Abstract:
Apart from being a security device holography has the potential to become the ultimate 3-D format within the next few decades as the holographic image can be called a true replica indistinguishable from reality. But there is much more to holographic imagery than mere replication. Holography had its beginnings in 1948. Denis Gabor, a Hungarian-born physicist working for the electrical company British Thompson Huston based in Rugby, UK, who was atempting to improve the resolution of electron microscope images and hit upon the idea of recording the actual radiated wavefront emanating from the object. As a beam of electrons could not at the time be made coherent he used green-filtered light light from a mercury vapour lamp. In a seminal paper describing his findings (Gabor 1949) he explained how light of a single frequency carried all the information describing the object contained in the light wavefront and soon after named his invention holography, the word holography comes from the Greek words ὅλος (hólos; "whole") and γραφή (grafē; "writing" or "drawing"). This, he argued, could be recorded on a photographic emulsion. He succeeded in achieving this after a fashion, though his mercury lamp produced a band of wavelengths nowhere near as narrow as he would have desired. As a result of this large bandwidth his earliest images had to be very small two-dimensional transparencies no larger than a pinhead, and even these were blurred, and distorted by an unwanted complementary image directly in front. But although his experiment was crude and unconvincing his theory was sound, and he was eventually to receive the Nobel Prize for Physics in 1971 for his ingenuity, though others had needed to find methods of making his ideas workable. Today holograms appear everywhere, on bank cards, passes and any document that needs security protection. Holography also finds applications in the decorative trade, and in engineering, where it is used in nondestructive testing in the form of holographic interferometry.
