Introduction

What distinguishes engineering from other technical areas is inventiveness in the solution to a problem even when complete understanding is lacking. Consider that steam engines were developed before thermodynamics was well understood and it took mathematicians to put Fourier's method on a firm theoretical foundation. Once established, theory is used to make continued advances. Such is the case in imaging as well. Spectacles were used long before an understanding of optics was developed, but that understanding is what led to the development of more complicated instruments.