Laser TV

Laser color television(laser TV), or laser color video display, is a type of television that utilizes two or more individually modulatedoptical (laser) raysof different colors to produce a combined spot that is scanned and projected across the image plane by a polygon-mirror system or less effectively byoptoelectronicmeans 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 acathode 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 withdigital light processing(DLP).

The special case of one ray reduces the system to amonochrome displayas, for example, inblack and white television.This principle applies to a direct view display as well as to a (front or rear)laser projectorsystem.

Laser TV technology began to appear in the 1990s. In the 21st century, the rapid development and maturity ofsemiconductor lasersand other technologies gave it new advantages.

History

The laser source for television orvideo displaywas originally proposed by Helmut K.V. Lotsch in the GermanPatent1 193 844.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.18 years later the German-based companySchneider AGpresented a functional laser-TV prototype at IFA'95 inBerlin,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 VegasConsumer Electronics Showin 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, 2006with 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,MitsubishiDigital Electronics America, a key player in high-performance red-laser and large-screen HDTV markets, unveiled their first commercial Laser TV, a 65 "1080pmodel. APopular Sciencewriter 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 aconsumer productthat displays images and videos measuring 100 inches (254 centimeters) with afull high-definitionresolution of 1920 x 1080 pixels. It can project images onto the screen at a distance of 22 inches (56 centimeters).

InChina,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 billionCNY.

Principle

Laser TV images arereflectedby thescreenand enter the human eye for imaging. The principle of laser TV is to useDLPtechnology for image display. Take theDMDchip 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 threeprimary colorsthat are irradiated on the samepixelat high speed are mixed and superimposed to form a color.

Technology

Lasers may become an ideal replacement for theUHP lampswhich are currently in use in projection display devices such asrear-projection TVand front projectors. LG claims a lifetime of 25,000 hoursfor their laser projector, compared to 10,000 hours for a UHP. Current televisions are capable of displaying only 40% of thecolor gamutthat humans can potentially perceive.

Laser TVs utilize a laser light source, which offers several advantages over traditionalLEDandOLEDtechnologies. The lasers typically use specific wavelengths of light, resulting in a wider color gamut and superior brightness. Unlike LED or OLED, laser light sources can produce purer colors, enhancing the viewing experience with more vibrant and accurate color reproduction. Additionally,laser lightsources generally have a longer lifespan and are more energy-efficient, contributing to lower operational costs and environmental impact.

Color television requires light in three distinctwavelengths—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 doublingcan 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.

AVECSELis 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 powerIR-laser diodes is converted into visible light by means of extra-cavity waveguidedsecond-harmonic generation.Laser pulses with about 10kHz repetition rate and various lengths are sent to adigital micromirror devicewhere each mirror directs the pulse either onto screen or into the dump. Because the wavelengths are known all coatings can beoptimizedto reduce reflections and therefore speckle.

Characteristics

Laser TV images are reflected by the screen and enter thehuman eyefor imaging. According toophthalmologistsand professional evaluations, laser TV products are display products that are harmless to the naked eye. The screen has noelectromagnetic radiation,which is eye-protecting, healthy and comfortable.Compared with paper reading comfort, it is 20% higher. Laser TVs are mainly large-sized, with pure light sources, bright colors, and authenticity, also support4K display resolution.

Laser TVs have lower power consumption than LCD TVs of the same size. For example, a 100-inch laser TV consumes less than 300 watts, which is ½-⅓ of the same size LCD TV. Laser TVs are about one-tenth the weight of LCD TVs of the same size, and people can watch 80-inch laser TVs at a viewing distance of 3 meters.

Assembly

Laser signal modulation

Thevideosignalis introduced to the laser beam by anacousto-optic modulator(AOM) that uses aphotorefractivecrystal to separate the beam at distinct diffraction angles. The beam must enter the crystal at the specificBragg angleof that AOM crystal. Apiezoelectricelement transforms the video signal into vibrations in the crystal to create an image.

Horizontal and vertical refresh

A rapidly rotating polygonal mirror gives the laser beam the horizontal refresh modulation. It reflects off of a curved mirror onto agalvanometer-mounted mirror which provides thevertical refresh.Another way is to optically spread the beam and modulate each entire line at once, much like in a DLP, reducing the peak power needed in the laser and keeping power consumption constant.

Display characteristics

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

Applications

There are several realizations of laser projectors, one example being based on the principle of a flying light spot writing the image directly onto a screen. A laser projector of this type consists of three main components — a laser source uses the video signal to provide modulated light composed of the three sharp spectral colors — red, green, and blue — which a flexible, fiber-optic waveguide then transports to a relatively small projection head. The projection head deflects the beam according to the pixel clock and emits it onto a screen at an arbitrary distance. Such laser projection techniques are used inhandheld projectors,planetariums, and for flight simulators and other virtual reality applications.

Due to the special features of laser projectors, such as a highdepth of field,it is possible to project images or data onto any kind of projection surface, even non-flat. Typically, the sharpness, color space, and contrast ratio are higher than those of other projection technologies. For example, the on-off contrast of a laser projector is typically 50,000:1 and higher, while modern DLP andLCD projectorsrange from 1000:1 to 40,000:1. In comparison to conventional projectors, laser projectors provide a lower luminous flux output, but because of the extremely high contrast the brightness actually appears to be greater.

An example of an image ofplastic ballson a Laser TV compared to aPlasma TV

Development status

In order to further accelerate the adoption of laser displays, the China Ministry of Science and Technology has prioritized the "engineering and development of next-generation laser display technology" as one of the eight major industrial development directions. As related technical problems are gradually resolved, the popularization of laser TV products in households remains a major goal.

At the end of December 2019, theCESILaboratory of the China National Institute of Electronic Standardization and a team of ophthalmologists from Peking Union Medical College Hospital conducted a research project regarding the visual perception and eye strain of laser displays. In the study, 32 subjects were placed in the same environmental conditions comparing a laser TV and a LCD TV. Eye blinking frequency and the subjective perception score were compared and analyzed between the displays. The results found that watching the LCD TV for an extended period of time produced certain symptoms such as eye swelling, eye pain, photophobia,dry eyes,and blurred vision, while watching the laser TV, there was no obvious visual change or eye discomfort.

On January 16, 2020, the Laser Television Industry Branch of the China Electronic Video Industry Association released the industry's first White Paper on Laser TV Eye Care in Shanghai. The white paper published the eye-care evaluation data of laser TVs and traditionalLCD TVsby ophthalmology experts of China Electronics Technology Standardization Institute's CESI Laboratory andPeking Union Medical College Hospital,and made scientific suggestions on how to protect the visual health of adolescents.The market for laser TVs has seen an overall compound growth rate of 281% from 2014 to 2019. In 2019, the Hisense Laser TV 80L5 ranked first in the annual TV bestseller list. According to user survey data, more than 93% of users chose laser TVs because of the claimed benefits of eye health protection.

Prospect

Compared withLED backlit LCD TVs,laser TVs have many advantages in large-screen imaging. In terms of technical composition, a laser TV is composed oflaser lightsource, imaging module, circuit control system, and display. The technological progress of each of these units will help to increase market share compared to competing display technologies. Additionally, laser light sources have the advantages of lower manufacturingcarbon emissions,highercolor gamut,andhigher energy efficiency.The advancement of laser television combined with better optical imaging technology can be lucrative in the future home display market.

Technical challenges

Lasers are the most expensive components of laser televisions. More advanced laser diodes usually need moresemiconductormaterials to be manufactured, so reducing costs will remain an issue for the industrialization of laser TV for the foreseeable future. Existing laser TV products generally use imported semiconductor devices. In current large-screen display solutions, there are a variety of competing technologies such as LCD,OLED,and upcomingMicro LEDdisplays. Laser TVs must continue to develop to maintain a competitive advantage in order to occupy a larger market share.