Foreword

Natural scientists belong to one of two categories: either they deal with matter and energy, or they are concerned with signals and systems. Sometimes collaboration of these two kinds of scientists is essential for solving problems at hand. The emergence of holography was a typical case, where systems people saved the physics people. Originally, holograms caused amusing displays. Now holograms are also used at industrial jobs. To do that the physical optics people had to adapt the working style of systems people to what is now often called "digital holography", the subject of this book.

Back in 1948 Dennis Gabor succeeded in producing holograms. The objects usually consisted of a few dark lines on a large transparent background. The method did not work properly with a negative as object, i.e. a few bright narrow lines. More annoying was the twin image that appeared at an undesirable location. Gabor attempted to solve this problem with the help of tools from physical optics: lenses, prisms, and beam-splitters in a Mach-Zehnder interferometer. No luck, he gave up. When appointed Professor at the Imperial College, London, in 1959, he presented, in his acceptance speech, his three most noticeable inventions. Holography was not a part of it.

Meanwhile, I had learned from a systems scientist what single side-band modulation can do. We tried it with a modest success, shortly before Emmett Leith solved the problems with his tilted reference method. Leith, in his memoirs, wrote that he was lucky to be a physicist surrounded by signal-processing experts. Systems theory is much richer in concepts beyond side-band processing. Another interesting concept is matched filtering. It was soon translated from electronic filtering to optical spatial filtering.

This new book is a tremendous collection of digital signal and image processing in general, and specifically on digital holography. It presents digital holography in one unified language called "algorithmics". The volume appears at an appropriate time, i.e. while optics is mutating from micro to nano with typical dimensions 10-3 and 10-6 microns.

I am amazed when I compared today's capabilities with what was available around 1950-1960. When will we have mobile-3D-in color impressions? The youth is so powerful. They will simply demand it, and get it because of the market. Good luck!