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Liquid Crystal Displays: Fundamental Physics and Technology by Robert H. Chen

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16

Engineering the Liquid Crystal

To review the fundamental operation of a liquid crystal display pixel cell: Light from a backlight source is linearly polarized by a first linear polarizer. Upon entering the liquid crystal medium, an applied electric field changes the orientation of the liquid crystal molecules, which engenders a phase retardation that changes the polarization state of the light. Then passing through a color filter and various compensation films to improve viewing angle, contrast, and color quality, in conjunction with a second linear polarizer, the light’s intensity has been modulated pixel by pixel to simulate the light from the scene being imaged.

From the perspective of physical optics, if the polarization state of the light traversing each optical element in the display system can be characterized mathematically, then appropriately designed optical elements may be combined to produce and improve the desired image. This characterization of the polarization state can be achieved by the methods of mathematical physics, such as the following.

Poincaré Sphere

The Poincaré sphere* is a purely geometrical construct to describe polarization, wherein a point on the sphere represents a specific polarization state, and a curve on the surface of the sphere represents the traversal of the light through the optical system from the different polarization states. The Poincaré sphere approach leads to a formulation of components of the polarizaton vectors representing light ...

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