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Holography may be better understood via an examination of its differences from ordinary photography: A hologram represents a recording of information regarding the light that came from the original scene as scattered in a range of directions rather than from only one direction, as in a photograph.
The exposure time required to record the hologram depends on the laser power available, on the particular medium used and on the size and nature of the object(s) to be recorded, just as in conventional photography. This determines the stability requirements.
Since its introduction, vibrometry by holographic interferometry has become commonplace. Powell and Stetson have shown that the fringes of the time-averaged hologram of a vibrating object correspond to the zeros of the Bessel function (), where (,) is the modulation depth of the phase modulation of the optical field at , on the object. [1]
The term hologram stands for “whole”—holo in Greek, plus “information” or “message”—gram in Greek. In a holographic photography, the information describing a 3D object is encoded on a two-dimensional photographic film, ready to be regenerated into a holographic image or hologram. A characteristic feature is the “whole in every ...
The phase-shifting (or phase-stepped) digital holography process entails capturing multiple interferograms that each indicate the optical phase relationships between light returned from all points on the illuminated object and a controlled reference beam of light. The optical phase of the reference beam is shifted from one sampled interferogram ...
Electronic speckle pattern interferometry (ESPI), [1] also known as TV holography, is a technique that uses laser light, together with video detection, recording and processing, to visualise static and dynamic displacements of components with optically rough surfaces. The visualisation is in the form of fringes on the image, where each fringe ...
Lytro Illum 2nd generation light field camera Front and back of a Lytro, the first consumer light field camera, showing the front lens and LCD touchscreen. A light field camera, also known as a plenoptic camera, is a camera that captures information about the light field emanating from a scene; that is, the intensity of light in a scene, and also the precise direction that the light rays are ...
(Note that in the 1960s, "digital holography" could mean either to compute an image from a hologram or to compute a hologram from a 3D model. The latter developed in parallel with classical holography during the hiatus, and during that time, "digital holography" was synonymous with what is now known as computer generated holography .)