Polaroid (polarizer)

Polaroid filters comprise a group of Edwin Herbert Land and employees of Polaroid in the second third of the 20th century, developed and marketed polarizing filter. The name " Polaroid " is on while polarizers whose thickness is perpendicular to the propagation direction of the light is much smaller than its width. The polarization films (english sheet polarizer ), films with polarizing effect, are distinguished from polarizers used until then mainly by low-cost production. Are used such filters, especially in the field of photography.

J- foils

J- foils (English J -sheet ) were the first of Edwin H. Land (1929 ) developed polarizing films. They are made of dichroic herapathite crystallites embedded in a film of cellulose acetate. The polarizing effect of the film, is based on the parallel arrangement of the sub-micron sized acicular crystallites and the polarization dependent absorption ( dichroism ). Since the size of the crystallites in the range of wavelength of visible light and the light scatters so, see J- films generally somewhat murky.

H-sheet

H-sheet (English H -sheet ) are one of the most widely used polarizing films. They were first introduced in 1938 by Edwin H. Land and consist of a colorless polyvinyl alcohol film (PVA ) with embedded Jodkristalliten. A directed polarization reached land by first heating the PVA film and stretched in a particular direction. Thereby, the long-chain hydrocarbon molecules were aligned. During the subsequent introduction of the Jodkristallite these outsourced to the PVA molecules and formed themselves long electrically conductive chains. The diffused carriers is available iodine, which are movable in the direction of the chain molecules, resulting in the absorption of the electric field component parallel thereto. H films thus function as a metallic grid Drahtgitterpolarisators. Since the accumulated Jodkristallite few nanometers in size, the scattering of the H-sheet is negligible and they appear different from the J- foils not cloudy.

K-sheet

The K-sheet (English K -sheet ) as the H films are prepared by heating a polyvinyl alcohol film in the presence of a catalyst similar. The heating is used to remove water and the production of polyvinyl dichromophorem. They are particularly suitable for applications where a higher resistance to elevated temperatures and high humidity is necessary. Similar to H films they show no turbidity.

Furthermore, there are also combinations of the H and K films, whose absorption maximum is at about 1.5 microns in the infrared. They are referred to as HR Polaroid.