Patent ID: 7537352

Claim:
A light emitting diode (LED) illumination device, comprising: a light guiding member having a light input surface and a light output surface opposite to the light input surface, the light guiding member being tapered along a direction oriented from the light output surface to the light input surface, the light guiding member being configured to uniformize light entered therein through the light input surface and output the uniformized light through the light output surface; a LED comprising a LED chip and a reflective substrate on which the LED chip is mounted, the LED chip being configured to emit the light toward the light input surface, wherein the light has a first polarization state and a second polarization state; a reflective polarizer disposed to face toward the light output surface, the reflective polarizer allowing the light of the first polarization state to pass therethrough and reflecting the light of the second polarization state back into the light guiding member through the light output surface; a quarter-wave retarder provided between the LED and the reflective polarizer, wherein the reflective substrate of the LED is configured to reflect the light from the LED of the second polarization state reflected by the reflective polarizer so as to make the second polarization state convert into the first polarization state after the light passes through the quarter-wave retarder a plurality of times.