Holography
Hologram (Disambiguation)
A hologram is a physical structure that uses light diffraction to make an image;the image can appear to be three-dimensional. 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 highpowered 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.
How It Work
Holography is a technique that enables a light field (which is generally the result of a light source scattered off objects) to be recorded and later reconstructed when the original light field is no longer present, due to the absence of the original objects.Holography can be thought of as somewhat similar to sound recording, whereby a sound field created by vibrating matter like musical instruments or vocal cords, is encoded in such a way that it can be reproduced later, without the presence of the original vibrating matter. However, it is even more similar to Ambisonic sound recording in which any listening angle of a sound field can be reproduced in the reproduction. In laser holography, the hologram is recorded using a source of laser light, which is very pure in its color and orderly in its composition.
Various setups may be used, and several types of holograms can be made, but all involve the interaction of light coming from different directions and producing a microscopic interference pattern which a plate, film, or other medium photographically records. In one common arrangement, the laser beam is split into two, one known as the object beam and the other as the reference beam. The object beam is expanded by passing it through a lens and used to illuminate the subject. The recording medium is located where this light, after being reflected or scattered by the subject, will strike it. The edges of the medium will ultimately serve as a window through which the subject is seen, so its location is chosen with that in mind. The reference beam is expanded and made to shine directly on the medium, where it interacts with the light coming from the subject to create the desired interference pattern.
Like conventional photography, holography requires an appropriate exposure time to correctly affect the recording medium. Unlike conventional photography, during the exposure the light source, the optical elements, the recording medium, and the subject must all remain perfectly motionless relative to each other, to within about a quarter of the wavelength of the light, or the interference pattern will be blurred and the hologram spoiled. With living subjects and some unstable materials, that is only possible if a very intense and extremely brief pulse of laser light is used, a hazardous procedure which is rare and rarely done outside of scientific and industrial laboratory settings. Exposures lasting several seconds to several minutes, using a much lowerpowered continuously operating laser, are typical.
Overview & History
The Hungarian-British physicist Dennis Gabor (in Hungarian: Gábor Dénes)was awarded the Nobel Prize in Physics in 1971 "for his invention and development of the holographic method".His work, done in the late 1940s, was built on pioneering work in the field of X-ray microscopy by other scientists including Mieczysław Wolfke in 1920 and William Lawrence Bragg in 1939.The discovery was an unexpected result of research into improving electron microscopes at the British Thomson-Houston (BTH) Company in Rugby, England, and the company filed a patent in December 1947 (patent GB685286). The technique as originally invented is still used in electron microscopy, where it is known as electron holography, but optical holography did not really advance until the development of the laser in 1960. The word holography comes from the Greek words ὅλος (holos; "whole") and γραφή (graphē; "writing" or "drawing").The development of the laser enabled the first practical optical holograms that recorded 3D objects to be made in
1962 by Yuri Denisyuk in the Soviet Union and by Emmett Leith and Juris Upatnieks at the University of Michigan, USA.Early holograms used silver halide photographic emulsions as the recording medium. They were not very efficient as the produced grating absorbed much of the incident light. Various methods of converting the variation in transmission to a variation in refractive index (known as "bleaching") were developed which enabled much more efficient holograms to be produced. Several types of holograms can be made. Transmission holograms, such as those produced by Leith and Upatnieks, are viewed by shining laser light through them and looking at the reconstructed image from the side of the hologram opposite the source.A later refinement, the "rainbow transmission" hologram, allows more convenient illumination by white light rather than by lasers.Rainbow holograms are commonly used
Another kind of common hologram, the reflection or Denisyuk hologram, can also be viewed using a white-light illumination source on the same side of the hologram as the viewer and is the type of hologram normally seen in holographic displays. They are also capable of multicolour-image reproduction. Specular holography is a related technique for making three-dimensional images by controlling the motion of specularities on a two-dimensional surface. It works by reflectively or refractively manipulating bundles of light rays, whereas Gabor-style holography works by diffractively reconstructing wavefronts. Most holograms produced are of static objects but systems for displaying changing scenes on a holographic volumetric display are now being developed. Holograms can also be used to store, retrieve, and process information optically.
In its early days, holography required highpower and expensive lasers, but currently, massproduced low-cost laser diodes, such as those found on DVD recorders and used in other common applications, can be used to make holograms and have made holography much more accessible to low-budget researchers, artists and dedicated hobbyists. It was thought that it would be possible to use X-rays to make holograms of very small objects and view them using visible light.Today, holograms with x-rays are generated by using synchrotrons or x-ray free-electron lasers as radiation sources and pixelated detectors such as CCDs as recording medium. The reconstruction is then retrieved via computation. Due to the shorter wavelength of x-rays compared to visible light, this approach allows imaging objects with higher spatial resolution.As free-electron lasers can provide ultrashort and x-ray pulses in the range of femtoseconds which are intense and coherent, x-ray holography has been used to capture ultrafast dynamic processes.
13 Hologram Projections Around the World
Few things seem quite as futuristic as holograms and holographic projections. Having said that, a lot of the things we class as being "holograms" aren't exactly holograms in the strictest definition of the world. For the purpose of this article, we'll be looking at any projection that creates a 3D image or the illusion of a 3D image, through various different methods. From concerts and advertising, to communication and art installations, holographic projections have been delighting and astounding audiences all over the globe. Here are just some examples of mind-blowing holograms that have more to them than just stunning visuals.
1. The Tupac Hologram: The Act that Kickstarted the Hologram Trend There have been plenty of similar performances since, but the 2012 Coachella performance - which saw Snoop Dogg rap alongside a virtual rendering of Tupac Shakur - was a watershed moment in music and hologram technology. While headlines reported the display as a "hologram", it can more accurately be described as a "Pepper's Ghost" - an optical illusion that dates back to the 19th Century.
While the image of Tupac himself was carefully rendered through state-of-the-art CGI by Digital Domain, the overall 3D effect of him strutting the stage was created through more analog means. The stage was fitted with a pane of glass, behind which was a projector playing the animation of Tupac. The image bounced and reflected off the glass, giving the illusion of a three-dimensional figure.
2. Hatsune Miku: Blurring the Lines Between Cartoons and Reality You may have already come across videos of Vocaloids - the fully-synthetic Japanese pop stars whose voices and images are created entirely on computers. Perhaps the most famous Vocaloid is Hatsune Miku, a pig-tailed anime superstar who delights human audiences all over the globe. Much like Coachella's Tupac stunt, Miku is brought to life through computer graphics and carefully-placed glass panes. Through doing this, she can not only tour the world without actually traveling, but also blur the lines between cartoons and our reality. Though the technology behind her performances is old, the Vocaloid trend has opened the door for an exciting future of performers who don't need to be human or even physically present to entertain us.
3. Holograms For Freedom: Technology Gets Political In 2015 a mob of holographic protestors marched to the Spanish parliament as part of the world's first ever virtual protest. The protest was in response to a so-called "gag law", which saw heavy penalties directed at Spanish citizens who protested in person outside of government buildings.
It was a clever way to work around the prohibitive new laws, and also a major moment in hologram technology. The images were created from 2,000 submissions by citizens, who sent their own likenesses to be used in the protest. Organized in large part by Javier Urbaneja, the display consisted of a large transparent scrim onto which the images were projected.Â
4. Pixie Dust Tech's Fairy Lights: Holograms You Can Touch 2015 proved to be a landmark year for hologram technology. Not only did it see the first ever holographic protest, but also the unveiling of touchable holograms. Japanese company, Pixie Dust Technologies, created Fairy Lights in Femtoseconds - tangible holograms created by ultra-fast lasers. The lasers burst forth at one quadrillionth of a second, and create three-dimensional images by ionizing the air. Apparently, the tiny apparitions feel not unlike sandpaper. The future application of such technology could bring us closer to realistic holograms that not only look real, but feel real too.
5. Pixie Dust Tech's Holographic Whisper: Audible Holograms Ever the innovators, Pixie Dust Technologies attracted more attention in 2016 for their Holographic Whisper - a device that concentrates sound into a visible, 3D shape. The remarkable technology uses ultrasonics to suspend soundwaves in thin air. These soundwaves are concentrated into a single focal point, allowing them to operate similarly to speakers without any of the hardware. With technology like this available, maybe someday concerts and events where holographic sound is used instead of speakers could become the norm.Â
6. Aerial Burton: 3D Laser Plasma Holograms Pixie Dust Technologies aren't the only ones utilizing femtosecond bursts of lasers to create incredible holograms. Japanese company, Aerial Burton, have also created touch-sensitive holograms using similar technology. Their holograms caught the attention of the press in 2015 as some of the first holograms that didn't require a screen for their projections. The groundbreaking technology didn't come together overnight though. The first Aerial Burton prototypes ionized the air into a plasma so hot that it could burn through leather. By quickening the speeds and frequency of their laser bursts, they were able to make the holograms safe to touch.
7. VNTANA'S Hologram Concierge: The Future of Customer Service In the near future, a hologram could assist you with finding the right items in a store. That's all thanks to VNTANA and their partners, Satisfi Labs, who have created a holographic AI that could greet and serve human guests. While Satisfi Labs handled the AI side of things, VNTANA provided the hologram technology. The projection responds in real-time to human users, and utilizes cloud technology to learn and adapt to its role. The hologram would even be able to order out of stock items for a customer, should they request it.
8. The Princess Leia Project: Recreating the Most Iconic Hologram Ever There are few fictional depictions of holograms as iconic as that of Princess Leia's desperate plea for Obi Wan's help in A New Hope. The famous scene inspired generations of scientists and engineers, so it's not surprising that researchers at BYU decided to use their breakthroughs to recreate the film's holographic message. Leading the project is Daniel Smalley, who is quick to explain that the image of Leia is not technically a hologram, but rather a volumetric image. A volumetric images are created by trapping a particle with a laser. When the particle is moved by the laser, it creates the image. Smalley describes the process as being similar to that of a 3D printer, but using light in mid-air.Â
9. Euclideon Hologram Table: The First Multi-User Hologram Table Australian company, Euclideon, unveiled their hologram table last year and it's cited to be available for purchase at some point this year. The table is the first of its kind, in that it allows multiple users to interact with data visually.
Users have to wear special glasses in order to interact with the table's holograms, which separate the light frequencies and arrange the image as it's meant to be seen. Application of the tech ranges from everything from military strategies to architectural design.
10. Hypervsn: Changing How We Advertise Of all the entries on this list, Hypervsn probably looks like most like something out of a sci-fi film. The impressive displays can be used to advertise pretty much any product, and appear like 3D objects floating in the air. It's important to note, however, that Hypervsn doesn't create holograms in the strictest sense. Instead, the image is the result of LEDs spinning quickly to create the illusion of a three-dimensional object.
11. THÉORIZ Interactive Holograms: Where Art and Science Collide French art collective, THÉORIZ, create mindblowing interactive hologram projections. Their installations typically see an entire room projected with images that respond in real-time to movement. The collective is made up of artists and engineers who create everything from large-scale projectionmapping events to interactive installations. Their work typically uses a combination of projection, motion-tracking technology, and augmented reality techniques.
12. Volume by Looking Glass: Your Own Hologram Player Soon you could be watching holograms in the comfort of your own home as casually as you watch TV. In 2016 Looking Glass revealed Volume - a device they're marketing as a personal volumetric display. The device appears like a glass box, and allows users to view and interact with volumetric images without the aid of glasses or headsets. Looking Glass promises a host of possible applications for the tech, including allowing expectant mothers the opportunity to view scans of their unborn babies in full 360 degrees.Â
13. TeleHuman 2: The Next Best Thing To Being There In Person Who needs Skype when you could chat with a life-sized hologram of your loved ones? Earlier this year, researchers from Canada's Queen's University unveiled TeleHuman 2 - a holographic platform for chatting in real-time with a fully 3D, 360 degree display. Three cameras record the image of the person whose likeness is being transmitted, where it is then transmitted and displayed within a glass cylinder. The reflective glass, paired with a hoop of 40 projectors, gives the image its 3D appearance.Â
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Yu Min Chen