CONCAVE TRANSDUCER FOR FOCUSING ULTRASONIC WAVE OF ULTRASONIC MICROSCOPE

PURPOSE:To obtain a concave transducer for wide range of focusing ultrasonic wave without much loss of ultrasonic waves by forming a matching layer of thickness of odd number times a quater of the wave length between a piezoelectric body and a substrate and also between the substrate and a sound field medium. CONSTITUTION:A substrate 10 is a gold metal plate with a concavity on one side. A matching layer 13 is formed by using silicon dioxide at the concave part of the substrate 10, and its thickness is made odd number times a quarter of the wave length of an ultrasonic frequency. A piezoelectric body 11 is formed with zinc oxide at the convex part of the back of the concavity. An upper electrode 12 is formed with an electric conductive material such as alminum, and the substrate 10 serves as a lower electrode. A sonic field medium 6 is water. An electric field of an ultrasonic frequency is added to the upper electrode 12 and the substrate which is the lower electrode, and ultrasonic waves are generated. At this time, acoustic discontinuity between gold forming the substrate 10 and water which is a sonic field medium is cancelled by having used silicon dioxide as the matching layer 13. Therefore this kind of structure gives wide range characteristic without much loss.