PRZEGLĄD ELEKTROTECHNICZNY, ISSN 0033-2097, R. 84 NR 8/2008                                                                              105 

Maciej 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. Wyświetlacze LCD emitują strumień świetlny w sposób zbliżony do lambertowskiego i dodatkowo pozwalają na sterowanie rozkładem 
widmowym emitowanego promieniowania. Zaprezentowano koncepcję oprawy oświetleniowej umożliwiającej sterowanie ilością emitowanego 
strumienia świetlnego oraz zmianę parametrów kolorymetrycznych. (Planarna oprawa oświetleniowa typu LCD, DLP). 
 
Keywords: planar lighting fitting, LCD, DLP, display. 
Słowa kluczowe: planarna oprawa oświetleniowa, LCD, DLP, wyświetlacz. 
 
 

Introduction 
  Basic task of the lighting fitting is to make suitable 
illuminance or luminance distribution on the working 
surface. This task is dissolved through elaboration of light-
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 
flux distributions, through applying the planar optical 
structures. 
 

+10

~70

a)                   b)                         c)                                       d)

 

Fig. 1. The conception of planar lighting fitting: a) module LCD with 
side illumination, b) module LCD with back illumination, c)  LCD 
module with the lamp forming luminous intensity curve, d)  DLP 
module with the matrix of light sources. 
 

Planar LCD fitting  

Liquid crystals displays are built from basic elements: 

- the liquid crystal cells, 
- the electrodes,  
- two thin foils of which one functions as the ploughland of 
polarizer and second as the analyser, 
- the light source (backlight) [1]. 

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 

distribution (figure 2). Analysing the distribution of the 
luminous flux one affirms the considerable rotatory 
symmetry of the light distribution, whose shape depends on 
quality and the technology of the realization of LCD display. 

 

 

Fig. 2. Building LCD display cell. 

 
The light source are linear fluorescent lamps. The 

fluorescent lamp with the cold cathode (Cold Cathode 
Fluorescent Lamps CCFL) assures low waste of energy and 
relatively large value of the luminous flux. Two technologies 
are applied: the back and side illumination (backlight).  

This kind of illumination allows to the cheap production 

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 
screen. The merit of "fluorescent lamps" is small quantity of 
warmth, so the chassis of monitor can be comparatively 
small in relation to the surface of screen and cooled passive 
[2]. 

To the screen illuminations instead of fluorescent lamps 

are also used the matrices of LED diodes (one module 
consists diodes in the red, green and blue colour), which 
they even step out in number a few hundred. In the result, 
the surface of the screen is illuminated very evenly. The 
user can correct the value of luminous flux of every diode. 
The LED backlight is introduced in figure 6. 

 

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PRZEGLĄD ELEKTROTECHNICZNY, ISSN 0033-2097, R. 84 NR 8/2008

 

 

 

 

Fig. 3. The example of luminous intensity and distribution of 
luminance in equal lighting conditions, two various LCD displays: a) 
HP, b) NEC. 
 
 
 
 
 
 
 
 
 
 
Fig. 4. Type of  back illumination 
 
 
 
 
 

 
 
 
 
 
 
. 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. 

 
The conception of fitting using micro-mirrors 

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 
diodes. 
 
 
 
 

 

PRZEGLĄD ELEKTROTECHNICZNY, ISSN 0033-2097, R. 84 NR 8/2008                                                                              107 

 

 

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 
of expensive and inconvenient in exploitation light sources 
like discharge lamps or high energy  LED diodes. The 
waste of energy in comparison with classic solutions got 
lower about approx. 50%, causes enlargement of the range 
of colours (figure 9a) to the level approx. simultaneously 
95% range of colours perceived by the man. The light is 
additionally polarized, and laser module is characterized by 
high efficiency and lifetime about 55 000 hours. 

 

Conclusions 

Conception of planar lighting fitting leaning on the LCD 

or DLP technology lets achieve and obtain the new guilds of 
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 
colorimetric parameters like colour temperature or colour of 
the light. Light, emitted from planar fitting, shows high 
degree of polarization because of applying polarizing filters 
in its construction. The construction of low-luminance  
fittings is inconvenient in classic formulation, however it lets 
utilization of planar structures (planar optical fibres) and 
LCD or DLP technology, on projects and production of such 
light-optical devices. The additional feature of devices 
emitting the luminous flux through liquid crystals structures 

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].  

 

 

 

a)    

 

 

       b) 

Fig. 9. The laser RGB module: a) CIE1931 space of colours, b) 
building of laser module. 

 

Financed by Ministry of Science and Higher Education – 
No. W/WE/4/08. 
 

REFERENCES 

[1]  

http://www.pcworld.pl

 

[2] de Gennes P.G,. Prost J: The Physics of Liquid   Crystals, 

Claredon Press 1993 

[3] Dybczyński W.: Miernictwo promieniowania Optycznego, WPB, 

Białystok 1996 

[4] http://www.novalux.com/display/ 

 
 

Authors:

  

dr inż. Maciej Zajkowski,  Politechnika Białostocka 
Wydział Elektryczny, Katedra Promieniowania Optycznego,  
ul. Wiejska 45D/218, 15-351 Bialystok,  
e-mail: 

maczak@we.pb.edu.pl

 

 
mgr inż. Tomasz Stalbowski, Politechnika Białostocka 
Wydział Elektryczny, Katedra Promieniowania Optycznego,  
ul. Wiejska 45D/218, 15-351 Bialystok