A holographic display uses light diffraction to create a 3 dimensional image. There are now four types of holographic displays: Laser plasma, Holographic television display, micro magnetic piston display and touchable holograms. These types of displays all work in a different fashion.
Laser plasma displays make use of oxygen and nitrogen molecules to project on. In combination with lasers that focus the light in the desired position, three dimensional images are created.

A holographic television display makes use of a Kinect camera to obtain a three dimensional image of an object. Laser diodes project the image onto a translucent surface.

The micro magnetic piston display uses tiny pistons. These pistons can be manipulated and can therefore reflect light in the desired wavelength, providing a three dimensional image.

Touchable holograms can detect user’s touch by movement in the air. The display makes use of a varifocal lens, galvano scanner and a lens to create a three dimensional plasma voxel. The system can also provide haptic feedback, by sending out ultrasonic air blasts.

A fifth type of holographic display is now in development, called Aerial display hologram. It makes use of a beam splitter, that divides incoming light into reflected light and transmitted light. In combination with a retro-reflective sheet, a three dimensional image can be protected onto thin air.

For the TfCD assignment we created a variation of the holographic television display. By projecting a video of an object on four sides of a translucent pyramid, a three dimensional image is created on the inside of the pyramid.

Holographic displays make it possible to create three dimensional images, which can be seen in perspective from all sides. This is an adventage comparing it to two dimensional imagery.

Holographic display technologies encounter various weaknesses. The technology often uses various expensive and relatively large equipment, which is costly to applicate to products. The construction of the three dimensional images is also relatively time consuming. The images that can be projected nowadays are not fully solid, which has an influence on the visibility in bright environments.

Alternative solutions for the projection of three dimensional images can be found in virtual reality technologies. These technologies require an optical device, such as glasses or a screen, to let the user see the three dimensional object. When comparing virtual reality devices with holographic displays, the use of additional devices could be a disadvantage for some purposes. On the other hand, virtual reality offers a wide range of applications, that holographic displays can not facilitate.

In science fiction movies all sorts of holographic displays can be seen. These holograms can appear from thin air and are projected from a small device. These science fiction movies show what people might be expecting from the future of holographic displays and this is pretty much what is in development right now. With the Aerial display holograms, science fiction from nowadays might be feasible in the near future. For the future we can therefore expect devices similar as the devices in sci-fi movies, where holograms can be adjusted by touching them in the air, they will provide feedback to its users and can be projected in large sizes. With these new possibilities, new products will be developed and might inspire a whole new branch of the holographic technologies.

<p>This looks neat :) I've seen some fun projection projects for Halloween things as well, but it has a lot of applications.</p>

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