Lasers As A Light Source to Take Aim at Rear-Projection TV Applications
After years of laboring in the industrial and bioinstrumentation markets, lasers are being repositioned as light sources for rear-projection TVs, said executives polled by Consumer Electronics Daily. Cost remains a major barrier to mainstream commercialization, but if lasers achieve can price parity with the incumbent UHP lamps at around $100 per device, volume production could begin within 2-3 years, said Colin Seaton, new business dir. at laser developer Coherent.
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While Coherent has demonstrated a laser in a 50W DLP- based rear-projection TV and Mitsubishi is expected to showcase a prototype set at its dealer line show next week, more work needs to be done to increase power to the 4-5 w range from the 1w or less common in industrial applications, Seaton said. Coherent’s prototype laser-based TV contains about 500 lumens, company officials said. “Power is important because if you want to have an laser or LED-based rear-projection TV, but it’s half as bright as the other ones, the consumer isn’t going to want it,” Seaton said.
In a conventional microdisplay, a UHP white-light lamp works with a color filter and optical engine to achieve the desired red, green, blue (RGB) spectrum. In a laser projector, the light engine is a combination of 3 solid-state sources including those with wavelengths of 620-630 nanometers for, 532 for green and 460 for blue. The lasers mesh directly with microdisplay electronics, eliminating the need for a color filter.
Coherent has focused on commercializing optically pumped semiconductor (OPS) lasers. It has demonstrated a compact RGB source for projection displays based on OPS technology for 460-nm blue, 530-nm green and 638-nm red diode laser. Each laser yields more than 4 w, making them sufficient to illuminate large rear-projection screens, Seaton said.
For its part, Novalux recently demonstrated low-power lasers with 460-, 488, and 532-nanometer output. It achieved more than 1 w at 532 nm with its extended cavity surface emitting laser (ECSEL) and has signed a licensing agreement with Seiko Epson for developing lasers for use in rear- projection TVs, Novalux Chmn. Jean-Michael Pelaprat said. Novalux’s technology will enable rear-projection TVs to be 30% more cost-effective than existing products and could be commercialized by late 2007, Pelaprat said. Quintessence Photonics also is targeting CE with single-mode diode-laser technology originally developed for telecom. It has achieved 3 w of single transverse mode per emitter and demonstrated this on a 40-W bar that has 12 emitters.
Laser-based rear-projection TVs are expected to focus on 60-80” screen sizes as they seek to avoid competition with LCD TV and plasma, which will dominate the 40"-60” segment of the flat-panel sector, industry officials said. “The projection space is going to be pushed toward bigger displays to be cost-effective against LCDs and plasma so therefore the power premium becomes really important,” Seaton said: “You have to have enough power to do a big bright screen so you will need 4-5 or more watts.”
Mitsubishi Product Development Dir. Marty Zanfino declined comment on where his company will source lasers for its prototype rear-projection TV, but he conceded that the technology, once ready, will likely target larger sizes. “It’s an expensive engine so the product is a better value when it has a larger screen,” he said. “Once you get to the engine you can make it whatever screen size you want.” Estimates that 4-5 w lasers will be needed for rear- projection TVs are “not unreasonable,” Zanfino said.
The burning question isn’t only whether the technology can deliver form, fit and function, but can it also meet “cost performance,” Seaton said: “Only CE manufacturers can really do that with the economies of scale and can afford the investment and make the commitment required.” Coherent has had discussions with several potential CE partners, but hasn’t landed an agreement, Seaton said. Coherent typically will seek a pact specifying upfront technology transfer fees and royalties based on TV sales, he said.
Coherent’s advanced technology research group has about 30 engineers working on rear-projection TV applications for lasers, Seaton said: “We have to get something out there before too long. It won’t go on forever and it has to be an agreement that makes sense for us. We've shipped a few lasers to companies, but the feedback is incredibly slow and sometimes non-existent. So we decided initially to do an off-the-shelf display to understand what’s required of a rear-projection TV laser.”