Over the past couple of years, a variety of flat-screen technologies such as plasma have been replacing the bulky home-theater screens that have dominated the market for large televisions. Now, the newest entrant into the field is called laser TV, a flat-panel display based on projection-television technology that uses high-powered lasers to light up the screen. Mitsubishi and Samsung are expected to have laser TVs on shelves by Christmas 2007.
Using lasers to illuminate screens is not a new idea, but until now, there hasn’t been a light source powerful and cheap enough to be tapped for consumer displays. Sunnyvale, CA-based Novalux has developed laser technology that exploits a new type of laser architecture that combines a few relatively simple components to pump up the power. The patented laser, called Necsel, was invented by Aram Mooradian, CTO of the company and former head of the quantum-electronics group at MIT’s Lincoln Laboratory. Mooradian claims the technology will allow laser TVs to outdo existing displays larger than 50 inches–mostly traditional projection systems and plasma displays–in terms of both price and quality.
At the heart of a laser TV is the same technology found in projection-television systems. Indeed, many of the laser TVs sold by Mitsubishi and Samsung next year will include a popular projection system called digital light processing, or DLP, developed by Texas Instruments. The main difference between traditional projection and laser TV is the light source: most projection systems use a white-light lamp, whereas laser TV uses an array of lasers.
Lasers, emitting beams of red, green, or blue light, shine on an array of thousands of micro mirrors. Each mirror represents a single pixel. The mirrors are controlled by an electrical signal that causes it to tilt either toward or away from the light source. If the mirror tilts away from the laser, the corresponding pixel is black; if it tilts toward the laser, the corresponding pixel is the color of the laser light. These mirrors switch “on” and “off” thousands of times a second, and the lasers shine on the mirrors in varying intensity, mixing the fundamental red, green, and blue. The result is a huge gamut of colors.
In contrast, lamp projection systems produce color by using a color wheel–a spinning disk usually containing red, green, and blue–that is placed between the lamp and the micro mirrors. This spinning wheel also produces an array of hues. However, the main advantage that lasers offer over traditional projection is an increased richness in colors, says Mooradian. The color of light produced by a laser is, by definition, spectrally narrow, varying less than one nanometer on either side of the peak wavelength. The filters used for lamp-based projection systems aren’t as spectrally pure, varying as much as 20 nanometers, he says. Our eyes can detect this difference, and when the colors are more spectrally pure, they appear more vivid.