Definitions

projection tv

Laser TV

Laser TV is a new video display technology using laser optoelectronics.

History

Proposed as long ago as 1966, laser illumination technology remained too costly to be used in commercially viable consumer products and too poor in performance to viably replace lamps except in some rare ultra-high-end projectors. At the Las Vegas Consumer Electronics Show in 2006, Novalux Inc., developer of Necsel semiconductor laser technology, demonstrated their laser illumination source for projection displays and a prototype rear-projection "laser" TV. First reports on the development of a commercial Laser TV were published as early as February 16, 2006 with a decision on the large-scale availability of laser televisions expected by early 2008. On January 7 2008, at an event associated with the Consumer Electronics Show 2008, Mitsubishi Digital Electronics America, a key player in high-performance red-laser and large-screen HDTV markets, unveiled their first commercial Laser TV, a 65" 1080p model. First audiences who were shown reference clips from popular movies reported that they were blown away by a Laser TV's hitherto unseen color-display prowess. Some even described it as being too intense to the point of seeming artificial. This Laser TV, branded "Mitsubishi LaserVue TV", is expected to go on sale in late September 2008 in the North American market with a RRP of $6,999.

Technology

Lasers may become an ideal replacement for the UHP lamps which are currently in use in projection display devices such as rear projection TV and front projectors. Current televisions are capable of displaying only 40% of the color gamut that humans can potentially perceive. In contrast, proponents of Laser TV technology claim that the standard will be able to reproduce about 80% of the colors visible to the human eye.

A Laser TV requires lasers in three distinct wavelengths: Red, Green and Blue. While red laser diodes are commercially available, there are no commercially available green and blue laser diodes which can provide the required power at room temperature with an adequate life time. Instead frequency doubling can be used to provide the blue and green wavelengths. Several types of lasers can be used as the frequency doubled sources: fibre lasers, inter cavity doubled lasers, external cavity doubled lasers, eVCSELs and OPSLs (Optically Pumped Semiconductor Lasers). Among the inter cavity doubled lasers VCSELs have shown much promise and potential to be the basis for a mass produced frequency doubled laser.

A VECSEL is a vertical cavity, and is composed of two mirrors. On top of one of them is a diode as the active medium. These lasers combine high overall efficiency with good beam quality. The light from the high power IR-laser diodes is converted into visible light by means of extra-cavity waveguided second harmonic generation. Laser-pulses with about 10 kHz repetition rate and various lengths are sent to a Digital Micromirror Device where each mirror directs the pulse either onto screen or into the dump. Because of the well known wavelengths all coatings can be optimized to reduce reflections and therefore speckle.

Advantages

One major claim of laser advocates is the ability to produce undiluted, perfect colors allowing precise hue mixing. Advocates claim that 90% of the perceptible color gamut can potentially be reproduced. Other improvements that laser advocates claim are bulbs that will never blow out, and increased efficiency by using two-thirds less power than traditional rear projection televisions. Historically, however, lasers have been too bulky and expensive for widespread adoption.

The laser technology advocates claim that the technology will allow displays with a richer, more vibrant color palette than the conventional plasma, LCD or CRT displays.

They also claim the displays will:

  • be half the weight and cost of Plasma or LCD displays
  • require around 25% of the power required by Plasma or LCD displays
  • be very thin like Plasma and LCD displays are today
  • have a very wide colour gamut. Twice the color of today's HDTVs.
  • have a 50,000 hour life
  • maintain full power output for the lifespan of the laser, resulting in a picture that doesn't progressively degrade over time, such as with plasma and LCD technology

Drawbacks

Together with the advantages of laser sources, there are reports that also describe some of the current shortcomings of laser displays, such as the following:

  • Safety. The high power emitted by the coherent laser sources is inherently dangerous to human vision. Proponents claim that integrating the devices with the needed diffusion filters removes this risk.
  • Speckle. Due to the narrowband coherent light source, speckle will be an issue at the display. This has also been a problem in laser lighting displays and has been solved through modulation of the light source thus widening the bandwidth and reducing the possibility for coherent interference. Proponents claim that this issue can be minimized by the use of diffusing elements and multiple sources. These, however, may impact display resolution and system cost.

References

External links

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