1. Field of the Invention
The present invention relates to a light emitting device, and particularly to a polarized light emitting device.
2. Description of Related Art
In recent years, light emitting diodes (LEDs) have gradually improved the light emitting efficiency and replacing fluorescent lamps and incandescent lamps in some fields, including highly responsive speed lamps for scanners, backlight sources or front light sources for liquid crystal displays (LCDs), light sources for instrument panel of automobiles, traffic signal lamps, light sources for projection devices and even ordinary illumination devices. Typical LEDs are usually semiconductor devices using III-V compounds, such as GaP, GaAs. LEDs convert electrical energy into light. As the current is applied to a typical compound LED, through the combination of the electron and electron hole, excessive energy is released in the form of light. The light emission of LEDs is typically cold light emission, rather than by heat or discharge, therefore LEDs often have relatively long operating lifetime of up to 100,000 hours, and with no idling time required. LEDs also have such advantages as faster responsive speed (about 10−9 S), smaller size, lower power consumption, lower contamination, higher reliability, capability for mass production. Accordingly, LEDs are wildly used in many fields.
Take the projector as an example, LEDs that have longer life span are used inside its light system. As disclosed by U.S. Pat. Nos. 5,962,971, 5,813,753, TW Patent No. 569,467 and TW Patent Application No.93141534, LEDs can be used in light source systems for projector. The conventional technologies disclosed in the foregoing publications are generally about using ultraviolet (UV) filters, long wave/short wave pass filters, pseudo omni-directional reflectors or omni-directional reflectors for improving total light emitting efficiencies thereof. However, how to polarize light provided by the LEDs are not yet disclosed.