Anybody pls tell me the technology of LCD projector?

Question

how does it work? what s the need of the lamp in that?

Answer 1

See the article at the link for an explanation of how an LCD (and DLP and CRT) front projector works.

The lamp is necessary as the source of light.

Answer 2

The light from the lamp is divided into three paths. Red, Green & Blue. The colored light then goes through LCD panels that are approx 1" X 1" in size. The LCD panels make up the image, like a 35mm slide. Each light path (now a picture) is then bounced off mirrors to reconverge and is finally send out the lens.

  There are more optics involved but that is the basics.