Showing papers on "Acoustic interferometer published in 1971"

Michelson Interferometer as a Remote Gauge

Abstract: The Michelson interferometer may be used to measure the separation between two parallel surfaces which are distant from the interferometer. A beam of light incident normal to these surfaces must be at least partially reflected back to the interferometer by each surface in order for the technique to work. The results of three measurements using this technique are described, and the effect of dispersion is discussed.

Acoustic Waves Transmitted Through Solid Elastic Cylinders

Abstract: The acoustic field of a plane wave incident on an elastic cylinder may be decomposed into two parts, one representing circumferential waves that propagate around the cylinder, the other part obeying in the high‐frequency limit the laws of geometrical optics. The latter part is studied in this paper, and is decomposed into the specularly reflected wave and into a series of transmitted waves which traverse the cylinder either directly along a secant, or undergo additional internal reflections with and without mode convention (compressional to shear type, or vice versa). Wavefront loci and amplitudes of these waves are calculated using the saddle‐point method, and the corresponding reflection and transmission coefficients are shown to reduce, for the case of a large cylinder, to the known expressions for a flat elastic half‐space in contact with a liquid.

Velocity of sound and acoustic attenuation in pure gallium single crystals

Abstract: The velocity of sound for both transverse and longitudinal waves has been measured in single crystals of pure gallium These velocity data have been used to calculate a complete set of elastic cons

Theoretical computations on ridge acoustic surface waves using the finite-element method

Abstract: Theoretical computations have been carried out on ridge acoustic surface waves using the finite-element method. The results obtained agree substantially with experiments performed previously.

Acousto-optical systems

Abstract: An acousto-optical system which diffracts or modulates light passing through a crystal of Tl3AsSe3 by means of sound waves in the crystal is disclosed. Sound waves are generated in the crystal by means of a transducer connected to an RF generator. The acousto-optical system may be in the form of a display device, a laser modulator, or other devices. An acoustic delay line using a crystal of Tl3AsSe3 is also disclosed.

New high-coupling low-diffraction cut for acoustic surface waves on LiNbO3

Abstract: The existence of a new high-coupling low-diffraction-loss cut for acoustic surface-wave propagation on LiNbO3 has been theoretically predicted and experimentally verified. The propagation direction lies 16½° from the Z axis with the plate normal 16½° from the negative Y axis.

Acoustic waves in beryllium oxide crystal

Abstract: Experimental results are reported on the coupling between electromagnetic signals and acoustic waves in beryllium oxide crystals via interdigital transducers deposited on a natural y face of a BeO crystal. The transducers are oriented to propagate acoustic waves along the z axis.

Analysis of an interferometer with acoustic surface waves on one mirror.

Abstract: It has been demonstrated that surface waves propagating on one mirror of an interferometer form an optical diffraction grating. Experimentally confirmed analyses of an interferomet er with 95.5% reflectivity mirrors now indicate that a surface wave power density of 0.028 mW/mm.MHz is required to diffract 1% of transmitted light into the first order beam. This power can be diminished by a factor of more than 20 by increasing the mirror reflectivity to 99%.

Evaluation of acoustic testing techniques for spacecraft systems

Abstract: External acoustic environments, structural responses, noise reductions, and the internal acoustic environments have been predicted for a typical shroud/spacecraft system during lift-off and various critical stages of flight. Spacecraft responses caused by energy transmission from the shroud via mechanical and acoustic paths have been compared and the importance of the mechanical path has been evaluated. Theoretical predictions have been compared extensively with available laboratory and in-flight measurements. Equivalent laboratory acoustic fields for simulation of shroud response during the various phases of flight have been derived and compared in detail. Techniques for varying the time-space correlations of laboratory acoustic fields have been examined, together with methods for varying the time and spatial distribution of acoustic amplitudes. Possible acoustic testing configurations for shroud/spacecraft systems have been suggested and trade-off considerations have been reviewed. The problem of simulating the acoustic environments versus simulating the structural responses has been considered and techniques for testing without the shroud installed have been discussed.

Modifying a Shear Interferometer to Obtain a Neutral Reference Beam

Abstract: An absolute interferometer may be obtained from a differential-shear interferometer if a very small pinhole stop is introduced into one of the two spatially separated point-source images that the differential-shear interferometer produces. The technique and one example are discussed.

The Role of Acoustic Surface Waves in Signal Processing

Abstract: On Fig. 1 is shown an actual plot of wavecrests on the surface of crystal. Notice that these wavecrests are not regular, they appear to be relatively flat within the beam then they appear to fall back rapidly away from the beam center. That is because lithium niobate crystal is highly anisotropic, and the waves moving slightly off the beam direction tend to move more slowly than waves directly on the beam direction. The straight-crested surface wave is generated on lithium niobate with a transducer shown in Fig. 2. The position of the fingers in the transducer matches the position of the crests and troughs of Fig. 1, and if an electrical signal at the appropriate frequency is applied to the transducer then a surface acoustic wave beam radiates from these transducers. The transducer is relatively efficient--a bit less than half the available electrical energy is put into the desired acoustic wave with this particular design.

Feasibility of Measuring Radiative Amplification of Acoustic Waves

Abstract: A calculation shows that amplification of acoustic waves by absorption of laser radiation should be measurable in the laboratory.