"Fifty years after the first synthetic polarizers, we find them the essential layer in digital liquid crystal."
Edwin Land, scientist
In 1854, an English doctor called William Bird Herapath recounted how unusual crystals formed when iodine was dropped into the urine of a dog that had been fed quinine. The crystals (later called herapathite) appeared dark alone, but light when they overlapped. This was an example of polarizing: the crystals formed a screen allowing light through in only one direction.
While still a teenager, U.S. scientist Edwin Land (1909-1991) became fascinated by polarizing effects, which he observed in button-sized crystals of the mineral tourmaline. He combed through past attempts to create polarizing filters, but the problem lay in creating crystals large enough for practical use. Land's breakthrough was to create much smaller crystals and fuse them together in a syrupy suspension, drying into a solid sheet of film. He called it Polaroid film.
Land's main purpose for the filter was to filter out glare from car headlights, to avoid oncoming drivers from briefly blinding one another, but his filters found an important use in World War II, by filtering out bright sunlight in binoculars and enabling German submarines to be spotted more easily.
This naturally led to the use of his increasingly improved Polaroid filters in sunglasses, as well as for photography. Today's ubiquitous liquid crystal displays rely on his polarizing filters.
