DISPLAY 101
#11 Polarizers
Light is always around us and is used to transmit almost all of the information that we see. But despite being the most familiar natural phenomenon, it can be hard to get how it technically works.
| Polarizer: An optical film that allows display to show its image by adjusting the direction of light |
For instance, light comes in waves. It vibrates. It oscillates. It goes up and down, back and forth, and side to side as it travels around. Just like in the picture above, it vibrates all over the place. Also, there is a “polarizer,” or polarizing plate, a thin film that will block all light waves except the ones vibrating in a certain direction. Only the light that vibrates in alignment with the polarizing plate can pass through it.
Polarizers in LCD
An LCD is a transmissive display that uses liquid crystals between two polarizers to change the direction or adjust the intensity of light. Look at the LCD structure above. There is a backlight at the back and two polarizers and a liquid crystal in front of it. The two polarizers are opposite from each other. One is vertical and the other is horizontal.
When the light from the backlight meets the first polarizing plate, only vertically vibrating light can pass through. The light passes through the liquid crystal and the angle of the light’s vibration is adjusted according to the movement of the liquid crystal. Then, it reaches the second polarizing plate, and once again only the matching light can pass through. The incorrectly aligned light is blocked to determine the brightness of the screen. If the light is vertical even after passing through the liquid crystal, it eventually gets stuck in the horizontal polarizing plate. These two polarizers are there to filter out any extra light from the backlight that doesn’t go through a liquid crystal, because that light would make the screen look blurry.
