Untitled - Journal of Lighting Engineering

from 12 lm/W to 80 lm/W, but the average of
the category as a whole (45-55 lm/W) exceeds
the average CFL benchmark (30-40 lm/W).
LED downlights have high average CRI
values (82) and have a small spread of CRI
values pointing to the more demanding
color requirements of residential
applications.
• Edge-lit LED flat panels – area
light sources poised to replace fluorescent
general lighting have originated from LED
backlight technology in LCD displays.
Emission from LEDs at panel edge is
coupled into the waveguide, propagates and
is scattered by surface features (v-groove,
microlens) with efficiencies (panel
output/LED output) varying widely from
55% to 95%. The emission spectrum is byand-large
the same as the LEDs used. It is
possible to use both cool and warm white
LEDs and have a CCT tunable source (e.g.
LG Innotek), or to use RGB LEDs and
perform color mixing within the waveguide.
Since tens or even hundreds LEDs may be
used, tight binning of individual LEDs is not
as critical to panel-to-panel color matching.
Alone or in combination with additional
optical films it is possible to realize high
angle cut-off for glare control and bat-wing
distribution for indirect, volumetric lighting.
Harnessing the rapid development of LEDs
in both performance and cost, edge-lit LED
panels will certainly be a major area source
technology. There are currently few
manufacturers that can deliver more than
5000 lm for a typical 2x4 troffer benchmark or
3000 lm for a 2x2 at comparable 50-70 lm/W
overall luminaire efficiency.
• High-flux modular luminaires –
mainly used to replace high-lumen fixtures
Information
in medium to high ceiling or outdoor
applications. The multi-watt LEDs are
designed for 350-700 mA currents and can
be under or overdriven for longer life or
respectively higher output. The
photometrical enhanced lenses are built in
the individual LED assembly according to
the chosen distribution. While some
manufacturers lay LEDs in patterns that will
complement the photometrical delivery
(circular, ellipsoid, asymmetric), other
simply use rectangular modules (bars) with
individual lensed LEDs. The apparent
advantage is that incremental luminous
output can be obtained using the same
chassis by adding or subtracting the
modules without significantly affecting the
photometrics. This not only reduces the
costs by standardizing the components,
facilitates effective maintenance (easy
replacement) but also allows for an easier
upgrade (to more efficient, higher-flux
newer LED generations). Some luminaires
are built with open spaces between the bars
to allow for enhanced and efficient
(chimney-effect or rain-wash) cooling.
• OLEDs - As futuristic as they may
seem, OLEDs are also edging toward the
brink of market-readiness. The opportunity
to surface printable luminescent materials
can dramatically revolutionize the way we
know lighting. Acuity Brands Lighting has
presented OLED luminaires prototypes that,
of 3000-4000 lm, >70 lm/W) and colortunable
(2700 K-4000 K). Imagine your wall
or ceiling being now the luminous source!
• Dynamic sources – color-changing
or tunable sources using RGB LED chips
mainly for decorative or mood-setting light
concepts. While the color-changing LEDs
Ingineria Iluminatului 2012; 14, 2: 67-70 69