Creating Left/Right Eye Vision
(ChromaDepthô, Anaglyph, Linear and Circular Polarization)

In order to create the illusion of depth in a 2D picture, you must be able to restrict what each eye can see so that each eye's view is slightly different.  There are a number of ways to do this.  I will outline a few very briefly.

ChromaDepthô

This method uses the varying wavelength of different colors and refractive lenses to send slightly different images to the brain.  In general, on a black background, red will appear closest, blue furthest, and the other colors will fall in-between according to their place in the rainbow (red, orange, yellow, green, blue).

In order to view a ChromaDepth image, you must have a pair of light-refracting glasses.

Anaglyph

Anaglyph comes from a Greek word meaning relief; an anaglyph is one of those pictures that was carved into a wall.  Presently, anaglyphs are probably the most recognized form of 3D used for static images.  To see them you must wear red-blue (or red-cyan) glasses, and generally the red lens is over the left eye.

Like the ChromaDepth, the anaglyph uses colors to control which images go to which eye.  The color layers of the images are split up.  Any color image can be broken into Red, Blue and Green (RBG) elements, which in different combinations create nearly the entire color spectrum.  The anaglyph image merely sends the red information of one image to the left right eye and the blue and green information of the other image to the left eye.  The glasses prevent each eye from seeing the wrong image.  In your brain, the different images are assembled as depth, and the colors are combined to give you a fairly close approximation to the original colors of the image.

Linear Polarization

Image from here

This is the method of left-right eye differentiation used by our Geowall.  The electro-magnetic light 'particle,' called a photon, is divided into electric and magnetic components which are perpendicular to each other if viewed end-on.  Any photon at any given moment has a certain orientation with regard to it's components.  In the example above, the electro wave is vertical while the magnetic wave is horizontal. The orientation isn't definite; the electric component can be any angle from 0 to 360.

Something to think about: Reflected light is often polarized at the angle of the surface it is reflected off of.  If it is the surface of the lake, the light will be polarized horizontally.  If a vertical wall is the reflector, the light will be polarized vertically.  This is the technology behind glare-reduction filters or "Blue-Block Sunglasses."  The polarized lenses can block out this reflected light since it tends to be polarized the same way.

A linear polarizing filter allows only light that is oriented a certain way to pass through.  If you can polarize the left eye to be perpendicular to the right eye, and then wear glasses where in which each lens is polarized perpendicular to the other, each lens will allow only one image through - blocking the other.  Each eye will see a different image leading to stereoscopic vision.

Because any photon can be oriented to any angle, most photons will probably not be oriented in the direction that the lenses allow.  Thus, linear filters can block as much as 60% of the light from reaching your eyes.

Circular Polarization

Image from here

The concept of circular polarization is similar to that to linear polarization.  Each photon is rotating around it's long-axis either clockwise or counter-clockwise.  The filters are able to block all photons rotating in one direction while allowing those going in the other direction to pass.  So if one image is polarized right-circular and the other is polarized left-circular you will see different images for each eye.  This is advantageous because you don't need to calibrate polarizing filters on the glasses or projectors.

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