Improvements in methods for producing ultrasonic images

摘要

754,799. Ultrasonic inspection devices. VEB C. ZEISS JENA. Aug. 18, 1954, No. 24076/54. Class 118(2) A method of depicting objects with the aid of ultrasonic vibrations (especially for material testing purposes) wherein a relief-image is formed on the surface of a fluid is characterized by the additional formation upon said relief-image of a system of parallel bands or of concentric rings due to the production of interfering vibrations. This ensures that a flaw in the material, such as a shrinkage cavity through which no waves are transmitted is shown not only by its contour but by a void in the formation of interfering bands, as at 19 in the image of a circular plate 20 shown in Fig. 4. The image may be produced by situating the object 3 to be depicted between a sound transducer 4 and an image-forming lens 5 immersed in a coupling fluid 1 (e.g. water) in a contained 2. By reflection at an inclined glass plate 6 the lens 5 forms a reliefimage in known manner on the fluid surface 7. By means of a point source of light 8 and a window 11 in the bottom of the container 2 a Schlieren-type optical image is projected on to a screen 15. A thin foil 17 fixed in a frame that can be pivoted to make a small angle # to the surface of the liquid is interposed in the path of the ultrasonic waves to produce reflections within the wedge of fluid above the foil, thereby producing interference bands; the frame may be rotatable so that the parallel bands can be orientated to give optimum legibility of the image. Alternatively, the foil may be cone-shaped to produce concentric rings. In either case there will be an absence of the interference phenomenon at points where there are no ultrasonic waves, e.g., where defects occur in the material under examination.