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ÿþMaciej ZAJKOWSKI, Tomasz STALBOWSKI Bialystok Technical University LCD, DLP planar lighting fitting Abstract. The LCD displays emit the luminous flux similar to lambertian emission and additionally allow to control the spectral distribution. Conception of lighting fitting enabling the control of emitted luminous flux quantity and change of colorimetric parameters was presented. Streszczenie. Wy[wietlacze LCD emituj strumieD [wietlny w sposób zbli|ony do lambertowskiego i dodatkowo pozwalaj na sterowanie rozkBadem widmowym emitowanego promieniowania. Zaprezentowano koncepcj oprawy o[wietleniowej umo|liwiajcej sterowanie ilo[ci emitowanego strumienia [wietlnego oraz zmian parametrów kolorymetrycznych. (Planarna oprawa o[wietleniowa typu LCD, DLP). Keywords: planar lighting fitting, LCD, DLP, display. SBowa kluczowe: planarna oprawa o[wietleniowa, LCD, DLP, wy[wietlacz. Introduction distribution (figure 2). Analysing the distribution of the Basic task of the lighting fitting is to make suitable luminous flux one affirms the considerable rotatory illuminance or luminance distribution on the working symmetry of the light distribution, whose shape depends on surface. This task is dissolved through elaboration of light- quality and the technology of the realization of LCD display. optical system, using the light source and elements forming the light distribution e.g.: reflector, lampshade, lens. The possibility of any decorating with mouldings the light bundle through suitable reflector form or parameters selection of lens or lampshade is the unquestionable advantage of the typical constructions of lighting equipment. The problem exists because of fitting geometry (mainly its depth) and the possibility of controlling colorimetric parameters. The depth of the lighting fitting causes that fitting must be built in hanging ceilings or utilization of recess in ceilings or walls. The control of colorimetric parameters is also inconvenient. To obtain the colourful lighting with dynamic exposition, it is necessary to bind in fitting several light sources with control of spectral distribution. The RGB LED diodes are such elements that can fulfil this task at present. Conception of planar lighting fitting, leaning about liquid crystals cells or arrangements micro-mirrors (figure 1), gives control possibilities of both the spectral and luminous Fig. 2. Building LCD display cell. flux distributions, through applying the planar optical structures. The light source are linear fluorescent lamps. The fluorescent lamp with the cold cathode (Cold Cathode a) b) c) d) Fluorescent Lamps CCFL) assures low waste of energy and relatively large value of the luminous flux. Two technologies ~70 are applied: the back and side illumination (backlight). This kind of illumination allows to the cheap production +10 of monitors, but the serious technological limitation makes up simultaneously. The CCFL backlight does not allow to get the wide spectrum of colours, approximate or larger than in standard kinescope monitors. The agreement is standard in the case of monitors made in this technology with the sRGB space of colours. Additional problem is to create the monitor which has smooth illumination surface of Fig. 1. The conception of planar lighting fitting: a) module LCD with side illumination, b) module LCD with back illumination, c) LCD screen. The merit of "fluorescent lamps" is small quantity of module with the lamp forming luminous intensity curve, d) DLP warmth, so the chassis of monitor can be comparatively module with the matrix of light sources. small in relation to the surface of screen and cooled passive [2]. Planar LCD fitting To the screen illuminations instead of fluorescent lamps Liquid crystals displays are built from basic elements: are also used the matrices of LED diodes (one module - the liquid crystal cells, consists diodes in the red, green and blue colour), which - the electrodes, they even step out in number a few hundred. In the result, - two thin foils of which one functions as the ploughland of the surface of the screen is illuminated very evenly. The polarizer and second as the analyser, user can correct the value of luminous flux of every diode. - the light source (backlight) [1]. The LED backlight is introduced in figure 6. To form light bundle one uses backlight systems. There is a little information about photometric propriety of arrangements backlight in the literature. In our own studies we mark LCD s, because of luminous flux and luminance PRZEGLD ELEKTROTECHNICZNY, ISSN 0033-2097, R. 84 NR 8/2008 105 . Fig. 5. Type of side illumination. Fig. 6. The LED backlight. LED diode allows to get the considerably wider spectrum (figure 7) of colours than standard LCD monitors. The covered space of colours is AdobeRGB the most often, however in the standard LCD it is sRGB or NTSCRGB. The fault of such displays is high cost of applying this technology and large quantities of warmth emitted through diodes, which could deform planar plate of backlight, so it is necessary to use active cooling chassis of display. Fig. 7. Spectral distribution of LED and CCFL backlights. Fig. 3. The example of luminous intensity and distribution of The conception of fitting using micro-mirrors luminance in equal lighting conditions, two various LCD displays: a) HP, b) NEC. Since several years light-optical devices using DLP modules have been built. This are matrices of micro-mirrors (figure 8), which are able to modulate luminous flux through its reflection from mirror surfaces. Elements reflecting in DLP modules lean out in the range ± 10 ° from the axis of the DLP matrix. Through arrangement of light sources in space (e.g. the LED diodes), one can get the obtusity of the light bundle not larger than 70 °. The colourful parameters of such light- optical arrangement are the result of utilization of RGB LED Fig. 4. Type of back illumination diodes. 106 PRZEGLD ELEKTROTECHNICZNY, ISSN 0033-2097, R. 84 NR 8/2008 or micro-mirrors arrangements is the possibility of image presentation or production of dynamic light scenes, through single optical construction, what has not been possible until now, in the case of the classic constructions of lighting fittings [3]. Fig. 8. The single micro-mirror in DLP matrix . The laser is the modern source of the light. The coherent radiation is its basic feature, and also miniaturization [4]. Laser modules RGB (figure 9b) are used in presentation and lighting systems, because of elimination a) b) of expensive and inconvenient in exploitation light sources Fig. 9. The laser RGB module: a) CIE1931 space of colours, b) like discharge lamps or high energy LED diodes. The building of laser module. waste of energy in comparison with classic solutions got lower about approx. 50%, causes enlargement of the range Financed by Ministry of Science and Higher Education  of colours (figure 9a) to the level approx. simultaneously No. W/WE/4/08. 95% range of colours perceived by the man. The light is additionally polarized, and laser module is characterized by REFERENCES [1] http://www.pcworld.pl high efficiency and lifetime about 55 000 hours. [2] de Gennes P.G,. Prost J: The Physics of Liquid Crystals, Claredon Press 1993 Conclusions [3] DybczyDski W.: Miernictwo promieniowania Optycznego, WPB, Conception of planar lighting fitting leaning on the LCD BiaBystok 1996 or DLP technology lets achieve and obtain the new guilds of [4] http://www.novalux.com/display/ luminaire. Except of forming light distribution (dynamic with utilization of the matrix micromirrors in the DLP technology), such fittings let control in the dynamic way, and control of Authors: colorimetric parameters like colour temperature or colour of dr in|. Maciej Zajkowski, Politechnika BiaBostocka the light. Light, emitted from planar fitting, shows high WydziaB Elektryczny, Katedra Promieniowania Optycznego, ul. Wiejska 45D/218, 15-351 Bialystok, degree of polarization because of applying polarizing filters e-mail: maczak@we.pb.edu.pl in its construction. The construction of low-luminance fittings is inconvenient in classic formulation, however it lets mgr in|. Tomasz Stalbowski, Politechnika BiaBostocka utilization of planar structures (planar optical fibres) and WydziaB Elektryczny, Katedra Promieniowania Optycznego, LCD or DLP technology, on projects and production of such ul. Wiejska 45D/218, 15-351 Bialystok light-optical devices. The additional feature of devices emitting the luminous flux through liquid crystals structures PRZEGLD ELEKTROTECHNICZNY, ISSN 0033-2097, R. 84 NR 8/2008 107

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