Po·lar·oid / ˈpōləˌroid/ • n. trademark 1. material in thin plastic sheets that produces a high degree of plane polarization in light passing through it. ∎  (Polaroids) sunglasses with lenses made from such material.2. a photograph taken with a Polaroid camera.• adj. Photog. denoting a type of camera with internal processing that produces a finished print rapidly after each exposure. ∎  denoting film for or a photograph taken with such a camera: a Polaroid snapshot.

Polaroid The trade name of a plastic sheet impregnated with an organic iodide compound which strongly absorbs light in one vibration direction and allows it to pass freely in the other vibration direction. The compound, iodocinchonidine sulphate, was first discovered by W. D. Herapath in 1852 and was named ‘herapathite’ in his honour. In 1928 E. H. Land combined the compound with plastic to produce the Polaroid sheet. It is now used in the polarizer and analyser of all polarizing microscopes to produce plane-polarized and cross-polarized (see CROSSED POLARS) light respectively.