Seeing The Light: Old-Fashioned Fresnel Lenses Keep Modern Ships On Course

Maneuvering two ships in close proximity in the dim of night is always a challenging event, but when radio communications were lost between the two ships, crews were forced to rely on old-fashioned flashing lights that took a not-so-speedy 25 minutes to relay just one message.

The mishap would likely never have occurred if the carrier had been outfitted with something equally as old-fashioned, but one that would have clearly signaled to the Leyte Gulf the course change of the Theodore Roosevelt.

Recently, the Office of Naval Research funded the development of a simple array of six lights outfitted with Fresnel lenses mounted on the stern of a ship, called a Tactical Vectoring Equipment (TVE) display. Fresnel lenses – around since the early 19th century – concentrate and magnify a beam of light with terrific intensity. The TVE display projects red or green light based on viewing angle.

A surface ship on plane guard tasking behind a carrier, for example -– where a conning officer must gauge the location of the carrier, monitor aircraft traffic, and watch for other vessels and foreign obstacles -– often receives ambiguous cues.

With a TVE display, he will be able to tell whether the desired station was being maintained based on the number of red or green lights visible. He will gauge his range by size and spacing of the lights. The TVE’s position on the carrier’s stern will be invisible to carrier pilots during flight operations.

“We’re using old technology in a new way,” observed Joel Davis, program manager for the TVE project at the Office of Naval Research. “This is an example of a technology that is ready to go from basic research directly to the fleet. Commercially, TVE could also be used to keep tankers on course in shipping lanes and canals.”