Holography | Wikipedia audio article
Channel: wikipedia tts
Date: 2019-05-06

This is an audio version of the Wikipedia Article:
https://en.wikipedia.org/wiki/Holography


00:02:12 1 Overview and history
00:06:28 2 How it works
00:07:07 2.1 Laser
00:09:04 2.2 Apparatus
00:10:31 2.3 Process
00:11:33 2.4 Vs. photography
00:14:04 3 Physics of holography
00:14:49 3.1 Plane wavefronts
00:16:00 3.2 Point sources
00:16:57 3.3 Complex objects
00:18:14 3.4 Mathematical model
00:23:06 4 Recording a hologram
00:23:16 4.1 Items required
00:27:39 4.2 Hologram classifications
00:28:06 4.2.1 Amplitude and phase modulation holograms
00:29:13 4.2.2 Thin holograms and thick (volume) holograms
00:30:31 4.2.3 Transmission and reflection holograms
00:31:36 4.3 Holographic recording media
00:33:29 4.4 Copying and mass production
00:36:43 5 Reconstructing and viewing the holographic image
00:39:08 5.1 Volume holograms
00:40:07 5.2 Rainbow holograms
00:41:38 5.3 Fidelity of the reconstructed beam
00:43:21 6 Applications
00:43:30 6.1 Art
00:46:25 6.2 bPerformance/b
00:47:24 6.3 Data storage
00:49:41 6.4 Dynamic holography
00:52:02 6.5 Hobbyist use
00:56:25 6.6 Holographic interferometry
00:57:11 6.7 Interferometric microscopy
00:57:55 6.8 Sensors or biosensors
00:58:17 6.9 Security
00:59:11 6.10 Other applications
01:00:13 6.10.1 Electrical and electronic products
01:00:39 6.10.2 Hologram dockets for vehicle number plate
01:01:00 6.10.3 High security holograms for credit cards
01:01:30 7 Non-optical
01:03:28 8 False holograms
01:06:27 9 In fiction



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SUMMARY
=======
A hologram is an image that appears to be three dimensional and which can be seen with the naked eye. Holography is the science and practice of making holograms. Typically, a hologram is a photographic recording of a light field, rather than an image formed by a lens. The holographic medium, i.e., the object produced by a holographic process (which itself may be referred to as a hologram) is usually unintelligible when viewed under diffuse ambient light. It is an encoding of the light field as an interference pattern of variations in the opacity, density, or surface profile of the photographic medium. When suitably lit, the interference pattern diffracts the light into an accurate reproduction of the original light field, and the objects that were in it exhibit visual depth cues such as parallax and perspective that change realistically with the relative position of the observer. That is, the view of the image from different angles represents the subject viewed from similar angles.
In its pure form, holography requires the use of laser light for illuminating the subject and for viewing the finished hologram. A microscopic level of detail throughout the recorded scene can be reproduced. In common practice, however, major image quality compromises are made to eliminate the need for laser illumination to view the hologram, and in some cases, to make it. Holographic portraiture often resorts to a non-holographic intermediate imaging procedure, to avoid the hazardous high-powered pulsed lasers otherwise needed to optically "freeze" moving subjects as perfectly as the extremely motion-intolerant holographic recording process requires. Holograms can now also be entirely computer-generated to show objects or scenes that never existed.
Holography is distinct from lenticular and other earlier autostereoscopic 3D display technologies, which can produce superficially similar results but are based on conventional lens imaging. Images requiring the aid of special glasses or other intermediate optics, stage illusions such as Pepper's Ghost and other unusual, baffling, or seemingly magical images are often incorrectly called holograms.