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A NEW METHOD FOR RECORDING ULTRASONIC WAVES
Ultrasound is now widely used for testing the quality of manufactured products. This possibility (ultrasonic flaw detection) was first discovered by S. Ya. Sokolov.¹ The action of material inhomogeneities on the propagation of ultrasound in it is great. There exist various optical methods for detecting the result of a test—diffraction of light by ultrasonic waves that have passed through the substance being studied, reflection of light from the surface of a liquid that has been subjected to the action of ultrasound transmitted through the substance, and many others.
The authors of the papers reviewed²˒³ investigated the influence of ultrasound on a phosphorescent screen and used this influence to obtain directly an image of ultrasonic waves that had passed through the substance under investigation. They used ordinary phosphorescent screens employed in practice and made of various phosphors of the sulfide group. If such a screen is made to glow uniformly, then ultrasound incident upon it causes the phosphorescence to fade, more or less strongly depending on the energy of the ultrasound at the given point of the screen.
The parts of the screen exposed to ultrasound at first glow more brightly than the unexposed areas; then, as the exposed areas fade, they appear as dark spots on a light background.
The image of the object being transilluminated can be transferred to a photographic plate by contact printing.
The fading of the phosphorescence is caused, in all probability, by the heat that appears at the locations on the screen struck by the ultrasound; however, there are indications of other causes as well, which are being investigated.
V. Bredel’
CITED LITERATURE
- S. Ya. Sokolov, UFN 40, 3 (1950).
- H. Schreiber and W. Degner, Ann. d. Phys. 7, 275 (1950).
- A. Eckardt and O. Lindig, Ann. d. Phys. 7, 410 (1950).