light scattering in rare gases, it predicts a peak at the incident frequency, with a height of about 25% of the intracollisional peak and a width proportional to the density.

Interferometer utilizing gratings to measure motion

Abstract: An interferometer and method of making same are disclosed wherein two energetic beams are used to record an interference pattern to form a grating having a period of a substantially exact multiple or standard submultiple of a standard measuring unit and wherein this interference pattern is utilized in an interferometer fringe counter wherein relative movement of the grating and source produce a fringe count which is a measure of the relative movement. The grating is disclosed as a hologram, and in one embodiment light is transmitted through the hologram in one direction and then back through the hologram in another direction whereby the interference fringes are established on the same side of the hologram as the source. In another embodiment two holograms are utilized, one fixed and one movable relative to the source, and interference fringes are established on the side of the hologram opposite the side where the source is located.

Real time interferometry contour mapping system

Abstract: A real time holographic interferometer for measuring height variations or contours on the surface of an object is disclosed. Two interference patterns are formed, one of an object whose surface is to be mapped and one of a reference plane or other standard surface using holographic techniques. The interference patterns form visual inputs to a television camera which converts them into electrical signals. These electrical signals are combined to produce an output which contains information relative to the height variations or altitude contours of the object and the height contour information is displayed on an appropriate display device.

New High-Power Source of Coherent Microwave Phonons

Abstract: A new scheme for optically exciting intense microsound is proposed. The intense acoustic waves are generated by the enormous spatially periodic pressure gradients that arise under certain conditions from the interference of two high‐power optical beams of short time duration. The technique provides a tuneable source of bulk and surface micro‐acoustic waves.

Intensity Correlations from Pseudothermal Light Sources

Abstract: An experiment for observing intensity correlations from pseudothermal light sources is described. Analog rather than digital electronics is used. Results are obtained that show clearly the relation between amplitude interference and intensity interference. Gaussian, two-slit, and uniform-brightness disk sources are used. The application of this experiment to the understanding of stellar-intensity interferometry is pointed out.

Correlation Measurements on Partially Coherent Beams by Means of an Integration Technique

Abstract: A method based on the measurement of the time-integrated irradiance obtained in an interference experiment is described. This method is of particular utility in cases in which amplitude and phase or both are stochastic fluctuating variables. When only phase fluctuations are present or when amplitude and phase are stochastic independent variables, simple relations can be derived from which the parameters of the distribution can be derived. In these cases, if a gaussian-distribution law for the phase fluctuations is assumed, the mean-square value of the phase fluctuations is directly measured. The method has been applied to the study of phase fluctuations of a laser beam, caused by atmospheric turbulence, with results that agree with the findings of other techniques. The anisotropy of turbulence can also be evaluated.

Coupling device in modulated coherent light transmission system

Abstract: FOR COUPLING TWO OPTICAL DEVICES TOGETHER IN SERIES FOR THE TRANSMISSION OF A COHERENT, MODULATED LIGHT BEAM, A HOLOGRAM IS FORMED BY THE INTERFERENCE OF A COHERENT WAVE WITH THE LIGHT PRODUCED BY TRANSMITTING THE SAME COHERENT WAVE IN THE REVERSE DIRECTION THROUGH THE OPTICAL DEVICE TO WHICH THE LIGHT BEAM IS TO BE TRANSMITTED AND SUCH HOLOGRAM IS PLACED BETWEEN THE TWO OPTICAL DEVICES WHICH ARE TO BE COUPLED.

Experimental and computational studies of the dynamics of a fixed bed chemical reactor

Abstract: Experimental measurements of the temperature response of a fixed bed reactor to sinusoidal disturbances in the feed concentration, temperature, and flow rate show that a simple one-dimensional mathematical model with distributed thermal capacitance satisfactorily describes the dynamic behavior of the reactor for modest excursions about an operating point. The reaction considered is a liquid-phase exothermic reaction whose rate depends on the concentration of two reactants and the temperature. A computational analysis reveals that the amplitude and phase of the traveling concentration and temperature waves are influenced in a complex manner by the interaction between the two waves. The interaction, which is treated here as interference between traveling waves, is made complex by the difference in the rates of propagation of the temperature and concentration waves and by the variation of their speeds throughout the bed.

Method and apparatus for interference pattern recording

Abstract: Interference pattern recording is accomplished by simultaneous holographic and Lippmann holographic methods by directing the otherwise wasted radiation of the noninformation modulated beam back into the storage medium. Interference again takes place with the information-bearing beam to form another image in the medium. After processing the medium, reconstruction of the stored information is performed and a substantially stronger output image is generated.

Apparatus for measuring current in high-voltage lines

Abstract: An apparatus for measuring the current flowing through a highvoltage line and transferring the result to a low-potential locality has at the high line-voltage side a magnetic or electric field which varies in dependence upon the current to be measured. An optical modulator controlled by the field variations is interposed in one of two beams of coherent light to modulate this one beam relative to the other. An interferometer or the like device superimposes the modulated and unmodulated beams to produce an interference fringe pattern of alternately bright and dark stripes which travel from one to the other side of the pattern area. Light conductors transmit the resulting optical pulses to photoelectric sensors on low potential. The corresponding electric pulses control a device for counting the interference stripes. At any time the count corresponds to the then obtaining intensity value of the current.

Holographic associative memory permitting conversion of a pattern to a machine-readable form

Abstract: A holographic device for producing output image patterns in response to different input pattern wave fronts is described. A novel hologram is formed by the interference of a first pattern of electromagnetic waves and a second pattern of electromagnetic waves. The resultant hologram may be irradiated with a pattern of electromagnetic waves corresponding to the first pattern to reconstruct the second pattern of electromagnetic waves, and vice versa. To form the hologram a coherent light beam, such as from a laser, is directed on an object such as a transparency having a pattern thereon. The light from the object is directed onto a photographic emulsion. A coherent light beam also illuminates a second pattern, such as a coded apertured plate, and the light passing through the apertures is directed onto the photographic emulsion where it forms an interference pattern with the light from the first pattern. A hologram is thereby formed which, when illuminated by a pattern similar to one of the original patterns will reconstruct an image of the other original pattern.

Hologram generator using superposition of plane waves

Abstract: A SYSTEM WHICH GENERATES HOLOGRAM FROM ELECTRICAL SIGNALS SUPERIMPOSES A SERIES OF LIGHT WAVES IN A THICK HOLOGRAM RECORDING MEDIUM. A PROCESSOR DETERMINES THE AMPLITUDE, PHASE, AND ANGLE OF INCIDENCE OF THE SERIES OF LIGHT WAVES NEEDED TO GENERATE THE HOLOGRAM FROM THE ELECTRICALL SIGNAL. THESE LIGHT WAVES ARE THEN GENERATED WITH AMPLITUDE MODULATION, PHASE MODULATION, AND DE- FLECTION DEVICES, AND ARE MADE TO INTERFERE WITH REFERENCE LIGHT WAVES. THIS CAUSES A SERIES OF INTERFERENCE PATTERNS TO BE SUPERIMPOSED IN THE RECORDING MEDIUM, THEREBY PRODUCING THE HOLOGRAM.

A Stabilized 70 Gc Plasma Interferometer

Abstract: A 70 Gc microwave interferometer for plasma density measurements has been constructed which separates the time varying amplitude and phase signal components induced by the plasma. A superheterodyne technique is used with amplitude limiting and phase detection at the 30 Mc intermediate frequency. Amplitude detection is performed prior to limiting. Phase stability is achieved by locking the local oscillator frequency to the sum or difference of the master oscillator and intermediate frequencies with an AFC loop.

Apparatus for producing an interference pattern

Abstract: A beam splitter and a mirror form from a laser beam a pair of converging collimated beams directed to the primary focal point of a spreading lens. The lens combines and spreads the beams so that they overlap to produce an interference zone. A device is provided for adjustably moving the above-mentioned optical elements to vary the fringe spacing of the interference pattern.

A Laser Interferometer for Highly Transient Plasma Diagnostics

Abstract: A description is given of a modified Michelson interferometer that is particularly useful for locally probing highly transient plasmas such as occur behind incident shock waves in high performance shock tubes. The interferometer has the following features: (a) It is of a modified Michelson form with spherical mirrors to minimize effects of spatial variations in the index of refraction normal to the beam, (b) the light source is a cw laser that provides a very narrow coherent beam to allow high spatial and temporal resolution of the probe, and (c) it is operated in a single fringe mode over the narrow beam (constant phase difference between the two interfering beams over the illuminated field) and fringe shifts are observed through the time response of single channel detectors. Because photon transit time is negligible in shock tube diagnostics, the response time of the interferometer is determined solely by detection capabilities. Rapid response is achieved because nearly the entire laser energy is available for detection and high contrast interference takes place, allowing high signal‐to‐noise ratios at wide bandwidths. The spatial resolution can be diffraction limited. Thus, one‐dimensional observations can be made of temporally and spatially varying events with a combined temporal and spatial resolution exceeding that available with other current interferometric techniques. Index of refraction profiles behind strong shock waves have been observed at two wavelengths simultaneously and verify the usefulness of the design. A further design modification is discussed which removes the uncertainty in the sign of the temporal gradient of index of refraction and would allow accurate fractional fringe interferometry.

Wireless communication system for railway vehicle including an open type transmission line mounted on a radiowave absorbent support

Abstract: A communication system for eliminating interference in communications between a fixed station and a mobile vehicle. The fixed station includes a support base for supporting an open type transmission line, along the path of the mobile vehicle. The transmission line transmits radio waves from the fixed station and receives radio waves from the mobile vehicle. The mobile vehicle includes an antenna positioned to transmit radio waves from said mobile vehicle and to receive radio waves from the fixed station. The support base is positioned relative to the transmission line and the antenna, such that radio waves from the antenna not received by the transmission line and radio waves from the transmission line not received by the antenna and radio waves from other communication systems, are absorbed by the support base. The system may also include wave absorbing means positioned on the mobile vehicle to further reduce interference.

Spatial Modulation of Light Using Surface Waves in AN Interferometer

Abstract: An optical phase grating has been generated by introducing surface waves on one face of a Fabry‐Perot interferometer. This device called SWIM (Surface Wave Interference Modulator) produces a diffraction pattern at the Fourier plane in which the light intensity of the first‐order modulated beam is 1% of the zeroth order with an acoustic power of 0.85 mW/mm beam width. First‐order intensities greater than 10% have been realized; however, the process is not linear at this modulation depth.

VI Coherence Theory of Source-Size Compensation in Interference Microscopy

Abstract: Publisher Summary This chapter reviews the general theory of two-beam interferometer and the unified theory of image-formation and interference in terms of coherence. Its applications to the theory of localized fringes and to the theory of source-size compensation are described. The chapter presents the classification of practical methods of source-size compensation which is achieved. The description of the images produced by a compensated interference microscope is also given. It is formulated in terms of four coherence functions between the radiation from the beams i and j at two points. This representation applies to both the localization of fringes and the source-size compensation in any plane of interest, whereas the latter is described formerly as the superposition of two systems of localized fringes. These studies yielded simple formulae, which serve as an analytic tool for devising new designs.

Lloyd Mirror Laser Interferometer for Diffusion Layer Studies

Abstract: A Lloyd mirror laser interferometer is described which determines the refractive index gradient in a diffusion layer. The interference fringe movement is detected by an array of n‐p‐n planar silicon photodevices the output of which is recorded by oscillographs. Various modes of measurement are discussed which are suitable for transparent or opaque electrodes. The presently used measuring mode is based on the determination of the reflected ray's optical path length change at various angles of incidence. The refractive index gradient is obtained by an iterative solution of the derived equation for the optical path length change on a digital computer. The time dependence of the fringe movement during electrodeposition from CuSO4 solutions is discussed in addition to the effect of incidence angle and cathode displacement. The use of this interferometer is not limited to electrochemical processes and it can be used for the study of refractive index gradients in heat and other mass transfer boundary layers at solids.

Rho0 omega interference

Abstract: The structure of ρ0−ω interference is discussed. Applications are made to photoproduction of 3π states, π+π− production in electron-positron colliding beams, as well as in other processes, and lepton-pair photoproduction. The various parameters that appear in all these experiments are discussed, and the correlations of the various results are pointed out.