But First, the foldable OLED 2D Display

Last time we discussed the evolution of 2D display technologies. One of the main points of display technology lies in the ability to "fool" the brain. That is, as long as you can manipulate the display pixels on a timescale faster than your brain can process, the display can then take advantage of the fact that the brain is doing time averaging over the full array of pixels in order to form an image. IN other words, the alteration of an individual pixels degree of illumination/brighntess is done so fast that the eye-brain just sees one image. In reality, for an LCD display, at any given microsecond, many of the pixels are black (the light is totally blocked).

Note that there is still a lot of research to be done on the eye-brain image processing machine and how it works.

Here are some things we think we know:

• Cinema standards are 24 frames per second which translates to 41 milliseconds per frame. This clicker eliminates "flicker" so our eye-brain system clear does not refresh fast than 40 milliseconds. example

• The refresh rate of vision is the speed at which signals travel from the eye to the brain; and the speeds at which visual information is decoded and recorded in the brain.

• However, its possible/likely that we have just trained our brains to respond to moving images in this way. Its possible that the refresh time is actually faster, we just don't compose media to test that. Some tests suggest that the refresh rate may be as low as 10 milliseconds (100 Hz) and there is likely to be a wide distribution of refresh rates for humans. (Great hitters in baseball may have high refresh rates)

• The eye-brain is easily tricked: example

Therefore one way to effect a 3D display is to trick the eye again.

Multiview lenticular technology allows multiple viewers wide freedom of movement without sacrificing 3D perception.

A sheet of transparent lenses, is fixed on an LCD screen. This sheet sends different images to each eye, and so a person sees two images. These two images are combined by the brain, to create a 3D effect. This is what stereovision essentially is, but it requires good alignment between the viewer and the screen.

Separation between pupils for a standard person is 6.5 cm. Therefore each independent eye views a scence from a different angle and therefore generates a unique image in the brain. These slight differences between left eye and right eye images allow the brain to render "depth" in an image.

In this way, a 2D display device can turn into 3D but precise image control is necessary to pull this off.

Another alternative is to sue deformable mirrors. In this case, the "pixels" can be controlled to direct light to your eyes from different angles.

As the voltage canges, the light path from the mirror to your eye changes. This requires mirrors that are easily deformable and such mirrors are usually called deformable membrane mirrors in principle this gives you a more direct 3D viewing experience that the sterographic approach because the deformable mirrors can be tuned to match your specific eye-brain response.

Toward true 3D display

Another alternative, less desireable really, is an enclosed rotating device. In the case below the actual screen is made of phosphorous elements but it rotates sufficiently fast to produce a 3D effect (but it still is a 2 D screen)

Still another example basically consists of projecting 2D images onto a series of multiplanar optical elements (MOE) (usually a single LCD panel). A horizontal and vertical arrangement of these panels can then create a 3D image. To make this work there has to be good synchronization between the high speed projector and the orientation of the MOE. As long as this can be controlled at rates faster than your eye can process the data, the 3D effect will be perceived:

But none of these approaches are really true 3D. A real 3D display would render an image in a real, physical, 3D volume. This is called Volumetric 3D and each volume resolution element is known as a voxel. So a pixel becomes a voxel.

Ultimately, all 3D volumetric displays make use of the fact that light can scatter in 3 dimensions off the surface or particles or other stuff. If the scattering can be controlled and focused then true 3D images can be rendered.

There are a variety of scattering mechanisms that are being tested and we will see some examples below. The current technically difficult is that as the size of the volume increases, it becomes increasing difficult to produce coherent images.

• Using Air as the Scattering Medium Problems here include a) scalability of image size b) brightness and c) full color reproducibility - the scattering properties of most materials are highly wavelength dependent.

• Project on the Fog Screen

Ultimately, however, someone will develop the 3D electrostatic mist projection system consisting of a network of lasers projecting into an electrostatically contained chemical mist to produce "floating" 3D images.

The technical demands of doing this on the human/life size scale are quite formidable, however, so don't expect to see this anytime soon.