Liquid crystal projectors (LCD) operate the same as slide projectors, instead of a slide, but they have small, transparent liquid crystal elements. Nowadays, the usual devices use three LCD panels - one for each primary color - whose projection on a speciallyarranged projection system with dichroic mirrors is combined into one image. Thus in each pixel, each color can be produced.Especially high-quality optical devices employ a unit with four LCD panels, with one extra panel is for the sophisticated and powerfulrepresentation of the used light yellow. This allows you to connect high light output with good color balance, which is conventional units with three LCD panels quite heavy - their green display has a slight yellow tinge, a correction of color cast is usually associatedwith a relatively high loss of brightness. For devices with only one liquid crystal element of the three primary colors as LCD flat screens are displayed side by side, resulting in a coarser image impression.