Diffusers

For a non-ELP backlight to produce even lighting, which is critical for displays, the light is first passed through a lightguide - a specially-designed layer of plastic that diffuses the light through a series of unevenly-spaced bumps. The density of bumps increases further away from the light source according to a diffusion equation. The diffused light then travels to either side of the diffuser; the front faces the actual LCD panel, the back has a reflector to guide otherwise wasted light back toward the LCD panel. The reflector is sometimes made of aluminum foil, a simple white-pigmented surface, or, as in the 3M Vikuiti ESR, hundreds of polymer layers alternating between a low and high refractive index. Between the lightguide and the LCD panel is usually placed a reflective polarizer film which vastly increases efficiency by repeatedly reflecting any unpolarized light back, which would otherwise be absorbed by the LCD's rear polarizer.