The main difference between the LCD rear projection system
and the standard tube type rear projection television is the use of LCDs
instead of picture tubes. Instead of using three tubes this system uses three
LCDs. Since there are no picture tubes, there is no High Voltage, deflection,
sub deflection or tube biasing circuits. These are replaced with a High
Intensity Discharge (HID) Lamp and a timing generator for the three LCDs.
ONE PIECE LIGHT ENGINE
The HID Lamp and LCDs are used in conjunction with a
dichroic prism and various lens assemblies to form the one-piece light engine.
The engine works when light is emitted from the HID Lamp. The HID Lamp emits
light when the Power Lamp Block applies 25kV to it. The HID Lamp works by using
the 25kV to create a short arc that creates an even, uniform white light which
contains color components across the spectrum of light.
The light is sent through a lens array that separates the
light into its various colors. This light is sent through a series of one-way
mirrors that pass or reflect only specific colors of light. These colors are
red, green and blue. These mirrors work to deliver only red, green and blue
light to the LCD for that color.
After the light passes through the three LCDs, it is sent
through a dichroic prism. The dichroic prism takes the three colors of light
and recombines them. The recombined colors now contain the picture due to the
manipulation of the crystals inside each of the LCDs. This picture is sent
through a focusing lens. The focusing lens keeps the picture focused on a
mirror. The mirror is used to reflect
the picture onto the fresnel and lenticular screens. These screens are similar
to the screens used in standard rear projection televisions.
