Increasing retinal
image size
Decreasing
retinal irradiance
regulations | SAFETY
Researchers around the world have raised concerns about the safety of LED lighting on a regular basis, with
the focus ranging from the impact of blue
light to issues such as disability glare. In a
multipart series of articles that concluded
in February 2012, we discussed the photobiological safety of solid-state lighting (SSL)
and other non-laser sources of optical radiation ( ledsmagazine.com/features/9/2/9). This
article builds on the prior work and discusses
new work being done in standards bodies and
research labs centric to the issue of blue light.
The photobiological safety of lamps and
luminaires intended for general lighting service (GLS) applications is currently evaluated by implementing the GLS classification
criterion of the IEC/EN62471 specification
— namely by reporting (but not necessarily
measuring) at a distance at which the source
produces an illuminance of 500 lx, not less
than 200 mm.
This current situation has provided lit-
tle satisfaction in the lighting industry on a
number of points:
• Disagreement over which lamps should be
considered in the GLS category (does this
include, for example, spotlights or desk
lamps?)
• Questions regarding the value of an evalu-
ation at 500 lx, which may not represent a
realistic exposure scenario
• Lack of information provided by evaluation
at 500 lx, since for the majority of sources an
exempt risk group classification is obtained
• Issues with the implementation of a method,
provided in IEC/TR 62471-2, to permit the
transfer of LED manufacturers’ data to fin-
ished products. Such an evaluation, based
on worst-case conditions (not a realistic
representation of the use of the LED), often
results in RG2 classification, requiring the
use of warning labels, and presents the
problem of how this classification should
be transferred to finished products.
The photobiological safety panel of IEC
sub-committee SC34A: Lamps (part of IEC
technical committee 34: Lamps and related
equipment) has looked at this question, the
result of which includes the publication of
IEC/TR 62778 Edition 1: “Application of IEC
62471 for the assessment of blue light hazard to light sources and luminaires,” and the
amendment of various lamp and luminaire
standards, many of which have already been
published and updated under the Low Voltage
Directive. This approach is in line with the
idea of IEC 62471 as a horizontal standard vs.
a vertical, product-specific standard.
Safety concerns of lighting products
IEC 62471 gives consideration to two ultraviolet (UV), two retinal, and two infrared
(IR) hazards to the skin and eye over the
spectral range 200–3000 nm. The optical
radiation emitted by GLS products, broadly
encompassing incandescent, fluorescent,
discharge, and LED sources, need not cover
the entire spectral range nor be of a level to
present cause for concern. A consideration
of photobiological safety depends therefore
on lamp type and is treated by technology-specific standards.
While the actinic UV hazard has been
considered in certain standards, and
in guidance on the provision of luminaire protective shields for lamps emitting a high level of UV radiation, the retinal blue light hazard has not been hitherto
addressed; it is on this aspect that IEC/
TR 62778 has focused. The IR hazard will,
where required, be dealt with by marking
with labels warning of the presence of IR
radiation.
The IEC addresses characterization
of the blue light hazard
Following a previous series of articles considering the evaluation of the photobiological safety of
products comprising LEDs, LESLIE LYONS provides an overview of a new approach adopted by the
lighting industry to evaluate the retinal blue light hazard for which the advent of SSL has given some
cause for concern.
LESLIE LYONS is the technical support
manager of Bentham Instruments Limited,
and a member of BSI and IEC committees
TC76, Optical Radiation and Laser Safety.
FIG. 1. Retinal image size and irradiance vary with exposure time.
