Adventures in Holograms
My friend, Jonathon Henriksen, and I, after completing our course in AP Physics, took an independent course to study and make holograms. After about a month of research, we ordered some holographic plates (they're made in Russia) and some developing chemicals from Integraf. We went to Home Depot and bought about 600 pounds of sand and some carpet scraps. We also went to a carpet warehouse and got some free carpet padding.
At about one o'clock on a Sunday, we, with the help of our physics teacher, Mr. Lund, began. The chemicals we used were all sorts of nasty ones, including the deadly cathechol, which could provide us with anything from liver malfunction to mental retardation. We mixed those up in the proper amounts under the hood in the chemistry lab, being extra careful to wear the full complement of chemistry attire: goggles, apron, and gloves. When finished mixing, we obtained two developing agents (that were mixed together just before developing was to occur), a bleach solution, and a final rinse solution. We grabbed the laser, the chemicals, a slew of ring stands, test tube clamps, and some dissection trays and drove to my house.
We put the carpet scraps, carpet padding, and some bike innertubes (we had gotten those at Target) down onto my pool table. On top of the padding, we put a big triangular box, and into that we placed about 200 pounds of sand. Thus we completed our table. It had to be done as such because the holograms required absolute still. Any vibrations would distort the image such that only a red smear can be seen.
We then set up the laser and beam-spreading mirror to aim at our display of two porcelin panda bears (the pictures you see of our second attempt, which was of a pewter horse and cactus on a piece of pyrite). Once it was set, we placed a piece of black construction paper in front of the laser. After duct-taping blankets and planks over the windows, we turned on our safety light, a green light that would not interfere with the red-sensitive holographic plates. We turned off all the white lights and asked for peace and quiet upstairs. The box and its massive layers of red protective paper were removed, and the first glistening holographic plate revealed. The plates we used were about 2.5" by 2.5". We positioned that in front of the pandas and held our breaths for an infinite five minutes. The construction paper blocking the laser was then lifted ever so slightly from the bed of sand. We waited another minute for the vibrations of lifting the card to dissipate. The paper was then lifted entirely out of the way, and the plate exposed for about five seconds.
Now, the way a hologram works, as near as I can tell, is by a pattern of constructive and destructive interference. The laser light passing directly from the laser is called the reference beam. Light also bounces off of the display, in our case the pandas, and this is called the object beam. The lengths traveled by the reference beam and the object beam vary slighty, producing interference. The holographic plate records this interference.
After exposing the plate, we quickly ran it through the chemicals. Actually, that took about twenty minutes. We couldn't see anything at first, but as the plate dried, we gradually began to see little red spots in one corner of the plate. After about ten or fifteen minutes, both pandas could be seen, in what looked like full 3D, "behind" the plate. They were only red, as white light holographic plates (those that can pick up the colors as well as the shapes) are much more expensive. We shone a flashlight onto the plate at the same angle that the laser light hit the plate, and were able to see both pandas perfectly. Beautiful!
At this point it was ten o'clock at night, and we had only just begun. Mr. Lund reluctantly agreed to stay while we completed one more hologram, this time of the pewter cactus and horseman atop a piece of pyrite (fool's gold). While Lund scared us with his jokes of train conductors and electric chairs, we produced a second hologram. Because the object was metal, light was reflected very easily, and the image produced was spectacular. When the plate was tilted from side to side, one could see the pyrite sparkle as if actual light were being shone onto it.
Jonathon and I spent two other long evenings experimenting with holograms and trying to make scenes with seashells and flowers. The scenes worked, but our exposure time had to be adjusted for the matte surfaces of the shells and flowers, so it took us four tries to get another decent image, one of a spiral shell, coral, and lilies. Thus completed our beginning adventures into the land of Holography. We have since helped several physics classes create fabulous holographic images.
(Thanks to my dad for helping to document our experience through photos.)