Laser color television (laser TV), or laser color video display, is a type of television that utilizes one 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 systems work either by scanning the entire picture a dot at a time and modulating the laser directly at high frequency, much like the electron beams in a cathode ray tube, or by optically spreading and then modulating the laser and scanning a line at a time, the line itself being modulated in much the same way as with digital light processing (DLP). The special case of one ray reduces the system to a monochrome display as, for example, in black and white television. This principle applies to a direct view display as well as to a (front or rear) laser projector system. Laser TV technology began to appear in the 1990s. In the 21st century, the rapid development and maturity of semiconductor lasers and other technologies gave it new advantages.
History The laser source for television or video display was originally proposed by Helmut K.V. Lotsch in the German Patent 1 193 166. In December 1970 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. 18 years later the German-based company Schneider AG presented a functional laser-TV prototype at IFA'95 in Berlin, Germany. Due to the bankruptcy of Schneider AG, however, the prototype was never developed further to a market-ready product. Proposed in 1966, laser illumination technology remained too costly to be used in commercially viable consumer products. 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. A Popular Science writer was impressed by the color rendering of a Mitsubishi laser video display at CES 2008. Some even described it as being too intense to the point of seeming artificial. This laser TV, branded "Mitsubishi LaserVue TV", went on sale, November 16, 2008 for $6,999, but Mitsubishi's entire laser TV project was killed in 2012. LG introduced a front projected laser TV in 2013 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). In China, the Sixth Session of the Seventh Council of the China Electronic Video Industry Association formally approved the establishment of a laser TV industry branch. The establishment of the industry branch also symbolizes that the entire industrial chain connecting the upstream and downstream of the laser TV field is officially opened, in order to make the laser TV industry bigger and stronger. By 2022, sales of laser TVs in the Chinese market will exceed 1 million units, and sales will reach 11.8 billion CNY.
Principle Laser TV images are reflected by the screen and enter the human eye for imaging. The principle of laser TV is to use DLP technology for image display. Take the DMD chip as an example. The DMD chip is the imaging core component of a laser TV. There are millions of small mirrors arranged, and each small mirror can flip in the positive and negative directions at a frequency of tens of thousands of times per second. The light reflects directly on the screen through these small mirrors to form an image. Due to the visual inertia of the human eye, the three primary colors that are irradiated on the same pixel at high speed are mixed and superimposed to form a color.
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. LG claims a lifetime of 25,000 hours 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. Color television requires light 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 10kHz 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.
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