Polarizer

A polarizer is an optical element that transmits light with selected polarization states while attenuating others. It can produce polarized light or analyze the polarization of incoming light.

Dichroism: Dichroism is the differential absorption of light depending on its polarization or propagation direction. Absorptive polarizers use differential absorption to suppress one polarization.
Polarization: Polarization describes the orientation and evolution of the electric-field oscillations in an electromagnetic wave. A polarizer acts selectively on the polarization state of light.
Polarizing filter: A polarizing filter is an optical filter that passes selected polarization states and blocks others. Photographic filters use this action to reduce reflections and alter sky contrast.
Absorptive polarizer: An absorptive polarizer selectively absorbs one polarization state while transmitting another. It dissipates rejected light instead of directing it elsewhere.
Étienne-Louis Malus: Étienne-Louis Malus was a French engineer and physicist whose studies of reflected light led to the discovery of polarization. His observations of light reflected from glass helped establish polarization as an optical phenomenon.
Wire-grid polarizer: A wire-grid polarizer uses closely spaced conductive wires to transmit one linear polarization and reflect or absorb the orthogonal one. Its subwavelength metal grid selects polarization through selective reflection and absorption.
Linear polarization: Linear polarization is a state in which an electromagnetic wave's electric field oscillates along a fixed direction. The transmission axis of a common polarizer selects one linear orientation.
Liquid-crystal display: A liquid-crystal display forms images by electrically controlling light transmission through liquid-crystal layers. Crossed polarizers convert electrically controlled polarization changes into visible brightness.
Reflective polarizer: A reflective polarizer transmits one polarization state and reflects the orthogonal state. It can recycle rejected light rather than losing all of it to absorption.
Erasmus Bartholinus: Erasmus Bartholinus was a Danish physician and mathematician who described double refraction in Iceland spar. The crystal's double images supplied an early route to separating light by polarization.

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