Application of IEC 62471 for the assessment of blue light hazard to light sources and luminaires

IEC/TR 62778:2014 brings clarification and guidance concerning the assessment of blue light hazard of all lighting products which have the main emission in the visible spectrum (380 nm to 780 nm). By optical and spectral calculations, it is shown what the photobiological safety measurements as described in IEC 62471 tell us about the product and, if this product is intended to be a component in a higher level lighting product, how this information can be transferred from the component product (e.g. the LED package, the LED module, or the lamp) to the higher level lighting product (e.g. the luminaire). This second edition cancels and replaces the first edition published in 2012. This edition constitutes a technical revision. This edition includes the following significant technical change with respect to the previous edition: inclusion of the photobiological assessment of LED arrays (Annex D). The contents of the corrigendum of July 2014 have been included in this copy.

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Publication Date
26-Jun-2014
Current Stage
PPUB - Publication issued
Start Date
27-Jun-2014
Completion Date
27-Jun-2014
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IEC TR 62778
Edition 2.0 2014-06
TECHNICAL
REPORT
colour
inside

Application of IEC 62471 for the assessment of blue light hazard to light sources

and luminaires
IEC TR 62778:2014-05(en)
---------------------- Page: 1 ----------------------
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---------------------- Page: 2 ----------------------
IEC TR 62778
Edition 2.0 2014-06
TECHNICAL
REPORT
colour
inside

Application of IEC 62471 for the assessment of blue light hazard to light sources

and luminaires
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
PRICE CODE
ICS 29.140 ISBN 978-2-8322-1615-6

Warning! Make sure that you obtained this publication from an authorized distributor.

® Registered trademark of the International Electrotechnical Commission
---------------------- Page: 3 ----------------------
– 2 – IEC TR 62778:2014 © IEC 2014
CONTENTS

FOREWORD ........................................................................................................................... 4

1 Scope .............................................................................................................................. 6

2 Normative references ...................................................................................................... 6

3 Terms and definitions ...................................................................................................... 6

4 General ......................................................................................................................... 11

5 Spectrum, colour temperature, and blue light hazard ..................................................... 12

5.1 Calculation of blue light hazard quantities and photometric quantities from

emission spectra ................................................................................................... 12

5.2 Luminance and illuminance regimes that give rise to t values below
max

100 s .................................................................................................................... 15

6 LED packages, LED modules, lamps and luminaires ...................................................... 17

7 Measurement information flow ....................................................................................... 18

7.1 Basic flow ............................................................................................................. 18

7.2 Conditions for the radiance measurement ............................................................. 20

7.3 Special cases (I): Replacement by a lamp or LED module of another type ............ 22

7.4 Special cases (II): Arrays and clusters of primary light sources ............................. 22

8 Risk group classification ................................................................................................ 22

Annex A (informative) Geometrical relations between radiance, irradiance and radiant

intensity ................................................................................................................................ 23

Annex B (informative) Distance dependence of t for a certain light source ..................... 25

max
Annex C (informative) Summary of recommendations to assist the consistent

application of IEC 62471 for the assessment of blue light hazard to light sources and

luminaires ............................................................................................................................. 27

C.1 General ................................................................................................................. 27

C.2 Situation of RG0 or RG1 classification not requiring radiance or irradiance

measurement ........................................................................................................ 27

C.2.1 Boundary conditions ...................................................................................... 27

C.2.2 True luminance values giving risk group not greater than RG1 ...................... 27

C.2.3 Illuminance values giving risk group not greater than RG1 ............................. 28

C.3 Situation for the classification of light sources larger than 2,2 mm and

luminaires using these light sources...................................................................... 29

C.4 Situation for the classification of light sources smaller than 2,2 mm and

luminaires using these light sources...................................................................... 30

C.5 Situation for the classification of light sources that pose practical difficulties

in measurements at 200 mm ................................................................................. 30

Annex D (informative) Detailed assessment of arrays and clusters of primary light

sources, comprised of LED packages ................................................................................... 31

D.1 General ................................................................................................................. 31

D.2 Approach .............................................................................................................. 31

D.2.1 Step by step assessment ............................................................................... 31

D.2.2 Type of arrays and additional steps ............................................................... 32

D.2.3 Complete flowchart ........................................................................................ 34

D.3 Derivation of the formula for average radiance of the full array ............................. 35

Bibliography .......................................................................................................................... 37

Figure 1 – Blue light hazard efficacy of luminous radiation, K , for a range of light

B,v

sources from different technologies, and for a few typical daylight spectra ............................ 13

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IEC TR 62778:2014 © IEC 2014 – 3 –
Figure 2 – Comparison between the curves involved in calculating K (the photopic
B,v

eye sensitivity curve and the blue light spectral weighting function) and the CIE 1931 Y

and Z curves involved in calculating the CIE 1931 x, y colour coordinates ............................ 14

Figure 3 – Correlation plot between the quantity (1 – x – y)/y, calculated from the CIE

1931 x, y colour coordinates, and the value of K , for all the spectra analysed to

B,v

generate Figure 1 ................................................................................................................. 15

Figure 4 – Estimate of the luminance level where L = 10 000 W/(m sr), border
between RG1 (t > 100 s) and RG2 (t < 100 s) in the large source regime, as a
max max

function of CCT ..................................................................................................................... 16

Figure 5 – Estimate of the illuminance level where E = 1 W/m , border between RG1

(t > 100 s) and RG2 (t < 100 s) in the small source regime, as a function of
max max
CCT 16

Figure 6 – Relation of illuminance E, distance d and intensity I ............................................. 20

Figure 7 – Flow chart from the primary light source (in blue) to the luminaire based on

this light source (in amber) ................................................................................................... 21

Figure A.1 – Schematic image of the situation considered in Annex A ................................... 23

Figure B.1 – General appearance of t as a function of viewing distance d, for any

max

light source with homogeneous luminance L and diameter D ................................................ 26

Figure C.1 – Luminance values from Table C.1 in relation to the RG1/RG2 border as

function of correlated colour temperature .............................................................................. 28

Figure C.2 – Illuminance values from Table C.2 in relation to the RG1/RG2 border as

function of correlated colour temperature .............................................................................. 29

Figure D.1 – Examples of secondary lenses with identical light distribution and

alignment .............................................................................................................................. 32

Figure D.2 – Examples of LED arrays with bare LED packages ............................................. 33

Figure D.3 – Evaluation whether one or more LED elements fall in 11 mrad field of

view at distance d ............................................................................................................... 33

Figure D.4 – Complete flowchart of the detailed assessment of arrays and clusters of

primary light sources ............................................................................................................. 35

Table 1 – Correlation between exposure time and risk group ................................................ 10

Table C.1 – Luminance values giving risk group not greater than RG1 .................................. 28

Table C.2 – Illuminance values giving risk group not greater than RG1 ................................. 29

Table D.1 – Applicability of steps 1 to 6 ................................................................................ 31

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– 4 – IEC TR 62778:2014 © IEC 2014
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
APPLICATION OF IEC 62471 FOR THE ASSESSMENT OF
BLUE LIGHT HAZARD TO LIGHT SOURCES AND LUMINAIRES
FOREWORD

1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising

all national electrotechnical committees (IEC National Committees). The object of IEC is to promote

international co-operation on all questions concerning standardization in the electrical and electronic fields. To

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2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international

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8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is

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The main task of IEC technical committees is to prepare International Standards. However, a

technical committee may propose the publication of a technical report when it has collected

data of a different kind from that which is normally published as an International Standard, for

example "state of the art".

IEC TR 62778, which is a technical report, has been prepared by subcommittee 34A: Lamps,

of IEC technical committee 34: Lamps and related equipment.

This second edition cancels and replaces the first edition published in 2012. This edition

constitutes a technical revision.

This edition includes the following significant technical change with respect to the previous

edition: inclusion of the photobiological assessment of LED arrays (Annex D).
---------------------- Page: 6 ----------------------
IEC TR 62778:2014 © IEC 2014 – 5 –
The text of this technical report is based on the following documents:
Enquiry draft Report on voting
34A/1737/DTR 34A/1758/RVC

Full information on the voting for the approval of this technical report can be found in the

report on voting indicated in the above table.

This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.

The committee has decided that the contents of this publication will remain unchanged until

the stability date indicated on the IEC web site under "http://webstore.iec.ch" in the data

related to the specific publication. At this date, the publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
A bilingual version of this publication may be issued at a later date.
The contents of the corrigendum of July 2014 have been included in this copy.

IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates

that it contains colours which are considered to be useful for the correct

understanding of its contents. Users should therefore print this document using a

colour printer.
---------------------- Page: 7 ----------------------
– 6 – IEC TR 62778:2014 © IEC 2014
APPLICATION OF IEC 62471 FOR THE ASSESSMENT OF
BLUE LIGHT HAZARD TO LIGHT SOURCES AND LUMINAIRES
1 Scope

This Technical Report brings clarification and guidance concerning the assessment of blue

light hazard of all lighting products which have the main emission in the visible spectrum

(380 nm to 780 nm). By optical and spectral calculations, it is shown what the photobiological

safety measurements as described in IEC 62471 tell us about the product and, if this product

is intended to be a component in a higher level lighting product, how this information can be

transferred from the component product (e.g. the LED package, the LED module, or the lamp)

to the higher level lighting product (e.g. the luminaire).

A summary of recommendations to assist the consistent application of IEC 62471 to light

sources and luminaires for the assessment of blue light hazard is given in Annex C.

NOTE It is expected that HID and LED product safety standards will make reference to this Technical Report.

2 Normative references

The following documents, in whole or in part, are normatively referenced in this document and

are indispensable for its application. For dated references, only the edition cited applies. For

undated references, the latest edition of the referenced document (including any
amendments) applies.
IEC 60050 (all parts), International Electrotechnical Vocabulary (available at
).
IEC 62471:2006, Photobiological safety of lamps and lamp systems
CIE S 017/E:2011, ILV: International Lighting Vocabulary
3 Terms and definitions

For the purposes of this document, the terms and definitions given in IEC 62471:2006,

CIE S 017/E:2011 and IEC 60050-845 as well as the following apply.
3.1
blue light hazard efficacy of luminous radiation
B,v
quotient of blue light hazard quantity to the corresponding photometric quantity

Note 1 to entry: Blue light hazard efficacy of luminous radiation is expressed in W/lm.

Note 2 to entry: The quantity Φ (λ) in the formula below can be replaced by L (λ) or E (λ).

λ λ λ
Φ (λ)⋅B(λ )⋅ dλ
K =
B,v
K ⋅ Φ (λ )⋅V(λ )⋅ dλ
m λ
where K = 683 lm/W.
Note 3 to entry: K = L /L = E /E.
B,v B B
---------------------- Page: 8 ----------------------
IEC TR 62778:2014 © IEC 2014 – 7 –
3.2
blue light hazard efficiency of radiation
ratio of blue light hazard quantity to the corresponding radiometric quantity

Note 1 to entry: The quantity Φ (λ) in the formula below can be replaced by L (λ) or E (λ).

λ λ λ
(λ )⋅B(λ )⋅dλ
(λ )⋅dλ
3.3
correlated colour temperature
CCT

temperature of the Planckian radiator having the chromaticity nearest the chromaticity

associated with the given spectral distribution on a diagram where the (CIE 1931 standard

observer based) u’, 2/3 v’ coordinates of the Planckian locus and the test stimulus are

depicted
Note 1 to entry: Correlated colour temperature is expressed in kelvin (K).

Note 2 to entry: The concept of correlated colour temperature should not be used if the chromaticity of the test

2 2 −2
source differs more than from the Planckian radiator, where
ΔC=[(u'−u' ) + (v'−v' ) ] =5×10
t p t p
u’ , v’ refer to the test source, u’ , v’ to the Planckian radiator.
t t p p

Note 3 to entry: Correlated colour temperature can be calculated by a simple minimum search computer program

that searches for that Planckian temperature that provides the smallest chromaticity difference between the test

chromaticity and the Planckian locus, or e.g. by a method recommended by Robertson, A. R. “Computation of

correlated color temperature and distribution temperature”, J. Opt. Soc. Am. 58, 1528-1535, 1968. (Note that the

values in some of the tables in this reference are not up-to-date).
[SOURCE: CIE S 017/E:2011, 17-258, modified — T is not referenced.]
3.4
illuminance

quotient of the luminous flux dΦ incident on an element of the surface containing the point, by

the area dA of that element
Note 1 to entry: Illuminance is expressed in lm/m or lx.

[SOURCE: IEC 60050-845:1987, 845.01.38, modified — The second half of the definition is

omitted.]
3.5
blue light weighted irradiance

irradiance spectrally weighted with the blue light spectral weighting function as defined in

IEC 62471
Note 1 to entry: Blue light weighted irradiance is expressed in W/m .
3.6
threshold illuminance
thr

threshold illuminance value, below which the light source can never give rise to an exposure

time t < 100 s, regardless of the light source’s L value
max B

Note 1 to entry: The threshold illuminance can be calculated by taking the E value for t = 100 s, which is

B max

E = 1 W/m , and dividing E by the K value corresponding to the spectrum of the light source.

B B B,v
---------------------- Page: 9 ----------------------
– 8 – IEC TR 62778:2014 © IEC 2014
Note 2 to entry: Threshold illuminance is expressed in lm/m or lx.
3.7
etendue

geometrical property of a collection of light rays in an optical system, given by the integral

over all positions in a plane that these light rays pass through and over all directions into

which they travel

Note 1 to entry: It takes the form of a product of area and solid angle. It can be seen as a volume in phase space.

Basic physical conservation laws, related to the ‘second law of thermodynamics’, dictate that optical components

that change only the direction of light (lenses, reflectors, all beam shaping optics) can never decrease the etendue

for a given packet of flux.
Note 2 to entry: Etendue is expressed in m sr.
3.8
irradiance

quotient of the radiant flux dΦ incident on an element of the surface containing the point, by

the area dA of that element
Note 1 to entry: Irradiance (at a point of a surface) is expressed in W/m .

Note 2 to entry: The spectral power distribution of the irradiance, as a function of wavelength, is denoted by

E (λ).

Note 3 to entry: For the purposes of this Technical Report, it is important to mention that when E (λ) is known, it

can be converted to illuminance (E) when weighted with the CIE 1924 photopic eye sensitivity spectrum V(λ), and

to blue light weighted irradiance (E ) when weighted with the blue light spectral weighting function as defined in

IEC 62471.
[SOURCE: IEC 60050-845:1987, 845.01.37, modified — Notes 2 and 3 to entry are
introduced.]
3.9

luminance

quantity defined by the formula
dA⋅cosθ⋅ dΩ

where dΦ is the luminous flux transmitted by an elementary beam passing through the given

point and propagating in the solid angle dΩ containing the given direction; dA is the area of a

section of that beam containing the given point; θ is the angle between the normal to that

section and the direction of the beam

Note 1 to entry: Luminance (in a given direction, at a given point of a real or imaginary surface) is expressed in

cd/m .

[SOURCE: IEC 60050-845:1987, 845.01.35, modified — “L” instead of “L ” is used. The note

is deleted.]
3.10
blue light weighted radiance

radiance spectrally weighted with the blue light spectral weighting function as defined in

IEC 62471
Note 1 to entry: Blue light weighted radiance is expressed in W/(m sr).
3.11
light source
any product that produces light
---------------------- Page: 10 ----------------------
IEC TR 62778:2014 © IEC 2014 – 9 –
EXAMPLE LED package, LED module, lamp, luminaire
3.12
luminaire

apparatus which distributes, filters or transforms the light transmitted from one or more lamps

and which includes, except the lamps themselves, all the parts necessary for fixing and

protecting the lamps and, where necessary, circuit auxiliaries together with the means for

connecting them to the electric supply
[SOURCE: IEC 60050-845:1987, 845.10.01, modified — Notes 1 and 2 are deleted.]
3.13
luminaire optics

all luminaire components that modify the spatial and directional characteristics of the radiation

emitted by the primary light source inside the luminaire
3.14
primary light source
surface or object emitting light produced by a transformation of energy

Note 1 to entry: For the purpose of this Technical Report, it may refer to an LED package, an LED module, or a

lamp.

[SOURCE: IEC 60050-845:1987, 845.07.01, modified — A new note to entry is added.]

3.15
radiance
quantity defined by the formula
L =
dA⋅cosθ⋅ dΩ

where dΦ is the radiant flux transmitted by an elementary beam passing through the given

point and propagating in the solid angle dΩ containing the given direction; dA is the area of a

section of that beam containing the given point; θ is the angle between the normal to that

section and the direction of the beam.

Note 1 to entry: Radiance (in a given direction, at a given point of real or imaginary surface) is expressed in

W/(m sr).

Note 2 to entry: The spectral power distribution of the radiance, as a function of wavelength, is denoted by L (λ).

Note 3 to entry: For the purposes of this document, it is important to mention, that when L (λ) is known, it can be

converted to luminance (L) when weighted with the CIE 1924 photopic eye sensitivity spectrum V(λ), and to blue

light weighted radiance (L ) when weighted with the blue light spectral weighting function as defined in IEC 62471.

[SOURCE: IEC 60050-845:1987, 845.01.34, modified — Notes to entry 1 to 5 are deleted and

new notes to entry are introduced.]
3.16
risk group

risk classification when the product, at the relevant evaluation position, gives rise to a certain

t value, according to Table 1, as defined in IEC 62471
max
---------------------- Page: 11 ----------------------
– 10 – IEC TR 62778:2014 © IEC 2014
Table 1 – Correlation between exposure time and risk group
Risk group number Risk group name Corresponding t range
max
RG0 Exempt > 10 000
RG1 Low risk 100 to10 000
RG2 Moderate risk 0,25 to100
RG3 High risk
< 0,25
3.17
maximum permissible exposure time
max

maximum permissible exposure time as calculated using the relevant formulae in 4.3.3 and

4.3.4 of IEC 62471:2006
3.18
true luminance

luminance value as obtained by integrating the equation as given in the definition of

luminance, over a certain area of a light source, such that only the light emitting surface (or

part of it) is included in the integration, and no dark surface area surrounding the light

emitting part of the light source

Note 1 to entry: When a luminance measurement is performed over a certain field of view, it will only give a true

luminance value when the field of view underfills the light emitting part of the light source.

3.19
true radiance

radiance value as obtained by integrating the equation as given in the definition of radiance ,

over a certain area of a light source, such that only the light emitting surface (or part of it) is

included in the integration, and no dark surface area surrounding the light emitting part of the

light source

Note 1 to entry: When a radiance measurement is performed over a certain field of view, it will only give a true

radiance value when the field of view underfills the light emitting part of the light source.

3.20
LED package

one single electrical component encapsulating principally one or more LED dies, possibly with

optical elements and thermal, mechanical, and electrical interfaces

Note 1 to entry: The component does not include the control unit of the controlgear, does not include a cap, and

is not connected directly to the supply voltage.

Note 2 to entry: An LED package is a discrete component and part of the LED module. For a schematic build-up

of an LED package, see Annex A of IEC 62504 .
3.21
secondary optics
optics that are not part of the LED package itself
3.22
threshold distance
thr
distance from the light source at which the illuminance produced by t
...

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