TABLE OF CONTENTS Two pulsed lazer and one air-coupled techniques for acoustic excitation of drug tablets have been proposed as excitation mechanisms and the results of evaluative tablet defect detection experiments are summarized. It is demonstrated that non-contact detection techniques based on these types of excitation are promising in drug tablet defect monitoring and characterization. In all excitation mechanisms, acoustic waves are imparted on the test tablets and their transient surface displacement responses are measured by a lazer interferometer. From the analysis of frequency spectra, and the time-frequency spectrograms obtained, it can be concluded that defective tablets can be effectively differentiated from the nominal ones. According to the vibration plate experimental results, it is possible to distinguish the degree of defect(s) in a tablet. From the frequency spectrum of the transient responses under LIP excitation, it is found that it is possible to distinguish even tablets with shallow circular holes with diameters of approximately 500 ?m (defect type H). The correlation data presented depicts the degree of similarity of defective tablets (defect type H) with a nominal tablet (A), thus it is possible that the level of defect can be predicted. The main use of the correlation data is that even very small defective levels (defects that are undetectable in time-domain) can be detected in tablets. It is demonstrated that a shallow hole (defect H) can be detected using the lazer-induced plasma excitation mechanism, this implies that LIP could be a more effective excitation mechanism than the...
