It seems strange to talk about achieving the 100-lumen threshold in a projector. This was the lumen level we saw over 10 years ago from some of the microdisplay-based projectors. That was with arc lamps. Today’s challenge is to use LED sources.

Chris Chinnock
Senior Analyst and Editor
for Insight Media

The first class of LED-based pocket projectors offered a paltry 25 lumens. This was improved to around 50 lumens a year ago, with several manufacturers offering products to consumers and professionals for mobile presentations. But these products have not exactly been hits in the market place. We believe that 100 lumens is the threshold where brightness is good enough for many professional and consumer applications, but the price of current products will relegate sales mainly to professionals - not consumers.

LG Electronics, who earlier in the summer, released the HS101 in Europe, priced at a rather high 799 euros, has achieved the 100-lumen mark. Like all of these pocket projectors, it is based on a 0.55" SVGA resolution DLP chip set. This particular unit uses LEDs from Luminus Devices and the lifetime is specified as 20,000 hours.

Luminus has developed LEDs that are surface emitters. Most surface emitting LEDs have a hemispherical output pattern, requiring optics to collect and direct the light onto the microdisplay panel. But Luminus adds a photonic lattice to the LED that helps to reduce the external optical collection requirements by providing light that is more focused in the LED’s surface normal direction. This helps to explain the higher brightness achieved in the LG projector.

But more pedestrian 1mm square LEDs can also be used to achieve high brightness. Today, we learned that SCRAM Technologies has developed a pocket projector that reaches the 92-lumen mark and does not use LEDs from Luminus. This was demonstrated in a retrofitted Samsung pocket projector where the original LED illumination stage was removed and replaced with one developed by SCRAM.

What’s nice about this development is that it’s a retrofit solution. This allows Samsung and others who use a similar projection engine core to rapidly upgrade the output of their projectors by adopting the SCRAM LED illumination module. And, SCRAM has an XGA-resolution engine in development too.

How did they do it? Apparently, the LED illuminator stage is a two-channel type with one channel devoted to producing green light and the other alternating between red and blue. This light is collected and combined for delivery to the DLP chip with the correct etendue. The company uses off-the-shelf LED chips, but has developed very good packaging and thermal management systems that allow the LEDs to be sealed in an enclosure that requires no external fans. The company also developed its own LED drive electronics. Even high power is possible with a 3-channel engine, but SCRAM chose a 2-channel approach to reach the 100-lumen goal with a smaller and more compact design.

And, SCRAM’s new design is quite energy efficient. For example, Samsung rates the power consumption of the 50-lumen version at less than 30W, while the LG 100-lumen model is rated at 80W. SCRAM says their LED illumination module consumes about 10-15W, which is probably about the same consumption as the Samsung 50-lumen illumination stage.

So, while LEDs continue to get brighter at the device level, clever packaging and collection can also boost light output in leaps and bounds, too (maybe to infinity and beyond!).

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