Talking over a beam of light: electro-optics suitable for K-12

A kit of electro-optical components is described which, when assembled and aligned, allows one to transmit voice signals over a beam of light. The kits were developed for TOPTICS '92, an optics convention held in the city of Tucson to showcase local optical companies and education opportunities to the public-at-large. One aspect of the convention was to involve school children with the world of optics. These kits proved to be an excellent way to link educators and their students with parents, optics professionals, and even the local media. The kits consist of all the necessary electrical components to build a transmitter (using an LED) and a receiver (using a phototransistor). The circuits are assembled on an electronic breadboard which is part of the storage case for the parts themselves. Optically, the light beam is collimated and focused using inexpensive Fresnel lenses. Distances over which one's voice may be sent are variable, determined by one's ability in optical alignment. Students in the 5th grade were the first to use the kits, sending their voices about 200 feet. The educational success of these kits is described in this paper.