Polarization is one of the fundamental properties of light. Light consists of vibrations perpendicular to the direction of propagation. A linear polarizer transforms unpolarized light into linear polarized light by absorbing some of the light and selectively allowing the rest to pass through.
When natural light reflects off objects, it becomes partially polarized. The reflected light is oriented predominately in the horizontal direction. This reflected light is commonly called glare. Linear polarizers eliminate glare by absorbing the horizontally polarized component while transmitting the vertically polarized component.
Circular polarizers improve the contrast of characters on electronic displays by reducing unwanted reflections. This enhances the readability of the display. They are widely used on, for example ATMs, medical equipment, signs, and instruments.
Circular polarizers are placed in front of a display. As light passes through a circular polarized film it is converted to a circularly polarized light. Circularly polarized light reflected off the back surface of the display is blocked from passing through the circular polarizer a second time.
Light originating from the display itself passes through the circular polarizer only one time and is not blocked. Thus characters on a display screen are seen without annoying reflections and have high contrast. As an example of their effectiveness, a circular polarizer can reduce reflections from a mirror from 92% to 0.5%.