19.1 INTRODUCTION

In an attempt to correct the spherical aberration of the electron microscope, Dennis Gabor1 ^,2 gave birth to the basic concepts of holography in 1948, for which he was awarded the Nobel Prize in physics in 1971. However, it was not until after the invention of the laser and further contributions by E. N. Leith and J. Upatnieks3 ^,4 ^,5 and independently by Yu. N. Denisyuk6 ^,7 ^,8 that holography was developed to the present stage.

In the discussion that follows, we will concentrate on optical holography, although the concepts involved are applicable to any type of coherent waves. In particular, we will analyze the recording and reconstruction of the wavefronts of a three-dimensional object. These analyses are applicable to hybrid developments summarized in Sec. 19.5.

Generally, the process of holography can be defined as the recording of the interference pattern between two mutually coherent radiation fields on a two- or three-dimensional medium. The result is said to be a hologram. It is a complex diffraction grating. When one of the fields is directed at the hologram, the diffraction reconstructs the wavefronts of the other field.

Holography can be studied and appreciated at many levels. It is sufficiently simple for those without a technical background to produce beautiful works of art. Indeed, it can now be pursued at the same level as photography.

19.2 THEORY OF HOLOGRAPHIC IMAGING

The most elegant exposition on holography is through the mathematics...