Volumetric images were made famous by Star Wars                                      The holodeck from Star Trek

 

 

 

 

Volumetric and Holographic Imaging

 

 

 

Volumetric imaging refers to producing images, which have volume to them.  The majority of the images that are artificially produced today consist of only two dimensions, height, and length.  However, volumetric images would also include depth, and provide viewers with a very realistic picture that they could view from all angles, and possibly interact with.

 

 

• The word “hologram” is often used in conjunction with the idea of volumetric imaging.  Holograms are three-dimensional images, but they are known as “stereoscopic” images.  This means that while holograms are three-dimensional in nature, they are shown on a two-dimensional plane, such as a piece of glass or film.

 

• On the other hand, volumetric images are images that can appear three-dimensional, but without the need for any two-dimensional surface.  In other words, a true volumetric image is one that can be displayed in thin air.

 

 

At this time, true volumetric images are not fully understood, and are quite difficult to produce.  Therefore, many three-dimensional imaging systems that exist today, utilize technology that is based off holographic imaging.  This means that these systems will use some type of two-dimensional surface to display a three-dimensional image. 

 

·         Sanyo’s LCD Holographic Projection System

§         Currently, Sanyo is working on a prototype model of a holographic projection system that uses multiple LCD projectors to display three-dimensional images.  Two LCD projectors project images for the left and right eye onto a special screen. Two lens systems for reflecting the images are placed behind the screen and in front of the screen. The rear lenses cause the images to appear as if they are floating off the screen, and the fontal lenses help to direct the images into the viewer’s eyes.

           

·         MIT’s “holo-video” Display System

§         Since the early 1990s, the Spatial Imaging Group at MIT has been working on a way to project moveable, and even interactive holograms using what they have termed a “holo-video” device.  This device projects a three-dimensional image onto a special screen, which is generated using advanced CAD technology, along with power lasers and mirrors. 

§         MIT has developed two models of their holo-video device.  The Mark I model, displays a 25 X 25 X 25 mm picture, in full color.  The Mark II is capable of displaying a 150 X 75 X 75 mm picture also in full color. 

§         Even though these pictures are small, there is a great amount of data in each image. For a 10 X 10 X 10 cm hologram, with a 30° viewing angle, it would require 25 gigabytes of storage space. Furthermore, in order to transfer and display this hologram at 60 frames per second with an 8-bit resolution it would require an astronomically large bandwidth of 12 terabits per second.

 

An image of MIT’s Mark I holo-video device.

 

·         Helix or dish holograms

§         Some holographic projectors use powerful lasers to project points of light onto a spinning dish or helix (spiral).  The Navy currently has such a device that uses two 36’’ semi-transparent spinning helixes.  Three-dimensional color images are obtained by having a group of red, yellow, and green lasers shine light onto the spinning helixes. 

An example of a spinning helix holographic display

 

 

 

True three-dimensional images that “float” in mid air, and that people can walk around and view from all angles, are nearly impossible to produce, except within controlled laboratory experiments.  The reasons for these difficulties stem from things such as proper lighting, and enormous bandwidth requirements.  Therefore, only one device exists today that is capable of producing volumetric images. 

 

·         Fluorescence vapor imaging device

§         This device uses mercury vapors, coupled with inferred beams of light to display images in mid air.  The inferred light rays are initially bounced off different chemically coated surfaces, which change the beam’s wavelengths.  When two inferred rays cross within the mercury vapors, they energize the vapors at that spot, which in turn cause the vapors to glow a certain color depending on the wavelengths of the inferred beams.  One drawback to this technique though, is that the glow of mercury vapors can only be seen in complete darkness. 

 

 

Three-dimensional imaging systems will eventually replace conventional two-dimensional screens that display the majority of visual information today.  This trend will develop over time, and will most likely first begin appearing in military and air traffic control technology.  In addition, continuing work with fluorescence technology may prove to be the greatest promise for developing future volumetric imaging devices.

 

 

The idea for television was first conceived of in the 1920s, and today, not even 90 years latter, we are developing televisions that can be as thin and as lightweight as pieces of paper.  Therefore, one might wonder where holographic imaging will bring us in the next 90 years.  Wherever it does it lead, it promises to be an exciting and dynamic area of future technology that should be watched closely.

 

 

www.vrclub.at/cybzin/cyberzine.htm

www.media.mit.edu/groups/spi/