Laser video display

Laser color television (in short, Laser TV), or Laser color video display utilizes two or more individually modulated optical (laser) rays of different colors to produce a combined spot that is scanned and projected across the image plane by a polygon-mirror system or less effectively by optoelectronic means to produce a color-television display. The special case of one ray reduces the system to a monochromatic display as, for example, in black-and-white television. This principle applies to a display as well as to a (front or rear) projection technique with lasers (a laser video projector).

History

The laser source for television or video display was originally proposed by Helmut K.V. Lotsch in the German Patent 1 193 844.^[1] In December 1977 H.K.V. Lotsch and F. Schroeter explained laser color television for conventional as well as projection-type systems and gave examples of potential applications.^[2] 18 years later the German-based company Schneider AG presented a functional laser-TV prototype at IFA'95 in Berlin/Germany. Due to bankruptcy of Schneider AG, however, the prototype was never developed further to a market-ready product.

Proposed in 1966,^[3] laser illumination technology remained too costly to be used in commercially viable consumer products^[4] 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.^[5] First reports on the development of a commercial Laser TV were published as early as February 16, 2006^[6][7] with a decision on the large-scale availability of laser televisions expected by early 2008.^[8] 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^[9] and large-screen HDTV markets, unveiled their first commercial Laser TV, a 65" 1080p model.^[10][11][12] A Popular Science writer was impressed by the color rendering of a Mitsubishi laser video display at CES 2008.^[13] Some even described it as being too intense to the point of seeming artificial.^[14] This Laser TV, branded "Mitsubishi LaserVue TV", went on sale, November 16, 2008 for $6,999, but Mitsubishis entire Laser TV project was killed in 2012.^[15][16][17]

LG introduced a front projected Laser TV in 2013^[18] as a consumer product that displays images and videos measuring 100 inches (254 centimeters) with a full high-definition resolution of 1920 x 1080 pixels. It can project images onto the screen at a distance of 22 inches (56 centimeters).

Technology

Lasers may become an ideal replacement for the UHP lamps^[19] which are currently in use in projection display devices such as rear projection TV and front projectors. LG claims a lifetime of 25,000 hours^[20] for their laser projector, compared to 10,000 hours for a UHP. Current televisions are capable of displaying only 40% of the color gamut that humans can potentially perceive.^[21]

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 laser diodes which can provide the required power at room temperature with an adequate lifetime. Instead frequency doubling can be used to provide the 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.

The blue laser diodes became openly available around 2010.

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 the wavelengths are known all coatings can be optimized to reduce reflections and therefore speckle.

Display Characteristics

• Maintain full power output for the lifespan of the laser; the picture quality won't degrade
• Have a very wide color gamut, which can produce up to 90% of the colors a human eye can perceive
• Capable of displaying 3D stereoscopic video
• Can be projected onto any depth or shape surface while maintaining focus.

References

External links

• Infos and News about laser-TV
• Evans and Southerland Laser Projector
• Laser-TV,Sed-Tv,Oled-Tv News and Infos
• Mitsubishi LaserVue web site
• Hungarian Laser TV links