DIGILENS® - (LEDC) - LED LIGHT ENGINE

New high brightness LED technology (HB-LED) is increasingly being used for a wide range of Lighting and Projection Display products. In projection display applications the hot sectors with CAGR of 50%+ include pico/pocket/ultra-portable projectors and large 60"-70" rear-projection TV’s (RPTV). Designers not only want to eliminate conventional, costly "short life" bulbs, which are also environmentally poisonous (Mercury), but also develop new product catagories that are more compact and solid state – generally suitable for our ever mobile world. Pico-projectors with 10-20 lumens of output and home-theater projectors operating in the 500-700 lumen range will now enter the market in 2009. LEDs are increasing brightness and efficiency (efficacy) almost 20-40% annually – so these fundemental designs will only get better and eventually replace the century old Bulbs.

LEDs based on photonic lattices and other technologies promise a route to robust, long lasting, safe and efficient LED projectors exhibiting an excellent color gamut. End users are also demanding ever more aggressive form factor and power requirements, particularly with regard to reducing size, improving optical/thermal efficiency and robustness for pocket portability – companion to cell phones. Thermal management is essential for maintaining high output and avoiding LED aging at elevated temperatures. But, conventional HB-LED light collection architectures butt up against the laws of Physics.

HB-LED efficiency cannot rely on diode improvement alone, it now requires NEW creative approaches to HB-LED light collection modules.

Traditionally, LED light is combined by using separate dichroic mirrors (see illustration with bulky reflectors) and separate LED sources with individual heat sinks. This results in bulky, costly and thermally inefficient solutions; the resulting image has often been barely bright enough, because the optical light collection efficiency has been low and the collimators and mirrors contribute to large losses.

SBG Labs has developed a fundamentally new method of collecting LED light which is more efficient and compact (see illustration with red, green and blue “snapshots” of same system). SBG’s DigiLens® is used to time sequentially bend and route the light from the red (25%) and blue (25%) LED’s using its holographic Switchable Bragg Gratings. During the 50% green duration, both SBGs are cleared. Optical prescriptions are added to the red and blue gratings to further tailor and condition the LED light onto the DLP microdisplay chip. In this scheme, the red grating is best considered a hybrid of a grating and holographic optic prescription combined. This breakthrough technique allows the HB-LED module size to have very high optical efficiency (by reducing conventional lens count and distance between each other) and thermal efficiency (by allowing the LED diodes to remain close but still be effectively cooled). The result, a breakthrough compact module, whose benefits can be scaled up or down. This fundamentally breaks the size and efficiency barrier to the LED light collection problem.