1, OLED is the control strength of the light emitting device to emit light through the current size; LCD is a light and controlled by controlling the rotation angle of the angle of the voltage control LCD (liquid crystal generally normal light can be rotated 90 degrees), and then through the polarizer to a certain direction through to control the strength of the light.
2, for LCD, because of the problem of liquid crystal rotation, we need to first pass the same direction of light with the liquid crystal direction, and then we need solid polarizer. When the liquid crystal rotates, we need polarizer to pass through the directional light, and we need solid polarizer.
3, because OLED is self luminous, it doesn't need LCD Polaroid. However, the external light will reflect the light through the cathode (usually metal), and will affect the contrast.
4, to solve these problems, we use Polaroid +1/4 wave plate (also called the combined Yuan Pianguang); when the external light passes through the polarizer has half the light cannot pass through, this half light after a 1/4 wave plate and reflection with the original partial light is 90 degrees, the reflected light cannot by polarized light to solve the problem of reflection film. So, OLED only needs a polarizer to solve the reflection problem; LCD needs up and down two polarizers to achieve the intensity of light.