显示技术的演进与应用

第3卷第1期中国光学与应用光学Vol 3 No. 12010年2月Chinese Journal of Optics and Applied OpticsFeb.2010文章编号1674-2915(2010)010027406Progress in display technologies and their applicationsCHENG Yu( Optoelectronics Research Centre, University of Southampton, Southampton, SO17 1BJ, UK)Abstract: This paper overviews some display technologies which play main roles on today's display marketAnd new technologies which may be used for tomorrow's display technologies have been discussed. New tech-nologies will boost the development of display technologiesKey words: display technology; LCD; PDP; OLED; DLP; fiber lasersome current technologies will be overviewed andIntroductionseveral new technologies for display have been discussed too. Low cost, ultra-bright, large-viewirDisplay technologies play an important role in hu- angle, large screen, flexible, and more colourfulan's life because it is a very important way that hu- will be the features of tomorrows display applicaman beings acquire information. Information is tionas the mostof the 21stcentury. Cathode Ray Tube technology( CRT)isused to be the most popular way that information is2 Current display technologiesconveyed. But now new technologies, such as Plas-a Display Panels( PDP), Liquid Crystal Displays 2.1 LCD display(LCD), Organic Light Emitting Diode (OLED and Liquid crystals were first researched in 1888 byDigital Light Processing( DLP ) et al., play main Friedrich Reinitzer, an Austrian botanist. Light isroles in our daily life. The truth to be told, each sent through the twisted liquid crystal structure curlstechnology has its advantages and disadvantages. following the molecular arrangement, and the lightMoreover, current and up-and-coming inventions propagation can be modulated according to the chanwill make some fantastic electronic products in our ges of the orientation of the liquid crystals. That isdaily lifewhy liquid crystal can be acted as a light modulatorThe display technologies have been motivated for display. LCD displays can be divided intoby the High-definition Television( HDTVassive matrix LCDs and active matrix LCDvision"market all over the world. Also the need of (AMLCD )according to the circuits that are responscreen desktop display encourages the scienI c AMLCD is a very popularto make more researches on the materials elec-中国煤化工lay. A typical AMLCDtrons, optics, and methods et al. In this paperCNMHGReceived date. 2009-10-12: Revised date: 2009-12-27中国光学与应用光学第3卷Active elementPixelElectrodeY electrodeLightig. 1 Structure of AM driving display and the circuitFluorescent lamps are widely used as LCD light brightness, the lamp with more power is neededsources for the reasons of low cost and high efficien- But the lamp life time decreases with the increase ofcy, but the lifetime is only 4 000-6 000 h3). the output power. Consumers may need to changeNowadays, LED seems to have better performance the lamps by themselves which make the producthen it is used as the light source for an lcd back inconvenientlight because it delivers displays that are brighter, 2more colourful and robust than ever before. LCD The color pdp as shown in Fig. 2 was invented at thedisplay technology can be used both for panels and University of Illinois in 1946 by Prof. Bitzer andprojectors, but the LCd projector uses UHP lamps Prof. Slottow. The operating principle of PDP is thatrather than fluorescent lamps. However, mercury a visible light emitting phosphor is excited by theHg) is not a green material and has theltraviolet ray generated by the gas discharge. Theproblem of damage to health. And a light source for inner space of the PDP panel is divided into numer-the LCD technology need to be polarization to imous IOcI cells. Each pixel has its address eleeprove the efficiency. The light emitted from lamps or trodes, display electrodes, RGB phosphors, xenonLED is unpolarized. The simple and efficient polariand neon gas mixturezation conversion scheme using induced SurfaceFront glassplasmon-Polariton( SPP )on metallic gratings is aDielectricy sustain electrodegood way to improve the efficiency without increasingX sustain electrodethe manufacture cost if silver- or aluminium-coatedMeo layergratings are built on the surface of the reflector/4)Barrier ribCompared with traditional CRT technology, the LCDRear glassdisplay technology has advantages of cost and per-Phosphor Address electrodethat therelatively small and I(R, G, B)compact, hence it is suitable for flexible display re-中国煤化工 e PDp with three elec-quirements. Furthermore, LCD display technologyCNMHGrequires no high-voltage power. Due to the reasonsmentionlcd display techneareOwning to the novel operating principle, eachwidely usedit may have some disadvantages, pixel generates its own light and as a result, thefor example, with the increase of the lCd projecteviewing angle is large, and the image quality is第1期CHENG Yu: Progress in display technologies and their applicationssuperior. The cell structure of the PDP can be built lifetimes(46000-230 000 h), while blue OLEDsbigger and bigger without changing any optical prop currently have much shorter lifetime(up to arounderties of the emission, therefore the PDP has the 14 000 h). The manufacturing processes are expen-to build ultra-large panel display. Compa-sIve. annd water can easily damage OLEDs 7Jring with OLED and LCD, PDP is ultra bright, so it 2. 4 DLP Displayhas advantages in large screen size, wide viewing DLP offers the best picture in the four kinds of disligh contrast ratio, and its thinness plays. The DLP optical system uses a digital micromakes PDP more suitable for a big-size displaymirror device( DMD developed by Texas InstrumentProfessional manufacture, shipment and instal- Co., and the DMd is a semiconductor light switchlation are needed for PDP due to the fragility of the where fine driving mirrors are integrated. In the DLPplasma screen, and the increase of power consuming display system, light is transmitted through a colouis its another disadvantage. As a results, the PDP wheel before the light is incident to the dmd. Themay not be suitable for small size display.brightness of each pixel is determined by the time for2.3 Oled displaywhich the light source illuminates the pixel, and theIt is well known that OLED has many advantages, process is realized through Pulse Width Modulationsuch as thinness display, light weight, display under (PWM). The advantage of the DLP display technollow temperature, high brightness and wide-viewing ogy is ultra clear picture and"hi-vision for largeangle. therefore oled attracts much research interscreendlp display technology also relysest all over the world. Other advantages such as faston light source such as UHP lamps or lasersresponse and significantly lower cost make them aThere are two display technologies which do notpotential candidate for the display in the furtureneed any light source. i. e. OLED and pdp, beOLEDs are thin-film multi-layer devices consisting of cause they can emit RGB light themselves. But LCDcover glass, electrode(-transparent-cathode ), funand dLp display technologies require light sourcetion layer, electrode (twhich is not perfect now. What's more, LCD andstrate(glass). A typical structure of OLED is shownDLP display technologies are main commercial prodin Fig. 3ucts available in the market. Therefore there is aneed for the develeelopingsourcesCathodeEmissive3 New technologies for future s dis-olay technology3. 1 SHG RGB laser for displayAnodeGlass substrateProjection displayral advanta-中国煤化工 mentioned above.TheFig 3 Scheme of the typical structure of OLEDHHaCN MH Gge colour gamut whichcan be obtained. Other advantages are high contrastAlthough OLEDs have many advantages in flex- ratio and high brightness. It is also possible toible display, they still have some problems. For obtain nice projection on curved surfaces due to theen OLED films have longer large focal depth of the laser bepower中国光学与应用光学第3卷systems, like home theatres, the semiconductor play a main role in display technology. A mixturetechnology is the most promising techDue to structure of rgb laser schematic diagram is shownthe high beam quality which can be obtained from in Fig. 5. The researchers achieved low electric con-the solid-state lasers, they will probably be competi- sumption and wide colour gamut by using the effitive to semiconductor lasers even in the future. But, cient and compact air-cooled green SHG laser unitas one cot, the output powand the new illumination optics for speckle noiselow; the conversion efficiencies from the input pumpduction and low light power loss[131power to the red and green powers were below 1%0and the conversion efficiency from the input pumpProjectionLCD panelwer to the blue power was much smaller thanRelay lens1%∞,0Red LD640nmHigh power infrared emitting Optically PumpedSemiconductor Disk Lasers( OPSDL with good effi532nmciency and good beam quality are the basis for gen-SHGerating blue and green laser radiation by Seconddevicelod integratorHarmonic Generation( SHG ). Disk lasers based onFiber laserthese pump scheme achieve infrared output power ofBlue ldRotating lens445nmore than 1. 5 W. Experiments with intracavity SHGGreen SHG laser unitare in an early stage, 300 mW of frequency doubledFig 5 Mixture structure of RGB laser schematic diaoutput power has been demonstratedAnother RGB-0PO light source is highly efficient as it derives all three wavelengths from one 3.2 RGB generation by photonic crystal fiberdrive laser. Four pump lasers with the total power of Microstructure fiber is a research focus in all over128 W are employed to generate an average power of the world. Novel idea and design method enable this30 W, 524 nm green pulse laser. Then this green fiber to have some special properties in optics. Plaser is used as a pump to generate total 15 W RGBHorak et al. in ORC use a special designed PCf tolaser 12(shown in Fig 4)generate RGB laser from one single fiber. The pumpPSingly resonant OPO Signal 898 nm+ Greensource in the experiment is a frequency-doubled yb-Green524m、524Type-I OPO LBOdoped fiber MOPa which generates 80 ps pulses at29 mm Type-II 1256 nr530 nm with a repetition rate of 32 MHz and up to 2SHG LBOW output power. Fiber parameters are d/A-0 935nmtracavitand 4-2. 5 um to 4. 7 um. And a total of 360 m WSWP: GR(a 1256 nmof rgb laser are obtained from this fiber 14)449mmHT(@ 524 628, and 898 nm3.3 Visible fiber laser by downconversiontype-I SHG LBO SignalThe first visible fiber operated at the wavelength of中国煤化工 silica optical fiber waLWPHCNMHG Southampton in 1990Fig 4 Scheme of RGB-OPO light sourceM. C. Farries et al. had successfully achieved aSm-doped silicate fiber laser which has a slopeDue to the rapid progress of NIR fiber lasers, efficiency of 12. 7% and output power more thanespecially yb'-doped fiber lasers, fiber lasers al25 mW by argon laser pump. Recent research shows第1期CHENG Yu: Progress in display technologies and their applications400500Fig 6 RGB laser generated from a PCF fiberFig. 8 Relaxation oscillation( the scale of x is millisecthat argon laser pump samarium fiber laser can belong lifetime running 15, 16) The pump used is an14000Ar laser, which is expensive and low electric-optical efficiency. The samarium has even bigger0000bsorption cross section at 405 nm than that of the6000488 nm The blue diode lasers are wicused inDVD writers, and they can act as a pump source forfiber laser as well. Therefore it is rea-a/nmto use blue diode laser instead ofas a pump source. The absorption spectra of Sm'tFig 9 Laser spectra of the blue diode laser pumpeddoped phosphor silicate fiber and the characterizationhosphor silicate fiberof the diode laser pumped samarium fiber laser areshown from Fig. 7 to Fig 9Tb't-doped fluoride fiber laser was reportedthat a visible fiber laser operated at 542. 8 nm whenSm-doped phosphor silicate fibreoutput power of the 542. 8 nm was 0. 28 mW and aslope efficiency of 4. 1% was achieved 17] Fiberlasers have properties as a merit for display, such asdiffractive limit beam quality and flexible deliveryFiber laser may have as long lifetime as 30 000 hwhich is the longest lifetime and less power consuming. Due to the advantage of modulation and poweramplifier of fiber lasers, the RGB fiber laser may1350a/nmre potential in the future's display applica-Fig 7 Sm-doped phosphor silicate fiber absorption中国煤化工 have some advantagesspectraCNMHGources, they are neededto improve the efficiency to make their advantage to中国光学与应用光学第3卷that LCD and DLP technologies are the most popular4 Conclusionstechnologies. And new light source technologies maycontinue to boost the fast development of the displayInrent display technologies haveWith the development of fiber lasthe advantages and disadvan-ore and more low cost fantastic fiberages of each technology have been discussed. One laser products will be used for future's display tech-can see that the technology developing trend showsReference[1 SLUCKIN T. Ueber die natur der kristallinischen FI ssigkeiten und fl ssigen kristalle(The early history of liquid crystals[J]. Bunsen-Magazin, 7. Jahrgang, 5/2005[2 KAWAMOTO H. The history of liquid crystal displays[J]. Proc. IEEE, 2002, 90(4): 460-50[3 LEE Y-P, CHEN L, KOU P-J. The projector light source: ultra-high performance( UHP)lamps[ C]//Industrial and Commercial Power Systems Technical Conference IEEE, Detroit, Michigan, 2006, (s): 1-6[4 TSAI CH-CH, WU SH-T. Efficient linearly polarized lamp for liquid crystal displays[ J]. J. Display Technol., 2009, 5(1):69[5 YI K-H, HAN S-K, CHOI S-W, et aL.. A simple and highly efficient energy recovery circuit for a plasma display panel(PDP)[J]. IEEE T. ind. ELECTRON, 2008, 55(2): 782-790[6 LIN S Y, CHEN C L, LEE K. Novel regenerative sustain drivers for plasma display panell c //IEee power Electronics[7 SHINAR J. Organic LighI-Emitting Devices: A Survey[M]. College Park, MD: AIP Press, 2004[8 LEE H K, Si CH J. DLP optical system: US, 0035701 Al[P]. 2007[9 BRENIER A, TU CH Y, ZHU ZH J, et aL.. Redgreen-blue generation from a lone dual-wavelength GdAl,( BO3): Ndaser[J].Ap.Phys.,2004,84(12):2034-2036[10] CAPMANY J. Simultaneous generation of red, green and blue continuous-wave laser radiation in Nd+-doped aperiodially poled lithium niobate[ J. Appl. Phys. Lett., 2001, 78(2): 144-146[11] STEEGMU LLER U, KUHNELT M, SCHWARZ T, et aL.. Compact semiconductor based RGB lasers[ C]//1Oth Microop-tics Conference( MOC 04),Jena, Germany, 1-3 Sept 2004[12] MOULTON P F, SNELL K J, LEE D, et aL.. High-power RGB laser source for displays[ EB/OL].(2002-02)[2007-0320http://www.gpeak.com/papers/imAgeo2/image%202002%20rgb%200po%20pAper.pdf[13] MIZUSHIMA T, FURUYA H, MIZUUCHI K, et aL.. L-9: late-news paper: laser projection display with low electric con-sumption and wide color gamut by using efficient green SHG laser and new illumination optics[ C]//SID Symposium Digest of Technical Papers, 2006, 37: 1681-1684[14 HORAK P, DUPRIEZ P, POLETTI F, et aL.. Eficient white light generation in secondary cores of holey fibers[ J]. OptExpress,2007,15(7):3729373[15] FARRIES M C, MORKEL P R, TOWNSEND J E. Spectroscopic and lasing characteristics of samarium doped glass fibre[J]. IEE Proc.J,1990,137(5):318-32[16 CHENG Y, OTON C J, BOYLAND A J, et al., Photodarkening of 488 nm-pumped Sm-doped germanosilicate fiber laser[C]//CLEO Pacific Rim 2009, Shanghai, 30 Aug-3 Sep 200中国煤化工[17 YAMASHITA T, OHISHI Y. Amplification and lasing characCNMHGfber in the 0. 54 um band].Jpm.J.Apl.Phys.,2007,46(41):991993yxc orc, soton. ac