Visual observation of surrounding objects can arbitrarily be divided into several consecutive stages. The first stage is the illumination of an object with some source of light. The light wave is reflected from the object and carries away the information on the object. The pupil of the eye selects a small part of the wave front and the crystalline lens in the eye forms an image which gives rise to a mental concept of the object formed in the brain by photochemical processes. The propagation of light from the object to the pupil is an autonomous process and this is expressed by the well known Huygens-Fresnel principle, which states that the wave reflected from an object becomes independent of it and is propagated in accordance with the laws of diffraction. Before the advent of holography all methods of storage or transmission of information have been concerned not with the light wave but with the image formed from this wave with the aid of a lens.
KeywordsInterference Fringe Reference Beam Photographic Plate Amplitude Transmittance Object Wave
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