When displaying images, we must first mention the light source of the LCD monitor. When an LCD monitor is taken apart, we see a row of LEDs at the bottom (edge), which is the "backlight" of the monitor and is the only light source in the monitor.

The light source from the bottom of the monitor to the front of the screen, the light source must be achieved through the LCD's "optical system".

The "optical system" consists of:

A film that provides a white background for the light.

A light guide plate covered with dots, so that when light enters from the bottom edge, it travels downward through total internal reflection, with the light touching one of the dots before it becomes visible.

A diffusion film, which helps to eliminate the dot pattern on the light guide.

Prismatic film, which helps to brighten the light.

Diffusion film, which results in a very uniform illuminated surface.

The light source that reaches the front of the screen is only a prerequisite for the image to be displayed, while the polarizer glass (LCD) is necessary to display the image. Polarizer glass is actually a glass interlayer. It includes upper and lower polarizer, glass substrate, color filter, liquid crystal, TFT, etc. Among them, the upper and lower polarizers and liquid crystal glass control light to achieve the key to color display.

Polarizer control light is reflected in: when the axis angle of the upper and lower polarizer is 0 degrees or 180 degrees, light can pass; when the axis angle of the front and back two polarizers is 90 degrees, light cannot pass. In general displays, the front polarizer does not rotate by itself. Therefore, the two polarizers in the polarizer glass in a display are placed at 90 degrees to each other (a configuration that does not allow light to pass through).

The light then passes through by "twisting" the light in the polarizer glass to match the front polarizer! This "twisting" is achieved with liquid crystals.

Liquid crystal crystals have properties that do not allow light to travel evenly along both axes. The two polarizers on the glass surface form a groove at a 90 degree angle to each other, and the molecules in between are arranged in a graceful spiral.

As light from the backlight enters the interlayer through the first polarizer, it is rotated by the liquid crystal, allowing it to pass through the second polarizer and appear in front of the screen, which is often referred to as the normal white mode. When we apply an electric field on the sandwich structure so that the crystals are aligned longitudinally, the light passing through the first polarizer is not rotated by the crystals and does not pass through the front of the screen, which is often referred to as normal black mode. When we apply an electric field on the sandwich structure so that the crystals will be in between rotation and longitudinal alignment, then other color modes will be presented.