Communications Technology

History
A Hungarian physicist, Dr. Dennis Gabor created the theory of holography while he was working in England in 1947. His initial research was to improve the resolution of electron microscopes. Lacking the coherent light of a laser, Dr. Gabor was able to create crude holograms using highly filtered light sources. Gabor published his work in 1948 and eventually received the Nobel Prize for Physics in 1971. Holography theories grew extensively during the 1950's but could not be fully tested until the development of the laser in the 1960's. Two University of Michigan students, Emmet Leith and Juris Upatnieks, used the laser along with Gabor's theory to create clear holograms with excellent levels of depth.

Assignment
Our group was to produce a 4" x 5" hologram of the TEMLP logo that we developed in previous activities. We first had to develop a 3D metalic model of our logo. We actually had to make this twice because our first model was too long for the hologram setup.

3D Model of Logo

Set-up
Because of numerous problems with a "black dot" appearing on the hologram, our group did not use the sandbox set-up. Instead, we set up the laser, lens, and mirror in a straight line in the darkroom. However, the "black dot" still appeared our first and second attempts. We discovered the lens was creating a shadow on the film area; thus creating the "black dot."

Lens, Mirror, and Film Set-up

Laser

Exposure
Holographic film is sensitive to red light therefore, green safety light must be used in the darkroom during exposure and developing. Exposure time will vary depending on the type and wattage of the laser. Vibration must be eliminated in order for a successful exposure. With the laser is armed, the subject matter is in place, and the mirrors angled correctly... we are ready for an exposure. For a shutter we used a piece of black matte board to cover the laser. With the shutter in place, laser on, and lights off... we removed the shutter for ten seconds to expose the film.

Exposing a Hologram

Developing
To develop holograms you need developer, bleach, and deionized water. Developing reflection holograms involves a four-step process. Equal parts of A and B holography developer is used first for approximately two minutes. After developing, the film is washed in deionized water for about three minutes followed by five minutes in a holography bleach solution. Then wash a second time in deionized water for three more minutes. Hang dry or blow dry before viewing.