Holograms and Other 3d Illusions
By: Adam

Holograms

www.howstuffworks.com - Holograms are all around us. Mostly they are used on driver's license and ID. Holograms are used for those objects becuase they are hard to forg, this is so since when you cut a hologram in half, the full image appears on both pieces. You can keep doing this, and the full hologram would appear on each little piece. Holograms are really 3d projections of a 2d object, that you can see no matter what angle you are facing. Holograms are made useing lasers. A laser is split into two beams, that then pass through a diverging lens to increse the laser's width. One laser bounces off the object onto the holographic film. The other beam hits the film without bouncing off of anything. Holographic film is diffrent from photographic film, becuase the film can record very small changes in the light.




Stereoscopic 3d

www.guru3d.com, www.howstuffworks.com, www.tomsguide.com, www.easystereogrambuilder.com, www.paulbourke.net - Stereoscopic 3d is the technique of projecting two images to your eyes, and have your brain meld them into one image. The final image pops out and is able to be viewed in 3d. One of the cheapest ways to do this is red, blue viewing, otherwise known as anaglyhpic viewing. An image with red and blue parts is presented, and when viewed with red, blue glasses, the 3d illusion is given. To do this, the glasses filter the color so each eye only sees one image. While this works it is only good for movies without color. Another similar viewing system is glasses called LCD shutterglasses. To use this, the glasses rapidly shift the image you are viewing, from your left eye to your right eye. When done faster then you can precive, the technology allows for 3d viewing. The best, and probably the most expensize is autostereoscopic 3d. This alows for 3d viewing without glasses or otherwise. This method works by using a parralex barrier. When the barrier is transparent, light can pass through it, and the same image is projected to both eyes. When the barrier is on, light does not pass through the barrier, and a diffrent image is projected to each eye. One other way to make 3d sterograms is with an online program, like the one below the image. The image below is actually a 3d sterogram, focus on the center and cross your eyes. These wallpaper sterograms work, by having subtle changes between depth points. These changes cause the illusion of 3d. There is also a type of autosteroscopic 3d called lenticular photography. Lenticular images use the same technology as a 3ds for 3d that shows depth, but for motion, the image uses small subangles, that when the image is moved, show a diffrent view, showing the illusion of motion.







image created on - www.flash-gear.com to view this image, look at the center and cross your eyes. Scroll over to see the rest of the image.




Mirages
www.britannica.com - Mirages are most commonaly know of appearing in a desert, and they are also a type of an illusion. Insted of being something you can make yourself, a mirage requires certain conditions. When pavement or a strip of desert is heated by sunlight, the air becomes more dense, and can reflect light better. So when the light is reflected downward off of an object, instead of going into the ground, the light is reflected upand toward a person. The person will see both the unreflected rays, and the reflected rays. This will cause you to see an illusion on the ground, that could be mistaken for water. When you are on water the opposite of a mirage can occur that is called looming. This occurrs when cool air is under hot air, and an object will be projected into the sky.



Mirage Experiment
www.madsci.org - This is an experiment to show how light refrats to create a mirage. You need to set up a hotplate, and put a laser pointer so the laser shines right across the hotplate's surface. You also need to hold an aluminum tent over the hotplate, so the thermal gradient is not interupted by outside air tempatures. Turn on the laser pointer and put a piece of paper at the point where the laser hits the wall, and mark the point. Turn on the hotplate, and observe how the laser reacts, and when the laser settles, mark the point,and then take off the aluminum tent, and observe the changes. Put the aluminum tent back on and see if the laser cchanges, to verify that the experiment is working. This procedure did not work for me, I did everything it said, but nothing happened. I took of the aluminum tent, and the light jiggled some, but that was all. This was also at a very small distance. I tried the experiment at a longer distance, and it worked. The light jiggled, and moved about 8 +or- 1 millimeter.