First we had tube TVs based on cathode ray tubes (CRTs). Then TV technology exploded into several: LCD TV, plasma TV, LCoS front/rear projection, DLP front/rear projection, LCD front/rear projection, CRT front/rear projection, SED. There are still others: OLED, TDEL, etc. These different technologies used a variety of light sources: CCFLs, EEFLs, FFLs, LEDs, UHPs, ELs, etc. Now comes something a bit different: Laser-based TVs. The term laser TV is a bit misleading because it’s just the backlight that’s laser and not the way video is displayed.
Why laser? First of all, front and rear projection systems (LCoS and DLP) are the prime targets for their backlights to be replaced. Currently, ultrahigh-pressure (UHP) lamps are used for these systems. UHP lamps have a fairly short lifetime and in 4-5 years, they need to be replaced with price ranging from $200 – $400. Recently, Samsung introduced a DLP-based TV that had a LED backlight. There are other examples of LED backlights in Sony’s TX-series notebook PCs and I believe Sharp has a LED backlit LCD monitor as does NEC. So, LED backlights can be applied to a variety of LCD applications. Lasers on the other hand are better for front/rear projection systems. Back to the question: why laser? Lasers have a very large color gamut, high brightness, high power conversion efficiency, and long lifetimes. What that means is that a laser-based backlight will generate really nice colors, will be very bright, consume very relatively little energy and will last a very long time.
Problems. There are reasons why we don’t see a laser TV today and that has something to do with price. Solid-state lasers have been developed for projection applications: Coherent had a demonstration DLP TV with a laser backlight system. However the prices are still too high for mass production.
Solutions. Novalux wants to change this with its new low-cost laser based on high-power surface-emitting diode lasers: Necsel. One of Nescel’s features is frequency doubling into the red, green and blue that has the potential reach price and performance requirements to manufacture more than a handful of prototypes. Nescel lasers emit saturated primary colors at fixed wavelengths that reach a color gamut of over 200% NTSC. The wavelength is selectable and multi-primary laser displays can be created. Compared to LEDs, brightness via a Necsel array is six orders of magnitude greater. The overall cost of manufacturing a projection TV may be reduced by incorporating a laser backlight system. On a DLP system, the laser backlight will eliminate the need for a color wheel, the color wheel motor, light tunnel and relay optics. On a LCD projection system, the polarizers, color filters, turning mirrors and fly’s eye lenses can all be eliminated.
New ways of reducing the cost of making projection TVs will be absolutely needed as LCD TVs will continue to get larger and cheaper. Currently, LCD TVs have challenged and have beaten plasma TVs as the king in the 40″-49″ range. With new and larger G8 LCD fabs that have commenced operations and soon will, LCD TVs will challenge plasma TVs at the 50″-59″ range. My guess is that within a couple of years, LCD TVs will rule all the way up to 60″. At least in the US, customers still want bigger and that means plasma and projection TVs still have a chance. I for one am waiting for a $1499 70″ LCoS-based TV. Maybe it will have a laser backlight.
For more information: Optics.org
Update April 5, 2007:
There is a great article by DailyTech on laser TV. To summarize: Novalux, a Sunnyvale, California-based developer of laser TV technology, claims laser-based TVs have deeper and more natural color, has greater color point accuracy, more uniform light emission and higher stability and efficiency compared to LCDs and PDPs. Compared to DLP, lasers allow for simpler optics and does not require a color wheel or an extra lens in front of a UHP lamp. Have a look at the images that I borrowed from DailyTech below:
The DLP optical system requires a lens in front of the UHP lamp in addition to a color wheel.
On the other hand, a laser optical system requires just three lasers eliminating the need for an extra lens and color wheel.
[tags]Laser, Laser TV, LED, DLP, PDP, Plasma Display Panel, Plasma TV, LCD TV[/tags]