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How can electric fields control individual pixels in a liquid crystal display?

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liquid crystal Figure 1: Arrangements of molecules.

Liquid crystal displays (LCDs) control individual pixels by utilizing the electro-optical effect, where an electric field alters the orientation of liquid crystal molecules to manipulate light.1

In a standard twisted nematic cell, liquid crystals are sandwiched between two polarizers oriented perpendicularly. In their natural state, the molecules adopt a twisted configuration that rotates the polarization of incoming light, allowing it to pass through the second polarizer, making the pixel appear transparent.23

When a small voltage is applied across a specific pixel, the electric field forces the molecules to realign perpendicular to the substrate plates. This "untwists" the liquid crystal, preventing it from rotating the light's polarization. Consequently, the light is blocked by the second polarizer, causing the pixel to appear dark.24

To manage complex images, displays use an active-matrix system where each pixel is controlled by an individual thin-film transistor. This allows for precise, rapid switching of specific pixels to create detailed, high-resolution images.45