Planar-Structure Focusing Lens for Acoustic Microscope

Abstract

A planar-structure acoustic focusing lens proposed by the authors is applied successfully to the scanning acoustic microscope as a substitute for the conventional concave lens. The lens is composed of a number of concentric annular grooves of uniform depth formed on the radiation plane according to the theory of a Fresnel zone plate. Because of the simple configuration with no spherical surface, the planar lens operating at a very high frequency can be fabricated easily using the conventional photolithographic tech nique.Good focusing capability of the lenses fabricated for operation at 100MHz and 200MHz has been demonstrated through the experimental and theoretical examinations.Images of satisfactory quality have been obtained using the scanning acoustic microscope equipped with the planar lenses.