Dipl.-Ing. Dr. Stefan J. Rupitsch
Supervisory committee: | Univ.-Prof. Dipl.-Ing. Dr. Bernhard Zagar |
Final exam: | August 21, 2008 |
The objective of this thesis is the development of a high resolution ultrasound microscope for non-destructive material testing. The realized microscope (see Figure 1) operates using a focused ultrasound transducer with a spherically curved active surface. By means of the transducer pressure waves are emitted as well as received. Synthetic aperture focusing (SAFT) is applied in order to achieve the optimal spatial resolution of the imaging system. This technique combines a sequence of transducer output signals at different transducer positions to improve spatial resolution.
Although synthetic aperture focusing essentially increases the spatial resolution, an additional improvement of the resolution is aspired in this thesis. On this account the locally resolved characteristic of the transducer surface for both transmission and reception is considered (see Figure 2). In order to determine the transducers spatial-temporal characteristic a novel method is presented in this thesis. As part of this method an ill-posed inverses problem is solved. The developed ultrasound microscope can be used to acquire B-mode images ("brightness") as well as C-mode images ("complex") of the object under test. For instance the microscope is able to precisely locate regions where delaminations of layered material occur (see Figure 3). Moreover the bonding areas of semiconductors and their connecting wires can be investigated.