It seems as though everyone is mesmerized with the possibilities and potential of holographic displays, especially since Star Wars brought the technology to the forefront in 1977. Holographic technology has been with us since 1948, but we are just beginning to see practical advantages of the technology with future advances just down the road.
In a 2008 Grammy performance, Alicia keys teamed up with a holographic image of Frank Sinatra. Large-scale holograms, such as this, are astonishing. They are two-dimensional surfaces that show accurate, three-dimensional images of real objects.
Just like looking at real objects, you can look at a hologram from different angles and see the object from different perspectives. This includes revealing part of the image which was hidden at another viewing angle. Some holograms look as though they are moving, as you walk past them and view them at different angles.
Holography is photography, but without a lens. The hologram is a record of the interference pattern created when two beams of laser light interfere (to come into collision or clash) on the holographic surface. One beam, called the reference beam, strikes the holographic plate directly from the laser. The other beam is called the object beam. It reaches the holographic plate after bouncing off of the object being photographed. These two beams are initially coherent and in phase with one another, but after the object beam bounces off of an object, it will be out of phase with the reference beam. The two beams will interfere at the plate. This creates areas of high amplitude and low amplitude, or light and dark bands. These bands are recorded on the holographic surface, and preserved through the developing process. The bands of light and dark act as an extremely sophisticated diffraction grating, so that when light passes through the plate or film, it interferes to form the exact image of the object that was recorded.
Viewing the hologram at different angles will give a different view of the object, giving it its three dimensional appearance. The eyes of a human are separated by several centimeters, giving different views, which the brain interprets as being in three dimensions.
The simplest hologram is a reflection hologram. This hologram is formed when the reference beam and the object beam meet on opposite sides of the holographic surface. They interfere and record an image. To reconstruct the image, a point source of white light illuminates the hologram from the proper angle, and the viewer looks at it from the same side as the light source. Reflection holograms require the simplest setup, and are visible without laser light.
The other type of hologram is a transmission hologram, where you look through the film and see the three dimensional image suspended in midair at a point which corresponds to the position of the real object which was photographed. This type of hologram is created when the reference beam and the object beam meet on the same side of the holographic surface. They are viewed by shining a spread out laser light through the emulsion side (dull side) of the hologram at the same angle that the hologram was recorded with the viewer looking on from the opposite side. Transmission holograms must be viewed with laser light, and they appear the same color as the laser used to view and create them.
Holographic projection is a 3-D technology where audiences can view 3-D virtual figures without wearing glasses. The technology is at present mainly used in museums and entertainment stages.
AirportONE.com introduced AVA, the Advanced Virtual Hologram and entered into the service and retail industry. The Port Authority of New York & New Jersey has installed three airportONE.com airport virtual assistants/holograms at Newark Liberty, LaGuardia and John F. Kennedy International Airports. The Port Authority virtual assistants have been programmed to answer basic questions most frequently asked by passengers. Additional virtual assistants have been installed at Long Beach Airport and other installations are in process at numerous locations. AVA can be used as a virtual receptionist to direct customers or as a model in department stores.
Holography can be used as a new artistic medium, as many artists use holograms to capture their subjects. Holograms also can be used to preserve art with a holographic copy, which can be made that is nearly as good as the original, without damaging the original.
Holographic optical elements are used for navigation by airplane pilots. A holographic image of the cockpit instruments appears to float in front of the windshield, allowing the pilot to keep his/her eyes on the runway or the sky while information is relayed through the windshield.
The military is already using heads-up displays (HUD) on holographic windshields installed in combat aircraft. Automotive manufacturers are experimenting with this technology for future use in cars.
Holographic interferometry is used in numerous laboratories for non-destructive testing (NDT). It visually reveals structural faults without damaging the sample. Holography offers a number of advantages, such as direct and overall visualization of defects, such as disbonding, formation of cracks, and inhomogeneities on large surfaces. This is done without interaction with the object under test and the surface to be studied. It is possible to detect deformations as small as a few microns. This kind of testing can be used to detect and observe cracking in fatigue tests; and it can be used for the visualization of the modes of vibration of mechanical structures.
Digital holograms—whether of DNA, cells, full-sized organs, or even the life-sized human body itself—can be holographically printed for a range of 3-D analysis applications in the biomedical industry.
3-D digital holograms can be created from almost any type of biomedical datasets from protein database files to medical scans, such as computed tomography (CT), magnetic resonance imaging (MRI), and ultrasound scans.
Holographic technology will play a more prominent role in the creation of 3-D architectural models. Such architectural renderings would be able to show if a building design had any critical flaws, or if any of the dimensions were improperly calculated.
Virtual holography provides an interactive 3-D model, which opens up considerable presentational opportunities, such as fully interactive virtual images. Architects can change the materials and interiors in real time with the help of a touchpad, tablet, or other device.
The military has developed holographic night vision goggles with 3-D vision perception and sensor fusion. They have been especially developed for the advanced future needs of individual soldiers, drivers, Special Forces, and helicopter crews.
For the soldier of the 21st century, they offer a distinctive concept of image mixture with total depth perception and day/night awareness of the battlefield situation. Due to the holographic optical elements, a see-through image is possible with a large field of view during unforeseen changes in the level of light. Reports, such as digitized battlefield information, are continuously available in the field of view and can be viewed by the soldier at any time without disturbing the observation of the battlefield.
Samsung has invested $10 million in the Israeli company, Mantis Vision, to produce a technology that allows 3-D holographic recording of moving images. The company has already produced a prototype, handheld 3-D image scanner that allows a playback of the scene that can be viewed from any angle. A new method for creating holograms significantly improves image clarity and makes the technology affordable. The technology holds promise for glasses-free 3-D televisions.
Using sinusoidal waves rather than dedicated pixels, as the basis for the holograms, a modulator can create more realistic color by superimposing red, green and blue light simultaneously instead of sequentially, as the existing pixelated modulators do.
“Computer, call Jack in the Hong Kong office.” Seconds later, Jack will be sitting in your office, or rather his holographic image. In Hong Kong, Jack will experience the same immersive connection. That's the concept of tele-immersion – bringing two or more distant people together in a single, simulated office setting. Business travel will be a thing of the past. The functions of immersive holographic environments are infinite.
The future of holography is very promising with the next generation of holographic images that will be startling in their realism. Using these astonishing images, we will see holographic displays expanding into many different technologies.
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Len Calderone – Contributing Editor
Len has contributed articles to several publications. He also writes opinion editorials for a local newspaper. He is now retired.