Non-destructive evaluation is a branch of science that is concerned with all the aspects of uniformity, quality and serviceability of materials and structures. By definition, nondestructive evaluations are the means by which materials and structures may be inspected without disruption or impairment of their serviceability. Using NDE, internal properties of hidden flaws are revealed or inferred by appropriate techniques. Another important application of NDE is in process control monitoring where NDE techniques are used in the development of new materials and their evaluation. NDE is becoming an increasingly vital factor in the effective conduct of research, development, design and manufacturing programs. Aircraft industry is a prime example of this need for NDE. The fleet of commercial and military aircraft that are in use today is aging and consequently it has become critical to develop economical and fast systems for inspection of turbine blades, wing structures etc. Also, the materials used in the manufacturing industries vary widely from exotic composite materials to conventional materials like aluminum and nickel. So, the inspection systems must be capable of handling such varied materials in addition to speed and cost considerations.