LCD Projectors

LCD stands for Liquid Crystal Display.

A Liquid Crystal Display Projector is a device which uses an LCD to project an image.

LCD projectors come in a variety of shapes and sizes, ranging from small head mounted ones for Virtual Reality headsets, to larger ones for cinema projectors.

LCD projectors work by modulating the light emitted from a lamp. A bright state on a projector screen is achieved by switching a pixel within the LCD panel 'on' thereby allowing the light to travel through the panel and on to the screen. A black state is achieved by switching a pixel 'off' and blocking the passage of light.

To achieve full colour LCD projectors modulate the Red, Green and Blue light from the lamp. This can be done using a single LCD panel, or more commonly by using three panels, each modulating a primary colour. By using three panels a brighter and higher resolution image is achieved than by using a single panel to modulate all three primary colours.

The light from the lamp in a three-panel configuration is separated into three beams of red, green and blue light using dichroic (colour-separating) filters. Each coloured beam is modulated independently by a liquid crystal panel before being recombined to form a full colour, high-resolution image.

Accurate overlap of the red, green and blue colour images is one of the major issues with three-panel systems. In addition, three-panel systems are usually more expensive than single-panel systems due to the increased number of panels, colour separation and recombination optics and the requirement for a sophisticated projection lens.