ISSN 1064-2269, Journal of Communications Technology and Electronics, 2009, Vol. 54, No. 1, pp. 107–118. © Pleiades Publishing, Inc., 2009.
Original Russian Text © E.M. Guttsait, 2009, published in Radiotekhnika i Elektronika, 2009, Vol. 54, No. 1, pp. 113–124.
In practical applications, the number of white LEDs
that can be used instead of incandescent or luminescent
lamps must be determined.
In this paper, we analyze various variants of the
LED modules that contain LEDs with various optical
systems (OSs). Most attention is paid to variations in
the illuminance with an increase in the distance
between the LED module and the illuminated surface.
Also, we consider possibilities of forming and keeping
uniform an illumination distribution with normal illu-
The relatively small dimensions of LEDs allow their
representation as point light sources for which the law
of inverse squared distance (LISD) is satisfied. How-
ever, the LISD is not satisfied in the near-field zone, and
is the axial luminous intensity and
tance, contains coefficient
, which depends on dis-
tance and reaches the level
= 1 in the far-field zone.
In addition to the illuminance distributions, we
present the results of calculations of coefficient
which is called the coefficient of deviation (CD) from
the LISD. We also demonstrate the effect of the LED-
module configuration (the number of LEDs, the inter-
vals between LEDs, and the LED emission angles) on
the value of coefficient
For the comparative analysis, we consider the LED
modules containing LEDs of two types (
= 3 and 5) in
accordance with the notation from . Azimuthally
symmetric optical systems of the LEDs with identical
luminous fluxes provide different flux densities, whose
values are determined by the luminous intensity curves
(LICs) with different emission angles (EAs). For a
type-3 LED, this angle is