Laser vs. LED: What Does the Future Hold?
Last week, longtime contributor David Stone laid out the basics of projector and light-engine mechanics in his superb Tech Talk article Lamp, Laser, or LED Projection: Which Light is Right? David discussed LED as a solid-state alternative to projection lamps, and rightfully pointed out that LED is still most likely to be found today in compact and pico projectors. Laser projection—that other solid-state option— inherently has the juice to drive tens of thousands of lumens of brightness—just have a quick look at this 75,000-lumen bad boy, the single brightest projector in our 11,000 model database. But LED, beyond a thousand ANSI lumens or so (not "LED lumens," as described in this article) can't usually muster much punch. Even for serious home theater it's mostly played the role of laser's maligned, weakling sibling.
So it was with some curiosity that, at last February's pre-pandemic ISE show in Amsterdam, I spied a placard about LED projection in ViewSonic's sprawling booth. I had watched the company announce and/or introduce a variety of LED-based projectors in recent months, including three UHD home theater and lifestyle models in its X-series that have generated interest among our readers. But I hadn't till then made the connection that ViewSonic was stepping out front as an early LED proponent, and is positioning itself for what it sees as emerging opportunity that goes well beyond today's portables.
The sign (shown below) points out the benefits of LED over both lamps and, notably, laser. As you can see, LED as a technology claims the potential for (accent on potential) longer life, wider color gamut, smaller form factor, lower noise/heat levels, and fewer rainbows from single-chip projectors. Of course, the poster conveniently leaves out the brightness factor, where LED still gets completely crushed by lamp and, especially, laser.
This is why the sudden aggressive push to solid-state projection in the last two years has been driven by laser and not LED, both in lower-cost/high-volume commercial models and in the most expensive high brightness, large venue models that represent projection's cutting edge. Much of the activity, especially in the entry-level laser segment, can be attributed to the dropping cost of blue-laser modules, which are now a well-proven and cost-effective technology, and from which (as David's article explains) you can derive all the required primary colors for projection. That solution, typically using a single blue laser combined with a phosphor wheel and a traditional color wheel (for single-chip projectors), gets the job done...though with some limitations on color accuracy and gamut. Nonetheless, it's good enough for most classrooms, conference rooms, retail environments, and other non-entertainment applications, and the consequence has been a near explosion of affordable laser options (starting at around $1,000) in the 3,000- through 6,000-ANSI lumen range. We're even seeing prices starting to drop slowly on some 15,000-20,000 lumen models for auditoriums, lecture halls, and houses of worship—such as NEC's latest 20K-lumen model that we honored with a Projection Expo 2020 Best of Show Award.
With all of this activity in laser, it's easy to dismiss talk of LED eventually overtaking it and becoming the defacto solid-state projection standard. But if we accept that LED is, by nature, the more efficient solution, then it puts today's relatively sparse high-brightness LED efforts by ViewSonic and some other manufacturers in a different perspective. Something like the ViewSonic X100-4K home theater projector ($1,699), another Expo 2020 Best of Show winner, won't deliver state-of-the-art performance, but still represents a cutting-edge product. Using what ViewSonic describes as its second-generation LED technology (another way of saying that it's brighter than earlier LEDs), the X100-4K achieves about 1,200-1,300 ANSI lumens, to which ViewSonic attributes 2,900 LED lumens (that is, they claim the perceived brightness of a 2,900 ANSI lumen lamp projector). No, it's not a blowtorch. But for a dark-room home theater projector driving a 100- or 120-inch screen, it ought to be enough.
Other manufacturers have, for the last few years, been toying with Philip's patented HLD (High Lumen Density) LED technology. This approach recognizes that along with inherent limitations on the brightness of LEDs, the nature of LEDs is that they spread their light over a wide path—typically 180 degrees. Consequently, much of their light energy escapes and can't be captured for projection. Compare that with the super-concentrated output of a laser beam.
HLD addresses this reality with multiple high brightness blue LEDs lining a tube, which then shoots the concentrated light out via a lens to give it a narrow distribution path more suitable for projection. A phosphor rod inside the light tunnel is used to alter the color to either green or yellow to generate or derive the other primary colors.
To date, BenQ's flagship HT9060 is the only serious home theater projector that has utilized HLD technology, which is no doubt one of the factors (along with a premium lens) that contributes to its $8,999 price tag. We had some issues with the HT9060's contrast performance in our 2019 review, but the projector impressively achieved its 2,200 ANSI lumen spec, or about 1,000 ANSI lumens more than what the ViewSonic X100-4K can do. Other currently available HLD projectors are commercial models that range from 3,500 up to 4,500 ANSI lumens. Panasonic is also about to ship its first pure RGB LED projector in the PT-LRZ35, yet another Expo 2020 Best of Show honoree, which is rated for 3,500 ISO lumens (essentially an ANSI equivalent). Panasonic makes no mention of HLD technology in its marketing materials, though we'll be curious to learn how the company has achieved this high brightness with today's LED technology.
In some ways, the promise of high-brightness LED projection behind the backdrop of these fledgling steps is reminiscent of how OLED was regarded for many years in the panel TV industry. The ultra-fast switching of OLED pixels, which permits the pixels to be fully turned off as needed to create total black and infinite contrast, was always the holy grail for display engineers. There were many attempts to commercialize the technology, but poor manufacturing yields on large panels and long-term reliability issues always got in the way. It took LG Electronics trying a completely new design approach to create the manufacturing breakthrough that allowed full-size OLED TVs to finally be realized at viable price points. How they did it is a great tech story for another day. But for now, we should all be looking at LED projection as the debutante emerging from the shadows to take its rightful place. All it takes is one big breakthrough...