Acoustical Holograms and Optical Reconstruction

Abstract

Theoretical and experimental investigations of the construction of acoustical holograms and the optical reconstruction of their images are described. The matrix representation of Gabor’s hologram is presented, and the matrix method is used to analyze the experimental results obtained. The acoustical holograms are constructed through use of sound waves of 10 kHz and 20 kHz frequency, and the virtual and conjugate images are reconstructed using laser light of 6328 A wavelength. The effect on the reconstructed image of the scanning lines produced by the scanning of a recording microphone is discussed. An improvement of the image is obtained by eliminating the spectra of the scanning lines. Furthermore, the reconstructed images are investigated as functions of the following conditions involved in constructing their acoustical holograms: (1) the level of the resultant light intensity converted from the acoustic fields, (2) the limitation of the scanning plane, and (3) the wavelength of the sound wave. The detection by use of holographic techniques of objects buried in a model of a turbid and turbulent medium is described. Three-dimensional information storage in acoustical holograms is also discussed.