Patent GB-1393742-A (GB)
Title: Ultrasonic data-processing systems
IPC: G06G7/195
Filed: 1972-06-13
Abstract: 1393742 Ultrasonic data processing THOMSON-CSF 13 June 1972 [15 June 1971] 27688/72 Heading H3U A phase modulating object 7, Fig. 1, or amplitude modulating object (29), Figs. 5, 6 (not shown), in the path of a beam of coherent acoustic waves in water modulates the waves, and disclosed analysis shows that at an image plane in the system, amplitudes representing the Fourier Transform of the modulation pattern can be detected. As shown in Fig. 1, acoustic waves from source 3, after passage through acoustic lenses 5, 6, modulating object 7 and lens 8 are detected by ultrasonic detector 10 on spectral plane 9 where the Fourier Transform appears, its signal being displayed at indicator 11. Alternatively, the waves pass through filter 12 and lens 13 to impinge on image plane 14 adjacent which there are a detector 15 and display 16. Filter 12 either has the effect of filtering frequency components of the data represented by modulation object 7, or a cross correlation function between data of 7 and 12 appears at plane 14. Lenses of rotational symmetry result in a two dimensional Fourier Transform but a one dimensional Transform is realized by lenses of cylindrical symmetry. In Fig. 7 (not shown) the filter 12 is replaced by a four quadrant phase plate, two of whose quadrants provide a phase shift differential of 180 degrees compared with the other two. Preparation of modulating objects.-Figs. 3, 4, 8 (not shown). Electrocardiogram, encephalogram or seismographic data (S A , S B , S C , Fig. 3) operates transducers and cutters (20, 21) producing a corresponding pattern on thermoplastic material (7) passing adjacent heated roller (19). Alternatively a bank of electrostatic cutters (123, Fig. 4) form material (7) in a shape corresponding to the instantaneous potential distribution across the cutters. Coherent sound waves from source (3, Fig. 3) are reflected from parabolic surface (5) and elliptical surfaces (8), both of either cylindrical or circular symmetry, and, upon passing through material (7), produce a corresponding pattern (23) on the fluid surface, which is sensed by unit (50, Fig. 8) a modulator (43) being engraved, or optically produced by head (48) moving in synchronism with unit (50), modulator 43 thus being cut with a pattern equivalent to the Fourier Transform of that on material 7. By additionally providing a reference acoustic wave, at the surface (2, Fig. 3), head (48, Fig. 8) produces a Fourier hologram. Devices using amplitude modulation, Figs. 5, 6 (not shown).-Data (29) characterized by two discrete levels in a plane, such as a text or fingerprint, is placed adjacent cell (26), elastic materials (27, 28) providing impedance matching between data (29) and fluid in tank (1). The acoustic waves are selectively reflected at the surface of unit (26), a corresponding transformed pattern appearing at a plane (35, Fig. 6) or at the surface (2, Fig. 5) of the fluid. Correlator, Fig. 9.-Data F, H to be correlated causes cutting of bands 60, 68 passing through the path of acoustic waves from sources 64, 73 and a corresponding transform surface pattern in units 59, 71 each comprising a film of oil on a membrane. Additional sound source 84 ensures that the transform represented at unit 71 is a Fourier hologram. Coherent light from source 53 is phase modulated at the surfaces of both of units 59 and 71, the total modulation representing the product of the two data sets. A pattern representing the correlation appears at plane 83. Diaphragm 81 enables choice of the " - 1" order of diffraction of light from unit 71, diaphragm 77 ensuring that only the zero order diffracted light passes from unit 59 to unit 71. For autocorrelation, the one band passes through both tanks, data source H and unit 66 being absent. Acoustic lens construction.-Converging lenses comprise either convex bounding walls containing a fluid such as methylene iodide in which acoustic wave velocity is less than the water in tank 1, or a concave structure of polystyrene, Fig. 2 (not shown). Unwanted reflected waves are absorbed by lining (17, Fig. 2).