As the display technology becomes increasingly mature, various displays have gradually developed. At present, liquid crystal displays (briefly known as LCDs) are more and more widely applied due to advantages such as little power consumption, miniaturization, light weight and thin thickness, and so on.
An existing liquid crystal comprises two polarizers having light transmitting axes perpendicular with each other and a liquid crystal panel located between the upper and lower polarizers. The principle of greyscale display is that the lower polarizer converts a natural light into linearly polarized light; the deflection status of liquid crystals is controlled by voltages so as to convert the linearly polarized light into elliptically polarized light, and the upper polarizer analyses polarization of the elliptically polarized light so as to realize different greyscale displays.