| 摘要 |
1,263,371. Ultrasonic diagnostic apparatus. HOLOTRON CORP. 6 March, 1969 [6 March, 1968; 20 May, 1968 (2)], No. 12037/ 69. Heading A5K. [Also in Division H4] Ultrasonic apparatus for producing a hologram of a human breast comprises means for supporting the breast in the path of an ultrasonic beam, means for forming on a detector surface an acoustic image of the beam after it has passed through the breast, and means for directing a second beam onto the detector surface to form a hologram thereon. The hologram is formed by extending and flattening the breast between two acoustically transparent polymeric membranes held under tension in movable frames 240, 242 in water tank 250, directing an ultrasonic beam through the breast from transducer 234, imaging the transmitted beam at hologram detector 246 by means of acoustic lens 244 and mirror 254, and directing a reference ultrasonic beam (not shown) via acoustic lens 264 and a second mirror to interfere with the first beam at detector 246. The detector (which may be a fluorocarbon liquid supported on a low-gloss black PVC film in a vibration-isolating frame 272) is illuminated by substantially monochromatic light and a first order diffraction beam 284 is selected by optics 280, 282 focussed on the detector surface and is then viewed or directed by tiltable mirror 292 to camera 294. A permanent optical hologram can be recorded by photographing the interference between the selected beam 284 and an off-axis reference beam (e.g. the other first order diffraction beam, 296) coherent with source 276. Resolution in the acoustic hologram is improved by the use of an acoustic lens and pinhole stop to give a regular wavefront to the reference ultrasonic beam. Alternative hologram detectors are a Pohlman cell (including specular reflecting flakes suspended in a liquid), an acousto-electric image converter camera, or a scanning point transducer. |
