Introduction to Holography
                     
A hologram can be a physique that diffracts light right into a picture. The term ‘hologram’ can reference both encoded material as well as the resulting image.  A holographic image is seen by searching into an illuminated holographic print or by shining a laser using a hologram and projecting the appearance onto a screen.  Different ways of projecting and reflecting images are often known as holographic - or possibly misleadingly holograms, since they provide an optical presence, spatial quality or iridescent colors.  Even though it yesteryear it there's a apparent distinction technology is evolving to create virtual holograms by steering light right into a picture.   Augmented reality systems like the HoloLens frequently utilize a Holographic Optical Elements to produce a video projection appear at comfortable viewing distance.  The virtual objects in augmented reality are a kind of ‘virtual hologram’  Kate Moss appears just like a Pepper's ghost video projection  Kate Moss appears just like a Pepper’s ghost video projection  Alexander McQueen A/W 06 show  via: GRAZIA   & not just a hologram -  The Pepper’s ghost technique, which relies on a partially reflective surface to mix an image while using scene beyond.  John Henry Pepper proven the procedure inside the 1860s from it becoming accustomed to overlay visual elements (frequently a sum - ‘ghost’) onto a real set or stage.  How can holography work?  Review of Holography video by Thomas G. Cruz (1972)  Holography is founded on the important thing of interference. A hologram captures the interference pattern between several beams of coherent light (i.e. laser light). One beam is shone onto it medium and processes just like a reference to light scattered within the illuminated scene.  how-does-holo-work_sources  via: Cornell College, the 3D Revolution, holmarc.com  how-does-holo-work_4steps  Sketch of process: Recording, Renovation, Transfer and Display  The hologram captures light since it interests the whole area of the film, hence being known as ‘window with memory’. In comparison a picture captures only one small area ‘aperture’ of perspective, the picture taking image being created by focusing this light onto film or possibly an electronic sensor.  The physical medium of holographic film is photo-sensitive getting an excellent grain structure1. Common materials used are silver-halide emulsions, dichromate gelatins and photopolymers - each getting their particular characteristics and need different processing. Holograms can also be embossed ‘stamped in to a foil’ with applications including in security identification, for instance on passports, bank cards, tickets and packaging, since they're difficult to copy without any master hologram.  The hologram could be the recorded interference pattern of constructive (intensity peaks) and destructive (elimination) in the superimposed light-wavefronts (the electromagnetic field). Utilizing a coherent laser light-source plus a stable geometry (or short ‘pulse’ duration) the interference pattern is stationary and is recorded to the hologram’s photosensitive emulsion. The hologram is going to be chemically processed2 therefore the emulsion features a modulated density, freezing the interference pattern into ‘fringes’.  A Moiré pattern  A Moiré pattern is because of the interference of two similar undulating patterns, for instance stripes  The Moiré pattern proven above originates from the superposition from the shifted wave-pattern  (source Kafri 1990, p31)  An plane wave passing using a barrier, resulting in diffraction and interference  An plane wave passing using a barrier (traveling left to right), resulting in diffraction and interference  When searching within the modulated structure within microscope it does not appear such as the look encoded within. The density fringes certainly are a distributed pattern of wavefront interference - a frozen distributed recording in the direction, phase and amplitude regarding (the visible spectrum of electron-magnetic radiation).  When the hologram is re-illuminated the sun's rays is diffracted using these fringes. Once the direction and shape (curvature) in the light is the same as the reference beam your hologram diffracts the sun's rays to the type of another wavefront, reconstructing the recorded image.  The relationships which may be setup while using holographic image advise a specific approach to considering optical information. While there are a number of how of making holograms, each getting their particular aesthetic characteristics each one has the identical underlying principle. Holography is really a way of encoding recording an interference pattern.  On encountering a hologram, what's most surprising is always that a surface seems to hold a place. The primary difference of scale involving the optical shaping with the hologram structure and our material sense of it a surface produces a sense of a web-based form, as if the sun's rays holds a unique shape.  Searching at holograms  Viewing a hologram print, the appearance changes when you maneuver around. Exactly like you were searching using a window onto a scene. For the reason that holography records the scene by having an portion of perspective. The viewing window from the hologram can also be broken around record a number of perspectives, this process known as as spatial multiplexing, and enables you to capture animation and/or create a holographic scene in the sequence of two-d images.  The development of holography  The Two fundamental geometries for holograms are - transmission - where light is shone using the hologram, and - reflection - in which the hologram reflects light. It of transmission and reflection holograms were developed from two different fields of enquiry and possess distinct optical appearance.  The reflection hologram was produced by Yuri Denisyuk3 (1927-2006) who used only one beam to both illuminate the product and be the reference. Denisyuk’s process follows the colour and spatial picture taking recording practices of Lippmann photography and Daguerreotypes, which have been created on polished metal surfaces. Gabriel Lippmann (1845-1921) claimed to own invented a technique for colour picture taking recording and provided a scientific explanation of the way the emulsion structure recorded then could rebuild optical standing waves patterns, the particular wavelengths which comprise one image.  Lippmann’s colour technique  While Lippmann was the first ones to explain this process, later analysis has shown that his method of recording appeared as if the Daguerreotype4. In a Daguerreotype/Lippmann recording as well as the reflection hologram, the colour in the image is selective, only being produced with the wavelengths that resonate while using spacing in the fringes.  Hendes Bjelkhagen BejeweledFish  Hendes Bjelkhagen, BejeweledFish  True colour (panchromatic) reflection hologram  Han Bjelkhagen can be a investigator which has labored extensively  to boost the colour reproduction characteristics of holograms.  Through the use of multiple colour lasers an entire colour Denisyuk reflection hologram might be recorded which is almost indistinguishable within the original object. The inclination on encountering this sort of image is always to check its authenticity - to look behind the dish for your object.  Gabor’s holographic imaging method  Gabor’s holographic imaging method  a) Original micrograph, 1.4 mm. diameter b) Micrograph, directly photographed c) Interference pattern, from acquired by projecting the micrograph onto a photograph taking plate getting a beam diverging from apoint focus d) Renovation from interference pattern  (source Gabor, 1948)  The whole process of transmission holography developed from numerous scientific experiments plus a developing understanding from the wave-nature of electro-magnetic radiation. In 1912 by Max von Laue proven the diffraction of x-sun sun rays using a very lattice of copper sulphate. Experimental effects were then formulated in 1913 by father and boy, William Henry Bragg and William Lawrence Bragg, into Bragg’s law of diffraction (2dsin ? = n?), which equates the perimeter spacing (d) for the position of deflection (?) for almost any given wave length (?)5. Applying this relationship diffraction gratings could be produced to handle the positioning of deflected light and separate different wavelengths regarding.  Train and Bird, 1964  Train and Bird, 1964  Laser-viewable transmission hologram  via: Holophile  The key factor area of the introduction of holographic imaging was utilizing a reference beam to encode one wave by superimposing it with another (to record the interference pattern). This ‘double diffraction’ process was recommended by Denis Gabor in 1948 to enable them to improve design for the x-ray (electron) microscope. Gabor’s experiments were limited to optical-waves traveling near the optical axis (paraxial sun sun rays) and for that reason when useful for optical holography the renovation beam was co-incident while using image, and for that reason would shine in to the viewer’s eyes.  Emmett Leith and Juris Upatnieks while coping with side-studying radar developed the entire process of off-axis optical holography in 1962. Their theory shown practically possible after they acquired utilization of a laser in 1964 and produced numerous holograms. The opportunity of holography was recognised when these holograms were printed, developing a flurry of research and Gabor’s awarding in the Noble Prize for Physics.  As transmission holograms diffract all of the illumination to the image, ‘mono-chromatic’ light (for instance in the laser) is needed to rebuild a obvious, crisp image. Stephen Benton developed transfer geometries that allowed transmission holographic prints to get viewed getting a white-colored-colored light like the rainbow hologram in 1969 and ultizing an achromatic geometry in 1977 to recombine the spectrum.  rainbow-spectrum-3  Left: Stephen Benton searching inside a rainbow hologram (via: http://internet.media.durch.edu/)  Center: Polaroid Patent Rainbow Hologram, 1975  Rainbow hologram on film in card mount, 4.5” x 7” (11.4 x 17.8 cm)  Right: Stephen Benton, Herbert Mingace, Junior. and William Houde-Walter, The Bartlett Mind (Aphrodite), 1978  Achromatic white-colored-colored-light transmission hologram on glass, 13.5 x 12.5” (34.3 times 31.8 cm)  Different types and techniques of holography employed by artists  There are a number of distinct types of display holograms which may be according to their optical-geometry as well as the recording medium.  Laser viewable transmission holograms  The laser viewable transmission hologram enables for just about any near perfect renovation in the optical field. Meaning the recorded scene appears behind the show, then when replayed having a laser this scene can be very deep and sharp. These holograms may also be utilized being an expert recording that could then be transferred in to a reflection or transmission holographic print.  Artist Paula Dawson which has labored extensively with laser viewable transmission holograms describes these tracks as ‘concrete’ holographic images since they create a sense of physical presence. 



Introduction 
to 

Holography
Image credit:statphys.sissa


A hologram can be a physique that diffracts light right 
into a picture. The term ‘hologram’ can reference both 
encoded material as well as the resulting image.

A holographic image is seen by searching into an 
illuminated holographic print or by shining a laser 
using a hologram and projecting the appearance onto 
a screen.

Different ways of projecting and reflecting images are 
often known as holographic ­ or possibly misleadingly 
holograms, since they provide an optical presence, 
spatial quality or iridescent colours.


How can holography work?

Holography is founded on the important thing of 
interference. A hologram captures the interference 
pattern between several beams of coherent light (i.e. 
laser light). One beam is shone onto it medium and 
processes just like a reference to light scattered within 
the illuminated scene.


Sketch of process: Recording, Renovation, Transfer 
and Display

The hologram captures light since it interests the 
whole area of the film, hence being known as ‘window 
with memory’. In comparison a picture captures only 
one small area ‘aperture’ of perspective, the picture 
taking image being created by focusing this light onto 
film or possibly an electronic sensor.


Searching at holograms

Viewing a hologram print, the appearance changes 
when you around. Exactly like you were searching 
using a window onto a scene. For the reason that 
holography records the scene by having an portion of 
perspective. The viewing window from the hologram 
can also be broken around record a number of 
perspectives, this process known as as spatial 
multiplexing, and enables you to capture animation 
and/or create a holographic scene in the sequence of 
two­d images.


Different types and techniques of holography 
employed by artists

There are a number of distinct types of display 
holograms which may be according to their optical­
geometry as well as the recording medium.


Laser viewable transmission holograms

The laser viewable transmission hologram enables for 
just about any near perfect renovation in the optical 
field. Meaning the recorded scene appears behind the 
show, then when replayed having a laser this scene 
can be very deep and sharp. These holograms may 
also be utilized being an expert recording that could 
then be transferred in to a reflection or transmission 
holographic print.


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